5G communications:race for more capacity triggers LTE in unlicensed band

5G needs to identify the necessary Radio Access Network (RAN) that meets the high expectations in bit rates, spectrum utilization, power efficiency, and cost reduction. However, the challenges of scarce spectrum and increasing traffic volumes motivate operators to comprise the LTE with WiFi technologies in the form of licensed-assisted carrier aggregation model to allow LTE accessing the unlicensed band. This combination of technologies namely Long Term Evolution in Unlicensed band (LTE-U) is operated using LTE features such as Carrier Aggregation (CA) allowing to offload data in the WiFi band in order to maximize the spectral efficiency and throughput. This paper defines the scope of undergoing technical work within the 3rd Generation Partnership Project (3GPP) to develop the new LTE-U and how this new technology can be co-located with WiFi using trading off performance for low cost and fair spectrum sharing. Also, this paper addresses the challenges for WiFi to maintain transmission as it loses its own privilege to use the spectrum because LTE takes over the band. Coexistence between LTE-U and WiFi is analyzed for both coordinated and noncoordinated scenarios to shape the potential solutions of simple spectrum sharing with minimum changes to the standards