DCAN 14: Siting and Design of Radio Telecommunication Equipment
Mobile Radio Telecommunication Systems
2.2 The UK is one of the world leaders in mobile telecommunications, with different network operators offering innovative and competitive services. The industry is continuing to grow as existing services are expanded, new services provided and consumer demands increase. Growth is likely to be driven by a range of factors including the increased capacity of digital broadband technology (including third generation 3G, fixed wireless and satellite systems), the growth in demand for communications of all kinds, especially mobile, non-voice or data services, more diverse services, continued growth of the internet, and greater competition. Change will also be driven by convergence, the integration of telecommunications, broadcasting and information technology sectors, and between fixed and mobile networks.
2.3 Mobile telecommunication systems work by using and re-using the same radio frequencies and allocating them to geographical cells. Mobile operators divide the country into hundreds of individual cells and at the centre of each is a base station. Base stations are connected to one another by central switching centres, which track calls and transfer them as the caller moves from one cell to the next. The area covered by each cell is governed by the anticipated capacity (i.e. volume of calls), the height of the antenna above the ground, the local terrain, the power output and the radio frequency - in general the higher the frequency, the shorter the distance the signal travels. The largest cells are in sparsely populated rural areas and the smallest in town and city centres. Splitting a cell into smaller cells can increase capacity. There is a great variety in the way cells are configured and split. Most base stations are in built-up areas and elsewhere tend to be located within a mile or two of the main transport corridors.
2.4 Base stations consist of antennas installed on supporting structures such as masts or mounted on buildings and connected by feeder cables to transmission and receiving equipment. Networks are comprised of three sizes of base station:
- Macrocell base stations provide the main radio coverage infrastructure. Antennas for macrocells are usually mounted on ground-based masts, rooftops and other existing structures but may occasionally be within a building.
- Microcell base stations are used to infill and improve the main network, especially where the volume of calls is high. They are usually deployed later in the network rollout. There are a number of different types of microcell antennas. The most common are small boxes about the size of burglar alarms, which are mounted at street level typically on the external walls of existing structures. Other types are suitable for lampposts and other street furniture. They have a range of a few hundred metres. Microcells base stations are most suitable for transmitting signals to pedestrians.
- Picocell base stations have even smaller antennas and are generally sited inside buildings such as airports, railway stations and shopping centres.
Examples of Macrocell, Microcell and Picocell equipment
2.5 Each base station is linked to the network by cable or by radio using one or more small microwave dish antenna. These dish antennas are usually between 0.3m to 0.6m in diameter, although in areas with high capacity demand they may measure 1.2m.
2.6 The original mobile systems, known as first generation (1G), date from the mid 1980’s, and have now been decommissioned. Second generation (2G) systems which operate using the Global System for Mobile (GSM) technology (a digital standard for mobile telecommunications) are now in place, though operators are still extending coverage in some areas and improving capacity. 2G base stations antennas vary in height between 1.5 and 2.5m in length. These can be placed on redundant 1G masts, new lattice or monopole masts or other existing structures. 2G ground based masts Examples of Macrocell, Microcell and Picocell equipment, are generally between 12.5m to 22.5m in height, although on occasion a 30m mast may be required. Short ‘stub’ masts on rooftops are typically 4m to 6m high. Standard 2G base stations have between 2 and 6 antennas per mobile operator. Antennas can be directional to cover a segment of the cell, or omni-directional sending the signals out in all directions. Some operators are enhancing their services to use a common standard known as General Packet Radio Service (GPRS), sometimes referred to as 2.5G. This permits higher data speeds without physical alterations to the apparatus.
2.7 In May 2000 the government awarded five telecommunications licences to develop a 3G network using Universal Mobile Telecommunications Systems (UMTS) technology to the four existing 2G operators and a new operator. The licences will be valid until the end of 2021 and require each licensee to develop a 3G network covering at least 80% of the UK population by the end of 2007. 3G will enable a data transfer rate that is 200 times faster than 2G as well as a range of new services. These services could include such things as Internet access, e-commerce and video services. The new licenses have been granted at a higher frequency from the existing 2G networks, which means:
- a signal from the same locations as current 2G mobile sites will not travel as far. Because of this factor, to cover the same geographical area, the 3G sites have to be located closer together.
- 3G apparatus can generally be sited at a lower height than 2G.
- as a site gets more use the size of the cells will shrink, normally referred to as ‘Cell Breathing’. Gaps in coverage therefore need to be filled.
Second Generation Mobile Telecommunications Mast Cell Sizes
2.8 G commercial services have been launched. The new operator is currently establishing a new network and is expected to primarily use existing buildings or other structures, including some masts used by other operators or radio site management organisations.
2.9 Standard 3G equipment looks similar to 2G. In most situations separate new 3G antennas will be required. However, in some circumstances it may be possible for existing 2G operators to replace their 2G antenna with a ‘dual band’ or ‘tri band’ antenna that can provide both 2G and 3G functionality. These multi band antennas tend to have a wider casing than 2G antennas.
Third Generation Mobile Telecommunications Mast Cell sizes
2.10 A new generation of mobile technology seems to come forward approximately every 10 years. Some telecommunication companies are already thinking about fourth generation systems.
2.11 The process by which mobile operators select their sites is explained in Annex B.