Essentials of Pervasive Computing

 These were the few things that provide the basis for pervasive computing

            We will see how others areas are contributing in pervasive computing. As the name of the course is Mobile and pervasive computing so we would look into the mobile part today.

            The concept of distributing computing is one step advanced from the use of traditional computer where all the tasks are going to be carried out using this single device. The working can only be started and resumed when the user will be physically available in the room in front of the computer screen. The concept of distributed computing in the concept of such a system where computer and computing like devices are connected through a wired network and user can perform the task using several computers connected through distant places.

            The limitation of using a single computer is minimized and we can perform our task while at home, office and other placed which are connected. This is the beautification and liberty of distributed computing.

            But we were still infrastructure dependent; the barriers of network connectivity are wire based. Connectivity depends on network infrastructure like cables, connectors, routers, switches and other. So beside lots of benefits which we derive from the distributed computing like remote computing, fault tolerance, high availability, remote information accessing, distributed security still there is a limitation of network attached with distributed computing. We are dependent of physical computer, which is connected through cable and power is supplied to that computer physically using power cable.

            The first and most apparent component in distributing computing is to use the network wirelessly. The bounding of connectivity is required to be replaced with something new, something different that allows the user of the technology to enjoy the features without any boundary limit. Then the concept of wireless technology came into existence.

            The concept of wireless technology is the solution to prevail the use of distributed computing while we are on the move on the go.

That technology was Wi-Fi and the limitation of using cables and routers ended.

            On the other side the race was started to shrink the size of desktop as much as they can. As wireless network connectivity was available everywhere so the users want to use their computers while they are travelling, portability of the desktop computer was demanded. The user of the technology can easily move their computer if they could be of smaller in size with portable batteries and wireless connectivity.

            That was the time when the concept of laptop computers emerged. As we discussed in earlier lectures that technology should brought into smaller in size, invincible.

We can say distributed computing – mobile client.

            All the principles of distributing computing are applied and they are still being used in original capacity, wirelessly.  Four keys constraints of mobility led the development of specialized techniques.

This merger of distributing computing with mobility called mobile computing.

Now the additional constraints of mobile computing came into consideration like

   Unpredictable variation in network quality

Wireless connectivity is not guaranteed. If we move around, the network connectivity varies. In few locations there is limited coverage or no coverage. As of mobile phone we have full bars of signals where coverage is fully available and few areas there is limited coverage.

Trust and robustness of mobile elements

The router which we are trying to connect may be a wireless device or may be a moveable device. Now everything is in the air and data may be of risk. Wireless devices may or may not be available all the times as sometimes they are not close to you and number of maximum participants are connected.  Security precautions are required to be enhanced.

Limitations on local resources imposed by weight and size constraints

The objective is to develop such a technology which would be smaller in size so that the size of hard disk was reduced, processor, RAM and most probably the size of the screen was reduced. Consequently the user started facing lack in performance, lack of storage, lack of ease of using devices.

Concern for battery power consumption

Now we are moving toward mobility and the electricity power as source for the device is required to be managed with the device. ow mobility affects the connectivity

Technology	Coverage	Speed
WiFi (802.11g)	38, 140 (m)	54Mbits
WiFi (802.11n)	70, 250 (m)	72.2 / 150 Mbits
WiMax	5-10 Miles	40 Mbits
UMTS		2Mbps
GSM		114kbps

        As much as we demand mobility same we fond decrease in speed and quality or we can say connectivity.

            If we talk about wireless networking then there are some other issues as compared with wired network. Mobile networking, including mobile IP, IPV6 ad hoc protocols, and techniques for improving TCP performance in wireless networks and research is in progress to enhance the procedures of wireless technology.

Example

            The IP address of a node consists of 2 portions like network id and host id. We can take that example like a binary tree. We can have the nodes like 1 and 0. 1 goes at right side and zeros goes at left. If we have to find a node which is 101001 it means that we have to go right then left then right then left again left and then finally right. So the desired node is available. A dedicated unique address is resolved.

            Now mobile computing came in and while we are moving from one place to another the wireless network infrastructure synch our data from one wireless base station to another and they coordinate with each other that the client mobile device is no longer connected at this base station and now the data being retrieved will required to be forwarded to another RBS. So the client start receiving the data while he is changing the location. So this domain where we are connecting through a wireless network is called mobile IP. New routing infrastructure is designed and developed for mobile computing.

            While we think about distributing computing in terms of mobile computing so we have to think about Mobile information access, including disconnected operation, bandwidth-adaptive file access and selective control of data.

            As long as we have connectivity we can access our data. But if we are not connected so that time is most crucial time like we have limited connectivity or no connected or we are connected with very low bandwidth so user of mobile computing is not able to send and receive information.

            Let’s take a scenario, we receive a file when we are connected and some changes are required to done. While we are modifying the data we have been disconnected and people are looking for the information and the old version of that file would be available as I am disconnected and data is not synched. This problem leads toward inconsistency. The changes in data are not reflected.

            So how to ensure uninterrupted data for the users and how to ensure consistent data for users and the organization.

            Mobility would be of physical movement. We move our computer from one way to another the wireless connectivity will be changed.  If we talk about a scenario in which the data is being moved from desktop to mobile phone and then mobile phone to projector computer this is also the movement but that is seamless movement.  That is application movement from one place to another or one platform to another. And this movement calls application adoption. All the applications developed for pervasive computing must be able to change their state according to the platform where they are moved to. 

            So mobile computing applications are required to be developed according to the platform and we know that computing platform is not the same at all the places.

         If we are working in office and there is Linux installed on that computer, at home you have Windows and on your mobile phone you are using Android or iOS. If we want to move our application seamlessly then we have to make sure that there are versions of the same applications for different environments and the operating system should know should have the capability that what is given to it. So application adoption is very much important in terms of mobile computing and pervasive computing.

            Usually we use transcoders and the process of transcoding is that they have all the information with them and according to the user who access them they decide that what and how the data is shown to the user screen.  The size of the screen is big issue. Mobile versions of websites are maintained separately to increase responsiveness. These mobile websites shows more information rather than graphics and other animated stuff and same website is opened on laptop so it would be rather in different more attractive style. So this task is done through transcoder protocols.

Platform- independent view component

            The Transcoding proxy protocol will receive the request form the client and keeping in view the network and device structure of the client it will convert the desired data. Weather the cellular devices are connected with low bandwidth, wireless LAN or wireline modem, CDPD or ISDN clients are connected.

            The orientation of data would be different on different devices, the orientation on smartphone will be different as compared to laptop screen.  So it will depend of the screen and other resources. Screen is not only the cause of change in orientation. Some websites contains very large files to be downloaded and some have heavy graphics to be display so they ask the user that your bandwidth is slow and would you like to see that information or we can show you in plan HTML format. This is the simple example of transcoding.

            Similar is the case with large files with heavy graphics so that the user will be facilitated with the required information but is simple pdf format or plan text. That is application adoption.

            Another major area of concern is power conservation. How to make the efficient use of energy.

            Energy-aware adaptation a mechanism is required to efficient use of power. Such operating systems are required which are energy efficient.  If we don’t use few minutes so screen will be dim and after some time the screen will be of and later on device will be turned into hibernate.

Power stepping down or up   

            Variable-speed processor may be working in full capacity as many applications are running. It can be power stepping down if there are fewer application are running. So operating systems are equipped with power stepping down and up. So many steps can be added from normal working to minimized working.

Energy-sensitive memory management: The energy used by the memory will be in an efficient manner.