U.S. patent application number 11/376737 was filed with the patent office on 2006-09-28 for method and apparatus for coordinating a wireless pan network and a wireless lan network.
This patent application is currently assigned to H-Stream Wireless, Inc.. Invention is credited to Roel Peeters, Katelijn Vleugels.
Application Number | 20060215601 11/376737 |
Document ID | / |
Family ID | 36992459 |
Filed Date | 2006-09-28 |
United States Patent
Application |
20060215601 |
Kind Code |
A1 |
Vleugels; Katelijn ; et
al. |
September 28, 2006 |
Method and apparatus for coordinating a wireless PAN network and a
wireless LAN network
Abstract
Devices of a personal area network (PAN) use a wireless medium
that is shared with a wireless local area network (WLAN). WLAN
devices communicate using protocols of the WLAN and PAN devices
communicate using PAN protocols allowing for lower power
transmissions over the wireless medium relative to transmissions
over the WLAN. A PAN coordinator device obtains access to the
wireless medium for the PAN devices by signalling a reservation of
the medium by the PAN coordinator device, such that the other
devices defer use of the wireless medium, including at least one
WLAN device, for a reservation period. During the reservation
period, the communication is done using the PAN protocol. The
signalling can be implicit in that the PAN coordinator device
transmits one or more frame using the PAN protocol but that is at
least partially understandable by WLAN devices such that they defer
upon receipt of one or more of the PAN protocol frames, which may
be a standard or modified HCCA-CF poll frame, a CTS frame with an
increased duration field, or other variation. A PAN coordinator
might also signal an access point to set up a DLS link between the
PAN coordinator and itself and use the DLS period for PAN
traffic.
Inventors: |
Vleugels; Katelijn; (San
Carlos, CA) ; Peeters; Roel; (San Carlos,
CA) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW, LLP
TWO EMBARCADERO CENTER
EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
H-Stream Wireless, Inc.
Palo Alto
CA
|
Family ID: |
36992459 |
Appl. No.: |
11/376737 |
Filed: |
March 14, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60661746 |
Mar 14, 2005 |
|
|
|
Current U.S.
Class: |
370/328 ;
370/338 |
Current CPC
Class: |
Y02D 70/23 20180101;
H04W 88/10 20130101; Y02D 70/144 20180101; H04W 74/06 20130101;
H04W 84/12 20130101; Y02D 70/142 20180101; H04W 84/10 20130101;
H04W 92/02 20130101; Y02D 30/70 20200801; H04W 52/0209 20130101;
H04W 88/06 20130101; H04W 84/22 20130101; H04W 88/04 20130101; Y02D
70/22 20180101; H04W 72/12 20130101; H04W 84/18 20130101; H04W
84/20 20130101; H04W 28/26 20130101; Y02D 70/1222 20180101; Y02D
70/26 20180101 |
Class at
Publication: |
370/328 ;
370/338 |
International
Class: |
H04Q 7/00 20060101
H04Q007/00; H04Q 7/24 20060101 H04Q007/24 |
Claims
1. A method of communicating between devices of a personal area
network (PAN) using a wireless medium that is shared with a
wireless local area network (WLAN), wherein WLAN devices
communicate using protocols of the WLAN and PAN devices communicate
using PAN protocols allowing for lower power transmissions over the
wireless medium relative to transmissions over the WLAN, the method
comprising: obtaining access to the wireless medium for a PAN
coordinator device, wherein transmission access to the wireless
medium is allocated to the PAN coordinator device to allow it to
transmit while other devices defer; signalling a reservation of the
medium by the PAN coordinator device, such that the other devices
defer use of the wireless medium, including at least one WLAN
device, for a reservation period; and communicating between the PAN
coordinator device and a PAN device over the wireless medium during
the reservation period, wherein communication is done using the PAN
protocol.
2. The method of claim 1, wherein signalling a reservation of the
medium is implicit in that the PAN coordinator device transmits one
or more frame using the PAN protocol but that is at least partially
understandable by WLAN devices such that they defer upon receipt of
one or more of the PAN protocol frames.
3. The method of claim 2, wherein the one or more frame using the
PAN protocol comprises a frame directed to a PAN device having an
increased duration field.
4. The method of claim 3, wherein the WLAN network is an 802.11x
network and one or more frame using the PAN protocol comprises an
802.11x frame of type "data", or a modification thereof, directed
to a PAN device and having an increased duration field.
5. The method of claim 3, wherein the one or more frame using the
PAN protocol comprises an 802.11x CTS frame with an increased
duration field.
6. The method of claim 3, wherein the one or more frame using the
PAN protocol comprises an 802.11x frame or modification thereof,
transmitted using a highest priority queue.
7. The method of claim 3, wherein the one or more frame using the
PAN protocol comprises an HCCA-CF poll frame having a plurality of
subtype fields including a "data" subtype field and a "poll"
subtype field, wherein the HCCA-CF poll frame is sent with its
"data" subtype field cleared and its "poll" subtype field set.
8. The method of claim 3, wherein the one or more frame using the
PAN protocol comprises a modified HCCA-CF poll frame only partially
compliant with a WLAN standard, the modified HCCA-CF poll frame
having a plurality of subtype fields including a "data" subtype
field and a "poll" subtype field, wherein the HCCA-CF poll frame is
sent with its "data" subtype field cleared and its "poll" subtype
field set.
9. The method of claim 3, wherein the PAN protocol frame includes
data addressed to a PAN device.
10. The method of claim 3, wherein the one or more frame using the
PAN protocol comprises an HCCA-CF poll frame having a plurality of
subtype fields including a "to DS" subtype field and a "from DS"
subtype field, wherein the HCCA-CF poll frame is sent with both
subtype fields cleared, thereby distinguishing from a valid WLAN
frame.
11. The method of claim 3, wherein the PAN protocol frame is
transmitted using a highest priority queue.
12. The method of claim 1, wherein signalling a reservation of the
medium is explicit in that the PAN coordinator device transmits one
or more frame using the WLAN protocol to signal WLAN devices,
wherein the one or more frame signals a reservation of the wireless
medium using WLAN protocol frames for that purpose.
13. The method of claim 12, wherein signaling to WLAN devices using
WLAN protocol frames occurs prior to each communication event with
a PAN device.
14. The method of claim 12, wherein signaling to WLAN devices using
WLAN protocol occurs once for the start of a series of SWN
communication events.
15. The method of claim 12, wherein the one or more frame using the
WLAN protocol to signal WLAN devices comprises an HCCA frame to set
up a traffic stream for the PAN coordinator device, the method
further comprising using the agreed on timeslots to communicate
with a PAN device.
16. The method of claim 12, wherein the one or more frame using the
WLAN protocol comprises a CTS frame with an increased duration
field.
17. The method of claim 1, wherein: signalling a reservation of the
medium by the PAN coordinator device comprises signalling a
reservation of the medium for a plurality of PAN devices; and
communicating between the PAN coordinator device and a PAN device
over the wireless medium comprises communicating between the PAN
coordinator device and each of a plurality of PAN devices.
18. The method of claim 17, further comprising sending a frame from
the PAN coordinator device to two or more of the plurality of PAN
devices with an indication of time offsets for each of the two or
more PAN devices indicating a scheduled time for the PAN device to
respond to the frame.
19. The method of claim 17, further comprising sending a frame from
the PAN coordinator device to two or more of the plurality of PAN
devices with an indication of the two or more PAN devices expected
to respond to the frame.
20. A wireless network interface circuit adapted to be coupled to a
wireless network for communicating, the wireless network interface
circuit comprising: circuitry for conveying signals between the
network interface circuit and a computing device to which the
network interface circuit is electrically coupled; logic for
determining a length of time for PAN-computing device
communication; and logic for reserving the wireless medium for the
length of time by signalling from the network interface circuit
using a protocol of a PAN network, wherein the PAN network protocol
is adapted such that devices operable in a second network will
defer use of a shared wireless medium even without being able to
completely interpret frames sent from the network interface circuit
according to the PAN network protocol logic for wirelessly
communicating with a PAN device using the wireless medium and the
PAN network protocol during the time, thereby allowing
communication between the wireless network interface circuit and
the PAN device without traffic expected from the second
network.
21. A wireless network interface circuit adapted to be coupled to a
wireless network for communicating, the wireless network interface
circuit comprising: circuitry for conveying signals between the
network interface circuit and a computing device to which the
network interface circuit is electrically coupled; logic for
wirelessly communicating with a network coordinator of a first
network; logic for wirelessly communicating with a node of a second
network, wherein an effective broadcast range of the node of the
second network is expected to be insufficient to communicate
directly with the network coordinator of the first network; logic
for determining a length of time for PAN-computing device
communication; and logic for reserving the wireless medium with the
network coordinator of the first network for the length of time,
thereby allowing communication from the node without traffic
expected from the network coordinator of the first network.
22. A method of interfacing a computing device to a wireless local
area network (WLAN) and a wireless personal area network (PAN),
wherein the WLAN is characterized by a plurality of nodes
intercommunicating over a wireless medium and the wireless PAN is
characterized by lower power transmissions over a wireless medium
relative to transmissions over the WLAN, the method comprising:
adapting a network circuit, comprising logic and at least one
antenna, for interfacing the computing device to the WLAN and to
the wireless PAN; setting up associations and communicating with
devices over the WLAN and the wireless PAN using at least one
common modulation scheme and at least one common frame formatting
layer; and coordinating with the WLAN coordinator and the wireless
PAN device, usage of the WLAN such that the wireless PAN device and
computing device can communicate without interference.
23. The method of claim 22, wherein the network circuit is
configured to go into a power-save mode and to communicate to the
access point device that it is entering the power-save mode, the
method further comprising: exiting the power-save mode to handle
secondary network traffic while not informing the access point
device of the wake-up, thereby reducing a chance that the access
point will attempt to communicate with the network circuit while it
is handling the secondary network traffic.
24. The method of claim 22, wherein the common modulation scheme is
at least in part compliant with an 802.11x PHY layer specification,
the common frame formatting layer is at least in part compliant
with an 802.11x MAC layer specification and coordination with the
WLAN coordinator and the wireless PAN device comprises reserving
the wireless medium for a length of time for PAN-computing device
communication.
25. The method of claim 22, further comprising: determining an
inactivity time; communicating between the wireless PAN device and
the computing device as needed to agree on the value of the
inactivity time; and disabling at least a part of a coordination
function of the computing device following a start of the
inactivity time, wherein disabling is such that less power per unit
time is consumed by the network circuit relative to power consumed
when not disabled.
26. A method of interacting with a primary network and a secondary
network, wherein a plurality of wireless local area network (WLAN)
devices communicate using protocols of the primary network and a
wireless medium and wherein one or more personal area network (PAN)
devices communicate using the protocols of the secondary network
and the wireless medium using lower power transmissions over the
wireless medium relative to transmissions over the WLAN, the method
comprising: configuring a dual-net device that is capable of
communicating over the primary network using its protocols and over
the secondary network using its protocols; determining, at the
dual-net device, that a reservation of the wireless medium is
needed for a PAN device that is not also a dual-net device;
signalling a request for a reservation of the wireless medium from
the dual-net device such that the request can be received and
understood by at least one other WLAN device; determining, at the
dual-net device, if the reservation was successful; if the
reservation was successful, signalling, using the protocols of the
secondary network, to the PAN device that is not also a dual-net
device that the wireless medium is reserved for that device for
communications using the protocols of the secondary network.
27. The method of claim 26, wherein the primary network is an
802.11x WLAN and the secondary network is an overlay network
wherein protocols of the overlay network are only partially
compliant with the protocols of the primary network.
28. The method of claim 26, wherein the plurality of WLAN devices
includes at least one access point.
29. The method of claim 26, wherein signalling the reservation
request comprises signalling the reservation request using the
protocols of the secondary network, wherein the protocols of the
secondary network are such that frames transmitted according to
those protocols are sufficiently compliant with the protocols of
the primary network such that the reservation request can be
received and understood by at least one other WLAN device.
30. The method of claim 26, wherein signalling the reservation
request comprises signalling the reservation request using the
protocols of the primary network.
31. The method of claim 30, wherein the reservation request
comprises setting up a traffic stream with the primary network and
having an access point grant a transmission opportunity for
transmissions between the dual-net device and the access point,
then using that transmission opportunity for communicating with PAN
devices of the secondary network.
32. The method of claim 26, wherein signalling the reservation
request comprises signalling the reservation request within a
reduced radius selected such that at least one of the WLAN devices
would not hear the reservation request, thereby allowing for
continued use of the wireless medium by WLAN devices outside the
reduced radius while the dual-net device and/or PAN devices inside
the reduced radius use the wireless medium.
33. The method of claim 32, wherein the dual-net device adjusts its
reservation request to vary the radius within which the request is
likely to be correctly received and the adjustment is based on
common wireless networking space activity.
34. The method of claim 32, wherein the dual-net device adjusts its
reservation request to vary the radius within which the request is
likely to be correctly received and the adjustment is based on
present activity in one or more of the primary network or a second
secondary network.
35. The method of claim 37, the dual-net device determines the
present activity at least in part by requesting activity
information from an access point with which the dual-net device is
associated in the primary network.
36. The method of claim 26, wherein the dual-net device adjusts its
reservation request based on present or future activity in the
primary network determined at least in part by requesting activity
and/or scheduling information from an access point with which the
dual-net device is associated in the primary network.
37. The method of claim 36, wherein the dual-net device is further
configured to coordinate and time secondary network traffic during
periods of expected inactivity in the primary network as the
dual-net device determines from activity and/or scheduling
information.
38. The method of claim 37, wherein the activity and/or scheduling
information includes information about the access point's
Controlled Access Phase (CAP).
39. The method of claim 26, wherein determining, at the dual-net
device, if the reservation was successful comprises sending a poll
frame with an increased duration field to reserve the wireless
medium.
40. A method of communicating in a wireless network between a
device as a station and an access point over a first network and
between the device as a coordinator and a peripheral over a second
network, comprising: communicating with the access point over the
first wireless network being an 802.11x network; communicating with
the peripheral over the second wireless network, wherein the second
wireless network operates using protocols are only partially
compliant with protocols of the first wireless network;
transmitting a first frame transmitted by the coordinator with
increased duration field, thereby reserving a wireless medium for
transmissions in the second network.
41. The method of claim 40, further comprising transmitting an
HCCA-CF poll frame addressed to the peripheral with the duration
field increased, with a subtype field "data" cleared and a subtype
field "poll" set.
42. The method of claim 40, further comprising transmitting an
HCCA-CF poll frame addressed to the peripheral with the duration
field increased, with the subtype fields "data" and "poll" both set
and including data in this frame addressed to the peripheral.
43. The method of claim 40, further comprising transmitting an
HCCA-CF poll frame addressed to the peripheral using a medium
access scheme regularly used by non-AP STAs.
44. The method of claim 43, further comprising transmitting the
HCCA-CF poll using a highest priority queue.
45. A method of communicating in a wireless network between a
device as a station and an access point over a first network and
between the device as a coordinator and a peripheral over a second
network, comprising: communicating with the access point over the
first wireless network, wherein the first wireless network is an
802.11x network; signalling, from the device to the access point,
for the use of DLS, DLS being a protocol that allows for two
stations associated with the access point to communicate directly;
and signalling, from the device to a second device, using DLS,
wherein the second device is not a device associated with the
access point.
46. The method of claim 45, further comprising associating the
device with the access point as a second associated device to cover
traffic between the device and the second device.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the benefit of and is a
non-provisional of U.S. patent application Ser. No. 60/661,746
filed on Mar. 14, 2005, which is incorporated by reference in its
entirety for all purposes.
FIELD OF THE INVENTION
[0002] The present invention relates generally to wireless
communications and more particularly to coordinating different
network uses of a common wireless medium.
BACKGROUND OF THE INVENTION
[0003] Wireless communication among electronic devices has been
increasing as the benefits and conveniences of wireless
communication become more preferred. A wireless communication
system or wireless network is often described as containing nodes
(or more precisely, circuitry associated with the concept of a
node) and a wireless medium (WM) over which the nodes' circuitry
communicate to convey information. Where some action or activity is
described as happening at (or being done at) a node, it should be
understood that the electronic device and/or network interface that
is at (or simply is) the node is the circuitry that is performing
the action or activity. For example, sending data from node A to
node B means transmitting a signal from circuitry associated with
node A and receiving that signal (or more precisely, the
transmitted signal modified by the medium) using circuitry
associated with node B.
[0004] The information conveyed between nodes can be digital data
and digitized analog signals, or other forms of information, but
communication system design often assumes that digital data is
being conveyed and higher network layers interpret the data
appropriately. For purposes herein, it is assumed that data exists
at one node, is provided to lower network layers, is conveyed to
another node over a WM, is received by another node correctly or
incorrectly and then is conveyed to upper network layers at the
receiver. In one model, two networked devices run applications that
pass data between themselves by having the sending device's
application convey data to an application layer of a network stack,
which conveys data to lower levels, ultimately to a medium access
control (MAC) layer and a physical network (PHY) layer, and the
process is inverted at the recipient.
[0005] To set up a wireless network, all that is needed is a
plurality of electronic "node" devices capable of transmitting and
receiving data in a manner understood by the two (or more) nodes
involved in a conversation, with the node devices appropriately
placed such that they can communicate in the medium that exists
between the devices. The medium could be some type of dielectric
material, but more commonly, the medium is the air space and
objects (walls, chairs, books, glass. etc.) that are between
devices or are positioned such that they have an effect on the
signals transmitted between devices. Presumably, the node devices
are assigned unique identifiers to distinguish transmissions, but
this might not always be necessary. Examples of such unique
identifiers are MAC addresses and IP addresses.
[0006] As the existence of various wireless media and their
properties are known and are not the focus of this disclosure, the
medium is often just shown in the attached figures as a cloud.
Thus, it should be understood that supplier of a set of two or more
powered devices that can communicate supplies a wireless network;
the wireless medium is presumed.
[0007] Wireless communication systems can be categorized based on
coverage range, which in some cases is dictated by use. A wireless
local area network or "WLAN", has a typical coverage range on the
order of 300 feet and is useful for providing communications
between computing devices in some (possibly loosely) defined space
such as a home, office, building, park, airport, etc. In some modes
of operation, one or more of the nodes is coupled to a wired
network to allow other nodes to communicate beyond the wireless
network range via that wired network. In 802.11 terminology, such
nodes are referred to as "access points" and the typical protocol
is such that the other nodes (referred to as "stations") associate
with an access point and communication is generally between a
station and an access point. Some wireless networks operate in an
"ad hoc" mode, wherein node devices communicate with each other
without an access point being present.
[0008] A personal area network or "PAN" is a short-range wireless
network, with typical coverage ranges on the order of 30 feet,
usable to connect peripherals to devices in close proximity,
thereby eliminating cables usually present for such connections.
For example, a PAN might be used to connect a headset to a mobile
phone or music/audio player, a mouse or keyboard to a laptop, a PDA
or laptop to a mobile phone (for syncing, phone number lookup or
the like), etc. Yet another example of a wireless PAN application
is wireless medical monitoring devices that wirelessly connect
monitoring hardware to a pager or similar read-out device. Yet
another example is a remote control that connects to a
wireless-enabled electronic device.
[0009] Some networks might fall in a gray area between a WLAN and a
PAN, but in many cases, a network is clearly one or the other. A
personal area network (PAN) is generally used for the
interconnection of information technology devices within the range
of an individual person, typically within a range of 10 meters. For
example, a person traveling with a laptop will likely be the sole
user of that laptop and will be the same person handling the
personal digital assistant (PDA) and portable printer that
interconnect to the laptop without having to plug anything in,
using some form of wireless technology. Typically, PAN nodes
interact wirelessly, but nothing herein would preclude having some
wired nodes. By contrast, a wireless LAN tends to be a local area
network (LAN) that is connected without wires and serves multiple
users.
[0010] Equipment connecting to a wireless communication system in
general, and to a wireless PAN communication system in particular,
is typically used for applications where power usage, weight, cost
and user convenience are very important. For example, with laptops,
low-cost accessories are preferable, and it is critical that the
power usage of such accessories be minimized to minimize the
frequency at which batteries need to be replaced or recharged. The
latter is a burden and annoyance to the user and can significantly
reduce the seamless user experience.
[0011] Weight and complexity are additional concerns in many
wireless communication systems. Particularly with mobile devices
such as laptops, weight is a concern and the user would rather not
have to deal with the hassle of carrying around a multiplicity of
devices. Mobile devices are devices that can be expected to be in
use while moving, while portable devices are devices that are
movable from place to place but generally are not moving when in
use. The considerations for mobile devices also apply to portable
devices, albeit sometimes with less of a concern. For example, with
a wireless connection of a peripheral to a laptop, both devices are
likely to be used while mobile or moved frequently and carried
around. Thus, weight and the number of devices is an important
consideration. With portable devices, such as a small desktop
computer with a wireless trackball, as long as the total weight is
below a user's carrying limit, the weight is not as much a concern.
However, battery life is often as much a concern with portable
devices as it is with mobile devices.
[0012] There are shades of grey between "portable" and "mobile" and
it should be understood that the concerns of mobile applications
and portable applications can be considered similar, except where
indicated. In other words, a mobile device can be a portable device
in the examples described herein.
[0013] Where a computing and/or communication device connects to a
WLAN, it uses wireless circuitry that often times are already built
into the computing device. If the circuitry is not built in, a WLAN
card (such as a network interface card, or "NIC") might be used.
Either way, some antenna circuitry is used and power is required to
run that circuitry.
[0014] Where a device also connects wirelessly to peripherals or
other devices over short links often referred to as forming a
"personal area network" or "PAN", circuitry is needed for that
connection as well. This circuitry is typically provided with an
external interface unit that is plugged into or onto the device.
For example, where the device is a laptop, the circuitry might be
provided by a Universal Serial Bus (USB) dongle that attaches to a
USB port of the laptop. The USB dongle contains the radio circuitry
needed to communicate wirelessly over the short wireless links.
[0015] In general, a wireless connection between two or more
devices requires that each device include wireless network
circuitry for conveying signals over the medium and receiving
signals over the medium, as well as processing/communication
circuitry to receive, process and/or convey data and/or signals to
that wireless network circuitry. The processing/communication
circuitry could be implemented with actual circuits, software
instructions executable by a processor, or some combination
thereof. In some variations, the wireless network circuitry and
processing/communication circuitry are integrated (such as with
some PDAs, wireless mice, etc.) or are separate elements (such as a
laptop as the processing/communication circuitry and a network
PCMCIA card as the wireless network circuitry).
[0016] For ease of understanding this disclosure, where it is
important to make the distinction between devices, a device that
exists to provide wireless connectivity is referred to as a
"network interface", "network interface device", "wireless network
interface device" or the like, while the device for which the
wireless connectivity is being provided is referred to as a
"computing device" or an "electronic device" notwithstanding the
fact that some such devices do more than just compute or might not
be thought of as devices that do actual computing and further
notwithstanding the fact that some network interface devices
themselves have electronics and do computing. Some electronic
devices compute and communicate via an attached network interface
device while other electronic devices might have their network
interface devices integrated in a non-detachable form. Where an
electronic device is coupled to a wireless network interface to a
wireless network, it is said that the device is a node in the
network and thus that device is a "node device".
[0017] An 802.11x (x=a, b, g, n, etc.) NIC (network interface card)
or 802.11x built-in circuitry might be used for networking an
electronic device to the outside world, or at least to devices at
other nodes of a WLAN 802.11x network, while using an external
dongle or a similar interface device with Bluetooth or proprietary
wireless circuitry for communication between the computing device
and the peripheral or other PAN node.
[0018] A device that is equipped with an 802.11x-conformant network
interface to the WM is herein referred to as a station or "STA". In
802.11 terminology, set of STAs constitutes a Basic Service Set
("BSS"). A set of STAs that communicate in a peer-to-peer
configuration is referred to as an "802.11x ad-hoc" network or an
independent BSS (IBSS). A set of STAs controlled by a single
coordinator is referred to as an 802.11x infrastructure network.
The coordinator of a BSS is herein referred to as the access point
or "AP".
[0019] A typical access point device is wired to a wired network
and is also wired to an external source of electricity, such as
being plugged into a wall socket or wired to a building's power
grid. For example, a building, an airport or other space people
might occupy might have fixed access points mounted throughout the
space to provide adequate network coverage for the purpose of
providing access to the Internet or other network for the people
occupying the space, via their portable or mobile devices. As such,
access points are typically always on so that the wireless network
is available whenever suitable portable or mobile devices are
carried into the space.
[0020] The use of different technologies for WLAN and wireless PAN
connectivity increases cost, weight and power usage (at the COORD
side and/or the PER side), and impairs a seamless user experience.
Those disadvantages could be resolved by equipping the peripheral
or PAN nodes with 802.11x wireless circuitry, thus eliminating the
dedicated PAN technologies altogether. However, PAN nodes are often
very power-sensitive devices. They usually are battery-operated
devices and their small form factor prohibits the use of bulky
batteries with large capacity. Instead, small batteries with
limited power capacity are used. Such peripherals cannot typically
support the power usage requirements typical of WLAN wireless
circuitry, such as 802.11x circuitry. A host of other difficulties
are present in view of the optimizations, goals and designs of
differing network protocols.
[0021] Another drawback is that independent LANs and PANs may
interfere if they share a common frequency band.
BRIEF SUMMARY OF THE INVENTION
[0022] In embodiments of wireless communication according to the
present invention, a computing device is interfaced to a wireless
personal area network (PAN) in an environment wherein coexisting
wireless local area networks (WLANs) might be present, and devices
of the wireless PAN coordinate usage of the wireless medium with
devices of the WLANs that are active in the same space, using the
same, or part of the same, wireless medium. Coordination is
achieved by the use of a wireless PAN communication protocol that
is an overlay protocol that is only partially compliant with the
WLAN protocol, but not entirely, in terms of power, frame contents
and sequences, timing, etc. The WLAN might have an access device
(infrastructure mode) or not (ad hoc mode). In either case, at
least some of the WLAN devices would be able to interpret part of
some PAN frames.
[0023] A given PAN device might also be a WLAN device, but it might
also be the case that all of the wireless PAN devices operate
within the wireless PAN. Coexisting WLANs can be 802.11x WLANs. The
wireless PAN devices preferably use a protocol that is at least
partially understood by nearby WLAN devices such that the WLAN
devices will sense that the wireless medium is busy and will
appropriately defer. The partially compliant protocol might be a
protocol optimized for PAN traffic and devices.
[0024] To reduce interference, a computing device that is a
coordinator in a wireless PAN network might determine to signal a
WLAN operating in the same wireless networking medium such that
devices therein defer access to the WM so that communication can
occur within the wireless PAN network, determine a length of time
for PAN-computing device communication, reserve the wireless medium
for at least that length of time and use that time for
communicating with the wireless PAN using protocols that overlap
with conventional WLAN protocols but are not necessarily
compliant.
[0025] Signalling to a coexisting WLAN and reservation of the
common wireless medium can be implicit or explicit. Implicit
signalling occurs when a wireless PAN device transmits a frame
within the wireless PAN network using a wireless PAN overlay
protocol, but at a minimum those portions of the overlay protocol
that are required to trigger a nearby STA in a coexisting WLAN to
defer accessing the WM are compliant with the WLAN protocol. A
nearby STA in a coexisting WLAN, upon hearing an overlay protocol
frame, will understand at least enough of the overlay protocol
frame to defer use of a common wireless networking medium. Explicit
signalling occurs when a computing device can join both networks,
exchanges one or more frames in the WLAN network using the WLAN
protocol to communicate times of wireless PAN traffic, and
communicates with devices in the wireless PAN network using a
wireless PAN overlay protocol during the times agreed on with the
devices in the WLAN.
[0026] The secondary network (PAN) protocols might use 802.11x
frames or modifications thereof, with new frame arrangements, frame
sequences etc. adapted for PAN needs.
[0027] The secondary network (PAN) protocols might use
synchronization and traffic scheduling methods to meet the power
and latency requirements of specific wireless PAN applications.
Such methods allow wireless PAN devices to agree on an inactivity
time, during which at least part of the circuitry can be disabled,
wherein disabling is such that less power per unit time is consumed
by the network circuit relative to power consumed when not
disabled.
[0028] The secondary network (PAN) protocols might support
connectivity states that are different from or an extension of
connectivity states supported by PWN (WLAN) protocols. Such
connectivity states may be supported to meet typical SWN needs.
Examples of typical SWN needs might include but are not limited to
(1) reducing the power consumption of the devices in the SWN, (2)
optimizing the network capacity, and (3) meeting the latency
requirements of a PER device. There may be different reasons for
supporting multiple connectivity states as well.
[0029] Other objects, features, and advantages of the present
invention will become apparent upon consideration of the following
detailed description and the accompanying drawings, in which like
reference designations represent like features throughout the
figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a block diagram illustrating various devices
operating as part of a primary wireless network (PWN), a secondary
wireless network (SWN), or both, wherein the SWN operates using an
SWN protocol that co-exists with the PWN protocol.
[0031] FIG. 2 is a block diagram illustrating a subpart of the
elements of FIG. 1, in greater detail.
[0032] FIG. 3 comprises several examples of elements of a PWN and
an SWN; FIG. 3(a) is a block diagram showing elements of a PWN and
an SWN that co-exist, but do not necessarily span the two networks;
FIG. 3(b) is a block diagram showing specific objects that might be
used as the elements of a PWN and an SWN; FIG. 3(c) is a block
diagram of a variation of subparts wherein objects might span the
PWN and the SWN; FIG. 3(d) is a block diagram showing further
examples.
[0033] FIG. 4 is a block diagram of an example wireless PAN
coordinator ("COORD") that might also operate as a dual-net device
that could simultaneously maintain connections with a PWN and a
SWN.
[0034] FIG. 5 is a block diagram of a network card that might be
used to interface a COORD/dual-net device to the various
networks.
[0035] FIG. 6 is a block diagram of software components that might
comprise software and/or logical constructs to interface
applications with the networks supported by a COORD/dual-net
device.
[0036] FIG. 7 is a block diagram of classes and objects that might
be used in an interface between a network and applications.
[0037] FIG. 8 is a block diagram of an example of a PER device.
[0038] FIG. 9 is a diagram illustrating a reduced wireless medium
reservation zone relative to two network spaces.
[0039] FIG. 10 is a timing diagram illustrating timing for a frame
exchange process.
[0040] FIG. 11 is a timing diagram illustrating timing for an
alternative frame exchange process.
[0041] FIG. 12 is a timing diagram illustrating timing for a
multi-PER coordination process.
[0042] FIG. 13 is a timing diagram illustrating timing for an
alternative frame exchange sequence for a multi-PER coordination
process.
[0043] FIG. 14 is a schematic diagram illustrating steps of a
direct link handshake.
[0044] FIG. 15 is a schematic diagram illustrating steps of a using
a direct link setup between two STAs.
[0045] FIG. 16 is a state diagram for an embodiment of stateful
operation of a COORD (which might be used for a dual-net device or
otherwise) and/or a PER.
[0046] FIG. 17 is a schematic diagram of frame formats usable for a
non-standard HCCA frame.
DESCRIPTION OF THE INVENTION
[0047] The present disclosure describes methods and apparatus for
operating a secondary wireless network ("SWN") in the presence of a
primary wireless network ("PWN"), including features, elements,
configurations and/or programming that allow for co-existence of
SWN devices in a space where PWN traffic might occur, as well as
features, elements, configurations and/or programming that include
coordination between a PWN and an SWN (or pluralities of these)
such that a device might handle traffic for each of the networks
present.
[0048] For example, a computing device might have a common network
interface that allows the computing device to be a node in the PWN
and a node in the SWN. In a particular example, a computing device
is an 802.11x STA that is a member of a PWN capable of associating
with and communicating with an AP for that PWN (as well as possibly
other devices in that PWN) using a network interface while also
elements of that same network interface are used to simultaneously
participate as a WPAN coordinator ("COORD") to coordinate the SWN,
such that the COORD can communicate with members of one or more SWN
without losing the COORD's connectivity to the primary network and
using common hardware components to interface to both networks.
Where a COORD is connectable to the PWN, it is referred to as a
"dual-net" device, as it coordinates communication over the SWN
such that it can be connected to both simultaneously, possibly
including steps that involve signaling within the PWN as part of
SWN activity (e.g., reserving the PWN to avoid interference before
using the SWN).
[0049] In some instances, the COORD is not set up to connect to the
PWN, but it still performs the necessary actions to coordinate
traffic for the SWN it coordinates, including performing actions
that improve coexistence of the PWN and SWN.
[0050] In the general example, the computing device is a portable
and/or mobile computing and/or communications device with some
computing capability. Examples of computing devices include laptop
computers, desktop computers, handheld computing devices, pagers,
cellular telephones, devices with embedded communications abilities
and the like. Examples of peripheral devices include typical
computer, telephone etc. accessories where wireless connections are
desired, but might also include less common devices, such as
wearable devices that communicate with other devices on a person or
even to communicate with other nearby devices, possibly using the
electrical conductivity of the human body as a data network. For
example, two people could exchange information between their
wearable computers without wires, by transmission through the air,
or using their bodies and/or clothing.
[0051] The computing devices may interface to 802.11 WLANs or other
wireless networks to communicate with other network nodes,
including nodes accessible through wired connections to the
wireless network (typically via an access point). The computing
devices also may interface to PAN devices over a personal area
network (PAN), such as wireless headsets, mice, keyboards,
accessories, recorders, telephones and the like. A wide variety of
PAN devices are contemplated that are adapted for short-range
wireless communications, typically bi-directional and typically low
power so as to conserve a PAN device's limited power source. Some
PAN devices might be unidirectional, either receive-only or
transmit-only, devices.
[0052] In a typical approach, where a STA needs to connect to more
than one wireless network, the STA associates with one wireless
network and then when associating with another wireless network, it
disassociates with the first wireless network. While this is useful
for a WLAN where a STA might move out of one network's range and
into the range of another network, this is not desirable when
latency needs to be less than an association set-up time. The
latency incurred with this switching procedure easily amounts to
several hundreds of milliseconds.
[0053] In certain applications, it may be desirable for a STA to
connect to multiple networks without incurring long
switching-induced latencies. For example, consider a typical PER
device, that of a cordless mouse. Since update rates for a cordless
mouse during normal operation are on the order of 50 to 125 times
per second, switching-induced latencies involved with 802.11x
association set ups are not acceptable. Furthermore, the switching
overhead significantly reduces the STA's usable communication time,
defined as the time that the STA is available to transmit or
receive data.
[0054] In a specific embodiment of the invention, a wireless
peripheral like a mouse, is attached to an 802.11x-enabled
computing device like a laptop computer, using the 802.11x wireless
circuitry inside the laptop, or connected to the laptop via a NIC
card. At the same time, the laptop may be connected to the Internet
via a regular WLAN network, using the same 802.11x circuitry.
Herein, a peripheral or PAN node will be referred to as "PER".
Multiple PERs can connect to a single wireless PAN. The wireless
device coordinating the wireless PAN is called the coordinator
("COORD"). Where the COORD is also able to connect to the 802.11x
network, the COORD is referred to as a "dual-net" device, since it
handles both networks. A typical dual-net device in this example is
a device that is a STA on an 802.11x network while also having
wireless peripherals used by applications running on that
device.
[0055] While not always required, the PERs are power-sensitive
devices. It should be understood that an object labeled "PER" need
not be a peripheral in the sense of an object with a purpose to
serve a particular purpose, but rather an object that performs the
behaviors herein referred to as behaviors of a PAN node. For
example, a printer can be a PER when it is connected to a desktop
computer via a PAN, but some other device not normally thought of
as a peripheral can be a PER if it behaves as one.
[0056] Examples of the concepts and disclosures provided above will
now be further explained with reference to the figures. In the
figures, like items are referenced with a common reference number
with parenthetical numbers to indicate different instances of the
same or similar objects. Where the number of instances is not
important for understanding the invention, the highest
parenthetical number might be a letter, such as in "100(1), 100(2),
. . . , 100(N)". Unless otherwise indicated, the actual number of
items can differ without departing from the scope of this
disclosure.
[0057] Specifically, FIG. 1 illustrates various devices operating
as part of a primary wireless network (PWN) 100, a secondary
wireless network (SWN) (such as 114 or 116), or both. In the
figure, an access point (AP) 110 supports an infrastructure mode
for PWN 100, coupling various stations to the network allowing, for
example, network traffic between a station and a wired network 112.
By communicating with the AP, a station can retrieve information
from the Internet and exchange data with other stations that may or
may not be part of the Basic Service Set (BSS) managed by the
AP.
[0058] As shown in the example, the stations present are STA1,
STA2, STA3 and STA4. Each station is associated with a node in PWN
100 and has the necessary hardware, logic, power, etc. to be a node
device in PWN 100. Station STA1 also coordinates SWN 114 as the
COORD for that network shown comprising PER1, PER2 and PER3.
Likewise, station STA4 coordinates SWN 116 as the COORD for the
network comprising STA4, PER10 and PER11. In FIG. 1, each node
device is shown with an antenna to indicate that it can communicate
wirelessly, but it should be understood that an external antenna is
not required.
[0059] Other network components and additional instances might also
be present. For example, more than one AP might be present, there
might be overlaps of BSSes and other network topologies might be
used instead of the exact one shown in FIG. 1 without departing
from the scope of the invention. Examples used herein for PWN 100
include 802.11x (x=a, b, g, n, etc.), but it should be understood
that the primary wireless network may well be another network
selected among those in present use or available when the primary
wireless network is implemented.
[0060] In this example, the secondary wireless networks are assumed
to be used for PAN functionality. The PAN can be used for, but is
not limited to, fixed data rate applications where exchange of data
can be scheduled and the amount of data to be exchanged is known
and a single dual-net device might interface with multiple PERs.
Because the dual-net device may be a regular STA in the first WLAN,
it can power-down as needed without problems, unlike an access
point. However, since it is also the COORD, peripheral
communication could be lost if the peripheral is powered up but the
dual-net device/COORD is not. This can be dealt with using mutually
agreeable inactivity periods.
[0061] FIG. 1 shows, at a high level, the interplay among various
nodes of various networks. FIG. 2 illustrates a subpart of the
elements of FIG. 1, illustrating in greater detail. In this figure,
AP 110 is coupled to wired network 112 via cable 120 and might
communicate using any suitable wire-based networking protocol. On
the other side, AP 110 transmits signals to a station device, in
this case a laptop 122, using the AP's antenna and those signals
are received by laptop 112 using its antenna. Signals can also flow
in the other direction. Such communications would be done according
to a PWN protocol, such as an 802.11x protocol.
[0062] Laptop 122 (a dual-net device in this example) in turn can
communicate with the peripherals shown, in this example a wireless
mouse (PER1) 124 and a wireless printer (PER2) 126. It may be that
power for wireless printer 126 comes from an external power outlet,
in which case power consumption might be less of a concern than
with mouse 124 if it operates on battery power. Nonetheless, both
peripherals might use the same power-saving protocol. Power
conservation might also be performed on the dual-net device, for
example, when it is a laptop.
[0063] FIG. 3 comprises several views of network layouts of
elements of a PWN and a SWN.
[0064] FIG. 3(a) is a block diagram showing wireless elements that
might be operating in a common space 300 such that they share a
wireless medium or parts of it. In the description that follows,
the examples assume that the range of an access point, AP 301, is
the common space 300. In other examples, the common space is the
range of the AP and STA devices in the AP's BSS, or some other
variation. As shown in FIG. 3(a), AP, STA1, STA2 and STA3 form the
primary wireless network PWN, while devices STA4, PER1, PER2, and
PER3 form the secondary wireless network SWN. STA4 is the master
for the SWN. Note that STA4 need not be associated as a STA with AP
301.
[0065] FIG. 3(b) illustrates a more specific example. In that
figure, PWN is managed by AP 301 and has node devices 302(1) and
302(2) (laptops in this example figure) associated with the PWN. A
mobile phone 304 is the master for the SWN that includes a headset
306. Mobile phone 304 may well not have the capability to join PWN,
but since the PWN and SWN share the same wireless medium,
preferably mobile phone 304 has COORD functions that would enhance
coexistence of PWN devices and SWN devices. AP 301 is also coupled
to a wired network 303.
[0066] The various protocols used between devices are marked as
"PP" for PWN protocol, which might be an 802.11x protocol or the
like and "SP" for SWN protocol, which might be a modified 802.11x
protocol, an overlay protocol, or the like. As used herein, an
overlay protocol is an SWN protocol that has elements that are
reuses of elements of a PWN protocol to provide one or more
advantages, such as ability to use some common hardware components
for both networks, the ability to communicate in the SWN without
having to disassociate with the PWN, the ability to signal in the
SWN with signals that are understood by SWN devices but are such
that they are, if not understood, are acted upon by PWN devices to
provide desirable actions. For example, an overlay protocol might
be such that a PWN-only device that hears an SWN packet will be
able to decode the packet enough to determine that the packet is
not for the PWN-only device and also determine how long the
wireless medium will be busy with SWN traffic so that the PWN-only
device can appropriately defer.
[0067] Of course, if all of the PWN devices and SWN devices had the
same constraints and could support a wider-area network standard
protocol, then perhaps all of the devices would just be nodes in
one network and use that network's protocol for contention,
coordination, and the like. However, where one-size-fits-all does
not work, it is preferred that some sort of coexistence enhancement
occur.
[0068] FIG. 3(c) is a block diagram of another topology example,
wherein at least one device spans a network. In that example, AP
301 communicates with an 802.11x-enabled Personal Digital Assistant
(PDA) 305 and an 802.11x-enabled mobile phone 307, while phone 307
acts as a COORD for a secondary network to interact with a wireless
headset 306. In some variations, PDA 305 and phone 307 might
communicate in ad hoc mode. As an example of the use of these
elements, phone 307 might be used to simultaneously conduct a
wireless Voice-over-IP (VoIP) call and attach wireless headset
306.
[0069] FIG. 3(d) is a block diagram illustrating a more complicated
example. As shown there, AP 301 is coupled to wired network 303 and
is wirelessly coupled with its associated stations: laptops 302(1)
and 302(2), as well as a laptop 310 that is a COORD for a secondary
wireless network, SWN1. Laptop 310 coordinates SWN1, which includes
mouse 320, keyboard 322 and mobile phone 304. Mobile phone 304 can
in turn be a COORD for another secondary wireless network, SWN2
while being a PER in SWN1. As shown, the communications with AP 301
use a PWN protocol, such as an 802.11x protocol, while the
communications among devices in SWN1 and SWN2 are done using the
SWN protocol. As explained elsewhere herein, there are many
benefits of using an SWN protocol such as an 802.11x overlay
instead of an all 802.11x protocol and by suitable design of the
SWN protocol, the SWNs and the PWN can co-exist and, in the case of
dual-net devices, can reuse common network interface devices for
the dual-net device's participation in both a PWN and an SWN.
[0070] In the example of FIG. 3(d), it may be expected that mouse
320, keyboard 322, mobile phone 340 and headset 306 are not
programmed for, and/or do not have circuits to support, use with an
802.11x primary network, but nonetheless they might use an SWN
protocol that has many aspects in common with an 802.11x protocol,
modified to accommodate the different needs of SWN devices while
providing a measure of co-existence. The network interface for a
dual-net device might comprise standard hardware for interfacing to
the PWN and software to control that standard hardware to use it
for SWN protocol traffic. Thus, with the selection of the SWN
protocol such as those described or suggested herein, SWN support
can be added to a computing device without requiring any new
hardware.
[0071] FIG. 4 illustrates an example of the internal details of a
COORD device. As explained herein, such devices might include
laptops, desktop computers, terminals, MP3 players, home
entertainment systems, music devices, mobile phones, game consoles,
network extenders or the like. What is shown is one example. In
this example, a COORD device 400 is shown comprising a processor
402, the memory 404, program and software instruction storage 406,
a wired input/output interface 407 for displays, keyboards and the
like, an internal clock 408, and a network I/O interface 410, each
coupled to a bus 412 for intercommunication. Network I/O interface
410 is in turn coupled to a network card 414, which includes its
own circuitry such as an internal clock 416 and other components
not shown. In some cases, the network card is not distinct and in
some cases there might not even be much hardware associated with
the networking function if it can be done by software
instructions.
[0072] Program and software instruction storage 406 might comprise
program code memory 420 and disk drive 422. Program instructions
for implementing computing, communication, etc. functions, as well
as network interfacing, can be stored in program code memory 420
and might be loaded in there from instructions stored on disk drive
422. Program code memory 420 might be just a portion of a common
memory that also has memory 404 as a portion. For example, both
memories might be allocated portions of RAM storage so that
instructions and data used by programs are stored in one memory
structure. With a general purpose, network-centric, signal
processing-centric or other style of processor, functional modules
that might be illustrated by blocks in a block diagram might be
implemented entirely in software, embodied only in code stored in
computer readable media. However, when executed as intended, the
processor and the stored instructions perform the functions of
those modules. For example, a device might be described as having a
network stack that performs certain functions, but the network
stack might not be represented in individual hardware elements.
[0073] FIG. 5 illustrates an example of a network card 500, shown
comprising interface circuits 502 for interfacing network card 500
to a computing device (not shown), control/datapath logic 504,
baseband modem circuitry 506, an RF section 508, an antenna 510 and
a card clock circuit 512. Control/datapath logic 504 is configured
to send and receive data to and from the computing device via
interface circuits 502, send and receive data to and from baseband
mode circuitry 506 and process that sent or received data as
needed. Card clock circuit 512 might provide circuit clocking
services as well as real-time clock signals to various other
elements of network card 500. Note that logic elements shown and
described might be implemented by dedicated logic, but might also
be implemented by code executable by a processor. For example, some
of the control/datapath logic's functionality may be implemented in
software rather than hardware. An example processor is the ARM7
processor available from ARM Limited of London, England.
[0074] In operation of an example network card, power might be
supplied via interface circuits 502 as well as providing a wired
datapath for data into and out of the network card. Thus, when the
connected computing device desires to send data over the network(s)
supported by the network card, the computing device sends the data
to an input circuit of interface circuits 502. The input circuit
then conveys the data to control/datapath logic 504.
Control/datapath logic 504 may format the data into packets if not
already so formatted, determine the PHY layer parameters to use for
the data, etc., and possibly other processes including some
well-known in the art of networking that need not be described here
in detail. For example, logic 504 might read a real-time clock from
card clock circuit 512 and use that for data handling or include a
real-time clock value in header data or other metadata.
[0075] Logic 504 then outputs signals representing the data to
baseband modem circuitry 506 which generates a modulated baseband
signal corresponding to the data. That modulated baseband signal is
provided to RF section 508. The timing of output of signals of
logic 504 and other parts of the network card might be dictated by
a timing clock signal output by card clock circuit 512. RF section
508 can then be expected to output an RF, modulated signal to
antenna 510. Such output should be in compliance with requirements
of nodes of the networks with which the computing device is
associating.
[0076] For example, if the computing device is expecting to be
associated as a node in an 802.11b network, the signal sent to
antenna 510 should be an 802.11b compliant signal. Also, the
control/datapath processes should process data in compliance with
the requirements of the 802.11b standard. Where the computing
device is expecting to be a dual-net device, the signals sent
should be compliant with the protocols and/or standards applicable
for the network to which the signals are directed, and be done in
such a way as to deal with the fact that while communication is
happening among devices of one network (such as the primary
wireless network or the secondary wireless network), those signals
might be heard by devices that are only devices in a different
network (such as the secondary wireless network, the primary
wireless network or other network) and the signals should be such
that devices can at least co-exist.
[0077] Where the computing device is a dual-net device, its network
card would provide signals for the primary network and the
secondary network. In one example mentioned herein, the primary
network is an 802.11x network and the computing device is a STA
node for that network and the secondary network is a PAN and the
computing device is the COORD for that network. In some
implementations, network communications are handled using a
software platform that supports network applications.
[0078] In some embodiments, wherein 802.11x or other PWN protocols
do not need to be supported, the built-in wireless circuitry or
network card could be designed to handle only SWN protocols, as
would be the case where the network comprises all devices that are
capable of handling SWN protocol communications. Examples of such
protocols include protocols that operate between devices built by
H-Stream Wireless, Inc. to communicate using an H-Stream protocol
such as their HSP protocol. In some HSP-enabled devices, the
network logic can be entirely represented with software that
accesses the RF section of a device that might be a generic network
interface, possibly using additional hardware. However, where both
ends are HSP-enabled devices, they might use their own hardware and
control it at whatever level is needed for best performance.
[0079] FIG. 6 illustrates a platform 600 as it might be present in
a dual-net device, that represents software and/or logical
constructs that together can be thought of as logical elements
available for processing data within the computing device. As such,
they need not be implemented as separate hardware components or
distinct software components, so long as their functionality is
available as needed. Other variations are possible, but in the
layout shown, applications and system services (shown as block 602)
are programmed to interface to various stacks, such as an IP
networking stack 610 (sometimes referred to as an "IP stack"), a
peripheral stack 612 (USB, HID, audio, etc.), a non-IP stack 614
(for IEEE 1394 interfacing) or other stack 616. For example, an
application such as an HTTP browser might expect to communicate
using TCP/IP and thus that application would have been configured
to communicate with the computing device's IP stack.
[0080] A convergence platform can be added between an 802.11x stack
and the different drivers to enable multi-protocol support, expose
and coordinate access to specific MAC service primitives and
coordinate the priority handling in Quality-of-Service (QoS)
sensitive applications. This convergence platform can be a separate
software layer or can also be integrated within the 802.11x
stack.
[0081] For certain stacks, additional services may be required that
might not be supported inside the 802.11x stack. If that is the
case, such overlay protocol services may reside either inside the
convergence layer or in between the convergence layer and the
respective stack. As an example, communication with peripherals may
require protocol services in addition to the protocol services
provided by the 802.11x stack in order to meet the power and
latency requirement typical of such applications. Such protocol
services may be part of the convergence layer, or may reside in
between the convergence layer and the Peripheral Interconnect
Stack. Of course, as an alternative, the 802.11x stack may have
been adapted to support such services.
[0082] Each of the stacks 610-616 is shown coupled to a convergence
layer 620, which provides the necessary and/or optional conversions
of data, protocol, timing, etc. so that each of the higher level
stacks 610-616 are interfaced to an 802.11x stack 622. 802.11x
stack 622 can then interface to the computing device's network card
(or other network circuitry). In this manner, for example, stack
622 might handle a browser's traffic that goes through IP stack 610
while also handling a mouse interface whose traffic goes through
peripheral stack 612. Note that with a single 802.11x stack, a
single network interface can carry traffic for more than one
higher-level stack. The single network interface needs to be tuned
to deal with the different requirements of the different
stacks.
[0083] Communication protocols can be implemented with drivers or
firmware that is installed on the dual-net device/COORD. The
drivers or firmware might comprise an 802.11x peripheral service
function (e.g., for implementing the services of the overlay
protocol that are not supported inside the 802.11x stack), which
can be application-independent, and an adapter driver to connect
the 802.11x stack and 802.11x peripheral service function to the
appropriate driver inside the dual-net device/COORD platform. The
adapter driver may be device class or device specific.
[0084] An example of this is illustrated in FIG. 7 for a wireless
PAN where a mouse is connected over the WM to the standard HID
class driver in a PC running on the Windows (or other applicable
Operating System (OS)). The driver or firmware resides between the
802.11x stack 706 and the standard HID class driver 703. In a
specific implementation, the driver or firmware can constitute an
HID adapter driver 704 and an 802.11x peripheral bus driver
705.
[0085] Other variations of what is shown in FIG. 7 are possible.
For example, the 802.11x peripheral service function might connect
up to the MOUHID driver 702 directly. In that case, the HID adapter
driver is written as an HIDCLASS miniport driver. This driver then
layers under the MOUHID 702 and MOUCLASS 701 drivers and allows
mouse data to be injected into the operating system.
[0086] Alternatively, the adapter driver may connect to the USB
stack instead. The adapter driver may, for example, be written as a
virtual USB bus driver and connect up to the standard USB stack
available as part of the operating system or operating system
modifications. Depending on the specific implementation, the
adapter driver may connect at different layers into the USB
stack.
[0087] In specific embodiments, the 802.11x peripheral service
function and adapter driver may be combined in a single driver.
Alternatively, two separate drivers may be used and a private
interface might be defined and used between both drivers.
[0088] The adapter driver receives the 802.11x frames from the
802.11x peripheral service function that are intended for the
higher layer driver (e.g., MOUCLASS driver). Similarly, the adapter
driver receives frames from the higher layer driver that are to be
transmitted to a PER using the 802.11x circuitry. The adapter
driver and 802.11x peripheral service function generate and decode
the necessary packet header for running a specific application,
like the HID protocol, over an 802.11x data channel. For example,
it removes the 802.11x-specific MAC header and performs the
necessary manipulation to transform it in the correct format to be
passed on to the respective class driver.
[0089] FIG. 8 is a block diagram illustrating an example of what
might be the components of a PER device. As shown, PER 800
comprises a wireless transceiver 802 coupled to sensor/stimulus
elements 804 and antenna 806. Additional components, such as a
filter, a balun, capacitors, inductors, etc., may be present
between wireless transceiver 802 and other elements. Generally,
wireless transceiver 802 allows other networked devices to
understand results of sensing (in the case of a PER that does
sensing, such as a mouse, microphone, remote condition sensor,
etc.) and/or to specify stimulus (in the case of a PER that outputs
visual, audio, tactile, etc. outputs, such as a printer, headset,
etc.). It should be understood from this disclosure that PER can be
a wireless input and/or output device and in many cases, the
wireless transceiver can be designed independent of the particular
input and/or output.
[0090] FIG. 8 also shows a battery 810 and a clock circuit 812.
Battery 810 provides power for wireless transceiver 802 and
elements 804 as needed. As weight and portability are likely to be
important in the design of the PER, battery consumption will often
have to be minimized for a good design. Clock circuit 812 might
provide real-time clock signals as well as providing circuit timing
clock signals.
[0091] As shown, wireless transceiver 802 comprises interface
circuits 820, control/datapath logic 822, a baseband modem 824, and
an RF section 826. Control/datapath logic 822 might be implemented
with circuitry that includes a central processing unit (CPU) 830
and memory 832 for holding CPU instructions and variable storage
for programs executed by CPU 830 to implement the control/datapath
logic. Control/datapath logic 822 might include dedicated logic
wherein CPU 24 and memory module 25 implement the portion of the
communication protocol that is not implemented in the dedicated
control and datapath logic. The CPU instructions might include
digital signal processing (DSP) code and other program code. The
other program code might implement MAC layer protocols and
higher-level network protocols.
[0092] Clock circuit 812 might include a crystal oscillator. Clock
circuit 812 might be aligned with clocks in other network devices,
but the clocks may drift over time relative to each other.
[0093] Although not shown, other components like capacitors,
resistors, inductors, filters, a balun, a Transmit/Receive (T/R)
switch, an external power amplifier (PA) and an external low-noise
amplifier (LNA) may also be included in PER 800.
[0094] Wireless transceiver 802 might be configured so as to
communicate over the physical layer (PHY) of a standard IEEE
802.11-compliant circuit chip. Wireless transceiver 802 may be an
embedded System-on-Chip (SoC) or may comprise multiple devices as
long as such devices, when combined, implement the functionality
described in FIG. 8. Other functionality, in addition to the
functionality of FIG. 8 may also be included. Wireless transceiver
802 might have the ability to operate, for example, in the
unlicensed 2.4-GHz and/or 5-GHz frequency bands.
[0095] One or more of the techniques described below might be
needed to deal with the characteristics of a wireless PAN that
differ from a WLAN, or just to improve performance of the devices
in the networks. Modifications that create an overlay protocol,
herein referred to as the PER service function, are described or
suggested herein. In some cases, a computing device is able to join
the WLAN and the wireless PAN (and even at the same time), while in
other cases, a computing device is only able to join the wireless
PAN. In either case, the same or a similar overlay protocol might
be used to obtain the benefits thereof. Where the computing device
is able to join both, the overlay protocol is preferably such that
the same networking hardware can be used for the computing device
to join both networks.
WM Reservation
[0096] Power conservation may tend to be more critical in a PER
device than in a COORD device. One technique described herein for
conserving power inside a PER device is to use lower transmit power
and relax the range requirements for a transmitter below that which
would be acceptable for an 802.11x transmission. This reduces the
reception range of the PER's signal, but in most cases, the COORD
is close enough to the PER to get the signal and this is not an
issue.
[0097] If the transmission and receive range of one or more members
of a SWN are reduced to conserve power, frames transmitted by the
PER might not be detectable by members of the PWN and communication
among members of the PWN might not be detected by the PER. This can
lead to interference between both networks, especially if both
networks operate in the same frequency band and on the same
channel. This can be addressed by using different frequency bands
or channels, but can also be dealt with using a common band or set
of bands and a common channel or set of channels. One such
coordination method comprises a novel WM access procedure where a
powerful STA, like the dual-net device, reserves the WM for a low
power node, like the PER. The WM reservation would be heard by
devices in a primary network that could not be reached by the
PER.
[0098] In a specific embodiment, a COORD might determine a length
of time for communication with a PER, transmit an 802.11x frame
with the proper fields (e.g., duration value) set so as to reserve
the WM for at least that amount of time, and listen for a response
frame from respective PER. The frame transmitted by the COORD might
be an actual 802.11x frame or a modification thereof. In any case,
the frame arrangement shall be such that STAs in nearby WLANs upon
reception of such frame from COORD defer access to the WM for at
least the length of time specified by the frame. In addition, the
frame arrangement is such that it can be successfully received by a
PER. A PER, upon reception of such frame can respond with a
response frame immediately or after a specified turn around time.
In any case, a PER can respond without requiring a separate WM
arbitration or WM reservation. As long as the length of the
response frame does not exceed the length of the WM reservation
made by the COORD, this communication can happen without
interference from a nearby WLAN, independent of whether or not the
PER is able to reach the primary network WLAN devices.
[0099] In a slightly different embodiment, a dual-net device might
determine a time and a length of time for communication with PER
devices in its SWN, signal to the PWN using the PWN (WLAN) protocol
such time and length of time, and communicate with PER devices
during the periods of time agreed upon with the PWN. The signalling
to the PWN can occur once prior to or at the start of a series of
SWN communication events. As an example, if the SWN communication
events are periodic, the dual-net device and PWN devices may at one
point in time agree on a start time and recurrence period for WSN
communication events. Alternatively, the signalling to the PWN
might occur prior to or at the start of each WSN communication
event. Variations are also possible, where specific portions of the
signalling to the PWN occur at the start or prior to the start of a
series of communication events, whereas additional signalling is
done at or prior to the start of each WSN communication event.
[0100] In the example where the PWN is an 802.11x WLAN network,
signalling of SWN communication events to the PWN can be done by
using features and functionality that are supported by the 802.11x
WLAN protocol, yet use such features and functionality in a
different arrangement and for a different purpose, that is to
accommodate reliable communication in a coexisting power-sensitive
secondary wireless network.
[0101] As an example, the 802.11(e) WLAN protocol supports a
channel access mechanism, called Hybrid coordination function
Controlled Channel Access or "HCCA" that allows an AP in an 802.11
WLAN to coordinate contention free media use and allows the
scheduling of WLAN traffic, as is desirable for high
Quality-of-Service ("QoS") applications. HCCA is a polling-based
mechanism, where a STA can set up a Traffic Stream ("TS") with the
AP of its BSS.
[0102] As part of the TS set-up, polling times and polling
intervals are negotiated and agreed upon between the AP and the
STA. The AP can access the medium in a prioritized manner with
respect to other STAs using basic access mechanisms, and as such
has more control over the use of the WM. Once the AP has taken
control of the WM, it can poll the STA at the agreed upon time and
grant the STA a transmission opportunity ("TXOP") by making an
adequate WM reservation for communication with the STA. The HCCA
mechanism might be used by a dual-net device to set up a TS with
the AP of its PWN. It can then make use of the TXOPs and related WM
reservations granted by the AP to communicate with PER devices in
its SWN. The dual-net device can communicate the QoS requirements
of the attached PER to the AP (e.g., during a TS set up),
"pretending" it to be requirements for itself. However, when
granted the TXOPs by the AP it can use these to conduct polling of
and communication with devices in its SWN and as such meet the QoS
requirements of the PER devices in its SWN.
[0103] In certain embodiments, it may be desirable to only reserve
the wireless medium in a limited radius around the SWN network to
allow other devices to communicate or operate without concern over
the reservation. This may be desirable to increase the capacity of
the wireless medium. To achieve this, the COORD or dual-net device
reserves the WM by transmitting a frame at a reduced transmission
power, compared to the transmission power it normally uses for
communication within the PWN. As an example, by reducing the
transmission power for the WM reservation frame from 20 dBm to 0
dBm, the range over which the WM will be reserved is typically
reduced from hundreds of feet to tens of feet. This is illustrated
in FIG. 9.
[0104] FIG. 9 illustrates wireless networks wherein a primary
network 902 is coordinated by an AP 904. Five STA devices (STA1
through STA5) are shown within primary network 902. A secondary
network 906 is shown, wherein a laptop 908 is a dual-net device, in
that it acts as a COORD for secondary network 906 and as a station
STA1 in primary network 902.
[0105] PER 910 is within secondary network 906. Laptop 908 issues a
reduced power WM reservation (or PER 910 does), to alert devices
within range 912. In the example shown, STA2 and STA3 hear the
reservation and defer, but STA4 and STA5 do not fall within the
reservation range of COORD 908. Thus, STA4 and STA5 can continue to
communicate with AP 904 in primary network 902. In such a
configuration, secondary network 906 takes less capacity away from
primary network 902. If the transmission range of a PER is reduced
to conserve power, this approach can be implemented without causing
significant interference between the secondary network and far-away
STAs in the primary network.
[0106] With only a "local" reservation of the WM, it is very well
possible that the AP does not detect that reservation and may try
to send a frame to the COORD, since it is a STA on the PWN. The
odds of that happening are pretty low though, since the COORD is
only communicating with a PER for a very short time. If this
collision happens, the AP will not get an ACK and will resend at a
later time.
[0107] To increase the capacity of the common wireless medium, a
novel method can be applied, where a COORD in a SWN adjusts the
range over which it reserves the WM based on activity in the PWN or
activity in separate nearby SWNs. As an example, if a lot of
traffic is detected, a COORD might decide to reduce the
transmission power for signalling to the PWN, so that fewer devices
in nearby wireless networks are affected by the WM reservation. If
the COORD is a dual-net device, it may communicate with the AP of
its PWN to receive information about current WM activity, bandwidth
usage, desirable transmission powers and WM reservation ranges
etc.
Synchronization and Traffic Scheduling
[0108] Another technique for conserving power is to power off a
portion or all of the circuitry in one or both of the PER and COORD
during quiescent times, preferably coordinating a wake-up time so
that the devices can check in with each other, to find pending
data, synchronize clocks, etc. In many wireless PAN applications,
it is important to minimize the power usage not only inside the PER
but also inside the COORD. This is typically the case when the
COORD is also a battery-operated device. An example of such
wireless PAN is the attachment of a wireless peripheral to a
laptop. Another example is the attachment of a headset to a mobile
phone or PDA. It is important to minimize the power usage inside
the laptop, mobile phone or PDA, since that determines how long
such device can be used before a recharge is needed.
[0109] 802.11x WLAN network power saving techniques are typically
found only in the STA devices, as most access points are wired for
electricity and data. For example, in the BSS shown in FIGS. 1-2,
power saving techniques might be implemented inside the STAs but
the AP stays awake all the time. A novel method comprises a
synchronization procedure wherein a frame exchange sequence occurs
between the COORD and the PER, in combination with a scheduling
method to coordinate traffic between a PER and its COORD. In
specific embodiments, a COORD communicates to a PER timing
information of its local timer as well as information about times
of desired communication with the PER referenced to its local
timer. A PER, upon reception of such information can synchronize
its timer to the timer of the COORD and based on the information
received from its COORD can determine at what time a communication
event with its COORD is scheduled to take place. The start of a
scheduled communication event is herein also referred to as the
start of a Service Period. In between communication events, both
the COORD and PER can power down a portion or all of their
circuitry to conserve power. At the start of a scheduled
communication event, or slightly before the start of a scheduled
communication event, both the COORD and PER power up the necessary
circuitry and exchange frames using an overlay protocol that avoids
interference with PWN STAs that might coexist in the same wireless
networking space. With synchronization and scheduling, power saving
can occur at both ends of the link.
[0110] When the COORD is a dual-net device (i.e., it is also a STA
in a PWN) and that dual-net device is in power-save mode in its
primary network, it is critical that the appropriate circuits be
powered up in time for communication with the PER, in order to
ensure reliable communication and accurate timing of frame
transmissions. Traditionally, when a STA receives a wake-up
request, the STA powers up, and an empty data frame with the power
management bit cleared is sent to the AP, to notify the AP of the
change in its power save mode. Where the STA is a COORD and the
wake-up request is triggered by the secondary network, there is no
need to notify the primary network's AP of a change in power-save
mode.
[0111] This "pseudo-power-save mode", where the necessary circuits
are powered up to transmit and receive data but the AP of the
primary network is not notified of a change in power-save mode has
the advantage that the AP will not attempt to send any pending
traffic for that STA. Ideally, the dual-net device's circuits are
powered on and off in synchronization with the PER medium access
times. Whether it is possible to power down the dual-net device's
circuits in between data exchanges depends on the hardware and
firmware implementation of the IEEE802.11 MAC and PHY, and the
duration of the pre-negotiated communication intervals.
[0112] It is possible that a COORD or dual-net device cannot get
access to the WM for extended periods of time because of traffic on
the PWN. This can introduce latency problems and may result in
additional power consumption as the PD may be kept awake waiting
for extended periods of time for the WM to become idle. If the
COORD is a dual-net device it can communicate with the AP of the
PWN, retrieve information from AP related to scheduled traffic
streams and other forms of AP or STA activity so as to be able to
track the activity on the PWN, and arrange the communication events
with devices in its SWN when the PWN is expected to be idle. As an
example, if the PWN is an 802.11(e) network, a dual-net device may
inquire information about the AP's Controlled Access Phase (CAP)
and schedule communication events with PERs in its SWN so as to
avoid the AP's CAP.
Frame Sequences
[0113] In a specific embodiment, a COORD and PER communicate at
mutually agreed upon time intervals, herein referred to as Service
Intervals. A Service Interval ("SI") is defined herein as the
interval between the start of two successive service periods
("SPs"). A service period (SP) is defined herein as a contiguous
time during which one or more attempts is made to communicate one
or more messages from a master device to a slave device and/or a
slave device to a master. In general, it is expected that during an
SP, both devices are attempting to communicate with each other by
either transmitting a packet or listening for a packet to be
transmitted by the other device. It is possible that there are
small inactivity times in between packet exchanges, but such
inactivity times are typically significantly shorter than the SI.
The service interval may be a constant value or can be irregular
from service period to service period. A service period may always
be a fixed length or may vary from service period to service
period. As an example, a master device and a slave device may have
to agree on timing so that they can power down some or all of their
circuitry between SPs. In that case, the master and slave device
preferably ensure that they power up the necessary circuits at, or
slightly prior to, the start of an SP.
[0114] The start of a Service Interval ("SI") is established,
mutually agreed upon and adopted by both the COORD and PER as part
of a synchronization and traffic scheduling method that is part of
the wireless PAN overlay protocol. With synchronization and traffic
scheduling, power saving can occur at both ends of the link. The
period of time during which frames are exchanged is hereafter
referred to as the Service Period (or "SP").
[0115] The frame exchange is illustrated in FIG. 10. As shown
there, at the start of an SP, T0, the COORD and PER are programmed
to start the frame exchange. If power-save modes are implemented in
the COORD or the PER, a wake-up request will be issued prior to T0,
to ensure that all necessary circuits are powered up at time T0. At
time T0, the COORD gains access to the WM. Access to the WM can be
obtained through various methods including but not limited to WM
contention, a priority access scheme (e.g., if the WM is detected
to be busy, the COORD waits for a length of time, but this length
of time is shorter than the amount of time other devices have to
wait) or a scheduled access scheme where slots of time are
pre-allocated such that no contention is required.
[0116] It is also possible that a different device, such as for
example the AP of the COORD's PWN gains access to the WM using
basic contention or a prioritized access scheme and grants a
transmission opportunity or "TXOP" to the COORD, which the COORD
can then use to communicate with PERs in its SWN. In any case and
independent of what access mechanism is used, upon gaining access
to the WM, the COORD transmits a first frame (Frame 1), hereafter
referred to as a "downlink frame". If the COORD uses WM contention
to gain access to the WM, the downlink frame may be transmitted
using priority queues available inside the COORD. For example, the
downlink frame may be transmitted using the highest priority queue.
The highest priority queue might be the priority of VoIP packets
(e.g., AC_VO), but in some cases it might not be necessary, not be
convenient or not be possible to use the highest priority
queue.
[0117] The frame format of the downlink frame is such that it
reserves the WM for the subsequent frame transmission by the PER.
As an example, if the downlink frame is an 802.11x frame or a
modification thereof, the duration field in its header might have
been increased to reserve the WM for at least the subsequent frame
transmission by the PER. The frame transmitted by the PER (frame 2)
is hereafter referred to as the "uplink frame". The sequence of
FIG. 10 assumes that the COORD has sufficient information to
determine an appropriate WM reservation for the subsequent uplink
frame. As an example, the COORD and PER may have exchanged
information about a typical uplink frame length (e.g., data size)
during an earlier communication. In addition, COORD and PER are
aware of the other and have knowledge of critical communication
information such as each other MAC addresses; encryption keys and
the like. Such critical communication information may have been
exchanged during an earlier communication.
[0118] In case of data traffic from the COORD to the PER hereafter
referred to as "downlink data" (e.g., headset application), or in
case additional information (e.g., management or control
information) needs to be communicated to the PER, such data and/or
information may also be included in the downlink frame.
[0119] A pre-defined time later, such as one short interface space
("SIFS") later, the PER responds with an uplink frame containing
the data and/or additional information (e.g., management and/or
control information) from the PER. Optionally, the COORD can
acknowledge reception of the uplink frame, which can be one SIFS
later. Alternatively, regular medium access procedures (e.g.,
contention) may be followed to transmit the ACK, or the ACK may be
included with communication in the next SP. The ACK may be a frame
in an 802.11x ACK frame format, or a different format, as defined
by the wireless PAN overlay protocol.
[0120] The duration of the WM need not be fixed and can vary. For
example, the time to send ACK may, may not or may partially be
included. Other variations may also be possible. The WM reservation
is preferably sufficient to allow a protected transmission of the
uplink frame by the PER device without requiring a contention for
the WM by the PER device.
[0121] If no downlink data/information is included with the
downlink frame (e.g., because the downlink frame format does not
allow for inclusion of data/information), and downlink
data/information is present inside the COORD, the sequence of FIG.
10 may be modified wherein the COORD can optionally send an
additional frame with data/information after transmission of the
first downlink frame, or following the reception of an uplink
frame. The first downlink frame may reserve the WM for the entire
duration of the frame exchange, or at least for a portion of the
frame exchange to allow a protected transmission of the uplink
frame by a PER device, and without requiring a contention for the
WM by the PER device. Optionally, the PER can acknowledge error
free reception of that frame.
[0122] Variations are possible, but in any case, the poll frame
reserves the medium for subsequent frames such that frame exchange
can happen with a single medium contention; and frames transmitted
by PER are protected by medium reservation by COORD. For example,
the COORD might send a downlink frame to PER1, send a downlink
frame to PER2, and receive an uplink frame, all within one medium
reservation.
[0123] An alternative frame exchange sequence is illustrated in
FIG. 11. The method disclosed in FIG. 11 avoids situations where
another STA accesses the WM right before the scheduled data
exchange between COORD and PER. This method can be used to minimize
the power dissipation in the PER and improve the Quality-of-Service
(QoS) of the COORD-to-PER communication link. To prevent other STAs
from accessing the WM in a time period Treserve prior to the start
of the scheduled data exchange, the COORD is awake prior to T0 and
transmits a frame (frame 0), hereafter referred to as a
"reservation frame" to reserve the WM.
[0124] At time TC0, a time Treserve prior to T0, the COORD gains
access to the WM, either through contention or through a different
medium access mechanism, and transmits a first frame (frame 0),
herein referred to as the "reservation frame". The frame
arrangement of the reservation frame is such that the WM is
reserved for a length of time equal or larger than
(Treserve-Taccess), where Taccess is the time needed to gain access
to the WM. In this way, no other STAs can transmit during the time
between frame 0 has been transmitted and the start of the scheduled
data exchange, T0. As an example, if the reservation frame is an
802.11x frame or a modification thereof, the duration field in the
header of the reservation field may be increased to reserve the WM
for at least the length of time specified above. At time T0, the
COORD immediately sends its first frame (frame 1) without having to
gain access to the WM again. The further frame exchange can be the
same as that of FIG. 10. The above described method minimizes the
awake time for the PER, and improves QoS, at the cost of somewhat
longer WM occupancy. Variations are also possible. As an example,
in a slightly different embodiment, the reservation frame might
reserve the WM for a longer length of time, thereby possibly
eliminating the need for the downlink frame to reserve the WM.
[0125] If at time T0, the COORD has not gained access to the WM or
has not yet transmitted frame 0, the COORD may decide to fall back
to the frame exchange sequence described in FIG. 10. In such
embodiment, the COORD continues to gain access to the WM (e.g.,
through contention) after time T0. Once the COORD has successfully
gained access to the WM, it might decide to skip the transmission
of the reservation frame, frame 0, and directly transmit the
downlink frame, frame 1.
[0126] In the frame exchange sequences described above, the COORD
reserves the WM for the PER to avoid interference between a PWN and
SWN. If the transmission power of the secondary network is
sufficiently low, a WM reservation mechanism may not be necessary.
In such embodiments, a PER can wake up and can directly access the
WM, without waiting for a signal from the COORD. Optionally, a PER
may wake up, detect whether the WM is idle and if not, contend for
the WM prior to initiating a transmission. As an example, upon
detection of a non-idle WM, the PER can follow a random back-off
procedure before attempting to access the WM. Alternatively, for
power conservation reasons, upon detection of a non-idle WM, a PER
may power down at least part of its circuitry and wake up a time
later to try to access the WM again. A PER could go back to sleep
for a pseudo-random period, which would result in the equivalent of
a semi-random back-off, but while conserving power inside the
PER.
[0127] Optionally, a PER may rely on RSSI circuitry (an only wake
up circuitry necessary for RSSI) to detect whether the WM is idle
and only wake up the necessary circuitry for transmission after the
WM has been detected to be idle. If the transmission power of the
PER is sufficiently low, communication in the secondary network
will not cause any significant interference to simultaneous traffic
in the primary network. However, traffic in the primary network can
cause transmission failures in the secondary network. If this
happens, a retry mechanism can be initiated, at the expense of some
additional power usage.
[0128] Other variations of frame sequences are also possible. As an
example, in case the HCCA mechanism is used to reserve the WM, the
frame exchange between the COORD and PER may be preceded by a poll
frame transmitted by the AP of the dual-net device to grant a PWN
TXOP to the dual-net device and the SWN traffic (downlink, uplink,
etc.) that fits can be send using the TXOP provided by the AP.
Coordination of Multiple PERs
[0129] When a SWN includes multiple PERs as illustrated in FIG. 1
and described herein, communication with such devices can be
scheduled independently., However, in specific implementations, it
may be desirable for a COORD to coordinate the communication with
multiple PERs that are part of the same SWN in order to minimize
the power dissipation, as well as to possibly reduce the WM
occupancy. A method to coordinate the communication between a COORD
and multiple PERs is shown in FIG. 12, and is an extension of the
scheme of FIG. 10 to account for communication with more than one
PER during a single SP.
[0130] At time T0, the COORD and PERs of a SWN (wireless PAN) are
programmed to start the frame exchange. If power-save modes are
implemented in the COORD or the PERs, a wake-up request will be
issued prior to T0, to ensure that all necessary circuits are
powered up at time T0. At time T0, the COORD tries to gain access
to the WM and, optionally using the highest priority queue (AC_VO)
transmits a first frame (frame 1), the downlink frame. Note that
different mechanisms to access the WM may also be used. The frame
format of the downlink frame is such that it reserves the WM for
the subsequent frame transmission possibly by more than one PER in
its SWN. As an example, if the downlink frame is an 802.11x frame
or a modification thereof, the duration field in its header might
be increased to reserve the WM for subsequent frame transmissions
by one or multiple PERs that are part of the COORD's SWN. The
duration field of this frame might for example be increased to
reserve the WM for subsequent frame transmission by all PERs of the
SWN that are scheduled for a frame exchange during that specific
SP.
[0131] Furthermore, the downlink frame contains a list of PERs it
expects to respond, as well as an offset for each scheduled PER. As
an example, this information can be included in a Traffic
Indication Map (TIM) that is part of the downlink frame
arrangement, but other implementations are also possible At the
specified offset, each PER is awake and responds with a frame, an
uplink frame, containing its data (frame 2P1 and frame 2P2).
Optionally, the COORD acknowledges error free reception of the
frame, or the COORD can respond with a frame that includes data to
be transmitted from the COORD to the frame. Optionally, the PER
acknowledges error free reception of the latter frame. Optionally,
PERs can return to sleep during the time slots where the COORD is
communicating with other PERs.
[0132] Modified versions of the scheme of FIG. 12 can be used to
compensate for packet loss and unsuccessful transmissions. As an
example, if one or more of the transmissions were not successful,
the COORD may send an additional frame immediately following the
above described frame sequence to reserve the WM for additional
time to allow for retransmissions. This frame contains the PERs for
which retransmission is desirable as well as the corresponding
offsets for each PER. PERs that received acknowledgment of their
transmission do not have to wake up to listen to this additional
frame. In one embodiment, it may be left up to a PER to decide
whether it will consider retransmission.
[0133] If the PWN is an 802.11(n) network, a Power Save Multi Poll
("PSMP") frame or a modification thereof may be used as the
downlink frame, but other frame formats are also possible.
[0134] An alternative frame exchange sequence for the coordination
of multiple PERs is illustrated in FIG. 13. In this embodiment, the
COORD polls each PER individually. At the start of a Service Period
("SP"), the COORD accesses the medium using regular medium access
procedures (e.g., contention) and after gaining access to the WM,
the COORD polls the PERs in its SWN one by one with 1 SIFS space
intervals. This is possible if the first downlink frame ("Frame 1")
reserves the WM for the subsequent frame sequence. The latter 30
avoids the situation where the COORD has to contend for the WM for
each PER in its secondary network.
[0135] To conserve power in the PERs, the expected time for
communication with each PER can be pre-calculated based on the
number of PERs that are scheduled to be polled prior to the
respective PER and their scheduled traffic size.
[0136] In case a transmission fails, a retransmission mechanism can
be initiated. Alternatively, the COORD may poll the next PER and
come back to the failed transmission later, after it has polled all
other PERs for which a communication event is scheduled during that
specific SP.
Frame Formats
[0137] Different frame formats and frame types might be used for
the downlink and uplink frames. Depending on requirements, the
frame formats/types might be those used elsewhere. For example, if
the PWN is an 802.11x WLAN network and the SWN uses an overlay
protocol that is an overlay with respect to the 802.11x WLAN
protocol, the frame formats/types might be of a form that a PWN
device does not entirely understand, but understands enough to
defer for a period to allow for SWN communication.
[0138] In one embodiment, the first frame transmitted by the COORD
(the downlink frame) is an 802.11x Clear-to-Send ("CTS") frame with
increased duration field, and can be self-addressed or addressed to
the PER.
[0139] In another embodiment, the downlink frame can be an 802.11x
HCCA-CF frame of type data addressed to the PER and with the
duration field increased, with the subtype field "data" cleared and
the subtype field "poll" set. In yet another embodiment, this frame
can be an 802.11x HCCA data frame addressed to the PER and with
increased duration field, with the subtype fields "data" and "poll"
both set, and with the data/information intended for the PER (that
is downlink data/information) included in the payload. Other
variations of HCCA frames might also be possible.
[0140] Typically, HCCA frames are only used for communication
within a PWN (WLAN) to handle, for example, allocation of
transmission opportunities. HCCA frames are used for communication
between an AP and a STA of a PWN where the STA has set up a TS with
the AP of the PWN. In that case, an HCCA-CF data frame of subtype
"poll" might be transmitted by an AP using an access scheme that is
prioritized over the access schemes used by non-AP STAs. A novel
use of HCCA frame formats and arrangements is disclosed in this
invention, where HCCA frame formats and modifications thereof
and/or novel WM access schemes are used for communication with PERs
in an SWN. Modifications may include but are not limited to the use
of specific SWN-related information like the SWN's BSSID or the use
of the "to DS" and "from DS" fields in the HCCA frame header (e.g.,
"To DS" and "From DS" both set to 0) to distinguish SWN (WPAN)
traffic from regular PWN (WLAN) HCCA traffic. Indeed, PWN (WLAN)
HCCA frames are always directed to or from an AP, resulting in
either the "To DS" or "From DS" fields to be set to 1.
[0141] In addition, this invention describes a novel use of HCCA
frames, in that such frames are transmitted by a non-AP STA
following non-AP medium access schemes. As an example, in a
specific embodiment, an HCCA-CF data frame of subtype "poll" may be
transmitted by a non-AP STA using basic non-AP access schemes or
possibly using the non-AP STA's priority queues (for example, the
HCCA frame may be transmitted over the highest priority queue for
Voice traffic (AC_VO)). Moreover, the wireless medium is reserved
without colliding with an AP that may be using regular HCCA-CF
frames of subtype "poll", as might be the case if there was a 1
PIFS delay before accessing the WM. HCCA-CF frames are used by
access points to ask a STA for a response to the HCCA, but they are
used in this example in a different way, for a different
purpose.
[0142] In a specific embodiment, a dual-net device may decide to
use some of the services from its PWN to schedule communication
with PER devices in its SWN. As an example, if the dual-net
device's PWN is an 802.11x WLAN, it may set up an 802.11 Traffic
Stream ("TS") with one or more PER devices and use 802.11
mechanisms such as TSPEC and TCLAS (or modifications thereof) to
communicate the length of SIs, the start of an SP and the like with
its PER devices. Unlike a conventional 802.11 network, where such
communication and negotiation occurs with an AP, when used for
communication within a wireless PAN, specific communication with
the AP of the PWN may be suppressed. As an example, the dual-net
device may suppress the transmission of elements like "ADDTS" and
"DELTS" to the AP it is associated with on its PWN.
[0143] In such an embodiment, a PER may initiate the creation of a
Traffic Stream (TS) to request the COORD for TXOPs, both for its
own transmissions as well as for transmissions from the COORD to
itself. In a specific implementation of this embodiment, a PER
sends an Add Traffic Stream (ADDTS) request frame to the COORD. The
ADDTS request frames may use Traffic Specification (TSPEC) and
optionally Traffic Classification (TCLAS) elements in its frame
body containing the set of parameters that define the
characteristics and QoS expectations of the TS. The Service Start
Time, Minimum Service Interval and Maximum Service Interval fields
in the TSPEC element may be used to request a desired service
period (SP) or update period as well as service time or update
time. In response to an ADDTS request frame, the COORD may send an
ADDTS response frame. This ADDTS response frame may use the TSPEC,
TCLAS and schedule element in its frame body to exchange relevant
parameters and announce the schedule that the COORD will follow for
traffic with the PER in the future. Following a successful
negotiation, a TS is created. Once a TS has been created, the COORD
polls the PER at the pre-negotiated service start time and with the
pre-negotiated service intervals. For this, HCCA-CF poll frames,
possibly with an identifier to indicate secondary network
communication, may be used. And HCCA-CF data frames may be used to
respond.
[0144] Different 802.11x frame formats, frame types, frame subtypes
and modifications thereof may also be used. As an example,
management frames or data frames might be used. Specific fields in
such frames may be adapted to indicate that the frames are part of
a SWN overlay protocol. In some embodiments, regular frames are
used, with their BSSID set to the PAN's BSSID. Alternatively, HCCA
frames or similar are used.
Direct Link Protocol
[0145] When the PWN is a WLAN network based on the 802.11x WLAN
protocol, a mechanism specified in the 802.11e specification,
called Direct Link Protocol or "DLP" may be re-used in a novel way
to implement or facilitate the communication in the SWN.
[0146] In one embodiment, the peripheral service function initiates
a Direct Link Set-up ("DLS"). DLS is being specified in the 802.11e
specification as a protocol that allows two non-AP STAs in the same
wireless LAN BSS to exchange frames directly without relying on the
AP for the delivery of the frames, and without having to
disassociate from the wireless LAN network. FIG. 14 illustrates the
steps involved in a regular direct link ("DL") handshake. A station
STA1 that intends to exchange frames directly with another non-AP
station STA2, invokes DLS by sending a DLS request frame, frame 1,
to the AP. Among other parameters, this request contains the MAC
address of STA1 (source) and STA2 (destination). If STA2 is
associated in the BSS, the AP can forward the DLS request to STA2,
frame 2. If STA2 accepts the direct stream, it sends a DLS response
frame, frame 3, to the AP, which among other parameters contains
the MAC addresses of STA1 and STA2. The AP forwards the DLS
response to STA1, frame 4, after which the DL becomes active and
frames can be sent from STA1 to STA2 and from STA2 to STA1 without
relying on the AP.
[0147] According to the 802.11e specification, a Direct Link Set-up
can only be requested for any two STAs that are associated with the
same BSS. This is not directly applicable to communication between
a COORD and a PER, since a PER is not associated with the primary
network BSS. Therefore, a standard DLS cannot be used. Below, two
novel methods are presented that allow the use of DLS between two
STAs, only one of which is associated with a wireless LAN BSS. Both
methods are described in more detail below. The STA that is
associated with the wireless LAN BSS is referred to as the COORD,
whereas the other STA is referred to as the PER.
[0148] A first method is illustrated in FIG. 15. In this method,
the COORD sends a DLS request frame to the AP of the primary
network, frame 1, requesting a self-addressed Direct Link (DL).
This can be achieved by setting both the source and destination MAC
address in the body of the DLS request frame equal to the COORD's
MAC address. The DLS timeout value can be set to zero such that the
DL is never terminated based on a timeout. Alternatively, the DLS
timeout value can be set to a value corresponding to a time period
at the expiration of which it is desirable that the DL be
terminated. In response to a DLS request frame, the AP forwards the
request, frame2, in this case back to the COORD. The COORD accepts
the direct stream and sends a DLS response frame to the AP, frame
3. The AP forwards this response to the STA specified by the MAC
address in the DLS response frame, in this case back to the COORD,
frame 4. At the end of DLS handshake, the COORD can communicate
directly with a PER in the secondary network without disassociating
from the primary network by using secondary network frames. A
secondary network frame is the same or similar to a regular primary
network frame but both the source address (SA) and destination
address (DA) are set equal to the COORD's MAC address. In such
frames the MAC address of the PER is included in a different field.
In one embodiment, the MAC address of the PER can be part of the
frame body field.
[0149] In an alternative method, the COORD uses an indirect
association and authentication procedure to set up an
authentication and association for the PER with the AP. Once the
PER has been associated and authenticated (indirectly) with the AP,
the COORD may initiate a DLS with the AP by sending a DLS request
frame with the source MAC address set to the COORD's MAC address
and the destination MAC address set to the PER's MAC address.
During the DLS procedure, the COORD responds to all frames sent by
the AP of its primary network, including frames that are addressed
to the PER.
Connectivity States
[0150] The overlay protocol described herein might support multiple
connectivity states to meet typical wireless PAN needs, such as
power conservation, low latency requirements or the desire to
minimize the network capacity taken up by a single PER device. The
latter is particularly important if a large number of PER devices
are operating within a common wireless networking space, possible
coexisting with a large number of WLAN STAs sharing the same common
wireless networking medium.
[0151] A possible state diagram illustrating connectivity states
for a wireless PAN device is illustrated in FIG. 16. It should be
understood that this is one example of a state diagram and devices
might implement other state diagrams instead. Thus, this detailed
example is for illustrative purposes only. For example, a different
state diagram might be applicable if a single COORD coordinates
multiple PER devices.
"CONNECTED"
[0152] When in the CONNECTED state, the COORD and PER have agreed
upon inactivity times, and communicate at agreed upon time
intervals to exchange frames using frame formats, arrangements and
sequences described herein. In addition, each is aware of the
other, i.e., they know relevant addresses, etc., from prior
communication that occurred during prior states (as described
below). Before entering the CONNECTED state, a COORD and PER might
first go through a PAIRING, an UNCONNECTED-SCAN and a CONNECTION
state.
[0153] To conserve power, the connected state might support
different activity levels. As an example, the Service Interval may
be increased when no data were sent for a specific length of
time.
"PAIRING"
[0154] The first step in establishing a new connection is device
PAIRING. Device pairing comprises the first time configuration
steps for linking a PER to a COORD. The pairing procedure typically
comprises at least two steps: device discovery and a security
pre-shared key exchange.
Device Discovery
[0155] During the device discovery procedure, MAC address
information is exchanged between the COORD and the PER. A dedicated
configuration pushbutton or a simple user action can be used to
initiate device discovery. Other mechanisms are also possible, and
several mechanisms have been documented in the literature. The
exact mechanism to initiate device discovery is beyond the scope of
this invention. Upon such user intervention, the COORD and PER
might both enter a "limited discoverable mode" for a certain period
of time that is long enough to finish the device discovery
procedure. Both COORD and PER can initiate the discovery procedure.
The device that initiates the discovery procedure is called the
"initiator"; the other device is hereafter referred to as the
"follower".
[0156] Upon entering discoverable mode, the initiator sends a
broadcast discovery request. The broadcast discovery request is a
broadcast frame, and may contain information such as the
initiator's MAC address, and the type of devices that should
respond. A follower in discoverable mode responds to a broadcast
discovery request with a discovery response. The discovery response
frame is a unicast frame that is addressed to the initiator.
[0157] For security reasons, it is advisable that the amount of
information exchanged while in discoverable mode is minimized.
However, if appropriate, additional information can be exchanged
during the device discovery procedure. For example, if generated by
the COORD, the broadcast discovery frame may optionally contain
information on the WLAN connectivity status
(infrastructure/ad-hoc/unconnected, operating channel, power-save,
etc.). If generated by the PER, the broadcast discovery frame may
optionally contain information about the type of PER.
[0158] In one embodiment, the COORD acts as the initiator and sends
an 802.11x probe request frame. The SSID parameter of the broadcast
probe request frame may be used to communicate specific information
to the PER, in this case the follower. More specifically, the SSID
field in the frame body can be used as a frame type identifier and
to send additional information to a follower. For example, specific
bits of the SSID can be used to identify the over-the-air protocol.
Other bits of the SSID can be reserved to identify the frame as a
broadcast discovery request frame. The remainder of the bits can be
reserved or used to communicate additional information about the
COORD or the wireless LAN network it is associated with to the PER
(follower).
[0159] In another embodiment, a data frame or standard or
proprietary IBSS beacon frame or other management frame is used as
a broadcast discovery request frame.
[0160] Upon receiving the broadcast device discovery request frame,
the PER in discoverable mode (the follower) responds by sending a
unicast discovery response frame. This can be a unicast 802.11x
probe response frame. The probe response frame is addressed to the
initiator, and structured such that it is recognized as a discovery
response frame by the initiator. Alternatively, the discovery
response frame can be a data frame formatted to be recognized by
the COORD as a discovery response frame.
[0161] A device discovery channel can be pre-defined in the
protocol. In that case, an initiator put into discoverable mode
will, by default, start sending broadcast discovery requests on the
pre-defined channel, and a follower put in discoverable mode will,
by default, listen for a broadcast discovery request on the
pre-defined channel.
[0162] When device discovery is initiated, and no device discovery
channel is pre-defined, the initiator and follower may need to
search for each other. Either the initiator or the follower may
perform this search. If the initiator performs the search, the
follower listens on a fixed channel, while the initiator scans
different channels, by subsequently transmitting broadcast
discovery request frames on different channels. Alternatively, when
the follower performs the search, the initiator transmits broadcast
discovery request frames on a fixed channel at Tdiscovery time
intervals, while the follower performs a passive scan by listening
for a broadcast discovery request on different channels. Note that
the follower should stay on a single channel for at least
Tdiscovery to ensure it will capture a broadcast discovery
frame.
[0163] At the conclusion of the device discovery procedure, at a
minimum, the initiator and follower have knowledge of each other's
MAC address and current operating channel of the COORD's primary
network.
Security Key Exchange
[0164] Initial key set-up and key management constitutes an
important aspect of secure wireless communication. The IEEE 802.11
standard specifies that the secret shared key be delivered to
participating stations via a secure channel that is independent of
IEEE 802.11. This is not necessarily possible when attaching a
power-sensitive device like a PER. Over-the-air transmissions may
be required to distribute a pre-shared encryption key between
participating stations.
[0165] Preferably, not the key itself, but the minimum required key
information from which the secret shared key can be derived by both
sides of the link is transmitted over-the-air.
[0166] After completing the device discovery procedure, the COORD
and PER exchange the necessary information to acquire common
knowledge of a shared secret key. This process is referred to as
the key setup, and the shared secret key exchanged in this phase is
called the pre-shared key. Several actions may be taken to minimize
chances of a pre-shared key interception. Such actions may include,
but are not limited to, (1) sending critical information from PER
to COORD, (2) intentionally reducing power levels for pre-shared
key information exchanges, and/or (3) using a key exchange process,
such as Diffie-Hellman, to avoid having critical key information
transmitted over the air in the clear. Sending critical information
from PER to COORD reduces the chances of interception, since the
transmission range of a PER might be significantly lower that that
of a COORD.
[0167] The pre-shared key is stored and can be used for encryption
of frames by the driver or firmware that performs the encryption of
frames for communication in the secondary network. For security
reasons, it is often desirable to regularly update the shared key.
The pre-shared key can be used to encrypt one or more temporary
keys before they are transmitted over the air. These temporary keys
are then used for encryption and authentication of data.
[0168] The COORD may initiate the initial key exchange, and may
reserve the WM by increasing the duration field of the frame it
sends to a PER. During the initial key exchange, frames sent to a
PER should not be encrypted. If the COORD is a dual-net device,
this can be achieved by either turning off encryption in the
COORD's 802.11x device driver or firmware or passing the frame on
to the 802.11x device driver beyond the encryption point.
Similarly, frames received from the PER during the initial key
exchange should not be decrypted by the 802.11 device driver or
firmware. This is achieved either by turning off encryption in the
COORD's 802.11x device driver or firmware, or by making sure that
the received frame is passed on to the peripheral service function
prior to decryption in the 802.11x device driver or firmware.
Furthermore, the data rate of frame transmissions is set to the
maximum data rate supported by the PER.
Completion of Pairing Procedure
[0169] After successful completion of the pairing procedure, the
MAC address of the COORD and the shared key information are stored
inside the PER, and the MAC address of the PER and the shared key
information are stored inside the COORD. Both the COORD and PER
abandon the limited discoverable mode. The COORD and PER are now
paired. After completion of the pairing procedure, the COORD
continues its regular WLAN activity.
[0170] The PER may subsequently decide to go enter the DEEPSLEEP
state or enter the UNCONNECTED-SCAN state.
BSS Notification
[0171] In case where the COORD, STA1, is associated with a primary
network BSS1, prior to starting the pairing procedure, it may be
desirable to notify the AP of BSS1 that STA1 will be temporarily
unavailable. This may be important to avoid the situation where
BSS1 tries to communicate with STA1 while STA1 is occupied with the
pairing. The BSS1 traffic may even be on a different channel (such
as where there is a pre-defined discovery channel). If
non-responsive, the AP might drop STA1 from association with the
AP.
[0172] A first method may comprise temporarily disassociating the
client from the primary network, BSS1. Since the pairing procedure
is normally done only once, at initial set-up, it may in many
applications be acceptable that, for the duration of the pairing
procedure, STA1 temporarily disassociates from BSS1.
[0173] In a second method, STA1 may notify the AP of its primary
network BSS1 of its temporary unavailability by sending a frame
with the power management bit set. After completing the pairing
procedure, STA1 may send a frame to the AP of BSS1 with the power
management bit cleared.
"UNCONNECTED-SCAN"
[0174] When in the UNCONNECTED-SCAN state, a PER device tries to
detect the COORD that it is paired with. Various scanning and
device detection schemes might be used when in the UNCONNECTED-SCAN
state.
[0175] In one embodiment, the connection request frame is a probe
request frame and can be generated with a scan request. The
broadcast probe request frame may have the SSID programmed to be
interpreted by the PER as a connection request frame. The SSID may,
among other parameters, contain the PER's MAC address information,
a secondary network protocol identifier, and a connection request
frame identifier. It may furthermore contain relevant additional
parameters, such as the wireless LAN connection mode
(infrastructure versus ad-hoc versus no connect), the operating
channel of the COORD's wireless LAN connection, etc. The COORD may
also reserve the WM for a single response frame from the PER. The
protocol states described herein (ACTIVE, PAIRING, etc.) might
collectively define portions of a secondary network protocol.
[0176] In another embodiment, a data frame or a standard or
proprietary IBSS beacon frame may be used as a connection request
frame. Alternative management, control or data frames beyond the
above specified examples may also be used as connection request
frames.
[0177] As with the pairing procedure, the connection request frames
are either transmitted on a pre-defined channel, or a COORD- or
PER-initiated search may be used to establish connection.
"CONNECTION"
[0178] A connection procedure can be initiated at any time between
a PER and a COORD that are paired, have detected each other, but
are not yet connected. The purpose of the connection procedure is
to prepare the COORD and PER for regular frame exchange ("ACTIVE
state"). During the connection procedure, the PER and COORD are
synchronized and, optionally, a new shared encryption key is
exchanged.
Authentication
[0179] Optionally, an authentication procedure may be added prior
to data exchange to ensure that the claimed recipient is indeed the
intended recipient. A standard shared key authentication procedure,
already supported by the 802.11x stack, may be used for
authentication. Alternatively, a new authentication mechanism may
be implemented in the 802.11x peripheral service function.
Update Shared Encryption Key
[0180] For security reasons, it may be desirable to regularly
update the encryption key, so that even if the key is intercepted,
the connection is not insecure indefinitely. In one specific
embodiment, the encryption key is temporary and may be updated
every time a new connection is established. In such embodiment, the
pre-shared key may be used to exchange information related to the
shared encryption key.
Completion of Connection Procedure
[0181] Upon completion of the connection procedure, the COORD and
the PER are ready to exchange data/voice traffic, and both enter
the CONNECTED state. At that point, the PER has knowledge of the
operating channel and other relevant parameters related to the
COORD's primary network.
[0182] Similar as during the pairing procedure, it may be desirable
that the COORD notifies the AP of its primary network that it will
temporarily be unavailable. This can among other mechanisms be done
by sending a frame to the AP with the power management bit set.
After completion of the connection procedure, COORD may send a
frame to the AP with the power management bit cleared.
"DEEPSLEEP"
[0183] If there has been no traffic for a time longer than a
pre-defined time interval Ttime_out, the PER may enter the
DEEPSLEEP state. In the DEEPSLEEP state, the PER powers down most
or all of its circuits and does no longer stay synchronized to the
COORD. When in the DEEPSLEEP state, prior to go back to ACTIVE
state, the PER first goes through the UNCONNECTED-SCAN and
CONNECTION states.
[0184] Alternatively, the PER may enter the DEEPSLEEP state after a
power-down event, when failing to receive frames from the COORD or
when receiving a PARK request from the COORD or from a higher level
management layer.
[0185] When the PER has entered the DEEPSLEEP state, the COORD
might determine to switch to the UNCONNECTED-SCAN state, where it
periodically or occasionally checks whether a PER is trying to
connect. Optionally, all connections might use a fixed, pre-defined
channel for rendezvous.
Overlay Protocol With PWN Feature/Hardware Reuse
[0186] In specific embodiments, a computing device is a dual-net
device and is interfaced to a wireless local area network (WLAN)
and a wireless personal area network (PAN). A network circuit,
comprising logic and at least one antenna, interfaces the computing
device to the WLAN and including logic to set up a LAN association
between the computing device and the access point prior to data
transfer therebetween, while also interfacing the computing device
to a PAN device via the wireless PAN.
[0187] Communication with the wireless PAN device might use an SWN
overlay protocol that is only partially compliant with the protocol
used over a conventional WLAN and might do so without interference
from the conventional WLAN, yet usage of the WLAN is such that the
wireless PAN device and computing device can communicate without
interference. To reduce interference, the computing device
coordinates the usage of the wireless medium with devices of a WLAN
that may be active in the same space. Coordination is achieved by
the use of a secondary network (PAN) protocol that is an overlay
protocol that is partially compatible with the WLAN protocol, but
not entirely, in terms of power, frame contents and sequences,
timing, etc. The secondary network (PAN) protocols might be 802.11x
frames with new frame arrangements adapted for PAN needs, such as
reduced latency, power etc. The computing device might determine to
signal the primary network (WLAN) such that devices therein defer
so that communications can occur with the secondary network. The
overlay protocol is preferably such that devices that can join both
networks can use a common network interface circuit.
[0188] In specific implementations, a shareable network circuit
stores parameters, addresses and other information necessary to
maintain sessions with both networks simultaneously. As an example,
a shareable network circuit may store two media addresses, one for
communication in the WLAN and one for communication in the wireless
PAN. The network circuit can maintain sessions with both
simultaneously. More than two networks and corresponding storage of
parameters, addresses and additional network related information
might be provided for. A recognition method is provided in the
computing device to distinguish and separate traffic from different
networks.
[0189] Where the PWN is a WLAN typically used for network traffic
over a relatively large space, such as a building and the SWN is a
PAN is typically used for peripheral traffic over a narrower space,
such as a room, a desk, a person's space, etc., the optimum
protocols for the two networks are likely to be different such that
what works well for one network does not work well for another
network. Nevertheless, if a single computing device is to be a part
of both networks, it is desirable to re-use specific PWN features
and networking hardware for communication in the SWN. Where the
first network is an 802.11x network and a computing device includes
802.11x networking equipment, an overlay protocol can be used for
the SWN, such that 802.11x equipment can be co-opted for use with
the SWN, optimized to deal with some of the differing requirements
of the two networks.
[0190] The overlay protocol allows a dual-net device that is
associated with a PWN to exchange information, possibly on the same
channel as the primary network, with PERs that are a member of a
SWN, and not a member of the PWN, and that may or may not be within
the coverage range of the PWN. Access to specific lower level
primitives in the 802.11x stack, like the ability to overwrite a
frame's duration field, or the ability to transmit/receive on a
separate SWN BSSID may or may not be necessary.
[0191] As an example of PWN feature reuse, the SWN overlay protocol
may use modulations schemes supported by the PWN protocol, so as to
enable re-use of the modulation/demodulation logic in the 802.11x
equipment. As another example of PWN feature reuse, the SWN overlay
protocol may use 802.11x frame arrangements and modifications
thereof, so as to ensure that frames in the SWN can be transmitted
and received by the 802.11x hardware.
[0192] In a specific implementation, for a dual-net device to
maintain multiple sessions simultaneously, it stores two media
addresses, one for communication with devices in the WLAN and one
for communication with devices in the wireless PAN. The media
addresses can be network Basic Service Set Identifiers (BSSIDs).
The BSSID for the primary network can be the MAC address of the AP
of the primary network, and the BSSID for the secondary network can
be a MAC address that identifies WPAN traffic. As an example, the
BSSID of a secondary network can be the WLAN MAC address of the
dual-net device, but it can also be a MAC address that is different
from the dual-net device's WLAN MAC address. As another example,
the BSSID of the secondary network may be global media address to
identify WPAN traffic, that is a single MAC address that uniquely
identifies all wireless PAN traffic independent of what COORD the
wireless PAN traffic is intended for.
[0193] In a different implementation of the protocol however, the
BSSID of the PWN is re-used and a separate MAC address for the
communication in the SWN is not needed.
[0194] More than two networks and corresponding storage of
addresses and parameters might be provided for.
[0195] A dual-net device that is simultaneously maintaining a
session with a WLAN and a wireless PAN can use a packet recognition
mechanism to distinguish traffic in the PWN (the WLAN) from traffic
in the SWN (the wireless PAN).
[0196] In a specific implementation where the wireless PAN BSSID is
different from the WLAN BSSID, a dual-net device can use the BSSID
in the packet to distinguish traffic in the primary network from
traffic in the secondary network.
[0197] Other identification mechanisms, like an Ethertype, an
organizationally unique identifier (OUI), specific reserved bits in
an 802.11x packet etc. may also be used to identify wireless PAN
traffic.
[0198] In yet another implementation, the SWN protocol may be such
that the dual-net device knows when a wireless PAN frame can be
expected. An example of such protocol is a "polling-based" protocol
where a PER only sends a frame to its COORD in response to
reception of a frame from its COORD. If the dual-net device knows
when to expect a wireless PAN frame, it can prepare a temporary
buffer for such frame. In the above example, each time the COORD
transmits a frame that is intended for a PER, a temporary buffer
for a single reply frame might be provided. This identification
method works if a PER does not access the WM autonomously, and
responds to a frame for the COORD with a single reply frame. The
method can easily be extended, using the teachings herein, to the
scenario where a PER responds to a frame from the COORD with
multiple reply frames by increasing the size of the temporary
buffer.
[0199] In yet another embodiment, a modified 802.11x frame format
is used for communication in the SWN. For example, HCCA data frames
with "from DS" and "toDS" fields both cleared might automatically
be recognized by the 802.11x stack as wireless PAN traffic.
[0200] Alternatively, if no recognition mechanism is provided by
the 802.11x stack, all received frames can be propagated up to the
802.11x peripheral service function, and a recognition mechanism
implemented inside the 802.11x peripheral service function selects
the frame originating from a PER.
[0201] In addition to a recognition mechanism to distinguish WLAN
traffic from wireless PAN traffic, an additional recognition method
may be needed to distinguish traffic from separate wireless PANs.
As an example, two or more COORDs of separate wireless PANs may be
sharing a common wireless networking medium. If that is the case, a
COORD may be receiving frames from devices that belong to different
wireless PANs and should be configured to distinguish frames from
its own wireless PAN from those that belong to a different wireless
PAN. If a different media address is used for each wireless PAN
(for example, each wireless PAN has a unique wireless PAN BSSID),
then identification can be done based on such media address.
[0202] In a specific implementation, a global unique media address
may be used to globally identify all wireless PAN traffic. As an
example, a global unique BSSID may be used to identify all wireless
PAN traffic. In such implementations, an additional identification
mechanism may be required to allow a COORD to identify the wireless
PAN traffic for which it is the intended recipient. As an example,
the Destination Address ("DA") or Receiver Address "RA") field of
the 802.11x packets can be used as such identifier. The DA or RA
can, for example, be the WLAN MAC address of the COORD. Other
similar approaches can be used instead.
Variations
[0203] In a common operation, a link is established between a
network circuit and a BSS while simultaneously linked with a
secondary network device. In one variation, some aspects could also
be used to establish a link between a standard 802.11x card and a
power-sensitive device, even if the standard 802.11x card is not
simultaneously connected to a BSS. For example, in a GSM/WiFi combo
phone, the device might be handling a call over the cellular
network and the WiFi card could still be used for headset
connectivity.
[0204] In the 802.11e draft, HCCA is proposed to be used by the QAP
to schedule traffic with QSTAs. In embodiments described herein, it
is used for communication in secondary network. Thus, while COORD
is regular client in the primary network, difference can be
signalled with specific fields in frame set differently (e.g., "to
ds" and "from ds" both set to zeroes, or via the use of some of the
reserved bits). An example is shown in FIG. 17.
[0205] Additionally, in order not to interfere with other "real"
HCCA APs, a different access procedure can be used (e.g., use the
VoIP queue instead of PIFS). The HCCA mechanism can be reused for a
service request (i.e., a connection) using ADDTS request and
response frames with TSPEC and schedule element, for HCCA CF polls
(e.g., COORD polling the PER in CONNECTED state), and/or for
schedule frame for changing update interval either because PER goes
into SNIFF mode or in case of congestion of the medium to free up
the WM and save power inside PER.
[0206] In many of the examples described herein, one feature is the
use of a common PHY and MAC layer for two networks, one being a
conventional 802.11x network with a BSSID and the other being a
secondary network connecting what would otherwise be an 802.11x STA
with peripherals and other low-power, low-range devices. In a more
general case in another network model, there is common use of a
modulation scheme and a frame formatting layer, wherein the PHY and
MAC are specific instances.
[0207] In many of the examples described herein, the station device
is wirelessly coupled to an 802.11x access point while being active
with devices over the secondary network. In other variations, the
station device is wirelessly coupled to another station over a
direct link while being active with devices over the secondary
network. In yet other variations, the station device may be the AP
of the primary network, while also being the COORD for the
secondary network.
[0208] In some embodiments, the communication between the COORD and
one or more PERs of the SWN occurs in the same frequency band and
on the same frequency channel as the communication of the PWN.
[0209] In other embodiments, the communication between the COORD
and one or more PERs of the SWN occurs in the same frequency band
as the communication in the PWN, but on a different frequency
channel than the communication within the PWN. As an example,
channel switching may be desirable if the frequency channel of the
PWN is crowded, or the SWN application requires a high Quality of
Service (QoS).
[0210] In other embodiments, the communication between the COORD
and one or more PERs of the SWN occurs in a different frequency
band and, therefore also on a different frequency channel, as the
communication of the PWN. As an example, frequency band switching
is necessary if the primary network is in an 802.11a mode,
operating in the 5 GHz unlicensed frequency band and the PER only
supports communication in the 2.4 GHz unlicensed frequency band, or
vice versa.
[0211] In still further embodiments, the dual-net device may be
communicating in a different mode with the PWN and the SWN. As an
example, the COORD may be communicating in an 802.11g mode inside
the PWN while using an 802.11b mode for communication within the
SWN, or vice versa. In such embodiment, the communication within
the SWN can be on the same or on a different frequency channel as
the PWN.
[0212] In yet another embodiment, communication in the SWN uses the
same mode as the PWN, with both networks using different data rates
or where it is not known whether the data rates are different or
the same (such as where they are set independently). For example,
the COORD might transmit frames at the same data rate as its data
rate for communication within the primary network while the PER
communicates with the COORD using a different data rate.
[0213] Different data rates might be used for downlink and uplink
communication within the SWN. Alternatively, the same data rate is
used for downlink and uplink communication within the SWN and this
data rate is different from the data rate used by the dual-net
device for communication within the PWN. It is also possible that
the data rates for PWN and SWN communication are set independently,
but at certain moments in time turn out to be the same.
[0214] In the typical embodiment in an 802.11x environment, an
802.11x client can talk to an access point and devices in the
secondary network without losing synchronization and association
and without requiring a reset of a connection at the 802.11x
client. The 802.11x client can reserve a wireless medium for a weak
peripheral, effectively solving a "hidden node" problem for the
low-power peripheral or other such device.
[0215] In a common operation, a link is established between a
network circuit and a BSS while simultaneously linked with a
secondary network device. In one variation, some aspects could also
be used to establish a link between a standard 802.11x card and a
power-sensitive device, even if the standard 802.11x card is not
simultaneously connected to a BSS. For example, in a GSM/WiFi combo
phone, the device might be handling a call over the cellular
network and the WiFi card could still be used for headset
connectivity.
[0216] In many of the examples described herein, one feature is the
use of a common PHY and MAC layer for two networks, one being a
conventional 802.11x network with a BSSID and the other being a
secondary network connecting what would otherwise be an 802.11x STA
with peripherals and other low-power, short-range devices. In some
embodiments, only part of the MAC layer is in common and other
variations are possible. In a more general case in another network
model, there is common use of a modulation scheme and a frame
formatting layer, wherein the PHY and MAC are specific
instances.
[0217] In many of the examples described herein, the station device
is wirelessly coupled to an 802.11x access point while being active
with devices over the SWN. In other variations, the station device
is wirelessly coupled to another station over a direct link while
being active with devices over the SWN. In yet other variations,
the station device may be the AP of the PWN, while also being the
COORD for the SWN.
[0218] In the typical embodiment in an 802.11x environment, an
802.11x STA can talk to an access point and to devices in the SWN
without losing synchronization and association and without
requiring a reset of a connection at the 802.11x STA. The 802.11x
STA can reserve a wireless medium for a weak peripheral,
effectively solving a "hidden node" problem for the low-power
peripheral or other such device.
[0219] In many of the examples herein, where a device is described
as a dual-net device it is intended to be a description of a device
that can be a coordinator for a SWN while being a station in a PWN.
Often the description of operations, features and/or elements of
the dual-net devices also apply to secondary wireless PAN COORDs
that may not have a capability to become a full node in the primary
network.
[0220] Even where differences between the PWN and SWN are such that
they don't interfere, the COORD might still reserve the WM, to
avoid signals from elsewhere interfering.
[0221] While the present invention has been described herein with
reference to particular embodiments thereof, a latitude of
modification, various changes, and substitutions are intended in
the present invention. In some instances, features of the invention
can be employed without a corresponding use of other features,
without departing from the scope of the invention as set forth.
Therefore, many modifications may be made to adapt a particular
configuration or method disclosed, without departing from the
essential scope and spirit of the present invention. It is intended
that the invention not be limited to the particular embodiments
disclosed, but that the invention will include all embodiments and
equivalents falling within the scope of the claims.
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