Per-user unitary rate control (PU2RC) is a multi-user MIMO (multiple-input and multiple-output) scheme.
Recently, PU2RC has been adopted in the IEEE 802.16m system description documentation (SDD) and the concept of this scheme was included in 3GPP LTE standard.
Per-user unitary rate control (PU2RC) is a practical multi-user MIMO solution.
PU2RC allows a base station to transmit different data streams to multiple users simultaneously.
Transmission data are multiplied by a pre-coding matrix selected from the set of predefined matrices before transmission.
The selection of a pre-coding matrix is determined based on the information provided by users.
The selection of both target users and a pre-coding matrix according to the information provided by mobiles enables the utilization of multi-user diversity and data multiplexing at the same time.
Moreover, using predefined precoding matrices reduces feedback overhead from users to the base station.
The operation of PU2RC is mathematically described for the transmitter and receiver sides, respectively.
based on the received finite channel status information, which is delivered to the base station from the user equipment (UE) through uplink feedback signaling.
The feedback signal consists of index in a look-up table of a precoding codebook.
The figure illustrates the throughput advantage of PU2RC over the conventional single-user and no scheduling scheme, assuming that the codebook size is one, i.e.,
Because of codebook-based multi-user scheduling, PU2RC outperforms the conventional single-user and no scheduling scheme when the number of users is larger than one.
Note that the performance plotted in the figure for the two systems were obtained assuming linear receiver.