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Wireless energy harvesting (WEH) enabled Device-to-Device (D2D) communication emerges as an effective technique to improve spectral and energy efficiencies. However, D2D users are usually power-constrained devices that may be monitored or attacked by adversaries easily. To confuse randomly distributed adversaries in WEH-enabled D2D underlaying cellular networks, power beacons (PBs) can be used to send jamming signals in idle time slots. A time slot is divided into two sub-slots, i.e., WEH sub-slot and covert transmission sub-slot. The energy collected by a D2D transmitter in the first sub-slot is used to support possible covert transmission in the second sub-slot. The performance of the proposed scheme is measured by covert throughput, which is defined as D2D communication rate with several constraints, e.g., wireless energy harvesting, covertness, and cellular link communication requirements. The closed-form expressions of energy outage probability, covert probability, and desired link connection outage probabilities are derived. The minimum covert probability is used to measure covertness. Moreover, an alternating optimization algorithm is adopted to maximize covert throughput. The analytical results are compared with Monte-Carlo simulation results to verify the analytical approach. In addition, the impacts of different parameters (e.g., density of PBs and covert signal transmit power) on covert performance are evaluated. [ABSTRACT FROM AUTHOR]

With the deployment of the fifth generation (5G) in many countries, people start to think about what the next-generation of wireless communications will be. The current communication technologies are already approaching the Shannon physical capacity limit with advanced encoding (decoding) and modulation techniques. On the other hand, artificial intelligence (AI) plays an increasingly important role in the evolution from traditional communication technologies to the future. Semantic communication is one of the emerging communication paradigms, which works based on its innovative “semantic-meaning passing” concept. The core of semantic communication is to extract the “meanings” of sent information at a transmitter, and with the help of a matched knowledge base (KB) between a transmitter and a receiver, the semantic information can be “interpreted” successfully at a receiver. Therefore, semantic communication essentially is a communication scheme based largely on AI. In this article, an overview of the latest deep learning (DL) and end-to-end (E2E) communication based semantic communications will be given and open issues that need to be tackled will be discussed explicitly. [ABSTRACT FROM AUTHOR]

Spectrum efficiency is a critical performance metric in wireless communications due to an increasing demand for radio spectrum to support high data rate applications. Direct sequence spread spectrum technology enables a code division multiple access (CDMA) system a strong anti-interference capability but with a relatively low spectrum efficiency. To address this issue, complementary coded scrambling multiple access (CCSMA) (X. Liu et al., in 2018) was proposed to use three-dimensional (space-time-frequency) resources for performance enhancement. However, in a CCSMA system, if the number of multipath returns is larger than the number of transmit (Tx) antennas, a code reuse problem occurs to degrade bit error rate performance significantly. This work designs a new scrambling code, namely generalized complementary coded scrambling multiple access (GCCSMA) codes, to overcome the code reuse problem in CCSMA. GCCSMA uses complementary codes, scrambling modulation, and multiple-input-multiple-output (MIMO) techniques jointly, which works well even in multipath channels with more paths than the number of Tx antennas. The analysis and simulations are conducted to validate the effectiveness of the proposed GCCSMA system. [ABSTRACT FROM AUTHOR]

Sparse code multiple access (SCMA), which helps improve spectrum efficiency (SE) and enhance connectivity, has been proposed as a non-orthogonal multiple access (NOMA) scheme for 5G systems. In SCMA, codebook design determines system overload ratio and detection performance at a receiver. In this paper, an SCMA codebook design approach is proposed based on uniquely decomposable constellation group (UDCG). We show that there are $N+1$ ($N\ge 1$) constellations in the proposed UDCG, each of which has $M (M\ge 2)$ constellation points. These constellations are allocated to users sharing the same resource. Combining the constellations allocated on multiple resources of each user, we can obtain UDCG-based codebook sets. Bit error ratio (BER) performance will be discussed in terms of coding gain maximization with superimposed constellations and UDCG-based codebooks. Simulation results demonstrate that the superimposed constellation of each resource has large minimum Euclidean distance (MED) and meets uniquely decodable constraint. Thus, BER performance of the proposed codebook design approach outperforms that of the existing codebook design schemes in both uncoded and coded SCMA systems, especially for large-size codebooks. [ABSTRACT FROM AUTHOR]

Growing computation requirements in emerging intelligently connected vehicle (ICV) networks has posed a big challenge for vehicles to process computation-intensive tasks on-board, and thus computation partition and offloading plays a critical role. Owing to broadcast nature of wireless channels, confidential messages without proper security protection in ICVs may be easily exposed to malicious users. In this paper, a mobile crowdsourcing (MCS) based mobile crowd computing framework for ICV networks is proposed, where multiple vehicles act as workers to provide computing services for end user (EU). In particular, artificial noise (AN) assisted physical (PHY) layer security approaches are used to enhance the security in offloading links. Ergodic secrecy rates in different offloading phases in time-varying channels are derived. In addition, an incentive-driven mechanism is introduced to encourage workers to share their idle computing resources, and an optimization problem is formulated to minimize the overall price paid for computing tasks, subject to energy consumption and delay constraints. Finally, Monte Carlo simulations verify the analysis on the ergodic secrecy rates. [ABSTRACT FROM AUTHOR]

Ultra-dense network (UDN) is one of the most important techniques to support massive number of different types of user equipments (UEs). It is essential to understand the impact of densification on various system performance metrics in future cellular networks. Two contradictory conclusions were made from the existing research works. Some works indicated that the network densification has reached its upper limit and deploying more UEs may only reduce UDN performance; whereas the others claimed that more UEs can still be supported by deploying more small cell base stations (SBSs). The existence of above different conclusions is due mainly to the difficulties to find an effective means to take into account different path loss models in UDNs. In this paper, we aim to propose a unified analytical approach, which is effective to simplify UDN performance analysis based on different path loss models with a low computation complexity. Using the proposed approach with idle mode of SBSs enabled, we can identify the impact of the densities of SBSs and UEs on various performance metrics, i.e., coverage probability and average area spectral efficiency (ASE). The conclusions will be supported by the analytical and simulation results verifying the effectiveness of the proposed unified analytical approach. [ABSTRACT FROM AUTHOR]

This article aims to provide a comprehensive overview on PHY layer security assisted ICV networks. Beginning with a discussion from a general perspective of the ICV network architecture, this work summarizes the major security threats faced by ICV networks. To achieve confidential data transmission with a low latency and a high data rate, several physical layer security schemes are surveyed in this article, which include RRM, cooperative jamming, multi-antenna technologies, and PHY-layer key generation. In addition, the performances of the aforementioned schemes are compared in terms of different aspects, followed by a discussion on some major challenges that need to be tackled in the implementation of ICV networks. [ABSTRACT FROM AUTHOR]

Machine-type data traffic volume in 5G networks will grow rapidly with widespread applications of MTC. The MTC devices, including home appliances, sensors, wearable devices, vehicles, and even low-altitude UAVs, will be made smarter with embedded advanced communication modules. However, a massive number of MTCDs with diverse QoS requirements cannot be served well by traditional wireless systems, which were primarily designed for human-type devices. New wireless technologies are needed to support distinct MTC network applications. In this article, five emerging MTC technologies, including Bluetooth 5, WiFi HaLow, LTE-M, NB-IoT, and WURs, are discussed, followed by a survey of 3GPP activities on vehicle-based and UAV-based MTC technologies, such as LTE-V2X and C-UAV for aerial vehicles. In the end, we also address the issues on the new trends for MTC networks with identified research challenges. [ABSTRACT FROM AUTHOR]

This paper investigates an integrated wireless communication system including non-orthogonal multiple access, full-duplex relaying, and energy harvesting techniques (named as EH-FD-NOMA). In this scheme, an energy-limited full-duplex relay harvests energy from a source at the first stage. Then, the relay detects the superimposed signal from the source and transmits the decoded signal to destination. Closed-form outage probabilities and ergodic rates at the relay and destination are derived. Numerical results verify the analytical results and show the superior performance of the EH-FD-NOMA if compared to its counterparts. [ABSTRACT FROM AUTHOR]

In wireless powered communication networks (WPCNs), base station (BS) and power beacons (PBs) can offer supplement power for uplink transmission of user equipments (UEs). However, the aggregate power consumption of massively deployed PBs may exceed that of a BS. We propose a non-uniform deployment scheme for PBs in WPCNs, where a cell is divided into inner and outer areas, such that BS and PBs can cooperate to power UEs. To be more specific, a BS located in the center of a cell provides downlink power supply for the inner area UEs and uplink information decoding for all the UEs in the cell; while the PBs power UEs in the outer area. With multiple antennas, maximum ratio transmission and maximum ratio combining are adopted for downlink energy beamforming and uplink information reception. Considering a finite area of the network, we derive the distribution of the distance from a non-center-located UE to its nearest PB in the outer area. An optimization problem is formulated to minimize total average power consumption while satisfying BS average transmission power constraint and coverage probability threshold. Moreover, coverage probability is derived for performance evaluation. The numerical results show that the power consumption of the proposed scheme is reduced significantly compared to PB-only WPCNs. [ABSTRACT FROM AUTHOR]

Millimeter-wave (mmWave) communication is one of the most promising technologies in the fifth generation (5G) mobile networks due to its capability to access a large amount of available spectrum resources. Despite theoretical potential of a high data rate, there are still several key technical challenges to use mmWave in mobile networks, such as severe path loss, high penetration loss, and narrow beamwidth. Hence, accurate and reliable knowledge on mmWave channel propagation characteristics is essential for developing 5G wireless communication systems. In this article, the fundamental characteristics of mmWave are presented first. Then two main channel modeling methods are discussed. In order to investigate the channel characteristics at mmWave bands, measurements using three different large-scale array topologies are carried out, and typical channel parameters are extracted and analyzed. [ABSTRACT FROM AUTHOR]

Virtual multiple-input multiple-output (V-MIMO) is an effective way to achieve a diversity gain in uplink channels. A well-designed user pairing scheme in V-MIMO systems can exploit multiuser diversity to yield a significant performance gain. This paper investigates joint user pairing and power allocation problems in V-MIMO systems to maximize energy efficiency (EE) while guaranteeing spectrum efficiency (SE) under a total power consumption constraint. We formulate such a joint problem as a complex nonlinear optimization problem, which can be solved in two steps in $M\times K$ V-MIMO systems, i.e., power allocation with known user group and joint user pairing and power allocation. A multi-level water-filling method is used, and an iterative algorithm based on the outputs from the first step is employed in the second step. Finally, we propose a joint user pairing and power allocation scheme to find a user group that can achieve the maximum EE with power allocation. Simulation results and performance comparisons illustrate improved performance of the proposed scheme. Compared to the existing user pairing approaches, the proposed scheme achieves a significantly high EE gain while guaranteeing SE of a V-MIMO system. [ABSTRACT FROM AUTHOR]

In a traditional complementary coded CDMA (CC-CDMA) system, signals are spread using the direct sequence (DS) technique to suppress multipath interference (MI) and multiple access interference (MAI). However, DS spreading suffers from very poor bandwidth efficiency. This paper proposes a scrambling-based CC-CDMA system, namely complementary coded scrambling multiple access (CCSMA). A CCSMA system offers a unified platform to integrate CC-CDMA, multiple-input multiple-output (MIMO), and scrambling technique seamlessly. Utilizing complementary codes in scrambling modulation, a CCSMA system is able to suppress MI and MAI effectively. With the help of space domain scrambling, the CCSMA system offers much higher bandwidth efficiency than a CC DS-CDMA system. Bit error rate and system capacity are evaluated explicitly in this paper, verifying that CCSMA is a viable multiple access technique for providing high capacity in downlink MIMO channels. [ABSTRACT FROM PUBLISHER]

Statistical signal transmission (SST) is an emerging orthogonal frequency-division multiplexing (OFDM) technology that can carry additional information over conventional OFDM signal streams without extra bandwidth cost. This additional information can be exploited to carry control information, location/speed data, or cooperative schedule signals, etc., to improve the performance of wireless communications. However, existing detection methods used in this technique work-based mainly on time-invariant channels (i.e., channel state is quasi-static within a detection period), and cannot work well in diverse channel variations caused by different user velocities. In this paper, we propose a mobility adaptive detection method for SST. First, we analyze the influence of nonstatic channels on SST detection and identify a negative factor, called cyclic autocorrelation function whitening effect. Correspondingly, we probe the feasibility of antiwhitening concept and carry out relevant experiments for verification purpose. Based on this, a complete version of mobility adaptive detection method is proposed. Numerical results manifest that the proposed method outperforms the existing ones in high velocity scenarios. In addition, the properties of the proposed method are investigated, based on which we show a specific application for SST to reveal the potential for SST to be used in 5G wireless communications. [ABSTRACT FROM AUTHOR]

Heterogeneous network (HetNet) plays an important role in the upcoming 5G communications. A HetNet in futuristic communications is envisaged to provide full access data services, such that users will always have the best service with their available radio resources. To realize a full access HetNet, statistical signal transmission (SST) can be an important enabling technique. SST exploits statistical features of ordinary signals as a data transmission scheme to carry information data. Due to its inherent unique properties, SST signal is more robust than ordinary signals in conventional quasi-static channels. However, detection of SST signals in fast time-varying channels will face challenges. Motivated by this fact, this paper aims to analyze the impact of fast time-varying channels to SST, and reveals negative effects of burst of deep fading channel-state (BDFC) and feature dissipation with out-of-phase (FDOP). Accordingly, we design an automatic re-transmission scheme and a fragmental feature capturing method to mitigate the aforementioned issues, respectively. Based on these studies, we propose a channel condition aware detection scheme for SST, aiming to enhance SST detection performance in fast time-varying channels. Numerical results show that with the proposed scheme, a maximum gain of more than 10 dB can be obtained under either BDFC or FDOP condition. Furthermore, it is also demonstrated that the proposed scheme is robust with imperfect channel coherence time information, which is attractive for practical applications. [ABSTRACT FROM PUBLISHER]

Radio frequency energy transport is a viable technology to power small-sized sensors in wireless industrial sensor networks (WISNs). 60 GHz wireless communication emerges as one of the leading technologies for next generation wireless networks, and it can also be useful to build up WISNs. In this article, we investigate the efficiency of RF energy transport in WISNs with 60 GHz communications. We present a spherical antenna design with supported analytics on directional antennas in 60 GHz wireless communications. We introduce and solve the spherical distribution problem of directional antennas to maximize the energy transport efficiency in WISNs. The extensive simulations given in this article verify that the proposed antenna configuration performs much better than the existing solutions in WISN applications. [ABSTRACT FROM PUBLISHER]

Providing diverse and strict quality-of-service (QoS) guarantees is one of the most important requirements in machine-to-machine (M2M) communications, which is particularly need for appropriate resource allocation for a large number of M2M devices. To efficiently allocate resource blocks (RBs) for M2M devices while satisfying QoS requirements, we propose group-based M2M communications, in which M2M devices are clustered based on their wireless transmission protocols, their QoS characteristics, and their requirements. To perform joint RB and power allocation in SC-FDMA-based LTE-A networks, we formulate a sum-throughput maximization problem, while respecting all the constraints associated with SC-FDMA scheme, as well as QoS requirements in M2M devices. The constraints in uplink SC-FDMA air interface in LTE-A networks complicate the resource allocation problem. We solve the resource allocation problem by first transforming it into a binary integer programming problem and then formulate a dual problem using the Lagrange duality theory. Numerical results show that the proposed algorithm outperforms traditional Greedy algorithm in terms of throughput maximization while satisfying QoS requirements, and its performance is close to the optimal design. [ABSTRACT FROM PUBLISHER]

Nowadays, computation is playing an increasingly more important role in the future generation of computer and communication networks, as exemplified by the recent progress in SDN for wired networks as well as C-RAN and mobile cloud computing (MCC) for wireless networks. This article proposes a unified concept (i.e., computation diversity) to describe the impact and diverse forms of the computation resources on both wired and wireless communications. By linking the computation resources to the communication networks based on quality of service requirements, we can show how computation resources influence the networks. Moreover, by analyzing the different functionalities of computation resources in SDN, C-RAN, and MCC, we can show the diverse and flexible forms that the computation resources present in different networks. The study of computation diversity can provide guidance in future networks design as far as how to allocate the resources jointly between computation (e.g., CPU capacity) and communication (e.g., bandwidth), thereby saving system energy and improving users' experiences. [ABSTRACT FROM PUBLISHER]

A smart utility network (SUN), as defined in the IEEE 802.15.4g standard, is an emerging technology enabling reliable data transmissions in smart grid (SG) neighbourhood area networks. However, a SUN operates on unlicensed bands that are overlapped with most of the channels of wireless local area networks (WLANs). Thus, it is critical to investigate the coexistence issues for SUNs and WLANs in SG. This article aims to propose a dynamic spectrum sharing (DSS) coexistence scheme working with cognitive radio techniques, including the designs of network topology and channel detection/allocation schemes. We also establish Markov chain models based on channel state transitions for the proposed schemes, which are used to analyze network performance from the viewpoint of SUN services. The analytical results show that a channel reservation strategy is critical to ensure satisfactory performance of SUNs. [ABSTRACT FROM AUTHOR]

This letter studies power allocation for simultaneous wireless information and power transfer in downlink coordinated multipoint (CoMP) systems. A central unit (CU) conveys data and channel information to multiple radio remote units (RRUs) via a capacity-limited backhaul. We provide a dual polarized (DP) antenna-based double side signal splitting method. Specifically, signals are split up into information decoding part [user equipment (UE) data transmitted from CU] and energy harvesting part (deterministic data created at RRUs), which are transmitted and received via vertical and horizontal polarizations of DP antennas, respectively. Normal beamformers (such as zero forcing and maximum ratio transmission) are used to reduce complexity. The problem is to maximize the sum rate satisfying per-UE received power, per-backhaul-link capacity, and per-RRU power transmission constraints. The results are provided to verify the effectiveness of the proposed scheme. [ABSTRACT FROM PUBLISHER]

This paper aims to analyze coexistence performance and study the impact of WLAN interferences on SUNs. To quantitatively reveal packet error rate (PER) performance of SUNs under multiple WLAN interferers, a segmentation scheme for desired data packet with multiple interferers is developed, based on which a packet collision model in a multi-interferer environment is proposed. The new packet collision model captures interference scenarios in every time segment of a desired packet using the proposed segmentation scheme. It paves a way to make a precise estimation of the PER of SUNs under multiple WLAN interferers. Furthermore, we design a channel agility scheme for coexistence of SUNs and WLANs via improving the existing ones, and analyze its performance in interference identification and avoidance. The proposed scheme performs interference detection for every data packet, and thus, an SUN is able to avoid WLANs interferences in a timely manner. [ABSTRACT FROM PUBLISHER]

Mobile cloud computing (MCC) can significantly improve the processing/storage capacity and standby time of mobile terminals by migrating data processing and storage to the remote cloud. However, due to the wireless resource limitations of access points/base stations, data streaming of MCC suffers poor quality-of-service (QoS) in multiuser multiservice scenarios, such as long buffering time and intermittent disruptions. In this paper, we propose a backoff-based wireless resource scheduling (BWRS) scheme, in which real-time services have higher priority than non-real-time services. BWRS can improve the QoS of real-time streams and the overall performance of MCC networks. We formulate an M/M/1 queueing model and propose a queueing-delay-optimal control algorithm to minimize the average queueing delay of non-real-time services. Furthermore, a delay-constrained control algorithm is developed not only to minimize the queueing delay of non-real-time services of multiservice users but to support users' non-real-time services under delay constraints as well. The simulation results show that the proposed scheme can minimize the average queueing delay while still meeting the delay requirement and can significantly improve blocking probability and channel utilization. [ABSTRACT FROM PUBLISHER]

Due to the popularity of mobile user devices, D2D communications become a key technology to improve local services in the next generation cellular networks. However, the benefits count on efficient radio resource allocation between cellular links and D2D links, which poses critical challenges. By exploiting the network knowledge extracted from underlying mobile social networks (MSNs), this article proposes a socially aware D2D communication scheme to improve the spectrum and energy efficiency in cellular networks. First, by jointly considering the social and network knowledge, we propose a cluster formation scheme to categorize a group of UEs into multiple D2D clusters. Within each cluster, highly spectrum-efficient D2D multicasting (from the cluster head, i.e., a D2D transmitter UE to multiple cluster member UEs) is enabled. Next, a half-duplex scheme and a full-duplex scheme are proposed to coordinate the channel sharing between the cellular links and the D2D links. Simulation results show that the proposed schemes can form D2D clusters rationally among a group of UEs, and therefore largely increase the spectrum and energy efficiency of the network. [ABSTRACT FROM PUBLISHER]

Smart metering utility network (SUN) is an emerging wireless technology for achieving intelligent control and information transfer in smart grid applications. However, the operation of SUNs on unlicensed bands is very sensitive to external interferences generated from other networks working on the same spectrum bands, such as wireless local area networks (WLANs). This paper aims to analyze packet error rate (PER) performance of a victim SUN receiver under the interferences of one or more WLAN transmitting nodes. To deal with a scenario leveraged by multiple random variables, such as offset between desired SUN data packet and WLAN packet, duration of WLAN data packet, and time interval between two consecutive WLAN packets, we propose a segmented packet collision model with the help of the probability theory. We first divide all the packets into small segments and then calculate the collision probability of each segment to acquire a more accurate bit error rate (BER). Then, based on different BERs in distinct segments of the desired SUN packet, average PER of the victim SUN receiver is obtained. Finally, the proposed analytical model is validated by simulations as an effort to evaluate PER performance of a SUN receiver under the WLAN interferences. [ABSTRACT FROM PUBLISHER]

Wireless information and power transfer (WIPT) enables more sustainable and resilient communications due to the fact that it avoids frequent battery charging and replacement. However, it also suffers from possible information interception due to the open nature of wireless channels. Compared to traditional secure communications, secrecy wireless information and power transfer (SWIPT) has several distinct characteristic features. Wireless power transfer may increase vulnerability to eavesdropping, since a power receiver as a potential eavesdropper usually has a shorter access distance than an information receiver. On the other hand, wireless power transfer can be exploited to enhance wireless security. This article reviews the security issues in various SWIPT scenarios, with an emphasis on revealing the challenges and opportunities for implementing SWIPT. Furthermore, we provide a survey on a variety of physical layer security techniques to improve secrecy performance. In particular, we propose to use massive MIMO techniques to enhance power transfer efficiency and secure information transmission simultaneously. Finally, we discuss several potential research directions to further enhance the security in SWIPT systems. [ABSTRACT FROM PUBLISHER]

Bit-interleaved coded modulation (BICM) has been widely used in capacity-achieving communication systems. In this paper, we propose an enhanced BICM, namely, arithmetic-BICM (A-BICM), which is able to achieve high channel throughput and seamless rate adaptation in time-varying wireless channels. The A-BICM generates modulation symbols through arithmetic weighted sum operations, and it adapts to data rate via adjusting the number of transmitted symbols. Our contributions in the design of A-BICM are twofold. First, we use an extrinsic information transfer chart to analyze a demapping procedure, and this facilitates the selection of the weighting multiset, which is a key design parameter in A-BICM mapping. Second, we employ a systematic channel code in A-BICM and design an adaptation scheme to strike a balance between the performances in both high- and low-SNR regions. Simulation results show that the A-BICM outperforms the conventional BICM with length-864 low-density parity check coding in both additive white Gaussian noise and fading channels. The experiments in real WLAN environments reveal that A-BICM achieves 42.1% and 20.9% throughput gain over conventional BICM and hybrid automatic repeat request rate adaptation schemes. Furthermore, the channel coding rate and its constellation in A-BICM do not need to change within a fairly wide SNR region from 1 to 30 dB to reduce communication overhead. [ABSTRACT FROM PUBLISHER]

With the growing popularity of mobile Internet, providing secure wireless services has become a critical issue. Physical layer security (PHY-security) has been recognized as an effective means to enhance wireless security by exploiting wireless medium characteristics, for example, fading, noise, and interference. A particularly interesting PHY-security technology is cooperative relay due to the fact that it helps to provide distributed diversity and shorten access distance. This article offers a tutorial on various multi-antenna relaying technologies to improve security at physical layer. The state-of-the-art research results on multi-antenna relay aided PHY-security as well as some secrecy performance optimization schemes are presented. In particular, we focus on large-scale MIMO relaying technology, which is effective in tackling various challenging issues for implementing wireless PHY-security, such as short-distance interception without eavesdropper CSI and with imperfect legitimate CSI. Moreover, the future directions are identified for further enhancement of secrecy performance. [ABSTRACT FROM AUTHOR]

This paper proposes a framework to construct 3-D complementary codes (3DCCs), which enable chip-level space–time coding to integrate multiantenna and multiple-access techniques in a unified platform. The 3DCCs are generated based on an extension method with the help of traditional complementary codes and well-designed matrices. The relationship between the correlation properties and flock size of the constructed 3DCCs is analyzed, and the proposed framework provides a generic way to construct different families of 3DCCs with a controllable tradeoff between their correlation properties and flock sizes. As examples, three families of 3DCCs with different characteristic features are constructed using the framework, and their correlation properties are simulated to validate their properties. The general architecture of the 3DCC-based multiple-input multiple-output (MIMO) system is also proposed in this paper. The simulated bit-error-rate (BER) performance of the corresponding system over both flat and multipath fading channels show that the constructed 3DCCs can eliminate both multiuser and multipath interferences in multiuser MIMO communications. The property to provide both transmit diversity and multiplexing with its uniquely flexible tradeoff between the two also makes it particularly well suited for futuristic wireless communications to fit to varying channel conditions and application requirements. [ABSTRACT FROM PUBLISHER]

Cognitive radio (CR) is a critical technology for improving spectrum utilization and solving the radio spectrum scarcity problem. In CR devices, spectrum sensing is important to implement opportunistic spectrum access. Many spectrum sensing schemes have been proposed, including uncooperative, cooperative, centralized, and distributed algorithms. However, they aimed to obtain a global consensus sensing result, which may not always be possible in large-scale cognitive radio networks (CRNs) due to heterogeneous spectrum availability in different areas. Hence, some new spectrum sensing schemes should be designed to discover idle heterogeneous spectrum in CRNs. In this paper, we propose an intelligent cooperative spectrum sensing algorithm based on a non-parametric Bayesian learning model, namely the hierarchical Dirichlet process, which groups spectrum sensing data without the need to know the number of hidden spectrum states, and discovers a common sparse spectrum within each group. Furthermore, a concisely distributed information exchange scheme is designed, where intra-cluster and inter-cluster spectrum information is shared for global spectrum cognition. Experimental results show that the proposed algorithm can exploit the spatial relationship among sensed data to achieve a better spectrum sensing performance in terms of detection probability and false alarm probability. [ABSTRACT FROM AUTHOR]

This article reviews an emerging wireless information and power transfer (WIPT) technique with an emphasis on its performance enhancement employing multi-antenna techniques. Compared to traditional wireless information transmission, WIPT faces numerous challenges. First, it is more susceptible to channel fading and path loss, resulting in a much shorter power transfer distance. Second, it gives rise to the issue of how to balance spectral efficiency for information transmission and energy efficiency for power transfer in order to obtain an optimal tradeoff. Third, there exists a security issue for information transmission in order to improve power transfer efficiency. In this context, multi-antenna techniques, e.g. energy beamforming, are introduced to solve these problems by exploiting spatial degree of freedom. This article provides a tutorial on various aspects of multi-antenna based WIPT techniques, with a focus on tackling the challenges by parameter optimization and protocol design. In particular, we investigate the WIPT tradeoffs based on two typical multi-antenna techniques: the limited feedback multi-antenna technique for short-distance transfer; and the large-scale multiple-input multiple-output (LS-MIMO, also known as massive MIMO) technique for long-distance transfer. Finally, simulation results validate the effectiveness of the proposed schemes. [ABSTRACT FROM PUBLISHER]

Complete complementary codes (CCC) refer to a set of two-dimensional matrices, which have zero non-trivial aperiodic auto- and cross- correlation sums. A modern application of CCC is in interference-free multicarrier code-division multiple-access (MC-CDMA) communications. In this paper, we first show that in asynchronous “fractional-delay” uplink channels, CCC-MC-CDMA systems suffer from orthogonality loss, which may lead to huge interference increase when a conventional correlator based receiver is deployed. Then, by exploiting the correlation properties of CCC, we present a fractional-delay-resilient receiver which is comprised of a chip-spaced correlating array. Analysis and simulations validate the interference-free achievability of the proposed CSCA receiver in strong interference scenarios. [ABSTRACT FROM PUBLISHER]

Smart grid is an intelligent power network featured by its two-way flows of electricity and information. With an integrated communication infrastructure, smart grid manages the operation of all connected components to provide reliable and sustainable electricity supplies. Many advanced communication technologies have been identified for their applications in different domains of smart grid networks. This paper focuses on wireless communication networking technologies for smart grid neighborhood area networks (NANs). In particular, we aim to offer a comprehensive survey to address various important issues on implementation of smart grid NANs, including network topology, gateway deployment, routing algorithms, and security. We will identify four major challenges for the implementation of NANs, including timeliness management, security assurance, compatibility design, and cognitive spectrum access, based on which the future research directions are suggested. [ABSTRACT FROM PUBLISHER]

Traditional \alpha-fairness resource allocation in wireless multimedia communications assumes that the quality of experience (QoE) model (or utility function) of each user is available to the base station (BS), which may not be valid in many practical cases. In this paper, we consider a blind scenario where the BS has no knowledge of the underlying QoE model. Generally, this consideration raises two fundamental questions. Is it possible to set the fairness parameter \alpha in a precisely mathematical manner? If so, is it possible to implement a specific \alpha-fairness resource allocation scheme online? In this work, we will give positive answers to both questions. First, we characterize the tradeoff between the performance and fairness by providing an upper bound of the performance loss resulting from employing \alpha-fairness scheme. Then, we decompose the \alpha-fairness problem into two subproblems that describe the behaviors of the users and BS and design a bidding game for the reconciliation between the two subproblems. We demonstrate that, although all users behave selfishly, the equilibrium point of the game can realize the \alpha-fairness efficiently, and the convergence time is reasonably short. Furthermore, we present numerical simulation results that confirm the validity of the analytical results. [ABSTRACT FROM PUBLISHER]

Device-to-device (D2D) communications help improve the performance of wireless multicast services in cellular networks via cooperative retransmissions among multicast recipients within a cluster. Resource utilization efficiency should be taken into account in the design of D2D communication systems. To maximize resource efficiency of D2D retransmissions, there is a tradeoff between multichannel diversity and multicast gain. In this paper, by analyzing the relationship between the number of relays and minimal time-frequency resource cost on retransmissions, we derive a closed-form probability density function (pdf) for an optimal number of D2D relays. Motivated by the analysis, we then propose an intracluster D2D retransmission scheme with optimized resource utilization, which can adaptively select the number of cooperative relays performing multicast retransmissions and give an iterative subcluster partition algorithm to enhance retransmission throughput. Exploiting both multichannel diversity and multicast gain, the proposed scheme achieves a significant gain in terms of resource utilization if compared with its counterparts with a fixed number of relays. [ABSTRACT FROM PUBLISHER]

The necessity to promote smart grid (SG) has been recognized with a strong consensus. The SG integrates electrical grids and communication infrastructures and forms an intelligent electricity network working with all connected components to deliver sustainable electricity supplies. Many advanced communication technologies have been identified for SG applications with a potential to significantly enhance the overall efficiency of power grids. In this paper, the challenges and applications of communication technologies in SG are discussed. In particular, we identify three major challenges to implement SG communication systems, including standards interoperability, cognitive access to unlicensed radio spectra, and cyber security. The issues to implement SG communications on an evolutional path and its future trends are also addressed. The aim of this paper is to offer a comprehensive review of state-of-the-art researches on SG communications. [ABSTRACT FROM PUBLISHER]

Code-hopping multiple access (CHMA) is a newly emerging multiple-access technique with the potential to offer high capacity. Unfortunately, orthogonality among user signals in existing CHMA schemes can be preserved only in synchronous channels under an assumption that neither multipath interference (MI) nor multiple-access interference (MAI) exists. Exploiting their ideal orthogonality, we apply orthogonal complementary codes to CHMA systems to overcome problems with existing CHMA schemes. In particular, we will show that the application of orthogonal complementary codes can significantly improve the performance of a CHMA system due to its unique collision-resistant capability. To deal with destructive collisions among spreading codes in CHMA systems, convolutional coding is employed in complementary-coded CHMA systems. The properties and bit error rate (BER) performance of the proposed system are analyzed for both uplink and downlink applications, where the system may simultaneously suffer MI and MAI. Simulation results show that the complementary-coded CHMA with channel coding can provide much higher capacity than complementary-coded code-division multiple access (CDMA) systems in varying operational scenarios. [ABSTRACT FROM PUBLISHER]

Orthogonal frequency division multiplexing (OFDM) technique has been widely used in high data rate wireless applications, but it suffers performance degradation at low signal-to-noise (SNR) regions due to the impairments caused by noise-induced channel estimation errors. In this article, we propose to use frequency-shift (FRESH) filtering technique to exploit temporal and spectral correlation of the OFDM signals for noise reduction purpose. A closed form time-varying minimum mean squared error (MMSE) expression has been derived to analyze the performance of FRESH filtering under additive white Gaussian noise (AWGN) and Rayleigh fading channels. The MMSE analysis carried out here can be a reference for the design of practical OFDM systems. In addition, theoretical SNR is analyzed in this article to show the performance gain achieved by FRESH filtering. The numerical results verify that the maximum SNR improvements offered by FRESH filtering are over 0.6 dB and 1.6 dB under AWGN and Rayleigh fading channels, respectively. [ABSTRACT FROM PUBLISHER]

Dear readers, Time flies! The holiday season comes again. It is time for us to prepare for the annual celebration of Christmas and the New Year. Therefore, I would like to take this wonderful opportunity to send my warmest greetings to all of you. In particular, I would like to send my best wishes to all Editorial Board members, who have worked extremely hard to handle the reviews of submissions for this magazine. My greetings should also go to the publications staff of IEEE Communications Society for their great help to the magazine in publishing papers in a timely manner. [ABSTRACT FROM PUBLISHER]

The widespread availability and demand for multimedia capable devices and multimedia content have fueled the need for high-speed wireless connectivity beyond the capabilities of existing commercial standards. While fiber optic data transfer links can provide multigigabit- per-second data rates, cost and deployment are often prohibitive in many applications. Wireless links, on the contrary, can provide a cost-effective fiber alternative to interconnect the outlining areas beyond the reach of the fiber rollout. With this in mind, the ever increasing demand for multi-gigabit wireless applications, fiber segment replacement mobile backhauling and aggregation, and covering the last mile have posed enormous challenges for next generation wireless technologies. In particular, the unbalanced temporal and geographical variations of spectrum usage along with the rapid proliferation of bandwidth- hungry mobile applications, such as video streaming with high definition television (HDTV) and ultra-high definition video (UHDV), have inspired millimeter-wave (mmWave) communications as a promising technology to alleviate the pressure of scarce spectrum resources for fifth generation (5G) mobile broadband. [ABSTRACT FROM PUBLISHER]

Dear Readers, Based on the most recent "Journal Citation Reports (JCR)," which was just released by Thomson Reuters "ISI Web of Knowledge" in July 2014, IEEE Wireless Communications has been ranked as the number one publication (in terms of its Impact Factor, IF) in all three of the following important publication categories: · Engineering, Electrical & Electronic (247 publications) · Telecommunications (78 publications) · Computer Science, Hardware & Architecture (50 publications). [ABSTRACT FROM PUBLISHER]

Dear readers, First of all, I am very pleased to announce that the IEEE Communications Society has recently appointed a new Associate Editor-in-Chief for IEEE Wireless Communications, Dr. Hamid Gharavi, National Institute of Standards and Technology (NIST), United States, who has been working in wireless communications in both industry and academia for a long time. Dr. Gharavi served as the Editor-in-Chief for IEEE Transactions on CAS for Video Technology from 1996 to 2006, and thus has rich experience working on IEEE publications. Dr. Gharavi received the Charles Babbage Premium Award from the Institute of Electronics and Radio Engineering in 1986 and the IEEE CAS Society Darlington Best Paper Award in 1989. He served as a Distinguished Lecturer of the IEEE Communication Society. In 1992 Dr. Gharavi was elected as a Fellow of IEEE for his contributions to low-bit-rate video coding and research in subband coding for image and video applications. Currently, Dr. Gharavi is leading a research group working extensively on smart grid communications in NIST. Upon the appointment of Dr. Hamid Gharavi as Associate Editor-in-Chief of IEEE Wireless Communications, I believe that he will contribute to bring the magazine to a new and higher level. For more information about Dr. Hamid Gharavi, please refer to his statement following this Editor's Note. [ABSTRACT FROM PUBLISHER]

The papers in this special section focus on the topic of smart grids. Smart Grids are an essential component of future energy systems, which are characterized by distributed, volatile energy production (solar, wind) and entirely new components (electric vehicles) and operation concepts (virtual power plants). Smart Grids are also a prominent example of Cyber Physical Systems, as they combine wide-area control, computation, and communications. While traditional automation of the power grid makes use of wireline communications (copper, fiber), Smart Grids require wide-area coverage with flexible, cost-efficient, but also very reliable communications networks. Therefore, wireless communication technologies will play an increasingly important role in future deployment scenarios. The investigated options range from cellular networks over satellite systems to wireless mesh networks. Also, the ongoing discussion of future 5G systems is driven by the requirements of Smart Grids as one major use case. Particular challenges for wireless communication options include availability, real-time capabilities for incident mitigation, and resilience. The performance evaluation of Smart Grids calls for new methods, such as the interdisciplinary hybrid simulation of energy and communication networks. [ABSTRACT FROM PUBLISHER]

In the September 2014 issue of IEEE Communications Magazine, the first part of this Feature Topic included five articles that covered the fundamentals of mmWave communications with topics ranging from propagation to coverage, presenting a holistic view of research challenges and opportunities in the emerging area of mmWave radio systems and 5G mobile broadband. The use of this technology is expected to surge in the next few years and to transform the Internet industry in the next 10 years. This part of the Feature Topic will address in more detail many technical and application issues related to beamforming, device-to-device communications, heterogeneous networks, and multimedia transmission. [ABSTRACT FROM PUBLISHER]

Dear readers, This is the second issue of 2014, and I hope that all of you are already enjoying the spring season of the year. [ABSTRACT FROM PUBLISHER]

With the proliferation of mobile devices and the popularity of mobile multimedia applications, systematic research of the overall aspects of security in mobile multimedia communications is crucial. The emerging mobile wireless multimedia communications can be used for various pervasive and ubiquitous applications in consumers, businesses, and government agencies. Besides the consumer cellular systems and residential homes, mobile devices are being rapidly integrated into enterprises with the increase in bring-your-own-device (BYOD) in many organizations. As mobile multimedia communications become more popular in both the consumer and business markets, the need for tighter security is inevitable. [ABSTRACT FROM PUBLISHER]

Smart grid is a term referring to the next generation power grid in which electricity distribution and management is upgraded by incorporating advanced two-way digital technology and communication capabilities for improved control, efficiency, reliability, and safety. A communication infrastructure is an essential part of the success of the emerging smart grid. A scalable and pervasive communication infrastructure is crucial in both the construction and operation of a smart grid. To ensure the correct functioning of a smart grid, it is essential that communications are secured, devices are protected from physical attack, and privacy is respected. Communications require authentication and confidentiality, devices require protection from physical attacks, and the system as a whole must be robust. Authorization will be vital to support secure remote configuration and multihoming scenarios. The privacy of smart grid customers needs to be protected. [ABSTRACT FROM PUBLISHER]

Smart grid is a term referring to the next generation power grid in which the electricity distribution and management is upgraded by incorporating advanced twoway digital technology and communication capabilities for improved control, efficiency, reliability, and safety. A communication infrastructure is an essential part in the success of the emerging smart grid. A scalable and pervasive communication infrastructure is crucial in both construction and operation of a smart grid. To ensure the correct functioning of a smart grid, it is essential that communications are secured, devices are protected from physical attack, and privacy is respected. Communications require authentication and confidentiality, devices require protection from physical attacks, and the system as a whole must be robust. Authorization will be vital to support secure remote configuration and multihoming scenarios. The privacy of smart grid customers must be protected. [ABSTRACT FROM PUBLISHER]