‘Shield’: protecting high priority channel access attempts in overlapped wireless cells
A method and system reduce interference between overlapping first and second wireless LAN cells contending for the same medium. Each cell includes a respective plurality of member stations. An inter-cell contention-free period value is assigned to a first access point station in the first cell, associated with an accessing order in the medium for member stations in the first and second cells. The access point in the first cell transmits an initial shield packet to deter other stations from contending for the medium. The access point then transmits a beacon packet containing the inter-cell contention-free period value to member stations in the second cell. A second access point in the second cell can then delay transmissions by member stations in the second cell until after the inter-cell contention-free period expires.
1. A method for reducing an interference between a first wireless local area network cell and a second wireless local area network cell in a medium, the method comprising:
transmitting, by an access point station in the first wireless local area network cell, a shield packet to deter a plurality of member stations from contending for the medium; and
transmitting, by the access point station in the first wireless local area network cell, a beacon packet containing an inter-cell contention-free period value, wherein the inter-cell contention-free period value is deterministically set and represents a time period that the first wireless local area network cell has seized the medium.
2. The method of claim 1 , further comprising:
receiving the beacon packet at member stations of the plurality of member stations in the second wireless local area network cell; and
delaying transmissions by the member stations of the plurality of member stations in the second wireless local area network cell until after the time period.
3. The method of claim 1 , further comprising:
transmitting in the beacon packet to member stations of the plurality of member stations in the first wireless local area network cell a value of an intra-cell contention-free period, during which the member stations of the plurality of member stations in the first wireless local area network cell will delay accessing the medium.
4. The method of claim 3 , further comprising:
transmitting by the access point station in the first wireless local area network cell during the time period a polling packet to a first member station of the member stations in the first wireless local area network cell authorizing the first member station to transmit data.
5. The method of claim 4 , wherein the member stations of the plurality of member stations in the first wireless local area network cell wait to be polled with the polling packet from the access point station before transmitting data during the time period.
6. The method of claim 3 , further comprising:
assigning to the member stations of the plurality of member stations in the first wireless local area network cell a shorter backoff time value for a backoff time for high quality of service data and a longer backoff time value for the backoff time for lower quality of service data, wherein the backoff time being a time interval that the member stations of the plurality of member stations in the first wireless local area network cell wait after an expiration of the intra-cell contention-free period before the member stations of the plurality of member stations in the first wireless local area network cell contend for access to the medium.
7. A wireless communications system for reducing an interference between a first wireless local area network cell and a second wireless local area network cell in a medium, the system comprising:
a first access point station in the first wireless local area network cell having a value of an inter-cell contention-free period, wherein the first access point station transmits a shield packet to deter a plurality of member stations from contending for the medium, and wherein the first access point station transmits a beacon packet containing the value of the inter-cell contention-free period, wherein the value of the inter-cell contention-free period is deterministically set.
8. The wireless communications system of claim 7 , further comprising:
a second access point station in the second wireless local area network cell receiving the value of the inter-cell contention-free period and delaying transmissions by member stations of the plurality of member stations in the second wireless local area network cell until after the inter-cell contention-free period.
9. The wireless communications system of claim 8 , further comprising:
the first access point station transmitting in the beacon packet to member stations of the plurality of member stations in the first wireless local area network cell a value of an intra-cell contention-free period, during which member stations of the plurality of member stations in the first wireless local area network cell delay accessing the medium.
10. The wireless communications system of claim 9 , further comprising:
the first access point station transmitting in the first wireless local area network cell during the intra-cell contention-free period a polling packet to a first member station of the member stations in the first wireless local area network cell authorizing the first member station to transmit data.
11. The wireless communications system of claim 10 , wherein member stations of the plurality of member stations in the first wireless local area network cell wait to be polled with the polling packet from the first access point station before transmitting data during the intra-cell contention-free period.
12. The wireless communications system of claim 9 , further comprising:
wherein member stations of the plurality of member stations in the first wireless local area network cell are assigned a shorter backoff time value for a back off time for high quality of service data and a longer backoff time value for the back off time for lower quality of service data, wherein the back off time being a time interval that the member stations of the plurality of member stations in the first wireless local area network cell wait after an expiration of the intra-cell contention-free period before the member stations of the plurality of member stations in the first wireless local area network cell contend for access to the medium.
13. A method for reducing an interference between a first wireless local area network cell and a second wireless local area network cell in a medium, the method comprising:
receiving, by a member station in the second wireless local area network cell, a shield packet sent from the first wireless local area network cell for deterring the member station in the second wireless local area network cell from contending for the medium;
receiving, by the member station in the second wireless local area network cell, a beacon packet with a value of an inter-cell contention-free period that represents a time period that the first wireless local area network cell has seized the medium; and
delaying, by the member station in the second wireless local area network cell, a transmission until after the time period.