Title :
Non-Orthogonal Transmission in Multi-User Systems with Grassmannian Beamforming
Author :
Xia, Minghua ; Wu, Yik-Chung ; Aïssa, Sonia
Author_Institution :
King Abdullah Univ. of Sci. & Technol. (KAUST), Thuwal, Saudi Arabia
Abstract :
Aiming to achieve the sum-rate capacity in multi user multi-input multi-output (MIMO) channels with Nt antennas implemented at the transmitter, opportunistic beamforming (OBF) generates Nt orthonormal beams and serves Nt users during each transmission, which results in high scheduling delay over the users, especially in densely populated wireless networks. Non-orthogonal OBF with more than Nt transmit beams can be exploited to serve more users simultaneously and further decreases scheduling delay. However, the inter-beam interference will inevitably deteriorate the sum-rate. Therefore, there is a tradeoff between the sum-rate and the increasing number of transmit beams. In this context, the sum-rate of non-orthogonal OBF with N >; Nt beams are studied, where the transmitter is based on the Grassmannian beamforming. Our results show that non-orthogonal OBF is an interference-limited system. Moreover, when the inter-beam interference reaches its minimum for fixed Nt and N, the sum-rate scales as N ln (N/N-Nt) and it decreases monotonically with N for fixed Nt. Numerical results corroborate the accuracy of our analyses.
Keywords :
MIMO communication; array signal processing; radiofrequency interference; telecommunication channels; Grassmannian beamforming; MIMO channels; interbeam interference; multiinput multioutput channels; multiuser systems; nonorthogonal transmission; opportunistic beamforming; Array signal processing; Delay; Distribution functions; Interference; Limiting; Signal to noise ratio; Wireless communication;
Conference_Titel :
Communications (ICC), 2011 IEEE International Conference on
Conference_Location :
Kyoto
Print_ISBN :
978-1-61284-232-5
Electronic_ISBN :
1550-3607
DOI :
10.1109/icc.2011.5962841