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The principle of a MESH Radio network is that multiple radio nodes bond together flexibly to form a fluid self-healing network that carries IP (network) data. A node can move around freely within a MESH-covered area and retain network connectivity to all other nodes.
Most MESH Radio systems are designed for commercial use, typically using the 802.11 standards family, and suffer from:
Breaks a broadband channel into many discrete, narrow sub channels or subcarriers
Coded Orthogonal Frequency Division Multiplexing (COFDM) is an alternative to a single carrier waveform which is often used because of the limitations of single carrier systems for broadband applications where multipath is present. These limitations are due to the frequency selective fading that causes widely varying receive signal strength across the broadband channel, as well as the inter-symbol interference that can occur in environments with long delay spread.
COFDM breaks a broadband channel into many discrete narrow sub channels or subcarriers, as depicted below.
The term orthogonal refers to the fact that each of the subcarriers is created in a way that inherently does not interfere with the other subcarriers without the need for filtering each one in the frequency domain as is done traditionally to isolate channels from each other.
The frequency selective fading problem is solved by combining the use of subcarriers with the use of Forward Error Correction coding, which is the C in COFDM*. FEC coding transforms a given number of bits into a larger number of bits which contain information redundancy. Roughly speaking, if x bits are turned into 2x bits, half of these can be lost and still the original data recovered. This scenario is called a rate ½ code.
Turning every 5 bits of data into 6 bits would be a rate 5/6 code. A 5/6 code allows more user data to get through but is more susceptible to lost or corrupted bits. This FEC coding is used to spread the data among the subcarriers of a COFDM system. In this way, even if a particular subcarrier suffers from frequency selective fading to the point that it is totally lost, the data can be recovered because it has been redundantly coded onto other subcarriers.
COFDM wireless also provides a practical solution to the problem of inter-symbol interference (ISI). This problem can be demonstrated with the following illustration:interval
Between each transmitted symbol, a silent guard interval is left so that at the receiver there is time for a copy of the symbol arriving on a longer reflected path to be received without overlapping with the next symbol. The above illustration shows what happens at the receiver when the guard interval is long enough versus when it is too short resulting in ISI.
The problem with a broadband single carrier system is that the symbol length becomes very short for a given data transfer rate. In practical scenarios, the guard interval necessary to account for path length differences can become as long or longer than the symbol. This greatly decreases the amount of data that can be sent because the silent period starts to dominate.
The symbols of a wireless COFDM system become longer in direct proportion to the number of subcarriers used. In this manner, a guard interval of a given length will have much less of an impact on the amount of data that can be transmitted, as the data carrying symbol dominates over the silent guard interval.
*COFDM is sometimes used as a synonym for DVB-T within the wireless video community. In reality all practical OFDM based systems utilize FEC coding and are thus COFDM.
The revolutionary waveform, now known as Mobile Networked MIMO (MN-MIMO), is a proprietary implementation of 3 powerful communications technologies:
Stream voice, data and video via an “infrastructureless” network
Infrastructure-based systems that use as cellular or WiFi technology utilize a central ‘hub’ node to deliver high speed connectivity and good Quality of Service (QoS) to the user. Removing this infrastructure and adding mobility, coupled with time varying connectivity profile without adversely affecting the user’s QoS is the formidable challenge faced by developers of Wireless Mesh Networking (also called MANET, or Mobile Ad hoc Networking) systems.
A MANET system is a group of mobile (or temporarily stationary) devices which need to provide the ability to stream voice, data, and video between arbitrary pairs of devices utilizing the others as relays to avoid the need for infrastructure.
There are many techniques which are employed in order to provide robust MANET capability, including the following:
Self-Forming / Self-Healing is a crucial characteristic of MANET systems. In a true mesh network, radios can join or leave the network at any time, and the network will continuously adapt its topology as nodes move in relation to one another. This implies a decentralized architecture in that there are no central “master” hub radios required to administer control of the network, and communications will continue to persist even when one or more nodes are lost.
Link Adaptation is the ability for each radio to optimally configure its transmission parameters (constellation, FEC coding, and MIMO techniques) to maximize the data rate and robustness of the links to each of the other radios it is communicating with. A particular radio may communicate with another close by radio using a data rate of over 50 Mbps, while using a rate of only 2 Mbps to provide a robust link to a radio much further away. These are packet burst rates, where using a 50Mbps burst is very useful even for a much lower rate data stream because it leaves free channel airtime for other nodes in the network to use. Having high potential data burst rates is important because the less airtime is consumed for the shorter links, the more airtime is left to use slower and much more robust modulation and coding on the distant links.
Adaptive Routing is a mechanism for determining which potential relay paths are used when a stream of data needs to be sent between a given pair of radios. It needs to support self-forming self-healing functionality by adapting dynamically to use all radios present as potential relays and be resilient to the loss of relaying radios. It must also work in conjunction with the link adaptation because determining the optimal route for a stream of data requires consideration of other data which is flowing through the network, as well as the dynamic capacity of each link within the network. This problem is complex and requires all radios to share information about the data traffic flowing through them and the link capacity from each to the other neighboring nodes. This sharing of information must be done in an intelligent manner so that it does not consume too much of the precious available network throughput.
Transparent IP Networking means that any number of standard computer, IP video camera or other devices may be connected to each of the mobile radios and communicate through the mesh network just as if all of the devices were in a single office with wired Ethernet. There are different ways this can be accomplished within the MANET. To enable the most flexibility and ease of use, the best choice is to have the entire MANET network appear as if it is a single Layer 2 networking switch. This means that without any reconfiguration of IP addresses or other settings, a group of IP-based devices that work together on a simple Ethernet switch can be connected to MANET radios and resume operations with the new freedom of wireless mobility.
Multicast Traffic presents a set of unique challenges for MANET systems. The multicast support implemented in basic wired Layer 2 switches is to replicate multicast packets coming into one port on all of the other ports. For instance, if an IP video camera is connected to one port it would send its video using packets tagged as multicast. Then computers wired to any of the other ports of the switch can tap into the wireless video stream. This simplistic method turns out to not work very well in a wireless network acting as a Layer 2 switch because many devices within the network might not need to see a particular multicast, and blindly sending the multicast to all devices thus congests the limited throughput of the wireless network unnecessarily. More advanced MANET systems allow manual and/or automatic optimization, limiting the transmission of multicast to only those devices that need a particular multicast stream.
Multi-channel Networks is an advanced capability of some MANET systems which allows a network to utilize multiple RF channels or even multiple frequency bands within a network while still providing the plug and play functionality of a single Layer 2 switch. A simple example of the usefulness of this might be a scenario where soldiers have radios operating on one frequency while vehicles have radios not only operating on that frequency but also ones in a different band. This additional band might be with higher power or higher gain antennas to provide a high speed “backbone” layer between the vehicles. Any soldier’s radio device can communicate with any other soldier’s radio over the air, but the secondary layer on a different frequency can reduce congestion on the soldier frequency and increase to area covered by the network.
All of these MANET networking capabilities combine to provide robust high speed connectivity similar to what is offered by state of the art 3G/4G networking, but in mission critical operational scenarios where permanent wireless infrastructure is not available.
The StreamCaster radio family from Silvus Technologies are extensively deployed in the Broadcast, Military and Security fields to deliver mobile and temporary network requirements for personnel and vehicles both manned and unmanned. Due to the high bitrates achievable with MN-MIMO, they are often used for video transmission, but can happily carry multiple Voice, Video and Data feeds simultaneously, lending themselves perfectly to situations where a full suite of mobile video, voice communications and situational awareness (mapping) information is needed.
Silvus offer 4 x 4 and 2 x 2 MIMO Meshing Radios with superior performances to conventional Microwave COFDM in point-to-point configurations. The radios form self-healing peer-to-peer meshes over extended coverage areas, delivering seamless IP connectivity between all “nodes”.
Network availability in mobile environments has become completely routine in day to day operations, due to the global availability of cellular data provided by ISPs and Telco companies. Cellular networks (including PSMB - Public Safety Mobile Broadband) have proven themselves to be highly capable in this role for the vast majority of circumstances, ensuring that network-enabled tools have become and are rapidly becoming even more ubiquitous in a huge range of applications from Mining through Emergency Services to Broadcast and the Military. If however those networks are not available, the resultant loss of connectivity can be disastrous fpr workflows that have become dependent on them. Unfortunately this can happen all too often through natural disasters (eg Bushfires, Floods), operating in areas without coverage (remote areas or overseas).
Silvus Radios deliver a deployable IP network to the field, managed and maintained by the user themselves, independent of 3rd party infrastructure or services. This network can deliver extended connectivity amongst members of a team working either in an urban environment or in isolation, and in challenging environments such as remote bush locations, ravines, caves and flood plains, and can also connect that team directly back to base or through the internet using any backhaul systems that may be deployed – including the PSMB and public cellular systems. A whole range of network-based communications, video and management systems can be freely deployed to working areas without fear of loss of connectivity due to infrastructure failure. The system has the potential to deliver:
2X2 MIMO RADIO
50% thinner, 30% lighter, 100% Silvus
SL4200 is a low-SWaP, low-cost 2×2 MIMO radio powered by the same MN-MIMO waveform as our flagship StreamCaster counterparts.
SC4200 series radios are available in 1-watt and 4-watt output versions and are effective when size and weight are of concern. These are ideal for body-worn systems, un-manned vehicles, and other applications where the increased power of the SC4400 series is not required.
SC4400 series radios are available in 1-watt and 8-watt output versions and are effective for applications that require the benefit of additional power and receive sensitivity. These are ideal for vehicle integration, fixed infrastructure, long range airborne and maritime systems.
A range of accessories for the radios are available, ranging from PTT Headsets for communications through bodyworn and PTZ Video cameras to mounting systems for poles, vehicles and buildings. Tracking antennas are available for Ground to air applications to extend range out to 150kms plus.
MULTI-MISSION PAN/TILT/ZOOM CAMERAReal-time situational awareness & actionable intelligence
Compact and lightweight, the Obscura PTZ Camera is an ideal tactical video surveillance solution for fixed, vehicle or maritime applications. Waterproof (IP66) design, 360° continuous Pan with ±90° Tilt, Full HD video with 33X optical Zoom and IR LED illumination delivers enhanced day/night performance in any environment.
MULTI-MISSION CAMERAPurpose-built for tactical operations
Obscura XP is a ruggedized (IP66), HD IP Camera capable of streaming and/or optionally recording high-resolution 3.1MP video and audio in day-light or low-light environments. With an 85° field of view, built-in infrared illuminator, on-board microphone & SD card, and modular mounting options, Obscura XP provides flexibility for use in body-worn, concealment or remote surveillance operations.