Abstract
Multiuser multiple-input-multiple-output (MIMO) systems are a prime candidate for use in massive connection density in machine-type communication (MTC) networks. One of the key challenges of the MTC networks is to obtain accurate channel state information (CSI) at the access point (AP) so that the spectral efficiency can be improved by enabling the enhanced MIMO techniques. However, current communication mechanisms relying upon the frequency-division duplexing (FDD) might not fully support an enormous number of devices due to the rate-constrained limited feedback and the time-consuming scheduling architectures. In this paper, we propose a user cooperation-based limited feedback strategy to support high connection density in massive MTC networks. In the proposed algorithm, two close-in users share the quantized version of channel information in order to improve channel feedback accuracy. The cooperation process is performed without any transmitter interventions (i.e., in a grant-free manner) to satisfy the low-latency requirement that is vital for the MTC services. Moreover, based on the sum-rate throughput analysis, we develop an adaptive cooperation algorithm with a view to activating/deactivating the user cooperation mode according to channel and network conditions.
Highlights
Internet of things (IoT), which refers to the connected future world in which every mobile device and machines are linked to the internet via wireless link, has received attention from both academia and industry in recent years [1]
It is of considerable importance to support high connection density with limited resources because the number of devices is at least two orders of magnitude higher than current human-centric communication
NUMERICAL RESULTS we evaluate the performance of the cooperative feedback algorithm based on the sum-rate defined as log2(1 + γ|m), m=1 where the signalto-interference-plus-noise ratio (SINR) for the m-th scheduled user is computed numerically according to γ|m
Summary
Internet of things (IoT), which refers to the connected future world in which every mobile device and machines are linked to the internet via wireless link, has received attention from both academia and industry in recent years [1]. Massive connectivity is one of the most important requirements of a fully connected IoT society [3], [4]. In accordance with this trend, the international telecommunication union (ITU) defined massive machine-type communication (mMTC) as one representative service category.. In mMTC networks, data communications may occur between an MTC device and a server or directly. It is of considerable importance to support high connection density with limited resources because the number of devices is at least two orders of magnitude higher than current human-centric communication
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