January 2015 doc IEEE 802 19 150007 r

January 2015 doc. : IEEE 802. 19 -15/0007 r 0 Comments on LAA EVM Date: 2015 -01 -14 Authors: Notice: This document has been prepared to assist IEEE 802. 19. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Submission Slide 1 Alireza Babaei, Cable. Labs

January 2015 doc. : IEEE 802. 19 -15/0007 r 0 Abstract • This document provides recommendations related to Annex A (Evaluation methodology) of the 3 GPP draft study item document on Licensed-Assisted Access to Unlicensed Spectrum: 3 GPP TR 36. 889 v 0. 1. 0 (2014 -11). • The purpose of this contribution is to include these recommendations in an upcoming liaison from 802 to 3 GPP on its ongoing LAA study item Submission Slide 2 Alireza Babaei, Cable. Labs

January 2015 doc. : IEEE 802. 19 -15/0007 r 0 Summary of Recommendations • Incorporate Truncated Exponential Backoff in LBT requirements and simulate its effect. • For a complete understanding of LAA impact on Wi-Fi, a range of load densities should be simulated. • Include Vo. IP and other traffic types as mandatory traffic models and evaluate corresponding performance metrics. • Consider 256 QAM, LDPC and RTS/CTS mandatory for simulation. Submission Slide 3 Alireza Babaei, Cable. Labs

January 2015 doc. : IEEE 802. 19 -15/0007 r 0 LBT • Listen-Before-Talk (LBT) based on European regulations (ETSI 301 893 v 1. 7. 1) is mainly considered as a coexistence mechanism in 3 GPP contributions. • LBT, as defined in the above ETSI document, has two forms : – Load Based and Frame Based Equipment (LBE and FBE) – 3 GPP contributions indicate majority opinion is tending towards LBE • Concerns: – Fixed linear backoff window for extended CCA (q is fixed for a given device) – No increase with collision (q is fixed during operation) CCA 20 µs Extended CCA Channel Busy Extended CCA = N * 20 µs N ∈ {0, 1, … , q} and q ∈ {4, 5, … , 32} 4 Submission Slide 4 Alireza Babaei, Cable. Labs

January 2015 doc. : IEEE 802. 19 -15/0007 r 0 LBT Simulation Results • Assume Load Based Equipment LBT, q = 32 • Tx Success Rate: probability of any client sending successful burst • Transmission Success Rate Gain/Loss 1. 68 X 1 X Steps to Tx Success: Results relative to the Tx Success Rate when both operators use Wi -Fi – 1 X applies to any client count r co exis t ence 0. 23 X – Client must pass CCA – Client must Tx without collision • Poo with 1. 53 X Wi- Fi 0. 12 X Wi-Fi (both Operators) Operator A: Wi-Fi. Operator B: LAA-LBT 20 devices/operator Simulation Assumptions: Full buffer traffic, all nodes within CCA range of each other, single 20 MHz channel, co-channel operation, clients and APs/e. NBs are stationary, Wi-Fi STAs use EDCA, BE AC (AIFS = 3, CWmin = 15) Conclusion: Version 1. 7. 1 of ESTI LBT rules are not sufficient for fair Coexistence of LTE and Wi-Fi 5 Submission Slide 5 Alireza Babaei, Cable. Labs

January 2015 doc. : IEEE 802. 19 -15/0007 r 0 What version of LBT to use? • 802. 11 has proven success in enabling sharing between independent systems in a wide variety of use cases an load scenarios. • The basis of this success is EDCA which is based on CSMA/CA; CSMA/CA is an LBT mechanism using truncated exponential backoff. • The use of a similar mechanism by LAA should provide the basis for fair sharing between LAA and Wi-Fi (and also between LAA and LAA) – The Wi-Fi Alliance made a proposal to ETSI BRAN that defines LBT with exponential backoff for LAA (See [3]) Recommendation: Incorporate Truncated Exponential Backoff in LBT requirements and simulate its effect Submission Slide 6 John Doe, Some Company

January 2015 doc. : IEEE 802. 19 -15/0007 r 0 System Load • Section A. 1. 1 lists the parameters for indoor LAA coexistence evaluation. • Only 10 LAA UEs or Wi-Fi clients is assumed per unlicensed band carrier for DL-only LAA coexistence evaluation. • The impact of LAA (using EU LBT) on Wi-Fi clients is more evident at high system load particularly when number of nodes is large – See the backup slides. Recommendation: For a complete understanding of LAA impact on Wi-Fi, a range of load densities should be simulated Submission Slide 7 Alireza Babaei, Cable. Labs

January 2015 doc. : IEEE 802. 19 -15/0007 r 0 Traffic model • Wi-Fi and LAA have to operate in unlicensed spectrum carrying a variety of traffic types including voice, video, FTP, etc. • However, the simulations evaluating the fairness of LAA with Wi-Fi is currently limited to FTP. • Once initial simulations showing basic fairness between Wi-Fi and LAA are complete, further simulations will be required to ensure fairness and functionality are maintained using a variety of traffic types in a diversity of use and load scenarios. Recommendation: Include Vo. IP and other traffic types as a mandatory traffic models and evaluate corresponding performance metrics. Submission Slide 8 Alireza Babaei, Cable. Labs

January 2015 doc. : IEEE 802. 19 -15/0007 r 0 Assumptions on Wi-Fi Parameters • Section A. 2. 1 lists Wi-Fi system evaluation assumptions. • 256 QAM and LDPC are considered optional. – Use of lower order modulation (when SINR is sufficient for 256 QAM) means unnecessarily longer frame duration. Longer frame duration increases the backoff period and decreases the channel utilization for other Wi-Fi clients. • RTS/CTS is considered optional. – The hidden node behavior of two wireless systems is key to coexistence. RTS/CTS is optional but commonly used in congested environments. Recommendation: Consider 256 QAM, LDPC and RTS/CTS mandatory for simulation Submission Slide 9 Alireza Babaei, Cable. Labs

January 2015 doc. : IEEE 802. 19 -15/0007 r 0 References [1] Study on Licensed-Assisted Access to Unlicensed Spectrum, 3 GPP TR 36. 889 v 0. 1. 0 (2014 -11) [2] 802. 19 -14/0082 r 0: Overview of EU LBT and its Effectiveness for Coexistence of LAA LTE and Wi-Fi [3] ETSI BRAN(14)000102 Submission Slide 10 Alireza Babaei, Cable. Labs

January 2015 doc. : IEEE 802. 19 -15/0007 r 0 Backup Submission Slide 11 Alireza Babaei, Cable. Labs

January 2015 doc. : IEEE 802. 19 -15/0007 r 0 Simulation Parameters • • 12 Overall Simulation Assumptions: – All nodes are within CCA range of each other – Single channel access scenario – Full buffer traffic – 802. 11 EDCA channel access modeled – Best Effort access category (AIFSN = 3, CWmin = 15) – Stationary nodes – Monte Carlo simulations with 1, 000 TXOPs evaluated per data point ETSI LBT Assumptions: – Always use extended CCA – LBE rules Implemented by LAA nodes Submission Slide 12 Alireza Babaei, Cable. Labs

January 2015 doc. : IEEE 802. 19 -15/0007 r 0 Successful Packet Transmission • ETSI LBT performs poorly compared to Wi-Fi channel access – Lower q value = worse performance • Poor coexistence behavior when sharing and >5 clients/operator – – 13 LAA clients get significantly higher P(success) compared to Wi-Fi clients i. e. black lines are all above the red lines. At a certain client count, LAA clients nearly starve Wi-Fi clients i. e. P(success) approaches zero • This value varies with q, best case shown Submission Slide 13 Alireza Babaei, Cable. Labs

January 2015 doc. : IEEE 802. 19 -15/0007 r 0 Collisions in the Shared Channel • ETSI LBT performs poorly compared to Wi-Fi channel access – Collision rate increases rapidly to 1 for low q values – Even for q = 32, collision rate dominates after 12 transmitting clients per operator • Inefficient channel usage for low q and/or scenarios with ~25 or more transmitting nodes. • Attributed to non-increasing backoff range 14 Submission Slide 14 Alireza Babaei, Cable. Labs