Abstract :

Orthogonal space-time block codes (OSTBCs), such as the famous Alamouti code, represent a popular class of space-time codes in multi-antenna communications. They guarantee the maximal diversity order and have simple maximum-likelihood (ML) receiver implementations, two of the main reasons why OSTBCs attracted so much interest. These advantages are under the premise that channel state information (CSI) is available at the receiver, and much of the interest in the community has been based on this coherent assumption. However, CSI may not be always available in certain fast fading environments. This seminar considers the problem of OSTBC without CSI, also known as blind OSTBC or noncoherent OSTBC. Our investigation shows that the special OSTBC structures can bring about many advantages in the blind scenario, namely that the blind ML receiver can be very effectively implemented using semidefinite programming relaxation or sphere decoding (which, in comparison, blind ML detection for general space-time codes is a very hard problem), that OSTBCs can exhibit appealing blind identifiability conditions, and that we can develop systematic ways of constructing OSTBCs that show a "perfect" identifiability condition.