Wireless sensor networks (WSNs) are one of the very active research area. They have many applications like military, health care, environmental monitoring and industrial monitoring. The sensor nodes have limited energy source. Since in many cases the nodes are deployed in unreachable areas, hence recharging or replacing the battery of the sensor nodes is not an option. Therefore, one must employ techniques to conserve the energy by reducing the energy consumption by the nodes. In this paper, we discuss about the different energy saving schemes investigated by different research community in WSNs to reduce the energy consumption of the nodes and thereby improving the lifetime of the overall network. Energy saving protocols such as duty cycle, energy efficient routing, energy efficient medium access control (MAC), data aggregation, cross layer design and error control code (ECC) are discussed. Sleep/wake up method is adopted by the duty cycle approach to reduce the active time of the nodes and conserve their energy. The routing and MAC protocols use suitable energy efficient algorithms for saving energy. The data aggregation aims to save energy by reducing the number of transmissions. On the other side, cross layer approach looks for a cross layer optimization solution to improve the energy efficiency of the network. ECC reduces energy consumption by virtue of coding gain it offers which allows lower signal-to-noise ratio (SNR) to achieve the same bit error rate (BER) as an uncoded system. Some techniques such as use of directional antennas, topology control and transmission power control which have been widely investigated for other ad-hoc networks for energy conservation are also discussed in brief in this paper.

无线传感器网络（WSN）是非常活跃的研究领域之一。它们具有许多应用，例如军事，医疗保健，环境监测和工业监测。传感器节点的能源有限。由于在许多情况下，节点都部署在无法到达的区域，因此不能为传感器节点的电池充电或更换电池。因此，必须采用通过减少节点的能量消耗来节省能量的技术。在本文中，我们讨论了不同研究团体在WSN中研究的不同节能方案，以减少节点的能耗，从而提高整个网络的寿命。节能协议，例如占空比，节能路由，节能媒体访问控制（MAC），数据聚合，讨论了跨层设计和错误控制代码（ECC）。占空比方法采用睡眠/唤醒方法，以减少节点的活动时间并节省其能量。路由和MAC协议使用合适的节能算法来节省能源。数据聚合旨在通过减少传输数量来节省能源。另一方面，跨层方法正在寻找一种跨层优化解决方案，以提高网络的能源效率。ECC通过其提供的编码增益降低了能耗，从而允许较低的信噪比（SNR）达到与未编码系统相同的误码率（BER）。一些技术，例如使用定向天线，