AEROHIVE NETWORKS ax DAVID SIMON, SENIOR SYSTEMS ENGINEER Aerohive Networks. All Rights Reserved.

802.11n and 802.11ac 802.11n and 802.11ac technology introduced new PHY and MAC layer enhancements to achieve high data rates We built bigger highways and faster cars 3 2018 Aerohive Networks. All Rights Reserved.

Data Rates versus Throughput Data rate is not TCP throughput Medium contention protocol of CSMA/CA consumes much of the available bandwidth Aggregate TCP throughput in a legacy a/b/g environment is 40% 50% of data rate in ideal conditions Aggregate TCP throughput in an 802.11n/ac environment is 60% 70% of data rate in ideal conditions 7 2018 Aerohive Networks. All Rights Reserved.

Traffic nightmare High density of clients The bulk of of data frames (75-80%) are small and under 256 bytes 9 2018 Aerohive Networks. All Rights Reserved. The result is overhead at the MAC layer and medium contention overhead for each small frame

The future: 802.11ax 802.11ax High Efficiency(HE) 802.11ax uses PHY and MAC layer enhancements for better traffic management The goal is to increase average throughput 4X per user in high-density scenarios Operates in both the 2.4 GHz and 5 GHz frequency bands 10 2018 Aerohive Networks. All Rights Reserved.

The future: 802.11ax What is new? OFDMA better use of the frequency space BSS Coloring Mitigate OBSS Uplink and Downlink MU-MIMO for up to 8 devices!!802.11ac only had DL MU-MIMO for up to 4 devices! 1024-QAM Higher data rates Target Wake Time (TWT) Great for IoT devices 11 2018 Aerohive Networks. All Rights Reserved.

802.11n vs. 802.11ac vs. 802.11ax 802.11n 802.11ac 802.11ax Channel Size (MHz) 20, 40 20, 40, 80, 80 + 80 and 160 20, 40, 80, 80 + 80 and 160 Subcarrier (KHz) 312.5 312.5 78.125 Symbol time (µs) 3.2 3.2 12.8 Frequency multiplexing OFDM OFDM OFDM and OFDMA Modulation BPSK, QPSK, 16-QAM, 64-QAM BPSK, QPSK, 16-QAM, 64-QAM, 256-QAM BPSK, QPSK, 16-QAM, 64-QAM, 256-QAM 1024-QAM MU-MIMO N/A Downlink Downlink and Uplink Spectrum Bands 2.4GHz & 5GHZ 5GHZ 2.4GHz & 5GHZ 12 2018 Aerohive Networks. All Rights Reserved.

Multi-user (MU) What is the definition of Multi-User (MU)??? The term multi-user (MU) simply means that transmissions between an AP and multiple clients can occur at the same time dependent on the supported technology. However, the MU terminology can be very confusing when discussing 802.11ax. MU capabilities exist for both OFDMA and MU-MIMO. Please understand the differences as explained further in this field note. 13 2018 Aerohive Networks. All Rights Reserved.

OFDM subcarriers OFDM divides bandwidth into subcarriers: Data subcarriers Carry modulated data Management Subcarriers Don t carry data, they are used for synch and interference protection purposes 15 2018 Aerohive Networks. All Rights Reserved.

OFDMA Orthogonal Frequency-Division Multiple Access (OFDMA) Multi-user version of the popular orthogonal frequency-division multiplexing (OFDM) digital modulation scheme. Multiple access is achieved in OFDMA by assigning subsets of subcarriers to individual clients. This allows simultaneous low data rate transmission to/from multiple users. - From Wikipedia 18 2018 Aerohive Networks. All Rights Reserved.

802.11a/n/ac vs. 802.11ax subcarriers 312.5 khz 802.11a/n/ac subcarrier spacing 78.125 khz 802.11ax subcarrier spacing 256 subcarriers (tones) in 20 MHz, (40MHz/512, 80MHz/1024, 160MHz/2048)!Data subcarriers: 234 / 468 / 980 / 1960!Pilot subcarriers: 8 / 16 / 16 / 32!Unused subcarriers 11/ 23 / 23 19 2018 Aerohive Networks. All Rights Reserved.

OFDMA Resource Units 26 26 26 26 26 13 13 26 26 26 26 52 52 52 52 106 106 Frequency allocations for both uplink and downlink OFMDA define resource units(ru) with 26, 52, 106, 242, 484 or 996 subcarriers (tones) 242 20 MHz The subcarriers (tones) are in fixed locations of each 20, 40 or 80 MHz channel 21 2018 Aerohive Networks. All Rights Reserved.

OFDMA Resource Units 26 26 26 26 26 13 13 26 26 26 26 9 users 52 52 52 52 106 106 242 4 users 2 users 1 user 22 2018 Aerohive Networks. All Rights Reserved. 20 MHz Based on multi-user traffic needs, the AP decides how to allocate the channel

OFDMA Resource Units 26 26 26 26 26 13 13 26 26 26 26 9 users 52 52 52 52 106 106 242 4 users 2 users 1 user 23 2018 Aerohive Networks. All Rights Reserved. 20 MHz AP may allocate the whole channel to only one user at a time or it may partition it to serve multiple users simultaneously

OFDMA The AP is in charge! AP controls the medium both downlink and uplink frame by frame AP transmit power can be adjusted per resource unit (RU) Number of sub-channels and users can vary packet per packet 24 2018 Aerohive Networks. All Rights Reserved. The AP decides how the client transmits on the UPLINK

DOWNLINK MU-OFDMA OVERVIEW AP controls the medium Process Overview:!MU-RTS (An extended trigger frame from AP to sync upstream CTS client response)!mu-rts sent across whole 20 MHz so legacy clients understand.!txop is for entire exchange,!cts responses from the clients in parallel (Resource Units)!DL MU-PPDU data transmissions from the AP to the OFDMA clients!block ACK Auto BlockACK or BAR/BA AP transmit power can be adjusted per resource unit (RU) 25 2018 Aerohive Networks. All Rights Reserved.

Downlink MU-OFDMA AP AIFS Trigger MU-RTS STA 4 RU 3 : 52 tones STA 3 RU 3 : 52 tones STA 2 RU 2 : 52 tones STA 1 RU 1 : 52 tones BAR STA 4 STA 3 STA 2 STA 1 CTS CTS CTS CTS BlockACK BlockACK BlockACK BlockACK 26 2018 Aerohive Networks. All Rights Reserved.

UPLINK MU-OFDMA OVERVIEW AP still controls the medium Process Overview:!AP sends a Buffer Status Report Poll (BSRP)!Clients reply with synchronized Buffer Status Report (BSR) frames Information about their AID, data length, type of data (QoS), etc.!ap builds RU schedule with following information: Start, Stop times / Client RU mapping / RUs per clients / MCS setting/ Power levels per RU!AP may send a trigger frame variant: MU-RTS (An extended trigger frame from AP to sync upstream CTS client response)!cts responses from the clients in parallel (RU)!AP sends a basic Trigger frame to allocate the RUs and time-sync!clients send UL-DATA via their assigned RUs!Multi-User Block ACK from the AP 27 2018 Aerohive Networks. All Rights Reserved.

Uplink MU-OFDMA AP AIFS Trigger BSRP Trigger MU-RTS MU-ACK STA 4 STA 3 CBSR CSSR CTS CTS UL-MU-PPDU UL-MU-PPDU PAD STA 2 CBSR CTS UL-MU-PPDU STA 1 CSBR CTS UL-MU-PPDU 28 2018 Aerohive Networks. All Rights Reserved.

802.11AX MU-OFDMA: UPLINK TRAFFIC AP sends Trigger to alert clients when to transmit Client 1 Client 2 Subcarriers Client 3 Client 4 Client 5 Client 6 29 2018 Aerohive Networks. All Rights Reserved. Time

MU-OFDMA summary Ideal for low bandwidth application Better frequency reuse Reduced latency Increased efficiency Remember. 802.11ax is about High Efficiency 32 2018 Aerohive Networks. All Rights Reserved.

MU-MIMO User1 AP User2 AP use DL MU-MIMO to serve multiple clients requires spatially diverse position. AP can specify multiple STA to simultaneously send uplink frames via trigger frames. 34 2018 Aerohive Networks. All Rights Reserved. 34

CCA 20 MHz Clear Channel Assessment (CCA): CCA: SD = 4 db SNR ED = SD + 20 dbm Signal Detect (SD) threshold is statistically a 4 db signal-to-noise ratio (SNR) to detect 802.11 preamble Energy Detect (ED) is 20 db above the signal detect threshold 36 2018 Aerohive Networks. All Rights Reserved.

CCA 20 MHz Clear Channel Assessment (CCA): Think of the preamble carrier sense as a method of detecting and deferring for 802.11 radio transmissions CCA example: SD = -95 dbm ED = -75 dbm Think of the energy detect as a method of detecting and deferring for any RF transmissions 37 2018 Aerohive Networks. All Rights Reserved.

BSS Coloring PHY header creates a color bit Channel access behavior will be dependent on the color detected AP radios and client radios will be able to apply adaptive CCA thresholds 40

BSS Coloring BSS Coloring potentially solves the CCI problem that is a result of the current 4 db carrier sense threshold BSS coloring adds a number to different BSSs on the same channel 42 2018 Aerohive Networks. All Rights Reserved.

BSS Coloring PHY header creates a color bit Channel access behavior will be dependent on the color detected AP radios and client radios will be able to apply adaptive CCA thresholds 43 2018 Aerohive Networks. All Rights Reserved.

BSS Coloring Adaptive CCAs with Dual NAV timers Same color bit = Intra-BSS Different color bit = Inter-BSS Inter-BSS detection means that a listening radio treats the medium as BUSY and will defer The Signal Detect(SD) threshold can be dynamic The Energy Detect (ED) thresholds may remain static 44 2018 Aerohive Networks. All Rights Reserved.

BSS Coloring -62 dbm CCA Energy Detect threshold intra-bss inter-bss + 4 dbm CCA Signal Detect threshold Adaptive CCA implementation could raising Signal Detect threshold for inter-bss frames, while maintaining a lower threshold for intra-bss traffic 45 2018 Aerohive Networks. All Rights Reserved.

BSS Coloring If BSS Coloring works as described. Will 80 MHz channels in the enterprise be okay? Will protocol analyzers and Wi-Fi scanners be able to decode the BSS color bit in the Radiotap header? Will RRM and ACSP algorithms be able to perform auto-coloring to prevent contention overhead? 46

TARGET WAKE TIME

Target Wake Time Target Wake Time (TWT) is a power saving mechanism in 802.11ah, negotiated between a STA and its AP, which allows the STA to sleep for periods of time, and wake up in pre-scheduled (target) times to exchange information with its AP This allows the station to sleep longer and reducing energy consumption. Key feature for IoT type sensors 48 2018 Aerohive Networks. All Rights Reserved.

1024-QAM modulation Much like 256-QAM, we anticipate that very high SNR thresholds (~ 37dB) will be needed in order for 802.11ax radios to use 1024-QAM modulation. 51 2018 Aerohive Networks. All Rights Reserved.

Longer Symbol Time The increase in the number of subcarriers (tones) also increases in the OFDM symbol duration (from the maximum of 4 µs used in IEEE 802.11ac to the maximum of 16 µs used in 802.11ax) and additional guard interval (GI) durations (legacy 0.8 µs and new 1.6 µs and 3.2 µs) are supported. The use of longer OFDM symbols allows for larger coverage areas as the system becomes more robust to propagation delays, and longer GIs decrease inter-symbol interference. 52 2018 Aerohive Networks. All Rights Reserved.

AP uplink Some of our competitors are claiming we will need 10 Gbps uplinks from 802.11ax APs. Is this true? Will we at least need 2.5 MultiGig (802.3bz) Ethernet ports? Bandwidth bottlenecks are almost always the WAN uplink 55 2018 Aerohive Networks. All Rights Reserved.

AP650X Features: External antennas 4x4 + 4x4 11ax Dual 5 GHz radio 2.5G + 1G ports BLE / USB Outdoor mode Industrial Temp Range (-20C to +55C) POE+/DC Power 60 2018 Aerohive Networks. All Rights Reserved.