WLAN - 802.11ax                                                          Home : www.sharetechnote.com

 

 

 

 

WiFi 802.11ax is also called as WiFi 6. It has features as summarized below. Some of them are the evolutionary features comparing to previous version and some of them are brand new features introduced in 802.11ax.

  • Increased Throughput : As always, there is a part to increase the throughput and it is done by Higher modulation like almost always. ==> Even though throughput increase would attract the attention of many users, this is not the most important aspect of 802.11ax. The major focus of 802.11ax is increase the efficiency rather than the increased throughput.
  • Narrow Subcarrier Spacing/Long OFDM Symbol length : Subcarrier spacing get narrower, implying that frequency domain capacity would get increased. But the decreased subcarrier spacing cause increlased OFDM symbol length. The increased OFDM symbol length would offset the effect of decreased subcarrier in terms of throughput, but it would result in the increased robustness in long distance communication by allowing wider delay spreading.
  • Support multiple users at the same time and Frequency. This is done by Multiuser mimo and spatial multiplexing. These were supported to some degree in previous release in downlink, but it would expand to uplink in this release.
  • OFDMA : The most important technical component for simultaneous multi-user support in this release would OFDMA, implying that it would get the flexibility of multi-user scheduling similar to LTE or NR cellular network. This implies that one user does not wait until all other user finish their communication. Multiple user can transmit/recieve simultaneously using differect sections of frequency spectrum (Simultaneous transmission/reception in both time and frequency domain is still not allowed). OFDMA would help to shorten the latency of the communication. (See this note for the details)
  • Low Power Consumption by the mechanism of Target Wakeup Time. Understandably the main use case for this feature would be targeted for IoT application.

 

 

main features of 802.11ax in comparison with previous release is well summarized by the following table which is quoted from Aruba White Paper. I would stronly recommend you to read through this whitepaper if you are interested in the further technical details.

 

         Source : Aruba Whitepaer

 

 

NOTE : I think WiFi 6 (802.11ax) introduced some of the features that are similar to 4G/5G Cellular technology mainly for more efficient use of radio resources. The first one is OFDMA and the second one is the concept of RU(Resource Unit). The minimum size of resource unit is 26 subcarriers. To me, RU seems to be similar to the concept of RB (Resource Block) in 4G/5G cellular technology.

 

 

 

Similarity to 4G/5G Cellular Technology

 

Many experts say that the main focus of WiFi 6G is to increase the efficiency. Even though WiFi 6G includes the technical components to increase the throughput comparing to previous specification, the efficiency improvement is higher priority than the throughput boost. It seems to me that many of the technical features introduced in WiFi 6G to improve the efficiency are very similar to the technologies that have been used in 4G(LTE)/5G(NR) cellular technology. Of course, the details on how to implement these features is not exactly same as those in cellular technology, but the fundamental concept is very similar. Followings are the list of these features.

  • OFDMA - Obviously it is hard to deny that this idea came from 4G/5G cellular technology.
  • The concept of RU (Resource Unit) - this is similar to RB (Resource Block) in 4G/5G cellular technology.
  • Target Wake Time - To me, this seems to be similar to PSM(Power Saving Mode) in 4G/5G cellular technology,
  • BSR (Buffer Status Report) - Same concept as BSR in 4G/5G cellular technology

 

 

 

References :

 

 

 

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