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Multi-RAT Coexistence Analysis and Frame Configuration (15.3.3)
Document Number: IEEE C802.16m-09/2124Date Submitted: 2009-08-31
Source: Yujian Zhang [email protected] Hujun Yin [email protected] Xinrong Wang [email protected] Zhu [email protected]
Intel Corporation
Re: IEEE 802.16m-09/0037, “Call for Contributions on Project 802.16m Amendment Content” Venue: IEEE Session#63, Jeju
Base Contribution: NonePurpose: Discussion and Adoption by TGmNotice:
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Executive Summary (1)
• For 16m CP ratio 1/8, BW 5/10/20 MHz.• Legends:
– For TD-SCDMA: Yes/No: whether coexistence is possible or not.– For LTE TDD
• All: all cases in LTE-TDD can coexist with 16m scenario.• Most: two DwPTS categories of LTE-TDD can coexist with 16m.• Few: only 3 OFDM symbol DwPTS category of LTE-TDD can coexist with 16m.• N/A: the case violates the constraint that there should be at least 2 type-1 subframes / frame.
• Notes– D:U ratio in bracket is 16m D:U ratio which can coexist with TD-SCDMA/LTE TDD.– UL-DL Configuration 1 is the most important LTE-TDD case to consider.
# of type-3 subframes / frame
TD-SCDMA LTE TDD
4:3 5:2 UL-DL Cfg. 0 UL-DL Cfg. 1 UL-DL Cfg. 2
1 No No All (3:5) Few (4:4) Most (6:2)
2 No Yes (6:2) N/A (3:5) Most (5:3 & 4:4) Most (6:2)
3 Yes (5:3) Yes (6:2) N/A (3:5) All (5:3) Most (6:2)
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Executive Summary (2)
• Changes to Frame Structure– For 16m 1/8 CP ratio, BW 5/10/20 MHz, allow 2 and 3 DL type-3 subframes.– This effectively increases TTG, which is friendly for cell coverage.
• Configurations to add: (please refer to contribution C80216m-09/1971).• 2 type-3 subframes, 6:2• 3 type-3 subframes, 5:3• 2 type-3 subframes: 5:3
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Current Status in 802.16m
• Examples are given in section 11.4.4.1 of SDD.
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Criterion of Coexistence (1)• Principle: avoid simultaneous transmission of DL from one RAT and UL from another RAT, i.e.
align switching points of two RATs. • Assumption: base stations of two RATs are co-site.• Notations:
– D1, T1, U1, R1 and D2, T2, U2, R2 denote the length of DL, TTG, UL, and RTG for RAT1 and RAT2 respectively, with the constraint D1+T1+U1+R1 = D2+T2+U2+R2 = F = 5 ms
– Assume the UL end of RAT1 can be left shifted x relative to the UL end of RAT2.– 60μs RTG assumed for LTE-TDD, although not officially specified.
• When considering BS-to-BS interference only– At UL->DL switching point, to avoid interference: -R2 ≤x≤R1.– At DL->UL switching point, to avoid interference between RAT1 DL to RAT2 UL: U2 ≤T1+U1+x; to avoid
interference between RAT1 UL to RAT2 DL: U1+x ≤T2+U2
– So if there is any x satisfying both -R2 ≤x≤R1 and U2-U1-T1 ≤ x≤ U2-U1+T2, then coexistence is possible. It is equivalent to max(-R2 , U2-U1-T1) ≤ x ≤ min(R1, U2-U1+T2).
– The simplified criterion is D1+U2 ≤F, and D2+U1 ≤F. Distributions of TTG and RTG within each RAT does NOT impact coexistence.
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Criterion of Coexistence (2)• When considering MS-to-MS interference in addition to BS-to-BS
interference– Requirements for BS-to-BS interference should be satisfied.
– For every RAT, at MS side, TTG is reduced by RTD while RTG is increased by RTD, with RTD = 2r/c, where r is cell radius and c is the speed of light. RTD is 0. 667 ms for 100 km cell radius.
– Additional inequalities to satisfy: max(-(R2+RTD) , U2-(T1-RTD)-U1) ≤ x ≤ min(R1+RTD, T2-RTD+U2-U1).
– It is equivalent to D1+U2 ≤F-RTD, D2+U1 ≤F-RTD, and T1+T2≥2RTD.
– There is NO need to support quite large cell radius, since in that case, even the same RAT will have MS-to-MS interference. • In the analysis, we assume the maximum cell radius is 5 km, which corresponds to 33.3
μs.
• In addition, RTD should be selected so that there is no self-interference for each RAT, i.e. RTD = min(33.3 μs, F-D1-U1, F-D2-U2, T1, T2).
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16m CP ratio 1/8 – 1 type-3 subframeLTE UL-DL Configuration 1 (16m D:U=4:4)
LTE UL-DL Configuration 2 (16m D:U=6:2)
LTE UL-DL Configuration 0 (16m D:U=3:5)
Background color• Green: coexistence possible• Yellow: coexistence impossible• Cyan: coexistence is possible when MS-to-MS interference is not considered; impossible when such interference is considered.
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16m CP ratio 1/8 – 2 type-3 Subframes
LTE UL-DL Configuration 1 (16m D:U=5:3, 4:4 for 4 cases)
LTE UL-DL Configuration 2 (16m D:U=6:2)
LTE UL-DL Configuration 0 (16m D:U=3:5)
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16m CP ratio 1/8 – 3 type-3 Subframes
LTE UL-DL Configuration 1 (16m D:U=5:3)
LTE UL-DL Configuration 2 (16m D:U=6:2)
LTE UL-DL Configuration 0 (16m D:U=3:5)
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Backup
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TD-SCDMA Frame Structure
UpPTS
(160chips)
Subframe 5ms (6400chip)
1.28Mcps
DwPTS
(96chips)GP (96chips)
Switching Point
Switching Point
• In current TD-SCDMA deployment, the common D:U ratios are 4:3 and 5:2.
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LTE TDD Frame Structure (1)
One slot, Tslot=15360Ts
GP UpPTSDwPTS
One radio frame, Tf = 307200Ts = 10 ms
One half-frame, 153600Ts = 5 ms
30720Ts
One subframe, 30720Ts
GP UpPTSDwPTS
Subframe #2 Subframe #3 Subframe #4Subframe #0 Subframe #5 Subframe #7 Subframe #8 Subframe #9
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LTE TDD Frame Structure (2)