Skip to content Skip to navigation Skip to collection information

OpenStax-CNX

You are here: Home » Content » Principles of Digital Communications » Large-Scale Fading

Navigation

Table of Contents

Recently Viewed

This feature requires Javascript to be enabled.
 

Large-Scale Fading

Module by: Ha Ta-Hong, Tuan Do-Hong. E-mail the authorsEdited By: Ha Ta-Hong, Tuan Do-HongTranslated By: Ha Ta-Hong, Tuan Do-Hong

In general, propagation models for both indoor and outdoor radio channels indicate that mean path loss as follow

Lp¯(d)~d/d0nLp¯(d)~d/d0n size 12{ {overline {L rSub { size 8{p} } }} \( d \) "~" left (d/d rSub { size 8{0} } right ) rSup { size 8{n} } } {}(1)

Lp¯(d)dB=Ls(d0)dB+10n.log(d/d0)Lp¯(d)dB=Ls(d0)dB+10n.log(d/d0) size 12{ {overline {L rSub { size 8{p} } }} \( d \) ital "dB"=L rSub { size 8{s} } \( d rSub { size 8{0} } \) ital "dB"+"10"n "." "log" \( d/d rSub { size 8{0} } \) } {} (2)

Where dd size 12{d} {} is the distance between transmitter and receiver, and the reference distance d0d0 size 12{d rSub { size 8{0} } } {} corresponds to a point located in the far field of the transmit antenna. Typically, d0d0 size 12{d rSub { size 8{0} } } {} is taken 1 km for large cells, 100 m for micro cells, and 1 m for indoor channels. Moreover d0d0 size 12{d rSub { size 8{0} } } {} is evaluated using equation

Ls(d0)=4πd0λ2Ls(d0)=4πd0λ2 size 12{L rSub { size 8{s} } \( d rSub { size 8{0} } \) = left ( { {4πd rSub { size 8{0} } } over {λ} } right ) rSup { size 8{2} } } {}(3)

or by conducting measurement. The value of the path-loss exponent n depends on the frequency, antenna height and propagation environment. In free space, n is equal to 2. In the presence of a very strong guided wave phenomenon (like urban streets), nn size 12{n} {} can be lower than 2. When obstructions are present, nn size 12{n} {} is larger.

Measurements have shown that the path loss LpLp size 12{L rSub { size 8{p} } } {} is a random variable having a log-normal distribution about the mean distant-dependent value Lp¯(d)Lp¯(d) size 12{ {overline {L rSub { size 8{p} } }} \( d \) } {}

Lp(d)(dB)=Ls(d0)(dB)+10nlog10(d/d0)+Xσ(dB)Lp(d)(dB)=Ls(d0)(dB)+10nlog10(d/d0)+Xσ(dB) size 12{L rSub { size 8{p} } \( d \) \( ital "dB" \) =L rSub { size 8{s} } \( d rSub { size 8{0} } \) \( ital "dB" \) +"10"n"log" rSub { size 8{"10"} } \( d/d rSub { size 8{0} } \) +X rSub { size 8{σ} } \( ital "dB" \) } {}(4)

Where XσXσ size 12{X rSub { size 8{σ} } } {} denote a zero-mean, Gaussian random variable (in dB) with standard deviation  (in dB). XσXσ size 12{X rSub { size 8{σ} } } {} is site and distance dependent.

As can be seen from the equation, the parameters needed to statistically describe path loss due to large-scale fading, for an arbitrary location with a specific transmitter-receiver separation are (1) the reference distance, (2) the path-loss exponent, and (3) the standard deviation XσXσ size 12{X rSub { size 8{σ} } } {}.

Collection Navigation

Content actions

Download:

Collection as:

PDF | EPUB (?)

What is an EPUB file?

EPUB is an electronic book format that can be read on a variety of mobile devices.

Downloading to a reading device

For detailed instructions on how to download this content's EPUB to your specific device, click the "(?)" link.

| More downloads ...

Module as:

PDF | EPUB (?)

What is an EPUB file?

EPUB is an electronic book format that can be read on a variety of mobile devices.

Downloading to a reading device

For detailed instructions on how to download this content's EPUB to your specific device, click the "(?)" link.

| More downloads ...

Add:

Collection to:

My Favorites (?)

'My Favorites' is a special kind of lens which you can use to bookmark modules and collections. 'My Favorites' can only be seen by you, and collections saved in 'My Favorites' can remember the last module you were on. You need an account to use 'My Favorites'.

| A lens I own (?)

Definition of a lens

Lenses

A lens is a custom view of the content in the repository. You can think of it as a fancy kind of list that will let you see content through the eyes of organizations and people you trust.

What is in a lens?

Lens makers point to materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

Who can create a lens?

Any individual member, a community, or a respected organization.

What are tags? tag icon

Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.

| External bookmarks

Module to:

My Favorites (?)

'My Favorites' is a special kind of lens which you can use to bookmark modules and collections. 'My Favorites' can only be seen by you, and collections saved in 'My Favorites' can remember the last module you were on. You need an account to use 'My Favorites'.

| A lens I own (?)

Definition of a lens

Lenses

A lens is a custom view of the content in the repository. You can think of it as a fancy kind of list that will let you see content through the eyes of organizations and people you trust.

What is in a lens?

Lens makers point to materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

Who can create a lens?

Any individual member, a community, or a respected organization.

What are tags? tag icon

Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.

| External bookmarks