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Han S.I.,University of Texas at Dallas | Fonseka J.P.,University of Texas at Dallas | Dowling E.M.,Trellis Phase Communications
Electronics Letters | Year: 2013

A novel bit by bit row/column interleaver (BBRCI) design technique is proposed to significantly increase the minimum Hamming distance (MHD) of block accumulate codes (BACs), making them suitable for optical applications. The proposed BBRCI design method employs a separate row/column interleaver (RCI) for the transmission of each bit position of the outer block code. The numbers of rows of these individual RCIs are properly selected to increase the MHD of the resulting BAC and to reduce the frame size. It is demonstrated that BACs constructed with a BBRCI can be designed to have significantly higher MHD than similar BACs constructed with uniform inter-leavers (UI) and S type interleavers. Simulations show example BACs constructed with BBRCIs that perform significantly better than those BACs constructed with a UI. © The Institution of Engineering and Technology 2013. Source


Naim M.A.,University of Texas at Dallas | Fonseka J.P.,University of Texas at Dallas | Dowling E.M.,Trellis Phase Communications
IEEE Communications Letters | Year: 2015

A novel building block (BB) design approach is presented for systematically constructing multilevel codes (MLCs) under the balanced distances rule (BDR). In contrast to the traditional method of starting from an overall signal constellation and then using a mapping policy, the BB approach starts by designing a BB constellation for the first level of the MLC and then uses two copies of this BB to construct a second level constellation. This process is continued to the highest level by constructing the next level constellation using multiple copies of the current level constellation as a BB. Compared to the traditional method of construction of MLCs according to the BDR, the BB approach provides additional flexibility in selecting component codes and is able to exactly balance the distances of all levels. Compared with MLCs constructed using the traditional BDR approach, MLCs constructed using the BB approach have the same decoding complexity and perform better in the error floor region, which is typically the operating region for MLCs constructed with convolutional component codes. © 2014 IEEE. Source


Fonseka J.P.,University of Texas at Dallas | Dowling E.M.,Trellis Phase Communications | Han S.I.,University of Texas at Dallas | Hu Y.,University of Texas at Dallas
IEEE Communications Letters | Year: 2013

A novel constrained interleaving technique is proposed to improve serially concatenated codes (SCCs) with inner recursive convolutional codes (IRCCs). In this study, constrained interleavers are designed to achieve a minimum Hamming distance (MHD) for the SCC, dSCC, between dodi and do2di while simultaneously maximizing the interleaver gain, where do and di are the MHD of the outer and inner codes respectively. Constrained interleavers can be constructed to achieve dSCC=dodi while almost maintaining the interleaver gain of uniform interleaving. By imposing additional inter-row constraints, dSCC of constrained interleaving is increased beyond dodi up to do2di, however, at the expense of some interleaver gain. Numerical results demonstrate that constrained interleaving is an efficient way to construct SCCs with low error floors while achieving interleaver gain at relatively short interleaver sizes. © 1997-2012 IEEE. Source


Fonseka J.P.,University of Texas at Dallas | Dowling E.M.,Trellis Phase Communications | Brown T.K.,University of Texas at Dallas | Han S.I.,University of Texas at Dallas
IEEE Communications Letters | Year: 2012

Constrained interleaving is presented to improve the performance of turbo product codes. Traditional row/column interleaving achieves the highest possible minimum distance while ignoring the error coefficients, whereas uniform interleaving focuses on reducing the error coefficients while ignoring the minimum distance. Constrained interleaving achieves the highest possible minimum distance thereby forcing error coefficients of all contributions below the highest achievable minimum distance to zero while simultaneously lowering the error coefficients of the remaining contributions close to those of uniform interleaving. We present a lower bound for the error rate with constrained interleaving, and demonstrate using 2D and 3D SPC codes that the bound can be approached reasonably well with a constrained interleaver that is only 2 to 3 times the size of a row/column interleaver. Constrained interleaving performs better than row/column interleaving and the improvement becomes more significant with increasing order of SPC. While uniform interleaving typically uses large interleaver sizes and creates an undesirable error floor, constrained interleaving performs better at much shorter interleaver sizes and eliminates the error floor. © 2012 IEEE. Source


Naim M.A.,University of Texas at Dallas | Fonseka J.P.,University of Texas at Dallas | Dowling E.M.,Trellis Phase Communications
IEEE Communications Letters | Year: 2013

An improved hard iterative decoding (IHID) algorithm is presented to efficiently terminate hard iterations in the decoding of multi-level codes. The proposed terminating policy stops iterations as soon as a valid path on the super trellis is found thereby only running the minimum required number of iterations. The IHID decoding algorithm performs better than the conventional multi-stage decoding by reducing the effects of error multiplicity. Compared with known hard iterative decoding with fixed number of iterations, the IHID algorithm can significantly reduce decoding complexity and decoding delay. © 1997-2012 IEEE. Source

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