A Context-Aware Cognitive SIMO DL Transceiver for LTE HetNet Enhanced Pico-Cell Range Expansion

Deploying small cells (pico, femto or relays) in a macro-cell network is an advantageous solution to increase system capacity. However, small cells usually transmit with a weaker power compared to macro-cells, this fact causes a serious interference problem for these former. Range Expansion technique is among the solutions proposed to overcome this problem. The idea is to bias the received signal power from pico-cells in an advantage manner so that we have more UEs offloaded from macro-cell than the real case. Many solutions were proposed in the literature to enhance Range Expansion technique performances. In this paper, we design a new single-input multiple-output (SIMO) context-aware cognitive transceiver (CTR) that is able to switch to the best performing modem in terms of link-level throughput. On the top of conventional adaptive modulation and coding (AMC), we allow the context-aware CTR to make best selection among three different pilot-utilization modes: conventional decision-aided (DA) or pilot- assisted, non-DA (NDA) or blind, and NDA with pilot which is a newly proposed hybrid version between the DA and NDA modes. We also enable the CTR to make best selection between two different channel identification schemes: conventional least-square (LS) and newly developed maximum-likelihood (ML) estimators. Depending on whether pilot symbols can be properly exploited or not at the receiver, we further enable the CTR to make best selection among two data detection modes: coherent or differential. We note that a considerable gains reaching $48\%$ and $42\%$ for $5^{th}$ percentile cell-site and average cell-site throughput respectively can be achieved by using jointly our cognitive transceiver with Range Expansion technique.