LTE: Serendipity?

Renuka Bhalerao

Editor’s note:  This blog was inspired by the recent Wireless Watch column by Caroline Gabriel of Rethink Wireless (as seen on TelecomsEurope). 


Yes, this is how we can describe the emergence of LTE Time Division (TDD) technology onto the mobile infrastructure tech scene in the U.S. The Sprint-Clearwire LTE tie up is proof of it, and also a new beginning. Sprint has selected the Clearwire LTE TDD network to complement its own FD-LTE roll out in 800 MHz and PCS bands.

The world concluded 2011 acknowledging that the predictions of a wireless data explosion have actually come true. More and more users are going after bandwidth-consuming applications like Netflix, and operators globally are searching for technology to stay ahead of this ever-growing demand. As far as the radio interface is concerned, HSPA+ and LTE have grabbed the top ranks. While HSPA+ is enticing as an easy near-term upgrade, LTE is the clear choice of the future with a promise of significant reduction in cost per bit.

In a race for providing a wireline-like experience to wireless users, operators are not leaving any stone unturned. With plenty of data offload techniques, the introduction of the Hetnet concept, the improvements in spectral efficiency, and innovative data plans now being offered …we are inching closer to realizing the mobile broadband dream. Just when operators are at a point where they have exhausted all possible approaches, TDD in the form of LTE shines through.

TDD technology, as in TDSCDMA, was looked at in China for UMTS but not so much elsewhere. With the migration to LTE, it was ensured by China Mobile and its allies that adoption of this technology is easier this time around:

Let us recap the facts here,

  • LTE TDD is officially part of the 3GPP release 8, defined for six carrier bandwidths ranging from 1.4 to 20 MHz. albeit guesses are, like FDD, it will be mostly used in higher bandwidths.
  • 3GPP support by ensuring larger economy of scale benefit by utilizing common core network architecture wherever possible for both FDD and TDD.
  • TDD can be deployed by the side of FDD using the same EPC infrastructure. (Hello! savings in OPEX/CAPEX.)
  • Only significant difference is in frame structure and physical layer definition; higher layers and rest of network architecture remains as applicable for FDD.
  • Comparable to FDD in data throughput as well as latency measurements
  • Telecom community already working on additional definitions for backward compatibility aspects and reselection and HO procedures to be enabled from FDD to TDD and vice versa through protocols.

The list above is pretty convincing, but leaves out one key advantage. I’ll continue my point in part two of this blog…so stay tuned!

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