Special issue: Towards green mobile networks

Vol. 67, n° 3-4, March-April 2012
Content available on Springerlink

Guest editors
Régis Esnault, Orange Labs, France
Timothy O’Farrell, Sheffield University, UK
Gee Rittenhouse, Bell Labs, USA

In Memoriam of Man Faï Wong

Joe Wiart
Orange Labs, France


Joe Wiart
Orange Labs, France

Survey and applications of standardized energy metrics to mobile networks

Hassan Hamdoun1, Pavel Loskot1, Timothy O’Farrell2 , Jianhua He1
Swansea University, UK
2 University of Sheffield, UK

Abstract The energy consumption and the energy efficiency have become very important issue in optimizing the current as well as in designing the future telecommunications networks. The energy and power metrics are being introduced in order to enable assessment and comparison of the energy consumption and power efficiency of the telecommunications networks and other transmission equipment. The standardization of the energy and power metrics is a significant ongoing activity aiming to define the baseline energy and power metrics for the telecommunications systems. This article provides an up-to-date overview of the energy and power metrics being proposed by the various standardization bodies and subsequently adopted worldwide by the equipment manufacturers and the network operators.

Keywords  Energy and power efficiency – Energy and power metrics – Wireless access network

Towards passive cooling solutions for mobile access network

Stéphane Le Masson1, David Nörtershäuser1, Denise Mondieig2, Hasna Louahlia-Gualous3
1 Orange Labs, France
2 CNRS / University Bordeaux I, France
3 University de Caen Basse Normandie, France

Abstract The amount of electricity used by mobile networks has become an important issue in recent years as demand for new services has become more widespread. In 2006, energy consumption of Orange mobile network was estimated at 290 GWh per year. Recent works show that thermal architecture must be improved in order to increase thermal efficiency of buildings, shelters, and outdoor cabinets. This paper shows some new approaches on thermal management for telecom enclosures in order to reduce energy consumption of this network.

Keywords  Thermal – Ventilation – Thermosyphon loop – Phase change material

Impact of picocells on the capacity and energy efficiency of mobile network

Louai Saker1, Gilbert Micallef2, Salah Eddine Elayoubi1, Hans-Otto Scheck3
1 Orange Labs, France
2 Aalborg University, Denmark
3 Nokia Siemens Networks, Finland

Abstract The deployment of small cells in mobile networks has aroused a large interest in the last few years. This paper investigates the impact of picocell deployment on the performance and power consumption of mobile networks. Since different network upgrades introduce different performance gains, comparing different configurations exclusively on their overall power consumption can be rather biased. For this reason, a new key performance indicator, termed “energy efficiency”, is introduced and used throughout this study, bringing together network performance and its overall power consumption. In the first section of the study, a theoretical analysis for the Erlang-like capacity of a network, considering a uniform topology and traffic, is performed, using queuing theory analysis, namely processor-sharing queues. Results show that in all cases the deployment of picocells improve the performance of the network, however the energy efficiency is noted to be dependent on the deployment scenario considered. In the second part of the study, a more realistic scenario with non-uniform topology and traffic is considered, which is carried out through a large-scale system level simulator. Results show that by deploying picocells in areas experiencing high levels of traffic, the energy efficiency of the network can be considerably improved.

Keywords  Mobile networks – Picocells – Energy efficiency – Capacity – Sleep mode

An application aware discontinuous reception mechanism in LTE-advanced with carrier aggregation consideration

Fei Yin
Renesas Mobile Corporation, Shanghai, China

Abstract 3GPP Release 8 specifications define a mechanism named DRX (Discontinuous Reception) to save UE’s (User Equipment) energy consumption in LTE (Long Term Evolution). The DRX allow an UE to stop monitoring PDCCH (Physical Downlink Control CHannel) on a CC (Component Carriers) during some periods of the operation time. Obviously, the duration and the frequency of these non-monitoring periods are important parameters that can significantly impact the ES (Energy Saving) efficiency and the performance of applications running on the CC. In Release 9, 3GPP introduces an advanced technology named CA (Carrier Aggregation) for LTE-Advanced to achieve higher bandwidth and throughput: the UE may operate over up to 5 CCs. The conventional DRX operations are no longer appropriated in the CA case: applying the same DRX configuration for all the CCs is neither performance-optimal nor energy-efficient if applications with different QoS requirements operating simultaneously on the CCs in realistic environment. A DRX mechanism by taking both applications’ QoS requirement and CA into account to achieve reasonable ES might be an optimal choice. In this paper, based on the survey of various conventional DRX energy saving protocols in LTE networks, we propose a simple but efficient application aware DRX mechanism to optimize the performance in LTE-Advanced networks with CA consideration. The simulation results verify that the ES efficiency is conditioned to the fulfillment of the DRX parameters, and our proposed optimal scheme can significantly improve energy saving efficiency as compared to the conventional DRX mechanism.

Keywords  LTE-advanced – Discontinuous reception – Carrier aggregation – Component carrier – Energy saving

Reducing the power of wireless terminals by adaptive baseband processing

Claude Desset, Rodolfo Torrea Duran
Imec, Leuven, Belgium

Abstract In this paper, we illustrate specific power savings obtained from exploiting a reconfigurable mobile terminal under the 3GPP LTE standard. Building on traditional link adaptation towards maximum throughput and extended towards minimal power consumption, we add two flexible baseband components: the turbo decoder and the multiple input multiple output (MIMO) detector. Optimizing their configuration leads to larger power savings when compared to non-flexible systems only performing link adaptation. The gain observed strongly depends on the scenario. For low-activity set-ups with a few minutes of voice per day, the idle power dominates and the active data rate is relatively low. This makes analog front-end and time-domain processing dominant given their constant power consumption while MIMO detection and turbo decoding that scale with data rate play a smaller role. Still, because of its ability to improve the system spectral efficiency and hence reduce its duty cycle, an advanced MIMO detector can save 10% in power consumption, on the condition that the network requires to use MIMO. Otherwise single input single output is more power-efficient in downlink. In high-throughput scenarios, larger gains are obtained. The flexible MIMO detector can save up to 35% of average power consumption. The turbo decoding also brings some gain, saving up to 12% of power when the full bandwidth is allocated to a single user.

Keywords  Low-power – Adaptivity – Software-defined radio – Wireless terminal – MIMO detection – Turbo decoding – 3GPP LTE – Green cellular networks

Cross-layer sensors for green cognitive radio

Jacques Palicot
Supélec/IETR, France

Abstract Green cognitive radio is a cognitive radio (CR) that is aware of sustainable development issues and deals with an additional constraint as regards the decision-making function of the cognitive cycle. In this paper, it is explained how the sensors distributed throughout the different layers of our CR model could help on taking the best decision in order to best contribute to sustainable development.

Keywords  Green radio – Green communications – Cognitive – Software radio – Electromagnetic pollution – Consumption – Sustainable development

Traffic-based topology control algorithm for energy savings in multi-hop wireless network

Steven Martin1, Khaldoun Al Agha1, Guy Pujolle2
1 University Paris 11, France
2 University Paris 6, France

Abstract This paper presents a traffic-based topology control algorithm for multi-hop wireless networks, in order to optimize the global energy consumption while maximizing the aggregate throughput. Contrary to major related works, we do not consider that reducing transmission powers implies reducing interferences and that the traffic is uniformly distributed among the links. Thus, we propose to dynamically calculate the transmission power of nodes depending on the traffic. First, we redefine the N-hop interference model for varying transmission powers. Then, we define a function giving the minimum interference according to the transmission powers. We propose several algorithms minimizing this function: global optimization, local optimization, and distributed optimization for a limited computation cost. Our first algorithm is used as a reference for limited cases. We show by simulation that our heuristics are relevant compared to existing works.

Green networking – Ad hoc – Power – Interference

Open topics

Dynamic bandwidth management in IEEE 802.11-based multihop wireless network

Cheikh Sarr1, Sofiane Khalfallah2, Isabelle Guérin-Lassous3
1 University of Thiès, Sénégal
2 UTC / Heudiasyc, Compiègne, France
3 INRIA / University Lyon 1 / CNRS / ENS Lyon, France

Abstract In this paper, we propose a new protocol named dynamic regulation of best-effort traffic (DRBT) which supports quality of service (QoS) throughput guarantees and provides a distributed regulation mechanism for best-effort traffic in multihop wireless networks. By adapting dynamically the rate of best-effort traffic at the link layer, DRBT increases the acceptance ratio of QoS flows and provides a good use of the remaining resources through the network. Our protocol also provides an accurate method to evaluate the available bandwidth in IEEE 802.11-based ad hoc networks which is able to differentiate QoS applications from best-effort traffic. Through extensive simulations, we compare the performance of our proposal scheme with some others protocols like QoS protocol for ad hoc real-time traffic for instance.

Keywords  QoS – Traffic differentiation – Available bandwidth – IEEE 802.11

Effect of opportunistic scheduling on the quality of service perceived by the users in OFDMA cellular networks

Bartłomiej Błaszczyszyn1, Mohamed Kadhem Karray2
1 INRIA / ENS, Paris, France
2 Orange Labs, France

Abstract Our objective is to analyze the impact of fading and opportunistic scheduling on the quality of service perceived by the users in an orthogonal frequency-division multiple access cellular network. To this end, assuming Markovian arrivals and departures of customers that transmit some given data volumes, as well as some temporal channel variability (fading), we study the mean throughput that the network offers to users in the long run of the system. Explicit formulas are obtained in the case of allocation policies, which may or may not take advantage of the fading, called respectively opportunistic and non-opportunistic. The main practical results of the present work are the following: Firstly, we evaluate for the non-opportunistic allocation the degradation due to fading compared to additive white Gaussian noise (AWGN; that is, a decrease of at least 13% of the throughput). Secondly, we evaluate the gain induced by the opportunistic allocation. In particular, when the traffic demand per cell exceeds some value (about 2 Mbits/s in our numerical example), the gain induced by opportunism compensates the degradation induced by fading compared to AWGN.

Keywords  Radio communication – Opportunistic – Scheduling – Quality of service – Information theory – Markov processes