Low-complexity Detection Scheme Research Articles

Simple low-complexity detection schemes for M -ary quadrature amplitude modulation spatial modulation

In this study, the authors propose a simple low-complexity detection scheme for Nt×NrM-ary quadrature amplitude modulation spatial modulation that exhibits a much lower computational complexity compared to the conventional maximum-likelihood (ML) detection scheme. The proposed simple low-complexity detection scheme firstly detects the transmitted symbol for each transmit antenna based on modified suboptimal detection, and secondly chooses N (N≤Nt) pairs of the most probable transmit antenna index and transmitted symbol subset, which the transmitted signal most probably belongs to, and finally searches the pair of transmit antenna index and transmitted symbol among these pairs. To further reduce detection complexity of the proposed simple detection scheme the authors also propose an adaptive detection scheme. Simulation results validate that the average bit-error-rate (BER) performance of the proposed simple detection scheme is almost the same as that of the conventional ML optimal detection with significant complexity reduction. Simulation results also show that the adaptive detection scheme can achieve optimal detection BER performance with further complexity reduction compared to the proposed simple low-complexity detection scheme.

Generalised Spatial Modulation System with Multiple Active Transmit Antennas and Low Complexity Detection Scheme

A generalised spatial modulation (SM) scheme with multiple active transmit antennas, named as multiple active-spatial modulation (MA-SM), is proposed in this paper. By allowing multiple transmitting antennas in the SM system to transmit different symbols at the same time instant, MA-SM takes advantages of the low complexity of SM and high multiplexing gain of Vertical-Bell Lab Layered Space-Time (V-BLAST) system. In the MA-SM system, the transmitted symbols are mapped into a high dimensional constellation space including the spatial dimension. The general principle for designing the efficient MA-SM for arbitrary number of transmit antennas and modulation scheme is presented. Moreover, a near-optimal detection scheme with low complexity for MA-SM is also proposed and analyzed. A closed form bound for the bit error probability (BEP) of the proposed detection scheme is also derived in this paper. Numerical results with the comparison among the existing multiple-input multiple-output (MIMO) systems such as space time block code (STBC) and V-BLAST demonstrate the efficiency of MA-SM.

Ultra-spectra communication system (USCS): a promising way to energy-efficient green communication networks

In this article, we investigate a promising transmission approach for green communication networks. By combining the appealing single-cycle modulation technique with traditional pulse modulation found on the underlay communication philosophy, the presented ultra-spectra communication system can improve the energy efficiency significantly. In transceiver, the emission signal contains two parts, the information-bearing baseband waveform with an extremely short duration and the information-synchronized carrier component. Alternatively, without carrier signaling the intermittent emission can be adopted to further reduce its operational power. By optimally allocating the power in different bands, a water-filling emission spectrum inspired by a novel conception of radius basis function neural-network is proposed for maximizing transmission energy efficiency in the presence of external interference. In receiver, the carrier-synchronized signal greatly alleviates the power-consumed timing acquisition, and provides extremely precise synchronization for information detection in intensive multipath environments. In addition, from a pattern classification perspective, a low-complexity noncoherent detection scheme is suggested to enhance receiving performance and minimize energy consumption. Performance analysis demonstrated that the whole transmission scheme can indeed be realized within an ultra-low-power framework, which shows great advantages to traditional strategies.

Low-Complexity MIMO Detection Based on Post-Equalization Subspace Search

Two low-complexity effective detection schemes for multiple-input-multiple-output (MIMO) systems based on post-equalization subspace search are proposed in this paper. With the initial solution given by the linear detector, calibrated constellation search is conducted in symbol subspace and eigenspace associated with the largest estimation errors in linear detection to identify improved solutions. Complexity analysis is performed to understand the cost of the proposed add-on procedures. Simulation results demonstrate that the proposed schemes yield noticeable performance gains over linear detectors at moderate additional computational cost.

Improved Network-Coded Cooperative Transmission with Low-Complexity Adaptation to Wireless Channels

The relay employs network coding to transmit the packets from the source nodes simultaneously, for increasing spectral efficiency in wireless environments. The cooperative transmission based on network coding usually works on decode-and-forward (DF) protocols. However, detection errors at the relay cause error propagation, which degrades the performance of cooperative communications. To overcome this problem, we model the error propagation effect of the DF-based system at the destination as the addition of virtual noise, and then design a low complexity detection method. We derive the achievable diversity gain to evaluate the proposed model and corresponding detection scheme. To extend the proposed model to network-coded systems, we first express the channel conditions between the sources and relay as a single equivalent channel gain. Then, we develop low complexity detection schemes for the network-coded systems. From the error propagation model, we propose a dual mode network coding technique, which exploits different network coding schemes adaptively according to channel qualities. Simulation results show that the proposed model and detection scheme effectively reduce the error propagation effects. Also, the proposed dual mode network coding has gains for all channel conditions and thus gives better BER performance than conventional methods.

A frequency domain coherent detection scheme to realize DAA technique for WiMedia UWB systems

In this paper, a low complexity detection scheme is proposed to detect so-called victim systems in the WiMedia UWB environment. According to regulation of DAA in world-wide radio frequency, many detection schemes have been studied and time-domain coherent detection (TDCD) scheme is known as the best approach with respect to the detection performance. However, this scheme requires the additional filter and down-sampler to reconstruct victim signal from the received signal and these requirements lead to increase of hardware complexity. The proposed frequency-domain coherent detection (FDCD) scheme is based on the cross-correlation with frequency-domain reference sequences (FDRS), which are derived from the preamble sequence of the victim system. The detection performance is almost the same as that of the TDCD scheme and the computational complexity is about half.

Low-Complexity Cyclostationarity Feature Detection Scheme of Localized SC-FDMA Uplink System for Application to Detect and Avoid

This paper proposes a low-complexity cyclostationarity feature detection scheme for detect and avoid (DAA) of Ultra-Wideband (UWB) system in order to solve the coexistence issues between UWB system and Long Term Evolution-Advanced (LTE-Advanced) system. The proposed scheme is suitable for the detection of a localized Single-carrier Frequency Division Multiple Access (SC-FDMA) signal utilized in the uplink of LTE-Advanced system. Compared with conventional cyclostationarity feature detection, the proposed scheme utilizes all possible cyclic-spectrums located in a distributed window function, which is decided by the frequency distribution of the Primary User (PU) signal. The computational complexity of the proposed scheme is low, due to only one window width instead of all occupied spectrum interval will be searched for the possible cyclic-spectrums. On the other hand, the proposed scheme can also avoid the estimation of the cyclic-spectrums when the type of PU signal is unclear or the cyclic-spectrums are hard to estimate. Simulation results indicate that the proposed scheme can make a tradeoff between detection performance and computational complexity. The low-complexity cyclostationarity feature detection also provides a substitute for the energy detection when the later approach suffers from the noise uncertainty and cannot distinguish the target signal type.

Reduced-Rank Adaptive Least Bit-Error-Rate Detection in Hybrid Direct-Sequence Time-Hopping Ultrawide Bandwidth Systems

The design of high-efficiency low-complexity detection schemes for ultrawide bandwidth (UWB) systems is highly challenging. This paper proposes a reduced-rank adaptive multiuser detection (MUD) scheme that is operated in least bit-error-rate (LBER) principles for hybrid direct-sequence time-hopping UWB (DS-TH UWB) systems. The principal component analysis (PCA)-assisted rank-reduction technique is employed to obtain a detection subspace, where the reduced-rank adaptive LBER-MUD is carried out. The reduced-rank adaptive LBER-MUD is free from channel estimation and does not require knowledge about the number of resolvable multipaths and the multipaths' strength. In this paper, the BER performance of the hybrid DS-TH UWB systems using the proposed detection scheme is investigated, assuming communications over UWB channels modeled by the Saleh-Valenzuela channel model. Our studies and performance results show that, given a reasonable rank of the detection subspace, the reduced-rank adaptive LBER-MUD can efficiently mitigate both multiuser and intersymbol interference (ISI) and achieve the diversity gain promised by the UWB systems.

Low-complexity detection by exploiting suboptimal detection order and subcarrier grouping for Multi-Layer MIMO-OFDM

By combining the transmit diversity and space multiplexing, the multi-layer multiple-input multiple-output orthogonal frequency division multiplexing (Multi-Layer MIMO-OFDM) system can exploit the potentials of both techniques. The transmit antennas are divided into several layers and each layer is encoded by a certain Multi-Antenna Coding. The antennas transmit OFDM signals in order to deal with frequency-selective fading. In addition to Exhaustive Detection which applies the same detection at each subcarrier independently, we exploit the subcarrier correlation to develop a subcarrier grouping based Low-Complexity Detection scheme. The subcarriers bound into the same group share the same Layer Detection Order which is obtained by the Post-Nulling Signal Power comparison at the center subcarrier of that group. The simulation results show that compared with Exhaustive Detection, the proposed Low-Complexity Detection scheme is capable of reducing 50.7% complexity with only 0.8 dB performance degradation for 6 × 6 system, and reducing 60.7% complexity with about 1.0 dB performance degradation for 8 × 8 system, respectively.

Joint Timing and Channel Estimation for Ultra-Wideband Signals

This paper is concerned with timing synchronization of high rates UWB signals operating in a dense multipath environment, where access must tackle inter-frame interference (IFI), inter-symbol interference (ISI) and even multi-user interference (MUI). A training-based joint timing and channel estimation scheme is proposed, which is resilient to IFI, ISI, MUI and pulse distortion. A low-complexity detection scheme similar to transmit-reference (TR) scheme comes out as a by-product. For saving the training symbols, we further develop an extended decision-directed (DD) scheme. A lower bound on the probability of correct detection is derived which agrees well with the simulated result for moderate to high SNR values. The results show that the proposed algorithm achieves a significant performance gain in terms of mean square error and bit error rate in comparison to the “timing with dirty templates” (TDT) algorithms.

Low-complexity sphere decoding for detection of OFDM systems in doubly-selective fading channels

A low-complexity detection scheme consisting of a sphere decoder and a parallel interference cancellation (PIC) equaliser is proposed for OFDM systems in doubly-selective fading channels. Theoretical analysis and simulation results show that this detection scheme substantially improves the symbol error rate performance of OFDM systems compared with the traditional PIC equaliser while requiring lower complexity at moderate and high signal-to-noise ratios.

Low Complexity MIMO Detection Based on the Slowest Descent Method

This contribution presents a novel multiple-input multiple-output (MIMO) detection scheme for quadrature amplitude modulation (QAM). The proposed method is based on the slowest descent (SD) method and is suitable for both iterative and non-iterative detectors. Similar to other low-complexity detection schemes, such as sphere decoding;, the new SD approach restricts the maximization/marginalization to a small set of candidate vectors. Simulation results indicate that the method achieves a close-to-optimal performance, with a complexity that scales only linearly with the number of transmit antennas

Sequence Detection Based on a Variable State Trellis for Multidimensional ISI Channels

Near-optimum sequence detection in channels with intersymbol interference (ISI) is based on the Viterbi algorithm. However, its complexity increases exponentially with the number of taps within the span of the ISI and with the number of symbol levels. We present a low-complexity sequence detection scheme, based on the Viterbi detection algorithm, which is generalized for multidimensional ISI channels in the presence of the predominant signal-dependent noise. The proposed variable state trellis (VST) approach detects and discards in real time states that are unlikely to correspond to the survivor path, thus reducing the complexity of the sequence detection significantly. After analyzing and exploiting a number of criteria (such as a priori reliability information, channel characteristics, and probability of error occurrences among different symbol levels), we propose three approaches to implement the VST scheme. The VST can be applied to any multidimensional ISI channel, including magnetic and optical storage. We compare the performance of the VST and conventional Viterbi algorithms for the multilevel two-dimensional optical storage channel, where media noise is predominant, and show that, with negligible performance loss, the computational complexity is reduced significantly

Reducing Detection Complexity of MIMO-OFDM by Using New Nulling Vectors

We propose new nulling vectors for the subcarrier grouping based low-complexity detection scheme of V-BLAST (vertical Bell Laboratories layered space-time) coded MIMO-OFDM. In each subcarrier group, the center subcarrier uses the conventional ZF-DFE (zero-forcing decision-feedback- equalization) algorithm and the non-center subcarriers use the reduced-complexity ZF-DFE with the new nulling vectors. The subcarrier grouping based detection scheme, ZF-DFE-SG, can significantly reduce the detection complexity compared with ZF-DFE-EX which exhaustively applies the conventional ZF-DFE at each subcarrier independently. The performance loss is very small. We conduct the simulations for channel coded V-BLAST OFDM system under estimated channel frequency responses. It is shown the complexity can be reduced by 80.6% with only 1.0 dB performance loss for a 4x4 system.

A maximum a posteriori MIMO detector using recursive metric computations

A complexity reduction technique for soft-output maximum a posteriori probability detection in wireless multiple-input multiple-output (MIMO) channels using rectangular quadrature amplitude modulation (QAM) constellations is derived. In contrast to existing low-complexity detection schemes that reduce the number of candidate tests, we instead focus on lowering the computational burden per candidate. The search over a large number of hypotheses to generate output L-values is facilitated by a doubly recursive mechanism, exploiting differential updates of the distance metrics from candidate to candidate. Moreover, the search over all transmit candidates is simplified using a hierarchical "triangular" (zig-zag) shaped candidate scanning order. The technique is derived conceptually using mathematical terms, and then illustrated by means of a 2 times 2 MIMO system using 64-QAM modulation. Under certain practical assumptions, the new scheme is shown to reduce the overall number of operations per candidate by a factor of about 50-100. While the concept is demonstrated by means of the exhaustive search case, it can be combined with other search-based MIMO detection techniques such as spherical decoding

Low-density Parity-check codes with run length limited (RLL) constraints

This paper addresses a new scheme by Vasic and Pedagani to combine low-density parity-check (LDPC) codes with run length limited (RLL) constraints. In this method, the RLL constraints are embedded into the LDPC codewords by deliberately flipping the bits of LDPC codewords that violate the RLL constraints. It is important to keep the number of flipped bits small in order to not overburden the LDPC decoder. In this paper, we introduce a method to control the number of flipped bits by using pseudorandom sequences. We present a new low-complexity iterative decoding and detection scheme to correct both the flipped bits and channel errors in a partial response channel. Analyses and simulation results show that the proposed method has good performance and reasonable complexity for (0,k) RLL constraints.

Hidden preamble detector for acquisition of frequency hopping multiple-access communication system

The problem of acquisition of frequency hopping multiple-access communication systems is addressed. The receiver uses the hidden preamble detector to accomplish the acquisition process. An upper bound on mean acquisition time is provided and the results are compared with an active correlator and a matched filter. The results show that the hidden preamble detector has a low-complexity detection scheme and an acquisition speed that is nearly as fast as the matched filter.