M. Oguz Sunay

Cross-layer optimized rate adaptation and scheduling for multiple-user wireless video streaming

We present a cross-layer optimized video rate adaptation and user scheduling scheme for multi-user wireless video streaming aiming for maximum quality of service (QoS) for each user,, maximum system video throughput, and QoS fairness among users. These objectives are jointly optimized using a multi-objective optimization (MOO) framework that aims to serve the user with the least remaining playback time, highest delivered video seconds per transmission slot and maximum video quality. Experiments with the IS-856 (1timesEV-DO) standard numerology and ITU pedestrian A and vehicular B environments show significant improvements over the state-of- the-art wireless schedulers in terms of user QoS, QoS fairness, and the system throughput.

Improving the performance of wireless H.264 video broadcasting through a cross-layer design

In a wireless video broadcasting service, number of users receiving the service and the average video quality of the received stream have to be maximized for improving the system performance. To solve this problem optimally, one may adjust parameters at the physical and the application layers in a cross-layer fashion while utilizing the characteristics of the video that is being transmitted. In this paper, we propose a multi-objective optimized, cross-layer video broadcasting scheme for a wireless system capable of supporting a multitude of transmission data-rates using the H.264/AVC. The multi-objective, cross-layer optimization aims to find the H.264/AVC as well as the physical layer system parameters jointly to reach the optimal compromise between maximizing the average received video PSNR and minimizing the video broadcast service outage probability. Simulations conducted for the ITU Pedestrian A and Vehicular B channels show that further gains in system performance can be achieved for video broadcasting when such a cross-layer design is used.

Architecture for a distributed openflow controller

Considering the modern internet traffic rates, the network architecture is of particular importance as the running services itself. On the other hand, due to the increasing complexity and black-box structure of the available networking hardware (switches, routers, etc.), the necessary network innovation imposed by the running services becomes infeasible in practice. The software-defined networking notion introduced to solve this problem and one of its emerging and powerful implementations, the OpenFlow protocol, advocate the idea of providing the control and data paths in separate planes. A network operating system running on this control plane, is anticipated to provide necessary measures for scalability and reliability in order to stand against the gigantic traffic pumped by the network. In this paper, we propose a distributed OpenFlow network operating system built with necessary scalability and reliability qualifications without requiring any changes to the existing OpenFlow protocol and networking equipment.

Cross-Layer scheduling with content and packet priorities for optimal video streaming over 1xEV-DO

Maximization of received video quality and application-level service fairness are the two principal objectives of multi-user wireless video streaming. The user and packet scheduling mechanisms employed are the determining factors on the communication system performance and must utilize multiple layers of the OSI protocol stack. The semantic and decodability (concealment related) importance and hence priorities of video packets can be considered at the application layer. In this paper, the use of video content and packet priorities for multi-objective optimized (MOO) scheduling in 1xEV-DO system is introduced. Rate adaptive AVC/H.264 encoding is used for content adaptation and a user with the least buffer fullness, best channel throughput and highest video packet importance is targeted for scheduling. Hence, losses are forced to occur at packets with low semantic/decodability importance. Results show that the proposed framework achieves 1-to-2 dBs better PSNR in high importance temporal regions compared to the state-of-the-art CBR encoding case.

On the importance of application based scheduling for femtocell access points

In this paper, it is proposed that in order to guarantee a certain level of Quality of service (QoS) for different applications in a femtocell network, it is necessary to use application-based scheduling in femtocell access points (FAP). A novel scheduler is designed which can prioritize each application considering their various QoS requirements. The scheduler aims to divide the limited wireless resources among applications in an application specific notion of fairness. Unlike current solutions, proposed scheduler differentiates between not only users but each and every application of users and allocates wireless resources considering the specific QoS requirements of different type of applications. Extensive simulation results prove that the proposed scheduler achieves tremendous results compared to the current user-based schedulers.

Enhancing 3G High Speed Wireless Data Performance Through Utilization of 3G---WLAN System Cooperation: A Cross-Network, Cross-Layer Approach

The third generation (3G) wireless networks and wireless local area networks (WLANs) possess complementary characteristics. Recently, there has been significant interest in providing algorithms and specifications that enable their inter-operability. In this paper we propose a novel cross-network, cross-layer algorithm that jointly performs 3G resource allocation and ad-hoc mode WLAN routing towards effectively increasing the performance of the 3G system. The metrics used in this joint design ensures that multi-user diversity is exploited without causing user starvation in the 3G system and the WLAN assistance does not cause an unfair treatment to any of the mobiles from a battery usage point of view. Furthermore, the design attempts to select the WLAN route so that the assistance does not become a major part of the overall link traffic and the internal WLAN traffic can continue almost without any disturbances.

Investigations on multi-user MIMO feature in IEEE 802.11ac networks

This paper studies the multi-user MIMO feature of IEEE 802.11ac networks that serve, along with IEEE 802.11ac nodes, also legacy IEEE 802.11n nodes. For this purpose, we develop a simulator that models the IEEE 802.11ac and IEEE 802.11n networks. Then, using a setup, we first study the tradeoff between the amount of overhead used in channel sounding and the corresponding rate of information, concluding that in this setting, channel sounding with all clients lead to better throughput. Secondly, we observe the negative impact of IEEE 802.11n nodes on the IEEE 802.11ac traffic due to the deafness problem, and analyze the performance of the usage of RTS/CTS handshake and cts2self mechanisms to mitigate this effect. We show that the regular RTS/CTS handshake mitigates the deafness problem to a certain degree. However, the cts2self mechanism achieves a better performance since no airtime is wasted to collisions with the RTS frames.

Performance of TCP congestion control algorithms with interference in IEEE 802.11ac WLANs

In order to meet the incremental requirements from clients, fifth generation Wireless Local Area Network(WLAN) protocol IEEE 802.11ac provides a lot more throughput than his predecessors. However, in all distributed channel access 802.11 protocols, probability of packet loss increases with respect to number of available stations; consecutive packet losses in link layer activates congestion control mechanism of TCP which decreases throughput. In this work, we investigated the performance of congestion control algorithms of TCP protocol when interference available wireless medium is used in between the IEEE 802.11ac capable devices. As a benchmark, we repeated the experiments with UDP protocol which does not have reliable connection and congestion control mechanism. According to our experiments, we observed that UDP provides more throughput than all other TCP congestion control algorithms. When we compare TCP congestion control algorithms by themselves, we observed that the algorithms which does not decrease congestion window size too much during interference and have more aggressive increment of congestion window -such as Cubic and Illinois, Scalable have better performance in terms of throughput and standard deviation.

P2P file sharing application with ALTO server

In current Internet, the most significant and the growing promotion rate of the network resources usage is due to the Peer to Peer(P2P) applications. These studies show us that the main traffic type, that Internet Service Providers (ISPs) should route, is P2P traffics. Since P2P overlay network model is networkoblivious, due to its nature, it causes inefficient network utilization, and low quality of experiences, from the perspective of the network providers and the end users respectively. Therefore, this unnecessary resource utilization increases inter-ISP traffic, and lead to serious disruption on ISPs economics. In this paper, we will implement a BitTorrent-Like simulator and Application Layer Traffic Optimization (ALTO) Server, in order to analyze and improve the performance of the overall system, by using a novel peer selection algorithms. Our results show that using this type of P2P overlay, reduces the Data Download Completion Time about and Inter-ISP Link Utilization about 50%.

On the broadcast capacity of wireless multihop interference networks

This paper is concerned with wireless broadcasting in multihop networks where a selected number of relay nodes may aid the source node in the broadcast under a given total energy and hop constraint. We study an ad-hoc network with infinitely many nodes and analytically find the number and positions of rebroadcasting relay nodes to achieve the optimal broadcast capacity. The interference due to multiple transmissions in the geographical area is taken into account. Based on the theoretical findings, we then propose one distributed and one centralized heuristic for relay selection in wireless broadcasting. We discuss the broadcast capacity performances and CSI (channel state information) requirements of these algorithms. The results illustrate that the benefits of peer-assisted broadcasting are more pronounced in the centralized relay selection algorithm when compared to the fully randomized and distributed selection under a realistic system model.