Open Topics

Vol. 71, n° 5-6, May-June 2016
Content available on Springerlink


Multi-layer coding strategy for multi-hop block fading channels with outage probability

Simin Keykhosravi, Soroush Akhlaghi
Shahed University, Tehran, Iran

Abstract This paper considers communication over a multi-hop Rayleigh block-fading channel, where there is no direct link between the transmission ends, and communication is carried out through the use of multiple cascaded relays, employing the Decode and Forward (DF) strategy. It is assumed that the relays cannot do buffering or apply coding over consecutive transmission blocks, and they can merely re-encode the retried information and forward an encoded version of information to the next hop. In this case, assuming the channel information of each hop is not available at the corresponding transmitter and considering the destination either receives a minimum rate R 0 or declare an outage event, a multi-layer coding strategy in addition to a single-layer code of the minimum rate R 0 are employed, where the optimal power allocation policy across code layers is derived, leading to the maximum average achievable rate for a given outage probability.

Keywords Wireless network – Channel state information – Cooperative communication


A statistical trust system in wireless mesh networks

Rida Khatoun1, Youcef Begriche1, Juliette Dromard2, Lyes Khoukhi2, Ahmed Serhrouchni1
1 Télécom ParisTech, France
2 University of Technology of Troyes, France

Abstract Most trust and reputation solutions in wireless mesh networks (WMNs) rely on the intrusion detection system (IDS) Watchdog. Nevertheless, Watchdog does not consider packet loss on wireless links and may generate false positives. Consequently, a node that suffers from packet loss on one of its links may be accused wrongly, by Watchdog, of misbehaving. To deal with this issue, we propose in this paper a novel trust system which considers packet loss of links. Our trust system is based on a statistical detection method (SDM) implemented on each node of the network. Firstly, the SDM, via CUSUM test, analyzes the behavior of the packets loss in order to detect a dropping attack. Secondly, the SDM, through the Kolmogorov-Smirnov test, compares the behavior of the total packets loss with that of the control packets in order to identify the attack type. Our system allows every WMN’s node to assign to each of its neighbors, a trust value which reflects its real behavior. We have validated the proposed SDM method via extensive simulations on ns2 and have compared our trust system with an existing solution. The results display that our SDM solution offers better performance.

Keywords Trust system – Kolmogorov-Smirnov test – CUSUM tests – Wireless mesh networks


Interaction of electromagnetic waves with a resistive half-plane

Yusuf Z. Umul
Cankaya University, Ankara, Turkey

Abstract The interaction process of electromagnetic waves by a resistive half-plane is investigated. The scattered geometrical optics fields are obtained by subtracting the incident field from the total geometrical optics waves. The physical optics integral of the scattered waves is derived with the aid of the scattered geometrical optics fields. The edge diffracted waves are derived from the physical optics integral by the edge point technique. A correction field is added to the diffracted fields in order to obtain a solution that satisfies the resistive boundary conditions on the surface of the half-screen. The uniform diffracted fields are expressed in terms of the Fresnel function and the resultant field representations are compared with the literature numerically.

Keywords Edge diffraction – Resistive surfaces – Physical optics


On the benefits of location-based relay selection in mobile wireless networks

Jimmy J. Nielsen1, Tatiana K. Madsen1, Hans-Peter Schwefel1,2
1 Aalborg University, Denmark
2 FTW, Vienna, Austria

Abstract We consider infrastructure-based mobile networks that are assisted by a single relay transmission where both the downstream destination and relay nodes are mobile. Selecting the optimal transmission path for a destination node requires up-to-date link quality estimates of all relevant links. If the relay selection is based on link quality measurements, the number of links to update grows quadratically with the number of nodes, and measurements need to be updated frequently when nodes are mobile. In this paper, we consider a location-based relay selection scheme where link qualities are estimated from node positions; in the scenario of a node-based location system such as GPS, the location-based approach reduces signaling overhead, which in this case only grows linearly with the number of nodes. This paper studies these two relay selection approaches and investigates how they are affected with varying information update interval, node mobility, location inaccuracy, and inaccurate propagation model parameters. Our results show that location-based relay selection performs better than SNR-based relay selection at typical levels of location error when medium-scale fading can be neglected or accurately predicted.

Keywords Relay selection Location-aided communications Network simulation


Calculation of packet jitter for non-poisson traffic

H. Dbira1, A. Girard1,2, B. Sansò1
1 École polytechnique de Montréal, QC, Canada
2 INRS-EMT, Montréal, Qc, Canada

Abstract The packet delay variation, commonly called delay jitter, is an important quality of service parameter in IP networks especially for real-time applications. In this paper, we propose the exact and approximate models to compute the jitter for some non-Poisson FCFS queues with a single flow that are important for recent IP network. We show that the approximate models are sufficiently accurate for design purposes. We also show that these models can be computed sufficiently fast to be usable within some iterative procedure, e.g., for dimensioning a playback buffer or for flow assignment in a network.

Keywords Jitter Queue – Inter-arrival distribution – Service time distribution – Analytic model


Quantized lower bounds on grid-based localization algorithm for wireless sensor networks

Aws Al-Qaisi1, A. I. Alhasanat2, Abdelwadood Mesleh1, B. S. Sharif3, C. C. Tsimenidis3, J. A. Neasham3
1 Al-balqa Applied University, Amman, Jordan
2 Al-Hussien Bin Talal University, Ma’an, Jordan
3 University of New Castle upon Tyne, UK

Abstract In this paper, we introduce a Quantized Cramer Rao Bound (Q-CRB) method, which adapts the use of the CRB to handle grid-based localization algorithms with certain constraints, such as localization boundaries. In addition, we derive a threshold granularity level which identifies where the CRB can be appropriately applied to this type of algorithm. Moreover, the derived threshold value allows the users of grid-based LSE techniques to probably avoid some unnecessary complexities associated with using high grid resolutions. To examine the feasibility of the new proposed bound, the grid-based least square estimation (LSE) technique was implemented. The Q-CRB was used to evaluate the performance of the LSE method under extensive simulation scenarios. The results show that the Q-CRB provided a tight bound in the sense that the Q-CRB can characterize the behaviour of location errors of the LSE technique at various system parameters, e.g. granularity levels, measurement accuracies, and in the presence or absence of localization boundaries.

Keywords WSN Localization – Grid-based localization – Wireless sensor networks


Exact outage analysis of a decode-and-forward cooperative communication network with Nth best energy harvesting relay selection

Pham Ngoc Son1, Hyung Yun Kong2, Alagan Anpalagan3
1 Ho Chi Minh City University of Technology and Education
2 University of Ulsan, Republic of Korea
3 Ryerson University, Toronto, Canada

Abstract In this paper, a decode-and-forward cooperative communication network (DFCCN) with energy harvesting relays is investigated in which a selected best relay with the N t h channel gain harvests energy from received radio frequency signals and then consumes the harvested energy by forwarding the recoded signals to a destination. Based on the studied energy harvesting receivers, two operation protocols are proposed: (1) power splitting relays in DFCCN (PSDFCCN protocol) and (2) time switching relays in DFCCN (TSDFCCN protocol). The system performances of the proposed protocols are evaluated based on the exact outage probabilities and compared to that of the direct transmission protocol. The theoretical results are confirmed by Monte Carlo simulations. It is found that (1) the system performances of the proposed PSDFCCN and TSDFCCN protocols are improved when the number of energy harvesting relays increases and when the parameter N is small; (2) the proposed PSDFCCN and TSDFCCN protocols with a small N value outperforms the direct transmission protocol; (3) the target signal-to-noise Ratio (SNR), the location of cooperative relays, and the energy harvesting parameters, e.g., the power splitting ratio, energy harvesting time, and energy conversion efficiency, have significant impacts on the system performance; and (4) the theoretical results agree well with the simulations.

Keywords Energy harvesting – Cooperative communication – Nth best relay – Power splitting – Time switching – Decode-and-forward – Maximum ratio combining – Outage probability


Generalized diversity combining of energy harvesting multiple antenna relay networks: outage and throughput performance analysis

Sang Quang Nguyen, Hyung Yun Kong
University of Ulsan, Republic of Korea

Abstract In this paper, the generalized diversity combining of an energy constrained multiple antenna decode-and-forward relay network is considered. Using power splitting and time switching architectures in consort with diversity combining at the relay, six protocols are proposed, i.e., power splitting with selection combining (PSSC), power splitting with maximum ratio combining (PSMRC), power splitting with generalized selection combining (PSGSC), time switching with selection combining (TSSC), time switching with maximum ratio combining (TSMRC), and time switching with generalized selection combining (TSGSC). The outage probability and throughput performance of each protocol is analyzed by first developing the closed form analytical expressions and then verifying these through the Monte Carlo simulation method. Simulation results show that system performance improves both with increasing the number of antennas and decreasing the distance between the source and relay. The TSSC/TSMRC/TSGSC protocols yield better outage performance whereas the PSSC/PSMRC/PSGSC protocols achieve relatively higher throughput performance. Finally, the effects of power splitting ratio, energy harvesting time ratio, energy conversion efficiency, sample down conversion noise, and the target signal-to-noise ratio on system performance are analyzed and presented.

Keywords Power splitting – Time switching – Generalized selection combining – Maximum ratio combining – Selection combining – Decode-and-forward