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    A combined channel assignment mechanism for hierarchical cellular systems
    (1998-09-01)
    Lo, KR
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    Chang, CJ
    ;
    Chang, C
    ;
    Shung, CB
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    電子工程學系及電子研究所
    This paper proposes a combined channel assignment (CCA) mechanism for hierarchical cellular systems with overlaying macrocells and overlaid microcells. The proposed CCA mechanism combines overflow, underflow, and reversible schemes, where new or handoff calls having no available channel to use in the overlaid microcell can overflow to use free channels in the overlaying macrocell, handoff calls from a neighboring macrocell can underflow to use free channels in the overlaid microcell, and handoff attempts from a macrocell-only region to an overlaid microcell can be reversed to use free channels in the microcell. We apply the CCA mechanism in two different hierarchical cellular systems of Strip type and Manhattan type and compare the CCA with the overflow channel assignment (OCA) scheme. Simulation results show that the CCA mechanism outperforms the OCA scheme by once in forced termination probability, by several times in new call blocking probability, and by 4.7% in system utilization for a hierarchical cellular system, and the CCA mechanism is more suitable for the Manhattan type than for the Strip type. (C) 1998 Elsevier Science B.V.
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    Load-balancing channel assignment for dual-band PCS networks
    (2002-03-01)
    Chang, MF
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    Li, LS
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    資訊工程學系
    ;
    Department of Computer Science
    This paper investigates the channel assignment problem of dual-band PCS systems where single-band and dual-band handsets co-exist. Load-balancing channel assignment schemes are proposed to improve the system performance. To balance the loads of both bands, the BSC selects a band to serve a call request of a dual-band handset based on the loads of both bands. In addition, a channel re-assignment scheme is used to further improve the system capacity. Analytic models and computer simulations have been developed to evaluate the performance of the load-balancing schemes. The results indicate that both load-balancing and channel re-assignment techniques significantly increase the system capacity as the percentage of dual-band handsets increases. Furthermore, the load-balancing with channel re-assignment scheme that combines both techniques achieves the best system performance even when the percentage of dual-band handset is as low as 25%. In addition, we describe an approach to reduce the signal overhead of the load-balancing schemes. Copyright (C) 2002 John Wiley Sons, Ltd.
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    Repacking on demand for two-tier wireless local loop
    (2004-05-01)
    Hung, HN
    ;
    Lin, YB
    ;
    Peng, NF
    ;
    Tsai, HM
    ;
    統計學研究所
    This paper proposes a radio channel assignment scheme called repacking on demand (RoD) for two-tier wireless local loop (WLL) networks. A two-tier WLL overlays a macrocell with several microcells. When a new call arrives at a two-tier WLL with RoD, if no idle channel is available in both the microcell and the macrocell, repacking is performed (i.e., a call in the macrocell is moved to its corresponding microcell), and then the reclaimed macrocell channel is used to serve the new call. An analytic model is proposed to compute the call blocking probability of the two-tier WLL with repacking. This analytic model is validated against simulation experiments.We prove that the blocking probability is not affected by the call holding time distributions, but is only dependent on the mean of the call holding times. Compared with some previous proposed schemes, RoD has low blocking probability and significantly reduces repacking rate.
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    Repacking on demand for speed-sensitive channel assignment
    (2005-01-14)
    Tsai, HM
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    Pang, AC
    ;
    Lin, YC
    ;
    Lin, YB
    ;
    資訊工程學系
    In mobile telecommunications networks, radio channels are limited resources that should be carefully allocated. To increase network capacity, channel assignment can be exercised in a hierarchical cellular network (HCN). By considering the speeds of MSs, we propose an HCN channel assignment approach called repacking on demand (RoD). A simulation model is developed to investigate the performance of RoD and some previously proposed approaches for HCN. Our study quantitatively shows that RoD significantly outperforms the previous proposed approaches. (C) 2004 Elsevier B.V. All rights reserved.
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    Modeling channel assignment of small-scale cellular networks
    (2005-03-01)
    Hung, HN
    ;
    Lee, PC
    ;
    Lin, YB
    ;
    Peng, NF
    ;
    統計學研究所
    In a cellular telecommunications network, the call blocking, forced termination, and call incompletion probabilities are major output measures of system performance. Most previous analytic studies assumed that the handover traffic to a cell is a fixed-rate Poisson process. Such assumption may cause significant inaccuracy in modeling. This paper shows that the handover traffic to a cell depends on the workloads of the neighboring cells. Based on this observation, we derive the exact equation for the handover force-termination probability when the mobile station (MS) cell residence times are exponentially distributed. Then, we propose an approximate model with general MS cell residence time distributions. The results are compared with a previously proposed model. Our comparison study indicates that the new model can capture the handover behavior much better than the old one for small-scale cellular networks.
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    Repacking on demand for hierarchical cellular networks
    (2005-11-01)
    Tsai, HM
    ;
    Pang, AC
    ;
    Lin, YC
    ;
    Lin, YB
    ;
    資訊工程學系
    In mobile telecommunications operation, radio channels are scarce resources and should be carefully assigned. One possibility is to deploy the hierarchical cellular network (HCN). This paper studies a HCN channel assignment scheme called repacking on demand (RoD). RoD was originally proposed for wireless local loop networks. We expend this work to accommodate mobile HCN. A simulation model is proposed to study the performance of HCN with RoD and some previously proposed schemes. Our study quantitatively indicates that RoD may significantly outperform the previous proposed schemes.
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    A MAC protocol for multi-channel multi-interface wireless mesh network using hybrid channel assignment scheme
    (2007-07-01)
    Li, Chi-Yu
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    Jeng, An-Kai
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    Jan, Rong-Hong
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    資訊工程學系
    ;
    Department of Computer Science
    In recent years, Wireless Mesh Network (WMN) which uses a multi-hop configuration to extend the reach of the last-mile access to Internet has come into public notice. WMN improves network performance by the use of multiple orthogonal (non-overlapping) channels and multiple wireless interfaces. However, the Medium Access Control (MAC) protocol in IEEE 802.11 standard was designed and suited for only one channel and one interface. In this paper, we present a new MAC protocol which is specially designed for multi-channel and multi-interface WMNs. The proposed MAC protocol employs a hybrid channel assignment strategy to solve the rendezvous problem and a waiting time scheme for updating network allocation vectors (NAVs) to solve the multi-channel hidden terminal problem. Simulation results show that the proposed protocol can achieve a better utilization of both interfaces and channels.