Jen-Jee Chen
National University of Tainan
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Publication
Featured researches published by Jen-Jee Chen.
IEEE Transactions on Wireless Communications | 2003
Yi-Bing Lin; Wei-Ru Lai; Jen-Jee Chen
In wireless data transmission, the capacity of wireless links is typically limited. Since many applications exhibit temporal locality for data access, the cache mechanism can be built in a wireless terminal to effectively reduce the data access time. This paper studies the cache performance of the wireless terminal by considering a business-card application. We investigate the least-recently used replacement policy and two strongly consistent data access algorithms called poll-each-read and callback. An analytic model is proposed to derive the effective hit ratio of data access, which is used to validate against simulation experiments. Our study reports how the data access rate and the data update distribution affect the cache performance in a wireless terminal.
IEEE Transactions on Vehicular Technology | 2007
Yu-Chee Tseng; Jen-Jee Chen; Yu-Li Cheng
As portable devices are gaining more popularity, maintaining Internet connectivity anytime and anywhere becomes critical, particularly for mobile and vehicular networks. Network mobility (NEMO) and internet protocol mobility are gaining more and more importance. In this paper, we develop a session initiation protocol (SlP)-based mobile network architecture to support NEMO for vehicular applications. We propose to form a mobile ad hoc network (MANET) by the mobile hosts (MHs) inside a vehicle or a cluster of vehicles. The MANET is connected to the outside world via a SIP-based mobile network gateway (SIP-MNG), which is equipped with one or multiple external wireless interfaces and some internal IEEE 802.11 interfaces. The external interfaces of the SIP-MNG support Internet connectivity by aggregating user traffic to and from the Internet. In addition, exploiting the session information carried by SIP signaling, the SIP-MNG supports resource management and call admission control for the MHs. However, wireless access incurs charges, power consumption, and overhead of mobility management. So, it is desirable to allow the SIP-MNG to disconnect its external interfaces when necessary. To guarantee that users inside the mobile network will not lose any incoming request, we propose a push mechanism through short message service to wake up these wireless interfaces in an on-demand manner. We show the detailed signaling to support such a mechanism. The proposed system is fully compatible with existing SIP standards. Our real prototyping experience and some experimental results are also reported.
innovative mobile and internet services in ubiquitous computing | 2013
Cheng-Hao Chu; Wan-Chuen Wu; Cheng-Chi Wang; Tzung-Shi Chen; Jen-Jee Chen
Along with the rapid growth of Internet, many social websites are founded, and gradually begin to influence the peoples life. Such as Facebook, the social network site provides the personalized recommendation system with friends-of-friends method to recommend new friends to users. The intuition is derived from the idea that it is more probable a person will know a friend of their friends rather than a random person. However, this approach does not consider any insights into human cognitive components such as social interactions. Thus, we propose a brand-new friend recommendation approach. The main concept is to recommend friends who have the similar interests or another thing with self to users. Besides utilizing the information on social networks, such as interests, the concept of real-life location and dwell time is further added in our approach. In this paper, we develop two comparison methods to provide quality friend recommendation. First method combines the existing landmark and users dwell time at certain landmark to make the Voronoi diagram, and analyzes location similarity between users. Second methods is to analyze the interest lists from each social network accounts by using pattern matching and finding longest common subsequence. Through this two comparison methods, we assess the acceptable degree between two, and successfully implement the friend recommendation system.
IEEE Transactions on Vehicular Technology | 2011
Jia-Ming Liang; Jen-Jee Chen; You-Chiun Wang; Yu-Chee Tseng
IEEE 802.16 orthogonal frequency-division multiple access (OFDMA) downlink subframes have a special 2-D channel-time structure. Allocation resources from such a 2-D structure incur extra control overheads that hurt network performance. Existing solutions try to improve network performance by designing either the scheduler in the medium access control layer or the burst allocator in the physical layer, but the efficiency of overhead reduction is limited. In this paper, we point out the necessity of “codesigning” both the scheduler and the burst allocator to efficiently reduce overheads and improve network performance. Under the partial-usage-of-subcarriers model, we propose a cross-layer framework that covers overhead reduction, real-time and non-real-time traffic scheduling, and burst allocation. The framework includes a two-tier priority-based scheduler and a bucket-based burst allocator, which is more complete and efficient than prior studies. Both the scheduler and the burst allocator are tightly coupled together to solve the problem of arranging resources to data traffic. Given available space and bucket design from the burst allocator, the scheduler can well utilize the frame resource, reduce real-time traffic delays, and maintain fairness. On the other hand, with priority knowledge and resource assignment from the scheduler, the burst allocator can efficiently arrange downlink bursts to satisfy traffic requirements with low complexity. Through analysis, the cross-layer framework is validated to give an upper bound to overheads and achieve high network performance. Extensive simulation results verify that the cross-layer framework significantly increases network throughput, maintains long-term fairness, alleviates real-time traffic delays, and enhances frame utilization.
IEEE Communications Letters | 2007
Jen-Jee Chen; Yu-Chee Tseng; Hung-Wei Lee
IEEE 802.11 wireless networks have gained great popularity. However, handoff is always a critical issue in this area. In this paper, we propose a novel seamless handoff mechanism for IEEE 802.11 wireless networks which support IEEE 802.11i security standard. Our approach consists of a dynamic tunnel establishing procedure and a seamless handoff mechanism. Both intra- and inter-subnet handoff cases are considered in our seamless handoff approach. Our work focuses on handoffs in DHCP-based IP networks rather than mobile IP-supported networks, but the proposed scheme can be easily tailored to mobile IP-supported networks.
international conference on communications | 2010
Jen-Jee Chen; Jia-Ming Liang; Yu-Chee Tseng
Power management is one of the most important issues in IEEE 802.16e wireless networks. In the standard, it defines three types of power saving classes (PSCs) for flows with different QoS characteristics. It allows a mobile device to turn off its wireless radio when all its PSCs are in sleep states. In this paper, we consider the scheduling of power saving classes of type II in an IEEE 802.16e network with a BS and multiple MSSs (mobile subscriber stations). Previous work proposes to enforce all MSSs to have the same sleep cycle, thus leading to higher energy cost for those MSSs with less strict delay bounds. We observe that if the sleep cycles of MSSs can be assigned according to their delay bounds, MSSs can significantly reduce their duty cycles. We propose an efficient tank-filling algorithm, which is standard-compliant and can allocate resources to MSSs according to their QoS characteristics with the least number of active frames. Simulation results verify that our algorithm incurs less power consumption and leads to higher bandwidth utilization than the previous schemes.
international workshop on quality of service | 2006
Jen-Jee Chen; Ling Lee; Yu-Chee Tseng
With the increasing popularity of wireless networks and the growing demand for VoIP services, there is a need to guarantee QoS for VoIP calls while supporting as many calls as possible. This paper considers the handoff and QoS issues of VoIP calls under IEEE 802.11e WLANs. Assuming that VoIP calls can be supported by multiple levels of QoS, we show how to conduct call admission control and handoff by integrating SIP and QoS mechanisms of IEEE 802.11e. The proposed scheme is designed to dynamically adjust the resource distribution among existing calls according to the network condition. Multi-level QoS is achieved by adjusting codecs and packetization intervals of calls. The result shows better utilization of bandwidth, decreased blocking rate for new calls, and less dropping rate for handoff calls. In addition, we also show how to achieve early resumption of resources as calls leave a QAP. Simulation result is presented to evaluate the performance of the proposed schemes
international conference on wireless communications and mobile computing | 2014
Jen-Jee Chen; Jia-Ming Liang; Zeng-Yu Chen
For M2M (Machine-to-Machine) machines in cellular networks, employing high transmission rates or transmitting in large power actually cost them much energy. This is harmful to the machines, especially they are operated by batteries. The Relay Node (RN) in Long-Term Evolution-Advanced (LTE-A) networks is used to enhance the coverage of high data rate and solve the coverage hole problem. Considering the limited energy nature of machines, connecting to the RN instead of the BS is a better choice for cell-edge machines. In this paper, we consider an uplink resource and power allocation problem for energy conservation in LTE-A relay networks. The objective is to minimize the total energy consumption of machines while guarantee their quality of service (QoS). We prove this uplink resource and power allocation problem to be NP-complete and develop an energy-conserved resource and power allocation method to solve the problem. Simulation results show that our algorithm can effectively reduce the energy consumption of machines and guarantee their required service qualities.
mobile data management | 2009
Jen-Jee Chen; Shih-Lin Wu; Shiou-Wen Wang
Power saving is a critical issue in the IEEE 802.16e broadband wireless networks. In order to reduce the power consumption, the IEEE 802.16e provides three types of power saving classes (PSCs) for the Mobile Subscriber Stations (MSSs), where each PSC may contain one or several connections. However, how to define a PSC and assign PSCs to connections are open issues in the standard. Focusing on real-time traffics, a single MSS and base station (BS) pair, previous studies use a single PSC of type II to manage the awake and sleep of the MSS. In this paper, two power saving class management algorithms based on multiple PSCs in the IEEE 802.16e are proposed. These two schemes define PSCs for real-time connections by referring to the delay bound and packet interarrival time of connections. Simulation results demonstrate that our schemes outperform the previous single PSC approach in both energy efficiency and resource utilization.
vehicular technology conference | 2010
Jia-Ming Liang; Jen-Jee Chen; Ho-Cheng Wu; Yu-Chee Tseng
This work addresses the mini-slot scheduling problem in IEEE 802.16d wireless mesh networks (WMNs). A practical mini-slot scheduling needs to take into account following issues: the transmission overhead, the scheduling complexity, and the signaling overhead to notify the scheduling results to subscriber stations. We focus in a grid-based WMN, which is the most recommended topology due to its high capacity and connectivity. In this paper, we propose scheduling schemes featured by low complexity and low signaling overhead. The proposed schemes help find periodical and regular schedules, which can balance between transmission overhead and pipeline efficiency. They can achieve near-optimal transmission latencies. Simulation results show that our schemes outperform other schemes, especially when the network size is larger.