Multi-antenna Transmission and Scheduling in IMT-Advanced Project summary The project will study technical solutions for next generation mobile access technologies. The project intends to develop and validate techniques for scheduling and controlling transmission to/from multiple users over multiple antennas. This includes multiantenna base stations and transmission over multiple relay nodes (cooperative relaying). Such techniques are crucial for obtaining high data rates over extended areas in beyond-3G systems, in particular for increasing the data rates to cell-edge users far from base station sites. All IMT-Advanced candidate systems in discussion today would offer high data rate packet transmission by using multicarrier radio interfaces, multi-antenna transmission and possibly also relay nodes. Interference between the transmissions will be unavoidable and it can severely reduce the performance. A main challenge is to explore ways to predict and control the mutual interference between users. Only transmissions which are predicted to create low mutual interference would then be allowed to use the same time-frequency resources. If channel state information to/from other users is available, it is possible to significantly improve the transmission rate of each communication link, as well as the interference situation. However, collecting such information and distributing it to other nodes requires a substantial overhead for training and control signalling, which penalizes the spectral efficiency. Therefore, a major challenge is to exploit partial channel state information and long-term averages and still get close to the performance that can be obtained with full channel knowledge. The resulting computational complexity and computational delays may also become prohibitive, since a low latency (delay) over the air interface is becoming a crucial requirement of evolving wireless broadband systems. A second main challenge is to predict the channel properties for mobile terminals and to adjust the transmission scheme to the channel predictability. A third main challenge is to integrate the whole design into a multiuser multi-antenna scheduling algorithm that takes quality of service constraints and predicted channel properties into account. The partners of this project are working on such issues in the projects WINNER, WINNERII, COOPCOM and SENDORA (under negotiation within FP7) funded by the European Commission. This work is based on theoretical studies and simulation studies in which channel models were used in the simulators. However, the multi-antenna radio environment is extremely complicated and its properties cannot be captured in any single propagation model. This lack of realism is a main obstacle to further progress. The industrial partner of the consortium, Ericsson, is intending to perform measurement campaigns to obtain broadband channel measurements in realistic propagation environments. In addition, KTH will do complementary measurements on the joint characteristics of multiple channels. The availability of these data sets will provide the consortium with new means to evaluate existing techniques and to find clues for improvements.