ode on the 3. The air interface between the handset and base has a common specification for telephony SO that a common handset design can be used in all applications. 4. Speech quality equivalent to that of a wired telephone. 49.2.3 Traffic capacity Research has shown (Swain, 1985) that a modest CT penetration of 32 kbit/s ADPCM each way. 7% of all telephone terminals in a city centre could produce mean Channel bandwidth = 100kHz traffic densities in excess of 800 Erlangs per square km. (Note an Erlang is the amount of traffic carried by one line operating for Figure 49.1 Single-carrier burst-mode duplex system 100% of the time. See Chapter 5). Other studies (ETSI, 1992a) indicate the following traffic densities by application: same carrier frequency for both directions. This technique was Residential suburban house, 150E per sq. km at 0.05E per appropriate for a low cost instrument since both ends are identical. telephone and cordless penetration of 30%. Furthermore the technique only required a single block of radio 2. Residential apartment block, 200E per sq. km at 0.05E per spectrum rather than the duplex bands favoured by other mobile telephone and cordless penetration of 30%. radio systems. Hence the band 864-868MHz was allocated to the 3. Cordless business system, 10000 E per sq. km per floor at 0.2E service to support forty 100kHz duplex channels. per terminal and cordless penetration of 100%. By adopting the CCITT standard 32kbit/s ADPCM speech coding Telepoint service (examples of railway stations and airports), algorithm it was possible to contain the transmitted symbol rate to 5500E per sq. km. 72kbit/s with some allowance for framing and signalling bits. In practice the corresponding B-channel capacity is 32kbit/s and that 49.2.4 Digital cordless standards for the D-channel 1kbit/s or 2kbit/s depending on manufacturer's choice. The foregoing requirements clearly point towards a new digital By adopting a common air interface the radio interface is stand- cordless telecommunications standard and as ear