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Hier finden Sie wissenschaftliche Publikationen aus den FraunhoferInstituten. On the optimal transmission for the MIMO bidirectional broadcast channel
 IEEE Communications Society: IEEE International Conference on Communications, ICC 2009. Proceedings : June 1418, 2009, Dresden, Germany Piscataway, NJ: IEEE, 2009 ISBN: 9781424434350 ISBN: 1424434351 ISBN: 9781424434343 Art. 5199259 
 International Conference on Communications (ICC) <2009, Dresden> 

 English 
 Conference Paper 
 Fraunhofer HHI () 
Abstract
In this work the transmit covariance matrix optimization problem for the MIMO Gaussian bidirectional broadcast channel is studied. A halfduplex relay node establishes bidirectional communication between two nodes using a decodeandforward protocol. In the initial multiple access phase both nodes transmit their messages to the relay node. In the succeeding phase the relay broadcasts an optimal reencoded message so that both nodes can decode the other's message using their own message as side information. We show that if the channels are orthogonal then there exist equivalent transmit strategies with different ranks. The study of special cases reveals some of the difficult structure of the optimal solution. In particular a closed form procedure for the case of full rank transmission for invertible channels is derived. Moreover, for parallel channels the optimal solution is completely characterized and discussed.