Accurate Energy Modeling and Characterization of IEEE 802.11ah RAW and TWT

Abstract

Minimizing the energy consumption is one of the main challenges in internet of things (IoT) networks. Recently, the IEEE 802.11ah standard has been released as a new low-power Wi-Fi solution. It has several features, such as restricted access window (RAW) and target wake time (TWT), that promise to improve energy consumption. Specifically, in this article we study how to reduce the energy consumption thanks to RAW and TWT. In order to do this, we first present an analytical model that calculates the average energy consumption during a RAW slot. We compare these results to the IEEE 802.11ah simulator that we have extended for this scope with an energy life-cycle model for RAW and TWT. Then we study the energy consumption under different conditions using RAW. Finally, we evaluate the energy consumption using TWT. In the results, we show that the presented model has a maximum deviation from the simulations of 10% in case of capture effect (CE) and 7% without it. RAW always performs better than carrier-sense multiple access with collision avoidance (CSMA/CA) when the traffic is higher and the usage of more slots has showed to have better energy efficiency, of up to the 76%, although also significantly increasing the latency. We will show how TWT outperforms pure RAW, by over 100%, when the transmission time is over 5 min.

Resource Management for Massive Internet of Things in IEEE 802.11ah WLAN: Potentials, Current Solutions, and Open Challenges

“…Table 9 provides an in-depth overview of the various resource allocation MAC protocols suggested for TWT. Some earlier works have focused on TWT [ 149 , 150 , 151 , 152 ]. As RAW may be used to safeguard TWT STAs from collisions with other STAs, Ref.…”

On the Joint Usage of Target Wake Time and 802.11ba Wake-Up Radio

“…Many surveys of new amendments for Wi-Fi standard [2], [7], [8] mention the TWT. The authors of [9] implemented the TWT mechanism in the simulation platform ns-3 [10] and revealed that the TWT reduces the sensor's power consump-This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/ This article has been accepted for publication in a future issue of this journal, but has not been fully edited.…”

“…The authors of [11] examine the mutual influence of the TWT and Restricted Access Window mechanisms, and [12] shows the effectiveness of their joint usage. However, [9], [11], and [12] study only the variant of TWT described in the IEEE 802.11ah amendment.…”

“…where CW r is the contention window corresponding to the retransmission counter r, R is the upper bound of retransmission counter, C * (i, r) is the sensor's collision probability in the slot i with the retransmission counter r. The first and the second formulas in (9) mean that the first transmission attempt is always performed in one of the slots selected from the contention window CW min . The third formula means that after making R transmission attempts, the sensor discards the current frame and does not further transmit it.…”

Location-Based Vertical Handovers in Wi-Fi Networks With IEEE 802.11ah

“…It features a communication range of up to 1 kilometer and provides megabits per second data-rates [2]. It also offers higher energy efficiency and scalability, as it is able to simultaneously establish connections from a single Access Point (AP) to more than 8000 stations [3], [4]. On the other end, traditional Wi-Fi technologies offer higher data-rates, however their communication range is limited to tens of meters and their energy efficiency and scalability is significantly lower compared to IEEE 802.11ah.…”