Known as one spectrum agile transceiver technology in the cognitive radio (CR) contexts, the transform domain communication system (TDCS) has the characteristic of 1ow 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 CEbased 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.

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Known as one of the Cognitive Radio (CR) transceiver technologies, the transform domain communication system (TDCS) has the characteristic of 1ow probability of intercept (LPI) and the capability of multiple access (MA). In this paper, basing on the random phase mapping, the characteristics of the pseudorandom (PR) phase vector and the Basis Function (BF) are investigated. After that, two methods of generating random phase, the least common multiple method and the equal interval method are proposed, which both can generate the PR phase vector and the BF of TDCS. In matlab, simulation results indicate that the two methods both can generate the BFs, which have the characteristic of strong autocorrelation and weak crosscorrelation in TDCS.

For the particularity of some departments' work and mission, the command and dispatch system based on TD-SCDMA network is proposed. Their needs for the point-to-point communication service and the group call service of the one-tomultipoint communication can be met in 3G mobile communication network. In view of the fact that people need this particular communication mode and the communication features of command and dispatch system, the centralized transmission network structure and the scattered transmission network structure of command and dispatch system based on TD-SCDMA network are given. At the same time, the communication protocols of the group call are discussed in detail. Finally, the command and dispatch system is simulated by using OPNET software. The result shows that the command and dispatch system can need the different stages of development and can reduce the blocking probability of leading to core network by adopting the rational network structure.