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

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CDMA Technology HighlightsCDMA Technology Overview
There are two types of CDMA Reverse Channels:
TRAFFIC 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
ACCESS 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
REG
1-800
242
4444
BTS
its CDMA RF carrier Frequency
the unique Long Code PN Offset of the individual handset
CDMA
Frequency
MTX
BSC
Respond to Paging Channel messages
Has a fixed data rate of 4800 bps
Each Access Channel is associated with only one Paging Channel
Up to 32 access channels (0-31) are supported per Paging Channel
4800 bps
Two 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
February, 2001 - Page 3-*
Access Channel Block Interleaving
576 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
Block 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
(4800 x 2 bps - Write Matrix)
1 17 33 49 65 81 97 113 129 145 161 177 193 209 225 241 257 273
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
16 32 48 64 80 96 112 128 144 160 176 192 208 224 240 256 272 288
CDMA Technology Overview
(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
CDMA Technology Overview
4800 bps
96 x Nf bits (not exceeding 3 + MAX_CAP_SZ frames)
Access Channel Slot
Voice traffic from the subscriber
Response to commands/queries from the base station
Requests to the base station
Supports variable data rate operation for
8 Kbps vocoder
Multiplex Option 1
13 Kbps vocoder
Multiplex Option 2
CDMA Technology Overview
Transmission
Rate
Total
Erasure
Information
CRC
Rate
Set
Convolutional 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
Symbol repetition maintains a constant 28.8 ksps output to block interleaver
PCM Voice
28.8 ksps (No repetition)
Symbol
Repetition
20 ms symbol blocks are sequentially reordered
Combats the effects of fast fading
Separates repeated symbols at 4800 bps and below
Improves survivability of symbol data
“Spreads” the effect of spurious interference
28.8 ksps
From Coding
Lesson Review
The two types of CDMA Reverse Channels are Traffic Channels and Access Channels. [True/False]
True
Phase Modulation
How many access channels are supported by a single paging channel?
32 (0 - 31)
When generating the Access Channel, why are message attempts randomized?
To reduce the probability of collision
What is the access channel preamble?
A frame comprised of 96 zeroes that aids the base station in acquiring access channel transmission.
CDMA Technology Overview
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
a and c
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
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.
What is used in the reverse path: direct sequence spreading or data scrambling?
Direct sequence spreading
CDMA Technology Overview

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