14 April 2018

WBHF comms in the 9 MHz band (188-110C/D Appendix D)


Just a couple of good quality recordings of the wideband activity that can be monitored in 9 MHz band. Both the waveforms belong to WBHF 188-110C/D App.D.

The 6 KHz burst is modulated at a symbol rate of 4800Bd and has a 192 symbols frame consisting of 96 data symbols (user data) followed by 96 known symbols (mini-probes): according to TABLE D-XI and TABLE D-XII, this the Waveform ID 1 or ID 2, (scrambled) BPSK modulation, depending on the used data rate (300 or 600 bps, as in TABLE D-II). Note that the BPSK constellations are scrambled to appear, on-air, as a PSK-8 constellation.
 
Fig. 1 - 6 KHz bandwidth bursts
Fig. 2
The 9 Khz burst has symbol-rate of 7200Bd and a period length of 2048 symbols. The period length helps to identify the waveform as the Waveform ID 0. Quoting D.5.1.4 "For the case of Waveform ID 0, an 8-PSK data scrambling sequence is utilized [...] this implementation is used to generate 256*8 or 2048 values. For the Walsh Orthogonal Modes the sequences are continuously wrapped around the 2048 symbol boundary". Since the 9 KHz bandwidth, the data rate is 300bps (TABLE D-II).

Fig. 3
Linking is performed using 3GWB extensions (3G ALE FLSU + WBALE). WBHF modes could also deliver video for awareness, such bandwidth allows information rather than data.

Fig. 4