The following is from
http://www.lancasterfire.com/board/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=8;t=000373 , a local fire message board in Lancaster County PA. Please note that these questions came from a individual that is very familiar with the system in Lancaster County.....
Does it sound like the system is up and running? A meeting is to take place today (March 3rd) for the area fire departments and other emergency services and a brief summary to the answer to the questions will be posted on the Lancaster 911 website next week (hopefully!!)
[bold]Here are the questions!!
Here are a few questions I have on the new system that I do not remember seeing addressed elsewhere:
1 – How many frequency pairs/channels have been assigned overall and how many are in which towers?
2 – The original design was for 50+ towers. This provided both capacity and coverage. Each frequency pair/channel is multiplexed to allow 4 simultaneous transmissions. A tower site with two ‘channels’ theoretically can handle 8 simultaneous transmissions.
By relying on V-TAC ‘repeater’ units, portable coverage was enhanced, meaning fewer tower sites were needed. However, by reducing the number of towers, it seems capacity was reduced unless extra frequency pairs were added to other tower sites?
3 – How many talk-around (analog) frequencies will there be? Will all system users (fire, ems, police, public works, etc) ‘compete’ for the same talk around?
4 – Will the portable in-building to V-TAC link be an analog or digital signal? Extensive field testing in Phoenix showed analog 800 to be better than digital 800 (and analog 460) for in-building operations, but product literature on the V-TAC seems like it is digital only from the portable. (The V-TAC only picks up a portable that ‘lost its way’ and cannot locate a main tower).
5 – How will frequencies be allocated for maydays: RIT on analog talk around? RIT on V-Tac repeated channel? RIT takes main talk-group? RIT on both the main talk group and talk around? If a lost firefighter is unable to hit a tower site, the talk around channel would be the only way to communicate with the RIT team.
6 – How many simultaneous V-Tac’s at a single location have been tested? Some working incidents could have 10+ V-Tac units and signal processing could be an issue.
7 – What is the number of peak users the system is expected to handle during a disaster? The Seattle area earthquake several years ago had 13,000 users on their system and users experienced 12 second delays.
8 – How easy will it be to obtain additional frequency pairs for the system in the future as users and data application usage increases? I believe re-banding was to create 90 additional channels for public safety.
9 – Since most field radios have not been purchased, what is the status of 700 MHz for our area? 700 MHz was not an option when this project was first started. I believe there are less than 200 public safety channels in 800 MHz (after re-banding), but 1000+ public safety channels in 700 MHz.
10 – Is the V-Tac available in 700 MHz? To ensure future interop, are dual band (700/800) radios the way to go?
11 – How many talk groups and talk-arounds will be usable on a 16 channel portable? I’m guessing 1 & 16 will be talk-around so that personnel in trouble can rotate the channel selector in either direction to the stop and be on the talk-around. Will all 5 national interops be on each portable and available as additional talk arounds? Are additional channels required for P25 compliance?
12 – Is there a noticeable delay in transmissions when using the V-TAC compared to direct to the tower links?
13 – Will some talkgroups be disabled from some towers during high usage? Ex: There is a working incident in Ephrata assigned to the FD-Tac1 talkgroup. With OpenSky, I believe every radio in the County on the FD-Tac1 talkgroup will be able to hear local fireground communications. (Armchair IC’s rejoice!) So, every tower site with an active user on FD-Tac1 is re-broadcasting the talkgroup and using tower capacity.
Now Quarryville has a working incident on FD-Tac2 and water supply on FD-Tac3. The whackers throughout the county go get 3 portables, one tuned to each FD Tac. Now every tower site is re-broadcasting 3 talk-groups. This could pose a problem for tower sites with only one channel (not sure if there are any in the County). This is one issue created with an OpenSky receive-only radio as a scanner.
It seems at some point, to maintain system capacity for local ‘metro’ and Northwest users, FD-Tac 1, 2 and 3 could be temporarily disabled from these area towers. If at times talk groups will be limited to a subset of towers, will field testing also be done with tower subsets?
14 - What happened to the old radio system design documents?
15 - Will any analog frequencies be installed at the tower sites?
16 - How will P25 radios communicate with OpenSky units: only via the national interop frequencies or will NetworkFirst be deployed?
Some more questions.....
In the month that Troy's questions have gone unanswered I've come up with some questions of my own. Maybe they can be added to the Q&A.
This purpose of this post to add to Troy Neville's original list of questions. While he has asked excellent questions, sometimes it helps hear some questions from someone who was intimately involved in the project.
You may or may not feel the same concern, or view these questions with the same importance as I do.
I hope answers to these questions will give the potential users of the OpenSky system a better view of the big picutre, and help to dispel rumors.
1. When is the target date for the rumored discontinuation of the P800 and P801 portables? How long will M/A Com continue to support these radios after that date?
2. How much will the new P7200 radios cost? (including ALL software to provide AT LEAST the same functionality as the present portables) Is the figure of $4000-4500 accurate?
3. Will the 500mW (1/2) ERP from the V-TAC provide sufficient in-building penetration? Has the problem with V-TAC's overloading nearby portable radios been addressed?
a. Has the coaxial attenuator on the output of the combiner solution been revised? If so what is the output power (ERP) of the V-TAC with the new hardware changes in place?
4. Has anyone investigated licensing SMR frequencies for V-TAC use in place of NPSPAC frequencies to help decrease adjacent channel interference?
5. Has anything been done to fix the receivers in the P801 portables so they are no longer so susceptible to interference and front-end overload, even from nearby OpenSky radios?
6. Is it true that the P800 portable has a receiver of lesser performance level than the P801? Is it also true that when P801 receivers are tested at the factory, those that don't meet spec are put in the P800 radio?
7. How will broken/damaged radios be handled after the system launches? Will there be a immediate (within a day or so) swap out by a M/A Com Authroized Service Center? Will the customer have to keep spares on hand or will the ASC have the radios on hand? How long is the turnaround to get back a broken/damaged radio?
8. Have the OpenSky "over-the-air" downloads been perfected as of yet? Is it also true that M/A Com engineers have had to, in the past, physically go to the customer's location and confirm the downloads actually "took"?
8. At the baud rate for data communications of 19,200 kbps (best case scenario), what benefit will this provide users of the system with such low bandwidth? How long will a user wait for a mugshot for example, to download at a rate 1/3 of that of a 56K dial-up modem?
10. Has version 6 improved voice quality?
11. Is decreased voice quality still an issue when in areas of "lesser signal"?
12. Are "Emergency button activations" still getting "lost" in the OpenSky system?
13. Has the Version 6 software upgrade exacerbated channel list deletions in the portable radios as well as mobiles, or are they occuring at about the same rate in the portables as they were in the past?
14. At a $110 an hour rate for custom installs (which MUST be done by a M/A Com ASC), what is the average cost to fully install a dual-head system in a ladder-truck, for example?
*Note, the ASC does NOT receive this much money. They get their normal hourly install/shop billing rate (typically $60-70/hr), M/A Com gets the rest.
15. Have the ASCs (installers) been chosen for Lancaster County yet? If so, who are they?
16. Why are the monthly Radio Project Committee meeting minutes still not published on the LCWC website?
17. Has the new microwave system been fixed or is it still susceptible to outages due to fade during heavy rain?[/bold]
