Dostoevsky and Franzen Essay Example for Free

Dostoevsky and Franzen Essay Fyodor Dostoevsky is indisputably one of the greatest writers of his time, and arguably of all time. He earned this status not only by being an unmatched story teller- writing novels so gripping that they are hard to put down- but by infusing his dramas with timeless comedy, poignant social commentary, insightful psychology, and universal philosophical inquiries. His extremely in-depth character development allows for unlimited societal references that every reader can relate to. A most common feeling expressed among readers is that he puts into words what they have always thought about, but never had the words- or the sharp observation- to express. A similar feeling is created by Jonathan Franzen, whose novel, The Corrections, is a bestseller, and not only on account of its hilarious banter and piercing insight. The Corrections is widely hailed as an epic masterpiece that perfectly brings to light the problems of materialism, technology, and alienation in American culture. This is perhaps even more impressive because he is British and not American. Franzen has risen quickly to the top, and The Corrections will continue to be read for many years to come. Though their personal beliefs are entirely different, Franzen and Dostoevsky address many of the same questions regarding family. The psychological breakdown of relationships between family members is key and not only addresses psychology, but also society. Both authors utilize the family as a microcosmic representation for society, and Dostoevsky’s 1880 novel, The Brothers Karamazov, the last of Dostoyevsky’s famous and well-regarded novels, is the best example of this tactic. The Brothers Karamazov begins with a brief family history. The patriarch, Fyodor Karamazov, has three sons (Dimitri, Ivan, and Alyosha) by two different women. Fyodor, preoccupied with hedonistic debauchery, sends his sons to various relatives to be taken care of. Dimitri and Fyodor become enemies as soon as Dimitri is old enough to realize that his father not only has taken no responsibility for him, but is also withholding his inheritance left to him by his dead mother. The feud intensifies when they both fall in love with Grushenka, a woman of notoriously poor reputation. Dimitri, though vengefully abhorrent of his father, has inherited Fyodor’s taste for wine and women. Ivan, the second oldest, is a brooding intellectual, and Alyosha, the youngest, has moved to the monastery under the well-respected Father Zossima. Smerdyakov, the fourth and illegitimate son, is Fyodor’s cook. Smerdyakov is anti-social and epileptic, but loves to talk about philosophy with Ivan. Understandably, Dimitri is blamed when Smerdyakov murders Fyodor, because of the â€Å"overwhelming facts† against him. Ivan loses his mind when he realizes that he is more to blame than the innocent Dimitri, because he subconsciously encouraged, and even hoped for the murder, and Alyosha leaves the monastery on Zossima’s instructions. The Karamazovs forcefully confront the reader with the timeless questions of family. Is love entitled or earned? Are children unconditionally innocent? Are children obliged to love and respect their parents despite neglect and abuse? â€Å"Even while The Brothers Karamazov insists on the innocence of children, it also undercuts this idea, showing how children can be sinful even while they suffer†¦the tension between childhood innocence and childhood guilt is at the very heart of the novel†¦they resemble another category of natural victims, the peasants†¦Ã¢â‚¬  (Hruska, 472) It is not only the idea of children that is representative of a larger social construct, but nearly every character. Alyosha is the devout Christian. He believes wholeheartedly in the good of human kind and Christ. He is honest, loyal, and compassionate. He is not just a person of faith- he embodies faith. He has faith not only in God, but also in humanity. Though not representative of Dostoevsky himself, Alyosha is an extremely sympathetic character, designed to uphold the principals of faith and Christ against all opposition- and Dostoevsky’s representation of opposition is not slight, but in fact, very thorough. Ivan represents doubt and rationality. His intellectualism is both his strength and his eventual downfall. Though brilliant, it is precisely his doubt that drives him to madness. He is a respectable character, but he is ultimately unsuccessful, exhibiting Dostoevsky’s view on where the path of doubt leads. Fyodor Pavlovich is obviously deplorable and pathetic. He is selfish and greedy. He seeks nothing but pleasure at all costs and is completely uncaring, except, presumably, for Grushenka. He believes that his recognition of his own disgraceful behavior frees him not from outside condemnation, but from true inferiority. His illegitimate son, Smerdyakov, becomes the manifestation of all that is impure in Fyodor. The Lambert family in The Corrections, though lacking in murderous rivalry and unbridled sensuality, is equally disturbing, if only because of its realism. â€Å"We are talking about the family values of the House of Atreus, the Brothers Karamazov, the Mafia, and the Manson Gang. † (Leonard, 6) While Alfred loses his body and mind to Parkinson’s, his wife, Enid, tries desperately to reunite the family for Christmas. The oldest, Gary, is well off and living with his own wife and children in an affluent area of Philadelphia. Denise, the middle child, is a successful and beautiful young chef. Chip is a failed screenplay writer, a failed boyfriend, a failed professor, and a failed son. The Corrections, then, addresses not only the gap between generations, but also the grasp of one on the other. The flyaway children who feel themselves wronged return like boomerangs to the parents whose business it has always been to stamp out errancy†¦ (Leonard, 9) Both Dostoevsky and Franzen push the reader’s limit for sympathy with their extremely flawed, but perhaps forgivable characters. The reader is forced to examine the limits of redemption from greed and â€Å"base† behavior, both in society and in the family. In both novels, the reader is ultimately compelled to forgive any sin where repentance is present. In The Brothers Karamazov, for example, it is easier to forgive Dimitri’s aggression and lies because of his genuine sincerity, while his father, a victim of cold blooded murder, does not evoke the slightest feelings of sympathy, aside, maybe, from sheer pity. In The Corrections, Chip is likable despite his follies not only because of his self-deprecation, but because he has moral principals. Contrary to his brother, Gary, who has a wife, children, and a steady job, but a very capitalistic mindset and a depressed, numb state of living. Denise is a competitive workaholic but is genuinely confused, and the reader his hoping for her salvation because she is so desperately isolated. The novel shifts from a condemnation of the contemporary American materialism to the possibility of family (and, by implication, human) forgiveness. The narrative has been dallying with philosophical questions, but now it lingers†¦I cannot say whether Franzen could have pulled off this miraculous redemption of his story had he not so cruelly set up his Lamberts as crass sinners, but I was sorry it took him so long to acknowledge their capacity for decency†¦(Sayers 23) Perhaps the biggest difference between these two novels is the philosophical dissonance between Dostoevsky and Franzen. While Dostoevsky’s characters clearly represent specific and largely unchanging ideals, Franzen’s creations are muddled and confused. They resemble a deer in the headlights of post-modern America, racing inside, but paralyzed by the chaos of the situation, and unable to move in either direction. Interestingly, though Dostoevksy was a staunch advocate of deep faith while fairly exploring doubt, his ultimate message when is comes to family is far less optimistic than the obviously anti-religious Franzen. This is perhaps dependent on the opposing characters’ abilities to change. Since Dostoevsky’s characters remain of largely the same beliefs and convictions throughout and in spite of their life-changing experiences, they are incapable of true metamorphosis. Franzen’s initially detestable Lambert family is eventually redeemed by each character’s inner-changes, which leads ultimately to a realistically cynical, but still heart-warming loyalty to one-another. The only character who doesn’t change for the better is Alfred, who simply loses his mind, and though the reader is respectful of his work ethic, he is obviously the yoke of the family, whose death is seen as ultimately positive for his wife and children. There is a sense of triumph by the end of the novel, when Enid, who initially looked like an idiot compared to Alfred, is really just in need of independence, and proves to be a lot smarter than she seems. If anyone in The Corrections is radically transformed—and all of them are turned like sucklings on a spit— its Enid at age seventy-five. When Alfred at last is safely dead, she puts on her sudden freedom like a jaunty hat. (Leonard, 8) When the charismatic and brilliant defense attorney asserts the child’s right to demand proof that he should love his father, the audience wholeheartedly approves and supports him, even so far as to applaud despite the judge. The audience, like a Shakespearean chorus, representing the author’s prediction of the reader’s reaction, is totally in favor of Dimitri’s salvation despite full knowledge of past offenses. The reader blames his father for raising a violent deviant. Franzen, on the other hand, provokes a feeling of pity for Enid that makes the reader want to scold her children, understandably irritated though they may be, for not treating their mother with more kindness. The result is a surprising one. Franzen, the postmodern critic of just about everything, takes the route of sympathy and even optimism. His characters change for the better in a very real way. They don’t proclaim that they have decided to devote themselves to God, they have no fear of damnation, they just genuinely have tried and succeeded in improving their relationships. Dostoevsky is focused much more on religion, for a variety of justifiable reasons, but his characters are less fluid. Though each of his characters transforms throughout the novel, it is only by way of rigorous philosophical inquiry. Franzen’s characters, on the other hand, are merely growing up. Enid does not plan to improve her life when her husband dies- she just does. It is a natural progression as opposed to a constant battle fought with violent imagery and empty threats. Franzen frees his characters from every limit set by Dostoevsky- especially God and the fear of moral judgment. The result is not a depressing tale of a family who does not feel an obligated loyalty to one another. On the contrary, the Lambert family transforms only for love. They are not motivated by religion or society. They simply learn to love one another for no other reason than their shared DNA. This is far more optimistic than the picture of a family according to Dostoevsky, because it is universally attainable. SOURCES Hruska, Anne. The Sins of Children in the Brothers Karamazov. Christianity and Literature 54 (2005): 471-495. Parenthetical Citation Leonard, John. Nuclear Fission. Rev. of The Corrections, by Jonathan Franzen. New York Review of Books 20 Sept. 2001. Parenthetical Citation Polka, Brayton. Psychology and Theology in the Brothers Karamazov. Journal of Literature and Theology 5 (1991): 1-24. Parenthetical Citation Sayers, Valerie. Caffeinated Realism. Commonweal 21 Dec. 2001: 23-24. Parenthetical Citation

Mathematical description of OFDM

Mathematical description of OFDM When we talk about the Mathematical description of OFDM then we cannot neglect the following mathematical treatments: The Fourier transform The use of the Fast Fourier Transform in OFDM The guard interval and its implementation As we have discussed above that a large number of narrowband carriers which are spaced close to each other in frequency domain are transmitted by OFDM. The modern digital technique that is used in the OFDM is FFT i-e Fast Fourier transform (FFT) and due to the use of FFT it reduces the number of modulators and demodulators both at the receiver and transmitter side. Fig. 4 Examples of OFDM spectrum (a) a single subchannel, (b) 5 carriers At the central frequency of each subchannel, there is no crosstalk from other subchannels. Mathematically, each carrier can be described as a complex wave: (1) sc(t) = the real part of original signal. Ac(t) = the Amplitude f c(t) = Phase of carrier (t)= symbol duration period Ac(t) and f c(t) use to fluctuate on symbol by symbol basis. Parameter values are constant over (t). As we know that OFDM posses many carriers. So the complex signals ss(t) is represented as: (2) where This is of course a continuous signal. If we consider the waveforms of each component of the signal over one symbol period, then the variables Ac(t) and f c(t) take on fixed values, which depend on the frequency of that particular carrier, and so can be rewritten: If the signal is sampled using a sampling frequency of 1/T, then the resulting signal is represented by: (3) At this point, we have restricted the time over which we analyse the signal to N samples. It is convenient to sample over the period of one data symbol. Thus we have a relationship: t =NT If we now simplify eqn. 3, without a loss of generality by letting w 0=0, then the signal becomes: (4) Now Eq. 4 can be compared with the general form of the inverse Fourier transform: (5) In eq. 4, the function is no more than a definition of the signal in the sampled frequency domain, and s(kT) is the time domain representation. Eqns. 4 and 5 are equivalent if: (6) This is the same condition that was required for orthogonality (see Importance of orthogonality). Thus, one consequence of maintaining orthogonality is that the OFDM signal can be defined by using Fourier transform procedures. The Fourier transform Fourier transform actually relate events in time domain to events in frequency domain. There are different version of FFT which are used according to requirement of different sort of work The conventional transform provide the relation of continuous signals. Note that Continuous signals are not limited in both time and frequency domain. Though, it is better to sample the signal so that the signal processing becomes simpler. But it lead to an aliasing when we sample the signals with infinite spectrum and the processing of signals which are not time limited can lead to another problem that is referred to as space storage. DFT (discrete Fourier transforms) is use to overcome the above problem of signal processing. The original definition of DFT reveals that the time waves have to repeat frequently and similarly frequency spectrum repeat frequently in frequency domain. Basically in DFT the signals can be sampled in time domain as well as in frequency domain. The Fourier transform is the process in which the signal represented in the time domain transformed in frequency domain, while the reverse process uses IFT which is the inverse Fourier transform. The use of the Fast Fourier Transform in OFDM The main reason that the OFDM technique has taken a long time to become a prominence has been practical. It has been difficult to generate such a signal, and even harder to receive and demodulate the signal. The hardware solution, which makes use of multiple modulators and demodulators, was somewhat impractical for use in the civil systems. The ability to define the signal in the frequency domain, in software on VLSI processors, and to generate the signal using the inverse Fourier transform is the key to its current popularity. The use of the reverse process in the receiver is essential if cheap and reliable receivers are to be readily available. Although the original proposals were made a long time ago [Weinstein and Ebert], it has taken some time for technology to catch up. At the transmitter, the signal is defined in the frequency domain. It is a sampled digital signal, and it is defined such that the discrete Fourier spectrum exists only at discrete frequencies. Each OFDM carrier corresponds to one element of this discrete Fourier spectrum. The amplitudes and phases of the carriers depend on the data to be transmitted. The data transitions are synchronised at the carriers, and can be processed together, symbol by symbol (Fig. 5). Fig. 5 Block diagram of an OFDM system using FFT, pilot PN sequence and a guard bit insertion [Zou and Wu] The definition of the (N-point) discrete Fourier transform (DFT) is: (DFT) (7) and the (N-point) inverse discrete Fourier transform (IDFT): (IDFT) (8) A natural consequence of this method is that it allows us to generate carriers that are orthogonal. The members of an orthogonal set are linearly independent. Consider a data sequence (d0, d1, d2, †¦, dN-1), where each dn is a complex number dn=an+jbn. (an, bn= ± 1 for QPSK, an, bn= ± 1,  ± 3 for 16QAM, †¦ ) k=0,1,2, †¦, N-1 (9) where fn=n/(ND T), tk=kD t and D t is an arbitrarily chosen symbol duration of the serial data sequence dn. The real part of the vector D has components k=0,1,..,N-1 (10) If these components are applied to a low-pass filter at time intervals D t, a signal is obtained that closely approximates the frequency division multiplexed signal (11) Fig. 5 illustrates the process of a typical FFT-based OFDM system. The incoming serial data is first converted form serial to parallel and grouped into x bits each to form a complex number. The number x determines the signal constellation of the corresponding subcarrier, such as 16 QAM or 32QAM. The complex numbers are modulated in a baseband fashion by the inverse FFT (IFFT) and converted back to serial data for transmission. A guard interval is inserted between symbols to avoid intersymbol interference (ISI) caused by multipath distortion. The discrete symbols are converted to analog and low-pass filtered for RF upconversion. The receiver performs the inverse process of the transmitter. One-tap equalizer is used to correct channel distortion. The tap-coefficients of the filter are calculated based on the channel information. Fig. 6 Example of the power spectral density of the OFDM signal with a guard interval D = TS/4 (number of carriers N=32) [Alard and Lassalle] Fig 4a shows the spectrum of an OFDM subchannel and Fig. 4b and Fig. 6 present composite OFDM spectrum. By carefully selecting the carrier spacing, the OFDM signal spectrum can be made flat and the orthogonality among the subchannels can be guaranteed. The guard interval and its implementation The orthogonality of subchannels in OFDM can be maintained and individual subchannels can be completely separated by the FFT at the receiver when there are no intersymbol interference (ISI) and intercarrier interference (ICI) introduced by transmission channel distortion. In practice these conditions can not be obtained. Since the spectra of an OFDM signal is not strictly band limited (sinc(f) function), linear distortion such as multipath cause each subchannel to spread energy into the adjacent channels and consequently cause ISI. A simple solution is to increase symbol duration or the number of carriers so that distortion becomes insignificant. However, this method may be difficult to implement in terms of carrier stability, Doppler shift, FFT size and latency. Fig. 7 The effect on the timing tolerance of adding a guard interval. With a guard interval included in the signal, the tolerance on timing the samples is considerably more relaxed. Fig. 8 Example of the guard interval. Each symbol is made up of two parts. The whole signal is contained in the active symbol (shown highlighted for the symbol M) The last part of which (shown in bold) is also repeated at the start of the symbol and is called the guard interval One way to prevent ISI is to create a cyclically extended guard interval (Fig. 7, 8), where each OFDM symbol is preceded by a periodic extension of the signal itself. The total symbol duration is Ttotal=Tg+T, where Tg is the guard interval and T is the useful symbol duration. When the guard interval is longer than the channel impulse response (Fig. 3), or the multipath delay, the ISI can be eliminated. However, the ICI, or in-band fading, still exists. The ratio of the guard interval to useful symbol duration is application-dependent. Since the insertion of guard interval will reduce data throughput, Tg is usually less than T/4. The reasons to use a cyclic prefix for the guard interval are: to maintain the receiver carrier synchronization ; some signals instead of a long silence must always be transmitted; cyclic convolution can still be applied between the OFDM signal and the channel response to model the transmission system. http://www.wirelesscommunication.nl/reference/chaptr05/ofdm/ofdmqual.htm Multipath Challenges In an OFDM-based WLAN architecture, as well as many other wireless systems, multipath distortion is a key challenge. This distortion occurs at a receiver when objects in the environment reflect a part of the transmitted signal energy. Figure 2 illustrates one such multipath scenario from a WLAN environment. Figure 2: Multipath reflections, such as those shown here, create ISI problems in OFDM receiver designs. Click here for larger version of Figure 1b Multipath reflected signals arrive at the receiver with different amplitudes, different phases, and different time delays. Depending on the relative phase change between reflected paths, individual frequency components will add constructively and destructively. Consequently, a filter representing the multipath channel shapes the frequency domain of the received signal. In other words, the receiver may see some frequencies in the transmitted signal that are attenuated and others that have a relative gain. In the time domain, the receiver sees multiple copies of the signal with different time delays. The time difference between two paths often means that different symbols will overlap or smear into each other and create inter-symbol interference (ISI). Thus, designers building WLAN architectures must deal with distortion in the demodulator. Recall that OFDM relies on multiple narrowband subcarriers. In multipath environments, the subcarriers located at frequencies attenuated by multipath will be received with lower signal strength. The lower signal strength leads to an increased error rate for the bits transmitted on these weakened subcarriers. Fortunately for most multipath environments, this only affects a small number of subcarriers and therefore only increases the error rate on a portion of the transmitted data stream. Furthermore, the robustness of OFDM in multipath can be dramatically improved with interleaving and error correction coding. Lets look at error correction and interleaving in more detail. Error Correction and Interleaving Error correcting coding builds redundancy into the transmitted data stream. This redundancy allows bits that are in error or even missing to be corrected. The simplest example would be to simply repeat the information bits. This is known as a repetition code and, while the repetition code is simple in structure, more sophisticated forms of redundancy are typically used since they can achieve a higher level of error correction. For OFDM, error correction coding means that a portion of each information bit is carried on a number of subcarriers; thus, if any of these subcarriers has been weakened, the information bit can still arrive intact. Interleaving is the other mechanism used in OFDM system to combat the increased error rate on the weakened subcarriers. Interleaving is a deterministic process that changes the order of transmitted bits. For OFDM systems, this means that bits that were adjacent in time are transmitted on subcarriers that are spaced out in frequency. Thus errors generated on weakened subcarriers are spread out in time, i.e. a few long bursts of errors are converted into many short bursts. Error correcting codes then correct the resulting short bursts of errors. OR for guard interval Handling ISI The time-domain counter part of the multipath is the ISI or smearing of one symbol into the next. OFDM gracefully handles this type of multipath distortion by adding a guard interval to each symbol. This guard interval is typically a cyclic or periodic extension of the basic OFDM symbol. In other words, it looks like the rest of the symbol, but conveys no new information. Since no new information is conveyed, the receiver can ignore the guard interval and still be able to separate and decode the subcarriers. When the guard interval is designed to be longer than any smearing due to the multipath channel, the receiver is able to eliminate ISI distortion by discarding the unneeded guard interval. Hence, ISI is removed with virtually no added receiver complexity. It is important to note that discarding the guard interval does have an impact on the noise performance since it reduces the amount of energy available at the receiver for channel symbol decoding. In addition, it reduces the data rate since no new information is contained in the added guard interval. Thus a good system design will make the guard interval as short as possible while maintaining sufficient multipath protection. Why dont single carrier systems also use a guard interval? Single carrier systems could remove ISI by adding a guard interval between each symbol. However, this has a much more severe impact on the data rate for single carrier systems than it does for OFDM. Since OFDM uses a bundle of narrowband subcarriers, it obtains high data rates with a relatively long symbol period because the frequency width of the subcarrier is inversely proportional to the symbol duration. Consequently, adding a short guard interval has little impact on the data rate. Single carrier systems with bandwidths equivalent to OFDM must use much shorter duration symbols. Hence adding a guard interval equal to the channel smearing has a much greater impact on data rate. http://www.commsdesign.com/design_corner/showArticle.jhtml?articleID=16504605 As we know that cyclic prefix is used to restore the orthogonality and preserve ISI, but the question that arises is that how the orthogonality destroyed between the subcarriers and how cyclic prefix restore the orthogonality. [1] [2] The orthogonality between subcarriers is destroyed due to the channel dispersion whenever the signal is transmitted over a channel and this cause ICI and due to the longer delay ISI occur among the OFDM symbols which are in sequence. [1] Further more there is no any interference in uncorrupted OFDM signal when they are demodulated but when we talk about the time dispersive channel the OFDM subcarriers lost there orthogonality. The main cause behind this is that the demodulator correlation interval for one path will overlap with the symbol boundary of a different path as show in the figure [ ] [ 2] Fig. 4.11 16QAM constellation We will see that this makes equalization in the receiver very simple. If multipath exceeds the CP, then constellation points in the modulation is distorted. As can be seen from Fig. 4.11, when multipath delay exceeds the CP, the subcarriers are not guaranteed to be orthogonal anymore, since modulation points may fall into anywhere in the respective contour. As delay spread gets more severe, the radius of the contour enlarges and crosses the other contours. Hence, this causes error. The CP is utilized in the guard period between successive blocks and constructed by the cyclic extension of the OFDM symbol over a period Ï„ : (4.3) The required criteria is that Ï„ is chosen bigger than channel length Ï„h so as not to experience an ISI. The CP requires more transmit energy and reduces the bit rate to (Nb/NT +Ï„ ), where b is the bits that a subcarrier can transmit. The CP converts a discrete time linear convolution into a discrete time circular convolution. Thus, transmitted data can be modeled as a circular convolution between the channel impulse response and the transmitted data block, which in the frequency domain is a pointwise multiplication of DFT samples. Then received signal becomes Where (4.5) Hence, kth subcarrier now has a channel component Hk, which is the fourier transform of h(t) at the frequency fk. The OFDM symbol is sampled (t = nT and fk = k/NT) in the receiver and demodulated with an FFT. Consequently, the received data has the following form yk = Hk xk, k = 0, . . . ,N −1. (4.6) The received actual data can be retrieved with N parallel one-tap equalizers. One-tap equalizer simply uses the estimated channel ( ˆHk) components and use it to retrieve estimated ˆ xk as follows (4.7) Also note that the spectrum of OFDM decays slowly. This causes spectrum leakage to neighboring bands. Pulse shaping is used to change the spectral shape by either commonly used raised cosine time window or passing through a filter. An OFDM system design considers setting the guard interval (Ï„ ) as well as the symbol time (T) and FFT size with respect to desired bit rate B and given tolerable delay spread. The guard interval is selected according to delay spread, and typically it is 2–4 times the root-mean-squared delay spread with respect to chosen coding and modulation. Symbol time is set with respect to guard time and it is desirable to select much larger than the guard time since the loss in SNR in the guard time is compensated. Symbol time as we know determines the subcarrier spacing ( fb = 1/T). Number of subcarriers N is found with respect to desired bit rate, since total number of bits (bT ) to carry in one symbol is found with B/(T +Ï„ ) and selected coding and modulation determines the number of bits (b) in one subcarrier. Hence, the number of subcarriers is N = bT /b. For instance, b is two for 16QAM with rate 1/2. The required bandwidth (W) is then N âˆâ€" fb. Alternatively, this method is reversed to find out the symbol time starting from the given bandwidth. OR Cyclic-prefix insertion As I m talking about the time dispersive channel I want to include that in time dispersive channel the subcarrier not only have inter symbol interference within them but they also posses interference between them. As we know that in case of time dispersive channel the frequency-selective channel frequency response is equivalent to time dispersion on the radio channel. There are two reasons of orthogonality between OFDM subcarriers. Due to frequency-domain separation. The specific frequency-domain structure of each subcarrier. Even if the frequency-domain channel is constant over a bandwidth corresponding to the main lobe of an OFDM subcarrier and only the subcarrier side lobes are corrupted due to the radio-channel frequency selectivity, the orthogonality between subcarriers will be lost with inter-subcarrier interference as a consequence. Due to the relatively large side lobes of each OFDM subcarrier, already a relatively limited amount of time dispersion or, equivalently, a relatively modest radio-channel frequency selectivity may cause non-negligible interference between subcarriers. Time dispersion and corresponding received-signal timing Figure 9 Time dispersion and corresponding received-signal timing. To deal with this problem and to make an OFDM signal truly insensitive to time dispersion on the radio channel, so-called cyclic-prefix insertion is typically used in case of OFDM transmission. As illustrated in Figure 10, cyclic-prefix insertion implies that the last part of the OFDM symbol is copied and inserted at the beginning of the OFDM symbol. Cyclic-prefix insertion thus increases the length of the OFDM symbol from Tu to Tu +TCP, where TCP is the length of the cyclic prefix, with a corresponding reduction in the OFDM symbol rate as a consequence. As illustrated in the lower part of Figure 10, if the correlation at the receiver side is still only carried out over a time interval Tu =1/∆f , subcarrier orthogonality will then be preserved also in case of a time-dispersive channel, as long as the span of the time dispersion is shorter than the cyclic-prefix length. Cyclic-prefix insertion Figure 10. Cyclic-prefix insertion Cyclic-prefix insertion is beneficial in the sense that it makes an OFDM signal insensitive to time dispersion as long as the span of the time dispersion does not exceed the length of the cyclic prefix. The drawback of cyclic-prefix insertion is that only a fraction Tu /( Tu +TCP) of the received signal power is actually utilized by the OFDM demodulator, implying a corresponding power loss in the demodulation. In addition to this power loss, cyclic-prefix insertion also implies a corresponding loss in terms of bandwidth as the OFDM symbol rate is reduced without a corresponding reduction in the overall signal bandwidth. One way to reduce the relative overhead due to cyclic-prefix insertion is to reduce the subcarrier spacing ∆f , with a corresponding increase in the symbol time Tu as a consequence. http://wirelesscafe.wordpress.com/2009/04/20/ofdm-as-downlink-transmission-scheme-for-lte/

Internet, a network that revolutionized how information technology is s

Internet, a network that revolutionized how information technology is seen, is a medium for marketing that changed the way marketers and consumers think. Marketing as a concept has existed long before the Internet. Abstract Internet, a network that revolutionized how information technology is seen, is a medium for marketing that changed the way marketers and consumers think. Marketing as a concept has existed long before the Internet. The four Ps of marketing are well known: Product, Price, Place, and Promotion. Approaching the consumer through the Internet is very different than through common media. Marketers had to think twice, now they must think trice. Marketers, however, have a wider audience and in some cases, they may have the whole world as an audience. Consumers have many more choices and they are free to convince themselves before they buy. Consumers actively go to the location of their interest, and they are not passive anymore. Internet is a medium that offers many tools for the marketers and a wide range of choices for the consumers. 1 Introduction ============== The way of marketing changed because the Internet is used as a medium. In the past, the way of marketing had to adjust to new media in several cases. For example, when the radio appeared or even better when the TV became a domestic must. Internet, however, is a medium different from the common ones. For the first time, the consumer is not passive and is seen as the "end user". This has changed the way marketers must work in order to succeed using the Internet to promote products. This change however did not happen in one day. Internet exists for more than two decades. Its use as a marketing media, however, started recently. The purpose of this report is to investigate how marketing using the Internet is different from using other media. This investigation is separated in two views: (1) the merchants scope, and (2) the consumers scope. Merchants do not have an easy job as it is thought by many people. Marketing using the Internet is not an easy task. One can loose its severity very easily. Nevertheless, there are many benefits if used properly. Consumers can use their free will in order to choose where they want to go and not where they are told to go. There are of course the search engines that may impose the sites they want, but... ...12/1999 WWW4 Welcome to internet.com's Marketing Channel http://www.internet.com/sections/marketing.html Site visited: 12/12/1999 WWW5 The E-Commerce Advisor Internet marketing newsletter-e-zine http://www.sotkin.com/nl/ Site visited: 12/12/1999 WWW6 Netcommerce Magazine http://www.netcommercemag.com/ Site visited: 12/12/1999 WWW7 Marketing - WebMaster Article Index http://www.cio.com/archive/wm_index_marketing.html Site visited: 12/12/1999 WWW8 InternetDay - Web Site Promotion, Internet Advertising, and Web Marketing Newsletter http://www.internetday.com/archives/111899.html Site visited: 12/12/1999 WWW9 Internet Marketing Center http://www.marketingtips.com/ Site visited: 12/12/1999 WWW10 Free E-mail and Web Newsletter - Web Marketing Today http://www.wilsonweb.com/wmt/ Site visited: 12/12/1999 WWW11 E-Commerce Times Front Page Everything You Need to Know About Doing Business Online http://www.ecommercetimes.com/ Site visited: 12/12/1999 WWW12 Internet Market Programs http://www.internetmarketprogram.com/img.htm Site visited: 12/12/1999 WWW13 InternetNews.com E-Commerce News http://www.internetnews.com/ec-news/ Site visited: 12/12/1999

Birth Control Availibilty :: Contraceptives, Birth Control Essays

Some believe contraceptives should be available at cost to those who can afford them, available to legal adults who cannot, and/or available to students through public schools. Some religious traditions, based on their view of reproduction, oppose birth control availability for everyone. There are religious traditions that oppose women's autonomy, and as such, are especially opposed to contraceptives for women. Some who oppose sex outside of marriage believe that distribution of condoms in schools encourages adolescent sexual activity. Those who oppose abortion but not birth control often favor condom distribution to reduce pregnancies. The government is interested in preventing the spread of sexually-transmitted diseases and reducing the number of unwanted pregnancies and children who are wards of the state or supported by state funds. One reason that many students are not sexually active, is because of the lack of protection or the embarrassment of buying protection at a local dru g store. And while this would mean sex without protection to many young adults, there are a lot who would refrain from experimenting with sex because of not having protection. By putting a condom dispenser in high school bathrooms, this gives that percentage of teens nice, easy, and anonymous access to condoms. Thus possibly resulting in an increase of sexually active students. Why not leave condoms at the local drug stores, and make it as hard as possible to comfortably buy protection. The embarrassment alone, might keep a few teenagers from having sex.   Ã‚  Ã‚  Ã‚  Ã‚  Not only would putting condom dispensers in high school allow anonymous purchasing of protection, but it might also promote sex to the crowd of people that should not even know what sex is. Imagine walking into the bathroom one morning and there against the back wall is a condom machine.

Families Values in Knoxville, Tennessee, Those Winter Sundays, and Two Kinds :: Two Kinds, Amy Tan

Family. What do you think of when you hear that word? Some people think of relatives or the people that they live with. Maybe a stepfather, stepmother, brothers, or sisters. To me, family is love, devotion, and caring. People of a family want to be together and love to do things for each other, such as do the dishes or wash the car for them. The poems that most represent my family values are â€Å"Knoxville, Tennessee† by Nikki Giovanni and â€Å"Those Winter Sundays† by Robert Hayden. The one that does not represent my family as much as the others is â€Å"Two Kinds† by Amy Tan. I love the poem â€Å"Knoxville, Tennessee† by Nikki Giovanni. It gives me a sense of people wanting to be together, family, wanting to be together. Giovanni wrote this poem so that it is told through a child (under the age of ten). The child’s world is made up of his or her family. He or she is mostly with the family â€Å"at the church picnic† (Giovanni 50, line 12) or â€Å"at the church / homecoming† (Giovanni 50, lines17-18). The child goes places with the family and is with them all of the time. He or she has not reached the teenage stage of rebellion and does not mind being with his or her parents. That is why I like this poem. It shows love for family through the uncontaminated eyes of a child. â€Å"Those Winter Sundays† represents family devotion to me. The father in the poem is so devoted to his family that he gets â€Å"up early / and put his clothes on in the blueback cold† (Hayden 51, lines 1-2) to warm the house for them. He does not care about anything except driving the cold away for his family. That is the kind of thing that is done out of true, deep, unconditional love. Families stick together and support each other, even if one is not so kind, like the teenager who fears â€Å"the chronic angers of the house† (Hayden 51, line 9). Families forgive, forget, and keep loving each other. â€Å"Two Kinds† is a story that does not represent my idea of family. The young daughter (Tan) does not obey her mother and continually disappoints her. Her mother wants her to learn piano and believes that she has talent, but Tan does not agree. â€Å"Unlike my mother, I did not believe that I could be anything.

Bad Boys

Nick Stephens 4/3/13 Albritton Sociology 3255 Bad Boys Ann Arnett Ferguson’s book â€Å"Bad Boys† discusses the way educators and other people in the school systems, and society as a whole view black youth in today’s world. There are many stereotypes that are discussed and stigmas that stick with black children through their entire lives in Ferguson’s book. In order to prevent further damage to this part of our society the reader should take a long hard look at the problems brought forth by â€Å"Bad Boys†.One problem that Ferguson discusses in her book is adultification. According to her definition adultification is the idea that teachers and other adults see black children as willfully bad. Since they are seen in this light it creates an idea that black boys have adult motivations thus, making black boys seem like criminals instead of kids. Also, along the same lines, black girls are perceived as dangerously sexual. While this issue seems sort of ridiculous, these things actually happen in our public school system.While white children are seen as naturally naughty, essentially authority figures adopt the â€Å"boys will be boys† mentality when white boys get in trouble or act out, instead of issuing punishment equally to white children who act out. Ferguson states, â€Å"One the one hand children are assumed to be dissembling, devious, because they are more egocentric. On the other hand, there is an attribution of innocence to their wrongdoing. In both cases, this is understood to be a temporary condition, a stage prior to maturity. †(80)Another problem that Ferguson observes in her book is the two controlling images of black males in schools. She says, â€Å"Two cultural images stigmatize black males in the United States today: one represents him as a criminal, and the other depicts him as an endangered species. I found that both of these images were commonly invoked at Rosa Parks School for identifying, clas sifying, and making punishment decisions by the adults responsible for disciplining the kids. †(20) The way that black boys are seen creates a social hierarchy based solely on class.Ferguson is able, through her first-hand experience, to record instances that show these problems in action and give the reader insight to the problems that are being addressed. The image of black children being criminals is inherent to their development. If they are treated from a young age as criminals, they will eventually come to accept that as part of their social identity, leading them to actually commit crimes in the future. If they were treated equally then black children, especially males, may not be on a definite path into the heart of the criminal justice system by the time they are adults.Ferguson addresses another problem that has a severe effect on the psyche of young black boys in public schools. Teachers and administrators alike are guilty of assuming that these children are headed for a future of crime. They are labeled as unsalvageable and bound for jail. She uses the example, â€Å"There is a jail cell with your name on it† coming from the teacher to one of their students. This is damaging to the child’s development because it seemingly predetermines their fate. The punishing room that Ferguson discusses is primarily made up of black boys.The punishing room makes these boys truly believe that they are bad, and that since even their teachers and other superiors cannot see through this it tends to give the children a sense of identity as someone who is bad, and does not really count. With the punishing room the idea is solidified in the minds of these children, which is a problem. Ideally these troubled children should be worked with individually in order to get to the root of the reason that they are acting out in school. Ferguson says about the punishing room, â€Å"The child who gets in trouble is the norm. Identities and reputations are mad e and remade here.It is the space in the school in which everyone is like yourself-in trouble-and you are no longer different. † This quote gives the reader a visible reference of why some of these children, deemed unsalvageable by their teachers, may get into trouble on purpose so they have to go to this place where at least they are not alone. This leads into the idea of the importance of group identity. Ferguson explains the importance of group identity in her book by basically saying that kids need to feel like they fit it, and they will use whatever tools necessary in order to do so.This is all brought together by the idea of cultural capital. Ferguson explains that in the school system there is a hierarchy of the children, â€Å"The disciplinary techniques of the school actively produce social identities of â€Å"good†, â€Å"bad†, â€Å"gifted†, â€Å"having potential†, â€Å"troubled†, and â€Å"troublesome,† rather than ferre t them out and reveal them as they naturally exist. The importance of group identity is essential in the development of all children. It helps them to develop a sense of self, who they are, and who they want to be.The problem lies in the fact that children are becoming fine with the idea that they are â€Å"bad† and come to accept that as reality, which allows them to form that identity, in turn making them into bad kids, because the only way that they are able to fit in to the social atmosphere is by acting out and getting in trouble. The boys in Ferguson’s study use the importance of group identity, coping mechanisms in public, and classroom performance in tandem to secure their own personal identities. Most of the kids are not really that â€Å"bad† they often have extenuating circumstances outside of school that make school not seem important to them.They often feel secluded, which draws from the problem with adultification by their teachers and other superi ors. So by acting out in the classroom they get attention, even though it is negative attention, it is still attention. Through the eyes of the teachers it seems like they are just putting forth a poor classroom performance. They do not see the struggles that the children go through outside of school, which tends to directly have an impact on the way the handle themselves in social situations, craving the need to belong to some sort of group. So they turn to what is presented to them, being bad.In conclusion, there are many flaws with the education system in the United States. The processes in which black children are dealt with need to be reformed. The idea of adultification as defined by Ferguson is a serious issue that plagues schools, where even teachers who are conscious of this fall into the category of looking at black children as small adults, holding them to different standards than their white counterparts. They are still subject to the controlling images of black males as being criminals, and assuming that they are on the path to prison anyway, so what is the use. This is unacceptable.Different strategies in dealing with this problem should be implemented than the ones that the public school system has to offer at the present time. Through Ferguson’s first-hand accounts of what she observed during her time in Rosa Parks School the reader is painted a picture of the very real problems at hand. Most people outside of these schools do not even realize what is going on and that is a problem as well. By studying Ferguson’s work one can hope that in the near future there will be some sort of reconstruction of the schools in order to help prevent further damage and stigmatization to black children.

A Wall of Fire Rising Essay

An image that was prevalent in this story was the hot air balloon. The hot air balloon represented freedom for Guy, who was trying to escape the unfair poverty that his family was experiencing. This symbol of freedom is first introduced to the reader when Guy, his wife Lili, and their son all go down to the sugar mill to hear the evening news that is displayed for them. This is a little place of enjoyment that they have found since they don’t go and sit with everyone else, â€Å"where in the past year they had discovered their own wonder.† I thought it was fitting that Danticat separated Guy and the balloon with barbed wire. It was like he wasn’t supposed to be free. â€Å"As Guy pushed his hand through the barbed wire, she could tell from the look on his face that he was thinking of sitting inside the square basket while the sooth rainbow surface of the balloon itself floated above his head†, this was foreshadowing that he would end up in that balloon of freedom one day. Before Guy jumped out of the balloon, he was asking Lili how she thought a man is judged after he is gone. She responded with â€Å"A man is judged by his deeds, the boy never goes to bed hungry.† Guy took this as an approval to go forth with his search for freedom. Guy is not judged after death based on the act of killing himself, he is judged based on his deeds and actions while he was alive. I was definitely caught off guard when he jumped out of the balloon. Why didn’t he take his family with him!? When Lili and Guy were lying in the grass together he said â€Å"Sometimes I just want to take that big balloon and ride it up in the air. I’d like to sail off somewhere and keep floating until I got to a really nice place with a nice plot of land where I could be something new. I’d build my own house, keep my own garden. Just be something new.† I was left wondering what his little family would do to survive now. He was the main provider and Lili was always building him up and trying to make him feel like a man. I was also confused as to why Guy would want to put his son on the list to work at the mill if that’s not what Guy even wanted to do in his life. I would have thought he would feel the same way as his wife in that he would want a better life for their son instead of just working at the only mill in the area.