1 COPYRIGHT 2 3 This package is copyright 2006 by Phil Karn, KA9Q. It may be used 4 under the terms of the GNU Lesser General Public License (LGPL). See 5 the file "lesser.txt" in this package for license details. 6 7 INTRODUCTION 8 9 This package provides a set of functions that implement several 10 popular forward error correction (FEC) algorithms and several low-level routines 11 useful in modems implemented with digital signal processing (DSP). 12 13 The following routines are provided: 14 15 1. Viterbi decoders for the following convolutional codes: 16 17 r=1/2 k=7 ("Voyager" code, now a widely used industry standard) 18 r=1/2 k=9 (Used on the IS-95 CDMA forward link) 19 r=1/6 k=15 ("Cassini" code, used by several NASA/JPL deep space missions) 20 21 2. Reed-Solomon encoders and decoders for any user-specified code. 22 23 3. Optimized encoder and decoder for the CCSDS-standard (255,223) 24 Reed-Solomon code, with and without the CCSDS-standard "dual basis" 25 symbol representation. 26 27 4. Compute dot product between a 16-bit buffer and a set of 16-bit 28 coefficients. This is the basic DSP primitive for digital filtering 29 and correlation. 30 31 4. Compute sum of squares of a buffer of 16-bit signed integers. This is 32 useful in DSP for finding the total energy in a signal. 33 34 5. Find peak value in a buffer of 16-bit signed integers, useful for 35 scaling a signal to prevent overflow. 36 37 SIMD SUPPORT 38 39 This package automatically makes use of various SIMD (Single 40 Instruction stream, Multiple Data stream) instruction sets, when 41 available: MMX, SSE and SSE2 on the IA-32 (Intel) architecture, and 42 Altivec on the PowerPC G4 and G5 used by Power Macintoshes. 43 44 "Altivec" is a Motorola trademark; Apple calls it "Velocity Engine", 45 and IBM calls it "VMX". Altivec is roughly comparable to SSE2 on the 46 IA-32. 47 48 Many of the SIMD versions run more than an order of 49 magnitude faster than their portable C versions. The available SIMD 50 instruction sets, if any, are determined at run time and the proper 51 version of each routine is automatically selected. If no SIMD 52 instructions are available, the portable C version is invoked by 53 default. On targets other than IA-32 and PPC, only the portable C 54 version is built. 55 56 The SIMD-assisted versions generally produce the same results as the C 57 versions, with a few minor exceptions. The Viterbi decoders in C have 58 a very slightly greater Eb/No performance due to their use of 32-bit 59 path metrics. On the other hand, the SIMD versions use the 60 "saturating" arithmetic available in these instructions to avoid the 61 integer wraparounds that can occur in C when argument ranges are not 62 properly constrained. This applies primarily to the "dotprod" (dot 63 product) function. 64 65 The MMX (MultiMedia eXtensions) instruction set was introduced on 66 later Pentium CPUs; it is also implemented on the Pentium II and most 67 AMD CPUs starting with the K6. SSE (SIMD Streaming Extensions) was 68 introduced in the Pentium III; AMD calls it "3D Now! Professional". 69 Intel introduced SSE2 on the Pentium 4, and it has been picked up by 70 later AMD CPUs. SSE support implies MMX support, while SSE2 support 71 implies both SSE and MMX support. 72 73 The latest IA-32 SIMD instruction set, SSE3 (also known as "Prescott 74 New Instructions") was introduced in early 2004 with the latest 75 ("Prescott") revision of the Pentium 4. Relatively little was 76 introduced with SSE3, and this library currently makes no use of it. 77 78 See the various manual pages for details on how to use the library 79 routines. 80 81 Copyright 2006, Phil Karn, KA9Q 82 karn (a] ka9q.net 83 http://www.ka9q.net/ 84 85 This software may be used under the terms of the GNU Lesser General 86 Public License (LGPL); see the file lesser.txt for details. 87 88 Revision history: 89 Version 1.0 released 29 May 2001 90 91 Version 2.0 released 3 Dec 2001: 92 Restructured to add support for shared libraries. 93 94 Version 2.0.1 released 8 Dec 2001: 95 Includes autoconf/configure script 96 97 Version 2.0.2 released 4 Feb 2002: 98 Add SIMD version override options 99 Test for lack of SSE2 mnemonic support in 'as' 100 Build only selected version 101 102 Version 2.0.3 released 6 Feb 2002: 103 Fix to parityb function in parity.h 104 105 feclib version 1.0 released November 2003 106 Merged SIMD-Viterbi, RS and DSP libraries 107 Changed SIMD Viterbi decoder to detect SSE2/SSE/MMX at runtime rather than build time 108 109 feclib version 2.0 (unreleased) Mar 2004 110 General speedups and cleanups 111 Switch from 4 to 8-bit input symbols on all Viterbi decoders 112 Support for Altivec on PowerPC 113 Support for k=15 r=1/6 Cassini/Mars Pathfinder/Mars Exploration Rover/STEREO code 114 Changed license to GNU Lesser General Public License (LGPL) 115 116 feclib version 2.1 June 5 2006 117 Added error checking, fixed alignment bug in SSE2 versions of Viterbi decoders causing segfaults 118 119 feclib version 2.1.1 June 6 2006 120 Fix test/benchmark time measurement on Linux 121
