Fast Rayleigh Channels Research Articles

Asymptotic BER EXIT chart analysis for high rate codes based on the parallel concatenation of analog RCM and digital LDGM codes

This paper proposes an extrinsic information transfer (EXIT) chart analysis and an asymptotic bit error rate (BER) prediction method to speed up the design of high rate RCM-LDGM hybrid codes over AWGN and fast Rayleigh channels. These codes are based on a parallel concatenation of a rate compatible modulation (RCM) code with a low-density generator matrix (LDGM) code. The decoder uses the iterative sum-product algorithm to exchange information between the variable nodes (VNs) and the two types of constituent check nodes: RCM-CN and LDGM-CN. The novelty of the proposed EXIT chart procedure lies on the fact that it mixes together the analog RCM check nodes with the digital LDGM check nodes, something not possible in previous multi-edge EXIT charts proposed in the literature.

Differentially Detected GMSK Signals in CCI and Restricted Bandwidth Fast Rayleigh Channels

Error rate performance of Gaussian minimum shift keying (GMSK) signals with centre sampling single and double differential detection (CSDD, CSDDD) is analyzed in restricted bandwidth (BW) fast Rayleigh channel. The performance of CSDD and CSDDD schemes is analyzed in the presence of carrier random frequency shift, Doppler frequency shift, co-channel interference (CCI), and additive white Gaussian noise (AWGN), while the receiver rejects a specified amount of adjacent channel interference (ACI). For the interference, we adopt a model which includes N statistically independent faded CCI. A formula for the error floor is also presented. It is shown that the CSDD scheme is sensitive to frequency offset and in many instances can not be used at all. However, the CSDDD scheme has a potential to combat the effect of frequency shifts and its performance is better than the CSDD scheme with about 2.6 dB when random frequency shifts are introduced into the carrier. Furthermore, the performance of these schemes is improved by utilizing the conventional decision feedback (CDF) technique.

An efficient decision feedback with center sampling differential detector for restricted bandwidth fast Rayleigh channels

An efficient decision feedback technique (EDF) is proposed to improve the performance of premodulation Gaussian minimum shift keying (GMSK) signals. Center sampling differential detector (CSDD) over restricted bandwidth (BW) fast Rayleigh channels is employed. The intersymbol interference (ISI) is partially eliminated by using the conventional decision feedback (CDF) technique. In the present modification ISI is drastically eliminated by using EDF technique resulting in the minimization of probability of error. The new receiver structure, is useful in mobile radio (MR) and mobile satellite communications where power efficiency, synchronization and implementation complexity are of primary concern. Numerical results show that the receiver structure under consideration yields a superior performance in narrowband channels where conventional differential detector (CDD) becomes unusable.

Performance of offset receiver diversity for GMSK and spread spectrum GMSK with one-bit differential detection using decision feedback in fast Rayleigh channels

This paper introduces the application of three techniques to improve the performance of one-bit differential detection (DD). The Gaussian minimum shift keying (GMSK) modulation technique is employed. The proposed techniques are spread spectrum, offset receiver diversity and decision feedback (DF). A comparative study shows that when applying the direct sequence spread spectrum (DS-SS), the performance is improved by 9.3 dB at a bit error rate (BER) of 10?3 and the processing gain is equal to 10 relative to that given by Elnoubi [IEEE Trans. Veh. Tech. VT-35(1986)162---167]. When using the offset receiver diversity technique, the corresponding relative improvement is 13 dB. When employing both SS and offset diversity at the same BER, 22 and 25.7 dB improvements are attained for DS and frequency hopping (FH), respectively. A further improvement of about 1 dB is obtained when DF is used.