In this paper, we propose and analyze a new non coherent receiver with PN code tracking for direct sequence code division multiple access (DS-CDMA) communication systems in multipath channels. We employ the decision-feedback differential detection method to detect MDPSK signals. An “; error signal”; is used to update the tap weights and the estimated code delay. Increasing the number of feedback symbols can improve the performance of the proposed non coherent receiver. For an infinite number of feedback symbols, the optimum weight can be derived analytically, and the performance of the proposed non coherent receiver approaches to that of the conventional coherent receiver. Simulations show good agreement with the theoretical derive
The telecommunications industry faces the problem of providing telephone services to rural areas, where the customer base is small, but the cost of installing a wired phone network is very high. One method of reducing the high infrastructure cost of a wired system is to use a fixed wireless radio network. The problem with this is that for rural and urban areas, large cell sizes are required to get sufficient coverage. This presents extra problems as there are long delay times in multi path signal propagation.
Currently Global System for Mobile telecommunications (GSM) technology is being applied to fixed wireless phone systems in rural areas or Australia. However, GSM uses time division multiple access (TDMA), which has a high symbol rate leading to problems with multi path causing inter-symbol interference. Several techniques are under consideration for the next generation of digital phone systems, with the aim of improving cell capacity, multi path immunity, and flexibility. These include CDMA and OFDM. Both these techniques could be applied to providing a fixed wireless system for rural areas. However, each technique as different properties, making it more suited for specific applications.