Volume 18, Issue 2, February 2013

Improved CR-MAC By Geographic Greedy Forwarding Algorithm in WSN [Full Text]
Shweta Parode and Shubhangi Mahamuni

Abstract— In this paper, a Cognitive Radio based Medium Access Control (CR-MAC) protocol for Wireless Sensor Networks that utilizes cognitive radio transmission is used. In cognitive radio (CR) networks, identifying the available spectrum resource through spectrum sensing, deciding on the optimal sensing and transmission times, and coordinating with the other users for spectrum access are the important functions of the medium access control (MAC) protocols for that purpose geographic greedy forwarding algorithm is followed. In this paper, the sensor nodes are classified into nodes of critical information, and nodes of non-critical information. The CR- MAC protocol prioritizes the critical packets access to the transmission medium by transmitting them with higher power while transmitting lower priority packets using lower or higher transmission power depending upon the priority. The network throughputs can be improved by increasing number of traffic rate, also the end-to-end delay will be minimized by CR-MAC protocol. And a motive to take advantage of heavy traffic rate which may occur at the receiver, a higher priority packet experiences congestion only when there are more than one critical packet transmission at the same time slot while non critical packets experience congestion when there are more than one transmission at the same time slot. Self CR-MAC is created for avoiding congestions, the coordinate find out the nearest node to forward the data, Information remains forwarding. 

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Wavelet and FFT based BER Analysis for Multicarrier Communication [Full Text]

Shivaji Sinha and Chakresh Kumar

Abstract—In 4G wireless communication systems, bandwidth is a precious parameter, and service providers are continuously met with the challenge of accommodating more users with in a limited allocated bandwidth. To increase data rate of wireless medium with higher performance, Recently DWT- OFDM is adopted in place of FFT –OFDM for frequency translation in OFDM system. Modulation schemes such as 4-PSK, DPSK & QAM have been used in the developed OFDM system for both DWT and FFT based model. In this paper comparative studies on DWT-OFDM & FFT-OFDM systems are presented. Results also show that DWT-OFDM is superior as compared to FFT-OFDM with regards to the BER performance, especially when it uses bior 5.5 or rbior 3.3 wavelet family for AWGN channel. This shows that the DWT families better over the IFFT-FFT implementation. The results presented in the paper are based on Matlab based simulations; a highly efficient tool for different applications. 

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Conceptualising VLAN Operation Through a VLAN Teaching Model (VTM): Deployed for sub-Saharan Institutions [Full Text]

Jameson Mbale

Abstract—The VLAN technology involved defining set of ports and criteria of VLAN membership on a switch for workstations connected to the ports that allowed the given edge devices to communicate exclusivelywith the targeted stations on the same VLAN. Teaching such advanced technology to institutions in the sub-Saharan region that lack a VLAN infrastructure posed a challenge to the learners’ability to conceptualise and to clearly understand. Thus, teaching the technology while limiting it to theory only,failed to allow students to witness VLAN operational principles. It was in view of this, that the VLAN Teaching Model (VTM) was envisaged to simplify the methodology of introducing the essence of VLANs into a classroom environment. To ascertain the effectiveness of the model,a CASE Control study was conducted where a class of one hundred and twenty (120) students was divided into two groups. The Control group which used the model had fifty one (51) studentsand managed to attainan eighty five percent (85%) conceptualiasation level of the technology, a high to very high result. The CASE Group comprised of 60 students had only eight (8) students who managed to attain a high/very high conceptualization level. Thus only thirteen point three-three percent (13.33%) high/of the case group managed to attain a very high conceptualiasation level. From such statistical results, the VTM proved to be an effective teachingtool in the absence of the actual infrastructure.