Download - CDMA m1 Overview[1]

Fundamentals of CDMA - Luis Font CDMA Technical Market Support, CALA & EMEA - Nov. 9, 1998 - Page 1

Fundamentals of CDMA

Alexander Sierra

Lesson 1 - Overview


Basics


Why CDMA?

Is the technology of choice for both 800 MHz Cellular and 1900 MHz PCS service providers

Satisfies CTIA Users’ Performance Requirements

Provides high capacity (many times the capacity of AMPS)

Provides privacy through its coding scheme

CDMA

CDMA

ode

ivision

ultiple

ccess

CDMA is extremely robust and provides excellent audio quality


What is Multiple Access?

Since the beginning of telephony and radio, system operators have tried to squeeze the maximum amount of traffic over each circuit

Types of Media -- Examples:· Twisted pair - copper· Coaxial cable· Fiber optic cable· Air interface (radio signals)

Advantages of Multiple Access· Increased capacity: serve more users· Reduced capital requirements since fewer

media can carry the traffic· Decreased per-user expense· Easier to manage and administer

Transmission

Medium

Each pair of users enjoys a dedicated,

private circuit through the transmission

medium, unaware that the other users exist.

Multiple Access: Simultaneous private use of a transmission medium by multiple, independent users.


Multiple Access Technologies

The physical transmission medium is a resource that can be subdivided into individual channels according to different criteria depending on the technology used:

Here’s how the three most popular technologies establish channels:· FDMA Frequency Division Multiple Access

- each user on a different frequency- a channel is a frequency

· TDMA Time Division Multiple Access- each user on a different window period in time

(“time slot”)- a channel is a specific time slot on a specific

frequency· CDMA Code Division Multiple Access

- each user uses the same frequency all the time, but mixed with different distinguishing code patterns

- a channel is a unique (set of) code pattern(s)Frequency

Time

Power

FrequencyTime

Power

FrequencyTime

Power

FDMA

TDMA

CDMA

Channel: An individually-assigned, dedicated pathway through a transmission medium for one user’s information


Defining Our Terms

CDMA Channel or CDMA Carrier or CDMA Frequency· Duplex channel made of two 1.25 MHz-wide bands of electromagnetic

spectrum, one for Base Station to Mobile Station communication (called the FORWARD LINK or the DOWNLINK) and another for Mobile Station to Base Station communication (called the REVERSE LINK or the UPLINK)

· in 800 Cellular these two simplex 1.25 MHz bands are 45 MHz apart· in 1900 MHz PCS they are 80 MHz apart

CDMA Forward Channel· the 1.25 MHz Forward Link

CDMA Reverse Channel· the 1.25 MHz Reverse Link

CDMA Code Channel· each individual stream of 0’s and 1’s contained in either the CDMA Forward

Channel or in the CDMA Reverse Channel· Code Channels are characterized (made unique) by mathematical codes· code channels in the forward link: Pilot, Sync, Paging and Forward Traffic

channels· code channels in the reverse link: Access and Reverse Traffic channels

45 or 80 MHz

CDMA CHANNELCDMA

ReverseChannel 1.25 MHz

CDMAForwardChannel 1.25 MHz


Other Technologies: Avoiding Interference

In conventional radio technologies, the desired signal must be strong enough to override any interference

AMPS, TDMA and GSM depend on physical distance separation to keep interference at low levels

Co-channel users are kept at a safe distance by careful frequency planning

Nearby users and cells must use different frequencies to avoid interference

2

3

4

5 6

7

4

6

4

7 2

7

2

5

3

5

36

1

1

1

1

1

1

1

AMPS-TDMA-GSM

Figure of Merit: C/I(carrier/interference ratio)

AMPS: +17 dBTDMA: +14 to 17 dBGSM: +12 to 14 dB


CDMA: Using a New Dimension

All CDMA users occupy the same frequency at the same time! Frequency and time are not used as discriminators

CDMA operates by using CODES to discriminate between users

CDMA interference comes mainly from nearby users

Each user is a small voice in a roaring crowd -- but with a uniquely recoverable code

Transmit power on all users must be tightly controlled so their signals reach the base station at the same signal level

Figure of Merit: Ec/Io, Eb/No

(energy per chip [bit] /interference [noise] spectral density)

CDMA: Ec/Io -17 to -2 dBCDMA: Eb/No ~+6 dB


CDMA Is a Spread-Spectrum System

Traditional technologies try to squeeze the signal into the minimum required bandwidth

Direct-Sequence Spread spectrum systems mix their input data with a fast spreading sequence and transmit a wideband signal · The spreading sequence is

independently regenerated at the receiver and mixed with the incoming wideband signal to recover the original data

The de-spreading gives substantial gain proportional to the bandwidth of the spreading signal

CDMA uses a larger bandwidth but then uses resulting processing gain to increase capacity

Spread Spectrum Payoff:Processing Gain

Spread SpectrumTRADITIONAL COMMUNICATIONS SYSTEM

SlowInformation

Sent

TX

SlowInformationRecovered

RX

NarrowbandSignal

SPREAD-SPECTRUM SYSTEM

FastSpreadingSequence

SlowInformation

Sent

TX

SlowInformationRecovered

RX

FastSpreadingSequence

Wideband Signal


Spread Spectrum Principles

1.25 MHz30 KHz

Power is “Spread” Over a Larger Bandwidth

MATHHAMMER

MATHHAMMER



Many code channels are individually“spread” and then added together tocreate a “composite signal”



UNWANTED POWERFROM OTHER SOURCES

Using the “right” mathematicalsequences any Code Channelcan be extracted from the receivedcomposite signal


Anything We Can Do, We Can Undo

Any data bit stream can be combined with a spreading sequence The resulting signal can be de-spread and the data stream

recovered if the original spreading sequence is available and properly synchronized

After de-spreading, the original data stream is recovered intact Note - The spread sequences actually shown are icons, not accurate or to scale

ORIGINATING SITE DESTINATION

SpreadingSequence

SpreadingSequence

InputData

(Base Band)

RecoveredData

(Base Band)

Spread Data Stream(Base Band + Spreading Sequence)


“Shipping and Receiving” via CDMA

Whether in shipping and receiving, or in CDMA, packaging is extremely important!

Cargo is placed inside “nested” containers for protection and to allow addressing

The shipper packs in a certain order, and the receiver unpacks in the reverse order

CDMA “containers” are spreading codes

Fed

Ex

Data Mailer

Fed

Ex

DataMailer

Shipping Receiving


CDMA’s Nested Spreading Sequences

CDMA combines three different spreading sequences to create unique, robust channels

The sequences are easy to generate on both sending and receiving ends of each link

The sequences are applied in succession at the sending end and then reapplied in opposite order to recover the original data stream at the receiving end

SpreadingSequence

A

SpreadingSequence

B

SpreadingSequence

C

SpreadingSequence

C

SpreadingSequence

B

SpreadingSequence

A

InputData

X

RecoveredData

X

X+A X+A+B X+A+B+C X+A+B X+ASpread-Spectrum Chip Streams

ORIGINATING SITE DESTINATION


How Many Spreading Codes Do We Need?(Discriminating Among Forward Code Channels)

A Mobile Station, tuned to a particular CDMA frequency, receives a Forward CDMA Channel from a sector in a Base Station.

This Forward CDMA Channel carries a composite signal made of up to 64 “forward code channels”

Some of these code channels are “traffic channels” while other are “overhead channels” needed by the CDMA system to operate properly.

A set of 64 mathematical codes is needed to differentiate the 64 possible forward code channels that can be contained in a Forward CDMA Channel.· The codes in this set are called “Walsh Codes”

SyncPilot

FW Traffic(for user #1)

Paging




How Many Spreading Codes Do We Need?(Discriminating Among Base Stations)

A mobile Station is surrounded by Base Stations, all of them transmitting on the same CDMA Frequency

Each Sector in each Base Station is transmitting a CDMA Forward Traffic Channel containing up to 64 distinct forward code channels

A Mobile Station must be able to discriminate between different Sectors of different Base Stations and listen to only one set of code channels

Two binary digit sequences called the I and Q Short PN Sequences (or Short PN Codes) are defined for the purpose of identifying sectors of different base stations

These Short PN Sequences can be used in 512 different ways in a CDMA system. Each one of them constitutes a mathematical code which can be used to identify a particular sector of a particular base station

A B

Up to 64Code Channels

Up to 64Code Channels


How Many Spreading Codes Do We Need?(Discriminating Among Reverse Code Channels)

The CDMA system must be able to uniquely identify each Mobile Station that may attempt to communicate with a Base Station

A very large number of Mobile Stations will be in the market

One binary digit sequence called the Long PN Sequence (or Long PN Code) is defined for the purpose of uniquely identifying each possible reverse code channel

This sequence is extremely long and can be used in trillions of different ways. Each one of them constitutes a mathematical code which can be used to identify a particular user (and is then called a User Long Code) or a particular “access channel” (explained later in this course)

RV Trafficfrom M.S.

#1837732008RV Trafficfrom M.S.

#8764349209

RV Trafficfrom M.S.

#223663748

System AccessAttempt by M.S.#4348769902

(on access channel #1)


Putting it All Together: CDMA Channels

The three spreading codes are used in different ways to create the forward and reverse links

A forward channel exists by having a specific Walsh Code assigned to the user, and a specific PN offset for the sector

A reverse channel exists because the mobile uses a specific offset of the Long PN sequence

BTS

WALSH CODE: Individual UserSHORT PN OFFSET: Sector

LONG CODE OFFSET: individual handset

FORWARD CHANNELS

REVERSE CHANNELS

LONG CODE:Data

Scrambling

WALSH CODES:used as symbols

for robustness

SHORT PN:used at 0 offset

for tracking


Pilot Walsh 0

Walsh 19

Paging Walsh 1

Walsh 6

Walsh 11

Walsh 20

Sync Walsh 32

Walsh 42

Walsh 37

Walsh 41

Walsh 56

Walsh 60

Walsh 55

Code Channels in the Forward Direction

PILOT: WALSH CODE 0· The Pilot is a “structural beacon” which

does not contain a character stream. It is a timing source used in system acquisition and as a measurement device during handoffs

SYNC: WALSH CODE 32· This carries a data stream of system

identification and parameter information used by mobiles during system acquisition

PAGING: WALSH CODES 1 up to 7· There can be from one to seven paging

channels as determined by capacity needs. They carry pages, system parameters information, and call setup orders

TRAFFIC: any remaining WALSH codes· The traffic channels are assigned to

individual users to carry call traffic. All remaining Walsh codes are available, subject to overall capacity limited by noise


BTS (1 sector)MTX BSC

FECWalsh #1

Sync FECWalsh #32

Walsh #0

FECWalsh #12

FECWalsh #23

FECWalsh #27

FECWalsh #44

Pilot

Paging

Vocoder

Vocoder

Vocoder

Vocoder

more moremore

Trans-mitter,

Sector X

S

I Q

Short PN CodePN Offset 246

Coding Process in the Forward Direction

A Forward Channel is identified by:

its CDMA RF carrier Frequency

the unique Short Code PN Offset of the sector

the unique Walsh Code of the user

CDMAFrequency


REG

1-800242

4444

BTS

Code Channels in the Reverse Direction

There are two types of CDMA Reverse Channels:

TRAFFIC CHANNELS are used by individualusers during their actual calls to transmit trafficto 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


MTX BSC BTS (1 sector)

Channel Element

Access Channels

Vocoder

Vocoder

Vocoder

Vocoder

more more

Receiver,Sector X

Channel Element

Channel Element

Channel Element

Channel Element

Long Code Gen

Long Code Gen

Long Code Gen

Long Code Gen

Long Code Gen

more

UserLongCode User

LongCode User

LongCode

UserLongCode

UserLongCode

UserLongCode

Coding Process in the Reverse Direction

A Reverse Channel is identified by: its CDMA RF carrier Frequency the unique Long Code PN Offset

of the individual handset

CDMAFrequency


Details of Operation


Variable Rate Vocoding & Multiplexing(Traffic Channels Only)

Vocoders compress speech, reduce bit rate

CDMA uses a superior Variable Rate Vocoder· full rate during speech· low rates in speech pauses· increased capacity· more natural sound

Voice, signaling, and user secondary data may be mixed in CDMA frames

DSP QCELP VOCODER

Codebook

PitchFilter

FormantFilter

Coded Result Feed-back

20ms Sample

Rate Set 2 Frame Sizesbits

Full Rate Frame

1/2 Rate Frame

1/4 Rt.

1/836

72

144

288

Frame Contents: can be a mixture ofVoice Signaling Secondary


Converting Bits into Symbols

The bits in a 20 ms traffic frame may include one or more of the following· voice information (from the vocoder)· signaling information· secondary traffic information

When Forward Error Correction algorithms are applied to these information bits, the resulting 0s and 1s are called symbols· bits and symbols are related in a complex

many-to-many fashion- the information in one bit is distributed among

many symbols, and one symbol carries some of the information of many bits

· all forward traffic frames contain 384 symbols· all reverse traffic frames contain 576 symbols

Bits

Symbols

Forward ErrorCorrection


Spreading Symbols into Chips

Symbols are converted into special 64-chip patterns for transmission· there are 64 such patterns called “Walsh

codes”· in the forward link, just one of these patterns is

assigned to each user’s stream of symbols (code channel)

- each ‘0’ symbol is replaced by the selected pattern (Walsh code)

- each ‘1’ symbol is replaced by the logical negation of the selected pattern

· in the reverse link, all the 64 patterns (but not their logical negations) are used in every code channel

- each group of six symbols is interpreted as a binary value in the 0-63 range and replaced by the corresponding Walsh code

Symbols

Chips

Coding andSpreading


Reverting The Process To revert the process, first the symbols are

recovered as follows· in the forward direction, the mobile station correlates

the received signal with the selected Walsh code pattern (integrating the power over 64 chips); a perfect match corresponds to a ‘0’ symbol; a perfect no-match corresponds to a ‘1’ symbol; for anything between these extremes, the mobile station guesses based on which case the partial match resembles closer

· in the reverse direction, the BTS matches the received signal with each possible Walsh code and selects the pattern that produces the highest degree of correlation as the representation of the last group of six symbols sent

When all the symbols for a 20 millisecond frame have been recovered, the Viterbi decoder is used to guess the block of bits (frame) that most probably corresponds to this block of symbols

Then, the CRC of this frame is calculated to determine if the guess was successful; if not, the frame is discarded (or “erased”)

Symbols

Chips

Despreading(integraton)

Bits

ViterbiDecoder


Spectrum Usage and System Capacity:Signal Bandwidth, Vulnerability and Frequency Reuse

Each wireless technology (AMPS, NAMPS, D-AMPS, GSM, CDMA) uses a specific modulation type with its own unique signal characteristics

The total traffic capacity of a wireless system is determined largely by radio signal characteristics and RF design

RF signal vulnerability to Interference dictates how much interference can be tolerated, and therefore how far apart same-frequency cells must be spaced

For a specific S/N level, the Signal Bandwidth determines how many RF signals will “fit” in the operator’s licensed spectrum

AMPS, D-AMPS, N-AMPS

CDMA

30 30 10 kHz

200 kHz

1250 kHz

1 3 1 Users

8 Users

22 Users1

1

11

1

11

11

1

11

1

1

12

34

43

2

56

17

Typical Frequency Reuse N=7



Vulnerability:C/I @ 17 dB

Vulnerability:C/I @ 12-14 dB

Vulnerability:Eb/No @ 6 dB

GSM

17 dB = 101.7 @ 5014 dB = 101.4 @ 25 12 dB = 101.2 @ 16


Relationship Between Eb/N0 and S/N

Eb =S

R

Signal Power

Bit Rate = N0 =

N

W

Noise Power

Bandwidth=

=S

R

W

N X =

S

N

W

R X

S

R

N

W

Eb

N0

=

Signal to Noise

ProcessingGain

E / t

B / t=

W

R=

1,250,000

14,400= 87 =

1.94

10 = 19.4dB

W

R=

1,250,000

9,600= 130 =

2.11

10 = 21.1dB8 Kb vocoder

(Full Rate)

13 Kb vocoder(Full Rate)


S/N Advantage of CDMA

AMPS

N-AMPS

D-AMPS

GSM

CDMA

Analog FM

Analog FM

DQPSK

GMSK

QPSK/OQPSK

30 KHz.

10 KHz.

30 KHz.

200 KHz.

1,250 KHz.

C/I @ 17 dB

C/I @ 17 dB

C/I @ 17 dBC/I @ 12-14

dBEb/No @ 6dB

Tech-nology Modulation Type Channel

BandwidthQuality

Indicator

S/N @ 17 dB

S/N @ 17 dB

S/N @ 17 dB

S/N @ 12 to 14 dB

S/N @ –13.4 dB

S/N

17 dB = 101.7 @ 5014 dB = 101.4 @ 25 12 dB = 101.2 @ 16

-13.4 dB = 10-1.34 @ 0.046 =

S

NÞ 10 0.6

10 1.94= = 10 -1.34 = -13.4 dB

Signal to NoiseProcessing Gain (W/R)

S

NX = 10 0.610 1.94

Eb N0

122


Overlaying CDMA on an AMPS System

Each CDMA Channel: 1.250 MHz ÷ 30 kHz = 41.7 = ~41 AMPS channelsEach Guard Band: 260 kHz ÷ 30 kHz = 8.7 = ~9 AMPS channels

260 KHz 260 KHz1.25 MHz Nominal Bandwidth

Frequency

Po

we

r1.77 MHz

CDMA CARRIER

41 AMPS channels 41 AMPS channels

9 AMPSchannels

41 AMPS channels

41 AMPS channels

CDMA CDMA CDMA CDMA CDMA

AVAILABLE AVAILABLE

885 MHzMinimum Separation between AMPS/TDMA and CDMA center frequency:

(1,250 kHz ÷ 2) + 260 kHz = 885 kHz

TOTAL: 1.77 MHz ÷ 30 kHz = 59 AMPS channels

GUARDBAND

GUARDBAND


CDMA Frequency Channel Assignment

IS-95 RECOMMENDS TO START CDMA DEPLOYMENTWITH EITHER THE PRIMARY OR THE SECONDARY CHANNEL

1

334

667

991

1023

333

666

715

799

716

ChannelNumbers

A (non-Wireline) B (Wireline) A’A” B’

1013 31 73 115 157 199 241 283 384 426 468 510 552 594 636 691 777

CDMA A-Band Carriers CDMA B-Band Carriers

8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 9 9 8

* **** Requires frequency coordination with

non-cellular interferers

** Requires frequency coordination with A-band carrier

A Band Primary Channel 283A Band Secondary Channel 691

B Band Primary Channel 384B Band Secondary Channel 777


CDMA Frequency Clearing: A-band(N=7 Reuse Pattern)

To deploy a CDMA carrier centered on AMPS/TDMA Channel 283, AMPS/TDMA Channels 254 through 312, inclusive, must be cleared from the CDMA coverage area

The CDMA channel is implemented, centered on AMPS/TDMA Channel 283. The first usable AMPS/TDMA Channels (outside of the Guard Zone) are Channels 253 and 313

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

312 311 310 309 308 307 306 305 304 303 302 301 300 299 298 297 296 295 294 293 292

291 290 289 288 287 286 285 284 283 282 281 280 279 278 277 276 275 274 273 272 271

270 269 268 267 266 265 264 263 262 261 260 259 258 257 256 255 254 253 252 251 250

249 248 247 246 245 244 243 242 241 240 239 238 237 236 235 234 233 232 231 230 229

228 227 226 225 224 223 222 221 220 219 218 217 216 215 214 213 212 211 210 209 208

207 206 205 204 203 202 201 200 199 198 197 196 195 194 193 192 191 190 189 188 187

186 185 184 183 182 181 180 179 178 177 176 175 174 173 172 171 170 169 168 167 166

165 164 163 162 161 160 159 158 157 156 155 154 153 152 151 150 149 148 147 146 145

144 143 142 141 140 139 138 137 136 135 134 133 132 131 130 129 128 127 126 125 124

123 122 121 120 119 118 117 116 115 114 113 112 111 110 109 108 107 106 105 104 103

102 101 100 99 98 97 96 95 94 93 92 91 90 89 88 87 86 85 84 83 82

81 80 79 78 77 76 75 74 73 72 71 70 69 68 67 66 65 64 63 62 61

60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40

39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19

18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

1A 2A 3A 4A 5A 6A 7A 1B 2B 3B 4B 5B 6B 7B 1C 2C 3C 4C 5C 6C 7C

a b g

N = 7


Overlay Guard Zone Deployment

AMPS Only Cellsapprox 19 channels per sector

CDMA & AMPS Cellsapprox 16 channels per sector

one CDMA channel/carrier/frequency

( 42 + 9 + 9 ) ÷ 21 = 2.8 = ~3 AMPS channels must be cleared per sector in the CDMA & AMPS area and in the Guard Zone to make

room for the first CDMA channel/carrier/frequency

The Guard Zones are needed between CDMA and other systems because CDMA increases the noise floor for those systems

AMPS Only Cells (GUARD ZONE)approx 16 channels per cell


a b g

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

N = 7

CDMA Frequency Clearing: B-band(N=7 Reuse Pattern)

To deploy a CDMA carrier centered on AMPS/TDMA Channel 384, AMPS/TDMA Channels 355 through 413, inclusive, must be cleared from the CDMA coverage area

The CDMA channel is implemented, centered on AMPS/TDMA Channel 384. The first usable AMPS/TDMA Channels (outside of the Guard Zone) are Channels 354 and 414


CDMA 800 MHz Cellular Spectrum Usage

All CDMA RF carriers are 1.25 MHz. wide· can serve ~22 users w/8 kb vocoder (~17 users w/13 kb vocoder)

The cellular spectrum of one operator is 12.5 MHz. wide. You’d expect that 10 CDMA carriers would fit. However, only 9 carriers can be used· operators must maintain a “token” AMPS presence for several years· “guard bands” are required at the edges of frequency blocks or any

frequency boundaries between CDMA/non-CDMA signals· no guard bands are required between adjacent CDMA carriers

Possible CDMA Center Freq. Assignments

Channel Numbers

Forward link (i.e., cell site transmits)Reverse link (i.e., mobile transmits)824MHz

849MHz

869MHz

894MHz

otherusesA” A”A B A’ B’

1 10 10 1.5 2.5

A B A’ B’

1 10 10 1.5 2.5

991

10231 333

334

666667

716717

799

991

10231 333

334

666667

716717

799

~300 kHz. “guard bands” possibly required if adjacent-frequency signals are non-CDMA (AMPS, TDMA, ESMR, etc.)


Number of Voice Channels (As AMPS Channels Are Converted to Digital)

0

50

100

150

200

1 2 3 4 5 6 7 8 9 10S1

S4

AMPS

TDMA

13 kbpsCDMA

8 kbpsCDMA

Num

ber

of V

oice

Cha

nnel

s

Number of CDMA Carriers0 1 2 3 4 5 6 7 8 9

200

150

100

50

0


Overlaying CDMA on the 1900 MHz Band

Each CDMA Channel: 1.250 MHz ÷ 50 kHz = 25 channels

Each Guard Band: 260 kHz ÷ 50 kHz = 5.2 = ~5 channels

TOTAL: 1.77 MHz ÷ 50 kHz = 35.4 = ~ 35 channels

260 KHz 260 KHz1.25 MHz Nominal Bandwidth

Frequency

Po

we

r

1.77 MHz

CDMA CARRIER

Just as with the CDMA on AMPS overlay, a GUARD ZONE is also needed

GUARDBAND

GUARDBAND


CDMA PCS 1900 MHz Spectrum Usage

A, B, and C licenses can accommodate 11 CDMA RF channels in their 30 MHz of spectrum

D, E, and F licenses can accommodate 3 CDMA RF channels in their 10 MHz of spectrum

260 kHz guard bands are required on the edges of the PCS spectrum to ensure no interference occurs with other applications just outside the spectrum

Guard Bands

Forward link (i.e., cell site transmits)Reverse link (i.e., mobile transmits)1850 MHz

BTA

BTA

BTA

BTA

BTA

BTA

Paired Bands

MTA BTAMTABTA MTAMTA

1910 MHz

1930MHz

1990MHz

Data Voice

A D B E F C A D B E F C

15 51010 1515151515 555 55

Licensed Licensed

Unlicensed

0

Channel Numbers 299

300

400

699

700

800

900

1199 0

299300

400

699700

800

900

1199


Nortel CDMA System Architecture


Nortel CDMA System Architecture

BSC-BSMMTX BTS

CDSU DISCO

Ch. Card ACC

Sa

Sb

Sc

TFU1

GPSRBSM

CDSU

CDSU

DISCO 1

DISCO 2

SBSVocodersSelectors

CDSU

CDSU

CDSU

CDSU

CDSU

CDSU

CMSLM

LPP LPPENET

DTCs

DMS-BUS

TxcvrA

TxcvrB

TxcvrC

RFFEA

RFFEB

RFFEC

TFU

GPSR

PSTN & Other MTXs

GPS GPS

IOC

Billing


Signal Flow: Two-Stage Metamorphosis

BSC-BSMMTX BTS

Ch. Card ACC

Sa

Sb

Sc

TFU1

GPSRBSM

CDSU

CDSU


CDSU

CDSU

CDSU

CDSU

CDSU

CMSLM

LPP LPPENET

DTCs

DMS-BUS

TxcvrA

TxcvrB

TxcvrC

RFFEA

RFFEB

RFFEC

TFU

GPSR

GPS GPS

IOC

PSTN

CDSU DISCOCDSU

DISCO 1

DISCO 2

DS0 in T1Packets

ChipsRFChannel

ElementVocoder


Architecture: The MTX

Primary functions· Call Processing· Mobility Management

- HLR-VLR access- Intersystem call delivery (IS-41C)- Inter-MTX handover (IS-41C)

· Billing Data Capture· Calling Features & Services· Collecting System OMs, Pegs

High reliability, redundancy

MTX

CMSLM

LPP ENET

DTCs

DMS-BUS

PSTN & Other MTXs

CDMABSC

Unch. T1

IOC

CDMASBS

MAP,VDUs

Billing

LPP

CCS7

Ch.T1

ChT1


Architecture: The BSC

Primary functions· vocoding· soft handoff management· FER-based power control· routing of all traffic and control

packets Scaleable architecture

· expand SBS to keep pace with traffic growth

· expandable DISCO

BSC

TFU1

GPSRBSM

CDSU

CDSU

DISCO 1

DISCO 2


CDSU

CDSU

CDSU

CDSU

CDSU

CDSU

GPS

MTX(voicetrunks)

MTXLPP

BTSs

T1 channelized (24 DS0)T1 unchannelizedBCN link (HDLC)


Architecture: The BTS

Primary function: Air link · generate, radiate, receive CDMA RF

signal IS-95/J.Std. 8· high-efficiency T1 backhaul· test capabilities

Configurations· 1, 2, or 3 sectors· 800 MHz.: indoor· 1900 MHz.: self-contained outdoor,

remotable RFFEs· future: 1900 MHz. indoor, 800 & 1900

multi-carrier options

BTS

CDSU DISCO

Ch. Card ACC

Sa

Sb

Sc

TxcvrA

TxcvrB

TxcvrC

RFFEA

RFFEB

RFFEC

TFU

GPSR

GPS

BSC


Architecture: The BSM

Primary functions: OA&M for CDMA components· Configuration management

- BSC, BTS configuration and parameters

· Fault management- Alarm Reporting

· Performance management- interface for CDMA statistics

and peg counts collection· Security management· Unix-based

BSC BTS

CDSU DISCO

Ch. Card ACC

Sa

Sb

Sc

TFU1

GPSR

CDSU

CDSU

DISCO 1

DISCO 2


CDSU

CDSU

CDSU

CDSU

CDSU

CDSU

TxcvrA

TxcvrB

TxcvrC

RFFEA

RFFEB

RFFEC

TFU

GPSR

GPS GPS

BSM

X-Windows terminals

Ethernet LAN

BSM Workstation

GNP TELCOWORKSERVER

SHELF---------HIGH

AVAILABILITY

NORTEL CDMA BSM

BCN Links