TABLE OF CONTENTS Orthogonal frequency division multiplexing (OFDM) is a modulation technique where source symbols are transmitted in parallel by applying to a large number of orthogonal subcarriers. The OFDM signal s( t) can be expressed
| (8.111) |  |
The complex envelope ?( t) of an OFDM signal s( t) can be expressed [20]
| (8.112) |  |
where A is the carrier amplitude and k is the kth block of N serial source symbols.
The N orthogonal waveforms 
in Eq. (8.112) are chosen as
| (8.113) |  |
and h a( t) can be a rectangular amplitude shaping pulse, h a( t) = U T( t). The source symbol block x k at time t = kT s can be expressed as
A block of N serial source symbols has a symbol duration T s, where T s can be less than the rms time delay spread ? of the medium ( T s < ?). The block of N serial source can be converted to a block of N parallel modulated symbols, each in a duration of T = NT s. Let the block length N be chosen so that NT s >> ?. Since the symbol rate (1/ T) on each subcarrier is much less than the serial source rate
the effects of delay spread are greatly reduced, and we...
