U.S. patent application number 13/966883 was filed with the patent office on 2013-12-12 for system and method for providing a mesh network using a plurality of wireless access points (waps).
This patent application is currently assigned to Broadcom Corporation. The applicant listed for this patent is Broadcom Corporation. Invention is credited to Jeyhan Karaoguz, Nambirajan Seshadri.
Application Number | 20130329676 13/966883 |
Document ID | / |
Family ID | 31950776 |
Filed Date | 2013-12-12 |
United States Patent
Application |
20130329676 |
Kind Code |
A1 |
Karaoguz; Jeyhan ; et
al. |
December 12, 2013 |
SYSTEM AND METHOD FOR PROVIDING A MESH NETWORK USING A PLURALITY OF
WIRELESS ACCESS POINTS (WAPs)
Abstract
A first access point located in a first cell may be coupled to a
second access point located in a second cell. Service may be
initially provided to an access device by the first access point
cell. The access device may subsequently be serviced by a second
access point whenever a signal for the access device falls below a
specified threshold level. The second cell may be a neighboring
cell, which may be located adjacent to the first cell. A first
signal may be transmitted from a first beamforming antenna coupled
to the first access point, to the second access point via an uplink
channel. Similarly, a second signal may be transmitted from a
second beamforming antenna coupled to the second access point, to
the first access point via a downlink channel. The uplink and
downlink channels may be a backhaul channel.
Inventors: |
Karaoguz; Jeyhan; (Irvine,
CA) ; Seshadri; Nambirajan; (Irvine, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Broadcom Corporation |
Irvine |
CA |
US |
|
|
Assignee: |
Broadcom Corporation
Irvine
CA
|
Family ID: |
31950776 |
Appl. No.: |
13/966883 |
Filed: |
August 14, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12872141 |
Aug 31, 2010 |
8537780 |
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13966883 |
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10606565 |
Jun 26, 2003 |
7787419 |
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12872141 |
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60433094 |
Dec 13, 2002 |
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60435984 |
Dec 20, 2002 |
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Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04L 47/15 20130101;
H04W 84/12 20130101; H04L 47/14 20130101; H04L 47/24 20130101; H04L
47/125 20130101; H04L 69/40 20130101; H04W 72/04 20130101; H04W
28/12 20130101; H04W 28/20 20130101; H04L 1/1607 20130101; H04L
69/329 20130101; H04L 47/70 20130101; H04W 84/18 20130101; H04L
47/824 20130101; H04W 16/16 20130101; H04L 47/767 20130101; H04L
67/04 20130101; H04L 67/14 20130101; H04L 69/32 20130101; H04W
28/16 20130101; H04W 36/30 20130101; H04L 29/06 20130101; H04L
49/351 20130101; H04W 92/20 20130101; H04W 88/08 20130101 |
Class at
Publication: |
370/329 |
International
Class: |
H04W 72/04 20060101
H04W072/04 |
Claims
1-99. (canceled)
100. A non-transitory computer readable medium having a program
that, when executed by processing circuitry within a first wireless
access point, causes the processing circuitry to: establish a
communication link between the first wireless access point and the
second wireless access point via a beamforming antenna
communicatively couple to the first wireless access point; assign a
dedicated frequency to the communication link; and send network
traffic from the first wireless access point to the second wireless
access point via the communication link.
101. The non-transitory computer readable medium of claim 100,
wherein the dedicated frequency is between 2.401 Gigahertz and
2.495 Gigahertz.
102. The non-transitory computer readable medium of claim 100,
wherein the dedicated frequency is between 4.905 Gigahertz and
5.865 Gigahertz.
103. The non-transitory computer readable medium of claim 100,
wherein the first wireless access point and the second wireless
access point are configured to communicate with a wireless client
device on a separate frequency from the dedicated frequency.
104. The non-transitory computer readable medium of claim of 103,
further causing the processing circuitry to send, via the
communication link, session context data associated with the
wireless client device to the second wireless access point in
response to receiving a message from the second wireless access
point indicating a dissociation from the first wireless access
point by the wireless client device and a re-association with the
second wireless access point by the wireless client device.
105. The non-transitory computer readable medium of claim 104,
wherein the message is associated with a signal strength of a
wireless communication link between the second wireless access
point and the wireless client device rising above a predefined
threshold.
106. A system comprising one or more processors, one or more
circuits, or a combination thereof within a first wireless device,
wherein the one or more processors, the one or more circuits, or
the combination thereof are operable to: establish a communication
link between the first wireless access point and the second
wireless access point via a beamforming antenna communicatively
couple to the first wireless access point; assign a dedicated
frequency to the communication link; and send network traffic from
the first wireless access point to the second wireless access point
via the communication link.
107. The system of claim 106, wherein the dedicated frequency is
between 2.401 Gigahertz and 2.495 Gigahertz.
108. The system of claim 106, wherein the dedicated frequency is
between 4.905 Gigahertz and 5.865 Gigahertz.
109. The system of claim 106, wherein the first wireless access
point and the second wireless access point are configured to
communicate with a wireless client device on a separate frequency
from the dedicated frequency.
110. The system of claim 109, wherein the one or more processors,
the one or more circuits, or the combination thereof are further
operable to: send, via the communication link, session context data
associated with the wireless client device to the second wireless
access point in response to receiving a message from the second
wireless access point indicating a dissociation from the first
wireless access point by the wireless client device and a
re-association with the second wireless access point by the
wireless client device.
111. The system of claim 110, wherein the message is associated
with a signal strength of a wireless communication link between the
first wireless access point and the wireless client device falling
below a predefined threshold.
112. A method of communicating between wireless access points in a
wireless mesh network, the method comprising: establishing a
backhaul communication link between a first wireless access point
located in a first cell and a second wireless access point located
in a second cell; assigning a dedicated frequency to the backhaul
communication link; and communicating between the first wireless
access point and the second wireless access point via the dedicated
frequency.
113. The method of claim 112, wherein the first cell comprises a
first wireless network and the second cell comprises a second
wireless network.
114. The method of claim 112, wherein the first cell and the second
cell are components of a wireless network.
115. The method of claim 112, wherein the first wireless access
point and the second wireless access point are configured to
communicate with a wireless client device on a separate frequency
from the dedicated frequency.
116. The method of claim 115, further comprising determining
whether to create a client communication link between the wireless
client device and the first wireless access point or the second
wireless access point based at least on a comparison of a first
signal strength and a second signal strength, wherein the first
signal strength measures a first signal level between the wireless
client device and the first wireless access point and the second
signal strength measures a second signal level between the wireless
client device and the second wireless access point.
117. The method of claim 112, wherein the dedicated frequency is
between 2.401 Gigahertz and 2.495 Gigahertz.
118. The method of claim 112, wherein the dedicated frequency is
between 4.905 Gigahertz and 5.865 Gigahertz.
119. The method of claim 112, wherein communicating between the
first wireless access point and the second wireless access point is
provided by a first beamforming antenna communicatively coupled to
the first wireless access point and a second beamforming antenna
communicatively coupled to the second wireless access point.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY
REFERENCE
[0001] This application is a continuation of U.S. application Ser.
No. 10/606,565 filed Jun. 26, 2003, which in turn makes reference
to, claims priority to, and claims the benefit of U.S. Provisional
Patent Application Ser. No. 60/433,094 entitled "Method and System
for Providing Bandwidth Allocation and Sharing in a Hybrid
Wired/Wireless Network" filed on Dec. 13, 2002; and U.S.
Provisional Application Ser. No. 60/435,984 entitled "Communication
System and Method in a Wireless Local Area Network" filed on Dec.
20, 2002.
[0002] The above stated applications are filed concurrently
herewith, and are all incorporated herein by reference in their
entirety.
FIELD OF THE INVENTION
[0003] Embodiments of the present application relate generally to
hybrid wired/wireless networking, and more particularly to a method
and system for providing a mesh network using a plurality of
wireless access points.
BACKGROUND OF THE INVENTION
[0004] The Open Systems Interconnection (OSI) model promulgated by
the International standards organization (ISO) was developed to
establish standardization for linking heterogeneous computer and
communication systems. The OSI model describes the flow of
information from a software application of a first computer system
to a software application of a second computer system through a
network medium. FIG. 1a is a block diagram 100 of the OSI model.
Referring to FIG. 1a, the OSI model has seven distinct functional
layers including layer 7, an application layer 114; layer 6, a
presentation layer 112; layer 5, a session layer 110; layer 4, a
transport layer 108, layer 3, a network layer 106; layer 2: a data
link layer 104; and layer 1, a physical layer 102. The physical
layer 102 may further include a physical layer convergence
procedure (PLOP) sublayer 102b and a physical media dependent
sublayer 102a. The data link layer 104 may also include a Medium
access control (MAC) layer 104a.
[0005] In general, each OSI layer describes certain tasks which are
necessary for facilitating the transfer of information through
interfacing layers and ultimately through the network.
Notwithstanding, the OSI model does not describe any particular
implementation of the various layers. OSI layers 1 to 4 generally
handle network control and data transmission and reception,
generally referred to as end-to-end network services. Layers 5 to 7
handle application issues, generally referred to as application
services. Specific functions of each layer may vary depending on
factors such as protocol and/or interface requirements or
specifications that are necessary for implementation of a
particular layer. For example, the Ethernet protocol may provide
collision detection and carrier sensing in the physical layer.
Layer 1, the physical layer 102, is responsible for handling all
electrical, optical, opto-electrical and mechanical requirements
for interfacing to the communication media. Notably, the physical
layer 102 may facilitate the transfer of electrical signals
representing an information bitstream. The physical layer 102 may
also provide services such as, encoding, decoding, synchronization,
clock data recovery, and transmission and reception of bit
streams.
[0006] The PLOP layer 102b may be configured to adapt and map
services provided by the physical layer 102 to the functions
provided by the device specific PMD sublayer 102a. Specifically,
the PLOP layer 102b may be adapted to map PHY sublayer service data
units (PDSUs) into a suitable packet and/or framing format
necessary for providing communication services between two or more
entities communicating via the physical medium. The PMD layer 102a
specifies the actual methodology and/or protocols which may be used
for receiving and transmitting via the physical medium. The MAC
sublayer 104a may be adapted to provide, for example, any necessary
drivers which may be utilized to access the functions and services
provided by the PLOP sublayer 102b. Accordingly, higher layer
services may be adapted to utilize the services provided by the MAC
sublayer 104a with little or no dependence on the PMD sublayer
102a.
[0007] 802.11 is a suite of specifications promulgated by the
Institute of Electrical and Electronics Engineers (IEEE), which
provide communication standards for the MAC and physical (PHY)
layer of the OSI model. The 801.11 standard also provides
communication standards for wired and wireless local area networks
(WLANs). More specifically, the 802.11 standard specifies five (5)
types of physical layers for WLANs. These include, frequency
hopping spread spectrum (FHSS), direct sequence spread spectrum
(DSSS), infrared (IR) communication, high rate direct sequence
spread spectrum spread spectrum (HR-DSS) and orthogonal frequency
division multiplexing (OFDM). The 802.11 standard also provides a
PLOP frame format for each of the specified PHY layers.
[0008] Over the past decade, demands for higher data rates to
support applications such as streaming audio and streaming video,
have seen Ethernet speeds being increased from about 1-2 megabit
per second (Mbps), to 10 Mbps, to 100 Mbps, to 1 gigabit per second
(Gbps) to 10 Gbps. Currently, there are a number of standards in
the in the suite of specifications, namely 802.11b, 802.11a and
802.11g which have been adapted to facilitate the demands for
increased data rates. The 802.11g standard for example, provides a
maximum data rate of about 54 Mbps at a transmitter/receiver range
of 19 meters (m) in a frequency range of 2.4 GHz to 2.4835 GHz. The
802.11b standard for example, provides a maximum data rate of about
11 Mbps at a transmitter/receiver range of 57 meters (m) in a
frequency range of 2.4 GHz to 2.4835 GHz. Finally, the 802.11a
standard for example, may be adapted to provide a maximum data rate
of about 54 Mbps at a transmitter/receiver range of 12 meters (m)
in a 300 MHz segmented bandwidth ranging from 5.150 GHz to 5.350
GHz and from 5.725 GHz to 5.825 GHz.
[0009] The 802.11 standard forms the basis of the other standards
in the suite of specifications, and the 802.11b, 802.11a and
802.11g standards provide various enhancements and new features to
their predecessor standards. Notwithstanding, there are certain
elementary building blocks that are common to all the standards in
the suite of specifications. For example, all the standards in the
suite of specifications utilize the Ethernet protocol and utilize
carrier sense multiple access with collision avoidance (CSMA/CA)
for distribution coordination function (DCF) and point coordination
function (PCF).
[0010] CSMA/CA utilizes a simple negotiation scheme to permit
access to a communication medium. If a transmitting entity wishes
to transmit information to a receiving entity, the transmitting
entity may sense the communication medium for communication
traffic. In a case where the communication medium is busy, the
transmitting entity may desist from making a transmission and
attempt transmission at a subsequent time. In a case where the
communication transmission is not busy, then the transmitting
entity may send information over the communication medium.
Notwithstanding, there may be a case where two or more transmission
entities sense that the communication medium is not busy and
attempt transmission at the same instant. To avoid collisions and
retransmissions, CSMA/CA or a ready to send (RTS) and clear to send
(CTS) messaging scheme may be employed, for example. Accordingly,
whenever a transmitting device senses that the communication medium
is not busy, then the transmitting device may send a ready to send
message to one or more receiving device. Subsequent to the receipt
of the ready to send message, the receiving device may send a clear
to send message. Upon receipt of the clear to send message by the
transmitting device, the transmitting device may initiate transfer
of data to the receiving device. Upon receiving packets or frames
from the transmitting device, the receiving device may acknowledge
the received frames.
[0011] The 802.11b standard, commonly called Wi-Fi, which
represents wireless fidelity, is backward compatible with its
predecessor standard 802.11. Although 802.11 utilizes phase-shift
keying (PSK) as a modulation scheme, 802.11b utilizes a hybrid PSK
scheme called complementary code keying (CCK). CCK permits higher
data rate and particularly less susceptible to interference effects
such as multipath-propagation interference, the PSK.
[0012] The 802.11a standard provides wireless asynchronous transfer
mode (ATM) support and is typically utilized in access hubs.
802.11a utilizes orthogonal frequency-division multiplexing (OFDM)
modulation/encoding scheme, which provides a maximum data rate 54
Mbps. Orthogonal frequency-division multiplexing is a digital
modulation technique which splits a signal into several narrowband
channels, with each channel having a different frequency. Each
narrowband channel is arranged so as to minimize the effects of
crosstalk between the channels and symbols in the data stream.
[0013] Since equipment designed to provide support for 802.11a
operates at frequencies in the ranges 5.150 GHz to 5.350 GHz and
from 5.725 GHz to 5.825 GHz, 802.11a equipment will not
interoperate with equipment designed to operate with the 802.11b
standard which defines operation in the 2.4 to 2.4835 GHz frequency
band. One major drawback is that companies that have invested in
802.11b equipment and infrastructure may not readily upgrade their
network without significant expenditure.
[0014] The 802.11g standard was developed as an extension to
802.11b standard. The 802.11g standard may utilize a similar OFDM
modulation scheme as the 802.11a standard and delivers speeds
comparable with the 802.11a standard. Since 802.11g compatible
equipment operates in the same portion of the electromagnetic
spectrum as 802.11b compatible equipment, 802.11g is backwards
compatible with existing 802.11b WLAN infrastructures. Due to
backward compatibility of 802.11g with 802.11b, it would be
desirable to have an 802.11b compliant radio card capable of
interfacing directly with an 802.11g compliant access point and
also an 802.11g compliant radio card capable of interfacing
directly with an 802.11b compliant access point.
[0015] Furthermore although 802.11g compatible equipment operates
in the 2.4 GHz to 2.4835 GHz frequency range, a typical transmitted
signal utilizes a bandwidth of approximately 22 MHz, about a third
or 30% of the total allocated bandwidth. This limits the number of
non-overlapping channels utilized by an 802.11g access point to
three (3). A similar scenario exists with 802.11b. Accordingly,
many of the channel assignment and frequency reuse schemes
associated with the 802.11b standard may be inherent in the
802.11g.
[0016] RF interference may pose additional operational problems
with 802.11b and 802.11g equipment designed to operate in the 2.4
GHz portion of the electromagnetic spectrum. The 2.4 GHz portion of
the spectrum is an unlicensed region which has been utilized for
some time and is crowded with potential interfering devices. Some
of these devices include cordless telephone, microwave ovens,
intercom systems and baby monitors. Other potential interfering
devices may be Bluetooth devices. Accordingly, interference poses
interference problems with the 802.11b and 802.11g standards.
[0017] 802.11a compatible equipment utilizes eight non-overlapping
channels, as compared to three non-overlapping channels utilized by
802.11b. Accordingly, 802.11a access points may be deployed in a
more dense manner than, for example 802.11b compatible equipment.
For example, up to twelve access points each having a different
assigned frequency may be deployed in a given area without causing
co-channel interference. Consequently, 802.11a may be particularly
useful in overcoming some of the problems associated with channel
assignment, especially in areas that may have a dense user
population and where increased throughput may be critical.
Notwithstanding, the higher operating frequency of 802.11a along
with its shorter operating range, may significantly increase
deployment cost since a larger number of access points are required
to service a given service area.
[0018] In hybrid wired/wireless network systems that may utilize
one or more protocols in the 802.11 suite of protocols, the
mobility of access devices throughout the network may pose
additional challenges for conventional switches and switching
equipment. Since access devices are continuously changing their
point of access to the network, conventional switches may not have
the capability to control other network devices and/or entities to
provide seamless communication throughout the network. Allocation
and de-allocation of certain network resources can be challenging
in a network in which the traffic dynamics are continuously
changing. Moreover, particularly in network systems that may handle
large volumes of access device traffic, providing adequate coverage
while access devices are mobile within the network may be
critical.
[0019] Further limitations and disadvantages of conventional and
traditional approaches will become apparent to one of skill in the
art, through comparison of such systems with some aspects of the
present invention as set forth in the remainder of the present
application with reference to the drawings.
BRIEF SUMMARY OF THE INVENTION
[0020] Aspects of the invention provide a system and method for
providing a mesh network using a plurality of access points. A
method for providing a mesh network using a plurality of access
points may include the step of coupling a first access point
located in a first cell to at least a second access point located
in a second cell. Service may be initially provided to an access
device by a first access point located in the first cell. The
access device may be serviced by a second access point located in a
second cell whenever a signal for the access device falls below a
specified threshold level. The second cell may be a neighboring
cell, which may be located adjacent to the first cell.
[0021] A first signal may be transmitted from a first beamforming
antenna to the second access point. The first beamforming antenna
may be coupled to the first access point. Similarly, a second
signal may be transmitted from a second beamforming antenna to the
first access point. The second beamforming antenna may be coupled
to the second access point. A path for facilitating transmission of
the first signal between the first beamforming antenna and the
second beamforming antenna may be an uplink channel. Also, a path
for facilitating transmission of the second signal between the
second beamforming antenna and the first beamforming antenna may be
a downlink channel. The uplink channel and the downlink channel may
be a backhaul channel.
[0022] The first access point located in a first cell may be
coupled to a third access point located in the first cell.
Accordingly, an access device may be serviced by a third access
point located in the first cell whenever a signal level of the
access device falls below a specified threshold level. Either of
the first access point and the access device may be configured to
determine when the signal of an access device falls below a
specified threshold level.
[0023] Another embodiment of the invention may provide a
machine-readable storage, having stored thereon a computer program
having at least one code section adapted to facilitate
communication in a mesh network using a plurality of access
devices, the at least one code section being executable by a
machine for causing the machine to perform the steps described
above.
[0024] In another embodiment of the invention, a mesh network using
a plurality of access points is provided. The system may include
means for coupling a first access point located in a first cell to
at least a second access point located in a second cell and means
for providing service initially to at least one of a plurality of
access devices by the a first access point located in the first
cell. The invention provides a means for servicing an access device
by a second access point located in the second cell whenever a
signal for the access device falls below a specified threshold. In
this regard, the second cell may be a neighboring cell located
adjacent to the first cell.
[0025] The system may further include a first beamforming antenna
coupled to the first access point for transmitting a first signal
from the first access point to the second access point. A second
beamforming antenna coupled to the second access point may be
adapted to transmitting a second signal from a second access point
to the first access point. A path for facilitating transmission
between a first beamforming antenna and the second beamforming
antenna may be an uplink channel. Similarly, a path for
facilitating transmission between the second beamforming antenna
and the first beamforming antenna may be a downlink channel. The
uplink channel and the downlink channel may be a backhaul channel.
The system may further include means for coupling the first access
point located in a first cell to at least a third access point
located in the first cell.
[0026] The system may further include means for servicing an access
device by a third access point located in the first cell whenever a
signal level corresponding to the access device falls below a
specified threshold. Either of the first access point and/or an
access device may include means for determining when a signal level
corresponding to the access device falls below a specified
threshold.
[0027] These and other advantages, aspects and novel features of
the present invention, as well as details of an illustrated
embodiment thereof, will be more fully understood from the
following description and drawings.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0028] FIG. 1a is a block diagram of the OSI model.
[0029] FIG. 1b is a block diagram illustrating a general PLOP frame
as defined by 802.11.
[0030] FIG. 1c is a block diagram illustrating a PLOP frame
utilized by frequency hopping spread spectrum as defined by
802.11.
[0031] FIG. 1d is a block diagram illustrating a PLOP frame for
direct sequence spread spectrum and high rate direct sequence
spread spectrum as defined by 802.11.
[0032] FIG. 1e is a block diagram illustrating a PLOP frame for
orthogonal frequency division multiplexing as defined by
802.11.
[0033] FIG. 2 is a block diagram of system for providing a mesh
network using a plurality of wireless access points in accordance
with an embodiment of the invention.
[0034] FIG. 3 is a block diagram of a inter-mesh network handoff in
accordance with an embodiment of the invention.
[0035] FIG. 4 is a block diagram of an intra-mesh network handoff
in accordance with an embodiment of the invention.
[0036] FIG. 5 is a block diagram of an exemplary system that
utilizes beam forming in accordance with an embodiment of the
invention.
[0037] FIG. 6 is a block diagram of a system for providing a mesh
network in accordance with an embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0038] Aspects of the invention provide a system and method for
providing a mesh network using a plurality of access points. A
method for providing a mesh network using a plurality of access
points may include the step of coupling a first access point
located in a first cell to at least a second access point located
in a second cell. Service may be initially provided to an access
device by a first access point located in the first cell. The
access device may be serviced by a second access point located in a
second cell whenever a signal for the access device falls below a
specified threshold level. The second cell may be a neighboring
cell, which may be located adjacent to the first cell.
[0039] FIG. 1b is a block diagram 120 illustrating a general PLOP
frame as defined by 802.11. Referring to FIG. 1b, there is shown
preamble 122, PLOP header 124, MAC data 126, and CRC 128. Preamble
122 may include synchronization (SYNC) data 122a and
synchronization delimiter 122b. The PLOP header 124 may include,
for example PLOP signal field (PSF) 124a, service data 124b, length
124c and other fields. The preamble 122 may be dependent on the
PHY. The SYNC data 122a may include a unique bit stream that may be
adapted to signal timing parameters such as the start of a frame.
The SYNC data 122a is used for bit synchronization and
demodulation. The SYNC delimiter 122b provides frame timing
information and may be adapted to delimit the end of
synchronization information. The PLOP header 124 may be adapted to
contain information used for decoding the frame. For example, the
PSF 124a may be adapted to include communication data rate
information. The service data 124b is generally reserved, but may
be utilized to provide application specific functionality. The
length 124c may be adapted to indicate the length of the MAC data
126. In this regard, the length 124c may be expressed in terms of
the time required to transmit the MAC data 126.
[0040] FIG. 1c is a block diagram 130 illustrating a PLOP frame
utilized by frequency hopping spread spectrum as defined by 802.11.
Referring to FIG. 1c, there is shown a SYNC data 132, PLOP header
134 and PSDU 136. The PLOP header 134 may include, for example,
PSDU length word (PLW) 134a, PLOP signaling field (PSF) 134b,
header error check field or CRC 134c and other fields. The PLW 134a
may specify the number of octets contained in the PSDU 136. The PSF
134 be may be 4-bits in length and may be used to denote the
communication data rate.
[0041] FIG. 1d is a block diagram 140 illustrating a PLOP frame for
direct sequence spread spectrum and high rate direct sequence
spread spectrum (HR-DSS) as defined by 802.11. Referring to FIG.
1d, there is shown preamble 142, PLOP header 144 and MPDU 146.
Preamble 142 may include synchronization (SYNC) data 142a and
synchronization delimiter 142b. The PLOP header 144 may include
PLOP signal field (PSF) 144a, service data 144b, length 144c, and
CRC field 144d. The SYNC data 142a may be 128 bits as compared to 8
bits for SYNC data 132a for frequency hopping spread spectrum. The
CRC 144d is 16 bits, which is similar to CRC 134c for frequency
hopping spread spectrum.
[0042] FIG. 1e is a block diagram 150 illustrating a PLOP frame for
orthogonal frequency division multiplexing as defined by 802.11.
Referring to FIG. 1e, there is shown preamble 152, PLOP header 154
and PSDU 156, tail 158 and pad 160. Preamble 152 may include
synchronization (SYNC) data 152a and synchronization delimiter
152b. The PLOP header 154 may include length 154a, PLOP signal
field (PSF) 154b, reserved field 154c, parity 154d, tail 154e and
service 154f. The length 154a is a 12-bit field that may be adapted
to indicate the length of the frame. The PSF 154b is a 4-bit field
that may indicate a modulation scheme utilized and its associated
coding rate of the PSDU. For example, the specification utilizes
binary 1011 to represent 6 Mbps, 1111 to represent 9 Mbps, 1010 to
represent 12 Mbps, 1110 to represent 18 Mbps, 1001 to represent 24
Mbps, 1011 to represent 36 Mbps, 1000 to represent 48 Mbps and
finally, 1100 to represent the maximum standardized rate if 54
Mbps. The reserved field 154c is a 1 bit field that is reserved for
future use and may be adapted for application specific use. The
parity field 154d may indicate odd or even parity. The tail field
154e is a 6-bit field. The service field 154f is a 16-bit field
that may be adapted to indicate the type of service.
[0043] FIG. 2 is a block diagram of system 200 for providing a mesh
network using a plurality of wireless access points (WAPs) in
accordance with an embodiment of the invention. Referring to FIG.
2, there is illustrated a plurality of cells 202, 204, 206, 208,
210, 212, 214, 216, 218, 220, 222, 224, with each cell containing
an access point (AP) 202a, 204a, 206a, 208a, 210a, 212a, 214a,
216a, 218a, 220a, 222a, 224a, respectively. It should be recognized
that although each cell is illustrated as a hexagon, the actual
shape of a cell may be dependent on various propagation and
interference characteristics, and also geographical topology.
Accordingly, the invention is not limited in this regard.
[0044] Each cell may represent a separate mesh network. For
example, cell 220 may represent a first mesh network and cell 214
may represent a second mesh network. Within each cell or mesh
network, there may be at least one access point which may be
adapted to provide WLAN service within the cell. For example,
access point 202a may be adapted to provide WLAN service within a
coverage area indicated by cell 202. Similarly, access point 214a
may be adapted to provide WLAN service within a coverage area
indicated by cell 214.
[0045] In one embodiment of the invention, the range of an access
point located within and serving a particular cell may be extended
by interconnecting or coupling neighboring and surrounding cells.
Cell 202, for example, has six (6) neighboring cells, namely 204,
206, 214, 216, 218, 224. Each of the access points 204a, 206a,
214a, 216a, 218a, 224a located in the cells 204, 206, 214, 216,
218, 224 respectively, may be adapted to provide WLAN service
within a coverage area indicated by cell 204, 206, 214, 216, 218,
224, respectively. In accordance with an embodiment of the
invention, the coverage area of access point 202 may be extended
into any portion of any one or more of the neighboring cells 204,
206, 214, 216, 218, 224 by coupling the access points 204a, 206a,
214a, 216a, 218a, and 224a, to access point 202a. In a case where
the access point 202a may be coupled to each one of access points
204a, 206a, 214a, 216a, 218a, 224a, then an access device located
in any one of cells 202, 204, 206, 214, 216, 218, 224 may
communicate with a device located in any one of the cells 202, 204,
206, 214, 216, 218, 224. For example, an access device located in
cell 214 serviced by access point 214a may communicate with an
access device located in cell 202 which may be serviced by access
point 202a. Similarly, an access device located in cell 216
serviced by access point 216a may communicate with an access device
located in cell 224 which may be serviced by access point 224a.
[0046] In another aspect of the invention, a mobile access device
may actively roam from a first mesh network to a second mesh
network. For example, an access device may move from a first mesh
network represented by cell 216 into second mesh network
represented by cell 202.
[0047] In accordance with another aspect of the invention,
intra-mesh network and inter-mesh network hand-off may be provided.
In the case of inter-mesh network handoff, an access device moving
from a first cell representing a first mesh network may be handed
off to a second cell representing a second mesh network. In the
case of intra-mesh network handoff, an access device being serviced
by a first access point located within a particular cell may be
handed off to a second access point located within the same
particular cell.
[0048] FIG. 3 is a block diagram 300 of a inter-mesh network
handoff in accordance with an embodiment of the invention.
Referring to FIG. 3, there is shown a first cell 302 corresponding
to a first mesh network having an access point AP1 302a and a
second cell 304 corresponding to a second mesh network having an
access point AP2 304a. Located in the first cell is an access
device 306. Inter-mesh handoff may involve handoff from a first
serving access point, for example access point 302a, to a second
access point, for example access point 304a, both access points
being located within different cells or on different mesh networks.
For example, an inter-mesh network handoff may occur from access
point 302a to 304a.
[0049] In operation, access point 302a may initially provide
service to access device 306 which may be mobile within the cell
302. However, as access device 306 migrates to the fringe of the
cell 302, a signal received from access point 302a may fade until
it reaches, for example, a handover threshold. In one aspect of the
invention, the handover threshold may be dependent on one or more
signal parameters such as the signal strength received from one or
more of access point 302a and access point 302b. The access device
306 may dynamically keep a record of the frequency and
corresponding signal strength of any received channel it
encounters. For example, the access device 306 may be adapted to
actively scan a list of frequencies for available channels. The
record of the frequency and corresponding signal strength of any
received channel may serve as a handoff candidate list. The access
device 306 may be adapted to select the best candidate for a
handoff from the candidate list based on, for example, a channel
having the strongest signal strength. In a case where the access
device 306 determines that the best access point for a handoff is
access point 304a, then the access device may tune it transceiver
to an available transmit and/or receive channel corresponding to
the access point 304a. At this point, the access point 304a
provides service to the access device 306.
[0050] FIG. 4 is a block diagram 400 of an intra-mesh network
handoff in accordance with an embodiment of the invention.
Referring to FIG. 4, there is shown cell 402 corresponding to a
mesh network having a first access point API 402a and a second
access point AP2 402b. Located in cell 402 is an access device 406.
Intra-mesh handoff may include handoff from a first serving access
point to a second access point, both access points being located
within the same cell or on the same mesh network. For example, an
intra-mesh network handoff may occur from access point 402a to 402b
which may both be located in the same mesh network or cell.
[0051] In operation, access point 402a may initially provide
service to access device 406 which may be mobile within cell 402.
However, as access device 406 migrates away from access point 402a
and towards access point 402b, a signal received from access point
402a may fade until it reaches, for example, a handover threshold.
Simultaneous with the fading of the signal received from access
point 402a, a signal having increasing signal strength may be
received from access point 402b. The access device 406 may
dynamically keep a record of the frequency and corresponding signal
strength of any received channel it encounters including the
frequencies and signal strength for available channels of access
point 402b in its handoff candidate list. The access device 406 may
be adapted to select the best candidate for a handoff from the
candidate list based on, for example, a channel having the
strongest signal strength. In a case where the access device 406
determines that the best access point for a handoff is access point
402b, then the access device 406 may tune its transceiver to an
available transmit and/or receive channel corresponding to the
access point 402b. At this point, the access point 402b provides
service to the access device 406.
[0052] A client or access device may initiate dissociation when
signal strength drops below a threshold level. The client may
initiate re-association when a signal strength of the new access
point is above a threshold level. The new access point may send a
message to the current access point informing the switch of a
possible association of the client with the new access point. The
current access point may send a response to the new access point to
handover session context data. The current access point may send,
for example, a security block to the new access point. The new
access point may acknowledge the receipt of the security block. The
new access point may identify the new switch serving the access
point of the move. The new switch may notify the current switch of
the re-association. The current switch may respond to the new
switch with switch filtering information.
[0053] An access device may initiate disassociation when signal
strength falls below a specified threshold. The access device may
initiate re-association when signal strength of a new access point
is above a certain threshold. The new access point may send a
message to the current AP to announce its re-association. The
current access point may send a response to the new access point to
handover session context data. The session data may be, for
example, encryption data which may prevent re-authentication. The
current access point may send a security block to the new access
point. The new access point may acknowledge receipt. The new access
point may notify a switch of the move. The switch may transfer
filtering information from one port to another.
[0054] In order to minimize the effects of interference, a beam
forming technique may be utilized to provide communication between
two or more access points co-located within the same cell or
located within different cells or mesh networks. FIG. 5 is a block
diagram of an exemplary system 500 that utilizes beam forming in
accordance with an embodiment of the invention. Referring to FIG.
5, there is shown a first cell 502 having an access point 502a and
an access device 502b located therein. A second cell 504 may have
an access point 504a and an access device 504b located therein.
[0055] In an embodiment of the invention, a beam forming antenna
associated with access point 502a may be adapted to provide
communication with an access point 504b. In this regard, one or
more transmit and receive frequencies may be assigned as
communication channels to provide communication between access
point 502a and access point 504a using the beam forming antenna
path. The assigned channels may constitute a backbone channel 506.
In one aspect of the invention, the backbone channel 506 may be
adapted to utilize an 802.11b standard, while a mesh network 502
associated with access point 502a and a mesh network 504 associated
with access point 504a may utilize an 802.11b or 802.1g standard.
Accordingly, the backbone channel may provide a communication path
that may reduce interference with other channels in a particular
cell, thereby increasing transmission throughput. A plurality of
access devices located in cell 502, for example access device 502b,
may utilize channels other than those assigned to the backbone
channel. Similarly, a plurality of access devices located in cell
504, for example access device 504b, may utilize channels other
than those assigned to the backbone channel.
[0056] FIG. 6 is a block diagram of a system for providing a mesh
network in accordance with an embodiment of the invention.
Referring to FIG. 6, there is shown a processor 604, a transmitter
606, an application block 608, a database 610 and a receiver 612.
Processor 604, transmitter 606, application block 608, database 610
and receiver 612 may be variously coupled to processor 604. The
processor 604, transmitter 606 and receiver 612 may contain
suitable logic and/or software that may be adapted to facilitate
communication in a mesh network in accordance with the invention.
FIG. 6 may also include a beamforming antenna 614. The beamforming
antenna 614 may include a plurality of receiver antenna elements
and transmitter antenna elements. Accordingly, each of the
plurality of receiver antenna elements and transmitter elements may
be adapted to function as a beamforming antenna. Database 610 may
store applications and/or data that may be utilized by processor
606.
[0057] Processor 604, under control of one or more applications
such as application 608, may be adapted to control transmitter 606
and receiver 608 to facilitate communication in a mesh network in
accordance with an embodiment of the invention. Processor 604 may
be adapted to control communication over a first access point
located in a first cell, which may be coupled to a second access
point located in a second cell. The processor 604 may be adapted to
control receiver 612 and transmitter 606 to initially provide
service to an access device by the first access point. The
processor 604 may be configured to determine when a signal level of
an access device falls below a specified threshold level. A second
processor similar to processor 604, which may be associated with a
second access point located within a second neighboring cell, may
be configured to provide service to the access device. Accordingly,
processor 604 may be adapted to terminate or discontinue serving
the access device once the second processor starts to provide
service to the access device.
[0058] Processor 604 may be adapted to control transmitter 606 to
transmit a first signal from, for example, a first antenna element
or sector of beamforming antenna 614. Similarly, processor 604 may
be adapted to control receiver 612 to receive a second signal that
may be transmitted from a second beamforming antenna coupled to the
second access point. Alternatively, processor 604 may be adapted to
control transmitter 606 to transmit a first signal via a wired
connection coupling the first and second access points. Similarly,
processor 604 may be adapted to control receiver 612 to receive a
second signal that may be transmitted from the second access point
to the first access point via a wired connection.
[0059] In accordance with various embodiments of the invention,
dependent on the modulation scheme utilized, one or more of the
PLOP frames illustrated in FIG. 1b, FIG. 1c, FIG. 1d and FIG. 1e
may be adapted to contain information which may be utilized for
providing communication between the plurality of access points in
one or more mesh networks in accordance the embodiments of the
invention. Additionally, the PLOP frames may be adapted to convey
information for any one or more of the 801.11a, 802.11g and 802.11g
modes of operation utilized by access points and/or access devices
in accordance the embodiments of the invention.
[0060] A method for providing a mesh network using a plurality of
access points may include the step of coupling a first access point
located in a first cell to at least a second access point located
in a second cell. Service may be initially provided to an access
device by a first access point located in the first cell. The
access device may be serviced by a second access point located in a
second cell whenever a signal for the access device falls below a
specified threshold level. The second cell may be a neighboring
cell, which may be located adjacent to the first cell.
[0061] A first signal may be transmitted from a first beamforming
antenna to the second access point. The first beamforming antenna
may be coupled to the first access point. Similarly, a second
signal may be transmitted from a second beamforming antenna to the
first access point. The second beamforming antenna may be coupled
to the second access point. A path for facilitating transmission of
the first signal between the first beamforming antenna and the
second beamforming antenna may be an uplink channel. Also, a path
for facilitating transmission of the second signal between the
second beamforming antenna and the first beamforming antenna may be
a downlink channel. The uplink channel and the downlink channel may
be a backhaul channel. A backhaul link or channel between mesh
network access points may be utilize a higher data rate protocol
than the individual mesh networks or cells. In this regard, the
backhaul link or channel may utilize 802.11a while the individual
cell may utilize 802.11g or 802.11g. Additionally, the backhaul
channel or link may utilize long distance type wireless standards
such as 802.16.
[0062] The first access point located in a first cell may be
coupled to a third access point located in the first cell.
Accordingly, an access device may be serviced by a third access
point located in the first cell whenever a signal level of the
access device falls below a specified threshold level. Either of
the first access point and the access device may be configured to
determine when the signal of an access device falls below a
specified threshold level.
[0063] Accordingly, the present invention may be realized in
hardware, software, or a combination of hardware and software. The
present invention may be realized in a centralized fashion in one
computer system, or in a distributed fashion where different
elements are spread across several interconnected computer systems.
Any kind of computer system or other apparatus adapted for carrying
out the methods described herein is suited. A typical combination
of hardware and software may be a general-purpose computer system
with a computer program that, when being loaded and executed,
controls the computer system such that it carries out the methods
described herein.
[0064] The present invention also may be embedded in a computer
program product, which comprises all the features enabling the
implementation of the methods described herein, and which when
loaded in a computer system is able to carry out these methods.
Computer program in the present context means any expression, in
any language, code or notation, of a set of instructions intended
to cause a system having an information processing capability to
perform a particular function either directly or after either or
both of the following: a) conversion to another language, code or
notation; b) reproduction in a different material form.
[0065] While the present invention has been described with
reference to certain embodiments, it will be understood by those
skilled in the art that various changes may be made and equivalents
may be substituted without departing from the scope of the present
invention. In addition, many modifications may be made to adapt a
particular situation or material to the teachings of the present
invention without departing from its scope. Therefore, it is
intended that the present invention not be limited to the
particular embodiment disclosed, but that the present invention
will include all embodiments falling within the scope of the
appended claims.
* * * * *