Date: Mon, 22 Jan 2001 22:51:29 -0000 (GMT) From: Duncan Barclay <dmlb@dmlb.org> To: Brad Knowles <brad.knowles@skynet.be> Cc: freebsd-chat@FreeBSD.ORG, Kris Kennaway <kris@FreeBSD.ORG>, Michael C.Wu <keichii@peorth.iteration.net> Subject: Re: VCD (was Re: cvs commit: src/sys/dev/ata atapi-cd.c) Message-ID: <XFMail.010122225129.dmlb@computer.my.domain> In-Reply-To: <v04220821b691222656eb@[10.0.1.2]>
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On 21-Jan-01 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. CDMA as a physical layer technology does not allow significantly more calls in the same bandwidth as TDMA. However, what is does do is allow a greater efficiency of bandwidth*time*location/range. This is important as networks are becoming more congested. 3G is not just about higher data rates to users - for example GPRS will do 384kb/s just as 3G will (3G has 2Mb/s for stationary users close to a local basestation, i.e. in a building). What 3G gives operators is greater flexibility in handling calls. Remember that the operators define the standards to serve their needs. > 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. 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. Not correct for 3G, everything above the RLC - Radio Link Contoller layer is the same as GSM networks. This is how basestations connect to switching centres and all the location tracking stuff. If anything IS-95 and IS-95b networks have to change more than GSM ones. GSM networks change basestations, IS-95 change basestations and trunks. > 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. It's on continual replacement anyway. This is not a huge issue. Duncan --- ________________________________________________________________________ Duncan Barclay | God smiles upon the little children, dmlb@dmlb.org | the alcoholics, and the permanently stoned. dmlb@freebsd.org| Steven King To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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