We can really expect to improve on this technology because we got the spectrum compression and drastic increase in data capacity of channel. Its a good way for telecom to go on with this.

It should examine application except IFFT.

e.g. wavelet, Walsh and other narrow-band orthogonal functions.

I think the basic idea of multi-carrier modulation will be used widely. Different technologies might choose other orthogonal basis.

Dear dr. Ismat,

It seems that the orthogonal frequency division multiplexing and multiple accessing is the most suitable modulation technique for the wide band communication systems either wireless or wired. Compared to single carrier system, it has many advantages especially the inter symbol interference in multipath channels. OFMD has more immunity against multipath effects. OFDM is more easier to implement and equalize. It is also more robust against deep frequency selective fading. Compared to FDM it is more band width efficient since the subcarriers are allowed to overlap as they are orthogonal by making their frequency is an integral multiple of the inverse of the symbol time.. Every carrier is M-QAM modulated according to the available signal to noise ratio. So, the bandwidth efficiency can be increased for higher signal to noise ratio.Consequently, one can make full use of the channel conditions to increase the bandwidth efficiency and increase the bit rate of the communication system.

It out performs the wideband code divination multiplex accessing as it has a higher bandwidth efficiency and easier to control than the spread spectrum in WCDMA. Time division multiplexing is used with single carrier systems which outlined at the beginning of the comment.

The OFDM sums many advantages against the other modulation and multiple accessing techniques more than its drawbacks.

The drawbacks are the high peak to average power ratio which makes the power amplifier expensive and more power hungry. The other drawback is the intercarrier interference. But there are powerful techniques to mitigate these draw backs.

In the foreseen future, OFDM may remain the most preferable modulation and multiple accessing technique. It is even the recommended modulation technique for the ultrawideband UWB communication systems.

Thanks to all for the comments and to Prof. Zekry for the detailed review on OFDM. Yes, as OFDM is having such nice characteristics we would all expect that it will prevail. Comparing it with CDMA or TDMA techniques will also favor OFDM as you clearly pinpointed.

However, future networks have new complications that might lead to that OFDM is not the one, and even going back on to older or more simpler techniques. This is beside the power efficiency problem of OFDM which necessitated that LTE uses SC-FDM. Some of the new dimensions of future networks are

- The resort to higher MIMOs or the massive MIMOs: In this regard, the increased complexity of MIMO system incited new ideas to simplify the system especially that the power efficiency of Massive MIMOs might be jeopardized by the increased processing capacity. "Spatial modulation" is one new technique in which MIMO systems are simplified. In spatial modulation, one antenna element is energized at any single time (hence in interference between elements). Now, such technique is a multiple access (space division multiple access) as well as a modulation technique in which the space is utilized as a new dimension to the signal constellation (besides phase and amplitude).

- The resort to higher frequencies in the order of tens or hundreds of GHz might as well render many of the advantages of OFDM obsolete at these frequencies. Resort to such frequencies might even enforce more simpler modulations as simple On-Off (ASK) or PSK. BW is after all available and it can be divided between users easily.

Again, OFDM is best at present circumstances and even future similar circumstances but the above is some alternative of looking at the its future that might be dictated by other circumstances. Thanks. @AlDmour.