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1.
On multilevel block modulation codes 总被引:1,自引:0,他引:1
Kasami T. Takata T. Fujiwara T. Lin S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1991,37(4):965-975
The multilevel technique for combining block coding and modulation is investigated. A general formulation is presented for multilevel modulation codes in terms of component codes with appropriate distance measures. A specific method for constructing multilevel block modulation codes with interdependency among component codes is proposed. Given a multilevel block modulation code C with no interdependency among the binary component codes, the proposed method gives a multilevel block modulation code C ' that has the same rate as C , a minimum squared Euclidean distance not less than that of C , a trellis diagram with the same number of states as that of C , and a smaller number of nearest neighbor codewords than that of C . Finally, a technique is presented for analyzing the error performance of block modulation codes for an additive white Gaussian noise (AWGN) channel based on soft-decision maximum likelihood decoding. Error probabilities of some specific codes are evaluated by simulation and upper bounds based on their Euclidean weight distributions 相似文献
2.
Schlegel C. Costello D.J. Jr. 《Selected Areas in Communications, IEEE Journal on》1989,7(9):1356-1368
The authors apply a general method of bounding the event error probability of TCM (trellis-coded modulation) schemes to fading channels and use the effective length and the minimum-squared-product distance to replace the minimum-free-squared-Euclidean distance as code design parameters for Rayleigh and Rician fading channels with a substantial multipath component. They present 8-PSK (phase-shift-keying) trellis codes specifically constructed for fading channels that outperform equivalent codes designed for the AWGN (additive white Gaussian noise) channel when v ⩾5. For quasiregular trellis codes there exists an efficient algorithm for evaluating event error probability, and numerical results which demonstrate the importance of the effective length as a code design parameter for fading channels with or without side information have been obtained. This is consistent with the case for binary signaling, where the Hamming distance remains the best code design parameter for fading channels. The authors show that the use of Reed-Solomon block codes with expanded signal sets becomes interesting only for large value of E s/N 0, where they begin to outperform trellis codes 相似文献
3.
Johannesson R. Wittenmark E. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1998,44(4):1602-1604
For rate R=1/2 convolutional codes with 16 states there exists a gap between Heller's (1968) upper bound on the free distance and its optimal value. This article reports on the construction of 16-state, binary, rate R=2/4 nonlinear trellis and convolutional codes having d free=8; a free distance that meets the Heller upper bound. The nonlinear trellis code is constructed from a 16-state, rate R=1/2 convolutional code over Z4 using the Gray map to obtain a binary code. Both convolutional codes are obtained by computer search. Systematic feedback encoders for both codes are potential candidates for use in combination with iterative decoding. Regarded as modulation codes for 4-PSK, these codes have free squared Euclidean distance dE, free2=16 相似文献
4.
Calderbank A.R. Pottie G.J. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1992,38(6):1791-1795
An upper bound on the minimum squared distance of trellis codes by packing Voronoi cells is derived and compared with previously known bounds. The authors focus on codes with small memory for modulation formats such as pulse amplitude modulation (PAM), m -ary quadrature amplitude modulation (QAM), and m -ary phase shift keying (PSK). The bound is tight to search results for coset codes with a small number of states 相似文献
5.
Hole K.J. Ytrehus O. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1994,40(2):482-493
A coset of a convolutional code may be used to generate a zero-run length limited trellis code for a 1-D partial-response channel. The free squared Euclidean distance, dfree2, at the channel output is lower bounded by the free Hamming distance of the convolutional code. The lower bound suggests the use of a convolutional code with maximal free Hamming distance, dmax(R,N), for given rate R and number of decoder states N. In this paper we present cosets of convolutional codes that generate trellis codes with dfree 2>dmax(R,N) for rates 1/5⩽R⩽7/9 and (d free2=dmax(R,N) for R=13/16,29/32,61/64, The tabulated convolutional codes with R⩽7/9 were not optimized for Hamming distance. Instead, a computer search was used to determine cosets of convolutional codes that exploit the memory of the 1-D channel to increase dfree2 at the channel output. The search was limited by only considering cosets with certain structural properties. The R⩾13/16 codes were obtained using a new construction technique for convolutional codes with free Hamming distance 4. Newly developed bounds on the maximum zero-run lengths of cosets were used to ensure a short maximum run length at the 1-D channel output 相似文献
6.
The concept of punctured convolutional codes is extended by punctuating a low-rate 1/N code periodically with period P to obtain a family of codes with rate P /(P +l), where l can be varied between 1 and (N -1)P . A rate-compatibility restriction on the puncturing tables ensures that all code bits of high rate codes are used by the lower-rate codes. This allows transmission of incremental redundancy in ARQ/FEC (automatic repeat request/forward error correction) schemes and continuous rate variation to change from low to high error protection within a data frame. Families of RCPC codes with rates between 8/9 and 1/4 are given for memories M from 3 to 6 (8 to 64 trellis states) together with the relevant distance spectra. These codes are almost as good as the best known general convolutional codes of the respective rates. It is shown that the same Viterbi decoder can be used for all RCPC codes of the same M . the application of RCPC codes to hybrid ARQ/FEC schemes is discussed for Gaussian and Rayleigh fading channels using channel-state information to optimise throughput 相似文献
7.
Pietrobon S.S. Costello D.J. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1993,39(2):325-336
Trellis coding using multidimensional quadrature amplitude modulation (QAM) signal sets is investigated. Finite-size 2D signal sets are presented that have minimum average energy, are 90° rotationally symmetric, and have from 16 to 1024 points. The best trellis codes using the finite 16-QAM signal set with two, four, six, and eight dimensions are found by computer search (the multidimensional (multi-D) signal set is constructed from the 2-D signal set). The best moderate complexity trellis codes for infinite lattices with two, four six, and eight dimensions are also found. The minimum free squared Euclidean distance and number of nearest neighbors for these codes were used as the selection criteria. Many of the multi-D codes are fully rotationally invariant and give asymptotic coding gains up to 6.0 dB. From the infinite lattice codes, the best codes for transmitting J , J +1/4, J +1/3, J +1/2, J +2/3, and J +3/4 b/sym (J an integer) are presented 相似文献
8.
Wu J. Costello D.J. Jr. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1992,38(3):933-939
Set partitioning is applied to multidimensional signal spaces over GF(q ), i.e., GFn1(q ) (n 1⩽q ), and it is shown how to construct both multilevel block codes and multilevel trellis codes over GF(q ). Multilevel (n , k , d ) block codes over GF(q ) with block length n , number of information symbols k , and minimum distance d min⩾d are presented. These codes use Reed-Solomon codes as component codes. Longer multilevel block codes are also constructed using q -ary block codes with block length longer than q +1 as component codes. Some quaternary multilevel block codes are presented with the same length and number of information symbols as, but larger distance than, the best previously known quaternary one-level block codes. It is proved that if all the component block codes are linear. the multilevel block code is also linear. Low-rate q -ary convolutional codes, word-error-correcting convolutional codes, and binary-to-q -ary convolutional codes can also be used to construct multilevel trellis codes over GF(q ) or binary-to-q -ary trellis codes 相似文献
9.
Vinck H. Post K. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1989,35(4):902-906
The application of a combined test-error-correcting procedure is studied to improve the mean time to failure (MTTF) for degrading memory systems with defects. The degradation is characterized by the probability p that within a unit of time a memory cell changes from the operational state to the permanent defect state. Bounds are given on the MTTF and it is shown that, for memories with N words of k information bits, coding gives an improvement in MTTF proportional to (k /n ) N (d min-2)/(d min -1), where d min and (k /n ) are the minimum distance and the efficiency of the code used, respectively. Thus the time gain for a simple minimum-distance-3 is proportional to N -1. A memory word test is combined with a simple defect-matching code. This yields reliable operation with one defect in a word of length k +2 at a code efficiency k /(k +2) 相似文献
10.
The trellis coding technique is applied to line-coded baseband digital transmission systems. For R =n /n +1(n =1,2,3) coding rates, a new codeword assignment model is proposed to accomplish basic requirements for line coding in which each length n binary data sequence is encoded into a length n +1 ternary (+,0,-) line codeword chosen among the code alphabet with 2n+2 elements. Assuming Viterbi decoding, the system error performance is improved by increasing the free Euclidean distance between coded sequences. A new algorithm is given for the calculation of the free distance between line-coded sequences so obtained. For R =1/2 and R =3/4 rates, the analytical error performance upper bounds are derived. The power spectral densities of the new line codes are also calculated and compared with those of known line codes 相似文献
11.
Channel coding due to trellis modulation has been proved to be useful for bandlimited channels. However, these modulations, mostly designed with n -use of 2D signals, are primarily aimed at coding gain only. It is pointed out that utilization of all available signal dimensions, which is limited by the time-bandwidth product, may improve the bandwidth efficiency and simultaneously bring an additional coding gain. Trellis coding with a spectrally efficient 4D signal set based on Q2PSK is addressed. Without any expansion of the Q 2PSK signal set, a simple hand-designed 16-state trellis code provides a coding gain of 6.02 dB. With the same number of states in G. Ungergoeck's (1982) 8-PSK trellis, the gain is 4.1 dB. In low intersymbol interference situations, the bandwidth efficiency of this coded Q2PSK is twice that of coded 8-PSK; if both operate at 2 b/s Hz and P b(E )=10-5, the coded Q2PSK provides a saving of about 4 dB over the coded 8-PSK. Some fully connected trellises with an expanded signal due to 2-use of Q2PSK signals are also presented. Two such codes ar rate-7/8 achieve a gain of 5.45 dB with only eight states 相似文献
12.
Ehrhard D. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1993,39(3):743-751
A decoding algorithm for codes arising from algebraic curves explicitly constructable by Goppa's construction is presented. Any configuration up to the greatest integer less than or equal to (d *-1)/2 errors is corrected by the algorithm whenever d *⩾6g , where d * is the designed minimum distance of the code and g is the genus of the curve. The algorithm's complexity is at most O ((d *)2 n ), where n denotes the length of the code. Application to Hermitian codes and connections with well-known algorithms are explained 相似文献
13.
The quantitative relationship between field-effect mobility (μ FE) and grain-boundary trap-state density (N t ) in hydrogenated polycrystalline-silicon (poly-Si) MOSFETs is investigated. The focus is on the field-effect mobility in MOSFETs with N t 1×102 cm-2. It is found that reducing N t to as low as 5×1011 cm-2 has a great impact on μFE. MOSFETs with the N t of 4.2×1011 cm-2 show an electron mobility of 185 cm2/V-s, despite a mean grain size of 0.5 μm. The three principal factors that determine μFE, namely, the low-field mobility, the mobility degradation factor, and the trap-state density N t are clarified 相似文献
14.
Maruyama A. Shen D.S. Chu V. Liu J.Z. Campbell I. Fauchet P.M. Wagner S. 《Electron Devices, IEEE Transactions on》1989,36(12):2853-2858
A detailed study of the growth of amorphous hydrogenated fluorinated silicon (a-Si:H, F) from a DC glow discharge in SiF4 and H2 is discussed. The electrical properties of the films can be varied over a very wide range. The bulk properties of the best films that were measured included an Urbach energy E u =43 meV, a deep-level defect density N s=1.5×1015 cm-3, and a hole drift mobility of 8×10-3 cm2 V-1 s-1, which reflects a characteristic valence band energy of 36 meV. It was found that E u, N s, and the density of surface states N ss are related to each other. Under the deposition condition of the films with the best bulk properties, N ss reaches its highest value of 1×1014 cm-2. It is suggested that in growth from SiF4/H2, the density of dangling bonds at the growing surface is very sensitive to the deposition conditions 相似文献
15.
The carrier-induced index change was measured using a novel injection-reflection technique in combination with differential carrier lifetime data. The observed relation between index change and injected carrier density at bandgap wavelength is nonlinear and is approximately given by δn act=-6.1×10-14 ( N )0.66 for a 1.5-μm laser and δn act=-1.3×10-14 (N )0.68 for a 1.3-μm laser. The carrier-induced index change for a 1.3-μm laser at 1.53-μm wavelength is smaller and is given by δn act=-9.2×10-16 (N )0.72 相似文献
16.
On the Hamming distance properties of group codes 总被引:1,自引:0,他引:1
Forney G.D. Jr. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1992,38(6):1797-1801
Under certain mild conditions, the minimum Hamming distance D of an (N , K , D ) group code C over a non-abelian group G is bounded by D ⩽N -2K +2 if K ⩽N /2, and is equal to 1 if K >N /2. Consequently, there exists no (N , K , N -K +1) group code C over an non-abelian group G if 1<K <N . Moreover, any normal code C with a non-abelian output space has minimum Hamming distance equal to D =1. These results follow from the fact that non-abelian groups have nontrivial commutator subgroups. Finally, if C is an (N , K , D ) group code over an abelian group G that is not elementary abelian, then there exists an (N , K , D ) group code over a smaller elementary abelian group G '. Thus, a group code over a general group G cannot have better parameters than a conventional linear code over a field of the same size as G 相似文献
17.
A concatenated coded modulation scheme is presented for error control in data communications. The scheme is achieved by concatenating a Reed-Solomon outer code and a bandwidth efficient block inner code for M -ary phase-shift keying (PSK) modulation. Error performance of the scheme is analyzed for an additive white Gaussian noise (AWGN) channel. It is shown that extremely high reliability can be attained by using a simple M -ary PSK modulation inner-code and a relatively powerful Reed-Solomon outer code. Furthermore, if an inner code of high effective rate is used, the bandwidth expansion required by the scheme due to coding will be greatly reduced. The scheme is particularly effective for high-speed satellite communications for large file transfer where high reliability is required. A simple method is also presented for constructing block codes for M -ary PSK modulation. Soome short M -ary PSK codes with good minimum squared Euclidean distance are constructed. These codes have trellis structure and hence can be decoded with a soft-decision Viterbi decoding algorithm. Furthermore, some of these codes are phase invariant under multiples of 45° rotation 相似文献
18.
It has been well established that the appropriate criterion for optimum trellis-coded modulation design on the additive white Gaussian noise channel is maximization of the free Euclidean distance. It is shown that when the trellis-coded modulation is used on a Rician fading channel with interleaving/deinterleaving, the design of the code of optimum performance is guided by other factors, in particular, the length of the shortest error-event path, and the product of branch distances (possibly normalized by the Euclidean distance of the path) along the path. Although maximum free distance (d free) is still an important consideration, it plays a less significant role the more severe the fading is on the channel. These considerations lead to the definition of a new distance measure of optimization of trellis codes transmitted over Rician fading channels. If no interleaving/deinterleaving is used, then once again the design of the trellis code is guided by maximizing d free 相似文献
19.
衰落信道下TCM好码的设计准则是使有效码长度最长,同时使其对应路径的欧几里德距离乘积最大。本文首先从理论上得到有效码长度与卷积编码器的状态数,并行输入数之间的关系。提出了一种能达到最大自由长的状态转移图-标准拓扑篱笆图的概念,在此基础上,对衰落信道下采用速率为(2/3)8PSK信号集合时的TCM好码进行搜索,与文献中已有码相比,利用准则判别和进行蒙特-卡洛模拟都说明了新码在抗衰落方面的良好性能。 相似文献
20.
Perotti A. Benedetto S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2006,52(12):5501-5509
This correspondence presents an upper bound on the minimum distance of serially concatenated codes with interleaver where the inner code is a systematic recursive convolutional encoder and the outer code is any convolutional encoder. The resulting expression shows that the minimum distance of the concatenated code cannot grow more than O(K1-1/df (O)), where K is the information word length, and df (O) is the free distance of the outer code. The obtained upper bound is shown to agree with and, in some cases, improve over previously known results 相似文献