Protocols and the TCP/IP Protocol Suite

Protocol architecture

Overview of TCP/IP

Open systems interconnection (OSI) reference model

Internetworking

Wireless Comes of Age

Guglielmo Marconi invented the wireless telegraph in 1896

Communication by encoding alphanumeric characters in analog signal

Sent telegraphic signals across the Atlantic Ocean

Communications satellites launched in 1960s

Advances in wireless technology

Radio, television, mobile telephone,communication satellites

More recently

Satellite communications, wireless networking,cellular technology

Breaking down the issues in Mobile Computing

• Technical Challenges of Mobile Computing
– portability,
– mobility,
– wireless communications
– system issues

•Traveling people and their needs with respect to applications and technologies
– application perspective: which applications are of benefit?
– Which applications can be implemented and used effectively regarding the often narrow bandwidth, limited computing power, small memory and battery capacity and other resources of the terminals?


•Wireless Networks
– to main types: terrestrial cellular and satellite networks – determine to a large extent application architectures and usable protocols
– communication autonomy is an important feature of the terminals in these networks: thus the terminals are not always reachable for variety of reasons

•Data Management issues
– where to keep the data, when to transmit it, whether to use caching and where in the network, how to optimize data placement, pull/push approach, transactional services, location-dependent queries etc
– these questions are closely related with the
networking issues and properties of the terminals

Nomadic or Mobile Computing

Nomadic computing is concerned with the connection of portable (mobile) computers, and with the migration of software, from a home platform to a remote one;

– It is now recognized that access to computing and communications is necessary not only from one's "home base," but also while one is in transit and when one reaches one's destination.

– The goal of "transparent virtual networking" or "nomadic" computing is precisely to permit users and programs to be as effective as possible in this environment of uncertain connectivity, without changes to the manner in which they operate.

– Using diverse phones from everywhere in the world is not activity that could be called nomadic computing (because there is no computing (data processing) involved)

– Dragging around a laptop and working with it without being able to set up a connection to the “home base” through a computer network is neither nomadic
computing in a strong sense; one must be able to communicate with “home base” and people in other organizations

– Does nomadic computing require some devices to be dragged around by the people?
(not necessarily, an infrastructure with suitable access devices could be offered to traveling people - in the same manner as telephones are offered in hotels, airports, etc.)

– Another important development are the advances in computer networking infrastructure that make global connectivity possible.

– One notable development is the Internet as a global networking infrastructure, but in this context especially the wireless technologies are very important.

• The role of wireless technologies in mobile computing:

– wired portable devices can be connected to the network infrastructure only in certain locations for a certain period of time => communication activity of a
nomad is spatially and temporally restricted – wireless portable devices, especially those operating with radio transmitter/receiver avoid the above problem to a great extent


• nomadic or mobile computing consists of: traveling people using
• portable wireless computing and communication devices connected to
• computer network infrastructure supporting global connectivity and remote computing