IET Communications
Volume 14, Issue 19, 01 December 2020
Volumes & issues:
Volume 14, Issue 19
01 December 2020
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- Author(s): Xiang Cheng ; Ziwei Huang ; Shanzhi Chen
- Source: IET Communications, Volume 14, Issue 19, p. 3303 –3311
- DOI: 10.1049/iet-com.2020.0531
- Type: Article
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As vehicular communications for beyond fifth-generation (B5G) and sixth-generation (6G) is picking up interests from academia and industry recently, more and more research and development have been devoted towards the establishment of vehicular communications for B5G and 6G that is capable of supporting the ever more intelligent transportation systems. One key facilitating the design and improvement of vehicular communications for B5G and 6G is channel modelling, which is widely regarded as the foundation of all communication and networking systems. In this paper, the authors focus on the research and analysis of B5G and 6G vehicular channel measurements and modelling. By emphasising the new requirements and challenges that the emerging B5G and 6G technologies and frequency bands bring to vehicular communication channel measurements and modelling, they present an overview of the existing work and identify the limitations therein, and provide guidelines on the channel model development and adoption for various system development and verification objectives. Finally, future challenges related to vehicular channel measurements, modelling, and their application for B5G and 6G are addressed.
Vehicular communication channel measurement, modelling, and application for beyond 5G and 6G
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- Author(s): Anees Al-Najjar ; Furqan Hameed Khan ; Marius Portmann
- Source: IET Communications, Volume 14, Issue 19, p. 3312 –3323
- DOI: 10.1049/iet-com.2020.0335
- Type: Article
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Software-defined networking (SDN) is an emerging technology of efficiently controlling and managing computer networks, such as in data centres, wide-area networks, as well as in ubiquitous communication. In this study, the authors explore the idea of embedding the SDN components, represented by SDN controller and virtual switch, in end-hosts to improve network performance. In particular, the authors consider load balancing across multiple network interfaces on end-hosts with different link capacity scenarios. The authors have explored and implemented different SDN-based load-balancing approaches based on OpenFlow software switches, and have demonstrated the feasibility and the potential of this approach. The proposed system has been evaluated with MultiPath transmission control protocol (MPTCP). The proposed results demonstrated the potential of applying the SDN concepts on multi-homed devices resulting in an increase in achieved throughput of 55% compared to the legacy single network approach and 10% compared to the MPTCP.
- Author(s): Xiang Liu ; Jie Huang ; Yiyang Yao ; Chunyang Qi ; Guowen Zong
- Source: IET Communications, Volume 14, Issue 19, p. 3324 –3333
- DOI: 10.1049/iet-com.2019.1372
- Type: Article
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Network coding is a promising technique to improve the throughput and robustness of wireless ad hoc networks. However, the packet-mixing nature of network coding also renders it more prone to pollution attacks. Most existing schemes to combat pollution attacks did not consider the defender's resource limit, nor the trade-off between defensive performance and other metrics such as delay and resource consumption. The authors investigate how to achieve such a trade-off optimally by proposing a two-player strategic game model between the attack and the defender. In this model, the utilities of both players are well defined, and thus the defender can obtain its best strategy by maximising its utility. To do so, a graph-based simulated annealing algorithm is proposed to derive the utility-maximising strategy. Finally, they conduct extensive experiments to evaluate their scheme from different aspects. The results show that their scheme can achieve better utility than existing schemes, and is more computationally efficient in the meanwhile. Moreover, their scheme can obtain a sub-optimal solution within a small number of iterations, which implies that it can be implemented in the short-session communication scenario where it is required to find a sufficiently good solution within a short time.
- Author(s): Arti M.K. ; Pratibha Rani ; Pradeep Kumar Dimri ; Munish Vashishath
- Source: IET Communications, Volume 14, Issue 19, p. 3334 –3339
- DOI: 10.1049/iet-com.2019.0762
- Type: Article
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A beamforming and combining method for a multi-user large multiple-input multiple-output (MIMO) system is proposed, in this study. A transmitter is equipped with a very large number of antennas to serve many users. At the transmitter, a group of antennas is allocated to each user. For a particular group of antennas, a specific beamforming vector is employed at the transmitter for transmission of a signal of a specific user. At the user end, a distinct combining vector is utilised for detecting the transmitted signal. In the proposed scheme, first, the interference due to unwanted signals of undesired users is nullified by using the concept of null space. Then the method of maximum ratio transmission is used to calculate the beamforming vector. The calculation of combining vector depends upon the maximum eigenvalue criterion. The analytical performance of the proposed method is discussed in terms of symbol error rate (SER). An expression of SER is derived by using the moment generating function approach. It is shown by simulations and analysis that the proposed scheme performs better if more antennas are equipped either at the transmitter or users.
- Author(s): Juan Zhou ; Ying Shen ; Li Li ; Ya-Juan Xue
- Source: IET Communications, Volume 14, Issue 19, p. 3340 –3349
- DOI: 10.1049/iet-com.2020.0263
- Type: Article
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In orthogonal frequency-division multiplexing (OFDM)-based full-duplex (FD) systems, the terminal is allowed to transmit and receive signals simultaneously in the same frequency band. This leads to new challenges to pilot for channel estimation. The conventional pilot design methods are no longer effective for such systems. In this study, the authors propose a new practical pilot design method for OFDM-based FD systems and its performance is analysed in terms of the self-interference cancellation capability. Unlike the existing OFDM-based FD pilot design schemes, which require the channel to be constant during multiple continuous OFDM symbols, the authors' proposed scheme can be implemented in the block fading channel (i.e. channels that vary from one OFDM symbol to another). Besides, the optimal pilot pattern of the proposed scheme is studied. Their simulation results demonstrate the efficiency of the proposed pilot design.
- Author(s): Apoorva ; Sainath Bitragunta ; Sumukh Nitundil
- Source: IET Communications, Volume 14, Issue 19, p. 3350 –3362
- DOI: 10.1049/iet-com.2020.0515
- Type: Article
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Free space optical (FSO) inter-satellite links could often be non-reliable due to the imperfect line of sight (LOS) links. To achieve more reliable communication, the authors propose hybrid inter-satellite links. However, this leads to new challenges like switching physical (PHY) layers at the satellite's transmitter. In this work, they propose a novel hybrid radio frequency-FSO (RF/FSO) satellite system. For it, they develop a novel best beam selection policy (BBSP) and switching of FSO and RF to improve the reliability of the inter-satellite links. To obtain more insights, they investigate the performance of BBSP by deriving expressions for the outage probability, average spectral efficiency, and average bit error rate of the BBSP. For the PHY switching, they compare the instantaneous error probabilities of RF and FSO links and find the signal-to-noise ratio threshold at which it is more efficient to switch to RF. They further improve this threshold by considering a satellite transmitting multiple beams and choosing the best source beam. To validate the analytical findings, they simulate the proposed model with CubeSat level parameters. They and that the BBSP delivers superior performance in terms of various performance measures, which shows its applicability in next-generation satellite systems.
- Author(s): Malvern Chamisa ; Fambirai Takawira ; Jules M. Moualeu
- Source: IET Communications, Volume 14, Issue 19, p. 3363 –3372
- DOI: 10.1049/iet-com.2020.0157
- Type: Article
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This study investigates the performance of a cooperative non-orthogonal multiple access cognitive network with imperfect successive interference cancellation under Rayleigh fading conditions. Specifically, the authors consider an underlay cognitive network that consists of a primary transmitter–receiver pair and a secondary system where a source node communicates with two destinations nodes directly and indirectly through a relay node selected from a set of decode-and-forward relays. A partial relay selection scheme is used to determine the best relay. The authors present an analytical framework, with closed-form analytical expressions for the outage probabilities at the two destinations as well the primary destination. Moreover, to simplify the analysis and to provide further insights into the impact of key system parameters, asymptotic studies of the outage probabilities were carried out. To this end, the authors focus on two cases: (i) the maximum allowable transmit power of the secondary network grows sufficiently large and (ii) the interference power approaches infinity. Finally, Monte Carlo simulations are provided in an effort to assess the accuracy of the proposed mathematical framework.
- Author(s): Dong-Nhat Nguyen ; Jan Bohata ; Stanislav Zvanovec ; Lim Nguyen ; Zabih Ghassemlooy
- Source: IET Communications, Volume 14, Issue 19, p. 3373 –3379
- DOI: 10.1049/iet-com.2019.1166
- Type: Article
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The authors propose an integrated Mach–Zehnder interferometer and diversity combining receiver to mitigate the atmospheric turbulence-induced fading in a millimetre-wave (mmW) radio-over-free-space optics (RoFSO) link. They use a carrier frequency of 28 GHz as recommended for the fifth-generation wireless access networks and consider two optical mmW signal generation schemes, namely double-sideband (DSB) and single-sideband (SSB). In direct detection (DD)-based RoFSO, the link performance is limited by atmospheric turbulence. They show that the proposed Rx can overcome this detrimental effect, which is verified by investigation of a 10 Gb/s 16-quadrature amplitude modulation orthogonal frequency-division-multiplexing signal at 28 GHz over a 1 km free-space optics link under weak and strong turbulence regimes. For the DSB scenario, the proposed Rx offers improved error vector magnitudes of about 0.8 and 5.7%, and modulation error ratios of 1.3 and 4.9 dB under weak and strong turbulence regimes, respectively, compared with the DD receiver (DD Rx). For the SSB scenario under weak turbulence, the proposed Rx achieves a 4 dB improvement in the receiver sensitivity and four orders of magnitude enhancement in the bit error rate over the DD Rx. The proposed Rx can be integrated on a single chip for further cost reduction.
- Author(s): Li Yao ; Youjiang Liu ; Jian Zhang ; Yudong He ; Yongtao Qiu ; Dalong Yang ; Tao Cao
- Source: IET Communications, Volume 14, Issue 19, p. 3380 –3387
- DOI: 10.1049/iet-com.2020.0277
- Type: Article
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In this study, the authors proposed the optimal beamforming (BF) design for multiuser broadcast secure transmission under secrecy outage probability constraint with artificial noise technique. Different from former research papers, their model assumes that different users have different priority and importance. Some users are regarded as main users with a stricter constraint, which make the normal BF algorithm not to gain the best performance. For this reason, they proposed a new BF design method for this specific system model. To deal with intractable non-convex problems, they employed a series of optimisation algorithm like Bernstein-type inequality and second-order cone constraints method to transform these problems into solvable functions. After that, they show the feasibility of their new BF algorithm by Monte-Carlo simulation method, and analyse the influence on transmission and security performance caused by different system parameters. Furthermore, they compare the security performance of their method with the normal BF method, which demonstrates the advantage of the new BF method.
- Author(s): Xue Jiang ; Baoyu Zheng ; Wei-Ping Zhu ; Lei Wang ; Yulong Zou
- Source: IET Communications, Volume 14, Issue 19, p. 3388 –3393
- DOI: 10.1049/iet-com.2019.1039
- Type: Article
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Simultaneous wireless information and power transfer (SWIPT) is a promising solution for future wireless networks as it provides convenient and perpetual energy supplies to wireless users. This study proposes three new transceiver design schemes in two-way relay networks with SWIPT. Firstly, a transmit power minimisation solution is proposed with an aim to minimise the transmit power while meeting an energy harvesting requirement. Then, a harvested energy maximisation solution that has the same complexity as the first solution but provides a much better sum harvested energy is proposed. Finally, a signal-to-interference-plus-noise ratio maximisation solution is developed, which gives the best sum-rate performance for the two-way relay networks while ensuring a desired level of energy harvesting. Furthermore, the complexity of the three new transceiver solutions is discussed. Simulation results have demonstrated the effectiveness of the proposed transceiver design schemes in two-way relay networks with SWIPT.
- Author(s): Hamada Esmaiel ; Zeyad A.H. Qasem ; Haixin Sun ; Jie Qi ; Junfeng Wang ; Yaping Gu
- Source: IET Communications, Volume 14, Issue 19, p. 3394 –3403
- DOI: 10.1049/iet-com.2020.0053
- Type: Article
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The acoustic signal transmission over the underwater channel has a limited sum rate and it consumes high power due to the properties of the underwater environment. This study attempts to use the non-orthogonal multiple access (NOMA) technologies for underwater communications. NOMA can be an attractive candidate for underwater communication due to its high spectral efficiency, resistance for carrier frequency offset, and efficient energy consumption. To cope with the hard-recharging capability of the underwater wireless sensor nodes caused by the ocean environment, this study proposes a novel transmission scheme called time-reversed NOMA (TR-NOMA) for underwater communication. In the proposed TR-NOMA, a single-input multiple-output NOMA scheme with a passive-time reversal technique is proposed to reduce the time–frequency dispersion of the underwater acoustic channels. Consequently, simultaneous wireless information and power transfer (SWIPT) can be applied for underwater TR-NOMA. In this study, a SWIPT-NOMA is postposed to harvest energy in downlink transmission from the transmitted signal. The bit error rate (BER) and the outage probability are used to characterise the performance of the proposed TR-NOMA scheme and simulation results show how the proposed TR-NOMA significantly outperforms the conventional NOMA schemes. Additionally, a mathematical framework for the average BER of TR-NOMA is delineated.
- Author(s): Chuyen T. Nguyen ; Quoc-Viet Pham ; Huong-Giang T. Pham ; Nhu-Ngoc Dao ; Won-Joo Hwang
- Source: IET Communications, Volume 14, Issue 19, p. 3404 –3409
- DOI: 10.1049/iet-com.2020.0344
- Type: Article
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The explosive growth of end devices and mobile applications calls for novel schemes that can enable computation-hungry applications at small end-devices and meet the massive connectivity requirement. Cognitive radio (CR), non-orthogonal multiple access (NOMA) and multi-access edge computing (MEC) are envisioned as the key technologies in fifth-generation and beyond. In this work, the authors introduce the concept of CR-NOMA in MEC offloading, where a secondary user (SU) can utilise the spectrum allocated to a primary user (PU) to offload its computation task to the MEC server for remote execution. For the spectrum utilisation, an equation to specify the minimum transmit power that must be allocated to the PU is derived. The authors also develop an algorithm to determine the offloading decision (i.e. offloading or not) and the paired PU (i.e. subcarrier used for computation offloading) for SUs, using one-to-one matching game. Moreover, through numerical simulations, the authors demonstrate the superior performance of the proposed algorithm compared with several baseline schemes.
- Author(s): Getenet Tefera ; Kun She ; Min Chen ; Awais Ahmed
- Source: IET Communications, Volume 14, Issue 19, p. 3410 –3419
- DOI: 10.1049/iet-com.2020.0630
- Type: Article
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Multi-access edge computing (MEC) has attracted much more attention to revolutionising smart communication technologies and Internet of Everything. Nowadays, smart end-user devices are designed to execute sophisticated applications that demand more resources and explosively connected to the global ecosystem. As a result, the backhaul network traffic congestion grows enormously and user quality of experience is compromised as well. To address these challenges, the authors proposed congestion-aware adaptive decentralised computing, caching, and communication framework which can orchestrate the dynamic network environment based on deep reinforcement learning for MEC networks. MEC is a paradigm shift that transforms cloud services and capabilities platform at the edge of ubiquitous radio access networks in close proximity to mobile subscribers. The framework can evolve to perform augmented decision-making capabilities for the upcoming network generation. Hence, the problem is formulated using non-cooperative game theory which is nondeterministic polynomial (NP) hard to solve and the authors show that the game admits a Nash equilibrium. In addition, they have constructed a decentralised adaptive scheduling algorithm to leverage the utility of each smart end-user device. Therefore, their methodical observations using theoretical analysis and simulation results substantiate that the proposed algorithm can achieve ultra-low latency, enhanced storage capability, low energy consumption, and scalable than the baseline scheme.
- Author(s): Jie Zhou ; Zhen Chen ; Hao Jiang ; Hisakazu Kikuchi
- Source: IET Communications, Volume 14, Issue 19, p. 3420 –3427
- DOI: 10.1049/iet-com.2018.6010
- Type: Article
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This study presents a multiple-input multiple-output (MIMO) statistical channel model for vehicle-to-vehicle (V2V) line-of-sight (LOS) and non-LOS mobile communication system in a rectangular tunnel environment. In order to improve the V2V communication system performance, the authors introduced the elevation and azimuth angles in three-dimensional modelling based on the original literature. In the proposed reference channel model, the single-bounced scattering propagation path of electromagnetic signals is considered and it is assumed that the scatterers are randomly distributed on the rectangular tunnel wall. Starting from the statistical physical channel model, the time-variant transfer functions are derived. Thereafter, the analytical expressions of the space–time–frequency cross-correlation function, the space cross-correlation function, the temporal autocorrelation function, the frequency correlation function, and MIMO channel capacity are derived. The influence of model parameters on the performance of the V2V communication system is also analysed. This work provides an innovative approach to channel modelling in a rectangular tunnel mobile communication environment.
- Author(s): Mai Kafafy and Yasmine Fahmy
- Source: IET Communications, Volume 14, Issue 19, p. 3428 –3439
- DOI: 10.1049/iet-com.2020.0244
- Type: Article
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Optimising the coding bit-rates and activity rates of sensor nodes is essential for the functionality and survival of wireless sensor networks as these rates not only affect the amount of information collected by the network, but also affect its power consumption. This study proposes a framework for joint coding bit-rates and activity rates optimisation (CARO) of sensor nodes in wireless visual sensor networks under limited energy constraints. The framework uses the concept of accumulative visual information (AVI) as a measure of the amount of visual information collected from a sensor node. The authors propose two optimisation algorithms for the following two cases: (I) networks with predetermined operation time, where algorithm CARO I maximises the AVI of the network over its predetermined operation time. (II) Best effort networks, where algorithm CARO II maximises the network operation time under constraints on the collected visual information. Simulations show that optimising the rates using CARO maximises the AVI of the network and extends its operation time compared to the straightforward solution when all nodes have equal activity rates. This is because the authors' framework takes into consideration that different nodes in different locations may operate under different conditions and collect information of different significance.
- Author(s): Kardes Aslan and Tansal Gucluoglu
- Source: IET Communications, Volume 14, Issue 19, p. 3440 –3447
- DOI: 10.1049/iet-com.2020.0475
- Type: Article
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Mathematical analyses of wireless systems mostly consider fading and exclude the effect of shadowing since the derivation of performance metrics usually becomes extremely difficult. However, shadowing has to be studied to get better insights about the practical realisations. Therefore, generalised-K distribution has been widely used recently to model the impact of both fading and shadowing. In this study, the performance of popular maximal ratio transmission, which is a practical multiple antenna technique, is obtained for generalised-K fading channels. Particularly, outage probability, average channel capacity and symbol error rate expressions are derived and verified by computer simulations.
- Author(s): Amarjit Malhotra ; Sanjay K. Dhurandher ; Megha Gupta ; Bijendra Kumar
- Source: IET Communications, Volume 14, Issue 19, p. 3448 –3457
- DOI: 10.1049/iet-com.2019.1234
- Type: Article
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Growing urbanisation has lead to the concept of smart cities. The idea of smart city is realised with the help of internet of things (IoT) devices. The existing cloud services lack the potential to meet the peculiar requirements of IoT devices. IoT devices generate a huge amount of data and demand quick response time. Fog computing can be used to process the IoT tasks since fog nodes are comparatively closer to the IoT devices. The fog node selection for prospective IoT tasks is a multiple-criteria decision-making problem due to the diversity in the IoT requirements and the presence of a number of heterogeneous fog nodes in the smart city. However, there is no study that focused on the fog node selection mechanism keeping in view the user preferences, user requirements (URs), and optimised resource usage. This study presents the best fit-power weighted difference (BF-PWD) method for fog node selection that is used to rank and subsequently select the fog nodes for task offloading from IoT devices. The simulation results show that the proposed technique BF-PWD not only improves the success rate but also reduces the communication latency and the UR violations compared to the existing protocols.
- Author(s): Junliang Lin ; Gongpu Wang ; Rongfei Fan ; Yulong Zou ; Theodoros A. Tsiftsis ; Chintha Tellambura
- Source: IET Communications, Volume 14, Issue 19, p. 3458 –3463
- DOI: 10.1049/iet-com.2020.0372
- Type: Article
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In this6study, the channel estimation problem is investigated for a wireless communication system assisted by a reconfigurable intelligent surface (RIS). The RIS thus creates an assistant channel, which has the features of positivity and dominance. Owing to these features, the channel estimation problem is formulated as a constrained residual sum of squares minimisation problem, which differs radically from the traditional channel estimation issue. An efficient Lagrange multiplier and dual ascent-based estimation scheme is then designed to obtain an iterative solution for the estimator. Moreover, the Cramér–Rao lower bounds are deduced as a performance benchmark. Simulation results show that the authors' designed scheme improves the estimation accuracy up to 33%, compared with the conventional least-square method in the low signal-to-noise ratio regime.
- Author(s): Raghavendra Pal ; Nishu Gupta ; Arun Prakash ; Rajeev Tripathi ; Joel J. P. C. Rodrigues
- Source: IET Communications, Volume 14, Issue 19, p. 3464 –3471
- DOI: 10.1049/iet-com.2020.0451
- Type: Article
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Channel selection is a challenging task in cognitive radio vehicular networks. Vehicles have to sense the channels periodically. Due to this, a lot of time is wasted which could have been utilised for transmission of data. Employing road side units (RSUs) in sensing can prove to be useful for this purpose. The RSUs may select the channel and allocate it to the vehicles on demand. However, this sensing should be proactive. RSUs should know in advance the channel to be allocated when requested. For this purpose, a deep reinforcement learning algorithm namely deep reinforcement learning based optimal channel selection is proposed in this study for training the network according to the previously sensed data. Proposed protocol is simulated and results are compared with the existing methods. The packet delivery ratio is increased by 2%, throughput is increased by 1.8%, average delay is decreased by 2% and primary user collision ratio is reduced by 3.2% when compared with similar recent work by varying number of vehicles. On the other hand, when compared with similar recent work by varying channel availability, the packet delivery ratio is increased by 4.5 %, throughput by 4.3%, average delay is decreased by 3% and PU collision ratio by 5.5%.
- Author(s): Mohammad Torabi and David Haccoun
- Source: IET Communications, Volume 14, Issue 19, p. 3472 –3479
- DOI: 10.1049/iet-com.2019.1344
- Type: Article
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This study presents an analysis for evaluating the physical layer (PHY) security performance of a two-hop amplify-and-forward cooperative relaying system employing Alamouti orthogonal space–time block coding (OSTBC) in the presence of an eavesdropper, where the transmit antennas for OSTBC are assumed to be spatially correlated. It is also assumed that the authorised main channels as well as the non-authorised eavesdropper channels follow Rayleigh fading distribution. Closed-form mathematical expressions are derived for three performance metrics for evaluating the PHY security, namely the probability of non-zero secrecy capacity, the secrecy outage probability, and the average secrecy capacity. Using the extensive numerical results obtained from the derived mathematical expressions, the impact of antennas correlation on the PHY secrecy performance of the system is studied and evaluated under different parameters. It is also shown that the antennas correlation corresponding to the main channels has more impact than the antennas correlation corresponding to the eavesdropper channels.
- Author(s): Prisca Dube and Tom Walingo
- Source: IET Communications, Volume 14, Issue 19, p. 3480 –3489
- DOI: 10.1049/iet-com.2019.1078
- Type: Article
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The conventional carrier-sense multiple access/collision avoidance (CSMA/CA) IEEE 802.11 protocol uses the rigid binary exponential backoff algorithm of the distribution coordination function (DCF) for channel access. The protocol poorly performs under loss by wireless links with high packet error rates and dense networks with numerous collisions from hidden nodes. Furthermore, the scheme is not cognisant of the state of the wireless link in its operation. This work develops hybrid adaptive orthogonal frequency division multiple access (OFDMA) CSMA/CA (hybrid AO–CSMA/CA) protocol that adapts the backoff and congestion window size according to the knowledge of the wireless channel conditions to mitigate against the effects of the loss by wireless links. The protocol utilises OFDM for effective resource allocation and solving the problem of the hidden terminal node on an OFDMA IEEE 802.11-based wireless network. The teletraffic performance analysis of the developed protocol is investigated in terms of throughput and delay metrics on a real dynamic Markovian wireless channel. The performance results indicate that the developed hybrid protocols perform better than the DCF protocol on the lossy wireless communication links.
- Author(s): Mohammad Karimi and Shadi Ahmadi
- Source: IET Communications, Volume 14, Issue 19, p. 3490 –3497
- DOI: 10.1049/iet-com.2019.1305
- Type: Article
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Multiband cognitive radio (CR) signalling allows CR networks to efficiently take advantage of the unused frequency bands. On the other hand, joint spectrum sensing and power allocation in CR systems has been shown to enable higher opportunities for CR transmission. In this work, the authors perform joint spectrum sensing and resource allocation (power and bandwidth) in a multiband CR system. This is achieved by defining an optimisation problem, which is formulated to maximise the average opportunistic CR data rate under constraints on interference, power budget, and total available bandwidth leading to a non-convex optimisation problem. As the original formulated optimisation problem is inherently non-convex, they convert it into a convex problem where the optimal solution is obtained using the Lagrange multipliers method and linear programming. For performance comparison, they consider the classical method based on equal bandwidth allocation for each subchannel. They provide several numerical results to contrast the performance of the proposed method compared to the classical method in terms of the average achievable CR data rate.
- Author(s): Soumita Hazra and Arti M.K.
- Source: IET Communications, Volume 14, Issue 19, p. 3498 –3503
- DOI: 10.1049/iet-com.2020.0501
- Type: Article
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In this study, a binate hop cooperative satellite–terrene link with correlated line-of-sight (LOS) components has been considered. The satellite–terrene link is assumed to follow shadowed-Rician fading. Specifically, higher-order moments of the considered system have been derived. Using the expression of higher-order moments, the expressions of the amount of fading and channel quality estimation index of the considered cooperative complex have been obtained. The symbol error rate of the considered cooperative satellite–terrene link for M-ary phase-shift keying constellation has been derived and the denouement of signal-to-noise ratio and inclination angle has been scrutinised as well. Moreover, outage probability and average channel capacity of the considered system have been derived with the help of the Meijer-G approach. It has been manifested by simulation and analysis that the performance of the considered system enhances with the inflation in the aggregate of antennas and inclination angle.
- Author(s): Rui Zhang ; Feng Yan ; Yaping Zhu ; Weiwe Xia ; Shanjie Zhang ; Lianfeng Shen
- Source: IET Communications, Volume 14, Issue 19, p. 3504 –3511
- DOI: 10.1049/iet-com.2019.0814
- Type: Article
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In vehicle ad-hoc networks (VANETs), the full coverage of roadside units (RSUs) is not necessary with the assistance of dead reckoning (DR) for the RSU-based vehicle localisation. This study proposes an optimisation strategy of RSUs deployment, which seeks an optimal RSU layout ensuring the best localisation accuracy with a minimum number of RSUs. With the assistance of DR, first, the average geometric dilution of precision (GDOP) for a specific localisation region is derived through a non-linear recursive model. Then the RSUs deployment is formulated into an optimisation problem, and the objective is as a function of the average GDOP and deploying interval. Finally, the optimisation problem is solved by a centre particle swarm optimisation (CPSO) algorithm. The convergence and stability of CPSO are evaluated via simulations. Furthermore, simulations also show that the proposed strategy can optimise the localisation accuracy of RSUs deployment in the VANET scenario.
- Author(s): Sharu Bansal and Dilip Kumar
- Source: IET Communications, Volume 14, Issue 19, p. 3512 –3520
- DOI: 10.1049/iet-com.2020.0486
- Type: Article
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Designing a scalable and efficient application layer protocols for the Internet of Things (IoT) environment is an ongoing problem. The constrained application protocol (CoAP) offering RESTful services for IoT devices implements a simple congestion control mechanism. This study proposes and analyses the distance-based congestion control CoAP (DCC-CoAP) for the current state of the network and accordingly calculate the future flow rate to handle congestion. The authors’ main idea is to use the combination of distance between nodes and round trip time (RTT) measurements which limits the losses of CoAP messages, which is an efficient way to predict the network congestion. The user-defined options, i.e. retransmission counter and timestamp of sent and received CON and ACK messages are introduced for mapping CON to ACK and measure RTT. The comparative analysis of the DCC-CoAP with other congestion control mechanism like default CoAP, CoCoA+ is also highlighted in this study. With low additional computations, future RTT can be measured for avoiding congestion, and retransmission timeout varies with distance to avoid transaction losses. An algorithm with varying data rate has been used in homogeneous and mixed traffic to calculate the parameters in terms of packet delivery ratios, delay and retransmission count.
Network traffic control for multi-homed end-hosts via SDN
Defending pollution attacks in network coding enabled wireless ad hoc networks: a game-theoretic framework
Beamforming and combining for multi-user large MIMO communication system
Efficient pilot design scheme for OFDM-based full-duplex systems
Best beam selection and PHY switching policy for hybrid FSO/RF inter-satellite communication link
Underlay spectrum-sharing non-orthogonal multiple access network with imperfect successive interference cancellation
Turbulence mitigation in a 28 GHz radio-over-free-space optics link using an integrated Mach–Zehnder interferometer and a diversity combining receiver
Secure beamforming method for artificial-noise-aided multiuser broadcast system with users of different importance under secrecy outage probability constraint
Optimal transceiver design for energy harvesting two-way relay networks
Wireless information and power transfer for underwater acoustic time-reversed NOMA
Computation offloading in cognitive radio NOMA-enabled multi-access edge computing systems
Congestion-aware adaptive decentralised computation offloading and caching for multi-access edge computing networks
Channel modelling for vehicle-to-vehicle MIMO communications in geometrical rectangular tunnel scenarios
Joint coding bit-rate and activity rate optimisation in wireless visual sensor networks
Performance of maximal ratio transmission over generalised-K fading channels
Best fit power weighted difference method for fog node selection in smart cities
Feature-oriented channel estimation in reconfigurable intelligent surface-assisted wireless communication systems
Deep reinforcement learning based optimal channel selection for cognitive radio vehicular ad-hoc network
Impact of antenna correlation on the physical layer security of cooperative relaying with OSTBC system
Performance analysis of an adaptive OFDMA-based CSMA/CA scheme on a wireless network
Joint spectrum sensing, power, and bandwidth allocation for multiband cognitive radio systems
Analysis of binate hop cascaded satellite terrene link with correlated LOS constituents
Optimisation strategy of roadside units deployment towards VANET localisation with dead reckoning
Distance-based congestion control mechanism for CoAP in IoT
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