信道編碼和差錯控制ppt課件

1、混合信道混合信道 停止等待ARQ系統(tǒng)接收數(shù)據(jù)ACKACKNAKACKACKNAKACK1233455t發(fā)送數(shù)據(jù)12334556t有錯碼組有錯碼組拉后ARQ系統(tǒng)214365798接收數(shù)據(jù)有錯碼組有錯碼組910 1110 11 12576ACK1NAK5NAK9ACK55769521436798發(fā)送數(shù)據(jù)10 1110 11 12重發(fā)碼組重發(fā)碼組選擇重發(fā)ARQ系統(tǒng)9接收數(shù)據(jù)有錯碼組有錯碼組214365759810 11131412發(fā)送數(shù)據(jù)9958521436710 1113 1412重發(fā)碼組重發(fā)碼組NAK9ACK1NAK5ACK5ACK9000 111 就能檢測兩個以下錯碼，或糾正一個錯碼。就能檢測

2、兩個以下錯碼，或糾正一個錯碼。k個信息位r個監(jiān)督位an-1an-2.arar-1an-2.a0t碼長 n = k + r分組碼的結(jié)構(gòu)(0,0,0)(0,0,1)(1,0,1)(1,0,0)(1,1,0)(0,1,0)(0,1,1)(1,1,1)a2a0a110 ed0123BA漢明距離ed0碼距等于3的兩個碼組120 tdBtA漢明距離012345td0碼距等于5的兩個碼組AB1tt漢明距離e碼距等于(e+t+1)的兩個碼組)(10teted10-610-510-410-310-210-1編碼后Eb/n0 (dB)編碼和誤碼率關(guān)系PeCDEAB2PSK10-610-510-410-310-21

3、0-1編碼后Eb/n0 (dB)編碼和誤碼率關(guān)系PeCDEAB2PSKBsssbRnPTnPnTPnE0000)/1 (10-610-510-410-310-210-1編碼后Eb/n0 (dB)編碼和誤碼率關(guān)系PeCDEAB2PSK)(/00dBnEnEGcbubdB0021aaann1021aaannjnjnjppCnjP)1 (),()!( !jnjnCnj2/1222)1 (njjnjnjuppCP2/ )1(1222)1 (njjnjnjuppCP2/1222)1 (njjnjnjuppCP82443242204442242212424210666126)1 (6)1 ()1 ()1

4、(ppppppppppCppCppCPjjjjunmnmnk)1()1(0021aaann021aaaSnn021aaaSnn021aaaSnn1212rknrr或1212rknrr或24561aaaaS13562aaaaS03463aaaaS000034613562456aaaaaaaaaaaa346035614562aaaaaaaaaaaa24561aaaaS13562aaaaS03463aaaaS10 ed120 td1212rrrnk000034613562456aaaaaaaaaaaa010011010010101100010111012345601234560123456aaaaa

5、aaaaaaaaaaaaaaaa010011010010101100010111012345601234560123456aaaaaaaaaaaaaaaaaaaaa0001011001110101011101000123456aaaaaaa101100111010101110100HrPIH0011011010110110011103456012101111011110aaaaaaa346035614562aaaaaaaaaaaaQ34563456012011101110111aaaaaaaaaaa0110001101001011001001111000QGkI IG34560123456aa

6、aaaaaaaaaA0121aaaaAnn0121bbbbBnnB A = E (模2)0121eeeeEnniiiiiababe當當, 1, 0的距離即對應位不同的數(shù)目必定是另一個碼組的距離即對應位不同的數(shù)目必定是另一個碼組(A1 + A2)的重量即的重量即“1的數(shù)目）。因此，碼的最小距離就是的數(shù)目）。因此，碼的最小距離就是碼的最小重量除全碼的最小重量除全“0碼組外）。碼組外）。向右移一位即得到第向右移一位即得到第7碼組。碼組。012211)(axaxaxaxTnnnn11010011)(25623456xxxxxxxxxxTnpnpQnm,)()()()(xRxQxNxF）（模)()()(

7、xNxRxF）（模) 1(133xx）（模) 1(113224xxxxx結(jié)論：一個長為結(jié)論：一個長為n的循環(huán)碼必定為按模的循環(huán)碼必定為按模(xn + 1)運算的一個余式。運算的一個余式。）（模) 1()()(nixxTxTx012211)(axaxaxaxTnnnn)()(1102211011112211xTaxaxaxaxaxaxaxaxaxaxTxininininniniinininninni1)(256xxxxT）（模) 1()(723535893xxxxxxxxxxTxG34560123456aaaaaaaaaaaA0110001101001011001001111000QGkI I)

8、()()()()(21xgxxgxgxxgxxkkG)()()()(2xgxxgxgxxG001011101011101011100)(xG)()()()()()()()()()(452645262456456xgaxaxaxgaxxgaxgxaxgxxgxgxaaaxaaaxTG）（模) 1()()(nixxTxTx1)()(1)(nnkxxTxQxxTx)() 1()(xTxxTxnk)() 1()(xTxxTxnk)()(1xhxxgxkn) 1)(1)(1(13237xxxxxx1) 1)(1(2423xxxxxx1) 1)(1(2343xxxxxx)()()()()(xgxrxQxg

9、xmxkn11) 1(1)()(24222456xxxxxxxxxxxxgxmxkn10111101111101111100000)(/)()()(/)(xgxrxQxgxR)(/ )()()(/ )(xgxrxQxgxR2PSK漢明碼(7, 4) t=1 漢明碼(31, 26) t=1擴展戈萊碼(24, 12) t=3BCH碼(127, 64) t=10Eb / n0 (dB)Pe編碼輸出每次輸入k比特1k1k1k1k 1 k2k3kNk 12nNk級移存器n個模2加法器每輸入k比特旋轉(zhuǎn)1周123b3b1輸入b2編碼輸出c2c1c3321331211bbbcbbcbc000111001110

10、011100010101000111001110011100010101c1c2c3000100111011001101110010c1c2c3111000001110c1c2c3信息位 1 1 0 1ba起點信息位000111c1c2c3abcdabcdabcdabcd上半部下半部10a形狀 b3b2 a 0 0 b 0 1 c 1 0 d 1 1abcdabcdcdab011001321331211bbbcbbcbc123b3b1輸入b2編碼輸出c2c1c3abcd000111101110010011100001110110110110011011011010010010101101101

11、001001001001abcdabcd000000000000000111111111111111100100100abcd000111101110010011100001abcdabcd110010001111100110110110110011011011010010010101101101001001001001abcdabcd000000000000000111111111111111100100100abcd011010010101001abcd111100100110110110011010010101101001001abcdabcd000 111100100000 01101

12、1001101110011010010101101001001abcdabcd000 111100100000 011011001110011010010101101001001abcdabcd000 111100100000 011011001101和在低信噪比條件下得到接近理想的性能。和在低信噪比條件下得到接近理想的性能。內(nèi)編碼器(n, k)調(diào)制器信道解制器內(nèi)解碼器(n, k)外解碼器(N, K)外編碼器(N, K)輸入輸出RSCC交織器RSCCbibic1ic2iDDbibicia11a12a1ma21a22a2man1an2anmxxx1234xxx1234x x x 1 xxx1xxx x x x (a) 第14比特輸入時的狀態(tài)xx2567834x5678x x 2 5 x2x51xx x x x (b) 第58比