SCIENTIA SINICA Informationis, Volume 47 , Issue 5 : 560(2017) https://doi.org/10.1360/N112017-00035

## Energy efficient resource optimization and transmission strategies for hyper-cellular mobile communication systems

• AcceptedMar 20, 2017
• PublishedMay 4, 2017
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### Abstract

This paper provides an overview on our research on energy-efficient resource optimization and transmission strategies for hyper-cellular systems over the past five years. It summarizes the fundamental relationship between energy efficiency (EE) and spectral efficiency (SE), as well as the impact of physical resources on the relationship, such as time, frequency, antenna, and cache, and reviews the energy-efficient transmission strategies adapted to dynamic channels and traffic. It is in the context of key technologies in fifth-generation (5G) mobile communication systems, including massive centralized/distributed antenna systems, ultra-dense networks (UDNs), device-to-device (D2D) communications, and coordinated multi-point transmission (CoMP). It is shown that the EE-SE relationship in all representative systems exhibits a “bell-shaped curve”, meaning SE and EE increase simultaneously when SE is low while there is a tradeoff between SE and EE otherwise. Furthermore, the SE loss in EE-optimal policies is low, but the EE loss in SE-optimal policies is high. EE approaches zero with an increase in the number of antennas. Universal frequency reuse can maximize EE when the base station (BS)-to-user density ratio is large while partial frequency reuse is better for EE otherwise. Caching at BSs can improve EE and EE gain is high in scenarios with weak interference, low-capacity backhaul, and large content popularity skewness.

### Funded by

• Figure 1

Relationship between energy efficiency (EE) and spectral efficiency (SE) in an additive white Gaussian noise (AWGN) channel [3]

• Figure 2

(a) EE-SE curve of distributed antenna system under different power allocation policies (9 distributed protectłinebreak antennas) [9]; (b) EE-SE curve of centralized massive MIMO system with different power consumption parameters protectłinebreak (128 antennas at base station) [10]

• Figure 3

(a) EE and (b) SE achieved by the EE-optimal and SE-optimal strategies in D2D system [15]

• Figure 4

EE-SE curves for different number of antennas $n_t$ in MIMO-OFDMA system [18]

• Figure 5

Relation between EE and backhaul capacity (a) and normalized cache size (b) [24]

• Figure 6

Comparison of EE and SE achieved by cooperative and non-cooperative BS sleeping schemes [27]

• Figure 7

EE gain and SE loss of the EE-oriented design over the SE-oriented design [33]

• Figure 8

Gain of average data rate (a) and reduction of average downloading time (b) achieved by precaching over prefetching [39]

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