Enhanced C-V2X Mode-4 Subchannel Selection Luis F. Abanto-Leon - - PowerPoint PPT Presentation

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Enhanced C-V2X Mode-4 Subchannel Selection

Luis F. Abanto-Leon

Co-authors: Arie Koppelaar Sonia Heemstra de Groot

Department of Electrical Engineering Eindhoven University of Technology

IEEE 88th Vehicular Technology Conference (VTC 2018-Fall)

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Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Contents

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1 Background 2 Sidelink Subchannels 3 C-V2X Mode-4 4 Modified Power Averaging 5 Simulation Results 6 Conclusions

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Figure 1:Connected world

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Background

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3GPP1 proposed in Release 14, two novel schemes to support sidelink vehicular communications

– C-V2X mode-3 (centralized) – C-V2X2 mode-4 (distributed)

13GPP: The 3rd Generation Partnership Project 2C-V2X: Cellular Vehicle–to–Everything 3D2D: Device–to–Device communications Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Background

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3GPP1 proposed in Release 14, two novel schemes to support sidelink vehicular communications

– C-V2X mode-3 (centralized) – C-V2X2 mode-4 (distributed)

C-V2X modes are based on LTE-D2D3 technology, where similar communication modalities were proposed.

13GPP: The 3rd Generation Partnership Project 2C-V2X: Cellular Vehicle–to–Everything 3D2D: Device–to–Device communications Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Background

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3GPP1 proposed in Release 14, two novel schemes to support sidelink vehicular communications

– C-V2X mode-3 (centralized) – C-V2X2 mode-4 (distributed)

C-V2X modes are based on LTE-D2D3 technology, where similar communication modalities were proposed. However, in LTE-D2D (introduced for public safety) the ultimate objective is to prolong batteries lifespan (at the expense of compromising on latency).

13GPP: The 3rd Generation Partnership Project 2C-V2X: Cellular Vehicle–to–Everything 3D2D: Device–to–Device communications Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Background

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To fulfill the low latency and high reliability requirements:

4Pilot symbols more closely spaced for channel estimation in high Doppler. 5A subchannel is a time-frequency resource chunk. Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Background

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To fulfill the low latency and high reliability requirements: Modifications at PHY layer

– Denser distribution of DMRS4

4Pilot symbols more closely spaced for channel estimation in high Doppler. 5A subchannel is a time-frequency resource chunk. Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Background

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To fulfill the low latency and high reliability requirements: Modifications at PHY layer

– Denser distribution of DMRS4

Modifications at MAC layer

– A novel subchannelization5 containing

(i) sidelink control information (e.g. MCS) (ii) transport block (data)

in the same subframe to minimize latency.

4Pilot symbols more closely spaced for channel estimation in high Doppler. 5A subchannel is a time-frequency resource chunk. Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Background

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To fulfill the low latency and high reliability requirements: Modifications at PHY layer

– Denser distribution of DMRS4

Modifications at MAC layer

– A novel subchannelization5 containing

(i) sidelink control information (e.g. MCS) (ii) transport block (data)

in the same subframe to minimize latency.

4Pilot symbols more closely spaced for channel estimation in high Doppler. 5A subchannel is a time-frequency resource chunk. Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Sidelink Subchannels

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Control Data

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... TL (ms) Frequency (MHz) T T T r1 r2 rK rK+1 r2K

rK(L−1)+1 rK(L−1)+2

rKL B B B T: duration of a subframe K: number of subchannels per subframe L: total number of subframes for allocation B: subchannel bandwidth

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

C-V2X Mode-4 Scenario

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Figure 2:C-V2X Mode-4 Scenario

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

C-V2X Mode-4 Operation

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Vehicles typically exchange cooperative awareness messages (CAMs)6.

6It is assumed that a CAM message can fit in a subchannel. 7In the order of several hundred of milliseconds. Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

C-V2X Mode-4 Operation

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Vehicles typically exchange cooperative awareness messages (CAMs)6. A CAM message contains relevant information of each vehicle: position, velocity, direction, etc.

6It is assumed that a CAM message can fit in a subchannel. 7In the order of several hundred of milliseconds. Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

C-V2X Mode-4 Operation

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Vehicles typically exchange cooperative awareness messages (CAMs)6. A CAM message contains relevant information of each vehicle: position, velocity, direction, etc. CAM messages must be received reliably in order not to jeopardize safety.

6It is assumed that a CAM message can fit in a subchannel. 7In the order of several hundred of milliseconds. Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

C-V2X Mode-4 Operation

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Vehicles typically exchange cooperative awareness messages (CAMs)6. A CAM message contains relevant information of each vehicle: position, velocity, direction, etc. CAM messages must be received reliably in order not to jeopardize safety. Vehicles autonomously reserve a subchannel on a semi-persistent basis7 to add predictability.

6It is assumed that a CAM message can fit in a subchannel. 7In the order of several hundred of milliseconds. Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Semi-Persistent Scheduling (SPS) Principle

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B Hz sub-band f

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

k = 1 k = 2 k = 3 k = 4 k = 5 k = 6 k = 100 k = 1 k = 2 k = 3 k = 100

s(f,k) Tw = 100 ms

message rate-dependent time window

Tw

n = 1 n = 2 n = Nw

TSP S = NwTw

Figure 3:SPS operation principle

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Mode-4 Scheduling

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The scheduling scheme in C-V2X mode-4 consists of the following stages.

– Power sensing in each subchannel – Subchannel ranking – Subchannel selection for semi-persistent transmissions – (Optional) Random retransmissions

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Mode-4 Scheduling

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The scheduling scheme in C-V2X mode-4 consists of the following stages.

– Power sensing in each subchannel – Subchannel ranking – Subchannel selection for semi-persistent transmissions – (Optional) Random retransmissions

Vehicles sense the received power across all the subchannels before selecting one for their own utilization.

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Mode-4 Scheduling

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The scheduling scheme in C-V2X mode-4 consists of the following stages.

– Power sensing in each subchannel – Subchannel ranking – Subchannel selection for semi-persistent transmissions – (Optional) Random retransmissions

Vehicles sense the received power across all the subchannels before selecting one for their own utilization. A vehicle autonomously reserves a subchannel on a semi-persistent basis to add predictability.

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Mode-4 Scheduling

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The scheduling scheme in C-V2X mode-4 consists of the following stages.

– Power sensing in each subchannel – Subchannel ranking – Subchannel selection for semi-persistent transmissions – (Optional) Random retransmissions

Vehicles sense the received power across all the subchannels before selecting one for their own utilization. A vehicle autonomously reserves a subchannel on a semi-persistent basis to add predictability. Thus, vehicles can understand the subchannels utilization patterns and reduce the number of packet collisions.

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Mode-4 Scheduling

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Figure 4:Scheme with joint SPS scheduling and random retransmissions

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Power Sensing

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ε(n,f,k)

i

=       

• j={u|vu∈V(n,k)}

u=i

IpPj Gt · Gr X (n)

ij

· PL(n)

ij

+ Pσ, if (∗) ∞,

• therwise

(1)

where (∗) : k = {m | S(n)

i

∩ {s(1,m), . . . , s(F,m)} = ∅}

Pj = PT : transmit power from vehicle vj. PL(n)

ij

: path loss between vehicles vi and vj. X (n)

ij

: correlated shadowing between vehicles vi and vj. V(n,k): Set of vehicles that use the any subchannel in subframe k.

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Exponentially-Weighted Moving Average

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When α = 1, the power averaging is compliant with the standardized linear average proposed by 3GPP. The proposed average power is given by

˜ ε(n,f,k)

i

=

10

• l=1

αlε(n−l,f,k)

i 10

• l=1

αl , (2)

where α ≤ 1 is an exponential weighting factor.

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Simulation Parameters

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Table 1:Simulation parameters

Description Symbol Value Units Number of RBs per subchannel (per subframe)

• 30
• Number of sub-bands

F 3

• Number of subchannels per sub-band
• 100
• Number of subchannels
• 300
• CAM message rate

∆CAM 10 Hz CAM size MCAM 190 bytes MCS

• 7
• Transmit power per CAM
• 23

dBm Transmit power per RB PT 6.67 mW Effective coded throughput (24 CRC bits) ρ 0.9402 bps/Hz Throughput loss coefficient [?] λ 0.6

• SINR threshold

γT 2.9293 dB Distance between Tx and Rx Dx 50-300 m Scheduling period [?] TSP S 0.5-1.5 s Antenna gain Gt, Gr 3 dB Shadowing standard deviation Xσ 7 dB Shadowing correlation distance

• 10

m Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Vehicular Traces

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Figure 5:Real vehicular traces

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Simulations

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50 100 150 200 250 300 0.8 0.9 1.0

Dx [meters] Packet Reception (PRRdisk)

3GPP / α = 1 Proposed / α = 0.4 Proposed / α = 0.6 Proposed / α = 0.8 3GPP - Random / α = 1 3GPP - Greedy / α = 1 280 290 300 0.79 0.80 0.81 0.82 0.83 0.84

Figure 6:PRRdisk for an urban scenario with pkeep = 0

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Simulations

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50 100 150 200 250 300 0.6 0.7 0.8 0.9 1.0

Dx [meters] Packet Reception (PRRring)

3GPP / α = 1 Proposed / α = 0.4 Proposed / α = 0.6 Proposed / α = 0.8 3GPP - Random / α = 1 3GPP - Greedy / α = 1 280 290 300 0.58 0.59 0.60 0.61 0.62 0.63 0.64 0.65

Figure 7:PRRring for an urban scenario with pkeep = 0

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

PRR Degradation Origin

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Figure 8:Classification (in percentage) of missed/undecodable packets - Urban scenario with α = 1 and pkeep = 0 – PRR: packet reception ratio – HD-SF: errors due half-duplex impairment in the same subframe – HD-SC: errors due half-duplex impairment in the same subchannel – Propagation: errors due to path-loss and shadowing – CCI: errors due to co-channel interference – IBE: errors due to in-band emissions

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Conclusions

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In this work, we have presented link-level simulation results

• n the recently introduced technology C-V2X Mode 4.

A new power averaging idea based on exponential weighting was proposed. It was shown that this modification improves the performance of the distributed scheduling C-V2X. In addition, the nature of each type of conflict was

• classified. We have observed that most of the packet

errors are due to either CCI or IBE. Future work: Decentralized channel congestion control approaches will be studied in order to improve the performance of this distributed technology.

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :

Elapsed time: Background Sidelink Subchannels C-V2X Mode-4 Modified Power Averaging Simulation Results Conclusions

Questions

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Email: l.f.abanto@ieee.org

Luis F. Abanto-Leon Eindhoven University of Technology Enhanced C-V2X Mode-4 Subchannel Selection :