User selection with perfect and no primary CSIT in MIMO cognitive radio networks
Spectrum is one of the most precious resources in the field of wireless communication field. As the number of users and demand for fast data transmission increases, the current spectrum resources become insufficient. Cognitive radio (CR) networks are one of the promising ways to increase the efficiency of spectrum use. While a licensed primary user (PU) occupies a certain bandwidth, CR users try to utilize the same bandwidth under the condition that interference is minimized and the licensed user is able to achieve its required data rate. It is desirable to allow as many CR users into the bandwidth as possible, thus maximizing spectrum efficiency. However, with a large number of secondary users (SUs), interference becomes significant. Hence, only a portion of the CR users can be served in most cases. This work involves the study of user selection (US) strategies for a multiple-input multiple-output (MIMO) CR downlink network, where the r-antenna underlay CR SUs coexist with the PU, and all terminals are equipped with multiple antennas. Two main scenarios are considered: (1) the t-antenna cognitive base station (CBS) has perfect or partial channel state information at the transmitter (CSIT) from the CBS to the PU receiver (RX), and (2) the CBS has absolutely no PU CSIT. For these scenarios, multiple SU selection schemes that are applicable to both best-effort PU interference mitigation and hard interference temperature constraints are proposed and evaluated. Also, in this dissertation scheduling methods for non-orthogonal resource sharing between device-to-device (D2D) and cellular-user equipment (C-UE) in a multi-carrier multi-antenna network are examined. The cellular eNodeB (eNB) allocates a pool of subchannels that may be used autonomously by D2D user equipment (UE) for D2D discovery and communication. Then, the scheduling of C-UE uplink transmissions in the same subchannel pool based on a best-effort C-UE-to-D2D interference mitigation method that does not require knowledge of C-UE to D2D UE channels is proposed. The selection criterion is a combination of the number of spatial streams, subchannels, and transmit power needed by C-UE to achieve their target data rate.
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