The overarching goal of this thesis is to investigate network architectures,
and find the trade-off between low overall energy use and maintaining the
level of quality of service (QoS), or even improve it. The ubiquitous wireless
communications environment supports the exploration of different network
architectures and techniques, the so-called heterogeneous network. Two
kinds of heterogeneous architectures are considered: a combined cellular
and femtocell network and a combined cellular, femtocell and Wireless Local
Area Network(WLAN) network.
This thesis concludes that the investigated heterogeneous networks can
significantly reduce the overall power consumption, depending on the uptake
of femtocells and WLANs. Also, QoS remains high when the power
consumption drops. The main energy saving is from reducing the macrocell
base station embodied and operational energy. When QoS is evaluated based
on the combined cellular and femtocell architecture, it is suggested that use
of resource scheduling for femtocells within the macrocell is crucial since
femtocell performance is affected significantly by interference when installed
in a co-channel system. Additionally, the femtocell transmission power mode
is investigated using either variable power level or a fixed power level. To
achieve both energy efficiency and QoS, the choice of system configurations
should change according to the density of the femtocell deployment. When
combining deployment of femtocells with WLANs, more users are able to
experience a higher QoS. Due to increasing of data traffic and smartphone
usage in the future, WLANs are more important for offloading data from the
macrocell, reducing power consumption and also increasing the bandwidth.
The localised heterogeneous network is a promising technique for achieving
power efficiency and a high QoS system
