Josip Lorincz

Measurements and Modelling of Base Station Power Consumption under Real Traffic Loads

Base stations represent the main contributor to the energy consumption of a mobile cellular network. Since traffic load in mobile networks significantly varies during a working or weekend day, it is important to quantify the influence of these variations on the base station power consumption. Therefore, this paper investigates changes in the instantaneous power consumption of GSM (Global System for Mobile Communications) and UMTS (Universal Mobile Telecommunications System) base stations according to their respective traffic load. The real data in terms of the power consumption and traffic load have been obtained from continuous measurements performed on a fully operated base station site. Measurements show the existence of a direct relationship between base station traffic load and power consumption. According to this relationship, we develop a linear power consumption model for base stations of both technologies. This paper also gives an overview of the most important concepts which are being proposed to make cellular networks more energy-efficient.

Optimized network management for energy savings of wireless access networks

The energy consumption of wireless access networks is rapidly increasing and in some countries it amounts for more than 55% of the whole communication sector and for a non negligible part of the operational costs of mobile operators. The new wireless technologies with a growth of data rates by a factor of roughly 10 every 5years and the increase in the number of users result in a doubling of the power consumption of cellular networks infrastructure every 4-5 years - to 60TWh in 2007.In this paper we consider possible energy savings through optimized management of on/off state and transmitted power of access stations according to traffic estimates in different hours of the day or days of the week. We propose an optimization approach based on some ILP models that minimizes energy consumption while ensuring area coverage and enough capacity for guaranteeing quality of service. Proposed models capture system characteristics considering different management constraints that can be considered based on traffic requirements and application scenarios. Energy minimization problems are solved to the optimum or with a gap to the optimum of less than 2.7% on a set of synthetic instances that are randomly generated. Obtained results show that remarkable energy savings, up to more than 50%, can be obtained with the proposed management strategies.

Impact of service rates and base station switching granularity on energy consumption of cellular networks

Over the last two decades we have witnessed significant growth of the cellular network energy consumption caused by a rapid increase in the number of mobile users and data volumes. This is contributed to by a tenfold increase of data rates every 5 years, and such a trend in up growth of energy consumption will continue with the introduction of a new throughput demanding services. Hence, development of new energy-saving techniques and estimation of the influence on energy savings when ensuring different service rates are the focus of this article. For the purpose of reducing cellular network energy consumption, this article proposes a new approach to energy-efficient management of network resources. The energy-efficient management is based on adaptive changes of on/off states of a complete base station (BS) site in accordance with the traffic pattern variations. Besides adaptations to the temporal traffic variations, the BS can adapt capacity to the spatial traffic variations through dynamic scaling of transmitted power according to capacity demand. We formulate the problem of energy-efficient management as a binary integer programming problem dedicated to energy consumption minimization of a complete network. Proposed methodology is simulated on a set of real size Universal Mobile Telecommunications System network instances consisting of different radio propagation environments. In addition, this article analyzes the influence on the energy savings potential of BSs switching granularity. Obtained results show that the proposed optimization approach offers significant reductions in the network energy consumption while preserving the most important QoS constraints like full area coverage and guaranteed service rates.

Is green networking beneficial in terms of device lifetime

This article analyzes the impact that sleep mode (SM)-based green strategies have on the reliability performance of optical and cellular network elements. First, we consider a device in isolation (i.e., not plugged into a network in operation), showing how operational temperature and temperature variations, both introduced by SM, impact its lifetime. We then evaluate, from an operational cost perspective, the impact of these lifetime variations, showing that some devices are critical, that is, their achievable energy savings might not cover the potential additional reparation costs resulting from being put in SM too frequently. Moreover, we present a model for evaluating the impact of SM on the lifetime of a device plugged into an operational network. The analysis considers two case studies (one based on the optical backbone and one on cellular networks) showing that the lifetime of a device is influenced by both the hardware parameters, which depend on the specific design of the device, and the SM parameters, which instead depend on the energy-efficient algorithm used, the network topology, and the traffic variations over time. Our results show that (i) the changes in the operational temperature and the frequency of their variation are two crucial aspects to consider while designing a SM-based green strategy, and (ii) the impact of a certain SM-based strategy on the lifetime of network devices is not homogeneous (i.e., it can vary through the network).

Physical layer analysis of emerging IEEE 802.11n WLAN standard

In January 2004 IEEE announced that it had formed a new 802.11 Task Group N (TGn) to develop a new amendment to the 802.11 standard for wireless local-area networks that is known as the IEEE 802.11n standard. The real data throughput is at least 100 Mbps, with the possibility of even higher raw data rate at the physical layer (PHY), and should be up to 5 times faster than 802.11a or 802.11g, and perhaps 25 times faster than 802.11b in mandatory modes of operation. It is projected that 802.11n also offer better operating distance and full compatibility with current WLANs. There are two competing proposals of the 802.11n standard, expected to be ratified: WWiSE and TGnSync. This paper on PHY compares new technical solutions of these two proposals believing that the best of these proposals is incorporated in 802.11n standard. We also emphasize features and technical solutions on PHY that is inevitably built in the emerging 802.11n standard

Increasing device lifetime in backbone networks with sleep modes

We study the impact of sleep modes capabilities on the lifetime of backbone devices. We first define a model that integrates sleep modes in the device lifetime. We then derive a model for the network topology to compute the average network lifetime. Finally, we consider a realistic case study driven by operator feedback. Results indicate that the application of sleep modes can increase the average network lifetime. However, frequent power state transitions of network devices can deteriorate the network lifetime. Thus, we argue that the design and the management of energy-aware networks need to take into account the device lifetime.

On interdependence among transmit and consumed power of macro base station technologies

Dynamic adaptation of the base stations on/off activity or transmit power, according to space and time traffic variations, are measures accepted in the most contemporary resource management approaches dedicated to improving energy efficiency of cellular access networks. Practical implementation of both measures results in changes to instantaneous base station power consumption. In this paper, extensive analyses presenting influence of the transmit power scaling and on/off switching on instantaneous macro base stations power consumption are given. Based on real on-site measurements performed on a set of macro base stations of different access technologies and production years, we developed linear power consumption models. These models are developed by means of linear regression and precisely model the influence of transmit power on instantaneous power consumption for the second, third and fourth generations of macro base stations. In order to estimate the potential energy savings of transmit power scaling and on/off switching for base stations of different generations, statistical analyses of measured power consumptions are performed. Also, transient times and variations of base stations instantaneous power consumption during transient periods initiated with on/off switching and transmit power scaling are presented. Since the developed power consumption models have huge confidence follow measured results, they can be used as general models for expressing the relationship between transmitted and consumed power for macro base stations of different technologies and generations.

Renewable Energy Sources for Power Supply of Base Station Sites

An overview of research activity in the area of powering base station sites by means of renewable energy sources is given. It is shown that mobile network operators express significant interest for powering remote base stations using renewable energy sources. This is because a significant percentage of remote base station sites on the global level are still diesel powered due to lack of connections to the electricity grid. Besides huge expenses that mobile operators pay for diesel fuel and its transport to base station sites, it is pointed out that such base station sites represent major pollutants due to enormous green-house gas emissions. Since base stations are major consumers of cellular networks energy with significant contribution to operational expenditures, powering base stations sites using the energy of wind, sun, fuel cells or a combination gain mobile operators’ attention. It is shown that powering base station sites with such renewable energy sources can significantly reduce energy costs and improve the energy efficiency of the base station sites in rural areas. In addition, technical descriptions of the different power supply systems based on renewable sources with corresponding energy controllers for scheduling the flow of energy to power base station sites are discussed. According to the presented, hybrid systems which combine different renewable energy sources outperform those with only one energy source, and depend on the configuration of base stations installed on a particular site, such systems can offer autonomous functionality throughout the year. Renewable Energy Sources for Power Supply of Base Station Sites

Throughput Comparison of AODV-UU and DSR-UU Protocol Implementations in Multi-hop Static Environments

In this paper, we present throughput analysis of two popular Mobile Ad hoc NETwork (MANET) routing protocol implementations, AODV-UU (Uppsala University) and DSR-UU. Both implementations are Linux based user space implementations developed using C language. Instead of using simulator for throughput analysis, the investigated scenario involves a stationary test-bed that consists of real wireless nodes in ad-hoc mode connected using IEEE 802.11b standard. Influence of number of wireless nodes on overall throughput, with and without predefined static routes between nodes has been investigated. Specially developed java-based configuration and management utility was used for static route selection. Disabling or enabling of predefined wireless connections is accomplished by discarding frames according to their hardware address at MAC layer. Throughput performance of both protocols during FTP data transfer over real multi-hop network of wireless nodes has been analyzed. Additionally, a delay introduced by AODV-UU and DSR-UU protocol implementations in dynamic route change situations caused by wireless link breakage has been studied.

A measurement study of short-time cell outages in mobile cellular networks

We study the Short-Time Cell Outages (STCO) phenomena affecting Base Stations (BSs) in a mobile cellular operator network. The STCO is defined as a short-time outage of all or some BS cells (sectors) that lasts up to 30?min in a day, thus still guaranteeing more than 98% of operation. It is type of outage which cannot be detected directly through an operator network monitoring system. Although a complete characterization of STCOs has never been reported in the literature, such events are affecting the cellular network of every mobile operator. In particular, a statistical analysis of STCOs based on BSs measurements of a complete operator mobile network is performed. Our results show that: (i) STCOs impact everyday life of an operator network, (ii) high load of cells corresponds to an increase in the number of STCOs and their duration, (iii) the impact of STCOs to single sectors and whole BSs is not negligible, (iv) most of STCOs are recorded in urban areas compared to rural ones, (v) the impact of STCOs on users is higher in rural areas compared to urban ones, and (vi) the STCOs are correlated with the transferred traffic rather than the outside air temperature.