PLC Modem questions

John J Wu

1. We have fired up the PLC modems and are not getting the performance we would expect. With two PLC modems plugged into the end of an extension cord we initiate the test frames function. The transfer starts off fine but starts to degrade quickly stalling completely within a few minutes. We have the modems set to 12 carriers, 1-DPSK, FEC on so we should have fairly robust communications. We are finding that we can achieve only ~ 7 kbps throughput and then under only the most pristine conditions. 2. Is the zero crossing input to the SoM required? We are planning on using the power line modem on DC power lines, not AC. 3. The temperature range of the audio amplifier they are using to drive the channel is 0 to +125 deg C. Does TI have a recommended substitute part that will do -40 to +85 deg C? Thanks in advance!

over 16 years ago

0 Arefeen over 16 years ago

Genius 5170 points

Hello Arrow

There are PLC solutions which require zero-crossing information - if this is one of those then communication over a DC line will not work. Have you tried this with a regular AC line so that atleast your setup can be verified? I am sure TI folks will clarify the DC line communication question.

0 John J Wu over 16 years ago in reply to Arefeen

Genius 3870 points

Thanks Arefeen. I think TI PLC modem has used 2 modulation schemes: FSK and OFDM. OFDM can be used in DC, but FSK requires zero-crossing. Can anybody confirm? How to get a higher speed?

0 Arefeen over 16 years ago in reply to John J Wu

Genius 5170 points

hello Arrow

TI folks need to confirm this but I believe this OFDM transmission is synchronized with zero crossings. By the way, you may have already seen this but here is what I found after some Google [:D] http://addgrup.com/info/Drutsa.pdf . I am not sure but most likely you are working with this or very similar to this solution.

0 John J Wu over 16 years ago in reply to Arefeen

Genius 3870 points

Thanks Arefeen for the good info. ADD did the firmware in this release, I guess. So looks like zero-crossing is required even in OFDM modulation scheme, for synchronization purpose. Not sure why 7kbps can only be achieved. EVerybody is claiming that a 70kbps should be doable. Any comments?

0 Arefeen over 16 years ago in reply to John J Wu

Genius 5170 points

Sorry Arrow - I am not sure why the numbers are not matching - although the actual through put always depends on many system conditions like line noise, impedance etc. However your set up sounds like a simple one and you should achieve max through put - by the way, did you try this demo/development kit with an AC line? It will be good to check the performance of this kit using the suggested setup to get a baseline.

0 Matthew Webster over 16 years ago in reply to Arefeen

TI__Prodigy 470 points

Arrow,

Please send your PLC support request topics to, plc_modem_support@list.ti.com

0 John J Wu over 16 years ago in reply to Matthew Webster

Genius 3870 points

I did it on Oct 19, but no answer so far.

0 Matthew Webster over 16 years ago in reply to John J Wu

TI__Prodigy 470 points

Arrow,

I apologize for the confusion. I recently reponded to a similar request from "John" at Arrow, but I have not seen any more requests. I'm not sure if he is at your site.

If you don't mind, please resend your request to the list and I will work with you directly.

Thanks!

0 John J Wu over 16 years ago in reply to Matthew Webster

Genius 3870 points

That's me. But I did not receive any info from TI. I will go to see the customer tomorrow morning at 9:00am. It'll be great if you can forward the message to me again. Thanks Mdub.

0 Matthew Webster over 16 years ago in reply to John J Wu

TI__Prodigy 470 points

John,

I resent the message. I sent it twice, one is without the attachement, the other is the same message with the attachemt. Please let me know if you recieve either or both.

0 John J Wu over 16 years ago in reply to Matthew Webster

Genius 3870 points

Thank you very much Matthew. I just replied your email. Funny I did not receive 2 emails you sent with attachment. This might be something related to file format (or simply file extension) of the attachment. Is there anyway I can download the file? We are meeting customer at 9:15am, in 60 minutes.

Thanks again Matthew,

John

0 LeonardEllis over 15 years ago in reply to Matthew Webster

TI__Guru 71526 points

mdub (Matthew??) since your email is not displayed, I don't know how to contact you, and the plc_modem_support list is no longer valid, please let me know how to contact you, as I have PLC questions

-Leonard

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