3GPP TSG RAN WG1 Meeting #86bis
`Lisbon, Portugal 10th – 14th October 2016
`
` R1-1608808
`
`Agenda Item: 8.1.2.2
`Source:
` Fujitsu
`Title:
` Discussion on subframe design with symbol level
`alignment
`Document for: Discussion/Decision
`
`1 Introduction
`
`In RAN1#86 meeting, the agreements about the subframe design are shown as follows [1]:
` Subframe duration in ms for a reference numerology with subcarrier spacing (2m*15)kHz is
`exactly 1/2m ms
` A subframe duration is defined by the duration of x OFDM symbols given a reference
`numerology
` With the same CP overhead, a single value of x is specified irrespective of the
`subcarrier spacing value chosen for the reference numerology
` This does not preclude multiple data transmission opportunities in time within a
`subframe duration
` This does not preclude multiple control transmission opportunities in time for both DL
`and UL within the subframe duration
` This does not prclude one data transmission to span over multiple subframe durations
` A UE has one reference numerology in a given NR carrier which defines subframe duration for
`the given NR carrier
` FFS: In a given NR carrier, whether different UEs may have different reference
`numerologies or may not
`In addition, a working assumption about the symbol alignment is given as
` Alignment within a subframe
` Symbol level alignment across different subcarrier spacings with the same CP overhead
`is assumed within a subframe duration in a NR carrier
` FFS: Unlicensed spectrum case
`Based on the agreements, different UEs using a given carrier may have the same or different reference
`numerologies. Thus, in this contribution, we will address the subframe design with respect to cases with
`one common reference numerology and with different reference numerologies.
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`2 Observations from the existing agreements
`
`Based on the existing agreements, we can have the following observations:
` Observation 1: subframe is defined based on reference numerology with the duration of 1/2m ms
` Observation 2: a subframe of 1ms includes 14 symbols for the reference numerology with the
`subcarrier spacing of 15KHz
` Observation 3: 14 will be one of possible number of symbols for the subframe irrespective of
`subcarrier spacing
` Observation 4: symbol alignment should be achieved for different subcarrier spacings as long as
`the CP overhead is the same.
`
`3 Subframe design for the reference numerology
`
`In this section, we will discuss the subframe design for two cases: 1) different UEs have the same
`reference numerology; and 2) different UEs have different numerologies.
`
`3.1 Case 1: different UEs with the same reference numerology
`In this case, we can consider the reference numerology with the subcarrier spacing of 15KHz as an
`example. As LTE, the subframe of 1ms includes 14 symbols, which consists of 2 long symbols (2208Ts
`for each, Ts is the sampling interval), and 12 short symbols (2192Ts for each). If the symbols with
`different numerologies are multiplexed in the same NR carrier, a half of subframe, i.e., 0.5ms, can be
`illustrated as Fig. 1 considering the symbol-level alignment.
`Proposal 1: the LTE based subframe design can be applied to the case that different UEs have the
`same reference numerology.
`
`0. 5ms
`
`: : : : ~
`
`1
`
`I I I 1 1 1 I 1 1 1 I 1 1 1
`I
`I
`I 1 1 1
`1
`2208
`4400
`6592
`8784
`10976
`13168
`15360
`Fig. 1 A half subframe (or slot) multiplexing different UEs with the same reference numerology but
`different subcarrier spacings (the numbers in the figure indicates the number of Ts)
`
`1
`
`1
`
`3.2 Case 2: different UEs with different numerologies
`In this cases, as an example, we consider three reference numerologies with subcarrier spacings being
`15kHz, 30kHz, and 60kHz, respectively. For the same CP overhead, by using LTE-like subframe design,
`the subframe duration for those three reference numerologies are 1ms, 0.5ms, and 0.25ms, respectively. If
`those subframes are multiplexed in the same NR carrier, the subframes located in a period of 0.5ms can
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`be illustrated as Fig. 2. From the figure, it can be seen that the target of symbol-level alignment cannot be
`satisfied.
`Observation 5: The LTE based subframe design cannot satisfy the symbol-level alignment for the case
`that different UEs have different reference numerologies.
`
`44001
`2208!
`22001 ! 32961 43921
`11041
`I
`I ;
`I
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`I
`1100: I 2196: I !3292: I
`
`54881
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`
`6592
`
`65841
`I
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`
`76801
`I
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`
`8784'
`
`8784
`
`8780:
`
`10976
`
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`
`15360
`
`98801 10976
`I
`9876: I 10972:
`
`120721 13168; 142641 15360
`I
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`
`15KHz
`
`30KHz
`
`60KHz
`
`0.25ms (one subframe for 60KHz)
`
`0.25ms
`
`0.5ms (one subframe for 30KHz)
`
`
`
`Fig. 2 Period of 0.5ms multiplexing different subframes with LTE like design (the numbers in the figure
`indicates the number of Ts)
`To achieve the aim of symbol level alignment, and also having subframe (or slot) durations that do not
`vary in time for a given numerology, we give two possible designs of a subframe as follows:
`a. A subframe contains symbols with the equal length and some reserved duration(s)
`In this design, the symbols within a subframe have the same length, as shown in Table 3.1. In
`addition, the subframe has at least one reserved duration. Fig. 3 illustrates the period of 0.5ms
`multiplexing different subframes for different reference numerologies. For large subcarrier spacing
`(e.g., 60kHz, 120kHz, 240kHz), the locations of the reserved duration(s) in the neighbouring
`subframes are different.
`Table 3.1 Symbol length for different reference numerologies
`Reference numerologies 15kHz 30kHz 60kHz 120kHz 240kHz
`Symbol length (Ts)
`2192
`1096
`548
`274
`137
`
`Half subframe (0.5ms) for reference numerology 1 (e.g., SCS =15KHz)
`
`Subframe of 0.5ms for reference numerology 2 (e.g., SCS =30KHz)
`
`nune
`
`I
`Subframe of 0.25ms for reference numerology 3 (e.g., SCS =60KHz)
`I
`Scbfr :oo;f< 25 • '1" fe(ent:e
`.g. ~Cf= 2!]1<1 Z)
`1,,1, ,d, ,ls(l.h l ,f' IZ~ ~m 11
`Hr
`~ ~ ~
`
`I
`
`I
`
`I
`
`I
`
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`
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`
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`
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`
`1 I I 1
`
`1
`
`1 111 11
`
`I I 1
`
`1 11 11 I I 11 1
`
`1
`
`111
`
`Reservation duration (2Ts)
`
`Fig. 3 Period of 0.5ms multiplexing different subframes (the symbol length within the subframe is
`the same for the same reference numerology)
`
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`b. A subframe contains symbols with different lengths
`In this design, for each reference numerology, a subframe consists of long symbol(s) and short
`symbols, as given in Table 3.2. Fig. 4 illustrates the period of 0.5ms multiplexing different subframes
`for different reference numerologies. For large subcarrier spacing (e.g., 60kHz, 120kHz, 240kHz),
`the locations of long symbol(s) in the neighbouring subframes are different.
`Table 3.2 Lengths of long symbol and short symbol for different reference numerologies
`Reference numerologies
`15kHz 30kHz 60kHz 120kHz 240kHz
`Long Symbol length (Ts) 2208
`1104
`560
`288
`152
`I
`I
`I
`I
`I
`Short symbol length
`2192
`1088
`544
`272
`136
`
`I
`
`Long symbol for reference
`numerology 1 (e.g., SCS=15KHz)
`
`Short symbol for reference
`numerology 1 (e.g., SCS=15KHz)
`
`(cid:127) Long symbol for reference
`(cid:143) Short symbol for reference
`
`numerology 3 (e.g., SCS=60KHz)
`
`numerology 3 (e.g., SCS=60KHz)
`
`-(cid:143)
`
`Long symbol for reference
`numerology 2 (e.g., SCS=30KHz)
`
`Short symbol for reference
`numerology 2 (e.g., SCS=30KHz)
`
`Long symbol for reference
`numerology 4 (e.g., SCS=120KHz)
`
`D Short symbol for reference
`
`numerology 4 (e.g., SCS=120KHz)
`
`Long symbol for reference
`numerology 5 (e.g., SCS=240KHz)
`
`n Short symbol for reference
`
`LJ numerology 5 (e.g., SCS=240KHz)
`
`
`
`Fig. 4 Period of 0.5ms multiplexing different subframes (the symbol length within the subframe is
`different for the same reference numerology)
`Proposal 2: The following two subframe designs can be applied to align symbol boundaries in the
`case that different UEs have different reference numerologies.
` A subframe contains the symbols with the same length and reserved duration(s)
` A subframe contains symbols with different lengths
`
`4 Conclusions
`
`This contribution discussed the subframe design regarding to the cases of a common reference
`numerology and different reference numerologies, and we propose:
`
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`Proposal 1: The LTE based subframe design can be applied to the case that different UEs have the
`same reference numerology.
`Proposal 2: The following two subframe designs can be applied to align symbol boundaries in the
`case that different UEs have different reference numerologies.
` A subframe contains the symbols with the same length and reserved duration(s)
` A subframe contains symbols with different lengths
`
`5 References
`[1] “Draft_Minutes_report_RAN1#86_v20”, RAN1#86, Aug. 2016.
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