Evolved Packet System (EPS): The LTE and SAE Evolution of 3G UMTS

3.5 The E-UTRAN Physical Layer Standard

Although last 3GPP enhancements like HSDPA or HSUPA should provide a highly competitive access technology, 3GPP aims to define a longer time frame evolutionary path to ensure competitiveness. The new access technology is called E-UTRAN (Evolved UTRAN).

Requirements for this new technology include:

• Higher data rates.
• Reduced latency.
• Improved capacity and coverage.
• Reduced operational costs.
• Future additional spectrum allocations compatibility.
• Less than 5-MHz bandwidth compatibility.

Like in classical 3G/UTRAN, both FDD and TDD mode are still considered; both duplex schemes are still being imposed in most countries by the regulatory bodies.

At the early stage of E-UTRAN discussions in mid-2005, six new radio concepts were competing:

1. FDD UL based on SC-FDMA, FDD DL based on OFDMA.
2. FDD UL based on OFDMA, FDD DL based on OFDMA.
3. FDD UL/DL based on MC-WCDMA.
4. TDD UL/DL based on MC-TD-SCDMA.
5. TDD UL/DL based on OFDMA.
6. TDD UL based on SC-FDMA, TDD DL based on OFDMA.

We will not detail, in the following, the technical aspects of all the proposals; neither we will come back to the choice of the selected variant which is the first on the list.

All of these propositions had some attractiveness arguments and the classical game of industrial lobbies did the rest, as usual.

It has rapidly been decided that future radio interface would be based on OFDM, especially for receivers processing simplification purposes and spectral efficiency improvements compared ...