Inter-cell interference is the major problem we are now coping with in any cellular network. The inter-cell interference reduces the system spectral efficiency and the quality of service (QoS) especially for the user equipments (UEs) who are close to the cell edge. Down tilting the antenna pattern at the base transceiver station (BTS) appears to be the most effective solution to relieve the effect of inter-cell interference. However, this method has a drawback that creates some holes where UEs located in that region will not be served. Due to the tilting of the antennas, the coverage of the cellular system is also reduced.
Due to the propagation loss, UEs who are close to the cell-edge also suffered from the degradation in the quality of the received signal. This may leads to the cases that at the cell-edge, some UE can not be served due to either the low signal quality or the high level of inter-cell interference. Unnecessary incensement in the number of handovers can be foreseen. Thereby, the overall performance of the cellular system is degraded.
Recently, there has been much research interest on the cooperative antenna system (CAS). It is shown that, theoretically CAS can alleviate the two major problems of the cellular systems afford mentioned. The performance of CAS depends very much on the degree of cooperation. In one extreme, the CAS consists of several distributed antennas which are connected to a center processing unit. This type of CAS is often called distributed antenna system (DAS) which has the best performance. In other extreme, the BTS only exchange limited information normally in order to boost the performance of the UEs at the edge of the cell i.e. Coordinated Multiple Point Transmission and Reception (COMP) system . In this case, the transmission of the data is coordinated in time, frequency or space so as to minimize the inter-cell interferences and propagation loss effects.
In this project we aim at investigating practical solutions for CAS in cellular networks. In the design of CAS, we will pay particular attention to the trade-off between the system performance enhancement and implementation cost. We expect to derive a frame work for the design of an optimal CAS where the practical issues and reasonable assumptions are both taken into account. For each of the proposed CAS, its performance enhancement and implementation cost will be jointly evaluated. The possibility of implementing those proposed CASs to the standardized cellular systems will also be investigated at system level. In the investigations, we may use current and future cellular systems like 3G, LTE and LTE-Advanced as the study cases.
The project is carried out in co-operation with Nokia and Siemens Network Branch in Aalborg
|Periode||01-02-08 → 31-01-10|