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Towards Green Wireless Access Networks: Main Tradeoffs, Deployment Strategies and Measurement Methodologies
KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.ORCID iD: 0000-0002-5016-5044
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Wireless access networks today consume 0.5 percent of the global energy. Rapidly growing demand for capacity will further increase the energy consumption. Thus, improving energy efficiency has a great importance not only for environmental awareness but also to lower the operational cost of network operators. However, current networks which are optimized based on non-energy related objectives introduce challenges towards green wireless access networks. In this thesis we investigate the solutions at the deployment level and handle energy efficiency assessment issues in wireless access networks.

The precise characterization of the power consumption of the whole network has a crucial importance in order to obtain consistent conclusions from any proposed solution at the network level. For this purpose, we propose a novel power consumption model  considering  the impact of backhaul for two established technologies, i.e., fiber and microwave, which is often ignored in the literature. We show that there is a tradeoff between the power saved by using low power base stations and the excess power that has to be spent for backhauling their traffic which therefore needs to carefully be included into energy efficiency analysis. Furthermore, among the solutions that are analyzed, fiber-based backhaul solution is identified to outperform microwave regardless of the considered topology. The proposed model is then used to gain a general insight regarding the important design parameters and their possible impact on energy- and cost oriented network design. To this end, we present a  high-level framework to see the main tradeoffs between energy, infrastructure cost, spectrum and show that future high-capacity systems are increasingly limited by infrastructure and energy costs where spectrum has a strong positive impact on both.

We then investigate different network deployment strategies to improve the energy efficiency where we focus on the impact of various base station types, cell size, power consumption parameters and the capacity demand. We propose a refined power consumption model where the parameters are determined in accordance with cell size. We show that network densification can only be justified when capacity expansion is anticipated and over-provisioning of the network is not plausible for greener network. The improvement through heterogeneous networks is indicated to be highly related to the traffic demand where up to 30% improvement is feasible for high area throughput targets.

Furthermore, we consider the problem of energy efficiency assessment at the network level in order to allow operators to know their current status and quantify the potential energy savings of different solutions to establish future strategies. We propose elaborate metric forms that can characterize the efficiency and a methodology that indicate how to perform a reliable and accurate measurement considering the complexity of wireless networks. We show the weakness of the current metrics reporting the "effectiveness" and how these might indicate disputable improvement directions unless they are properly revised. This illustrates the need for a standardized network level energy efficiency evaluation methodology towards green wireless access.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2012. , ix, 60 p.
Series
Trita-ICT-COS, ISSN 1653-6347 ; 1212
Keyword [en]
Energy efficiency, wireless access, green radio
National Category
Communication Systems
Research subject
SRA - ICT
Identifiers
URN: urn:nbn:se:kth:diva-104328OAI: oai:DiVA.org:kth-104328DiVA: diva2:563905
Presentation
2012-11-30, Sal/Hall C2, Electrum, KTH-ICT, Isafjordsgatan 26, Kista, 10:00 (English)
Opponent
Supervisors
Projects
Energy-efficient wireless networking (eWIN)
Funder
ICT - The Next GenerationWireless@kth
Note

QC 20121109

Available from: 2012-11-08 Created: 2012-10-31 Last updated: 2014-05-05Bibliographically approved
List of papers
1. Energy- and cost-efficient ultra-high-capacity wireless access
Open this publication in new window or tab >>Energy- and cost-efficient ultra-high-capacity wireless access
2011 (English)In: IEEE wireless communications, ISSN 1536-1284, E-ISSN 1558-0687, Vol. 18, no 5, 18-24 p.Article in journal (Refereed) Published
Abstract [en]

Mobile communication networks alone today consume 0.5 percent of the global energy supply. Meeting the rapidly increasing demand for more capacity in wireless broadband access will further increase the energy consumption. Operators are now facing both investing in denser and denser networks as well as increased energy cost. Traditional design paradigms, based on assumptions of spectrum shortage and high cost base station sites, have produced current cellular systems based on 3G and 4G (LTE) standards. The latter ones are characterized by very high spectrum efficiency, but low energy efficiency. Deployment has favored strategies with few high-power bases stations with complex antenna systems. The key method for indoor coverage has so far been to literally "blast signals through walls" - a solution that is neither energy-efficient nor very sound from a radiation perspective. As environmental aspects may be perceived as important from a societal perspective, the cost remains the short-to medium-term concern for operators of future mobile broadband systems. What becomes evident now is that the so far mostly neglected energy cost will be a major concern. Future system deployment has to balance infrastructure deployment, spectrum, and energy cost components. Ongoing incremental improvements in electronics and signal processing are bringing down the power consumption in the base station. However, these improvements are not enough to match the orders-of-magnitude increase in energy consumption cause by demands for more capacity. It is clear that solutions to this problem have to be found at the architectural level, not just by increasing the efficiency of individual components. In this article we propose a framework for a total cost analysis and survey some recent, more radical, "clean slate" approaches exploiting combinations of new spectrum opportunities, energy-efficient PHY layers, and novel deployment and backhauling strategies that target minimizing overall system cost. The latter involve network deployment tightly tailored to traffic requirements, using low-power micro base stations tailored specifically to decrease the power consumption compared to today's high-power macro base station schemes. To illustrate our findings, a power consumption model for mobile broadband access networks taking backhaul into account is presented, and the main trade-offs between infrastructure, energy, and spectrum costs are analyzed. We demonstrate optimal deployment strategies in some simple scenarios where a certain capacity has to be provided in a dense interference-limited scenario.

National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-48521 (URN)10.1109/MWC.2011.6056688 (DOI)000296242000005 ()2-s2.0-80155201296 (Scopus ID)
Projects
Energy-efficient wireless networking (eWIN)
Funder
Wireless@kth
Note

QC 20111201

Available from: 2011-12-01 Created: 2011-11-21 Last updated: 2017-12-08Bibliographically approved
2. Impact of Densification on Energy Efficiency in Wireless Access Networks
Open this publication in new window or tab >>Impact of Densification on Energy Efficiency in Wireless Access Networks
2012 (English)In: Globecom Workshops (GC Wkshps), 2012 IEEE, IEEE , 2012, 57-62 p.Conference paper, Published paper (Refereed)
Abstract [en]

Mobile communication networks alone consume 0.5 percent of the global energy today. Rapidly growing demand for capacity will further increase the energy consumption. Thus, improving energy efficiency has recently gained great interest within the research community not only for environmental awareness but also to lower the operational cost of network operators. Base station deployment strategy is one of the key challenges to be addressed for fulfilling the future capacity demand in an energy efficient manner. In this paper, we investigate the relationship between energy efficiency and densification with regard to network capacity requirement. To this end, we refine the base station power consumption model such that the parameters are determined by the maximum transmit power and develop a simple analytical framework to derive the optimum transmit power that maximizes energy efficiency for a certain capacity target. Our framework takes into account interference, noise and backhaul power consumption. Numerical results show that deployment of smaller cells significantly reduces the base station transmit power, and thus shifts the key elements of energy consumption to idling and backhauling power. Network densification can only be justified when capacity expansion is anticipated.

Place, publisher, year, edition, pages
IEEE, 2012
Series
IEEE Globecom Workshops, ISSN 2166-0069
Keyword
Energy Efficiency, Backhaul, Densification, Network Capacity, Power Consumption
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-104658 (URN)10.1109/GLOCOMW.2012.6477544 (DOI)000320611800011 ()2-s2.0-84875679320 (Scopus ID)978-1-4673-4941-3 (ISBN)
Conference
2012 IEEE Globecom Workshops, GC Wkshps 2012; Anaheim, CA; United States; 3 December 2012 through 7 December 2012
Projects
Energy-efficient wireless networking (eWIN)
Funder
ICT - The Next GenerationWireless@kth
Note

QC 20121109

Available from: 2012-11-08 Created: 2012-11-08 Last updated: 2014-05-05Bibliographically approved
3. Impact of backhauling power consumption on the deployment of heterogeneous mobile networks
Open this publication in new window or tab >>Impact of backhauling power consumption on the deployment of heterogeneous mobile networks
Show others...
2011 (English)In: 2011 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE (GLOBECOM 2011), 2011, 6133999- p.Conference paper, Published paper (Refereed)
Abstract [en]

Energy efficiency in cellular mobile radio networks has recently gained great interest in the research community. The development of more energy efficient hardware and software components aside, effect of different deployment strategies on energy efficiency are also studied in the literature. The latter mainly consist of optimizing the number and the location of different types of base stations in order to minimize the total power consumption. Usually, in the literature, the total network power consumption is restricted to the sum of the power consumption of all base stations. However, the choice of a specific deployment also affects the exact implementation of the backhaul network, and consequently its power consumption, which should therefore be taken into account when devising energy efficient deployment. In this paper, we propose a new power consumption model for a mobile radio network considering backhaul. We then handle a case study and perform a comparison of the power consumption of three different heterogeneous network deployments, and show how backhaul has a non-negligible impact on total power consumption, which differs for different deployments. An energy efficiency analysis is also carried out for different area throughput targets.

Series
IEEE Global Telecommunications Conference (Globecom), ISSN 1930-529X
Keyword
Power Consumption Model, Heterogeneous Networks, Energy Efficiency, Backhaul, Network Deployment
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-92083 (URN)000300509002127 ()2-s2.0-84863142017 (Scopus ID)978-1-4244-9268-8 (ISBN)
Conference
54th Annual IEEE Global Telecommunications Conference (GLOBECOM) DEC 05-09, 2011 Houston, TX
Projects
Energy-efficient wireless networking (eWIN)
Funder
ICT - The Next GenerationWireless@kth
Note

QC 20120326

Available from: 2012-03-26 Created: 2012-03-26 Last updated: 2016-04-22Bibliographically approved
4. Mobile backhaul in heterogeneous network deployments: Technology options and power consumption
Open this publication in new window or tab >>Mobile backhaul in heterogeneous network deployments: Technology options and power consumption
2012 (English)In: 14th International Conference on Transparent Optical Networks, 2012, 1-7 p.Conference paper, Oral presentation only (Refereed)
Abstract [en]

Mobile communication networks account for 0.5% of the global energy consumption, a value that is expected to double within the next five years. For this reason, means of reducing the energy consumption in cellular mobile radio networks has recently gained great interest within the research community. In mobile networks the backhaul contribution to the total power consumption is usually neglected because of its limited impact compared to that of the radio base stations. However, meeting the almost exponential increase in mobile data traffic requires a large number of (mainly small) base stations. This means that backhaul networks will take a significant share of the cost and the energy consumption in future systems. Their actual contribution to the energy consumption will depend on the radio base station deployment scenario as well as on the technology and topology choices for the backhaul itself. This paper presents an initial assessment of the power consumption of two established backhaul technologies, i.e., fiber and microwave. For the microwave case, three backhaul topologies are considered, i.e., tree, ring and star, while for the fiber case only one topology is analysed, i.e., a dedicated point-to-point star. The presented results, assuming off-the-shelf products and based on todays network capacity levels, confirm the importance of considering the backhaul when minimizing the total power consumption in heterogeneous network scenarios. They also show the impact of the basic technology and topology choices of the backhaul for minimizing total power consumption.

Keyword
Green networks, fiber-based backhaul, heterogeneous wireless networks, microwave-based backhaul, mobile backhaul, pico base stations
National Category
Communication Systems
Research subject
SRA - ICT
Identifiers
urn:nbn:se:kth:diva-103700 (URN)10.1109/ICTON.2012.6253839 (DOI)000335346900136 ()2-s2.0-84867002609 (Scopus ID)
Conference
14th International Conference on Transparent Optical Networks (ICTON), 2012
Projects
Energy-efficient wireless networking (eWIN)Wireless@KTH
Funder
ICT - The Next GenerationWireless@kth
Note

QC 20121108

Available from: 2012-10-18 Created: 2012-10-18 Last updated: 2014-10-14Bibliographically approved
5. Energy Efficiency Improvements Through Heterogeneous Networks in Diverse Traffic Distribution Scenarios
Open this publication in new window or tab >>Energy Efficiency Improvements Through Heterogeneous Networks in Diverse Traffic Distribution Scenarios
2011 (English)In: 2011 6th International ICST Conference on Communications and Networking in China (Chinacom11), 2011, 708-713 p.Conference paper, Published paper (Refereed)
Abstract [en]

Energy Efficiency in cellular mobile radio networks has recently gained great interest in the research community. Besides the positive effect on global climate change, lowering power consumption of mobile networks is beneficial in terms of decreasing the operational cost for network operators. In this regard, the development of more energy efficient hardware and software components aside, effect of different deployment strategies on energy efficiency are also studied in the literature. In this paper, we investigate the energy efficiency improvements through different heterogeneous networks for both uniform and non-uniform traffic distribution scenarios. It has been shown that, using small power low base stations at the cell border decreases the power consumption significantly for both traffic scenarios and the most energy efficient deployment strategy highly depends on the area throughput demand of the system.

Keyword
Power Consumption, Heterogeneous Networks, Energy Efficiency, Hotspots, Network Deployment
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-75003 (URN)10.1109/ChinaCom.2011.6158246 (DOI)000305758800138 ()2-s2.0-84858257733 (Scopus ID)
Conference
6th International ICST Conference on Communications and Networking in China(Chinacom11), Harbin, China, 17-19 Aug. 2011
Projects
Energy-efficient wireless networking (eWIN)
Funder
Wireless@kth
Note

QC 20120416

Available from: 2012-02-04 Created: 2012-02-04 Last updated: 2014-05-05Bibliographically approved
6. Energy Efficiency in Network Level: Definition, Measurement and Prediction
Open this publication in new window or tab >>Energy Efficiency in Network Level: Definition, Measurement and Prediction
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this paper, network level energy efficiency assessment issues are described in wireless access networks. High level definitions of energy efficiency are introduced and existing heterogeneous metrics proposed in the literature in order to quantify the energy savings are overviewed. The weaknesses of the current metrics in order to evaluate NLEE have been discussed in detail and more elaborate metric forms have been suggested. Then, a NLEE evaluation methodology is proposed to calculate the suggested indicator, and unlike GSMA method it is based on network segmentation, direct measuring in both network and terminal side, and prediction. We believe that network modularization and frequent observation are the only ways in order to understand the reasoning behind the obtained NLEE metric and propose solutions for the improvement. However, it comes with the increased complexity and challenges to be resolved. We present a summary of the most important difficulties, our suggestions and open questions in order to answer “How to accurately assess the NLEE in wireless access network”.

Keyword
Energy Efficiency Metrics, Wireless Access Networks, Measurement Methodology, Utility function
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-104659 (URN)
Projects
Energy-efficient wireless networking (eWIN)
Funder
ICT - The Next GenerationWireless@kth
Note

QS 2012

Available from: 2012-11-08 Created: 2012-11-08 Last updated: 2016-04-22Bibliographically approved

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