Greedy Detection Research Articles

Performance Analysis of RIS-Aided Index Modulation With Greedy Detection Over Rician Fading Channels

Performance Analysis of RIS-Aided Index Modulation With Greedy Detection Over Rician Fading Channels

RIS-Assisted Receive Quadrature Spatial Modulation With Low-Complexity Greedy Detection

RIS-Assisted Receive Quadrature Spatial Modulation With Low-Complexity Greedy Detection

Optimized Greedy Detection for OFDM-IM Systems

Recently, a new transmission method has been proposed for power-efficient wireless communication systems called Orthogonal Frequency Division Multiplexing with Index Modulation (OFDM-IM). This method offers high spectral efficiency with good error performance. The greedy detection (GD) scheme of subcarrier indices is often used to reduce the complexity of the OFDM-IM system in comparison to other relevant detectors. In this letter, an optimized greedy detection (OGD) scheme is proposed. The received subblock is divided into mini-subblocks to decrease the risk of error. The Total Symbol Error Probability (TSEP) is derived using a closed-form expression to evaluate the performance. Simulation and analytic results demonstrate the superiority of the proposed detector.

Joint RIS Grouping Design Assisted Generalized Quadrature Reflection Modulation

In this paper, a novel joint reconfigurable intelligent surface (RIS) grouping design assisted generalized quadrature reflection modulation (JGD-GQRM) scheme is proposed for a single radio frequency (RF) multiple-input multiple-output (MIMO) system. In JGD-GQRM, a limited number of RIS elements are spatially grouped, and the remaining reflection patterns are utilized for joint mapping to improve the reliability of the transmission. Moreover, it maps additional information bits by full reflection passive beamforming to improve the system's spectral efficiency (SE). In addition to the optimal maximum likelihood (ML) detector that has high computational complexity, a low-complexity sequential greedy detection (SGD) for JGD-GQRM is proposed. Simulation results show that the proposed scheme can achieve better bit error rate (BER) performance than the existing reflection modulation.

Performance evaluation of RIS-based SSK and SM schemes with perfect and imperfect channel phase estimation over Weibull fading channels

In this paper, we present the re-configurable intelligent surfaces (RIS) based space shift keying (SSK) and spatial modulation (SM) schemes with both perfect and imperfect channel phase knowledge over Weibull fading environments. At the receiver, we consider the sub-optimal Greedy Detection (GD) for proposed RIS-based SSK and SM schemes. Central Limit Theorem (CLT) caused by RIS schemes facilitates to adopt of a unified framework for error performance analysis of Weibull fading channels without loss of generality. In this study, it has been obtained the theoretical bit error probability (BEP) of the proposed schemes. It should be underlined that unlike the literature, the BEP of the proposed schemes is formulated in the presence of a Gaussian imperfect phase estimation at RIS. These analytical results were then validated with Monte-Carlo Simulations under the various system settings (e.g., the severity of fading parameters, number of reflectors, different antenna numbers).

Greedy Kernel Change-Point Detection

We consider the problem of detecting abrupt changes in the underlying stochastic structure of multivariate signals. A novel non-parametric and model-free off-line change-point detection method based on a kernel mapping is presented. This approach is sequential and alternates between two steps: a greedy detection to estimate a new breakpoint and a projection to remove its contribution to the signal. The resulting algorithm is able to segment time series for which no accurate model is available: it is computationally more efficient than exact kernel change-point detection and more precise than window-based approximations. The proposed method also offers some theoretical consistency properties. For the special case of a linear kernel, an even faster implementation is provided. The proposed strategy is compared to standard parametric and non-parametric procedures on a real-world data set composed of 262 accelerometer recordings.

Adaptive OFDM-IM System Over Faded Shadowing Channel

Spectral efficiency (SE) and energy efficiency (EE) play major roles in evaluating the quality of service (QoS) of a wireless communication system. Designing an efficient wireless communication system requires trade-off between these two parameters. Orthogonal frequency division multiplexing technique with Index Modulation (OFDM-IM) has been introduced in the literature to increase the SE compared to traditional OFDM. In this paper, an adaptive technique with OFDM-IM is introduced in an M-QAM based scheme to maintain a guaranteed level of average bit error probability (ABEP) with enhanced SE. It has been demonstrated that by adaptively varying the number of active subcarriers and modulation levels in M-QAM scheme, maximum EE can also be achieved for an acceptable ABEP. The closed-form expressions of ABEP and pairwise error probability (PEP) for OFDM-IM with M-ary QAM modulation are derived and examined over the composite Nakagami-m Gamma (NG) fading channel model using greedy detection (GD). In addition, the performance of adaptive OFDM-IM with M-QAM Modulation scheme is evaluated in terms of efficiency metrics, outage probability, and ABEP. The obtained results show that the adaptive scheme offers high potential for accomplishing significant improvement in SE and EE while maintaining acceptable ABEP even under severe channel impairment.

Cooperative OFDM-IM Relay Networks With Partial Relay Selection Under Imperfect CSI

In this paper, we investigate the performance of cooperative orthogonal frequency division multiplexing with index modulation (OFDM-IM) with the low complexity greedy detection (GD). In particular, we propose a novel partial relay selection scheme whose search criteria are designed to exploit the IM subcarriers. To provide low-complexity receiver, we further examine the energy-sensing based GD design for the cooperative OFDM-IM. For the performance analysis, we derive novel upper bound and approximate closed form solutions for both the average index error probability and the average symbol error probability over Nakagami- $m$ fading channels with imperfect channel state information (CSI) at the relays and destination. Unlike the information theoretical works, in presence of positive detection error in the relays, the derived expressions provide a useful insight into the error performance of cooperative OFDM-IM under various fading conditions. The numerical and simulation results clearly present that the proposed scheme harmonizing partially selected relays and their IM subcarriers with GD can outperform the benchmark schemes, under uncertain CSI, at reduced complexity.

The BER Analysis of MRC-Aided Greedy Detection for OFDM-IM in Presence of Uncertain CSI

This letter investigates the bit error rate (BER) performance of orthogonal frequency division multiplexing index modulation, employing the maximal ratio combining-based low-complexity greedy detector (MRC-GD) and the PSK modulation. For performance analysis, we derive tight expressions for both index error probability (IEP) and BER, taking into account channel state information (CSI) uncertainty. This provides insight into various impacts of CSI uncertainty on the diversity gain and error floor of the IEP and the BER, respectively. We clearly show that under imperfect CSI, the MRC-aided GD can perform like the MRC-maximum likelihood detector, at lower complexity. Finally, simulation results are presented to verify the accuracy of derived expressions and the theoretical analysis.

Low Complexity Compressive Sensing Greedy Detection of Generalized Quadrature Spatial Modulation

Low Complexity Compressive Sensing Greedy Detection of Generalized Quadrature Spatial Modulation

A Tight Bound on BER of MCIK-OFDM With Greedy Detection and Imperfect CSI

This letter first investigates bit error rate (BER) of Multi-Carrier Index Keying–Orthogonal Frequency Division Multiplexing using a low-complexity greedy detector (GD). We derive a tight, closed-form expression for the BER of the GD in the presence of channel state information (CSI) uncertainty. Particularly, exploiting the fact that the GD detects the active indices first, and then detects the data symbols, we divide the BER into two terms: the index BER and the symbol BER. The asymptotic analysis is also provided to analyze impacts of various CSI conditions on the BER. Interestingly, via theoretical and simulation results, we discover that the GD is not only less sensitive to imperfect CSI, but also better than the maximum likelihood detector under certain CSI conditions. In addition, the derived expression is accurate in a wide range of signal-to-noise ratio regions.

On the SEP Analysis of OFDM Index Modulation With Hybrid Low Complexity Greedy Detection and Diversity Reception

In this work, we investigate the performance of multicarrier index keying (MCIK) orthogonal frequency division multiplexing (OFDM) proposing a hybrid low complexity detection and diversity reception. For performance analysis, we derive novel exact closed-form expressions for the average pairwise error probability (PEP) and symbol error probability (SEP) of three detection methods: a greedy detector (GD), and a GD with maximal ratio combining, or selection combining. Approximate and accurate expressions for the average PEP and SEP are also analyzed in closed-form. The derived expressions provide a useful insight into the error performance of MCIK-OFDM with the hybrid detector in low, moderate, and extreme rate of sparse sub-carrier indices activation. The effects of multiple antennas and sparse sub-carriers activation on the SEP are addressed in several extreme cases; decreasing the average SEP exponentially with proper choice of both subcarrier activation rate and number of antennas. In comparison with the benchmark detection, the numerical results and simulations clearly show that the proposed schemes can benefit from diversity gain, at substantially reduced complexity. The derived SEP expressions and analyses will be useful to evaluate various concepts of MCIK OFDM in low-power device applications.

GDVAN: A New Greedy Behavior Attack Detection Algorithm for VANETs

Vehicular Ad hoc Networks (VANETs), whose main objective is to provide road safety and enhance the driving conditions, are exposed to several kinds of attacks such as Denial of Service (DoS) attacks which affect the availability of the underlying services for legitimate users. We focus especially on the greedy behavior which has been extensively addressed in the literature for Wireless LAN (WLAN) and for Mobile Ad hoc Networks (MANETs). However, this attack has been much less studied in the context of VANETs. This is mainly because the detection of a greedy behavior is much more difficult for high mobility networks such as VANETs. In this paper, we propose a new detection approach called GDVAN (Greedy Detection for VANETs) for greedy behavior attacks in VANETs. The process to conduct the proposed method mainly consists of two phases, which are namely the suspicion phase and the decision phase. The suspicion phase is based on the linear regression mathematical concept while decision phase is based on a fuzzy logic decision scheme. The proposed algorithm not only detects the existence of a greedy behavior but also establishes a list of the potentially compromised nodes using three newly defined metrics. In addition to being passive, one of the major advantages of our technique is that it can be executed by any node of the network and does not require any modification of the IEEE 802.11p standard. Moreover, the practical effectiveness and efficiency of the proposed approach are corroborated through simulations and experiments.

A new approach to greedy multiuser detection

We propose a new suboptimum multiuser detector for synchronous and asynchronous multiuser communications. In this approach, a greedy strategy is used to maximize the cost function, the maximum-likelihood (ML) metric. The coefficients of the ML metric are utilized as weights indicating in which order bits can be estimated. The complexity of the algorithm is approximately K/sup 2/ log K per bit, where K is the number of users. We analyze the performance of the greedy multiuser detection in the additive white Gaussian noise channel as well as in the frequency-nonselective Rayleigh fading channel, and compare it with the optimum detector and several suboptimum schemes such as conventional, successive interference cancellation, decorrelator, sequential, and multistage detectors. The proposed greedy approach considerably outperforms these suboptimum schemes, especially for moderate and high loads in low and moderate signal-to-noise ratio regions. The results show that when there is a significant imbalance in the values of the coefficients of the ML metric due to moderate to high noise, fading, and asynchronous transmission, near-optimum performance is achieved by the greedy detection.