In order to avoid call dropping and hapless quality of service, ongoing call of Mobile while go forthing UMTS coverage needed to be manus over to GSM. 3GPP criterions have defined the necessary signaling and a scope of parametric quantities which may be used to execute intersystem handover from UMTS to GSM. But, the determination on the status for inter-RAT handover and the optimisation of the handover parametric quantities are web dependent. Inter-System handover can be divided into the undermentioned stairss:
1 ) Decision to trip measuring on GSM cells ;
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2 ) Measurement of different parametric quantities and their coverage
3 ) Based on these measurings, determination to execute the handover
4 ) Execution of handover process
By and large the standards used to trip measurings on the GSM cells are based on the measurings performed by the Mobile on the current active cells. Parameters like CPICH RSCP and CPICH Ec/Io of the cells in the active set is chiefly taken into history to make up one’s mind whether the current UMTS coverage is non good plenty or non, and RXLEV of neighbouring GSM cell to make up one’s mind whether GSM coverage is good plenty or non.
Common Pilot Channel ( CPICH ) is a downlink channel broadcast by Node Bs with changeless power and of a known spot sequence. And CPICH-RSCP is the power-per-chip received on a common pilot channel. And Ec/Io is chip-to-noise ( intervention and thermal ) energy ratio. And RXLEV, the measurement measure of neighbouring cell is defined as the norm of the standard signal degree measured in dbm.
Compressed manner consists in disrupting the transmittal and/or response in order to let the nomadic to alter the frequence during the blanking. Depending on the UE execution and the mensural frequence, compressed manner may be activated in downlink merely, in uplink merely or both in uplink and downlink. The break of transmission/reception is called a transmittal spread and it lasts from 3 to 14 slots. The transmittal spread distribution is defined by two Transmissions Gap Patterns that are repeated in turn a certain figure of times. This sequence of the two repeated forms is called the Transmission Gap Pattern Sequence ( TGPS ) . At the terminal of the TGPS, compressed is deactivated and the UE switches back to its old bearers uplink and downlink. Data shall non be lost when the tight manner is activated. Thus the informations transmittal clip is reduced in order to make these spreads. Three methods can be used to make these spreads
a ) Decrease of the distributing factor by 2
B ) Puncturing ( rate matching )
degree Celsius ) Higher bed scheduling
Puncturing can non be used on the uplink, and can merely make short spreads. Scheduling can non use to existent clip services. Thus the spreading factor halving method has been considered in most of the paper that I have used for refrences. For this method, the spreading factor is reduced by two during the tight frames. This enables informations transmittal in the staying portion of the frames but the informations transmittal power is increased to counterbalance. These alterations in tight frames have following impacts on:
1 ) Radio nexus public presentation: due to the transmittal clip decrease, the informations are less protected, the power control cringle is interrupted and the channel appraisal is stopped ;
2 ) System public presentation: due to the increased power in tight frames, extra interventions are introduced and system capacity is reduced ;
3 ) Coverage: every bit more power is needed in the tight frames, the uplink coverage is reduced.
Other Impact of Compressed manner.
The tight manner form impacts the measurement continuance: normally, the more frequent the spreads are, the faster the BSIC is found, but as pointed out in this subdivision, the more degraded the public presentation is. On the contrary, if spreads are excessively spaced out, measurings holds are longer, which could ensue in hold for handover executing and loss of connexion. Therefore, happening a via media is of import every bit good as disputing portion to any web operator.