HSPA Evolution MIMO [Under LTE]
» MIMO in UTRA - 25.876, Rel 7 «
As seen in Diversity articles, with spatial/space diversity helps in improving performance of wireless systems. After study on benefits and complexity, 3GPP decided to go for MIMO space diversity technique for HSPA Evolution. 3GPP TS 25.876 details 12 MIMO proposals (11 for FDD and one for TDD); following schemes were chosen after discussion:
— PARC (Per-Antenna Rate Control) MIMO for TDD
—
Dual-codeword MIMO based on Dual-stream TxAA (Transmit Adaptive
Array) for FDD
We will look at FDD MIMO in brief; 3GPP TS 25.876 provide sufficient details for all proposals including selected ones.
The major impact is on PHY layer. MIMO was chosen for HSDPA transmissions with HS-DSCH modified to support upto 2 transport blocks per TTI. Channel coding, interleaving, and spreading still remain the same; a simple representation is shown below:
Further work items (not detailed here) are:
1) with MIMO at
Node B and/or UE, how the pilot channels would be configured ?
2)
how MIMO specific PHY parameters (e.g. multiple antenna matric
weight factors) are communicated between Node B and UE ?
3) how
UE (and at what point in initialisation) will start using its own
and/or Node B's MIMO capability ?
To explore these items, you may to refer 3GPP TS 25.876 and other impacted PHY specifications listed in release 7 document at 3GPP.
Remaining HSPA Evolution additions
— 64QAM support was provided for HSDPA and 16QAM for HSUPA; resulting in capacity gains where signal conditions are favorable.
— Further RAN improvements included Enhanced CELL_FACH state, Optimisation of channelisation codes, Delay optimisations for CS & PS connections, Improved support to IMS realtime services etc.
Please refer release 7 document at 3GPP for complete list of features, details, and impacted specifications.
References: 3G Evolution: HSPA and LTE by Dahlman, Parkvall, Sköld, and Beming and release 7 document at 3GPP.
| Copyright © Samir Amberkar 2010-11 | § |
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