View File - University of Engineering and Technology, Taxila

More documents

Recommendations

Info

SecurityData security is a matter of great concern to many Internet users. Two broadtypes of security have been discussed in the literature and in practice: firewallsand encryption. A prominent public-key encryption method for e-mail is thePretty Good Privacy (PGP), which is based on the Rivest–Shamir–Adleman(RSA) algorithm [15]. A secured network can be built over the network byencrypting and decrypting information at both end terminals and stations.Chapter 1, Sec. 1.4 discusses the principles of encryption and decryption.Firewalls attempt to provide filters for both incoming and outgoingpackets in order to improve the security of the networks connected to theInternet. Examples includePacket filters, which use the IP address and TCP port number to decideif a packet can pass through the routers. This filter type is used at thenetwork layer to regulate traffic flow.Proxy servers (also called circuit-level gateways) prevent direct connectionfrom the outside to the service on the inside.Stateful packet inspection (also called dynamic firewall technology) usesa comparison-basis technique, where a packet under filtering iscompared with the saved state of the previously forwarded packets.If the record shows that the packet under inspection appears reasonable,then permission is granted to pass the packet to the intendeddestination.Several firewall products are currently available.8.3.2 The Internet Via SatelliteCurrent technology allows the Internet interaction channel to remain withinthe ISDN link. Satellite technologies are uniquely poised to address some ofthe key challenges that must be met for the Internet to continue its rapidexpansion and advancement: specifically, high-speed access for rural andremote areas; the distribution and delivery of media-rich content; and tightintegration with existing technologies. With advances in technology and theminiaturization of electronic components, bidirectional communications canbe carried over satellite, eliminating the necessity of the subscribers’ (endusers’) terrestrial Internet connections that are inherent with the existing onewaysatellite systems.Figure 8.15 shows a basic Internet access through satellite. The Internetuser (subscriber) accesses the Internet via his=her ISP, which then establishesCopyright © 2002 by Marcel Dekker, Inc. All Rights Reserved.
Page 2:
SatelliteCommunicationEngineeringMi
Page 6:
This book is dedicated to my famili
Page 10:
Because of the immense importance o
Page 14:
means of a combination of applicati
Page 18:
about my promise to my students, an
Page 22:
2.3 Coverage Area and Satellite Net
Page 26:
1Basic Principles of SatelliteCommu
Page 30:
and voice (telephone) communication
Page 34:
FIGURE 1.2Communication between two
Page 38:
interpreting or uncovering the deci
Page 42:
cryptographic keys K ti (where i ¼
Page 46:
FIGURE 1.6Block ciphering technique
Page 50:
FIGURE 1.7Part of block ciphering w
Page 54:
Based on the ordering sequence of (
Page 58:
TABLE 1.1 (continued )S612 1 10 15
Page 62:
For an uncoded message x and the fe
Page 66:
2. Your task is to develop a commun
Page 70:
FIGURE 2.1Geometry of a satellite.
Page 74:
Future trends in satellite antennas
Page 78:
In the United States, the three sat
Page 82:
TABLE 2.3Typical Links Frequency Ba
Page 86:
FIGURE 2.4Satellite period and orbi
Page 90:
FIGURE 2.6An illustration of covera
Page 94:
FIGURE 2.7constellation.A sketch of
Page 98:
width of 1:73 with reduced coverag
Page 102:
y ¼ elevation angle of satellite f
Page 106:
We can conclude that the antenna mu
Page 110:
FIGURE 2.9Design flowchart of a sat
Page 114:
Risk control and monitoring measure
Page 118:
TABLE 2.4Antenna Selection Criteria
Page 122:
Then the system availability can be
Page 126:
In fact, MTBF is the reciprocal of
Page 130:
2.7 ANTENNASBased on function, sate
Page 134:
Two kinds of horns in common use ar
Page 138:
FIGURE 2.13Geometry of a parabolic
Page 142:
FIGURE 2.14 Axisymmetric reflector
Page 146:
A transceiver antenna is a single a
Page 150:
The gain, in the axial mode, of a h
Page 154:
angles, spacecraft may shadow the s
Page 158:
3. The probability of both parallel
Page 162:
the baseband signal (more details a
Page 166:
matrix in the communications subsys
Page 170:
FIGURE 2.24Typical transfer charact
Page 174:
4. Iridium LCC (1997). Iridium Syst
Page 178:
3Earth StationsIn Chap. 2 we discus
Page 182:
The most popular forms of modulatio
Page 186:
Small earth stations are antennas w
Page 190:
FIGURE 3.2BPSK space diagram.Instea
Page 194:
OQPSKOffset QPSK (OQPSK) is a modif
Page 198:
FIGURE 3.7An 8-PSK space diagram.an
Page 202:
aud. The word ‘‘baud’’ hono
Page 206:
Noise power density N 0bandwidth:N
Page 210:
We observe in (3.11) that E b =N 0
Page 214:
to (3.23) shows that a margin of 11
Page 218:
FIGURE 3.12 Principle of scrambling
Page 222:
Equalization FilterAn equalization
Page 226:
that is, N zeros at the top and bot
Page 230:
Example 3.2: Consider a transmissio
Page 234:
which can be written as89>=R xy ðt
Page 238:
ecause a voice signal is usually hi
Page 242:
systems is discussed in Sec. 4.2. O
Page 246:
where T e is the equivalent tempera
Page 250:
operating principle of all directio
Page 254:
performance of the satellite commun
Page 258:
3. For two independent sources, wit
Page 262:
FIGURE 3.21 A representation of mut
Page 266:
In practice, Eqs. (3.78) and (3.76)
Page 270:
This condition is always satisfied
Page 274:
Copyright © 2002 by Marcel Dekker,
Page 278:
epeaters overshooting into subseque
Page 282:
6. Conventional BPSK modulation all
Page 286:
4Satellite LinksA satellite link co
Page 290:
FIGURE 4.2 Basic antenna parameters
Page 294:
For unity efficiency, and substitut
Page 298:
This expression neglects losses oth
Page 302:
This expression is equally valid fo
Page 306:
and Lin [5]:whereL ¼L o1 þ L oðr
Page 310:
3. Calculate attenuation A r in dB
Page 314:
4.2.1 Intersatellite LinksAs indica
Page 318:
We know from (4.4b) that f c is dep
Page 322:
FIGURE 4.9 Cross-link transmission
Page 326:
Follow the uplink procedure for the
Page 330:
Satellite:Frequencies:14.75 GHz up
Page 334:
6. For link to be maintained betwee
Page 338:
5.1 PRINCIPLES OF MULTIPLE ACCESSAs
Page 342:
neously, their transmissions collid
Page 346:
technique and would remain the most
Page 350:
FIGURE 5.4 Typical TDMA frame struc
Page 354:
FIGURE 5.6TDMA throughput for an IN
Page 358:
and transmits through the satellite
Page 362:
FIGURE 5.8FDMA total capacity respo
Page 366:
tion; that is, log e ð1 þ xÞ x t
Page 370:
REFERENCES1. Spilker, J.J. (1977).
Page 374:
6.1 CHANNEL CODINGNoise within a tr
Page 378:
where G is a generator matrix that
Page 382:
The syndrome is a single word of le
Page 386:
SolutionComparing (i) and (ii) with
Page 390:
Cyclic CodesCyclic codes are a subs
Page 394:
When errors occur in bursts, the nu
Page 398:
FIGURE 6.3Rate 1/2 convolutional en
Page 402:
us to a particular node in the tree
Page 406:
FIGURE 6.6 Trellis diagram of Fig.
Page 410:
FIGURE 6.9 Trellis diagram of Fig.
Page 414:
A generalized Viterbi algorithm is
Page 418:
3. Huffman, D.A. (1952). A method f
Page 422:
4. Draw a block diagram for a convo
Page 426:
1. The first essential requirement
Page 430:
use. The ITU Radio Regulations gove
Page 434:
Within the CCITT structure exist a
Page 438:
7.2 NATIONAL AND REGIONAL REGULATIO
Page 442:
8Mobile Satellite System Services8.
Page 446: Copyright © 2002 by Marcel Dekker,
Page 450: may reside within a single LDSN. Th
Page 454: destination through the intermediat
Page 458: can be used at separate user-to-net
Page 462: where0 n 40 m 246n þ m 24ð8:
Page 466: elationship between OSI and ISDN: t
Page 470: network and for networks to communi
Page 474: Copyright © 2002 by Marcel Dekker,
Page 478: shown in Fig. 8.1. Some of the attr
Page 482: It is possible to formulate a metho
Page 486: transmitting power. The smaller the
Page 490: FIGURE 8.12Tessellated clusters of
Page 494: 8.3.1 The InternetThe Internet cons
Page 500: access to an Internet point of pres
Page 504: message security via satellite is d
Page 508: REFERENCES1. Wu, W.W. (1989). Eleme
Page 512: Appendix ANotationsThe symbols have
Page 516: N sPP rP sP TRRðtÞR cR eR rR vSS
Page 520: g Central anglez Channel gainZ Ante
Page 524: AttenuationBandwidthBearer serviceB
Page 528: Frequency divisionmultiple accessFr
Page 532: MultiplexingNetworkOmnidirectionala
Page 536: UplinkUser-to-networkinterfaceThe e
show all

View File - University of Engineering and Technology, Taxila

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

Delete template?

Save as template?