The Long Term Evolution (LTE) in unlicensed spectrum is an emerging topic in the 3rd Generation PartnershipProject (3GPP), which is about an operation of the LTE system in the unlicensed spectrum via license-assisted carrier aggregation. The 5 GHz Unlicensed National Information Infrastructure (U-NII) bands are currently under consideration, but these bands are also occupied by Wireless Local Area Networks (WLAN), specifically those based on the IEEE 802.11a/n/ac technologies. Therefore, an appropriate coexistence mechanism must be augmented to guarantee a peaceful coexistence with the incumbent systems. With this regard, our focus lies on the evaluation of all the proposed coexistence mechanisms so far in a single framework and making a fair comparison of them. The coexistence mechanisms covered in this work includes static muting, listenbefore-talk (LBT), and other sensing-based schemes that make a use of the existing WLAN channel reservation protocol.
Communication in millimeter wave (mmWave) spectrum has gained an increasing interests for tackling the spectrum crunch problem and meeting the high network capacity demand in 4G and beyond. Considering the channel characteristics of mmWave bands, it can be fit into heterogeneous networks (HetNet) for boosting local-area data rate. In this paper, we investigate the challenges in deploying an anchor-booster based HetNet with mmWave capable booster cells. We show that due to the channel characteristics of mmWave bands, there could be a mismatch between the discoverable coverage area of booster cell at mmWave band and the actual supportable coverage area. Numerical results are provided in validating the observation. We suggest possible ways in addressing the coverage mismatch problem. This work provides insights on the deployment and implementation challenges in mmWave capable HetNets.
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