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1.
Error probability analyses are performed for a coded M -ary frequency-shift keying system (MFSK) using L hops per M -ary word frequency-hopping spread-spectrum waveforms transmitted over a partial-band Gaussian noise jamming channel. The bit error probabilities are obtained for a square-law adaptive gain control receiver with forward-error-control coding under conditions of worst-case partial-band noise jamming. Both thermal noise and jamming noise are included in the analyses. Performance curves are obtained for both block codes and convolutional codes with both binary and M -ary channel modulations. The results show that thermal noise cannot be neglected in the analysis if correct determinations of the optimum order of diversity and the worst-case jamming fraction are to be obtained. It is shown that the combination of nonlinear combining, M -ary modulation, and forward-error-control coding is effective against worst-case partial-band noise jamming 相似文献
2.
The authors consider frequency-hopped spread-spectrum multiple-access communications using M -ary modulation and error-correction coding. The major concerns are multiple-access interference and the network capacity in terms of the number of users that can transmit simultaneously for a given level of codeword error probability. Block coding is studied in detail. The authors first consider the use of Q -ary Reed-Solomon (RS) codes in combination with M -ary modulation with mismatched alphabets so that Q >M . It is shown that the network capacity is drastically reduced in comparison with the system with matched alphabets. As a remedy, the use of matched M -ary BCH codes is proposed as an alternative to mismatched RS codes. It is shown that when the number of users in the system is large, a BCH code outperforms an RS code with a comparable code rate and decoding complexity. The authors consider the use of a robust technique for generation of reliable side information based on a radio-threshold test. They analyze its performance in conjunction with MFSK and error-erasure correction decoding. It is shown that this nonideal ratio-threshold method can increase the network capacity in comparison with the system with perfect side information 相似文献
3.
A concatenated coded modulation scheme is presented for error control in data communications. The scheme is achieved by concatenating a Reed-Solomon outer code and a bandwidth efficient block inner code for M -ary phase-shift keying (PSK) modulation. Error performance of the scheme is analyzed for an additive white Gaussian noise (AWGN) channel. It is shown that extremely high reliability can be attained by using a simple M -ary PSK modulation inner-code and a relatively powerful Reed-Solomon outer code. Furthermore, if an inner code of high effective rate is used, the bandwidth expansion required by the scheme due to coding will be greatly reduced. The scheme is particularly effective for high-speed satellite communications for large file transfer where high reliability is required. A simple method is also presented for constructing block codes for M -ary PSK modulation. Soome short M -ary PSK codes with good minimum squared Euclidean distance are constructed. These codes have trellis structure and hence can be decoded with a soft-decision Viterbi decoding algorithm. Furthermore, some of these codes are phase invariant under multiples of 45° rotation 相似文献
4.
Xiupu Zhang Peixuan Jiang 《Lightwave Technology, Journal of》1992,10(8):1127-1131
The performance of a coherent optical M -ary continuous-phase frequency-shift-keying (CPFSK) receiver using limiter-discriminator (L-D) detection is investigated. It is shown that L-D detection of CPFSK optical signals offers the best performance for a large normalized IF beat spectral linewidth, ΔνT . When the modulation index is unity, the receiver is immune to laser phase noise and can produce (M /4) exp (-SNR) symbol error probability, which may be considered as the upper bound if the optimal modulation index is used (SNR is the signal-to-noise ratio per symbol). Optimum modulation indexes are 0.8 and 1 at ΔνT =1% and ΔνT =2%, respectively, for M =4, 8, and 16 相似文献
5.
A low-complexity pseudo-analog speech transmission scheme is proposed for portable communications. It uses a speech coder based on adaptive differential pulse code modulation (ADPCM) in combination with a multilevel digital modulation technique such as M -ary DPSK or M -ary FSK and features low quantization noise, bandwidth efficiency, and robustness to transmission errors. A nonsymmetric M -ary DPSK scheme called skewed M -ary DPSK is proposed to enhance the noisy channel performance. Comparison to conventional analog FM and a digital speech transmission scheme using adaptive predictive coding and forward error correction (FEC) based on convolutional coding shows that the pseudo-analog system has the best objective signal-to-noise ratio performance under most channel conditions. Informal subjective evaluations rate the digital system superior to the pseudo-analog scheme for bad channels and conversely for good channels. It is concluded that the pseudo-analog system can be designed with low delay and high speech quality for good channels with high spectral efficiency 相似文献
6.
Using a new representation for continuous-phase modulated (CPM) signals, it is shown how a closed-form expression for the power spectral density of full-response M -ary CPM with modulation index J /M can be obtained by straightforward computations. This result is used to provide an explanation of the fact that this power spectral density depends only on J and not on M 相似文献
7.
Cannone G. Majumder S.P. Gangopadhyay R. Prati G. 《Communications, IEEE Transactions on》1991,39(10):1433-1437
Performance of convolutionally coded M -ary pulse position modulation (M -PPM) systems in the presence of slot synchronization errors is evaluated for the shot-noise-limited photon-counting receiver and the avalanche photodetection receiver. Both hard and soft (δ-max) demodulation results are given, and two soft-decision metrics are investigated 相似文献
8.
A fully digital implementation of digital modems is the preferred option of system designers because high performance can be achieved at reasonable cost. The author explains the beneficial features inherent in fully digital demodulator implementations. Other features which are required for land mobile satellite communication systems are also discussed. Recently reported techniques for the synchronisation and detection of M -ary PSK and M -ary QAM modulation schemes are reviewed with emphasis placed on those which are well suited to digital implementation 相似文献
9.
Consideration is given to the problems related to the design of M -ary continuous-phase frequency-shift keying (CPFSK) systems with modulation index h =J /M , combined with eternal rate r binary convolution encoders. The following questions are raised and answered: (1) how should different encoder-modulator systems be compared and how can comparable systems be recognized from the system parameters, i.e. M , h , and r ?; (2) what are the limits on the information rate per unit bandwidth, versus signal-to-noise ratio, when reliable transmission is required?; (3) how does one choose the system parameters M , h , and r when the overall system has to achieve a specified performance?; and (4) how does one design the external rate r binary convolutional encoder to put in front of the M -ary CPFSK modulation system with h =J /M ? A simple approximation for the bandwidth of a CPFSK signal is given and shown to be sufficiently accurate for system design purposes. The design of the external convolutional encoder is carried out in a novel way that leads to fewer states in the combined encoder-modulator system and thus yields improved performance for a given demodulation-decoding complexity compared to previous approaches for the design of coded CPFSK systems 相似文献
10.
The symbol error probability of two selection schemes, namely, maximum signal-to-noise ratio (M γ) selection and maximum output (MO) selection, for M -ary multidiversity reception over a Rayleigh fading channel are discussed. The symbol error probability of the MO scheme is lower than that of the M γ scheme. The more diversity receptions that are used, the larger is the difference. A simple expression of crossover average signal-to-noise ratio (per bit) is presented as a guideline for increasing the number of diversity receptions 相似文献
11.
Kasami T. Takata T. Fujiwara T. Lin S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1991,37(1):164-167
Two important structural properties of block M (=2' )-ary PSK modulation codes, linear structure and phase symmetry, are investigated. An M -ary modulation code is first represented as a code with symbols from the integer group S M-PSK=(0,1,2,---,M -1) under modulo-M addition. Then the linear structure of block M -PSK modulation codes over S M-PSK with respect to modulo- M vector addition is defined, and conditions are derived under which a block M -PSK modulation code is linear. Once the linear structure is developed, the phase symmetry of block M -PSK modulation codes is studied. In particular, a necessary and sufficient condition for a block M -PSK modulation code that is linear as a binary code to be invariant under 2h/180°M phase rotation, for 1⩽h ⩽l is derived. Finally, a list of short 8-PSK and 16-PSK modulation codes is given, together with their linear structure and the smallest phase rotation for which a code is invariant 相似文献
12.
The generalized cutoff rate of time- and frequency-selective fading channels is evaluated for M -ary frequency-shift keying (MFSK) and M -ary differential phase-shift keying (MDPSK) modulation with soft decoding. The optimal signaling rate and code rate for dispersive channels are evaluated. The guard time effect, is used in multipath spread channels, is evaluated for frequency-selective channels, and the optimal combination of signaling rate, code rate, and guard time is presented. Special attention is given to CCIR (International Radio Consultative Committee) HF channel models 相似文献
13.
It is shown how to derive formulas for the error probability for M -ary differential phase shift keying with differential phase detection (DPD) and M -ary frequency shift keying with DPD, limiter-discriminator detection and limiter-discriminator-integrator detection in the satellite mobile channel (SMC) with narrowband receiver filter if such formulas are available for the Gaussian channel. The modification of the formulas involves only a redefinition of the noise power and autocorrelation function. Since the SMC contains as special cases the land mobile (Rayleigh) channel and the Gaussian channel, the derived formulas are valid for these channels as well. In fact the formula for the land mobile channel is in many cases reduced to a closed form, which does not contain an integral. The author computes the error probability for the four systems, and compares their performance assuming a third-order butterworth filter and M =2,4,8 symbols 相似文献
14.
A method for the integration of the modulation operation in an automatic-repeat-request (ARQ) scheme is described. This method uses a memory for the successive transmissions of a codeword and, through a suitable encoding operation, the Euclidean distances among the codewords are significantly increased with the number of transmissions. The application of the described method to some different modulation schemes, such as M -ary PSK with M >2 and continuous-phase frequency shift keying modulation, is described. The optimum combination of the modulation and channel coding operations for some short block codes is also presented. The results of the theoretical analysis show that the method described permits improving both the error probability and the throughput of an ARQ protocol with respect to similar schemes 相似文献
15.
An expression is derived for the error probability of M -ary frequency shift keying with a limiter-discriminator-integrator detector and a narrowband receiver filter in the satellite mobile channel. This channel contains, as special cases, the Gaussian and Rayleigh (land mobile) channels. The error probability is computed as a function of various system parameters for M =2, 4, 8 symbols and a third-order Butterworth receiver filter 相似文献
16.
The asymptotic (M →∞) probability of symbol error P e,m for M -ary orthogonal modulation in a Nakagami-m fading channel is given by the incomplete gamma function P (m , mx ) where x =In 2/(E b/N 0) and E b is the average energy per bit. For large signal-to-noise ratio this leads to a channel where the probability of symbol error varies as the inverse m th power of E b/N 0. These channels exist for all m ⩾1/2. The special case of m =1 corresponds to Rayleigh fading, an inverse linear channel 相似文献
17.
Decoding performance of Reed-Solomon (RS) coded M -ary FSK with noncoherent detection in a frequency-hopping spread spectrum mobile radio channel is theoretically analyzed. Exact formulas and an approximate one for evaluating word error rates (WERs) of error correction and error-and-erasure correction schemes on decoding the RS codes are derived. It is shown that with K symbol erasure and C symbol error detection, RS coded M -ary FSK achieves the equivalent diversity order of (K +1)(C +1) 相似文献
18.
An expression is derived for the error probability of M -ary offset differential phase-shift keying (DPSK) with the differential phase detector and narrowband receiver filter in the satellite mobile (Rician) channel, which includes as special cases the Gaussian and land mobile (Rayleigh) channels. The error probability is computed as a function of various system parameters for M =2, 4, and 8 symbols and third-order Butterworth receiver filter. Both symmetric and conventional DPSK systems are considered. The optimal normalized bandwidth is close to 1.0. Symmetric and conventional DPSK differ significantly in error probability only for M =2 and in the lower range filter bandwidth. In most cases, symmetric DPSK outperforms conventional DPSK. This was particularly noted when the time delay between the specular and diffused signal components was taken into account 相似文献
19.
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 相似文献
20.
It is shown that for worst-case partial-band jamming, the error probability performance (for fixed E b/N I) becomes worse with increasing M for (M >16). The asymptotic probability-of-error is not zero for any E b/N I(>ln 2), but decreases inverse linearly with respect to it. In the fading case, the error-probability performance (for fixed E b/N 0) improves with M for noncoherent detection, but worsens with M for coherent detection. For large E b/N 0 the performance of the Rayleigh fading channel asymptotically approaches the same limit as the worst case partial-band jammed channel. However, for values of M at least up to 4096, the partial-band jammed channel does better. While it is unlikely that an M -ary orthogonal signal set with M >1024 will be used in a practical situation, these results suggest an important theoretical problem; namely, what signal set achieves reliable communication 相似文献