AWGN

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Noise Figure of cascaded stages

by Krishna Sankar on April 21, 2012

cascaded_noise_sources_noise_figure

Following the discussion on thermal noise and it’s modeling and noise figure computation for a simple resistor network, in this article let us discuss the Noise Figure of cascaded stages.

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Noise Figure of resistor network

by Krishna Sankar on April 13, 2012

thermal_noise_parallel_resistor

The post on thermal noise described the noise produced by resistor  ohms over bandwidth  at temperature Kelvin. In this post, let us define the noise voltage at the input and output of a resistor network and further use it to [...]

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Thermal Noise and AWGN

by Krishna Sankar on March 25, 2012

spectral_density_thermal_noise

A friend called me up couple of days back with the question – How white is AWGN? I gave him an answer over phone, which he was not too happy about. That got me thinking [...]

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Hamming (7,4) code with soft and hard decoding

by Krishna Sankar on March 15, 2012

ber_plot_hamming_7_4_code_soft_and_hard_decode_in_awgn

An earlier post we discussed hard decision decoding for a Hamming (7,4) code and simulated the the bit error rate. In this post, let us focus on the soft decision decoding for the Hamming (7,4) [...]

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Symbol Error rate for QAM (16, 64, 256,.., M-QAM)

by Krishna Sankar on January 1, 2012

plot_symbol_error_rate_16qam_64qam_256qam_ofdm_awgn

In May 2008, we derived the theoretical symbol error rate for a general M-QAM modulation (in  Embedded.com, DSPDesignLine.com and dsplog.com) under Additive White Gaussian Noise. While re-reading that post, felt that the article is nice and warrants a [...]

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Non coherent demodulation of pi/4 DQPSK (TETRA)

by Krishna Sankar on April 12, 2010

Constellation of pi/4 DQPSK specification

In TETRA specifications, one of the modulation technique used is Differential Quaternary Phase Shift Keying (DQPSK). We will discuss the bit error rate with non-coherent demodulation of DQPSK in Additive White Gaussian Noise (AWGN) channel.

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Hamming (7,4) code with hard decision decoding

by Krishna Sankar on September 29, 2009

BER plot for Hamming (7,4) code with hard decision decoding in AWGN

In previous posts, we have discussed convolutional codes with Viterbi decoding (hard decision, soft decision and with finite traceback). Let us know discuss a block coding scheme where a group of information bits is mapped [...]

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Viterbi with finite survivor state memory

by Krishna Sankar on July 27, 2009

BER_vs_traceback_viterbi_decode_ebno_4db

In the post on Viterbi decoder and soft input Viterbi decoder, we discussed a convolutional encoding scheme with rate 1/2, constraint length and having generator polynomial and having generator polynomial . If the number of [...]

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MSK transmitter and receiver

by Krishna Sankar on June 16, 2009

OQPSK and MSK transmit sequence

In a post on Minimum Shift Keying (MSK), we had discussed that MSK uses two frequencies which are separated by and phase discontinuity is avoided in symbol boundaries. In that post, we had discussed MSK [...]

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BER with Matched Filtering

by Krishna Sankar on May 8, 2009

Transmit spectrum for a rectangular matched filter

In the post on transmit pulse shaping filter, we had discussed pulse shaping using rectangular and sinc. In this post we will discuss about optimal receiver structure when pulse shaping is used at the transmitter. [...]

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Soft Input Viterbi decoder

by Krishna Sankar on January 14, 2009

BER plot for BPSK with AWGN in soft decision Viterbi decoding

In two previous posts, we have discussed Convolutional Coding and the associated hard decision Viterbi decoding. In this post lets extent Viterbi decoding algorithm to soft input decision scheme. The modulation used is BPSK and [...]

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Viterbi decoder

by Krishna Sankar on January 4, 2009

Branch Metric and Path Metric computation for Viterbi decoder

Coding is a technique where redundancy is added to original bit sequence to increase the reliability of the communication. Lets discuss a simple binary convolutional coding scheme at the transmitter and the associated Viterbi (maximum [...]

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Download free e-book on error probability in AWGN

by Krishna Sankar on October 1, 2008

We have quite a few articles discussing bit and symbol error rates for popular digital modulation schemes in Additive White Gaussian Noise (AWGN) channel. This post summarizes the articles discussing the theoretical and simulated error [...]

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Receive diversity in AWGN

by Krishna Sankar on August 19, 2008

BER BPSK AWGN Receive diversity

Some among you will be aware that in a wireless link having multiple antenna’s at the receiver (aka receive diversity) improves the bit error rate (BER) performance. In this post, let us try to understand [...]

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