Detect-and-forward relaying aided cooperative spatial modulation for wireless networks

A novel detect-and-forward (DeF) relaying aided cooperative SM scheme is proposed, which is capable of striking a flexible tradeoff in terms of the achievable bit error ratio (BER), complexity and unequal error protection (UEP). More specifically, SM is invoked at the source node (SN) and the information bit stream is divided into two different sets: the antenna index-bits (AI-bits) as well as the amplitude and phase modulation-bits (APM-bits). By exploiting the different importance of the AI-bits and the APM-bits in SM detection, we propose three low-complexity, yet powerful relay protocols, namely the partial, the hybrid and the hierarchical modulation (HM) based DeF relaying schemes. These schemes determine the most appropriate number of bits to be re-modulated by carefully considering their potential benefits and then assigning a specific modulation scheme for relaying the message. As a further benefit, the employment of multiple radio frequency (RF) chains and the requirement of tight inter-relay synchronization (IRS) can be avoided. Moreover, by exploiting the benefits of our low-complexity relaying protocols and our inter-element interference (IEI) model, a low-complexity maximum-likelihood (ML) detector is proposed for jointly detecting the signal received both via the source-destination (SD) and relay-destination (RD) links. Additionally, an upper bound of the BER is derived for our DeF-SM scheme. Our numerical results show that the bound is asymptotically tight in the high-SNR region and the proposed schemes provide beneficial system performance improvements compared to the conventional MIMO schemes in an identical cooperative scenario.<br/

On the Identification Accuracy of the I/Q Imbalance-Based Specific Emitter Identification

Specific emitter identification (SEI) is a powerful technique that identifies different emitters utilizing the features generated from hardware imperfections. The features, also known as radio frequency fingerprints (RFFs), can be extracted via model-based methods or data-based methods. In this paper, we analyze the identification accuracy of SEI system and provide criteria for evaluating different SEI schemes. We use in-phase/quadrature (I/Q) imbalance as an example to examine the identification performance by analyzing the Euclidean distance between radio frequency (RF) signals of different emitters. This derivation can also be generalized to different modulation schemes and distortion models

Adaptive Jamming Suppression in Coherent FFH System Using Weighted Equal Gain Combining Receiver over Fading Channels with Imperfect CSI

Fast frequency hopping (FFH) is commonly used as an antijamming communication method. In this paper, we propose efficient adaptive jamming suppression schemes for binary phase shift keying (BPSK) based coherent FFH system, namely, weighted equal gain combining (W-EGC) with the optimum and suboptimum weighting coefficient. We analyze the bit error ratio (BER) of EGC and W-EGC receivers with partial band noise jamming (PBNJ), frequency selective Rayleigh fading, and channel estimation errors. Particularly, closed-form BER expressions are presented with diversity order two. Our analysis is verified by simulations. It is shown that W-EGC receivers significantly outperform EGC. As compared to the maximum likelihood (ML) receiver in conventional noncoherent frequency shift keying (FSK) based FFH, coherent FFH/BPSK W-EGC receivers also show significant advantages in terms of BER. Moreover, W-EGC receivers greatly reduce the hostile jammers’ jamming efficiency

Soft-feedback time-domain turbo equalization for single-carrier generalized spatial modulation

In this paper, a new class of soft-decision feedback aided time-domain turbo equalizer (TDTE) based on the minimum mean-square error criterion is proposed for broadband single-carrier (SC) generalized spatial modulation (GSM) systems. First, a time-domain soft-decision feedback (TDSDF) aided TDTE is proposed, which operates on a vector-by-vector basis. In order to provide a flexible tradeoff between complexity and performance, time-invariant filter coefficients are derived to provide a low-complexity approximate solution to the proposed TDSDF-TDTE. Furthermore, a soft-feedback interference cancelation (SFIC) aided TDTE is proposed for SC-GSM systems with a lower complexity, where the computation of the second-order moment of matrices is completely avoided. Finally, bi-directional soft-decision feedback aided TDTEs are proposed by using a time-reversed TDSDF-TDTE/SFIC-TDTE in conjunction with a ordinary TDSDF-TDTE/SFIC-TDTE so as to harvest time-reverse diversity and to mitigate the error propagation. An extrinsic information transfer chart based analysis and bit error rate simulation results are presented to demonstrate the superior performance of the proposed soft-decision feedback aided TDTEs as opposed to the original TDTEs, while achieving a lower complexity

Joint iterative channel estimation and frequency-domain turbo equalization for single-carrier spatial modulation

Single carrier frequency-domain turbo equalization (SC-FDTE) has gained widespread adoption in the emerging broadband spatial modulation (S-M) systems operating in frequency selective channels, where the channel model considered is a quasi-static Rayleigh fading channel. In this paper, a new class of robust FDTE designs based on the minimum mean-square error (MMSE) criterion is conceived for broad-band single-carrier SM (SC-SM) systems relying on realistic imperfect channel knowledge. First, a robust time-domain soft-decision feedback (TDSDF) aided FDTE is proposed to cope with channel estimation errors at the receiver. Furthermore, its robust frequency-domain soft-decision feedback (FDSDF) aided counter-part is derived to offer a low-complexity approximate solution. Finally, by exploiting the carefully selected reliable soft-decision output of the channel decoder as pilots, we refine the resultant decision-directed channel estimation. As a benefit, the performance of the two robust FDTEs can be further improved. Both our simulation results and our extrinsic information transfer (EXIT) chart analysis demonstrate that the proposed robust FDTEs achieve significant performance improvements over the conventional FDTEs

Adaptive Jamming Suppression in Coherent FFH System Using Weighted Equal Gain Combining Receiver over Fading Channels with Imperfect CSI

Fast frequency hopping (FFH) is commonly used as an antijamming communication method. In this paper, we propose efficient adaptive jamming suppression schemes for binary phase shift keying (BPSK) based coherent FFH system, namely, weighted equal gain combining (W-EGC) with the optimum and suboptimum weighting coefficient. We analyze the bit error ratio (BER) of EGC and W-EGC receivers with partial band noise jamming (PBNJ), frequency selective Rayleigh fading, and channel estimation errors. Particularly, closed-form BER expressions are presented with diversity order two. Our analysis is verified by simulations. It is shown that W-EGC receivers significantly outperform EGC. As compared to the maximum likelihood (ML) receiver in conventional noncoherent frequency shift keying (FSK) based FFH, coherent FFH/BPSK W-EGC receivers also show significant advantages in terms of BER. Moreover, W-EGC receivers greatly reduce the hostile jammers&apos; jamming efficiency

An improved frequency domain turbo equalizer for single-carrier spatial modulation systems

In this paper, a new time-domain soft-decision feedback (TDSDF) aided frequency domain turbo equalizer (FDTE) is proposed for broadband single-carrier (SC) spatial modulation (SM) systems. Specifically, the proposed equalizer operates on a frame-by-frame basis and is designed based on the minimum block-averaged mean-square error (MBMSE) criterion. To tackle the error propagation problem, a metric in consideration of the reliability of the feedback information is considered. The optimal coefficients of the forward and feedback filters involved in the TDSDF-FDTE design are derived analytically. Simulation results show that the proposed nonlinear TDSDF-FDTE detector is capable of offering a better tradeoff between the bit-error-rate (BER) performance and the imposed computational complexity than the conventional linear frequency domain turbo demapper (FDTD) conceived for SC-SM systems. Furthermore, a 4 dB improvement is observed for the unbalanced channel

Efficient detection of spatial modulation OFDM systems with multiple carrier frequency offsets

In this letter, an efficient detection scheme is proposed to mitigate the effect of the carrier frequency offset (CFO) in spatial modulation orthogonal frequency division multiplexing (SM-OFDM) systems. Specifically, the proposed scheme employs a novel symbol-by-symbol-aided iterative detector to the SM-OFDM systems with multiple CFOs, where the zero symbols are considered as constellation points. Simulation results demonstrate that the proposed scheme is capable of effectively mitigating the effect of multiple CFOs and of providing about considerable system performance improvement compared with the conventional parallel interference cancellation-aided maximum likelihood detector at a moderate complexity cost