By Colin Abrey, Zinwave, UK
Within the power generation industry, ensuring the health and safety of the plant and its employees is paramount. It is imperative that nuclear plants, for example, can deal with any sort of emergency, which could occur within any particular part of the site, at any time of the day, quickly and efficiently. In such high security, high risk working environments where employees are typically widely dispersed over a vast area across multiple building sites, it is crucial that personnel are able to communicate clearly at all times, wherever they may be located within the site. Nowhere is the need for constant and reliable communication as important as in the power generation industry.
Ensuring reliable, ubiquitous coverage
Governing bodies worldwide have put various health and safety regulations in place that power generation sites must adhere to. In the US for example, the Department of Energy (DOE) imposes the implementation of reliable telecommunications throughout the entire infrastructure on power generation sites. The DOE technical standards guide stipulates that a nuclear power site is required to support information technologies including telecommunications and must, importantly, provide reliable coverage for public safety and emergency services.
A concept image of a power station and wireless radio signals being distributed throughout
In this dynamic environment, a multitude of commercial wireless services are employed including multi-operator cellular, public safety, Push-to-Talk (PPT), paging, automation and Wi-Fi, all of which operate on different frequencies and have varying levels of difficulty in penetrating buildings. Additionally, there are also dedicated wireless services including 900 MHz wireless remote dosimetry monitoring, optimized for measuring radioactivity levels within plants, which is essential for preserving the safety of the workforce.
The sheer size of power generation stations, combined with the wide variety of structures that make up the site, brings its own set unique challenges to achieving ubiquitous in-building wireless coverage. Different building shapes and sizes as well as the diversity of construction materials used such as steel and concrete, cause in-building penetration of radio frequency (RF) signals to weaken significantly. This ultimately results in reduced data rates and even complete loss of signal, preventing personnel from communicating in some areas of the plant. This issue will become even more problematic over the next few years with the emergence of pioneering new 4G technologies which will require considerably higher signal qualities, making the RF signals more susceptible to attenuating materials. This makes meeting health and safety requirements extremely difficult and could lead to employees being left open to significant risk.
Advancements in technology mean that today there is a multitude of competing and conflicting ways of improving in-building wireless coverage. However, power generation sites are notably difficult and complex environments in which to deploy such systems. The use of high voltage machinery and extensive distances between buildings make the integration of any in-building wireless system challenging. It is essential that in-building wireless coverage solutions are able to minimize the radio signal interference caused by heavy-duty industrial equipment and building materials as well as coping with the long distances between the various buildings that make up the plant. With a myriad of options available on the market today health and safety officers are facing the daunting task of working out the benefits and downsides of each. How can they ensure they have chosen an in-building wireless solution that will support the complex maze of wireless communication services required, whilst effectively adhering to the plant’s health and safety regulations for today and for the future?
Wireless coverage can be required for a variety of purposes from voice calls to data traffic, security systems and emergency services to name a few. There are many different types of sources for these services including base stations, repeaters, access points, two-way radios etc, for each system with varying capacities, coverage and ranges. These days, in-building wireless solutions can be separated into two different groups à‚— single service and multiple service solutions.
Single service equipment
Put simply, single service in-building coverage solutions cover any wireless technology solution that supports just one type of wireless service. This group includes traditional approaches such as cellular base stations, Wi-Fi routers, proprietary short-range radio systems as well as some newer entrants on the market such as femtocells.
Inside a power station which shows the heavy duty infrastructure of the environment
Proprietary short-range radio systems provide very effective means of communication in their individual uses. An example of the wireless technologies that fall into this group include Bluetooth, Wi-Fi and Land Mobile Radio Systems (LMRS), most commonly used within power plants for security, emergency service and public safety applications. LMRS can often be connected to other fixed systems such as cellular networks, however the slight downside to these systems is that in their individual use they can be relatively expensive to maintain and can lead to customers being tied into one supplier to avoid interoperability issues.
As with other proprietary technologies, the software and hardware is fraught with licensing and patents giving customers less control over adapting and customizing their individual wireless networks. The range of these technologies is implied in its name à‚— but even when connected to wider ranging systems such as cellular, LMRS will still ultimately be affected by the attenuating materials within a plant’s infrastructure.
Wi-Fi technology is becoming more and more prevalent for wireless networking because it is cost effective and simple to set up. Within a power plant Wi-Fi offers many advantages, from access to network servers, Internet, and also to Voice over Internet Protocol (VoIP) technologies such as Skype, which enable voice transmissions to be carried over the Internet as opposed to the telephone network. On a power generation site, an IT manager could install numerous Wi-Fi distribution routers which integrate a DSL-modem or cable modem and a Wi-Fi access point to connect to the Internet over a local telephone network, gathering and relaying data from various sites across the entire facility. However, even though it has a simplistic design and is easy to implement, Wi-Fi routers are ultimately limited in that they can only distribute radio outputs at short range, meaning multiple routers are needed throughout the sites. This makes maintenance time consuming and difficult, as it proves hard to pinpoint broken or faulty routers in such a complex network of access points.
When looking broadly at cellular networks, there are four single service solutions which address poor in-building signal penetration – increased power of the nearby macro base station, repeaters, picocells and femtocells.
The most obvious solution may be to increase the power of the nearby base station. However, with 3G technologies it is just not cost efficient or technically proficient as you cannot add more coverage without reducing maximum traffic and subscriber density. Repeaters on the other hand can extend the outdoor base station cell into a building without changing the capacity of the network.
A repeater is fed from the macro base station via a donor antenna, which eliminates cost of additional network equipment. Still, repeaters have a limited bandwidth and typically can only support one or two frequency bands. To ensure coverage for multiple services a number of repeaters need to be installed and for high data traffic environments repeaters are inefficient as they cannot provide extra capacity for the building.
Picocells are typically very well suited to providing additional capacity to the cellular network in smaller buildings. In large building deployments, where high capacity is required, a large number of picocells are needed. As each wireless service will require its own dedicated infrastructure this leads to very high investment in equipment.
The newest player in the single service market is the femtocell. Basically, a femtocell acts as a small base station that connects to a cellular network via broadband to improve wireless coverage indoors. A femtocell much like a Wi-Fi router is relatively easy to deploy. Despite this, the downside is that femtocells have a short-range and a small capacity, typically only supporting two to four cellphone users. Not only would adding increased numbers of femtocells within a building be costly but multiple deployments can cause interference issues between cells. For this reason, femtocells are better suited to domestic environments. Improvements to the total capacity supported have been made with the introduction of the enterprise femtocell but at the moment these systems are still a very expensive solution.
Multiple service equipment
A Distributed Antenna System (DAS) is typically favoured in moderate to large infrastructures for being able to offer improved and unified indoor wireless coverage at lower capital expenditure and running costs. A typical DAS comprises a network of antennas, which are distributed throughout a building to provide dedicated in-building coverage. Traditionally there are two types of distributed antenna systems available today, passive and active.
Hybrid solutions are also in common use where active units are distributed throughout a building with each feeding a small passive antenna network. Both active and passive distributed antenna systems can support multiple service connectivity, meaning they can be used to simultaneously carry multi operator and multi service solutions. Traditional active/hybrid systems achieve multi service support by deploying service specific hardware overlays which are then combined on to a common antenna.
One of the limitations with a traditional solution is that not all service frequencies are supported in the range of service specific hardware; particularly true for specialist services such as dosimetry. More recently, a third DAS option has been introduced which has taken a truly wideband, active approach. This alternative DAS solution simultaneously supports any number or combination of wireless services, protocols or frequencies on one system without the need for service specific overlays. In this way, the system is future proof as services can be added without any additional cost.
Passive distributed antenna systems consist of a network of coaxial cables, couplers and power splitters to distribute wireless signals throughout buildings. Active distributed antenna systems on the other hand feed cellular signals from a base station or repeater and distribute amplified wireless signals inside buildings over optical and RF cable, which connects to multiple remote antennas placed in various areas of the building.
A passive DAS is arguably cheaper than its active counterpart and is still probably the most commonly used type today. The drawback with these solutions is that the RF signals do not travel very far over the cable. In turn, this means that these systems are susceptible to signal loss over large distances as well as when used with higher frequency technologies. By its very nature, the end components of the system are passive and as a result there is no inherent fault reporting, which can lead to increased maintenance time and cost. An active DAS therefore has advantages over passive systems in power generation sites where such systems encounter length limitations. In addition, since the components are active if there is a problem with one of the antennas this can be easily pinpointed, providing more reliable connectivity and manageability.
Differing implementation techniques
Once IT managers have decided which wireless technologies actually need to be supported within the plant, they need to decide if deploying multiple dedicated single service solutions dotted around nuclear plants in desired areas is more beneficial than a system that can combine all radio outputs on a single platform to transmit RF signals throughout the entire infrastructure. Whichever wireless in-building technology is chosen, in the power engineering sector there are key issues that need to be considered. Due to the sheer size of nuclear power plants, as well as and the varying shapes and distances of and between the buildings, offering flexible installation is crucial.
Taking a wideband approach
By taking a wideband approach to in-building wireless infrastructure, all specifications for this particular working environment can be easily met. Active ‘wideband’ distributed antenna systems can provide the power generation industry with a comprehensive in-building coverage solution because it is capable of simultaneously supporting any number or combination of wireless services, protocols or frequencies without the need for service specific overlays. This means that specialist/unique services are supported. This will guarantee the safety of the plant and its staff, no matter where they are on the site or what service they are using at the time. The wideband capability also eliminates the need for service-specific equipment, keeping hardware and installation costs low. By being service agnostic, active wideband DAS also provides peace of mind to health and safety officers by future-proofing new investments in in-building wireless infrastructure, and is highly scalable, allowing new services to be added without extra components or costly upgrades.
There is a clear and immediate need to introduce improved in-building wireless coverage to allow power generation plants to more effectively adhere to today’s health and safety regulations. Nuclear power plant managers need to act now and educate themselves on the wireless technologies available if they are to guarantee the protection of the site and the safety of its staff. Active wideband DAS is unique in the solution’s ability to deliver on a financial level, while also bringing widespread coverage of must-have wireless services to personnel, for today and tomorrow.
Colin Abrey joined Zinwave from Cambridge Broadband Networks Limited, where he was VP of Business Development and Sales. Prior to that he was VP, International Sales & Marketing for Global Network Solutions, a division of L-3 Communications, where he successfully developed new markets for the company in Asia and Africa. Colin qualified as an electrical engineer before moving into sales and brings to Zinwave over 20 years experience of selling leading-edge technology.