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Good overview and review and hopefully setting up for the remaining classes ...

Thanks 

I very much enjoyed this lecture

more relevant to me 

 

I'm not using radios so no data rate to report

no I have not studied that standard

I am not using any radios or freq at this time

planning on it for the future

yesterday was okay 

hoping for more useful info (to me specifically) today

thanks Paul; evcellent presentation

Iron

better late than never. hello from sunny miami.

Currently using only 915 FHSS

Iron

Interesting stuff... Worked with some of this since the beginning and have tried to ignore the details...-- oh well!

Iron

Catching up -- had to miss the first lectures.

Iron

Sorry.  See the slide 10 typo was already caught.  Might want to update the slide deck.

I too had to miss the live lecture, thanks for the archives.

Iron

@Ann - both 915 MHz and 2.4 GHz

Iron

Great to have access to the recorded sessions!

Iron

Missed the live lecture today...

Iron

Thanks for the information

Iron

well well, thats about time for today.

see you all tomorrow.

Paul.

 

Blogger

thats preamble:  PREAMBLE

Blogger

yes, there is a sync preable in every packet.  Its important

and everything does hang on it.  We'll discuss that in quite

a bit of detail tomorrow.

Blogger

Is there a synchronization preample in every packet? Seems like everything hangs on it.

Iron

Excellent comment about the clocks!!  That is right

the clocks must be very stable for a number of reasons.

There are the obvious RF and frequency tuning reasons,

there are the less obvious network synchronization and

message synch reasons too.  An Rx node can drift in time

from a Tx node.  That can matter.

 

Blogger

o-pqsk - the offset part, I think,

but am not sure, that the offset

keeps the signal AC neutral, ie no

DC offset in the transmitted signal.

Blogger

@Paul: Wow! Better hope our clocks are stable. By the way, I now note that the relationship between the chip values for 8 and 9 is not unique: every single row in the table is the row above it shifted right by 2.

Iron

I suppose the reason why cellphone radio networks uses GPS disciplined clock to maintain sychnoniztion for chip demodulation.

Iron

The Lecturer appears to have limited this lecture to a 6 year old version (year 2006) of the IEEE 802.15.4 standard. The year 2011 version (IEEE 802.15.4 - 2011) has many more modulation types and frequency bands defined in the standard. And since the year 2011 release, several more have been defined in the 802.15.4f and 802.15.4g standards.

Iron

@kraig:  that old radio still works.

Blogger

@mr.e  excellent observation.  No chips are not

like HDLC bit stuffing.  There are not codes to maintain

sync on these radios.  Synch is established at the transmit

header start - then and only then, CRC at the end is used

to validate a whole packet.  In between, its the wild-wild-west

of data transmission.   For the small radios that is...

Blogger

The advantage of using 802.15.4 even on your

own network  - other than interoperability - is

the standard's robustness.  Many vendors support

the modulation standard - and its good.  One can

experiment with shorter chip lengths and code, but

one does so at the gain of higher data through put and

the loss of data integrity.

 

Blogger

@Paul: concerning the unique decoding of chips: I expected to see limited repeated sequences of 0s or 1s so that synchronization could be more easily maintained. In some modulation schemes bit stuffing is used to do this. However, I also expected to see unique overall sequencing of groups of 0s and 1s in the chip values for each of the data symbols. This is apparently not the case. For example, at 915MHz on slide 14, the chip values for data symbol 9 are identical to those for data symbol 8, but two bit times later (9's chip values lag those of 8 by 2 bit times). So 8 starts 01101 and 9 starts 0001101. I would think this would cause problems maintaining sync. Are there other symbols that resync the bit values that make up the chips?

Iron

@jdbc - yes that's good.  The chip coding

is special - its not arbitrary.  Its considered

an orthogonal code - there is a name for this

type of coding - its not coming to my mind right

now, perhaps someone will look it up - this is

information theory stuff...

Blogger

What's the advantage to use the offset in O-QPSK?

Iron

@levitondave  -  Yes that's right

well said.

Blogger

Are chip values kind of like ASCII characters in the sense that it takes 1 byte for one ASCII character and for the chip values they may have to be 16 or 32 bits to represent one value?

Iron

Chip rate - this is the DEFINED BY 802.15.4 code

for each symbol.  The chip-rate is not up to a vendor

to decide.  The chips (32 in length for 2.4GHZ) are chosen

in such a way as to be a unique bit configuration such that

their decode may be accomplished even in the face of channel

noise.

Blogger

Very interesting thanks

 

Iron

So it's unlikely that noise would look like a symbol -- possible but not likely?

Gold

The advantage of sending chips instead of just symbols

is a few.  One is that by sending chips, the chip values

themselves are chosen to a) look like noise  and b) be

uniquely decodable.  Thus a symbol decode can be received

in the presence of channel noise, fading and interference.

Blogger

1 Mbps GFSK modulation at 2.4 GHz

Iron

Paul does chip rate mean each chip spits out it's own particular number based on it's 4 bit symbol?

 

Iron

That was a Super Hetrodyne and not the TRF (Tuned Radio Frequence) which would have had more than one tuner. Good Radio.

 

Iron

What is the incentive in using 802.15.4 standard if interoperability is not required for an application... One could achieve higher bit rate without have to spread the signal.. .

Thanks Paul. That was a helpful nice introduction for me to chip values.

Iron

It shows my age as I learned my radio with crystal set ans spark transmitter and coherer detectros.

Iron

Hello everyone,


Yes I noticed slide 15 should read

One 1 bit symbol is mapped to a 15 bit chip. 

A confusing two typos...

Blogger

When the uses Chip rate is he saying that there are that many chips used where each chip has a specific number?

 

Iron

One of the advantages of the chips is the ability to withstand transmission corruption and still get the desired information through.

Good lecture missed yestereday will have to pick it up on the archive to see what I missed.

Iron

Nice radio....thank you for today's lecture.

Iron

"Hot Chassis" radio!!   :)

How does transmission error get corrected?

Gold

Thank you Ann & Paul.

Iron

We are at 8224 bits/sec on the 2.4G band

Iron

Thanks for the class today! Very informative

Iron

 

Thank you Paul, very informative 

Iron

We used to have one like the one on slide 20 in an old lab here. Fun to play with.

I figured it was something like that David. Thx Kind of threw me a little by just showing 0 then reffering to 4 bit symbol on the slide. I wanted to make sure I was not missing something.

Iron

looking for 20KBps throughput...

Iron

@Paul: slide 15 shows 15 chip values c0 to c14 for each input bit but the text above the table says that a "16 bit chip" is in use. Is there a missing or assumed bit to make the 16th bit in the chip value?

Iron

I am not using radio yet

Today's next audience question is

If you are using ISM radios now, what is your maximum data transfer rate?

Blogger

How does the power consumption vary between the modulation scheme's?

 

4 bit symbol - consider 0000 => 0, 0001 =>1... 1010=> 10... 15=> 15, these are your  4bits that are encoded in to the map

 

Iron

The term chip rate is new to me. I think I need to look this up

 

Iron

What are a couple of advantaqes to using chips vs. just TXing symbols?

Iron

Sorry, tried many things and I too have no audio, not a corporate blocking or Adobe thing.

 

Iron

The addendums (i.e. 802.15.4e, 4f, 4g, and coming soon 4k) are expected to rollup into the upcoming 802.15.4-2013 standard release.

Iron

What do you mean by 4 bit symbol? I got the part of mapped Chip

Iron

The 802.15.4f standard adds MSK modulation to the 2.4 GHz band and a new 433 MHz band.

 

Iron

We use the standard too

Iron

I did work on the standard

Iron

with me the audio problems is that in IE I have to constantly re-start audio and with Chrome/Firefox I have to wait for a long while before they start playing

Iron

For those of you just joining us, today's questions are: 1) If you are using ISM radios now, in which frequency band are you operating? 2)Has anyone listening studied the IEEE 802.15.4 standard?

Blogger

If you're having audio issues, please note that some companies block live audio streams. If you don't hear any audio, try refreshing your browser. The show will be archived and available on this page.

Blogger

There are three recent amendments to 802.15.4. Two of which add new frequency bands and modulation methods 802.15.4f, 802.15.4g and the third adds new Medium Access Control layer frame formats.

 

Iron

Well, phooey, it looks like my audio feed is blocked...

I've studied the standard a bit.

Have used 900 Mhz on previous applications.

Iron

I have not studied 802.15.4 yet.

Iron

Have not studied the standard

Iron

Unfortunately not

would be very interesting to study indeed

I'm more into BT

Iron

future apps not using now.

Iron

yes, but 2003 version..

 

No, haven't studied the 802.15.4 standard, but have studied other 802 standards.

Iron

Read most of the 2003 version, which is a lot smaller

 

Iron

Not using ISM and I have not read 802.15.4 yet.

Iron

At one time I did but I've forgotten most of it. :(

no, have not studied 802.15.4

Iron

Today's next audience question is

Has anyone listening studied the IEEE 802.15.4 standard?

Blogger

Audio is excellent.

 

Iron

Any news about audio?

 

Mostly 2.4, some 900 Mhz based on range requirements & other interference.

 

No using at this time.

Iron

We are using the 2.4GHz ISM band so that we can operate in Eurpoe as well as North America

Iron

2.4 Ghz and 900 Mhz (with hopes of longer range)

Iron

Not at present. Looking at future possibilities for lighting control.

we are using 915 Mhz band operating at 300 Kbps

 

2.4 GHz and 5.8 GHz

Iron

Not using now....but interesting topic

Iron

not using ISM at this time.

Iron

Today's first audience question is

If you are using ISM radios now, in which frequency band are you operating?

Blogger

If you're having audio issues, please note that some companies block live audio streams. If you don't hear any audio, try refreshing your browser. The show will be archived and available on this page.

Blogger

Slide deck, page 10 has an error - BPSK is spelled out as Binary Frequency Shift Keying, where it obviously is
Binary Phase Shift Keying... just in case

Iron

I got the audio finally

Iron

@rswanson - rmember to use the Swish and flick for effective RF :)

Hello from far western Kentucky

 

Hello from Melbourne Beach Florida

Iron

Hello from nortwest Montana

Gold

It will start in bout 8 mins

Iron

Hello from Corona, Ca. I got my pointy hat on. I'm ready.

Iron

Are we there yet? Not yet started?

Iron

Hello again from Cedar Park, Texas

Iron

Tonight's forecast: Dark. Continued dark throughout most of the evening, with some widely scattered light towards morning

Iron

Hello from Minneapolis.  Sunny & high of 35 degF today.

Iron

Hi from Soggy Portland OR

Hello all from Edmonton, Alberta

Iron

Hello from Longmont, CO

Iron

Another Day - Another Lesson! May I never stop learning.

Iron

Hallo from teklava in HNL

Iron

Morning Paul & EE Times

Iron

Hello from Auburn, AL

Iron

Hello from Piney Flats, TN

Iron

Hello for Huntsville, Al

Iron

Hello from Ottawa, Canada

Please join our Digi-Key Continuing Education Center LinkedIn Group at http://linkd.in/yoNGeY

Blogger

The streaming audio player will appear on this web page when the show starts at 2pm eastern today. Note however that some companies block live audio streams. If when the show starts you don't hear any audio, try refreshing your browser. 

Blogger

Be sure to click 'Today's Slide Deck' under Special Educational Materials above right to download the PowerPoint for today's session.

Blogger

Hi All From California

Iron

Good morning from Los Angeles.

Iron

Good morning from Cupertino

Iron

good morning from San Diego

Iron

Good morning from Milwaukee!

Iron

Good morning from Edmonton.

Iron

Good morning from Fresno, CA

Iron

Good Morning from Sunny San Jose, CA.

Expecting RAIN Tonight.

It's 53°F now and a High of 64°F.

Iron


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