A high capacity CDMA array-receiver requiring reduced pilot power
Sofiène Affes, A. Louzi, Nema Mohamed Kandil, Paul G. Mermelstein · 2002
The use of coherent modulation for the uplink of wireless CDMA systems requires pilot signals which contribute to the interference seen by other users. In previous work we showed that blind array-receivers outperform pilot-channel assisted array-receivers in capacity for various operating conditions. These array-receivers avoid additional interference due to pilot signals and achieve better channel identification using relatively stronger data signals. However, for BPSK signals they identify the channel within a sign ambiguity and require differential modulation and decoding of coherently detected bits. In this contribution we implement coherent modulation and detection and further increase the advantage of this blind channel identification scheme by introducing a new pilot called "pilot-sign". This pilot simply allows resolution of the channel sign ambiguity after its estimation by long-term averaging of the pilot-channel combiner output. Analysis indicates that the resulting pilot-sign assisted array-receiver requires very weak pilot power ratios, in the range of a fraction of a percent, and allows very significant pilot power savings and large capacity gains compared to pilot-channel array-receivers.