The Universal Mobile Telecommunications System (UMTS) adopts the WCDMA technology as the radio access interface to provide variable transmission rate services. There are four classes of connections identified in UMTS, which are the conversational, streaming, interactive, and background connections. To efficiently utilize radio bandwidth, the shared channel approach is proposed to deliver the packets for the interactive and background connections. This paper proposes a "Shared-Channel As- * A preliminary version [11] of this work has been accepted by IEEE Wireless Communications and Networking Conference 2004. This paper is an extension of the proposed algorithm, and simulation and analysis are conducted to investigate the performance of the proposed algorithm. signment and Scheduling" (SCAS) algorithm to periodically allocate shared channels to serve interactive and background connections. We conduct formal mathematical proofs and simulation experiments to investigate the performance of the SCAS algorithm. We formally prove that with SCAS, a shared channel can be fully utilized (i.e., the utilization of a shared channel can be up to 100%) to serve the interactive connections. Our analysis indicates that compared with the previously proposed shared channel allocation and scheduling algorithms, there are less computation and communication overheads introduced in the SCAS algorithm. The results of the simulation experiments indicate that it is preferred to set up the Transmission Time Interval (TTI; that is, the unit of time interval for shared channel allocation) smaller to optimize the performance of the SCAS algorithm, including the shared channel utilization and the average waiting time of a connection before getting transmission service.
Third Generation Partnership Project working group proposes the high-speed downlink packet access to speed up downlink transmission for the universal mobile telecommunication system, where the time-division-based high-speed downlink shared-channel (HS-DSCH) approach is adopted. Our previous work proposed the shared-channel assignment and scheduling (SCAS) scheme to efficiently schedule the DSCH to serve different connections, which guarantees the requested transmission rate for each connection. However, limitations exist in the SCAS scheme: 1) the requested transmission rates of connections must be two's power numbers of the basic transmission rate and 2) all served connections should be rescheduled while a new request is granted, which introduces extra rescheduling overhead to the system. This paper proposes the elastic shared-channel assignment and scheduling (eSCAS) scheme to overcome these limitations. We formally prove the correctness of the eSCAS scheme. An analytical model and simulation experiments are conducted to compare the performance for eSCAS and SCAS. Our study shows that eSCAS can significantly improve the acceptance rate for new connections without increasing the rescheduling overhead.Index Terms-High-speed downlink packet access (HSDPA), high-speed downlink shared-channel (HS-DSCH), orthogonal variable spreading factor (OVSF), scheduling, universal mobile telecommunication system (UMTS).
Dynamically reconfigurable hardware provides useful means to reduce the time-to-prototype and even the time-to-market in product designs. It also offers a good alternative in reconfiguring hardware logics to optimize the system performance. This paper targets an essential issue in reconfigurable computing, i.e., the minimization of configuration contexts. We explore different constraints on the CONTEXT MIN-IMIZATION problem. When the resulting subproblems are polynomial-time solvable, optimal algorithms are presented. We also present a greedy algorithm for the CONTEXT MINIMIZATION problem, that is proved N P-complete. The capability of the proposed algorithm is evaluated by a series of experiments.
Abstract. The purpose of this paper is to propose a budget-based RTAI (Real-Time Application Interface) implementation for real-time tasks over Linux on x86 architectures. Different from the past work, we focus on extending RTAI API's such that programmers could specify a computation budget for each task, and the backward compatibility is maintained. Modifications on RTAI are limited to few procedures without any change to Linux kernel. The feasibility of the proposed implementation is demonstrated by a system over Linux 2.4.0-test10 and RTAI 24.1.2 on PII and PIII platforms.
To minimize the hardware fabrications in reconfigurable devices, this paper explores hardware synthesis to derive reconfiguration plans during the design time based on schedules derived by CAD tools, where a schedule includes the starting time, the execution time, and the intertask data transmissions for each task. We propose scheduling algorithms to derive optimal solutions for hardware descriptions with the same reconfiguration latency based on backward configuration and backward ordering strategies. For general cases, where a hardware description might be shared by tasks, we develop an algorithm based on a duplication merging strategy with performance evaluations. Our proposed algorithms could be applied after the hardware/software codesign procedures of task partitioning and scheduling to optimize the hardware requirements during the design time.
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