Cross-layer scheduling for multi-user MIMO systems

The increasing demand of wireless services associated with the scarcity of the radio spectrum and the trend to provide end-to-end QoS in emerging and future applications calls for the design of spectrally efficient systems with QoS support. To fulfill these two requirements of spectral efficiency and QoS provision in the highly dynamic environment of mobile radio requires the collaboration of several layers in the system as well as the use of multiple transmit and receive antennas. In a packet network, one important component to achieve the aforementioned efficiency goals is a properly designed scheduling algorithm. Using an information-theoretic framework, we present an overview of the issues associated with the design of packet scheduling algorithms and review several proposed solutions. The article focuses on the advantages of a cross-layer approach to the resource allocation problem and identifies the trade-offs associated with the increased signaling needs. Also, we thoroughly discuss the additional degrees of freedom that multiple transmit and receive antennas can provide.