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'[EE] Radio modules'
2007\07\30@110538 by David VanHorn

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I'm looking for radio modules.

I need >10mbps. Bluetooth, Zigbee, and wifi are not suitable.
I also need small (matchbox sized?), and <2W power.
I need something that I can get my hands on in a week or two.
I need to be able to interface it to a PC-104 system, by lan, USB, or ?

Anyone know vendors?

2007\07\30@112341 by Xiaofan Chen

face picon face
On 7/30/07, David VanHorn <spam_OUTmicrobrixTakeThisOuTspamgmail.com> wrote:
> I'm looking for radio modules.
>
> I need >10mbps. Bluetooth, Zigbee, and wifi are not suitable.
The current Bluetooth and Zigbee standard are much slower than 10Mbps...

> I also need small (matchbox sized?), and <2W power.
> I need something that I can get my hands on in a week or two.
> I need to be able to interface it to a PC-104 system, by lan, USB, or ?
>

Xiaofan

2007\07\30@114856 by David VanHorn

picon face
> > I need >10mbps. Bluetooth, Zigbee, and wifi are not suitable.
> The current Bluetooth and Zigbee standard are much slower than 10Mbps...

Hence the disqualification.
Wifi is performing rather dismally at the moment, with an 802.11G link
giving about 3mbps of actual throughput.

I need to push four cameras worth of data at 640x480, plus a few
kbytes/sec of other sensor data.

2007\07\30@120416 by Michael Rigby-Jones

picon face


>-----Original Message-----
>From: .....piclist-bouncesKILLspamspam@spam@mit.edu [piclist-bouncesspamKILLspammit.edu]
>On Behalf Of David VanHorn
>Sent: 30 July 2007 16:49
>To: Microcontroller discussion list - Public.
>Subject: Re: [EE] Radio modules
>
>
>> > I need >10mbps. Bluetooth, Zigbee, and wifi are not suitable.
>> The current Bluetooth and Zigbee standard are much slower than
>> 10Mbps...
>
>Hence the disqualification.
>Wifi is performing rather dismally at the moment, with an
>802.11G link giving about 3mbps of actual throughput.

Is this possibly down to signal strength and/or interference issues?  802.11G should give significantly better throughput than that.  Would 802.11N be a possibility?

What are the range requirements?  Is it line of sight?

Regards

Mike


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2007\07\30@121653 by Alex Harford

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On 7/30/07, David VanHorn <.....microbrixKILLspamspam.....gmail.com> wrote:
> > > I need >10mbps. Bluetooth, Zigbee, and wifi are not suitable.
> > The current Bluetooth and Zigbee standard are much slower than 10Mbps...
>
> Hence the disqualification.
> Wifi is performing rather dismally at the moment, with an 802.11G link
> giving about 3mbps of actual throughput.
>
> I need to push four cameras worth of data at 640x480, plus a few
> kbytes/sec of other sensor data.

What codec is the video data in?  I'm wondering if you can get more
compression on the pre-transmit side, ie an MPEG4 codec?

802.11n might be another option.

Alex

2007\07\30@123717 by Bob Axtell

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Michael Rigby-Jones wrote:
{Quote hidden}

While RF is not my main strength, I have a close friend who is an
expert, so I learned a few things by osmosis.
It seems that the biggest problem with wireless is that the speed can
drop precipitously with additional users. In
general, everybody knows this, but  in practice, strange things happen.

I was planning a design in which police cars would dump their video
surveillance data by wireless. Police cars were
parked in a protected building with a high ceiling. Tests indicated that
it would work fine- in general- but overlooked
was the fact that all policemen change shifts at the SAME time- so 50+
users would be dumping at the same time.
The idea wasn't usable because the upload speed with 50 users was slower
than molasses, and the cars had to be
gassed up, oil checked as well as other routine things attended to
between shifts . We had to use CAT5E
and have multiple servers online to get this to work. The wear on the
CAT5 jumpers was awful; at least one was replaced
daily.

The final design was that the sargeant's cars (5-6) were kept as
wireless, all the lower-level police used CAT5 jumpers.
The servers simply stored data temporarily, since it took hours to
properly archive that much data. Computers on the network
would slowly copy in the stored data, then process it. Active
transactions (tickets, arrests) were clipped out and attached to
the paper files of the case.

It was fun.

--Bob A
/ /

2007\07\30@124550 by Dario Greggio

face picon face
Bob Axtell wrote:

> It seems that the biggest problem with wireless is that the speed can
> drop precipitously with additional users. In
> general, everybody knows this, but  in practice, strange things happen.

absolutely agreed, Bob


--
Ciao, Dario

2007\07\30@130130 by William \Chops\ Westfield

face picon face

On Jul 30, 2007, at 8:48 AM, David VanHorn wrote:

>>> I need >10mbps. Bluetooth, Zigbee, and wifi are not suitable.
>
> Hence the disqualification.
> Wifi is performing rather dismally at the moment, with an 802.11G link
> giving about 3mbps of actual throughput.

Getting 10Mbps+ on a radio link is pretty tough; I'd think your best
chance is to debug your 802.11G link and figure out why it's not
performing as well as it ought to.

BillW

2007\07\30@132850 by alan smith

picon face
4 cams aggregated?  what about independent streams?  Check out WiLife see what they are doing?

David VanHorn <@spam@microbrixKILLspamspamgmail.com> wrote:  > > I need >10mbps. Bluetooth, Zigbee, and wifi are not suitable.
> The current Bluetooth and Zigbee standard are much slower than 10Mbps...

Hence the disqualification.
Wifi is performing rather dismally at the moment, with an 802.11G link
giving about 3mbps of actual throughput.

I need to push four cameras worth of data at 640x480, plus a few
kbytes/sec of other sensor data.

2007\07\30@133107 by David VanHorn

picon face
> Is this possibly down to signal strength and/or interference issues?

Test distance was about 3 meters.
Interference is a possibility, but given the band, it's just a fact of life.

> 802.11G should give significantly better throughput than that.

I would have expected so.  I'm not sure where the bottleneck is, but
connecting the systems by wire is MUCH faster, and taking the laptop
through an external wifi router is also significantly faster.

> Would 802.11N be a possibility?

Not likely,  I haven't seen any small N adaptors, and I'd have to deal
with kernel issues.
The main system is a PC-104 running Ubuntu.


> What are the range requirements?  Is it line of sight?

Umm.. right.  :)    We have reasonable expectations of range, and
there will be impairments.

2007\07\30@135543 by David VanHorn

picon face
On 7/30/07, alan smith <KILLspammicro_eng2KILLspamspamyahoo.com> wrote:
> 4 cams aggregated?  what about independent streams?

Physically impractical. I barely have room for the one Wi-Fi board now.

> Check out WiLife see what they are doing?

Probably compression, which isn't acceptable. Image quality is important.


We also discussed using four analog transmitters, but finding those
with good picture quality isn't very easy either. We have four cameras
that give good images (ptgrey fire-eye) and we really don't want to
throw away the quality in a crummy radio.

In the end, the video needs to end up on a laptop where we can do
stitching, filtering, edge/motion detection, etc, so lossy compression
isn't an option, and lossless seems to end up taking more processor
bandwidth than we have.

2007\07\30@143522 by Alex Harford

face picon face
On 7/30/07, David VanHorn <RemoveMEmicrobrixTakeThisOuTspamgmail.com> wrote:
>
> Not likely,  I haven't seen any small N adaptors, and I'd have to deal
> with kernel issues.
> The main system is a PC-104 running Ubuntu.

What chipsets are you using for the wifi radios?

2007\07\30@145811 by Herbert Graf

flavicon
face
On Mon, 2007-07-30 at 11:48 -0400, David VanHorn wrote:
> > > I need >10mbps. Bluetooth, Zigbee, and wifi are not suitable.
> > The current Bluetooth and Zigbee standard are much slower than 10Mbps...
>
> Hence the disqualification.
> Wifi is performing rather dismally at the moment, with an 802.11G link
> giving about 3mbps of actual throughput.

Then I'd say there's something wrong with how you're doing your WiFi. My
G links go at around 22Mbps. 3Mbps means you're either too far from the
AP (in which case getting directional antennas would help), or you're
using a transport that can't handle the speed reliably (a misconfigured
TCP stack can easily limit you to 3Mbps). TTYL

> I need to push four cameras worth of data at 640x480, plus a few
> kbytes/sec of other sensor data.

Does it have to be digital? Analog video transmitters/receivers are a
dime a dozen these days, getting one that allows you to set what channel
they transmit on shouldn't be too hard. TTYL

2007\07\30@150107 by Herbert Graf

flavicon
face
On Mon, 2007-07-30 at 13:31 -0400, David VanHorn wrote:
> > Is this possibly down to signal strength and/or interference issues?
>
> Test distance was about 3 meters.
> Interference is a possibility, but given the band, it's just a fact of life.
>
> > 802.11G should give significantly better throughput than that.
>
> I would have expected so.  I'm not sure where the bottleneck is, but
> connecting the systems by wire is MUCH faster, and taking the laptop
> through an external wifi router is also significantly faster.

3m? There was something wrong with either you hardware or drivers. I
regularly get 22Mbps at distances MUCH more then 3m on my G links.

Another possibility, if interference is really a problem is try some
802.11a hardware, very little is on that band. TTYL

2007\07\30@151011 by David VanHorn

picon face
>
> What chipsets are you using for the wifi radios?

Ralink rt73

2007\07\30@152633 by Michael Rigby-Jones

picon face


>-----Original Message-----
>From: spamBeGonepiclist-bouncesspamBeGonespammit.edu [TakeThisOuTpiclist-bouncesEraseMEspamspam_OUTmit.edu]
>On Behalf Of David VanHorn
>Sent: 30 July 2007 18:31
>To: Microcontroller discussion list - Public.
>Subject: Re: [EE] Radio modules
>
>
>> What are the range requirements?  Is it line of sight?
>
>Umm.. right.  :)    We have reasonable expectations of range, and
>there will be impairments.


Yeah, I know that sounded a bit silly as you are talking about cameras :D  I was actualy thinking it could be an aerial appllication?

Cheers

Mike

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law. If you are not the intended recipient of this message, you must
not make any use of this information, or copy or show it to any
person. Please contact us immediately to tell us that you have
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2007\07\30@155820 by David VanHorn
picon face
> Then I'd say there's something wrong with how you're doing your WiFi. My
> G links go at around 22Mbps. 3Mbps means you're either too far from the
> AP (in which case getting directional antennas would help), or you're
> using a transport that can't handle the speed reliably (a misconfigured
> TCP stack can easily limit you to 3Mbps). TTYL

Could be.. I know I've linked Motorola 850 APs with DD-WRT and had
transfer rates up around 6M, probably more but that's as fast as
matters, since that's the cap on my comcast link at home.

We're only working at a few meters range at the moment, signal
strength isn't an issue.


> Does it have to be digital? Analog video transmitters/receivers are a
> dime a dozen these days, getting one that allows you to set what channel
> they transmit on shouldn't be too hard. TTYL

In the end, it's all analog :)

No, we're not married to digital, but the analog transmitters that
I've seen are all excrement.   Low bandwidth, not true VSB, basically
just cheap AM or FM modulation with no thought to what the passband
looks like.   In the end, I need to get the video into a laptop for
processing, so it has to go digital somewhere.  We intend to do some
processing before it's transmitted, so that would push the transition
point up twoard the cameras.

2007\07\30@155939 by David VanHorn

picon face
> >
> >Umm.. right.  :)    We have reasonable expectations of range, and
> >there will be impairments.
>
>
> Yeah, I know that sounded a bit silly as you are talking about cameras :D  I was actualy thinking it could be an aerial appllication?


You know the drill, if I told ya, i'd hafta k!#@!#$!@# (message
terminated for national security reasons).

2007\07\30@163148 by peter green

flavicon
face

> I was planning a design in which police cars would dump their video
> surveillance data by wireless. Police cars were
> parked in a protected building with a high ceiling. Tests indicated that
> it would work fine- in general- but overlooked
> was the fact that all policemen change shifts at the SAME time- so 50+
> users would be dumping at the same time.
> The idea wasn't usable because the upload speed with 50 users was slower
> than molasses, and the cars had to be
> gassed up, oil checked as well as other routine things attended to
> between shifts . We had to use CAT5E
> and have multiple servers online to get this to work. The wear on the
> CAT5 jumpers was awful; at least one was replaced
> daily.
>
>  

Did you consider using something a bit tougher than a RJ connector for
the download cable?

2007\07\30@210709 by Jake Anderson

flavicon
face
David VanHorn wrote:
>> Then I'd say there's something wrong with how you're doing your WiFi. My
>> G links go at around 22Mbps. 3Mbps means you're either too far from the
>> AP (in which case getting directional antennas would help), or you're
>> using a transport that can't handle the speed reliably (a misconfigured
>> TCP stack can easily limit you to 3Mbps). TTYL
>>    
>
> Could be.. I know I've linked Motorola 850 APs with DD-WRT and had
> transfer rates up around 6M, probably more but that's as fast as
> matters, since that's the cap on my comcast link at home.
>
> We're only working at a few meters range at the moment, signal
> strength isn't an issue.
Just a wild thought, you aren't too close to the AP are you? Just
wondering if your seeing near field effects or some such.
Other option is to take a look at a MIMO AP that might bump your signal
up without needing to change anything inside your device.


'[EE] Radio modules'
2007\08\01@205030 by John La Rooy
flavicon
face
On 7/31/07, Bob Axtell <RemoveMEengineerspamTakeThisOuTcotse.net> wrote:
> I was planning a design in which police cars would dump their video
> surveillance data by wireless. Police cars were
> parked in a protected building with a high ceiling. Tests indicated that
> it would work fine- in general- but overlooked
> was the fact that all policemen change shifts at the SAME time- so 50+
> users would be dumping at the same time.
> The idea wasn't usable because the upload speed with 50 users was slower
> than molasses,

I read of a similar problem in a school/university situation where
everyone was supposed to download wirelessly the lesson notes at the
beginning. it was only a few megs or so, but multiplied by 50 or 100
users... They ended up putting multiple 802.11a access points in the
ceiling in a hexagonal/cellular arrangement. 802.11g only has 3 non
overlapping channels. 802.11a has a heap more.

John

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