Search Results

For example, pilot sequence in LTE is 31-length Gold code which is reinitialized at the start of each OFDM symbol with a value that depends on cell id. …

For OFDM we select the known gold sequence as the preamble or pilots. We can correctly estimate the channel(10 to 20taps). … pilots, which is $n_p \Delta f$ Hz, must respect the Nyquist theorem: $$\frac{1}{n_p \Delta f} > \tau_m \iff \frac{N}{n_p} > N \Delta f \tau_m = B\tau_m=\frac{B}{B_c}$$ where $B\triangleq N \Delta f$ is OFDM …

The second inquality is what you have said, to avoid ISI between OFDM symbols and to convert linear convolution to circular convolution so that we can use single-tap equalizer. …

There are many intepretation of OFDM to answer your question. One way I find intuitive is looking at the resolution of (Discrete) Fourier Transform. …

The first h is not single-tap. Also, if txSig_cp is time domain signal, and if you want to emulate channel, the element-wise multiplication is simply wrong. The second h is single-tap and using conv() …

Your pilots are not pseudo-random. For example, try THEPILOTS = qammod(randi([0 3], N/4, 1), 4, 'UnitAveragePower', true); for i = 1 : iter bits = randi([0 3], N, 1); %generate binary bits …

With a sufficient cyclic prefix ("sufficient" means greater than delay spread, thus OFDM receiver captures all delayed versions of OFDM symbol, proof can be found at single-tap OFDM regardless subcarrier …

By using cyclic prefix and its associated demodulation techniques, LTE OFDM (nearly) eliminates the inter-symbol inteference (ISI). …

Just want to provide some details to complement Marcus's answer. (1) 5G NR does not avoid DC carrier, (2) it is possible to use it to modulate data (accepting degradation), and (3) 3GPP does not speci …

Assuming no timing/sampling error, the time domain samples of the m-th OFDM symbol (index from 0) are $$y[n] = x\left[m(N+N_p)+N_p+n\right] \exp\left(j2\pi \frac{\epsilon}{N} \big(m(N+N_p)+N_p+n\big) \ … Take the FFT of (1), the demoludated sample of the m-th OFDM symbol $Y_m[k]$ is \begin{align} Y_m[k]&=\exp\left(j2\pi \frac{\epsilon}{N} \big(m(N+N_p)+N_p\big) \right) \times\\ &\sum_{n=0}^{N-1} x\left …

As the comment of MBaz, If we start with the discrete-time OFDM symbol s[n], and increase the sampling rate (defined by the time interval between successive samples of s[n]), then the OFDM symbol … It is easier to think OFDM as FDM. …

You are mixing two things modulation and multiple access. SC-FDMA has been chosen because it is battery-friendly modulation. SC-FDMA is used in both FDD and TDD modes. There are several reasons why b …

And an antenna can transmit several subcarriers (OFDM). One can imagine that QAM symbols are modulated on a 3-dimensional grid frequency-space-time. …

In general, it means several waveforms will coexist in 5G ecosystem. In the context of LTE-based 5G (up to now), several subcarrier spacings (hence CP) coexist. The first and foremost motivation for …

As specified in documentation, using 'ParityCheckMatrix' you can configure the Parity Check Matrix (PCM) during the constructions of the encoder/decoder objects. The syntax is encoder = comm.LDPCEncod …