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 TH-cam. this person explained what I not understanding why the answer was a certain way. I sux at formulas and math concepts
Simply Yobi Can a diploma holder get admission in bachelor degree of ECE. Plzz tell if not then tell me should I jump of a high building to take my whale 🤨
When do we put a 1 in quotient in long division? why did you say that when the leftmost bit = 1 ? i know it's only when the part of the divident >= the divisor. Please correct if i am wrong.
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.
My prof took an hour to explain this, and you did the job in less than 10 minutes- and better. Thank you!
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! 😉
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
You provided the first explanation that I actually understood. I can do it now! Thanks :)
Thanks brother, this really helped me understand the assignment I was given...Am a master on CRC now. most grateful
8 YEARS GOIN8 years going and still helpful, thanks man
sir, you are a man, who teach me the process absolutely correct.
Thanks "The BootStrappers".
Can hear ur frnd telling "Change pen! Change pen!" 😂😂
Kuch padai bhi kr lo 😁
lol
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
I watched a lot of videos trying to figure out how this works...yours made the most sense, so thanks
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!!
Thank you for helping this Kiwi student catch up after being sick!
+Shigeruken
Thank you, feels really good to be able to help someone :)
your clarity on the topic is awesome!!!!!!!!!!!!!!!!
love to you my brother from india, took less than 10 minutes to explain this concept
my dad was explaining CRC and your video helped out a lot
Bhai peeche wala banda gazab hai.........And the video, it's superb
Lol
Change Pen :P..nice video ! :D
thank you man you just saved my mid term result
Thank you so much it's now easy to understand crc coding because of you....😊
Thanks bro... u helped me a lot .. those CRC things was my worst nightmare
How do you determine which numbers to write above the data word? And what are they used for?
thank you man tomorrow was my paper and this video helps me lot :D
Your voice is so nice. I mean it is soothing to hear and also clearly audible. Thank You for this tutorial.
Really nice video... helping me pass my exam...!! Thnx a lot..!!
Thank you for the simple easy to understand explanation
Thanks for kindly share this. Now I understand how CRC works. Very helpful video.
the only example I understood is yours. Thank you. keep uploading video!
Thank you I have an exam tomorrow and it helped me good work
Really to good and i just understood within the half of the explaintion.👏👏👏👏👏👏👏👏
FINALLY A GOOOOD TUTORIAL. THANKS BRO
really it helps me to learn the CRC at the exam time. thank u.
+abhisek datta
Thank you :)
thanks man tomorrow is my exam and u helped me a lot
you’re an absolute legend
Thanks for the explaination , it was really easy as you explained
Video still useful after 6-7 years 🧮🧮
What is we do not get zero in the end? Do we need to again add remainder or something else?
Oh brother such an wonderful work.
thanks, friend, now I understand completely.
you have a similar accent as my professor, that makes me feel better about this =D
thank you very much brother you explained it so easily hats offf to you.
Thanks bro..u solved my problem..I was unable to understand how d subtraction was taking place..now I got it.
This video was very helpful actually it made me understand CRC with ease. Great Job
By watchg once..... I understd...tqsm 😀😀😀
Thank you :) This video helped me to understand CRC at last!!
Awesome brother .......... Thanks for this tutorial......Have a awesome days ahead 👍👍👍👍
Really a nice video and please do continue to upload a lots of video in the future
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
Very useful basic simple crystal clear
Thank you
Thanks for helping explaintion is very nice 👌👌👌👌😉
tomorrow is my exam and u saved me ..thanks a lot
Great Tutorial. It's really helpful for me and hope everybody will get help from this video.
+Maruf Abdullah
Thank you :)
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 TH-cam. this person explained what I not understanding why the answer was a certain way.
I sux at formulas and math concepts
While doing division, why yu do xor instead of subtraction?
you guys are just awesome, killed it in the least time
better than my teacher :s
+mundrey topey
Thanks :)
Always has been
Beauty ! the concept of amending zeros was my question and that's been cleared now.
Thanks legend
Thank you :)
Thank you so much for explaining the concept in such an easy way👏👏👏
Thanks.. It was quick and easy for me to understand. Appreciate ur effort..
GOD BLESS YOU! U are a saviour❤️♥️
Helped a lot.
Good work
Was very useful at the last minute revision.... Thanks bro
Thankx bro...u made all my confusions clear now...keep posting...keep rocking 😀
Thanks bhai for this example , I have my exam in 4 days .
It's was so helpful..nice video.👌
Bro i understood.very good explanation.
Thanks a lot really helped me in my exam....:)
+Anitha Manoharan
Thank you :)
NICE explanation ..!!..Informative !
You are better than my teacher
Nyc bro❤👌
good explanation , cleared all my doubts
Thank u soo much🤗👍👍 explanation was simple and easy to understand 👏 well done
Kdkkk bhai tujya mule udya 4mark bhetle exam mdhey 🫂
😂😂💥
Very helpful video keep up the good work.
Thanks a ton :)
Thanx sir for such a clean explaination
keep continuing the good work! much appreciated...
Grt explanation and thanks for the video
it was really helpful buddy. thanks alot :)
i got help after watching this video,thank you :)
your explanation is very detailed and very easy to understand, thank you very much.
Thank you for your wonderful explanation.
Thanks bro m goona pass my exam coz of ur help hahaha xd thank ya\ :")
Tysm..... Helped a lot! 😊
Very useful
4 years later. thank u :3
Great....helped in understanding CRC to a greater extend
Ur video really helped ✌🏻
Thank you for explaining it very clear!
Very good Work.Keep it up.
awesome teaching bhai ❤
Thankyou so much it was very helpful
Great Explanation,
Greetings from a German Student, struggeling with this topic ;)
Nic german boii
Simply Yobi
Can a diploma holder get admission in bachelor degree of ECE.
Plzz tell
if not then tell me should I jump of a high building to take my whale 🤨
Nice and simple explanation.thanks
Amazingly explained 🙌
Tq bro..... Great explanation...... Once again tq.....
When do we put a 1 in quotient in long division? why did you say that when the leftmost bit = 1 ? i know it's only when the part of the divident >= the divisor. Please correct if i am wrong.
awesome !
very good explanation
good job bro you made it simple for me!!
Bro is it a rule to remove first zero after every division ,and if yes then can't we cut 2 zeros
thank u a lot i was not aware of the CRC ,However because of u , i got it now kkk