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A receive diversity power line communication (PLC) system subject to correlated multipath channel fading and corrupted by additive Nakagami- $m$ background noise is considered. The optimal receiver employing a 4-ary imbalanced-phase-amplitude modulation (I-PAM) scheme for data transmission is obtained, using which closed form expressions for the symbol error probability (SEP) in the union bound sense and the SEP in the asymptotic sense at high signal-to-noise ratio (SNR) are derived. The diversity order of the system is found to be independent of the shape parameter of the additive noise. Furthermore, the optimal 4-ary I-PAM constellation minimizing the SEP at lower SNR values is computed numerically. The optimal 4-ary I-PAM constellation is found to be elliptical in shape as opposed to the traditional circular QPSK constellation generally employed in wireless communication systems. The effects of the correlation among the multipath channel gains and the shape parameter of the noise on the optimality of the considered constellation are also presented via numerical studies. [ABSTRACT FROM AUTHOR]

An $N$ -branch receive diversity power line communication (PLC) system subject to Rayleigh fading and corrupted by additive Nakagami- $m$ background noise is considered. A suboptimal maximal-ratio-combining (MRC), an optimal diversity combining, and a Gauss-optimal receiver are proposed for the PLC system. A closed form expression for the exact symbol error probability (SEP) and a union bound SEP expression are obtained for the proposed MRC and Gauss-optimal receivers, respectively, using a characteristic function (c.f.) approach for the system employing $M$ -ary phase-shift keying (MPSK) at the transmitter, conditioned to $mN$ being an integer. The asymptotic expression for the SEP obtained for the MRC receiver at high signal-to-noise (SNR) demonstrates that the diversity order of the system is independent of the shape parameter $m$ of the additive noise which is identical to the diversity order of the optimal and the Gauss-optimal receivers. Further, numerical studies justify the advantages of employing receive diversity to achieve superior SEP performance. The effect of increasing the diversity branches on the PLC system performance with varying $m$ and the power efficiency of the PLC system are also presented. [ABSTRACT FROM AUTHOR]

A noncoherent diversity detection power line communication (PLC) system employing multi-level amplitude-shift keying (ASK) modulation in the presence of Middleton Class-A impulsive noise is considered. Hermite numerical integration technique is used iteratively to obtain the statistics of the decision variable of an asymptotically optimal detector, which is utilized to derive series expressions for the symbol error probability (SEP). Numerical optimization of the ASK levels is done to achieve the minimum SEP, which results in the optimal solution being close to the equally spaced ASK constellation. The asymptotic optimality of the proposed detector is validated by the SEP variation with the impulsive index of the noise. [ABSTRACT FROM AUTHOR]

Multihop communication is considered to be a useful approach for improving the coverage area with reduced transmit power. In this paper, we consider a path-selection-based multihop decode-and-forward (DF) cooperative system. A simple parallel multihop path-based cooperative communication system is considered. It is assumed that all hops in all cooperative paths are subject to independent Rayleigh fading. The best path, that is, the best multihop link between the source and the destination, is selected based on the max–min selection criterion. The relays in the selected cooperative path use the symbol-wise DF protocol, in which they demodulate the received data from the preceding node in a symbol-wise manner and forward it to the succeeding node. An analytical framework is developed for finding an accurate (almost close to exact) error performance of the considered system. To be more specific, we derive an accurate expression of the average bit error rate of the max–min-criterion-based best-path selection scheme, in terms of convergent power series. The coding gain and the diversity order of the scheme are also analytically obtained. [ABSTRACT FROM AUTHOR]

In this paper, the transmission of orthogonal space–time block codes (OSTBCs) in amplify-and-forward (AF) multiple-input–multiple-output (MIMO) relay networks, with imperfect channel state information (CSI), is considered. Individual channel estimation and time-efficient cascaded (for estimating the product of channel matrices) channel estimation protocols are used for estimating the channel matrices required for decoding of OSTBC data at the destination. We derive tight approximations for the moment-generating function (m.g.f.) of the received signal-to-noise ratio at the destination node with imperfect CSI, by ignoring higher order noise terms, in Rayleigh fading. Using the derived m.g.f. expression, we obtain the analytical symbol error rate (SER) of the AF MIMO relay system for general OSTBCs with $M$-ary phase-shift keying constellation. The diversity order of the MIMO OSTBC relay system is also derived for some special cases by using the SER expression. [ABSTRACT FROM PUBLISHER]

In the presence of heterogeneous service provider (SP) networks such as wireless local area networks and cellular networks, users have to make a choice. The quality of service provided and the price charged by an SP play a crucial role in this decision process. In this paper, we study the network selection behavior of mobile users. A novel probabilistic framework is presented, with explicit analytical expressions for the transition and steady state network selection probabilities of the users. The proposed framework utilizes the price charged and the utility obtained at the SPs in obtaining the transition probabilities, even in the presence of multi-homing users. Furthermore, network-level parameters such as call blocking probabilities and throughput are obtained in terms of the steady state probabilities. Numerical results indicate that the prices and utilities at the heterogeneous SPs have considerable impact on the overall network performance. [ABSTRACT FROM PUBLISHER]

Cooperative diversity through decode-and-forward (DF) relaying is an effective method for improving the performance of mobile wireless systems. We consider here the performance of a cooperative diversity system in which the relay employs the DF protocol to transmit data from a source to a destination using binary phase-shift keying (BPSK). A flat Rayleigh fading environment with statistically independent links is assumed. The optimum receiver for this system is presented, and from the decision rule, the end-to-end symbol error probability (SEP) is derived. Numerical results on the SEP are obtained and compared with those for a suboptimum receiver, which does not need the channel state information of the source-to-relay link. [ABSTRACT FROM PUBLISHER]

Consider a cooperative diversity network that consists of a source, N cooperating relays, and a destination. The relays cooperate with the source through the decode and forward protocol to transmit a data symbol from the source to the destination. In a conventional signal-to-noise ratio based selection combining scheme at the destination, the effect of the source-to-relay links is not accounted for when choosing one link from the set consisting of the source-to-destination and N relay-to-destination links. To overcome this drawback, we modify the conventional scheme by including, in the selection process, a deterministic scale factor that incorporates the effect of the source-to-relay links. For statistically independent links that undergo flat Rayleigh fading, we derive, in closed form, the exact end-to-end symbol error probability (SEP) of this modified scheme, which we call a scaled selection combining scheme for M-ary phase-shift keying constellation. We also give a method of obtaining the optimum scale factor that minimizes the end-to-end SEP. A system designer should select the optimum scale factor to achieve the best performance of the scheme. [ABSTRACT FROM PUBLISHER]

This paper investigates detection mechanisms for time hopping pulse position modulated (TH-PPM) multiple access systems in both additive white Gaussian noise and fading environments. In such systems, the raw data is not linearly related to the received signal. One technique is to express the pulse position modulated signal as the sum of linearly modulated signals with the input being a nonlinear function of the raw data. This reduces the system to an equivalent pulse amplitude modulated system with a significant increase in complexity. We present two new lower complexity detectors. The first detector, which is a frame-level maximum likelihood (ML) detector, uses the proper- ties of the pulse correlation matrix to develop a lower complexity detection method. The second detector, which is a chip-level ML detector, relies on the knowledge of the time hopping sequence to despread the received signal. The detection is then done on a chip-by-chip basis. The performance of these detectors is compared in terms of the bit error rate for the user with weakest power and the average number of correctly decoded users. [ABSTRACT FROM AUTHOR]

We consider a space-time block coded system having L time slots and using decision feedback channel estimation with a finite window size. The channel matrix estimate is updated every L time slots by: 1) a least-squares (LS) estimate and 2) a minimum mean-square error (MMSE) estimate. Using a Markov model of the decision process, we analyze the decoding error probability (DEP) of this scheme in Rayleigh fading. The transition probability matrix is obtained by simulation of the decision process for a system using the Alamouti code. From this matrix, the DEP can be computed for any time shift. We find from computations that the DEP increases with increase in the time shift but tends to saturate with time to a steady-state value. It is also observed that both the state and the transition probabilities tend to saturate with the increase in average signal-to-noise ratio per diversity branch. [ABSTRACT FROM AUTHOR]

We analyze the error performance of minimum selection generalized selection combining (MS-GSC), in which the minimum number of diversity branches are selected such that their combined signal-to-noise ratio (SNR) is above a given threshold. A flat Rayleigh fading channel with independent and distinctly distributed branch SNRs is considered. By transforming the ordered instantaneous branch SNRS to their differences, we derive the distribution of the number of selected branches in closed form. We then modify the derivation of this distribution to get the characteristic function (cf.) of the combiner output SNR. This cf. is used to obtain the symbol error probability for different coherent digital modulation schemes. [ABSTRACT FROM AUTHOR]

The paper proposes a multiple-input multiple-output-based power line communication (PLC) system subject to Rayleigh fading and corrupted by additive cyclostationary Gaussian noise. The proposed coherent receiver structure employs a block reception rule at the reception unit for detecting the space-time block-coded transmitted data symbols. A closed-form expression for the pairwise error probability (PEP) is derived using a characteristic function approach. Exact and asymptotic expressions for the average PEP are obtained for the special case of Alamouti code transmission which show that the PLC system under consideration offers full diversity. Numerical results depict the improvement in the system performance with increase in the number of receive diversity branches and the average signal-to-noise ratio per branch and decrease in the correlation value between the noise samples. [ABSTRACT FROM AUTHOR]

In this paper, we consider a hybrid smart grid communication network consisting of power line communication (PLC) at the transmitter side and the device-to-device (D2D) cellular communication on the receiver side which provides last mile connectivity. The PLC channel is assumed to experience Rayleigh fading and is corrupted by impulsive noise, and the D2D communication being a short range communication system, is assumed to experience Nakagami- $m$ fading with additive Gaussian noise. We propose a maximal-ratio combining (MRC) receiver for the considered hybrid smart grid communication system employing binary phase shift keying (BPSK) modulation at the transmitter and derive a closed-form symbol error probability (SEP) expression for the proposed receiver. The interference between the D2D links is assumed to be negligible for the tractability of the error probability analysis. Numerical results demonstrate the optimality of operating the D2D links at lower signal-to-noise ratio (SNR) values to overcome the effect of the impulsive PLC channel by utilizing diversity branches. [ABSTRACT FROM AUTHOR]

In this paper, we present a method of utilizing channel diversity to improve the secrecy outage probability and the intercept probability in a cognitive radio (CR) network. With the presence of channel diversity, an intended receiver can achieve a relatively better secrecy outage probability and intercept probability. We consider a CR network in which a single antenna, which maximizes the secrecy capacity, is selected at the CR transmitter. To demonstrate the advantages of our proposed framework, we derive new exact closed-form expressions for the secrecy outage probability and the intercept probability of the secondary network in Rayleigh fading. The positive impact of the number of receive antennas and the negative impact of the number of primary users on the secondary network are shown. The derived secrecy outage probability is found to be in precise agreement with simulation results. The numerical results strongly support our conclusion that maximal-ratio combining of channel diversity can enhance the physical layer security of a multiantenna based CR network. Furthermore, the numerical results reveal the impact of the primary network on the secondary network in the presence of a multiantenna wiretap channel. [ABSTRACT FROM AUTHOR]

Cooperative spectrum sensing in a multihop cognitive radio (CR) network based on multiple antennas using an improved energy detector is studied in this paper. The improved energy detector uses the $p$th power of the absolute value of samples of primary user's (PU's) signals. We replace the conventional energy detector by an improved energy detector to enhance the performance of CR. Analytical expressions of the probability of false alarm and missed detection in each CR are derived. Furthermore, we extend our study to a multihop cooperative diversity system containing multiple multihop secondary transmission paths between the PU and the fusion center. Performance analysis of multihop cooperative diversity is discussed using an improved energy detector. We introduce a framework to derive a closed-form expression of the optimal number of multihop cooperative diversity branches by minimizing the total error rate. An efficient quick spectrum sensing algorithm is proposed, which requires fewer than the total number of cooperative multihop diversity branches. It is shown, through various numerical examples, that by using the optimal number of secondary transmission paths, it is possible to perform quick spectrum sensing while satisfying an upper bound on the total error rate. [ABSTRACT FROM PUBLISHER]

We consider an antipodal signaling system using wavelet modulation (WM) with scale diversity over a frequency-selective fading channel. The channel introduces a random gain for each scale. These scale gains are estimated by sending a block of pilot symbols before the data. Coherent demodulation is carried out along with maximal-ratio combining using the estimated scale gains. From the characteristic function of the resulting decision variable, we analyze the bit error performance. For the case of large signal-to-noise ratio (SNR), we obtain a closed-form expression for the bit error probability (BEP). It is seen that BEP decreases with increase in the number of pilot symbols. We also find a significant improvement in BEP with increase in the number of scales for a fixed pilot length. It is also found that, when compared with frequency diversity, WM can perform better over a certain range of SNR, with the range decreasing with increase in the number of scales. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

This paper considers the problem of resource allocation for a large-scale wireless network consisting of multiple amplify-and-forward (AF) cooperative links. To effectively manage interlink interference and achieve efficient resource allocation, we propose a novel two-stage game model in which links form coalitions in the first stage, and in the second stage, they engage in a noncooperative game given the coalition structure determined in the first stage. This model is distinct from the classic coalitional game theory as it captures the important possibilities of externalities across coalitions. In the coalitional game formulation, we have derived an analytical expression for the asymptotic throughput of an AF cooperative system in the regime of large number of relays and have incorporated opportunistic relaying as an effective technique to combat harmful interferences. In the sequential noncooperative game formulation, the uniqueness of the Nash equilibrium has been established for the general N-player case, which generalizes previous works on the two-player game. Simulation results demonstrate over 200% sum rate enhancement relative to the noncooperative approach, primarily due to the improved pattern of frequency reuse and the benefit of multiuser diversity. [ABSTRACT FROM PUBLISHER]

In orthogonal frequency-division multiple access (OFDMA) on the uplink, the carrier frequency offsets (CFOs) and/or timing offsets (TOs) of other users with respect to a desired user can cause multiuser interference (MUI). Analytically evaluating the effect of these CFO/TO-induced MUI on the bit error rate (BER) performance is of interest. In this paper, we analyze the BER performance of uplink OFDMA in the presence of CFOs and TOs on Rician fading channels. A multicluster multipath channel model that is typical in indoor/ultrawideband and underwater acoustic channels is considered. Analytical BER expressions that quantify the degradation in BER due to the combined effect of both CFOs and TOs in uplink OFDMA with M-state quadrature amplitude modulation (QAM) are derived. Analytical and simulation BER results are shown to match very well. The derived BER expressions are shown to accurately quantify the performance degradation due to nonzero CFOs and TOs, which can serve as a useful tool in OFDMA system design. [ABSTRACT FROM PUBLISHER]