Small-net vs. relays in a heterogeneous low energy LTE architecture

The paper analyzes the energy consumption impact of introducing heterogeneous elements to a homogeneous deployment. Two contrasting low energy heterogeneous architectures are investigated: small cells (Small-Nets) and wireless relays. The investigation employs a multi-cell multi-user dynamic LTE simulator and both deployments are investigated for a range of urban traffic loads. The paper shows that compared to a homogeneous baseline deployment of micro-cells, both deployments reduce the total radio network energy consumption significantly (50 to 60%). The Small-Net approach reduces energy consumption by deploying more low power cells with a macro-overlay and achieves increased network capacity by spectrum reuse. The relaying approach reduces energy consumption by deploying fewer macro-cells and increases network capacity through increasing cell-edge performance. A combination of deployment factors were investigated in order to find the lowest energy architecture within the heterogeneous deployments. For a range of targeted traffic loads, it was found that the lowest energy solution depends on the percentage of high mobility traffic. If the percentage of high-mobility users is below 8%, the Small-Net architecture is the lowest energy architecture. Otherwise, the wireless cell-edge relaying concept offers a greater energy reduction. The paper also presents theoretical upper-bounds on energy reduction for a fixed and changing deployment