Stu Fisher
18-07-2007, 01:45 PM
Continued.....
Network providers positioned their cell sites after carrying out extensive testings on the frequency, geographical position, and potential transmission/reception hazards. Network planners more often than not governed by planning permission, often cell sites are located in not necessarily the ideal position, due to refused planning permissions, or unsuitability of the terrain or buildingExtensive maps of these tests are kept by the network providers, showing the specific cover of each transmitter and receiver.
Even when mobile phones are not executing a call, they are still logged on the network providers systems, ready for their next call/message. This information is not stored historically, however when a call is made or received, it is. When a phone is ?live? i.e. switched on and connected to the network providers, it is possible to track it by the non recorded records which get switched on manually. Everytime a chargable event takes place, i.e sending an sms or making a call, a record of this is produced. This is then complied into what is know as CDRs (Call Data Records). These records are the basis of Call Billing Records, which inturn becomes that large bill you have to pay at the end of the month. CDRs contain masses amount of data, most of which isn't used for billing. The rest is used for network optimisation and statistics. CDR's are the life line of Cell Site Analysis, without these it is not possible to conduct this type of examination.
Geographical locations can be specified for a mobile phone by referring to the call detail records, (CDR?s). This can give you information of which cell site was being used. From checking the records about the specific site in question, it is then possible to find out about if the aerial was a full 360 degrees, or an azimuth of 120 degrees, (these can vary). If the call was coming from aerial 3 on a cell site, then it is right to assume that the specific geographic location of that cell phone is now only a third or the original area it was thought to be in, (e.g. If a call was made from the south of a cell site, then it is likely that the mobile phone was within a reasonable, (varies) distance from the south of that cell site).
Things to take into consideration:
1. Cell Site Analysis is not a proven science. Even if a mobile phone was used in position A, to the south of a cell site, it doesn?t necessarily mean that the phone was actually there. It could well be anywhere up to a theoretical 35Kms away to throw a spanner in the works here, this can actually be extended up to 120kms, but to the best of my knownledge isn't commonly used within the UK. Some networks may use this on costal sites going out to sea, but I certainly have not come accross this in the mainland, and either way, as the need for mapping the north sea for an escaped whale trying to phone his accompanist is going to be rare to say the least, this isn't such an issue in my opinion (providing it not used on the mainland that is!)if all the cell sites between the phone and the used cell site had achieved maximum usage, (cell sites can only accommodate a finite amount of traffic at one time) or are not in service.
2. The cell site chosen is not necessarily chosen by the phone, it may be the network ?re-directing? the phone to a ?not so busy? cell site.During idle mode, it is always the phone which will chose which cell site it will use, if for some reason that particular cell site is full then there is the capability for the cell to re-direct the call, known as 'directed retry' however this is a network parameter or function which as far as i am aware isn't used in the UK by any network. Hence why you can still get the 'network busy' displayed on your phone and those annoying 3 tones indicating that the call has been dropped. There is an exception to this however, and that is with emergency calls (999 or 112) if the network or cell site is full, and an emergency call is attempted, then another subscriber will be automatically ejected, and that timeslot made available for the emergency call. I have also heard that some of the top guy or gals at the network providers may also have this priority when making calls, however I cannot confirm this, its just what I have heard.
3. Geographical locations may also prevent the usage of a cell site, (large building in the way, dense woodland etc)not only prevent, but also bounce signals in different directions. Tall glass buildings are nutorious for reflecting RF signals and can make network planning quite the headache!.[/QUOTE]
Network providers positioned their cell sites after carrying out extensive testings on the frequency, geographical position, and potential transmission/reception hazards. Network planners more often than not governed by planning permission, often cell sites are located in not necessarily the ideal position, due to refused planning permissions, or unsuitability of the terrain or buildingExtensive maps of these tests are kept by the network providers, showing the specific cover of each transmitter and receiver.
Even when mobile phones are not executing a call, they are still logged on the network providers systems, ready for their next call/message. This information is not stored historically, however when a call is made or received, it is. When a phone is ?live? i.e. switched on and connected to the network providers, it is possible to track it by the non recorded records which get switched on manually. Everytime a chargable event takes place, i.e sending an sms or making a call, a record of this is produced. This is then complied into what is know as CDRs (Call Data Records). These records are the basis of Call Billing Records, which inturn becomes that large bill you have to pay at the end of the month. CDRs contain masses amount of data, most of which isn't used for billing. The rest is used for network optimisation and statistics. CDR's are the life line of Cell Site Analysis, without these it is not possible to conduct this type of examination.
Geographical locations can be specified for a mobile phone by referring to the call detail records, (CDR?s). This can give you information of which cell site was being used. From checking the records about the specific site in question, it is then possible to find out about if the aerial was a full 360 degrees, or an azimuth of 120 degrees, (these can vary). If the call was coming from aerial 3 on a cell site, then it is right to assume that the specific geographic location of that cell phone is now only a third or the original area it was thought to be in, (e.g. If a call was made from the south of a cell site, then it is likely that the mobile phone was within a reasonable, (varies) distance from the south of that cell site).
Things to take into consideration:
1. Cell Site Analysis is not a proven science. Even if a mobile phone was used in position A, to the south of a cell site, it doesn?t necessarily mean that the phone was actually there. It could well be anywhere up to a theoretical 35Kms away to throw a spanner in the works here, this can actually be extended up to 120kms, but to the best of my knownledge isn't commonly used within the UK. Some networks may use this on costal sites going out to sea, but I certainly have not come accross this in the mainland, and either way, as the need for mapping the north sea for an escaped whale trying to phone his accompanist is going to be rare to say the least, this isn't such an issue in my opinion (providing it not used on the mainland that is!)if all the cell sites between the phone and the used cell site had achieved maximum usage, (cell sites can only accommodate a finite amount of traffic at one time) or are not in service.
2. The cell site chosen is not necessarily chosen by the phone, it may be the network ?re-directing? the phone to a ?not so busy? cell site.During idle mode, it is always the phone which will chose which cell site it will use, if for some reason that particular cell site is full then there is the capability for the cell to re-direct the call, known as 'directed retry' however this is a network parameter or function which as far as i am aware isn't used in the UK by any network. Hence why you can still get the 'network busy' displayed on your phone and those annoying 3 tones indicating that the call has been dropped. There is an exception to this however, and that is with emergency calls (999 or 112) if the network or cell site is full, and an emergency call is attempted, then another subscriber will be automatically ejected, and that timeslot made available for the emergency call. I have also heard that some of the top guy or gals at the network providers may also have this priority when making calls, however I cannot confirm this, its just what I have heard.
3. Geographical locations may also prevent the usage of a cell site, (large building in the way, dense woodland etc)not only prevent, but also bounce signals in different directions. Tall glass buildings are nutorious for reflecting RF signals and can make network planning quite the headache!.[/QUOTE]