Source: https://patents.google.com/patent/US20130343210A1/en
Timestamp: 2018-04-25 08:38:51
Document Index: 493333488

Matched Legal Cases: ['art 11', 'art 11', 'art 11', 'art 11', 'art 11', 'art 11', 'art 11', 'art 11', 'art 900']

US20130343210A1 - System for allocating channels in a multi-radio wireless lan array - Google Patents
System for allocating channels in a multi-radio wireless lan array Download PDF
US20130343210A1
US20130343210A1 US13732841 US201313732841A US2013343210A1 US 20130343210 A1 US20130343210 A1 US 20130343210A1 US 13732841 US13732841 US 13732841 US 201313732841 A US201313732841 A US 201313732841A US 2013343210 A1 US2013343210 A1 US 2013343210A1
US13732841
US8798069B2 (en )
James Kirk Mathews
A channel allocation system for allocating channels in a frequency band to a plurality of radios in close proximity so as to minimize co-channel interference. One method for allocating channels involves initially tuning each of the plurality of radios to the same one of the plurality of channels. All of the radios then receive signals from whatever sources and a signal score is determined for each radio. The radios are then tuned to another one of the plurality of channels. The steps of receiving a signal and determining a signal score for each radio are repeated for each of the remaining channels until all channels have been used. The signal scores are then tested against a table of mapping schemes to determine maximum isolation.
This application is a continuation application of U.S. patent application Ser. No. 11/816,065 titled “SYSTEM FOR ALLOCATING CHANNELS IN A MULTI-RADIO WIRELESS LAN ARRAY”, filed on May 13, 2008 by inventors Dirk I. Gates and James T. Mathews, the contents of which are incorporated herein by reference in its entirety.
This application further claims priority of the following provisional patent applications:
1. Prov. App. Ser. No. 60/660,171, titled “Wireless LAN Array,” by Dirk I. Gates, Ian Laity, Mick Conley, Mike de la Garrigue, and Steve Smith, filed on Mar. 9, 2005;
2. Prov. App. Ser. No. 60/660,276, titled “Wireless LAN Array,” by Dirk I. Gates, Ian Laity, Mick Conley, Mike de la Garrigue, and Steve Smith, filed on Mar. 9, 2005;
3. Prov. App. Ser. No. 60/660,375, titled “Wireless Access Point,” by Dirk I. Gates and Ian Laity, filed on Mar. 9, 2005;
4. Prov. App. Ser. No. 60/660,275, titled “Multi-Sector Access Point Array,” by Dirk I. Gates Ian Laity, Mick Conley, Mike de la Garrigue, and Steve Smith, filed on Mar. 9, 2005;
5. Prov. App. Ser. No. 60/660,210, titled “Media Access Controller For Use In A Multi-Sector Access Point Array,” by Mike de la Garrigue and Drew Bertagna filed on Mar. 9, 2005;
6. Prov. App. Ser. No. 60/660,174, titled “Queue Management Controller For Use In A Multi-Sector Access Point Array,” by Mike de la Garrigue and Drew Bertagna filed on Mar. 9, 2005;
7. Prov. App. Ser. No. 60/660,394, titled “Wireless LAN Array,” by Dirk I. Gates, Ian Laity, Mick Conley, Mike de la Garrigue, and Steve Smith, filed on Mar. 9, 2005;
8. Prov. App. Ser. No. 60/660,209, titled “Wireless LAN Array Architecture,” by Dirk I. Gates, Ian Laity, Mick Conley, Mike de la Garrigue, and Steve Smith, filed on Mar. 9, 2005;
9. Prov. App. Ser. No. 60/660,393, titled “Antenna Architecture of a Wireless LAN Array,” by Abraham Hartenstein, filed on Mar. 9, 2005;
10. Prov. App. Ser. No. 60/660,269, titled “Load Balancing In A Multi-Radio Wireless Lan Array Based On Aggregate Mean Levels,” by Mick Conley filed on Mar. 9, 2005;
11. Prov. App. Ser. No. 60/660,392, titled “Advanced Adjacent Channel Sector Management For 802.11 Traffic,” by Mick Conley filed on Mar. 9, 2005;
12. Prov. App. Ser. No. 60/660,391, titled “Load Balancing In A Multi-Radio Wireless Lan Array Based On Aggregate Mean Levels,” by Shaun Clem filed on Mar. 9, 2005;
13. Prov. App. Ser. No. 60/660,277, titled “System for Transmitting and Receiving Frames in a Multi-Radio Wireless LAN Array,” by Dirk I. Gates and Mike de la Garrigue, filed on Mar. 9, 2005;
14. Prov. App. Ser. No. 60/660,302, titled “System for Allocating Channels in a Multi-Radio Wireless LAN Array,” by Dirk I. Gates and Kirk Mathews, filed on Mar. 9, 2005;
15. Prov. App. Ser. No. 60/660,376, titled “System for Allocating Channels in a Multi-Radio Wireless LAN Array,” by Dirk I. Gates and Kirk Mathews, filed on Mar. 9, 2005; and
16. Prov. App. Ser. No. 60/660,541, titled “Media Access Controller For Use In A Multi-Sector Access Point Array,” by Dirk I. Gates and Mike de la Garrigue, filed on Mar. 9, 2005.
This application further claims priority to the following PCT patent applications:
1. PCT patent application no. PCT/US2006/008747, titled “Antenna Architecture of a Wireless LAN Array,”
2. PCT patent application no. PCT/US2006/008743, titled “Wireless LAN Array,” filed on Mar. 9, 2006, which claims priority to the above provisional patent applications;
3. PCT patent application no. PCT/US2006/008696, titled “Assembly and Mounting for Multi-Sector Access Point Array,” filed on Mar. 9, 2006;
4. PCT patent application no. PCT/US2006/08698, titled “System for Allocating Channels in a Multi-Radio Wireless LAN Array,” filed Mar. 9, 2006; and
5. PCT patent application no. PCT/US2006/008744, titled “Media Access Controller for use in a Multi-Sector Access Point Array,” filed on Mar. 9, 2006.
All of the above-listed US patent applications, US provisional patent applications, and PCT applications are incorporated by reference herein.
The use of wireless communication devices for data networking is growing at a rapid pace. Data networks that use “WiFi” (“Wireless Fidelity”) are relatively easy to install, convenient to use, and supported by the IEEE 802.11 standard. WiFi data networks also provide performance that makes WiFi a suitable alternative to a wired data network for many business and home users.
WiFi networks operate by employing wireless access points to provide users having wireless (or ‘client’) devices in proximity to the access point with access to data networks. The wireless access points contain a radio that operates according to one of three standards specified in different section of the IEEE 802.11 specification. Radios in access points communicate using omni-directional antennas in order to communicate signals with wireless devices from any direction. The access points are then connected (by hardwired connections) to a data network system that completes the users' access to the Internet.
1. IEEE 802.11a, which operates on the 5 GHz band with data rates of up to 54 Mbps;
2. IEEE 802.11b, which operates on the 2.4 GHz band with data rates of up to 11 Mbps; and
3. IEEE 802.11g, which operates on the 2.4 GHz band with data rates of up to 54 Mbps.
The 802.11b and 802.11g standards provide for some degree of interoperability. Devices that conform to 802.11b may communicate with 802.11g access points. This interoperability comes at a cost as access points will incur additional protocol overhead if any 802.11b devices are connected. Devices that conform to 802.11a may not communicate with either 802.11b or g access points. In addition, while the 802.11a standard provides for higher overall performance, 802.11a access points have a more limited range due to their operation in a higher frequency band.
Each standard defines ‘channels’ that wireless devices, or clients, use when communicating with an access point. The 802.11b and 802.11g standards each allow for 14 channels. The 802.11a standard allows for 12 channels. The 14 channels provided by 802.11b and g include only 3 channels that are not overlapping. The 12 channels provided by 802.11a are non-overlapping channels. The FCC is expected to allocate 11 additional channels in the 5.47 to 5.725 GHz band.
In view of the above, an example of a method consistent with the present invention is a method for allocating channels in a wireless access device having a plurality of radios capable of operating on a plurality of channels. Each channel has a frequency band with a center frequency. Each center frequency is spaced at equal frequency intervals within a larger frequency band. Any one channel may have at least one adjacent channel located in the next frequency band. The method includes allocating one of the plurality of channels to each one of the plurality of radios, where each of the allocated channels is not adjacent to any one of the other allocated channels.
FIG. 8 illustrates operation of channel allocation in an implementation of the wireless access device.
FIG. 9 is a flowchart of an example of an implementation of a method performed by a wireless access device.
FIG. 1 is a block diagram of network 10 that uses a wireless access device 100 to provide client devices (or “stations”), such as a laptop computer 20, access to data network services available on the Internet 160. The wireless access device 100 is connected to a wired network 120, which provides the connection to the Internet 160. Depending on the number of stations and the size of the area of coverage, the network 10 may include additional wireless access devices 130. A network management system 120 may be used to configure and manage the wireless access devices 100, 130.
The wireless access device 100 in FIG. 1 has a substantially circular structure 108 and includes an array controller 102, a plurality of transceiver modules 110, and a network interface 114. The transceiver modules 110 contain one or more transceivers, radios, for example, and each transceiver is connected to an antenna 112. The transceiver modules 110 are also connected to the array controller 102, which operates to configure the transceiver modules 110 and manage any communications connections involving the transceivers.
The wireless access device 100 shown in FIG. 1 has sixteen antennas 112. One of ordinary skill in the art will appreciate that any number of antennas may be used. The antennas 112 that correspond to the transceivers in the transceiver modules 110 are disposed near the perimeter of the substantially circular structure 108 of the wireless access device 100. The antennas 112 are preferably directional antennas configured to transmit and receive signals communicated in a radial direction from the center of the wireless access device 108. Each antenna 112 covers a portion of the substantially circular area surrounding the wireless access device 100 called a “sector” Si. The total area covered by all of the sectors defines a 360° area of coverage of the wireless access device 100. This means that a station 20 located in a sector of the area of coverage would be able to communicate wirelessly with the antenna 112 corresponding with that sector. Multi-sector coverage is discussed in more detail below with reference to FIG. 4.
The network 10 in FIG. 1 implements well-known standards and protocols used to communicate over the Internet 160. The transceivers in the wireless access device 100 in FIG. 1 communicate with stations 20 in accordance with the IEEE 802.11 standard (802.11a, 802.11b, 802.11g), which is incorporated herein by reference. The remainder of this specification describes operation of examples of the wireless access device 100 in the context of systems that implement IEEE 802.11a, b, or g. However, the present invention is not limited to systems that implement any particular standard.
The wireless access device 100 in FIG. 1 has four transceiver modules 110. Each transceiver module 110 contains four transceivers, each of which is programmable. In a preferred configuration, three of the four transceivers (shown in FIG. 1 with antennas labeled ‘a’) in each transceiver module 110 are designated to operate as 802.11a radios. The remaining transceiver (shown in FIG. 1 with antenna labeled ‘abg’) may be programmed to operate according to any of 802.11a, b, or g. Each transceiver is configured to operate on an assigned channel. The channel may be one of the twelve channels available using the 802.11a standard or one of the fourteen channels available using the 802.11b/g standard.
The wireless access device 100 communicates with stations 20 wirelessly. The stations 20 may be any device enabled to communicate wirelessly with the wireless access device 100 such as, without limitation, laptop computers, mobile telephones (for voice-over-LAN, or VOWLAN applications), personal digital assistants, handheld computers, etc. In examples described here, the stations are enabled to operate in accordance with one or more of the 802.11 standards. When the station 20 enters the coverage area of the wireless access device 100, it may send a request to connect to the Internet 160. The wireless access device 100 may perform an authentication process in a login session. Once authenticated, the user of the station 20 may be connected to the Internet 160.
FIG. 2 is a block diagram of a transceiver module 210 that may be implemented in the wireless access device 100 shown in FIG. 1. The transceiver module 210 includes four radios, one of which is an ‘abg’ radio 220 and three of which are ‘a’ radios 222. All four radios 220, 222 include an amplifier 230, a radio signal processor 240, and a baseband processor 250. The four radios 220, 222 communicate with a transceiver module interface 260, which allows the transceiver module 210 to communicate with the rest of the wireless access device.
Each radio 220, 222 connects to an antenna 212, which transmits and receives radio signals received from the amplifier 230. As described with reference to FIG. 1, the antennas 212 are directional antennas, which concentrate signal power in one direction. Directional antennas can therefore cover greater distances than omni-directional antennas used in typical wireless access devices. The multiple radios with radially disposed directional antennas advantageously provides a 360° coverage pattern that is larger than that of radios with omni-directional antennas used in current access points.
It is noted that the following description refers to transceivers as radios. Those of ordinary skill in the art will appreciate that the term “radio” is not intended as limiting the transceiver to any particular type.
1. General implementation IEEE 802.11 Access Point functionality.
2. Non-blocking packet processing from/to any radio interface. In typical wireless access devices that employ a single, omni-directional radio, a packet that is being transmitted may block other packets from access to the medium. This may occur in either direction. Stations typically transmit packets to an access point when the medium is not busy. If the medium is busy with packets from other stations, for example, the packet is blocked. Similarly, the access point may be attempting to send a packet to a station. If other packets are being sent to another station, the original packet is blocked from access to the medium. In the wireless access device 100, when a station is blocked from communicating a packet to one radio, it may switch to another radio that is not blocked. If the wireless access device 100 is blocked from sending a packet via one radio, it may switch to another radio.
3. Dynamic automatic channel assignment. The array controller 300 implements algorithms and/or other schemes for assigning channels of the 802.11 standards to the multiple radios. Channels are allocated to radios in a manner that reduces adjacent channel interference (ACI).
4. Directional awareness of where a wireless station is in geographic relationship to the wireless access device 100. The array controller 300 receives information such as signal strength, and for each station, may keep track of how the signal strength changes over time. In addition, even if one radio is locked in and “connected” to a station, another radio may receive signals and thus, “listen” to the station. The signal strength in relation to the specific radios gathering signal information provide the array controller with sufficient information to create a directional awareness of the location of the wireless station.
5. Station mobility services whereby a station can instantly roam from one sector to another without requiring re-authentication of the station. As a wireless station moves in the coverage area space of the wireless access device, the signal strength sensed by the array controller changes. As the signal strength of the station becomes weaker, the radio associated with the adjacent sector locks in and “connects” with the station without requiring re-authentication.
6. Wireless quality of service.
7. Enhanced load balancing of wireless stations.
8. Constant RF monitoring of channel conditions and security threats
9. Wireless Security processing
10. Internal Authentication Server. Typically, authentication takes place at a server or router that is wired to the access points. In the wireless access device 100, authentication may be done by the array controller 300.
11. Wired Networking protocol support.
12. System failover handling and error handling. Because sectors overlap, when a radio fails, the adjacent radios may lock in with stations being handled by the failed radio. In some examples of the wireless access device 100, the array controller 300 may increase power to adjacent sectors to ensure coverage in any area covered by the failed sector. In addition, when multiple access devices are deployed, one wireless access device may increase power and expand a sector to cover area left without service when a radio fails in an adjacent wireless access device.
13. System management functions.
As discussed above, examples of wireless access devices and systems that employ wireless access devices described in this specification (without limitation) operate in the wireless LAN environment established by the IEEE 802.11 standardization body. The IEEE 802.11 standards including (without limitation):
IEEE 802.11, 1999 Edition (ISO/IEC 8802-11: 1999) IEEE Standards for Information Technology—Telecommunications and Information Exchange between Systems—Local and Metropolitan Area Network—Specific Requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications
IEEE 802.11a-1999 (8802-11:1999/Amd 1:2000(E)), IEEE Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications—Amendment 1: High-speed Physical Layer in the 5 GHz band
IEEE 802.11b-1999 Supplement to 802.11-1999, Wireless LAN MAC and PHY specifications: Higher speed Physical Layer (PHY) extension in the 2.4 GHz band
802.11b-1999/Cor1-2001, IEEE Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications—Amendment 2: Higher-speed Physical Layer (PHY) extension in the 2.4 GHz band—Corrigendum1
IEEE 802.11d-2001, Amendment to IEEE 802.11-1999, (ISO/IEC 8802-11) Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: Specification for Operation in Additional Regulatory Domains
IEEE 802.11F-2003 IEEE Recommended Practice for Multi-Vendor Access Point Interoperability via an Inter-Access Point Protocol Across Distribution Systems Supporting IEEE 802.11 Operation
IEEE 802.11g-2003 IEEE Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications—Amendment 4: Further Higher-Speed Physical Layer Extension in the 2.4 GHz Band
IEEE 802.11h-2003 IEEE Standard for Information technology—Telecommunications and Information Exchange Between Systems—LAN/MAN Specific Requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: Spectrum and Transmit Power Management Extensions in the 5 GHz band in Europe
IEEE 802.11i-2004 Amendment to IEEE Std 802.11, 1999 Edition (Reaff 2003). IEEE Standard for Information technology—Telecommunications and information exchange between system—Local and metropolitan area networks Specific requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications—Amendment 6: Medium Access Control (MAC) Security Enhancements
IEEE 802.11j-2004 IEEE Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications—Amendment 7: 4.9 GHz-5 GHz Operation in Japan
Channel Number Frequency (MHz)
IEEE 802.11 A (5.0 GHz Band)
36 5180
40 5200
44 5220
48 5240
52 5260
56 5280
60 5300
64 5320
IEEE 802.11 B/G (2.4 GHz Band)
FIG. 4 is a diagram illustrating the formation of sectors by the wireless access device of FIG. 1. The wireless access device 100 has 16 radios 412 divided into groups of four radios 412 mounted on each of four transceiver modules 410. An array controller 402 is located roughly in the center of the wireless access device 100 where it connects with each of the four transceiver modules 410 at inter-module connections 408. The inter-module connections 408 contain communication paths (via a bus or set of signal paths on a connector) that implement the interface between the array controller 402 and the radios 412.
FIG. 6A is a diagram of a wireless access device 100 of FIG. 1 labeled by radio type and number. Radios that communicate, or are configured to communicate, as 802.11a radios only are labeled ‘a.’ Radios that may be programmed or configured to communicate using 802.11a, b, or g radios are labeled ‘abg.’ The twelve ‘a’ radios 610 (a1-a12) are assigned a unique one of the twenty-three channels available under the 802.11a standard. Three of the four ‘abg’ radios are assigned the three non-overlapping channels available under the 802.11b/g standards. The fourth ‘abg’ radio is implemented as an omni-directional radio in listen mode exclusively.
FIG. 6B shows coverage patterns formed by the different radio types on the wireless access device. The twelve ‘a’ radios 610 each have a coverage area emanating in a sector that spreads out more than 30°. The sectors of the twelve ‘a’ radios 610 may combine to form a substantially circular 802.11a coverage pattern 620. Preferably, the sectors are larger than 30° in order to create overlap between the sectors, such as for example, the overlap 650 between sectors 630 and 640. FIG. 6B also shows the three ‘abg’ radios 611 with the coverage area of more than 120°. The sectors combine to provide a 360° coverage pattern. However, each sector is more than 120° to create overlap between the sectors. The fourth ‘abg’ radio 613 is configured as an omni-directional radio able to communicate in all directions. The fourth ‘abg’ radio 613 is used as a monitor or a sniffer radio in a listen-only mode. This radio listens to each channel in sequence to build a table of all stations and access devices. This table may be compared to an administrator controlled list of allowed stations and access devices. Stations and access devices not in the administrator controlled list are termed rogues. One function performed by the fourth ‘abg’ radio 613 is to detect unauthorized stations in the coverage area.
No. Channel Frequency (MHz)
A9 36 5180
A12 40 5200
A3 44 5220
A6 48 5240
A10 52 5260
A1 56 5280
A4 60 5300
A7 64 5320
A11 149 5745
A2 153 5765
A5 157 5785
A8 161 5805
M — Monitor radio that
abg1 1 2412
abg3 6 2437
abg4 11 2462
If the radio to which station 720 a fails, or is otherwise unable to provide service to station 720 a, the array controller is able to switch the connection to station 720 a over to one of the adjacent radios. The IEEE 802.11a, b, and g protocols permit radios to “listen” to signals being communicated with stations that are connected to another radio. The array controller may obtain data such as signal strength and directional awareness and other factors that allow it to determine which radio is best suited to continue communicating with the station 720 a.
The wireless access device 700 is connected to a Gigabit Ethernet port 780, which provides a direct connection to the user's network.
The radios in the wireless access device 700 are advantageously enclosed in proximity to one another providing the wireless access device 700 with increased throughput, capacity and coverage area. In order to minimize interference between radios, each radio is assigned a unique channel. To further minimize the likelihood of interference, radios may be assigned channels according to a channel allocation scheme.
To illustrate a scheme for allocating channels so as to minimize interference, reference is made to FIG. 8, which shows a top view of a wireless access device 802 having 12 radios. A first radio 800 in the wireless access device 802 is between a first adjacent radio 804 and a second adjacent radio 806. Adjacent to the second adjacent radio 806 is a fourth radio 810 and adjacent to the first adjacent radio 804 is a fifth radio 808. Each of the twelve radios in the wireless access device 802 is tuned to a unique IEEE 802.11a channel.
A channel is the 20 MHz band of frequencies surrounding a specified center or carrier frequency. The channel consists of 18 MHz of actively used frequencies and 2 MHz of guard band. A channel number in the five GHz band is the number derived by subtracting 5 GHz from the channel center frequency and dividing the result by 5. Table 1 shows the channel numbers and corresponding center frequencies for each channel as defined in the IEEE 802.11a and 802.11b/g standards.
With the radios in close proximity, the operation of the wireless access device 802 may generate co-channel interference, which is a signal generated outside a given channel that lies in the adjacent channel or channels. In the 802.11a bands, co-channel interference is that part of the transmission spectrum that lies between −10 MHz and −30 MHZ and or that part of the transmission spectrum that lies between 10 MHz and 30 MHZ. The wireless access device 802 in FIG. 8 advantageously implements a scheme that minimizes co-channel interference.
In the wireless access device 802, the first radio 800 may be set to a first channel. The adjacent channel is the 20 MHz band of frequencies lying just above or just below the subject channel. As an example, channels 36 and 44 are adjacent to channel 40. In order to minimize interference, the wireless access device 802 assigns channels to the radios without using adjacent channels. That is, if a channel is assigned to a radio, the wireless access device 802 avoids using an adjacent channel to that channel. To the extent the use of adjacent channels cannot be avoided, an adjacent channel may be assigned with a radial separation of between 90° and 150°.
In one example implementation, a channel allocation scheme may start by setting the first radio 800 (in FIG. 8) to a specific channel. The two adjacent radios 804, 806 may then be assigned channels that are a minimum number (nch) of channels away. If nch is 4, the adjacent radios 804, 806 are assigned channels that are at least 80 MHz away. The next adjacent radios 808, 810 may then be assigned channels that are at least 40 MHz or 60 MHz (a smaller number neha) away from the first radio 800.
In one example channel mapping scheme, the radios of a twelve radio circular array may be assigned to the twelve channels of the 802.11a 1999 specification. If nch=16 and ncha=12, co-channel assignment is limited to radios placed at 90, 120 and 150 degrees, approximately 25,248 mapping schemes may be generated. An example of one of those schemes is shown below in Table 3.
Radio Number Channel No.
The maps can be generated once and stored in non-volatile memory for use as needed or can be generated on the fly by a recursive program running on the array control computer. For example, a computer program may be implemented that generates, in sequence, all possible channel assignment for a circular, arbitrary-sized array of radios and searches the possible assignments for channel maps which have the largest possible values of nch and ncha while also avoiding the use of adjacent data channels, where possible, and by limiting their positions, when avoidance is not possible, to locations that fall between 90 degrees and 150 degrees of radial separation. This process determines a number of map candidates sharing equally advantageous nch and ncha values. The map to be used by the access device may then be selected at random, for example, using a random number generation function from the set of equally advantageous maps.
The selected channel allocation map may be applied to the radios of the wireless access device 800 array.
Interference may also come from foreign associated stations (stations associated with other wireless access devices), other wireless access devices, or sources not related to the wireless access device. An example of a system for allocating channels in a multi-radio circular wireless access device may be extended to optimize performance in the presence of other wireless access devices and/or wireless LAN access points and/or foreign-associated clients and/or sources of radio interference not emanating from wireless LAN devices. Several factors and calculations should be defined.
First, the RSSI may be monitored by the wireless access device. The RSSI is the receive signal strength in DBm. For wireless access devices, the number falls between −30 DBm and −95 DBm with −30 DBm being the strongest signal. The wireless access device may also determine a non wireless access device signal duty cycle, which is the percentage of time that the radio receives energy above −85 DBm from signal sources not recognized as that of the wireless access device. The channel usage factor is a number obtained from the calculation of [(Packet length/bit rate)*(100+RSSI)]+[(Non wireless access device Signal Duty Cycle)*70]. The spectrum usage matrix is a tabulation of the channel usage factor measured for each radio in an array of radios on each channel potentially available for use by said radio. The channel map quality score is the number calculated for each possible channel mapping scheme by summing the channel usage factors for each radio measured on the channel designated for that radio by the channel mapping scheme. The number will lie between 0 (for no interfering signals on any channel) and 70 times the number of radios (for all channels experiencing severe interference).
FIG. 9 is a flowchart 900 of an example implementation of a method performed by the wireless access device. As an example, when the wireless access device powers up (step 902), all radios in the wireless access device may be tuned to the same channel (such as channel 36) (step 904). The radios all listen for signals from any source arriving on this channel. Radios whose antennas are oriented towards the possible emitting source will receive substantially more signal than those not so oriented. Each radio receives the signal (906). Each radio then determines a signal score, i.e. each radio's Channel Usage Factor, which is recorded in a table (step 908). All of the radios are then tuned to the next channel (step 912). The radios receive the signals (step 906) and each radio determines the channel usage factor for the channel (908), and expands the table of channel usage factors. The process is repeated and each time, a check is performed to see if all of the channels have been used (step 910). When all of the channels have been used, the channel usage factors are tabulated in a spectrum usage matrix. The process continues by testing the spectrum usage matrix against a table of possible mapping schemes that provide approximately maximum isolation (step 914). The wireless access device then sets the radios to the channel scheme that is most appropriate for the situation of the environment.
Each possible allocation map is weighted by calculating its Channel Map Quality Score. The Channel Allocation Maps having the best Channel Map Quality Score is chosen. Several Channel Allocation Maps may share the same Channel Map Quality Score and, therefore, be equally advantageous. The map to be used by the access device may then be selected at random, for example, using a random number generation function from the set of equally advantageous maps.
The following illustrates one example of a process for allocating channels in a wireless access device.
Channel Allocation in a Wireless Access Device
Determine all possible channel maps (preferably using a recursive computer program.)
Initialize the computer variable NoCoChannels to false.
Examine the first channel map and find the number of co-channels that are used. (co-channels, or adjacent channels, are channels that are 20 MHz away from any other channel.)
If this value is zero, set a computer variable: NoCoChannels to true.
If this value is not zero, find the largest and smallest angles between co-channels.
If the largest angle is greater than 150 degrees eliminate this map from consideration and go to Step 3.
If the smallest angle is less than 90 degrees eliminate this map from consideration and go to Step 3.
Find the lowest value of Nch for any radio in the first channel map this is the Nch score for the first map.
Store this value in a computer variable: MaxNch
Find the lowest value of Ncha for any radio in the first channel map this is the Ncha score for the first map.
Store this value in a computer variable: MaxNcha
Examine a second channel map and find the number of co-channels that are used.
If this value is zero, set the computer variable: NoCoChannels to true
If this value is not zero, and the computer value NoCoChannels is true eliminate this map from consideration and go to Step 4.
Otherwise, if this value is not zero, find the largest and smallest angles between co-channels.
If the largest angle is greater than 150 degrees eliminate this map from consideration and go to Step 4.
If the smallest angle is less than 90 degrees eliminate this map from consideration and go to Step 4.
Otherwise, find the lowest value of Nch for any radio in the second channel map this is the Nch score for the second map.
If the Nch value is greater than the stored value of MaxNch replace MaxNch with this larger value and also find the lowest value of Ncha for any radio in the second channel map this is the Ncha score for the second map. Store this value in a computer variable MaxNcha
If the Nch value is equal to the stored value of MaxNch find the lowest value of Ncha this is the Ncha score for the second map. Store this value in a computer variable MaxNcha
If the Nch score is less than MaxNch do not evaluate Ncha and eliminate this map from consideration
Examine the next channel map and find the number of co-channels that are used.
If this value is zero set the computer variable NoCoChannels to true
If this value is not zero and the computer value NoCoChannels is true eliminate this map from consideration and go to Step 5.
Otherwise if this value is not zero find the largest and smallest angles between co-channels.
If the largest angle is greater than 150 degrees eliminate this map from consideration and go to Step 5.
If the smallest angle is less than 90 degrees eliminate this map from consideration and go to Step 5.
Otherwise, find the lowest value of Nch for any radio in the channel map this is the Nch score for the map.
If the Nch score is greater than the stored value of MaxNch replace MaxNch with this larger value and also find the lowest value of Ncha for any radio in the this channel map this is the Ncha score for the map. Store this value in the computer variable MaxNcha and eliminate all previously examined maps from consideration.
If the Nch value is equal to the stored value of MaxNch find the lowest value of Ncha this is the Ncha score of the map. If it is greater than the stored value of MaxNcha replace MaxNcha with this value and eliminate all previously examined maps from consideration.
If the Nch score is less than MaxNch do not evaluate Ncha and eliminate this map from consideration.
Repeat Step 4 for each of the many (usually many thousands) of possible channel maps. The results of this iterative process are:
If any channel map does not use co-channels then all maps having co-channels will be eliminated from consideration.
MaxNch will grow to be the largest possible value for an Nch score MaxNcha will grow to be the largest possible value for an Ncha score among maps having the largest possible Nch score.
All channel maps whose Nch score is not equal to MaxNch and whose Ncha score is not equal MaxNcha will be eliminated from consideration.
The result of this process yields only the most advantageous channel maps (that is, those having the largest Ncha from among those having largest Nch score). There may be many channel maps sharing the same most advantageous scores.
The chosen Channel Allocation map is applied to the radios of the wireless access device.
Referring to FIG. 8, the wireless access device 802 is capable of utilizing the error vector measurement (“EVM”) data in improving the performance of the radios in the wireless access device 802. It is appreciated by those skilled in the art that the EVM is not a function of the ambient conditions, and that the EVM is a performance measure defined by the specification of IEEE 802.11.
In an example of operation, the first radio 800 may transmit a signal that is received by any of the other radios in the wireless access device 802. As an example, if a second radio 804 receives the transmitted signal, the second radio 804 may calculate the EVM of the second radio by comparing the received signal (from the transmitted signal) at the second radio with the known characteristics of the transmitted signal at the first radio. This method compensates for variations in gain characteristics of the different amplifiers and receivers in the wireless access device 802 by providing a comparison of the radios based on the measured EVM. This comparison may allow for a maximum allowable transmit power to be varied to each radio circuit to allow for the highest transmit rates for the EVM. The EVM for each radio may be stored in a table in the memory of the wireless access device 802 and used for improving the performance of the radios.
The EVM for each radio may be used for channel allocation in manner similar to the manner in which the Channel Usage Factor is used in the example described with reference to FIG. 9. The EVM may be compared against a predefined table in the wireless access device 802 as described above. Instead of calculating the channel usage factor, the EVM may be calculated for each radio at each channel for a signal transmitted by each of the other radios. Once these values are known, EEPROMs may be programmed with the information and included in each radio circuit. The EVM values may be tested against possible mapping schemes that provide approximately maximum isolation. The wireless access device 802 then sets the radios the channel scheme that is most appropriate for the characteristics of each radio.
1. A method for allocating channels in a wireless access device having a plurality of radios capable of operating on a plurality of channels, the method comprising:
initially tuning each of the plurality of radios to a selected same one of the plurality of channels;
transmitting a signal at the selected same channel from a transmitting one of the plurality of radios;
receiving the signal at the selected same channel on the plurality of radios that are not the transmitting radio;
determining an error vector measurement (“EVM”) for each one the plurality of radios that are not the transmitting radio;
storing the EVM for each one of the plurality of radios that are not the transmitting radio for the selected same channel for the transmitting radio;
selecting a next one of the plurality of radios to transmit the signal at the same selected channel;
repeating the steps of transmitting the signal at the selected same channel, receiving the signal at the selected same channel, determining the EVM, storing the EVM, and selecting the next radio until each one of the plurality of radios has transmitted the signal at the same selected channel;
tuning each of the plurality of radios to another one of the plurality of channels;
repeating the steps of transmitting the signal at the selected same channel, receiving the signal at the selected same channel, determining the EVM, storing the EVM, selecting the next radio, and tuning the plurality of radios to the other one of the plurality of channels until each channel has been used; and
testing the EVM scores against a table of mapping schemes to determine maximum isolation.
2. A method according to claim 1 where the EVM scores for each radio at each channel is stored in memory for use in determining highest transmit rates by varying a maximum allowable transmit power in each radio.
3. A method according to claim 1 where the step of calculating the EVM comprises:
at each one of the plurality of radios that is not transmitting the signal at the selected same channel, determining characteristics of a received signal;
retrieving characteristics of a transmitted signal at the selected same channel;
comparing the characteristics of the received signal with the characteristics of the transmitted signal;
determining the EVM based on the comparison.
US13732841 2008-05-13 2013-01-02 System for allocating channels in a multi-radio wireless LAN array Active 2028-05-31 US8798069B2 (en)
US81606508 true 2008-05-13 2008-05-13
US13732841 US8798069B2 (en) 2008-05-13 2013-01-02 System for allocating channels in a multi-radio wireless LAN array
US14446091 US20150098407A1 (en) 2005-03-09 2014-07-29 System for allocating channels in a multi-radio wireless lan array
PCT/US2006/008698 Continuation WO2006096853A3 (en) 2005-03-09 2006-03-09 System for allocating channels in a multi-radio wireless lan array
US81606508 Continuation 2008-05-13 2008-05-13
US14446091 Continuation US20150098407A1 (en) 2005-03-09 2014-07-29 System for allocating channels in a multi-radio wireless lan array
US20130343210A1 true true US20130343210A1 (en) 2013-12-26
US8798069B2 US8798069B2 (en) 2014-08-05
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US13732253 Active 2028-10-12 US9001764B2 (en) 2008-05-13 2012-12-31 System for allocating channels in a multi-radio wireless LAN array
US13732841 Active 2028-05-31 US8798069B2 (en) 2008-05-13 2013-01-02 System for allocating channels in a multi-radio wireless LAN array
US14446091 Abandoned US20150098407A1 (en) 2005-03-09 2014-07-29 System for allocating channels in a multi-radio wireless lan array
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