Stand-Alone and Cooperative Deep Sleep for Battery-Driven Optical Network Unit

In the era of the Internet of Things (IoT), the access network should provide Internet connectivity to huge numbers of wireless sensor nodes that are collecting data. For most sensor nodes, the macro cells of cellular networks provide cost-effective connectivity. However, covering the remaining nodes, which are either in the out-of-service state or have short-range wireless interfaces only, is a difficult issue. For example, when deploying small cells densely to provide fuller node coverage, the cost of the small cells should be well considered. From the perspective of economy, small cells that use the passive optical network (PON) and moderately priced wireless interfaces, called fiber-wireless (Fi-Wi) in this paper, seem the most promising candidates. However, the flexibility in Fi-Wi system deployment is strictly constrained by the need for a stable power source. Because most of the PON systems have been developed for fiber to the home (FTTH), the gateway node on the customer premise continuously consumes power and thus requires a stable power source. Therefore, the key issue is how to reduce the power consumption of the Fi-Wi gateway node drastically enough to run continuously with only battery and/or solar power. Additionally, the power-saving approach must meet the requirements of the IoT applications at the same time. We focus on the deep sleep approach, which turns OFF almost all the components, with significant power savings at the cost of a drop in quality of service (QoS). This paper proposes methods to control the deep sleep while assuring successful packet reception.