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Cooperative spectrum sensing in realistic RF environment

- Shahid, Mohammad, Kamruzzaman, Joarder

  • Authors: Shahid, Mohammad , Kamruzzaman, Joarder
  • Date: 2009
  • Type: Text , Conference paper
  • Relation: 20th Personal Indoor & Mobile Radio Communications Symposium 2009 (PIMRC2009) p. 2290-2294
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  • Description: Fixed spectrum licensing policies are unsuitable to meet RF spectrum demand by emerging technologies. Spectrum scarcity is hindering the enhancement of current services or deployment of new services operating in RF spectrum. On the contrary, many portions of the licensed spectrum remain unused or underused for significant period of time creating possibility of opportunistic spectrum access without license. Spectrum sensing is practiced in most of the existing opportunistic spectrum access methods. However, these methods consider identical fading or shadowing channels and ignore spatial variation of unlicensed users, hence fail to capture realistic scenario. We introduce an improved cooperative spectrum sensing technique which incorporates non-identical fading and shadowing, and weighs each non-licensee user's contribution appropriately considering the received power and positional displacements of the users. The proposed method demonstrates better detection accuracy and higher spectrum utilization with fewer cooperating users than other existing methods.

Predicting mobile tourists

- Matthew, Michael, Karmakar, Gour, Kamruzzaman, Joarder

Predicting protein protein interfaces as clusters of optimal docking area points

- Arafat, Yasir, Kamruzzaman, Joarder, Karmakar, Gour, Fernandez-Recio, Juan

  • Authors: Arafat, Yasir , Kamruzzaman, Joarder , Karmakar, Gour , Fernandez-Recio, Juan
  • Date: 2009
  • Type: Text , Journal article
  • Relation: International Journal of data mining and bioinformatics Vol. 3, no. 1 (2009), p. 55-67
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  • Description: Abstract: Desolvation property is used here to predict protein-protein binding sites exploiting the fact that lower-valued 'optimal docking area' ODA (Fernandez-Recio et al., 2005) points form cluster at the interface. The proposed method involves two steps; clustering the ODA points and representing ODA points by average ODA values. On 51 nonredundant proteins, results show the success rate improved considerably. Considering only significant ODA, the previous ODA method has obtained a success rate of 65% with overall success rate of 39%. The proposed method improved the overall success rate to 61%. Further, comparable results were found for X-ray and NMR structures.

VoIP capacity over PCF with imperfect channel

- Siddique, Md, Kamruzzaman, Joarder

  • Authors: Siddique, Md , Kamruzzaman, Joarder
  • Date: 2009
  • Type: Text , Conference paper
  • Relation: IEEE Global Communications Conference (IEEE GLOBECOM2009) p. 1-6
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  • Description: Voice, in the form of VoIP, has emerged as a dominating traffic category in the Internet. VoIP traffic suffers from severe voice quality degradation if the end-to-end delay and loss becomes high. PCF medium access mechanism offers delay bound delivery which is a crucial attribute for delay sensitive applications like VoIP. But due to its unavailability in most commercial products, little analysis has been done on PCF for supporting VoIP traffic. Most importantly, standard voice quality assessment methods are not used in the capacity studies. We propose a VoIP capacity model for PCF that uses voice quality as the limiting factor and takes imperfect channel condition into account. The effects of aggregation level, packet error rate and voice quality on VoIP capacity are investigated, and a comparison between voice capacities under PCF and DCF is presented. The proposed model will be extremely useful in designing networks to support quality voice calls.

A framework for collaborative multi class heterogeneous wireless sensor networks

- Azad, Arman, Kamruzzaman, Joarder

  • Authors: Azad, Arman , Kamruzzaman, Joarder
  • Date: 2008
  • Type: Text , Conference paper
  • Relation: Proceedings of the 2008 IEEE International Conference on Communications p. 1-6
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  • Description: For many applications, simultaneous sensing of a number of parameters is crucial that leads to the deployment of multiple classes of sensors having different initial energy, data generation rate and deployment density within the vicinity of a cluster as opposed to identical sensors assumed in the existing heterogeneous sensor networks. For data transmission to cluster head, such networks use single hop, multi hop and their hybrid as intra-cluster transmission policy which suffer highly from non-uniform energy usage among sensors, thereby reducing the lifetime drastically leaving considerable amount of energy in many nodes. In this paper, we propose a framework for multi-class heterogeneous sensor networks where incoming traffic is relayed towards cluster head in collaboration among multiple classes of sensors considering their heterogeneity. We also propose two transmission policies for this framework considering generic polygonal cluster and limited transmission range for individual sensors. Performance analysis shows substantial improvement of overall lifetime by the collaborative framework of multi-class sensors. Our proposed transmission policies further improve the lifetime over existing multi hop and hybrid communications through better distribution of energy usage among sensors.kam

An intelligent model to control preemption rate of instantaneous request calls in networks with book- ahead reservation

- Ahmad, Iftekhar, Kamruzzaman, Joarder, Habibi, Daryoush, Islam, Farzana

  • Authors: Ahmad, Iftekhar , Kamruzzaman, Joarder , Habibi, Daryoush , Islam, Farzana
  • Date: 2008
  • Type: Text , Conference proceedings
  • Relation: 2008 Australasian Telecommunication Networks and Applications Conference, ATNAC, Adelaide 2008. Published in Proceedings of Australasian Telecommunication Networks and Applications conference , IEEE (pp.344-34)
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  • Description: Resource sharing between Book-Ahead (BA) and Instantaneous Request (IR) reservation often results in high preemption rate of on-going IR calls. High IR call preemption rate causes interruption to service continuity which is considered as detrimental in a QoS-enabled network. A number of call admission control models have been proposed in literature to reduce the preemption rate of on-going IR calls. Many of these models use a tuning parameter to achieve certain level of preemption rate. This paper presents an Artificial Neural Network (ANN) model to dynamically control the preemption rate of on-going calls in a QoS-enabled network. The model maps network traffic parameters and desired level of preemption rate into appropriate tuning parameter. Once trained, this model can be used to automatically estimate the tuning parameter value necessary to achieve the desired level of preemption rate. Simulation results show that the preemption rate attained by the model closely matches with the target rat

Asynchronous variable hop size transmission with stochastic data model for sensor networks

- Azad, Arman, Kamruzzaman, Joarder

  • Authors: Azad, Arman , Kamruzzaman, Joarder
  • Date: 2008
  • Type: Text , Conference proceedings
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  • Description: Most existing data models and transmission policies for sensor network assume uniform periodic data generation and unconstrained transmission range for sensor nodes, both assumptions being too restrictive to capture and analyze real- world operation for practical deployment. In this paper, we consider these two practical aspects and present a new transmission policy formulated after (i) stochastic data model where a set of events occur with certain probabilities and rate of data generation by a sensor varies based on sensed event and (ii) limited transmission range of sensors. Assuming co-centric rings around the base station, located at a generic location (internal or external to the network area), ring thickness and hope sizes over lifetime is determined by formatting an optimization problem where nodes in each ring may transmit data at different hop sizes at a given instant and also vary hop sizes over lifetime. Performance analysis shows significant improvement in network lifetime and better uniformity in energy usage distribution in the proposed policy irrespective of network size and maximum allowable transmission range of nodes.

Energy efficient and hop constraint intra-cluster transmission for heterogeneous sensor networks

- Azad, Arman, Kamruzzaman, Joarder

  • Authors: Azad, Arman , Kamruzzaman, Joarder
  • Date: 2008
  • Type: Text , Conference proceedings
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  • Description: Although transmission policy is crucial in extending lifetime of sensor networks, most existing policies make simplified assumptions which include: i) circular cluster with cluster head (CH) at the center, ii) uniform periodic data generation model and iii) unrestricted transmission range for nodes. But, in practice, these assumptions are too restrictive for real-world deployment of heterogeneous sensor networks where clusters are usually polygonal. Moreover, in multi hop transmission energy consumption by sensors varies greatly with their distance from CH and even among sensors in the critical ring due to non-uniform relay traffic caused by asymmetric polygonal structure of cluster. In this paper, we propose a new transmission policy where sensors transmit at optimally determined hop sizes that varies over lifetime and a distributed hop selection algorithm that regulates each packet's arrival to CH within a given hop limit. Our formulation considers generic polygonal cluster, stochastic data generation model where data generation rate by sensors vary with events and limited transmission range for sensors. Performance analysis shows significant improvement in lifetime and better uniformity in energy usage among sensors in the proposed policy irrespective of cluster size, hop limit and maximum allowable transmission range of nodes

Geographic constraint mobility model for ad hoc network

- Ahmed, Sabbir, Karmakar, Gour, Kamruzzaman, Joarder

  • Authors: Ahmed, Sabbir , Karmakar, Gour , Kamruzzaman, Joarder
  • Date: 2008
  • Type: Text , Conference paper
  • Relation: Proceedings of the 2008 IEEE International Symposium on Modeling, Analysis & Simulation of Computer & Telecommunication Systems
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  • Description: In this paper, we propose a mobility model and present its simulation tool to generate realistic mobility traces for mobile ad hoc network. The mobility model is capable of creating realistic node movement pattern in the presence of geographic constraints by exploiting the concepts of anchors. The model dynamically places anchors depending upon the context of the environment through which nodes are guided to move towards the destination, and obstacles of arbitrary shapes with or without doorways and any existing pathways, in full or part of the terrain can be incorporated which makes the simulation environment more realistic. The characteristics of the proposed mobility model tested on a real world university campus map at various movement patterns are presented that illustrate the impact of the mobility model on the performance of a routing protocol and usefulness of the proposed scenario generation tool.

Hidden Markov models Incorporating fuzzy measures and integrals for protein sequence identification and alignment

- Bidargaddi, Niranjan, Chetty, Madhu, Kamruzzaman, Joarder

Rerouting in advance for preempted IR calls in QoS-enabled networks

- Ahmad, Iftekhar, Kamruzzaman, Joarder, Habibi, Daryoush

  • Authors: Ahmad, Iftekhar , Kamruzzaman, Joarder , Habibi, Daryoush
  • Date: 2008
  • Type: Text , Journal article
  • Relation: Computer Communications Vol. 31, no. 17 (2008), p. 3922-3928
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  • Description: When network resources are shared between Instantaneous Request (IR) and Book-Ahead (BA) connections, activation of future BA connections may cause preemption of on-going IR connections due to resource scarcity. Rerouting of preempted calls via alternative feasible paths is often considered as the final option to restore and maintain service continuity. Existing rerouting techniques, however, do not ensure acceptably low service disruption time and suffer from high failure rate and low network utilization. In this work, a new rerouting strategy is proposed that estimates the future resource scarcity, identifies the probable candidate connections for preemption and initiates the rerouting process in advance for those connections. Simulations on a widely used network topology suggest that the proposed rerouting scheme achieves a higher successful rerouting rate with lower service disruption time, while not compromising other network performance metrics like utilization and call blocking rate.

VoIP call capacity over wireless mesh networks

- Siddique, Md, Kamruzzaman, Joarder

  • Authors: Siddique, Md , Kamruzzaman, Joarder
  • Date: 2008
  • Type: Text , Conference paper
  • Relation: 2008 IEEE Global Telecommunications Conference p. 1-6
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  • Description: In recent years, research on VoIP over wireless mesh network (WMN) has gained particular attention because of its commercial prospect. This paper presents an analytical method to estimate VoIP call capacity in an WMN employing IEEE 802.11 devices. We used Markov chain analysis of IEEE 802.11 for network delay and loss to estimate the capacity while using rating factor, R score, defined by ITU-T, to ensure call quality. A detailed analysis of queueing delay and loss in terms of network parameters is also carried out along with their impacts on voice quality. The capacity model estimates call capacity in a single hop WLAN and is extendable to multi hop scenario and for video communications. The theoretical results are verified by simulation and compared to related previous works.

Weighted soft decision for cooperative sensing in cognitive radio networks

- Shahid, Mohammad, Kamruzzaman, Joarder

  • Authors: Shahid, Mohammad , Kamruzzaman, Joarder
  • Date: 2008
  • Type: Text , Conference paper
  • Relation: 2008 16th International Conference on Networks (ICON) p. 1-6
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  • Description: Enhancing the current services or deploying new services operating in RF spectrum requires more licensed spectrum which may not be provided by the regulatory bodies because of spectrum scarcity. On the contrary, recent studies suggest that many portions of the licensed spectrum remains unused or underused for significant period of time raising the issue of spectrum access without license in an opportunistic manner. Among all the spectrum accessing techniques, sensing based methods are considered optimal for their simplicity and cost effectiveness. In this paper, we introduce a new cooperative spectrum sensing technique which considers the spatial variation of secondary (unlicensed) users and each user's contribution is weighted by a factor that depends on received power and path loss. Compared to existing techniques, the proposed one increases the sensing ability and spectrum utilization, and offers greater robustness to noise uncertainty. Moreover, this cooperative technique uses very simple energy detector as its building block thereby reduces the cost and operational complexity.

Wireless security and privacy issues

- Kamruzzaman, Joarder

Neural networks for detection and classification of walking pattern changes due to ageing

- Begg, Rezaul, Kamruzzaman, Joarder

  • Authors: Begg, Rezaul , Kamruzzaman, Joarder
  • Date: 2006
  • Type: Text , Journal article
  • Relation: Australasian Physical & Engineering Sciences in Medicine Vol. 29, no. 2 (2006), p. 188-195
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  • Description: With age, gait functions reflected in the walking patterns degenerate and threaten the balance control mechanisms of the locomotor system. The aim of this paper is to explore applications of artificial neural networks for automated recognition of gait changes due to ageing from their respective gait-pattern characteristics. The ability of such discrimination has many advantages including the identification of at-risk or faulty gait. Various gait features (e.g., temporal-spatial, footground reaction forces and lower limb joint angular data) were extracted from 12 young and 12 elderly participants during normal walking and these were utilized for training and testing on three neural network algorithms (Standard Backpropagation; Scaled Conjugate Gradient; and Backpropagation with Bayesian Regularization, BR). Receiver operating characteristics plots, sensitivity and specificity results as well as accuracy rates were used to evaluate performance of the three classifiers. Cross-validation test results indicate a maximum generalization performance of 83.3% in the recognition of the young and elderly gait patterns. Out of the three neural network algorithms, BR performed superiorly in the test results with best sensitivity, selectivity and detection rates. With the help of a feature selection technique, the maximum classification accuracy of the BR attained 100%, when trained with a small subset of selected gait features. The results of this study demonstrate the capability of neural networks in the detection of gait changes with ageing and their potentials for future applications as gait diagnostics.

MPDF: Movement predicted data forwarding protocol for Underwater Acoustic Sensor Networks

- Nowsheen, Nusrat, Karmakar, Gour, Kamruzzaman, Joarder

  • Authors: Nowsheen, Nusrat , Karmakar, Gour , Kamruzzaman, Joarder
  • Type: Text , Conference paper
  • Relation: 20th Asia-Pacific Conference on Communication, APCC 2014 p. 100-105
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  • Description: Due to the unique characteristics of acoustic communication channel, reliable data transfer in underwater is difficult in applications such as pollution monitoring, oceano-graphic data collection, surveillance, etc. To handle this issue, an Opportunistic Message Forwarding Protocol (OMFP) [1], which selects next hop forwarders based on link reliability and data transfer reachability, was proposed for Underwater Acoustic Sensor Networks (UASNs). The protocol shows improved performance over some existing popular and reputed underwater data forwarding approaches. However, OMFP has not considered node movement which is a natural phenomenon underwater. Besides high error probability and dynamicity of underwater acoustic channel, node movement also makes data forwarding process difficult. In addition to the link reliability and reachability, incorporation of neighbors' coverage probability in terms of their movement pattern in the next hop selection will further increase the reliability of forwarder selection process and decrease the chances of packet loss. To address this issue, this paper presents a new approach, namely, Movement Predicted Data Forwarding (MPDF) protocol. In MPDF, every node predicts its future movement pattern due to various contributory factors and estimates node's location, coverage probability without using any 'active' localization technique. The simulation results show that the proposed technique improves data delivery ratio, routing overhead with comparable energy consumption.