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There's been a few requests for info on usable signal ranges. I asked the Radio guys to comment on ranges from GPRS or 3G towers:
The general LOS distance for GSM 900 varies as follows:
-The basic frame structure allows a theoretical around 35 km when assuming propagation at the speed of light and without considering the impact of path loss.
-Free space attenuation as well as losses associated with bending/scattering of the radio waves due to topography and morphology also have a major impact on the situation.
-With small terrain undulation and rural environment you may see actual distances of a radius of more than 20 km and in extremely ideal conditions up to 30 km.
-Once you have heavy terrain undulation, and extreme clutter in an urban environment this will reduce to smaller radii of well under 10 km.
There are other factors that can influence the above:
-we can slip time frames and introduce deliberately extended range cells (theoretical 70 km radius and more, practically up to 140 km).
-ducting (through temperature inversion), most often at the coast can take a normal cell and extends its received signal strength significantly and unexpectedly.
-design can of course also impact this and we deliberately dimension cells with very small radii (through power adjustment, antenna optimisation and other parameter settings) where we have to achieve very tight frequency reuse.
For GSM 1800 the above comments generally hold true theoretically, but the impact of greater free space attenuation of the 1,8 GHz band when compared to the 900 MHz band now also play a role.
The issues that impact coverage in the 3G environment are vastly different when compared to GSM.
In essence, GSM coverage is constant and your ability to use the coverage available is then limited by capacity and the C/I requirement for the service that you intend to use. Adding capacity is undertaken by adding transceivers on separate frequency spectrum and this is done to the extent that the suitable C/I can be maintained to support the required services. To some extent the effectively available power is retained per user as capacity is added due to the TDMA access methodology per transceiver, save for combiner losses.
In a W-CDMA environment the use of capacity within a cell effectively shrinks the available coverage since in simple terms everyone uses the same frequency spectrum but different coding is used per signal sent. What this means is that the total available power is used for the first user and then shared and shared again as more users are added. This loss of power per user added effectively is the main contributor to the cell coverage shrinkage as the number of users increases since lower power implies shorter propagation distances.
Furthermore, since everyone uses the same frequency at the same time the type of service requested is also material to the power equation. In simple terms, greater throughput requires more power so a 384 kbit/s user vastly reduces available capacity for other users compared to the impact of a voice user (12,2 kbit/s). Also as the users are added so the noise floor in the cell deteriorates and this in itself reduces capacity since each service requested needs to be able to generate a signal sufficiently higher than the noise floor to be successful.
Depending on the number of users assumed and the mix of services assumed coverage can in the extreme reduce to a few hundred meters in radius and at best is unlikely to be more than a few kilometres in radius.
The general LOS distance for GSM 900 varies as follows:
-The basic frame structure allows a theoretical around 35 km when assuming propagation at the speed of light and without considering the impact of path loss.
-Free space attenuation as well as losses associated with bending/scattering of the radio waves due to topography and morphology also have a major impact on the situation.
-With small terrain undulation and rural environment you may see actual distances of a radius of more than 20 km and in extremely ideal conditions up to 30 km.
-Once you have heavy terrain undulation, and extreme clutter in an urban environment this will reduce to smaller radii of well under 10 km.
There are other factors that can influence the above:
-we can slip time frames and introduce deliberately extended range cells (theoretical 70 km radius and more, practically up to 140 km).
-ducting (through temperature inversion), most often at the coast can take a normal cell and extends its received signal strength significantly and unexpectedly.
-design can of course also impact this and we deliberately dimension cells with very small radii (through power adjustment, antenna optimisation and other parameter settings) where we have to achieve very tight frequency reuse.
For GSM 1800 the above comments generally hold true theoretically, but the impact of greater free space attenuation of the 1,8 GHz band when compared to the 900 MHz band now also play a role.
The issues that impact coverage in the 3G environment are vastly different when compared to GSM.
In essence, GSM coverage is constant and your ability to use the coverage available is then limited by capacity and the C/I requirement for the service that you intend to use. Adding capacity is undertaken by adding transceivers on separate frequency spectrum and this is done to the extent that the suitable C/I can be maintained to support the required services. To some extent the effectively available power is retained per user as capacity is added due to the TDMA access methodology per transceiver, save for combiner losses.
In a W-CDMA environment the use of capacity within a cell effectively shrinks the available coverage since in simple terms everyone uses the same frequency spectrum but different coding is used per signal sent. What this means is that the total available power is used for the first user and then shared and shared again as more users are added. This loss of power per user added effectively is the main contributor to the cell coverage shrinkage as the number of users increases since lower power implies shorter propagation distances.
Furthermore, since everyone uses the same frequency at the same time the type of service requested is also material to the power equation. In simple terms, greater throughput requires more power so a 384 kbit/s user vastly reduces available capacity for other users compared to the impact of a voice user (12,2 kbit/s). Also as the users are added so the noise floor in the cell deteriorates and this in itself reduces capacity since each service requested needs to be able to generate a signal sufficiently higher than the noise floor to be successful.
Depending on the number of users assumed and the mix of services assumed coverage can in the extreme reduce to a few hundred meters in radius and at best is unlikely to be more than a few kilometres in radius.
