Directional antennas and wireless channel access
First Claim
1. A method for distributed medium access that schedules transmission of frames on a channel in a wireless access network comprising an access point and a plurality of stations illuminated by multiple beams of an antenna system emanating from said access point, which antenna system does not enable simultaneous communication on the same channel in opposite directions between said access point and any two stations covered by different beams, in a way that reduces channel capture, comprising the steps of:
- Said stations transmit according to a medium access protocol that allows the initiation of transmission only when the channel is idle; and
requiring all stations engaged in uplink transmission to release the channel at the same time, causing the channel to become idle at that time and thus preventing capture of the channel by uplink transmissions.
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Abstract
A method is disclosed for addressing the problem of uplink capture, which arises in a multiple-cell wireless LAN using directional antennas. The use of directional antennas may adversely impact the performance of channel access protocols. CSMA-type MAC protocols provide dynamic bandwidth allocation in a distributed manner, eliminating idle time intervals. With such protocols, time-overlapped uplink transmissions by stations illuminated by different beams cooperate to capture the channel for long time periods. Without special measures, an imbalance could arise in the opportunity for the AP to access the channel, which could result in downlink delay and jitter and overall capacity loss. According to this invention, the uplink capture problem is mitigated by requiring all (non-AP) stations to release the channel at pre-specified times.
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Citations
20 Claims
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1. A method for distributed medium access that schedules transmission of frames on a channel in a wireless access network comprising an access point and a plurality of stations illuminated by multiple beams of an antenna system emanating from said access point, which antenna system does not enable simultaneous communication on the same channel in opposite directions between said access point and any two stations covered by different beams, in a way that reduces channel capture, comprising the steps of:
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Said stations transmit according to a medium access protocol that allows the initiation of transmission only when the channel is idle; and
requiring all stations engaged in uplink transmission to release the channel at the same time, causing the channel to become idle at that time and thus preventing capture of the channel by uplink transmissions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification