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Tuesday, June 14, 2011

The concept of Wide - area ubiquitous networks

The “ubiquitous computing” concept has been studied as an aspect of computer technology. The concept requires computers to be out in the real world with people. In a society where this concept is actualized, these computers are embedded in many products/objects with sensors or actuators, but people are not aware of them. The computers calmly work and communicate with each other to offer a variety of services. This concept introduced in the 1980s is no longer only a dream. Recent developments in computer technologies as well as electronics and micromechanics enable us to make small, low - cost, low - power internal battery - powered sensor (actuator) nodes with computing functions. These nodes can be attached to anything and placed anywhere. ´

The need to build networks with these sensor/actuator nodes, capable of providing communication anytime through a wireless link, to sense and detect events of interest and to operate machines and products is eminent. Instigating this ubiquitous networked society is a technical challenge for network engineers as well as computer engineers, and the necessary technology for achieving this society has great potential s a new revenue source for network operators. It’s based on this fact that the concept Wide – area ubiquitous networks arises. The objective of these networks is to globally provide a networked infrastructure of sensors and actuators to implement the ubiquitous networked society. This network concept is illustrated below;
The WAUN works as a middle box between a WT and a wired terminal. It does not provide a transparent session between them.

WTs are not Internet protocol (IP) terminals and do not use transmission control protocol (TCP)/IP because TCP/IP has too much overhead and WTs have low - performance central processing units (CPUs) and little memory. The APs offered by the network provider convert the wireless link protocol dedicated to WAUN WTs into protocols developed in the IP community. APs also convert identification numbers (IDs) between those used at the wireless link and those used in the core (fixed) network to identify a WT. The radio access network gateway servers (RANSs) distinguish the signal (e.g., user data and authentication request) sent from each WT and switch it to the appropriate destination on the basis of the distinguished result.

WTs can move. The mobility management function maintains the area in which a WT exists. This function is implemented by location registration technologies similar to those used in cellular networks.

Wired terminals are IP terminals that communicate with WTs in WAUN and are accommodated through the IP gateway (IP - GW). Their interface with WAUN is a widely used common interface such as TCP/IP, but wired IP terminals are prevented from directly accessing WAUN network entities such as RANSs for security reasons. WAUN does not support mutual communication between wired IP terminals.

In WAUN, several IDs are used to make the service convenient, secure, and efficient. WAUN offers security functions and ID conversion/resolution. In particular, to prevent tracking by a stranger, the ID of the WT is assigned temporarily and often updated. This ID management with mutual authentication between the terminal and the network enables us to achieve secure communication. The subscriber authentication and ID management (SAI) server stores the subscriber profile information including the wireless/ wired terminal information for authentication and ID management.

The WAUN core network controls communication between pairs of a wired terminal and a mobile WT and offers functions of ID management, location management, security, and access control. It needs to have enough scalability to process these functions for huge numbers of WTs. There are two important points in designing the WAUN core network. First, the processing necessary for communication control in a WT should be reduced as much as possible because the WT has low power consumption and low capability. Second, a limited radio - frequency band should be shared efficiently among many WTs. Thus, we need to decrease the communication overhead to increase the number of WTs that WAUN can accommodate.

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