Energy Efficiency of Wireless Access - Impact of Power Amplifiers and Load Variations

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School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2016-06-22
Degree programme
83 + app. 64
Aalto University publication series DOCTORAL DISSERTATIONS, 117/2016
In order to ensure seamless coverage and sustainable exponential growth of capacity, there is a keen interest in the development and deployment of highly energy efficient wireless systems and solutions. To design an energy efficient network, it is important to consider the facts that the variations in traffic demand in both temporal and spatial domains are significant, and the power consumption of cellular networks is mostly dominated by macro base stations where the power amplifiers (PAs) consume around 55-70 percent of total energy. One of the main challenges lies in coping with this load variations considering that the PAs attain high efficiency only at around the maximum output power level. In this thesis, we propose energy efficient system level solutions for wireless access network that consider the non-ideal efficiency characteristics of the PA and the load variations.  We model and incorporate the PA efficiency in the energy-delay trade-off present in Shannon's channel capacity model in order to investigate the energy saving potential in a wireless access network at the cost of additional flow-level delay. We propose a best response iteration based distributed power control algorithm where the cells identify the power levels for different user locations to minimize energy consumption under delay constraints. We observe that energy saving potential strongly depends on the network load and PA efficiency characteristics. We also investigate the impact of additional delay in the downlink on the energy consumption of the mobile terminal.  Heterogeneous network is the leading technology for the next-generation cellular networks. We investigate the energy-efficient densification and load sharing between the layers of a heterogeneous network while taking into consideration the PA efficiency and temporal load variations (TLV). We also study the impact of PA efficiency and energy-delay trade-off on the energy efficient network densification.  Massive MIMO (MM) is another leading candidate technology to cater for very high capacity demand. We consider a multi-cell MM system and provide the guidelines to dimension the PA for the antennas. We also develop energy efficient antenna adaptation schemes that allow the cells to dynamically adapt the number of antennas to the TLV in order to maintain high energy efficiency (EE) throughout the day. Our results indicate that these proposed antenna adaptation schemes can improve the EE significantly.
Supervising professor
Jäntti, Riku, Prof., Aalto University, Department of Communications and Networking, Finland
Thesis advisor
Koufus, Konstantinos, Dr., University of Bristol, England
energy efficiency, power amplifier efficiency, energy-delay trade-off, load variations, heterogeneous network, massive MIMO
Other note
  • [Publication 1]: Hossain M. M. A. and Jäntti R. Impact of efficient power amplifiers in wireless access. In IEEE Online Conference on Green Communications (GreenCom), New York, pp. 36 - 40, Sep 2011.
    DOI: 10.1109/GreenCom.2011.6082504 View at publisher
  • [Publication 2]: Hossain M. M. A., Koufos K. and Jäntti R. Minimum-energy power and rate control for fair scheduling in the cellular downlink under flow level delay constraint. IEEE Transactions on Wireless Communications, vol. 12, no. 7, pp. 3253 - 3263, Jul 2013.
    DOI: 10.1109/TWC.2013.062413.120686 View at publisher
  • [Publication 3]: Hossain M. M. A., Koufos K. and Jäntti R. How much energy can be saved by energy-delay tradeoff in Radio access network?. In IEEE Online Conference on Green Communications (GreenCom), Piscataway, NJ, pp. 121 - 126, Oct 2013.
    DOI: 10.1109/OnlineGreenCom.2013.6731039 View at publisher
  • [Publication 4]: Hossain M. M. A., Koufos K. and Jäntti R. Energy efficient deployment of Het- Nets: Impact of power amplifier and delay. In IEEE Wireless Communications and Networking Conference (WCNC), Shanghai, pp. 778 - 782, Apr 2013.
    DOI: 10.1109/WCNC.2013.6554662 View at publisher
  • [Publication 5]: Hossain M. M. A., Cavdar C. and Jäntti R. Dimensioning of PA for massive MIMO system with load adaptive number of antennas. In IEEE Globecom Workshops, Austin, TX, pp. 1102 - 1108, Dec 2014.
    DOI: 10.1109/GLOCOMW.2014.7063580 View at publisher
  • [Publication 6]: Hossain M. M. A., Cavdar C., Björnson E. and Jäntti R. Energy-efficint loadadaptive massive MIMO. In IEEE Globecom Workshops, SanDiego, CA pp. 1 - 6, Dec 2015.
    DOI: 10.1109/GLOCOMW.2015.7414181 View at publisher
  • [Publication 7]: Hossain M. M. A., Cavdar C., Björnson E. and Jäntti R. Energy saving game for Massive MIMO: Coping with daily load variations. Submitted to IEEE Transactions on Vehicular Technology, May 2016.