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Wednesday, August 25, 2010

How this wireless communication started from the lap of this universe?

Note: All this information is collected from Google and most of the content is from Wiki but trying to give the entire wireless systems evolution.

After getting a break (fortunate or unfortunate will be known later :--) ) from my project, I was just thinking on how all this wireless communication started. Even though I studied all that stuff in my education I never realized that I was studying nothing but about how few people had spent their lives by observing this nice universe. I used to listen (in my school days) “why should I learn so many subjects when I am not going to do these”. I think learning a subject also teach us the history and how that history had been created just by few amazing people.

How this mobile communication, In fact any wireless communication started?
Every thing is radio waves but how it was started?

In Nutshell
1) One of the Four fundmental universal Laws by the universe—electricity and magnetism.
2) One genius found the relation ship between electricity and magnetism.
3) Applied that theory and experimented.
4) It has led to the prediction of electro magnetic induction---Result is motors, transformers etc
5) The continued experiment given us the prediction of electro magnetic waves
6) Proven the electromagnetic waves existence and generated radio waves,micro waves, gamma rays etc.
7) One step where some one had thought these electro magnetic waves are of no use for communication. If every one had stopped there? Hmm no cell phones or remotes or no wireless communication.
8) Few more applying minds proved the transmission of radio waves over the space.
9) Proven that radio waves can be used for communication but not commercialized.
10) With many controversies One person came and commercialized the wireless communication and the rest has led the way to today’s 3G and coming 3.5G, 4G, 5G(No specifications yet) systems.

If you are interested in the history here it is.

After all it started with one of the fundamental principles of this universe i.e electricity and magnetism(More details at the end). In 1802 Gian Domenico Romagnosi suggested the relationship between electric current and magnetism.( But he could not popularize it . Is it lack of presentation skill? Or simplicty?). Then after that In 1820 Hans Christian orsted preparing for a seminar and observed that his compass has been moved from Magnetic North to South while switching on and off the current. So he realized that magnetic field is deflected due to the electricity. With such a simple thing but a deep thought he popularized the relation between electricity and magnetism.
Hand Christian influenced another person called André-Marie Ampère to produce a theory called electromagnetism. Already the earlier genius proved the relation then what is theory he developed newly. Orsted, the earlier scientist just observed and realized but was not able to explain why was it happening. Ampere heard of the discovery that a magnetic needle moved by the current and he has done number of experiments to find out the exact relationship between electric current flow and magnetism. I hope you are also interested here to know what was the exact relation. While going through them you realize what definitions you read. A galvanometer (just a refined compass) is made of a free pivoting coil and a needle attached in the magnetic field of a permanent magnet. When the current is passed through the coil it experiences a torque due to the interaction of the current with the magnetic field. As a result coil pivots and needle deflected.

Hmmmm. Now after wide use of this electromagnetism, as per the history, disputes persisted as who could claim sole credit for this boom. (So is there any exception to the humans emotions and lust for popularity. Still a puzzle to me.).

In 1831,Michael Faraday discovered electro magnetic induction.oh God what is this new invention again? Some one came to teach some thing but a lesson from the universe just universe. It is nothing but an electric current will be induced in any closed circuit when the magnetic flux changes in surface and that surface is bounded with any conductor. Result of this Generators,electric motors,transformers, many. One person changed the universe once again.

In 1861 Maxwell, Scottish, predicted the existence of electromagnetic waves. Initially he found out that the speed of propagation of an electromagnetic field is approximately equal to the speed of light. So he predicted that disturbance in the electromagnetic field could propagate through space.

In 1872 , two people william Henryward and Mahlon Loomis received patents for radio development but could not prove the transmission and reception of radio waves.
In 1875 Edison tried some thing new concept called etheric force and abandoned his research and Elithu Thomson ridiculed his idea. Hmm No appreciation?? J

In 1878 David Hughes noticed that sparks could be heard in a telephone receiver. He developed his carbon-based detector but abandoned further research ( why? Curious to know? Any thing which I can learn from there?)
In 1884 Calzecchi-Onesti found a device which responded to the radio waves called coherer which is further radio detector.

In 1886 and 1888 Hertz,German, proved that rapid variations of current could be projected into space in the form of radio waves just similar to light and heat. Radio waves ,a form of electromagnetic radiation with wavelengths too long for our eyes to see. He practically transimitted and received the radio waves. Electromagnetic waves at different frequencies are nothing radio waves, gamma rays,micro waves etc etc.

Nathan Stubblefield in 1892 invented radio and landell de Moura Brazilian conducted experiments in wireless transmission but did not publicize. It seems there were many disputes about the invention of radio.

There was a claim that Hertz said “There is no practical use of these electromagnetic waves. It is just experiment to prove maxwell was right.” There was also another opinion that he was not interested to develop wireless communication he is just in electromagnetic theory. In 1894 he left this world giving the radio inventions to others

In 1891 Nikola Telsa reported a presentation that messages could be sent with out wires and radio waves can be used in telecommunications but no independent evidence to support.

Oh yes Bose, Jagadish Chandra Bose, Indian from Calcutta, shown publicly the use of radio waves. He ignited gunpowder and rang a bell at a distance using electromagnetic waves but not at all interested in patenting his work and become popular(Microsoft,Oracle known to most of the people? Why?).

His experiment clearly shown wireless communication. He did not even commercially exploit his achievement.In 1895, May 7th, Russian, Alexander Popov,performed public transmission of radio waves for communications and Russia celebrated it as Radio day. He also did not patent his work. Propov built a communication system based on his Coherer (Radio detector). Russians considered him as inventor of radio.

In 1894 itself,Marconi started understanding the radio waves could be used for wireless communications. He used a transmitter to ring a bell and then moved his experiments out of doors. He replaced Hertz’s dipole with a vertical wire topped on metal sheet, with an opposing terminal connected to the ground. On the receiver side Mark replaced the spark gap with a metal powder detector. He transmitted signals for a mile. In 1896 he came out with a public device asserting his invention. There was controversy that most of that resembled Telsa’s descriptions.

Marcon’s reputation is based on the commercialization of practical system. He equipped ships with wireless communication systems. Marconi would later found the Marconi Company and would jointly receive the 1909 Nobel Prize in Physics with Karl Ferdinand Braun for contributions to the existing radio sciences.

Next planning to come up with first Mobile phone and protocols and First Antenna systems.

Electro magnetism

electromagnetism is the force that creates interaction between elecrtically charged particles. electrically
charged particles means what. all matters in this universe are made of atoms which are nothing but combination of electrons,neutrons,protons. when electrons and protons stops being equal in atom then it is electrically charged

Monday, August 9, 2010


What is TDMA and CDMA? why do we need them?
Over the years simultaneous cellular calls are increased over networks but no of accessible channels are limited. Hence there is a necessity of techniques which can solve this problem i.e increasing the number of simultaneous calls even though channels are limited. They expand the capacity of the radio channel.

There you got TDMA and CDMA. TDMA is a (Time division multiple access access)multiple access technology in which the channel is divided into sequential time slots.only a single user is using the channel at any given time. Here I would like introduce the term TDM(Time division multiplexing). Oh! then what is the difference between TDM and TDMA.
TDM is multiplexing technique and TDMA is multiple access technology. In TDM cetain time slot is dedicated forever for a given user even though he is not using it. ISDN is the example for this. In TDMA the time slot get freed up once the user finishes using the time. Here the time slots are dynamically allocated and the user may get different time slot each time accessing the network. GSM is an example for this. Of course GSM is not using ONLY TDMA.(FDMA as well clubbed with TDMA).
In TDMA the channel gets divided into 3 to 8 channels=8 simultaneous conversations.
Lets take an example for TDMA.
1) There are two stations and at each station 3 people. station1--A,B,C Station 2--D,E and F. Station1 and station 2 people want to exchange the messages.
2) The train with three carriages stops at station1 for some time.
3) All three people put the messages in three carriages.
4) The train goes to station 2 and the people there receives the messages from the carriages.
5) Again the train goes to station1 and the loop continues till the messages are completed.

Now coming to the CDMA(Code division multiple access) technology, It uses spread spectrum technology i.e a method in which a signal generated in a bandwidth is spread in the frequency domain resulting a signal with a wider bandwidth. In CDMA each caller will be given certain unique code so that others can not understand and allow multiple users use the same physical channel. The very common example for CDMA is In a room(considering as channel) several people want to communicate each other and each user will speak in different languages (Code divided) .
Now apply the same example to TDMA so that we understand the difference between these two. In TDMA all the people will take out certain time and speak one by one till every one finish their speech. In CDMA each user will speak in different languages. In FDMA each user will speak in different pitches.
Don't confuse this CDMA (channel accessing method) with CDMA phones which is a mobile phone standard called cdmaone and CDMA2000(Reliance CDMA phones which are famous in India). GPS is the first application of this CDMA and qualcomm's standard IS-95 published it as cdmaone and IS2000 as CDMA2000