Monday, June 14, 2010

Note of caution: HSPA, WiMAX, LTE comparisons

There is feverish speculation in the media regarding the BWA plans of RIL. Among the many articles in the media, one in particular caught my eye. DNA India carried a report, apparently based on an investor briefing from Reliance. According to this article:

“HSPA carries 2.88 bits per hertz, whereas Wimax carries 5.6 bits and (the future) LTE would carry 16.32 bits per hertz,” RIL said.

These numbers should be treated with caution for several reasons. Firstly, peak data rates vary between different releases of the same technology. It's quite obvious that the HSPA rate quoted above is for Rel-6, the very first generation of HSPA systems. Since then, advanced versions of HSPA have been developed and normalized data rates as high as 8.1 bits per second per Hertz are now supported (in HSPA Rel-8). Secondly, the peak rate calculation depends on a number of factors such as antenna configuration, modulation scheme, code rate etc. The figures quoted above for LTE are most probably for a 4x4 MIMO configuration whereas for WiMAX, these are surely for 2x2 antenna configuration. Hence, a direct comparison is not really meaningful.

BTW, the correct units are bits per second per Hertz!

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