Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!accuvax.nwu.edu!nucsrl!telecom-request From: Gary Segal Newsgroups: comp.dcom.telecom Subject: Re: Is Analog Cellular Dead? Message-ID: <8863@accuvax.nwu.edu> Date: 11 Jun 90 16:19:59 GMT Sender: news@accuvax.nwu.edu Organization: Motorola INC., Cellular Infrastructure Division Lines: 55 Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 10, Issue 427, Message 4 of 12 peter@ficc.ferranti.com (Peter da Silva) writes: >I thought one idea behind cellular was to push the cells closer together >when that happened. Put in more, smaller cells. There is a limit to how small a cell can be. Once that limit is reached, the only way to increase capacity is to add more channels. When you run out of channels, you have maxed out the system. Digital cellular will allow many more channels in a given cell. >And do the digital phones have the same bandwidth as the analog ones? >Do they still give you a full-time 3 KHz channel, suitable for >modeming? If you mean "can I put a modem on the phone?", the answer is "no". If you mean "can I still access analog data services?", the answer is "yes", if the digital cellular system is properly designed. A properly designed digital cellular system is best described as a radio ISDN (Integrated Services Digital Netork), that has one B (bearer) channel that is capable of transmitting data or compressed voice. Typical data rates on the B channel are anywhere from 6kbps to 24kbps, depending on the system. To send voice down this pipe, it must be compressed. Because of the compression, it is impossible to send most modem modulations down the B channel (300 buad Frequancy Shift Keying [FSK] might work, but not 2400bps V.22bis or 9600bps V.32). In order to allow subsribers to access modem based data services, these systems make provisions for a modem pool (again, much like an ISDN) at the connection point to the PSTN (Public Switched Telephone Network). With a modem pool, the connection from the modem to the mobile terminal is digital. Data rates can be up to the maximum B channel rate of the system. In addition, the system can supply an error correcting or error controlling protocol to run between the modem pool and the mobile terminals, giving the subscribe a much cleaner link then could ever be established in an analog cellular enviroment. In addition, connection to an ISDN is straight forward. Digital Cellular will be a great improvent over analog cellular for both the subscribers and the providers. For providers, more subsribers can be supported. For subscribers, ISDN like data services will be available from a mobile phone. As an example of digital cellular done well, I suggest you watch what is happening in Europe, with the Pan-Euorpean Digital Cellular standard (also called GSM). Gary Segal ...!uunet!motcid!segal +1-708-632-2354 Motorola INC., 1501 W. Shure Drive, Arlington Heights IL, 60004 The opinions expressed above are those of the author, and do not consititue the opinions of Motorola INC.