U.S. patent application number 10/785637 was filed with the patent office on 2004-08-26 for mechanism and technique for dynamically optimizing antenna orientation and transmit power in a meshed network environment.
Invention is credited to Lumelsky, Leon.
Application Number | 20040166812 10/785637 |
Document ID | / |
Family ID | 32869881 |
Filed Date | 2004-08-26 |
United States Patent
Application |
20040166812 |
Kind Code |
A1 |
Lumelsky, Leon |
August 26, 2004 |
Mechanism and technique for dynamically optimizing antenna
orientation and transmit power in a meshed network environment
Abstract
The present invention provides methods, systems, devices, and
computer program instructions for enabling low-power wireless
devices (such as wireless telephones and personal digital
assistants, or PDAs) to connect to a fast wired or wireless
voice/data network. A novel relay point device, referred to as an
"extension point", is defined that flexibly extends the effective
reach of network access points. Use of extension points enables the
network infrastructure to be expanded (and subsequently
re-configured, if necessary) simply and cost-effectively, requiring
little or no additional physical wiring. The defined techniques
provide an infrastructure that is scalable, supporting a large
number of end users without substantial degradation to connection
establishment time and data rates. Using the disclosed techniques,
end devices are able to reach network services, and to communicate
with other end devices, beyond the nominal working range of these
devices and without limitation to the numbers of such devices.
Inventors: |
Lumelsky, Leon; (Stamford,
CT) |
Correspondence
Address: |
MARCIA L. DOUBET
P. O. BOX 422859
KISSIMMEE
FL
34742
US
|
Family ID: |
32869881 |
Appl. No.: |
10/785637 |
Filed: |
February 24, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10785637 |
Feb 24, 2004 |
|
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09685715 |
Oct 10, 2000 |
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Current U.S.
Class: |
455/67.11 ;
455/41.2 |
Current CPC
Class: |
H04B 7/0602 20130101;
H04W 88/02 20130101; H04W 16/28 20130101; H04W 52/50 20130101; H04W
84/18 20130101 |
Class at
Publication: |
455/067.11 ;
455/041.2 |
International
Class: |
H04B 017/00 |
Claims
That which is claimed is:
25. A method for dynamically tuning a directional antenna of a
wireless device for communicating with an access point in a
short-range wireless networking environment, comprising the steps
of: providing at least one wireless device; providing at least one
access point; establishing a network link between a selected one of
the wireless devices and a selected one of the access points using
the directional antenna of the selected wireless device and an
omnidirectional antenna of the selected access point; and setting a
position of the directional antenna to minimize a bit error rate
along the established link.
26. The method according to claim 25, wherein the step of setting
the position of the directional antenna further comprises the steps
of: positioning the directional antenna at a plurality of angles
toward the omnidirectional antenna; recording the bit error rate at
each of the angles; and selecting one of the angles which exhibits
a minimal value of the bit error rate to be the position of the
directional antenna.
27. The method according to claim 26, wherein the plurality of
angles are selected by first locating an initial position beyond
which communication using the directional antenna is not
possible.
28. The method according to claim 25, further comprising the step
of setting a power of transmission of the directional antenna to a
minimum value required to communicate on the established link.
29. The method according to claim 28, wherein the step of setting
the power of transmission of the directional antenna further
comprises the steps of: setting the power of transmission to a
default value; recording a bit error rate at the default value;
successively reducing the power of transmission until connectivity
is lost or the bit error rate crosses a threshold; and setting the
power of transmission to be a value that results in the bit error
rate staying below the threshold.
30. The method according to claim 29, wherein the threshold is a
maximum acceptable value for the bit error rate.
31. The method according to claim 25, wherein the selected wireless
device is an extension point device.
32. The method according to claim 25, wherein the selected wireless
device is an end-user device.
57. Computer program instructions for dynamically tuning a
directional antenna of a wireless device for communicating with an
access point in a short-range wireless networking environment, the
computer program instructions embodied on one or more computer
readable media and comprising: computer program instructions for
communicating with at least one wireless device; computer program
instructions for communicating with at least one access point;
computer program instructions for establishing a network link
between a selected one of the wireless devices and a selected one
of the access points using the directional antenna of the selected
wireless device and an omnidirectional antenna of the selected
access point; and computer program instructions for setting a
position of the directional antenna to minimize a bit error rate
along the established link.
58. The computer program instructions according to claim 57,
wherein the computer program instructions for setting the position
of the directional antenna further comprise: computer program
instructions for positioning the directional antenna at a plurality
of angles toward the omnidirectional antenna; computer program
instructions for recording the bit error rate at each of the
angles; and computer program instructions for selecting one of the
angles which exhibits a minimal value of the bit error rate to be
the position of the directional antenna.
59. The computer program instructions according to claim 58,
wherein the plurality of angles are selected by first locating an
initial position beyond which communication using the directional
antenna is not possible.
60. The computer program instructions according to claim 57,
further comprising computer program instructions for setting a
power of transmission of the directional antenna to a minimum value
required to communicate on the established link.
61. The computer program instructions according to claim 60,
wherein the computer program instructions for setting the power of
transmission of the directional antenna further comprise: computer
program instructions for setting the power of transmission to a
default value; computer program instructions for recording a bit
error rate at the default value; computer program instructions for
successively reducing the power of transmission until the bit error
rate crosses a threshold; and computer program instructions for
setting the power of transmission to be a value that results in the
bit error rate staying below the threshold.
62. The computer program instructions according to claim 61,
wherein the threshold is a maximum acceptable value for the bit
error rate.
63. The computer program instructions according to claim 57,
wherein the selected wireless device is an end device.
77. A system for dynamically tuning a directional antenna of a
wireless device for communicating with an access point in a
short-range wireless networking environment, comprising: at least
one wireless device; at least one access point; means for
establishing a network link between a selected one of the wireless
devices and a selected one of the access points using the
directional antenna of the selected wireless device and an
omnidirectional antenna of the selected access point; and means for
setting a position of the directional antenna to minimize a bit
error rate along the established link.
78. The system according to claim 77, wherein the means for setting
the position of the directional antenna further comprises: means
for positioning the directional antenna at a plurality of angles
toward the omnidirectional antenna; means for recording the bit
error rate at each of the angles; and means for selecting one of
the angles which exhibits a minimal value of the bit error rate to
be the position of the directional antenna.
79. The system according to claim 78, wherein the plurality of
angles are selected by first locating an initial position beyond
which communication using the directional antenna is not
possible.
80. The system according to claim 77, further comprising means for
setting a power of transmission of the directional antenna to a
minimum value required to communicate on the established link,
further comprising: means for setting the power of transmission to
a default value; means for recording a bit error rate at the
default value; means for successively reducing the power of
transmission until the bit error rate crosses a threshold; and
means for setting the power of transmission to be a value that
results in the bit error rate staying below the threshold.
81. The system according to claim 80, wherein the threshold is a
maximum acceptable value for the bit error rate.
Description
[0001] The present invention is a divisional of commonly-assigned
U.S. Pat. No. ______ (Ser. No. 09/685,715, filed Oct. 10, 2000),
which is hereby incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to wireless communication
networks, and more particularly to methods, systems, devices, and
computer program instructions for flexibly and efficiently enabling
end-user communication devices to access a remote network from a
short-range networking environment.
BACKGROUND OF THE INVENTION
[0003] The recent explosion of small and portable wireless
battery-powered devices (hereinafter, "WBPDs"), such as cellular
phones and personal digital assistants (PDAs), has escalated both
the desire to exchange information directly between such devices
and the desire to obtain access to conventional network and
application services from these devices. Due to the relatively
short battery life of these devices, tradeoffs must be made between
the available network bandwidth and the wireless transmission
range. The need to support reasonable bandwidth for interactive
applications, multimedia, and so forth on these devices
consequently drove the emergence of short-range communication
technologies.
[0004] Examples of these short-range communication technologies
include IEEE 802.11, HomeRF, and Sharewave. (IEEE 802.11 is a
standard of the Institute for Electrical and Electronics Engineers,
which was approved in 1997 for wireless Local Area Network, or LAN,
signaling and protocols. HomeRF and Sharewave are directed towards
in-home networking solutions. More information on these techniques
can be found on the Internet at www.ieee.org, www.homerf.com, and
www.sharewave.com, respectively.)
[0005] Devices using these prior art technologies typically comply
to a wireless peer-to-peer networking protocol, allowing for
multiple simultaneous device interactions at ranges of 50 meters or
more, with data rates well above 1 Megabit per second (Mbps).
However, the power consumption requirements for these technologies
are too high to make them good candidates for use with WBPDs.
Consequently, simpler, less power demanding wireless networking
technologies are beginning to appear. Unfortunately, to achieve the
reduced power requirements, these newer technologies place more
severe restrictions on the distance and data rate of the wireless
communication, as well as on the number of devices that may
communicate simultaneously.
[0006] One of the most recent examples of these newer wireless
technologies is known as "Bluetooth". (Refer to location
www.bluetooth.com on the Internet for more information on
Bluetooth.) Bluetooth was initially designed to replace cables
between closely located devices. Bluetooth technology is therefore
optimized for short-haul, point-to-point connectivity.
Bluetooth-enabled devices also consume less power than devices that
are designed according to the older wireless technologies such as
802.11. Because of these factors, Bluetooth is one obvious
candidate for use as WBPDs.
[0007] However, although Bluetooth-enabled devices have a number of
beneficial attributes, the Bluetooth design point leads to severe
disadvantages when compared with the older wireless technologies in
terms of the previously-stated factors of distance, data rate, and
number of communicating devices.
[0008] The disadvantage in terms of distance can be seen by
comparing Bluetooth to 802.11. 802.11 technologies provide
connections between a base station and end devices over distances
that may exceed 100 meters. Bluetooth connects across much shorter
distances, typically less than 10 meters for those devices
classified in the Bluetooth standard as "Class 3 devices." (Class 1
Bluetooth devices are the most powerful devices defined according
to the Bluetooth standard, and they provide connections over
distances up to 100 meters; however, these Class 1 devices require
considerably more power than Class 3 devices.) The working distance
between Class 3 and Class 1 Bluetooth devices is required to be 10
meters or less. (This is because different class devices must tune
their receivers to have equal sensitivity; in this case, they must
tune to the sensitivity of the Class 3 device, on the order of -70
decibels relative to 1 milliwatt, or -70 dBm.)
[0009] In terms of data rate, the older wireless technologies
provide much higher data rates than Bluetooth. 802.11, for example,
offers data rates of up to 11 Mbps. Bluetooth, on the other hand,
has a shareable raw data rate of less than 1 Mbps. For pure
asynchronous connection-less (ACL) links, the effective data rate
is approximately 720 Kilobits per second (Kbps). A device may
participate in up to three synchronous connection-oriented (SCO)
links, in which case the effective ACL data rate is reduced to less
than 440 Kbps.
[0010] Regarding the third disadvantage, the number of devices
supported in the older wireless technologies is typically limited
only by the performance of the individual end devices that are
communicating via the shared wireless LAN. The number of Bluetooth
devices, however, is severely restricted by the Bluetooth
architecture. The architecture defines master and slave roles for a
group of devices connected in an ad-hoc network configuration
referred to as a "piconet," and it specifies that a device serving
as a master in a piconet may not control more than 7 active slave
devices at one time.
[0011] In spite of the limitations of existing wireless
connectivity solutions suitable for personal WBPDs, users have an
ever-increasing desire to connect their personal WBPDs to networks,
including large Internet Protocol (IP) networks, home networks,
corporate LANs, and the Internet.
[0012] Two approaches have emerged for satisfying these consumer
demands. In the first solution, an intermediary device that is
customarily referred to as an "Access Point" (AP) has been produced
by several companies. In the second solution, a "scatternet"
approach is used to expand a network to accommodate multiple WBPDs.
Each of these approaches will now be described.
[0013] FIG. 1 illustrates a networking environment according to the
first approach, in which several access points 140, 141, . . . are
used to connect end user devices such as those depicted at 130,
131, and 132 to an IP data network 120. (The IP data network in
this prior art scenario may be either wired or wireless; the
distinction is not pertinent to the present discussion.) These AP
devices of the prior art may be based on a conventional computing
device, which has both Bluetooth and LAN network adapters (for
communicating with end devices 130, 131, 132 and network 120,
respectively). Or, the AP device may be a special-purpose,
dedicated device that combines both of these adapters and provides
the necessary bridging functions between them.
[0014] However, these existing Bluetooth-based access points have
distinct disadvantages when compared to longer-range wireless
communication solutions, such as 802.11, or wide area wireless
communications. While an AP based on Bluetooth technology (and its
10 meter limitations) may be fine for home or small office
environments, these disadvantages make it a less attractive choice
as compared to a wireless LAN for serving a crowded wireless
environment like a conference room (or for serving a large space
such as an airport or school) as will now be described.
[0015] A first disadvantage of Bluetooth AP solutions is that the
number of APs may need to be excessively large due to limitations
of the Bluetooth design specifications. A single AP (i.e. a
Bluetooth Class 3 device) operating in the role of a master within
a piconet can serve an area having a 10 meter radius, providing a
circular area of coverage of approximately 314 square meters.
Adapting this circular coverage area to a conference room having a
square shape (while covering the entire room), one AP can serve a
square room of approximately 14.2 meters by 14.2 meters, or 200
square meters. In compliance with the Bluetooth specifications,
however, this AP can support only 7 active Bluetooth slave devices.
Hence, if the conference room has 50 seats and all the users seated
in the room must be provided with on-line connections at the same
time, then the minimal number of required APs is 8. (In the general
case, the number of APs required to support N users distributed
within the circular coverage range of a single AP is the ceiling of
the expression N/7, or .left brkt-top.N/7.right brkt-bot..)
[0016] Second, the number of APs may depend on the shape of the
place in which the APs are used. For example, if the same
200-square meter conference room in the above example has an
elongated or L-shape, rather than a square shape, then 8 APs is no
longer sufficient. Suppose that the dimensions of the room are 10
meters by 20 meters. Because the lengthwise distance of the room is
longer than 14.2 meters, a single AP is no longer capable of
serving users located throughout the room. To provide network
connectivity throughout this rectangular shaped 200-square meter
room, the number of APs must be doubled to 16 because it may happen
that all 50 users are crowded first at one end of the room and
later at the other end.
[0017] Third, the number of APs may need to be even larger, because
the locations of the end devices may be dynamic and unpredictable,
and network capacity must be able to accommodate the worst-case
number of active users as the users move around the room. For
example, suppose APs are used within a museum to provide
information to museum visitors as they view each painting within a
large open space. To ensure that each museum visitor can make a
connection as he views each painting, enough network capacity must
be provided at each painting to support the entire group of
visitors, even though most of the time little to none of this
capacity is required (i.e. most of the time, no users or a very
small number of users is standing in front of any one
painting).
[0018] Another, and perhaps the most important, disadvantage of
Bluetooth AP solutions is that the installation of APs requires
additional wiring, making the infrastructure installation very
expensive. Each AP requires an additional power plug and an
additional network connection or port. In other words, a Bluetooth
network using APs may require a large number of wired jacks, making
the supposedly "wireless" network wireless only for the end
devices. Extensive wiring causes high labor costs, and may possibly
even surpass the cost of the APs in the near future, as AP cost
decreases with proliferation of the technology. As a result,
installation of a Bluetooth AP network may be as costly as
installation of a fully wired network.
[0019] A further disadvantage of building a network infrastructure
using Bluetooth APs is that such networks are not easily scalable
to add more users, nor are they easily reconfigurable to modify the
area of coverage. Both types of changes will typically require
installation of additional wiring to support additional APs or
movement of existing APs to new locations (in which case, new
wiring may be required at the new location).
[0020] Using a wireless LAN such as 802.11 in the AP configuration,
instead of Bluetooth, does not eliminate these problems: Power
wiring is still required. Furthermore, in an area where Bluetooth
communication is already in use, it may not be a good idea to
introduce a wireless LAN using another technology because the
wireless LAN shares the same radio spectrum (i.e. 2.4 GHz, the ISM)
as Bluetooth, along with microwaves, cordless telephones, and other
technologies. Interference in this environment may lead to
unacceptably low performance of both networks when a large number
of wireless dongles is concentrated in a space that provides
service to a large number of users.
[0021] The scatternet approach of the second solution to providing
network access for multiple WBPDs uses multiple piconets
communicating with each other in a daisy-chained fashion, wherein
an end device may play a dual role of a master in one piconet and a
slave in another. One AP may support more than 7 end devices in
this configuration. For example, if a first piconet lacks an AP and
therefore cannot communicate with the network, but the master of
this first piconet is within range of a second piconet which does
have an AP connected to the network, then the devices of the first
piconet can communicate with the network (and with the devices of
the second piconet) by virtue of the first piconet's master also
playing the role of a slave in the second piconet. Additional
wiring is not required in this scatternet approach, because any of
the end devices may serve as bridges between the two piconets and
thereby extend the reach of the network.
[0022] On a negative side, however, such an easy solution to
scalability may cause a substantial diminishing of performance.
Continuing the previous example of 50 users in a room, if this room
is served by a single AP that is daisy-chained to multiple
piconets, the daisy-chaining approach leads to a degradation of the
useful payload rate to less than {fraction (1/50)}th of 720 Kbps,
or about 10-14 Kbps. This number is comparable with wide-area
network data rates, which do not require any additional hardware to
install. Moreover, network delay is longer for those devices that
connect to the network through the daisy chain. For example, if the
connection set-up time within one piconet is from 1 to 5 seconds,
then the last user in a daisy-chained scatternet comprised of 8
piconets will require approximately 8 to 40 seconds before being
connected to the network.
[0023] Furthermore, if one or several of the portable end devices
serving as masters in the ad-hoc daisy chain fails, is turned off,
or leaves the room, then the rest of the chain will be cut off from
the network permanently or temporarily (i.e. until one of the slave
devices is found that can become a master). When this happens,
considerable complexity is introduced to maintain an up-to-date
routing structure for data through the scatternet between the APs
and the end devices.
[0024] Using a scatternet also leads to unpredictable data rates
and latencies for the end devices, because the number of
daisy-chained piconets is unpredictable. There is no minimum
guaranteed performance for the end devices positioned lower in the
chain, because it will depend on the number of devices that are
higher in the chain and the resources they consume. Moreover, as
the piconet routing structure changes, as described above, the data
rates and latencies may also change dynamically.
[0025] Accordingly, what is needed is an efficient, cost-effective
technique for enabling multiple WBPDs to connect to a network that
avoids the limitations of prior art techniques.
SUMMARY OF THE INVENTION
[0026] The present invention is directed to methods, systems,
devices, and computer program instructions for flexibly expanding
the number of end-user communication devices or WBPDs supported in
a short-range networking environment with minimal added
installation and configuration costs and enabling these devices to
access a remote network. Relay points, referred to herein
equivalently as "extension points" or "EPs", are defined and are
used to provide network connectivity to WBPDs that may be out of
range of a network access point.
[0027] An objective of the present invention is to provide an
efficient, cost-effective technique for enabling multiple WBPDs to
connect to a network.
[0028] A further object of the present invention is to provide a
short-range wireless network that allows for easy network
installation of relay points with minimal or no additional
wiring.
[0029] Another object of the present invention is to provide a
short-range wireless network that is easily scalable with minimal
or no additional wiring.
[0030] Yet another object of the present invention is to provide a
short-range wireless network in which little or no additional
maintenance (such as battery replacement, adjustment of
transmission power or location, etc.) of relay points is required
for a substantially long time.
[0031] A further object of the present invention is to provide a
short-range wireless network that is easily customized to
accommodate a coverage area having a particular size and shape.
[0032] Still another object of the present invention is to provide
a short-range wireless network that has a fixed network
configuration but is easily changeable to another
configuration.
[0033] An additional object of the present invention is to provide
a short-range wireless network that serves a large number of users
with a relatively constant data rate and set-up time for connection
establishment.
[0034] Another object of the present invention is to provide a
short-range wireless network that is scalable with only minimal
degradation of set-up time for connection establishment and in data
rate.
[0035] Objectives of the present invention are realized by
providing a hierarchical topology having intermediary tiers between
APs and end devices. These intermediary tiers are comprised of
devices which are defined herein, and which are referred to as
extension points (EPs). These EPs are designed as devices having
low power consumption requirements, comparable with the power
consumption of WBPDs. Connectivity is provided between EP devices,
between EP and AP devices, and between EP and WBPD devices, using
only short-range communication technologies. (In the preferred
embodiment, radio frequency or "RF" technology is used, and in
particular, Bluetooth technology.)
[0036] A high-gain directional antenna is added to a low-power
radio on the EP device, which also has a conventional short-range
omnidirectional Bluetooth antenna. The directional antenna enables
the EP to be placed at a further distance from the AP than when
using conventional Class 3 Bluetooth devices. (According to the
preferred embodiment, the high-gain directional antenna enables the
EP to transmit to an AP that is approximately 100 meters away.) The
area of coverage provided by EPs may be balanced with the potential
density of end devices by choosing a suitable spatial layout of the
EPs.
[0037] A novel installation procedure for EPs is defined, wherein
each EP dynamically tunes the beam of the directional antenna to
optimize the bit error rate for communications with its upstream
AP, and dynamically determines a power ratio that maintains
connectivity with the AP while minimizing the power consumption of
the EP (and while keeping the bit error rate within an acceptable
range).
[0038] A table (or other data structure) is maintained that
specifies the routes to particular end devices through the EPs of
the hierarchical topology.
[0039] An alternative, portable source of energy is preferably used
for powering up the EP devices. For example, a photovoltaic (PV)
array or PV module may be used, which recharges using the incident
lighting within the space in which the EP is located. The low
efficiency of a collector panel when using incident light can be
compensated for by enlarging the size of the collector panel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 illustrates use of an access point configuration used
to connect end-user devices to a network, according to the prior
art;
[0041] FIG. 2 depicts a configuration in which the extension points
of the present invention are used to connect end-user devices to a
network;
[0042] FIG. 3 illustrates the AP and EP devices in more detail,
showing how these devices provide a network connection for multiple
end devices, according to a preferred embodiment of the present
invention;
[0043] FIG. 4 illustrates a system in which APs communicate with
end-user devices through an intermediate tier of EPs, according to
a preferred embodiment of the present invention;
[0044] FIG. 5 illustrates a voice/data unit in which multiple APs
are located to provide communications between a voice network
and/or a data network and multiple EPs and/or multiple end-user
devices, according to an embodiment of the present invention;
[0045] FIG. 6 depicts the architecture of an EP, according to a
preferred embodiment of the present invention;
[0046] FIG. 7 provides a flowchart that depicts the logic with
which an EP is installed in an infrastructure, according to a
preferred embodiment of the present invention;
[0047] FIG. 8 illustrates a multi-tier layout using EPs, and the
connections between them, that may be provided according to an
embodiment of the present invention; and
[0048] FIG. 9 depicts a table in which information may be stored
regarding the current communication structure between EPs and APs,
according to a preferred embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0049] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings, in which a
preferred embodiment of the invention is shown. Like numbers refer
to like elements throughout.
[0050] Flowchart illustrations of aspects of the present invention
are described below. The logic of these flowcharts may be provided
as methods, systems, and/or computer program instructions embodied
on one or more computer readable media, according to an embodiment
of the invention. As will be obvious to one of ordinary skill in
the art, these flowcharts are merely illustrative of the manner in
which the associated aspects of the present invention may be
implemented, and changes may be made to the logic that is
illustrated therein (for example, by altering the order of
operations shown in some cases, by combining operations, etc.)
without deviating from the inventive concepts disclosed herein.
[0051] The present invention provides an efficient, cost-effective
technique for enabling multiple low-power wireless devices such as
PDAs or wireless telephones to connect to a fast wired or wireless
voice/data network.
[0052] FIG. 2 illustrates the topology of a system in which the
present invention operates, comprising some number of APs, EPs, and
end user devices (or simply "end devices"). These AP, EP and end
devices are structured generally in some number of tiers, with APs
at the highest tier, EPs in the middle tiers, and end devices at
the lowest tier. As shown in FIG. 2, AP devices 140-144 of the
prior art connect to a prior art network 120. There may be zero,
one, or many middle tiers of EPs, depending on the needs of a
particular environment in which the present invention is
implemented. Thus, EP 211 is shown as a single middle tier between
AP 141 of the upper tier and end device 131 of the lowest tier,
while end device 130 is connected directly to AP 141 (without an
intervening EP). In the preferred embodiment, Bluetooth is used as
the underlying wireless network technology. EP 211 therefore
functions in the master role for a piconet that has a single slave
device 131. End devices 132 and 133 each belong to a piconet having
a master represented by an EP one level higher in the topology (EPs
221 and 231, respectively).
[0053] In alternative embodiments, short-range technologies (which
are preferably RF technologies, and which may be as yet
undeveloped) other than Bluetooth may be used, without deviating
from the scope of the present invention. (It will be obvious to one
of ordinary skill in the art how the novel teachings disclosed
herein are to be adapted to other such technologies.)
[0054] EPs 212, 213, 214 form a second tier of a multi-tier
topology option, being located in the tier beneath AP 142. In turn,
these second-tier EP devices may communicate with lower-tier EP
devices, and thus EP 213 is shown as communicating with EPs 221,
222, etc., while EP 214 is not connected to any tiers in the
downstream direction. A particular EP may be connected to end
devices as well as to other lower-tier EPs, as shown for EP 231 and
its lower-tier device 133 and EP 241.
[0055] The configuration in FIG. 2 is merely illustrative of the
configurations that are possible when using the present invention.
There may be more or fewer APs than shown in this example, as well
as more or fewer EPs and tiers of EPs. When using Bluetooth, each
EP (and each AP as well) may support from 0 to 7 devices comprising
a combination of end devices and other lower-tier EPs.
[0056] End devices may establish a connection to a network such as
network 120 via any AP or EP device reachable from that end device
(provided, of course, that the AP or EP grants the request). For
example, if a Bluetooth piconet of which EP 221 is the master has
some number of active slave devices less than 7, then the piconet
can theoretically add more slave devices. End device 133 might
therefore join the piconet of EP 221, rather than the piconet of EP
231, if end device 133 can reach either EP. (In the general case,
if an end device can reach several EPs and/or APs belonging to the
same or different piconets, then the end device's network
connection can be established using any of the reachable EPs or
APs.)
[0057] Preferably, the EP devices of the present invention use a
photovoltaic (PV) array or module (commonly referred to as
solar-powered batteries, although in the present context, this is
not meant to imply a power source that is powered only by solar
radiation), in order to recharge through use of an available light
source such as the incident lighting in a room of a building.
(Traditional alkaline batteries, rechargeable batteries, or other
battery technologies may be used in alternative embodiments.) Each
AP device may have a connection to an AC or DC power network.
[0058] Referring now to FIG. 3, the design characteristics of an EP
and its connection to an AP and remote network are illustrated. In
this example, EP 320 is coupled to AP 350. The AP 350 is
communicating, via router 340 and network 120, with a remote server
342. As a result, end devices such as devices 343 and 344 can also
communicate wirelessly with server 342.
[0059] AP 350 comprises a high-power wireless communication unit
including a Bluetooth module 351, a network card 352, an
omnidirectional high power antenna 353, and other components such
as a processor, memory, and power supply (not shown in FIG. 3).
Bluetooth module 351 and omnidirectional antenna 353 are used for
communicating with EP 320, and other devices that may be located in
the piconet shown generally as area 360. The network card 352 is
used for communicating with router 340. Also, the AP is connected
to an external power supply via a power plug 355.
[0060] AP 350 and EP 320 have radio receivers (not shown) of
approximately equal sensitivity (preferably, -70 dBm). The
transmitting power of the AP is typically 20 dBm, corresponding to
Class 1 Bluetooth power requirements.
[0061] In the preferred embodiment, EP 320 includes a short-range
wireless communication unit 321 (which is preferably a Bluetooth
Class 3 module), an omnidirectional antenna 322, a directional
antenna 323, and a rechargeable power supply utilizing a collector
panel (shown at 324). Communication unit 321 enables the EP to
communicate with AP 350 (using directional antenna 323) as well as
with end devices and other EPs in its piconet (using
omnidirectional antenna 322). The range of the piconet of EP 320 is
shown generally as area 361.
[0062] The EPs of the preferred embodiment are designed as
low-power devices with minimal processing capabilities (e.g. just
enough processing capability to support functions up through the
network layer of the Bluetooth protocol stack), and minimal power
management tasks. These Bluetooth-based EPs are well suited for use
with WBPDs, as communications unit 321 generates 70 dBm
transmitting power and (through the omnidirectional antenna) covers
a range limited to 10 meters. As a result, the EP has a power
consumption similar to that of a typical end-user device. Collector
panel 324 uses a less powerful rechargeable power device such as a
PV array or module, which collects energy from the incident light
of external light sources.
[0063] Because government regulations limit the total radiation
allowed in each ISM band, both the power of the transmitter and the
gain of the antenna must be considered. Directional antenna 323
(which may be a Yagi antenna, for example) is designed to provide
about 20 dB gain in the direction of focus, therefore increasing
the radiated power to be approximately equal to that emitted by AP
Bluetooth devices, allowing it to reach distant AP receivers (that
is, AP receivers which may be greater than 10 meters away, but less
than or equal to 100 meters away).
[0064] During system installation, the narrow directional antenna
323 of the EP is oriented toward the omnidirectional antenna 353 of
the AP. As a result, the range of an EP device (via the directional
antenna 323) will now be comparable with the range of an AP (that
is, approximately 100 meters). Consequently, the EP and AP can
communicate to pass packets to and from the end devices that are
communicating with the EP, thereby giving these end devices access
to remote servers such as server 342. (The orientation procedure
that is used during system installation will be described in more
detail below, with reference to FIG. 7.)
[0065] Referring now to FIG. 4, an example short-range wireless
installation according to the present invention is shown which
comprises multiple APs (shown as elements 401-403) and multiple
EPs. Large circles 431, 432, 433 show working ranges of the APs
401, 402, 403, respectively. In the preferred embodiment, the
working range has a 100 meter radius. The small circles (e.g. as
shown at elements 420 and 421) show the working range of EPs when
they use their omnidirectional antennas (having a 10 meter radius,
in the preferred embodiment). For example, the circle 421
illustrates a short working range of EP 411. Each EP, when using
the Bluetooth technology of the preferred embodiment, may serve up
to 7 end devices. As an example, the end devices of EP 211 are
depicted generally at 412.
[0066] An EP may be capable of communicating with multiple APs, but
it only connects to one AP at a time (as will be discussed further
in the context of FIG. 5). Preferably, a device providing a network
control server function (not shown in FIG. 4) maintains a table or
other data structure (referred to hereinafter as a table, for ease
of reference) that records the current EP-to-AP associations. This
association information is used to route packets to end devices.
FIG. 9, described below, illustrates an example table structure
that may be used. The information in this table may be stored
within each AP, or a centralized repository may be used as an
alternative.
[0067] As an example of EP-to-AP associations that may be in
effect, FIG. 4 uses the numbering scheme "1.x" and horizontal hash
marks to denote the EP access ranges for all EP devices that are
active members of a piconet controlled by AP device 401. Circles
with the numbering scheme "2.x" and vertical hash marks denote the
ranges of EP devices of a piconet where AP 402 is the master, and
white circles numbered "3.x" belong to EP members of a piconet
having AP 403 as the master.
[0068] The directional range of an AP may be wide enough to cover
more than 7 EP devices. However, a limit of 7 EPs is enforced by
the Bluetooth architecture of the preferred embodiment. The
connection set-up procedure for an EP (depicted in FIG. 7 and
described below) ensures that an AP device is connected primarily
to the EP devices that are the closest to that AP, or that require
the least power to transmit reliably to that AP. The power
consumption of the EP is therefore reduced accordingly. As a result
of this set-up procedure, AP 401 communicates with all end devices
in the areas 1.1-1.7 via the corresponding EP devices. Similarly,
AP 402 communicates with all end devices in the areas 2.1-2.7, and
AP 403 communicates with all end devices in the areas 3.1-3.7.
[0069] Depending on performance requirements of a particular
environment in which the present invention is used, it may be
necessary to add more APs. The example configuration shown in FIG.
4 may serve 147 end devices simultaneously with a data rate of 14
Kbps per device. (That number of end devices is computed as
follows: (1) each of the 3 APs may support up to 7 EPs, for a total
of 21 EPs; and (2) each of these 21 EPs may support up to 7 end
devices, for a total of 147 end devices. The data rate is computed
by dividing the 720 Kbps capacity of each AP by the 49 end devices
which are supported by that AP.) The system shown in FIG. 4 can
support only 9 synchronous connection-oriented (SCO) voice channels
from those 147 devices. (The Bluetooth technology places a limit of
3 on the number of voice channels supported by a Class 1 device at
one time. Thus, the 3 APs in this example configuration can support
a maximum of 9 such channels.) In an environment where SCO channels
are in use, each AP can support approximately 400 Kbps using
asynchronous connection-less (ACL) connections (according to the
aforementioned limitations prescribed in the Bluetooth
specification). The resulting performance of each active end device
will therefore be in the range of 8 Kbps, as each AP may serve up
to 49 active end devices in this example configuration. If more AP
devices are used, or if fewer EP devices are present, the data rate
will be increased.
[0070] While FIG. 4 shows only a two-tier architecture for the
wireless network (that is, an architecture having one tier of APs
and another tier of EPs), configurations with more tiers are also
possible. (See the discussion of FIG. 8, below.) This would be
appropriate in two situations:
[0071] 1) In order to reallocate bandwidth to support high
bandwidth connections, for example by having some second-tier EPs
be designated for direct use by high-Bandwidth end devices while
other second-tier EPs support third-tier EPs which, in turn,
support low-bandwidth end devices. In a situation such as this
where the end devices are grouped according to their bandwidth
usage characteristics, the AP can pre-allocate bandwidth among the
different second-tier EPs for more efficient operation.
[0072] 2) To support more users. For example, as long as the data
rate may go as low as 3 Kbps without causing problems (and no more
than 3 simultaneous voice channels are required), a single AP using
a three-tier topology could support the same number of devices
supported by the 3 APs and two-tier topology shown in FIG. 4. In
this case, the AP will communicate with 3 EP devices on the next
lower logical tier, and each of these EP devices will be used to
connect with 7 more EP devices on the next lower tier. Each of
these 21 EPs is capable of supporting up to 7 end devices, for a
total of 147. In this manner, a total of 147 end devices can be
supported from a single AP. (A drawback to this approach is that
network set-up time and network latency grow as the number of tiers
increases.) The total number of end devices that an AP can support
in such a three-tier topology is 343, because the AP communicates
with seven EPs, each communicating with seven EPs at the next tier
(for a total of 49 EPs at this lower tier), each communicating with
7 end devices.
[0073] FIG. 5 illustrates another embodiment of the present
invention in conjunction with both voice transmission and data
transmission between end devices, data networks, and telephony
networks. A voice/data unit 510 includes several Bluetooth devices
(shown as 521, 522, 523, and 524 in this example) functioning as
APs, a network card 511, and a digital voice multiplexor 512. An
internal bus 530 feeds the ACL data to the network card 511 and to
the multiplexor 512. The multiplexor separates the voice channels
and sends them to PBX unit 541, preferably via a T1 connection. The
T1 connection may in turn be connected to a central office switch
on PSTN (public switched telephony network) 541.
[0074] Network card 511 provides IP data flow to IP network 550. A
network control server function in a server 551 coordinates the
flow of IP traffic.
[0075] The gray circles 560-566 illustrate working ranges of EP
devices numbered as EP 1.1, EP 2.1, and so forth. Assume that all
EP devices except for EP 563 are handling one active phone
conversation, and that EP 563 is idle. AP 521 is connected to EPs
560 and 561, AP 522 is connected to EP 562, AP 523 is connected to
EP 564, and AP 524 is connected to EPs 565 and 566. Now assume that
a new end device 570 enters the range of EP 563. To support this
device, the EP should establish a connection with one of the four
AP devices 521, 522, 523, or 524. Several techniques can be used to
determine which AP should be associated with the EP in order to
avoid over-burdening any of the APs (and consequently denying
service). In the preferred embodiment, the EP device 563 requests a
connection with all of the AP devices 521, 522, 523, and 524. EP
563 then completes the connection with the AP that accepts the
connection first. Because in practice the AP devices are not
synchronized with each other, a random choice of AP is assured, and
because the EP only connects with an AP that accepts the connection
request, it is sure not to over-burden the AP with which it
communicates.
[0076] FIG. 6 illustrates an architecture of an EP 600. Those
components and features of an EP that relate to the present
invention will now be discussed. (Other components and features
which use prior art technology will not be described in detail
herein.)
[0077] Bluetooth module 601 is preferably a conventional Bluetooth
radio and baseband controller. Control module 610 provides overall
control of the load on EP antennas 661 and 662, the power
functions, and some Bluetooth protocol features which are not
handled by a standard Bluetooth radio (such as higher-layer
Bluetooth protocol stack functions which do not require the radio,
including RFCOMM, Service Discovery Protocol, and the Host
Controller Interface). RF antenna control module 620 is a switching
mechanism for switching between the directional antenna 661 and
omnidirectional antenna 660. Power supply unit 630 supplies power
for operation of the EP 600.
[0078] The radio output of the Bluetooth module 601 is amplified by
the power amplifier 622 and, via the RF demultiplexor or switch
621, is fed to one of the antennas 660 or 661. The control
processor 611 controls 614 the amplification ratio and switching
direction.
[0079] The optimal amplification ratio is determined during system
installation (or perhaps during subsequent troubleshooting) to
provide a signal that is transmitted from EP 600 and received by an
AP device while having a minimal bit error rate (BER). During
installation, the Bluetooth transmitter power is preferably set
initially to its maximum value, and a tuning process is then
performed which reduces the transmission ratio until reaching an
optimal level (as will be described with reference to FIG. 7). The
control processor 611 utilizes this ratio until completion of the
tuning process.
[0080] Based on input from control processor 611, demultiplexor 621
connects the output of the power amplifier to (1) the directional
antenna 661 feeder for all the transmissions between an AP and EP,
or between an EP and other EP devices, and to (2) the
omnidirectional antenna 660 feeder for transmissions between an EP
and end devices.
[0081] The native radio amplifier (not shown) within the radio 602
of Bluetooth module 601 dynamically adjusts the power of the radio
output to keep the BER below a threshold value prescribed by the
Bluetooth specifications, as in Bluetooth modules of the prior
art.
[0082] Power supply unit 630 includes a rechargeable battery unit
632 and a charge control system 634. Based on the measurements of
current supplied by collector panel 631, and depending on the power
consumption of the EP, control processor 611 varies the current
which is received from the collector panel 631, thereby
compensating the power consumed by the system and keeping the
current below the threshold specified for battery charging by the
battery manufacturer.
[0083] An EP installation procedure includes the set-up of the
nominal power of transmission, and pointing the directional antenna
toward an AP. The installation procedure determines the nominal
power and proper direction for the antenna dynamically, in a manner
that is targeted to achieve reliable communication between the AP
and EP with minimal EP radio transmission power. A power ratio "R"
determines the amplification of the power amplifier 622, and an
angle "A" characterizes the position of the directional antenna
beam relevant to the base of the EP. The values for power ratio R
and directional angle A are preferably stored in a non-volatile
memory 671, and may be changed during a new installation or tuning
process.
[0084] FIG. 7 provides a flowchart depicting the logic that may be
used for the EP installation procedure, according to the preferred
embodiment. The procedure involves first positioning the
directional antenna (element 661 of FIG. 6) at the edge of the
usable angle for communicating with the AP. Having done this, the
EP determines the angle A that provides the lowest BER. Finally,
the EP determines the minimal power R that is required to maintain
connectivity with the AP. This installation process is performed
for the EPs at the highest tier, which communicate directly with
APs, as well as for those EPs in intermediate tiers which
communicate with another upstream EP as if the upstream EP was an
AP. (Thus, references in the description of FIG. 7 to communicating
with an AP are intended to include actual AP devices as well as
these upstream EPs.)
[0085] The process begins at Block 701, where the power ratio R is
set to 100 percent (providing the maximum transmission power of the
EP) and the angle A is set to 0 (establishing a starting position
for the directional antenna). In an alternative approach to tuning
the power ratio, the value of R may be set to 50 percent in Block
701, representing the midrange of the transmission power of the EP
(with corresponding modifications to the logic in Blocks 716-719).
Or, other initial values may be used as a starting point, as
desired in a particular implementation of the present
invention.
[0086] At Block 702, the EP requests a connection with an AP. The
EP processor checks to see if a connection with the AP is
established (Block 703). If the test in Block 703 has a negative
result (i.e. the connection is not established), then at Block 704
the EP beam direction is changed by a small angle "a" in a
particular predetermined direction (e.g. counterclockwise). Control
then returns to Block 702 to re-attempt connection with the AP.
[0087] For simplicity, the direction of the beam is rotated only
around the vertical dimension, so that only one angle is applicable
to the tuning and positioning procedure; alternative embodiments of
the present invention may rotate the beam along multiple axes, as
will be evident to those skilled in the art. While the direction of
the beam may be changed by several means, including manually (e.g.
by hand) or automatically (e.g. by using a step motor or
capacitance array), the specific method used does not form part of
the present invention and is not illustrated in detail herein.
[0088] Block 705 is reached when the test in Block 703 has a
positive result (i.e. the connection with the AP is established).
Blocks 705 and 706 then perform an iterative process of determining
how far the antenna can move while still remaining connected to the
AP. Thus, Block 705 moves the EP directional beam again in the same
predetermined direction, by the same angle "a". Block 706 tests to
see if the connection has now been broken. If not, control returns
to Block 705 to change the angle again. When the connection breaks,
the test in Block 706 has a positive result and control reaches
Block 707. Blocks 707-709 perform an iterative process to return to
the edge of the usable angle. At Block 707, the EP directional beam
moves in the opposite direction, by the same angle "a". At Block
708, the EP requests connection to the AP. Block 709 checks to see
if the connection is (re)established. If not, control returns to
Block 707 to move the antenna again; otherwise, when the connection
is established, it means that the antenna beam is now on the edge
of the usable angle, and processing continues at Block 710.
[0089] It should be noted that the sequence of steps in Blocks 702
through 709 supports the possibility that the antenna is initially
positioned within contact with the AP. If the antenna is not
initially positioned within contact with the AP, then these steps
can be optimized as a single direction sweep until it first comes
in contact with the AP.
[0090] At Block 710, the processor measures the BER of a test
sequence sent by the AP and stores this measured value. This BER is
preferably stored in a two-dimensional table which shows the BER as
a function of the current value of angle A. Blocks 711-713 then try
other angles in an iterative manner to see what the BER of those
angles is, such that the angle providing the lowest BER can be
selected. At Block 711, the beam angle is changed again, in the
same direction as in Block 707. Block 712 records the BER of this
value of angle A, and Block 713 then tests to see whether
connectivity with the AP has been lost. (For purposes of Blocks 713
and 717, connectivity is considered to be lost when either (1) no
communication is possible or (2) the encountered BER exceeds some
threshold.) If so, then the angle of the directional antenna has
been changed too far, and control transfers to Block 714 to
determine the most suitable angle to use; otherwise, control
returns to Block 711 to repeat the movement of the beam and testing
of the BER.
[0091] Testing of the BER as a function of angle A, and using this
information to determine an optimum angle for the directional
antenna on the EP device, are novel teachings of the present
invention. The calculation of BER values, as implemented by the
native Bluetooth protocol, may be used as the antenna angle is
being repeatedly changed. (Note that while the Bluetooth
specification teaches computing a BER value, once the value is
within the range required by the specification no further movements
or tests are performed in the prior art technique. The present
invention, on the other hand, continues to perform tests to
determine the proper angle adjustment.)
[0092] Upon reaching Block 714, connectivity with the AP has been
lost. The processor thus searches through the pairs of (angle. A,
BER) information that were recorded at Blocks 710 and 712, in order
to find an angle whose corresponding BER is minimal. The value of
angle A from the pair thus located is recorded in non-volatile
memory (such as non-volatile memory 671 depicted in FIG. 6) at
Block 715. The antenna is then re-positioned to angle A before
continuing at Block 716.
[0093] Blocks 716 and 717 then iteratively determine the minimal
power ratio R required to maintain connectivity with the AP (and
thereby minimize the EP's power consumption). Recall that a default
value to use as a starting point was set in Block 700. At Block
716, the EP processor reduces its transmission power by some small
step "r" as the AP continues to transmit a test pattern. Block 717
checks to see if connectivity has been lost. If not, control
returns to Block 716 to reduce the power yet again. This reducing
of the power and checking the connectivity continues until the
connection is lost, at which time control transfers to Block
718.
[0094] Upon reaching Block 718, the current power ratio R yields an
unacceptable BER, so a constant "k" is used to increase the power
and ensure that the transmitting power will stay at a level
sufficient for reliable communication. In actual practice, the
value of "r" is chosen so that the precision of measurement will be
sufficient to determine the proper value for R under a minimal
number of steps with the standard noise power (which is
predetermined in the Bluetooth specification). The number "k" is
chosen to provide sufficient reliability of transmission without a
substantial increase in power consumption (and is therefore an
engineering decision).
[0095] At Block 719, the value of power ratio R is preferably
stored in non-volatile memory along with the value of angle A, and
the installation procedure of FIG. 7 then ends. The EP is now ready
for establishing connections with end devices. (Note that the
tuning procedure described with reference to FIG. 7 may also be
used for end devices, when those devices have a directional
antenna.)
[0096] Referring now to FIG. 8, a configuration is shown for a
possible layout and connections between tiers of EP devices. This
example shows three intermediate tiers of EP devices, designated by
reference numbers 810, 820, and 830. AP device 800 represents the
upper tier of this configuration. AP 800 serves as a master of the
piconet which includes the EP devices comprising tier 810.
[0097] For simplicity of illustration, all EP devices in FIG. 8 are
assigned a four digit number sequence that describes the path
between that EP and the AP. The first non-zero digit represents the
Bluetooth device address ("BD_ADDR") of the EP that is directly
communicating with the AP; subsequent digits designate EPs along
the path communicating with the EP identified by the previous
digit. Thus, the number 1000 refers to the BD_ADDR of EP 811
connected to AP 800; the number 2000 refers to the BD_ADDR of
second EP 812 connected to AP 800; etc., and "i000" refers to the
BD_ADDR of the i-th EP 813 connected to AP 800. (Recall that in the
Bluetooth environment of the preferred embodiment, values for the
"i", "j", "k" and "l" of FIG. 8 are all less than or equal to
7.)
[0098] Likewise, the sequence 1100 represents the BD_ADDR of EP 821
connected to the EP identified by 1000 (because EP 1000 is a master
of a piconet in tier 820, which includes EP 1100). If tier 820
includes "i" piconets with "i" masters on the upper tier 810, then
the last EP in the "i-th" piconet will have a number ik00.
[0099] Considering that end devices sporadically request services
from a closely located EP or AP in practice, a centralized control
mechanism is preferably provided for use by the EP and AP devices.
In the preferred embodiment, a network control server function is
utilized, which supports a table (or other equivalent data
structure) representing the current communication structure between
EPs and APs. Each EP or AP preferably has a unique record, referred
to herein as an "extension point parameters block" or "EP_PB", in
this table. The EP_PB table may be used for a number of purposes,
including provision of information to applications that are
concerned with locations of (and routes to) the end devices.
[0100] FIG. 9 illustrates a preferred embodiment of the structure
of the table 900 that stores the EP_PB records. For purposes of
illustration but not of limitation, the table is shown as having
four fields. These fields will now be described in more detail.
[0101] Field 902 stores the routing path, where "a1, a2, a3, . . .
a(i-1)" represents the BD_ADDR fields of the routing path of data
flowing between this EP or AP device and the AP master at the top
of the hierarchical topology. (The sequence a1, a2, . . .
corresponds to the numerical identifiers assigned to. EPs, as shown
in FIG. 8.)
[0102] Optional field 903 stores 3-dimensional coordinates of the
EP or AP device, which in the preferred embodiment are either earth
coordinates or local coordinates that are relative to the zero
coordinates in this particular installation. Those coordinates are
established during installation of the device (using prior art
techniques).
[0103] Optional fields 904 and 905 represent the load on this EP or
AP device. In the preferred embodiment, this comprises a
specification of the number of SCO links and ACL links that are
active at this device, respectively.
[0104] Referring again to FIG. 8, EPs may communicate with other
EPs. This communication may happen in two ways. First, an EP may
communicate with another EP using their omnidirectional antennas
(as in standard Bluetooth communications). For example, device
EP1000 (element 811) may communicate with device EP1100 (element
821), where EP1100 is a member of a piconet for which EP1000 is the
master. Second, a lower-tier EP may use its directional antenna to
communicate with a higher-tier EP. From this point of view, the
lower-tier EP would not see a difference between talking to the
higher-tier EP and talking to a standard AP. As an example (not
illustrated in FIG. 8), EP device i110 (element 831) may
communicate directly with EP device i000 (element 813), without
passing the communications through intermediate EP device i100
(element 822). (This second type of communication is not strictly
limited to EPs that are in different hierarchical tiers. For
example, device EP1100 may communicate with device EPi100 using its
directional antenna, if desired, even though these devices are
shown as being in the same logical tier.)
[0105] Commonly-assigned U.S. Pat. No. 6,633,761 (Ser. No.
09/637,742, filed Aug. 11, 2000) and U.S. Pat. No. 6,691,227 (Ser.
No. 09/657,745, filed Sep. 08, 2000), which are titled "Enabling
Seamless User Mobility in a Short-Range Wireless Networking
Environment" and "Location-Independent Packet Routing and Secure
Access in a Short-Range Wireless Networking Environment",
respectively, deal with providing seamless network connectivity by
having access points coordinate with a core server to perform
various functions and with providing transparent address
translation as a client device roams through a short-range wireless
networking environment. The network control server functionality
described in the present invention may be co-located with either,
or both, the core server and the routing table coordinator of these
commonly-assigned inventions.
[0106] As has been demonstrated, the present invention provides a
number of advantages over prior art solutions for connecting WBPDs
to remote networks. Wireless EPs are defined and are used to relay
information between APs and end devices. Minimal or no additional
wiring is needed to add the wireless EPs to an infrastructure.
Maintenance, such as replacing the rechargeable power supply or
batteries, adjusting transmission power, and adjusting location of
EPs for covering a fixed area, should need to be done quite
infrequently. (It is anticipated that maintenance will be limited
to replacement of batteries, which should be required no more often
than once per year.) Customizing the topology of an installation is
simple and inexpensive when using the present invention: Existing
EPs may be moved, or additional EPs added, with no change (or at
worst, with a minor amount of change) to the physical wiring.
Furthermore, such changes require a simple reconfiguration process
wherein the installation set-up procedure is repeated. A novel
tuning technique is used for EP installation, wherein the EP
dynamically learns the best angle and power ratio for communicating
with its AP. A larger number of WBPDs can be supported efficiently
than when using prior art solutions, yet the connection
establishment time and data rate do not suffer the degradation that
occurs in prior art scatternet systems.
[0107] The foregoing description of a preferred embodiment is for
purposes of illustrating the present invention, and is not to be
construed as limiting thereof. Although a preferred embodiment has
been described, it will be obvious to those of skill in the art
that many modifications to this preferred embodiment are possible
without materially deviating from the novel teachings and
advantages of this invention as disclosed herein. Accordingly, all
such modifications are intended to be within the scope of the
present invention, which is limited only by the claims hereafter
presented (and their equivalents).
* * * * *
References