E-Fi: Evasive Wi-Fi Measures for Presenter: Carlos Bocanegra and - - PowerPoint PPT Presentation

E-Fi: Evasive Wi-Fi Measures for Surviving LTE on the Unlicensed Band

Next GEneration NEtworks and SYStems Lab

Presenter: Carlos Bocanegra and Zhengnan Li Advisor:

• Prof. Kaushik R. Chowdhury

Why are we here today? – Objectives of the talk

• 5. E-Fi code execution

Configure environment, download and execute E-Fi code

2

• 1. Provide a brief insight of the LTE-WiFi coexistence paradigm

Why coexistence? What issues hinder the coexistence?

• 2. Overview of E-Fi, our LTE-WiFi coexistence mechanism

How does it work? How is it different from other coexistence mechanisms?

• 3. Performance evaluation of E-Fi

How much better is it from others? Advantages and disadvantages?

• 4. Matlab Tools as key enablers in E-Fi

Overview of the Communication-, WLAN- and LTE-Systems Toolbox

Agenda of the talk

3

1. Coexistence in the Unlicensed band – Why? 2. LTE and WiFi – Coexistence issue? Why? 3. Proposed LTE-WiFi Coexistence mechanisms 4. Almost Blank Subframes (ABS) in LTE 5. E-Fi Overview 6. E-Fi Performance evaluation 7. WLAN and LTE Matlab Toolboxes to emulate real protocols 8. E-Fi Code analysis and execution 9. Conclusions of the talk

Agenda of the talk

4

• 1. Coexistence in the Unlicensed band – Why?

2. LTE and WiFi – Coexistence issue? Why? 3. Proposed LTE-WiFi Coexistence mechanisms 4. Almost Blank Subframes (ABS) in LTE 5. E-Fi Overview 6. E-Fi Performance evaluation 7. WLAN and LTE Matlab Toolboxes to emulate real protocols 8. E-Fi Code analysis and execution 9. Conclusions of the talk

LTE-WiFi Coexistence in 5GHz band - Why?

[1] Cisco Visual Networking Index: Forecast and Methodology, 2016–2021 White Paper [2] C. Hoymann, “”LTE in unlicensed spectrum – technical and regulatory aspects

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ØAvailable Bandwidth in the Licensed band is limited [2]

100MHz 100MHz 255MHz 100MHz 100MHz 100MHz 255MHz

5.150 5.350 5.470 5.725 5.825

US EU

+ Bandiwdth = + Users + Bandwidth = + Data Rates

Ø Exponentially increasing Traffic demand [1]

FCC opened up unlicensed spectrum in the 5GHz in 2014!

frequency

Higher number of connections § The number of connected devices has increased linearly since 2014 (356 M in 2014 and 1,409 in 2018). Traffic is mostly video oriented § Video traffic accounted for 60% of total traffic in 2016, 55% in 2015. Foreseen the horizon 2020 § Video traffic will represent the 78% of total traffic and 11.6 Billion devices connected

Mobile Protocols today (LTE) can’t support it!

§ Current LTE operational band in MHz(USA): 700 (Verizon), 850 (At&T), 600 (T-Mobile), etc § Current LTE available Bandwidth: 100MHz with carrier aggregation

Agenda of the talk

6

1. Coexistence in the Unlicensed band – Why?

• 2. LTE and WiFi – Coexistence issue? Why?

3. Proposed LTE-WiFi Coexistence mechanisms 4. Almost Blank Subframes (ABS) in LTE 5. E-Fi Overview 6. E-Fi Performance evaluation 7. WLAN and LTE Matlab Toolboxes to emulate real protocols 8. E-Fi Code analysis and execution 9. Conclusions of the talk

ØThe Unlicensed band is used by other technologies

§ 2.4GHz: WiFi (802.11b/g/n), Bluetooth (802.15.1), Zigbee (802.15.4) § 5GHz: Mainly WiFi (802.11a/n/ac)

Subframe (1ms)

LTE-WiFi Coexistence in 5GHz band - Why?

7

100MHz 100MHz 255MHz 100MHz

5.150 5.350 5.470 5.725 5.825

US LTE US WiFi 20 MHz channel

WiFi Distributed Coordination Function (DCF) LTE coordinated and scheduled access (FDD or TDD)

Resources for User 1 Resources for User 2 Control information

DL UL

§ Sense channel prior to transmission § Backoff to bring fairness amongst users § ACK to evaluate LTE WiFi 4,36x 4,13x 1,00x 0,39x Relative average User Throughput [1] LTE Coexist. WiFi Coexist.

frequency

Ø Channel Access Mechanism – Unfairness between technologies

[1] E. Almeida et al., "Enabling LTE/WiFi coexistence by LTE blank subframe allocation," 2013 IEEE ,ICC, 2013,

LTE: Unfair and unconsiderate channel access WiFi: Fair and balanced channel access

Agenda of the talk

8

1. Coexistence in the Unlicensed band – Why? 2. LTE and WiFi – Coexistence issue? Why?

• 3. Proposed LTE-WiFi Coexistence mechanisms

4. Almost Blank Subframes (ABS) in LTE 5. E-Fi Overview 6. E-Fi Performance evaluation 7. WLAN and LTE Matlab Toolboxes to emulate real protocols 8. E-Fi Code analysis and execution 9. Conclusions of the talk

Criterion LAA* LTE-U LWA* ABS*

Description (3GPP), uses Listen-Before- Talk (LBT) [3] (Qualcomm), combines Duty Cycling and Channel Selection (3GPP), it encapsulates LTE

• info. into Wi-Fi frames in the

U-band (3GPP) Extension of the eICIC/feICIC techniques for

• Coexist. with Wi-Fi.

Co-Existence with Wi-Fi Dynamic Channel selection LBT operation is Mandatory Dynamic Channel selection CSAT [4] based on Duty Cycle LBT support not needed TDD of Transmissions LBT not needed (supported) Coordination needed (LBT/X2) 3GPP Release Release 13 Release 13 Release 13 Release 10, 11 and 12 Commercialization Late, due to ongoing standardization Late, due to high changes in the PHY and MAC Late, due to interconnection between LTE-BS and WiFi-AP Early deployment possible due to the use of current system Required Changes PHY and MAC layer PHY, MAC and Transport layer Transport Layer (Network). Software upgrade (User) MAC layer Drawbacks High Cost due to Infrastructural Changes High Cost due to Infrastructural Changes Reduction on the LTE Transmit rate due to WiFi Packet adoption Needs to deal with Interference from CRS

9

*LAA = Licensed-Assisted Access *LWA = LTE-WiFi link Aggregation

Proposed LTE-WiFi Coexistence mechanisms

§ LBT emulates WiFi and senses the channel prior transmitting. Small changes in the backoff § CSAT evaluates the WiFi presence and comes up with an ON/OFF LTE duty cycle § LTE encapsulates the Packet into WiFi frames for a more efficient transmission

ABS = Almost Blank Subframes *CRS = Cell/Specific Ref. Signals CCA = Clear Channel Assesement

Agenda of the talk

10

1. Coexistence in the Unlicensed band – Why? 2. LTE and WiFi – Coexistence issue? Why? 3. Proposed LTE-WiFi Coexistence mechanisms

• 4. Almost Blank Subframes (ABS) in LTE

5. E-Fi Overview 6. E-Fi Performance evaluation 7. WLAN and LTE Matlab Toolboxes to emulate real protocols 8. E-Fi Code analysis and execution 9. Conclusions of the talk

ØLTE Release 11 - feICIC (Further Enhanced Inter-Cell Interference Coordination)

§ UE’s are able to cancel the Cell-specific Reference Signals (CRS) in the ABS in order to eliminate the interference.

ABS as an Interference Mitigation Technique

ØLTE Release 10 - eICIC (Enhanced Inter-Cell Interference Coordination)

§ Macro cell reduces interference to Co-located cells using ABS. § Macro cell schedule transmissions during non-ABS while co-located cell use ABS subframes.

Problem 1: Prior Work do not consider Control signals in the ABS: Not Realistic. Problem 2: WiFi devices may not be able to cancel the Control Signals (feICIC).

11

*ABS = Almost Blank Subframes

Agenda of the talk

12

1. Coexistence in the Unlicensed band – Why? 2. LTE and WiFi – Coexistence issue? Why? 3. Proposed LTE-WiFi Coexistence mechanisms 4. Almost Blank Subframes (ABS) in LTE

• 5. E-Fi Overview

6. E-Fi Performance evaluation 7. WLAN and LTE Matlab Toolboxes to emulate real protocols 8. E-Fi Code analysis and execution 9. Conclusions of the talk

13

E-Fi Overview

*eICIC = enhanced Inter-Cell Interference Coordination - *feICIC = further enhanced Inter-Cell Interference Coordination

ØThe Coexistence scenario

CRS causing the Interference Physical and operational configuration § Consider 1 BS, 1 AP and N Wi-Fi devices § Channel: WiFi and LTE Downlink operate on the same channel § Coverage area: BS and AP overlap their coverage areas LTE configuration § Interference mechanism: LTE uses eICIC*/feICIC* § Reference Signals: ABS subframes contain Cell-Specific Reference Signals (CRS), which Interfere with Wi-Fi transmissions § Transmissions: LTE schedule transmissions during non-ABS WiFi configuration § Transmissions: Wi-Fi schedules its transmissions during ABS § Other capabilities: Wi-Fi devices are equipped with Wi-Fi Direct capabilities LTE WiFi

E-Fi Overview

ØPreliminary studies – Impact of CRS at the Transmitter and Receiver side

Impact at the Transmitter Impact at the Receiver § The time the channel is sensed busy is directly related with the amount of CRS the LTE-ABS carries. § The longer the channel is sensed busy, the more the node backsoffs and, in turn, the longer it defers its transmission.

BS-AP distance

n1 m1 c3 BS AP

§ The CRSs reduce the *Coverage Area. *Coverage area is the area within which WiFi nodes experiment a PER lower than 10%. Ø TRANSMIT RATE DECREASES SUBSTANCIALLY Ø THE PER INCREASES IN THE AREA

E-Fi Overview

ØPreliminary studies – Impact of CRS at the Transmitter and Receiver side

Impact at the Transmitter Impact at the Receiver

BS-AP distance

n1 m1 c3 BS AP

Ø TRANSMIT RATE DECREASES SUBSTANCIALLY Ø THE PER INCREASES IN THE AREA How do we tackle the issue? How do we tackle this issue? GROUP THE NODES ⟶ REDUCE THE NUMBER OF RETRANSMISSIONS RELAYING ⟶ INCREASE THE COVERAGE AREA

16

ØE-Fi’s Goal

Minimize the total number of transmissions in the network (due to LTE-CRS)

ØProcedure

• 1. Categorize nodes into:

ü Relay ü Wi-Fi Direct Client ü Client

• 2. *Group the nodes (Relay ⟶ Wi-Fi Direct Client)
• 3. Distributing resources (ABS) amongst them

ØEnablers

• 1. Wi-Fi Direct as the key enabler in the network
• 2. Hungarian Algorithm to group the nodes
• 3. Load balanced scheduling

*PSR = Packet Success Rate = 1– PER PER = Packet Error Rate = BER>0 or not Detected

E-Fi Overview

*E-Fi defines Safe Zone as the area within which the nodes experience a PSR* higher than a threshold. *An E-Fi Group is composed by a Relay and several Wi-Fi Direct Clients

17

E-Fi Overview

ØE-Fi ABS Awareness mechanism – How do WiFi nodes know where ABSs are?

LTE Frame generation with ABS ABS Pattern Detection § A drop in WiFi performance of the Wi-Fi network caused by in- band LTE triggers the initialization of the E-Fi procedure. § As for determining the start of the frame, the Wi-Fi devices may employ pattern recognition techniques such as symbol folding, which detects periodic signals in noisy environments. § AP notifies the devices and forces them to defer their transmission and detect the LTE ABS Pattern configured at the BS.

18

Decentralized

*PSR Calculation Node Pre-characterization Candidacy analysis RX Power and SINR Calculation Device Discovery & PSR Exchange PSR table determine PSR 𝑄𝑇𝑆 ≥ 𝑄𝑇𝑆&' Group Owner (GO) 𝑄𝑇𝑆 < 𝑄𝑇𝑆&' Wi-Fi Direct Client (WDC) Criteria to evaluate candidacy: z

) *+,-.→012 + ) *+,45→-. < ) *+,45→012

Defining the following categories: § GO: Wi-Fi relays § WDC: Device connected to a relay § Clients S.Z.: connected to AP § Clients N.S.Z: connected to AP 𝑜) 𝑛) 𝐵𝑄 𝑛9 𝑄𝑇𝑆&' 𝑸𝑻𝑺𝑯𝑷→𝑿𝑬𝑫 𝑸𝑻𝑺𝑩𝑸→𝑯𝑷 𝑸𝑻𝑺𝑩𝑸→𝑿𝑬𝑫

Group Owner Wi-Fi Direct Client

ØAlgorithm Overview

E-Fi Overview

*PSR = Packet Success Rate = 1– PER PER = Packet Error Rate = BER>0 or not Detected

19

ABS are allocated according to: § Load Factor 𝜃D: relates the PSR of the links within a Group and the Application rate (Packets per second) at each node. § Application load: represents the estimated packets per second for each node. “Modified Hungarian Algorithm”: Matching in a Weighted bipartite graph in Polynomial time § 𝜚F = Set of Candidates. § M = Number of Nodes in S.Z.* § N = Number of Nodes in N.S.Z.* § K = Number of Allowed WiFi- Direct Connections. *S.Z. = Safe Zone *N.S.Z. = Non-Safe Zone

Decentralized Centralized

PSR Calculation Node Grouping Notify devices and wait Node Pre-characterization Candidacy analysis RX Power and SINR Calculation Device Discovery & PSR Exchange Inter/Intra tx scheduling in ABS

ØAlgorithm Overview

E-Fi Overview

Agenda of the talk

20

1. Coexistence in the Unlicensed band – Why? 2. LTE and WiFi – Coexistence issue? Why? 3. Proposed LTE-WiFi Coexistence mechanisms 4. Almost Blank Subframes (ABS) in LTE 5. E-Fi Overview

• 6. E-Fi Performance evaluation

7. WLAN and LTE Matlab Toolboxes to emulate real protocols 8. E-Fi Code analysis and execution 9. Conclusions of the talk

21

E-Fi – Performance evaluation

ABS 1 Initial PSR (WiFi) Improved PSR (E-Fi)

Location AP located at (0,0) BS located at (60,0) Tx Power Tx power AP = 17dBm Tx power BS = 17dBm Protocol and Tx properties Wi-Fi standard: 802.11n MIMO: NO E-Fi design PSR threshold: 80% LTE ABS Configuration ABS Pattern: (ABS 0) 10000000000 (ABS 1) 01000000000

ØImprovement on the Coverage area § E-Fi helps the nodes that are closer to the LTE-BS § E-Fi increases the coverage área (nodes perceiving a PSR higher or equal tan the threshold)

22

E-Fi – Performance evaluation

Group size PSR Improvement Throughput Improvement

Wi-Fi Direct Nodes experience an improvement of 70-100% on their throughput regardless of the ABS Configuration selected Wi-Fi Direct Nodes experience an improvement of 10-20% on their PSR regardless of the ABS Configuration selected In 85-90% of the cases, the relay is assigned 2 or less WiFi nodes to be served through it.

23

E-Fi – Performance evaluation

80ms 80ms 80ms 80ms

s0 s1 s2 s3 s4 s5 s6 s7 s8 s9 s0 s1 s2 s3 s4 s5 s6 s7 s8 s9

LTE ON LTE OFF LTE ON LTE OFF

ØLTE-U

ALL WiFi nodes contend for the channel LTE Takes over the channel

ØE-Fi

E-Fi Group 1 (2 nodes) take over the channel E-Fi Group 2 (4 nodes) take over the channel E-Fi Group 3 (3 nodes) take over the channel E-Fi Group 4 (4 nodes) take over the channel

§ Grouping mechanism reduces the average transmission time. § The assignation of the correct Relay reduces the PER and increases Coverage Area

LTE Frame (10 ms) LTE Frame (10 ms)

Agenda of the talk

24

1. Coexistence in the Unlicensed band – Why? 2. LTE and WiFi – Coexistence issue? Why? 3. Proposed LTE-WiFi Coexistence mechanisms 4. Almost Blank Subframes (ABS) in LTE 5. E-Fi Overview 6. E-Fi Performance evaluation

• 7. WLAN and LTE Matlab Toolboxes to emulate real protocols

8. E-Fi Code analysis and execution 9. Conclusions of the talk

LTE and WLAN Toolbox in E-Fi

Distance range § The STA within the same circle share the same P

HI.

§ The AP-BS Distance define the SINR for a certain P

HI.

§ For every STA location, the PSR is measured.

• Standard (a,n,ac)
• Channel Bandwidth
• MIMO
• MCS
• Resource Blocks
• CQI Report Period
• MCS
• # LTE frames
• ABS Pattern
• Ptx WiFi
• Ptx LTE

Signal Model Tx Properties TGn Channel Model A, B, C, D, E, F, G Channel Prop. Receiver & Report Noise Pnoise

• Distance from AP
• Distance from BS
• BER
• Throughput
• PSR
• BER
• Throughput
• MCS Adaptation

WiFi LTE

25

ØPSR Pre-Characterization

Agenda of the talk

26

1. Coexistence in the Unlicensed band – Why? 2. LTE and WiFi – Coexistence issue? Why? 3. Proposed LTE-WiFi Coexistence mechanisms 4. Almost Blank Subframes (ABS) in LTE 5. E-Fi Overview 6. E-Fi Performance evaluation 7. WLAN and LTE Matlab Toolboxes to emulate real protocols

• 8. E-Fi Code analysis and execution

9. Conclusions of the talk

E-Fi Code Analysis and Execution

ØCode available in Github

https://github.com/MathworksProjects/LTE-WiFi-Coexistence.git

ØMatlab Version requirements

Code requires a Matlab version R2016a or above.

ØNo need to have Matlab installed

For those who DO NOT have installed Matlab, you can use the COE Servers to execute it. You’ll need:

• 1. COE Account
• 2. X Window Server installed
• 3. SSH client installed

§ MAC/Linux users can download X11 from Xquartz § Windows users can download Xming (X Window Server) and Putty (ssh client) Alternatively, Matlab offers an online graphic interface accessible in https://matlab.mathworks.com/

Agenda of the talk

28

1. Coexistence in the Unlicensed band – Why? 2. LTE and WiFi – Coexistence issue? Why? 3. Proposed LTE-WiFi Coexistence mechanisms 4. Almost Blank Subframes (ABS) in LTE 5. E-Fi Overview 6. E-Fi Performance evaluation 7. WLAN and LTE Matlab Toolboxes to emulate real protocols 8. E-Fi Code analysis and execution

• 9. Conclusions of the talk

All good, Then? - Conclusions

29

1) LTE in the 5GHz band to deal with the high user and application demands 2) Require coexistence mechanism due to disparity on channel access mech, 3) Existing Coexistence mechanism require PHY/MAC/TR layer changes 4) E-Fi is an coordinated uncooperative coexistence mechanism 5) E-Fi works under the existence of Almost Blank Subframes 6) E-Fi uses Wi-Fi Direct to enable P2P communication, uses the Hungarian algorithm to form the groups and a Load Balancing algorithm to distribute the ABS 7) E-Fi achieves a better performance than LTE-U under a reasonable number of ABS available for WiFi transmissions

30

Thanks!

31

Appendix 1

Individual (1 Node) Link Characterization

32

Appendix 1

Node Categories PSR Improvement Throughput Improvement

[1] C. Bocanegra, M. DiFelice, K. R. Chowdhury, “E-Fi: Evasive Wi-Fi Measures for Surviving LTE within 5GHz Unlicensed Band”

> <

Drop Image Here 33

E-Fi

𝑂KL = N

F ∈ P2

1 𝑄𝐹𝑆ST

U*

Throughput based on: The amount of time needed to Transmit succesfully 1 Packet to all the Wi-Fi devices Considerations: 1. The AP schedules packets in a round-robin fashion. 2. The groups are already formed, thus no overhead is considered. 3. The number of packets per ABS is consistent.

• 1. Calculate the number of Packets to be transmitted (Table 1)
• 2. Calculate the number of Packets that can be sent per ABS (Table 2)
• 3. Calculate throughput

Steps: 𝑈ℎ𝑠𝑝𝑣𝑕ℎ𝑞𝑣𝑢(𝑁𝑐𝑞𝑡) = 𝑚*+de 𝑂KL 𝑁 ×𝑢

Symbols Meanings 𝑢ℎ Throughput 𝑚*+de PSDU Length 𝑂 Number of transmissions 𝑁 Number of Wi-Fi Packet within 1 ABS (1ms) 𝑢 ABS Duration (1ms) 𝑜F, 𝑗 ∈ Ψ

D

Wi-Fi Direct CLIENT 𝑗 connected to RELAY𝑘 𝑛D Wi-Fi Direct RELAY (or client of Wi-Fi) indexing 𝑘 Ψ

D

Connection set for RELAY 𝑘 𝑄𝐹𝑆U

k

PER link from A to B PSDU (bits) Frame Time (𝜈𝑡)

• N. Pkts / ABS

100 270 3 200 394 2 300 518 1 400 638 1 500 762 1 600 886 1 700 1010

Table 1. Notation for Throughput calculation Table 2. Wi-Fi frames per ABS as a function of the Payload in bits

𝑂KL = N

Dm)

1 𝑄𝐹𝑆no

U*

+ N

Dm)

Ψ

D

𝑄𝐹𝑆no

U* + N F∈Po

1 𝑄𝐹𝑆ST

no

+ N

F∈P2

1 𝑄𝐹𝑆ST

no

Wi-Fi Relays Wi-Fi Direct Clients Clients in N.S.Z.

E-Fi – Throughput analysis

> <

34

Criteria 1: PER-oriented

𝑄𝐹𝑆no

U*×𝑄𝐹𝑆ST no ≷ 𝑄𝐹𝑆ST U*

1 𝑄𝐹𝑆no

U* +

1 𝑄𝐹𝑆ST

no ≶

1 𝑄𝐹𝑆ST

U*

Criteria 2: Throughput-oriented

• Combines the PER calculation into 1 modified link
• Does not account for the multi-hop impact on the throughput
• Checks for the number of expected transmissions
• Accounts for the multi-hop impact on the throughput

𝑄𝐹𝑆nr

U*

𝑄𝐹𝑆Sr

nr

𝑄𝐹𝑆Ss

U*

𝑄𝐹𝑆ns

U*

AP Relay Wi-Fi Direct Cliennt Client in S.Z. Client in N.S.Z.

• N. of expected

transmissions to succesfully receive a Packet from AP to node 𝑜F

E-Fi – Node association criteria

> <

35

Matlab does not account for the overhead due to processing at the relay. Goal: analyze changes on the beneficial region* from simulations to real devices Beneficial region* = Combination of 𝑄𝑇𝑆U*

tu and 𝑄𝑇𝑆tu vd that increases the

throughput against 𝑄𝑇𝑆U*

vd

Two links are evaluated: 1. AP -> WD (Regular communication): 𝑄𝑇𝑆U*

vd

2. AP -> GO -> WD (E-Fi Communication): 𝑄𝑇𝑆U*

tu and 𝑄𝑇𝑆tu vd

Beneficial Region + Final Selection In blue, all the

• combinations. In green, the

final selection. PSR threshold selected: 0.4 𝑄𝑇𝑆U*

vd < 𝑄𝑇𝑆U* tu w 𝑄𝑇𝑆tu vd ) *+,45

01 <

) *+,45

• . +

) *+,-.

01

Criteria PSR Criteria Throughput

E-Fi – Node association criteria