Time Division Broadcast Protocol Research Articles

Performance analysis and optimization of energy harvesting cognitive multi-hop relay network over mixed Rayleigh and double-Rayleigh fading channels

In this paper, we investigate the outage performance of an energy harvesting underlay cognitive multi-hop relay network. In the network, energy-constrained secondary network (SN) nodes harvest energy from radio frequency signal of a power beacon (PB) node. The source node transmits information to destination node via multiple intermediate relay nodes by using a time division broadcast protocol, and the hardware impairments of SN nodes’ transceiver are modeled. The outage performance of SN is analyzed and evaluated by accurately approximate and asymptotic closed-form expressions of outage probability (OP) over quasi-static mixed Rayleigh and double-Rayleigh fading channels. Additionally, due to the complexity of OP expression, a chaotic dragonfly algorithm (CDA) is proposed to jointly optimize energy harvesting ratio and PB node’s abscissa, which can achieve OP minimization of SN. Extensive simulations demonstrate the correctness of theoretical analysis and the effectiveness of the proposed CDA.

Performance of Dynamic Time Division Broadcast Protocol with Rateless Coding

Two-way relaying channel (TWRC) improves the throughput of one-way relaying channel through network coding at the relay. Time division broadcast (TDBC) is one typical protocol for TWRC, but with three time slots for one round information exchange leading to throughput loss. To enhance throughput performance, incremental redundancy transmission is usually incorporated into TDBC (i.e., TDBC-IR) by one bit feedback, indicating the successful or failed transmission. Nevertheless, TDBC-IR still suffers in throughput since it cannot fully exploit and adapt to the varying channel dynamics. In the paper, we propose a dynamic TDBC protocol with incremental redundancy in the form of rateless coding (i.e., DTDBC-RC) to fully utilizing the varying channel dynamics. In DTDBC-RC, the two sources first transmit in rateless coding way with given maximum allowable transmission time, and then the relay retransmits or not based on its decoding results. To reveal the advantages of DTDBC-RC, we analyze its performance comprehensively in terms of outage probability, expected rate, and diversity-multiplexing trade-off (DMT). We also present a subslot realization scheme for DTDBC-RC (i.e., sub-DTDBC-RC) since the DMT of DTDBC-RC cannot be obtained directly. Simulation and numerical results show the performance advantage of DTDBC-RC (or sub-DTDBC-RC) over TDBC-IR in terms of both expected rate and DMT.

Security-Reliability Tradeoff Analysis for Underlay Cognitive Two-Way Relay Networks

We consider an underlay wiretap cognitive two-way relay network (CTWRN), where two secondary sources exchange their messages via multiple secondary decode-and-forward digital network coding relays in the presence of an eavesdropper by using a three-phase time division broadcast protocol and sharing the licensed spectrum of primary users. To mitigate eavesdropping attacks, an artificial noise (AN)-aided opportunistic relay selection scheme, called generalized max-min (GMM) relay selection is proposed to enhance physical layer security for the wiretap CTWRNs. The performance of the GMM scheme is analyzed, and evaluated by the exact closed-form outage probability and intercept probability. Additionally, we also provide asymptotic approximations for the outage probability and intercept probability at high signal-to-noise ratio. For comparison, we analyze the performance of the conventional max-min (MM) relay selection scheme as well. It is shown that the GMM scheme outperforms the MM scheme in terms of the security-reliability tradeoff (SRT), where the security and reliability are quantified by the intercept probability and outage probability, respectively. Moreover, the SRTs of the MM and GMM schemes can be substantially improved by increasing the number of secondary relays, while the improvement of the GMM scheme is more evident than that of the MM scheme.

Optimal Combining and Performance Analysis for Two-Way EH Relay Systems With TDBC Protocol

In this paper, we investigate a simultaneous wireless information and power transfer (SWIPT) based two-way decode-and-forward (DF) relay network, where time switching (TS) is employed for SWIPT and time division broadcast (TDBC) is employed for two-way relaying. We focus on the design of a combining scheme that decides how the relay combines the signals received from two terminals through a power allocation ratio at the relay. We formulate an optimization problem to minimize the system outage probability and obtain the optimal power allocation ratio in closed form. For the proposed optimal combining scheme, we derive the expressions for the system outage probability and capacity. Simulation results verify our derived expressions and show that the proposed scheme achieves a higher system outage capacity than the existing schemes.

Adaptive Link Utilization in Two-Way Spectrum Sharing Relay Systems Under Average Interference-Constraints

In this paper, we investigate the performance of an underlay cognitive two-way relay system with direct link using time division broadcast protocol in the presence of primary user's interference. Herein, relying on the practicability and low complexity of statistical channel state information, the secondary transmissions are in compliance with the fading-averaged interference constraints imposed by the primary receiver. For this setup, we study an adaptive link utilization scheme (ALUS) that can exploit both direct and relay links with appropriate diversity combining methods to improve the performance of secondary users. Based on ALUS, we evaluate and compare the performance of two decode-and-forward based relaying strategies viz., fixed relaying and incremental relaying. We derive the tight closed-form expressions of outage probability of the secondary communications for both the strategies over Nakagami- m fading channels. We further conduct asymptotic high signal-to-interference-plus-noise ratio analysis to examine the achievable diversity order of the considered system. In addition, we quantify the expected spectral efficiency and average transmission time for both relaying strategies. Our results illustrate that the incremental relaying strategy can significantly improve the system performance in comparison with fixed relaying. Numerical and simulation results are provided to attest our theoretical studies.

A Spectrally Efficient Signal Space Diversity-Based Two-Way Relaying System

This work proposes a new transmission scheme for multirelay two-way relaying systems, where two end- sources communicate with each other via a set of relays. In the proposed scheme, we consider signal space diversity and time division broadcast protocol jointly to increase spectral efficiency without sacrificing the system reliability. The idea behind this consideration is that original data symbols are rotated before transmission, and then the in-phase and quadrature components of these rotated symbols are transmitted through the cooperation of the end-sources and the relays. By doing so, the end-sources exchange four symbols over three time slots instead of two, i.e., doubling the number of transmitted symbols. In addition, relay selection is incorporated into this scheme to achieve a further increase in spectral efficiency. For relay selection, two different strategies are discussed: reactive and proactive relay selections. These strategies differ depending on whether relay selection is performed after or before the start of transmission. Specifically, for each relay-selection strategy, we first obtain a closed-form expression for the end-to-end (E2E) error probability with an arbitrary constellation, which accounts for all the resulting nonuniform constellation cases due to constellation rotation. Subsequently, with the derived expressions, we then formulate an optimization problem that considers the joint optimization of the rotation angle and the transmit powers at the end-sources and the relays. The objective of the optimization problem is to minimize the E2E error probability of one of the end-sources, while satisfying a set of total and individual transmit power constraints and a predefined threshold for the E2E error probability of the other end-source. Numerical results verify the theoretical analysis, and show that the scheme proposed herein provides not only higher spectral efficiency, but also more reliable transmission.

Wireless Energy Harvesting Assisted Two-Way Cognitive Relay Networks: Protocol Design and Performance Analysis

This paper analyzes the effects of realistic relay transceiver on the outage probability and throughput of a two-way relay cognitive network that is equipped with an energy-harvesting relay. In this paper, we configure the network with two wireless power transfer policies and two bidirectional relaying protocols. Furthermore, the differences in receiver structure of relay node that can be time switching or power splitting structure are also considered to develop closed-form expressions of outage and throughput of the network providing that the delay of transmission is limited. Numerical results are presented to corroborate our analysis for all considered network configurations. This paper facilitates us not only to quantify the degradation of outage probability and throughput due to the impairments of realistic transceiver but also to provide an insight into practical effects of specified configuration of power transfer policy, relaying protocol, and receiver structure on outage and throughput. For instance, the system with multiple access broadcast protocol and the power splitting-based receiver architecture achieves ceiling throughout higher than that of the transmission rate of source nodes. On the contrary, a combination of dual-source energy transfer policy and the time division broadcast protocol is contributed the highest level of limiting factor in terms of transceiver hardware impairments on the network throughput.

Two‐way relay networks with wireless power transfer: design and performance analysis

This study considers amplify-and-forward two-way relay networks, where an energy constrained relay node harvests energy from the received radio-frequency signal. Based on time switching receiver, they separate the energy harvesting (EH) phase and the information processing (IP) phase in time. In the EH phase, three practical wireless power transfer policies are proposed: (i) dual-source (DS) power transfer, where both sources transfer power to the relay; (ii) single-fixed-source power transfer, where a fixed source transfers power to the relay; and (iii) single-best-source (SBS) power transfer, where a source with the strongest channel transfers power to the relay. In the IP phase, a new comparative framework of the proposed wireless power transfer policies is presented in two bi-directional relaying protocols, known as multiple access broadcast (MABC) and time division broadcast (TDBC). To characterise the performance of the proposed policies, new analytical expressions are derived for the outage probability, the throughput, and the system energy efficiency. Numerical results corroborate the authors’ analysis and show: (i) the DS policy performs the best in terms of both outage probability and throughput among the proposed policies, (ii) the TDBC protocol achieves lower outage probability than the MABC protocol, and (iii) there exits an optimal value of EH time fraction to maximise the throughput.

Cooperative spectrum sharing in two‐way multi‐user multi‐relay networks

In this study, the authors consider a cooperative spectrum sharing network with multiple primary users (PUs) and multiple secondary users (SUs). Hereby, one end-PU communicates bidirectionally with one of the best selected other end-PUs with the cooperation of the best selected SU using time division broadcast protocol. Based on an overlay approach, the selected SU allocates its partial power to relay the PUs’ signals and utilises the remaining power to transmit its own signal. The authors devise a low-complexity distributed PU–SU selection strategy to minimise the overall outage probability of the primary system. For Nakagami-m fading, the authors derive tight expressions of outage probability for both primary and secondary systems of the considered scheme. Further, by deriving their asymptotic behaviour at high signal-to-noise ratio, the authors highlight the performance gain accrued by cooperative and multiuser diversity along with that offered by the channels under Nakagami-m fading. Besides, the authors demonstrate the effective locations for the SUs to access the spectrum. Above all, the authors illustrate that the increase of the number of SUs is more desirable than the number of PUs to explore the spectrum sharing opportunities. Numerical and simulation results substantiate the effectiveness of the proposed scheme and the theoretical analysis.

Performance analysis of bidirectional cloud networks with imperfect channel state information

SummaryWith the rapid growth of cloud computing services, there is an increasing need to expand applications across data centers. In these paradigms, common information exchange between two data centers can be assisted via one or more substrate nodes, which correspond to bidirectional relaying communication. In this paper, we investigate the performance of time division broadcast (TDBC) protocol in bidirectional cloud networks in the presence of channel estimation errors (CEEs). The tight asymptotic expressions for individual and system outage probabilities are first presented in closed‐form. It is shown that CEE causes outage probability to remain fixed even if the channel is noiseless. Then, the symbol error rate performance for TDBC protocol with M‐ary Phase Shift Keying and M‐ary quadrature amplitude modulation signals is analyzed. Simulation results validate the accuracy of our analytical results. Furthermore, comparison of signal‐to‐noise ratio gap ratio shows that TDBC protocol is less sensitive to the effect of CEE than analog network coding protocol. Copyright © 2014 John Wiley & Sons, Ltd.

Corrections to “Performance Analysis of Cognitive Spectrum Sharing With Time Division Broadcast Protocol” [Feb 14 305-308

We provide corrections of the published paper (ibid., vol. 18, no. 2, pp. 305-308, Feb. 2014). The corrections are mainly in few expressions, which were presented with mistakes in the referenced paper. These corrections therefore do not affect the results and the insights presented in that paper.

Performance Analysis of Cognitive Spectrum Sharing with Time Division Broadcast Protocol

We investigate the performance of a cognitive spectrum sharing system where a best selected secondary user (SU) assists two-way communication between two primary users (PUs) by employing time division broadcast over Rayleigh channels. We derive tight lower-bound expressions for the overall outage probability (OOP) of both the primary and secondary systems of the considered scheme. We also provide valuable insights into the achievable diversity order, cell coverage, and optimal power allocation factor to ensure spectrum sharing. Numerical and simulation results corroborate the theoretical analysis and illustrate the effectiveness of the considered scheme.

Two-Way Relaying Cooperative Wireless Networks: Resource Allocation and Performance Analysis

Abstract Relay-based cooperative wireless networks have been widely considered one of the cost-effective solutions to meet the demands in future wireless networks. In order to maximize the overall sum-rate while maintaining proportional fairness among users, we investigate different resource allocation algorithms in two-way relay networks with analog network coding (ANC) protocol and time division broadcast (TDBC) protocol. The algorithms investigated are different from traditional proportional fairness schemes in terms of fairness and computational complexity as we have applied Access Proportional Fairness (APF) and Minimum Rate Proportional Fairness (MRPF) along with load balancing at the relays. A MATLAB simulation has been performed and simulation results show the effectiveness of these algorithms.

Outage Probability of TDBC Protocol in Multiuser Two-Way Relay Systems with Nakagami-m Fading

This paper considers a multiuser two-way relay system with time division broadcast (TDBC) protocol, where multiple end-sources compete to exchange information with another end-source through the help of a single half-duplex amplify-and-forward (AF) relay. We derive a tight closed-form lower bound for the system outage probability over Nakagami-m fading channels with integer fading parameters. An asymptotic expression for the outage probability in high signal-to-noise ratio (SNR) regime is also obtained. Numerical results corroborate the theoretical analysis.

Performance analysis of time division broadcast protocol with incremental relaying and symmetric users

SUMMARYThis paper investigates two‐way relaying with direct link transmission. We propose to combine incremental relaying (IR) with the time division broadcast protocol (TDBC) to form a new scheme, termed TDBC‐IR, to increase the spectral efficiency of TDBC. Assuming half‐duplex decode‐and‐forward relaying, the performance of three protocols, that is, TDBC, TDBC‐IR, and physical‐layer network coding (PNC), are studied and compared, in terms of outage probability, expected rate (ER), and diversity‐multiplexing tradeoff. First, we reveal that the outage probability performance of TDBC‐IR is the same as that of TDBC and better than that of PNC. Second, we compare the ER and diversity‐multiplexing tradeoff performance of the three protocols based on the derived outage probability. The numerical results reveal that (1) the ER of TDBC‐IR is greater than that of TDBC and PNC in the whole signal‐to‐noise ratio (SNR) region, that is TDBC‐IR has improved spectral efficiency performance; (2) the ER performance of TDBC is better than PNC in the low SNR region but worse in the high SNR region; (3) the maximum achievable diversity order of TDBC‐IR and TDBC are both two whereas that of PNC is one; (4) the maximum achievable multiplexing gain of TDBC‐IR is one, which is better than TDBC (its maximum achievable is 2/3) and achieves the maximum of PNC (its maximum achievable is one). Copyright © 2012 John Wiley & Sons, Ltd.

Two Birds with One Stone: Exploiting Direct Links for Multiuser Two-Way Relaying Systems

This Letter proposes a mechanism to combine multiuser diversity (MUD) and incremental relaying in a multiuser two-way relaying system, where one end-source exchanges messages with one out of N available end-sources by using a half-duplex amplify-and-forward (AF) relay. Outage analysis for the proposed scheme is carried out and, compared with the time division broadcast (TDBC) protocol, reveals that it not only realizes full diversity order (N+1) but also achieves improved expected spectral efficiency. Also, it is indicated that the expected spectral efficiency of the proposed scheme approaches that of the analog network coding (ANC) protocol in high signal-to-noise ratio (SNR) regime. Furthermore, the finite-SNR diversity-multiplexing tradeoff (DMT) is examined, from which the superiority of the proposed scheme to TDBC is confirmed as well. Other insightful comparisons in terms of the outage performance are presented that show the practical usefulness of our multiuser two-way relaying framework.

Performance Analysis of Two-User Cooperative Multiple Access Systems With DF Relaying and Superposition Modulation

In this paper, a two-user cooperative multiple access (CMA) system is considered. Using the superposition modulation scheme, we propose a low-complexity suboptimal detector at the destination to achieve the performance close to that of the optimal maximum-likelihood sequence detector (MLSD). For independent and non-identically distributed (i.n.d.) Rayleigh-faded channels, we derive error decision regions and present the exact bit-error rate (BER) expression in an integral form, which is validated by simulation results. We also approximate the decision regions and obtain the BER bound in closed form. Another efficient transmission scheme, i.e., the time-division broadcast (TDBC) protocol operating in three time slots, is also considered and analyzed. BER results show that the superposition modulation outperforms the others and can achieve both full diversity order and high coding gain.

Outage Probability and Optimum Combining for Time Division Broadcast Protocol

Time division broadcasting (TDBC) is a well-known bidirectional protocol. In this protocol, two sources exchange information with the help of a relay terminal. For amplify-and-forward (AF)-based TDBC, we first derive a tight lower bound of the outage probability in closed-form, and it is very close to the exact outage probability in the whole signal-to-noise ratio (SNR) range irrespective of the values of channel variances. Using the tight lower bound, diversity-multiplexing tradeoff of the TDBC protocol is obtained for finite-SNR. Furthermore, we investigate how to optimize the TDBC protocol; specifically, an optimum method to combine the received signals at the relay terminal is developed. This method minimizes the outage probability and maximizes the total mutual information of the TDBC protocol at the same time.

Relay Selection with ANC and TDBC Protocols in Bidirectional Relay Networks

We study relay selection (RS) with the analog network coding (ANC) and time division broadcast (TDBC), which are two major amplify-and-forward (AF)-based protocols in bidirectional relay networks. We consider a bidirectional network consisting of two different end-sources and multiple relays, where each terminal has a single antenna and operates in a half-duplex mode. In this network, a single best relay is selected depending on channel conditions to help bidirectional communication between the two end-sources. Specifically, we first consider RS schemes for the ANC and TDBC protocols based on a max-min criterion to minimize the outage probabilities. Then, for the RS in the ANC protocol, we derive a closed-form expression of the outage probability; for the RS in the TDBC protocol, we derive a one-integral form of the outage probability and its lower bound in closed-form. Numerical results confirm that the closed-form expression of the ANC protocol and the one-integral form of the TDBC protocol are very accurate, and that the closed-form lower bound of the TDBC protocol is also tight.

Performance Analysis of Bidirectional Communication Protocols Based on Decode-and-Forward Relaying

We study and compare the performance of three very typical bidirectional communication protocols based on the decode-and-forward relaying: time-division broadcast (TDBC), physical-layer network coding (PNC), and opportunistic source selection (OSS). We first derive the exact closed-form outage probabilities for the PNC and OSS protocols and an exact but one-integral form outage probability for the TDBC protocol. To gain more insight, we also derive closed-form asymptotic outage probability expressions for all protocols, with which we obtain further analytical results on the asymptotic optimal power allocation, the asymptotic optimal relay location, and the performance gain of the OSS protocol over the TDBC protocol in the high signal-to-noise ratio (SNR) regime. Finally, we study the diversity-multiplexing tradeoff (DMT) for each protocol both in the finite and infinite SNR regimes.