2G HO Algorithm

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2G Handover Optimization
Classification by Reason
Timing advance (TA) Emergency HO

Triggering condition
_ The actual TA > TA HO Thrsh.
Object cell selection
_ The cell must be of the highest priority in the candidate cell sequence and
meet the following restrictions.
Restriction
_ The service cell cannot be the object cell.
_ HO is not allowed when TA Thresh. of the neighboring cell with the same
BTS is smaller than that of the service cell.
Bad Quality HO
Triggering condition
_ UL receiving quality >=UL receiving quality thrsh. of the service cell.
_ OR DL receiving quality >=DL receiving quality thrsh. of the service
cell.
Object cell selection
_ The cells must be of the highest priority in the candidate cell
sequence and meet the following restrictions.
Restriction
_ Handover to the neighboring cell with the highest priority. If there is no
neighboring cell, handover to the service cell, and the channel at
different TRX is preference.
_ Rx Level (n) > Rx Level (s) + Inter Cell HO Hysteresis + BQ HO Margin
Signal Level Rapid Drop HO
Triggering condition
_ Due to downlink signal level drop
_ Triggered upon detecting rapid level drop during MS busy mode
_ Object cell selection
_ The neighboring cell with the highest priority and whose priority is higher
than that of the service cell in the candidate cell group.
_ Restriction
_ The service cell cannot be the object cell.
Interference HO
Triggering condition
_ UL receiving quality>=Service cell UL receiving quality Thrsh. AND
UL receiving level>=Service cell UL receiving level Thrsh.
_ OR DL receiving quality>=Service cell DL receiving quality Thrsh.
AND DL receiving level>=Service cell DL receiving level Thrsh.
Object cell selection
_ The cells must be of the highest priority in the candidate cell
sequence and meet the following restrictions.
Restriction
_ The service cell that is not in the penalty time for intra-cell handover.
_ The neighboring cell with the receiving level higher than the inter
layer HO Thrsh.
Load HO
Triggering condition
_ The load HO switch of the service cell is enabled.
_ The system signaling flow is not larger than the Load HO system flow Thrsh.
_ The service cell traffic is larger than the Load HO Thrsh.
_ The DL receiving level is in the load HO zones.
Object cell selection
_ The service cell cannot be the object cell.
_ The traffic of the neighboring cell must be lower than its load HO receiving
thrsh.
_ The neighboring cell with the receiving level higher than the inter layer HO
Thrsh.
Restriction
_ It is not available with SDCCH.
_ Load HO just occur within the same BSC.
Edge HO
Triggering condition
_ The DL receiving level < Edge HO DL RX_LEV Thrsh.
_ OR The UL receiving level < Edge HO UL RX_LEV Thrsh.
_ Satisfying P/N rule.
Object cell selection
_ The service cell cannot be the object cell.
_ The neighboring cell with the highest priority and whose priority is
higher than that of the service cell.
Layer HO
Triggering condition
_ The layer of the object cell is lower than that of the service cell.
_ The DL level of the object cell is higher than the inter layer HO thrsh.
_ Satisfying P/N rule.
Object cell selection
_ The service cell cannot be the object cell.
_ The neighboring cell with the highest priority and whose priority is
higher than that of the service cell

PBGT HO         
Triggering condition
_ The layer and level of the object cell are the same as those of the
service cell.
_ The DL level must be the result of the following formula.
Object cell selection
_ The service cell cannot be the object cell.
_ The neighboring cell with the highest priority and whose priority is
higher than that of the service cell.
Restriction
_ It is not available with SDCCH.


 Fast-Moving HO
Triggering condition
_ In Fast Moving Watch Time, the mobile phone moves through P cells
of N.
_ The layer of N cells must be less than four (none Umbrella cell).
Object cell selection
_ The neighboring cell with the highest priority and meet the following
condition.
_ The layer of the object cell must be no less than four, that is, the
Umbrella cell.
_ The receiving level of the object cell >= the inter layer HO thrsh. +
inter layer HO hysterisis.

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