Current Issue : April - June Volume : 2017 Issue Number : 2 Articles : 5 Articles
Full-duplex technology has become an attractive solution for future 5th generation (5G) systems for accommodating\nthe exponentially growing mobile traffic demand. Full duplex allows a node to transmit and receive simultaneously in\nthe same frequency band, thus, theoretically, doubling the system throughput over conventional half-duplex systems.\nA key limitation in building a feasible full-duplex node is the self-interference, i.e., the interference generated by the\ntransmitted signal to the desired signal received on the same node. This constraint has been overcome given the\nrecent advances in the self-interference cancellation technology. However, there are other limitations in achieving the\ntheoretical full-duplex gain: residual self-interference, traffic constraints, and inter-cell and intra-cell interference. The\ncontribution of this article is twofold. Firstly, achievable levels of self-interference cancellation are demonstrated using\nour own developed test bed. Secondly, a detailed evaluation of full-duplex communication in 5G ultra-dense small\ncell networks via system level simulations is provided. The results are presented in terms of throughput and delay.\nTwo types of full duplex are studied: when both the station and the user equipments are full duplex capable and\nwhen only the base station is able to exploit simultaneous transmission and reception. The impact of the traffic profile\nand the inter-cell and intra-cell interferences is addressed, individually and jointly. Results show that the increased\ninterference that simultaneous transmission and reception causes is one of the main limiting factors in achieving the\npromised full-duplex throughput gain, while large traffic asymmetries between downlink and uplink further\ncompromise such gain....
We investigate the application of wireless multicast technology in public safety network (PSN) in future wireless communication\nsystem. The hybrid unicast/multicast transmission system is proposed and analyzed in 3D massive multi-input multi output\n(MIMO) channel.The mutual coupling channel model is adopted under the different antenna array configuration scenarios. The\nproposed hybrid system adopts multicast beamforming in the multicast groups as well as multiuser-MIMO (MU-MIMO) linear\nprecoding in the unicast group to increase system throughput. The null space method based interference cancellation is further\nperformed between each group to eliminate signal leakage generated from each group. Comparisons between two types of antenna\narray configurations, different channel models, linear precoding as well as multicast beamforming, and user grouping strategies for\nmulticast services are presented and analyzed by simulation....
Collected telecom data traffic has boomed in recent years, due to the development of 4G mobile devices and other similar highspeed\nmachines.Theability to quickly identify unexpected traffic data in this streamis critical formobile carriers, as it can be caused\nby either fraudulent intrusion or technical problems. Clustering models can help to identify issues by showing patterns in network\ndata, which can quickly catch anomalies and highlight previously unseen outliers. In this article, we develop and compare clustering\nmodels for telecom data, focusing on those that include time-stamp information management. Two main models are introduced,\nsolved in detail, and analyzed: Gaussian Probabilistic Latent Semantic Analysis (GPLSA) and time-dependent Gaussian Mixture\nModels (time-GMM). These models are then compared with other different clustering models, such as Gaussian model and GMM\n(which do not contain time-stamp information). We perform computation on both sample and telecom traffic data to show that\nthe efficiency and robustness of GPLSA make it the superior method to detect outliers and provide results automatically with low\ntuning parameters or expertise requirement....
In this paper, a novel and efficient scheme for jamming the Universal Mobile Telecommunications System (UMTS)\nsignal without the assistance from the base station or operator is proposed and evaluated. The scheme is based on\nnew orthogonal multi-sequences developed in this paper. These sequences are specially designed to interfere all the\nOrthogonal Variable Spread Factor (OVSF) codes that are used in the UMTS transmission and thus, any signal spread\nby these multi-sequences will interfere all the transmitted data channels at the same time. A power gain of about 7 dB\nis obtained with respect to the traditional jamming method based on high power wide-band noise injection can be\nobtained when no channel is used and 10.4 dB in a more realistic scenario with multipath Rayleigh channel....
As one of the key enabling technologies of the fifth generation wireless network (5G), software defined network\n(SDN) offers a logically centralized control model, flexible programmability, and a flow-based paradigm that is ideally\nsuited for highly scalable wireless networks, from access to core part. Following this paradigm, a novel software-defined\nradio access network (SDRAN) architecture and the function modules have been proposed in this paper. In particular,\nthe motivation, challenge, and deployment roadmap of SDRAN framework are discussed. The relationships between\nalternative solutions (Cloud RAN, network function virtualization) and complementary technologies (cognitive radio,\nself-organizing network, big data analysis) are analyzed in detail. Taking interference management of heterogeneous\nmobile network as the example use case, scheme design and preliminary system evaluations are given to show the\nbenefit of SDRAN architecture....
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