Enabling the Internet of Things With Wi-Fi Halow—Performance Evaluation of the Restricted Access Window

Abstract

IEEE 802.11ah, a new amendment to the Wi-Fi standard, adapts Wi-Fi networks to the emerging Internet of Things (IoT). A key component of .11ah is the Restricted Access Window (RAW), a new channel access mechanism, which reduces contention when even thousands of IoT devices operate in the same area by assigning them different channel times. This paper shows that existing studies incorrectly understand the RAW behavior, oversimplify its modeling and thereby overestimate the real system throughput in several times, especially for short durations of the reserved RAW slots. The core contribution of this paper is a new mathematical model based on a completely different approach, which yields more accurate results and thereby enables better IoT system dimensioning. The developed model is suitable for many scenarios typical for IoT. It allows finding RAW parameters that optimize system performance in terms of throughput, power consumption, and packet loss ratio. The proposed solution is can be used for various traffic patterns: when each device transmits a single packet, a batch of packets of random size, or it has full-buffer traffic.

Restricted Access Window-Based Resource Allocation Scheme for Performance Enhancement of IEEE 802.11ah Multi-Rate IoT Networks

“…The authors of [20] implemented an analytical model to improve the throughput of IEEE 802.11ah WLAN. In [21], the authors developed a mathematical model which is suitable for the IoT scenario according to the RAW mechanism. Here, the system performance was optimized by finding the optimal RAW parameters.…”

“…The analytical models developed by the authors of [11], [13], [16]- [20], [23]- [27], [33] did not consider this important aspect of RAW mechanism, which is the reset and renewal of BO process at the beginning of RAW slot as per the IEEE 802.11ah standard [7]. Also, in [21] and [22], the authors proposed the analytical models for single-rate IEEE 802.11ah network; but neither of these two works provided a closed-form expression of throughput. In [32], the authors developed an analytical model which does not consider the checking of BO at each state in the DTMC model of the IEEE 802.11ah RAW mechanism.…”

Fast and Reliable Alert Delivery in Mission-Critical Wi-Fi HaLow Sensor Networks

“…With new channel access mechanisms, namely, RAW and TWT, Wi-Fi HaLow can improve this experience by providing low-cost low-power data transmission infrastructure for massive heterogeneous IoT applications. While the performance of Wi-Fi HaLow in general IoT applications has been studied in [5]- [12], in this paper, we consider a specific scenario of alert delivery in mission-critical deployments.…”

Resource Allocation for Machine-Type Communication of Energy-Harvesting Devices in Wi-Fi HaLow Networks

“…The RAW mechanism has been extensively studied via simulation [16,17] and mathematical modeling [18][19][20][21][22][23][24][25][26][27][28][29]. In this paper, we focus on analytical approaches to estimate the network performance and note that most papers that analyze the efficiency of Wi-Fi networks with RAW incorrectly describe the data transmission with RAW.…”

“…Most related works [18][19][20] consider saturated traffic which is not a typical IoT scenario, while those that consider non-saturated traffic [21][22][23][24][25][26] mostly neglect the fact that the data transmission process within the allocated time intervals is non-stationary, i.e., the probabilities of transmission attempt and collision change with time. At the same time, the papers which correctly model the non-stationary data transmission process [27][28][29] do not consider the possibility of STAs running out of energy during the transmission process, but such an event is quite likely and important in IoT scenarios due to the following reasons. Firstly, the packet losses in wireless sensor networks can be caused not only by noise in the channel and contention for channel access but also by the depletion of STA energy.…”