1 / 7

An AWGN Multiaccess Channel*

An AWGN Multiaccess Channel*. Ballard Blair 6.441 - Transmission of Information Massachusetts Institute of Technology May 10, 2007. *Paper: Gallager, R, A Perspective on Multiaccess Channels , IEEE transactions on Information Theory, March 1985. T 1. T 2. Channel. R. T 3. T N.

karlyn
Download Presentation

An AWGN Multiaccess Channel*

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. An AWGN Multiaccess Channel* Ballard Blair 6.441 - Transmission of Information Massachusetts Institute of Technology May 10, 2007 *Paper: Gallager, R, A Perspective on Multiaccess Channels, IEEE transactions on Information Theory, March 1985

  2. T1 T2 Channel R T3 TN Multiaccess Network Motivation • Generalization of point to point • Transmitter not always ready • Applicable to many situations • Cell phones • Ethernet • Encoding Easy (Random), Decoding Hard • Conclusion: Need better models and approaches AWGN Multiaccess channel - Ballard Blair

  3. x T1 Coding R y=w+x+z w T2 Coding z Gaussian Multiaccess Setup AWGN Channel Setup Types of Errors • Only X decoded incorrectly (type 1) • Only Y decoded incorrectly (type 2) • X and Y decoded incorrectly (type 3) Capacity of AWGN Channel: • Energy Constraint for each transmitter (S1 and S2) AWGN Multiaccess channel - Ballard Blair

  4. R2 I(W;Y|X) I(W;Y) I(X;Y) I(X;Y|W) R1 Achievable Rates Constraints 2-Parallel AWGN Channels AWGN Multiaccess channel - Ballard Blair

  5. Higher Dimensionality R3 R1 R2 3 Transmitters (7 constraints) Constraints quickly get out of hand (2n-1 constraints for n-dim) AWGN Multiaccess channel - Ballard Blair

  6. Conclusions • AWGN Multiaccess • Interesting, not practical • Better Models needed (other than power lim) • Modern Approaches • CDMA • OFDM AWGN Multiaccess channel - Ballard Blair

  7. Questions? http://www.ukuleleman.net/2005_08_01_ukemanspeaks_archive.html AWGN Multiaccess channel - Ballard Blair

More Related