Forums

Wireless short/medium range data transfer

Started by Jyrki Holopainen October 11, 2006

We have a device that collects data from vehicles. Currently the data is 
transferred to office with GSM modems. Some customers would like to 
avoid the costs involved to this option and have another wireless method 
  to transfer the data. GPRS is not acceptable solution, there should 
not be any costs at all.

In this case the vehicles visit a terminal regualiry, so short/medium 
range wireless transfer solutions could be used. The range should be at 
least 1 km. 100 m is (probably) not enough.

The data transfer rate does not need to be high, 9600 bit/s is enough. 
Our device has a serial port (and limited amount of memory).

There can be many vehicles (100?) at the terminal at the same time, so 
there must be a way to address them separately. Only one vehicle needs 
to be addressed at a time. A master node (office) initiates the data 
transfer.

Cost matters, as always. All options are however worth investigating.

Jyrki Holopainen wrote:
> We have a device that collects data from vehicles. Currently the data is > transferred to office with GSM modems. Some customers would like to > avoid the costs involved to this option and have another wireless method > to transfer the data. GPRS is not acceptable solution, there should > not be any costs at all.
900MHz RF transponders. Same range as portable phones. In fact, same problems as portable phones. Additional frequency switchings would be necessary to acheive reliable data communications.
> > In this case the vehicles visit a terminal regualiry, so short/medium > range wireless transfer solutions could be used. The range should be at > least 1 km. 100 m is (probably) not enough.
That might be tough for license-free option. But if the teminal is big enough, lower frequency and higher power could be used. However, legal (license) issues might be involved.
> > The data transfer rate does not need to be high, 9600 bit/s is enough. > Our device has a serial port (and limited amount of memory).
No problem, 900MHz can do 100K bit/s.
> > There can be many vehicles (100?) at the terminal at the same time, so > there must be a way to address them separately. Only one vehicle needs > to be addressed at a time. A master node (office) initiates the data > transfer.
A transponder protocol would address this issue.
> > Cost matters, as always. All options are however worth investigating.
Hello Jyrki,

> > We have a device that collects data from vehicles. Currently the data is > transferred to office with GSM modems. Some customers would like to > avoid the costs involved to this option and have another wireless method > to transfer the data. GPRS is not acceptable solution, there should not > be any costs at all. > > In this case the vehicles visit a terminal regualiry, so short/medium > range wireless transfer solutions could be used. The range should be at > least 1 km. 100 m is (probably) not enough. > > The data transfer rate does not need to be high, 9600 bit/s is enough. > Our device has a serial port (and limited amount of memory). > > There can be many vehicles (100?) at the terminal at the same time, so > there must be a way to address them separately. Only one vehicle needs > to be addressed at a time. A master node (office) initiates the data > transfer. > > Cost matters, as always. All options are however worth investigating. >
As Linnix already mentioned 1km range can be a problem with UHF and higher. Especially in case you have to deal with containers and other large metal objects getting in the way. I don't know the regulatory situation in Finland but I suggest to look into lower frequency ISM bands such as 40.68MHz, maybe even 6.78MHz. 13.56MHz is quite polluted in industrial areas because all kinds of RF heaters operate there, similar near hospitals because of diathermia equipment. 27.12MHz used to be swamped by CB radios, and here in the US by all kinds of garage door remotes and stuff. -- Regards, Joerg http://www.analogconsultants.com
Joerg wrote:
> Hello Jyrki, > > > > > We have a device that collects data from vehicles. Currently the data is > > transferred to office with GSM modems. Some customers would like to > > avoid the costs involved to this option and have another wireless method > > to transfer the data. GPRS is not acceptable solution, there should not > > be any costs at all. > > > > In this case the vehicles visit a terminal regualiry, so short/medium > > range wireless transfer solutions could be used. The range should be at > > least 1 km. 100 m is (probably) not enough. > > > > The data transfer rate does not need to be high, 9600 bit/s is enough. > > Our device has a serial port (and limited amount of memory). > > > > There can be many vehicles (100?) at the terminal at the same time, so > > there must be a way to address them separately. Only one vehicle needs > > to be addressed at a time. A master node (office) initiates the data > > transfer. > > > > Cost matters, as always. All options are however worth investigating. > > > > As Linnix already mentioned 1km range can be a problem with UHF and > higher. Especially in case you have to deal with containers and other > large metal objects getting in the way. > > I don't know the regulatory situation in Finland but I suggest to look > into lower frequency ISM bands such as 40.68MHz, maybe even 6.78MHz. > 13.56MHz is quite polluted in industrial areas because all kinds of RF > heaters operate there, similar near hospitals because of diathermia > equipment. 27.12MHz used to be swamped by CB radios, and here in the US > by all kinds of garage door remotes and stuff.
For a truck terminal, I am sure that's controlled air-space. Why can't they (the trucks) go through a destinated data dump area. Perhaps dumping other stuffs too. Anyway, this topic is very close to what I proposed this morning. Please continue in the same thread if possible. Thanks.
> > -- > Regards, Joerg > > http://www.analogconsultants.com
On Wed, 11 Oct 2006 22:26:04 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

> 27.12MHz used to be swamped by CB radios, and here in the US >by all kinds of garage door remotes and stuff.
Currently he 27 MHz CB band might work well, but in a few years during the sun spot maximum, the band will be swamped by CB signals from all over the continent. Some CB operators use 1200 bit/s AX.25 packet radio with unmodified CB transceivers. The AX.25 protocol would also take care of the addressing issue. The other problem with the 27 MHz band is that it requires a quite large antenna to get even a half decent antenna efficiency, which can be a problem on the truck, thus an external antenna may be required. I would suggest getting a licensed frequency in the VHF/UHF band to avoid the interference from other users. UHF should not be a problem up to 1 km, since the master (office) antenna (and transmitter) can be located at a high place e.g. at the roof of the building. Paul
Hello Paul,

> >>27.12MHz used to be swamped by CB radios, and here in the US >>by all kinds of garage door remotes and stuff. > > Currently he 27 MHz CB band might work well, but in a few years during > the sun spot maximum, the band will be swamped by CB signals from all > over the continent. Some CB operators use 1200 bit/s AX.25 packet > radio with unmodified CB transceivers. The AX.25 protocol would also > take care of the addressing issue. > > The other problem with the 27 MHz band is that it requires a quite > large antenna to get even a half decent antenna efficiency, which can > be a problem on the truck, thus an external antenna may be required. > > I would suggest getting a licensed frequency in the VHF/UHF band to > avoid the interference from other users. UHF should not be a problem > up to 1 km, since the master (office) antenna (and transmitter) can be > located at a high place e.g. at the roof of the building. >
But would a licensed frequency come with a substantial price tag? It's been a while that I lived in Europe but I remember that was the case in Germany. In this case I'd look into 40.68MHz if legal in Finland. For a 1km range a small stub antenna (basically a long coil in rubber) should do. Even in sun spot maxima it's rare that this frequency gets hit with over-range signals although I've seen it happen on very isolated occasions. -- Regards, Joerg http://www.analogconsultants.com
Joerg wrote:
> Hello Paul, > >> >>> 27.12MHz used to be swamped by CB radios, and here in the US by all >>> kinds of garage door remotes and stuff. >> >> >> Currently he 27 MHz CB band might work well, but in a few years during >> the sun spot maximum, the band will be swamped by CB signals from all >> over the continent. Some CB operators use 1200 bit/s AX.25 packet >> radio with unmodified CB transceivers. The AX.25 protocol would also >> take care of the addressing issue. >> The other problem with the 27 MHz band is that it requires a quite >> large antenna to get even a half decent antenna efficiency, which can >> be a problem on the truck, thus an external antenna may be required. >> >> I would suggest getting a licensed frequency in the VHF/UHF band to >> avoid the interference from other users. UHF should not be a problem >> up to 1 km, since the master (office) antenna (and transmitter) can be >> located at a high place e.g. at the roof of the building. >> > > But would a licensed frequency come with a substantial price tag? It's > been a while that I lived in Europe but I remember that was the case in > Germany. > > In this case I'd look into 40.68MHz if legal in Finland. For a 1km range > a small stub antenna (basically a long coil in rubber) should do. Even > in sun spot maxima it's rare that this frequency gets hit with > over-range signals although I've seen it happen on very isolated occasions.
The point is that for the range required by the OP, a relatively interference-free radio system has to be licensed, with the associated frequency usage fees. The fees in Finland are based on ERP and bandwidth, i.e. the area covered and frequency range occupied by the radio system. The license-free radio systems are restricted on ERP (Effective Radiated Power) to keep the range small. -- Tauno Voipio tauno voipio (at) iki fi
Hello Tauno,

>>> >>>> 27.12MHz used to be swamped by CB radios, and here in the US by all >>>> kinds of garage door remotes and stuff. >>> >>> Currently he 27 MHz CB band might work well, but in a few years during >>> the sun spot maximum, the band will be swamped by CB signals from all >>> over the continent. Some CB operators use 1200 bit/s AX.25 packet >>> radio with unmodified CB transceivers. The AX.25 protocol would also >>> take care of the addressing issue. >>> The other problem with the 27 MHz band is that it requires a quite >>> large antenna to get even a half decent antenna efficiency, which can >>> be a problem on the truck, thus an external antenna may be required. >>> >>> I would suggest getting a licensed frequency in the VHF/UHF band to >>> avoid the interference from other users. UHF should not be a problem >>> up to 1 km, since the master (office) antenna (and transmitter) can be >>> located at a high place e.g. at the roof of the building. >>> >> >> But would a licensed frequency come with a substantial price tag? It's >> been a while that I lived in Europe but I remember that was the case >> in Germany. >> >> In this case I'd look into 40.68MHz if legal in Finland. For a 1km >> range a small stub antenna (basically a long coil in rubber) should >> do. Even in sun spot maxima it's rare that this frequency gets hit >> with over-range signals although I've seen it happen on very isolated >> occasions. > > The point is that for the range required by the OP, > a relatively interference-free radio system has to > be licensed, with the associated frequency usage > fees. > > The fees in Finland are based on ERP and bandwidth, > i.e. the area covered and frequency range occupied > by the radio system. > > The license-free radio systems are restricted on ERP > (Effective Radiated Power) to keep the range small. >
That's different in the US. You can buy license-free products that offer several kilometers of range. My wife and I have license-free walkie-talkies that we use when she goes clothes shopping and my patience runs thin ;-) These reach from inside a hardware store (lots of metal around) to inside the clothes store a mile or two down the road. Same with 40.68MHz gear. Once I wanted to know and took a common wireless microphone on a little hike. Definitely more than one mile, crystal clear sound (they are FM). -- Regards, Joerg http://www.analogconsultants.com
Joerg wrote:
> Hello Tauno, > >>>> >>>>> 27.12MHz used to be swamped by CB radios, and here in the US by all >>>>> kinds of garage door remotes and stuff. >>>> >>>> >>>> Currently he 27 MHz CB band might work well, but in a few years during >>>> the sun spot maximum, the band will be swamped by CB signals from all >>>> over the continent. Some CB operators use 1200 bit/s AX.25 packet >>>> radio with unmodified CB transceivers. The AX.25 protocol would also >>>> take care of the addressing issue. >>>> The other problem with the 27 MHz band is that it requires a quite >>>> large antenna to get even a half decent antenna efficiency, which can >>>> be a problem on the truck, thus an external antenna may be required. >>>> >>>> I would suggest getting a licensed frequency in the VHF/UHF band to >>>> avoid the interference from other users. UHF should not be a problem >>>> up to 1 km, since the master (office) antenna (and transmitter) can be >>>> located at a high place e.g. at the roof of the building. >>>> >>> >>> But would a licensed frequency come with a substantial price tag? >>> It's been a while that I lived in Europe but I remember that was the >>> case in Germany. >>> >>> In this case I'd look into 40.68MHz if legal in Finland. For a 1km >>> range a small stub antenna (basically a long coil in rubber) should >>> do. Even in sun spot maxima it's rare that this frequency gets hit >>> with over-range signals although I've seen it happen on very isolated >>> occasions. >> >> >> The point is that for the range required by the OP, >> a relatively interference-free radio system has to >> be licensed, with the associated frequency usage >> fees. >> >> The fees in Finland are based on ERP and bandwidth, >> i.e. the area covered and frequency range occupied >> by the radio system. >> >> The license-free radio systems are restricted on ERP >> (Effective Radiated Power) to keep the range small. >> > > That's different in the US. You can buy license-free products that offer > several kilometers of range. My wife and I have license-free > walkie-talkies that we use when she goes clothes shopping and my > patience runs thin ;-) > > These reach from inside a hardware store (lots of metal around) to > inside the clothes store a mile or two down the road. > > Same with 40.68MHz gear. Once I wanted to know and took a common > wireless microphone on a little hike. Definitely more than one mile, > crystal clear sound (they are FM).
Kinda same applies to the 27 MHz CB band, but you then cannot offer any kind of interference protection against others having similar radios. -- Tauno Voipio tauno voipio (at) iki fi
Hello Tauno,

>>>> >>>> In this case I'd look into 40.68MHz if legal in Finland. For a 1km >>>> range a small stub antenna (basically a long coil in rubber) should >>>> do. Even in sun spot maxima it's rare that this frequency gets hit >>>> with over-range signals although I've seen it happen on very >>>> isolated occasions. >>> >>> The point is that for the range required by the OP, >>> a relatively interference-free radio system has to >>> be licensed, with the associated frequency usage >>> fees. >>> >>> The fees in Finland are based on ERP and bandwidth, >>> i.e. the area covered and frequency range occupied >>> by the radio system. >>> >>> The license-free radio systems are restricted on ERP >>> (Effective Radiated Power) to keep the range small. >>> >> >> That's different in the US. You can buy license-free products that >> offer several kilometers of range. My wife and I have license-free >> walkie-talkies that we use when she goes clothes shopping and my >> patience runs thin ;-) >> >> These reach from inside a hardware store (lots of metal around) to >> inside the clothes store a mile or two down the road. >> >> Same with 40.68MHz gear. Once I wanted to know and took a common >> wireless microphone on a little hike. Definitely more than one mile, >> crystal clear sound (they are FM). > > > Kinda same applies to the 27 MHz CB band, but you > then cannot offer any kind of interference protection > against others having similar radios. >
You run that risk on any license free or secondary usage band. I have seen cases where the 2.45GHz band was choking up. You couldn't squeeze in one more shoehorn. However, on 40.68MHz that chance is pretty low in the US. It is not at all in heavy use. Except maybe around RC car race tracks but you won't find those near loading docks. -- Regards, Joerg http://www.analogconsultants.com