4 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
Open Cell-less Network Architecture and Radio Resource Management for Future Wireless Communication Systems
In recent times, the immense growth of wireless traffic data generated from massive mobile
devices, services, and applications results in an ever-increasing demand for huge
bandwidth and very low latency, with the future networks going in the direction of achieving
extreme system capacity and ultra reliable low latency communication (URLLC). Several
consortia comprising major international mobile operators, infrastructure manufacturers,
and academic institutions are working to develop and evolve the current generation
of wireless communication systems, i.e., fifth generation (5G) towards a sixth generation
(6G) to support improved data rates, reliability, and latency. Existing 5G networks are
facing the latency challenges in a high-density and high-load scenario for an URLLC network
which may coexist with enhanced mobile broadband (eMBB) services. At the same
time, the evolution of mobile communications faces the important challenge of increased
network power consumption. Thus, energy efficient solutions are expected to be deployed
in the network in order to reduce power consumption while fulfilling user demands for
various user densities. Moreover, the network architecture should be dynamic according
to the new use cases and applications. Also, there are network migration challenges for
the multi-architecture coexistence networks.
Recently, the open radio access network (O-RAN) alliance was formed to evolve
RANs with its core principles being intelligence and openness. It aims to drive the mobile
industry towards an ecosystem of innovative, multi-vendor, interoperable, and autonomous
RAN, with reduced cost, improved performance and greater agility. However,
this is not standardized yet and still lacks interoperability. On the other hand, the cell-less
radio access network (RAN) was introduced to boost the system performance required for
the new services. However, the concept of cell-less RAN is still under consideration from
the deployment point of view with the legacy cellular networks. The virtualization, centralization and cooperative communication which enables the cell-less RAN can further
benefit from O-RAN based architecture.
This thesis addresses the research challenges facing 5G and beyond networks towards
6G networks in regard to new architectures, spectral efficiency, latency, and energy efficiency.
Different system models are stated according to the problem and several solution
schemes are proposed and developed to overcome these challenges. This thesis
contributes as follows. Firstly, the cell-less technology is proposed to be implemented
through an Open RAN architecture, which could be supervised with the near real-time
RAN intelligent controller (near-RT-RIC). The cooperation is enabled for intelligent and
smart resource allocation for the entire RAN. Secondly, an efficient radio resource optimization
mechanism is proposed for the cell-less architecture to improve the system
capacity of the future 6G networks. Thirdly, an optimized and novel resource scheduling
scheme is presented that reduces latency for the URLLC users in an efficient resource
utilization manner to support scenarios with high user density. At the same time, this radio
resource management (RRM) scheme, while minimizing the latency, also overcomes
another important challenge of eMBB users, namely the throughput of those who coexist
in such a highly loaded scenario with URLLC users. Fourthly, a novel energy-efficiency
enhancement scheme, i.e., (3 × E) is designed to increase the transmission rate per energy
unit, with stable performance within the cell-less RAN architecture. Our proposed
(3 × E) scheme activates two-step sleep modes (i.e., certain phase and conditional phase)
through the intelligent interference management for temporarily switching access points
(APs) to sleep, optimizing the network energy efficiency (EE) in highly loaded scenarios,
as well as in scenarios with lower load. Finally, a multi-architecture coexistence (MACO)
network model is proposed to enable inter-connection of different architectures through
coexistence and cooperation logical switches in order to enable smooth deployment of a
cell-less architecture within the legacy networks.
The research presented in this thesis therefore contributes new knowledge in the cellless
RAN architecture domain of the future generation wireless networks and makes important
contributions to this field by investigating different system models and proposing
solutions to significant issues.Programa de Doctorado en Multimedia y Comunicaciones por la Universidad Carlos III de Madrid y la Universidad Rey Juan CarlosPresidenta: Matilde Pilar Sánchez Fernández.- Secretario: Alberto Álvarez Polegre.- Vocal: José Francisco Monserrat del Rí