References & FAQs

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0><script> (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o), m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m) })(window,document,'script','//www.google-analytics.com/analytics.js','ga'); ga('create', 'UA-47423994-1', 'fortunecity.ws'); ga('send', 'pageview'); </script> <center> <br> <div> <script language="javascript" type="text/javascript" src="http://ad.broadcaststation.net/ads/show_ad.php?width=728&height=90"></script> </div> </center> <table cellpadding=0 cellspacing=0 border=0 height="100%"><tr> <td valign="top" width=190 BGCOLOR="#339900" TEXT="#080000"> <div> <A HREF="id19.htm" TARGET="_top" TITLE="References FAQs"><U><B><IMG SRC="0c982550.jpg" border=0 width="130" height="85" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></U></A></div> <div> <A HREF="id24.htm" TARGET="_top" TITLE="Wideband CDMA "><U><B>back to Wideband CDMA</B></U></A></div> <bR> <div> <A HREF="id56.htm" TARGET="_top" TITLE="Mobile Communications Terms"><U>Mobile Communications Ter</U></A><A HREF="id56.htm" TARGET="_top" TITLE="Mobile Communications Terms"><U>ms</U></A></div> <div> <A HREF="id54.htm" TARGET="_top" TITLE="Abbreviations of the WORLD of Communicat"><U><B>Abbreviations of the</B></U></A><B> </B><A HREF="id54.htm" TARGET="_top" TITLE="Abbreviations of the WORLD of Communicat"><U><B>WORLD of Communications</B></U></A></div> <div> <A HREF="id57.htm" TARGET="_top" TITLE="Wireless Terms"><U>Wireless Terms</U></A></div> <div> <A HREF="id68.htm" TARGET="_top" TITLE="Tables of References"><U>Tables of References</U></A></div> <div> <B><U>___________________</U></B></div> <div> <B><U>Fast clicks to know terms.</U></B></div> <div> <A HREF="id19_m.htm#automatic_request_for_repeat__an_error" TARGET="TRLX_Middle" TITLE="References FAQs"><U>Automatic request for repeat</U></A></div> <div> <A HREF="id19_m.htm#channel_codingforward_error" TARGET="TRLX_Middle" TITLE="References FAQs"><U>Channel coding/Forward error correction</U></A></div> <div> <A HREF="id19_m.htm#fading__fluctuation_in_the_signal" TARGET="TRLX_Middle" TITLE="References FAQs"><U>Fading</U></A></div> <div> <A HREF="id19_m.htm#frequency_hopping__a_technique_where" TARGET="TRLX_Middle" TITLE="References FAQs"><U>Frequency hopping</U></A></div> <div> <A HREF="id19_m.htm#interleaving__a_form_of_data" TARGET="TRLX_Middle" TITLE="References FAQs"><U>Interleaving</U></A></div> <div> <A HREF="id19_m.htm#outrage_probability__" TARGET="TRLX_Middle" TITLE="References FAQs"><U>Outrage probability</U></A></div> <div> <A HREF="id19_m.htm#rake_receiver__" TARGET="TRLX_Middle" TITLE="References FAQs"><U>RAKE receiver</U></A></div> <div> <A HREF="id19_m.htm#why_use_turbo_codes__" TARGET="TRLX_Middle" TITLE="References FAQs"><U>Turbo Codes</U></A></div> <div> <A HREF="id19_m.htm#supported_primary_modem_standards" TARGET="TRLX_Middle" TITLE="References FAQs"><U>Supported Primary Modem Standards</U></A></div> <bR> <bR> </td> <td valign="top" BGCOLOR="#FFFFFF" TEXT="#080000"> <bR> <div> <FONT SIZE="5" COLOR="#003333" FACE="Arial" ><IMG SRC="13b6d2b0.gif" border=0 width="365" height="43" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></FONT>   |    <B> </B><A HREF="index.htm" TARGET="_top" TITLE="Lemonrain_First_Page"><U><B>home</B></U></A></div> <div> <A HREF="id87.htm" TARGET="_top" TITLE="3GPP"><U><B>3GPP</B></U></A><B>   |   </B><A HREF="id51.htm" TARGET="_top" TITLE="3G Market Overview and Technology Basics"><U><B>3G Market Overview and Technology Basics</B></U></A><B>   |   </B><A HREF="id18.htm" TARGET="_top" TITLE="Heritage"><U><B>Heritage</B></U></A><B>   |   </B><B>References & FAQs</B><B>   |   </B><A HREF="id50.htm" TARGET="_top" TITLE="QUALCOMM Developments on MSM"><U><B>QUALCOMM Developments on MSM</B></U></A><B>   |   </B><A HREF="id21.htm" TARGET="_top" TITLE="Useful Links"><U><B>Useful 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<tD VALIGN=TOP HEIGHT= 208 ><NOBR><div> <A HREF="#what_is_cdma__" TITLE="References FAQs"><U><B><IMG BORDER="0" SRC="Wing0a7300a800c899003300.gif" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">What is CDMA ?</B></U></A></div> <div> <A HREF="#what_are_the_diversities_in_cdma_" TITLE="References FAQs"><U><B><IMG BORDER="0" SRC="Wing0a7300a800c899003300.gif" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">What are the diversities in CDMA?</B></U></A></div> <div> <A HREF="#what_is_3g__" TITLE="References FAQs"><U><B><IMG BORDER="0" SRC="Wing0a7300a800c899003300.gif" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">What is 3G?</B></U></A></div> <div> <A HREF="#what_is_space_to_frequency__" TITLE="References FAQs"><U><B><IMG BORDER="0" SRC="Wing0a7300a800c899003300.gif" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">What is Space to Frequency ?</B></U></A></div> <div> <A HREF="#what_is_space_to_time__" TITLE="References FAQs"><U><B><IMG BORDER="0" SRC="Wing0a7300a800c899003300.gif" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">What is Space to Time ?</B></U></A></div> <div> <A HREF="#defining_terms" TITLE="References FAQs"><U><B><IMG BORDER="0" SRC="Wing0a7300a800c899003300.gif" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Defining Terms</B></U></A></div> <div> <A HREF="id24.htm#wideband___wide_relative_to_what__" TARGET="_top" TITLE="Wideband CDMA "><U><B><IMG BORDER="0" SRC="Wing0a7300a800c899003300.gif" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Wideband - Wide relative to WHAT ?</B></U></A></div> <div> <A HREF="#what_are_pseudorandom_noise__pn_codes_" TITLE="References FAQs"><U><B><IMG BORDER="0" SRC="Wing0a7300a800c899003300.gif" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">What are Pseudorandom Noise (PN)codes?</B></U></A></div> <div> <A HREF="#why_use_reed_solomon_codes" TITLE="References FAQs"><U><B><IMG BORDER="0" SRC="Wing0a7300a800c899003300.gif" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Why use Reed-Solomon codes ?</B></U></A></div> <div> <A HREF="#why_use_turbo_codes__" TITLE="References FAQs"><U><B><IMG BORDER="0" SRC="Wing0a7300a800c899003300.gif" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Why use Turbo Coding ?</B></U></A></div> <div> <A HREF="#what_is_rayleigh_fading__" TITLE="References FAQs"><U><B><IMG BORDER="0" SRC="Wing0a7300a800c899003300.gif" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">What is Rayleigh fading ?</B></U></A></div> <div> <A HREF="#what_is_spreading_factor__sf___" TITLE="References FAQs"><U><B><IMG BORDER="0" SRC="Wing0a7300a800c899003300.gif" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">What is Spreading Factor (SF) ?</B></U></A></div> <bR> </NOBR></tD> <tD VALIGN=TOP WIDTH="99"><div> <IMG SRC="09b465f0.gif" border=0 width="70" height="95" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><A HREF="http://www.google.com/" TARGET="_top" TITLE="http://www.google.com"><U><IMG SRC="2e340190.gif" border=0 width="64" height="25" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> </tD> <tD VALIGN=TOP><NOBR><bR> <div>  <CENTER> <FORM action="http://www.bravenet.com/metasearch/search.php" method="post"> <INPUT type="hidden" name="usernum" value="1151322712"> <TABLE border="1" cellspacing="0" bgcolor="cornsilk"><TR><TD> <TABLE border="0" cellpadding="5" cellspacing="0" bgcolor="cornsilk"> <TR><TD align="center"><B>Internet Super Search</B></TD></TR> <TR><TD><INPUT type="text" size="15" name="query"> <FONT face="Arial, Helvetica" size="2"><B><INPUT type="submit" value=" Find It! "></B></FONT></TD></TR> <TR><TD align="center"><A href="http://www.bravenet.com/" target="_top"></A></TD></TR></TABLE></TD></TR></TABLE> </FORM></CENTER>  </div> <bR> <bR> <bR> <bR> <bR> </NOBR></tD> </tR> </TABLE></B></div> <div> <U> <A NAME="what_is_cdma__"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></U></div> <div> <TABLE BORDER="0" CELLPADDING="0" CELLSPACING="1" WIDTH="794" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP BGCOLOR=#330099 HEIGHT= 15 WIDTH="792"><div> <B>  What is CDMA ?</B></div> </tD> </tR> </TABLE></div> <div> A coding scheme, used as a modulation technique, in which multiple channels are independently coded for transmission over a single wideband channel.  In some communication systems, CDMA is used as an access method that permits carriers from different stations to use the same transmission equipment by using a wider bandwidth than the individual carriers.  On reception, each carrier can be distinguish from the others by means of a specific modulation code, thereby allowing for the reception of signals that were originally overlapping in frequency and time.  Thus, several transmissions can occur simultaneously within the same bandwidth, with the mutual interference reduced by the degree of orthogonality of the unique codes used in each transmission.</div> <div> CDMA permits a more uniform distribution of energy in the emitted bandwidth.</div> <div> <B> <A NAME="what_are_the_diversities_in_cdma_"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B></div> <div> <TABLE BORDER="0" CELLPADDING="0" CELLSPACING="1" WIDTH="794" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP BGCOLOR=#330099 HEIGHT= 15 WIDTH="792"><div> <B>  What are the diversities in CDMA?</B></div> </tD> </tR> </TABLE></div> <div> Frequency Diversity (Spread Spectrum)</div> <div> Time Diversity (Symbol interleaving and coding, rake receiver)</div> <div> Cell Diversity (Soft Handover)</div> <div> Channel Diversity (QPSK modulation)</div> <div> Spatial Diversity (Two receiving antennas at the BTS (Base-station Transceiver Subsystem) to combat fading)</div> <div> Selective Diversity (Best of two signals are chosen at the selector card in BSC (Base Station Controller))</div> <div> <U> <A NAME="what_is_3g__"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></U></div> <div> <TABLE BORDER="0" CELLPADDING="0" CELLSPACING="1" WIDTH="794" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP BGCOLOR=#330099 HEIGHT= 15 WIDTH="792"><div> <B>  What is 3G ?</B></div> </tD> </tR> </TABLE></div> <div> What is 3rd Generation (3G) ? - Is it the same as UMTS and IMT-2000, or are they different in some way?</div> <bR> <div> 3rd Generation is the generic term used for the next generation of mobile communications systems. 3G systems will provide enhanced services to those - such as voice, text and data - predominantly available today.</div> <bR> <div> UMTS is a part of the International Telecommunications Union's (ITU's) 'IMT-2000' vision of a global family of third-generation mobile communications systems.</div> <bR> <div> The  technology concepts for 3rd Generation systems and services are currently under development</div> <div> industry wide. The global 3G Partnership Project (3GPP), a collaboration of organisations which includes</div> <div>  the GSM Association, are committed to bringing us the 3rd Generation mobile systems.</div> <bR> <div> The GSM Association's vision of 3G is based on today's GSM standard, but evolved, extended and enhanced to include an additional radio air interface, better suited for high speed and multimedia data services. This system will enable users of current 2nd Generation GSM wireless networks to migrate easily to the new 3rd Generation services, with minimal disruption. This new evolved phase of GSM will in addition be an important and integral part of the ITU's IMT-2000 family. This definition is complied by gsmworld.  Lemonrain are pleased to acknowledge gsmworld for this piece of information.   </div> <div>  <A NAME="what_is_space_to_frequency__"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <TABLE BORDER="0" CELLPADDING="0" CELLSPACING="1" WIDTH="794" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP BGCOLOR=#330099 HEIGHT= 15 WIDTH="792"><div> <B>  What is Space to Frequency ?</B></div> </tD> </tR> </TABLE></div> <div> <I><IMG BORDER="0" SRC="Symb075c00b700a000000000.gif" HEIGHT="11" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Antenna-delay.</I>  In this example, the signal is transmitted from two or more antennas with delays of the order of a chip or symbol period in CDMA or TDMA, respectively.  The different transmissions simulate resolved path arrivals that can be used as diversity branches by the RAKE or MLSE equalizer.</div> <div> <I><IMG BORDER="0" SRC="Symb075c00b700a000000000.gif" HEIGHT="11" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Multicarrier modulation</I>.  The data stream after interleaving and coding is modulated as a multicarrier output using an inverse DFT.  The carriers are then mapped to the different antennas.  The space selective fading at the antennas is now transformed to frequency selective fading and diversity is obtained during decoding.</div> <div>  <A NAME="what_is_space_to_time__"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <TABLE BORDER="0" CELLPADDING="0" CELLSPACING="1" WIDTH="794" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP BGCOLOR=#330099 HEIGHT= 16 WIDTH="792"><div> <B>  What is Space to Time ? </B></div> </tD> </tR> </TABLE></div> <div> <I><IMG BORDER="0" SRC="Symb075c00b700a000000000.gif" HEIGHT="11" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Antenna hopping/phase rolling</I>.  In this method the data stream after coding and interleaving is switched randomly from antenna to antenna.  The space selective fading at the transmitter is converted into a time selective fading at the receiver.  This is a form of  "active" fading.</div> <div> <I><IMG BORDER="0" SRC="Symb075c00b700a000000000.gif" HEIGHT="11" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Space-time coding.</I>  the approach in space-time coding is to split the encoded data into multiple data streams each of which is modulated and simultaneously transmitted from different antennas.  The received signal is a superposition of the multiple transmitted signals.  Channel decoding can be used to recover the data sequence.  Since the encoded data arrive over uncorrelated fade branches, diversity gain can be realised.</div> <div>  <A NAME="defining_terms"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <TABLE BORDER="0" CELLPADDING="0" CELLSPACING="1" WIDTH="794" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP BGCOLOR=#330099 HEIGHT= 16 WIDTH="792"><div> <B>  Defining Terms</B><B> </B></div> </tD> </tR> </TABLE></div> <div> <B> <A NAME="automatic_request_for_repeat__an_error"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>Automatic request for repeat:</B>  An error control mechanism in which received packets that cannot be corrected are retransmitted.</div> <bR> <div> <B> <A NAME="channel_codingforward_error"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>Channel coding/Forward error correction:</B>  A technique that inserts redundant bits during transmission to help detect and correct bit errors during reception.</div> <bR> <div> <B> <A NAME="fading__fluctuation_in_the_signal"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>Fading:</B>  Fluctuation in the signal level due to shadowing and multipath effects.</div> <bR> <div> <B> <A NAME="frequency_hopping__a_technique_where"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>Frequency hopping:</B>  A technique where the signal bursts are transmitted at different frequencies separated by random spacing that are multiples of signal bandwidth.</div> <bR> <div> <B> <A NAME="interleaving__a_form_of_data"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>Interleaving:</B>  A form of data scrambling that spreads burst of bit errors evenly over the received data allowing efficient forward error correction.</div> <bR> <div> <B> <A NAME="outrage_probability__"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>Outrage probability:</B>  The probability that the signal level falls below a specified minimum level.</div> <bR> <div> <B> <A NAME="rake_receiver__"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B><B>RAKE receiver:</B>  A receiver used in direct sequence spread spectrum signals.  The receiver extracts energy in each path and then adds them together with appropriate weighting and delay.</div> <div> <B><U> <A NAME="supported_primary_modem_standards"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></U></B></div> <div> <TABLE BORDER="0" CELLPADDING="0" CELLSPACING="1" WIDTH="794" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP BGCOLOR=#330099 HEIGHT= 16 WIDTH="792"><div> <B>  Supported Primary Modem Standards</B><B> </B><A HREF="#top" TITLE="References FAQs"><U><IMG SRC="0621a0c0.gif" border=0 width="26" height="12" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> </tD> </tR> </TABLE></div> <bR> <div> <TABLE BORDER="2" CELLPADDING="2" CELLSPACING="1" WIDTH="302" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#330099" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP HEIGHT= 26 ><NOBR><div> <B>Modem Standard</B></div> </NOBR></tD> <tD VALIGN=TOP WIDTH="175"><div> <B>Rate </B></div> <div> <B>(if Applicable)</B></div> </tD> </tR> <tR> <tD VALIGN=TOP HEIGHT= 13 WIDTH="108"><div> V.21</div> </tD> <tD VALIGN=TOP WIDTH="175"><div> 300 bps</div> </tD> </tR> <tR> <tD VALIGN=TOP HEIGHT= 13 WIDTH="108"><div> V.22/V.22bis</div> </tD> <tD VALIGN=TOP WIDTH="175"><div> 1200/2400 bps</div> </tD> </tR> <tR> <tD VALIGN=TOP HEIGHT= 15 WIDTH="108"><div> V.32/V.32bis</div> </tD> <tD VALIGN=TOP WIDTH="175"><div> 9600/14400 bps</div> </tD> </tR> <tR> <tD VALIGN=TOP HEIGHT= 13 WIDTH="108"><div> V.34</div> </tD> <tD VALIGN=TOP WIDTH="175"><div> 33600 bps</div> </tD> </tR> <tR> <tD VALIGN=TOP HEIGHT= 13 WIDTH="108"><div> Bell 103/212A</div> </tD> <tD VALIGN=TOP WIDTH="175"><div> 300/1200 bps</div> </tD> </tR> <tR> <tD VALIGN=TOP HEIGHT= 68 WIDTH="108"><div> V.42/V.42bis</div> </tD> <tD VALIGN=TOP WIDTH="175"><div> These error correction and compression standards will also be transparently supported by the core PCS system.</div> </tD> </tR> </TABLE></div> <div> <B><U> <A NAME="what_are_pseudorandom_noise__pn_codes_"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></U></B></div> <div> <TABLE BORDER="0" CELLPADDING="0" CELLSPACING="1" WIDTH="794" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP BGCOLOR=#330099 HEIGHT= 16 WIDTH="792"><div> <B>  What are Pseudorandom Noise (PN)codes?</B><B> </B></div> </tD> </tR> </TABLE></div> <div> PN codes are deterministic codes that mimic randomness properties.  The state of the code resembles the outcome of tossing a two-sided coin with '1' and '0', rather that heads or tails.  However, if the state and generating function of the PN code is known, the future state of the code can also be known.  The two short codes and one long code used in CDMA are time-synchronised to midnight, January 6, 1980.</div> <bR> <div> All base stations and all mobiles use the same three sequences.  The sequences are shifted in time to reduce correlation virtually to zero.<FONT SIZE="1" COLOR="#000000" FACE="Arial" >         </FONT></div> <div> <B> <A NAME="why_use_reed_solomon_codes"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B></div> <div> <TABLE BORDER="0" CELLPADDING="0" CELLSPACING="1" WIDTH="794" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP BGCOLOR=#330099 HEIGHT= 15 WIDTH="792"><div> <B>  Why use Reed-Solomon codes ?</B></div> </tD> </tR> </TABLE></div> <div> There are several reasons for using Reed Solomon codes, such as: </div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700a000000000.gif" HEIGHT="11" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">These codes are maximum distance separable codes, and hence, they make highly efficient use of the redundancy </div> <div> <IMG BORDER="0" SRC="Symb075c00b700a000000000.gif" HEIGHT="11" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Reed Solomon codes are burst error correcting codes, which are suitable for non-Gaussian channels. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700a000000000.gif" HEIGHT="11" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Reed Solomon codes provide a wide range of code rates that can be chosen such that the coded scheme has bandwidth efficiency compatible with the reference uncoded system. </div> <bR> <div> For each code, we use (n,k) Reed Solomon codes over GF(2^q) having code symbol length n = 2^q -1, minimum Hamming distance (n - k + 1) and error correcting capability (n - k)/2.</div> <bR> <div> In partitioned RSCM, each of the m bits defining an MPSK symbol, where M = 2^m is coded and decoded by different Reed Solomon codecs. The set partitioning principle is applied to define subsets with distances D(i), (i = 1 to m) that are nondecreasing with i. Each of the m bits defines a subset and is decoded in multistage decoding schemes. </div> <bR> <div> The multistage decoding here is using a hard decision decoding algorithm for each component code of a multilevel modulation code. The new idea here is that in the receiver, a rotated 2^(m+1)-PSK detector will be used if the transmitter uses a 2^m-PSK modulator. This ensures that the received level does not fall on a decision boundary when decoding any of the bits in the symbol.</div> <bR> <div> This system is compared with non-partitioned RSCM, a Reed Solomon code combined with an MPSK signal set using Gray mapping; and BCM using binary codes, Reed Muller codes, (RMCM). </div> <div>  <A NAME="why_use_turbo_codes__"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <TABLE BORDER="0" CELLPADDING="0" CELLSPACING="1" WIDTH="794" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP BGCOLOR=#330099 HEIGHT= 15 WIDTH="792"><div> <B>  Why use Turbo codes ?</B></div> </tD> </tR> </TABLE></div> <div> Another difference with EDGE for packet transmission is the use of turbo coding as an FEC scheme (EDGE mostly uses convolutional coding). Turbo coding is a technique that provides low BERs—even in noisy environments. The corresponding decoder (turbo decoder) uses an iterative process to gradually improve the quality of the received signal before making a final decision on the bits received. Turbo coding is also used in the TDD component of UMTS as well as the multi-carrier (MC) mode. As with EDGE, ARQ (Automatic Repeat Request) schemes are also used in order to ensure virtually error-free transmission of data in packet mode.</div> <div>  <A NAME="what_is_rayleigh_fading__"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <TABLE BORDER="0" CELLPADDING="0" CELLSPACING="1" WIDTH="794" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP BGCOLOR=#330099 HEIGHT= 15 WIDTH="792"><div> <B>  What is Rayleigh fading ?</B></div> </tD> </tR> </TABLE></div> <div> In terrestrial propagation, with multiple reflections and refractions arriving at the receiver with minimal relative delay and random phases, such signal is called Rayleigh fading.</div> <bR> <div> Rayleigh fading is slow enough that amplitude as well as phase remain constant over N chips times but fast enough that successive N chip segments are essentially independent.</div> <div> <B> <A NAME="what_is_spreading_factor__sf___"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></B></div> <div> <TABLE BORDER="0" CELLPADDING="0" CELLSPACING="1" WIDTH="794" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP BGCOLOR=#330099 HEIGHT= 16 WIDTH="792"><div> <B>  What is Spreading Factor (SF) ?   </B><A HREF="#top" TITLE="References FAQs"><U><IMG SRC="0621a0c0.gif" border=0 width="26" height="12" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> </tD> </tR> </TABLE></div> <div> A signal is combined with a code, the bandwidth of the original siganl increases.  The spectrum is 'spread' which justifies the name 'spread spectrum'.  The spectral power density increases as the total transmitted power stays equal.  The ratio of the transmission and information bandwidth is therefore an important parameter in spread spectrum systems.  This ratio is referred to as 'processing gain':  Gp= BW(tx)/BW(i)  which is the '<B>SPREADING FACTOR</B>'.</div> <bR> <div> The processing gain determines the number of users that can be allowed in a system, the amount of multi-path effect reduction, the difficulty to jam or detect a signal etc..  It is advantageous to have a processing gain as high as possible for spread spectrum systems.</div> <bR> <div> Spreading factors are from 256 to 4 with FDD uplink, from 512 to 4 with FDD downlink, and from 16 to 1 for TDD uplink and downlink. </div> <bR> <div> CDMA separates the arriving signals preventing fading by using correlators (no need for equalisers).  This results in more diversity, higher quality, and higher capacity.</div> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <div> ____________________________________________________________________________________________________________________________________</div> <DIV ALIGN="LEFT"></DIV> <div> <A HREF="id89.htm" TARGET="_top" TITLE="About Lemonrain"><U><U>About Lemonrain.com</U></U></A><FONT SIZE="1" COLOR="#000000" FACE="Verdana" > </FONT><A HREF="id20.htm" TARGET="_top" TITLE="Contact Us"><U><U>Contact Us</U></U></A><FONT SIZE="1" COLOR="#000000" FACE="Verdana" > </FONT><U>Lemonrain Japan</U></div> <div> <A HREF="id90.htm" TARGET="_top" TITLE="Advertise on Lemonrain"><U><U>Advertise on Lemonrain</U></U></A><FONT SIZE="1" COLOR="#000000" FACE="Verdana" > </FONT><A HREF="id91.htm" TARGET="_top" TITLE="Privacy Statement"><U><U>Privacy Statement</U></U></A><FONT SIZE="1" COLOR="#000000" FACE="Verdana" > </FONT><A HREF="id92.htm" TARGET="_top" TITLE="Copyright"><U><U>Copyright Info</U></U></A><FONT SIZE="1" COLOR="#000000" FACE="Verdana" > </FONT><A HREF="id93.htm" TARGET="_top" TITLE="Terms of use"><U><U>Terms of Use</U></U></A></div> <bR> <bR> </td> </tr></table></body>