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					Project         IEEE 802.20 Working Group on Mobile Broadband Wireless Access
                <http://ieee802.org/20/>
Title           Dynamic PA backoff techniques and SC-FDMA
Date            2007-01-17
Submitted
Source(s)       Jim Tomcik
                Qualcomm Incorporated 5775 Morehouse Drive
                San Diego, California, 92121
                Voice: 858-658-3231
                Fax: 858-658-2113
                E-Mail: jtomcik@qualcomm.com


Re:             Assessment of PAPR effect for MBWA Reverse Link
Abstract        This contribution introduces a scheduling technique that mitigates the effect of PA on spectrum mask
                resulting in a dynamic PA backoff that depends on the scheduled bandwidth. Localized SC-FDMA (LFDMA)
                and OFDMA are compared in the context of dynamic PA backoff in terms of power efficiency, spectrum
                mask margin and interference caused by PA distortion.

Purpose         For consideration of 802.20 in its efforts to adopt an TDD proposal for MBWA.
Notice          This document has been prepared to assist the IEEE 802.20 Working Group. It is offered as a basis for discussion and is not binding
                on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after
                further study. The contributor(s) 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 any
                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 portions 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 also acknowledges and accepts that this contribution
                may be made public by IEEE 802.20.

Patent Policy   The contributor is familiar with IEEE patent policy, as outlined in Section 6.3 of the IEEE-SA Standards Board Operations Manual
                <http://standards.ieee.org/guides/opman/sect6.html#6.3> and in Understanding Patent Issues During IEEE Standards Development
                <http://standards.ieee.org/board/pat/guide.html>.
 January, 2007                                                        doc.: IEEE C802.20-07/05


 Overview - I
     OFDMA has link level advantage over LFDMA
              equalization loss for moderate to high C/I up to 2dB


     L-FDMA has PAPR advantage over OFDMA
              ranging from ~1.5dB for 16QAM to ~2.5dB for QPSK
              PAPR advantage offset by multiplexing multiple waveform


     PAPR advantage of LFDMA is often interpreted as power efficiency
      advantage
              “LFDMA can use a smaller backoff and transmit a higher average
               power that for the same power amplifier (PA) size”
              “hence PAPR advantage = C/I advantage”



Submission                                                                              Slide 2
 January, 2007                                                       doc.: IEEE C802.20-07/05

 Overview - II
     We analyze performance loss of OFDMA versus LFDMA when both
      systems operate at the same backoff value and PA model
              spectral mask margin: measured as proximity to the allowed limit of
               out-of-band emission level
              self distortion: SINR loss seen by the user due to self-interference
               caused by non-linear distortion
              in-band distortion: average SINR loss seen by other users from a user
               that experiences non-linear distortion
              our analysis assumes 5MHz spectrum allocation


     We introduce and analyze a simple mitigation technique that
      reduces the effect of non-linear distortion on spectral mask margin
              mitigation through a simple scheduling rule: no added complexity
              based on the suggested MBWA design
              helps all multiple access schemes, including OFDMA and LFDMA

Submission                                                                             Slide 3
 January, 2007                                                                          doc.: IEEE C802.20-07/05

 Mitigation of mask margin reduction - I
     Out-of-band emission level depends not only on PAPR, but also on
      the total bandwidth spanned by the assignment and proximity of
      this span to the edge of spectrum allocation
              smaller assignment span  lower out-of-band emission level
              further away from the edge  lower out-of-band emission level
     MBWA features subband hopping
              channels within a sub-tree of 128 tones (8 channels) hop locally within
               a subband
              gain through subband scheduling: based on user channel fading
              interference diversity through hopping within a subband



                                                                               base nodes

                                                                                   frequency


                            subband #1   subband #2                  subband #n
                     hops                     sets of 16 contiguous tones
Submission                                                                                                Slide 4
 January, 2007                                                   doc.: IEEE C802.20-07/05


 Mitigation of mask margin reduction - II
    Schedule power limited users predominantly on the inner subbands:
     away from the edge of spectrum allocation
         high QoS users with limited PA size at sector/cell edge
         best effort users at sector/cell edge that are not constrained by
          interference control (user’s TX power limited by a busy bit from adjacent
          sectors)
    Schedule users without power limitation on the remaining spectrum:
         best effort users at sector/cell edge that are constrained by interference
          control (user’s TX power not limited by a busy bit from adjacent sectors)
         users with large enough PA size
         users with high C/I: these users marginally benefit from a further increase
          in C/I
    Subband selection: scheduler takes into account user’s power
     limitation as well as channel selectivity across subbands
    AT adjusts its PA backoff according to its assignment location
Submission                                                                         Slide 5
 January, 2007                                                        doc.: IEEE C802.20-07/05


 Power amplifier model
     We assume a popular Solid State Power Amplifier (SSPA) model
      commonly known as Rapp model
              amplitude distortion given by the following equation

     PA output voltage                                   PA input voltage




                                                                         Rapp model
                                                                          parameter
                     PA saturation level                              typical: P = 2 -- 3


              In this study we assume
              No phase distortion according to Rapp model
              Input PA backoff is w.r.t. 1dB compression point:


              Output PA backoff w.r.t. 1dB compression point

Submission                                                                                  Slide 6
 January, 2007                                                      doc.: IEEE C802.20-07/05

 Spectrum mask margin
     Out of band emission level is measured according to FCC mask
      requirements for MMDS band meets three conditions:
              total transmit power integrated over any contiguous region of 1% of
               bandwidth allocation within 1MHz adjacent to the channel allocation
               should not exceed -13dBm
              total transmit power integrated over 1MHz which is 1MHz away from
               the edge of the channel allocation should not exceed -13dBm
              total transmit power integrated over 1MHz which is 5.5MHz away from
               the edge of the channel allocation should not exceed -25dBm
     Definition of the mask margin
              difference between the allowed and the actual emission level
                 Measurement bandwidth                  PSD at PA output
                                                                     Mask limit




                                                                     Total TX power: 23dBm
              select the worst case margin out of the three conditions
Submission                                                                            Slide 7
 January, 2007                                          doc.: IEEE C802.20-07/05


   Mask margin versus PA backoff




                 User assignment in the edge subband, 16 tones
Submission                                                                Slide 8
 January, 2007                                           doc.: IEEE C802.20-07/05


   Mask margin versus PA backoff



                                                       Note that such a difference
                                                     between OFDMA and LFDMA
                                                     in out-of-band emission level
                                                       is due to scattered OFDMA
                                                      assignment versus localized
                                                          LFDMA assignment for
                                                      assignment sizes >16 tones
                                                      rather than PAPR difference




                 User assignment in the edge subband, 32 tones
Submission                                                                    Slide 9
 January, 2007                                           doc.: IEEE C802.20-07/05

   Mask margin versus PA backoff




                 User assignment in the edge subband, 112 tones
Submission                                                                Slide 10
 January, 2007                                          doc.: IEEE C802.20-07/05

   Mask margin versus PA backoff




                 User assignment in the middle subband, 16 tones
Submission                                                                Slide 11
 January, 2007                                           doc.: IEEE C802.20-07/05

   Mask margin versus PA backoff




                                                     Note that a drastic difference
                                                     between OFDMA and LFDMA
                                                     in out-of-band emission level
                                                       is due to scattered OFDMA
                                                      assignment versus localized
                                                          LFDMA assignment for
                                                      assignment sizes >16 tones
                                                      rather than PAPR difference




                 User assignment in the middle subband, 32 tones
Submission                                                                     Slide 12
 January, 2007                                           doc.: IEEE C802.20-07/05

   Mask margin versus PA backoff




                 User assignment in the middle subband, 128 tones
Submission                                                                Slide 13
 January, 2007                                                    doc.: IEEE C802.20-07/05

Conclusions
     Users scheduled in an edge subband
              for medium and large assignments, OFDMA needs about 2 dB
               additional PA backoff than LFDMA, in order to maintain similar margin
               to the spectral mask
              however, for small assignments, both OFDMA and LFDMA can
               operate with similar PA backoffs, while maintaining adequate
               margin to the spectral mask
     Users scheduled in a middle (interior) subband
              both OFDMA and LFDMA can operate at similar (low) PA backoffs,
               while maintaining (more than) adequate margin to the spectral mask
     By scheduling users in a middle subband, both OFDMA and
      LFDMA maintain sufficient mask margin even at 0dB backoff
              both OFDMA and LFDMA can operate at 0dB backoff
     PAPR disadvantage of OFDMA does not affect its power
      efficiency relative to LFDMA as far as spectrum mask is
      concerned, when users are scheduled away from the edge of
      spectrum allocation
Submission                                                                         Slide 14
 January, 2007                                          doc.: IEEE C802.20-07/05

 Self distortion
     Defined as degradation in C/I of a user caused by non-linear
      distortion of its waveform by PA
                                                     distortion
                                                      power
                        PA distortion
                           model

         unit power
           input
                                                        Receiver




     SINR loss through self distortion


     Signal to distortion ratio


Submission                                                               Slide 15
 January, 2007                                            doc.: IEEE C802.20-07/05


   Signal to distortion ratio versus PA backoff




                 User assignment in the middle subband, 16 tones
Submission                                                                 Slide 16
 January, 2007                                            doc.: IEEE C802.20-07/05


   Signal to distortion ratio versus PA backoff




                 User assignment in the middle subband, 128 tones
Submission                                                                 Slide 17
 January, 2007                                      doc.: IEEE C802.20-07/05


   Self distortion SINR loss versus C/I




User assignment in the middle subband, 16 tones, 0dB output backoff
Submission                                                           Slide 18
 January, 2007                                        doc.: IEEE C802.20-07/05


   Self distortion SINR loss versus C/I




   User assignment in the middle subband, 16 tones, 2dB output backoff
Submission                                                             Slide 19
 January, 2007                                       doc.: IEEE C802.20-07/05


   Self distortion SINR loss versus C/I




  User assignment in the middle subband, 16 tones, 4dB output backoff
Submission                                                            Slide 20
 January, 2007                                        doc.: IEEE C802.20-07/05


   Self distortion SINR loss versus C/I




   User assignment in the middle subband, 16 tones, 6dB output backoff
Submission                                                             Slide 21
 January, 2007                                      doc.: IEEE C802.20-07/05


   Self distortion SINR loss versus C/I




User assignment in the middle subband, 128 tones, 0dB output backoff
Submission                                                           Slide 22
 January, 2007                                      doc.: IEEE C802.20-07/05


   Self distortion SINR loss versus C/I




 User assignment in the middle subband, 128 tones, 2dB output backoff
Submission                                                           Slide 23
 January, 2007                                       doc.: IEEE C802.20-07/05


   Self distortion SINR loss versus C/I




  User assignment in the middle subband, 128 tones, 4dB output backoff
Submission                                                            Slide 24
 January, 2007                                      doc.: IEEE C802.20-07/05


   Self distortion SINR loss versus C/I




User assignment in the middle subband, 128 tones, 6dB output backoff
Submission                                                           Slide 25
 January, 2007                                                        doc.: IEEE C802.20-07/05


Conclusions
     Both OFDMA and LFDMA incur fairly small SINR loss even at low
      backoff values
              OFDMA with 2dB output backoff:
                 less than 0.2dB @ C/I = 0dB, less than 1.2dB @ C/I = 13dB
              L-FDMA with 2dB output backoff:
                 less than 0.1dB @ C/I = 0dB, less than 0.4dB @ C/I = 13dB


     SINR loss at high C/I has limited effect for user throughout
     The advantage of LFDMA at high C/I within 1dB is offset by
      equalization loss of about 1-2dB in this C/I region for relatively large
      assignments




Submission                                                                             Slide 26
 January, 2007                                                         doc.: IEEE C802.20-07/05

 In-band distortion
     Defined as degradation in C/I to other users within subband due to
      increased interference level cased by PA distortion of a given user
                                                          average in-band
                                                          distortion power
                   PA distortion
                      model                             average transmit power

              Note that depends on PA model & backoff, assignment size & location,
               modulation order & multiple access scheme


                  Total RX interference PSD
                                                          Receiver
                          average received in-
                          band distortion PSD

                                                                       Receive C/I of the
                                                                        distorted user

     SINR loss through in-band distortion

        = ratio of user assignment to the remaining bandwidth within subband
Submission                                                                                  Slide 27
 January, 2007                                       doc.: IEEE C802.20-07/05


   In-band distortion SINR loss versus C/I




 User assignment in the middle subband, 122 tones, 0dB output backoff
Submission                                                            Slide 28
 January, 2007                                       doc.: IEEE C802.20-07/05


   In-band distortion SINR loss versus C/I




 User assignment in the middle subband, 122 tones, 2dB output backoff
Submission                                                            Slide 29
 January, 2007                                      doc.: IEEE C802.20-07/05


   In-band distortion SINR loss versus C/I




User assignment in the middle subband, 122 tones, 4dB output backoff
Submission                                                           Slide 30
 January, 2007                                       doc.: IEEE C802.20-07/05


   In-band distortion SINR loss versus C/I




 User assignment in the middle subband, 122 tones, 6dB output backoff
Submission                                                            Slide 31
 January, 2007                                                        doc.: IEEE C802.20-07/05


Conclusions
     Both OFDMA and LFDMA have fairly small SINR loss even at low
      backoff values
              OFDMA with 2dB backoff:
                 less than 0.2dB @ C/I = 0dB, less than 0.9dB @ C/I  13dB
              LFDMA with 2dB backoff:
                 less than 0.1dB @ C/I = 0dB, less than 0.4dB @ C/I  13dB


     The difference between OFDMA and LFDMA w.r.t. in-band
      distortion SINR loss is within 0.5dB for the C/I range of interest
              this is the worst case scenario in terms of in-band distortion. since the
               assignment size was assumed to be large




Submission                                                                             Slide 32
 January, 2007                                                   doc.: IEEE C802.20-07/05


 Observations - I
    LFDMA has advantage over OFDMA in terms of spectrum mask
     margin when power limited users with relatively small size
     assignments get resources close to the edge of spectrum allocation


    Both OFDMA and LFDMA benefit from scheduling power limited
     users in a middle subband in terms of spectrum mask margin


    Both OFDMA and LFDMA have an adequate spectrum mask margin
     when user is scheduled in a middle subband at a very low backoff
     values
          output backoff of 0dB w.r.t. 1dB PA compression point

    LFDMA has ~1dB advantage in self-distortion SINR at high C/I
          this advantage is offset by LFDMA equalization loss (1-2dB) for relatively
           large assignments at high C/I
Submission                                                                        Slide 33
 January, 2007                                                      doc.: IEEE C802.20-07/05

 Observations - II
    The advantage of LFDMA in terms of in-band distortion SINR loss is
     small (within 0.5dB) in the C/I region of interest
          worst case (pessimistic) scenario
    LFDMA suffers equalization loss for large assignments at medium to
     high C/I
    At low C/I and relatively small assignment sizes LFDMA PAPR
     advantage is offset by multiplexing traffic with control
          alternatively time division multiplexing of traffic and control results in a
           permanent link budget hit for either or both of them because of a
           reduced duty cycle
    To maintain PAPR advantage, LFDMA pilot design is limited to a
     narrow family of signals that have low PAPR and flat p.s.d.
          the number of such signals is limited (essentially GCL sequences)
          different sequences should be used in different sectors and/or by
           different overlapping users of the same sector (RL SDMA)
          the use of low PAPR pilot sequences requires careful cell planning
Submission                                                                           Slide 34
 January, 2007                      doc.: IEEE C802.20-07/05




                 System level analysis




Submission                                           Slide 35
 January, 2007                                                doc.: IEEE C802.20-07/05


  Assumptions (I)
  •    Eight cases:
       –     21 dBm Max Output Power (equivalent to 28 dBm PA with 7 dB static
             backoff)
       –     23 dBm Max Output Power (equivalent to 28 dBm PA with 5 dB static
             backoff)
       –     28 dBm PA (Output power at 1 dB compression point), with dynamic
             backoff for OFDMA and LFDMA
             •   Minimum backoff 5 dB
       –     26 dBm PA with dynamic backoff for OFDMA and LFDMA
             •   Minimum backoff 3 dB
       –     23 dBm PA with dynamic backoff for OFDMA and LFDMA
             •   Minimum backoff 0 dB
  •    Dynamic backoff adjusts PA backoff based on assignment size and
       location, so as to maintain an acceptable margin to spectral mask



Submission                                                                      Slide 36
 January, 2007                                                doc.: IEEE C802.20-07/05


  Assumptions (II)
  •    With dynamic PA backoff, max transmit power at the AT is modeled
       as a function of assignment size and location (interior vs. edge
       subband)
  •    Impact of all associated distortions are modeled in the system sim
             •   self-distortion & in-band distortion
  •    Scheduler assigns each user to a subband that provides the largest
       assignment with the user’s max power constraint for that subband
  •    Equalization and diversity losses for LFDMA are not modeled
  •    Simulation assumptions:
       –     Evaluation methodology in the following slides
       –     PedB 3 km/h
       –     4 and 10 users per sector




Submission                                                                     Slide 37
 January, 2007                                                                                       doc.: IEEE C802.20-07/05


  Simulation Parameters
                                                                                    System Parameters
         Network Topology                                      Hexagonal Grid, 19 cells. 3 sectors/cell
         Site-to-Site distance                                 2.0 km
         Carrier Frequency                                     2 GHz
         Bandwidth                                             5 MHz
         Horizontal Antenna Pattern                            70 deg @3 dB bandwidth, 20 dB maximum attenuation.
         Vertical Antenna Pattern                              None
         Propagation Model.                                    Modified urban HATA: PL[dB] = 28.6 + 35log10(D in meter)
         BT-MS Minimum Separation                              35m
         BTS Antenna Height                                    32m
         AT Antenna Height                                     1.5m
         Log-normal Shadowing                                  8.9 dB
         Site-to-Site Shadow Correlation Coefficient           0.5
         Thermal Noise Density                                 –174 dBm/Hz
         Noise Figure                                          10 dB
                        Peak BS Antenna Gain with Cable Loss   15dB
         Total
                        Penetration Loss                       10 dB
         Antenna                                                                                          15 -10 -1 = 4 dB
         Gain           MS Antenna Gain                        -1 dB
         Admission Control                                     140dB path loss




Submission                                                                                                                   Slide 38
 January, 2007                                                                             doc.: IEEE C802.20-07/05


  Simulation Parameters (Cont’d)

                                                                               System Parameters
                          Traffic Model                   Full Buffer
                                       BS Tx/Rx (1/ 2)    IID
         Antenna Correlation           MT Tx/Rx ( 1/2 )   IID
               MT Rx Antenna Gain Mismatch                0 dB
       Channel Profiles                                   Ped B, 3 Km/h

                                                      YODA Numerology
                            FFT size                                    512                        points
                     Subcarrier spacing                                 9.6                         kHz
                          Guard carriers                                32                    subcarriers
                          Cyclic Prefix                                 6.51                        μs
                    Windowing Duration                                  3.26                        μs
                  OFDM Symbol Duration                              113.93                          μs
                   PHY Frame Duration                                    8                  OFDM Symbols
                 HARQ Interlaces (FL/RL)                                 6




Submission                                                                                                  Slide 39
          January, 2007                                                                            doc.: IEEE C802.20-07/05

           4 Users/Sector, System Loading
           Loading Statistics, 2.0 Km Site-to-Site, 2 Rx Antennas, 5 MHz, FDD,
                               4 Mobiles/Sector, PF Fairness                      • System is power limited
           1
                                                                                  • Transmit PSD is determined by
          0.9
                                                                                    delta-based power control
          0.8
                                                                                  • Transmit bandwidth is limited by
          0.7
                                                                                    maximum PA size
                                                                                     – 21 dBm max output power results
          0.6
                                                                                       in 49% bandwidth usage
CDF (%)




                                                       21 dBm Tx Power,
          0.5                                          Avg. = 48.81%                 – 23 dBm max output power results
                                                       23 dBm Tx Power,
          0.4
                                                       Avg. = 55.45%                   in 55% bandwidth usage
                                                       23 dBm PA, OFDMA Dynamic
                                                       Backoff, Avg. = 54.84%
                                                       23 dBm PA, LFDMA Dynamic
                                                                                     – Dynamic PA backoff results in
          0.3
                                                       Backoff, Avg. = 54.90%          54-55% bandwidth usage for
                                                       26 dBm PA, OFDMA Dynamic
          0.2                                          Backoff, Avg. = 54.51%          both OFDMA and LFDMA
                                                       26 dBm PA, LFDMA Dynamic
          0.1
                                                       Backoff, Avg. = 54.86%          (essentially the same as 23
                                                       28 dBm PA, OFDMA Dynamic
                                                       Backoff, Avg. = 54.98%          dBm max output power)
           0                                           28 dBm PA, LFDMA Dynamic
                0       20           40          60    Backoff, Avg. = 55.19%
                                                              80          100
                                      Loading (%)

      Submission                                                                                                    Slide 40
      January, 2007                                                                        doc.: IEEE C802.20-07/05

       4 Users/Sector, User Throughput
                                                                           • 21 dBm max output power is
      Mobile Throughput, 2.0 Km Site-to-Site, 2 Rx Antennas, 5 MHz, FDD,
                         4 Mobiles/Sector, PF Fairness                       shown to have 10% loss in
       1
                                                                             sector throughput compared to
      0.9                                                                    23 dBm max output power
      0.8
                                                                           • Dynamic PA backoff (with 26
                                                                             dBm PA or 28 dBm PA)
      0.7                                                                    achieves almost identical
                                                                             performance as fixed, 23 dBm
      0.6
                                  21 dBm Tx Power,                           max output power
                                  Sector Throughput 3078 Kbps
                                                                           • Same sector throughput
CDF




      0.5                         23 dBm Tx Power,
                                  Sector Throughput 3333 Kbps

      0.4
                                  23 dBm PA, OFDMA Dynamic Backoff,
                                  Sector Throughput 3083 Kbps
                                                                              – Same mobile throughput
                                  23 dBm PA, LFDMA Dynamic Backoff,             fairness
                                  Sector Throughput 3229 Kbps
                                                                           • With 23 dBm PA, dynamic PA
      0.3
                                  26 dBm PA, OFDMA Dynamic Backoff,
                                  Sector Throughput 3271 Kbps
      0.2                         26 dBm PA, LFDMA Dynamic Backoff,          backoff yields a difference of
                                  Sector Throughput 3307 Kbps
                                  28 dBm PA, OFDMA Dynamic Backoff,          less than 5% between LFDMA
                                  Sector Throughput 3306 Kbps
      0.1
                                  28 dBm PA, LFDMA Dynamic Backoff,
                                                                             and OFDMA throughput
                                  Sector Throughput 3335 Kbps
       0
            0    500      1000       1500      2000      2500      3000
                          Mobile Throughput (Kbps)

  Submission                                                                                                Slide 41
      January, 2007                                                                               doc.: IEEE C802.20-07/05

       4 Users/Sector, Resource Allocation
       Normalized Resource Allocation, 2.0 Km Site-to-Site, 2 Rx Antennas,
           5 MHz, FDD, 4 Mobiles/Sector, PF Fairness, Avg. = 1.03            •   Proportional fairness scheduler
       1
                                                                                 tries to equalize the bandwidth
      0.9
                                                                                 resources allocated to each user.
                                                                                  – Edge users are allocated
      0.8                                                                           subcarriers over all interlaces.
                                                                                  – Maximum allocation size is
      0.7                                                                           subjected to PA constraints.
      0.6
                                                                                  – On X-axis: subcarriers allocated for
                                                                                    each user is normalized by the
CDF




      0.5                                                                           average number of subcarriers per
                                                                                    user.
      0.4
                                                                             •   21 dBm max output power results
                                      21 dBm Tx Power
      0.3
                                      23 dBm Tx Power
                                                                                 in fewer subcarriers allocated to
                                      23 dBm PA, OFDMA Dynamic Backoff           the edge users.
      0.2                             23 dBm PA, LFDMA Dynamic Backoff
                                      26 dBm PA, OFDMA Dynamic Backoff       •   Dynamic PA backoff (with a 23
                                      26 dBm PA, LFDMA Dynamic Backoff
      0.1
                                      28 dBm PA, OFDMA Dynamic Backoff
                                                                                 dBm PA) results in similar fairness
       0
                                      28 dBm PA, LFDMA Dynamic Backoff           as 23 dBm max output power.
            0          0.5              1              1.5              2
                         Normalized Resource Allocation


  Submission                                                                                                           Slide 42
      January, 2007                                                                             doc.: IEEE C802.20-07/05

       4 Users/Sector, Decode C/I
             Decode C/I, 2.0 Km Site-to-Site, 2 Rx Antennas, 5 MHz, FDD,
                             4 Mobiles/Sector, PF Fairness
                                                                                • Edge users are often allocated
       1
               21 dBm Tx Power,
                                                                                  the minimum channel size due
      0.9
               Avg. = 7.07 dB                                                     to PA constraints
               23 dBm Tx Power,
               Avg. = 7.08 dB
      0.8
               23 dBm PA, OFDMA Dynamic                                         • Decoding C/I of edge users
               Backoff, Avg. = 6.30 dB
               23 dBm PA, LFDMA Dynamic
                                                                                  reflects the available PA output
               Backoff, Avg. = 6.73 dB
      0.7
               26 dBm PA, OFDMA Dynamic
                                                                                  power
               Backoff, Avg. = 7.06 dB
      0.6      26 dBm PA, LFDMA Dynamic                                         • Dynamic PA backoff provides
               Backoff, Avg. = 7.16 dB
               28 dBm PA, OFDMA Dynamic                                           0.5 to 1 dB C/I gain over 21
CDF




      0.5
               Backoff, Avg. = 7.13 dB
               28 dBm PA, LFDMA Dynamic
                                                                                  dBm
      0.4      Backoff, Avg. = 7.21 dB


      0.3


      0.2


      0.1


       0
        -4       -2      0      2      4      6       8   10     12        14
                                    Decode C/I (dB)


  Submission                                                                                                     Slide 43
      January, 2007                                                                                  doc.: IEEE C802.20-07/05

       10 Users/Sector, User Throughput
      Mobile Throughput, 2.0 Km Site-to-Site, 2 Rx Antennas, 5 MHz, FDD,
                        10 Mobiles/Sector, PF Fairness                     •   System is not power limited; hence PA limitation
       1                                                                       does not impact the total sector throughput.
                                                                           •   Geometric mean throughput:
      0.9
                                                                                –   21dBm Max Output Power: 2475 Kbps
                                                                                –   23dBm Max Output Power: 2790 Kbps
      0.8
                                                                                –   28dBm PA,OFDMA dynamic backoff: 2818 kbps
      0.7                                                                       –   28dBm PA, LFDMA dynamic backoff: 2832 kbps
                                                                                –   26dBm PA, OFDMA dynamic backoff: 2784 kbps
      0.6
                              21 dBm Tx Power,                                  –   26dBm PA, LFDMA dynamic backoff: 2807 Kbps
                              Sector Throughput 4404 Kbps
                                                                                –   23dBm PA, OFDMA dynamic backoff: 2493 Kbps
                              23 dBm Tx Power,
CDF




      0.5
                              Sector Throughput 4380 Kbps                       –   23dBm PA, LFDMA dynamic backoff: 2634 Kbps
                              23 dBm PA, OFDMA Dynamic Backoff,
      0.4                     Sector Throughput 3953 Kbps                  •   Improved geometric mean throughput shows
                              23 dBm PA, LFDMA Dynamic Backoff,                fairness gain of 23dBm output power over
                              Sector Throughput 4162 Kbps                      21dBm output power
      0.3                     26 dBm PA, OFDMA Dynamic Backoff,
                              Sector Throughput 4342 Kbps                  •   Dynamic PA backoff with 26 and 28 dBm PA
      0.2
                              26 dBm PA, LFDMA Dynamic Backoff,                (1dB comp. point) achieves almost identical
                              Sector Throughput 4367 Kbps                      performance as fixed 23 dBm output power
                              28 dBm PA, OFDMA Dynamic Backoff,
      0.1                     Sector Throughput 4402 Kbps                  •   With 23 dBm PA (1dB comp. point) and
                              28 dBm PA, LFDMA Dynamic Backoff,                dynamic PA backoff, the difference in the
                              Sector Throughput 4398 Kbps                      LFDMA and OFDMA throughput is only 5%
       0
            0    500      1000       1500      2000      2500      3000
                          Mobile Throughput (Kbps)

  Submission                                                                                                           Slide 44
          January, 2007                                                                                             doc.: IEEE C802.20-07/05


          10 Users/Sector, Loading and Resource Allocation
           Loading Statistics, 2.0 Km Site-to-Site, 2 Rx Antennas, 5 MHz, FDD,          Normalized Resource Allocation, 2.0 Km Site-to-Site, 2 Rx Antennas,
                               10 Mobiles/Sector, PF Fairness                               5 MHz, FDD, 10 Mobiles/Sector, PF Fairness, Avg. = 1.08
           1                                                                            1
                       21 dBm Tx Power, Avg. = 85.60%
                       23 dBm Tx Power, Avg. = 89.97%
          0.9                                                                          0.9
                       23 dBm PA, OFDMA Dynamic Backoff,
                       Avg. = 91.11%
          0.8          23 dBm PA, LFDMA Dynamic Backoff,                               0.8
                       Avg. = 90.53%
                       26 dBm PA, OFDMA Dynamic Backoff,
          0.7          Avg. = 89.89%                                                   0.7
                       26 dBm PA, LFDMA Dynamic Backoff,
                       Avg. = 89.95%
          0.6                                                                          0.6
                       28 dBm PA, OFDMA Dynamic Backoff,
                       Avg. = 90.21%
CDF (%)




                       28 dBm PA, LFDMA Dynamic Backoff,




                                                                                 CDF
          0.5                                                                          0.5
                       Avg. = 90.34%

          0.4                                                                          0.4


          0.3                                                                          0.3                       21 dBm Tx Power
                                                                                                                 23 dBm Tx Power
                                                                                                                 23 dBm PA, OFDMA Dynamic Backoff
          0.2                                                                          0.2                       23 dBm PA, LFDMA Dynamic Backoff
                                                                                                                 26 dBm PA, OFDMA Dynamic Backoff
          0.1                                                                          0.1                       26 dBm PA, LFDMA Dynamic Backoff
                                                                                                                 28 dBm PA, OFDMA Dynamic Backoff
                                                                                                                 28 dBm PA, LFDMA Dynamic Backoff
           0                                                                            0
                0       20           40          60           80          100                0   0.5       1       1.5       2       2.5       3        3.5
                                      Loading (%)                                                         Normalized Resource Allocation


      Submission                                                                                                                                   Slide 45
        January, 2007                                                                                                doc.: IEEE C802.20-07/05

         10 Users/Sector, IoT and and Decode C/I
       IoT, 2.0 Km Site-to-Site, 2 Rx Antennas, 5 MHz, FDD, 10 Mobiles/Sector,               Decode C/I, 2.0 Km Site-to-Site, 2 Rx Antennas, 5 MHz, FDD,
         0
                                      PF Fairness                                                           10 Mobiles/Sector, PF Fairness
       10                                                                               1
                                                      21 dBm Tx Power,
                                                      Avg. = 5.92 dB
                                                      23 dBm Tx Power,                 0.9
                                                      Avg. = 6.16 dB
                                                      23 dBm PA, OFDMA Dynamic
                                                      Backoff, Avg. = 6.19 dB          0.8
                                                      23 dBm PA, LFDMA Dynamic
                                                      Backoff, Avg. = 6.26 dB
                                                                                       0.7
                                                      26 dBm PA, OFDMA Dynamic
                                                      Backoff, Avg. = 6.13 dB
                                                      26 dBm PA, LFDMA Dynamic         0.6
                                                      Backoff, Avg. = 6.25 dB
                                                      28 dBm PA, OFDMA Dynamic                                                         21 dBm Tx Power,
CCDF




                                                                                 CDF
         -1
       10                                             Backoff, Avg. = 6.13 dB          0.5                                             Avg. = 5.43 dB
                                                      28 dBm PA, LFDMA Dynamic                                                         23 dBm Tx Power,
                                                      Backoff, Avg. = 6.26 dB                                                          Avg. = 5.34 dB
                                                                                       0.4
                                                                                                                                       23 dBm PA, OFDMA Dynam
                                                                                                                                       Backoff, Avg. = 4.35 dB
                                                                                       0.3                                             23 dBm PA, LFDMA Dynam
                                                                                                                                       Backoff, Avg. = 4.82 dB
                                                                                                                                       26 dBm PA, OFDMA Dynam
                                                                                       0.2                                             Backoff, Avg. = 5.31 dB
                                                                                                                                       26 dBm PA, LFDMA Dynam
                                                                                                                                       Backoff, Avg. = 5.39 dB
                                                                                       0.1
                                                                                                                                       28 dBm PA, OFDMA Dynam
                                                                                                                                       Backoff, Avg. = 5.41 dB
       10
         -2
                                                                                        0                                              28 dBm PA, LFDMA Dynam
              0   2       4       6       8      10       12    14      16                   -5              0               5         Backoff, Avg. = 5.41 dB
                                                                                                                                            10
                                      IoT (dB)                                                                    Decode C/I (dB)


       Submission                                                                                                                                Slide 46
 January, 2007                                                 doc.: IEEE C802.20-07/05


  Conclusions
    • With PA sizes of 28 dBm and 26 dBm (at 1 dB compression point),
      OFDMA and LFDMA with their corresponding dynamic PA backoff
      values achieve a performance almost identical to the fixed, 23 dBm
      max output power (28 dBm PA with 5 dB fixed backoff)
         – Same sector throughput
         – Same fairness among users
    • With PA size of 23 dBm and dynamic PA backoff with a minimum
      backoff value of 0 dB, the difference in the LFDMA and OFDMA
      throughputs is at most 5%
    • OFDMA reverse link provides link performance gains at high SNR
      (not included in the above analysis)

    • OFDMA reverse link provides much better design flexibility
         – Different types of waveforms (pilot tones, control channel segments etc)
           may be frequency-multiplexed, without incurring additional PAPR
           penalties
         – Can be exploited to improve handoff performance, control-channel link
           budget etc

Submission                                                                      Slide 47

				
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