Notker Gerlich

Efficient Design of Voice Carrying Fixed-Network Links in CDMA Mobile Communication Systems

Code Division Multiple Access (CDMA) technology is gaining momentum as the preferred wireless system for the next generation Personal Communication Systems (PCS). In CDMA systems, voice is encoded and packaged in variable length packets that are transported between the mobile station and the switching center. Although the packetization provides a great flexibility in resource allocation, it poses a Quality of Service (QoS) problem on voice. In this paper, we discuss link dimensioning for a typical CDMA system. We consider a T1/E1 link between a CDMA Basestation Transceiver System (BTS) and the Base Station Controller (BSC). Traffic from various voice sources is subject to a framing scheme, which presents a semi-periodic batch input at the T1/E1 interface cards. We analyze the resulting queuing system using discrete-time analysis and large deviations theory and verify our results by simulation. We provide results for the minimum link capacity needed to support a given number of CDMA voice sources. Our results show the potential statistical gain that can be achieved by voice packetization for all practical values of link capacities.