# A really simple question on channel gain and path loss

Started by February 11, 2007
```Hello all,

I am a newbie to Matlab and DSP.

I am trying to write a Matlab code that simulates the effect of IEEE
802.11a interference on UWB communication.

The question is wrt the Matlab implementation of the received signal.

I want to implement the code as follows:

r(t) = UWB_ChannelGain * s(t) + AWGN + 80211a_ChannelGain*I(t)

where,

s(t) = transmitted UWB signal
I(t) = transmitted 802.11a signal

My question -

Assuming the distance between the UWB transceivers as well as between
the UWB receiver and 802.11a sources are known -

How do I calculate the channel gains - UWB_ChannelGain and
80211a_Channel gains

Applogies if the question is too somplistic...or for that matter too
general.

All leads will be gratefully accepted.

cheers and regards,

```
```hi good question you posted.
long back i happened to see a girl working
on this topic specifically regarding interference. Minakshmi roy from
IISc and she is still working on that topic.

Try to contact that researcher for further help.

http://www.cedt.iisc.ernet.in/index.php?title=Spectrum%20Sharing%20in%20ISM%20Band&page=cngroup&pid=24&Cid=6

Research Topic 	  :   	Spectrum Sharing in ISM Band

Abstract :-

Proliferation of wireless devices in ISM band results in mutual
interference. Bluetooth, 802.11b/g, microwave oven etc are operating
in same 2.4GHz band. So there is growing concern for coexistence. From
my experimental and simulation work it is seen performance of 802.11g
(WLAN) and Bluetooth detoriates in presence of each other. Regarding
my work till now, I have simulated transceiver model for 802.11g and
Bluetooth and obtained BER, Data Throughput for both devices
individually and in presence of other device in AWGN channel. I have
also done experiments to measure throughput of 802.11g and Bluetooth.
Comparing the results of the two scenarios (coexistence and
individual) it is seen that performance of both systems in coexistence
scenario decreases. Presently I am doing the same work in frequency
selective rayleigh fading channel. My goal is to get some generalized
solution for coexistence.
Student Name 	  :   	Minakshmi Roy
Guide Names 	  :   	H S Jamadagni and Pavan S Nuggehalli

Regarding your question, first thing is UWB operates at -40dbm power
(according to paper in IEEE commn magazine) and find out at what power
level does the 802.11a operates? (This turns out to be very important
second thing CHANNEL MODELS of both are available in IEEE database
(with matlab programs in pdf format).
third thing take care of all related aspects of
power,samplingfrequency,distance(very important since UWB distance is
just below 10 meters).

And final aspect is simulation.
and UWB signal pass it through channel.
see the impact..
well, i thought in this way and replied..also clarify with this group
experts who are there

regards
particlereddy

> Hello all,
>
>  I am a newbie to Matlab and DSP.
>
> I am trying to write a Matlab code that simulates the effect of IEEE
> 802.11a interference on UWB communication.
>
> The question is wrt the Matlab implementation of the received signal.
>
> I want to implement the code as follows:
>
> r(t) = UWB_ChannelGain * s(t) + AWGN + 80211a_ChannelGain*I(t)
>
> where,
>
> s(t) = transmitted UWB signal
> I(t) = transmitted 802.11a signal
>
> My question -
>
> Assuming the distance between the UWB transceivers as well as between
> the UWB receiver and 802.11a sources are known -
>
> How do I calculate the channel gains - UWB_ChannelGain and
> 80211a_Channel gains
>
> Applogies if the question is too somplistic...or for that matter too
> general.
>
> All leads will be gratefully accepted.
>
> cheers and regards,

```
```On 11 Feb 2007 06:10:17 -0800, "lmadank@gmail.com" <lmadank@gmail.com>
wrote:

>Hello all,
>
> I am a newbie to Matlab and DSP.
>
>I am trying to write a Matlab code that simulates the effect of IEEE
>802.11a interference on UWB communication.
>
>The question is wrt the Matlab implementation of the received signal.
>
>I want to implement the code as follows:
>
>r(t) = UWB_ChannelGain * s(t) + AWGN + 80211a_ChannelGain*I(t)
>
>where,
>
>s(t) = transmitted UWB signal
>I(t) = transmitted 802.11a signal
>
>My question -
>
>Assuming the distance between the UWB transceivers as well as between
>the UWB receiver and 802.11a sources are known -
>
>How do I calculate the channel gains - UWB_ChannelGain and
>80211a_Channel gains
>
>Applogies if the question is too somplistic...or for that matter too
>general.
>
>All leads will be gratefully accepted.
>
>cheers and regards,

You might want to look into the channel models for each and apply
those as s(t) and I(t) before combining them.   The delay spread and
pathloss models for each are somewhat different because the expected
ranges are different and the bandwidths differ substantially.   With
the pathloss models you could apply the appropriate input power to
each and get the expected output power at the simulated range for
each, then apply the channel delay-spread model to each as well.

Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org
```
```one interesting paper for you

http://ietcom.oxfordjournals.org/cgi/content/abstract/E90-B/2/251?etoc

On the Coexistence of DS-UWB Systems with Wi-Max/IEEE-802.16 Based
Systems
Khodayar SARFARAZ1, Seyed Ali GHORASHI2, Mohammad GHAVAMI1 and Hamid
AGHVAMI2

1 The authors are with the Ultra Wideband Communications Group,
Division of Engineering, King's College, University of London, London,
UK. E-mail:

In this paper the coexistence issue between the DS-UWB systems and Wi-
Max/IEEE-802.16 based Fixed Broadband Wireless Access (FBWA) systems
has been investigated. The aim is to evaluate the impact that the
interference resulting from a realistic UWB hot spot scenario may have
on the performance of a FBWA receiver. A mathematical model is
developed through which the interference power produced by the UWB hot
spot can be calculated. The benchmarks against which the UWB
interference is assessed are also developed using the specifications
of Wi-Max/IEEE-802.16 systems. Several simulations have been done to
both validate the analytical results and calculate the UWB
interference. In doing so, the effects of parameters like victim
receiver bandwidth, carrier frequency, activity factor, the number of
users and the distance from victim receiver in a realistic hot spot
scenario have been studied.

Key Words: coexistence, DS-UWB, Wi-MAX, IEEE 802.16

Manuscript received September 26, 2005. Manuscript revised May 11,
2006.

```
```Dear particlereddy and Eric,

Many many thanks for your responses. I am much more clearer now wrt
the implementation of the scheme.

For starters, instead of applying the UWB and 802.11a models, I intend
to simplify things by considering a very basic FREE Space model.
Indeed this is way too simplistic...but still....

Given this assumption, for known values of UWB transceiver distances
as well as the distance between UWB receiver and 802.11a transmitter,
the path loss due to UWB and 802.11a can be easily found out using
FRII's equation.

However, I have a new question in mind -

How to obtain the variables 'UWB_ChannelGain'  and
'80211a_ChannelGain'  to be used in the following equation  -

r(t) = UWB_ChannelGain * s(t) + AWGN + 80211a_ChannelGain*I(t)

from the path-loss of UWB and 802.11a ??

Is Path-Loss = 1/Channel gain ??
Or
is Path-loss = 1/sqrt(Channel gain) ??
(Afterall Pathloss is a ratio of power facors while channel gain is a
relation in amplitude)
Or
is there some other relationship ??

Many thanks..

ParticleReddy - Many thanks for the reference to a similar work
conducted by an IISc student :)

On Feb 11, 7:37 pm, Eric Jacobsen <eric.jacob...@ieee.org> wrote:
> wrote:

>
> >Hello all,
>
> > I am a newbie to Matlab and DSP.
>
> >I am trying to write a Matlab code that simulates the effect of IEEE
> >802.11a interference on UWB communication.
>
> >The question is wrt the Matlab implementation of the received signal.
>
> >I want to implement the code as follows:
>
> >r(t) = UWB_ChannelGain * s(t) + AWGN + 80211a_ChannelGain*I(t)
>
> >where,
>
> >s(t) = transmitted UWB signal
> >I(t) = transmitted 802.11a signal
>
> >My question -
>
> >Assuming the distance between the UWB transceivers as well as between
> >the UWB receiver and 802.11a sources are known -
>
> >How do I calculate the channel gains - UWB_ChannelGain and
> >80211a_Channel gains
>
> >Applogies if the question is too somplistic...or for that matter too
> >general.
>
> >All leads will be gratefully accepted.
>
> >cheers and regards,
>
> You might want to look into the channel models for each and apply
> those as s(t) and I(t) before combining them.   The delay spread and
> pathloss models for each are somewhat different because the expected
> ranges are different and the bandwidths differ substantially.   With
> the pathloss models you could apply the appropriate input power to
> each and get the expected output power at the simulated range for
> each, then apply the channel delay-spread model to each as well.
>
> Eric Jacobsen
> Minister of Algorithms
> Abineau Communicationshttp://www.ericjacobsen.org- Hide quoted text -
>
> - Show quoted text -

```
```ParticleReddy,

cheers

On Feb 13, 9:31 am, "PARTICLEREDDY (STRAYDOG)"
<particlere...@gmail.com> wrote:
> one interesting paper for you
>
> http://ietcom.oxfordjournals.org/cgi/content/abstract/E90-B/2/251?etoc
>
> On the Coexistence of DS-UWB Systems with Wi-Max/IEEE-802.16 Based
> Systems
> Khodayar SARFARAZ1, Seyed Ali GHORASHI2, Mohammad GHAVAMI1 and Hamid
> AGHVAMI2
>
> 1 The authors are with the Ultra Wideband Communications Group,
> Division of Engineering, King's College, University of London, London,
> UK. E-mail:
>
> In this paper the coexistence issue between the DS-UWB systems and Wi-
> Max/IEEE-802.16 based Fixed Broadband Wireless Access (FBWA) systems
> has been investigated. The aim is to evaluate the impact that the
> interference resulting from a realistic UWB hot spot scenario may have
> on the performance of a FBWA receiver. A mathematical model is
> developed through which the interference power produced by the UWB hot
> spot can be calculated. The benchmarks against which the UWB
> interference is assessed are also developed using the specifications
> of Wi-Max/IEEE-802.16 systems. Several simulations have been done to
> both validate the analytical results and calculate the UWB
> interference. In doing so, the effects of parameters like victim
> receiver bandwidth, carrier frequency, activity factor, the number of
> users and the distance from victim receiver in a realistic hot spot
> scenario have been studied.
>
> Key Words: coexistence, DS-UWB, Wi-MAX, IEEE 802.16
>
> Manuscript received September 26, 2005. Manuscript revised May 11,
> 2006.

```
```On 13 Feb 2007 00:52:00 -0800, "lmadank@gmail.com" <lmadank@gmail.com>
wrote:

>Dear particlereddy and Eric,
>
> Many many thanks for your responses. I am much more clearer now wrt
>the implementation of the scheme.
>
>For starters, instead of applying the UWB and 802.11a models, I intend
>to simplify things by considering a very basic FREE Space model.
>Indeed this is way too simplistic...but still....
>
>Given this assumption, for known values of UWB transceiver distances
>as well as the distance between UWB receiver and 802.11a transmitter,
>the path loss due to UWB and 802.11a can be easily found out using
>FRII's equation.

Many propagation models use pathloss exponents with magnitudes other
than 2.   For heavily-faded enviroments (i.e., outdoor NLOS, urban
canyon) it can be very large, 3-4 and higher, and for indoor
applications (like you're proposing) it can be _less_ than two due to
multipath gain.   Indoor exponents around 1 or so are not unusual.

Simplifying your model is fair, probably a good idea depending on what
you're doing.   Just be aware that practical application performance
can be different from what you'll see with a free space model.

>However, I have a new question in mind -
>
> How to obtain the variables 'UWB_ChannelGain'  and
>'80211a_ChannelGain'  to be used in the following equation  -
>
>r(t) = UWB_ChannelGain * s(t) + AWGN + 80211a_ChannelGain*I(t)
>
>from the path-loss of UWB and 802.11a ??
>
>Is Path-Loss = 1/Channel gain ??
>Or
>is Path-loss = 1/sqrt(Channel gain) ??
>(Afterall Pathloss is a ratio of power facors while channel gain is a
>relation in amplitude)
>Or
>is there some other relationship ??

Hard to say if the source of this equation:

r(t) = UWB_ChannelGain * s(t) + AWGN + 80211a_ChannelGain*I(t)

isn't known.   I think whoever came up with that would be right person