BS/MS power summary

[Dieter Spaar]

Hello,

I try to give a short summary of the MS and BS power settings.
It is not intended to replace the GSM specs, it just contains
the important things for the current BS-11 configuration.

MS power:

  - The MS power is usually specified as an absolute value,
    a lower value means higher power. Some values for GSM 900 
    (GSM 1800 has a different encoding):

        15 ->  13 dBm (0.02 W)
        10 ->  23 dBm (0.2  W)
         5 ->  33 dBm (2    W)

         
  - The power used to access the RACH before any channel is active, 
    is defined by a Cell Selection parameter in SYSTEM INFORMATION 
    TYPE 3 and 4. 

    Remark: bsc_hack currently uses "2" which should be increased
    (lower power) to avoid interference with the public networks.
    
    
  - When the BTS activates a channel, it sets the MS power. 
    bsc_hack currently sets it to 15 which should be OK for testing
    (see rsl_rx_chan_rqd() in abis_rsl.c).
     
    
  - Dynamic power control of the MS power by the BTS is currently 
    not enabled.
    
  
BS power:
  
  - For the BS-11 the PA power can be configured to 0.03W, 0.08W,
    0.25W or 2W (b11_config can be used for this purpose).
    
    
  - The attribute NM_ATT_RF_MAXPOWR_R of each TRX of the BS-11 
    can be set to a value from 0 (0dB) to 6 (12dB) to reduce
    the power in steps of 2dB (see bsc_hack.c).
      
    
  - for the TRX which carries the BCCH, there is no dynamic 
    BS power control possible. In the meantime I have read
    at several places that the BCCH TRX has to use a fixed power
    and additionally cannot use a different ARFCN for example
    for the TCH (which also means that no hopping is possible). 
    To use hopping or dynamic BS power control, the second TRX 
    has to be used and configured in a way that it does not carry
    a BCCH.
  
    
Best regard,
  Dieter
-- 
Dieter Spaar, Germany                           spaar at mirider.augusta.de