Two Types Of Spread Spectrum Computer Science Essay

Two Types Of Spread Spectrum Computer Science Essay There are two types of spread spectrum that have been approved for use. This article analyzes the approach in to determining performance comparison of Frequency Hopping and Direct Sequence Spread Spectrum Systems in the 2.4 GHz range. The analyses till present show that up to 13 collocated FH networks can be placed before network throughput peaks. (A. Carl, S. Harris B. Palm, n.d.). The article further lists in categorizing the advantages and limitations of spread spectrum and the comparisons between the Frequency Performance and Direct Sequence. The article details itself via valid resources obtained from researched websites and journals with more details available with those references being provided. The Spread-spectrum is or are a series of techniques which are methods by which a signal that could be of electrical or electromagnetic or acoustic signals that are being generated in an exacting bandwidth which is then by design spread in the frequency domain, ensuing in a signal with a vast or wider bandwidth. These techniques are utilized for a range of reasons, together with the establishment of safe and sound communications, increasing resistance to natural interference and congestions, to prevent uncovering, and to frontier power flux density. Out of many Spread Spectrums, this report analyses the two main spread spectrum systems which are the Frequency Hopping and Direct Sequence and in addition an overview of the Chirp Spread Spectrum. Spread Spectrum technologies The spread spectrum technology is more of a technique in which a telecommunication signal is transmitted on a bandwidth significantly bigger than the regularity content of the original information. Spread-spectrum telecommunications is a signal structuring technique that employs direct sequence, frequency hopping, or a hybrid of these, which can be used for multiple access and/or multiple functions.(Anonymous, 2007). This technique reduces the possible intrusion to other receivers while achieving privacy. Spread spectrum in general makes use of a chronological noise-like signal formation to spread the normally narrowband information signal over a comparatively wideband (radio) band of frequencies. The receiver correlates the received signals to retrieve the original information signal. Initially there were two motivations: either to resist enemy efforts to jam the communications known as an Anti-Jam or to conceal the fact that communication was even taking place, sometimes called low probability of intercept. Spread-spectrum clock signal generation The Spread-spectrum clock generation is used in some synchronous digital systems, especially those containing microprocessors, to cancel of the spectral density of the electromagnetic interference that these systems generate. A synchronous digital system is one that is driven by a clock signal and because of its periodic nature, has an unavoidably narrow frequency spectrum. (Anonymous, 2007). In fact, a perfect clock signal would have all its power determined at a single frequency and its harmonics, and would therefore radiate energy with an inestimable spectral concentration. Practical synchronous digital systems radiate electromagnetic force on a number of narrow bands spread on the clock frequency and its harmonics, follow-on in a frequency spectrum that, at certain frequencies, can exceed the regulatory limits for electromagnetic interference The Spread Spectrum Systems Overview Frequency Hopping Spread Spectrum This is a method of transmitting radio signals by speedily switching a mover among many frequency channels, using a pseudorandom cycle known to both transmitter and receiver. It is utilized as a several access method in the frequency-hopping code division multiple access scheme. The three main advantages over a fixed-frequency transmission: -Its signals are highly resistant to narrowband intervention. The procedure of re-collecting a spread signal spreads out the interfering signal, causing it to retreat into the background. -Spread-spectrum signals are tricky to interrupt. A Frequency Hopping Spread Spectrum signal plainly appears as a boost in the background noise to a narrowband receiver. An eavesdropper would only be able to seize the transmission if the pseudorandom sequence was known. -The Spread-spectrum transmissions can contribute to a frequency band with many types of conventional transmissions with minimum interference. The spread-spectrum signals affix minimal noise to the narrow-frequency communications, and vice versa. As an effect, bandwidth can be utilized more resourcefully. The Basic algorithm The initiation of a Frequency Hopping Spread Spectrum (FHSS) communication is as follows: -The initiating party sends a request via a predefined frequency or control channel. -The receiving party sends a number, known as a seed. -The initiating party uses the number as a variable in a predefined algorithm, which calculates the sequence of frequencies that must be used. Most often the period of the frequency change is predefined, as to allow a single base station to serve multiple connections. -The initiating party sends a synchronization signal via the first frequency in the calculated sequence, thus acknowledging to the receiving party it has correctly calculated the sequence. -The communication begins, and both the receiving and the sending party change their frequencies along the calculated order, starting at the same point in time. Technical considerations The overall bandwidth necessary for frequency hopping is a great deal, wider than that required to transmit the same information using only one carrier frequency. Nevertheless, because transmission occurs only on a small segment of this bandwidth at any given time, the effectual interference bandwidth is actually the same. Even as providing no extra protection against wideband thermal noise, the frequency-hopping approach does reduce the deprivation caused by narrowband interferers. One of the challenges of frequency-hopping systems is to coordinate the transmitter and receiver. One approach is to have an assurance that the transmitter will use all the channels in a set period of time. The receiver can then discover the transmitter by picking a random channel and listening for suitable data on that channel. The transmitters data is recognized by a unique series of data that is unlikely to occur over the section of data for this channel and the segment can have a checksum for reliability and further detection. The transmitter and receiver can use fixed tables of channel sequences so that once synchronized they can maintain communication by following the table. On each channel segment, the transmitter can send its current position in the table. Direct Sequence Spread Spectrum Direct-sequence spread spectrum (DSSS) is a modulation method. As with other spread spectrum technologies, the transmitted signal takes up more bandwidth than the information signal that is being modulated. In this technology the transmissions multiply the data being transmitted by a noise signal. This noise signal is a pseudorandom sequence of 1 and à ¢Ã‹â€ Ã¢â‚¬â„¢1 values, at a frequency much higher than that of the original signal, thereby spreading the energy of the original signal into a much wider band. (W. Jimmy, n.d.) The resultant signal resembles white noise, like an audio recording of static. On the other hand, this noise-like signal can be used to precisely recreate the original data at the receiving ending, by multiplying it by the same pseudorandom sequence. This process, known as de-spreading, mathematically constitutes a correlation of the transmitted PN sequence with the PN sequence that the receiver believes the spreader is using. For de-spreading to operate correctly, the transmit and receive sequences must be synchronized. This requires the receiver to coordinate its sequence with the transmitters sequence via some sort of timing search process. However, this noticeable drawback can be a significant benefit: if the sequences of multiple transmitters are synchronized with each other, the relative synchronizations the receiver must make between them can be used to resolve relative timing, which, in turn, can be used to compute the receivers point if the transmitters positions are known. This is the base for many satellite direction-finding systems. The resultant outcome of enhancing signal to noise ratio on the channel is called process gain. Benefits in Direct Sequence Spread Spectrum -It is resistant to planned or unintentional jamming. -The sharing of a single channel between numerous users. -Reduced signal/background-noise level hampers interception (stealth). -Determination of relative timing between transmitter and receiver. Chirp Spread Spectrum On the other hand, the Chirp spread spectrum (CSS) is a spread spectrum technique that uses wideband linear frequency modulated chirp pulses to encode information. A chirp is a sinusoidal signal whose frequency increases or decreases over a certain amount of time. (W. Jimmy, n.d.) Chirp Spread Spectrum is ideal for applications requiring low power usage and needing relatively low amounts of data rate. CSS uses its entire owed bandwidth to televise a signal, building it robust to channel noise. Further, because the chirps utilize a broad band of the spectrum, Chirp Spread Spectrum is also challenging to multi-path fading even when working at very low power. However, it is not like direct-sequence spread spectrum or frequency-hopping spread spectrum in that it does not add any pseudo-random elements to the signal to help differentiate it from noise on the channel, instead relying on the linear nature of the chirp pulse. Moreover, Chirp Spread Spectrum is resistant to the Doppler Effect, which is typical in mobile radio applications. Comparisons against Performance between Frequency Hopping and Direct Sequence Spread Spectrum Systems A Simulated Model/Design Conclusion

Corrections and Treatment Essay

Community based treatment plays a large role in the criminal justice system. Community based treatment includes probation, treatment services and restitution. There is community based housing like small group homes, foster homes and boarding schools where juveniles can spend time while they are undergoing treatment. There are also nonresidential programs, where the juvenile can remain in their family home while attending treatment. A juvenile that is ordered to a foster home could be placed there because they do not have proper supervision in their family home, or they do not have a family home. A foster home is a place where the juvenile has the ability to live in a safe environment, in a place that they can call home. Restitution is often used as a community treatment when an offender has caused damage to property, this is the courts way of making the juvenile pay for the damages they caused. This could also be repaired by completing community service, if the damage was done to a public area where the juvenile can repair the damage with supervision. Institutionalization started by the juvenile offenders spending their sentence in the adult prison facilities, since there were no juvenile facilities. The adult facilities provided inhumane conditions for juveniles, where they were exposed to the evils of adult offenders and conditions that were not made for juveniles (Larry J. Siegel, 2005). The first juvenile institutions were created like the adult facilities, but they were created to protect the juveniles from the evils in the adult prisons. The juvenile facilities were also created to protect children. As juvenile institutions evolved, reform schools were made; they resembled boarding schools, providing education as well as confinement. Early institutions focused on punishment, which did not better the juveniles once they were released from the facilities. Later faciliti es changed the focus from punishment to rehabilitation. One great step towards  rehabilitation was the creation of a cottage system for an institute. In a cottage system, several juveniles shared a cottage with a set of â€Å"parents† that watched over them. Aftercare programs are similar to parole for adults. In an aftercare program, the juvenile is provided with a transitional program to transition the juvenile from a juvenile institute back to the community. Just like parolees in the adult system, juveniles have to abide by terms of The Intensive Aftercare program. Some of the terms are abiding by curfew, attend school, abstain from drugs and alcohol, avoid committing crimes and reporting to a youth worker when required (Larry J. Siegel, 2005). If the terms of the Intensive Aftercare program are not followed this can result in the juvenile returning to the institution. Bibliography Larry J. Siegel, B. C. (2005). Juvenile Delinquency: The Core. Wadsworth, a division of Thomson Learning, Inc.

A Modest Proposal Questions Essay

1.The initiator perceived that the worst problems in Dublin were the poverty level being very high and that poor children are a burden to their parents because of the cost to take care of them. The issues that trouble him make him appear to be someone who cares about the economic well being of his country but not the well being of the people because he sees poor children as a burden to their families and society. 2.The initiator uses a serious tone to explain his solution and six main methods to try to persuade readers to accept his proposal. He states his solution would decrease the amount of Roman Catholics, the poor would have some money to pay their landlord, and the economy would grow. He also declares that the parents would no longer have to take care of their child after year one, a new popular food would be created, and there would also be an increase the tenderness of mothers towards their children. 3.Breeder frequently replaces mother in the proposal creating the perception that the initiator sees people as numbers; he doesn’t see people for who they are. 4.The expert is a cannibal, which suggests that the initiator is a cannibal or is exceptive of cannibalism. 5.Being a satire, A Modest Proposal, is an ironic title because the solution the initiator proposes is anything but modest, since he suggests roasting children. Although, the author also makes the initiator’s solution sound ridiculous to create the idea that readers should pity the poor Irish, creating a modest proposal. Being modest is being humble and Swift’s proposal to feel bad for the poor isn’t asking much. 6.a. Some shocking details of life the essay reveals would be that some poor Irish woman are selling themselves to planters in Barbados, Ireland is in a horrible economic situation and that England is oppressing Ireland. b. The previous details cause the reader to feel sympathy for th e Irish people in their time of hardship and disregard the proposal of the initiator because he is probably of wealth since his attitude is insensitive. 7. Swift intends for the reader to disregard the proposed solution of the initiator and accept the modest proposal. Swift uses the outlandish remarks of the initiator to create the feeling of sorrow for the Irish people due to their poverty and their struggles with England. 8. The major targets of this satire would be the wealthy and the noblemen because the satire mocks the heartless attitude towards the poor that the rich exude. The Irish are responsible for their sorry situation because Ireland doesn’t export enough goods, which harms their economy and as well as the fact that the Irish sell their goods for more than they are worth, but not many people can afford their high prices. Another way the Irish are accountable for their own plight is because poor people continue to have children that they cannot afford to take care of.

Jane Austen s Dracula As Well As Pride And Prejudice

Women are held to different standards than men. Our culture is encompassed by prejudices concerning women in society, especially in regards to social gender roles of men and women. In Victorian society, it was a socially accepted concept that women were inferior to men in all aspects with the exception of childbearing and raising. A woman’s personal choices were and are still subject to the review of modern society, and women are continually ostracized for veering from what is considered socially acceptable. This criticism severely restricts what a woman is â€Å"allowed† to and â€Å"not allowed† to do. This can be seen in works of literature dating back to the Victorian era, such as Brahm Stoker’s Dracula as well as Pride and Prejudice by Jane Austen. Women are not allowed to express their sexual desires. Through the two main female characters in Dracula, Mina and Lucy, Stoker shines light on his sexist opinion of the role of women in society by illustra ting both the ideal model of what a woman should strive to be as well as the repercussions if a woman were to veer from this accepted role. According to LITCRITXXX, Dracula is among the most strikingly erotic works published in Britain during the Victorian era...its conscientious representation of female voluptuousness and sexual appetite as a manifest disgrace is...consciously hypocritical† (xxxxxxxxxx 16). Women, although sexualized, objectified, and undermined, are still disgraced for their behavior if it is different thanShow MoreRelatedCause and Impact Analysis on the Main Character’s Suffering in Elizabeth Gilbert’s Novel Eat, Pray, Love7348 Words   |  30 PagesImaginative literature is the writing contains fact explanation or real people life and history which aim at conveying knowledge to article, history book, dictionaries and text book. On the other hand, imaginative literature aims an entertaining as well as giving information. In this case the auth or tries to tell about his though, ideas and feeling. A novel is a book length story in prose, whose author tries to create the sense that while we need, we experience actual life, (Kennedy, 1983:180)