In 3GPP, Common Packet Channel(CPCH) is newly introduced to support data ervice more efficiently. CPCH is an uplink common channel that transports packets of medium size. CPCH is evolved out of 3GPP Random Access Channel(RACH). RACH is a contention based common channel which is used to transport bursts of 10ms size. Generally, short control messages are transported in RACH.
As traffic volume increases, it is necessary to use some methods that divide these traffic into some groups and treat differently. For example, audio traffic is latency sensitive but data traffic is less influenced by delay.
In this paper, we make some changes for the CPCH access scheme. We suggest a non-preemptive scheme and a preemptive scheme for the basic CPCH and the CPCH with channel assignment. Then, the performance of CPCH with the proposed scheme is evaluated through Equilibrium Point Analysis(EPA) and computer simulation. Both schemes, serve the high priority class services very efficiently with small latency.