Adaptive Energy-Efficient Packet Transmission for Voice Delivering in Wireless Sensor Networks Junfeng Xu 1 , Keqiu Li 1 , Yanming Shen 1 , Geyong Min 2 , Wenyu Qu 3 1 Department of Computer Science and Engineering Dalian University of Technology No. 2, Linggong Road, Dalian, 116024, China 2 Department of Computing University of Bradford Bradford, BD7 1DP, UK 3 Department of Computer Science and Technology Dalian Maritime University 1 Linghai Road, Dalian, 116026, China (fibger@gmail.com, keqiu@dlut.edu.cn) Abstract It is challenging to deal with the tradeoff between en- ergy efficiency and Quality of Service (QoS) for multime- dia applications in Wireless Sensor Networks (WSNs). The packet aggregation scheme is widely applied to reduce over- head for high throughput and energy saving in wireless sen- sor networks. However, it may cause unacceptable delay in WSNs. In order to solve the problem for voice deliver- ing with energy efficiency and proper QoS in WSNs, in this paper, we propose an adaptive waiting packet aggregation (AWPA) algorithm. First, we formulate the problem as an optimization problem. Then we optimize the problem and implement the proposed algorithm. Furthermore, we ana- lyze the performance of the proposed algorithm. Finally, we conduct simulations in the NS-2 platform to evaluate the performance. The results show that AWPA outperforms ex- isting algorithms for the performance. Key Words: WSN, QoS, Packet Aggregation, Energy Efficiency. 1. Introduction Recently, the availability of inexpensive hardware such as CMOS cameras and microphones that are able to ubiq- uitously capture multimedia content from the environment has fostered the development of Wireless Multimedia Sensor Networks (WMSNs), i.e., networks of wirelessly interconnected devices that allow retrieving video streams, audio streams, still images, and scalar sensor data [1]. However, due to limited computing, communication and energy resources, energy efficiency and Quality of Service (QoS) are still fundamental concern in WMSNs [4]. There- fore, protocols, algorithms and architectures to maximize the network lifetime with QoS guarantees required by the multimedia application are critical issues [5]. The main characteristic of voice delivering is time- critical in WSNs. Thus, it is important to provide the end-to-end delay guarantee in the overall application performance. Furthermore, many small packets compose the multimedia data flow. This suggests that these small packets cause overhead. The overhead leads to much energy consumption consequentially. So, it is a paradox to guarantee both energy savings and low delay for WMSNs [11]. In order to decrease overhead, the packet aggregation- based (PA) scheme which assembles multiple small packets into one large packet is adopted in intermediate node. Several versions of PA have been proposed in WSNs. The idea of PA was first introduced in [7], and the authors proposed a framework for routing, data compression, and packet aggregation. In [8] and [9], classifications of aggregation protocols for periodic measures have been proposed. In [3], the authors resolved disparity problems by using adaptive report-rate scheme and packet aggregation scheme. In [6], the authors reported some illustrative examples, namely, distributed source coding and packet aggregation. Another influential scheme concerning PA is 2009 Sixth IFIP International Conference on Network and Parallel Computing 978-0-7695-3837-2/09 $25.00 © 2009 IEEE DOI 10.1109/NPC.2009.14 86 2009 Sixth IFIP International Conference on Network and Parallel Computing 978-0-7695-3837-2/09 $26.00 © 2009 IEEE DOI 10.1109/NPC.2009.14 86