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BASE STATIONS AND HEALTH - L2What is a base station and wireless network? What is a base station and wireless network? Wireless systems use a network of radio base stations to provide service for mobile phones and other wireless devices. Base stations send and receive low powered radio signals to and from mobile phones, and provide the connection to the main telephone network. A mobile network is usually configured in a cellular grid format. Base stations need to be located close to mobile phone users to provide good quality reception.
Example wireless network with cellular grid overlay. Click here for a short animated explanation of how networks work (wmv) What do base stations look like? Base stations usually consist of a small equipment cabinet or hut, and antennas mounted on a support structure. The antenna support structure can vary considerably. Typical examples are:
Base station antennas are usually located on the most suitable structure in the area for example an existing building, tower or structure. Sometimes a new tower or mast is required if there are no existing structures. Each base station is connected to the main telephone network either via a microwave link using a small dish antenna, or via optical fibre cable. How do mobile network operators decide where to site base stations? To provide a good quality mobile service, base stations need to be located where people use their mobile phones. A mobile network is typically designed on a "cell grid" basis covering a geographic area. Base stations are located either in the centre of each cell or on the corner of a group of cells. The number of base stations required for a given area will depend on the terrain and number of people using mobile phones. The radio signals that base station antennas transmit are primarily transmitted from the centre of the antenna outwards. This means that the antennas need to be placed in locations where there are no obstructions, such as building rooftops and masts. In built-up and mountainous areas with many buildings, trees and obstructions, it is likely that more base stations will be required to provide service to the local community. In rural areas with fewer obstructions, less base stations will be required. How many base stations are required in a given area? Mobile networks have a finite capacity which means the ability to cater for simultaneous phone calls. The more people using mobile phones, the more capacity is required and this usually means more base stations closer together. Mobile networks must be designed according to the local population and number of people using the network. What different types of base stations are there? Base stations are broadly divided into the following categories
How strong are the environmental EMF levels near a base station? Base station transmitters use relatively low power and environmental EMF surveys conducted in many countries around the world have shown background EMF levels to be equally very low. The World Health Organization has reviewed the background EMF levels from wireless systems and says,
Specifically on EMF levels in public areas the WHO says,
Do base station EMF levels vary? Mobile networks are specifically designed to use the lowest possible power from base stations and mobile phones necessary to quality voice or data services. The network automatically adjusts the base station transmitter power according to how far away the mobile phone users are. The further away base stations are located from mobile phone users, the higher the power required resulting in higher EMF levels. Should base stations be located near homes and schools? Today’s society relies on mobile phones working everywhere including at home, at school and at work. When base stations are located close to users, the transmitter power required by the mobile phone and the base station to communicate is relatively low. If base stations were located further away, the power required is generally higher, and this means a higher EMF. Therefore to provide good reception and minimise EMF, base stations need to be located close to users and where we live. Are base stations safe – Is it safe to live near a base station? Base stations operate at low power. Independent surveys demonstrate that the background EMF level in the community from base stations is very low, and similar to environmental EMF levels from broadcast radio and television. The World Health Organization monitors scientific research into EMF and concludes,
In 2009 and 2010, the International Commission for Non Ionizing Radiation Protection (ICNIRP) reaffirmed the EMF safety guidelines following a review of national and international EMF research and published scientific literature. RF safety at base station and antenna sites The MMF and GSMA has prepared a document giving practical rf safety guidance for personnel working at base station and antenna sites. Click here to download. Download the Mobile Communications and Health Booklet from the GSMA
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