LTE - Measurement Reports
We all heard of the word "Handoff". UE moving from the serving cell to a Neighbour cell. 2 Level of functionalities happens here for this process. NAS level control Messages & AS level control Messages.
We see the AS level messages which triggers the Handoff. the Basic Funda behind Handoff is when the Target cell becomes better than the Serving Cell, UE will move on to the better cell for better user experiences.
So How UE will come to know that the Target Cell is better than the Serving Cell? Here comes the Measurement Reports for that purpose. The Measurement reports are carried by the RRC Connection Reconfiguration message in the Connected state.
There are as many as 8 Measurement Events for this purpose. They are classified as Intra-system Handover related events & Inter system Handover related Events.
Intra-system Handover:
This is TAU within the LTE cells moving from source to target. It can be of same frequency or different frequency based on the availability & configuration of the Target Cell.
The measurement Events used for this Handover are A1, A2, A3, A4, A5, A6
A1 - Serving becomes better than Threshold
A2 - Serving becomes worse than Threshold
A3 - Neighbour becomes Offset better than Primary Cell
A4 - Neighbour becomes better than Threshold
A5 - Serving becomes worse than Thresold1 & Neighbour becomes better than Threshold2
A6 - Neighbour becomes Offset better than Secondary Cell
Inter-System Handover:
This is IRAT handover moving from LTE Cell to UMTS Cell or GSM cell based on the availability of the Cell.
The measurement Events used for this Handover are B1 & B2
B1 - Inter RAT neighbour becomes better than Threshold
B2 - Serving cell becomes worse than Threshold1 & Inter RAT neighbout becomes better than Threshold2
All the Thresholds mentioned above are configurable in the E-UTRAN Provisioning file. Once the Events get triggered, Handover happens accordingly.
Spec reference: 36.331, Sec 5.5 Measurements.
We all heard of the word "Handoff". UE moving from the serving cell to a Neighbour cell. 2 Level of functionalities happens here for this process. NAS level control Messages & AS level control Messages.
We see the AS level messages which triggers the Handoff. the Basic Funda behind Handoff is when the Target cell becomes better than the Serving Cell, UE will move on to the better cell for better user experiences.
So How UE will come to know that the Target Cell is better than the Serving Cell? Here comes the Measurement Reports for that purpose. The Measurement reports are carried by the RRC Connection Reconfiguration message in the Connected state.
There are as many as 8 Measurement Events for this purpose. They are classified as Intra-system Handover related events & Inter system Handover related Events.
Intra-system Handover:
This is TAU within the LTE cells moving from source to target. It can be of same frequency or different frequency based on the availability & configuration of the Target Cell.
The measurement Events used for this Handover are A1, A2, A3, A4, A5, A6
A1 - Serving becomes better than Threshold
A2 - Serving becomes worse than Threshold
A3 - Neighbour becomes Offset better than Primary Cell
A4 - Neighbour becomes better than Threshold
A5 - Serving becomes worse than Thresold1 & Neighbour becomes better than Threshold2
A6 - Neighbour becomes Offset better than Secondary Cell
Inter-System Handover:
This is IRAT handover moving from LTE Cell to UMTS Cell or GSM cell based on the availability of the Cell.
The measurement Events used for this Handover are B1 & B2
B1 - Inter RAT neighbour becomes better than Threshold
B2 - Serving cell becomes worse than Threshold1 & Inter RAT neighbout becomes better than Threshold2
All the Thresholds mentioned above are configurable in the E-UTRAN Provisioning file. Once the Events get triggered, Handover happens accordingly.
Spec reference: 36.331, Sec 5.5 Measurements.
No comments:
Post a Comment