LTE (the GSMA-adopted roadmap to 4G for GSM/UMTS carriers) has been getting a lot of attention of late. Verizon Wireless plans to begin network deployment in 2009 (using their newly acquired 700MHz spectrum) with full network deployment in 2010 and beyond. AT&T has also announced LTE rollout plans in 2012. Vodafone is also making the obligatory statements about rollout plans in 2011-2012 time frame – its ex-CEO, Arun Sarin has made snarky comments about Verizon needing LTE more than Vodafone owing to the inability of EV-DO to scale up to near-4G speeds like HSPA.
With the possible exception of Verizon, how real are these LTE rollout plans especially given the current financial turmoil? My bet is that 3G operators will look to squeeze the last ounce of return by upgrading their 3G/HSPA networks to HSPA+ (also called Evolved-HSPA or Advanced HSPA) long before they consider LTE. In fact, Japan’s Softbank Mobile has already chosen HSPA+ over LTE because of cost and backward compatibility. The reasons are as follows:
- No marked difference in spectral efficiency – LTE proponents talk about 144Mbps Downlink (DL) and 50+Mbps Uplink (UL) speeds. But realization of these speeds require available spectrum in excess of 20 Mhz. Now probably is not a good time to be buying spectrum. As the chart shows (courtesy: Qualcomm), spectral efficiency of HSPA+ (when MIMO is included) is close to that of LTE when you consider 5Mhz spectrum.
- Significant less Investment in Infrastructure – It is much easier and less expensive to upgrade HSPA to HSPA+ given that LTE is based on OFDM – a completely new modulation scheme while HSPA+ is still based on W-CDMA. LTE needs a completely new set of radio access and core infrastructure components – not only are the radio access algorithms different, the signaling and control protocols from the access to the core are also significantly different.
- Backward compatibility – It is simpler for a HSPA+ subscriber to gracefully handover to a HSPA network – the connectivity between RNC and the core (SGSN and GGSN) remains as before. Significant complexity exists for handover to be implemented between 4G/LTE and HSPA+ networks.
- Handset and terminal availability – Availability of LTE handsets may be less of an issue – clearly, the initial application for both HSPA+ as well as LTE is in mobile broadband (with USB dongles). It is reasonable to expect that HSPA+ dongles will be cheaper than those supporting LTE – given that a new semiconductor ecosystem needs to emerge that supports LTE.