statistical multiplexingotransmitter assigns slots to nodesaccording to priority needomore efficient than TDM-frequency division multiplexing (FDM)ounique frequency band for each communications subchennelocellular telephone transmissionoDSL internet access-Wavelength division multiplexing (WDM)oOne fiber optic connectionoCarries multiple light signals simultaneously-Dense wavelength multiplexing (DWDM)oUsed on most modern fiber optic networksoExtraordinary capacity
Relationships Between NodesPoint-to-point transmissionOne transmitter and one receiverPoint-to-multipoint transmissionOne transmitter and multiple receiversBroadcast transmissionOne transmitter and multiple, undefined receiversUsed on wired and wireless networksSimple and quickNonbroadcastOne transmitter and multiple, defined recipientsThroughput and BandwidthThroughputAmount of data transmitted during given time periodAlso called capacity or bandwidthExpressed as bits transmitted per secondBandwidth (strict definition)Difference between highest and lowest frequencies medium can transmitRange of frequenciesMeasured in hertz (Hz)Baseband and BroadbandBaseband transmissionDigital signals sent through direct current (DC) pulses applied to wireRequires exclusive use of wire’s capacityTransmit one signal (channel) at a timeExample: EthernetBroadband transmissionSignals modulated as radio frequency (RF) analog wavesUses different frequency rangesDoes not encode information as digital pulsesTransmission Flaws-noiseoany undesirable unfluence degrading or distorting signal-types of noiseoEMI (electromagnetic inference)Radio requecny interference
oCross talkSignal on one wire infringes in adjacent wire signal Near end cross talk (NEXT) occurs near source-attenuationoloss of signals strength as it travels away from source-signal boosting technologyoanalog signals pass through amplifiernoise also amplified-regenerationodigital signals retransmitted in original formorepeater: device regenerating digital signals-amplifiers and repeatersoOSI model physical layer-LatencyoDelay between signal transmission and receiptoMay cause network transmission errors-Latency causesoCable lengthoIntervening connectivity device-Round trip time (RTT)oTime for packet to go from sender to receiver and then back from receiver to senderCommon media characteristics*-selecting transmission mediaomedia networking needs with media characteristics-physical media characteristicsothroughput ocostonoise immunityosize and scalabilityoconnectors and media convertersthroughput-most significant factor in choosing transmission method-cause of throughput limitationsolaws of physicsonoiseosignalling and multiplexing techniquesodevces connected to transmission medium-fiber optic cables allow faster throughput compared to wireless or coppercost -precise costs difficult to pinpoint
-media cost dependenciesoexisting hardware, network size, labour costs-
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Twisted pair, shielded twisted pair, data networks, transmission media