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Cognitive radio networks have been proposed as a solution to both spectrum inefficiency and spectrum scarcity problems. However, they face to a unique challenge based on the fluctuating nature of heterogeneous spectrum bands as well as the diverse service requirements of various applications. In this paper, a spectrum decision framework is proposed to determine a set of spectrum bands by considering...
Time synchronization is one of the key points in distributed real-time computer system. At first, a time synchronization method under 1PPS signal is put forth. Secondly, two kinds of relevant synthetic disturbance are analyzed, and time synchronization logic is studied to cope with the disturbance. Arena software is chosen to model and simulate the time synchronization procedure. At last, the whole...
The vehicle control system based on Network communication becomes increasingly complicated recently. The traditional research only focuses on the improvement of network communication quality or system control performance. The network configuration had been carried out to study the vehicle chassis integrated control system. Based on the MATLAB/Simulink and TrueTime Toolbox, the distributed CAN network...
With the development of the wireless communications technology and the multimedia technology, the wireless internet multimedia transport of real-time becomes an important applications field. We will meet a problem that the distinguish of the status of package loss is not very good which will affect the QoS when we transport multimedia data in wireless internet. Based on this problem the article comes...
Quality of service (QoS) provisioning generally assumes more than one QoS measure which implies that QoS routing can be categorized as an instance of routing subject to multiple constraints: delay-jitter, bandwidth, cost, etc. We study the problem of constructing multicast trees to meet the QoS requirements of real-time interactive applications where it is necessary to provide bounded delays and bounded...
In order to reduce MAP overhead for periodic small-sized services such as voice over IP (VoIP) service, a persistent scheduling scheme has been proposed in IEEE 802.16e/m. Although this persistent scheduling scheme is designed for periodic services, we propose to adopt the persistent scheduling for non-periodic real-time services with small-sized packets by considering the advantage of MAP overhead...
Received video quality is dependent on the available link rate and the packet loss rate, which are inter-related in a busy network link. Even low packet loss ratios (PLRs) can significantly reduce the video quality. In this paper, a packet level parity FEC is applied to the video stream in order to reduce the video PLR. A constant gross data rate is assumed, such that adding a FEC leads to a decrease...
Real time traffic such as voice and video have strict requirements on the acceptable end-to-end packet delay. When there are different types of traffic with different requirements on tolerable latency, priority based packet scheduling schemes are normally used in order to reduce the queuing delay for real time services. However, in cognitive radio networks, the time that the system spends on spectrum...
Embedded control systems with hard real-time constraints require that deadlines are met at all times or the system may malfunction with potentially catastrophic consequences. Schedulability theory can assure deadlines for a given task set when periods and worst-case execution times (WCETs) of tasks are known. While periods are generally derived from the problem specification, a task's code needs to...
For many control systems, control performance is strongly dependent on delay variations of the control tasks. Such variations can come from a number of sources including task preemptions, variations in task workloads and perturbations in the physical environment. Existing work has considered improving control task delay variations due to task preemption only. This paper presents a general adaptive...
It is challenging to support the timeliness of real-time data service requests in data-intensive real-time applications such as online auction or stock trading, while maintaining the freshness of temporal data that capture the current real-world status. Although deadline-aware real-time scheduling would significantly enhance the timeliness of data services, it is not clear how to assign explicit feasible...
A full exploitation of the computational power available in a multi-core platform requires the software to be specified in terms of parallel execution flows. At the same time, modern embedded systems often consist of more parallel applications with timing requirements, concurrently executing on the same platform and sharing common resources. To prevent reciprocal interference among critical activities,...
Consistency and responsiveness are two important factors in providing the sense of reality in Distributed Virtual Environment (DVE). However, it is not easy to optimize both aspects because of the trade-off between these two factors. As a result, most existing consistency maintenance methods ignored the responsiveness requirements, or just assumed a simple responsiveness requirement model which cannot...
K-coverage is a classic issue in wireless sensor network (WSN) deployment. Existing works typically assumes that every position in the monitoring field is covered by at least k sensor nodes at any given time. This may not always be necessary because certain events to be monitored will last only for a short period of time. Based upon such observation, we include the time dimension in the original k-coverage...
The Mellin transform (MT) is a form of a signal representation similar to Fourier transform (FT) which has been widely used in signal processing owing to its distinct properties like scale invariance. In this work, a 2D form of MT which is termed as 2D discrete Mellin transform (DMT) is introduced. The paper also proposes an area efficient, power aware and multiplier less VLSI architecture for 2D...
As the Internet is rapidly growing and its popularity increases, users tend to use creative, time-conservative, entertained and economical technologies. Real-time applications such as online gaming, voice and video applications are becoming more popular. Research effort to improve scheduling mechanisms in routers is currently given less attention by network researchers. This trend is far behind in...
HCF controlled channel access (HCCA), defined in the IEEE 802.11e document, provides a sample scheduler to allocate transmission opportunity (TXOP) to QoS-aware stations (QSTAs). Since the calculation of TXOP duration is based on mean data rate, it is efficient for constant bit rate (CBR) traffic. For variable bit rate (VBR) traffic, however, delay bound of some admitted traffic flows may be violated...
In order for the base station to respond quickly and efficiently to the uplink bandwidth request in broadband wireless access (BWA) networks using time-division duplex (TDD), a dual feedback control algorithm has recently been proposed. In this algorithm the bandwidth request is adjusted in accordance with both the length of the backlogged queue and the mismatch between packet arrival and service...
Long Term Evolution (LTE) has being standardized by the 3rd generation partnership project (3GPP) as the evolution of WCDMA. Different from the conventional mobile communication technologies that deliver voice traffic through circuit switched networks, in LTE, all kinds of traffic are transferred through packet switched networks based on Internet Protocol (IP). In order to provide Quality of Service...
The staged event-driven architecture (SEDA) is a new software framework, which is used to construct extreme concurrency Internet services systems. When the system is overloaded maintaining the quality of the requests processing is a difficult problem because both the processing costs and requests arrival rate are highly unpredicted. This paper presents a feedback control quality adaptation framework...
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