OFDM stands for **o**rthogonal, **f**requency-**d**ivision **m**ultiplexing.

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What type of correlation is this equation?

In a book [1], gives an equation (equation 5.31 in the book) for estimating frequency offset in OFDM systems proposed by Classen. Here is the equation: $ \hat \epsilon_{acq} = \dfrac{1}{2\pi \cdot ...
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Image to Binary stream for OFDM with qpsk/qam modulation matlab

Im looking to covert a .png or .jpeg image into bitstream so that I can further use it as input bit stream for OFDM with QPSK/QAM modulation in Matlab. I would really appreciate the help on that. ...
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21 views

basic question about OFDM

I'm going to simulate OFDM system and reighley channel in MATLAB. I create array of 128 symbols (for example) and then get IFFT, add CP. passing through AWGN channel in easy, but in Reighley there is ...
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1answer
68 views

IFFT and OFDM upconversion

I am trying to understand some basic concepts with IFFT as represented here OFDM Modem page 50-53, and 108-114. Some basics that are represented - The base sampling rate is 8khz. The symbol period ...
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36 views

Underwater Acoustic OFDM [closed]

What are the steps involved in making an Underwater Acoustic receiver In matlab Using OFDM? I want to send a picture through an underwater tank and receive it at the other end, using OFDM. Can ...
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2answers
73 views

generating pilot sub-carriers in matlab

I wanted to simulate OFDM system in MATLAB. I'm using Fixed WiMAX OFDM parameters in my simulation, where the number of data sub-carriers are 192, number of Pilot sub-carriers are 8, number Null ...
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1answer
43 views

Using Pilot tones to estimate carrier frequency offset in ofdm

I have been studying carrier frequency offset estimation techniques in OFDM systems. I have understood several of them. when using Pilot tones, as stated in paper (1), the process involves two methods ...
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1answer
71 views

Oversampling in OFDM

Why do we need an oversampling in OFDM signal? and how to do it? If around half of the Sub-carriers are only used to send data, then do we need to perform oversampling to the signal? Is it necessary ...
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87 views

Carrier frequency offset (CFO) estimation based on Symbols

In (1), it's said that: If two identical training symbols are transmitted consecutively, the corresponding signals with CFO of $\epsilon$ are related with each other as follows: ...
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1answer
63 views

Choosing clock frequency and number of bits of an OFDM transceiver

I want to implement an OFDM transceiver chip and my question is how to choose the clock frequency of the IFFT block? The number of output bits of the IFFT block? Also, how has the clock frequency and ...
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2answers
223 views

Carrier frequency offset (CFO) estimation using cyclic prefix

I understand the cyclic prefix, but in (1) it's said that: "If we consider that the channel effect is minimal and can be neglected. then the phase difference of the CP and the OFDM symbol which the ...
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1answer
45 views

Software-based sound card OFDM

I'm trying to implement an sound card-based OFDM modem. A paper says: ...A serial to parallel converter is applied and the IFFT operation is performed on the parallel complex data. Say I have ...
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40 views

OFDM DA conversion problem

I'm working on a sound card based OFDM system and ran into some problems: How can I perform DAC on the real and imaginary parts of the IFFT? I think they are real numbers instead of 0 and 1. ...
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2answers
612 views

How to Show A OFDM Symbol's PSD in Matlab

I'm trying to suppress the sidelobe of OFDM but having troubles showing its spectrum in Matlab. After IFFT, I get a time-domain signal, but in which way I can get its spectrum(or PSD)? I want to ...
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50 views

Hilbert Transform Filter for OFDM Signals

I am trying to design a Hilbert Transform Filter for OFDM signals. The specifications for the ofdm system are as follow: ...
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2answers
464 views

Coherence bandwidth and coherence time in an OFDM system

While studying an OFDM system, I have encountered statements like coherence bandwidth is the reciprocal of delay spread and coherence time is the reciprocal of the Doppler spectrum. Can somebody help ...
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2answers
107 views

What's the rationale behind this pulse shaping function?

Section 13.2 of the HD Radio standard for AM defines a pulse shaping function that appears to be some strange variant on a raised cosine filter: More specifically, H(ξ) is a raised cosine filter ...
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30 views

3-user OFDM with beamforming [duplicate]

I have a scenario where 3 users are located within range of each other. Users 1 and 2 are communicating with each other, user 1 is the transmitter and user 2 is the receiver. These two users will ...
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1answer
129 views

OFDM with beamforming

I'm trying to compute the the interference that one OFDM user with beamforming causes to another user. The two systems are fully overlapped in frequency and time. I know how to generate an OFDM signal ...
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1answer
565 views

What does the one-tap equalizer used with OFDM accomplish?

I've read that OFDM normally uses a one-tap equalizer. It seems that a one-tap equalizer could only scale and delay a signal. Why is this useful? I thought multipath was handled through the ...
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2answers
272 views

what does the output of ifft in ofdm look like?

i have a problem in ofdm modulation .... there is a stream of bits that is converted from serial to parallel and is applied to an IFFT block. based on the definition of IFFT the output should be an ...
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1answer
223 views

OFDM training symbol format

For OFDM synchronisation, we are using two training symbols according to the Schmidl and Cox method of frequency synchronization and timing synchronization. The paper says: The first OFDM training ...
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2answers
719 views

Need for Oversampling in OFDM and symbol time determination

I am trying to implement OFDM on gnuradio. I have two questions. The sampling frequency which is slightly higher than available bandwidth satisfies Nyqvist criterion for complex baseband signals. ...
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211 views

Ricean Multipath channel model implementation

I'm trying to implement a multipath ricean channel model. I had found several resources but I'm kind of lost with too much information. What I have from now is the following step: ...
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1answer
205 views

Windowing a time domain OFDM signal

Windowing is a popular method of reducing the spectral sidelobes of OFDM. A popular window usually used for this purpose in the raised cosine (RC) window, because of its tapered and smooth edges. I ...
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3answers
170 views

OFDM coarse freq estimation

I am trying to read OFDM synchronization paper by Schmidl and Cox. The math is slightly overwhelming. What is the formula that they use in implementation that distinguishes between coarse estimation ...
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1answer
768 views

Determining sampling rate in OFDM demodulation

I have seen that in OFDM, the sampling rate is much lesser than twice the bandwidth of signal. why is it so? How is sampling rate calculated in OFDM? Does it depend on the modulation type used inside ...
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2answers
140 views

Fixed point channel model for OFDM system

I'm testing an OFDM system implemented in fixed point. The data format is Q11. My system work's fine but I need to test it under some channel for evaluation of the design before field testing. The ...
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1answer
718 views

Apply AWGN noise to QPSK-OFDM symbol

I'm working on an OFDM-QPSK based system and I'm having some trouble to match the BER of my system with the theoretical curve. My OFDM implementation fills all the subcarriers and have t_symbol s ...
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1answer
477 views

Spectrum of OFDM with raised cosine window

I'm having trouble implementing OFDM with a raised cosine (RC) window in Matlab. I know how to generate an OFDM signal and how to show its spectrum, I just don't know how to generate the window ...
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1answer
2k views

Why does OFDM use cyclic-prefix while QPSK uses root-raised cosine filters?

My understanding is that BPSK/QPSK/... are often implemented with root-raised cosine (RRC) filters to reduce ISI and bandwidth. OFDM can be understood to be BPSK/QPSK/... implemented on multiple ...
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4answers
2k views

How is symbol synchronization with OFDM done?

I'm trying to understand how symbol synchronization is done in OFDM using pilot tones, cyclic prefixes, or any other technique. I've read the following answers which provide some explanation, but I ...
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3answers
2k views

IFFT Concept in OFDM

can any one explain how actually IFFT generating sub carriers in OFDM.... when we are simulating OFDM transmitter in matlab, we are taking input data stream, encoding it and modulating the encoded ...
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1answer
702 views

OFDM transmitter data rate

i am simulating OFDM transmitter in matlab....As u all know OFDM consists of different sub systems such as FEC coding, Bit interlever , Modulator , IFFT block and Adding cyclic prefix.... i have ...
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1answer
468 views

Half Subcarrier spacing in LTE Uplink

First post here, trying to make it as good as possible. Do not know how to make the Python code look nice - any tips? :) Anywho - to the main problem: I am currently working on simulating the uplink ...
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2answers
1k views

what's the baseband FFT size of LTE?

In standard of 3GPP LTE physical layer(3GPP TS 36.211), the FFT size for baseband signal generation for both Dl and UL is 2048 and CP size is also determined. However there is a table in several ...
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2k views

How to demodulate an OFDM signal

I'm looking at decoding an OFDM signal which consists of 6 carriers (or tones) which are BPSK modulated and a pilot tone which aids tuning. This is the first time I have worked with OFDM so I need to ...