Hi, my name is Neil Harrison and way back in the 1980s I was an engineer working for BT. I created the CRC4 frame/mult structure for the 2.048Mbit/s transmission system that became a CCITT standard in G.704/706. Did all the modelling work on a BBC Micro. Seems a long time ago now. Amazed how it lasted. Been retired as a engineer for about 9 years.
Hi Neil, I presume you are in the UK (because you mentioned British Telecom!). I am a Computer Science student who currently learning Computer Networking and I'm afraid I don't understand what CRC 4 is but I would genuinely love to know more. If you have the time, I would really appreciate if you could provide more insight. Cheers,
@@DaBestAround CRC4 - this is a cyclic redundancy code of degree 4 (polynomial is X^4 + X + 1) that I used to detect errors in the 2Mbit/s transmission systems and also to prevent timeslots from mimicking the frame alignment signal (FAS) and thus stop incorrect frame alignment. If you really want to know more see CCITT Rec G.704/G.706....and/or do a search on CRC4. A long time ago for me.....amazed anyone still has interest in this work I did back then.
@@neilharrison01 Hey Neil, Thanks for the response. I looked into it and I tried to find your name somewhere throughout the documents but I couldn't find it. I totally believe you mate - everything you've said has been bang on and I don't know why anyone would even lie about that 😆 There is still a bit of interest in CRC4. See, I clicked on this video to learn about CRC (for my upcoming networking exam) If you don't mind me asking, how did you even get into the field - I know things were different back then but I'm genuinely curious. Also, even if it is a bit tedious, how did you end up creating the frame structure? - was it assigned as a task to you by BT or did you just do it? Cheers.
@@DaBestAround I graduated with a 1st class Hons BSc in Electrical/Electronic Engineering in 1981. My final year project was creating a pulse width modulated microwave radio link....so I was heavily into Maxwell's equations and stuff like that. I took a job with BT in Nov 1981....originally I wanted to do microwave research at Martlesham but optical fibres had just hit the news so there was not much call for microwave engineer research. So I ended up working in London at BT HQ. My first boss asked me to look at what was happening with the US 1.5M transmission standards as they were using a CRC6 polynomial to detect errors and prevent false framing. Our 2M transmission structure was better than the 1.5M system (for many reasons) but I only had room in bit 1 of timeslot zero to create a frame/mult structure and so I was restricted in the size of CRC I could use....ergo why it is CRC4 and not of higher degree (higher degree = better error burst detection). However, CRC4 is perfectly OK for what I designed it to do. After getting the CCITT standards G.703/704/706 sorted, that define the physical and frame/mult stuff, in Geneva in mid/late 1980s, I spent many years afterwards researching what real error distributions on digital metallic/optical/radio systems looked like....they for sure are not Poisson-like (as was the case on the old analogue transmission systems), but follow complex self-similar burst characteristics (weather is a key cause, and weather is bursty/self-similar). I spent the next few years working as the UK expert at CCITT meetings defining standards for error distributions detection and stuff related to that area. Later got promoted to more senior management roles and stopped doing hands on real engineering....hated this stuff, but it was well paid. Hope that background helps.
Did this not suffice? CCITT Recs don't mention author's names. You can find my name listed amongst IETF stuff related to OAM. But they are old now. Quite a few patents listed against my name wrt OAM topics in protocols like MPLS.
What you said at 4:42 was incorrect. You are trying to find the bits to append to the word that will serve as the CRC check. The remainder is exactly those bits. You will append them to the original word and this is sent to the receiver. The receiver then divides the received bits by the same divisor and the remainder should be zero. Other than that, good video :)
Nice video. I had issues doing the division, I got it wrong each time and my lecturer made me feel dull instead of explaining where I was not getting it (typical of China lol)... Now I see where i was confusing the whole thing lol. Thanks a lot.
I just had a Singaporean lecturer try to teach me that is the same race as the person who did this video. He was going way too fast on the power point for me to understand. It's not the race it's the explanation. I am Chinese too by the way , sometimes these academics go way too fast and probably taught too many classes of the same thing that they don't realise every student is different
I don't understand the lecturer either that's why I am looking on UA-cam. this person explained what I not understanding why the answer was a certain way. I sux at formulas and math concepts
My prof took an hour to explain this, and you did the job in less than 10 minutes- and better. Thank you!
Hi, my name is Neil Harrison and way back in the 1980s I was an engineer working for BT. I created the CRC4 frame/mult structure for the 2.048Mbit/s transmission system that became a CCITT standard in G.704/706. Did all the modelling work on a BBC Micro. Seems a long time ago now. Amazed how it lasted. Been retired as a engineer for about 9 years.
Hi Neil,
I presume you are in the UK (because you mentioned British Telecom!). I am a Computer Science student who currently learning Computer Networking and I'm afraid I don't understand what CRC 4 is but I would genuinely love to know more.
If you have the time, I would really appreciate if you could provide more insight.
Cheers,
@@DaBestAround CRC4 - this is a cyclic redundancy code of degree 4 (polynomial is X^4 + X + 1) that I used to detect errors in the 2Mbit/s transmission systems and also to prevent timeslots from mimicking the frame alignment signal (FAS) and thus stop incorrect frame alignment. If you really want to know more see CCITT Rec G.704/G.706....and/or do a search on CRC4. A long time ago for me.....amazed anyone still has interest in this work I did back then.
@@neilharrison01 Hey Neil,
Thanks for the response. I looked into it and I tried to find your name somewhere throughout the documents but I couldn't find it.
I totally believe you mate - everything you've said has been bang on and I don't know why anyone would even lie about that 😆
There is still a bit of interest in CRC4. See, I clicked on this video to learn about CRC (for my upcoming networking exam)
If you don't mind me asking, how did you even get into the field - I know things were different back then but I'm genuinely curious.
Also, even if it is a bit tedious, how did you end up creating the frame structure? - was it assigned as a task to you by BT or did you just do it?
Cheers.
@@DaBestAround I graduated with a 1st class Hons BSc in Electrical/Electronic Engineering in 1981. My final year project was creating a pulse width modulated microwave radio link....so I was heavily into Maxwell's equations and stuff like that. I took a job with BT in Nov 1981....originally I wanted to do microwave research at Martlesham but optical fibres had just hit the news so there was not much call for microwave engineer research. So I ended up working in London at BT HQ. My first boss asked me to look at what was happening with the US 1.5M transmission standards as they were using a CRC6 polynomial to detect errors and prevent false framing. Our 2M transmission structure was better than the 1.5M system (for many reasons) but I only had room in bit 1 of timeslot zero to create a frame/mult structure and so I was restricted in the size of CRC I could use....ergo why it is CRC4 and not of higher degree (higher degree = better error burst detection). However, CRC4 is perfectly OK for what I designed it to do. After getting the CCITT standards G.703/704/706 sorted, that define the physical and frame/mult stuff, in Geneva in mid/late 1980s, I spent many years afterwards researching what real error distributions on digital metallic/optical/radio systems looked like....they for sure are not Poisson-like (as was the case on the old analogue transmission systems), but follow complex self-similar burst characteristics (weather is a key cause, and weather is bursty/self-similar). I spent the next few years working as the UK expert at CCITT meetings defining standards for error distributions detection and stuff related to that area. Later got promoted to more senior management roles and stopped doing hands on real engineering....hated this stuff, but it was well paid. Hope that background helps.
Did this not suffice? CCITT Recs don't mention author's names. You can find my name listed amongst IETF stuff related to OAM. But they are old now. Quite a few patents listed against my name wrt OAM topics in protocols like MPLS.
First video on this topic ive found with an indian guy whose accent i can actually understand! awesome!
@@snowzley2389 lolz
You are awesome. Congrats. Also you understanding his accent has nothing to do with his knowledge or awesomeness too! 😉
You provided the first explanation that I actually understood. I can do it now! Thanks :)
sir, you are a man, who teach me the process absolutely correct.
Thanks "The BootStrappers".
I'm here cuz I was curious how file integrity check works. I think I'm dividing more than I really needed and I love it.
Thank you
8 YEARS GOIN8 years going and still helpful, thanks man
Can hear ur frnd telling "Change pen! Change pen!" 😂😂
Kuch padai bhi kr lo 😁
lol
What you said at 4:42 was incorrect. You are trying to find the bits to append to the word that will serve as the CRC check. The remainder is exactly those bits. You will append them to the original word and this is sent to the receiver. The receiver then divides the received bits by the same divisor and the remainder should be zero. Other than that, good video :)
+Zumerjud but it was clear anyway
+1
Was it you calling to tell him he said something wrong?
yes u r right
yes you are right
I watched a lot of videos trying to figure out how this works...yours made the most sense, so thanks
Thanks brother, this really helped me understand the assignment I was given...Am a master on CRC now. most grateful
your clarity on the topic is awesome!!!!!!!!!!!!!!!!
love to you my brother from india, took less than 10 minutes to explain this concept
Thank you for helping this Kiwi student catch up after being sick!
+Shigeruken
Thank you, feels really good to be able to help someone :)
Thank you bro,bravo!! You're smart,i've been trying to find a video about crc and this vid is the only one can make me get it!!
my dad was explaining CRC and your video helped out a lot
Thank you so much it's now easy to understand crc coding because of you....😊
thank you man you just saved my mid term result
really it helps me to learn the CRC at the exam time. thank u.
+abhisek datta
Thank you :)
Thank you for the simple easy to understand explanation
Change Pen :P..nice video ! :D
Thanks bro... u helped me a lot .. those CRC things was my worst nightmare
Very useful basic simple crystal clear
Thank you
Thanks for kindly share this. Now I understand how CRC works. Very helpful video.
Thank you so much.... so helpful.... i have an exam now and i didn’t understand it before.... thanks to you!
the only example I understood is yours. Thank you. keep uploading video!
Bhai peeche wala banda gazab hai.........And the video, it's superb
Lol
thank you very much brother you explained it so easily hats offf to you.
thanks, friend, now I understand completely.
thank you man tomorrow was my paper and this video helps me lot :D
Really to good and i just understood within the half of the explaintion.👏👏👏👏👏👏👏👏
Your voice is so nice. I mean it is soothing to hear and also clearly audible. Thank You for this tutorial.
Thank you I have an exam tomorrow and it helped me good work
thanks man tomorrow is my exam and u helped me a lot
Really nice video... helping me pass my exam...!! Thnx a lot..!!
you guys are just awesome, killed it in the least time
Thanks bhai for this example , I have my exam in 4 days .
tomorrow is my exam and u saved me ..thanks a lot
you’re an absolute legend
FINALLY A GOOOOD TUTORIAL. THANKS BRO
Really a nice video and please do continue to upload a lots of video in the future
Thanx sir for such a clean explaination
By watchg once..... I understd...tqsm 😀😀😀
Thanks bro..u solved my problem..I was unable to understand how d subtraction was taking place..now I got it.
Thanks for the explaination , it was really easy as you explained
Video still useful after 6-7 years 🧮🧮
Thank you :) This video helped me to understand CRC at last!!
Beauty ! the concept of amending zeros was my question and that's been cleared now.
Thanks legend
Thank you :)
Very useful
Thanks.. It was quick and easy for me to understand. Appreciate ur effort..
Oh brother such an wonderful work.
I've got an exam tomorrow on this. Thank you!
Your teaching was perfect and really nice.. I could follow up and understand everything thanks for this video
good explanation , cleared all my doubts
Great....helped in understanding CRC to a greater extend
Thank you for your wonderful explanation.
Thanks for helping explaintion is very nice 👌👌👌👌😉
Awesome brother .......... Thanks for this tutorial......Have a awesome days ahead 👍👍👍👍
NICE explanation ..!!..Informative !
you have a similar accent as my professor, that makes me feel better about this =D
Grt explanation and thanks for the video
Great Tutorial. It's really helpful for me and hope everybody will get help from this video.
+Maruf Abdullah
Thank you :)
Thank you so much for explaining the concept in such an easy way👏👏👏
You are better than my teacher
Helped a lot.
Good work
GOD BLESS YOU! U are a saviour❤️♥️
woowww simple and clear explanationnn
This video was very helpful actually it made me understand CRC with ease. Great Job
Nice video. I had issues doing the division, I got it wrong each time and my lecturer made me feel dull instead of explaining where I was not getting it (typical of China lol)... Now I see where i was confusing the whole thing lol. Thanks a lot.
I just had a Singaporean lecturer try to teach me that is the same race as the person who did this video. He was going way too fast on the power point for me to understand. It's not the race it's the explanation. I am Chinese too by the way , sometimes these academics go way too fast and probably taught too many classes of the same thing that they don't realise every student is different
I don't understand the lecturer either that's why I am looking on UA-cam. this person explained what I not understanding why the answer was a certain way.
I sux at formulas and math concepts
Thanks brother
thank u a lot i was not aware of the CRC ,However because of u , i got it now kkk
Was very useful at the last minute revision.... Thanks bro
Thanks a lot really helped me in my exam....:)
+Anitha Manoharan
Thank you :)
Nice and simple explanation.thanks
Very helpful video keep up the good work.
Thanks a ton :)
Thanks for the clear video.
Thanq so much....very good explain :)
Thank you very ,very help full for me..........!
thank you sir, very clear explanation
Very good Work.Keep it up.
It's was so helpful..nice video.👌
Nyc bro❤👌
keep continuing the good work! much appreciated...
i got help after watching this video,thank you :)
Very well explained.
Bro i understood.very good explanation.
this video helped a lot thank you
Thanks, simple and clear.
thanks man...very easy way to understand :)
+pritam chatterjee
Thank you :)
Thankx bro...u made all my confusions clear now...keep posting...keep rocking 😀
Thank you for explaining it very clear!
thank you a lot I finally was able to understand it
Thank you, it helps a lot
very helpful video....thanks a lot
I wish I'd a sir like you
This will help on my test
Tysm..... Helped a lot! 😊
Great efforts. Thanks
It was helpful, thank you!
thank you so much for this lecture
Great explanation
Thank you