A smart home gateway plays an important role in the Internet of Things (IoT) system that takes responsibility for the connection between the network layer and the ubiquitous sensor network (USN) layer. Even though the home network application is developing rapidly, researches on the home gateway based open development architecture are less. This makes it difficult to extend the home network to support new applications, share service, and interoperate with other home network systems. An integrated access gateway (IAGW) is proposed in this paper which upward connects with the operator machine-to-machine platform (M2M P/F). In this home network scheme, the gateway provides standard interfaces for supporting various applications in home environments, ranging from on-site configuration to node and service access. In addition, communication management ability is also provided by M2M P/F. A testbed of a simple home network application system that includes the IAGW prototype is created to test its user interaction capabilities. Experimental results show that the proposed gateway provides significant flexibility for users to configure and deploy a home automation network; it can be applied to other monitoring areas and simultaneously supports a multi-ubiquitous sensor network.
The IoT (Internet of Things) is considered one of the major communication advances in recent years, since it offers the basis for the development of independent cooperative services and applications [
For HNAs, the home gateway is the most important sink node (SN) that provides access and management capabilities for the child nodes (CNs), such as home devices or smart home terminals. Many articles about ZigBee-based home gateways have been published recently [
Machine-to-machine platform (M2M P/F) integrated service schemes which offer self-configuration and expandability have significant potential for improving the efficiency of traditional home automation systems [
In this paper, an integrated access gateway (IAGW) architecture is proposed with standard interfaces for supporting various application nodes in home environments, ranging from on-site configuration to node and service access. Both the upward and downward communication interfaces of the IAGW are standardized. The IAGW based home network system architecture adopts a separation principle between terminal management and service implementation; the former is realized by the M2M P/F, and the latter is provided by the home service layer. The working mode and parameter configuration of the IAGW gateway can be set using a web console. If the configuration of the IAGW is completed correctly, it will allow management by the M2M P/F automatically. Meanwhile, the system service data are directly transferred to the home service layer through the IAGW. Based on the proposed IAGW and the M2M P/F fusion architecture, the home sensors and services can be standardized and easily managed. Thus, it can reduce the redevelopment workload and promote the interoperability between the multi-HNA systems. The system architecture, the design methods of the IAGW based HNA, and the demonstration experiment will be discussed in Sections
As shown in Figure
A M2M platform based home network architecture.
The main role of the IAGW is data transmission between the CNs and the network layer. The CNs in the USN layer include indoor air quality (IAQ), wireless control socket (WCS), infrared proximity sensor (IPS), video camera, and other sensors or actuators in the HNA. Except for the video camera, the other CNs are integrated with ZigBee modules and network ability. The video camera connects to the IAGW gateway through a Wi-Fi wireless interface or an RJ45 wired interface. Users enjoy the convenience and safety of HNA services through the personal computer (PC), mobile phone (MP), and PAD. The network layer consists of a wired network and a 3G/4G wireless cellular network. The service layer includes an HNA service center (HNASC) and a home M2M platform (HM2M P/F); the former is responsible for home services management, while the latter provides interfaces to the IAGW and supports gateway management. The HNASC supports receiving, authenticating, and storing real-time data collected by the IAGW. It also connects with the business operating support system (BOSS) to realize operations like business order synchronization and push information to users in the form of hand-held terminal and short message service (SMS).
Figure
Hardware architecture of the proposed gateway. (a) Stack structure of the proposed gateway. (b) Front view of the gateway interface side.
The IAGW proposes an onboard 22-pin internal interface and an RS232/485 external interface connected to the mainboard, which are convenient for ZigBee SN integration. If user needs to connect and control other wireless standard home devices, the corresponding SN can be redeveloped and integrated through the two interfaces. The dimensions of the onboard internal interface that adjusts to the ZigBee SN are shown in Figure
Dimensions of the onboard internal interface (unit: mm).
The functional architecture of the IAGW is shown in Figure
Functional architecture of the proposed IAGW gateway.
The “Registration” module is used to manage node registration to the IAGW and request gateway registration to the HM2M P/F. Meanwhile, the “Gateway Configuration” module provides the communication parameters and working mode configuration of the IAGW through HM2M P/F. The “Node Mngr” module manages CNs, including aspects such as node ID management, node status monitoring, and node control. The node monitor is a submodule of the node manager that monitors the node’s status. The “Packet Mngr” module of the proposed IAGW repacketizes data received from CNs to a standard form and sends them to HNASC P/F, parses requests initiated by the platform, and packetizes them into the appropriate form to send to the CNs. The “Security” module includes authorization/authentication and en/decryption, and the “QoS (Quality of Service)” module guarantees service quality. The “Remote Maintenance” module supports remote maintenance, such as IAGW and SN software upgrades from the HM2M P/F.
As shown in Figure
Interaction architecture of the IAGW based home network application.
The HMMP-S interface (step
The HM2M P/F uses
Configuration procedure of the home terminal.
Aiming at CN node management based on HMMP-S protocol, the IAGW takes appropriate action based on the status, such as adjusting the data sending rate or the error status. Meanwhile, it reports node status to the HM2M P/F through the IAGW, allowing to manage the status regularly. HMMP-S protocol also implements control of the CNs’ working behaviors, and node control commands are initially issued by the IAGW or HNASC P/F. Home node data acquisition and processing flow are shown in Figure
Data acquisition and processing flow of the home node.
Figure
Control flow of the IAGW based M2M system.
If the HMMP-S communication configuration is finished, then the communication parameters of the HMMP-A can be set. The main parameters that should be configured include the IP address, the port, and the secret keys of the HNASC P/F. The IAGW also can be configured in encryption mode. When the COMM_CONFIG data are executed, the IAGW sends a communication key request to the HM2M P/F, which is automatically assigned by the latter. Between the CNs and the IAGW, also the IAGW and the M2M P/F, monitoring and maintenance of communication are implemented with HEART_BEAT and HEART_BEAT_ACK packets. Hence, the data transmission link of the HNA system has been established; the HM2M P/F can implement remote management for the IAGW and CNs, and through the HNASC P/F to support kinds of home services for user.
As shown in Figure
The comparison between the traditional gateway and the IAGW.
ID | Characteristic | Conventional gateways [ |
IAGW |
---|---|---|---|
1 | Multi-interface | Mainly support ZigBee radio and have poor expansion | Using the stack hardware structure, it supports ZigBee, Wi-Fi, and Bluetooth radio and is easy to expand |
|
|||
2 | Secondary development ability | Need a large amount of work | New development workload is relatively small |
|
|||
3 | Communication link monitoring | Need to add custom development | Automatic support after system development |
|
|||
4 | System openness | Based on terminal development, all interfaces are private | The interfaces are standard and the openness and source utilization of the system are enhanced |
Testbed setup for the demonstration experiments.
The IAGW starts up after connecting to PC using RJ-45 cable, and its working parameters are configured by a web browser, as shown in Figure
Parameters setting GUIs of the prototype IAGW with the web console. (a) Connection configuration GUI. (b) ZigBee communication configuration GUI. (c) Side view of the proposed prototype gateway.
Figure
Digital map navigation GUI for monitoring platform.
User can remotely check the home environment parameters in real-time and access live video through the hand-held MPs. The GUI running on the user MPs consists of 5 modules, including warning information, node management, real-time data, service instruction, and system configuration. As shown in Figure
Graphic user interfaces running on hand-held terminals. (a) Indoor temperature GUI. (b) Remote video access GUI.
Some tests are carried out to evaluate the stability of our IAGW based HNA system. The IAQ node in the proposed testbed senses the home environment in real time; the temperature, humidity, and CO2 data are collected and sent to the HNASC P/F through the IAGW at intervals of 5 seconds. The tests last for 24 hours, and the data are stored and visualized at the HNASC P/F in real time. The sample results of the home environmental monitoring experiments are shown in Figure
Sample results of the indoor environmental monitoring experiments in 24 hours: (a) temperature and humidity and (b) CO2.
Figure
Node-to-node spacing capability.
The IAGW supports both ZigBee and Wi-Fi 2.4 GHz band wireless standards. In our proposed HNA system, the demand for ZigBee-based data transmission is much larger than that for Wi-Fi communication. The influence of Wi-Fi-based video transmission on ZigBee wireless communication is shown in Figure
Performance evaluation between the two same frequency technologies.
Based on the HM2M P/F, the remote data interaction between the IAGW and the USN layer can be monitored in real time. Figure
The packet loss monitoring based on the HM2M P/F.
A smart gateway architecture for improving the efficiency of home network applications is proposed in this paper. The gateway has stack architecture and provides on-board standard internal and external interfaces which make wireless communication module integration convenient. Among the gateway and various home sensor nodes, as well as between the gateway and the service layer, the gateway realizes the interface standard. Therefore, it can easily realize the standardization of the home network system. The hardware and business management logic separation of the gateway improve the scalability of the system. The working mode and parameter configuration of the gateway can be set through a web browser. After the completion of the configuration, the system will directly enter the work mode properly, which can reduce the development workload of new home network applications. Experimental results show that the proposed gateway successfully realizes home network applications using little infrastructure, and it provides a faster and more flexible approach for building and deploying home automation networks.
The authors declared that they have no conflict of interests regarding this work.
This work is partially supported by National Major Project (Grant no. 2010ZX03006-006), National 863 Program (Grant no. 2014AA01A702), National Natural Science Foundation Project of China (Grant nos. 61272379 and 61325018), Jiangsu Provincial Key Technology R&D Program (Grant no. BE2012165), and the Ministry of Education Science and Technology Innovation Engineering Major Cultivation Project of China (Grant no. 107053). The authors would like to thank Ke-fa Wang and Kai-jian Yin for help with the experiments.