, 253-54 Introduction to Telecommunications Network Engineering OSI reference model (continued) FDMA and TDMA, 217 presentation layer, 258 separation of transmission directions, session layer, 257-58 217-18 TCP/IP stack and, 256 See also GSM transport layer, 256-57 Physical layer, 253-54 defined, 253 Packet control units (PCUs), 230, 231 protocol examples, 253-54 Packet switching, 33, 243-45 See also OSI reference model data transfer, 244 Plain old telephone service (POTS), 16 network design, 243 Plesiochronous digital hierarchy (PDH), networks, voice over, 338 164-66 See also Circuit switching defined, 164 Paging networks, 48 European, 164-65 Parallel transmission, 238-39 North American, 165-66 PBX/PABX, 57-58 problems, 166-67 PCM, 92-106 Poisson formula, 68, 69, 72 1.544-Mbps frame structure, 162-64 Polling, 246-48 2-Mbps frame structure, 160-62 Post Office Protocol (POP), 327 adaptive (APCM), 108 Power binary coding, 103-5 absolute, 117 decoder, 106, 107 gain, 115, 116 defined, 92 levels, 116-18 differential (DPCM), 108-9 loss, 115, 116 encoder, 105-6 signal, 149 frame structure, 159-64 Presentation layer, 258 illustrated, 93 Private mobile radio (PMR), 198-202 nonuniform quantizing, 99-101 defined, 198-99 processing phases, 92 operating principle, 199 quantizing, 96-97 TETRA, 201-2 quantizing noise, 97-99 trunked networks, 200-201 sampling, 92-96 uses, 199 sampling rate, 160 Private networks, 51-58 standardization, 106-7 data communication, 52 See also Speech-coding methods voice communication, 51 PCS-1900, 204 See also Telecommunications network(s) Peak information rate, 80 Professional mobile radio (PMR), 51 Periodic time, 83 Propagation loss, 144 Personal access communication system Propagation modes, 140 (PACS), 198 Protocol stack Personal area network (PAN), 211 data flow through, 260-62 Personal communication service defined, 250 (PCS), 204 TCP/IP, 260 Phase modulation (PM), 135-38 Public land mobile systems (PLMN), 176 defined, 135 Public networks, 47-51 digital, 135, 136 data, 48-49 principle, 135 def