Core Concepts
This work presents an extensive simulation-based performance evaluation of the IEEE 802.11bf protocol for Wi-Fi sensing in the sub-7 GHz band, focusing on the impact of sensing on data communication.
Abstract
The paper provides a detailed overview of the IEEE 802.11bf sensing procedure, including the different phases involved in a Trigger-Based Sensing Measurement Exchange (TB SME). It then outlines the simulation setup and the performance metrics used to evaluate the protocol.
The authors conducted experiments in three different configurations to study the impact of varying the number of sensing stations, the number of sensing applications, and the number of transmit and receive antennas on the protocol's performance. Key findings include:
- EDCA access is not suitable for sensing as it can lead to missed sensing, while PIFS access is more suitable as it ensures 0% missed sensing.
- Very short Sensing Availability Window (SAW) duration (e.g., 10) is not recommended, even at low sensing load, as it can lead to missed sensing.
- With PIFS access and maximum SAW duration (127), the sensing overhead is around 5% and the throughput drop is about 5% compared to the "no sensing" case, even at a very high sensing load (16 stations, 4 applications).
- The performance can exhibit sudden changes at discrete points where the Resource Unit (RU) size allocated to each station changes, leading to counter-intuitive results.
The authors suggest that a system can be designed with an upper limit on the sensing overhead, allowing the sensing load to increase until the overhead limit is reached.
Stats
Sensing information bytes = ⌈1.5 × Ntx × Nrx⌉ + Ntx × Nrx × Nb × Nsc / 4 + 2 × Nrx
Where:
Ntx is the number of transmit antennas
Nrx is the number of receive antennas
Nb is the number of bits used for quantization of each CSI value
Nsc is the number of subcarriers reported in CSI
Quotes
"EDCA access is not a suitable option as it can lead to missed sensing in almost all cases. So, PIFS based access should be used for sensing."
"A good rule of thumb is to have PIFS access with SAW duration set to a large value (e.g., its maximum value of 127), which ensures 0 % PSO in almost all the cases."