Training WCDMA Handover Fundamentals GSM to UMTS
April 30, 2017 | Author: Obimma Ambrose Chukwudi | Category: N/A
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Download Training WCDMA Handover Fundamentals GSM to UMTS...
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WCDMA Handover Fundamentals GSM-to-UMTS Training Series V1.0
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Change History Date
Revision
Description
Author
Version 2008-11-22
1.0
Draft completed.
Gao Bo
2009-01-07
1.1
Comments in pages 12, 16, 22, 34, 49, 69, 72, and 94 are added.
Cheng Fangyuan
2009-01-19
1.2
Comments on the GPRS state are added in page 5.
Kuang Jun
Comments on the GSM handover purpose are added in page 9. Comments on the GSM handover types are added in page 10. Comments on the GSM handover procedure are added in page 14.
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Preface: Why the Handover is Required? l A major characteristic in the mobile communications:
Mobility of the UE
l As a key component of the mobile communication
system, the cell has a limited coverage area.
l The primary function of the handover is to provide the
continuous service for the moving UEs in the coverage of the network.
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Preface: Mobility Management on the RAN Side l
Handover and directed retry [ Serving cell change for the UE in CELL_DCH state
l
Cell selection and reselection [ Camped cell change for the UE in IDLE, CELL_FACH, CELL_PCH, or URA_PCH state [ Also referred to as the forward handover
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Preface: UE Mode and State UTRAN Connected Mode URA_PCH
Cell_PCH
Cell reselection
Cell_DCH
GSM: Handover
UTRAN: Inter-System Handover
Cell_FACH
GSM Connected Mode
GPRS Packet Transfer Mode Release RR Connection
Release RRC Connection
Establish RRC Release RRC Connection Connection
Release of temporary block flow
Establish RRC Connection
Initiation of temporary block flow
GPRS Packet Idle Mode1 Camping on a UTRAN cell1
Camping on a GSM / GPRS cell1
Idle Mode
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Establish RR Connection
Scope After this course, you are able to: l Learn about the differences between the GSM
handover and the WCDMA handover l Grasp the WCDMA handover decision algorithm l Grasp the WCDMA handover procedure l Grasp the WCDMA handover parameters l Grasp the WCDMA blind handover and directed retry
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Contents
Chapter 1 Introduction: GSM vs. WCDMA Chapter 2 Handover Measurement Chapter 3 Basic Handovers Chapter 4 Blind Handover and Directed Retry
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Chapter 1 Introduction: GSM vs. WCDMA
l Handover Purpose l Handover Types l Soft Handover and Hard
Handover l Handover Procedure l WCDMA Handover Concepts
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Handover Purposes in WCDMA and GSM WCDMA HO Purpose
GSM HO Purpose
lMain purpose: to provide the continuous service for the moving UEs in the coverage of the network
lMain purpose: to maintain the continuity of the conversation for the moving mobile stations (MSs)
lLoad balancing: resource sharing
lQoS improvement for the network Ø Call drop rate reduction Ø Congestion rate reduction
lSpeed steering and service steering (HSDPA): efficient resource usage
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Handover Types in WCDMA and GSM WCDMA HO Types
GSM HO Types
l In terms of signaling: Soft handover (softer handover) Hard handover l In terms of source cell and target cell attributes: Intra-frequency handover Inter-frequency handover Inter-mode handover (FDD TDD) Inter-RAT handover (UMTS GSM/CDMA2000) l In terms of handover purpose: Coverage-based handover (primary function) Load balancing-based handover (optional) Service sharing-based handover (optional) Speed estimation-based handover (optional) HUAWEI TECHNOLOGIES CO., LTD.
l In terms of triggering conditions: üEmergency handover TA handover Bad quality handover Rapid Rx_level drop handover Interference handover üLoad handover üNormal handover Edge handover Hierarchical handover PBGT handover üSpeed-sensitive handover (Fast moving handover) üConcentric cell handover l In terms of the time that the link configuration takes effect: Synchronous handover Asynchronous handover
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Handover Types in WCDMA and GSM — WCDMA Handovers Intra-frequency handover Soft/Softer handover Hard handover Based on coverage
Inter-RAT handover Based on
Based on Based on
Coverage
Load/
Based on
UE Speed
Coverage
WCDMA Freq. 1
Load/Service
Inter-frequency handover
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WCDMA Freq. 2
Page 11
Comparison Between Soft Handover and Hard Handover Comparison
Soft Handover
Hard Handover
Number of radio links in the active set after handover
Multiple
One
Service interruption due to handover
No
Yes
Cell frequency before and after handover
Cells of the same frequency
Cells of the same frequency, different frequencies, or different systems.
l Differences between the soft handover and the softer handover: [ In the softer handover, the maximum ratio combination is performed on the uplink signals at the NodeB. In the soft handover, the selection combination is performed on the uplink signals at the RNC. As the gain of maximum ratio combination is larger than the gain of selection combination, the softer handover is better than the soft handover. [ Because the combination of the softer handover is performed at the NodeB, the transmission resources on the Iub interface are saved. HUAWEI TECHNOLOGIES CO., LTD.
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Page 12
Comparison Between the Soft Handover and the Hard Handover RNC
RNC frame processing board
RNC
NodeB
NodeB 1
NodeB 1
NodeB 2
Soft handover
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Softer handover
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NodeB 2
Hard handover
Page 13
Comparison Between WCDMA Handover Procedure and GSM Handover Procedure Three phases in the WCDMA handover: MeasurementDecisionExecution
Measurement Phase
Decision Phase
Execution Handover
Overall procedure of the GSM handover algorithm
MR preprocessing
Penalty processing
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Network characteristic HO decision adjustment
Page 14
Primary WCDMA Handover Procedure — Three Phases of a Handover l
Measurement [ Measurement control [ Measurement implementation and result processing [ Measurement report
Measurement
[ Mainly accomplished by the UE
Decision l
Decision [ On the basis of measurement [ Resource application and assignment [ Mainly accomplished by the network (RNC RRM)
Execution l
Execution [ Signaling procedure [ Failure rollback supported [ Measurement control update
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Basic Concepts in the WCDMA Handover l l l
Active set Monitored set Detected set
l
Event report [ Event-to-period report (1A, 1C) l Periodical report l l
Radio Link (RL) Radio Link Set (RLS)
l
Combing mode: maximum ratio
combining and selection combing l l l l
Soft handover gain Pilot channel (CPICH) Soft HO, softer HO, and hard HO Blind handover
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Questions
l Differences between soft handover, softer
handover, and hard handover l Typical scenarios of the WCDMA handover l Basic concepts of the WCDMA handover
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Summary l This chapter describes the handover purpose and the common
types of the WCDMA handover.
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Contents
Chapter 1 Introduction: GSM vs. WCDMA Chapter 2 Handover Measurement Chapter 3 Basic Handovers Chapter 4 Blind Handover and Directed Retry
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Chapter 2 Handover Measurement
l Measurement Control and
Measurement Report l Basic Concepts of Measurement l Intra-Frequency Measurement Event l Inter-Frequency and Inter-RAT
Measurement Event l UE-Internal Measurement
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Measurement Control and Measurement Report Measurement control: UE
UTRAN MEASUREMENT CONTROL
Measurement control, normal case
The RNC informs the UE of measurement objects, neighboring cell list, reporting mode, and event parameters. When the measurement conditions change, the RNC informs the UE of the new measurement conditions.
Measurement report: UE
UTRAN MEASUREMENT REPORT
The UE sends the measurement report to the RNC when the triggering conditions are satisfied.
Measurement report, normal case
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Basic Concepts of Measurement l
Measurement quantities of the handover [ Intra-frequency and inter-frequency: CPICH RSCP, CPICH Ec/N0, Pathloss [ Inter-frequency: CPICH RSCP, CPICH Ec/N0 [ Inter-RAT: GSM Carrier RSSI, BSIC Identification, BSIC Reconfirmation
l
Reporting mode of the MR [ Periodical report (event-to-period report) [ Event report
l
Events indicating the report mode [ Intra-frequency events: 1A, 1B, 1C, 1D, 1F [ Inter-frequency events: 2D, 2F, 2B, 2C [ Inter-RAT events: 3A, 3C [ Others: 6G, 6F
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Measurement Model
parameters
A
Layer 1 filtering
B
Layer 3 filtering
parameters
C C'
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Evaluation of reporting criteria
Page 23
D
Basic Concepts of Measurement l
Measurement ID
l
Measurement command: create, modify, and delete
l
Measurement event ID
l
Measurement object list: neighboring cells
l
Filtering coefficient
l
Report hysteresis
l
Trigger delay time
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Reporting Criteria l Reporting criteria
[ Judge the inequation, in the case of Event1A: NA 10⋅ LogMNew + CIONew ≥ W ⋅10⋅ Log ∑M i + (1−W ) ⋅10⋅ LogMBest − (R1a − H1a / 2), i =1 NA 10⋅ LogMNew + CIONew < W ⋅10⋅ Log ∑Mi + (1 −W ) ⋅10⋅ LogMBest − (R1a + H1a / 2), i =1
[ Judge the inequation, in the case of Event 1F: 10⋅ LogM Old +CIO Old≤T1f − H1f / 2, 10⋅ LogM Old +CIO Old ≥T1f + H1f / 2,
Reporting range Threshold Hysteresis Trigger delay time
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Descriptions of Key Parameters CPICH Ec/No
A
△
T
△
T
△
T
Reporting Range
Hyst
B
C
1A Event
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1B Event
Not triggered
Page 26
Intra-Frequency Measurement Events l
The intra-frequency measurement event is identified by 1X where X is A, B, C…. − Event 1A: Relative threshold addition event. A primary CPICH enters the reporting range (FDD only), indicating that the quality of a cell reaches the quality of the best cell or active set quality. When the active set of the UE is full, the event 1A reporting stops. − Event 1B: Relative threshold deletion event. A primary CPICH leaves the reporting range (FDD only), indicating that the quality of a cell is far lower than the quality of the best cell or active set quality. − Event 1C: Replacement event. A non-active primary CPICH becomes better than an active primary CPICH (FDD only). − Event 1D: Change of the best cell (FDD only). − Event 1F: A primary CPICH becomes worse than an absolute threshold (FDD only).
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Inter-Frequency and Inter-RAT Measurement Events l The inter-frequency measurement event is identified by 2X. Ø
Event 2B: The estimated quality of the currently used frequency is below a certain threshold and the estimated quality of a non-used frequency is above a certain threshold.
Ø
Event 2C: The estimated quality of a non-used frequency is above a certain threshold.
Ø
Event 2D: The estimated quality of the currently used frequency is below a certain threshold. Used to enable the compressed mode.
Ø
Event 2F: The estimated quality of the currently used frequency is above a certain threshold. Used to disable the compressed mode.
l The inter-RAT measurement event is identified by 3X. Ø
Event 3A: The estimated quality of the currently used UTRAN frequency is below a certain threshold and the estimated quality of the GSM cell is above a certain threshold.
Ø
Event 3C: The estimated quality of the GSM cell is above a certain threshold.
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UE-Internal Measurement l Event 6G: The UE DL Rx-UL Tx time difference for a RL included in
the active set becomes less than an absolute threshold. l Event 6F: The UE DL Rx-UL Tx time difference for a RL included in
the active set becomes larger than an absolute threshold.
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Questions
l Which events do the intra-frequency
measurements involve? l Which events do the UE-internal measurements
involve? l Which events do the inter-frequency
measurements involve?
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Summary l This chapter details the meaning and applications of intra-
frequency measurements, inter-frequency measurements, and inter-RAT measurements.
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Contents
Chapter 1 Introduction: GSM vs. WCDMA Chapter 2 Handover Measurement Chapter 3 Basic Handovers Chapter 4 Blind Handover and Directed Retry
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Chapter 3 Basic Handovers
l Soft Handover l Intra-Frequency Hard Handover l Inter-Frequency Hard Handover l Inter-RAT Hard Handover l HSDPA Handover l Compressed Mode
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Soft Handover l Overview l Measurement l Algorithm l Procedure l Execution l Common Parameters
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Overview l
l
Characteristics [ RLs between the UE and multiple cells in the UTRAN after the handover—Active set [ Softer handover can be implemented between multiple cells in a RLS. − Soft handover. Selection combination on the uplink and maximum ratio combination on the downlink. − Softer handover. Maximum ratio combination on the uplink and downlink. Advantages [ Soft handover gain, which involves − Multi-cell gain: Multiple unrelated branches in the soft handover reduce the requirements on shadow fading margin. − Macro diversity combining gain: The improvement on the link demodulation performance brings the power gain against the fast fading. [
l
Load sharing: On the uplink, multiple cells receive the UE signals, which reduces the transmit power of the UE. On the downlink, multiple cells transmit the RF signals, which reduces the transmit power of each cell. [ Number of call drops due to ping-pong handovers is reduced. Disadvantages [ [ [
The downlink resource consumption is large, especially the code resources consumed by the high-speed BE services. The downlink power gain is usually negative. In case of power imbalance, side effect occurs.
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Measurement l
Measurement on soft handover/softer handover [ Measurement type: CPICH RSCP, CPICH Ec/N0, and Pathloss [ Measurement processing: Layer 1 filtering and layer 3 filtering [ Measurement reporting mode − Periodical reporting − Event reporting ▪ Report type: 1A, 1B, 1C, 1D, and 1F ▪ UE observed CFN-SFN time difference ▪ Reporting criteria: Triggering conditions, reporting range, threshold, hysteresis, and trigger delay time. ▪ Event-to-period report
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Measurement Events l
Measurement events of soft handover/softer handover [ Intra-frequency measurement event types − Event 1A: Relative threshold addition event. The quality of a cell reaches the quality of the best cell or active set quality. When the active set of the UE is full, the event 1A reporting stops. − Event 1B: Relative threshold deletion event. The quality of a cell is far lower than the quality of the best cell or active set quality. − Event 1C: Replacement event. A non-active primary CPICH becomes better than an active primary CPICH. − Event 1D: Change of the best cell. − Event 1F: A primary CPICH becomes worse than an absolute threshold.
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Decision Algorithm l
Decision algorithm of the soft handover/softer handover (using the relative threshold handover algorithm under the condition that the minimum quality threshold of the soft handover is satisfied) [ Event 1A: Soft handover branch addition [ Event 1B: Soft handover branch deletion [ Event 1C: Cell replacement in the active set [ Event 1D: In the case of a cell in the active set, replace the best cell. In the case of a cell in the monitored set, add the cell to the active set and replace the best cell. Meanwhile, change the measurement control, and set the algorithm parameters based on the best cell configuration.
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Execution l
Execution [ Updating principle of the measurement control − Set the neighboring cell and algorithm parameters according to the best cell configuration [ RLC mode − AM mode [ Compensation and limit of the soft handover failure − Event-to-period report (Event 1A and 1C): leading to directed retry ▪ Controllable parameters: reporting period and number of reports
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Procedure_RL Addition l
Execution (RL addition)
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Procedure_RL Deletion l
Execution (RL deletion)
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Common Parameters l
Relative threshold [ Respectively configured for event 1A and 1B. [ Threshold of 1A < Threshold of 1B, thus making it difficult to delete the RL and therefore avoiding the ping-pong handover. [ Generally set 3 dB for event 1A and 6 dB for event 1B.
l
Trigger delay time [ Respectively configured for each event. [ Generally set the parameter value for 1B larger than that for 1A, thus making it difficult to delete the RL and therefore avoiding the ping-pong handover. [ Generally set 320 ms for 1A and 640 ms for 1B.
l
Layer 3 filter coefficient [ All intra-frequency measurements share one such parameter. [ This parameter is sensitive to the trigger delay time and ping-pong handover. [ Generally set to 3.
l
Minimum quality threshold of the soft handover
MML command: SET INTRAFREQHO
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Intra-Frequency Handover Parameter Configuration lEvent Parameters lEvent 1A
[IntraRelThdFor1ACS,IntraRelThdFor1APS dB) [Hystfor1A
0
[TrigTime1A
D320 (320 ms)
6 (3
lEvent 1B
[IntraRelThdFor1BCS, IntraRelThdFor1BPS ( 5 dB) [Hystfor1B
0
[TrigTime1B
D640 (640ms)
10
E1A
E1B
lEvent 1C
[ Hystfor1C
4 (2 dB)
[TrigTime1C
D640 (640ms)
lEvent 1D
[TrigTime1D
D640 (640ms)
[Hystfor1D
8 (4 dB)
ØOther lCell Offset 0
E1C
lINTRAFREQMEASQUANTITY
E1D
CPICH_EC/NO lMAXCELLINACTIVESET
3
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Chapter 3 Basic Handovers
l Soft Handover l IntraIntra-Frequency Hard Handover l Inter-Frequency Hard Handover l Inter-RAT Hard Handover l HSDPA Handover l Compressed Mode
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Intra-Frequency Hard Handover l
Overview
l
Measurement and Decision
l
Procedure
l
Common Parameters
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Overview
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Characteristics l
Characteristics [ After the handover, the UE is connected to only one cell. [ Disconnect the original RRC connection first, and then perform the handover. [ The original cell and the target cell have the same frequency. [ Generally, the hard handover with synchronization is adopted.
l
Advantages [ The code resources and hardware resource consumption is reduced.
l
Disadvantages [ High call drop rate due to co-frequency interference
l
Application scenarios [ No Iur-interface or Iur-interface congestion (mandatory) [ The specific strategy can be based on code resources or signal quality, subject to the practical applications.
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Measurement Decision and Execution l
Measurement [ Similar to the soft handover
l
Decision [ Event 1D
l
Execution [ The UE reports the CFN-SFN message − Synchronized hard handover − Use the existing DOFF − Continuous CFNs [ The UE does not report the CFN-SFN message − Hard handover with the re-establishment timer − Reconfigure the DOFF − Calculate the CFNs according to DOFF
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Procedure l
Signaling Procedure Target 目标NODEB
UE
原 NODEB Source
SRNC
1.RADIO LINK SETUP REQUEST 2. RADIO LINK SETUP RESPONSE
3. ALCAP SETUP 3.ALCAP建立 4. PHYSICAL CHANNEL RECONFIGURATION 5. RADIO LINK FAILURE INDICATION 6. PHYSICAL CHANNEL RECONFIGURATION COMPLETE 7. RADIO LINK DELETION REQUEST 8. RADIO LINK DELETION RESPONSE
9. ALCAP RELEASE 9.ALCAP释放
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Common Parameters l
BEBITRATETHD: Decision threshold of the BE services handover rate [ When the maximum rate of the transmission channel of the BE services is less than or equal to this threshold, the system performs the soft handover on the UEs that are using the BE services. [ When the maximum rate of the transmission channel of the BE services is larger than this threshold, the system performs the intrafrequency hard handover on the UEs that are using the BE services.
l
Parameters related to Event 1D [ Trigger delay time and hysteresis [ Trace the cell changes to accomplish the handover in time, and reduce the number of ping-pong handovers.
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Chapter 3 Basic Handovers
l Soft Handover l Intra-Frequency Hard Handover l InterInter-Frequency Hard Handover l Inter-RAT Hard Handover l HSDPA Handover l Compressed Mode
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Inter-Frequency Hard Handover l
Overview
l
Measurement and Decision
l
Procedure
l
Common Parameters
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Overview l
Characteristics [ Different frequencies before and after the handover [ For the UEs with only one set of receivers, the auxiliary measurements in compressed mode are required. [ Generally use the hard handover with the re-establishment timer
l
Advantages [ The handover success rate is higher than that of the intra-frequency hard handover. [ The load balance is maintained among the carriers. [ For hierarchical cells, a proper configuration of different data rates can be implemented.
l
Disadvantages [ The extra radio resources are consumed due to the compressed mode. [ The hard handover with the re-establishment timer prolongs the handover duration and introduces the risk of call drops.
l
Applications [ Discontinuous coverage of carriers (coverage-based handover) [ Non-coverage handover
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Inter-frequency Hard Handover Measurement Quantities and Measurement Events l
Measurement of the inter-frequency hard handover [ Measurement quantities: − CPICH RSCP and CPICH Ec/N0 [ Select the measurement type based on the specific handover purpose: − Edge of the cell covered by carriers: CPICH RSCP − Center of the cell covered by carriers: CPICH Ec/No
l
Measurement report [ Event report − Event 2D: The estimated quality of the currently used frequency is below a certain threshold. Used to enable the compressed mode. − Event 2F: The estimated quality of the currently used frequency is above a certain threshold. Used to disable the compressed mode. − Event 2B: The estimated quality of the currently used frequency is below a certain threshold and the estimated quality of a non-used frequency is above a certain threshold. Used to trigger the coverage-based handover. − Event 2C: The estimated quality of a non-used frequency is above a certain threshold. Used to trigger the speed estimation inter-layer handover. [ Periodical report
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Compressed Mode Enabling Algorithm in the Inter-Frequency Hard Handover l
Measurement enabling criteria [ Event 2D: The estimated quality of the currently used frequency is below a certain threshold. Used to enable the compressed mode. [ The speed estimation algorithm enables the inter-frequency measurement.
l
Measurement disabling criteria [ Event 2F: The estimated quality of the currently used frequency is above a certain threshold. Used to disable the compressed mode. [ After the best cell changes, the neighboring cells of the best cell do not involve the inter-frequency neighboring cells. [ The timer for inter-frequency measurement expires. [ If the UE estimated speed changes, the hierarchical cell algorithm disables the corresponding inter-frequency measurements. [ The handover is stopped in the case of a hard handover based on coverage.
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Speed Estimation Algorithm for Hierarchical Cells (Not Considered Currently) l
When the UE is in coverage of the hierarchical cells, the speed estimation algorithm is enabled. [ According to the measurement events in a period, determine whether the UE speed meets the requirements of the current layer. − If the estimation result is medium speed, maintain the UE in the current layer. − If the estimation result is high speed, hand over the UE to higher layers. If the estimation result is low speed, hand over the UE to lower layers. [ According to the estimation result, initiate the inter-frequency blind handover or inter-frequency measurement handover procedure if the inter-frequency hierarchical structure is used, and initiate the intra-frequency hard handover if the intra-frequency hierarchical structure is used.
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Decision Algorithm l
Decision of the inter-frequency hard handover [ Triggering conditions of the coverage-based handover − Event 2B: The estimated quality of the currently used frequency is below a certain threshold and the estimated quality of a non-used frequency is above a certain threshold. [ Triggering conditions of the speed estimation handover − Event 2C: The estimated quality of a non-used frequency is above a certain threshold.
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Execution l
Execution of the inter-frequency hard handover [ The UE reports the timing information. − The compressed mode may not be used on the UE with two transceivers. − Synchronized hard handover − Use the existing DOFF − Continuous CFNs [ The UE does not report the timing information. − The compressed mode must be used on the UE with only one transceiver. − In the case that the target cell and the cells in the active set do not belong to one NodeB, ▪ Hard handover with the re-establishment timer ▪ Reconfigure the DOFF ▪ Calculate the CFN according to the DOFF − In the case that the target cell and the cells in the active set belong to one NodeB (not considered currently) ▪ Internally calculate the timing relation of the target cell ▪ Synchronized hard handover ▪ Use the existing DOFF ▪ Continuous CFNs
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Procedure l
Signaling procedure 目标NODEB
UE
原 NODEB
SRNC
1.RADIO LINK SETUP REQUEST 2. RADIO LINK SETUP RESPONSE
3.ALCAP建立 4. PHYSICAL CHANNEL RECONFIGURATION 5. RADIO LINK FAILURE INDICATION 6. PHYSICAL CHANNEL RECONFIGURATION COMPLETE 7. RADIO LINK DELETION REQUEST 8. RADIO LINK DELETION RESPONSE
9.ALCAP释放
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Common Parameters (1) Parameters related to the inter-frequency coverage handover: [ Inter-frequency measurement report mode: periodical reporting or event trigger [ Inter-frequency measurement quantities: CPICH Ec/No or CPICH RSCP [ Inter-frequency measurement layer 3 filter coefficient, trigger delay time, and hysteresis [ Inter-frequency measurement start/stop threshold: configured specific to CPICH Ec/No and CPICH RSCP, or CS and PS, or 2D and 2F [ Inter-frequency coverage handover threshold: target cell quality threshold [ Inter-frequency hard handover used frequency quality threshold [ Inter-frequency handover min. access threshold
MML command: ADD CELLINTERFREQHOCOV
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Common Parameters (2) l
Parameters related to the inter-frequency non-coverage handover: [ Inter-frequency measurement layer 3 filter coefficient, trigger delay time, and hysteresis [ Inter-frequency non-coverage handover threshold
MML command: ADD CELLINTERFREQHONCOV
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Parameters Related to Inter-Frequency Handover l Event 2D/2F
l Event 2B
lINTERFREQREPORTMODE EVENT_TRIGGER
InterFreqCSThd2FEcN0,InterFreq R99PsThd2FEcN0,InterFreqHT hd2FEcN0“ -9
l InterFreqCovHOCSTh
lINTERFREQMEASQUANTITY
InterFreqCSThd2FRSCP,InterFreq R99PsThd2FRSCP,InterFreqHT hd2FRSCP -99 HYSTFOR2F
0
TrigTime2F
1280
InterFreqCSThd2DEcN0,InterFreq R99PsThd2DEcN0,InterFreqHT hd2DEcN0 -12 InterFreqCSThd2DRSCP,InterFreq R99PsThd2DRSCP,InterFreqHT hd2DRSCP -102 Hystfor2D
dEcN0,TargetFreqHTh dEcN0,TargetFreqR99 PsThdEcN0 -13 l "InterFreqCovHOCST
hdRSCP,TargetFreqH ThdRSCP,TargetFreq R99PsThdRSCP" 105 l HYSTFOR2B 1 db l TRIGTIME2B 100ms
0
TRIGTIME2D 200ms
Handover Trigger
Measurement Phase
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CPICH_Ec/No
Chapter 3 Basic Handovers
l Soft Handover l Intra-Frequency Hard Handover l Inter-Frequency Hard Handover l InterInter-RAT Hard Handover l HSDPA Handover l Compressed Mode
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Inter-RAT Hard Handover l
Overview
l
Inter-frequency measurement: compressed mode start/stop
l
Algorithm
l
Procedure
l
Common Parameters
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Overview l
l
l
l
Scope [ WCDMA FDD GSM [ WCDMA FDD WCDMA TDD [ WCDMA FDD CDMA2000 Characteristics [ Different Radio Access Technologies (RATs) before and after the handover [ Auxiliary measurement in compressed mode generally required Advantages [ Coverage: solve the transition between different RATs [ Capacity: leverage the existing equipment to a maximum extent (2G->3G) Disadvantages [ The procedure is complex and has the high requirements on the equipment compatibility. [ The UE is complex.
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Inter-RAT Measurement: Compressed Mode Start/Stop l
Inter-RAT handover measurement (GSM measurement) [ Measurement type − GSM Carrier RSSI − BSIC Identification − BSIC Reconfirmation [ Measurement processing: layer 1 filtering and layer 3 filtering [ Measurement report − Event report ▪ Event 2D: start the GSM measurement ▪ Event 2F: stop the GSM measurement
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Decision Algorithm l
Inter-RAT handover decision [ Inter-RAT coverage handover − Event mode ▪ Event 3A: The estimated quality of the currently used UTRAN frequency is below a certain threshold and the estimated quality of the GSM cell is above a certain threshold. − Periodical mode ▪ Estimation: According to the periodically reported GSM RSSI measurements and the BSIC confirmation state of the GSM target cell, estimate the cells of which the GSM RSSI exceeds the absolute threshold. If multiple cells meet this requirement, preferentially select the cell confirmed by the BSIC. [ Inter-RAT non-coverage handover − Event mode ▪ Event 3C: The estimated quality of the GSM cell is above a certain threshold.
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Procedure l
Execution UE
N o de B
SR N C
CN
M SC
1 . R elo catio n R equ ired
2 . P repare H ando ver
5 . P re pare H ando ver R espo nse
6 . R elo catio n C o m m and
B SC
3 . H ando ver R equ est 4 . H ando ver R e qu est Ac k
7 . D C C H : H ando ver fro m U T R A N C o m m and 8 . H ando ver D ete ct 9 . H ando ver C o m plete
1 2 . Iu R e lea se C o m m and 1 3 . Iu R elease C o m plete
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1 4 . Send E nd Signal R espo nse
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1 0 . H ando ver C o m plete
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Common Parameters (1) l
Inter-RAT coverage handover parameters [ Inter-RAT measurement start/stop threshold: Set the event 2D and 2F thresholds. The related measurement quantities are CPICH Ec/No and CPICH RSCP. One set for CS services and PS services respectively. [ Inter-RAT 2D/2F measurement quantities: CPICH Ec/No or CPICH RSCP [ BSIC verify switch [ Inter-RAT coverage handover threshold: the GSM RSSI threshold of the inter-RAT coverage handover, specific to CS or PS services. [ Inter-RAT handover used frequency quality threshold [ Trigger delay time and hysteresis: one set for each event
l
MML command: ADD CELLINTERRATHOCOV
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Common Parameters (2) l
Inter-RAT non-coverage handover parameters [ Inter-RAT measurement report period [ Inter-RAT handover decision threshold: CS, PS, and individually configured signaling [ Trigger delay time: configured on the basis of verified BSIC and non-verified BSIC [ Inter-RAT measurement layer 3 filtering coefficient and hysteresis [ Penalty time
l
MML command: ADD CELLINTERRATHONCOV
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Inter-RAT Handover Key Parameters l Event 2D
InterRATCSThd2DEcN0,InterRATR 99PsThd2DEcN0,InterRATHThd 2DEcN0 -12 "InterRATCSThd2DRSCP,InterRAT R99PsThd2DRSCP,InterRATHTh d2DRSCP -102 HYSTFOR2D
0
TRIGTIME2D
200ms
l Event 2F
InterRATCSThd2FEcN0,InterRATR9 9PsThd2FEcN0,InterRATHThd2 FEcN0 -9 "InterRATCSThd2FRSCP,InterRAT R99PsThd2FRSCP,InterRATHTh d2FRSCP -97 HYSTFOR2F
2(1db)
l Event 3A
l2D2FMeasQuantity CPICH_RSCP
IRHOUsedFreqCSThdEcN 0,UsedFreqR99PsThdE cN0,UsedFreqHThdEcN 0 -10
lINTERRATREPORTMODE
EVENT_TRIGGER
lBSICVERIFY
REQUIRE
"IRHOUsedFreqCSThdRS CP,UsedFreqR99PsThd RSCP,UsedFreqHThdR SCP -100 "InterRATCovHOCSThd,T argetRatR99PsThd,Targ etRatHThd 95 HYSTFOR3A
0
TRIGTIME3A 60ms
TRIGTIME2F 1280ms
Handover Trigger
Measurement Phase
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Chapter 3 Basic Handovers
l Soft Handover l Intra-Frequency Hard Handover l Inter-Frequency Hard Handover l Inter-RAT Hard Handover l HSDPA Handover l Compressed Mode
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HSDPA Handover l
Overview
l
HSDPA Handover Measurement
l
Serving Cell Change Algorithm
l
HSDPA Directed Retry Algorithm
l
Serving Cell Update Process
l
Common Parameters
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Overview of the HSDPA Handover l
Scope [ HS-DSCH handover related to HSDPA − HSDPA serving cell update − Handover between HSDPA and DCH
l
Principle [ For services meeting the threshold, the HSDPA resources are used. To maximize the throughput, the HS-DSCH serving cell follows the best cell in the active set.
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HSDPA Handover Measurement l
HSDPA handover measurement [ Measurement type: CPICH RSCP, CPICH Ec/N0, and Pathloss [ Measurement processing: Layer 1 filtering and Layer 3 filtering [ Measurement report − Periodic report − Event-triggered report ▪ Report type: 1A, 1B, 1C, and 1D ▪ Event-triggered to periodic report
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Serving Cell Change Algorithm l
For the serving cell of which the HS-PDSCH is changed in the active set [ The best cell is decided according to 1D event, and the handover is performed in time. [ The handover protection timer is started after the handover to avoid ping-pong handover.
l
For the serving cell of which the HS-PDSCH is changed in hard handover [ The HSDPA channel is established in the target cell while the hard handover is performed. [ If the target cell does not support the HSDPA, the DCH is established.
l
For the serving cell of which the HS-PDSCH is changed in soft handover [ If the best cell does not support the HSDPA, and the currently serving HSDPA cell is deleted, the data services are preferred to be established on the HSDPA channel.
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HSDPA Directed Retry Algorithm l
For newly-established services [ When the UE establishing only signaling connection initially establishes the PS services, the conditions for mapping to the HSDPA are met according to the mapping principle of the channel type. The current cell, however, does not support the HSDPA or supports the HSDPA but has insufficient resources. In this case, the directed retry to the non-emergency blind handover cell which supports the HSDPA and has available resources is triggered.
l
For traffic volume [ When the UE starts the handover from common channel to dedicated channel in CELL-FACH state due to the traffic volume, the conditions for mapping to the HSDPA are met. The current cell, however, does not support the HSDPA or supports the HSDPA but has insufficient resources. In this case, the directed retry to the non-emergency blind handover cell which supports the HSDPA and has available resources is triggered.
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Serving Cell Update Process
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Common Parameters l
HSDPA handover protection duration [ To avoid the impact of the ping-pong handover on data services, the handover protection timer T-hsdpa is set. When the timer is active, the change of the serving cell in the HSDPA active set is not performed. [ Value range: 0 to 1,024 seconds
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Chapter 3 Basic Handovers
l Soft Handover and Softer Handover l Intra-Frequency Hard Handover l Inter-Frequency Hard Handover l Inter-RAT Handover l HSDPA Handover l Compressed Mode
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Compressed Mode l
Purpose
l
Figure
l
Implementation
l
HSDPA Directed Retry Algorithm
l
Limitations of the Sequences in Compressed Mode
l
Common Parameters
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Purpose l
Purpose [ Inter-frequency or inter-RAT measurement can be performed in FDD.
l
Causes [ Downlink compression: one transceiver can work with only one TRX frequency. If the transceiver needs to measure the signals of other frequencies, the transceiver must stop working and switch the working frequency over to the target frequency for measurement. To ensure that the downlink signals can be properly transmitted, the transceiver must transmit the original signals in the remaining transmitting duration. [ Uplink compression: When the measurement frequency is close to the uplink transmit frequency, that is, the operating frequencies of GSM 1800 or GSM 1900 is close to the uplink working frequencies in FDD, the transceiver must stop transmitting the uplink signals to guarantee the quality of the measurement.
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Figure l
Figure
One frame (10 ms)
Transmission gap available for inter-frequency measurements
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Implementation l
Implementation [ Halving the spreading factor − The spreading factor of the compressed frame is used as a half and is replaced by the scrambling code if necessary. − Advantage: The processing of the RNC is simple, and relatively greater TGL can be provided. − Disadvantage: The NodeB processing capability is occupied, and the code resource usage is decreased. It cannot be used in the case of SF = 4. In addition, it has a significant impact on the coverage, and the replacement of the scrambling code brings about relatively greater interference. [ Hole-drilling mode (protocol cancellation) − The encoding redundancy can be decreased. − Advantage: The higher layer is simple. In addition, it can be used in the case of SF = 4, and the code resource usage is not affected. − Disadvantage: It is restricted by the channel encoding feature. The encoding gains are reduced. [ Higher layer scheduling − By restricting the TFCS, the Mac layer changes the data transmission rate. − Advantage: The introduced interference is relatively low. − Disadvantage: The processing of the higher layer (layer 2) is complicated and can be used only in non-real-time data services.
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Compressed Mode l
Key points [ FDD cell search capability and complementary format queue
Frame#1 Slot#1
Frame#1
#1
Frame#3
#1
#7
#2
#1
#15
#3
Frame#3
Frame#2
#4
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#5
#6
Frame#4
#9
#7
#15 #9 #10 #11 #12 #13 #14 #15
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Compressed Mode [ Power control performance − Power TX after the timeslot is compressed: possibly in line with the radio channel − Recovery period power control process: speeding the power control process towards target − ITP: Initial Transmit Power (the uplink power control method to be used to compute the initial transmit power after the compressed mode gap) − Recovery period power control: RPP − Power control compensation: DeltaSIR and DeltaSIRAfter [ Tracing performance − There exists clock drift. Therefore, the TGPL cannot be large to reduce the cell synchronization loss during the frequency handover. (Duration of step loss is around 300 ms.) [ Interference control − Compressed mode method selection [ Synchronization of compressed mode − Activation synchronization ▪ CFN takes 256 chips as the cycling period. ▪ The UE and NodeB have different delays for receiving signaling. ▪ The start time of the UE and NodeB is not more than 256 chips. − Soft handover synchronization ▪ After the compressed mode is started, the handover is still preferably soft handover. ▪ Soft handover can possibly occur in different NodeBs. ▪ The synchronization of the newly-added compressed frame in radio link and original link must be guaranteed. HUAWEI TECHNOLOGIES CO., LTD.
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Limitations of the Compressed Mode Pattern Sequences l
Limitations [ Overlap of gap pattern sequences cannot be created, that is, two or more gap pattern sequences cannot be created in the same frame. [ Only seven timeslots can be compressed in each frame. [ Three consecutive compressed frames cannot co-exist. [ When multiple compressed modes run simultaneously, the above conditions must be met. [ TGPL1 must equal TGPL2. [ Each compressed mode pattern sequence is used for only one kind of measurement. [ The uplink and downlink compressed mode pattern sequence parameters cannot be separately set.
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Compressed Mode Sequence Parameters
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Common Parameters (1) l
TGCFN: Connection Frame Number of the first frame of the first pattern within the Transmission Gap Pattern Sequence
l
TGSN: Transmission Gap Starting Slot Number (slot number of the first transmission gap slot within the TGCFN)
l
TGL1: length of the first Transmission Gap within the transmission gap pattern expressed in number of slots TGL2: length of the second Transmission Gap within the transmission gap pattern TGD: transmission gap distance indicating the number of slots between starting slots of two consecutive transmission gaps within a transmission gap pattern TGPL1: duration of transmission gap pattern 1 TGPL2: duration of transmission gap pattern 2 Frame mode [ Single frame mode: one complete compressed gap in one frame [ Double frame mode: one complete compressed gap in two frames Frame type [ Frame Type A: obtaining the maximum compressed gap [ Frame Type B: The TPC bit is inserted into a fixed position in the compressed gap so that the medium-to-high rate power control performance can be improved. It works with the ITP.
l l l l l
l
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Common Parameters (2) l
Power control parameters [ RPP: Recovery Period Power control mode during the frame after the transmission gap within the compressed frame [ ITP: Initial Transmit Power (uplink power control method to be used to compute the initial transmit power after the compressed mode gap) [ DeltaSIR: Delta in DL SIR target value to be set in the UE during the frame containing the start of the first transmission gap in the transmission gap pattern (without including the effect of the bit-rate increase) [ DeltaAfterSIR1: Delta in DL SIR target value to be set in the UE one frame after the frame containing the start of the first transmission gap in the transmission gap pattern [ DeltaSIR2: Delta in DL SIR target value to be set in the UE during the frame containing the start of the second transmission gap in the transmission gap pattern (without including the effect of the bit-rate increase) [ DeltaAfterSIR2: Delta in DL SIR target value to be set in the UE one frame after the frame containing the start of the second transmission gap in the transmission gap pattern
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Questions
l What are the differences between soft handover
and softer handover? l What is compressed mode? l Can you illustrate the signaling flows for hard
handover?
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Summary l This chapter describes the basic handovers in the WCDMA system. The
basic concepts, differences, scenarios, and signaling flows of soft handover, softer handover, intra-frequency hard handover, interfrequency hard handover, and inter-RAT handover are provided. l In addition, this chapter describes the compressed mode.
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Contents
Chapter 1 Introduction: GSM vs. WCDMA
Chapter 2 Handover Measurement
Chapter 3 Basic Handovers
Chapter 4 Blind Handover and Directed Retry Training.huawei.com
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Scope and Triggering Conditions l
RRC Directed Retry [ The initial signaling connection is established, and the cell request is rejected.
l
RRC Redirection [ The initial signaling connection is established, the cell request is rejected, and the RRC directed retry fails. (Directed retry has a higher priority than redirection. When the directed retry fails, redirection is triggered after the cell request is rejected.)
l
RAB Directed Retry [ The signaling connection is successful, but services fail to be established.
l
Blind Handover [ Inter-frequency load balancing (blind handover to inter-frequency cells) [ RRC Directed Retry [ RAB Directed Retry
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RRC Directed Retry (1) l
Scenario (1) [ Between inter-frequency overlapped coverage cells
UE initial camping cell
cell1 1
2
cell2
Inter-frequency overlapped coverage cell of Cell1
3
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Signaling process: 1 RRC CONNECTION REQUEST 2 RRC CONNECTION SETUP 3 RRC CONNETION SETUP COMPLETE
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RRC Directed Retry (2) l
Scenario (2) [ Between intra-frequency cells, and the UE is in the soft handover area
UE initial camping cell
Soft handover area Intra-frequency neighboring cell of Cell1
cell1
cell2 2 1
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Signaling process: 1 RRC CONNECTION REQUEST 2 RRC CONNECTION SETUP 3 RRC CONNETION SETUP COMPLETE
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Common Parameters Related to RRC Directed Retry ADD CELLDRD l
DRMAXUMTSNUM: maximum number of times for inter-frequency directed retry
l
MaxRelatingTime: maximum time for continuously using the RACH measurement report
l
LinearFactor: linear coefficient of selecting the candidate set compared with the threshold and time interval
l
CSTHRESHOLD: absolute threshold for the candidate set [ Directed retry candidate set absolute threshold: basic threshold for a cell entering the candidate set in the RACH measurement report. The threshold is the smallest Ec/N0 value required by the UE for normal communication.
l
INTRAFDRMAXNUM: maximum number of times for intra-frequency directed retry
ADD INTERFREQNCELL l
BLINDHOPRIO: blind handover priority
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RRC Redirection l
Scenario [ The UE fails to initiate signaling connection, and the RRC directed retry fails.
GSM cell Inter-freq cell
1’’
1’ cell1 2 UE initial camping cell
1
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Signaling process: 1 RRC CONNECTION REQUEST 2 RRC CONNECTION REJECT 1’ The UE initiates access to the specified cell of other frequencies after cell reselection. 1’’ The UE initiates access to the specified GSM cell after inter-RAT cell reselection
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More Information About the RRC Directed Retry and Redirection l
The triggering condition is that the signaling access grant fails. [ If no access grant is performed (directly accepted) for the signaling, the algorithm fails. The algorithm is effective during congestion. [ If access grant is performed for the signaling, the possibility for triggering the RRC directed retry and redirection is low. Only when cell congestion occurs, the possibility is high.
l
Comparison of advantages and disadvantages [ For the RRC directed retry, subscribes feel shorter delay. [ RRC redirection is more flexible and can be used to reselected to the GSM cell. Subscribers, however, feel longer delay.
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RAB Directed Retry l
Scenario
GSM CELL 4 UTRAN CELL 1 2
3
CN
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Signaling process: 1 RAB Assignment (from CN) 2 SRNS relocation (to CN) 3 Handover from UTRAN ( Inform UE access to GSM system) 4 Handover Complete (GSM message)
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Questions
l What are the differences between the processes
of the RRC directed retry and RRC redirection? l What are the triggering conditions for the RRC
directed retry and RRC redirection?
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Summary l This chapter describes the triggering scenarios for the RRC directed retry,
RRC redirection, and RAB directed retry, as well as the application of blind handover.
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