Throughput Guarantees Research Articles

Providing throughput guarantees in heterogeneous wireless mesh networks

In this paper, we propose to provide throughput guarantees in heterogeneous wireless mesh networks by jointly optimizing routing and Medium Access Control configuration. Our solution is based on the notion of linearized capacity region, which provides a technology-independent way of representing the capacity of a wireless link thereby hiding the technology specifics to the upper layers. From the available capacity of the underlying links as given by the linearized capacity region, we propose two routing algorithms based on multipath and single path that find optimal paths for all the flows in the network given their throughput requirements. The throughput allocation resulting from routing is then provided to each link, which uses this information to optimize its technology-specific Medium Access Control parameters. The proposed approach is evaluated in a heterogeneous scenario comprising Wireless Local Area Networks WLAN and Worldwide Interoperability for Microwave Access WiMAX technologies and is shown to outperform previous solutions by at least a factor of 2.Copyright © 2012 John Wiley & Sons, Ltd.

Throughput Guarantee for Maximal Schedulers in Sensor Networks with Cooperative Relays

This paper addresses the question of throughput guarantees through distributed scheduling in sensor networks with relay based cooperative communications. We prove that in a single frequency network with bidirectional, equal power communication and low complexity distributed maximal scheduling attains a guaranteed fraction of the maximum throughput region in arbitrary wireless networks. We also show that the guarantees are tight in the sense that they cannot be improved any further with maximal scheduling. Simulation results are also provided to show the performance of a distributed, maximal scheduling algorithm under different network settings.

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.

Opportunistic scheduling policies for improved throughput guarantees in wireless networks

Offering throughput guarantees for cellular wireless networks, carrying real-time traffic, is of interest to both the network operators and the customers. In this article, we formulate an optimization problem which aims at maximizing the throughput that can be guaranteed to the mobile users. By building on results obtained by Borst and Whiting and by assuming that the distributions of the users' carrier-to-noise ratios are known, we find the solution to this problem for users with different channel quality distributions, for both the scenario where all the users have the same throughput guarantees, and the scenario where all the users have different throughput guarantees. Based on these solutions, we also propose two simple and low complexity adaptive scheduling algorithms that perform significantly better than other well-known scheduling algorithms. We further develop an expression for the approximate throughput guarantee violation probability for users in time-slotted networks with the given cumulants of the distribution of bit-rate in a time-slot, and a given distribution for the number of time-slots allocated within a time-window.

Dynamic bandwidth management in IEEE 802.11-based multihop wireless networks

In this paper, we propose a new protocol named dynamic regulation of best-effort traffic (DRBT) which supports quality of service (QoS) throughput guarantees and provides a distributed regulation mechanism for best-effort traffic in multihop wireless networks. By adapting dynamically the rate of best-effort traffic at the link layer, DRBT increases the acceptance ratio of QoS flows and provides a good use of the remaining resources through the network. Our protocol also provides an accurate method to evaluate the available bandwidth in IEEE 802.11-based ad hoc networks which is able to differentiate QoS applications from best-effort traffic. Through extensive simulations, we compare the performance of our proposal scheme with some others protocols like QoS protocol for ad hoc real-time traffic for instance.

Joint congestion control and distributed scheduling for throughput guarantees in wireless networks

We consider the problem of throughput-optimal cross-layer design of wireless networks. We propose a joint congestion control and scheduling algorithm that achieves a fraction 1/ d I ( G ) of the capacity region, where d I ( G ) depends on certain structural properties of the underlying connectivity graph G of the wireless network, and also on the type of interference constraints. For a wide range of wireless networks, d I ( G ) can be upper bounded by a constant, independent of the number of nodes in the network. The scheduling element of our algorithm is the maximal scheduling policy. Although this scheduling policy has been considered in several previous works, the challenges underlying its practical implementation in a fully distributed manner while accounting for necessary message exchanges have not been addressed in the literature. In this article, we propose two algorithms for the distributed implementation of the maximal scheduling policy accounting for message exchanges, and analytically show that they still can achieve the performance guarantee under the 1-hop and 2-hop interference models. We also evaluate the performance of our cross-layer solutions in more realistic network settings with imperfect synchronization under the Signal-to-Interference-Plus-Noise Ratio (SINR) interference model, and compare with the standard layered approaches such as TCP over IEEE 802.11b DCF networks.

On the Complexity of Scheduling in Wireless Networks

We consider the problem of throughput-optimal scheduling in wireless networks subject to interference constraints. We model the interference using a family of -hop interference models, under which no two links within a -hop distance can successfully transmit at the same time. For a given , we can obtain a throughput-optimal scheduling policy by solving the well-known maximum weighted matching problem. We show that for , the resulting problems are NP-Hard that cannot be approximated within a factor that grows polynomially with the number of nodes. Interestingly, for geometric unit-disk graphs that can be used to describe a wide range of wireless networks, the problems admit polynomial time approximation schemes within a factor arbitrarily close to 1. In these network settings, we also show that a simple greedy algorithm can provide a 49-approximation, and the maximal matching scheduling policy, which can be easily implemented in a distributed fashion, achieves a guaranteed fraction of the capacity region for "all ." The geometric constraints are crucial to obtain these throughput guarantees. These results are encouraging as they suggest that one can develop low-complexity distributed algorithms to achieve near-optimal throughput for a wide range of wireless networks.

The Concurrent Matching Switch Architecture

Network operators need high-capacity router architectures that can offer scalability, provide throughput guarantees, and maintain packet ordering. However, current centralized crossbar-based architectures cannot scale to fast line rates and high port counts. On the other hand, while load-balanced switch architectures that rely on two identical stages of fixed configuration meshes appear to be an effective way to scale Internet routers to very high capacities, they incur a large worst-case packet reordering that is at best quadratic to the switch size. In this paper, we introduce the concurrent matching switch (CMS) architecture, which also uses two identical stages of fixed configuration meshes with the same scalability properties as current load-balanced routers. However, by adopting a novel contention-resolution architecture that is scalable and distributed, the CMS architecture enforces packet ordering throughout the switch. Using the CMS architecture, we show that scalability, 100% throughput, packet ordering, and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</i> (1) amortized time complexity with sequential hardware per linecard can all be achieved. We further demonstrate a delay analysis for the CMS architecture.

Iterative MIMO sphere decoding throughput guarantees under realistic channel conditions

Block-based early termination has been proposed for depth-first based MIMO sphere decoders (SD) in order to provide throughput guarantees. We show in this letter that such termination incurs, even under simple tree and norm choices, significant overhead in the required number of iterations under realistic channel conditions due to the depth-first search's highly variable complexity (number of iterations to achieve a target performance). We propose the use of a constrained version of Dijkstra's metric-first search which exhibits indistinguishable performance while avoiding the impractical memory requirements of Dijkstra's search. We show that for a 4×4 64-subcarrier OFDM system, the proposed alternative achieves ~2x decrease in complexity as compared to the depth-first SD with block early termination for the same throughput guarantee.

An Algorithm for Improving Throughput Guarantee of Topology-Transparent MAC Scheduling Strategy

Topology-transparent MAC scheduling strategies nowadays are all based on combinatorial design. To get throughput guarantee, a cover-free set is output as scheduling strategy of network. In this paper, we aim to modify the cover-free set so that better throughput can be guaranteed. At the first step, the redundant slot of the cover-free set is proposed and found to have negative influence on the minimal guaranteed throughput. Second, we prove that any subset of a cover-free set is still a cover-free set after its redundant slots were squashed out. Our algorithm chooses the subset which has the maximal number of redundant slots, squashes all of its redundant slots, and then designates it as the network scheduling strategy. Therefore, better through- put can be guaranteed if the squashed subset is adopted as network scheduling strategy. For any topology- transparent node scheduling strategy, both the increased minimal throughput and decreased maximal transmission delay can be gotten by just using our algorithm as an extra accessory.

Flow-based packet-mode load-balancing for parallel packet switches

Parallel Packet Switch (PPS) is broadly used in designing large-capacity switching fabrics, since it resolves the bottlenecks of scheduling algorithm, memory bandwidth, and serial transmission technology simultaneously. Current packet-based load-balancing algorithms for PPS cannot preserve intra-flow packet orders without costly reordering mechanisms. In this paper, we study the feasibility of flow-based packet-mode load-balancing algorithm, which thoroughly avoids packet out-of-order. Through performance analysis based on traffic model from real-trace, we show that given moderate speedups, all the three proposed flow-based algorithms can provide throughput and delay guarantees under admissible traffic input. Trace-driven simulations are carried out to verify our results.

Practical scheduling schemes with throughput guarantees for multi-hop wireless networks

In wireless communication systems, the interference between links results in a challenging scheduling problem. A K-hop interference model is defined as one for which no two links within K-hops can successfully transmit at the same time (note that IEEE 802.11 DCF corresponds to a 2-hop interference model). For a given K, a throughput-optimal scheduler needs to solve a maximum weighted matching problem subject to the K-hop interference constraints. Previous work has mainly focused on developing scheduling algorithms with performance guarantees for the primary interference model (K=1). For K>=2, the problem is NP-Complete and cannot be approximated within a constant factor by any polynomial time algorithm. Our algorithm achieves at least a constant fraction (1/3) of the capacity region under any K-hop interference model. The simplicity of the solution and low control complexity makes it highly amenable for practical implementation. Simulation results show that when the communication overhead is taken into account, the delay characteristics of the proposed scheme may be better than the ideal optimal scheduler (given the prices at all the links, the ideal scheduler computes the optimal schedule instantaneously).

Supporting real-time traffic in multihop vehicle-to-infrastructure networks

In this paper, a new Controlled Vehicular Internet Access protocol with QoS support (CVIA-QoS) is introduced. CVIA-QoS employs fixed gateways along the road which perform periodic admission control and scheduling decisions for the packet traffic in their service area. The CVIA-QoS protocol is based on Controlled Vehicular Internet Access (CVIA) protocol that was designed only for the best-effort traffic. The most important contribution of the CVIA-QoS protocol is providing delay bounded throughput guarantees for soft real-time traffic, which is an important challenge especially for a mobile multihop network. After the demands of the soft real-time traffic is met, CVIA-QoS supports the best-effort traffic with the remaining bandwidth. Simulation results confirm that in CVIA-QoS protocol, the real-time throughput is not affected from the best-effort load and its delay is much smaller than CVIA delay when both the real-time and best-effort load exist in the channel. It has been observed that, unlike, CVIA-QoS, IEEE 802.11e with multi-hopping suffers from lower throughput and high number of real-time packet drops.

On Throughput Guarantee of Aloha-Like Multi-Hop Wireless Networks

Providing Quality of Service (QoS) is one of significant issues for multimedia traffic. One approach to achieve the requested QoS is to characterize the traffic flows and guarantee their committed throughput. In a typical multi-hop wireless ad hoc network, determining the feasibility for a given set of flow characteristics is challenging due to the multi-user interference problem. To that end, this paper presents the following contributions. First, we describe a simple Aloha-like Medium Access Control (MAC) protocol that enables each flow to maintain its requested bandwidth, and thus is suitable for multimedia traffic. Second, we propose a bandwidth feasibility algorithm based on the Variable Elimination (VE) technique. The bandwidth feasibility algorithm determines whether or not a given network can support a set of flows of certain bit rates. Simulations indicate that our solution can precisely control the bit rates over all hosts while providing the throughput guarantees.

Design of an Area-Efficient and Low-Power Hierarchical NoC Architecture Based on Circuit Switching

This paper presents a hierarchical NoC architecture to support GT (Guaranteed Throughput) signals to process multimedia data in embedded systems. The architecture provides a communication environment that meets the diverse conditions of communication constraints among IPs in power and area. With a system based on packet switching, which requires storage/control circuits to support GT signals, it is hard to satisfy design constraints in area, scalability and power consumption. This paper proposes a hierarchical 4 × 4 × 4 mesh-type NoC architecture based on circuit switching, which is capable of processing GT signals requiring high throughput. The proposed NoC architecture shows reduction in area by 50.2% and in power consumption by 57.4% compared with the conventional NoC architecture based on circuit switching. These figures amount to by 72.4% and by 86.1%, when compared with an NoC architecture based on packet switching. The proposed NoC architecture operates in the maximum throughput of 19.2Gb/s.

A low-power high-throughput link splitting router for NoCs

In this paper, we propose a technique for lowering the latency of the communication in a NoC (network on chip). The technique, which can support two qualities of service (QoS), i.e., the guaranteed throughput (GT) and best effort (BE), is based on splitting a wider link into narrower links to increase throughput and decrease latency in the NoC. In addition, to ease the synchronization and reduce the crosstalk, we use the 1-of-4 encoding for the smaller buses. The use of the encoding in the proposed NoC architecture considerably lowers the latency for both BE and GT packets. In addition, the bandwidth is increased while the power consumption of the links is reduced.

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.

TCP throughput guarantee in the DiffServ Assured Forwarding service: what about the results?

Since the proposition of quality of service (QoS) architectures by the Internet Engineering Task Force (IETF), the interaction between TCP and the QoS services has been intensively studied. This paper proposes to look forward to the results obtained in terms of TCP throughput guarantee in the DiffServ assured forwarding (DiffServ/AF) service and to present an overview of the different proposals to solve the problem. It has been demonstrated that the standardized IETF DiffServ conditioners such as the token bucket color marker and the time sliding window color maker were not good TCP traffic descriptors. Starting with this point, several propositions have been made, and most of them present new marking schemes in order to replace or improve the traditional token bucket color marker. The main problem is that TCP congestion control is not designed to work with the AF service. Indeed, both mechanisms are antagonists. TCP has the property to share in a fair manner the bottleneck bandwidth between flows while DiffServ network provides a level of service that is controllable and predictable. In this paper, we build a classification of all the propositions made during the past few years and compare them. As a result, we will see that these conditioning schemes can be separated into three sets of action levels and that the conditioning at the network edge level is the most accepted one. We conclude that the problem is still unsolved and that TCP, conditioned or not conditioned, remains inappropriate for the DiffServ/AF service.

Performance Optimization for Delay-Tolerant and Contention-Based Application in IEEE 802.16 Networks

IEEE 802.16 standard suite defines the air interface specifications for fixed and mobile broadband access in wireless metropolitan area networks. Although the IEEE 802.16 MAC has been well defined by various bandwidth allocation and scheduling mechanisms to support QoS for different applications, efficient bandwidth allocation still remains as an open issue. We analyze and develop a mathematical model to evaluate the performance of the contention-based and delay-tolerant applications in IEEE 802.16 networks. We focus our attentions on allocating the uplink bandwidth efficiently, the basic goal is to optimize the performance with an optimal bandwidth allocation mechanism. The results of our analysis lay out clearly that a maximum uplink throughput and a minimum number of pending bandwidth request transmission can always be acquired by optimizing the contention period size in a frame. This optimal size is also influenced by the number of terminals in the network, which is also analyzed in the later part of the paper. Our results can be used for providing probabilistic throughput guarantee and determining the optimal contention period.

Model driven middleware: A new paradigm for developing distributed real-time and embedded systems

Distributed real-time and embedded (DRE) systems have become critical in domains such as avionics ( e.g., flight mission computers), telecommunications ( e.g., wireless phone services), tele-medicine ( e.g., robotic surgery), and defense applications ( e.g., total ship computing environments). These types of system are increasingly interconnected via wireless and wireline networks to form systems of systems. A challenging requirement for these DRE systems involves supporting a diverse set of quality of service (QoS) properties, such as predictable latency/jitter, throughput guarantees, scalability, 24x7 availability, dependability, and security that must be satisfied simultaneously in real-time. Although increasing portions of DRE systems are based on QoS-enabled commercial-off-the-shelf (COTS) hardware and software components, the complexity of managing long lifecycles (often ∼15–30 years) remains a key challenge for DRE developers and system integrators. For example, substantial time and effort is spent retrofitting DRE applications when the underlying COTS technology infrastructure changes. This paper provides two contributions that help improve the development, validation, and integration of DRE systems throughout their lifecycles. First, we illustrate the challenges in creating and deploying QoS-enabled component middleware-based DRE applications and describe our approach to resolving these challenges based on a new software paradigm called Model Driven Middleware (MDM), which combines model-based software development techniques with QoS-enabled component middleware to address key challenges faced by developers of DRE systems — particularly composition, integration, and assured QoS for end-to-end operations. Second, we describe the structure and functionality of CoSMIC (Component Synthesis using Model Integrated Computing), which is an MDM toolsuite that addresses key DRE application and middleware lifecycle challenges, including partitioning the components to use distributed resources effectively, validating software configurations, assuring multiple simultaneous QoS properties in real-time, and safeguarding against rapidly changing technology.