New article: "GMSK and OQPSK"

It's a small article, which dealt with the problem of identifying GMSK and OQPSK.
We hope this will be useful...


It's a small fragment...


OQPSK and GMSK are tightly connected, as well as SDPSK and CPFSK, as well as pi/4 DQPSK and C4FM.


Such "dualism" is spread enough, and connected/linked by the fact that often some modes of frequency shift keying at some conditions, smoothly flowing and/or aspire to acquire the shape of phase manipulation.


*** GMSK ***


The general features of  GMSK manipulation formation, we had already considered in the article FSK, GFSK, MSK, GMSK and some other modes . Also it was marked, that application of the filter of the Gauss allows to narrow the main spectrum of a signal considerably.


The filter of the Gauss is characterized by parameter BT, interested ones can independently learn this subject, us interested in the practical for the analysis moments.


The value range of parameter BT lies within 1 > BT > 0 limits. The lesser BT value, the more compact spectrum at resultant signal GMSK.




GMSK with the filter of the Gauss with BT = 1, is turning into classical MSK.


For formation of GSM signals the filter of the Gauss with BT = 0.3 is standardly used, and on an example of the synthesized signals it is possible to look as it looks from positions of tasks of the analysis.




Some preliminary remarks.


As, the finished result of concerning of GMSK nuances will be some conclusions about signal TETRAPOL

, then the synthesized signals have the same speed of manipulation equal 8000 Hz.

Besides, sometimes I will add a bit of white noise in the synthesized signals, because ideal signals though look beautifully, nevertheless, having absolute accuracy, in some cases these ideal signals conceal/hide the general details or make these details badly watched. This moment should be well clear from a picture below.

The full description here.

SA update to version v 6.2.6.4: Visualization improvement.

SA Update to version v 6.2.6.4.

The planned SA update.

The error, which has been found out by users is fixed: At the opening of stereo files with wav tag, which differs from 1 and 3, the program was going into "deep dream". 

Also the displayment of the expanded information about the codec, which is applied in a current wav file is added. I specify, that it is not type of codec which the program supports it, it is the codec title, which is used in the current wav file. Sometimes it allows to communicate with suppliers of records/signals more in detail.

  
Visual displayment of the  constellations and transitions in them is increased in phase viewer , at least visually, the new format looks much more attractive than the old. 

Also, as always, the number of minor bugs is fixed.

PSK: TETRAPOL

TETRAPOL

The trunking system for VHF, Br - 8000, mode GMSK

Author: SergUA6 

Band Width ~9000-1000 Hz

Baud Rate 8000 Hz

n-Ary (PSK/MPSK) GMSK

ACF  20 ms

RX mode  source I/Q record

Perfect by the quality example of TETRAPOL. Sent by foregin collegues.

An example of TETRAPOL (two channeles). Sent by foregin collegues.

Sonograms:

pic.1 General view

pic.2 Manipulation speed

Diagrams:

pic.3 The graphical spectrum

pic.4 Allocation of the channeles

 Pictures:

pic. 5 Phase constellation

 pic.6  Transitions in the constellation

pic.7 The signal's ACF

TETRAPOL - an old enough system of digital trunking communication/connection, which had gotten wide enough spreading. The standard is developed in the mid-eighties the last century. Usage of GMSK modulation with the shaping/forming filter of the Gauss with BT = 0.25 is very interesting. I Will remind, GSM uses the filter of the Gauss with BT = 0.3 and has compact enough spectrum, reduction of this parameter allows to narrow further the spectrum, but as a whole, it does already noticeably reduce interference immunity or restricts/reduces the zone of confident communication. It Was unexpected enough to find out, that on the signals sent by foreign colleagues BT is even less than 0.25, that even more worses interference immunity.


Nevertheless, in TETRAPOL standard it is marked, that it is possible use both channeles as with band 12.5 kHz (most likely it is with BT = 0.25), so in case of need, with a band 10 kHz, and it already implies smaller BT values.


Considering that the standard isn't oriented on commercial networks, and intended for the organization of communication services of public safety, then some lowering of a confident cover zone isn't serious lack according to the developers opinion.

CROWD-36 (SERDOLIK) - OFDM mode

CROWD-36(SERDOLIK) - OFDM mode

Ch-34, Br-40, Sh-40, PSK-4, The OFDM without CP

Author: SergUA6 

Band Width ~1400 Hz

Baud Rate 40 Hz

n-Ary (PSK/MPSK) PSK-4

Count of Carriers 34

Step between carriers 40 Hz

Pilot tone(s) 393 Hz, this tone or pilot, or continue transmit data of zero in PSK-4 mode

RX mode SSB

The example of CROWD-36 (SERDOLIK) OFDM MODE

Sonograms:

pic.1 General view

pic.2 Manipulation speed

pic.3 Detalization of the second channel

 Diagrams:

pic.4 The first channel in the fourth degree

 pic.5 Constellation of the first channel

CROWD-36 (SERDOLIK) - OFDM mode - is curious enough signal, where the principles of OFDM technologies usage  for formation of a various type of manipulations/modulations are perfectly shown. 


MFSK and OFDM segments are generated/formed absolutely equally, the difference is only in the form of used modulation, besides this OFDM signal has no cyclical prefix. Speed of manipulation is precisely equal to frequency space (step between frequencies) - that is the big rarity, and it is possibly linked with the fact, that initial synchronization is provided on the operation stage in MFSK a mode. 


The presence of pilot-tone or the continuous transmission of zero in PSK-4 mode is viewed In the second channel of OFDM segment, alghough i can't say definitely.


Though OFDM signals without CP  are very difficult for the analysis, in this record  it is even possible to define a manipulation mode in the first (lower) channel thus this channel is rather easily possible to select/mark this channel confidently enough, thanking presence of the pilot-tone in the second channel. 


Absence of the prefix allows to use as much as possible densely all the spectrum, with the maximum real speed that in this signal makes 34*40*2=2720 bps. If the second channel is really the pilot, then the maximum technical speed is slightly less - 2640 bps.

MFSK: CROWD-36 (SERDOLIK)

CROWD-36(SERDOLIK)

MFSK-34, Br-40, Sh-40, Ch-34

Author: SergUA6 

Band Width ~1400 Hz

Baud Rate 40 Hz

Count of Carriers 34 manipulation frequency

Step between carriers 40 Hz

RX mode SSB

An excellent example of CROWD36 (SERDOLIK) MFSK. Send by Ware.

Sonograms:

pic.1 General view at the different spectrum resolution.

pic.2 Manipulation speed

Diagrams:

pic.3 Allocation and quantity of the frequencies

pic.4 demodulation in SA

CROWD-36(SERDOLIK) MFSK From the different sources, it is used by various diplomatic services of the CIS countries, Russia is defined in general easily enough. Spacing is 40, speed 40, frequencies 34.Alghough it is necessary to manage to count the frequencies, because to do it on the spectrum it not so that easy. ;) The number "36" in the name of the signal is the mystery for me. I haven't ever seen 36 frequencies, so I may suppose that 36 frequencies are very seldom used or quantity of frequencies does not play a role in the name of the signal. 
Speed of manipulation in chat-mode makes 10 hertz.  Mazielka 2 tone and it is possible Mazielka 6 tones are Very closely connected with Crowd-36.

OFDM, COFDM: DRM+ (DRM-E)

DRM+ (DRM-E)

Ch - 213, PSK-4, Br - 400 Hz, Sh - 444.4(4) Hz, k = 1/9

Author: SergUA6 

Band Width ~95500 Hz

Baud Rate 400 Hz

n-Ary (PSK/MPSK) PSK-4

Count of Carriers 213

Step between carriers 444.4(4) Hz

ACF      100 ms

RX mode Source I/Q record

The excellent example of DRM+. Thanks to IK1YDE.

Sonograms:

pic.1 General view

pic.2 The main signal's parameters.

Diagrams:

pic.3 The constellation in the channel

pic.4 Detalization

Pictures:

pic.5 ACF of the signal.

DRM+(DRM-E) - DRM format for VHF broadcasting, it is intended to extrude the analogue decisions in this sphere. It posseses range of attractive advantages: the necessary band is about 95-96 kHz on the broadcast channel, the transmission till 4 of independed programs is possible in one channel.


The signal itself is the typical representative of OFDM tecnology. All the parameters are defined in SA easyly enough. The maximum technical speed for PSK-4 and 213 channeles is 170 kbit/sec. In reality, the real speed of data transmission is a bit lower (about 130-150 kbit/sec), at the expencse of usage of part of the channels and symbols as the pilot/service.


As far as i know, the prespective of this standard in Russia are *foggy* enough, this record sent by collegues from Europe.

SA update to versionv 6.2.6.3

SA update to version v 6.2.6.3 

This is the planned SA update.

In this version support of Drag-and-Drop function is added.

The function of detection/determinition of the offset modes of the phase manipulation is introduced in the Phase viewer. 

It is necessary to show certain care, as any automatic system of identification, this function can be mistaken, especially on the signals, which are damaged by various distortions. Nevertheless in some cases, the presence of this automatization is justified. 


Also a number of minor errors found out by users is corrected.

~ Good Luck

Scrambler: Hagelin HC-256, HF

Hagelin HC-256, HF
Analogue dynamical synchronized scrambler.

Author: SergUA6 
Band Width  ~3000 Hz
Low Range  ~300 Hz
RX mode  SSB
 

The signal is here. Send by Angstrem.

Sonorgam

pic.1

HAGELIN HC-256, HF - the analogue dynamical synchronized scramler. It sounds like "Pinocchio" :-).

The features of this signal: the preamble is the same as two-channeles FSK-2 with the parameters ( look pic.1). There are short synchro-bursts also every ~400 ms  (look pic.1). 

Update SA to version 6.2.6.0

Update SA to version 6.2.6.0

This is planned update SA.

Added possibility insert the saved path to the file/directory. This is really handy because sometimes a very long way, and clicking on directories rather tedious, easier to insert from the clipboard.

Added the possibility of fast increase in the desired part of the signal in the WF module. Fragment between V-markers scaled over the entire window.

Function of oversampling uses parallel computing, in general, it increases the speed and quality.

 

Quality resampling improved by revising the algorithm and its optimization.

The examples old and current solutions.

Extreme caution should be taken with to any external processing program. As minimum all need thorough inspection and testing, otherwise You may experience various unpleasant incidents, such as this one.

SA provides accuracy of 1 Hz resampling at sampling rates up to 100 MHz.

In fact, precision in 1 Hz is not a fundamental limitation, and the internal procedures of SA uses precision oversampling in fractional values SR, if needs.

In the OFDM module, function of "Find CT" also uses parallel computing.
 

As well as the usual fixed various minor problems.

Good Luck.

OFDM, COFDM: DVB-T (Digital Video Broadcasting — Terrestrial)

DVB-T (Digital Video Broadcasting — Terrestrial)

Ch-1705, QAM-16, Br~2232, Sh~2790, k=1/4 (not standard/typical mode - 4K)

Author: SergUA6 

Band Width ~4800000 Hz

Baud Rate ~2232 Hz

n-Ary (PSK/MPSK) QAM-16

Count of Carriers 1705

Step between carriers ~2790 Hz

RX mode direct output from modulator

The signal is here. Send by horizon.

Sonograms:

pic.1 General view

Diagrams:

pic.2 Quantity of the chanells, manipulation speed

pic.3 Constellation in the channel

pic.4 Constellation in the channel

DVB-T(Digital Video Broadcasting — Terrestrial) - The digital standard of the television, which wide spread all over the world has begun long time ago. In Russia implementation of this standard is carried out since 2004.


This example is received from modulator DVB-MidiMod2 — 2×TS it possesses not absolutely standard parameters. The standard modes for DVB-T modes are 8K and 2K, with a standard band of a signal approximately 7600 kHz. 8K and 2K are the sizes FFT/IFFT blocks, which are used at modulation/demodulation, where K = 1024. In this example the size of the block is not typical for DVB-T - it is equal 4K. 1K, 2K, 4K etc - this are the typified values oriented on usage of the fast algorithms FFT, which hardware implementation is well mastered. Nevertheless, within the limits of coefficient k = 1/4 for this signal, there is a big set of other, absolutely correct sizes of FFT blocks, at which the signal modulation/demodulation is possible, as it is shown. The signal has mass of distinctive features, to enumerate which there is no sense. 
Standard DVB-T itself is well documentated and pretty difficult. 


From explicit features of this signal, it is possible to mark offset/shift of the central channel of the constellation, what is most likely is a consequence of malfunction of the modulator. At total quantity of channels in 1705, loss of one, certainly isn't a fatal problem as in standard DVB-T powerful noise-resistant coding is used. It is necessary to mark that in 2007, the new standard DVB-T2, which had been accepted, possessing considerably more ample opportunities than DVB-T.

Update SA to the version v 6.2.5.8 : implementing technology of parallel computings

Update SA to the version v 6.2.5.8 

Planned SA update. 

At the desire of users, in this version support of 8bit data in unsigned and signed formats is added. The unsigned format is typical for the standard wav files, signed format for the various exterior devices, programs and calculators. 

Also, since this version, we are implementing technology of parallel computings. It allows to double, quadruple etc. speed of the main operations, depending on an amount of cores in the processor. 


The maximum quantity of CPU cores supported by SA is equal 8, it is not the principle limitation, simply we have considered that it will be enough for beginning , and if composition CPU includes 16 cores or more, SA won't use all of them, but SA will try to involve all accessible cores to 8 inclusively. 

On the current moment, the functions of the main working window are already parallelized. The screenshot above, shows: 


- Red color - means already parallelized operations 
- Green color - means not parallelized operations, but very strongly optimized 
- Not selected by any colour - means it is left "as is" yet. 


It is the initial stage of increasing of SA computing power, further gradually, we will translate/turn whenever possible, all functions of the program in this parallel mode. 


Though this version already had preliminary and careful beta testing, some errors are still possible, which will be corrected in the process of their detection. 


Good Luck~

Updating SA to the version v 6.2.5.4.

Updating SA to the version v 6.2.5.4.

This is planned update SA. We had added function of inversion of the whole spectrum at once. This function, in difference from regular procedure, works much more quickly. Very often similar problems arise at the analysis of various I/Q (SDR) records.

At coincidence/combination of H-markers and a call of the regular procedure of in-band inversion, the special case of fast inversion of the whole spectrum is working.


 ***
 two popular enough in analysis functions ACF and CCF are introduced into module WF. Basically, it duplicates similar decisions in the basic working window, but for the module of the form of a signal, this opportunity is far not superfluous.

Please pay attention, that the result of ACF function is displayed in the new window.

The result of function CCF is mapped in the same window, whence the function has been caused. Thus, the basic signal is mapped as a background, and the working element of the window is function CCF, its graphic is scaled, displaced, etc. the Segment/fragment of a signal, which is chosen as example for calculation CCF, is painted in yellow color.


*** 
The work with long symbols (up to 32000 samples (LS) and higher) is provided in module OFDM. The previous versions had restriction in 9000-10000 samples. However, it is necessary to notice, that analysis of OFDM signals with such sizes LS (~ 16000-20000 samples), demands certain, sometimes essential expenses of time.


As usual, a number of internal small (sometimes even funny) bugs, which had been found out by users are eliminated. To a category of the "funny bugs", we bringh a recent turn of image CT, in this version all is returned on former positions.:-) actually, both variants are correct. But as, the left part at us has been proved as "good" in one of early SA articles - "work with module OFDM, FFT spectrum", we decided to return to a former format of CT display.

Good Luck ~