Skuola Screenshot Piece Christos Bouras is Professor in the University of Patras, Department of Computer Engineering and Informatics. Also he is a scientific advisor of Research Unit 6 in Computer Technology Institute and Press - Diophantus, Patras, Greece. His research interests include Analysis of Performance of Networking and Computer Systems, Computer Networks and Protocols, Mobile and Wireless Communications, Telematics and New Services, QoS and Pricing for Networks and Services, e-learning, Networked Virtual Environments and WWW Issues. He has extended professional experience in Design and Analysis of Networks, Protocols, Telematics and New Services. He has published more than 450 papers in various well-known refereed books, conferences and journals. He is a co-author of 9 books in Greek and editor of 2 in English. He has been member of editorial board for international journals and PC member and referee in various international journals and conferences. He has participated in R&D projects.

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Spectral Efficiency (SE) refers to the data rate that can be transmitted over a given bandwidth in a communication system. Several studies have shown that SE is directly related to the modulation and coding scheme (MCS) selected for the transmission. Additionally, the most suitable MCS is selected according to the measured SINR as a certain block error rate (BLER) target to be achieved. It is important to focus on a dynamic user distribution, with users distributed randomly in the MBSFN area and therefore experiencing different SINRs. On the basis of the measured SINRs, we investigate the selection of the MCS that better suits each examined user deployment and should be used by the base stations when transmitting the MBMS data.

To select the MCS and calculate the SE in the case of a single receiver, we use the following four-step procedure:

  • Step 1: signal-to-interference plus noise ratio calculation
  • Step 2: modulation and coding scheme selection
  • Step 3: throughput estimation
  • Step 4: single-user spectral efficiency

TheMCS selection and the SE evaluation in the multiple-users case are deduced from the single-user case described in the previous section. In general, when multiple users are located in the MBSFN area, the value of the total SE depends on the selected MCS. This section examines four approaches for the selection of the MCS during MBSFN transmissions. These approaches are carefully selected so as to match different users' deployments and media traffic conditions that could be realized in real word scenarios. More specifically, the selected approaches are listed below:
  • The first approach selects the MCS that ensures that all users, even those with the lowest SINR, receive the MBSFN service (bottom-up approach).
  • The second approach selects the MCS that ensures the maximum SE in the MBSFN area (top-down approach).
  • The third approach sets a predefined SE threshold for the area and selects the MCS that ensures that the average SE over the MBSFN area exceeds this threshold (area-oriented approach).
  • The fourth approach selects the MCS that ensures that at least the 95% of the users receive the MBSFN service with a predefined target SE (user-oriented approach).