Kah C. Teh

Performance analysis of an FFH/BFSK product-combining receiver under 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.

Partial-band jammer suppression in FFH spread-spectrum system using FFT

This paper presents the performance evaluation of partial-band jammer suppression using fast Fourier transform (FFT) as an alternative in a fast frequency-hopped spread-spectrum (FFH/SS) communication system. The FFH/SS system employs a clipper to restrict the effect of a partial-band jammer before diversity combining. No additional side information of the jammer is required, and the analytical expression for the bit error rate (BER) is derived. It is shown that the performance of the FFT-based clipper receiver is better than that of the square-law linear combining receiver and comparable to that of the square-law clipper receiver.

Jammer suppression in spread spectrum

This paper addresses the performance evaluation of the suppression of a real single tone jammer using singular valve decomposition (SVD). A system model employing the proposed SVD-based technique to reject the single-tone jammer in a direct sequence binary phase shift keying (DS/BPSK) spread spectrum system is presented. The performance of this system is based on the BER results obtained through simulations. The results are shown to compare favorably to those obtained by the conventional two-sided transversal filter method, especially when the jammer power is more dominant.

Performance analysis of an FFH/BFSK product-combining receiver with multitone jamming over Rician-fading channels

The effects of band multitone jamming (MTJ) and additive white Gaussian noise (AWGN) on the bit-error rate (BER) performance of a fast frequency-hopped binary frequency-shift-keying (FFH/BFSK) product-combining receiver are studied. The FFH system is assumed to experience independent Rician fading channels. The analytical expressions are derived based on the quantization approach which is applicable to higher diversity levels. Numerical results, validated by simulation results, show that system performance is not sensitive to different types of MTJ fading conditions. When the signal amplitude does not experience severe fading, the product-combining receiver is found to be superior to the linear-combining receiver and is only slightly outperformed by the clipper receiver which requires signal side information. However, the converse is true under Rayleigh-fading signal conditions.

Performance of carrier frequency offset estimation in MC-CDMA systems over frequency selective fading channels

Multicarrier code division multiple access (MC-CDMA) systems are more sensitive to the carrier frequency offset than single-carrier systems. Carrier frequency offset destroys the orthogonality among subcarriers in MC-CDMA systems and degrades the system performance seriously. To mitigate the effect of carrier frequency offset, it should be estimated and compensated before demodulation. A blind MUSIC-like estimation algorithm for MC-CDMA systems is studied in this paper. The MUSIC-like algorithm exploits the inherent orthogonality between information bearing carriers and virtual carriers to estimate the carrier frequency offset. The performance of the estimation is evaluated over frequency-selective fading channels in this paper. From the simulation results, the MUSIC-like estimation algorithm is effective in MC-CDMA systems over frequency-selective fading channels.

Performance study of selection diversity systems with non-identical fading branches

Error performance of a selection diversity (SD) receiver is evaluated over non-identical fading channels, where the fading statistics of individual branches are different. Bit-error rate (BER) results are directly obtained from the cumulative distribution function, which drastically reduces the complexity of analysis and simplifies BER expressions. In particular, using this approach, we are able to generate unified simple, closed-form BER expressions for different modulation schemes under non-identical fading conditions in Rayleigh and Nakagami fading channels. Theoretical results are corroborated with simulation results.

BER performance of transmitted-reference UWB systems with notch filter in the presence of inter-pulse interference and partial-band interference

In this paper, we propose an ultra wideband (UWB) system which, through the use of transmitted reference (TR) and a finite impulse response (FIR) or infinite impulse response (FIR) notch filter, is able to mitigate both narrowband interference (NBI) and inter-pulse interference (IPI). The bit-error rate (BER) performance of the auto-correlation receiver (ACR) is investigated over an IEEE802.15.4a wireless channel. The NBI arising from the existing wireless services is modeled as partialband Gaussian noise. Numerical results show that the proposed TR-UWB receiver has stable BER performance against variations in various system parameters over wireless channels.

Error probabilities of an FFT-based FFH/BFSK linear-combining receiver with partial-band noise jamming and AWGN

This paper presents the performance analysis of a fast frequency-hopped binary frequency-shift-keying (FFH/BFSK) linear-combining receiver in conjunction with a fast Fourier transform (FFT) processor. Under the conditions of partial-band noise jamming (PBNJ) and additive white Gaussian noise (AWGN), the bit-error rate (BER) expressions of the proposed FFT-based linear-combining receiver are derived in terms of the characteristic functions of the decision statistics. The BER expressions, validated by simulation results, are applicable to any arbitrary diversity level. The proposed FFT-based receiver provides an alternative to the conventional matched-filter receiver. The FFT-based receiver is shown to give comparable performance with the corresponding matched-filter receiver. The worst-case PBNJ fraction is shown to be inversely proportional to the signal-to-jamming ratio and the performance of the FFT-based linear-combining receiver is degraded as the diversity level is increased.

BER analysis of selection diversity receivers over generalized-K fading environments

We evaluate the error performance of a selection diversity (SD) receiver over generalized-K fading channels. The bit-error rate (BER) expression is obtained directly from the cumulative distribution function (CDF), and thus eliminating the need for differentiating the CDF of the combiner output as in the analysis technique used hitherto. Using this approach, we are able to conveniently analyze the error performance of a SD receiver with arbitrary diversity order operating over generalized-K fading environments, which was earlier considered as quite complicated. A unified BER expression for different binary modulation schemes is derived. Error performance of different modulation schemes in compound fading channels is discussed along with numerical results, and analytical results are corroborated with the simulation results.

MIMO-OFDM systems based on space-time coding and OFDM carrier block spreading

In this paper, we propose a space-time coding and carrier block spreading based multiple-input-multiple-output (MIMO) orthogonal-frequency-division-multiplexing (OFDM) system. The proposed system exploits the potential spatial and frequency diversity of MIMO systems in frequency-selective fading environments through a two-stage procedure. In the first stage, we use space-time coding to exploit the spatial diversity, and in the second stage, we adopt block spreading among blocks of OFDM carriers to obtain frequency diversity. Moreover, by using rotated Hadamard matrix or rotated discrete Fourier transform (DFT) matrix as the carrier spreading matrix, the system can also possess a certain degree of modulation diversity. Our proposed system enjoys the advantage of high flexibility and low complexity. It allows the use of any existing space-time coding scheme as its component space-time code, and the diversity gains are obtained with only moderate transmit and receive processing complexity. Simulation results show that our proposed system can achieve desired spatial and frequency diversity with low detection complexity. Comparing to some existing space-frequency coding schemes, our proposed system enjoys the merit of low complexity, although it could suffer from some performance degradation, which is caused by the separation of space-time coding and frequency-domain spreading process.