Abstract
Reusing a frequency band to increase capacity in heterogeneous fifth-generation small cell networks may lead to inter-cell interference where co-channel interference propagates over shorter distances between cells. Cellular base station antennas normally consist of three separate antennas to cover three 120° sectors around the base station. Their design is crucial to ensure that they provide coverage to their intended sector whilst minimising interference to a nearby cell sector using the same frequency band, allowing a shorter distance to reuse the frequency. Conventional base station antennas for larger cells would radiate downwards into the cell sector area, thereby reducing interference to nearby cells. However, for smaller cells, this will be insufficient, and more control is required over how the antenna will radiate around the base station.
This thesis presents a new cell sector antenna pattern configuration that can mitigate co-channel interference to improve the reuse of frequency in a densified small cell network. This is achieved by reducing the gain at the sector edges, which are the critical directions, to reduce interference using current and new cell sector topologies proposed in this work. Multiple input multiple output communication is also supported to improve link quality to desired users. Two new antenna concepts for small cells have been simulated and prototyped for both fourth- and fifth-generation frequencies of 1.8 to 2.7 GHz and 3.4 to 4.2 GHz. Their capability to reduce interference within an urban street canyon environment is evaluated through the use of ray-tracing simulation, which has been shown to allow interference to be reduced by more than 10 dB compared to conventional antennas. This could lead to a substantial reduction in the required spectrum reuse distance.