A Distributed Testbed for 5G Scenarios: An Experimental Study

Abstract

This paper demonstrates the use of Universal Software Radio Peripheral (USRP), together with Raspberry Pi3 B+ (RP3) as the brain (or the decision making engine), to develop a distributed wireless network in which nodes can communicate with other nodes independently and make decision autonomously. In other words, each USRP node (i.e., sensor) is embedded with separate processing units (i.e., RP3), which has not been investigated in the literature, so that each node can make independent decisions in a distributed manner. The proposed testbed in this paper is compared with the traditional distributed testbed, which has been widely used in the literature. In the traditional distributed testbed, there is a single processing unit (i.e., a personal computer) that makes decisions in a centralized manner, and each node (i.e., USRP) is connected to the processing unit via a switch. The single processing unit exchanges control messages with nodes via the switch, while the nodes exchange data packets among themselves using a wireless medium in a distributed manner. The main disadvantage of the traditional testbed is that, despite the network being distributed in nature, decisions are made in a centralized manner. Hence, the response delay of the control message exchange is always neglected. The use of such testbed is mainly due to the limited hardware and monetary cost to acquire a separate processing unit for each node. The experiment in our testbed has shown the increase of end-to-end delay and decrease of packet delivery ratio due to software and hardware delays. The observed multihop transmission is performed using device-to-device (D2D) communication, which has been enabled in 5G. Therefore, nodes can either communicate with other nodes via: (a) a direct communication with the base station at the macrocell, which helps to improve network performance; or (b) D2D that improve spectrum efficiency, whereby traffic is offloaded from macrocell to small cells. Our testbed is the first of its kind in this scale, and it uses RP3 as the distributed decision-making engine incorporated into the USRP/GNU radio platform. This work provides an insight to the development of a 5G network.Sensors 2020, 20, 18 2 of 23 either as a licensed user (or a primary user, PU) to utilize its licensed channels (or cellular channels), or as an unlicensed user (or a secondary user, SU) to explore and utilize white spaces, which are the underutilized licensed channels (or cognitive channels) [4]. D2D enables nodes to access both cellular and cognitive channels to improve spectrum efficiency in order to improve data transmission rate and quality of service (QoS) [5-7]. Our ContributionsAt present, the majority of the research related to 5G presents theoretical analysis [8][9][10][11][12] and simulation studies [11][12][13][14][15][16]. In general, various theoretical state of the art and open issues are presented in [8], the effects of ultra-densification are investigated in [9], various network architectures, medium access mechanisms, and open issues a...

A Review of Technical Standards for Smart Cities

“…The most common consensus is that the smart city employs various kinds of digital and electronic technologies to transform the living environments with ICTs [16,17]. Deakin [18] labeled the smart city as a city that employs ICT to meet the market (the citizens') needs.…”

An Experimental Study on D2D Route Selection Mechanism in 5G Scenarios

“…This helps to improve the accuracy of network performance measurement compared to that in simulation, which generally applies some assumptions, whereby: (a) nodes in simulation may be homogeneous, rather than heterogeneous with different processing and transmission capabilities, resources, and so on; and (b) the absence of the ambient environment that affects the quality of communication due to the presence of ambient signals (or interference) and white noise. This paper is an extension to our previous paper [16]. Although our focus is on route selection in this paper, in [16], the focus is on the testbed and to investigate and compare network performance, such as software and hardware processing delays, of a single two-hop route in both traditional and our proposed testbeds with fewer nodes and routes.…”

“…This paper is an extension to our previous paper [16]. Although our focus is on route selection in this paper, in [16], the focus is on the testbed and to investigate and compare network performance, such as software and hardware processing delays, of a single two-hop route in both traditional and our proposed testbeds with fewer nodes and routes.…”

“…UDP has been the preferred transport layer protocol for multimedia applications because it is connectionless and does not perform retransmission during packet loss, which reduces delay at the expense of acceptable packet loss. Due to the challenges of meeting the stringent QoS requirements of multimedia applications, most investigations using testbeds in the literature use UDP rather than transmission control protocol (TCP) [15,16,[28][29][30]. In this experiment, we use multimedia applications, whereby the source host sends a video stream to the destination host that plays out the video using the VLC media player.…”

“…The communication between a node pair incurs: (a) software processing delay t s l n incurred in processes (i.e., GNU radio initialization) running on RP3; (b) hardware processing delay t h l n incurred in data packet transmission (i.e., data packet transmission) performed by USRP; and (c) propagation delay t p l n incurred in wireless signal broadcast [16]. The end-to-end delay increases with the number of hops of a D2D route, and it is the accumulated link delay of the links l n ∈ L of a route as follows:…”