Hi Folks,
I am sorry that i was away for couple of days and could not respond actively.
Thank you for the discussion (m_lla) and all others.
I replied that capacity may be different than data rate and i still believe in this. The argument is as follows.
Lets consider that we have a water pipe which can allow the flow of maximum 2Liter/sec through it. But the water that is flowing through it is 1L/sec. So what is the capacity of the pipe and what rate it is offering right now.
Same is the analogy with channel capacity. To be very humble, i know the Shannon formulation of capacity and work of Foschini and Teletar on the capacity of single antenna (SISO) and scaling laws for the MIMO, and to be very specific i am talking about point to point link, bcz capacity for the Broad cast channel may differe from point to point link calculations due to many factors. So lets assume that the capacity of my wireless channel is C, but the data that I want to send on that channel is with rate R where R ≤ C. Now data rate (R) can be equal or less than the capacity of the channel. According to my understanding C is the channel charactersitc that is just like pipe available to some one, and data rate (R) is the actual data that some one sending/receiveing on that particular channel. Now that data rate can be equal or less to the capacity according to the application.
To give more specific example, consider the ISDN telephone line which normally offer (128Kbps). Now if you are only using this ISDN line for just single telephone and not for any data purpose, you might be using only 64Kbps (while ur capacity is still 128Kbps i.e. your pipe is still capable of carrying 128 Kbps) but you are using only 64Kbps. So in this sense capacity and data rate may differe from each other and can be treated as different terms, but usually we consider R as same as C.
I hope I cleared my point of view.
BR,
MAK
Added after 6 minutes:
cancer06 said:
Capacity is the maximum data rate that can be achieved with error free transmision and is a purely theoretical concept. The maximum data-rate is determined by the system design, and is associated with a given error rate.
Further to my previous discussion on the topic, i fully agree with subahik and cancer (sorry friends if i m not spelling ur nicks correctly). Their explanation that the capacity can be equal to the maximum error free data rate that can be achived is very much correct.
BR,
MAK