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1C00-20001204-014_LGE_CDSA
Title : CDSA : A Fast and Robust PN Code Acquisition Scheme for Cellular DS/CDMA Application
Abstract : This contribution discusses the key concepts, organization and operations of Correlation-Aided Distributed Sample Acquisition (CDSA) Based DS/CDMA Cellular System
Source : B.K Yi Y.J Song B.H Kim B.G Lee LGE Inc. LGE Inc. GCT SNU [email protected] [email protected] Date : December 04, 2000
Recommendation : Discussion for 1xEV-DV
Notice ©2000 LGE Incorporated. All rights reserved.The information contained in this contribution is provided for the sole purpose of promoting discussion within the 3GPP2 and its Organization Partners and is not bindingon the contributor. The contributor reserves the right to add to, amend, or withdraw the statements contained herein.LGE Incorporated grants a free, irrevocable license to 3GPP2 and its Organization Partners to incorporate text or other copyrightable material contained in the contribution and any modifications thereof in the creation of 3GPP2 publications; to copyright and sell in Organizational Partner’s name any Organizational Partner’s standards publicationeven though it may include portions of the contribution; and at the Organization Partner’s sole discretion to permit others to reproduce in whole or in part such contributionsor the resulting Organizational Partner’s standards publication.The contributor may hold one or more patents or copyrights that cover information contained in this contribution.A license will be made available to applicants under reasonable terms and conditions that are demonstrably free of any unfair discrimination.Nothing contained herein shall be construed as conferring by implication, estoppel, or otherwise any license or right under any patent, whether or not the use of information hereinnecessarily employs an invention of any existing or later issued patent, or copyright. The contributor reserves the right to use all material submitted in this contributionfor his own purposes, including republication and distribution to others.
2C00-20001204-014_LGE_CDSA
Outline
I. Introduction
Serial Search (SSA)
Parallel Search (PSA)
Rapid Acquisition by Sequential Estimation (RASE)
Distributed Sample Acquisition (DSA)
II. Correlation-Aided Distributed Sample Acquisition (CDSA) Based DS/CDMA Cellular System
III. Application of CDSA to Inter-cell Asynchronous W-CDMA Cell Search
VI. Concluding Remarks
3C00-20001204-014_LGE_CDSA
I. Introduction
Issues on PN Code Acquisition Acquisition Time Speed-up Low Complexity (Hardware and Computation) Robustness
Low-SNR (Cell-boundary, Shadowing) Fading Frequency Offset
PN Code Acquisition Techniques
4C00-20001204-014_LGE_CDSA
Correlation - based Search (SSA, PSA)
Threshold Detector
| | 2 NI
( )
Search Control Clock
dL-1dL-2d0 d1d1 d2 d3 d4 d0 d2 d3 d4 dL-2 dL-1
Transmitter SRG Receiver SRG
sk sk
bk
bk+skbk+sk+sk
Scrambling Descrambling
(continued)
(User Channel)
(Pilot Channel)
5C00-20001204-014_LGE_CDSA
Rapid Acquisition by Sequential Estimation: State Loading
(AWGN, Moderate SNR, Coherent Acquisition)
Transmitter SRG Receiver SRG
Scrambling Descrambling
dL-1dL-2d0 d1 d2 d3 d4 dL-1dL-2d0 d1 d2 d3 d4
sk sk
bk+sk
bk+sk+skbk
(continued)
(User Channel)
(Pilot Channel)
6C00-20001204-014_LGE_CDSA
(continued)
Goal of the Work Design of Noncoherent (or Differentially-coherent), Rapid, and Ro
bust Acquisition / Cell-search Schemes with Minimal Complexity by employing Generalized State Loading Techniques
7C00-20001204-014_LGE_CDSA
Distributed Sample Acquisition (DSA)
User Data
State Correction
ComparisonState
SamplingState
Sampling
dL-1d0 d1 d2 d3 dL-1d0 d1 d2 d3
sm sm
zn zn
Main SRG (long)
Main SRG (long)
Scrambling DescramblingUser Data
MainSequence
Data Signal(User Channel)
MainSequence
dS-1d0 d1
Igniter SRG (short)
State Signal(Pilot Channel)
Transmitter Receiver
cm
IgniterSequence
(continued)
8C00-20001204-014_LGE_CDSA
II. Correlation-Aided DSA Based DS/CDMA Cellular System
BS (Tx) and MS (Rx) have two kinds of SRG's Igniter SRG with short period NI (=2S) Main SRG with long period NM (=2L): targeted scrambling sequence
BS samples a main SRG state sample in every NI chip interval, spread it with a short igniter code of length NI, and then transmit it as a state signal (or the common pilot signal) of the BS.
Several samples may be transmitted concurrently to speed up the synchronization in a moderate SIR environment
After igniter code acquisition applying a conventional search method, MS’s detect the main SRG state samples sequentially.
State sample comparison-correction based main SRG Synchronization L corrections and V verifications by a set of pertinent sampling-comparison-correc
tion circuits synchronize the MS main SRG to the BS main SRG. Asymptotically, 2L / (2S +L+V) times faster acquisition than Serial-search with
minimal complexity increase (IS95/cdma2000: L=15) (L=15, S=7): 256 times; (L=15, S=8): 128 times
State Symbol Correlation Process for Robust Acquisition in Worst-case Channel Environment
9C00-20001204-014_LGE_CDSA
CDSA-based DS/CDMA System (BS)
Data signal(1)
Sampling Timing
Data signal(2)
DSA - Spreader Sample - Spreader
Data signal(J)
Q-main SRG
I-main SRG Time-advanced Sampling
NITc
{sm}
{sm}
{sm}
ai [1]
{wm }[1]
Igniter SRG-2
Igniter SRG-1
{cm}
ai [2]
{wm }[2]
ai[J]
{wm }[J]
Spreading
Spreading State
signal (CPICH)
PSK SymbolMapping
{zi} xi fi
v0
10C00-20001204-014_LGE_CDSA
Common Pilot Channel Modulation Example for CDSA As I-channel PN state and Q-channel PN state have a one-to-one
correspondence in cdma2000, the BS has only to broadcast I-main SRG state samples to the MS’s.
Each cell employ one of 16 Complex Igniter Codes (Group Codes)
16 igniter codes (group codes) of length 256
512 modulated common pilot codes of length 32768
(DBPSK encoding of state samples: fj)
208 usec
co c1 c255
fo Ci f1 Ci f2 Ci f3 Ci f4 Ci f127 Ci fj Ci
26.67 ms 1 Sync Frame
Ci , i=0,1,…15
11C00-20001204-014_LGE_CDSA
Global Timing Relations and Cell Group Plan
Neighboring cells shall employ different igniter codes Trade-off relation between the number of igniter sequences in a cellul
ar system and the amount of co-channel (co-igniter) cell interference: complexity and performance trade-off
Multiple main sequences and igniter sequences can be obtained by phase shifts in the inter-cell synchronous systems such as IS95 and cdma2000.
Ex: 512 main and 7 [or 16] igniter sequences can be derived from an extended m-sequence of length 32768 and 2 [or 4] Gold sequences of length 256 through the cyclic shifts by 64*n chips
12C00-20001204-014_LGE_CDSA
26
NI = 2 8
26
NM = 2 15
Main Sequences
Igniter Sequences
0: {sm[0]}
1: {sm[1]}
2: {sm[2]}
3: {sm[3]}
510: {sm[510]}
511: {sm[511]}
0: {cm[0]}
1: {cm+64[0]}
2: {cm+128[0]}
3: {cm+192[0]}
4: {cm[1]}
5: {cm+64[1]}
6: {cm+128[1]}
Timing relations among igniter/main sequences (Ex: 7 groups and 512 cells)
13C00-20001204-014_LGE_CDSA
Cell group (igniter code) plan (Ex: 7 groups and 48 cells)
6,6
1,1
0,0
2,2
0,42
5,19
3,3
5,12
6,13
0,35
0,7
1,8
1,36
6,20
6,12
0,14
1,15
5,5
4,18
3,17
2,16
4,4
5,26
6,27
0,21
1,22
2,23
3,24
5,33
6,34
4,11
3,10
1,43
4,32
0,28
1,29
4,25
2,9
2,30
3,31
2,37
3,38
4,39
5,40
6,41
2,44
3,45
4,46
5,47
14C00-20001204-014_LGE_CDSA
State signal
Despreading
Data signal(u)
Correction Timing
Sampling Timing
Sample - Despreader
Sampling
Correction
Despreading
DSA - Despreader
NITc
iNITc
(i-1)NITc
dtNITc
1
( )*
PSK Symbol Detection
gi
{sm} {wm }[u]
+ Noise
+ NoiseiNITc
(i-1)NITc
dtNITc
1
Q-main SRG
I-main SRG Igniter SRG-2
Igniter SRG-1
Comparison
{cm}
ai [u]
yi
Store State Symbols for B Symbol Periods
State Symbol Correlation Based Frame Boundary Search
{zi}
h0
c0{zi}
CDSA-based DS/CDMA System (MS)
15C00-20001204-014_LGE_CDSA
System Timing Diagram
Igniter seq.
Igniter seq.
Tx
Main seq.
DBPSK symbol
State signal
Rx
Detected sample
Main seq.
Comparison
Sampling
resultCorrection
sampling
NI
NI -advanced
Dc (=1)
16C00-20001204-014_LGE_CDSA
• IS-95 I-Phase PN (x) = 1 + x5 + x7+ x8 + x9 + x13 + x15
T= A(x)t , h= [1 0 0 0]t , NI= 128
(a) DSA-Spreader
(b) DSA-Despreader
Sampling pulse
ComparisonCorrection pulse{zi}
{zi}
{sm}
c0
{bm+ sm} + sm+ sm}{bm
{zi}
Sampling pulsev0
{sm}
{bm} {bm+ sm}
Design Example
17C00-20001204-014_LGE_CDSA
III. Mean Acquisition Time Performance
512 Cells / System 100 Hz Classical Rayleigh Fading Igniter Seq. Period (Dwell Time), NI = 256
Main Seq. Period NM = 32768
False Acquisition Penalty Time = 1280NI (10 Frames) False Alarm Prob. = 0.05 (Acq. Detection), 0.001 (Verification) Verification Time = 10NI
Igniter Seq. Reuse Factor = 16 (4 Seq.’s, 4 Phase Offsets) Symbol Sequence Length for State Symbol Correlation Process
B = 128 Symbols Conventional PSA : 4 Correlators Operate in Parallel : Comparable co
mplexity
18C00-20001204-014_LGE_CDSA
(sec)
Ove
rall
Mea
n A
cqui
siti
on T
ime
SNR( c)
-25 -20 -15 -10 -510
-1
100
101
102
DSA
CDSA
PSA
(continued)
19C00-20001204-014_LGE_CDSA
IV.Concluding Remarks
CDSA scheme for rapid and robust acquisition of long-period PN sequences: Igniter Sequence + Comparison-correction Process : DSA
+ State Symbol Correlation Process : CDSA Revisit the goal of the work !
Acquisition / Cell Search Time Reduction Minimal Complexity Robustness: Shadowing, fading, frequency offset, etc.