Cellular MIMO Multihop Communication

The aim of this project “Cellular MIMO Multihop Communication” is to develop transmission strategies for cellular infrastructure multihop networks. The intermediate nodes (relays) shall increase the maximum distance to the base station and also increase the capacity of the network. They are dedicated relay stations that have a sufficient power supply, higher signal processing power than the mobiles and a better antenna. Also an antenna array can be utilized at the relay stations. Therefore, and also because relays might be mounted on points with good connection to the base station, this results in a larger relay station coverage of the base station than mobile station coverage. These intermediate relays can operate in an Amplify-and-Forward (AF) or Decode-and-Forward (DF) fashion. Which strategy is optimum in an infrastructure multihop network is one of the issues to be investigated. A major focus lies on the MIMO relay case. The possibility of spatial processing at the relay station might change the comparison of AF and DF significantly. Different (but realistic) channel knowledge states at the relay stations and also at the base station shall be taken into account. Space-time coding is one of the concepts that shall be considered for developing a multihop transmission scheme. The focus also lies on the necessary signalling schemes.

The underlying scenario is an outdoor scenario with multiple users within a cell. This means there might be limited possibility to cooperate between different users and each user might also see only a small number of relay stations. One of the questions that arise here is whether it is advantageous to use the direct path in addition to the signals arriving from the relays or not. Also the possibility of relay slot reuse, i.e. transmitting from well separated relays to different mobiles at the same time, comes into play. Reusing the relay slot would significantly increase the overall throughput.

System level considerations will also be considered in the project. In a multiuser scenario, scheduling and interference become important issues. Scheduling algorithms shall be considered that allow a fair and efficient distribution of resources. The interference situation shall also be considered. This includes intra-cell and inter-cell interference. Also routing aspects, in particular the question of relay selection, will be included in the considerations.