Information Systems: Wireless Computing

Fitness and Sport Tracker

Receiver that can track user activities

Free Optical Space Communication, FSO

Technologies that use light to transmit information through air. IR light is an example. LED or LASER sources are used for high speed data links. Technology originally created for use with PANs, Personal Area Networks, but replaced by Bluetooth and wifi.

LTE (4G)

Technology to transmit data over cellular telephone network that can support live streaming services. 5G is in the process of being standardized.

GPRS and EDGE

Technology to transmit data over cellular telephone network that is able to transmit at lower speeds. Useful for text-based services like instant messaging or email.

Name the 4 Main GPS Systems

1.) NAVSTAR - USA network 2.) GLONASS - Soviet Union network 2000 3.) BeiDuo - Chinese network 2011 4.) Galileo - European Union network, first satellite launched in 2011, operational in 2016 Japan is creating a regional GPS system, QZSS, to complement and enhance NAVSTAR coverage over Japan. The first satellite was launched in 2010

Name the 4 Components of a One-way Microwave Link

1.) transmitter 2.) receiver 3.) transmission lines 4.) antenna These basic components exist in every radio communication system where the technology used differs from those of lower frequency. Wires and cables function poorly as microwave signal conductors. Often a parabolic dish antenna is used to focus a narrow microwave beam.

Wifi Hotspots

A common way to connect to a wireless network, also called a wifi access point. The existence of these points provides wireless access in public places like hotels, airports, libraries, or open areas on the street. Some are free and some charge.

GPS Augmentation

A satellite signal can be distorted by atmospheric factors, including errors in calculated position that cannot be ignored in things like airplane navigation and landing or land measurements. A mechanism called augmentation corrects for these errors by receiving a GPS position at known positions and calculating the error in real-time to send to one or more geostationary satellites to broadcast them for receiving stations to then broadcast. A network of receiving points and infrastructure is needed to broadcast errors known as the SBAS network, Satellite Based Augmentation System. There are several augmentation systems in the world: 1.) WASS Wide Area Augmentation System for US 2.) EGNOS, Europe 3.) MSAS, Japan

Geopositioning System, GPS

Allows for the location of an object on the surface of the Earth with high precision. To locate a point, 3 points are needed: 1.) latitude 2.) longitude 3.) altitude. To calculate coordinates, receiver gets the signal of several satellites of a network in orbit.

Active Satellite

Amplifies received signal before re-transmitting to the receiver on the ground. Has higher power needs with a shorter active life.

Microwave Link Transmission Line

Carries the signal from the transmitter to antenna and then from antenna to receiver. Microwave frequencies cause media excessive signal losses so engineers use coaxial cables and hollow pipes called waveguides. In electrical engineering, anything that conducts current from one point to another.

Maximum Cell Capacity

Characteristic of cellular networks where cells have a maximum number of users that can be connected. The trend in places where many users are expected is to use smaller cells with less transmitting power to attend more users Rural areas use less cells with more transmission power For big events like football games, a special reinforcement network of mobile base stations is installed, but is sometime still not enough for all the traffic.

Low Earth Orbit, LEO

Circular orbit 2000km above Earth's surface that completes a revolution every 90 minutes. They change position relative to ground position quickly so several satellites are necessary for uninterrupted connectivity. Requires large constellations of small satellites in order to deliver full-time communications service which makes deployment and operation more expensive. Less expensive to launch than into geostationary orbit and does not require as strong of a signal.

Frequency Allocation

Complicated process requiring international coordination and planning carried out under the auspices of the ITU, International Telecommunication Union. For better facilitation, the world is divided into 3 regions: 1.) Europe, Africa, formerly the Soviet Union, and Mongolia region 2.) North and South America, and Greenland region 3.) Asia, Australia, and Southwest Pacific Within these regions, frequency bands are allocated to various satellite services where a given service may be located in a different band in a different region. Services: Fixed Satellite Service FSS Broadcasting Satellite Service BSS Mobile Satellite Service Radio navigation Satellite Service Meteorological Satellite Service Amateur Satellite Service

Wireless Modem

Connection to a data cellular network does not always require a cell phone as there are other devices that can share connection with other devices using wifi.

Mobile Broadband

Connection to cell phone towers to create remote connections through wireless ISPs or WISPs. Allows for near ubiquitous access to Internet where users can be miles away from a base station

802.11a

Defined in 1999, allowing for speeds between 1.5 and 5.4MB per second using a 5GHz band divided into 12 or 13 non-overlapping channels At first reserved for European users, but more used in North America Less crowded than 2, 4 GHz with more non-overlapping channels, but has less range and penetration of obstacles due to a higher frequency.

802.11b

Defined in 2000, allowing for data transmission speeds at 11MB/s. Defined 14 channels (only 11 can be used in US) that overlap where only 3 can be used at the same time.

802.11g

Defined in 2003 as an update of 802.11b using the same band; is backward compatible with 802.11b and incompatible with 802.11a. Up to 54MB

802.11n

Defined in 2007, with 54 to 600MB/s. Can handle more than one antenna in the same device using MIMO, Multiple Input Multiple Output, that uses several channels all around the world.

802.11ac

Defined in 2013, with 1GB/s using a 5GHz band. Expensive

Wifi Channels and Bands

Each of the wifi standards defines a set of radio communication channels that make up one or more bands of the radio spectrum. Wifi bands help to free use in the case of different applications. The 2, 4 GHz band has widespread use for wifi known as the Industrial, Scientific, and Medical radio band.

Cellular Wireless Transmission

Expansion of mobile phones has created a ubiquitous infrastructure allowing us to be connected almost all over the urban world using a cellular radio frequency network. Cellular communication called cellular due to its supporting network being organized in wireless cells created around a base station that provides transmission and reception services. Towers providing access to communication network where devices are included in a region with the shape of a hexagon for optimal covering of territory. Also allows for reuse of radio frequencies in non-adjacent cells. When a person moves, the handset transparently changes from one base station to another, called a handover. There are several frequency bands allocated for cellular service and differ in each country. Modern handsets can work in all different bands.

Satellite Communication

Form of wireless computing using an artificial satellite that relays and amplifies radio signals. Used for television, telephone, radio, Internet, and military applications with over 2000 communications satellites in Earth's orbit. Provides Internet access to rural classrooms. Most commonly use microwave frequency bands for services. There are 4 radio bands used for civil communication and military satellite services, from lower to higher frequency: 1.) C 2.) X 3.) Ku 4.) Ka Where Lowe frequencies have less bandwidth and need a bigger antenna.

Geostationary Orbit

From Earth, a satellite will appear motionless or in a fixed position due to the satellite revolving at Earth's angular velocity. 360 degrees every 24 hours in an equatorial orbit. The satellite must be located in circular orbit 22,236 miles above Earth's equator following the direction of its rotation. Useful for communication due to ground antennas not needing to track satellite motion. First proposed by Arthur C. Clarke in 1945 in an article titled "Extraterrestrial Relays" to relay radio signals where the description of the orbit is referred to as the Clark Belt.

Infrared Light-based Communication

IR beams used as a transmission medium for short distances. In TV remotes and some datalinks, but replaced almost entirely by Bluetooth for personal data transmission. Visible Light Communications (VLC) and Free Space Optical Communications (FSO) technology uses LEDs or LASERs to achieve GB/s speeds up to a couple kilometers.

Wireless Frequency Allocations

In order to avoid interference, a careful distribution of frequencies must be used for different applications. Data, television, and radio have their own allotments. Government agencies in each country dictate use of the radio frequency spectrum.

UMTS (3G) and HSDPA (3G+)

Most extended technology for data transmission over a cellular telephone network allowing for multimedia content download.

Microwave Link Antenna

On the transmission end, emits a microwave signal from the transmission line into free space, an electrical engineering term for the void between the transmitting and receiving ends where air is not necessary for radio transmission. On reception end, antenna is pointed toward the transmitting station and collects the signal energy then feeds it into the transmission line for receiver processing. Allow communication over long distances using small amounts of power and interference.

Passive Satellite

Only redirects, usually via reflection, received signals from source to receiver on ground where the signal is not amplified making it weaker and a big antenna necessary

Outdoor GPS

Outdoor receivers that include maps with level curves and altitudes. Coverage is worse in the mountains that obscure satellite vision.

Microwave Link Transmitter

Produces a signal to carry information being communicated, the input, and can be anything capable of being sent by electronic means. Has 2 main jobs: 1.) generating microwave energy at a required frequency and power level 2.) modulating microwave energy with an input signal to convey meaningful information. This is accomplished by varying some characteristic of the energy in response to transmitter input.

Wireless Access Control and Encryption

Radio signals are sent using open space so systems must ensure there are only authorized users of a wifi access point with no connection eavesdropping. There are different protocols to ensure the authorization, authentication, and accounting of users like WPA2 and 802.12X.

NAVSTAR

Relies on a network of 24 satellites 20,000km above sea level with synchronized trajectories. The broadcast signal is based on an accurate on-board atomic clock using 2 radio frequencies: 1.) 1GHz, L1 2.) 1227.60MHz, L2 The system has 3 elements: 1.) space (satellites) 2.) control 3.) user (receivers) The direct vision of 4 satellites is needed to triangulate position in 3D where accuracy increases with the number of satellites

Satellite Receiver

Required to receive satellite transmissions. They have larger or smaller antennas and transmission power depending on distance from the ground station. Used for two-way satellite communication with small, parabolic antennas called VSAT, Very Small Aperture Terminal, with data rates from 4KB/s to 4MB/s.

Bluetooth

Short distance, between 10 and 15m, data transmission based on radio waves. Used to connect devices like headphones or speakers. Most used to create a PAN formed by Bluetooth connected devices.

IrDA

Standard regulating short-range data transmission using IR connections defined by the Infrared Data Association, IrDA. Necessary to have direct or reflected line of sight.

IEEE 802.11

Standard that regulates wifi connections covering the media access and physical layers of the OSI stack. Several versions were developed to accommodate more features and bigger bandwidths.

Wireless Computing

Wireless communications use waves as a transmission medium. Depending on the frequency, there are technologies based on light, conventional radio waves, which is a high frequency electromagnetic radio wave.

Wifi Channel Saturation

The biggest wifi interference is often other users. There are several channels defined for wifi in each band of the radio spectrum. The 2, 4GHz band has 13 channels defined that overlap where only 3 can be used in the same area without interference.

Bluetooth Pairing

The connection process before two Bluetooth devices connect. Necessary to enhance the privacy and security so ink authorized devices can connect. Easy process, device must be set to discoverable node and the other device searches for it in available devices. Once found, a PIN must be provided

Satellite Coverage Footprints

The footprint of a communication satellite is the ground area over which the transponder offers coverage. With transponder power known, can properly determine the antenna dish diameter required to receive each transponder signal. The bigger the footprint, the bigger the antenna needed.

Vehicle GPS

The most extended of GPS functions that replaced paper maps.

Wifi or Wireless LAN

Trademark referring to wireless LAN based on radio waves. Most used to connect mobile devices when user is in range of a wifi access point.

Satellite Network Communication

Used by telecommunication companies to cover larger distances and connect difficult access areas. Satellite is in space so, depending on the application, may need large antennas or high power devices.

Microwave Link

Used for point to point connections. Directs a beam to a receiving antenna in order to minimize interference with other equipment. A communication system that uses a beam of radio waves in microwave frequency range to transmit information between two fixed locations. Used by broadcasters to send programs from a studio to the transmitter which could be miles away, to carry cellular telephone calls between cell sites, wireless ISPs to provide clients with high speed Internet access without the need for cable connections, telephone companies to transmit calls between switching centers, and companies and government agencies to provide communication network between distributed facilities. Adaptable broadband moving large amounts of information at a high speed that requires no equipment or facilities between two terminal points. Must be within operating range and is able to penetrate most atmospheric factors, but line of sight is still necessary.

Visible Light High Speed Data Links

Visible Light is used in high speed data communications in the 1 to 2km range. Some commercial systems that use LED or LASER services require line of sight, transmitting up to 10GB/s depending on distance and atmospheric factors.