Serge Willenegger

cdma2000 physical layer: An overview

cdma2000 offers several enhancements as compared to TIA/EIA-95, although it remains fully compatible with TIA/EIA-95 systems and allows for a smooth migration from one to the other. Major new capability include: 1) connectivity to GSM-MAP in addition to IP and IS-41 networks; 2) new layering with new LAC and MAC architectures for improved service multiplexing and QoS management and efficient use of radio resource; 3) new bands and bandwidths of operation in support of various operator needs and constraints, as well as desire for a smooth and progressive migration to cdma2000; and 4) flexible channel structure in support of multiple services with various QoS and variable transmission rates at up to 1 Mbps per channel and 2 Mbps per user. Given the phenomenal success of wireless services and desire for higher rate wireless services, improved spectrum efficiency was a major design goal in the elaboration of cdma2000. Major capacity enhancing features include: 1) turbo coding for data transmission; 2) fast forward link power control; 3) forward link transmit diversity; 4) support of directive antenna transmission techniques; 5) coherent reverse link structure; and 6) enhanced access channel operation. As users increasingly rely on their cell phone at work and at home for voice and data exchange, the stand-by time and operation-time are essential parameters that can influence customers satisfaction and service utilization. Another major goal of cdma2000 was therefore to enable manufacturers to further optimize power utilization in the terminal. Major battery life enhancing features include: 1) improved reverse link performance (i.e., reduced transmit power per information bit); 2) new common channel structure and operation; 3) quick paging channel operation; 4) reverse link gated transmission; and 5) new MAC states for efficient and ubiquitous idle time operation. This article provides additional details on those enhancements. The intent is not to duplicate the detailed cdma2000 radio access network specification, but rather to provide some background on the new features of cdma2000 and on the qualitative improvements as compared to the TIA/EIA-95 based systems. The article is focused on the physical layer structure and associated procedures. It therefore does not cover the MAC, LAC, radio resource management [1], or any other signaling protocols in any detail. We assume some familiarity with the basic CDMA concepts used in TIA/EIA-95.

WCDMA uplink system performance

In WCDMA, uplink radio resources are shared by multiple users and the radio resource management (RRM) is done at the UTRAN (UMTS Terrestrial Radio Access Network). In this paper, the link and system performance of the WCDMA uplink is evaluated using different techniques such as retransmissions with incremental redundancy (IR), short frame durations and fast scheduling. It is seen that the radio link efficiency can be improved using IR, while the traffic delays can be reduced and cell throughput can be enhanced by using fast scheduling and short frame durations.