Performance Analysis of Wi-Fi 6 and Wi-Fi 7


Wi-Fi 6, a.k.a., IEEE 802.11ax, is the next generation of Wi-Fi. Wi-Fi 6 is a major overhaul over it's predecessor Wi-Fi standard (802.11ac) and introduces many new features to the 802.11 family. Among these is the use of Multi-User Orthogonal Frequency Division Multiple Access (MU-OFDMA) in the downlink and uplink. This mode of transmission is significantly different from the currently-used Carrier Sense Multiple Access (CSMA) protocol, and requires the Wi-Fi Access Point to co-ordinate transmissions among it's associated clients. The design of MU-OFDMA is challenging, especially, in the uplink where the Access Point may be unaware of the buffer occupancy status of it's clients. To facilitate this, 802.11ax introduces Uplink OFDMA-based random access (UORA), which allows ALOHA-like contention on Wi-Fi sub-channels (a.k.a. Resource Units, RUs). In this project, we look the performance of uplink OFDMA in IEEE 802.11ax.

External Resources

Introductory Videos

Introductory Papers

Our Contributions

  • We perform the performance analysis of uplink MU-OFDMA in 802.11ax in the combined random access/scheduled access mode of transmission.
  • We propose an algorithm to achieve the optimal balance between random access RUs and scheduled access RUs and validate the algorithm using ns-3 simulations.
  • We study the coexistence of Wi-Fi 6 and 5G NR-U in the context of their operations in the 6 GHz Bands. We highlight that the MU OFDMA mode of operation in IEEE 802.11ax not only benefits Wi-Fi 6 networks but also benefits the 5G NR-U network when the two networks coexist.
  • We study the impact of Multi Link Aggregation---a feature likely to be introduced in Wi-Fi 7---on the latency of packets sent by Wi-Fi devices.


  • One of the notable features of the upcoming Wireless Fidelity (Wi-Fi) standard---namely, IEEE 802.11ax---is the use of Multi-User Orthogonal Frequency Division Multiple Access (MU-OFDMA). MU-OFDMA facilitates multiple users to transmit simultaneously in smaller sub-channels (a.k.a. resource units (RUs)), thereby improving the 802.11ax MAC efficiency. The 802.11ax MAC enables MU-OFDMA transmissions in the uplink (UL) by using two types of RUs: i) Random Access (RA) RUs, and ii) Scheduled Access (SA) RUs. In this paper, we investigate the impact of different distributions of RA RU and SA RU on the MAC layer performance. We leverage our analysis in devising a practical UL RU allocation scheme that maximizes the overall 802.11ax network throughput. We implement the 802.11ax MAC in network simulator-3 (NS-3) and perform extensive simulations to validate the efficacy of our proposed scheme.

    [Download | IEEE Xplore]
  • IEEE 802.11ax is the upcoming standard of the IEEE 802.11 wireless local area networks (WLAN) family. Until its most recent standard, i.e. 802.11ac, the primary focus of the 802.11 Working Group has been to increase the overall throughput of the physical (PHY) layer using innovative mechanisms such as multi-user multiple input multiple output (MU- MIMO), higher order modulation and coding schemes etc. However, these PHY layer gains often fail to translate to high throughput at the medium access control (MAC) layer, particularly in dense deployment scenarios. To address this limitation, IEEE 802.11ax introduces new features, most notably the use of Orthogonal Frequency Division Multiple Access (OFDMA), thereby enabling concurrent MU transmissions. In this paper, we first provide an overview of the uplink MU OFDMA in IEEE 802.11ax. Second, we provide an analytical model for characterizing the performance of the 802.11ax MAC layer. We investigate the trade-off between providing high network throughput and supporting new users using a metric-namely, BSR delivery rate. Finally, we validate our analyses using extensive NS-3 simulations, and present the resulting findings.

    [Download | IEEE Xplore | Slides]
  • Regulators in the US and Europe have stepped up their efforts to open the 6~GHz bands for unlicensed access. The two unlicensed technologies likely to operate and coexist in these bands are Wi-Fi 6E and 5G New Radio Unlicensed (NR-U). The greenfield 6~GHz bands allow us to take a fresh look at the coexistence between Wi-Fi and 3GPP-based unlicensed technologies. In this paper, using tools from stochastic geometry, we study the impact of Multi User Orthogonal Frequency Division Multiple Access, i.e., MU OFDMA---a feature introduced in 802.11ax---on this coexistence issue. Our results reveal that by disabling the use of the legacy contention mechanism (and allowing only MU OFDMA) for uplink access in Wi-Fi 6E, the performance of both NR-U networks and uplink Wi-Fi 6E can be improved. This is indeed feasible in the 6~GHz bands, where there are no operational Wi-Fi or NR-U users. In so doing, we also highlight the importance of accurate channel sensing at the entity that schedules uplink transmissions in Wi-Fi 6E and NR-U. If the channel is incorrectly detected as idle, factors that improve the uplink performance of one technology contribute negatively to the performance of the other technology.

    [Download | IEEE Xplore]
  • Multi Link Aggregation (MLA) is a feature likely to be introduced in Wi-Fi 7, the next-generation of Wi-Fi, which will be based on the IEEE 802.11be specifications. MLA will allow Wi-Fi devices that support multiple bands (such as the 2.4 GHz, 5 GHz, and 6 GHz bands) to operate on them simultaneously. The resulting throughput and latency gains are likely to bring Wi-Fi one step closer to supporting emerging real-time applications like augmented and virtual reality. While throughput gains resulting from the use of MLA are mostly linear, the latency gains exhibit interesting characteristics and are the subject of this paper. We use our in-house simulator to study the latency enhancements resulting from MLA and seek to answer whether Wi-Fi 7 devices can meet the challenging latency requirements demanded by most real-time applications. In this pursuit, we observe that allowing Wi-Fi devices to contend on even a single additional link without changing any physical layer parameters can lead to an order of magnitude improvement in the worst-case latency in many scenarios. In addition, we highlight that even in dense conditions, MLA can help Wi-Fi devices meet the challenging latency requirements of most real-time applications.

    [Download | IEEE Xplore]