could be viewed as the throughput performance with the ideal adaptive modulation and
coding. From Fig. 9 and Fig. 10, we can observe that the introduction of OCC can improve
throughput to some extent when some of the following situations are satisfied, i.e., the antenna
number is large, the RB number is small, and the sigal-to-noise ratio is high.
5. Some basic conclusions and standardization progress
DMRS enhancement is a key step to support MIMO transmission, including SU-MIMO,
MU-MIMO and CoMP, for LTE-A uplink. In this study different DMRS design schemes as
well as channel estimation are investigated. In addition to the baseline of CS extension, the
further combination of CS with OCC is also discussed. In addition to the special advantage
for MU-MIMO and CoMP, CS + OCC is also attractive for high-order SU-MIMO to further
suppress the interferences among the increasing multiple spatial layers. With the enhanced
DMRS design and improved channel estimation, a higher spectrum efficiency can be realized
in LTE-A uplink. Meanwhile, considering the backwards compatibility, as less as possible
modification to the current LTE specification is preferred.
In the recent 3GPP RAN1 meetings, it was agreed that (3GPP, R1-102601)
• Introduce the OCC in Rel-10 without increasing uplink grant signaling overhead
• OCC can be used for both SU-MIMO and MU-MIMO
More design details about DMRS enhancement, such as CS and OCC linkage, DMRS hopping,
etc., are still under discussions and hopefully the uplink DMRS enhancement for LTE-A will
be finalized by the end of 2010.
6. References
3GPP. R1-102601: Final report of 3GPP TSG RAN WG1 #60bis, 3GPP TSG RAN WG1 Meeting
#61, Montreal, Canada, May 10-14, 2010.
3GPP TR 36.814 http://www.3gpp.org/ftp/specs/html-info/36814.htm
3GPP TS 36.211 http://www.3gpp.org/ftp/specs/html-info/36211.htm
Chu, D. C. (1972). Polyphase codes with good periodic correlation properties. IEEE Trans. Info.
Theory, Vol. 18, No. 4, July 1972, pp. 531-532, ISSN 0018-9448
Edfors, O.; Sandell, M.; van de Beek, J. J.; Wilson, S. K. & Borjesson, P. O. (2000). Analysis of
DFT-based channel estimators for OFDM. Wireless Pers. Commun., Vol. 12, No. 1, Jan.
2000, pp. 55-70, ISSN 0929-6212
Hou, X.; Zhang, Z. & Kayama, H. (2009). DMRS design and channel estimation for
LTE-Advanced MIMO uplink, Proc. IEEE VTC09-Fall, Alaska, USA, Sept. 20-23, 2009.
Oppenheim, A. V.; Schafer, R. W. & Buck, J. R. (1999). Discrete-Time Signal Processing, 2nd ed.,
Prentice Hall, ISBN 013216292X, New Jersey
Texas Instruments. R1-091843: Discussion on UL DM RS for SU-MIMO, 3GPP TSG RAN WG1
Meeting #57, San Francisco, USA, May 4-8, 2009.
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