Open Topics

Vol. 66, n° 5-6, May-June 2011
Content available on Springerlink

Congestion-aware fair rate control in wireless mesh networks

Muhammad Mahbub Alam* · Md. Shariful Islam* · Md. Abdul Hamid** · Choong Seon Hong* and Sungwon Lee*
Department of Computer Science, North Carolina State University, Raleigh, NC 27695–8206, USA

Abstract This paper presents a fair and efficient rate control mechanism, referred to as congestion-aware fair rate control (CFRC), for IEEE 802.11s-based wireless mesh networks. Existing mechanisms usually concentrate on achieving fairness and achieve a poor throughput. This mainly happens due to the synchronous rate reduction of neighboring links or nodes of a congested node without considering whether they actually share the same bottleneck or not. Furthermore, the achievable throughput depends on the network load, and an efficient fair rate is achievable when the network load is balanced. Therefore, existing mechanisms usually achieve a fair rate determined by the mostly loaded network region. CFRC uses an AIMD-based rate control mechanism which enforces a rate-bound to the links that use the same bottleneck. To achieve the maximum achievable rate, it balances the network load in conjunction with the routing mechanism. Furthermore, it allows the intra-mesh flows to utilize the network capacity, and the intra-mesh flows achieve a high throughput. Finally, we investigate the performance of CFRC using simulation in ns-2, and the results demonstrate that CFRC increases the throughput with the desired fairness.

Keywords Wireless mesh networks  • Congestion control  • Rate control  • AIMD  • Fairness

QoS routing across multiple autonomous systems using the path computation element architecture

Geza Geleji and Harry G. Perros
* Department of Computer Engineering, Kyung Hee University, Gyeonggi 449-701, Korea
** Department of Information and Communications Engineering, Hankuk University of Foreign Studies, Gyronggi-do 449-791, Korea

Abstract We examine various algorithms for calculating quality of service (QoS)-enabled paths spanning multiple autonomous systems (ASs) using the path computation element (PCE) architecture. The problem is divided into two parts. We first calculate an AS path, then the node-by-node path. Using extensive simulation, we compared various AS-path calculation algorithms based on border gateway protocol (BGP) and various AS-aggregation procedures, such as mesh, star and nodal aggregation. For node-to-node path calculation, we employed the per-domain backward algorithm and the per-domain backward tree algorithm (also known as backward recursive PCE-based computation). Results point to the fact that complex AS-path calculation algorithms do not perform significantly better than BGP. However, if the service quality provided by ASs varies greatly, either in time or space, then we expect a QoS-aware AS-path computation algorithm, e.g., static nodal aggregation, to outperform BGP. Although the per-domain backward tree algorithm generally performs better than the per-domain backward algorithm, using a persistent variant of the latter makes it outperform the per-domain backward tree algorithm. The cost is a negligible increase in computational complexity and a slightly increased connection setup delay.

Keywords BGP  •  QoS  • PCE  •  AS-path calculation algorithm

Optimal audio watermarking scheme using genetic optimization

Hong Peng* and Jun Wang**
* School of Mathematics and Computer Engineering, Xihua University, Chengdu, Sichuan, 610039, China
** School of Electrical and Information Engineering, Xihua University, Chengdu, Sichuan, 610039, China

Abstract Designing an optimal audio watermarking system is an open difficult issue since its two basic performance measures, i.e., imperceptibility and robustness, are conflicting with each other. So, an optimal audio watermarking scheme needs to optimally balance both imperceptibility and robustness. In order to realize such an optimal watermarking system, by considering the balance as an optimization problem, we propose an optimal audio watermarking scheme using genetic optimization with variable-length mechanism in this paper. The presented genetic optimization procedure can automatically determine optimal embedding parameters for each audio frame of an audio signal. Specially, employed variable-length mechanism can effectively search most suitable positions for watermark embedding, including suitable audio frames and their AC coefficients. By dint of the genetic optimization with variable-length mechanism, proposed audio watermarking scheme can not only guarantee good quality of watermarked audio signal but also effectively improve its robustness. Experimental results show that proposed watermarking scheme has good imperceptibility and high capability against common signal processing and some desynchronization attacks.

Keywords  Genetic algorithm • Audio signal • Digital audio watermarking • Optimal watermarking

Network coding for MPR-based flooding in ad hoc wireless networks under mobility conditions

Nour Kadi and Khaldoun Al Agha
LRI, CNRS, INRIA, Université Paris 11, Orsay, France

Abstract We propose a novel distributed coding scheme for broadcast over mobile ad hoc networks. In this scheme, we combine MPR technique with network coding. Only multipoint relay (MPR) nodes perform coding using a rateless code. Rather than waiting for a large number of encoded packets to be received before MPR nodes could decode and resend coded packets, we design a new degree distribution that enables the nodes to start decoding even when small number of encoded packets are received. Thus, we decrease the delay introduced at the intermediate nodes. The main advantage of using a rateless code for encoding instead of using a random linear combination of the previously received packets is to reduce significantly the encoding and decoding complexities. We provide a performance evaluation using a simulation to demonstrate the efficiency of our code even under mobility condition.

Keywords  Ad-hoc networks • Broadcast • Network coding • Fountain code • Multipoint relay

Analysis and improvement of a new authenticated group key agreement in a mobile environment

Qing-Feng Cheng, Chuan-Gui Ma and Fu-Shan Wei
Zhengzhou Information Science and Technology Institute, Zhengzhou, People’s Republic of China

Abstract In 2009, Lee et al. (Ann Telecommun 64:735–744, 2009) proposed a new authenticated group key agreement protocol for imbalanced wireless networks. Their protocol based on bilinear pairing was proven the security under computational Diffie–Hellman assumption. It remedies the security weakness of Tseng’s nonauthenticated protocol that cannot ensure the validity of the transmitted messages. In this paper, the authors will show that Lee et al.’s authenticated protocol also is insecure. An adversary can impersonate any mobile users to cheat the powerful node. Furthermore, the authors propose an improvement of Lee et al.’s protocol and prove its security in the Manulis et al.’s model. The new protocol can provide mutual authentication and resist ephemeral key compromise attack via binding user’s static private key and ephemeral key.

Keywords  Group key agreement  • Bilinear pairings • Computational Diffie–Hellman problem • Impersonation attack

Virtual networks: isolation, performance, and trends

Natalia C. Fernandes*, Marcelo D. D. Moreira*, Igor M. Moraes**, Lyno Henrique G. Ferraz*, Rodrigo S. Couto*, Hugo E. T. Carvalho*, Miguel Elias M. Campista*, Luís Henrique M. K. Costa* and Otto Carlos M. B. Duarte*
*Grupo de Teleinformática e Automação (GTA), Universidade Federal do Rio de Janeiro (UFRJ)
**Instituto de Computação (IC), Universidade Federal Fluminense (UFF), Niterói, RJ, Brazil

Abstract Currently, there is a strong effort of the research community in rethinking the Internet architecture to cope with its current limitations and support new requirements. Many researchers conclude that there is no one-size-fits-all solution for all of the user and network provider needs and thus advocate for a pluralist network architecture, which allows the coexistence of different protocol stacks running at the same time over the same physical substrate. In this paper, we investigate the advantages and limitations of the virtualization technologies for creating a pluralist environment for the Future Internet. We analyze two types of virtualization techniques, which provide multiple operating systems running on the same hardware, represented by Xen, or multiple network flows on the same switch, represented by OpenFlow. First, we define the functionalities needed by a Future Internet virtual network architecture and how Xen and OpenFlow provide them. We then analyze Xen and OpenFlow in terms of network programmability, processing, forwarding, control, and scalability. Finally, we carry out experiments with Xen and OpenFlow network prototypes, identifying the overhead incurred by each virtualization tool by comparing it with native Linux. Our experiments show that OpenFlow switch forwards packets as well as native Linux, achieving similar high forwarding rates. On the other hand, we observe that the high complexity involving Xen virtual machine packet forwarding limits the achievable packet rates. There is a clear trade-off between flexibility and performance, but we conclude that both Xen and OpenFlow are suitable platforms for network virtualization.

Keywords  Future Internet • Virtual networks • Routing

RBF network assisted adaptive path selective decorrelating detector under impulsive noise for multipath fading CDMA systems

Ali Hakan Ulusoy and Ahmet Rizaner
Department of Information Technology, School of Computing and Technology, Eastern Mediterranean University, Magosa/North Cyprus, Turkey

Abstract This paper proposes a novel radial basis function assisted adaptive path selective decorrelating detector for direct sequence code division multiple access systems with time-varying multipath fading channels under impulsive noise. The proposed detector combines adaptive path selective decorrelating detector (APSDD) with a radial basis function (RBF) network to eliminate the effect of impulsive noise. Simulation results clearly show that the proposed detector eliminates the effect of impulsive noise and improves the performance of APSDD under high impulsive noise

Keywords  CDMA • Adaptive path selection • Decorrelating detector • Radial basis function • Impulsive noise • Multipath fading

Impact of scheduling algorithms on performance of crosspoint-queued switch

Milutin Radonjic and Igor Radusinovic
Faculty of Electrical Engineering, University of Montenegro, 20000 Podgorica, Montenegro

Abstract The performance analysis of the 32 × 32 crosspoint-queued switch is presented in this paper. Switches with small buffers in crosspoints have been evaluated in the late 1980s but mostly for uniform traffic. However, due to technological limitations of that time, it was impractical to implement large buffers together with switching fabric. The crosspoint-queued switch architecture has been recently brought back into focus since modern technology enables an easy implementation of large buffers in crosspoints. An advantage of this solution is the absence of control communication between linecards and schedulers. In this paper, the performances of four algorithms (longest queue first, round robin, exhaustive round robin, and frame-based round robin matching) are analyzed and compared. The results obtained for the crosspoint-queued switch are compared with the output queued switch. Throughput, average cell latency and instantaneous packet delay variance are evaluated under uniform and nonuniform traffic patterns. The results will show that the longest queue first algorithm has the highest throughput in many simulated cases but the highest average cell latency and delay variance among observed algorithms. It will also be shown that the choice of the scheduling algorithm does not play a role in the switch performance if the buffers are long enough. This will prove that some form of round-robin-based algorithms become a better choice for implementation due to their simplicity, small hardware requirements, and avoidance of the starvation problem, which is a major drawback of the longest queue first algorithm.

Keywords  Crosspoint-queued switch • Buffer length • Throughput • Average cell latency • Jitter

Rain rate analysis and total rain accumulation in the North of Malayan Peninsula

J. S. Mandeep
Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia
Institute of Space Science, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

Abstract Using the 1-min data for 13 years (1993–2005) of rainfall measurements in Penang in the northwestern part of the Malayan Peninsula, we estimate rain occurrence to be ~12% of the year. At the same location during 0.01% of a year, rainfall exceeds 126 mm/h. The 13-year average 1-min rainfall data are analyzed to study the diurnal, monthly, and annual variation of total rain accumulations. The Southern Oscillation values were low in 1993, 1995, and 1998 and the percentage exceedance of rain rates during the La Niña years were higher than El Niño years.

Keywords  1-min rain rate • Equatorial climate • Southern Oscillation

Analysis of a new annular multi-slits antenna using wave concept iterative process in cylindrical coordinates

Zied Houaneb*, Hassen Zairi*, Ali Gharsallah* and Henri Baudrand**
*Département de Physique, Faculté des Sciences de Tunis, Université de Tunis, Tunis, Tunisia
**Laboratoire LAPLACE UPS-INP Toulouse, Toulouse, France

Abstract In this paper, a new antenna for satellite applications is proposed. This antenna is designed to operate at any frequency desired. It consists of a circular microstrip patch antenna which incorporates concentric annular slits, and it is printed on a grounded substrate. The details of the proposed antenna design and numerical results are presented and discussed. The wave concept iterative procedure in cylindrical coordinates is used to analyze this new antenna. Using the proposed procedure, less computing time and memory are needed to calculate the electromagnetic parameters of the annular multi-slits antenna.

Keywords  Wave concept • Hankel transforms • Leaky waves • Multi-slits antenna • Radiation pattern • Far field