TELECOM Digest Tue, 19 Jul 94 09:10:00 CDT Volume 14 : Issue 327 Inside This Issue: Editor: Patrick A. Townson Call for Papers ICCC95 (yonsei@usenet.hana.nm.kr) Australian InfoCall Service Launched (John Hacking) Re: Recommendations For Lightning Protection (Fernando Lagrana) Re: Baud vs. bps (William H. Sohl) Re: Baud vs. bps (H. Peter Anvin) Re: Cellular Towers and Frequencies (Paul Robinson) Re: Cellular Towers and Frequencies (Bill Walker) Re: Bridge vs. Router Performance (Lars Poulsen) Re: IP Over Cable TV (Supak Lailert) TELECOM Digest is an electronic journal devoted mostly but not exclusively to telecommunications topics. It is circulated anywhere there is email, in addition to various telecom forums on a variety of public service systems and networks including Compuserve and GEnie. It is also gatewayed to Usenet where it appears as the moderated newsgroup 'comp.dcom.telecom'. Subscriptions are available at no charge to qualified organizations and individual readers. Write and tell us how you qualify: * telecom-request@eecs.nwu.edu * The Digest is edited, published and compilation-copyrighted by Patrick Townson of Skokie, Illinois USA. You can reach us by postal mail, fax or phone at: 9457-D Niles Center Road Skokie, IL USA 60076 Phone: 708-329-0571 Fax: 708-329-0572 ** Article submission address only: telecom@eecs.nwu.edu ** Our archives are located at lcs.mit.edu and are available by using anonymous ftp. The archives can also be accessed using our email information service. For a copy of a helpful file explaining how to use the information service, just ask. ************************************************************************* * TELECOM Digest is partially funded by a grant from the * * International Telecommunication Union (ITU) in Geneva, Switzerland * * under the aegis of its Telecom Information Exchange Services (TIES) * * project. Views expressed herein should not be construed as represent-* * ing views of the ITU. * ************************************************************************* Additionally, the Digest is funded by gifts from generous readers such as yourself who provide funding in amounts deemed appropriate. Your help is important and appreciated. All opinions expressed herein are deemed to be those of the author. Any organizations listed are for identification purposes only and messages should not be considered any official expression by the organization. ---------------------------------------------------------------------- From: yonsei@usenet.hana.nm.kr (Yonsei News Adm) Subject: Call For Papers ICCC95 Date: 19 Jul 1994 19:08:49 +1000 Organization: HANAnet Operating Centre(KTRC) Following is the FIRST CALL FOR PAPER for ICCC'95 to be held in Seoul Korea 1995. CALL FOR PAPERS ICCC '95 "Information Highways for a Smaller World & Better Living" Seoul, Korea August 21 - 24, 1995 The ICCC, the International Council for Computer Communication (ICCC), founded in 1972, is an Affiliate Member of the International Federation for Information Processing (IFIP). Its purposes are to foster: scientific research and the development of computer communication; progress in the evaluation of applications of computer communication to educational, scientific, medical, economic, legal, cultural and other peaceful purposes; study of the potential social and economic impacts of computer communcation and of policies which influence those impacts. This 12th conference aims at providing a forum to exchange ideas, discuss key issues and to present the late research results for "Information Highways for a Smaller World & Better Living." The main program includes technical presentations, invited talks, tutorials, and technical visits. TOPICS : Areas of interest include but are not limited to Strategies, Policies, and User Wireless Communications Perspectives of Information Intelligent Networks Superhighways Personal Communications Systems Social and Economical Impacts Broadband Communication of Information Superhighways ATM Switching Computer Communication for International Emergencies Developing Countries Distance Learning Network Planning Optical Communications Security and Privacy in Computer Multimedia Communication and its Communications Applications Evolution towards the High-Speed High-Speed Protocols Networks including Frame Relay Network Management and SMDS Protocol Engineering Packet Radio Technologies Satellite Communications SUBMISSION OF PAPERS Prospective authors should send five copies of a full paper to the following address: ICCC'95 Dr. Seon Jong Chung ICCC'95 Technical Program Chairman ETRI, Yusong P.O.Box 106, Taejon, Korea, 305-606 Tel: +82-42-860-8630 Fax: +82-42-860-6465 E-mail: iccc95@giant.etri.re.kr The manuscript should not exceed 4000 words in length and should include author's name, affiliation, and addresses(telephone, e-mail, fax), and 150-200 words abstracts in the title page. Also, authors are encouraged to send a Postscript version of their full paper to the Technical Program Committee Chairman by e-mail iccc95@giant.etri.re.kr |-------------------------------| | Important Dates | | Submission of Paper | | February 1st, 1995 | | Notification of Acceptance | | May 1st, 1995 | | Camera-ready Papers | | June 15th, 1995 | |-------------------------------| Sponsored by The International Council for Computer Communication Hosted by Electronics and Telecommunications Research Institute Korea Information Science Society Under the Patronage of Ministry of Communication, The Republic of Korea Conference Governor Ronald P.Uhlig, Northern Telecom, U.S.A. Conference Organizing Committee Chair : Chongsun Hwang, KISS, Korea Co-Chair : Seungtaik Yang, ETRI, Korea Local Arrangement Dongho Lee, Kwangwoon Unvi., Korea Publication Keosang Lee, Dacom, Korea Publicity Jaiyong Lee, Yon-Sei Univ., Korea Registration Samyoung Suh, NCA, Korea Treasurer Seungkyu Park, Ajou Univ., Korea Tutorial Sunshin An, Korea Univ., Korea Social Program Nosik Kim, KTRC, Korea Secretariate Yanghee Choi, SNU, Korea Jinpyo Hong, ETRI, Korea Technical Program Chair : Seonjong Chung, ETRI, Korea Co-Chairs : Serge Fdida, MASI, France Nicholas Georganas, Univ. of Otawa, Canada Roger Needham, Univ. of Cambridge, U.K. Otto Spaniol, Aachen Tech. Univ., Germany Hideyoshi Tominaga, Waseda Univ., Japan Pramode Verma, AT&T, U.S.A. Members : Byungchul Shin, KAIST, Korea Yongjin Park, Hanyang Univ., Korea Donggyoo Kim, Ajou Univ., Korea Kwangsue Chung, Kwangwoon Univ., Korea Daeyoung Kim, Cheoungnam National Univ., Korea Ilyoung Chung, ETRI, Korea Chimoon Han, ETRI, Korea Woojik Chon, ETRI, Korea Hoon Choi, ETRI, Korea Tadao Saito, Tokyo Univ., Japan Tahahiko Kamae, HP Lab., Japan Reigo Yatsuboshi, Fujitsu Lab., Japan Kinji Ono, NCIS, Japan Michael Diaz, LAAS, France Christophie Diot, INRIA, France Georgio Ventre, Univ. di Napoli, France David Hutchison, Lonchaster Univ., U.K. Augusto Casaca, IST-INESC, Spain Martina Zitterbart, Univ. of Karlsiuhe, Germany Ulf Koerner, Lund Univ., Sweden Albert Kuendig, Swiss Federal Inst. of Tech., Swiss ------------------------------ Date: Tue, 12 Jul 1994 12:29:00 +1000 From: JOHN.HACKING@telecom.telememo.au Subject: Australian InfoCall Service Launched People seeking fast, expert advice on subjects ranging from the state of their health to the state of the nation now have access to it over the telephone. InfoCall is a telephone information service featuring "live" advice. InfoCall, which uses a 190 prefix, is available to all customers in Australia who currently receive itemised bills from Telecom for STD and international calls. Callers will be able to speak to an increasing number of experts including doctors, lawyers, gardening gurus, veterinarians and various tradespeople. They can also access recorded voice information services, receive information via a fax or have information downloaded to a desktop computer. InfoCall was today launched nationally following a pilot program in Victoria which confirmed the service's technical functionality and its acceptability in the marketplace. "This is the sort of service which only an advanced telecommunications network can provide," said Martin Turner, Telecom National Portfolio Manager for Telemedia. "Telecom's network enables service providers to tailor services more and more to meet individual needs and the clear message from our customer research is that customers want access to information on their own terms. "The telephone allows them that access, and the InfoCall service brings it to them in the privacy of their homes and offices." Telecom has provided over 150 InfoCall lines and service providers have indicated their strong intention to provide a wide range of services over the coming weeks. These services will include information on the stock market, weather reports, study tips, computer software support, ticket bookings, state industrial awards, average real estate prices, racing, gardening and wedding and legal advice. Service providers' charges will range from a flat rate of 35cents to $30 or at a timed rate, ranging from an average of 35 cents to $5 per minute. Telecom has worked with consumer groups and service providers to ensure that customer safeguards are in place. At the start of every service, customers receive an introductory message explaining exactly what the service is and the charge rate. The message introduction costs 15 cents and no further charges can be applied until the caller dials a number to activate the chosen InfoCall service. Callers hear a pip tone every five minutes on timed-fee live advice services and are asked to dial a number if they want to proceed beyond ten minutes on timed-fee recorded voice services. The caller can terminate the service at any time by hanging up. Households and businesses can have InfoCall barred so access cannot be gained from their telephone. Details about barring the service can be obtained by calling the InfoCall Helpline on Freecall 1800 035 055. A test call to 1900 909 000 will indicate to customers whether they can access InfoCall. They can also obtain more information on the InfoCall Helpline. MELBOURNE Australia ------------------------------ Date: Tue, 19 Jul 1994 08:39:51 CET Subject: Re: Recommendations For Lightning Protection From: lagrana@itu.ch (Fernando Lagrana) Organization: International Telecommunication Union The Telecommunication Standardization Sector of the ITU (ITU-T) developed a whole set of Recommendations relative to Protection against interference (K-Series). The following Recommendations are of particular relevance for lightning protection: K.1 Connection to earth of an audio-frequency line in cable K.11 Principles of protection against overvoltages and overcurrents K.21 Resistibility of subscribers' terminals to overvoltages and overcurrents K.22 Overvoltage resistibility of equipment connected to an ISDN T/S bus K.25 Lightning protection of optical fibre cables K.31 Bonding configurations and earthing of telecommunication installations inside a subscriber's building Fernando Lagrana International Telecommunication Union Telecommunication Standardization Bureau Editor, Catalogue of Recommmendations Internet: lagrana@itu.ch Voice: + 41 22 730 58 94 Fax: + 41 22 730 58 53 X.400: SURNAME=3Dlagrana, PRIVATE_DOMAIN=3Ditu, ADMIN_DOMAIN=3Darc= om,=20 COUNTRY=3Dch ------------------------------ From: whs70@cc.bellcore.com (sohl,william h) Subject: Re: Baud vs. bps Date: 19 Jul 1994 01:01:14 -0400 Organization: Bell Communications Research (Bellcore) In article , Hugh Pritchard wrote: > Now, I'm willing to accept that the copper phone wires will only > handle 2400 baud, and that the modem makers have come up with ways to > signify 6 bits (14,400 is 6 times 2400) for each different state > change. The modem makers have come up with 2 to the 6th = 64 > different states (some combination of frequencies, phases, and phase > changes) to fit into the 2400 baud limit. Actually the copper wires will pass much higher rates. The limitation is the design of the network facilities (especially the inter-office trunking) which will only pass an analog signal within the 300 to 3000 KHz range. Modem makers must design their analog modems to operate within that 300-3000KHz range. So, with those analog limitations, modem manufacturers have been able to develope modems that go up to 28.8KHz while still having the entire signal within the 300-3000KHz range. Bill Sohl (K2UNK) BELLCORE (Bell Communications Research, Inc.) Morristown, NJ email via UUCP bcr!cc!whs70 201-829-2879 Weekdays email via Internet whs70@cc.bellcore.com ------------------------------ From: hpa@eecs.nwu.edu (H. Peter Anvin) Subject: Re: Baud vs. bps Reply-To: hpa@nwu.edu (H. Peter Anvin) Organization: United Federation of Planets Date: Mon, 18 Jul 1994 17:35:03 GMT In , Hugh Pritchard wrote: > Now, I'm willing to accept that the copper phone wires will only > handle 2400 baud, and that the modem makers have come up with ways to > signify 6 bits (14,400 is 6 times 2400) for each different state > change. The modem makers have come up with 2 to the 6th = 64 > different states (some combination of frequencies, phases, and phase > changes) to fit into the 2400 baud limit. That's basically the idea. However, in order to obtain even further noise resistance, they actually use 128 states, only 64 of which are valid at any one time. This is called "trellis coding", because the amplitude/phase plots(*) of the valid states look somewhat like a flower trellis. I would presume that V.34 (28,800 bps) would use 8192 states at the minimum, 4096 of which would be valid at any one time (whew!). The Nyquist limit of an analog phone line is somewhere in the vincinity of 32 kbps. If not otherwise it would be dictated by the fact that it will be digitized to 64 kbps in the switch, and I would presume trying to obtain more than 50% of that data rate would depend on some pretty strange factors such as the (in)ability to synchronize with the ADC clock, as well as on any intermediate D-A-D conversions that may be done. Not to mention bit robbing... (*) = The standard state diagram are amplitude/phase plots when read as a polar diagram. They can also be read as an XY plot of the 0-degree and 90-degree components that make up the signal. INTERNET: hpa@nwu.edu FINGER/TALK: hpa@ahab.eecs.nwu.edu IBM MAIL: I0050052 at IBMMAIL HAM RADIO: N9ITP or SM4TKN FIDONET: 1:115/511 or 1:115/512 STORMNET: 181:294/101 Allah-u-abha ------------------------------ Date: Mon, 18 Jul 1994 21:15:56 EDT From: Paul Robinson Reply-To: Paul Robinson Subject: Re: Cellular Towers and Frequencies Organization: Tansin A. Darcos & Company, Silver Spring, MD USA Shawn Gordhamer , writes: > I understand that cellular towers with small cell radius allow the > cellular frequencies to be used over and over ... [and] no two > adjacent towers can use the same frequencies because there will be > interference... However, as cellular (hopefully) becomes cheaper > even 333 channels for a small town may not be enough. At which point, they ramp down the power level on the tower and add another one some distance away. With the way things are going, cellular towers are getting cheaper, enough so that if a place gets more volume of calls, the amount of usage means that it becomes economically viable to add more cells, since if people can't get through they will stop their service or switch carriers. Or move to PCS which isn't going to be too far away. > A one-tower town cannot just put up another tower, because the towers > will be adjacent, and they cannot use the same frequencies. I'm not a cellular engineer, but I do know something about the way the system works. It's not quite as bad as you see it. Let's say that in a particular area, the tower handles a ten-square mile area, five miles in each direction. If a small town, let's say two miles away, is getting so much calls that it is overloading the cell, then what you do is that you do a traffic analysis to see where most of the calls are being taken at; perhaps most of the calls are in the central business district. So you have a pattern like this: Tower1-----!-----Tower2-----!-----Tower3--x---!-----Tower4-----!-----Tower5 When a call gets to a ! it's going to hand off to the next tower because that one is giving a stronger signal. The 'x' is where the small town is that is overloading Tower 3. So you put in another tower, perhaps near the break point, like this !-----Tower3--x--Tower3a---!---Tower4 Tower3a will pick up about 1/2 of the calls in the Tower3 area, and part of Tower4's service. By making it an equal distance from the town, you can thus split about 1/2 the traffic to each tower, since at some point one of them is a stronger signal than the other, or is available because one of them is overloaded. Thus each tower only has to handle 1/2 of the area of the prior one. Or you go even further: you put one very small, inexpensive lower powered cell right in the center of town where most of the calls originate from (many people in vehicles passing through a congested area, perhaps because it's the only gas station for several miles). This cell would be the strongest one for perhaps 1/2 mile or so, then as they move on they revert back to one of the towers handling the much sparser traffic areas. > In fact, for a large town with dozens of towers, each tower would have to > use at most 1/4 of the channels, making a grid pattern > A B A B A > C D C D C > A B A B A > C D C D C Actually, the term "cells" as used in cellular is more similar to a honeycomb or hexogonal pattern, which each cell using a block frequencies not used by any of the cells that is next to it, so we more often have something similar to the following: _ _ _ _/A\_/C\_/A\_ A cell frequency cannot be used by a cell that is /D\_/B\_/D\_/B\ touching any other, so they break up the available \_/C\_/A\_/C\_/ cells such that in each area only some of the /B\_/D\_/B\_/ frequencies can be used. But in each area, each cell \_/ \_/ \_/ in group "A" can use all of the available group "a" frequencies. In short, if a cell gets too many calls, the cell can be made to cover a smaller area and another cell inserted into the matrix to change the size of the coverage area. Paul Robinson - Paul@TDR.COM ------------------------------ From: wwalker@qualcomm.com (Bill Walker) Subject: Re: Cellular Towers and Frequencies Date: Tue, 19 Jul 1994 06:04:51 -0700 Organization: Qualcomm, Inc. In article , shawnlg@netcom.com (Shawn Gordhamer) wrote: > I understand that cellular towers with small cell radius allow the > cellular frequencies to be used over and over, allowing thousands of > simultanious cellular conversations. I also understand that no two > adjacent towers can use the same frequencies because there will be > interference. > Where I live, there are lots of small towns that have only one > cellular tower. [which is plenty for now, but may not be in the future when everybody in town has a wireless phone. And you can't just put up more towers because the population is not geographically dispersed] > In fact, for a large town with dozens of towers, each tower would > have to use at most 1/4 of the channels, making a grid pattern like > the following: [...] > Am I correct in this assumption? Yes. The most common reuse pattern, to my knowledge, is called K=7, which basically means that you have to get seven cells away before you can reuse the same frequency. To some extent, you _can_ put in more cells (probably not "towers") even in a small town. You just have to limit the coverage and interference of each cell, by doing things like using lower antennae, lower power, directional antennae (all of which come under the general label of "microcells"). Or [WARNING! BIASED STATEMENT COMING!] you could replace your analog cellular system with a CDMA digital cellular system, which will provide about 10 times as many calls in the same frequency allocation [QUALCOMM, my employer, is the chief proponent of CDMA digital cellular]. No new towers, no new antennae, but everybody who wants to use the new system has to get a new phone (but the new and old systems can coexist). Disclaimer: I'm a software guy with a rusty, old digital-oriented EE degree, so I've probably over-generalized the RF stuff about propagation and microcells. Bill Walker - WWalker@qualcomm.com - QUALCOMM, Inc., San Diego, CA USA ------------------------------ From: lars@Eskimo.CPH.RNS.COM (Lars Poulsen) Subject: Re: Bridge vs. Router Performance Organization: Rockwell Network Systems, Copenhagen DENMARK Date: Tue, 19 Jul 94 09:05:09 GMT In article sthomas@mitchell.hac.com (Scott D. Thomas) writes: > I have a puzzling (at least to me) situation. We have a simple > network with a satellite link included. Orginally, we bridged three > ethernet segments ... ... ... ... ... ... and got poorer that expected > results. We decided to replace the bridges with routers, one per > segment. The throughput was tripled! > I was under the impression that bridges were more efficient because of > lower overhead, less complexity, etc. and therefore would offer the > better performance. The most likely reason for your poor performance, is that one of the sites in question is a LARGE network (maybe several hundred stations or more ?) and the amount of broadcast/multicast traffic floating around in the network is eating up all the bandwidth of the DS-1 link. When connecting multiple LANs into one extended network, the connection can be implemented with different logical models. Bridging is the lowest level model; it takes to similar networks (such as two Ethernets or two Token-Rings) and joins them intpo one logical network. A bridge device on each end of the link: - goes into promiscuous mode (snooping on all traffic) - keeps track of which devices (identified by their Ethernet addresses) are on each end, and - forwards traffic for any device not know to be on the same LAN as the sender, as well as all broadcast/multicast messages across the link. Because this is done at Media Attachment Control (MAC) level, it is protocol independent, and requires very little setup. The downside is that all broadcast/multicast traffic is forwarded, as well as traffic from protocols that are entirely unsuited for wide area traffic. The larger the combined network, the larger the amount of background "slosh" og broadcasts, even as a percentage of total traffic. (For instance, every ARP request will be sent everywhere, theough almost all of them are for stations local to the sender.) When you have a couple hundred workstations, you are likely to have about 32 Kbps worth of "slosh". (Meaning you need a T1 to get any WORK done.) To overcome the deficiencies of bridging, you need a router. Routers must understand each protocol and must be configured appropriately for each protocol. This means that somewhere in the organization there has to be a person who understands each protocol that is being routed, and who can set up an addressing plan and troubleshoot when problems arise. For a good textbook in this area, I recommend Radia Perlman's book "Interconnections: Bridges and Routers". Addison-Wesley, 1992. ISBN 0-201-56332-0. I think I paid $53.26 (incl CA tax). Lars Poulsen Internet E-mail: lars@RNS.COM Rockwell Network Systems Internets: designed and built while you wait Hvidovre Strandvej 72 B Phone: (011-) +45-31 49 81 08 DK-2650 Hvidovre, DENMARK Telefax: +45-31 49 83 08 ------------------------------ From: lailert@ucssun1.sdsu.edu (Supak Lailert "spk") Subject: Re: IP Over Cable TV Date: 18 Jul 1994 18:15:14 GMT Organization: San Diego State University Computing Services Lubos Elias (Lubos.Elias@uakom.sk) wrote: > I am looking for information about possibility to provide IP service > over cable TV wires. Are there any products? In San Diego, our local cable company, Cox Cable, has successfully tested the system that allow access to Prodigy via the cable TV network. I think it acts like a very fast modem so I think we could use SLIP or PPP over it, too. Regarding their TV commercial, Cox claims over 50 times higher throughput over modem access. Is it 9600BPS times 50? (I don't know what the highest modem speed at Prodigy.) As I heard from local computer magazine, the service has not been ready yet. Regards, Supak Lailert -- MBA (Information System) Program, San Diego State University lailert@ucssun1.sdsu.edu lailert@aol.com ------------------------------ End of TELECOM Digest V14 #327 ******************************