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.
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