Systems and techniques for multicell-MIMO and cooperative relaying in wireless networks

Papadogiannis, Agisilaos




The constantly increasing demand for wireless services, the scarcity of radio

spectrum and the characteristics of the global wireless market, necessitate

that future wireless systems (Fourth Generation Mobile - 4G) provide higher

peak data rates and better QoS, especially for the cell-edge users. Furthermore

it is essential that they achieve high spectral efficiencies and they are

easily deployed. In order to be able to accomplish these objectives, wireless

systems need to incorporate technologies that increase the cell throughput

without increasing spectral consumption.

A very promising technique that can achieve the aforementioned targets

is Multicell Cooperative Processing (MCP) or Multicell-MIMO. MCP has

the potential to mitigate Inter-Cell Interference (ICI) and augment data

rates without sacrificing additional spectrum but at the cost of some overhead

and complexity. According to the concept of clustered MCP proposed

in this thesis, Base Stations (BSs) are grouped into cooperation clusters,

each of which contains a subset of the network BSs. The BSs of each cluster

exchange information and jointly process signals as they form virtual

antenna arrays distributed in space. In these systems, each user receives

useful signals from several BSs and therefore the notion of a cell transcends

the one of the conventional cellular systems. Although Multicell-MIMO is

a technique that can help meet a lot of the challenges towards 4G systems,

it has some intrinsic drawbacks that need to be addressed in order for it to

be brought into practice; this is the main focus of the present thesis.

Firstly the problem of how to optimally form BS cooperation clusters of

limited size has been investigated. MCP's overheads are proportional to the

size of cooperation clusters, therefore this size should be kept limited. The

straightforward solution of forcing neighboring BSs to collaborate provides

limited gains. In this thesis it is proposed that the BSs which interfere the

most with each other should cooperate rather the ones that are in close

proximity. This is shown to lead to significant spectral efficiency gains while

cluster sizes are kept very small.

Systèmes de Communication
Eurecom Ref:
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