Define the freq. hopping parameters?

Q:Define the freq. hopping parameters?


Ans: 

              Frequency Hopping Parameters

            GSM defines the following set of parameters:

   Mobile Allocation (MA): Set of frequencies the mobile is allowed to hop over.  Maximum of 63 frequencies can be defined in the MA list.

 

 Hopping Sequence Number (HSN): Determines the hopping order used in the cell.  It is possible to assign 64 different HSNs.  Setting HSN = 0 provides cyclic hopping sequence and HSN = 1 to 63 provide various pseudo-random hopping sequences. 

  Mobile Allocation Index Offset (MAIO): Determines inside the hopping sequence, which frequency the mobile starts do transmit on.  The value of MAIO ranges between 0 to (N-1) where N is the number of frequencies defined in the MA list.  Presently MAIO is set on per carrier basis.

Motorola has defined an additional parameter, FHI.

   Hopping Indicator (FHI): Defines a hopping system, made up by an associated set of frequencies (MA) to hop over and sequence of hopping (HSN).  The value of FHI varies between 0 to 3.  It is possible to define all 4 FHIs in a single cell. 

Motorola system allows to define the hopping system on a per timeslot basis.  So different hopping configurations are allowed for different timeslots.  This is very useful for interference averaging and to randomize the distribution of errors.