Byung-Jang Jeong

Coexistence between 802.22 and 802.11af over TV white space

Using OPNET simulation we evaluate performance of 802.22 system operating over TV white space when 802.11af system coexist with 802.22 system at a given geo-location considering co-channel interference. To do that, we consider coexistence scenario that 802.11af system is located near 802.22 base station (BS) or customer-premises equipment (CPE). We compare upstream and downstream performance of 802.22 system. Upstream performance of 802.22 system is heavily degraded when 802.11af system exists near 802.22 CPE due to significant loss of upstream MAP data at 802.22 CPE.

MIMO/multi-channel RF transceiver for Cognitive Radio system

Cognitive Radio (CR) technology is one of the favorable technology to efficiently deploy the underutilized frequency spectrum. Currently, the Federal Communications Commission (FCC) allowed TV white space (TVWS) which should protect the licensed user communication to utilize for data communication. The first actual deployment of communication system operating on TVWS is implemented in our group. However, it operates in SISO and single-channel procedure. So, we will develop a second version test-bed operating various modes such as SIMO, 2×2 MIMO and multi-channel communications. From these diverse operation methods, we expect that data rate is enhanced. In this paper, we will introduce a CR RF transceiver which is equipped in our second version of test-bed based on ECMA-392 international standard.

Link level performance of SC-FDMA with SDMA, turbo equalization and real channel estimation

In this paper, we present the link level performance of SC-FDMA with SDMA (Space Division Multiple Access), real channel estimation and low complexity frequency-domain turbo equalization. We give the implementation of the minimum-mean-squared-error based turbo equalization which is suitable for DFT-S-OFDM based SDMA systems. The block error rate performance of SC-FDMA and OFDMA with SDMA and turbo receiver is compared under different code rate and modulation order.

Implementation of PHY module for personal and portable Cognitive Radio devices

The interest on Cognitive Radio (CR) technology is increased to efficiently utilize the unused spectrum. To investigate the feasibility of the CR system operating in TV white space, we have developed a CR test-bed which is based on the Ecma-392 standard. This paper presents the modem algorithms and implementation of physical layer module within the CR test-bed.

The Efficient Detection Algorithm of Various CR signals using Channel Bonding in TV White Space

For efficient utilization of spectrum resources in TV white space after DTV transition, FCC allowed usage of the spectrum for CR system. The CR system is required to cognize channel usage state for utilizing the unused spectrum in TV white space which coexists various primary and secondary systems. In the meantime, as a demand for high throughput communication had been increased recently, CR systems also consider to adopt channel bonding technology, thus spectrum sensing for channel bonded system is essentially required. In this paper, we propose a novel spectrum sensing algorithm for channel bonding system using a single channel receiver. For IEEE 802.l1af signal, the proposed algorithm provide detection probability of 90% with false alarm probability 10% at SNR -18dB for single channel system and at SNR -7dB for 8 channel bonded system, respectively. Utilizing the proposed scheme, we can detect channel bonded signal using only a single receiver, therefore system overhead for spectrum sensing can be reduced significantly.

The Novel ATSC Signal Detection and Data Fusion Algorithms for CR System in TV White Space

FCC of U.S. permitted usage of unlicensed system on unused spectrum in TV white space after DTV transition. The unlicensed systems are required to avoid harmful interference to licensed users by employing geo-location database and spectrum sensing. The conventional spectrum sensing algorithms for ATSC signal were focused on detection of pilot signal. However, they can not guarantee detection of ATSC signal when pilot signal is attenuated by channel environment such as fading. To overcome drawbacks of conventional schemes, in this paper, we propose a signal detection and data fusion algorithm using cyclo-stationary feature weighted by signal energy. Simulation results verify that the proposed algorithm can provide 2dB SNR gain for 90% detection probability compare with the conventional scheme. We can reduce quiet period for spectrum sensing and improve signal detection probability by employing the proposed algorithm.

The Signal Detection Algorithms for Reducing False Alarms of CR System in Real Environment

After permission for utilization of TV white space by FCC, a lot of attentions are focused on spectrum sensing, and various spectrum sensing methods have been proposed. However, they do not consider real environment, thus they are hard to achieve the required performance. In this paper, we propose resolutions for the problem which could be occurred in implementation of spectrum sensing module and verify performance of the proposed methods with computer simulation. The first proposed method utilizes channel status information to separate received signal and spurious for reducing false alarm probability caused by system internal spurious. The another proposed scheme is subband normalization method to prevent miss detection caused by multiple narrow band signals with different received signal strength. The simulation results verify that we can prevent false alarm cause by spurious components with the proposed system internal spurious cognition. Moreover, the proposed subband normalization method shows that it could overcome performance degradation caused by received signal strength difference.