# Context-Based Dynamic Meshed Backhaul Construction for 5G Heterogeneous Networks
###### Abstract  
Five-G heterogeneous network overlaid by millimeter-wave (mmWave) access employs mmWave meshed backhauling as a promising cost-efficient backhaul architecture. Due to the nature of mobile traffic distribution in practice which is both time-variant and spatially non-uniform, dynamic construction of mmWave meshed backhaul is a prerequisite to support the varying traffic distribution. Focusing on such scenario of outdoor dynamic crowd (ODC), this paper proposes a novel method to control mmWave meshed backhaul for efficient operation of mmWave overlay 5G HetNet through Software-Defined Network (SDN) technology. Our algorithm is featured by two functionalities, i.e., backhauling route multiplexing for overloaded mmWave small cell base stations (SC-BSs) and mmWave SC-BSs' ON/OFF status switching for underloaded spot. In this paper, the effectiveness of the proposed meshed network is confirmed by both numerical analyses and experimental results. Simulations are conducted over a practical user distribution modeled from measured data in realistic environments. Numerical results show that the proposed algorithm can cope with the locally intensive traffic and reduce energy consumption. Furthermore, a WiGig (Wireless Gigabit Alliance certified) device based testbed is developed for Proof-of-Concept (PoC) and preliminary measurement results confirm the proposed dynamic formation of the meshed network's efficiency. m 2018 7 43 2018  
the proposed architecture can be applied for future sensor and actuator networks (SANs) which require high-speed transmission e.g., exchanging of high definition dynamic maps for automated driving [6] or supporting massive amount of sensors and actuators [7]. Densification of SC-BSs produces massive backhaul traffic in the core network and employing optical fibers for dense SC-BS backhauling would result in prohibitively high cost and practical difficulty in implementation. Wireless backhaul may offer a scalable and cost-effective solution [8]. However, traditional microwave frequency bands, e.g., sub-6 GHz [9], are limited in bandwidth to support gigabit data rate at the access level. Moreover, interference becomes a limiting factor, especially in densely-populated HetNets. An excellent solution to this issue is to employ mmWave backhauling. Millimeter-wave (mmWave) techniques ranging from 30 to 300 GHz have become feasible and promising means to overcome the above-mentioned issues [10; 11; 12]. Currently, the two most potential mmWave bands are 28 GHz and 60 GHz [6; 13], where the latter is unlicensed, thus easy to deploy. With GHz bandwidth, the gigabit data rate is practically achievable, which solves the capacity problem that exists in lower frequency backhaul systems. In mmWave networks, directional links are commonly established to compensate for the high path loss and high directivity also paves the way for spatial reuse. The use of highly steerable antennas greatly reduces interference and is suitable for the case of dense deployment of SC-BSs. Recently, the feasibility of mmWave transmission within a range of a few hundred meters is proven by systematic outdoor measurements [14], which offer sufficient coverage for small cell backhaul. Another advantage of mmWave networks with meshed topology is their capability of flexible routing of traffic, which is highly appropriate for ODC [6; 15], a typical scenario considered in this paper where traffic distribution dynamically varies in both space and time [16]. Conventional works had proposed several approaches to operate mmWave meshed backhaul (This paper mainly focuses on the mmWave backhaul part. Readers who are interested about mmWave technologies for improving throughput and delay performance with varying traffic demand at the access layer might refer to related works in [17; 18; 19]). For example, anchored BSs with wired backhaul working as gateways for other BSs were introduced in [20]. The weakness of the paper is that only direct link between anchored BSs and other BSs was considered.