UWB Channel Impulse Response Acquisition G.C. Ferrante ⋆ † , Y. Elhillali ∗ , M.-G. Di Benedetto ⋆ , F. Boukour • , R. Atika ∗ ⋆ Sapienza, Rome, Italy † ´ Ecole Sup´ erieure d’Electricit´ e, Gif-sur-Yvette, France ∗ Univ. Valenciennes, Valenciennes, France • IFSTTAR, Lille, France October 9, 2013 Ferrante et al. UWB Channel Impulse Response Acquisition October 9, 2013 1 / 14
Introduction Outline 1 Introduction 2 Coherence time 3 MISO UWB systems with TR Ferrante et al. UWB Channel Impulse Response Acquisition October 9, 2013 2 / 14
Introduction Introduction Goal • report on experimental activities on UWB; • show examples of collected data; • future post-processing works aimed at studying: 1 coherence time in UWB; 2 TR MISO-UWB insensitivity to lack of correlation between channels. Equipment • waveform generator (DAC up to 10 GHz); • receiver front-end (ADC up to 20 GHz, quantization 8 bits); • antennas (2 directive, 1 omni, up to 18 GHz); • anechoic chamber, reflectors. Ferrante et al. UWB Channel Impulse Response Acquisition October 9, 2013 3 / 14
Coherence time Outline 1 Introduction 2 Coherence time 3 MISO UWB systems with TR Ferrante et al. UWB Channel Impulse Response Acquisition October 9, 2013 4 / 14
Coherence time Introduction • time interval T c during which the channel remains “unchanged”; • in narrowband communications, fading remains constant during T c ; • in UWB communications, multipath remains correlated during T c ; • important for estimating the blocklength and the training repetition period; • Novelty: no available measurements beyond 1 . 5 GHz. Ferrante et al. UWB Channel Impulse Response Acquisition October 9, 2013 5 / 14
Coherence time Description on how to study coherence time in UWB • 1 tx antenna, 1 rx antenna (distance ≈ 4 meters); • pulse bandwidth: W ∈ (0 , 3] GHz. • pulse repetition time: 400 ns; • 500 realizations of sampled and quantized rx signal averaged and saved; • 200 times with interval of 5 secs. Scheme . Ferrante et al. UWB Channel Impulse Response Acquisition October 9, 2013 6 / 14
Coherence time Example of collected data 0.03 200 s 100 s 0.02 0 s 0.01 0 − 0.01 − 0.02 − 0.03 − 0.04 12 14 16 18 20 22 24 26 28 30 time (ns) Ferrante et al. UWB Channel Impulse Response Acquisition October 9, 2013 7 / 14
MISO UWB systems with TR Outline 1 Introduction 2 Coherence time 3 MISO UWB systems with TR Ferrante et al. UWB Channel Impulse Response Acquisition October 9, 2013 8 / 14
MISO UWB systems with TR Multi-antenna TR Scheme of single-antenna TR . Scheme of multi-antenna TR ( N t = 2 ) . Ferrante et al. UWB Channel Impulse Response Acquisition October 9, 2013 9 / 14
MISO UWB systems with TR Description on how to study MISO UWB systems with TR • recent result: SNR with TR is insensitive to lack of correlation between channels; • why is this important? . • decorrelate LOS channels by increasing the distance between tx antennas: decorrelation was negligible up to ≈ 1 m; • decorrelate channels in an anechoic chamber by introducing reflectors: channels were totally different Ferrante et al. UWB Channel Impulse Response Acquisition October 9, 2013 10 / 14
MISO UWB systems with TR Signals • tx signal: y = Hp b + n = x b + n ; = E� p � 2 = E ; • power constraint: E � � p b � 2 � • channel model: �� � h T ( ℓ ) = √ v ℓ · � 1 κ 1 + κρ h T 1 + κρ h T w ( ℓ ) Θ 1 / 2 0 δ ℓ 0 + ; Example: identical channels Θ = 11 T ; uncorrelated channels: Θ = I . • rx signal after detection: z � w T y = w T x b + w T n = ζ + ν ; Example: • one-finger Rake (tap i ): w = e i ; • All-Rake: w = Jx ( J reflection matrix); � | ζ | 2 � · ( w T Hp ) 2 • performance measure: SNR � E E [ | ν | 2 ] = E , σ 2 � w � 2 N Ferrante et al. UWB Channel Impulse Response Acquisition October 9, 2013 11 / 14
MISO UWB systems with TR Signals Given h : L E 2 � h T ( ℓ ) 1 � � • All-Rake: SNR = N t σ 2 N ℓ =0 L • TR, one-finger: SNR = E � h r � 2 = E � � h ( ℓ ) � 2 . σ 2 σ 2 N N ℓ =0 On average: E G � κρ 1 � 0 1 ) 2 + 1 + κρ · ( h T 1 + κρ · ( 1 T Θ1 ) • All-Rake: E [ SNR ] = . N t σ 2 N Example: • identical channels: E [ SNR ] = E G N t /σ 2 N ; E G � κρ 1 � < E G • uncorrelated channels: E [ SNR ] = 1 + κρ · N t + ; N t σ 2 1 + κρ σ 2 N N • TR, one-finger: E [ SNR ] = E G N t ← − Goal (future): to be verified experim. σ 2 N Ferrante et al. UWB Channel Impulse Response Acquisition October 9, 2013 12 / 14
MISO UWB systems with TR Further investigations with the data set • Diversity order. Sub-linear behavior at very high bandwidth (tens of GHz) by studying the rank of the sample-covariance matrix. • Sparsity. Confirm measurements suggesting non-sparse behavior up to 3 GHz by evaluating power-delay profile. • Non-Gaussianity. Verify the validity of the Ricean uncorrelated scatter model beyond 3 GHz. Ferrante et al. UWB Channel Impulse Response Acquisition October 9, 2013 13 / 14
MISO UWB systems with TR Thank you for your attention! Ferrante et al. UWB Channel Impulse Response Acquisition October 9, 2013 14 / 14
Recommend
More recommend
