# what is bandwidth and its relation with bitrate?

Digital signal consists of many sine waves. Now the signal with waves of frequencies 1Mhz to 5Mhz has bandwidth of 5-1 = 4Mhz. Now the fundamental period of this signal is decided by lowest frequency that is 1Mhz. So one cycle sends 2 bits let's say, therefore 2 bits are transmitted in 1/1Mhz = 1 μs. Hence 1 bit in 0.5μs. Hence bitrate is 2Mbps.

If I increase bandwidth, from 4 to 8Mhz, for the same, does the spectrum still vary from 1Mhz to 1 + 8 = 9Mhz ? because this way by doubling bandwidth and using same lowest frequency, data rate will be same. Unless i increase bandwidth as well as increase minimum frequency. also by doubling bandwidth is it that the range also shifts towards right? eg for bandwidth 4mhz, spectrum was 1 to 5, for 8mhz bandwidth spectrum becomes 2 to 10 or how does it work?

Please explain. I'm a beginner in this and currently going through William stalling's data and computer communication book which states bandwidth increases with data rate and vice-versa where as I feel it's just lowest frequency of bandwidth thats increasing the bitrate or data rate.

• can someone refer a source to help me understand the concept behind signals and bandwidth ? – saurav Sep 14 '16 at 14:40
• Paste your question in the physics or electrical engineering SE for a proper answer. – Ronnie Royston Sep 14 '16 at 15:35
• Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 15 '17 at 2:35

## 1 Answer

Bandwidth increases as a result of using higher modulation frequencies, not the other way around. Bandwidth is a function of the modulation frequency. So if that is constant, so is your bandwidth.