CDMA Fundamentals
Agenda • • • • • • •
2
CDMA introduction CDMA makes use of Diversity Power control CDMA Forward Link CDMA Reverse Link CDMA call processing CDMA Measurement
Cellular Access Methods Power
Time Time Power
FDMA
Frequency Time
Power
CDMA
TDMA 3
Frequency
Frequency
The CDMA Concept Code Domain Power (cdma2000/IS-95) Pilot Synch Paging
Frequency Domain User #3 User #2 User #1 freq
1.2288 MHz
Code Domain Walsh Code 0 1 2 Pilot Paging
4
3
4
5
6
7
8 User 1
9 User 2
32 Synch
40 User 3
63
CDMA is Also Full Duplex
Amplitude
US Cellular Channel 384 Forward Link
Reverse Link
45 MHz
AMPS
Frequency 881.52 MHz
836.52 MHz
Amplitude Forward Link
Reverse Link
CDMA
45 MHz
Frequency 836.52 MHz
5
881.52 MHz
What is CDMA ?
Code Division Multiple Access • • • • • •
6
Spread spectrum technique Multiple users share the same frequency in one cell Same frequency in all the cells Operates under presence of interference Takes advantage of multipath Capacity is soft
Cellular Frequency Reuse Patterns
1 3
2 6
4
1 2
6
5
7
1 1
1 1
1 1
1
7
1
FDMA Reuse
CDMA Reuse
The CDMA Concept 10 Khz BW
0
1.23 Mhz BW
fc CDMA Transmitter
Baseband Data
1.23 Mhz BW
fc
0
CDMA Receiver
Encoding & Interleaving
Walsh Code Spreading
Walsh Code Correlator
Decode & DeInterleaving
19.2 kbps
1228.8 kbps
1228.8 kbps
19.2 kbps
9.6 kbps
Baseband Data
-113 dBm/1.23 Mhz
Spurious Signals
1.23 Mhz BW
fc
fc
fc
fc
Background Noise
External Interference
Other Cell Interference
Other User Noise
Interference Sources 8
10 Khz BW
1.23 Mhz BW
9.6 kbps
Direct Sequence Spread Spectrum • Baseband data multiplied by a Pseudo Random Noise (PN) Code, which is a sequence of chips valued -1 & +1 or 0 & 1 • PN code is a noise-like code with certain properties (ex: orthogonal)
z
9
Multiple user data can be spread by using combinations of this PN code
Direct Sequence Spread Spectrum • Direct sequence spread spectrum signal is generated by multiplying narrowband user data with a well-defined wideband pseudo-random sequence. • Recovering the narrowband user data is achieved by multiplying the received signal by an identical, accurately timed pseudorandom sequence.
Power Spectral Density
Narrowband user data
Direct sequence spread signal
Freq
Direct Sequence Spread Spectrum
10
Direct Sequence Spread Spectrum I-Q Modulator Source Information Bits
Bits to I-Q
Code Generator Bit Stream Block diagram of a Direct Sequence Spread Spectrum Transmitter
11
Transmit DSSS Signal
Carrier
Direct Sequence Spread Spectrum Received DSSS signal
Demodulator
Carrier Code Synchronization
Code Generator
Block diagram of a Direct Sequence Spread Spectrum Receiver
12
Data
What is Correlation ?
• Is a Measure of How Well a Given Signal Matches a Desired Code • The Desired Code is Compared to the Given Signal at Various Test times
Received Signal
Correlation = 1
Correlation = 0 Time
Correlation = 0
Correlation = 0
13
Auto-Correlation • Is a Comparison of a Signal Against Itself • Good Pseudo-Random Patterns Have:
Pseudo-Random Sequence 1 0 1
¾ Strong Correlation at Zero Time0 Offset
10
5
15
20
25
30
Auto-Correlation Versus Time Offset
¾ Weak Correlation at Other Time Offsets
0 0
5
10
15
Chip Offset
14
20
25
30
CDMA Paradigm Shift ¾ Multiple Users on One Frequency 9 Analog/TDMA Try to Prevent Multiple Users Interface
¾ Channel is Defined by Code 9 Analog Systems Defined Channels by Frequency
¾ Traditional FDMA/TDMA are capacitylimited 9 Given N timeslots per frame and K frequency channels, maximum number of users is KN; 9 To increase the number of users in the system, frequency reuse is used
¾ Capacity Limit is Soft 9 Allows Degrading Voice Quality to Temporarily Increase Capacity 9 Reduce Surrounding Cell Capacity to Increase a Cell’s Capacity 15
g g o l o l a a n AAn C
A M D
CDMA Capacity Gains
(Chan BW) (1) (1) X (Fr) Capacity = _____________ X _____ X ____ (Data Rate) (S/N) (Vaf) (1,230,000) X _____ (1) CDMA = ____________ X (1) _____ X (0.67) (9,600) (5.01) (.40) CDMA = 42 Calls ( Using 1.5 MHz BW )
AMPS = 1.5 MHz / 30 kHz = 50 Channels Capacity = 50 Channels / 7 ( 1/7 Frequency Reuse ) AMPS = 7 Calls ( Using 1.5 MHz BW )
16
Processing Gain
CDMA makes use of Diversity • Spatial Diversity ¾ Making Use of Differences in Position
• Frequency Diversity ¾ Making Use of Differences in Frequency
• Time Diversity ¾ Making Use of Differences in Time
17
CDMA Spatial Diversity • Diversity Reception: ¾ Multiple Antennas at Base Station 9 Each Antenna is Affected by Multipath Differently Due to Their Different Location 9 Allows Selection of the Signal Least Affected by Multipath Fading
• If Diversity Antennas are Good, Why Not Use Base Stations as a Diversity Network? ¾ Soft Handoff
18
Spatial Diversity During Soft Handoff
MTSO
Land Link
Vocoder / Selector
Base Station 1
19
Base Station 2
CDMA Frequency Diversity • Combats Fading, Caused by Multipath • Fading Acts like Notch Filter to a Wide Spectrum Signal • May Notch only Part of Signal
Amplitude
1.23 MHz BW
Frequency
20
CDMA Time Diversity • Rake Receiver to Find and Demodulate Multipath Signals • Data is Interleaved ¾ Spreads Adjacent Data in time to Improve Error Correction Efficiency
• Convolutional Encoding ¾ Adds Error Correction and Detection
• Viterbi Decoding ¾ Most Likely Path Decoder for Convolutionaly Encoded Data
21
Why Interleaving Works
Original Data Frame 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Errors/Time
TX 1
3
4
5
6
7
8
9
10 11 12 13 14 15 16
Errors/Time
RX 1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16
Errors/Time
Interleaved Data Frame
TX
1
2
3
4
1
5
9
13
5
6
7
8
2
6
10
14
9
10
11
12
3
7
11
15
13
14
15
16
4
8
12
16
1
5
9 13
2
6 10 14 3
7 11 15 4
8 12 16
Errors/Time
RX 1
22
2
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16
The Rake Receiver
Time
Amplitude
Frequency
23
Rake Receiver Design Antenna
T0
T1
T2
T3
T4
Delay Taps
W0
W1
W2
W3
W4
Tap Weights
+ Output 24
Synchronization • All Direct Sequence, Spread Spectrum Systems Should be Accurately Synchronized for Efficient searching • Finding the Desired Code Becomes Difficult without Synchronization
25
Power Control
Near-end Far-end Problem - 60dBm
B
- 30dBm
A
At the BS receiver, SNR for A reception = 30 dB, certified SNR for B reception = -30 dB, not certified 26
Power Control
z
Acceptable SNR is at least 7 dB
z
For B, the signal needs 37 dB gain to meet the condition
z
What if we increase the processing gain from 21 dB to 37 dB? Pgain = 10 log ( W / R ) R is fixed at 9600 bps, W can be increased In this case, W = 48 MHz
not practical
Is there another way to improve S/N? 27
Power Control
z
In this case, B is the Signal and A is the Noise
z
Both A and B are transmitting at constant power
z
Since A is near, it can be asked to transmit at low power
z
Since B is far, it can increase the power
This is Power Control ! z
z
28
Base Station will change power levels based on the Path loss. Base Station will also command Mobile to increase or decrease power levels.
Reverse Link Power Control • Maximum System Capacity is Achieved if: 9 All Mobiles are Power Controlled to the Minimum Power for Acceptable Signal Quality 9 As a Result, all Mobiles are Received at About Equal Power at the Base Station Independent of Their Location
• Two Types of Control • Open Loop Power Control • Closed Loop Power Control
• Open & Closed Loop Power Control are
Always Both Active
29
Open Loop Power Control • Assumes Loss is Similar on Forward and Reverse Paths • Receive Power + Transmit Power = -73(-76dB for
PCS Band ¾ All Powers in dBm
• Example: ¾ For a Received Power of -85 dBm Transmit Power = (-73) - (- 85) Transmit Power = +12 dBm
• Provides an Estimate of Reverse TX Power for Given Propagation Conditions
30
Closed Loop Power Control • Directed by Base Station • Updated Every 1.25 msec • Commands Mobile to Change TX Power in +/- 1 dB Step Size • Fine Tunes Open Loop Power Estimate • Power Control Bits are “Punctured” over the Encoded Voice Data • Puncture Period is Two 19.2 kbps Symbol Periods = 104.2 usec
31
CDMA Variable Rate Speech Coder • DSP Analyzes 20 Millisecond Blocks of Speech for Activity • Selects Encoding Rate Based on Activity: a High Activity
Full Data Rate Encoding (9600 bps)
a Some Activity
Half Data Rate Encoding (4800 bps)
a Low Activity
Quarter Data Rate Encoding (2400 bps)
a No Activity
1/8 Data Rate Encoding (1200 bps)
• How Does This Improve Capacity? ¾ Mobile Transmits in Bursts of 1.25 ms
• System Capacity Increases by 1/Voice Activity Factor
32
Mobile Power Bursting
• Each Frame is Divided into 16 Power Control Groups • Each Power Control Group Contains 1536 Chips (represents 12 encoded voice bits) • Average Power is Lowered 3 dB for Each Lower Data Rate
33
CDMA Frame = 20 ms
Full Rate
Half Rate Quarter Rate
Eighth Rate
The CDMA2000 evolution path is flexible and future-proof
• Voice
• Voice
• 2x increases in voice capacity
• Data up to 14.4 kbps
• Data up to 115 kbps
• Up to 307 kbps* packet data on a single (1.25 MHz) carrier • First 3G system for any technology worldwide
34
From CDG
• Optimized, very high-speed data (Phase 1) • Up to 2.4 Mbps* packet data on a single (1.25 MHz) carrier • Integrated voice and data (Phase 2); up to 4.8 Mbps
*downlink
CDMA Protocol Stacks EIA/TIA/IS-2000 Rev C(1x EV-DV)
EIA/TIA/IS-856(1x EV-DO)
Segment channel between Voice and Data
Optimized for packet data.
EIA/TIA/IS-2000 Rev B Add new functionality and support
EIA/TIA/IS-2000 Rev A Add BCH,CCCH,CACH…new channel
EIA/TIA/IS-2000 Rev 0 First release of IS-2000 standard(add QPCH)
EIA/TIA-95 Rev B Combines TSB-74 & J-STD-008 for a Universal Protocol
J-STD-008 Not Backwards Compatible, PCS only Protocol
TBS- 74 Cellular Protocol that adds 14400 Channel Support
IS -95 Rev A Backwards compatible with IS-95. First Deployed Protocol
IS -95 Rev 0 Original System-never actually deployed 35
ARIB T53 Japan CDMA System Cellular Protocol
The architecture for CDMA2000 Cell Phones
From CDG
HLR/AUC
PSTN MSC Smartphones and PDAs
IS634
BSC
Core Elements
AAA Server
PSDN
IWF Laptops with Cell Phones
Internet IP Router 36
cdma2000 Key Standards • EIA/TIA/IS-2000 rev. 0 Interoperability Standard for cdma2000 Spread Spectrum Systems ¾ Defines channel coding, call processing procedures, protocol and other mobile / base procedures and RF requirements to ensure interoperability of equipment from multiple vendors ¾ Defines how entire system works together in extreme detail ¾ Revision 0 was first release of standard. ¾ Revision A adds enhanced channels for paging, call set-up and call control. ¾ Revision B enhanced from the cdma2000 Release A specifications
37
cdma2000 Standards Overview - IS-2000 Release 0 versus Revision A TIA/EIA-95-B
IS-2000
IS-2000-A
F-Pilot F-Sync
F-Pilot F-Sync
F-PCH
F-PCH
F-Pilot F-Sync F-BCCH F-CCCH
Forward Channels
F-Traffic
Reverse Channels
38
N/A R-ACH R-Traffic
F-QPCH optional
F-QPCH optional
F-FCH F-SCH F-DCCH optional
F-CACH F-CPCCH F-FCH F-SCH F-DCCH optional
R-Pilot R-ACH R-FCH R-SCH R-DCCH optional
R-Pilot R-EACH or R-CCCH R-FCH R-SCH R-DCCH optional
Benefits of cdma2000 • Improved Performance and Capacity: ¾ About 2X Voice Capacity of TIA/EIA-95-B ¾ Handles a Wide Range of Data Rates: 9 Voice and Low Speed Data while Driving 9 Up to 384 kbps Packet or Circuit Data while Moving 9 Up to 2 Mbps Data Rates for Fixed Installations
• Meets All IMT-2000 Requirements • Easy Upgrade for Service Providers Who Currently Operate TIA/EIA-95 Systems
39
Performance Enhancements • • • •
Reverse Link Pilot for Each Mobile True QPSK Modulation Continuous Reverse Link Waveform Improved Convolutional Encoding for 14.4 kbps Voice Channels • Fast Forward & Reverse Link Power Control • Supports Auxiliary Pilots for Beam Forming • Forward Link Transmit Diversity - OTD, STS, Multi-Antenna
40
cdm a 2000
Reuse of TIA/EIA-95-B • cdma2000 is Fully Backwards Compatible with TIA/EIA-95-B • Reused Aspects of TIA/EIA-95-B: 9 TIA/EIA-95-B Air Interface (RC1, RC2) 9 IS-127 EVRC 8 kbps Vocoder and IS-733 13 kbps Vocoder 9 All Existing Service Options 9 IS-637 SMS & IS-683 Over the Air Activation 9 IS-98 and IS-97 Minimum Performance Standards 9 Common Broadcast Channels (Pilot, Sync ,Paging)
• Allows cdma2000 to be Deployed Sooner
41
Terms and Definitions • Chip 9 Is the period of a data bit at the final spreading rate
• SR - Spreading Rate 9 Defines the final spreading rate in terms of 1.2288 Mcps(SR1). So a 3.6864 Mcps system is called a SR3 system.
• RC - Radio Configuration 9 Defines the physical channel configuration based upon a base channel data rate. 9 RCs contain rates derived from their base rate. For example, RC3 is based on 9.6 kbps and includes 1.5, 2.7, 4.8, 9.6, 19.2, 38.4, 76.8, 153.6, and 307.200 kbps. 9 RCs are coupled to specific Spreading Rates
42
IS-2000 SR1 (aka 1xRTT) • Is an Improved TIA/EIA-95-B Narrowband System • Occupies the Same 1.23 MHz Bandwidth as TIA/EIA-95-B ¾ Forward Link: 9 Adds Fast Power Control 9 Quick Paging Channel to Improve Standby Time 9 Uses QPSK Modulation Rather than Dual BPSK to: – Use 3/8 Rate Convolutional Encoder instead of 3/4 for 14.4 Service (improves error correction) – 128 Walsh Codes to Handle More Soft Handoffs for 9.6 service
¾ Reverse Link: 9 Uses Pilot Aided BPSK to Allow Coherent Demodulation 9 Uses 1/4 Rate Convolutional Encoder Instead of 1/2 or 1/3 9 Uses HPSK Spreading
• Doubles System Voice Capacity 43
SR1 Forward Radio Configurations • Radio Configuration 1 - Required 9 Backwards compatible mode with TIA/EIA-95-B 9 Based on 9,600 bps Traffic(RS1)
• Radio Configuration 2 9 Backwards compatible mode with TIA/EIA-95-B 9 Based on 14,400 bps Traffic(RS2)
• Radio Configurations 3, 4, and 5 9 All use new cdma2000 coding for improved capacity 9 RC3 is based on 9,600 bps and goes up to 153,600 bps 9 RC4 is based on 9,600 bps and goes up to 307,200 bps 9 RC5 is based on 14,400 bps and goes up to 230,400 bps
44
SR1 Forward Channels • • • •
F-Pilot (Using TIA/EIA-95-B Coding) F-Sync (Using TIA/EIA-95-B Coding) Up to 7 F-Paging (Using TIA/EIA-95-B Coding) IS-2000 Rev.0 ¾ 0 to 3 F-QPCH (Quick Paging Channel)
• IS-2000 Rev.A/B ¾ ¾ ¾ ¾
0 or 8 F-BCH (Broadcast Channel) 0 to 4 F-CPCCH (Common Power Control Channel) 0 to 7 F-CACH (Common Assignment Channel) 0 to 7 F-CCCH (Common Control Channels)
• Many F-Traffic Channels, Each Consisting of:
45
9 0 or 1 F-DCCH (Dedicated Control Channels) 9 1 F-FCH (Fundamental Channel) 9 0 to 7 F-SCCH (Supplemental Code Channels for RC1 & RC2) 9 0 to 2 F-SCH (Supplemental Channel for RC3, 4, 5)
Base Station Variable Rate Vocoder • Base Stations Do Not Pulse TX Channels • How Does the Base Station Handle Variable Rate Vocoding? ¾ Repeats Data Bits When Transmitting at Reduced Rates ¾ Repeating Data Adds 3 dB Coding Gain ¾ Lowers the TX Power 3dB for Each Lower Rate
46
Forward Link Traffic Channel Physical Layer (RC1,RC2)
Power Vocoded Control Speech Convolutional Puncturing Encoder Interleaver Data 800 bps Walsh Long Code 9.6 19.2 Coder Scrambling kbps 1/2 kbps Rate P.C. Mux 19.2 19.2 19.2 3/4 kbps kbps kbps 14.4 Rate 19.2 kbps kbps 20 msec blocks Long Code
19.2 kbps
800 bps
1.2288 Mbps I Short Code 1.2288 Mbps
1.2288 Mbps Walsh Code Generator
FIR Short Code Scrambler FIR
Q Short Code 1.2288 Mbps
47
I
Q
Forward FCH Physical Layer RC3 (9.6 kbps) Full Rate Data Bits
Add CRC and Tail Bits
Power Control Puncture
9.6 kbps
8.6 kbps
Complex Scrambling
1/4 Rate Conv. Encoder
Orthogonal Spreading 1228.8 kcps
P.C. Bits
I
38.4 ksps
User Long Code Mask
38.4 ksps
Gain
Gain
PC
Puncture Timing 1228.8 kbps
Long Code Generator
38.4 kbps
Long Code Decimator
800 bps
PC Dec
FIR
I
-
1228.8 kcps
1228.8kbps
S -P
Q
Walsh 64 Generator 1228.8 kbps
+
19.2 ksps
Decimate by Walsh Length/2
Q 1228.8 kcps
Optional Can be Carried by F-DCCH
48
1228.8 kcps
I
800 bps
38.4 ksps
I
I Short Code
19.2 ksps
Interleaver
+
Q Short Code
Q
1228.8 kcps
FIR +
1228.8 kcps
Q
CDMA Vocoders • Vocoders Convert Voice to/from Analog Using Data Compression • There are Three CDMA Vocoders: ¾ IS-96A
Variable Rate (8 kbps maximum)
¾ CDG
Variable Rate (13 kbps maximum)
¾ EVRC
Variable Rate (improved 8 kbps)
• Each has Different Voice Quality:
49
• IS-96A
- moderate quality
• EVRC
- near toll quality
• CDG
- toll quality
CDMA Frame Formats 9600 bps Frame Mixed Mode Bit
4800 bps Frame Mixed Mode Bit
192 bits in a ms frame 171
Information Bits
288 bits in a ms frame 12
CRC
14400 bps Frame
8
Encoder Tail Bits
1-bit Reserved
96 bits in a ms frame 79
Information Bits
Mixed Mode Bit
39
8 8
CRC
Mixed Mode Bit
50
Information Bits
Encoder Tail Bits
CRC
Encoder Tail Bits
1-bit Reserved
124
Mixed Mode Bit
Information Bits
10
8
Encoder Tail Bits
CRC
72 bits in a ms frame
3600 bps Frame
8
Encoder Tail Bits
Information Bits
15
8
144 bits in a ms frame
1-bit Reserved
24 bits in a ms frame
1200 bps Frame
12
Mixed Information Bits Mode Bit
7200 bps Frame
48 bits in a ms frame
2400 bps Frame
266
54
Mixed Mode Bit
Information Bits
8 8
Encoder Tail Bits
CRC
36 bits in a ms frame
1800 bps Frame
8
Encoder Tail Bits
1-bit Reserved
20
Information Bits Mixed Mode Bit
6 8
CRC
Encoder Tail Bits
Forward Error Protection • Uses Half-Rate Convolutional Encoder • Outputs Two Bits of Encoded Data for Every Input Bit Data Out 9600 bps
+ Data In 9600 bps
D
z
D
z
D
z
D
z
D
z
D
D
z
D
z
+ Data Out 9600 bps
51
14.4 Traffic Channel Forward Link Modifications • Replaces 8 kbps Vocoder with a 13 kbps Vocoder(both Variable Rate) • Effects:
Vocoded Speech Data
¾ Provides Toll Quality Speech
Convolutional
¾ Uses a 3/4 Rate Encoder
Encoder
¾ Reduces Processing Gain 1.76 dB
3/4 rate
¾ Results in Reduced Capacity or Smaller Cell Sizes
14.4 kbps
20 msec blocks 52
19.2 kbps
Interleaver • •
Process of permuting a sequence of symbols to achieve time diversity CDMA uses block interleaving with 20 ms blocks 16
19.2 ksps 9.6 ksps 4.8 ksps 2.4 ksps
Symbol Repetition
19.2 ksps
384 Symbols
Block Interleaver output Input Array Array
/
Interleaved Output
24
16 x 24 Array
20 ms
• 384 symbols are sequentially written in an input array • Interleaved symbols are then read from the output array
53
CDMA System Time • How Does CDMA Achieve Synchronization for Efficient searching?
11
¾ Use GPS Satellite System
• Base Stations Use GPS Time via Satellite Receivers as a Common Time Reference • GPS Clock Drives the Long Code Generator
54
12
1
10
2 3
9
4
8 7
6
5
Long Code Generation Long Code Output Modulo-2 Addition
User Assigned Long Code Mask 42 bits 42
41
5
4
3
Long Code Generator
55
2
1
Long Code Generation
Long Code Output Modulo-2 Addition
User Assigned Long Code Mask 42
41
5
4
3
2
1
42 bits
Long Code Generator
(Driven by System Time)
Long Code Mask 41
32 31 1100011000
56
0 Permuted ESN
Long Code Scrambling • User’s Long Code Mask is Applied to the Long Code • Masked Long Code is Decimated Down to 19.2 kbps • Decimated Long Code is XOR’ed with Voice Data Bits • Scrambles the Data to Provide Voice Security
XOR Encoded Voice Data
19.2 kbps
19.2 kbps Long Code Decimator
Long Code Generator
57
19.2 kbps
1.2288 Mbps
Closed Loop Power Control Puncturing • Long Code is Decimated Down to 800 bps • Decimated Long Code Controls the Puncture Location • Power Control Bits Replace Voice Data • Voice Data is Recovered by the Mobile’s Viterbi Decoder
Closed Loop Power Control Bits 800 bps Long Code Scrambled Voice Data
P. C. Mux
19.2 kbps
800 bps Long Code Decimator Long Code Decimated Data
58
19.2 kbps
19.2 kbps
Power Control Bit Puncturing
Long Code Decimat ed Dat a
z z
z
19.2 ksps
Decimat or
19.2 ksps: 384 symbols / 20ms frame Each 20ms frame is divided into 16 power control group (1.25 ms each) 24 modulation symbols in each power control group 20ms 1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16
1.25ms 0
1
2
3
4
5
6
7
8 9
10 11 12 13 14 15 16 17 18 19 20 21 22 23
If [20,21,22,23]=[1,1,0,1],then puncture bit 11,12 59
4 symbols = 16 combinations
SR1, RC4 (152.4 kbps) F-SCH Payload Data Bits
Channel Convolutional Coder Encoder
152.4 kbps
Complex Scrambling
153.6 kbps
Orthogonal Spreading
1/2 Rate Add CRC and Tail Bits
307.2 ksps
1228.8 kcps
I Interleaver
1228.8 kbps
Long Code Generator
FIR -
1228.8 kcps
1228.8 kcps
I 1228.8kbps
307.2 ksps
Gain
307.2 ksps
Long Code Decimator Decimate by Walsh Length/2
60
I
I Short Code
153.6 ksps
307.2 ksps
User Long Code Mask
+
S -P
Q
Walsh 8 Generator 1228.8 kbps
+
153.6 ksps
Q 1228.8 kcps
Q Short Code + 1228.8 kcps
Q
1228.8 kcps
FIR
Walsh Codes
W1 = 0
Wn Wn W2n = Wn Wn
61
0 0 W2 = 0 1 0 0 W4 = 0 0
0 1 0 1
0 0 1 1
0 1 1 0
Checking for Orthogonality
Cross N agreements- N disagreements = Correlation N total_number_of_digits 0 0 W4 =0 0 62
0 1 0 1
0 0 1 1
0 1 1 0
0 0 0 0 0 0 1 1 Y Y N N
2 Match - 2 don’t = 0
Effects of Using Variable Length Walsh Codes for Spreading • Using Shorter Walsh Codes Precludes Using all Longer Codes Derived from the Original • Shorter Codes on a Branch map into Longer Codes
SF=2 SF=4
SF=8 1 1 1 1 1 1 1 1
SF=16 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 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
63
Walsh Code Spreading
Encoded Voice Data
Walsh Code Generator
64
19.2 kbps
1.2288 Mbps
1.2288 Mbps
What is the Spreading Rate Increase ?
Why Spread Again with the Short Sequence • Provides a Cover to Hide the 64 Walsh Codes • Each Base Station is Assigned a Time Offset in its Short Sequences • Time Offsets Allow Mobiles to Distinguish Between Adjacent Cells • Also Allows Reuse of All Walsh Codes in Each Cell
1.2288 Mbps
Walsh Coded Data at 1.2288 Mbps
To I/Q Modulator
1.2288 Mbps
65
I Channel Short Sequence Code Generator
Q Channel Short Sequence Code Generator
Multi-Layer Code Assignment
Short Code Walsh Code Long code
CDMA as an Onion W64,0
Convolutional Encoder
W64,1
PN 0 W64,2
Cells A/Sector A
W64,1
W64,0
PN 1
Full code set per cell Cells B/Sector B
W64,2
Walsh Code layer (spreading code) 66
Short Code (PN) Generation
z
z z z
PN sequence codes are generated using 15-bit shift registers PN sequence pattern repeats every 26.666 ms 75 PN sequences repetition occur every 2 seconds On every even second clock, MS will get PN sequence initial state
2 sec
2 6.
Jan 6, 1980 00:00:00
8 76 32
PN Code Combinations: 215 = 32768 Clock Rate = 1.2288 Mcps Return of Initial State = 26.666 ms
67
75 74
ms
1 2
8 3276
R1,R2,R3,R4..........R15 1, 0, 0, 0.............. 0 ( initial state of 15 registers )
6 66
327 68
PN Offsets • Each BS scrambles PN sequence with data by some time offset • Time offsets are in intervals of 64 clock chips (52.08 us) from even second clock • 512 unique offsets are created (32768/64 = 512) • Each BS is allotted an offset for PN PN 237 sequence scrambling PN 0
PN 120
68
PN 511
PN 489
Short Code Correlation • Short Codes are Designed to Have: ¾ Strong Auto-Correlation at Zero Time Offset
Auto-Correlation Versus Time Offset With 17 dB Noise Added
¾ Weak Auto-Correlation at Other Offsets ¾ Good Auto-Correlation in Very Poor Signal-to-Noise Ratio Environments
• Allows Fast Acquisition in Real World Environment
69
0
5
10
15
20
Chip Offset
25
30
Forward Link Channel Format Walsh Code 0 Pilot Channel
All 0’s
1228.8 kbps
Convert to I/Q & PN Spreading
I Data
FIR LP Filter & D/A Conversion
Q Data
Walsh Code 32 Sync Channel
4.8 kbps
1228.8 kbps
Convert to I/Q & PN Spreading
I Data
Σ
I
Σ
Q
FIR LP Filter & D/A Conversion
Q Data
Walsh Codes 1 to 7 Paging Channels 19.2 kbps
1228.8 kbps
1 up to 7 Channels
Convert to I/Q & PN Spreading
I Data
FIR LP Filter & D/A Conversion
Q Data
Walsh Codes 8-31,33-63 Traffic Channels 19.2 kbps 1 up to 55 Channels
70
1228.8 kbps
Convert to I/Q & PN Spreading
I Data Q Data
FIR LP Filter & D/A Conversion
Walsh Coding Example User A
0 0 - User A W2 = 0 1 - User B
+1
For a 0 Input Use Code 00 -1
Channel A Voice Data
1
1
1
0
0
0
For a 1 Input Use Code 10
-1
Channel B Voice Data
0
1
1
0
1 0
1
0
0 +2
Sum of A & B Walsh Encoded Data Streams
+1
-1 -2
71
0
+1
+1
+1 Channel A Walsh Encoded -1 Voice Data
For a 0 Input Use Code 01
0
+1
-1
+1
-1
0 For a 1 Input Use Code 11
User B
+ 0
1
0
+1 0
1
0
0
1
+1
Channel B Walsh Encoded -1 Voice Data
1
0
0
1 0
1
1
0
Walsh Decoding Example
Correlation Coefficient
Original User A Voice Data +1
zij =
0
1
0
0
1
1 T 0
∫
Original User B Voice Data
T
+1
f i (t) r f j (t) dt
0
1
User A & B Walsh Data
+2
+1
+1
-1
-1
-2
-2
Multiply Summed Data with Desired Walsh Code +2 +1
-1 -2
72
-1
+1
1
1
Multiply Summed Data with Desired Walsh Code
+2
X
0
User A & B Walsh Data
+2
+1
0
1
= -1 -2
+2
∫ -1
+1
=
+2 +1
+1
=
+ -1 -2
-1
1
0
-1 -2
∫
=
1
What if Walsh Codes are Not Time Aligned ?
Original Channel A +1 Walsh Encoded Voice Data -1
Time Delayed
+ 0
0
1
1
0
0
Sum of A & B Walsh Encoded Data Streams
0
0
Channel B +1 Walsh Encoded Voice Data -1
1
0
0
1 0
1
+1
-1 -2
Multiply Summed Data with Desired Walsh Code +2 +1
+2 +1
+1
=
X -1 -2
73
-1
1
1
-1 -2
∫
=
-0.75
Original Data Was 0 (-1), We Have Interference Now!
1
0
Pilot Channel Physical Layer • Uses Walsh Code 0: 1.2288 Mbps
¾ All 64 bits are 0 Walsh Modulator
I Short Code
• All Data into Walsh 1.228 All 0 Modulator is 0 8 Inputs FIR Mbps • Output of Walsh 19.2 Short Code Scrambler Modulator is therefore all kbps 0’s FIR 1.228 8 • Pilot Channel is just the Mbps Walsh Code Short Codes Q Short Code Generator Walsh Code 0
74
1.2288 Mbps
I
Q
Sync Channel Physical Layer
Sync Channel Message Data Convolutional Encoder
Symbol Repetition
1/2 Rate 1.2 kbps
1.2288 Mbps
Walsh 32 Coder
Interleaver
1.2288 Mbps
2x 2.4 kbps
I Short Code
4.8 kbps
4.8 kbps
FIR
Short Code Scrambler
1.2288 Mbps Walsh Code Generator
FIR
Q Short Code 1.2288 Mbps
75
I
Q
Paging Channel Physical Layer
Paging Channel Message Data Convolutional Encoder
1.2288 Mbps
Walsh Interleaver 1 to 7 Long Code Symbol Coder Scrambling Repetition
4.8 kbps
1/2 Rate
1.2288 Mbps
2x 9.6 kbps
I Short Code
19.2 kbps
19.2 kbps
Paging Channel Long Code 19.2 kbps
19.2 kbps
FIR
Short Code Scrambler
1.2288 Mbps Walsh Code Generator
FIR
QShort Code 1.2288 Mbps
76
I
Q
SR1 Reverse Radio Configurations • Radio Configuration 1 - Required 9 Backwards compatible mode with TIA/EIA-95-B 9 Based on 9,600 bps Traffic
• Radio Configuration 2 9 Backwards compatible mode with TIA/EIA-95-B 9 Based on 14,400 bps Traffic
• Radio Configurations 3 and 4 9 All use new IS-2000 coding for improved capacity 9 RC3 is based on 9,600 bps and goes up to 307,200 bps 9 RC4 is based on 14,400 bps and goes up to 230,400 bps
77
SR1 Reverse Channels
• Each Mobile Transmits Several Channels: ¾ 1 R-Pilot (Reverse Pilot) 9 Includes Power Control SubSub-Channel
¾ 1 R-ACH or R-EACH (Access or Enhanced Access Channel) 9 Used to Initiate Calls
¾ 0 or 1 R-CCCH (Common Control Channel) 9 Used to Initiate Calls in the Reservation Access Mode
¾ 0 or 1 R-DCCH (Dedicated Control Channel) 9 Provides Signaling while a Traffic Channel is Active
¾ 0 or 1 R-FCH (Reverse Fundamental Channel) 9 Primary Channel, usually Voice
¾ 0 to 2 R-SCHs (Reverse Supplemental Channels) 9 Carries High Speed Data 78
R-FCH Coding for SR1(RC1,RC2)
Convolutional Encoder Vocoded Speech Data 9.6 kbps
14.4 kbps 20 msec blocks
Interleaver 1/3 28.8 Rate kbps
64-ary Modulator 1 of 64 Walsh Codes Walsh Code 63 Walsh Code 62
1/2 Rate 28.8
28.8 kbps
1.2288 Mbps I Short Code
Long Code Modulator 1.2288 Mbps
Walsh Code 61
307.2 kbps
kbps
Walsh Code 0
79
FIR
Q
1/2 Chip Delay
Walsh Code 1
Long Code
I
Short Code Scrambler
t/ 2
Walsh Code 2
FIR
Q Short Code 1.2288 Mbps
1.2288 Mbps
Reverse Error Protection • Uses Third-Rate Convolutional Encoder • Outputs Three Bits for Every Input Bit Data Out 9600 bps
+ Data In 9600 kbps
D
z
D
z
D
z
D
z
D
z
D
z
D
z
D
z
z z
+ +
80
z
Data Out 9600 bps Data Out 9600 bps
14.4 Traffic Channel Reverse Link Modifications • Replaces 8 kbps Vocoder with a 13 kbps Vocoder (both Variable Rate) • Effects:
Vocoded Speech Data
¾ Provides Toll Quality Speech ¾ Uses a 1/2 Rate Encoder
Convolutional Encoder
¾ Reduces Processing Gain 1.76 dB
1/2 Rate
¾ Results in Reduced Capacity or Smaller Cell Sizes
14.4 kbps
20 msec blocks
81
28.8 kbps
64-ary Modulation • Every 6 Encoded Voice Data Bits Points to one of the 64 Walsh Codes • Spreads Data from 28.8 kbps to 307.2 kbps ¾ (28.8 kbps * 64 bits) / 6 bits = 307.2 kbps)
28.8 kbps
>
Walsh Code 63 Walsh Code 62 Walsh Code 61
307.2 kbps
• Is Not the Channelization for the Reverse Link Walsh Code 2 Walsh Code 1 Walsh Code 0
82
Why Aren’t Walsh Codes Used for Reverse Channelization ? • All Walsh Codes Arrive Together in Time to All Mobiles From the Base Station • However, Transmissions from Mobiles DO NOT Arrive at the Same Time at the Base Station
83
Reverse Channel Long Code Spreading • Long Code Spreading Provides Unique Mobile Channelization • Mobiles are Uncorrelated but not Orthogonal with Each Other
XOR Walsh Modulated Voice Data
Long Code Generator
84
307.2 kbps
1.2288 kbps
1.2288 kbps
Data Burst Randomizer
20 ms = 576 code symbols (28.8ksps) 96 modulation symbols (576 / 6) 1.25 ms =36 code symbols 6 modulation symbols Previous Frame 12
13
14
15
0
1
2
3
4
5
6
7
8
9
b9
b10
10
11
12
13
14
15
Long Code Bits used for spreading PCG14 b0
b1
b2
b3
b4
b5
b6
b7
b8
b11
b12
b13
Algorithm At 4800 bps rate, Transmission should occur on the PCG's numbered:
b0, 2 + b1, 4 + b2, 6 + b3, 8 + b4,10 + b5, 12 + b6, 14 + b7 0
1
2
3
4
5
6
7
8
9
10
11
12
(50% Gated-On, 50% Gated-Off) 85
13
14
15
(Example)
Data Burst Randomizer Algorithm At 2400 bps rate
,
Transmission should occur on the PCG's numbered: b0 if b8 = 0, or 2 + b1 if b8 = 1 4 + b2 if b9 = 0, or 6 + b3 if b9 = 1 8 + b4 if b10 = 0, or 10 + b5 if b10 = 1 12+b6 if b11 = 0, or 14 + b7 if b11 = 1 0
1
2
3
4
5
6
7
8
9
10
(i.e. 1 out of PCG 0...3) (i.e. 1 out of PCG 4...7) (i.e. 1 out of PCG 8...11) (i.e. 1 out of PCG 12..15) 11
12
13
14
15
(Example)
( 25% Gated-On, 25% Gated-Off ) At 1200 bps rate , Transmission should occur on the PCG's numbered: b0 if (b8 = 0 and b12=0), or 2 + b1 if or 4 + b2 if (b9 = 0 and b12=0), or 6 + b3 if 8 + b4 if (b10 = 0 and b13=0), or 10 + b5 if or 12 + b6 if (b11 = 0 and b13=0), or 14 + b7 if 0
1
2
3
4
5
6
7
8
9
(b8 = 1 and b12=1) (b9 = 1 and b12=1) (i.e. 1 out of PCG 0...7) (b10 = 1 and b13=1) (b11 = 1 and b13=1) (i.e. 1 out of PCG 8..15) 10
11
12
13
(12.5% Gated-On, 12.5% Gated-Off) 86
14
15
(Example)
Gated-On and Gated-Off Power Mean output of the ensemble average
7 us
7 us
3 dB 20 dB or to the noise floor (-60dBm)
1.247 ms
Ensemble average: Average of power control groups, all with the same output power 87
Reverse Channel Short Sequence Spreading • Same PN Short Codes Are Used by Mobiles • Short Sequence spreading Aids Base Station Signal Acquisition • Extra 1/2 Chip Delay is Inserted into Q Path to Produce OQPSK Modulation to Simplify Power Amplifier Design
1.2288 Mbps I Short Code
1.2288 Mbps
FIR
I
FIR
Q
Short Code Scrambler
t/ 2
1/2 Chip Delay I Short Code 1.2288 Mbps
88
OQPSK Modulation
• QPSK Makes one Symbol Change Every Period • OQPSK Makes two Symbol Changes Every Period if Q Data Changes • Example Symbol Pattern is: - 00,10,01,11
89
I 00
n 01
n
Q 10 n
n 11
I 00
n
n 01
Q 10 n
n 11
CDMA Modulation Formats
Base Station Pilot Channel TX Q
I
Filt ered QPSK
90
Mobile Station TX Q
I
Filt ered Offset QPSK
Reverse Pilot/Power Control Multiplexing (RC3,4) • • • •
There are 16 Power Control Groups per 20 ms Frame Each Power Control Group is Split into 4 Sub-Groups 1 Power Control Bit is Sent per Power Control Group Pilot and Power Control are Multiplexed Together
Pilot Data MUX Power Control Bits
91
To I Channel Summer
One Power Control Group Pilot
Pilot
Pilot
PC Bits
312.5 us 312.5 us 312.5 us 312.5 us 1.25 ms
SR1, RC3 R-FCH Coding(RC3,RC4) • R-FCH Carries Voice Information • Uses a 20 ms Frames Length • Using ¼ rate convolutional coding
R-FCH Coding for a 20 ms Frame R-FCH Data Bits
Channel Coder
8.6 kbps
9.6 kbps
Add CRC and Tail Bits
92
Convolutional Encoder 1/4 Rate
Interleaver 38.4 ksps
1 Frame
Orthogonal Spreading
Symbol Repeat 38.4 ksps
76.8 ksps
1228.8 kcps
2 Reps 1,1, 1, 1,-1, -1, -1, -1, 1,1, 1, 1,-1, -1, -1, -1
Spread Factor = 16
Walsh Code Generator
SR1 Reverse Channel Spreading(RC3,RC4) Gain 1228.8 kcps Scale
R-SCH 2
I Channel Short Code Generator
1, 1, -1, -1 or 1, 1, -1, -1, -1, -1, 1, 1
R-Pilot + Power Control
Complex Scrambling
Walsh 4/8 Generator
1228.8 kcps
+
1228.8 kcps
I -
R-DCCH 1228.8 kcps
Gain Scale
1228.8 kcps
1,1,1,1,1,1,1,1,-1,-1,-1,-1,-1,-1,-1,-1
R-SCH 1 or R-EACH or R-CCCH
Walsh 16 Generator
User Long Code Mask
Long Code Generator
1,-1
Gain 1228.8 kcps Scale
Deci by 2
1-Chip Delay
+
1,-1 or 1 -1 1,-1, or 1,1,-1,-1,1,1,-1,-1
Walsh 2/4/8 1,1,1,1,-1,-1,-1,-1 for Generator R-EACH or R-CCCH Gain 1228.8 kcps Scale
R-FCH
1,1, 1, 1 -1,-1, -1, -1, 1, 1, 1, 1, -1, -1, -1, -1
Walsh 16 Generator
93
Walsh 2 Generator
1228.8 kcps
Q
1228.8 kcps
+
Q Channel Short Code Generator
1228.8 kcps
Channelization Summary
94
Function
Forward Link (Base to Mobile)
Reverse Link (Mobile to Base)
9.6 kbps Convolutional Encoder
1/2 Rate
1/3 Rate
(9600 in 19200 out)
(9600 in 28800 out)
14.4 kbps Convolutional Encoder
3/4 Rate
1/2 Rate
(14400 in 19200 out)
(14400 in 28800 out)
Walsh Coding
Channelization
64-ary Modulation
Long Code Spreading
Voice Privacy
Channelization
Short Code Spreading
Base Station Identification
Aid Base Station Searching
CDMA Multiplex Sublayer
Layer 3 Call Processing & Control
Layer 2
Layer 2
Primary Traffic
Signaling
Multiplex Sublayer Traffic Channel
Layer 2 Link Layer Paging & Access Channels
Layer 1 Physical Layer Channel Data - 9600 bps or 14400 bps
95
Station Class Mark (SCM) Function
Setting
Extended SCM Indicator
7
Band Class 0 Band Class 1
0 XXXXXXX 1 XXXXXXX
Dual Mode
6
Slotted Class
5
IS- 54 Power Class
4
CDMA Only Dual Mode Non-Slotted Slotted Always 0
X0 XXXXXX X 1XXXXXX XX0XXXXX XX1XXXXX XXX0XXXX
25 MHz Bandwidth
3
Always 1
XXXX1XXX
Transmission
2
Continous Discontinous
XXXXX0XX XXXXX1XX
Class I Class II Class III Reserved
XXXXXX00 XXXXXX01 XXXXXX10 XXXXXX11
Power Class for Band Class "0" Analog Operation ( For CDMA only "00")
96
Bit(s)
1- 0
Ten Minutes in the Life of a CDMA Mobile Phone • Turn-on ¾ System Access
• Travel ¾ Idle State Hand-Off
• Initiate Call • System Access • Continue Travel ¾ Initiate Soft Handoff ¾ Terminate Soft Handoff
• End Call
97
CDMA Turn On Process • Find All Receivable Pilot Signals ¾ Choose Strongest One
• Establish Frequency and PN Time Reference (Base Station I.D.) • Demodulate Sync Channel • Establish System Time • Determine Paging Channel Long Code Mask
98
Sync Channel Message • Contains the Following Data: ¾ Base Station Protocol Revision ¾ Min Protocol Revision Supported ¾ SID, NID of Cellular System ¾ Pilot PN Offset of Base Station ¾ Long Code State ¾ System Time ¾ Leap Seconds From Start of System Time ¾ Local Time Offset from System Time ¾ Daylight Savings Time Flag ¾ Paging Channel Data Rate ¾ Channel Number 99
C N SY
Read the Paging Channel • Demodulate the Paging Channel: ¾ Use Long Code Mask Derived from the Pilot PN Offset Given in Sync Channel Message
• Decode Messages • Register, if Required by Base Station • Monitor Paging Channel
100
g n i g Pa
CDMA Idle State Handoff • No Call In Progress • Mobile Listens to New Cell • Move Registration Location if Entering a New Zone
101
Access Procedures • Controlled by BS by broadcasting Access Parameters Message on the paging channel • Access attempt is the process of sending one message and receiving (or failing to receive) an ACK for that message = groups of access probe sequence • Access probe sequence = groups of access probes • Access probe = each transmission in an access attempt
102
Access Probe Access Probe (or Access Channel Slot) ( 4 + PAM_SZ + MAX_CAP_SZ) x 20ms [ Max value = 26 frames ]
Access Chan Frame 96 b/20ms
Preamble 96 bits “0”s
Preamble
Access Channel Message Capsule
(1 + PAM_SZ) x 20ms [ max = 16 frames ]
(3 + MAX_CAP_SZ) x 20 ms [ Max = 10 frames ]
Access Chan Frame 96 b/20ms
Access Chan Frame 96 b/20ms
Preamble 96 bits “0”s
Access Chan Frame 96 b/20ms
Frame Body T 88 bits 8
PAM_SZ = No. of preamble frames MAX_CAP_SZ = No. of message capsule frames
Access Chan Frame 96 b/20ms
……
Access Chan Frame 96 b/20ms
Frame Body T 88 bits 8
Access Channel Message 40 - 880 bits
Padding as reqd
Access Channel Message Capsule 103
Access Probe Sequence Preamble + Access Message Capsule Max = 26 frames P3
Access Probe n
P2
Access Probe 3 Access Probe 2
P1 Access Probe 1
IP
RN
TA
RT
RN
TA
RT
RN
TA
Access Probe Sequence IP = Open Loop Power + NOM_PWR + INIT_PWR where Open Loop Power = -( Received Power ) - 73 104
RT
RN
Access Attempt
Process for Response Messages MAX_RSP_SEQ Access Attempt
Access Probe Sequence
RS
RS
RS Access Probe Sequence
Access Probe Sequence
Access Probe Sequence
message ready for transmission
RS : Backoff delay, which is random value between 0 to BKOFF slots
105
Access Attempt Process for Request Messages MAX_REQ_SEQ Access Attempt
RS
PD Access Probe Sequence
RS
PD Access Probe Sequence
PD
RS Access Probe Sequence
PD Access Probe Sequence
message ready for transmission
PD: (Persistence Delay) resulted from a pseudo-random test by MS; the first access probe of the sequence begins in the slot only if the test passes within that slot The test result depends on the ESN, reason for attempt (call origination, register, etc.) and the access overload class of the MS, and a PSSIST value broadcasted by BS for that access class. If the PSSIST is all “1”s for some access class, the test for that access class will always fail
106
Access Channel Messages Registration Message - for registration as well as Global Challeng Authentication Process
Order Message - for transmission of order messages (e.g., BS challenge order, SSD update confirmation, MS acknowledgement order, etc.)
Data Burst Message - to get a trigger from the user to send a message to BS (information message like SMS)
Origination Message-MS information Page Response message Authentication Challenge Response Message Status Response Message - response to BS status request 107
order which may include MS terminal information, station class mark, service option supported, multiplex option support, IMSI, ESN, etc.
CDMA Call Initiation
• Dial Numbers, Then Press Send • Mobile Transmits on a Special Channel Called the Access Channel • The Access Probe Uses a Long Code Mask Based On: bAccess & Paging Channel Numbers bBase Station ID bPilot PN Offset
108
CDMA Call Completion
• Base Answers Access Probe using the Channel Assignment Message • Mobile Goes to A Traffic Channel Based on the Channel Assignment Message Information • Base Station Begins to Transmit and Receive Traffic Channel
109
CDMA Soft Handoff Initiation • Mobile Finds Second Pilot of Sufficient Power (exceeds T_add Threshold) • Mobile Sends Pilot Strength Message to First Base Station • Base Station Notifies MTSO • MTSO Requests New Walsh Assignment from Second Base Station • If Available, New Walsh Channel Info is Relayed to First Base Station
110
Hard, Soft, and Softer Handoffs f2
• Hard Handoff ¾ “Break before make.”
• Soft Handoff ¾ “Make before break.” ¾ MS communicates with more than one BS at a time. ¾ Improves reception on cell boundaries. ¾ MS will receive different power control from the two BSs.
• Softer Handoff ¾ MS communicates with more than one sector of a cell. ¾ MS will receive identical power control from both sectors.
111
f1 Hard Handoff
f1 f1 Soft Handoff
f1 Softer Handoff
cdma2000 CONCEPT: Soft Handoff Pilot Ec/I0
• Terms:
T_ADD
¾ Active Set: MS is in soft handoff. ¾ Candidate Set: MS identifies as strong.
• Parameters: ¾ T_ADD ¾ T_COMP ¾ T_DROP
BS1
Pilot Ec/I0
Pilot Ec/I0
0.5xT_COMP
¾ T_TDROP
T_DROP
BS1 112
BS2
BS2
BS1
BS2
CDMA Soft Handoff Completion • First Base Station Orders Soft Handoff with new Walsh Assignment • MTSO Sends Land Link to Second Base Station • Mobile Receives Power from Two Base Stations • MTSO Chooses Better Quality Frame Every 20 Milliseconds
MTSO
Land Link
Vocoder/ Selector
Base Station 1 113
Base Station 2
Ending CDMA Soft Handoff • First BS Pilot Power Goes Low at Mobile Station (drops below T_drop) • Mobile Sends Pilot Strength Message • First Base Station Stops Transmitting and Frees up Channel • Traffic Channel Continues on Base Station Two
114
CDMA End of Call • Mobile or Land Initiated • Mobile and Base Stop Transmission • Land Connection Broken
115
cdma2000 Standards Overview - TIA/EIA-98D/E • I.e.3GPP2 C.S0011-A/B: ¾ “Recommended Minimum Performance Standards for cdma2000 Spread Spectrum Mobile Stations.”
• Important test sections: ¾ 2 Standard Radiated Emissions Measurement Procedure ¾ 3 CDMA Receiver Minimum Standards ¾ 4 CDMA Transmitter Minimum Standards
• Covers both SR1 and SR3 ¾ No Minimum Standards specified for SR3. ¾ This presentation only covers SR1 testing. 116
CDMA Service Options ¾ Service Options Are: 9 1- Voice Using 9600 bps IS-96-A Vocoder 9 2- Rate Set 1 Loopback (9600 bps) 9 3- Voice Using 9600 bps (EVRC) 9 4- Asynchronous Data Service (circuit switched) 9 5- Group 3 Fax 9 6- Short Message Service (9600 bps) 9 7- Internet Standard PPP Packet Data 9 8- CDPD Over PPP Packet Data 9 9- Rate Set 2 Loopback (14400 bps) 9 14-Short Message Service (14400 bps) 9 32,768- Voice Using 14400 bps (CDG)
117
Section 3 - Receiver Test Receiver Test 3.1 Frequency Coverage Requirements 3.4.1 Demod of Fwd Traffic Channel with AWGN 3.4.2 Demod of Fwd Traffic Channel with Multipath Fading 3.5.1 Receiver Sensitivity and Dynamic Range 3.5.2 Single Tone Desensitization 3.5.3 Intermodulation Spurious Response Attenuation 3.5.4 Adjacent Channel Selectivity 3.5.5 Receiver Blocking Characteristics 3.7.1 Supervision Paging Channel
118
Section 4 - Transmitter Test
Transmitter Test 4.1 Frequency Accuracy 4.2 Handoff 4.3 Modulation Requirements 4.4 RF Output Power Requirements 4.4.1 Range of Open Loop Output Power 4.4.2 Time Response of Open Loop Power Control 4.4.3 Access Probe Output Power 4.4.4 Range of Closed Loop Power Control 4.4.5 Maximum RF Output Power 4.4.6 Minimum Controlled Output Power 4.4.7 Standby Output Power and Gated Output Power 4.4.8 Power Up Function Output Power 4.4.9 Code Channel to Reverse Pilot Channel Output Power Accuracy 4.4.10 Reverse Pilot Channel Transmit Phase Discontinuity 4.4.11 Reverse Traffic Channel Output Power During Changes in Data Rate 119
CDMA Conclusions • New Access Method ¾ Code Based
• • • •
Designed for Use in Interfering Environment Uses Multipath to Improve Reception in Fading Conditions cdma2000 is Backwards Compatible with TIA/EIA-95-B Provides 2x Capacity Improvement Over TIA/EIA-95-B 9 Improved Coding 9 Improved Modulation 9 Coherent Reverse Link Demodulation (Mobile Pilot) 9 Fast Forward Link Power Control
• Has Options for Green Field and Overlay Operation: 9 Direct Spread for Green Field Spectrum Applications
• Supports High Speed Data for New Applications 120
