Eon Kyeong Joo

A novel subblock partition scheme for partial transmit sequence OFDM

In general, there has been a trade-off between performance of peak-to-average power ratio (PAPR) reduction and computational complexity in partial transmit sequence (PTS) orthogonal frequency division multiplexing (OFDM). In this paper, a novel subblock partition scheme (SPS) for PTS OFDM is proposed and analyzed. In this scheme, signals assigned randomly in partial subbands are duplicated and concatenated repetitively to generate each subblock. The proposed scheme, therefore, has a form of concatenation of pseudo-random and interleaved SPS. As results of simulations, the proposed scheme shows almost same PAPR reduction performance as compared to the conventional pseudo-random SPS which has been known to have the best performance. However, computational complexity can be reduced extensively. Hence, the proposed scheme may be considered to be more suitable than the conventional ones for application in high speed transmission systems such as digital terrestrial broadcasting.

A comparative investigation on channel estimation algorithms for OFDM in mobile communications

A comparative investigation on various channel estimation algorithms for OFDM system in the mobile communication environment is presented and analyzed in terms of computational complexity, mean square error, and bit error rate in this paper. As a result, Wiener filter estimation shows the best error performance. Concerning the computational complexity as well as the performance, however, the piecewise linear estimator is considered as a proper choice when the reference signal spacing is relatively narrow. And the cubic-spline estimator is a good alternative to the Wiener filter estimation if the reference signal spacing is wider than the coherent bandwidth of transmission channel.

Performance of STBC with turbo code in HARQ scheme for mobile communication systems

The performance of STBC (space time block codes) concatenated with turbo codes in an HARQ (hybrid automatic repeat request) scheme is analyzed. When two transmitter antennas are used, up to 5dB and 10dB gains are obtained in AWGN and Rayleigh fading channels, respectively, as compared to the conventional one antenna system. Gain in the fading channel is much larger than in the AWGN channel. Therefore, STBC with turbo codes may be a suitable HARQ scheme for future third generation mobile communication systems such as cdma2000 and W-CDMA.

Bit probability transition characteristics of LDPC code

The characteristics of message bit probability transition, which appears in iterative decoding of LDPC (low density parity check) code, are analyzed. If sufficient iterative decoding is done, three types of bit transition characteristics are found in simulation. These bit probability transition characteristics seem to be related to the parity check matrix which makes iterative decoding possible, instead of the initial probability, which is dependent on channel condition.

Reduction of computational complexity in two-step SOVA decoder for turbo code

A new two-step soft output Viterbi algorithm (SOVA) for turbo decoder with reduced decoding complexity is proposed and analyzed in this paper. Due to the algebraic structure of the proposed scheme, state and branch metrics can be obtained with parallel processing of matrix arithmetic. As a result, the number of multiplications to calculate state metrics of each stage can be decreased tremendously. Therefore, it can be expected that the proposed algebraic two-step SOVA decoder is suitable for applications in future mobile communication systems in which less computational complexity is essential.

Corrections to “ A Comparative Investigation on Channel Estimation Algorithms for OFDM in Mobile Communications”

• The correct BER for Fig. 9(b) is illustrated. • The affiliation of Seog Geun Kang was printed incorrectly. The corrected affiliation should be: S. G. Kang is with the School of Electrical and Electronic Engineering, Gyeongsang National University, Jinju, Gyeongnam 660-701, Korea, and also with the Research Institute for Computer and Information Communication (RICIC) (e-mail: sgkang@gsnu.ac.kr).

An improved DC- and Nyquist-free error control line code

An improved DC- and Nyquist-free error control line code based on the (8,4) extended Hamming code is proposed and its performance is analyzed. To increase its code rate, two blocks of error control codes are used as a line code with simple pre-coding. The proposed code can be well suited for high speed communication links, where DC- and Nyquist-free pulse format, channel error control, and low-complexity encoder-decoder implementations are required. As results of performance analysis, the proposed code shows null points at DC and Nyquist frequency and low levels of complexity. In addition, the proposed code shows wider eyewidth due to its Nyquist-free property.<<ETX>>