13.9 As was mentioned, the one-way bandwidth available to a single operator in the AMPS system is 12.5 MHz with a channel bandwidth of 30 kHz and 21 control channels. We would like to calculate the efficiency with which this system utilizes bandwidth for a particular installation. Use the following parameters: Cell area = 8 km Total coverage area = 4000 km Frequency reuse factor 7 Average number of calls per user during the busy hour = 1.2 Average holding time of a call = 100 s Call blocking probability = 2% a. How many voice channels are there per cell? b. Use Table 13.1 and a simple straight-line interpolation to determine the total traffic carried per cell, in Erlangs/cell. Then convert that to Erlangs/km2. c. Calculate the number of calls/hour/cell and the number of calls/hour/km2. d. Calculate the number of users/hour/cell and the number of users/hour/channel. e. A common definition of spectral efficiency with respect to modulation, or mod- ulation efficiency, in Erlangs/MHz/km, is 11 (Total traffic carried by the system) (Bandwidth) (Total coverage area) Determine the modulation efficiency for this system.