PU2RC

Per-User Unitary Rate Control (PU²RC) is the world first codebook based multi-user MIMO platform [cite conference|author=Niranjay Ravindran, Nihar Jindal, and Howard Huang|title=Beamforming with FiniteRate Feedback for LOS MIMO Downlink Channels|booktitle=To Appear: IEEE Global CommunicationsConference|date=November 2007] , which is a similar to world-wide OS platforms in computing technology such as Linux (cooperative OS development platform), Symbian, Mac OS X, Windows. It also shows an example of how to use transmit precoding and user scheduling efficiently.

On the other hand, R. Heath and et. al have discussed multiuser MIMO scheduling [1] . A. Kogiantis and et al. have analysized optimal power allocation for MISO multiuser scheduling channels [2] . Earlier than two papers, K.K. Wong and et al. have considered a full CSIT based precoding scheme of multiuser MIMO system [3] .

* Background technologies: [1] R. W. Heath, Jr., M. Airy, and A. J. Paulraj, "Multiuser Diversity for MIMO Wireless Systems with Linear Receivers," Proc. of the IEEE Asilomar Conf. on Signals, Systems, and Computers, pp. 1194 -1199, vol.2, Pacific Grove, California, Nov. 4 - 7, 2001.: [2] A. Kogiantis and L. Ozarow, "Downlink best-effort packet data with multiple antennas," ICC’03, Volume 1, 11-15 May 2003 Page(s):715 - 719. : [3] K.K. Wong, R.D. Murch and K.B. Letaief, "Performance Enhancement of Multiuser MIMO Wireless Communication Systems," IEEE Transactions on Communications, Vol 50 No 12 , Dec. 2002, pp 1960 –1970

Technology

PU²RC allows the network to allocate each antenna to the different user, unlike in single-user MIMO scheduling. Instead of a physical antenna, the network can transmit to a user through a codebook based spatial beam, i.e., a virtual antenna. Additionally, efficient user scheduling such as pairing spatially distinguishable users with codebook-based spatial beams is used for the simplification of wireless networks in terms of additionally required wireless resource and complex protocol modification.

Mathematical description

The operation is described mathematically below for the transmitter and receiver side.

Transmitter Side

The transmitter antenna array has $N\_t$ elements. The transmit signal vector is modeled as follows::$mathbf\{x\}\; =\; sum\_\{i=1\}^K\; mathbf\{w\}\_i\; P\_i\; s\_i$ where $mathbf\{x\}$ is the $N\_t\; imes\; 1$ vector of transmitted symbols and $mathbf\{w\}\_i$ is the $N\_t\; imes\; 1$ linear precoding vector. PU²RC generates $\{mathbf\{w\}\_i\}$ based on the received finite channel status information, which is delivered to the base station by the user equipment (UE) using a coded look-up table index.

Receiver Side

Every receiver has a receive antenna array with $N\_r$ elements. The receive signal vector at user $k\; (=1,2,ldots,K)$ is modeled as follows::$mathbf\{y\}\_k\; =\; mathbf\{H\}\_kmathbf\{x\}+mathbf\{n\}\_k$where $mathbf\{y\}\_k$ and $mathbf\{n\}\_k$ are the $N\_r\; imes\; 1$ received symbol and noise, respectively, and $mathbf\{H\}\_k$ is the $N\_t\; imes\; N\_r$ matrix with the channel coefficients.

Throughput performance

The figure illustrates the throughput advantage of PU²RC over the conventional single-user and no scheduling scheme, assuming that the codebook size is one, i.e., $(G=1)$. For larger codebook sizes the performance can be better than the performance of the unit-size codebook. Because of codebook-based multi-user scheduling, PU²RC outperforms the conventional single-user and no scheduling scheme when the number of users is larger than one. Note that the performance plotted in the figure for the two systems were obtained assuming linear receiver.

ee also

Books

* [http://www.amazon.com/dp/0470015756 Radio Network Planning and Optimisation for UMTS by Jaana Laiho, Achim Wacker, and Tomá Novosad (Hardcover - Feb 10, 2006)]
** Page 366: "... backward incompatibility with previous standard releases. Per-User Unitary Rate Control (PU2RC) is based on the singular value decom- position of MIMO .
* [http://www.amazon.com/dp/0849341906 MIMO System Technology for Wireless Communications (Electrical Engineering and Applied Signal Processing) by George Tsoulos (Hardcover - Mar 28, 2006)]
** Page 237: "... I due to additional transmit antennas. Per-User Unitary Rate Control (PU2RC). This algorithm is based on the singular value decomposition of ..."

PU²RC reference materials and sites

* [http://userver.ftw.at/~cfm/389039/lecture13/HSDPA_Lecture_2004-01-15.pdf Forschungszentrum Telekommunikation, Wien LVA 389.089, Lecture January 15, 2004., High Speed Downlink Packet Access (HSDPA)]
* [http://www.dbpia.co.kr/view/ar_view.asp?pid=243&isid=35948&arid=747821&topMenu=&topMenu1= M. Cho, Y. Kim, D. Hong, "Feedback Reduction of Channel Quality Information for Multiuser MIMO Systems", pp. 798~803 (6 pages), UCI : G300-j12264717.v31n8Ap798]
* http://ettrends.etri.re.kr/PDFData/21-3_048_058.pdf
* http://mobile.snu.ac.kr/mcl_list/papers/conference/ew200504_sjkim_hjkim_kblee.pdf
* http://onyx.yonsei.ac.kr/~tta2007/files/5_WiBro.pdf
* S. J. Kim, H. J. Kim, C. S. Park, and K. B. Lee, "On the Performance of Multiuser MIMO Systems in WCDMA/HSDPA: Beamforming, Feedback and User Diversity," IEICE Transactions on Communications , vol. E98-B, no. 8, pp. 2161-2169, Aug. 2006.
* 802.11vht (Motorola), July 2007, [http://www.google.com/url?sa=t&ct=res&cd=23&url=https%3A%2F%2Fmentor.ieee.org%2F802.11%2Fpublic%2F07%2F11-07-2187-01-0vht-another-resource-to-exploit-multi-user-diversity.ppt&ei=fTPhRtS-CqbqswKWwtHiCw&usg=AFQjCNFbcdvbbAh7-6aRdUFKVLqMveVbVA&sig2=SvMsuX5lYIyDfbErFq_S7g Another resource to exploit: multi-user diversity]
* [http://www.ist-mascot.org/deliverables/deliverable-4-4-first-industry-course-on-mu-mimo/mumimo_industry_course_mecklenbraeuker_part2.pdf/download Christoph Mecklenbräuker, MU-MIMO schemes in current standards for 3GPP Long Term Evolution, Wireless LAN, and WiMax, November 16, 2007.]
* [http://www.douglaschan.com/pubs/DSChan_VHT_SG_CSMA-MPR_Whitepaper.pdf Douglas S. Chan, Technologies Delivering Multiuser Transmission for Next-Generation IEEE 802.11 Wireless Networks, November 5, 2007]
* Tae Hyun Kim, Robert W. Heath Jr., Sunghyun Choi, "Multiuser MIMO Downlink with Limited Feedback using Transmit-Beam Matching,", IEEE ICC2008
* [http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_31/docs/Zips/R1-030354.zip 3GPP TSG RAN WG1#31 R1-030354, "Unitary Basis Stream User and Rate Control (PU2RC)"]
* M. Trivellato, F. Boccardi, and H. Huang, [http://www.dei.unipd.it/~trivella/papers/TBH_PIMRC08.pdf "Zero-Forcing vs Unitary Beamforming in Multiuser MIMO Systems with Limited Feedback,"] in Proc. PIMRC 2008, Cannes, France, Sept. 2008.
* K. Huang, J. G. Andrews, and Jr R. W. Heath, “Performance of Orthogonal Beamforming for SDMA with Limited Feedabck,” accepted for publication in IEEE Trans. Vehic. Tech., May 2008.
* N. Ravindran, N. Jindal, and H. Huang, [http://www.ece.umn.edu/~nihar/papers/mimo_bc_los.pdf Beamforming with Finite Rate Feedback for LOS MIMO Downlink Channels] , IEEE Globecom, Nov. 2007.
* Lucent Technologies, [http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_46bis/Docs/R1-062925.zip “Link-level results for nonunitary precoding using zero-forcing in LOS channels,”] 3GPP TSG-RAN WG1
#46-bis, no. R1-062925, Oct. 2006.

Codebook and Signal Processing

* Quantized Principal Component Selection Precoding for Limited Feedback Spatial Multiplexing, 2006 ICC
* System level performance evaluation of spatial multiplexing with per common basis rate control, 2005-fall VTC
* Multimode basis selection for spatial multiplexing with limited feedback, 2005 Electronics Letters

Feature added contributions

* [http://www.eurecom.fr/~gesbert/presentations/federico.ppt F. Boccardi (joint work with H. Huang) MIMO MULTIUSER schemes for downlink transmissions: theoretic bounds and practical techniques]
* “Link-level results for nonunitary precoding using zero-forcing in LOS channels,” 3GPP TSG-RAN WG1 #46-bis, no. R1-062925, Oct. 2006.
* [http://www.freshpatents.com/Structured-codebook-and-successive-beamforming-for-multiple-antenna-systems-dt20070816ptan20070191066.php M. Khojastepour, X. Wang, M. Madihian, Structured codebook and successive beamforming for multiple-antenna systems]
* [http://ieee802.org/16////tgm/contrib/C80216m-08_406.doc MU-MIMO Comparison(C80216m-08_406.doc), May 3, 2008,Intel]

MU-MIMO papers

* [http://www.eurecom.fr/~gesbert/papers/TutorialMUMIMOv3.pdf D. Gesbert, M. Kountouris, R W. Heath Jr., C. B. Chae, T. Sälzer, From Single User to Multiuser Communications: Shifting the MIMO Paradigm]
* [http://www.ll.mit.edu/asap/asap_04/DAY1/14_PR_POOR.PDF V. Poor, Multiuser MIMO Systems]

Internal pages

* Multiple-input multiple-output communications
* Multi-user MIMO as the advanced MIMO communication technology
* Precoding
* Spatial multiplexing

References