Generalized Selection Combining Research Articles

SYMBOL ERROR PROBABILITY PERFORMANCE FOR GENERALIZED SELECTION COMBINING DIVERSITY RECEPTION OF M-QAM OVER RAYLEIGH FADING CHANNEL

The performance of generalized selection combining (GSC) diversity reception symbol error probability (SEP) of square M-ary quadrature amplitude modulation (M-QAM) signals over frequency-flat Rayleigh fading channels is investigated in this work. The combining techniques considered in this paper are maximum ratio combining and selection combining (SC). We present closed-form approximate expressions for the average combined signal-to-noise ratio (SNR) and SEP in the fading channel for M-QAM signal reception in the GSC using diversity pathways that are independently, identically distributed. The simulation results validate the SEP expressions and demonstrate that, for a given number of accessible diversity paths, combining the strongest paths results in the majority of the diversity gain, and that the SNR declines as the number of combined paths increases. On the other hand, the numerical results demonstrate that, for a certain number of combined paths, increasing the number of available diversity paths can lead to a significant performance improvement.

Enchancement of GSC Using OFDM and QAM Over Reiyleign Fading Channel: A Review

As indispensable as communication has been to human endeavors, geographical and physical distance would have been a barrier to its effective deployment if not for the advent of wireless mobile communication. In the world today, most of the developments we see in all spheres of our modern life are influenced by communication technologies. However, the performance of each modulation scheme deployed in the communication system dictates the Quality of Service (QoS), effective cost management, efficient power, available bandwidth, Bit Error Rate (BER), and Signal to Noise Ratio (SNR). Extensive research has been done with different authors proffering wide ranging solutions for generalized selection combining (GSC) algorithms in the presence of noise and interfering signals. Some of the reported approaches include varying modulation schemes, changing the channel, and using different equalizing techniques. Many of these proposed solutions worked effectively in some areas while they understandably left other areas untouched, others show better performance by analyzing the channel using; Log-likelihood Ratio (LLR), integral expression, and multiple-mode transmission scheme which in turns proof to be of better performance with a good result. Despite all the efforts, overcoming the issue of noise interference in the communication channel has still been somewhat elusive. Conclusively, to reduce noise to the barest minimum in mobile/cellular communication, this review proposes modulation scheme synchronization with combined diversity technique over an improved channel that is less prone to noise.

Performance analysis of NOMA with generalised selection combining receivers

In this Letter, the authors present a comprehensive performance analysis of a non-orthogonal multiple access (NOMA) system with generalised selection combining (GSC), which bridges the gap between the performance of NOMA with selection combining (SC) and NOMA with maximal-ratio combining (MRC). In particular, the authors derive a closed-form expression for an upper bound on the average achievable sum rate and an exact closed-form expression for the outage probability. The analysis reveals a tradeoff between the number of implemented receiver radio-frequency (RF) chains and the achieved performance and can be used to determine the appropriate number of paths to combine into a practical receiver design. A demonstrated agreement between the analytical and simulation results confirms the correctness of the analysis.

On the sum of ordered random variables and its applications to physical‐layer security of communication over η‐μ fading channels with generalized selection combining

AbstractOrder statistics have attracted the interest of the research community since they find numerous applications in several areas of communications and signal processing fields. This paper introduces an approximate yet accurate approach to determine the statistics of the sum of ordered independent but not necessarily identically distributed η‐μ random variables, which is an accurate model in a generic non–line‐of‐sight propagation environment. The proposed method is used to assess the secrecy performance of wiretap η‐μ fading channels employing generalized selection combining (GSC) diversity. We consider the case of GSC(L,2L), where L branches with the largest instantaneous signal‐to‐noise‐ratio (SNR) values, from a total of 2L available branches, are selected. By introducing a novel modified cascade combining receiver structure whose output SNR statistics closely approximate that of GSC(L,2L), a simple and accurate closed‐form approximation for the moment generating function of the GSC(L,2L) output SNR is derived. This expression is further employed to evaluate the secrecy outage probability and the secrecy capacity of a wiretap channel consisting of a single‐antenna transmitter, a multiantenna receiver, and a multiantenna eavesdropper. Using the proposed analytical approach, various numerical performance evaluation results accompanied with complementary Monte Carlo simulations are further presented. These results have shown that the proposed approach is accurate over the entire range of SNR values, thus enabling a low‐complexity computation of important performance metrics.

Secrecy Outage Performance of Transmit Antenna Selection for MIMO Underlay Cognitive Radio Systems Over Nakagami- $m$ Channels

This paper considers a multiple-input–multiple-output (MIMO) cognitive wiretap system over Nakagami- $m$ channels with generalized selection combining (GSC), where confidential messages transmitted from a multiple-antenna transmitter to a multiple-antenna legitimate receiver are overheard by a multiple-antenna eavesdropper. Depending on whether the source node has the global channel state information (CSI) of both the main and wiretap channels, we investigate the secrecy outage performances of optimal antenna selection (OAS) and suboptimal antenna selection (SAS) schemes for MIMO underlay cognitive radio systems over Nakagami- $m$ channels, and we compare them with the space-time transmission (STT) scheme. The closed-form expressions for the exact and asymptotic secrecy outage probability (SOP) for various schemes are derived. Simulations are conducted to validate the accuracy of our derived analytical results.

Generalized Selection Combining Scheme for Orthogonal Space—Time Block Codes with M-QAM and M-PAM Modulation Schemes

Multiple-input multiple-output (MIMO) systems implement multiple antennas to enhance diversity gain of wireless communication systems. Earlier work in generalized selection combining (GSC) focused on single-input multiple-output systems without space---time coding. Recently, with the aid of space---time coding, diversity gain became possible using multiple transmit antennas. In this paper, GSC scheme is applied to orthogonal space---time block codes (OSTBC) for 4 × L and 8 × L MIMO systems with various modulation schemes like M-PSK, M-QAM, and M-PAM in a slowly fading Rayleigh channel. The performance of GSC for half rate-full diversity, full rate-full diversity, and 3/4 rate-full diversity OSTBC is discussed and compared. Approximate closed-form expressions for symbol error rate (SER) and ergodic capacity for various OSTBCs are derived. The impact of channel estimation errors on system performance is also examined. Approximate closed-form expressions for performance bounds on SER and ergodic capacity of GSC for MIMO OSTBC are also derived and plotted.

Generalised selection at multi‐antenna sources in two‐way relay networks

A generalised selection transmission (GST) and generalised selection combining (GSC) scheme is proposed for two-way relay networks where two multi-antenna sources exchange information via a single-antenna relay. New exact and asymptotic expressions are derived for the outage probability and symbol error rate (SER) in Rayleigh fading. Moreover, a tight upper bound on the ergodic sum-rate is presented. These results are used to demonstrate that the proposed GST/GSC scheme preserves the full diversity order, which equals the minimum number of antennas at the two sources. It is also shown that the impact of the number of selected antennas lies in the array gain only. Furthermore, the GST/GSC scheme significantly improves the performance relative to single-antenna selection, and only incurs a negligible reduction in performance relative to all-antenna beamforming. Finally, the optimal relay location that minimises the SER is determined analytically. It is observed that the optimal relay location shifts towards one source when the number of selected or available antennas at the other source increases.

Secure Full-Duplex Spectrum-Sharing Wiretap Networks with Different Antenna Reception Schemes

In this paper, we investigate the secrecy performance of full-duplex multi-antenna spectrum-sharing wiretap networks in which a jamming signal is simultaneously transmitted by the full-duplex secondary receiver (Bob) based on the zero forcing beamforming (ZFB) algorithm. For the security enhancement, we propose the two antenna reception schemes: 1) random selection combining (RSC) where Bob selects $L_{\mathrm{B}}$ antennas at random to combine the received signals and 2) generalized selection combining (GSC) where Bob selects $L_{\mathrm{B}}$ strongest antennas to combine the received signals. We derive the exact closed-form expressions for the secrecy outage probability of full-duplex multi-antenna spectrum-sharing wiretap networks with ZFB algorithm. In order to explore a new design of the proposed schemes, we provide tractable asymptotic approximations for the secrecy outage probability in high signal-to-noise ratio regime under two distinct scenarios. From the analysis, we demonstrate that: 1) when the main channel is much better than the eavesdropper’s channel, GSC/ZFB scheme achieves full diversity $N_{\mathrm{B}}$ , while RSC/ZFB scheme only achieves partial diversity $L_{\mathrm{B}}$ and 2) GSC/ZFB scheme achieves better secrecy performance than RSC/ZFB with different antenna numbers at Bob.

Secure Transmission With Antenna Selection in MIMO Nakagami- <inline-formula> <tex-math notation="TeX">$m$</tex-math></inline-formula> Fading Channels

This paper considers transmit antenna selection (TAS) and receive generalized selection combining (GSC) for secure communication in the multiple-input-multiple-output wiretap channel, where confidential messages transmitted from an NA-antenna transmitter to an NB-antenna legitimate receiver are overheard by an NE-antenna eavesdropper. We assume that the main channel and the eavesdropper's channel undergo Nakagami-m fading with fading parameters mB and mE, respectively. In order to assess the secrecy performance, we present a new unifying framework for the average secrecy rate and the secrecy outage probability. We first derive expressions for the probability density function and the cumulative distribution function of the signal-to-noise ratio with TAS/GSC, from which we derive exact expressions for the average secrecy rate and the secrecy outage probability. We then derive compact expressions for the asymptotic average secrecy rate and the asymptotic secrecy outage probability for two distinct scenarios: 1) the legitimate receiver is located close to the transmitter, and 2) the legitimate receiver and the eavesdropper are located close to the transmitter. For these scenarios, we present new closed-form expressions for several key performance indicators: 1) the capacity slope and the power offset of the asymptotic average secrecy rate, and 2) the secrecy diversity order and the secrecy array gain of the asymptotic secrecy outage probability. For the first scenario, we confirm that the capacity slope is one and the secrecy diversity order is mBNBNA. For the second scenario, we confirm that the capacity slope and the secrecy diversity order collapse to zero.

A Low Complexity Antenna Switching for Joint Wireless Information and Energy Transfer in MIMO Relay Channels

In this paper, we investigate a low-complexity technique for simultaneous wireless information and energy transfer in multiple-input multiple-output relay channels. The proposed technique exploits the array configuration at the relay node and uses the antenna elements either for conventional decoding or for rectifying (rectennas). In order to keep the complexity low, a dynamic antenna switching between decoding/rectifying is proposed based on the principles of the generalized selection combiner (GSC); the L strongest paths are allocated for decoding while the remaining channel paths for rectifying (and vice versa). The optimal L as well as the allocation strategy that minimizes the outage probability are investigated via theoretical and numerical results. In addition, two performance bounds that provide the optimal performance without the limitation of GSC are proposed by solving a linear programming and a binary knapsack problem, respectively. The proposed technique is extended to scenarios with multi-user interference, where a zero-forcing receiver is used at the relay node; closed-forms expressions for the outage probability are also derived.

Generalized Diversity Reception in the Presence of Multiple Distinct Interferers: An Outage Performance Analysis

The analytical performance evaluation of various coherent diversity combining reception techniques in the presence of multiuser interference is presented into this paper. Particularly, the outage probability of the generalized selection combining (GSC) and its two extreme cases, namely the maximum ratio combining (MRC) and the selection combining (SC), are evaluated. The multiple interferers undergo independent and non-identically distributed Nakagami-m fading channels, with distinct average received powers and arbitrary fading scales. New analytical outage expressions are presented including several channel fading conditions regarding the desired user's signal. Although the proposed approach is formed as an infinite series representation, it includes only simple elementary and Gamma functions, while it delivers a rapidly converging formula achieving a sufficiently high precision level. Moreover, the derived computational complexity of this function is thoroughly discussed, while a corresponding comparison with another popular technique indicates the usefulness of the proposed approach. Finally, the accuracy of the approach is verified with the aid of selected numerical results accompanied with equivalent simulation ones.

Effect of Noise on the Average Received SNR of Different Combining Schemes

In wireless communication system, the multipath fading affects the performance of the system. Diversitycombining scheme is one of the powerful tools to mitigate the effect of fading. The multiple antennas provide an improvement in the capacity and reliability of the system. The performance of four combining schemes Selection Combining (SC), Maximum Ratio Combining (MRC), Equal Gain Combining (EGC), and Generalised Selection combining (GSC)- in the presence of both the perfect and an imperfect channel state information (CSI) at the receiver is studied in this contribution by Monte Carlo simulations in the MATLAB environment, when communicating over Rayleigh fading channels. Our results show that the presence of the complex noise in the channel degrades the performance of the system in all four combining schemes, but the degradation in performance is found to be maximum in MRC and minimum in SC. Performance of EGC lies in between the performance of MRC and SC, whereas the performance of GSC depends upon the number of antennas being selected and it is upper bounded by the MRC and lower bounded by the SC. Also, the results show that as the value of SNR is increased the average received SNR increases in both the channels.

Virtual Branch Analysis of Symbol Error Rate for OSTBC MIMO Systems with Generalized Selection Combining Using MPSK and MQAM Modulation Schemes

We consider a system where Generalized Selection Combining (GSC) is applied to a 4 x L Multiple-Input Multiple-Output (MIMO) system using Half rate-Full diversity Orthogonal Space-Time Block Codes (OSTBCs) at the transmitter. The Symbol Error Rate (SER) of M-ary Quadrature Amplitude Modulation (MQAM) for a slow, flat Rayleigh fading channel is derived and compared to that of the M-ary Phase Shift Keying (MPSK) modulation scheme. Performance comparisons of various antenna configurations are made. The channel statistics are assumed to be identical for the independent diversity branches. The effects of channel estimation errors on the SER performance for GSC are plotted and discussed in this paper. Index Terms—Multiple-input multiple-output (MIMO) systems, channel estimation error, generalized selection combining (GSC), space-time block codes (STBCs), quadrature amplitude modulation (QAM), symbol error rate (SER).

Impact of Primary Network on Secondary Network with Generalized Selection Combining

We propose cognitive spectrum sharing with generalized selection combining (GSC) at the secondary user (SU) in the presence of multiple primary transceivers with outdated channel information. Our main motivation is to determine the impact of GSC and outdated channel information on the outage probability of cognitive spectrum sharing subject to two practical power constraints: 1) maximum transmit power at the SU transmitter and 2) peak interference temperature at the primary user (PU) receiver. We derive new closed-form expressions for the exact and asymptotic outage probability in Rayleigh fading. Our expressions provide concise representations of the diversity order and the array gain. We confirm that the diversity order of GSC is entirely dependent on the secondary network and is equal to the available number of receiver antennas at the SU. This result is consistent with those of maximal-ratio combining (MRC) and selection combining (SC) in cognitive spectrum sharing. More importantly, our results show that the outage probability decreases with the increasing correlation coefficient of the outdated channel.

An MGF-Based Unified Framework to Determine the Joint Statistics of Partial Sums of Ordered i.n.d. Random Variables

The joint statistics of partial sums of ordered random variables (RVs) are often needed for the accurate performance characterization of a wide variety of wireless communication systems. A unified analytical framework to determine the joint statistics of partial sums of ordered independent and identically distributed (i.i.d.) random variables was recently presented. However, the identical distribution assumption may not be valid in several real-world applications. With this motivation in mind, we consider in this paper the more general case in which the random variables are independent but not necessarily identically distributed (i.n.d.). More specifically, we extend the previous analysis and introduce a new more general unified analytical framework to determine the joint statistics of partial sums of ordered i.n.d. RVs. Our mathematical formalism is illustrated with an application on the exact performance analysis of the capture probability of generalized selection combining (GSC)-based RAKE receivers operating over frequency-selective fading channels with a non-uniform power delay profile. We also discussed a couple of other sample applications of the generic results presented in this work.

Comparative Analysis of Normalized Switching Rate for Different Fading Channels

Performance of Generalized Selection Combining (GSC) receivers channels mainly in terms of switching rate with nonidentical branches has been studied in Rician fading and the graphical results obtained using Mat-lab after implementing the derived switching rate expression for Rician are compared with the performance of Rayleigh Fading Channels as per the research presented in an earlier paper by Paul Ho [1]. General Terms Switching Rate, Rayleigh fading, Rician fading, Diversity Techniques

Effective Capacity of Cognitive Radio Systems with GSC Diversity under Imperfect Channel Knowledge

In this paper, we investigate the effective capacity of opportunistic spectrum sharing with generalized selection combining (GSC) diversity at the secondary receiver in fading environments. In particular, we study the impact of outdated channel information between the secondary transmitter and the primary receiver on the performance of the secondary user. An exact closed-form expression for the effective capacity of the secondary user with GSC diversity is derived under the peak interference constraint at the primary receiver. Comparisons done using simulations show the effect of the uncertainty of channel information on the effective capacity. Specially, the performance gap due to imperfect channel information becomes smaller with the increase of the number of selected antennas {k}. Theoretic analysis and simulations show that the system performance is robust against imperfect channel information and selection combining (SC) should be adopted under strict delay quality of service (QoS) requirements.

레일레이 페이딩 채널에서 MRC/GSC 수신하는 DOT 릴레이 시스템의 성능

Opportunistic transmit cooperative relaying (OTR) system has been interested for its ability to mitigate the fading in wireless channel without multiple antennas in a small terminal. In OTR system, only the relays that the received Signal-to-noise ratio (SNR) from a source is greater than the threshold transmit to the destination. However, the receiving branches of a destination in a realistic system is fixed, the excess number of signals from the transmit relays does not improve the system performance and consequently increases power consumption. In this paper, we adopt Double Opportunistic Transmit (DOT) cooperative diversity system which controls the average number of transmit relays. Although the average number of the transmit relays can be controlled by adjusting the two thresholds in DOT system, the instantaneous number of transmit relays is varying in fading channel. Thus we propose Maximal Ratio Combining (MRC) or Generalized Selection Combining (GSC) according to the number of the signals from relays at the destination. The outage probability of the proposed system is derived in closed form. The analytical results show that the system performance is improved with the number of the branches. Also it is noticed that when the number of the branches is fixed, the outage probability decreases with the increase of the average SNR of S-R path and R-D path.

Performance of Amplify-and-Forward Cooperative Diversity Networks with Generalized Selection Combining over Nakagami-m Fading Channels

This letter investigates the symbol error rate (SER) and outage behavior of the amplify-and-forward (AF) protocol with the generalized selection combining (GSC) scheme over Nakagami-m fading channels. The asymptotic expressions of the SER and outage probability at the high SNR regions have been derived. The diversity gain has been investigated as well. Simulation results verify the tightness and accuracy of the presented analysis at the high SNR regions. These results are quite simple and general for the arbitrary value of Nakagami-m fading figure. More importantly, the proposed approach is applicable to other fading channels. Performances for Rayleigh, Rician and Hoyt fading channels are also evaluated in this letter.

End‐to‐end performance of transmit antenna selection and generalized selection combining in dual‐hop amplify‐and‐forward relay network in the presence of feedback errors

ABSTRACTIn this paper, end‐to‐end performance of transmit antenna selection (TAS) and generalized selection combining (GSC) is studied in a dual‐hop amplify‐and‐forward relay network over flat Rayleigh fading channels. In the system, source and destination equipped with multiple antennas, communicate by the help of single relay equipped with single antenna. Source‐destination link is not available. TAS is used for transmission at the source, and GSC is used for reception at the destination. By considering the relay location and the presence of error in feedback channel from the relay to the source, we derive closed‐form outage probability, moment generating function and moments of end‐to‐end signal‐to‐noise ratio, and closed‐form symbol error probability (SEP) expressions for channel state information (CSI)‐based and fixed relay gains. The diversity order and array gain of the network are obtained for both CSI‐based and fixed relay gains by deriving asymptotical outage probability and SEP expressions. The analytical results are validated by the Monte Carlo simulations. Copyright © 2012 John Wiley & Sons, Ltd.