Resources for 128 QAM demodulator design

Hi...
I am designing a 128 Digital Demodulator onto xilinx FPGA.
I'm using Xilinx System generator and Simulink tools for this design.
I've seen the demo for 16-QAM demodulator Design using System Generator and Simulink.
If anyone has seen this demo, plz give me some suggestions for modifying this existing 16-QAM design to 128, since i'm very new to this Digital Demodulator design.


Or can anyone plz give some useful links for 128 QAM Demodulator.

Regards,
Renjith

qam demodulator

First you should look at the Comunication book by Prokias or others and understand how to modulate/demodulate the QAM signal. The principles of demodulater for 16 QAM and 128 QAM are the same. 128 QAM needs much high Eb/Nt.

128 qam constellation

Hi,
If you're just a beginner then you started with one of the most advanced projects you can imagine.
Also if you're now just at the level of "tweeking a reference design" then I should advise you to study a lot.
128QAM demodulation involves a lot of signal processing techniques like carrier synchronization, timing recovery, FIR pulse shaping, fractional interpolation, etc, etc.

Just changing a design which is suited for 16QAM to 128QAM might require some deep study in what to change in order to achieve the correct performance.
So there will be more to be done than just changing the demapping of the 128 QAM constellation.

Good luck!

qam demodulation

Hi: Im working on the same kind of project for MS investigation. The objective is a multimode platform for CDMA and OFDM based systems. Im also using Xilinx System Generator.

Even if it is a difficult project you can get started with the simple things. Try to make your own code on matlab to simulate a QPSK system under AWGN and ALWAYS compare with theory. Then try to model a Rayleigh channel. At this moment you asume that channel estimation and synchronization tasks are already performed.

Try other modulations like 16QAM, 64QAM and 8PSK. Understandin how many bits per symbol carry each modulation is crucial (specialy for information theoretic aspects like capacity).

When you get this done, you can try a simulink model. When you start with System Generator you will have to take care of a lot of things more. For example precission handling and rate handling through the chain. You can start with a simple modulator/demodulator forming both I/Q channels.

Rigth now Im having trouble demodulating the real signal (at IF=20MHz). At the transmitter I have a convolutionaly coded, 64 OFDM system with QPSK. The real signal should be the superposition of a sine and a cosine which I genarate with a DDS each carring the real and imaginary data. My problem is that when I multiply the received real signal with the DDS at the receiver (assuming synchronization) I only get one component back (the real). For the moment Im not using raised cosine filtering but by looking at the HW simulations I know that I need one. This is the other problem. Im having trouble to get the original signal with the same kind of filter (Im using root raised cosine).

Using the QAM demo in the Xilinx System Generator to get started may be difficult. It deals with equalizing and carrier recovery. And deals only with hardware at the receiver. The transmitter process is carried in software using simulink.

Mario

128 qam

hi,I haven't seen the demo for 16-QAM demodulator Design using System Generator and Simulink.but i think they will be helpful for me for my project, so can you please specify the link where I can get them.

Thank you.

128qam modulation and demodulation

hi saurabhmimani,

u just go to the help tab at simulink and choose xilinx system generator. then u will see the demos there.