Page 407 - Integrated Wireless Propagation Models

T h e l e e C o m p r e h e n s i v e M o d e l - I n t e g r a t i o n o f t h e T h r e e l e e M o d e l s 385

is convenient for performance predictions of narrowband and wide band satellite com­
munication systems.
2. Multistate Models There are two-state (good state and bad state) models, three-state
(clear state, shadowing states, and blocked state) models, five-state model.
Five-State Model: This channel model is based on the Markov modeling approach
in which two-state and three-state models are extended to five-state models under dif­
ferent time share of shadowing.4 0
We may illustrate the three-state model as follows:
1
Three-State Model: This statistical channel model,4 based on three states, namely,
clear or LOS state, the shadowing state, and the blocked state, provides the analysis
of improvement in nongeostationary LMS communication systems. The clear state
is characterized by Rice distribution (Sec. . 8.4). The shadowing state is described
1
by Loo's pdf in Eq. (6.7.1.4), and the blocked state is illustrated by Rayleigh fading.
The pdf of the received signal envelope is a weighted linear combination of these
distributions:

1
P (r) = M PRice (r) + L PLoo (r) + N PRay leigh (r) (6.7. . 5)

where M, L, and N are the time share of shadowing of the Rice, Loo, and Rayleigh dis­
tributions, respectively. The three states are as follows:

State A: LOS path plus scattered and reflected paths
State B: Shadow path plus scattered and reflected paths
State C: Block path plus scattered and reflected paths

The time-share of three states can be operated by the Markov process. The distribu­
tion parameters for the model were found by means of the data obtained from measure­
ments using the "INMARSAT" satellite and other available data sets. The model was
validated by comparing the theoretical cumulative distributions with those obtained
from measurement data.
Another model also can be formed by a five-state model. This channel model is
based on Markov modeling approach in which two-state and three-state models are
extended to five-state models under different time share of shadowing.4 0
The model is basically a composition of the Gilbert-Elliot channel model and the
three-state Markov channel model, in which shadowing effects are split into five
states:

State 1: good state--clear LOS without shadowing, and LOS state with low shadowing
State 2: good state-clear LOS with low shadowing
State 3: not good not bad state--characterizes moderate shadowing
State 4: bad state-describes heavy shadowed area
State 5: bad state-describes completely shadowed or blocked areas

The transitions of the states can take place from low and high shadowing conditions
to moderate shadowing conditions but cannot occur directly between low and high
shadowing environments.