Jitter Detection for synchronization of Wireless Multimedia Sensor Networks - Embedded.com

Jitter Detection for synchronization of Wireless Multimedia Sensor Networks

Collaborative in-network processing operations in Wireless multimedia sensor networks (WMSNs) often require effective synchronization control. Extensive researches in the traditional networks mainly focus on the synchronization control with the buffer management in the receiver.

However, for WMSNs, the chaotic transport channel and low bandwidth introduce serious jitter. Jit- ter degrades the timing relationship among packets in a single media stream and between packets from different media streams and, hence, creates multimedia synchronization problems.

Moreover, too much jitter will also degrade the performance of the streaming buffer. Only by employing a buffer management scheme in the receiver, we can barely satisfy the synchronization requirement of the in-network processing.

Essentially, smooth in-network collaboration requires effective synchronization control which can minimize packet delays, reduce the jitter effect and maintain synchronization among the various multimedia streams.

Currently, extensive research has focused on the synchronization control of the distributed multimedia systems in the traditional networks . For most of the multimedia systems, such as Audio/Video (A/V) conferencing, Video on demand (VOD) and distance learning, a local buffer management scheme is usually performed in the receiver to provide the smooth synchronized streams.

However, in WMSNs, the chaotic transport channel and low bandwidth introduce more serious jitter . The network jitter complicates the synchronization problem among packets from a single multimedia stream or between packets from different multimedia streams.

It is difficult to re-adjust the timing relationships between packets from the same or several multimedia streams to assure the smooth synchronized streams provision. On the other hand, a large number of packets that have accumulated too much jitter (where the accumulated jitter is larger than the jitter tolerance of the application ) will be rendered useless and discarded when received by the synchronization controller.

Actually, these jitter-corrupted multimedia packets transmission is continuing to consume network bandwidth and thus increasing the network congestion. In a word, by only employing the passive buffer management in the receiver, we can hardly sat- isfy the synchronization requirement of the collaborative in-network processing in WMSNs.

In this study, we propose an active jitter detection mechanism for the synchronization control in WMSNs. This mechanism will improve the quality of service in multimedia networking by discarding the jitter-corrupted packets immediately and balancing the delay and jitter actively.

An active jitter detection scheme is proposed for the synchronization control, which aims at decreasing the packet average jitter, reducing the serious jitter effect and improving the synchronization controlling performance in WMSNs. The major contributions of this work are as follows:

(1) We introduce a precise jitter evaluation mechanism which can calculate the packet delay and jitter in each router during the stream transmission and provide a foundation for the correct jitter- corrupted packet detection.

(2) By analyzing the jitter features of the packet transmission in WMSNs, we propose a dropping decision scheme in which differ- ent discarding thresholds are established for the streams from the different sources.

(3) To improve the system flexibility, we also propose an adap- tive parameter adjustment mechanism for the dropping decision ac- cording to the dynamic network condition.

(4) We implement the proposed active jitter detection scheme and verify its effectiveness in our practical WMSNs. The experiment results show that, without incurring additional average delay and communication overhead, our approach can actively decrease the jitter and reduce the serious jitter effect during the transmission.

The experiment results show that our scheme can reduce the average packet jit- ter effectively and improve the synchronization controlling performance significantly.

To read this external in full, download the complete paper from the author archives at the Chinese Journal of Electronics.

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