point of presence), 175 traffic profile of, 333f ports, 326 United States, 16-17 positive acknowledgment with retransmission waiting systems in, 63 (PAR) mechanism, 325-326 pull-in/hold-in, 141 positive justification, 125, 126 pulse amplitude modulation (PAM) highway, 118 postdialing delay, 160, 363 pulse amplitude modulation wave, 109, 110f potential drop, 576 pulse code modulation (PCM), 108-118. See also POTS (plain old telephone service), 170, 318 PCM entries power budget, 243 coding step in, 113-118 power factor, 596 quantization step in, 109-113 power levels, video transmission, 409 sampling step in, 108-109 power-limited fiber-optic link, 233 standards, 108 power-limited system, 242 system enhancements for, 122 power splitter, 433 system operation of, 118-119 Preamble field, MAC frame, 302 pulse stuffing synchronization, 123f preemphasis, 414 push-button codes, 158 preventive cyclic retransmission error correction, push service, 326-327 369-370 pX64 kbps codec, 423-427 primary station, HDLC, 284 source coder, 424-427 printed circuit board (PCB), 31 video multiplex coder, 427 priority control, 532 priority service queue discipline, 63 probability-distribution curves, 60-61 QPSK modulator, 210f probability of blockage, 58 quadratic equations, 609-610 probability of delay, 63 quadratic formula, 609-610 probes, 559 quadrature-amplitude modulation (QAM), 209-210 "proceed-to-send" signal, 161 quadrature phase shift keying (QPSK), 208, 229, processing gain, spread spectrum system, 473 273-274. See also QPSK modulator processing satellites, 217 Qualcomm CDMA design, 474 program channel, 108, 413 quality of service (QoS), 14-15, 41-45 transmission methods, 413-414 ATM, 531-532 data circuits and, 44-45 program store SPC function, 73, 74 progressive call control, 183 frame relay, 336 propagation, non-LOS path, 480 grant per subscriber station operation, 356 propagation delay, 394 in long-distance network design, 173 propagation time, 262 signal-to-noise ratio and, 41-42 in satellite communications, 218 video (televis