A two-user approximation-based transmit beamforming for physical-layer multicasting in mobile cellular downlink systems |
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Authors: | Chang-Lung Hsiao Jiann-Ching Guey Wern-Ho Sheen Ren-Jr Chen |
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Affiliation: | 1. ICL ITRI, 310 Hsinchu, Taiwanclhsiao@itri.org.tw;3. MediaTek, 300 Hsinchu, Taiwan;4. Department of Communications Engineering, National Chung Cheng University, 621 Chiayi, Taiwan;5. ICL ITRI, 310 Hsinchu, Taiwan |
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Abstract: | Multicast has been known as an efficient transmission technique for group-oriented applications such as multi-party video conferencing, video streaming for paid users, online gaming, and social networking. In this paper, we investigate physical-layer multicasting in mobile cellular downlink systems, where the antennas at base station are employed to transmit common signals to multiple users simultaneously. A central design problem of downlink physical-layer multicasting is the search for the optimal beamforming vector that maximizes the multicast rate. Traditionally, the problem has been formulated as a quadratically constrained quadratic programming problem and shown to be NP-hard in general. In this paper, starting from examining the Karush–Kuhn–Tucker stationary conditions, a new method based on two-user approximation is proposed for the search for the optimal beamforming vector. The method is able to achieve a much higher multicast rate than the existing methods and provides an attractive trade-off between performance and complexity, especially for the case of using a large number of antennas. Using a large number of antennas at base station, also known as the large-scale multiple-input and multiple-output technique, has been regarded widely as one of the most promising technologies to increase system capacity, coverage, and user throughput for future generations of mobile cellular systems. |
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Keywords: | physical-layer multicasting mobile cellular downlink systems multiple antennas transmit beamforming |
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