Mingfu Li

Design and Implementation of Smart Home Control Systems Based on Wireless Sensor Networks and Power Line Communications

Wireless sensor networks (WSNs) and power line communications (PLCs) are used in this work to implement a smart home control network. The goals are to reduce the impact of wireless interference on a smart home control network and unnecessary energy consumption of a smart home. An isolated WSN with one coordinator, which is integrated into the PLC transceiver, is established in each room. The coordinator is responsible for transferring environmental parameters obtained by WSNs to the management station via PLCs. The control messages for home appliances are directly transferred using PLCs rather than WSNs. According to the experimental results, the impact of wireless interference on the proposed smart home control network is substantially mitigated. Additionally, a smart control algorithm for lighting systems and an analysis of the illumination of a fluorescent lamp were presented. The energy saving of lighting systems relative to those without smart control was evaluated. Numerical results indicate that the electricity consumption on a sunny or cloudy day can be reduced by at least 40% under the smart control. Moreover, a prototype for the proposed smart home control network with the smart control algorithm was implemented. Experimental tests demonstrate that the proposed system for smart home control networks is practically feasible and performs well.

A cost-effective resource allocation and management scheme for content networks supporting IPTV services

This study presents a cost-effective resource allocation approach, which takes the storage and bandwidth costs into consideration, for the proposed content network. The designed content network for supporting IPTV services is composed of several peer service areas, and all video servers are classified into two types - Type 1 and Type 2. Type 1 video servers only store the contents with high hit rates, while Type 2 video servers store other contents with lower hit rates. A novel scheme that allocates contents and video servers based on the hit rate distribution is proposed. The allocation strategy aims at minimizing the cost of the proposed content network. Numerical results show that the optimal resource allocation is strongly related to the hit rate distribution of contents, but is not sensitive to the content size distribution. Additionally, compared with the fully replicated storage method, the proposed allocation scheme can save a considerable percentage of storage space and reduce the total cost of the content network. Based on these findings, we believe that implementing the proposed resource allocation and management scheme will be of benefit to content network operators, especially to infrastructure-based IPTV operators, for reducing the operating expenses.

Arrival process-controlled adaptive media playout with multiple thresholds for video streaming

To improve the playout quality of video streaming services, an arrival process-controlled adaptive media playout (AMP) mechanism is designed in this study. The proposed AMP scheme sets three threshold values, denoted by Pn, L and H, for the playout controller to start playback and dynamically adjust the playout rate based on the buffer fullness. In the preroll period, the playout can start only when the buffer fullness n is not less than the dynamic playback threshold Pn,xa0which is determined by the jitters of incoming video frames. In the playback period, if the buffer fullness is below L or over H,xa0the playout rate will slow down or speed up in a quadratic manner. Otherwise, the playback speed depends on the instantaneous frame arrival rate, which is estimated by the proposed arrival process tracking algorithm. We employ computer simulations to demonstrate the performance of the proposed AMP scheme, and compare it with several conventional AMP mechanisms. Numerical results show that our AMP design can shorten the playout delay and reduce both buffer underflow and overflow probabilities. In addition, our proposed AMP also outperforms traditional AMP schemes in terms of the variance of distortion of playout and the playout curve. Hence, the proposed arrival process-controlled AMP is really an outstanding design.

Available bandwidth estimation for the network paths with multiple tight links and bursty traffic

Available bandwidth (ABW) estimation is useful for various applications such as network management, traffic engineering, and rate-based multimedia streaming. Most of the ABW estimation methods are based on the fluid cross-traffic model. Inevitably, their estimation accuracy is limited in the network environments with bursty cross-traffic. In this paper, we apply packet trains (a series of probing packets) and a modified Ping to probe the ABW of a network path. Our proposed probing method can identify several tight links along a path and can infer their individual ABWs. The ABW estimation algorithm developed in this study, GNAPP, is also based on the fluid traffic model, but it can effectively filter out probing noise incurred in networks that carry bursty traffic. The algorithm employs not only the gaps of any two consecutive probing packets but also those of nonadjacent probing packets for ABW estimation. Thus, the number of samples for ABW estimation increases significantly without resorting to sending more probing packets and the estimation efficiency and accuracy are improved. In addition, two-stage filtering and moving averages are used in GNAPP for reducing estimation errors. Numerical results demonstrate that the estimation scheme based on GNAPP can achieve good accuracy even when the traffic is bursty and there are multiple tight links on the path being observed. Thus, it outperforms other well-known ABW estimation tools.

QoE-Based Performance Evaluation for Adaptive Media Playout Systems

To improve the playout quality of video streaming services, several adaptive media playout (AMP) mechanisms were proposed in literature. However, all performance evaluations and comparisons for AMPs were made in terms of quality of service (QoS) metrics. As one knows, there may exist a trade-off between QoS metrics, such as buffer underflow and overflow performance. Thus, it is not sufficient to nonly evaluate the performance of AMPs in terms of QoS metrics. In this paper, we will evaluate and compare the performance of several AMPs from the aspect of quality of experience (QoE). Numerical results will show that some existing AMP systems do not perform better than the nonadaptive playout system from the point of view of overall QoE.

A two-way available bandwidth estimation scheme for multimedia streaming networks adopting Scalable Video Coding

Multimedia streaming applications have been increasing significantly due to the rapid growth of broadband access networks. Among the latest real-time streaming technologies, the Scalable Video Coding (SVC) which is a layered coding scheme attracts more attention. The SVC encodes an original video into several streaming layers of different bit rates simultaneously. Thus, clients can subscribe a part of the coded layers of SVC video according to their available bandwidth, which should be measured by a bandwidth estimation methodology. Additionally, in SVC clients can augment or abate the number of subscribed streaming layers to fit the time-varying bandwidth during viewing programs. In this paper1, we exploit the concepts of Traceroute and ICMP timestamps to design a two-way available bandwidth estimation mechanism which is never presented in literature. The proposed scheme can infer the available bandwidth of both uplink and downlink paths, and is feasible to the paths with multiple tight links. Hence, it is specially applicable to the multimedia streaming applications adopting SVC. Numerical results show that the presented bandwidth estimation approach can achieve good accuracy.

Analysis of Blocking Rate and Bandwidth Usage of Mobile IPTV Services in Wireless Cellular Networks

Mobile IPTV services over wireless cellular networks become more and more popular, owing to the significant growth in access bandwidth of wireless cellular networks such as 3G/4G and WiMAX. However, the spectrum resources of wireless cellular networks is rare. How to enhance the spectral efficiency of mobile networks becomes an important issue. Unicast, broadcast, and multicast are the most important transport schemes for offering mobile IPTV services over wireless cellular networks. Therefore, bandwidth usages and blocking rates of unicast, broadcast, and multicast IPTV services were analyzed and compared in this paper. Simulations were also conducted to validate the analytical results. Numerical results demonstrate that the presented analysis is correct, and multicast scheme achieves the best bandwidth usage and blocking rate performance, relative to the other two schemes.

Resource allocation with different MCSs for mobile IPTV services in wireless cellular networks

The required bandwidth for mobile IPTV services is usually much higher than that of voice and data services. Thus, how to enhance the spectrum efficiency of the mobile network supporting IPTV services becomes an important issue. In this paper, the performance of mobile IPTV services which use the adaptive Modulation and Coding Scheme (MCS) according to channel conditions or SNRs of group users, will be investigated. For the adaptive MCS scheme, if the multicast IPTV group consists of only cell-center users, the MCS at a higher data rate may be employed; otherwise, the MCS at a lower data rate must be used. According to simulation results, the adaptive MCS can achieve a better blocking rate performance and consume less spectrum, compared with the fixed MCS scheme that always employs the MCS at the worst data rate for all multicast IPTV groups.

Arrival Process-Controlled Adaptive Media Playout for Video Streaming

To enhance the video quality of multimedia streaming services, an Adaptive Media Playout (AMP) mechanism is designed in this study. The proposed AMP mechanism sets two threshold values, denoted as L and H , for the playout controller to dynamically adjust the playout rate according to the number of buffered packets. When the number of buffered packets is below L or over H , the playout rate will slow down or speed up quadratically. While the number of buffered packets is between L and H , the playback speed is determined based on the instant packet arrival rate, which is estimated by the proposed Arrival Process Tracking Algorithm (APTA). We employ computer simulations to demonstrate the performance of our proposed AMP scheme, and compare it with conventional AMP mechanisms. Numerical results show that our AMP design can reduce both buffer underflow and buffer overflow probabilities, and is superior to conventional AMP approaches.

Fast computation of time deviation and modified Allan deviation for telecommunications clock stability characterization

Time and frequency characterization of precision clocks and oscillators is an important task in the maintenance of time and frequency standards. Recently, time domain signal characterization of clocks is generally preferred and several performance measures of clocks and oscillators are defined in ITU-T Recommendation G.810. Among these measures, maximum time interval error (MTIE), time deviation (TDEV) and modified Allan deviation (MDEV) are frequently used, especially in telecommunications measurement. However, the direct computation of MTIE, TDEV and MDEV, defined in ITU-T Recommendation G.810, tends to be unmanageable when the number of samples becomes large. We propose a fast computation approach for TDEV and MDEV. The approach is based on the recursive algorithm and the computation exactly conforms to the ITU-T G.810 definition. As compared with the direct computation approach, the time complexity of the proposed approach is reduced by a factor of N, the number of samples. It reveals that the real-time measurement or monitoring will be feasible by employing the proposed computation approach.