MSIT 413: Wireless Technologies Week 10

Transcription

1 MSIT 413: Wireless Technologies Week 10 Michael L. Honig Department of EECS Northwestern University November

2 Technologies on the Horizon Heterogeneous networks Massive MIMO Millimeter wave Spectrum sharing Wireless (near-field) power Internet of Things 2

3 The Cellular Crisis Service providers invested $$$ in infrastructure to support data services (3G). Wished for more data traffic to justify their investment. Their wish was granted 3

4 Demand is Increasing

5 Spectrum Crunch Petabytes per month 5

6 Increases in Cellular Capacity Capacity (Spectral Efficiency

7 How can we increase capacity further? Smaller cells More antennas, bandwidth Cooperation 7

8 Cooper s Law The data rate available to a wireless device doubles roughly every 30 months. --- Martin Cooper, Arraycom (paraphrased) Held over 100 years (since Marconi) 1,000,000 x increase since 1950 s! Where is this gain coming from?? 8

9 Cooper s Law Held over 100 years (since Marconi) 1,000,000 x increase since 1950 s! Where is most of this gain coming from?? 9

10 Cooper s Law The data rate available to a wireless device doubles roughly every 30 months. --- Martin Cooper, Arraycom (paraphrased) Held over 100 years (since Marconi) 1,000,000 x increase since 1950 s! Still not enough to meet projected usage forecasts 10

11 Femto-Cell 11

12 Radio Access Points Pico-cell BTS: small, inexpensive, low-power, coverage ~ 100 m, mounted on walls, lamp posts Macro-cell base station (BTS): Expensive, high-power, wide coverage, mounted on tower Femto-cell access point: cost/coverage similar to WiFi for house, apartment, office self-deployed, possibly closed subscriber list 12

13 Urban Macrocell Difficult to accommodate varying user density, different levels of mobility, indoor users, and provide uniform coverage. 13

14 Heterogeneous Network 14

15 Heterogeneous Deployments 15

16 Issues with Heterogeneous Networks Interference management Resource allocation, fairness Restricted access to femto-cells Scalability Network planning, maintenance, and operation Integration with WiFi / unlicensed high-power macro-cell low-power femto-cell 16

17 More Antennas 17

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21 Millimeter Wave Communications 28 GHz and above Why such high frequencies? Lots of spectrum available (multiple GHz) Offers extremely high data rates (multi-gbits/sec) Challenges Relatively high attenuation Need focused beamsteering Electronics: input/output becomes difficult Potential applications Local high-speed data transfers (e.g., PC peripherals, connecting to display) Wireless backhaul (Base to Base and/or MSC) Communications within data centers 21

22 Millimeter Wave Attenuation 22

23 Gigabit Wireless Provides WiFi (unlicensed) service in 60 GHz band Standard: ad Supports rates up to 7 Gbps (> 10 times n rate) Precise beamforming needed to focus energy, track devices need lots of antennas! 23

24 Other Applications 24

25 Spectrum Sharing LTE in unlicensed spectrum Citizens Broadband Radio Service (CBRS) 25

26 LTE-U (unlicensed) 26

27 Challenges LTE designed for exclusive use; WiFi designed for open access. LTE must adapt a politeness protocol to avoid shutting out WiFi users. Duty cycle (on-off) restrictions Listen before talk LTE-LAA (License-Assisted Access) Uses licensed spectrum as fallback when unlicensed band becomes too congested. 27

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30 Naval Radar in 3.5 GHz Band 30

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32 Three-Tier Sharing 32

33 Spectrum Access System (SAS) 33

34 Cellular Service Providers, Alphabet/Google, manufacturers (Qualcomm, Nokia, Ericsson, etc). 34

35 Cooperative Base Stations channel 2 channel 1 information exchange Can coordinate scheduling across cells to avoid interference Exchanging channel information allows cooperative beamforming 35

36 Cooperative Base Stations: Network MIMO Signals from other base stations / cells act as interference. 36

37 Cooperative Base Stations: Network MIMO Base Stations share messages, act as multiple antennas Creates MIMO channels between Base Stations and mobiles. Interference now carries useful information. 37

38 Issues with Cooperation Lots of overhead (exchanging channels and messages) Channels change need to estimate and track; introduces inaccuracies Moderate gains with significant complexity about a factor of 2 improvement in spectral efficiency 38

39 Battery Technology Falling Behind Power Demand Always on connectivity All-day battery life Instant on (no standby/sleep states) Location aware 39

40 Wireless Charging 40

41 Wireless Power Demo of wireless power 41