-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi Mohammed,
I forgot to reply to the list in my previous mail, so I do this now. On 05.02.2014 16:14, Mohammed Karmoose wrote: > Hi Johannes > > Thank you for your prompt reply. I'm just trying to get my hands > as dirty as possible with Gnuradio. I'm trying to do some > pre-equalization at the transmitter side, but right now I'm just > trying to achieve a unity effective channel response, just to prove > that I'm able to do something meaningful at the transmitter side. > > I checked with the channel response that the USRPs exhibit at the > current setup I'm working on, and it seems that it does not change > across a relatively long period of time, so it might seem that this > kind of equalization is possible. However, I noticed something > which suggested that there is something "more" than just simply > estimating the channel taps that is done at the receiver side. > > I simply divide the samples that are transmitted by a constant > value prior to transmission (I'm not using the channel coefficients > in anything right now) and see the effective channel response: it > seems that the effective channel response is reduced by the factor > I'm dividing by. However, when the factor I'm dividing by is less > than 0.8 (which means that the effective channel response in this > case should be magnified), the effective channel response somehow > is transformed back to the original (unaltered case) channel > response. An example flowgraph would be very helpful in this case. Where exactly do your samples get "transformed back"? > > Does any of that make sense to you? Please tell me if something is > not clear in the previously mentioned details. > > > On Wed, Feb 5, 2014 at 5:04 PM, Johannes Demel > <[email protected] <mailto:[email protected]>> wrote: > > Hi Mohammed, > > what exactly do you want to achieve? Those channel estimates are > usually used to do equalization on the receive side. That's why a > system always transmits pilot symbols along with the data symbols. > If your system is meant to do some pre-equalization on the > transmit side, make sure those channel estimates are still valid by > the time you use them on the transmit side. > >> Are these coefficients valid to use in equalization, i.e., can I >> divide the transmitted symbols by the corresponding channel >> coefficients, and therefore achieve an almost unity channel >> taps? > > Those coefficients should be valid. Nevertheless depending on the > channel quality and your chosen method of estimation your results > may vary. > > happy hacking Johannes > > > > > -- *---------------------------------------------------* *Mohammed > Hassan Karmoose* */Teaching Assistant, Electrical Engineering > Dept./* */Faculty of Engineering, Alexandria University/* > /Al-Horeya Rd, El-Hadara,/ */Alexandria, Egypt - 21544/* */Tel: > /*/*++203-592-1852*/ | */Fax: /**/++203-592-1853/* */Email: /m > <mailto:[email protected]>.h.karmoose@ > <mailto:[email protected]>ieee.org <http://ieee.org>* */Website: > /www.mkarmoose.com <http://www.mkarmoose.com/>* /"The people before > you were ruined because when a noble person amongst them committed > theft, they would leave him, but if a weak person amongst them > committed theft, they would execute the legal punishment on him. > By Allah, were Fatimah, the daughter of Muhammad, to commit the > theft, I would have //executed the legal punishment on her//.'' - > Prophet Muhammad (PBUH)/ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQIcBAEBAgAGBQJS8liXAAoJEO7fmkDsqywMKKsQAJ6nhLqd6UazvRONAl8afe98 uRmyZMJi7ktuaJ6DxMIY02AkLdXtAol60/cgdwmGQbsXuunDcP28HFOSN9JE216R 7zjPjYb58CrzQdzAY1NExDq+RphvCX3GeCExSgvPhZR3TIz3pniEnqpNT/ik42cJ J1VGlu5nH2cRSov2qliPoFtX3jNeppOirAk51HUOKXe0ATQRTi+lcyFB4GMEuYJ2 6Rq39eVoT30IaZRWVMxdqhwDP2qhMQIXKHx3b7E1lZnjN3fltXaQX7h5ijnCftdh FnimScpS4P6cXU/tSWRGk+brXLh26BVC+g+zG5BmrrZNuh+eNWtB0CAJjTaRlSre eUqQAbrpbzh2CkQr9o/Lvbfzu8V6sSAGy9fb25bVLCSckhDoFVCDiuaDD4rC5cJY BThqsUL9eMh6P2M+XRmTuerOk1u/kcuV7d4HD9nH+6XU3scdGCEgpL5qlcKc670W 9vfbtO5P8KNRE3SnjnLxLC3ERH5FAAyPuHR1DQsSwmrJEB7aYD7Kgl3mCaoTG1b6 gR3ae3D2Y5ppPmmeb42rEvlotJQqCF6CKgzZQo4WChsdEW7q6CbJxruRrBSI9lQi yLDlvzaHtv+OEUvN1i8GIVvPdf2ZR4Hye9jHtJXW+TBX4qDM1pOSzkat2SkDKXwK gAz40iS6WFC0ETg3Y8iq =DRvG -----END PGP SIGNATURE----- _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
