In this study, a practical coding scheme is designed for the binary Wyner–Ziv (WZ) problem by using nested low-density generator-matrix (LDGM) and low-density parity-check (LDPC) codes. This scheme contains two steps in the encoding procedure. The first step involves applying the binary quantisation by employing LDGM codes and the second one is using the syndrome-coding technique by utilising LDPC codes. The decoding algorithm of the proposed scheme is based on the sum-product algorithm with the help of a side information available at the decoder side. It is theoretically shown that the compound structure has the capability of achieving the WZ bound. The proposed method approaches this bound by utilising the iterative message-passing algorithms in both encoding and decoding, although theoretical results show that it is asymptotically achievable.

This study presents a performance analysis for a cognitive radio network with multi-user scheduling in which a primary user can share its licenced spectrum with several secondary users (SUs), each employing Alamouti orthogonal space-time block coding (OSTBC) with spatially correlated antennas over Rayleigh fading channels. Closed-form formulae are obtained for the cumulative density function of the signal-to-noise-ratio of SUs with multi-user scheduling under correlated antennas. Closed-form mathematical expressions are then derived for three important system performance metrics: the average channel capacity, outage probability, and the average bit error rate of the system. From the numerical results obtained from the derived mathematical expressions, the system performances with different parameters are studied, evaluated and compared showing the effects of spatial correlation on the performance of the system. It is observed that spatially correlated antennas can improve the average channel capacity of the cognitive radio system with user scheduling.

In this study, the authors develop a pilot assignment algorithm to alleviate the effect of pilot contamination over time-varying channels. They study the effect of correlated channel states over consecutive blocks under different Doppler frequencies using a moving-average channel estimation process. They show that it is possible to mitigate the pilot contamination problem by assigning pilot hopping sequences such that each user experiences different contaminating users across time. The proposed algorithm has the advantage that it does not require the cooperation between the base stations, is robust to the channel time-variations and can significantly increase the spectral efficiency compared to existing algorithms as shown in the simulation results.

In a social network, spreading information through the powerful leader of the community is highly valuable. Applying effective methods to identify influential nodes will leverage cellular networks in device-to-device local communication. In this study, entropy of betweenness centrality (EBC) combining the degree of the node and the degree of the neighbour node is proposed as a metric to select nodes from large and complex networks to disseminate information easily. EBC describes how the node is essential to connect two regions of the network. In the authors' work, nodes are identified by EBC, which is evaluated by susceptible-infected (SI) model. Hence, if the source of infection in the SI model is one node and the percentage of infected nodes is the largest, which means that the source node is the most powerful node in the network. Simulation results show that the proposed method performs better than the existing methods to spread information in the mobile social network.

This study considers the state-dependent diamond channel (DC) in which the transmission is affected by another source, the interferer. Basically, the transmission from the source to its destination is carried out with the help of two parallel relays. All nodes forming the DC are assumed to be cognitive in the sense that these nodes can estimate the interference signal and then cooperate to remove its effect. For this channel model, the authors initially establish the achievable rate in the case that different noisy versions of the interference signal are non-casually available at all nodes. Then, a three-phase practical transmission scheme is proposed such that these nodes may estimate the interference signal causally and then start transmission. The authors' numerical results show that it is sufficient to have the interference signal at both the relays to get an interference-free achievable rate. In addition, the achievable rate of the DC channel is inversely proportional to the interference coding rate.

In this work, the authors study the performance of decode-and-forward cognitive multi-hop networks in an underlay spectrum sharing strategy for Nakagami-m fading channels with additive white generalised Gaussian noise. To this end, new exact analytical expressions for the average bit error rate of M-ary quadrature amplitude modulation (M-QAM) and M-ary phase shift keying are derived and evaluated. In addition, an exact expression for the average symbol error rate of M-QAM is provided. Moreover, lower- and upper-bound expressions for the ergodic capacity are obtained. Different scenarios are presented to study the influence of various key system parameters, such as fading severity, noise shaping parameter, and interference temperature, on the system performance. The obtained analytical results are supported with Monte Carlo simulations to confirm the accuracy of the analytical derivations.

The recent advances in drone technology significantly improved the effectiveness of applications such as border surveillance, disaster management, seismic surveying, and precision agriculture. The use of drones as base stations to improve communication in the next generation wireless networks is another attractive application. However, the deployment of drone base stations (DBSs) is not an easy task and requires a carefully designed strategy. Fairness is one of the most important metrics of tactical communications or a disaster-affected network and must be considered for the efficient deployment of DBSs. In this study, a fairness-aware multiple DBS deployment algorithm is proposed. As the proposed algorithm uses particle swarm optimisation (PSO) that requires significant processing power, simpler algorithms with faster execution times are also proposed and the results are compared. The simulations are performed to evaluate the performance of the algorithms in two different network scenarios. The simulation results show that the proposed PSO-based method finds the three-dimensional locations of DBSs, achieving the best fairness performance with a minimum number of DBSs for deployment. However, it is shown that the proposed suboptimal algorithm performs very close to the PSO-based solution and requires significantly less processing time.

The link adaptive transmission system chooses the optimum combinations of modulation order and code rate according to the characteristics of wireless channels to make use of the channel resources. To improve the spectral efficiency further, the authors apply the faster-than-Nyquist (FTN) signalling to the adaptive coding and modulation (ACM) system. The ACM system based on FTN signalling can take advantage of the channel resources by adjusting the packing ratios, modulation orders and code rates. However, the variable packing ratios correspond to variable sampling rate, which challenges the receiver of the ACM system. They propose a new transceiver of the FTN-based ACM system which can detect the FTN signal at a constant sampling rate. Moreover, they search for the optimum modulation and coding schemes of ACM based on FTN by analysing the extrinsic information transfer diagram. The simulation results show that the FTN-based ACM system has additional gains compared with the traditional way and the proposed transceiver may be a better choice in the ACM system.

Interference management and supporting quality-of-service (QoS) requirements are the main challenges for the spectral resource allocation in orthogonal frequency division multiple access (OFDMA) small cells networks. In this study, the authors propose an algorithm for assigning physical resource block (PRB) with QoS constraints to eliminate interference among femtocells. They formulate the proposed resource allocation scheme as an optimisation problem where interference among femtocells is entirely avoided and multiple QoS for different services are supported. The proposed optimisation problem imposes the fairness among different femtocells and maximises the PRB efficiency. However, this problem is NP-complete, and thus, they offer a greedy algorithm for solving the problem. Simulation results show the throughput of their greedy algorithm is close to the optimal solution of the optimisation problem. Moreover, the proposed algorithm improves the network throughput by over 30–50% in different simulation scenarios with various femtocells densities in comparison to the previous methods. Furthermore, simulations illustrate the rejection ratio for all classes of services is lower than . Besides, the delays of different services are lower than the delay constraints.

The existing literatures have not considered either the fair power consumption in multi-user cooperative networks or the fairness-adjustable relay selection scheme. The authors propose a fairness-adjustable opportunistic relay selection in the multi-user dual-hop decode-and-forward cooperative networks with the optimal simultaneous power and rate adaptation under realistic power constraints, where the selection result is determined by the instantaneous signal-to-noise ratios over the relay links, the power load (PL) of the relays and the weight factor. The weight factor, also behaving as the metric of fairness, is introduced to adjust the bias between the average channel capacity for the relaying user and the fair PL distribution and is obtained by the proposed capacity-fairness bias criterion for the required fairness target. The average channel capacity has been derived approximately for the proposed scheme and the numerical results underscore the significant benefits of jointly exploiting the channel capacity and fairness.

A reliable vehicle-to-vehicle communication (V2VC) is essential to enable safe and highly automated driving system. Addition of a relay station (RS) can improve packet delivery rate (PDR) of CSMA/CA-based V2VC. However, the improvement is limited by packet collision at RS due to a hidden terminal (HT). This HT problem can be alleviated by employing sectorised receive antenna at RS, i.e. sectorised relay-assisted (SR-) V2VC. However, SR-V2VC still faces another problem, i.e. packet congestion at RS under high traffic conditions due to the improved packet reception rate. This leads to packet drop at RS and hence limits the improvement brought by SR-V2VC. Consequently, it is crucial to introduce a kind of traffic congestion avoidance methods to RS. In this article, the authors propose SR-V2VC with a payload combining forwarding (PCF) method (SR-V2VC/PCF) and theoretically evaluate the system performance using a CSMA/CA collision model. Large-scale computer simulations are also conducted to confirm the performance improvement brought by SR-V2VC/PCF. It is shown that the lowest broadcast PDR of 62% for the non-relay system is improved to higher than 81% by SR-V2VC/PCF and the directivity of the sector antenna has impact on the benefit of the proposed scheme.

The recently proposed quadrature spatial modulation (QSM) has drawn an increasing attention due to its high spectral efficiency compared with the previous space modulation schemes. In this study, the performance of QSM in two-way decode-and-forward relaying cooperative networks is investigated. In two-way relaying cooperative networks, two source nodes are allowed to simultaneously transmit data on the same time slot to a relay node. The relay node decodes the transmitted data from both transmitting nodes and retransmits them in the next time slot. Using network coding techniques, each node is able to decode the data of the other node upon accomplishing the second time slot. Considering QSM as the adopted modulation at all nodes, the average bit error rates at the source nodes and the relay are formulated in a closed form expression. Obtained results reveal that QSM-based two-way relaying can achieve better error performance than other related scenarios.

In complex landform the satellite signals are blocked so seriously that BeiDou satellite navigation system (BDS) cannot achieve real-time high-precision dynamical positioning, which seriously restrict its widespread in precise mapping and disaster relief. This study proposes global positioning system (GPS)/BDS vector tracking loop (VTL) assisted by the neural network (NN) to improve the performance of receivers in complex environments. In GPS/BDS VTL, pre-filter and navigation extended Kalman filter are both used, and discriminators are replaced by pre-filter structure; then, the output information of pre-filter is used as input of the navigation filter, at the same time the pseudorange rate of pre-filter is updated by pseudorange rate of navigation filter; finally, the NN is used in the GPS/BDS vector tracking structure, in the training stage, the output from navigation filter is adopted as the input of the NN. This method can prevent the error growth due to weak signal from deteriorating the entire tracking loop performance. Moreover, the NN is employed to provide a better prediction of residuals such as the Doppler frequency and code phase. The results show that the proposed adaptive GPS/BDS VTL shows a better tracking performance compared with the conventional VTL.

This study presents the design and simulated validation of some multi-passive optical network (PON) schemes based on polarisation multiplexing using a centralised light-source system. The main goal is to achieve cost reduction due to the maximum exploitation of the power supplied by the light source that provides data to several PONs, working at a bit rate of 10 Gbps through a single mode fibre link of 20 km. One of the proposed architectures was tested experimentally to validate the results obtained by simulation, achieving a bit error rate of for downstream and of for upstream.

This study presents a novel message-driven frequency-hopping (MDFH) scheme leveraging slow frequency-hopping (FH). Since the typical MDFH scheme requires a large amount of detectors to obtain the information that is transmitted through carrier frequency selection, the authors aim at a low-cost MDFH implementation in this study. The basic idea of the proposed FH scheme is to transmit a part of information through the hop rate instead of the carrier frequency selection of an FH signal, which results in reduced hardware cost and better system efficiency. Moreover, a collision-free multi-carrier extension is also introduced in this study. The lower bound on the bit error rate (BER) performance of the proposed scheme is analysed and is verified by numerical results. The numerical results also reveal that the proposed scheme has a better BER and throughput performances than the typical MDFH systems at a low signal-to-noise ratio.