Kihong Kim

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.

Interference Mitigation in MIMO Systems by Subset Antenna Transmission

This paper investigates subset antenna transmission (SAT) for multiple-input multiple-output (MIMO) systems in the presence of strong dominant co-channel interferer. The capacity gain from SAT is investigated in the context of optimal antenna subset selection and power allocation. The SAT does not require channel state information of the co-channel interference, and achieves capacity gains by distributing the transmit power equally over a selected subset of the transmit antennas. The capacity gain of the SAT method is analyzed in terms of transmit power and eigenvalues of channel matrix, and its performance in V-BLAST MIMO systems with various signal constellations is evaluated by computer simulation.

Interference Mitigation in Asynchronous Slow Frequency Hopping BluetoothNetworks

In asynchronous slow frequency hopping Bluetooth networks, packet collisions diminish the total link throughput. However, interference mitigation capability can reduce packet losses due to collisions. In this paper, an interference cancelling dual decision feedback (IC-DDF) Bluetooth receiver is proposed and its performance is evaluated for slow fading indoor channels. In addition to the bit error rate (BER) performance, the system level performance is evaluated by using the packet error rate (PER). To integrate the BER performance into the PER performance, a new geometric interpretation of packet error rate is introduced that uses an ensemble average of the received carrier to interference ratio (CIR). Also, a generalized packet collision probability is derived to analyze total link throughput.

Interference mitigation in asynchronous slow frequency hopping Bluetooth networks

In asynchronous slow frequency hopping Bluetooth networks, packet collisions diminish the total link throughput. However, interference mitigation capability can reduce packet losses due to collisions. In this paper, an interference cancelling dual decision feedback (IC-DDF) Bluetooth receiver is proposed and its performance is evaluated for slow fading indoor channels. In addition to the bit error rate (BER) performance, the system level performance is evaluated by using the packet error rate (PER). To integrate the BER performance into PER performance, a new geometric interpretation of packet erasure rate using the received carrier to interference ratio (CIR) is introduced. Also, a generalized packet collision probability is derived to analyze total link throughput.