Analysis and Coding of Multiple Access Channels I, II.
Generally speaking Sidon type problems have the following form. Given some operation on a finite set we want maximize the number of the elements in this set such that all outcomes of this operation on the chosen elements are different. E.g., union free sets are those where an arbitrary pair gives a different union. This `uniqness' can be utilized in coding and information theory, and below we give a more practical description of such a problem.
The concept of multiple-access channel turned out to be very useful if one would like to share a usually expensive common communication channel between a large number of users. The most popular model of code-division multiple-access (CDMA) led to the standards of the third generation mobil telephony. However, the spectral utilization of these systems is extremely poor, their data rates is just a small fraction of the information-theoretic capacity.
The CDMA principles do not assume any central intelligence, there is no coordination between the transmitters, so fit to the usual conditions of an ad-hoc network. In general, each transmitter has an own code forever. A coding rule should be able to detect the set of active users and to decode the messages of the active users. In this project investigate the most important deterministic channels:
- OR channel
- ADDER channel
- Collision channel
- Slow frequency hopping.
Participating institutes:
- MTA SZTAKI (Discrete Structures Group)
- Technical University of Budapest
- ONR, AFOSR