M.Sc. Tahir Akram
Ich bin seit dem 1. April 2012 wissenschaftlicher Mitarbeiter im Fachbereich Elektrotechnik und Informatik an der Fachhochschule Lübeck. Ich beschäftige mich im Rahmen des Cognitive Radio Technologie für Medizinische Anwendungen.
Geboren am 14. Januar 1985
Studium Bachelor Elektrotechnik, 2007 University of Engineering & Technology Lahore.
Studium Master Information & Kommunikationstechnik 2012, TU Hamburg-Harburg.
seit April 2012 wissenschaftlicher Mitarbeiter an der Fachhochschule Lübeck
|||Cooperative Sensing Protocols and Evaluation via IEEE 802.15.4 Devices , In Special Issue of Self Optimized Radio Technologies (Journal of Physical Communication) Elsevier Science Publishers B. V., volume 19, 2016. [bib] [pdf] [abstract]|
Spectrum Sensing is one of the important tasks for wireless devices. By sensing the spectrum, wireless devices sense their radio environment and perform spectrum access accordingly to reduce collisions. Due to radio propagation effects and inherent noise in the measurements, performance of todays wireless technologies with individual spectrum sensing cannot solve the hidden node problem. Cooperative sensing is seen as a way to improve the performance of wireless devices improving the radio bandwidth utilization and minimizing interference among wireless devices. To the best of our knowledge, this is the first work which provides protocols for cooperative sensing and presents experimental results with IEEEź802.15.4 devices. We present and implement protocols and applications for primary, secondary and cooperative users with a dedicated control channel. Thereby, the secondary user receiver serves as a first cooperative node in the system which reduces collisions between primary and secondary users. We evaluate the system performance with receiver sensing and additional cooperative nodes. We also propose a mechanism to extend the protocol for multiple secondary users sharing the same control channel. Based on the evaluations, we also provide recommendations for usage of cooperative sensing with focus on IEEE 802.15.4.
|||Performance Evaluation of Cooperative Sensing via IEEE 802.15.4 Radio , In Wireless Communications and Networking Conference, IEEE (WCNC 2015), 2015. [bib] [abstract]|
Spectrum Sensing is one of the important tasks for the wireless devices but due to fading, shadowing and noise the performance of individual spectrum sensing devices is not ideal. Cooperative Sensing is seen as a way to improve the performance of individual spectrum sensing devices resultantly improving the efficient utilization of radio bandwidth and minimizing the interference among wireless devices. State of the art are extensive simulations and analysis on cooperative sensing although there are also number of performance evaluations of various fusion rules of cooperative sensing using software defined radios and FPGAs. The limitation of previous work is that they do not address the question how we can improve the overall performance of real systems with cooperative sensing. To the best of our knowledge, this is the first experimental work which presents cooperative sensing protocols with standard radios and evaluates the system performance using cooperative sensing. With IEEE 802.15.4 equipped radio devices we model primary, secondary and cooperating users. We implement cooperative sensing protocols, setup a scenario, perform measurements and compare system performance with and without cooperative sensing. All the experiments are automated with the wisebed testbed software. The evaluation results of cooperative sensing protocols indicate new challenges for optimization and provide awareness to the problem of improving the overall system performance
|||Performance Evaluation Metric for Cooperative Sensing in Heterogeneous Radio Environments , In European Wireless Conference, IEEE, 2013. [bib] [abstract]|
Spectrum sensing is a major task for wireless devices in order to improve coexistence among them in heterogeneous radio environments. Wireless communication includes at least two partners: transmitter and receiver. Therefore, cooperation between partners can improve the performance of spectrum sensing by reducing effort, improving sensing result or a combination of both. An optimal cooperative sensing scheme is a first step to achieve complete awareness of the radio environment for wireless devices. To the best of our knowledge, this is the first theoretical work performed in order to understand the problem of developing optimal cooperative sensing schemes for heterogeneous radio environments for multiple users and single channel. We analyze the problem and perform analytical work which results in a cooperative sensing model. The model comprises sensing schedule, data fusion rules, PU's traffic pattern, and detection performance of the sensing device. A new performance evaluation metric is introduced for optimum spectrum sensing in heterogeneous radio environments. An evaluation of available exemplary cooperative sensing schemes shows that none provides optimality in all scenarios.
|||Development of a Low Cost Sun Sensor using Quadphotodiode , In Position Location and Navigation Symposium (PLANS), 2010 IEEE/ION, 2010. [bib] [abstract]|
This paper describes about the design and hardware implementation of a low cost model of a two axis sun sensor using a quad photo diode, which can determine the azimuth and elevation angles of Sun in sensor's body frame of reference. The sensor uses quad photodiode to obtain angular information of Sun. It weighs less than 100g (which can be further reduced by optimizing the housing design). The relevant software requires 50K bytes of memory and little processing. We have also developed sensor calibration test bed (SCTB) which will also be the part of this paper. SCTB is used to calibrate the developed Sun Sensor; during calibration the whole surface of sun sensor (quad photodiode) is scanned for a field of view (FOV) equal to 60 ï¿½ 60. Step size during calibration is set to one degree so we get elevation and azimuth matrices each having 3721 values. The calibration process is fully automated with the help of algorithms written in Matlab. The step size used in calibration is adjustable and we can calibrate the sensor even less than one degree using this SCTB. Azimuth and elevation matrices generated during calibration are used as error correcting tables during real-time measurements taken by the sun sensor. Sun sensor is calibrated in front of Sun simulator made by the Optical Energy Technologies USA.
|||A Reusable and Extendable Testbed for Implementation and Evaluation of Cooperative Sensing , In The 8th ACM International Workshop on Performance Monitoring, Measurement and Evaluation of Heterogeneous Wireless and Wired Networks PM2HW2N'13, 2013. [bib] [abstract]|
Cooperative sensing has been identi?ed as a potential improvement for cognitive radios to perceive their radio environment. In the past, algorithms have been developed by analysis and simulations exclusively. With cheaper hardware experimental platforms have been used for evaluation purpose recently. Simulations lack realistic propagation models for radio transmission but are reproducible compared to experimental evaluation done by hand. The effects of reduced detection probability and false alarms are not realistic in these simulations. In this paper, we suggest a reusable and extendable automated testbed software and instructions for deployment of own testbeds. Primary users as well as secondary users with cooperating cognitive radios can be flexibly deployed in the testbed within seconds. The advantage is that a series of even long lasting measurements including automatic logging of results can be easily repeated. Results can be assessed on the fly during the ongoing evaluation by accessing debug output remotely. The testbed supports stationary, portable, and in the future mobile radio devices for flexible scenarios as well as monitoring devices for debugging. The testbed and the radio devices are validated by deploying primary and secondary user in a small scenario whose outcome was analyzed beforehand. The results are as predicted and show the usefulness of this approach.