baseband, 145 transmission channel, 126 defined, 20 transmitter, 126 facsimile, 267 Transmitters, 126 media, 20 Transport layer, 256-57 microwave radio, 182 defined, 256 parallel, 238-39 as interference layer, 256 radio, 129-44, 175 service classes, 257 satellite, 175-76 See also OSI reference model serial, 238-39 Trivial File Transfer Protocol (TFTP), 330 synchronous, 239-42 Trunk code, 32 Index Trunked networks, 45-46, 199-201 extranets, 53 analog, 200 firewalls, 52 defined, 199 intranet, 52 operating principle, 199 principle, 52 TETRA, 201-2 See also Telecommunications network(s) Twisted pair, 170-71 Visitors location register (VLR), 192-93 Twisted-pair Ethernet, 292-94 functions, 214-15 10BaseT, 292, 293 GSM, 214-15 defined, 292 See also Home location register (HLR) illustrated, 292 Vocoders, 107, 113 See also Ethernet Voice-band modems. See Modems Voice communication networks, 51 UMTS, 208-9 Voice over DSL (VoDSL), 276 core network, 209 Voice over IP (VoIP), 337-41 defined, 208 applications, 339-40 Uniform Resource Locators (URLs), protocols, 340-41 331-32 defined, 331 Waveform coding, 111 structure, 332 Wavelength-division multiplexing (WDM), See also World Wide Web (WWW) 179-80 Universal Mobile Telecommunications defined, 179 System (UMTS) Forum, 14-15 DWDM, 180 Universal synchronous bus (USB), 248 optical fiber system and, 179 Unshielded twisted pair (UTP), 171 Wide-area networks (WANs), 60 User Datagram Protocol (UDP), 326-27 Wideband CDMA (WCDMA), 209 datagrams, 326 Wireless access, 279-80 defined, 326 Wireless application protocol (WAP), 17 headers, 326, 331 Wireless communications, 358-59 payload, 331 Wireless LANs (WLANs), 49, 210-11, use, 327 280-81 User network interface (UNI), 344 access points (APs), 211 networks, 211 Variable-bit-rate (VBR) service, 343 technology, 210 Variable delay tolerance, 80 Wireless telegraphy, 4 Very-high-bit-rate DSL (VDSL), 276 World Wide Web (WWW), 6, 302, Vestigal-sideband (VSB) modulation, 131, 331-37 132-33 defined, 331 defined, 132 HTML, 334-37 derivation, 133 HTT