Chi-Yun Chen

Low-complexity pixel detection for images with misalignment and interpixel interference in holographic data storage

This paper presents an efficient solution to recovering data pixels of images that have undergone optical and electrical channel impairments in holographic data storage systems. The channel impairments considered include interpixel interference, three types of misalignment, and noise. The proposed misalignment-compensation scheme, consisting of realignment and rate conversion, can effectively eliminate misalignment with more than 84% reduction in additions and 74% reduction in multiplications. In addition, several low-complexity techniques are introduced to reduce the complexity of a two-dimensional maximum a posteriori pixel detection method by up to 95% and do so with negligible degradation in detection performance.

Design of a MIMO-OFDM baseband receiver for next-generation wireless LAN

In this paper, based on the IEEE 802.11n proposal, a MIMO-OFDM baseband receiver design for next-generation WLAN is proposed. A MIMO-OFDM receiver with algorithms for timing and frequency synchronization and MIMO detection is designed and simulated. Moreover, the circuits for all functional blocks in the receiver are also designed. Functional simulation results demonstrate that the proposed receiver design is capable of high link throughput with efficient spectrum utilization and is suitable for the application of next-generation wireless LAN

Design of a dual-mode baseband receiver for 802.11n and 802.16e MIMO OFDM/OFDMA

A dual mode 2×2 MIMO OFDM & OFDMA receiver is implemented with shared hardware resources. This dual mode receiver functions well in both static and mobile channels. It follows the specification requirement of EWC HT PHY V1.27 and IEEE 802.16e-2005, and proposes a PHY baseband simulation model to meet the specifications. Additionally, equalization supports both static and dynamic channel estimation. 2×2 MIMO STBC and V-BLAST are supported as well. A low cost ICI (inter-carrier interference) cancellation hardware is also proposed.

Turbo Receiver with ICI-Aware Dual-List Detection for Mobile MIMO-OFDM Systems

This paper presents a turbo receiver using the proposed ICI-aware Dual-List (IDL) MIMO detection method that can efficiently detect signals deteriorated by both inter-carrier interference (ICI) and inter-antenna interference (IAI). These two interferences often occur simultaneously in mobile multiple-input multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) communication systems. The IDL detector enhances ICI mitigation and avoids the notorious error propagation problem encountered in conventional interference mitigation/cancellation schemes. In addition, this study proposes three techniques to reduce the required computational complexity by 99.63% in complex additions, 99.69% in complex multiplications, and 67.25% in comparison operations. Simulation results confirm the theoretical upper bound and also show that the bit error rate performance of the receiver in high-mobility channels is comparable to that of a maximum-likelihood MIMO-OFDM receiver in stationary channels, i.e., the ICI-free scenario.

A Low-Complexity High-Performance Modulation Code for Holographic Data Storage

We propose a new two-dimensional (2D) modulation code for holographic data storage (HDS) systems. This code has a code rate of 3/4 and is called 6:8 variable-weight (VW) modulation code. Simulation results show that the 6:8 VW modulation code achieves a bit-error-rate (BER) of 10-3 with a coding gain of 5 dB and it outperforms the conventional balanced codes. In addition, we propose a modified decoding process, called two-step correlation, to further reduce the decoder complexity.

Hardware implementation of pixel detection in gray-scale holographic data storage systems.

This paper presents hardware implementation of an efficient solution to recovering gray-scale data pixels of images that have undergone interpixel interference in holographic data storage systems. The adopted algorithm, called the turbo receiver using interference-aware dual-list (TRIDL) detection, enjoys benefits of low error rate performance and low complexity. To verify the functionality and feasibility, this paper implements TRIDL detection with some circuit design techniques such as resource sharing on a field-programmable gate array.

Finite Rate Channel Feedback Design for Multiuser MIMO Downlink Beamforming Systems

An efficient finite rate channel feedback design for multiuser multi-input multi-output (MIMO) downlink beamforming systems with individual signal-to-interference-plus-noise ratio (SINR) constraints is proposed. We find that part of the decomposed channel matrix is irrelevant to the performance, and can be discarded to reduce the feedback load. The remaining information is further decomposed into two parts, and we find that unevenly quantizing these two parts is better than traditionally quantizing the whole matrix evenly. We then show that linearly scaling the number of quantization bits for only one of these two parts is sufficient to maintain a bounded system performance loss. Thus quantization bit allocation between these two parts can be easily done for different signal-to-noise ratios (SNR). Simulation results verify our analysis and show that the proposed design outperforms the existing scheme.

Modulation Codes for Optical Data Storage

In optical storage systems, sensitive stored patterns can cause failure in data retrieval and decrease the system reliability. Modulation codes play the role of shaping the characteristics of stored data patterns in optical storage systems. Among various optical storage systems, holographic data storage is regarded as a promising candidate for next-generation optical data storage due to its extremely high capacity and ultra-fast data transfer rate. In this chapter we will cover modulation codes for optical data storage, especially on those designed for holographic data storage. In conventional optical data storage systems, information is recorded in a one-dimensional spiral stream. The major concern of modulation codes for these optical data storage systems is to separate binary ones by a number of binary zeroes, i.e., run-length-limited codes. Examples are the eight-to-fourteen modulation (EFM) for CD (Immink et al., 1985), EFMPlus for DVD (Immink, 1997), and 17 parity preserve-prohibit repeated minimum run-length transition (17PP) for Blu-ray disc (Blu-ray Disc Association, 2006). Setting constraint on minimum and maximum runs of binary zeros results in several advantages, including increased data density, improved time recovery and gain control and depressed interference between bits. In holographic data storage systems, information is stored as pixels on two-dimensional (2D) pages. Different from conventional optical data storage, the additional dimension inevitably brings new consideration to the design of modulation codes. The primary concern is that interferences between pixels are omni-directional. Besides, since pixels carry different intensities to represent different information bits, pixels with higher intensities intrinsically corrupt the signal fidelity of those with lower intensities more than the other way around, i.e., interferences among pixels are imbalanced. In addition to preventing vulnerable patterns suffering from possible interferences, some modulation codes also focus on decoder complexity, and yet others focus on achieving high code rate. It is desirable to consider all aspects but trade-off is matter-of-course. Different priorities in design consideration result in various modulation codes. In this chapter, we will first introduce several modulation code constraints. Next, onedimensional modulation codes adopted in prevalent optical data storage systems are discussed. Then we turn to the modulation codes designed for holographic data storage. These modulation codes are classified according to the coding methods, i.e., block codes vs. strip codes. For block codes, code blocks are independently produced and then tiled to form a 1