Talk on 2G,3G,4G and now 5G at AITD,Goa
Hello everyone, today i attended a talk by Mr. Rohin Parker, who has 12–13 years of industrial experience. He first briefly introduced himself to the crowd which consisted of students of from second , third and final year of electronics and communication engineering.
He started the talk by asking the crowd “what do we know about cellular communication?”, to that a few answered communication by means of the network technologies.
So he said that there are many things which constitute to the drastic change in cellular communication such as signal processing, battery technology , modulation technique etc. He also stated that the software capabilities have also improved to a great extent.
Next he went on to speak about how after 2020 India would be capable to use 5G communication and how we would have something called as LTE advance and LTE advance pro.
Then he went on to talk about the various WiFi technologies such as 802.11,802.11n,802.11ac and 802.11ad.
so what was the secret behind all these high speeds?
well the answer to that is the advanced digital signal processing algorithms to do complex calculations, the amplifier devices , battery technology and advanced manufacturing techniques such as SoC.
Why do we need modulation?
we need it so that the signal is not lost due to noise and it can travel a longer distance.So the 2 basic types of modulation are Amplitude modulation and Frequency modulation.
Amplitude modulation is when you superimpose your message signal over a carrier signal so that it can travel a longer distance. Well it is also to reduce the antenna size as the length of the antenna is the order of 1/10th of the wavelength of the carrier frequency.
Frequency modulation is when you change the frequency of the carrier signal depending on the message signal . This technique is more immune to noise. This was more advantageous than Amplitude modulation and you would also notice that stations on frequency modulation is much clearer to hear on amplitude modulation.
Then he went on to talk about Digital modulation techniques.
so first up we have BPSK or binary phase shift keying where you change the phase of the carrier signal depending on the bits being transmitted. The phase shift is between 0 and 180 degrees depending on the transmission bits.
next we have QPSK or quadrature phase shift keying where the phase can be changed between 4 symbols or phases each symbol consisting of 2 bits each and separated from the other by a total of 90 degrees.
next we have 8PSK where the phase can be changed between 8 symbols or phases each symbol consisting of 3 bits each and separated from the other by a total of 45 degrees.This is the technology behind EDGE that runs at 500kbps.
next we have 8QAM or 8 quadrature amplitude modulation, where there are 8 symbols on the constellation diagram 2 in each quadrant having a change in amplitude but same angel within the quadrant and each 2 symbols from 1 quadrant is separated from the quadrant by 90 degrees. Similarly for 16QAM and 32QAM. Then he also stated that the current WiFi technology runs on 1024 QAM technique.
Then he spoke about FSK or frequency shift keying how you vary the frequency depending on the message being transmitted.
Then he spoke on OFDM or orthogonal frequency division multiplexing and how it is used in LTE or 20–40MHz with higher order modulation like 32QAM
Finally he ended the talk by answering a few questions that the students asked him.
