This study investigates the decoding algorithms of binary Reed–Muller (RM) codes. The main goal of the study is to modify majority-logic decoding using sum-product or min-sum decoding algorithms at the highest-order information bits in RM codes. Numerical results show that compared with the traditional majority-logic decoding algorithm, the modified majority-logic decoding method proposed in this study can reduce the bit error rate by a large margin. This is achieved without incurring a significant increase in decoding complexity because soft-decision decoding is only used in the highest information bits in RM codes whereas majority-logic decoding is still applied at the other orders of information bits in RM codes.

A hybrid algorithm is proposed to decrease the integration phase measurement error accumulation in open-loop Doppler receiver which is designed for space orbit determination and positioning applications when cooperated closed-loop system is unavailable. Firstly, adaptive-neuro-fuzzy inference system (ANFIS) module α is implemented for the interrupted closed-loop measurement data prediction. Then to improve the prediction accuracy of the ANFIS module α, an adaptive Kalman filter is employed for data fusion with predicted data from ANFIS module α and open-loop measurement data for complementation and corrections. Meanwhile, ANFIS module β is embedded in the Kalman filter for adaptive error compensation to optimise the filter performance. Finally, the time costly ANFIS computations are accelerated by reconfigurable software–hardware co-design module implemented in the receiver system to improve the computing capability and efficiency of system. Experiment results are analysed to demonstrate the effectiveness of proposed hybrid algorithm. It suppresses error accumulation in open-loop receiver phase measurement by 85.89% compared to the directly integration results when closed-loop system is off-line and has 61.02% enhancement compared to the algorithm without adaptive error compensations. Thus, the whole combinatory system accuracy is improved.

Millimetre-wave (MMW) in 60 GHz extremely high-frequency band is deemed as a promising technique in indoor localisation based on its high multipath resolution, which can achieve higher measurement precision than ultra-wideband system. To reduce the positioning errors, this study presents a new threshold determination scheme based on the extreme learning machine by analysing the characteristics of the received MMW pulses from the energy detector receiver. For each given signal-to-noise ratio, the thresholds are examined. The impacts on ranging accuracy are analysed due to the integration periods and propagation models. Results show the developed method can extensively improve the ranging precision.

The discrete alphabet and memoryless relay channel (RC) with side information (SI) and its extension to the continuous alphabet Gaussian version with uncorrelated noises have been studied by Zaidi et al. Zhang et al. have studied a Gaussian RC with correlated noises and uninformed relay. Aggarwal et al. have analysed a coverage region for a RC without any SI and with uncorrelated noises. In this study, the authors have investigated the impact of SI on the coverage region as an important wireless performance factor for a wireless RC, and also derived the capacity upper and lower bounds for such a channel with SI and correlated noises. The results of this research include previous studies as special cases, and that under special circumstances, noise correlation can tighten the upper bound, and furthermore, SI enlarges the coverage region as expected intuitively. Mathematical derivations and numerical results are obtained to support the claims.

This studies the capacity of a class of K-user Gaussian broadcast channels with additive i.i.d. Gaussian state sequences which are non-causally known at the transmitter (GBC-SKT). The transmitter wishes to reliably communicate both a common and a private message to each receiver, thus attempting to simultaneously pre-code the common message against different states presented in channel outputs. The authors first derive the approximate capacity for the 2-user GBC-SKT to within 1.25  bits per channel use (bpcu) for all channel parameters and state variances. Then they extended the result to derive the approximate capacity for a class of K-user GBC-SKT to within 1.5 bpcu. In the capacity-approaching strategy, the channel input is obtained as the superposition of two codewords: a bottom codeword treating the channel state as noise and a top codeword pre-coded against the channel state at each user for a portion of the transmission block length or power. For the outer bound, they use the fact that the capacity should be decreasing in state variance in order to get to the tighter outer bound for high values of state variances.

High peak-to-average power ratio (PAPR) is one of the major drawbacks of orthogonal frequency-division multiplexing (OFDM) systems. The precoding method is famous for providing a flexible way to reduce PAPR efficiently via adjustable precoding matrix (PM) but it also leads to high computational complexity. This study proposes a generalised precoding method that uses a generalised PM to provide a flexible scheme to generate precoded data with low PAPR and complexity. As compared to the OFDM system, the proposed generalised precoding OFDM systems achieve close bit-error ratio (BER) performance with lower PAPR reduction. Moreover, the BER performance of generalised precoding-based OFDM system is superior to that of OFDM system at low signal-to-noise ratio. The well known single-carrier frequency-division multiple access is a special case of discrete Fourier transform (DFT)-based generalised precoding method; therefore, the proposed method is promising in OFDM systems for achieving low PAPR and complexity with better BER performance.

This work describes the simplest chaotic system with a hyperbolic sine non-linearity, accompanied by analysis of Lyapunov exponents, bifurcations, and stability. The corresponding simple chaotic circuit using only diodes and linear components is designed and implemented. Finally, an application of the system to spread spectrum communication based on differential chaos shift keying (DCSK) is presented. Since the hyperbolic sine is an odd function of its argument, the system is antisymmetric and exhibits symmetry breaking where the attractors split or merge as some bifurcation parameter is changed. The proposed system is especially simple both from the structure of the equations and in its electronic circuit realisation. Compared with the traditional DCSK scheme of a Chebyshev sequence, the system can reduce the bit error rate in the presence of noise.

The authors consider a single-channel power line communication (PLC) system in the presence of Middleton Class-A impulsive noise employing multi-level amplitude-shift keying (ASK) modulation at the transmitter and non-coherent detection at the receiver. An asymptotically optimal detector for the PLC system is obtained using a tight approximation of the noise statistics. The magnitude of the received symbol is obtained as the decision variable, whose statistics is utilised to derive a series expression for the symbol error rate (SER). An asymptotic expression for the SER at high signal-to-noise ratio (SNR) is also obtained which is further utilised to find the optimal ASK constellation minimising the SER. It is shown by numerical examples that the optimal solution is extremely close to the equally spaced ASK constellation set at high SNR. It is also observed that the SER variation of the system with the impulsive index of the noise validates the optimality of the proposed detector at high SNR.

A passive optical network (PON) with multiple optical line terminals (OLTs) will play an important role in the optical access network. In this study, a novel dynamic bandwidth allocation (DBA) algorithm for the downstream channel in a multi-OLT PON is proposed. To take care of bandwidth demands of different users, weight factors are introduced. Based on different weight factors, a core framework of the algorithm is constructed. Moreover, by combining a decision criterion and a bandwidth surplus ratio, a mathematical model of release bandwidth is established. Furthermore, by uniting judgement conditions and overload amount, a mathematical model of allocation bandwidth is also built. By constructing two mathematical models, the order and amount of release and allocation bandwidth are effectively solved. Moreover, to describe accurately the power of bandwidth transfer, a new concept ‘bandwidth-transfer work’ is introduced. Based on the bandwidth-transfer work, a ranking model is created to maximise the efficiency of the DBA. Finally, the effectiveness of the DBA algorithm and ranking model is demonstrated by the simulation and analysis.

In this study, the authors study the interference exploitation problem in multi-input multi-output (MIMO) multi-way relay channel, which is MIMO Y channel. In this channel, multiple users complete the exchange of information among users through a common relay in the multiple access channel phase and broadcast phase. Each user sends signals to other users and receives the signals sent by other users. For a three-user transmission model, each user and relay have three antennas, respectively. To achieve better decoding performance at the relay, they design precoding vectors on the basis of traditional signal space alignment (SSA) so that the intersection subspaces hold orthogonal. Corresponding optimisation rules are proposed for zero-forcing and maximum-likelihood decoders. It is seen from the simulation results that the proposed algorithm greatly improves the decoding accuracy compared with the traditional SSA relay decoding, and reduce the computational complexity. Because of the improvement of the performance of relay decoding, the reliability of the whole transmission system will be improved.

In this study, the authors consider an energy-constrained secondary user which harvests energy from the primary signal and forwards this latter with the guarantee of spectrum access. Two key protocols are proposed, namely time-splitting cooperative spectrum sharing (TS-CSS) and power-sharing cooperative spectrum sharing (PS-CSS), based on time splitting and power sharing at the relay, respectively. Assuming a Nakagami-m fading model, exact closed-form expressions for the outage probabilities of the primary and secondary users are derived in decode-and-forward and amplify-and-forward relaying modes. From the obtained results, it is shown that the secondary user can carry its own transmission without any adverse impact on the performance of the primary user and that the PS-CSS protocol outperforms the TS-PSS protocol in terms of outage probability over a wide range of signal-to-noise ratio. Furthermore, the effect of various system parameters, such as splitting ratio, distance between nodes and harvesting efficiency, on the system outage performance on employing the proposed protocols is investigated and several insights are drawn.

This study considers the problem of indoor localisation in which the authors try to generate the radio map of the environment based on both labelled and unlabelled measurements (i.e. measurements with and without information about the location that they have been collected). In such problems, the method that has been used for radio-map generation as well as the quality of the measurements (the received signal strength from different environment's WiFi Access Points) are very critical in the overall accuracy of the generated radio map. In this study, they apply two of the well-known graph-based signal processing schemes (namely iterative least square reconstruction and graph-based label propagation) for polishing the input data, determining the outliers and radio-map generation. Experimental results show the superior performance of the proposed method compared to previous schemes.

Complex quadrature spatial modulation transmits two signal symbols at each channel use, each is drawn from a different constellation set. The indices of the antennas from which the symbols are transmitted carry information to the receiver. When both symbols are transmitted from the same antenna, the symbols resulting from the addition of the two signal symbols belong to the Minkowski sum of the original two constellation sets. Therefore, the size of the modulation set at the transmitter increases and the minimum distance between transmitted symbols is reduced, leading to degradation in the error performance. In this study, the authors propose to equip the transmitter with an additional antenna which is used to transmit the second signal symbol only when the information bits representing the antenna indices are identical. The design of the optimum modulation sets that maximise the Euclidean distance is also addressed. Furthermore, based on the probability of antenna use, they advise an antenna ranking algorithm that improves the performance. The simulation results show that the proposed scheme achieves a signal-to-noise ratio gain of 6.4 and 9.5 dB using 16 quadrature amplitude modulation and 16 phase-shift keying, respectively.

Ultra-dense networks (UDN) can provide extremely high throughput and data rate. However, there are severe interference due to dense and random deployment of femto base stations (FBSs). To mitigate interference and allocate network resource efficiently while ensuring quality of service (QoS) of user equipments (UEs), a cluster-based resource allocation scheme for UDN is proposed in this paper. Two stages, clustering and resource allocation, are involved in the scheme. In clustering stage, a modified K-means clustering algorithm is advanced to divide FBSs into different disjoint clusters dynamically according to the density of FBSs. Thus the number of clusters can be adjusted flexibly to fit for the dynamic network topology. In resource allocation stage, a greedy-based compensatory resource allocation algorithm (GCRAA) is further proposed to maximize the throughput of UDN. Herein the orthogonal resource blocks (RBs) are initially assigned among the UEs with a greedy algorithm. In order to ensure the fairness and QoS of UEs, a compensatory resource allocation algorithm is further proposed to allocate the remaining RBs. The simulated results show that the proposed resource allocation scheme can mitigate the interference in UDN effectively, and improve the system throughput while ensuring the QoS for UEs.

Bloom filters (BFs) are widely utilised to speed up string matching in crucial network applications such as real-time intrusion detection and spam filters. This study introduces a new approach to improve the efficiency of BFs for string matching functions. The approach splits each target string into two substrings and considers the second substring for programming the BF. The objective is to minimise the false positive rate by maximising the common hash signatures from the second substring. Results show that compared to the traditional means of using BFs, the proposed approach reduces the false positive rate by averages of 76 and 88% for 32 and 64 Kb BFs, respectively. Moreover, a complete string matching architecture has been developed in hardware based on the proposed approach. Results demonstrate the advantages of this new architecture compared to similar previous works.

Channel quality metric is an important parameter for the adaptive Long Term Evolution (LTE) uplink, and has a great effect on the performance of the uplink. By modelling the data transmission in the LTE uplink as the complex modulated data pass through the additive Gaussian channel in the transform domain, the authors proposed a new metric, the ratio of the received equivalent average bit power to the average bit error power based on the idea of the modulation error ratio. The adaptive scheme with the proposed metric in the LTE uplink is also given. Simulation results demonstrate that the authors' proposed metric has a better control of the block error rate and can improve % in the throughput compared with the best metric among the conventional channel quality metrics.