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Home Netwoks Home Networks Personal Area Networks Wireless Local Area Networks by Engin Erentürk

Home Networks l l 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 l A home network may consist of the following components: l l l 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 Ti. Vo, digital audio players and Internet-ready stereo systems, etc.

Home Networks l l 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) l l l 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: l l l 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) l The following characteristics differentiate one LAN from another: l l l 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) l l l 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: l l carrier sense multiple access collision detect (CSMA/CD) token passing

Home Networks CSMA and CSMA/CD l 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. l l "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 l CSMA/CD is a modification of pure CSMA. l 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. l 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 l l 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 l LLC : Logical Link Control MAC : Media Access Control OSI : Open Systems Interconnection

Home Networks LAN Topologies l 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 l 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 l 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 l 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 l A wireless LAN or WLAN is a wireless local area network that uses radio waves as its carrier l Areas may range from a single room to an entire campus l 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 l Peer-to-peer or ad-hoc mode: l l 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 l Access Point / Client l l 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 l Wireless distribution system l l 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 l 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 l 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. 11 X standards l l l l l l l IEEE 802. 11 - The original 1 Mbit/s and 2 Mbit/s, 2. 4 GHz RF and IR standard (IEEE 802. 11 legacy) (1999) IEEE 802. 11 a - 54 Mbit/s, 5 GHz standard (1999, shipping products in 2001) IEEE 802. 11 b - Enhancements to 802. 11 to support 5. 5 and 11 Mbit/s (1999) IEEE 802. 11 c - Bridge operation procedures; included in the IEEE 802. 1 D standard (2001) IEEE 802. 11 d - International (country-to-country) roaming extensions (2001) IEEE 802. 11 e - Enhancements: Qo. S, including packet bursting (2005) IEEE 802. 11 F - Inter-Access Point Protocol (2003) Withdrawn 2005 IEEE 802. 11 g - 54 Mbit/s, 2. 4 GHz standard (backwards compatible with b) (2003) IEEE 802. 11 h - Spectrum Managed 802. 11 a (5 GHz) for European compatibility (2004) IEEE 802. 11 i - Enhanced security (2004) IEEE 802. 11 j - Extensions for Japan (2004) IEEE 802. 11 k - Radio resource measurement enhancements IEEE 802. 11 l - (reserved, typologically unsound) IEEE 802. 11 m - Maintenance of the standard; odds and ends. IEEE 802. 11 n - Higher throughput improvements IEEE 802. 11 o - (reserved, typologically unsound) IEEE 802. 11 p - WAVE - Wireless Access for the Vehicular Environment (such as ambulances and passenger cars) IEEE 802. 11 q - (reserved, typologically unsound, can be confused with 802. 1 Q VLAN trunking) IEEE 802. 11 r - Fast roaming IEEE 802. 11 s - ESS Mesh Networking IEEE 802. 11 T - Wireless Performance Prediction (WPP) - test methods and metrics IEEE 802. 11 u - Interworking with non-802 networks (e. g. , cellular) IEEE 802. 11 v - Wireless network management IEEE 802. 11 w - Protected Management Frames IEEE 802. 11 x - reserved IEEE 802. 11 y - Contention Based Protocol

Home Networks Personal Area Network l 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. l The reach of a PAN is typically a few meters. l 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 l Personal area networks may be wired with computer buses such as USB and Fire. Wire. A wireless personal area network (WPAN) can also be made possible with network technologies such as Ir. DA and Bluetooth.

Home Networks IEEE 802. 15 l IEEE 802. 15 is the 15 th working group of the IEEE 802 which specializes in Wireless PAN (Personal Area Network) standards

Home Networks IEEE 802. 15 l It includes four task groups (numbered from 1 to 4): l l 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 3 a (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 Zig. Bee set of high level communication protocols is based upon the specification produced by 802. 15. 4 b taskgroup.

Home Networks Infrared Data Association l The Infrared Data Association (Ir. DA) defines physical specifications communications protocol standards for the short range exchange of data over infrared light, for uses such as personal area networks (PANs). l l Ir. DA is a very short-range example of free-space optical communication. Ir. DA interfaces are used in palmtop computers and mobile phones. Ir. DA specifications include Ir. PHY, Ir. LAP, Ir. LMP, Ir. COMM, Tiny TP, Ir. OBEX, and Ir. LAN. Ir. DA has now produced another standard, Ir. FM, for Infrared financial messaging also known as "Point & Pay". For the devices to communicate via Ir. DA they must have a direct line of sight

Home Networks Bluetooth l l 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 l 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 l The name was originally only a code-name for the project, but ended up sticking

Home Networks Bluetooth l Bluetooth is a radio standard primarily designed for low power consumption, with a short range (power class dependent: 10 centimeters, 100 meters) and with a low-cost transceiver microchip in each device. l 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 m. W: milli watt. Watt is the SI derived unit of power. d. Bm: is an abbreviation for the power ratio in decibel (d. B) of the measured power referenced to one milliwatt (m. W).

Home Networks Bluetooth l Communication & connection l l 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 l 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 l Any Bluetooth device will transmit the following sets of information on demand l l Device Name Device Class List of services Technical information eg: device features, manufacturer, Bluetooth specification, clock offset

Home Networks Bluetooth l Specifications and Features l 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 l Bluetooth 1. 0 and 1. 0 B l l 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. 0 B 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 l Bluetooth 1. 1 l l l many errata found in the 1. 0 B specifications were fixed added support for non-encrypted channels Received Signal Strength Indicator (RSSI)

Home Networks Bluetooth l Bluetooth 1. 2 l l l 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 (e. SCO), 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 l Bluetooth 2. 0 l l l 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 l Bluetooth next Generation l l l 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 Qo. S 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 l Future of Bluetooth l l 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 Zig. Bee l l Zig. Bee 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 Zig. Bee l l The most capable Zig. Bee 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. Zig. Bee chip vendors announced 128 -kilobyte devices.

Home Networks Zig. Bee l l Zig. Bee'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 Zig. Bee

Home Networks Zig. Bee l There are three different types of Zig. Bee devices l l l Zig. Bee 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 Zig. Bee coordinator in each network. It also acts as the repository for security keys. Zig. Bee Router (ZR): Routers can act as an intermediate router, passing data from other devices. Zig. Bee End Device (ZED): Contains just enough functionality to talk to its coordinator; it cannot relay data from other devices.

Home Networks Zig. Bee l 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 Zig. Bee l l 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 Zig. Bee l As of 2005, the estimated cost of the radio for a Zig. Bee node is about $1. 10 to the manufacturer in very high volumes. Most Zig. Bee 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 l l l l 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. html Personal Area Networks: Near-field intrabody communication; by T. G. Zimmerman

Home Networks END

Glossary - 1 l l l l Ti. Vo: 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. 11 x 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. 11 x standard. The term IEEE 802. 11 is also used to refer to the original 802. 11, which is now sometimes called "802. 11 legacy. " m. W: milli watt. Watt is the SI derived unit of power. d. Bm: is an abbreviation for the power ratio in decibel (d. B) of the measured power referenced to one milliwatt (m. W).

Glossary - 2 l l 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. Ir. FM: a wireless payment standard developed by the Infrared Data Association.