Frequency-selective Fast Rayleigh Fading Research Articles

Spread Spectrum‐Based Subcarrier Recovery Method for Multi‐Carrier Code Division Multiplexing System

AbstractA time domain Spread Spectrum (SS)‐based subcarrier recovery method is proposed for down‐link Multi‐Carrier Code Division Multiplexing (MC‐CDM) system, which periodically inserts SS pilot signals into data signal stream in a time division manner at the transmitter. Instantaneous channel impulse response is first estimated by correlating the received pilot signal at the receiver, and then corresponding instantaneous frequency response essential for subcarrier recovery is calculated from the Discrete Fourier Transform (DFT) of the estimated impulse response. The SS pilot‐assisted method is also applicable to Direct Sequence (DS)‐CDM system as a means to estimate instantaneous channel impulse response for Rake combining, and taking the same approach in both MC‐CDM and DS‐CDM systems, there is no large difference between them in terms of transmission efficiency and receiver complexity. The proposed MC‐CDM system must be a promising down‐link multiplexing protocol, because it can achieve better bit error rate (BER) performance than the DS‐CDM system with the same SS pilot‐assisted Rake combiner in frequency selective fast Rayleigh fading channel.

Transmission performance analysis of Multi-Carrier Modulation in frequency selective fast Rayleigh fading channel

In this paper, we discuss the transmission performance of Multi-Carrier Modulation (MCM) in frequencyselective fast Rayleigh fading channels. First, we optimize the transmission parameters of MCM withM-ary differential phase shift keying/differential detection (DPSK):the guard duration andthe number of sub-carriers for frequency-selective fast Rayleigh fading channels, and then show the bit error rate (BER) performance of the optimizedM-ary DPSK MCM. Next, we propose an MCM with pilot-assistedM-ary quadrature amplitude modulation/coherent detection (QAM), and discuss the BER performance when we reduce the number of pilot signals from the view-point of frequency-time utilization efficiency. Finally, we propose a two-stage frequency offset compensation method.

Performance of GMSK with two-bit differential detection in a land mobile radio channel

The performance of two-bit differential detection of Gaussian minimum-shift keying (GMSK) in a cellular mobile communication channel is theoretically analyzed. The channel is modelled to reflect those encountered in a practical system; i.e., a frequency-selective fast Rayleigh-fading channel corrupted by cochannel interference and additive white Gaussian noise. A two-ray model for the channel is used and a single cochannel interferer is considered in the analysis. The Doppler effect is included as well. A closed-form expression for the probability of error is obtained. Numerical computation is used to obtain GMSK bit-error-rate performance for various combinations of channel parameters. The results are compared with those for limiter-discriminator detection with the same channel parameters. The performance of limiter-discriminator detection is found to be superior to that of two-bit differential detection. As two-bit differential detection is generally simpler to implement, the choice of detection method involves a performance versus complexity trade-off. The results presented can be used to make this trade-off.