Rate-Splitting with Hybrid Messages: DoF Analysis of the Two-User MIMO Broadcast Channel with Imperfect CSIT
IEEE Transactions on Wireless Communications(2023)
摘要
Most of the existing research on degrees-of-freedom (DoF) with imperfect
channel state information at the transmitter (CSIT) assume the messages are
private, which may not reflect reality as the two receivers can request the
same content. To overcome this limitation, we therefore consider the hybrid
unicast and multicast messages. In particular, we characterize the optimal DoF
region for the two-user multiple-input multiple-output (MIMO) broadcast channel
(BC) with imperfect CSIT and hybrid messages. For the converse, we establish a
three-step procedure to exploit the utmost possible relaxation. For the
achievability, since the DoF region is with specific three-dimensional
structure regarding antenna configurations and CSIT qualities, we verify the
existence or non-existence of corner point candidates via the feature of
antenna configurations and CSIT qualities categorization and provide a hybrid
message-aware rate-splitting scheme. Besides, we show that to achieve the
strictly positive corner points, it is unnecessary to split the unicast
messages into private and common parts, implying that adding a multicast
message may mitigate the rate-splitting complexity.
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关键词
DoF region,hybrid messages,rate-splitting,imperfect CSIT,two-user MIMO BC
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