Research on Network Technology and experiment of Wireless Mesh Network (1)

This article describes the problems and technologies in WMN networking from the aspects of network configuration, power control, mobility management and access control, and routing protocol design) the design of the network routing protocol is compared, and a WMN Test Bed Implementation Scheme Based on WLAN and Layer 2 switching technology is provided.

I. Introduction to wireless Mesh Networks

The Wireless Mesh Network (WMN), also known as the Wireless Mesh Network and the wireless Mesh network, appeared around the middle of 1990s. With the development of mobile communication technology, in addition to the voice business needs of wireless communication networks, the demand for high-speed Internet access is also increasing. Traditional wireless access methods face problems such as insufficient access bandwidth and unsatisfactory service quality. In addition, there is a lack of unified planning for wireless spectrum resources and topology structures, making it difficult to adapt to flexible and changing use conditions. WMN provides a new way to solve the problems faced by wireless access networks.

The topology of a communication network is generally abstracted into a figure G (V, E). V represents the set of communication nodes, and E represents the set of communication links. The initial definition of a wireless Mesh network is that the network topology of a wireless communication network can be abstracted into a connected graph, which is connected to any two vertices vi, vj, V, vi, and vj in the figure, that is, one or more paths from vi to vj are defined as vertex sets (vi = vp, 0, vp, 1 ...... Vp, m = vj), where (vp, n-1, vp, n) ε E, 1 ≤ n ≤ m.

The topology 1 of the traditional wireless access network is mainly point-to-point (P2P) or point-to-point (P2MP). For example, the cellular network belongs to the P2MP topology, and the Wireless LAN (WLAN) there are two structures, center and self-organizing, which belong to the P2MP and P2P types respectively. The topology of WMN is a mesh, also known as multi-point to multi-point (MP2MP ). This network structure enables WMN to better solve some problems in traditional wireless access networks.

The coverage of the cellular network is relatively large, mainly providing voice services, but the construction and maintenance costs are high. In addition, in the hotspot areas of multimedia transmission services, the communication speed is relatively low. WLAN provides a high communication rate and is suitable for multimedia data access services. In a P2MP structure with a center, due to the limited coverage of the Access Point (AP), in order to provide wireless access in a larger area, multiple APs need to be deployed, making the cost high; for a self-organized P2P structure, network connectivity depends on nodes with strong mobility, resulting in reduced network reliability and high performance requirements for gateway nodes, the billing and management methods are also unclear.

WMN consists of two types of network nodes: Mesh router and Mesh client. When WMN is used as the access network, the Mesh client accesses the Internet through other adjacent nodes in a wireless multi-hop mode. This MP2MP structure gives WMN the following advantages:

Self-configuration: nodes form a single-hop or multi-hop connection through an open wireless link to automatically complete networking;

Self-regulation: nodes have multiple communication paths, and the service can flexibly select the appropriate (such as the shortest path, least interference, and fastest speed) path for transmission;

Self-healing: When a node suffers a fault or a link is congested, services in the network can bypass the corresponding node or link to improve network reliability;

Scalability: You can easily add or delete network nodes, adjust network coverage, and reduce system construction and management costs.

Therefore, WMN is suitable for the "Last Mile" Wireless Access Solution of the Internet, which has been reflected in IEEE 802.11 s, 802.15 and 802.16 standards, it will become an important part of next-generation Wi-Fi and WiMAX.

In addition, there are a variety of Wireless Access networks that use different wireless transmission technologies and standards to provide their appropriate applications. For example, the cellular network is suitable for voice communication, Wi-Fi is suitable for broadband multimedia data access in some regions, and wireless sensor networks are suitable for data collection in environmental detection. In the future, wireless networks will coexist and integrate various heterogeneous networks to provide users with ubiquitous networks that can be accessed anytime, anywhere. This is the development direction of wireless networks and may become a new application direction of WMN.

As shown in figure 2 of the network structure of WMN that integrates multiple wireless networks, the core device in the network is a Mesh router, which forms a core network with a dynamic topology. Mesh routers are equipped with a variety of wireless transmission standard interface devices to achieve the interconnection of Various wireless networks, including cellular networks, WiMAX networks, WLAN, Mobile Ad hoc Networks, and wireless sensor networks. User Terminals using various wireless transmission technologies can connect to the core network through a wireless access network anytime and anywhere. The configuration and maintenance cost of WMN is more advantageous than that of the traditional wired network. It can be used as an implementation method for ubiquitous heterogeneous networks in the future.