Operating system
The core functionality of every pervasive computing device is determined by its operating system.
The major differences of operating systems for pervasive devices from the user's point of view are the human-machine interface, and the speed with which a task can be performed.
For pervasive devices, there will likely be no equivalent to the Windows/Intel monopoly in the near future because pervasive devices do have a wide range of usages (from mobile phones to set-top boxes) with very constrained hardware.
Palm OS:
Suitable and easy to use operating system for PDAs, optimized restricted features are available which leads to lower memory and CPU usage which results in longer battery life.Features: Enhanced Communication Support and Multimedia with Mobile Phones.
Palm OS
User Interface:
It recognizes only the palm handwriting alphabets, one button access to applications; minimize taps for often used operations.
Memory Management:
Applications should be well tested since if one application crashes then the system crashes. Thus memory is divided into dynamic heap which is execution based and clears on reset and storage is designed to hold permanent data.
Software can be developed with both C and C++ in Palm OS.
EPOC:
The EPOC operating system was designed specifically for phones. There are two versions: EPOC16 for 16-bit processors and EPOC32 for 32-bit processors.
Core operating system functionality:
Heavily Multitasking.
The base layer provides the fundamental APIs.
The middleware layer provides the graphics, data, and other components to support the graphical user interface and applications.
EIKON is the system graphical user interface framework.
User Management: Single user operating system
Task management: Provides multitasking with a pre-emptive, priority-driven scheduler.
User interface: The EPOC user interface supports display, keyboard, and sound. . It is also responsible for handling the data and command input. Figure shows the EPOC user interface of an Ericsson device with a map application.
Memory management: EPOC has a memory management unit (MMU) concept to provide separate address spaces for each application. These tools include design patterns, stack clean-up heap failure, and heap-checking tools.
Programming languages supported by EPOC are C++, Java and OPL. C++ used to develop system development and high performance application programming.
Window CE:
Windows CE is an embedded operating system developed by Microsoft.
Windows CE 3.0 offers real-time support, a smart card subsystem for PC/SC compliant readers, is Unicode based, and supports grayscale and color graphics up to 32-bit depth.
Windows CE is a modular operating system that can be configured by the device manufacturer. This is a result of the read-only memory (ROM)-based design of Windows CE, in contrast to more desktop-oriented, disk-based operating systems like Linux or BeOS. It can even be configured at runtime.
The kernel provides memory management, task scheduling, and interrupt handling.
The graphics/window/event manager (GWE) integrates the user interface functions of graphical output and user input.
The object store is the persistent memory of Windows CE and includes files, the registry, and a database.
Finally, the communication interfaces include infrared communication via IrDA, TCP/IP, and serial drivers.
QNX Neutrino:
QNX is a real time operating system consisting of microkernel surrounded by a collection of optimal processes that provides UNIX based system services. Due to microkernel architecture even if the file system driver or network driver crashes, still the system will work which leads to stable system. QNX is very well suitable for car devices.
Be OS:
Be OS is highly optimized for multimedia application. It posses sound and graphic processor. It deals with 64 bit file system .
The architecture is based on a symmetric multi processor model, allowing each processor full access to resources and also it provides pre-emptive multitasking and pervasive multithreading (rapid switching between several task).
Embedded Linux:
Embedded Linux is a stripped down operating system with special support to pervasive devices. Mainly used for handheld devices.
The core features are Configurable kernel, Scalability and Networking.
5.6 Device Connectivity
Device connectivity aspect of pervasive computing.
Pervasive devices cannot be used in stand-alone mode. They have to be connected to the services and applications through Internet for them to be very useful. The integrating of the devices in to different applications is through various device-to-device or device-to-server protocols.
The types of protocols used are wireless protocols, mobile phone technologies, Bluetooth, Mobile IP, synchronization protocols (such as SyncML), transaction protocols and protocols that enable distributed services (such as Jini). Apart from protocols, security issues and device management are also to be considered.
5.6.1 Protocols
Protocols
Pervasive devices require protocols to be effective in their functions. Many of the devices are not useful as stand-alone. It is imperative that these devices exchange data with other devices or server for them to be effective. For exchanging data with other devices or servers they have to use standard protocols such as wireless protocols.
Wireless protocol mobile IP is designed to allow mobile device users to move from one network to another while maintaining a permanent IP address. Moreover, the data consistency must be ensured between the data in the server and the data in the pervasive devices. Data synchronization (replication) is used for maintaining this consistency. It is found that a number of pervasive devices form a distributed network. So, there is a requirement for suitable distributed services and architecture. For ensuring message delivery even at times of switching off of a mobile device or breakdown of the network, message and transaction protocols are required.
Connection protocols such as Bluetooth and WAP are also important from the point of view of data transfer especially in networks with large scale deployment of pervasive devices.
Wireless Protocols
Small handheld devices such as PDAs and mobile phones naturally opt for wireless protocols. There are many protocols existing already and many are being evolved continuously. IEEE 802.1 IB protocol is wireless LAN protocol to be used by a laptop for wireless connection to LAN. Pervasive devices cannot find this protocol suitable for their use as this protocol species a bandwidth of 11 MB/s. WAP with Object Exchange (OBEX), IrD A, Bluetooth and mobile phone technologies are of immense use for pervasive devices.
WAP
Wireless Application Protocol (WAP) is an open international standard. It offers fast and efficient access to Internet to mobile users. WAP Forum drives the development in WAP. It integrates telephony services and browser technology. A WAP browser is a easy-to-use web browser for small mobile devices such as cell phones. Before the introduction of WAP, mobile service providers had extremely limited opportunities to offer interactive data services, but needed interactivity to support Internet and Web applications such as:
·Email by mobile phone
·Tracking of stock-market prices
·Sports results
·News headlines
·Music downloads
Typical WAP application is over-the-air e-commerce transactions (r.i commerce), online banking, and information provisioning and messaging. WAP is similar to HTTP and it has been optimized for narrow band wireless channels and limited display capabilities of pervasive devices. WML is equivalent to HTML and it defines textual format and compressed binary format.
Security is an issue of concern in WAP. WAP is not a mature standard and the discussions are underway for integration of WML in to XHTML (extensible HTML) or unification of HTML and WML. Mobile Internet is expected to usher newer business models and increase mobile devices.
OBEX
OBEX (Object Exchange) was originally defined for IrD A. It is independent of transport protocol. With Bluetooth, it has become high level protocol to be independent of under lying transport protocol.
GBEX was originally intended to make communication through IrDA as complete as possible. The pull and push commands signifying bidirectional communications are introduced in OBEX. It has two modes. They are:
1.The Session Mode: For structuring the dialogue between two devices. It is based on binay pocket -based client / server request / response model.
2.The Object Model: This model carries the information about the objects or the objects themselves. The object is a sequence of headers. Header describes the aspects of the object such as name, length or descriptive text. The headers can be parsed in a way similar to HTTP.
Bluetooth
Bluetooth is a proprietary technology standard for exchanging data over short distances using short wavelength radio transmissions in the ISM band from 2400-2480 MHz from fixed and mobile devices, with high levels of security. The characteristics of Bluetooth are as follows:
1.Frequency Range: 2.45 GHz ISM (Industrial Scientific Medical) band.
2.Security: Many methods such as authentication based on private keys and encryption are specified.
3.Transmission Capabilities: Bluetooth has a range of 10m supporting isochronous and synchronous transmission that is Omni directional.
4.Bandwidth: Data rate up to 1 Mbps.
5.Speech: Three digital speech channels can be supported simultaneously.
Bluetooth can be a preferred protocol to connect two or more devices such as two or more mobile phones or a digital camera and a few mobile phones that may not be in direct line of sight. There are different security modes such as authentication based on private keys and encryption to provide security in Bluetooth devices.
IrDA
There are many IrDa communication standards. The one that is used mostly in pervasive devices is IrDA- Data and Infrared Mobile communication {IrMC}. IrDA characteristics are as follows:
1.Frequency Range: Infrared light is the physical transport medium.
2.Security: No inbuilt security. Depends on higher level protocol security.
3.Transmission Capabilities: Point to point connections with a narrow angle {30®} between center and receiver is only feasible. It is meant for short distance {up to 30 cm} communication.
4.Bandwidth: Data rates up to 4 Mbps are supported.
5.Speech: One digital speech channel is supported.
IrDA senders and receivers are very economical. Though they are suited for high speed data connections, there is a requirement for IrDA devices to be in direct line of sight with each other.