An Adaptive Small Cell Architecture Based On Smart Antenna

With the development of 4th generation of mobile communication technology, the number of mobile user equipment as well as the need for high speed data access grows rapidly, exceeding the growth of network capacity. Meanwhile it places higher requirements on mobile network as traffic shifting from voice to multimedia data. The problem cannot be solved by deploying more macro cells which are expensive and cost much energy. Besides, large amount of macro cells will increase the burden of network planning and operation, and may cause the over coverage. Therefore small cells which are energy-saving and easy to deploy become an efficient way to improve network capacity and coverage.Further, as users are distributed unevenly in both time and space, tidal effects exist commonly in indoor and hot spots. Therefore if small cells are deployed in accordance with the peak of traffic, a large percentage of allocated resource will be wasted during idle time. To address this, new adaptive small cell network architecture was proposed in this thesis.Firstly, smart antenna was applied to small cells to achieve higher flexibility. Based on this, new small cell architecture was proposed which consists of two kinds of small cells. A traditional kind is equipped with only omnidirectional antenna and a new kind of small cell equipped with both omnidirectional antenna and smart antenna.Secondly, a traffic-aware adaptive algorithm was proposed to the unevenness of user distribution. Small cells equipped with smart antennas are able to offload traffic for nearby busy small cells using FDM(frequency division multiplexing) and balance system traffic load. These small cells can also benefit themselves using SDM(space division multiplexing) when they experience high traffic demand themselves. The proposed algorithm can thus help to improve user access rate and system throughput.Lastly, an improved interference management algorithm was developed. After a careful study of existing interference managing methods, this thesis mitigates antenna interference by controlling the percentage of occupied frequency of FDM and SDM.The proposed architecture and algorithm can help to improve user access rate and system throughput and cut down the required number of small cells. Simulation results show that compared with existing schemes, the proposed adaptive algorithm can reduce the number of small cells by approximately 13% while maintaining the required user access rate and system throughput, thus reducing deployment costs and energy consumption.