Hello Bob,
Answers are in-line:
On 3/22/21 4:21 PM, Robert Bruninga wrote:
Additionally, GMSK's performance (probability of error) is close, but not equal, to BPSK for a given Eb/N0. The difference is up to several dB of required signal power for the same bit error rate. These numbers assume no channel coding to correct for errors on either system.THE DIFFERENCE WHICH WAY?
GMSK requires up to several dB more SNR than BPSK to achieve the same bit-error rate (BER).
There's always a trade-off between bandwidth and power. GMSK trades off power for better-constrained bandwidth, while BPSK does the opposite. Not having to have a well-linear amplification system helps out with system efficiency, but noise performance offsets this gain.TRADES OFF... Means works better at low power received?, or needs more power to transmit??
For a given BER and a given noise power, GMSK will require more signal power as compared to BPSK. However, the GMSK signal, when viewed in the frequency domain, will have a narrower bandwidth than the BPSK signal.
A completely AWGN (additive white Gaussian noise) system is assumed here, as there isn't much in space to produce significant multi-path fading. (This is also why the JTxx and WSPR multi-tone systems are not at all energy efficient for VHF+ space communications, while they excel at ionospheric bounce on HF.)
--- Zach N0ZGO