Contribution - IEEE Standards Association

Contribution - IEEE Standards Association

IEEE 802.15-14-0664-05-004q Dec 2014 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: Choice of BCH and SiPC Codes. Date Submitted: December, 2014 Source: Chandrashekhar Thejaswi PS(Samsung), Kiran Bynam(Samsung), Jinesh Nair(Samsung), Youngsoo Kim(Samsung), Li Huang(IMEC), Guido Dolmans(IMEC), Peng Zhang (IMEC) E-Mail: [email protected] Abstract: Comment resolutions. Purpose: Response to the letter ballot comments. Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. Submissio n Slide 1 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 Comments on FEC/multiple FECs No. Reviewer Pg. Claus Ln. No e no. Timothy 1015, Harrington, 1239, James 16 1301 Gilb, M. Lynch 30.4.3 2

No. Reviewer Pg. Claus Ln. No e no. 1298 Ben Rolfe 13 1019 Guido Dolamns 17 30.1.2. 3 2.4 30.5 Comment Proposed Change There is no need to define a new FEC as there are already many defined in 802.15.4. The new FEC does not enable lower power than the existing FECs Replace the BCH and SiPC with a single FEC from the base standard. Comment Proposed Change Support for 2 FEC schemes adds complexity without clear benefit. Pick a codeing method and stick with see comment it.

The proposed SiPC code has comparable code gain and decoding complexity compared to the chosen BCH code. The start 2 - bit-to-data-symbol SiPC block can be reused from the encoding add SipC code end 6 of BCH code (please see figure 12, functional diagram in the draft proposal) such that not too much complexity is added when these two FEC codes are both implemented. Resolution: Revised Justification are given in slide #3 to slide # 11. Resolution and the changes are provided in slide#12 onwards. Submissio n Slide 2 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 Comments impacted by the changes in FEC Pg. No No. Cla Ln. use no. 1056 15 30.4.1 13 1091 15 30.4.1 13 1284 12

30.1.2 .1.2 3 Comment Proposed Change insert a remark in 30.4.1 as "In each MCS mode, the preamble format P2 and SFD/PHR explicitly mention when the preamble formats spreading format C2 is mapped on to the coding P1/P2 and SFD formats C1/C2 are used. format BCH, and the preamble format P1 and SFD/PHR spreading format C1 is mapped on to the coding format SPC." insert a remark in 30.4.1 as "In each MCS mode, the preamble format P2 and SFD/PHR explicitly mention when the premable formats spreading format C2 is mapped on to the coding P1/P2 and SFD formats C1/C2 are used. format BCH, and the preamble format P1 and SFD/PHR spreading format C1 is mapped on to the coding format SPC." Delete P1 is employed along with the 4 highrate PSDU to ensure good payload efficiency. The only real purpose of the differing P2 is employed along with the low-rate PSDU to preambles is that it is used to signal the avoid 5 any degradation in the PER spreading that will be used, as there is no other performance. as it is meaningless (and wrong) way to know this. and replace it with a description of how these are used to select the spreading.. Resolution. Revised. Deleted multiple preambles and retained only 1 premable and SFD combination All comments (1056, 1091, 1284) related to multiple preamble are resolved by the resolution proposed for CIDs mentioned in the previous slide(1019, 1298). Please see slides 14 to 20. Submissio n Slide 3 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014

General Comparison of BCH and RS codes The BCH codes are binary block-codes while the Reed-Solomon codes are non-binary block-codes. The coefficient multiplication in the BCH encoder is a simple binary operation while the coefficient multiplication in the RS encoder is a nonbinary operation over GF(2^m) The (63,51) BCH code corrects two errors in a block of n=63 bits of which k=51 are the message bits. The Reed-Solomon code of comparable parameters is the (15,13) RS code which corrects a single erroneous symbol in a block of 15 symbols. This corresponding binary parameters are n=60 and k=52 with ability to upto 4 bit errors so long as the 4 errors are confined to a single symbol. The possibility of all errors being confined to within a single symbol is remote, especially in presence of interleaving. The (63,51) BCH, which can correct two errors located anywhere in the 63 length block is a better option than (15,13) RS code which fails beyond a single symbol. The low complexity (63,51) BCH avoids the complex algorithms such as Berlekamp-Massey algorithm, Peterson's algorithm etc required for the conventional BCH decoding or RS decoding Submissio n Slide 4 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 Encoding complexity The encoding circuit for BCH codes is a binary division circuit while for Reed-Solomon codes, the division circuit is defined over where is the size of the symbol. The addition in the BCH encoder as shown in Fig (a) is binary XOR while the addition in the RS encoder in Fig(b) is addition over .

In Fig(a), g(x) represents the generator polynomial for (7,4) BCH code, while g(x) in Fig (b) corresponds to a (7,5) RS code. Here, is the primitive element of generated by the primitive polynomial Submissio n Slide 5 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 Decoding complexity Start Start Syndrome Computation Syndrome Computation Simple procedure exist that avoids the error locator polynomial and hence the dedicated algorithms Determining Error locator polynomial using a dedicated algorithm(BM, PGZ algorithm) Solving the error locator polynomial using Chien search to obtain error locations Deterministic method to solve for error locations exists in literature Solving for the error values at error locations(Forneys algorithm) NA Stop Stop The (63,51) BCH avoids the complex algorithms such as Berlekamp-Massey algorithm, Petersons algorithm etc. Substituting the Chien search with a deterministic method with huge complexity reduction. Solving error values is not required. Submissio

n Slide 6 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 Low complexity (63,51) BCH decoder (One Shot Algorithm) START Compute syndrome S1 from received word Y Is Estimated Codeword =received word S1=0 N Compute syndrome S3 Y Is S3= S13 N Obtain Error Locations as roots of quadratic equation S 1 x2+S12 x+S3+ S13=0 Error Location= S 1 N using procedure to solving quadratic equation . Estimat ed codeword=received word with values at error locations inverted the message block inverted Decoded message=last k bits of Estimated +++

codeword STOP Submissio n Slide 7 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 (63,51) BCH step by step decoder decoder The algorithm is known as the modified step-by-step decoding algorithm [1]. The algorithm enhances the step by step algorithm in [2] for the particular case of double error correcting BCH codes. The number of original errors are determined based on the syndromes. Each location is inverted and the syndromes recomputed to determine if there is reduction in number of original errors. If there is a reduction in the number of original errors, the inversion is retained else the inversion is undone. Submissio n Slide 8 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 Complexity of SiPC (9,8) decoder After bit to symbol mapping, GF(2^m) addition is required for calculating parity

After MPPM detection, store the correlation matrix of size 9xN, N is length of M-PPM code After the block of 9 symbols received, calculate Syndrome Add Syndrome to all 9 symbols received ( Submissio n Slide 9 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 Complexity of SiPC(9,8) decoder Reliability measure for any symbol out of 9 symbols Submissio n Slide 10 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 Solution for single FEC Use the concatenation of codes with SiPc as inner code and BCH as outer code SiPC code is optional. All data rates using SiPC code are optional for implementation Submissio n Slide 11 P S C Thejaswi , Samsung

IEEE 802.15-14-0664-05-004q Dec 2014 Resolution: In MCS, apart from BCH+interleaving mode, a new set of modes with the concatenation of BCH codes and SiPC codes are proposed. Usage of concatenated BCH+SiPC is optional. Only one preamble format (P2) and one spreading format (C2) is used for SFD+PHR for all MCS modes. The following changes are be implemented into the draft Change all the MCS levels from MSC (0-5) to MCS (0-7). Submissio n Slide 12 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 In Page 5, Table 46, Col. 4 Replace the sentence . For TASK PHYs, values 0-5 are valid: each data rate value corresponds to one of the MCS as described in 30.4. with For TASK PHYs, values 0-7 are valid: each data rate value corresponds to one of the MCS identifiers as described in 30.4. Submissio n Slide 13 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 In Page 11, Sub-clause 30.1.2.1.2 Delete Figure 7 and its caption. Delete Table 4 and its caption Replace the paragraph with the following text:

The preamble field shall have a unique ternary base sequence of length 32 chips repeated 8 times. This 32-chip base sequence is given by [1 0 -1 0 0 -1 0 -1 1 0 1 0 0 -1 0 1 1 0 1 0 0 -1 0 1 -1 0 1 0 0 1 0 1]. In coherent reception mode, the preamble is equivalent to a string of eight bits spread by a sequence with a spreading factor of 32, and in the non-coherent reception mode, the preamble is equivalent to a string of 32 bits spread by a sequence with a spreading factor of eight. Submissio n Slide 14 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 In Page 11, Sub-clause 30.1.2.1.3 Replace the entire paragraph with the following text The SFD field indicates end of SHR field and the beginning of the packet data. The SFD field shall consist of a pattern of eight bits, [0 1 0 1 1 0 0 1]. The bits in this field are mapped on to a ternary spreading code comprising of two orthogonal ternary sequences. The bit-to-sequence mapping shall be as given in Table 4. Table 4Spreading of the SFD field Submissio n SFD bit Bit to-sequence mapping 0 [1 0 -1 0 0 -1 0 1] 1 [0 -1 0 1 1 0 -1 0] Slide 15 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q

Dec 2014 MFI/CFI fields have been merged into a single field MCS. References to MFI/ CFI are replaced with MCS. In Pg. 12, replace Figure 8 with the following figure: Pg. 12-13, delete sub-clauses 30.1.2.2.3 and 30.1.2.2.4 and create a sub-clause under the title MCS field. Add the following text The MCS field specifies the modulation and the coding scheme applied on the PSDU. There are four modulation formats and two FEC mechanisms provided. Valid values of the MCS field and the corresponding mapping of the modulation and coding schemes are given in Table 5. Submissio n Slide 16 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 In Pg. 13, replace Table 5 with the following table: [1] MCS field Modulation format FEC (0, 0, 0) (1, 0, 0) 1/1-TASK 2/4-TASK BCH BCH with interleaving (0, 1, 0) 3/8-TASK BCH with interleaving

(1, 1, 0) (0, 0, 1) (1, 0, 1) 5/32-TASK 1/1-TASK 2/4-TASK BCH with interleaving BCH+SiPC BCH+SiPC (0, 1, 1) 3/8-TASK BCH+SiPC (1, 1, 1) 5/32-TASK BCH+SiPC BCH+SiPC: concatenated code generated by BCH with interleaving as the outer code and the SiPC as the inner code Change the caption for table to Table 5Mapping of the MCS field Delete the sub-clause 30.4.2 and the Table 7. Submissio n Slide 17 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 In Pg. 13, In sub-clause 30.1.2.2,: Introduce a new sub-clause 30.1.2.2.5 (after HCS field) with title, and the sub-clasue and tables: 30.1.2.2.5 Spreading of PHR field Similar to the spreading performed on the SFD field, bits in the PHR field are also mapped on to a ternary spreading code comprising of two orthogonal ternary sequences. The bit-tosequence mapping shall be as given in Table 6. Table 6Spreading of the PHR field Submissio

n PHR bit Bit to-sequence mapping 0 [1 0 -1 0 0 -1 0 1] 1 [0 -1 0 1 1 0 -1 0] Slide 18 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 In Page 14, Sub-clause 30.1.3: Replace the entire paragraph with following text For the given MCS, the PPDU signal shall be generated by the following procedure: a) Construct the preamble field (as given in 30.1.2.1.2), the SFD field (as given in 30.1.2.1.3) and the PHR field (as given in 30.1.2.2). b) Apply the modulation and coding on the PSDU as determined by the MCS of the PHR field. Perform pseudo-random chip inversion on the resultant chips to obtain the DATA field. This process is described in 30.4. c) Concatenate the preamble field, the spread SFD field, the PHR field, and the DATA field, according to the format given in Figure 5, to generate PPDU. d) Pass the resultant chip sequence of the PPDU through the modulation block (as described in 30.5), followed by the Gaussian pulse shaping filter as described in 30.6. The steps for generating a PPDU are pictorially presented in Figure 9. Submissio n Slide 19 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 In Page 14, Sub-clause 30.1.3: Replace Figure 10 with the following figure Preamble

PPDU SFD Concatenation Modulation Pulse shaping PHR PSDU Submissio n Encoding, Ternary sequence spreading and pseudo-random chip inversion DATA Slide 20 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 In Page 14-15 Delete clauses 30.2 and 30.3. and all the corresponding tables and figures. (Figure 11, Table 9) Submissio n Slide 21 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 In Pg. 15, Sub-clause 30.4:

Change the title to: MCS identifiers, MCS, data rates and related parameters In Pg. 15, Sub-clause 30.4.1 Change the title of the subclause to MCS identifier Replace the entire paragraph the following text: MCS identifier is determined by the higher layers based on the data rate requirements, as mentioned in 6.3.1. MCS identifier specifies modulation and coding schemes to be applied on the PSDU. In any given frequency band of operation, eight MCS identifiers (0-7) are defined based on the data rates. First four identifiers specify mandatory modes and the last four identifiers specify optional modes. When MCS identifier takes values from zero to three (MCS identifier = 0, 1, 2, 3), BCH with interleaving shall be used for FEC, otherwise (MCS identifier = 4, 5, 6, 7), concatenation of BCH with interleaving and SiPC shall be used for FEC. MCS identifiers (0-3) are mandatory and MCS identifiers (4-7) are optional. The MCS identifier and the corresponding data rates for different frequency bands are provided in Table 7, Table 8 and Table 9. Also, for each MCS, the parameters such as constellation size (Q), modulation order (M), spreading sequence length (L), and spreading factor (SF) are given in these tables. Delete sub-clause 30.4.2, its subtext and the table. Submissio n Slide 22 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 In Pg. 16, Replace Table 8 with the following table M L (Mcps) (Bits/data symbol) (Chips/data symbol) rate

Data rate (kbps) BCH 1 1 1 51/63 809.5 2/4- TASK BCH 1 2 4 51/63 404.8 2 3/8- TASK BCH 1 3 8 51/63 303.5 3 5/32- TASK BCH

1 5 32 51/63 126.5 4 (Optional) 1/1-TASK BCH+ SiPC 1 1 1 408/567 719.5 5 (Optional) 2/4- TASK BCH+SiPC 1 2 4 408/567 359.8 6 (Optional) 3/8- TASK

BCH+SiPC 1 3 8 408/567 269.7 7 (Optional) 5/32- TASK BCH+SiPC 1 5 32 408/567 112.4 MCS Coding format Chip rate identifier Modulation format 0 1/1-TASK 1 Submissio n

Slide 23 Code P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 In Pg. 16, Replace Table 9 with the following table MCS identifier Modulation format Coding format Chip rate (Mcps) M (Bits/data symbol) L (Chips/data symbol) Code rate Data rate (kbps) 0 1/1-TASK BCH 0.6

1 1 51/63 485.7 1 2/4- TASK BCH 0.6 2 4 51/63 242.8 2 3/8- TASK BCH 0.6 3 8 51/63 182.14 3 5/32- TASK BCH 0.6 5

32 51/63 75.9 4 (Optional) 1/1-TASK BCH+ SiPC 0.6 1 1 408/567 431.74 5 (Optional) 2/4- TASK BCH+SiPC 0.6 2 4 408/567 215.87 6 (Optional) 3/8- TASK BCH+SiPC 0.6

3 8 408/567 161.9 7 (Optional) 5/32- TASK BCH+SiPC 0.6 5 32 408/567 67.4 Submissio n Slide 24 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 In Pg. 16-17, Replace Table 10 with the following table MCS identifier Modulation format Coding

format Chip rate (Mcps) M (Bits/data symbol) L (Chips/data symbol) Code rate Data rate (kbps) 0 1/1-TASK BCH 0.25 1 1 51/63 202.375 1 2/4- TASK BCH 0.25 2 4 51/63 101.2

2 3/8- TASK BCH 0.25 3 8 51/63 75.875 3 5/32- TASK BCH 0.25 5 32 51/63 31.625 4 (Optional) 1/1-TASK BCH+ SiPC 0.25 1 1 408/567 179.9

5 (Optional) 2/4- TASK BCH+SiPC 0.25 2 4 408/567 89.94 6 (Optional) 3/8- TASK BCH+SiPC 0.25 3 8 408/567 67.4 7 (Optional) 5/32- TASK BCH+SiPC 0.25 5 32 408/567 28.1

Submissio n Slide 25 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 In Pg. 17, Replace Figure 12 with the new set of figures Binary data from the PSDU Shortened Shortened BCH BCH encoding encoding Bit-level interleaving Ternary sequence spreading: Data-symbol-to-chip mapping (L chips/data-symbol) Bits-to-data-symbol conversion (M bits/data-symbol) Pseudo-random chip inversion Modulated and encoded PSDU Figure 11Functional diagram of the ULP-TASK PHY modulation and encoding for PSDU: mandatory mode Binary data from the PSDU Shortened

Shortened BCH BCH encoding encoding Bit-level interleaving Ternary sequence spreading: Data-symbol-to-chip mapping (L chips/data-symbol) Non-binary SiPC(9,8)Q encoding Pseudo-random chip inversion Modulated and encoded PSDU Figure 12Functional diagram of the ULP-TASK PHY modulation and encoding for PSDU: optional mode Submissio n Slide 26 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 In Pg. 17, Replace the text in 30.5 with the following text: Functional block diagrams in Figure 11 and Figure 12 provide a reference for specifying the ULPTASK PHY modulation and coding functionalities for the PSDU. There are two modes of operation based on the FEC mechanisms: 1. Mandatory mode: (MCS identifier = 0, 1, 2, 3) BCH with interleaving shall be used for the FEC. The reference diagram for this mode is provided in Figure 11. 2. Optional mode: (MCS identifier = 4, 5, 6, 7) Concatenation of BCH with interleaving and SiPC shall be used for the FEC. The reference diagram for this mode is provided in Figure 12. Submissio

n Slide 27 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 In Pg. 17, Replace Figure 12 with the new set of figures (figures will be provided) In Pg. 22 sub-clause 30.5.1.2 Delete sentences from line 16-19. Replace them with the following text: When MCS identifier = 4,5,6,7, FEC shall be the concatenation of BCH with interleaving as the inner code and SiPC (8,9) code as the outer code. These modes are optional. SiPC (8,9) encoding on the datasymbols shall be performed as explained in following sub-clause. Delete sub-clauses 30.5.1.2.1 and 30.5.1.2.2 Submissio n Slide 28 P S C Thejaswi , Samsung IEEE 802.15-14-0664-05-004q Dec 2014 In Pg. 23, sub-clause 30.5.1.2.3 : Replace the sentences in Ln.7-9 with the following sentences. First, bits from the interleaving block are packed into a sequence of M-tuples. These M-tuples are then converted into message symbols by uniquely mapping them on to the elements of . Then these message symbols are segregated into each consisting of 8 message symbols (over ). SiPC encoder encodes each message block as follows: In Pg.23 Ln 18-19: Replace the sentences by the following sentences: Once the codewords are generated, the coded symbols, which are the elements of , are converted into data symbols by uniquely mapping them on to the -ary alphabet . Submissio n Slide 29 P S C Thejaswi , Samsung

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