A Low-Complexity Joint Synchronization and Detection Algorithm for Single-Band DS-CDMA UWB Communications
- PDF / 669,112 Bytes
- 9 Pages / 600 x 792 pts Page_size
- 94 Downloads / 183 Views
A Low-Complexity Joint Synchronization and Detection Algorithm for Single-Band DS-CDMA UWB Communications Lars P. B. Christensen Information and Mathematical Modelling, Technical University of Denmark, 2800 Kongens Lyngby, Denmark Email: [email protected] Received 1 October 2003; Revised 2 June 2004 The problem of asynchronous direct-sequence code-division multiple-access (DS-CDMA) detection over the ultra-wideband (UWB) multipath channel is considered. A joint synchronization, channel-estimation, and multiuser detection scheme based on the adaptive linear minimum mean square error (LMMSE) receiver is presented and evaluated. Further, a novel nonrecursive least-squares algorithm capable of reducing the complexity of the adaptation in the receiver while preserving the advantages of the recursive least-squares (RLS) algorithm is presented. Keywords and phrases: ultra-wideband, direct-sequence code-division multiple-access, multiuser detection, low-complexity adaptive receivers, synchronization.
1.
INTRODUCTION
Over the last couple of years, the interest in ultra-wideband (UWB) wireless communications has been growing. Among the reasons for this increased awareness of UWB are the promises of low-power, high-bitrate wireless connections without the need for spectrum allocation, and the approval of the technology by authorities as, for example, the American FCC [1]. UWB signals for wireless communication typically have a bandwidth of several GHz and can be utilized in many ways each presenting the designer with tradeoffs between cost, power, bitrate, range, and the number of users supported. The system considered in this paper is a single-band UWB direct-sequence code-division multiple-access (DS-CDMA) receiver with all signal processing done on the received signal sampled directly from an amplified and filtered antenna signal. This enables the removal of traditional up- and downconverters present in today’s narrowband transceivers at the expense of increasing the required sampling rate and thus the complexity of the signal processing. It is therefore of great interest to reduce the complexity of such receivers to make them feasible. The receiver considered is fully adaptive making it possible to track changes not only in the multipath channel, but also in the received pulse shape. This is desirable in order to maximize performance even under conditions distorting the received pulse shape as discussed in [2], but distortions orig-
inating from the electromagnetic propagation environment can also be adaptively compensated for. Combined LMMSE synchronization and detection for DS-CDMA systems have already been studied (see, e.g., [3, 4, 5, 6, 7]). This paper is a continuation of [8] extended with the synchronization method in [3], but having a lowcomplexity adaptive algorithm with recursive least-squares (RLS)-speed convergence. Furthermore, this paper uses the channel model presented in [9] instead of the model in [8] as the latter may prove too optimistic for typical office use as a result of the larger dimensions typically p
Data Loading...
