‘Shield’: protecting high priority channel access attempts in overlapped wireless cells

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:

• a first access point station in the first cell having an inter-cell contention-free period value associated with an accessing order in the medium for member stations in the first and second cells during a transmission frame;
• said first access point station transmitting a shield packet to deter other stations from contending for the medium;
• said first access point station transmitting a beacon packet containing the inter-cell contention-free period value;
• and
• a second access point station in the second cell receiving the inter-cell contention-free period value and delaying transmissions by member stations in the second cell until after said inter-cell contention-free period.

A method for reducing interference between overlapping wireless LAN cells, each cell including an access point station and a plurality of member stations, comprising:

• assigning to a first access point station in a first wireless LAN cell a first contention-free period value;
• assigning to first member stations in said first cell a first shorter backoff value for high QoS data and a first longer backoff value for lower QoS data;
• assigning to a second access point station in a second wireless LAN cell that overlaps said first cell a second contention-free period value longer than said first contention-free period value;
• assigning to second member stations in said second cell a second shorter backoff value for high QoS data and a second longer backoff value for lower QoS data;
• transmitting by the first access point station in the first cell a shield packet to deter other stations from contending for the medium;
• transmitting a first beacon packet, including said first contention-free period value, from said first access point to said first member stations in said first cell;
• transmitting a second beacon packet, including said second contention-free period value, from said second access point to said second member stations in said second cell;
• transmitting a first contention-free time response frame containing said first contention-free period value from said first member stations, thereby alerting said second access point and said second member stations in said second cell that the medium has been seized by said first access point;
• waiting for said first contention-free period at said first member stations to begin counting down said first shorter backoff for high QoS data and then transmitting first high QoS data;
• waiting for said second contention-free period at said second member stations to begin counting down said second shorter backoff for high QoS data and then transmitting second high QoS data;
• waiting for said first contention-free period at said first member stations to begin counting down said first longer backoff for low QoS data and then transmitting first low QoS data;
• and
• waiting for said second contention-free period at said second member stations to begin counting down said second longer backoff for lower QoS data and then transmitting second lower QoS data.