WCDMA P6 AIR INTERFACE Chapter 4: WCDMA Procedures
Objectives of Chapter 4
After this chapter the participants will be able to:
© Ericsson AB 2007
Explain base station downlink timing
Explain the synchronization procedure
Explain the random access procedure
Explain the establishment of dedicated channels
Explain soft handover timing
04_03813 LZU 108 6909 Rev . A
Figure 4 2-
WCDMA Procedures
2007-12-03
Downlink Transmission Timing 10 ms Frame
SCH (PSC+SSC) P-CCPCH S-CCPCH PICH AICH DPCH HSDPA
Primary SCH Secondary SCH Common Pilot Channel
CPICH (Common Pilot Channel) P-CCPCH, (SFN modulo 2 = 0)
Primary CCPCH (Broadcast Data) Secondary CCPCH (Paging, Signaling)
τS-CCPCH,k τPICH
Paging Indicator Channel Dedicated Physical Control/Data Channel
P-CCPCH, (SFN modulo 2 = 1)
k:th S-CCPCH PICH for n:th S-CCPCH
τDPCH,n
n:th DPCCH/DCDPH
MBMS Information Channel
MICH
Secondary CCPCH (MBMS Traffic channel)
τMICH
S-CCPCH
τ
High Speed Shared Control Channel High Speed Physical Downlink Shared Channel
S-CCPCH,k
E-AGCH 10ms
Enhanced Relative Grant Channel (non-serving cell)
E-RGCH 10ms
AICH access slots © Ericsson AB 2007
τ
DPCH,n
τHS-PDSCH,n = τE-AGCH,n = τE-RGCH = 2 slots
Enhanced Absolute Grant Channel (serving cell)
Enhanced HARQ Indication Channel
3GPP TS 25.211 ¶ 7.0 3GPP TS 25.211 ¶ 7.0
τ
PICH
= N x 256 chips
= N x 256 chips
= 7680 chips (3 slots)
τ MICH = 7680 Chips (3 slots)
τ
= 2 slots
HS-PDSCH,n
E-HICH 8ms
τE-HICH,n #0
#1
04_03813 LZU 108 6909 Rev . A
#2
#3
#4 Figure 4 3-
#5
τE-HICH,n = see 3GPP 25.211 #6
#7
#8
#9
#10
#11
#12
WCDMA Procedures
#13
#14 2007-12-03
Downlink Scrambling Codes 3GPP TS 25.213 ¶ 5.2.2 3GPP TS 25.213 ¶ 5.2.2
Used to distinguish different cell transmissions on Downlink Each Cell is assigned one and only one Primary Scrambling Code (Secondary Scrambling Codes may be used over part of a cell, or for other data channels) 8192 Downlink Scrambling Codes Each code is 38,400 chips of a 218 - 1 (262,143 chip) Gold Sequence
Code Group #1
© Ericsson AB 2007
Code Group #64
Primary SC0
Primary SC7
Primary SC504
Primary SC511
Secondary Scrambling Codes
Secondary Scrambling Codes
Secondary Scrambling Codes
Secondary Scrambling Codes
(15)
(15)
(15)
(15)
04_03813 LZU 108 6909 Rev . A
Figure 4 4-
WCDMA Procedures
2007-12-03
Synchronization Codes, PSC and SSC 3GPP TS 25.213 ¶ 5.2.3 3GPP TS 25.213 ¶ 5.2.3
256 Chips
PSC SSCi
2304 Chips
P-CCPCH (PSC + SSC + BCH)
Broadcast Data (18 bits)
Broadcast by RBS
© Ericsson AB 2007
First 256 chips of every P-CCPCH slot Allows UE to achieve fast synchronization in an asynchronous system Primary Synchronization Code (PSC) Fixed 256-chip sequence with base period of 16 chips Provides fast positive indication of a WCDMA system Allows fast asynchronous slot synchronization Secondary Synchronization Codes (SSC) A set of 16 codes, each 256 chips long Codes are arranged into one of 64 unique permutations Specific arrangement of SSC codes provide UE with frame timing, Scrambling Code Group 04_03813 LZU 108 6909 Rev . A
Figure 4 5-
WCDMA Procedures
2007-12-03
Primary Synchronization Code, PSC 3GPP TS 25.213 ¶ 5.2.3 3GPP TS 25.213 ¶ 5.2.3
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 > Note: PSC is transmitted “Clear” (Without scrambling)
SCH
P-CCPCH
256 Chips
2304 Chips
PSC
Broadcast Data (18 bits)
SSCi
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
1 Frame = 15 slots = 10 mSec
© Ericsson AB 2007
04_03813 LZU 108 6909 Rev . A
Figure 4 6-
WCDMA Procedures
2007-12-03
Slot Synchronization 3GPP TS 25.214 Annex C 3GPP TS 25.214 Annex C
Slot Synchronization using Primary Synchronization Code 10 mSec Frame (15 slots x 666.666 uSec) PSC [1]
BCH Data
PSC [2]
BCH Data
PSC [3]
BCH Data
PSC [4]
BCH Data
PSC [15]
BCH Data
Matched Filter (Matched to PSC)
P-CCPCH (PSC) Matched Filter Output
time © Ericsson AB 2007
04_03813 LZU 108 6909 Rev . A
Figure 4 7-
WCDMA Procedures
2007-12-03
Secondary Synchronization Code Groups
3GPP TS 25.213 ¶ 5.2.3 3GPP TS 25.213 ¶ 5.2.3
16 Fixed 256-bit Codes; Codes arranged into one of 64 patterns SSC1 SSC2 SSC3 SSC4 SSC5 SSC6 SSC7 SSC8 SSC9 SSC10 SSC11 SSC12 SSC13 SSC14 SSC15 SSC16
Scrambling Code Group
slot number #1
#2
#3
#4
#5
#6
#7
#8
#9
#10
#11
#12
#13
#14
#15
Group 1
1
1
2
8
9
10
15
8
10
16
2
7
15
7
16
Group 2
1
1
5
16
7
3
14
16
3
10
5
12
14
12
10
Group 3
1
2
1
15
5
5
12
16
6
11
2
16
11
15
12
•
SSC1
•
SSC15
•
•
•
•
•
•
•
Group 62
9
10
13
10
11
15
15
9
16
12
14
13
16
14
11
Group 63
9
11
12
15
12
9
13
13
11
14
10
16
15
14
16
Group 64
9
12
10
15
13
14
9
14
15
11
11
13
12
16
10
0
1
2
3
4
5
6
7
8
9
10
11
12
1 Frame = 15 slots = 10 mSec 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.
© Ericsson AB 2007
04_03813 LZU 108 6909 Rev . A
Figure 4 8-
WCDMA Procedures
2007-12-03
13
14
Frame Synchronization, SCG ID 3GPP TS 25.214 Annex C 3GPP TS 25.214 Annex C
Frame Synchronization using Secondary Synchronization Code 10 mSec Frame (15 slots x 666.666 uSec) SSC [1]
BCH Data
SSC [2]
BCH Data
SSC [3]
BCH Data
SSC [4]
BCH Data
SSC [15]
BCH Data
Matched Filter SSC 1
SSC1 1
SSC 2
SSC 8
SSC 9
SSC 10
SSC 15
SSC 8
SSC 10
SSC 16
SSC 2
SSC 7
SSC 15
SSC 7
SSC 16
Matched to SSC code group pattern 1
SSC Code Group Pattern provides Matched Filter Output
• Frame Synchronization • Positive ID of Scrambling Code Group Remember, no cyclic shift of any SSC is equal to any other SSC
time © Ericsson AB 2007
04_03813 LZU 108 6909 Rev . A
Figure 4 9-
WCDMA Procedures
2007-12-03
Acquisition and Synchronization ď&#x201A;§ Physical Layer Procedures
P-CCPCH (PSC + SSC + BCH)
1) UE Acquisition and Synchronization Initiate Cell Synchronization
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 ------> UE Monitors and decodes BCH data BCH data, Super-frame synchronization determined ------> UE adjusts transmit timing to match timing of BS + 1.5 Chips
Cell Synchronization Complete
Š Ericsson AB 2007
04_03813 LZU 108 6909 Rev . A
Figure 4 10 -
WCDMA Procedures
2007-12-03
Random Access Random Access Attempt and AICH Indication
3GPP TS 25.211 ¶ 7.3 3GPP TS 25.211 ¶ 7.3
RACH AICH
4096 chips (1.066 msec)
UE
Preamble
BS
© Ericsson AB 2007
Preamble
Preamble
No Ind.
04_03813 LZU 108 6909 Rev . A
No Ind.
Figure 4 11 -
RACH message part (UE Identification)
Acq. Ind.
WCDMA Procedures
2007-12-03
Random Access Procedure 3GPP TS 25.214 ¶ 6.1 3GPP TS 25.214 ¶ 6.1
Prior to initiating a Random Access attempt, the UE receives: The preamble scrambling code for this cell The available random access signatures and set of available RACH sub-channels The available spreading factors for the message part The message length (10 ms or 20 ms) Initial preamble power parameter The power-ramping factor Power Ramp Step [integer > 0] The parameter Preamble Retrans Max [integer > 0] The AICH transmission timing parameter [0 or 1] The power offset DPp-m between preamble and the message part. Transport Format parameters
© Ericsson AB 2007
04_03813 LZU 108 6909 Rev . A
Figure 4 12 -
WCDMA Procedures
2007-12-03
Random Access Preamble Signatures 3GPP TS 25.213 ¶ 4.3.3.3 3GPP TS 25.213 ¶ 4.3.3.3
Random Access Preamble Signature Symbols
© Ericsson AB 2007
Signature
P0
P1
P2
P3
P4
P5
P6
P7
P8
P9
P10
P11
P12
P13
P14
P15
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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 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 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 -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 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 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 -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 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
•
Preamble codes are 16-long Orthogonal Codes.
•
Preamble = [ P0, P1, … P15 ] repeated 256 times (4096 chips total).
•
Preamble codes help the BS distinguish between UE making simultaneous Random Access Attempts.
04_03813 LZU 108 6909 Rev . A
Figure 4 13 -
WCDMA Procedures
2007-12-03
Random Access Scrambling Codes 3GPP TS 25.213 ¶ 4.3.3 3GPP TS 25.213 ¶ 4.3.3
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 n1 ”
© Ericsson AB 2007
04_03813 LZU 108 6909 Rev . A
Figure 4 14 -
“All UE accessing this cell shall use Random Access Preamble Spreading Code n2 ”
WCDMA Procedures
2007-12-03
Uplink Scrambling Code Uplink Scrambling Code Type depends on the Application
Random Access, Packet Access
Dedicated Traffic Connection
• Cell-specific Scrambling Code(s)
• UE-specific Scrambling Code(s)
• Code(s) are assigned by UTRAN
• Code(s) are assigned by UTRAN
• Code(s) are conveyed to UE via the BCH or FACH
• Code(s) are conveyed to UE via the FACH • 224 possible codes
• 8,192 PRACH codes • 32,768 PCPCH codes • Code allocation corresponds to the cell’s DL scrambling code group
© Ericsson AB 2007
04_03813 LZU 108 6909 Rev . A
Figure 4 15 -
Note: Note: Short (256) Scrambling Codes may be used in place of the Short (256) Scrambling Codes may be used in place of the long scrambling codes. This is to support operation of long scrambling codes. This is to support operation of advanced BS receivers (e.g., multi-user detection receivers). advanced BS receivers (e.g., multi-user detection receivers). See TS25.213 Section 4.3.2 See TS25.213 Section 4.3.2
WCDMA Procedures
2007-12-03
Random Access Offset Timing
3GPP TS 25.211 ¶ 5.2.2.1.1 3GPP TS 25.211 ¶ 5.2.2.1.1
Random Access Procedure Set of available RACH sub-channels determined by upper layers, sent over BCH. UE derive available access slots in the next full access slot set and selects slot based on pseudo-random algorithm radio frame: 10 ms SFN mod 2 = 0 AICH access slot RX at UE
PRACH access slot TX at UE
RACH sub-channel number
© Ericsson AB 2007
{
#0
#0
#1
#1
#2
#2
#3
#3
#4
Access slot set 1 #0 #1
#4
#5
radio frame: 10 ms SFN mod 2 = 1
#5
#6
#6
#7
#7
#8
#8
#9
#9
#10
#10
#11
#11
#12
#12
#13
#14
P P
#3 • • # 10
+ every 12th access slot + every 12th access slot
P P
P
+ every 12th access slot + every 12th access slot
P
+ every 12th access slot
P P
# 11
04_03813 LZU 108 6909 Rev . A
#14
Access slot set 2
P
#2
#13
Figure 4 16 -
WCDMA Procedures
+ every 12th access slot
2007-12-03
Establishing a Dedicated Channel, Mobile terminated call
UE in Idle Mode
1. PI on the PICH 2. PCH message on the S-CCPCH 3. UE ramps up the power by sending preambles 4. RBS responds on the AICH 5. UE sends the RACH message 6. FACH message on S-CCPCH 7. DL-DPCH ramp up 8. UE sends UL-DPCH DPCH established Š Ericsson AB 2007
04_03813 LZU 108 6909 Rev . A
Figure 4 17 -
WCDMA Procedures
2007-12-03
The WCDMA Soft Handover Problem...
WCDMA Base Stations have Asynchronous timing references
IS-95/cdma2000 RBSs are synchronized to GPS! 0.666 msec DPCCH/DPDCH slot Data 1
1
2
3
TPC
4
5
TFCI
6
7
Data 2
8
9
10
11
Pilot
12
13
14
15
10 msec DPCCH/DPDCH frame
RBS 2 RBS 1
10 msec frame
CPICH 2
CPICH 2
CPICH 2
CPICH 2
DPCCH/DPDCH
DPCCH/DPDCH
DPCCH/DPDCH
DPCCH/DPDCH
CPICH 1
CPICH 1
CPICH 1
CPICH 1
DPCCH/DPDCH
DPCCH/DPDCH
DPCCH/DPDCH
DPCCH/DPDCH
Toffset
© Ericsson AB 2007
04_03813 LZU 108 6909 Rev . A
Figure 4 18 -
WCDMA Procedures
2007-12-03
WCDMA Soft Handover
Soft Handover Initiation (1)
(2)
(3)
(4)
RNC informs UE of neighboring cell information
UE measures CPICH power and time delay from adjacent cells
UE Reports measurements to RNC
RNC decides the handover strategy
RBS 2 RBS 1
CPICH 2
CPICH 2
CPICH 2
CPICH 2
10 msec frame CPICH 1
CPICH 1
CPICH 1
CPICH 1
DPCCH/DPDCH
DPCCH/DPDCH
DPCCH/DPDCH
DPCCH/DPDCH
UE Reports Toffset to RNC
Toffset
RNC
© Ericsson AB 2007
04_03813 LZU 108 6909 Rev . A
Figure 4 19 -
WCDMA Procedures
2007-12-03
WCDMA Soft Handover Soft Handover Execution (8)
(5)
(6)
(7)
UTRAN Commands RBS2 to adjust DPCH timing by Toffset
UE Rake Receiver Synchronizes to RBS2 DPCCH/DPDCH
UE in soft handover with RBS1 and RBS2 DPCCH/DPDCH’s
When RBS2 sufficiently strong compared to RBS1, drop RBS1. (Handover complete)
RBS 2 RBS 1
CPICH 2 10 msec frame
CPICH 2
DPCCH/DPDCH
DPCCH/DPDCH
CPICH 1
CPICH 1
CPICH 1
CPICH 1
DPCCH/DPDCH
DPCCH/DPDCH
DPCCH/DPDCH
DPCCH/DPDCH
UE Reports Toffset to RNC
CPICH 2
DPCCH/DPDCH
04_03813 LZU 108 6909 Rev . A
Figure 4 20 -
DPCCH/DPDCH
Toffset
Toffset
UTRAN Commands RBS2 to adjust DPCH timing by Toffset
RNC
© Ericsson AB 2007
CPICH 2
WCDMA Procedures
2007-12-03
Š Ericsson AB 2007
04_03813 LZU 108 6909 Rev . A
Figure 4 21 -
WCDMA Procedures
2007-12-03