Kyujin Lee

PAPR Reduction in SC-FDMA by Pulse Shaping Using Parametric Linear Combination Pulses

A linear combination between two intersymbol interference (ISI) free parametric linear pulses was proposed in order to obtain a new family of Nyquist pulses. The new family of pulses is utilized for pulse shaping to reduce peak-to-average power ratio (PAPR). The proposed pulse contains a new design parameter, μ, giving an additional degree of freedom to minimize PAPR for a given roll-off factor, α, and transmission scheme. While keeping the same bandwidth, the frequency responses of the proposed pulses differ with different values of the parameter μ for a fixed roll-off factor. Simulations showed that PAPR reduction is achieved when compared to that of other existing filters for the interleaved subcarrier mode of single carrier frequency division multiple access (SC-FDMA).

Performance analysis of visible light communication using the STBC-OFDM technique for intelligent transportation systems

Visible light communication (VLC) applied in an intelligent transportation system (ITS) has attracted growing attentions, but it also faces challenges, for example deep path loss and optical multi-path dispersion. In this work, we modelled an actual outdoor optical channel as a Rician channel and further proposed space-time block coding (STBC) orthogonal frequency-division multiplexing (OFDM) technology to reduce the influence of severe optical multi-path dispersion associated with such a mock channel for achieving the effective BER of 10−6 even at a low signal-to-noise ratio (SNR). In this case, the optical signals transmission distance can be extended as long as possible. Through the simulation results of STBC-OFDM and single-input-single-output (SISO) counterparts in bit error rate (BER) performance comparison, we can distinctly observe that the VLC–ITS system using STBC-OFDM technique can obtain a strongly improved BER performance due to multi-path dispersion alleviation.

PAPR reduction in single carrier FDMA uplink system using parametric linear pulses

Parametric linear pulses are implemented for pulse shaping in order to reduce peak-to-average power ratio (PAPR) in single carrier frequency division multiple access (SC-FDMA) schemes. The parametric linear pulses reduce the PAPR, while maintain the same excess bandwidth and the zero intersymbol condition; therefore, satisfying the Nyquist-I criterion. In this paper, we analytically derive the time and frequency domain parametric linear pulse (for n=1) based on the analysis from [10] and then verify the result using Scanlans [9] observations. Simulation results show that the parametric linear pulse (for n=1) has a lower PAPR compared to the PAPR of the RC filter, which is widely used in wireless communications.

PAPR Reduction in Single Carrier FDMA Uplink by Pulse Shaping Using a β-α Filter

A novel pulse shaping filter satisfying the Nyquist-I criterion was derived and implemented to reduce the peak-to-average power ratio (PAPR) over a Single Carrier Frequency Division Multiple Access (SC-FDMA) scheme. The new filter reduces the PAPR, while maintaining the same excess bandwidth and the zero intersymbol interference condition. The novel filter contains a new design parameter β to minimize PAPR, which is independent from the roll-off factor α. The minimum PAPR of the SC-FDMA scheme is linked to the value given to the parameter β for a specific roll-off factor α. Several simulations showed that PAPR is reduced greatly compared to that of the raised cosine filter, which is widely used in wireless communications. The performance of the proposed pulse shaping filter, regarding PAPR, is also compared with those of other conventional filters, demonstrating that the new filter has a superior performance.

Adaptive Resource Allocation for the PB/MC-CDMA System in Frequency Selective Fading Channels

We propose Adaptive Resource Allocation for the Partial Block MC-CDMA (ARA-PB/MC-CDMA) system. The ARA-PB/MC-CDMA system aims to improve total throughput performance and frequency efficiency across various channel conditions. It adaptively changes the number of blocks to improve the throughput performance and frequency efficiency according to the Signal to Interference Ratio (SIR). Therefore, the proposed system supports various Quality of Service (QoS) requirements for various SIR values.

Clustered OFDMA in the multi-path fading channel

In this paper, we proposed a new modulation and multiplexing technique named Adaptive Spreading Orthogonal Frequency Division Multiple Access (AS-OFDMA). AS-OFDMA might be an efficient system which is more robust against multi-path fading channel. Therefore, the performance of the proposed system is better than the conventional MC-CDMA. Moreover, AS-OFDMA solves the problem of inter code interference. In this paper, we introduce the proposed system and demonstrate the superiority of the proposed system by the computer simulation. We also show the performance comparison between the proposed system and the conventional MC-CDMA technique.

Indoor LED-Based identification systems using adaptive MMSE equalizer for optical multipath dispersion reduction

In this paper, we investigate a novel identification (ID) system using LED light as emitter, named as LED-ID. In such a system, the optical signals are typically modeled as a reflection component and a directed line of sight (LOS) component, since the signals are transmitted over the non-directed LOS links. Therefore, inter-symbol interference (ISI) induced by multipath dispersion that results from optical signals passing through more than one path critically influences the performance of optical wireless (OW) communications. In this paper, we propose the adaptive MMSE equalizer scheme to suppress the multipath ISI, since this scheme can minimize the mean square error (MSE) between the desired equalizer output and the actual equalizer output. We compared the following two algorithms: least mean square (LMS) and recursive least square (RLS). Our computer simulations demonstrated that LED-ID using an adaptive MMSE equalizer can alleviate the serious effects of optical multipath dispersion.

Outdoor environment LED-identification systems integrate STBC-OFDM

In an outdoor environment light emitting diodes-identification (LED-ID) systems, the provision of real-time location information to mobile users has become an active area of research. Visible light communication (VLC) in a LED-ID system offers the promise of a safe, efficient, reliable, and environmentally friendly ID technique. However, there are still several problems associated with such a combination, especially optical multipath dispersion, which has a severe impact on the communication performance. In this paper, we simulated a realistic optical channel in outdoor environment and modeled it as a Rician channel. Based on such a channel model, we further proposed an effective scheme of STBC-OFDM to solve the severe optical multipath dispersion problem and to obtain a target BER of 10−6 at a low SNR, where the received optical signals suffer from deep optical path loss over a long propagation distance. By comparing the BER performances of STBC-OFDM and SISO, our simulation results demonstrated that the STBC-OFDM technique used in a LED-ID system can alleviate the serious effects of multipath dispersion and can tolerate a low SNR for a target BER of 10−6.

Study on Scalable Video Coding Signals Transmission Scheme using LED-ID System

In this paper, using the indoor LED-ID communication system have researched for how to transmit video signals. In LED-ID communications use the LEDs for lighting features at the same time communication is an effective way to implement. This proposed system using Visible light(RGB) as way to transmit signals, depends on the mixture RGB, which decided the color of light, moreover, each things determined their performance. However, if the video signal were fixed allocated RGB to transmit such as the original system, the importance of the each signals a different occur the limit on the quality of the video than SVC signals. In order to solve this problem in this paper, according to the RGB mixture ratios analyze the performance for the White LED, which analyzed based on allocating the SVC signal by transmitting to improve the quality of the video was about how researched.

Efficient Channel Allocation Algorithm with Partial CSI for the PB/MC-CDMA System

An efficient channel allocation algorithm is proposed for the Partial Block MC-CDMA system. Partial channel state information is used for determining the signal-to-noise ratio of all frequency-block-bands. The prior is done to maximize the frequency-block-band allocated to each block user. The proposed system improves the fairness among users and allocates frequency-block-bands with better channel conditions to each block user; hence, maximizes the system’s total throughput. The fairness of the proposed channel allocation algorithm is analyzed by using Jain’s fairness index, and compared to that of the conventional scheme. Moreover, the processing time needed to execute the proposed algorithm is calculated and compared with the conventional and optimal algorithms.