Wireless Technology: the new vision Wireless Long Distance 1G Analog AMPS TACS NMT RTMS 2G narrowband Digital GSM IS-54/136 TDMA ISS-85/cdmaOne PDC 2G+ or 2.5G Voice and Data GPRS, HSCDS GSM IS-136A & 8 TDMA IS-95c cdmaOne 3G Broadband Digital W. CDMA UWC-136 cdma2000 Voice Very small data American Roaming Enhanced Voice some data International Roaming Voice Enhanced data E-mail Internet Broadband data Video Fast Internet Remote Access
Wireless Technology: the new vision Wireless Long Distance: GSM The most popular 2G cellular standard developed to cater voice services and data delivery using digital modulation.
Development background :
Developed by Groupe Sp éciale Mobile (founded 1982) which was an initiative of CEPT (Conference of European Post and Telecommunication).
In 1989, ETSI (European Telecommunications Standards Institute) took the control of GSM and defined new acronym “ Global System for Mobile Communications .”
Commercial use has been started since 1991 .
Features of GSM Standards :
Supports international roaming and handheld terminals .
Good subjective speech quality and wide-range of new services .
Low cost (?) .
Compatible with other systems, say ISDN and PSTN.
Extends the 2G technologies – GSM, TDMA, CDMA. GPRS (general packet radio systems) technology is used to add data capacity .
Wireless Technology: the new vision Wireless Long Distance
The goals of 3G are to provide-
WANs for PC and multimedia, allowing for bandwidth on demand.
flexibility to support multiple standards
integrate fixed wireless access services, satellite services and cellular at data rates 384 kbps for mobile, and 2 mbps for fixed.
CDMA is the universal standard for 3G, but face the same pricing issue at 2.5G (time basis charge).
Court battles over the leased spectrum.
costs to deploy not seen as tenable.
Broadband IP could provide 4G services (since 2003).
Users pay for different kind of services.
The service is IP based and looks like wired services accessed via a browser.
New entrants are looking for 3G alternatives.
VSAT (very small aperture terminal) :
Stationary wireless Broadband is best provided by VSAT.
Mobile equipment for transmitting and receiving signals.
Subscriber Identity Module (SIM) for storing necessary permanent and temporary data.
Base Station (BS)
Base Transceiver System (BTS) for
transmitting and receiving signals; and
Base station Controller (BSC) for
assigning and managing resources,
controlling handoff and power level, etc.
Mobile Switching Centre (MSC)
Manage communications, mobility, and billing information.
Home Location Register (HLR): central master database for users under the MSC.
Visitor location Register (VLR): Local database for the users currently under the domain of MSC.
Authentication Center (AuC): Authenticate mobile terminals and encrypt user data.
Equipment Identity Register (EIR): register MTs and locked stolen or malfunctioning MTs.
Wireless Technology: the new vision Wireless Long Distance: GSM Network Components Base Transceiver System (BTS) Base Station Controller (BSC) Base Station (BS) VLR HLR EIR AuC Mobile Switching Centre (MSC) PSTN Other GSM Mobile Terminal (MT) Wireless Connection P2P Wireless or optic fiber connection
Wireless Technology: the new vision Wireless LAN
Used within a building or among buildings on a campus .
Wireless LANs are not generally replacing existing wired LANs but extending them to portable devices.
Example: In hospitals, doctors and nurses can use handheld or notebook computers to record patient data at the bedside, which is faster than using a wired computer.
WLANs use two technologies: infrared and microwave .
Cannot penetrate solids such as walls, ceiling, dust or rain. So, transmitter and receiver must be in line of sight.
Microwave and radio-frequency (RF) are the most popular WLAN technology because the signals can go through the walls.
Wireless Technology: the new vision Wireless LAN Wireless LAN use two topologies: peer-to-peer and client-server .
Peer-to-peer: each unit communicate with every other units.
Less expensive because the system has no central controlling unit.
Performance decreases as traffic increase because more and more collisions occur.
Client-Server: Server is the central coordinating node. It communicates with the clients wirelessly and links to a wired LAN on behalf of those clients.
Wireless Technology: the new vision Wireless LAN
Wi-Fi is the 802.11b wireless Ethernet standard that transmits up to 11 Mbps
connection is easy .
Wi-Fi networks run in unlicensed bandwidth .
Appear in a place where people congregate such as airports, hotels, conference centers, and coffee houses.
For many people, WLAN services could be equivalent to 3G at about 1/13 th the current cost.
Self-organizing Mesh is a new idea in WLAN arena
Operate in peer-to-peer mode
A message is routed to the nearest access point – the closest device – which routes it to the next nearest point, and so on.
The unusual phenomenon is that the more users, the more capacity . This technology could strongly influence the future of wireless.
With the goal of replacing the wireline link . This “fixed wireless” solves “the last mile” problem.
Use RF technology between a home or business and a telephone company’s central office.
One approach is to place antennas on light posts to form a wireless mesh.
Fixed wireless is being used in developing countries and remote locations in place of wire because these networks are more rapidly deployed and less costly that buying cables.
Some developing countries are bypassing wiring altogether.
Wireless PAN (Personal Area Network) :
A short distance network – about 30 feet (10 meters).
The main technologies used are infrared and Bluetooth .
This new kind of network could be used to synchronize laptop and a PDA, link several laptops in a rooms, etc.
M- Commerce: Conduct commerce digitally from wireless devices.
Location-based services and personalization are important part of wireless economy .
Due to small antennas and low power, the handheld device can’t send signals to satellite for measuring location using GPS.
Research Challenges Wireless Resources …………… . Bandwidth in wired media 600 Mbps for 1 ATM line 600 Mbps for 1 ATM line Bandwidth in wireless media 384 Kbps for cell radius 10 km ( 2G / 2.4G) / 2 Mbps for cell radius < 100 m (Pico-cell, 3G)
Most GSM Networks operate at 900 MHz and/or 1800MHz ,
850 MHz and/or 1900MHz in Parts of Americas (including USA and Canada).
900 MHz Frequency Band Time slot duration 577 µs
Each frame contains 8 time slots.
Channel data rate: 270.833 kbps
Frame duration: 4.615 mS
There are two types of logical channels:
Signaling Channels – for broadcasting, common control, and dedicated control.
Research Challenges Wireless Resources: GSM Uplink Downlink 124 carriers 890 MHz 915 MHz 935 MHz 960 MHz Downlink Uplink 124 carriers Each Carrier has 200KHz Frequency band TDMA divides each RF channel (i.e., carrier) to 8 voice Channel t 1 t 2 t 3 t 4 t 5 t 6 t 7 t 8 Time-slots
Microwave frequencies are more dangerous than radio-wave frequencies, because
microwave cause molecule to vibrate faster , causing heat as the molecules rub against each other.
The power limit on cell-phones, wireless modems, and WLANs (3 watts) aims to protect people from this short-term microwave heating phenomenon.
Some studies shows that long-term effects from low-level vibration do not raise body temperature, but damage to DNA , which may cause disease like cancer.
Electromagnetic radiation from power lines, electronic appliances, and computers can interfere with the body’s bio-electromagnetic fields, causing an imbalance. These imbalances leave people feeling drained, fatigued, and stressed out.
Although our body can rebalance disruptions caused by occasional exposure to electromagnetic radiation, frequent exposure will lower body’s immunity and causes diseases.
Research Challenges Other Open Research Problems on Cellular Network