  Energy efficiency (EE) plays a key role in future wireless communication
network and it is easily to achieve high EE performance in low SNR regime. In
this paper, a new high EE scheme is proposed for a MIMO wireless communication
system working in the low SNR regime by using two dimension resource
allocation. First, we define the high EE area based on the relationship between
the transmission power and the SNR. To meet the constraint of the high EE area,
both frequency and space dimension are needed. Besides analysing them
separately, we decided to consider frequency and space dimensions as a unit and
proposed a two-dimension scheme. Furthermore, considering communication in the
high EE area may cause decline of the communication quality, we add
quality-of-service(QoS) constraint into the consideration and derive the
corresponding EE performance based on the effective capacity. We also derive an
approximate expression to simplify the complex EE performance. Finally, our
numerical results demonstrate the effectiveness of the proposed scheme.
