Wireless Mesh Network Technology and Its Applications

       In recent years, wireless networks have witnessed rapid development. To meet various applications and demands, many new wireless communication technologies and standards have emerged. Among them, wireless mesh networks are one of the technologies that have attracted much attention. WMN is a new networking technology, namely mesh network. Its topology is dynamic and has the functions of self-organization and self-healing, meaning it can automatically form a network without the need for human intervention, and each terminal can freely join or leave. During information transmission, the information is continuously forwarded through multiple hops until it reaches the destination terminal. If this technology is used to network wireless sensors, Wi-Fi (Wireless Fidelity), WiMAX (worldwide inter-operability for microwave access), etc., it can extend their application scope, enhance their functions, thereby forming wireless sensor networks, improving the coverage of wireless local area networks, and establishing metropolitan area networks. Also due to its broad application prospects, it has been increasingly attracting people's attention and being applied in life and work.

1 WMN Technology

1.1 Technical principle

       Wireless Mesh networks are low-power multi-hop systems. They handle messages by transferring information packets from one node to another until the packets reach their destination. Point-to-point network nodes filter out all information packets and only keep their own packets. In contrast, Mesh network nodes receive information packets to be sent to other nodes and retransmit them. Each node in a wireless Mesh network can act as an access terminal, or it can have routing and information forwarding capabilities, offering extremely high network flexibility. The operation mode of wireless Mesh networks is similar to the Internet and provides multiple redundant communication paths from the source to the destination. If one path stops working due to hardware failure or interference, the Mesh network will automatically change the routing of the packets, allowing them to pass through an alternative path.

1.2 Network structure

       The nodes of WMNs have two types: routers or clients. Among them, the routers that form the backbone of the network have very little mobility. They provide gateway and bridge functions for mesh networks to connect with other networks (such as the Internet, cellular networks, IEEE 802, sensor networks); clients can be either stationary or mobile, and clients can either form their own networks or jointly form networks with the routers of the mesh network.

1.3 Main feature

       Wireless multi-hop. By reducing the transmission power of wireless nodes, multi-hop transmission between nodes is achieved. This not only effectively reduces the energy consumption of nodes but also reduces the interference between nodes, increases the spatial multiplexing degree of the wireless channel, and thereby improves the capacity of the network.

       Self-organization and self-repairing capabilities. The wireless mesh networking method is flexible in setup, easy to configure, capable of self-repairing, with nodes distributed in a mesh pattern, and has strong network scalability, enabling multi-point-to-multi-point wireless communication.       

       Mobility. Depending on the type of nodes, it is required that the routing nodes have the minimum mobility, while the client nodes can move flexibly.

       Access method. Flexible and diverse, it can be combined with the Internet, cellular networks, sensor networks, etc. to form a network.

       Energy consumption mode. Generally, there are no strict restrictions on the energy consumption of routing nodes, while for client nodes, it is usually required to implement power-efficient protocols.

       Compatibility and interoperability. It has good compatibility with existing wireless networks and strong interoperability.

2 WMN Protocol

       From another perspective, when analyzing the topology and architecture of WMN, it incorporates the advantages of both star and mesh networks, achieving a seamless integration of the two. This integration is accomplished by implementing the WMR (Wireless Mesh Routing) protocol at the network nodes (as shown in Figure 1).

（Figure 1）

       As can be seen from Figure 1, in order to provide multiple reflection wireless routing functionality, the WMR routing protocol is executed both at the access point and the mobile node. Additionally, to achieve compatibility with IP, WMR is placed as an intermediate layer protocol between the MAC layer and the IP layer. Thus, the WMR protocol can be executed effectively without requiring significant modifications to other protocol layers. This enables WMR to be well-compatible with most existing applications (including wireless standards represented by 802.11x).

3 The advantages of WMN

WMN has many advantages compared to traditional wireless networks.

(1)The reliability has been significantly enhanced.

       The grid topology structure adopted by WMN avoids the point-to-multipoint star structure seen in technologies such as 802.11 WLAN and cellular networks. These technologies suffer from issues like service convergence, central network congestion, interference, and single-point failures due to centralized control methods, thereby incurring additional reliability guarantees at the cost of investment.

(2)With conflict protection mechanism

       WMN can identify the links that cause collisions, and the angle between the selected link and the original link can be obtuse, thereby reducing interference between the links.

(3)Simplified link design

       WMN usually requires a shorter wireless link length, which reduces the cost of antennas (transmission distance and performance), on the one hand. At the same time, it reduces the transmission power, and this will also reduce the interference between different system radio frequency signals and system self-interference, ultimately simplifying the design of the wireless link.

(4)The coverage area of the network has expanded.

      Due to the introduction of WR and IAP, end users can access the network or communicate with other nodes at any location. Compared with traditional networks, the coverage area of access points has been significantly expanded, the spectrum utilization rate has increased, and the system capacity has also been enhanced.

(5)Flexible networking and convenient maintenance

      Due to the networking characteristics of the WMN network itself, as long as a few wireless devices such as WR are added at the required locations, it can form a wireless broadband access network with the existing facilities. The routing selection feature of the WMN network ensures that link interruptions or local expansion and upgrade do not affect the operation of the entire network. Therefore, it enhances the flexibility and feasibility of the network, and is more powerful and complete in function compared to traditional networks.

4 Practical application

Mesh networks have broad application prospects in various fields such as homes, enterprises and public places.

(1)Family

      One of the important applications of wireless Mesh networks is to establish a home wireless network. Home-based wireless Mesh networks can connect desktop PCs, laptops, HDTVs, DVD players, game consoles, and various other consumer electronic devices without the need for complex wiring and installation processes. In a home wireless Mesh network, various household appliances are both users on the network and components of the network infrastructure that provide access services for other devices. When the number of household appliances increases, this networking method can provide more capacity and a larger coverage area. Another advantage of wireless Mesh networks in home applications is that it can support bandwidth-intensive applications, such as high-definition video.

(2)Enterprise

      Currently, most enterprise wireless communication systems adopt traditional cellular phone-style wireless links to provide point-to-point and point-to-multipoint transmission services to users. However, wireless Mesh networks are different. They allow network users to share bandwidth, eliminating the bottleneck of current single-hop networks and enabling dynamic balance of network load. Adding or adjusting APs in wireless Mesh networks is also easier, more flexible in configuration, and has lower installation and usage costs compared to wired APs. Especially for enterprises that need to frequently move access points, the multi-hop structure and flexible configuration of wireless Mesh networks will be very beneficial for adjusting and upgrading the network topology.

(3)School

      The campus wireless network is very similar to that of large enterprises, but it also has its own unique features. Firstly, the scale of the campus WLAN is large. Not only is the geographical area extensive, but there are also many users and a large amount of communication traffic. This is because students use more multimedia compared to general enterprise users. Secondly, the requirements for network coverage are high. The network must be able to achieve seamless roaming among indoor, outdoor, auditoriums, dormitories, libraries, and public places. Thirdly, load balancing is extremely important. Since students often engage in concentrated activities, when students are using the network simultaneously at a certain location, communication congestion may occur.

      The traditional solution to these problems is to install APs densely indoors while using very few APs outdoors. However, due to the significant changes in user demands in campus networks, it is often necessary to add new APs or adjust their deployment locations frequently, which will result in a considerable increase in costs. On the other hand, using a wireless Mesh network for networking not only makes it easy to upgrade and adjust the network structure, but also enables seamless roaming between indoor and outdoor areas.

(4)Hospital

      Wireless Mesh networks also provide an ideal networking solution for public places such as hospitals. Due to the dense and complex structure of hospital buildings and the need to prevent electromagnetic radiation in some areas, it is one of the most challenging fields for installing wireless networks. The hospital network has the characteristics of difficult wiring and high requirements for network robustness. Adopting wireless Mesh networking is an ideal solution to these problems. If the topology of the hospital wireless network needs to be adjusted, simply moving the positions of the existing Mesh nodes or installing new Mesh nodes is sufficient. The process is very simple and installing new Mesh nodes is also very convenient. Moreover, the robustness and high bandwidth of wireless Mesh make it more suitable for deployment in hospitals.

(5)Tourism and leisure venues

      Wireless Mesh networks are highly suitable for use in locations that are geographically remote, have difficult wiring conditions, or are economically impractical, yet require providing users with broadband wireless Internet access, such as tourist attractions, resorts, motels, etc. Wireless Mesh networks can offer broadband services to these places at the lowest cost.

(6)Quick deployment and temporary installation

      For those places that require rapid deployment or temporary installation, such as exhibitions, trade fairs, or disaster relief operations, wireless Mesh networks are undoubtedly the most cost-effective networking method. For instance, if a meeting or exhibition needs to be held for a few days in a certain location temporarily, using a wireless Mesh network for networking can minimize costs.

5 Epilogue

      WMN not only has broad application prospects in many fields such as homes, enterprises and public places, but also can be combined with data and image acquisition modules to monitor or collect data of target objects, and is widely applied in fields such as environmental detection, industry, transportation, etc. With the continuous update and improvement of other technologies, WMN can better integrate and complement with them, thereby being able to leverage their strengths and avoid their weaknesses to fully exert their respective advantages.