weinstoc@SEI.CMU.EDU (Chuck Weinstock) (09/24/88)
If I call a number associated with a cellular phone, how does the cellular phone operator know which phone to ring and where it is. I can think of two possible answers: 1. Periodically each cellular phone emits a "here I am" which is received by the nearest cells and recorded in a database. 2. When a call for a particular phone comes through all cells in the system broadcast a "where are you" and the cellular phone responds. If anyone knows the details of the protocol used I'd appreciate hearing from them. Chuck Weinstock
dave@rutgers.edu (Dave Levenson) (10/01/88)
In article <telecom-v08i0146m03@vector.UUCP>, weinstoc@SEI.CMU.EDU (Chuck Weinstock) writes: > If I call a number associated with a cellular phone, how does the > cellular phone operator know which phone to ring and where it is... When you dial a number assigned to a cellular mobile telephone, all of the cell-sites in the mobile phone user's home region broadcast the incoming call alert. The mobile unit periodically scans the page channels upon which such a message can be broadcast, and locks on the one with the strongest signal. Thus the mobile, while not busy, locates itself wrt the cellular network, and decides which cell-site to monitor for incoming calls. When it hear's its own number in the data-stream it receives on the page channel, it transmits an acknowlegement on the access channel specified in the page channel's message. When a mobile phone user originates a call, the mobile phone transmits a service request on this same access channel, and expects to receive a channel-assignment in reply. Once a call is in-progress, the mobile telephone switching office (MTSO) decides which channel on which cell-site station will handle the call, and directs the appropriate hand-offs. In summary, idle cellular telephones locate themselves. Busy cellular telephones are located by the MTSO. -- Dave Levenson Westmark, Inc. The Man in the Mooney Warren, NJ USA {rutgers | att}!westmark!dave
brian@umbc3.UMD.EDU (Brian Cuthie) (10/05/88)
In article <telecom-v08i0146m03@vector.UUCP> weinstoc@SEI.CMU.EDU (Chuck Weinstock) writes: >X-Administrivia-To: telecom-request@vector.uucp (USENET Telecom Moderator) > >If I call a number associated with a cellular phone, how does the >cellular phone operator know which phone to ring and where it is. I [stuff deleted] Your second guess was correct. When a call comes in, if the cellular phone in question is already involved in a conversation, then the matter is simple. Otherwise, the entire system sends out a page for the phone. When the phone answers, it's location is determined and it is sent a command to ring. In most Cellular One (tm) systems, the clicking you here when you call a cell phone, is designed to keep you on the line while the system pages the phone. Ringback is only heard if the phone is actually located. In typical Bell systems, ringback is given immediately. Then if the phone doesn't answer by the second page, you are transfered to the intercept. Personally, I like the Cell One approach. I would rather not hear "ringing" unless the phone is actually ringing. One trick I sometimes use is to set my Motorola 8000X (the best phone ever made) into the mode where it will not answer pages. Instead, it beeps like a pocket pager. Since it doesn't answer the page the caller gets transfered to the voice-mail system. I know I've gotten a message because the phone beeps. Then I can call at *my* convenience. -brian
woerz@uunet.UU.NET (Dieter Woerz) (11/18/88)
In article <telecom-v08i0146m03@vector.UUCP> weinstoc@SEI.CMU.EDU (Chuck Weinstock) writes: >X-Administrivia-To: telecom-request@vector.uucp (USENET Telecom Moderator) > >If I call a number associated with a cellular phone, how does the >cellular phone operator know which phone to ring and where it is. I >can think of two possible answers: > >1. Periodically each cellular phone emits a "here I am" which is > received by the nearest cells and recorded in a database. Here in Germany, the cellular phones emit a "here I am" on administartive frequency, which is associated with the Cell-sender, they hear the best. Then the Cell-sender returns a short message on that channel together with some data on how good the reception of the phone is at the sender. On this channel the connect requests and the frequency changes during a call, while talking with in one cell or while changing cells are negociated. I think, this takes only a short packet of binary data to be transmitted. >2. When a call for a particular phone comes through all cells in the system > broadcast a "where are you" and the cellular phone responds. > >If anyone knows the details of the protocol used I'd appreciate >hearing from them. > >Chuck Weinstock Hope this helps ------------------------------------------------------------------------------ Dieter Woerz Fraunhofer Institut fuer Arbeitswirtschaft und Organisation Abt. 453 Holzgartenstrasse 17 D-7000 Stuttgart 1 W-Germany BITNET: iaoobel.uucp!woerz@unido.bitnet UUCP: ...{uunet!unido, pyramid}!iaoobel!woerz
Al Ginbey <Al.Ginbey@f666.n285.z1.fidonet.org> (04/07/90)
Yes there is a limit to the number of cellular channels available. The specific limit and the method used in the detection and use of the next available channel differs by city/system. I believe the limit of U.S. West in the Omaha area is 10 channels. The next available channel is marked with a tone. When no channels are available the handset probably generates the trunk busy signal. It will be interesting to see what happens in the futrue as more and users come on-lline. --- Ybbat (DRBBS) 8.9 v. 3.07 r.2 * Origin: [1:285/666@fidonet] DRBBS Technical BBS, Omaha (1:285/666) --- Through FidoNet gateway node 1:16/390 Al.Ginbey@f666.n285.z1.fidonet.org
macy@cwjcc.ins.cwru.edu (04/13/90)
In article <6109@accuvax.nwu.edu> you write: X-Telecom-Digest: Volume 10, Issue 235, Message 5 of 11 >Yes there is a limit to the number of cellular channels available. >The specific limit and the method used in the detection and use of the >next available channel differs by city/system. I believe the limit of >U.S. West in the Omaha area is 10 channels. The next available >channel is marked with a tone. When no channels are available the >handset probably generates the trunk busy signal. Good grief! Does this mean US West has managed to make an IMTS system out of a cellular system? Telecommunications technology takes a giant step backwards... Seriously, this is a very basic description of IMTS (Improved Mobile Telephone Servce), which until cellular service came online, was the primary method of providing dial mobile service in the US. Cellular has 832 channels, all of them of short range, available. One half of them are available to each of the two carriers in a market. The actual number of conversations possible in a given cell area depends on a great many design and propagation factors. In the Cleveland area, the lowest capacity cell site I am aware of has a ten simultaneous call capacity. The largest can handle over one hundred (achieved by using directional antennas to subdivide the cell). A number of schemes exist (and are being developed) to maximize the capacity of cell sites in high density locations. Talk of micro-cells with 300 foot ranges (or less) is now heard. Digital cellular telephony will be introduced in the US shortly. This will further increase the capacity of cell systems, often by threefold or more. I'll leave a detailed technical description of cellular system design for traffic engineering to one of the experts ... I'm just an old pole climber myself. Yessir ... that's it ... life would be simpler if we just went back to open wire and cans ... (does anyone here remember "transpostion brackets" or frogs?) > It will be interesting to see what happens in the future as more > and users come on-line. On an IMTS it was always interesting if too many phones were put on the air ... and most cities only had two to six IMTS channels. I'll start a discussion of IMTS if anyone is interested ... I spent a few years working on these animals. Macy M. Hallock, Jr. macy@NCoast.ORG uunet!aablue!fmsystm!macy F M Systems, Inc. {uunet!backbone}!usenet.cwru.edu!ncoast!fmsystm!macy 150 Highland Drive Voice: +1 216 723-3000 Ext 251 Fax: +1 216 723-3223 Medina, Ohio 44256 USA Cleveland:273-3000 Akron:239-4994 (Dial 251 at tone) (Please note that our system name is "fmsystm" with no "e", .NOT. "fmsystem")