By applying Algorithm 1, the values of the channel indicators are determined and hence for notation simplicity, single user notation can be used.
In the uplink, Channel Quality Indicator (CQI), Precoding Matrix Indicator (PMI), and Rank Indicator (RI) are signalled, which together form the Channel State Information (CSI) feedback.
In LTE-A, the channel quality indicator (CQI) index is defined in terms of a channel coding rate and modulation schemes such as quadrature phase shift keying (QPSK), 16 quadrature amplitude modulation (QAM), and 64QAM [20].
In LTE system, there is a loop for the adaptive modulation and coding (AMC) scheme in DL transmission, which requires UE feedback of the channel quality indicator (CQI) index.
In the second part of this work, we consider the non-homogeneous multiuser system with limited and quantized channel quality indicator (CQI) and channel direction indicator (CDI) feedbacks.
In the second part of this work, we examine the MMSE precoding design for the system with limited and quantized channel quality indicator (CQI) and channel direction indicator (CDI) feedbacks.
Users calculate the optimal inner precoding matrix index (PMI1), the optimal outer precoding matrix index (PMI2), the optimal pairing cluster index (CI), and channel quality indicator (CQI) according to downlink channel estimation results and feed these values back to the BS, and then the BS uses feedback values to implement user pairing and scheduling.
The effective SINR is then quantised into a channel quality indicator (CQI) value, indicative of the highest modulation and code rate the base station may use while keeping a packet error rate (PER) below a target of 10%% as shown in Table 1 [17].
These CSI reports include a channel quality indicator (CQI) and a precoding matrix indicator (PMI), while the PMI reports belong to predefined codebooks.
This feedback includes a channel quality indicator (CQI) and optionally a precoding matrix indicator (PMI).
