User Association in 5G Networks: A Survey and an Outlook

Abstract

The fifth generation (5G) mobile networks are envisioned to support the deluge of data traffic with reduced energy consumption and improved quality of service (QoS) provision. To this end, the key enabling technologies, such as heterogeneous networks (HetNets), massive multiple-input multiple-output (MIMO) and millimeter wave (mmWave) techniques, are identified to bring 5G to fruition. Regardless of the technology adopted, a user association mechanism is needed to determine whether a user is associated with a particular base station (BS) before the data transmission commences. User association plays a pivotal role in enhancing the load balancing, the spectrum efficiency and the energy efficiency of networks. The emerging 5G networks introduce numerous challenges and opportunities for the design of sophisticated user association mechanisms. Hence, substantial research efforts are dedicated to the issues of user association in HetNets, massive MIMO networks, mmWave networks and energy harvesting networks. We introduce a taxonomy as a framework for systematically studying the existing user association algorithms. Based on the proposed taxonomy, we then proceed to present an extensive overview of the state-of-the-art in user association conceived for HetNets, massive MIMO, mmWave and energy harvesting networks. Finally, we summarize the challenges as well as opportunities of user association in 5G and provide design guidelines and potential solutions for sophisticated user association mechanisms.Comment: 26 pages; accepted to appear in IEEE Communications Surveys and Tutorial

Design and Implementation of 5G mmWave LTE-TDD HD Video Streaming System for USRP RIO SDR

“…밀리미터파는 광대역폭을 지녔기 때문에 기가 비트 단위의 무선 서비스를 제공할 수 있어 미래의 무선 백홀 네트워크에서 각광을 받고 있다 [2] . 우리나라는 2018년에 있을 평창 동계올림픽에서 세계 최초로 5G 시범서비스를 선보일 예정으로, KT 그룹은 평 창 동계올림픽을 통해 28 GHz 이상의 주파수를 사용하는 표준화 추진을 계획 중이다.…”

An Improved User Association Algorithm for MAP–FAPs Heterogeneous Networks

“…However, the shortcoming of biased user association is that the users who are forced to access FAPs due to the added bias will experience severe interference from nearby MAPs. As a result, the gain obtained by offloading traffic from MAP to FAPs will be decreased by the severe interference [1]. As for the received power-based user association criterion, users always prefer to access the specific AP which can provide the maximum received signal strength (max-RSS) [6].…”

“…User association-namely associating users with a specific AP-substantially affects the network performance. Four metrics are commonly used for user association in HetNets: spectrum efficiency, energy efficiency, quality of service (QoS), and fairness [1]. Problem formulation is too complicated to implement if all four metrics are considered at the same time, so we mainly consider spectrum efficiency and fairness in this paper.…”

“…According to the latest visual network index (VNI) report from Cisco [1], the global mobile data traffic will increase nearly ten-fold from 2014 to 2019, reaching 24.3 exabytes per month by 2019, wherein three-fourths will be video. Due to the explosion of data traffic and limited spectrum, new wireless communication technology (e.g., heterogeneous networks (HetNets), massive multiple input and multiple output (MIMO)) is emerging to improve utilization efficiency of spectrum resources.…”

Coverage and Rate Analysis for Location-Aware Cross-Tier Cooperation in Two-Tier HetNets

“…A typical HetNet consists of different types of base stations (BSs) such as macro, pico, and femto BSs (MBSs, PBSs and FBSs, respectively), which operate simultaneously to serve users, but differ in terms of their coverage range, spatial density, and most importantly, transmit power [3]. However, the large transmit power disparity of macrocells and small cells will lead to unbalanced user loads among different BSs [4]; that is, most users will prefer to associate with MBSs when the conventional maximum-received-power (MRP) user association scheme is applied. This results in an underutilization of resource utilization at small cells.…”