Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Product Superposition for MIMO Broadcast Channels   This paper considers the multiantenna broadcast channel without transmit-side
channel state information (CSIT). For this channel, it has been known that when
all receivers have channel state information (CSIR), the degrees of freedom
(DoF) cannot be improved beyond what is available via TDMA. The same is true if
none of the receivers possess CSIR. This paper shows that an entirely new
scenario emerges when receivers have unequal CSIR. In particular, orthogonal
transmission is no longer DoF-optimal when one receiver has CSIR and the other
does not. A multiplicative superposition is proposed for this scenario and
shown to attain the optimal degrees of freedom under a wide set of antenna
configurations and coherence lengths. Two signaling schemes are constructed
based on the multiplicative superposition. In the first method, the messages of
the two receivers are carried in the row and column spaces of a matrix,
respectively. This method works better than orthogonal transmission while
reception at each receiver is still interference free. The second method uses
coherent signaling for the receiver with CSIR, and Grassmannian signaling for
the receiver without CSIR. This second method requires interference
cancellation at the receiver with CSIR, but achieves higher DoF than the first
method.

12
The categories of this paper are: nucl-th
24
The categories of this paper are: dg-ga
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph