LTE on track to be finalized this year, with WiMAX2 on the horizon
Published: 29 January, 2008
We have seen the Ericsson-led LTE community stepping more aggressively into WiMAX' traditional TDD territory (see Wireless Watch January 15 2008), and despite ambivalence by the WiMAX Forum about making official statements, 802.16e will respond with an increased focus on FDD profiles this year. Now the 3GPP has approved the official technology specifications for the LTE RAN, which will now be included in the forthcoming 3GPP Release 8, a milestone crossed only three months later than originally promised, punctuality that contrasts with the repeated delays in WiMAX Forum deadlines over the years - and highlights how speed is now of the essence for both platforms, with operators seeing the need to step up their own progress towards true mobile broadband in order to increase revenues and ARPU, and see off new challengers.
LTE is now in the 'change control procedure' phase - with basic specs approved, any further changes must be officially agreed but the standard is now 80% complete and Release 8 should be frozen around year end, by which time some vendors will have created pre -standard test equipment for early mover carriers. Release 8 does not just focus on LTE in the RAN but is also expected to enhance HSPA+ (or HSPA Evolution), introduced in Release 7. By combining MIMO with a 64QAM modulation scheme, theoretical downlink speeds of up to 42Mbps can be reached in a 5MHz channel - similar to LTE using the same channel size - enabling HSPA operators to exploit their technology to the limit before making the leap to LTE. This suggests that early adoption of LTE will be by non-3G operators, perhaps for fixed and converged usage, and for non-voice devices and applications (see inset), bringing it even more directly into conflict with WiMAX, which because of its OFDM head start is widely seen as being the natural choice for carriers with no W-CDMA legacy.
The LTE air interface has been three years in the making, and uses OFDMA (like Mobile WiMAX), although only in the downlink channel, choosing SC-FDMA (Single Carrier - Frequency Division Multiple Access) instead in the uplink path. It takes data download rates to 100Mbps and upload rates to 50Mbps in 20MHz of spectrum, while increasing network capacity and boosting performance at the cell edge, and it has a path towards 300Mbps using 4x4 MIMO.
Another element in the LTE family is System Architecture Evolution (SAE), which specifies the mobile core network and provides the migration path to all-IP. This should also be finalized around the end of this year. In addition, the LTE test specifications, which are necessary for handset manufacturers to test their devices with network elements, are "much further advanced" than normal, according to the 3GPP.
Verizon and Vodafone, and other major operators that have committed to LTE as their primary next generation network are pressurizing vendors to have equipment read for initial trials by the end of this year, while commercial, certified systems are likely to be available in 2010-11, after Mobile WiMAX but before 802.16m, the future successor to 802.16e, (also known as Wi- MAX2, and which some are dubbing with the snappier EC label WiMagic).