ELEC 456 - Mobile Communications
Assignment #4 - Due March 26, 1999

1. A mobile radio system receives a coherent FSK signal with an average SNR per bit of 18 dB. Compute the probability of a word error for a 12-bit word for each of the following cases:
   a) no diversity or error-correcting coding,
   b) 3-out-of-5 multiple transmission,
   c) (17,12) Hamming code,
   d) (23,12) Golay code,
   e) two-branch spatial diversity with equal-gain combining.
2. We want to use a (23,12) Golay code over a mobile channel where burst errors can have a duration of up to 6 symbol periods. Explain how interleaving can be used to get an acceptable BER.
3. Consider three channels:
   channel A: 940.1 MHz
   channel B: 940.4 MHz
   channel C: 940.7 MHz
   
   A base station is transmitting these signals with equal power using a power combiner having an output voltage e_O given by
   e_O = 2e_i + 0.05 e_i² + 0.01 e_i³
   Compute the ratio of in-band IM distortion power to desired signal power for channel B. Assume a 25 kHz bandwidth and ignore terms that cause only amplitude distortion.
4. For a cell radius of 8 km, what is the minimum filter slope required to attain a carrier-to-interference ratio of 18 dB when there is a mobile 300 m from the base station. Assume a=4 and a channel separation of three channels.