Requirements, concept and design of uplink symbol structure for 802.16m
Document Number: IEEE S802.16m-08/266
Date Submitted: May-05-2008
Source:
Yuval Lomnitz
Huaning Niu
Jong-kae (JK) Fwu
Sassan Ahmadi
Hujun Yin
Intel Corp.
Yuval.Lomnitz@intel.com
Huaning.Niu@intel.com
Jong-kae.Fwu@intel.com
Sassan.Ahmadi@intel.com
Hujun.Yin@intel.com
Venue:
IEEE Session #55, Macau.
Base Contributions:
This presentation supports four contributions:
IEEE C80216m-08/266: UL symbol structure design for 802.16m -- symbol structure and pilot design
IEEE C80216m-08/267: UL symbol structure design for 802.16m – mixed network support
IEEE C80216m-08/268: UL symbol structure design for 802.16m – tile selection and pilots
IEEE C80216m-08/269: UL symbol structure design for 802.16m – hopping localized transmission to improve TX power
Purpose:
For discussion as introduction to base contributions
Notice:
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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.
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Table of Content
• Section 1:
– 802.16m UL symbol structure design -- symbol structure and pilot design.
– Supporting material for “IEEE C80216m-08/266”
• Section 2:
– 802.16m UL symbol structure: mixed network support (Multiplexing
Schemes).
– Supporting material for “IEEE C80216m-08/267”
• Section 3:
– 802.16m UL symbol structure: Tile selection and pilot design
– Supporting material for “IEEE C80216m-08/268”
• Section 4:
– 802.16m UL symbol structure: Hopping Localized Allocation to
Improve UL Tx Power
– Supporting material for “IEEE C80216m-08/269”
2
Section 1
802.16m UL symbol structure:
Symbol Structure and Pilot Design
Supporting material for “IEEE C80216m-08/266: UL symbol structure
design for 802.16m”
3
Scope and methodology
•
This contribution proposes an initial symbol structure concept and design
for uplink 802.16m
Symbol structure includes:
•
1. Subchannelization:
– logical resource block definition
– mapping slots to physical subcarriers (“permutation”)
2. Pilots
The two aspects are tightly related
•
Relation between symbol structure and PHY functionality
–
–
–
Symbol structure is a tool to support PHY functionality (such as various
MIMO modes, interference mitigation, etc), so is dependent on this
functionality
However symbol structure affects feasibility of PHY features and a baseline
symbol structure is needed to unify simulation assumptions and align
thoughts
To solve this tie we need to iterate between structure and functionality
Structure
Function
4
Key points (1)
• General Concepts
– Design symbol structure to support broadly potential PHY features
(FFR, collaborative MIMO, precoding, etc) with considerable
flexibility
– Based on SRD explicit and derived requirements and trade-offs
– Allow flexibility to add future advanced features
• Symbol Structure and Resource Blocks
– Hierarchical symbol structure for dynamic and effective resource
allocation.
– Support FDM with 16e AMC, TDM with 16e PUSC
– Support 3 types of resource allocations: distributed, localized and
hopping localized
– UL is tile based but with different tiles than 802.16e
5
Key points (2)
• Pilot Design
– Optimize the tradeoff between diversity and pilot efficiency for
distributed resources
– Optimized for collaborative MIMO as main mode (rather than for
SISO), resulting in larger tiles
– Reuse the same pilot pattern as DL for localized resources
– Support different MIMO modes, # of antennas, and # of streams
– Pilot patterns obtained by computer optimization with manual finetuning
• Specific SDD texts are proposed for
– UL Symbol Structure and general concepts
– Various types of UL logical resource blocks
– UL Pilot patterns for distributed/localized/hopping localized resources
6
Contents of this contribution
• Requirements and tradeoffs
• Overview UL resource block and
subchannelization
• Multiplexing scheme for mixed network
support
• Tile size selection and pilot optimization for
distributed resources
• HL OFDMA for power boosting
• Review of text proposal
7
Requirements
8
PHY functions
• Localized/distributed resources
• Open-loop SISO and MIMO transmission with 2 and 4
antennas
• UL precoding/beamforming for multi TX antenna MS
• Collaborative MIMO
– Collaborative spatial multiplexing, with 2,4 RX antennas, and 1,2 TX
antennas
•
•
•
•
•
FFR (reuse partitioning)
Relay
Multi-carrier support
Power control
PAPR reduction
9
Derived Requirements and tradeoffs
Requirements related to frame structure [7,8]
• Fixed-duration 6 symbol subframe
• Multiplexing with 16e network
– Minimize the 16e link budget and performance loss
– Optimize 16m performance
– Desired: Mixed mode should be the superset and greenfield
(WiMAX 2 only) a subset of this mode
10
Overview of UL Resource Unit and
Subchannelization
11
UL Symbol Structure Summary
• Hierarchical UL Physical Structure for support of FFR by
frequency partitions
• Three type of resources:
– Localized:
PRU/LRU size: 18x6
– Diversity:
PRU/LRU size: 18x6, Tile sizes: 9x3
– Hopping Localized (HL): Hopping unit size (18x3)
 Multiplexing with 16e
 Diversity and pilot tradeoff
 HL for Tx power
• HL inside freq partition or separate freq partition for HL only
• n chunks of (18m x 6) are reserved for hopping users, where n is an even
number, m is the maximum subchannels for a single HL user
• UL Control:
– Support 16m CQICH, ACKCH and ranging
– Support control in both diversity, localized zone, and HL
• Allocation order: Hopping Localized / Localized  Diversity
12
Hierarchical UL Physical Structure
Entire
subframe
Frequency
Partition 2
Frequency
Partition 1
Hopping
Localized
Distributed
Localized
Multi cell
Cell/
sector
User
Sc9 Sc8 Sc7
Sc6 Sc5 Sc4 Sc3 Sc2 Sc1
13
UL Slot Allocation Process
(2)
Distribute clusters to
localized and diversity
groups
(3)
Distribute subcarriers
to subchannels (LRUs)
Freq. Part1
(Optional)
Permutation
(Optional) Permutation
Localized
Freq. Part2
Physical frequency
(1)
Distribute PRU to Freq.
Partitions
Diversity group
Resource groups
Tile
permutation
00
01
02
03
04
05
06
07
08
09
...
Localized
HL group
Hopping of
hopping unit
Diversity group
Tile
permutation
Single resource
Intra-cell (potentially dynamic)
14
UL resource allocation process
• The UL PRUs are partitioned into different frequency
partitions.
• In each frequency partition, distribute PRUs between
localized, distributed and HL resource group. The size of each
group is flexible.
• In localized resource group each PRU is a subchannel
• In HL resource, n chunks of (18m x 6) HL resources are
reserved for hopping users, where n is an even number, m is
the maximum number of subchannels each HL user can
choose. Each HL user is allocated a continuous chunk of UL
units changing each dwell time
• In distributed resource group, each distributed subchannel is a
pseudo random selection of 4 tiles (9x3 tile)
15
UL Pilot Pattern for 18x6 PRU
Pattern B (18 x 6), OH 3.7 % per stream
0
-2
-2
-4
-4
-6
-6
-8
-8
subcarrier
subcarrier
Pattern A 1+2 (18 x 6), OH 5.6 % per stream
0
-10
-10
-12
-12
-14
-14
-16
-16
-18
-18
0
1
2
3
4
5
symbol
Pilot pattern for 1 and 2 pilot streams
6
7
0
1
2
4
3
5
6
7
symbol
Pilot pattern for 4 pilot streams
16
UL Pilot Pattern for 9x3 tile &
18x3 HL unit
9x3 (9 x 3), OH 11.1 % per stream
0
-1
-2
subcarrier
-3
-4
-5
-6
-7
-8
-9
-10
0
0.5
1
1.5
2
symbol
2.5
3
3.5
4
18x3 HL pilots are 2x duplication of 9x3 pilots
17
UL RBs example
UL structure
6 symbols
36
18
9x3
HL-units
(2 chunks 36x6)
Each color depicts one user:
(1) Hopping, 36 subcarriers allocation
(2) Hopping, 18 subcarriers allocation
(3) Localized
(4) Diversity
18
UL CQICH concept
2-level primary/secondary CQICH architecture
• Primary CQICH
– Facilitate reliable basic connection and maintain coverage
– Can be used as a reference for UL power control
– Periodic, low & fixed rate
– Localized/Hopping localized permutation mode
– Resource Unit size: 9x6
• Secondary CQICH
– Provide optimized performance with reduced overhead
–
–
–
–
Periodic/Event-driven
Link adaptation to achieve high spectrum efficiency
Diversity/Hopping localized permutation mode
Resource Unit size: 9x3
19
Section 2
802.16m UL symbol structure:
mixed network support (Multiplexing
Schemes)
Supporting material for “IEEE C80216m-08/267: UL symbol structure
design for 802.16m – mixed network support”
20
16e/16m UL Multiplexing Schemes Summary
• TDM UL 16e and 16m
– suffers link budget loss due to shorter UL
transmission time
• FDM 16e/16m for UL
– FDM 16e PUSC put severe design constraint on
16m symbol structure
• Solution: TDM 16e PUSC and FDM 16e AMC
21
Mixed Mode Legacy Support
DL subframe
UL subframe
TDM for 16e/16m zones
16e AMC
FDM for 16e AMC allocation and others
16 m allocations: divesity, localized
16e PUSC zone
16e PUSC/AMC zone
16 m allocations all types
TDM for 16e PUSC zone
22
Hybrid TDM/FDM
• 18x6 based FDM: AMC subchannels for WiMAX 1,
WiMAX 2 uses the rest
– Pros:
• Full flexibility for WiMAX 2, can use all modes
• FDM is not a separate operating mode for WiMAX 2
– Cons: potential diversity loss for WiMAX 1 PUSC users
• Performance loss is evaluated in the next slide
• WiMAX 1 control channels (Ranging and ACK) use
the TDM PUSC mode
• “UL AMC Allocated physical bands bitmap” TLV in
UCD may be used to interleave AMC with 16m
23
clusters
Performance Discussion
• FDM 16e AMC with 16m achieve similar performance as
FDM 16e PUSC for ITU-Veh-A 120Km/h
 LLS simulation
– PUSC is 2dB better in link level
– AMC has 1.25dB higher SNR with the same transmit power due to
narrower frequency width (18 vs 24 subcarriers per subchannel)
– AMC has 0.7dB improvement with better channel estimation  Estimation Loss
• 2dB loss in Ped-B 3Km/h
 Scheduling Gain
– Can compensate the loss by scheduling
– Can also be improved with H-ARQ
• We do not expect a large difference in SLS when including
channel estimation; Real life performance might be degraded
in some cases
24
Other Mixed Mode Options
• FDM 16e PUSC with 16m
– Severe limitation on 16m optimization due to the
PUSC permutation
• FDM 16e PUSC and 16m mixed mode,
redesign 16m green field mode
– Green field is not a sub-set of mixed mode
25
Conclusion
• Design challenge for mixed mode legacy support in UL
– TDM only loss link budget for 16e
– FDM UL PUSC pose severe limitation on 16m symbol structure
• Hybrid TDM/FDM mixed mode in UL
–
–
–
–
TDM 16e PUSC and FDM 16e AMC with 16m
Full flexibility for 16m optimization
Reasonable compromise between 16e and 16m
Combination of FDM and TDM mechanisms facilitates a wide range
of solutions to mitigate mixed mode issues, with minimal impact on
16m flexibility and performance
26
Section 3
802.16m UL symbol structure:
Tile selection and pilot design
Supporting material for “IEEE C80216m-08/268: UL symbol structure
design for 802.16m – tile selection and pilots”
27
Tile Selection and Pilot Design
Summary
• Subchannel size is 18x6
– Choice from the FDM 16e AMC with 16m
– Same subchannel size for localized and distributed resource
– 18x6 subchannel includes both data and pilots
• Tile size selection for distributed resource
– Tradeoff of diversity and pilot efficiency
• Small tile => more tiles: more diversity, smaller pilot efficiency
• Large tile => less diversity, better pilot efficiency
– Comparison of 6x3, 9x3, 18x3 tiles size
• 3x3 is not considered due to pilot
• 3x6 is similar to 6x3 and 9x6 is similar to 18x3
– Optimized for 2 pilot streams (collaborative MIMO)
• Recommend 9x3 tile for UL Distributed Resource
28
Optimization Method
• In order to compare the diversity gain with different
tile size, link level simulation is done to generate
throughput curve with perfect CSI for different tile
size
– 480 bits coding block
– MIMO 2x2 (CSM)
– Number of tiles is calculated based on MCS and placed
evenly across frequency
– SE curve is fitted with 1% PER requirement
• Pilot is optimized using different SE curve for
different tile shape
29
Ideal SE with different tile
Througput with 1% PER constraint
8
7
Per subcarrier
6x3 * 6
9x3 * 4
18x3 * 2
SE (bit/s/Hz)
6
5
4
3
2
1
0
-10
-5
0
5
10
15
20
25
SNR
Ideal SE with perfect channel estimation
6x3 tile and 9x3 tile achieve similiar diversity gain
18x3 tile suffers large diversity loss especially at low SNR
30
Pilot Patterns
9x3 (9 x 3), OH 11.1 % per stream
6x3 (6 x 3), OH 16.7 % per stream
0
0
-1
-1
-2
-3
subcarrier
-3
-4
-4
-5
-6
-7
-5
-8
-6
-7
0
-9
-10
0.5
1
1.5
2
symbol
2.5
3
3.5
4
0
0.5
1
1.5
2
symbol
2.5
3
3.5
4
18x3 (18 x 3), OH 9.3 % per stream
Boost 4dB
0
Boost 5dB
-2
-4
-6
subcarrier
subcarrier
-2
-8
-10
-12
-14
-16
-18
0
0.5
1
1.5
2
symbol
Boost 5dB
2.5
3
3.5
4
31
Effective SE
Effective SE / best SE
Effective SE
1
7
9x3
18x3
6x3
Ideal SE
6
0.98
5
4
ratio
SE [B/s/hz]
0.96
0.94
3
0.92
2
0
-10
9x3
18x3
6x3
0.9
1
-5
0
5
10
SNR[dB]
15
20
25
0.88
-10
-5
0
5
10
SNR[dB]
15
20
25
Effective spectral efficiency considering pilot overhead and channel estimation loss
 N
 1 Nt
SE  1  p NTX   idealSE SNRdecoder t 
Nt

 N t t 1
Np is the number of pilot, Nt is the number of tones in one cluster
SNRdecoder 
h
1
2
 eff 2

2
h
2
 e2
Eh
 N TX
2

 e2
Eh
2
1  SNRH ,MMSE
1
SNR1  N TX SNRH ,MMSE
1
32
Conclusion
• 6x3 tile size suffers high pilot overhead
• 18x3 tile size suffers low diversity gain
• Recommend 9x3 tile for UL PUSC
33
Summary of pilot patterns
• For the downlink the following pilot patterns were
proposed in S80216m-08/120r1
– Pattern A: 18x6, 2 streams, 3 versions for interlacing
– Pattern B: 18x6, 4 streams, 1 version
• 1 new pilot pattern is added for the UL
– Patten C: 9x3, 2 streams, 1 version
• In all cases one stream is supported by using one stream
of the 2 stream pilot pattern
Localized
Distributed and HL
1 TX
A
C
2 TX or collaborative MIMO (2x1TX)
A
C
4 TX or collaborative MIMO (4x1TX, 2x2TX)
B
Not supported
34
Section 4
802.16m UL symbol structure:
Hopping Localized Allocation to
Improve UL Tx Power
Supporting material for “IEEE C80216m-08/269: UL symbol structure
design for 802.16m – hopping localized transmission to improve TX
power”
35
Hopping Localized Key Concepts
• UL link budget is transmit power limited
• Transmit Power Advantage: Allocate narrow localized chunk
of subcarriers (hopping unit) for power limited users to
maximize TX power efficiency
• Diversity: Frequency Hopping for better diversity gain
• Hopping Localized: Combining the above two factors for
better power efficiency and diversity gain  hopping
localized
• Allocation mechanism targeted for cell-edge (power and
throughput limited) users
36
Link budget issue in the
uplink
• From 802.16m SRD, section 7.4, Cell coverage:
– “the link budget of the limiting link (e.g. DL MAP, UL bearer) of IEEE
802.16m shall be improved by at least 3 dB compared to the WirelessMANOFDMA Reference System.”
• One of the factors affecting UL link budget is the transmit power
• Mobile TX power is limited due to the following factors:
– High PAPR - large variation of the of OFDM signal envelope
– Non-linear “practical” power amplifier
– Constraints
• Out of band emission is limited by spectral mask (varies by regulation)
• Minimum EVM is needed (in-band noise limitation), depending on MCS
• PA may have power consumption limitation (in addition to peak power limitation)
• 802.16e OFDMA uplink performance is limited with respect to the
downlink (TX power 23 dBm vs. 46 dBm, while maximum subchannelization gain ~12 dB)
• Maximum TX power (of lowest rate) is limited by spectral mask
requirement (since EVM requirement loosens for low rates)
37
Facing the spectral mask –
localized-OFDMA
• Non-linear PA causes spectral expansion of the transmitted
signal. Narrower signal’s spectrum will cause narrower
expansion.
• We suggest to allocate narrow localized chunk of subcarriers
for power limited users
• This simple mechanism has very good performance,
although it doesn’t change the signal’s PAPR.
Original OFDM signal with OOB
Narrow band signal with same spectral
density
Narrow band signal amplified to meet spectral
mask requirement
38
Localized-OFDMA
Spectral density and masks. TX power = 23.30
-30
The following results show the gain obtained
with actual OFDM signal and the following
parameters:
OFDM parameters: 10Mhz, FFT1024,
wideband=PUSC 3 subchannels, narrowband =
72 subcarriers
-50
xx(f) [dBm/Hz]
PA model: RAPP-3
23.3 dBm
-40
-60
-70
-80
-90
-100
Mask: FCC & HUMAN
-110
-30
-20
-10
0
Frequency [MHz]
10
20
30
Wide-band OFDM signal
Spectral density and masks. TX power = 25.15
Spectral density and masks. TX power = 30.53
-30
-20
30.5 dBm
-30
-40
-50
-50
xx(f) [dBm/Hz]
xx(f) [dBm/Hz]
25.2 dBm
-40
-60
-70
-60
-70
-80
-80
-90
-90
-100
-100
-110
-30
-20
-10
0
Frequency [MHz]
10
20
30
Narrow-band OFDM signal, band center
-110
-30
-20
-10
0
Frequency [MHz]
10
20
Narrow-band OFDM signal, band edge
30
39
Adding frequency diversity by
hopping
• For high mobility user the frequency diversity gain in MIMO
2x2 is ~2-4dB (distributed versus localized)
• In localized transmission we lose this diversity gain
• To combine the frequency diversity of distributed allocation
with power advantage of localized allocation, frequency
hoping should be applied (e.g. hop duration of 3 symbols),
therefore we propose hopping localized transmission
• On the other hand hopping localized requires continuous
chunk of spectrum to be allocated to a single user which
poses a limit on other users.
• Therefore we propose to limit this type of allocation to celledge (power and throughput limited) users
40
Hopping localized allocations
• We propose that a mix of three allocation types will be
supported by the UL symbol structure:
• The power boosting in HL allocation
can be a function of the location in
the band (maximum power can be
applied to ~80% of the band, lower
power in the edges)
Minimum allocation
width (#tone)
– Power limited diversity users: hoping localized (HL) allocation
– Closed loop (low mobility) users: localized allocation
– High throughput diversity users: distributed allocation
Dwell time
Freq
Time
4 hops
41
Dwell time tradeoffs
• The basic allocation unit is a time-frequency rectangle. It’s size is affected
by:
– Large number of sub-carriers reduces the maximum sub-channelization gain,
therefore span maximum time (e.g. 2 subframes) minimum frequency
– Given the frequency width, the tradeoff on dwell time:
• Small dwell time => more hops, more diversity
• Large dwell time => higher pilot efficiency
• Recommended parameters:
– A hop tile size is 18 subcarriers and 3 OFDMA symbols. Assuming UL
transmission may span TTI=2 subframes, we assume 4 hops within one TTI
– The 18x3 tile size optimizes the tradeoff of diversity and pilot efficiency.
– The 18x3 tile size aligns well with the 9x3 tile size for distributed resource and
18x6 tile size for localized resource
42
Review of text proposal
43
Specific Text Recommendations for
SDD Section 11 – UL Physical Structure
11.x: UL Physical Structure
• The uplink physical structure supports three different resource allocation
schemes simultaneously in the same subframe/zone, including localized,
distributed and hopping localized (HL) allocations.
• Localized resources are mainly intended for utilizing frequency selective
scheduling gain using channel information/feedback, while distributed
and HL resources supply frequency diversity. HL allocations are used by
power-limited users to enable higher transmit power.
• The uplink physical structure is provided through a hierarchical structure
as depicted in Figure XXX, where the symbol is first split into frequency
partitions. These partitions are mainly intended for FFR, and are assumed
to be slowly changing based on mutli-cell decisions. Each partition can
be split into localized, distributed and hopping localized groups, and then
these groups are split into individual subchannels or logical resource
units (LRUs).
• Insert Figure XXX here.
* System description document [9]
44
Specific Text Recommendations for
SDD Section 11 – UL Physical Structure
11.x: UL Physical and Logical Resource Unit
• An UL physical resource unit (PRU) is the basic
physical unit for resource allocation that comprises
Psc consecutive subcarriers by Nsym consecutive
OFDMA symbols. Psc equals to 18 subcarriers and
Nsym equals to 6.
• An UL logical resource unit (LRU) is the basic
logical unit for resource allocation that comprises
Lsc subcarriers by Nsym consecutive OFDMA
symbols. In the case UL LRU, Lsc is equal to Psc.
* System description document [9]
45
Specific Text Recommendations for
SDD Section 11 – UL Physical Structure
11.x: UL Symbol Structure
• An UL tile is physically contiguous group of 9 subcarriers by 3
symbols.
• An UL hopping unit (HU) is physically contiguous group of
18 subcarriers by 3 symbols.
• An UL slot/LRU is logical block of Lsc subcarriers by Nsym
symbols unit, with default value of 18 subcarriers by 6 OFDM
symbols, i.e. Lsc=18, Nsym=6 including both pilots and data
tones.
– In localized resource allocation, a LRU is one PRU
– In distributed resource allocation, a LRU contains 4 tiles distributed
across the distributed allocation
– In HL allocation, a LRU contains 2 HUs that are hopping across
subframe
46
Specific Text Recommendations for
SDD Section 11 – UL Physical Structure
11.x: UL Localized Resource Unit (LLRU)
• Localized subchannels contain subcarriers which are
contiguous in frequency.
11.x: UL Distributed Resource Unit (DRU)
• Distributed subchannels contain tiles which are spread across
frequency within the frequency partition. The tiles within the
distributed groups are permuted across distributed group to
maximize frequency diversity.
11.x: UL Hopping Localized Resource Unit (HLRU)
• Hopping Localized subchannels contain contiguous hopping
units which hop in time with the same Nsym symbol duration.
47
Specific Text Recommendations for
SDD Section 11 – UL Physical Structure
11.x: UL Subchannelzation and Resource Mapping
• Add “UL RB Allocation Process” figure here.
• The UL RB allocation process is defined as follows:
(1) The UL PRUs are partitioned into different frequency partitions.
(2) Each frequency partition is divided into localized, distributed
and/or hopping localized groups. The size of each group is flexible.
(3) n chunks of (18m x 6) HL resources are reserved for hopping
users and are divided into hopping units (with size 18x3). Each HL
user is allocated a continuous chunk of UL units changing each
dwell time.
(4) The localized and distributed groups are mapped into localized
(by direct mapping) and distributed RBs (by “tile permutation”).
48
Specific Text Recommendations for
SDD Section 11 – UL Physical Structure
11.x: Pilot patterns
• The UL pilot pattern for localized allocation with PRU/LRU size of 18x6
is the same as for the DL.
• Insert UL Pilot Figure XXX for localized allocation here.
• An UL pilot pattern for distributed allocation with tile size of 9x3 is shown
in Figure XXX.
• Insert UL Pilot Figure XXX for distributed allocation here (pattern C).
• An UL pilot pattern is designed for HL allocation with HU size of 18x3.
The pilots for 18x3 HU are concatenation of pilots from two 9x3 tiles.
• For 1 stream transmission, a single stream out of the 2 stream pilot pattern
will be used (the pilot locations of the other stream are used for data)
Localized Distributed and HL
1 TX
A
C
2 TX or collrborative MIMO (2x1TX)
A
C
4 TX or collaborative MIMO (4x1TX, 2x2TX)
B
Not supported
49
References
[1] Cosovic, I.; Auer, G., "Capacity Achieving Pilot Design for MIMO-OFDM over Time-Varying FrequencySelective Channels," Communications, 2007. ICC '07. IEEE International Conference on , vol., no.,
pp.779-784, 24-28 June 2007
[2] Hassibi, B.; Hochwald, B.M., "How much training is needed in multiple-antenna wireless links?,"
Information Theory, IEEE Transactions on , vol.49, no.4, pp. 951-963, April 2003
[3] Lang Tong; Sadler, B.M.; Min Dong, "Pilot-assisted wireless transmissions: general model, design criteria,
and signal processing," Signal Processing Magazine, IEEE , vol.21, no.6, pp. 12-25, Nov. 2004
[4] IEEE 802.16m-07/002r4, “802.16m System Requirements”
[5] IEEE 802.16m-008/004, “802.16m Evaluation Methodology”
[6] 3GPP TS 36.211 V8.1.0 (2007-11) Technical Specification, 3rd Generation Partnership Project; Technical
Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA);
Physical channels and modulation (Release 8)
[7] IEEE C80216m-08/082, “Proposal for IEEE 802.16m Frame Structure”
[8] IEEE C80216m-08/118r1, “Initial Document output of the IEEE 802.16 TGm Frame Structure Rapporteur
Group”
[9] IEEE 80216m-08/003, “The Draft IEEE 802.16m System Description Document”
[10] IEEE C80216m-08/xxx: A high level description of a UL symbol structure concept for 802.16m
[11] IEEE C80216m-08/xxx: UL symbol structure design for 802.16m – mixed network support
[12] IEEE C80216m-08/xxx: UL symbol structure design for 802.16m – tile selection and pilots
[13] IEEE C80216m-08/xxx: UL symbol structure design for 802.16m – hopping localized transmission to
improve the TX power
[14] IEEE S80216m-08/120r1 “Proposal for IEEE 802.16m Downlink Symbol Structure Concept”
50
Backup
51
Diversity loss of AMC in Peb-B at
3kmh/h
10
10
PER
• Ped-B, 3kmh/h, Perfect CSI
at receiver
• QPSK with ½ CTC code
• 1x2 SIMO configuration
• 2 subchannels, 3 subframes
for both AMC and PUSC
• PUSC has 4.3dB gain over
AMC due to higher
frequency diversity with
subchannel rotations
10
10
10
Ped-B, 2 subchannels, 18 OFDM symbols
0
-1
-2
-3
-4
-2
0
2
4
SNR (dB)
6
8
10
52
Diversity loss of AMC in Veh-A at
120kmh/h
10
10
PER
• Veh-A, 120kmh/h, Perfect
CSI at receiver
• QPSK with ½ CTC code
• 1x2 SIMO configuration
• 2 subchannels, 3 subframes
for both AMC and PUSC
• PUSC has 2dB gain over
AMC
10
10
10
Ved-A, 2 subchannels, 18 OFDM symbols
0
-1
-2
-3
-4
1
2
3
4
5
SNR (dB)
6
7
8
9
53
Diversity loss of AMC in Veh-B at
120kmh/h
10
10
Veh-B, 2 subchannels, 18 OFDM symbols
0
-1
PER
• Veh-B, 120kmh/h, Perfect
CSI at receiver
• QPSK with ½ CTC code
• 1x2 SIMO configuration
• 2 subchannels, 3 subframes
for both AMC and PUSC
• PUSC has 1.5dB gain over
AMC
10
10
-2
-3
1
2
3
4
5
Transmit power/ (dB)
6
7
54
Implementation loss due to channel
estimation
Physical implementation loss (mean SNR loss not considering overhead)
Physical implementation loss (mean SNR loss not considering overhead)
6
6
AMC (18x6)
UL-PUSC (4x3)
5
5
4
4
Loss [dB]
Loss [dB]
AMC (18x6)
UL-PUSC (4x3)
3
3
2
2
1
1
0
-10
-5
0
5
10
15
SNR[dB]
20
25
Ped-B, 3kmh, MMSE filter
30
35
0
-10
-5
0
5
10
15
SNR[dB]
20
25
30
35
Veh-A, 120kmh, MMSE filter
• PUSC has about 0.7 – 1dB SNR loss compare to AMC due to channel estimation
• AMC channel estimation can be further improved by interpolating across
sub-channels and sub-frames
55
Scheduling Gain Evaluation for AMC
•
•
•
•
2x2 MIMO, 18x6 RB
ITU Ped-B Channel & Veh-A Channel @ SNR=10dB
Relative scheduling gain is calculated for mean values
SNR mapped from average subchannel SE, where the average
subchannel SE is calculated using all tones in the
subchannel(i.e. log2(1+power*10^(SNRdB/10)/Ntx)).
56
Ped-B/Veh-A Scheduling Gain Results
Ped-B Scenarios vs.
Localized Clusters
8 RBs
(16.7%)
16 RBs
(33.3%)
24 RBs
(50%)
32 RBs
(67.7%)
40 RBs
(83.3%)
2 best SubCh w. scheduling
9.0523
9.8423
10.1418
10.4032
10.6232
2 best SubCh wo. Scheduling
5.7656
5.6746
5.6729
5.6928
5.7785
Net Gain
3.2867
4.1677
4.4689
4.7104
4.8447
Veh-A Scenarios vs.
Localized Clusters
8 RBs
(16.7%)
16 RBs
(33.3%)
24 RBs
(50%)
32 RBs
(67.7%)
40 RBs
(83.3%)
2 best SubCh w. Scheduling
Gain
8.8651
9.6901
9.9848
10.1406
10.2951
2 best SubCh wo. Scheduling
5.6007
5.6425
5.7093
5.6604
5.6702
Net Gain
3.2644
4.0476
4.2754
4.4802
4.6249
57
PAPR reduction methods
•
•
•
PAPR reduction techniques improve peak power
The actual performance gain from PAPR reduction methods like tone-reservation,
tone-injection etc. is very small
Reasons:
– Improving the peak power doesn’t have a 1:1 impact on the maximum TX power:
• It has small effect on OOB and in-band distortion since most of them created by non-peak signal
• EVM and OOB improvement relates in a ratio of approx 1:3 to TX power improvement (in dB)
• For example ideally limiting the OFDM amplitude to 7dB has ~0.5dB gain in TX power
(depending on model and mask)
– These methods insert some overhead or loss in performance that balances some of the
gain
•
•
Clipping & filtering is an effective method to be applied in the transmitter and no
standardization is needed for it, except correct definition of the EVM levels
We propose to further improve the maximum TX power not by changing the signal
amplitude distribution but by different use of the spectrum
=> “PAPR reduction” methods evaluation 58