# IoT's Tiny Steps towards 5G: Telco's Perspective
## 5 IoT in 5G Enabling Technologies
### Access Architecture Related Radio Technology  
This technological group includes ultra-densification, enhanced wireless backhaul, moving networks, and D2D communication.  
**Advanced small cell**[66; 123] deployment is considered to be one of the key enablers for achieving many of the requirements currently envisioned for 5G [67], with higher data rates [68; 171; 250] and more capacity [171; 172; 173; 174], as most important. Higher data rates and smaller battery consumption can be achieved using short distances in the small cell [69]. Solving the capacity and data rate challenge with network densification could be very expensive in terms of equipment, maintenance,and operations [200]. With denser cell deployment come significant challenges in the design of a high-performance backhauling system for RAN and the impact of backhaul on radio resource management (RRM) [70]. However, there are in existence many interesting topics to be further investigated which can be grouped around several problem areas [34]: user association, backhauling, interference management, energy efficiency, and propagation modelling.  
**Moving networks (MN)** are the combination of multi-hop and vehicular communications concepts [69; 71]. The MN deploys one or several moving relay node(s) (MRNs) [175; 176; 251] on vehicles that form their own cell(s) inside the vehicle to serve vehicular users [72]. Challenges in using MRN are efficient backhauling, design of efficient resource allocation and interference management techniques, as well as mobility management schemes to exploit the benefit of group handovers for vehicular user equipment (UE) devices served by the same MRN [72]. The main research challenges related to MN concept are associated with complexity management due to the mobility of access points and providing a high-rate wireless backhaul link from the moving cell to the fixed network [69].  
**Enhanced wireless backhaul** is one of the main challenges in hyper-dense 5G networks [34; 217]. The performance of wireless backhaul is dictated by the environment and traffic profile of the intended use case [9]. In UDN except mmWave, new approaches are needed, e.g., interface aware routing and intelligent resource allocation [9], as these links may occupy part of the spectrum used in the access network [73]. Latency and reliability of this link are important issues to be considered being prone to blocking and fading [69]. In any case, further research is necessary to explore TDD multi-flow coordination schemes to avoid bottlenecks in the downlink backhaul [9]. The guidelines for deploying future 5G wireless backhaul networks in economical and highly energy-efficient ways are provided in [74].  
**D2D communication** is defined as a direct route of data traffic between spatially closely located mobile UE [75; 177; 178]. The advantages of D2D communication compared with the traditional cellular method include the reduction of transmission latency [73; 75] and power consumption [75], improvements in coverage [71; 76; 179], spectral and energy efficiency [77], and throughput, when power control and resource allocation methods are used [78]. The use of D2D communications has an overall positive impact on system capacity in cellular environments. D2D communication brings challenges and complexities related to interference management [79; 80], QoS requirements [79], and resource allocation [34; 215]. The design of D2D direct communication link is still a hot topic [29].