A New Construction of Signature Waveforms for Multi-rate Multi-cell QS-CDMA Systems |
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Authors: | Lifang Feng Pingzhi Fan Li Hao Kok-keong Loo Vahid Tarokh |
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Affiliation: | (1) The Provincial Key Lab of Information Coding and Transmission, Institute of Mobile Communications, Southwest Jiaotong University, Chengdu, 610031, China;(2) School of Engineering and Design, Brunel University, London, UB8 3PH, UK;(3) School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA |
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Abstract: | In this paper, we propose a new construction of signature waveform sets based on Generalized Loosely Synchronization (GLS) sets and different chip waveforms. The new signature sets are applied into the multi-rate multi-cell quasi-synchronous CDMA (QS-CDMA) system where each cell is assigned with a GLS set; different users in the same cell are assigned with different GLS sequences in the same GLS set; user’s different streams are assigned with the same GLS sequence but different chip waveforms. According to the properties of GLS sets, the inter-cell interference (ICI) and the multi-user interference (MUI) in the same cell can be reduced significantly. The interferences among different streams of the same user are handled by an optimal (or suboptimal) multi-stream detector(s), notice that the multi-stream detector mentioned here is also named as multi-user detector in other references. We compare the performance of the multi-rate multi-cell QS-CDMA system employing the proposed sets with that of multi-rate system employing well-known concatenated orthogonal/PN sets and that of single-rate system employing GLS sets. The results show that the multi-rate system employing the proposed sets can achieve significant interference reduction. Meanwhile the performance of multi-rate system is similar to that of single-rate system due to the inclusion of multi-user detection. |
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Keywords: | GLS sequences Generalized orthogonal Multi-rate Quasi-synchronous CDMA system |
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