469 research outputs found
Optimal Resource Allocation for Multi-user OFDMA-URLLC MEC Systems
In this paper, we study resource allocation algorithm design for multi-user
orthogonal frequency division multiple access (OFDMA) ultra-reliable low
latency communication (URLLC) in mobile edge computing (MEC) systems. To meet
the stringent end-to-end delay and reliability requirements of URLLC MEC
systems, we propose joint uplink-downlink resource allocation and finite
blocklength transmission. Furthermore, we employ a partial time overlap between
the uplink and downlink frames to minimize the end-to-end delay, which
introduces a new time causality constraint. The proposed resource allocation
algorithm is formulated as an optimization problem for minimization of the
total weighted power consumption of the network under a constraint on the
number of URLLC user bits computed within the maximum allowable computation
time, i.e., the end-to-end delay of a computation task. Despite the
non-convexity of the formulated optimization problem, we develop a globally
optimal solution using a branch-and-bound approach based on discrete monotonic
optimization theory. The branch-and-bound algorithm minimizes an upper bound on
the total power consumption until convergence to the globally optimal value.
Furthermore, to strike a balance between computational complexity and
performance, we propose two efficient suboptimal algorithms based on successive
convex approximation and second-order cone techniques. Our simulation results
reveal that the proposed resource allocation algorithm design facilitates URLLC
in MEC systems, and yields significant power savings compared to three baseline
schemes. Moreover, our simulation results show that the proposed suboptimal
algorithms offer different trade-offs between performance and complexity and
attain a close-to-optimal performance at comparatively low complexity.Comment: 32 pages, 9 figures, submitted for an IEEE journal. arXiv admin note:
substantial text overlap with arXiv:2005.0470
Robust URLLC Packet Scheduling of OFDM Systems
In this paper, we consider the power minimization problem of joint physical
resource block (PRB) assignment and transmit power allocation under specified
delay and reliability requirements for ultra-reliable and low-latency
communication (URLLC) in downlink cellular orthogonal frequency-division
multiple-access (OFDMA) system. To be more practical, only the imperfect
channel state information (CSI) is assumed to be available at the base station
(BS). The formulated problem is a combinatorial and mixed-integer nonconvex
problem and is difficult to tackle. Through techniques of slack variables
introduction, the first-order Taylor approximation and reweighted
-norm, we approximate it by a convex problem and the successive convex
approximation (SCA) based iterative algorithm is proposed to yield sub-optimal
solutions. Numerical results provide some insights into the impact of channel
estimation error, user number, the allowable maximum delay and packet error
probability on the required system sum power
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