Frequency assignment for multi-cell IEEE 802.11 wireless networks
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Abstract
A frequency planning method for use in an IEEE 802.11 wireless network is described. The frequency planning method obtains traffic load information associated with access points belonging to a multi-cell wireless network and assigns channels to the access points based on the traffic load information.
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Citations
40 Claims
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1-20. -20. (canceled)
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21. A method for frequency planning in wireless networks comprising:
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obtaining traffic load information for access points belonging to a wireless network having a plurality of Access Points (APs) where a channel between a terminal and an AP of said network is employed to communicate both traffic and control information and communication is established between said terminal and said AP by use of multiple access protocol; and
assigning channels to the access points based on the traffic load information where traffic load information for a considered AP includes load of traffic between the considered AP and terminals that communicate with the considered AP, and effective load that results from detections of channel busy conditions due to interfering communication by terminals with other APs of said network.
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22. The method of claim 21 wherein the step of assigning comprises:
determining, for each considered AP, at least one set of interferers from among the other APs relative to said considered AP.
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23. The method of claim 22 wherein the step of determining comprises:
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determining, for each of the other access points, if any co-channel interference by any of the other access points is greater than or equal to a detection threshold, the detection threshold indicative of an additional perceived load arising from the CSMA protocol; and
if it is determined that the co-channel interference is greater than or equal to the detection threshold, identifying the other access point as belonging to the set of interferers for the access point that increases the load that is considered to burden the access point.
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24. The method of claim 23 wherein the co-channel interference between an access point and another access point is derived from values of signal path loss between the access point and the other access point and transmission power of the other access point.
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25. The method of claim 23 wherein the at least one set of interferers comprises a second set of interferers, and wherein the step of determining comprises:
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determining, for any pair of the other access points, if any combined co-channel interference by such pair is greater than or equal to a detection threshold, the detection threshold indicative of an additional perceived load arising from the CSMA protocol; and
if it is determined that the combined co-channel interference is greater than or equal to the detection threshold, identifying the other access points in such pair as belonging to the second set of interferers for the access point that increases the load that is considered to burden the access point.
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26. The method of claim 22 wherein the step of assigning further comprises:
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generating random channel assignments for the access points;
determining effective channel utilization values for each access point;
modifying the random channel assignment for interferers in the at least one set of interferers such that the highest one of the effective channel utilization values is minimized;
repeating said step of modifying until the highest one of the effective channel utilization values cannot be reduced by further modification; and
saving the modified random channel assignment as a final assignment.
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27. The method of claim 26 wherein the step of assigning further comprises:
providing the final assignment to the access points.
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28. The method of claim 22 wherein the step of assigning further comprises:
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assigning randomly a channel to each of the access points; and
computing, based on the random channel assignment, an effective channel utilization value for each access point, the effective channel utilization value representing the sum of an offered load associated with the access point and total traffic load associated with each set of interferers.
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29. The method of claim 28 wherein the step of assigning further comprises:
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determining which access point has the highest effective channel utilization value;
identifying which channel is assigned to the access point having the highest effective channel utilization value; and
for each access point in the first set of interferers, modifying the random channel assignment;
recomputing the effective channel utilization value for the modified random channel assignment; and
repeating modifying and recomputing for each available channel other than the channel assigned to the access point having the highest effective channel utilization value;
determining a minimum effective channel utilization from among the recomputed effective utilization values;
comparing the minimum effective channel utilization and the recomputed effective channel utilization values; and
replacing the highest effective channel utilization with the determined minimum effective channel utilization and saving the modified random channel assignment as a best solution if the determined minimum effective channel utilization is lower than the highest effective channel utilization.
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30. The method of claim 29 wherein the step of assigning further comprises:
with a pre-specified probability, replacing the highest effective channel utilization with the determined minimum effective channel utilization and saving the modified random channel assignment as a best solution if the determined minimum effective channel utilization is equal to the highest effective channel utilization.
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31. The method of claim 26 wherein the step of assigning further comprises:
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computing an effective utilization value for each access point based on the final assignment; and
determining if the effective utilization value for each access point is less than a value of one.
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32. The method of claim 21 wherein the channels comprise non-overlapping channels.
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33. The method of claim 21 wherein the channels comprise overlapping and non-overlapping channels.
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34. The method of claim 21 wherein the access points employ the CSMA/CA protocol.
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35. The method of claim 21 wherein the step of assigning comprises:
seeking to minimize effective channel utilization of a most heavily loaded of the access points.
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36. The method of claim 21 wherein the step of assigning comprises:
seeking to minimize total effective channel utilization of all access points.
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37. The method of claim 21 wherein the step of assigning comprises:
seeking to maximize network throughput.
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38. An article comprising:
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a storage medium having stored thereon instructions that when executed by a machine result in the following;
obtaining traffic load information for access points belonging to a wireless network having a plurality of Access Points (APs) where a channel between a terminal and an AP of said network is employed to communicate both traffic and control information and communication is established between said terminal and said AP by use of multiple access protocol; and
assigning channels to the access points based on the traffic load information where traffic load information for a considered AP includes load of traffic between the considered AP and terminals that communicate with the considered AP, and effective load that results from detections of channel busy conditions due to interfering communication by terminals with other APs of said network.
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39. An apparatus comprising:
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a processor; and
a memory storing a computer program product residing on a computer-readable medium comprising instructions to cause a computer to;
obtain traffic load information for access points belonging to a multi-cell IEEE 802.11-type wireless network; and
assign channels to the access points based on the traffic load information where traffic load information for a considered AP includes load of traffic between the considered AP and terminals that communicate with the considered AP, and effective load that results from detections of channel busy conditions due to interfering communication by terminals with other APs of said network.
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40. An access point for use in wireless network comprising:
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logic configured to obtain traffic load information for access points belonging to the wireless network having a plurality of Access Points (APs) where a channel between a terminal and an AP of said network is employed to communicate both traffic and control information and communication is established between said terminal and said AP by use of multiple access protocol; and
logic configured to assign channels to the access points based on the traffic load information where traffic load information for a considered AP includes load of traffic between the considered AP and terminals that communicate with the considered AP, and effective load that results from detections of channel busy conditions due to interfering communication by terminals with other APs of said network.
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Specification