720 research outputs found
Unified and Distributed QoS-Driven Cell Association Algorithms in Heterogeneous Networks
This paper addresses the cell association problem in the downlink of a
multi-tier heterogeneous network (HetNet), where base stations (BSs) have
finite number of resource blocks (RBs) available to distribute among their
associated users. Two problems are defined and treated in this paper: sum
utility of long term rate maximization with long term rate quality of service
(QoS) constraints, and global outage probability minimization with outage QoS
constraints. The first problem is well-suited for low mobility environments,
while the second problem provides a framework to deal with environments with
fast fading. The defined optimization problems in this paper are solved in two
phases: cell association phase followed by the optional RB distribution phase.
We show that the cell association phase of both problems have the same
structure. Based on this similarity, we propose a unified distributed algorithm
with low levels of message passing to for the cell association phase. This
distributed algorithm is derived by relaxing the association constraints and
using Lagrange dual decomposition method. In the RB distribution phase, the
remaining RBs after the cell association phase are distributed among the users.
Simulation results show the superiority of our distributed cell association
scheme compared to schemes that are based on maximum signal to interference
plus noise ratio (SINR)
Joint Beamforming and Power Control in Coordinated Multicell: Max-Min Duality, Effective Network and Large System Transition
This paper studies joint beamforming and power control in a coordinated
multicell downlink system that serves multiple users per cell to maximize the
minimum weighted signal-to-interference-plus-noise ratio. The optimal solution
and distributed algorithm with geometrically fast convergence rate are derived
by employing the nonlinear Perron-Frobenius theory and the multicell network
duality. The iterative algorithm, though operating in a distributed manner,
still requires instantaneous power update within the coordinated cluster
through the backhaul. The backhaul information exchange and message passing may
become prohibitive with increasing number of transmit antennas and increasing
number of users. In order to derive asymptotically optimal solution, random
matrix theory is leveraged to design a distributed algorithm that only requires
statistical information. The advantage of our approach is that there is no
instantaneous power update through backhaul. Moreover, by using nonlinear
Perron-Frobenius theory and random matrix theory, an effective primal network
and an effective dual network are proposed to characterize and interpret the
asymptotic solution.Comment: Some typos in the version publised in the IEEE Transactions on
Wireless Communications are correcte
Power Efficient and Secure Full-Duplex Wireless Communication Systems
In this paper, we study resource allocation for a full-duplex (FD) radio base
station serving multiple half-duplex (HD) downlink and uplink users
simultaneously. The considered resource allocation algorithm design is
formulated as a non-convex optimization problem taking into account minimum
required receive signal-to-interference-plus-noise ratios (SINRs) for downlink
and uplink communication and maximum tolerable SINRs at potential
eavesdroppers. The proposed optimization framework enables secure downlink and
uplink communication via artificial noise generation in the downlink for
interfering the potential eavesdroppers. We minimize the weighted sum of the
total downlink and uplink transmit power by jointly optimizing the downlink
beamformer, the artificial noise covariance matrix, and the uplink transmit
power. We adopt a semidefinite programming (SDP) relaxation approach to obtain
a tractable solution for the considered problem. The tightness of the SDP
relaxation is revealed by examining a sufficient condition for the global
optimality of the solution. Simulation results demonstrate the excellent
performance achieved by the proposed scheme and the significant transmit power
savings enabled optimization of the artificial noise covariance matrix.Comment: 6 pages, invited paper, IEEE Conference on Communications and Network
Security (CNS) 2015 in Florence, Italy, on September 30, 201
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