Telecommunications Networking IINext Generation WirelessSlide 3Slide 4Achieve the 100kbps+ objectiveUtilize spectrum efficientlyContinue to support existing 2nd generation cell phonesAvoid massive new infrastructure investments until justified by demand/revenues3rd generation infrastructure is not always available and/or appropriate for ordinary cell phone callsSlide 10Slide 11Interference MitigationAdjustable Rate CDMASlide 14Software-defined RadioSlide 16Telecommunications Networking IILecture 39 Next Generation WirelessNext Generation Wireless•What are we trying to do?-Add the capability to provide relatively high speed packet-based services (target: 100 kbps or higher) to wireless appliances; extending current cellular/PCS services.-Reduce the cost of providing today’s cellular/PCS services-Expand the aggregate capacity of cellular/PCS networksNext Generation Wireless•Challenges-Achieve the 100kbps+ objective-Utilize spectrum efficiently-Continue to support existing, 2nd generation cell phones-Avoid massive new infrastructure investments until justified by demand (revenues)Next Generation Wireless•Challenges-Design the new system in a way that makes it technically/economically feasible for new appliances to utilize existing 2nd generation infrastructure (when 3rd generation infrastructure is not always available and/or if appropriate for ordinary cell phone calls)Achieve the 100kbps+ objective•Issues:-Support for: fixed (in-building), pedestrian, and vehicular applications-Multi-path (delay differences among multiple propagation paths)-Various and varying data rates-Interference among users-Congestion- Brief drop-outs can cause new applications or connections to disconnect or freezeUtilize spectrum efficiently•Issues-New applications produce bursty and asymmetrical traffic flows-Accumulated experience with 2nd generation systems regarding actual performance with respect to achievable utilizationContinue to support existing 2nd generation cell phones•Issues-New infrastructure may operate in the same or in different frequency bands vs existing 2nd generation infrastructure-New layer 2 protocols may be significantly different from 2nd generation layer 2 protocolsAvoid massive new infrastructure investments until justified by demand/revenues•Issues/Implications-Need to start out with a “thin” new infrastructure-Need to reuse/overly existing 2nd generation cell sites3rd generation infrastructure is not always available and/or appropriate for ordinary cell phone calls•Issues/Implications-3rd generation appliances must be able (one way or another) to utilize 2nd generation infrastructure-Dual “personality” appliances-Complex interoperability functionality in appliances and infrastructure elementsRadio PortControllerPSTN3rd GenerationRadio Port ControllerInternetInterference MitigationInterference Mitigation•Adaptive Antennas -Highly directional-Can be aimed at a given user•Spatial-Temporal Processing-Use multiple receiving antennas-Take advantage of differences among antenna outputsAdjustable Rate CDMA1 1 10 0Low bit-rate signalHigh bit rate signalAdjustable Rate CDMA•Multiply input sequences by spreading sequences to obtain CDMA signals•Use longer spreading sequences for lower rate input sequences•Higher rate input sequences, after being spread, must be transmitted at higher power levels (power level proportional to bit rate)Software-defined Radio•Implement as much of the signal and protocol processing functions as possible using a combination of digital signal processors and microprocessors•Limitations are:A/D converter sampling rateA/D converter dynamic rangeSoftware-defined RadioRF AmplifierLocal OscillatorMixer FilterA/D DSP Chain~ GHz
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