CH02 Wireless Transmission

Mobile Communications

Mobile CommunicationsChapter 2: Wireless Transmission Types of electromagnetic carriersAdvantages and disadvantages of wireless communicationBasics of Radio CommunicationThe Wireless Landscape

Mobile Communications: Wireless communications

ObjectivesExplain how the major wireless technologies are used todayDescribe various applications of wireless communications technologyExplain the advantages and disadvantages of wireless communications technologyList several different wireless technologies


Mobile Communications2

What is Wireless Communication ?Transmitting voice and data using electromagnetic waves in open space (atmosphere)Electromagnetic waves Travel at speed of light (c = 3x108 m/s)Has a frequency (f) and wavelength (l)c = f x l Higher frequency means higher energy photons The higher the energy photon the more penetrating is the radiationMobile Communications: Wireless communications

Types of wireless communication

celullarwireless computer networkradio serviceMobile Communications: Wireless communications

Electromagnetic radiation spectrum


Wavelength of Some TechnologiesGSM Phones: frequency ~= 900 Mhz wavelength ~= 33cmPCS Phonesfrequency ~= 1.8 Ghzwavelength ~= 17.5 cm Bluetooth: frequency ~= 2.4Gz wavelength ~= 12.5cmMobile Communications: Wireless communications

Types of electromagnetic carrierswhen the distance between the sender and receiver is short (e.g. TV box and a remote control) infrared waves are usedfor long range distances between sender and receiver (e.g. TV broadcasting and cellular service) both microwaves and radio waves are usedradio waves are ideal when large areas need to be coverd and obstacles exist in the transmission pathmicrowaves are good when large areas need to be coverd and no obstacles exist in the transmission path


Wireless applications (services)


Advantages and disadvantages of wireless communicationadvantages:mobilitya wireless communication network is a solution in areas where cables are impossible to install (e.g. hazardous areas, long distances etc.)easier to maintaindisadvantages:has security vulnerabilitieshigh costs for setting the infrastructureunlike wired comm., wireless comm. is influenced by physical obstructions, climatic conditions, interference from other wireless devices Mobile Communications: Wireless communications

Frequency Carries/ChannelsThe information from sender to receiver is carrier over a well defined frequency band. This is called a channelEach channel has a fixed frequency bandwidth (in KHz) and Capacity (bit-rate)Different frequency bands (channels) can be used to transmit information in parallel and independently. Mobile Communications: Wireless communications

ExampleChannel 1 (b - b+30) Channel 2 (b+30 - b+60)Channel 3 (b+60 - b+90) Station A Station B

Assume a spectrum of 90KHz is allocated over a base frequency b for communication between stations A and B Assume each channel occupies 30KHz. There are 3 channels Each channel is simplex (Transmission occurs in one way) For full duplex communication: Use two different channels (front and reverse channels) Use time division in a channelMobile Communications: Wireless communications

Radio waves generationwhen a high-frequency alternating current (AC) passes through a copper conductor it generates radio waves which are propagated into the air using an antena

radio waves have frequencies between:3 Hz 300 KHz - low frequency300 KHz 30 MHz high frequency30 MHz 300 MHz very high frequency300 MHz 300 GHz ultra high frequencyBasics of Radio CommunicationMobile Communications: Wireless communications

Radio propagation

radio waves are generated by an antenna and they propagate in all directions as a straight lineradio waves travel at a velocity of 186.000 miles per secondradio waves become weaker as they travel a long distanceMobile Communications: Wireless communications

there are 3 modes of propagation:surface mode for low frequency wavesdirect mode for high frequency wavesionospheric mode long distance high frequency waves


Modulationmodulation = adding information (e.g. voice) to a carrier electromagnetic (radio) signal

Frequency Modulation (FM).Amplitude Modulation (AM)


Radio frequency interference

Radio signal attenuation (path loss)


How Wireless Technology is UsedWirelessDescribes devices and technologies that are not connected by a wireWireless communicationsTransmission of user data without the use of wiresWireless data communications technologies include:BluetoothWireless LAN and WANSatelliteCellularMobile Communications: Wireless communications


A Wireless WorldWireless devicesDistance: 300 feet (90 meters)Bandwidth: 54 MbpsCan also include Voice over IP (VoIP)Wireless network interface card (Wireless NIC)Sends and receives data over radio wavesSmartphoneCombination mobile phone and personal digital assistant (PDA)Mobile Communications: Wireless communications


A Wireless WorldMobile Communications: Wireless communications


Bluetooth and Ultra Wide BandRadio frequency identification device (RFID) tagsSmall chips containing radio transpondersCan be used to track inventoryBluetooth and Ultra Wide Band (UWB)Wireless standards designed for very short rangesCommunicate using small, low-power transceiversLink managerSpecial software that helps identify other Bluetooth devices



Bluetooth and Ultra Wide Band (continued)BluetoothDistance: up to 33 feet (10 meters)Bandwidth: 1 MbpsUltra Wide BandDistance: 150 feet (50 meters)Bandwidth: 100 Mbps to 2 GbpsPiconetWireless personal area network (WPAN)Consists of two or more Bluetooth devices that are exchanging data with each otherMobile Communications: Wireless communications


Bluetooth and Ultra Wide BandMobile Communications: Wireless communications


Wireless Local Area NetworksWireless Local Area Network (WLAN)Extension of a wired LANConnecting to it through a device called a wireless access pointAccess point (AP)Relays data signals between all of the devices in the networkEach computer on the WLAN has a wireless network interface card (NIC)With an antenna built into itMobile Communications: Wireless communications


The original version of the standard IEEE 802.11 was released in 1997 and clarified in 1999, but is today obsolete. It specified two net bit rates of 1 or 2 megabits per second (Mbit/s), plus forward error correction code. It specified three alternative physical layer technologies: diffuse infrared operating at 1 Mbit/s; frequency-hopping spread spectrum operating at 1 Mbit/s or 2 Mbit/s; and direct-sequence spread spectrum operating at 1 Mbit/s or 2 Mbit/s. The latter two radio technologies used microwave transmission over the Industrial Scientific Medical frequency band at 2.4 GHz. IEEE 802.11Mobile Communications: Wireless communications

Some earlier WLAN technologies used lower frequencies, such as the U.S. 900 MHz ISM band.Legacy 802.11 with direct-sequence spread spectrum was rapidly supplanted and popularized by 802.11b.

802.11a

The 802.11a standard uses the same data link layer protocol and frame format as the original standard, but an OFDM based air interface (physical layer). It operates in the 5 GHz band with a maximum net data rate of 54 Mbit/s, plus error correction code, which yields realistic net achievable throughput in the mid-20 Mbit/s.802.11aMobile Communications: Wireless communications

Since the 2.4 GHz band is heavily used to the point of being crowded, using the relatively unused 5 GHz band gives 802.11a a significant advantage. However, this high carrier frequency also brings a disadvantage: the effective overall range of 802.11a is less than that of 802.11b/g. In theory, 802.11a signals are absorbed more readily by walls and other solid objects in their path due to their smaller wavelength and, as a result, cannot penetrate as far as those of 802.11b. In practice, 802.11b typically has a higher range at low speeds (802.11b will reduce speed to 5 Mbit/s or even 1 Mbit/s at low signal strengths). 802.11a also suffers from interference,[11] but locally there may be fewer signals to interfere with, resulting in less interference and better throughput.

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`802.11b has a maximum raw data rate of 11 Mbit/s and uses the same media access method defined in the original standard. 802.11b products appeared on the market in early 2000, since 802.11b is a direct extension of the modulation technique defined in the original standard. The dramatic increase in throughput of 802.11b (compared to the original standard) along with simultaneous substantial price reductions led to the rapid acceptance of 802.11b as the definitive wireless LAN technology.802.11b devices suffer interference from other products operating in the 2.4 GHz band. Devices operating in the 2.4 GHz range include microwave ovens, Bluetooth devices, baby monitors, cordless telephones and some amateur radio equipment802.11bMobile Communications: Wireless communications

Wireless Local Area NetworksInstitute of Electrical and Electronic Engineers (IEEE) standards802.11a, 802.11b, and 802.11g



Wireless Local Area NetworksMobile Communications: Wireless communications


Wireless Local Area NetworksMobile Communications: Wireless communications


Major WLAN ComponentsDistribution System (DS). A wired/wireless medium which connect the Access Points to one another. The backbone network used to relay frames between access points Access Points (AP). APs form a bridge between wired and wireless medium. Coordinate the connection of wireless stations to the DS Wireless Medium. The Radio Frequency spectrum used to transfer frames between the wireless station and the AP or between wireless stations. Wireless Stations. Computing devices with wireless network interfaces. Typically battery operated laptops or handheld computers.


WLAN Types

Independent Basic Service Set (IBSS). No Access Point An ad-hoc group of wireless nodes. Peer-to-peer transmission One node is elected to act as a proxy to perform the functions of the AP.


Basic Service Set (BSS). A single Access Point The AP acts as a bridge between clients and the wireline. Roaming is limited to the single radio cell All clients operate on the same channel. A BSS connected to a wired network is called an Infrastructure BSS. The clients must request to join and be accepted to associate with the AP before they can send data. A BSS is identified by a 48 bit hex value called the BSS identifier BSSID. This is the MAC address of the AP

Access Point

NetworkWireline Network WLAN TypesMobile Communications: Wireless communications

Access Point

Access Point

Wireline Network

Extended Service Set (ESS). Multiple Access Points that communicate through the DS. The APs share the same Service Set Identifier (SSID) an Extended SSID or ESSID. The AP acts as a bridge between clients and the wireline. Each AP forms a radio cell that overlap. Each AP is assigned a different channel All clients operate on the same channel in the same cell but can communicate through the DS. The APs interconnected through the Wireline constitute a Distributed System. WLAN TypesMobile Communications: Wireless communications

Access Point

Access Point

Wireline Network

Extended Service Set (ESS) Contd. The SSID is used to control APs with which the stations can associate. Clients may also associate with an AP using a special "null" SSID value which indicates they would like to associate with any AP within range regardless of the assigned APs SSID.AP can be configured to reject this "null" value.The BSSID identifies a single BS.The ESSID denotes a group of APs sharing a common SSID within which a client can roam. WLAN TypesMobile Communications: Wireless communications

Station Services Authentication - The client identifies itself to the AP in order to form an Association. This can be done by: Service Set Identifier (SSID) MAC Filtering. De-authentication - Destroys a previously known station identity- terminates the current Association. The device shuts down. Out of AP range802.11 Network ServicesMobile Communications: Wireless communications

361. The first mobile telephone systems began n 1946 in St Louis Mo. The cost was approximately $2500.2. The first Mobile radio was in 1921and was employed by the Detroit police department.


Distribution Services. Association - establish a logical connection between the client and the AP, i.e., A station registers with an AP. Determines the location of the client for the DS. Determines the path to reach the DS needs to reach the client. A client can be authenticated to multiple APs but Associated with only one AP. Reassociation - Retains network session information when the wireless client passes from one AP to another AP. This information tells the new AP the identify of the last AP. This allows the old AP to forward any remaining frames to the new AP for delivery via the DS.802.11 ArchitectureMobile Communications: Wireless communications



Distribution ServicesDisassociation - Tear down the association between the AP and the wireless device. The device leaves the AP area. The AP is shutting down. Distribution - Determines the location to which the frame should be forwarded by the AP - An AP uses the DS to deliver frames. Another AP. A Wireless client. The Wired Network. Integration - Provides a MAC framing service to the AP. Translates the 802.11 format to the Wired LAN format. Translates the Wired LAN format to the 802.11 format. 802.11 ArchitectureMobile Communications: Wireless communications

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Fragmentation. Spatial Density results in interference which requires data retransmission. 802.11 can be configured to send smaller packets. Power Management. Mobile clients can enter the sleep mode to conserve power but still remain connected. A 20 byte Power Save Poll (PS-Poll) is sent to the AP. The AP buffers all packets destined for he device until it comes back on line. Multicell Roaming. Roaming is based upon determining the S/N ratio. AP sends out beacon messages containing link measurement data The client listens and determines which AP has the stronger signal802.11 - Other OperationsMobile Communications: Wireless communications

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Locating a WLANThe wireless client locates the Access Point by scanning the airways for its RF signal. It locates the AP by identifying its Service Set Identifier (SSID) through: Passive Scanning Active Scanning BeaconsMobile Communications: Wireless communications

Service Set Identifier (SSID)The SSID is used by WLAN as a network name. Unique Case sensitive Alphanumeric value 2-32 characters The SSID is used for Segmenting networks Rudimentary security measure Joining a network. The SSID is used in: Beacons Probe Requests Probe Responses, etc.


Passive Scanning Passive Scanning is the process of listening for Beacons on each channel for a specific period after the station has initialized. The beacons are sent by: Access Points in the Independent Basic Service Set (BSS) or Extended Basic Service Set (EBSS) mode. Client stations in the Ad Hoc mode. If there are multiple APs in the area then the client attempts to join the strongest signal strength and lowest bit rate. Passive Scanning continues after association to allow the Client to create a list of available access points should the current connection be broken.Mobile Communications: Wireless communications

Active Scanning

Active Scanning is the process of sending a Probe Request frame from a wireless client.The station is actively seeking a network to join.The probe contains either the network Service Set Identifier (SSID) or a broadcast SSID. Only Access Points servicing that SSID will respond with a Probe Response frame.This frame is identical to the Beacon frame with the exception that it does not contain a Traffic Indication Map (TIM) All APs respond to the Broadcast SSID. The wireless station then initiates the Authentication and Association steps.Mobile Communications: Wireless communications

Probe Request

Frame ControlDuration ID

DA

SA

BSSIDSequence Control

FCS2 2 6 6 6 2 0-2,312 4

Frame Body

SSID

Var Var

Supported Rates Probe Requests are used by stations to scan an area for 802.11 networks. The station sends our Probe Requests sequentially on all channels with its SSID and listens for Probe Responses All Access Points must respond with a Probe Response. Some APs are configured to ONLY send a Probe Request to a matching SSID. The Probe Response contains: Service Set Identity (SSID) - The identity of the service set. Supported Rates - Data rates supported by the 802.11 network.Mobile Communications: Wireless communications

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Probe Request Indicates a Probe Request is contained within the MAC headerMobile Communications: Wireless communications

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Probe RequestMobile Communications: Wireless communications



Probe Response


DA

SA


FCS2 2 6 6 6 2 0-2,312 4

Frame Body

TimestampBeacon Interval

Capability Info

SSID

FH Param Set

8 2 2 Var 7 2 8 4 DS Param SetCF Param Set

IBSS Param Set

The Probe Response is sent by the AP in response to the Probe Request. The Probe Response format is the same as the Beacon with the exception that it does not include the TIM Element. The station is not yet associated with the AP therefore it does not need to now the TIM parameter. Mobile Communications: Wireless communications

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Probe Response Contd


DA

SA


FCS2 2 6 6 6 2 0-2,312 4

Frame Body


Capability Info

SSID

FH Param Set

8 2 2 Var 7 2 8 4 DS Param SetCF Param Set

IBSS Param Set

Timestamp - Synchronization between stations. Beacon Interval - Announce existence of 802.11 network. Capability Info - Advertisement of network's capabilities. Service Set Identity (SSID) - The identity of the service set. FH Parameter Set - Specifies such things a Dwell time, Hop Set and Hop Pattern. DS Parameter Set - Specifies the DSSS channel number. CF Parameter Set Specifies the parameters relating to the duration of the Contention Free period. It is only sent by APs supporting the Point Coordination Function (PCF). Very few APs support this function. IBSS Parameter Set - Specifies the number of Time Units between Announcement Traffic Indication Map (ATIM) windowsMobile Communications: Wireless communications



Probe Response ContdIndicates a Probe ResponseMobile Communications: Wireless communications



Probe Response ContdMobile Communications: Wireless communications

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BEACONThe Beacon Management frame serves the following major purposes. Time Synchronization.The Beacon time stamp synchronize the client to the transmitter.This ensures all time sensitive functions, (FHSS, etc) are properly timed. FH/DS (FHSS/DSSS) Parameter Sets. FHSS hop sequence, hop time and dwell time. DSSS channel information SSID Information The beacon contains the SSID the client wishes to join and sends an authentication request to the MAC address contained in the Beacon. Conversely, the client can be set to join ANY network that: (1) sends a beacon or (2) the strongest signal if there are multiple APs.Mobile Communications: Wireless communications

BEACONBeacon frame is one of the management frames in IEEE 802.11 based WLANs. It contains all the information about the network. Beacon frames are transmitted periodically to announce the presence of a Wireless LAN network. Beacon frames are transmitted by the Access Point (AP) in an infrastructure BSS. In IBSS network beacon generation is distributed among the stations. Traffic Indication Map (TIM) The TIM indicates which sleeping stations have traffic queued by the Access point. The time synchronized stations power up, listen to the Beacon, and check the TIM to see if they have traffic queued. Supported Rates Informs the clients the speed capability of the Access PointMobile Communications: Wireless communications

Beacon Frame


DA

SA


FCS2 2 6 6 6 2 0-2,312 4

Frame Body


Capability Info

SSID

FH Param Set

TIM8 2 2 Var 7 2 8 4 VarDS Param SetCF Param Set

IBSS Param Set

Timestamp - Synchronization between stations. Beacon Interval - Announce existence of 802.11 network. Capability Info - Advertisement of network's capabilities. Service Set Identity (SSID) - The identity of the service set. FH Parameter Set - Specifies such things a Dwell time, Hop Set and Hop Pattern. DS Parameter Set - Specifies the DS channel number.Mobile Communications: Wireless communications

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Beacon Frame


DA

SA


FCS2 2 6 6 6 2 0-2,312 4

Frame Body


Capability Info

SSID

FH Param Set

TIM8 2 2 Var 7 2 8 4 VarDS Param SetCF Param Set

IBSS Param Set

CF Parameter Set Specifies parameters relating to the duration of the Contention Free period. It is only sent by APs supporting the Point Coordination Function (PCF). Very few APs support this function. IBSS Parameter Set - Specifies the number of Time Units between Announcement Traffic Indication Map (ATIM) windows Traffic Indication Map (TIM) - Traffic Indication map to indicate which stations have buffered traffic.

Mandatory

OptionalMobile Communications: Wireless communications

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Beacon Frame The Basic Service Set identifier (BSSID) is a 6 byte hex number identifying the Access Point.It is not the same as the SSIDThis is the MAC HeaderIndicates the Beacon is contained within the MAC headerMobile Communications: Wireless communications



Beacon FrameThis is the Beacon frameMobile Communications: Wireless communications

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Beacon FrameThis is the SSIDSupported RatesDSS ElementTIM ElementMobile Communications: Wireless communications

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802.11Authentication and Association- Joining a Wireless LAN-Mobile Communications: Wireless communications

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Authentication & Association There are two separate sub-processes for connecting a client to a WLAN. These are:Authentication: The process by which a node's identity is verified. Authentication must occur before Association Association: A state in which a node is allowed to pass traffic through an access pointThere are three distinct states. Unauthenticated and Unassociated Authenticated and Unassociated. Authenticated and Associated.Mobile Communications: Wireless communications

States of Authentication & Association Unauthenticated and Unassociated The initial state. The client is not connected to the WLAN and is unable to pass data. Authenticated and Unassociated.The Client has passed the Authentication state but is not yet associated with an Access Point. The Client cannot send or receive packets.Authenticated and Associated.The client is completely connected and is able to send and receive packets. A client can be authenticated with multiple Access Points but only associated with one .Pre-authentication makes for faster roaming Mobile Communications: Wireless communications

Fixed Broadband WirelessIntegrated Services Digital Networks (ISDN)Transmit at 256 Kbps over regular phone linesT1 linesTransmit at 1.544 MbpsCable modems and digital subscriber lines (DSL)Generally only available in residential areasMaximum transmission speed is only about 8 MbpsMobile Communications: Wireless communications


Fixed Broadband WirelessWireless metropolitan area network (WMAN)Covers a distance of up to 35 milesBased on the IEEE 802.16 Fixed Broadband Wireless standardUses small custom antennas on the roof of each buildingTransmission speeds75 Mbps at distances of up to 4 miles (6.4 km)17 to 50 Mbps at distances over 6 miles (10 km)Mobile Communications: Wireless communications


Fixed Broadband WirelessMobile Communications: Wireless communications


Wireless Wide Area NetworkHypertext Markup Language (HTML)Standard language for displaying content from the InternetMicrobrowserMiniaturized version of a Web browserWireless Application Protocol version 2.0 (WAP2)Provides a standard way to transmit, format, and display Internet dataFor small wireless devices such as cell phonesMobile Communications: Wireless communications


Wireless Wide Area NetworkMobile Communications: Wireless communications


Wireless Wide Area NetworkProgramming languagesBREW (Binary Run-Time Environment for Wireless) J2ME (Java 2 Micro Edition)Wireless Wide Area Network (WWAN)Enables employees to access corporate data and applications from virtually anywhereMobile Communications: Wireless communications


The Wireless LandscapeMobile Communications: Wireless communications


The Wireless LandscapeMobile Communications: Wireless communications


Digital ConvergenceDigital convergenceRefers to the power of digital devices to combine voice, video, and text processing capabilitiesAs well as to be connected to business and home networks and to the Internet



Wireless ApplicationsMain areasEducationHome entertainmentHealth CareGovernment and MilitaryOffice environmentsEvent managementTravelConstruction and warehouse managementEnvironmental researchIndustrial controlMobile Communications: Wireless communications


EducationIdeal application for colleges and schoolsIt frees students from having to go to a specific computer lab or the libraryTo get on the schools computer networkWireless technology translates into a cost savings for colleges as wellMobile Communications: Wireless communications


Home EntertainmentWireless communicationEnables movie and audio enthusiasts to download, distribute, and control all forms of digital entertainment from anywhere in the house



Health CareAdministering medication in a hospital settingA major problem area for the health care industryWireless point-of-care computer systemsAllow medical staff to access and update patient records immediatelyEven telephones are now being connected to hospital IEEE 802.11 WLANsEmploying VoIP technology



GovernmentWireless communicationLets city employees and contractors at remote sites access data stored in a central databaseDelivers broadband connectivity to schools, libraries, and government buildingsProvides free Internet access to residents and attracts visitors and businesspeopleMobile Communications: Wireless communications


MilitaryUniversal HandsetA 1.5-pound deviceAllows military personnel in the field to communicate through a variety of methodsUsing wireless technologiesMilitary is currently working on preventing enemies from eavesdropping on or jamming the signal



Office EnvironmentsEmployees in all lines of work no longer have to be away from the data they needTo help them make decisionsWireless technologies allow businesses to create an officeWhere the traditional infrastructure doesnt already exist



Event ManagementWireless networksHelp identify a stolen or counterfeit ticketCan also give a real-time look at traffic flowIn-progress game statistics are available to any fan in the stadium with a wireless device



TravelWireless global positioning systems (GPS)Tie into emergency roadside assistance servicesSatellite radioTransmits over 150 music and talk stationsAirport terminals are likewise turning to wireless technologiesAirplanes themselves are being equipped with wireless data accessMobile Communications: Wireless communications


ConstructionWireless communicationsSend information from the job site to the main officeAlert when maintenance operations need to be performed on equipmentMobile Communications: Wireless communications


Warehouse ManagementImplementing wireless technology is key for many warehouse operationsWarehouse management system (WMS) softwareUsed to manage all of the activities from receiving through shippingIn the near futureMost of the bar code functions, including inventory counting, will be replaced by RFID tags



Environmental ResearchScientists are now using small, battery- or solar-cell-powered WLAN sensorsIn places that were previously difficult to access and monitorMobile Communications: Wireless communications


Industrial ControlMotesRemote sensorsCan connect to a WLANThen collect data and transmit it to a central locationMobile Communications: Wireless communications


Wireless Advantages and DisadvantagesAs with any new technology, wireless communications offers both advantages and disadvantages

MobilityFreedom to move about without being tethered by wiresPermits many industries to shift toward an increasingly mobile workforceGives team-based workers the ability to access the network resourcesEasier and less expensive installationInstalling network cabling in older buildings can be a difficult, slow, and costly taskMakes it easier for any office to be modified with new cubicles or furnitureAdvantages of Wireless NetworkingMobile Communications: Wireless communications


Advantages of Wireless Networking (continued)Increased reliabilityNetwork cable failures may be the most common source of network problemsDisaster recoveryIn the event of a disaster, managers can quickly relocate the officeMobile Communications: Wireless communications


Disadvantages of Wireless NetworkingRadio signal interferenceThe potential for two types of signal interference existsSecurityIt is possible for an intruder to be lurking outdoors with a notebook computer and wireless NICWith the intent of intercepting the signals from a nearby wireless networkSome wireless technologies can provide added levels of securityHealth risksHigh levels of RF can produce biological damage through heating effectsWireless devices emit low levels of RF while being used



SummaryWireless communications have become commonplaceWireless networks and devices are found in all circles of life todayWireless wide area networks will enable companies of all sizes to interconnect their officesWithout the high cost charged by telephone carriers for their landline connectionsWLAN applications are found in a wide variety of industries and organizationsRemote sensorsCapable of communicating using wireless technologies Used in large manufacturing facilitiesTo monitor equipment and for scientific research



Wireless communication advantagesMobilityEasier and less expensive installationIncreased network reliabilitySupport for disaster recoveryWireless communication disadvantagesRadio signal interferenceSecurity issuesHealth risks



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CH02 Wireless Transmission