Talk:Orthogonal frequency-division multiple access

This is perhaps the lowest quality page I've seen on Wikipedia in some time. It obviously needs to be completely cleaned up. user:209.166.211.66 02:17, 17 August 2005
 * I have rewritten it. Some illustrations would help. Mange01 13:11, 15 November 2006 (UTC)

Different reader: I would be interested in understanding how OFDMA actually works. A graphic would be nice too. user:212.117.152.156 14:22, 15 November 2006


 * Perhaps the OFDM explains it all? But that article would also need some illustrations. Mange01 13:11, 15 November 2006 (UTC)

For SOFDMA page is redirected to here. But it's not mentioned at all!!! —Preceding unsigned comment added by Damithad (talk • contribs) 14:44, 8 October 2007 (UTC)

Cell breathing
Per the clarification request; no I don't think OFDMA suffers from cell breathing. In a CDMA system, cell breathing is caused by an increased interference floor as more users start transmitting, so the cell radius decreases. In OFDMA, the users are orthogonal, so the intra-cell interference is constant. Oli Filth(talk&#124;contribs) 14:46, 1 June 2010 (UTC)
 * Hi Oli. CDMA does not "suffer" from cell-breathing - it is an advantage of CDMA. To my understanding, it is a traffic-adaptive behaviour, making it possible for CDMA cells to easily borrow resources from each other, for example if the traffic load is higher near one basestation than near adjacent basestations.
 * In 1G and 2G systems, you also had a simple form of cell breathing, based on traffic-adaptive handover thresholds. A cell with low load may grow and attract traffic from the overlap area of adjacent overloaded cells.
 * OFDMA may be combined with dynamic channel allocation, and then cells can borrow resources from each other in a similar fashion, resulting in a form of cell breathing. Am I right?
 * Should we remove cell breathing from the list of OFDMA advantages? Mange01 (talk) 15:29, 1 June 2010 (UTC)


 * Cell-breathing is definitely not an advantage. Cell planning becomes more difficult because effective cell radius is not fixed, and therefore handovers, etc. are not predictable; instead they're determined by the instantaneous loading.


 * For OFDMA, I don't see how dynamic channel allocation affects intra-cell interference, and therefore how it affects cell radius! Oli Filth(talk&#124;contribs) 16:05, 1 June 2010 (UTC)
 * Cell breathing in the sense traffic adaptive handover increases the throughput. So from spectral efficiency point of point, it is an advantage. Regarding DCA+OFDMA, I was probably wrong.Mange01 (talk) 20:24, 2 June 2010 (UTC)
 * Ok, but that's not what people usually mean when they talk about "cell breathing"! Oli Filth(talk&#124;contribs) 20:46, 2 June 2010 (UTC)

Boosted subcarriers
From the image of the OFDMA subcarriers, does this mean, that pilot subcarriers have more power? In Fundamentals of WiMAX on the page 282: "The power in the pilot subcarriers, as shown here, is boosted by 2.5 dB, allowing reliable channel tracking even at low-SNR conditions." This chapter is about OFDMA used in WiMAX, so I think piot subcarriers have more power, than the other subcarriers. — Preceding unsigned comment added by Csolaszol86 (talk • contribs) 01:55, 13 December 2010 (UTC)


 * Typically yes. Also in OFDM systems like DVB-T, pilot subcarriers are boosted. Mange01 (talk) 16:06, 17 January 2011 (UTC)