Both GSM and DECT use GMSK, but with different Gaussian filters (BGT = 0.3 in GSM, BGT = 0.5 in DECT). What are the advantages of having a larger bandwidth time product? Why is the lower ones used in GSM?
A system should transmit as high a data rate as possible within a 1-MHz bandwidth, where to use MSK or BPSK with root-raised cosine filters with α = 0.35? Note: this question concentrates on spectral efficiency, and avoids other considerations like the peak-to-average ratio of the signal.
Consider a point-to-point radio link between two highly directional antennas in a stationary environment. The antennas have antenna gains of 30 dB, distance attenuation is 150 dB, and the RX has a noise figure of 7 dB. The symbol rate is 20M symb/s and Nyquist signalling is used. It can be assumed that the radio link can be treated as an AWGN channel without fading. How much transmit power is required (disregarding power losses at TX and RX ends) for a maximum BER of 10-5.
(a) When using coherently detected BPSK, FSK, differentially detected BPSK, or noncoherently detected FSK.
(b) Derive the exact bit and symbol error probability expressions for coherently detected Gray-coded QPSK. Start by showing that the QPSK signal can be viewed as two antipodal signals in quadrature.
(c) What is the required transmit power if Gray-coded QPSK is used?
(d) What is the penalty in increased BER for using differential detection of Gray- coded QPSK in (c)?