Information and Communications Technology (ICT) has changed our society remarkably in the last few years, one key feature is its great and continuously-increasing size. There seems no end in sight to the proliferation of mobile communications as over 120,000 new base stations are deployed yearly, and there is growth across every demographic from teenagers to businessmen to the poorest Indian villagers. The intersection of two undeniably increasing trends, escalating energy costs and meteoric growth in voice and data communications usage, creates an urgent need to address the development of more energy-efficient 'Green' communications. According to BCC (Blind Carbon Copy) Research, the ICT global market is worth was $38.4 billion in 2010; the forecast is a growth to $58.4 billion and the downlink traffic from cellular handsets is expected to grow more than eight fold rising from 56MB per month to 455MB by 2015. This meteoric rise in users and data demand alone does not create a crisis; however, when one evaluates the communications ecosystem from a carbon footprint and energy cost perspective, the results are startling. Although its effects on our everyday lives are obvious, the hazardous effects that this technology may have on the environment are much less clear and seldom talked about and are often neglected or overlooked. These impacts can be expressed throughout the lifecycle (from the manufacturing, use and disposal) of the ICT product. This article presents a research vision for Green Communications. The core tenant of our Green Communications vision is to reduce overall energy consumption within framework of optimizing system capacity and maintaining user Quality of Service.
The need for Energy-Efficient Networking has become evident due to the massive amounts of energy consumption and carbon footprints within the Information and Communication Technology (ICT) sector. The cellular radio network is the largest factor contributing to the mobile industries.
Environmental impact [1]] with the emissions from the telecommunications business sector is accounting for an astounding 1% of the entire world's carbon footprint [2]. The BCC research reveals the ICT global market is worth has increased which means that many people all over the world use ICT products, and that in the future, even more people will use ICT devices [3].Two major drivers of the energy efficient networking are:
The ICT sector is identified to be responsible for the production of approximately 0.75 million tons of CO2 for every 1 Terawatt hour (TWH) energy consumption. Moreover, 2 % of the total CO2 emissions are also attributed to the ICT sector [4]. The GHG emission of the ICT sector is almost equivalent to the CO2 emissions by the aviation industry. Furthermore, an increase of approximately 6 % of CO2 emission is expected each year until 2020 [5]. In developing countries like India, CO2 emission rate is even higher and reaches approximately 4 % [5]
To overcome the following problem, recently the term 'Green Communications' has been marketed and sloganized as a solution to addres the growing cost and environmental impact of telecommunications. The issue of green communications is compounded by the incredible growth of wireless communications in the developing world which uses wireless as a medium to 'leapfrog' past traditional wire-line technologies. Until very recently, Cellular operators have focused technological developments primarily on meeting capacity and Quality-of-Service demands of the consumer as well as addressing the insatiable appetite for increased broadband data. However, the recent dramatic increase in energy costs and greater awareness of the cellular industry's impact on the environment is shedding new urgency on improving power efficiency in communication. Placing the energy usage of cellular networks in perspective, each base station antenna and its supporting equipment consumes an average power of 1 Kilowatt, using a total of 8,800 Kilowatt-hours each year, which is equivalent to the energy used to run two typical 3 bedroom family houses in India [6]. In some telecommunications markets, energy costs account for as much as half of a mobile operator's operating expenses while over 1% of the entire world's carbon footprint is due to telecommunications [2].
The combination of growth, energy consumption costs and our insatiable appetite for connectivity and data will lead to significant environmental impact unless the issue is looked and solved by a unified strategy rapidly.
Hence, addressing the issue of Green Communications has benefits to many stakeholders including the Industry, Academic Researchers and Government Agencies. The cellular industry can realize cost savings and lower their impact on the environment. The government agencies realize the fulfillment of administrative goals for energy savings as well as development of standards and metrics, while researchers can push the boundaries of current technologies and theories in Material Science, Distributed Computing and System Engineering. Research in this field also has great synergy with developments in a Smart Grid, given the significant impact that cellular base stations have on power usage. Coordinated power control of cellular equipment and dynamic load balancing within the greater power grid can lead to transformational improvements in both communications and the energy systems.
A key aspect of this paper is the analysis and development of performance metrics for systemically defining green communications in order to provide a foundation for analyzing and comparing strategies for energy efficiency. This paper will also synergize the concept of green communications within the larger framework of smart grids given the significant burden that information and communication places on the energy distribution network. Current analysis has focused on the component level, single layered strategies as well as narrowly focusing on the deployment and operational life cycles for addressing energy efficiencies. The authors will examine across the life cycle from individual components such as power amplifiers to end of-life component
Data communication services such as video-conference and tele-presence reduce the carbon dioxide emissions associated with business travels [7]. Similar considerations can be drawn if we plan to send a copy of a document via fax or via email instead of delivering the original document moving between two different geographical locations.
In any case, the impact of communications networks on Green Planet cannot be ignored. Currently, manufacture, use and disposal of Information and Communication Technology (ICT) equipment contribute to around 2% of global carbon dioxide emissions, and 37% of carbon dioxide emissions of all ICT is due to the telecommunication sector. Furthermore, the volume of exchanged data increases by a factor of approximately 10 in every 5 years. Wireless networks (including wireless networks in wide area, metropolitan area, local area and personal area) are responsible for the transmission of a large part of these data.
Therefore, reducing the energy consumption of wireless networks with the consequent reduction of carbon dioxide emission for the required energy generation is considered a very important factor for the future of the Planet. This can be achieved, at least partially, by means of an energy efficient design of wireless networks.
In this context, the authors define “Green Communications” as the framework for the design and disposal of communication networks which aims to a sustainable growth of telecommunications networks including wired and wireless networks: out of that, the author only focuses on the wireless part.
There is significant variance in the definition of Green Communications within the telecommunications community and is most often a marketing term. Many people misunderstood the term as green communication is only related to preserving environment But they don't know that by using green communication techniques, they also decrease their long-term communication expenses.
In simple words, Green communication can be defined as a communication causing less environmental pollution:
Green Communications can also be defined as striving to reduce CO2 within the context of maintaining Quality of Service in terms of coverage needs, capacity and user needs. When comparing system designs and improvements in energy-efficient components, the reduction of green house gases alone is not adequate. The quality of service must be considered in tandem with energy efficiency.
So in this paper, the authors focus on the improvement of the energy efficiency of wireless networks with the aim to reduce the energy consumption and consequently the carbon dioxide emissions due to the energy generation through fossil fuels.
Generally speaking, energy efficiency means using less energy to accomplish the same task. In the case of communication systems, the task to be accomplished could be a file transfer, a phone call and so on. The authors assume that the task to be accomplished is the transfer of nu bits of the Medium Access Control (MAC) payload. Therefore, also assuming an Automatic Repeat request (ARQ) error recovery mechanism at link layer, the energy efficiency can be defined as follows:
Where Etot is the average energy consumed for a packet transmission (also considering the necessary retransmissions due to an ARQ mechanism) and Pres is the residual packet error rate after having reached a maximum number of retransmissions.
This section mainly proposes the critical national need to scientifically define and develop metrics and measurement technologies for realizing Green Communications
Information and Communications Technology usage has grown at an almost exponential rate worldwide with an estimated 6 billion users in 2007 [8]. With the introduction of the IPhone and other software-driven smart phones, the Internet is now accessible from a mobile platform which will place an even greater demand for broadband. By 2015, the downlink traffic from cellular handsets is expected to grow more than eight fold rising from 56MB per month to 455MB [2]. Addressing the issue of greener communications has significant broader impacts beyond, just as the developing world will account for more than 75% of the cellular users by 2015. Remote regions will rely on inefficient fuel sources, such as diesel generators that will significantly grow the carbon footprint of telecommunications even more.
Cellular operators have focused technological developments primarily on meeting the demands of the consumers for increased broadband.
Combining the growth in demand with the ever increasing cost of energy, and the related environmental fallout, it creates societal challenge than will negatively affect society in the United States and across the world, if not the addressee.
ICT is an industry in a state of constant change and development, with the continuous production of new, different, and more advanced devices. The manufacturing of these products implies a very high level of technology and the use of specific elements/chemical compounds.
Some of these elements can be very toxic; heavy metals such as Cadmium (Cd), Lead (Pb) and Arsenic (As), for instance, are all present in desktop computers or in standard computer monitors. Other compounds are also hazardous. An example can be the use of Brominated Flame Retardants (BFRs). BFRs are chemicals which are applied to the electronic parts of the devices for safety reasons.
Exposure to the toxic compounds mentioned above leads to the disposal of the ICT devices. There can be exposure, for instance, if these elements/chemicals leach from a landfill into the environment. This process can cause damage and have noticeable impacts on the environment, both short and long term.
The incineration of parts of the ICT devices may also cause exposure to hazardous substances. The incineration of waste which contains these kinds of chemicals is forbidden by law. However, these parts may be accidentally incinerated together with other domestic waste. This can be particularly dangerous if FBRs are present, as during the combustion they can form brominated dioxins – very toxic molecules.
The energy consumption associated with ICT devices is also an important issue to consider. For the majority of ICT devices, a greater proportion of the energy is necessary for manufacturing the device than for using the device itself.
Professor Williams explains: “If we consider the energy used by a car, 12% is the proportion necessary for its manufacturing, while a much higher quantity (88%) is due to its use. For many ICT products, the situation is reversed. For a laptop computer, for instance, 64% of the energy is consumed for the manufacturing and only 36% for its use.”
This difference between ICT devices and other products is due to the combination of two factors: on one side, manufacturing these objects requires a lot of energy, due to the high level of technology. On the other side, the average life span of ICT devices is shorter, as these kinds of devices are generally replaced much more often than other objects.
The ubiquity of communications technology is inextricably tied to the use of the Internet which is experiencing a societal integration that the Energy Information Administration has stated will grow annual energy consumption dramatically [9]. Increasing cell phone usage and mobile broadband downloads will create a cascade affect requiring more powerful base stations and in turn higher capacity backhaul requirements from fiber optic and microwave links. The societal momentum behind information and communications technology is too great to expect a slowdown.
The current status quo for designing communications systems inherits the layered architecture of the OSI model with distinct separation between layers. While this model has enabled dramatic technological innovations, it also creates a roadblock to transformational improvements. A new design paradigm is required that holistically integrates the entire communications network from the physical layer through global networking systems.
The critical need for a programmatic focus on Green Communications encompasses cross discipline aspects of communications, networking and alternative energy. A cursory viewpoint might only consider efficient power amplifiers or the use of alternative energy sources for cellular base stations. The reality is that to truly address this problem on a transformational level, high-risk high-reward research is required that integrates all aspects of communication stack and peripheral interactions. Most importantly, metrics and their associated measurement science that define green communications from combined energy efficiency and network optimization perspectives must be developed. Metrics are essential for providing guidance to manufacturers and service providers to help them make better decisions regarding infrastructure development and purchases.
The pathway to green communications will lead to further transformational breakthroughs such as power-efficient distributed computing. The ubiquity of wireless communications combined with improved processor capabilities of devices, such as smart phones, will enable a new paradigm in networking design.
The development of scientifically rigorous definitions and metrics for Green Communications is a critical national need that is not currently being met by other agency efforts or through industry action. Only an Administrative lead programmatic interdisciplinary endeavor founded in the methodical technical rigor can truly create transformational results.
This section will summarize existing efforts towards green communications. Most work is narrowly defined within an elemental area of the communications cycle such as radio components, system architecture, or integration of renewable energy sources. This project will leverage the existing works and aggregate these separate results underneath a unified umbrella ‘Green Communications’.
Three primary parts comprise a base station: the baseband unit, the radio and the feeder network. Of these elements, the radio consumes more than 80% of a base station's energy needs, 50% of which is consumed by the power amplifier (PA) [10, 11]. Therefore, the improvement in the efficiency of the power amplifier is one of the key areas that need to be considered in order to enhance energy efficiency within the base station equipment.
Switch-mode Power Amplifiers have shown promise on wire line applications and are being applied to the higher operating frequencies of mobile wireless systems [12]. The high frequencies seen in wireless systems combined with switch-mode architectures is pushing research in the material sciences aspects of transistor technology. Lateral Double-diffused Metal Oxide Semiconductors (LMDOS) technology has dominated that market, However High Electron Mobility Transistors (HEMT's) that utilize Aluminum Gallium Nitride (AlGaN/GaN) structures show promise. GaN HEMT has potential to provide a higher power output due to its ability to work under higher temperature and higher voltage [12, 13]. Some more traditional technologies such as multi-stage Doherty PAs have shown theoretical power efficiencies of 70% for Rayleigh distributed envelope signals. More recently, a high power (190W Peak-Envelope-Power), 32% efficient LDMOS Doherty PA was designed with compact invert-load network for base stations. Dynamic Voltage Scaling is a technique used to increase the efficiency of RF power amplifiers.
Utilizing different methods of linearization such as Cartesian feedback, digital pre-distortion and feed forward have been suggested along with focusing on digital signal processors that decrease the requirement of linear amplification [14].
Huawai's green GSM Base Transceiver Station (BTS) efforts attack energy efficiency on several fronts including power amplifier improvements, operational strategies, and cooling requirements [14]. Operational software upgrades address shut down technologies such as TRX, timeslot and channel shutdown to reduce static power consumption by 60%. Multi-density radio transceivers have enabled a single module to support up to six carrier frequencies. This has fostered smaller and lighter base stations that require less cooling and auxiliary equipment.
Topology-specific design perspectives and improved planning methodologies are yielding improved power efficiency through reduction in the number of sites. These smaller, agile base stations dovetail to a distributed base station architecture, which can replace larger more power hungry macro base stations. Actual deployments of these more agile base stations have achieved more than 40% power savings without affecting overall output signal power [15]
Fluctuations in cellular usage are often correlated spatially and temporally with location and time of day. For example, during evening rush hours usage is high and decreases later in the night while also decreasing geographically around business districts in the evenings and weekends. BTS equipment can learn from these patterns and turn off completely or decrease the number of transmitting antennas [15]. This site-level turn off approach to manage power has significant potential to lower power usage however requires coordinated management of base stations in order to maintain desired capacity and customer quality of service.
Communications networks have traditionally followed a layered architecture where specific functional requirements such as over-the-air transmission and Medium Access Control are completely separate and independent. This vertical hierarchy allows each service to utilize the output of the layer above. It will also be forwarding its own services to the layer below it allowing interaction only between adjacent layers. A new paradigm in network architecture, called cross layer design, broadly addresses performance gains enabled by designing protocols with dependence between different layers [16].
Cross-layer design for resource allocation has been applied to 3G networks from the perspective of maximizing radio resources within bit error rate constraints. In this study, information exchange across protocol layers shows better performance especially with heterogeneous data and video service.
Quality of Service (QoS) metrics such as average conditional expectation of delay is typically correlated to channel gain. If delay is constrained to a fixed level across all channel gains then average power can be minimized subject to a specific delay constraint. By imposing this tighter delay constraint, power savings can be achieved through cross-layer design source-channel coding as opposed to the typical power control methodology .
In the transportations of communications equipment, packaging consumes a large amount of natural resources – for example timber, with continued industry use seen as a long-term threat for forests. In order to reduce the consumption of timber, the industry's leading suppliers are working hard to promote renewable packaging materials and improve the recycling of these resources.
At the same time, we have reduce the consumption of packaging materials by utilizing lightweight materials and smaller packaging, continually investigating more appropriate packaging, and extending the life cycle of the packaging products through the establishment and improvement of an effective Recovery System. These can be summarized by using the 6 R concept, that of: rational design, reducing supplies, recycle, reuse, recovery, and renewable.
The "Transportation cabinet" is typically a reusable unit with associated reusable packaging. The "Transportation cabinet" solution reduces the consumption of natural resources such as wood from forests in the packaging and logistics stage, and promotes sustainable development of resource-saving and environmentally friendly packaging and logistics within the industry.
The "Transportation cabinet" solution can save about 50% of timber, reduce about 20% to 30% of the packaging weight, and extend up to 2 to 4 times the service life of the Packaging, while reducing about 5% to 10% the life-cycle cost, and raising operational efficiency about 80% to 90%.
Building on the positions proposed and the analysis of the current situation and the measures to be taken, the range of action within the Indian Union to facilitate the achievement and smooth implementation of these goals is summarized below in extending the existing telecommunications policy of the Union to the mobile communications sector for which the following measures can be anticipated.
To implement the principles set out in the markets for telecommunications services, we are required to include these principles:
Beside these points, the mobile companies can inculcate the following commitments in their production:
In this section, the authors have presented a vision for a holistic strategy for approaching Green Communications that goes beyond improvements made in isolation at one level of the communications cycle. We reviewed existing developments within singular aspects of the communications network stack as well as operations, deployment and metrics.
The statistics communication network will continue to expand in the future due to increasing demand for mobile subscribers in developing market, broadband build-out in developed markets and continuing demand for high bandwidth services. Due to the meteoric rise of the cellular phone in the global context as well as the ever increasing cost of energy, there can be no denying regarding the impact that wireless communications has on the environment. The most direct way to reduce CO2 emission is through the introduction of renewable energy systems, such as solar energy, wind energy and bioenergy plants. These emission-free energy or low-emission energy are the most effective choices for companies to reduce carbon emissions. In this paper, the authors presented a vision for a holistic strategy for approaching Green Commun icat ions that goes beyond improvements made in isolation at one level of the communications cycle while maintaining the Quality of Service(QoS). The ubiquity of wireless communications combined with improved processer capabilities of devices, will help in enabling a new paradigm and preserving the environment.
A conclusion might elaborate on the importance of the work or suggest applications and extensions. Authors are strongly encouraged not to call out multiple figures or tables in the conclusion—these should be referenced in the body of the paper.