Bluetooth Based Software Defined Function in Internet of Things

Transcription

1 ETIS Bluetooth Based Software Defined Function in Internet of Things Haoxuan Wang, Yuan Gao, Kai Zheng, Jie Zhang, Yang Du and Xin Huang Abstract Internet of Things (IoT) is becoming a focal point of Internet development. However, most of existing functions in IoT devices are rigid to modify because the reprogramming process under traditional IoT architecture cannot be executed remotely or even requires physical reassembly. Hence, in this paper, Bluetooth Based Software Defined Function (BT-SDF), a framework derived from Software Defined Function (SDF), is designed to simplify the IoT function redefining process. Additionally, to verify its availability, the authors deploy BT-SDF in a functional reprogramming process of a Photovoltaic (PV) energy system. Experimental outcomes ascertain the BT-SDF allows a remote function modification without any physical alterations. By extension, this framework can satisfy the majority of requirements of current IoT applications and enables to reconstruct those applications to highly flexible IoT networks. Index Terms Flexibility, Internet of Things (IoT), Remote reprogramming, Software Defined Function (SDF) T I. INTRODUCTION he Internet of Things (IoT) is a promising paradigm that undergoes a rapid growth and might represent the future state of Internet [1, 2]. Nonetheless, for most IoT system, if being necessitated to alter some functions of the end devices, the redundant operations might not be avoided since this process under traditional IoT architectures cannot be completed remotely or even requires physical reassembly [3]. This can be deemed as a problem to hinder IoT further development. Some innovative ideas raised the new possibilities to resolve the aforementioned problem. Software Defined Internet of Things (SDIoT) is a general architecture aiming to efficiently manage the IoT network. Specifically, it is a combination of the Software Defined Networking (SDN) and IoT devices [4]. Derived from SDN, the Software Defined Function (SDF) (also called IBNet [5]) is reached out as a component of SDIoT. It This work was submitted to the 1 st ETIS conference held on th August 2016, Suzhou, China. Haoxuan Wang, Yuan Gao, Kai Zheng, Jie Zhang and Xin Huang is with Department of Computer Science and Software Engineering, Xi'an Jiaotong-Liverpool University, Suzhou, China ( {Haoxuan.Wang14, Yuan.Gao14, Kai.Zheng14}@student.xjtlu.edu.cn, Xin.Huang@xjtlu.edu.cn). Yang Du is with Department of Electrical and Electronic Engineering, Xi an Jiaotong-Liverpool University, Suzhou, China ( Yang.Du@xjtlu.edu.cn). Jie Zhang is also with School of Electrical Engineering and Electronics and Computer Science, University of Liverpool, Liverpool, UK, ( Jie.Zhang3@liverpool.ac.uk). is an IoT framework designed to reprogram securely and remotely [3, 5, 6]. However, the SDF framework does not present a specific way of connection in its data infrastructure layer, which needs further discussions. Inspired by SDF, this paper makes the following main contributions listed below. A new framework called Bluetooth Based Software Defined Function (BT-SDF) is defined and implemented. It specifies the Bluetooth as the connection way in its data infrastructure layer. By doing this, the IoT device reprogramming procedure can be simplified. The BT-SDF framework is also applied to a reprogramming process of Photovoltaic (PV) energy system. This evidences that the framework can accomplish a quick remote functional modification of a specified IoT system without any physical adjustments. II. FRAMEWORK A. An Overview of BT-SDF (SDF) Framework The SDF and BT-SDF maintain the same main framework, but in BT-SDF, a Bluetooth based remote reprogramming method is implemented between the function station and other IoT devices, allowing the existing IoT system to swiftly acquire the remote reprogramming capability. Both SDF and BT-SDF comprise three logic layers: physical infrastructure layer, control layer and application layer [3, 5, 6]. The details of these layers are listed below. The application layer on the top contains some applications and offers its users or administrators various services through a Northbound Interface (NBI) [3, 5, 6]. The middle one is the control layer holding various types of controllers matching to different applications. For example, the SDN controller in this layer is responsible for network traffic controlling, function forwarding, and etc., while the SDF controller is in charge of reprogramming IoT end devices [3, 5, 6]. The data infrastructure layer is in the lowest position. The BT-SDF and SDF framework distinguish a typical kind of device called station, which is in charge of executing commands from the upper controller and managing its subordinate end devices. Particularly, the function station executes functional renewing operations if the SDF controller presents a command through OpenFunction interface [3, 5, 6].

2 ETIS A streamlined model converging to data infrastructure layer is illustrated in Figure 1. is connected to the IoT Device (Arduino Nano). The emulation of serial ports offered by the RFCOMM protocol enables the serial communication between the function station and the IoT Devices [11]. The HC-06 chip possesses the exact same baud rate as that of Arduino and its role should be set to slave mode. A wired connection between a spare Arduino digital pin and the Arduino reset pin should be also established to accomplish the programmable reset process. Beside physical configurations, a piece of code to periodically supervise the Arduino serial buffer, called resident code, should be preinstalled in the Arduino. The code enables the Arduino to reset itself when it receives a specific string. The program running on function station (Raspberry Pi) will receive the refresh command from SDF controller, and then send the specific string to a particular Arduino through the established RFCOMM emulation serial port. Subsequently, it will reprogram this Arduino via invoking AVRDUDE tool through the same serial port. It should be noted that the resident code should always runs on Arduino to enable the wireless refresh in the next time. III. USE CASE EXPERIMENT Fig. 1. Logic view of Software Defined Internet of Things with BT-SDF In BT-SDF framework, the users can submit their requests remotely through the services provided by the application layer. Then, the SDF controller will identify the corresponding function station and send a request command to the target function station through a secured OpenFunction connection. After receiving the refresh request command, the function station will refresh corresponding IoT end devices through Bluetooth [3, 5, 6]. B. between the function station and other IoT devices As a partition of BT-SDF, the prototype should realize a Bluetooth based method to enable remote reprogramming between the function station and other IoT devices. In fact, some existing Bluetooth-integrated solutions such as have been created to accomplish that process via Bluetooth Low Energy (BLE) [7]. Some pioneering Wireless Sensor Network (WSN) practices based on those solutions have also been constructed [8, 9]. However, for those existing IoT systems which cannot be reprogrammed remotely, the availability of these solutions is restricted, not only because they are not compatible with other brand BLE devices [10] but also because they lead to numerous discards of IoT devices inevitably when updating original IoT system. Therefore, the researchers prefer to a different implementation described below rather than using these existing Bluetooth-integrated solutions. In this prototype, a Universal Serial Bus (USB) Bluetooth adapter is plugged to the simulated function station (Raspberry Pi). A Bluetooth chip HC-06 supporting Bluetooth 2.1 protocol A. Experiment Background In the conventional PV system, the control algorithms are downloaded to the microcontroller of the PV inverter. A physical wire connection is required for reprogramming the controller. It is time consuming and can be relatively hard for the system installed in a remote area. Many researches regarding PV system focus on maximum power point tracking (MPPT) [12], but few of studies concentrate on flexible reprograming of inverter. Because the BT-SDF framework may solve the problems mentioned above, it might be an appropriate scenario to verify the availability of BT-SDF framework. B. Experiment Procedures The main facilities used in this photovoltaic (PV) energy system experiment contained a personal computer (PC), a Raspberry Pi, a DC/DC inverter with a built-in Arduino Nano, a router, a PV panel, a red head lamp and an oscilloscope. Router DC load PC Raspberry Pi Fig. 2. Equipment used in experiment Buck inverter Oscilloscope PV Panel

3 ETIS As Figure 2 illustrated, the experiment was constructed to simulate the communication between the controller layer and the data infrastructure layer in the BT-SDF framework. PC and router were used for delivering instructions to Raspberry Pi. The PC was considered as a SDF controller, the Raspberry Pi was intended to simulate a function station and the DC/DC inverter was treated as an IoT end device. The DC/DC inverter was a buck one. It was connected to a PV panel and a load (resistor). The PV panel was used to provide an input voltage. The voltage that inverter offered to the load was the output voltage. The red head lamp provided luminous energy to the PV in the almost same functionality as the sunlight, but its light can be treated as a constant light. The relationship between the input voltage and the output voltage of the buck inverter is: V out = V in D (1) Where V in is input voltage, V out is output voltage, and D is duty cycle. This experiment was proceeding under controlled conditions to ensure the accuracy of results. The function of code constrained the Arduino to provide a duty cycle with a certain value (25%, 75% and etc.). Along with the duty cycle change, the output voltage will also change. Initially, the researchers fed a 5.1V power supply to the buck inverter as the input voltage. When the duty cycle is adjusted to 75%, the output voltage (2.748 V) of buck inverter is shown in Figure 3. Fig. 4. Output voltage under 75% duty cycle and 3.8V PV input voltage Similarly, the transmission loss should be considered. Thus, the output voltage is also reasonable. At the same time, the PWM waveform with a 75% duty cycle is shown in Figure 5. Fig. 5. Oscilloscope (duty cycle) output under 75% duty cycle Following that, the researchers compiled the new code which altered the duty cycle to 25% and remotely refreshed the new code to Arduino Nano via wirelessly controlling the Raspberry Pi through the PC. Fig. 3. Output voltage under 75% duty cycle and 5.1V input voltage Theoretically, the output voltage under the 75% duty cycle could be: V out = V in D = 5.1 V 75% = V (2) This verifies that systemic transmission loss exists. The value of V is reasonable due to the systemic transmission. Then the PV panel was used to supply the electricity instead of the original power supply. The input voltage from PV panel is 3.8V. Correspondingly, the output voltage is 1.930V, which is presented in Figure 4. Fig. 6. Remote Reprogramming Process After reprogramming process, the PWM waveform with a 25% duty cycle is shown in Figure 7.

4 ETIS T = T C + T W + T V (3) T Tv Tw Tc Fig. 7. Oscilloscope (duty cycle) output under 25% duty cycle As explicitly shown in Figure 7, the duty cycle has been modified to 25%, indicating that the remotely reprogramming process works. IV. PROTOTYPE PERFORMANCE EVALUATION To verify the performance of the prototype mentioned above, the researchers executed 10 times remotely reprogramming using the prototype and the solution (one of existing Bluetooth-integrated solutions), respectively. The test code accounts for bytes. The outcomes recorded from AVRDUDE are presented in TABLE I. TABLE I. Solution COSTED TIME BETWEEN TWO SOLUTIONS (UNIT: SECOND) Items Times T T Fig. 8. A comparison between the two solutions on their average time The average and variance of onfirm that the prototype has higher speed and almost same stability compared with the solution. V. CONCLUSION AND FURTHER WORK In this paper, the researchers have defined and implemented a new framework called BT-SDF and successfully modified functional parameter in a PV energy system through this framework. BT-SDF allows the existing IoT system to be upgraded to acquire wireless reprogramming capability without unnecessary discards of original IoT devices. It also simplifies the function redefining process of IoT system installed in remote area and saves the costed time on this process. There might be a slight issue that the reset design of Arduino may conflict with some codes if the codes also supervise the serial buffer. Moreover, transplantation using BLE protocol may ameliorate this framework. These could be solved or enhanced in the further studies. REFERENCES Unit: Second TABLE I. COSTED TIME BETWEEN TWO SOLUTIONS (CONTINUED) Solution Items Times Avg. Var T T In TABLE I, stands for the time consumed on connecting to the Arduino bootloader, represents the time on transiting and rewriting the code, and denotes the time for integrity verification. T stands for the total time of the whole reprogramming process, where: [1] H. M. O'Brien, "THE INTERNET OF THINGS," Journal of Internet Law, vol. 19, pp. 1-20, [2] Y. Jararweh, M. Al-Ayyoub, A. Darabseh, E. Benkhelifa, M. Vouk, and A. Rindos, "SDIoT: a software defined based internet of things framework," Journal of Ambient Intelligence and Humanized Computing, vol. 6, pp , [3] N. Xue, J. Zhang and X. Huang, OpenFunction: Enabling Innovation in Software Defined Internet of Things, unpublished. [4] S. Choi and J. Kwak, "Enhanced SDIoT Security Framework Models," International Journal of Distributed Sensor Networks, pp. 1-12, [5] R. Y. Xu, X. Huang, J. Zhang, Y. Lu, G. Wu, and Z. Yan, "Software Defined Intelligent Building," International Journal of Information Security and Privacy, [6] N. Xue, X. Huang and J. Zhang, "S2Net: A Security Framework for Software Defined Intelligent Building Networks, " presented at The 15th IEEE International Conference on Trust, Security and Privacy in Computing and Communications (IEEE TrustCom-16), Tianjin, Aug , [7] (2016, Jul. 22). - An Arduino Uno with Bluetooth 4.0 [Online]. Available: 044#.V5Fe0E0Vjug

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