A superposition modulation based cooperative transmission scheme in regenerate-and-forward relaying networks

In this paper, performances of joint transmit and receive antenna selection (JTRAS), transmit antenna selection/maximal ratio combining (TAS/MRC), and transmit antenna selection/receive antenna selection (TAS/RAS) techniques are examined in a unified manner in the (42) presence of feedback errors. Exact and closed-form outage probability, moments, moment-generating function, ergodic capacity, and symbol error probability (SEP) expressions are derived for flat Nakagami-m fading channels. In addition, to obtain diversity order and array gain of the investigated techniques in the presence of feedback errors, asymptotic outage probability and SEP expressions are also derived. Analytical results are validated by Monte Carlo simulations. Results show that the diversity order is significantly reduced in the presence of feedback errors, whereas all the systems provide full diversity order for a perfect feedback channel.

In this work, we derive exact closed-form expressions for the average symbol error probability (SEP) of arbitrary rectangular quadrature amplitude modulation (QAM) when used along with orthogonal space-time block coding (OSTBC) over independent but not necessarily identically distributed multiple-input multiple-output (MIMO) Nakagami-m fading channels. The derived SEP expressions account for diversity branches which may exhibit identical or distinctive power levels while their associated Nakagami indexes can take arbitrary real values not less than 1/2. Our work extends previous results pertaining to the performance analysis of OSTBC using M-ary rectangular QAM over Rayleigh fading channels and M-ary square QAM over Nakagami-m fading channels. For a MIMO diversity system with n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> transmit and n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> receive antennas and a corresponding set of arbitrary real-valued Nakagami indexes, our rectangular QAM SEP results are expressed in terms of Lauricella's multivariate hypergeometric functions F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(L)</sup> and F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(L + 1)</sup> where L = n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> is the total number of diversity branches.

The impact of unavailable relays is a serious issue in cooperative communication schemes, where the operation state of relays affects optimal relay selection. In addition, secure signal transmission is an interesting approach to prevent the wiretapping actions of eavesdropper nodes in a wireless environment. In this paper, we propose two cooperative secrecy transmission schemes: a secrecy decode-and-forward protocol and a hybrid of direct secrecy and cooperative secrecy transmission schemes to enhance the spectrum utilization efficiency. In the proposed schemes, a source transmits data signals to a destination with the assistance of relays. At the same time, these data signals are eavesdropped by another node. The best relays are successfully selected in a safe manner based on both decoding from a source to a destination and the available state of cooperative relays. The secrecy performance of each scheme is analyzed and evaluated by the exact outage probability over Rayleigh fading channels. Monte Carlo simulations were performed to verify the theoretical analysis. Finally, a discussion and comparison of the cooperative secrecy transmission schemes and the direct secrecy transmission approach are presented.

Since the existing full-rate cooperative transmission schemes have a serious defect in low Bit Error Rate (BER) performance while the existing high-rate cooperative transmission schemes have a serious defect in low spectral efficiency, a distributed high-rate cooperative relay transmission scheme based on full-rate cooperative communication model is proposed in this paper, in which Cyclic Delay Diversity (CDD) technology and Linear Constellation Precoding (LCP) technology are employed. Moreover, the proposed scheme addresses the issue of obtaining maximum spatial and multipath diversity with low decoding complexity and high transmission reliability. The BER performance of the proposed scheme is contrasted to that of the full-rate transmission scheme where better performance is achieved, and is improved when the number of the multipath or the relay nodes increases.

Underwater acoustic channels normally have low data rate, long propagation delay, severe multipath effect, and time varying fading. Cooperative transmission is a new wireless communication technique in which diversity gain is achieved by utilizing relay nodes as virtual antennae. In this paper, we investigate cooperative transmission techniques for underwater acoustic communications. First, we study the performance of several cooperative transmission schemes, originally designed for radio communications, in an underwater scenario. Second, by taking advantage of the low propagation speed of sound, we design a new wave cooperative transmission scheme. In this scheme, the relay nodes amplify the signal received from the source node, and then forward the signal immediately to the destination. The goal is to alter the multipath effect at the receiver. Third, we derive the performance upper bound for the proposed wave cooperative transmission scheme. The simulation results show that the proposed wave cooperative transmission has significant advantages over the traditional direct transmission and the existing cooperative transmission schemes originally designed for radio wireless networks.

In this paper, we derive closed-form expressions for the average symbol error probability (SEP) of arbitrary rectangular I × J-ary quadrature amplitude modulation (QAM) in cooperative amplify-and-forward (A&F) relaying systems, when no direct line-of-sight exists between the source and the destination nodes and when the links between the K successive nodes forming the multihop cooperation chain (including the source and the destination nodes) follow independent but not-necessarily identical Nakagami-m fading distributions with arbitrary real indexes {m <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</sub> } <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k=1</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</sup> not less than 1/2 and arbitrary average power levels {γ̅k} <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k=1</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</sup> . The average SEP of rectangular QAM for this set-up is provided in closed-form as a linear combination of the first Lauricella's multivariate hypergeometric function, F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(K+1)</sup> , K being the number of multihop links, which can be efficiently evaluated using standard numerical softwares. Simulation results sustaining our analysis are provided, and the impacts of various parameters on the overall multihop system performance are investigated.

Nowadays, a high level of security is required for the transmission of critical information. Quantum Key Distribution (QKD) systems are considered the best option to protect such information. Many studies have shown the efficiency of the QKD optical fiber inspired by M-ary pulse position modulation (MPPM). Free-Space Optical (FSO) links provide an efficient and effective data transmission system. However, cumulative effects of laser beam divergence, misalignment, and turbulence-induced fading on the received irradiance in the FSO link might allow an external eavesdropper located near the authorized receiver to break the transmission under certain conditions. This paper introduces the development of an FSO system based on the MPPM and the BB84 protocol (MPPM-BB84) over the Gamma-Gamma (GG) turbulence channel with pointing errors. Time Binning is implemented using MPPM to increase system security and reduce the quantum bit error rate (QBER). The system security is investigated under photon number splitting attack and excess noise. Closed-form expressions for asymptotic expressions of the average symbol error probability (SER), raw key rate (RKR), and secret key rate (SKR) are introduced. Moreover, the Monte-Carlo simulations are then used to prove the validity of the analytical results. The optimal values for the average photon number per pulse (to achieve the maximum RKR and SKR) for each symbol length can guarantee the stability of the FSO system under different weather conditions. Smaller symbol lengths are more tolerant of detector loss. The proposed system supports linking distances from 1 km to 3 km while keeping the SKR almost constant.

An efficient cooperative transmission scheme has been recently proposed based on superposition modulation. Analytical results are necessary to fully understand the superiority of this new scheme, which is the main contribution of this paper. Tight upper and lower bounds of the outage probability of this scheme are first proposed and then the large SNR behavior of the outage probability is studied. Our analytical results prove that the superposition cooperative transmission scheme can achieve around 3 dB better performance and larger diversity order than the selection relaying scenario, which are consistent with the simulation results reported earlier. Finally, we provide outage, delay-limited and ergodic capacity results of cooperative techniques

We derive the symbol error probability (SEP) expressions for orthogonal space-time block codes with any form of generalized complex orthogonal design (GCOD) employing arbitrary rectangular quadratic-amplitude modulation signaling over correlative fading channels. By first decorrelating the physical branches into uncorrelated virtual branches, a general expression for the moment generating function of the received signal-to noise ratio (SNR) is obtained, from which the SEP is derived. The result can be applied to correlative fading channels with any form of Gaussian fading gains. Moreover, channels having joint fading models, as well as mixed channel powers, are considered. We also discover that, for certain GCOD codes, different information symbols may exhibit different SEPs. The above features are demonstrated by two GCOD examples used for simulations. Theoretical performance curves are compared with Monte Carlo simulated results in excellent agreement.

This letter presents a study on statistical and symbol error performance analysis of the two-hop orthogonal frequency division multiplexing (OFDM) relay link with amplify-and-forward (AF) protocol and subcarrier mapping (SCM) scheme. Closed-form expressions for probability density function (PDF) and symbol error probability (SEP) of the signal-to-noise ratio (SNR) for the kth mapped subcarrier pair link (k-MSPL) are provided. Our asymptotic SEP analysis reveals that the traditional SCM which can maximize the capacity can not improve the average SEP for uncoded OFDM system, however the average SEP can be decreased significantly by dropping several worst links.

We consider a transmit-receive diversity system in correlated Rayleigh fading in which the receiver estimates the channel through pilot symbols, and feeds this information back to the transmitter through a feedback path. The imperfect channel state information is used by the transmitter to obtain the transmit weight vector for data transmission. The optimum receiver in the maximum likelihood sense obtained from the conditional distribution of the received signal vector, conditioned on the imperfect channel estimate and the transmit weight vector, is derived for the system. For the case of M-ary phase-shift keying, an analytical expression for the conditional symbol error probability (SEP), conditioned on the channel estimate and the transmit weight vector, is obtained. The transmit weight vector is chosen to minimize this conditional SEP. Numerical results are presented to compare the performance of our receiver with that of a conventional receiver.

A novel cooperative transmission scheme utilizing superposition modulation and incremental relaying together is proposed. Incremental relaying is provided by a hybrid automatic repeat request (H-ARQ) type feedback channel. Decode-and-forward method with superposition modulation is performed under the control of feedback data. The outage probability analysis is effectuated, and it is shown that the new scheme outperforms the classical superposition modulated decode-and-forward scheme in terms of achieved diversity level at low signal-to-noise ratios (SNRs).

Outage performance of cognitive DF relay networks with nonidentical Rayleigh fading channels and maximal ratio combining

Millimeter-wave (mm-Wave) communication links have been modeled and investigated in the literature, given its importance and advantages in the fifth-generation (5G) networks. Analytical modeling of a mm-Wave link is challenging due to the gigahertz (GHz) frequency band complications that arise during the transmission as well as the reception. We consider and model a mm-Wave downlink to investigate its symbol error probability (SEP), a significant link reliability measure. We derive the analytical expressions for fading-averaged SEP for three analytically rich scenarios: i). SEP as a function of signal power to noise power ratio, ii). SEP as a function of signal power to interference power ratio, and iii). SEP as a function of the signal power to interference power plus noise power ratio. In addition to insightful analysis, we numerically evaluate the SEP performance in the scenarios mentioned above. SEP performance analysis and numerical results that we present are useful to investigate more complex and generalized mm-Wave communication systems further.

Railway wireless communication networks demand good system coverage and high transmission rate. To meet these requirements, in the railway wireless communication networks, we propose a cooperative hierarchical transmission scheme with the deployment of relay nodes. In our scheme, the requested data of each user at its serving evolved NodeB is firstly divided into high priority data stream and low priority data stream. The high priority data stream, which ensures basic service requirements, is sent to the user through both the direct-link and the relay-link so as to provide the reliable transmission by exploiting the time and space diversity gains. For the low priority data, it is only transmitted through the direct-link in order to enhance the service quality. Simulations demonstrate that the proposed scheme outperforms the conventional wireless network without relays in terms of channel capacity, outage probability and system coverage.