Haksun Kim

A Fully Integrated UHF-Band CMOS Receiver With Multi-Resolution Spectrum Sensing (MRSS) Functionality for IEEE 802.22 Cognitive Radio Applications

Fast and accurate spectrum sensing is one of the most important functions in a cognitive radio (CR) seeking to use the licensed but unoccupied spectrum segments. In this paper, we present a fully integrated CMOS receiver with a CR spectrum sensing capability in the UHF band. We propose multi-resolution spectrum sensing (MRSS), which is a digitally-assisted analog energy detection technique. Without using bulky analog filters, detection bandwidth can be flexibly controlled by correlating the received analog signals with window signal generated by built-in digital window generator. The integrated chip has been fabricated in a standard 0.18-mumm CMOS technology, and has achieved 32 dB of detection dynamic range with minimum detection sensitivity of -74 dBm by using a 100-kHz cos4 window.

A Fully-Integrated UHF Receiver with Multi-Resolution Spectrum-Sensing (MRSS) Functionality for IEEE 802.22 Cognitive-Radio Applications

Recently, cognitive radio (CR) technology has been proposed as a way of increasing spectrum utilization efficiency. A CR system seeks to use the unoccupied spectrum segments by sensing the spectrum before transmitting to preserve the rights of privileged primary users (Haykin, 2006). IEEE 802.22 is the working group on wireless regional area network (WRAN) for the license-exempt use of the U.S. TV broadcasting band. Such use requires that new transceivers possess CR functionality. A fully-integrated CMOS receiver is presented with a CR spectrum-sensing functionality of arbitrary detection bandwidth over the UHF band. This capability is called multi-resolution spectrum sensing (MRSS).

Interference Analysis and Sensing Threshold of Detect and Avoid (DAA) for UWB Coexistence with WiMax

Although ultra wideband (UWB) is a promising wireless technology for the future due to its high data rate, low power consumption, and low cost, its worldwide acceptance is conditioned by coexistence issues because of the frequency overlap with other wireless standards such as WiMax. In many countries, a detect and avoid (DAA) scheme has been promoted as a means to mitigate interference and it is now regarded as an indispensable solution for commercialization of UWB. A detailed specification for DAA can be determined by analyzing co-channel interference for a victim receiver. This paper presents a quantitative interference analysis using desired to undesired (D/U) signal power ratio as well as verification results using an equipment-based WiMax testbed. Finally, the D/U ratio results were used to determine minimum keep-out distance and the sensing threshold level for DAA in a UWB device.

Implementation Issues of A Wideband Multi-Resolution Spectrum Sensing (MRSS) Technique for Cognitlve Radio (CR) Systems

Spectrum sensing is a key function for a cognitive radio (CR) system. An analog-based multi-resolution spectrum sensing (MRSS) technique was proposed as a flexible, low-power, high-speed spectrum-sensing solution. In this paper, implementation issues of the MRSS technique are investigated, and the corresponding practical specifications are suggested. First, nonlinear effects from a voltage-controlled oscillator (VCO) and multipliers are explored. System simulation results show that harmonic distortion components of VCO and wavelet-pulse power levels should be controlled to alleviate these nonlinear effects. Afterward, I/Q phase- and gain-mismatch effects ore addressed. Specifically, narrow-band signals are more sensitive to these gain and phase mismatches compared to broadband digital modulated signals. Overall, phase mismatch is more sensitive than gain mismatch on MRSS performance, showing a linear degradation of a detected power-level up to a 60-degree phase-mismatch

A Cognitive Radio (CR)-Based Mobile Interactive Digital Broadcasting Application adopting a Multi-Resolution Spectrum-Sensing (MRSS) Technique

Digital interactive mobile broadcasting application realizes the delivery of multimedia service and new value-added services for consumers and business areas. Meanwhile, one of the challenging issues for its successful deployment is radio spectrum resource management for the interactive feature and the broadcasting of additional contents besides the existing digital TV programs. In this paper, a Cognitive Radio (CR)-based digital interactive mobile broadcasting application is introduced. User terminals may scan or sense the received spectrum to find the spectrum resource, which is effectively unused for the certain time, area and location. These additional spectrum resources may be recycled and utilized as the return channel spectrum resource for the interactive broadcasting feature. Moreover, this work suggested a wideband Multi-Resolution Spectrum-Sensing (MRSS) technique based on a wavelet transform and a tri-stage detection algorithm. Accordingly, the MRSS technique offers flexible spectrum-sensing resolutions providing accurate, reliable and fast detection performance. Simulations were performed for detection of the American digital TV

An Ultra-Wideband Antenna Design Using Sierpinski Sieve Fractal

A trapezoid ultra-wideband antenna using Sierpinski sieve fractal was proposed to reduce the size and expand the bandwidth of the antenna. The effect of the fractal iteration factor (Kn) on the return loss of the antenna was simulated. The return loss, group delay, and path loss (|S 21|) of the antenna were simulated and measured to show that the proposed antenna may be used well for UWB applications with the wide operating bandwidth and good impedance matching. The radiation characteristics of dipole-like pattern and gain variation (2–4 dBi) were obtained over the frequency band.

A CR Platform for Applications in TV Whitespace Spectrum

A cognitive radio platform for whitespace spectrum in UHF TV band is introduced. The purpose of the CR platform is to evaluate the feasibility of the unlicensed wireless service in the UHF TV band. The platform consists of RF, baseband modem and MAC including spectrum sensing function. The performance of the spectrum sensing function combined with wideband RF IC which is designed for mobile broadcasting service in multiple bands is presented.

Analog integrator and analog-to-digital converter effect on a Multi-Resolution Spectrum Sensing (MRSS) for cognitive radio systems

The proposed multi-resolution spectrum sensing (MRSS) technique is a flexible, low-power, high-speed spectrum-sensing solution for cognitive radio systems. Meanwhile, impairments of analog building blocks may degrade the accuracy of the proposed MRSS performance. In this paper, the effect of non-idealities of an integrator is explored. The dominant pole position is suggested to be less than 20% of the spectrum-sensing resolution- bandwidth. Then, the quantization effect of an analog-to-digital converter (ADC) is addressed when one of a linear amplifier and logarithmic amplifier is present in front of the ADC, respectively. A 7-bit ADC is suggested when a high-dynamic- range logarithmic amplifier is accompanied.

A Direct IQ-Regeneration Technique for Five-Port Digital Receiver

Many papers have been proposed in order to demonstrate that the multi-port system. The main advantage of the multi-port system is the frequency direct conversion. However, this kind of system must be calibrated for each frequency in order to demodulate the exact inphase (I) and quadrature (Q) signal transmitted and further be compensated to the path errors of multi-port. But, this paper is to show the new method to recover the wanted signals without calibration and iteration procedure to update the information. This technique uses the least square solution using pseudo inverse caused to the singular value decomposition (SVD) receiving matrix of multi-ports. The pseudo-inverse operation can separate desired branches from the observation of multi-port output and this method is introduced in this paper. Also, this paper shows the full digital five port receiver which uses the only digital processor applied the down sampling conception to be low the carrier frequency sampling rate. Except the antenna and low noise amplifier of the analog signals at front-end of the system, this system is consists of the digital five-port network and digital signal processing (DSP) sections. Ultimately, the target of this system is on software defined radio (SDR) system implemented down sampling method and regeneration skill of I and Q signals.

A novel linear polar transmitter architecture using low-power analog predistortion for EDGE applications

This paper presents a new polar transmitter architecture that employs analog predistortion to provide substantially instantaneous correction of amplitude and phase errors in RF PAs. This approach enables to enhance the linear output power capability and efficiency of a PA, simultaneously. Unlike conventional architectures using a closed-loop feedback, no downconversion receiver is included in the transmitter. Moreover, only even-order distortion components are used to predistort the input signal in a multiplicative manner so that the effective correction bandwidth is greatly enhanced. For validation of the architecture, a PA circuit model was designed, based upon the TSMC 0.18-um CMOS technology. In the simulation results, the proposed architecture reduced PA nonlinearity from 2 dB to 0.5 dB for gain and from 18deg to plusmn0.5deg for phase. Also, the simulation results exhibited EVMs of less than 0.5% in RMS and 5% in peak, a PAE of 58% at the output power of 33 dBm.