Spreading-Sequences-for-Multi-Carrier-CDMA-System

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Spreading-Sequences-for-Multi-Carrier-CDMA-System
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<html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta charset="utf-8"> <meta name="generator" content="pdf2htmlEX"> <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> <link rel="stylesheet" href="https://static.pudn.com/base/css/base.min.css"> <link rel="stylesheet" href="https://static.pudn.com/base/css/fancy.min.css"> <link rel="stylesheet" href="https://static.pudn.com/prod/directory_preview_static/622b8a4015da9b288bec5a91/raw.css"> <script src="https://static.pudn.com/base/js/compatibility.min.js"></script> <script src="https://static.pudn.com/base/js/pdf2htmlEX.min.js"></script> <script> try{ pdf2htmlEX.defaultViewer = new pdf2htmlEX.Viewer({}); }catch(e){} </script> <title></title> </head> <body> <div id="sidebar" style="display: none"> <div id="outline"> </div> </div> <div id="pf1" class="pf w0 h0" data-page-no="1"><div class="pc pc1 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/622b8a4015da9b288bec5a91/bg1.jpg"><div class="t m0 x1 h2 y1 ff1 fs0 fc0 sc0 ls0 ws0">Spreading <span class="_ _0"></span><span class="ls1">Sequences </span></div><div class="t m1 x2 h2 y1 ff1 fs0 fc0 sc0 ls2 ws0">for </div><div class="t m0 x3 h2 y1 ff1 fs0 fc0 sc0 ls1 ws0">Multi-Carrier </div><div class="t m2 x4 h3 y1 ff1 fs1 fc0 sc0 ls3 ws0">CDMA </div><div class="t m0 x5 h2 y1 ff1 fs0 fc0 sc0 ls1 ws0">Systems </div><div class="t m3 x6 h4 y2 ff1 fs2 fc0 sc0 ls4 ws0">Branislav </div><div class="t m4 x7 h5 y2 ff1 fs3 fc0 sc0 ls5 ws0">M. </div><div class="t m3 x8 h4 y2 ff1 fs2 fc0 sc0 ls6 ws0">Popovic' </div><div class="t m3 x9 h4 y3 ff1 fs2 fc0 sc0 ls7 ws0">Ericsson <span class="ls8">Radio </span></div><div class="t m5 xa h6 y4 ff2 fs4 fc0 sc0 ls9 ws0">Systems </div><div class="t m6 xb h7 y4 ff3 fs5 fc0 sc0 lsa ws0">AB </div><div class="t m3 xc h4 y5 ff1 fs2 fc0 sc0 ls7 ws0">Core <span class="_ _1"></span>Unit Radio <span class="_ _1"></span>Systems <span class="_ _2"></span><span class="lsb">and <span class="lsc">Technology </span></span></div><div class="t m7 x9 h4 y6 ff1 fs2 fc0 sc0 lsd ws0">S164 </div><div class="t m5 xd h8 y6 ff1 fs4 fc0 sc0 lse ws0">80 </div><div class="t m3 xe h4 y6 ff1 fs2 fc0 sc0 lsf ws0">Stockholm, <span class="ls7">Sweden </span></div><div class="t m8 xc h9 y7 ff4 fs6 fc0 sc0 ls10 ws0">email: </div><div class="t m9 xf ha y7 ff3 fs7 fc0 sc0 ls11 ws0">branislav.popovic@era-t.ericsssn.se </div><div class="t ma x10 hb y8 ff2 fs8 fc0 sc0 ls12 ws0">Abstract </div><div class="t mb x11 hc y8 ff5 fs9 fc0 sc0 ls13 ws0">- </div><div class="t mc x12 hd y8 ff1 fsa fc0 sc0 ls13 ws0">The <span class="_ _3"></span>paper <span class="_ _3"></span>contains <span class="_ _2"></span>an <span class="_ _1"></span>analysis <span class="_ _4"></span><span class="ls14">of <span class="_ _5"> </span><span class="ls13">the <span class="_ _1"></span><span class="ls15">basic <span class="_ _3"></span>crite- </span></span></span></div><div class="t mc x13 hd y9 ff1 fsa fc0 sc0 ls16 ws0">ria <span class="_ _6"></span><span class="ls13">for <span class="_ _7"></span>the <span class="_ _8"></span><span class="ls15">selection <span class="_ _7"></span><span class="ls17">of <span class="_ _9"> </span></span></span>spreading <span class="_ _7"></span><span class="ls15">sequences </span>for <span class="_ _7"></span>the <span class="_ _7"></span><span class="ls15">Multi- </span></span></div><div class="t mc x13 hd ya ff1 fsa fc0 sc0 ls18 ws0">Camer <span class="_ _2"></span><span class="ls19">CDMA <span class="_ _7"></span>(MC-CDMA) <span class="ls13">systems <span class="_ _a"></span>with spectrum <span class="_ _a"></span>spread- </span></span></div><div class="t mc x10 hd yb ff1 fsa fc0 sc0 ls1a ws0">ing <span class="_ _6"></span><span class="ls1b">in <span class="_ _8"></span></span>the <span class="_ _b"> </span><span class="ls13">frequency <span class="_ _8"></span><span class="ls15">domain. <span class="_ _b"> </span></span></span>It </div><div class="t md x14 he yc ff1 fsb fc0 sc0 ls1c ws0">is </div><div class="t mc x15 hd yc ff1 fsa fc0 sc0 ls13 ws0">shown <span class="_ _6"></span>that <span class="_ _b"> </span>the <span class="_ _b"> </span><span class="ls15">time- </span></div><div class="t mc x13 hd yd ff1 fsa fc0 sc0 ls13 ws0">domain <span class="_ _c"> </span><span class="ls15">crosscorrelation <span class="_ _b"> </span></span>function <span class="_ _b"> </span>between <span class="_ _d"> </span>the <span class="_"> </span>spreading </div><div class="t mc x13 hd ye ff1 fsa fc0 sc0 ls13 ws0">sequences </div><div class="t md x16 he yf ff1 fsb fc0 sc0 ls1d ws0">is </div><div class="t mc x17 hd yf ff1 fsa fc0 sc0 ls13 ws0">not a <span class="_ _1"></span>proper <span class="_ _3"></span><span class="ls15">interference <span class="_ _3"></span>measure <span class="_ _1"></span><span class="ls13">for <span class="_ _3"></span>the <span class="ls15">asyn- </span></span></span></div><div class="t mc x13 hd y10 ff1 fsa fc0 sc0 ls15 ws0">chronous <span class="_ _7"></span><span class="ls19">MC-CDMA <span class="_ _6"></span><span class="ls16">users. <span class="_ _8"></span></span></span>Therefore <span class="_ _7"></span><span class="ls13">the <span class="_ _7"></span></span>spectral <span class="_ _7"></span><span class="ls16">correla- </span></div><div class="t mc x13 hd y11 ff1 fsa fc0 sc0 ls13 ws0">tion <span class="_ _7"></span>function </div><div class="t me x18 hf y12 ff6 fsc fc0 sc0 ls1e ws0">is </div><div class="t mc x1 hd y12 ff1 fsa fc0 sc0 ls13 ws0">introduced <span class="ls15">and, <span class="_ _7"></span>together </span>with <span class="_ _7"></span>the <span class="_ _8"></span><span class="ls16">peak-to- </span></div><div class="t mc x13 hd y13 ff1 fsa fc0 sc0 ls15 ws0">average <span class="_ _8"></span><span class="ls13">power <span class="_ _8"></span>ratio <span class="_ _8"></span>and <span class="_ _b"> </span><span class="ls1a">the <span class="_ _6"></span></span></span>dynamic <span class="_ _8"></span>range <span class="_ _6"></span><span class="ls14">of <span class="_ _e"> </span><span class="ls13">the <span class="_ _6"></span><span class="ls16">corre- </span></span></span></div><div class="t mc x13 hd y14 ff1 fsa fc0 sc0 ls13 ws0">sponding <span class="_ _1"></span>multicamer <span class="ls16">waveforms, <span class="_ _1"></span><span class="ls13">is <span class="_ _1"></span><span class="ls15">used <span class="ls13">for <span class="_ _1"></span><span class="ls1a">the <span class="_ _3"></span><span class="ls13">evaluation </span></span></span></span></span></span></div><div class="t mc x13 hd y15 ff1 fsa fc0 sc0 ls17 ws0">of <span class="_ _f"> </span><span class="ls19">MC-CDMA <span class="_ _10"> </span><span class="ls15">sequences. <span class="_ _5"> </span><span class="ls16">Some <span class="_ _5"> </span></span>well-known <span class="_ _9"> </span>classes <span class="_"> </span><span class="ls14">of </span></span></span></div><div class="t mc x13 hd y16 ff1 fsa fc0 sc0 ls15 ws0">sequences, <span class="_ _7"></span><span class="ls13">such <span class="_ _8"></span>as <span class="_ _7"></span><span class="ls1f">Walsh <span class="_ _6"></span></span>and <span class="_ _6"></span></span>Gold <span class="_ _8"></span>sequences, </div><div class="t mf x19 h10 y17 ff1 fsd fc0 sc0 ls13 ws0">as </div><div class="t mc x1a hd y17 ff1 fsa fc0 sc0 ls15 ws0">well <span class="_ _6"></span><span class="ls13">as </span></div><div class="t mc x13 hd y18 ff1 fsa fc0 sc0 ls13 ws0">Orthogonal <span class="_ _2"></span>Gold <span class="_ _7"></span><span class="ls1a">and <span class="ls16">Zadoff-Chu <span class="_ _7"></span><span class="ls15">sequences, <span class="_ _3"></span><span class="ls13">are evaluated </span></span></span></span></div><div class="t mc x10 hd y19 ff1 fsa fc0 sc0 ls13 ws0">with <span class="_ _8"></span><span class="ls15">respect <span class="_ _7"></span></span>to <span class="ls1a">the <span class="_ _7"></span><span class="ls15">aforementioned <span class="_ _7"></span>basic <span class="ls16">criteria. <span class="_ _6"></span></span></span>It </span></div><div class="t m10 x2 h11 y1a ff1 fse fc0 sc0 ls20 ws0">is </div><div class="t mc x1b hd y1a ff1 fsa fc0 sc0 ls13 ws0">also </div><div class="t mc x13 hd y1b ff1 fsa fc0 sc0 ls13 ws0">shown <span class="_ _c"> </span>that <span class="_"> </span><span class="ls1a">the <span class="_ _c"> </span></span>multicamer <span class="_"> </span>spread <span class="_ _c"> </span>spectrum <span class="_ _8"></span><span class="ls15">waveforms </span></div><div class="t mc x10 hd y1c ff1 fsa fc0 sc0 ls13 ws0">based <span class="_ _3"></span>on <span class="_ _3"></span><span class="ls1a">the <span class="_ _3"></span><span class="ls13">(multilevel) <span class="_ _11"></span><span class="ls15">Huffman <span class="_ _2"></span>sequences <span class="_ _4"></span>have <span class="_ _1"></span><span class="ls13">the <span class="_ _3"></span>lower </span></span></span></span></div><div class="t m11 x10 h12 y1d ff3 fsf fc0 sc0 ls21 ws0">PAPR </div><div class="t mc x1c hd y1d ff1 fsa fc0 sc0 ls13 ws0">than <span class="_ _1"></span>a <span class="_ _3"></span>single <span class="_ _3"></span><span class="ls1a">sine <span class="_ _a"></span><span class="ls1f">wave. </span></span></div><div class="t m12 x10 h13 y1e ff3 fs4 fc0 sc0 ls13 ws0">1 </div><div class="t m3 x1d h4 y1e ff1 fs2 fc0 sc0 lsb ws0">Introduction </div><div class="t m3 x10 h4 y1f ff1 fs2 fc0 sc0 ls7 ws0">Several <span class="_ _3"></span><span class="ls8">types <span class="_ _1"></span><span class="ls22">of <span class="_ _5"> </span><span class="ls7">Code <span class="_ _1"></span>Division <span class="_ _3"></span><span class="ls8">Multiple <span class="_ _2"></span><span class="lsc">Access <span class="ls23">(CDMA) </span></span></span></span></span></span></div><div class="t m3 x10 h4 y20 ff1 fs2 fc0 sc0 ls8 ws0">systems <span class="_ _12"></span>based <span class="_ _b"> </span><span class="ls7">on <span class="_ _b"> </span><span class="lsb">the <span class="_ _6"></span></span>combination </span></div><div class="t m13 x1e h14 y21 ff1 fs10 fc0 sc0 ls24 ws0">of </div><div class="t m3 x1f h4 y21 ff1 fs2 fc0 sc0 lsf ws0">Direct <span class="_ _b"></span>Sequence </div><div class="t m14 x10 h15 y22 ff3 fs11 fc0 sc0 ls25 ws0">(Ds) </div><div class="t m3 x20 h4 y22 ff1 fs2 fc0 sc0 ls26 ws0">CDMA <span class="_ _7"></span><span class="ls13">and <span class="_ _1"></span><span class="ls8">orthogonal <span class="_ _3"></span><span class="ls7">frequency <span class="ls8">division <span class="_ _3"></span><span class="ls23">(OFDM) </span></span></span></span></span></div><div class="t m3 x10 h4 y23 ff1 fs2 fc0 sc0 ls8 ws0">multiple <span class="_"> </span><span class="lsf">access <span class="_ _5"> </span></span>techniques </div><div class="t m15 x21 hf y24 ff3 fsc fc0 sc0 ls27 ws0">are </div><div class="t m3 x22 h4 y24 ff1 fs2 fc0 sc0 ls8 ws0">proposed <span class="_"> </span><span class="ls7">recently <span class="_"> </span><span class="ls13">[l]. </span></span></div><div class="t m3 x10 h4 y25 ff1 fs2 fc0 sc0 lsf ws0">Among <span class="_ _6"></span><span class="ls8">them, </span></div><div class="t m16 x23 h16 y26 ff7 fs12 fc0 sc0 ls28 ws0">Multi-Carrier </div><div class="t m17 x24 h17 y26 ff6 fs13 fc0 sc0 ls29 ws0">CDMA </div><div class="t m3 x25 h4 y26 ff1 fs2 fc0 sc0 ls23 ws0">(MC-CDMA) <span class="ls8">trans- </span></div><div class="t m3 x10 h4 y27 ff1 fs2 fc0 sc0 ls7 ws0">mission <span class="_ _c"> </span><span class="lsf">scheme, <span class="_ _c"> </span><span class="ls8">characterized <span class="_ _7"></span><span class="lsc">by <span class="_ _5"> </span><span class="lsb">spreading <span class="_ _12"></span></span></span>operation </span></span></div><div class="t m3 x10 h4 y28 ff1 fs2 fc0 sc0 lsf ws0">in <span class="_ _8"></span><span class="ls8">the frequency <span class="_ _1"></span>domain, is <span class="_ _12"></span><span class="ls7">one which <span class="_ _12"></span></span>represents <span class="ls7">quali- </span></span></div><div class="t m3 x10 h4 y29 ff1 fs2 fc0 sc0 ls8 ws0">tatively <span class="_ _2"></span><span class="ls7">new <span class="_ _12"></span><span class="lsb">spread <span class="_ _3"></span>spectrum <span class="_ _a"></span><span class="ls7">technique, which </span></span></span></div><div class="t m18 x6 h18 y2a ff1 fs14 fc0 sc0 ls2a ws0">is </div><div class="t m16 x26 h16 y2a ff7 fs12 fc0 sc0 ls2b ws0">dual </div><div class="t m3 x27 h4 y2a ff1 fs2 fc0 sc0 ls7 ws0">to </div><div class="t m3 x10 h4 y2b ff1 fs2 fc0 sc0 ls26 ws0">DS-CDMA </div><div class="t m19 x28 h19 y2c ff2 fs14 fc0 sc0 ls2c ws0">[2]-[3]. </div><div class="t m3 x29 h4 y2c ff1 fs2 fc0 sc0 lsf ws0">However, <span class="_ _c"> </span><span class="ls8">not </span></div><div class="t m1a x2a h1a y2c ff1 fsf fc0 sc0 ls2d ws0">so </div><div class="t m3 x2b h4 y2c ff1 fs2 fc0 sc0 ls7 ws0">recognized <span class="_ _b"></span><span class="lsf">fact </span></div><div class="t m1b x2c h14 y2c ff1 fs10 fc0 sc0 ls2e ws0">is </div><div class="t m3 x10 h4 y2d ff1 fs2 fc0 sc0 lsb ws0">that <span class="_ _c"> </span>spreading <span class="_ _b"> </span><span class="lsf">in <span class="_ _9"> </span></span>the <span class="_ _c"> </span><span class="ls7">frequency <span class="_"> </span><span class="ls8">domain <span class="_ _b"></span>is <span class="_ _c"> </span></span>originally </span></div><div class="t m3 x10 h4 y2e ff1 fs2 fc0 sc0 ls8 ws0">proposed <span class="lsb">rather <span class="ls7">earlier, <span class="_ _1"></span><span class="lsb">the <span class="_ _1"></span><span class="ls7">very <span class="_ _12"></span>first time <span class="ls8">in </span></span></span></span></span></div><div class="t m1c x2d h1b y2f ff8 fsa fc0 sc0 ls2f ws0">141 </div><div class="t m1d x2e h1c y2f ff8 fse fc0 sc0 ls30 ws0">as </div><div class="t m3 x2f h4 y2f ff1 fs2 fc0 sc0 ls8 ws0">far <span class="_ _1"></span><span class="lsb">as </span></div><div class="t m3 x10 h4 y30 ff1 fs2 fc0 sc0 lsf ws0">we know. The <span class="ls8">same <span class="_ _3"></span>type <span class="ls31">of <span class="_ _10"> </span><span class="lsb">spreading <span class="_ _4"></span><span class="ls7">waveforms <span class="ls8">is <span class="_ _3"></span><span class="ls7">also </span></span></span></span></span></span></div><div class="t m3 x10 h4 y31 ff1 fs2 fc0 sc0 ls8 ws0">discussed <span class="_ _1"></span>in </div><div class="t m1e x30 h1d y31 ff3 fs15 fc0 sc0 ls32 ws0">[5] </div><div class="t m3 x31 h4 y31 ff1 fs2 fc0 sc0 ls8 ws0">later <span class="lsf">on. </span></div><div class="t m1f x32 h1e y32 ff3 fs12 fc0 sc0 ls33 ws0">FIGURE </div><div class="t m20 x33 h1f y32 ff2 fsb fc0 sc0 ls34 ws0">1. </div><div class="t m21 x34 h20 y32 ff2 fse fc0 sc0 ls35 ws0">Transmitter </div><div class="t m1d x35 h21 y32 ff2 fs16 fc0 sc0 ls36 ws0">in </div><div class="t m21 x22 h20 y32 ff2 fse fc0 sc0 ls37 ws0">a MC-CDMA <span class="_ _1"></span><span class="ls35">system. </span></div><div class="t m22 x13 he y33 ff1 fsb fc0 sc0 ls38 ws0">In </div><div class="t m23 x36 h22 y33 ff1 fs17 fc0 sc0 ls39 ws0">the </div><div class="t m24 x37 hd y33 ff1 fsa fc0 sc0 ls1f ws0">MC-CDMA </div><div class="t m23 x38 h22 y33 ff1 fs17 fc0 sc0 ls3a ws0">scheme <span class="_ _1"></span><span class="ls3b">the <span class="_ _3"></span>same </span></div><div class="t m25 x39 h23 y33 ff3 fs18 fc0 sc0 ls3c ws0">data </div><div class="t m26 x3a h24 y33 ff2 fs19 fc0 sc0 ls3d ws0">symbol </div><div class="t m27 x3b hb y33 ff2 fs8 fc0 sc0 ls13 ws0">Dm(t) </div><div class="t m28 x2c h25 y33 ff3 fs1a fc0 sc0 ls3e ws0">is </div><div class="t m3 x13 h4 y34 ff1 fs2 fc0 sc0 ls8 ws0">transmitted </div><div class="t m29 x30 h26 y34 ff1 fsc fc0 sc0 ls3f ws0">in </div><div class="t m3 x31 h4 y34 ff1 fs2 fc0 sc0 ls8 ws0">parallel <span class="_"> </span><span class="lsb">(spread) <span class="_ _12"></span><span class="ls7">over </span></span></div><div class="t m2a x1f h15 y34 ff6 fs11 fc0 sc0 ls13 ws0">N </div><div class="t m3 x3c h4 y34 ff1 fs2 fc0 sc0 ls8 ws0">carriers, <span class="_ _6"></span><span class="lsf">each </span></div><div class="t m3 x13 h4 y35 ff1 fs2 fc0 sc0 ls8 ws0">multiplied <span class="_ _10"> </span><span class="lsc">by <span class="_ _e"> </span><span class="lsb">a <span class="_ _10"> </span></span></span>different <span class="_ _5"> </span><span class="ls7">element <span class="_ _13"> </span><span class="ls31">of <span class="_ _14"> </span></span></span>the <span class="_ _10"> </span>spreading </div><div class="t m3 x13 h4 y36 ff1 fs2 fc0 sc0 ls7 ws0">sequence </div><div class="t m2b x3d h27 y37 ff7 fs14 fc0 sc0 ls40 ws0">sm(k) </div><div class="t m3 x1 h4 y37 ff1 fs2 fc0 sc0 ls8 ws0">assigned <span class="_ _7"></span><span class="lsb">to <span class="_ _7"></span></span>the <span class="_ _7"></span><span class="ls7">user </span></div><div class="t m2c x1e h28 y37 ff6 fs1b fc0 sc0 ls41 ws0">m. </div><div class="t m3 x3e h4 y37 ff1 fs2 fc0 sc0 lsc ws0">The <span class="_ _8"></span><span class="ls26">MC-CDMA </span></div><div class="t m3 x3f h4 y38 ff1 fs2 fc0 sc0 ls8 ws0">transmitter </div><div class="t m2d x40 h14 y39 ff1 fs10 fc0 sc0 ls42 ws0">is </div><div class="t m3 x41 h4 y39 ff1 fs2 fc0 sc0 lsb ws0">shown </div><div class="t m2e x42 h1d y39 ff3 fs15 fc0 sc0 ls43 ws0">jn </div><div class="t m3 x43 h4 y39 ff1 fs2 fc0 sc0 ls44 ws0">Fig.1. <span class="_"> </span><span class="lsc">The <span class="lsb">despreader <span class="_ _3"></span><span class="ls8">consists <span class="_ _2"></span><span class="ls22">of </span></span></span></span></div><div class="t m3 x3f h4 y3a ff1 fs2 fc0 sc0 lsb ws0">a <span class="ls7">bank <span class="_ _b"></span><span class="ls31">of </span></span></div><div class="t m2f x44 h7 y3b ff6 fs5 fc0 sc0 ls13 ws0">N </div><div class="t m3 x45 h4 y3b ff1 fs2 fc0 sc0 lsb ws0">band-pass <span class="ls8">filters <span class="_ _12"></span></span>(usually <span class="_ _1"></span><span class="ls8">implemented </span></div><div class="t m30 x46 h29 y3b ff3 fs6 fc0 sc0 ls13 ws0">by </div><div class="t m3 x3f h4 y3c ff1 fs2 fc0 sc0 ls8 ws0">Inverse <span class="lsf">Discrete <span class="_ _8"></span></span>Fourier <span class="ls7">Transform) </span>followed <span class="lsc">by <span class="_ _6"></span></span>multi- </div><div class="t m3 x3f h4 y3d ff1 fs2 fc0 sc0 ls7 ws0">plication </div><div class="t m31 x47 h8 y3e ff1 fs4 fc0 sc0 ls45 ws0">of </div><div class="t m3 x45 h4 y3e ff1 fs2 fc0 sc0 ls7 ws0">filters' <span class="_ _9"> </span><span class="ls13">output <span class="_ _b"></span><span class="ls8">samples <span class="_ _b"> </span><span class="lsb">with <span class="_ _c"> </span>the <span class="_ _c"> </span></span></span></span>complex </div><div class="t m3 x3f h4 y3f ff1 fs2 fc0 sc0 ls7 ws0">conjugate </div><div class="t m31 x44 h8 y40 ff1 fs4 fc0 sc0 ls45 ws0">of </div><div class="t m3 x45 h4 y40 ff1 fs2 fc0 sc0 ls13 ws0">the <span class="_ _1"></span><span class="ls7">Spreading <span class="ls8">sequence <span class="_ _3"></span>corresponding <span class="lsf">ele- </span></span></span></div><div class="t m3 x3f h4 y41 ff1 fs2 fc0 sc0 lsf ws0">ments, <span class="_ _b"></span><span class="lsb">and </span></div><div class="t m32 x48 h2a y42 ff5 fs1c fc0 sc0 ls13 ws0">fin all^ </div><div class="t m33 x49 h17 y42 ff3 fs13 fc0 sc0 ls46 ws0">by </div><div class="t m3 x4a h4 y42 ff1 fs2 fc0 sc0 ls8 ws0">coherent <span class="lsb">summation </span></div><div class="t m34 x4b h2b y42 ff1 fs12 fc0 sc0 ls47 ws0">of </div><div class="t m35 x4c h2c y42 ff5 fs16 fc0 sc0 ls48 ws0">all </div><div class="t m3 x4d h4 y42 ff1 fs2 fc0 sc0 ls8 ws0">multi- </div><div class="t m3 x4e h4 y43 ff1 fs2 fc0 sc0 ls7 ws0">plied <span class="_ _12"></span>filters' <span class="_ _8"></span><span class="lsb">outputs. <span class="_ _1"></span><span class="ls8">It </span></span></div><div class="t m36 x4f h1a y44 ff1 fsf fc0 sc0 ls49 ws0">is </div><div class="t m3 x50 h4 y44 ff1 fs2 fc0 sc0 lsb ws0">shown <span class="_ _2"></span><span class="ls8">in <span class="ls44">Fig.2. </span></span></div><div class="t m37 x51 h13 y21 ff3 fs4 fc0 sc0 ls4a ws0">FIGURE </div><div class="t m20 x52 h1f y21 ff2 fsb fc0 sc0 ls34 ws0">2. </div><div class="t m21 x53 h20 y21 ff2 fse fc0 sc0 ls37 ws0">Dospreader </div><div class="t m38 x54 h2d y21 ff2 fsa fc0 sc0 ls16 ws0">in </div><div class="t m39 x55 h2d y21 ff2 fsa fc0 sc0 ls16 ws0">a </div><div class="t mc x56 hd y21 ff1 fsa fc0 sc0 ls17 ws0">MC-CDMA </div><div class="t m3a x57 h2e y21 ff8 fs1d fc0 sc0 ls4b ws0">system. </div><div class="t m3 x4e h4 y45 ff1 fs2 fc0 sc0 lsc ws0">In <span class="_ _b"></span><span class="ls7">general, <span class="_ _8"></span><span class="lsb">the <span class="_ _12"></span><span class="ls8">multic,arrier <span class="_ _a"></span>transmission <span class="_ _7"></span><span class="ls7">schemes <span class="_ _12"></span></span>have </span></span></span></div><div class="t m3 x4e h4 y46 ff1 fs2 fc0 sc0 ls8 ws0">the <span class="_ _7"></span><span class="ls7">increased </span></div><div class="t m16 x41 h16 y47 ff7 fs12 fc0 sc0 ls4c ws0">peak-to-average <span class="_ _1"></span><span class="ls28">power <span class="_ _8"></span><span class="ls13">ratio </span></span></div><div class="t m3b x58 h2f y47 ff7 fs4 fc0 sc0 ls4d ws0">(PAPR), </div><div class="t m3c x59 h30 y47 ff3 fs1e fc0 sc0 ls4e ws0">as </div><div class="t m3 x5a h4 y47 ff1 fs2 fc0 sc0 ls7 ws0">well </div><div class="t m3c x4e h30 y48 ff3 fs1e fc0 sc0 ls4f ws0">as </div><div class="t m3 x5b h4 y48 ff1 fs2 fc0 sc0 lsb ws0">the <span class="ls7">increased </span></div><div class="t m3d x5c h12 y48 ff6 fsf fc0 sc0 ls50 ws0">signal </div><div class="t m16 x5d h16 y48 ff7 fs12 fc0 sc0 ls4c ws0">envelope <span class="_ _12"></span><span class="ls28">dynamic <span class="_ _7"></span></span>range </div><div class="t m3 x5e h4 y48 ff1 fs2 fc0 sc0 ls7 ws0">compared </div><div class="t m3 x4e h4 y49 ff1 fs2 fc0 sc0 ls8 ws0">with <span class="_ _8"></span>the <span class="_ _6"></span><span class="ls7">single-carrier <span class="_ _8"></span>schemes. These <span class="_ _8"></span></span>two <span class="_ _8"></span><span class="ls7">drawbacks, </span></div><div class="t m3 x4e h4 y4a ff1 fs2 fc0 sc0 lsf ws0">which <span class="_ _f"> </span>reflect <span class="_ _e"> </span>in <span class="_ _f"> </span><span class="ls8">the <span class="_ _e"> </span>reduced </span></div><div class="t m16 x5f h16 y4b ff7 fs12 fc0 sc0 ls28 ws0">power <span class="_ _15"> </span><span class="ls13">ej'iciency </span></div><div class="t m3 x60 h4 y4b ff1 fs2 fc0 sc0 ls8 ws0">and </div><div class="t m3 x4e h4 y4c ff1 fs2 fc0 sc0 ls7 ws0">increased <span class="_ _7"></span><span class="ls8">required </span></div><div class="t m16 x49 h16 y4d ff7 fs12 fc0 sc0 ls2b ws0">range </div><div class="t m3e x61 h13 y4d ff6 fs4 fc0 sc0 ls51 ws0">of </div><div class="t m3f x62 h29 y4d ff6 fs6 fc0 sc0 ls52 ws0">linearity </div><div class="t m3 x63 h4 y4d ff1 fs2 fc0 sc0 ls31 ws0">of <span class="_ _13"> </span><span class="ls8">power <span class="_ _6"></span><span class="lsf">amplifier, </span></span></div><div class="t m3 x4e h4 y4e ff1 fs2 fc0 sc0 ls8 ws0">in the <span class="_ _3"></span><span class="ls53">OFDM <span class="_ _6"></span><span class="ls7">systems <span class="_ _1"></span><span class="ls54">ican <span class="_ _6"></span><span class="ls7">be <span class="ls8">mitigated <span class="_ _3"></span><span class="lsc">by <span class="_ _8"></span><span class="ls8">careful <span class="_ _3"></span><span class="lsf">choice </span></span></span></span></span></span></span></span></div><div class="t m3 x4e h4 y4f ff1 fs2 fc0 sc0 ls55 ws0">of </div><div class="t m16 x5b h16 y50 ff7 fs12 fc0 sc0 ls4c ws0">carrier <span class="_ _1"></span>phases. </div><div class="t m3 x64 h4 y50 ff1 fs2 fc0 sc0 lsc ws0">The </div><div class="t m40 x65 h31 y50 ff2 fs15 fc0 sc0 ls56 ws0">l?APR </div><div class="t m3 x66 h4 y50 ff1 fs2 fc0 sc0 ls8 ws0">minimization <span class="_ _1"></span>consists </div><div class="t m41 x4d h2b y50 ff1 fs12 fc0 sc0 ls57 ws0">of </div><div class="t m3 x67 h4 y50 ff1 fs2 fc0 sc0 lsb ws0">the </div><div class="t m3 x4e h4 y51 ff1 fs2 fc0 sc0 ls7 ws0">minimization <span class="_ _b"> </span><span class="ls31">of <span class="_ _f"> </span><span class="ls8">the <span class="_ _6"></span>signal <span class="_ _6"></span>envelope <span class="_ _8"></span></span></span>maximum <span class="_ _b"> </span>value, </div><div class="t m3 x4e h4 y52 ff1 fs2 fc0 sc0 ls7 ws0">while <span class="_ _1"></span><span class="lsf">for <span class="ls8">the <span class="ls7">dynamic range <span class="_ _3"></span><span class="ls8">minimization <span class="_ _3"></span>the <span class="lsf">difference </span></span></span></span></span></div><div class="t m3 x68 h4 y53 ff1 fs2 fc0 sc0 ls7 ws0">between <span class="_ _b"></span><span class="ls8">the </span></div><div class="t m42 x45 h32 y54 ff2 fs1f fc0 sc0 ls58 ws0">"uni </div><div class="t m3 x43 h4 y54 ff1 fs2 fc0 sc0 ls8 ws0">and </div><div class="t m43 x69 h33 y54 ff1 fs20 fc0 sc0 ls59 ws0">the </div><div class="t m3 x6a h4 y54 ff1 fs2 fc0 sc0 ls7 ws0">maximum <span class="_ _6"></span><span class="ls8">signal enve- </span></div><div class="t m3 x68 h4 y55 ff1 fs2 fc0 sc0 ls8 ws0">lope <span class="ls7">values <span class="_ _6"></span></span>has <span class="_ _7"></span><span class="ls7">to <span class="_ _7"></span><span class="lsc">be <span class="_"> </span></span>minimized. <span class="_ _12"></span><span class="lsf">The </span></span></div><div class="t m44 x6b h15 y56 ff3 fs11 fc0 sc0 ls5a ws0">PAPR </div><div class="t m3 x6c h4 y56 ff1 fs2 fc0 sc0 ls5b ws0">"iza- </div><div class="t m3 x4e h4 y57 ff1 fs2 fc0 sc0 lsf ws0">tion, <span class="_ _e"> </span><span class="ls7">which <span class="_ _16"> </span><span class="ls8">has <span class="_ _16"> </span></span>been <span class="_ _16"> </span><span class="ls8">the <span class="_ _16"> </span></span>goal <span class="_ _e"> </span>for </span></div><div class="t m45 x6d h34 y58 ff3 fs20 fc0 sc0 ls5c ws0">all </div><div class="t m3 x57 h4 y58 ff1 fs2 fc0 sc0 ls8 ws0">previously </div><div class="t m3 x68 h4 y59 ff1 fs2 fc0 sc0 ls8 ws0">proposed <span class="_ _3"></span>phasing <span class="ls7">schemes, <span class="_ _2"></span><span class="lsb">does <span class="_ _a"></span><span class="ls13">not <span class="_ _2"></span><span class="ls7">necessarily <span class="ls8">leeds <span class="_ _1"></span><span class="ls7">to </span></span></span></span></span></span></div><div class="t m3 x4e h4 y5a ff1 fs2 fc0 sc0 ls8 ws0">the <span class="_ _9"> </span><span class="ls7">minimization <span class="_ _13"> </span><span class="ls5d">of <span class="_ _14"> </span></span></span>signal <span class="_ _5"> </span>dynamic <span class="_ _9"> </span><span class="ls7">range, <span class="_ _13"> </span><span class="lsb">as <span class="_"> </span></span></span>it </div><div class="t m46 x6e h35 y5b ff1 fs19 fc0 sc0 ls5e ws0">is </div><div class="t m3 x68 h4 y5c ff1 fs2 fc0 sc0 ls8 ws0">pointed out <span class="lsf">in </span></div><div class="t m47 x6f h36 y5c ff2 fs10 fc0 sc0 ls5f ws0">[3]. </div><div class="t m3 x68 h4 y5d ff1 fs2 fc0 sc0 ls23 ws0">The <span class="_ _b"> </span><span class="ls53">MC-CDMA <span class="_ _9"> </span></span>systeims, <span class="_ _6"></span><span class="lsf">however, <span class="_"> </span>offer <span class="_ _b"></span><span class="ls8">an <span class="_ _b"></span><span class="lsb">additional </span></span></span></div><div class="t m3 x4e h4 y5e ff1 fs2 fc0 sc0 ls7 ws0">degree <span class="_ _5"> </span><span class="ls5d">of <span class="_ _15"> </span></span>freedom <span class="_"> </span>for <span class="_"> </span><span class="ls8">the <span class="_"> </span>minimization <span class="_ _b"> </span><span class="ls31">of </span></span></div><div class="t m1d x70 h8 y5f ff1 fs4 fc0 sc0 ls60 ws0">PAPR </div><div class="t m3 x46 h4 y5f ff1 fs2 fc0 sc0 ls23 ws0">or </div><div class="t m3 x4e h4 y60 ff1 fs2 fc0 sc0 ls7 ws0">dynamic <span class="_ _8"></span>range. <span class="_ _6"></span><span class="lsc">Namely, <span class="_ _b"></span><span class="ls8">the <span class="_ _8"></span>phasing <span class="_ _6"></span>technique <span class="_ _8"></span><span class="lsf">can <span class="_ _8"></span></span></span></span>be </div><div class="t m3 x4e h4 y61 ff1 fs2 fc0 sc0 ls7 ws0">generalized </div><div class="t m48 x71 h33 y62 ff1 fs20 fc0 sc0 ls61 ws0">so </div><div class="t m3 x64 h4 y62 ff1 fs2 fc0 sc0 lsb ws0">that </div><div class="t m49 x72 h37 y62 ff1 fs1e fc0 sc0 ls13 ws0">also </div><div class="t m3 x73 h4 y62 ff1 fs2 fc0 sc0 lsb ws0">the </div><div class="t m16 x5 h16 y62 ff7 fs12 fc0 sc0 ls13 ws0">carrier <span class="_"> </span>envelopes </div><div class="t m3 x59 h4 y62 ff1 fs2 fc0 sc0 lsf ws0">can <span class="_ _9"> </span><span class="ls7">be </span></div><div class="t m3 x4e h4 y63 ff1 fs2 fc0 sc0 ls8 ws0">manipulated <span class="_ _b"></span><span class="ls7">to <span class="_ _b"></span></span>produce <span class="_ _6"></span>multicarrier <span class="_ _b"></span><span class="lsb">spread <span class="_ _6"></span></span>spectrum </div><div class="t m3 x4e h4 y64 ff1 fs2 fc0 sc0 lsf ws0">waveform <span class="_ _12"></span><span class="ls8">with <span class="_ _1"></span>reduced </span></div><div class="t m4a x74 ha y65 ff3 fs7 fc0 sc0 ls62 ws0">PAPR </div><div class="t m3 x75 h4 y65 ff1 fs2 fc0 sc0 ls8 ws0">or dynamic <span class="_ _2"></span>range. <span class="_ _1"></span><span class="lsc">There- </span></div><div class="t m3 x4e h4 y66 ff1 fs2 fc0 sc0 ls7 ws0">fore <span class="_ _b"></span>the <span class="_"> </span><span class="ls8">spreading <span class="_ _6"></span></span>sequences <span class="_ _b"></span>for <span class="_ _b"> </span><span class="ls26">MC-CDMA <span class="_ _10"> </span><span class="ls8">systems </span></span></div><div class="t m3 x4e h4 y67 ff1 fs2 fc0 sc0 ls8 ws0">should <span class="_ _10"> </span>not <span class="_ _13"> </span><span class="lsc">necessarilly <span class="_ _13"> </span></span>have <span class="_ _13"> </span>the <span class="_ _13"> </span>constant <span class="_ _10"> </span>envelope </div><div class="t m3 x4e h4 y68 ff1 fs2 fc0 sc0 ls7 ws0">(binary <span class="_ _12"></span><span class="lsf">or <span class="_ _7"></span><span class="ls8">polyphase </span></span>sequences), <span class="_ _1"></span><span class="lsb">as <span class="ls8">opposed <span class="_ _7"></span><span class="ls7">to <span class="_ _12"></span></span></span>the </span></div><div class="t m2a x60 h15 y69 ff3 fs11 fc0 sc0 ls25 ws0">Ds- </div><div class="t m27 x4e h38 y6a ff1 fs8 fc0 sc0 ls63 ws0">CDMA </div><div class="t m3 x51 h4 y6a ff1 fs2 fc0 sc0 ls8 ws0">systems <span class="_ _f"> </span><span class="lsc">wh.ere <span class="_ _17"> </span></span>the <span class="_ _17"> </span>multilevel <span class="_ _18"> </span><span class="lsb">spreading </span></div><div class="t m3 x4e h4 y6b ff1 fs2 fc0 sc0 ls7 ws0">sequences <span class="_ _b"></span>directly <span class="_ _c"> </span>increase <span class="_ _b"> </span><span class="lsb">the <span class="_ _c"> </span>signal <span class="_ _8"></span><span class="ls8">dynamic <span class="_ _b"></span>range </span></span></div><div class="t m3 x4e h4 y6c ff1 fs2 fc0 sc0 ls8 ws0">and <span class="ls7">therefore </span>are <span class="_ _3"></span>not <span class="_ _12"></span><span class="ls7">recommended. </span></div><div class="t m18 x76 h18 y6d ff1 fs14 fc0 sc0 ls64 ws0">(In </div><div class="t m3 x58 h4 y6d ff1 fs2 fc0 sc0 ls53 ws0">OFDM <span class="_ _6"></span><span class="ls8">systems </span></div><div class="t m4b x5b h39 y6e ff6 fs21 fc0 sc0 ls13 ws0">0 </div><div class="t m4c x77 h3a y6e ff8 fs1a fc0 sc0 ls65 ws0">1997 </div><div class="t m1d x78 h3b y6e ff8 fs17 fc0 sc0 ls3b ws0">The <span class="_ _3"></span><span class="ls66">Institution </span></div><div class="t m4d x42 h2e y6e ff8 fs1d fc0 sc0 ls13 ws0">ol </div><div class="t m1d x79 h3b y6e ff8 fs17 fc0 sc0 ls3a ws0">Electrical <span class="_ _a"></span><span class="ls66">Engineers. </span></div><div class="t m1d x5b h3b y6f ff8 fs17 fc0 sc0 ls66 ws0">Printed <span class="_ _2"></span>and published <span class="_ _a"></span><span class="ls67">by <span class="_ _12"></span><span class="ls3a">the <span class="_ _12"></span><span class="ls3b">IEE, <span class="_ _2"></span><span class="ls68">Savoy <span class="_ _12"></span><span class="ls3a">Place, <span class="_ _3"></span><span class="ls68">London </span></span></span></span></span></span></div><div class="t m4e x7a h3c y70 ff8 fs18 fc0 sc0 ls69 ws0">WC2R </div><div class="t m1d x7b h3b y70 ff8 fs17 fc0 sc0 ls67 ws0">OBL, </div><div class="t m4f x7c h2e y70 ff8 fs1d fc0 sc0 ls6a ws0">UK. </div><div class="t m4a x7d h3d y71 ff2 fs7 fc0 sc0 ls62 ws0">8/ </div><div class="t m50 xe h3e y71 ff5 fsf fc0 sc0 ls13 ws0">1 </div><div class="t m1d x12 h3f y72 ff9 fs22 fc1 sc0 ls13 ws0">Authorized licensed use limited to: IEEE Xplore. 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