OFDM

OFDM has emerged as the leading modulation technique in the RF domain, and it has evolved into a fast-progressing and vibrant field. It has been triumphant in almost every major communication standard, including wireless LAN (IEEE 802.11 a/g, also known
as Wi-Fi), digital video and audio standards (DAV/DAB), and digital subscriber loop (DSL). It is not surprising that the two competing fourth-generation (4G) mobile network standards, Worldwide Interoperability for Microwave Access (WiMAX, or IEEE
802.16) from the computing community and Long-Term Evolution (LTE) from the telecommunication community, both have adopted OFDM as the core of their physical interface

The recent advances in miniaturization and the creation of low-power circuits, combined with small-sized batteries have made the development of wireless sensor networks a working reality. Lately, the production of cheap complementary metal-oxide semiconductor cameras and microphones, which are able to capture rich multimedia content, gave birth to what is called Wireless Multimedia Sensor Networks (WMSNs). WMSNs will boost the capabilities of current wireless sensor networks, and will fuel several novel applications, like multimedia surveillance sensor networks. WMSNs introduce several new research challenges, mainly related to mechanisms to deliver application-level Quality-of-Service (e.g., latency minimization). To address this goal in an environment with extreme resource constraints, with variable channel capacity and with requirements for multimedia in-network processing, the caching of multimedia data, exploiting the cooperation among sensor nodes is vital. This article presents a cooperative caching solution particularly suitable for WMSNs. The proposed caching solution exploits sensor nodes which reside in “positions” of the network that allow them to forward packets or communicate decisions within short latency. These so-called “mediator” nodes are selected dynamically, so as to avoid the creation of hot-spots in the communication and the depletion of their energy. The mediators are not more powerful than the rest of the nodes, but they have some special role in implementing the cooperation among the sensors. The proposed cooperative caching protocol includes components for locating cached data as well as for implementing data purging out of the sensor caches. The proposed solution is evaluated extensively in an advanced simulation environment, and it is compared to the state-of-the-art cooperative caching algorithm for mobile ad hoc networks. The results confirm that the proposed caching mechanism prevails over its competitor.

Page 1. FAST ACTIVE CONSTELLATION EXTENSION FOR MIMO-OFDM PAR REDUCTION Brian S. Krongold ARC Special Research Centre for Ultra-Broadband Information Networks Dept. of Electrical & Electronic Engineering University of Melbourne, Australia ...

We present a theoretical model developed for estimating the power, the optical signal to noise ratio and the number of generated carriers in a comb generator, having as a reference the minimum optical signal do noise ratio at the receiver input, for a given fiber link. Based on the recirculating frequency shifting technique, the generator relies on the use of coherent and orthogonal multi-carriers (Coherent WDM) that makes use of a single laser source (seed) for feeding high capacity (above 100 Gb/s) systems. The theoretical model has been validated by an experimental demonstration, where 23 comb lines with an optical signal to noise ratio ranging from 25 to 33 dB, in a spectral window of ~ 3.5 nm, are obtained.

The WiMAX technology, based on the IEEE 802.16-2004 Air Interface Standard is rapidly proving itself as a technology that will play a key role in fixed broadband wireless metropolitan area networks. The first certification lab, established at Cetecom Labs in Malaga, Spain is fully operational and more than 150 WiMAX trials are underway in Europe, Asia, Africa and North and South America. Unquestionably, Fixed WiMAX, based on the IEEE 802.16-2004 [1] Air Interface Standard, has proven to be a cost-effective fixed wireless alternative to cable and DSL services. In December, 2005 the IEEE ratified the 802.16e amendment [2] to the 802.16 standard. This amendment adds the features and attributes to the standard necessary to support mobility. The WiMAX Forum is now defining system performance and certification profiles based on the IEEE802.16e Mobile Amendment and, going beyond the air interface, the WiMAX Forum is defining the network architecture necessary for implementing an end-to-end...

The fourth generation mobile communication has used MIMO (Multiple Input Multiple Output) technology to improve system performance .MIMO can be used to get better capacity, coverage, high data rates and throughputs. Land mobile satellite (LMS) systems are an important element of the third and fourth generation of wireless systems. In satellite communication system, the use of nonlinear Traveling Wave Tube (TWT) amplifier exhibits severe nonlinear distortions to the transmitted signal, in particular when the TWT works near saturation. As Single Carrier Frequency Division Multiple Access (SC-FDMA) has lower Peak to Average Power Ratio (PAPR) it can be used for uplink satellite communications. SC-FDMA is precoded version of OFDM and has low Peak to Average power Ratio (PAPR). Its performance is not as good as OFDM over Rayleigh channel .In the presence of Line Of Sight (LOS), SCFDMA has shown better performance than OFDM. In this work, SC-FDMA performance over correlated LMS Rician cha...

Wireless Local Area Networks (WLANs) are commonly deployed in various environments. The WLAN data packets are not transmitted continuously but often worst-case exposure of WLAN is assessed, assuming 100% activity and leading to huge overestimations. Actual duty cycles of WLAN are thus of importance for time-averaging of exposure when checking compliance with international guidelines on limiting adverse health effects. In this paper, duty cycles of WLAN using Wi-Fi technology are determined for exposure assessment on large scale at 179 locations for different environments and activities (file transfer, video streaming, audio, surfing on the internet, etc.). The median duty cycle equals 1.4% and the 95th percentile is 10.4% (standard deviation SD = 6.4%). Largest duty cycles are observed in urban and industrial environments. For actual applications, the theoretical upper limit for the WLAN duty cycle is 69.8% and 94.7% for maximum and minimum physical data rate, respectively. For lowe...

Wireless Networking has become an important area of research in industry and academics in recent years. The main objectives of this paper are to gain knowledge about the WiMAX technology, its security and application. WiMAX (Worldwide Interoperability for Microwave Access) technology is based upon the IEEE 802.16 standard (IEEE Wireless MAN Air Interface) which enables wireless broadband services anytime, anywhere. The WiMAX specification provides symmetrical bandwidth over large area and range with stronger encryption and typically less interference. WiMAX based system can be used to transmission of signal over maximum 50 km. WiMAX outdistances WiFi by miles. WiMAX can deliver high data rate to multiple users. The WiMAX Forum describes WiMAX as " a standards-based technology enabling the delivery of last-mile wireless broadband access as an alternative to cable and DSL ". The main goal/purpose of this technology is to deliver wireless communications with quality of service in a secured environment. This standard was developed to deliver line-of-sight (LoS) and non-line-of-sight (NLoS) wireless services between subscriber and base station and to address " last mile " problem.

ABTRACT One of vital parts of the mobile wireless channel is channel estimation significantly improve the performance of the system, especially for 4G LTE and 5G systems. The main goal of this project is to test the time-variant channel estimation using F-OFDM model. It investigates the Mean Square Error (MSE), the Least Squares (LS) method and compares performance of OFDM and F-OFDM using BER vs SNR.

This paper compares MIMO vs SISO and mention difference between SISO and MIMO techniques. These are techniques based on number of antennas used at the transmitter and the receiver. SISO has been in use since the invention of wireless system.MIMO concept has been recently added to the wireless system. There are different MIMO algorithms which have been developed for two main reasons to increase coverage and to increase the data rates. SISO means Single Input Single Output while MIMO means Multiple Input Multiple Output.

All  over  the  world,  security has  been  a  major  concern  in  every  home.  Automated  security  systems  are  a  useful  addition  to  todays
home  where  safety  is  an  important  issue.  Vision-based  security  systems  have  the  advantage  of  being  easy  to  set  up,  inexpensive  and  non-obtrusive. Here, a security system has been developed that uses sensors to detect  any security  violation and sends out  the alert signal  by high
intensity  Buzzer.  In  this paper  it  has  been  ensured three  level  security  systems.  NFC  tag  use,  providing Password  and PIR  motion sensor.  To
open  the  door  a  person  should  provide  NFC  tag  and  password.  If  one  of  them  absence  the  door  will  not  open.  The  door  will  opened  by
servomotor with a lock coupled in its shaft. When wrong password is pressed, error text  is displayed in the LCD. When an authorized person
leaves the door, he has to show his tag in the reader. Otherwise the door will not close. Now if an unwanted man enters the room by password
breaking or without NFC the PIR sensor works .It sounds the buzzer. NFC card reader, PIC 16F877A, Arduino Uno, PIR sensor is used for this
project  .So,  maximum  security  will  be  maintained  in  home.  This  security  can  be  applied  not  only  home  but  also  the  place  where important
document, file are preserved also the bank vault.

Wavelets have been favorably applied in almost all aspects of digital wireless communication systems including data compression, source and channel coding, signal denoising, channel modeling and design of transceivers. The main property of wavelets in these applications is in their flexibility and ability to characterize signals accurately. In this paper recent trends and developments in the use of wavelets in wireless communications are reviewed. Major applications of wavelets in wireless channel modeling, interference mitigation, denoising, OFDM modulation, multiple access, Ultra Wideband communications, cognitive radio and wireless networks are surveyed. The confluence of information and communication technologies and the possibility of ubiquitous connectivity have posed a challenge to developing technologies and architectures capable of handling large volumes of data under severe resource constraints such as power and bandwidth. Wavelets are uniquely qualified to address this challenge. The flexibility and adaptation provided by wavelets have made wavelet technology a strong candidate for future wireless communication.

To achieve better calculative performance in optical fiber communication and for simplicity of implementation different digital modulation, detection and multiplexing techniques are used. These techniques maximize the spectral efficiency. This paper reviews a tabular comparative analysis with 3D graphical representation for different optical digital modulation formats and multiplexing techniques within and beyond 400 Gb/s. In this particular article we survey about different parameters related to digital fiber optic communication.

Energy consumption is one of the important challenges in WSNs deployment and applications. This is because power of WSNs is limited by battery which is difficult if not impossible to replace or recharge in some manner in the sensor nodes. Power consumption can be controlled in WSNs in more than one layer. In this thesis, power efficiency problems and techniques of enlarging battery life using WSNs physical layer are investigated in the second layer MAC sub-layer. The latter has been achieved using the multiple access techniques, TDMA and CDMA.
Initially, the research attempt to divide the WSN nodes into clusters such that at any time only one specific cluster will operate and the remaining cluster sill be switched off to reduce the power consumption. Each cluster consists of several nodes and one sub-station (SS), the total number of nodes equal to 128 nodes at each case of cluster, all the nodes in one cluster send its data to this (SS) and this (SS) forwards this data to main station (MS). Furthermore, the link between nodes, SS, and MS is controlled and scheduled such that cluster and node switched to active or sleep. Four systems with multi-types of multiple access are proposed and tested with each case of clustering have been adopted. These systems are classified according to the way multiple access provided in the link: TDMA-TDMA-OFDM system, CDMA-CDMA system, CDMA-TDMA-OFDM system, and TDMA-OFDM-TDMA-OFDM system. These systems have been simulated and investigated. By comparing the results of each system with different case of cluster, it has been found that the less consumed powers achieved with 8 clusters of 16 nodes/cluster case. The results also show that the best performance is achieved with CDMA-CDMA system with 8 clusters of 16 nodes/cluster case.
Extra power consumption reduction has been achieved in this research via the application of convolutional coding and interleaving with four proposed systems. It has been found that convolutional code makes better performances and less error rates with different ratio in the proposed system. Furthermore, more enhancement has been achieved by using convolutional code with interleaving to all system except CDMA-CDMA system which gives results similar to the results of convolutional code only. By comparing the results of the proposed system with each other after enhancement, the results show that the CDMA-CDMA system is still has the less error bit ratio and the best performance and achieves the most power consumption reduction.

Abstract—The telecommunication industry has been through disruptive times, but data networking service revenue has continued to rise. The telecom industry is expected to continue to grow as demand increases for cable and high-speed Internet in previously unserviced locations ...

— Electrical machines are devices that change either mechanical or electrical energy to the other and also can alternate the voltage levels of an alternating current. The need for electrical machines cannot be overemphasized since they are used in various applications in the world today. Its design is to meet the specifications as stated by the user and this design has to be an economical one. The design therefore revolves around designing the machine to meet the stipulated performance required, the cost available and the lasting life of the machine. This work aims to eliminate the tediousness involved in the manual hand calculations of designing the machines by making use of a graphical user interface and using iterations in situations where the data would have been assumed.

Modern radar systems often have the conflicting requirements of a large phased array antenna for increased power-aperture product and/or angular resolution versus wide instantaneous signal bandwidth for fine range resolution. Pulse-to-pulse diversity may also be desired as a countermeasure against coherent repeater jammers. Using the multicarrier nature of orthogonal frequency-division multiplexing to encode wide instantaneous bandwidth pulses we propose a novel digital phased array architecture which mitigates dispersion effects experienced when the array main beam is electronically steered off broadside. The result is the ability to transmit and receive wideband pseudo-random phase coded pulses with a phased array antenna. Simulation results are used to quantify the benefit of the architecture. An overview of digital orthogonal frequency-division multiplexing waveform generation is also provided.