Parallelized architectures for low latency turbo structures

Download
2007
Gazi, Orhan
In this thesis, we present low latency general concatenated code structures suitable for parallel processing. We propose parallel decodable serially concatenated codes (PDSCCs) which is a general structure to construct many variants of serially concatenated codes. Using this most general structure we derive parallel decodable serially concatenated convolutional codes (PDSCCCs). Convolutional product codes which are instances of PDSCCCs are studied in detail. PDSCCCs have much less decoding latency and show almost the same performance compared to classical serially concatenated convolutional codes. Using the same idea, we propose parallel decodable turbo codes (PDTCs) which represent a general structure to construct parallel concatenated codes. PDTCs have much less latency compared to classical turbo codes and they both achieve similar performance. We extend the approach proposed for the construction of parallel decodable concatenated codes to trellis coded modulation, turbo channel equalization, and space time trellis codes and show that low latency systems can be constructed using the same idea. Parallel decoding operation introduces new problems in implementation. One such problem is memory collision which occurs when multiple decoder units attempt accessing the same memory device. We propose novel interleaver structures which prevent the memory collision problem while achieving performance close to other interleavers.

Suggestions

Direction finding for coherent, cyclostationary signals via a uniform circular array
Atalay Çetinkaya, Burcu; Koç, Arzu; Department of Electrical and Electronics Engineering (2009)
In this thesis work, Cyclic Root MUSIC method is integrated with spatial smoothing and interpolation techniques to estimate the direction of arrivals of coherent,cyclostationary signals received via a Uniform Circular Array (UCA). Cyclic Root MUSIC and Conventional Root MUSIC algorithms are compared for various signal scenarios by computer simulations. A cyclostationary process is a random process with probabilistic parameters, such as the autocorrelation function, that vary periodically with time. Most of ...
Fpga implementation of jointly operating channel estimator and parallelized decoder
Kılcıoğlu, Çağlar; Yılmaz, Ali Özgür; Department of Electrical and Electronics Engineering (2009)
In this thesis, implementation details of a joint channel estimator and parallelized decoder structure on an FPGA-based platform is considered. Turbo decoders are used for the decoding process in this structure. However, turbo decoders introduce large decoding latencies since they operate in an iterative manner. To overcome that problem, parallelization is applied to the turbo codes and the resulting parallel decodable turbo code (PDTC) structure is employed for coding. The performance of a PDTC decoder and...
Dense depth map estimation for object segmentation in multi-view video
Çığla, Cevahir; Alatan, Abdullah Aydın; Department of Electrical and Electronics Engineering (2007)
In this thesis, novel approaches for dense depth field estimation and object segmentation from mono, stereo and multiple views are presented. In the first stage, a novel graph-theoretic color segmentation algorithm is proposed, in which the popular Normalized Cuts 59H[6] segmentation algorithm is improved with some modifications on its graph structure. Segmentation is obtained by the recursive partitioning of the weighted graph. The simulation results for the comparison of the proposed segmentation scheme w...
Improvements to neural network based restoration in optical networks
Türk, Fethi; Bilgen, Semih; Department of Electrical and Electronics Engineering (2008)
Performance of neural network based restoration of optical networks is evaluated and a few possible improvements are proposed. Neural network based restoration is simulated with optical link capacities assigned by a new method. Two new improvement methods are developed to reduce the neural network size and the restoration time of severed optical connections. Cycle based restoration is suggested, which reduces the neural network structure by restoring the severed connections for each optical node, iterativel...
Neural network based beamforming for linear and cylindrical array applications
Güreken, Murat; Dural Ünver, Mevlüde Gülbin; Department of Electrical and Electronics Engineering (2009)
In this thesis, a Neural Network (NN) based beamforming algorithm is proposed for real time target tracking problem. The algorithm is performed for two applications, linear and cylindrical arrays. The linear array application is implemented with equispaced omnidirectional sources. The influence of the number of antenna elements and the angular seperation between the incoming signals on the performance of the beamformer in the linear array beamformer is studied, and it is observed that the algorithm improves...
Citation Formats
O. Gazi, “Parallelized architectures for low latency turbo structures,” Ph.D. - Doctoral Program, Middle East Technical University, 2007.