|| "مناقشة السؤال الثاني T324 tma Question 2" °•°

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اذا احد عرف ويش حل يكتب ب عربي اهم شي نعرف ويش نكتب
والله راسي داخ

[هدوء .!]

الفقرة الثالثه موجود حلها بالكتاب الأول صفحة 99

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اعتقد اجابه الفقرة الثانيه بنفس الصفحة 99
بس الفقرة الاولى و الاخيره ما عرفت !

[رونقه]

معليش سؤال تاريخ كم تسليم الواجب

[buterflly]

المشاركة الأصلية كتبت بواسطة رونقه

معليش سؤال تاريخ كم تسليم الواجب

30/4/2015

[شوق الشمال]

امممممم صح كذا
1. Briefly describe the reason for the difference between the symbols marked as “+” and the others around them.
Modulation is often followed by pulse shaping, and demodulation is often preceded by a filtering or an integrate-and-dump operation. This section presents an example involving rectangular pulse shaping. For an example that uses raised cosine pulse shaping, see Pulse Shaping Using a Raised Cosine Filter.

Rectangular Pulse Shaping. Rectangular pulse shaping repeats each output from the modulator a fixed number of times to create an upsampled signal. Rectangular pulse shaping can be a first step or an exploratory step in algorithm development, though it is less realistic than other kinds of pulse shaping. If the transmitter upsamples the modulated signal, then the receiver should downsample the received signal before demodulating. The "integrate and dump" operation is one way to downsample the received signal.
-----------------------------------------
2. What kind of modulation scheme is depicted in the above diagram? Clarify the reason.

The scatter plot does not look exactly like a signal constellation. Where the signal constellation has 16 precisely located points, the noise causes the scatter plot to have a small cluster of points approximately where each constellation point would be.

[yaghi]

1. صف باختصار سبب الفرق بين رموز علامة "+" والآخرين من حولهم.

2. ما هو نوع من مخطط التشكيل هو مبين في الرسم البياني أعلاه؟ توضيح السبب.

3. إعطاء ميزة واحدة وعيب واحد عند استخدام 16-qam بدلا من qpsk.

4. توفير ميزة واحدة رئيسية والعيب الرئيسي واحد من نبض الرقمية نظام تعديل السعة.



الترجمه للاسئله

[yaghi]

1. Briefly describe the reason for the difference between the symbols marked as “+” and the others around them.
1- صف باختصار سبب الفرق بين رموز علامة "+" والآخرين من حولهم.
الحل بيكون وهذ اجتهاد شخصي انو الان من الرسمه علامه + هيا عباره عن سيمبل او عينه قد تم اخذها للقرائه والتعريف عنها وقياس المده اما الباقي هيا باقي اششارات وقرائات وهنا
بجيب تفصيل الها وهكذا وكل يصيغ بطريقتوا هذا حل اول
As in many digital modulation schemes, the constellation diagram is useful for QAM. In QAM, the constellation points are usually arranged in a square grid with equal vertical and horizontal spacing, although other configurations are possible (e.g. Cross-QAM). Since in digital telecommunications the data are usually binary, the number of points in the grid is usually a power of 2 (2, 4, 8, …). Since QAM is usually square, some of these are rare—the most common forms are 16-QAM, 64-QAM and 256-QAM. By moving to a higher-order constellation, it is possible to transmit more bits per symbol. However, if the mean energy of the constellation is to remain the same (by way of making a fair comparison), the points must be closer together and are thus more susceptible to noise and other corruption; this results in a higher bit error rate and so higher-order QAM can deliver more data less reliably than lower-order QAM, for constant mean constellation energy. Using higher-order QAM without increasing the bit error rate requires a higher signal-to-noise ratio (SNR) by increasing signal energy, reducing noise, or both.

If data-rates beyond those offered by 8-PSK are required, it is more usual to move to QAM since it achieves a greater distance between adjacent points in the I-Q plane by distributing the points more evenly. The complicating factor is that the points are no longer all the same amplitude and so the demodulator must now correctly detect both phase and amplitude, rather than just phase.

64-QAM and 256-QAM are often used in digital cable television and cable modem applications. In the United States, 64-QAM and 256-QAM are the mandated modulation schemes for digital cable (see QAM tuner) as standardised by the SCTE in the standard ANSI/SCTE 07 2013. Note that many MARKETING people will refer to these as QAM-64 and QAM-256.[citation needed] In the UK, 64-QAM is used for digital terrestrial television (Freeview) whilst 256-QAM is used for Freeview-HD.

Communication systems designed to achieve very high levels of spectral efficiency usually employ very dense QAM constellations. For example current Homeplug AV2 500-Mbit powerline Ethernet devices use 1024-QAM and 4096-QAM,[citation needed] as well as FUTURE devices using ITU-T G.hn standard for networking over existing HOME wiring (coaxial cable, phone lines and power lines); 4096-QAM provides 12 bits/symbol. Another example is VDSL2 technology for copper twisted pairs, whose constellation size goes up to 32768 points.[citation needed]

Ultra-high capacity Microwave Backhaul Systems also use 1024-QAM.[3] With 1024-QAM, Adaptive Coding and Modulation (ACM), and XPIC, Vendors can obtain Gigabit capacity in a single 56 MHz channel.[citation needed] حسب فهمي للسؤال

وهذا حل ثاني وشاوروني ايش الصح في الحل او الاصح في الموضوع

The first rectangular QAM constellation usually encountered is 16-QAM, the constellation diagram for which is shown here. A Gray coded bit-assignment is also given. The reason that 16-QAM is usually the first is that a brief consideration reveals that 2-QAM and 4-QAM are in fact binary phase-shift keying (BPSK) and quadrature phase-shift keying (QPSK), respectively. Also, the error-rate performance of 8-QAM is close to that of 16-QAM (only about 0.5 dB better[citation needed]), but its data rate is only three-quarters that of 16-QAM.

Expressions for the symbol-error rate of rectangular QAM are not hard to derive but yield rather unpleasant expressions. For an even number of bits per symbol, \******style k, exact expressions are available. They are most easily expressed in a per carrier sense:

P_{sc} = 2\left(1 - \frac{1}{\sqrt M}\right)Q\left(\sqrt{\frac{3}{M-1}\frac{E_s}{N_0}}\right)
so

\,P_s = 1 - \left(1 - P_{sc}\right)^2
The bit-error rate depends on the bit to symbol mapping, but for \******style E_b/N_0 \gg 1 and a Gray-coded assignment—so that we can assume each symbol error causes only one bit error—the bit-error rate is approximately

P_{bc} \approx \frac{P_{sc}}{\frac{1}{2}k} = \frac{4}{k}\left(1 - \frac{1}{\sqrt M}\right)Q\left(\sqrt{\frac{3k}{M-1}\frac{E_b}{N_0}}\right).



2. What kind of modulation scheme is depicted in the above diagram? Clarify the reason.

2. ما هو نوع من مخطط التشكيل هو مبين في الرسم البياني أعلاه؟ توضيح السبب.

الحل Constellation diagram for rectangular 16-QAM. لانه يحدد لدي 16 نقطه وتقسيمه في الرسمه وهنا التعليل تبعها السؤال

Rectangular QAM constellations are, in general, sub-optimal in the sense that they do not maximally space the constellation points for a given energy. However, they have the considerable advantage that they may be easily transmitted as two pulse amplitude modulation (PAM) signals on quadrature carriers, and can be easily demodulated. The non-square constellations, dealt with below, achieve marginally BETTER bit-error rate (BER) but are harder to modulate and demodulate

وهنا كمان حل شوروني وان شاء الله صح


3. Give one advantage and one drawback when using 16-QAM instead of QPSK.

3. إعطاء ميزة واحدة وعيب واحد عند استخدام 16-qam بدلا من qpsk.

QAM advantages and disadvantages
Although QAM appears to increase the efficiency of transmission for radio communications systems by utilising both amplitude and phase variations, it has a number of drawbacks. The first is that it is more susceptible to noise because the states are closer together so that a lower level of noise is needed to move the signal to a different decision point. Receivers for use with phase or frequency modulation are both able to use limiting amplifiers that are able to remove any amplitude noise and thereby improve the noise reliance. This is not the case with QAM.

The second limitation is also associated with the amplitude component of the signal. When a phase or frequency modulated signal is amplified in a radio transmitter, there is no need to use linear amplifiers, whereas when using QAM that contains an amplitude component, linearity must be maintained. Unfortunately linear amplifiers are less efficient and consume more power, and this makes them less attractive for mobile applications.

4. Provide one major advantage and one major disadvantage of digital pulse amplitude modulation system.

4. توفير ميزة واحدة رئيسية والعيب الرئيسي واحد من نبض الرقمية نظام تعديل السعة.


FM is widely used because of the many advantages of frequency modulation. Although, in the early days of radio communications, these were not exploited because of a lack of understand of how to benefit from FM, once these were understood, its use grew.

There are many advantages of FM, but also some disadvantages, and as a result it is suitable for many applications, but other modes may be more suited to other applications.

An understanding of the disadvantages and advantages of FM will enable the choice of the best modulation format to be made.

Advantages of frequency modulation
There are many advantages to the use of frequency modulation. These have meant that it has been widely used for many years, and will remain in use for many years.

Resilient to noise: One of the main advantages of frequency modulation that has been utilised by the broadcasting industry is the reduction in noise. As most noise is amplitude based, this can be removed by running the signal through a limiter so that only frequency variations appear. This is provided that the signal level is sufficiently high to allow the signal to be limited.
Resilient to signal strength variations: In the same way that amplitude noise can be removed, so too can any signal variations. This means that one of the advantages of frequency modulation is that it does not suffer audio amplitude variations as the signal level varies, and it makes FM ideal for use in mobile applications where signal levels constantly vary. This is provided that the signal level is sufficiently high to allow the signal to be limited.
Does not require linear amplifiers in the transmitter: As only frequency changes are required to be carried, any amplifiers in the transmitter do not need to be linear.
Enables greater efficiency than many other modes: The use of non-linear amplifiers, e.g. class C, etc means that transmitter efficiency levels will be higher - linear amplifiers are inherently inefficient.
Disadvantages of frequency modulation
There are a number of dis-advantages to the use of frequency modulation. Some are can be overcome quite easily, but others may mean that another modulation format is more suitable.

Requires more complicated demodulator: One of the minor dis-advantages of frequency modulation is that the demodulator is a little more complicated, and hence slightly more expensive than the very simple diode detectors used for AM. Also requiring a tuned circuit adds cost. However this is only an issue for the very low cost broadcast RECEIVER market.
Some other modes have higher data spectral efficiency: Some phase modulation and quadrature amplitude modulation formats have a higher spectral efficiency for data transmission that frequency shift keying, a form of frequency modulation. As a result, most data transmission system use PSK and QAM.
Sidebands extend to infinity either side: The sidebands for an FM transmission theoretically extend out to infinity. To limit the bandwidth of the transmission, filters are used, and these introduce some distortion of the signal.
There are many advantages to using frequency modulation - it is still widely used for many broadcast and radio communications applications. However with more systems using digital formats, phase and quadrature amplitude modulation formats are on the increase. Nevertheless, the advantages of frequency modulation mean that it is an ideal format for many analogue applications.




اوان اكدولي الحل الصحيح وهدا اجتهاد مني وعدلولي لو انا غلطان لان انا هنا اساعدكم لان تخرجت من زمان عقبالكم

وهدي مصادري من الانترنت
اقرائوها

http://www.academia.edu/6378824/Type...cation_Systems

http://en.wikipedia.org/wiki/Pulse-amplitude_modulation

http://www.radio-electronics.com/inf...m-tutorial.php

http://www.mathworks.com/help/comm/u...odulation.html

[zenzon]

السلام عليكم...


يا جماعه في احد عنده حل أو موقع ممكن يفيدنا في هذه الفقرة:

4. Provide one major advantage and one major disadvantage of digital pulse amplitude modulation system.


يا ريت تردون بسرعة

[هدوء .!]

^

^

بحثت عن الاجابة و ما عرفت !

[violet flower 4]

المشاركة الأصلية كتبت بواسطة yaghi

1. Briefly describe the reason for the difference between the symbols marked as “+” and the others around them.
1- صف باختصار سبب الفرق بين رموز علامة "+" والآخرين من حولهم.
الحل بيكون وهذ اجتهاد شخصي انو الان من الرسمه علامه + هيا عباره عن سيمبل او عينه قد تم اخذها للقرائه والتعريف عنها وقياس المده اما الباقي هيا باقي اششارات وقرائات وهنا
بجيب تفصيل الها وهكذا وكل يصيغ بطريقتوا هذا حل اول
as in many digital modulation schemes, the constellation diagram is useful for qam. In qam, the constellation points are usually arranged in a square grid with equal vertical and horizontal spacing, although other configurations are possible (e.g. Cross-qam). Since in digital telecommunications the data are usually binary, the number of points in the grid is usually a power of 2 (2, 4, 8, …). Since qam is usually square, some of these are rare—the most common forms are 16-qam, 64-qam and 256-qam. By moving to a higher-order constellation, it is possible to transmit more bits per symbol. However, if the mean energy of the constellation is to remain the same (by way of making a fair comparison), the points must be closer together and are thus more susceptible to noise and other corruption; this results in a higher bit error rate and so higher-order qam can deliver more data less reliably than lower-order qam, for constant mean constellation energy. Using higher-order qam without increasing the bit error rate requires a higher signal-to-noise ratio (snr) by increasing signal energy, reducing noise, or both.

If data-rates beyond those offered by 8-psk are required, it is more usual to move to qam since it achieves a greater distance between adjacent points in the i-q plane by distributing the points more evenly. The complicating factor is that the points are no longer all the same amplitude and so the demodulator must now correctly detect both phase and amplitude, rather than just phase.

64-qam and 256-qam are often used in digital cable television and cable modem applications. In the united states, 64-qam and 256-qam are the mandated modulation schemes for digital cable (see qam tuner) as standardised by the scte in the standard ansi/scte 07 2013. Note that many marketing people will refer to these as qam-64 and qam-256.[citation needed] in the uk, 64-qam is used for digital terrestrial television (freeview) whilst 256-qam is used for freeview-hd.

Communication systems designed to achieve very high levels of spectral efficiency usually employ very dense qam constellations. For example current homeplug av2 500-mbit powerline ethernet devices use 1024-qam and 4096-qam,[citation needed] as well as future devices using itu-t g.hn standard for networking over existing home wiring (coaxial cable, phone lines and power lines); 4096-qam provides 12 bits/symbol. Another example is vdsl2 technology for copper twisted pairs, whose constellation size goes up to 32768 points.[citation needed]

ultra-high capacity microwave backhaul systems also use 1024-qam.[3] with 1024-qam, adaptive coding and modulation (acm), and xpic, vendors can obtain gigabit capacity in a single 56 mhz channel.[citation needed] حسب فهمي للسؤال

وهذا حل ثاني وشاوروني ايش الصح في الحل او الاصح في الموضوع

the first rectangular qam constellation usually encountered is 16-qam, the constellation diagram for which is shown here. A gray coded bit-assignment is also given. The reason that 16-qam is usually the first is that a brief consideration reveals that 2-qam and 4-qam are in fact binary phase-shift keying (bpsk) and quadrature phase-shift keying (qpsk), respectively. Also, the error-rate performance of 8-qam is close to that of 16-qam (only about 0.5 db better[citation needed]), but its data rate is only three-quarters that of 16-qam.

Expressions for the symbol-error rate of rectangular qam are not hard to derive but yield rather unpleasant expressions. For an even number of bits per symbol, \******style k, exact expressions are available. They are most easily expressed in a per carrier sense:

P_{sc} = 2\left(1 - \frac{1}{\sqrt m}\right)q\left(\sqrt{\frac{3}{m-1}\frac{e_s}{n_0}}\right)
so

\,p_s = 1 - \left(1 - p_{sc}\right)^2
the bit-error rate depends on the bit to symbol mapping, but for \******style e_b/n_0 \gg 1 and a gray-coded assignment—so that we can assume each symbol error causes only one bit error—the bit-error rate is approximately

p_{bc} \approx \frac{p_{sc}}{\frac{1}{2}k} = \frac{4}{k}\left(1 - \frac{1}{\sqrt m}\right)q\left(\sqrt{\frac{3k}{m-1}\frac{e_b}{n_0}}\right).



2. What kind of modulation scheme is depicted in the above diagram? Clarify the reason.

2. ما هو نوع من مخطط التشكيل هو مبين في الرسم البياني أعلاه؟ توضيح السبب.

الحل constellation diagram for rectangular 16-qam. لانه يحدد لدي 16 نقطه وتقسيمه في الرسمه وهنا التعليل تبعها السؤال

rectangular qam constellations are, in general, sub-optimal in the sense that they do not maximally space the constellation points for a given energy. However, they have the considerable advantage that they may be easily transmitted as two pulse amplitude modulation (pam) signals on quadrature carriers, and can be easily demodulated. The non-square constellations, dealt with below, achieve marginally better bit-error rate (ber) but are harder to modulate and demodulate

وهنا كمان حل شوروني وان شاء الله صح


3. Give one advantage and one drawback when using 16-qam instead of qpsk.

3. إعطاء ميزة واحدة وعيب واحد عند استخدام 16-qam بدلا من qpsk.

Qam advantages and disadvantages
although qam appears to increase the efficiency of transmission for radio communications systems by utilising both amplitude and phase variations, it has a number of drawbacks. The first is that it is more susceptible to noise because the states are closer together so that a lower level of noise is needed to move the signal to a different decision point. Receivers for use with phase or frequency modulation are both able to use limiting amplifiers that are able to remove any amplitude noise and thereby improve the noise reliance. This is not the case with qam.

The second limitation is also associated with the amplitude component of the signal. When a phase or frequency modulated signal is amplified in a radio transmitter, there is no need to use linear amplifiers, whereas when using qam that contains an amplitude component, linearity must be maintained. Unfortunately linear amplifiers are less efficient and consume more power, and this makes them less attractive for mobile applications.

4. Provide one major advantage and one major disadvantage of digital pulse amplitude modulation system.

4. توفير ميزة واحدة رئيسية والعيب الرئيسي واحد من نبض الرقمية نظام تعديل السعة.


Fm is widely used because of the many advantages of frequency modulation. Although, in the early days of radio communications, these were not exploited because of a lack of understand of how to benefit from fm, once these were understood, its use grew.

There are many advantages of fm, but also some disadvantages, and as a result it is suitable for many applications, but other modes may be more suited to other applications.

An understanding of the disadvantages and advantages of fm will enable the choice of the best modulation format to be made.

Advantages of frequency modulation
there are many advantages to the use of frequency modulation. These have meant that it has been widely used for many years, and will remain in use for many years.

Resilient to noise: One of the main advantages of frequency modulation that has been utilised by the broadcasting industry is the reduction in noise. As most noise is amplitude based, this can be removed by running the signal through a limiter so that only frequency variations appear. This is provided that the signal level is sufficiently high to allow the signal to be limited.
Resilient to signal strength variations: In the same way that amplitude noise can be removed, so too can any signal variations. This means that one of the advantages of frequency modulation is that it does not suffer audio amplitude variations as the signal level varies, and it makes fm ideal for use in mobile applications where signal levels constantly vary. This is provided that the signal level is sufficiently high to allow the signal to be limited.
Does not require linear amplifiers in the transmitter: As only frequency changes are required to be carried, any amplifiers in the transmitter do not need to be linear.
Enables greater efficiency than many other modes: The use of non-linear amplifiers, e.g. Class c, etc means that transmitter efficiency levels will be higher - linear amplifiers are inherently inefficient.
Disadvantages of frequency modulation
there are a number of dis-advantages to the use of frequency modulation. Some are can be overcome quite easily, but others may mean that another modulation format is more suitable.

Requires more complicated demodulator: One of the minor dis-advantages of frequency modulation is that the demodulator is a little more complicated, and hence slightly more expensive than the very simple diode detectors used for am. Also requiring a tuned circuit adds cost. However this is only an issue for the very low cost broadcast receiver market.
Some other modes have higher data spectral efficiency: Some phase modulation and quadrature amplitude modulation formats have a higher spectral efficiency for data transmission that frequency shift keying, a form of frequency modulation. As a result, most data transmission system use psk and qam.
Sidebands extend to infinity either side: The sidebands for an fm transmission theoretically extend out to infinity. To limit the bandwidth of the transmission, filters are used, and these introduce some distortion of the signal.
There are many advantages to using frequency modulation - it is still widely used for many broadcast and radio communications applications. However with more systems using digital formats, phase and quadrature amplitude modulation formats are on the increase. Nevertheless, the advantages of frequency modulation mean that it is an ideal format for many analogue applications.




اوان اكدولي الحل الصحيح وهدا اجتهاد مني وعدلولي لو انا غلطان لان انا هنا اساعدكم لان تخرجت من زمان عقبالكم

وهدي مصادري من الانترنت
اقرائوها

http://www.academia.edu/6378824/type...cation_systems

http://en.wikipedia.org/wiki/pulse-amplitude_modulation

http://www.radio-electronics.com/inf...m-tutorial.php

http://www.mathworks.com/help/comm/u...odulation.html

بورك فيك وجزاك الله كل خير

[violet flower 4]

هاد السؤال جا منه في ال T324 TMA Fall 2012 و هي مناقشته ,,, يارب تنفعني و ياكم

http://www.aoua.com/vb/showthread.php?t=332981

[renooo]

المشاركة الأصلية كتبت بواسطة violet flower 4

هاد السؤال جا منه في ال T324 TMA Fall 2012 و هي مناقشته ,,, يارب تنفعني و ياكم

http://www.aoua.com/vb/showthread.php?t=332981

[اتحرى]

المشاركة الأصلية كتبت بواسطة violet flower 4

هاد السؤال جا منه في ال T324 TMA Fall 2012 و هي مناقشته ,,, يارب تنفعني و ياكم

http://www.aoua.com/vb/showthread.php?t=332981

للاسف نبي السؤال الثالث والرابع

thanks