E-Fi: Evasive Wi-Fi Measures for Presenter: Carlos Bocanegra and Zhengnan Li Surviving LTE on the Advisor: Prof. Kaushik R. Chowdhury Unlicensed Band Next GEneration NEtworks and SYStems Lab
Why are we here today? – Objectives of the talk 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 5. E-Fi code execution Configure environment, download and execute E-Fi code
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? 5 Ø Exponentially increasing Traffic demand [1] 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 Mobile Protocols § Video traffic accounted for 60% of total traffic in 2016, 55% in 2015. today (LTE) can’t Foreseen the horizon 2020 § Video traffic will represent the 78% of total traffic and 11.6 Billion devices connected support it! Ø Available Bandwidth in the Licensed band is limited [2] § Current LTE operational band in MHz(USA): 700 (Verizon), 850 (At&T), 600 (T-Mobile), etc § Current LTE available Bandwidth: 100MHz with carrier aggregation + Bandiwdth = + Users FCC opened up unlicensed spectrum in the 5GHz in 2014! + Bandwidth = + Data Rates US 100MHz 100MHz 255MHz 100MHz 100MHz 100MHz 255MHz EU frequency 5.150 5.350 5.470 5.725 5.825 [1] Cisco Visual Networking Index: Forecast and Methodology, 2016–2021 White Paper [2] C. Hoymann, “”LTE in unlicensed spectrum – technical and regulatory aspects
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
LTE-WiFi Coexistence in 5GHz band - Why? 7 4,36x Ø The Unlicensed band is used by other technologies 4,13x Relative average User Throughput [1] § 2.4GHz : WiFi (802.11b/g/n), Bluetooth (802.15.1), Zigbee (802.15.4) § 5GHz : Mainly WiFi (802.11a/n/ac) 5.150 5.350 5.725 5.470 5.825 1,00x 100MHz 100MHz 255MHz 100MHz US LTE 0,39x US WiFi WiFi LTE WiFi LTE Coexist. Coexist. 20 MHz channel Ø Channel Access Mechanism – Unfairness between technologies WiFi Distributed Coordination Function (DCF) LTE coordinated and scheduled access (FDD or TDD) WiFi: Fair and LTE: Unfair DL balanced and frequency channel unconsiderate UL access channel access Sense channel prior to transmission § Subframe (1ms) Backoff to bring fairness amongst users § Resources for User 1 ACK to evaluate § Control information Resources for User 2 [1] E. Almeida et al., "Enabling LTE/WiFi coexistence by LTE blank subframe allocation," 2013 IEEE ,ICC, 2013,
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
Proposed LTE-WiFi Coexistence mechanisms 9 Criterion LAA* LTE-U LWA* ABS* ( Qualcomm ), combines ( 3GPP ), it encapsulates LTE ( 3GPP ) Extension of the ( 3GPP ), uses Listen-Before- Description Duty Cycling and Channel info. into Wi-Fi frames in the eICIC/feICIC techniques for Talk (LBT) [3] Selection U-band Coexist. with Wi-Fi. TDD of Transmissions Dynamic Channel selection Dynamic Channel selection Co-Existence with Wi-Fi LBT support not needed LBT not needed (supported) LBT operation is Mandatory CSAT [4] based on Duty Cycle Coordination needed (LBT/X2) 3GPP Release Release 13 Release 13 Release 13 Release 10, 11 and 12 Late , due to ongoing Late , due to high changes in the Late , due to interconnection Early deployment possible due Commercialization standardization PHY and MAC between LTE-BS and WiFi-AP to the use of current system Transport Layer (Network). Required Changes PHY and MAC layer PHY, MAC and Transport layer MAC layer Software upgrade (User) Reduction on the LTE High Cost due to High Cost due to Needs to deal with Interference Drawbacks Transmit rate due to WiFi Infrastructural Changes Infrastructural Changes from CRS Packet adoption § LBT emulates WiFi and senses the § CSAT evaluates the WiFi § LTE encapsulates the Packet into WiFi channel prior transmitting. Small changes presence and comes up with an frames for a more efficient transmission in the backoff ON/OFF LTE duty cycle *LAA = Licensed-Assisted Access ABS = Almost Blank Subframes CCA = Clear Channel Assesement *LWA = LTE-WiFi link Aggregation *CRS = Cell/Specific Ref. Signals
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
ABS as an Interference Mitigation Technique 11 Ø LTE 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). Ø LTE 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 = 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
E-Fi Overview 13 Ø The Coexistence scenario Physical and operational configuration WiFi § 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 LTE § 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 CRS causing the Interference *eICIC = enhanced Inter-Cell Interference Coordination - *feICIC = further enhanced Inter-Cell Interference Coordination
E-Fi Overview Ø Preliminary studies – Impact of CRS at the Transmitter and Receiver side Impact at the Transmitter Impact at the Receiver BS AP BS-AP distance n1 c3 m1 § The time the channel is sensed busy is directly related § The CRSs reduce the *Coverage Area . with the amount of CRS the LTE-ABS carries. *Coverage area is the area within which WiFi § The longer the channel is sensed busy, the more the nodes experiment a PER lower than 10%. node backsoffs and, in turn, the longer it defers its transmission. Ø THE PER INCREASES IN THE AREA Ø TRANSMIT RATE DECREASES SUBSTANCIALLY
E-Fi Overview Ø Preliminary studies – Impact of CRS at the Transmitter and Receiver side Impact at the Transmitter Impact at the Receiver BS AP BS-AP distance n1 c3 m1 How do we tackle this issue? How do we tackle the issue? Ø TRANSMIT RATE DECREASES SUBSTANCIALLY Ø THE PER INCREASES IN THE AREA GROUP THE NODES ⟶ REDUCE THE NUMBER OF RELAYING ⟶ INCREASE THE RETRANSMISSIONS COVERAGE AREA
Recommend
More recommend
