Cross-layer Model Research Articles

Cross-Layer Modeling of Dynamic Service Addition Performance in IEEE 802.16 Networks

The IEEE 802.16 standard enables high transmission rates and supports mobility and quality of service (QoS) in cellular networks. To achieve such objectives, multicarrier transmission based on orthogonal frequency-division multiplexing (OFDM) is used and is combined with a connection-oriented approach at the medium access control (MAC) layer. Such connections, or service flows, are dynamically established using a three-way handshake protocol called the Dynamic Service Addition (DSA) protocol. This paper proposes an analytical model to analyze the performance of the DSA protocol in terms of signaling blocking, admission control blocking, and latency in an IEEE 802.16 network. The analytical model based on queueing theory is combined with the quality estimation of the OFDM-based physical layer, using a cross-layer approach. Two mobile radio channels have been considered to validate the analytical model: a block flat-fading channel and a time-varying frequency-selective fading channel in the presence of mobility at different speeds. The analytical model closely matches the results obtained by computer simulations for both types of radio channels. The impact of mobility on the DSA performance is assessed under various settings of DSA parameters and mobile station (MS) speeds. The results highlight the different impacts of DSA parameters on the various performance metrics. Such an evaluation is fundamental for optimally selecting the DSA parameters while taking into account the channel quality. In addition, this paper shows the need for the management of the service flows activated without knowledge of the involved MS, particularly in the case of high error rates.

An OPNET based novel cross-layer model for analyzing SOA-based information services

Service Oriented Architecture (SOA) based information systems and services are finding wider applicability in complex, mission-critical operational environments. In order to effectively help design and prepare information sharing services for such complex operational environments, designers have to consider various architecture tradeoffs and interactions across the SOA application, communication middleware and network infrastructure layers. In this paper, we describe a novel modeling and analysis framework for analyzing and evaluating the performance of SOA-based information services and their myriad design & deployment options over varying network infrastructures under varying conditions of network load. Our modeling framework developed in OPNET defines critical Measures of Effectiveness (MOEs) to characterize performance of candidate applications considering the SOA interaction characteristics, as well as the underlying SOA communication middleware and network infrastructures. Our modeling framework provides the ability to both analyze as-is application scenarios as well as potential alternative architectures that may include differing application characteristics (e.g. increase in the application’s data generation rate), varying the SOA interaction characteristics (e.g. pub-sub vs. requestresponse communication styles, use of JSON vs. XML for data-interchange, use of SAML security tokens etc.) or network characteristics (e.g. varying background traffic and latency). A key feature of our modeling framework is the ability to uncover issues resulting from adverse or unforeseen interactions between the Application, SOA interactions and Network layers. Our initial results on evaluating Information sharing services across enterprise inter-agency infrastructures interconnected by public/private networks demonstrate the viability of our cross-layer modeling framework.

Performance Evaluation of Cellular Networks Offering TV Services

In this paper, the capacity of orthogonal frequency-division multiple-access (OFDMA) networks is evaluated when serving mobile TV traffic. To introduce the service within the network, we develop analytical cross-layer models to assess the performance of the system when carrying TV calls over unicast connections. The presented cross-layer analysis is general and can be adapted to all types of multimedia services. We then focus on a TV-specific capacity analysis, exploiting the possibility of broadcasting TV channels over point-to-multipoint (PtM) connections. This includes investigating an enhanced broadcast solution where the modulation is dynamically adapted to the radio conditions of connected TV users. The more complete broadcast solution over single-frequency networks (SFNs) is then evaluated, based on a novel physical-layer model integrating the combined signal gain from neighboring cells. We finally show how to maximize the system capacity through a secondary usage of the SFN resources by elastic traffic. The presented models are evaluated using numerical applications and further validated through network simulations.

Cross-Layer Resource Allocation Model for Cellular-Relaying Network Performance Evaluation

The enhancement of cellular networks with relaying technologies is expected to bring significant technoeconomic benefits at the expense of more complex resource allocation. Suitable models for solving network dimensioning problems in cellular-relaying networks must handle radio resource allocation among hundreds of links and tackle interactions between networking layers. For this purpose, we propose a novel cross-layer resource allocation model based on average interference and ideal rate adaptation for the physical layer (PHY), time shares for the medium access layer, and fluid flows for the transport and network layers. We formulate a centralized social welfare maximization problem. When the routes are selected with an a priori algorithm, we show that the resource allocation problem admits an equivalent convex formulation. We show a numerical example for how to use the proposed framework for configuring the backhaul link in a practical relaying network. The overall problem of selecting routes and allocating time shares and link rates is nonconvex. We propose an iterative suboptimal algorithm to solve the problem based on a novel approximation of PHY. We state and prove several convergence properties of the algorithm and show that it typically outperforms routing based on signal-to-noise ratio only.

MIMO Muti-Hop Wireless Networks

综述了多跳无线网络MIMO(multiple-input multiple-output)技术的研究进展,分析了MIMO技术的引入对多跳无线网络各层及整体设计的影响.以跨层协议设计为重点,详细介绍了当前典型的基于MIMO的多跳无线网络协议算法的核心机制,并比较分析了这些算法的特点和性能差异与存在的缺陷.最后,结合本领域内的研究现状,指出了基于MIMO的多跳无线网络走向实际工程应用环境所亟待解决的关键问题,指出了基于MIMO技术设计自适应调整、高性能多跳无线网络跨层模型及协议的重要性.;After surveying the research of MIMO (multiple-input multiple-output) multi-hop wireless networks, this paper analyzes the MIMO mechanisms for multi-hop wireless networks and discusses the effect of MIMO upon separate network layer and the whole design of multi-hop wireless networks. Focusing on cross-layer design, it expounds the fundamental mechanism of existing representative protocols and algorithms for MIMO-based multi-hop wireless networks, and compares and analyzes their characteristics, performance as well as deficiencies. Finally, by pointing out current research development, it summarizes the restrictions to the practical applications of MIMO-based multi-hop wireless networks, and proposes the importance of designing an adaptive and high performance cross-layer model which based on MIMO technology for multi-hop wireless networks.

Modeling TCP SACK performance over wireless channels with semi-reliable ARQ/FEC

Providing reliable data communications over wireless channels is a challenging task because time-varying wireless channel characteristics often lead to bit errors. These errors result in loss of IP packets and, consequently, TCP segments encapsulated into these packets. Since TCP cannot distinguish packet losses due to bit corruption from those due to network congestion, any packet loss caused by wireless channel impairments leads to unnecessary execution of the TCP congestion control algorithms and, hence, sub-optimal performance. Automatic Repeat reQuest (ARQ) and Forward Error Correction (FEC) try to improve communication reliability and reduce packet losses by detecting and recovering corrupted bits. Most analytical models that studied the effect of ARQ and FEC on TCP performance assumed that the ARQ scheme is perfectly persistent (i.e., completely reliable), thus a frame is always successfully transmitted irrespective of the number of transmission attempts it takes. In this paper, we develop an analytical cross-layer model for a TCP connection running over a wireless channel with a semi-reliable ARQ scheme, where the amount of transmission attempts is limited by some number. The model allows to evaluate the joint effect of stochastic properties of the wireless channel characteristics and various implementation-specific parameters on TCP performance, which makes it suitable for performance optimization studies. The input parameters include the bit error rate, the value of the normalized autocorrelation function of bit error observations at lag 1, the strength of the FEC code, the persistency of ARQ, the size of protocol data units at different layers, the raw data rate of the wireless channel, and the bottleneck link buffer size.

Blockage and directivity in 60 GHz wireless personal area networks: from cross-layer model to multihop MAC design

We present a cross-layer modeling and design approach for multigigabit indoor wireless personal area networks (WPANs) utilizing the unlicensed millimeter (mm) wave spectrum in the 60 GHz band. Our approach accounts for the following two characteristics that sharply distinguish mm wave networking from that at lower carrier frequencies. First, mm wave links are inherently directional: directivity is required to overcome the higher path loss at smaller wavelengths, and it is feasible with compact, low-cost circuit board antenna arrays. Second, indoor mm wave links are highly susceptible to blockage because of the limited ability to diffract around obstacles such as the human body and furniture. We develop a diffraction-based model to determine network link connectivity as a function of the locations of stationary and moving obstacles. For a centralized WPAN controlled by an access point, it is shown that multihop communication, with the introduction of a small number of relay nodes, is effective in maintaining network connectivity in scenarios where single-hop communication would suffer unacceptable outages. The proposed multihop MAC protocol accounts for the fact that every link in the WPAN is highly directional, and is shown, using packet level simulations, to maintain high network utilization with low overhead.

Advances in cooperative and relay communications [Guest Editorial

The six articles in this feature topic cover various aspects of cooperative and relay communications involving physical later (PHY), MAC, network layer, and cross-layer modeling and design.

A Cross-Layer Model for Video Multicast Based TCP-Adaptive FEC over Heterogeneous Networks

In this article, we present a simple cross-layer model that leads to the optimal throughput of multiple users for multicasting MPEG-4 video over a heterogeneous network. For heterogeneous wired-to-wireless network, at the last wireless hop there are bit errors associated with the link-layer packets that are arising in the wireless channel, in addition of overflow packet dropping over wired links. We employ a heuristic TCP function to optimize the cross-layer model of data link and physical (radio-link) layer. An adaptive Forward-Error-Correction (FEC) scheme is applied at the byte-level as well as at the packet-level. The corresponding optimal video quality can be evaluated at each client end. The results show that a server can significantly adapt to the bandwidth and FEC codes to maximize the video quality of service (QoS) in terms of temporal scaling when a maximum network throughput for each client is reached.

Resource allocation for end-to-end QoS provisioning in a hybrid wireless WCDMA and wireline IP-based DiffServ network

In the future UMTS network, the heterogeneous traffics of multimedia services demand various QoS provisioning. At the same time, the seamlessly conveying of information between mobile users and a hybrid network requires the networking from wireless to wireline domains. However, in both academia and industries, the end-to-end QoS provisioning in the integration of wireline and wireless networks remains a challenge. In this paper, a modeling of a hybrid wireless WCDMA and wireline IP-based DiffServ network is presented to investigate the resource allocation for end-to-end QoS provisioning for multimedia services. In the wireless domain, the mathematical modeling of the cross-layer model including the physical layer, the link layer and the network layer is built. The connection admission control scheme is implemented based on the cross-layer model to determine the amount of resource for different services. In the wireline domain, we define the mapping of QoS classes between UMTS and DiffServ networks according to different QoS requirements. We propose a bandwidth allocation scheme to provide satisfactory packet loss and delay guarantee in DiffServ networks. The final end-to-end admission control scheme combines the resource allocation and admission control in both wireless and wireline domains. The analytical and simulation results show that the proposed resource allocation and admission control schemes work cooperatively in the presented hybrid wireless and wireline networks to guarantee the end-to-end QoS requirements for multimedia services.

Using MPEG-21 for cross-layer multimedia content adaptation

This paper presents a cross-layer model— formulated using interoperable description formats—for the adaptation of scalable H.264/MPEG-4 AVC (i.e., SVC) content in a video streaming system operating on a Wireless LAN access network without QoS mechanisms. SVC content adaptation on the server takes place on the application layer using an adaptation process compliant with the MPEG-21 Digital Item Adaptation (DIA) standard, based on input comprised of MPEG-21 DIA descriptions of content and usage environment parameters. The latter descriptions integrate information from different layers, e.g., device characteristics and packet loss rate, in an attempt to increase the interoperability of this cross-layer model, thus making it applicable to other models. For the sake of deriving model parameters, performance measurements from two wireless access point models were taken in account. Throughout the investigation it emerged that the behavior of the system strongly depends on the access point. Therefore, we investigated the use of end-to-end-based rate control algorithms for steering the content adaptation. Simulations of rate adaptation algorithms were subsequently performed, leading to the conclusion that a TFRC-based adaptation technique (TCP-Friendly Rate Control) performs quite well in adapting to limited bandwidth and varying network conditions. In the paper we demonstrate how TFRC-based content adaptation can be realized using MPEG-21 tools.

Error-Resilient Video Encoding and Transmission in Multirate Wireless LANs

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, we present a cross-layer approach for video transmission in wireless LANs that employs joint source and application-layer channel coding, together with rate adaptation at the wireless physical layer (PHY). While the purpose of adopting PHY rate adaptation in modern wireless LANs like the IEEE 802.11a/b is to maximize the throughput, in this paper we exploit this feature to increase the robustness of wireless video. More specifically, we investigate the impact of adapting the PHY transmission rate, thus changing the throughput and packet loss channel characteristics, on the rate-distortion performance of a transmitted video sequence. To evaluate the video quality at the decoder, we develop a cross-layer modeling framework that considers jointly the effect of application-layer joint source-channel coding (JSCC), error concealment, and the PHY transmission rate. The resulting models are used by an optimization algorithm that calculates the optimal JSCC allocation for each video frame, and PHY transmission rate for each outgoing transport packet. The comprehensive simulation results obtained with the H.264/AVC codec demonstrate considerable increase in the PSNR of the decoded video when compared with a system that employs separately JSCC and PHY rate adaptation. Furthermore, our performance analysis indicates that the optimal PHY transmission rate calculated by the proposed algorithm, can be significantly different when compared with rate adaptation algorithms that target throughput improvement. </para>

System-level Verification of Multi-Core Embedded Systems using Timed-Automata

A key challenge of implementing an embedded systems application on a heterogeneous multi-core platform is to find the right mapping of the application onto the execution platform. The right mapping is dependent on the characteristics of the platform, i.e. processors and the network connecting them, as well as the application. As embedded systems are heavily resource constrained and often safety-critical, there is a strong desire to be able to reason about properties of the system at an early stage in the design process, i.e. at the system-level. In this paper, we present a system-level modelling framework which allows for cross-layer modelling and verification, covering the application layer, middelware layer (RTOS), and hardware layer. The modelling framework allows the designer to verify the impact of execution platform and application mapping on the schedulability (meeting hard real-time requirements), power consumption and memory utilization, while taking communication into account. The modelling framework is implemented using timed-automata in UPPAAL, Behrmann et al. [2004] and the feasibility of the framework is illustrated through a case-study of a real-time multimedia application consisting of 3 applications with a total of 103 tasks executing on a platform with 4 cores.

Cross-layer modeling for quality of service guarantees over wireless links

We propose a cross-layer approach to investigate the impact of physical-layer infrastructure on data-link-layer quality-of-service (QoS) performance over wireless links in mobile networks. At the physical layer, we take multiple-input-multiple-output (MIMO) diversity schemes as well as adaptive-modulation-and-coding (AMC) techniques into account. At the data-link layer, our focus is on how this physical-layer infrastructure influences the real-time multimedia delay-bound QoS performance. To achieve this goal, we first model the physical-layer service process as a finite-state Markov chain (FSMC). Based on this FSMC model, we then characterize the QoS performance at data-link-layer using the effective capacity approach, which turns out to be critically important for the statistical QoS guarantees over wireless links in mobile networks. We also investigate the impact of physical-layer power control and channel-state information (CSI) feedback delay on the QoS performance. The numerical results obtained demonstrate that our proposed cross-layer model can efficiently characterize the interactions between the physical-layer infrastructure and data-link-layer QoS performance.

ARTS: A SystemC-based framework for multiprocessor Systems-on-Chip modelling

One of the challenges of designing a heterogeneous multiprocessor SoC is to find the right partitioning of the application for the target platform architecture. The right partitioning is dependent on the characteristics of the processors and the network connecting them as well as the application. We present an abstract system-level modelling and simulation framework (ARTS) which allows for cross-layer modelling and analysis covering the application layer, middleware layer, and hardware layer. ARTS allows MPSoC designers to explore and analyze the network performance under different traffic and load conditions, consequences of different task mappings to processors (software or hardware) including memory and power usage, and effects of RTOS selection, including scheduling, synchronization and resource allocation policies. We present the application and platform models of ARTS as well as their implementation in SystemC. We present the usage of the ARTS framework as seen from platform developers' point of view, where new components may be created and integrated into the framework, and from application designers' point of view, where existing components are used to explore possible implementations. The latter is illustrated through a case study of a real-time, smart phone application consisting of 5 applications with a total of 114 tasks mapped onto different platforms. Finally, we discuss the simulation performance of the ARTS framework in relation to scalability.

Advances in Mobile Multimedia Networking and QoS [Guest Editorial

The six articles in this special section cover various aspects of mobile multimedia broadcasting involving physical layer (PHY), medium access control (MAC), cross-layer modeling and design, security, and services. The articles are summarized here.

Cross-Layer Modeling for QoS-Driven Multimedia Multicast/Broadcast over Fading Channels in [Advances in Mobile Multimedia

In this article we propose a cross-layer design model for multimedia multicast/broadcast services to efficiently support the diverse quality of service requirements over mobile wireless networks. Specifically, we aim at achieving high system throughput for multimedia multicast/broadcast while satisfying QoS requirements from different protocol layers. First, at the physical layer, we propose a dynamic rate adaptation scheme to optimize the average throughput subject to the loss rate QoS constraint specified from the upper-layer protocol users. We investigate scenarios with either independent and identically distributed (i.i.d.) or non-i.i.d. fading channels connecting to different multicast receivers. Then, applying the effective capacity theory at the data link layer, we study the impact of the delay QoS requirement (i.e., QoS exponent) on the multimedia data rate of mobile multicast/broadcast that our proposed scheme can support. Also presented are simulation results which show the trade-off among different QoS metrics and the performance superiority of our proposed scheme as compared to the other existing schemes.

Cross-layer modeling of capacity in wireless networks: Application to UMTS/HSDPA, IEEE802.11 WLAN and IEEE802.16 WiMAX

We investigate in this work the cross-layer modeling of the capacity of wireless systems in the presence of two types of flows: streaming and elastic, under a dynamic configuration wherein users join the system and leave it after a finite duration. For streaming traffic, this duration is independent of the resources these flows get from the network. This is not the case of (TCP-based) elastic traffic whose flows have a service rate that is proportional to the share of resources each flow gets from the network, as obtained in a cross-layer manner from lower layers. We focus in this paper on the MAC/PHY layer and consider three different types of scheduling: CDMA with opportunistic scheduling, used in UMTS/HSDPA, CSMA/CA in use in IEEE802.11 WLAN and OFDMA as in IEEE802.16 WiMax.

Resilience of all-optical network architectures under in-band crosstalk attacks: a probabilistic graphical model approach

An important question for secure all-optical networks (AONs) is how to incorporate security against attacks in the design and engineering of network architectures. In this work, we study the resilience of AON architectures under in-band crosstalk attacks. Crosstalk attack propagation depends on both optical devices at the physical layer and wavelength usage at the network layer. This motivates us to employ probabilistic graphical models to model attack propagation. At the physical layer, we use a directed probabilistic graph (Bayesian Belief Network) to model the attack propagation under static network traffic and a given source of attack. At the network layer, we use an undirected probabilistic graph to represent the probability distribution of active connections in the network. The cross-layer model is obtained by combining the physical- and the network-layer models into a factor graph representation. Graphical models provide an explicit representation of interactions between the physical- and the network layer. Furthermore, graphical models facilitate derivations of analytical results on resilience with respect to physical-layer vulnerability, physical topology, and network load. Specifically, we derive bounds on the network resilience for regular topologies. For ring, star, and mesh-torus networks with link-shortest path routing and all-to-all traffic, we show that the average network resilience loss grows linearly with respect to the network load when the network load is small, and polynomially with respect to the probability of attack propagation from node to node along the attacker's route. In addition, numerical results suggest that the sum-product algorithm based on the factor graph representation can be used for computationally efficient evaluation of network resilience for irregular/large topologies

A MAC and PHY Cross-Layer Analytical Model for the Goodput an Networks Operating Under Basic Access and RTS/CTS DCF Schemesd Delay of IEEE 802.11a

We have developed a theoretical cross-layer model that allows assessing the goodput and delay of IEEE 802.11 local area networks (WLANs) operating simultaneously under the distributed coordination function (DCF) basic access (BA) and request-to-send/clear-to-send (RTS/CTS) medium access control (MAC) protocols under saturated traffic over correlated fading channels. Acomparison between numerical and simulation results is carried out assuming the IEEE 802.11a PHY layer.