Coherence in signal level measurements between GSM900 and GSM1800 bands and its application to single BCCH operation

In this paper we investigate the possibility of operating a dual band GSM network having co-located GSM900 and GSM1800 cells, with a single broadcast channel (BCCH). Our investigations are based on simultaneous dual band signal strength measurements using a test measurement system, neighbour channel measurements from a dual band GSM phone, and Abis trace data. Our results indicate that base station antennas with dissimilar radiation patterns for the two bands will effect a change in mean signal level difference. The characteristics of the dual band antenna on the mobile station, especially when interacting with the hand and head of the user, tend to strongly de-correlate the mean signal level variations in the two bands. Both issues, and in particular the latter, may negatively influence the performance of single BCCH operation of co-located GSM900 and GSM1800 cells.