Sherry Wang

Cooperative Service Level Agreement

With ever increasing mobility of the workforce and of the communication infrastructure itself, we will continue to see the growth in diversity of network domains and diversity of applications. The global information grid (GIG) is a prime example of such a networking environment. In most networking scenarios, the component network domains are owned and operated by different organizations. This paper discusses how to deliver end-to-end service with requisite quality of service (QoS) to such networks so that overall mission goals are maximally achieved with minimal cost while allowing autonomous operations within each component network. In particular, this paper proposes a cooperative service level agreements (SLA) approach and describes related SLA processes and roles

A resource management design for cognitive radio ad hoc networks

To fully utilize radio resources by intelligently filling in as much radio spectrum gaps as possible, the concept of cognitive radio network has been well accepted. A challenge inherent in this technology is how to build a mechanism that can allocate resource by learning and adapting to a specific radio transmission environment. In this paper, we propose a cognitive resource management scheme that is specifically designed for allocating radio resource in a cognitive radio ad hoc network (CRAHN) environment. The proposal applies cognitive processes in a cross-layer design, which acquires knowledge from the physical layer, the medium access control (MAC) layer, and application layer. It intelligently allocates resources according to traffic demands, traffic priorities, link capabilities, and link qualities.

A QoS enhanced hybrid SR-ARQ for mobile video communications

A hybrid QoS aware SR-ARQ (HQSR-ARQ) is proposed to increase the network throughput for video delivery in a bandwidth limited and error prone wireless mobile environment with certain deterministic guarantees. HQSR-ARQ balanced the pros and the cons of the conventional SR-ARQ and FEC for error control. It also utilized the layer property of MPEG to provide more network resources for important data sections within a video stream. Comprehensive computer simulations were used to compare the performance of HQSR-ARQ with a conventional SR-ARQ and the original QSR-ARQ in terms of the same QoS matrix. The results demonstrated the effectiveness and performance improvement of HQSR-ARQ.

Precedence and Quality of Service (QoS) Handling in IP Packet Networks

In military networks, precedence and preemption (P&P) and quality of service (QoS) are both required. QoS refers to meeting the performance requirements of an application (packet delay, packet loss, packet delay variation, service availability, connection set up time, connection acceptance ratio, etc.) while P&P refers to meeting the QoS requirements of the highest importance applications under congestion conditions, in which there are not enough network resources to satisfy the QoS requirements of all applications. In particular, preemption refers to taking away network resources from a lower precedence application in order to give the resources to a higher precedence application. Per Hob Behaviors (PHBs) are used by network nodes to implement QoS. A service level agreement (SLA) is a QoS contract that is used to assure that the QoS requirements of admitted applications are met by the network transport for defined traffic profiles. SLAs and P&P are often perceived to have an adversarial relationship. This paper proposes a way to resolve this conflict by making QoS PHBs precedence-aware, while remaining agnostic of the specific PHB mechanism

SIP-based VoIP experiment for sisadvantaged tactical edge networks

Session Initiation Protocol (SIP) has potential to be selected as a control plane signaling protocol for delivering real-time multimedia applications in military networks. It is necessary to study behaviors of SIP and SIP-based real-time applications as well as to understand their limitations in a tactical network environment. The goals of this study are to assess SIP signaling protocol performance and SIP-based Voice over Internet Protocol (VoIP) performance in an emulated disadvantaged tactical edge network environment and to contribute some feasible solutions.

QoS Management in Disadvantaged Tactical Environments

The tactical Network is one of the major components in DoD Global Information Grid (GIG). The key challenge of quality of service (QoS) management tactical networks is how to deal with negative factors that result from varying network capability demanding and a disadvantaged physical environment. These factors could include network mobility, dynamic network formation, unusual network protocol behaviors, communication channel fading, channel bandwidth fluctuation, as well as platform/application characteristics. This paper investigates the challenges of several well-known QoS management mechanisms in disadvantaged tactical network environments and provides some recommendations on the directions of mitigations and improvements.

QoS constrained resource allocation for multimedia wireless networks

To deliver high bandwidth demanding video traffic over the resource limited wireless systems is becoming a challenge issue. To control quality of service (QoS) of the delivery is even more difficult. A QoS constrained multilevel resource allocation scheme (QML-RA) is proposed to tackle the problem of how to flexibly allocate wireless network resources for carrying video traffic with certain QoS guarantees. This scheme utilizes the layer property of MPEG frames and considers the QoS requirements of different data sections within a video stream. It also takes the advantage of the channel allocation flexibility provided by CDMA/TDD systems and statistically assigns bandwidth to video traffic according to their QoS requirements. Moreover, an optimal smoothing technique is used to preprocess the video traffic so that bit-rate variability could be reduced, which enhances performance of QML-RA. The scheme significantly improves the channel utilization and increases the network throughput.

Reliable Session Initiation Protocol

The IP Multimedia Subsystem (IMS) is a maturing technology. It has the potential to be used in Mobile Ad Hoc Networks (MANETs) to provide multimedia Internet experience for much diversified users with a variety of applications in a highly mobile environment. The introduction of the IMS into MANETs and futuristic mobile networks face unique challenges and needs. The underlying signalling protocol for the IMS is the Session Initiation Protocol (SIP). In this chapter, we first investigate the “unreliable signalling” problem of using SIP for mobility support. Based on the investigation and the analysis, this chapter introduces an enhanced SIP signalling mechanism called Chain-Based SIP signalling (CBS) to mitigate the problem. The analytical performance analysis results will be given in the chapter as well.

Multi-Plane Network Model Realization in an Optical/RF Hybrid System

To facilitate the Quality of Service (QoS) interoperability, a multi-plane end-to-end (E2E) QoS architecture reference model has been developed. This modelprovides a network-functional-plane-based QoS architecture and defines different interfaces for composing a coherent data transfer and management. In this model, QoS functions are categorized into Data Plane, Control Plane, and Management Plane. However, a lack of sufficient network resource hinders the support for such sophisticated network architecture. A major mitigation approach is to implement an optical/Radio Frequency (RF) hybrid system. This paper proposes a resource management scheme for an optical/RF hybrid system and looks into the realization of multi-planes model in this hybrid system that supports an acceptable QoS level.

Reliability enhancement for SIP signaling in tactica environments

The importance of tactical networks that support military operations is well known in the DoD community for their ability to rapidly deploy anywhere at anytime without pre-existing infrastructure. Tactical networks provide a battle space where warfighters possess dynamic and ad hoc mobile communications to support operations against a broad array of threats. Managing mobility to provide undisrupted network connectivity to support continuous operation is a fundamental component of tactical networks. This study proposes a reliability enhancement for SIP mobility support.