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International audience; The paper presents the studies that have been led toward the integration of device-to-device (D2D) communications within LTE networks in the frame of the project ACCENT5 (Advanced Waveforms, MAC Design and Dynamic Radio Resource Allocation for Device-to-Device in 5G Wireless Networks) supported by the French National Research Agency. The solutions presented in this paper cover several aspects of D2D communications; they are the result of a close cooperation between four partners Thales Communications and Security, CNAM, TeamCast and CentraleSupélec. Physical Layer aspects have been investigated, especially concerning waveforms envisioned for D2D communications within 5G networks. Also, a new MAC protocol has been designed to address the issues raised by the integration of D2D transmissions within LTE cells. The solution coming out of the study guarantees a minimum QoS for both types of users (D2D users and regular users) and aims at reusing spectrum while offloading the burden on the base station. © 2017 IEEE.

International audience; The paper presents the studies that have been led toward the integration of device-to-device (D2D) communications within LTE networks in the frame of the project ACCENTS (Advanced Waveforms, MAC Design and Dynamic Radio Resource Allocation for Device-to-Device in SG Wireless Networks) supported by the French National Research Agency. The solutions presented in this paper cover several aspects of D2D communications; they are the result of a close cooperation between four partners: Thales Communications and Security, CNAM, TeamCast and CentraleSupelec. Physical Layer aspects have been investigated, especially concerning waveforms envisioned for D2D communications within SG networks. Also, a new MAC protocol has been designed to address the issues raised by the integration of D2D transmissions within LTE cells. The solution coming out of the study guarantees a minimum QoS for both types of users (D2D users and regular users) and aims at reusing spectrum while offloading the burden on the base station.

This paper presents a hardware processor for 100Gbps wireless data link layer. A serial Reed-Solomon decoder requires a clock of 12.5GHz to fulfill timings constraints of the transmission. Receiving a single Ethernet frame on a 100 Gbps physical layer may be faster than accessing DDR3 memory. Processing so fast streams on a state-of-the-art FPGA (field programmable gate arrays) requires a dedicated approach. Thus, the paper presents lightweight RS FEC engine, frames fragmentation, aggregation, and a protocol with selective fragment retransmission. The implemented FPGA demonstrator achieves nearly 120 Gbps and accepts bit error rate (BER) up to 2e - 3. Moreover, redundancy added to the frames is adopted according to the channel BER by a dedicated link adaptation algorithm. At the end, ASIC synthesis results are presented including detailed statistics of consumed energy per bit.

This work introduces a physical-layer secure multiple-users communication scheme. Our scheme employs the multi-path nature of the wireless channel to provide a different secure communication link for each of the legitimate users. We show that the proposed scheme highly degrades the eavesdroppers channel even for the worst case scenarios. We also provide the secrecy capacity and secrecy outage probability for the proposed scheme. We analyze the effect of the number of users, channel paths, and antenna elements on the secrecy performance of the scheme. Institute of Engineers and Everyone Else IEEE Communications Society

We consider the energy harvesting two user Gaussian multiple access channel (MAC), where both users harvest energy from nature. The users cooperate at the physical layer (data cooperation) by establishing common messages through overheard signals and then cooperatively sending them. In addition, the users cooperate at the battery level (energy cooperation) by wirelessly transferring energy to each other. We find the jointly optimal offline transmit power and rate allocation policy together with the energy transfer policy that maximizes the departure region. We provide necessary conditions for energy transfer, and prove some properties of the optimal transmit policy, thereby shedding some light on the interplay between energy and data cooperation. Publisher's Version

Silicon-photonics bus and ring networks-on-chip are evaluated in terms of transfer function and bit error rates at 10Gb/s, demonstrating that the ring architecture can be effectively used with physical layer performance similar to the bus.

Privacy and security have an increasingly important role in wireless networks. A secure communication enables a legitimate destination to successfully retrieve information sent by a source, while it disables the eavesdropper (illegitimate destination) to interpret the intercepted information. Physical (PHY) layer security approaches for wireless communications can prevent eavesdropping without encryption. It exploits the physical characteristics of the wireless channel in order to transmit messages securely. They are typically feasible when the source-destination channel is better than the source-eavesdropper channel. Cooperative schemes are a means to improve the performance of secure wireless communications. We propose an improved relay selection scheme, based on source-eavesdropper channel SNR restriction, that will guarantee the best secrecy rate at the destination under QoS condition. Performance has been studied in terms of secrecy rate, outage probability and average error probability. Simulations shows that the proposed scheme outperforms in terms of the secrecy rate at the destination when compared to techniques in the literature. Scopus

We present a novel cross layer approach to random access (RA) that combines physical-layer network coding (PLNC) with multiuser detection (MUD). PLNC and MUD are applied jointly at the physical level in order to extract any linear combination of messages experiencing a collision. The set of combinations extracted from a whole frame is then processed by the receiver to recover the original packets. A simple pre-coding stage at the transmitting terminals allows the receiver to further increase system diversity. We derive an analytical bound on the system throughput and present simulation results for the decoding at the physical level as well as several performance measures at frame level in block fading channels, namely throughput, packet loss rate and energy efficiency. The results we present are promising and suggest that a cross layer approach leveraging on the joint use of PLNC and MUD can significantly improve the performance of RA systems.

Within the paradigm of physical layer secrecy, typically a physical layer specific characteristic is used as key generator to guarantee information hiding from eavesdroppers. In this paper, we propose a novel secret key generation algorithm based on two reciprocal physical layer parameters; the channel measurements and the distances between the two communicating nodes. The two parameters are estimated experimentally using implementations of our algorithm on three FPGA-based WARP kits emulating the two communicating nodes and the eavesdropper. The parameters are used as common sources of randomness to generate the secret key. We evaluate the performance of our algorithm through extensive iterations. We compare the bit mismatch rate as well as the entropy of the generated secret key of our algorithm versus classical channel only and distance only based algorithms. Our results reveal that even in the worst case scenarios, our algorithm outperforms the two other algorithms and overcomes their vulnerabilities. 2014 IEEE. Scopus

It was well known from Shannon's days that characteristics of the physical channel like attenuation, fading and noise can impair reliable communication. But it was more recently that the beneficial side effects of channel characteristics in ensuring secret communication started getting attention. Studies have been made to quantify the amount of secrecy that can be reaped by combining channel coding with security protocols. The Wiretap channel proposed by Wyner is arguably one of the oldest models of physical layer security protocols. In this paper, we present a brief tutorial introduction to the Wiretap channel, followed by an application of the physical layer model to a class of Key Distribution protocols. We present results from an implementation of key distribution protocols using Software Defined Radio tools along with physical RF hardware peripherals. We believe this approach is much more tangible and informative than computer based simulation studies. � 2013, DESIDOC.

Machine-to-machine networks are spreading over every sector of our society due to their self-organisation capabilities. In these networks, thousands of devices are left unattended for years of operation without the possibility of human intervention. In this sense, every step forward into avoiding early exhaustion of the network nodes is of paramount importance. We have introduced a novel authentication scheme that is able to discard non-intended and/or non-legitimate packets just after the reception of the physical preamble. This proposal was shown to yield enormous energy saving with regard to both node exhaustion attacks and normal network operation. In this paper, we extend that work with a novel synchronization protocol that addresses previous desynchronisation issues. Besides, we analyse and propose the more appropriate deployment parameters that maximise the overall energy savings. We also detail the necessary key generation and key updating processes required to manage the in use keying material. Moreover, we show how to fit the proposed mechanism into the IEEE 802.15.4e amendment to the IEEE 802.15.4-2006 standard, as many companies have decide to go for this technology for the development of machine-to-machine networks. © 2013 John Wiley & Sons, Ltd.

In the field of Networking and Telecommunications, researchers have often the choice between several environments (real, experimental, emulated or simulated) to validate their results. Each facet of our work, from the study of network behavior, to protocol improvements, including the characterization of specific phenomena, can be related to different environments more or less realistic. We are thus confronted to a trade-off mixing the level of abstraction, bias of measurement, and implementation complexity (in term of cost and time). Nevertheless, because simulations are often regarded as quicker, easier to use and simpler environments than real testbeds, they are mostly used despite their accuracy limits. This is particularly true when simulating wireless communication, where cross-layer effects and physical medium are complex to isolate and understand.While some effort have been made to improve simulators, their comparison with real environments are still in progress and requires experimental equipments, especially for wireless networks. In this context, we built a controlled test-bed environment to calibrate wireless simulators. This paper compares the results obtained for scenarii respectively played within this environment and the Ns3 platform. Our analysis method is based on network traces comparison using classification trees. On a first basis the construction of the tree is supervised, but later, it could be unsupervised and feed the need for a comparison tool of different network environments.

In recent years, sensor networks characteristics have led to incremental utilization in different types of applications. Several techniques have been proposed to evaluate the performance of WSNs the two most popular being mathematical analysis and simulations. An important drawback of these techniques is that they provide evaluation results that usually are not similar to those of real deployments. One reason for this is the fact that both techniques introduce physical layer modeling assumptions, which do not usually corresponded to real-life environments. In this paper, we used measurements from an industrial environment to develop a new radio propagation model for use in simulators and mathematical tools. The proposed radio model was implemented in the COOJA simulator and validated against real-life results obtained from a testbed inside a running oil refinery, which were found not to conform to any legacy radio propagation model. The proposed model has been shown to successfully match the refinery testbed behavior. 125 131 Sponsors: ACM SIGSIM Conference code: 93968 Cited By :5

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2012, Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2012, Son yıllarda telsiz iletişim sistemleri için kaliteli ses iletimi yanında yüksek hızlı veri iletimi gereksinimi de artmaktadır. Artan bu gereksinimi karşılamak için iletişim sistemlerinin başarım oranları ve sığaları artırılmalıdır. Bu amaçla bu çalışmada çift-yönlü röle ağları ele alınmaktadır. Çalışmada ele alınan sistem iki uç düğüm ve aralarında röleden oluşmaktadır. İki uç birim birbirlerine röle üzerinden bilgi iletmektedir. Klasik durumda bu iş dört evrede, geleneksel ağ kodlama yönteminde üç evrede, bu tezde ele alınan fiziksel katman ağ kodlamada (PNC) ise iki evrede gerçekleşmektedir. PNC’de rölenin yarı dupleks çalışmasından kaynaklanan zaman kaybı giderilmektedir. Bu yöntemde, telsiz iletişim sistemlerinde oluşan bozucu etki girişimden yararlanarak sistem başarımı iyileştirilmektedir. Fiziksel katman ağ kodlama yönteminde kanal sönümleme durumları dikkate alınmadığı için derin sönümleme noktaları oluşur. Yeni önerilen uyarlamalı ağ kodlama yönteminde, uç düğümlerde kullanılan modülasyon tipine göre rölede oluşan derin sönümleme noktaları dikkate alınmaktadır. Kanal durumlarına göre, rölede kullanılan ağ kodlama matrisinin seçilmesi hata başarımını artırmaktadır. Özellikle Rician sönümlemeli kanallarda kanal parametresi K’nın yüksek değerleri için kodlama kazancı artmaktadır. Kanal durumlarına göre, rölede kullanılan ağ kodlama matrislerinin oluşturulması için Latin kareler yöntemi basit ve etkin bir yöntemdir. Literatürde uyarlamalı eşleme ile ilgili pek çok çalışma vardır. Ancak asimetrik hızlarda çalışan uç düğümlerden oluşan röle ağı için uyarlamalı eşleme ile ilgili çalışma bulunmamaktadır. Bu tez çalışmasının ilk kısmında, iki uç düğümün röle yardımıyla bilgi alışverişi yaptığı çift yönlü röleli kanallarda fiziksel katman ağ kodlama ve uyarlamalı eşleme yöntemi incelenmektedir. Sistemde QPSK modülasyonu ve çöz-aktar iletim tekniği kullanılmaktadır. Her düğümün ve rölenin yarı dupleks çalıştığı ve bir anteni olduğu varsayılmaktadır. Farklı Rician sönümleme parametreleri için her iki sistemin bilgisayar benzetim sonuçları karşılaştırılmaktadır. Çalışmanın ikinci kısmında uyarlamalı eşlemenin asimetrik hızlarda çalışan çift yönlü röleli kanallara uygulanması gerçekleştirilmektedir. İlk olarak iki uç düğümde BPSK ve QPSK modülasyonu ile uyarlamalı eşleme yönteminin kullanıldığı sistem için derin sönümleme noktaları ve kanal bölgeleri elde edilmektedir. Bu sistem için sönümleme noktaları ve çevrelerindeki bölgelerde hata başarımını iyileştiren ağ kodlama matrisleri Latin dikdörtgenler yardımıyla oluşturulmaktadır. Bilgisayar benzetimleri yardımıyla elde edilen hata olasılığı eğrileri incelendiğinde, Rician kanal parametresi K=10 iken 〖10〗^(-4) lük bir bit hata başarımını sağlamak için E_b⁄N_0 oranında uyarlamalı eşleme yöntemi PNC yöntemine göre 4.5 dB kazanç sağlamaktadır. Daha sonra uç düğümlerde BPSK ve 8-PSK modülasyonu ile uyarlamalı eşleme yönteminin kullanıldığı sistem için derin sönümleme noktaları ve kanal bölgeleri elde edilmektedir. Bu sistemler için Latin dikdörtgenler yardımıyla ağ kodlama matrisleri bulunarak hata başarımları bilgisayar benzetimleri yardımıyla değerlendirilmektedir. Benzetim sonuçları incelendiğinde, Rician kanal parametresi K=10 iken 〖10〗^(-3) lük bir bit hata başarımı sağlamak için uyarlamalı eşleme yöntemi PNC yöntemine göre E_b⁄N_0 oranında 1.5 dB kazanç sağlamaktadır., In recent years, besides the need for high quality voice transmission for wireless communication systems, the need for high-speed data transmission is also increasing. In order to respond to these needs, the reliability and capacity of the communication systems should be increased. In the current 3G systems, increase in data rates has been provided by larger bandwidths and multiple antennas techniques. However, in a typical cellular system, the signal to noise ratio required to use multiple antennas techniques is observed on a very small fraction of the cell. The motivation for relay-based architecture comes from achieving larger gains by using this techniques for all cell. For this reason, two-way relay channel has been studied in this thesis. In a wireless two-way relay channel, intermediate node called relay assists communication between two end nodes. The relay receives the signal from the source, processes and transmits the signal to the destination. The relays are classified into two classes as analog relays or digital relays. Analog relays that also known as nonregenerative relays just amplify and transmit the received signal to the destination. Digital relays also known as regenerative relays process the received signal. The received signal first demodulated and then modulated before transmission to the destination. In literature, analog relays are called amplify and forward whereas digital relays are called decode and forward. In relay-based wireless systems frequency division duplexing or time division duplexing techniques are used frequently. In a TDD technique, the transmissions need to be orthogonal in time in order to avoid from interference since the same frequency is used for all tranmissions. There are efficient coding strategies at the relay that provide utilization of the channel in literature. One of the well studied coding strategy is called physical-layer network coding. In PNC, the relay receives the signal from both sources, process and forwards an appropriate signal satisfying the exclusive law to the end nodes. In PNC, the bi-directional transmission is completed in two phases whereas in classical and conventional network-coding systems it is completed in four phases and three phases, respectively. Thus, the PNC protocol avoids the loss in spectral efficiency that occurs due to the half-duplex nature of the communication devices. PNC and its counterpart adaptive network coding (ANC) are the latest protocols for two-way communication systems. Conventional network coding is implemented in the network layer, where relay node combines bits by XOR operation and forwards to the end nodes. In PNC strategy, two end nodes send information to the relay simultaneously. Naturally, the signals from end nodes overlap in free space as electromagnetic waves. Then, the relay decodes the superposition of mixed signals. Although broadcast nature of wireless communication system makes interference a destructive nuisance in common case, PNC turns the broadcast property into a capacity-increasing advantage. Nevertheless, PNC scheme does not give the best performance for all channel fade coefficients. To reduce the impact of multiple access interference which occurs at the relay during the MA phase a new scheme that is called adaptive network coding is introduced. In ANC, network coding mapping employed at the relay during the broadcast phase is adaptively changed according to the channel fade coefficients. Thus, the impact of the multiple access interference is decreased. The set of all possible channel realizations is quantized into a finite number of regions. In each region a specific network coding map is used to reach the best error performance. These network coding maps should satisfy the exclusive law. In certain regions any network coding map which satisfies the exclusive law gives the best performance and changing network coding map doesn’t impact error performance. These regions are called non-removable singular fade states. The non-removable singular fade states ocur due to channel outage. In certain regions the choice of the network coding map affects the performance. These ones are called removable singular fade states. An upper bound on the average end-to-end Symbol Error Rate is given with and without adaptive network coding at the relay, for a Rician fading scenario. It is clear that without ANC, at high Signal to Noise Ratio, three error events contribute to the end-to-end SER. The first error event is associated with the removable singular fade states. The second one is associated with the non-removable singular fade states. The third one comes from the error event during the BC phase. All these error events decrease as SNR-1 without ANC. In the other hand, when adaptive network coding is used at the relay, the error events associated with the removable singular fade states decrease as SNR-2. As a result adaptive network coding strategy provides a coding gain over the physical layer network coding. In TWRC, the contribution to the average end-to-end SER during the MA phase is dominant for a Rician fading channel. Since adaptive network coding improves the error performance during the MA phase, ANC provides more coding gain in a Rician fading environment than in a Rayleigh fading environment. Network coding map that satisfies the exclusive law can be obtained by Latin Square. It is shown that the requirement of satisfying the exclusive law is same as the clustering being constructed by a Latin squares. An adaptive network coding has been well studied in the literature for systems where symmetric data rates are used at the end nodes, such as M-PSK modulations. However, there is not too much study for asymmetric systems for which transmission rates of the two end nodes differ. On the other hand, end-nodes can be located on different distances to the relay. The quality of the signal that reaches the relay from one of the end nodes can be weak while that of the other end node signal being strong. Thus, different modulation schemes can be used at the end nodes. In the first part of the thesis, adaptive physical layer network coding in two-way relay systems is investigated for the symmetric scheme where both end nodes employ the same signal constellation. It is assumed that the same QPSK modulation is employed at the end-nodes and decode-and-forward relaying strategy is applied in the considered system. In addition, each nodes and relay are assumed having each one antenna and cannot receive and transmit simultaneously. The BER and SER performances of the PNC and ANC schemes are evaluated via computer simulations are compared for both Rayleigh and Rician channels. In the second part, adaptive network coding is implemented for the scenario that the data rates of the end nodes are asymmetric. First, quantization of the complex plane is obtained for the scenario that the end nodes use BPSK and QPSK modulation. In this scenario network coding maps that give the best performance for a given region are determined by Latin Rectangles. It is shown that for the Rician fading scenarios considered for the Rician fading parameter K=10, at a BER of 〖10〗^(-4), the ANC provides an SNR gain of 4.5 dB over the classical PNC system. Second, quantization of the complex plane is obtained for the scenario that the end nodes employ BPSK and 8-PSK modulation. For all regions, specific network coding maps that satisfy the exclusive law are acquired by Latin rectangles. It is shown that to achieve a bit error rate of 〖10〗^(-3) ANC scheme provides a coding gain of 1.5 dB compared to the reference PNC scheme for a Rician fading parameter value of K=10. Finally, theoretical error probability upper bounds valid at high SNR values are obtained for the considered asymmetrical two-way relaying systems. As well as these upper bounds are loose, their relative behaviour compares well with the simulation curves., Yüksek Lisans, M.Sc.

Les réseaux sans-fil se généralisent, notamment en tant que techniques d'accès à l'Internet avec les dispositifs sans-fils portatifs actuels (ordinateurs portables, tablettes, smartphones...). Cependant, la nature de ces réseaux offrant des ressources réduites par rapport aux réseaux filaires ou mettant en oeuvre des techniques d'accès indéterministes temporellement posent des problèmes au niveau de la gestion des ressources. Par conséquent la métrologie de ces réseaux sans fil est un élément prépondérant. Etant donnée la nature spécifique de ces réseaux, cette article introduit une approche "cross-layer" de la métrologie, i.e. une approche qui va réaliser des mesures et des observations à tous les niveaux du réseau sans fil: couches physique, MAC, liaison et réseau. Cet article insiste sur l'importance et la difficulté de réaliser des mesures fiables au niveau de la couche physique et du médium hertzien. Il illustre au travers d'une expérience, l'impact de la qualité du support hertzien sur la qualité et les performances du service réseau.

DVB-T2 implements a very flexible time interleaving that allows multiple tradeoffs in terms of time diversity, latency and power saving. In this paper, we study in detail these tradeoffs in the context of mobile reception. Together with time diversity, we also investigate the impact of reduced time de-interleaving memory and Alamouti-based MISO in the mobile reception of DVB-T2 services. In addition, we propose the utilization of upper layer FEC protection in order to overcome the limitations of the DVB-T2 physical layer for the provision of long time interleaving, and enable fast zapping. The performance is evaluated by means of simulations in mobile channels that include the presence of fast fading and shadowing in the received signal. © 2010 IEEE., Manuscript received October 13, 2010; revised April 22, 2011; accepted May 11, 2011. Date of publication July 25, 2011; date of current version August 24, 2011. This work was supported in part by the Spanish Ministry of Industry, Tourism, and Commerce under the Celtic project Enabling Next-Generation Networks for Broadcast Services ENGINES (TSI-020400-2010-108). The work of D. Gozalvez was supported by the FPU Grant AP2008-03293 of the Spanish Ministry of Education.

[EN] The paper addresses the problem of distribution of highdefinition video over fiber-wireless networks. The physical layer architecture with the low complexity envelope detection solution is investigated. We present both experimental studies and simulation of high quality high-definition compressed video transmission over 60 GHz fiberwireless link. Using advanced video coding we satisfy low complexity and low delay constraints, meanwhile preserving the superb video quality after significantly extended wireless distance. © 2011 Optical Society of America., This work has been partly funded by the European Commission under FP7 ICT-249142 FIVER project and by the by the Spanish Ministry of Science and Innovation under the TEC2009-14250 ULTRADEF project.

The paper reports our last advances in the realization of mobile wireless sensor networks (WSNs), able to reveal unknown tracks and leakages within underground pipelines used to distribute water. This WSN technology is based on a concept recently proposed by the authors, which makes use of mobile acoustic sensors able to flow within a pipe, transported by the fluid, and equipped with a wireless interface that reports the acquired information to the surface. The paper starts from the early and simplified realization that has been already presented to demonstrate the feasibility of the concept and describes the realization of advanced prototypes, using wireless modules that work in different frequency ranges with specifically designed antennas with the auxiliary possibility to track the position of the device. Ad-hoc solutions have been identified for the construction of the microwave front-end, allowing an improved stability despite the mobility and the rotations. Battery life, compared to application requirements, have been investigated and optimized. Moreover, the technology has been adapted to different operational contexts, making use of different choices of the Physical Layers and various transmission protocol optimizations. At last, results are presented and discussed. Qatar National Research Fund Scopus

Mobil Haberleşme sistemleri; birinci nesil olarak adlandırılan analog mobil haberleşme sistemleri ile başlamıştır. Birinci nesil mobil haberleşme sistemlerinin sadece ses temelli hizmetler sunabilmesi, hizmet kalitesinde sıkıntılar yaşanması neden olmuş, ikinci nesil mobil haberleşme sistemlerine (2G) ihtiyaç duyulmuştur. İkinci nesil haberleşme sistemleri sesin yanında düşük hızlı veri iletimine de imkan tanıyan sayısal bir mobil haberleşme teknolojisidir. İkinci nesil haberleşme sistemlerinde düşük hızlarda oluşan veri iletimindeki yetersizlik 2,5 Nesil (2,5 G) sistemine geçişi gerçekleştirmiştir.2,5 Nesil, 2G ye göre daha hızlı veri iletimini sağlayan bir teknolojidir. 2,5 Nesilde GPRS ve EDGE teknolojisi maksimum 59,2Kbps hızına ulaşabilmiştir. 2,5G sisteminden sonra yeni bir kuşak olan hem ses hem de hızlı veri iletimine imkan sağlayan; zaman ve frekansı aynı anda kullanabilen üçüncü nesil (3G) genişband teknolojisi geliştirilmiştir. Üçüncü Nesil (3G) genişband haberleşme sistemlerinin en büyük avantajı ses ve görüntü datalarının belirlenmiş kodlar yardımıyla güvenli ve hızlı bir şekilde iletilmesine olanak sağlamasıdır. Genişband haberleşme sistemlerinde 5 Mhz bant genişliğinde data hızı 384 kbps/2 Mbps'na ulaşmaktadır.Bu çalışmada, mobil haberleşme sistemlerinin tarihçesi, çoklu erişim teknikleri, üçüncü nesil genişband haberleşme sistemlerinden W-CDMA tekniğinin hava arayüzü, fiziksel katman performansı, UMTS yayma ve derleme hesaplamaları, Rayo Kaynak Yönetimi, hava arabirim yukarı ve aşağı bağlantı yük faktörü hesaplamaları, 3GPP performans gereksinimleri ve iyileştirmeleri, uplink-downlik performans analizi ve hesapları incelenmiştir. Mobile Communication systems began with analog communication technology as first generation. Since the first generation mobile communication systems serve only voice-based service, there had been some problems with the service quality. Second generation communication systems (2G) had taken place because of these problems. Beside voice, second generation communication systems has digital mobile communication technology which presents the possibility to low rate data transmission. Because of insufficiency in low rate data transmission, 2.5 generation (2.5G) system had been developed temporarily.2.5 Generation serves higher rate of data transmission compared with 2G. GPRS and EDGE technology reaches to a maximum value of 59.2Kbps rate in 2.5G. Third generation (3G) wideband communication systems had been developed after the 2.5 G system, which serves higher rate of voice and data transmission and which makes it possible to use both time and frequency. The biggest advantage of the the third generation (3G) wideband communication systems is the ability of transmitting both the voice and image data?s in secure and with high rates by determined codes. Data rate reaches to a value of 384Kbps/2Mbps with 5 MHz of bandwidth in wideband communication systems.In this thesis, the development of mobile communication systems, the air interface of W-CDMA technique in third generation wideband mobile communication systems, physical layer performance, calculation of UMTS spreading and despreading, radyo resource management, 3GPP performance requirements and enhancements, uplink-downlink performance analysis and calculations have been studied. 138

Internal vehicle communication networks are becoming highly distributed systems. The increase of the internal vehicle electronic system complexity requires higher performance and reliability, and the necessity of ensuring enough bus signal integrity increases the design verification effort. In this paper we present a system verification methodology of Flexray communication networks through behavioral simulations as well as the analysis of important parameters which influence the communication. The paper presents the verification of different network topologies through mixed-mode behavioral simulations and the evaluation of the most critical aspects of the physical layer. Modifications in the original topologies have been performed, and their effects have been analyzed. Additionally, we give special attention to the computational effort required for the behavioral simulations. The different topologies have been simulated with two bus line models (a lossless and a lossy), and the results are evaluated in terms of CPU usage time and accuracy.

In this paper a novel signaling protocol for coexistence and spectrum sharing among cognitive radio nodes is proposed. This protocol allows the radios to rendezvous with each other in a statically allocated spectrum band through on-off keying signaling and reliable spectrum sensing. It enables the radios to have non-cooperative communication in the sense that they do not need to exchange their modulation schemes and frequency channel. The proposed protocol requires no synchronization and is augmented with power control mechanisms. Analysis of the proposed protocol in terms of timing, probability of a successful connection and energy efficiency is also given. ©2010 IEEE.

In this paper a novel signaling protocol for coexistence and spectrum sharing among cognitive radio nodes is proposed. This protocol allows the radios to rendezvous with each other in a statically allocated spectrum band through on-off keying signaling and reliable spectrum sensing. It enables the radios to have non-cooperative communication in the sense that they do not need to exchange their modulation schemes and frequency channel. The proposed protocol requires no synchronization and is augmented with power control mechanisms. Analysis of the proposed protocol in terms of timing, probability of a successful connection and energy efficiency is also given. ©2010 IEEE.

Mobile and wireless communication systems are becoming more and more complex, making understanding the interaction of different technologies on different layers a very difficult task. The introduction of sophisticated techniques on the physical layer that react to changes of the wireless channel on small timescales requires new paradigms for modeling, simulating, and analyzing current and future wireless networks. Investigating the relationship of new physical layer techniques, application-specific requirements and performance measures will become a major research topic for future wireless networks. A continuous change in the methodology for evaluating the network performance takes place in the Internet. In the past, network performance was mainly evaluated using concretely measurable values like packet loss rate, delay, or jitter. The current trend in the Internet goes toward application-specific quality measures that judge more the subjective experience of the end user than they do network parameters. In the terminology, this is expressed as the change from quality of service (QoS-Quality of Service (QoS)) to quality of experience (QoE). For wireless networks this leads to interesting consequences, as currently the traffic requirements for MAC layer connections are mainly formulated in terms of QoS parameters. Accomplishing the change from QoS to QoE also in the definition of connection parameters is a future challenge for wireless networks, for which the first approaches are presented.

Mobile and wireless communication systems are becoming more and more complex, making understanding the interaction of different technologies on different layers a very difficult task. The introduction of sophisticated techniques on the physical layer that react to changes of the wireless channel on small timescales requires new paradigms for modeling, simulating, and analyzing current and future wireless networks. Investigating the relationship of new physical layer techniques, application-specific requirements and performance measures will become a major research topic for future wireless networks. A continuous change in the methodology for evaluating the network performance takes place in the Internet. In the past, network performance was mainly evaluated using concretely measurable values like packet loss rate, delay, or jitter. The current trend in the Internet goes toward application-specific quality measures that judge more the subjective experience of the end user than they do network parameters. In the terminology, this is expressed as the change from quality of service (QoS-Quality of Service (QoS)) to quality of experience (QoE). For wireless networks this leads to interesting consequences, as currently the traffic requirements for MAC layer connections are mainly formulated in terms of QoS parameters. Accomplishing the change from QoS to QoE also in the definition of connection parameters is a future challenge for wireless networks, for which the first approaches are presented.

Η παρούσα διπλωματική εργασία έγινε στα πλαίσια του Προγράμματος Μεταπτυχιακών Σπουδών Ηλεκτρονικής και Υπολογιστών, στο Τμήμα Φυσικής του Πανεπιστημίου Πατρών. Αντικείμενό της αποτελεί η μελέτη του φυσικού επιπέδου συστημάτων κινητής τηλεφωνίας τρίτης γενιάς και η εξομοίωση χαρακτηριστικού καναλιού του φυσικού επιπέδου σύμφωνα με την παγκόσμια προτυποποίηση 3GPP. Στο πρώτο κεφάλαιο γίνεται ιστορική ανασκόπηση των συστημάτων προηγούμενων γενεών. Αναφέρονται βασικά προβλήματα που πρέπει να αντιμετωπίσει ένα τηλεπικοινωνιακό σύστημα καθώς και η βασική δομή των κυψελοειδών συστημάτων. Γίνεται εισαγωγή στα συστήματα τρίτης γενιάς ως προς τις απαιτήσεις, τις υπηρεσίες που προσφέρουν, την προτυποποίηση και την αρχιτεκτονική τους. Στο δεύτερο κεφάλαιο μελετώνται οι τρόποι πολλαπλής πρόσβασης με ιδιαίτερη έμφαση στην προσπέλαση με διαίρεση κωδικών. Αναλύονται τα συστήματα διάχυσης φάσματος. Γίνεται εκτενής αναφορά και υλοποίηση προγραμμάτων για τις ψευδοτυχαίες ακολουθίες και τις ακολουθίες Gold. Στο τρίτο κεφάλαιο μελετάται η δομή δικτύων επικοινωνίας κατά το μοντέλο OSI. Αναφέρονται τα επίπεδα των τηλεπικοινωνιακών συστημάτων με διεξοδική μελέτη του φυσικού επιπέδου και στις διεπαφές που χρησιμοποιεί για επικοινωνία καθώς και στις υπηρεσίες που προσφέρει. Αναλύεται η δομή όλων των φυσικών καναλιών και εξομοιώνεται η διαδικασία ενθυλάκωσης του καναλιού PRACH. Στο τέταρτο κεφάλαιο αναλύονται οι κώδικες διάχυσης των φυσικών καναλιών ανερχόμενης ζεύξης καθώς και η διαδικασία διάχυσης τους. Δημιουργούνται προγράμματα που παράγουν αυτούς τους κώδικες και γίνεται εξομοίωση της διάχυσης και της αποδιάχυσης του PRACH καναλιού. Στο πέμπτο κεφάλαιο αναφέρεται η διαδικασία κωδικοποίησης πηγής και μελετάται η PSK διαμόρφωση και αποδιαμόρφωση που χρησιμοποιούν τα συστήματα τρίτης γενιάς. Υλοποιούνται προγράμματα που εξομοιώνουν τη συνολική διαδικασία σε ενθόρυβο κανάλι AWGN μελετώντας την επίδραση του θορύβου σε μεταδιδόμενο σήμα. Όλες οι εξομοιώσεις υλοποιήθηκαν με το πρόγραμμα Matlab 7.1. This master thesis is a part of the post-graduate course of the Physics department of the University of Patras, on Electronics and Computers. Its main objective is the study of the physical layer of 3rd generation telecommunication systems and the simulation of a particular channel, in accordance to 3GPP specifications. In the first chapter we review telecommunication systems of previous generations. We also refer to major problems that need to be dealt with and also the basic structure of cellular networks. 3rd generation telecommunication systems, their requirements, offered services, standardisation and architecture are all introduced. In the second chapter we study multiple access methods, emphasising CDMA methods. Moreover, spread spectrum systems are analysed. Finally we refer to pseudorandom and Gold sequences. Programs are created which generate these sequences. In the third chapter we look into the structure of communication networks according to the OSI model. The layers of telecommunication systems are mentioned, laying emphasis on the physical layer, the interfaces used for communication as well as the offered services. We report all physical channels and we simulate the encapsulation of the PRACH channel. In the fourth chapter we analyse the spreading and scrambling codes referring to the uplink channels. Next we point out the code allocation process. Programs are created which generate these spreading and scrambling codes and we finally simulate the spreading and de-spreading process of the PRACH channel. In the fifth chapter we outline the source coding process using PCM, and we study PSK modulation and demodulation which are used by 3rd generation telecommunication systems. We create programs that simulate the whole procedure in a noisy channel, and we study the effect of AWGN. The programs were created and the simulations were run using Matlab version 7.1.

Two aspects of DVB-RCS standard can worsen performance of TCP data connections: DAMA access scheme, since it introduces additional and variable delay to the already significant propagation delay and the adoption of Adaptive Coding on the return link to maximize bandwidth efficiency to face variable weather conditions, because it results in variable bandwidth allocation. Both aspects can severely impact TCP performance, especially for what concerns flow adaptation to varying channel conditions and channel usage efficiency. To optimize performance, in this paper cross-layer signaling among transport, MAC and physical layers of a DVB-RCS system is addressed. In particular MAC-TCP cross-layer is analyzed through the use of NS2 network simulator, showing the possible benefit in a DVB-RCS scenario.

The IEEE 802.15.4 standard provides a framework for low data rate communications systems, typically sensor networks. The 802.15.4a revision introduces new options for the physical layer, in order to support higher data rates and accurate ranging capability, enabling new applications based on information on distance and positions of the devices in the network. In this paper the differences among physical layers of 802.15.4 vs. 802.15.4a are briefly reviewed. Next, the MAC layer of 802.15.4 vs. 802.15.4a are reviewed and compared. Device functionalities, network topologies as well as access strategies in both standards are described, and the impact of the new physical layer features on MAC and higher layers are discussed, with particular attention to the ranging scheme adopted in the new revision of the standard.