Sensitivity function of soft decision carrier sense MAC protocols for wireless CDMA networks with specified QoS
Savo Glisic, V. Phan-Van · 2002
The system throughput, outage probability and packet delay are analyzed for a feedback channel state information (FCSI) based soft decision MAC protocol in a centralized asynchronous CDMA packet radio system with finite population. The relative system performance loss due to effects of the feedback delay, access delay and imperfect channel sensing is investigated in terms of sensitivity functions. The motivation behind this protocol is to control the access of data transmission by dynamically changing permission probability depending on FCSI. The channel state is defined as a number of packets currently being transmitted in up-link (UL) multiple access channel. The FCSI is sensed and emitted periodically by a central base station (BS). The UL interfering load is therefore softly controlled under a certain threshold for a QoS requirement. The system performance can be improved significantly compared with conventional ALOHA or statically hard decision MAC packet radio system. The system is modeled with a modified Erlang loss queuing system, which has a variable number of servers and Erlang distributed service function. Tradeoff of the system parameters and performance characteristics is discussed based on number of numerical results.