 1.5GHz 1.8GHz 1.5GHz 2.5GHz 2.5GHz 2.7GHz 2.7GHz 800MHz 2.4GHz Number of 10 X 64kbit/s 15 x 32kbit/s 64kbit/s 28 x 64kbit/s 30 X 64kbit/s X 64kbit/s x 64kbit/s 60 X 64kbit/s trunks 16kbit/s 64kbit/s or 64kbit/s channels 12 x 32 kbit/s Aggregate 64 (x26) bit rate (kbit/s) Frame TDMA/ 0.125 0.125 0.125 0.125 period 0.125 down-link (ms) up-link Modulation 16 level 8 QAM or 2-FSK PPM-FM 2-FSK OQPSK 32 QAM (modulation (modulation index 0.5) index 0.5 Number of > 500 128 max 128 (or 256) 94 max 128 max up to 250 512 (or 512 (or 512 or 480 customers 1024) 1024) (2Mbit/s links) Number of 1 X 64kbit/s 8, 16, 32, 96 1 or 6, 12 up to 6 up to 24 32, 48, 128 8 to 32 6 (increase customers or 2x 64kbit/s or (extendable (steps of (ISDN 12 256 (rack (expandable in steps of 6) 32kbit/s to 67) max 160 mounted) to 80) outstation 32kbit/s kbit/s) Transmit 0.1 min 0.3 or 1 4 (1.5GHz) 0.2/2 (800 0.1 or 1 5 (1.5GHz) power 0.8 max 3 (1.8GHz) MHz) 0.2/1 1 (1.7- (Watts) 2 (2.4GHz) 2.7GHz) Threshold -111 10-3 -94 10-4 -97 10 4 -91 10-3 -92 10 3 Analogue - -91 10 4 -92 10 (dBm) BER (8QAM) 10-4 (1.5GHz) - 110 10-3 (32QAM) 10 -4 (2.5GHz) 52/10 Point to multipoint urban and rural radio from just below 1Mbit/s to below 5Mbit/s. The number of trunks or time slots varies between 10 and 60. The smaller systems tend to employ polling technique for accessing time slots, whereas random request slotted ALOHA is used for larger systems (Le-Ngoc, 1985). The systems are designed for operation in remote locations and consequently low power consumption through use of VLSI and high system reliability are their main features. Figure 52.7 shows a typical solar powered outstation. The outstations can be generally mains powered with battery back up or solar powered. Figure 52.8 shows a pole mounted outstation with a power and junction pack. Figure 52.8 A solar powered outstation showing the antenna, solar panels and equipment box (Photo courtsey of TRT, France) that fading exceeds a given margin, M, is given by Equation 52.3, where D is path length (km), and F 