Modelo de canal de banda ancha discreto para HAPS

1. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 1
“A Statistical switched broadband channel
model for a HAPS links”
José Luis Cuevas-Ruíz José A. Delgado-Penín
Presented by J.A. Delgado-Penín
Department of Signal Theory and Communications
Universitat Politècnica de Catalunya
Barcelona, Spain

2. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 2
Objective
To propose a new statistical switched
broadband channel model in L band for HAPS links
using three kinds of propagation modes (three
states).

3. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 3
Outline
• Overview.
• What the HAPS systems are?
• HAPS vs Terrestrial Systems
• Features
• Switched channel model.
• Three states Markov chain.
• Three states semi-Markov chain.
• Data from ITU-R (681-6).

4. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 4
Outline
• Broadband channels models.
• Bello´s model.
• Switched broadband channel.
• Two states.
• Three states
• Simulation results.
• Conclusions.

5. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 5
Overview.
What the HAPS systems are?

6. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 6
HAPS Advantages :
Serve a large number of people from a
distance –Less obstructions.
Provide Line of Sight Communications –
Higher Frequencies – Higher Data Rates
Portable – Can be re-positioned at any time.
Affordable – Cheaper than the terrestrial and
Satellite infrastructure.
HAPS Disadvantages :
Station Keeping – Need to make sure
that users can maintain tracking.
Clouds and Rain can significantly
attenuate the signal.
Overview.
HAPS vs Terrestrial Systems

7. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 7
Coverage areas
Semi-urban Urban Rural
HAP
h=21-25 km
Area
Angle of
Elevación
Coverage (radio. km)
h=21 km h=25 km
Urban 90-30 0-36 0-43
Semi-urban 30-15 36-76.5 43-90.5
Rural 15-5 76.5-203 90.5-
Features.
Coverage.

8. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 8
h
SPP
θ
receiver
d
shadowing
Multipath
Features.
Propagation effects.
LOS

9. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 9
• Height of the ship ( 21-25 km).
• Angle of reception (θ) .
• Distance of SPP (d). }
•The shadowing level is a function of the angle of
reception and the distance of the receiver to the SPP.
• Inside the urban area a LOS condition can be supposed
(a Rice constant, K, with a high value).
• If the angle of reception diminishes then the multipath
effect increase (diminishes K value) [1].
COVERAGE
AREA{Geometrical
characteristics
Features.

10. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 10
Switched Channel Model.
Markov Chain
As the environmental properties change, the received
signal cannot be represented by a model with constant
parameters. This dynamic behavior was implemented in
the model using a Markov chain.
A state B state
C state
P BA
P CB
P BC
P AC
P CA
P AB
A state B state
C state
P BA
P CB
P BC
P AC
P CA
A state B state
C stateC state
P BA
P CB
P BC
P AC
P CA
P AB
P BCP BCP BC
PCC
PBB
PAA

11. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 11
The transitions between states are determined by a
matrix P, where each element Pij represent the
probability that the channel changes from the i to the j
state. For the channel model with three states A, B and
C, is defined the transitions matrix P
Switched Channel Model.
Markov Chain

12. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 12
A stationary state vector π is calculated, using the
properties of the Markov processes expressed by
where I is the identity matrix, P is the transition
matrix and e= [1 1 ….]T [7]. Each element πi represent
the percentage of the total time that the processes
remains in the i state.
π (I-P) = 0
π e = 1
π = ( πA πB πC )
Switched Channel Model.
Markov Chain

13. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 13
A semi-Markov process is a Markov chain where the time
between changes of states are random and defined for
some kind of distribution. From the Markov process, a
new semi-Markovian process is defined. This process will
be described by a new transition matrix r, which is
calculated using
Switched Channel Model.
Semi-Markov Chain

14. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 14
Semi-Markovian Processes
Some distributions are described for fade
duration in the ITU-R Recommendation P.681-6
[8]. In this Recommendation are defined three types
of channel:
A state. LOS condition.
B state. Slight shadowing.
C state. Total obstruction.
A s t a t e B s t a t e
C s t a t e
P B A
P C B
P B C
P A C
P C A
P A B
A s t a t e B s t a t e
C s t a t e
P B A
P C B
P B C
P A C
P C A
A s t a t e B s t a t e
C s t a t eC s t a t e
P B A
P C B
P B C
P A C
P C A
P A B
Switched Channel Model.
Markov Chain

15. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 15
For the A state, the duration follows an exponential
distribution given by
)
where the parameters β and γ are in function of the level of
the shadowing and for d > β1/γ . The duration for the others
states follows a lognormal distribution valid for d > 0.1 m,
and is expressed as
where σ is the standard deviation of ln(d), the mean value of
ln(d) is ln(α) and the error function is defined in the ITU-R.
Switched Channel Model.
Markov Chain

16. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 16
Enviroments
Parameters Suburban I Suburban II Forest
A state β 0.88 0.83 0.60
γ 0.61 0.66 0.84
B state α 1.73 1.89 2.05
σ 1.11 0.93 1.05
C state α 2.62 3.28 1.55
σ 0.98 1.04 1.02
P PAB 1 1 1
PAC 0 0 0
PBA 0.65 0.65 0.42
PBC 0.35 0.35 0.58
PCA 0 0 0
PCB 1 1 1
Switched Channel Model.
Data from ITU-R (681-6)

17. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 17
Broadband channel model.
Bello`s Model
τi
τi τi
A
Σ
x(t )
y(t )
a(t) a(t ) a(t ) a(t )
τ1
τ2 τn
A0
Σ
x(t )
y(t )
a(t) a(t ) a(t ) a(t )
A1 A2 An

18. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 18
Switched Broadband channel model.
Two states
Semi -Markov
process
Rayleigh Ray-Ln
Rayleigh Ray-Ln
A1
An
y(t)
x(t)
bad state
good state
Lognormal
bad state
good state
τ1
τn
Σ
An-1
tn-1
Semi -Markov
process
Semi -Markov
process
Semi -Markov
process
Rayleigh Ray-LN-
Rayleigh Ray-LN
A1
An
y(t)
x(t)
bad state
good state
LN
bad state
good state
τ1
τn
Σ
An-1
tn-1
Semi -Markov
process
Semi -Markov
process

19. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 19
x(t)
bad state
good state
LN
Semi-Markov
process
Tx
Rx
y(t)
good state
Σ
An-1
Rayleigh Ray-LN
Semi-Markov
process
τ1
bad state
good state
An-1
Rayleigh Ray-LN
Semi-Markov
process
τν
bad state
Switched Broadband channel model. Three states.

20. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 20
x(t)
LN
Semi-Markov
process
Tx
Rx
y(t)
Σ
An-1
Rayleigh Ray-LN
Semi-Markov
process
τ1
An-1
Semi-Markov
process
τν
Rayleigh Ray-LN LN
(A) STATE
(A) STATE
(A) STATE
(B) STATE
(B) STATE
(B) STATE
(C) STATE
(C) STATE
(C) STATE
(C) STATE
LN

21. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 21
Simulation Results.

22. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 22
0 2 4 6 8 10 12 14 16
10
-5
10
-4
10
-3
10
-2
10
-1
Broadband switched channel model. L Band. QPSK modulation.
EbN0(dB)
BER
A state
B state
C state
Switched channel
Switched channel + RS-CONV code
Simulation Results.

23. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 23
Conclusions.
• A switched broadband channel model for L (2GHz)
band was proposed for HAPS systems following ITU-R with
two and three states.
•The analysis by simulation indicates that when the number
of channel states increases the performance of the system is
worse. This situation represents a more realistic scenario
versus Bello´s model.

24. J. L. Cuevas-Ruíz J.A. Delgado-Penín WCNC2004 Atlanta USA 24
Thanks for your attention.
Questions!!