WCDMA Air Interface Training Part 5 WCDMA Acquisition, Synchronization, and Handover

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WCDMA Air Interface Training Part 5 WCDMA Acquisition, Synchronization, and Handover. WCDMA Physical Layer Procedures. Physical Layer Timing and procedures BS Downlink timing Fast Synchronization Codes Synchronization Code 1 (PSC) Synchronization Code 2 (SSC i ) Downlink Scrambling Codes - PowerPoint PPT Presentation

Transcript of WCDMA Air Interface Training Part 5 WCDMA Acquisition, Synchronization, and Handover

Fundamentals of W-CDMA Part IV IMT-2000 W-CDMA Proposals5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
WCDMA Air Interface Training
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
WCDMA Physical Layer Procedures
BS Downlink timing
Fast Synchronization Codes
8192 possible codes, 64 Scrambling Code Groups
Slot Synchronization
Frame Synchronization
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Downlink Transmission Timing
CPICH (Common Pilot Channel)
3GPP TS 25.211 ¶ 7.0
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Downlink Scrambling Codes
Downlink Scrambling Codes
Used to distinguish Base Station transmissions on Downlink
Each Cell is assigned one and only one Primary Scrambling Code
The Cell always uses the assigned Primary Scrambling Code for the Primary and Secondary CCPCH’s
Secondary Scrambling Codes may be used over part of a cell, or for other data channels
Primary SC0
8192 Downlink Scrambling Codes
Each code is 38,400 chips of a 218 - 1 (262,143 chip) Gold Sequence
3GPP TS 25.213 ¶ 5.2.2
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Downlink Scrambling Codes
Downlink Scrambling Code Generation
10 mSec Gold Code formed by Modulo-2 Addition of 38,400 chips from two m-sequences
Initial Conditions:
y(0) ... Y(17) = 1
Primary Scrambling code i (where i = 0,...,511) is generated
by offsetting the X sequence by (16*i) clock cycles from the Y sequence
I
Q
1
1
0
0
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
17
17
16
16
15
15
14
14
13
13
12
12
11
11
10
10
X
Y
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Synchronization Codes
Allows UE to achieve fast synchronization in an asynchronous system
Primary Synchronization Code (PSC)
Provides fast positive indication of a WCDMA system
Allows fast asynchronous slot synchronization
Secondary Synchronization Codes (SSC)
A set of 16 codes, each 256 bits long
Codes are arranged into one of 64 unique permutations
Specific arrangement of SSC codes provide UE with frame timing, BS “code group”
P-CCPCH
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Primary Synchronization Code
Primary Synchronization Code (PSC)
let a = <1, 1, 1, 1, 1, 1, -1, -1, 1, -1, 1, -1, 1, -1, -1, 1>
PSC(1...256) = < a, a, a, -a, -a, a, -a, -a, a, a, a, -a, a, -a, a, a >
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Note: PSC is transmitted “Clear” (Without scrambling)
3GPP TS 25.213 ¶ 5.2.3
Broadcast Data (18 bits)
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Secondary Synchronization Code Group
16 Fixed 256-bit Codes; Codes arranged into one of 64 patterns
Note:
The SSC patterns positively identify one and only one of the 64 Scrambling Code Groups.
This is possible because no cyclic shift of any SSC is equivalent to any cyclic shift of any other SSC.
3GPP TS 25.213 ¶ 5.2.3
SSCi
SSC1
SSC15
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Slot Synchronization
Matched Filter
Matched
Filter
Output
time
P-CCPCH
(PSC)
BCH
Data
PSC
[1]
BCH
Data
PSC
[2]
BCH
Data
PSC
[3]
BCH
Data
PSC
[4]
BCH
Data
PSC
[15]
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Frame Synchronization, SCG ID
BCH
Data
SSC
[1]
BCH
Data
SSC
[2]
BCH
Data
SSC
[3]
BCH
Data
SSC
[4]
BCH
Data
SSC
[15]
10 mSec Frame (15 slots x 666.666 uSec)
Matched
Filter
Output
time
SSC
[2]
SSC
[3]
SSC
[4]
SSC
[1]
SSC
[6]
SSC
[7]
SSC
[8]
SSC
[5]
SSC
[10]
SSC
[11]
SSC
[12]
SSC
[9]
SSC
[14]
SSC
[15]
SSC
[13]
Frame Synchronization
Positive ID of Scrambling Code Group
Remember, no cyclic shift of any SSC is equal to any other SSC
3GPP TS 25.214 Annex C
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Random Access
Pre-amble
Pre-amble
Pre-amble
AICH
RACH
UE
BS
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Random Access Procedure
the UE receives:
The available random access signatures
The available spreading factors for the message part
The message length (10 ms or 20 ms)
Initial preamble transmit power
The power offset DPp-m between preamble and the message part.
Transport Format parameters
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Random Access Preamble Signatures
Preamble = [ P0, P1, … P15 ] repeated 256 times (4096 chips total).
Preamble codes help the BS distinguish between UE making simultaneous Random Access Attempts.
3GPP TS 25.213 ¶ 4.3.3.3
Signature
P0
P1
P2
P3
P4
P5
P6
P7
P8
P9
P10
P11
P12
P13
P14
P15
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
-1
1
-1
1
-1
1
-1
1
-1
1
-1
1
-1
1
-1
2
1
1
-1
-1
1
1
-1
-1
1
1
-1
-1
1
1
-1
-1
3
1
-1
-1
1
1
-1
-1
1
1
-1
-1
1
1
-1
-1
1
4
1
1
1
1
-1
-1
-1
-1
1
1
1
1
-1
-1
-1
-1
5
1
-1
1
-1
-1
1
-1
1
1
-1
1
-1
-1
1
-1
1
6
1
1
-1
-1
-1
-1
1
1
1
1
-1
-1
-1
-1
1
1
7
1
-1
-1
1
-1
1
1
-1
1
-1
-1
1
-1
1
1
-1
8
1
1
1
1
1
1
1
1
-1
-1
-1
-1
-1
-1
-1
-1
9
1
-1
1
-1
1
-1
1
-1
-1
1
-1
1
-1
1
-1
1
10
1
1
-1
-1
1
1
-1
-1
-1
-1
1
1
-1
-1
1
1
11
1
-1
-1
1
1
-1
-1
1
-1
1
1
-1
-1
1
1
-1
12
1
1
1
1
-1
-1
-1
-1
-1
-1
-1
-1
1
1
1
1
13
1
-1
1
-1
-1
1
-1
1
-1
1
-1
1
1
-1
1
-1
14
1
1
-1
-1
-1
-1
1
1
-1
-1
1
1
1
1
-1
-1
15
1
-1
-1
1
-1
1
1
-1
-1
1
1
-1
1
-1
-1
1
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Random Access Scrambling Codes
Random Access Preamble Scrambling Codes
Preamble Scrambling Code is a 4096-chip segment of a 225-long Gold Code
The UE targets one BS by using the BS’s indicated preamble scrambling code
“All UE accessing this cell shall use Random Access Preamble Spreading Code n2 ”
“All UE accessing this cell shall use Random Access Preamble Spreading Code n1 ”
3GPP TS 25.213 ¶ 4.3.3
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Acquisition Indication Channel
Transmits Acquisition Indicators in response to UE Access Attempts
AI’s are derived from the UE’s Access Preamble Signature
Identifies the UE which is the target of the AICH response
1024 chips
AS #0
AS #1
AS #i
AS #14
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Random Access Message
Random Access Message
3GPP TS 25.211¶ 5.2.2
Random Access Message (10, 20, 40, or 80 bits per slot)
RACH Data Slot (0.666 mSec)
Pilot (8 bits)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
I
Q
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Random Access Offset Timing
Random Access Procedure
Available RACH time slots determined by upper layers, sent over BCH
UE selects slot based on pseudo-random algorithm
5120 chips
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Acquisition and Synchronization
Physical Layer Procedures
Initiate Cell Synchronization
(PSC + SSC + BCH)
UE Monitors Primary SCH code, detects peak in matched filter output
Slot Synchronization Determined ------>
UE Monitors Secondary SCH code, detects SCG and frame start time offset
Frame Synchronization and Code Group Determined ------>
UE Determines Scrambling Code by correlating all possible codes in group
Scrambling Code Determined ------>
BCH data, Super-frame synchronization determined ------>
Cell Synchronization Complete
UE adjusts transmit timing to match timing of BS + 1.5 Chips
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Random Access
Cell Synchronization Complete
Calculates Random Access probe power
Initiate Random Access Attempt;
Respond to Authentication challenge
UE enters Idle mode
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Establishing a Dedicated Channel
UE in Idle Mode
3GPP TS 25.214 ¶ 4.3.2
UE Establishes chip and frame sync to UTRAN
UE begins transmission of Reverse Link Channel,
Responds to TPC bits from BS
UTRAN establishes Reverse Link chip and frame sync,
Responds to TPC bits from UE
UE and BS notify upper layers
that synchronization is complete
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Packet Channel Access
DL-DPCCH Slot (SF=256)
DPCCH Slot (SF=256)
Power Control
CSICH
AP
AP
AP-AICH
CD/CA-ICH
CDP
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Packet Channel Access
Prior to Packet Access, the UE receives from the UTRAN:
UL Access Preamble (AP) scrambling code.
UL Access Preamble signature set.
The Access preamble slot sub-channels group.
AP- AICH preamble Channelization code.
UL Collision Detection(CD) preamble scrambling code.
CD Preamble signature set.
CD-AICH preamble Channelization code.
CPCH UL scrambling code.
CSICH/CA message indicating channel availability
3GPP TS 25.211 ¶ 7.4
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
CPCH Status Indication Channel
Transmits Indicators to convey PCPH Channel Availability
1024 chips
8 bits/slot
SF = 256
AS #0
AS #1
AS #i
AS #14
b4
b5
b3
b7
b6
Higher layers provide mapping of status indicators to availability of CPCH resources
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Access Preamble Indication Channel
Transmits Indicators in response to UE CPCH Access Attempt
API’s are derived from the UE’s CPCH Access Preamble Signature
Identifies the UE which is the target of the AP-AICH response
1024 chips
AS #0
AS #1
AS #i
AS #14
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
CD/CA Indication Channel
Transmits Acquisition Indicators in response to UE CD preambles
CDI’s are derived from the UE’s CD Preamble Signature
Optionally may transmit CPCH Channel Assignment Indicators
1024 chips
AS #0
AS #1
AS #i
AS #14
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
WCDMA Soft Handover
CPICH and System Frame timing between cells is arbitrary
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
The WCDMA Soft Handover Problem...
WCDMA Base Stations have Asynchronous timing references
IS-95/cdma2000 BS’s are synchronized to GPS!
Data 2
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
WCDMA Handover Scenarios
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
WCDMA Soft Handover
To facilitate asynchronous handover, timing adjustments are made by the UE, the RNC, and the Core Network
Time
Alignment
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
WCDMA Soft Handover
Soft Handover Initiation
(3)
(1)
(4)
DOCUMENTTYPE
TypeUnitOrDepartmentHere
TypeYourNameHere
TypeDateHere
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
WCDMA Soft Handover
Soft Handover Execution
(7)
UE in soft handover with BS1 and BS2 DPCCH/DPDCH’s
(5)
(8)
(Handover complete)
CPICH 1
CPICH 1
CPICH 1
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Inter-Frequency Handover
Inter-frequency Handover
To allow inter-frequency measurements, data is compressed in time so that some of the 10 mSec frame is available for measurements.
8 to 14 slots per frame may be used
Data compression can be accomplished by:
Decreasing the Spreading Factor by 2:1
Increases Data Rate so bits get through twice as fast!
Puncturing bits
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Compressed Mode Operation
1 to 7 slots per frame diverted for hard handover processes
3GPP TS 25.212 ¶ 4.4.3
Normal Operation
Transmission Gap
Transmission Gap
The complete TFCI word must be transmitted every frame, even in Compressed Mode.
Compressed Mode Slot formats (A,B) contain higher proportion of TFCI bits per slot compared with normal slots.
5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface
Handover to/from GSM
Handover to/from GSM
Facilitated by commonality of multi-frame structures
1
2
3
4
5
6
7
8
9
10
11
12
T
T
T
T
T
T
T
T
T
T
T
S
T
T
T
T
T
T
T
T
T
T
T
T
T
I
GSM 26-frame TCH multiframe (120 ms)
T = Traffic Frame
S = SACCH Frame
I = Idle Frame