Access method for periodic contention-free sessions
First Claim
1. A method for reducing interference between overlapping first and second wireless LAN cells in a medium, each cell including a respective plurality of member stations, comprising:
- coordinating by a first member station in the first cell a sequence of first periodic contention-free sessions, each said session including multiple bursts with other member stations in the first cell, and retaining control of the medium by said first member station by using interframe spaces sufficiently short between the bursts that the multiple bursts appear to contending stations to be a single instance of activity in the medium during a session until an end of a session;
setting a fixed cycle time by the first member station to repeat transmitting said first periodic contention-free sessions, the cycle time being a cycle period (CP), which is the contention-free period (CFP) of a member station times a factor which is a function of the number of overlapping cells;
transmitting said first periodic contention-free session by the first member station;
coordinating by said second member station in the second cell a sequence of second periodic contention-free sessions, each said second session including multiple bursts with other member stations in the second cell, and retaining control of the medium by said second member station by using interframe spaces sufficiently short between the bursts that the multiple bursts appear to contending stations to be a single instance of activity in the medium during a session until an end of a session;
setting said fixed cycle time by the second member station to repeat transmitting said second periodic contention-free sessions following said first periodic contention-free sessions; and
transmitting said second periodic contention-free session by the second member station.
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Accused Products
Abstract
An access method for periodic contention-free sessions (PCFS) reduces interference between overlapping first and second wireless LAN cells contending for the same medium. Each cell includes a respective plurality of member stations and an access point (AP) station. The access method for periodic contention-free sessions (PCFS) includes a fixed cycle time that reduces conflicts with PCFS from other cells. The PCFS from several cells are repeated in cycles of cycle period (CP), which is the contention-free period (CFP) of an access point times a factor that is a function of the number of overlapping cells. Periodic contention-free sessions (PCFSs) are generated, one from each overlapping cell. PCFS transmission attempts occur at the fixed specified time spacing following the start of the previous cycle. Each active AP sets a timer at CP and a PCFS is initiated when the timer expires. The timer is then reset to CP and this starts a new cycle. Contention transmissions are attempted by stations based on their assigned priority. If a channel is busy at the designated start time for transmitting a PCFS, the PCFS is shortened by the time lost. Interleaving PCFSs and CFSs reduces conflicts with CFSs from other cells. To lessen the contention between APs of different cells, each station'"'"'s Network Allocation Vector (NAV) and Inter-BSS Network Allocation Vector (IBNAV) is updated by an increased value of the next CFS length, the increment being the inter-BSS contention period (IBCP). APs will attempt to access the channel during the IBCP only for transmitting a PCFS, while they will wait for the NAV and IBNAV expirations before attempting to transmit a CFS. Interleaving PCFSs and CFSs also enables maintaining quality of service (QoS).
94 Citations
8 Claims
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1. A method for reducing interference between overlapping first and second wireless LAN cells in a medium, each cell including a respective plurality of member stations, comprising:
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coordinating by a first member station in the first cell a sequence of first periodic contention-free sessions, each said session including multiple bursts with other member stations in the first cell, and retaining control of the medium by said first member station by using interframe spaces sufficiently short between the bursts that the multiple bursts appear to contending stations to be a single instance of activity in the medium during a session until an end of a session;
setting a fixed cycle time by the first member station to repeat transmitting said first periodic contention-free sessions, the cycle time being a cycle period (CP), which is the contention-free period (CFP) of a member station times a factor which is a function of the number of overlapping cells;
transmitting said first periodic contention-free session by the first member station;
coordinating by said second member station in the second cell a sequence of second periodic contention-free sessions, each said second session including multiple bursts with other member stations in the second cell, and retaining control of the medium by said second member station by using interframe spaces sufficiently short between the bursts that the multiple bursts appear to contending stations to be a single instance of activity in the medium during a session until an end of a session;
setting said fixed cycle time by the second member station to repeat transmitting said second periodic contention-free sessions following said first periodic contention-free sessions; and
transmitting said second periodic contention-free session by the second member station. - View Dependent Claims (2, 3, 4)
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5. A wireless communications system having reduced interference between overlapping first and second wireless LAN cells in a medium, each cell including a respective plurality of member stations, comprising:
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a first access point station in the first cell;
said first access point station coordinating in the first cell a sequence of first periodic contention-free sessions, each said session including multiple bursts with other member stations in the first cell, and retaining control of the medium by said first access station by using interframe spaces sufficiently short between the bursts that the multiple bursts appear to contending stations to be a single instance of activity in the medium during a session until an end of a session;
said first access point station setting a fixed cycle time to repeat transmitting said first periodic contention-free sessions, the cycle time being a cycle period (CP), which is the contention-free period (CFP) of a member station times a factor which is a function of the number of overlapping cells;
said first access point station transmitting said first periodic contention-free session;
a second access point station in the second cell;
said second access point station coordinating in the second cell a sequence of second periodic contention-free sessions, each said second session including multiple bursts with other member stations in the second cell, and retaining control of the medium by said second access station by using interframe spaces sufficiently short between the bursts that the multiple bursts appear to contending stations to be a single instance of activity in the medium during a session until an end of a session;
said second access point station setting said fixed cycle time to repeat transmitting said second periodic contention-free sessions following said first periodic contention-free sessions; and
said second access point station transmitting said second periodic contention-free session. - View Dependent Claims (6, 7, 8)
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Specification