Talk:GSM services

Cleanup-technical tagging

Commentary on the "too technical" issue has been requested, so I'll try to provide some. I guess I have a lot of criticism...I hope it doesn't sound too harsh by sheer bulk. The subject is very complex and it's difficult to explain clearly and concisely even to a technical audience, so extra special thanks to all you editors trying to make this come through well to a general audience. (This is also going to be quite disorganized because...oh, I'll just make it worse if I try to explain why.)

• The first question I would have here would be, what is the difference between GSM and a GSM service? Aren't they both just collections of technical standards for mobile telephony? If you're trying to separate out "descriptions" from "how it works", then I would put "how it works" front and center, and leave "descriptions" for something like looks like a pumped up glossary. (Otherwise the article(s) read very hard, not like an abstract technical specification.) Also don't forget all the social context - history, adoption, economics, geography, politics, etc. - which can be cleanly separated from a "how it works" discussion, so maybe we'd want to split the articles that way. Certainly the diagrams in Global System for Mobile Communications (and then some) would be helpful in the "how it works" discussion.

This article now focuses more on what the standard services are and why they are important for inter-operability. The GSM page should be used for the social context etc of GSM. The GSM core network page with be used to describe the actual elements involved in a GSM call rather than the end to end service. Anybody agree/disagree with this approach? ChrisUK 00:01, 30 Dec 2004 (UTC)

still to do - create and add diagrams to this page ChrisUK 00:01, 30 Dec 2004 (UTC)

• This article would benefit, I think from separating discussion of voice calls and data calls entirely, basically just moving the "data calls" section down after "Call set up process for incoming calls" and then refactoring. Voice calls are a lot easier to explain, and the data call process is a lot easier to understand once you already understand voice calls. Actually, should all consideration of data calls be moved to General_Packet_Radio_Service?

done, although the data call section still needs work. It should be here as well as GPRS page because we are referring here to circuit switched data calls - rewrite of data section should clarify ChrisUK 00:01, 30 Dec 2004 (UTC)

• "Call set up process for incoming calls" is an excellent start at a smooth, non-technical explanation.
  • We need to say something like "cell phone" instead of "MS" (Mobile Station, I presume)
  • It might better to explain the simple case "I call you from my landline on your cell phone and it rings and you pick up" first, then go back and explain complexities like call forwarding and voicemail. Otherwise, it's all a little much to hold in your head all at once. This might be easier if the steps were more fine-grained (and still numbered, of course).
  • It's better to refer to the various parts of the system with unambiguous nouns rather than acronyms, or possibly both with the acronym in parens. For example, instead of repeatedly referring to "the GMSC", call it "the gateway (GMSC)". It's hard to remember what all the acronyms mean, especially the first time you are exposed to them, and having a word which relates to the entity's role in the system helps a lot. Ooo, Mobility management actually uses "Gateway MSC", which is nice (though that page seems to have some borken links).
  • Step one - instead of using technical language like "static" and "dynamic", it might be better to say something like, "Having received an incoming call from the general telephone network (PSTN), the gateway (GMSC) knows the identity of the device it needs to contact (i.e. its phone number), but not its location on the network. So it simply checks the Home Location Register (HLR) to determine the phone's location." Whoa, wait a minute. We haven't yet explained how the HLR knows where the phone is. If our explanation is to proceed chronologically (which is good), maybe we should start with the sequence of events that happens when you power on your cell phone first thing in the morning. Your phone contacts the nearest cell tower, which has a computer connected to it that lets your phone company know where you are (so it can send incoming calls your way) and requests some data about you, like what types of phone calls you're allowed to make. Perhaps it's best to have a simple, non-technical overview of the system first (that essentially says what I just did), and then take things step-by-step and explain the various computer-entity-acronyms and protocols and ephemeral phone numbers that are involved along the way. It may also be simpler to explain outgoing calls first, then, if a separate explanation is warranted.

done this - added two new section. Incoming calls now needs tweaking to match the format and language of the preceding sections ChrisUK 00:01, 30 Dec 2004 (UTC)

• It's entirely unclear from the article what levels of abstraction everything is working at. A table showing protocol stacks for voice and data calls would be very helpful, along with an English explanation of the sequence. (Something like: When you speak, the phone digitally encodes that with X codec. When the phone is ready to send the data, it divides it up into chunks and passes it to the Y protocol, which encapsulates the data and passes it to the Z protocol, which the actual transmitter uses to modulate the radio signal.) This will clarify whether GRPS is just another protocol in a "GSM" collection, or running on top of an older protocol, or what, and how the user's data ends up on the public Internet or someone else's phone or wherever it needs to go. Hopefully that will also show what's the same and what's different about voice vs. data calls.

I think this should be done on another page (maybe GSM protocols??) otherwise page will descend into jargon again very quickly. ChrisUK 00:01, 30 Dec 2004 (UTC)

• The circuit switched/packet switched issue needs to be explained clearly...GSM_core_network mentions at the beginning that there are both circuit-switched and packet-switched data calls in GSM. It's a little confusing when it says that the packet-switched GPRS is an "overlay" on the circuit-switched GSM. Does this mean that GSM circuits are created, over which GPRS packets are sent? It also seems to imply that SMS messages are carried over a circuit-switched core, but I can't help thinking of text messages as anything other than packets, really. And hey, General Packet Radio Service seems to think SMS is a GPRS service, whatever that means. Having the protocol stacks explained will help clear this up, I think, because then you can point to a specific layer, and say, OK, this is continually transmitting data for the life of the connection in one smooth but digital and forward-error-correcting stream; this is a circuit. This other layer in this other scheme is not; it's packet-switched.

Agreed. Need to rewrite the GPRS section to reflect. Also need to change the GSM core network page. By the way there are two ways to send SMS, one via the circuit switched MSC and the other via the packet switched SGSN ChrisUK 00:01, 30 Dec 2004 (UTC)

• Data calls: Discussion of using GPRS phones as wireless modems for laptops or PDAs should be consolidated instead of being interspersed with discussion of applications on the phone (like SMS) using its data capabilities. Both segments should be made more concrete with examples (at mention the words "laptop" and "PDA" and whatnot).

Agreed - perhaps also a reference should be made on the mobile phone page as well. ChrisUK 00:01, 30 Dec 2004 (UTC)

• Intro section: "SMS" should at the very least link to an article which explains what SMS is. "Common language" is a bit of a stretch, at least for people who don't have a cell phone, but OK.

deleted this phrase as it doesnt fit anyway into the new intro ChrisUK 00:01, 30 Dec 2004 (UTC)

• Voice calls, 1st paragraph - All this business about codecs and bits and sampling and quantization is very confusing. Non-technical readers need some context. Some implicit facts that would benefit from being made explicit: 9600bits/sec is a measure of data transmission speed, which happens to be about 20% of the speed of a typical (56k) modem, right?
• Voice calls, 2nd paragraph - OK, even I'm not sure what this paragraph is saying. I'm sure I could figure it out if I read it three more times, but *ouch*.
• Voice calls, 3rd paragraph - OK, this is a good place to put technical details, after the general picture has already been explained in English.

rewritten entirely and put into a new section ChrisUK 00:01, 30 Dec 2004 (UTC)

• Data calls: Mixing 9600 and 9.6k will definitely confuse some people.
• Data calls: "value added services" is a largely contentless buzz-phrase.

• Section on CAMEL: So, CAMEL exists, and can be used to add stuff to GSM. What sort of things has it been used for or could it be used for? What level of abstraction does it operate at? Alongside SMS on top of GPRS/GSM?

moved to separate CAMEL page for proper flesh out of the topic there. CAMEL isn't a user service directly anyway so it doesnt really belong here. ChrisUK 00:01, 30 Dec 2004 (UTC)

• Paging in GSM networks: This seems to be very duplicative of the content in Mobility management. Either the whole of the paging/location area/routing area process needs to be abstracted cleanly away and kept in the other article, or the whole explanation needs to be in GSM services. Actually, looking at Mobility management, that article covers the same concept for GSM, GPRS, and UMTS. Does the same thing happen for all three, or are there technical differences worth explaining?

moved this and merged in with mobility management and referenced from this page.

• I assume the various Call Forward numbers are listed in the Home LR and Visited LRs?

yes they are ChrisUK 00:01, 30 Dec 2004 (UTC)

Ug, thanks for reading all that. I suddenly have a hankering to watch an episode of The Secret Life of Machines. If only cell phones had been popular in the 80s. -- Beland 10:39, 29 Dec 2004 (UTC)

---

Yay, the re-write made a world of difference!

They are offered by all mobile phone operators as part of their basic offering, and because they are standard, they work the same when a subscriber roams in a different country.

So I was surfing the Cingular site earlier, and they say that GSM phones do not work in Japan and South Korea, and that you need to get a 3G phone when you go there. I wonder whether every other phone provider, including those in developing countries, offer GSM. Also, don't satellite phone providers have non-GSM systems? For now, I just changed "all" to "most".

Working on general clarification now... -- Beland 10:18, 9 Jan 2005 (UTC)

Voice charges

I think I read elsewhere on Wikipedia that in the UK, the caller pays different rates for calls to mobile phones than landlines, which is why all mobile numbers have a different prefix. Here in the US, cell phone subscribers pay for their airtime. Callers pay the same rates for calls to mobile and fixed phones, and there are usually no special prefixes. For US subscribers, roaming simply means they may be charged more for their airtime, unless they have free roaming on their plan. I think I'll convert the "Roaming" section into a general "Charges" section. Someone should please add info about the different charges in the UK and other countries if that's correct. -- Beland 12:31, 9 Jan 2005 (UTC)

Article coordination

OK, so this article now makes a lot of sense and seems really helpful, but it seems to have outgrown its title. It not only describes the various services than GSM provides, but also the elements in the GSM system and several event sequences. It seems to me that a more appropriate title would be something like, "How GSM works". I like the suggestion of relegating description of the network components to GSM core network and GSM protocols.

Remaining todo items, then:

• Create and add diagrams to this page
• Clean up GSM core network and GSM
• Write GSM protocols

-- Beland 16:38, 9 Jan 2005 (UTC)

I assumed that this page was about Suplimentary Services offered by GSM providers. I think that content related to GSM architecture belongs in Base Station Subsystem and Network Switching Subsystem, but I don't know where call flow comes into the picture then. Each of those subsystems is certainly large enough to warrent its own article. Cacophony 07:54, 23 December 2005 (UTC)

Incoming call setup

I've noticed that if someone calls me when I've turned my phone off, it goes straight to my voicemail. However, if my phone loses a signal because it goes out of range, the other party still hears a ring--but it's a different ring than is heard when I'm within range and my phone is ringing. In fact, if I move within range while the third party is hearing the ring pattern, they will hear a change in the ring pattern when my cell picks up the ring signal.

So it appears the GSM standard incorporates a method of determining if a particular mobile station (phone) has powered down or has simply temporarily moved out of range. Furthermore, the MSC or Gateway MSC is able to determine the difference and create a different ring pattern based on which condition is in effect.

It appears that someone who has experience in engineering a GSM system has contributed to this article. Can that person (or people) put something in this article addressing this?

cluth 05:46, 5 November 2006 (UTC)

Copyright problem removed

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why is AOC / Advice of Charge redirecting here?

advice of charge is a general phone network feature. It is present in GSM but also in various ISDN standards. I would even argue that it originated from there.

Why is is it forwarded to GSM in English Wikipedia? Wefa (talk) 18:27, 2 July 2022 (UTC)