Cooperative Communications inWireless Local Area Networks: MAC Protocol Design and Multi-layer Solutions

This dissertation addresses cooperative communications and proposes multi-layer solu- tions for wireless local area networks, focusing on cooperative MAC design. The coop- erative MAC design starts from CSMA/CA based wireless networks. Three key issues of cooperation from the MAC layer are dealt with: i.e., when to cooperate (opportunistic cooperation), whom to cooperate with (relay selection), and how to protect cooperative transmissions (message procedure design). In addition, a cooperative MAC protocol that addresses these three issues is proposed. The relay selection scheme is further optimized in a clustered network to solve the problem of high collision probability in a dense network. The performance of the proposed schemes is evaluated in terms of through- put, packet delivery rate and energy efficiency. Furthermore, the proposed protocol is verified through formal model checking using SPIN. Moreover, a cooperative code allo- cation scheme is proposed targeting at a clustered network where multiple relay nodes can transmit simultaneously. The cooperative communication design is then extended to the routing layer through cross layer routing metrics. Another part of the work aims at enabling concurrent transmissions using cooperative carrier sensing to improve the per- formance in a WLAN network with multiple access points sharing the same channel

WIMAX Basics from PHY Layer to Scheduling and Multicasting Approaches

WiMAX (Worldwide Interoperability for Microwave Access) is an emerging broadband wireless technology for providing Last mile solutions for supporting higher bandwidth and multiple service classes with various quality of service requirement. The unique architecture of the WiMAX MAC and PHY layers that uses OFDMA to allocate multiple channels with different modulation schema and multiple time slots for each channel allows better adaptation of heterogeneous user’s requirements. The main architecture in WiMAX uses PMP (Point to Multipoint), Mesh mode or the new MMR (Mobile Multi hop Mode) deployments where scheduling and multicasting have different approaches. In PMP SS (Subscriber Station) connects directly to BS (Base Station) in a single hop route so channel conditions adaptations and supporting QoS for classes of services is the key points in scheduling, admission control or multicasting, while in Mesh networks SS connects to other SS Stations or to the BS in a multi hop routes, the MMR mode extends the PMP mode in which the SS connects to either a relay station (RS) or to Bs. Both MMR and Mesh uses centralized or distributed scheduling with multicasting schemas based on scheduling trees for routing. In this paper a broad study is conducted About WiMAX technology PMP and Mesh deployments from main physical layers features with differentiation of MAC layer features to scheduling and multicasting approaches in both modes of operations

FAIR: Forwarding Accountability for Internet Reputability

This paper presents FAIR, a forwarding accountability mechanism that incentivizes ISPs to apply stricter security policies to their customers. The Autonomous System (AS) of the receiver specifies a traffic profile that the sender AS must adhere to. Transit ASes on the path mark packets. In case of traffic profile violations, the marked packets are used as a proof of misbehavior. FAIR introduces low bandwidth overhead and requires no per-packet and no per-flow state for forwarding. We describe integration with IP and demonstrate a software switch running on commodity hardware that can switch packets at a line rate of 120 Gbps, and can forward 140M minimum-sized packets per second, limited by the hardware I/O subsystem. Moreover, this paper proposes a "suspicious bit" for packet headers - an application that builds on top of FAIR's proofs of misbehavior and flags packets to warn other entities in the network.Comment: 16 pages, 12 figure

Eighth Workshop and Tutorial on Practical Use of Coloured Petri Nets and the CPN Tools, Aarhus, Denmark, October 22-24, 2007

This booklet contains the proceedings of the Eighth Workshop on Practical Use of Coloured Petri Nets and the CPN Tools, October 22-24, 2007. The workshop is organised by the CPN group at the Department of Computer Science, University of Aarhus, Denmark. The papers are also available in electronic form via the web pages: http://www.daimi.au.dk/CPnets/workshop0

Game Theoretical Approach for Joint Relay Selection and Resource Allocation in Mobile Device Networks

With the improvement of hardware, more and more multimedia applications are allowed to run in the mobile device. However, due to the limited radio bandwidth, wireless network performance becomes a critical issue. Common mobile solutions are based on the centralized structure, which require an access point to handle all the communication requirement in the work area. The transmission performance of centralized framework relies on the density of access points. But increasing the number of access points will cost lot of money and the interference between access point will reduce the transmission quality. Thanks to the wireless sensor network implementations, the distributed wireless network solution has been well studied. Now, many mobile network studies introduce the device to device idea which is a distributed structure of mobile network. Unlike wireless sensor networks, mobile networks have more movability and higher transmission speed requirement. In order to be used in mobile networks, a distributed network management algorithm needs to perform faster and more accurate. In this thesis, a new pairing algorithm is proposed to provide a better transmission quality for multimedia data. In the proposed approach, the multimedia data is quantized by distortion reduction. Then, the source-relay pairing solution is optimized by a history tracing system using game theory to improve the expected overall distortion reduction of the entire network. Several parameters are introduced in the proposed solution, so the optimization would fit for different situations. Simulation results show that the proposed algorithm achieves higher overall distortion reduction by avoiding the competition between nodes. Simulation results also show the parameters would affect the system performance, such as optimization speed, system stability and system overall transmit speed