Help you understand wireless Mesh network standards (1)

Currently, wireless Mesh networks are applied in more and more fields. Any technology must be standardized by technical standards, so wireless Mesh network technology must be standardized by IEEE802 standards. This article will introduce the wireless Mesh network standards in detail and hope to help you.

Standards Related to wireless Mesh networks in the IEEE802 series.

1. IEEE802.11s wireless Mesh network standard

One difficulty encountered by IEEE 802.11 in large-scale applications is that the coverage of the system is limited. WLAN is limited by the transmit power, and the coverage is generally within the range of 100 m. In order to expand the coverage of the network, we usually increase the AP, but this method increases the construction cost of the public network. As a new networking technology, wireless Mesh networks provide a new way to solve the above problems.

The IEEE802.11s task group mainly studies the protocols supporting the Wireless Distributed System (WDS) and defines the Media Access Control (MAC) layer and physical layer protocols for WMN, to enable a WLAN to establish a network between multiple APS through self-configured multi-hop mode to improve the coverage of the WLAN. WDS is a part of the 802.11 Network. It is used as a relay bridge function to enable Wireless AP bridging (relay) without affecting its Wireless AP coverage function. The Wireless AP or wireless router supporting WDS technology has a hybrid Wireless LAN working mode and supports point-to-point and point-to-point data transmission [2].

IEEE 802. 11s proposes a reference architecture for wireless Mesh networks. The Mesh Media Access coordination component (MMACFC) is located on the physical layer and under the Mesh routing component. It is responsible for effective competition access and scheduling of packet sending and receiving between multiple hop nodes in WMN. After a secure Mesh link is established, the Mesh nodes need to coordinate with other Mesh nodes to solve the competition and sharing of wireless media, to ensure that data packets of the node itself and other nodes are effectively forwarded through the multi-hop WMN. Intuitively, MMACFC is equivalent to the distributed coordination function (DCF) in 802.11 WLAN or the Enhanced Distributed Channel Access Mechanism (EDCA) in 802.11e ). Make necessary improvements to DCF or EDCA to efficiently work in multi-hop Mesh networks. MMACFC has the following problems to solve: hiding terminal problems, exposing terminal problems, traffic control from the source node to the target node on the multi-hop Mesh path, effective scheduling on the multi-hop transmission path, and multi-hop multimedia services (videos or voice) distributed access control and distributed service quality assurance (QoS) service management, effective processing of local services and forwarding services, scalability in different network environments, scheduling of channel operation and access between Mesh nodes, and multi-channel improvement of Mesh network performance [3].

The goal of IEEE802.11s is to break through the functional limitations of the traditional AP, so that it has the Mesh router function, and the business flow is forwarded to the neighboring AP for multi-hop transmission. This method determines that WMN has high reliability, great scalability, and low investment costs. In this way, in the new WLAN architecture, the wlan ap automatically forms the wlan wmn backbone network [4]. The IEEE 802.11 Mesh network can be a backbone network Mesh or a client Mesh. In the client Mesh structure, all devices work in the WLAN Ad hoc network mode. WMN automatically configures the interconnection between nodes, freeing you from the previous AP dependencies.

2. IEEE 802.15 wireless Mesh network standard

The IEEE 802. 15 standard cluster is mainly developed for wireless networks, and mainly defines the physical layer and MAC layer of WPAN. Currently, 802. 15. 1-802. 15. 3. Essentially, the network structure cannot be directly supported, but only the network structure of the micro network in the point-to-point mode, but the scattering network already has the prototype of WMN [5].

The IEEE 802.15.4 standard is designed for applications with low data rate and long battery life requirements. It provides a comprehensive network solution for WPAN. The ZigBee protocol is a high-level protocol running on MAC and physical layer of 802.15.4. Its network layer clearly defines three network topologies, Star, cluster, and Mesh. In the Mesh structure, all wireless nodes in the network are the same and can communicate with each other directly. Each network selects one or more routes for multi-hop transmission, transmit the data to the central node. Each node of the Mesh network has multiple paths to reach the central node, so it has a strong fault tolerance capability. In addition, this multi-hop system replaces the transmission distance of a single hop with multiple hops, reduces the sending power required by the source node.

IEEE 802.15.5 is still under development. It is located on the MAC layer of WMN and does not require ZigBee or IP route support. It inherits some basic ideas of 802.15.1-802.15.4, but fully supports the Mesh structure. In the 802.15.5 standard, a Mesh network is defined as a Network (PAN). There are two network modes: full Mesh topology and partial Mesh topology. In a full-mesh topology, each node is directly connected to any other node. In some mesh topologies, only some nodes are connected to all other nodes, other nodes are connected to nodes that exchange more data. The 802.15.5 standard mainly involves the following problems: collision-avoidance beacon Scheduling Policies, routing algorithms, distributed security issues, energy efficiency operation modes, and support for mesh nodes and network PAN mobility.