Home location register (HLR) database – stores information about each subscriber that belongs to it
Visitor location register (VLR) database – maintains information about subscribers currently physically in the region
Authentication center database (AuC) – used for authentication activities, holds encryption keys
Equipment identity register database (EIR) – keeps track of the type of equipment that exists at the mobile station
Showing posts with label mobile. Show all posts
Showing posts with label mobile. Show all posts
Tuesday, December 30, 2008
Types of Antennas
Isotropic antenna (idealized)
Radiates power equally in all directions
Dipole antennas
Half-wave dipole antenna (or Hertz antenna)
Quarter-wave vertical antenna (or Marconi antenna)
Parabolic Reflective Antenna
Radiates power equally in all directions
Dipole antennas
Half-wave dipole antenna (or Hertz antenna)
Quarter-wave vertical antenna (or Marconi antenna)
Parabolic Reflective Antenna
Limitations and Difficulties of Wireless Technologies
Wireless is convenient and less expensive
Limitations and political and technical difficulties inhibit wireless technologies
Lack of an industry-wide standard
Device limitations
E.g., small LCD on a mobile telephone can only
displaying a few lines of text
E.g., browsers of most mobile wireless devices use
wireless markup language (WML) instead of HTML
Background
Provides preview and context for rest of
book
Covers basic topics
Data Communications
TCP/IP
Broadband Wireless Technology
Higher data rates obtainable with broadband wireless technology
- Graphics, video, audio
Shares same advantages of all wireless services: convenience and reduced cost
- Service can be deployed faster than fixed service
- No cost of cable plant
- Service is mobile, deployed almost anywhere
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
– 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
– 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
First & Second Generation Mobile Phones
Mobile phones were born when a number of mobile radio users decided to make mobile phone technology more popular. Mobile telephones were firstly installed in vehicles on a permanent basis, later some versions appeared which were named transportables, could also be carried. Motorola developed a two way radio in a rucksack, the walkie-talkie, and this was widely regarded as one of the first mobiles.
First Generation Phones
First mobile phones are called as first generation (1G) mobile phones. Mobile phones started to gain popularity with the introduction of cellphones that were based on cellular networks.
Mobile phones were originally much bigger than current ones, they were designed for installation in vehicles only, which is called the car phone. These big phones were later converted for use as transportable phones the size of a small.
This system used a single large transmitter on top of a tall building and had a single channel, used for both sending and receiving. To talk, the user had to push a button that enabled the transmitter and disabled the receiver. This system is known as push – to - talk systems.
Second Generation Phones
Second generation, is also called 2G. Second generation telephone systems were different because of their use of digital circuit switched transmission. 2G is the introduction of advanced & quick telephone to network signals. The introduction of 2-G systems saw telephones move from historic 1G telephones to small hand held items, which were much more portable. This change was made useful improvements in technology for example more advanced batteries and energy efficient electronics.
The second generation mobile telephones had several advantages over 1G items. These included SMS messaging, which initially became possible on GSM networks & eventually on all digital networks. SMS text messaging soon became the communication method of choice & the general public now prefer sending messages to placing voice calls.
The first generation of mobile phones was analog; the second generation was digital. The voice signal picked up by the microphone is digitized and compressed.
First Generation Phones
First mobile phones are called as first generation (1G) mobile phones. Mobile phones started to gain popularity with the introduction of cellphones that were based on cellular networks.
Mobile phones were originally much bigger than current ones, they were designed for installation in vehicles only, which is called the car phone. These big phones were later converted for use as transportable phones the size of a small.
This system used a single large transmitter on top of a tall building and had a single channel, used for both sending and receiving. To talk, the user had to push a button that enabled the transmitter and disabled the receiver. This system is known as push – to - talk systems.
Second Generation Phones
Second generation, is also called 2G. Second generation telephone systems were different because of their use of digital circuit switched transmission. 2G is the introduction of advanced & quick telephone to network signals. The introduction of 2-G systems saw telephones move from historic 1G telephones to small hand held items, which were much more portable. This change was made useful improvements in technology for example more advanced batteries and energy efficient electronics.
The second generation mobile telephones had several advantages over 1G items. These included SMS messaging, which initially became possible on GSM networks & eventually on all digital networks. SMS text messaging soon became the communication method of choice & the general public now prefer sending messages to placing voice calls.
The first generation of mobile phones was analog; the second generation was digital. The voice signal picked up by the microphone is digitized and compressed.
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