cross sector and cross feeder

[simmus0300]

Cross Sectors: You have this situation when at BTS level or Tower Level the cableling are wrong connected to an especific Antenna array,that means, as an example, Sector A is connected to Sector B or C Antenna of the cell, this is a common issue in installation process, and the affectation is the interference due Frequency Plan.

Cross Feeders: This can occurs when 1 feeder (of 2 or more from 1 sector) are connected to an antenna of other sector, this problem may cause high dropped calls and stablishment failures deppending if it carries BCCH or SDCCH channels, this can occurs at Installation process or Capacity Expansion

Both problems can be founded by Drive Test and Statistical ways,
anyone who have more idea and solution for finding the cross feeder and cross sector is welcomed.
pl add reputation and thanks if found useful.

[Processor]

i really can't spot the difference between cross sector and cross feeder.

I would have thot that cross sectors is as a result of cross feeder cables.

[ghassen]

Cross Sectors: You have this situation when at BTS level or Tower Level the cableling are wrong connected to an especific Antenna array,that means, as an example, Sector A is connected to Sector B or C Antenna of the cell, this is a common issue in installation process, and the affectation is the interference due Frequency Plan.

Cross Feeders: This can occurs when 1 feeder (of 2 or more from 1 sector) are connected to an antenna of other sector, this problem may cause high dropped calls and stablishment failures deppending if it carries BCCH or SDCCH channels, this can occurs at Installation process or Capacity Expansion

Both problems can be founded by Drive Test and Statistical ways,
anyone who have more idea and solution for finding the cross feeder and cross sector is welcomed.
pl add reputation and thanks if found useful.

try to use a spectrometer and you ll find that there is superious modes are created behind the central frequency and then leading to a higher coupling between the antennas

[cdmahn]

try to use a spectrometer and you ll find that there is superious modes are created behind the central frequency and then leading to a higher coupling between the antennas

Could you explain in more details?

Is spectrometer is the same as spectrum analyser?

TIA

[ghassen]

Could you explain in more details?

Is spectrometer is the same as spectrum analyser?

TIA

yes you got it

[guess.who]

did nt really get it ..plz explain ...are nt these both the same things...is nt feeder and cables both the same thing....you have confused me...plz elaborate

[venom]

Cross Sectors: You have this situation when at BTS level or Tower Level the cableling are wrong connected to an especific Antenna array,that means, as an example, Sector A is connected to Sector B or C Antenna of the cell, this is a common issue in installation process, and the affectation is the interference due Frequency Plan.

Cross Feeders: This can occurs when 1 feeder (of 2 or more from 1 sector) are connected to an antenna of other sector, this problem may cause high dropped calls and stablishment failures deppending if it carries BCCH or SDCCH channels, this can occurs at Installation process or Capacity Expansion

Both problems can be founded by Drive Test and Statistical ways,
anyone who have more idea and solution for finding the cross feeder and cross sector is welcomed.
pl add reputation and thanks if found useful.

Ok guys seems like all of you above dont have a good concept of cross feeders or cross sectors. I will try to make you guys understand in a simplest language, also you can see the pictures which i made for your understand.

In Mobile communications, cross feeders or cross sectors is generally named as a Swap or cable swap. Cable Swap have many types and and i have shown a few of them for your understandings. Please find below the description of few types of cable swap:

1. Sector Swap or Cross Sectors: Every Antenna is connected with 2 cables called feeders. If the feeders of 1 sector is interchanged with the other sector then this is called a sector swap or cross sectors. It means that the sectors will behave differently, for example 1st sector and 2nd sectors cables are swapped then 1st Sector will behave as a 2nd Sector and vice versa. Diagram is shown for your understanding.

2. Antenna Swap: If we have two or more antenna in each sector then there is always a possibility of having an Antenna Swap. It means that the feeders of a single Antenna Can be swapped with the other antenna. This can happen between sectors and also in a same sector.

3. Partial Swap or Cross Feeder: In this type of swap we observe that a single cable (out of 2) in 1 antenna gets swapped with the single cable of another antenna. This can again happen within the same sector or between sectors. Again see the Diagram for your understandings.

4. Cross Swap: Cross swap is the most difficult type of swap that exists, it means that all the three sectors are actually partially swapped. which means that single feeder in each antenna gets swapped with the other feeder in another antenna. It can happen between 900/1800/2100 Antenna altogether.

All of the above can be removed easily if you know how to connect the feeders (directly or through combiner or splitter) in to the CU. The best way is to track the cables from top to the BTS. I hope it is helpful for your understanding :)

[Processor]

@ Venom

Still a bit confusing:)...Could u try and put them into real life scenarios(i.e as to how a drive tester would be able to tell or an optimizer be able to tell from his KPIs)

Many thanks.

[davidbrayan]

Cross sector is easy to find,here i explain cross feeder(cross feeder TCH trx only,if it is a Cross feeder BCCH trx, it is believed to be Cross sector although still its cross feeder,you need to rectify it)
for a drive tester to test it(before going to BTS and arranging a cable trace):
the site should have atleast 2 trx each sector without combiner,(combiner bypassed)each trx connected to seperate antenna port.
now go into main beam of the suspected sector,make calls on all the trx it has,
first BCCH trx,note the Rxlevel,disable downlink power control before making the tests if you can.
than TCH trxs of the same sector,distinguish them with their differnt MAIO values,again note Rxlevel of all these trx.it should be same in ideal conditions but if there is cross feeder it would be different,the trx connected to(feeder swapped) different sector antenna will show alot lower Rxlevel then others, being transmitted in different direction as it is connected to some different antenna,now if you lock the call on that feeder swapped trx on which you are getting 20 - 30 dB less level and go around the site,it'll show better level in some different sector in which it is swapped to.
same way try other sectors and trx too.its somewhat complicated and time consuming but can serve the purpose before going to BTS.
now if there are 2 or 3 trx per sector and combining is used,drive tester cant figure out the cross feeder since the crossed feeder has no transmission assosiated with it.it only serve as RX diversity.till the time anyone get that much experiance to figure it out,he is not a drive tester anymore.
Now for optimisers.
it'll effect handovers,call establishments,SDCCH assignments.
if you look at sector wise and trx wise reports.
the crossed trx would cause maximum number of call drops HO failures, SD failures if SD is assigned on those Trx.and other services being served by those trx.
the performance of those trx degrade with TA,more the TA worst it would be.
Handovers based on Rxlevel can fail and result in a dropped call if the timeslot is reserved on the crossed trx,although the Rxlevel of BCCH was good enough to trigger a handover but since the trx on which the TCH timeslot for that call is allotted is transmitting in some different direction and the power in too less in the direction where the handover is being performed,either it will fail or drop.
same way while establishing a call when latched to the effected sector,if the call is matured on crossed trx it may drop or sustain after intracell handover.and if SD is assigned on crossed trx,it'll cause more problems.
Diversity gain is reduced as well.
and much more,find such cells and have detailed study for more information on the system you are working on.
its based on my experiance,correct me if im wrong

BR
db

[davidbrayan]

it is a two sector site with two trx each sector and two port antenna, combiner bypassed.
see how TCH trx transmitts in another direction when feeder crossed.

BR
db

[zaebolll]

Nice image, thank you.

[asiantiger]

Hi Venom

A very nice explination about the swaps,, this shows that you have had from your great experience from field with graet team. :p

BR

Tiger

[hakimgsm]

Hi friend
Can you please tell me how I can found the cross feeder and the cross sectors by the Statistical way.
I’m waiting for your replay
Thanks in advance,
Best Regards.




Cross Sectors: You have this situation when at BTS level or Tower Level the cableling are wrong connected to an especific Antenna array,that means, as an example, Sector A is connected to Sector B or C Antenna of the cell, this is a common issue in installation process, and the affectation is the interference due Frequency Plan.

Cross Feeders: This can occurs when 1 feeder (of 2 or more from 1 sector) are connected to an antenna of other sector, this problem may cause high dropped calls and stablishment failures deppending if it carries BCCH or SDCCH channels, this can occurs at Installation process or Capacity Expansion

Both problems can be founded by Drive Test and Statistical ways,
anyone who have more idea and solution for finding the cross feeder and cross sector is welcomed.
pl add reputation and thanks if found useful.

[adewijaya]

rather hard to found this without doing DT on site, its because of all Kpis most case looks find, but please consider this

1. Sudennly high drop call, refer to adj/co-channel with their neighbour
2. High HO attempt to other direction, its happend actually wrong direction after re-checking on Map plot
3. High HO Failure because of different direction neighbour

last but not least is doing some DT is final solution :cool: