As a novel non-orthogonal multiple access scheme, pattern division multiple access (PDMA) has been proposed for the fifth generation mobile communication technology (5G) to enhance spectrum efficiency and increase connexion capability. This study analyses the theory performance of uplink PDMA. The exact closed-form expressions for outage probability (OP) are derived in the Rayleigh fading channel, and the OPs of each user with different pattern and target signal-to-interference-plus-noise ratio are evaluated. In addition, the comparison between PDMA and conventional orthogonal multiple access (OMA) in terms of sum data rate (SDR) is conducted. Numerical simulation results verify the authors' analysis and show that PDMA outperforms OMA in terms of OP and SDR.

This study investigates the benefits offered by random matrix theory (RMT) towards the design of reliable channel estimation algorithms for a multi-user massive multiple-input multiple-out (MIMO)–orthogonal frequency-division multiplexing uplink. Assuming no a priori knowledge of channel statistics (KCS) at the massive base station, the authors propose RMT-aided minimum mean square estimation (MMSE) and RMT-aided sparse Bayesian learning (SBL) approaches for massive channel estimation. These approaches render efficient channel estimates, as illustrated through mean square error (MSE) performance, extracted via Monte-Carlo simulations. The results also show that with increasing antennas at the base station, MSE from the RMT-aided MMSE approach decreases, suggesting its aptness to massive MIMO systems. To further enhance the MSE performance, the MMSE and SBL estimated channel impulse responses are pruned using threshold computed from RMT analysis. The authors characterise MSE degradation due to the randomness in the threshold, with the help of the Marcenko–Pastur law-based non-asymptotic framework and concentration inequalities. Analysis results show that, for channels with approximate sparse common support, this MSE degradation is quite insignificant. Altogether, the study demonstrates that RMT analysis is competent in improving channel estimation at a massive MIMO system, when a priori KCS is completely unavailable.

Body area networks (BANs) are systems of wearable computing devices for long-term monitoring of personal health care. BAN is an emerging technology for the worldwide ageing population. In the BAN system, the transceiver is the most energy-consuming part of a sensor node and radio transmission in the vicinity of the human body is highly lossy and inefficient. Therefore, the energy of the sensor node constraints the life cycle and quality of service of the network; consequently, low-cost protocol shaves attracted wide interest. This study proposes a frame structure model of a self-adaptive guard band protocol, which introduces a GB in each time slot according to the allowed maximum time drift of the crystal, adaptively adjusts the value of the GB based on the actual time drift, and then ensures that the node simultaneously maintains the sleeping state and synchronisation with the coordinator during beacon transmission, thus reducing the energy consumption.

In a satellite disruption/delay-tolerant network, bundle delivery is obviously affected by time-varying parameters, i.e. bit error rate and propagation latency, due to constantly changing distance and connectivity between paired orbital nodes. The authors proposed a Markov decision-based optimisation approach for bundle size, which could efficiently improve the expected time of delivery over a dynamic two-hop inter-satellite link. In particular, a group of optimal bundle sizes are adaptively selected according to current distance-dependent channel parameters, leading to a full utilisation on intermediate node's memory. The simulation results verified the proposed method under different conditions with comparison.

Recently, long-term evolution (LTE) technology has been considered as a promising solution for realisation of ubiquitous machine-to-machine communications. However, this solution faces massive access of machine-type communication (MTC) devices as one of the most important challenges. In this study, access class barring (ACB) scheme and timing advance information (TAI) are combined to manage massive access of stationary MTC devices to LTE networks. Although, using TAI can help contention alleviation, it can destroy fairness among devices. So, the aim of this study is maximisation of number of successfully served devices, while fairness is achieved too. Three analytical approaches are proposed. In the first scheme, the probability of success for the most serious contending devices is maximised. In the second and third schemes, one ACB factor is allocated to each annulus. In the second scheme, the expected number of successful devices in one random access (RA) slot has been maximised and in the third scheme fairness has been established among devices. Furthermore, two methods are introduced that estimate the number of backlogged devices in every RA slot. The performances of three schemes and results of a recent attempt in this field are compared with each other. Through simulations, it has been shown that the third scheme represents the best performance in terms of fairness and number of slots required to serve total MTC devices.

With the development of fifth generation wireless communication technology, how to improve system capacity and spectrum efficiency is a crucial problem in resource sharing of heterogeneous networks (HetNets). Most of existing resource allocation (RA) schemes in HetNets focus on perfect channel state information, however, exact channel information is difficult to obtain under link delay and stochastic channel condition. In order to resolve the RA issues under channel uncertainties, a robust RA algorithm is proposed to maximise the sum data rate of microcell users where the users are subjected to the individual transmission power constraint and the cross-tier interference constraint of macrocell users. The multiuser RA problem in HetNets is formulated under the consideration of bounded channel gain uncertainties where both the cross-tier channel and intra-tier channel are simultaneously considered. The non-linear optimisation problem is converted into a geometric programming problem that is solved by using Lagrange dual methods in a distributed way. Simulation results show that the proposed algorithm can well restrain the effect of channel uncertainty and achieve a good robustness.

This study derives in the closed-form the probability density function and characteristic function of the ratio of two products of arbitrary number of Nakagami-m random variables. Then, the resulting mathematical framework is applied to analyse and gain insights into the bit error rate performance of the dual-hop channel state information-assisted amplify-and-forward relaying system in the presence of co-channel interference. All analytical results are corroborated by Monte–Carlo simulation results and they are shown to be efficient tools to evaluate system performance.

This study investigates the application of artificial fish swarm algorithm (AFSA) in the power allocation for multiple-input and multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) relay underwater acoustic (UWA) communication systems. First, by using the singular value decomposition technique, the two-hop transmission links are converted into the virtual direct links in an single-input and single-output OFDM (SISO-OFDM) system. Then, a power allocation optimisation problem, together with the assignment of subcarriers and relay nodes, are formulated for the virtual SISO-OFDM system. Finally, the problem-solving algorithms are proposed in two parts. Computer simulation results show that the proposed AFSA scheme improves in both power consumptions and diversity gains compared with two existing schemes for UWA communication systems.

The authors employ the conditional moment generating function approach to analyse the performance of orthogonal space-time block codes over Nakagami- q (Hoyt) multiple-input multiple-output radio frequency identification backscattering channels. New exact and asymptotic symbol error rate expressions are derived for the case of two and four receiving antennas . The exact expressions are in the form of a sum of infinite series while the asymptotic ones are in the closed form. The diversity order that the system can achieve is found to be L , where L is the number of tag antennas, and the performance of this system is found to be more sensitive to the channel condition (the q parameter) of the forward link than that of the backscattering link. The theoretical results (exact and asymptotic) are verified through comparison with simulation results.

Low-density parity-check (LDPC) codes have excellent performance for a wide range of applications at reasonable complexity. LDPC codes with short blocks avoid the high latency of codes with large block lengths, making them potential candidates for ultra reliable low-latency applications of future wireless standards. In this work, a novel informed dynamic scheduling (IDS) strategy for decoding LDPC codes, denoted reliability-based residual belief propagation (Rel-RBP), is developed by exploiting the reliability of the message and the residuals of the possible updates to choose the messages to be used by the decoding algorithm. A different measure for each iteration of the IDS schemes is also presented, which underlies the high cost of those algorithms in terms of computational complexity and motivates the development of the proposed strategy. Simulations show that Rel-RBP speeds up the decoding at reduced complexity and results in error rate performance gains over prior work.

Bistable parallel array system can efficiently improve the signal-to-noise ratio (SNR) gain and further significantly lower bit-error-rate (BER) when the SNR is low. The bistable parallel array system is widely studied due to its outstanding advantages. This study presents a new method that applies combining techniques including maximum ratio combining (MRC), equal gain combining (EGC), and selection combining (SC) to the bistable parallel array system, and derives the formulas of the SNR gain, energy efficiency, and numerically calculates the BER. Through comparative analysis of these three combining techniques, it demonstrates the BER performance of the EGC technique in bistable parallel array system slightly inferiors to MRC, and the worst is SC. While the performance of all these three kinds of combining techniques is better than that of the single branch case. Importantly, higher SNR gain, higher EE and lower BER can be obtained in non-Gaussian noise cases than that in Gaussian noise cases.

A hybrid overlay/underlay cognitive radio network (CRN) is demonstrated to provide high spectrum efficiency and channel capacity. Decision-making in joining CRNs is one of the major issues of secondary users (SUs). Each SU has the option of joining the spectrum or balking according to the trade-off between the service profit and the delay cost. In this study, the decision-making problem in accessing the hybrid overlay/underlay CRN is addressed using queuing models and game theory. An almost unobservable queuing server is used to model hybrid overlay/underlay CRN. The interaction between the cognitive users is treated as a non-cooperative game. A closed-form expression for the average number of cognitive users as well as associated expected waiting time in both overlay and underlay CRNs is derived. The strategic behaviour for spectrum access of cognitive users in hybrid overlay/underlay CRN is investigated and the existence of symmetric Nash equilibrium is proved as well. Finally, we provide extensive validation results using a wide range of realistic simulation scenarios. The proposed model gives detailed guidance to the decision makers to deploy the suitable strategy according to the available channel situation.

To overcome the drawback of bit-error rate (BER) performance decrement caused by intrasignal interference (ISI) in correlation-delay-shift-keying (CDSK) and its enhanced schemes, in this brief, a reliable and effective chaotic communication scheme: phase-orthogonality CDSK is proposed. In the proposed scheme, quadrature sinusoidal wavelets are alternately selected to modulate the reference signal. This operation makes the reference signal strictly orthogonal to the information-bearing signal and the ISI component is eliminated during the demodulation. The BER performance is analytically studied and the simulations are performed in additive white Gaussian noise channel and Rayleigh multipath fading channels. Theoretical analysis and simulations show that, since there is no ISI component and better bandwidth efficiency, the proposed BER performance is much better than differential-chaos-shift-keying (DCSK) and CDSK. With the length of multiframe increasing, the proposed BER performance gradually becomes better, and can even outperform reference-adaptive CDSK and improved DCSK.

Based on p-ary pseudorandom sequences, this study proposes a construction of degree-k Gaussian integer sequences of period by utilising kth power residue symbol satisfying , where p is an odd prime and positive integers . The periodic autocorrelation values are 0 at shifts of the resultant sequences. Specially, there is exactly one non-zero out-of-phase periodic autocorrelation value of the resultant sequences for . The non-zero elements of the sequences are balanced and can be predefined flexibly. Moreover, the maximum energy efficiency of the proposed sequences is close to for sufficiently large m.

In wireless communication systems, it is well known that inter-symbol interference (ISI) can be avoided by using a pair of matched square-root-raised-cosine (SRRC) filters in the transmitter and receiver. In an effort to find methods which minimise the number of filter taps in the matched filter, numerous studies have been done. However, in practise, when the communication specification is fixed by the standard, it is not possible to change the coefficients of the transmit filter. In this study, the authors propose a new SRRC filter design with the reduced number of filter taps for a receiver of a wireless communication system. The proposed design utilises a recursive steepest-descent algorithm when the filter coefficients of the transmitter are fixed. That is, relaxing the ISI criterion while maintaining the stopband attenuation, the proposed receiver filter has fewer filter taps than that in the conventional case without undergoing bit error rate performance degradation. The proposed receiver filter design with the reduced number of filter taps reduces the computational complexity and the detection delay in the receiver.

This study focuses on the reception strategy and the detection method of a wideband orthogonal frequency-division multiplexing (OFDM) signal, which is passing through a Doppler channel. Most prior works regarded the Doppler effect as a reason of interchannel interference due to its destruction of the subcarrier orthogonality. Distinguishing from those works, the authors point out that the wideband OFDM signal is still an OFDM signal with subcarrier orthogonality after passing the channel with single Doppler scaling factor. Thus, the received OFDM signal passing the Doppler spreading channel is a linear superposition of a set of transmitted OFDM signals associated with different parameters. To make full use of the diversity gain offered by the superposition, the authors propose a strategy of diversity reception and a belief propagation detection method for the received wideband OFDM signal. The simulation results show that the proposed strategy improves the performance obviously with increase of the diversity order in a Doppler spreading channel. It offers different options for system demands. Furthermore, the proposed detection method can offer an acceptable performance even it combined with the conventional sampling process. It makes the conventional structure replacing the common resampling structure possible in a wideband OFDM system.

In amplify-and-forward relay networks, accurate channel estimation of individual links is essential for coherent reception and optimal design. To acquire the channel state information of individual links, a novel in-band superimposed training is proposed, where relay superimposes its own training sequence directly on top of the information-bearing received data. As a result, the training sequences from the source and relay nodes are independent of each other, thus making it more flexible and robust in relay-training design. However, the proposed training scheme induces extra data interference that degrades the estimation performance. The authors first adopted the detected symbols to mitigate the data-induced interference during channel estimation. However, the estimation performance is degraded by the symbol detection error and relay propagated noise. To resolve this problem, the interference nulling at the relay is proposed, where some special frequency components of the received data are nulled prior to training superimposition. As a result, both the data-induced interference and relay propagated noise are totally removed during channel estimation. Simulation results are provided to assess the performance of the proposed schemes.

Long-term evolution (LTE) adopts rate matching (RM) to reach high-speed data transmission. According to the LTE hybrid automatic repeat request scheme, the receiver can correct multiple transmission data with distinct code rates. Here, the window-stopped (WS) criterion is reinvestigated for the single-binary (SB) turbo code in LTE RM. The parallel SB WS turbo decoding for LTE RM with distinct parameters is analysed in terms of window stopping rate, kernel stopping rate, and correcting performance. Experimental results reveal that the early termination technique does not work well for high-code-rate decoding. However, the SB WS criterion significantly achieves up to 19% window stopping for decoding large codeword blocks and 37% kernel stopping for decoding small codeword blocks. Moreover, the SB WS criterion is implemented within a parallel turbo decoder for LTE RM using a 90 nm CMOS process. The evaluation results show that the power dissipation of the implemented WS parallel turbo decoder can be significantly reduced by 17% with a 0.7% area overhead for high-code-rate decoding and high channel quality.