A scalable energy-efficient continuous nearest neighbor search in wireless broadcast systems

When the mobile environment consists of light-weight devices, the energy consumption of location-based services (LBSs) and the limited bandwidth of the wireless network become important issues. Motivated by this, we propose new spatial query processing algorithms to support Mobile Continuous Nearest Neighbor Query (MCNNQ) in wireless broadcast environments. Our solution provides a general client–server architecture for answering MCNNQ on objects with unknown, and possibly variable, movement types. Our solution enables the application of spatio-temporal access methods specifically designed for a particular type, to arbitrary movements without any false misses. Our algorithm does not require any conventional spatial index for MCNNQ processing. It can be adapted to static or moving objects, and does not require additional knowledge (e.g., direction of moving objects) beyond the maximum speed and the location of each object. Extensive experiments demonstrate that our location-based data dissemination algorithm significantly outperforms index-based solutions.     

分布式VoD系统的分级存储调度

提出了一种适于大规模分布式ＶｏＤ系统的分级存储调度算法。该算法建立在多队列的排队模型之上,使用上系统均衡方法及基于优先级的缓冲区管理算法,并提供了迁移等待时间的计算方法。通过仿真实验给出了缓冲区大小与业务量和节目驻留时间的关系,为ＶｏＤ分级存储系统的设计提供了依据。     

Order and parameter identification in continuous linear systems via Walsh functions

This letter presents a method, via Walsh functions, for simultaneous identification of the order and parameters of a single-input-single-output linear lumped continuous dynamic system based on input-output data from an arbitrary but active record. Walsh spectra are impressively immune to zero-mean additive noise to some extent, and so are the identification algorithms employing them.     

Mitigating jamming attacks in wireless broadcast systems

Wireless communications are vulnerable to signal jamming attacks. Spread spectrum mitigates these attacks by spreading normal narrowband signals over a much wider band of frequencies and forcing jammers who do not know the spreading pattern to expend much more effort to launch the attack. In broadcast systems, however, jammers can easily find out the spread pattern by compromising just a single receiver. Several group-based ideas have been proposed to deal with compromised receivers; they can tolerate up to t malicious receivers by adding 2t extra copies for each broadcast message. In this paper, we propose a novel scheme with random channel sharing. This scheme reduces the communication cost from 2t to (1 + p)t extra copies, where p determines the channel sharing probability (0 < p < 1). In addition, it does not increase the hardware complexity as it does not require a receiver to operate on multiple channels at the same time.     

Analytic modeling of interactive systems

An overview is presented of queueing theoretic modeling and analysis of interactive computing systems. While the emphasis is on recent advances, an introduction is given which briefly trices the historical development of this area to put current research in perspective. Models, methods of analysis, and applications to real systems are described. An extensive bibliography provides the references for a more in-depth study.     

Use of blind equalization for teletext broadcast systems

A new application of blind equalization that appears to ameliorate the delays and improve the reliability of teletext systems is presented. The compatibility with the existing TV system and the cost-effectiveness of this application were considered for practical purposes. Equalizer adaptation does not require a knowledge of the transmitted data sequence or carrier phase recovery. Therefore, a reduction in the existing teletext circuitry has been achieved. In addition, the proposed quadrature phase shift keying (QPSK) modulation scheme doubles the teletext data transmission rate and uses the allocated TV bandwidth efficiently. The performance of the proposed blind equalizer has been evaluated in the presence of a multipath broadcast channel. Simulations have shown that substantial improvements are observed in the bit-error-rates for both two-phase PSK and QPSK modulation schemes     

Comparison of multicarrier DS-CDMA broadcast systems in a multipathfading channel

The performance of a multicarrier direct sequence code-division multiple-access (CDMA) system employed in the forward link of a cellular system operating over a Rayleigh fading channel is analyzed and compared to the performance of both single-carrier CDMA and hybrid multicarrier CDMA/frequency division multiplexing systems. A RAKE receiver is provided for each subcarrier. We compare the performance of all three systems for various multipath intensity profiles. It is found that for a service requiring high quality and a small number of users, the multicarrier system is the best, but for a service requiring low quality and a large number of users, the hybrid system can support more users than the others. Also, for the case when nonorthogonal codes are used, the multiple-access interference in different resolvable paths are correlated. In that case, to maximize the signal-to-noise ratio in a correlated interference environment; maximal-ratio combining (MRC) is not optimal. However, we found that there is not much difference between the optimum combining and the conventional MRC     

NB-IoT系统中窄带物理广播信道的盲检测

在窄带物联网（NB-IoT）系统中,为了正确解调窄带物理广播信道（NPBCH）以获取系统信息,提出了两种NPBCH的盲检测算法,包括常规检测算法和功率检测算法。常规检测算法采用遍历1/2两种发射天线数和8种不同扰码序列的方法进行盲检测,而功率检测算法是在常规检测算法的基础上改进天线端口数的获取方式,主要采用两种天线端口下窄带参考信号（NRS）的功率比值进行判断天线端口数的方法,以降低常规检测算法的计算复杂度。仿真结果表明,当信噪比小于-17 dB时,常规检测算法相比于功率检测算法解调有3~4 dB的增益,检测可靠性能较好;当信噪比大于-17 dB时,两种算法的检测正确率均超过0.98,但功率检测算法较常规检测算法降低了近50%的时间复杂度,更加有利于工程的实践。     

Design of multicast delivery for providing VCR functionality ininteractive video-on-demand systems

Multicast delivery is one of the solutions to reduce the cost in a large video-on-demand (VoD) system. However, multicast transmission makes much more difficult the implementation of interactive functions for individual users and introduces start-up delays for the users, which contradicts the idea of on-demand services. In this paper, we first try to explore and evaluate the performance of different multicast VoD systems. A new scheme called single-rate multicast double-rate unicast (SRMDRU) is then developed to minimize the system resources for supporting full VCR functionality in a multicast VoD system. This scheme also allows multicast systems to support true VoD services so customers can be served as soon as the system receives the requests. Computer simulations show that the multicast systems using the SRMDRU scheme perform much better than other multicast systems in terms of system blocking probabilities     

VoD系统的负载均衡存储策略及调度算法研究

介绍了使用集群技术的VoD系统结构,并就适用于VoD系统的负载均衡存储策略和调度算法进行了分析,提出了基于节目流行度的存储策略和最强能力优先调度算法,利用仿真环境进行了试验和性能对比分析.     

On-demand data broadcast scheduling based on AHP and GRA methods in wireless broadcast/UMTS integrated systems

The increasing demand for interactive mobile multimedia service is causing the integration of 3rd generation (3G) cellular systems and wireless broadcast systems. The key challenge is to support data dissemination with low response time, request drop rate, and the unfairness of request drop. This article proposes a novel scheduling algorithm called DAG (on-demand scheduling utilizing analytic hierarchy process (AHP) and grey relational analysis (GRA)), which takes multiple factors-waiting time, number of active requests, deadline-into consideration, and models the data scheduling process as a multiple factors' decision-making and best option-selecting process. The proposed approach comprises two parts. The first part applies AHP to decide the relative weights of multiple decision factors according to user requests, while the second adopts GRA to rank the data item alternatives through the similarity between each option and the ideal option. Simulation results are presented to demonstrate that DAG performs well in the multiple criterions mentioned above.     

Performance model of interactive video-on-demand systems

An interactive video-on-demand (VoD) system allows users to access video services, such as movies, electronic encyclopedia, interactive games, and educational videos from video servers on a broadband network. This paper develops a performance evaluation tool for the system design. In particular, a user activity model is developed to describe the usage of system resources, i.e., network bandwidth and video server usage, by a user as it interacts with the service. In addition, we allow batching of user requests, and the effect of such batching is captured in a batching model. Our proposed queueing model integrates both the user activity and the batching model. This model can be used to determine the requirements of network bandwidth and video server and, hence, the trade-off in communication and storage costs for different system resource configurations     

Spectrally efficient digital broadcast systems operated in a phasenoise environment

High spectral efficiency combined with power efficiency, is a requirement for high speed digital broadcast satellite systems. The effect of the recovered carrier phase noise and the nonlinearity on the performance of 16-QAM (quadrature amplitude modulation) and staggered 16-QAM is investigated and compared. It is found that for the phase noise, 16-QAM is more degraded for a roll-off factor of less than 0.4. For roll-off factor of more than 0.8, staggered 16-QAM has superior performance. For the nonlinearity staggered 16-QAM is more sensitive for a roll-off factor of less than 0.4. It is concluded that coincident 16-QAM is suitable for spectrally efficient digital broadcast systems     

Communicating expressiveness and affect in multimodal interactive systems

Multisensory integrated expressive environments is a framework for mixed reality applications in the performing arts such as interactive dance, music, or video installations. MIEEs address the expressive aspects of nonverbal human communication. We present the multilayer conceptual framework of MIEEs, algorithms for expressive content analysis and processing, and MIEEs-based art applications.     

Queueing network model of interactive computing systems

A closed queueing network model with state dependent routing probabilities is developed for the study of interactive computing systems which use swapping as a memory managmnent strategy. An algorithm to obtain an approximate solution of the mathematical model is proposed. Based on meamuements of a dual-processor PDP-10 system, the model is found to be better in predicting the system performance than the classical model without state dependent routing probabilities.     

An analysis of queuing strategies for SCA data broadcast systems

Subcarrier audio channels (SCAs) are used to support a wide-area data communication system. Text or data messages can be transmitted nationally using satellite delivery, and locally using FM broadcasting stations' subcarriers. The time delay that messages experience in the national buffer at the satellite head-end or the local buffer is examined. The delay for various throughput data rates is evaluated to identify an optimum range for this capacity. A realistic set of messages statistics is developed to model SCA traffic. Three different queueing strategies are used to examine the delay that messages obeying these statistics would experience: first-come-first-served, fixed-priority, and delay-dependent priority. It is shown that, as the throughput is increased, the effect of priority on the system is less discernible. As the output capacity is decreased, the effect of a priority structure can be seen to enhance traffic flow. Total message time delay is examined using a delay-dependent priority scheme. Results indicate that the choice of an appropriate queuing strategy will enhance the flow of priority message traffic     

Code design for adaptive coding and modulation indicator in broadcast systems

In this paper, we address the coding problem for adaptive coding and modulator indicators in communication systems where users are divided into several classes according to their channel quality. Two novel methods are described to construct codebooks with variable length codewords forsuch an application. The proposed constructions satisfy all constraints of the system model, showing considerable gain in both the maximal and average length of codebook with respect to the current state of the art. The methodology includes a systematic way for constructing variable length codebooks where codewords are not uniformly distributed in the space, and thus, some codewords are more protected than others. The proposed construction can be easily adapted, by zero padding, to obtain a fixed block‐length code, with length equal to the maximal length of the designed variable‐length code but still smaller than that of the best state‐of‐the‐art code. Copyright © 2015 John Wiley & Sons, Ltd.     

Error repair for broadcast transmissions in DVB‐H systems

People travelling in public transportation vehicles are foreseen to be a relevant use case of future Digital Video Broadcast—Handhelds (DVB‐H) systems. However, it is also one of the critical user cases, since, besides the vehicle penetration loss, the received signal quality is strongly affected by the high mobility of the users, which is accompanied by temporary shadowing and fast fading. On the other hand, mobility can be also beneficial thanks to the bursty character of DVB‐H transmissions, as additional repair data can be sent in the time intervals between original service bursts in order to hide the coverage discontinuities from the users' perception. In this way, users which miss the original transmission have more chances to receive the information correctly. By managing the amount of repair data the network operator can trade system capacity and network latency for improved vehicular user satisfaction in a DVB‐H network with imperfect coverage of the service area (as perceived by the vehicular users). To illustrate the potential of this approach, we evaluate the mentioned trade‐off in a DVB‐H system dimensioned for pedestrian outdoor users, for both streaming and filecasting services. To enable an easy and efficient implementation of the repair mechanisms, we adopt application layer forward error correction (FEC), as it can provide a multi‐burst protection of the transmission. Copyright © 2008 John Wiley & Sons, Ltd.     

有线电视视频点播解决方案分析

针对有线电视网络,分析了基于IP-QAM和双模VoD技术解决方案.为了避免建设IP回传通道,提出利用GPRS或CDMA手机的WAP功能作为回传手段,形成的一种WAP VoD技术,并进一步借鉴网络VoD的CDN思想,实现了一种不需改造现有有线电视网的广播型VoD技术.     

在线连续交互式英语语音智能识别系统设计

英语语音智能识别系统的发展方向是在线、连续性的人机交互,为此,设计在线连续交互式英语语音智能识别系统,并基于梅尔频率倒谱系数设计语音识别函数。系统的参考数据库选取NOSE算法计算语音评价分数并查错,利用专家知识库纠正用户英语语音。系统由语音训练模块和在线连续交互式识别模块组成,前者为系统数据库提供英语语音的语料、音标资源,后者实施系统数据库的评价、纠正工作。实验结果证明设计的系统语音识别率高且识别时间短,有效性强。