Communication System for High speed objects

Hi list,

I want to design communication system for high speed objects say 600Km/h.
And I plan to use 4FSK or 8-FSK as modulation scheme. Data rate would be
around 125Kbps and symbol rate 62.5ksps. What kind of channel, neglecting
multi-path,  should I use to test my design. Any body who can point me to
literature, papers anything that discusses this type of system in a
practical way.

Regards,
ML   

On Wed, 29 May 2013 01:47:27 -0500, mite_learner wrote:

> Hi list,
> 
> I want to design communication system for high speed objects say
> 600Km/h.
> And I plan to use 4FSK or 8-FSK as modulation scheme. Data rate would be
> around 125Kbps and symbol rate 62.5ksps. What kind of channel,
> neglecting multi-path,  should I use to test my design. Any body who can
> point me to literature, papers anything that discusses this type of
> system in a practical way.
> 
> Regards,
> ML

Not enough information.

If it's radio communications then doppler probably isn't going to be a 
significant issue -- but you can check if you're worried.

You haven't said what environment your objects are traveling through, or 
how close they get to the fixed antenna, or even if there are fixed 
antennas, or how far they travel at this speed, etc.

If they're out in the clear blue sky with uninterrupted line of sight to 
them, then you probably don't have to do much of anything special.

-- 
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

On 5/29/2013 1:47 AM, mite_learner wrote:
> Hi list,
>
> I want to design communication system for high speed objects say 600Km/h.
> And I plan to use 4FSK or 8-FSK as modulation scheme. Data rate would be
> around 125Kbps and symbol rate 62.5ksps. What kind of channel, neglecting
> multi-path,  should I use to test my design. Any body who can point me to
> literature, papers anything that discusses this type of system in a
> practical way.

On Wed, 29 May 2013 11:14:13 -0500, Vladimir Vassilevsky wrote:

> On 5/29/2013 1:47 AM, mite_learner wrote:
>> Hi list,
>>
>> I want to design communication system for high speed objects say
>> 600Km/h. And I plan to use 4FSK or 8-FSK as modulation scheme. Data
>> rate would be around 125Kbps and symbol rate 62.5ksps. What kind of
>> channel, neglecting multi-path,  should I use to test my design. Any
>> body who can point me to literature, papers anything that discusses
>> this type of system in a practical way.

(From sci.electronics.design)

"I have to make low power SMPS operable up to several hundred volts. For 
obvious reasons, it would be good to use off the shelf SMT inductors.
In datasheets, they always specify inductor max. current, however they 
don't say anything about max. voltage.

Any advice or relevant experience?

Vladimir Vassilevsky
DSP and Mixed Signal Designs
www.abvolt.com
"

-- 
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

On Wed, 29 May 2013 01:47:27 -0500, "mite_learner" <94814@dsprelated>
wrote:

>
>Hi list,
>
>I want to design communication system for high speed objects say 600Km/h.
>And I plan to use 4FSK or 8-FSK as modulation scheme. Data rate would be
>around 125Kbps and symbol rate 62.5ksps. What kind of channel, neglecting
>multi-path,  should I use to test my design. Any body who can point me to
>literature, papers anything that discusses this type of system in a
>practical way.
>
>Regards,
>ML   

As Tim mentioned, usually something moving that fast is airborne, and
if a directive antenna is used to track the object there may not be
any significant multipath reflections to deal with.   In that case,
you're just dealing with Doppler and your receiver needs to be able to
handle the expected frequency offsets and track frequency within the
motion parameters that affect how the Doppler rate may change
dynamically.

If you're receiving with an omnidirectional antenna, or an antenna
that lets in a fair amount of multipath, then you may want to look at
the usual mobile multipath channel models that include Doppler.   Most
of those models are made for vehicular speeds and down, so you may
have to modify things a bit to get what you need.

Without more info on what you're doing, that's about all I can offer.


Eric Jacobsen
Anchor Hill Communications
http://www.anchorhill.com

>On Wed, 29 May 2013 01:47:27 -0500, mite_learner wrote:
>
>> Hi list,
>> 
>> I want to design communication system for high speed objects say
>> 600Km/h.
>> And I plan to use 4FSK or 8-FSK as modulation scheme. Data rate would
be
>> around 125Kbps and symbol rate 62.5ksps. What kind of channel,
>> neglecting multi-path,  should I use to test my design. Any body who
can
>> point me to literature, papers anything that discusses this type of
>> system in a practical way.
>> 
>> Regards,
>> ML
>
>Not enough information.
>
>If it's radio communications then doppler probably isn't going to be a 
>significant issue -- but you can check if you're worried.
>
>You haven't said what environment your objects are traveling through, or 
>how close they get to the fixed antenna, or even if there are fixed 
>antennas, or how far they travel at this speed, etc.
>
>If they're out in the clear blue sky with uninterrupted line of sight to 
>them, then you probably don't have to do much of anything special.
>
>-- 
>Tim Wescott
>Control system and signal processing consulting
>www.wescottdesign.com
>

Sorry for not providing all of the information. It is radio communciation.
Its airborne channel, luckily a clear blue sky :) 

Thanks you and Eric always help irrespective of how much information is
provided.  

Regards,
ML

>On Wed, 29 May 2013 01:47:27 -0500, "mite_learner" <94814@dsprelated>
>wrote:
>
>>
>>Hi list,
>>
>>I want to design communication system for high speed objects say
600Km/h.
>>And I plan to use 4FSK or 8-FSK as modulation scheme. Data rate would be
>>around 125Kbps and symbol rate 62.5ksps. What kind of channel,
neglecting
>>multi-path,  should I use to test my design. Any body who can point me
to
>>literature, papers anything that discusses this type of system in a
>>practical way.
>>
>>Regards,
>>ML   
>
>As Tim mentioned, usually something moving that fast is airborne, and
>if a directive antenna is used to track the object there may not be
>any significant multipath reflections to deal with.   In that case,
>you're just dealing with Doppler and your receiver needs to be able to
>handle the expected frequency offsets and track frequency within the
>motion parameters that affect how the Doppler rate may change
>dynamically.
>
>If you're receiving with an omnidirectional antenna, or an antenna
>that lets in a fair amount of multipath, then you may want to look at
>the usual mobile multipath channel models that include Doppler.   Most
>of those models are made for vehicular speeds and down, so you may
>have to modify things a bit to get what you need.
>
>Without more info on what you're doing, that's about all I can offer.
>
>
>Eric Jacobsen
>Anchor Hill Communications
>http://www.anchorhill.com
>
Eric, glad to have your comment.

Yes I am receiving via a omnidirectional antenna and the channel is
airborne. What kind of modificaiton would be required in channel models?.
What other info is needed? 

Thank you, alreay gave a detailed comment.

Regards,
ML

On Wed, 29 May 2013 14:34:28 -0500, "bradsdr" <95105@dsprelated>
wrote:

>>On Wed, 29 May 2013 01:47:27 -0500, "mite_learner" <94814@dsprelated>
>>wrote:
>>
>>>
>>>Hi list,
>>>
>>>I want to design communication system for high speed objects say
>600Km/h.
>>>And I plan to use 4FSK or 8-FSK as modulation scheme. Data rate would be
>>>around 125Kbps and symbol rate 62.5ksps. What kind of channel,
>neglecting
>>>multi-path,  should I use to test my design. Any body who can point me
>to
>>>literature, papers anything that discusses this type of system in a
>>>practical way.
>>>
>>>Regards,
>>>ML   
>>
>>As Tim mentioned, usually something moving that fast is airborne, and
>>if a directive antenna is used to track the object there may not be
>>any significant multipath reflections to deal with.   In that case,
>>you're just dealing with Doppler and your receiver needs to be able to
>>handle the expected frequency offsets and track frequency within the
>>motion parameters that affect how the Doppler rate may change
>>dynamically.
>>
>>If you're receiving with an omnidirectional antenna, or an antenna
>>that lets in a fair amount of multipath, then you may want to look at
>>the usual mobile multipath channel models that include Doppler.   Most
>>of those models are made for vehicular speeds and down, so you may
>>have to modify things a bit to get what you need.
>>
>>Without more info on what you're doing, that's about all I can offer.
>>
>>
>>Eric Jacobsen
>>Anchor Hill Communications
>>http://www.anchorhill.com
>>
>Eric, glad to have your comment.
>
>Yes I am receiving via a omnidirectional antenna and the channel is
>airborne. What kind of modificaiton would be required in channel models?.
>What other info is needed? 
>
>Thank you, alreay gave a detailed comment.
>
>Regards,
>ML

There are a number of mobile multipath channel models that account for
Doppler in both the direct and reflected paths, but most assume
pedestrian to vehicular speeds and have various terrain models, e.g.,
rural, suburban, hilly, urban canyon, etc.   So the terrain models
won't be the same as what your system will experience, and the Doppler
for your system will be higher.   Those aren't difficult changes to
make to the models, but they are a departure from the channels that
the models are trying to fit.

What terrain model to use will depend on the environment around your
omnidirectional receiver.   If there are a lot of reflections around
the receiver it will experience richer multipath, or if it's in the
middle of a rural field there may be very little multipath.  

I'd suggest researching the various Rician mobile multipath models
that include Doppler (ITU, etc.) and go from there.  There are a
variety of models and you'll need to evaluate which is the closest to
what you need based on your system, but it sounds like you're looking
for a Rician (i.e., has LOS) model with low to moderate multipath.
You can figure out the expected delay spread profile to use in the
model from the expected receive power and some assumptions about the
reflecting environment(s) around the receiver.

The same analysis about the channel will also help you determine
whether an equalizer will be beneficial for your system or not.


Eric Jacobsen
Anchor Hill Communications
http://www.anchorhill.com

Eric Jacobsen <eric.jacobsen@ieee.org> wrote:

(snip)

> There are a number of mobile multipath channel models that account for
> Doppler in both the direct and reflected paths, but most assume
> pedestrian to vehicular speeds and have various terrain models, e.g.,
> rural, suburban, hilly, urban canyon, etc.   So the terrain models
> won't be the same as what your system will experience, and the Doppler
> for your system will be higher.   Those aren't difficult changes to
> make to the models, but they are a departure from the channels that
> the models are trying to fit.

This reminds me of stories that ATSC (broadcast digital TV) doesn't
work in moving vehicles. Though there seem to be plenty of people
selling ATSC receivers for car use. I wonder which of the above
apply in the ATSC case.

-- glen

On Wed, 29 May 2013 22:05:09 +0000 (UTC), glen herrmannsfeldt
<gah@ugcs.caltech.edu> wrote:

>Eric Jacobsen <eric.jacobsen@ieee.org> wrote:
>
>(snip)
>
>> There are a number of mobile multipath channel models that account for
>> Doppler in both the direct and reflected paths, but most assume
>> pedestrian to vehicular speeds and have various terrain models, e.g.,
>> rural, suburban, hilly, urban canyon, etc.   So the terrain models
>> won't be the same as what your system will experience, and the Doppler
>> for your system will be higher.   Those aren't difficult changes to
>> make to the models, but they are a departure from the channels that
>> the models are trying to fit.
>
>This reminds me of stories that ATSC (broadcast digital TV) doesn't
>work in moving vehicles. Though there seem to be plenty of people
>selling ATSC receivers for car use. I wonder which of the above
>apply in the ATSC case.
>
>-- glen

I think that's just a difference of the standard not being designed or
specified for mobile, but implementers doing a good enough job to
support it in reasonable conditions.  Nothing stops an implementer
from going beyond the requirements of a standard and building
something better.   That's a bit easier to do with a single-carrier
waveform (like ATSC) than it is with something like OFDM.

Where it gets tricky is when features of the air interface get in the
way of supporting applications or conditions beyond the design space.
For example, 802.11 (WiFi) is intended for LAN applications, where the
range is relatively short, so things like the OFDM guard interval are
kept short to maintain efficiency and handle the expected delay
spreads.   That hasn't kept people from playing around with it and
using it at much longer ranges and higher mobility than was ever
intended by the scope of the spec.

That being said, ATSC, like DVB, does now also have extensions
specifically for mobile applications.  (ATSC-M/H and DVB-H).

Eric Jacobsen
Anchor Hill Communications
http://www.anchorhill.com