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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/6265557f4f8811599e787092/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/6265557f4f8811599e787092/bg1.jpg"><div class="t m0 x1 h2 y1 ff1 fs0 fc0 sc0 ls0 ws0">A Review of Joint Source-Channel Coding</div><div class="t m0 x2 h3 y2 ff2 fs1 fc0 sc0 ls0 ws0">Fredrik Hekland</div><div class="t m0 x3 h4 y3 ff3 fs2 fc0 sc0 ls0 ws0">1</div><div class="t m0 x4 h3 y4 ff2 fs1 fc0 sc0 ls0 ws0">Dept. of Electronics and Telecommunications</div><div class="t m0 x5 h3 y5 ff2 fs1 fc0 sc0 ls0 ws0">Norwegian University of Science and Technology (NTNU)</div><div class="t m0 x6 h3 y6 ff2 fs1 fc0 sc0 ls0 ws0">July 5, 2005</div><div class="t m0 x7 h5 y7 ff4 fs3 fc0 sc0 ls0 ws0">1</div><div class="t m0 x8 h6 y8 ff5 fs4 fc0 sc0 ls0 ws0">hekland@iet.ntnu.no</div></div><div class="pi" data-data='{"ctm":[1.611850,0.000000,0.000000,1.611850,0.000000,0.000000]}'></div></div> </body> </html>

<div id="pf2" class="pf w0 h0" data-page-no="2"><div class="pc pc2 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/6265557f4f8811599e787092/bg2.jpg"><div class="t m0 x9 h7 y9 ff6 fs5 fc0 sc0 ls0 ws0">Abstract</div><div class="t m0 xa h8 ya ff7 fs5 fc0 sc0 ls0 ws0">This article presents methods for robust and eﬃcient communication over wireless</div><div class="t m0 xa h8 yb ff7 fs5 fc0 sc0 ls0 ws0">chann els. Both beneﬁts and limitations of the classical approach of separate source</div><div class="t m0 xa h8 yc ff7 fs5 fc0 sc0 ls0 ws0">and channel coding are discussed. Joint source-channel coding (JSCC) is presented</div><div class="t m0 xa h8 yd ff7 fs5 fc0 sc0 ls0 ws0">as the most promising scheme for communication of analogue sources over wireless</div><div class="t m0 xa h8 ye ff7 fs5 fc0 sc0 ls0 ws0">chann els, due to its ability to cope with varying channel qualities and to approach</div><div class="t m0 xa h8 yf ff7 fs5 fc0 sc0 ls0 ws0">the theoretical bounds of transmission rates. Diﬀerent schemes for implementing joint</div><div class="t m0 xa h8 y10 ff7 fs5 fc0 sc0 ls0 ws0">source-chann el coding are presented, ranging from a traditional tandem structure with</div><div class="t m0 xa h8 y11 ff7 fs5 fc0 sc0 ls0 ws0">resource control to hybrid digital-analogue JSCC techniques providing both bandwidth</div><div class="t m0 xa h8 y12 ff7 fs5 fc0 sc0 ls0 ws0">reduction and expansion. The direct source-channel mapping schemes are shown to</div><div class="t m0 xa h8 y13 ff7 fs5 fc0 sc0 ls0 ws0">be good candidates for joint source-channel coding, providin g both robustness and</div><div class="t m0 xa h8 y14 ff7 fs5 fc0 sc0 ls0 ws0">eﬃciency.</div></div><div class="pi" data-data='{"ctm":[1.611850,0.000000,0.000000,1.611850,0.000000,0.000000]}'></div></div>

<div id="pf3" class="pf w0 h0" data-page-no="3"><div class="pc pc3 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/6265557f4f8811599e787092/bg3.jpg"><div class="t m0 xa h9 y15 ff8 fs6 fc0 sc0 ls0 ws0">Part I</div><div class="t m0 xa ha y16 ff9 fs7 fc0 sc0 ls0 ws0">The Source-Channel Problem</div><div class="t m0 xa h9 y17 ff8 fs6 fc0 sc0 ls0 ws0">1 Introduction</div><div class="t m0 xa h8 y18 ff7 fs5 fc0 sc0 ls0 ws0">Commu nica tion is all about trying to convey as much information as possible over a</div><div class="t m0 xa h8 y19 ff7 fs5 fc0 sc0 ls0 ws0">given channel with as few errors as possible. Before 1948 it was generally conceived</div><div class="t m0 xa h8 y1a ff7 fs5 fc0 sc0 ls0 ws0">that it was impossible to attain arbitrarily low error rates when communicating in the</div><div class="t m0 xa h8 y1b ff7 fs5 fc0 sc0 ls0 ws0">presence of noise. This misconception was di sproved by Shannon (1948) in his ground -</div><div class="t m0 xa h8 y1c ff7 fs5 fc0 sc0 ls0 ws0">breaking work “A Mathematical Theory of Communication”. Here, he introduced the</div><div class="t m0 xa h8 y1d ff7 fs5 fc0 sc0 ls0 ws0">concept of channel capacity and proved that as long as the transmission rate is below</div><div class="t m0 xa h8 y1e ff7 fs5 fc0 sc0 ls0 ws0">the channel’s cap acity, reliable communication with a non-zero, but arbitrarily small</div><div class="t m0 xa h8 y1f ff7 fs5 fc0 sc0 ls0 ws0">error rate is possible. Furthermore, he presented a theorem stating that a source with</div><div class="t m0 xa h8 y20 ff7 fs5 fc0 sc0 ls0 ws0">entropy H can be reliably transmitted over a channel with capacity C as long as H ≤ C.</div><div class="t m0 xa h8 y21 ff7 fs5 fc0 sc0 ls0 ws0">In p rincip le this can be achieved by ﬁrst applying a source coder that reduces the rate</div><div class="t m0 xa h8 y22 ff7 fs5 fc0 sc0 ls0 ws0">of the source down to the minimum, called the entropy H, and subsequently applying</div><div class="t m0 xa h8 y23 ff7 fs5 fc0 sc0 ls0 ws0">a channel code. In the receiver, the channel decoder, which is unaware of the type of</div><div class="t m0 xa h8 y24 ff7 fs5 fc0 sc0 ls0 ws0">source, outputs the most probable codeword to the source decoder. Finally, the source</div><div class="t m0 xa h8 y25 ff7 fs5 fc0 sc0 ls0 ws0">coder reconstructs the source without any knowledge of the channel statistics. This</div><div class="t m0 xa h8 y26 ff7 fs5 fc0 sc0 ls0 ws0">independence between source and channel coder is the reason why this theorem is also</div><div class="t m0 xa h8 y27 ff7 fs5 fc0 sc0 ls0 ws0">known as the separation theorem; the simpliﬁcations it provides makes it prevalent in</div><div class="t m0 xa h8 y28 ff7 fs5 fc0 sc0 ls0 ws0">the communication community.</div><div class="t m0 xb h8 y29 ff7 fs5 fc0 sc0 ls0 ws0">However, this theorem does not hold in every situation. In those cases where it</div><div class="t m0 xa h8 y2a ff7 fs5 fc0 sc0 ls0 ws0">breaks down, there are usually systems with combined or joint source-channel coding</div><div class="t m0 xa h8 y2b ff7 fs5 fc0 sc0 ls0 ws0">that perform better. This article will discuss such joint co din g schemes in the context of</div><div class="t m0 xa h8 y2c ff7 fs5 fc0 sc0 ls0 ws0">analogue sources, where errors in the transmission are allowed. In the ﬁrst part of this</div><div class="t m0 xa h8 y2d ff7 fs5 fc0 sc0 ls0 ws0">article, the limitations of the separation theorem are described, and some earlier source-</div><div class="t m0 xa h8 y2e ff7 fs5 fc0 sc0 ls0 ws0">chann el coding systems are mentioned. Furthermore, the need for explicit channel</div><div class="t m0 xa h8 y2f ff7 fs5 fc0 sc0 ls0 ws0">coding is examined. The second part d escribes proposed systems and concepts for joint</div><div class="t m0 xa h8 y30 ff7 fs5 fc0 sc0 ls0 ws0">source-chann el coding, from purely digital systems to both hybrid digital-analogu e and</div><div class="t m0 xa h8 y31 ff7 fs5 fc0 sc0 ls0 ws0">analogue systems.</div><div class="t m0 xa h3 y32 ffd fs1 fc0 sc0 ls0 ws0">1.1 Shortcomings of the Channel Coding Theorem</div><div class="t m0 xa h8 y33 ff7 fs5 fc0 sc0 ls0 ws0">The fact that we can perform source coding independently of channel coding and vice</div><div class="t m0 xa h8 y34 ff7 fs5 fc0 sc0 ls0 ws0">versa simpliﬁes th e construction of the system since we can optimis e the coders sepa-</div><div class="t m0 xa h8 y35 ff7 fs5 fc0 sc0 ls0 ws0">rately and still achieve optimality. Also, having either a diﬀerent source or channel, we</div><div class="t m0 xa h8 y36 ff7 fs5 fc0 sc0 ls0 ws0">can change the aﬀected coder while leaving the other unchanged. However, there are</div><div class="t m0 xa h8 y37 ff7 fs5 fc0 sc0 ls0 ws0">some drawbacks with this approach. First of all, we have to allow inﬁnite complexity</div><div class="t m0 xa h8 y38 ff7 fs5 fc0 sc0 ls0 ws0">and delay in the coders in order to reach optimality. Evidently this is problematic for</div><div class="t m0 xa h8 y39 ff7 fs5 fc0 sc0 ls0 ws0">real-time communication. Secondly, the theorem is no longer valid for non-ergo d ic and</div><div class="t m0 xa h8 y3a ff7 fs5 fc0 sc0 ls0 ws0">mul ti-user channels, and in those cases we no longer have an optimal system. Thirdly,</div><div class="t m0 xa h8 y3b ff7 fs5 fc0 sc0 ls0 ws0">such systems tend to break down completely when the channel quality falls under a cer-</div><div class="t m0 xa h8 y3c ff7 fs5 fc0 sc0 ls0 ws0">tain threshold, and the channel code is n o longer capable of correcting the errors. This</div><div class="t m0 xa h8 y3d ff7 fs5 fc0 sc0 ls0 ws0">phenomenon is often referred to as the threshold eﬀect. Thus, these systems are not</div><div class="t m0 xa h8 y3e ff7 fs5 fc0 sc0 ls0 ws0">robust with respect to changing channel qualities. Knowing that wireless channels have</div><div class="t m0 xa h8 y3f ff7 fs5 fc0 sc0 ls0 ws0">ﬂuctuating channel qualiti es and hi gh bit-error rates, trying to evade (or at least re-</div><div class="t m0 xa h8 y40 ff7 fs5 fc0 sc0 ls0 ws0">duce) the threshold eﬀect should be important when designing wireless communication</div><div class="t m0 xa h8 y41 ff7 fs5 fc0 sc0 ls0 ws0">systems.</div><div class="t m0 xc h8 y42 ff7 fs5 fc0 sc0 ls0 ws0">1</div><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m1"></div></a></div><div class="pi" data-data='{"ctm":[1.611850,0.000000,0.000000,1.611850,0.000000,0.000000]}'></div></div>