Kyu-Min Kang

Maximum Transmission Rate of PSR/TSR Protocols in Wireless Energy Harvesting DF-Based Relay Networks

In this paper, we consider the power splitting relaying (PSR) and time switching relaying (TSR) protocols for decode-and-forward (DF)-based relay networks consisting of a source, a relay, and a destination. For the networks, the relay is assumed to have a rechargeable battery with a certain amount of remaining energy for energy harvesting through the received signal transmitted from the source. Specifically, for the PSR protocol with and without the direct-path, we present the outage probability expression with a given power splitting coefficient, and we obtain the optimum power splitting coefficient to maximize the transmission rate and derive its transmission rate and outage probability, where the optimum coefficient depends on channel conditions and remaining energy. For the TSR protocol with and without the direct-path, we present the outage probability expression with a given time switching coefficient, and we obtain the optimum time switching coefficient to maximize the transmission rate and derive its transmission rate, where the optimum coefficient also depends on channel conditions and remaining energy.

Implemention of 128-Point Fast Fourier Transform Processor for UWB Systems

In this paper, we present a 4-parallel fast Fourier transform (FFT) processor for a multi-band orthogonal frequency division multiplexing (MB-OFDM) ultra wideband (UWB) system. The proposed FFT processor utilizes radix-24 structure so as to significantly enhance the hardware complexity by reducing the numbers of multipliers and adders. The hardware efficient 4-parellel 128-point FFT processor employing the decimation-in-frequency (DIF) and the single-path delay feedback (SDF) algorithms can support throughput rates of up to 1 Gsample/s. The proposed FFT processor is implemented and tested by adopting the 0.18 mum CMOS technology with a supply voltage of 1.8 V.

A new scheme for compliance with TV white space regulations using Wi-Fi modules in a cognitive radio system

This paper presents a cognitive radio system (CRS) that complies with the maximum allowable transmit power and emission limits of TV band devices (TVBDs). The CRS consists of a TVBD that uses the existing Wi-Fi module and two Wi-Fi modules operating in the 2.4 GHz and 5 GHz bands. Design methods are proposed for a radio frequency (RF) module, a digital signal processing (DSP) module, and a circuit for transmit-receive mode switching in the TV band device (TVBD). The performance of the implemented TVBD is investigated in both wired and wireless environments. The measured data rates of the implemented TVBD at the application layer are approximately 60 % of the theoretical data rates at the physical layer in the Wi-Fi system. The service coverage of a TVBD network is also measured according to several modulation and coding schemes (MCSs) of the TVBD for a single spatial stream. The coverage measurements of a TVBD network are conducted in both a suburban area, Jeju Island, and a nearly open area, Incheon, South Korea. The results show that the service coverage of a mobile network in TV white space (TVWS) can be enlarged by more than 2 km in the suburban area and by more than 8 km in the nearly open area.

TV band device for TV white space field trial

This paper presents a TV white space (TVWS) field demonstration system complying with the maximum transmit power and emission regulatory requirements of the Federal Communications Commission (FCC). Recently, the service coverage measurement of a TV band device (TVBD) network has been conducted in Jeju Island, South Korea. The measurement results show that the service coverage of a mobile network can be enlarged up to more than 2 km with TVBDs operating in the available TV bands.

Cognitive Radio Networks With Secondary Network Selection

In this paper, we study cognitive radio (CR) networks that consist of multiple secondary TV band device (TVBD) station-user pairs and one primary digital TV (DTV) station-user pair, where each terminal has a single antenna. Specifically, we consider spectrum sharing (SS)-based secondary TVBD networks to effectively utilize limited spectrum resources in the presence of cochannel primary DTV interference. We first present an opportunistic single secondary network selection scheme to maximize the mutual information over all secondary TVBD networks under the constraint of the availability of the primary DTV service. Then, the performance bound of CR networks with the secondary network selection is obtained through the derivation of an exact and closed-form outage probability. It is shown that the derived outage probability is given as a function of transmission power, channel coefficients, and target rates of both the primary DTV network and the secondary TVBD networks.

FIR Filter of DS-CDMA UWB Modem Transmitter

This letter presents low-complexity digital pulse shaping filter structures of a direct sequence code division multiple access (DS-CDMA) ultra wide-band (UWB) modem transmitter with a ternary spreading code. The proposed finite impulse response (FIR) filter structures using a look-up table (LUT) have the effect of saving the amount of memory by about 50% to 80% in comparison to the conventional FIR filter structures, and consequently are suitable for a high-speed parallel data process.

Packet Detection for Zero-Padded OFDM Transmission

A packet detection method for zero-padded orthogonal frequency division multiplexing (OFDM) transmission is presented. The proposed algorithm effectively conducts packet detection by employing both an M-sample time delayed cross correlation value, and a received signal power calculated by using the received input samples corresponding to the zero padding (ZP) intervals or less.

Initial Acquisition for Next Generation MB-OFDM UWB Transmission

We present an efficient acquisition algorithm for a next-generation multi-band orthogonal frequency division multiplexing (MB-OFDM) ultra wideband (UWB) system. The simulation results show that the proposed packet detection algorithm which employs both an M-sample time delayed cross correlation value, and a received signal power calculated by using the received input samples less than zero padding (ZP) outperforms the conventional packet detection algorithms.

A design approach of radio frequency module for TV white space based on filter bank

This paper presents a design scheme of radio frequency (RF) module using filter bank in order to operate the overall TV broadcast band (470 MHz ~ 698 MHz). To this end, several band pass filters (BPFs) with a relatively sharp skirt characteristic are employed for compliance with TV white space (TVWS) regulations. Performance test results show that the error vector magnitude (EVM) of the implemented RF transmitting chain is less than 1.5 %. The noise figure (NF) of the RF receiving chain is measured to be 6.0 dB. From the results, the proposed RF module can be adequately utilized for TV white space applications.

A 24-parallel processing DS-UWB system

We present a hardware efficient 24-parallel processing architecture for the binary phase-shift keying (BPSK) direct sequence ultra-wideband (DS-UWB) system. A DS-UWB baseband modem is implemented and tested on the field programmable gate arrays (FPGAs) with a digital-to-analog (D/A) converter operating at the sampling rate of 1.32 GHz. Experimental results show that the DS-UWB prototype system delivers high definition (HD) content over a 5-m UWB channel with less than 1×10−9 bit error rate.