Open Topics

Vol. 66, n° 9-10, September-October 2011
Content available on Springerlink

A distributed MAC scheme to achieve QoS in ad hoc networks

Ulf Körner, Ali Hamidian, Michal Pioro, Christian Nyberg
Lund University, Sweden

Abstract – Real-time applications introduce new requirements on wireless networks and impose quality thresholds on parameters like delay, jitter, throughput, and packet loss in order to run smoothly. This paper addresses this issue by presenting a MAC scheme that offers real-time applications the opportunity to reserve transmission time based on their QoS requirements for contention-free medium access. Our scheme, which is called EDCA with Resource Reservation (EDCA/RR), operates in a fully distributed manner, is compatible with IEEE 802.11, and provides both prioritized and parameterized QoS. In this study, we have extended EDCA/RR to handle reservation collisions and, through extensive simulations, we show that our proposal can handle multiple reservations as well as uninformed stations that lie outside the transmission range of both the transmitter and the receiver while providing QoS guarantees. We compare EDCA/RR with EDCA and our results show that, as the traffic in the network increases, EDCA/RR succeeds providing the required service to QoS-demanding applications whereas EDCA fails in this task. In addition, when the medium is lossy we show that, not only does EDCA/RR give better service to real-time traffic, but also to contending non-real-time traffic.

Keywords: QoS in wireless networks – IEEE802.11e – Distributed MAC

A novel UWB channel identification parameter for indoor positioning applications

Jasurbek Khodjaev1, Yongwan Park1 and Jeonghee Choi2
1 Yeungnam University, South Korea
2 Daegu University, South Korea

Abstract – We propose a new channel identification parameter that is based on the number of significant paths within the received signal. Our proposed parameter can achieve similar or better results compared to other existing methods with lower complexity. Moreover, our results show that it is possible to use only two channel identification parameters instead of three in joint channel identification techniques, as it was used in conventional methods.

:  Channel identification – UWB – Positioning – Indoor channel

Cooperative communications with multilevel/AES-SD4-CPFSK in wireless sensor networks

Hakan Cam1, Volkan Ozduran2, Gokmen Altay3 and Osman N. Ucan4
1 Turkish Airforce Academy, Istanbul, Turkey
2 Istanbul University, Avcilar, Turkey
3 Queen’s University Belfast, UK
4 Istanbul Aydin University, Turkey

Abstract – In this paper, a new joint multilevel data encryption and channel coding mechanism is proposed, which is called “multilevel/advanced encryption standard–systematic distance 4–continuous phase frequency shift keying” (ML/AES-SD4-CPFSK). In the proposed scheme, we have not only taken advantage of spatial diversity gains but also optimally allocated energy and bandwidth resources among sensor nodes as well as providing high level of security and error protection for cooperative communications in wireless sensor networks. Relay protocols of cooperative communications, such as amplify-and-forward and decode-and-forward with/without adversary nodes, have been studied for 4CPFSK, 8CPFSK, and 16CPFSK of ML/AES-SD4-CPFSK. We have evaluated the error performances of multilevel AES for data encryption, multilevel SD-4 for channel coding, and various CPFSK types for modulation utilizing cooperative communications in wireless sensor networks. According to computer simulation results, significant diversity gain and coding gain have been achieved. As an example, bit error rate (BER) performance of 10−5 value has been obtained at a signal-to-noise ratio (SNR) of −6 dB for SD-4-CPFSK scheme in a compared related journal paper, whereas in our proposed system, we have reached the same BER value at a SNR of −23 dB with amplify-and-forward with direct path signal protocol in 16-level AES, two-level SD-4 coded 16CPFSK, and at the same time, we have reached the same BER value at a SNR of −22 dB with amplify-and-forward without direct path signal protocol in 16-level AES, two-level SD-4 coded 16CPFSK.

Keywords: Wireless sensor networks – Cooperative communications – Advanced encryption standard – Systematic distance-4 codes – Continuous phase frequency shift keying

Scene analysis indoor positioning enhancements

Apostolia Papapostolou and Hakima Chaouchi
Télécom SudParis, Institut Télécom, France

Abstract – The emergence of innovative location-oriented services and the great advances in mobile computing and wireless networking motivated the development of positioning systems in indoor environments. However, despite the benefits from location awareness within a building, the implicating indoor characteristics and increased user mobility impeded the implementation of accurate and time-efficient indoor localizers. In this paper, we consider the case of indoor positioning based on the correlation between location and signal intensity of the received Wi-Fi signals. This is due to the wide availability of WLAN infrastructure and the ease of obtaining such signal strength (SS) measurements by standard 802.11 cards. With our focus on the radio scene analysis (or fingerprinting) positioning method, we study both deterministic and probabilistic schemes. We then describe techniques to improve their accuracy without increasing considerably the processing time and hardware requirements of the system. More precisely, we first propose considering orientation information and simple SS sample processing during the training of the system or the entire localization process. For dealing with the expanded search space after adding orientation-sensitive information, we suggest a hierarchical pattern matching method during the real-time localization phase. Numerical results based on real experimental measurements demonstrated a noticeable performance enhancement, especially for the deterministic case which has additionally the advantage of being less complex compared to the probabilistic one.

Keywords:  IEEE 802.11 – Indoor positioning – Scene analysis – Wireless communications

Secure geolocalization of wireless sensor nodes in the presence of misbehaving anchor nodes

Joaquin Garcia-Alfaro1, Michel Barbeau2 and Evangelos Kranakis2
1 Institut Télécom, Télécom Bretagne, France
2 Carleton University, Canada

Abstract – Geolocalization of nodes in a wireless sensor network is a process that allows location-unaware nodes to discover their spatial coordinates. This process requires the cooperation of all the nodes in the system. Ensuring the correctness of the process, especially in the presence of misbehaving nodes, is crucial for ensuring the integrity of the system. We analyze the problem of location-unaware nodes determining their location in the presence of misbehaving neighboring nodes that provide false data during the execution of the process. We divide and present potential misbehaving nodes in four different adversary models, based on their capacities. We provide algorithms that enable the location-unaware nodes to determine their coordinates in the presence of these adversaries. The algorithms always work for a given number of neighbors provided that the number of misbehaving nodes is below a certain threshold, which is determined for each adversary model.

Keywords:  Network security – Wireless security – Wireless sensor networks – Secure geolocalization

Distributed multi-target tracking using joint probabilistic data association and average consensus filter

Tohid Yousefi Rezaii and Mohammad-Ali Tinati
University of Tabriz, Iran

Abstract – In this paper, a distributed multi-target tracking (MTT) algorithm suitable for implementation in wireless sensor networks is proposed. For this purpose, the Monte Carlo (MC) implementation of joint probabilistic data-association filter (JPDAF) is applied to the well-known problem of multi-target tracking in a cluttered area. Also, to make the tracking algorithm scalable and usable for sensor networks of many nodes, the distributed expectation maximization algorithm is exploited via the average consensus filter, in order to diffuse the nodes’ information over the whole network. The proposed tracking system is robust and capable of modeling any state space with nonlinear and non-Gaussian models for target dynamics and measurement likelihood, since it uses the particle-filtering methods to extract samples from the desired distributions. To encounter the data-association problem that arises due to the unlabeled measurements in the presence of clutter, the well-known JPDAF algorithm is used. Furthermore, some simplifications and modifications are made to MC–JPDAF algorithm in order to reduce the computation complexity of the tracking system and make it suitable for low-energy sensor networks. Finally, the simulations of tracking tasks for a sample network are given.

Keywords: Target tracking – Monte Carlo simulations – JPDAF – Expectation Maximization – Consensus filter

nW-MAC: multiple wake-up provisioning in asynchronously scheduled duty cycle MAC protocol for wireless sensor networks

Md. Obaidur Rahman, Muhammad Mahbub Alam, Muhammad Mostafa Monowar, Choong Seon Hong and Sungwon Lee
Kyung Hee University, Seoul, South Korea

Abstract – To reduce the energy cost of wireless sensor networks (WSNs), the duty cycle (i.e., periodic wake-up and sleep) concept has been used in several medium access control (MAC) protocols. Although these protocols are energy efficient, they are primarily designed for low-traffic environments and therefore sacrifice delay in order to maximize energy conservation. However, many applications having both low and high traffic demand a duty cycle MAC that is able to achieve better energy utilization with minimum energy loss ensuring delay optimization for timely and effective actions. In this paper, nW-MAC is proposed; this is an asynchronously scheduled and multiple wake-up provisioned duty cycle MAC protocol for WSNs. The nW-MAC employs an asynchronous rendezvous schedule selection technique to provision a maximum of n wake-ups in the operational cycle of a receiver. The proposed MAC is suitable to perform in both low- and high-traffic applications using a reception window-based medium access with a specific RxOp. Furthermore, per cycle multiple wake-up concept ensures optimum energy consumption and delay maintaining a higher throughput, as compare to existing mechanisms. Through analysis and simulations, we have quantified the energy-delay performance and obtained results that expose the effectiveness of nW-MAC.

Keywords: Wireless sensor network (WSN) – Medium access control (MAC) – Wake-up schedule – Operational cycle – Duty cycle – Energy – Delay

An intelligent agent-based scheme for vertical handover management across heterogeneous networks

Atiq Ahmed, Leïla Merghem-Boulahia and Dominique Gaïti
Université de Technologie de Troyes, France

Abstract – Advances in technology have enabled a proliferation of mobile devices and a broad spectrum of novel and outbreaking solutions for new applications and services. The increasing demand for all time and everywhere services requires the network operators to integrate different kinds of wireless and cellular networks. To enable this integration, it is important that users can roam freely across networks. As different technologies are involved in the current infrastructure, the problem of vertical handover needs to be addressed. To cope with the problem of seamless connectivity, several solutions have been presented. But most of them either lack intelligence or are not adaptable for reducing the packet loss and delay involved in the handover procedure. An intelligent technique is needed in order to perform the service continuity in the heterogeneous environment. This paper presents a cooperative agent based approach for the vertical handover using a knowledge plane. We propose to introduce the agents in the mobile nodes and access points to collect the necessary information from the environment. Based on this information, agents take a handover decision. A selection function is also introduced in this work which helps in choosing a best network from the available ones for handover. Finally, the proposed approach is validated with the help of simulations.

Keywords:  Vertical handover – Heterogeneous wireless networks – Multi-agent systems – Knowledge plane