Device-to-Device communications in LTE-Unlicensed heterogeneous network

In this paper, the authors examine how the envisaged Device-to-Device (D2D) networks can efficiently scale its capacity by utilizing the unlicensed spectrum with appropriately designed LTE-Unlicensed (LTE-U) protocols. The LTE-U Listen Before Talk (LBT) algorithm is adapted for collision avoidance between traditional unlicensed user equipment (UEs), e.g. Wi-Fi UEs, and the LTE-U enabled D2D UEs. By considering different traffic loads, the analysis found that whilst the D2D UEs reduce the unlicensed network capacity, it increases the combined licensed and unlicensed network capacity by 63%.