Wi-Fi 6E白皮书（英文版）.pdf

2020 LitePoint, A Teradyne Company. All rights reserved. WHITEPAPER A Guide to Wi-Fi 6E Wi-Fi 6 in the 6 GHz BandA Guide to Wi-Fi 6E Wi-Fi 6 in the 6 GHz Band 2 Contents 1. Introduction . 3 2. Why do we need more spectrum and why the 6 GHz band? . 4 Wi-Fis Successes . 4 Wi-Fis Challenges . 5 Benefits of Wi-Fi 6E . 5 3. Wi-Fi 5, Wi-Fi 6 and Wi-Fi 6E, how do they differ? . 6 New Naming Scheme . 6 Technology Evolution . 6 4. Who are the incumbents in the 6 GHz band? . 7 5. What are the rules of operation in the 6 GHz band? . 9 Standard Power Access Point . 10 Low Power Indoor Access Point . 11 Emissions Masks . 12 6. How does the IEEE define operations in the 6 GHz band? . 14 Rules of Operation . 14 HE PHY in the 6 GHz band . 14 Scanning and Probing in the 6 GHz band . 14 Channelization . 15 7. Wi-Fi 6E Challenges . 17 The 6 GHz Barrier . 17 Consistent Performance across 1200 MHz . 17 Dual Band or Tri Band Devices . 17 Emissions . 17 80 MHz and 160 MHz Channels . 17 Higher Order Modulation: 1024-QAM . 19 OFDMA . 20 8. LitePoints Solutions for Wi-Fi 6E. 22 IQxel-MW 7G . 22 IQfact+ . 23A Guide to Wi-Fi 6E Wi-Fi 6 in the 6 GHz Band 3 1. Introduction On April 23, 2020 the FCC voted unanimously to make 1,200 megahertz of spectrum available for unlicensed use in the 5.925-7. 125 GHz (6 GHz) band. This historic event was the culmination of several years of work by Wi-Fi advocates underscoring the FCCs commitment to promote unlicensed standards as the indispensable engine for wireless connectivity for American consumers. The extension of Wi-Fi in the 6 GHz band, named Wi-Fi 6E by the Wi-Fi Alliance 1, has been strongly advocated for by many in the Wi- Fi industry. From chipset and equipment manufacturers to service providers and end users, everyone agrees that more than doubling the available spectrum will revolutionize the Wi-Fi user experience. Chipset manufacturers 2 3 have already announced new products capable of supporting the 6 GHz band and consumer equipment could become available as early as the end of the 2020. To understand the importance of this event, deemed by many as the biggest revolution in Wi-Fi, this paper will review what makes the 6 GHz band compelling for unlicensed use and why additional spectrum is so badly needed to sustain Wi-Fi growth. The paper will also explore how the 6 GHz band will fit into Wi-Fi 6 deployments and analyze the challenges associated with bringing Wi-Fi 6E devices to market.A Guide to Wi-Fi 6E Wi-Fi 6 in the 6 GHz Band 4 2. Why do we need more spectrum and why the 6 GHz band? Wi-Fis Successes As the most prevalent connectivity technology, Wi-Fi has proven to be a success story beyond the highest expectations. It is estimated that Wi-Fi contributes more than $2 trillion to the global economy each year 4 and now, more than ever Wi-Fi has become an essential part of how businesses, healthcare, retail, hospitality and education operate. The availability of unlicensed spectrum in the 2.4 GHz and 5 GHz bands has been the driver of Wi-Fis successes, as it lowered the barrier of entry for new comers and enabled new and innovative use cases to emerge. In the past 20 years, Wi-Fi evolved to become the ubiquitous local network connectivity technology that it is today. The “little engine that could” of the wireless world, Wi-Fi carries more internet traffic than any other wireless technology. Yet, this was accomplished despite having less than 300 MHz of unrestricted spectrum available. 80 MHz in the 2.4 GHz band (channels 1 to 13) (U.S. only allows channels 1 to 11, Japan allows channel 14 for 802.11b only) 180 MHz unrestricted in the 5 GHz band or 500 MHz requiring Dynamic Frequency Selection (DFS) spectrum sharing channels DFS channels require a spectrum sharing mechanism to ensure that they do not interfere on frequencies used by nearby weather or military radar stations. The Wi-Fi AP must continuously monitor for the presence of radar signals to avoid interference. Due to the complexity and delay incurred by this implementation, the DFS channels are often not supported in consumer equipment or not used by network administrators. Figure 1: Wi-Fi spectrum comparison 5925 MHz AP Standard Power Indoor or Outdoor AFC Required AP Low Power Indoor only Client Devices Indoor or Outdoor Under control of the Access Point 6425 MHz UNII-5 UNII-6 UNII-7 UNII-8 6525 MHz 6875 MHz 7125 MHz 5925 MHz 6425 MHz U-NII 5 U-NII 6 U-NII 7 U-NII 8 6525 MHz 6875 MHz 7125 MHz 41 x 20 MHz Channel Standard Power AP and Client 20 x 40 MHz Channel 9 x 80 MHz Channel 4 x 160 MHz Channel 5925 MHz 6425 MHz U-NII 5 U-NII 6 U-NII 7 U-NII 8 6525 MHz 6875 MHz 7125 MHz 59 x 20 MHz Channel Low Power Indoor AP and Client 29 x 40 MHz Channel 6GHz band 20 MHz Channel 14 x 80 MHz Channel 7 x 160 MHz Channel 20 MHz Channels 5925 MHz 6425 MHz U-NII 5 PSC Non- PSC Non- PSC Non- PSC Non- PSC Non- PSC Non- PSC PSC U-NII 6 UNII-4 U-NII-6 U-NII-5 18 1 1 201 205 20 213 217 221 225 22 233 237 241 245 24 253 257 261 265 26 1 1 211 203 235 267 2 331 363 3 227 243 25 275 2 307 323 33 355 371 387 403 1 207 215 223 231 23 247 255 263 271 27 287 2 303 311 31 327 335 343 351 35 367 375 383 3 3 407 415 273 277 281 285 28 2 2 301 305 313 30 317 321 325 32 333 337 341 345 34 353 357 361 365 36 377 381 385 38 3 3 401 405 40 413 417 421 373 1 1 1 203 207 211 215 21 223 227 231 235 23 243 247 251 255 25 263 267 271 275 27 283 287 2 2 2 303 307 315 311 31 323 327 331 335 33 343 347 351 355 35 363 367 371 37 383 387 3 3 3 403 407 411 415 41 423 375 55 55 55 6005 6025 6045 6065 6085 6105 6125 6145 6165 6185 6205 6225 6245 6065 6285 6305 6325 6345 6365 6385 6405 6425 6445 6465 6485 6505 6525 6565 6545 6585 6605 6625 6645 6665 6685 6705 6725 6745 6765 6785 6805 6825 6845 6885 65 65 65 65 65 7005 7025 7045 7065 7085 7105 7125 6865 U-NII-7 U-NII-8 U-NII 7 U-NII 8 6525 MHz 5850 MHz 6875 MHz 7125 MHz Between Sub-bands In-Band Out of Band Out of Band 40 MHz Channels 80 MHz Channels 160 MHz Channels Center Frequency (MHz) 20 MHz Channels U-NII-6 U-NII-5 1 1 213 205 237 26 301 333 365 3 22 245 261 277 2 30 325 341 357 373 38 405 201 20 217 225 233 241 24 257 265 273 281 28 2 305 313 321 32 337 345 353 361 36 377 385 3 401 40 417 55 55 55 55 6015 6035 6055 6075 60 6115 6135 6165 6175 61 6215 6235 6055 6275 62 6315 6335 6355 6375 63 6415 6435 6455 6475 64 6515 6555 6535 6575 65 6615 6635 6655 6675 66 6715 6735 6755 6775 67 6815 6835 6875 687 65 65 65 65 65 7015 7035 7055 7075 70 7115 6855 U-NII-7 U-NII-8 40 MHz Channels 80 MHz Channels 160 MHz Channels 59 x 20 MHz 29 x 40 MHz 14 x 80 MHz 7 x 160 MHz DFS Channels 6 GHz Band Total Spectrum 1200 MHz 5 GHz Band Total Spectrum 500 MHz (180 MHz without DFS) 25 x 20 MHz 12 x 40 MHz 6 x 80 MHz 2 x 160 MHz 2.4 GHz Band Total Spectrum 80 MHz 3 x 20 MHz 1 x 40 MHz Non-Overlapping ChannelsA Guide to Wi-Fi 6E Wi-Fi 6 in the 6 GHz Band 5 Wi-Fis Challenges Additional unlicensed spectrum is needed to address the main challenges facing Wi-Fi users as outlined below: Congestion The low number of Wi-Fi channels available today forces users to share available bandwidth and creates congestion. As each client station waits its turn to transmit (or receive) data, congestion is caused by devices, AP and Stations, sharing the same channel. Restricted 80-MHz and 160-MHz channel availability Today, the limited amount of contiguous spectrum makes it difficult to enable 80 MHz or 160 MHz channels, thereby limiting higher throughput which can only be achieved with wide channel bandwidth. In dense environments such as stadiums or airports or in large enterprises, its hard to find an 80 MHz or 160 MHz channel free from interference caused by devices on overlapping channels. In response, network administrators often choose to disable these capabilities, thereby restricting the data speeds available on their network. Legacy devices IEEE 802.11 standards have always ensured that newer standards were backward compatible with previous standards. Older and newer devices can all interoperate, however overall data throughput is limited by the slowest devices. Legacy devices such as 802.11b/g/n require more air time to transmit data, therefore increasing latency and reducing throughput for all users. To sustain Wi-Fis projected growth and unlock new applications, a study 5 commissioned by the Wi-Fi Alliance predicted a shortfall of 800 MHz of spectrum to handle busy hour traffic by 2020 and a shortfall of 1.12 GHz by 2025. The study stressed the importance of making available continuous spectrum in order to enable 160 MHz (or future 320 MHz) wide channels. The 6 GHz band and its 1200 MHz of contiguous spectrum make an ideal candidate to fulfill the growth requirements and this is why it has been chosen for unlicensed use. Benefits of Wi-Fi 6E Wi-Fi 6E devices operating in the 6 GHz band will be immediately able to take advantage of the benefits provided by this greenfield spectrum. High Capacity With 59 new 20 MHz channels available in the 6 GHz band, congestion issues will be immediately relieved. Wi-Fi 6E APs will not need to compete for spectrum and will be able to operate on congestion-free channels. Higher Speed 1200 MHz of contiguous spectrum enables 7 new 160 MHz channels and 14 new 80 MHz channels. Network administrators will be able to enable widespread use of wider channels without the risk of interference from overlapping channels and sufficient spatial reuse. Wider channels deployments will unlock multi-Gigabit Wi-Fi speeds for end users. Low Latency IEEEs decision to reserve access of the 6 GHz band to 802.11ax devices will reduce the latency and enable 1 ms latency for 6E devices 6. First by removing all legacy slower devices and also by allowing only 802.11ax (OFDMA, MU-MIMO, 1024 QAM) capable devices, that can take full advantage of the capacity and latency improvement features provided by this technology. Channel Width 2.4 GHz Band 5 GHz Band 6 GHz Band # of available 20 MHz channels 3 (non-overlapping) 25 (9 without without DFS) 59 # of available 40 MHz channel 1 12 (4 without without DFS) 29 # of available 80 MHz channels 0 6 (2 without without DFS) 14 # of available 160 MHz channels 0 2 (0 without without DFS) 7 # of available 320 MHz channels (future capability 802.11be) 0 0 3 Table 1: Channel availability in 2.4, 5 and 6 GHz bandsA Guide to Wi-Fi 6E Wi-Fi 6 in the 6 GHz Band 6 3. Wi-Fi 5, Wi-Fi 6 and Wi-Fi 6E, how do they differ? To understand the benefits that Wi-Fi 6E will bring, lets compare the evolution of the most recent Wi-Fi standards. New Naming Scheme In order to make it easier for the general public to identify device generations without remembering the complex IEEE alphabet soup, the Wi-Fi Alliance has created a naming scheme using a number to identify the generation. Using this new consumer-friendly scheme, the 802.11ac generation devices have been renamed Wi-Fi 5, while devices based on the IEEE 802.11ax standard have been named Wi-Fi 6. Although the 802.11ax standard includes the 2.4 GHz, 5 GHz and 6 GHz bands, the Wi-Fi Alliance has introduced the denomination of Wi-Fi 6E to identify 802.11ax devices operating in the 6 GHz band. Wi-Fi Alliance Naming Scheme IEEE Equivalent Standard Wi-Fi 5 802.11ac Wi-Fi 6 802.11ax Wi-Fi 6E 802.11ax Table 2: Wi-Fi generations naming Technology Evolution Some of the key technology features of the Wi-Fi standards are highlighted below. As shown in Table 3, Wi-Fi 6 and Wi-Fi 6E devices are similar in all aspects except for the operation in the 6 GHz band. Wi-Fi 5 Wi-Fi 6 Wi-Fi 6E Operating bands 5 GHz 2.4 GHz, 5 GHz 6 GHz Modulation scheme OFDM OFDMA OFDMA Channel width 20 MHz, 40 MHz, 80 MHz, 160 MHz 20 MHz, 40 MHz, 80 MHz, 160 MHz 20 MHz, 40 MHz, 80 MHz, 160 MHz Highest modulation 256-QAM 1024-QAM 1024-QAM MIMO streams Up to 8x8 Up to 8x8 Up to 8x8 MU-MIMO Downlink MU-MIMO Downlink and Uplink-MU-MIMO Downlink and Uplink-MU-MIMO Target Wake Time (TWT) No Yes Yes BSS Coloring No Yes Yes Extended Range Improvements No Yes Yes Table 3: Wi-Fi technology evolutionA Guide to Wi-Fi 6E Wi-Fi 6 in the 6 GHz Band 7 4. Who are the incumbents in the 6 GHz band? While it is clear that the 6 GHz band provides great benefits to Wi-Fi, it is important to understand who its current incumbents are and appreciate the efforts that have been made to make this band available for unlicensed use. The 6 GHz band (5.925 7.125 GHz) is host to incumbent services operating on a primary basis. These services include fixed point-to-point, fixed satellite service (FSS), broadcast auxiliary service (BAC), and cable television relay service (CARS). Figure 2 below from the FCC NPRM FCC 18-147, shows the density of assignments per megahertz in the FCC databases for the terrestrial services (excluding FSS) and shows 47,695 unique uses between 5.925 and 7.125 GHz. Figure 2: Licensed 6 GHz band users Each of the 6 GHzs four U-NII Unlicensed - National Information Infrastructure (U-NII) sub-bands has a different set of incumbent services and operators. The table below shows the main users for each band: U-NII Band Frequency Range (GHz) Usage Incumbent Services U-NII 5 5.925-6.425 Fixed Fixed Satellite Services (earth to space) Fixed Microwave U-NII 6 6.425-6.525 Mobile Fixed Satellite Services (earth to space) Broadcast Auxiliary Service Cable Television Relay Service U-NII 7 6.525-6.875 Fixed Fixed Microwave Fixed Satellite Services (earth to space) U-NII 8 6.875-7.125 Fixed and Mobile Broadcast Auxiliary Service Fixed Microwave Cable Television Relay Service Fixed Satellite Services (earth to space and space to earth) Table 4: Incumbent users of 6 GHz frequency bandsA Guide to Wi-Fi 6E Wi-Fi 6 in the 6 GHz Band 8 Fixed Satellite Services Used for earth-to-space and space-to-earth communication to geostationary satellites, the incumbents in the band use the 6 GHz band mostly for content distribution to television and radio broadcast. The 7.025 to 7.075 GHz section (lower U-NII 8) is used for satellite digital audio radio service (SDARS), i.e. Sirius XM. Fixed Microwave Services Fixed microwave services are used for point-to-point microwave links. Users include commercial service providers such as AT&T or Verizon that carry traffic for wireless backhaul between base stations and wireline network. There are also industrial and business operators, carrying traffic for utilities, including power grid or natural gas and oil operation. Fixed microwave services are also deployed to carry critical traffic from public safety and emergency services like backhaul for police and fire vehicle dispatch. Broadcast Auxiliary Services (BAS) These include mobile television pickups and remote pickup stations which relay signals from a remote location back to the television studio for special events or remote locations. Cable Television Relay Service (CARS) These links are used by cable carriers to transmit video and audio back to the receivers. Most of these incumbents have expressed valid concerns about coexistence with unlicensed technolo