1. November 2002
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: Time variance for UWB wireless channels
Date Submitted: 11 November, 2002
Source: Andreas F. Molisch, Mitsubishi Electric Research Laboratories
Address MERL Murray Hill 558 Central Avenue Murray Hill, NJ 07974, USA
Voice: , FAX: ,
Re: [Response to Call for Contributions on Ultra-wideband Channel Models, Doc. IEEE P /208r1-SG3a]
Abstract: We consider a simple model for the time variance of the UWB channel. We start out by reviewing some properties of UWB systems that put restrictions to what has to be modeled. Subsequently, we present a simple model for the angular spectrum, namely a rectangular function whose width increases with delay. Next, we introduce time variations due to shadowing by persons walking through the LOS path. Finally, we discuss how the model can be adapted to fit the "samples impulse responses approach" currently under consideration by the IEEE a group..
Purpose: [Proposing a model for the time variance of UWB indoor channels for the use in the standardization process of the UWB channel model]
Notice: This document has been prepared to assist the IEEE P It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.
Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P
Molisch, Time variance of UWB channels

2. Time variance of UWB channels
November 2002
Time variance of UWB channels
Andreas F. Molisch
Molisch, Time variance of UWB channels

3. Contents Introduction Movement of TX/RX Movement of scatterers
November 2002
Contents
Introduction
Movement of TX/RX
Movement of scatterers
Implementation issues
Impact on system evaluation
Summary and conclusions
Molisch, Time variance of UWB channels

4. Introduction Current status of model:
November 2002
Introduction
Current status of model:
SV model – uses several clusters
Distinction between small-scale and large-scale statistics
4 different environments (LOS, NLOS)
Temporal variations of channel not yet defined
Molisch, Time variance of UWB channels

5. Basic modeling approach
November 2002
Basic modeling approach
Two causes of temporal variation:
TX/RX movement
Scatterer movement (shadowing)
Different modeling approaches:
TX/RX: WSSUS model
Scatterer movement: geometrical approach
Molisch, Time variance of UWB channels

6. TX-RX movement WSSUS model (Bello 1963)
November 2002
TX-RX movement
WSSUS model (Bello 1963)
Angular spectrum Doppler spectrum
Doppler spectrum temporal autocorrelation
Fourier transformation
Molisch, Time variance of UWB channels

7. November 2002
Angular spectrum
Simple model for angular spectrum: rectangular (instead of Laplacian)
Angular spread increases with delay
Total angular spread: 38 degree [Cramer et al. 2002]
Molisch, Time variance of UWB channels

8. Moving scatterers Model scenario: person moving through LOS
November 2002
Moving scatterers
Model scenario: person moving through LOS
On straight line 80cm from receiver
Person modeled as cylinder with 40cm radius
No transmission through or diffraction around scatterer considered
Shadowing certain angular region
Means different attenuation for different delays
Molisch, Time variance of UWB channels

9. Implementation recipe (I)
November 2002
Implementation recipe (I)
TX/RX movement:
Compute ACF for each delay from angular spectrum
Generate iid random variables
Filter (FFT implementation most efficient)
“standard” implementations for Rayleigh fading do not work
Molisch, Time variance of UWB channels

10. Implementation recipe (II)
November 2002
Implementation recipe (II)
Scatterer movement
Geometrical approach
At discrete position of scatterers:
Compute blocked angular range
For each delay compute what percentage of power is blocked
Gives modified power delay profile
Linear interpolation between discrete scatterer positions
Molisch, Time variance of UWB channels

11. Impact on system evaluation
November 2002
Impact on system evaluation
Current suggestion: independent channel realization for each data block
Other extreme case: no temporal variations
Best case: no problems with acquisition
Worst case: no possible temporal diversity
Why smooth transitions required?
Channel tracking and synchronization
How long are outages (needs application model)
Smart antennas
Molisch, Time variance of UWB channels

12. Summary Simple model for temporal variations Two cases:
November 2002
Summary
Simple model for temporal variations
Two cases:
RX/TX movement, use WSSUS model
Person walking through LOS; use geometrical approach
Suggestion for system evaluation:
All proposals: with independent data blocks and complete coherence
For system with trackers (if desired by proponent): continuous model
Molisch, Time variance of UWB channels