transmission issue(High RSL)

[meilah]

Dear All,
As per TT need frequency interference test
Freq. Interference test
design RSL
need you support to solve this issue












2/2/2011 WED
ZRY531 ZRY009
TN 6P








After change freq
TX-57261 ZRY531 RX-38521 ZRY009
TO
TX-37275 ZRY531 RX-38535 ZRY009

[zakiuddin]

Dear All,
As per TT need frequency interference test
Freq. Interference test
design RSL
need you support to solve this issue




Text above is too brief to describe the problem and secondly, the attachments are blur and can't be read..
Can you please explain in detail, what is the problem and where are you stuck right now?

[meilah]

the interference frequency test already attached and the Link budget (Design) also attached and the current satuation

[zakiuddin]

the interference frequency test already attached and the Link budget (Design) also attached and the current satuation

fist of all, the attached Screenshots are not much DIRECTED; anyways here are my observations:

1. what actually is the problem?; site is down due to external interference?
how do you know for sure that the link outage cause is an interference? what i can see is that there's an interference level of -95.3dbm (it is quite low already) on one end. what is the interference level on the far end of the link?
2. let's say that you are sure about the site outage due to the interference captured in the attached screenshots (-95.3dbm) but still, -95.3 dbm is very low interference level in practical networks. link shouldn't face any outage due to this much interference.

Here are my suggestions to rectify the link on urgent basis:
1. The link is running on RTPC, change it to MTPC and increase the Tx power from -5 to more than 20db. this should increase the fade margin by more than 25dbm(which is enough to combat any threshold degradation due to interference). the current fade margin is only 20db Approx.

2. Mute the Tx on both ends. Change the Tx/Rx channel to any new random channel (in your licensed frequency spectrum).Check Rx levels on both ends. If the Rx levels are lower than -95(or whatsoever you desire), switch on the Tx on both ends. If you get interference even on the new channel, repeat the process. Make sure to involve your local Transmission Planning engineer while making changes to Link budget like frequency channel and Tx powers.

regards

[ivandgreat]

what kind of link budget tools are you using?...

[raid75]

may you can increase antenna height

[zakiuddin]

may you can increase antenna height

There is no way an increase in antenna height would result in reduced interference unless the interferer system is physically colocated.. Yes, You may decrease the antenna height to lower any possible OHLOSS

[meilah]

the link budget is Trends

[meilah]

sukiuddin I will decrease the antenna height after that I will feed back

[rm77]

Dear all;
I think to put the TX more than 20dbm might be risky for the Far RX equipment meanwhile the distance is 1.6km and it can cause probably other link interference specially if it was in Urban dense .
BR.

[meilah]

dear rm77,
what is your comments

[zakiuddin]

Dear all;
I think to put the TX more than 20dbm might be risky for the Far RX equipment meanwhile the distance is 1.6km and it can cause probably other link interference specially if it was in Urban dense .
BR.

1. Currently RSL at -5db Tx power is -60, increasing the Tx power to +20dbm would increase the RSL to -35 which is more than sustainable for any 16QAM link; Rx saturation level in this link should be around -20db so we'll be safe.
2. Screenshots show that we are receiving a Maximum interference level of -95dbm. assuming the interferer is at Maximum Tx, Interference that can be generated by the local transmitter should be around -90 to -100. It is workable.

anyways, as i said earlier, it is recommended to involve the Local transmission planner.

[zakiuddin]

sukiuddin I will decrease the antenna height after that I will feed back

i won't recommend lowering antennae. it is a possible solution but it depends on the nature of the problem. if the interference path is correlated to the link LOS path than lowering antennae won't do any good. plus at the same time you need to make sure that LOS is not being obstructed. main thing is that you should consult the local planning guy and ask for his recommendations as he's the caretaker of the network.

[rm77]

Hi;
I agree with zakiuddin to decrease the antennas to achieve the minimum necessary LOS to avoid any OHLOSS and to rise the TX level but not at max (less than 10dbm),don’t forget also to check the respect of the parity violation in this site.
BR.

[Cepillo]

When has the TT appeared, after installation or later? What was the best RSL? May be your subcontractors have made some mistakes like "side lob", or different polarisation (adds -30 dB), etc.? What kind of antenna's type (size) do you use in this short distance?

[dNoB]

may be there is a need to check when the issue started, and what change/s have been made on that link before the issue arised. If some work was done before the issue arised, it is probable that the work affected the transmission; otherwise it could be external; or could be some other things... just a thought.

[meilah]

THE PROBLEM WE WANT TO UPGRADE THIS LINK AND THIS LINK NOT MATCHING DESIGN.
WE ALREADY CHANGE THE FREQUENCY AND IT IS THE SAME(NO INTERFERENCE).
BUT STILL THE RSL HIGH.
WHAT I CAN DO?

[dNoB]

if it's not external interference, just proper tuning of the hardware shall resolve your worries.

[meilah]

WE ALREADY CHECK EVREY THING

[rm77]

hi;
It happened to me once time when the Rx was suffering (alarm: if demodulation ,in SRAL equipememt) we thought that it was external interference from another operator and it’s solved by changing of Polarization, so try may be.
thanks

[Cepillo]

WE ALREADY CHECK EVREY THING

pls describe what you've checked on the both ends