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.)