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more on communication networks for humans
From: David Farber <dave () farber net>
Date: Sat, 10 Sep 2005 20:20:52 -0400
Begin forwarded message: From: Andrew Seybold <andy () 4mobility com> Date: September 10, 2005 7:56:16 PM EDT To: dave () farber net Subject: RE: [IP] communication networks for humans I have several comments about public safety--first responder communications since I am deeply involved in this. 1) There is, in the fire service, what is known as the Incident Command system. It says that the first on the scene becomes the incident commander, as the incident grows and 'bosses' show up the IC is handed upwards. As the incident grows so does the command structure, it is quickly divided into groups including incident control, logistics, and many more, as the size of the incident continues to grow the teams are splint into divisions. One of the key principals of this system is that NO ONE ever has more than five direct reports to them, if they need more they split the command structure yet again-- 2) Public safety equipment is old (mostly analog FM) because these departments do not have the money to upgrade. Many of the public safety systems I designed and sold in the late 1970's and 1980's are still in use (by the way we did install mobile data terminals in those days in many cities and counties). 3) There is a new digital standard for public Safety communications developed by APCO, known as APCO 25 and most of the newer radios today include the capabilities of both analog and digital communications. But since it is only for public safety the prices for the equipment are very high. But GSM, CDMA, WI-FI, WiMAX and other commercial technologies cannot meet the needs of the public safety community. 4) Public safety channels are not contiguous, they are in the 30-50 MHz, 150-172 MHz, 450-470 MHz, on shared TV channels in the 470-512 MHz range as well as in the 800 Mhz band. There is 24 MHz of "new" public safety spectrum coming (someday) in the 700 MHz UHF TV band but who really knows when. The feds have their own channels, again spread out over a lot of spectrum and have duplicate systems in most cities. In fact the FBI and SS have systems that rival the locals but will not permit local use of their channels even during a major emergency. 5) Command and control of a net is normally handled by the dispatch center-which coordinates traffic on the channels. Normally in a major event there is a command and control channel that permits the bosses to communicate directly with the command center (dispatch center), and then the orders are relayed on working channels including additional wide area and simplex channels as needed. Note--a dispatcher can "normally" handle about 60 individual units on a single channel, not more which is why large cities have many channels and they are usually divided into sectors. 6) There are common fire and public safety channels in at least one band (150 Mhz) which every unit is supposed to have in their radios (Fire White for example which is 154.280 MHz), and the police have Clemars also in the same band. 7) There is a move to update the public safety radios--one proposal is to use the 700 MHz band to supply radios to local, state, feds and have these radios programmed over the air as people and equipment arrive at a scene. 8) Data is done either using their own channels or on public networks there is no consistency here at the moment and the "new" Apco 25 channels are so narrow that data services require a number of channels to be aggregated in order to provide even slow data speeds. 9) Secondary and admin communications is usually off-loaded to public networks such as Nextel's Direct Connect service but often times in a major event these channels--which have No priority are jammed. 10) Commercial wireless technology, in most cases, will NOT work for these agencies because they need one-to-many and dispatch capabilities, they need wide-area systems so everyone can hear everyone else, and they need incident simplex channels for local coordination. 11) Many dispatch systems are making use of IP routers to tie together two or more different PS channels during an event. This occurs at the dispatch center BUT it means that a single conversation is taking up more than a single voice channel. 12) While public safety communications frequencies are coordinated by volunteers to minimize interference between departments and areas, many departments are OUT of capacity and have been waiting for years for one or two extra channels, while gobs of unlicensed spectrum has been handed out for Wi-Fi and now WiMAX systems--ok, ok, mesh networks? Tell me how to do that over all of these channels, tell me how to coordinate all of this without any money to make it happen. 13) During major incidents the public networks are so jammed as to be useless, and John J. Citizen has as much priority to get a call through as the fire chief in charge of an incident. 14) The ONLY way to fix all of this is with money and a vision, and that vision will take YEARS to accomplish--by the way, there is a reason that the CHP, for example, are still using 42 MHz (yes 42 MHz) for their systems, if they moved to 800 MHz they would need hundreds, yes hundreds of new radio sites and still would not be able to provide radio coverage in the mountains and rural areas--the higher you go in frequency the less range you can cover-- Public Safety communications is the most miss-understood and maligned of all of the radio services and it is because few understand the issues--in closing one more point--I guarantee that the public safety systems, when up and operating cover their areas better than ANY public network--they have been designed to do that over the years--inside, outside, and everywhere, they HAVE to provide that level of coverage. They are all backed up with emergency power and batteries, redundant circuits and the best in tower locations. But it is a fact of life that generators and batteries do not work very well under water. Many a police officer has been asked if they had to do without their gun or their radio which they would pick and the answer is always, take my gun, leave me my radio! Just my three or four cents Andy ------------------------------------- You are subscribed as lists-ip () insecure org To manage your subscription, go to http://v2.listbox.com/member/?listname=ip Archives at: http://www.interesting-people.org/archives/interesting-people/
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