Talk:Minimum-shift keying

Question
How MSK is placed ?


 * What does your question mean?? Oli Filth 11:59, 22 September 2006 (UTC)

Merging to CPM
MSK is a special case of CPM, but not necessarily have to be merged. I disagree on merging. Memming 16:17, 2 May 2007 (UTC)

I agree that it should not be merged. MSK is an important enough topic to keep separate. —Preceding unsigned comment added by 75.85.42.213 (talk) 20:08, 6 September 2007 (UTC)

MSK is a separate topic and should not be merged. However more can be written on this page. —Preceding unsigned comment added by 203.110.243.21 (talk) 14:24, 18 September 2007 (UTC)

I think the question is coming from the fact that a popular method of CPM is GMSK, which is a popular version of MSK. However, that doesn't necessarily branch out to mean that MSK should be included in CPM. —Preceding unsigned comment added by 66.180.108.83 (talk) 21:35, 26 September 2007 (UTC)

Modulation memory?
In the section "Gaussian minimum-shift keying", the term "modulation memory" is used and is linked to http://en.wikipedia.org/wiki/Modulation_memory whose target is actually http://en.wikipedia.org/wiki/Modulation_memory#Digital_modulation_methods. The target page does not define or even use the term "modulation memory". I lack the technical knowledge to remedy this. I hesitate to simply remove the link, since I would like someone with the necessary knowledge to edit the target page (or create a new one) to define the term. Dhikr (talk) 14:28, 23 September 2012 (UTC)

Bluetooth LE as an example of GMSK
Yesterday, I inserted Bluetooth Low Energy into the list of notable GMSK examples as "in a close approximation [of GMSK]". I used the phrase "close approximation" because the BLE standard only requires that the modulation index be close to 0.5, not exactly 0.5. User Glrx reverted this stating that "approx should not be most notable".

Frankly, I think that my edit was entirely reasonable based on, for example, this article:

http://www.digikey.com/us/en/techzone/wireless/resources/articles/bluetooth-goes-ultra-low-power.html

"Finally, Bluetooth Low Energy’s modulation scheme also contributes to its low energy profile as well as greater robustness. Both Classic Bluetooth and Bluetooth Low Energy utilize Gaussian frequency shift keying (GFSK). However, Classic Bluetooth uses a modulation index of 0.35, while the modulation index for Bluetooth Low Energy is set at between 0.45 and 0.55, which is close to the level for Gaussian minimum shift keying (GMSK)."

If, after a reasonable time, no one other than Glrx objects, I'm going to re-instate this edit. We could use at least one more example of GMSK in the real world and Bluetooth Low Energy is probably the most-common example after GSM.

Atlant (talk) 20:12, 3 September 2013 (UTC)

Modulation Index
I am concerned by the statement that the modulation index is 0.25. My understanding is that it has a modulation index of 0.5. The best online description of MSK that that I have found so far is http://www.winlab.rutgers.edu/~narayan/Course/WSID/Lectures02/lect11.pdf. J.G Proakis in “Digital Communications” also states that the index is 0.5.

I think that the problem lies in the use of the definition of modulation index for analogue FM. For 2FSK it is the difference in the upper and lower frequencies divided by the symbol rate (see http://www.cdt21.com/resources/Modulation/modulation_FSK.asp).

Sweng1158 (talk) 08:02, 2 November 2013 (UTC)

GMSK is based on two ideas: one is shaping of data pulses with gaussian filter, the other is FSK. MSK uses index that is much lower than indices for FSK. There is no rule that it has to be 0.5 or 0.25. Anything "low enough" is good enough to rename FSK as MSK. Such modulation has very different spectrum so that it may be distinguished from FSK. Its spectrum looks more like AM (center freq visible plus sidebands) but it is not AM. As far as I know Bluetooth since it early days used GMSK. I don't know about BLE specification, but probably GMSK is available for backward compatibility. So reverting change which introduced here Bluetooth was wrong. Check Bluetooth page - there is GFSK mentioned, which has really low modulation index therefore it should/can be name GMSK. 79.184.111.69 (talk) 19:56, 21 February 2020 (UTC)

GMSK ISI a non-issue in clever receiver designs
It might be worth noting that the so-called complexity of GMSK ISI is not really an issue in many receiver implementations, since the successive symbols are always in relative quadrature phase, and so the ISI is always 90 degrees out of phase with the symbol it is interfering with.

--DavidABurgess (talk) 17:45, 26 November 2018 (UTC)

Wrong Q-function
The Marcum-Q-function seems to be misplaced in this context should be replaced with the usual one, Q-function. 2001:4C80:50:42:155B:EF67:91F8:4D4D (talk) 13:51, 18 December 2019 (UTC)
 * Done. cathartid - talk 05:58, 26 April 2020 (UTC)