Wireless Networks and Mobile Communication Systems

NET 332D(PRIMER)

OUTLINE› Computer Network and Elements of a Computer

Network

› Classification of Networks› Host Role› Geographical Proximity/Scale› Signaling› Network Topology› Network Architecture/Protocol architecture› Type of Communication Medium

› Guided Medium› Unguided Medium

OUTLINE› Why is Wireless Different than Wired Networks?

› Wired Versus Wireless

› Elements of a wireless Network

› Wireless Networking Technologies

Computer Network and Elements of a Computer Network

› Definition› Two or more devices connected together to share resources.

› Devices: Laptops, PC, Tablet, Network Enabled Printers, mobile phones etc.

› Connected via Media: Twisted Pair, Coaxial Cable, Ethernet Cable, Wireless link

› Resources: Files, Webpages, Songs, Video, Facebook Statuses

› Elements of a Network› Sender/Receiver (Nodes)› Transmission Media› Shared Resources› Protocols

Classification of NetworksHost Roles: What does the host do in the network

› Client Server Model: › Defined Roles of nodes: Client requests/consumes and host

provides network resources.› Peer to Peer Model:

› Hosts can provide and consume network resources.

Geographical Proximity/Scale– Local Area Network

› Small geographic area Example of classes, Inside the different floors of an organization

› Governed by a single organization, Example: Home Network› Size: Home devices versus a class devices versus a small corporation› Small network administered by a single organization or individual who have a

common goal interest and set of resources: Example class meets to discuss 332D so this class can be considered as one local area network

Classification of Networks– Metropolitan area Network

› MANs are networks between a LAN and WAN. › They are a type of interconnecting networks for big businesses in a metropolitan

area. Example: ABC Corp

– Wide Area Network› Hosts in the network are very widely distributed geographically.› Group of interconnected LANs geographically separated, e.g XYZ coop with

offices in different parts of the world. The employees in these offices are connected together via a large internetwork or a WAN. Example: Internet

› Note: Local resources should reside locally in the local office so that a frequently accessed resource in one office(reside on the local server) does not need to be accessed via the WAN.

› Useful if the worker in one office needs to access some documents that reside in another office.

› An inter-connection of connected LANS is a WAN.

– PAN› PANs are networks interconnecting the devices of personal use that could, in

general, be carries around. Examples of such devices are personal digital assistant (PDA), various wireless phones, remote control, etc.

› Usually, the design of these networks entails replacing the wire only, as they aren't expected to be interconnected via WANs and MANs in near future.

Classification of NetworksSignaling

› Baseband Networks : One signal at a time on the channel, Entire channel bandwidth utilized by one signal, No multiplexing. Example Old PSTN.

– Broadband Networks: Medium bandwidth divided into multiple channels. Multiplexing, Multiple signals being transmitted on the channel at the same time.

Network Topology› Ring, Star, Bus, Mesh and Hybrid topology.

Network Architecture– Classification of a network based on the Network

Architecture/Protocol Architecture.

Classification of Networks›Protocol architecture/network architecture–Protocol

› Protocol: Language or the Rules of communication–Standards

› Standards are protocols that have gone through a standardization process and after standardization it has been documented by some organization

–Standardization Agencies › Internet society› International organization for standardization (ISO)› IEEE Institute of Electrical and Electronics Engineer› ANSI American Standards Institute› ETSI Euro Telecomm Standards Institute› ITU International Telecomm Union

Classification of Networks›Protocol architecture/network architecture

–Network architecture› Each network can be defined and thus be classified as a set of

protocol and layers. › Such a set of protocols is called the Network or Protocol

architecture. › Network architecture is a set of layer and associated protocols

that can achieve complete communication among the nodes in that network.

–How to study a network› Define the network Layers› Define all the protocol layers› Define interconnection between layers

What is the OSI Reference Model13

› The OSI Reference Model is a seven-layer conceptual model developed by ISO in 1984.–Describes the standards for inter-computer communication.

› The seven layers of the OSI model are: –Application–Presentation–Session–Transport–Network–Data link–Physical

Computer networks / Andrew S. Tanenbaum-- 5th ed

What is the OSI Reference Model14

Computer networks / Andrew S. Tanenbaum-- 5th ed

Classification of Networks› In a data transmission system, the transmission medium is the physical

path between transmitter and receiver.› Transmission media can be classified as:

– Guided medium– Unguided medium

› In both cases, communication is in the form of electromagnetic waves.› The electromagnetic spectrum and indicates the frequencies› at which various guided media and unguided transmission techniques

operate.› Guided Medium

– With guided media, the waves are guided along a solid medium, such as copper twisted pair, copper coaxial cable, or optical fiber.

› Unguided Medium– The atmosphere and outer space are examples of unguided media,

which provide a means of transmitting electromagnetic signals but do not guide them; this form of transmission is usually referred to as wireless transmission.

Guided MediumBounded Media/Guided Media

› Coaxial› Coaxial Cable (Not commonly

used now)› Data rate limited to 10Mb/s

› Twisted Pair Cable(UTP )› Used in Wired Ethernet

standard so called Ethernet Cable.

› Suffers from EMI› Flexible and Inexpensive

› Shielded Twisted Pair (STP)

› Rates Cat 3 10-16Mbps› Rates Cat 5 100-1000Mb/s› Rates Cat 5c 10,000Mbps

› Fiber Optic cable› No EMI› Very expensive Hard

installation › Not flexible (Breaks and bends

easily)

Unguided Medium› For unguided media, transmission and reception are achieved by

means of an antenna. › For transmission, the antenna radiates electromagnetic energy into the

medium (usually air), and for reception, the antenna picks up electromagnetic waves from the surrounding medium.

› Three general ranges of frequencies are of interest in wireless transmission.

› Microwave: Frequencies in the range of about 1 GHz (gigahertz = 109 Hz) to100 GHz are referred to as microwave frequencies. At these frequencies, highly directional beams are possible, and microwave is quite suitable for point-to-point transmission. Microwave is also used for satellite communications.

› Radio Range: Frequencies in the range 30 MHz to 1 GHz are suitable for omnidirectional applications.

› The infrared portion of the spectrum. This covers, roughly, from to Hz. Infrared is useful in local point-to-point and multipoint applications within confined areas, such as a single room.

Terrestrial Microwave › Line-of-sight transmission› Common frequencies used for transmission are in the range 2 to 40

GHz.› Applications:

– Long-haul telecommunications service, as an alternative to coaxial cable or optical fiber.

– Short point-to-point links between buildings. This can be used for closed-circuit TV or as a data link between local area networks.

– Cellular systems

Satellite Microwave› A communication satellite is, in effect, a microwave relay station. It is

used to link two or more ground-based microwave transmitter/receivers, known as earth stations, or ground stations.

› The optimum frequency range for satellite transmission is in the range 1 to 10 GHz.

› Applications– Television distribution– Long-distance telephone transmission– Private business networks

Infrared› Infrared communications is achieved using transmitters/receivers

(transceivers) that modulate infrared light. › Transceivers must be within the line of sight of each other either

directly or via reflection from a light-colored surface such› as the ceiling of a room.› One important difference between infrared and microwave transmission

is that the former does not penetrate walls. Thus the security and interference problems encountered in microwave systems are not present.

› Furthermore, there is no frequency allocation issue with infrared, because no licensing is required.

Types of Communication›Types of Communication

› Simplex – (one way communication, Example: Broadcast Radio)

› Half Duplex– (Two way communication but not at the same time, Example: CB Radio)

› Full Duplex: – Two way communication but at the same time. Example Telephone and cellular

phones.

Why is wireless different than wired?

› Noisy, time-varying channel– Environnemental conditions affect transmission

› Shared medium– Other users create interference– Must develop ways to share the channel

› Bandwidth is limited– FCC determines how spectrum is allocated– ISM band for unlicensed use (902-928 MHz, 2.4-2.5 GHz and 5.725-5.875 GHz)– Requires intelligent way to make efficient use of limited bandwidth in error-prone environment

› Major differences due to broadcast nature of wireless communication – Transmitted signals can be received by an arbitrary (and perhaps unknown) number of other

users– Cannot guarantee a link from every transmitting node to every intended receiving node

› Each transmitted message utilizes scares resources (BW) – Need to provide means for fair and efficient utilization of available bandwidth among transmitting

nodes

› Transmitted signal power important parameter– Require enough signal power to reach destination node.– Want to limit signal power to minimize interference and max battery life.

WIRED VERSUS WIRELESSAdvantages:

People want connectivity anywhere anytime for example, at airports, hotels, customers place, or group of people wants to share data at any location. Such requirements have made the wireless connectivity indispensable.

– Convenience: Access your network resources from any location within your wireless network's coverage area or a wireless hot spot

– Mobility: You're no longer tied to your desk, as you were with a wired connection. You and your employees can go online in conference room meetings, for example.

– Productivity: Wireless access to the Internet and to your company's key applications and resources helps your staff get the job done and encourages collaboration.

– Easy setup: You don't have to string cables, so installation can be quick and cost-effective.

– Expandable: You can easily expand wireless networks with existing equipment, while a wired network might require additional wiring.

– Cost. Because wireless networks eliminate or reduce wiring costs, they can cost less to operate than wired networks.

WIRED VERSUS WIRELESSDisadvantages:

– Wireless LANs using 802.11b support a maximum theoretical bandwidth of 11 Mbps, roughly the same as that of old, traditional Ethernet. 802.11a and 802.11g WLANs support 54 Mbps , that is approximately one-half the bandwidth of Fast Ethernet.

– In theory, wireless LANs are less secure than wired LANs, because wireless communication signals travel through the air and can easily be intercepted.

– Wireless LANs suffer a few more reliability problems than wired LANs, though perhaps not enough to be a significant concern. 802.11b and 802.11g wireless signals are subject to interference.

– One medium shared by all the users.

– Signal attenuation is high

– High interference i.e noise; co-channel interference; adjacent channel interference etc

ELEMENTS OF A WIRELESS NETWORK

ELEMENTS OF A WIRELESS NETWORK

ELEMENTS OF A WIRELESS NETWORK

WIRELESS NETWORKING TECHNOLOGIES

› Wireless Communication applies across a wide range of network types and size.

› Many wireless communication technologies exist and are used to create Wireless LAN, MANs, WANs and PANs.

› Wireless technologies can be classified broadly according to the network type as:

› PANS– PAN technology provides communication over a short distance and is

intended for use with devices that are owned by or operated by a single user. e.g: Communication between a wireless handset and cell phone. Computer and a nearby wireless mouse or keyboard.

› Bluetooth: (802.15.1.a) IEEE standard for short distance wireless communication technology

› Zigbee: (802.15.4) is a wireless remote control technology (not data) especially for industrial equipment. Remote control sends only short commands so high data rates are not required. Applications industry and home automation.

PAN Technologies and Standards

› Wireless technologies (not grouped under PANs) but used for short distance wireless communication

– InfraRED: InfraRed technology used often in remote controls may also be used as a cable replacement.

– IrDA(Infrared data association produced a set of standards for infraRed communication.

› Some characteristics– Various speeds and purposes– Data rates between 2.4Kbps (control) and 16Mbps for data.– Low power consumption and signals can not penetrate solid

objects.– LOS (Line of sight)

› RFID: Radio Frequency Identification– Wireless Communication primarily used for inventory and shipping– RFID technology uses an interesting form of wireless

communication to create a mechanism whereby a small tag contains an identification information that the receive can pull from the tag.

Other short distance communication

technologies

› A variety of wireless LAN technologies exist that use various frequencies, modulation techniques and data rates.

› IEEE provides the Wireless LAN standards which are categorized as IEEE 802.11.

Wireless LAN Technology

› WIMAX is a (family of standards based on the IEEE 802.16) wireless MAN technology standardized under the IEEE standard 802.16.

› WIMAX offers broadband communication. › Two main versions of WIMAX are the

– Fixed WIMAX-standard 802.16-2004› Designed to provide between service providers and a fixed

location such as a residence or a building.– Mobile WIMAX-standard 802.16e-2005

› Mobile WIMAX system can be used with portable devices such as laptop computers or cell phones

Wireless MAN Technology and WIMAX

› Wireless Wan technologies can be divided into two categories:

– Cellular Communication systems – Satellite Communication systems

Wireless WAN technologies