Performance analysis of a multi-access protocol for a packet switched CDMA radio network using channel load sensing

A modified multi-access protocol for data traffic in a packet radio network using code division multiple access (CDMA) is introduced and analysed. The scheme employs CDMA in a centralised channel load-sensing scheme with channel overload (collision) detection. The data users contend for channel access using a slotted spread spectrum inhibit-sense multiple access (ISMA) scheme. For a given maximum bit error rate due to mutual multi-access interference (MAI), an upper threshold (β) on the number of users allowed into the channel can be determined. This paper proposes a second lower threshold α to improve the system performance by adding an access control mechanism. This extension attempts to avoid overloading the channel by blocking new packets when the load is nearing the threshold β. Analytical and simulation results show that an improved throughput performance can be obtained by implementing a centralised load sensing scheme and channel control mechanism. In addition, it is shown that the blocking threshold should be dynamic with respect to the measured channel load, as an optimum value for throughput exists for a given load