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14 - Femtocell interference control in standardization
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- By Zubin Bharucha, Docomo Europe, Gunther Auer, Docomo Europe
- Edited by Tony Q. S. Quek, Singapore University of Technology and Design, Guillaume de la Roche, İsmail Güvenç, Florida International University, Marios Kountouris
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- Book:
- Small Cell Networks
- Published online:
- 05 May 2013
- Print publication:
- 02 May 2013, pp 332-356
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Summary
User-deployed femtocells, each exclusively serving a set of registered users and sharing the same frequency spectrum as the overlay macrocells, are already defined in 3rd Generation Partnership Project (3GPP) specifications. Such a co-channel and random deployment of femtocells can cause heavy downlink (DL) control and data channel interference especially to mobile user equipment (MUE) in the vicinity of one or more femtocells and not belonging to their closed subscriber groups (CSGs). This chapter is dedicated to addressing this issue, termed as inter-cell interference coordination (ICIC), paying particular attention to the control channel. In systems that employ full frequency reuse, such as long term evolution (LTE), the issue of inter-cell interference (ICI) is a very serious one and can severely compromise cell-edge performance. The situation is further exacerbated in systems with femtocells randomly distributed within the underlying macrocellular network. In such a system, ICI is not only experienced by MUEs at the edge of macrocells, but can also be experienced by those MUEs in the vicinity of one or more femtocells, whose CSGs they are not members of. While scheduling strategies do not come under the purview of LTE standardization, LTE does provide standardized signaling methods so that an appropriate signaling strategy may be employed to avoid excessive ICI for the data channels. However, these signaling methods are developed to be exchanged between macro base stations (BSs) over the X2 interface. It is expected that LTE femtocells will not have access to such an interface. Furthermore, unlike the data channel, the various control channels cannot be conveniently relocated in order to avoid interference.
16 - How much energy is needed to run a wireless network?
- from Part V - Green radio test-bed, experimental results, and standardization activities
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- By Gunther Auer, DOCOMO Euro-Labs, Germany, Vito Giannini, IMEC, Belgium, István Gódor, Ericsson Research, Hungary, Oliver Blume, Alcatel-Lucent Bell Labs, Germany, Albrecht Fehske, Technische Universität Dresden, Germany, Jose Alonso Rubio, Ericsson Research, Sweden, Pål Frenger, Ericsson Research, Sweden, Magnus Olsson, Ericsson Research, Sweden, Dario Sabella, Telecom Italia, Italy, Manuel J. Gonzalez, Technologies of Telecommunication and Information (TTI), Spain, Muhammad Ali Imran, University of Surrey, UK, Claude Desset, IMEC, Belgium
- Edited by Ekram Hossain, University of Manitoba, Canada, Vijay K. Bhargava, University of British Columbia, Vancouver, Gerhard P. Fettweis, Technische Universität, Dresden
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- Book:
- Green Radio Communication Networks
- Published online:
- 05 August 2012
- Print publication:
- 05 July 2012, pp 359-384
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Summary
Introduction
The global mobile communication industry is growing rapidly. Today there are already more than 4 billion mobile phone subscribers worldwide [1], more than half the entire population of the planet. Obviously, this growth is accompanied by an increased energyconsumption of mobile networks. Global warming and heightened concerns for the environment of the planet require a special focus on the energy efficiency of these systems [2].
Many approaches to wireless energy-efficiency are limited to the power consumption of single nodes, e.g. a base station [3]–[5]. This scope is comparably easy to specify and to measure, but it fails to capture the network performance aspects (e.g. system throughput) implied by coverage and interference issues. Other methodologies are very broad, capturing the ICT industry in total [6]. Recently an assessment framework for the power consumption of deployed wireless networks has been published, the mobile energyefficiency (MEE) network benchmarking service [7], based on metering all components of a network. However, for the energy efficiency it is not possible to directly compare, e.g. an Indian network with a Scandinavian network, therefore MEE has to introduce correction terms for the climate, for the number of base stations operated off-grid, and for the generations of equipment in the field.
However, the above approaches do not give insight into which parts of a network are most energy intensive or which provide the highest energy-saving potentials. There is a need for a simulation tool studying theoretically the effect of improvements in hardware, deployment strategies, and network management.
12 - Cellular OFDMA-TDD
- Edited by Harald Haas, Universität Bremen, Stephen McLaughlin, University of Edinburgh
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- Book:
- Next Generation Mobile Access Technologies
- Published online:
- 02 September 2009
- Print publication:
- 10 January 2008, pp 336-376
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Summary
Motivation and problems
High peak data rate transmission, network self-organisation and universal frequency reuse are considered important features for future cellular, ad hoc, multi-hop and hybrid wireless networks (Prehofer and Bettstetter, 2005). OFDMA is viewed as a promising modulation/multiple-access technique for providing very high data-rates and flexible resource allocation while at the same time enabling low complexity receivers (Stimming et al., 2005). Time-division duplexing (TDD) supports traffic asymmetry very well which is inherent to packet data services. Moreover, TDD offers channel reciprocity which is exploited in this research in a novel fashion for medium access and subchannel allocation. The problems that arise from TDD are the requirement for time synchronisation and additional interference scenarios. This is particularly important as OFDMA performs poorly under conditions of universal frequency reuse because of the high CCI. Figure. 12.1 illustrates the CCI problem in a cellular network using TDD with frequency reuse of one. The figure shows two adjacent BSs (base stations), namely BS1 and BS2 with a MS (mobile station) associated with each BS, namely MS1 and MS2. MS1 is transmitting data to BS1. Consequently, MS1 causes interference to MS2, since MS2 is in receiving mode. Similarly, BS2 causes interference to BS1. Due to the potentially small spatial separation between transmitter and ‘victim’ receiver and the low path loss between BSs due to line-of-sight conditions, in a full frequency reuse network, CCI poses a major challenge on the MAC protocol design and channel assignment procedure.