Summary of offline discussion for PDCCH structure 3GPP TSG RAN WG1 Meeting 90bis Prague, CZ, 9th – 13th, October 2017 Agenda item: 7.3.1.1 R1-17xxxxx Summary of offline discussion for PDCCH structure NTT DOCOMO, INC.

Highlights Following are identified as key discussion topics: Issue 0: Wideband RS (working assumption) Let’s focus on whether to conform the working assumption Issue 1: Interleaver design Let’s focus on discussion on 1-step interleaver vs 2-step interleaver Issue 2: Details on DMRS design Let’s discuss after making progress on issue 0 and issue 1

Issue 0: Wideband RS - Background Whether to conform the working assumption? For a CORESET, precoder granularity in frequency domain is: Configurable between i) equal to the REG bundle size in the frequency domain; or ii) equal to the number of contiguous RBs in the frequency domain within the CORESET For ii), DMRS is mapped over all REGs within the CORESET. Situation on Monday online: Cannot see the performance benefit (ZTE and Ericsson) 0.7 – 1.5dB performance gain showed (Qualcomm, Samsung, and CATT)

Issue 0: Wideband RS - Discussions Parameter Value Carrier Frequency 4 GHz Control Resource Set Bandwidth 18 MHz Sub-carrier Spacing 15 kHz DCI Payload Size 20 bits + CRC Modulation QPSK Channel Coding Polar code with CRC-aided list-8 decoder; 19bit CRC Aggregation Level 8 REG bundle size 6 REGs per bundle Number of OFDM symbols for NR-PDCCH 1 Channel Model TDL-A 30ns; TDL-B 300ns; TDL-C 30ns; TDL-C 300ns; 3kmph UE speed gNB antenna configuration 2Tx UE antenna configuration 2Rx Channel Estimation Practical with MRC Noise Estimation Ideal Transmission Diversity Scheme 1-port precoder cycling for ’inband RS’ S-CDD for ’wideband RS (65ns delay) Resource mapping Distributed transmission DMRS density 1/4 R1-1718799 (Ericsson)

Issue 0: Wideband RS - Discussions R1-17117039 (ZTE) Item Value Channel TDL-A DS = 300ns, 1000ns Speed = 3kmph Antenna 2*2 Frequency 4GHz Numerology BW = 10MHz(50RB) SCS = 15kHz DMRS overhead 1/4 Aggregation level 8 CCE size 6 REGs per CCE Bundle size 3/6 Payload size 20+16(CRC) Transmit scheme sCDD Mapping scheme Interleaving CORESET duration 3OFDM symbol(s) Coding TBCC Channel estimation MMSE

Issue 0: Wideband RS - Discussions R1-17117822 (CATT) Parameter Value   NR LTE Channel TDL-C-1000ns System BW (RBs) 10 MHz CORESET BW 50 CORESET duration 2 CFI = 2 Number of TX ports 1 2 CRS ports Tx Diversity 1 port with precoder cycling SFBC Antenna configuration 2Tx 2Rx AL 2,4,8 CCE-to-REG mapping Time-first mapping, LTE PDCCH interleaver DCI size 60bits+16bits CRC DMRS density 1/4 REG bundling size 6 For 6 BS: 3 in freq, 2 in time Precoder granularity REG Bundle size in frequency domain; Wideband RS

Issue 0: Wideband RS - Discussions ZTE comments: 1: SINR of -6dB is achievable even without wideband RS 2: Wideband RS consumes more energy 3: Wideband RS creates more inter-cell interference 4: Wideband RS makes resource sharing b/w PDCCH and PDSCH more difficult 5: Wideband RS makes beam-forming/multiplexing more difficult

Issue 0: Wideband RS - Proposals Whether to conform the working assumption? For a CORESET, precoder granularity in frequency domain is: Configurable between i) equal to the REG bundle size in the frequency domain; or ii) equal to the number of contiguous RBs in the frequency domain within the CORESET For ii), DMRS is mapped over all REGs within the CORESET.

Issue 1: Interleaver design - Background 1-step interleaver vs 2-step interleaver 1-step interleaver is supported by: Ericsson, ZTE, Intel, Samsung, OPPO, InterDigital, Nokia, Motorola Mobility, Lenovo, CATT (10) 2-step interleaver is supported by: Huawei, vivo, LG, DOCOMO, MediaTek, Qualcomm (6)

Issue 1: Interleaver design - Discussions Considering the current situation, it would be better to consider 1- step interleaver; following are questions to 2-step interleaver camps Q1: What problem is found on 1-step interleaver? If it is the blocking probability in case of overlapped CORESET, how much 2-step interleaver can reduce it? Q2: What 1-step interleaver design is acceptable for 2-step interleaver supporting companies?

Issue 1: Interleaver design - Discussions 1-step vs 2-step 1-step interleaver: Firstly, no strong motivation for overlapping CORESETs are found (Samsung) If the number of columns/rows is configurable, and by choosing proper values for overlapping CORESETs, it is possible to achieve the same/similar benefit as 2-step interleaver (Samsung, Nokia) 2-step interleaver: As long as the second step interleaver is common among overlapping CORESETs, the blocking can be suppressed simply, which is also beneficial for operators. Configuring proper settings for 1-step interleaver is complicated (Qualcomm, Huawei) The value of X affects how much frequency-diversity order is obtained. According to the preliminary simulation results, diversity order of 2 would offer similar performance with full distribution of 1-step interleaver. Therefore, the value of X can be fixed to 12 – Try to obtain the results within the day (Huawei) If no consensus is made by Friday, we will define LTE based interleaver with a specific design with the interleaver unit as a REG bundle

Annex – RS aspects Wideband RS DMRS pattern DMRS sequence/scrambling Confirm the WA (Intel, Samsung, CATT, ITRI, DOCOMO, MediaTek, Qualcomm) Use wideband RS for CORESET configured MIB (Samsung) Do not confirm the WA (ZTE, Nokia, Ericsson) Confirm the part of the WA (only precoder-granularity) (Ericsson) Modify the WA such that DMRS is mapped over all REGs within the PDCCH only when AL=8 (FFS: AL=4) (Nokia) DMRS pattern Conform the WA that DMRS are evenly distributed (Ericsson, Intel, vivo, CMCC, DOCOMO, Nokia) #2, #6, #10 (Ericsson, ITRI) #1, #5, #10 (Nokia) VCID-based cyclic-shift position (Intel) No cyclic-shift with possible time-domain OCC (CMCC) DMRS sequence/scrambling Gold sequence as in LTE (Ericsson, Intel) VCID-based initialization for RRC connected case (Intel, Samsung, MediaTek, Qualcomm) Cell-ID based initialization for CSS during initial access (Samsung, LGE, MediaTek, Qualcomm)

Annex – Interleaver aspects 1-step interleaver (Ericsson, ZTE, Intel, Samsung, OPPO, InterDigital, Nokia, Motorola Mobility, Lenovo, CATT) 𝑓(𝑖)= 𝑖 𝑚𝑜𝑑 𝑁 𝑆𝐸𝐺 𝐶𝑆 𝑁 𝑅𝐵 𝑆𝐸𝐺 𝐿/ 𝑁 𝑆𝑌𝑀 𝐶𝑆 + 𝑖/ 𝑁 𝑆𝐸𝐺 𝐶𝑆 where L is the number of REGs in a REG bundle, N_SEG is the number of segments in the CORESET, N_SYM is the number of OFDM symbols in the CORESET, and N_RB is the number of contiguous RBs in a segment (Ericsson) A block interleaver with configurable rows with the interleaving unit as a REG bundle (ZTE, Intel) The interleaving function is LTE sub-block interleaver (Intel) A block interleaver with configurable number of columns and with configurable inter-column permutation and cyclic-shift based on cell-ID for interleaver input (Samsung) LTE sub-block interleaver (OPPO, InterDigital, Nokia) With cyclic REG bundle randomization with number of rows being determined by REG bundle size and possible inter-column permutation and cell-ID based cyclic shift (Nokia) 2-step interleaver (Huawei, vivo, LG, DOCOMO, MediaTek, Qualcomm) First step is an interleaver I1 within X logical REG bundles with the interleaving unit equal to a REG bundle (Huawei, vivo, LG, DOCOMO, Qualcomm) Interleaver I1 is EPDCCH interleaver based (Huawei) Interleaver I1 is PDCCH or EPDCCH interleaver (vivo) Interleaver I1 is a block interleaver (LG) The value of X is configurable (DOCOMO) X=12 (Qualcomm) Second step is an interleaver I2 within the CORESET with the interleaving unit equal to M RBs (Huawei, vivo, LG, DOCOMO, Qualcomm) Interleaver I2 is a block interleaver (Huawei, vivo) Interleaver I2 is the sub-block interleaver (LG) M is 6 (Huawei, Qualcomm?)