Per-user unitary rate control: Difference between revisions

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Per-User Unitary Rate Control (PU²RC) is the advanced multi-user [[MIMO]] technique which utilizes the concept of both pre-coding matrices and scheduling to enhance the system performance of multiple antenna wireless networks.

{{Use dmy dates|date=October 2017}}

'''Per-user unitary rate control''' ('''PU²RC''') is a multi-user [[MIMO]] (multiple-input and multiple-output) scheme. PU²RC uses both transmission pre-coding and multi-user scheduling. By doing that, the network capacity is further enhanced than the capacity of the single-user MIMO scheme.

;* Background technologies: A single-user MIMO was initially developed to improve the spectral efficiency of point-to-point wireless transmission link. A multi-user MIMO was developed for cellular systems where the base station simultaneously communicates with multiple users.

;* Principle: The concept of Per-User Unitary Rate Control (PU²RC) was proposed in [http://www.google.com/patents/about?id=lpWnAAAAEBAJ&dq=7,324,480 US Patent No. 7,324,480, ''Mobile communication apparatus and method including base station and mobile station having multi-antenna''] by James S. Kim, Kwang Bok Lee, Kiho Kim and Changsoon Park.

Recently, PU²RC has been adopted in the IEEE 802.16m system description documentation (SDD) and the concept of this scheme was included in 3GPP [[3GPP Long Term Evolution|LTE]] standard.

==Technology==

Per-user unitary rate control (PU²RC) is a practical multi-user [[MIMO]] solution. PU²RC allows a base station to transmit different data streams to multiple users simultaneously. The base station selects target users from candidate users based on the information fed by users. Transmission data are multiplied by a pre-coding matrix selected from the set of predefined matrices before transmission. The selection of a pre-coding matrix is determined based on the information provided by users. The selection of both target users and a pre-coding matrix according to the information provided by mobiles enables the utilization of multi-user diversity and data multiplexing at the same time. Moreover, using predefined precoding matrices reduces feedback overhead from users to the base station. Pre-coding matrices used in this scheme is unitary. The use of unitary pre-coding matrices facilitates the estimation of interference from other users' data to the unintended user.

Per-User Unitary Rate Control (PU²RC) is the first practical multi-user MIMO scheme. In this scheme different data may simultaneously be transmitted to multiple users from the base station.

Users to be served are selected from the set of service-requesting users by the base station using the information provided by users.

Data transmitted to mobile users are multiplied by a pre-coding matrix selected from the set of predefined matrices before transmission. The selection of a pre-coding matrix is made based on the information provided by users.

The selection of users and a pre-coding matrix using the information provided by mobiles enables the utilization of multi-user diversity and reduces feedback overhead from users to the base station.

Pre-coding matrices used in this scheme is unitary. The use of unitary pre-coding matrices facilitates the estimation of interference from other users’ data to the unintended user.

==Mathematical description==

The operation isof describedPU²RC is mathematically belowdescribed for the transmitter and receiver sidesides, respectively.

[[Image:Pu2rc over single user.png|thumb|400px|right|Throughput performance of PU²RC over the single-user & no scheduling scheme]]

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

===TransmitterBase Sidestation===

TheIt transmitteris antennaassumed arraythat hasthe base station employs <math>N_t</math> elementstransmission antennas. The transmit<math>N_t \times 1</math> transmission signal vector is modeled asgiven follows:by

:<math> \mathbf{x} = \sum_{i=1}^K \mathbf{w}_i P_i s_i</math>

where <math>\mathbf{x}</math> is the <math>N_t \times 1</math> vector of transmitted symbols and <math>\mathbf{w}_i</math> is the <math>N_t \times 1</math> linear precoding vector. PU²RC generates <math>{\mathbf{w}_i}</math> based on the received finite channel status information, which is delivered to the base station byfrom the user equipment (UE) usingthrough auplink feedback signaling. The feedback signal consists of index codedin a look-up table indexof a precoding codebook.

===Receiver Sideside===

Every receiver has a receive antenna array with <math>N_r</math> elements. The receive signal vector at user <math>k (=1,2,\ldots,K)</math> is modeled as follows:

:<math>\mathbf{y}_k = \mathbf{H}_k\mathbf{x}+\mathbf{n}_k</math>

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===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., <math>(G=1)</math>. 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.

==PU²RC Source and Background Materials==

=== Source Materials ===

* James S. Kim, K. B. Lee, et al., Mobile communication apparatus and method including base station and mobile station having multi-antenna, US PTO 7,324,480

* [http://mobile.snu.ac.kr/mcl_list/papers/journal/IEICEtcomm_200608_sjkim_hjkim_cspark_kblee.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.]

* 3GPP TSG RAN WG1#31 R1-030354, [http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_31/docs/Zips/R1-030354.zip Per unitary basis stream user and rate Control (PU2RC)], 3GPP TSG-R1-030354, Tokyo, Fed 18-21, 2003. (See also R1-030130)

* Samsung, SNU, [http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_44/Docs/R1-060335.zip “Downlink MIMO for EUTRA,” in 3GPP TSG RAN WG1 # 44/R1-060335]

=== Enhanced Methods ===

* [http://mobile.snu.ac.kr/mcl_list/papers/conference/ew200504_sjkim_hjkim_kblee.pdf Multiuser MIMO Scheme for Enhanced 3GPP HSDPA]

* Kim, J.S., Hojin Kim, Yongxing Zhou, Jianjun Li, ``Multi-Mode Multi-User MIMO System with Finite Rate Feedback'', IEEE Wireless Communication Systems, 2006. ISWCS '06. 3rd International Symposium on, 6-8 Sept. 2006

===Background References===

* 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.&nbsp;1194 -1199, vol.2, Pacific Grove, California, Nov. 4 - 7, 2001.

* 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.

* 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

* Further benefits of the revised definition of CQI for TxAA, 3GPP TSG-R1-030130, San Diego, Jan. 7-10, 2003.

== MU-MIMO Standard Contributions ==

The following documents are standard contributions about both PU2RC related and general MU-MIMO issues.

=== General MU-MIMO issues ===

# [http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_49/Docs/R1-072464.zip 3GPP, R1-072464, MU-MIMO for E-UTRA DL, Ericsson]

# [http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_49/Docs/R1-072513.zip 3GPP, R1-072513, Details on MU-MIMO, Freescale Semiconductor]

# [http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_49/Docs/R1-072514.zip 3GPP, R1-072514, Codebook design for MU-MIMO, Freescale Semiconductor]

# [http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_49/Docs/R1-072515.zip 3GPP, R1-072515, Reference Signalling for MU-MIMO, Freescale Semiconductor]

=== PU2RC related issues ===

# [http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_31/docs/Zips/R1-030354.zip 3GPP TSG RAN WG1#31, R1-030354, Per unitary basis stream user and rate Control (PU2RC), 3GPP TSG-R1-030354, Tokyo, Fed 18-21, 2003. (See also R1-030130)]

# [http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_44/Docs/R1-060335.zip 3GPP, TSG RAN WG1#44/R1-060335 “Downlink MIMO for EUTRA,” Samsung and SNU]

# [http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_49/Docs/R1-072401.zip 3GPP, R1-072401, User Grouping Method for PU2RC Downlink MU-MIMO, Alcatel-Lucent]

==See also==

===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

=== Wikipedia Articles ===

* [[Multiple-input multiple-output communications]]

* [[Multi-user MIMO]] as the advanced MIMO communication technology

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* [[Spatial multiplexing]]

===Background References===

===MU-MIMO papers===

* James S. Kim, K. B. Lee, et al., Mobile communication apparatus and method including base station and mobile station having multi-antenna, US PTO 7,324,480

* [http://mobile.snu.ac.kr/mcl_list/papers/journal/IEICEtcomm_200608_sjkim_hjkim_cspark_kblee.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.]

* 3GPP TSG RAN WG1#31 R1-030354, [http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_31/docs/Zips/R1-030354.zip Per unitary basis stream user and rate Control (PU2RC)], 3GPP TSG-R1-030354, Tokyo, Fed 18-2118–21, 2003. (See also R1-030130)

* Samsung, SNU, [http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_44/Docs/R1-060335.zip “Downlink"Downlink MIMO for EUTRA,”" in 3GPP TSG RAN WG1 # 44/R1-060335]

* [http://mobile.snu.ac.kr/mcl_list/papers/conference/ew200504_sjkim_hjkim_kblee.pdf Multiuser MIMO Scheme for Enhanced 3GPP HSDPA]

* Kim, J.S., Hojin Kim, Yongxing Zhou, Jianjun Li, `'`Multi-Mode Multi-User MIMO System with Finite Rate Feedback'', IEEE Wireless Communication Systems, 2006. ISWCS '06. 3rd International Symposium on, 6-86–8 Sept.Sep 2006''

* 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.&nbsp;1194 -1199–1199, vol.2, Pacific Grove, California, 4–7 Nov. 4 - 7, 2001.

* A. Kogiantis and L. Ozarow, "Downlink best-effort packet data with multiple antennas," ICC’03ICC'03, Volume 1, 11-1511–15 May 2003 Page(s):715 -– 719.

* 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

* Further benefits of the revised definition of CQI for TxAA, 3GPP TSG-R1-030130, San Diego, 7–10 Jan. 7-10, 2003.

==Further reading==

* [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]

#*[https://web.archive.org/web/20110722145413/http://www.ieee.li/pdf/viewgraphs/wireless_mimo.pdf Dr. Jacob Sharony, "Introduction to Wireless MIMO – Theory and Applications", IEEE LI, 15 November 15, 2006]

#*[http://www.ll.mit.edu/publications/journal/pdf/vol15_no1/15_1mimo.pdf Daniel W. Bliss, Keith W. Forsythe, and Amanda M. Chan, MIMO Wireless Communication, VOLUME 15, NUMBER 1, 2005 LINCOLN LABORATORY JOURNAL]

===KNOL Article===

* [http://knol.google.com/k/james-sungjin-kim/pu2rc/2ycwib2vxc76q/90 Kim, James Sungjin. PU2RC:Per-user unitary and rate control (Web). Version 4. Knol. 2009 Oct 17. Available from: http://knol.google.com/k/james-sungjin-kim/pu2rc/2ycwib2vxc76q/90.]

==MIMO Literature==

#[http://www.ieee.li/pdf/viewgraphs/wireless_mimo.pdf Dr. Jacob Sharony, "Introduction to Wireless MIMO – Theory and Applications", IEEE LI, November 15, 2006]

#[http://www.ll.mit.edu/publications/journal/pdf/vol15_no1/15_1mimo.pdf Daniel W. Bliss, Keith W. Forsythe, and Amanda M. Chan, MIMO Wireless Communication, VOLUME 15, NUMBER 1, 2005 LINCOLN LABORATORY JOURNAL]

[[Category:3GPP]]

[[Category:IEEE 802]]

[[Category:Information theory]]

[[Category:Radio resource management]]

[[ko:PU2RC]]