Routing Protocol Design for WMN

WMNA multi-hop Network with a dynamic topologyAd hoc NetworkTherefore, most WMNRouting ProtocolThe source is the Ad hoc network. Ad hoc network routing protocols can be divided into geographical location-assisted routing and non-geographical location-assisted routing. The former requires the support of the GPS Positioning System, and the latter can be divided into plane routing protocol and hierarchical routing protocol.

The plane routing protocol is divided into on-demand routing, such as on-demand distance vector protocol (OSCAR), Dynamic Source Routing Protocol (DSR), segment-by-segment routing protocol (SSR), and active routing, for example, the distance vector of the destination station number (DSDV ),WirelessRouting Protocol (WRP), topology broadcast (TBRPF) based on reverse path forwarding, and hierarchical routing protocols include Cluster Gateway switching protocol (CGSR) and regional routing protocol (ZRP.

Currently, WMN adopts the TBRPF-based routing protocol, the DSR-based routing protocol, the DSDV-based routing protocol, and the routing-based routing protocol. However, there are some fundamental differences between WMN and Ad hoc networks, as shown in table 1. The direct application of Ad hoc network routing protocols in WMN cannot optimize the performance of WMN.

To design the WMN routing protocol, consider the following factors:

(1) routing selection basis

You need to consider multiple parameters, including:

Hop count: the number of wireless links that the path between the source node and the target node goes through.

Expected transmission frequency (ETX): The number of retransmissions caused by Media Access conflicts. It is a common parameter in wireless communication.

Expected transmission time (ETT): it is more commonly used than ETX, and takes into account the bandwidth characteristics of the channel itself.

Round-trip transmission time (RTT): the time required for back-trip transmission between the source and destination nodes of the group.

Energy consumption: the total energy consumption caused by a certain transmission route.

Route stability: This article describes how stable a route is and how long it can last.

(2) Network Support Scale

The network scale of WMN is generally large, and the routing protocol needs to support more nodes. If the traditional Ad hoc network routing protocol is used directly, the routing search process may take too long, the cost is also high.

(3) Fault Tolerance

InMeshWhen the client moves, the wireless link is congested, or the Mesh router is faulty, You Can reselect the route.

(4) link interference

Wireless signals sent from neighboring nodes interfere with each other. When selecting a route, you should select a link with little interference to increase the system capacity.

(5) Cross-layer protocol design

Combined with some technologies of the physical layer, such as the directional antenna, multi-input, multi-output (MIMO), and the link layer, protocols at each layer are designed to work collaboratively and comprehensively.

The Wireless Mesh Network Supports Wireless Access and wireless network interconnection. Due to different application scenarios, the focus is also different.

The routing protocol for wireless access applications must be fully adapted to Mesh clients and Mesh routers, including user nodes with Strong Mobility and limited power consumption, and weak mobility, access nodes and gateway nodes with unlimited power consumption. Currently, when designing the vast majority of WMN routing protocols, the Mesh clients and Mesh routers are treated equally without considering the differences between the two, and the two types of nodes are distinguished to study the routing protocol, it may become a noteworthy topic. In network convergence applications, a wireless network composed of user nodes can be considered as an autonomous domain and can directly adopt the Internet routing concept, this solves the Routing Problem of the wireless core network composed of Mesh routers.

The four common Ad hoc network routing protocols are described in the document (two types of on-demand routing protocols are DSR and Oscar, and two types of active routing are OLSR and DSDV respectively) it is used to evaluate the performance of the Mesh core network. It compares the routing overhead, the packet transmission success rate, and the end-to-end latency. The results show that, because the WMN routing overhead is relatively small, in general, the on-demand routing protocol has better performance than the active routing protocol. However, due to the weakening of the mobility of WMN nodes, you need to increase the routing expiration time and the routing Cache Time of the on-demand routing protocol to avoid overhead increase when too many routing messages are exchanged.

In wireless access applications, most of the services from user nodes to Gateway nodes are point-to-point services, and network services are sudden. In network convergence applications, services between Mesh routers come from one network, and business flows are aggregated, which is similar to Internet services, for example, the business scope and average group size follow the 24-hour model. Most of the IP services are TCP services, while most of the TCP services are Web browsing services and file transmission services. According to the characteristics of different business types, the routing protocol design that differentiates business types and guarantees service quality needs to be treated differently.

Mesh routers are equipped with more than two Wireless Transceiver Devices in the application of network convergence. The design of the routing protocol needs to consider the characteristics of Multi-wireless transceiver and multi-channel. In wireless access applications, generally, this parameter is not considered. In view of the above problems, in view of the characteristics of the WMN network structure and application characteristics, based on the basis of the wireless self-organizing network technology, WMN routing technology can be studied to improve the WMN network performance.