EE 345S Real-Time Digital Signal Processing Lab Fall 2007

EE 345S Real-Time Digital Signal Processing Lab Fall 2007

EE 445S Real-Time Digital Signal Processing Lab Fall 2013 Lab 4 Generation of PN sequences Debarati Kundu and Andrew Mark Outline Pseudo Noise Sequences and Applications. Generation of Pseudo Noise Sequences. Scrambling and Descrambling. Autocorrolation Function. 2 Pseudo Noise Sequences

Special class of periodic sequence, composed of 1s and 0s, which looks like random noise But a PN sequence is deterministic Used widely in data scramblers, noise generators, calibration By convention, PN sequence is composed of chips, duration of which is much shorter than bit duration Hence, the bandwidth of PN sequence is much higher than that of the data 3 Spread Spectrum(SS) Communications and other PN sequence modulates the data, thus uses spreading the spectrum greatly. Due to this spreading, SS signals are hard to detect.

Only authorized receivers knowing the correct PN sequence can recover the SS signal from noise. More robust to jamming, interference, and multipath effects. Allows CDMA, where multiple users share the same frequency band, by appropriately choosing PN sequences having low cross correlation Enables precise timing measurement, and robust4 Simple Shift Register Generator An r-stage simple feedback shift register with one feedback tap Also

called Fibonacci implementation. Each stage stores one bit (0 or 1), called chirp. At each clock tick, contents at stage n shifts to the right to stage n+1. Additions are mod-2 additions (EX-OR) One or more intermediate stages are fed back in mod-2 addition, but final stage always fed back. 2 r 1 Proper selection ofN feedback taps yield maximal length PN sequences (m-sequences) of length 5

SSRG example y (n) y (n 1) y (n 2) y (n 3) y (n) y (n 1) y (n 3) mod 2 ([3,1]s)] n y(n) y(n-1) y(n-2) y(n-3) 0 1 1 0

0 1 1 1 1 0 2 0 1 1 1 3 1 0 1

1 4 0 1 0 1 5 0 0 1 0 6 1 0

0 1 7 1 1 0 0 6 PN Sequences for Data Long strings of 1s or 0s in the input sequence Scrambling must be randomized before transmission through a communication system. Otherwise, carrier recovery, equalization, and symbol clock tracking wont work properly.

Use a self-synchronizing data scrambler, where hk defines the scrambler connections. Modulo arithmetic! Descrambler To descramble the data, we invert the scrambling process. This is simply an FIR filter with m+1 taps that uses modulo arithmetic. Note that errors in y(n) caused by the channel will cause errors in the recovered sequence. Autocorrelation Function Let y(n) be a periodic sequence with period N. The transformed sequence is: 1,

y (n) 1, The periodic autocorrelation function is: 1 R ( n) N y (n) 1 y (n) 0 N1 y (k ) y (n k ) k 0 This sum is performed by normal addition. r N 2period 1 For maximal length sequences with 1 , for n not a multiple of N R( n) N

1 for n a multiple of N 9 An example: Waveform generated: Autocorrelation: 10 Skipped content Modular Shift Register Generator method for generating PN sequences Details on cross-correlation of PN sequences Please go through the book for the theory 11

Recently Viewed Presentations

  • Project Overview and Breakdown of Staging/Contracts

    Project Overview and Breakdown of Staging/Contracts

    Stage 4 Stage 4 includes the construction of the new Stearns Road corridor from McLean Boulevard to IL 25, including a new Stearns/IL 25 intersection, IL 25/Gilbert intersection, widening of IL 25 Bridge over Brewster Creek and the construction of...
  • www.franklinboe.org

    www.franklinboe.org

    The Fan . Fandom explains why people propose at sporting events or feature a themed wedding centered on their favorite sports team. The existence of fandom is what ultimately fuels today's non-stop, around the clock media coverage of celebrities and...
  • Cell Physiology Part 3  Membrane Transport 9-08-09 Agenda

    Cell Physiology Part 3 Membrane Transport 9-08-09 Agenda

    Cell Physiology Part 3 - Membrane Transport 9-08-09 Agenda Review Membrane Potentials Membrane Transport Passive Active Summary of Membrane Function Membrane Transport Key to maintaining homeostasis Homeostasis does not mean equilibrium!
  • Chapter Twenty-One Lecture One

    Chapter Twenty-One Lecture One

    Chapter 22 Lecture One of Two The Return of Odysseus ©2012 Pearson Education Inc. The Return of Odysseus More folktale patterns than the Iliad Ends happily, hence it was compared with comedy, not tragedy (as was the Iliad) ©2012 Pearson...
  • The origins of - ComancheISD

    The origins of - ComancheISD

    The Soviet Union wanted Germany to pay for war damages, but the U.S. and Britain did not. The U.S. and Britain wanted the Soviet Union to promise free elections in Poland, but Stalin hesitated. The U.S. wanted Stalin to declare...
  • Transfer Pricing Course - Universitas Indonesia

    Transfer Pricing Course - Universitas Indonesia

    Standar Akuntansi. Untuk keseragaman laporan keuangan, laporan keuangan yang relevan dan reliable (representational faitfullness) Memudahkan penyusun laporan keuangan karena ada pedoman baku sehingga meminimalkan bias dari penyusun
  • The Atom and the Periodic Table - Effingham County School ...

    The Atom and the Periodic Table - Effingham County School ...

    Bohr Models. A Bohr model of the atom is a simplistic representation using an element's symbol as the nucleus and circles to represent the energy levels in the atom. Dots are used to represent electrons in the energy levels. Remember,...
  • The Cavalier Cadet

    The Cavalier Cadet

    finished in 4th place, only two points from winning a medal. The Raider team competed in all five events, which included the Modified PT Test, One Mile Run, Commanders Event, 5K Run, and ... To kickoff the event, the Cavalier...