Capacity and coverage enhancement for multi-hop relay in long term evolution-advanced network

Abstract

Cellular networks known have difficulty to provide satisfactory SINR level to users at the cell boundaries. Therefore, multi-hop relay is considered as one of the main keys for Long Term Evaluation - Advanced (LTE-A) to meet the growing demand for coverage extension and capacity enhancement. However these benefits of multi-hop depend on location of Relay Node (RN) which mitigates interference among the cells. In this work three novel models to enhance the capacity and expand the coverage area for LTE-A cellular networks are proposed. The first model called Optimum RN Deployment (ORND) and based on mathematical modelling of modified Shannon formula of capacity distribution. In ORND the determination of optimal location for RN ( ) is formulated to maximize capacity for users at cell edge region. Optimum number of relays ( ) is derived to ensure the best coverage with low cost implementation. Based on both and , transmission power for each RN is allocated to avoid overlapping among neighbouring RNs and optimize the power consumption. Frequency reuse of multi-hop relay is applied to avoid interference between the RN and Base Station (BS) while preserving the same available spectrum for the cell. Mathematical results are validated by multi-cell simulation through using first tier of cells (i.e. six cells surround a particular cell) and showed 40% of capacity enhancement for cell size with interference- limited compared to conventional cellular network. The second model is called Enhance Relay Link Capacity (ERLC) and aims to enhance capacity for the relay link to overcome outages in mobile services due to channel fluctuations. ERLC is based on the usage of two antennas types, Omni directional Antenna (OA) and Directional Antenna (DA). The transmission power of each antenna is allocated while preserving the same consumption of the feeder power to the RN. ERLC increased capacity of the relay link to 46% in comparison with conventional relay link. Finally, Moving Relay (MR) is proposed to improve throughput for passengers on public transportation and provide reliable connection with cellular networks along the route, especially at the cell boundaries. A new algorithm called Balance Power Algorithm (BPA) is proposed to minimize the transmission power consumption for MR. The results shows that BPA substantially reduced 75% the transmission power consumption for MR and increased throughput for active users linked with the MR around 88% compared to direct link.