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June 2001 Copyright 2001 Global Wireless Education Consortium FRP-CCC 1

Cellular Coverage Cellular Coverage ConceptsConcepts

(FRP-CCC)(FRP-CCC)


FRP-CCCFRP-CCC

© Copyright 2001 Global Wireless Education Consortium

All rights reserved. This module, comprising presentation slides with notes, exercises, projects and Instructor Guide, may not be duplicated in any way without the express written permission of the Global Wireless Education Consortium. The information contained herein is for the personal use of the reader and may not be incorporated in any commercial training materials or for-profit education programs, books, databases, or any kind of software without the written permission of the Global Wireless Education Consortium. Making copies of this module, or any portion, for any purpose other than your own, is a violation of United States copyright laws.

Trademarked names appear throughout this module. All trademarked names have been used with the permission of their owners.


FRP-CCCFRP-CCC

Partial support for this curriculum material was provided by the National Science Foundation's Course, Curriculum, and Laboratory Improvement Program under grant DUE-9972380 and Advanced Technological Education Program under grant DUE‑9950039.

GWEC EDUCATION PARTNERS: This material is subject to the legal License Agreement signed by your institution. Please refer to this License Agreement for restrictions of use.


Table of ContentsTable of Contents

Overview 5

Learning Objectives 6

History of Wireless Communication 7

Cell Splitting 12

Channel Grouping 16

Carrier to Interference (C/I) Ratio 26

Tower Distance to Cell Radius (D/R) Ratio 30

Cellular Network Architecture 41

Summary 45

Contributors 48


OverviewOverview

In this module, you will learn about about cellular coverage concepts that affect the ability to provide the best cellular coverage in the most efficient manner.


Learning ObjectivesLearning Objectives

After completing this module, you will be able to:

Explain how cell splitting and channel grouping are achieved in a cellular network

Explain how to calculate a C/I ratio

Calculate a D/R ratio

Determine the C/I interference for a given D/R ratio

Draw a diagram of a cellular network architecture


History of Wireless History of Wireless CommunicationCommunication


History of Wireless History of Wireless CommunicationsCommunications

About 100 years of Radio...

• 1914 Radio first used for practical communication in WWI

• 1920s First radio broadcasting and simplex mobile broadcast

• 1940s Radar first used in WWII

• 1950s First commercial television

• 1950s First mobile telephony


Specialized Mobile Radio Specialized Mobile Radio (SMR)(SMR)

SMR was used primarily for commercial use Two way over air communication between two or more mobile units

Coverage limited to area the signal could reach

If signal got too weak, call was dropped

No handoffs

Calls to the PSTN through a provided dial pad

Public Service Telephone Network

(PSTN)

SMRProvider


Cellular Telephone ArrivesCellular Telephone Arrives

Make coverage areas smaller, but more of them

Develop a means to hand call from one coverage area to another

Call these coverage areas cells

Make coverage areas smaller, but more of them

Develop a means to hand call from one coverage area to another

Call these coverage areas cells

Delicious Catering Base Station

Digital Mobile Switching Center

Delicious

Delicious

Delicious

Public SwitchedTelephone Network(PSTN)


Cells Become CrowdedCells Become Crowded

Digital Mobile Switching Center

Public SwitchedTelephone Network(PSTN)

Number of users outgrew number of channels available

More efficient reuse plan had to be developed

Number of users outgrew number of channels available

More efficient reuse plan had to be developed


Cell Cell SplittingSplitting


Cell SplittingCell Splitting

3

6

6

2

2

5

7

4

1

Basic N=7 frequency reuse plan




3

6

25

74

1



3

66

25

74

1

3

6

22

5

74

1

3

6

25

74

1

25

74

1

325

7

7



3

6

6

2

2

5

7

4

1

Basic N=7 frequency reuse plan with split cells

Basic N=7 frequency reuse plan with split cells

1

6

3

1

1 4

5

3


Channel Channel GroupingGrouping


AMPS Cellular BandsAMPS Cellular Bands

• Cellular telephony provides full-duplex communications• Two-way simultaneous conversation requires simultaneous voice paths in both

directions• 25 MHz band of frequencies used for mobile transmission (uplink)• 25 MHz band of frequencies used for cell site transmission (downlink)

• Cellular bands divided equally between two competing operators• A operator• B operator

824 835 845 870 880 894

869

849

846.5825

890

891.5

Uplink Downlink

Paired Bands

Frequency ( MHz)

Uplink

Downlink


800 MHz Channel Assignments by Band

FunctionNo. of

ChannelsBand A

Channel numbersBand B

Channel numbers

Control channels

Voice channels

Voice channels,extended spectrum

Total number ofchannels per carrier

21

312

83

313-333

001-312

667-716991-1023

416

334-354

355-666

717-799

416


800 MHz Telecommunications Band

A, non-extended VCH

B, non-extended VCH

A, extended VCH

B, extended VCH

A, Control Channels

B, Control Channels

799717667666 716355312 3543340011023991 333313

Legend:

System A System B

VOICE CHANNELSCONTROLCHANNELSCHANNELS

VOICE CHANNELS

non-extendedexten-ded

non-extended extended

A’ B

VOICE

A”


Transmit and Receive Transmit and Receive Channel SeparationChannel Separation

45 MHz

CELLSITE

REVERSE CHANNEL835 MHz ( f1 )

(up-link)

FORWARD CHANNEL880 MHz ( f1 + 45 MHz)

(down-link)


Cell Clusters – Frequency Cell Clusters – Frequency ReuseReuse

R

12

34

56

7

D

N=7

12

34

56

7

12

34

56

7

1112

10

98

12

34

56

7

1112

10

98

DR

N=12

32

1

2

4

3

4

R

D

N=4

1


A Band N = 7 Channel SetsA Band N = 7 Channel Sets

Channel Set 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21Designations A1 B1 C1 D1 E1 F1 G1 A2 B2 C2 D2 E2 F2 G2 A3 B3 C3 D3 E3 F3 G3

Control Ch. 333 332 331 330 329 328 327 326 325 324 323 322 321 320 319 318 317 316 315 314 313

Voice 312 311 310 309 308 307 306 305 304 303 302 301 300 299 298 297 296 295 294 293 292Channels 291 290 289 288 287 286 285 284 283 282 281 280 279 278 277 276 275 274 273 272 271

270 269 268 267 266 265 264 263 262 261 260 259 258 257 256 255 254 253 252 251 250249 248 247 246 245 244 243 242 241 240 239 238 237 236 235 234 233 232 231 230 229228 227 226 225 224 223 222 221 220 219 218 217 216 215 214 213 212 211 210 209 208207 206 205 204 203 202 201 200 199 198 197 196 195 194 193 192 191 190 189 188 187186 185 184 183 182 181 180 179 178 177 176 175 174 173 172 171 170 169 168 167 166165 164 163 162 161 160 159 158 157 156 155 154 153 152 151 150 149 148 147 146 145144 143 142 141 140 139 138 137 136 135 134 133 132 131 130 129 128 127 126 125 124123 122 121 120 119 118 117 116 115 114 113 112 111 110 109 108 107 106 105 104 103102 101 100 99 98 97 96 95 94 93 92 91 90 89 88 87 86 85 84 83 8281 80 79 78 77 76 75 74 73 72 71 70 69 68 67 66 65 64 63 62 6160 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 4039 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 1918 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

Expanded 1023 1022 1021Spectrum A' 1020 1019 1018 1017 1016 1015 1014 1013 1012 1011 1010 1009 1008 1007 1006 1005 1004 1003 1002 1001 1000

999 998 997 996 995 994 993 992 991

Expanded 716 715 714 713 712 711 710 709 708 707 706 705Spectrum A" 704 703 702 701 700 699 698 697 696 695 694 693 692 691 690 689 688 687 686 685 684

683 682 681 680 679 678 677 676 675 674 673 672 671 670 669 668 667

416Control 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Normal A 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 14 14 14A" 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 2 2 2A' 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 2 2 2 2

Total Voice 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 19 18 18 18 18

Set Channel Count Summary


B Band N = 7 Channel Sets

Channel Set 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21Designations A1 BI C1 D1 E1 F1 G1 A2 B2 C2 D2 E2 F2 G2 A3 B3 C3 D3 E3 F3 G3

Control Ch. 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354

Voice 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375Channels 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396

397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666

Expanded 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732Spectrum 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753

754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795796 797 798 799

416Control 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Normal B 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 14 14 14B' 4 4 4 4 3 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

Total Voice 19 19 19 19 18 19 19 19 19 19 19 19 19 19 19 19 19 19 18 18 18

Set Channel Count Summary



3C1(17)

6F2(8)

6F1(11)

2B1(18)

2B2(19)

5E1/2(24)

7G1(14)

4D1(12)

1A1(15)




Sector Cell ClusterSector Cell ClusterN=7

B1

B2

B3

C1

C2

C3G1

G2

G3

A1

A2

A3

D1

D2

D3

E1

E2

E3

F1

F2

F3

F1

F2

F3

REUSE

120 degree sector


Carrier to Carrier to Interference Interference

(C/I) Ratio (C/I) Ratio


C/I is Carrier-to-Interference Ratio AMPS modulation characteristics

require 18 dB co-channel C/I over single interferer (17dB over

multiple interferers ) Between a pair of sites using same channel,

three C/I regions exist:Site A C/I better than 18 dBNeither site gives usable C/ISite B C/I better than 18 dB

Other sites needed to serve region where neither A nor B has good C/I

Rate of signal decay determines how close next co-channel site can be and how many additional sites on other channels are needed in between

With proper planning, it is possible to determine required separation between co-channel sites to avoid interference

Co-Channel Interference Co-Channel Interference ModelModel

-120

-110

-100

-90

-80

-70

-60

Distance, km1 3 5 7 9 11 13 15 17 19 21 23 250

Site A Site B-50

C/I = 18 dB C/I = 18 dB

Good Service

Good ServiceInterference

RSSI,dBm

Frequency Reuse Scenario


Co-Channel Interference Co-Channel Interference Uplink/Reverse PathUplink/Reverse Path

Co-channel interference can occur on uplink, downlink, or both

On the uplink, interference occurs at cell site receiver, from mobiles in surrounding co-channel cells

1

1

1

2

3

4

5 6

7

4

6

47 2

7

2

5

35

36

1

1

1

1


Co-Channel InterferenceCo-Channel InterferenceDownlink/Forward PathDownlink/Forward Path

On the downlink, interference occurs at mobile user’s receiver due to signals from surrounding co-channel cells

1

1

1

1

2

3

4

5 6

7

4

6

47 2

7

2

5

35

36

1

1

1

1


Tower DistanceTower Distanceto Cell Radius (D/R) to Cell Radius (D/R)

RatioRatio


Use D/R to determine how few cells (N) can be tolerated in frequency assignment repetition pattern Co-channel cells must be

separated by at least D/R

D/R Determines Required D/R Determines Required Minimum NMinimum N

D = Distance between twoco-channel transmitters

R = Coverage radius where a cell is the best server

Example of N=7

N = ( )2 3D

R /

D

f1f7

f2

f1

f3

f6

f4

f2

f5

f4 f7

f1

R R


Reuse Plan Design CriteriaReuse Plan Design Criteria

Two design constraints with cellular reuse plans Need to maintain C/I ratio of 18 dB to avoid co-channel

interference, but... Want to divide channel sets into as few groups as possible to

maximize number of channels per cell

Closely related to development is the D/R ratio Distance between cells using same channel sets versus radius

of each cell

We can show that NRD 3/


Frequency ReuseFrequency ReuseImplications of NImplications of N

N is number of cells in frequency reuse pattern and is critically important since it determines: Capacity of an individual cell

Channels per cell = (total channels) / N As N goes up, capacity

progressively decreases

Interference As N goes up, interference

becomes progressively less troublesome

Channelsper Cell* D/R

395198132997966564944

1.7322.4493.0003.4643.8734.2434.5834.8995.196

40 5.47736 5.745

N

12345678910

11

12 33 6.000

* Assumes use of 395 voice channels including expanded spectrum


Channel AssignmentChannel Assignment Channel set - collection of

channels which could be assigned at one cell

Channels in a channel set Normally are N channels

apart, where N is reuse factor

Must meet combiner minimum frequency spacing requirements

Sets 1 and 3 (i.e.,1 and N) are adjacent frequencies

If N=3, for example:

1 2 3 4 5 6 7 8 9 10 12Channels

Freq.

Channel Set 1 1, 4, 7, 10, . . .Channel Set 2 2, 5, 8, 11, . . .Channel Set 3 3, 6, 9, 12, . . .

12

3

2

31 1

1

2

3

32

N=3


Cell Arrangement as a Cell Arrangement as a Function of NFunction of N

N=1 Lethal, works well in CDMAAwful C/I: Every neighbor is co-

channelEvery neighbor cell is adjacent

channel too!Center 1/3 of each cell OK, rest is

lost in horrible interference N=2 Better, but still lethal

Each cell still has 2 co-channel neighbors

Each cell has 4 adjacent channel neighbors

1

11

11

1

1

1

1 21

1

1

1

1

22

2

2

2

2


N = 3 Better, but still lethal Co-channel neighbors are now

spaced at D/R of 3.0 - better, but not 18 dB....

Each cell has 6 adjacent channel neighbors - all neighbors are adjacent!!

N = 4 Better, but still lethal Co-channel neighbors are now

spaced at D/R of 3.464 Each cell has 4 adjacent channel

neighbors

2

3

11

1 1

1

11

2

2 2

22

23

3 3

3

3

3

1

2

34

1

1

1

1

1

1

2

2

2

2

2 3

3

3

3

3

3

44

42

4 4

4



N = 5 Better, but not good enough Co-channel neighbors farther away

• 2 at D/R of 3.0• 4 at D/R of 4.58

Some cells have 2 adjacent channel neighbors, some have 3

N = 6 Better, but not by much Co-channel neighbors farther away

• 2 at D/R of 3.464• 2 at D/R of 4.58• 2 at D/R of 6.0

Some cells have 2 adjacent channel neighbors, some have 3

15

23

4

15

2

12

12

31

5

23

4

15

4

15

1 56

23

4

1 56

23

4

1 56

4

16

2

12

3

61

23

4

5

1



N = 7 First arrangement that works in most propagation environments, giving 18+ dB C/I Co-channel neighbors farther away

• 6 at D/R of 4.58 Each cell always has 2 adjacent

channel neighbors

N = 8 Better, but not worthwhile Co-channel neighbors farther away


Of the eight cells in the cluster, 2 have 2 adjacent-channel neighbors and 4 have 1 adjacent channel neighbor


15

38

2

6

47

15

3

7

1

7

15

38

2

6

41

82

6

1

82

6

4

15 4

71

47

15

38

12

3

4

5 6

7

4

6

1

1

11

1

147 2

7

2

5

35

36


N = 9 Significant improvement Co-channel neighbors farther away

• 6 at D/R of 5.20

Out of 9 cells in cluster, 4 have 1 adjacent channel neighbor and 3 have 2 such neighbors

N = 10 Not impressively better Co-channel neighbors farther away


Out of 10 cells in cluster,• 6 have 1 adjacent channel neighbor• 3 have 2 adjacent-channel neighbors


12

3

4

5

6

7

89

12

3

6

7

126

7

44

5

891

35

891

1

46 8

1

357

12

3

4

5

6

7

8

910

12

46

1

35

912

6

7

910

1

37

910

1

48

15

8


N = 11 Slightly better Co-channel neighbors farther

away• 2 at D/R of 4.58• 2 at D/R of 6.06• 4 at D/R of 7.14

Out of 11 cells in cluster, eight each have one adjacent channel neighbor

N = 12 Excellent but inefficient Co-channel neighbors farther

away• 6 at D/R of 6.0

No adjacent-channel neighbors

3

711

61010

912

4

128

1

5

1

81

9 81

95 5

2 3 2 3

610

711

85

19

4

122 3 2

11

11

107 7

1076


2

3

4

5

6

7

10

111

9

8

2

3

6

7

101

26

101

2

5

610

19

3

47

10

111

83

71

4

511

19

8

511

19

411

1

8


Cellular Cellular NetworkNetwork

Architecture Architecture


Diagramming a NetworkDiagramming a Network

Build a basic cluster of cells using the N factor Try to minimize number of

adjacent channels Build a cluster that is

repeatableG

B

DE

AF

C


Building a NetworkBuilding a Network

Duplicate the cluster as many times as needed to cover designated area

Only one thing is left Supervisory audio tone (SAT)

code

DG

B

EA

FC

GBD

EA

FC G

BD

EA

FC

GBD

EA

FC

GBD

EA

FC

GBD

EA

FC

1G

B

EA

FC


SAT AssignmentSAT Assignment Plan for N=7 Omni SystemsPlan for N=7 Omni Systems

SAT frequencies are transmitted on analog voice channels to: Provide circuit supervision Validate identity of

measured signals during locate process preceding handoff

SATs are assigned so that: No cell has near co-channel

neighbors with same SAT No adjacent cell has same

SAT

20

1

10

10

201

02

02 1

20

21

21

012

10

10

201

02

02

012

10

10

12

0

02

02

SAT FrequenciesSAT 0 5970 Hz

SAT 1 6000 Hz

SAT 2 6030 Hz


SummarySummary


SummarySummary

In this module, you were introduced to:

History of wireless communication Cell splitting Channel grouping C/I ratio D/R ratio Network architecture


SummarySummary

In this module, you were introduced to:

The history of wireless communication Cell splitting Channel grouping C/I ratio D/R ratio Network architecture


Industry ContributorsIndustry Contributors

AT&T Wireless (http://www.attwireless.com) Lucent Technologies, Inc. (http://www.lucent.com) Motorola (http://www.motorola.com) RF Globalnet (http://www.rfglobalnet.com) Telcordia Technologies, Inc (http://www.telcordia.com)

The following companies provided materials and resource support for this module:


Individual ContributorsIndividual ContributorsThe following individuals and their industry or educational institutions provided materials, resources, and development input for this module: Dr. Cheng Sun

California Polytechnic State University http://www.calpoly.edu/

Dave Voltmer Rose-Hulman Institute of Technology http://www.rose-hulman.edu/

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