Sunday, June 22, 2008

Why OFDM Is Used In Broadband?

Why to use OFDM in broadband?

To implement the wireless broadband
Communication systems, the following challenges must be considered:
1-Frequency allocation and selection
2-Channel characterization
3-Air interface multiple access techniques
4-Protocols and networks and
5-Systems development with efficient modulation, coding, and smart antenna Techniques.

In the 1990s, OFDM was exploited for wideband data communications over the mobile radio FM channels, high-bit-rate digital subscriber lines (HDSL), asymmetric digital subscriber lines (ADSL), very-high-speed digital subscriber lines (VDSL), digital audio broadcasting (DAB), and high-definition television (HDTV) terrestrial broadcasting.

The OFDM transmission scheme has the following key advantages:

1-OFDM allows efficient spectral usage by allowing overlapping in the frequency domain.
2-OFDM makes single frequency networks possible, which is especially
3-Attractive for broadcasting applications.
4-OFDM is highly immune to multipath delay spread that causes inter-symbol interference
in wireless channels.
5-OFDM has the inherent feature of robustness against frequency selective fading channels;
the implementation complexity is significantly lower than that of a single carrier system
with an equalizer.
6-In relatively slow time-varying channels, it is possible to significantly enhance the capacity
adapting the data rate per subcarrier according to the signal- to-noise ratio of that
particular subcarrier.
7-OFDM is robust against narrowband interference, because such interference affects only a

small percentage of the subcarriers.
8-The modulation and demodulation can be done using IFFT and FFT Operations, which are

computationally efficient.
check it


curt said...

In modern communication it is commonly used technique worldwide.