HYBRID CONTENTION-ADDRESSING ALGORITHM FOR ENERGY EFFICIENCY IN IEEE 802.11 WAKE-UP BASED RADIO NETWORK UPLINK

ABSTRACT

Power consumption is a key consideration in every Wireless Local Area Network Medium Access  Control  (WLAN  MAC)  algorithm  design  for  wireless  devices  and  extending battery life requires more efficient power management scheme considering that carrier sensing by WLAN modules, false wake-ups, collisions and number of contention rounds are major contributors to energy overhead. Researchers over the years have proposed and implemented various schemes using a low power wakeup radio for carrier sense which has proven to be effective. This thesis analyzes the energy efficiency and latency performance of IEEE 802.11 wake-up based radio network uplink using Hybrid Contention-Addressing Algorithm. In this algorithm, Wake-up radio (WuR) senses the channel and wakes its co- located WLAN module when the channel is available for transmission. The station (STA) that wakes up to transmit packet is decided by distributed contention. But the technique put forward in this thesis differs from previous method because each contention round is used to select and queue a set of STAs as against one. The selected and queued STAs then goes on in the addressing stage to transmit as soon as they receive the wake-up message (WuM) in quick succession. The problem of false wakeup stemming from wakeup latency and delay between sleep and wake up of successive STAs is dealt with by the addressing technique which broadcasts an ACK frame modulated with a WuM bearing the unique address  of  the  STA  to  transmit  next.  In  this  way,  two  stations  cannot  wakeup simultaneously nor can one wakeup while the other is still in the process of waking. Extensive  analysis  confirmed  that  the  HCA-CSAM/CA  effectively  reduces  energy overhead by up to 97%, 60hrs increase in battery lifetime and 68.3% reduction in latency compared with ESOC with a better tradeoff between energy consumption and throughput.

CHAPTER ONE

1.0 INTRODUCTION

1.1 Background to the Study

The IEEE 802.11 WLAN has developed over the years as a preferred technology for wideband wireless technology, therefore, requiring WLAN modules implant into wireless devices such as tablets and smartphones. However, the power-sapping nature of WLAN radio limits battery life making it necessary to improve energy efficiency of the radio. A WLAN radio is required to receive messages immediately by staying in the continuous wake-up mode (CAM) but idle awaiting period spent in sensing the channel leads to much power consumption.

Using low power Wake-up Radio (WuR) in conjunction with the Wireless Local Area Network (WLAN) module lowered power consumption of the WLAN by assuming the responsibility of sensing the channel giving room for further reduction in power consumption by clever adjustment of the algorithms (Magno et al., 2016; Piyare et al., 2017; Kondo et al., 2012). The aim of developing the wireless telecommunication technologies was to provide services equivalent to those of wireline networks.

Wireless networks have come to support high-bandwidth data transmission for wireless device users while providing voice communication. Depending on area of coverage, Wireless data networks are classified (Boukerche, 2005) into: Wireless Local Area network (WLAN), in which cell radius is approximately 100m, especially in office environments and homes, Wireless Metropolitan Area Network (WMAN) masking areas as giant as whole cities and Wireless Wide Area Network (WWAN) of approximately 50000 m cell radius.

IEEE 802.11 is a component of the Local Area Network (LAN) technical standards IEEE 802 set that stipulates PHYsical layer (PHY) and Medium Access Control (MAC) algorithms in computer communication for realizing wireless local area network (WLAN) first released in 1997 as contained in MAN, Committee and Computer (2009). The IEEE 802.11 and HiperLAN standard are both under the Wireless Fidelity (Wi-Fi) alliance. The standard uses frequency bands of 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. Wi-Fi initially provided an 11Mbps approximate throughput with recent developments increasing it to 30 Gbps (Fabris Hoefel R. P., 2020; Lopez-Perez et. al., 2019).

A WLAN network is comprised of an Access Point (AP) at the  centre with multiple stations (STAs) linked to it (Chen et al., 2016; Tang and Obana, 2018; Kondo et al., 2012). In centralized mode, all STA communication is over the access point (APs) while in the decentralized mode, communication between STAs takes place directly without going through the AP in an ad hoc manner.

Due to its high market acceptability, numerous amendments have been developed for the basic IEEE 802.11-1997, the prominent among them being 802.11a, 802.11b, 802.11g, 802.11n and 802.11p as shown in Figure 1.1. Carrier-Sense Multiple Access with Collision Avoidance (CSMA/CA) technique is adopted for every standard with support for both centralised and ad-hoc networks (Sanabria-Russo and Bellalta, 2018; Oller et al., 2014).

Carrier-Sense Multiple Access (CSMA) has been developed as a media access control (MAC) protocol that requires that a station (STA) ascertains that the channel is free of other traffic prior to transmission. In a wake-up radio enabled STA, the wake-up radio (WuR) determines if transmission is in progress by another STA on the shared channel before waking its WLAN module using carrier-sense mechanism (Ghose et al., 2018; Chen et al., 2013; Spenza et al., 2015). When a channel is detected in use, the STA waits for an in- progress transfer to complete before setting up its transmission. CSMA allows multiple STAs to communicate with the AP over the same channel.

Earlier IEEE 802.11 contention based algorithms allows a single station (STA) to win the contention and then transmit while numerous other STAs wait their turn to contest for the channel (Tang et al., 2018), which translates to prolonged wait for the STA and possible loss of buffered data due to power outage by the devices in large networks. There also exists a latency period between “sleep” of a STA that transmitted and the “wake-up” of the succeeding STA (Tang and Obana, 2018), this could be leveraged to further reduce latency and save energy.

1.2 Statement of the Research Problem

The traditional contention based algorithms allows numerous stations (STAs) to contend for access to the channel with a single station winning at the end of the contention period. This means that other stations would have to wait for subsequent contention rounds which they may not also win. There is therefore the need to have a technique that allows a set of multiple stations to win contention and all transmit in a defined order. This would reduce the STA waiting time, save energy as the number of contention rounds reduces and also improve throughput as the ordering reduces collision. The research issues that still has to be addressed include: how to further reduce energy consumption thereby improving battery life using hybrid contention- addressing approach and how to develop techniques of achieving more efficient channel access scheme that limits collision in the system, reduces latency and gives better throughput.

1.3 Aim and Objectives of the Study

The Aim of this research work is to design a Hybrid contention-addressing algorithm for energy efficiency and latency reduction in IEEE 802.11 wake-up based radio network uplink.

The Objectives of this work are to:

i.          Evaluate the Wake-up Radio Based Early Sleep Optimal Contention Window (WuR-ESOC) algorithm, the backoff algorithm and the Broadcast-based wake- up control framework.

ii.         Develop   a   mathematical   model   for   the   Hybrid   Contention-Addressing CSMA/CA (HCA CSMA/CA) algorithm and test the model with parameters applied to the evaluated algorithms using MATLAB.

iii.        Evaluate the energy efficiency, latency and throughput of the HCA-CSMA/CA and carry out comparative analysis of HCA-CSMA/CA and WuR ESOC (Tang and Obana, 2018.)

1.4 Justification for the Study

To improve energy efficiency, there is need to reduce latency in the system. The longer it takes for data to get from source to destination, the longer the transmitting radio will have to stay awake and in the process consuming much energy. The more the number of devices connected to an AP, the more the likelihood of collision. When data collides on a network, data could be lost or become corrupted and need resending which slows down the system and decreases performance.

In addressing latency in the system, collision must be considered and to deal with collision there is the need to design an algorithm that allows multiple stations to access the channel without any two of them transmitting simultaneously and guarantees minimal recovery time from failed transmissions. Though the introduction of wake-up radio (WuR) into the WLAN system worked in reducing power consumption, the collaboration is yet faced with issues such as collision, wake-up latency, throughput maximization, contention window adjustment, spectral efficiency and the need for further reduction in energy consumption.

1.5 Scope of the Study

The research focuses on contention based wake-up-radio (WuR) enabled IEEE 802.11 algorithm. This research work looks at energy efficiency in the uplink by developing an algorithm.

1.6 Thesis Outline

This thesis is divided into five (5) chapters. The first Chapter is the introduction to the topic. Chapter two includes the review of the literature while Chapter three covers the methodology and design considerations. The results obtained are discussed in Chapter four while Chapter five carries the conclusions with the recommendations.

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