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The memory hierarchy of high performance and embedded processors has been shown to be one of the major energy consumers. Extrapolating the current trends, this portion is likely to be increased in the near future. In this paper, a technique is proposed which uses an additional mini cache, called the L0-cache, located between the I-cache and the CPU core. This mechanism can provide the instruction stream to the data path, and when managed properly, it can efficiently eliminate the need for high utilization of the more expensive I-cache.

Five techniques are proposed and evaluated which are used to the dynamic analysis of the program instruction access behavior and to proactively guide the L0-cache. The basic idea is that only the most frequently executed portion of the code should be stored in the L0-cache, since this is where the program spends most of its time.

Results of the experiments indicate that more than 60% of the dissipated energy in the I-cache subsystem can be saved.

INTRODUCTION

                  In recent years, power dissipation has become one of the major design concerns for the microprocessor industry. The shrinking device size and the large number of devices packed in a chip die coupled with large operating frequencies, have led to unacceptably high levels of power dissipation. The problem of wasted power caused by unnecessary activities in various parts of the CPU during code execution has traditionally been ignored in code optimization and architectural design.

                       Higher frequencies and large transistor counts more than offset the lower voltages and the smaller the devices and they result in large power consumption in a newest version in a processor family.

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Download Full Article Steganography – The Art of Hiding Information

Steganography, from the Greek, means covered or secret writing, and is a long-practiced form of hiding information. Although related to cryptography, they are not the same. Steganography’s intent is to hide the existence of the message, while cryptography scrambles a message so that it cannot be understood.

More precisely, 

“the goal of steganography is to hide messages inside other harmless messages in a way that does not allow any enemy to even detect that there is a second secret message present.”

Steganography includes a vast array of techniques for hiding messages in a variety of media. Among these methods are invisible inks, microdots, digital signatures, covert channels and spread-spectrum communications. Today, thanks to modern technology, steganography is used on text, images, sound, signals, and more.

The advantage of steganography is that it can be used to secretly transmit messages without the fact of the transmission being discovered. Often, using encryption might identify the sender or receiver as somebody with something to hide. For example, that picture of your cat could conceal the plans for your company’s latest technical innovation.

However, steganography has a number of disadvantages as well. Unlike encryption, it generally requires a lot of overhead to hide a relatively few bits of information. However, there are ways around this. Also, once a steganographic system is discovered, it is rendered useless. This problem, too, can be overcome if the hidden data depends on some sort of key for its insertion and extraction.

In fact, it is common practice to encrypt the hidden message before placing it in the cover message. However, it should be noted that the hidden message does not need to be encrypted to qualify as steganography. The message itself can be in plain English and still be a hidden message. However, most steganographers like the extra layer of protection that encryption provides. If your hidden message is found, and then at least make it as protected as possible.

This seminar aims to outline a general introduction to steganography – what it is, and where it comes from. Methods for hiding data in three varied media (text, image, and audio) will be described, and some guidelines for users of steganography will be provided where necessary. In addition, we will take a brief look at steganalysis, the science of detecting steganography, and destroying it.

Introduction to Terms used

In the field of steganography, some terminology has developed.

The adjectives cover, embedded and stego were defined at the Information Hiding Workshop held in Cambridge, England. The term “cover” is used to describe the original, innocent message, data, audio, still, video and so on. When referring to audio signal steganography, the cover signal is sometimes called the “host” signal.

The information to be hidden in the cover data is known as the “embedded” data. The “stego” data is the data containing both the cover signal and the “embedded” information. Logically, the processing of putting the hidden or embedded data, into the cover data, is sometimes known as embedding. Occasionally, especially when referring to image steganography, the cover image is known as the container.

Steganography under Various Media

In the following three sections we will try to show how steganography can and is being used through the media of text, images, and audio.

Often, although it is not necessary, the hidden messages will be encrypted. This meets a requirement posed by the “Kerckhoff principle” in cryptography. This principle states that the security of the system has to be based on the assumption that the enemy has full knowledge of the design and implementation details of the steganographic system. The only missing information for the enemy is a short, easily exchangeable random number sequence, the secret key. Without this secret key, the enemy should not have the chance to even suspect that on an observed communication channel, hidden communication is taking place. Most of the software that we will discuss later meets this principle.

When embedding data, it is important to remember the following restrictions and features:

• The cover data should not be significantly degraded by the embedded data, and the embedded data should be as imperceptible as possible. (This does not mean the embedded data needs to be invisible; it is possible for the data to be hidden while it remains in plain sight.)
• The embedded data should be directly encoded into the media, rather than into a header or wrapper, to maintain data consistency across formats.
• The embedded data should be as immune as possible to modifications from intelligent attacks or anticipated manipulations such as filtering and resampling.
• Some distortion or degradation of the embedded data can be expected when the cover data is modified. To minimize this, error correcting codes should be used.
• The embedded data should be self-clocking or arbitrarily re-entrant. This ensures that the embedded data can still be extracted when only portions of the cover data are available. For example, if only a part of image is available, the embedded data should still be recoverable.

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Download Full Article TUNABLE_LASERS

In a wavelength-division multiplexed (WDM) network carrying 128 wavelengths of information, we have 128 different lasers giving out these wavelengths of light. Each laser is designed differently in order to give the exact wavelength needed. Even though the lasers are expensive, in case of a breakdown, we should be able to replace it at a moment’s notice so that we don’t lose any of the capacity that we have invested so much money in. So we keep in stock 128 spare lasers or maybe even 256, just to be prepared for double failures.

What if we have a multifunctional laser for the optical network that could be adapted to replace one of a number of lasers out of the total 128 wavelengths? Think of the money that could be saved, as well as the storage space for the spares. What is needed for this is a “tunable laser,”

                Tunable lasers are still a relatively young technology, but as the number of wavelengths in networks increases so will their importance. Each different wavelength in an optical network will be separated by a multiple of 0.8 nanometers (sometimes referred to as 100GHz spacing. Current commercial products can cover maybe four of these wavelengths at a time. While not the ideal solution, this still cuts your required number of spare lasers down. More advanced solutions hope to be able to cover larger number of wavelengths, and should cut the cost of spares even further.

                The devices themselves are still semiconductor-based lasers that operate on similar principles to the basic non-tunable versions. Most designs incorporate some form of grating like those in a distributed feedback laser. These gratings can be altered in order to change the wavelengths they reflect in the laser cavity, usually by running electric current through them, thereby altering their refractive index. The tuning range of such devices can be as high as 40nm, which would cover any of 50 different wavelengths in a 0.8nm wavelength spaced system. Technologies based on vertical cavity surface emitting lasers (VCSELs) incorporate moveable cavity ends that change the length of the cavity and hence the wavelength emitted. Current designs of tunable VCSELs have similar tuning ranges.

LASERS

                Lasers are devices giving out intense light at one specific color. The kinds of lasers used in optical networks are tiny devices — usually about the size of a grain of salt. They are little pieces of semiconductor material, specially engineered to give out very precise and intense light. Within the semiconductor material are lots of electrons — negatively charged particles. Not just one or two electrons, but billions and billions of them. Some of these electrons can be in what is known as an “excited” state, meaning that they have more energy than regular electrons. An electron in an excited state can just spontaneously fall down to the regular “ground” state. The ground state has less energy, and so the excited-state electron must give out its extra energy before it can enter the ground state. It gives this energy out in the form of a “photon” — a single particle of light.

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Download Full Article Voice User Interface

Definition

In its most generic sense a voice portal can be defined as “speech enabled access to Web based information”. In other words, a voice portal provides telephone users with a natural language interface to access and retrieve Web content. An Internet browser can provide Web access from a computer but not from a telephone. A voice portal is a way to do that.

Overview

The voice portal market is exploding with enormous opportunities for service providers to grow business and revenues. Voice based internet access uses rapidly advancing speech recognition technology to give users any time, anywhere communication and access-the Human Voice- over an office, wireless, or home phone. Here we would describe the various technology factors that are making voice portal the next big opportunity on the web, as well as the various approaches service providers and developers of voice portal solutions can follow to maximize this exciting new market opportunity.

Why Voice?

Natural speech is modality used when communicating with other people. This makes it easier for a user to learn the operation of voice-activate services. As an output modality, speech has several advantages. First, auditory input does not interfere with visual tasks, such as driving a car. Second, it allows for easy incorporation of sound-based media, such as radio broadcasts, music, and voice-mail messages. Third, advances in TTS (Text To Speech) technology mean text information can be transferred easily to the user. Natural speech also has an advantage as an input modality, allowing for hands-free and eyes-free use. With proper design, voice commands can be created that are easy for a user to remember .These commands do not have to compete for screen space. In addition unlike keyboard-based macros (e.g., ctrl-F7), voice commands can be inherently mnemonic (“call United Airlines”), obviating the necessity for hint cards. Speech can be used to create an interface that is easy to use and requires a minimum of user attention.

VUI (Voice User Interface)

 For a voice portal to function, one of the most important technology we have to include is a good VUI (Voice User Interface).There has been a great deal of development in the field of interaction between human voice and the system. And there are many other fields they have started to get implemented. Like insurance has turned to interactive voice response (IVR) systems to provide telephonic customer self-service, reduce the load on call-center staff, and cut overall service costs. The promise is certainly there, but how well these systems perform-and, ultimately, whether customers leave the system satisfied or frustrated-depends in large part on the user interface.

Many IVR applications use Touch-Tone interfaces-known as DTMF (dual-tone multi-frequency)-in which customers are limited to making selections from a menu. As transactions become more complex, the effectiveness of DTMF systems decreases.

In fact, IVR and speech recognition consultancy Enterprise Integration Group (EIG) reports that customer utilization rates of available DTMF systems in financial services, where transactions are primarily numeric, are as high as 90 percent; in contrast, customers’ use of insurers’ DTMF systems is less than 40 percent.
Enter some more acronyms. Automated speech recognition (ASR) is the engine that drives today’s voice user interface (VUI) systems. These let customers break the ‘menu barrier’ and perform more complex transactions over the phone. “In many cases the increase in self-service when moving from DTMF to speech can be dramatic,” said EIG president Rex Stringham.

The best VUI systems are “speaker independent”-they understand naturally spoken dialog regardless of the speaker.  And that means not only local accents, but regional dialects, local phrases such as “pop” versus “soda,” people who talk fast (you know who you are), and all the various nuances of speech. Those nuances are good for human beings; they allow us to recognize each other by voice. For computers, however, they make the process much more difficult. That’s why a handheld or pocket computer still needs a stylus, and why the ‘voice dialing’ offered by some cell-phone companies still seems high-tech.

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Download Full Article Voice Over Internet Protocol

I N T R O D U C T I O N

Using an ordinary phone for most people is a common daily occurrence as is listening to your favorite CD containing the digitally recorded music. It is only a small extension to these technologies in having your voice transmitted in data packets. The transmission of voice in the phone network was done originally using an analog signal but this has been replaced in much of the world by digital networks. Although many of our phones are still analog, the network that carries that voice has become digital.

In todays phone networks, the analog voice going into our analog phones is digitized as it enters the phone network. This digitization process, shown in Figure 1 below, records a sample of the loudness (voltage) of the signal at fixed intervals of time. These digital voice samples travel through the network one byte at a time.

At the destination phone line, the byte is put into a device that takes the voltage number and produces that voltage for the destination phone. Since the output signal is the same as the input signal, we can understand what was originally spoken.
The evolution of that technology is to take numbers that represent the voltage and group them together in a data packet similar to the way computers send and receive information to the Internet. Voice over IP is the technology of taking units of sampled speech data .

So at its most basic level, the concept of VoIP is straightforward. The complexity of VoIP comes in the many ways to represent the data, setting up the connection between the initiator of the call and the receiver of the call, and the types of networks that carry the call.

Using data packets to carry voice is not just done using IP packets. Although it won’t be discussed, there is also voice over Frame Relay (VoFR) and Voice over ATM (VoATM) technologies. Many of the issues VoIP being discussed also apply to the other packetized voice technologies.

The increasing multimedia contents in Internet have reduced drastically the objections to putting voice on data networks. Basically, the Internet objections to putting voice on data networks. Basically, the Internet Telephony is to transmit multimedia information in discrete packets like voice or video over Internet or any other IP-based Local Area Network (LAN) or Wide Area Network (WAN). The commercial Voice Over IP (Internet Protocol) was introduced in early 1995 when VocalTec introduced its Internet telephone software. Because the technologies and the market have gradually reached their maturity, many industry leading companies have developed their products for Voice Over IP applications since 1995.

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