| At present, with the development of information technology, the industrial field devices have been upgraded gradually, becoming more systematic, intelligent and networked. In industrial control system, the control network which formed with these field devices has been the most important part. As the networking technology develops, the control network expands on the way towards industrial wireless network, and it has achieved a great success, such as the Protocol of SP100, Wireless Hart Network etc. The industrial network develops on the base of traditional wireless sensor network. It inheritances the superiorities of sensor network, such as low-cost, ubiquitous perception, low power consumption and easy-maintenance etc. Moreover, it develops its own technical characteristics on the aspects of real-time communication and network anti interference. The industrial wireless network is widely applied in real-time monitoring and process control of industrial process automation.WIA-PA ((Wireless Networks for Industrial Automation-Process Automation) was developed by the Chinese Academy of Sciences, together with Shenyang Institute of Automation, Chongqing Posts and Telecommunications University, Southwest University etc. The research work was carried out by the support of "863national key project". WIA-PA is a industrial wireless networking protocol standard used in process automation. This protocol introduces the wireless communication technology into the field of industrial process control, and its network communication has the properties of real-time communication, high reliability, low power consumption etc. WIA-PA network uses a double mesh and star network architecture, which take a combination of centralized and distributed management as the network resources managing methods.In this manner, the WIA-PA network has a good performance.MAC protocol lays in the bottom part of the sensor network protocol, which has a greater impact on the performance of the network, and is one of the key network protocols that guarantee the efficient communication of wireless sensor networks. The MAC protocol determines the manner of using wireless channels in the communication link, it allocates the limited communication resources between the sensor nodes. Traditional single channel MAC protocol will be possible to have data conflicts during data transmission. Compared with single channel MAC, the multi-channel MAC protocol is possible to increase network throughput and reducing the delay on the basis of the full use of the channel resource. At present, there is no special effective multi-channel MAC mechanism for WIA-PA network, and the existing multi-channel MAC mechanism cannot be directly applied to WIA-PA network. In this paper, the author proposes a Multi-Channel MAC mechanism for WIA-PA network on the base of the characteristics and requirements of industrial control, combined with the medium access control mechanism after taking part in the research work of WIA-PA network.In this paper, the author make an overview on the network architecture, technical features, resource management, the key technology of WIA-PA based on the analysis of industrial wireless network development background and research significance of the WIA-PA industrial wireless networks firstly. Secondly, this paper laborites the media access control principle and make analysis of a typical single-channel MAC protocol together with the characteristics of existing Multi-Channel MAC protocol, pointing out that the shortcomings of application in WIA-PA. Finally, this paper presents a high performance Multi-Channel MAC mechanism according to WIA-PA network characteristics. The mechanism mainly includes the channel allocation algorithm for Multi-Channel and multi-channel MAC communication. In the work of channel assignment, it use the method of combination with dynamic and static channel assignment algorithm, which can improve the efficiency of channel allocation and can reduce the impact of interference in the industrial field environments on network performance. It uses virtual link in the inter-cluster communication design, combined with Multi-Radio mechanisms, which effectively reduce the data transmission conflict in SINK node. During intra-cluster communication phase, it uses polling-based communication mechanism to effectively reduce the cluster communication channel switching frequency, which can reduce network overhead and latency.More, the author uses NS2network simulation platform to design a comparative experiment between the proposed multi-channel MAC protocol and the traditional single-channel MAC protocol, focusing on the throughput and delay of the network. The simulation results show that the proposed multi-channel MAC mechanism can improve network throughput, reduce latency, enhance network reliability and timeliness, which has a good result. |
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