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Timo Unger

Multiple-antenna two-hop relaying for bi-directional transmission in wireless communication systems. Timo Unger. Future wireless communication systems. high data rate services increasing bandwidth higher center frequencies higher order modulation. Node S1. Node S2. non-sufficient SNR.

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Timo Unger

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  1. Multiple-antenna two-hop relaying for bi-directional transmission in wireless communication systems Timo Unger 08.11.2014 | Timo Unger

  2. Future wireless communication systems high data rate services • increasing bandwidth • higher center frequencies • higher order modulation Node S1 Node S2 non-sufficient SNR typical problem solutions • higher transmit powers  EMC, health • additional base stations  infrastructure costs 08.11.2014 | Timo Unger 2

  3. Relaying: providing high data rate services to shadowed areas relaying • lower transmit powers • no additional base stations Node S1 Node S2 Relay Station RS • non-regenerative relaying • linear signal processing • no error propagation • no delay due to decoding • transparency to modulation and coding of S1 and S2 08.11.2014 | Timo Unger 2

  4. Relaying: providing high data rate services to shadowed areas assumptions • non-regenerative relaying • bi-directional transmission • multiple antennas Node S1 Node S2 • multiple antennas • adaptive beamforming • spatial multiplexing Relay Station RS • relaying schemes • one-way relaying • two-way relaying 08.11.2014 | Timo Unger 2

  5. Time slot allocation one-way relaying two-way relaying S1 S1 S2 S2 RS RS time slot cancellation of duplex interference (CDI) time time 08.11.2014 | Timo Unger 3

  6. Overview state of the art novel contributions one-way relaying two-way relaying System with full capabilities single-antenna [Shannon ´61, Rankov ´05] [v. d. Meulen ´71] maximum sum rate multiple-antenna [Munoz ´05, Hammerström ´06] maximum sum rate • Systems with • limited capabilities • availability of channel state information (CSI) • node capabilities maximum sum rate obtaining CSI linear beamforming algorithms: MMSE, ZF, MF 08.11.2014 | Timo Unger 4

  7. Overview state of the art novel contributions one-way relaying two-way relaying System with full capabilities single-antenna [Shannon ´61, Rankov ´05] [v. d. Meulen ´71] maximum sum rate multiple-antenna maximum sum rate [Munoz ´05, Hammerström ´06] 08.11.2014 | Timo Unger 4

  8. Problem formulation: maximization of sum rate S1 RS S2 1/4 for one-way 1/2 for two-way = : covariance matrix of useful signal : covariance matrix of noise plus interference • Tx power constraints at S1 & S2 • Tx power constraint at RS subject to: 08.11.2014 | Timo Unger 5

  9. Time slot allocation one-way relaying S1 S2 RS time slot time 08.11.2014 | Timo Unger 6

  10. Sum rate maximization in one-way relaying eigenvalues RS • singular value decomposition (SVD) • adaptation to the eigenmodes • orthogonal spatial sub-channels S2 S1 S2 S1 time [Munoz ´05, Hammerström ´06] 08.11.2014 | Timo Unger 7

  11. Time slot allocation two-way relaying S1 S2 RS cancellation of duplex interference (CDI) time 08.11.2014 | Timo Unger 8

  12. Sum rate maximization in two-way relaying RS S2 S1 BF cannot be adapted to the eigenmodes of both channels simultaneously S2 S1 numerical optimization of G, Q(1), Q(2): sequential quadratic programming time 08.11.2014 | Timo Unger 9

  13. Time slot allocation two-way relaying S1 S2 RS cancellation of duplex interference (CDI) time 08.11.2014 | Timo Unger 10

  14. Time slot allocation two-way relaying S1 S2 RS cancellation of duplex interference (CDI) time 08.11.2014 | Timo Unger 10

  15. Average sum rate vs. SNR i.i.d. Rayleigh fading channel upper bound: “2*one-way“ rate loss due to retransmission of already known data two-way SNR(1) = 20 dB SNR(2) average sum rate in bit/s/Hz one-way SNR(2) in dB 08.11.2014 | Timo Unger 11

  16. Average sum rate vs. number of antennas i.i.d. Rayleigh fading channel two-way SNR(1) = 10 dB SNR(2) = 10 dB … average sum rate in bit/s/Hz one-way number L of antennas at RS 08.11.2014 | Timo Unger 12

  17. Multiple-antenna gains i.i.d. Rayleigh fading channel two-way SNR(1) = 10 dB SNR(2) = 10 dB … average sum rate in bit/s/Hz one-way spatial multiplexing gain one bit/s/Hz per antenna diversity and array gain L 08.11.2014 | Timo Unger 13

  18. Overview state of the art novel contributions one-way relaying two-way relaying System with full capabilities single-antenna [Shannon ´61, Rankov ´05] [v. d. Meulen ´71] maximum sum rate multiple-antenna maximum sum rate [Munoz ´05, Hammerström ´06] • Systems with • limited capabilities • availability of channel state information (CSI) • node capabilities 08.11.2014 | Timo Unger 14

  19. Availability of channel state information (CSI) RS S1 S2 08.11.2014 | Timo Unger 15

  20. Node capabilities adaptive beamforming (BF) equal weighting RS S1 S2 08.11.2014 | Timo Unger 16

  21. Overview state of the art novel contributions one-way relaying two-way relaying System with full capabilities single-antenna [Shannon ´61, Rankov ´05] [v. d. Meulen ´71] maximum sum rate multiple-antenna maximum sum rate [Munoz ´05, Hammerström ´06] • Systems with • limited capabilities • availability of channel state information (CSI) • node capabilities maximum sum rate 08.11.2014 | Timo Unger 17

  22. Average sum rate vs. number of antennas for different system capabilities i.i.d. Rayleigh fading channel full capabilities at all nodes local CSI at S1 & S2 limited capabilities at S1 & S2 SNR(1) = 10 dB SNR(2) = 10 dB … average sum rate in bit/s/Hz one-way limited capabilities at RS number L of antennas at RS 08.11.2014 | Timo Unger 18

  23. Overview state of the art novel contributions one-way relaying two-way relaying System with full capabilities single-antenna [Shannon ´61, Rankov ´05] [v. d. Meulen ´71] maximum sum rate multiple-antenna maximum sum rate [Munoz ´05, Hammerström ´06] • Systems with • limited capabilities • availability of channel state information (CSI) • node capabilities maximum sum rate linear beamforming algorithms: MMSE, ZF, MF 08.11.2014 | Timo Unger 19

  24. Adaptive beamforming only at the RS Sum rate maximization problem Other optimization problems (known from point-to-point) • problems are neither convex nor concave • local / global optima can be found by sequential quadratic programming • minimize MSE ( MMSE) • minimize MSE under zero forcing constraint ( ZF) • maximize SNR ( MF) 08.11.2014 | Timo Unger 20

  25. Sum rate for different BF algorithms in a system with local CSI at S1 & S2 i.i.d. Rayleigh fading channel maximum sum rate MMSE SNR(1) = 20 dB ZF SNR(2) average sum rate in bit/s/Hz MF SNR(2) in dB 08.11.2014 | Timo Unger 21

  26. Overview state of the art novel contributions one-way relaying two-way relaying System with full capabilities single-antenna [Shannon ´61, Rankov ´05] [v. d. Meulen ´71] maximum sum rate multiple-antenna [Munoz ´05, Hammerström ´06] maximum sum rate • Systems with • limited capabilities • availability of channel state information (CSI) • node capabilities maximum sum rate obtaining CSI linear beamforming algorithms: MMSE, ZF, MF 08.11.2014 | Timo Unger 22

  27. Pilot transmission schemes m: antenna index t: time Obtaining CSI of at the RS S2 RS S1 m one pilot symbol per transmit antenna t Obtaining CSI of at the S2 S2 S1 RS m retransmission of the same pilot symbols t 08.11.2014 | Timo Unger 23

  28. Pilot transmission schemes m: antenna index t: time Obtaining CSI of at the RS S2 RS S1 m one pilot symbol per transmit antenna t Obtaining CSI of at the S2 S2 S1 RS m retransmission of the same pilot symbols t 08.11.2014 | Timo Unger 23

  29. Pilot transmission schemes m: antenna index t: time Obtaining CSI of at the RS S2 RS S1 m one pilot symbol per transmit antenna t Obtaining CSI of at the S2 S2 S1 RS m m CDI can also be applied for pilot symbols t t 08.11.2014 | Timo Unger 23

  30. Pilot transmission schemes - overview m System with full capabilities t m System with limited capabilities at RS t m System with limited capabilities at S1 & S2 t m System with local CSI at S1 & S2 t 08.11.2014 | Timo Unger 24

  31. Sum rate with degradation due to pilot overhead i.i.d. Rayleigh fading channel full capabilities at all nodes local CSI at S1 & S2 limited capabilities at S1 & S2 SNR(1) = 10 dB SNR(2) = 10 dB … average sum rate in bit/s/Hz • v = 20 km/h • f0 = 5 GHz • tmax = 2 ms • uT = uB = 5 limited capabilities at RS number L of antennas at RS 08.11.2014 | Timo Unger 25

  32. Sum rate with degradation due to pilot transmission i.i.d. Rayleigh fading channel full capabilities at all nodes local CSI at S1 & S2 limited capabilities at S1 & S2 SNR(1) = 10 dB SNR(2) = 10 dB … average sum rate in bit/s/Hz • v = 20 km/h • f0 = 5 GHz • tmax = 2 ms • uT = uB = 5 limited capabilities at RS number L of antennas at RS 08.11.2014 | Timo Unger 25

  33. Conclusions • Two-way relaying significantly outperforms one-way relaying for bi-directional transmission • Categorizing systems of different capabilities with respect to CSI and signal processing capabilities • Performance bounds for the systems of different capabilities • Linear adaptive beamforming algorithms for systems with exclusive BF at the RS • Pilot transmission schemes for two-way relaying • Impact of imperfect CSI on the performance • Multiple access for two-way relaying 08.11.2014 | Timo Unger 26

  34. References • T. Unger and A. Klein, “Linear Adaptive Beamforming Algorithms for Multiple-Antenna Non-Regenerative Two-Way Relaying ," submitted for publication in: IEEE Transactions on Signal Processing, Dec. 2008 • S. Berger, T. Unger, M. Kuhn, A. Klein, and A. Wittneben, “Recent advances in amplify-and-forward two-hop relaying,” accepted for publication in: IEEE Communications Magazine, 2009. • T. Unger and A. Klein, "Duplex Schemes in Multiple Antenna Two-Hop Relaying," EURASIP Journal on Advances in Signal Processing, vol. 2008, Article ID 128592, May 2008. • T. Unger and A. Klein, "Maximum Sum Rate for Non-regenerative Two-way Relaying in Systems of Different Complexities," in Proc. 19th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), Cannes, France, Sep. 2008 (invited paper). • T. Unger and A. Klein, "Applying Relay Stations with Multiple Antennas in the One- and Two-Way Relay Channel," in Proc. 18th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), Athens, Greece, Sep. 2007 (invited paper). • T. Unger and A. Klein, "On the Performance of Relay Stations with Multiple Antennas in the Two-way Relay Channel," in Proc.16th IST Mobile and Wireless Communications Summit, Budapest, Hungary, July 2007. • T. Unger and A. Klein, "Linear Transceive Filters for Relay Stations with Multiple Antennas in the Two-Way Relay Channel," in Proc. 16th IST Mobile and Wireless Communications Summit, Budapest, Hungary, July 2007. 08.11.2014 | Timo Unger 27

  35. 08.11.2014 | Timo Unger

  36. Future wireless communication systems Ubiquitous high data rate services Approach Approach Approach Increasing bandwidth Higher center frequencies Higher order modulation schemes Problem Problem Problem Increased noise power Increased pathloss Increased sensitivity to noise Higher transmit power for sufficient SNR / smaller mobile radio cells EMC, health and costs 08.11.2014 | Timo Unger

  37. Availability of channel state information (CSI) RS S2 S1 • Global CSI at the RS • required for adaptive beamforming (BF) RS S2 S1 • Local CSI at S1 & S2 • required for cancellation of duplex interference (CDI) RS S2 S1 • Global CSI at S1 & S2 • required for adaptive BF 08.11.2014 | Timo Unger

  38. Node capabilities Nodes of full capabilities • S1, S2 and RS perform adaptive BF Limited capabilities at RS • RS cannot perform adaptive BF Limited capabilities at S1 and S2 • S1 and S2 cannot perform adaptive BF 08.11.2014 | Timo Unger

  39. Different cases of system capabilities System with full capabilities System with limited capabilities at RS System with limited capabilities at S1 & S2 System with local CSI at S1 & S2 global CSI at all nodes no CSI at RS no CSI at S1 & S2 only local CSI at S1 & S2 full capabilities at all nodes limited capabilities at RS limited capabilities at S1 & S2 limited capabilities at S1 & S2 adaptive BF at all nodes CDI equal weighting at RS CDI equal weighting at S1 & S2 no CDI equal weighting at S1 & S2 CDI 08.11.2014 | Timo Unger

  40. Sum rate maximization in one-way relaying RS S2 S1 S2 S1 time [Munoz ´05, Hammerström ´06] 08.11.2014 | Timo Unger

  41. 0 0 0 0 0 0 Sum rate maximization in one-way relaying RS S2 S1 Waterfilling at RS S2 S1 time [Munoz ´05, Hammerström ´06] 08.11.2014 | Timo Unger

  42. Sum rate maximization in two-way relaying RS S2 S1 S2 S1 time 08.11.2014 | Timo Unger

  43. Sum rate maximization in two-way relaying RS S2 S1 BF cannot be adapted to the eigenmodes of both channels simultaneously S2 S1 time 08.11.2014 | Timo Unger

  44. Sum rate maximization in two-way relaying RS: L ant. S2: M ant. S1: M ant. S2 S1 • numerical optimization of G, Q(1), Q(2): sequential quadratic programming (SQP) • M2optimization variables in Q(1)/ Q(2), L2 optimization variables in G time 08.11.2014 | Timo Unger

  45. Sum rate maximization in two-way relaying RS: L ant. S2: M ant. S1: M ant. projection to the range space of the joint receive channel range space null space for L > 2M time 08.11.2014 | Timo Unger

  46. Sum rate maximization in two-way relaying range space null space projection to the range space of the joint transmit channel S2 S1 number of optimization variables in G can be reduced for L > 2M: time 08.11.2014 | Timo Unger

  47. Average sum rate vs. SNR for different system capabilities in two-way relaying i.i.d. Rayleigh fading channel full capabilities at all nodes local CSI at S1 & S2 limited capabilities at RS SNR(1) = 20dB SNR(2) average sum rate in bit/s/Hz limited capabilities at S1 & S2 one-way SNR(2) in dB 08.11.2014 | Timo Unger

  48. Single antenna S1 & S2 • single-antenna S1 & S2 (M = 1) • multiple-antenna RS (L ≥ 2) transmission rate of the form: sub-optimum approach: maximize individual SNRs 08.11.2014 | Timo Unger

  49. Sub-optimum BF algorithm transmit matched filter receive matched filter weighting matrix 08.11.2014 | Timo Unger

  50. Sub-optimum BF algorithm transmit matched filter receive matched filter weighting matrix 08.11.2014 | Timo Unger

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