Near far self resistant CDMA wireless network

We introduce a new concept of multiple access called /spl tau/-CDMA. The abbreviation stands for code division multiple access with delay (or) modulation and hopping. The concept is based on a modification of direct sequence spread spectrum (DSSS) system where transmitted waveform includes multiple amplitude and delay replicas of DSSS signal. In general notation amM/spl tau/-DSDH is used for the DS signal that includes m delayed (/spl tau/) replicas of different amplitudes (a), sent in a limited delay window of M chip intervals. The position of the delay window is hopped (delay hopping-DH) in the range of the code length N. This provides resistance to near far effect without the need for complex multiuser detectors. The variable impacts of the near far effect, for different positions of the delay window and fading, are simultaneously reduced by interleaving. If the signal energy is split to m>1 separate components, making it more vulnerable to noise and fading, the overall flow of useful information will be still increased. The results demonstrate that under the large range of the signal, channel and interference parameters this system offers better performance. This system combines the good characteristics of DSSS and FHSS systems. The near far effect is mitigated without need for complicated multiuser detectors and at the same time the simplicity of the DSSS system is preserved. There is no need for a frequency synthesizer. The coherency for coherent RAKE reception is maintained in a much simpler way than in the FH system. Higher suppression of the multipath component is achieved than in a standard DSSS system. For the above signal formats this paper offers a number of receiver configurations ranging from very simple to more complex ones providing better and better performance. The application is energy aware software radio where a configuration control algorithm would chose the simplest configuration in order to provide the required QoS for the given environment with the minimum processing power resulting in minimum energy consumption.