1. CDMA Technology OverviewFebruary, 2001 - Page 3-1 CDMA Technology Overview Lesson 4 - CDMA Reverse Channels

2. CDMA Technology OverviewFebruary, 2001 - Page 3-2 Access Channels

3. CDMA Technology OverviewFebruary, 2001 - Page 3-3 REG 1-800 242 4444 BTS Code Channels in the Reverse Direction There are two types of CDMA Reverse Channels: nTRAFFIC CHANNELS are used by individual users during their actual calls to transmit traffic to the BTS  a reverse traffic channel is defined by a user-specific public or private Long Code mask  there are as many reverse Traffic Channels as there are CDMA phones in the world nACCESS CHANNELS are used by mobile stations not yet in a call to transmit registration requests, call setup requests, page responses, order responses, and other signaling information  an access channel is defined by a user-independent public long code mask  Access channels are paired with Paging Channels. There can be up to 32 access channels per paging channel

4. CDMA Technology OverviewFebruary, 2001 - Page 3-4 MTXBSCBTS (1 sector) Channel Element Access Channels Vocoder more Receiver, Sector X Channel Element Long Code Gen more User Long Code User Long Code User Long Code User Long Code User Long Code User Long Code Coding Process in the Reverse Direction A Reverse Channel is identified by: v its CDMA RF carrier Frequency v the unique Long Code PN Offset of the individual handset CDMA Frequency

5. CDMA Technology OverviewFebruary, 2001 - Page 3-5 Access Channels nUsed by the mobile station to  Initiate communication with the base station  Respond to Paging Channel messages nHas a fixed data rate of 4800 bps nEach Access Channel is associated with only one Paging Channel nUp to 32 access channels (0-31) are supported per Paging Channel 4800 bps

6. CDMA Technology OverviewFebruary, 2001 - Page 3-6 Access Channel Generation nMessage attempts are randomized to reduce probability of collision nTwo message types:  A response message (in response to a base station message)  A request message (sent autonomously by the mobile station) 28.8 ksps Convolutional Encoder & Repetition R = 1/3 1.2288 Mcps Access Channel Long Code Mask Long PN Code Generator 28.8 ksps Orthogonal Modulation 307.2 kcps 1.2288 Mcps Q PN (No Offset) I PN (No Offset) D 1/2 PN Chip Delay Block Interleaver Access Channel Information (88 bits/Frame) 4.8 kpbs Direct Sequence Spreading

7. CDMA Technology OverviewFebruary, 2001 - Page 3-7 Rate 1/3 Convolutional Encoder + + + g0g0 g1g1 g2g2 Information bits (INPUT) Code Symbols (OUTPUT) Code Symbols (OUTPUT) Code Symbols (OUTPUT) 12345678

8. CDMA Technology OverviewFebruary, 2001 - Page 3-8 Access Channel Block Interleaving n576 code symbols (288 x 2) are written sequentially by columns, then read by rows in a particular order (called “bit-reverse readout of the row addresses”) every 20 ms nBlock interleaving separates repeated symbols in two identical sets: one set is transmitted during the first 10 ms and the second set, with the repetitions, is transmitted during the second 10 ms  Improves survivability of symbol information  “Spreads” the effect of spurious interference and fast fading 28.8 ksps from Conv. Encoding & Symbol Repetition (2x) Input Array (Normal Sequence) 32 x 18 Output Array (Reordered Sequence) 32 x 18 28.8 ksps to Orthogonal Modulation

9. CDMA Technology OverviewFebruary, 2001 - Page 3-9 Access Channel Block Interleaving (4800 x 2 bps - Write Matrix) 1 17 33 49 65 81 97 113 129 145 161 177 193 209 225 241 257 273 2 18 34 50 66 82 98 114 130 146 162 178 194 210 226 242 258 274 3 19 35 51 67 83 99 115 131 147 163 179 195 211 227 243 259 275 4 20 36 52 68 84 100 116 132 148 164 180 196 212 228 244 260 276 5 21 37 53 69 85 101 117 133 149 165 181 197 213 229 245 261 277 6 22 38 54 70 86 102 118 134 150 166 182 198 214 230 246 262 278 7 23 39 55 71 87 103 119 135 151 167 183 199 215 231 247 263 279 8 24 40 56 72 88 104 120 136 152 168 184 200 216 232 248 264 280 9 25 41 57 73 89 105 121 137 153 169 185 201 217 233 249 265 281 10 26 42 58 74 90 106 122 138 154 170 186 202 218 234 250 266 282 11 27 43 59 75 91 107 123 139 155 171 187 203 219 235 251 267 283 12 28 44 60 76 92 108 124 140 156 172 188 204 220 236 252 268 284 13 29 45 61 77 93 109 125 141 157 173 189 205 221 237 253 269 285 14 30 46 62 78 94 110 126 142 158 174 190 206 222 238 254 270 286 15 31 47 63 79 95 111 127 143 159 175 191 207 223 239 255 271 287 16 32 48 64 80 96 112 128 144 160 176 192 208 224 240 256 272 288

10. CDMA Technology OverviewFebruary, 2001 - Page 3-10 Access Channel Block Interleaving (4800 x 2 bps - Read Matrix) 1 17 33 49 65 81 97 113 129 145 161 177 193 209 225 241 257 273 9 25 41 57 73 89 105 121 137 153 169 185 201 217 233 249 265 281 5 21 37 53 69 85 101 117 133 149 165 181 197 213 229 245 261 277 13 29 45 61 77 93 109 125 141 157 173 189 205 221 237 253 269 285 3 19 35 51 67 83 99 115 131 147 163 179 195 211 227 243 259 275 11 27 43 59 75 91 107 123 139 155 171 187 203 219 235 251 267 283 7 23 39 55 71 87 103 119 135 151 167 183 199 215 231 247 263 279 15 31 47 63 79 95 111 127 143 159 175 191 207 223 239 255 271 287 2 18 34 50 66 82 98 114 130 146 162 178 194 210 226 242 258 274 10 26 42 58 74 90 106 122 138 154 170 186 202 218 234 250 266 282 6 22 38 54 70 86 102 118 134 150 166 182 198 214 230 246 262 278 14 30 46 62 78 94 110 126 142 158 174 190 206 222 238 254 270 286 4 20 36 52 68 84 100 116 132 148 164 180 196 212 228 244 260 276 12 28 44 60 76 92 108 124 140 156 172 188 204 220 236 252 268 284 8 24 40 56 72 88 104 120 136 152 168 184 200 216 232 248 264 280 16 32 48 64 80 96 112 128 144 160 176 192 208 224 240 256 272 288 1 17 33 49 65 81 97 113 129 145 161 177 193 209 225 241 257 273 9 25 41 57 73 89 105 121 137 153 169 185 201 217 233 249 265 281 5 21 37 53 69 85 101 117 133 149 165 181 197 213 229 245 261 277 13 29 45 61 77 93 109 125 141 157 173 189 205 221 237 253 269 285 3 19 35 51 67 83 99 115 131 147 163 179 195 211 227 243 259 275 11 27 43 59 75 91 107 123 139 155 171 187 203 219 235 251 267 283 7 23 39 55 71 87 103 119 135 151 167 183 199 215 231 247 263 279 15 31 47 63 79 95 111 127 143 159 175 191 207 223 239 255 271 287 2 18 34 50 66 82 98 114 130 146 162 178 194 210 226 242 258 274 10 26 42 58 74 90 106 122 138 154 170 186 202 218 234 250 266 282 6 22 38 54 70 86 102 118 134 150 166 182 198 214 230 246 262 278 14 30 46 62 78 94 110 126 142 158 174 190 206 222 238 254 270 286 4 20 36 52 68 84 100 116 132 148 164 180 196 212 228 244 260 276 12 28 44 60 76 92 108 124 140 156 172 188 204 220 236 252 268 284 8 24 40 56 72 88 104 120 136 152 168 184 200 216 232 248 264 280 16 32 48 64 80 96 112 128 144 160 176 192 208 224 240 256 272 288

11. CDMA Technology OverviewFebruary, 2001 - Page 3-11 Access Channel Structure

12. CDMA Technology OverviewFebruary, 2001 - Page 3-12 Access Channel Probing Access Probe 1 Access Probe 1 Access Probe 1 Access Probe 1 Access Probe 1 + NUM_STEP (16 max) System Time TARTTARTTARTTA PI IP (Initial Power) See previous figure ACCESS PROBE SEQUENCE Select Access Channel (RA) initialize transmit power

13. CDMA Technology OverviewFebruary, 2001 - Page 3-13 Reverse Traffic Channels

14. CDMA Technology OverviewFebruary, 2001 - Page 3-14 CDMA Reverse Traffic Channels nUsed when a call is in progress to send  Voice traffic from the subscriber  Response to commands/queries from the base station  Requests to the base station nSupports variable data rate operation for  8 Kbps vocoder  Rate Set 1 - 9600, 4800, 2400 and 1200 bps  Multiplex Option 1  13 Kbps vocoder  Rate Set 2 - 14400, 7200, 3600, 1800 bps  Multiplex Option 2

15. CDMA Technology OverviewFebruary, 2001 - Page 3-15 Reverse Traffic Channel Generation 9600 bps 4800 bps 2400 bps 1200 bps or 14400 bps 7200 bps 3600 bps 1800 bps 28.8 ksps R = 1/3 1.2288 Mcps User Address Mask Long PN Code Generator 28.8 ksps Orthogonal Modulation Data Burst Randomizer 307.2 kcps 1.2288 Mcps Q PN (no offset) I PN (no offset) D 1/2 PN Chip Delay Direct Sequence Spreading R = 1/2 Convolutional Encoder & Repetition Block Interleaver

16. CDMA Technology OverviewFebruary, 2001 - Page 3-16 Reverse Traffic Channel Frame Structure Transmission Rate Total Erasure InformationCRCTail Bits 9600 192 —172128 4800 96 —8088 2400 48 —40—8 1200 24 —16—8 14400 2881 267128 7200 1441 125108 3600 721 5588 1800 361 2168 1 2 Number of Bits per Frame Rate Set

17. CDMA Technology OverviewFebruary, 2001 - Page 3-17 Reverse Traffic Channel Convolutional Encoding & Symbol Repetition nConvolutional encoding:  Results in 3 code symbols out for each bit in, at Rate Set 1, and in 2 code symbols out for each bit in, at Rate Set 2  Also allows for reduction in transmit power  Reduces overall noise & increases capacity nSymbol repetition maintains a constant 28.8 ksps output to block interleaver PCM Voice Convolutional Encoding Code Symbol Repetition Block Interleaving Orthogonal Modulation Data Burst Randomizer Direct Sequence Spreading Quadrature Spreading Baseband Filtering Vocoder Processing Baseband Traffic to RF Section Variable Rate Output from Vocoder R=1/3 K=9 Convolutional Encoder R=1/2 K=9 28.8 ksps to Block Interleaver 28.8 ksps (No repetition) 14.4 ksps (2 X repetition) 7.2 ksps (4 X repetition) 3.6 ksps (8 X repetition) 28.8 ksps (No repetition) 14.4 ksps (2 X repetition) 7.2 ksps (4 X repetition) 3.6 ksps (8 X repetition) Symbol Repetition 9.6 kbps 4.8 kbps 2.4 kbps 1.2 kbps 14.4 kbps 7.2 kbps 3.6 kbps 1.8 kbps

18. CDMA Technology OverviewFebruary, 2001 - Page 3-18 Reverse Traffic Channel Block Interleaving n20 ms symbol blocks are sequentially reordered nCombats the effects of fast fading nSeparates repeated symbols at 4800 bps and below  Improves survivability of symbol data  “Spreads” the effect of spurious interference PCM Voice Convolutional Encoding Code Symbol Repetition Block Interleaving Vocoder Processing Baseband Traffic to RF Section Orthogonal Modulation Data Burst Randomizer Direct Sequence Spreading Quadrature Spreading Baseband Filtering 28.8 ksps From Coding & Symbol Repetition Output Array (Reordered Sequence) 32 x 18 28.8 ksps to Orthogonal Modulation Input Array (Normal Sequence) 32 x 18

19. CDMA Technology OverviewFebruary, 2001 - Page 3-19 Lesson Review 1.The two types of CDMA Reverse Channels are Traffic Channels and Access Channels. [True/False] True 2.Short PN sequences are used to achieve _____________________. Phase Modulation 3.How many access channels are supported by a single paging channel? 32 (0 - 31) 4.When generating the Access Channel, why are message attempts randomized? To reduce the probability of collision 5.What is the access channel preamble? A frame comprised of 96 zeroes that aids the base station in acquiring access channel transmission.

20. CDMA Technology OverviewFebruary, 2001 - Page 3-20 Lesson Review, cont’d 6.All Access Channels associated with a particular Paging Channel a. have the same slot size b. do not have the same slot size c. all slots begin at the same time d. all slots do not begin at the same time e. a and c f. a and d g. none of the above a and c 7.Why is the Reverse Traffic Channel preamble transmitted by the mobile to the base station? To help the base station acquire the Reverse Traffic Channel 8.The pilot PN sequences are offset relative to system time, not mobile station time. Why? The mobile draws its time reference from the earliest usable pilot component it receives. 9.What is used in the reverse path: direct sequence spreading or data scrambling? Direct sequence spreading

21. CDMA Technology OverviewFebruary, 2001 - Page 3-21