Inter-RAT Handover ( IRAT Handover)

The 2G/3G inter-RAT handover involves the handover from GSM to UMTS and the handover from UMTS to GSM. The handover is controlled mainly by the network. For MSs in dedicated mode, inter-RAT handovers can be performed, including the emergency handover, better cell handover, inter-RAT load handover, and inter-RAT service handover.

Inter-RAT Handover from UMTS to GSM

MSs in dedicated mode can be handed over from a UMTS cell to a GSM cell. The handover decision and handover procedure are controlled by the RNC. The BSS considers the incoming handover from UMTS to GSM as a common inter-BSC handover.

 The parameter Inter-RAT In BSC Handover Enable determines whether inter-RAT handover from UMTS to GSM is enabled. If Inter-RAT In BSC Handover Enable is set to No, the BSS rejects all the requests for the handover from UMTS to GSM.

Inter-RAT Handover from GSM to UMTS

The parameter Inter-RAT In BSC Handover Enable determines whether the inter-RAT handover from GSM to UMTS is enabled. If Inter-RAT In BSC Handover Enable is set to NO(No), the BSS rejects all the requests for the handover from GSM to UMTS and does not select a UMTS cell as the target cell.

In dedicated mode, an MS obtains the list of neighboring UMTS cells and other information from the Measurement Information. Then, the MS reports the measurement result to the BSS through the measurement report. After receiving the measurement result, the BSS determines whether to initiate the inter-RAT handover from GSM to UMTS based on the measurement result and the handover algorithm.

Evolved Node B (eNB)

Inter-cell RRM: HO, load balancing between cells

Radio Bearer Control: setup, modifications and release of Radio Resources

Connection Mgt. Control: UE State Management, MME-UE Connection

Radio Admission Control

eNode B Meas. collection and evaluation

Dynamic Resource Allocation (Scheduler)

IP Header Compression/ de-compression

Access Layer Security: ciphering and integrity protection on the radio interface

MME Selection at Attach of the UE

User Data Routing to the SAE GW

Transmission of Paging Msg coming from MME

Transmission of Broadcast Info (e.g. System info, MBMS)

What is the difference between CONGESTION and BLOCKING

Congestion = all resources (Time-slot) are used and congestion measure in seconds and unit of congestion is Millisecond.

 BLOCKING = Blocked requests, blocking measure in per event 

GSM CELL LOAD SHARING Parameter

CELL LOAD SHARING
Parameter	Description	Range	Ericsson Default Value	Remarks
CLSSTATE	Cell load sharing active/inactive for an individual cell	ACTIVE, INACTIVE	INACTIVE	For CLSSTATE activation to have effect, CLSSTATE must be activated
CLSACC	Percentage of available full rate capable traffic channels in a target cell at or below which no handovers due to Cell Load sharing will be accepted	1 to 100 %	40%	-
CLSLEVEL	Percentage of available full rate capable traffic channels at which or below which Cell load sharing evaluations are initiated.	0 to 99 %	20%	The value of of CLSLEVEL must be less than the value of CLSACC
HOCLSACC	Handover due to cell load sharing accepted to this cell	ON, OFF	OFF	-
RHYST	Hysteresis reduction parameter - determines how much hysteresis can be reduced in the cell load sharing evaluation	0 to 100 %	75%	-
CLSRAMP	Cell load sharing ramping time parameter.	0 to 30 seconds	5 seconds	The interval during which value of RHYST is ramped up from zero to the final value.

GSM Overlaid Subcell Locating data

Overlaid Subcell Locating data
Parameter	Description	Range	Ericsson Dafault Value	Remarks
LOL	Pathloss threshold.	0 to 200		Pathloss threshold. It defines the OL subcell coverage border in terms of the pathloss from the serving cell.
LOLHYST		0 to 63		Hysteresis for the pathloss criterion during evaluations for the OL subcell coverage.
DTCB:		-63 to 63	-63	Distance to cell border threshold. It defines the OL subcell coverage border in terms of the signal strength difference between the active channel and the strongest neighbouring BCCHs.
DTCBHYST		0 to 63		Hysteresis for the DTCB criterion during evaluations for the OL subcell coverage.
NDIST		0 to 63		Distance to cell border additional threshold.
NNCELLS		1 to 5		Number of strongest neighbouring BCCHs for the DTCB criterion. See the comments for NDIST.
TAOL		0 to 61 Bit periods (bp)		Timing advance threshold. It defines the OL subcell timing advance border
TAOLHYST		0 to 61 Bit periods (bp)		Hysteresis for the timing advance criterion during evaluations for the OL subcell coverage.

GSM Intra cell handover Parameter

Intra cell handover
Parameter	Description	Range	Ericsson Dafault Value	Remarks
IHO	Intra handover switch: ON - Intra cell handover is allowed; OFF - Intra cell is not allowed	ON, OFF	OFF	-
TMAXIHO	Timer for handover counter	0 to 60 seconds	6	-
TIHO	Intra cell handover inhibition timer	0 to 60 seconds	10	-
MAXIHO	Maximum number of consecutive intra-cell handovers	0 to 15	3	-
QOFFSETUL	Offset for quality uplink	-50 to +50 dtqu	0	-
QOFFSETDL	Offset for quality downlink	-50 to +50 dtqu	0	-
SSOFFSETUL	Offset for signal strength uplink	-30 to +30 db	0	-
SSOFFSETDL	Offset for signal strength downlink	-30 to +30 db	0	-

GSM Locating urgency cell Parameter

Urgency Conditions for Handover [Locating Algorithm]
Parameter	Description	Range	Ericsson Dafault Value	Remarks
TALIM	Timing advance limit for handover - Urgency detection parameter	0 to 63 (normal cell) Bits periods (bp)	62	TALIM determines the maximum timing advance that the MS is recommended to use in the cell
PSSBQ	Signal strength penalty when handover due to bad quality. This penalty  is valid during PTIMBQ	0 to 63 db	10 dB	-
PSSTA	Signal strength penalty when handover doe to too large timing advance. It is valid during PTIMTA	0 to 63 db	63	-
PTIMBQ	Penalty time when handover due to bad quality	0 to 600 seconds	10	-
PTIMTA	Penalty time when handover due to too large timing advance	0 to 600 seconds	10	-
QLIMDL	Quality limit downlink for handover. Urgency detection parameter	0 to 100 dtqu	55	Deci transformed GSM quality units (dtqu).
QLIMUL	Quality limit uplink for handover. Urgency detection parameter	0 to 100 dtqu	55	Deci transformed GSM quality units (dtqu).