Telecommunications Networking II Lecture 39 Next 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 networks

Next 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 freeze

Utilize spectrum efficiently Issues -New applications produce bursty and asymmetrical traffic flows -Accumulated experience with 2nd generation systems regarding actual performance with respect to achievable utilization

Continue 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 protocols

Avoid 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 sites

3rd 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 elements

Radio Port Controller PSTN 3rd Generation Radio Port Controller Internet

Interference 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 outputs

Adjustable Rate CDMA Low bit-rate signal High bit rate signal

Adjustable 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 rate A/D converter dynamic range

Software-defined Radio RF Amplifier Local Oscillator MixerFilter A/D DSP Chain ~ GHz~MHz