MULTIPLE DIFFERENTIAL DETECTION OF CONTINUOUS-PHASE MODULATION SIGNALS

A new sequence estimation algorithm for the differential detection of the continuous phase modulation signals, yielding significant gains in BER performance and with considerable resistivity to fading, is introduced. These advantages, along with the reduced hardware complexity, low cost, and fast synchronization which characterize the differential detector, make the proposed receiver useful for land mobile radio and mobile-satellite communications, where the power efficiency, synchronization, and implementation complexity are of primary importance. The new receiver is based on multiple differential detection. The multiple differential detection strategy provides the decoder with more information regarding the transmitted data and applies a noise decorrelation process on the received signal, useful to the sequence estimation. The algorithm is derived in a general form, and can be applied on any CPM scheme, with any degree of complexity. We have evaluated the receiver for two of the most popular CPM schemes, the tamed frequency modulation (TFM) and Gaussian minimum shift keying (GMSK) (with B(t)T = 0.25), in the presence of additive white Gaussian noise and Rician fading. The BER performance evaluation results indicated significant gains and considerable reduction of error floors. In additive white Gaussian noise, improvements close to 9 dB have been verified.