Dear all, I have a basic question regarding modeling of a multipath channel for OFDM in Matlab and would appreciate your help. My intention...

Dear all, I have a basic question regarding modeling of a multipath channel for OFDM in Matlab and would appreciate your help. My intention is to simulate an 802.11a transmission which uses OFDM. From the 802.11a standard I know that: -Number of Subcarriers, Nsc = 64 -Sampling Rate at the receiver, fs = 20e6 samples/sec -BW = 20Mhz -Carrier Frequency, fc = 5.25 Ghz Now consider that I...

hey all, I made an ofdm simulation in matlab, I want it to output Ber/EbNo plot, and I use the awgn function in order to add white noise in...

hey all, I made an ofdm simulation in matlab, I want it to output Ber/EbNo plot, and I use the awgn function in order to add white noise in the channel, and as u know the awgn function requires SNR as input, so I need to convert from Eb/No to SNR. I know this: Es/No(dB)=10log10(Tsymb*Fs)+SNR(dB) now I need to convert the Es/No of the ofdm signal to Eb/No: Es/No(dB)=Eb/No(dB)+10log10(...

Hello: I have a question regarding filtfilt function in Matlab. Due to forward and backward filtering, filtfilt function will have zero-phase...

Hello: I have a question regarding filtfilt function in Matlab. Due to forward and backward filtering, filtfilt function will have zero-phase response at any frequency. If I apply this filter to a time domain OFDM sequence, does that mean I can set the FFT start window the same as the transmitted IFFT starting point? In my test, I have an OFDM sequence of 5 symbols each with 80 samples at 20 M...

I am simulating an OFDM system and want to employ concatenated codes with different modulation schemes. I have a few queries about it. 1. RS code...

I am simulating an OFDM system and want to employ concatenated codes with different modulation schemes. I have a few queries about it. 1. RS code works on frame-by-frame basis like for a shortened code RS(32,24) on byte boundary. In this case, I need a minimum of 24*8 uncoded data bits. If i work on this boundary, the resulting symbols dont map completely to the OFDM symbol. How can i make it sat...

Hi, in 802.16e-2005, table 266 is Rx SNR for OFDM and table 338 is Rx SNR for OFDMA. I find that the Rx SNR is different for OFDM and OFDMA, why...

Hi, in 802.16e-2005, table 266 is Rx SNR for OFDM and table 338 is Rx SNR for OFDMA. I find that the Rx SNR is different for OFDM and OFDMA, why is that?

Hi guys I have a question about the use of LDPC codes and different bit- loadings which naturally occur as part of a large number of...

Hi guys I have a question about the use of LDPC codes and different bit- loadings which naturally occur as part of a large number of OFDM systems (802.16e, for example). I have seem a few methods in the literature for using LDPC with multi-level (e.g. BICM, MLC, etc.) but none of them seem to tackle the problem I'm interested in. Specifically, consider two of the sub-carriers in an OFDM ...

I recently started simulating a HiperMAN/WiMAX PHY on MATLAB. However, in the standard available in the ETSI website, there is mention of a...

I recently started simulating a HiperMAN/WiMAX PHY on MATLAB. However, in the standard available in the ETSI website, there is mention of a "sampling frequency" and a term "bandwidth over sampling frequency". I haven't a clue as to what these terms mean and where they're used in the OFDM process. Could somebody shed some light on what these terms mean in the context of OFDM? Thanks Neelabh...

Hi there, I have a question on OFDM. As we know, most OFDM systems nowadays do not use all the available tones (subcarriers) for data...

Hi there, I have a question on OFDM. As we know, most OFDM systems nowadays do not use all the available tones (subcarriers) for data modulation. Let us say we have 64 tones in total and we might end up with 48 data tones, 4 pilot tones, 3 DC tones and 9 null tones, which is kind of an typical setup. My question is regarding the null tones, which are usually placed on the two boundaries...

Hello, I m currently simulating a channel estimation based preamble in OFDM system. The ofdm signal is convolved with the channel taps which...

Hello, I m currently simulating a channel estimation based preamble in OFDM system. The ofdm signal is convolved with the channel taps which is in this case 3 taps. The technique is to correlate the received preamble with its local copy in time domain before FFT. This kind of correlation should give an impulse as the result and in this matter, these impulses should be the channel taps. But th...

Hi all!! I'm a student and for my thesis I have to implement a flexible OFDM modulator in VHDL. That means that it has to be applicable in...

Hi all!! I'm a student and for my thesis I have to implement a flexible OFDM modulator in VHDL. That means that it has to be applicable in more than one systems. For example DVB and WiMAX. The elements to implement are the Mapper the OFDM and the Guard Interval Insertion. As you understand the mapper part should support all the possible constellations given from those two standards and th...

Hi, I am actually new in sparse signal processing and first trying to get the basics of the sparse signals. In OFDM systems the sparse channel...

Hi, I am actually new in sparse signal processing and first trying to get the basics of the sparse signals. In OFDM systems the sparse channel is estimated by using some sparse signal processing algorithms such as compressive sensing. Could anyone please explain me how to model the sparse channel/sparse signal in OFDM systems? What is the logic behind the sparse representation? Thanks i...

Hi All,, Plz help me for ofdm simulation. I have tried to simulate ofdm signal with 64 subcarriers, with an oversampling of factor 4 in...

Hi All,, Plz help me for ofdm simulation. I have tried to simulate ofdm signal with 64 subcarriers, with an oversampling of factor 4 in frequency domain. Now I've got 256 QPSK symbols with zero paddings.I'm doing IFFT of 256 points. But I need to modulate my data on 64 subcarriers. then how would it be possible if i'm doing IFFT/FFT of 256 points. plz clarify me this thing, if i have zeronpadde...

Hi, I have a question on IFFT input in OFDM systems. Why center tone is always set to ZERO for IFFT input ? is it one method to reduce...

Hi, I have a question on IFFT input in OFDM systems. Why center tone is always set to ZERO for IFFT input ? is it one method to reduce PAPR in OFDM systems ? _____________________________ Posted through www.DSPRelated.com

why center tone is null in input of IFFT in OFDM systems ? is it for reducing PAPR ...? or to reduce complexity in OFDM receiver ? ...

why center tone is null in input of IFFT in OFDM systems ? is it for reducing PAPR ...? or to reduce complexity in OFDM receiver ? _____________________________ Posted through www.DSPRelated.com

Hi, I am trying to understand the difference(s) between OFDM and GFDM which are used as a multicarrier modulation techniques in wireless...

Hi, I am trying to understand the difference(s) between OFDM and GFDM which are used as a multicarrier modulation techniques in wireless communication. As far as I know the OFDM uses the orthogonal subcarriers and the GFDM is with the non-orthogonal subcarriers when designing a transmitter. Could anyone please explain further about their design and differences? What is the purpose of using...

Hello, In an OFDM system, by using N subcarriers we get one OFDM symbol. But before that the data is first mapped into frequency domain by...

Hello, In an OFDM system, by using N subcarriers we get one OFDM symbol. But before that the data is first mapped into frequency domain by the constellation mapper and we get N-parallel streams as an input to the IFFT process. The IFFT takes these N-parallel streams and produces N-parallel subcarriers in time domain, all these subcarriers are in digital form and has different frequencies. Let?...

Hello, In LTE specification, OFDM is implemented using FFT of sizes 128/256/512/1024/1536/2048. These correspond to Downlink bandwidth...

Hello, In LTE specification, OFDM is implemented using FFT of sizes 128/256/512/1024/1536/2048. These correspond to Downlink bandwidth of 1.4/3/5/10/15/20 MHz. I don't know how these N point FFT are selected for OFDM implementation. Let us take 1.4 MHz and 128 point FFT for example. 128 point FFT has N value of (2^N = 128) of 7. With a sub-carrier spacing of 15 KHz, this covers = 7*15 KH...

I have been given a OFDM signal of crest factor of 12dB. The crest factor is the ratio of peak power to the average power of the signal. Does...

I have been given a OFDM signal of crest factor of 12dB. The crest factor is the ratio of peak power to the average power of the signal. Does anyone have any idea how crest factor of 12dB is derived for an OFDM signal?(assumptions on peak power,average or RMS power etc). I would highly appreciate any input on this. --------------------------------------- Posted through http://www.DSPRelated.co...

I have been wondering if OFDM based system use PLL or DLL as in single carrier system e.g. GSM to do synchronization at all? Currently, a lot of...

I have been wondering if OFDM based system use PLL or DLL as in single carrier system e.g. GSM to do synchronization at all? Currently, a lot of ofdm based systems talk about implementing the frequency offset and time offset compensation in the digital domain. Do they also implement the time and frequency synchronization in hardware?

Hi guys, I have an OFDM signal (with DBPSK) received using four differents antennas (four unknown delays then). how i can sum the four...

Hi guys, I have an OFDM signal (with DBPSK) received using four differents antennas (four unknown delays then). how i can sum the four OFDM signals "in phase"? in others words, how i can estimate the phase compensation in each "bin" for each signal delayed? many thanks --------------------------------------- Posted through http://www.DSPRelated.com