Bandwidth vs. Bitrate

[dwm1120]

Can anyone shed some light on the relationship of bandwidth to bitrate, symbol rate, and spectral efficiency?

[swatantra]

hi
BANDWIDTH:-
The amount of data that can be transmitted in a fixed amount of time. For digital devices, the bandwidth is usually expressed in bits per second(bps) or bytes per second. For analog devices, the bandwidth is expressed in cycles per second, or Hertz (Hz).
BITRATE:-
The ratio of the number of bits that are transferred between devices in a specified amount of time, typically one second.
SYMBOL RATE:-
symbol rate is the bit rate divided by the number of bits transmitted in each symbol. The symbol rate is identical to the Baud rate.
SPECTRAL EFFICIENCY
It is basically the maximum average rate at which information can be transmitted over the channel of unit band width.
C/W=Log(base 2)[1+P/N]
where P/N is the ratio of the signal power diveded by noise.

[charan langton]

Let me give you a long answer to your short question. Bandwidth has very many definitions. Here are a few.
1. Absolute bandwidth - We are transmitting a signal. The spectrum of this signal (its power) is contained completely within a frequency range from f1 to f2. The bandwidth in this case is f2 - f1. But mathematically this number is very large as most signal expectrums extend to infinity.
2. 3 dB bandwidth - Here the magnitude spectrum at the band edge is 3 dB down from the maximum which is somewhere between f1 and f2. This is also called the half power bandwidth and is often used to specify the bandwidths of filters.If the bit rate is rb, then 3 dB bandwidth is app. .88Rb
3. Noise Bandwidth - This an equivalent bandwidth of a rectrangular spectrum so that the power contained in this rectangular spectrum is equal to the actual spectrum which may have long tails. The formula for this bandwidth is given in many books. This bandwidth is used to determine the noise bandwidth which we need to compute Eb/N0 and is equal to the symbol or bit rate.
4. Null to Null bandwidth - we can measure the bandwidth just from null to null of the spectrum. This equal to 2 times the symbol or bit rate.
5. Power Bandwidth - this is the range f1 to f2 which contains 99% of the power of the signal. This bandwidth is very large.
6. FCC bandwidth - Some bands are defined by the FCC with out of band power density defined in a 4 kHz band.

Charan Langton