U.S. patent application number 10/725818 was filed with the patent office on 2005-03-17 for infrastructure for wireless lans.
This patent application is currently assigned to Symbol Technologies, Inc., a Delaware corporation. Invention is credited to Beach, Robert, Schwede, Heiner.
Application Number | 20050058087 10/725818 |
Document ID | / |
Family ID | 22100484 |
Filed Date | 2005-03-17 |
United States Patent
Application |
20050058087 |
Kind Code |
A1 |
Beach, Robert ; et
al. |
March 17, 2005 |
Infrastructure for wireless lans
Abstract
A wireless data communications system includes simplified access
points which are connected to ports of an intelligent switching
hub. The switching hub relays data packets to the access points in
accordance with destination address data in the data
communications. In a preferred arrangement the access points are
provided with power over the data cable from the switching hub
location.
Inventors: |
Beach, Robert; (Los Altos,
CA) ; Schwede, Heiner; (Los Altos, CA) |
Correspondence
Address: |
Watts, Hoffmann Co., L.P.A.
P. O. Box 99839
Cleveland
OH
44199-0839
US
|
Assignee: |
Symbol Technologies, Inc., a
Delaware corporation
|
Family ID: |
22100484 |
Appl. No.: |
10/725818 |
Filed: |
December 1, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10725818 |
Dec 1, 2003 |
|
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|
09231625 |
Jan 14, 1999 |
|
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|
60071302 |
Jan 16, 1998 |
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Current U.S.
Class: |
370/257 |
Current CPC
Class: |
H04W 52/0216 20130101;
H04W 8/26 20130101; H04W 52/0203 20130101; Y02D 70/142 20180101;
Y02D 30/70 20200801; H04W 88/08 20130101; H04L 12/4625 20130101;
H04W 84/12 20130101 |
Class at
Publication: |
370/257 |
International
Class: |
H04L 012/28 |
Claims
1. In a wireless data communications system wherein data
communications are provided between mobile units and a central
computer via access points, the improvement wherein at least some
of said access points are connected to said central computer
through at least one data switching hub, and wherein said data
switching hub is arranged to selectively provide data
communications to access points connected to said hub in accordance
with destination address data in said communications, wherein at
least some of the access points each provides a conduit for data
communications to the mobile units independently of destination
address data in said communications that identify a mobile
unit.
2. The improvement specified in claim 1 wherein said data switching
hub is arranged to monitor source address data in communications
received from each access point connected to a port of said data
switching hub, wherein said switching hub is arranged to maintain a
routing list correlating said source address data with said port of
said data switching hub and wherein said switching hub is arranged
to use said list to selectively provide said data communications to
said access points.
3-7. (cancelled)
8. A method for providing data communications between mobile units
and a central computer comprising: connecting said central computer
to at least one switching hub over a wired data communications
network; connecting a plurality of access points to ports of said
switching hub; associating mobile units with selected ones of said
access points; providing data communications packets on said wired
communications network, said packets including destination
addresses each identifying a mobile unit; maintaining a routing
list at said switching hub relating said ports to said access
points and to said mobile units associated with said access points;
operating said switching hub to relay data communications packets
from said wired data communications network to said access points
in accordance with said routing list; and relaying data
communications received from said switching hub by said access
points to associated mobile units by radio communications
independently of the destination addresses identifying the mobile
units in the data communications packets.
9. A method as specified in claim 8 wherein said access points are
arranged to not relay a selected type of data communications
received from said switching hub.
10. A method as specified in claim 8 further including the steps of
providing data communications packets from one of said mobile units
by radio communications to an associated access point, said packets
including a destination address and a source address corresponding
to said mobile unit; relaying data communications packets received
by said access points from said mobile units to a port of said
switching hub; and operating said switching hub to relay said data
communications packets received from said access points to said
wired data communications network or said other access points in
accordance with said destination address and to update said routing
list at said switching hub by relating said port of said switching
hub to said source address of said data packet.
11. A method as specified in claim 10, wherein said mobile units
are arranged to associate with one of said access points for radio
data communications therewith, and wherein said mobile units are
further arranged to send a data communications message upon
association with an access point, said message causing said
switching hub to update said routing list with the address of said
mobile unit.
12. A method as specified in claim 10 wherein said mobile units are
arranged to associate with one of said access points for radio data
communications therewith, and wherein said access points are
arranged to send a data communications to said switching hub, when
a mobile unit becomes newly associated with said access point, said
message having a source address corresponding to said newly
associated mobile unit and causing said switching hub to update
said routing list with the address of said mobile unit.
13. A data communications system for providing data communications
between at least one computer and a plurality of mobile units,
comprising: a plurality of access points, each arranged for
providing radio data communications and having a wired data
interface; a plurality of mobile units, each arranged to associate
itself with one of said access points and conduct radio data
communications therewith; at least one switching hub having a first
wired data port and a plurality of additional wired data ports,
each connected to said wired data interface of one of said access
points; and a wired data communications network for providing wired
data communications between said at least one computer and said
first wired port of said switching hubs wherein data is
communicated over said wired data communications network as data
packets, each of said packets having destination address data
identifying one of the mobile units and wherein said switching hub
is arranged to examine said destination address data and provide
said data packets to one of said additional wired ports if said
destination address data corresponds on a routing list to an
address associated with said one additional wired port, and wherein
at least some of the access points are arranged to process the data
packets independently of the destination address data.
14. (cancelled)
15. A data communications system as specified in claim 13 wherein
data is communicated as data packets from said access points via
said wired data interface to one of said additional wired data
ports of said switching hub, said data packets including source
address data, and wherein said switching hub is arranged to examine
said source address data and to associate the corresponding source
address data with said one additional port on said routing
list.
16. A data communications systems as specified in claim 13 wherein
said wired data interface of said access points are connected to
said additional wired data ports of said switching hubs over
multiconductor cables, and wherein said multiconductor cables are
arranged to provide power to said access points.
17. A data communications system as specified in claim 16 wherein
there is provided a power supply module associated with said
switching hub for providing power to said multiconductor
cables.
18. In a wireless data communications system wherein there are
provided access points for interconnecting mobile units in radio
communications with said access points and a wired data
communications network, the improvement wherein at least some of
said access points are supplied with power using data
communications cables of said wired data communications network,
wherein at least some of the access points are arranged to forward
data communications received from the wired data communication
network independently of address data in said communications
identifying the mobile units.
19. A distributed wireless communication system comprising: a
communication hub including a communication interface for receiving
data packets each addressed to a corresponding one of a plurality
of mobile units; a plurality of access points distributed remotely
from the hub, wherein each access point includes a wired
communication interface for communicating with the communication
hub, and a transmitter/receiver for communicating with one or more
of the mobile units; wherein the communication hub is arranged to
forward each received data packet addressed to one of the mobile
units to a selected one of the access points; and wherein each of
the access points are arranged to forward each data packet
addressed to one of the mobile units that is received from the
communication hub independently of address data in said received
packet identifying said mobile unit.
20. The system of claim 19 further comprising cables each coupling
the communication hub to a corresponding one of the access points,
wherein each cable is coupled to the wired communication interface
at the corresponding access point for communicating with the
communication hub.
21. The system of claim 20 wherein each of the cables includes
conductors for carrying supply power from the communication hub to
the corresponding access point.
22. A method for providing wireless access using a wireless
communication system comprising a communication hub and a plurality
of access points distributed remotely from the communication hub,
the method comprising: receiving at the communication hub a data
packet including address data identifying a corresponding one of a
plurality of mobile units; selecting one of the plurality of access
points according to the address data in the received packet;
forwarding the data packet to the selected access point; and
receiving the data packet at the selected access point and
transmitting the data packet over a wireless network independently
of the address data in the data packet.
23. The method of claim 22 further comprising: powering each of the
access points by passing supply power over a corresponding cable
from the communication hub to the access point, wherein said cable
is also used for passing data packets between the communication hub
and the access point.
Description
BACKGROUND OF INVENTION
[0001] This invention relates to wireless data communications
networks, and in-particular to arrangements for communications
between mobile data handling units and a central computer using
such networks.
[0002] The assignee of the present invention supplies a wireless
data communications systems known as the Spectrum 24.RTM. System,
which follows the communications protocol of IEEE Standard 802.11.
In the system as implemented, mobile units are in data
communication with a central computer through access points. The
access points communicate with the computer over an Ethernet wired
network. Each of the mobile units associates itself with one of the
access points. In order to maintain order and reduce radio
communications each access point must determine which of the
communications received over the Ethernet link from the central
computer is destined for a mobile unit associated with that
particular access point. This requirement adds significant
computational capacity to the access point, increasing the cost
thereof.
[0003] In addition, in applications that must support a high volume
of data communications from multiple users, such as systems
supporting a self-service shopping system, hospital systems,
systems that include paging or voice data links to many users, or
systems supporting communicating with electronic shelf labels,
additional access points are required to support the data
communications traffic, increasing the overall system cost.
[0004] The cost of an operational access point is dependent not
only on the complexity thereof and the requirement for high speed
processing of data pockets for purposes of selecting those destined
for mobile units associated with an access point, but the
additional cost of the installation of electrical power to the
location of the access point, and the cost of a power supply to
convert AC electrical power to DC power for the circuits of the
access point. Further cost may be involved in physically mounting
the access point hardware and antenna.
[0005] It is therefore an object of the present invention to
provide an improved wireless data communications network with lower
cost access points, to enable the economical provision of reliable
wireless data communications with increased capacity and in complex
installations at reasonable cost.
SUMMARY OF THE INVENTION
[0006] In accordance with the invention there is provided an
improvement in a wireless data communications system wherein data
communications are provided between mobile units and a central
computer by access points. In accordance with the improvement, some
of the access points are connected to said computer through at
least one data switching hub, and said data switching hub is
arranged to selectively provide data communications to the access
points connected to the hub in accordance with destination address
data in the communications. The data switching hub may also be
arranged to monitor source address data in communications received
from each access point connected to a port of the data switching
hub. The switching hub can be arranged to maintain a routing list
correlating the source address data with the port. The switching
hub is arranged to use the list to selectively provide the data
communications to the access points.
[0007] In accordance with the invention there is provided an access
point for use in a wireless data communications system wherein
access points in radio data communication with mobile units are
connected to at least one data switching hub for selectively
providing data communications to the access points. A
transmitter/receiver provides the radio data communication with the
mobile units. A data interface is provided for data communications
with the switching hub over a cable. A processor is provided for
coupling data between the data interface and the transmitter
receiver and a power supply is provided for receiving operating
power from the cable and to provide power to the interface, the
processor and the transmitter/receiver.
[0008] In accordance with the invention there is provided a method
for providing data communications between mobile units and a
central computer. The method includes the steps of connecting the
central computer to at least one switching hub over a wire data
communication network and connecting a plurality of access points
to ports of the switching hub. Mobile units associate themselves
with selected ones of the access points. Data communication packets
are provided on the wired communication network which include
destination addresses. The switching hubs maintain a routing list
relating ports to the access points and the mobile units associated
with the access points. The switching hub is operated to relay data
communication packets from the wired data communications network to
the access points in accordance with the routing lists. Data
communications received from the switching hub by the access points
are sent to the associated mobile units by radio
communications.
[0009] In a further arrangement of the method data communications
are provided from one of the mobile units by radio communications
to an associated access point, the packets including a destination
address and a source address corresponding to the mobile unit. The
access points relay the data communications packets to a port on
the switching hub, and the switching hub is, operated to relay the
data communications packets received from the access points to the
wired data communication network or to other access points in
accordance with the destination address. The switching hub also
updates the routing list at the switching hub by relating the port
of the switching hub to the source address of the data packet.
[0010] In accordance with the invention there is provided a data
communications system which provides data communications between at
least one computer and a plurality of mobile units. The system
includes a plurality of access points, each arranged for provided
radio data communications and having a wired data interface. There
is also provided a plurality of mobile units, each arranged to
associate itself with one of the access points and conduct radio
data communications therewith. There is provided at least one
switching hub having a first wired data port and a plurality of
additional wired data ports, each connected to the wired data
interface of one of the access ports. There is finally provided a
wired data communication network for providing wired data
communications between at least one computer and the first wired
port of the switching hub.
[0011] In such a data communications system, wherein data is
communicated over the wired data communication network as data
packets, each having a destination address data, the switching hub
is arranged to examine the destination address data and provide the
data packets to one of the additional wired ports if the
destination address data corresponds to an address on a routing
list associated with the additional wired port. In a preferred
embodiment, data is communicated from the access points over the
wired data interface as data packets to one of the additional wired
data ports of the switching hub. The data packets include source
address data and the switching hub is arranged to examine the
source address data and to associate the corresponding source
address data with both the additional port on the routing list. In
a preferred arrangement the access points are connected to the data
ports of the switching hub over multi-conductor cables and the
cables can be arranged to provide power to the access points. The
power may be provided using a power supply module adjacent to
switching hub. Alternatively, the power supply module may be housed
inside the switching hub.
[0012] For a better understanding of the present invention,
together with other and further objects, reference is made to the
following description, taken in conjunction with the accompanying
drawings, and its scope will be pointed out in the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a block diagram of a wireless communications
system in accordance with the present invention.
[0014] FIG. 2 is a flow diagram illustrating the processing in a
hub of the FIG. 1 system.
[0015] FIG. 3 is a block diagram illustrating one embodiment of an
access point useable in the FIG. 1 system.
[0016] FIG. 4 is a cross-sectional view of a building showing the
use of the FIG. 1 system.
[0017] FIG. 5 is a block diagram of an alternate embodiment of an
access point usable in the FIG. 1 system.
[0018] FIG. 6 is a top view of a building showing the use of the
FIG. 1 system.
[0019] FIG. 7 is a block diagram showing supply of power to access
point cables.
[0020] FIG. 8 is a block diagram showing a radio-module according
to the prior art used with the access point of FIG. 3.
[0021] FIG. 9 is a block diagram showing a further alternate
embodiment of an access point usable in the FIG. 1 system.
[0022] FIG. 10 is a block diagram showing one arrangement for
providing d.c. power to an access point.
[0023] FIG. 11 is a perspective view of an access pointy enclosure
according to one embodiment of the invention.
[0024] FIG. 12 is a side view of an alternate embodiment of an
access point enclosure.
[0025] FIG. 13 is a circuit diagram of choke circuit useful in
practicing the present invention.
DESCRIPTION OF THE INVENTION
[0026] Referring to FIG. 1,.there is shown a wireless data
communications systems according to the present invention for
providing data communications between a central computer 10 and a
plurality of mobile units 12. The system uses access points 14 to
provide radio packet communications with the mobile units 12 using
the frequency hop. spread spectrum communications protocol of TFI
Standard 802.11, whereby the radio modules in the mobile units 12
monitor polling signals from the access points 14 and associate
with an access point for purposes of data communications. The radio
modules of the mobile units and access points may, for example, be
identical to those used in the Spectrum 24.RTM. system.
[0027] In prior systems each access point is connected on an
Ethernet wired network to the central computer. The access points
are required to determine the identity of mobile units which have
become associated with them and to extract from the data packets on
the network those packets addressed to a mobile unit associated
with the access point. This requirement has led to significant
processing burden for the access points and led to increased cost
for the access points.
[0028] In the system of FIG. 1, the central computer 10
communicates over an Ethernet wired network 18 with intelligent
switching hubs 16. Alternately a Token ring network can be used.
Switching hubs 16 determine the destination of each packet and
route packets to access points 14 if the destination of the packet
is a mobile unit 12 associated with the access point 14. To achieve
this function, the hub is an intelligent hub which maintains a
routing list of mobile units 12 and their associated access point
14 according to the port of each hub. These lists are generated
using the packet handling process of FIG. 2, wherein at step 30 the
hub processor reads the packet source address data and packet
destination address data of each packet received on one of its
ports. The source address data is used at step 32 to update a
routing list 34 which identifies a hub port with a data source
address. The destination address data of the packet is used at step
36 to determine which port to route the packet to, according to the
port associated with that address in routing list 34. At step 38
the packet is routed to the appropriate port.
[0029] In practice, the hub need only maintain a source list 34 for
those access points 14 connected to the hub 16 and mobile units
associated with access points 14 connected to the hub 16. Thus, if
a packet is received at a hub over the Ethernet 18 with a
destination address which is not associated with that hub, the
source address need not be maintained on list 34. The hub will
route the packet to an access point only if the destination address
of the packet is identified on list 34, otherwise the packet is
ignored. When a packet is received on a hub port associated with a
communications line 20 connected to an access point, the source
address is associated with the hub port in list 34. The packet is
routed either to the Ethernet connection 18 or to another port
according to the destination address.
[0030] Advantageously, in order to update the list maintained by
hub 16, upon initial association of a mobile unit with an access
point, either the mobile unit or the newly associated access point
provides a message packet, such as a broadcast message to the hub
16, with the source address of the message corresponding to the
mobile unit. Upon receiving this message, the hub update its list
to include the association of the mobile unit with the port at
which the access point is connected.
[0031] By determining destination address in hub 16 and maintaining
the association of a mobile unit 12 with an access point 14
connected to a port of hub 16 in routing list 34 of hub 16, the
functionality required of the access points is greatly reduced. The
access point acts merely as a conduit sending RF transmissions of
packets received on communication line 20, and receiving
transmission from associated mobile units 12 and providing Ethernet
packets to hub 16. In addition, the access point 14 must provide
mobile unit association functions as provided in the Spectrum
24.RTM. system and may also provide proxy polling responses for
associated mobile units 12 that are in power saving mode.
[0032] While the access point 14 routinely functions as a conduit
of communication to its associated mobile units, some limited
selection of data packets is possible. In particular, for example,
the access point 14 may be arranged not to relay certain types of
broadcast messages, such as router broadcast messages, that are not
required to be received by the mobile units. In another
arrangement, multiple access points may be connected in parallel to
a single hub, in which case the access points can be arranged to
not relay messages directed at mobile units associated with other
access points.
[0033] FIG. 8 is a block diagram of a radio module 50 for use in
the Spectrum 24.RTM. system. The module includes components,
including a microprocessor and program, for carrying out
frequency-hop, spread-spectrum communications utilizing the IEEE
Standard 802.11 in the 2.4 GHz. frequency band. Radio module 50
includes 80C188 processor 60, operating under the Galaxy firmware
from Symbol Technologies and associated with the interface protocol
of the Spectrum 24.RTM. system. Firmware is stored in flash memory
62, and SRAM 64 provides processing memory and data buffer
functions. Interface 58 may be an S24 DRVP low-level polled
interface module.
[0034] Utilizing radio module 50 as a unit, a simplified access
point configuration is shown in FIG. 3. Radio module 50 is
connected via its PCMCIA interface 58 to data bus 71, which is also
connected to processor 72, SRAM 70 and to Ethernet interface module
74, comprising a CS8900 Ethernet controller available from Cirrus.
Firmware for processor 72 may be provided on memory 62 coupled to
bus 56, or alternately may be booted from flash memory 62 to SRAM
70. Processor 72 operates with Ethernet controller 74 as part of
its memory space accessible through DMA to transfer messages
between Ethernet controller 74 and radio module 50 via buffer
70.
[0035] An alternate arrangement is shown in FIG. 5. In the access
point 14' of FIG. 5, the components of radio module 50 are modified
to provided direct interface via ASIC 84 to Ethernet controller 74
via a DMA channel in interface 84. The radio module and interface
transfer are handled by CPU 78, which is provided with combined
firmware on flash memory 82 and using an enlarged SRAM 80.
[0036] Still another alternate arrangement is shown as access point
14", in FIG. 9. In access point 14", the CPU, ASIC, and Ethernet
controller functions are provided by CPU 90, so that only a single
processor is required.
[0037] In accordance with a further feature of the present
invention, the simplified access points 14, 14' and 14" are
provided with power over the Ethernet cabling. In particular, the
Ethernet data communication with the access points are carried on
two of the four wire pairs on the Ethernet cable 20. The remaining
two pairs of cable 20 are used to supply dc power to the access
points. Referring to FIG. 7, hub 16 includes an intelligent
switching hub 40 of standard design having an Ethernet port to
cable 18 and, for example, seven additional Ethernet ports to
cables 20 for connection to access points 14. D.C. power module 42
is connected between the access point ports of hub 40 and cables 20
to provide D.C. power, e.g. 12 to 50 V.D.C. to the extra wire pairs
of cables 20. The D.C. power module may be incorporated internally
to the hub.
[0038] Each access point includes a DC-DC power supply 76 for
converting the DC voltage from cable 20 to an appropriate level,
e.g. 5 volts, to operate the logic and radio circuits of the access
point.
[0039] Another arrangement for providing power to the access point
is shown in FIG. 10. Choke circuits 42 are interposed in cable 20
from switching hub 40 to access point 14. D.C. power from a power
supply 41, which may also serve hub 40, is coupled to cable 20
using, for example, the choke circuit 42, shown in FIG. 13, which
is available from Pulse of San Diego, Calif., Model P0421. Using
this circuit the D.C. power is carried on all lines of cable 20.
Capacitors in circuit 42 isolate the D.C. source from the data
ports at hub 40 and access point 14, while the inductive circuits
prevent the power supply from loading the high frequency data
signals.
[0040] Using the features of the present invention, the cost,
complexity and size of the access point is reduced significantly.
The access point requires no connection to primary power and is
connected only by the Ethernet cable 20 to the hub 16. In addition,
a simple antenna 102 may be mounted within, or directly on the
module as shown in FIG. 11 to provide a simple package, about the
size of a portable tape player, that can be easily mounted on a
wall or ceiling, possibly using Velcro or adhesive attachment. The
access point may include a pair of cable sockets 104, 106 to
accommodate a cable to the hub 16, and possibly an extension cable
to accommodate an additional access point or other device connected
to the same port of hub 16. Sockets 104 and 106 are wired in
parallel.
[0041] In another arrangement, access point 14 may be provided with
a connector jack 108, which is received in a socket 110 on a wall
or surface mounted unit 112, as shown in FIG. 12.
[0042] FIGS. 4 and 6 show examples of how the system of the present
invention can be advantageously used to provide extensive access
point installation in facilities. FIG. 4 shows installation in a
multi-storied building, such as an office building or hospital,
wherein access points 14 can be installed economically in many
rooms on a floor and connected to a hub 16 on each floor. Improved
coverage and improved capacity can be provided.
[0043] FIG. 6 shows installation in a large-store, e.g. a store
using a self service shopping system with radio data communications
using portable terminals or electronic shelf labels with wireless
communication. Access points can be provided at many locations
throughout the store to avoid dead zones, and additional access
points can be provided near the check-out stations to handle the
possibility of greater usage demand in that area.
[0044] While there have been described what are believed to be the
preferred embodiments of the present invertion those skilled in the
art will recognize that other changes and modifications may be made
thereto without departing from the spirit of the present invention,
and it is intended to claim all such changes and modifications as
fall within the true scope of the invention.
* * * * *