Kweh Yeah Lun

Greedy---knapsack algorithm for optimal downlink resource allocation in LTE networks

Abstract The long term evolution as a mobile broadband technology supports a wide domain of communication services with different requirements. Therefore, scheduling of all flows from various applications in overload states in which the requested amount of bandwidth exceeds the limited available spectrum resources is a challenging issue. Accordingly, in this paper, a greedy algorithm is presented to evaluate user candidates which are waiting for scheduling and select an optimal set of the users to maximize system performance, without exceeding available bandwidth capacity. The greedy–knapsack algorithm is defined as an optimal solution to the resource allocation problem, formulated based on the fractional knapsack problem. A compromise between throughput and QoS provisioning is obtained by proposing a class-based ranking function, which is a combination of throughput and QoS related parameters defined for each application. The simulation results show that the proposed method provides high performance in terms of throughput, loss and delay for different classes of QoS over the existing ones, especially under overload traffic.

x-Folded TM

Massively parallel computers (MPCs) are currently being actively studied. Interconnection networks are used for the connection of a significant number of processors in such parallel systems because they are introduced as one of the key elements in parallel processing. Meshes, torus, and hypercubes were initially introduced as simple topologies of interconnection networks. At present, these have been replaced by more complicated topologies that also exhibit high performance. Because the diameter, average distance, and cost of topologies have a marked influence on network performance, this paper presents a novel topology called x-Folded TM, which is a TM topology that is folded according to the x-axis. For an n × n network, the diameter of an x-Folded TM is less than that of a TM and a torus, and the average distance of an x-Folded TM is less than that of a mesh, torus, and TM. Compared with mesh, torus, and TM networks, a Folded TM network presents reductions in the average distance, diameter, and cost, which accounts for its efficient performance. As observed from the presented simulation results, the performance of an x-Folded TM is similar to that of most torus networks and better than that of some torus networks. The results verify the effectiveness of the x-Folded TM network, as determined through its comparison with networks with other topologies.

Reliability Review of Interconnection Networks

ABSTRACT Interconnection networks provide communication among processors, memory modules, and other devices in parallel computer systems. The number of stages, interconnection topology, and the types of SE used in the network configuration differentiate each interconnection network. As an illustration, there are numerous aspects that are important in the development of interconnection networks. Reliability can be considered as an important factor to measure the performance in the network. The reliability for interconnection network depends on the reliability of its components. In this paper, we examine the various topologies of interconnection, communication protocol, and discuss reliability issues related to interconnection network.

Two-Level Frames Aggregation with Enhanced A-MSDU for IEEE 802.11n WLANs

IEEE 802.11n defines two schemes of frames aggregation aimed at maximize utilizing WLAN PHY efficiency at MAC level, through sharing headers and timings overheads. Despite their efficiencies in enhancing the MAC throughput, the schemes are characterized with yet other overheads due to the aggregation. Moreover, none of the two schemes is optimal in every condition: Both should work together to achieve this. In this paper, in order to optimize channel’s bandwidth utilization, we proposed an enhanced A-MSDU with minimal headers overhead, and an efficient two-level aggregation scheme utilizing the enhanced A-MSDU. Results from the simulation show superiority of the proposed two-level aggregation in respect of throughput and overall channel utilization.

Fair-QoS Broker Algorithm for Overload-State Downlink Resource Scheduling in LTE Networks

Efficiently scheduling various service classes while fulfilling performance targets is one of the main challenges in 3GPP Long-Term Evolution (LTE) communication systems. However, Quality of Service (QoS) and fairness provisioning for all different service classes are generally unstable due to insufficient radio resources, especially in heavily loaded states of the network, which leads to the deterioration of overall system performance. In this paper, we address these challenging issues by proposing a two-level downlink scheduling algorithm to deliver all traffic types while attempting to provide a compromise for the LTE performance targets. For the higher level of the algorithm, a coherent resource distribution approach is developed by applying a game theory model in a nested manner to provide per-class fairness. At the lower level, the greedy-knapsack algorithm is properly tailored to optimally allocate resources to the best potential bearers for QoS and throughput enhancement. The performance of the proposed algorithm was evaluated for normal and overload states of the network. The simulation results clearly demonstrate that the proposed scheduling algorithm, compared with the reference scheduling algorithms, provides the best tradeoff for fairness, throughput, and QoS performance in terms of packet loss rate and packet latency for different service classes.

Adaptive routing algorithm in x-Folded TM topology

In recent days, more complicated interconnection topologies have been replaced with previously simple topologies that also exhibit high performance. x-Folded TM network is a TM network that is folded according to the imaginary x-axis in interconnection networks. For a x-Folded TM network, there is a reduction in the average distance and diameter which corroborates the efficient performance. Also many routing algorithms can be applied to interconnection network for the efficient use of network resources. This paper presents the effectiveness of the x-Folded TM network with the average latency and network throughput under the adaptive routing algorithm to improve dynamic communication performance. We evaluate the communication performance with simulating the topology under the adaptive routing algorithm. It is found from the result that the performance of a x-Folded TM network has been improved compared with other topologies.

Downlink scheduling for heterogeneous traffic with Gaussian weights in LTE-A

In Long Term Evolution-Advanced (LTE-A) networks, different aspects of radio resource scheduling such as fairness and Quality of Service (QoS) assurance must be provided for heterogeneous traffic, having different characteristics. However, the ever-growing number of mobile devices sharing the limited radio resources leads to the high cost and difficulty for information acquisition and computations in resource scheduling process. In the present paper, we propose a proportional knapsack scheduling approach for fairness- and QoS-aware downlink transmission of all different service classes in LTE-A networks. Moreover, we assess the computational cost created by the uncertainty and lack of information on user operations, and propose a Gaussian-based approach for ranking the bearers in presence of limited information and computational capabilities. This approach is particularly suitable for emerging next generation wireless networks to support a wide range of applications with huge number of users. The results indicate that significant advantages are achieved both in terms of QoS and fairness and that it is a scalable solution for overload states of the network.

Multi-Targeted Downlink Scheduling for Overload-States in LTE Networks: Proportional Fractional Knapsack Algorithm With Gaussian Weights

In Long-Term Evolution (LTE) and beyond systems, radio resource scheduling mechanism plays one of the main roles in system performance maximization. From this perspective, due to the conflicting quality requirements of different traffic types, providing a compromise among all performance targets for heterogeneous traffic is difficult. Moreover, the centralized scheduling mechanism for the ever growing number of users along with the massive variety of services, especially in overload states, is infeasible due to the extensive cost of information acquisition and computations. In this paper, we design resource scheduling policies for supporting the efficient delivery of heterogeneous traffic in overload states of a cell. To this end, we cast the class-based bearer-level resource distribution problem as a Proportional Fractional Knapsack model. The objective of the formulated problem is to meet Quality of Service (QoS) requirements and provide fairness for all standardized service classes. Since the solution of this problem is computationally expensive, due to the uncertainty and limited information on network and user operation, we develop a Gaussian-based analytical model and drive a formula for simplified computation of the weight of service bearers. Then, we propose Proportional Fractional Knapsack algorithm for guaranteeing effective utilization of resources for heterogeneous traffic. Finally, performance evaluation results are provided and demonstrate that the proposed scheduling approach can provide a significant level of fairness, in balance with the QoS and throughput performance targets, comparable with optimal ones.

QoS class-based proportional resource allocation for LTE downlink

In LTE multi-service communication system, a trade-off between QoS assurance and fairness is a challenging issue, since the QoS provisioning at the cost of starving users in low service demand classes is not favorable for the operator. In this paper, we adopt the time-domain Knapsack algorithm and fine tune it to provide fair resource allocation while support QoS requirements in LTE downlink scheduling system when the bearers are from different classes of service, having different QoS characteristics. We demonstrate that more efficient performance can be achieved in two aspects of fairness and QoS provisioning in terms of normalized throughput, and packet loss and delay rate, which are evaluated using simulation results.

Mathematical Modelling of Wormhole-Routed x-Folded TM Topology in the Presence of Uniform Traffic

Recently, x-Folded TM topology was introduced as a desirable design in k-ary n-cube networks due to the low diameter and short average distance. In this article, we propose a mathematical model to predict the average network delay for (\(k \times k\)) x-Folded TM in the presence of uniform traffic pattern. Our model accurately formulates the applied traffic pattern over network virtual channels based on the average distance and number of nodes. The mathematical results indicate that the average network delay for x-Folded TM topology is reduced when compared with other topologies in the presence of uniform traffic pattern. Finally, the results obtained from simulation experiments confirm that the mathematical model exhibits a significant degree of accuracy for x-Folded TM topology under the traffic pattern even in varied virtual channels.