700 research outputs found
Optimal Beamforming for Physical Layer Security in MISO Wireless Networks
A wireless network of multiple transmitter-user pairs overheard by an
eavesdropper, where the transmitters are equipped with multiple antennas while
the users and eavesdropper are equipped with a single antenna, is considered.
At different levels of wireless channel knowledge, the problem of interest is
beamforming to optimize the users' quality-of-service (QoS) in terms of their
secrecy throughputs or maximize the network's energy efficiency under users'
QoS. All these problems are seen as very difficult optimization problems with
many nonconvex constraints and nonlinear equality constraints in beamforming
vectors. The paper develops path-following computational procedures of
low-complexity and rapid convergence for the optimal beamforming solution.
Their practicability is demonstrated through numerical examples
Joint Fractional Time Allocation and Beamforming for Downlink Multiuser MISO Systems
It is well-known that the traditional transmit beamforming at a base station
(BS) to manage interference in serving multiple users is effective only when
the number of users is less than the number of transmit antennas at the BS.
Non-orthogonal multiple access (NOMA) can improve the throughput of users with
poorer channel conditions by compromising their own privacy because other users
with better channel conditions can decode the information of users in poorer
channel state. NOMA still prefers that the number of users is less than the
number of antennas at the BS transmitter. This paper resolves such issues by
allocating separate fractional time slots for serving the users with similar
channel conditions. This enables the BS to serve more users within the time
unit while the privacy of each user is preserved. The fractional times and
beamforming vectors are jointly optimized to maximize the system's throughput.
An efficient path-following algorithm, which invokes a simple convex quadratic
program at each iteration, is proposed for the solution of this challenging
optimization problem. Numerical results confirm its versatility.Comment: IEEE Communications Letters (To Appear
MIMO Beamforming for Secure and Energy-Efficient Wireless Communication
Considering a multiple-user multiple-input multiple-output (MIMO) channel
with an eavesdropper, this letter develops a beamformer design to optimize the
energy efficiency in terms of secrecy bits per Joule under secrecy
quality-of-service constraints. This is a very difficult design problem with no
available exact solution techniques. A path-following procedure, which
iteratively improves its feasible points by using a simple quadratic program of
moderate dimension, is proposed. Under any fixed computational tolerance the
procedure terminates after finitely many iterations, yielding at least a
locally optimal solution. Simulation results show the superior performance of
the obtained algorithm over other existing methods.Comment: 12 pages, 2 figure
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