Title: Μελέτη και ανάλυση μηχανισμών επιλογής σχημάτων διαμόρφωσης και κωδικοποίησης για τη μετάδοση πολυμεσικών δεδομένων σε κινητά δίκτυα επικοινωνιών LTE-ADVANCED
Abstract: Today we are witnesses of a rapidly increasing market for mobile multimedia applications, such as Mobile TV and Mobile Streaming. Services like these have or are expected to have high penetration in the mobile multimedia communications industry. In order to confront such high requirements for services that demand higher data rates, the 3rd Generation Partnership Project (3GPP) developed the Long Term Evolution Advanced (LTE-A) technology which constitutes the evolution of the 3rd Generation (3G) mobile telecommunications technologies. LTE-A utilizes Orthogonal Frequency Division Multiple Access (OFDMA). This radio technology is optimized to enhance networks by enabling new high capacity mobile broadband applications and services, while providing cost efficient ubiquitous mobile coverage.
In addition, 3GPP has introduced the Multimedia Broadcast/Multicast Service (MBMS) as a means to broadcast and multicast information to mobile users, with Mobile TV being the main service offered. LTE-A infrastructure offers to MBMS an option to use an uplink channel for interaction between the service and the user, which is not a straightforward issue in usual broadcast networks.
In the context of LTE-A systems, the MBMS will evolve into e-MBMS (“e-” stands for evolved). This will be achieved through the increased performance of the air interface that will include a new transmission scheme called MBMS over Single Frequency Network (MBSFN). In MBSFN operation, MBMS data are transmitted simultaneously over the air from multiple tightly time-synchronized cells. A group of those cells, which are targeted to receive these data, is called MBSFN area. Since the MBSFN transmission greatly enhances the Signal to Interference plus Noise Ratio (SINR), the MBSFN transmission mode leads to significant improvements in Spectral Efficiency (SE) in comparison to multicasting over 3G systems. This is extremely beneficial at the cell edge, where transmissions (which in 3G systems, like Universal Mobile Telecommunications System - UMTS, are considered as inter-cell interference) are translated into useful signal energy and hence the received signal strength is increased, while at the same time the interference power is largely reduced.
In order to fully exploit the benefits of MBSFN and to improve its performance in terms of SE, the Modulation and Coding Scheme (MCS) for the transmission of the data should be carefully selected. The relationship between MBSFN performance and MCS selection has been thoroughly studied in previous research works; however most (if not all) of these works focus only on the users’ side and therefore may not be sufficient. Sometimes the operator’s goal may be the maximization of the SE over all users of the topology or the provision of the service to all the users irrespectively of the conditions that they experience. In addition, most of these works determine the MCS scheme for MBSFN considering only the case of single antenna transmissions and they do not examine the benefits that Multiple Input Multiple Output (MIMO) transmissions may offer on the overall performance.
The goal of this thesis is to extend the previous research works and, furthermore, to tackle the problems addressed. To this direction, we first analyze a 3-step procedure that selects the MCS and calculates the SE in the case of a single user. Then, we generalize the single-user case and we propose three approaches that select the MCS for the delivery of the MBSFN data in multiple-users scenarios. The approaches are evaluated for three different transmission modes, so as to examine the impact of multiple antennas techniques on the MCS selection, and for different users’ distributions. The evaluation results indicate that depending on the target that the operator may set (i.e. SE maximization or achievement of a specific SE) each approach could lead to improved performance.
Publication Year: 2013
Publication Date: 2013-10-01
Language: en
Type: dissertation
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