Uplink MIMO proposal for IEEE 802.16m

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					                                           Uplink MIMO proposal for IEEE 802.16m

Document Number: C80216m-08/538
Date Submitted: 2008-07-06
Source:
   Yang-seok Choi[1]
   Alexei Davydov[2]                       Voice:      +1 503 712 1773 [1], +7 831 4162444[2]
   Alexander Maltsev[2]                    E-mail:      yang-seok.choi@intel.com, alexei.davydov@intel.com, alexander.maltsev@intel.com
   Intel Corporation
   [1] Portland, OR, US
   [2] Russia, Nizhny Novgorod, Ul. Turgeneva, 30

Venue:
   Call for contributions on project 802.16m SDD: Uplink MIMO
   Session #56: Denver, USA
Base Contribution:
   IEEE C80216m-08/538
Purpose:
   For discussion and adoption by IEEE 802.16m group
Notice:
   This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups . It represents only the views of the participants listed in
   the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material
   contained herein.
Release:
   The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and an y modifications thereof, in the creation of an
   IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portion s of this contribution; and at the IEEE’s
   sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor a lso acknowledges and accepts that this
   contribution may be made public by IEEE 802.16.
Patent Policy:
   The contributor is familiar with the IEEE-SA Patent Policy and Procedures:
                                     <http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and <http://standards.ieee.org/guides/opman/sect6.html#6.3>.
   Further information is located at <http://standards.ieee.org/board/pat/pat-material.html> and <http://standards.ieee.org/board/pat >.
                      Generic Block Diagram for UL MIMO
                                                                                                        Precoded Antenna
                                                                                                            Symbols


         Data bits                                 QAM Symbols                         Number of
                                                                                     Spatial Channels
                                                                                           NSCH

                                                                                                                       OFDMA
                                                                                                                      Modulation




                                                            MIMO Mapping
 Data                                                                          MIMO               MIMO
                     FEC encoder            Modulation                        Encoding          Precoding
Stream

                                                                                                                       OFDMA
                                                                                                                      Modulation


                                                              Number of                                     Number of
                                                            Spatial Streams                             Transmit Antennas
                               Coded bits
                                                                  NSS                                         NT X



                                                                                    Space Frequency
                                                                                    (Time) Encoded
                                                                                        Symbols

                                                                                                                                    2
                                                                                                                  IEEE C802.16m-08/538
                  Space Frequency Block Codes

                          s1       s2 
                                      *
                                                               s1 
                       A           * 
                                                            B 
                          s2       s1                        s2 

                             Rate – 1                       Rate – 2



•   In accordance to IEEE 802.16m system requirement document the system shall
    support the connection up to the highest supported speed of 350 kmph
•   Space Time Block Code (STBC) is not appropriate for such high speeds due to
    orthogonally loss in fast channel fading
•   Space-frequency Block Code (SFBC) should be considered as a baseline scheme
    for IEEE 802.16m due to it’s robustness to the mobility
•   Space Frequency Block Codes offers other advantages:
     – Less buffering requirements – the decoding is performed for single OFMDA symbol
     – Flexible to any frame structure design – easy to satisfy the requirement on even number
       interval transmissions
                                                                                                 3
                                                                               IEEE C802.16m-08/538
          SFBC Link Layer Performance
Baseline SIMO in Ped.-B (3kmph)    STC-A SFBC in Ped.-B (3kmph)




STC-A SFBC in Veh.-A (60 kmph)    STC-A SFBC in Veh.-A (120 kmph)




                                                                       4
                                                     IEEE C802.16m-08/538
SFBC Link Layer Performance (Cont’d)

  s      s2 
            *
                              s1 
A 1      * 
                           B 
   s2    s1                 s2 




 Matrix A rank-1          Matrix B rank-2
  transmission             transmission

                                                        5
                                      IEEE C802.16m-08/538
                                            Collaborative MIMO
                                     s1                                                  s1 ,  s2
                                                                                                 *
                                                                                                                                      s1 ,  s2
                                                                                                                                              *




                                                                                                                               MS 1
                                                                                  MS 1
Base Station




                                                   Base Station
                                     MS 1




                                                                                                     Base Station
                                                                                               *                                             *
                                                                                         s2 , s1                                       s2 , s1
                                     MS 2

                                                                                                                                      s3 ,  s 4
                                                                                                                                               *




                                                                                  MS 2
                                                                                           s3




                                                                                                                               MS 2
                                    s2                                                                                                       *
                                                                                                                                      s 4 , s3
               •   The UL network capacity is limited by the peak data rate of MS due to
                    –   channel bandwidth, small modulation order and transmit power limitations
                    –   small number of transmit antennas at the MS due to
                         •   small form factor of hand held MS devices
                         •   higher implementation cost of multiple power amplifiers
               •   Collaborative MIMO is an effective solution to increase the network capacity in the UL for
                   such scenario
                    –   collaborative MS may reuse the same time-frequency resource and transmit data simultaneously
                    –   collaborative MS uses orthogonal pilot allocation to enable MIMO processing at the BS
               •   The efficiency of interference mitigation at the BS is provided by
                    –   proper scheduling of collaborative MS
                    –   rich direction of arrival distribution of received signal energy at the BS
               •   Codebook precoding may be used to improve the efficiency of collaborative MIMO                                       6
                                                                                                                    IEEE C802.16m-08/538
Collaborative MIMO Link Layer Performance

    Collaborative MIMO                                  Spatial Multiplexing




            Further gain of collaborative MIMO over SU-MIMO
            spatial multiplexing may be achieved by proper MS
                            scheduling and pairing
                                                                                   7
                                                                 IEEE C802.16m-08/538
          UL MIMO Codebook Based Precoding

                                                                     s1




                                                                MS
•                                  Base Station
    The usage of the precoding at the MS is essential to achieve IEEE 802.16m requirements
•   Codebook precoding should be used in conjunction with SU MIMO and Collaborative MIMO
•   Legacy IEEE802.16e codebook is not constant modulus scheme and causes antenna power
    imbalance problem for power limited MS
•   Low PAPR codebooks constructions is required for IEEE 802.16m UL MIMO
     –   Constant amplitude with antenna subset selection codebook (see next slide)
     –   Example 1-TX (4 antenna MS) rate-1 antenna selection codebook construction
                           1               0         0               0 
                           0               1         0               0 
                      V0             V1       V2             V3   
                           0               0         1               0 
                                                                      
                           0               0         0               1 
•   Codebook based precoding procedure
     –   MS performs uplink sounding
     –   BS determines the precoding vector from channel state information
     –   BS signals the precoder index assigned for UL transmission using UL control channel               8
                                                                                         IEEE C802.16m-08/538
  Constant Amplitude with Antenna Subset Selection
              Codebook Construction
                                    Selection of the TX
                                      antenna subset
            Constant amplitude                            Constant amplitude
          codebook with antenna                           baseline codebook
             subset selection



                                  Vissj  Pi  Vj
                                    ,



                                     Antenna selection       Precoding on selected
                                          matrix                antenna subset


• Advantages of the proposed codebooks
   –   Low PAPR
   –   Structured construction
   –   Easy extensible to any number of MS antennas
   –   Optimized to low power MS
   –   Limits the actual number of transmitting antenna
                                                                                            9
                                                                          IEEE C802.16m-08/538
Precoding Link Layer Performance




                                              10
                              IEEE C802.16m-08/538
   Summary of Proposed Uplink MIMO Modes

• SU-MIMO
    – Rate 1
       • Transmit Diversity
       • Space Frequency Block Code (SFBC)
       • Open loop and codebook precoding
    – Rate 2
       • Spatial Multiplexing
       • Single Codeword (SCW)
       • Open loop and codebook precoding
• MU-MIMO
       • Up to four collaborative MS
       • Open loop and precoded collaborative MIMO
• Two stage codebook precoding based on constant amplitude and antenna
  subset selection codebooks
                                                                           11
                                                           IEEE C802.16m-08/538
                        Proposed Text for SDD (Cont’d)
Text Proposal for the 802.16m SDD
--------------------- Start of proposed text ---------------------

11.x UL MIMO Transmission Scheme

11.x.1 Generic UL MIMO Architecture
The generic architecture of the UL multiple antenna transmitter is shown in Figure XXX

                                                                                                        Precoded Antenna
                                                                                                            Symbols


           Data bits                                QAM Symbols                        Number of
                                                                                     Spatial Channels
                                                                                           NSCH

                                                                                                                       OFDMA
                                                                                                                      Modulation

                                                             MIMO Mapping
   Data                                                                        MIMO               MIMO
                       FEC encoder           Modulation                       Encoding          Precoding
  Stream

                                                                                                                       OFDMA
                                                                                                                      Modulation


                                                              Number of                                     Number of
                                                            Spatial Streams                             Transmit Antennas
                                Coded bits                                                                    NTX
                                                                  NSS



                                                                                   Space Frequency
                                                                                   (Time) Encoded
                                                                                      Symbols
                             Figure XXX. Generic Uplink MIMO transmitter architecture

11.x.1.1. UL MIMO Mapping
The UL MIMO Mapping block performs QAM symbols to spatial stream mapping function.

11.x.1.2. UL MIMO Encoding
The UL MIMO Encoding block performs spatial stream to spatial channel encoding function.

11.x.1.3. UL MIMO Precoding
                                                                                                                                                   12
The UL MIMO Precoding block performs spatial channel to physical antenna precoding function.
                                                                                                                                   IEEE C802.16m-08/538
                    Proposed Text for SDD (Cont’d)
11.x.1. UL MIMO Transmission

11.x.1.1. Single-user MIMO
Single-user MIMO (SU-MIMO) is used to improve the MS link performance and increase the MS
peak data rate.

11.x.1.1.1. Open-loop Single-user MIMO
Open-loop SU-MIMO transmission scheme is optimized for high mobility scenario.

11.x.1.1.1.1. Transmit Diversity
Transmit Diversity is used to improve link performance using multiple antenna transmission. Space-
Frequency Block Coding is a baseline UL SU-MIMO transmission scheme.

11.x.1.1.1.2. Spatial Multiplexing
Spatial Multiplexing is used to increase the MS peak data rate using multiple antenna transmission.

11.x.1.1.2. Closed-loop Single-user MIMO
Closed-loop SU-MIMO transmission scheme is optimized for low and moderate mobility scenario.

11.x.1.1.2.1. Precoding
Codebook precoding is used as a baseline precoding scheme for UL MIMO. Code book design
criteria for UL MIMO are based on minimization of antenna power imbalance, limitation of actual
transmitting antennas, link performance enhancement and feedback signaling overhead reduction.

11.x.1.1.2.2. Sounding
MS performs UL channel sounding to enable channel state information estimation at the BS.

11.x.1.2. Multi-user MIMO
Multi-user MIMO (MU-MIMO) is used to increase the network capacity. Multiple MS may
concurrently transmit the data using the same resource unit. MS’s operating in MU-MIMO mode use
orthogonal pilot allocation to enable MIMO processing at the BS.

11.x.1.2.1. Open-loop Multi -user MIMO
Open-loop MU-MIMO transmission scheme is optimized for high mobility scenario.

11.x.1.2.2. Closed-loop Multi -user MIMO                                                                              13
Closed-loop MU-MIMO transmission scheme is optimized for low and moderate mobility scenario.          IEEE C802.16m-08/538
--------------------- End of proposed text ---------------------

				
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