Dual FH/MFSK system over a Rayleigh fading channel

A dual frequency-hopped/multilevel frequency shift keying (FH/MFSK) system is proposed for a Rayleigh fading channel. The dual FH/MFSK system is achieved by frequency-hopping a carrier frequency of the FH/MFSK system proposed by Goodman et al. (1980). The numerical results show that the proposed system allows more users than does the conventional system     

Independent multitone jamming of FH/MFSK in Rician channels

We derive exact expressions of the symbol error rate (SER) performance of orthogonal, frequency-hopped, noncoherent M-ary frequency-shift-keying (FH/MFSK) receivers in the presence of independent multitone jamming (MTJ), as well as thermal and other wideband Gaussian noises. Both the signal tones and the multiple jamming tones are affected independently by Rician fading. Both the slow-hopping and fast-hopping systems are considered. In our derivation, we exploit the fact that the multipath components of the signal and jamming tones can be combined with the other Gaussian noises to form a single Gaussian process. Using this technique, we are able to obtain compact exact SER expressions which can be computed efficiently. From the computation results we provide physical explanations on the effects of several system parameters, such as jamming fraction, fading conditions and number of hops per symbol, on the SER performance of slow and fast FH/MFSK systems under independent MTJ     

Analysis of two-stage address coding scheme for FFH/MFSK systemsover Rician fading channels

The author investigates the effect of fade distributions on various FH/MFSK systems, and subsequently provides a fair comparison between the performance of the dual FH/MFSK system proposed by Park and Lee (1996) with that of the conventional system suggested by Goodman et al. (1980)     

Diversity and coding for FH/MFSK systems with fading and jamming.II. Selective diversity

For pt.1 see ibid., vol.COM-35, p.1329-41 (1987). A performance evaluation is presented for selective diversity with feedback for frequency-hopping M-ary frequency-shift-keyed systems operating over Rayleigh faded channels in the presence of partial-band noise and partial-band tone jamming. The behavior of uncoded and coded systems is studied. For coded systems, the performance is evaluated for hard-decision receivers without channel state information and soft-decision receivers with perfect jammer state information. The results demonstrate that the performance of uncoded FH/MFSK with selective diversity is unacceptable. However, this diversity technique can offer definite improvements for coded FH/MFSK systems. Specifically, the effectiveness of selective diversity signaling depends on the provision of a feedback channel between the transmitter and receiver to provide the transmitter with the fading gains of the independently faded channels. To obtain an improvement from the selective diversity signaling scheme described here, there must be multiple independently faded channels between the transmitter and receiver. If not, the performance of the selective diversity signaling scheme will be identical to the performance of FH/MFSK without diversity     

Asymptotical performance of M-ary and binary signals overmultipath/multichannel Rayleigh and Rician fading

This paper presents a general framework for computing the asymptotic error probability (i.e., at high average SNRs) of M-ary and binary signaling schemes over Rician and Rayleigh fading diversity channels. A general theorem (Theorem 1) relates the asymptotic error rate of multipath and multichannel receivers (over AWGN, ISI free channels) to the multidimensional integral of the conditional error probability. Two other theorems are presented for the particular cases where the conditional error probability is a function of the sum of received SNRs (Theorem 2) or received amplitudes (Theorem 3). Theorems 2 and 3 are related for linear coherent systems, and closed form expressions are obtained for equal gain combining systems. Detection structures for typical diversity schemes (coherent/noncoherent maximal ratio and equal gain combining, and quadratic noncoherent combining) are considered. We analyze the asymptotic error rates of some M-ary signaling schemes (MPSK/MPAM with Kth order diversity and orthogonal signals with K=1 and with coherent and noncoherent detection). Binary signaling is also considered in our study     

Channel coding for narrow-band Rayleigh fading with robustnessagainst changes in Doppler spread

For digital transmission over frequency-nonselective fading channels, data security can be obtained by error correction coding, but the coding scheme has to be adapted to the channel properties. For many vehicular applications, the range of possible vehicle speeds is large and in the UHF band the resulting Doppler frequency may not be small relative to the symbol rate-suggesting a differential detection scheme. Therefore, the channel coding should be robust against changes in Doppler spread. A combination of a convolutional code (soft-decision decoding) and a Reed-Solomon (RS) code is considered, and the performance in a narrow-band Rayleigh-fading channel with differential quaternary phase shift keying (DQPSK) modulation without interleaving is evaluated as a function of signal-to-noise ratio (SNR) and Doppler spread by computer simulations. This transmission scheme is proved to have good performance over a large variety of vehicle speeds     

Performance of MHPM in Rician and Rayleigh fading mobile channels

This paper evaluates the error probability of the rectangular frequency pulse multi-h modulation (MHPM) scheme in slowly-fading, frequency-nonselective or frequency-selective Rician and Rayleigh channels. The evaluation is performed with a method combining analysis and computer simulation. Performance degradations are evaluated for various direct-to-reflected signal ratio, Doppler shifts, and relative time delays in Rician fading channels. Compared with minimum shift keying (MSK), MHPM schemes appear to have retained their coding gains     

New closed-form bounds on the performance of coding in correlated Rayleigh fading

New, simple bounds are presented for the probability of error in a binary hypothesis test for communications using diversity signaling in correlated Rayleigh fading. The bounds are developed in the context of pairwise error-event probabilities in decoding an error-correction code. A long-standing conjecture regarding the form of worst-case error events in exponentially correlated Rayleigh fading is also proven. The utility of the results is illustrated by their application to transfer-function bounds on the probability of bit error for a system using a convolutional code. The closed-form transfer-function bounds are shown to be tighter than previously developed transfer-function bounds for communications in exponentially correlated Rayleigh fading.     

A micro-cellular CDMA system over slow and fast Rician fading radiochannels with forward error correcting coding and diversity

The microcellular radio environment is characterized by a Rician fading channel. The use of a slotted code division multiple access (CDMA) scheme is considered in single- and multi-microcell systems. The throughput and delay performance of a slotted CDMA network are analyzed for slow and fast Rician fading radio channels using differential phase shift keying (DPSK) modulation. The application of selection diversity (SD) and maximal ratio combining (MRC) improve the performance for both slow and fast fading. It is also shown that the use of forward error correcting (FEC) codes enhances the system performance. Computational results are presented for maximum rms delay spread in the order of 2 μs and data rates of 32 and 64 kbit/s. A comparative analysis of macro-, micro- and pico-cellular CDMA systems is also presented     

Maximum-likelihood receiver with side information for asynchronous FFH-MA/MFSK systems over Rayleigh fading channels

The maximum-likelihood (ML) receiver structure and the corresponding analytical bit-error rate (BER) expressions for a fast-frequency hopped multiple-access (FFH-MA) M-ary frequency-shift-keying (MFSK) system over Rayleigh-fading channels are derived. Numerical results are also presented to illustrate the superiority of the proposed ML receiver in terms of BER. However, the proposed ML receiver requires some side information of the noise and interfering users.     

Impact of Doppler spread and adaptive modulation on TCP throughput in Rayleigh fading channels

A number of wireless systems have recently adopted adaptive modulation (AM) schemes to improve its efficiency. In this letter, our aim is to study the impact Doppler spread and adaptive modulation has on transmission control protocol (TCP) throughput in Rayleigh fading channels. We consider a finite state Markov channel (FSMC) model, which is a useful model for analyzing radio channel with nonindependent fading. Furthermore, we use a Markov model for TCP evolution and evaluate the TCP performance by computer simulations. In our simulations we have compared the TCP Reno scheme with TCP Tahoe scheme. The results indicate that a large Doppler spread leads to lower TCP throughput due to more frequent transitions of channel states and modulation schemes which make it difficult for the TCP congestion control mechanism to accommodate the dynamic link characteristics.     

The impact of fading correlation on the error performance of MIMO systems over Rayleigh fading channels

This paper analyzes the impact of receive fading correlation on the error performance of a multiple-input multiple-output (MIMO) system that employs a zero-forcing detection scheme over frequency-nonselective Rayleigh fading channels. Error rate expressions as a function of the eigenvalues of the fading correlation matrix and the number of transmit and receive antennas are derived. Numerical results indicate that MIMO systems are resistant to receive fading correlation.     

Channel capacity and error exponents of variable rate adaptivechannel coding for Rayleigh fading channels

We have evaluated the information theoretical performance of variable rate adaptive channel coding for Rayleigh fading channels. The channel states are detected at the receiver and fed back to the transmitter by means of a noiseless feedback link. Based on the channel state informations, the transmitter can adjust the channel coding scheme accordingly. Coherent channel and arbitrary channel symbols with a fixed average transmitted power constraint are assumed. The channel capacity and the error exponent are evaluated and the optimal rate control rules are found for Rayleigh fading channels with feedback of channel states. It is shown that the variable rate scheme can only increase the channel error exponent. The effects of additional practical constraints and finite feedback delays are also considered. Finally, we compare the performance of the variable rate adaptive channel coding in high bandwidth-expansion systems (CDMA) and high bandwidth-efficiency systems (TDMA)     

Impact of channel prediction on adaptive coded modulation performance in Rayleigh fading

Adaptive coded modulation (ACM) is a promising tool for increasing the spectral efficiency of time-varying mobile channels while maintaining a predictable bit-error rate (BER). An important restriction in systems with such a transmission scheme is that the transmitter needs to have accurate channel-state information (CSI). Earlier analysis of ACM systems usually assumes that the transmitter has perfect knowledge of the channel or that the CSI is accurate but outdated. In this paper, we investigate the effects of predicting the CSI using a linear fading-envelope predictor in order to enhance the performance of an ACM system. For the case in which multidimensional trellis codes are used on Rayleigh-fading channels, we obtain approximative closed-form expressions for BER and average spectral efficiency. Numerical examples are given for the case of Jakes correlation profile and maximum a posteriori-optimal predictor coefficients.     

Performance of fast frequency-hopped MFSK receivers with linear andself-normalization combining in a Rician fading channel withpartial-band interference

An error probability analysis is performed for both self-normalized and conventional M-ary orthogonal frequency-shift-keying (MFSK) noncoherent receivers using fast frequency-hopped (FFH) spread-spectrum waveforms transmitted over a Rician fading channel with partial-band interference. The self-normalization receiver uses a nonlinear combination procedure to minimize performance degradation due to partial-band interference. The performance of the conventional receiver is significantly degraded by worst-case partial-band interference regardless of the modulation order or number of hops per data symbol used, while the self-normalization receiver can provide a significant immunity to worst-case partial-band interference for many channel conditions when diversity is used, provided the signal-to-thermal-noise ratio is large enough to minimize degradation due to nonlinear combining losses. The improvement afforded by higher modulation orders is dependent on channel conditions     

Error performance of noncoherent MFSK with L-diversity oncorrelated fading channels

Noncoherent diversity reception of M-ary frequency-shift keying (MFSK) signals becomes increasingly important due to its widespread use in wireless communications. Its error performance analysis, however, is not available in the literature except for the simple case using binary modulation. We address the problem directly based on the decision variables, ending up with closed-form solutions to both conditional and average error probabilities for a general noncoherent MFSK diversity system operating on Rayleigh, Rician, and Nakagami fading channels. The solutions involve some higher order derivatives, and efficient recursive algorithms have been derived for their calculation. The solutions are very general permitting arbitrary diversity order, symbol size, channel parameters, and antenna-array covariance matrix. Numerical examples are also presented for illustration     

Bit error rate performance of π/4-DQPSK in a frequency-selectivefast Rayleigh fading channel

The bit error rate (BER) performance of π/4-differential quadrature phase shift keying (DQPSK) modems in cellular mobile communication systems is derived and analyzed. The system is modeled as a frequency-selective fast Rayleigh fading channel corrupted by additive white Gaussian noise (AWGN) and co-channel interference (CCI). The probability density function of the phase difference between two consecutive symbols of M-ary differential phase shift keying (DPSK) signals is first derived. In M-ary DPSK systems, the information is completely contained in this phase difference. For π/4-DQPSK, the BER is derived in a closed form and calculated directly. Numerical results show that for the 24 kBd (48 kb/s) π/4-DQPSK operated at a carrier frequency of 850 MHz and C/I<20 dB, the BER will be dominated by CCI if the vehicular speed is below 100 mi/h. In this derivation, frequency-selective fading is modeled by two independent Rayleigh signal paths. Only one co-channel is assumed in this derivation. The results obtained are also shown to be valid for discriminator detection of M-ary DPSK signals     

Outage probability analysis for microcell mobile radio systems with cochannel interferers in Rician/Rayleigh fading environment

A microcell mobile radio system where the desired signal within a cell experiences Rician fading while interfering signals from cochannel cells experience Rayleigh fading is studied. This model is named a Rician/Rayleigh fading environment. Expressions of outage probabilities are presented for the mobile radio system in the Rician/Rayleigh fading environment.<>     

Unified analysis of error performance for binary signalling over Rayleigh fading channels

Using the unified expression as devised by Wojner, an analytical framework is presented to determine error performance of all binary modulation schemes employing coherent or non-coherent detection and operating over a slow flat Rayleigh fading channel with different diversity combining. A class of generalised expressions for the bit error probability has been obtained following the probability density function or the cumulative distribution function approach.     

FH／MFSK系统抗干扰性能研究

跳频技术以其良好的抗干扰性,成为战术通信领域应用最广的一种抗干扰手段.本文首先推导出FH/MFSK系统在高斯白噪声信道下的信噪比与误比特率关系函数,再根据关系函数分析了FH/MFSK系统在宽带干扰和部分频带干扰下的抗干扰性能.最后通过Matlab/Simulink建模测得相应数据,并分析了仿真结果,同时给出了提高跳频系统抗干扰能力的相应措施.