A Mesh network topology is considered to be one of three varieties of ad hoc network requires that each node must not only capture and disseminate its own data, but also serve as a relay for other nodes.
A mesh network can be designed to propagate the message along a path, by hopping from node to node until the destination is reached. To ensure the availability of a path, a routing network must allow for a continuous connection and reconfiguration around broken or blocked paths, using self-healing algorithms.
There are three types of Mesh as explained below but for the greatest flexibility a hybrid configuration is the most useful.
- Client - an EKI-6340-3, as a client mesh, provides peer-to-peer networks among client devices and the client nodes to perform routing and configuration functions.
- Infrastructure - By using routers as the infrastructure, the routers form a mesh of self-configuring, self-healing links. Mesh routers can also be connected to the Internet, thereby providing a backbone for traditional networks and allowing the integration with existing wireless networks.
- Hybrid - A combination of the previous two architectures, hybrid architecture performs the functions of infrastructure and client and can access the network through mesh routers as well as communicating with other mesh clients; making it the most suitable configuration for a majority of applications.
These three configurations have the following three features that can be applied to each of them.
- Self-healing and Self-forming
Intelligent Mesh capabilities with self-healing and route choosing algorithms (self-forming) follow the calculation of a number of hops and radio signal quality.
- Multiple Hopping
Intelligent wireless Mesh systems have a throughput of higher than 150 Mbps at 2 hops and can still be 100 Mbps at 10 hops. Such high throughput rates ensure continuity of video images and self-healing saves the burden of maintenance and the cost of trouble shooting.
- Ultra-Fast Roaming for Mobile Connectivity
Fast roaming is a unique feature of a Mesh Station and its handover time between two Mesh APs can be as low as 20ms.
These Mesh network configurations use the following technologies to provide the connection:
IEEE 802.11n
The protocol, 802.11n includes many enhancements such as: an increase in speed, range and reliability over the earlier a/b & g versions. To improve the range, throughput and reliability of the wireless networks 802.11n made three core innovations: MIMO, packet aggregation and channel bonding, to give a fivefold increase in performance over 802.11a/b/g networks.
MIMO
MIMO systems are built using multiple vector antennas on both the transmitter and the receiver and it is this multiplicity that makes a MIMO system. Since it can utilize both the diversity and muxing of simultaneous data streams it can potentially increase system capacity by three times or more and has been adopted into IEEE 802.11n.
Receiver Processing Only
Receivers do not need MIMO signal processing but multiple front ends, therefore antennas at the receiver are connected to multiple independent front ends with separate data streams, which are then muxed into a single data stream providing a much higher data rate than a single antenna system.
Transmitter Processing Only
A transmitter is just a transmitter. A single data stream is demuxed into multiple substreams. When the signals from different antennas arrive at the receiver, MIMO signal processing must be performed using one of three schemes: space-time coding, vertical Bell Lab Layered Space-Time (V-Blast), and maximum likelihood detection (MLD). MLD provides the best performance of the three.
Both Transmitter and Receiver Processing
These are very complicated to configure and administer. The most popular method of performing the two functions is called singular value decomposition which diagonalizes the MIMO channels to form independent channels, to which water filling schemes can be applied to maximize overall system capacity.
Packet Aggregation
Packet aggregation aggregates multiple packets of an application into a single transmission frame and enabling them to be sent with a fixed overhead cost of just a single frame. Packet aggregation works best for data applications such as file transfers, for real-time applications like voice or video packet aggregation has no effect.
Channel Bonding (40MHz Channels)
802.11n works at 20MHz to carry a maximum of 150Mbps of raw data per channel and by using a technique called channel bonding it combines two adjacent 20MHZ channels into a single 40MHz channel, thereby doubling the throughput to over 300Mbps. Channel bonding works best at 5Ghz because of the far larger (over 100) number of channels.
In conclusion it’s only by the inclusion of the algorithms, MIMO and IEEE 802.11n technologies that Advantech are able to create the tools necessary to transmit data continuously across large distances regardless of the difficulties and obstacles put in the way of the signal. Advantech’s EKI radio devices are specifically designed for the rigors of harsh environments and too send data as quickly as the technology allows without any interruptions.
