Eonpyo Hong

Low Complexity Data Decoding for SLM-Based OFDM Systems without Side Information

Selected mapping (SLM) scheme is a well-known technique for peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems. To recover data at receiver, the SLM scheme requires transmission of the selected phase sequence index, e.g., side information (SI). In this letter, a new pilot phase sequence enabling data recovery without SI and a low complexity decoding scheme are proposed. The BER performance of the proposed scheme is approximately the same in comparison with the SLM scheme with SI and considerably better than that of the Maximum Likelihood (ML) decoding scheme. In addition, the computational complexity of the proposed decoding scheme is much lower, as compared to the ML decoding scheme.

Peak-to-Average Power Ratio Reduction in OFDM Systems Using All-Pass Filters

A low-complexity peak-to-average power ratio (PAPR) reduction scheme for orthogonal frequency division multiplexing (OFDM) systems is proposed. The proposed scheme produces OFDM sequences by rotating the symbol phase using multiple all-pass filters, whereas the phase rotation of conventional selected mapping (SLM) scheme is performed with multiple complex multiplication modules in conjunction with inverse fast Fourier transform (IFFT) modules. As such, the proposed scheme does not require multiple IFFT modules that incur a heavy computational burden. Analysis results show that the proposed PAPR reduction scheme can significantly decrease computational complexity over the SLM scheme, though the reduction is achieved at the cost of slightly worse PAPR reduction performance. As an instance, the proposed scheme with eight first order all-pass filters for 2048 subcarriers reduces the number of required multiplications by 69.2% and additions by 63.1% at a sacrifice of only 0.25 dB PAPR increase over the conventional SLM scheme with eight IFFT modules.

Pilot-Aided Side Information Detection in SLM-Based OFDM Systems

Selected mapping (SLM) based schemes effectively reduce the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) systems. However, they require side information (SI) transmission, which incurs a loss in the data throughput in addition to the increased system complexity. This paper presents a blind SLM scheme based on a decision metric obtained from pilot sub-channel responses. A novel SI detection method enabling low complexity data decoding is proposed. The SI is detected by exploiting the high autocorrelation between adjacent pilot sub-channel responses. The SI detection error rate is analytically derived and compared with that obtained by simulations. Simulation results of the data decoding scheme based on the proposed SI detection method show the bit error rate performance comparable to that of the simplified maximum likelihood (ML) data decoding scheme, while the computational complexity is close to that of the embedded SI based decoding scheme.

A Pilot Symbol Pattern Enabling Data Recovery Without Side Information in PTS-Based OFDM Systems

Partial transmit sequence (PTS) scheme is one of the most popular peak-to-average power ratio (PAPR) reduction schemes for orthogonal frequency division multiplexing (OFDM) systems. In the PTS scheme, one OFDM symbol is partitioned into disjointed sub-blocks, and each sub-block is multiplied by a phase factor to generate signals with low PAPR. For data recovery, receivers must have side information (SI), e.g., phase factors, from transmitters. In this letter, a novel data recovery scheme in PTS-based OFDM systems without SI is proposed. In the proposed scheme, an additional pilot symbol is intentionally inserted at the end of each sub-block, so that efficient data decoding based on channel estimation can be executed with known pilot symbols. Simulation results show that the BER performance of the proposed scheme without SI is approximately the same as those of the PTS scheme with perfect SI and a maximum likelihood decoding scheme. Considering the cost for SI encoding and decoding, the proposed scheme is practically more advantageous over the PTS scheme.

Adaptive phase rotation of OFDM signals for PAPR reduction

High peak-to-average power ratio (PAPR) of the orthogonal frequency division multiplexing (OFDM) signal causes signal distortion, due to nonlinear high power amplifier at the transmitter, and affects received signal quality at the receiver. To reduce the PAPR, various PAPR reduction schemes have been developed. Of these schemes, the tone reservation (TR) scheme and the active constellation extension (ACE) scheme are used for commercial OFDM systems such as the DVB-T2 system. This paper presents an adaptive allpass filter (AAPF)-based PAPR reduction scheme. The AAPF scheme does not incur mean power increment and spectral efficiency decrement unlike the TR scheme. The AAPF scheme can be used with constellation rotation whereas the ACE scheme has a fundamental limitation with it. Comparison of the PAPR performance and the computational complexity with the TR scheme is made and discussed. Bit error rate (BER) performance demonstrates that adoption of the AAPF scheme does not affect signal reception quality at the receiver.1.

Spectrum Sensing by Parallel Pairs of Cross-Correlators and Comb Filters for OFDM Systems With Pilot Tones

This paper proposes a new spectrum sensing method for orthogonal frequency division multiplexing (OFDM) systems with pilot tones for equalization convenience. The time-domain signal cross-correlation (TDSC) method exploits the periodic feature of pilot signals embedded in time-domain OFDM signals, while random data signals deteriorate the detection performance. The new spectrum sensing method employs parallel pairs of cross-correlators and comb filters, reducing the effect of random data signals by comb filters. Simulation results of the proposed method demonstrate that the sensing performance for any given misdetection probability is improved by around 1.2 dB in SNR over the TDSC method.

Merged SLM scheme for PAPR reduction of OFDM system with low complexity

Merged selected mapping (SLM) scheme is presented for reducing peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM). The concept of the proposed SLM scheme is based on a combination of advantages of the conventional low complexity SLM schemes by dividing inverse fast Fourier transform (IFFT) into k stage and remaining n-k stage and, then generating additional OFDM signal sequences without performing IFFT to the conventional SLM scheme. This scheme dramatically reduces computational complexity comparing with the conventional SLM schemes under the similar PAPR reduction performance.

Peak-to-Average Power Ratio Reduction for MISO OFDM Systems with Adaptive All-Pass Filters

A peak-to-average power ratio (PAPR) reduction based on adaptive all-pass filters (AAPFs) for multiple-input single-output orthogonal frequency division multiplexing systems with space-frequency block coding is proposed. The AAPF creates phase rotation to reduce the PAPR. With the scattered pilot pattern, the AAPF enables data recovery without side information (SI). The PAPR reduction performance and the BER performance with considered system parameters are comparable to those of the blind SLM (B-SLM) scheme and the low complexity SLM (LC-SLM) scheme with SI. The computational complexity is much lower than that of the B-SLM scheme and comparable to that of the LC-SLM scheme.

Efficient phase sequence generation for SLM scheme without side information

Selected mapping (SLM) scheme without side information (SI) using specially designed phase symbols to reduce peak-to-average power ratio (PAPR) was recently published. The PAPR reduction performance was achieved at the cost of degraded bit error rate (BER) performance. This paper will present a new pilot phase symbol generation improving the PAPR reduction performance without BER performance deterioration.

Parallel 4/spl times/4 transform architecture based on bit extended arithmetic for H.264/AVC

H.264/AVC, the latest standard for the coding of video signal, utilizes a 4/spl times/4 integer transform to concentrate energy of residual data in a few coefficients. In this paper, a new parallel 4/spl times/4 transform architecture based on bit extended arithmetic is proposed for H.264/AVC. Compared with the existing parallel architecture, the proposed architecture eliminates redundant logic through bit extended arithmetic. Simulation results show that the hardware complexity is decreased by 25% and the data processing rate is increased by 16%.