2,624 research outputs found
On Robustness of Massive MIMO Systems Against Passive Eavesdropping under Antenna Selection
In massive MIMO wiretap settings, the base station can significantly suppress
eavesdroppers by narrow beamforming toward legitimate terminals. Numerical
investigations show that by this approach, secrecy is obtained at no
significant cost. We call this property of massive MIMO systems `secrecy for
free' and show that it not only holds when all the transmit antennas at the
base station are employed, but also when only a single antenna is set active.
Using linear precoding, the information leakage to the eavesdroppers can be
sufficiently diminished, when the total number of available transmit antennas
at the base station grows large, even when only a fixed number of them are
selected. This result indicates that passive eavesdropping has no significant
impact on massive MIMO systems, regardless of the number of active transmit
antennas.Comment: 7 pages, 2 figures; To be presented in IEEE Global Communications
Conference (Globecom) 2018 in Abu Dhabi, UA
Energy-Efficient NOMA Enabled Heterogeneous Cloud Radio Access Networks
Heterogeneous cloud radio access networks (H-CRANs) are envisioned to be
promising in the fifth generation (5G) wireless networks. H-CRANs enable users
to enjoy diverse services with high energy efficiency, high spectral
efficiency, and low-cost operation, which are achieved by using cloud computing
and virtualization techniques. However, H-CRANs face many technical challenges
due to massive user connectivity, increasingly severe spectrum scarcity and
energy-constrained devices. These challenges may significantly decrease the
quality of service of users if not properly tackled. Non-orthogonal multiple
access (NOMA) schemes exploit non-orthogonal resources to provide services for
multiple users and are receiving increasing attention for their potential of
improving spectral and energy efficiency in 5G networks. In this article a
framework for energy-efficient NOMA H-CRANs is presented. The enabling
technologies for NOMA H-CRANs are surveyed. Challenges to implement these
technologies and open issues are discussed. This article also presents the
performance evaluation on energy efficiency of H-CRANs with NOMA.Comment: This work has been accepted by IEEE Network. Pages 18, Figure
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