3- Scrambling Code Planning.pdf

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2 Nokia Siemens Networks BSS12 Release Content / TAL & PJD / 05 2008

Confidential

Primary Scrambling Code Planning

Collected & Presented: Mohammad Tourchian

June 2010


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Scrambling Code Planning

Primary Scrambling Code is used to distinguish base station transmissions on the downlinkdirection.

Although, the use of Scrambling Codes does not lower the interference level of thecells, it does assist on theIDENTIFICATION "of Node B within areas of interference.

If the SC are repeated within a short distance , there is a risk that two identical SC(from two cells) will be present in the Monitored Set. This can occur when for exampleActive Set=3 and three neighbor cell list are merged.

Same/Co-SC will result into dropped calls and poor network quality.

Therefore, it is a Planning & Optimization advantage if the neighboring cells are not

under the same group and there is a considerable distance in between each group.

To address the forecasted demand for more 3G based subscribers application, it isimportant to assume that more 3G sites for both Indoor and Outdoor would be needed .Thus, proper SC plan which is future proof, expansion ready and applicable for dense-urban area is a must.


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Hereunder the used and proposed SC planning scheme forDU network in Dubai

will be discussed.

Disadvantages of old plan:

1. Unbalanced SC allocation /re-used for Outdoor & Indoor Sites

SC30 was used 5 times for Indoor, while 1 time for Outdoor.

SC31 was used 7 times for Indoor, while 1 time for Outdoor.

SC 30, SC 31 are originally allocated for IBS use, there fore should not be used forany Macro Sites.

To avoid cases like this, different set of SC should be allocated for Indoor &Outdoor sites respectively.

2. Insufficient distance between two similar SCs (particularly IBS)

Same SCs were observed on building located within short proximity from eachother.

Example below are DIFC Indoor Sites:


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3. SC Collision (Merged Neighbour List)

ADJS Relat ion:

Combined Neighbour:

The above example shows that there is noconsiderable separation in between sitescausing SC collision once the neighbour list aremerged.

WBTSId PriScrCode AdjsCI PriScrCode

37973 181 34812 244

34773 181 31592 289

34812 244 31592 289

Active Set PriScrCode Monitored Set PriScrCode

34812 244 37973 181

31592 289 34773 181


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Proposed SC Plan Strategy Dubai

There are 512 Primary Scrambling Code available.

These 512 available codes will be divided into 8 groups. Each group will be assigned into 1Cluster.

Clusterswill be named as Cluster 1, Cluster 2 Cluster 8.

Each cluster will consist of 64 codes.

These 64 codes are good for 21 sites (3 sector /site) plus 1 reserved scrambling code.

The available 64 codes can be group (Code Group) in accordance to the Site/Coverage Type.a. Outdoor (Macro, Micro)

b. Indoor

Eventhough, 21 sites can be allocated per Cluster, it is safe to assume that 1 Cluster willconsist of around 16 Macro Sites (3 sector) only. The remaining SC will be specificallyallocated for Indoor use.

There is no standard on the number of cell an IBS could have, where as most design has morethan 3 sector per site.

Thus, separate set of SC will be allocated for Indoor Sites. In case that this is not enough tocater big developments, it is recommended to re-use the codes following the proposedseparation.


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There should be at least 2 cluster separation when re-using the SC Group. Meaning that there will

be enough distance between two same cluster in a dense urban network scenario such as Dubai.

This strategy will ensure the following:

a. No cells on the Neighbour List will have the same code

b. No duplicate scrambling code present on Active Set, Monitored Set

c. No code re-use in a user definable distance

Preferably, Special Projects/Developments such as Palm Jumeirah should be assigned as 1Cluster ,assuming that the number of sites will fall on the proposed method.

Cluster assignment will be from Left to Right convention.

To determine the proper Scrambling Code allocation, it is vital to consider the following:

a. Existing number of 3G Sites

b. Future number of 3G Sites

c. Site Distribution between Indoor & Outdoor (Macro, Micro)



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To allocate sufficient Scrambling Code for both site type, it is proposed to use the belowconvention.

+10% margin site are added for both Indoor & Outdoor Site.

Reserved Scrambling Codes (SC 0,1,2,3,4,5,6,7) will be used for VIP , Special Events andother immediate requirement.

Indoor sites are intentionally allocated with high Scrambling Code number (SC Range: 392-

511)to immediately distinguish it from the rest of the Outdoor sites in one particular area.

Site Type No. Of Sites % SC Needed Code Group

Outdoor (Macro/Micro) 688 73% 370 48 (46)

Indoor 250 27% 134 15 (17)

Reserved 8 1

Total 937 100% 512 64



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LEGEND:

Cluster 1

Cluster 2

Cluster 3

Cluster 4

Cluster 5

Cluster 6

Cluster 7

Cluster 8



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1 2 3 4 5 6 7 8

Reser ved 0 0 1 2 3 4 5 6 7

1 8 9 10 11 12 13 14 15 1

2 16 17 18 19 20 21 22 23 2 1

3 24 25 26 27 28 29 30 31 3

4 32 33 34 35 36 37 38 39 1

5 40 41 42 43 44 45 46 47 2 2

6 48 49 50 51 52 53 54 55 3

7 56 57 58 59 60 61 62 63 1

8 64 65 66 67 68 69 70 71 2 3

9 72 73 74 75 76 77 78 79 3

10 80 81 82 83 84 85 86 87 1

11 88 89 90 91 92 93 94 95 2 4

12 96 97 98 99 100 101 102 103 3

13 104 105 106 107 108 109 110 111 1

14 112 113 114 115 116 117 118 119 2 5

15 120 121 122 123 124 125 126 127 3

16 128 129 130 131 132 133 134 135 1

17 136 137 138 139 140 141 142 143 2 6

18 144 145 146 147 148 149 150 151 3

19 152 153 154 155 156 157 158 159 1

20 160 161 162 163 164 165 166 167 2 7

21 168 169 170 171 172 173 174 175 3

22 176 177 178 179 180 181 182 183 1

23 184 185 186 187 188 189 190 191 2 8

24 192 193 194 195 196 197 198 199 3

25 200 201 202 203 204 205 206 207 1

26 208 209 210 211 212 213 214 215 2 9

27 216 217 218 219 220 221 222 223 3

28 224 225 226 227 228 229 230 231 1

29 232 233 234 235 236 237 238 239 2 10

30 240 241 242 243 244 245 246 247 3

31 248 249 250 251 252 253 254 255 1

32 256 257 258 259 260 261 262 263 2 11

33 264 265 266 267 268 269 270 271 3

34 272 273 274 275 276 277 278 279 1

35 280 281 282 283 284 285 286 287 2

36 288 289 290 291 292 293 294 295 3

37 296 297 298 299 300 301 302 303 1

38 304 305 306 307 308 309 310 311 2

39 312 313 314 315 316 317 318 319 3

40 320 321 322 323 324 325 326 327 1

41 328 329 330 331 332 333 334 335 2 14

42 336 337 338 339 340 341 342 343 3

43 344 345 346 347 348 349 350 351 1

44 352 353 354 355 356 357 358 359 2

45 360 361 362 363 364 365 366 367 3

46 368 369 370 371 372 373 374 375 1

47 376 377 378 379 380 381 382 383 2

48 384 385 386 387 388 389 390 391 3

49 392 393 394 395 396 397 398 399 1

50 400 401 402 403 404 405 406 407 2

51 408 409 410 411 412 413 414 415 3

52 416 417 418 419 420 421 422 423 1

53 424 425 426 427 428 429 430 431 2

54 432 433 434 435 436 437 438 439 3

55 440 441 442 443 444 445 446 447 1

56 448 449 450 451 452 453 454 455 2

57 456 457 458 459 460 461 462 463 3

58 464 465 466 467 468 469 470 471 1

59 472 473 474 475 476 477 478 479 2

60 480 481 482 483 484 485 486 487 3

61 488 489 490 491 492 493 494 495 1

62 496 497 498 499 500 501 502 503 2

63 504 505 506 507 508 509 510 511 3

18

19

20

16

17

Indoor

21

12

13

Allocat ion Code Group Cluster (Scrambling Set)

Sector SC Group

Outdoor(Macro/Micro)

15



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Proposed SC Plan Strategy Tehran

The same strategy is used to SC planning in Tehran city. The nominal sites have been already

Planned with primarily assumptions. However, here supposed to have 12 macro sites in a

cluster.

The remaining SC will be specifically allocated for future outdoor & Indoor new phases use.

LEGEND

Cluster 1

Cluster 2

Cluster 3

Cluster 4

Cluster 5

Cluster 6

Cluster 7

Cluster 8



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Below figure indicates the SC distribution in part of Tehran. Each code determine by different colors.


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For instance if you look

for the SC 89 which

belong to Cluster 2 , you

can see the reuse

distance for than 15km

which is good results.Take into consideration

that around 200 code

also have been reserved

for upcoming sites.

Cells with used SC 89

15km


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The future is not somethingwe travel to

its something we build

Mohammad Tourchian

Nokia Siemens Network

Network Planning & Optimization

[email protected]

3- Scrambling Code Planning.pdf

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