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In this paper, the transform domain code division multiple access (TDCDMA) is proposed, which synthesizes the excellence of the transform domain communication system (TDCS) and the code division multiple access (CDMA) technology. The TDCDMA has the characteristic of low probability of intercept (LPI) and the capability of multiple access (MA), and it's great potential to be applied in the cognitive radio (CR) contexts. Compared with the traditional TDCS and CDMA, the complex RAKE receiver is avoided in TDCDMA. The transceiver block diagram and the signal model of TDCDMA are given, and it's performance is investigated, discussed and simulated in Additive White Gaussian Noise (AWGN) and multi-path fading channels. Computer simulation results show that the TDCDMA is much more superior than the traditional TDCS and can be a promising transmission scheme in CR contexts.

Known as one spectrum agile transceiver technology in the cognitive radio (CR) contexts, the transform domain communication system (TDCS) has the characteristic of low probability of intercept (LPI) and the capability of multiple access (MA). In this paper, The primary work is to give a detailed description of the FFT-Based channel estimation (CE) in TDCS receiver, which is applied in receiving symbol demodulation, where the CE-based demodulation algorithm is given. In matlab, simulation results indicate that the FFT-Based CE of TDCS is realizable and available, and the performance of CE-based demodulation algorithm is better than the one of RAKE receiver algorithm in both the Additive White Gaussian Noise (AWGN) and the multi-path fading channels.