Design and development of a new spreading scheme for S-CDMA cellular mobile systems

Design of a wide band metasurface as a linear to circular polarization converter ALTINTAŞ, OLCAY; ÜNAL, EMİN; AKGÖL, OĞUZHAN; KARAASLAN, MUHARREM; KARADAĞ, FARUK; Sabah, Cumali (2017-10-30) In this paper, we present a wide band metasurface (MS) polarization converter which converts a linearly polarized signal to a right-handed or left-handed circularly polarized signal both numerically and experimentally. The unit cell of MS has three nested rectangular resonators which have two metallic patches at its crossed corners. The simulated and measured results are achieved by a commercial full wave EM simulator and a vector network analyzer with two horn antennas in microwave frequency regime. The S-...
Sequence families with good correlation distribution Tekin, Eda; Özbudak, Ferruh; Department of Cryptography (2016) In this thesis we focus on two main properties of sequences which have wide range of applications in code division multiple access: autocorrelation and cross-correlation. First, necessary properties of sequences, some known perfect autocorrelation sequences and some known sequence families with their cross-correlation properties are given. Then, a perfect autocorrelation sequence [18] is generalized with respect to a number theoretic constraint of n for a given prime power q. This generalization enables the...
Evaluation of a Duty-cycled Protocol for TDMA-Based Wireless Sensor Networks Hasan, Mohammed Zaki; Al-Turjman, Fadi; Al-Rizzo, Hussain (2016-09-09) Contention-free Medium Access Control (MAC) protocols in Wireless Sensor Networks (WSNs) have higher energy efficiency and lower packet latency than contention-based ones due to reduced idling and allow efficient utilization of energy supplies of sensors. This paper presents evaluation the performance of Time Division Multiple Access (TDMA) dutycycled MAC for multihop WSNs. We propose a semi-Markov chains by considering power consumption in different operational models to analyze the Quality of Services (Qo...
Evaluation of priority dependent and time scheduled MAC layer protocols for ad-hoc networks Erdeğer, İsmail; Baykal, Buyurman; Department of Electrical and Electronics Engineering (2015) Ad-hoc networks have very unique features, such as dynamic topologies, relatively limited bandwidth and wireless signal propagation schemes, which present various challenges for wireless communication. In this thesis, control mechanisms for channel access scheduling and topology in ad-hoc networks are evaluated, which utilize the information from two-hop neighborhood to cope with the communication difficulties in ad-hoc networks. Channel assignment is one of the most important topics for ad-hoc networks. Ch...
Design, construction and performance evaluation of axial flow fans Keklikoğlu, Hayrettin Özgür; Albayrak, Kahraman; Department of Mechanical Engineering (2019) The primary purposes of this study are to examine the methods used in axial flow fan design, to perform these methods on the design of an axial fan, to develop a design application in order to reduce the design errors and spent time in the design process, and to determine the reliability of the application with numerical and experimental methods. This study is concerned with the design of axial flow fans. It provides detailed information about the design process — additionally, a design code is implemented....

Citation Formats

B. Ünal, “Design and development of a new spreading scheme for S-CDMA cellular mobile systems,” Ph.D. - Doctoral Program, Middle East Technical University, 1997.