Unslotted DS/CDMA packet radio network using rate/space adaptive CLSP

This paper presents a throughput-delay analysis of a centralized unslotted DS/CDMA packet radio network using rate adaptive channel load sensing protocol (CLSP). CLSP is an access control protocol used to limit the contentions, i.e. multiple access interference (MAI) of the CDMA unslotted ALOHA radio channel, under a certain threshold to improve the system throughput. A mobile-location (space) based rate adaptive extension of CLSP is proposed to: (i) compensate the near-far effects and transmitter power control (TPC) difficulty of datagram packet transmissions under changing channel conditions; (ii) enhance the system performance and coverage; (iii) increase the energy-efficiency of the mobile unit. An analytical method is developed based on a multi-rate loss network model, of which each system load state is described with a two-state hidden Markov model (HMM) taking into account the impacts of TPC inaccuracy, spatial user distributions and channel attenuation. The results show that the proposed rate/space adaptive CLSP system gains significant improvement in throughput-delay tradeoffs compared to the fixed rate counterpart with the same coverage, offered traffic and QoS requirements. Also, in the new system the mobile terminal can operate with much lower maximum power.