Application Layer QoS Research Articles

A cross-layer QoS model for space DTN

Delay/disruption tolerant networking (DTN) technology is considered as a new solution for highly stressed communications in space environments. IP-based DTN network can support more flexible communication services, which is one of the research hotspots of space networking. At the same time, it is still an important and difficult problem to optimise the limited network resources allocation and guarantee the QoS of different services in DTN network. For this challenge, a cross-layer QoS model that considers application, network, and node layer QoS requirements and resource limitations is proposed in this paper. In addition, a comprehensive admission control scheme that ensures productivity and fairness is employed. The results of experiments and analyses conducted demonstrate the benefits to be derived from this approach.

Content-aware optimization on rate-distortion and network traffic for scalable video multicast networks

This paper aims to optimize the content-aware prioritization of scalable video multicast, which is coupled with multipath streaming and network coding based routing. It constructs multiple layer distribution meshes for the scalable video stream to minimize the total video distortion at all the receivers, determines the base layer meshes with minimum costs to maintain application-layer QoS and the layer synchronization of SVC streaming, and improves the network throughput by encouraging path-overlapping transmissions and thus allowing bandwidth sharing among different receivers for the same video layer by utilizing network coding. The targeted problem is formulated into a minimization programming in which the quality variation between layers, the transmission cost of the base layer, as well as the efficient resource utilization are jointly considered. By decomposition and dual approach, the global convex problem is solved by a two-level decentralized iterative algorithm. The implementation of the distributed algorithm is discussed with regard to the communication overhead, and the convergence performance is validated by numerical experiments. Packet-level simulations demonstrate that the proposed algorithm could approximately achieve the maximum flow rates determined by Max-Flow Min-Cut Theorem and benefit the overall received video quality.

Application-aware dynamic spectrum access

Dynamic Spectrum Access (DSA) allows unlicensed wireless devices to opportunistically access unoccupied licensed spectrum bands. DSA yields efficient spectrum utilization which can greatly improve wireless networking performance. In this paper, we advocate application-awareness to effectively manage the side-effects of DSA that can offset its benefits by adversely impacting application QoS. Simple application hints are found to be able to serve as key inputs in evaluating current spectrum conditions relative to application needs, leading to an informed DSA mechanism that minimizes the impact of undesirable DSA side-effects. Towards this goal, we propose a wireless service architecture called Context-Aware Spectrum Agility (CASA). The key elements of CASA are: (a) semantic dependency equations that provide the relationship between application-layer QoS state and lower-layer DSA parameters, (b) CASA Algorithm that adapts DSA parameters and activities to better suit application needs, and, (c) a low overhead interface to provide application context to DSA. CASA has been explicitly designed with the goals of practical deployment, low overhead operation, and is compatible with any DSA protocol. Compared to state-of-art DSA, the deployment of CASA along with DSA protocols is shown to improve QoS metrics, such as delay and jitter, by an average of 30 and 64%, respectively. CASA is also found to match the application QoS demands for more than 90% of the duration of a communication session—a 300+% improvement over conventional application-agnostic DSA.

Uplink Cross-Layer Scheduling with Differential QoS Requirements in OFDMA Systems

Fair and efficient scheduling is a key issue in cross-layer design for wireless communication systems, such as 3GPP LTE and WiMAX. However, few works have considered the multiaccess of the traffic with differential QoS requirements in wireless systems. In this paper, we will consider an OFDMA-based wireless system with four types of traffic associated with differential QoS requirements, namely, minimum reserved rate, maximum sustainable rate, maximum latency, and tolerant jitter. Given these QoS requirements, the traffic scheduling will be formulated into a cross-layer optimization problem, which is convex fortunately. By separating the power allocation through the waterfilling algorithm in each user, this problem will further reduce to a kind of continuous quadratic knapsack problem in the base station which yields low complexity. It is then demonstrated that the proposed cross-layer method cannot only guarantee the application layer QoS requirements, but also minimizes the integrated residual workload in the MAC layer. To further enhance the ability of QoS assurance in heavily loaded scenario, a call admission control scheme will also be proposed. The simulation results show that the QoS requirements for the four types of traffic are guaranteed effectively by the proposed algorithms.

Pushback: A hidden Markov model based scheme for energy efficient data transmission in sensor networks

In sensor networks, application layer QoS requirements are critical to meet while conserving energy. One of the leading factors for energy wastage is failed transmission attempts due to channel dynamics and interference. Existing techniques are unaware of the channel dynamics and lead to suboptimal channel access patterns. We propose a MAC layer solution called pushback, that appropriately delays packet transmissions to overcome periods of poor channel quality and high interference, while ensuring that the throughput requirement of the node is met. It uses a hidden Markov model (HMM) based channel model that is maintained without any additional signaling overhead. The pushback algorithm is shown to improve the packet success rate by up to 71% and reduce the number of transmissions needed by up to 38% while ensuring the same throughput.

Fabric Level and Application Level QoS Guarantees in Grid Computing

In the paper, a cross-layer optimization between application layer and fabric layer is proposed. The aim is to optimize the end-to-end quality of the dynamic grid application as well as efficiently utilizing the grid resources. The application layer QoS and fabric layer QoS are closely interrelated in Grids since the upper layer service is based on the lower level's capabilities. A fabric level and application level QoS scheduling algorithm is proposed. We formulate the integrated design of resource allocation and user QoS satisfaction control into a constrained optimization problem. The optimization framework provides a layered approach to the sum utility maximization problem. The application layer adaptively adjusts user's resource demand based on the current resource conditions, while the fabric layer adaptively allocates CPU, storage and bandwidth required by the upper layer.

Low-bandwidth Internet streaming of multimedia lectures

Traditional modes of communications are inadequate for distance learning in the information age. With advances in computer technology, the Internet offers great opportunities for educational exchange of ideas across vast distances. This paper proposes an end-to-end solution for streaming 'live' and recorded multimedia lectures over the Internet. The technical issues involved are first discussed and the importance of application-layer QoS control in ensuring an acceptable quality of multimedia lecture play-out emphasised. A hybrid architecture that uses an exchange server to handle communications and represents an optimal balance between several conflicting requirements is then proposed. In this architecture video/audio data are transferred directly between the streaming servers and clients. Objective and subjective tests have validated the effectiveness of the design.