Cooperative communication relaying in hybrid heterogeneous networks

Coverage and capacity are the two most vital aspects of any cellular technology. Coverage, in particular, is of prime importance in a Long Term Evolution network. However, both come at a significant cost. Deployment of additional eNodeBs (macro layer) to cover small dead zones might often result in a negative return on investment. Instead a scheme that augments the macro layer by making use of low power relay nodes can satisfy coverage and capacity demands in a satisfactory manner. The same being proven across a number of studies. Research in this domain has so far dealt with the deployment of relay nodes with LTE over either licensed or unlicensed spectrum. Wirth et al. test one such model in an indoor office environment and compare performance results for the cooperative and standalone systems. In this paper, we present a non-transparent, type-1, amplify and forward relaying scheme based on the use of Wi-Fi access points as relays. The link between the eNodeB and the relay node (backhaul) is wireless. In both the uplink and the downlink, the Wi-Fi access point serves as the relay. In the downlink, the eNodeB is the source, while, in the uplink, the user equipment is the source. While the use of LTE for relay nodes causes interference with the macro base station, Wi-Fi based nodes present a lesser probability of interference due to the different bands (2.4 GHz and 5 GHz) in which they operate. The primary purpose of the purported scheme is coverage extension. Further, we analyze the performance of the model by comparing symbol-error-rate versus signal-to-noise ratio curves for direct and cooperative scenarios, using them to determine the ideal position of the relay; and the effect of path loss and variation in eNB-UE distance. Thus, we show that coverage extension can be achieved in a reliable manner without any hardware addition, through this scheme.