Jeong-Woo Jwa

A Dual-Channel MAC Protocol with Directional Antennas for Mobile Ad-Hoc Networks

The directional medium access control (MAC) protocol improves the throughput of mobile ad hoc networks but has a deafness problem and requires location information for neighboring nodes. In the dual-channel directional MAC protocol [12], the use of omnidirectional packets does not require the exact location of destination node. In this letter, we propose a tone dual-channel MAC protocol with directional antennas to improve the throughput of mobile ad hoc networks. In the proposed MAC protocol, we use a directional CTS and an out-of-band directional DATA tone with a new blocking algorithm to improve the spatial reuse. We confirm the throughput performance of the proposed MAC protocol by computer simulations using the Qualnet simulator. Keywords: Ad hoc MAC protocol, directional antennas, tone, dual-channel, deafness.

Interleaved TC 8DPSK/OFDM with decision-directed channel estimation on frequency-selective Rayleigh fading channels

Trellis-coded modulation (TCM) is a power and bandwidth efficient signaling scheme. In this letter, we propose interleaved trellis-coded (TC) 8DPSK/OFDM combined with decision-directed (DD) channel estimation on frequency-selective Rayleigh fading channels. We use a subchannel block interleaver in an OFDM symbol interval to randomize the burst errors due to the correlated dispersive fading channel. We also use DD channel estimation using the previous detected 8DPSK symbols in the temporal direction to improve the performance at fast fading. Computer simulations show that the proposed technique has good performance at fast fading.

Development of Mobile Context Awareness Restaurant Recommendation Services

Mobile network evolution and development of USN technologies introduce new business model based on context awareness. Cellular operators provide friend finding service using cell based location information and telematics service using GPS location information. Recently cellular operators provide yellow page service based cell based location information. In this paper, we develop mobile tour application on WIPI platform based on location information. Mobile tour information services provide the best information based on context awareness using user location information from LBS(Location Based Service) Platform, season, weather conditions, time from Web server, and personal preference information stored in database. Mobile tour information service application is developed on WIPI platform.

Development of Conversion Solutions for Interoperability of Applications on Different Mobile Internet Platforms

Cellular operators develop high speed mobile internet and multi-function cellular phones to activate new business model based on mobile internet services. Domestic cellular operators evolve their mobile networks from cdma2000-1x and EvDo to HSDPA to activate high speed mobile internet services. They also develop mobile internet platforms such as WIPI, BREW, and J2ME on multi-function cellular phones having multimedia solutions such as camera, MP3, MPEG, 3D game engine, DMB, PAN such as bluetooth, IrDA, W-LAN, and location information using GPS. But, content providers have problems of redevelopment of the same mobile internet application on different mobile internet platforms provided by cellular operators. In this paper, we develop conversion solutions for interoperability of mobile internet applications on WIPI and BREW using an one-pass compiler. We confirm the performance the proposed conversion solutions for the API conversion rate, the converted file size, and the full conversion time using the popular mobile games which are the killer applications on WiPI and BREW.

A Dual-Tone DMAC Protocol for Mobile Ad Hoc Networks

Ad hoc DMAC protocols have been proposed to improve spatial reuse, but directional transmissions have the problem of deafness. In the ToneDMAC protocol [9], an omnidirectional out-of-band tone after transmitting DATA or ACK mitigates deafness, but cannot prevent the interference packets caused by retransmissions to node in deafness. In this paper, we propose a dual-tone DMAC protocol with the out-of-band start-tone and stop-tone. In the proposed MAC protocol, a start-tone prevents retransmissions to node in deafness and decreases the packet collision probability. Throughput performance of the proposed MAC protocol is confirmed by simulations using Qualnet ver. 3.8 simulator.

The AODV Routing Protocol based on Location Information for Inter-Vehicle Communication

In order to realize Intelligent Transport System (ITS) without any road facilities support, Inter-vehicle Communication (IVC) is increased attention. IVC makes it possible to exchange real-time information among vehicles without centralized infrastructure. The IVC systems use multi-hop broadcast to disseminate information. In this paper, we propose the improved AODV routing protocol based on location information. The proposed AODV routing protocol transmits Hello packet with location information to calculate the distance between nodes. Then it achieves fast link recovery. We confirm the throughput performance of the proposed AODV routing protocol compared with the AODV routing protocol using Qualnet ver.3.8 simulator.

RFID Reader Antenna with Hilbert Curve Fractal Structure over Partially Grounded Plane

In this paper, UHF band RFID reader antenna using filbert curve fractal structure and adding the partially grounded plane at the bottom of antenna, which has a resonant frequency at 910MHz, is proposed. Input impedance of antenna is matched with the feed line of 50ohm by varying the length and width of line segment making up the antenna, and by moving the position of via hole. The gain and directivity of antenna is enhanced as varying the dimension of the partially grounded plane and adding the line segment. The size of fabricated antenna is . The impedance band width(VSWR. The return loss and the gain of fabricated antenna are -18.2dB, 5.3dBi at 910MHz.

Power Controlled Dual-Channel MAC Protocol in Ad hoc Networks based on Location Awareness

Ad hoc network is a wireless network without fixed base stations or any wired backbone infrastructure. In the DUDMAC protocol, ORTS and OCTS in control channel solve the problem of deafness and DDATA and DACK in data channel improve spatial reuse by using the efficient blocking algorithm for directional antennas. In this paper, we propose the PCDUDMAC (Power Controlled DUDMAC) protocols. In the PCDUDMAC protocol, the power control of DATA/DACK in data channel saves transmission power and improves spatial reuse. We confirm the throughput performance of the proposed MAC protocol by computer simulations using Qualnet ver.3.8 simulator.