Wireless Ad Hoc and Sensor Networks

More documents

Recommendations

Info

Distributed Power Control and Rate Adaptation 235Jung and Vaidya (2002) suggested that calculating the transmitter powerusing a DPC scheme for the DATA and ACK frames in 802.11 results inthe degradation of QoS. More collisions will occur, thus causing a largeincrease in the number of retransmissions. Consequently, this results inhigher power consumption, lower throughput per node, and lower networkutilization. Additionally, previous DPC schemes for wireless ad hocnetworks (Park and Sivakumar 2002, Jung and Vaidya 2002, Gomez et al.2001, Karn 1990, Pursley et al. 2000) ignore performance guarantees usinganalytical methods. The work from Zawodniok and Jagannathan (2004)overcomes these limitations.In this chapter, the DPC scheme with an embedded channel predictionscheme from the previous chapter is extended to ad hoc wireless networksand a medium access control (MAC) protocol is designed using the DPCfor wireless ad hoc networks in the presence of radio channel uncertaintiessuch as path loss, shadowing, and Rayleigh fading. This embeddedscheme predicts the time-varying fading channel state for the next transmission,in contrast to (Jung and Vaidya 2002, Gomez et al. 2001) wherethe delayed channel parameters from the previous transmission are usedto select the power for the subsequent transmission. The MAC protocolfrom Zawodniok and Jagannathan (2004) uses the DPC scheme to updatethe power so that a target SIR is maintained at the receiver. To minimizethe effect of sudden changes in the channel state in the power selection,a safety factor is incorporated. This DPC scheme is shown to convergeanalytically to any target SIR value in the presence of channel uncertainties.Moreover, the proposed MAC protocol assigns power adaptively forall MAC frames (RTS, CTS, DATA, and ACK) while overcoming the hidden-terminalproblem. As a result, a modest improvement in spatial reusefactor is observed. Finally, a comparison with the standard 802.11 protocolis also included.6.2 Channel UncertaintiesUnlike wired channels that are stationary and predictable, radio channelsinvolve many uncertain factors, and as a result they are difficult to analyze.We focus our effort on these main channel uncertainties, such aspath loss, shadowing, and Rayleigh fading.6.2.1 Signal-to-Interference Ratio (SIR)Each receiving node on a given link measures the interference present inthe channel and communicates this information to the transmitter. In addition,each link autonomously decides how to adjust its transmitter power.
236 Wireless Ad Hoc and Sensor NetworksTherefore, the decision-making is fully distributed at the link level. Consequently,the overhead due to the feedback control is minimal in DPCcompared to its counterpart for centralized operations. Because eachreceiver provides feedback to the transmitter, the DPC presented in theprevious chapter can be extended to ad hoc wireless and sensor networks.The goal of transmitter power control is to maintain a target SIR thresholdfor each network link although the transmitter power is adjusted so thatthe least possible power is consumed in the presence of channel uncertainties.Suppose there are N ∈ Z + links in the network. Let g ij be thepower loss (gain) from the transmitter of the jth link to the receiver of theith link. The power attenuation is considered to follow the relationshipgiven in the following paragraph.Calculation of SIR, R i (t), at the receiver of ith link at the time instant t,is given bygii() t Pi() tRi()t = = gii() t Pi () t gij() t Pj( t) + ηi( t)I () t(6.1)where i, j {1, 2, 3,…, n}, I i (t) is the interference, P i (t) is the link’s transmitterpower, P j (t) are the transmitter powers of all other nodes, and i (t) > 0 isthe variance of the noise at its receiver node. For each link i, there is alower SIR threshold i and upper threshold i *. Therefore, we require(6.2)for every i = 1, 2, 3,…, n the lower threshold value for all links can betaken equal to for convenience, reflecting a certain QoS that the link hasto maintain to operate properly. An upper SIR limit is also set, to managethe interference.6.2.2 Radio Channel Model with UncertaintiesiThe radio channel places fundamental limitations on wireless communicationsystems. The path between the transmitter and the receiver canvary from clear line-of-sight to one that is severely obstructed by buildings,mountains, and foliage. In ad hoc wireless networks, channel uncertaintiessuch as path loss, shadowing, and Rayleigh fading can attenuatethe signal power during transmission and thus cause variations in thereceived SIR which degrades the performance of any DPC scheme. Theeffect of these uncertainties (see Chapter 5) is represented via a channelloss (gain) factor that typically multiplies the transmitter power. Therefore,the channel loss or gain, g, can be expressed as (Rappaport 1999,Canchi and Akaiwa 1999)∑j≠i*γ ≤R () t ≤ γi i ing= f( d,n,X, ζ)=d − ζ⋅ ⋅X10 0.1 2(6.3)
Page 2 and 3:
Wireless Ad Hocand SensorNetworksPr
Page 4:
18. Chaos in Automatic Control, edi
Page 7 and 8:
CRC PressTaylor & Francis Group6000
Page 10 and 11:
Table of Contents1 Background on Ne
Page 12 and 13:
3 Congestion Control in ATM Network
Page 14 and 15:
5.4.2 Distributed Power Controller
Page 16 and 17:
7.3 Adaptive and Distributed Fair S
Page 18:
9.2.2 Overview.....................
Page 21 and 22:
the number of connections in each l
Page 23 and 24:
y Maheswaran Thiagarajan, and tirel
Page 25 and 26:
2 Wireless Ad Hoc and Sensor Networ
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
10 Wireless Ad Hoc and Sensor Netwo
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 72 and 73:
2BackgroundIn this chapter, we prov
Page 74 and 75:
Background 51u(k)x n (k + 1)x n (k)
Page 76 and 77:
Background 53with x( 0)being the in
Page 78 and 79:
Background 55with tr(.) the matrix
Page 80 and 81:
Background 57nGiven a function ft (
Page 82 and 83:
Background 592.3.2 Lyapunov Stabili
Page 84 and 85:
Background 61as well as Jagannathan
Page 86 and 87:
Background 63The subsequent example
Page 88 and 89:
Background 65Evaluating this along
Page 90 and 91:
Background 67Now, select the feedba
Page 92 and 93:
Background 69is SISL if and only if
Page 94 and 95:
Background 71L 1 (x)L(x, t)L 0 (x)0
Page 96 and 97:
Background 73for some R > 0 such th
Page 98 and 99:
Background 75Evaluating the first d
Page 100:
Background 77Section 2.4Problem 2.4
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
100 Wireless Ad Hoc and Sensor Netw
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 170 and 171:
4Admission Controller Design for Hi
Page 172 and 173:
Admission Controller Design for Hig
Page 174 and 175:
Page 176 and 177:
Page 178 and 179:
Page 180 and 181:
Page 182 and 183:
Page 184 and 185:
Page 186 and 187:
Page 188 and 189:
Page 190 and 191:
Page 192 and 193:
Page 194 and 195:
Page 196 and 197:
Page 198:
Page 201 and 202:
Page 203 and 204:
Page 205 and 206:
Page 207 and 208: 184 Wireless Ad Hoc and Sensor Netw
Page 257: 234 Wireless Ad Hoc and Sensor Netw
Page 309 and 310:
Page 311 and 312:
Page 313 and 314:
Page 315 and 316:
Page 317 and 318:
Page 319 and 320:
Page 321 and 322:
Page 323 and 324:
Page 326 and 327:
7Distributed Fair Scheduling in Wir
Page 328 and 329:
Distributed Fair Scheduling in Wire
Page 330 and 331:
Page 332 and 333:
Page 334 and 335:
Page 336 and 337:
Page 338 and 339:
Page 340 and 341:
Page 342 and 343:
Page 344 and 345:
Page 346 and 347:
Page 348 and 349:
Page 350 and 351:
Page 352 and 353:
Page 354 and 355:
Page 356 and 357:
Page 358 and 359:
Page 360 and 361:
Page 362 and 363:
Page 364 and 365:
Page 366 and 367:
Page 368 and 369:
Page 370 and 371:
Page 372 and 373:
Page 374 and 375:
Page 376 and 377:
Page 378 and 379:
Page 380 and 381:
8Optimized Energy and Delay-Based R
Page 382 and 383:
Optimized Energy and Delay-Based Ro
Page 384 and 385:
Page 386 and 387:
Page 388 and 389:
Page 390 and 391:
Page 392 and 393:
Page 394 and 395:
Page 396 and 397:
Page 398 and 399:
Page 400 and 401:
Page 402 and 403:
Page 404 and 405:
Page 406 and 407:
Page 408 and 409:
Page 410 and 411:
Page 412 and 413:
Page 414 and 415:
Page 416 and 417:
Page 418 and 419:
Page 420 and 421:
Page 422 and 423:
Page 424 and 425:
Page 426 and 427:
Page 428 and 429:
Page 430 and 431:
Page 432 and 433:
Page 434 and 435:
Page 436 and 437:
Page 438 and 439:
Page 440 and 441:
Page 442 and 443:
Page 444 and 445:
Page 446 and 447:
Page 448 and 449:
Page 450 and 451:
Page 452 and 453:
9Predictive Congestion Control for
Page 454 and 455:
Predictive Congestion Control for W
Page 456 and 457:
Page 458 and 459:
Page 460 and 461:
Page 462 and 463:
Page 464 and 465:
Page 466 and 467:
Page 468 and 469:
Page 470 and 471:
Page 472 and 473:
Page 474 and 475:
Page 476 and 477:
Page 478 and 479:
Page 480 and 481:
Page 482 and 483:
Page 484 and 485:
10Adaptive and Probabilistic Power
Page 486 and 487:
Adaptive and Probabilistic Power Co
Page 488 and 489:
Page 490 and 491:
Page 492 and 493:
Page 494 and 495:
Page 496 and 497:
Page 498 and 499:
Page 500 and 501:
Page 502 and 503:
Page 504 and 505:
Page 506 and 507:
Page 508:
Page 511 and 512:
Page 513 and 514:
Page 515 and 516:
Page 517 and 518:
Page 519 and 520:
Page 521 and 522:
Page 523 and 524:
Page 525 and 526:
Page 527 and 528:
Page 529 and 530:
Page 531 and 532:
Page 533 and 534:
Page 535 and 536:
Page 537:
show all

Wireless Ad Hoc and Sensor Networks

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?