Abstract
When a wireless sensor node’s wireless communication fails after being deployed in an inaccessible area, the lost node cannot be repaired through a debugging interaction that relies on that communication. Visible light communication (VLC) as a supplement of radio wave communication can improve the transmission security at the physical layer due to its unidirectional propagation characteristic. Therefore, we implemented a VLC-based hybrid communication debugging system (HCDS) based on VLC using smartphone and sensor node. For the system’s downlink, the smartphone is taken as the VLC gateway and sends the debugging codes to the sensor node by the flashlight. To improve the transmission efficiency of the downlink, we also propose a new coding method for source coding and channel coding, respectively. For the source coding, we analyze the binary instructions and compress the operands using bitmask techniques. The average compression rate of the binary structure reaches 84.11%. For the channel coding, we optimize dual-header pulse interval (DH-PIM) and propose overlapped DH-PIM (ODH-PIM) by introducing a flashlight half-on state. The flashlight half-on state can improve the representation capability of individual symbols. For the uplink of HCDS, we use the onboard LED of the sensor node to transmit feedback debugging information to the smartphone. At the same time, we design a novel encoding format of DH-PIM to optimize uplink transmission. Experimental results show that the optimized uplink transmission time and BER are reduced by 10.71% and 22%, compared with the original DH-PIM.
Highlights
The wireless sensor network is composed of decentralized and self-organized sensor nodes
Data transmission during debugging interaction between sensor nodes and the cloud is mainly completed by radio wave communication (RWC) whose frequency is from 10 kHz to 3000 GHz, such as 2.4 GHz (Zigbee and Wi-Fi) or 800 MHz (GPRS), etc
With respect to channel coding, we propose an overlap dual-header pulse interval modulation (ODH-PIM)
Summary
The wireless sensor network is composed of decentralized and self-organized sensor nodes. Visible light communication (VLC) adopts unidirectional propagation different from RWC with broadcast way This unidirectional propagation guarantees intruders difficult to eavesdrop on and helps to reduce security risk. Once the sensor node is not able to recover wireless communication, some debugging information can be back to the cloud by VLC This debugging information helps developers to analyze the lost reason and possibility of malicious intrusion and further improve the overall security of the current network. We implemented a VLC-based hybrid communication debugging system (HCDS) applied in smartphones and sensor nodes. In the system uplink, debugging information from the sensor node is transmitted by the node’s LED and received by smartphone’s optical camera. In the system downlink, debugging codes are transmitted by the smartphone’s flashlight and received by the node’s ambient light sensor. The rest of this paper is structured as follows: Section 2 shows related work; Section 3 gives the overview of the VLC-based HCDS; Section 4 presents the optimization in transmission efficiency of the system downlink; Section 5 presents the optimization in transmission stability of the system uplink; Section 6 describes experiments and evaluates system performance, and Section 7 closes our work with a conclusion
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