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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 ...

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...

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. ...

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: 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...

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 ...

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 ...

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 ...

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 ...

SNR Gap for uncoded QAM

I have been reading about multi-carrier comms systems, and came across Cioffi's formulation of the SNR gap (e.g. in "A Multicarrier Primer"), gamma, which is essentially a measure of how much worse a practical system is compared to theory. It seems many others use the SNR gap in the same way,...

Re: Help regarding identification of modulation(GMSK) type of a signal

"ravi" wrote in message news:1138641487.576500.309770@z14g2000cwz.googlegroups.com... > need help regarding how to identofy that signal is GMSK modulated > ..plzz give advise in this regard.. > regards, > ...

QAM Flat Rayleigh Fading

Hello, I am trying to simulate QAM Flat Rayleigh Fading, but I keep getting 50% for BER with increasing SNR. I use qammod to encode the bits to QAM and deqammod to decode. I have the transmitted vector go through the Rayleigh channel by this: ry=h.*ty where ry is the received vector, ...

Modulation scheme with multiple phases and a two amplitudes?

Hi: QAM uses two carrier waves that are 90-degrees out of phases with each each and amplitude-modulates them. QAM only has two phases but can have more than two amplitude levels. Is there any modulation scheme that does the opposite -- i.e. the two carrier waves have only two amplitudes but...

Gardner/Mueller Symbol Recovery for QAM

I've been reading about symbol recovery loops using the Gardner and Mueller algorithms. All of the examples I have read seem clear, but the examples all use QPSK or BPSK. Also, I notice that Gardner's paper (which I haven't read) is titled "A BPSK/QPSK Timing Error Detector for Sampled Receiver...

BER in TCM

Hi all, Theory says that BER of a TCM for the same Eb/No is always lesser than the non-coded QAM (it is said that we can get up to some dBs called the assymptotically coding gain) I've designed a TCM simulation and I notice that for high SNR, 128TCM is better than 64QAM as expected. However...

Re: 16-PAM Demodulation and Viterbi

> Hi, > If I have a 16-QAM demodulator I know I can use the I and Q values to > access a lookup table and output soft codes for a Viterbi uisng LLR > > What do I do if I'm using 16-PAM? If my information is right its just > amplitude modulation. So out of the demodulator I will get 1 of 16 val...

QAM, PAM--Hardware Efficient reciever

Hi, Currently I am working on radio reciever architectures running QAM and PAM modulation schemes. Although lot of stuff is available describing theoratical working principles of these recievers, but I can not find any helpful material from Hardware implementation perspective. I am working on V...

Mimo model using Simulink

hi, I am trying to develope a MIMO model using Simulink, the modulation used is QAM . Can somebody tell me the different blocks which i should add in order to first make a simple SISO using QAM and get the BER for it. I knew about the simulink but i want to know the blocks which i should add...

Convolutional Soft-decision decoding for M>4 modulation schemes

Hello For higher order PSK/QAM (M-ary> 4), how does one convert the soft symbol decisions into bit metrics which can be passed into a soft decision decoder. To give an example, 256 QAM employs 8 bits per symbol, so the individual soft decisions coming out of the demodulator cannot be passed ...

QAM demapping to LDPC decoder

Hi all, LDPC decoder use soft information. But how to get the soft information from QAM? BTW, DVB-S2 use ASK demapping, is it suitable for soft information demapping? Best regards, Davy ...

Modem datatapping/sniffing

Can anyone help me in the way of datatapping/sniffing a dial-up modem connection by only access to the complex signals carries in the 2-wire link(listening to the voice)? For this purpose it should be to separate the incoming and outgoing signals in full-duplex mode, then demodulating them accordin...