Open Topics

Vol. 67, n° 9-10, September-October 2012
Content available on Springerlink

Nature-inspired optimization of Moving Access Point-based radio networks

Dimitrios Karvounas, Kostas Tsagkaris and Panagiotis Demestichas
University of Piraeus, Greece

Abstract Wireless communication systems have penetrated into almost all parts of human life. They have become essential and pervasive and do affect both personal and professional aspects of our lives. While most types of wireless networks, such as cellular mobile communication networks, have been exhaustively studied and optimized, in order to handle various situations, there are also contexts which require efficient handling, e.g., moving hotspots, areas that have lost their infrastructure, and areas with hard morphology. The motivation for this work is the efficient handling of these important contexts by the use of Moving Access Points (MAPs). MAPs are capable of autonomously moving and establishing a radio network in short time, with limited centralized management. The radio network provides wireless access to users, is based on ad hoc connectivity (self-adapting mesh network concept), and has some elements acting as gateways to a wide-area infrastructure. The main purpose of this paper is to find the optimal position of the MAPs, i.e., the ones which require minimum movement and telecommunication cost. In order to achieve this goal, an innovative algorithm that combines the well-known simulated annealing algorithm with the characteristic of pheromone of the ant colony optimization is proposed. This is done in order to exploit ant colony optimization concepts in the related problem of the optimization of the MAP-based radio network design. The operation of the algorithm is validated by being applied to three most indicative scenarios, in which it is compared to the pure simulated annealing and a brute-force method, respectively. Our scheme exhibits a 5% improved performance in terms of solution quality in medium and large size problems, a 9% improved speed for the estimation of the suboptimal solution and 15% quicker adaptation to new context, without impacting the computational complexity.

Moving access points – Simulated annealing – Ant colony – Ants – Pheromone – Optimization

Verifiably encrypted short signatures from bilinear maps

Zuhua Shao
Hangzhou Normal University, China

Abstract In 2003, Boneh et al. proposed the first efficient verifiably encrypted signature scheme (BGLS) from bilinear maps, which can be used in fair exchange protocols of short signatures. However, there are two weaknesses in the scheme. The security proof is built on a weaker security model, in which the key pair of the adjudicator is chosen by the simulator instead of the signature forger. The other is that the ordinary signatures to be verifiably encrypted are deterministic. They suffer from strong collision attacks of hash functions. In this paper, we propose an enhanced verifiably encrypted short signature scheme. The new scheme is strongly unforgeable in the random oracle model under a stronger security model, where two inside adversaries, malicious adjudicator and malicious verifier, have more power than ever. The new scheme would tally with the actual circumstances of electronic commerce.

Keywords Verifiably encrypted signature – Short signature – Fair exchange – Random oracle model

Modeling of the transmission of power line communication signal through the power electric transformer

M. Melit1, B. Nekhoul1, D. Sekki1 and K. Kerroum2
1 University of Jijel, Algeria
2 Blaise Pascal University, Clermont-Ferrand, France

Abstract In this work, we investigate the transmission of outdoor power line communication (PLC) in the power electric network. For this purpose, we propose an efficient and accurate modeling of the propagation of PLC signal through a power transformer using bond graph theory. Electrical energy is a univocally measurable physical quantity which is not the case of the voltage and the current. The analysis by bond graph where theoretical concept is based on energy and its conservation appear to be the most appropriate for modeling the transmission of low level PLC signals. To demonstrate this advantage, we treat an application on a power transformer and we compare our results to the measure and those obtained by another method of calculation.

Keywords  Power line communication – Power electric network – Power transformer – Bond graph

A group-based security scheme for wireless sensor networks

Md. Abdul Hamid and A. M. Jehad Sarkar
Hankuk University of Foreign Studies, Yongin, Korea

Abstract In recent years, wireless sensor networks have been a very popular research topic, offering a treasure trove of systems, networking, hardware, security, and application-related problems. Distributed nature and their deployment in remote areas, these networks are vulnerable to numerous security threats that can adversely affect their proper functioning. The problem is more critical if its purpose is for some mission-critical applications such as in a tactical battlefield. This paper presents a security scheme for group-based distributed wireless sensor networks. Our first goal is to devise a group-based secure wireless sensor network. We exploit the multi-line version of matrix key distribution technique and Gaussian distribution to achieve this goal. Secondly, security mechanisms are proposed for such a group-based network architecture in which sensed data collected at numerous, inexpensive sensor nodes are filtered by local processing on its way through more capable and compromise-tolerant reporting nodes. We address the upstream requirement that reporting nodes authenticate data produced by sensors before aggregating and the downstream requirement that sensors authenticates commands disseminated from reporting nodes. Security analysis is presented to quantify the strength of the proposed scheme against security threats. Through simulations, we validate the analytical results.

Keywords  Wireless sensor networks – Security – Group-based data aggregation – Gaussian distribution – Node capture attack

Low complexity LTS-based NLOS error mitigation for localization

Jasurbek Khodjaev, Soojung Hur and Yongwan Park
Yeungnam University, Gyeonsan, South Korea

Abstract In this paper, we propose a low complexity and robust non-line-of-sight error mitigation technique for positioning applications. It is based on the least trimmed squares estimation and it can reject BSs with large residuals from measured data while using the small ones for final position calculation. In moderate non-line-of-sight environments, our proposed algorithm achieves the best result while keeping the estimation simple. In heavy non-line-of-sight environments, our proposed algorithm achieves a similar performance to a more complex, more accurate techniques. We show that the least trimmed squares estimation can be used to mitigate non-line-of-sight errors under any channel condition.

Keywords  Least trimmed squares – NLOS error mitigation – Localization

Interference coordination for LTE-Advanced and FM broadcasting interoperability

Zaid Ahmed Shamsan1,2,3, Tharek Abd Rahman1 and Abdulaziz Mohammed Al-hetar2
1 Universiti Teknologi Malaysia, Johor
2 Taiz University, Yemen
3 Al-Imam Muhammad ibn Saud Islamic University, Riyadh, Saudi Arabia

Abstract The surest way to guarantee that multiple wireless systems can concurrently exist harmlessly, when operating in the same or adjacent channel, is by analyzing spectrum overlapping. This paper proposes a more accurate model to evaluate the interference power from co-channel and adjacent channel of orthogonal frequency division multiplexing-based long term evolution-advanced (LTE-Advanced) towards broadcasting frequency modulation systems at 800 MHz. Power spectral density overlapping factor is employed, and closed form of the interference power loss is derived. Numerical results demonstrate that the proposed method evaluates more exact interference power than the advanced minimum coupling loss (A-MCL) method, where the co-channel and adjacent channel interference powers are reduced by 1.3 and 3 dB, correspondingly, compared to that obtained using the A-MCL method. This decreases the minimum separation distance between the two systems, which can eventually lead to efficient radio spectrum resources utilization.

Keywords  Sharing analysis – LTE-Advanced – PSD – FM broadcasting – Interference

Pseudolites/repeaters infrastructure autopositioning approach—mathematics and first simulation-based results

Nel Samama and Anca Fluerasu
Institut Mines-Télécom, Télécom SudParis, France

Abstract In the various infrastructure-based indoor positioning systems using Global Navigation Satellite System signals, i.e. pseudolites, repeaters, and repealites, there is the need for the terminal to know the positions of the various transmitters. Some techniques have been proposed for high accuracy pseudolite systems, but they require carrier phase measurements and a careful choice of some specific test locations. Other approaches consider that these data are simply available by any means: Of course, this can be achieved through manual distance measurements and the use of maps of the indoor environment. In this paper, we describe a new method that is based on a two-step approach. The first one consists in deploying the system. The second one is the calculation of the position of the transmitters through classic code measurements for a few specific chosen locations. Thus, the system can be deployed without any constraint and the locations of the transmitters calculated through a basic set of elementary measurements. The theoretical method is first described and the resulting accuracy of the position of the transmitters is then evaluated through theoretical calculations. In addition, electromagnetic simulations are carried out in order to estimate the pseudo-range errors of the proposed measurements: The accuracy of the determination of the position of the transmitters is then estimated (note that two receiver tracking loop implementations are considered). Thus, the accuracy of the proposed method is evaluated theoretically and through simulations.

Keywords  Pseudolites – Repeaters – Repealites – Indoor positioning – Autopositioning

Multiservice capacity and interference statistics of the uplink of high altitude platforms (HAPs) for asynchronous and synchronous WCDMA system

Bazil Taha Ahmed1 and Miguel Calvo Ramón2
1 Universidad Autonoma de Madrid, Spain
2 Universidad Politecnica de Madrid, Spain

Abstract In this work, the capacity and the interference statistics of the uplink of high-altitude platforms (HAPs) for asynchronous and synchronous WCDMA system assuming finite transmission power and imperfect power control are studied. Propagation loss used to calculate the received signal power is due to the distance, shadowing, and wall insertion loss. The uplink capacity for 3- and 3.75-G services is given for different cell radius assuming outdoor and indoor voice users only, data users only and a combination of the two services. For 37 macrocells HAP, the total uplink capacity is 3,034 outdoor voice users or 444 outdoor data users. When one or more than one user is an indoor user, the uplink capacity is 2,923 voice users or 444 data users when the walls entry loss is 10 dB. It is shown that the effect of the adjacent channels interference is very small.

Keywords  Uplink capacity – HAPs – Power control – WCDMA – Walls entry loss – Walls penetration loss – HSUPA