Abstract
In existing dynamic spectrum sharing (DSS) systems, each node arbitrates channel access independently based on carrier-sensing mechanisms such as the listen-before-talk (LBT) protocol. Owing to the uncoordinated channel access between all nodes, the channel is occupied in a random pattern. This makes it difficult to reduce the mismatch in channel quality indicator (CQI) while increasing the spatial reuse gain between the different nodes; therefore, the areal capacity gain obtained by adding nodes is much lower in existing DSS systems than in the cellular system. In this paper, we propose a different means of improving the areal capacity for downlink DSS systems. It is a group-wise DSS approach that ensures full frequency reuse in each group of base stations (BSs) by performing LBT only between the representative BSs, each of them selected by each group. Once a channel is secured by each group, all its member BSs share a channel simultaneously. This approach makes closed-loop feedback-based link adaptation practical while boosting spatial reuse gain even in the DSS environment. To implement the group-wise DSS, we propose a single unified framework that employs elementary algorithms for BS grouping and carrier-sensing threshold adjustment. Our system-level simulation results demonstrate that the proposed framework boosts the areal capacity gain by approximately 4.42 times as much as the conventional approach.
Highlights
To deal with growing traffic demands, many studies have focused on the dynamic spectrum sharing (DSS) environment, where a spectrum is shared by various wireless technologies or multiple mobile network operators (MNO) [1]
Over the past decades, a common-sense approach to overcome the hidden node problem in the existing downlink DSS system has been confined to avoiding interference or relying on link adaption based on the previous transmission history, and various techniques have been developed based on these approaches
We argue that its fundamental limitation is the result of the uncoordinated channel access mechanism, which suffers from the unpredictable and random nature of co-channel interference
Summary
To deal with growing traffic demands, many studies have focused on the dynamic spectrum sharing (DSS) environment, where a spectrum is shared by various wireless technologies or multiple mobile network operators (MNO) [1]. It is not possible to improve the spatial reuse gain in existing DSS systems while allocating the optimal MCS owing to the unpredictable nature of co-channel interference (i.e., hidden node problem). This is attributed to the uncoordinated channel access mechanism of the current DSS systems. Allowing for adjacent BSs to occupy the channel concurrently as much as possible without incurring a CQI mismatch results in a higher areal capacity than in the conventional approach To implement this framework, we propose a joint optimization procedure by comprehensively designing the group-wise LBT protocol with the underlying BS grouping and CST control algorithms.
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