The revolution in IT has changed our lifestyles. Now it is possible to access our personal, financial, business and other assets at anytime from anywhere using hand held devices. There has been a dramatic increase in the use of mobile hand held computers, such as PDA, Pocket PCs, Smart Phones and Laptops. The widespread popularity of mobile computing devices led the researchers to develop newer framework to run applications that were previously considered feasible only on high-end Personal Computers and Workstations.
Improvement in embedded microprocessors and emerging standards in wireless communications enable mobile devices to inter-communicate and ubiquitously access information more efficiently over the network. The situation is becoming more interesting with the involvement of a combination of mobile Ad hoc and fixed Infrastructure networks having heterogeneous computational nodes with different capabilities. These devices can work in collaboration to process and deliver Multimedia contents and perform high level tasks efficiently.
With the ownership of multiple devices by single owners, there is an increasing demand of collaborative frameworks seamlessly sharing the computational burden and information contents available on all these devices whenever and wherever required. The interface or console used for retrieval of that information may change depending on the availability of suitable gadget with the owner. This potential presents excellent opportunities for the researchers to enhance all layers of network and computing for processing and distribution of Multimedia contents. This thesis proposes techniques to address these opportunities
The problem of special interest in this heterogeneous computing and networking environment is Multimedia content distribution and processing. This area poses a multifaceted problem constituting following functional aspects at different layers:
1. Transmission (on Physical Layer)
2. Routing (on Network Layer)
3. Multimedia Processing (implemented as Middle Ware)
4. Multimedia Task Scheduling (also implemented as Middle Ware)
Multimedia transmission over heterogeneous computation and networking environment involves nodes with diverse performance levels as well as wireless and wired networks of different bandwidths, latencies and reliability characteristics. The first aspect that is targeted in this research is the transmission mechanism among the communicating nodes. This is particularly important to mobile nodes that are communicating over wireless with static nodes that are connected to the wired Infrastructure network. Antennas must be placed at suitable locations so that all the mobile nodes remain connected to the static Infrastructure nodes at all times. Moreover range of wireless network must be sufficient to provide reliable coverage to the moving nodes. This thesis proposes an effective algorithm for antenna placement for optimal coverage of mobile nodes in an Ad hoc setting. Furthermore, novel techniques were developed during this research work by modification of key transmission parameter of CSMA/CD to increase the range of mobile communicating devices in adhoc scenario.
For proper delivery of data and control packets between the communicating nodes, certain rules must be defined that orchestrate the flow of packets over the networks via intermediary gateway nodes. The requirement of newer, more efficient routing protocols is increasing with the introduction of newer mobile computing applications. Furthermore the requirement for uniform load balancing and task distribution over different nodes is a key factor in today's computing environment. This thesis proposes routing algorithms; that leads to efficient routing for Multimedia delivery in a Hybrid network configuration.
Depending on the scenario of deployment, either reactive or proactive routing algorithms are utilized. Reactive routing protocols have the benefit of lesser resource requirements as well as low traffic overhead in the network since they find routes on demand. Proactive routing protocols maintain routing tables to forward packets. Thus communicating devices using proactive protocols must have sufficient RAM to maintain routing tables. Initial delay caused by route discovery mechanisms in the existing reactive protocols render them unsuitable for Multimedia transmission. A Hybrid solution between proactive and reactive routing schemes is worth investigating. The thesis proposes an extension to AODV; A Reactive routing protocol to make it suitable for Multimedia communication and further proposes the use of a modified version of OLSR protocol for the same
Multimedia services over heterogeneous Hybrid networks pose several challenges for the currently available hand held devices. The computational requirements for real-time processing of Multimedia and its timely delivery on the basis of a scheduling algorithm over the network are the two most critical challenges faced by researchers. The processing power needed to execute complex encoding and decoding algorithms is much higher than that available in current hand held devices. Schemes such as remote execution, load balancing, task migration and computation-offloading have promising results. In a collaborative setting breaking up of larger tasks into smaller sub tasks and distributing them over many low performance devices or migrating some of the tasks to a high performance power plugged computing platform is an effective way of processing computationally intensive Multimedia algorithms for hand held devices. This requires proper sequencing of execution of tasks and finding suitable nodes that are capable of processing and scheduling Multimedia information using a suitable scheduler is essential. The thesis proposes Middleware software that combines the performance of small hand held devices by splitting the original task into smaller chunks and later on gathers their results for presentation and delivery to solve the complete problem.
As mobile devices have limited computational capabilities and battery life, therefore the thesis focuses on various parameters that are important in successful processing and delivery of Multimedia content in real time or under bounded time constraints. To fulfill these constraints, the network characteristics such as delays, jitter, bandwidth fluctuations, connection availability and reliability etc. along with available resources on each participating node e.g. CPU performance capacity, Memory availability, Overall response time, Battery Life (in case of mobile nodes) and their average availability in the network are considered.
To summarize, this research deals with the complex task of transmission, routing, processing and scheduling of Multimedia contents by focusing on each layer