Browsing by Subject "Cellular telephone systems"

Now showing 1 - 7 of 7

Open Access
Bluetooth or 802.15.4 technologies to optimise lifetime of wireless sensor networks: Numerical comparison under a common framework
(IEEE, 2008-04) Buratti, C.; Körpeoğlu, İbrahim; Karasan, Ezhan; Verdone, R.
This paper aims at comparing through simulations the network lifetime of a wireless sensor network using Bluetooth-enabled or IEEE802.15.4 compliant devices. The evaluation is performed under a common reference framework, namely the EMORANS scenario for wireless sensor networks. Since the two enabling technologies rely on different MAC paradigms, suitable definition of the performance metrics is needed, in order to make the comparison meaningful. Thus, the paper has also a methodological objective. In particular, three different definitions of network lifetime are introduced, and a comparison of performance obtained by applying the different definitions is provided. Then, the comparison between the two standards is introduced: it is shown that there are no orders of magnitude of difference in network lifetime when the two technologies are used and the choice of the technology depends on the application requirements.
Open Access
Dikgen frekans bölmeli çoklu erişim sistemlerinde telsiz erişim terminallerinin işbirliği
(IEEE, 2009-04) Tokel, Turgut Barış; Aktaş, Defne
Gelecek nesil kablosuz iletişim sistemlerinde öngörülen veri hızlarına ulaşabilmek için bu sistemlerde frekans yeniden kullanım oranının 1 olmasına ihtiyaç¸ vardır, bu ise özellikle hücre sınırlarındaki kullanıcıların önemli ölçüde hücreler arası girişime maruz kalmalarına neden olur. Telsiz erişim terminalleri arasında işbirliği hücreler arası girişimin azaltılmasında önemli bir rol oynamaktadır. Bu bildiride çok hücreli, çok girdili çok çıktılı, dikgen frekans bölmeli çoklu erişim sistemlerinde telsiz erişim terminallerinden kullanıcılara işbirlikli veri iletimi problemini ele alıyoruz. Telsiz erişim terminallerinin aralarında kısıtlı ileti paylaşımı ile çizelgeleme ve veri iletimi yaptıkları etkin bir işbirlikli algoritma öneriyoruz.
Open Access
Mobile image search using multi-query images
(IEEE, 2015) Çalışır, Fatih; Bastan, M.; Güdükbay, Uğur; Ulusoy, Özgür
Recent advances in mobile device technology have turned the mobile phones into powerfull devices with high resolution cameras and fast processing capabilities. Having more user interaction potential compared to regular PCs, mobile devices with cameras can enable richer content-based object image queries: the user can capture multiple images of the query object from different viewing angles and at different scales, thereby providing much more information about the object to improve the retrieval accuracy. The goal of this paper is to improve the mobile image retrieval performance using multiple query images. To this end, we use the well-known bag-of-visual-words approach to represent the images, and employ early and late fusion strategies to utilize the information in multiple query images. With extensive experiments on an object image dataset with a single object per image, we show that multi-image queries result in higher average precision performance than single image queries. © 2015 IEEE.
Open Access
Novel predistortion algorithm for OFDMA
(IEEE, 2009) Ali, S.; Markarian, G.; Arıkan, Erdal
The RF amplifier in a wireless communication system is usually non-linear in nature. If such an amplifier is used in OFDMA based systems, it will cause serious degradation. This degradation will be both in terms of the reduction in BER and the generation of out of band noise. In this paper we have worked on the linearization method of the amplifier. This work is on a hybrid methodology, in which estimation of the model is performed in frequency domain and compensation is performed in time domain. The downlink preamble of the IEEE802.16e system is used here for the estimation purpose. The results for the suppression of spectra are shown at the end.
Open Access
An optimal network dimensioning and initial energy assignment minimizing the monetary cost of a heterogeneous WSN
(IEEE, 2009) Sevgi, Cüneyt; Kocyigit, A.
In this paper, a novel method is proposed to dimension a randomly deployed heterogeneous Wireless Sensor Network (WSN) of minimum monetary cost satisfying minimum coverage and minimum lifetime requirements. We consider WSNs consisting of two different types of nodes clusterheads and ordinary sensor nodes, randomly deployed over a sensing field. All devices are assumed to be stationary and have identical sensing capabilities. However, the clusterheads are more energetic and powerful in terms of processing and communication capabilities compared to sensor nodes. For such a network, finding minimum cost WSN problem is not a trivial one, since the distribution of the mixture of two different types of devices and the batteries with different initial energies in each type of device primarily determine the monetary cost of a WSN. Therefore, we formulated an optimization problem to minimize the monetary cost of a WSN for given coverage and lifetime requirements. The proposed optimization problem is solved for a certain scenario and the solution is validated by computer simulations. © 2009 IEEE.
Open Access
PocketDrive: A system for mobile control of desktop PC and its applications using PDAs
(IEEE, 2007-11) Yıldırım, Yenel; Körpeoğlu, İbrahim
Today, consumer electronic devices and PCs are inevitable parts of our daily life. Controlling those devices remotely is an important aspect of the technology. We have already universal remote control devices for controlling consumer electronic devices. Similarly, we may control our desktop and laptop PCs and their applications remotely via portable and smaller computers like PDAs and Pocket PCs. This paper presents a system and its architecture that enable a wireless-enabled PDA to control a PC and its applications remotely over a 802.11 or Bluetooth link. With such a system running on a PDA, a user can start, run and control PC applications from any location that is reachable via 802.11 link. This enables flexibility, ease of use, and freedom for the user of PC applications. ©2007 IEEE.
Open Access
A strong user authentication protocol for GSM
(IEEE, 2005-06) Aydemir, Özer; Selçuk, Ali Aydın
Traditionally, the authentication protocols for cellular phone networks have been designed for device authentication rather than user authentication, which brings certain limitations and restrictions on the functionality of the system. In this paper we propose a user authentication protocol for the Global Standards for Mobile (GSM) which permits the use of weak secrets (e.g. passwords or PINs) for authentication, providing new flexibilities for the GSM users. © 2005 IEEE.