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Guest Posted 21 years ago
Essay & Composition Writing
Proposal editing
can any one help me with my proposal? I need help in choice of words, grammar, and organizations.
Thank you in advance
Orthogonal Frequency Division Multiplexing is a multi carrier modulation scheme that splits a high data rate stream into a number of slower streams that are transmitted simultaneously. Thus, the bit period is increased while the data rate is not being affected. This makes the OFDM signal more robust in multi path environments. An added feature of OFDM is that it uses bandwidth effiently. The OFDM uses orthogonal sub carriers that have an overlapping spectrum.
Those features of OFDM make it an attractive modulation scheme for future applications such as digital audio and video broadcasting. In fact, OFDM has been already chosen as the modulation scheme for many standards such as IEEE 802.11a, and HYPERLAN/2 for wireless local area networks. However, OFDM suffers from some drawbacks that limit its applications areas. One of the main drawbacks is the high Peak to Average Power Ratio (PAPR) of the OFDM signal. A high PAPR has negative impact on the efficiency of power amplifiers that are present in the transmitter circuitry. The peaks of the OFDM signal drive the power amplifier to operate in the saturation region causing nonlinear signal distortion. Such distortion causes the level of the out of band radiation to increase and degrades the bit error performance of the system. A trivial solution is to operate the power amplifier with a large back off. However, this will reduce the efficiency of the PA leading to higher power consumptions. This can not be tolerated in portable devices such as cellular phones and laptops where battery life is an issue. Moreover, the PAPR problem continues to affect the complexity of the A/D circuit. Large dynamic range of the OFDM signal requires more quantized levels which translate into increasing the number of bits used to represent the signal.
Minimizing the PAPR is a hot research topic. There are many proposed solutions that exist in the literature. PAPR can be reduced by clipping the signal to a predefined level, histogram equalization that reduce the probability of large PAPR to occur, coding techniques that excludes code words with high PAPR, and phase carrier adjustment to ensure that the carriers adds up destructively. Those techniques differ in their trade offs that could be extensive computations, delay, higher BER, and increase the out of band radiation.
The purpose of this project is to develop a technique that reduces the PAPR and the out of band radiation caused by the nonlinearity of the PA of the OFDM signal. The technique should have reasonable amount of computations, minimum delay time, and good BER performance.
Thank you in advance
Orthogonal Frequency Division Multiplexing is a multi carrier modulation scheme that splits a high data rate stream into a number of slower streams that are transmitted simultaneously. Thus, the bit period is increased while the data rate is not being affected. This makes the OFDM signal more robust in multi path environments. An added feature of OFDM is that it uses bandwidth effiently. The OFDM uses orthogonal sub carriers that have an overlapping spectrum.
Those features of OFDM make it an attractive modulation scheme for future applications such as digital audio and video broadcasting. In fact, OFDM has been already chosen as the modulation scheme for many standards such as IEEE 802.11a, and HYPERLAN/2 for wireless local area networks. However, OFDM suffers from some drawbacks that limit its applications areas. One of the main drawbacks is the high Peak to Average Power Ratio (PAPR) of the OFDM signal. A high PAPR has negative impact on the efficiency of power amplifiers that are present in the transmitter circuitry. The peaks of the OFDM signal drive the power amplifier to operate in the saturation region causing nonlinear signal distortion. Such distortion causes the level of the out of band radiation to increase and degrades the bit error performance of the system. A trivial solution is to operate the power amplifier with a large back off. However, this will reduce the efficiency of the PA leading to higher power consumptions. This can not be tolerated in portable devices such as cellular phones and laptops where battery life is an issue. Moreover, the PAPR problem continues to affect the complexity of the A/D circuit. Large dynamic range of the OFDM signal requires more quantized levels which translate into increasing the number of bits used to represent the signal.
Minimizing the PAPR is a hot research topic. There are many proposed solutions that exist in the literature. PAPR can be reduced by clipping the signal to a predefined level, histogram equalization that reduce the probability of large PAPR to occur, coding techniques that excludes code words with high PAPR, and phase carrier adjustment to ensure that the carriers adds up destructively. Those techniques differ in their trade offs that could be extensive computations, delay, higher BER, and increase the out of band radiation.
The purpose of this project is to develop a technique that reduces the PAPR and the out of band radiation caused by the nonlinearity of the PA of the OFDM signal. The technique should have reasonable amount of computations, minimum delay time, and good BER performance.
Top answer
Hi, The conclusion needs a bit more punch. ' As the essay is now, readers have no idea what you're setting out to prove until they get to the end of the essay, which is likely to cause frustration. To understand what the "inverted pyramid" name means, picture an upside-down triangle -- one with the narrow tip pointing downward and the broad base pointing upward.
- Hi, The conclusion needs a bit more punch.
- ' As the essay is now, readers have no idea what you're setting out to prove until they get to the end of the essay, which is likely to cause frustration.
- To understand what the "inverted pyramid" name means, picture an upside-down triangle -- one with the narrow tip pointing downward and the broad base pointing upward.
- The broad base represents the most newsworthy information in the news story, and the narrow tip represents the least newsworthy information in the news story.
- When you write a story in inverted pyramid format, you put the most newsworthy information at the beginning of the story and the least newsworthy information at the end.
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1 Answers
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Hi,
The conclusion needs a bit more punch.
Use the inverted pyramid style, start with the concluding sentence: 'The purpose of this project is to develop a technique that reduces the PAPR and the out-of-band radiation caused by the nonlinearity of the PA of the OFDM signal.' As the essay is now, readers have no idea what you're setting out to prove until they get to the end
The conclusion needs a bit more punch.
Use the inverted pyramid style, start with the concluding sentence: 'The purpose of this project is to develop a technique that reduces the PAPR and the out-of-band radiation caused by the nonlinearity of the PA of the OFDM signal.' As the essay is now, readers have no idea what you're setting out to prove until they get to the end
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