Browsing by Author "Wan, CS"

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Fast dynamic code assignment in next generation wireless access networks
(2003-09-01)
Wan, CS
;
Shih, WK
;
Chang, RC
;
資訊工程學系
;
Department of Computer Science
In this paper, a fast dynamic code assignment (FDCA) algorithm is proposed to assign a single Orthogonal Variable Spreading Factor (OVSF)-code for a data rate requirement in next generation wireless access networks. Our algorithm uses the code assignment operation to evaluate the cost for an OVSF-code allocation. The cost is determined by maintaining the data structure that keeps track the number of available and occupied descendant codes of the code. Based on the cost assignment operation, FDCA algorithm can assign an OVSF-code by reassigning occupied descendant codes for a requested data rate. The OVSF-codes assigned by our algorithm is unrestricted with decreasing spreading factor. Moreover, two types of simulations and experimental measurements are presented. First, the proposed algorithm is applied on the OVSF-code assignment of restricted spreading vector. Our experimental results show that the number of reassigned OVSF-codes within FDCA algorithm is reduced comparing to other scheme proposed in the literature. Then, for serving higher data rate requirements, our scheme also shows significant improvement on the spectral efficiency over fixed code assignment scheme. (C) 2003 Elsevier Science B.V. All rights reserved.
Real-time data access on HSDPA for WCDMA
(2004-02-01)
Wan, CS
;
Shih, WK
;
Chang, RC
;
資訊工程學系
;
Department of Computer Science
This paper presents new High Speed Downlink Shared Channel (HS-DSCH) code management schemes on High Speed Downlink Packet Access (HSDPA) for IP-based multimedia provisioning. The proposed management schemes simplify HS-DSCH code allocation while simultaneously increasing HS-DSCH code utilization. Applying the code management schemes, furthermore, we implement two scheduling algorithms for real-time packets to guarantee the quality-of-service (QoS) requirement. The Real-Time Code Allocation (RTCA) algorithm applies the functionalities of the radio management framework to decide the admission for a new real-time service. Once a new real-time session is established, RTCA allocates HS-DSCH codes to that session such that all real-time packets in the session are scheduled before their related deadlines. Based on the RTCA algorithm, the Real-Time Code Sharing (RTCS) algorithm implements the Early-Deadline-First (EDF) scheme for the schedulability analysis, increasing the schedulable probability for the real-time sessions and thus to improve the utilization of HS-DSCH codes. Experimental results show that RTCS outperforms RTCA in terms of packet drop rates, HS-DSCH code blocking rates and the number of code-domain reassignments.
Real-time packet scheduling in next generation radio access system
(2003-11-01)
Wan, CS
;
Shih, WK
;
Chang, RC
;
資訊工程學系
;
Department of Computer Science
All IP-based radio access network enable packet-oriented connections to offer real-time applications. Radio access networks must provide efficient radio management for data session establishments because of scarce radio resources. In this paper, we present three real-time scheduling algorithms to support quality-of-service at IP-based radio access networks. The real-time generic scheduling (RTGS) algorithm applies the functionalities of the radio management framework to establish new data sessions for real-time service requests. The real-time bandwidth scheduling (RTBS) algorithm implements the early-deadline-first scheme to do the schedulability analysis and to schedule the data sessions to reduce power consumption. The RTBS algorithm can decrease the power consumption more than can RTGS. Based on the RTBS mechanism, we design the real-time code scheduling (RTCS) algorithm. In this algorithm, we apply the dynamic code assignment scheme to increase the probability of schedulable sessions and improve the radio resource utilization. Experimental results show that RTCS outperforms RTBS and, in turn, RTBS outperforms RTGS. (C) 2003 Elsevier B.V. All rights reserved.