Adaptive modulation and coding (AMC):
On the downlink, to optimize system capacity and coverage, eNodeB will try to match the information data rate for each user to the variations of its received signal quality. UE can be configured to report CQIs (Channel Quality Indicator), RI (Rank Indicator) and PMI to assist eNodeB in selecting an appropriate transmission parameters such as MCS index, number of MIMO ranks and pre-coding parameter for the downlink transmissions. On the uplink, eNodeB can dynamically choose MCS value to send in the DCI (Downlink control information), to specify uplink MCS to be used by the UE, according to CQI values that UE reports. ·
Rank and MIMO scheme adaption:
Rank adaption modifies the Tx layers based on UE feedback. MIMO scheme selection takes measurement statistics for PUCCH evaluated at eNB so that to select an appropriate MIMO scheme.
- Tx Diversity and 2×2 SU-MIMO transimission schemes, are dynamically updated per UE according to the channel conditions an UE experienced.
- Close loop MIMO is selected for low speed users, while for high speed users Tx diversity or OL MIMO is selected depend on UE feedback, e.g. CQIs.
Frequency hopping:
Type 1 (inter-TTI) or type 2 (Intra/Inter-TTI) frequency hopping in LR3.0. Frequency hopping is useful to combat frequency selective fading and minimize inter-cell interference.
TTI bundling:
For VoIP or other read time traffic, TTI bundling can be used to improve cell edge performance.
SIC:
A successive interference cancellation (SIC) receiver can detect and decode the CWs of the data streams in such a way that if the CW of one data stream is successfully decoded (indicated by a cyclic redundancy check (CRC) code), the decoded data is then reencoded, remodulated, etc., and cancelled from the originally received signal. Thus, interference is reduced for the remaining data streams.
