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The local oscillator phase noise can severely affect the performance of OFDM systems. In this paper a new method is presented for compensation of this phase noise. The method is based on the fact that the scattered pilots, which are used for channel estimation, are subject to the same phase error as the OFDM symbols. Least square approach is used to exploit the phase noise information that exists in the scattered pilots and compensate the phase noise on the OFDM symbols. Simulation results show that the method is very effective, especially in high SNR.

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In direct-sequence spread spectrum receivers complete detection of the modulated-spreaded signal after F W : down conversion consists of IF-carrier and PN-code wipe-off procedures. In the straightforward widely used method the carrier wipe-off is performed through using high frequency NCOs being clocked at rates with at least 2 times the highest frequency in the IF spectrum. This can yield in large amounts of power consumption especially in multi-channel receivers.On the other hand in these receivers faster and more reliable coarse acquisitionheacquisition requires parallel correlation while for tracking more than one channel DS/SS data in many spread spectrum applications (e.g. GPS) we have to duplicate or multiplex the correlators. This paper describes the design of a Multiplier-Free all digital quadrature mixer followed by a low power multiplexed multi-phase 12-channel parallel passive correlator and their comparison to some existing architectures. It is also showed that combining multiplexing, parallel passive features and the introduced mixer enables-us to implement simple circuits to reduce the power consumption of the baseband receiver as much as possible. The architecture is used for designing the first mixer and correlator section of a multi-channel GPS receiver baseband and is fully implemented and tested in an FPGA.