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What is frequency Hopping and Carrier Grooming

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Ex Member
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Sep 23rd, 2008 at 4:53am  

Dear All

What is frequency hopping and carrier grooming and How it influences a remote commisioning ?



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Ex Member
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Reply #1 - Sep 23rd, 2008 at 7:47am  
Frequency hopping refers to FDMA type of satellite access where you are given a frequency range. When your carrier pops out, it will find a vacant spectrum on the allocated range within the transponder.This simply means spectrum sharing. Carrier grooming in my knowledge refers to carrier spacing. Proper spacing of the carrier is needed to minimize co-channel interference.

im a newby..this will need valication. Smiley

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Eric Johnston
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Reply #2 - Sep 23rd, 2008 at 8:15am  
References to "Frequency hopping" may be referring to a spread spectrum technique whereby the centre frequency of the carrier jumps about over a wide range.  This provides privacy and resistance to interference.

"Carrier grooming" tends to be done every few months whereby all carriers across the transponder are systematically adjusted to get the levels correct and possibly the centre frequencies rearranged so as to get more useful gaps between the carriers for new carriers to be added.  Being able to remotely adjust carrier power and centre frequency is very helpful as it avoids site visits to every earth station.  But be very careful if you change the receive frequency of a remote - you will lose it if you make a mistake.  Some modems will revert to a previously known working configuration, after some time, in such circumstances, but not all !

Best regards, Eric.
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« Last Edit: Sep 23rd, 2008 at 10:19am by Admin1 »  
 
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Reply #3 - Sep 23rd, 2008 at 10:08am  
both of the above are valid answers, but I think the question refers to Frequency Hopping as it is implemented in the iDirect platform.

iDirect allow you to use multiple inbound, or return carriers in any single network, these carriers all have their own frequency.  the inbound carriers on the iDirect platform are not FDMA, but MF-TDMA (Multi Frequency - Time division Multiple Access).  when a system is configured with multiple inroute carriers the hub operator can define whether a remote will be allowed to use all the carriers or locked to a single carrier.  If a single remote is allowed to utilise all the carriers, this is frequency hopping.  the PP blade running the bandwidth allocation process tells the remotes which carrier to use - i.e. which frequency.  and for how long - number of slots etc.

Carrier Grooming mode - when the system in configured in this way a remote will come on line and will remain on the same return carrier.

so Frequency Hopping is the recommended way forward from my point of view, if a carrier becomes heavily utilised the system will move remotes to a less ustilised carrier = better customer experience.  Carrier grooming is very useful for fault finding though, if you have a remote causing Traffic CRC errors and this remote is in FH mode, he will cause errors across all your return channels, to identify and isolate this remote you can (in later versions) lock a remote to a single carrier individually, basically placing an individual remote in carrier grooming.  Very helpful when trying to isolate and solve issues. 

hope that helps.
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Ex Member
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Reply #4 - Sep 25th, 2008 at 9:13pm  
Really Thansk and its Very Clear
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