Collision properties of GSM hopping sequences

Properties of GSM pseudo-random frequency hopping sequences (FHSs) are investigated and it is concluded that they differ significantly from the properties of ideal random sequences. Such discrepancies are evident from correlations as well as collision rates between sequences. It is shown that the collision rate between two FHSs depends heavily on certain FHS parameters such as the hopping sequence number (HSN) and the mobile allocation index offset (MAIO). Another important parameter with significant impact on the collision rate is the frame number (FN) difference between two cells. A consequence is that co-channel interference between cells with fractional loading can be reduced by careful HSN/FN/MAIO planning based solely on collision rate information. This is demonstrated in examples involving two cells