A simplified block diagram of a DVB-T (digital video broadcasting-terrestrial) system is shown below

A simplified block diagram of a DVB-T (digital video
broadcasting-terrestrial) system is shown below

An MPEG encoder output is characterized by Ru bps. 48408
bits at the input of the BCH encoder become 48600 bits with the addition of
parity bits to correct random bit errors. The output of the low-density
parity-check (LDPC) encoder of rate 3 /4 has 64800 bits. Following the
concatenated FEC encoder (BCH + LDPC), the QPSKmodulated symbols are
transmitted via OFDM with 2048 subcarriers in a 8 MHz bandwidth allocated for
an analog TV channel. The cyclic prefix (guard interval) in the OFDMis

A simplified block diagram of a DVB-T (digital video
broadcasting-terrestrial) system is shown below

An MPEG encoder output is characterized by Ru bps. 48408
bits at the input of the BCH encoder become 48600 bits with the addition of
parity bits to correct random bit errors. The output of the low-density
parity-check (LDPC) encoder of rate 3 /4 has 64800 bits. Following the
concatenated FEC encoder (BCH + LDPC), the QPSKmodulated symbols are
transmitted via OFDM with 2048 subcarriers in a 8 MHz bandwidth allocated for
an analog TV channel. The cyclic prefix (guard interval) in the OFDMis 1/32 of
the useful symbol duration.

a. Calculate the frequency separation between neighbouring
subcarriers and the useful symbol duration and that including the cyclic
prefix.

b. The orthogonality between subcarriers may be assumed to
be preserved if the maximum Doppler shift does not exceed 1% of the frequency
separation between the subcarriers. Then, determine the maximum velocity of the
user terminal that can be served by this system operating at 300 MHz.

c. Determine the symbol rate Rs (symbols/ s) at the output
of the OFDM in terms of the raw bit rate Ru (bits/s) at the output of the MPEG
encoder.

d. Determine the maximum bit rate that can be supported by
this system. Assuming that a standard definition TV (SDTV) channel requires
approximately 4 Mbps, how many SDTV digital TV channels can be multiplexed in
an analog TV channel of 8 MHz bandwidth.