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H Advanced Concepts of CDMA SLIDE 1 Copyright Hewlett Packard © 1999 Advanced Training Version - 6th Edition Concepts of CDMA.

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Presentation on theme: "H Advanced Concepts of CDMA SLIDE 1 Copyright Hewlett Packard © 1999 Advanced Training Version - 6th Edition Concepts of CDMA."— Presentation transcript:

1 H Advanced Concepts of CDMA SLIDE 1 Copyright Hewlett Packard © 1999 Advanced Training Version - 6th Edition Concepts of CDMA

2 H Advanced Concepts of CDMA SLIDE 2 Copyright Hewlett Packard © 1999 Power Frequency Time FDMA Frequency PowerTime TDMA Frequency CDMA Power Time Cellular Access Methods

3 H Advanced Concepts of CDMA SLIDE 3 Copyright Hewlett Packard © 1999 US Cellular Channel 384 Frequency Amplitude Frequency Amplitude AMPS 45 MHz Forward Link MHz MHz Reverse Link CDMA 45 MHz MHz MHz Reverse Link Forward Link CDMA is Also Full Duplex

4 H Advanced Concepts of CDMA SLIDE 4 Copyright Hewlett Packard © CDMA ReuseFDMA Reuse Cellular Frequency Reuse Patterns

5 H Advanced Concepts of CDMA SLIDE 5 Copyright Hewlett Packard © 1999 Capacity = (Chan BW) (Data Rate) × (1) (S/N) × (1) (V af ) (Fr) × CDMA = (1,230,000) (9,600) × (1) (5.01) × (1) (.40) (0.67) × 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) Processing Gain Processing Gain CDMA Capacity Gains

6 H Advanced Concepts of CDMA SLIDE 6 Copyright Hewlett Packard © 1999 Interference Sources Walsh Code Spreading Encoding & Interleaving Decode & De- Interleaving Baseband Data Baseband Data Background Noise External InterferenceOther Cell Interference Other User Noise 9.6 kbps 19.2 kbps kbps 19.2 kbps 9.6 kbps CDMA Transmitter CDMA Receiver 1.23 MHz BW f c f c 10 kHz BW MHz BW f c f c f c -113 dBm/1.23 MHz f c Spurious Signals Walsh Code Correlator kbps The CDMA Concept

7 H Advanced Concepts of CDMA SLIDE 7 Copyright Hewlett Packard © 1999 Received Signal Time Correlation = 1 Correlation = 0 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

8 H Advanced Concepts of CDMA SLIDE 8 Copyright Hewlett Packard © 1999 CDMA Analog CDMA Paradigm Shift Multiple Users on One Frequency –Analog/TDMA Try to Prevent Multiple Users Interference Channel is Defined by Code –Analog Systems Defined Channels by Frequency Capacity Limit is Soft Allows Degrading Voice Quality to Temporarily Increase Capacity Reduce Surrounding Cell Capacity to Increase a Cell's Capacity

9 H Advanced Concepts of CDMA SLIDE 9 Copyright Hewlett Packard © 1999 CDMA Diversity Spatial Diversity – Making Use of Differences in Position Frequency Diversity – Making Use of Differences in Frequency Time Diversity – Making Use of Differences in Time

10 H Advanced Concepts of CDMA SLIDE 10 Copyright Hewlett Packard © 1999 CDMA Spatial Diversity Diversity Reception: – Multiple Antennas at Base Station Each Antenna Is Affected by Multipath Differently Due to Their Different Location Allows Selection of the Signal Least Affected by Multipath Fading If Diversity Antennas Are Good, Why Not Use Base Stations as a Diversity Network? – Soft Handoff

11 H Advanced Concepts of CDMA SLIDE 11 Copyright Hewlett Packard © 1999 MTSO Vocoder / Selector Base Station 2 Base Station 1 Land Link Spatial Diversity During Soft Handoff

12 H Advanced Concepts of CDMA SLIDE 12 Copyright Hewlett Packard © 1999 Amplitude Frequency 1.23 MHz BW CDMA Frequency Diversity Combats Fading, Caused by Multipath Fading Acts like Notch Filter to a Wide Spectrum Signal May Notch only Part of Signal

13 H Advanced Concepts of CDMA SLIDE 13 Copyright Hewlett Packard © 1999 CDMA Time Diversity Rake Receiver to Find and Demodulate Multipath Signals Data is Interleaved –Spreads Adjacent Data in Time to Improve Error Correction Efficiency Convolutional Encoding –Adds Error Correction and Detection Viterbi Decoding –Most Likely Path Decoder for Convolutionaly Encoded Data

14 H Advanced Concepts of CDMA SLIDE 14 Copyright Hewlett Packard © 1999 Original Data Frame Errors/Time Interleaved Data Frame Errors/Time Errors/Time TX RX Errors/Time TX RX Why Interleaving Works

15 H Advanced Concepts of CDMA SLIDE 15 Copyright Hewlett Packard © 1999 Time Frequency Amplitude The Rake Receiver

16 H Advanced Concepts of CDMA SLIDE 16 Copyright Hewlett Packard © 1999 Output T 0 W 0 T 4 T 1 T 2 T 3 W 1 W 2 W 3 W 4 + Delay Taps Tap Weights Antenna Rake Receiver Design

17 H Advanced Concepts of CDMA SLIDE 17 Copyright Hewlett Packard © 1999 Synchronization All Direct Sequence, Spread Spectrum Systems Should be Accurately Synchronized for Efficient Searching Finding the Desired Code Becomes Difficult Without Synchronization

18 H Advanced Concepts of CDMA SLIDE 18 Copyright Hewlett Packard © 1999 Reverse Link Power Control Maximum System Capacity is Achieved if: All Mobiles are Powered Controlled to the Minimum Power for Acceptable Signal Quality As a result, all Mobiles are Received at About Equal Power at the Base Station Independent of Their Location There are Two Types of Reverse Control: –Open Loop Power Control –Closed Loop Power Control Open & Closed Loop Power Control are Always Both Active !

19 H Advanced Concepts of CDMA SLIDE 19 Copyright Hewlett Packard © 1999 Open Loop Power Control Assumes Loss is Similar on Forward and Reverse Paths Receive Power+Transmit Power = -73 –All powers in dBm Example: –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

20 H Advanced Concepts of CDMA SLIDE 20 Copyright Hewlett Packard © 1999 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 = usec

21 H Advanced Concepts of CDMA SLIDE 21 Copyright Hewlett Packard © 1999 CDMA Variable Rate Speech Coder DSP Analyzes 20 Millisecond Blocks of Speech for Activity Selects Encoding Rate Based On Activity: High Activity: Full Data Rate Encoding (9600 bps) Some Activity: Half Data Rate Encoding (4800 bps) Low Activity: Quarter Date Rate Encoding (2400 bps) No Activity: 1/8 Data Rate Encoding (1200 bps) How Does This Improve Capacity? –Mobile Transmits in Bursts of 1.25 ms System Capacity Increases by 1/V af

22 H Advanced Concepts of CDMA SLIDE 22 Copyright Hewlett Packard © 1999 CDMA Frame = 20 ms Full Rate Half Rate Quarter Rate Eighth Rate 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 3dB for Each Lower Data Rate

23 H Advanced Concepts of CDMA SLIDE 23 Copyright Hewlett Packard © 1999 Base Station Variable Rate Vocoder Base Stations Do Not Pulse TX Channels How Does the Base Station Handle Variable Rate Vocoding ? –Repeats Data Bits When Transmitting at Reduced Rates –Repeating Data Adds 3 dB Coding Gain –Lowers the TX Power 3 dB for Each Lower Rate

24 H Advanced Concepts of CDMA SLIDE 24 Copyright Hewlett Packard © 1999 Walsh Cover I Short Code Q Short Code FIR Mbps Walsh Code Generator I Q Mbps Mbps Long Code 19.2 kbps Vocoded Speech data 20 msec blocks Interleaver Power Control Puncturing 19.2 kbps 800 bps P.C. MUX 9.6 kbps 19.2 kbps 3/4 rate 1/2 rate 14.4 kbps 19.2 kbps Convolutional Encoder Long Code Scrambling Short Code Scrambler Forward Link Traffic Channel Physical Layer

25 H Advanced Concepts of CDMA SLIDE 25 Copyright Hewlett Packard © 1999 CDMA Vocoders Vocoders Convert Voice to/from Analog Using Data Compression There are Three CDMA Vocoders: –IS-96A Variable Rate (8 kbps maximum) –CDG Variable Rate (13 kbps maximum) –EVRC Variable Rate (improved 8 kbps) Each Has Different Voice Quality: IS-96A - moderate quality EVRC - near toll quality CDG - toll quality

26 H Advanced Concepts of CDMA SLIDE 26 Copyright Hewlett Packard © bits in a 20 ms Frame Information Bits CRC Encoder Tail Bits 9600 bps Frame bits in a 20 ms Frame Information Bits 4800 bps Frame bits in a 20 ms Frame Information Bits Encoder Tail Bits 2400 bps Frame bits in a 20 ms Frame Information Bits Encoder Tail Bits 1200 bps Frame CRC Encoder Tail Bits bits in a 20 ms Frame Information Bits CRC Encoder Tail Bits bits in a 20 ms Frame Information Bits bits in a 20 ms Frame Information Bits bits in a 20 ms Frame Information Bits bps Frame 7200 bps Frame 3600 bps Frame 1800 bps Frame CRC Encoder Tail Bits 8 CRC Encoder Tail Bits 6 CRC Encoder Tail Bits 1-bit Reserved or Frame Erasure Mixed Mode bit Mixed Mode bit Mixed Mode bit Mixed Mode bit Mixed Mode bit CDMA Frame Formats 1-bit Reserved or Frame Erasure

27 H Advanced Concepts of CDMA SLIDE 27 Copyright Hewlett Packard © Data In 9600 bps Data Out 9600 bps Data Out 9600 bps D DDDDDDD + Forward Error Protection Uses Half-Rate Convolutional Encoder Outputs Two Bits of Encoded Data for Every Input Bit

28 H Advanced Concepts of CDMA SLIDE 28 Copyright Hewlett Packard © 1999 Convolutional Encoder 14.4 kbps 19.2 kbps Vocoded Speech data 3/4 rate 20 msec blocks 14.4 TCH Forward Link Modifications Replaces 8 kbps Vocoder with a 13 kbps Vocoder (both Variable Rate) Effects: Provides Toll Quality Speech Uses a 3/4 Rate Encoder Reduces Processing Gain 1.76 dB Results in Reduced Capacity or Smaller Cell Sizes

29 H Advanced Concepts of CDMA SLIDE 29 Copyright Hewlett Packard © CDMA System Time How Does CDMA Achieve Synchronization for Efficient Searching ? Use GPS Satellite System Base Stations Use GPS Time via Satellite Receivers as a Common Time Reference GPS Clock Drives the Long Code Generator

30 H Advanced Concepts of CDMA SLIDE 30 Copyright Hewlett Packard © 1999 Modulo-2 Addition Long Code Output User Assigned Long Code Mask 42 bits Long Code Generator Long Code Generation

31 H Advanced Concepts of CDMA SLIDE 31 Copyright Hewlett Packard © 1999 Long Code Generator Encoded Voice Data 19.2 kbps Mbps XOR Long Code Decimator 19.2 kbps 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

32 H Advanced Concepts of CDMA SLIDE 32 Copyright Hewlett Packard © 1999 Long Code Decimated Data Long Code Scrambled Voice Data 19.2 kbps Long Code Decimator 19.2 kbps 800 bps P.C. Mux Closed Loop Power Control Bits 800 bps 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

33 H Advanced Concepts of CDMA SLIDE 33 Copyright Hewlett Packard © 1999 W = W = W = 0 1 n n n n W W = 2n2n Walsh Codes

34 H Advanced Concepts of CDMA SLIDE 34 Copyright Hewlett Packard © 1999 Cross Correlation N agreements - N disagreements N total_number_of_digits = W = Y Y N N 2 match - 2 don't =0 Checking for Orthogonality

35 H Advanced Concepts of CDMA SLIDE 35 Copyright Hewlett Packard © 1999 What is the Spreading Rate Increase ? Encoded Voice Data 19.2 kbps Mbps XOR Walsh Code Generator Walsh Code Spreading

36 H Advanced Concepts of CDMA SLIDE 36 Copyright Hewlett Packard © 1999 To I/Q Modulator Mbps Q Channel Short Sequence Code Generator Walsh Coded Data at Mbps I Channel Short Sequence Code Generator 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

37 H Advanced Concepts of CDMA SLIDE 37 Copyright Hewlett Packard © 1999 chip Pseudo-Random Sequence 0 chip offset Auto-Correlation Versus Time Offset Auto-Correlation Is a Comparison of a Signal Against Itself Good Pseudo- Random Patterns Have: Strong Correlation at Zero Time Offset Weak Correlation at Other Time Offsets

38 H Advanced Concepts of CDMA SLIDE 38 Copyright Hewlett Packard © 1999 chip offset Auto-Correlation Versus Time Offset with 17 dB Noise Added Short Code Correlation –Short Codes Are Designed to Have: Strong Auto-Correlation at Zero Time Offset Weak Auto-Correlation at Other Offsets Good Auto-Correlation In Very Poor Signal-to -Noise Ratio Environments –Allows Fast Acquisition in Real World Environment

39 H Advanced Concepts of CDMA SLIDE 39 Copyright Hewlett Packard © kbps Walsh Code 32 Walsh Code 0 Pilot Channel Sync Channel Walsh Codes 1 to 7 Walsh Codes 8-31, Traffic Channels 1 up to 55 Channels All 0's 19.2 kbps kbps I Convert to I/Q & Short Code Spreading Convert to I/Q & Short Code Spreading Convert to I/Q & Short Code Spreading FIR LP Filter & D/A Conversion FIR LP Filter & D/A Conversion FIR LP Filter & D/A Conversion FIR LP Filter & D/A Conversion Q 4.8 kbps I Data Q Data Paging Channels 1 up to 7 Channels 19.2 kbps kbps Convert to I/Q & Short Code Spreading Forward Link Channel Format

40 H Advanced Concepts of CDMA SLIDE 40 Copyright Hewlett Packard © Sum of A & B Walsh Encoded Data Streams W = User A - User B For a 0 Input, Use Code 00 Channel A Voice Data Channel A Walsh Encoded Voice Data For a 1 Input, Use Code User A For a 0 Input, Use Code For a 1 Input, use code Channel B Voice Data Channel B Walsh Encoded Voice Data User B Walsh Coding Example

41 H Advanced Concepts of CDMA SLIDE 41 Copyright Hewlett Packard © 1999 Original User A Voice Data Multiply Summed Data with Desired Walsh Code User A + B Walsh Data +2 Correlation Coefficient x = Original User B Voice Data = 1 +2 Multiply Summed Data with Desired Walsh Code User A + B Walsh Data 1 T 0 T z = ij f i (t) f j dt = = x 1 - Walsh Decoding Example

42 H Advanced Concepts of CDMA SLIDE 42 Copyright Hewlett Packard © Sum of A & B Walsh Encoded Data Streams Channel A Walsh Encoded Voice Data Channel B Walsh Encoded Voice Data Multiply Summed Data with Desired Walsh Code x = = Original Data Was 0 (-1), We Have Interference Now! Original Time Delayed What if Walsh Codes are Not Time Aligned ?

43 H Advanced Concepts of CDMA SLIDE 43 Copyright Hewlett Packard © 1999 Uses Walsh Code 0: All 64 bits are 0 All Data into Walsh Modulator is 0 Output of Walsh Modulator is Therefore all 0's Pilot Channel is just the Short Codes Q Walsh Code 0 I Short Code Q Short Code FIR Mbps Walsh Code Generator I Mbps Mbps All 0 input Short Code Scrambler Walsh Modulator Pilot Channel Physical Layer

44 H Advanced Concepts of CDMA SLIDE 44 Copyright Hewlett Packard © 1999 Walsh 32 Cover I Short Code Q Short Code FIR Mbps Walsh Code Generator I Q Mbps Mbps Sync Channel Message Data Interleaver 4.8 kbps 1/2 rate Convolutional Encoder Short Code Scrambler 2x2x 4.8 kbps Symbol Repetition 2.4 kbps 1.2 kbps Sync Channel Physical Layer

45 H Advanced Concepts of CDMA SLIDE 45 Copyright Hewlett Packard © 1999 Walsh 1 to 7 Cover I Short Code Q Short Code FIR Mbps Walsh Code Generator I Q Mbps Mbps 19.2 kbps Paging Channel Long Code 19.2 kbps Long Code Scrambling Short Code Scrambler Paging Channel Message Data Interleaver 19.2 kbps 1/2 rate Convolutional Encoder 2x2x 19.2 kbps Symbol Repetition 9.6 kbps 4.8 kbps Paging Channel Physical Layer

46 H Advanced Concepts of CDMA SLIDE 46 Copyright Hewlett Packard © 1999 Interleaver I Short Code Q Short Code Mbps I Q kbps t/2 1/2 Chip Delay 28.8 kbps 20 msec blocks Vocoded Speech Data 64-ary Modulator Mbps 1 of 64 Walsh Codes Long Code Mbps FIR Walsh Code 1 Walsh Code 2 Walsh Code 0 Walsh Code 62 Walsh Code 63 Walsh Code 61 Convolutional Encoder 9.6 kbps 28.8 kbps 1/3 rate 1/2 rate 14.4 kbps 28.8 kbps Long Code Modulator Short Code Scrambler Reverse Link Traffic Channel Physical Layer

47 H Advanced Concepts of CDMA SLIDE 47 Copyright Hewlett Packard © 1999 Data In 9600 bps Data Out 9600 bps Data Out 9600 bps + D DDDDDDD + + Data Out 9600 bps Reverse Error Protection Uses Third-Rate Convolutional Encoder Outputs Three Bits for Every Input Bit

48 H Advanced Concepts of CDMA SLIDE 48 Copyright Hewlett Packard © 1999 Convolutional Encoder 14.4 kbps 28.8 kbps Vocoded Speech data 1/2 rate 20 msec blocks 14.4 TCH Reverse Link Modifications Replaces 8 kbps Vocoder with a 13 kbps Vocoder (both Variable Rate) Effects: Provides Toll Quality Speech Uses a 1/2 Rate Encoder Reduces Processing Gain 1.76 dB Results in Reduced Capacity or Smaller Cell Sizes

49 H Advanced Concepts of CDMA SLIDE 49 Copyright Hewlett Packard © kbps Walsh Code 1 Walsh Code 2 Walsh Code 0 Walsh Code 62 Walsh Code 63 Walsh Code 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 kbps: (28.8 kbps * 64 bits)/ 6 bits = kbps) Is Not the Channelization for the Reverse Link

50 H Advanced Concepts of CDMA SLIDE 50 Copyright Hewlett Packard © 1999 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

51 H Advanced Concepts of CDMA SLIDE 51 Copyright Hewlett Packard © 1999 Walsh Modulated Voice Data kbps Mbps XOR Long Code Generator Reverse Channel Long Code Spreading Long Code Spreading Provides Unique Mobile Channelization Mobiles are Uncorrelated but not Orthogonal with Each Other

52 H Advanced Concepts of CDMA SLIDE 52 Copyright Hewlett Packard © 1999 t/2 Q FIR I Short Code Q Short Code Mbps I 1/2 Chip Delay Mbps FIR 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

53 H Advanced Concepts of CDMA SLIDE 53 Copyright Hewlett Packard © 1999 I Q I Q OQPSK Modulation QPSK Makes one Symbol Change Every Period OQPSK Makes two Symbol Changes Every Period if both I and Q Data Changes Example Symbol Pattern is: – 00, 10, 01,11

54 H Advanced Concepts of CDMA SLIDE 54 Copyright Hewlett Packard © 1999 I Filtered Offset QPSK Filtered QPSK II QQ Base Station Pilot Channel TX Mobile Station TX CDMA Modulation Formats

55 H Advanced Concepts of CDMA SLIDE 55 Copyright Hewlett Packard © 1999 FunctionForward Link {Base to Mobile} Reverse Link {Mobile to Base} 9.6 kbps Convolutional Encoder 1/2 Rate {9600 in out} 1/3 Rate {9600 in out} 14.4 kbps Convolutional Encoder 3/4 Rate {14400 in out} 1/2 Rate {14400 in out} Walsh CodingChannelization64-ary Modulation Long Code Spreading Voice PrivacyChannelization Short Code Spreading Base Station Identification Aid Base Station Searching Channelization Summary

56 H Advanced Concepts of CDMA SLIDE 56 Copyright Hewlett Packard © 1999 Forward Link {Base to Mobile} Reverse Link {Mobile to Base} + -High Power Transmitter -Pilot Channel -Added Time Diversity -Orthogonal Code Channels -Wide Range Power Control -Diversity Reception at Base - -Complexity of Soft Handoff -Non-coherent Demodulation -Limited Power -Uncorrelated Code Channels Link Advantages & Disadvantages

57 H Advanced Concepts of CDMA SLIDE 57 Copyright Hewlett Packard © 1999 Layer 2 Multiplex Sublayer Layer 1 Physical Layer Channel Data bps or bps Traffic Channel Primary Traffic Layer 2 Signaling Layer 2 Link Layer Paging & Access Channels Layer 3 Call Processing and Control CDMA Multiplex Sublayer

58 H Advanced Concepts of CDMA SLIDE 58 Copyright Hewlett Packard © 1999 CDMA Service Options Service Options Are: 1- Voice Using 9600 bps IS-96-A Vocoder 2- Rate Set 1 Loopback (9600 bps) 3- Voice Using 9600 bps (EVRC) 4- Asynchronous Data Service (circuit switched) 5- Group 3 Fax 6- Short Message Service (9600 bps) 7- Internet Standard PPP Packet Data 8- CDPD Over PPP Packet Data 9- Rate Set 2 Loopback (14400 bps) 14-Short Message Service (14400 bps) 32,768- Voice Using bps (CDG)

59 H Advanced Concepts of CDMA SLIDE 59 Copyright Hewlett Packard © 1999 EIA/TIA 95-B Combines TSB-74 & J-STD-008 for a Universal Protocol J-STD-008 Not Backwards Compatible, PCS only Protocol IS-95 Rev A Backwards Compatible with IS-95. First Deployed Protocol IS-95 Rev 0 Original System- never actually deployed. TSB-74 Cellular Protocol that adds Channel Support ARIB T53 Japan CDMA System Cellular Protocol CDMA Protocol Stacks

60 H Advanced Concepts of CDMA SLIDE 60 Copyright Hewlett Packard © 1999 Ten Minutes in the Life of a CDMA Mobile Phone Turn-on –System Access Travel –Idle State Hand-Off Initiate Call System Access Continue Travel –Initiate Soft Handoff –Terminate Soft Handoff End Call

61 H Advanced Concepts of CDMA SLIDE 61 Copyright Hewlett Packard © 1999 CDMA Turn On Process Find All Receivable Pilot Signals –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

62 H Advanced Concepts of CDMA SLIDE 62 Copyright Hewlett Packard © 1999 SYNC Sync Channel Message Contains the Following Data: Base Station Protocol Revision Min Protocol Revision Supported SID, NID of Cellular System Pilot PN Offset of Base Station Long Code State System Time Leap Seconds From Start of System Time Local Time Offset from System Time Daylight Savings Time Flag Paging Channel Data Rate Channel Number

63 H Advanced Concepts of CDMA SLIDE 63 Copyright Hewlett Packard © 1999 Paging Read the Paging Channel Demodulate the Paging Channel: 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

64 H Advanced Concepts of CDMA SLIDE 64 Copyright Hewlett Packard © 1999 – Overhead Messages System Parameters Access Parameters CDMA Channel List Extended System Params Extended Neighbor List – Other Messages Order Channel Assignment Data Burst – More Messages Authentication SSD Update Feature Notification Status Request Service Redirection General Page Global Service Redirection TMSI Assignment J-STD-008 Paging Messages: Paging Channel Messages

65 H Advanced Concepts of CDMA SLIDE 65 Copyright Hewlett Packard © 1999 CDMA Idle State Handoff No Call In Progress Mobile Listens to New Cell Move Registration Location if Entering a New Zone

66 H Advanced Concepts of CDMA SLIDE 66 Copyright Hewlett Packard © 1999 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: Access & Paging Channel Numbers Base Station ID Pilot PN Offset

67 H Advanced Concepts of CDMA SLIDE 67 Copyright Hewlett Packard © 1999 Interleaver I Short Code Q Short Code Mbps I Q kbps t/2 1/2 Chip Delay 28.8 kbps 64-ary Modulator Mbps 1 of 64 Walsh Codes Access Channel Long Code Mbps FIR Walsh Code 1 Walsh Code 2 Walsh Code 0 Walsh Code 62 Walsh Code 63 Walsh Code 61 Long Code Modulator Short Code Scrambler Access Channel Message Data Convolutional Encoder 2x2x 28.8 kbps Symbol Repetition 14.4 kbps 4.8 kbps 1/3 rate Reverse Link Access Channel Physical Layer

68 H Advanced Concepts of CDMA SLIDE 68 Copyright Hewlett Packard © 1999 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

69 H Advanced Concepts of CDMA SLIDE 69 Copyright Hewlett Packard © 1999 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

70 H Advanced Concepts of CDMA SLIDE 70 Copyright Hewlett Packard © 1999 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

71 H Advanced Concepts of CDMA SLIDE 71 Copyright Hewlett Packard © 1999 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

72 H Advanced Concepts of CDMA SLIDE 72 Copyright Hewlett Packard © 1999 CDMA End of Call Mobile or Land Initiated Mobile and Base Stop Transmission Land Connection Broken

73 H Advanced Concepts of CDMA SLIDE 73 Copyright Hewlett Packard © 1999 CDMA CDMA Conclusions New Access Method –Code Based Designed for Use in Interfering Environment Uses Multipath to Improve Reception in Fading Conditions Has High Capacity –6 Times Analog for 14.4 kbps Voice –10 Times Analog for 9.6 kbps Voice


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