Designing Ultra-Wide Bandwidth (UWB) Receivers for Multi-User Interference Environments

Transcription

1 Designing Ultra-Wide Bandwidth (UWB) Receivers for Multi-User Interference Environments Norman C. Beaulieu Hua Shao Somasundaram Niranjayan Iraj Hosseini Bo Hu David Young 1

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3 Outline Introduction Soft-Limiting Structures Gaussian-Laplacian noise-plus-mui model based Receivers Zonal UWB Receiver P-order Metric Receiver (P-omr) Structure Alpha-stable Receiver Optimal Performance Benchmark New Rake Receiver Designs Conclusions N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 3

4 I. Introduction Bandwidth Concerns Frequency Reuse The UWB Concept Two Proposals for Implementing UWB Systems Impulse Radio Signalling Time-Hopping UWB Conventional MF UWB Receiver Multi-user Interference

5 source: N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 5

6 Bandwidth Concerns Radio spectrum is a scarce resource (3 KHz 300 GHz) Almost all portions are allocated for specific purposes Emerging wireless applications require a share in the radio spectrum If permitted, frequency can be reused at different times or in different geographical locations Simultaneous and/or collocated reuse is required to meet bandwidth demands N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 6

7 Frequency Reuse Recently, researchers are interested in techniques for reusage. Cognitive radio: Borrowing and Sharing Ultra-wide bandwidth communication: Sharing without disturbing others N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 7

8 The UWB Concept Large Bandwidth Wider than narrowband systems by orders of magnitude With average transmission power under 75 nanowatts/mhz Unnoticeable interference to current RF services, imperceptible random noise to conventional radios N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 8

9 The UWB Concept The FCC Regulations Fractional bandwidth should be larger than 25%, or Relative bandwidth should be over 500 MHz, regardless of the fractional bandwidth. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 9

10 The UWB Concept The FCC Regulations Indoor - Must show that they will not operate when taken outside Outdoor (Handheld)- Operate in a peer-to-peer mode without location restriction N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 10

11 The UWB Concept Advantages of UWB systems Ability to share the frequency spectrum with narrowband signals Improved channel capacity High immunity to detection and interception Less sensitive to multipath effects Simple transceiver structure Extremely high data rates possible Fine time resolution N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 11

12 The UWB Concept UWB Application 1: Wireless Personal Area Networks (WPAN) Enabling high-speed wireless USB connectivity for PCs and PC peripherals. Replacing cables between multimedia consumer electronics devices. Replacing cables in next generation Bluetooth technology devices. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 12

13 UWB Applications 2 The UWB Concept Communications and sensors. Security systems, medical situations Position location, ranging and tracking Pinpoint the location of objects indoor, in-house movement could be followed Radar imaging Used in open-air, through-wall or ground penetrating radar imagers Vehicular radar systems Used to avoid car collision and aid parking Medical Imaging N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 13

14 Two Proposals for Implementing UWB Systems Pulse based UWB (Impulse Radio) [Win & Scholtz 00] y(t) log( Y(f) 2 ) t (ns) GHz Multiband approach (MB-OFDM) [Batra et.al 04] source: N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 14

15 Impulse Radio Signalling Time hopping UWB (TH-UWB) [Win & Scholtz 00] Direct sequence UWB (DS-UWB) [Foerster 02] Modulation techniques Nominal pulse position shift Pulse position modulation (PPM) Pulse amplitude modulation (BPAM) N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 15

16 Time-Hopping UWB UWB Wireless High-speed, short-range communication systems Impulse Radio Signalling Modulated pulse trains Very short duration (T p <1ns) Modulation: pulse-position modulation (PPM), binary phase shift keying modulation (BPSK), etc. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 16

17 Repetition Code Structure T b =N s *T f One UWB pulse within a frame, all Ns pulses are used to transmit a single information bit. Time-hopping To eliminate catastrophic collisions in multiple access applications In each frame time, the pulse is positioned pseudo-randomly in time with a TH sequence Modulations BPSK, PPM Time-Hopping UWB N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 17

18 Time-Hopping UWB Time Hopping: A district pulse-shift pattern { C j } called a TH Sequence is introduced to eliminate catastrophic collisions in multiple access applications. In each frame time, the pulse is positioned pseudo-randomly in time with a TH sequence. Example: pulse has been shifted to hop position 4 in a frame with 8 possible hop positions. Since the pulses are so short, there are many time slots where one can locate them Pulses are repeated in many frames (repetition code) N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 18

19 Conventional MF UWB Receiver If users are transmitting on an AWGN channel, the received signal is modeled as The single-user UWB correlator receiver is used to coherently demodulate the desired user signal N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 19

20 Conventional MF UWB Receiver (Cont d) A conventional single-user matched filter (correlation receiver) is used to detect a desired UWB user signal in multiple access applications The BER was estimated by using a Gaussian approximation in which a central limit theorem (CLT) is employed to approximate the sum of the multiuser interference (MUI) as an additive Gaussian noise (AGN) process If a signal is corrupted only by AGN, the matched filter is an optimum receiver in the sense that it maximizes the output signal-to-noise ratio (SNR) and minimizes the average symbol error rate. However, the MUI in UWB systems cannot be reliably modeled as AGN and, hence, the conventional single-user matched filter (or correlation receiver) is not necessarily an optimal single-user receiver for UWB in an MUI environment N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 20

21 Conventional MF UWB Receiver (Cont d) Inaccuracy of the Gaussian Approximation Average BER of the TH-PPM UWB system versus SNR for a repetition code with Ns = 2 and Ns = 4 assuming 7 asynchronous interferers. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 21

22 Multi-user Interference Simulated Simulated GA Simulated Laplacian GAApproximation P (I) I I Comparison of the simulated PDF of MUI with theoretical model PDFs with Nu=4, Ns = 8, Nh = 8, Tf = 20 ns, Tc = 0.9 ns and tm = 0.55 ns. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 22

23 Multi-user Interference (Cont d) Simulated Simulated GA Simulated Laplacian GApproximation P (I) I I Comparison of the simulated PDF of MUI with theoretical model PDFs with Nu = 16, Ns = 8, Nh = 8, Tf = 20 ns, Tc = 0.9 ns and tm = 0.55 ns. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 23

24 Multi-user Interference (Cont d) PDF of the MUI - Simplified Example Let p(t) denote the UWB pulse with a duration, and R(t) denote the autocorrelation function of p(t) as Assuming the time shift difference between the desired user and the interferer is, which is uniformly distributed on, the interference resulting from this particular interferer can be represented as N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 24

25 Multi-user Interference (Cont d) N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 25

26 Multi-user Interference (Cont d) The simulated PDF of the amplitude of the total disturbance sample, including both MUI and AWGN. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 26

27 II. Soft-Limiting Structures 27

28 Decision Statistic The output of the conventional correlation receiver,, is the sum of integrals over N s frames. Each integration is a partial correlation for the corresponding frame r N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 28

29 Soft-Limiting Structure We propose a novel UWB receiver structure. Unlike the conventional correlation receiver which makes its decision based on decision variable is calculated as, the where The transmitted information bit is then decided according to the rule N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 29

30 Soft-Limiting Structure (Cont d) Novel Receiver Conventional Receiver The block diagram of the soft-limiting receiver with threshold N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 30

31 BER Results and Discussion The average BER versus SIR of the soft-limiting and conventional TH-BPSK UWB receivers assuming 15 asynchronous interferers. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 31

32 BER Results and Discussion (Cont d) The average BER versus SNR of two soft-limiting receivers and the conventional TH-BPSK UWB receiver assuming 3 asynchronous interferers. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 32

33 III. Gaussian-Laplacian Noise-Plus-MUI Model Based Receivers 33

34 Gaussian-Laplacian Mixture Noise-Plus-MUI Model Receivers r( t ) γ, ( t ) T ( ) i b gi ( ) dt 0 γ, m N s i= 1 i b ( t) Λ b Receiver 1 (GLM) A common block diagram for the proposed receivers ( ) The nonlinearity function g is the log likelihood function of the optimal (in the ML sense) receiver for the detection in the presence of Gaussian- Laplacian mixed noise. g(x) is given by N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 34

35 Gaussian-Laplacian Mixture Noise-Plus-MUI Model Receivers (Cont d) Receiver 2 (SGLM) This is a simplified form of the first receiver, derived by approximating the optimum nonlinearities in, the nonlinearity function of the simplified receiver is quite simple and has the following form where the parameter is a function of the present SNR and SIR and is given by N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 35

36 BER Results and Discussion A comparison of the BERs of the two new detectors with the BER of a linear detector with Nu = 4, Ns = 8, Nh = 8, Tf = 20 ns, Tc = 0.9 ns and tm = 0.55 ns and SIR = 10 db. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 36

37 IV. Zonal UWB Receiver 37

38 Conditional PDF of the Chip Correlator Output An example of the conditional PDF of the chip correlator output when the information bit +1 and -1 are sent, respectively. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 38

39 Zonal Correlator Output Transform N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 39

40 Transfer Characteristic The transfer characteristic of the receiver chip correlator output transform N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 40

41 Block Diagram of the Zonal UWB Receiver N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 41

42 BER Results and Discussion A comparison of the BER s of the conventional matched filter receiver, the soft-limiting receiver, the adaptive threshold soft-limiting receiver, and the zonal receiver. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 42

43 V. P-Order Metric Receiver (P-OMR) Structure 43

44 PDF s of the Generalized Gaussian N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 44

45 Multi-user Interference The simulated PDF of the amplitude of the total disturbance sample, including both MUI and AWGN. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 45

46 P-Order Metric Receiver (P-OMR) Structure N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 46

47 BER Results and Discussion A comparison of the BERs of the CMF UWB receiver, the soft-limiting UWB receiver and the p-omr, when only MUI is present. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 47

48 BER Results and Discussion (Cont d) A comparison of the BERs of the CMF UWB receiver, the soft-limiting UWB receiver and the p-omr operating in both MUI and AWGN N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 48

49 VI. Alpha-Stable Receiver Structure 49

50 Alpha Stable Noise Model and the New Adaptive Detector α The PDF of an stable process is not known in general. The model can be best described by its characteristic function as α -stable α where is known as the characteristic exponent and parameter. The new detector ζ is the shaping where the adaptive parameter K is determined by the intuitive expression Where C is a constant to be determined experimentally and variance of the AWGN at a frame correlator output. 2 σ is the N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 50

51 Alpha Stable Noise Model and the New Adaptive Detector γ i b + r( t ) T T f ( ) f, dt 0 Template signal generator N s ( γ ) 2 i, b s 2 K + i= 1 N s ( γ ) 2 i, b s 2 K + + i= 1 + Threshold detector d b Synchronization and parameter estimation K, s A block diagram of the new receiver, the alpha-stable distribution parameters alpha and zeta are estimated by matching the empirical characteristic function of the MAI. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 51

52 Cauchy detector Linear detector Myriad filter detector SGLM detector P order metric receiver 10 1 Cauchy detector Linear detector Myriad filter detector SGLM detector P order metric receiver 10 2 BER BER Eb/No Eb/No A comparison of the BER of the new adaptive detector with the BERs of the linear detector and 3 other non-linear detectors for Nu = 4. A comparison of the BER of the new adaptive detector with the BERs of the linear detector and 3 other nonlinear detectors for Nu = 16. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 52

53 BER Results and Discussion (Cont d) A comparison of the BERs of the CMF receiver, the soft-limiting UWB receiver, the adaptive threshold soft-limiting UWB receiver, the simplified Gaussian Laplace mixture UWB receiver, the zonal UWB receiver, and the p-omr UWB receiver. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 53

54 VII. Optimal Performance Benchmark 54

55 Optimal Error Rate Performance It is essential to have the optimal benchmark against which the performances of other receivers can be measured. The optimum performance is obtained based on the MAP rule. However, the MAP rule requires knowledge of the PDF of the MAI. The PDF of the MAI is obtained based on an exact mathematical model which explains impulses, singularities, and heavy tails found in the distribution of the MAI. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 55

56 The Optimal UWB Receiver Structure Suppose that r0, r1,..., rn s 1 are the correlator outputs for N s pulses transmitted to convey one bit of information, a. Assuming that a takes values {-1, +1} with the same probability, an optimum receiver decides a = +1 if otherwise it decides a = -1. denotes the conditional PDF of the correlator output when each of the information bits is transmitted. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 56

57 BER vs. SIR of TH-UWB Receivers The BER versus SIR for TH-UWB receivers together with the optimal performance, for 7 asynchronous Interferers. Curves for N s = 3 and 5 are depicted by dashed and solid lines, respectively. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 57

58 BER vs. SIR of TH-UWB Receivers The BER versus SIR for TH-UWB receivers together with the optimal performance, for 15 asynchronous interferers. Curves for N s = 3 and 5 are depicted by dashed and solid lines, respectively. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 58

59 VIII. New Rake Receiver Designs 59

60 Wireless Channels Source: N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 60

61 UWB Multipath Fading Channel Model UWB Multipath Fading Channel Model A modified version of Saleh-Valenzuela model Lognormal distribution rather than a Rayleigh distribution for the multipath gain amplitude Multipath components arrive in clusters and rays Arrivals of clusters and the rays within each cluster are modeled by Poisson processes. Discrete Time Impulse Response α k l X: lognormal shadowing,, : amplitude of the k th ray within the l th cluster : arrival time of the l th cluster, τ : arrival time of the k th ray within the l th k l cluster T l, N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 61

62 UWB Multipath Fading Channel Model Impulse response realizations of the IEEE CM1 channel model (Figure generated by the codes in IEEE P /490r1-SG3a). N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 62

63 New Rake Receiver Designs For all-rake receivers, the output SINR can be written as For a Rake receiver adopting the new nonlinear structure g() in each finger, the SINR is Let and denote the minimum gain and maximum gain, respectively, across the L fingers of the Rake receiver. One has that N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 63

64 BER Comparisons of Rake Receivers A comparison of the BERs of the conventional Rake receiver and the SGLM-Rake receiver for different numbers of equal-power interferers in IEEE a CM1 multipath fading channel. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 64

65 BER Comparisons of Rake Receivers(Cont d) A comparison of the BERs of the conventional Rake receiver and the SGLM-Rake receiver for different numbers of Rake fingers with N u =4 in IEEE a CM1 multipath fading channel. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 65

66 BER Comparisons of Rake Receivers(Cont d) The average BER versus SNR of the CMF based Rake receiver, the zonal based Rake receiver with thresholds based on the estimated SNR and SIR, and the zonal based Rake receiver with thresholds based on perfect knowledge of the SNR and SIR, in IEEE a CM1 channel, when the SIR is 10 db. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 66

67 BER Comparisons of Rake Receivers(Cont d) The BERs of the conventional Rake receiver and the SGLM-Rake receiver with perfect channel knowledge and practical channel estimation, for different SIR levels S with N u =4 in IEEE a CM1 channel. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 67

68 BER Comparisons of Rake Receivers(Cont d) The BERs of the conventional Rake receiver and the p-omr based Rake receiver with perfect channel knowledge and practical channel estimation, for different SIR levels with N u =4 in IEEE a CM1 multipath fading channel. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 68

69 Conclusions Novel (nonlinear) receiver designs have been proposed based on different modelings for the MUI. Soft-limiting receiver structures have been proposed. The proposed structures implement a nonlinear limiter for suppressing the MUI. Simulation results show that the proposed receivers achieve better performance than the CMF receiver when operating in MUI. A Receiver structure with an adaptive limiting threshold is further proposed to ensure the performance of a soft-limiting receiver always meets or surpasses the performance of the CMF UWB receiver for all values of SNR. A ML receiver structure has been derived based on the Laplace-Gaussian sum model of the MUI plus noise; a simplified form of this ML detector which has much less implementation complexity has also been proposed. Simulation results indicate that both new receivers outperform the CMF UWB receiver for practical UWB applications. N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 69

70 Conclusions (Cont d) A zonal UWB receiver has been proposed based on the observations of the conditional pdf s of the chip correlator outputs. It is seen that the zonal UWB receiver outperforms the CMF and the soft-limiting receivers for medium and large values of SNR. P-order Metric Receiver Structures have been proposed based on generalized Gaussian modeling of the MUI. It has been shown that the p- omatlr outperforms the CMF receiver, and the soft-limiting receivers in all operating conditions. An alpha-stable model for the MAI leads to an effective ML receiver design, the myriad filter detector The performance of a theoretically optimal receiver has been used to benchmark the performances of the difference receivers N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 70

71 Conclusions (Cont d) It has been shown that a Rake receiver employing the new (nonlinear) receiver structures in the fingers and operating in a multipath environment achieves similar enhancement in the SINR to that obtained by a single new receiver operating in a static MAI channel. The MRC Rake receiver using a new receiver structure in each finger outperforms the conventional Rake receiver using a matched filter in each finger when the new receiver structure outperforms the matched filter receiver N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 71

72 General References [1] M. Z. Win and R. A. Scholtz, Impulse radio: How it works, IEEE Commun. Lett., vol.2, pp.51-53, Feb [2] M. Z. Win and R. A. Scholtz, Ultra-wide bandwidth time-hopping spread-spectrum impulse radio for wireless multiple-access communications, IEEE Trans. Commun., vol. 48, pp , Apr [3] M. Z. Win and R. A. Scholtz, Characterization of ultra-wide bandwidth wireless indoor channels: A communication-theoretic view, IEEE Journal on Select. Areas Commun., vol.20, pp , Dec [4] M. L. Melborn, System consideration for ultra-wideband wireless networks, in Proc. IEEE Radio and Wireless Conf., Boston, MA, Aug. 2001, pp N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 72

73 General References (Cont d) [5] G. Durisi and S. Benedetto, Performance evaluation of TH-PPM UWB systems in the presence of multiple access interference, IEEE Commun. Lett., vol.7, pp , May [6] B. Hu and N. C. Beaulieu, Accurate performance evaluation of timehopping and direct-sequence UWB systems in multi-user interference, IEEE Trans. Commun., vol. 53, pp , June [7] F. Ramirez-Mireles, On the performance of ultra-wide-band signals in Gaussian noise and dense multi-path, IEEE Trans. Veh. Technol., vol. 50, pp , Jan [8] F. Ramirez-Mireles, `Performance of ultra-wideband SSMA using time hopping and M-ary PPM, IEEE J. Select. Areas Commun., vol.19, pp , June N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 73

74 General References (Cont d) [9] D. Goeckel and Q. Zhang, Slightly Frequency-Shifted Reference Ultra- Wideband (UWB) Radio: TR-UWB without the Delay Element, in Proc. MILCOM Conference, vol. 5, Oct. 2005, pp [10] L. Yang, G. B. Giannakis and A. Swami, Non-Coherent UWB Demodulation with Dirty Templates, in Proc. MILCOM Conference, vol. 2, Oct./Nov. 2004, pp [11] Ralph T. Hoctor and Harold W. Tomlinson, An overview of delayhopped, transmitted-reference RF communications, Report no. 2001CRD198, Technical Information Series, GE Research and Development Centre, Jan N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 74

75 References Related to the Talk [1] N. C. Beaulieu and D. J. Young, Designing time-hopping ultra-wide bandwidth receivers for multi-user interference environments, to appear in the Proceedings of the IEEE, early Invited Paper. [2] J. R. Foerster, Channel modeling sub-committee report (final), IEEE P /490r1-SG3a, Feb [3] N. C. Beaulieu, H. Shao and J. Fiorina, P-order metric UWB receiver structure with superior performance, IEEE Trans. Commun., vol. 56, pp , Oct [4] N. C. Beaulieu and B. Hu, Soft-limiting receiver structures for timehopping UWB in multiple-access interference, IEEE Trans. Veh. Technol., vol. 57, pp , Mar N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 75

76 References Related to the Talk (Cont d) [5] N. C. Beaulieu and B. Hu, A soft-limiting receiver structure for time-hopping UWB in multiple access interference, in Proc. IEEE International Symposium on Spread Spectrum Techniques and Application (ISSSTA 2006), pp [6] N. C. Beaulieu and B. Hu, An adaptive threshold soft-limiting UWB Receiver with improved performance in multiuser interference, in Proc. IEEE International Conference on Ultra-Wideband (ICUWB 2006), pp [7] H. Shao and N. C. Beaulieu, A novel zonal UWB receiver structure with improved performance in multiple access interference, in Proc. IEEE Globecom 2007, pp [8] H. Shao and N. C. Beaulieu, Analysis of a novel p-order metric UWB receiver structure with improved performance in multiple access interference, in Proc. IEEE Globecom 2007, pp N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 76

77 References Related to the Talk (Cont d) [9] N. C. Beaulieu and S. Niranjayan, New UWB receiver designs based on a Gaussian-Laplacian noise-plus-mai model, in Proc. IEEE Int. Conf. Commun. 2007, pp [10] H. Shao and N. C. Beaulieu, A novel zonal UWB receiver with superior performance, IEEE Trans. Commun., to appear. [11] N. C. Beaulieu and I. Hosseini, On the PDF of multiple access interference in time-hopping UWB systems, XXIX General Assembly of the Union of Radio Science International (URSI) 2008, Chicago, U.S.A., Aug. 7-16, Invited Paper. [12] I. Hosseini and N.C. Beaulieu, "Optimal Error Rate Performance of Binary TH-UWB Receivers in Multiuser Interference," to be presented at GLOBECOM 2008, New Orleans, LA, USA, Nov. 30-Dec. 4, N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 77

78 References Related to the Talk (Cont d) [13] S. Niranjayan and N. C. Beaulieu, The optimal BER linear Rake receiver for alpha-stable noise, in Proc. IEEE Int. Conf. Commun. 2008, pp [14] S. Niranjayan and N. C. Beaulieu, A myriad filter detector for UWB multiuser communications, in Proc. IEEE Int. Conf. Commun. 2008, pp [15] H. Shao and N. C. Beaulieu, An analytical method for calculating the bit error rate performance of Rake reception in UWB multipath fading channels, in Proc. IEEE Int. Conf. Commun. 2008, pp [16] B. Hu and N. C. Beaulieu, On characterizing multiple access interference in TH-UWB systems with impulsive noise models, in Proc. IEEE Radio and Wireless Symposium RWS 2008, pp N. C. Beaulieu: UWB Receiver Designs for Multiuser Interference Environments - p. 78

79 Thank You for Your Attention! Questions? Comments? Grøn Tuborg? 79