Performance analysis of an FFH/BFSK product-combining receiverunder multitone jamming

The performance of a fast frequency-hopped binary frequency-shift keying (FFH/BFSK) spread-spectrum (SS) communication system is studied in this paper. The FFH system employs a product-combining receiver against the worst case multitone jamming (MTJ) and additive white Gaussian noise (AWGN). The compact characteristic functions of the natural logarithm of the product-combiner outputs are obtained based on the Taylor series expansion. The characteristic functions are then used to derive the bit error rate (BER) expressions that are applicable to higher diversity levels. Our analysis, validated by the simulation results, shows that the band MTJ is generally more harmful than the corresponding independent MTJ. The BER performance of the product-combining receiver is shown to possess good MTJ rejection capability compared to that of the soft-decision linear-combining receiver, especially under both moderate and strong MTJ power conditions     

Multitone jamming rejection of FFH/BFSK spread-spectrum system overfading channels

Analytical expressions for bit-error probability are derived for a fast frequency-hopping binary frequency-shift keying (FFH/BFSK) spread-spectrum communication system over a fading channel with worst-case band multitone jamming (MTJ) and additive white Gaussian noise (AWGN). An FFH system employing either a linear-combining receiver or a clipper receiver is investigated. The desired signal and MTJ are assumed to undergo independent fading, and our analysis, validated with simulation results, shows that the performance of the system is slightly improved as the severity of the MTJ fading is increased. The clipper receiver is found to be superior to the linear-combining receiver when the jamming power is strong. The worst-case MTJ is shown to be more harmful than the corresponding worst-case partial-band noise jamming over a fading channel with AWGN     

Error probabilities of an FFH/BFSK self-normalizing receiver in aRician fading channel with multitone jamming

We derive the analytical bit-error rate (BER) expressions for a fast frequency-hopped binary frequency-shift keying self-normalizing receiver over a fading channel with the worst-case band multitone jamming (MTJ) and additive white Gaussian noise (AWGN). The desired signal and MTJ are assumed to undergo independent Rician fading and our analyses, validated with simulation results, show that the system performance is not sensitive to different types of MTJ fading conditions. The self-normalizing receiver is found to be superior to the linear-combining receiver when the signal amplitude does not experience severe fading, while the converse is true under Rayleigh fading signal conditions. Under a Rician fading channel and AWGN conditions, the worst-case MTJ and the worst-case partial-band noise jamming are shown to have similar effects on the BER performance of the self-normalizing receiver with diversity     

Performance analysis of FFH/BFSK product-combining receiver with partial-band jamming over independent Rician fading channels

This study investigates how independent Rician fading channels affect both the fast frequency-hopped binary frequency shift keying (FFH/BFSK) product-combining receiver (PCR) and partial-band jammer (PBJ). We demonstrate that the average bit-error-rate (BER) expressions of FFH/BFSK PCR can be derived with the aid of an approximation by quantizing the product-combiner's output. Numerical results show that system performance of the FFH/BFSK PCR over fading channels and PBJ is lower than that in nonfaded PBJ at a low signal-to-jammer density ratio E/sub b//N/sub J/.     

Multiple trellis coded frequency and phase modulation

Multiple trellis coded modulation of constant envelope frequency and phase modulated signal sets (MTCM/FPM) is investigated for performance on the additive white Gaussian noise (AWGN) channel and on the one-sided normal, Rayleigh and Rician fading channels. The Nakagami- m fading model is used as an alternative to the Rician fading model to calculate the error probability upper bound for trellis-coded schemes on the fading channel. The likeliness and the disparity between the upper bounds to the error probability for the two fading models are discussed. The design criteria for the one-sided normal fading channel, modeled by the Nakagami-m distribution, are observed to be the same as those for the Rayleigh-fading channel. For the MTCM/FPM schemes, it is demonstrated that the set partitioning designed to maximize symbol diversity (optimum for fading channels) is optimum for performance on the AWGN channel as well. The MTCM/FPM schemes demonstrate improved performance over MTCM/MPSK schemes and TCM/FPM schemes on the AWGN channel and the fading channel     

Double differential MPSK on the fast Rician fading channel

An analysis of adjacent and nonadjacent double differential M -ary PSK (M-ary D²PSK) on the fast Rician fading channel is presented. The probability density function (PDF) of the first-order phase error (FOPE) and the probability density functions of the second-order phase error (SOPE) for both adjacent and nonadjacent D²PSK on a fading channel have been derived. Asymptotic approximations for these PDFs are proposed in the case of channels with weak fading (including the additive white Gaussian noise (AWGN) channel) and high signal-to-noise ratio. For nonadjacent D²PSK with independent FOPEs a simplified PDF of SOPE has been obtained. The derived PDFs allow calculation of error performance of D²PSK, as well as of DPSK, on the Rician channel including the AWGN channel and the Rayleigh channel and verification of some results reported in the literature earlier. It is shown that nonadjacent D²PSK can be optimized by choosing a proper separation between the first-order phase differences     

Antijam performance of FFH/BFSK with noise-normalization combining in a Nakagami-m fading channel with partial-band interference

The bit error rate (BER) performance of a noncoherent fast frequency-hopped binary orthogonal frequency-shift-keying (FFH/BFSK) spread spectrum noise-normalization combining receiver is evaluated in the presence of partial-band interference (PBI) and additive white Gaussian noise (AWGN) over independent frequency-nonselective slowly Nakagami-m fading channels. It is shown from the analytical results, and verified by simulation, that a higher diversity level greatly improves the worst-case performance of the noise-normalization receivers over Rayleigh or more severe fading channels, while a lower diversity level is preferred for less severe fading channels. In the former case, a full band strategy is optimal for the interferer and a partial-band strategy is more disruptive in the latter case.     

Performance Enhancement of Space-Time Trellis Codes When Encountering AWGN and Ricean Channels

Space-time trellis codes (STTCs) have been designed for quasi-static Rayleigh channels. When these codes are directly used for additive white Gaussian noise (AWGN) channels or Ricean channels with a high$K$factor, their frame error-rate (FER) performance is no longer optimal. We propose open-loop (no feedback) preprocessing methods for improving the error-rate performance of these codes when used in channels with a high$K$. For$K=0$(Rayleigh channels), these open-loop schemes generally do not alter the FER performance of the STTCs. The preprocessing operation at the transmitter is either to rotate the constellation points in one of the transmit antennas relative to the other by some angle, or suitably divide (unequally) the total power between the two transmit antennas. The angle of rotation and power division is optimized by maximizing the$d_ free$of the STTCs. Simulation results show that for AWGN or Ricean fading channels with a large$K$, the FER performance can be significantly improved by doing either rotation or power division at the transmitter. While the FER performance is nearly unchanged for quasi-static Rayleigh channels, the improvement in performance is between 1 to 3 dB for Ricean or AWGN channels.     

移动衰落信道中设计多级编码(MLC)方案的一种非欧度量

本文提出了在移动衰落信道中设计多级编码(MLC)方案的一种非欧度量:"信道容量规则"+"映射规则".在AWGN信道中为:"信道容量规则"+"UP(Ungerboeck Partitioning) 规则";在Rayleigh衰落信道中为:"信道容量规则"+"BP(Block Partitioning)规则".并在此理论指导下,选用不同码长的BCH码作为MLC系统中各级分量码,通过计算机模拟,比较了在AWGN和Rayleigh衰落信道中,采用8ASK调制方式、多级译码(MSD)、三种不同映射方法下的三级MLC方案的性能.     

An Exact Error Probability Analysis of OFDM Systems with Frequency Offset

In this paper, we derive exact closed form bit error rate (BER) or symbol error rate (SER) expressions for orthogonal frequency division multiplexing (OFDM) systems with carrier frequency offset (CFO). We consider the performance of an OFDM system subject to CFO error in additive white Gaussian noise (AWGN), frequency flat and frequency selective Rayleigh fading channels. The BER/ SER performances of BPSK and QPSK modulation schemes are analyzed for AWGN and frequency-flat Rayleigh fading channels while BPSK is considered for frequency-selective Rayleigh fading channels. Our results can easily be reduced to the respective analytical error rate expressions for the OFDM systems without CFO error. Furthermore, the simulation results are provided to verify the accuracy of the new error rate expressions.     

衰落信道中不同集分割的多级编码调制方案的性能研究

本文以MLC系统各等价信道的信道容量为依据^[1],选用不同码长的BCH码系列作为MLC系统中各级的分量码,通过计算机模拟,比较了三种不同的集分割方法所构成的MLC/MSD方案,分别在AWGN和Rayleigh衰落信道中、8ASK调制方式下的性能.模拟结果表明:UP分割在AWGN信道中具有最好的性能;BP分割可自适应于AWGN和Rayleigh衰落混合的移动衰落信道,是MLC方案应用于移动衰落信道中的最佳集分割方案.     

Soft-decision COVQ for turbo-coded AWGN and Rayleigh fadingchannels

A robust soft-decision channel-optimized vector quantization (COVQ) scheme for turbo coded additive white Gaussian noise (AWGN) and Rayleigh fading channels is proposed, The log likelihood ratio (LLR) generated by the turbo decoder is exploited via the use of a q-bit scalar soft-decision demodulator. The concatenation of the turbo encoder, modulator, AWGN channel or Rayleigh fading channel, turbo decoder, and q-bit soft-decision demodulator is modeled as an expanded discrete memoryless channel (DMC). A COVQ scheme for this expanded discrete channel is designed. Numerical results indicate substantial performance improvements over traditional tandem coding systems, COVQ schemes designed for hard-decision demodulated turbo coded channels (q=1), as well as performance gains over a recent soft decoding COVQ scheme by Ho (see IEEE Commun. Lett., vol.3, p.208-10, 1999)     

Error rate performance of digital FM mobile radio withpostdetection diversity

An analysis of bit error rate (BER) in a binary digital FM system with postdetection diversity is presented. Expressions for the average BER due to additive white Gaussian noise (AWGN), random FM noise and delay-spread in the multipath channel are derived for reception using differential demodulation (DD), and frequency demodulation (FD) assuming independent fading signals. Calculated results for MSK show that the BER performance is strongly dependent on the RMS-delay/bit-duration ratio and that the delay-spectrum shape is of no importance when the receiver predetection filter product is optimized for the effect of AWGN. The effect of fading correlation on the diversity improvement is also analyzed for a two-branch case with multiplicative Rayleigh fading signals. Expressions for the average BER due to AWGN and random FM noise are derived. Calculated results are shown for the average BER due to random FM noise assuming a horizontally spaced antenna system at a mobile station. It is shown that the use of small antenna spacings leads to a diversity improvement greater than that obtainable for the case of independent AWGN     

Asymptotic error-rate behavior for noncoherent on-off keying in thepresence of fading

This article investigates the asymptotic error-rate behavior for the noncoherent on-off keying (OOK) signaling scheme in different fading environments and at both extremes of the signal-to-noise ratio (SNR). A transcendental equation to compute the optimum threshold level of noncoherent OOK operating over a Rician fading channel is derived. The optimum threshold level and its corresponding ratio of the mark and space error probabilities in additive white Gaussian noise (AWGN). Rayleigh, and Rician channels are tabulated as a function of the SNR. Geist (see ibid., vol.42, p.225, 1994) has shown that mark and space errors contribute equally to the average error probability in an AWGN channel when the SNR is large with optimum threshold setting. We show that mark errors predominate when the SNR is small and/or in fading channels     

Uplink performance of slow frequency-hop multiple-access networks using binary DPSK

The uplink performance of synchronous and asynchronous slow frequency-hop spread-spectrum multiple-access (SFHSS-MA) networks transmitting L bits per hop using binary differential phase shift keying (BDPSK) is analyzed under the additive white Gaussian noise (AWGN) and Rayleigh fading channels. Analytic expressions for the average conditional bit error probabilities given a hop is hit by K' interfering users are derived. Results show that SFHSS-MA networks using BDPSK achieve nearly twice the maximum normalized network throughput compared to networks using BFSK under both AWGN and Rayleigh fading channels.     

Bandwidth efficient coding for fading channels: code constructionand performance analysis

The authors apply a general method of bounding the event error probability of TCM (trellis-coded modulation) schemes to fading channels and use the effective length and the minimum-squared-product distance to replace the minimum-free-squared-Euclidean distance as code design parameters for Rayleigh and Rician fading channels with a substantial multipath component. They present 8-PSK (phase-shift-keying) trellis codes specifically constructed for fading channels that outperform equivalent codes designed for the AWGN (additive white Gaussian noise) channel when v⩾5. For quasiregular trellis codes there exists an efficient algorithm for evaluating event error probability, and numerical results which demonstrate the importance of the effective length as a code design parameter for fading channels with or without side information have been obtained. This is consistent with the case for binary signaling, where the Hamming distance remains the best code design parameter for fading channels. The authors show that the use of Reed-Solomon block codes with expanded signal sets becomes interesting only for large value of E_s/N₀, where they begin to outperform trellis codes     

Performance of MFSK signals with postdetection square-law diversity combining in arbitrarily correlated Nakagami-m fading channels

This letter presents an analysis of the error probability for noncoherent orthogonal multiple frequency-shift keying (MFSK) signals with postdetection square-law combining (SLC) when the signals transmitted over additive white Gaussian noise (AWGN) and slow frequency-nonselective arbitrarily correlated Nakagami-m fading channels. New exact expressions in a onefold integral for the probability of error of MFSK signals with postdetection square-law diversity combining operating in AWGN channel as well as in arbitrarily correlated Nakagami-m fading channels are derived. The effects of arbitrarily values of fading severity parameter m and the arbitrarily correlation between the L diversity channels are considered. The derived expressions can be easily computed, and hence, can be usefully exploited in the performance evaluation of digital mobile radio systems.     

A Comparison of Energy Detectability Models for Cognitive Radios in Fading Environments

In this work, we first analyze the accuracy of different energy detector models in approximating the exact solution in AWGN. These models motivate us to develop approximation analysis to address energy detection for fading channels. Our analysis develops approximation that has almost the same performance as the exact solution in Rayleigh channels. Our new model is simple enough to derive the relationship between the required number of samples (N) and the signal-to-noise ratio for a single Rayleigh channel similar to the one obtained for AWGN channels. We also define a fading margin for link budget calculations that relates N in fading channels to AWGN channels. Furthermore, we analyze the impact of multiple antennas for cognitive radios considering two receiver diversity schemes and quantify the improvement in performance regarding this margin. All the analytical results derived in this paper are verified by simulations. Finally, we have implemented and verified energy detection models in our multiple antenna wireless testbed.     

Convolutional codes with optimum distance spectrum

New convolutional codes with rates 1/2, 1/3, and 1/4 are presented for constraint lengths ranging from 3 to 15. These new codes are maximum free-distance codes. Furthermore, the codes have optimized information error weights, resulting in a low bit-error rate for binary communication on both additive white Gaussian noise (AWGN) and Rayleigh fading channels. Improved coding gains of as much as 0.6 dB compared to previously published codes have been observed for coherent BPSK over a Rayleigh fading channel and a wide range of signal-to-noise ratios     

采用基于互补序列分组编码的OFDM系统性能分析与仿真

为了减小正交频分复用（OFDM）信号的峰值-平均值功率之比（PAPR），本文利用互补序列和Reed-Muller码的关系，详细提出了一种构造互补序列的分组编码方法的具体实现方案。分析了其在AWGN和选频衰落信道中的性能，并做了相应的仿真。仿真结果表明，编码后每个OFDM信号的最大PAPR不超过3dB；采用该编码方法的OFDM在AWGN中当信噪比不到11dB时就可以实现BER为10^-6，在衰落信道中如果采用软判决译码，则当信噪比达到20dB左右时可以实现BER为10^-3。