Minimum Throughput Guarantee Research Articles

Efficient Computation of the Max-Plus Semantics of Synchronous Dataflow Graphs

Streaming systems are naturally modeled with synchronous dataflow graphs (SDFGs). The max-plus semantics of an SDFG is a compact matrix representation of its timing behavior. The max-plus semantics enables us to analyze and control timing properties of the systems, such as the obtainable minimum guaranteed throughput and maximum latency. Deriving the max-plus semantics, and consequently, performance analysis may be computationally expensive since the state-of-the-art method simulates one iteration of an SDFG. This holds, in particular, for systems whose components operate at different levels of granularity, as this results in many executions of some components in one iteration. This paper aims at efficiently calculating the max-plus semantics of SDFGs. The paper proposes an optimization framework exploring decompositions of a given SDFG and finding a composition sequence whose computational effort for compositionally obtaining the max-plus semantics is minimal. Not only does our proposed technique accelerate the performance analysis of multiscale streaming systems, but it also allows us to compute the max-plus semantics of some systems for which the state-of-the-art method does not succeed because of memory limitations.

Performance Assessment of QoS-Aware LTE Sessions Offloading Onto LAA/WiFi Systems

Fifth-generation (5G) cellular systems are expected to orchestrate a variety of air interfaces. In this heterogeneous setting 4G, LTE systems will remain of special importance providing service over a relatively large area not covered with the 3GPP new radio technology. However, the scarcity of radio resources below 6 GHz as well as constantly increasing user traffic demands call for efficient offloading strategy from the LTE network. In this paper, we consider and compare two LTE session offloading strategies, including LAA and WiFi offloading. Although by design, the LAA system supports quality-of-service (QoS) guarantees in terms of minimum throughput, the assured performance might still be violated by resource reallocations when satisfying the compulsory fairness criteria. To assess and compare the performance of these schemes, we develop an analytical framework that takes into account specifics of duty-cycle schedule-based Licensed Assisted LTE Access (LAA) system with connection admission control (CAC), resource reallocation mechanism, and realistic elastic traffic nature. As a special case of the developed framework, we also address the offloading of QoS-aware LTE sessions into conventional WiFi. Our numerical results indicate that WiFi offloading is characterized by a significantly greater number of offloaded sessions. However, this advantage comes at the expense of severe performance degradation in terms of minimum throughput guarantees. Implementing CAC procedures, LAA efficiently addresses this problem. We conclude that WiFi offloading of QoS-aware LTE sessions can be used in light traffic conditions only. On the other hand, offloading to the schedule-based LAA system allows preserving QoS over a wide range of arrival traffic statistics.

CSMA-Based Robust AP Throughput Guarantee Under User Distribution Uncertainty

We consider the problem of providing inter-access-point (AP) fairness guarantee in dense AP deployments where starvation can occur. In particular, we develop a framework for providing robust minimum throughput guarantee for each AP under the uncertainty of user distributions. Our framework consists of an AP throughput provisioning scheme and a distributed CSMA algorithm. The throughput provisioning scheme computes a robust feasible minimum AP throughput vector based on a random AP-level conflict graph and chance-constrained optimization. By incorporating the minimum throughput vector, we develop a distributed CSMA algorithm that fulfills the minimum requirement for each AP and is compatible with the IEEE 802.11 standard. We show through extensive simulations that our framework addresses the AP starvation problem by guaranteeing minimum throughput for each AP.

Topology-Transparent Scheduling in Mobile Ad Hoc Networks With Multiple Packet Reception Capability

Recent advances in the physical layer have enabled wireless devices to have multiple packet reception (MPR) capability, which is the capability of decoding more than one packet, simultaneously, when concurrent transmissions occur. In this paper, we focus on the interaction between the MPR physical layer and the medium access control (MAC) layer. Some random access MAC protocols have been proposed to improve the network performance by exploiting the powerful MPR capability. However, there are very few investigations on the schedule-based MAC protocols. We propose a novel m-MPR-l-code topology-transparent scheduling ((m, l)-TTS) algorithm for mobile ad hoc networks with MPR, where m indicates the maximum number of concurrent transmissions being decoded, and l is the number of codes assigned to each user. Our algorithm can take full advantage of the MPR capability to improve the network performance. The minimum guaranteed throughput and average throughput of our algorithm are studied analytically. The improvement of our (m, l)-TTS algorithm over the conventional topology-transparent scheduling algorithms with the collision-based reception model is linear with m. The simulation results show that our proposed algorithm performs better than slotted ALOHA as well.

A self‐organized resource allocation scheme for heterogeneous macro‐femto networks

AbstractThis paper investigates the radio resource management (RRM) issues in a heterogeneous macro‐femto network. The objective of femto deployment is to improve coverage, capacity, and experienced quality of service of indoor users. The location and density of user‐deployed femtos is not known a‐priori. This makes interference management crucial. In particular, with co‐channel allocation (to improve resource utilization efficiency), RRM becomes involved because of both cross‐layer and co‐layer interference. In this paper, we review the resource allocation strategies available in the literature for heterogeneous macro‐femto network. Then, we propose a self‐organized resource allocation (SO‐RA) scheme for an orthogonal frequency division multiple access based macro‐femto network to mitigate co‐layer interference in the downlink transmission. We compare its performance with the existing schemes like Reuse‐1, adaptive frequency reuse (AFR), and AFR with power control (one of our proposed modification to AFR approach) in terms of 10 percentile user throughput and fairness to femto users. The performance of AFR with power control scheme matches closely with Reuse‐1, while the SO‐RA scheme achieves improved throughput and fairness performance. SO‐RA scheme ensures minimum throughput guarantee to all femto users and exhibits better performance than the existing state‐of‐the‐art resource allocation schemes.Copyright © 2014 John Wiley & Sons, Ltd.

Scheduling in Centralized Cognitive Radio Networks for Energy Efficiency

With growing concern about environmental issues and an emerging green communications paradigm, cognitive radio (CR) networks (CRNs) have to be considered from the energy efficiency perspective. In this paper, we focus on scheduling in CRNs, in which a cognitive base station (CBS) makes frequency allocations to the CRs at the beginning of each frame. A cognitive scheduler must consider the diversity among CRs' queues and channel capacities in terms of number of bits and the channel switching cost from one frequency to another. Taking all these into account, we formulate the scheduling problem as an energy efficiency maximization problem, which is a nonlinear integer programming (NLP) problem and is thereby hard to solve. We seek alternate computationally easier solutions. To this aim, we propose a polynomial-time heuristic algorithm, i.e., the energy-efficient heuristic scheduler (EEHS), which allocates each idle frequency to the CR that attains the highest energy efficiency at this frequency. Next, we reformulate the original problem first as a throughput maximization problem subject to energy consumption restrictions and then as an energy consumption minimization problem subject to minimum throughput guarantees. These two schedulers also have the power to provide fairness in resource allocation. We analyze the energy efficiency and successful transmission probability of the proposed schedulers under both contiguous and fragmented spectrum scenarios. Performance studies show that, compared with a pure opportunistic scheduler with a throughput maximization objective, proposed schedulers can attain almost the same throughput performance with better energy efficiency.

Maximizing Minimum Throughput Guarantees: The Small Violation Probability Region

Providing minimum throughput guarantees is one of the goals for radio resource allocation schemes. It is difficult to provide these guarantees without defining violation probability due to limited power budget and rapidly changing conditions of the wireless channel. For every practical scheduling scheme, there is a feasibility region defined by the minimum guaranteed throughput and the corresponding probability that the users fail to get the guaranteed throughput (violation probability). In this work, we focus on minimizing the violation probability specifically in the small probability region. We compare our results with major schedulers available in literature and show that our scheme outperforms them in the small violation probability region.

Electromagnetic Interference-Aware Transmission Scheduling and Power Control for Dynamic Wireless Access in Hospital Environments

We study the multiple access problem for e-Health applications (referred to as secondary users) coexisting with medical devices (referred to as primary or protected users) in a hospital environment. In particular, we focus on transmission scheduling and power control of secondary users in multiple spatial reuse time-division multiple access (STDMA) networks. The objective is to maximize the spectrum utilization of secondary users and minimize their power consumption subject to the electromagnetic interference (EMI) constraints for active and passive medical devices and minimum throughput guarantee for secondary users. The multiple access problem is formulated as a dual objective optimization problem which is shown to be NP-complete. We propose a joint scheduling and power control algorithm based on a greedy approach to solve the problem with much lower computational complexity. To this end, an enhanced greedy algorithm is proposed to improve the performance of the greedy algorithm by finding the optimal sequence of secondary users for scheduling. Using extensive simulations, the tradeoff in performance in terms of spectrum utilization, energy consumption, and computational complexity is evaluated for both the algorithms.

DTSMA: Distributed time-spread multiple access for wireless mesh networks with IEEE 802.16d MAC protocol

This paper studies the use of IEEE 802.16d mesh MAC protocol for multi-hop networking in an indoor domestic environment. The mesh network is expected to support time-sensitive audio–video applications with stringent QoS requirement. In the literature, time-spread multiple access (TSMA) is a promising technology to provide a minimum throughput guarantee in a multi-hop mesh network with dynamic topology. However, existing TSMA schemes require the number of nodes in the entire network and their global maximum node degree, be known a priori to a central controller. The requirement is not practical. In view of this problem, this paper proposes a distributed time-spread multiple access (DTSMA) scheme. The proposed DTSMA has the following main contributions: (a) A method for each node to determine locally its polynomial coefficients without a priori global knowledge of node number and maximum node degree, and (b) A method to distribute to neighbours the locally determined polynomial coefficients, and to resolve collision between two sets of identical polynomial coefficients from two neighbouring nodes. The proposed DTSMA has been evaluated through extensive simulations to confirm that it can indeed preserve the capability of providing a minimum throughput guarantee in the absence of the a priori global knowledge. In benchmark against the de facto distributed coordinated scheduling (DCS) in the original IEEE 802.16d mesh MAC protocol under various domestic wireless channel conditions, DTSMA outperforms in terms of packet delivery ratio and average end-to-end packet delay which are important metrics for time-sensitive audio–video applications. Simulation results also show that DTSMA outperforms TSMA in terms of average end-to-end packet delay and average delay jitter when the severity of propagation impairment is high.

A hybrid cycle bandwidth allocation scheme with differentiated services support in Ethernet passive optical networks

The Ethernet passive optical network (EPON) has emerged as one of the most promising solutions for next generation broadband access networks. Designing an efficient upstream bandwidth allocation scheme with differentiated services (DiffServ) support is a crucial issue for the successful deployment of EPON, carrying heterogeneous traffic with diverse quality of service (QoS) requirements. In this article, we propose a new hybrid cycle scheme (HCS) for bandwidth allocation with DiffServ support. In this scheme, the high-priority traffic is transmitted in fixed timeslots at fixed positions in a cycle while the medium- and low-priority traffic are transmitted in variable timeslots in an adaptive dynamic cycle. A suitable local buffer management scheme is also proposed to facilitate QoS implementation. We develop a novel feature providing potentially multiple transmission opportunities (M-opportunities) per-cycle for high-priority traffic. This feature is significant in improving delay and delay-variation performance. The HCS provides guaranteed services in a short-cycle scale for delay and jitter sensitive traffic while offering guaranteed throughput in a moderately long-time scale for bandwidth sensitive traffic and at the same time maximizing throughput for non-QoS demanding best-effort traffic. We develop analytical performance analysis on the deterministic delay bound for high-priority traffic and minimum throughput guarantees for both high- and medium-priority traffic. On the other hand, we also conduct detailed simulation experiments. The results show a close agreement between analytical approach and simulation. In addition, the simulation results show that the HCS scheme is able to provide excellent performance in terms of average delay, delay-variation, and throughput as compared with previous approaches.

Combined packet scheduling and call admission control with minimum throughput guarantee in wireless networks

In this paper, a scheduling problem is considered in the cellular network where there exist CBR (constant bit rate) users requiring exact minimum average throughput guarantee, and EMG (elastic with minimum guarantee) users requiring minimum average throughput guarantee and more if possible. We propose a combined scheduling and call admission control algorithm that exactly guarantees the minimum requirements of CBR and EMG users, and then allocates the leftover capacity to EMG users. The proposed algorithm is developed using utility maximization problem without minimum throughput constraints and newly defined utility functions. In the algorithm, it is easy to give priority to particular users so that their requirements are guaranteed prior to any other user. Moreover, the priority structure enables the proposed measurement-based call admission control algorithm to perform admission trial without affecting the minimum required throughput of ongoing users. We verify the performance of our algorithm through mathematical analysis and simulations.

Mobility control for throughput maximization in ad hoc networks

AbstractPhysical topology of an ad hoc wireless network imposes fundamental limits on its throughput capacity. In this work, we present a network design algorithm for configuring node locations in an 802.11 ad hoc network with the goal of improving the throughput capacity of the network. Given a network configuration (i.e., a mapping of network nodes to physical locations), we establish an inverse proportional relationship between the interference degree of the network and the guaranteed link‐throughput. Motivated by this observation, we present an algorithm which progressively guides the network towards better configurations with lower interference degrees, which in turn increases the network's throughput capacity. Packet level simulations using the ns‐2 simulator shows that the reconfigured topologies obtained by our algorithm consistently outperform the original network topologies for throughput and delay‐related metrics. In particular, for many cases, we observed over 100% increase in the total network throughput and the minimum guaranteed throughput, over 60% increase in throughput fairness and over 50% reduction in the mean‐service delay of packets. Our algorithm admits a simple distributed implementation and can be viewed as a distributed mobility control primitive for improving the throughput performance of mobile ad hoc networks. Alternately, our techniques can also be employed by a centralized designer during network creation time to obtain a network configuration with a high throughput capacity. To the best of our knowledge, ours is the first work which explores the use of guided network configuration strategies for improving the throughput capacity in ad hoc wireless networks. Copyright © 2006 John Wiley & Sons, Ltd.

GTFRC, a TCP friendly QoS-aware rate control for DiffServ Assured Service

This study addresses the end-to-end congestion control support over the DiffServ Assured Forwarding (AF) class. The resulting Assured Service (AS) provides a minimum level of throughput guarantee. In this context, this article describes a new end-to-end mechanism for continuous transfer based on TCP-Friendly Rate Control (TFRC). The proposed approach modifies TFRC to take into account the QoS negotiated. This mechanism, named gTFRC, is able to reach the minimum throughput guarantee whatever the flow's RTT and target rate. Simulation measurements and implementation over a real QoS testbed demonstrate the efficiency of this mechanism either in over-provisioned or exactly-provisioned network. In addition, we show that the >frc mechanism can be used in the same DiffServ/AF class with TCP or TFRC flows.

Minimum TCP throughput guarantee on minimum rate guaranteed networks

The performance of Transmission Control Protocol (TCP) entirely depends on the network traffic conditions. It will be greatly advantageous if the throughput of the TCP is always maintained above a certain level. However, it is difficult to guarantee minimum throughput for each TCP connection even when enough bandwidth is reserved for it. This is because the TCP congestion control algorithm makes its transmission rate fluctuate so that, in some cases, the connection cannot fully utilize the portion of the bandwidth reserved for it. We propose a slightly modified traffic shaper that can help maintain the TCP transmission rate. It normally regulates traffic just as the conventional shapers, but when necessary, it adjusts its transmission rate depending on its own state, namely its queue length and packet-receiving rate, without explicit notification of the network conditions. It only requires a simple modification of the conventional shapers. However, this simple modification can improve TCP performance significantly and help guarantee minimum throughput when the network guarantees minimum bandwidth for the connection. Simulation results are presented for performance evaluation. The proposed scheme is practical in that it does not require end-host modifications. Also, it has scalability since it requires per-flow management only in the network access routers and not in the core routers.

Robust bounds and throughput guarantees for closed multiclass queueing networks

To use queueing theory for analyzing real computing systems, we may make assumptions that are strictly speaking untrue. The problem is especially severe for multiclass systems with widely differing service times. This paper provides an exact analysis for bounds for systems with greatly relaxed assumptions. Service times can have arbitrary NBUE distributions, different by class even at FIFO nodes. Routing can be arbitrary, including dependencies along the route, provided the number of visits to a device per response cycle is random with a known expectation. Only the mean service time and mean visit rates at nodes need to be specified. A new lower throughput bound is found which gives a minimum guaranteed throughput for each class; together with the familiar multiclass asymptotic upper bounds they give a convex feasible region in a multidimensional throughput space. A detailed analysis is given for queueing network models of systems with infinite-server nodes as well as queueing nodes with various service disciplines: FIFO, processor sharing, and priority (preemptive as well as non-preemptive) scheduling. Because the feasible region may be a complicated shape which is difficult to visualize, the results can be re-interpreted as a set of bounds on the separate throughputs. This is equivalent to a circumscribed rectangular region called the “robust box bounds”. Computation of these bounds is carried out by a novel technique based on interval arithmetic as implemented in BNR Prolog language. A method for computing approximate system throughput from the box bounds is also proposed in the paper. Using Little's law and utilization law with the bounds on throughput bounds on response times and device utilizations are obtained. These analytic techniques can be effectively utilized for analyzing the performance of distributed systems as well as other types of computing systems.