Date: Sun, 21 Jan 2001 18:20:33 -0600 From: "Michael C . Wu" <keichii@iteration.net> To: Greg Lehey <grog@lemis.com> Cc: Brad Knowles <brad.knowles@skynet.be>, Kris Kennaway <kris@FreeBSD.ORG>, freebsd-chat@FreeBSD.ORG Subject: Re: GSM vs. CDMA (was: VCD (was Re: cvs commit: src/sys/dev/ata atapi-cd.c)) Message-ID: <20010121182033.C44819@peorth.iteration.net> In-Reply-To: <20010122103136.L93049@wantadilla.lemis.com>; from grog@lemis.com on Mon, Jan 22, 2001 at 10:31:36AM %2B1030 References: <200101211447.f0LElEk04073@mobile.wemm.org> <KAECKEJJOLGHAFGGNIKMAELICAAA.res02jw5@gte.net> <20010121145018.A73989@citusc17.usc.edu> <20010121165422.A44505@peorth.iteration.net> <v04220821b691222656eb@[10.0.1.2]> <20010122103136.L93049@wantadilla.lemis.com>
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On Mon, Jan 22, 2001 at 10:31:36AM +1030, Greg Lehey scribbled: | On Monday, 22 January 2001 at 0:46:38 +0100, Brad Knowles wrote: | > At 4:54 PM -0600 2001/1/21, Michael C . Wu wrote: | > | >> I ask the same questions about why Americans not using | >> GSM but PCS cell phones. (FYI, the reason for using PCS in the U.S. | >> was a pure political reason, none other than America wanting | >> to "lead" the industry. :) ) | > | > Qualcomm invented Code Division Multiple Access (CDMA), the | > superior digital cell phone technology that is the basis for all 3G | > projects around the world. CDMA is supplanting TDMA in the US, | > because it allows you to carry more calls in the same amount of | > frequency bandwidth than TDMA, the previous digital technology. | > | > Anybody that has to replace TDMA technology with CDMA technology | > winds up pretty much completely replacing the entire network they | > built, which is why it's still taking time to make this conversion in | > the US. | | Hmm. This doesn't tie in with what I've been told by people in the | business of developing the equipment. According to my information, | the reason they took CDMA in the US was because it *was* easier to | upgrade from analogue to TDMA to CDMA. The costs are almost the same between TDMA and CDMA equipment. | > However, Europe made the "leap" to TDMA technology in GSM, before | > CDMA existed -- standard AMPS/NAMPS style analog cell phone | > technology had been stretched beyond its limits, and they had no | > choice but to go digital. | | It's true that GSM is a TDMA technology, but it's definitely not what | is called TDMA in the USA. GSM is a set of protocol for mobile phones, and so is PCS. I tend to think of them as being comparable to TCP vs. UDP. Believe it or not, the OSI 7-layer useless model applies to mobile phones and telecomm too. We have counterparts to TCP/IP OSI model in the mobile comm OSI model. Why do I think that OSI model is useless? To paraphrase/quote wpaul: "Nobody in the real world uses the OSI model, it was created just so that professors and other people can make paper tests that have no importance other than making students memorize useless things." | > Therefore, pretty much all European companies will end up | > ripping out their entire set of existing TDMA-based GSM networks and | > replacing them with brand-new CDMA-based 3G equipment. | | Have you seen any evidence of this? In Australia, we have both, but | there appear to be no efforts to supplant GSM. I've just spoken to | Hugh Blemings, the author of gnokii, and he points out that other | features of GSM are far superior to CDMA. Bandwidth utilization isn't | the only factor. | | > The same will happen in the US, as 3G takes over from existing | > TDMA, CDMA, AMPS/NAMPS networks, but at least many of those | > companies will have relatively less money thrown down the TDMA hole | > which they then have to completely write off. | | Don't forget that they have recently started introducing GSM into the | USA. I've found that it works better than the CDMA service. This has | nothing to do with the relative merits of the technology, but with the | fact that the service providers learnt that their cell placement was | too sparse for the old analogue/*DMA network, and they placed them | closer for GSM. Yes, I recently switched from AT&T PCS to Voicestream GSM in America. | >> But since the rest of the world uses SI units and GSM phones, | >> there is not much "leading" there. | > | > At least if you're in the US and you're in an area supposedly | > served by your carrier but their signal is too weak, you can roam on | > the networks in that same area that are operated by their competitors | > -- you can't do that over here. | | I'm not sure to what extent it works in the USA. | | > Of course, US phones also have the concept of "multiple NAMs" | > (Number Assignment Modules, i.e., account numbers), so that you can | > actually have accounts on multiple different carriers, and switch | > between them at your leisure. Many allow up to 99 NAMs on a single | > phone. Just try that with a GSM. | | Not a problem. You store each of them on a SIMM. When I go to other | countries, I often borrow a local SIMM to save on costs. Just try | that with CDMA. CDMA is not a cell phone protocol. :) CDMA is...what we can approximate as frequency-hopping between channels. (Yes, I know this is a bad approximation, but it is the best I can do in a sentence.) TDMA is time-sharing a channel. The reason that CDMA works better is because it resists noise and transmits more data. -- +------------------------------------------------------------------+ | keichii@peorth.iteration.net | keichii@bsdconspiracy.net | | http://peorth.iteration.net/~keichii | Yes, BSD is a conspiracy. | +------------------------------------------------------------------+ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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