2004-03-11
`
`Withdrawn
`
`IEEE C802.16d-04/19
`
`Project
`Title
`Date
`Submitted
`
`Source(s)
`
`Re:
`
`Abstract
`
`Purpose
`
`Notice
`
`Release
`
`Patent
`Policy and
`Procedures
`
`IEEE 802.16 Broadband Wireless Access Working Group <http://ieee802.org/16>
`A New Frame Structure for Scalable OFDMA Systems
`
`2004-03-11
`
`Inseok Hwang, Jaehee Cho, Sanghoon
`Sung Hun Huh, Soon Young Yoon,
`Panyuh Joo, Jaeweon Cho
`Samsung Elec.
`416, Maetan-3dong, Paldal-gu
`Suwon-si, Gyeonggi-do, Korea
`
`Voice: +82-31-279-5058
`Fax: +82-31-279-5515
`is91.hwang@samsung.com
`jaehee1.cho@samsung.com
`sanghoon.sung@samsung.com, hhuh@samsung.com
`soon.young.yoon@samsung.com,
`panyuh@samsung.com ,
`jaeweon.cho@samsung.com
`IEEE 802.16REVd/D3 Frame Structure for Scalable OFDMA Systems
`A new frame structure is proposed to improve system performance under scalable
`bandwidth. For scalability, tone spacing and symbol period are fixed and only FFT s i z e
`vary with system bandwidth. For system performance, the structure supports two new
`subchannels; band AMC subchannels for system throughput, safety subchannels for
`users in cell boundary. In addition, dedicated control symbols are introduced for
`signaling efficiency, the first downlink symbol after preamble is used for carrying
`system information while the first three uplink symbols are assigned for channel
`quality report, ranging, and Ack/Nack of downlink data reception. Finally, a new
`concept of bin and tile are introduced for carrier allocations of AMC subchannels and
`uplink diversity subchannels, respectively.
`Present how the IEEE802.16d OFDMA frame structure can be enhanced for system
`performance.
`This document has been prepared to assist IEEE 802.16. 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.
`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 802.16.
`The contributor is familiar with the IEEE 802.16 Patent Policy and Procedures
`<http://ieee802.org/16/ipr/patents/policy.html>, including the statement "IEEE standards may
`include the known use of patent(s), including patent applications, provided the IEEE receives
`assurance from the patent holder or applicant with respect to patents essential for compliance
`with both mandatory and optional portions of the standard." Early disclosure to the Working
`Group of patent information that might be relevant to the standard is essential to reduce the
`possibility for delays in the development process and increase the likelihood that the draft
`publication will be approved for publication. Please notify the Chair
`<mailto:chair@wirelessman.org> as early as possible, in written or electronic form, if patented
`technology (or technology under patent application) might be incorporated into a draft standard
`being developed within the IEEE 802.16 Working Group. The Chair will disclose this notification
`via the IEEE 802.16 web site <http://ieee802.org/16/ipr/patents/notices>.
`
`0
`
`ERIC-1005
`Ericsson v. IV
`Page 1 of 13
`
`

`
`2004-03-11
`
`IEEE C802.16d-04/19
`
`A New Frame Structure for Scalable OFDMA Systems
`
`Inseok Hwang, Jaehee Cho, Sanghoon Sung Hun Huh, Soon Young Yoon, Panyuh Joo, Jaeweon Cho
`
`Samsung Elec. Co, Ltd.
`
`1. Introduction
`Current frame structure in 802.16REVd/D3 2048 FFT OFDMA mode has a limitation to support
`bandwidth scalability and mobility simultaneously. For example, fixed FFT size cannot provide a unified frame
`structure since symbol period increases as the bandwidth decreases. In addition, it causes an unacceptable overhead
`in system with narrow bandwidth such as 1.25 and 2.5 MHz if dedicated symbols for MIMO/AAS preamble, initial
`random access are introduced. The problem becomes more severe in TDD system when a short frame length
`required for fast link control. To handle these limitations and improve overall system performance, a new flexible
`frame structure is proposed. For scalability, tone spacing and symbol period are fixed and only FFT size varies
`from 2048 to 256 as system bandwidth scales down from 20 MHz to 2.5 MHz. For better system performance,
`the proposed frame structure supports two new subchannels; band AMC subchannels for system throughput, safety
`subchannels for users in cell boundary. In addition, dedicated control symbols are introduced for signaling
`efficiency, the first downlink symbol after preamble is used for carrying system information while the first three
`uplink symbols are assigned for channel quality report, ranging, and Ack/Nack of downlink data reception. Finally,
`a new concept of bin and tile are introduced for carrier allocations of AMC subchannels and uplink diversity
`subchannels, respectively.
`2. Design Requirement
`Desired properties of frame structure for scalable OFDMA cellular operation can be summarized as follows
`1) Fixed tone spacing for unified frame structure
`2) Symbol time tradeoff between guard time overhead for delay spread and ICI from Doppler spread
`3) Short frame length for fast link control especially for TDD systems
`4) Dynamic allocation of diversity channels for mobile users and freq. selective AMC channels for stationary
`users
`5) Dedicated signaling channels for fast adaptive modulation coding and H-ARQ
`6) Dedicated uplink time slot for initial random access to reduce interference to traffic channels
`7) Safety channels for service quality of users in cell boundary
`8) Support frequency reuse of 1 and 3
`To satisfy the above requirement, a new frame structure is developed.
`3. Proposed Frame Structure
`
`A. System Parameter
`To support scalable bandwidth from 2.5 MHz to 20 MHz, the following system parameter was chosen
`after considering trade-off between guard time overhead and ICI from Doppler spread. The scalability of FFT size
`with system bandwidth should be kept for a unified frame structure while the exact values of sampling frequency
`can be changed
`
`Parameter
`System BW
`FFT Size
`Samp. Frequency
`
`2.5 MHz
`256
`2.5 MHz
`
`Table 1. System Parameter
`Values
`10 MHz
`1024
`10 MHz
`
`5 MHz
`512
`5 MHz
`1
`
`20 MHz
`2048
`20 MHz
`
`ERIC-1005
`Page 2 of 13
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`

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`2004-03-11
`
`IEEE C802.16d-04/19
`
`Tone Spacing
`Total OFDM Symbols
`Used Subcarriers
`Data Subcarriers
`Pilot Subcarriers
`B. Frame Structure
`
`216
`192
`24
`
`9.975625 kHz
`42
`
`864
`768
`96
`
`432
`384
`48
`
`1728
`1536
`192
`
`Figure 1 – TDD Frame Structure
`For a TDD system, each frame starts with downlink, a BS to SS transmission. The downlink transmission begins
`with two preambles followed by a SICH symbol as shown in Figure 1. In the uplink, transmission begins with
`control symbols. In order to allow BS to turn around, TTG and RTG shall be inserted between downlink (DL) and
`uplink (UL) in the middle of a frame and at the end of a frame, respectively. The number of downlink and uplink
`symbols can be changed with a granularity of six symbols.
`
`Both in downlink and uplink, there are two kinds of subchannels, diversity subchannels and AMC subchannels.
`Accordingly, transmission period can be divided into diversity subchannel period and AMC subchannel period.
`Diversity subchannel consists of 54 distributed tones within multiple symbols in downlink. In uplink, a tile, which
`is composed of the set of 3 contiguous subcarriers through 6 contiguous symbols, is a basic allocation unit for
`diversity subchannel. A diversity subchannel is made up of 3 tiles, which are spread over whole frequency band in
`uplink. A tile structure is shown in Fig. 2. For AMC subchannel, a bin, which is the set of 9 contiguous subcarriers
`within an OFDMA symbol, is a basic allocation unit both in downlink and uplink. A bin structure is shown in
`
`Figure 3. The pilot locations of within bins and tiles can be changed for better filtering gain for
`channel estimation.
`
`2
`
`ERIC-1005
`Page 3 of 13
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`

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`2004-03-11
`
`IEEE C802.16d-04/19
`
`16 data tones + 2 pilot tones
`
`8 data tones
`
`1 pilot tone
`
`
`Figure 2 – Bin Structure Figure 3 – Bin Structure
`
`A group of 4 rows of bins is called a band. AMC subchannel consists of 6 contiguous bins in a same band. A frame
`consists of multiple bands. Total number of bins in a whole frequency band depends on bandwidth as shown in
`Table 4.
`
`Table 4 – Number of bands and bins
`
`Bandwidth
`
`2.5 MHz
`
`5 MHz
`
`10 MHz
`
`20 MHz
`
`NFFT
`Number of bands
`Number of bins per bands
`
`256
`6
`4
`
`512
`12
`4
`
`1024
`24
`4
`
`2048
`48
`4
`
`The downlink symbol right after DL preamble is always used for diversity subchannels and constitutes a SICH
`(System Information Channel) symbol. Safety channel, which consists of the reserved subcarriers for safety
`operation, is also to be broadcasted in SICH symbol. In uplink, the first three OFDMA symbols are used for
`control symbols. Ranging channels, ACK channels, and CQI channels are transmitted through control symbols.
`For reuse 3 deployment, set of bands with the same index of modulo 3 consists a frequency group.
`
`1) Downlink Frame Structure
`Downlink frame structure is shown in Figure 4. Downlink transmission period can be divided into diversity
`subchannel period and/or AMC subchannel period. Diversity subchannels consists of distributed tones within
`multiple symbols and AMC subchannel consists of 6 contiguous bins in a same band. The number of diversity
`symbol (D) and AMC symbol (A) can vary depending on distribution of SS’s channel condition. The downlink
`symbol right after DL preamble is always used for diversity subchannels and constitutes a SICH (System
`Information Channel) symbol. Safety channel, which consists of the reserved subcarriers for safety operation, is
`also to be broadcasted in SICH symbol.
`
`3
`
`ERIC-1005
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`

`
`2004-03-11
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`IEEE C802.16d-04/19
`
`Bin for AMC SC
`
`Bin for Safety SC
`
`Tone for diversity SC
`
`A
`
`11
`23
`35
`47
`11
`23
`17
`
`11
`17
`23
`35
`
`...
`
`...
`
`...
`
`A
`
`...
`
`A
`
`4
`16
`28
`40
`4
`16
`9
`
`4
`9
`16
`28
`
`5
`17
`29
`41
`5
`17
`10
`
`5
`10
`17
`29
`
`...
`
`D
`
`D
`
`A
`
`A
`
`D
`
`A
`
`A
`
`D
`
`D
`
`Symbol :
`
`...
`
`0
`12
`24
`36
`0
`12
`2
`
`0
`2
`12
`24
`
`1
`13
`25
`37
`1
`13
`3
`
`1
`3
`13
`25
`
`2
`14
`26
`38
`2
`14
`5
`
`2
`5
`14
`26
`
`3
`15
`27
`39
`3
`15
`6
`
`3
`6
`15
`27
`
`4
`
`4
`
`7
`
`7
`
`8
`
`8
`
`Safety channel
`
`0
`
`0
`
`1
`
`1
`
`...
`
`Band b-1
`
`Band b
`
`Band b+1
`
`Note: Safety channel is each BS’s reserved frequency bin not used for the SS of the serving BS. Safety
`subchanne(SC) is the frequency bin allocated for the SS which is connected to the serving BS and has
`requested the bin in safety mode. This bin is other BS’s safety channel.
`
`Figure 4 – Downlink Frame Structure
`
`Bin for AMC subchannel #1
`Bin for AMC subchannel #2
`Bin for AMC subchannel #3
`
`Bin for AMC subchannel #4
`
`Bin for AMC subchannel #5
`Bin for AMC subchannel #6
`
`Tile for diversity subchannel #1
`Tile for diversity subchannel #2
`Tile for diversity subchannel #3
`
`tile
`
`Safety
`Channel
`
`Pilot tone
`
`Bin
`
`Figure 5. Uplink Frame Structure
`
`4
`
`...
`
`Band 0
`
`Band 1
`
`Band 2
`
`Band 3
`
`Band B-1
`
`bins
`
`OFDM symbol
`
`ERIC-1005
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`

`
`2004-03-11
`
`IEEE C802.16d-04/19
`
`2) Uplink Frame Structure
`In the uplink, there are two kinds of subchannels, AMC subchannels and diversity subchannels. The first three
`OFDMA symbols are used for ranging channels, ACK channels, and CQI channels as shown in
`5. Basic allocation unit for diversity subchannel is a tile. A diversity subchannel consists of 3 tiles spread over
`whole frequency band. Basic allocation unit for AMC subchannel is a bin. One AMC subchannel consists of 6 bins.
`As in downlink, the configuration of AMC and diversity uplink symbols can vary. Since uplink time interval for
`initial random access are separated from data symbols, interference from SS in initial access to traffic channels can
`be reduced. In addition, fast downlink link control such as adaptive modulation coding and H-ARQ is enabled
`through dedicated control channels such as ACK channels, and CQI channels. The H-ARQ is essential for higher
`system throughput and reliability under imperfect channel quality measurement and packet scheduling delay.
`C. Frame Structure for FDD Systems
`Downlink and uplink frame structure for FDD mode is shown in Figure 4,
`5, respectively. Downlink transmission period can be divided into diversity subchannel period and AMC
`subchannel period in the same way as in TDD mode. Uplink frame structure in FDD mode is also basically the
`same as the one in TDD mode.
`D. AAS Operation
`When operating in the AAS mode, only AMC subchannelization is used for uplink and downlink traffic bursts.
`Downlink frame structure can be divided into preambles, SICH, MAP bursts, and traffic bursts as shown in Figure 6.
`The SICH symbol and AAS_MAP_Burst_Location_IE can be transmitted by changing a beam index frame by
`frame while MAP Bursts #0 ~ #N-1 has the dedicated beam index for coverage extension.
`
`AAS_MAP_Burst_
`Location_IE
`
`Traffic Bursts #1
`
`Traffic Bursts #2
`
`MAP Bursts
`#0
`
`Traffic Bursts #3
`
`Traffic Bursts #4
`
`Preamble
`
`SICH
`
`MAP Bursts
`#1
`
`Traffic Bursts #5
`
`...
`
`...
`
`MAP Bursts
`#(N-1)
`
`Traffic Bursts #(M-1)
`
`Figure 6 – Downlink Frame Structure for AAS
`
`4. Summary and Conclusion
`
`5
`
`ERIC-1005
`Page 6 of 13
`
`

`
`2004-03-11
`
`IEEE C802.16d-04/19
`
`To achieve bandwidth scalability and better system performance, a unified frame structure was proposed. The
`proposed structure have flexibility of AMC and diversity channel management for system throughput while safety
`channel can give better service quality for users in cell boundary. In addition, the proposed structure can support
`AAS operation. For better signaling efficiency, the first downlink symbol after preamble is used for carrying
`system information while the first three uplink symbols are assigned for channel quality report, ranging, and
`Ack/Nack of downlink data reception. Finally, a new concept of bin and tile are introduced for carrier allocations
`of AMC subchannels and uplink diversity subchannels, respectively.
`
`Proposed Text Changes
`[Replace IEEE P802.16-REVd/D3-2004 “8.4.4 Frame structure” with the following text.]
`
`8.4.3 Frame structure
`
`8.4.3.1 Frame structure
`
`For a TDD system, each frame starts with downlink, a BS to SS transmission. The downlink transmission begins
`with two preambles followed by a SICH as shown in Figure 1. In the uplink, transmission begins with a control
`symbols. In order to allow BS to turn around, TTG and RTG shall be inserted between downlink (DL) and uplink
`(UL) in the middle of a frame and at the end of a frame, respectively.
`
`6
`
`ERIC-1005
`Page 7 of 13
`
`

`
`2004-03-11
`
`IEEE C802.16d-04/19
`
`Figure 1 – Frame structure
`
`Both in downlink and uplink, there are two kinds of subchannels, diversity subchannels and AMC subchannels.
`Accordingly, transmission period can be divided into diversity subchannel period and AMC subchannel period.
`
`Diversity subchannel consists of 54 distributed tones within multiple symbols in downlink. In uplink, a tile, which
`is composed of the set of 3 contiguous subcarriers through 6 contiguous symbols, is a basic allocation unit for
`diversity subchannel. A diversity subchannel is made up of 3 tiles, which are spread over whole frequency band in
`8 data tones
`
`1 pilot tone
`
`uplink. A tile structure is shown in
`
`.
`
`16 data tones + 2 pilot tones
`
`Figure 2 – Tile structure
`
`For AMC subchannel, a bin, which is the set of 9 contiguous subcarriers within an OFDMA symbol, is a basic
`allocation unit both in downlink and uplink. A bin structure is shown in Figure .
`
`8 data tones
`
`1 pilot tone
`
`Figure 3 – Bin structure
`
`A group of 4 rows of bins is called a band. AMC subchannel consists of 6 contiguous bins in a same band.
`
`A frame consists of multiple bands. Total number of bins in a whole frequency band depends on bandwidth as
`shown in Table .
`
`7
`
`ERIC-1005
`Page 8 of 13
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`

`
`2004-03-11
`
`IEEE C802.16d-04/19
`
`Table 1 – Number of bands and bins
`
`Bandwidth
`
`N FFT
`Number of bands
`
`Number of bins per bands
`
`2.5MHz
`
`5MHz
`
`10MHz
`
`20MHz
`
`256
`
`6
`
`4
`
`512
`
`12
`
`4
`
`1024
`
`2048
`
`24
`
`4
`
`48
`
`4
`
`The downlink symbol right after DL preamble is always used for diversity subchannels and constitutes a SICH
`(System Information Channel) symbol. Safety channel, which consists of the reserved subcarriers for safety
`operation, is also to be broadcasted in SICH symbol.
`
`In uplink, the first three OFDMA symbols are used for control symbols. Ranging channels, ACK channels, and
`CQI channels are transmitted through control symbols.
`8.4.3.2 FDD Frame structure
`
`8.4.3.2.1 Downlink frame structure
`
`Downlink frame structure for FDD mode is shown in Figure . Downlink transmission period can be divided into
`diversity subchannel period and AMC subchannel period in the same way as in TDD mode.
`8.4.3.2.2 Uplink frame structure
`
`Uplink frame structure for FDD mode is shown in
`
`. Uplink frame structure in FDD mode is basically the same as the one in TDD mode.
`
`8
`
`ERIC-1005
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`
`

`
`2004-03-11
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`IEEE C802.16d-04/19
`
`Bin for AMC SC
`
`Bin for Safety SC
`
`Tone for diversity SC
`
`A
`
`11
`23
`35
`47
`11
`23
`17
`
`11
`17
`23
`35
`
`...
`
`...
`
`...
`
`A
`
`...
`
`A
`
`4
`16
`28
`40
`4
`16
`9
`
`4
`9
`16
`28
`
`5
`17
`29
`41
`5
`17
`10
`
`5
`10
`17
`29
`
`...
`
`D
`
`D
`
`A
`
`A
`
`D
`
`A
`
`A
`
`D
`
`D
`
`Symbol :
`
`...
`
`0
`12
`24
`36
`0
`12
`2
`
`0
`2
`12
`24
`
`1
`13
`25
`37
`1
`13
`3
`
`1
`3
`13
`25
`
`2
`14
`26
`38
`2
`14
`5
`
`2
`5
`14
`26
`
`3
`15
`27
`39
`3
`15
`6
`
`3
`6
`15
`27
`
`4
`
`4
`
`7
`
`7
`
`8
`
`8
`
`0
`
`0
`
`1
`
`1
`
`...
`
`Band b-1
`
`Band b
`
`Band b+1
`
`Safety channel
`:
`N o t e
`Safety channel is each BS’s reserved frequency band which is not used for the BS’s SS. Safety
`subchannel(SC) is the frequency band allocated for the BS’s SS which has requested the band in
`safety mode. This band is other BS’s safety channel.
`
`Figure 4 – Downlink frame structure
`
`Bin for AMC subchannel #1
`Bin for AMC subchannel #2
`Bin for AMC subchannel #3
`
`Bin for AMC subchannel #4
`
`Bin for AMC subchannel #5
`Bin for AMC subchannel #6
`
`Tile for diversity subchannel #1
`Tile for diversity subchannel #2
`Tile for diversity subchannel #3
`
`tile
`
`Safety
`Channel
`
`...
`
`Pilot tone
`
`Bin
`
`OFDM symbol
`
`Figure 5 – Uplink frame structure
`
`9
`
`Band 0
`
`Band 1
`
`Band 2
`
`Band 3
`
`Band 23
`
`bins
`
`ERIC-1005
`Page 10 of 13
`
`

`
`2004-03-11
`
`8.4.3.3 AAS operation
`
`IEEE C802.16d-04/19
`
`When operating in the AAS mode, only AMC subchannelization is used for uplink and downlink traffic bursts.
`Downlink frame structure can be divided into preambles, SICH, MAP bursts, and traffic bursts as shown in Figure .
`
`AAS_MAP_Burst_
`Location_IE
`
`Traffic Bursts #1
`
`Traffic Bursts #2
`
`MAP Bursts
`#0
`
`Traffic Bursts #3
`
`Traffic Bursts #4
`
`Preamble
`
`SICH
`
`MAP Bursts
`#1
`
`Traffic Bursts #5
`
`...
`
`...
`
`MAP Bursts
`#(N-1)
`
`Traffic Bursts #(M-1)
`
`Figure 6 – Downlink frame structure for AAS
`
`8.4.3.3.1 Preambles
`
`First two OFDMA symbols are used as preambles, as described in Error! Reference source not found..
`Preambles are transmitted through broad beamforming pattern in the same way as in non-AAS mode. It is used for
`network synchronization and cell identification.
`
`10
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`

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`
`8.4.3.3.2 SICH
`
`IEEE C802.16d-04/19
`
`System information channel is assigned in a separated OFDMA symbol following preambles. SICH is transmitted
`by BS with the AAS beam in a specific direction in a given time.
`8.4.3.3.3 AAS_MAP_Burst_Location IE
`
`Subchannel 0 of the DL frame is used for delivering MAP allocation information.
`AAS_MAP_Burst_Location_IE() is transmitted in the same beamforming pattern as SICH. Position of starting
`subchannels for each MAP burst are indicated in AAS_MAP_Burst_Location _IE().
`
`Physical structure for the AAS_MAP_Burst_Location_IE () is shown in Figure 7. The
`AAS_MAP_Burst_Location_IE () is transmitted with QPSK rate 1/12.
`
`Subchannel 0
`
`AAS_MAP_Burst_Location_IE
`
`2 OFDM symbols
`
`Figure 7 – Example of allocation for AAS_MAP_Burst_Location IE
`
`The contents of the AAS_MAP_Burst_Location_IE () payload is described by Table 2.
`
`Table 2 – AAS_MAP_Burst_Location_IE format
`
`Syntax
`
`S i z e
`
`Notes
`
`AAS_MAP_Burst_Location _IE {
`
` No. symbol for AAS_MAP
`
`1 bits
`
` 0 : 2 OFDMA symbols
`
` 1 : 3 OFDMA symbols
`
`Subchannel_offset
`
` No. subchannels
`
`7 bits
`
`4 bits
`
`11
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`

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`IEEE C802.16d-04/19
`
`8.4.3.3.4 Broadcasting MAP bursts
`
`Each MAP burst is dedicated at the direction of the BS for active AAS scanning. These bursts are used to transmit
`AAS_DL_Scan_IE() as shown in Table 3. The AAS_DL_Scan_IE() will be transmitted with QPSK rate 1/12.
`
`Syntax
`
`AAS_DL_Scan_IE {
`
`AAS_Ranging_Allocation_IE() {
`
` Subchannel offset
`
` No. subchannels
`
` }
`
`AAS_MAP_Allocation_IE() {
`
` For ( n=0; n<N_user; n++ ) {
`
` TID
`
` Band ID
`
` Nep
`
` No. Subchannels
`
`}
`
`}
`
`Table 3 – AAS_DL_Scan_IE format
`
`Size
`
`Notes
`
`7 bits
`
`2 bits
`
`10 bits
`
`6 bits
`
`6 bits
`
`4 bits
`
`12
`
`ERIC-1005
`Page 13 of 13