Ambient intelligence applications differ from industrial automation in information technology. The ambient intelligence devices are usually embedded in the ambience and do not need any user interfaces.
5.1.1 Small size
A radio button installed in a wristwatch can for example monitor the behaviour of demented people without a user interface. The physical presence of wireless devices should be as invisible as possible. Therefore, the nodes should have a very small size without any connecting wires, thereby allowing freedom of movement. In many applications, the wireless button is in hard external conditions, such as in garments or in animals, so the button must also be waterproof and have a shockproof box.
5.1.2 Low power
In connection with small size and compact structure, the power supply must also be small and as service free as possible. This means that the radio button should have very low power consumption and use a small battery or a micro power energy- harvesting feature. In addition, communication protocol must support the low- power feature. The receiving state in wireless communication is a very active state, so the radio button cannot spend a long time listening for others. The button must be the active part in communication deciding when to transmit a message and waiting a very short time for a response message. When comparing wireless electronic power consumption, two criteria are important: the current at low- power or deep-sleep time and the energy per bit of a transmitted message. 5.1.3 Interfacing
The nodes in ambient intelligence interface with each other in one way or another. They can sense the nearness of others, identify the role of a neighbour and behave accordingly. The nodes can move randomly, and so the structure of a network can be modified dynamically. Traditionally, modifications in the network structure are exceptions needing a special setup period. In ambient intelligence, fast
modifications in the network is a normal working method and include specific information about events going on.
A single node requires the defined interfacing features described above. The radio modem should have Received Signal Strength Indication (RSSI) to measure the distance and to select its relationship to others, or the range should be short enough to sense the nearest neighbours directly as well as the next neighbours using the intelligent multi-hopping routing method. For relative positioning purposes in a network RSSI or an equivalent feature is needed to measure distance between nodes.
5.1.4 Open source
For connecting small objects wirelessly together and for monitoring them the applications used should be as simple as possible. In addition, developers should be able to make very special solutions not included in current standards. For these reasons, all electronic connections and software sources should be open. The best user interface is simple receive and transmit routines so that one node can tell to the network: ‘I’m here’ needing no any complicated functions. If the creation of a new application does not need deeper knowledge about protocol stacks etc., there are huge application developer resources, including students, hobbyist and small companies.
5.2
Standard versus non-standard
In developing, a new wireless mass product with demands for new features and a small size the best tool for this application is not necessarily a standard wireless solution. It can be tempting to implement new features into existing standards but the solution is not optimized, because the standard has many extra features that are not needed. The best result is reached by fully customized technology developed only for this one application. A big disadvantage is the costly development work made only for this project. The best solution lies between these two (Palomäki, 2008, ss. 10-11).
5.2.1 Need – toolbox – running fees
The alternatives become clearer by a parable with Figure 22. If you need to fix a screw with a screwdriver, you can ask a service man to give you a single screwdriver. Perhaps your organization does not have single screwdrivers, but
whole toolboxes with all the necessary tools for standard jobs. However, the toolbox is too heavy to carry, so you need a truck to take it to the work place. A large amount of work has been performed for a small need.
If these objects have real names in a wireless application, the aim of this parable becomes clearer. If you need to use wireless technology in a simple new application, the screwdriver means the technology needed in your application. The toolbox means extra investments: you need to start the development with a standard technology with some kind of a development kit and software. It takes extra costs to fit this standard into the hardware in your product. The truck means running fees: license, support and update fees, which you need to get a right to use for the newest standard of your product. As shown, in many applications standard wireless technology is too troublesome to use and to fulfil real needs.
Figure 22. Solution with standard tools 5.2.2 Life cycle of technologies
When a standard is created, the features fulfil the demands of the day and the predicted future demands. The quality of the result depends on how good at predicting the creators are. It also depends on how big redirections (modifications) are possible based on the original standard. If the cap between the demands and standard grows large enough, the life cycle of the standard is at an end. This means that the life cycle of a standard is always limited (Figure 23 a).
New technology can be made in a protected customized technology development project inside a company. Wireless technology is made for specific demands or even for a single product. The development investment is quite high for every new product and for every new development cycle. The life cycle of this technology is very short, that is, it is as long as the lifecycle of the product. Different companies make the same development work. If that kind of protected customized wireless technology is the only alternative for standards, then the standards are, in practice, the only reasonable choice (Figure 23 b).
The third alternative development style lies between the two alternatives discussed above. This is open customized i.e. non-standard public wireless technology. When the base technology is first created with a larger investment, the next developers continue from the point the others have reached. Thus, the investments are much lower in each development period or product. The problem is that every developer creates work that is free for others. This is not usually the principle of companies, which must live through profit. The key operators in this kind of open development are universities and individuals who are interested in development. The life cycle of this kind of technology development is very long, because the next developers can continue the development and make as big a modification as possible to fit the demands of a new application (Figure 23 c).
Standard b) Customized c) Open, non-standard Figure 23. Life cycles and investments of technologies