ITR: Information-Theoretic Limits in Data Storage Systems

数据存储系统是支撑现代信息时代的支柱之一。计算和通信技术的进步，以及将它们结合起来的网络，增加了从生物研究（例如，海量多媒体数据集的可视化和分析）到消费电子（例如，在数码相机中存储高分辨率图像、音频和视频数据）等应用中对大容量数据存储设备的需求。研究解决了确定记录信道中可实现的存储密度和数据传输速率的信息论限制的分析和数值方法。它还开发和评估可以接近或达到这些极限的调制，编码和信号处理技术。该研究既考虑了适用于“面向轨迹”存储设备（如磁盘和磁带）的一维通道模型，也考虑了与探索性面向页面和体积存储技术（如基于原子力显微镜的全息记录和热机械记录）相关的高维模型。更具体地说，新的信息理论和算法方法被用来研究记录信道容量的下限和上限，使用基于分析和经验的模型来研究纵向和垂直记录系统。二维和更高维度的信道信息速率的界限也正在开发中。为了达到接近理论极限的性能，需要新的信号处理和编码方法。在约束调制编码领域，本项目正在探索一维约束编码的分析和设计，以更有效地结合调制和纠错功能。二维及高维约束编码的新兴理论也在研究中，重点关注诸如多维约束系统的表示、约束容量的确定以及有效的编码和解码算法等基本问题。基于串联架构、图形代码模型和迭代解码的信道编码技术已被证明可以有效地实现某些无内存信道的容量。该项目的信道编码组件解决了与将这些新的强大编码概念应用于数据存储通道相关的理论和算法问题。特别是，该研究考虑了具有符号间干扰的信道的类涡轮和低密度奇偶校验码的设计和性能分析，消息传递解码器架构中延迟和复杂性之间的权衡，以及结合编码，均衡和检测的新方法，可以更接近记录信道容量。该项目还解决了二维记录系统中信道编码和检测的基本问题。

Data storage systems represent one of the pillars supportingthe modern information age. Advances in computing and communicationtechnologies, and the networks that incorporate them, have increasedthe demand for high capacity data storage devices in applicationsranging from biological research (e.g., the visualization and analysisof massive multimedia data-sets) to consumer electronics (e.g., thestorage of high-resolution image, audio, and video data in digital cameras).The research addressesanalytic and numerical methods for determining the information-theoreticlimits on achievable storage densities and data transfer rates inrecording channels. It also develops and evaluates modulation, coding,and signal processing techniques that can approach or achieve these limits.The research considers both one-dimensional channel models applicableto "track-oriented" storage devices, such as disks and tapes, as well ashigher-dimensional models relevant to exploratory page-oriented andvolumetric storage technologies, such as holographic recording andthermomechanical recording based upon atomic force microscopy.More specifically, new information-theoretic and algorithmic methods arebeing used to study lower and upper bounds on the capacity of recordingchannels, using analytical and empirically-based models for both longitudinaland perpendicular recording systems. Bounds on the information rates ofchannels in two and higher dimensions are also being developed.In order to achieve performance approaching the theoretical limits, newsignal processing and coding methods are required. In the areaof constrained modulation coding, the project is exploring the analysisand design of one-dimensional constrained codes that more efficientlycombine the functions of modulation and error-correction. The nascenttheory of constrained coding in two and higher dimensions is also beinginvestigated, with a focus on fundamental problems, such as representationof multi-dimensional constrained systems, determination of constraintcapacity, and efficient encoding and decoding algorithms.Channel coding techniques based upon concatenation architectures,graphical code models, and iterative decoding have been shown to effectivelyachieve capacity on certain memoryless channels. The channel codingcomponent of this project addresses theoretical and algorithmic problemsassociated with the application of these new and powerful coding conceptsto data storage channels. In particular, the research considers the designand performance analysis of turbo-like and low-density parity-check codesfor channels with intersymbol-interference, the trade-offs between latencyand complexity in message-passing decoder architectures, and new approachesto combining coding, equalization, and detection that can more closelyapproach the recording channel capacity. The project also addressesfundamental problems of channel coding and detection in two-dimensionalrecording systems.