Dynamic and Scalable Bandwidth Allocation for Beyond 3G CDMA Systems

Abstract

In this paper, we introduce an enhanced Direct Spread Code Division Multiple Access (DS-CDMA) based system, called Multi-Carrier DS-CDMA (MC DS- on transmissions on N DS-CDMA carriers, where N is scalable based on system bandwidth and each carrier transmits an independent DS-CDMA waveform. MC DS-CDMA is a fundamentally different concept than the straightforward bandwidth expansion of current CDMA systems in several aspects. First, it is strictly backward compatible, and thus can overlay with existing single carrier DS-CDMA system without any performance degradation. Moreover, variable and asymmetric radio bandwidth (or number of carriers) can be dynamically scheduled to a Mobile Station (MS) on the Forward Link (FL) and the Reverse Link (RL) on a per-scheduling time-slot basis. This introduces another dimension of fast resource/user multiplexing in the carrier domain, in addition to the time domain as in existing 3 rd generation systems, e.g. UMTS HSDPA, 1xEV-DO, 1xEV-DV. We also propose a novel service-driven layer 2/3 protocol design across multiple carriers to efficiently multiplex user traffic across multiple carriers and to exploit both multi-carrier diversity and multi- user diversity. Our performance results show that MC DS-CDMA provides significant improvements over single-carrier systems.