Real-time traffic over the IEEE 802.11 medium access control layer

This paper proposes multiple access procedures to transport real-time traffic over IEEE 802.11 wireless local area networks (LANs). As currently defined, the IEEE 802.11 standard supports real-time traffic by switching from its normal, distributed access mode — carrier sense multiple access/collision avoidance (CSMA/CA) — to a centralized one. The centralized mode severely constrains the operation of wireless LANs and provides inadequate performance. Our proposed procedures, on the other hand, are totally distributed and can be overlaid on CSMA/CA. They use the carrier sense capabilities of the network interfaces and require only the ability to jam the channel with pulses of energy of specified duration. The resulting scheme guarantees priority to real-time traffic and provides round-robin service and bounded access delays to real-time stations. This paper examines the behavior of the new access techniques to derive conditions under which they can be considered stable. In addition, it presents simulation results that assess the impact of these access procedures on the average delay of data packets. The simulations are also used to provide estimates of the number of real-time stations that can be supported under various network operating conditions.