TTA Standard Enacted on : 23 Dec. 2004 TTAS.KO-06.0064R1 Specifications for 2.3GHz band Portable Internet Service - Physical Layer - Telecommunications Technology Association
Preface 1. Purpose The purpose of this standard is to specify the physical layer of TDD OFDMA system providing portable internet service in 2.3GHz frequency band. 2. Normative standards and recommendations 2.1 International standards IEEE P802.16-REVd/D5-2004 Draft IEEE Standard for Local and metropolitan area networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems. IEEE P802.16e/D5-2004 Draft Amendment to IEEE Standard for Local and metropolitan area networks Part 16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems. 2.2 Domestic standards 2.3 Others 3. Intellectual property right Refer to the IPR list related to the standard for the portable internet services in 2.3GHz frequency band i
4. Requirements for conformance and certification No relationship 5. History of the standard Version Issue Date Contents 1.0 June 25, 2004 Established 2.0 December 23, 2004 Revised ii
Contents 1. Introduction 1 2. General Subject 2 2.1 Purse 2 2.2 Application Scope 2 2.3 Change and Approval 2 2.4 Reference 2 2.5 Definition 3 2.6 Abbreviation 4 3. Frequency 6 3.1 Frequency Tolerance 6 3.2 Spectrum Requests 6 3.2.1. Channel Placement 6 4. Duplex 7 5. Description of OFDMA Symbol, Symbol Variables and Sending Signal 8 5.1. Description of time area 8 5.2. Description of Frequency Area 9 5.3. Basic Symbol Variables 10 5.4. Derived Symbol Variables 10 5.5. Transfer Signal 11 5.6. Basic System Variables 12 6. Frame Structure 13 6.1 Frame structure 13 iii
6.1.1. Downlink Frame Structure 16 6.1.2. Uplink frame structure 17 6.1.3. Corresponding Rule for Multiple subchannel Allocation 18 6.1.4. Down Frame Prefix 19 6.1.4.1. Allocating subchannel to FCH and Sequence of Logical subchannel 21 6.2. Frame Structure Information 23 6.3. AAS Operation (Optional) 23 6.3.1. Preamble 24 6.3.2. AAS_FCH 24 6.3.3. MAP Burst Transfer 24 7. MAP Message Field and IE 25 8. OFDMA Subcarrier Allocation 27 8.1. Downlink 28 8.1.1. Preamble 28 8.1.1.1. Shared Synchronization Symbol (Optional) 35 8.1.1.2. Shared Synchronization Symbol Progression 36 8.1.2. Symbol Structure 36 8.1.3. Allocation to subchannel of Data Subcarrier in Downlink 39 8.1.3.1. AMC subchannel 39 8.1.3.2. Diversity subchannel 42 8.1.3.3. DL PUSC subchannel 44 8.1.3.3.1. Symbol Structure of DL PUSC subchannel 44 8.1.3.3.2. Subcarrier allocation method of DL PUSC subchannel 45 8.2. Uplink 47 8.2.1. AMC subchannel allocation 47 8.2.2. Uplink diversity subchannel allocation 47 8.2.3. Mini-subchannel 49 8.2.3.1. Partitioning subchannel to mini-subchannel 49 iv
8.2.3.2. subchannel number allocation to mini-subchannel 50 8.2.4. Uplink PUSC 51 9. OFDMA Ranging 54 9.1 Initial Ranging and Hands-off Ranging 55 9.2. Periodical Ranging and Bandwidth Request Ranging 56 9.3. Ranging Code 57 10. Space Time Processing (Optional) 59 10.1. Preamble structure for STP 59 10.2. Pilot structure for STP 59 10.3. 2 Antenna coding method 61 10.3.1. Sending Diversity 61 10.3.1.1. MISO channel assumption and synchronization 62 10.3.1.2. STC coding 62 10.3.1.3. STC descryption 64 10.4.4 Antenna coding method 64 11. Channel coding and modulation 66 11.1 H-ARQ supporting channel coding 66 11.1.1. Padding 66 11.1.2. Randomization Process 67 11.1.3. CRC coding 68 11.1.4. Partition process 68 11.1.5. Convolutional turbo code 68 11.1.5.1. CTC interleaver 70 11.1.5.2. Decision of CTC rotation condition 71 11.1.6. Interleaving 72 11.1.6.1 Partition of symbol 72 11.1.6.2 Sub-block Interleaving 73 11.1.6.3. Grouping symbols 74 v
11.1.7. Symbol Selection 75 11.1.7.1. Modulation exponent of downlink traffic burst 76 11.1.7.2. Modulation exponent of uplink traffic burst 87 11.2. CTC channel encoding 96 11.2.1. Randomization 96 11.2.2.Connection process 97 11.2.3. CTC coding, interleaving and symbol selection 123 11.2.3.1. CTC encoding 100 11.2.3.2. Interleaving 101 11.2.3.3. Symbol selection 102 11.2.3.4. Repeat process 102 11.3. Modulation 103 11.3.1. Scrambling progression 103 11.3.2. Mapping and modulation 104 11.3.3. Downlink preamble modulation 106 11.3.4. Downlink and uplink pilot subcarrier modulation 106 11.3.5. Ranging signal modulation 107 11.4. Convolution channel encoding 107 11.4.1. Randomization 107 11.4.2. Connection Process 109 11.4.3. Convolution encoding 110 11.4.4. Interleaver 113 11.4.5. Repetition 114 12. Uplink control channel 114 12.1. Uplink control channel (for CQI 5bit) 115 12.1.1. CQI channel coding 115 12.1.2. ACK channel encoding 117 vi
12.1.3. CQI/ACK channel modulation 118 12.1.4. CQI channel allocation for MIMO coefficient 120 12.1.5. CQI channel allocation for MIMO mode selection 120 12.2. Uplink control channel (in case of CQI 4bit) 121 12.2.1. CQI channel encoding 122 12.2.2. ACK channel encoding 123 12.2.3. CQI/ACK channel modulation 123 12.2.4. CQI channel allocation for MIMO coefficient 123 12.2.5. CQI channel allocation for selecting MIMO mode 124 12.3. Uplink control channel (in case of CQI 6bit) 125 12.3.1. CQI channel coding 125 12.3.2. ACK channel coding 128 12.3.3. CQI/ACK channel modulation 129 12.3.4. CQI channel allocation for MIMO number 129 12.3.5. CQI channel allocation for MIMO mode selection 129 13. Windwoing 130 14. Control Function 131 14.1. Synchronization 131 14.1.1. Network synchronization 131 14.1.2. Terminal synchronization 131 14.2. Power control 132 14.2.1. Downlink power control 132 14.2.2. Uplink power control 132 vii
Picture picture 1 - OFDMA Symbol Time Structure 8 picture 2 - Description of OFDMA Frequency Area (Example of 3 subchannels) 10 picture 3 - Frame Structure 13 picture 4 - Tile Structure 14 picture 5 - Bin structure 15 picture 6 - Downlink Frame Structure 17 picture 7 - Uplink Frame Structure 18 picture 8 - Subcarrier Allocation Rule 19 picture 9 - Allocating subchannel to FCH and Sequence of Logical subchannel 22 picture 10 - Frame Structure for AAS 23 picture 11 - Construction of a MAP message 26 picture 12 - Preamble Subcarrier Set 28 picture 13 - Shared Synchronization Symbol Structure (Frequency Domain) 35 picture 14 - shared synchronization symbol structure (time domain) 36 picture 15 - Example of Pilot Subcarrier Allocation in Downlink Diversity Symbol and Up/Downlink AMC Symbol 38 picture 16 - A Bin Composition Method of MC subchannel 40 picture 17 - Mapping of Subcarrier to AMC subchannel 42 picture 18 - Structure of Cluster Used in DL PUSC subchannel 45 picture 19 - Indexing method of Mini-subchannel 51 picture 20 - Structure of uplink PUSC tile 51 picture 21 - Initial Ranging to OFDMA and Hands-off Ranging 55 picture 22 - Periodic Ranging to OFDMA or Bandwidth Request Ranging Signal 56 viii
picture 23 - PRBS for Ranging code Generation 57 picture 24 - Pilot allocation method in a station that has two antennas 60 picture 25 - Pilot allocation method in a station that has four antennas 60 picture 26 - STC block diagram in OFDMA 61 picture 27 - Process of channel coding with H-ARQ supporting 66 picture 28 - PRBS generator of randomization block 67 picture 29 - PRBS initial structure of randomization block 67 picture 30 - CTC encoder 69 picture 31 - Interleaving method (sub-block symbol partition, interleaving, and grouping) 75 picture 32 - CTC channel encoding process 96 picture 33 - Randomized block diagram 96 picture 34 - Initialization of randomized block 97 picture 35 - Scrambling progression PRBS generator 104 picture 36 - QPSK, 16QAM, 64QAM time table 105 picture 37 - Convolution channel coding process 107 picture 38 - Randomization block diagram 108 picture 39 - Initialization randomization block 108 picture 40 - Convolution encoder of code rate 1/2 111 picture 41 - Subcarrier mapping method of CQI/ACK modulation code 119 picture 42 - MIMO coefficient mapping 120 picture 43 - MIMO coefficient mapping 123 picture 44 - Windwing of OFDMA code 130 ix
Table contents Table 1 - Basic OFDMA System Variables 12 Table 2 - Value of Frame Composition Variables 14 Table 3 - Number of Band and Bin 15 Table 4 - Type of OFDMA Down Frame Prefix 20 Table 5 - Preamble modulation progression 30 Table 6 - Shared Synchronization Symbol Progression 36 Table 7 - Downlink Subcarrier Allocation 37 Table 8 - Subcarrier Allocation in DL PUSC 44 Table 9 - Subcarrier Allocation of Uplink Diversity subchannel 47 Table 10 - Method of composing mini-subchannel from subchannel 50 Table 11 - Subcarrier allocation in uplink PUSC 52 Table 12 - Space time coding 62 Table 13 - CTC Intereaver parameter 70 Table 14 - Rotation condition table ( ) 72 Table 15 - Parameters for sub-block interleavers 74 Table 16 - Transfer types and modulation exponent for down link 79 Table 17 - N EP coding (N EP code) 87 Table 18 - Transfer types and modulation exponent for up link 89 Table 19 - Connecting rules 98 Table 20 - Subchannel connection variables by modulation method and 99 code rate Table 21 - CTC encoding rule 100 Table 22 - Sub-block interleaver parameter 101 x
Table 23 - Internal convolution coding rule 109 Table 24 - Encoding subchannel connection of allocation and modulation 110 Table 25 - Puncturing pattern of convolution encoding 112 Table 26 - Subchannel payload 112 Table 27 - CQI 5 bit information and code language allocation 115 Table 28 - ACK information and code language allocation 117 Table 29 - QPSK orthogonal modulation index for CQI/ACK channel 118 Table 30 - MIMO mode method being set through fast feedback channel 121 Table 31 - CQI 4 bit information and code language allocation 122 Table 32 - MIMO mode method being sent through fast feedback channel 124 Table 33 - CQI 6 bit information and code language allocation 126 Table 34 - MIMO mode method being sent through fast feedback channel 129 xi
1. Introduction This standard describes the physical layer of TDD OFDMA in 2.3GHz frequency band. It is designed to support 60 km/h portability with frequency reuse rate of 1 in multi-cell under NLOS (Non-Line-Of-Sight) environment. 1
2. General subject 2.1. Object This standard defines the physical layer standard of portable internet system which provides high speed wireless internet service. 2.2. Application scope This standard defines the physical layer between station (RAS) and terminal (PSS) of TDD OFDMA in 2.3GHz frequency details. 2.3. Change and approval This standard can be changed or altered depending on upper level requests of high speed portable internet. 2.4. Bibliography [1] IEEE P802.16-REVd/D5-2004 Draft IEEE Standards for local and metropolitan area networks part 16: Air interface for fixed broadband wireless access systems. 2
2.5. Definition ㆍ AAS (Adaptive Antenna System): A system which actively uses many number of antennas to improve coverage and capacity. ㆍ Subcarrier index: A number referring to each subcarrier used in signal transfer and has value of 0 or more. ㆍ DC subcarrier: A subcarrier has identical frequency with RF center frequency of station or terminal. ㆍ Frequency offset index: It is a number referred to each subcarrier frequency offset in relation with carrier index. It can have a positive or negative value. ㆍ Center frequency: Center of frequency band sent from a station or a terminal. ㆍ Rx/Tx Transition Gap (RTG): It is an interval between an uplink and the following downlink transferred. In this interval, stations and terminals operate a change from receiving-mode to sending-mode and from sending-mode to receiving-mode respectively. Both stations and terminals do not send an effective signal during this period, however they ramp up transmitter subcarrier in stations, change sending/receiving antenna, and activate terminal sink. ㆍ Tx/Rx Transition Gap(TTG): It is an interval between a downlink and the following uplink transferred. In this interval, stations and terminals operate a change from sending-mode to receiving-mode and from receiving-mode to sending-mode respectively. Both stations and terminals do not receive effective signal during this period, however they ramp down transmitter subcarrier in station, change sending/receiving antenna, and activate terminal sink. 3
2.6. Abbreviation AAS BPSK BW CDMA CINR CP CQI CRC CRSC CTC DIUC FEC FFT H-ARQ I IE IEEE LSB LOS MAC MCS MISO MSB NLOS OFDM OFDMA PAPR PDU PHY PN PRBS PSS adaptive antenna system binary phase shift keying bandwidth code division multiple access carrier to interference and noise ratio cyclic prefix channel quality indicator cyclic redundancy check circular recursive systematic convolutional convolutional turbo code downlink interval usage code forward error correction fast Fourier transform hybrid-automatic repeat request in-phase information element institute of electrical and electronics engineers least significant bit line of sight medium access control modulation and coding scheme multiple input single output most significant bit non line of sight orthogonal frequency division multiplexing orthogonal frequency division multiple access peak-to-average power ratio protocol data unit physical layer pseudo random noise pseudo random binary sequence portable subscriber station 4
Q QAM QoS QPSK RAS REQ RNG RSSI RTG Rx SDMA SICH SNR STC TTG Tx UIUC quadrature-phase quadrature amplitude modulation quality of service quadrature phase shift keying radio access station request ranging received signal strength indicator receive / transmit transition gap receiver spatial division multiple access system information channel signal-to-noise ratio space time coding transmit / receive transition gap transmitter uplink interval usage code 5
3. Frequency 3.1. Frequency tolerance Sending carrier center frequency, receiving carrier center frequency and symbol clock frequency in a station all originate from oscillators of identical standard. Allowed value of standard frequency error is ±0.02 ppm. In terminal, sending carrier center frequency and symbol clock frequency must be synchronized with error within ±1 % of frequency interval between subcarriers of station. Each terminal must be able to send an uplink signal after synchronizing frequency within allowed value. During normal operation, each terminal must consistently track frequency changes, and should withhold all uplink signal sendings in case of loosing frequency synchronization. 3.2 Spectrum requests 3.2.1. Channel placement 125kHz will be used as a carrier frequency setting unit(channel raster) in portable internet system. Absolute frequency value of carrier frequency is defined as center frequency, and center frequency is given as follows. Fc = Ncf 0.125[MHz] In the above formula, Fc is a center frequency of carrier and Ncf stands for center frequency number. 6
4. Duplex TDD(time division duplex) is used. 7
5. Description of OFDMA symbol, symbol variables and sending signal 5.1. Description of time area Time area OFDMA signal waveform is being made through reverse Fourier transform and as a result, OFDMA symbol interval is represented as effective symbol time T b. By attaching a copy (named as CP) as last T g of effective symbol time to beginning of OFDMA signal, multi-pathway signal is collected and orthogonality between subcarriers is maintained. Picture 1 shows such structure. Picture 1 - OFDMA Symbol Time Structure Transmitter energy is increased with length of protection interval, however loss with 10log(1-T g /T b +T g ))log(10)db occurs in E b/ N 0 since receiver energy is identical(cp interval is omitted from receiver). Such CP interval provides tolerance error about symbol time synchronization error as well as susceptibility about multi-pathway signal. 8
5.2. Description of frequency area Description of frequency area about OFDMA signal including basic structure of OFDMAsymbolisasfollows. OFDMA symbol consists of multiple subcarriers, and size of FFT being used is determined by number of subcarrier. Types of subcarrier are varied as shown below. - Data subcarrier: For data transfer - Pilot subcarrier: For various assumptions - Null subcarrier: No signal. For protection band and DC subcarrier Purpose of protection band is to let spectrum of OFDMA signal have a form of this 'brick wall.' When Fourier transforming by transferring 0 (no signal) to left and right side of several subcarriers, signal elements acting as an interference to adjacent frequency band can be reduced. In OFDMA mode, subcarriers are divided into subcarrier sub-sets, and each sub-set is named as subchannel. In downlink, subchannel exists for other (group of) receivers whereas transmitter in uplink is allocated to more than one subchannel. Several transmitters can simultaneously transfer signal. Subcarriers which constitute single subchannel are able to adjoin, however it is not mandatory. This concept is shown in Picture 2. 9
Picture 2 Description of OFDMA Frequency Area (Example of 3 subchannels) 5.3. Basic symbol variables Four basic variables that characterize OFDMA symbol are as follows. - BW: Channel bandwidth (Nominal channel bandwidth) - N used :: Number of subcarrier used in signal transfer - n: Sampling counter. It decides subcarrier interval and effective symbol time with BW and N used. This value is set to 8/7. - G: CP time ratio to "effective" time. G=1/8의 CP time is supported. 5.4. Derived symbol variables Following variables are expressed as basic variables in Section 5.3. - N FFT : the smallest number that is greater than N used among numbers expressed as power of 2. 10
- Sampling frequency: F s =n*bw (BW is MHz unit) - f: Subcarrier interval defined as f: F s /N fft. - Effective symbol time: T b -1/ f - CP time: T g =G T b - OFDMA symbol time: T s =T b +T g - Sampling interval: T b /N FFT 5.5. Transfer signal Numerical formula (1) shows OFDMA symbol being transferred to antenna as a time function. In this formula, t represents time being passed after starting point of OFDMA symbol with 0<t< T s, c k T g T s represents multi-decimal data being transferred to subcarrier that frequency offset index is k among OFDMA symbols. It shows a point on QAM time table. represents protection interval. represents OFDMA symbol time including protection interval. f represents frequency interval of subcarrier. 11
5.6 Basic system variables System variables are designed with a fixed frame structure of 5msec and basic system variables is shown in Table 1. Table 1 - Basic OFDMA System Variables Variables Bandwidth (Nominal Channel BW) Sampling frequency (F s ) Sampling interval (1/ F s ) Value of variables 8.75 MHz 10 MHz 100 nsec FFTsize (N FFT) 1024 Number of subcarrier being used 864 Number of data subcarrier being used 768 Number of pilot subcarrier being used 96 Subcarrier frequency interval 9.765625KHz Effective symbol time (T b =1/ f) 102.4 μs CP time (T b = T b /8) 12.8 μs OFDMA symbol time (T s =T b +T g ) 115.2 μs TDD frame length 5 ms 12
6. Frame structure 6.1. Frame structure Uplink and downlink of TDD system are distinguished by a transfer. As shown in picture 3, downlink transfer begins in sequence of a preamble symbol, FCH DL-MAP, and a data symbol. Uplink begins with control symbol transfer. TTG (121.2 μs) and RTG (40.4 μs), protection time for distinguishing uplink and down stream transfer time, are inserted between downlink (DL) and uplink (UL) at middle and end of frame. Table 2 shows main frame variables. downward interval Bin Upward interval Tile Bin Band 0 Band 1 Band 2 Band 3 Band B-1 Band B-2 PUSC subchannel interval AMC subchannel interval Diversity subchannel interval Situation control symbol interval Diversity subchannel interval AMC subchannel interval Picture 3 - Frame Structure 13
Table 2 - Value of Frame Composition Variables Variables Value of variables FFT size (N fft ) 1024 symbol time (T s) 115.2 μs Number of symbol per frame 42 TTG time 121.2 μs RTG time 40.4 μs PUSC subchannel, diversity subchannel and AMC subchannel exist in a downlink frame, where as diversity subchannel and AMC subchannel exist in an uplink frame. PUSC subchannel, diversity subchannel or AMC subchannel has additional transfer interval composed of consecutive symbol. PUSC subchannel of downlink is defined through two symbols, and one PUSC subchannel is composed of 4 pilot subcarriers and 48 data subcarriers. Diversity subchannel of downlink is composed of 48 subcarriers that are diffused to entire band from one symbol. In uplink, a tile composed of collection of 3 adjacent subcarriers in 3 consecutive symbol intervals is basic allocation unit for composing diversity subchannel. Diversity subchannel of uplink consists of six tiles and each tile is diffused to entire frequency band. Picture 4 shows tile structure. 8 data subcarrier + 1 pilot subcarrier Picture 4 - Tile Structure 14
Basic unit made up of AMC subchannel is Bin which constitutes of 9 subcarriers that are adjacent to identical symbols. Bin structure is shown in Picture 5. Four bins exist in one band, and AMC subchannel is composed of 6 adjacent bins in an identical band. This relationship is summarized in Table 3. Direction of pilot subcarrier is decided by that of bin and symbol. 8 Data Subcarrier 1 Pilot Subcarrier Picture 5 - Bin structure Table 3 Number of Band and bin Bandwidth (Nominal channel BW) 8.75 MHz N FFT 1024 Number of band 24 Number of band for each bin 4 Symbol interval with subcarriers forming one subchannel is defined as a slot. Therefore, length of slot is different depending on the type of subchannel that divides uplink and downlink. 2 symbols followed by preamble which are always used as PUSC subchannel in downlink, and include FCH (frame control header) for transferring 24bit of frame structure information. 15
Structure of FCH field is defined in MAC standard. Mapping to subchannel of FCH information consists of 2 steps. It first makes 24bit to 48bit by simple repeating, and then modulates it to QPSK 1/2 and maps to number 0 to 3 in subchannel by repeating it 4 times. Use channel coding method for MAP message defined in Section 11.4 as the coding method for this process. First three symbols in uplink are used for transferring control signal. Ranging channel, ACK channel and CQI channel are transferred through such control symbol. Diversity subchannel interval comes before AMC subchannel interval in uplink and downlink frame. 6.1.1. Downlink Frame Structure Downlink frame structure is the same as Picture 6. Down preamble can be used in initial synchronization, cell searching, frequency offset, and channel assumption. Data transfer interval of downlink is divided into PUSC subchannel interval, diversity subchannel interval and AMC subchannel interval. PUSC subchannel consists of subcarrier diffused through two symbols, where as diversity subchannel consists of subcarrier that is diffused from one symbol to the entire band. AMC subchannel consists of 6 adjacent bins in an identical band. Composition of PUSC symbol (P), diversity symbol (D) and AMC symbol (A) is determined by a station depending on channel distribution of terminals. Some symbols located at rear downlink can be used for broadcasting service. Number of broadcasting symbols and identical ID cell for composition of identical subchannel in each cell are defined in Format Configuration IE() and DL Zone_Switch_IE() of DL MAP respectively. 16
symbol Band b-1 Band b Band b+1 Preamble AMC subchannel for bin PUSC and diversity Carrier for subchannel Picture 6 - Downlink Frame Structure 6.1.2. Uplink frame structure First three symbols in uplink are used for ranging channel, ACK channel and CQI channel as shown in Picture 7. Basic unit that composes diversity subchannel in uplink is a tile. Diversity subchannel is composed of three tiles that are distributed to entire frequency band. Like the case of downlink, basic unit that constitutes AMC subchannel is bin, and one AMC subchannel consists of six bins. Distribution rate of AMC and diversity subchannel is changeable for each frame as it is in downlink. Since interval for initial connection of terminal is separated from traffic symbol interval, interruption to traffic channel can be reduced. Adaptive modulation of downlink, ACK channel and CQI channel for H-ARQ are defined in control symbol intervals. 17
Tile Bin Band 0 Band 1 Band 2 Band 3 Band B-2 Bin Pilot subcarrier Band B-1 Tile Upward control symbol interval Picture 7 - Uplink Frame Structure 6.1.3. Corresponding rule for multiple subchannel allocation Regarding methods of informing burst allocation in downlink, there is a two-dimensional allocation method which notifies start and end point in two-dimensional surface of symbol and subchannel, and a one-dimensional allocation method that notifies length of each burst in sequence. Burst allocation sequence in downlink orients subchannel to subchannel axis as illustrated in Picture 8. In case of allocating multiple subchannel to single burst in downlink, allocation is being made to subchannel axis first and data mapping is in progress towards subchannel axis as well. Data burst of uplink is allocated to one-dimension, and it allocates to symbol axis first and notifies only length of burst in sequence. 18
In case of allocating multiple subchannel to single burst in uplink, allocation is being made to subchannel axis first and data mapping is in progress towards subchannel axis. Allocation of two-dimensional ranging and CQI/ACK channel in control channel interval is to place subcarrier first to frequency axis. Subchannel Index Symbol Index (n) Picture 8 - Subcarrier Allocation Rule 6.1.4. Downlink frame prefix Downlink frame prefix (DL_Frame_Prefix) is a data structure being transferred to beginning part of each frame. It contains information about present frame being transferred and it is mapped to FCH. Table 4 below shows structure of downlink frame prefix. 24bit of downlink frame prefix is photocopied in double size in sequence to suit it to 48bit, the smallest FCH block size. 19
Table 4 Type of OFDMA Downlink Frame Prefix Syntax Size Notes DL_Frame_Prefix_Format() { Used subchannel bitmap Ranging_Change_Indication Repetition_Coding_Indication Coding_Indication DL-MAP_Length 6 bits 1 bit 2 bits 3 bits 8 bits Bit #0: use subchannel set 0-5 Bit #1: use subchannel set 6-9 Bit #2: use subchannel set 10-15 Bit #3: use subchannel set 16-19 Bit #4: use subchannel set 20-25 Bit #5: use subchannel set 26-29 No repeating symbol in 00 - DL-MAP Use additional repeating symbol once in 01 -DL-MAP Use additional repeating symbol three times in 10 - DL-MAP Use additional repeating symbol five times in 11 - DL-MAP Use CC encoding method in 0b000 - DL-MAP 0b001 - reserved Use CTC encoding method in 0b0010 - DL-MAP Use ZTCC encoding method in 0b0011 - DL-MAP 0b100 to 0b111 - reserved Reserved 4 bits Leave as 0 20
Used subchannel bitmap Bitmap used for notifying what types of subchannel set are allocated in PUSC area Ranging_Change_Indication Flag that notifies whether allocation for ranging (Periodic ranging/bw request) has been changed in present frame. Value 1 represents changes in allocation and value 0 represents same state as previous frame. Repetition_Coding_Indication Number of repetition in DL-MAP transfer. Coding_Indication Represents encoding method being used in DL-MAP transfer (DL-MAP is transferred with rate of QPSK 1/2). DL-MAP_Length Represents length of DL-MAP message followed by DL_Frame_Prefix (subchannel unit). 6.1.4.1. Allocating subchannel to FCH and sequence of logical subchannel At least 6 subchannels are allocated to each segment in PUSC. As defined in Section 6.1.4, first 4 subchannels of downlink include FCH. Subchannel sets basically allocated to segment 0,1,2 are subchannel 0-5, 10-15, 20-25 respectively. Picture 9 explains such structure. 21
OFDMA Symbol Index Segment 0 FCH Preamb Segment 1 FCH Subchannel Segment 2 FCH Down link Picture 9 - Allocating subchannel to FCH and Sequence of Logical subchannel When encoding DL_FRAME_PREFIX in FCH, terminal can detect the number of subchannel allocated to PUSC and information on types of subchannel allocated. In order to allocate subchannel in sequence in downlink, reallocation of subchannel is required. Reallocation is repetitiously processed from beginning of subchannel allocated to FCH to end of subchannel allocated to relevant segment. If it reaches to the end of subchannel, it returns to no.0 of subchannel and heads back to subchannel allocated to FCH. 22
6.2. Frame structure information Frame structure information about uplink and downlink ratio, and diversity and AMC application symbol in uplink and downlink is defined in format configuration IE of DL MAP. 6.3. AAS operation (optional) When operating in AAS mode, only subchannel is used in uplink and downlink traffic burst. Downlink frame is composed of preamble, AAS_FCH, MAP burst and traffic burst as illustrated in Picture 10, whereas uplink frame consist of control channel interval and traffic burst. Diversity Control Channel Down-link Burst #1 Up-link Burst #1 Preamble Downlink Burst #2 Down-link Burst #3 Down-link Burst #4 Down-link Burst #5 Control Symbol Up-link Burst #2 Up-link Burst #3 Up-link Burst #4 Picture 10 - Frame Structure for AAS 23
6.3.1. Preamble First as shown in Picture 10, two symbols are used as preamble. Preamble is transferred through wide beam form pattern in the same way as operating in non-aas mode. It is used in network synchronization and cell search. 6.3.2 AAS_FCH AAS_FCH, system information channel, is located right after preamble symbol and is sent with AAS beam that has specific direction at specific time. When operating with SDMA, simultaneous transfers to several beams are possible. AAS_FCH includes AAS beam direction index that is in accordance with direction appointed by AAS beam. 6.3.3. MAP burst transfer AAS mode MAP has the same format as non-aas mode MAP. MAP can be simultaneously transferred to several beams at the same time through SDMA in the same method as AAS-FCH. 24
7. MAP message field and IE FCH is located after preamble and MAP message is transferred later on. MAP message is transferred by being loaded on DL MAP and H-ARQ MAP. DL MAP or compressed MAP and H-ARQ MAP consist of bursts' IE that is transferred to downlink or uplink and structure information. DL MAP or compressed MAP is encoded as 1/2 CTC (refer to Section 11.2), modulated as QPSK, and applied by repetition symbol n. Number repetitions regarding this, subchannel allocated to DL MAP or compressed MAP is transferred through FCH. Allocation information about H-ARQ MAP is defined in DL MAP or compressed MAP as a type of IE. Each FCH and IE is defined in MAC standard. H-ARQ MAP is allocated from subchannel with the smallest subchannel index of the smallest OFDMA symbol index among all resources except for resources occupied by burst allocated by FCH, DL MAP, or compressed MAP and DL MAP, or compressed MAP. Downburst allocated by H-ARQ MAP is reallocated from subchannel that has the smallest subchannel index of the smallest OFDMA symbol index among remaining resources, in order. UL allocation information about burst except control symbol in H-ARQ MAP will be applied after up control symbol (3 OFDMA symbol). Burst will be allocated from subchannel that has the smallest subchannel index of OFDMA symbol index in remaining resources. 25
down link diversity subchannel data burst preamble Picture 11 - Construction of MAP message 26
8. OFDMA subcarrier allocation Set of used subcarrier N used can be obtained if DC subcarrier and protection subcarrier subtracted from N FFT (assume that N used is identical for certain period of time). In uplink and downlink, this N used number of subcarrier is allocated to pilot subcarrier and data subcarrier. AMC subchannel constitutes of a set of bin, a basic allocation unit that is composed of 9 adjacent subcarriers including one pilot subcarrier in one symbol, in uplink and downlink. However, diversity subchannel has different structure that depends on uplink and downlink. In downlink, pilot subcarrier is allocated first and remaining subcarrier is used for data transfer. But in case of uplink, diversity subchannel, a set of adjacent subcarrier, forms a tile in time-frequency surface, and pilot subcarrier is allocated into the tile. Also, in downlink PUSC subchannel, all subcarriers excluding null subcarrier and DC subcarrier are divided into cluster unit composed of 14 adjacent subcarriers, and pilot subcarrier is allocated to specific location in each cluster. Subcarrier will be appointed as subcarrier index k and corresponding frequency offset index K foi will be appointed as follows in later parts of this standard. N used, defined as above, represents remaining number of subcarriers after DC subcarrier and protection subcarrier is subtracted from N FFT. 27
8.1. Downlink 8.1.1. Preamble First symbol of downlink transfer is preamble. Subcarriers that constitute preamble are transferred as specific PN symbol is being modulated with BPSK. Preamble subcarrier set is divided into 3 types and each set is defined as below formula. PreambleCarrierSet n represents a set of all subcarriers allocated to specific preamble. n is index that represents preamble subcarrier set and has value of 0, 1 or 2. index k has a range from 0~283. Each segment use one subcarrier set among 3 preamble subcarrier sets as below. ㆍ 0 segment is 0 th preamble subcarrier set (Preamble CarrierSet 0 ) ㆍ 1 segment는 1 st preamble subcarrier set (Preamble CarrierSet 1 ) ㆍ 2 segment는 2 nd preamble subcarrier set (Preamble CarrierSet 2 ) But, DC subcarrier and last subcarrier are not modulated in 2 nd segment. Picture 12 shows a preamble subcarrier set of 0 th segment. Picture 12 - Preamble Subcarrier Set 28
PN progression transferred to preamble is arranged in Table 5. PN progression in use is determined by segment number and IDcell parameter value. Each PN progression defined is mapped to preamble subcarrier in ascending order. PN progression is expressed as a form hexadecimal in Table 5. After transforming presented hexadecimal progression as binary progression (Wk) to obtain appropriate PN symbol value, W k is mapped from MSB to LSB. (0 should be mapped as +1, 1 as -1. For example, in a zero segment whose index is 0, W k is 110000010010.; therefore, transformed PN symbol value is -1-1 +1 +1 +1 +1 +1-1 +1 +1-1 +1.) 29
Table 5 - Preamble modulation progression index segment modulation progression (hexadecimal number) 30
31
32
33
34
8.1.1.1. Shared synchronization symbol (optional) Last OFDM symbol in every 4 th downlink frame is shared synchronization symbol. In station, shared synchronization symbol is transferred through antenna 0. Shared synchronization symbol progression is mapped to shared synchronization symbol subcarrier according to the formula below. K is an index that has a range from 1 to (1024 N LEFT-FFT N RIGHT-FFT 1) / 2. N LEFT-EFT is number of subcarriers on the left protection band and N RIGHT-EFT is number of subcarriers on the right protection band. DC subcarrier is not modulated, and always has 0 value. Structure of shared synchronization symbol defined in frequency domain and time domainareshowninpicture13andpicture14respectively. Set of shared symbol ubcarrier Subcarrier Index Null Subcarrier Picture 13 - Shared Synchronization Symbol Structure (Frequency Domain) 35
Time Sequence Sequence Sample Copy Effective OFDMA Symbol Time Picture 14 - shared synchronization symbol structure (time domain) All station of network transfer identical shared synchronization symbol. 8.1.1.2. Shared synchronization symbol progression Shared synchronization symbol progression is shown in Table 6. Table 6 - Shared Synchronization Symbol Progression Progression(Hexadecimal) 8.1.2. Symbol structure Downlink diversity symbol and up/downlink AMC symbol are composed of pilot, data and null partial carriers, and each number of carriers is shown in Table 7. Here, null subcarrier refers to protection subcarrier and DC subcarrier. 36
Allocation of subcarrier is done in this order: of pilots and null subcarriers are allocated first and then all remaining subcarriers are used as data subcarriers afterwards (these data subcarriers again are divided into subchannel). As shown in Picture 15, allocation of pilot subcarrier is being made by allocating one specific subcarrier inside of bin that consists of 9 consecutive subcarriers. Location of pilot subcarrier inside of bin can be different depending on index of symbol. Supposing that index of 9 subcarriers inside of bin are 0~8 and index of symbol is m, that of pilot subcarrier can be 3 / + 1 ( / = m mod 3). Table 7 - Downlink Subcarrier Allocation Parameter Value Remark Number of DC subcarrier 1 Number of left subcarrier 80 Number of right subcarrier 79 Number of Used subcarrier(nused) 864 Number of pilot subcarrier 96 Index of pilot subcarrier 9k+3m+1, for k=0,, 95 and m=[symbol index]mod3 Number of data subcarrier 768 symbol the index 0, is first symbol of frame. 37
Symbol Symb ol 3 Symb ol 4 Symb ol 5 Symb ol 6 Subcarrier Bin Data Subcarrier Pilot Subcarrier Picture 15 Example of Pilot Subcarrier Allocation in Downlink Diversity Symbol and Up/Downlink AMC Symbol 38
Downlink PUSC symbol and uplink diversity symbol have different symbol structure from the one explained above. Downlink PUSC symbol also consists of pilot, data and null subcarrier, yet the number of null subcarrier and allocation method are different from diversity symbol and AMC symbol. In uplink diversity symbol, all subcarriers, excluding null subcarrier and DC subcarrier in consecutive 3 symbols, are divided into tiles, 3 3 frequency-time block containing 9 subcarriers (1 pilot subcarrier and 8 data subcarriers), and subchannel is shaped based on these titles. Section 8.2.2 will thoroughly explain about this. 8.1.3. Allocation to subchannel of data subcarrier in downlink 8.1.3.1. AMC subchannel To compose AMC subchannel, entire subcarrier excluding null subcarrier in each symbol is divided into bin, a unit consisting of 9 consecutive subcarriers. And band composition will be followed by tying up M number of adjacent bins in previous process. M, number of bin composing a band is decided by high layer. AMC subchannel consists of 6 adjacent bins in each band. Methods of composing 6 adjacent bins are 1 bin 6 symbol block, 2 bin 3 symbol block and 3 bin 2 symbol block on frequency-time axis. Finally, subchannel can be constituted by dividing it by 6 subchannels each from front after assigning index in sequence to frequency axis direction in each band. Picture 16 briefly illustrates such bin composition method of AMC subchannel. Since types of AMC subchannel are all identical in frames, information about which type used in present frame by high layer is notified. Name of each type is called by 1 6 type, 2 3 type, 3 2 type, and basic type (default type) in sequence as mentioned in Picture 16 39
Symbol Bin Bininnumber0subcarrier Bininnumber1subcarrier Picture 16 - A Bin Composition Method of MC Subchannel Picture17 also shows mapping data subcarrier of 6 bins in AMC subchannel. Define index of traffic subcarrier from 0 to 47 in AMC subchannel. First traffic subcarrier index of first bin is 0 and the next traffic subcarrier index is 1. Subcarriers in all bins are numbered by such method. Index for subcarrier is first increased by subcarrier and then increased by bin. Index for 6 bins in subchannel begins from bin of the lowest index in first symbol among symbols including the 6 bins and increase frequency direction first. And index increases to symbol direction afterwards. Index for subchannel is executed by each band, and it moves to symbol axis and increases once it first increases to bin direction and reaches to the end of band. 40
Symbol among 48 symbols is allocated with band AMC subchannel is mapped to -th subcarrier. is the element of progression. Range of j is 0~47. In this equation, Element of signal that repletively move basic permutation to left of number Basic progression defined in GF(7 2 ): {01, 22, 46, 52, 42, 41, 26, 50, 05, 33, 62, 43, 63, 65, 32, 40, 04, 11, 23, 61, 21, 24, 13, 60, 06, 55, 31, 25, 35, 36, 51, 20, 02, 44, 15, 34, 14, 12, 45, 30, 03, 66, 54, 16, 56, 64, 10} - express 7antilogarithm n mod m The remainer of n m. Maximum integer equal to or smaller than X. 41
Formula for getting above is defined in and operation on is applied. That is, addition on (56)+(34)=(13) in, for example. executes mod 7 arithmetic by each cipher. Empty Index Subcarrier Picture 17 - Mapping of Subcarrier to AMC Subchannel 8.1.3.2 Diversity subchannel Entire data subcarrier in slot is divided as data subcarrier group adjacent to each other in order to allocate diversity subchannel. Each subchannel is composed of subcarriers which are selected one by one from this group. Therefore, the number of group will be 48 which equals to the number of data subcarrier allocated to subchannel. The number of subcarrier in one group is identical with the number of subchannel, 16. Accurate partition method that composes subchannel follows numerical formula (6) which is called the downlink permutation formula 42
Subcarrier In this equation, subcarrier(s, m) = subcarrier index of m th subcarrier that is included in subchannel s k = (m + 23 s) mod 48, k' = k mod 15 m = subcarrier index in subchannel, = 0~47 s = index of subchannel, s = 0~15 P1,c1(j) = j th element of progression obtained from periodic c1 rotation of basic permutation progression P1 to the left. P1={1, 2, 4, 8, 3, 6, 12, 11, 5, 10, 7, 14, 15, 13, 9} P2,c2(j) = j th element of progression obtained from periodic c2 rotation of basic permutation progression P2 to the left. P2={1, 4, 3, 12, 5, 7, 15, 9, 2, 8, 6, 11, 10, 14, 13} 43
In numerical formula (6), operation in [ ] is operation above GF(16). Addition is treated as binary XOR operation GF(2 ⁿ). For instance, 13 + 4 is [(1101) 2 XOR (0100) 2 ]= (1001) 2 = 9 in GF(2 ⁴), and here (X) 2 presents binary of x. Subchannel index s is transformed as binary for practicing GF(16) above operation in [ ], and practices arithmetic as if it were GF(16) above element. In symbol interval for broadcasting service, every station use diversity subchannel by setting IDcell = 0x7F in above numerical formula. 8.1.3.3. DL PUSC subchannel 8.1.3.3.1. Symbol structure of DL PUSC subchannel Symbol of PUSC subchannel consists of pilot, data and null subcarrier. For subcarrier in symbol, null subcarrier is allocated first and remaining subcarriers are divided into basic cluster. Pilot and data subcarrier are allocated in each cluster. Table 8 below presents each parameter about such symbol structure. Table 8 - Subcarrier Allocation in DL PUSC Parameter Value Remark Number of DC subcarrier 1 index 512 Number of left protection Subcarrier Number of right protection subcarrier Number of Used subcarrier (N used) Renumbering sequence 92 91 841 6, 48, 37, 21, 31, 40, 42, 56, 32, 47, 30, 33, 54, 18, 10, 15, 50, 51, 58, 46, 23, 45, 16, 57, 39, 35, 7, 55, 25, 59, 53, 11, 22, 38, 28, 19, 17, 3, 27, 12, 29, 26, 5, 41, 49, 44, 9, 8, 1, 13, 36, 14, 43, 2, 20, 24, 52, 4, 34, 0 Number of subcarrier beingusedinone symbol including DC subcarrier and pilot subcarrier Used in reallocation of cluster before subchannel allocation 44
Per cluster Number of subcarrier 14 Number of cluster 60 Per subchannel Number of subcarrier 24 Number of subchannel 30 PermutationBase6 (about 6 subchannel) PermutationBase4 (about 4 subchannel) 3,2,6,4,5,1 3,4,2,1 Picture 18 below shows location of pilot subcarrier in cluster structure and cluster. Odd-number Symbol Even-number Symbol Pilot Subcarrier Data Subcarrier Picture 18 Structure of Cluster Used in DL PUSC subchannel 8.1.3.3.2. Subcarrier allocation method of DL PUSC subchannel Each subcarrier allocation to subchannel is conducted by below sequence. 1) Divide entire subcarrier into 60 clusters that are composed of 14 consecutive subcarriers. 2) Reallocate No.1) physical cluster to Logical cluster using the numerical formula below. LogicalCluster = RenumberingSequence((PhysicalClustre + 13*IDCell) mod60) 45
3) IDcell must to be set to 0 in case of first PUSC zone of downlink. 4) Divide logical cluster into 6 large groups. Large group No.0, No.1, No.2, No.3, No. 4, and No. 5 include cluster of 0~12, 12~19, 20~31, 32~39, 40~51, and 52~59 respectively. When any segment is in use, at least on large group must be allocated. Large group No.0 must be allocated to No.0 segment, large group No.2 must be allocated to No.1 segment and large group No.4 must be allocated to No.2 segment by default. 5) Inside of large group, subcarriers are divided into six or four subchannels depending on the number of clusters in large group. In each large group, data subcarriers excluding pilot are re-divided into groups of adjacent subcarriers Each subchannel includes subcarrier as number of subcarrier group through being allocated with single subcarrier from each divided subcarrier group. Therefore, number of subcarrier group is the same as that of subcarrier in subchannel and the value is 24. The number of subcarrier in subcarrier group is identical to that of subchannel in each large group, and their value is 6 or 4 depending on number of cluster in each large group. It is represented as N subch.. Allocation of subcarrier to subchannel is exercised by numerical formula below. Here, subcarrier (k, s) is subcarrier index of subcarrier k in subchannel s k = 0~23 s is index of subchannel and s = 0,, N subch - 1 This rotated PermutationBase progression to the left for s times. If PermutationBase is large group 0, 2 and 4, use PermutationBase6 and if it is large group 1, 3 and 5, use PermutationBase4. In case of integer between 0 to 31 in IDcell 0 and first PUSC zone in downlink, IDcell must to be set to 0. 46
8.2. Uplink 8.2.1. AMC subchannel allocation Uplink AMC subchannel allocation is basically identical with one in downlink. Remaining all data symbols after diversity subchannel symbol are allocated to subchannel. The location of pilot subcarrier in uplink AMC subchannel is to occupy location with three symbols as a period, and it is the same method as location of pilot subcarrier in downlink. 8.2.2. Uplink diversity subchannel allocation To allocate subchannel, 3 consecutive symbols in subcarrier are partitioned to tiles, 3 3 frequency-time block that has 9 tons (1pilot ton and 8 data tons). Entire frequency band is partitioned to groups that consist of adjacent tiles. As each subchannel consists of 6 tiles, it is constituted of 48 data subcarriers and 6 pilot subcarriers. Table 9 shows detailed value of parameter for symbol structure of this uplink diversity subchannel. Table 9 - Subcarrier Allocation of Uplink Diversity Subchannel Parameter Value Number of DC subcarrier 1 Number of left protection subcarrier 80 Number of right protection subcarrier 79 Number of used subcarrier (Nused) (pilot subcarrier and DC subcarrier included) 865 Number of subchannel 48 Number of tile 288 Number of subcarrier per tile (per 1 symbol) 3 Number of subchannel per tile 6 47
For 1024-FFT, the number of tile is 16 in one group, and there are 18 groups in each symbol. Since one subchannel consists of 6 tiles, it selects each tile from each different group after selecting 6 groups (distance between each six group is 3) that have equal interval distance between them. Precise method that constitutes subchannel follows numerical formula (7), called as uplink permutation formula. In this equation, Tile(s, m) = tile index of m th tile in subchannel s S=, s'=smod16 m = subchannel 내 tile index, m=0~5 s = subchannel index number s=0~47 P 1,c 1 (j)= j th element of progression obtained through repeating rotation of basic permutation progression P 1 to the left for C 1 time. P 1 = {1,2,4,8,3,6,12,11,5,10,7,14,15,13,9 } P 2,c2 (j)= j th element of progression obtained through repeating rotation of basic permutation progression P 2 to the left for C 2 time. P 2 = {1,4,3,12,5,7,15,9,2,8,6,11,10,14,13 } c 1 = ID cell mod16, c 2 = 48
In the equation (7), operation inside [ ] is practiced on GF(16). In GF(2 n ), addition is operated as binary XOR. For example, in GF(16), 13 + 4 is equal to [(1101) 2 XOR(0100) 2 ]=(1001) 2 =9 and, here (x) 2 is binary expression of x. When tile allocation to subchannel finishes, indexing to carrier in subchannel will be in process through following steps. 1. Subcarriers in a tile included in subchannel are indexed first in sequence of low index at first symbol, and subcarriers in a tile included in second and third symbol are indexed by the same method. At this point, tile in the center of carrier is omitted from the indexing as it is a pilot carrier thus index of carrier will be 0 ~ 47. 2. After finishing the indexing described above in No.1, real order of data being mapped to each carrier is decided by the numerical formula below. subcarrier(n)=(n+13 ㆍ s)mod48 Here,n=0...47,sissubchannelindex 8.2.3. Mini-subchannel 8.2.3.1. Partitioning subchannel to mini-subchannel Mini-subchannel consists of 6 3x3 tiles that is identical to existing diversity subchannel. Mini-subchannel is constituted by total of 6 tiles by allocating 6/M number of tiles in each interval of three symbols after connecting M(M=2,3,6) number of diversity subchannel to symbol direction. Table 10 shows four types of subchannel partition for composition of mini-subchannel. Tile index presents index about 6tiles in each subchannel in Section 8.2.2, numerical formula (7). Same method is used for indexing carrier in mini-subchannel as indexing method for broadcast band in subchannel in Section 8.2.2. 49
8.2.3.2. Subchannel number allocation to mini-subchannel In all symbols except 3 symbols being used for control channel among symbols allocated to diversity subchannel, burst is allocated using mini-subchannel by CType = 01 in composition of mini-subchannel previously defined. Among the above defined composition, burst is allocated using mini-subchannel by CType = 01. All subchannels in this area are repartitioned as a form of mini-subchannel by Ctype = 01 and at this point, two mini-subchannels in mini-subchannel are created for two subchannels that have same index in adjacent 6 symbols as shown in Table10. Hence, index of entire mini-subchannel over 6 symbols are set by the same method shown in Picture 19. Burst allocation method used in uplink will be used for afterwards burst allocation; however its allocation unit will be mini-subchannel. Table 10 Method of composing mini-subchannel from subchannel CType Number of connecting subchannel Number of mini subchannel Mini subchannel index Tile index in subchannel 0 1 2 3 4 5 00 2 2 0 0,1,2 3,4,5 1 3,4,5 0,1,2 01 2 2 0 0,2,4 0,2,4 1 1,3,5 1,3,5 10 3 3 0 0,1 2,3 4,5 1 4,5 0,1 2,3 2 2,3 4,5 0,1 11 6 6 0 0 1 2 3 4 5 1 5 0 1 2 3 4 2 4 5 0 1 2 3 3 3 4 5 0 1 2 4 2 3 4 5 0 1 5 1 2 3 4 5 0 50
3 Symbol 3 Symbol 1 Mini-Subchannel 0 Subchannel Subchannel 0 Mini-Subchannel 1 Mini-Subchannel 2 Mini-Subchannel 3 Mini-Subchannel 4 Mini-Subchannel 5 Subchannel 1 Subchannel 2 Mini-Subchannel 94 Mini-Subchannel 95 Subchannel 47 Picture 19 - Indexing method of Mini-subchannel 8.2.4. Uplink PUSC Subchannel in uplink PUSC is composed of 4 subcarrier 3 symbol tile 6 as shown in Picture 20. Symbol 0 Symbol 1 Symbol 2 Plot Subcarrier Data Subcarrier Picture 20 Structure of uplink PUSC tile 51
Table 11 - Subcarrier allocation in uplink PUSC Parameter Value Remark Number of DC subcarrier 1 index 512 Number of left protection subcarrier 92 Number of right protection subcarrier 91 Number of used subcarrier(n used ) 841 Number of subcarrier being used in symbol including DC subcarrier and pilot subcarrier Number of tile 210 Number of subchannel 35 Number of subchannel per tile 6 Number of subchannel per subcarrier 48 Allocation structure of subcarrier in uplink PUSC is shown in Table 11. 840 used subcarriers excluding DC subcarrier are divided into 210 tiles with the same structure as Picture 20, and these 210 tiles are divided into 6 groups consisting of adjacent 35 tiles. Each 6 groups allocate one tile to one subchannel and the subchannel consists a total of 6 tiles received from the 6 groups. Method for selecting 6 tiles is described in numerical formula below. Tile(s, n)=35n+(pt[(s+n) mod35]+ul_idcell)mod 35 52
In this formula, n =tileindex,n = 0~5 Pt = {11, 19, 12, 32, 33, 9, 30, 7, 4, 2, 13, 8, 17, 23, 27, 5, 15, 34, 22, 12, 14, 21, 1, 0, 24, 3, 26, 29, 31, 20, 25, 16, 10, 6, 28, 18} s = subchannel number UL_IDcell = integer from0~69 decided in MAC layer Subcarrier indexing in subchannel is made through steps explained below after finishing tile allocation for each subchannel. 1. Subcarriers in a tile included in subchannel are indexed first in order of low index in first symbol, and subcarriers in a tile included in second and third symbol are indexed by the same method. At this point, tile in the center of carrier is omitted from the indexing as it is a pilot carrier; thus index of carrier will be 0 ~ 47. 2. After finishing the indexing described above in No.1, the real order of data being mapped to each carrier is decided by numerical formula below. subcarrier(n,s)=(n+13 ㆍ s)mod48 Here, s = subchannel index n = 0 47 53
9. OFDMA ranging 4 types of ranging mode are defined in OFDMA physical layer. These ranging modes consist of early ranging, periodical ranging, hands-off ranging and bandwidth request ranging. Among the listed modes, bandwidth request ranging is used when terminal requests bandwidth to station, and the rest of the modes are used for obtaining uplink synchronization between terminal and station, and for controlling electric power. Simultaneous ranging signal sending from several terminals is allowed and each terminal distinguishes and uses ranging mode depending on purpose of using the methods explained. Terminal selects from any usable ranging symbol for ranging signal modulation and sends it as BPSK modulation. At this point, terminal can collide ranging channel since it tries to range with any selected ranging symbol. Terminals attempting to connected to network with new BS or register location information in idle state need more uplink resources because of 23bit HMAC, and these terminals can try hands-off ranging. BS that detected hands-off ranging signal must allocate more uplink resources for the terminal so that it can transfer RNG-REG and HMAC. The number of subcarrier allocated to ranging channel is 144 and uses No.0~143 subcarrier by allocating 3 3 tile type of 8 uplink diversity subchannels defined in Section. 8.2.2. The length of ranging symbol is also 144 since ranging symbol is modulated as BPSK. At this point, the number of ranging symbol per relative ranging mode that terminal is able to transfer by random selection is system operation parameter determined in system placement. Ranging transfer interval allowed to terminal varies according to ranging mode, however initial ranging and hands-off ranging transfer slots are composed of first and second OFDMA symbol in uplink frame interval whereas periodical ranging and bandwidth request ranging transfer slot consists of third OFDMA symbol in uplink frame interval. 54
The number of subchannel less than 8 can be allocated in 128 FFT and in this case, terminal should incur identical ranging symbol with the method defined below; however it modulates ranging symbol to subcarrier as many as the number of subchannels allocated (discard end of symbol that cannot be allocated). 9.1. Initial ranging and hands-off ranging Initial ranging consists of terminals initially trying to synchronize system channel and uplink whereas hands-off ranging is reached by terminals trying to synchronize with other stations while hands-off is being processed. Since initial ranging and hands-off ranging are being tried in condition that uplink synchronization is not secured at all, 2 consecutive OFDMA symbol intervals are used in composed ranging transfer slot above. At this point, identical ranging symbol is sent during 2 OFDMA symbol intervals. Picture 21 illustrates ranging signal for securing initial or hands-off synchronization on the time zone and discontinuity of waveform is not occurred in the boundary of two OFDMA symbol intervals. CP' copy CP copy Effective OFDMA Symbol First Ranging Symbol Second Ranging Symbol Picture 21 - Initial Ranging to OFDMA and Hands-off Ranging 55
9.2. Periodical ranging and bandwidth request ranging Periodical ranging is sent periodically for tracking of synchronization and bandwidth request ranging is sent when terminal requests bandwidth to station. Picture 22 depicts ranging signal for request of synchronization tracking and bandwidth allocation in the time zone. Since these two ranging signals are sent with secured synchronization they use one OFDMA symbol interval. Transfer slot of ranging signal is allocated through third OFDMA symbol interval in uplink frame interval, and terminal transfers ranging signal by selecting one symbol interval among this. CP copy Effective OFDMA Symbol Ranging Symbol Time Picture 22 - Periodic Ranging to OFDMA or Bandwidth Request Ranging Signal 56