Volume 22, Issue 1, October 2013

Performances of Code-Diversity with a Novel Spreading Sequence in DS/CDMA Communication Systems [Full Text]

Shin’ichi Tachikawa and Hayato Noguchi

Abstract—This paper proposes a novel spreading sequence for code-diversity in direct sequence/ code division multiple access (DS/CDMA) communication systems. In code-diversity, a composite sequence which is a sum of several branch sequences is adopted. By the proposed sequences, both the composite sequence and the branch sequences can be constructed from digital signal. Therefore, the hardware of the system can be simplified. By evaluations of computer simulations, bit error rate (BER) performance of the system to suppress multiple access interference (MAI) has a little degradation compared with that of the system using a conventional analog composite sequence. However, it can be obtained almost same BER performance of the system using a previous digital composite sequence by analog branch sequences. Further, to improve the BER performances and simplfy its hardware, modified code-diversity system with the proposed sequence is shown. 

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A Study of the readiness of the African Telecommunication industry to upgrade all GSM base stations to LTE.Case Study - Ghana [Full Text]

Affum Emmanuel, Shaddrack Y. Nusenu, Ansong E. Danso, Addo Emmanuel and Agyekum Kwame A-P

Abstract—The standardization of the Long Term Evolution (LTE) is currently carried through in 3GPP and the deployment of frequency plan- ning, the issue of upgrading from the current GSM networks in Ghana to LTE is becoming cliché and may even die out without any deploy- ment being done, since Ghana has already failed to meet its 2011 target for LTE. In this paper, the readiness of Ghana to migrate from GSM to LTE is investigated, including how Telecom companies and regulating bodies in Ghana will analyse the said network, network deployment, network infrastructure, digital dividends, availability of the right LTE-compatible User Equipment and its positive effects on Ghana as a devel- oping country. Further, the Technological, Technical, human resource and business aspects of deploying the LTE Network to facilitate the rolling-out of the said network in Ghana are discussed. Again, a thorough analysis of the technology and its effective deployment which will yield maximum and efficient usage of this network standard avoiding losses, yielding maximum profit thereby generating revenue for the country are addressed. It was realized that, Ghana is not ready to implement LTE mainly because of the unavailability of digital dividends, which will aid in an effective and cost-efficient roll-out with vast coverage providing more consumers with services of high QoS, in addition, as a results of less internet usage among Ghanaians Telcos may be in huge financial risk, rather prefer locating LTE base stations at industrial areas of the country. 

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Design and Simulation of Wideband and Low Phase Noise UHF Synthesizer [Full Text]

M. Majdi, F. Hodjat Kashani

Abstract—Design and simulation of a UHF wideband and low noise frequency synthesizer from 470 MHz to 860 MHz is presented. The proposed voltage controlled oscillator (VCO) in the phase lock loop (PLL) covers wide frequency bandwidth of 58% while phase noise performance has been optimized simultaneously, using parallel tuning diodes in the LC tank of modified Colpitts VCO. The result of the harmonic balance simulation shows an overall SSB phase noise less than -105 dBc/Hz at 10 KHz offset. The output power is more than 0dBm with maximum variation of 0.93 dB while using a high pass filter in the output. 

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LMS Algorithm for Optimizing the Phased Array Antenna Radiation Pattern [Full Text]
Dr. Saad Saffah Hassoon Hreshee

Abstract-This paper describes a usual application of LMS neural networks algorithm for evolving and optimizing of antenna array. The neural network allows not only establishing important analytical equations for the optimization step, but also a great flexibility between the system parameters in input and output. This research is based on some software that works on algorithms for the simulation of the beamforming techniques. Furthermore, the research has shown the response of the system before and after the use of adaptive algorithm. The results showed that the output for four-element antenna array pattern produces a narrower beam with the same amplitude, as that of the main beam before applying neural network. Along with a narrower beam, comes another positive result, that is, the reduction of side-lobes more than 5 decibels in comparison to the related work. 

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Effect of Inductive Posts on Y-junction Substrate Integrated Waveguide (SIW) Slot Antenna Array [Full Text]
Sourav Moitra, A. K. Mukhopadhay and A. K. Bhattacharjee

Abstract—The Effect of introduction of Inductive Posts over Single layer Y-junction Substrate Integrated Waveguide (SIW) Slot Antenna Array has been studied in this paper. Single and double Inductive posts have been introduced over basic SIW Antenna Array designed using Y-junction power divider consisting of symmetrical linearly polarized slot array antenna elements over a substrate of dielectric constant of 3.2 and thickness 0.782mm. Alternating offsets in the slots is used to generate in-phase electric field distributions on every radiating slot. The array configurations with different Inductive post alignment have been supported with necessary results. The results confirm the antenna suitable for K-band applications. The array has been simulated and optimized using full-wave EM CAD Tool CST Microwave Studio. The designs are simple and come with high gain over the operable bandwidth.