Nowa rodzina szerokopasmowych przebiegów OFDM

i56578-swl.blogspot.com 3 miesięcy temu

A fresh household of wideband OFDM signals has late appeared on-air, most likely tests of Russian origin, and which - at least according to the observations carried out so far - seems to be composed of six waveforms which for convenience I call OWF (OFDM Waveform):

OWF3: 3 KHz bandwidth, OFDM 64-tone
OWF6: 6 KHz bandwidth, OFDM 128-tone *
OWF12: 12 KHz bandwidth, OFDM 256-tone
OWF24: 24 KHz bandwidth, OFDM 512-tone
OWF48: 48 KHz bandwidth, OFDM 1024-tone
OWF96: 96 KHz bandwidth, OFDM 2056-tone **

* the OWF6 waveform has not been observed "directly" but its characteristics and main parameters can be obtained from early-test transmissions [1]
** 1 would anticipate a value of 2048 tones given the numerical progression of both the bandwidth and the number of channels of the erstwhile waveforms; the value 2056 may nevertheless have depended on the precision of SA in the analysis of specified an OFDM modulation (96 KHz wide)

Note that, unlike the western 188-110D App.D (single-tone waveforms, not OFDM), the bandwidths of 9, 15, 18, 21, 30, 36, 42 are missing.
The six waveforms share any common features:

1. first preamble consists of an LFM section followed by MFSK-64 37.5 Bd segment
2. MFSK segent is followed by up-chirped FMCW (Frequency Modulation Continuous Wave) sweeps
3. data transfer is arranged in 15 OFDM blocks, separated by chirps as in 2
4. OFDM blocks have all the same velocity of 37.5 Baud and same channel separation of 46.8 Hz
5. in any waveforms (OWF1, OWF24, OWF48) the first MFSK preamble is followed by the same up-chirped sweeps as in 2

It's interesing to note that OFDM parameters fit DRM-B ones.

OWF3 (3 KHz bandwidth)

Fig. 1 - 3 KHz bandwidth waveform

Fig. 2 - 3 KHz bandwidth OFDM

OWF6 (6 KHz bandwidth)

Fig. 3 - 6 KHz bandwidth waveform
Fig. 4 - 6 KHz bandwidth OFDM


OWF12 (12 KHz bandwidth)

Fig. 5 - 12 KHz bandwidth waveform
Fig. 6 - 12 KHz bandwidth OFDM


OWF24 (24 KHz bandwidth)

Fig. 7 - 24 KHz bandwidth waveform
Fig. 8 - 24 KHz bandwidth OFDM

OWF48 (48 KHz bandwidth)

Fig. 9 - 48 KHz bandwidth waveform
Fig. 10 - 48 KHz bandwidth OFDM

OWF96 (96 KHz bandwidth)

Fig. 11 - 96 KHz bandwidth waveform

Fig. 12 - 96 KHz bandwidth OFDM

While the vast majority of Western countries usage single speech waveforms (see the aforementioned MS-110D) Russian friends favour the improvement of multi-tone waveforms, as OFDM in this case: I am not able to make a comparison of performances, there is surely a valid reason behind preferring 1 approach or the other.

Thanks to my friends ANgazu, Joni, Linkz and KarapuZ for sending me their recordings.

(to be continued)

https://disk.yandex.com/d/s4FclhpM7ZFbAw

[1] http://i56578-swl.blogspot.com/2016/05/cis-ofdm-64-tone-qam-16-40bd.html

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