Current Issue : July - September Volume : 2017 Issue Number : 3 Articles : 5 Articles
In two-hop relay-aided cellular networks, both half-duplex (HD) and full-duplex (FD) transmission have been\nextensively studied. FD transmission can achieve twice throughput of HD transmission, but suffers from strong\nself-interference (SI), which may not be perfectly cancelled. In this paper, a hybrid HD/FD transmission scheme in a\nrelay-aided cellular network is proposed, which not only utilizes the throughput advantage of FD but also weakens\nthe negative effect of SI. The key idea is that a relay station (RS) switches between the HD and the FD modes\nbased on the received signal-to-interference-plus-noise ratio (SINR). If the information rate of the base station\n(BS)-to-RS link is lower than a preset threshold, the RSs adopt the FD mode to guarantee the throughput;\notherwise, the RSs adopt the HD mode to reduce the negative effect of SI. As FD transmission consumes more\npower than HD transmission, we try to maximize the system energy efficiency under the system spectral efficiency\nconstraint and the transmit power constraints. It is difficult to solve this optimization problem directly, so the\nalternate optimization method is adopted to solve it, i.e., optimizing the transmit power of the BS and the transmit\npower of RSs in turn. Simulation results show that under perfect SI cancellation, the hybrid scheme can achieve\nhigher energy efficiency than the HD mode by taking the throughput advantage of FD; while under poor SI\ncancellation, the hybrid scheme can greatly weaken the negative effect of SI and achieve higher energy efficiency\nthan the FD mode....
Device-to-device (D2D) communication underlaid cellular network is considered a key integration feature in future cellular\nnetwork. However, without properly designed interference management, the interference fromD2D transmission tends to degrade\nthe performance of cellular users and D2D pairs. In this work, we proposed a network-assisted distributed interference mitigation\nscheme to address this issue. Specifically, the base station (BS) acts as a control agent that coordinates the cross-tier interference\nfrom D2D transmission through a taxation scheme. The cotier interference is controlled by noncooperative game amongst D2D\npairs. In general, the outcome of noncooperative game is inefficient due to the selfishness of each player. In our game formulation,\nreference user who is the victim of cotier interference is factored into the payoff function of each player to obtain fair and efficient\noutcome.The existence, uniqueness of theNash Equilibrium(NE), and the convergence of the proposed algorithmare characterized\nusing Variational Inequality theory. Finally, we provide simulation results to evaluate the efficiency of the proposed algorithm....
A key problem in the design of cloud radio access networks (CRANs) is to devise effective baseband compression\nstrategies for transmission on the fronthaul links connecting a remote radio head (RRH) to the managing central unit\n(CU). Most theoretical works on the subject implicitly assume that the RRHs, and hence the CU, are able to perfectly\nrecover time synchronization from the baseband signals received in the uplink, and focus on the compression of the\ndata fields. This paper instead does not assume a priori synchronization of RRHs and CU, and considers the problem of\nfronthaul compression design at the RRHs with the aim of enhancing the performance of time and phase\nsynchronization at the CU. The problem is tackled by analyzing the impact of the synchronization error on the\nperformance of the link and by adopting information and estimation-theoretic performance metrics such as the\nrate-distortion function and the Cramer-Rao bound (CRB). The proposed algorithm is based on the Charnes-Cooper\ntransformation and on the Difference of Convex (DC) approach, and is shown via numerical results to outperform\nconventional solutions....
The next fifth generation (5G) of wireless communication networks comes with a set of new features to satisfy the demand of dataintensive\napplications: millimeter-wave frequencies, massive antenna arrays, beamforming, dense cells, and so forth. In this paper,\nwe investigate the use of beamforming techniques through various architectures and evaluate the performance of 5G wireless access\nnetworks, using a capacity-based network deployment tool. This tool is proposed and applied to a realistic area in Ghent, Belgium,\nto simulate realistic 5G networks that respond to the instantaneous bit rate required by the active users. The results show that,\nwith beamforming, 5G networks require almost 15% more base stations and 4 times less power to provide more capacity to the\nusers and the same coverage performances, in comparison with the 4G reference network.Moreover, they are 3 times more energy\nefficient than the 4G network and the hybrid beamforming architecture appears to be a suitable architecture for beamforming to\nbe considered when designing a 5G cellular network....
This paper investigates the secure communications of multiuser untrusted amplify-and-forward relay networks in the presence of\ndirect links. In the considered system, one user is selected among multiple ones for secure transmission to the destination node\nwith the help of an untrusted relay node. To reduce the information leakage to the untrusted relay, the paper considers two selection\ncriteria to select the user based on the direct and the relaying links, respectively.The impact of direct and the relaying link on the\nsystem secrecy performance is studied by deriving the close-form ergodic secrecy rate (ESR) as well as the asymptotic expression.\nFromthe asymptotic expression, it can be found that the asymptotic ESR increases linearlywith the logarithmof the average channel\ngain ratio of the direct link to the relaying link....
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