Chanho Yoon

A Hardware Efficient LDPC Encoding Scheme for Exploiting Decoder Structure and Resources

Previously, there has been no report on implementation effort to integrate LDPC encoder and decoder into a single hardware. In this paper, we propose a simple yet low complex systematic LDPC encoding method for class of quasi-cyclic low-density parity-check (QC-LDPC) codes to let LDPC encoder acquire an interchangeable structure, exploited in the decoder. With the proposed encoding scheme, implementation of the proposed encoder becomes much more hardware efficient than having a separate hardware due to LDPC encoder and decoder resource sharing. Moreover, the overall computational complexity of the proposed encoding scheme is lower than the well-known Richardsons efficient encoding scheme (A.T.J. Richardson and R.L. Urbanke, 2001).

Arbitrary Bit Generation and Correction Technique for Encoding QC-LDPC Codes with Dual-Diagonal Parity Structure

In this paper, we propose a simple yet low complex systematic LDPC encoding method for class of quasi-cyclic low-density parity-check (QC-LDPC) codes which have an efficient encoding/decoding algorithm due to the simple structure of their parity-check matrices. The proposed encoding method is applicable to parity-check matrices having dual-diagonal parity structure with single column of weight 3. Unlike finding a direct solution for parity bits in schemes (Richardson and Urbanke, 2001 and Classon and Blankeship, 2004), the proposed scheme first generates arbitrary parity bits. Then, given the parity bits for the first sub-block and exploiting the dual-diagonal structure, all parity bits are found through correction. With slight modification of parity-check matrix H, proposed LDPC encoding scheme is directly applicable to matrices defined in IEEE physical layer standards with almost negligible performance loss. Moreover, the overall computational complexity involving encoding process is lower than well-known Richardsons efficient encoding scheme (Richardson and Urbanke, 2001).

Combined ML and DFE Decoding for Coded Double STBC-OFDM System

An efficient combined maximum likelihood (ML) and decision feedback equalization (DFE) decoding method is proposed for a coded double space-time block code orthogonal frequency division multiplexing (DSTBC-OFDM) system. For the missing bit log likelihood ratios (LLRs) in the DFE part, our proposed detector effectively exploits Gaussian approximated LLRs with reference to the colored noise covariance matrix. Simulation results demonstrate that the proposed method can achieve comparable performance to the coded full ML detectors with deterministic and lower complexity.

Performance Evaluation of Space-Time Block Codes from Coordinate Interleaved Orthogonal Designs in Shadowed Fading Channels

In this correspondence, we evaluate the symbol error rate (SER) and information outage probability (IOP) of space-time block codes (STBCs) from coordinate interleaved orthogonal designs (CIODs) in the composite channel of lognormal shadowing and Rayleigh fading. By applying the Gauss-Hermite quadrature integration, we derive an accurate closed-form approximation for the symbol pairwise error rate (SPER) and corresponding tight upper and lower bounds on the SER of STBCs from CIODs. An accurate closed-form approximate formula for the IOP is also derived by formulating the composite squared lognormal/chi-square probability density function and exploiting the high-signal-to-noise-ratio (SNR) approximation technique. Furthermore, we investigate the achievability of full diversity in Rayleigh fading channels with shadowing effects. Finally, various Monte Carlo simulations are performed to validate our theoretical results.

A Novel ZF Detection Scheme for Double SFBC based OFDM System in Frequency Selective Fading Channel

In this paper, we propose an efficient low complexity MIMO detection method for double space-frequency block coded (D-SFBC) OFDM system. The proposed MIMO detector involves three-step filtering process to efficiently de-correlate spatially-multiplexed / space-frequency-coded signals without direct matrix inversion process. As the proposed MIMO detector takes advantage of frequency selectivity, not a favorable channel condition for SFBC system, performance degradation caused by low correlation between two consecutive subcarriers is compensated by assigning weighting factor for every subcarriers in frequency domain. From computer simulation results, our scheme in D-SFTD outperforms previously proposed suboptimal MIMO detection methods such as iterative interference cancellation based V-BLAST.

Joint Frame/Frequency Synchronization and Channel Estimation for Single-Carrier FDE 60 GHz WPAN System

It is well-known that the OFDM scheme has some tolerance for symbol/frame timing errors (i.e. valid starting position of FFT window). Such tolerance exist for SC-FDE. However, frame timing offset affects the receiver performance due to deviation in frequency domain channel estimation result when fractional channel estimation vector is applied in time domain. To achieve optimized receive performance at all times, symbol/frame timing must be estimated precisely in accordance to the exact starting position of the channel estimation sequence block. In this paper, we propose an efficient frame/frequency synchronization along with channel estimation technique suitable for implementation of SC-FDE based 60GHz WPAN physical layer systems employing a Frank-Zadoff preamble structure. The proposed method is designed for parallel processing, and is robust against carrier frequency offset in moderately dispersive multipath-fading LOS+NLOS channels.

FPGA implementation of 300Mbps 2×3 MIMO-OFDM transceiver for IEEE 802.11n wireless LANs

We present the design and implementation of a FPGA prototype for a 300Mbps 2x3 MIMO-OFDM transceiver that forms a complete IEEE 802.11n wireless LAN. We also demonstrate that the developed system provides robust and high-data-rate performance.

Effect of Generalized-K Fading on the Performance of Symmetric Coordinate Interleaved Orthogonal Designs

In this letter, an efficient method of evaluating the performance of space-time block codes (STBCs) from symmetrically structured coordinate interleaved orthogonal designs (CIODs) is presented over generalized-K MIMO fading channels. By effectively approximating the moment generating function (MGF), we derive approximate closed-form expressions for the symbol pairwise error rate (SPER) and corresponding tight approximate symbol error rate (SER) of STBCs from symmetric CIODs. Finally, various Monte-Carlo simulations are performed to validate our theoretical results.

Low-Complexity ZF Detection for Double Space-Frequency Transmit Diversity Based OFDM System in Frequency Selective Fading Channel

In this paper, we propose an efficient low complexity MIMO detection method for double space-frequency transmit diversity (D-SFTD) based coded OFDM system. The proposed MIMO detector involves three-step filtering process to efficiently de-correlate spatially-multiplexed and space-frequency-coded signals without direct matrix inversion process. As the proposed MIMO detector takes advantage of frequency selectivity, not a favorable channel condition for SFBC system, performance degradation caused by low correlation between two consecutive subcarriers is compensated by assigning weighting factor per subcarrier. From computer simulation results, our scheme in D-SFTD outperforms previously proposed suboptimal MIMO detection methods such as iterative interference cancellation based V-BLAST.

Efficient Soft-Output Demapping Method for MIMO-OFDM WLAN System

In this paper, a simplified soft-output demapping method is proposed for a coded MIMO-OFDM Wireless LAN system, only requiring 3-bit soft information. In particular, we apply bit-rounding and effective-bit threshold adjustment techniques, in order to effectively extract 3-bit soft information without performance degradation.