Question

Q1 Marks: 40 A digital communication system has 96 analog telephone signals, each band limited to 4 kHz. The telephone signals are converted to digital binary data using Pulse Code Modulator (PCM) system, which use a uniform quantiser followed by an 8-bit encoder. The system uses two bits for synchronization. The digital binary data are then time-division multiplexed and transmitted over a single communication channel. Analyse the communication system by considering the following principles: (i) Determine the number of quantization levels and the bit duration. [8 Marks] (i) Evaluate the bandwidth and the dynamic range of the PCM system. [10 Marks] (iii) Calculate the system total data rate. [7 Marks] (iv) Calculate the bandwidth efficiency. [5 Marks) (v) Provide your suggestions on how to improve the system efficiency. [10 Marks] Answer:

Answer 1

given : 96 Solution : Here following information No. of message Signal (channel) Noi Bits/sample=8 Рcom technique used fm це No. bits of Symchronization ie (2:2) 2 Na quantisation level im Pem is given by 2 (28) 256 level And, Bit duration (Tb) = (Ts) inn) cohere, Ts = sampling time a Caneloni te cene To where Ro= (Bit rate) Rb where ts=2fm Rb = (nn talts Rb = (8x96+2) x 2 x 4 Rb *, 6.16 bits/sec To 0.162 usec. (6160kHz) 6.168106 bitslaec Bit duration = 6'162 adec. R₂) are added at the where, Synchronization bits of each Curte frame end to ensure Speed Synchronizato So at the output cue can recover easily. the message

ii) Bandwidth = Nnt alts (96x2 + 2) 2x 4 6.16 MHz Bandwidth 6. 16 MHZ and Total Dynamic jange (2 AM) Am 22 Amplitude of message signal. Dara Rate = Bit Rare R R₂ = 6.16.8 100 bits/sec. (Already calculated) int Bandwidth efficiency Rb Bow + (6. 16 x 100 6.168106 Bandwidth efficiency = 1 v In order to improve System efficiency Subsquent rever of multiplexing need uge. to