Shiann-Tsong Sheu

National Central University, Таоюань, Taiwan, Taiwan

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Publications (112)40.4 Total impact

  • Shiann-Tsong Sheu · Yue-Ru Chuang · Hsueh-Wen Tseng
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    ABSTRACT: With the development of IEEE 802.11 WLAN techniques, the wireless network bandwidth has gradually become sufficient for many multimedia applications. However, the standard MAC protocol is originally designed for traditional data transmission fashions, which are asymmetric transmissions, and seems to be not an efficient transmission fashion for recently oncoming multimedia applications. A sort of interactive multimedia applications, such as video conference, interactive Internet game, and network phone (VoIP), etc., is more and more popular in the world. The features of these interactive applications are frequent and bi-directional data exchange, which will cause large and unnecessary transmission overheads for channel contention under the standard MAC protocol. To reduce these overheads and improve system transmission efficiency, an M-time inheriting transmission strategy (MITS) is proposed in this paper. The MITS is a dynamically bi-directional transmission strategy, which uses the token-like fashion to allow the receiver to send its data frame immediately without participating in following channel contention. Simulation results show that the MITS can indeed improve system goodput of the standard MAC protocol in the environments with interactive applications.
    Computer Communications 03/2007; 30(6):1187-1198. DOI:10.1016/j.comcom.2006.12.006 · 1.70 Impact Factor
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    Shiann-Tsong Sheu · Jung-Shyr Wu · Chi-Hao Huang · Yen-Chieh Cheng · LuWei Chen
  • Shiann-Tsong Sheu · Chih-Chen Yang · Hsu-Sheng Chang
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    ABSTRACT: In IEEE 802.16 Wireless Metropolitan Area Networks (WMAN) with Orthogonal Frequency Division Multiple Access (OFDMA) physical layer, dynamic subchannel allocation algorithm (DSAA) is essential for a Base Station (BS) to efficiently utilize bandwidth capacity. Conventional DSAAs usually group all subcarriers into a number of subchannels and allocate subchannels to Subscriber Stations (SS), one for each SS, according to its traffic demand and channel quality of the link between BS. However, the restriction of conventional DSAAs allocating N subchannels to N SSs (N≥1) is inflexible and inefficient with respect to spectrum efficiency. In this paper, a new DSAA with Hungary algorithm is proposed to enhance the subchannel capacity (in bits per subcarrier) by permitting more than one subchannel allocated for one SS for which channel quality is much better than others.
    Emerging Directions in Embedded and Ubiquitous Computing, EUC 2007 Workshops: TRUST, WSOC, NCUS, UUWSN, USN, ESO, and SECUBIQ, Taipei, Taiwan, December 17-20, 2007, Proceedings; 01/2007
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    ABSTRACT: Communication technology of broadband wireless access (BWA) system designed for wireless metropolitan area networks (WMANs) has become matured. The IEEE 802.16 standard has the potential to be the global standard for WMANs. In this paper, we first point out the inefficient data transmission in IEEE 802.16 point-to-multipoint network and then propose the virtual direct link access (VDLA) scheme which is based on smart scheduling strategy and location reporting protocol. The VDLA allows pairs of subscriber stations to communicate directly without passing through the base station. Simulation results show that the IEEE 802.16 WMANs with VDLA achieves higher average network throughout when handling Intranet traffic.
    Proceedings of the 65th IEEE Vehicular Technology Conference, VTC Spring 2007, 22-25 April 2007, Dublin, Ireland; 01/2007
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    Shiann-Tsong Sheu · Yun-Yen Shih
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    ABSTRACT: The standard IEEE 802.15.4 medium access control (MAC) protocol is designed for low-power transmissions in low-rate and short-distance wireless personal area networks (WPANs). The modified CSMA/CA contention protocol suffers from inefficient channel utilization that is mainly caused by no carrier sensing during backoff. Nodes usually perceive channel busy after backoff but channel may be idle during backoff period. Moreover, standard protocol can not get rid of collisions. In this article, we propose a rotational listening strategy (RLS) to improve the opportunity of success transmissions in IEEE standard protocol. In RLS, to behave like a contention-free network, channel access period is partitioned into a number of mini-slots, in which one mini-slot is allotted for one node, and channel sensing of a node is restricted on its own mini-slots. Simulation results demonstrate that RLS indeed improves the transmission efficiency and conserves energy.
    Proceedings of IEEE International Conference on Communications, ICC 2007, Glasgow, Scotland, 24-28 June 2007; 01/2007
  • Shiann-Tsong Sheu · Yue-Ru Chuang
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    ABSTRACT: The meta-heuristic methods, genetic algorithms (GAs), are frequently used to obtain optimal solutions for some complicated problems. However, due to the characteristic of natural evolution, the methods slowly converge the derived solutions to an optimal solution and are usually used to solve complicated and offline problems. While, in a real-world scenario, there are some complicated but real-time problems that require being solved within a short response time and have to obtain an optimal or near optimal solution due to performance considerations. Thus, the convergence speed of GAs becomes an important issue when it is applied to solve time-critical optimization problems. To address this, this paper presents a novel method, named hyper-generation GA (HG-GA), to improve the convergence speed of GAs. The proposed HG-GA breaks the general rule of generation-based evolution and uses a pipeline operation to accelerate the convergence speed of obtaining an optimal solution. Based on an example of a time-critical scheduling process in an optical network, both analysis and simulation results show that the HG-GA can generate more and better chromosomes than general GAs within the same evolutionary period. The rapid convergence property of the HG-GA increases its potential to solve many complicated problems in real-time systems
    IEEE Transactions on Computers 12/2006; 55(11):1435-1448. DOI:10.1109/TC.2006.171 · 1.66 Impact Factor
  • Shiann-Tsong Sheu · Yun-Yen Shih · Lu-Wei Chen
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    ABSTRACT: In the IEEE 802.15.4 MAC protocol, peer-to-peer transmission between a pair of neighboring nodes is not easy due to nodes frequently staying at sleeping mode. However, in star topology, data exchanging between two non-hidden nodes are relayed by a network coordinator which spends double power consumptions for one valid frame transmission from sender to destination. This paper proposes a day and night access (DNA) scheme to enhance transmission efficiency and to minimize power consumption simultaneously. Simulation results demonstrate that DNA scheme outperforms IEEE 802.15.4 MAC standard in terms of data update success rate, data update latency and energy dissipation per update.
    Vehicular Technology Conference, 2006. VTC-2006 Fall. 2006 IEEE 64th; 10/2006
  • Hsueh-Wen Tseng · Ai-Chun Pang · Chin-Fu Kuo · Shiann-Tsong Sheu
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    ABSTRACT: This paper proposes efficient and fast retransmission (EFR) schemes for IEEE 802.11 multi-rate wireless networks. Without major modification of IEEE 802.11 standard, EFR provides immediate data transmission for both ad hoc wireless local area networks (WLAN) and infrastructure WLAN. Also, EFR can compensate for high frame error rates resulting from existing poor rate control algorithms. We develop an analytical model and a simulation model to investigate the performance of EFR. Our study indicates that in terms of average medium access control delay, average queuing delay, completion rate and average collision times per transmission. EFR outperforms standard IEEE 802.11 carrier sense multiple access/collision avoidance mechanism.
    Computer Communications 09/2006; 29:2964-2974. DOI:10.1016/j.comcom.2006.04.014 · 1.70 Impact Factor
  • Shiann-Tsong Sheu · Yun-Yen Shih
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    ABSTRACT: IEEE 802.15.4 wireless personal area network (WPAN) requires devices to "frequently sleep to conserve power. Without hidden-device protection mechanism, collisions caused by hidden devices may last to frames from other later devices which may only hear some devices involving in previous collisions. Such collision chain problem (CCP) significantly degrades network throughput. This paper proposes a novel collision resolving scheme with P-frozen contention strategy (PFCS) to solve the CCP in WPAN. The coordinator could refer to two partially recognizable fields, frame length and source address, of corrupted frame to allocate dedicated bandwidth for correspondent device and to freeze its contention. Simulation results show that the proposed scheme can not only improve transmission efficiency and access delay but also conserve energy
    Vehicular Technology Conference, 2006. VTC 2006-Spring. IEEE 63rd; 06/2006
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    Jenhui Chen · Shiann-Tsong Sheu
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    ABSTRACT: In wired networks, broadcast and multicast transmissions can be easily achieved by data link layer (layer 2). Nevertheless, it is a big challenge to safely transfer broadcast or multicast data frames over multihop mobile ad hoc networks (MANETs) due to the high bit error rate, the high collision probability and the lack of acknowledgment. Additionally, most of MANET's routing protocols rely on the broadcast function to exchange essential routing packets between mobile nodes and need the multicast function to make more efficient use of network bandwidth for some particular multimedia applications. From our observations, the efficiency of the unicast/multicast routing protocol of finding the path/tree is highly dependent on supported broadcast schemes of the underlying media access control (MAC) protocol. Therefore, in this paper, we illustrate the uncertain broadcast problem due to no replying acknowledgment from any recipients when mobile nodes deliver broadcast frames in wireless networks. We, then, propose a novel reliable broadcast scheme to solve this problem as well as a reliable multicast scheme to enhance the network utilization in data link layer. Simulation results show that the proposed scheme, which is still compatible with IEEE 802.11 standard, can efficiently minimize the bandwidth consumption as well as propagation delay.
    IEICE Transactions on Communications 03/2006; E89B(3). DOI:10.1093/ietcom/e89-b.3.867 · 0.23 Impact Factor
  • Shiann-Tsong Sheu · Yun-Yen Shih · Yue-Ru Chuang
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    ABSTRACT: The infrastructure architecture of wireless local area networks (WLANs) has been widely established in many environments to provide convenient multimedia services. However, in this standard operation, arbitrary channel contention and frequent handshaking significantly affect data transmission efficiency between AP and stations (STAs). This paper proposes an ACK-based polling strategy (APS) to reduce the overheads of channel contention and frequent handshaking via adaptively arbitrating and scheduling the transmission sequence of STAs. That is, the proposed APS makes AP be able to defer the ACK frames replied to the STAs, which still have more data in their buffers, in order to temporarily terminate their subsequent contention accesses. A terminated STA is permitted to transmit data frame again only when it receives the ACK frame replied from AP. Using the ACK-based polling mechanism, the overheads of channel contention and frequent handshaking are reduced and the network goodput is improved. Using the ACK frames, the APS can be further enhanced to support the quality of service (QoS) for various multimedia applications. Simulation results demonstrate that the APS with enhanced QoS function is able to efficiently cope with various transmission requirements in multimedia WLANs.
    Computer Communications 02/2006; DOI:10.1016/j.comcom.2005.04.009 · 1.70 Impact Factor
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    ABSTRACT: In Dense Wavelength Division Multiplexing (DWDM) technologies, the optimal packet scheduling issue is commonly encountered in multiple channel networks. NP-hard problems deal with finding a way to rearrange packets from multiple channels into a finite and rare channel. Genetic Algorithm (GA) is one of the most efficient ways to solve these issues. We hope to find a better solution to our task through the GA characteristics of multiprocessor searching and survival of the fittest. Therefore, a modified and achievable hardware architecture of GA is presented in this paper. This architecture can increase both the speed of packet scheduling and the efficiency of DWDM in Optical Communication Networks. way to solve this problem. It is concluded that crossover and mutation of chromosome and fitness function calcu- lation can converge faster and therefore allow an effi- cient way to find the optimal solution (6). In this paper, besides using the Matlab simulation software to prove the practicality and superiority of GA, we also presented an achievable hardware architecture in DWDM of optimal packet scheduling (1, 2, 3, 7, 8). This paper is organized as follows: Section 2 intro- duces the ways in which GA solves the optimal packet scheduling and presents the simulation results. Section 3 describes a hardware architecture designed for GA. Sec- tion 4 contains our conclusion.
    Proceedings of the 2006 Joint Conference on Information Sciences, JCIS 2006, Kaohsiung, Taiwan, ROC, October 8-11, 2006; 01/2006
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    Wu-Hsiao Hsu · Jenhui Chen · Shiann-Tsong Sheu · Chih-Feng Chao
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    ABSTRACT: In the backbone network, a Steiner multicast tree (SMT) will be established for multi-cast members to minimize the traffic load on networks. However, a communication link or node may fail due to some accidental factors during the transmission period. Down-stream nodes with respect to the failed link/node will be forced to leave this tree. In order to guarantee the quality of service (QoS), it is desirable to have some schemes for the multicast tree so that such termination of service can be avoided or at least, reduced. In this paper, we propose a fixed SMT algorithm (FSA) to construct the Steiner backup mul-ticast tree (SBMT). Based on FSA, for each 'critical' path, an alternate route with enough bandwidth will be reserved such that most fatal failures in the network can be recovered immediately. The way to determine critical paths is based on statistical analysis. In ad-dition, an adaptive SMT algorithm (ASA) is proposed to construct both SMT and SBMT on unreliable networks. The adjustment of the SBMT when nodes dynamically join or leave the SMT is also discussed. The degree of fault tolerance of the proposed strategies is evaluated and compared by simulation. Simulation results demonstrate that FSA and ASA improve the reliability in stable and unstable networks, respectively. Moreover, the dynamic joining process of a node will be sped up by taking both SMT and SBMT into considerations. Simulation results are presented to demonstrate the effectiveness of the optimization.
    01/2006; 28(2). DOI:10.2316/Journal.202.2006.2.202-1419
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    Jenhui Chen · Ai-Chun Pang · Shiann-Tsong Sheu · Hsueh-Wen Tseng
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    ABSTRACT: All mobile stations (STAs) in IEEE 802.11 infrastructure wireless local area networks (IWLAN) are coordinated by an access point (AP). Within the 2.4 GHz unlicensed industry, science, and medicine (ISM) band defined in the IEEE 802.11 2.4 GHz physical layer (PHY) specifications, three channels are available for concurrently transferring data packets at the coverage area of an AP. In most of small/medium enterprises or home environments, an AP with one selected channel is sufficient for covering whole service area, but this implies that the radio resources for the remaining two channels are wasted. In order to overcome the drawback, we propose a new and simple media access control (MAC) protocol, named wireless switch protocol (WSP), for increasing the throughput of IEEE 802.11 IWLAN network to support high quality multimedia traffic. This is achieved by allowing any pair of STAs in IWLAN to exchange data packets in one of other idle channels after their handshake with each other in the common channel controlled by AP. Simulation results show that the total network throughput of WSP depends on the time taken by channel switching, and on the ‘Intranet’ and ‘Internet’ traffic distribution, where the Intranet and Internet mean data transmission between STAs in IWLAN and between the STA and wired host, respectively. When all data packets are Intranet traffic and the traffic load is heavy, the ratio of Goodput for the proposed WSP to that of IEEE 802.11 standard approximates 400%. In the worse case of all Internet traffic, the proposed WSP still obtains the similar throughput as that of IEEE 802.11 standard.
    Mobile Networks and Applications 10/2005; 10(5):741-751. DOI:10.1007/s11036-005-3367-6 · 1.05 Impact Factor
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    Lain-Jinn Hwang · Shiann-Tsong Sheu · Yun-Yen Shih · Yen-Chieh Cheng
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    ABSTRACT: The medium access control (MAC) protocol defined in IEEE 802.15.4 standard is able to achieve low-power transmissions in low-rate and short-distance wireless personal area networks (WPANs). The modified CSMA/CA protocol used to minimize power consumption does not have the hidden-node protection mechanism, such as RST/CTS mechanism, for the sake of reducing the control overheads. Referring to previous research results, which proved that the probability of any two nodes in infrastructure network unheard each other is about 41%, the hidden-node problem (HNP) could result in inefficient data transmission in WPAN and quick power consumption. In this paper, we propose a simple and efficient grouping strategy to solve the IEEE 802.15.4 HNP without needing extra control overheads in data transmissions. The proposed strategy groups nodes according to their hidden-node relationships and then separates the periodic transmission period into several non-overlapping sub-periods, one for each group. The WPAN coordinator is responsible for detecting the hidden-node situation and performing the grouping procedure if necessary. In this paper, we also prove that the maximal number of groups in a WPAN is five. Simulation results demonstrate that the proposed strategy is able to improve the standard transmission efficiency and to conserve energy by eliminating the unnecessary collisions.
    Wireless Internet, 2005. Proceedings. First International Conference on; 08/2005
  • Jenhui Chen · Shiann-Tsong Sheu
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    ABSTRACT: The IEEE 802.11 standard supports several independent and equal-capacity communication channels, which can be shared simultaneously and accessed by mobile stations in existing wireless local area networks (WLANs). However, under the restriction of one transceiver per network adapter, these mobile stations can only access one of these communication channels and, thus, the remainder channels are wasted inevitably. A multichannel carrier sense multiple access (CSMA) protocol, multichannel multiple access (MMA) protocol, is proposed in the paper for supporting parallel transmissions under the above single transceiver constraint. The MMA protocol enables mobile stations to contend for access of multiple data-transferring channels through the use of a dedicated service channel during each contention reservation interval (CRI). After granting the access right of these channels, these mobile stations can transmit data frames over different channels by using a pre-defined channel scheduling algorithm (CSA) in a distributed manner. The time complexity of the proposed heuristic CSA is O(|X|log|X|+|X|×M2) where |X| and M denote the number of successful requests in the CRI and the number of available channels, respectively. An improved MMA+ protocol with extending reserved transmission opportunities is also introduced and the goal is to maximize the channel utilization further. Simulation results show that the proposed MMA with CSA achieves a much higher throughput than conventional IEEE 802.11 WLAN with single channel. Simulation results also indicate that the achievable peek network throughput is not linearly proportional with the number of channels because of the native collision problem caused by single transceiver.
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    Shiann-Tsong Sheu · Yun-Yen Shih · Lu-Wei Chen
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    ABSTRACT: The key features of IEEE 802.15.4 wireless personal area network (WPAN) standard are the low data rate, short transmission distance, and low power consumption. The WPAN consisting of coordinator and device nodes is often established for monitoring the environmental information in a periodic fashion. The most critical issue of IEEE 802.15.4 WPAN is the capability of dealing with real-time or near real-time services, which require the limited latency and delay jitter. Two parameters, named as beacon order (BO) and superframe order (SO), are defined to control the superframe length as well as the active and inactive periods in superframe. However, using two parameters is very difficult to achieve deliver smooth and constant data stream from device nodes to coordinator. Although standard allots a portion of active period to be the guarantee time slots (GTS) for real-time services, the access interval of real-time frames is still affected by the assigned superframe length. Instead of using the inefficient GTS scheme, this paper proposes an adaptive interleaving access scheme (IAS) with a parameter interleaving order (IO) to adjust the superframe structure such that the active portion is spread over entire superframe in order to control the access latency as well as the bandwidth wastage. The simulation results demonstrate that the proposed IAS not only decreases average data renew interval (i.e. access latency) but also increases the battery lifetime of device nodes.
    Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st; 01/2005
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    Jenhui Chen · Shiann-Tsong Sheu · Sheng-Kun Shen
  • Shiann-Tsong Sheu · Wu-Hsiao Hsu · Hua-Chiang Yin · Chai-Wei Lai
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    ABSTRACT: Recent advancement in personal communication services (PCS) provides wireless multimedia services for users on the move. For establishing the convenient access environment, the evolution of IP-based integrated scheme becomes very urgent for public wireless access systems. In this paper, we clarify the well-known issues of integrating the general packet radio service (GPRS) network and IEEE 802.11 wireless local area network (WLAN). These issues include the inconsistence in transmission rate and coverage area, the difficulty in seamless handoff, the complexities of mobile IP and address translations, and so on. Based on classified cases, we propose the circular probe strategy (CPS) to measure the precise handoff latency of a mobile node roaming from one network to another. This information helps mobile nodes and its home agent (HA) to decide the appropriate handoff timing, to maximize the data transmission rate and to perform seamless handoff in the heterogeneous system.
    Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th; 06/2004
  • Shiann-Tsong Sheu · Yun-Yen Shih · Yue-Ru Chuang
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    ABSTRACT: In IEEE 802.11 infrastructure wireless local area networks (IWLANs), most of data frames are transmitted between access point (AP) and wireless stations (STAs). The data transmission in IWLAN is inefficiency since the excessive overhead generated from frequent handshakes between AP and STAs and contentions among STAs. For minimizing the bandwidth wastage, in this paper, we propose a new ACK-based polling strategy to efficiently coordinate and arbitrate the sequence of transmissions among STAs. The proposed strategy alters the consecutive handshake sequence between sender and receiver defined in IEEE 802.11 medium access control (MAC) protocol to minimize the handshaking overhead and to reduce or even eliminate the potential collisions in transmissions. Different from standard handshakes, the recipient of data frame postpones sending acknowledgement (ACK) control frame to schedule the timing of the next transmission from sender. The ACK frame is sent from receiver via standard contention protocol and the sender waits the ACK frame for the authorization to send the next data frame. The simulations and analytical results demonstrate that the proposed ACK-based contention strategy is able to improve the transmission efficiency by simply reducing the overheads of handshakes and collisions in the wireless networks.
    Global Telecommunications Conference, 2003. GLOBECOM '03. IEEE; 01/2004

Publication Stats

897 Citations
40.40 Total Impact Points


  • 2006–2013
    • National Central University
      • Department of Communication Engineering
      Таоюань, Taiwan, Taiwan
    • Chang Gung University
      • Department and Graduate Institute of Computer Science and Information Engineering
      Hsin-chu-hsien, Taiwan, Taiwan
  • 1997–2013
    • Tamkang University
      • Department of Electrical Engineering
      T’ai-pei, Taipei, Taiwan
    • University of Kang Ning
      T’ai-pei, Taipei, Taiwan
  • 2009
    • Institute for Information Industry
      T’ai-pei, Taipei, Taiwan