Current Issue : October - December Volume : 2017 Issue Number : 4 Articles : 5 Articles
Long-term evolution (LTE) is becoming the first choice of mobile network operators (MNOs) when constructing a wireless\nnetwork infrastructure because of its high data rate, high throughput, and low latency. These significant advancements\nare necessary for satisfying the delivery of a wide-range of mobile applications and managed network resources.\nHowever, deploying a new LTE network or a transition from current legacy cellular networks to LTE can take several years\nto roll out. In the meantime, working in a heterogeneous wireless communication network looks inevitable. This paper\ninvestigates Voice over LTE (VoLTE) Quality of Service (QoS) under a heterogeneous wireless communication scenario. The\ncontributions of this paper are twofold. First, a novel downlink (DL) semi-persistent scheduling scheme is proposed to\nreduce VoLTE end-to-end delay and increase system capacity. Second, an extensive network simulation model has been\ndesigned and implemented to evaluate the proposed scheme. The performance of the proposed scheme is compared\nwith the performance of two relevant and well-known DL packet scheduling methods. The simulation results confirm\nthat the proposed scheme is able to reduce VoLTE end-to-end delay and achieve a better system capacity than current\nmethods, and maintain the desired VoLTE QoS....
In-band full-duplex (FD) relays are useful for extending coverage areas and increasing overall throughput in wireless\nnetworks. The main technical difficulty hindering their implementation and use is their inherent self-interference (SI),\ngenerated due to simultaneous in-band reception and forwarding. Efficient SI mitigation is a practical necessity, and\nthe imperfections in transceiver electronics, from which power amplifier (PA) non-linearity is one of the most serious\nphenomena, have to be taken into account in order to not limit the performance of such techniques. The magnitude\nof the distortion introduced by the PA depends on the relay input back-off (IBO) whose optimization for alleviating\nthe effect of PA non-linearity is the main research objective in this paper. In particular, although plain signal-to-noise\nratio (SNR) at the destination obviously increases when the IBO decreases, increased transmit power also strengthens\nthe non-linear distortion leading to decreasing overall signal-to-interference-plus-noise ratio (SINR). We develop\nexpressions for bounding the optimal IBO setting that maximizes the SINR at the destination, considering all relevant\nhardware impairments and SI cancellation with I/Q imbalance compensation. We provide closed-form solutions for\nthe soft-limiter PA model and numerical results for more general PA models. Finally, the derived IBO bounds are\ncompared with the numerical maximization of the SINR and the minimization of the bit-error rate (BER) to\ndemonstrate that the theoretical bound settings provide good approximations to the optimal one....
Full-duplex (FD) wireless communication is evolving into a practical technique, and many studies are being\nconducting in this area, especially regarding the physical layer. However, to exploit FD benefit successfully, efficient\nmedium access control (MAC) protocols are crucial as well as physical layer advances. Numerous FD-MAC protocols\nhave been proposed, but these MAC protocols cannot address all the issues encountered in this area. In addition, many\nhalf-duplex (HD) capable devices are present in existing wireless local area networks (WLANs), so there is an urgent\nneed to integrate FD clients and HD clients in the same WLAN. We refer to this type of WLAN as a heterogeneous\nWLAN (Het-WLAN). In this paper, we propose an FD-MAC for Het-WLAN, which considers all possible types of FD\ntransmissions. Our proposed FD-MAC protocol suppresses inter-user interference. Simulation results demonstrated\nthat a significant throughput gain (about 96%) could be achieved by using our proposed FD-MAC compared with\ntraditional HD communications. Moreover, our proposed MAC obtained better performance (average throughput\ngain of about 11%) compared with another existing FD-MAC design. In addition, probability analysis suggested that\nthe total probability of FD transmissions increased rapidly as the WLAN approached saturation conditions....
Wireless sensor networks (WSNs) have been used extensively in a range of applications, which realizes data acquisition,\nprocessing, transmission, and analysis in an interesting area. Harsh surroundings and their inherent vulnerability often\nmean that these networks suffer from simultaneous node failure possibly causing the network to become partitioned\ninto multiple disjointed segments. This in turn can prevent the gathering of data from the sensors and subsequent\ntransmission to the sink, causing the whole network to fail. In this paper, a strategy is presented for restoring\nmulti-objective optimization connectivity of these segments using mobile data collectors (MDCs), by considering the\nsegments as collections of sensor nodes and not as some representative node. Different from existing uses of MDCs\nfor restoration, the delay in data collection and task balance is considered, and the network connectivity and data\nacquisition path optimization problem are transformed into an improved multi-travelling salesman problem (iMTSP).\nAn improved multi-objective optimization genetic algorithm for solving the optimal collection data collector position\nand moving paths is proposed, which introduces virtual segments and hierarchical chromosome structure, improved\npopulation diversity, and custom coding and decoding. The simulation results show that the proposed method can\neffectively solve the iMTSP of the Pareto optimal solution and can provide a new strategy for connectivity-restoring\ntechnology in WSNs. Compared with NSGA-II, the diversity of the proposed gene algorithm represents a clear\nimprovement....
We consider a cognitive wireless network in which users adopt a spectrum sharing strategy based on cooperation\nconstraints. The majority of cognitive radio schemes bifurcate the role of players as either cooperative or\nnon-cooperative. In this work, however, we modify this strategy to one in which players are hybrid, i.e., both\ncooperative and non-cooperative. Using a Stackelberg game strategy, we evaluate the improvement in performance\nof a cognitive radio network with these hybrid cognitive players using an M/D/1 queuing model. We use a novel\ngame strategy (which we call altruism) to ââ?¬Å?policeââ?¬Â a wireless network by monitoring the network and finding the\nnon-cooperative players. Upon introduction of this new player, we present and test a series of predictive algorithms\nthat shows improvements in wireless channel utilization over traditional collision-detection algorithms. Our results\ndemonstrate the viability of using this strategy to inform and create more efficient cognitive radio networks. Next, we\nstudy a Stackelberg competition with the primary license holder as the leader and investigate the impact of multiple\nleaders by modeling the wireless channel as an M/D/1 queue. We find that in the Stackelberg game, the leader can\nimprove its utility by influencing followersââ?¬â?¢ decisions using its advertised cost function and the number of followers\naccepted in the network. The gain in utility monotonically increases until the network is saturated. The Stackelberg\ngame formulation shows the existence of a unique Nash equilibrium using an appropriate cost function. The\nequilibrium maximizes the total utility of the network and allows spectrum sharing between primary and secondary\ncognitive users....
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