Some companies have shown their interest in the feasibility of a low output power FDD base station, because it would offer the following advantages:
It would not be necessary to use an expensive high power amplifier when a distribution system is connected after the node B. Distribution systems require low input powers. If a high power amplifier is used, the BS output signal must be attenuated before it is fed into the distribution system, thus the high power amplifier is not needed at all. Power consumption would be reduced, and this would also have positive environmental effects.
It would facilitate the sharing of infrastructures among operators, especially in locations where it is difficult to find sites, or where operators are forced by regulators to share infrastructures. A common distribution system could be connected to the low output power BS's from each operator.
It would increase the flexibility in radio network deployment, because it would allow the placement of one or several base stations in a centralised position with separate RF power amplifiers distributed closer to the subscriber positions. This would also reduce network interference.
A study item called "Low Output Powers for General Purpose FDD BSs" was created during TSG RAN plenary meeting #19, in order to study the feasibility of the low output power FDD base station. The main objectives of this study item are:
Identify the range of output powers to be considered. This SI must assess what must be understood as low output power.
Once the range of output powers to be considered has been delimited, it must be studied how the RAN specifications can be changed in order to allow that range of output powers.
This TR will collect the results of the study item. It must be clearly understood that the purpose of this SI is not to create a new interface within the base station. Its purpose is just to enlarge the output power range of the current base station, in order to allow lower output power values. It must also be stated that a BS doesn't have necessarily to comply with the whole allowed output power range. A BS will only fulfil a subrange of the allowed output power range. The manufacturer must declare the maximum output power of the base station, and the power range supported by it. The only requirements for the BS output power range are those imposed by the dynamic range requirements in TS 25.104