do you some sort of presentation that can be used to visit municipalities in our county with the intention of showing the "need" for them.
You have a Good Day now, Carl A Jeptha http://www.airnet.ca Office Phone: 905 349-2084 Office Hours: 9:00am - 5:00pm skype cajeptha Butch Evans wrote: > On Mon, 31 Mar 2008, Carl A jeptha wrote: > > >> people have been killed for less, spill the beans, or be stoned by >> the crowd. :-D >> > > Hmmm...weighing the two options of spilling the beans or death by > stoning, I think I'll take the former, as the latter sounds a bit > painful. ;-) > > Ok..here we go. First, I will say that I have installed a system > such as I will describe MANY times. I know that it works and works > well. The effectiveness of this type of network depends on MANY > factors, which are unique to each of the networks I have deployed. > Having said that, let me describe the steps and, later, some > options. > > First, the "freebie" part: > > The idea is that there is an existing 802.11(a|b|g) network deployed > already in MOST populated areas in the US and Canada. Since this is > the case, I began looking at ways to bring municipalities around to > a point where they NEED our existing networks. There are many > reasons for this, but the most important was that if they need the > network, they will be more likely to try to help us protect it as > well as be more willing to allow us to use space such as water > towers and such. Many cities already do this, but by providing > crucial services to them, they are more willing to make it > affordable as well as allow for "exclusivity" on the city's > property. > > At any rate, what I did was create a set of scripts that allowed me > to put Internet access in places like Fire Trucks, Police Cars and > other city owned vehicles. Each network is different, so I can't > just give a "cut and paste" script...What I CAN do, however, is > provide the LOGIC and description of the necessary parts. > > For the WAN part of the network, you will be able to use ANY > access point (not just Mikrotik). Well, any aps that you can > connect to with a MikroTik running as CPE. This includes a MT > access point that is running in 900, 2.4, 5.x AND 4.9 (emergency > services). Bear in mind that the higher frequencies are MUCH more > picky about LOS and the CPE side (the vehicle) is not going to have > much antenna. All we need here is the ability to connect with a MT > client device and access the network. I've used DHCP, static IP > addressing AND pppoe...the connection method is not important. > > Additionally, we will need, at least for some services, a MikroTik > router at the "head" of the network. The purpose of this MikroTik > is to provide a VPN server, so that we can provide the various > services (police department, fire dept, ambulance, etc) with a means > to contact the cars with a consistent IP address, regardless of the > location that device is currently using as a connection. This > allows for us to (for instance) let the dispatcher see a video > stream from "car 1" without having any knowledge of where or how > that car is connected to the network. > > Now, for the CPE that will be installed in the vehicle. There are > MANY ways to do this, depending on the set of services needed in the > car. In some cars, we have a CPE with just a single radio that will > be the internet connection and path back to the VPN server. What we > do in this router, is set up the following: > > 1. Using connect-list feature, we set up the APs that we are allowed > to connect to. This can be all the APs on a single ISP or even > multiple ISPs...it doesn't really matter. > > 2. We need to know how to configure the CPE for EACH access point we > can connect to. For example: > * SSID "sample1" needs pppoe with user/pass of "test/test" > * SSID "sample2" needs DHCP > * SSID "otherISP" needs static IP of x.x.x.x/24 > > 3. We have to monitor the RX signal level on the current AP so that > we can force the CPE to find a better AP when the signal is no > longer usable. This is necessary, since there are two "bad" things > happening. > 1. The CPE is moving (either closer to or further from) the > AP most of the time. > 2. 802.11a/b/g does NOT disconnect automatically until the > signal level is so low that it is completely unusable for > our purpose. > > SO, we have to constantly monitor the connection to FORCE the CPE to > disconnect, so that it will find the AP that is best for where we > are physically located NOW. > > 4. We have another script (or a portion of the above script) that > will detect our current AP and insure that the network parameters > (DHCP/PPPoE/etc.) is correct. This is the "tricky" part. > > The above description is all that's needed for a CPE that is a > single radio config. You can, also, add the ability for the car to > have it's own AP for devices such as a wireless SIP phone or PDA to > connect to. Obviously, a SIP phone will drop a call if the time to > switch towers is too long. It is because of this that I built a > script that allowed for 2 client radios. This script does all the > stuff that the above description says, but it does it in a different > way. What happens is this: > > 1. Radio 1 connects to the best AP and is configured as our > "current" connection (get's the correct IP information and a gateway > is added so that traffic uses this radio). > > 2. Radio 2 begins searching for the best AP and will be configured > with IP information ONLY if the current signal level on Radio 1 is > below a certain (definable) threshold. > > 3. If Radio 2 is now the "current" connection, then Radio 1 begins > the search for a new AP. and the cycle is repeated ad infinitum. > > Basically, we "walk" the network with 2 CPE devices. We can, also, > set the AP in the car so that it is not going to interfere with the > "current" radio's frequency, though this will cause problems with > calls if we aren't careful. In order to detect "call status", I use > a script that watches packet rate on the interface. If it is below > a certain number, I will assume that there is no call currently > connected, and it is safe to move the car mounted AP to a new > channel if it is interfering with the current connection. > > As you can see, it is doable, but it is VERY involved. I don't want > to make this a "sales pitch", but I will say this much... > > 1. Each install is VERY HIGHLY CUSTOMIZED, and, therefore, has to be > built according to the needs of the specific network > > 2. Cost may seem high, but MUCH of this can be paid for with grants > (homeland security has MILLIONS of dollars to build these types of > systems out) > > The first one of these that I built was WAY underbid. I only > charged about $3k for that one. The most expensive was about $18k, > but involved almost 2 weeks onsite. The average cost (my part) is > about $5k-7k. > > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.butchevans.com/pipermail/mikrotik/attachments/20080401/68b32a96/attachment.html
