A. Backhaul Traffic Model in Central Solutions
The backhaul traffic of the central solution includes the uplink and downlink traffic in the
macrocell and the small cells. The uplink throughput of a small cell is denoted as T Hcentra
small−up =
0.04 · Bcentra
sc · S
centra
sc , where Bcentra
sc is the bandwidth of a small cell and S
centra
sc is the average
spectrum efficiency of a small cell [11]. The downlink throughput of a small cell is calculated
by T Hcentra
small−down = (1 + 0.1 + 0.04) · Bcentra
sc · S
centra
sc , which is transmitted through the S1
interface of backhaul networks. The uplink throughput of a macrocell is denoted as T Hcentra
macro−up =
0.04 · Bcentra
mc · S
centra
mc , where Bcentra
mc is the macrocell bandwidth and S
centra
mc is the average
spectrum efficiency of a macrocell [10]. The downlink throughput of a macrocell is calculated
by T Hcentra
macro−down = (1 + 0.1 + 0.04) · Bcentra
mc · S
centra
mc , which is transmitted through the S1
interface of backhaul networks. Assume that the backhaul traffic is balanced in every small cell.
The total number of small cells in a macrocell is configured as N. The total uplink backhaul
throughput of the central solution is calculated as T Hcentra
sum−up = N ·T Hcentra
small−up+T Hcentra
macro−up and
the total downlink backhaul throughput of the central solution is calculated as T Hcentra
sum−down =
N ·T Hcentra
small−down+T Hcentra
macro−down. As a consequence, the total backhaul throughput of the central
solution is summed as T Hcentra
sum = T Hcentra
sum−up + T Hcentra
sum−down.