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Queries regarding Interference and Collision

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haisrilatha

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interference help

hi everyone,
In wireless scenario, say a source starts transmitting data (+1, -1, 0) to receiver and there exists many other nodes which are transmitting ( say +1, -1, 0) and are in the range of receiver.

My query is suppose if the source transmits +1,
1.does the other nodes become interferers if they all transmit +1 as well.

2.with the same scenario as above does ber (bit error rate) increase, if i reduce number of simultaneous transmissions. (with all of them transmitting +1 as well).

3.do collision at the receiver play any role or is it same as interference?

4.how does collision and interference differ?

Expecting your help in this...
Sri
 

Communications_Engineer

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haisrilatha said:
hi everyone,
In wireless scenario, say a source starts transmitting data (+1, -1, 0) to receiver and there exists many other nodes which are transmitting ( say +1, -1, 0) and are in the range of receiver.

My query is suppose if the source transmits +1,
1.does the other nodes become interferers if they all transmit +1 as well.


If all transmit at the same frequency or time or code... then yes [/quote]

haisrilatha said:
2.with the same scenario as above does ber (bit error rate) increase, if i reduce number of simultaneous transmissions. (with all of them transmitting +1 as well).
That is an incorrect way to look at it. You can never be sure if all transmit +1, so do not use it. They might well be transmitting -1. You need to design your system for worst case scenario

haisrilatha said:
3.do collision at the receiver play any role or is it same as interference?
collision of packets is like time-domain interference if I'm not mistaken

haisrilatha said:
4.how does collision and interference differ?
yeah.


haisrilatha said:
Expecting your help in this...
Sri
I've tried to understand the questions and answered.
 

haisrilatha

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So for the second question can i proceed by taking worst case i.e considering every node transmits -1. Then BER will decrease if i reduce the number of interferers. Is this analysis correct?
 

Communications_Engineer

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Yes, but then you'd be unfair too. Not all nodes would practically 'always' transmit -1

Look, I think you are not doing this properly. Why don't you explain what you are trying to.
 

haisrilatha

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I have seen a formula for ber as
BER=Σp{signal energy+(number of interfering nodes*its energy)+gaussian noise<0/interference vector} * p{interference vector}

where p{x/y} is probability of x given y

given that signal energy is the one when source transmits +1.

where p{signal energy+(number of interfering nodes*its energy)+gaussian noise<0/interference vector}=Q{(signal energy+(number of interfering nodes*its energy))/σstandard deviation}

where Q is Q function and σ is standard deviation

My doubt is-
if i use some good specific MAC (medium access control) protocol, then the number of interfering nodes will reduce, which normally should reduce BER.

But if i take worst case then only BER is getting reduced in the Q function, otherwise not.

So am i proceeding in right way? that is when i reduce number of interferers, BER shud reduce and it shud always work?
 

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