A Brief History of Space-Time Radio

Transcription

1 A Brief History of Space-Time Radio or The Past, Present, and Future of How Your Smart Phone Works Prof. Gregory D. Durgin, Georgia Tech School of ECE Personal History n Ph.D. at the end of 2000 from Virginia Tech n Doctoral research at the Mobile & Portable Radio Research Group (MPRG) n American researcher visiting Morinaga Laboratory (Osaka University) for 1 year n Professor in Georgia Tech School of ECE n Research program at 1

2 Outline of Talk n The Challenge with Mobile Radio n Using Multiple Antennas n The Most Important Equation? n LTE and 4G Cellular n mm-waves and Beyond 3 Cellular Industry Circa 1983 n First cellular system deployed in Chicago, 1983 n Had been on the drawing board since 1960s n Antenna is a long metal rod sticking out up top MOTOROLA DYNATAC 8000X depicted by The Evolution of Cell Phone Design from , 4 2

3 Transmission Line Analogy 5 Small-Scale Fading n Constructive or destructive wave interference n Leads to a random, unpredictable signal strength n PDF characterizes typical power or envelope levels 6 Copyright Prof. Durgin 3

4 Elitzur-Vaidman Experiment n Waves constructively/destructively interfere even when amplitudes drop below photonic coherence n Demonstrated in optics with apparatus similar to diagram below [Eli93]: 7 Copyright Prof. Durgin Cellular Industry Circa 1992 n Launch of digital, personal communications systems n Phones get smaller n Antenna is now a dualmode monopole whip/ stub-loaded helix Nokia 1011 depicted by The Evolution of Cell Phone Design from , 8 4

5 WHAT IS THE MOST IMPORTANT EQUATION? 9 The Most Important Equation? n Schrodinger s equation n Maxwell s equations n Newton s laws of motion n E=mc^2 n Ohm s law n Shannon channel capacity n Nyquist sampling theorem n Laws of Thermodynamics n Any suggestions? 10 5

6 SISO Channel Capacity n SISO = Single Input, Single Output n Power is the show-stopper, but there are diminishing returns on investment 11 SIMO Channel Capacity n SIMO = Single Input, Multiple Output n Beam-forming produces channel gain, which enhances capacity 12 6

7 Beam-forming Channel Capacity n Multiple antennas at both transmit and receive could provide very large gains, increase in channel capacity n Gains are always squashed by the logarithm: 13 MIMO Signal Processing n Transmitter and Receiver signal vector processing can be represented by unitary matrix operations, V and U. n Unitary matrices add no power, so any improvements will be genuine with respect to SINR 14 7

8 MIMO Processing Visualization 15 MIMO Channel Capacity n For an M x M system, there are now M separate data channels or streams n Aggregate channel capacity is the sum of each individual stream capacity n Brings M outside the logarithm 16 8

9 Cellular Industry Circa 2004 n Electronics are getting smaller, allowing the phone to get thinner n Incorporation of Planar F and similar antenna types allow hidden radiators MOTOROLA RAZR depicted by The Evolution of Cell Phone Design from , 17 First Textbook on Space-Time Radio Book Title: Space-Time Wireless Channels Prentice-Hall Inc. October

10 Cellular Industry Circa 2008 n First iphone introduced in 2007 n New brick form factor n Enabled by small, PCB/ multimode antennas APPLE IPHONE 3G depicted by The Evolution of Cell Phone Design from , 19 Migration of Antenna in Phones n PCB or thin substrate area across end of phone q Mechanically stable q Low profile q Minimal user effects q Allows metal housing & ground plane protrusion n True for 1 or 2 antennas T.W. Kang, K-L Wong, L-C Chou, M-R Hsu. Coupled- Fed Shorted Monopole With a Radiating Feed Structure for Eight-Band LTE/WWAN Operation in the Laptop Computer. IEEE Transactions on Antennas and Propagation, Feb

11 LTE/E-UTRA MIMO Support n MIMO Uplink q 2 x 2 antennas q SC-FDMA Single Carrier Frequency Division Multiple Access n MIMO Downlink: q (2 or 4) x (2 or 4) antennas q OFDMA Orthogonal Frequency Division Multiple Access 21 OFDMA-MIMO Transmission [Wikipedia, OFDMA, 2011] n Multiple users assigned various subcarriers n Pilot subcarriers transmit/receive coordination information n MIMO on each subcarrier (effectively narrowband) 22 11

12 Single- or Multi-User MIMO [Li10] Q. Li, G. Li, W. Lee, M. Lee, D. Mazzarese, B. Clerckx, MIMO Techniques in WiMAX and LTE: A Feature Overview. IEEE Communications Magazine. May Cellular Industry Circa 2017 n Antennas now excite waveguide modes inside a metal case with slots n Multiple slots allow different antennas for MIMO and diversity From Apple Computer 24 12

13 The Future n More functionality in 5G cellular q Higher data rates for High-Def video q Low latency for new types of mobile applictions n Move to higher frequencies, mm-wave spectrum q Studies suggest high-rate links are possible q More propagation losses means more spectral reuse q Issues involving power consumption and practicality n Massive MIMO q Dozens or hundreds of base station antenna elements q Lots of multi-user channels, highly directional links 25 13