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d. Identify interference scenarios stemming from different UL/<strong>DL</strong> configurations in TDD and<br />
corresponding CSI reporting requirements<br />
8.3 HSPA+ ENHANCEMENTS<br />
The 3GPP has initiated the work on a set of new HSPA features considered for inclusion in Rel-11. The<br />
features under discussion so far include 8-Carrier HSDPA, Uplink dual antenna beamforming and MIMO<br />
as well as Downlink Multipoint Transmission.<br />
8.3.1 8‐CARRIER HSDPA<br />
The 8-carrier HSDPA extends the HSDPA carrier aggregation up to 40 MHz aggregate bandwidth by<br />
enabling transmission simultaneously on up to eight carriers towards a single UE. The carriers do not<br />
necessarily need to reside adjacent to each other on a contiguous frequency block, as it is possible to<br />
aggregate carriers together from more than one frequency band.<br />
Band A<br />
<strong>DL</strong><br />
20 MHz<br />
+<br />
Band B<br />
<strong>DL</strong><br />
4 x 5 MHz 4 x 5 MHz<br />
Figure 8.4. 8-Carrier HSDPA Aggregates up to 8X5 MHz Carriers from Different Frequency Bands.<br />
Eight-carrier HSDPA is expected to increase the peak HSDPA data rate by a factor of 2 compared to 4carrier<br />
HSDPA, and it can be expected to bring similar gains as the other multi-carrier features<br />
standardized in Rel-8 to Rel-10. As a potential additional evolution step, 4X4 MIMO can be envisioned,<br />
with the potential to yet again double the peak rate over 2X2 MIMO.<br />
8.3.2 UPLINK DUAL ANTENNA BEAMFORMING AND MIMO<br />
20 MHz<br />
Uplink dual antenna beamforming and 2X2 MIMO allows for the HSUPA transmissions to originate from<br />
two transmit antennas. Both rank 1 (single stream beamforming) and rank 2 (dual-stream MIMO)<br />
transmission modes are being considered. The rank 1 beamforming gains allow for better uplink data rate<br />
coverage and the rank 2 MIMO doubles the achievable peak data rate on the carrier. In addition, 2X4<br />
antenna configurations with 4 Node B Rx antennas are considered in the 3GPP evaluation work even<br />
though additional receive antennae is more of a deployment option not impacting the standards. Fourway<br />
Rx is expected to roughly double the capacity and significantly improve the probability for rank 2<br />
transmission.<br />
www.4gamericas.org February 2011 Page 86
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