Detection Techniques for Massive Machine-Type Communications: Challenges and Solutions

Abstract

Massive machine-type communications (mMTC) is one of the key application scenarios of fifth generation (5G) and beyond cellular networks. Bringing the unique technical challenge of supporting a huge number of MTC devices (MTCD) in cellular networks, how to efficiently estimate the channel, detect the active users and data in this scenario is an open research topic. In this regard, this paper aims to present an overview of different techniques to address the problem of channel estimation, activity and data detection specifically for the mMTC scenario. In order to highlight potential solutions and to propose new research directions, we discuss the performance of the state-of-the-art techniques in the literature using a unified evaluation framework. INDEX TERMS 5G, channel estimation, detection, massive access, mMTC, random access.

Channel Estimation and Multiuser Detection Techniques for Machine-Type Communications

“…dx dy, (2)(3)(4)(5)(6)(7)(8)(9)(10)(11) where the integral is taken over the supports S x , S y of the random variables X and Y , respectively, and f (x), f (y), and f (x, y) denote the probability density functions of the random variables. Since the mutual information unit is bits per channel use, the base of the log is 2.…”

“…The authors of [26] considered a simplified version of (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21), that ignores the number of symbols, transmission power and time instant, as given by…”

“…In order to reduce computational complexity in (3)(4)(5)(6)(7)(8), the exponential Compute the LLR value according to Eq. (3-18) end function is approximated by the first order of the Taylor series expansion, given by…”

“…We notice that the function f ξ (w j,p [t]) in (3)(4)(5)(6)(7)(8)(9)(10)(11) imposes an attraction to zero of small coefficients. So, if the value of w j,p [t] is not equal or in the range [−1/ξ, 1/ξ], no additional attraction is exerted.…”

“…In spite of the sporadic transmission pattern of each device, future mobile communication systems will have to support a massive number of MTCDs, as it is expected up to 300, 000 devices per cell [7,8].…”