Giacinto Gelli » 2.Overview of wireless

Outline

Introduction
History of wireless communications
Wireless networks
Wireless applications
Wireless terminals
Spectrum and standards

The wireless market

Wireless communications is the fastest growing segment of the communications industry:

• cellular systems experimented exponential growth since 1982, with over 3 billion users worldwide today
• proliferation of laptop and palmtop computers enabled diffusion of wireless LAN based on IEEE 802.11
• many emerging new applications (e.g., wireless sensors, automated highways, smart homes) and systems (e.g., WiMax, Zigbee, UWB)

Wireless networks: coverage regions

WPAN (Wireless Personal Area Network):

• room (e.g., Bluetooth, ZigBee, UWB)

WLAN (Wireless Local Area Network):

• building, campus (e.g., IEEE 802.11/WiFi)

WMAN (Wireless Metropolitan Area Network):

• town (e.g., IEEE 802.16/WiMax)

WWAN (Wireless Wide Area Network):

• region, global (e.g., GSM, UMTS, satellite)

Wireless network: protocol reference model

Wireless applications

Vehicles:

• transmission of news, road conditions, weather, music via DAB
• personal communication using GSM
• positioning via GPS
• satellite anti-theft and assistance systems
• local ad-hoc network with vehicles close-by to prevent accidents, guidance system, redundancy
• vehicle data (e.g., from busles, high-speed trains) can be transmitted in advance for maintenance and fleet management

Example: road traffic management

Wireless applications

Emergencies:

• replacement of a fixed infrastructure in case of earthquakes, hurricanes, fire etc …
• crisis, war

Medicine:

• early transmission of patient data to the hospital, current status, first diagnosis
• remote patient monitoring and diagnosis

Wireless applications (cont’d)

Business

• Direct access to customer files stored in a central location
• Consistent databases for all agents
• Mobile office
• Inventory
• Location-aware services
• Surveillance, security
• M-commerce, M-banking, etc …

Wireless applications (cont’d)

Entertainment

• Outdoor Internet access
• Intelligent travel guide with up-to-date location dependent information
• Ad-hoc networks for multi user games

Education

• Remote classrooms
• M-learning

Wireless applications (cont’d)

Sensors

• Monitoring of weather and earth activities
• Monitoring of public service networks (e.g., water)
• Monitoring of fire hazards, toxic waste sites, stress and strain in buildings and bridges, pollution

Military

• Identification and tracking of enemy targets
• Detection of chemical and biological attacks
• Support of unmanned robotic vehicles
• Missile guidance systems
• Electronic warfare

Wireless terminals

Limitations of wireless terminals

Power consumption:

• limited computing power, low quality displays, small disks due to limited battery capacity

Loss of data:

• higher probability, has to be included in advance into the design (e.g., defects, theft)

Limited user interfaces:

• compromise between size of fingers and portability
• integration of character/voice recognition, abstract symbols

Limited memory:

• limited value of mass memories with moving parts

Wireless vs. wired networks (cont’d)

The radio spectrum is a scarce resource that must be allocated to many different applications and systems:

• the spectrum is controlled by regulatory bodies and can be very expensive
• frequencies have to be coordinated, useful frequencies are almost all occupied
• the medium cannot be easily “replicated”

Wireless networking is a significant challenge due to mobility:

• traffic patterns, user locations, and network conditions are constantly changing
• the network must be able to locate a given user and route information while the user moves

Spectrum regulation

Government agencies allocate and control the use of the spectrum: FCC in USA, ETSI in Europe, ITU worldwide.
Some spectrum reserved for specific applications (commercial/military).

Spectral auctions for selling spectral blocks to the highest bidder (e.g., UMTS, WiMax):

• Pros: most efficient way to allocate spectrum, high revenues for the governments
• Cons: competition limited to big companies, infrastructure investments are delayed

ISM bandwidth

Some portions of spectrum not licensed (ISM, Industrial, Scientific & Medical band):

• 900 MHz band (902-928 MHz)
• 2.4 GHz band (2.4-2.4835 GHz)
• 5.8 GHz band (5.725-5.850 GHz)

Everyone can use this spectrum according to a specific set of rules (modulation type, power level etc.):

• ETSI specification EN 300 328-1 (Europe)

Spectrum of some existing systems

Wireless standards

Necessary to assure interoperability between different products/networks.
Companies want their systems adopted as standards:

• alternatively try de-facto standards
• usually standards do not include all the details on system design, some aspects are left unspecified to allow for innovation and competition between companies

Standards determined by several organisms in many countries:

• TIA/CTIA and IEEE in USA, ETSI in Europe, ITU worldwide

Standardization is often a long and conflicting process:

• successes (GSM) vs. failures (Hiperlan)