Habib M. N. Ahmad Thanks, it was helpful.

Dear Ms. Farah Arabian

It is a good question.

Adaptive equalizers are used in majority of the modern wireless systems and networks. Their use in present day TDMA systems is particularly of interest owing to the fact that higher transmission bit rates in such systems lead to higher inter-symbol interference.

GSM system, for instance, is one example where adaptive equalizers are typically used.

It may however be noted that GSM standard does not specify the type of equalizer to be used. The equipment manufacturer is free to use their own choice of type / architecture / algorithm of the adaptive equalizer. In many cases, the manufacturer may not disclose the inner details of the type / architecture / algorithm of the adaptive equalizer.

I hope the above information is of use to you.

Thanks.

Dear Farah,

The are two types of equalizers: Time domain equalizers and frequency domain equalizers. The time domain equalizers are used in case of synchronous demodulation while the frequency domain equalizers are used with OFDM modulation where the channel bandwidth is divided into subchannels and every subchannel can be can be equalized by narrow band frequency domain equalizers.

The time domain equalizers are normally adaptive equalizers where the values of their tap coefficients are updated regularly to cope with the variations of the channel.

In their time domain adaptive equalizers, the most accurate equalizer is the MMSE one but it takes much longer time than the other less accurate adaptive algorithms such as the LMS and RLS. So,i expect that one uses the simplest one to save processing time and battery energy.

Conceptually one uses the simplest algorithm for power energy and processing time saving.

Best wishes

It's difficult to say what kind of equalizer is used on a device, because usually equalizers, as well as channel estimation methods, demodulation and decoding techniques are not standardized.

This allows manufacturers to develop different methods and differentiate themselves from competitors. Therefore, manufacturers are not interested in declare the particular scheme they are using.

For what concerns smartphones, different techniques are used depending on the technology. I'm not very confident on 3G, as it exploits spread spectrum modulations, but 4G is based on OFDM, so the most likely equalizer is the very common Zero Forcing scheme, which provides good performance and has a simple structure (Y[k]=X[k]/H[k])

Equalizers are used in 4G systems becoz of their frequency selective response.

The type of equalizer depends on the manufacturer.If u want energy efficient equalizer then Least mean square is best.If u want most accurate equalizer then Adaptive equalizer like MMSE is best.If u want a simplest equalizer with less complex algorithm then Zero Forcing is best.

Their are other complex techniques like VBLAST and Sphere Decoder that can be used at higher modulation techniques like 64QAM and 128QAM to get a considerable improvement in Snr while keeping ber at lowest.The techniques can be used in 4G beyond systems

Abdelhalim abdelnaby Zekry Thanks for your complete response, it makes sense to me. Do you know in frequency domain which algorithm is more common to use?

Farah Arabian you can see it here http://www.mobile.ecei.tohoku.ac.jp/COE/workshop_2008_08/pdf/Prof.%20Falconer.pdf

Techniques used in (Types of) "Equalizer,Interleaver,Scrambler" in 1G-5G ????