《电子工程师手册》学习资料（英文版）Personal and Office 75

75.1 Mobile Radio and Cellular Communications cation and The Difference between Fixed-to-Fixed Radio Communication an Mobile Communication-Natur tural Problems in Mobile Radio Communications. Description of Mobile Radio Systems

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75 Personal and office The Difference between Fixed- to- Fixed Radio Communication Mobile communication Natural problems in mobile rad Communications. Description of Mobile Radio Systems Data Systems. Personal Communication Service Systems 75.2 Facsimile William C. Y. Lee Scanning. Encoding. Modulation and Transmission Demodulation and Decoding. Recording. Personal Computer Facsimile.Group 4 Facsimile odger E. Ziemer 75.3 Wireless Local-Area Networks for the 1990s University of Colorado at Colorado The Wireless In-Building Vision. Market Research. LANMarket Factors. Cabling Problems. User Requirements Environment Mil Ovan Product Requirements: End User Reaction. Technology 75.4 Wireless PCs Giridhar D. Mandyam Cellular Band Systems. PCS Services.3rd Generation Nokia Research Center Enhancements 75.1 Mobile radio and Cellular Communications William C.y lee The Difference between fixed-to-Fixed Radio communication and Mobile communication In fixed-to-fixed radio communications, the transmitter power, antenna location, antenna height, and antenna gain can be determined after calculating the link budget. Also, depending on the frequency range of the carrier affected on the atmospheric variation, different"margin values will be put in the budget calculation for different system applications. The fixed-to-fixed radio links are usually 10 miles or longer and high above the ground The signal variation over the link is due mostly to atmospheric changes. Satellite communications, microwave links, troposcatter, etc are fixed-to-fixed radio communications. In mobile radio communications, the param eters such as transmitter power, antenna location, antenna height, and antenna gain are determined by covering suburban areas are less than 10 miles. In mobile radio communications, the design of cell coverage is baser d an area or cell In mobile radio communications at least one end is in motion the sizes of cells in urban he average power. No margin is applied in calculating the cell coverage. Natural Problems in mobile radio Communications In mobile radio communications, there are many problems which never occur in fixed-to-fixed radio commu 1. Excessive pathloss: Vehicles are referred to as mobile units. The antenna height of the mobile unit is very close to the ground. Therefore, the average signal strength received at the mobile unit has two components, c 2000 by CRC Press LLC

© 2000 by CRC Press LLC 75 Personal and Office 75.1 Mobile Radio and Cellular Communications The Difference between Fixed-to-Fixed Radio Communication and Mobile Communication • Natural Problems in Mobile Radio Communications • Description of Mobile Radio Systems • Mobile Data Systems • Personal Communication Service Systems 75.2 Facsimile Scanning • Encoding • Modulation and Transmission • Demodulation and Decoding • Recording • Personal Computer Facsimile • Group 4 Facsimile 75.3 Wireless Local-Area Networks for the 1990s The Wireless In-Building Vision • Market Research • LANMarket Factors • Cabling Problems • User Requirements Environment • Product Requirements: End User Reaction • Technology Alternatives in Meeting Customer Requirements 75.4 Wireless PCS Cellular Band Systems • PCS Services • 3rd Generation Enhancements 75.1 Mobile Radio and Cellular Communications William C. Y. Lee The Difference between Fixed-to-Fixed Radio Communication and Mobile Communication In fixed-to-fixed radio communications, the transmitter power, antenna location, antenna height, and antenna gain can be determined after calculating the link budget. Also, depending on the frequency range of the carrier affected on the atmospheric variation, different “margin” values will be put in the budget calculation for different system applications. The fixed-to-fixed radio links are usually 10 miles or longer and high above the ground. The signal variation over the link is due mostly to atmospheric changes. Satellite communications, microwave links, troposcatter, etc. are fixed-to-fixed radio communications. In mobile radio communications, the parameters such as transmitter power, antenna location, antenna height, and antenna gain are determined by covering an area or cell. In mobile radio communications, at least one end is in motion. The sizes of cells in urban and suburban areas are less than 10 miles. In mobile radio communications, the design of cell coverage is based on the average power. No margin is applied in calculating the cell coverage. Natural Problems in Mobile Radio Communications In mobile radio communications, there are many problems which never occur in fixed-to-fixed radio communication system: 1. Excessive pathloss: Vehicles are referred to as mobile units. The antenna height of the mobile unit is very close to the ground. Therefore, the average signal strength received at the mobile unit has two components, William C. Y. Lee AirTouch Communications, Inc. Rodger E. Ziemer University of Colorado at Colorado Springs Mil Ovan Motorola, Inc. Giridhar D. Mandyam Nokia Research Center

a direct wave and a ground-reflected wave. These two waves act in canceling their average signal strengths and result in excessive pathloss at the receiver 2. Multipath fading: Due to the human-made environment in which mobile units travel, the instantaneous ignal sent from the base station is reflected back and forth from buildings and other ground before arriving at the mobile unit and causes signal fading received in the time domain. This fading causes an increase in the bit error rate(BEr) and in the degradation of voice quality 3. Human-made noise: The antenna height of mobile units is usually low. Therefore, human-made industrial noise, automotive ignition noise, etc. are very easily received by the mobile unit. This noise will raise the noise floor and impact system perfor Ima 4. Dispersive medium: Due to the human-made environment and the low antenna height of the unit,the signal after bouncing back and forth from the human-made structures produces multiple reflected waves which arrive at the mobile unit at different times. One impulse sent from the base station propagating through the medium becomes multiple reflected impulses received at different times at the mobile unit. This medium is called a dispersive medium. First the dispersive medium does not affect the analog voice channel, but does affect the data channels. Second, the medium becomes effective depending on the transmission symbol rate of the system. The dispersive medium will impact the reception performance when the transmission rate is over 20 kbps. Third, the dispersive medium becomes more effective in urban areas than in suburban areas Description of Mobile Radio Systems There are two basic systems: trunked systems and cellular systems Trunked Systems A trunked system is assigned a channel from a number of available channels to a user. The user is never assigned to a fixed channel 1. Specialized mobile radio(SMR) is a trunked system. The SMR operator is licensed by the FCC to a group of 10 or 20 channels within 14 MHz of the spectrum between 800 and 900 MHz Loading requirement: A minimum of 70 mobile units per channel is required. SMR can offer privacy, channel access, and efficient services. It can serve up to 125-150 mobile units per channel. pacing: 25 kHz. Channel allocation: The FCC allocates a spectrum of either 500 kHz or 1 MHz to a SMr operator who will serve 10 or 20 paired transmit-receiver voice channels Coverage: Coverage is about 25 miles in radius since SMR uses only one high-power transmitting tower covering a large area. Telephone interconnect: The public service telephone network(PSTN) extends mobile telephone service to smr users Roaming: Mobile units are equipped with software that allows the radio to roam to any SmR syster in the network. Handoff: No tower-to-tower handoff capability; the channel frequency does not change as the unit moves from one cell to another ESMR(enhanced SMR): A system used to enhance the SMR system. It was called MIRS(Mobile Integrated Radio Systems). Now it is called IDEN (Integrated Dispatch and Enhanced Network). Features are: Uses the smr band Uses TDMA(time division multiple access)digital technology, the same digital TDMA standard adopted by the cellular Applies network of low-power cells Provides cell-to-cell handoffs through a centralized switching facility A spectrum average of 7-8 MHz is used in each market. The spectrum is not contiguous A channel bandwidth of 25 kHz is specified with three time slots per channel. Modulation 16 QAM is applied c 2000 by CRC Press LLC

© 2000 by CRC Press LLC a direct wave and a ground-reflected wave. These two waves act in canceling their average signal strengths and result in excessive pathloss at the receiver. 2. Multipath fading: Due to the human-made environment in which mobile units travel, the instantaneous signal sent from the base station is reflected back and forth from buildings and other ground objects before arriving at the mobile unit and causes signal fading received in the time domain. This signal fading causes an increase in the bit error rate (BER) and in the degradation of voice quality. 3. Human-made noise: The antenna height of mobile units is usually low. Therefore, human-made industrial noise, automotive ignition noise, etc. are very easily received by the mobile unit. This noise will raise the noise floor and impact system performance. 4. Dispersive medium: Due to the human-made environment and the low antenna height of the mobile unit, the signal after bouncing back and forth from the human-made structures produces multiple reflected waves which arrive at the mobile unit at different times. One impulse sent from the base station propagating through the medium becomes multiple reflected impulses received at different times at the mobile unit. This medium is called a dispersive medium. First the dispersive medium does not affect the analog voice channel, but does affect the data channels. Second, the medium becomes effective depending on the transmission symbol rate of the system. The dispersive medium will impact the reception performance when the transmission rate is over 20 kbps. Third, the dispersive medium becomes more effective in urban areas than in suburban areas. Description of Mobile Radio Systems There are two basic systems: trunked systems and cellular systems. Trunked Systems A trunked system is assigned a channel from a number of available channels to a user. The user is never assigned to a fixed channel. 1. Specialized mobile radio (SMR) is a trunked system. The SMR operator is licensed by the FCC to a group of 10 or 20 channels within 14 MHz of the spectrum between 800 and 900 MHz. • Loading requirement: A minimum of 70 mobile units per channel is required. SMR can offer privacy, speedier channel access, and efficient services. It can serve up to 125–150 mobile units per channel. • Channel spacing: 25 kHz. • Channel allocation: The FCC allocates a spectrum of either 500 kHz or 1 MHz to a SMR operator who will serve 10 or 20 paired transmit-receiver voice channels. • Coverage: Coverage is about 25 miles in radius since SMR uses only one high-power transmitting tower covering a large area. • Telephone interconnect: The public service telephone network (PSTN) extends mobile telephone service to SMR users. • Roaming: Mobile units are equipped with software that allows the radio to roam to any SMR system in the network. • Handoff: No tower-to-tower handoff capability; the channel frequency does not change as the unit moves from one cell to another. 2. ESMR (enhanced SMR): A system used to enhance the SMR system. It was called MIRS (Mobile Integrated Radio Systems). Now it is called IDEN (Integrated Dispatch and Enhanced Network). Features are: • Uses the SMR band. • Uses TDMA (time division multiple access) digital technology, the same digital TDMA standard adopted by the cellular industry. • Applies network of low-power cells. • Provides cell-to-cell handoffs through a centralized switching facility. • A spectrum average of 7–8 MHz is used in each market. The spectrum is not contiguous. • A channel bandwidth of 25 kHz is specified with three time slots per channel. • Modulation 16 QAM is applied. • No equalizer is used

(a)K=7 Ds/R'= 4.6 mearQ' (c)K=3 R·=R FIGURE 75.1 Four cases of expression of cochannel interference reduction factor Cellular Systems The cellular system [Lee, 1989]is a high-capacity system that uses the frequency reuse concept. The same frequency is used over and over again in different geographical locations. In large cities, the same frequency can be reused over 30 times Key Elements: There are several key elements in the cellular system. Cochannel interference reduction factor q(see Fig 75.1): Two cells using the same frequency channels are called cochannel cells. The required distance between two cochannel cells in order to receive the accepted voice quality is D, and the radius of the cell is R. Then the cochannel interference reduction factor q is q=D,/R There are six co-channel cells at the first tier seen from the center cell as shown in Fig. 75. 1(a). For an analog cellular system g, =4.6, and the cell reuse factor Kis K=9, 23=7. The K=7 means that a cluster of seven cells will reuse again and again in a serving area. The capacity increase in a cellular system can be achieved by reducing both the radius of cell r by one half and the separation D, by one half such at the gs remains constant and the capacity is increasing by four times. The reason is that a cell shown in Figure 75. 1(a)can fit in four small cells shown in Fig. 75.1(b). In Fig. 75.1(c), the size of cells is the same as Fig. 75.1(a),but , =3 is achieved by using an intelligent microcell system. The capacity of Fig. 75. 1(c)is 7= 2. 33 times over that of Fig. 75.1(a). In Fig. 75. 1(d), the radius of the cell is reduced by one half, and K is reduced to 3. The capacity of Fig. 75.1(d)is 4x 2.33=9.32 times over that of 751(a) The value of q is different in different kinds of cellular systems such as analog, TDMA, and CDMA(code Handoff: Handoff is a feature implemented in cellular systems to handoff a frequency of a cell while the mobile unit changes to another frequency of another cell while the vehicle is entering. The handoff is handled by the system and the user does not notice the handoff occurrences c 2000 by CRC Press LLC

© 2000 by CRC Press LLC Cellular Systems The cellular system [Lee, 1989] is a high-capacity system that uses the frequency reuse concept. The same frequency is used over and over again in different geographical locations. In large cities, the same frequency can be reused over 30 times. Key Elements: There are several key elements in the cellular system. • Cochannel interference reduction factor q (see Fig. 75.1): Two cells using the same frequency channels are called cochannel cells. The required distance between two cochannel cells in order to receive the accepted voice quality is Ds , and the radius of the cell is R. Then the cochannel interference reduction factor q is q = Ds/R There are six co-channel cells at the first tier seen from the center cell as shown in Fig. 75.1(a). For an analog cellular system qs = 4.6, and the cell reuse factor K is K = qs⅔ = 7. The K = 7 means that a cluster of seven cells will reuse again and again in a serving area. The capacity increase in a cellular system can be achieved by reducing both the radius of cell R by one half and the separation Ds by one half such that the qs remains constant and the capacity is increasing by four times. The reason is that a cell shown in Figure 75.1(a) can fit in four small cells shown in Fig. 75.1(b). In Fig. 75.1(c), the size of cells is the same as Fig. 75.1(a), but qs = 3 is achieved by using an intelligent microcell system. The capacity of Fig. 75.1(c) is  ⁄ = 2.33 times over that of Fig. 75.1(a). In Fig. 75.1(d), the radius of the cell is reduced by one half, and K is reduced to 3. The capacity of Fig. 75.1(d) is 4 ¥ 2.33 = 9.32 times over that of Fig. 75.1(a). The value of q is different in different kinds of cellular systems such as analog, TDMA, and CDMA (code division multiple access). • Handoff: Handoff is a feature implemented in cellular systems to handoff a frequency of a cell while the mobile unit changes to another frequency of another cell while the vehicle is entering. The handoff is handled by the system and the user does not notice the handoff occurrences. FIGURE 75.1 Four cases of expression of cochannel interference reduction factor

TABLE 75.1 Specifications of TDMA and CDMA Systems TDMA CDMA Bandwidth per channel 1.23 MHz Time slots Speech coder 8 kbps(max )a variable rate vocoder Modulation T/4-DQPSK Forward radio channels Pilot(1)sync(1), Paging(7) 8 kbps-VSELP code traffic channels(55), total 64 vector sum excited LPC) channels Channel coding ate 1/2 convolutional(13 kbps) Reverse radio channels (9), traffic channels (55) Total transmit rate 48 kbps per channel Power control rd, reverse Diversity LPC linear predictive code. Cell splitting: When a cell provides a maximum of 60 radio channels and all are used during bus hours, the cell has to be split into smaller cells in order to provide more radio channels, normally reducing by four subcells. Each subcell 60 channels. The total area of an original cell will provide 240 radio channels which is four times higher Spectrum Allocation in the United States, Europe, and Japan: In the United States there is 50 MHz of ectrum allocated to cellular radio within 800-900 MHz. Based on duopoly, each city has two licensed operators. Each one operates on a 25-MHz band. There are two bands, Band A and Band B. Each band consists of 416 channels. The channel bandwidth is 30 kHz. Among 416 channels, 21 channels are used for setting up and 395 are used for voice channels Analog: The frequency management of both Band A and Band B is shown in Table 75.5. Digital: There are two potential systems, TDMA and CDMA shown in Table 75.1 In Europe the spectrum allocation is as shown in Table 75.2 and 75.3 In Japan the spectrum allocation is as shown in Table 75.4 TABLE 75.2 Specification of Three European Systems TACS NMT* Transmission frequency(kHz) Base statio 935960 463-467.5 461.3-465.74 Mobile station 890-915 453-457.5 451.3-455.74 Spacing between transmission Spacing between channels(kHz)25 Number of channels 0 30 Type of modulation 4 Type of modulation FSK ±6.4 ±3.5 ±25 Data transmission rate(kbps) 8 .28 essage protection lesage is sent again decision is employed when an error g to the is detected ontent of the s TACS=total access cellular system; NMT = nordic mobile telephone c2000 by CRC Press LLC

© 2000 by CRC Press LLC • Cell splitting: When a cell provides a maximum of 60 radio channels and all are used during busy hours, the cell has to be split into smaller cells in order to provide more radio channels, normally reducing the cell by using a half radius. As a result a cell will be covered by four subcells. Each subcell provides 60 channels. The total area of an original cell will provide 240 radio channels which is four times higher in capacity as compared with the original cell capacity before splitting. Spectrum Allocation in the United States, Europe, and Japan: In the United States there is 50 MHz of spectrum allocated to cellular radio within 800–900 MHz. Based on duopoly, each city has two licensed operators. Each one operates on a 25-MHz band. There are two bands, Band A and Band B. Each band consists of 416 channels. The channel bandwidth is 30 kHz. Among 416 channels, 21 channels are used for setting up and 395 are used for voice channels. • Analog: The frequency management of both Band A and Band B is shown in Table 75.5. • Digital: There are two potential systems, TDMA and CDMA shown in Table 75.1. In Europe the spectrum allocation is as shown in Table 75.2 and 75.3. In Japan the spectrum allocation is as shown in Table 75.4. TABLE 75.1 Specifications of TDMA and CDMA Systems TDMA CDMA Bandwidth per channel 30 kHz Bandwidth per channel 1.23 MHz Time slots 3 Speech coder 8 kbps(max.)—a variable rate vocoder Modulation p/4-DQPSK Forward radio channels Pilot (1) sync (1), paging (7), Speech coder 8 kbps—VSELP code traffic channels (55), total 64 (vector sum excited LPC*) channels Channel coding Rate 1/2 convolutional (13 kbps) Reverse radio channels Access (9), traffic channels (55) Total transmit rate 48 kbps per channel Power control Forward, reverse Equalizer Up to 40 ms Diversity Rake receiver * LPC = linear predictive code. TABLE 75.2 Specification of Three European Systems Analog England Scandinavia West Germany System TACS* NMT* C450 Transmission frequency (kHz) Base station 935–960 463–467.5 461.3–465.74 Mobile station 890–915 453–457.5 451.3–455.74 Spacing between transmission 45 10 10 and receiving frequencies (MHz) Spacing between channels (kHz) 25 25 20 Number of channels 1000 180 222 (control channel 21 ¥ 2); interleave used Coverage radius (km) 2–20 1.8–40 5–30 Audio signal Type of modulation FM FM FM Frequency deviation (kHz) ±9.5 ±5 ±4 Control signal Type of modulation FSK FSK FSK Frequency deviation (kHz) ±6.4 ±3.5 ±2.5 Data transmission rate (kbps) 8 1.2 5.28 Message protection Principle of majority Receiving steps are Message is sent again decision is employed predetermined when an error according to the is detected content of the message * TACS = total access cellular system; NMT = nordic mobile telephone

TABLE 75.5 New Frequency Management( Full Spec Block A 1A 2A 3A 4A 5A 6A 7A 1B 2B 3B 4B 5B 6B 7B IC 2C 3C 4C 5C 6C 7C 123456789101112131415161718192021 222324252627282930313233343536373839404142 45464748495051525354555657585960616263 64656667686970772737475767778798081828384 858687888990919293949596979899100101102103104105 10610710810911011112113114115116117118119120121122123124125126 127128129130131132133134135136 4214 148149150151 153154155156157158159160 62163164165 169170171172 174175176177178179180181 183184185 8189 91 11212213214215216217218219220221222223224225226227228229230231 232233234235236237238239240241242243244245246247248249250251252 260261262263264265266267268269270271272273 274275276277278279280281282 284285286287288289290291292293294 308 671672673674675676677678679680681 684685686687688689690 92693694695696697698 712713714715716XXx991 992993994995996997998999100010011002 1003100410051006100710081009101010111012101310141015101610171018 1020102110221023 313*314315316317318319320321322323324325326327328 330331332333 Block B IA 2A 3A 4A 5A 6A 7A IB 2B 3B 4B 5B 6B 7B IC 2C 3C 4C 5C 6C 7C 以y顶mm如如如如如③m如那 373374375 397398399400401402403404405406407408409410411412413414415416417 418419420421422423424425426427428429430431432433434435436437438 439440441442443444445446447448 1452453454455 !物m0mm奶切切 49749849 502503504505506507508509510511512513514515516517518519520521522 523524525526527528529530531532533534535536537538539540541542543 545 56556656 587 92593594595 05606 607608609610611612613614615616617618619620621622623624625626627 62862963063163263364635636637638639640641642643644645646647648 649650651652653654655656657658659660661662663664665666xxX XxxX717718719720721722723724725726 728729730731732 7357367377387397407417427437447457 756757758759760761762763764765766767768769770771772773774 775776777778779780781782783784785786787788789790791792793794795 97798799 Boldface numbers indicate 21 control channels for Block A and Block B, respectively. c2000 by CRC Press LLC

© 2000 by CRC Press LLC TABLE 75.5 New Frequency Management (Full Spectrum) Block A 1A 2A 3A 4A 5A 6A 7A 1B 2B 3B 4B 5B 6B 7B 1C 2C 3C 4C 5C 6C 7C 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 X X X X 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 313* 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 Block B 1A 2A 3A 4A 5A 6A 7A 1B 2B 3B 4B 5B 6B 7B 1C 2C 3C 4C 5C 6C 7C 334* 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 X X X X X X X X 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 *Boldface numbers indicate 21 control channels for Block A and Block B, respectively

Mobile Data Systems The design aspect of developing a mobile data system is different from that of developing a cellular voice system, although the mobile radio environment is the same. The quality of a voice channel has to be determined based on a subjective test. The quality of a data transmission is based on an objective test. In a data transmission, the bit error rate and the word error rate are the parameters to be used to measure the performance at any given carrier-to-interference ratio(C/I). The burst errors caused by the multipath fading and the intersymbol inter- ence caused by the time delay spread are the major concerns in receiving the mobile data. The burst errors can be reduced by interleaving and coding. The intersymbol interference can be reduced by using equalizers or lowering the symbol rate or applying diversity. The wireless data transmission can be sent via a circuit switched network or a packet switched network. Also, mobile data transmission can be implemented on cellular systems or on a stand-alone syste ARDIS* Transmission rate 4.8 kbps and 19.2 kbps Transmission rate Transmit power 1 Transmit power Packet radio Cellular Plan ll Cellular Modems Transmission rate 19.2 kb Transmission rate Transmit power 0.6-1.2 w Transmission Channel Packet cellular cellular, carry data over cellular AT&T PowerTek vital ARDIS advanced radio data RAM= mobile data service Personal Communication Service Systems In June 1990, the FCC started to ask the wireless communication industry to study the development of future rsonal communication service(PCS)systems. (In late 1994, the FCC started to auction off two of the six ectral bands for over 7 billion dollars. In 1996, Band C was auctioned off for over 4 billion dollars. ) PCS systems need to have more capacity than cellular systems. The technologies of increasing the capacity not only apply to Gsm, but also apply to CDMA( code division multiple access)and the new microcell system. CDMA A San Diego field test held in 1991 showed that a cellular CDMa scheme can provide higher capacity than cellular TDMA (time division multiple access). A cellular CDMA system [Lee, May 1991] does not require a frequency reuse scheme. All the CDMA cells share the same radio channel. Therefore, the capacity of a cellular CDMA system is higher than either cellular FDMA(frequency division multiple access)or cellular TDMA systems. ssume that a spectral bandwidth of 1.2 MHz can be divided into 120 radio channels with a channel bandwidth of 10 kHz. This is an FDMA scheme. A spectral bandwidth of 1.2 MHz can also be divided into 40 radio channels with a radio channel bandwidth of 30 kHz but each radio channel carries three time slots herefore, a total of 120 time-slot channels is obtained. This is a TDMA scheme. A spectral bandwidth of 1.2 MHz can also be used as one radio channel but provide 40 code-sequence traffic channels for each sector of a cell. a cell of three sectors will have a total of 120 traffic channels this is a cdma scheme. now we can visualize that as far as channel efficiency is concerned, TDMA, FDMA, and CDMa provide the same number of traffic channels. However, in FDMA or TDMA, frequency reuse has to be applied. Let the frequency reuse factor K=7 maintain a required C/2 18 dB; then the total channels will be divided by 7 as: 17 channels/cell (in TDMA or FDMA) c 2000 by CRC Press LLC

© 2000 by CRC Press LLC Mobile Data Systems The design aspect of developing a mobile data system is different from that of developing a cellular voice system, although the mobile radio environment is the same. The quality of a voice channel has to be determined based on a subjective test. The quality of a data transmission is based on an objective test. In a data transmission, the bit error rate and the word error rate are the parameters to be used to measure the performance at any given carrier-to-interference ratio (C/I). The burst errors caused by the multipath fading and the intersymbol interference caused by the time delay spread are the major concerns in receiving the mobile data. The burst errors can be reduced by interleaving and coding. The intersymbol interference can be reduced by using equalizers or lowering the symbol rate or applying diversity. The wireless data transmission can be sent via a circuit switched network or a packet switched network. Also, mobile data transmission can be implemented on cellular systems or on a stand-alone system. Personal Communication Service Systems In June 1990, the FCC started to ask the wireless communication industry to study the development of future personal communication service (PCS) systems. (In late 1994, the FCC started to auction off two of the six spectral bands for over 7 billion dollars. In 1996, Band C was auctioned off for over 4 billion dollars.) PCS systems need to have more capacity than cellular systems. The technologies of increasing the capacity not only apply to GSM, but also apply to CDMA (code division multiple access) and the new microcell system. CDMA A San Diego field test held in 1991 showed that a cellular CDMA scheme can provide higher capacity than cellular TDMA (time division multiple access). A cellular CDMA system [Lee, May 1991] does not require a frequency reuse scheme.All the CDMA cells share the same radio channel. Therefore, the capacity of a cellular CDMA system is higher than either cellular FDMA (frequency division multiple access) or cellular TDMA systems. Assume that a spectral bandwidth of 1.2 MHz can be divided into 120 radio channels with a channel bandwidth of 10 kHz. This is an FDMA scheme. A spectral bandwidth of 1.2 MHz can also be divided into 40 radio channels with a radio channel bandwidth of 30 kHz but each radio channel carries three time slots. Therefore, a total of 120 time-slot channels is obtained. This is a TDMA scheme. A spectral bandwidth of 1.2 MHz can also be used as one radio channel but provide 40 code-sequence traffic channels for each sector of a cell. A cell of three sectors will have a total of 120 traffic channels. This is a CDMA scheme. Now we can visualize that as far as channel efficiency is concerned, TDMA, FDMA, and CDMA provide the same number of traffic channels. However, in FDMA or TDMA, frequency reuse has to be applied. Let the frequency reuse factor K = 7 maintain a required C/I ³ 18 dB; then the total channels will be divided by 7 as: ARDIS* RAM* Transmission rate 4.8 kbps and 19.2 kbps Transmission rate 8 kbps Transmit power 1 W Transmit power 4 W Channel Packet radio Channel Packet radio Vendors IBM/Motorola Vendor Ericsson Cellular Plan II Cellular Modems Transmission rate 19.2 kbps Transmission rate 38.4 kbps Transmit power 0.6–1.2 W Transmission 3 W Channel Packet cellular Channel Circuit cellular, carry data over cellular voice channels Modem vendor AT&T, PowerTek, Vital *ARDIS = advanced radio data *RAM = mobile data service 120 7 = 17 channels/cell (in TDMA or FDMA)

In CDMA no frequency reuse is required. Therefore, every cell can have the same 120 channels: number of annels/cell (in CDMA). In cellular, because the frequency reuse factor is applied on FDMA and TDMa schemes but not on CDMA, therefore, cellular CDMA has a greater spectrum efficiency than cellular FDMA or TDMA [ Lee, May 1991] New Microcell System The conventional microcell system [Lee, Nov. 1991, 1993] reduces the transmit power and makes a cell less than 1 km in radius. The concept of using cell splitting is to increase capacity. Furthermore, the new microcell system needs to find a way to make a conventional microcell to be intelligent. The conventional microcell does not have the intelligence to know where the mobile or portable units are located within the cell. Therefore, the cell site has to cover the signal strength over the whole cell or whole sector. The more unnecessary signal power transmitted, the more interference will be caused in the system and less capacity will be achieved. In this new intelligent microcell system, each cell is an intelligent cell. In a new microcell, there are three or more zones. The cell will know which zone a particular mobile unit is in. Then a small amount of power will be needed to deliver in that zone. The cochannel interference reduction factor(CiRF) now will be measured from two cochannel zones instead of two cochannel cells. Then the two cochannel cells can be located much closer. In this new microcell system, the frequency reuse factor K becomes K=3. As compared to the conventional microcell K= 7, the new microcell system has a capacity increase of 2. 33(= 7/3)times. These two techniques can be used in buildings and outside buildings. Defining Terms CDMA: A multiple access scheme by using code sequences as traffic channels in a comom radio channel. Cell splitting: A method of increasing capacity by reducing the size of the cell. Cochannel interference reduction factor(CIRF): A key factor used to design a cellular system to avoid the cochannel interference FDMA: A multiple access scheme by dividing an allocated spectrum into different radio channels. Frequency reuse factor(K): A number based on frequency reuse to determine how many channels per cell. GSM(Global System Mobile): European digital cellular standard using TDMA. Handoff: A frequency channel will be changed to a new frequency channel as the vehicle moves from one IDEN (Integrated Dispatch and Enhanced Network): A cellular-like system. Mobile cellular systems: A high-capacity system operating at 800-900 MHz using a frequency reuse scheme vehicle and portable telephone communications PHS(Personal Handy Phone System): A TDD system deployed in Japan. SMR(Specialized Mobile Radio): A trunked system for dispatch TDMA: A multiple access scheme by dividing a radio channel into many time slots where each slot carries a Related Topic 69.2 Radio References W. C. Y. Lee, Mobile Cellular Telecommunication Systems, New York: McGraw Hill, 1989 W. C. Y Lee," Overview of cellular CDMA, IEEE Trans. on Veh. Tech, vol. 40, PP. 290-302, May 1991 w. C.Y. Lee,"Microcell architecture--Smaller cells for greater performance, " IEEE Commun. Magazine, vol 29, PP.19-23,Nov.1991 W. C.Y. Lee, Mobile Communications Design Fundamentals, 2nd ed, New York: Wiley, 1993. c2000 by CRC Press LLC

© 2000 by CRC Press LLC In CDMA no frequency reuse is required. Therefore, every cell can have the same 120 channels: number of channels/cell (in CDMA). In cellular, because the frequency reuse factor is applied on FDMA and TDMA schemes but not on CDMA, therefore, cellular CDMA has a greater spectrum efficiency than cellular FDMA or TDMA [Lee, May 1991]. New Microcell System The conventional microcell system [Lee, Nov. 1991, 1993] reduces the transmit power and makes a cell less than 1 km in radius. The concept of using cell splitting is to increase capacity. Furthermore, the new microcell system needs to find a way to make a conventional microcell to be intelligent. The conventional microcell does not have the intelligence to know where the mobile or portable units are located within the cell. Therefore, the cell site has to cover the signal strength over the whole cell or whole sector. The more unnecessary signal power transmitted, the more interference will be caused in the system and less capacity will be achieved. In this new intelligent microcell system, each cell is an intelligent cell. In a new microcell, there are three or more zones. The cell will know which zone a particular mobile unit is in. Then a small amount of power will be needed to deliver in that zone. The cochannel interference reduction factor (CIRF) now will be measured from two cochannel zones instead of two cochannel cells. Then the two cochannel cells can be located much closer. In this new microcell system, the frequency reuse factor K becomes K = 3. As compared to the conventional microcell K = 7, the new microcell system has a capacity increase of 2.33 (= 7/3) times. These two techniques can be used in buildings and outside buildings. Defining Terms CDMA: A multiple access scheme by using code sequences as traffic channels in a comom radio channel. Cell splitting: A method of increasing capacity by reducing the size of the cell. Cochannel interference reduction factor (CIRF): A key factor used to design a cellular system to avoid the cochannel interference. FDMA: A multiple access scheme by dividing an allocated spectrum into different radio channels. Frequency reuse factor (K): A number based on frequency reuse to determine how many channels per cell. GSM (Global System Mobile): European digital cellular standard using TDMA. Handoff: A frequency channel will be changed to a new frequency channel as the vehicle moves from one cell to another cell without the user’s intervention. IDEN (Integrated Dispatch and Enhanced Network): A cellular-like system. Mobile cellular systems: A high-capacity system operating at 800–900 MHz using a frequency reuse scheme for vehicle and portable telephone communications. PHS (Personal Handy Phone System): A TDD system deployed in Japan. SMR (Specialized Mobile Radio): A trunked system for dispatch. TDMA: A multiple access scheme by dividing a radio channel into many time slots where each slot carries a traffic channel. Related Topic 69.2 Radio References W. C. Y. Lee, Mobile Cellular Telecommunication Systems, New York: McGraw Hill, 1989. W. C. Y. Lee, “Overview of cellular CDMA,” IEEE Trans. on Veh. Tech., vol. 40, pp. 290–302, May 1991. W. C. Y. Lee, “Microcell architecture—Smaller cells for greater performance,” IEEE Commun. Magazine, vol. 29, pp. 19–23, Nov. 1991. W. C. Y. Lee, Mobile Communications Design Fundamentals, 2nd ed., New York: Wiley, 1993

Further information T.S. Rappaport, The wireless revolution, "IEEE Commun. Magazine, Pp 52-71, Nov. 1991 Gilhousan et al., " On the capacity of cellular CDMA systems, " IEEE Trans. Vehicular Technol., vol. 40, no. 2, Pp.303-311,May1991 D J. Goodman, Trends in cellular and cordless communications, IEEE Commun. Magazine, Pp 31-39, June 1991 Raith, K and Uddenfeldt, J,Capacity of digital cellular TDMA systems, IEEE Trans. Vehicular Technol., voL. 40, no.2,PP.323-331,May1991 75.2 Facsimile Rodger e. Ziemer Facsimile combines copying with data transmission to produce an image of a subject copy at another location, either nearby or distant. Although the Latin phrase fac simile means to"make similar, "the compressed phrase facsimile has been taken to mean"exact copy of a transmission"since 1815 [Quinn, 1989]. The image of the bject copy is referred to as a facsimile copy or record copy. Often the abbreviated reference"fax"is used in place of the longer term facsimile. Facsimile was invented by Alexander Bain in 1842; Bain,s system used a synchronized pendulum arrangement to send a facsimile of dot patterns and record them on electrosensitive paper. Over the years, much technological development has taken place to make facsimile a practical and affordable document transmission process. An tant role in the wide acceptance of facsimile for image transmission has been the adoption of tandards by the Consultative Committee on International Telephone and Telegraph(CCITT). The advent of a nationwide dial telephone network in the 1960s provided impetus for the rebirth of facsimile after television up 2 fax machines wh red in the mid-1970s were cap of transmitting a page within a couple of minutes. These machines, based on analog transmission methods, were developed by Graphic Sciences and 3M. The Group 3 fax machines, developed in the mid-1970s by the Japanese, are based on digital transmission technology and are capable of transmitting a page in 20 seconds or less. They can automatically switch to an analog mode to communicate with the older group 1 and 2 fax machines Group 4 fax units offer the highest resolution at the fastest rates but rely on digital telephone lines which are just now becoming widely available[Quinn, 1989]. Group 3 facsimile will be featured in the remainder of this article. Group 3 facsimile refers to apparatus which is capable of transmitting an 8.5 X 11-inch page over telephone-type circuits in one minute or less. Detailed standards for Group 3 equipment may be found in Recommendation t4 of ccitt, Vol vil Facsimile transmission involves the separate processes of scanning, encoding, modulation, tran demodulation, decoding, and recording. Each of these will be ibed in greater detail below. Scanning Before transmission of the facsimile signal, the subject copy must be scanned. This involves the sensing of the diffuse reflectances of light from the elemental areas making up the subject copy. For CCITT Group 3 high resolution facsimile, these elemental areas are rectangles 1/208 inch wide by 1/196 inch high. The signa corresponding to an elemental area is called a pixel which stands for picture element For pixels that can assume only one of two possible states(i. e, white on black or vice versa), the term used is a pel. Various arrangements of illuminating sources, light-sensing transducers, and mechanical scanning methods can be employed. For more than six sweeps per second across the subject copy, electronic scanning utilizing a cathode-ray tube or photosensitive arrays or laser sources with polygon mirrors are utilized. a photosensitive array arrangement for scanning a flood-illuminated subject copy is illustrated in Fig. 75. 2. This is the most often encountered anning mechanism for modern facsimile scanners, and the sensors are typically silicon photosensitive devices Two photosensor arrays in common use are photodiode arrays and charge-coupled device linear image sensors For digital facsimile, the array is composed of 1728 sensors in a row 1.02 inches long with the optics designed so that an 8.5 inch subject copy can be scanned c 2000 by CRC Press LLC

© 2000 by CRC Press LLC Further Information T. S. Rappaport, “The wireless revolution,” IEEE Commun. Magazine, pp. 52–71, Nov. 1991. Gilhousan et al., “On the capacity of cellular CDMA systems,” IEEE Trans. Vehicular Technol., vol. 40, no. 2, pp. 303–311, May 1991. D. J. Goodman, “Trends in cellular and cordless communications, IEEE Commun. Magazine, pp. 31–39, June 1991. Raith, K. and Uddenfeldt, J., “Capacity of digital cellular TDMA systems,” IEEE Trans. Vehicular Technol., vol. 40, no. 2, pp. 323–331, May 1991. 75.2 Facsimile Rodger E. Ziemer Facsimile combines copying with data transmission to produce an image of a subject copy at another location, either nearby or distant. Although the Latin phrase fac simile means to “make similar,” the compressed phrase facsimile has been taken to mean “exact copy of a transmission” since 1815 [Quinn, 1989]. The image of the subject copy is referred to as a facsimile copy, or record copy. Often the abbreviated reference “fax” is used in place of the longer term facsimile. Facsimile was invented by Alexander Bain in 1842; Bain’s system used a synchronized pendulum arrangement to send a facsimile of dot patterns and record them on electrosensitive paper. Over the years, much technological development has taken place to make facsimile a practical and affordable document transmission process. An equally important role in the wide acceptance of facsimile for image transmission has been the adoption of standards by the Consultative Committee on International Telephone and Telegraph (CCITT). The advent of a nationwide dial telephone network in the 1960s provided impetus for the rebirth of facsimile after television put the damper on early facsimile use. Group 2 fax machines which appeared in the mid-1970s were capable of transmitting a page within a couple of minutes. These machines, based on analog transmission methods, were developed by Graphic Sciences and 3M. The Group 3 fax machines, developed in the mid-1970s by the Japanese, are based on digital transmission technology and are capable of transmitting a page in 20 seconds or less. They can automatically switch to an analog mode to communicate with the older Group 1 and 2 fax machines. Group 4 fax units offer the highest resolution at the fastest rates but rely on digital telephone lines which are just now becoming widely available [Quinn, 1989]. Group 3 facsimile will be featured in the remainder of this article. Group 3 facsimile refers to apparatus which is capable of transmitting an 8.5 ¥ 11-inch page over telephone-type circuits in one minute or less. Detailed standards for Group 3 equipment may be found in Recommendation T.4 of CCITT, Vol. VII. Facsimile transmission involves the separate processes of scanning, encoding, modulation, transmission, demodulation, decoding, and recording. Each of these will be described in greater detail below. Scanning Before transmission of the facsimile signal, the subject copy must be scanned. This involves the sensing of the diffuse reflectances of light from the elemental areas making up the subject copy. For CCITT Group 3 highresolution facsimile, these elemental areas are rectangles 1/208 inch wide by 1/196 inch high. The signal corresponding to an elemental area is called a pixel which stands for picture element. For pixels that can assume only one of two possible states (i.e., white on black or vice versa), the term used is a pel. Various arrangements of illuminating sources, light-sensing transducers, and mechanical scanning methods can be employed. For more than six sweeps per second across the subject copy, electronic scanning utilizing a cathode-ray tube or photosensitive arrays or laser sources with polygon mirrors are utilized. A photosensitive array arrangement for scanning a flood-illuminated subject copy is illustrated in Fig. 75.2. This is the most often encountered scanning mechanism for modern facsimile scanners, and the sensors are typically silicon photosensitive devices. Two photosensor arrays in common use are photodiode arrays and charge-coupled device linear image sensors. For digital facsimile, the array is composed of 1728 sensors in a row 1.02 inches long with the optics designed so that an 8.5 inch subject copy can be scanned

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