DPSK's relation with OFDM and Demodulation

Started by karthikbalaguru in comp.dsp11 years ago 2 replies

Hi, I understand that simplified equalization is one of the good reasons for going with OFDM. But, how do they manage it ? That is, The OFDM...

Hi, I understand that simplified equalization is one of the good reasons for going with OFDM. But, how do they manage it ? That is, The OFDM may be viewed as using many slowly-modulated narrowband signals rather than one rapidly-modulated wideband signal. So, The Differential modulation such as DPSK / DQPSK if applied to each sub-carrier, equalization can be completely omitted. ( Reason - ...


OFDM Block-type Pilot, channel estimation

Started by ezain in comp.dsp11 years ago 2 replies

Hi, I am working on channel estimation in OFDM systems, and have a question related to block-type pilot arrangement. Block-type pilot...

Hi, I am working on channel estimation in OFDM systems, and have a question related to block-type pilot arrangement. Block-type pilot arrangement is one where all subcarriers in an OFDM symbol carry pilots. Does this mean that this OFDM symbol contains no null subcarriers, even at DC? Or is it assumed that these 'pilot' carrying OFDM symbols contain some minimum number of null-subcarriers a...


ofdm preamble format used in 820.16

Started by premnerella in comp.dsp12 years ago 1 reply

can any one please tell me the format of ofdm preamble used in 802.16 ofdm system and also its generation

can any one please tell me the format of ofdm preamble used in 802.16 ofdm system and also its generation


Baseband OFDM matlab simulation question

Started by Dan Savio in comp.dsp13 years ago 3 replies

I am attempting to simulate a baseband OFDM communication system in MATLAB. I have the parallelized QAM symbols feeding into an IFFT, but this...

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 Quadrature signal, however this is not what I am trying to do. I am simulating OFDM in the base band, ...


Can LDPC and Bit-loaded OFDM be combined efficiently?

Started by Anonymous in comp.dsp10 years ago 5 replies

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 ...


BPSK + OFDM over a very wideband channel

Started by lsw00kor in comp.dsp13 years ago 1 reply

Hello, everyone. I would like to discuss OFDM's robustnesss againt freq-selective channel. 1) I'm using BPSK( for some reasons, even though...

Hello, everyone. I would like to discuss OFDM's robustnesss againt freq-selective channel. 1) I'm using BPSK( for some reasons, even though mostly we use QPSK, or QAM..) on a very very wide channel. 2) I didn't employ a channel equalizer at the frontend before fft. 3) I, as a reference, followed Richard Van Nee's 'OFDM for wireless multimedia communications' to set the parameters: [1] wor...


Q) MIMO-OFDM better than AWGN performance. Why..

Started by lsw00kor in comp.dsp12 years ago 1 reply

Hello. It's very shameful to ask this stupid question...but, if anyone woule help, can we have some discussion please? 1) I have a MIMO-OFDM...

Hello. It's very shameful to ask this stupid question...but, if anyone woule help, can we have some discussion please? 1) I have a MIMO-OFDM simulator. My problem is that, for example, if I use Alamouti's 2-by-2 diversity scheme, then my MIMO-OFDM curve in freq-selective channel works partially better than SISO QPSK curve in gaussian channel. The two curves also intersect. 2)It seems that t...


flexible OFDM modulator

Started by konstantinos in comp.dsp10 years ago 3 replies

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...


OFDM average power

Started by Snowball in comp.dsp13 years ago 11 replies

Hi, I understand the problem of high Peak to Average Power Ratio in OFDM. However, I am not sure how the average power of an OFDM signal...

Hi, I understand the problem of high Peak to Average Power Ratio in OFDM. However, I am not sure how the average power of an OFDM signal is calculated. Suppose you have an N-carrier transmitter where the average power per carrier is p, what would the average power of the OFDM signal be? Thanks.


OFDM simulation

Started by Lau in comp.dsp14 years ago 2 replies

Dear all, I am new to this group.I am bit confise about orthogonality in OFDM. I want to know what is orthogonal. Any help regarding this is...

Dear all, I am new to this group.I am bit confise about orthogonality in OFDM. I want to know what is orthogonal. Any help regarding this is greatly appreciate. Regards Lau


Sampling Time Difference in OFDM Demodulator

Started by insecuritate in comp.dsp12 years ago 5 replies

Dear all, in my diploma thesis i am realizing an ofdm modem. i am working with two adsp bf533 ez-kit-lites. one as transmitter and one as...

Dear all, in my diploma thesis i am realizing an ofdm modem. i am working with two adsp bf533 ez-kit-lites. one as transmitter and one as receiver. for d/a and a/d conversion i use the implemented audio codec. this works with nominally 48khz. and here is my problem. these 48khz are only a nominally value. the "real" values differ slightly. after receiving my ofdm signal and detecting the sta...


MIMO - OFDM

Started by Chambers in comp.dsp11 years ago

Hi guys, my question is: What is the minimum frame length for SF-OFDM schemes(2x1 or 4x1)??Any help is really appreciated. Thanks

Hi guys, my question is: What is the minimum frame length for SF-OFDM schemes(2x1 or 4x1)??Any help is really appreciated. Thanks


BER in OFDM

Started by Kumar Appaiah in comp.dsp12 years ago 2 replies

Dear comp.dsp, Though I did try looking at the previous posts related to this, my question has not been answered. So, here goes: I have a...

Dear comp.dsp, Though I did try looking at the previous posts related to this, my question has not been answered. So, here goes: I have a simple OFDM+QPSK code wherein I use one symbol to estimate the channel and do the zero forcing (multiply by reciprocal of channel FFT) to get derotated QPSK symbols. Note that the data is uncoded and not interleaved. 1. BER for QPSK+OFDM in an AWGN ...


Relationship (if any?) between OFDM receiver synchronisation and IF or baseband sampling rate

Started by Andrew FPGA in comp.dsp11 years ago 9 replies

Hi, I'm trying to understand how synchronision might work in an OFDM receiver with respect to the consequences it has for how the baseband or...

Hi, I'm trying to understand how synchronision might work in an OFDM receiver with respect to the consequences it has for how the baseband or IF signal is sampled. I have tried to read widely, but the IEEE literature around OFDM synchronisation never seems to mention the sample rate or the hardwarey aspects. Below is brief background to try and illustrate where I am coming from, followed by ...


OFDM

Started by sheen2411 in comp.dsp11 years ago

hi I really need some help to simulate an ofdm system. i need to show that graph of magnitude (amplitude) against frequency... Can somebody...

hi I really need some help to simulate an ofdm system. i need to show that graph of magnitude (amplitude) against frequency... Can somebody assist me in solving this problem. thanks all sheen


What is difference between OFDM and GFDM?

Started by Anonymous in comp.dsp4 years ago 3 replies

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...


Four antennas OFDM receiver. How sum "in phase"

Started by JAlbertoDJ in comp.dsp3 years ago 6 replies

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


Good intro books on OFDM?

Started by whatisofdm in comp.dsp13 years ago 5 replies

I'm a digital ASIC engineer looking for some *beginner* (not reference/advanced!) books on Orthogonal Frequency Division Multiplexing (OFDM.) ...

I'm a digital ASIC engineer looking for some *beginner* (not reference/advanced!) books on Orthogonal Frequency Division Multiplexing (OFDM.) Well, hopefully such a book exists? The book I already have "Multi-carrier Digital Communications: Theory and Applications of OFDM" (by Bahai, Saltzberg, and Ergen) seems a bit beyond me. It's a great reference for researchers, but as you've probab...


OFDM modulator

Started by marko1 in comp.dsp10 years ago 2 replies

Hi, I have problem concerning process of generating OFDM signal. From what I know, the real part of IFFT is sampled OFDM signal. So why after...

Hi, I have problem concerning process of generating OFDM signal. From what I know, the real part of IFFT is sampled OFDM signal. So why after IFFT block is IQ modulator that uses real and imaginalis part of IFFT? Why we do not take the real part of IFFT and then convert it to analog signal and then upconvert to the IF frequency? And what about real part of OFDM signal at the output of IQ modula...


I am new to OFDM, I need help.. Thanks...

Started by Halit in comp.dsp12 years ago

Recently, I am doing a project related to DAB receiver. And I knew very little about OFDM,and my question is very simple. In the DAB...

Recently, I am doing a project related to DAB receiver. And I knew very little about OFDM,and my question is very simple. In the DAB standard it said that there are some NULL symbols receiver can use to detect the begin of the OFDM Signal, after that there is the Phase reference symbol. I am wondering how can I get this phase reference symbol from the noise environment?