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eceivers. Examples of advanced receiver structures include mobile receive diversity, which improves<br />
downlink spectral efficiency by up to 50 percent, and equalization, which significantly improves downlink<br />
performance, particularly at very high data speeds. UMTS Rel-6 also introduced the MBMS feature for<br />
support of broadcast/multicast services. MBMS more efficiently supported services where specific content<br />
is intended for a large number of users such as streaming audio or video broadcast.<br />
Release 7 (Rel-7) moved beyond HSPA in its evolution to HSPA+ and also the standardization of Evolved<br />
EDGE; the final Stage 3 was published in March 2007. The evolution to 3GPP Rel-7 improved support<br />
and performance for real-time conversational and interactive services such as Push-to-Talk Over Cellular<br />
(PoC), picture and video sharing, and Voice and Video over Internet Protocol (VoIP) through the<br />
introduction of features like Multiple-Input Multiple-Output (MIMO), Continuous Packet Connectivity (CPC)<br />
and Higher Order Modulations (HOMs). These Rel-7 enhancements are called Evolved HSPA or HSPA+.<br />
Since the HSPA+ enhancements are fully backwards compatible with Rel-99/Rel-5/Rel-6, the evolution to<br />
HSPA+ has been made smooth and simple for operators.<br />
Release 8 (Rel-8) specifications, frozen in December 2008 and published in March 2009, included<br />
enhancements to the Evolved HSPA (HSPA+) technology, as well as the introduction of the Evolved<br />
Packet System (EPS) which consists of a flat IP-based all-packet core (SAE/EPC) coupled with a new<br />
OFDMA-based RAN (E-UTRAN/LTE).<br />
Note: The complete packet system consisting of the E-UTRAN and the EPC is called the EPS. In this<br />
paper, the terms LTE and E-UTRAN will both be used to refer to the evolved air interface and radio<br />
access network based on OFDMA, while the terms SAE and EPC will both be used to refer to the evolved<br />
flatter-IP core network. Additionally, at times EPS will be used when referring to the overall system<br />
architecture.<br />
While the work towards completion and publication of Rel-8 was ongoing, planning for content in Release<br />
9 (Rel-9) and Release 10 (Rel-10) began. In addition to further enhancements to HSPA+, Rel-9 was<br />
focused on LTE/EPC enhancements. Due to the aggressive schedule for Rel-8, it was necessary to limit<br />
the LTE/EPC content of Rel-8 to essential features (namely the functions and procedures to support<br />
LTE/EPC access and interoperation with legacy 3GPP and 3GPP2 radio accesses) plus a handful of high<br />
priority features (such as Single Radio Voice Call Continuity [SRVCC], generic support for non-3GPP<br />
accesses, local breakout and CS fallback). The aggressive schedule for Rel-8 was driven by the desire<br />
for fast time-to-market LTE solutions without compromising the most critical feature content. 3GPP<br />
targeted a Rel-9 specification that would quickly follow Rel-8 to enhance the initial Rel-8 LTE/EPC<br />
specification.<br />
At the same time that these Rel-9 enhancements were being developed, 3GPP recognized the need to<br />
develop a solution and specification to be submitted to the ITU for meeting the IMT-Advanced<br />
requirements (which are discussed in Section 6). Therefore, in parallel with Rel-9 work, 3GPP worked on<br />
a study item called LTE-Advanced, which defined the bulk of the content for Rel-10, to include significant<br />
new technology enhancements to LTE/EPC for meeting the very aggressive IMT-Advanced requirements,<br />
which were officially defined by the ITU as “<strong>4G</strong>” technologies. Section 6 provides details of the IMT-<br />
Advanced requirements, a timeline and process for technology evaluation, 3GPP’s role, IMT-Advanced<br />
candidate technology submissions received by ITU-R, and timeline and submission plans for an LTE/EPC<br />
submission (called LTE-Advanced) to the ITU for meeting the IMT-Advanced requirements. On October 7,<br />
2009, 3GPP proposed LTE-Advanced at the ITU Geneva conference as a candidate technology for IMT-<br />
Advanced and one year later in October 2010, LTE-Advanced was approved by ITU-R as having met all<br />
the requirements for IMT-Advanced (final ratification by the ITU occurred in November 2010).<br />
www.4gamericas.org February 2011 Page 9
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