Browse Prior Art Database

Method for Determining Fade Margin

IP.com Disclosure Number: IPCOM000110832D
Original Publication Date: 1994-Jan-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 80K

Publishing Venue

IBM

Related People

Camp Jr, WO: AUTHOR [+2]

Abstract

Disclosed is a method for measuring and reacting to the variable path loss in a wireless communications channel.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Method for Determining Fade Margin

      Disclosed is a method for measuring and reacting to the
variable path loss in a wireless communications channel.

      A communication channel has loss between transmitter source and
receiver.  This path loss is due to physical distance, antenna
orientations, multipath interference, obstacles, etc.  For a given
transmitter output power, channel bandwidth, antenna gains, and
output signal-to-noise ratio, a path loss greater than a certain
value, X, renders the communications channel unusable.  The
difference between X and the actual path loss is called "fade
margin".

      A well-instrumented communication channel often has elaborate
measurement devices to monitor the received signal level and, thus,
monitor the fade margin for the channel.  However, a communication
channel with the minimum amount of hardware will not have such
equipment.  Moreover, the portable communications hardware will be
used in such a way, moving it about, people walking nearby, random
installation position, etc., that the fade margin will vary greatly,
even going below zero.  It is in just such situations that one would
want to monitor fade margin in order to constructively modify the
situation for better and more reliable communication.  For instance,
one could change the position of the antenna, move closer to the base
station, or look for another station to communicate with.  The
problem, therefore, is to quantitatively determine the fade margin
with a minimum of additional equipment.

This disclosed invention consists of:

1.  a means for varying the path loss of the communications channel
    (either in the transmitter or receiver),

2.  a means for quantifying channel error rate while varying the path
    loss from zero to some maximum value,

3.  a preprogrammed set of adaptive reactions occur based on this
    measured fade margin.

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