Scratchpad memory management in a multitasking environment

This paper presents a dynamic scratchpad memory (SPM) code allocation technique for embedded systems running an operating system with preemptive multitasking. Existing SPM allocation schemes do not support multiple tasks or only a fixed number of processes that are known at compile time. These schemes rely on algorithms that select code depending on the size of the SPM. In contemporary portable devices, however, processes are created and terminated on demand and the SPM is shared among them. We introduce a dynamic scratchpad memory code alloca-tion technique for code that supports dynamically created processes. At runtime, an SPM manager (SPMM) loads code pages of the running applications into the SPM on de-mand. It supports different sharing strategies that deter-mine how the SPM is distributed among the running pro-cesses. We analyze several sharing strategies with regard to several preferable properties of multiprocess SPM allocation schemes. We evaluate the proposed multiprocess SPM allocation techniques and compare them to a fully-cached reference system by running several multiprocess benchmarks. The benchmarks comprise of multiple embedded applications such as H.264, MP3, MPEG-4, and PGP. On average, we achieve a 47 % improvement in throughput and a 32 % re-duction in energy consumption. A comparison with the un-achievable lower bound shows that the best SPM sharing strategy exploits 87 % of the runtime improvements and 89% of the energy savings possible

Efficient Error Control for Scalable Media Transmission over 3G Broadcast Networks

Abstract. Broadcast and mobile phone technologies have now combined to provide wireless multimedia services. 3GPP2 has introduced the Broadcast and Multicast Services (BCMCS) architecture in a 3G wireless network. BCMCS are capable of supplying multimedia content, which requires successive frames to arrive within a specific time interval. We analyze the execution time of Reed-Solomon decoding, which is the MAC-layer forward error correction scheme used in cdma2000 1xEV-DO BCMCS, under different air channel conditions. The results show that the time constraints of MPEG-4 cannot be guaranteed by Reed-Solomon decoding when the packet loss rate (PLR) is high, due to its long computation time on current hardware. To alleviate this problem, we propose three error control schemes. Our static scheme bypasses Reed-Solomon decoding at the mobile node to satisfy the MPEG-4 time constraint when the PLR exceeds a given boundary. Our second, dynamic scheme corrects errors in a best-effort manner within the time constraint, instead of giving up altogether when the PLR is high. The third, video-aware dynamic scheme fixes errors in a similar way to the dynamic scheme, but in a priority-driven manner which improves the quality of the final video. Extensive simulation results show the effectiveness of our schemes compared to the original FEC scheme

A Multi-resolution Video Scheme for Multimedia Information Servers in Mobile Computing Environment

Nowadays we envisage a large number of clients carrying portable multimedia terminal to access multimedia information over wireless links in the near future. The realization of such services requires the development of multimedia information servers that provide multimedia streams for mobile clients. This paper aims at identifying the server requirements in mobile computing environment and present a novel multi-resolution video layout scheme for the requirements. The proposed scheme is based on the multi-resolution video stream model which can be created by various scalable compression algorithms. Simulation studies show its optimality in terms of disk load balancing and its adaptability to the low and often fluctuant network bandwidth, the QoS change of video streams, and the request for interactive operations. I. INTRODUCTION Recent advances in computer technology and demands of video, audio, and text integration services have been the driving forces behind the emergence of various ..

Scheduling Algorithms in a Large-scale VOD Server

In this paper, we address the problems of designing a large-scale VOD server which stores a large number of movies and provides services to many clients. The server consists of multiple nodes connected with a high performance interconnection network. We intend to determine how to cluster such nodes and how to distribute and schedule movies, in the server. Two scheduling algorithms are proposed in this paper: First, we present a disk scheduling algorithm called round scheduling which fully utilizes the disk bandwidth, minimizing disk idle time to effectively retrieve data blocks. Second, a communication scheduling algorithm is developed to guarantee conflict-free communication over the multistage interconnection networks that are topologically equivalent to the Omega network. We also show some simulation results on the server configuration for given nodes. 1 Introduction Recent advances in computer technology and demands of video, audio, and text integration services have provided dri..

Design and Analysis of a Real-Time Storage Server for Multimedia Applications using Disk Arrays

This paper designs a real-time storage server (RTSS) for remote multimedia playback applications. The design goal is to maximize the number of clients which can be serviced simultaneously. RTSS must, however, maintain the continuity of each medium. To satisfy both the design goal and the constraint, we propose a new scheduling scheme called round scheduling to effectively retrieve multimedia disk blocks. The round scheduling is shown to minimize disk idle time. We also present SCAN-like disk arm scheduling that optimizes seek time to access multimedia blocks. Disk architecture for our server adopts a disk array, where data blocks are striped across all the disks