Chang Woo Pyo

Beam codebook based beamforming protocol for multi-Gbps millimeter-wave WPAN systems

In order to realize high speed, long range, reliable transmission in millimeter-wave 60 GHz wireless personal area networks (60 GHz WPANs), we propose a beamforming (BF) protocol realized in media access control (MAC) layer on top of multiple physical layer (PHY) designs. The proposed BF protocol targets to minimize the BF set-up time and to mitigate the high path loss of 60 GHz WPAN systems. It consists of 3 stages, namely the device (DEV) to DEV linking, sector-level searching and beam-level searching. The division of the stages facilitates significant reduction in setup time as compared to BF protocols with exhaustive searching mechanisms. The proposed BF protocol employs discrete phase-shifters, which significantly simplifies the structure of DEVs as compared to the conventional BF with phase-and-amplitude adjustment, at the expense of a gain degradation of less than 1 dB. The proposed BF protocol is a complete design and PHY-independent, it is applicable to different antenna configurations. Simulation results show that the setup time of the proposed BF protocol is as small as 2% when compared to the exhaustive searching protocol. Furthermore, based on the codebooks with four phases per element, around 15.1 dB gain is achieved by using eight antenna elements at both transmitter and receiver, thereby enabling 1.6 Gbps-data-streaming over a range of three meters. Due to the flexibility in supporting multiple PHY layer designs, the proposed protocol has been adopted by the IEEE 802.15.3c as an optional functionality to realize Gbps communication systems.

Throughput analysis and improvement of hybrid multiple access in IEEE 802.15.3c mm-wave WPAN

This paper studies the throughput of the IEEE 802.15.3c millimeter-wave (mm-Wave) WPAN system that is based on the hybrid multiple access of CSMA/CA and TDMA. In order to study the throughput of this system, we construct a novel analytical model by considering hybrid multiple access. Our throughput analysis shows that the throughput is significantly affected by the length of access time of CSMA/CA. A large length of access time of CSMA/CA will cause a low data transmission time in TDMA, while a short length of access time of CSMA/CA will cause a large number of data transmission collisions in CSMA/CA. The failure of data transmission channel release due to the collisions will lead to an increase in the unused data transmission time in TDMA. In order to improve the throughput, we introduce a private channel-release time to avoid the failure of data transmission channel release and provide the optimum access time of CSMA/CA, thereby maximizing the throughput. The proposed method can significantly improve the throughput of the IEEE 802.15.3c mm-wave WPAN system.

A dynamic and distributed domain-based mobility management method for mobile IPv6

We address mobility management for the internet protocol version 6 in mobile networks, namely mobile IPv6 (MIPv6). To correctly transfer IPv6 packets to a mobile node (MN), the MN has to update its binding to the home network while roaming away from its home network. Mobile IP networks suffer high binding update traffic from high rates of handoffs and long packet delivery delay from the large distance to the home network. In this paper, we introduce a dynamic and distributed domain-based mobility management protocol for MIPv6 to reduce the binding update and packet delivery delay and traffic. We describe the basic protocol operations and examine the performance improvement of our mobility management over the previous mobile IP mobility management method by using simulations. We show that the dynamic approach provides the optimal mobility solution for MIPv6 and the distributed approach can decentralize the network load.

Dynamic Location Management with Caching in Hierarchical Databases for Mobile Networks

In location management which is one of the key issues in mobile networks, the mobile user location update and the incoming calls behavior significantly affect the network performance. To reduce the signaling load and delay, this paper purposes dynamic location management with caching in hierarchical databases for personal communication networks. The performance analysis of dynamic location management has the complicated problems, since the local update area, namely the paging area, is dynamically changed by the mobile users mobility patterns. We propose an analytical model to analyze the mobility patterns with complexity in practical HLR/VLR architectures. By using the analytical model, we provide formulas for the performance analysis and the overall cost minimization of the proposed scheme. And also, the effect of the caching method on dynamic location management and the performance comparison among the proposed scheme, the existing static scheme, and the dynamic scheme without caching are studied.

A Predictive Channel Assignment Method (PCAM) for Interference Avoidance in IEEE 802.15.3 WPANs

This paper studies communication channel assign- ment in IEEE 802.15.3 WPANs. We clarify the channel inter- ference problems as well as introduce an interesting channel interference caused by a hidden PNC in IEEE 802.15.3 WPANs. In this paper, we propose a predictive channel assignment method (PCAM) to efficiently avoid the channel interference among piconets and to minimize throughput degradation by channel interference. The basic idea of the proposed method is to synchro- nize the communication channel time among the piconets residing in the channel interference area, to predict the future channel interference time and to make a schedule of the communication channel time to minimize throughput degradation. The obtained results show that the proposed PCAM highly improves the system throughput by avoiding channel interference compared to the existing method of IEEE 802.15.3 WPANs. Index Terms—IEEE 802.15.3, WPAN, channel interference, hidden PNC, PCAM

A caching scheme for dynamic location management in PCS networks

This paper addresses caching for location management in personal communication service (PCS) networks. Caching is useful to reduce the delay of locating frequently retrial calls to a mobile user. However, the cached information may be obsolete due to the mobility of mobile users, which is the reason for the degradation of system performance. We introduce an efficient caching scheme for dynamic location management to improve the location management performance. Moreover, we establish an analytical model and perform a performance evaluation to study the performance improvement of the caching scheme over the non-caching scheme. We provide a simple and direct way of caching based on dynamic location management.

Simulation studies on dynamic and distributed domain-based mobile IPv6 mobility management

We address mobility management for the Internet protocol version 6 in mobile networks, namely mobile IPv6 (MIPv6). To correctly transfer IPv6 packets to a mobile node (MN), the MN has to update its binding to the home network while roaming away from its home network. Mobile IP networks suffer high binding update traffic from high rates of handoffs and the long packet delivery delay from the large distance to the home network. In this paper, we introduce a dynamic and distributed mobility management protocol for MIPv 6 to reduce the binding update and packet delivery delay and traffic. We describe the basic protocol operations, and examine the performance improvement of our mobility management against the previous mobile IP mobility management methods. We show that the dynamic and distributed mobility management method outperforms other previous methods, and the dynamic approach provides the optimal mobility solution for MIPv6 and the distributed approach can decentralize the network load.