45 research outputs found
Channel Estimation for Ambient Backscatter Communication Systems with Massive-Antenna Reader
Ambient backscatter, an emerging green communication technology, has aroused
great interest from both academia and industry. One open problem for ambient
backscatter communication (AmBC) systems is channel estimation for a
massive-antenna reader. In this paper, we focus on channel estimation problem
in AmBC systems with uniform linear array (ULA) at the reader which consists of
large number of antennas. We first design a two-step method to jointly estimate
channel gains and direction of arrivals (DoAs), and then refine the estimates
through angular rotation. Additionally, Cramer-Rao lower bounds (CRLBs) are
derived for both the modulus of the channel gain and the DoA estimates.
Simulations are then provided to validate the analysis, and to show the
efficiency of the proposed approach.Comment: 5 figures, submitted to IEEE Transactions on Vehicular Technology, 29
March, 201
Secrecy Outage Probability Analysis of Multi-User Multi-Eavesdropper Wireless Systems
In this paper, we explore the physical-layer security of a multi-user
wireless system that consists of multiple users intending to transmit to a base
station (BS), while multiple eavesdroppers attempt to tap the user
transmissions. We examine the employment of multi-user scheduling for improving
the transmission security against eavesdropping and propose a multi-user
scheduling scheme, which only requires the channel state information (CSI) of
BS without the need of the passive eavesdroppers' CSI. We also consider the
round-robin scheduling for comparison purposes. The closed-form secrecy outage
probability expressions of the round-robin scheduling and proposed multi-user
scheduling are derived over Rayleigh fading channels. Numerical results
demonstrate that the proposed multi-user scheduling outperforms the round-robin
scheduling in terms of the secrecy outage probability. As the number of users
increases, the secrecy outage probability of round-robin scheduling keeps
unchanged. By contrast, the secrecy outage performance of the proposed
multi-user scheduling improves significantly with an increasing number of
users.Comment: 5 page