Design and Implementation of a Low-Cost Emb Linux Gateway for Smart Home Health Monito Mateusz Mittek, Jay D. Carlson, and Lance C. P´ erez Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln,NE 68588, USA Email: {mmittek, jcarlson, lperez}@unl.edu Abstract—Many wireless sensor network applications require a gateway device to interface with services running on the Internet. Because of the software complexity involved in this device, it is often realized using a real-time operating system running on an application processor. Most systemsburden the user with developing the protocol handling and device configuration and management inside the application. In this paper,we present the AngelosGateway– a turnkey,low-cost,Linux-powered WSN gateway thatprovidesa socket-based environment for rapid network-enabled application development. Experimental results demonstrate that the proposed device is capable of high- throughput packet I/O, confirming the efficacy of the proposed implementation. I. I NTRODUCTION One popular application of wireless sensor networks (WSN) is in smart home automation and monitoring systems. These systemsoften employ low-cost sensormotesdeployed in residential environments to measure enviornmental conditions, localize individuals living in the home, and actuate windows, lights, and other systems. While many homes are equipped with 802.11 (WiFi) networking, WiFi-enabled motes are expensive and often have power requirements making them unsuitable for minimally-invasive deployment. Because of this, many systems use alternative protocols and topologies that are designed to be low-power and easy to implement on low-cost hardware. One popular example is 802.15 (ZigBee), though other protocols, such as Texas Instruments’ SimpliciTI, are also popular. In many applications — especially smart home systems — the WSN does not operate alone; it must communicate with other servers, services, and devices — usually over TCP/IP. Because of this, one of the most important elements of a WSN is the gateway, which bridges the local WSN and the Internet (or private intranet). Depending on the gateway architecture and its processing power, it might also provide data processing, as well as a flexible interface allowing status monitoring, reconfiguration, debugging or even firmware updating. The gateway often has significantly higher processing power than a typical WSN end device, and is typically not required to be battery operated. All gateways have a WSN transceiver to communicate with the other WSN motes, a network transceiver (usually in the form of WiFi, Ethernet, or 3G cellular), and a processor for running software linking these two interfaces together. In the research community, a PC often serves the purpose of the gateway in this scenario – but PCs have limited usefulness in real-world deployments because they are bulky expensive, and power-hungry. Embedded operating systems provide task and memory management, as well as a unified hardware abstraction layer, pre-builtsoftwarecomponents, and usefuldocumentation for building embedded applications. While there are many embedded operating systems, GNU/Linux has mature support for many different processors and platforms from all major silicon manufacturers. Running GNU/Linux on an embedded device can provide a rich environment in which to quickly develop applications, while providing stability required for reliable operation. GNU/Linux can comfortably run many WSN applications on embedded processors operating in the 200-50 MHz range; though the latest easily-available ARM application processors have as many as 4 cores, and can operate at speeds in excess of 1.5 GHz. To this end, there is a rich ecosystem to choose from when developing WSN gateway hardware with GNU/Linux. This paperpresents the iterative design process of im- plementing the Angelos Gateway: a high-performance, low- costplatform designed for smarthome health monitoring applications. Angelos Gateway is capable of aggregating WSN data,pre-processing it, and relaying it to a centralized server over the Internet. II. BACKGROUND AND RELATED WORK Early work in general-purpose WSNs has shown that a multi-interfaced, embedded gateway utilizing a web-based administration and reporting interface improves the ease of u and flexibility of the WSN [ 1 ]. Y.-H. Song et all proposed a design based on a system-on-chip (SoC) with 32Mbytes of Flash Memory and 128Mbytes of SDRAM which allowed it to run embedded operating systems such as Windows CE o Linux along with a web server and services required to collect the data from the WSN. USB has become the standard bus to which the Network Interface Controllers are connected [2]. Implementation of the gateway’s WSN connectivity can be done on different levels. Four possibilities are presented in [ 3 ]. In the vast majority of WSN solutions, the gateway uses the Application-level Gateway model. Many applications run Linux because of its ease ofuse and development flexibility [ 4 ], [ 5 ], [ 6 ]. Most of the time, however, off-the-shelf hardware solutions are chosen, with 978-1-4799-4774-4/14/$31.00 ©2014 IEEE 485