Research Of Networking Technology Of LTE With AAS

In order to increase the capcity of LTE system,3GPP organization has taken Active Antenna System (AAS) as an enhanced technology at base station for LTE system.Currently, the standardization an investigation work of AAS is carried on in3GPP RAN4group. Funded by the enterprise project, the author joined in the standardization work of3GPP RAN4. The main contents are summarized as:Based on the fundamental RF structure of AAS,3D antenna model of AAS is introduced in this paper. Considering the difference of coorelation level between inner band signals and outer band signals in the RF transmitter array, spatial distributed ACLR of AAS is derived. By the system level simulation and evaluation, the necessity of independent optimization for uplink and downlink is verified; by the system level coexistence simulation and evaluation, we find that partial correlation level of outer band signals in the transmitter array of AAS has little impact on the the adjacent interference generated by AAS. When ACLR of the RF transmitter of AAS is larger than45dB, coexistence requirement is satisfied; meanwhile by the system level coexistence simulation, in band blocking of RF receiver of AAS is evaluated in different coexistence scenarios.According to the fundamental principle of vertical cell splitting of AAS, we derived the spatial distributed ACLR of AAS supporting vertical cell splitting. By the system level simulation, we demonstrate the performance improvement for LTE system that is enhanced by vertical cell splitting and independent optimization for uplink and downlink. By the system level coexistence simulation and evaluation, we find that that partial correlation level of outer band signals in the transmitter array of AAS has quite little impact on the the adjacent channel interference generated by AAS. However even ACLR of RF transmitter is lager than45dB, cell edge throughput loss of victim system in some coexistence scenarios also can not meet the coexistence requirement; meanwhile in band blocking of RF receiver of AAS is evaluated in some different coexistence scenarios where vertical cell splitting is implemented.Inspired by the classical waterfilling algorithm, we verfied the necessity of adaptive power allocation between inner cell and outer cell and then we investigated the coexistence performance when the different power allocation shcemes are adopted in AAS. First of all, considering the adaptive power allocation factor, we reformulated a more general ACLR model that is suitable for AAS supporting vertical cell splitting. By the system level simulation and evaluation, we also find that partial correlation level of outer band signals in the transmitter array of AAS has quite little impact on the the adjacent interference generated by AAS supporting vertical cell splitting function, even different power allocation schemes are implementd. With the increament of transmission power of inner cell, adjacent channel interference generated by AAS is increasing, but the degree is quite small and can be negligible.As the different coexistence scenarioas are required for AAS, the different RF parameters should be satisfied. Based on our research and evaluation analyses in different networking scenarios, we submitted several proposals to3GPP RAN4through the enterprise.