Author Topic: Wireless Broadband - Serial link  (Read 2902 times)

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Offline Flag

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Wireless Broadband - Serial link
« on: August 27, 2011, 06:43:08 PM »
Ok so what wireless broadband hardware is around that would allow remote access to a 115200 baud serial device via the internet. The system would also require a virtual com port capability/setup from the other end (PC/Router etc). 

Offline johnd

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Re: Wireless Broadband - Serial link
« Reply #1 on: August 28, 2011, 04:23:47 AM »
Ok so what wireless broadband hardware is around that would allow remote access to a 115200 baud serial device via the internet.

If I take 'wireless broadband...Internet' to mean something like a 3G modem then that's a tricky question to answer because (AIUI at least) the limitation is not necessarily in the hardware at all but in the data link that you have back to your nearest network base station.

So, if you're at relatively short range (ie strong signal) and there are few other users (of the same base station) then you can potentially achieve several Mbps (using say a device server hooked into a 3G modem/router). But a weaker signal (which can be worked around to some extent by using a high gain antenna) or - more likely - times of day when there might be many users of the same base station the available bandwidth per user can drop back as far as 14.4 or 9.6kbps. So I don't know of any way of getting a _guaranteed_ 115.2k baud using mobile broadband.

The only other approach that you can potentially use is to use a local data link that's fully under your control (eg VP2 repeaters or a long-range WiFi set-up) to get the signal back to a point which you can interface it to some sort of public cabled Internet access like ADSL. Then use the device server approach.
« Last Edit: August 28, 2011, 05:13:14 AM by johnd »
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Offline Flag

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Re: Wireless Broadband - Serial link
« Reply #2 on: August 28, 2011, 06:18:06 AM »
The 3G router/gateway coverage is not the problem but the remote serial link connection and the comm port setup on the connecting PC I have to do some thinking about. Only baud options are 19200 & 115200 both of which are over and above typical modem speeds.

BTW referring to an Envoy8X so no option for typical modems anyway, VP2 repeaters not an option and long-range WiFi ?? probably not over 20km?

 

Offline johnd

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Re: Wireless Broadband - Serial link
« Reply #3 on: August 28, 2011, 06:50:45 AM »
The 3G router/gateway coverage is not the problem but the remote serial link connection and the comm port setup on the connecting PC I have to do some thinking about.

Don't really understand.., thought I'd answered that but maybe not.

A device server - something like a UDS1100, but there are many alternatives - has a high-speed serial input (think I've seen it quoted up to 920k baud, but certainly 230k baud) and an Ethernet output. If you connect the UDS1100 output to a 3G router (but a router and not just a modem) then you can (potentially) pump data in at 115k so that's not the bottleneck. The limiting factor is the bandwidth that the 3G link has available at any one time. What always tends to be quoted is the _maximum_ bandwidth, which could be eg 3.6 Mbps, but typically what's available is _much_ less. If (more likely, when) this dips below 115k then you're in trouble.

But if you can get the speed and reliably then standard Com Port Redirector software on the target PC should reconvert the IP stream into a serial stream.

There's a separate discussion about the cost and specification of the hardware - MBB router/modems tend to be more costly, though there is the alternative of using a standard office router of the type that accepts a 3G dongle for backup connectivity (I know Draytek and Billion make some and I'm sure other makers do too). I've never tried this sort of set-up with an Envoy8x or with high-speed serial but can't see any reason in principle why it shouldn't work, provided you can guarantee sufficient bandwidth on the 3G data link, which is a big if.
Prodata Weather Systems
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Littleport, Ely, Cambs UK

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Re: Wireless Broadband - Serial link
« Reply #4 on: August 28, 2011, 07:25:23 AM »
Yes Lantronics does support up around that 920k baud link on most of the stuff including the WiFi/Serial box but only using one port so one would expect there would have to be some buffering going on? I have Com ports redirected via wireless network but haven't tried the IP option. Looks like there's some playing around to do?

Offline SLOweather

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Re: Wireless Broadband - Serial link
« Reply #5 on: August 29, 2011, 11:47:15 AM »

The Gridconnect NET 232 say it will do:

# Local or Worldwide Ethernet 10/100M or Internet Connection
# Serial baud rates (300, 600, 1200, 2400, 4800, 9600, 19.2k, 38.4k, 115.2K,...921.6K)

Ethernet it to a suitable cellular router and there you go. I've used these at 19.2 to connect to a VP2 over a 4 mile wireless link. They can be used in pairs for a virtual serial cable, or one to a virtual com port on a PC.

Is the 20 KM line-of-sight?

That's only 12 miles, and I've done one 23 mile link (37 km) in the US with 900 MHz wireless routers.

Offline Flag

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Re: Wireless Broadband - Serial link
« Reply #6 on: August 29, 2011, 08:22:04 PM »
Yes 20km line of sight, over water. 900 MHz is an option but the units are not cheap.

 

Offline Cynjut

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Re: Wireless Broadband - Serial link
« Reply #7 on: September 01, 2011, 12:00:21 AM »
Yes 20km line of sight, over water. 900 MHz is an option but the units are not cheap.

 
If you are looking for something that works in the 5.8Mhz band (802.11b), I recommend Tranzeo.  Canadian company - ships pretty much anywhere.

 

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