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LTE "Occupied Bandwidth"


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While Googling about LTE, I came across this document on the FCC's website. The tidbit I found most interesting was the section on bandwidth options. It listed the standard 6 options (1.4, 3, 5, 10, 15, 20) and then the "occupied bandwidth" for each carrier size (1.08, 2.7, 4.5, 9, 13.5, 18). I'm curious as to what exactly that means, and it brings up several questions.

  • Since the occupied bandwidths and channel sizes for 5 MHz and above are proportional, does this mean that there is no "waste" from using two 5 MHz carriers instead of one 10 MHz carrier? For example, the 5 MHz carrier would have a peak speed of exactly half of the 10 MHz carrier.
  • Is the unoccupied (so to speak) bandwidth required to be completely empty for the channel to work properly?
  • If not, what is stopping Sprint from using the unoccupied bandwidth for CDMA carriers in ESMR? A configuration where the LTE carrier is sandwiched between a 1x and an EVDO carrier would fit into the 7 MHz they have in most places. The .25 MHz "extra" on each end of the LTE carrier would be shared with the CDMA carriers. It would look like this: |1|.25|4.5|.25|1|. I've read about an Australian carrier doing something similar with WCDMA and GSM when they refarmed either the 900 MHz or 850 MHz band.

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While Googling about LTE, I came across this document on the FCC's website. The tidbit I found most interesting was the section on bandwidth options. It listed the standard 6 options (1.4, 3, 5, 10, 15, 20) and then the "occupied bandwidth" for each carrier size (1.08, 2.7, 4.5, 9, 13.5, 18). I'm curious as to what exactly that means, and it brings up several questions.

above are proportional, does this mean that there is no "waste" from using two 5 MHz carriers instead of one 10 MHz carrier? For example, the 5 MHz carrier would have a peak speed of exactly half of the 10 MHz carrier.

  • Since the occupied bandwidths and channel sizes for 5 MHz and above are proportional, does this mean that there is no "waste" from using two 5 MHz carriers instead of one 10 MHz carrier? For example, the 5 MHz carrier would have a peak speed of exactly half of the 10 MHz carrier.
  • Is the unoccupied (so to speak) bandwidth required to be completely empty for the channel to work properly?

 

Yes and yes. To see the second part (occupied bandwidth) in actual use, view my spectrum analyzer sweeps in this article:

 

http://s4gru.com/ind...trength-primer/

 

I will address your third point later tonight.

 

AJ

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Sorry to bump, but any more comments?

 

No need to apologize. Sometimes, I need a reminder.

 

While Googling about LTE, I came across this document on the FCC's website. The tidbit I found most interesting was the section on bandwidth options. It listed the standard 6 options (1.4, 3, 5, 10, 15, 20) and then the "occupied bandwidth" for each carrier size (1.08, 2.7, 4.5, 9, 13.5, 18). I'm curious as to what exactly that means, and it brings up several questions.

  • If not, what is stopping Sprint from using the unoccupied bandwidth for CDMA carriers in ESMR? A configuration where the LTE carrier is sandwiched between a 1x and an EVDO carrier would fit into the 7 MHz they have in most places. The .25 MHz "extra" on each end of the LTE carrier would be shared with the CDMA carriers. It would look like this: |1|.25|4.5|.25|1|. I've read about an Australian carrier doing something similar with WCDMA and GSM when they refarmed either the 900 MHz or 850 MHz band.

 

The primary problem with your proposal is that the occupied bandwidth of the two CDMA2000 carriers sandwiching one LTE carrier would add up to exactly 14 MHz (7 MHz x 7 MHz). In short, it would not allow for any guard bands.

 

3GPP has built internal guard bands into its carrier bandwidths. Look at any 3GPP airlink (e.g. W-CDMA, LTE) on a spectrum analyzer, and see its occupied bandwidth is significantly less than its specified carrier bandwidth. But 3GPP2 has not included guard bands into its carrier bandwidths. Look at any 3GPP2 airlink (e.g. CDMA1X, EV-DO) on a spectrum analyzer, and see its occupied bandwidth effectively match its specified carrier bandwidth.

 

Thus, 3GPP2 operators have to account for external guard bands. For example, in its PCS 1900 MHz A-F block licenses, Sprint incorporates a 625 kHz guard band at the top and bottom of each uplink and downlink license segment to ensure that out of band emissions from its CDMA2000 airlinks do not negatively affect adjacent licensees.

 

AJ

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