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16 QAM vs 16 PSK and 4QAM vs QPSK

Hello All, Just curious why in many standards, to achieve different rates, usually use QPSK and 16-QAM. Why can't we use 4-QAM instead of QPSK or 16-QPSK instead of 16 QAM? Thanks. Regards, Terry ...

VSB as QAM

Hi, I'm currently try to develop an 8-VSB demodulator (for ATSC terestrial digital TV). I saw that there is a simple way to covert to 8-VSB signal to 64-QAM (offset QAM, to be more precise). My question is: is demodulating QAM is more cost-efficient than woking directly on VSB signal? (by means o...

question about multistage decoding

Hi, I am working on a multistage channel decoding module for DRM system. I am confused about the QAM demapping. In case of 64 QAM, I begin with LSB ( with has highest protection) and get hard decodion. Then for the CSB, I got a shrinked 16 QAM. Then for MSB, 4 QAM. Now the second iteration begins. ...

QAM Example Programs?

Are there any good/simple QAM example programs online that I can look at and learn how to use QAM. Thanks, DspN00b. ...

Pilot Symbol Assisted QAM

Hi, How the pilot symbol assisted QAM works ? What are the symbol information sent on this Pilot ? It's in the same frequency band than the QAM modulation ? I think we send a BPSK pilot over the QAM modulation in time duplex ? Do you have good paper on that, I found nothing over googl...

BER for QAM

I have a system through which I send a QAM signal. After the system, I get a noisy version of the transmitted signal. I want to describe the system by its BER (or any conventional definitions related). I would like to use the definition of "Error Vector". I mean "complex transmitted QAM symbol -...

64 QAM

Hi, Anyone knows where to find Matlab source code to simulate 64 QAM modulation/demodulation. Regards, René ...

Capacity for QAM

Guys, I need a clarification on shannon capacity equation for QAM systems with coding. Lets assume M-QAM with code rate R Let m = log2(M) My goal is to find at what SNR (Eb/No) we achieve capacity with the shannon equation. C= Wlog2(1+SNR). I am a little confused. can someone ple...

pi/2 shift QPSK and QAM

Hello All, Can anybody tell me what would be the diffference in the constellation for pi/2-shift QPSK (not pi/4 QPSK). and normal QPSK. This is one of the modulation types proposed as part of the TG3c proposal(IEEE 802.15). There is also mention about pi/2 BPSK, pi/2 QAM etc. With regards ...

Re: QAM and Gardner synchronization

fpga.vhdl.designer@gmail.com wrote: > if gardner can't works for QAM what kind of symbol synchronisation > could we use for QAM ? Who said it can't work? As long as the excess bandwidth is more than something like 25%, it works quite well. Problems occur with narrowing bandwidth, so it ce...

QAM vs. APSK

I need a practical explanation as to why QAM (e.g. 16QAM) performs better than APSK (e.g. 16APSK) in a linear channel (AWGN). Thank you. ...

how to detect I and Q values from demodulators?

Basically I am a Computer Science student and I am new to electronics. As a part of my academic project,I am going to develop a tool that would analyse the signals from 64 QAM demodulator . The demodulator chip what I am dealing with has several registers related to BER,SNR,errored second(ES),se...

help with algorithm/schematic/Vhdl code for QAM

Hello Everyone, I am working on designing a digital modulator that will implement QAM on FPGA. The FPGA will be programmed in VHDL to modulate an input signal(maybefrom a function generator) A D/A converter will convert the digital signal to an analog one that canbe transmitted. Anyway,...

How do I evaluate the power spectra density of QAM signals?

My system comprises of a QAM mapping and up-sampling filter, now I need to evaluate the PSD of the I/Q data after up-sampling. How do I do that in Matlab? TIA. ...

QPSK or QAM on cable system

Please tell me which is a reliable modulation to use in CATV system, QPSK or QAM? What are the advantages and disadvantages. Please discuss it in a "lay man's term" and set some examples. Thank you and more power. ...

16-QPSK Vs 64 QAM

Hello All, As an additional question . I am just confused in terms of detecting errors , Can anyone please tell which modulation scheme 16-QPSK or 64 QAM would be easy to detect errors and where does the basic criteria lies. Thanks in Advance Syed ...

BPSK,QPSK,16-QAM constellation points

Hi everyone, I am trying to write a base band simulation of BPSK,QPSK and 16-QAM modulator(using only constellation points coordinates). I figured out from wikipedia.org and "Digital Modulation Technique" that constellation points will have following coordinates(in the complex plane): 1) (+-sqr...

16-QAM

Hi everyone, I have a question, A maximum transmission vector in 16-QAM constellation is 100 volts rms. I have to determine the long-term average power transmitted from a 50 ohm antenna if each point in the constellation is equally likely to be transmitted. Any ideas? Thank you ...

Re: Gray code for QAM

Krishna wrote: > Hi All, > > Can you please point me to reference(s) explaining the construction of > Binary to Gray code conversion > for a general QAM constellation. > > I just know that the QAM maybe treated as independent PAM links + some > added constraints to ensure > that ...

16-QAM modulation output values

Hi, In my 16-QAM constellation the symbol 0011 at located at I=1, Q=3. What binary or hex value do I output for 1 and 3 if I am using say 16 bit signed binary? Can I use say 7FFFh for 3 and e.g. 2AAAh for 1? Are standards available to show what values should be used? Many Thanks Bob ...

16-QAM modulation output values

Hi, In my 16-QAM constellation the symbol 0011 at located at I=1, Q=3. What binary or hex value do I output for 1 and 3 if I am using say 16 bit signed binary? Can I use say 7FFFh for 3 and e.g. 2AAAh for 1? Are standards available to show what values should be used? Many Thanks Bob ...

QAM; 1-amplitude, many phases, 1-baud, 1 gigabit-per-baud

Eric Jacobsen wrote in http://groups.google.com/group/comp.dsp/msg/dc369177d865440e : > On Sat, 17 May 2008 15:55:02 -0700, "Green Xenon [Radium]" > wrote: > > Let's say I am using QAM and want a baud-rate of only > > 1-symbol-per-second but I want there to be 1-billion-bits...

Using DSP to emulate g.DMT (g.992.1) in software. (Newbie question)

Hi all, For an amateur radio project I am looking at transmitting high-speed data over HF by using a technique similar to g.DMT in that it excludes busy channels to reduce interference to other users and ensure signal integrity. Like g.DMT I will be using QAM of varying word sizes depending...

Re: Coding/Modulation Question

On Aug 19, 7:47=A0pm, Randy Yates asked: > Does a modulation with q different symbol states absolutely require a > code over X^n, where X =3D {a_1, a_2, ..., a_q}? =A0Or can you use a > symbol set (X) with a different order (count)? This kind of stuff is routine. Consider, for example, ...

Re: BPSK demodulation with CORDIC

OK I see what you want to say... Because it's BPSK I only need the I (In-phase) signal. Compute the angle with CORDIC (from I signal) and send a new COS to multiply with the IF BPSK signal. In fact, I want to use a BPSK pilot to demodulate a QAM signal... So when I have my BPSK phase info...

How to get the average energy of QAM

Hi, For a M-ary QAM modulation, which has L (L is 2's power) amplitude levels {-L, -(L-1), ... -3, -1, 1, 3, ... L-3, L-1}. The average energy of equally distributed constellation symbols is: L/2 Eav=2[(2*E0/L) sum{(2*i-1)^2} = (2/3)*(L^2 - 1)* E0 ...

ldpc decoding with M-QAM channel symbols

With respect to the log likelihood decoding method for ldpc codes, how does it change when going from BPSK to M-QAM channel symbols? In particular, how does the check node update change? Thanks, Scott ...

Demodulator - Slicing by float to fixed conversion

Hello, I had a thread earlier about floating-point to fixed-point conversion for a confusion I had with the QAM demodulator code I have (SHARC dsp). This is my first time working with an demodulator assembly and it has really thrown me off. I am trying to figure out how the slicing is performed. ...

QAM of the most advanced dial-up modem

Hi: The most advanced dial-up modem [V.92] uses QAM [a mixture of amplitude and phase modulation]. Does this modem use more phases or more amplitudes to convey data? For the same amount of bits-per-baud, if you're using less amplitudes, you'll need more phases. Thanks, Radium ...

Re: Using to QAM to compress video/audio -- practical or not?

Green Xenon [Radium] wrote: > Hi: > > Is it rational to compress video/audio -- for storing in a device with > limited capacity or transferring on the internet via low-bandwidth > connection -- using QAM? > > Has this ever been done before? If so, what did the resulting artifacts ...

BPSK,QPSK,16-QAM constellation points

Hi everyone, I am trying to write a base band simulation of BPSK,QPSK and 16-QAM modulator(using only constellation points coordinates). I figured out from wikipedia.org and "Digital Modulation Technique" that for BPSK the points will have following coordinates(in the complex plane): (+-sqrt(E...

Re: Demodulator Timing Recovery Architecture Question

Hi, I know a scrambler is needed to timing recovery of QAM demodulator. If I want to realize a QAM demodulator software, that is, all is done by programming after A/D with fixed clock, how does a scrambler work? There is no training sequence available in multipoint broadcast system. If carrier ...

Another DMT Q: 180 degree phase reversals

Hi all, Ive come to another promblem with the project I'm doing on DSL. I can't seem to figure out if a 180 degree phase reversal (hardware inversion) will make the demodulation of the DMT signal impossible. As I see it there will be a problem with phaseshifts that holds the carrier wave...

QAM Modulator & Demodulator Design Using Matlab

HI All, I am working to design the QAM Modulator and Demodulator Using Matlab. But I dont know how to do. Can any one help me in this regard. Thanks............. ...

References of Decision Feedback Equalizers for QAM/QPSK systems

Hello all, Could anyone provide references (websites, books, articles) to Decision Feedback Equalizers for QAM/QPSK systems? Most of the information available is on baseband signals. I found several scientific articles in the WEB on this topics but they are very mathematical and complicated. ...

Baseband OFDM matlab simulation question

I am attempting to simulate a baseband OFDM communication system in MATLAB. I have the parallelized QAM symbols feeding into an IFFT, but this produces a vector of complex numbers. I found much information about taking the real and imaginary parts and modulating them with an In-phase and Quad...

QAM Shannon Limit?

Hi all, I am told that there are Shannon Limit (Eb/No) with every code-rate BPSK modulation. Are there Shannon Limit (Eb/No) with every code-rate QAM(like 16QAM and 64QAM) modulation? Any suggestions will be appreciated! Best regards, Davy ...

16 QAM using different coding scheme

I am trying to do some presentation comparison between Gray coded schemes in a 16 QAM and other kinds of arrangement . I can't find any other scheme apart from Gray codes which can be defined algorithmically. Which other coding schemes can I implement that has an algorithms Gray code algori...

Re: Variable data rate with fixed bandwidth

On Jun 18, 10:56=A0pm, Randy Yates wrote: > I should restate: > > =A0 =A0So, to remain in any specific bandwidth and transmit more > =A0 =A0bits/second at the same bit-error rate, you switch to a higher-ord= er > =A0 =A0QAM modulation and increase your Eb/No. Not quite. By switch...

Repetition Coding and Soft demodulation

Dear All, Okay, probably this sound a bit silly, but what happens when repetition coding is used and when soft demodulation is used ? Soft QAM demodulation produces Log Likelihood Ratio (LLR), and should I take average value of the repeated symbols ? Here's the simple view of the receiver ...