DISTRIBUTED WIRELESS COMMUNICATION SYSTEM

With the rapid progress in telecommunications, more and more services are provided on the basis of broadband communications, such as video services and high-speed Internet. With worldwide fundamental construction of a backbone network based on optical fiber providing almost unlimited communications capability, the limited throughput of the subscriber loop becomes one of the most stringent bottlenecks.Compared to the capacity of the backbone network, which is measured by tens of gigabits per second, the throughput of the subscriber loop is much lower, only up to hundreds of megabits

per second for wired systems (including fixed wireless access). However, for mobile access the throughput is even lower, and depends on the mobility of the terminal. For example, the peak data rate is only 2 Mb/s for 3G systems.

Since there will be more and more need for mobile services, the poor throughput of mobile access not only limits user applications based on interconnection, but also wastes the capability of the backbone network. This case is quite similar to the traffic conditions shown in Fig. a, which is an image of an ultra-wide expressway with a few narrow entrances.

Since the little paths are rough,narrow, and crowded, the problems in Fig. a are:

§  Terminals are far away from the expressway, which will consume much  power.

§  Too many cars converge into the same narrow paths.

§  Little paths converge several times before  going into the expressway.

§  The expressway is used insufficiently, since few cars are running on it.

§  In telecommunications, the optical fiber network (expressway) is relatively much cheaper than the wireless spectrum (little paths), while the capability of the former is much greater than that of the later. As shown in Fig. b, besides the backbone expressway, there are some dedicated subexpressways used to provide direct entrance for distributed subscribers.The above example implies that the high-capacity wired network, being so cheap, can help us solve the problem of wireless access(too many users crowded in a very narrow bandwidth). The key issue is to provide each mobile user a direct or one-hop connection to an optical network.This structure also follows the trend in network evolution: the hierarchical or tree-like structure of traditional networks will be gradually flattened to simple single-layer ones.

Digital water marking

In recent years, the distribution of works of art, including pictures, music, video and textual documents, has become easier. With the widespread and increasing use of the Internet, digital forms of these media (still images, audio, video, text) are easily accessible. This is clearly advantageous, in that it is easier to market and sell one's works of art. However, this same property threatens copyright protection. Digital documents are easy to copy and distribute, allowing for pirating. There are a number of methods for protecting ownership. One of these is known as digital watermarking.

Digital watermarking is the process of inserting a digital signal or pattern (indicative of the owner of the content) into digital content. The signal, known as a watermark, can be used later to identify the owner of the work, to authenticate the content, and to trace illegal copies of the work.

Watermarks of varying degrees of obtrusiveness are added to presentation media as a guarantee of authenticity, quality, ownership, and source.

To be effective in its purpose, a watermark should adhere to a few requirements. In particular, it should be robust, and transparent. Robustness requires that it be able to survive any alterations or distortions that the watermarked content may undergo, including intentional attacks to remove the watermark, and common signal processing alterations used to make the data more efficient to store and transmit. This is so that afterwards, the owner can still be identified. Transparency requires a watermark to be imperceptible so that it does not affect the quality of the content, and makes detection, and therefore removal, by pirates less possible.

The media of focus in this paper is the still image. There are a variety of image watermarking techniques, falling into 2 main categories, depending on in which domain the watermark is constructed: the spatial domain (producing spatial watermarks) and the frequency domain (producing spectral watermarks). The effectiveness of a watermark is improved when the technique exploits known properties of the human visual system. These are known as perceptually based watermarking techniques. Within this category, the class of image-adaptive watermarks proves most effective.

In conclusion, image watermarking techniques that take advantage of properties of the human visual system, and the characteristics of the image create the most robust and transparent watermarks.

Digital theatre

Digital Theatre System (Digital cinema, or d-cinema) is perhaps the most significant challenge to the cinema industry since the introduction of sound on film. As with any new technology, there are those who want to do it fast, and those who want to do it right. Both points of view are useful. This new technology will completely replace the conventional theatre system having projectors, film boxes, low quality picture, sound system.

Let's not forget the lesson learned with the introduction of digital audio for film in the '90s. Cinema Digital Sound, a division of Optical Radiation Corporation, was the first to put digital audio on 35mm film. Very, very few remember CDS, who closed their doors long ago. Such are the rewards for being first.  

Diffserver

Today's Internet provides a best effort service. It processes traffic as quickly as possible, but there is no guarantee at all about timeliness or actual delivery: it just tries its best. However, the Internet is rapidly growing into a commercial infrastructure, and economies are getting more and more dependent on a high service level with regard to the Internet. Massive (research) efforts are put into transforming the Internet from a best effort service into a network service users can really rely upon.

Commercial demands gave rise to the idea of having various classes of service. For instance one can imagine that companies might offer (or buy, for that matter) either a gold, silver or bronze service level. Each of them having their own characteristics in terms of bandwidth and latency with regard to network traffic. This is called Quality of Service (QoS). The Internet Engineering Task Force (IETF), one of the main driving forces behind Internet related technologies, has proposed several architectures to meet this demand for QoS. Integrated Services and Differentiated Services, developed in the “intserv” and “diffserv” IETF Working Groups, are probably the best known models and mechanisms. The IETF diffserv WG has also defined a DiffServ Management Information Base, a virtual storage place for management information regarding DiffServ. At time of writing, this MIB is still work in progress. This assignment contributes to the development of the DiffServ MIB by writing a prototype implementation of a DiffServ MIB agent and giving feedback to the IETF community. One of the likely uses of the DiffServ MIB is that it may act as part of a bigger policy-based management framework. Therefore an implementation of the DiffServ MIB might also help development in that area.

DEVELOPMENT OF WEARABLE BIOSENSOR

Wearable sensors and systems have evolved to the point that they can be considered ready for clinical application. The use of wearable monitoring devices that allow continuous or intermittent monitoring of physiological signals is critical for the advancement of both the diagnosis as well as treatment of diseases.

Wearable systems are totally non-obtrusive devices that allow physicians to overcome the limitations of ambulatory technology and provide a response to the need for monitoring individuals over weeks or months. They typically rely on wireless miniature sensors enclosed in patches or bandages or in items that can be worn, such as ring or shirt. The data sets recorded using these systems are then processed to detect events predictive of possible worsening of the patient’s clinical situations or they are explored to access the impact of clinical interventions.   

Design, analysis, fabrication and testing of composite leaf

In order to conserve natural resources and economize energy, weight reduction has been the main focus of automobile manufacturers in the present scenario. Weight reduction can be achieved primarily by the introduction of better material, design optimization and better manufacturing processes. The suspension leaf spring is one of the potential items for weight reduction in automobiles as it accounts for 10% - 20% of the unsprung weight. This achieves the vehicle with more fuel efficiency and improved riding qualities. The introduction of composite materials was made it possible to reduce the weight of leaf spring without any reduction on load carrying capacity and stiffness. Since, the composite materials have more elastic strain energy storage capacity and high strength to weight ratio as compared with those of steel, multi-leaf steel springs are being replaced by mono-leaf composite springs. The composite material offer opportunities for substantial weight saving but not always be cost-effective over their steel counterparts.

DWDM TECHNOLOGY

There has always been a technological talent to fulfill the constant need to extent the capacity of communication channel and DWDM (Dense Wavelength Division Multiplexing) has dramatically brought about an explosive enlargement of the capacity of fiber network, solving the problem of increasing traffic demand most economically.

DWDM is a technique that makes possible transmission of multiple discrete wavelengths carrying data rate as high as fiber plant allows over a single fiber unidirectionally or bidirectionally.

It is an advanced type of WDM in which the optical channels are more closely spaced than WDM.

In normal optical link there is one optical source at transmitting end and one photo detector at receiving end. Signals from different light sources use separate and unique assigned fiber for transmission of signal. As the spectral  bandwidth of the laser source is very narrow, this type of transmission makes use  of only a small portion of the entire optical band and remaining portion of the band is not used. In DWDM technology, the different light sources are first converted to pre-assigned wavelength according to the DWDM standards and then combined in such a manner that they occupy different portion of the available optical band. In between the two optical signals suitable guard band is also left, so that there is no interference from adjacent channels. Thus DWDM technology makes use of the entire optical bandwidth.

Delay torrent network

Consider a scientist who is responsible for the operation of robotic meteorological station located on the planet Mars (Fig. 1). The weather station is one of several dozen instrument platforms that communicate among themselves via a wireless local area network deployed on the Martian surface. The scientist wants to upgrade the software in the weather station’s data management computer by installing and dynamically loading a large new module. The module must be transmitted first from the scientist’s workstation to a deep space antenna complex, then form the antenna complex to a constellation of relay satellites in low Mars orbit (no one of which is visible from Earth ling enough on any single orbit to receive the entire module), and finally from the relay satellites to the weather station.

The first leg of this journey would typically be completed using the TCP/IP protocol suite over the Internet, where electronic communication is generally characterized by:

·         Relatively small signal propagation latencies (on the order of milliseconds)

·         Relatively high data rates (up to 40 Gb/s for OC-768 service)

·         Bidirectional communication on each connection

·         Continuous end-to-end connectivity

·         On-demand network access with high potential for congestion

However, for the second leg a different protocol stack would be necessary. Electronic communication between a tracking station and a robotic spacecraft in deep space is generally characterized by:

·         Very large signal propagation latencies (on the order of minutes; Fig. 2)

·         Relatively low data rates (typically 8-256 kb/s)

·         Possibly time-disjoint periods of reception and transmission, due to orbital mechanics and/or spacecraft operational policy

·         Intermittent scheduled connectivity

·         Centrally managed access to the communication channel with essentially no potential for congestion

Digital audio broad casting

Digital audio broadcasting, DAB, is the most fundamental advancement in radio technology since that introduction of FM stereo radio. It gives listeners interference — free reception of CD quality sound, easy to use radios, and the potential for wider listening choice through many additional stations and services.

DAB is a reliable multi service digital broadcasting system for reception by mobile, portable and fixed receivers with a simple, non-directional antenna. It can be operated at any frequency from 30 MHz to 3GHz for mobile reception (higher for fixed reception) and may be used on terrestrial, satellite, hybrid (satellite with complementary terrestrial) and cable broadcast networks.

DAB system is a rugged, high spectrum and power efficient sound and data broadcasting system. It uses advanced digital audio compression techniques (MPEG 1 Audio layer II and MPEG 2 Audio Layer II) to achieve a spectrum efficiency equivalent to or higher than that of conventional FM radio.

The efficiency of use of spectrum is increased by a special feature called Single. Frequency Network (SFN). A broadcast network can be extended virtually without limit a operating all transmitters on the same radio frequency.