IoT for Global Development to Achieve the United Nations Sustainable Development Goals: The New Scenario After the COVID-19 Pandemic

COVID-19 has not affected all countries equally: developing countries have been more disadvantaged by the pandemic. Regarding global development, the COVID-19 pandemic has forced a step back in the path to attaining the Sustainable Development Goals (SDGs). The SDGs most negatively affected by the pandemic are identified here: education, health, and work. Then using the SDGs as a reference, this research explores the new challenges faced by developing countries and the impact of the Internet of Things (IoT) after COVID-19’s emergence. IoT solutions carried out in developing countries during the pandemic have been identified and reviewed. Successful Internet of Things for Development (IoT4D) projects, in relation to the SDGs, are highlighted. New social and technical challenges that have emerged for the IoT4D as a consequence of the pandemic are then studied. This work concludes that the future of IoT4D in the wake of COVID-19 should focus on the use of low-cost IoT devices for the SDGs most affected by the pandemic. After an exhaustive study, the Intelligent Internet of Things (IIoT) has been determined to be a key actor in the pandemic’s wake, with a leading role in the health sector. The proposed approach includes an extensive study of the new role of the IoT4D for achieving the SDGs in our forever changed world.


I. INTRODUCTION
COVID-19 is the most devastating pandemic so far in the 21st century: according to the European Centre for Disease Prevention and Control [1], since 31 December'19 and as of 15 July'21, 187,509,874 cases of COVID-19 have been reported in the world, including 4,043,003 deaths (in alignment with the applied regulations and testing strategies in the affected countries). The consequences of COVID-19 are immense. Not only has the healthcare sector been subjected to high pressure but the entire world economy has been massively impacted; the post-COVID-19 marketplace will be irrevocably different [2].
The associate editor coordinating the review of this manuscript and approving it for publication was Ahmed A. Zaki Diab .
COVID-19 has especially affected developing countries [3], [4]. This is partly due to the absence of international support to ensure progress on the United Nations (UN) SDGs [5]. The success of the SDGs depends on two premises [6]: sustained economic growth and globalization, which the COVID-19 pandemic has torn apart. According to estimations, global growth contraction for 2020 was -3.5 percent because of the pandemic, and the expected recovery time frame is in years [7]. The UN Conference on Trade and Development's latest ''Global Investment Trends Monitor'' report released on 27 October'20 [8], announced that global Foreign Direct Investment (FDI) fell 49% in the first half of 2020 compared to 2019. Estimations reflect that overseas development aid could drop by 25 billion USD in 2021 [6]. VOLUME 9, 2021 This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/ In the 17 years since SARS [9], a new digital era has emerged, and the IoT is now exhibited as a possible tool for containing new viruses such as COVID-19 within reasonable limits [10]. In 2019, before the outbreak of the pandemic, several studies with main objectives to avoid pandemics already included the use of new technologies such as IoT and AI [10]. The IoT is not only presented as a solution to avoid new pandemics, like the one we are currently experiencing, but also as an enabler of many sectors in the wake of COVID-19. So much so that, the global IoT market size is estimated to grow from USD 150 billion in 2019 to USD 243 billion by 2021 [11]. Increased demand for laptops, work-from-home monitoring devices, and smart payments that reduce personal contact, as seen in cash transactions, have fostered growth in the IoT market.
In early 2020 a work entitled ''Challenges and Opportunities of the Internet of Things for Global Development to Achieve the United Nations Sustainable Development Goals'' was published [12]. This work, based on literature published until 2019, focused on the challenges to successfully utilizing the IoT in developing countries. The weakness and strengths of using the IoT in the developing world to achieve the Global Goals by 2030 were highlighted. But in 2020, the COVID-19 pandemic turned the world upside down, and the scenario totally changed.
The ultimate goal of this work is to carry out an extensive study on the new situation after the global pandemic, to evaluate the new role of the IoT4D (as a complementary partial set of development policies that can improve human well-being sustainably) to achieve the SDGs, and to explain how the integration of the IoT4D in development programs could improve quality of life for the world's most vulnerable populations. Regarding the structure, Section II presents the scenario before the COVID-19 pandemic for the IoT4D to achieve the SDGs, then in Section III the impact of COVID-19 on the achievement of the UN SDGs is studied. Section IV presents the new scenario for the IoT4D after COVID-19, highlighting the challenges and potential for the application of the IoT in developing countries. The future of IoT4D in the wake of the COVID-19 pandemic is presented in Section V. The limitations of the study are discussed in Section VI. Finally, a summary of conclusions is included in Section VII.

II. IoT4D AND SDGs (BEFORE THE COVID-19 PANDEMIC)
During the UN Conference on Sustainable Development (Rio de Janeiro, 2012) the SDGs were designed and launched with the purpose of replacing the Millennium Development Goals (MDGs) to continue leading the fight against poverty beyond 2015 [13]. The SDGs have three main objectives [14]: to eradicate poverty, to protect the planet, and to ensure that all people enjoy peace and prosperity (all to be accomplished by 2030).
Before the COVID-19 pandemic, experts estimated [15] that IoT in developing countries would generate 40% of its possible value add by 2025. The World Economic Forum's IoT for Sustainable Development project aimed to encour-age employment of the IoT to speed up progress on the 17 SDGs [15]. In 2018, the World Economic Forum [16] stated that around the 84% of IoT deployments addressed (or had the potential to address) SDGs. This report presented an IoT analytics database of 640+ IoT projects [15] for studying and understanding the potential of the IoT to support the SDGs achievement. It stated that 75% of the documented IoT projects were around only 5 SDGs; 25% of projects are focused on SDG9, 19% on SDG11, 19% on SDG7, 7% on SDG3, and 5% on SDG12. Based on the results, 95% of the projects could be categorized as small/medium sized and 70% of these IoT4D projects were devised by the private initiatives (80% of which originated in the Americas and Europe).
The work ''Challenges and Opportunities of the Internet of Things for Global Development to Achieve the United Nations Sustainable Development Goals'' [12], studied the context and identified the challenges for IoT4D to reach billions of people living in developing countries, to speed up economic growth and social development. As a result of this extensive study, the authors suggested combining cost-effective IoT and Pay-As-You-Go (PAYG) as the perfect duo to better disseminate IoT4D and achieve the SDGs. Open-Source Hardware (OSHW) platforms have been progressively used in the design of high performance and costeffective projects. High initial costs are not required for developing these OSHW based projects, allowing for better dissemination. To combine IoT technologies, seamless digital payments, and PAYG was a pattern in the developing world that obtained excellent results. To integrate IoT systems into the requirements of developing countries employing open-source tools and novel financing models was presented as a key strategy in achieving the SDGs [12]. Now, one year later, the COVID-19 pandemic has touched each and every SDG in significant ways: the scenario has totally changed, the assumptions taken are no longer valid and the pandemic challenges the global commitment toward vision 2030 [17].

III. THE NEGATIVE IMPACT OF THE COVID-19 OUTBREAK ON THE SUCCESSFUL ACHIEVEMENT OF THE UN SDGs
The COVID-19 pandemic has caused great damage mainly to the economic and health sectors, leaving behind high economic losses and millions of deaths. The United Nations published in July 2020 the ''Sustainable Development Goals Report 2020'' [18] assessing progress on the 17 Goals. This report stated that COVID-19 does not affect everyone equally: the poorest and most vulnerable (children, the elderly, disabled people, immigrants, and refugees) are being the most negatively affected by the COVID-19 pandemic. In 2020, an estimated 71 million people fell into extreme poverty because of the pandemic: the first rise in global poverty since 1998 [18]. More families living in extreme poverty means that children living in poor and disadvantaged communities are at greater risk of child marriages, child labor, and child trafficking: child labor levels are expected to rise for the first time in 20 years [18]. Women are also a category disproportionately affected by the pandemic [18]. Key findings of these reports are focused mainly on the impact of COVID-19 on 6 SDGs: SDG1, SDG2, SDG8, SDG4, SDG3, and SDG13.
In May 2020, Gulseven et al. [19] studied the impact of the COVID-19 pandemic on the SDGs. According to the authors, the COVID-19 pandemic has radically transformed the current state of global development, including the achievements of the SDGs. They argued that, while the deteriorating economic conditions will negatively affect most aspects of development, some positive developments may be observed in the long term. For example, the reduction of carbon emissions due to a decrease in transportation (SDG13) and the cutback of waste due to people consuming more responsibly (SDG12). The authors point to three targets as those most affected by the pandemic: SDG3, as people are avoiding hospitals unless it is absolutely necessary to visit; SDG4, with billions of students out of school staying at home; SDG8, with millions of people expected to lose their jobs. In July 2020, Barbier and Burgess [5] studied sustainable development after the COVID-19 crisis, in alignment with the SDGs. They indicated that the pandemic is likely to adversely impact 12 of the 17 goals and identified affordable policies that could yield immediate progress, mainly towards SDG6, SDG7 and SDG13. In addition, they concluded that the weakest economies (low/middle income) will additionally suffer from the absence of international funding available for achieving the 17 SDGs, climate change mitigation and adaptation, and biodiversity conservation. In July 2020, Filho et al. [20] identified the SDGs most directly affected by COVID-19, where there is a pressing need for urgent action. This is the case for SDG1, SDG2, SDG3, SDG4, SDG5, SDG8, SDG10, and SDG16. In July 2020, Robin Naidoo and Brendan Fisher published a study in the Nature website entitled ''Reset Sustainable Development Goals for a pandemic world'' [6]. The authors studied the impact of COVID-19 using the SDGs as a reference. For classifying the impact, they used 4 levels: a) most targets are unachievable, b) to achieve some targets would have helped prevent pandemic impacts, c) some targets affected and d) to achieve target would have made pandemic impacts worse. Results showed that 66% of the total SDGs targets (169) are either under threat because of the COVID-19 pandemic or not well-placed to mitigate its impacts. Some may get worse: 10% of the SDG targets could amplify the impacts of future pandemics. All SDGs are affected by COVID-19 according to the study. The authors place SDG1 as the target most affected by the pandemic being the only target cataloged as ''most targets unachievable''. Table 1 summarizes the most affected SDGs due to the COVID-19 pandemic according to the literature reviewed. All reviewed studies agree that the achievement of SDG3, SDG4 and SDG8 is negatively affected by COVID-19.

IV. THE NEW SCENARIO FOR THE IoT4D AFTER COVID-19
A. NEW CONTEXT AND POTENTIAL OF THE IoT4D AFTER THE COVID-19 OUTBREAK SDGs are often interlinked; frequently by addressing the problems of one objective issues associated with a different objective are solved. The report ''Harnessing the Internet of Things for Global Development'' [21] was a joint effort by the ITU and the UNESCO Broadband Commission for Sustainable Development that mapped the UN Global Goals to IoT sectors ( Table 2).
In ''Challenges and Opportunities of the Internet of Things for Global Development to Achieve the United Nations Sustainable Development Goals'' [12] IoT Sectors 1-5 (Table 2) were used for their study because they were the five sectors with the most potential to be addressed using the IoT [16]. In addition, these five sectors included SDG2, SDG6, and SDG7, three influential goals that together form the water-energy-food nexus (an indicator very often used for measuring development) [22]. Most SDGs affected by  the COVID-19 pandemic are included in these sectors (see Section II). Thus, to facilitate comparison, this work highlights Sectors 1-5 too (Table 2), as a reference for the analysis. The new IoT context in the developing world after the start of the COVID-19 pandemic is presented below (subsections 4.1.1. -4.1.5.). This includes reference to profitable IoT projects in this period. Fig. 1. shows the methodology followed in this Section for studying the IoT application in developing countries.
Four databases were used for the review of the research works: Google Scholar, ScienceDirect, Scopus, and IEEE Xplore. Reports were identified by using various keywords. Table 3 shows the results of the searching process listed by keywords.

1) HEALTH, WATER AND SANITATION
The ''Health, water, and sanitation'' IoT sector includes two SDGs intimately linked to the COVID-19 pandemic: SDG3 (''Good health and well-being'') and SDG6 (''Clean water and sanitation''). Although the studies reviewed differ on some aspects of the objectives most negatively affected by the COVID-19 pandemic (See Section III), all agree that the SDG most severely impacted by the pandemic is SDG3. The most immediate effects of the COVID-19 pandemic are evident in health centers, representing a threat to SDG3 [20]. In many countries, health centers such as hospitals have reached capacity, becoming unable to provide medical care to all people. In addition, people who need medical care try to avoid going to medical centers for fear of being infected by the virus. The lack of equipment and infrastructure in weak health systems means that the level of mortality may be high. According to the UN ''Sustainable Development Goals Report 2020'' [18] women and children are among the most affected by COVID-19. Disruption of health and vaccination services as well as limited access to diet and nutrition resources have the potential to generate hundreds of thousands of additional deaths in children under the age of 5 and tens of thousands of unexpected maternal deaths in 2020. Childhood vaccination services have not been spared from the ravages of the COVID-19 pandemic: about 70 countries reported moderate to severe disruptions, even the total suspension of this service during March and April of 2020 [18]. In many countries, there has been an increase in reports of domestic violence against women and children [18]. The COVID-19 pandemic has demonstrated that sanitation, adequate access to clean water, and hygiene (SDG6) is vital for avoiding the spread of diseases. The lack of safe access to sanitation and clean water makes developing countries extremely vulnerable to pandemic events. With some exceptions, the COVID-19 outbreak is expected to slow down investments in the water sector worldwide [23].
In April'20, the World Bank's Board approved an initial 25 projects to help countries respond to the coronavirus and shorten the time to recovery. This financing is intended to provide medical personnel and patients with access to water and sanitation at health centers. To fight infectious diseases, it is essential to ensure that health facilities have a supply of clean water and soap. In addition, having clean and well-maintained protective equipment allows for safe medical care and protects the well-being of medical staff. More than half of the health centers in the Democratic Republic of the Congo lack access to clean water and basic sanitation. More than one billion slum dwellers are vulnerable to the negative effects of the pandemic. Risks are aggravated by a lack of adequate housing, the absence of running water in the home, or shared toilets which can increase the spread of the virus. The absence of waste management systems, overcrowded public transport, and limited access to formal health care facilities also increases the risk of infection [18].
The application of the IoT in the health sector allows for remote monitoring in personal healthcare, medical device integration, and even the treatments of diseases, amongst other applications that move us closer to attaining SDG3. Table 4 includes a review of published works that use the IoT for fighting epidemic outbreaks in developing countries (2015-2020). The principal application for IoT technology to help achieve SDG3 after the COVID-19 pandemic is for controlling similar events. The detection of symptoms as well as the monitoring of patients are main uses of the IoT in this area [25]- [29], [37]. IoT can also be used for detecting and controlling mosquitoborne diseases. In the case of COVID-19, the examples found are focused on enforcing social distancing and real time monitoring of infected patients [34]- [36] (for ensuring quarantine time in many cases). There are several wireless standards on the market, usually operating in different frequency bands, and with differing communication protocols, so the selection of the most suitable connectivity technology for an IoT system can be challenging. IoT wireless technologies, especially mobile communications technologies [24], [27], [28], [34]- [37], have been widely used for fighting pandemic events. The IoT is utilized by combining other technologies; the most popular technologies are cloud and fog computing [24]- [26], [28], [32]- [35]. Some of the reviewed projects also use OSHW [26], [37].

2) AGRICULTURE AND LIVELIHOODS
The ''Agriculture and Livelihoods'' IoT sector includes three Global Goals adversely affected by COVID-19: SDG1 (''No poverty''), SDG2 (''Zero hunger''), and SDG8 (''Decent work & economic growth''). The UN ''Sustainable Development Goals Report 2020'' [18] estimated that 71 million people were expected to fall into extreme poverty in 2020 (the first rise in global poverty since 1998). A total increase VOLUME 9, 2021 of 150 million is expected by 2021 [38], directly affecting the achievement of the SDG1 [39]. The World Bank's ''Poverty and Shared Prosperity 2020'' report [40] has identified the three problems that are affecting world poverty most severely today and that threaten to continue to do so in the future: COVID-19, armed conflict, and climate change. This report estimated that, in 2020, between 88 million and 115 million people could fall back into extreme poverty because of the pandemic, with an additional increase of 23-35 million in 2021, potentially bringing the total number of new people living in extreme poverty to between 110 and 150 million. Figure 2 shows the global extreme poverty estimates before-after the COVID-19 pandemic. After the COVID-19 pandemic, lost incomes, limited social protection, and rising prices could change the situation of those who were previously secure. Now they could find themselves at risk of poverty and hunger [18]. The 2020 edition of ''The Global Report on Food Crises'' [41] describes the scale of acute hunger in the world. It is a study of the impact of COVID-19 on different aspects of life, such as health and nutrition, food availability or food access, estimating that 135 million people in 55 countries currently face acute hunger. The ''UN World Food Programme'' [42] has just doubled the estimated number of people who are likely to face critical food shortages this year, to 265 million, impairing the achievement of the SDG2. Regarding SDG8, the increase of underemployment and unemployment because of the COVID-19 crisis means some 1.6 billion already vulnerable workers in the informal or gig economy -around the half of the total workforce worldwide-may be significantly affected. Their incomes are estimated to have fallen by 60 percent in the first month of the crisis [18]. The COVID-19 pandemic has also positively affected the gig economy: the number of average daily tasks/jobs posted has increased since the start of the COVID-19 outbreak [43].
The IoT could play a key role in avoiding this new ''hunger pandemic'' [44], giving support for ensuring food safety, food security and reducing losses and waste of food [45]. The ''United Nations World Food Programme'' [42] has put out an urgent call to action for improving data analytics to avoid hunger and poverty. Collaborators in humanitarian and development projects must come together to address existing problems with data collection systems, establish data analysis standards in places where they are non-existent, and commit to additional data collection efforts in countries where there is limited data or consistent divergences in data interpretation. All types of food supply chains have been severely affected during the COVID-19 pandemic [46]. In 2020, Yadav et al. [47] identified the Agri-Food Supply chain as one of the weak points during the COVID-19 outbreak in India. They modelled a sustainable Agri-Food Supply Chain managed with different emerging IoT technologies (Blockchain, Robotics, Big data analysis, and Cloud computing). The consequences of COVID-19 on the food production chain are enormous. The ''Internet of Food & Farm 2020'' (IoF2020) project [48] explores the potential for IoT technologies in the European food and farming industry. IoF2020 use Case 3.4, Intelligent Fruit Logistics, was created to fight against various COVID-19 related challenges. First, seasonal workers were unable to support harvest activities because of border closures and the travel restrictions. Crops could not be harvested so they remained on the land much longer than usual, increasing food waste. Second, difficulties arose in transporting crops: many truck drivers were in COVID high risk groups and were unable to work. The driver shortage affected delivery times and transport capacity was reduced. Third, customer demands changed [49]: when the lockdown started the demand for nonperishable products increased [50].

3) EDUCATION
The COVID-19 pandemic caused the largest disruption of education systems in history, affecting around 1.6 billion students in more than 190 countries and every continent [51]. The closure of schools and educational centers has impacted 94% of the students in the world, up to 99% of whom are located in low and lower-middle income countries [51]. In 2020, 370 million children missed out on school meals they depend on. Lack of access to computers and the internet at home means that education is out of reach for many students who before the COVID-19 pandemic were in school [52]. Before the onset of COVID-19, between 2015 and 2020, the cumulative financing needed to achieve SDG4 by 2030 in developing countries remained unchanged. Now, the annual financing needed to attain SDG4 by 2030 has increased from 340 billion USD to 504 billion USD [53].
The IoT offers unique opportunities for the education system, helping students to attend courses without being physically present, avoiding the spread of COVID-19. The IoT provides more and more information for students to access, anytime and anywhere. The IoT for education applications is segmented as Learning Management Systems, Administration Management, Surveillance, and Other. The Learning Management area is expected to grow at a fast rate as IoT in Education is helping students by making learning easier and more effective [54]. The GSMA Report ''Education for All in the Time of COVID-19: How EdTech can be Part of the Solution'' [55] presented the use of EdTech as a solution for education after the COVID disruption (focusing on developing countries). In Lebanon, ''The International School of Innovation'' [56] has smart school infrastructure that includes sensors and cameras to enhance learning and the overall school experience. The IoT was used for a) finding patterns that affect student performance in specific subjects, b) providing learning analytics, including a learning objectives matrix for underperforming students and c) emotion detection and monitoring. Happiness can be tracked throughout the day as students attend different subjects.

4) ENVIRONMENT AND CONSERVATION
The ''Environment and conservation'' IoT sector includes four SDGs: SDG12 (''Responsible product & consump-tion''), SDG13 (''Climate action''), SDG14 (''Life below water''), and SDG15 (''Life on land''). The UN Conference on Trade and Development [57] estimates that the COVID-19 pandemic lockdowns around the globe have led to a dramatic 5% drop in greenhouse gas emissions. Figure 3 shows the average nitrogen dioxide concentrations from 14 to 25 March 2020 (coinciding with the total Spanish lockdown) compared to the monthly average concentrations from 2019, using data from the Copernicus Sentinel-5P satellite [58]. Not all measures to stem the pandemic have had a positive impact on the environment. In 2020, Zambrano-Monserrate et al. [59] studied the effects of COVID-19 on the environment (both, positive and negative) and concluded that the increased waste and the reduction of recycling are negative consequences of COVID-19. Due to quarantine policies, consumers have increased their demand for online shopping and home delivery, increasing organic waste generated by households as well as inorganic waste (shipping materials). Medical waste is also on the rise. Streets, beaches, and oceans have been hit by COVID-19 waste: plastic face masks, gloves, and hand sanitizer bottles [60]. In Wuhan (China), hospitals generated six times as much medical waste, at the peak of the outbreak, an average of 240 metric tons of medical waste per day, as they did before the crisis began [61]. Also, although there is no evidence on the survival of COVID-19 in drinking water or wastewater [62], the treatment plants of several countries have strengthened their disinfection routines (mainly by increasing chlorine additives) to prevent COVID-19 from spreading through wastewater [63].
Various initiatives based on the IoT have emerged to mitigate the effects of COVID-19 on the environment, mainly in the area of waste management. In 2020, Indian Scientists at the Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST) Trivandrum, developed a novel disinfection gateway and a UV-based facemask disposal bin to fight COVID-19 [64]. The disposal device, called BIN-19, for collecting and disinfecting used facemasks was subjected to a series of successful microbiological tests to evaluate its efficiency. To avoid spread of the virus, China used the IoT for COVID-19 waste management in Wuhan, making processes automatic and using the minimum number of workers for infectious waste handling. This was realized through IoT technologies, including internet enabled sensing equipment, locating systems, scanning devices, and video surveillance tools [65].

5) RESILIENCY, INFRASTRUCTURE AND ENERGY
The ''Resiliency, Infrastructure and Energy'' IoT sector is linked to the following SDGs: SDG7 (''Affordable & Clean Energy''), SDG9 (''Industry, Innovation & Infrastructure''), and SDG11 (''Sustainable Cities & Commun ities''). The COVID-19 pandemic has spotlighted the need for reliable and affordable electricity (SDG7). It is required for hospital and health facilities to treat patients, for communities to pump clean water, for access to vital information, and for out-ofschool children to learn remotely [18]. Manufacturing jobs are a vital source of income and are key for reducing poverty in developing regions; the effects of the COVID-19 outbreak have been highly destabilizing to industry, threatening to halt and even to reverse progress towards SDG9 [18]. The COVID-19 pandemic has highlighted the importance of increased investment in R&D, mainly in the pharmaceutical industry and in emerging technologies such as artificial intelligence or the IoT. COVID-19 has impacted business, speeding up the remote working revolution [66]. Over 90% of COVID-19 cases have occurred in urban areas so SDG11 has been hard impacted [67]. For many cities, the COVID-19 pandemic has expanded to a crisis of several aspects: urban access, urban equity, urban finance, safety, joblessness, public services, infrastructure, and transport; all of which are disproportionately affecting the most vulnerable in society [68].
After the COVID-19 pandemic, one of the main applications of the IoT sector is around smart cities. Cities will emerge from the pandemic, but how prepared for the next crisis they are will depend on how much they promote inclusive and sustainable urban development projects based on data [18]. In 2020, Costa and Peixoto [69] identified several smart cities initiatives to face new outbreaks. There are a lot of examples of using the IoT for maintaining social distancing [70]. In several countries, drones with loudspeakers were used for reminding people to stay at home [71] and for thermal imaging purposes. In 2020, De Vito et al. [72] deployed high-resolution air quality monitoring multisensor devices for mitigating new pandemic events by following the correlation of COVID-19 pandemic outbursts and air pollution levels. Automatic human body temperature sensing machines have been installed in many countries. Cameras are integrated with temperature sensors and send real time information to a central server [73]. Regarding energy, experts stated that COVID-19 has created an immediate need for remote, perpetual electricity grid monitoring [74]. Innovative projects such as EPIU Getafe [75] use IoT for attaining smart cities objectives, ensuring affordable energy for all. The monitoring of critical parameters in a remote way limits physical contact, avoiding new disease transmission. The IoT has a key role in industry, by integrating IoT devices into the supply chain in manufacturing plants teams can remotely access information, monitor, and manage the performance of their assets without being physically present [76].

B. CHALLENGES OF THE IoT4D IN THE WAKE OF THE COVID-19 PANDEMIC
In 2020, before the COVID-19 pandemic, [12] identified the challenges for the IoT4D to achieve the SDGs by 2030 ( Table 5). The authors grouped challenges into 5 different categories: technical aspects, environmental conditions, social differences, policy, and financial conditions. These challenges remain and some of them have worsened. New challenges have emerged because of the effects of the COVID-19 pandemic. The following sections comprise new challenges identified for IoT4D that have surfaced as a consequence of the COVID-19 pandemic.

1) POOR PEOPLE WITH NEW PROFILE
The World Bank's Report ''Poverty and Shared Prosperity '' [40] analyzed data from the Global Monitoring Database [77] showing how the COVID-19 pandemic is changing the profile of people living in poverty; the new poor who may have emerged as a result of the COVID-19 pandemic differ in ways that are important for policy. According to this report, much of the new poor will live in countries that are already struggling with high rates of poverty, but middle-income countries are expected to also be significantly affected, having more than 75% of the total new poor. As it was mentioned in Table 5, before COVID-19 large portions of the extreme poor were rural. However, there is a high probability that people who fall into poverty by COVID-19 live in highly populated urban environments that favor the transmission of the virus. Many of the new poor work in construction or factories, sectors that are severely affected by mobility restrictions and lockdowns caused by the pandemic.

2) TRAVELLING RESTRICTIONS
In 2020, international tourism will revert to levels seen 30 years ago as an effect of the COVID-19 pandemic [78]. According to the ''8th Travel Restrictions Report'' of the United Nations World Tourism Organization (UNWTO) [79] published in December'20, 118 destinations (54% of the total destinations worldwide) have completely or partially closed their borders due to the COVID-19 pandemic (1st November 2020). Figure 4 shows the distribution of destinations with travel restrictions. Travel restrictions are not only affecting tourism, but they are also impacting the delivery of humanitarian assistance [80], impeding the development of humanitarian works, and delaying cooperation projects.

3) DECREASE OF FINANCING FOR DEVELOPMENT
The United Nations' Report, ''Financing for Development in the Era of COVID-19 and Beyond'' [81] forecasts the decrease of financial flows by up to 45% in developing economies due to the COVID-19 pandemic. This threatens years of advancement made towards the achievement of the SDGs, including poverty descent, salary equality, nutrition, health improvements, and literacy rate progress.

4) SOCIAL ACCEPTANCE AND SECURITY DATA
In 2020, Ndiaye et al. [70] concluded that there is a need for social acceptance and security in data sharing for IoT management systems in the wake of COVID-19. A clear example: governments around the world have developed tracing applications for reducing and controlling the spread of COVID-19 based on the IoT. Although published studies support the use of tracing applications as an effective weapon in the fight against COVID-19 [82], the reality is that these types of smartphone applications are not being well accepted by society. Fears over privacy and the security of their data, resulted in download percentages of only 10% -20% in many countries [83].

5) DATA INNOVATION
The UN SDGs Report [18] focuses on the importance of timely, quality, open, disaggregated data, and statistics as a key piece for fighting the COVID-19 crisis. Investments in data and innovation are essential to responding to the crisis and supporting SDG acceleration, and for the IoT expansion as well.

6) DIGITAL INFRASTRUCTURE
According to the World Bank, after the COVID-19 pandemic, the primary challenge facing the IoT is to integrate and streamline digital infrastructure at various stages of the public health response, especially in epidemic forecasting and decision-making areas [84]. The closure of workplaces as well as home quarantines has led to a spike in the usage of telecommunication networks with an increase in the use of the internet by approximately 30% [85]. During March and April, decreases in broadband speed were identified because of reflecting peaks in Internet access combined with changes in behavior and traffic flow. This was particularly evident and more intense in countries such as Ecuador, Chile, Morocco, South Africa, and Turkey (where the quality of broadband network is lower) [86]. Experts consider that the overall increase in traffic will become a fixture of the future [85].

7) 5G DEPLOYMENT
The post COVID-19 era has two main actors: the IoT and 5G. Their application in areas such as telehealth, contact tracing and self-isolation, online education, retail and supply chains, smart manufacturing and factory automation, e-government and media, and e-tourism and entertainment offer solutions for combating the pandemic. However, the lack of widely available 5G communication networks imposes a limitation for the rapid adoption of proposed technologies [87]. Figure 5 shows the global distribution of 5G deployments/investments in 2020; Sub-Saharan Africa, Eastmiddle Asia and Latin America are the areas with a lower 5G deployment.

8) WORRIES ABOUT 5G TECHNOLOGY
The 5G network is required for the full expansion of the IoT. It promotes cellular operations, related to the security of the IoT and reduces network challenges [89]. During the COVID-19 pandemic false claims linking 5G to COVID-19 have been widely shared online. Prestigious institutions such as the International Telecommunications Union (ITU) and the Global System for Mobile Communications Association (GSMA) have been forced to issue official letters making clear that such claims linking 5G technology and the VOLUME 9, 2021 FIGURE 5. Countries where 5G has been deployed and where investments have been made. As of August 2020. Source: [88].
spread of COVID-19 have no scientific basis whatsoever [90]. However, 5G-COVID-19 conspiracies have animated antivaccination, anti-5G protests, and acts of vandalism that have occurred during the pandemic [91]. Even impeding the installation and repair of mobile antennas due to the fear of 5G in rural areas of developing countries [92].

9) EDUCATION GAP
COVID-19 has revealed the need for the digital transformation of education [93]. The digital education gap is higher in the developing world: computer and mobile phone access opportunities are more limited in developing countries [94]. Students from underprivileged families do not all have laptops and smartphones, so policies should pay attention to this issue providing the technological tools required for studying; in addition, governments should ensure that the internet is available in remote areas, in order to reach remote populations for the learning process [95].

10) INTERNET WASTE
The dependence on ICT infrastructure and connectivity has been spotlighted by the COVID-19 pandemic and overall numbers of demand and use have increased. The massive expansion of the IoT has caused collateral damage to environment due to infrastructure equipment, such as energy consumption from production and use, carbon emissions from power supply equipment, water consumption for cooling systems, waste from electrical and electronic equipment, and raw material scarcity [96]. In developing countries, challenges for facing Internet Waste are higher than in industrialized countries, because of the lack of infrastructure for appropriate waste management, the absence of legislation dealing specifically with this new type of waste, and the absence of any framework for end-of-life product take-back or implementation of extended manufacturer responsibility [97].

V. THE FUTURE OF THE IoT4D IN THE COVID-19 PANDEMIC ERA
After studying the new scenario after the onset of COVID-19 and challenges for applying IoT in developing countries, the future of IoT4D is applying low-cost IoT on the most affected SDGs including those in IoT Sectors 1, 2, and 3 (See Section 4.1.). On the other hand, after the COVID-19 pandemic another application of the IoT4D, the Intelligent Internet of Things, has emerged as a key actor in the pandemic wake, especially in Sector 1 which includes pharmaceutical research.

A. IoT4D PROJECTS ON THE MOST AFFECTED SDGs BY THE COVID-19
As the SDGs most affected by the COVID-19 pandemic are the SDG3, SDG4, and SDG8, the promotion of the IoT4D focused on Sectors 1-3 (defined in Section IV.A.) could be the best solution to face the worst effects of the COVID-19 pandemic on the UN SDGs. Since the beginning of the pandemic the application of the IoT to Sector 1 has been a trend. In 2020, the development of applications focused on the Internet of Medical Things was multiplied. Figure 6 shows the number of research works published in the last 5 years related to the ''Internet of Medical Things'' area using different scientific databases. Upgraded wearable technology, combining Artificial Intelligence (AI) and IoT for Healthcare or Making Health Services More Accessible have been identified as promising research and development directions for healthcare IoT in the aftermath of the COVID-19 pandemic [98].
Along this line, several initiatives are applying the IoT on Sector 2 (Education) in the wake of COVID-19. In 2020, at the onset of the COVID-19 outbreak, UNESCO launched an international multi-sector partnership called The Global Education Coalition (GEC) [99] to meet the urgent and unprecedented need for continuity of learning as the pandemic disrupted education systems across the world [100]. The Global Education Coalition was committed to equity and inclusion in access to quality education and lifelong learning for all, in line with the SDG4, integrating IoT as a key actor into its strategic planning. The coalition has prioritized Africa in its operations and at present 22 countries are benefiting from a wide range of support and actions such as setting up online learning platforms and developing teachers' capacities in Senegal, reinforcing TV and radio programmes in the Democratic Republic of Congo, or digitizing curricula in Ghana. Another example: in the Arab States region, the coalition is operating in 8 countries producing online education resources in Lebanon, supporting distance learning in Palestine, and offering digital skills training in Morocco. The IoT is a key piece in several initiatives promoted by GEC. Regarding the IoT Sector 3, with every industry affected by COVID-19, the number of potential effective applications designed to specific business areas is rising, and the IoT is leading this tech race. The main business segments that can reap most benefits from IoT systems in this time have been identified: Healthcare, Agriculture and Retail [101].

B. LOW COST IoT
The use of open-source SW/HW for designing IoT solutions reduces technology costs considerably allowing the installation of modern technology in unprivileged areas. During the last few years, the use of this type of technology in developing countries has been a trend and open HW platforms have been included in the design of precise low-cost IoT systems. The integration of these technologies also could be an optimal solution for fighting COVID-19 and encourage collaboration on the achievement of the SDGs in COVID-19's wake, while facing the lack of financing for development projects. Table 6 shows a literature review of low-cost IoT4D projects developed after COVID-19 disruption linked to SDGs.
In 2020, Tendolkar and Ramya [118] presented ''Care-Bro'', a solution for managing remotely an entire farm without requiring physical presence. The authors developed a solution that is always in touch with the farmer and, thought the cloud, provide monitoring in real time and decision making. The solution improves the productivity performance of farms, providing data for keeping plants safe, support in their productive growth and suggest improvements. CareBro was developed around Arduino and Node MCU microcontrollers. The connected sensors linked with the farm wide IoT network send data via the cloud all the way to the farmer's cell phone. In 2020, de Medeiros and Girão [106] presented the development of a device for accurately measuring the concentrations of the Particulate Material (PM2.5 and PM10), O3, C0, NO2, and NO3 by means of three sensors: PMSA003, MICS-6814, and MQ-131. The device was equipped with an ESP-WROOM-32 microcontroller that had Wi-Fi and Bluetooth wireless interfaces for sending data to a server in the cloud. In the IoT4D projects reviewed, the objective of low-cost hardware was achieved using Open Source HW. According to the literature review included in Table 6, the most popular platforms were ESP32 [122], Node MCU [123] and Arduino [124]. A key aspect of the IoT4D deployments is the communication technology. Most of the reviewed projects used Wi-Fi [102]- [104], [108], [109], [111]- [115], [117]- [121] for transmitting data. LoRa has emerged as the second alternative, for transmitting data, used in the reviewed works. Of the 20 works reviewed, 15 proposals were classified within the IoT Sector 1 [102], [103], [105]- [115], [119], [121]; 13 works aligned with the SDG3 [102], [103], [105]- [115]. Southern Asia was identified as the region with the most IoT4D projects based on low-cost technology deployed in the wake of COVID-19. A new a relevant aspect of the reviewed IoT4D works is the latest trend of deploying IoT in tandem with other technologies such as Blockchain or Artificial Intelligence to curb the spread of COVID-19; the integration of AI+IoT was the most popular combination [103], [107], [109]- [111], [117], [119], creating a new IoT application with a bright future: the Intelligent Internet of Things.

C. THE INTELLIGENT IoT
The Intelligent Internet of Things is the result of combining the Internet of Things and Artificial Intelligence. After the COVID-19 outbreak, the IIoT has so far grown in significance [125], [126]. As identified in Section IV, data innovation is essential in responding to the COVID-19 crisis and the IIoT helps to overcome new challenges by transforming data into smart data, wherein useful information could be obtained by applying cost-effective and new data processing methodologies [125]. The main expansion of this new combination of technologies is taking place in the medical area after the COVID-19 pandemic [127]. IIoT is employed for monitoring [128] and detecting [129] COVID-19 cases as well as for diagnosis [130], [131]; medical data analysis [132] is another key application of the IIoT for reducing time in data analysis (avoiding virus expansion). Table 7 comprises the IoT4D projects using the low-cost technology reviewed that included AI techniques (more than half of all projects reviewed are aligned to SDG3). In 2021, Mariammal et al. [119] proposed a system based on the IoT which included neural networks for prediction. It included various embedded sensors for measuring conductivity, pH, turbidity, and color. The measured sensor values were stored in the database and further directed for prediction analysis. The resulting neural network algorithm was used for forecasting the quality result. The system alerted the user when any of the measured parameters were less than defined fixed thresholds. In 2021, Biswas et al. [109] proposed an IoT based device for detecting the subsistence of COVID-19 based on a certain framework of body components. The presence of coronavirus was detected by measuring an individual's body temperature with the help of temperature sensors. RQ or respiratory quotient was used as another determining principle to detect coronavirus. Blood samples were also analyzed. Data was transmitted using Wi-Fi. The body parameters collected from the subject were compared with the data of normal noninfected humans using an Artificial Neural Network algorithm. Of the 6 works reviewed, Artificial Neural Network was the most used technique [109]- [111], [119], followed by Support Vector Machines [110], [111], [117].

VI. DISCUSSION
The role of the IoT and its contribution in developing countries as a part of development programs has been discussed extensively. In 2021, Dalal [133] carried out a study on the role of the IoT as a driving force for sustainable development. In this research, around 300 online surveys among the IoT industry experts, researchers, faculty members and educationists working in IoT area, were done. The 84% of respondents concluded that IoT can play an enormous and phenomenal role in achieving the SDGs. On the other side, 96% were agree that IoT applications is essential and indispensable to achieve the target of sustainable growth, but this is only possible if global/national and regional efforts are streamlined to accomplish sustainable development. Islam et al. [134] found that IoT technologies do not address all the problems of SDGs in developing countries; they concluded that the achievement of the SDGs also requires (in addition to IoT applications deployment) equitable legislation, regulatory outlines, and financial enablers. The IoT can make a difference in the achievement of the SDGs [135] but only if it is accompanied by adequate legislation, investment, education, and the modernization of the technological infrastructure. Two main limitations have been found carrying out this work. First, the lack of data and information on IoT4D projects in developing countries makes it difficult to find specific details such as the number of people impacted by the IoT4D solutions, or the results achieved. In addition to this limitation, due to the recent appearance of COVID-19 in December 2019 [136], many of the IoT4D projects developed for facing the pandemic are in an initial stage and there are no post-implantation studies published. Reference [134] studied the relationship between the IoT and SDGs but they considered the 17 SDGs as a single group. Other works studied the relationship between IoT and sustainability focused on an specific SDG [47]. The presented work aimed to conduct the study in depth on the IoT4D application for achieving each SDG in the wake of the COVID-19. SDGs were grouped by IoT sector (see Section IV). 2 IoT sectors were left outside this study [4] SDGs): the Governance and Human Rights sector (SDG10 and SDG16) and the Crosscutting sector (SDG5 and SDG17).

VII. CONCLUSION
COVID-19 is the most devastating pandemic so far of this century and the developing world is highly vulnerable to the outbreaks of COVID-19 because of the lack of international support to ensure progress towards SDGs of the United Nations. Progress towards the SDGs is now threatened by the consequences of the COVID-19 pandemic. All SDGs have been affected by COVID-19; after an exhaustive literature revision, the reviewed studies agreed that SDG3, SDG4 and SDG8 were the most negatively affected by COVID-19. The potential of IoT in the developing world for fighting against COVID-19 is to make an even greater and more significant impact than in industrialized countries. New challenges have emerged because of COVID-19. On the one hand, new social challenges have been identified: there is a new profile of poor population, countries have reduced their financial support for development, travel restrictions have affected millions of trips and citizens are worried about the 5G deployment and the security of IoT data. On the other hand, often, technical challenges such as the lack of digital infrastructure impedes the fast deployment of IoT4D projects. The future of IoT4D in the wake of the COVID-19 is presented by applying low-cost IoT on the most affected SDGs: education, health, and work. OSHW platforms have been integrated into the design of high performance and low-cost IoT systems for fighting against the COVID-19 pandemic in the developing world. Another application of the IoT4D, the Intelligent Internet of Things which applies IoT jointly with Artificial Intelligence, has emerged as a key actor in the pandemic wake, especially in the health sector.