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In this paper, a novel noncoherent detection algorithm for differential space-time modulation (DSTM) over flat-fading multiple-input-multiple-output channels is presented. This algorithm, which is referred to as decision-feedback subset multiple-symbol differential detection (DF-S-MSDD), combines ideas from decision-feedback differential detection (DFDD) and subset multiple-symbol differential detection (S-MSDD). More specifically, the DF-S-MSDD decision metric includes a number of previous decisions (i.e., decision feedback), and the optimization over the remaining hypothetical symbols returns decisions only on a subset of these symbols (i.e., S-MSDD). Furthermore, an implementation of DF-S-MSDD based on tree-search (TS) methods is devised. Due to the concept of subset detection, DF-S-MSDD outperforms MSDD in terms of error-rate performance. At the same time, due to the use of decision feedback, it also requires lower computational complexity than the TS-based MSDD schemes for the DSTM recently proposed in the literature. Index Terms--Decision-feedback differential detection (DFDD), differential space-time modulation (DSTM), fading channels, multiple-symbol differential detection (MSDD), noncoherent detection.

The combination of differential space-frequency modulation (DSFM) with orthogonal frequency-division multiplexing (OFDM) is attractive for transmission over time- and frequency-selective multiple-input-multiple-output (MIMO) channels and detection without the need for channel-state information (CSI) at the receiver. It is well known that a simple differential detection already results in a high error floor for moderate time and frequency selectivities of the channel. A more sophisticated multiple-symbol differential detection (MSDD), which jointly processes multiple received symbols, overcomes this limitation, usually at the price of higher detection complexity. In this paper, we consider the DSFM for the MIMO-OFDM transmission and MSDD at the receiver. Inspired by previous work presented in literature, we devise a novel DSFM scheme, which makes use of spatial and/or spectral (multipath) diversity and is particularly suited for the MIMO-OFDM and power-efficient low-delay MSDD. We further investigate the application of a 2-D observation window to the MSDD (2-D MSDD) in order to exploit channel correlations in both time and frequency directions. We develop a representation of the detection problem that is amenable to tree-search decoding, whose application leads to a tremendous reduction in the MSDD complexity or a 'fast' MSDD. An analytical approximation of the symbol-error rate of the 2-D MSDD for the MIMO-OFDM under spatially correlated fading is derived, which enables quick and accurate performance evaluations. Numerical and simulation results corroborate the efficacy of our approach and show that power efficiency close to that of a coherent detection with a perfect CSI is feasible in all standard fading scenarios at reasonable decoder complexity. Index Terms--Differential space-frequency modulation (DSFM), differential space-time modulation (DSTM), multiple-input-multiple-output (MIMO) transmission, multiple-symbol differential detection (MSDD), orthogonal frequency-division multiplexing (OFDM), sphere decoding, tree-search decoding.

Bluetooth is a popular short-range low-power radio standard for wireless personal area networks. Bluetooth transmitters employ Gaussian frequency shift keying (GFSK) and simple block codes for error correction. Recently, two new receiver designs for Bluetooth devices, which are the so-called modified limiter-discriminator detector with integrate-and-dump filtering (LDI) and noncoherent sequence detection (NSD), have been proposed in the literature. While the modified LDI receiver is a concatenation of a conventional LDI detector with an improved error-correction decoder, the NSD receiver fully takes into account the memory introduced by the GFSK. Both receivers have been shown to improve the Bluetooth system performance in terms of physical-layer metrics such as bit-error rate and packet-error rate. In this paper, we present a comprehensive performance evaluation considering practically more relevant metrics such as throughput, delay, and delay jitter at the medium-access control layer. To this end, we develop an evaluation framework, which includes the spatial distribution of Bluetooth devices, path loss, fading, realistic data traffic models, scheduling, automatic repeat request, and baseband packet selection. Our numerical and simulation results verify that the newly introduced Bluetooth receivers, especially NSD, offer a significant performance enhancement for Bluetooth systems in terms of practically relevant measures. Index Terms--Bluetooth, delay, limiter-discriminator detector with integrate-and-dump filtering (LDI) receiver, noncoherent sequence detection (NSD) receiver, performance evaluation, throughput.

In this paper, differential modulation diversity (DMD) is introduced. This diversity scheme is based on diagonal signal constellations which have been previously proposed for differential space-time modulation (DSTM). DMD can exploit both space and time diversity and DSTM, which is a pure space-diversity scheme, results as a special case. Low-complexity noncoherent receivers originally designed for DSTM are adapted to DMD and the power efficiency of DMD for Ricean fading with spatial correlation and imperfect interleaving is investigated. Based on analytical expressions for the pairwise error probability it is shown that space diversity increases the effective fading bandwidth, which has a negative influence on performance. Time diversity does not have this disadvantage and is preferable especially for fast fading channels. If space and time diversity are combined, a robust receiver results that yields high performance for a wide range of fading velocities. Index Terms--Diagonal signals, differential encoding, noncoherent reception, space and time diversity.

Power and bandwidth efficient noncoherent transmission over frequency nonselective Ricean-fading channels is studied. We propose a remarkably low-complexity receiver structure, which is very well suited to mobile communication scenarios with time-variant and nonstationary transmission channels. Applying bit-interleaved coded modulation with standard convolutional codes, substantial gains of several decibels in power efficiency compared to conventional differential detection are achieved. To obtain the novel noncoherent reception scheme, ideas of iterative decoding with hard-decision feedback and prediction-based branch metric calculation are combined and extended. Furthermore, the incorporation of combined phase and amplitude modulation for high bandwidth efficiency is focused on. The theoretical analysis of both the convergence and the achievable performance of iterative decoding are given by evaluating the corresponding prediction-error variance and the associated cutoff rate, respectively. The results from information theory are well confirmed by simulation results presented for different channel scenarios. Index Terms--Amplitude and differential phase modulation, bit-interleaved coded modulation, decision feedback, mobile communications, noncoherent detection, Ricean flat-fading channels.

Power- and bandwidth-efficient differentially encoded transmission over slowly time-varying fading channels with noncoherent reception and without channel state information is considered. For high bandwidth efficiencies, combined phase and amplitude modulation is used. For increased power efficiency, channel coding and multiple-symbol differential detection are applied, i.e., interleaving and detection are based on blocks of N [is greater than] 2 consecutive symbols. The presented concepts are directly applicable to transmission over flat fading channels. However, concentrating on the situation of frequency-selective channels, we consider their application to multicarrier transmission using orthogonal frequency-division multiplexing (OFDM). When coding across subcarriers, OFDM transforms the actual frequency-selective channel into a slowly time-varying frequency-nonselective fading channel. This paper presents a design for multilevel coding schemes to approach theoretical limits for power- and bandwidth-efficient noncoherent transmission over the equivalent fading channel. It is shown that bit-interleaved coded modulation, which relies on Gray labeling, is competitive only in the case of conventional differential detection with N = 2. The theoretic considerations are well approved by simulation results, where turbo codes are applied as component codes. Index Terms--Bit-interleaved coded modulation, differential encoding, multilevel coding, noncoherent reception, orthogonal frequency-division multiplexing (OFDM).

In this paper, we present a receiver design for Bluetooth transmission based on Laurent's decomposition of the Bluetooth transmit signal. The main features of this receiver are 1) its low complexity compared to alternative solutions; 2) its excellent performance close to the theoretical limit; and 3) its high robustness against frequency offsets, phase noise, and modulation index variations, which are characteristic for low-cost Bluetooth devices. In particular, we show that the devised noncoherent decision-feedback equalization receiver achieves a similar performance as a recently proposed two-state noncoherent sequence detector, while it is advantageous in terms of complexity. The new receiver design is therefore highly attractive for a practical implementation. [ABSTRACT FROM AUTHOR]