For many, Ethernet- and IP-based networks are the cast-iron solution to ITS's communications needs. However, there remain issues from manufacturer to manufacturer with interpretation of what are supposed to be common standards
The 'promise' of Ethernet was that different devices such as IP video cameras and traffic signals could be easily integrated into communications networks, simplifying the process of transporting data over copper, fibre or wirelessly. However, although Ethernet devices have come to predominate there remains an issue of standards within standards.Meeting the need
"The market requirement is for a signal transmission system which offers the ability to integrate and manage devices on the network with high levels of reliability and if manufacturers want to compete in this market by those rules they have to make sure the products they offer can coexist.
"There are different subsections to IEEE 802.3 which try to ensure interoperability. These exist to level the playing field and as an advantage to the user. This forces manufacturers to bring other product advantages to the market in order to differentiate themselves and their products. Those advantages and a company's willingness to help on all levels go a long way to increase market penetration."
Comnet has looked to differentiate itself with a line of fibre-optic products which feature many new innovations, he continues. These include advanced environmental hardening, transmission across one fibre (versus the more common two-fibre designs) and an interchangeability feature which allows one model to be used in either a standalone or rack-mounted application. A broad line of Ethernet over optical fibre products is combined with others which allow for some of benefits of Ethernet transmission to be achieved with a line of traditional video and data products.
"This line of self-healing ring products allows video and data be inserted at multiple locations on the same optical network. When used with a second optical fibre the network can actually self-heal in the event of an interruption," he adds.
"Ethernet over optical fibre is still the best way to transport IP data from one point to another or between multiple points. As the volume and speed of the IP data increase, the need increases for gigabit and terabyte network devices to manage that traffic. Gigabit over standard single-mode fibre can be extended to distances over 60km by simply selecting the correct optic on the network devices.
"Where there are many IP video and data sources on a network, the large volume of data created calls for managed Ethernet switches and a gigabit fibre-optic network. There's really no other medium available that offers the reliability, distance and bandwidth of fibre. The only limiting factor affecting the Ethernet over any media growth is the complexity inherent in deployment.
"At present, wireless transmission just doesn't offer the bandwidth. Optical fibre is still the only medium that can do so without flooding the network. It's not to say wireless transmission is by nature unreliable but it is susceptible to interference, especially in congested areas. It can also be affected by weather and geography but in areas where there is no real infrastructure, wireless is a good, cost-effective solution.
"There are also applications where the two systems can work together, such as bringing surveillance video and traffic signal data in for aggregation from a considerable distance to a mid-point traffic control centre and communicating it on from there to a local or wide-area network over a fibre-optic Ethernet network."
The rise of hybrids
Dan Szgatti of Encom Wireless says that many of his company's customers are currently designing just such networks. He also highlights the significant performance differences between different suppliers' wireless systems.
"The long-standing wireless networking standards have been 802.11a/b/g using the licence-free 2.4 and 5.8GHz frequency bands although there is a push to use 802.11n.
"These standards encourage equipment interoperability and cost reductions. The big differences in actual performance between different wireless systems' manufacturers' systems mean that it's not critical to have a standards-based system when building a wireless network. It's more important to choose the equipment with the best outdoor performance and field testing is the only way to compare the various vendors. The key element is that the networking equipment must be IP-based and contain the highest levels of network security, both on the wireless encryption side and within the network security policy.
He says that the economic downturn and budget restraints mean that Encom Wireless gets a lot of customer requests for an alternative to fibre-optic communication networks.
"We address that need with wireless, high-bandwidth IP communications networks that can cover long distances in both urban and rural environments. Generally our customers ask for data rates of 50-100Mb/s and systems that offer high security and reliability. Our product development is focused on IP-based networks and increasing range, bandwidth and reliability."
There is a strong long-term future for IP-based networks, adds Szgatti.
"No matter whether the communication medium is fibre optic or wireless, the relative data rates and the demands for more data are increasing. Fortunately there are concurrent advances in video compression technology and other advanced systems that are reducing bandwidth requirements.
"The need to bring the data back to analogue for analytics is independent of the type of network that is used to connect to the field devices.
"There has always been a strong relationship between fixed and wireless networks for ITS. The future will continue to use wireless equipment to reach remote sites. In reality, there is no need to have fibre-optic connectivity to all sites since the bandwidth requirement at most sites is actually very low."
IP video - an alternative
Alan Hayes of
"This creates demands above and beyond what would be normally required for a relatively 'simple' data network and may only become apparent as the camera count increases," he says.
"Large systems can require routing and quality of service protocols which are not available within 'simple', low-cost networks. Not having them can lead to network congestion and to anything from a lack of access to certain signals to a network crash. IP networks do crash, something which becomes more likely with size. Sometimes this is due to a mistake by an engineer, sometimes the cause is unknown.
"In the case of a fully IP network-based CCTV transmission system, none of the camera signals would be available. The use of a separate transmission system specifically designed for the collection of video to a distribution point, control room or processing point prior to being put onto an IP network ensures that the video will always be available at that location even in the event of a network crash. Another factor, which is not always taken into account, is the quality of the IP network support resource required to reinstate and maintain the network. This can be an expensive overhead. Other issues which one needs to take into consideration are latency, resilience to hacking and image freezing."
AMG Systems designs and develops transmission equipment which replicates the benefits associated with Ethernet and SDH networks but without compressing the video. The company's solutions, Hayes states, are immune from the limitations listed above.
"It's possible to collect channels of video and distribute Ethernet, low-speed data and audio signals on a single unit located at the roadside. These can be connected on a dual-redundant ring architecture with a single fibre daisy-chaining between each unit. The benefits of this approach are the minimal use of fibre, ease of adding a camera or other service, the ability to drop off signals at multiple locations and effectively unlimited transmission distance. The dual-redundant capability ensures that operations are maintained in the case of a fibre break or loss of power at a unit."
He points to England's National Roads Telecommunications Services project as an example, where AMG3700 series units are to be used for all the collection of data from all the cameras, approximately 1,400 of them, on the national network.
"The system can be fully managed via industry-standard SNMP or a proprietary GUI to highlight any faults in the fibre, whilst full operation is maintained. It also monitors video availability and loss of power. For high channel count video distribution, resilient and managed equipment can collect and distribute video and all other services to or from multiple locations.
"We are currently seeing a significant shift occurring because there is growing awareness that IP-based collection systems result in a lot of signals you cannot do anything with because information content has been stripped out. The future lies more with high-resolution cameras and high-bandwidth transmission systems. There is still the issue of non standards-based protocols and video processing at the edge of the network, which makes upgrading an issue. This is a significant issue when we're talking about large infrastructure projects with greater longevity."
Changes in compression standards are another issue as video processing is then limited by processing capability. The latter continues to improve and the only way implement these improvements then lies in hardware replacements. This is costly and difficult.
"Transmitting uncompressed video solves the problem. However, the proprietary nature of our solution is sometimes seen as a barrier, and many people fail to realise that the technology is available as an option.
"One could rightfully argue that to get the necessary performance out of a purely IP-based system you end up with a proprietary solution anyway, because the spanning-tree and fast spanning-tree resilience protocols within IP don't have the repair speed required for video systems."
