Introduction

In recent years, smart homes become increasingly dependent on consumer electronics especially towards convergence of communicating devices and services. Smart homes are defined as an entity that is able to acquire and apply knowledge about home dwellers and their environment in order to meet the goals of comfort and efficiency. This goal of comfort and efficiency can be reached through the convergence of consumer electronics appliances and application in homes.

For the past 20 years, most systems in smart homes were self contained and are not able easily to communicate with one another. Smart homes will have multiple systems and infrastructure that need to share the same physical media. Most smart homes systems developers tend to develop their intelligent systems in isolation. Systems developed in isolation don’t really lead to interoperation of multiple systems in smart homes. Internet has dramatically speeded up the convergence of communication, networks, systems and services in smart homes. Multiple application domains in smart homes need to share resources and may need to be “aware” about other systems and services as well as what source of information that they can provide in order to execute home operations. To provide the sharing platform among systems for smart homes, any systems or applications has to be developed in a standard way. When a system is build in a standard way, trust is incorporated among systems defined in smart homes to path ways for interoperation. Trust issues can be solved by having interoperability factor as it could make different system talk each other. Interoperability is predicted to be the next big thing for smart homes. There are seven application domains in smart home systems. Figure 1 below shows the application domains defined in smart home systems:

 

Application Domains in Smart Home Systems

Audio / Video System (Multimedia, Streaming, Intercom Paging, Evacuation)

Fire / Home Alarm System

Digital Surveillance System

Access Control Systems

Heating , Ventilating and Air Conditioning System (HVAC)

Lighting and Appliance Control System

Assistive Computing and Healthcare

Figure 1: Application Domains in Smart Home Systems

 

Interoperability for Smart Homes

In smart homes context, interoperability is the ability of systems, applications, appliances and services to work together reliably and in predictable fashion. With interoperability, all dissimilar entities in smart homes are able to exchange information between them, work together, share resources and use the exchanged information for task execution. It is desirable that entities in smart homes needing to interwork seamlessly to provide home dwellers with a variety of integrated applications without modification of their underlying protocols. Current trend is focused on convergence that drives the smart home systems to work together. Convergence is the key factor that drives the need for interoperability. Consumer electronics and in-home services are gradually becoming part of smart home systems. Although there are many vendors that already imposed standard and rules for their systems to work together, still in most cases, such dedicated systems do not connect with systems originated from different vendor. This results in the limitation of interoperability. For smart homes, interoperability can be defined in three main levels on how services and applications can be distributed:

1. Network Level – defines on interaction between entities especially on mechanism to exchange messages between multiple application domains in smart home systems at large
2. Syntactic level – defines names and signature of entities in smart home as well as their operations. It also defines on understanding of data structure in messages exchanged between smart home systems
3. Protocol and connectivity level – Defines the orders of message exchanges and blocking conditions. The protocol level provides mechanism to establish physical and logical connections between smart home systems.

In smart home systems, the key issue on interoperability is how to ensure interoperation and message exchange between smart home vendors systems and their desired services for home dwellers. Typically, this refers to capability for these systems communicating each other and exchange relevant information. To achieve this, some requirements has to be taken into consideration while defining the smart home interoperability. The list below highlights some requirements on working towards interoperability in smart homes:

1. Standard framework for system discovery, control and configuration. This requirement corresponds to ability of related systems in home to discover the presence of other systems and identify their functionalities.
2. Standard media formats and protocols for streaming. This requirement refers to audio and video sub-systems whereas they need to interoperate on common streaming protocol in order to establish streaming session. Standard media formats are needed so that the media can be shared and consumed among all sub-systems defined in smart home environment.
3. Standard authentication mechanism. This requirement is considered for device vendors to provide security mechanisms for access and control.
4. Common QoS mechanism. Some home users may want to apply certain rule on usage that governs how networks in their home are used by members. This requirement ensures all systems in smart home agreeing towards common framework to implement this function.

Solutions

Many solutions are proposed by consortiums and industries in tackling the interoperability issues in smart homes. TAHI (Interoperability for Smart Homes and Communities) launched Interoperability Framework Initiative to create a high-level and cross sector interoperability framework targeting home environment applications and services. Standardization has been identified as key contributor towards achieving interoperability. A good example would be initiative by Home Electronic System. There is some ongoing effort in ISO/IEC/SC25/WG1 Home Electronic System on establishing standard for home electronics interoperability. With many solution proposed and standards initiated, one solution seems to be getting recognized as an ideal approach for interoperability - Web Services. Web Services based on XML is an independent description language for any readable data. Web Services is penetrating the smart homes scenario rapidly by providing common generic platform of data exchange among application domains. Web Service is defined as standard way for application integration using the XML, SOAP, WSDL and UDDI open standards over an Internet protocol. SOAP or known as Simple Object Access Protocol is used to transfer data whereas WDSL (Web Services Description Language) describes the services availability. UDDI (Universal Description, Discovery and Integration) is used for services listing. All the information in Web Services is tagged by XML. Web Services transforms smart home as a node by itself and at same time maximizing the services available through Internet as well as providing services to all application domain within its context. Open Building Information Exchange Group (oBIX) is working to create a standard XML and Web Services guideline to facilitate exchange of information and interoperability for building operation. On the other hand, a SOA approach is proposed by the Device Profile for Web Services (DPWS) which combines the advantage of UPnP and Web Services compatibility. Another important solution comes from the OSGi (Open Service Gateway Initiative) Service Platform. OSGi is a standard, non-proprietary component framework for smart home vendors and developers that act as a gateway. This gateway represents entry point for home external and internal environment to acquire services provided by Internet. Figure 2 below shows the Web Services functionality in providing interoperability.

Figure 2: Interoperability with Web Services

 

Benefits of Interoperability

Interoperability provides several benefits for smart homes. Those benefits are:

1. When home appliances or devices become interoperable, market becomes competitive and this will eventually lead to less expensive products for smart homes operation.
2. Telemedicine and utility services will be easier to deploy since all components associated with the particular services are interoperable, therefore there will be less barriers on deployment and introduction of new services are enhanced.
3. Interoperability will ensure services to the smart home shares common information and resources, which results in lowering the service provision cost for home dwellers.
4. Smart home market will grow drastically and contribute in terms of GDP growth as well as encouraging multiple vendors and service providers to compete in the market.
5. Interoperability provides better security management
6. Reduces integration, operational and upgrading cost in smart homes.

Conclusion

Interoperability will allow devices and application in smart homes to collaborate and provide consumers with greater flexibility in selecting their desired services. This is clear benefit for home dwellers and drives the potential of demand towards more content, services and application in smart homes. For smart home service providers, interoperability will provide support for service or content protection mechanism. This feature will ensure that their services or content delivered to various application domains in smart home in a protected fashion.

Links:

1. OSGI Alliance , http://www.osgi.org/Main/HomePage
2. HAVi, http://www.havi.org/
3. Open Building Information Xchange(OBiX), http://www.obix.org
4. Continental Automated Buildings Association(CABA), http://www.caba.org
5. UPnP Forum, http://www.upnp.org/

About the Author:
Thinagaran Perumal is pursuing his PhD in Smart Technology and Robotics and attached with Institute of Advanced Technology, University Putra Malaysia. He has been involved in research areas of middleware technologies and interoperability for smart home environment. He can be reached at thinagaran@hotmail.com