Bongsue Suh

Design and performance analysis of hierarchical location management strategies for wireless mobile communication systems

In this paper, we propose three hierarchical location management strategies for wireless mobile communication systems. The first one is home server first (HSF) scheme in which callees location is queried at callees home location server first. Next, we propose least-common-ancestor server first (LSF) scheme in which a search starts at the least-common-ancestor server of callers current location and callees home server. Finally, we propose distributed LSF in which the location management is made on 2-layered distributed structure. We evaluate the performance of the proposed schemes and compare it with that of another hierarchical scheme proposed by Wang (J.Z. Wang, A fully distributed location registration strategy for universal personal communication systems, IEEE J. Select. Areas Commun., 11(6) (1993) 850-860) and IS-41-based scheme. It is shown that the proposed schemes have reduced location management cost and that the cost is less affected by the increment of communication cost than the compared schemes.

Mobile location management strategy with implicit location registration

We propose a new location management strategy by introducing the concept of implicit location registration. Implicit location registration is triggered whenever a transaction occurs between the backbone network and a mobile terminal. The mobiles most recently notified cell and its neighboring cells are paged to locate a mobile. It is shown that the proposed strategy has the lower paging cost than the simultaneous paging scheme. In addition, the proposed strategy can further reduce the paging cost when the terminal mobility is low and when there are many transactions between the backbone network and mobile terminals.

Minimizing sleep duration time for energy harvesting wireless sensor networks

In this paper1, we propose an optimal data forwarding strategy to minimize sleep duration time for one-dimensional wireless sensor networks with energy harvesting sensor nodes. Based on the values of remaining energy and harvested energy of sensor nodes, the base station (data sink) determines the sleep duration time and the data forwarding strategy for the next data gathering round. According to the proposed algorithm, each sensor node can act as a relay node that receives and forwards the data toward data sink. This strategy also guarantees that every sensor nodes do not reach the energy depletion while minimizing sleep duration time, resulting in the maximum data gathering frequency. From the mathematical analysis and the numerical simulation, the proposed strategy shows 2.5%to 50% smaller sleep duration time compared to the simple data forwarding algorithms such as single hop or multi-hop data forwarding only.

Development and application of an integrated course for procedural and object-oriented programming languages in EE

The EE(electrical engineering)-related departments in universities have courses for learning the procedural and object- oriented programming languages such as C and Java. Since C and Java programming languages have the distinctive similarities and differences, it would be effective to cover both programming skills in one course. We developed an integrated course for the students in the first year of EE-related degree, where both programming languages can be learned in an efficient way. We present the results in improvements of the education effectiveness after the actual lecturing for two semesters.

An algorithm to reduce call delivery costs in the personal communication systems

This paper proposes an enhanced location management algorithm for wireless personal communication systems. The proposed algorithms are based on the hierarchical network structure proposed by Wang (see IEEE J. Selected Areas on Commun., vol.11, no.6, 1993). When a mobile moves between the location areas (LAs), only the database servers on the path from the mobiles home server to new LA have the the location information. The resulting new tracing path is established. For the call delivery, we propose the HSF (home-server-first) algorithm, where the call is passed directly to the callees home server. This algorithm can get rid of the unnecessary database accesses between caller and callee. We analytically evaluate the call delivery costs with consideration given to the number of database accesses and the entry size of the databases. We show that the proposed algorithm can reduce the call delivery costs compared with the algorithm proposed by Wang.

Paging Strategy with Dynamic Wake-Up Period in Cellular Communication Systems

We propose that each mobile terminal should have the dynamic wake-up period for monitoring the paging slot in cellular communication systems. The value of wake-up period for a mobile terminal is determined depending on its movement and call behavior. The numerical results show that the proposed strategy significantly reduces the number of wake-ups for monitoring the paging slot, resulting in less battery power consumption of mobile terminal compared to the traditional strategy.

Design and Analysis of a Virtual Output Queueing Based Windowing Scheduling Scheme for IP Switching System

In this paper, we investigate the performance of a virtual output queueing (VOQ) based windowing (VOQW) scheduling scheme for IP switching systems. From the result, we observe that the proposed scheme can considerably reduce the arbitration complexity and improve the switch throughput under nonuniform and correlated bursty traffic. Moreover, the nonuniform IP traffic has no impact on the performance of the VOQW scheme, even through it has a severe impact on the performance of FIFO based windowing scheme. Therefore, we conclude that the VOQW scheme will be useful in designing of IP switching systems.

Terminal register-based paging strategy for cellular mobile networks

The broadcast paging strategy that pages over a whole location area of current standard becomes less efficient for the future cellular networks. While keeping the standard location management scheme, we propose a new paging strategy to reduce paging cost by adding terminal registers at base station controllers. When a mobile-terminated call occurs, the base station controllers lookup terminal registers to determine if the actual terminal paging is to be made over its coverage. An analytical model based on a Markov chain is used to evaluate the performance of the proposed strategy. The numerical results show that the proposed strategy significantly reduces the paging cost compared with the broadcast paging strategy.