Wireless Mesh Networks (WMNs) are formed by a set of gateways, mesh routers, and mesh clients. Gateways and stationary mesh routers constitute the network's backbone. Mesh clients include cell phones, laptops, or other wireless devices. Routers communicate with the external network (e.g. the Internet) by forwarding each other’s traffic towards the gateway nodes, which are directly connected to the wired infrastructure.
The diagram on the right illustrates a sample wireless mesh network consisting of six mesh routers, two of which also function as gateways. Advantages of WMNs include low upfront cost, rapid deployment, ease of installation and maintenance, and reliable service coverage. Additionally, in comparison to traditional ad hoc networks, the resources of routers in meshes are not limited, meaning that they can perform more resource-intensive functions.
In a WMN, each router forwards packets on behalf of other nodes (which may not be within direct wireless transmission range of their destinations). Moreover, the gateway functionalities enable the integration of WMNs with various existing wireless networks, such as Wi-Fi, cellular networks, WiMax, and others. In this type of network, the nodes automatically establish and maintain mesh connectivity among themselves (forming an ad hoc network). As a result, a WMN is self-organized, self-configured, and redundant (the failure of one node does not prevent other nodes from communicating).
WMNs have the potential to improve the performance and capacities of other types of ad hoc networks, including wireless local area networks (WLANs), wireless personal area networks (WPANs), and wireless metropolitan area networks (WMANs). WMNs are a universal solution applicable to a variety of small-, medium-, and large-scale scenarios, including personal, local, campus, and metropolitan areas. Mesh technology finds many applications in wireless multi-player gaming, campus connectivity, military communication, municipal networks, and more. Some of the specifications of WMNs include:
- Mesh routers and links used to support communication in the backbone of the network are relatively static.
- Mesh routers are typically connected to the electrical grid and therefore are not power constrained; mesh routing protocols do not have energy consumption restrictions.
- The traffic model may concentrate in certain paths, predominantly between mesh routers and gateways; the majority of links are used in the zones near the gateways.
- WMNs have high user and traffic volume capacity, making them suitable for establishing broadband connections for Internet access in populated communities.
The figure below illustrates the connectivity of a wire mesh network.
Infrastructure or backbone mesh, client mesh, and hybrid mesh are three different types of mesh network architectures.
Infrastructure or backbone meshes are formed by a set of mesh routers connected by self-configuring and self-healing wireless links. Some of the routers have a gateway function, providing Internet connectivity for other routers and clients that connect to them.
Client meshes are mobile ad hoc networks, where each client acts as an independent router with no centralized routing control. In this type of infrastructure, clients can perform network tasks such as routing and forwarding.
Hybrid meshes are the most generic type of architecture, combining both infrastructure and client meshes. Infrastructure provides connectivity to other networks such as internet, and clients provide a dynamic extension of the network.
The integration of WMNs with other networks such as the Internet, cellular, IEEE 802.11, IEEE 802.15, IEEE 802.16, sensor networks, etc., can be carried out through the gateway and bridging functions in the mesh routers.
By leveraging IEEE 802.11 (commonly known as Wi-Fi) hardware, wireless mesh networking reduces the dependency on wired infrastructure, which makes it useful for providing inexpensive Internet access to low-income and low-population areas. The capacity of effective throughput that can be utilized by the clients is a key challenge in the implementation of wireless mesh networking.
Signals transmitted from different devices over the same channel (frequency band) collide and cause data loss. In order to prevent this, transmissions over the channel must by coordinated by multiple access techniques, such as time division multiple access, frequency multiple access, or random access. However, the effectiveness of random access techniques used in IEEE 802.11 networks degrades as the number of devices increases.
To lessen the interference and increase the capacity of a wireless mesh network, the devices may also transmit over different non-overlapping channels provisioned in the IEEE 802.11 standards. This is done by equipping the routers with multiple radio interfaces tuned to isolated individual channels. The network capacity of a multi-radio wireless mesh network is dependent on how various channels are assigned to each radio interface to form a minimum-interference mesh network. For the mesh network to remain connected, the number of channels assigned to a router has to be at most the number of interfaces on the router.
Extended bandwidth and redundancy are the primary benefits of wireless mesh network architecture. By rerouting traffic through multiple paths, wireless mesh networks can cope with link failures, interference, power failures or network device failures. Each device in a wireless mesh network is typically called a mesh node and is connected with multiple other mesh nodes. Wireless mesh networks are also called multi-hop networks because each mesh node can reach another node by going through multiple hops and leveraging other nodes as repeaters.
Wireless mesh radios can communicate only with other mesh radios using similar protocols, such as SSID, end-to-end encryption, wireless encryption, etc. Mesh nodes do not function as wireless access points (APs) and communicate exclusively with other wireless mesh nodes, in a particular SSID and mesh ID network, which provides added security at the physical layer.
Routing protocols are employed to find and maintain routes between source and destination nodes for the purpose of forwarding network traffic. Most routing protocols for mesh and ad hoc networks are unipath, meaning that only a single route is used between source and destination nodes.
Routing protocols designed for mobile ad hoc networks (MANETs) focus chiefly on locating a single most efficient route to any destination out of the various paths available. In wireless mesh networks, traffic is primarily routed either towards the Internet gateways (IGWs) or from the IGWs to the access points. In order to perform effectively, WMN routing protocols must take into consideration the following:
- Transmission errors: the unreliability of the wireless medium may lead to transmission errors.
- Link and node failures: nodes and links may fail due to unfavorable environmental conditions.
- Incorrect routes: due to node/link failures or alterations in the network, routes may become obsolete or refer to an incorrect system state.
- Congested nodes or links: due to the topology of the network and the nature of the routing protocols, congestion among certain nodes or links may occur and cause higher delay or packet loss.
The objective of multipath (also called SAN multipathing or I/O multipathing) routing in a wireless mesh network is to use several effective paths to reach destinations without imposing excessive control overhead to maintain them. Multipath routing helps networks to stabilize and adapt to load.
Protocol constraints limit the self-organizing, -healing, and -conﬁguring advantages of WMNs. Implementations of WMNs mostly utilize single path MANET routing protocols, but this is not an optimal solution for the redundant, hierarchical, and layered architecture of wireless mesh networks. In WMNs where the number of redundant paths exceeds those in conventional last-hop wireless or wired networks, multipath routing would improve reliability and performance of end-to-end communication. Potential benefits of multipath routing include:
- Fault tolerance: introducing redundancy in the network or providing backup routes to be used in case of a failure increases fault tolerance at the routing level.
- Throughput enhancement: in a mesh network, some links can have limited bandwidth. Routing along a single path may not provide enough bandwidth for a connection. The establishment of multiple paths to route data could potentially satisfy greater bandwidth requirements.
- Load balancing: since traffic distribution is not uniform throughout the network, spreading traffic along multiple routes can alleviate congestion and bottlenecking.
- Security: single-path routing protocols are more vulnerable to routing attacks; multipath solutions offer superior attack resilience.
The global wireless mesh network market size was valued at USD 6.11 billion in 2018 and is projected to expand at a compound annual growth rate (CAGR) of 9.1% from 2019 to 2025. This expansion is driven by the accelerated usage of Artificial Intelligence (AI) and Internet of Things (IoT) technologies in various industries.
It is anticipated that the increased usage of mobile and handset devices along with developments in technologies used in such devices will contribute to further market growth, as well as the adoption of 3G, 4G, and LTE technologies. North America is expected to lead the global market in the future as the region has a large number of Wi-Fi/WLAN networks. Other contributors to the WMN market include:
- Advancements in smart city and smart device technology aimed at enhancing the mode of communication between government offices and municipalities.
- Improving the education sector through the adoption of technologies, such as online courses and webinars.
- Smart street lighting infrastructure to control the density of lights for optimal usage.
- Industrial sectors, such as oil and gas, chemicals, and mining, which use WMNs for improving communication facilities in remote locations.
- Video surveillance used by various government agencies as a security solution that keeps a record of employees and buildings.
- Security and safety purposes, smart metering applications in smart cities, and monitoring traffic conditions for road safety. The smart cities and warehouse segment led the WMN market in 2018.
- The disaster management and rescue operation segment—with the increasing proportion of climatic disasters due to rise in temperatures, there is incentive for rescue operations to be improved with the aid of mesh networks.
- Military applications for improving communications.
- The healthcare segment due to wireless mobility that makes patient information easily accessible.
The WMN market's impact is predicted to be significant in Asia-Pacific as it is considered to be an emerging economy. WMN networks are implemented in industrial and commercial segments including public safety, industrial automation and monitoring, mining automation, environmental monitoring, malls, shopping centers, and hi-tech city parks, which are a part of the smart infrastructure development in this region.
The 2.4 GHz radio frequency band segment made up the largest portion of the WMN market in 2018. Various industrial, medical, and scientific instruments mostly operate in the radio frequency bands, which is expected to boost the segment growth. Moreover, this radio frequency band covers long- and small-range antennae that are used to keep the system compact. This segment is also expected to dominate the North American market as this region has the largest number of innovations in communications infrastructure.
5 GHz is an effective solution to respond to the ubiquitous demand for faster network speeds and is estimated to be the fastest-growing radio frequency segment between 2019 and 2025. As per the World Telecommunications Conference, the 5 GHz spectrum was allocated for unlicensed usage by developed countries.
According to one research report, the global 5G Devices Market in 2019 was approximately USD 2.67 billion. The market is expected to grow at a CAGR of 38% and is anticipated to reach around USD 26.1 billion by 2026. Other estimates valued the global 5G services market size at USD 41.48 billion in 2020 and project expansion at a CAGR of 46.2% from 2021 to 2028.
5G is expected to provide benefits in three major areas, also known as the “5G triangle”:
- URLLC: ultra-reliable low-latency communication use cases
- mMTC: massive Machine-Type Communication (IoT) use cases
- eMBB: enhanced Mobile Broadband high speed use cases
The reduced latency provided by 5G networks will be beneficial for autonomous vehicles, as they will be able to respond 10-100 times faster than over ordinary cellular networks. A vehicle-to-everything (V2X) communication network is a possibility in the future. This would enable vehicles to automatically and instantaneously respond to objects and changes around them. It is necessary for autonomous vehicles to be able to send and receive signals in milliseconds in order to brake or shift directions in response to road signs, hazards, and people crossing the street.
As cities deploy intelligent transportation systems (ITS), the need for connected vehicle technology increases. Some aspects of these systems are relatively easy to install using communications systems that support smart traffic management to handle vehicle congestion and route emergency vehicles.
The key benefits of 5G in industrial automation are wireless flexibility, reduced costs, and the viability of applications that are not possible with older wireless technologies. 5G could enable industrial automation applications to be completely wireless.
The low latency of 5G will enhance the immersiveness and interactivity of AR and VR applications. In industrial applications, for instance, a technician equipped with 5G-powered AR goggles could have their vision augmented with an overlay that would aid them by identifying parts of machinery, providing repair instructions, or highlighting hazards.
Drone-powered solutions have become increasingly present in the consumer market (for filming, photography, or recreational flying) and across many industries, including utilities (e.g. equipment inspection), logistics, and retail (e.g. delivery of goods). As the market expands, the introduction of 5G can improve the range and interactivity of drones, strengthening both the drone and 5G markets.
Wearables, trackers, and sensors are projected to constitute a large share of the 5G market. Every device connected over a cellular connection can potentially benefit from 5G, which will enable yet more devices to gain connectivity and operate at low latency in any given area.