Home Netwoks
Home Networks
Personal Area Networks
Wireless Local Area Networks
by
Engin Erentürk
Home Networks
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A home network is a
residential local area
network.
With the increasing
availability of broadband
Internet service and
affordable PCs, more
people are networking
their multiple PCs and
network-capable devices
to use a single
broadband outlet, usually
through a cable or DSL
provider.
Home Networks
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A home network may consist of the following
components:
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A broadband modem connected to the phone line for DSL
or cable outlet for cable service.
A router between the modem and primary PC.
USB to Ethernet adaptors for devices without Ethernet
cards
USB to wireless adaptors for devices without wireless
interfaces.
Secondary PCs such as laptops or PCs owned by other
people in the house.
Home media devices such as DVRs like TiVo, digital audio
players and Internet-ready stereo systems, etc.
Home Networks
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As networking technology evolves, more
electronic devices and home appliances will
become Internet ready and accessible
through the home network.
Set-top boxes from cable TV providers
already have USB and Ethernet ports "for
future use".
Home Networks
LAN (Local Area Network)
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A local area network (LAN) is a group of computers and
associated devices that share a common communications line or
wireless link and typically share the resources of a single
processor or server within a small geographic area (for example,
within an office building).
Current LANs are most likely to be based on switched Ethernet
or Wi-Fi technology running at from 10 to 10000 Mbit/s.
The defining characteristics of LANs in contrast to WANs are:
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much higher data rates
smaller geographic range - at most a few kilometers
they do not involve leased telecommunication lines
Home Networks
LAN (Local Area Network)
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The following characteristics differentiate one LAN
from another:
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Topology : The geometric arrangement of devices on the
network. For example, devices can be arranged in a ring or
in a straight line.
Protocols : The rules and encoding specifications for
sending data. The protocols also determine whether the
network uses a peer-to-peer or client/server architecture.
Media : Devices can be connected by twisted-pair wire,
coaxial cables, or fiber optic cables. Some networks do
without connecting media altogether, communicating
instead via radio waves.
Home Networks
LAN (Local Area Network)
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Media contention occurs when two or more network
devices have data to send at the same time.
Because multiple devices cannot talk on the network
simultaneously, some type of method must be used
to allow one device access to the network media at
a time.
This is done in two main ways:
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carrier sense multiple access collision detect (CSMA/CD)
token passing
Home Networks
CSMA and CSMA/CD
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Carrier Sense Multiple Access (CSMA) is a probabilistic Media
Access Control (MAC) protocol in which a node verifies the
absence of other traffic before transmitting on a shared physical
medium, such as an electrical bus, or a band of electromagnetic
spectrum.
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"Carrier Sense" describes the fact that a transmitter listens for
carrier wave before trying to send. That is, it tries to detect the
presence of an encoded signal from another station before
attempting to transmit. If a carrier is sensed, the node waits for the
transmission in progress to finish before initiating its own
transmission.
"Multiple Access" describes the fact that multiple nodes send and
receive on the medium. Transmissions by one node are generally
received by all other nodes using the medium.
Home Networks
CSMA and
CSMA/CD
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CSMA/CD is a modification of pure CSMA.
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Collision detection is used to improve CSMA
performance by terminating transmission as soon as
a collision is detected, and reducing the probability
of a second collision on retry.
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Methods for collision detection are media
dependent, but on an electrical bus such as
Ethernet, collisions can be detected by comparing
transmitted data with received data.
Home Networks
Token Passing
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Token Passing is a technique in which only that
system can communicate that has token.
Token is a sort of control mechanism that gives
authority to the system to communicate or use the
resources of that network. Once the communication is
over, the token is passed to next candidate in a
sequential manner.
Home Networks
Popular LAN Protocols Mapped to
the OSI Reference Model
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LLC : Logical Link Control
MAC : Media Access Control
OSI : Open Systems Interconnection
Home Networks
LAN Topologies
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bus topology: is a linear LAN architecture in which transmissions from network stations
propagate the length of the medium and are received by all other stations
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ring topology: is a LAN architecture that consists of a series of devices connected to one
another by unidirectional transmission links to form a single closed loop
Home Networks
LAN Topologies
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star topology: is a LAN architecture in which the endpoints on a network are connected to a
common central hub, or switch, by dedicated links
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tree topology is a LAN architecture that is identical to the bus topology, except that branches
with multiple nodes are possible in this case
Home Networks
Wireless LAN
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A wireless LAN or WLAN is a
wireless local area network that
uses radio waves as its carrier
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Areas may range from a single
room to an entire campus
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The backbone network usually
uses cables, with one or more
wireless access points
connecting the wireless users to
the wired network.
Home Networks
WLAN - Modes of operation
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Peer-to-peer or ad-hoc mode:
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This mode is a method for wireless devices to directly
communicate with each other. Operating in ad-hoc
mode allows wireless devices within range of each
other to discover and communicate in peer-to-peer
fashion without involving central access points.
This is typically used by two PCs to connect to one
another, so that one can share the other's Internet
connection for example, as well as for wireless mesh
networks
Home Networks
WLAN - Modes of operation
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Access Point / Client
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The most common is to have access points wired to
Internet, and then having wireless clients (typically
laptops) accessing Internet through the access point
Home networks would typically have a stand-alone
access point wired up i.e. through an ADSL
connection, while hotspots and professional networks
(i.e. providing wireless coverage in an office building)
typically would have multiple access points, placed at
strategical points.
Home Networks
WLAN - Modes of operation
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Wireless distribution system
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When it's difficult to get all the Access Points wired up,
it's also possible to put up access points as repeaters.
Monitoring station
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Some wireless network cards can be set up to monitor
a network without connecting to an access point or
revealing itself. This can be used to sniff clear-text
activity, or to crack encryption
Home Networks
IEEE 802.11
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IEEE 802.11, the Wi-Fi standard, denotes a set
of Wireless LAN/WLAN standards developed by
working group 11 of the IEEE LAN/MAN
Standards Committee (IEEE 802)
Home Networks
IEEE 802.11X standards
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IEEE 802.11 - The original 1 Mbit/s and 2 Mbit/s, 2.4 GHz RF and IR standard (IEEE 802.11legacy) (1999)
IEEE 802.11a - 54 Mbit/s, 5 GHz standard (1999, shipping products in 2001)
IEEE 802.11b - Enhancements to 802.11 to support 5.5 and 11 Mbit/s (1999)
IEEE 802.11c - Bridge operation procedures; included in the IEEE 802.1D standard (2001)
IEEE 802.11d - International (country-to-country) roaming extensions (2001)
IEEE 802.11e - Enhancements: QoS, including packet bursting (2005)
IEEE 802.11F - Inter-Access Point Protocol (2003) Withdrawn 2005
IEEE 802.11g - 54 Mbit/s, 2.4 GHz standard (backwards compatible with b) (2003)
IEEE 802.11h - Spectrum Managed 802.11a (5 GHz) for European compatibility (2004)
IEEE 802.11i - Enhanced security (2004)
IEEE 802.11j - Extensions for Japan (2004)
IEEE 802.11k - Radio resource measurement enhancements
IEEE 802.11l - (reserved, typologically unsound)
IEEE 802.11m - Maintenance of the standard; odds and ends.
IEEE 802.11n - Higher throughput improvements
IEEE 802.11o - (reserved, typologically unsound)
IEEE 802.11p - WAVE - Wireless Access for the Vehicular Environment (such as ambulances and passenger cars)
IEEE 802.11q - (reserved, typologically unsound, can be confused with 802.1Q VLAN trunking)
IEEE 802.11r - Fast roaming
IEEE 802.11s - ESS Mesh Networking
IEEE 802.11T - Wireless Performance Prediction (WPP) - test methods and metrics
IEEE 802.11u - Interworking with non-802 networks (e.g., cellular)
IEEE 802.11v - Wireless network management
IEEE 802.11w - Protected Management Frames
IEEE 802.11x - reserved
IEEE 802.11y - Contention Based Protocol
Home Networks
Personal Area Network
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A personal area network (PAN) is
a computer network used for
communication among computer
devices (including telephones and
personal digital assistants) close
to one person.
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The reach of a PAN is typically a
few meters.
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PANs can be used for
communication among the
personal devices themselves
(intrapersonal communication), or
for connecting to a higher level
network and the Internet
Home Networks
Personal Area Network
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Personal area
networks may be
wired with computer
buses such as USB
and FireWire. A
wireless personal
area network (WPAN)
can also be made
possible with network
technologies such as
IrDA and Bluetooth.
Home Networks
IEEE 802.15
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IEEE 802.15 is the 15th
working group of the
IEEE 802 which
specializes in Wireless
PAN (Personal Area
Network) standards
Home Networks
IEEE 802.15
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It includes four task groups (numbered from 1 to 4):
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Task group 1 (WPAN/Bluetooth) deals with Bluetooth, having
produced the 802.15.1 standard, published on June 14, 2002.
It includes a medium access control and physical layer
specification adapted from Bluetooth 1.1.
Task group 2 (Coexistence) deals with coexistence of Wireless
LAN (802.11) and Wireless PAN.
Task group 3 is in fact two groups: 3 (WPAN High Rate) and
3a (WPAN Alternate Higher Rate), both dealing with high-rate
WPAN standards (20 Mbit/s or higher).
Task group 4 (WPAN Low Rate) deals with low rate but very
long battery life (months or even years). The ZigBee set of
high level communication protocols is based upon the
specification produced by 802.15.4b taskgroup.
Home Networks
Infrared Data Association
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The Infrared Data Association (IrDA) defines
physical specifications communications protocol
standards for the short range exchange of data over
infrared light, for uses such as personal area
networks (PANs).
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IrDA is a very short-range example of free-space optical
communication.
IrDA interfaces are used in palmtop computers and mobile
phones.
IrDA specifications include IrPHY, IrLAP, IrLMP, IrCOMM,
Tiny TP, IrOBEX, and IrLAN. IrDA has now produced
another standard, IrFM, for Infrared financial messaging
also known as "Point & Pay".
For the devices to communicate via IrDA they must have a
direct line of sight
Home Networks
Bluetooth
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Bluetooth is an industrial specification for
wireless personal area networks (PANs).
Bluetooth provides a way to connect and
exchange information between devices
like personal digital assistants (PDAs),
mobile phones, laptops, PCs, printers
and digital cameras via a secure, lowcost, globally available short range radio
frequency.
Home Networks
Bluetooth
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The system is named after a Danish king Harald
Blåtand (Harold I of Denmark in English), King of
Denmark and Norway from 935 and 936
respectively, to 940 known for his unification of
previously warring tribes from Denmark (including
Skåne, present-day Sweden, where the Bluetooth
technology was invented) and Norway
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The name was originally only a code-name for the
project, but ended up sticking
Home Networks
Bluetooth
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Bluetooth is a radio standard primarily designed for low
power consumption, with a short range (power class
dependent: 10 centimeters, 10 meters, 100 meters) and with
a low-cost transceiver microchip in each device.
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Bluetooth lets these devices talk to each other when they
come in range, even if they are not in the same room, as long
as they are within up to 100 meters of each other, dependent
on the power class of the product.
Home Networks
Bluetooth
• Bluetooth products are available in one of three power classes
mW: milli watt. Watt is the SI derived unit of power.
dBm: is an abbreviation for the power ratio in decibel (dB) of the measured
power referenced to one milliwatt (mW).
Home Networks
Bluetooth
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Communication & connection
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A Bluetooth device playing the role of the "master" can
communicate with up to 7 devices playing the role of
the "slave". This network of "group of up to 8 devices"
(1 master + 7 slaves) is called a piconet.
At any given time, data can be transferred between
the master and 1 slave; but the master switches
rapidly from slave to slave in a round-robin fashion.
(Simultaneous transmission from the master to
multiple slaves is possible, but not used much in
practice). Either device may switch the master/slave
role at any time.
Home Networks
Bluetooth
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Bluetooth specification
allows connecting 2 or more
piconets together to form a
scatternet, with some
devices acting as a bridge
by simultaneously playing
the master role in one
piconet and the slave role in
another piconet. These
devices have yet to come,
though are supposed to
appear in 2007.
Home Networks
Bluetooth
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Any Bluetooth device will transmit the following sets of
information on demand
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Device Name
Device Class
List of services
Technical information eg: device features, manufacturer,
Bluetooth specification, clock offset
Home Networks
Bluetooth
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Specifications and Features
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The Bluetooth specification was first developed by
Ericsson, and was later formalized by the Bluetooth
Special Interest Group (SIG). The SIG was formally
announced on May 20, 1999. It was established by
Sony Ericsson, IBM, Intel, Toshiba and Nokia, and
later joined by many other companies as Associate or
Adopter members. Bluetooth is also known as IEEE
802.15.1.
Home Networks
Bluetooth
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Bluetooth 1.0 and 1.0B
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Versions 1.0 and 1.0 B had numerous problems and
the various manufacturers had great difficulties in
making their products interoperable.
1.0 and 1.0B also had mandatory Bluetooth Hardware
Device Address (BD_ADDR) transmission in the
handshaking process, rendering anonymity impossible
at a protocol level, which was a major set back for
services planned to be used in Bluetooth
environments, such as Consumerium.
Home Networks
Bluetooth
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Bluetooth 1.1
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many errata found in the 1.0B specifications were
fixed
added support for non-encrypted channels
Received Signal Strength Indicator (RSSI)
Home Networks
Bluetooth
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Bluetooth 1.2
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this version is backwards compatible with 1.1 and the major
enhancements include
Adaptive Frequency-hopping spread spectrum (AFH),
which improves resistance to radio frequency interference
by avoiding using crowded frequencies in the hopping
sequence
Higher transmission speeds in practice
extended Synchronous Connections (eSCO), which
improves voice quality of audio links by allowing
retransmissions of corrupted packets
Host Controller Interface (HCI) support for 3-wire UART
HCI access to timing information for Bluetooth applications.
Home Networks
Bluetooth
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Bluetooth 2.0
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This version is backwards compatible with 1.x. The
main enhancement is the introduction of Enhanced
Data Rate (EDR) of 2.1 Mbit/s.
3 times faster transmission speed (up to 10 times in
certain cases)
Lower power consumption through a reduced duty
cycle
Simplification of multi-link scenarios due to more
available bandwidth
Further improved BER (bit error rate) performance
Home Networks
Bluetooth
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Bluetooth next Generation
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Atomic Encryption Change - allows encrypted links to change their encryption
keys periodically, increasing security, and also allowing role switches on an
encrypted link
Extended Inquiry Response - provides more information during the inquiry
procedure to allow better filtering of devices before connection. This
information includes the name of the device, and a list of services, with other
information
Sniff Subrating - reducing the power consumption when devices are in the
sniff low power mode, especially on links with asymmetric data flows. Human
Interface Devices (HID) are expected to benefit the most with mice and
keyboards increasing the battery life from 3 to 10 times those currently used
QoS Improvements - these will enable audio and video data to be transmitted
at a higher quality, especially when best effort traffic is being transmitted in the
same piconet
Simple Pairing - this improvement will radically improve the pairing experience
for Bluetooth devices, while at the same time increasing the use and strength
of security. It is expected that this feature will significantly increase the use of
Bluetooth
Home Networks
Bluetooth
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Future of Bluetooth
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Bluetooth technology already plays a part in the rising Voice
over IP (VOIP) scene, with Bluetooth headsets being used
as wireless extensions to the PC audio system. As VOIP
becomes more popular, and more suitable for general home
or office users than wired phone lines, Bluetooth may be
used in Cordless handsets, with a base station connected
to the Internet link.
In March 2006, the Bluetooth Special Interest Group (SIG)
announced its intent to work with UWB (Ultra-wideband)
manufacturers to develop a next-generation Bluetooth
technology using UWB technology and delivering UWB
speeds. This will enable Bluetooth technology to be used to
deliver high speed network data exchange rates required
for wireless VOIP, music and video applications
Home Networks
ZigBee
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ZigBee is a published specification set of
high level communication protocols
designed to use small, low-power digital
radios based on the IEEE 802.15.4
standard for wireless personal area
networks (WPANs)
The technology is designed to be simpler
and cheaper than other WPANs such as
Bluetooth
Home Networks
ZigBee
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The most capable ZigBee node type is
said to require only about 10% of the
software of a typical Bluetooth or
Wireless Internet node, while the
simplest nodes are about 2%.
However, actual code sizes are much
higher, more like 50% of Bluetooth
code size. ZigBee chip vendors
announced 128-kilobyte devices.
Home Networks
ZigBee
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ZigBee's current focus is to define a generalpurpose, inexpensive self-organizing mesh
network that can be shared by industrial
controls, embedded sensors, medical
devices, smoke and intruder alarms, buildingautomation and home automation.
The network is designed to use very small
amounts of power, so that individual devices
might run for a year or two with a single
alkaline battery.
Home Networks
ZigBee
Home Networks
ZigBee
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There are three different types of ZigBee devices
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ZigBee coordinator(ZC) : The most capable device, the
coordinator forms the root of the network tree and might
bridge to other networks. It is able to store information
about the network. There is exactly one ZigBee coordinator
in each network. It also acts as the repository for security
keys.
ZigBee Router (ZR): Routers can act as an intermediate
router, passing data from other devices.
ZigBee End Device (ZED): Contains just enough
functionality to talk to its coordinator; it cannot relay data
from other devices.
Home Networks
ZigBee
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The protocols build on recent algorithmic
research cribbed from Ad-hoc On-demand
Distance Vector to automatically construct a
low-speed ad-hoc network of nodes. In most
large cases, the network is a cluster of
clusters. It can also form a mesh or a single
cluster.
Home Networks
ZigBee
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The basic mode of channel access specified by
IEEE 802.15.4-2003 is "carrier sense, multiple
access/collision avoidance" (CSMA/CA), that is, the
nodes talk in the same way that people converse;
they briefly check to see that no one is talking
before they start. There are three notable exceptions
to the use of CSMA.
Beacons are sent on a fixed timing schedule, and do
not use CSMA. Message acknowledgements also
do not use CSMA. Finally, devices on Beacon
Oriented networks that have low latency real-time
requirements may also use Guaranteed Time Slots
(GTS) which by definition do not use CSMA.
Home Networks
ZigBee
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As of 2005, the estimated cost of the radio for
a ZigBee node is about $1.10 to the
manufacturer in very high volumes. Most
ZigBee solutions require an additional micro
controller driving the price further up at this
time. In comparison, before Bluetooth was
launched (1998) it had a projected price, in
high volumes, of $4-$6. The price of
consumer-grade Bluetooth chips are now
under $3.
Home Networks
References
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http://www.hometoys.com
http://www.cisco.com
http://research.telephonyonline.com
http://www.protocols.com/
http://www.irda.org
http://www.meshnetics.com/
http://www.cirronet.com/zigbee.htm
http://www.maxstream.net/
http://www.bluetooth.com/bluetooth/
http://www.palowireless.com/bluetooth/
http://www.nokia-online.co.uk/Nokia-Bluetooth-technologies/
http://www.media.mit.edu/physics/projects/pan/pan.html
Personal Area Networks: Near-field intrabody communication;
by T. G. Zimmerman
Home Networks
END
Glossary - 1
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TiVo: A personal video recorder (PVR) which allows users to capture television
programming to internal hard disk storage for later viewing
OSI : Open Systems Interconnection (is a layered abstract description for
communications and computer network protocol design)
LLC : Logical Link Control
MAC : Media Access Control
Wireless access point: In computer networking, a wireless access point (WAP or AP)
is a device that connects wireless communication devices
together to form a wireless network. The WAP usually connects to a
wired network, and can relay data between wireless devices and
wired devices. Several WAPs can link together to form a larger
network that allows "roaming". (In contrast, a network where the
client devices manage themselves - without the need for any
access points - becomes an ad-hoc network.)
802.11 : The term 802.11x is also used to denote this set of standards and is not to be
mistaken for any one of its elements. There is no single 802.11x standard. The term
IEEE 802.11 is also used to refer to the original 802.11, which is now sometimes called
"802.11legacy."
mW: milli watt. Watt is the SI derived unit of power.
dBm: is an abbreviation for the power ratio in decibel (dB) of the measured power
referenced to one milliwatt (mW).
Glossary - 2
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Frequency-hopping spread spectrum (FHSS): is a spread-spectrum method of
transmitting radio signals by rapidly switching a carrier among
many frequency channels, using a pseudorandom sequence
known to both transmitter and receiver.
IrFM: a wireless payment standard developed by the Infrared Data Association.