LTE Migration Paths

I found a nice chart in the latest 3G Americas report (Transition to 4G: 3GPP Broadband Evolution to IMT-Advanced), showing the different migration paths to LTE.

LTE migration

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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!

Re-defining Broadband?

The new TRAI Chairman, Dr J. S. Sarma, has been quoted as saying that "the target set for roll out of broadband by the Government can be achieved only if the definition of broadband is redefined and resources from USO fund are utilised." As per these reports, the minimum broadband speed will be increased to 2 Mbps instead of the current 256 Kpbs limit.

It's debatable whether re-defining broadband service characteristics can increase penetration. If the TRAI and DoT are really serious about achieving government targets, then a better idea would be to expedite spectrum auctions for 3G and BWA services. Both HSPA and WiMAX are very much capable for providing wireless broadband access to a large part of the country, especially where it's difficult to provide DSL and cable.

I have the feeling that we are going back in time as far as wireless technologies are concerned. Just like the CDMA vs GSM war a few years back, the government is again getting caught up in the war between HSPA/LTE and WiMAX proponents. What really matters is that India gets access to broadband services just like everyone else does in other countries. What technology/technologies are used to do so should be left to the market.