Title :
How Many Small Cells Can be Turned Off via Vertical Offloading Under a Separation Architecture?
Author :
Shan Zhang ; Jie Gong ; Sheng Zhou ; Zhisheng Niu
Author_Institution :
Tsinghua Nat. Lab. for Inf. Sci. & Technol., Tsinghua Univ., Beijing, China
Abstract :
To further improve the energy efficiency of heterogeneous networks, a separation architecture called hyper-cellular network (HCN) has been proposed, which decouples the control signaling and data transmission functions. Specifically, the control coverage is guaranteed by macro base stations (MBSs), whereas small cells (SCs) are only utilized for data transmission. Under HCN, SCs can be dynamically turned off when traffic load decreases for energy saving. A fundamental problem then arises: how many SCs can be turned off as traffic varies? In this paper, we address this problem in a theoretical way, where two sleeping schemes (i.e., random and repulsive schemes) with vertical inter-layer offloading are considered. Analytical results indicate the following facts: 1) under the random scheme where SCs are turned off with certain probability, the expected ratio of sleeping SCs is inversely proportional to the traffic load of SC-layer and decreases linearly with the traffic load of MBS-layer; 2) the repulsive scheme, which only turns off the SCs close to MBSs, is less sensitive to the traffic variations; and 3) deploying denser MBSs enables turning off more SCs, which may help to improve network energy-efficiency. Numerical results show that about 50% SCs can be turned off on average under the predefined daily traffic profiles, and 10% more SCs can be further turned off with inter-layer channel borrowing.
Keywords :
cellular radio; data communication; energy conservation; probability; telecommunication power management; telecommunication signalling; telecommunication traffic; wireless channels; HCN; MBS; control signaling; data transmission function; energy efficiency improvement; energy saving; heterogeneous network; hyper-cellular network; interlayer channel borrowing; macro base station; repulsive scheme; sleeping scheme; vertical interlayer offloading; Bandwidth; Computer architecture; Interference; Quality of service; Signal to noise ratio; Wireless communication; Green communication; cell sleeping; dynamic network planning; on-demand service; separation architecture;
Journal_Title :
Wireless Communications, IEEE Transactions on
DOI :
10.1109/TWC.2015.2438301