The Research Of Gateway In WSN Based On Data Compression And Congestion Control

The Wireless Sensor Networks (WSN) is widely used in many industries and our daily lives in the modern digital society. To manage the huge information and to transmit it in the networks are the key points of the network engineering. In this paper, the mobile telecommunication network technology and TCP/IP protocol are combined to complete a further research for data compression and congestion control. By this way, some key problems such as decreasing the data volume and modifying the transmission process can be solved in a certain extent.In order to implement the data process and transmission modification, a gateway device with three wireless communication models was designed. Three wireless models are ZigBee model, GPRS model and Wi-Fi model. The ZigBee model is used to communicate with the sensor nodes in the local monitoring network. GPRS model and Wi-Fi model are used for the data exchanging between monitoring network and control center through the Internet. ARM7 processor is used as the CPU of the gateway. With the power model, the components and devices on the gateway can work steadily.To solve the contradiction among storage space, transmission capacity and volume of data in the embedded monitoring system, a digital integrate circuit with the function of data compression was designed. The algorithm of difference and variable length coding was figured out as the process methods. By analyzing the data resource we obtained that this algorithm has more advantages in real-time performance, complication of implement, efficiency and practicability. Such circuits can reduce the data volume effectively and correctly. The probability of link congestion and the pressure of data process for the CPU can be also reduced.In order to overcome the defect and weakness of the classical TCP/IP in wireless link, in this paper, a congestion control algorithm that based on the package-lose differentiation was figured out. This algorithm used the idea of entropy, combined with the relative one-way delay (ROD), available bandwidth and wireless error rate to differentiate the reason of package loss, then chose the suitable scheme to control the congestion. Such algorithm for congestion control solved the low throughput in wireless link for the reason of ignoring the wireless-error package loss.At the end of this paper, the simulator tools of Quartus II and NS2 were used for testing the availability of data compression circuit and congestion controlling algorithm. The simulation result showed that this circuit can reduce the data volume effectively and correctly. By further test the stability was also certified. The result of test showed that the average compression rate is 53.3%, and 352% faster than the one which is using software scheme. The network simulation based on NS2 platform showed that there had a higher throughput and network availability rate by using this congestion controlling algorithm. The stability of data transmission in the wireless links was improved.