Decision-Feedback Differential Detection in Impulse-Radio Ultra-Wideband Systems

An architecture of decision feedback differential phase detection (DF-DPD) of M-ary DPSK signals is proposed. Conventional differential detection of M-ary DPSK signals uses the phase difference between a current symbol and the previous symbol. This method can make the receiver architecture simple. But it has poorer BER performance than coherent detection because it uses the previous noisy signal as the phase reference. To improve the BER performance of conventional differential detection, multiple symbol differential detection methods, such as maximum likelihood differential detection (ML-DD), Viterbi-DD, decision feedback differential detection (DF-DD), and DF-DPD, using L-1 past detected symbols, have been proposed. As L increases, the BER performance of DF-DPD improves but the complexity of the architecture increases dramatically. Thus, this paper proposes the simplified DF-DPD architecture, replacing the conventional delay and addition architecture with one accumulator. The proposed architecture also has a good BER performance with minimizing the phase error of the current received symbol using the accumulated phase differences of all DPD. The simulation results show that the BER performance of the proposed architecture approaches that of coherent detection.

Multiple-symbol differential detection (MSDD) is a robust maximum-likelihood (ML) receiver technique for frequency-nonselective fast Rayleigh fading channels. However, its complexity grows exponentially with the block size N and that makes it impractical to implement. Recently, multiple-symbol differential sphere decoder (MSDSD) is developed to alleviate this problem but its complexity at low signal-to-noise ratio (SNR) grows exponentially with decreasing SNR. In this paper, we explore the potential of the Fano algorithm as an efficient MSDD receiver. The bit-error performance and the complexity of the Fano-MSDD are evaluated and compared with other reduced complexity techniques. Our preliminary results indicate that Fano-MSDD is more attractive than decision-feedback differential detection (P.Y. Kam and CH Teh, 1983) and (R Schober and WH Gerstacker, 2000) from both the error performance and the complexity points of view. When compared to the MSDSD, the Fano-MSDD suffers a moderate degradation in power efficiency. However, its computational complexity is very steady even at low SNR. This translates into a dramatic saving in complexity over the MSDSD when SNR is low. Even at large SNR, the Fano-MSDD still provides a small edge over the MSDSD in terms of complexity. We believe that with some fine tuning of the decoder parameters, such as the bias and the threshold's step size, it is possible to extract better performance from the Fano decoder than it is now.

A novel approach to UWB data detection with symbol-level synchronization

In this paper, we propose a novel multiple symbol differential detection (MSDD) based on symbol error position estimation (SEPE) and compensation for use in terrestrial digital multimedia broadcasting (T-DMB) system. By estimating the symbol error position and compensating for the symbol error using MSDD outputs, it can improve the receive performance of T-DMB system. Also by providing soft-outputs to Viterbi decoder, an additional coding gain can be obtained. Simulation results in the typical urban (TU) channel show that the proposed algorithm is superior to the conventional differential detection (DD) and hard decision based MSDD T-DMB receivers.

We consider multiple?symbol differential detection (MSDD) for multiple?input multiple?output Rayleigh?fading channels. MSDD, which jointly processes blocks of received symbols to detect N -1 data symbols, allows for power?efficient transmission without requiring channel state information at the receiver. In previous work, we showed that computationally efficient sphere decoding algorithms can be used to accomplish MSDD. In this paper, we analyze the computational complexity of this sphere?decoding based MSDD. In particular, we prove by means of a lower bound that the complexity of the Fincke?Pohst multiple?symbol differential sphere decoder (FP?MSDSD), while being very low over wide ranges of N and signal?to?noise ratios, is exponential in N in principle. We further derive expressions for the exact complexity of FP?MSDSD, which allow for quick assessment of ranges of useful window sizes N.

The conventional multiple-symbol differential detection (MSDD) of differential phase-shift keying (DPSK) signals is studied in the presence of frequency offset. It is shown that in the case of nonzero frequency offset, the performance of the conventional MSDD receiver degrades by increasing the number of observed samples. A double DPSK (DDPSK) modulation scheme is then introduced and it is shown that in the presence of nonzero frequency offset, an MSDD receiver with DDPSK modulation outperforms a conventional MSDD receiver with DPSK modulation, when both receivers use a large number of received samples. Examples lead to a conjecture that the performance of an optimum MSDD receiver with DDPSK modulation and an infinite number of received samples, approaches that of a conventional DPSK demodulator with two received samples.

In this paper, multiple-symbol differential detection (MSDD) is applied to the differential single-carrier frequency-division multiple access (SC-FDMA) system. Both time domain and frequency domain MSDD are investigated to compensate for the performance loss of conventional differential detection comparing with coherent detection. The decision metric of time and frequency domain MSDD for SC-FDMA are derived respectively. Simulation results demonstrate the effectiveness of MSDD in some situations.

This paper addresses a multiple-symbol differential detection scheme for star 16QAM. At the outset, we analytically scrutinized conventional differential detection of star 16QAM. As a result, it emerged that the energy penalty of differential amplitude detection as compared with ideal coherent detection is larger than that of phase detection. Then to improve the overall performance of star 16QAM, we propose an MLSE algorithm for a large C/N as well as a suboptimum algorithm. Both of them allow multiple-symbol differential amplitude and phase detection. Their performances are also evaluated through computer simulation.KeywordsPhase DetectionEnergy PenaltyCoherent DetectionDifferential DetectionObservation SymbolThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Multiple-symbol differential detection (MSDD) is a promising technique to enhance the performance of ultra-wideband (UWB) communications without estimating the channel explicitly. In this context, the generalized log-likelihood ratio test (GLRT) for MSDD was developed, and the hard-output multiple-symbol detector was proposed, which exhibits considerable bit-error-rate (BER) performance improvement over transmitted reference transmissions. In this paper, we further improve the system performance by incorporating error correction code (ECC) and iterative processing at the receiver. The soft-input soft-output (SISO) MSDD is developed to deliver a posteriori information to the outer ECC decoder and enables iterative detection and decoding. Simulations show that the iterative processing achieves significant gains over the existing MSDD in UWB communications.

Multiple-symbol differential detection (MSDD) for multiple-input-multiple-output Rayleigh-fading channels is considered. MSDD, which jointly processes blocks of N received symbols to detect N-1 data symbols, allows for power-efficient transmission without requiring channel state information at the receiver. In previous work, the authors showed that computational efficient sphere decoding algorithms can be used to accomplish MSDD. In this correspondence, the computational complexity of this sphere-decoding based MSDD is analyzed. In particular, it is proven by means of a lower bound that the complexity of the Fincke-Pohst multiple-symbol differential sphere decoder (FP-MSDSD), while being very low over wide ranges of N and signal-to-noise ratios, is exponential in N in principle. Furthermore, both exact and simple approximate expressions for the complexity of FP-MSDSD are derived, which allow for quick assessment of ranges of useful window sizes N of FP-MSDSD and show that the exponential rate of growth of the complexity of FP-MSDSD is asymptotically equal to that of brute-force MSDD

Recently, the differential detection scheme has attracted considerable attention as a demodulated scheme for digital mobile communications because of its robustness in the frequency nonselective fading channel. A problem of the differential detection scheme is that its bit error rate (BER) performance in the additive white Gaussian noise (AWGN) channel is inferior to that of the coherent detection scheme. To solve this problem, many methods to improve BER performance of the differential detection in the AWGN channel have been proposed. However, those methods require complex signal processings.This paper proposes a novel differential detection scheme as a simpler improvement method which estimates the differential phase of the transmitted signal by a sequence estimation scheme using the Viterbi algorithm. The proposed scheme is simplified in a manner such that its signal processing is composed of only additions and subtractions on the phase information of the received signal. Results of computer simulation show that BER performance of the proposed scheme is close to that of the ideal coherent detection in the AWGN channel. In addition, the trellis diagram of the Viterbi algorithm can be reduced without performance degradation introducing the signal processing similar to the Scarece State Transition (SST) type Viterbi decoding. The proposed scheme also is useful in the case of the fast Rician fading channel and the slow Rayleigh fading channel.

In distributed space-time coding cooperative systems, differential detection gains much attention because it needs no channel state information at the receivers. But conventional differential detection performs about 3dB loss than coherent detection. In this paper, we propose a multiple-symbol differential detection algorithm for relay networks based on maximum-likelihood principle. The simulation results show that the multiple-symbol differential detection can narrow the performance gap between the conventional differential detection and coherent detection for Alamouti and square real orthogonal coding systems with corresponding numbers of relays, especially in high signal-tonoise ratio regime. And with the increase of observation window size, the Doppler effect on performance is decreased and the error floor encountered in conventional differential detection can be eliminated provided that the value of observation window size is sufficiently high.

In this paper, a Multiple-symbol differential detection (MSDD) receiver by using the Viterbi algorithm for double differential phase-shift keying (DDPSK) signals is presented. The structure of branch metric is also derived. It is shown that the proposed receiver has lower computational complexity, since it reduces the number of trellis paths searched in performing maximum likelihood sequence estimation (MLSE). Computer simulations demonstrate that the performance of the proposed receiver can reach the lower bound on the error probability of MSDD with very lower complexity.

This paper presents a multiple-symbol differential detection scheme for coded and interleaved transmission of MPSK data. The performance of this scheme is then evaluated for transmission of digitized voice over a Rayleigh fading channel. It is found that in terms of bit error rate, the improvement given by using multiple-symbol differential detection is minimal, but when evaluated in terms of frame-error rate, the multiple-symbol scheme gives about 1.25-dB improvement. Another 0.75-dB improvement can be obtained by also using a serial list Viterbi algorithm.

It is widely recognized that half-duplex-relay-aided differential decode-and-forward (DDF) cooperative transmission schemes are capable of achieving a cooperative diversity gain, while circumventing the potentially excessive-complexity and yet inaccurate channel estimation, especially in mobile environments. However, when a cooperative wireless communication system is designed to approach the maximum achievable spectral efficiency by taking the cooperation-induced multiplexing loss into account, it is not obvious whether or not the relay-aided system becomes superior to its direct-transmission based counterpart, especially, when advanced channel coding techniques are employed. Furthermore, the optimization of the transmit-interval durations required by the source and relay is an open issue, which has not been well understood in the context of half-duplex relaying schemes. Hence, we first find the optimum transmission duration, which is proportional to the adaptive channel-code rate of the source and relay in the context of Code-Rate-Optimized (CRO) TDMA-based DDF-aided half-duplex systems for the sake of maximizing the achievable network throughput. Then, we investigate the benefits of introducing cooperative mechanisms into wireless networks, which may be approached in the context of the proposed CRO cooperative system both from a pure capacity perspective and from the practical perspective of approaching the Discrete-input Continuous-output Memoryless Channel (DCMC) capacity with the aid of the proposed Irregular Distributed Differential (IrDD) coding aided scheme. In order to achieve a near-capacity performance at a low-complexity, an adaptive-window-duration based Multiple-Symbol Differential Sphere Detection (MSDSD) scheme is employed in the iterative detection aided receiver. Specifically, upon using the proposed near-capacity system design, the IrDD coding scheme devised becomes capable of performing within about 1.8 dB from the corresponding single-relay-aided DDF cooperative system's DCMC capacity.