Today I got the query about Ec/I0 and Eb/N0, What is the Difference between these terms? Here are a possible short explanations for them.
What is Ec/I0?
A special term is used to describe the SNR of the pilot channel: energy per chip per interference density, or Ec/I0. The energy per chip Ec is different from energy per bit Eb in that “chips” refer to PN sequences that are spread. Since there is no base-band information contained in the pilot channel, the pilot is not de-spread and bits are not recovered. Therefore, in order to describe the signal strength of the pilot channel, the raw SNR, or Ec/I0, is used. Note that since the pilot is not de-spread, Ec/I0 remains less than 1 most of the time.
The Ec/I0 is the energy per chip per interference density measured on the pilot channel; it is effectively the signal strength of the pilot channel.
Why it is needed?
This mobile-assisted handoff (MAHO) is evident in that the mobile makes a measurement of forward link Ec/I0 and reports the measurement result to the base station. Since each base station transmits its own pilot on a different PN offset, the Ec/I0 of a pilot gives a good indication of whether or not the particular sector should be the serving sector for the mobile. With accordance of Ec/I0 of different pilots, they switched between different sets like Candidate or neighbor set.
The candidate set contains those pilots whose Ec/I0s are sufficient to make them handoff candidates. This means that if the Ec/I0 of a particular pilot is greater than the pilot detection threshold T_ADD, then that pilot will be added to the candidate set. A pilot is removed from this set and placed in the neighbor set if the strength of that pilot drops below the pilot drop threshold T_DROP for more than the duration specified by the handoff drop timer expiration value T_TDROP. The candidate set can contain at least six pilots.
What is Eb/N0?
In digital communication, we are primarily interested in a link metric called Eb/N0, or energy per bit per noise power density. The link requires a particular Eb/N0 to attain an acceptable BER and ultimately an acceptable frame error rate (FER). Capacity is inversely proportional to the required Eb/N0 of the link. The lower the required threshold Eb/N0, the higher the system capacity.
Why it is needed?
What is Ec/I0?
A special term is used to describe the SNR of the pilot channel: energy per chip per interference density, or Ec/I0. The energy per chip Ec is different from energy per bit Eb in that “chips” refer to PN sequences that are spread. Since there is no base-band information contained in the pilot channel, the pilot is not de-spread and bits are not recovered. Therefore, in order to describe the signal strength of the pilot channel, the raw SNR, or Ec/I0, is used. Note that since the pilot is not de-spread, Ec/I0 remains less than 1 most of the time.
The Ec/I0 is the energy per chip per interference density measured on the pilot channel; it is effectively the signal strength of the pilot channel.
Why it is needed?
This mobile-assisted handoff (MAHO) is evident in that the mobile makes a measurement of forward link Ec/I0 and reports the measurement result to the base station. Since each base station transmits its own pilot on a different PN offset, the Ec/I0 of a pilot gives a good indication of whether or not the particular sector should be the serving sector for the mobile. With accordance of Ec/I0 of different pilots, they switched between different sets like Candidate or neighbor set.
The candidate set contains those pilots whose Ec/I0s are sufficient to make them handoff candidates. This means that if the Ec/I0 of a particular pilot is greater than the pilot detection threshold T_ADD, then that pilot will be added to the candidate set. A pilot is removed from this set and placed in the neighbor set if the strength of that pilot drops below the pilot drop threshold T_DROP for more than the duration specified by the handoff drop timer expiration value T_TDROP. The candidate set can contain at least six pilots.
What is Eb/N0?
In digital communication, we are primarily interested in a link metric called Eb/N0, or energy per bit per noise power density. The link requires a particular Eb/N0 to attain an acceptable BER and ultimately an acceptable frame error rate (FER). Capacity is inversely proportional to the required Eb/N0 of the link. The lower the required threshold Eb/N0, the higher the system capacity.
Why it is needed?
FER is a good indicator of link quality. But because it takes a long time for the base station to accumulate enough bits to calculate FER, Eb/N0 is used as an indicator of reverse link quality.
The reverse-link closed-loop power control is as follows:
1. The base station continuously monitors Eb/N0 on the reverse link.
2. If Eb/N0 is too high (i.e., if it exceeds a certain threshold), then the base station commands the mobile to decrease its transmit power.
3. If Eb/N0 is too low (i.e., if it drops below a certain threshold), then the base station commands the mobile to increase its transmit power.
Summary:
Ec/I0: Used for Forward Link (Pilot) Measurement & MAHO.
Eb/N0: Used for Reverse Link Measurement & Power Control.
4 comments:
Hey great artical. It is useful.
Good Stuff man
Great explanation
Thank you very much
very good article keep up the good work
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