MIMO precoding enabling spatial multiplexing, power allocation and adaptive modulation and coding
AssigneeFreescale Semiconductor, Inc.
InventorsJayesh H. Kotecha, Kaibin Huang
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Abstract
In a closed-loop wireless communication system, a codebook-based feedback mechanism is provided to enable non-unitary precoding for multi-stream transmission, where in each stream is optimized with suitable transmission power allocation and AMC. The codebook-based feedback mechanism uses a precoding codebook having a power allocation matrix which is constrained to specify that beamforming always applies full power to a predetermined beam. With this constraint, a one-bit power allocation feedback index may be used to switch between beamforming and spatial multiplexing.
Claims18
A method for precoding signals in a multiple input multiple output (MIMO) communication system, comprising:
- estimating channel state information for a transmission channel from a transmitting device to a first receiving device by receiving one or more signals;
- generating precoding information for the transmission channel by identifying a first precoding profile from a first codebook that corresponds to the channel state information, where the first codebook comprises a plurality of codewords, where each codeword comprises:
- a unitary precoding matrix portion, and
- a diagonal power control matrix portion to provide power control values for a plurality of streams, where a first power control value for beamforming specifies that full power is always applied to a predetermined one of the streams such that the unitary precoding matrix chosen for beamforming aligns the predetermined one of the streams to a dominant spatial channel of the plurality of streams, and where a second power control value for spatial multiplexing specifies that equal power is applied to each of the plurality of streams;
- and
- quantizing the precoding information corresponding to the first precoding profile into a precoding index.
A receiver for precoding signals in a multiple input multiple output (MIMO) communication system, comprising:
- a precoding module for generating a transmission profile for a transmission channel by:
- identifying a first precoding value for a unitary precoding matrix that corresponds to estimated channel state information for the transmission channel;
- quantizing the first precoding value into a precoding index;
- computing a channel quality indicator (CQI) value for at least a first spatial stream based on the estimated channel state information;
- encoding the CQI value into an encoded cqi value to indicate whether the first spatial stream is turned on or off and to indicate the cqi value for the first spatial stream if the first spatial stream is turned on;
- and
- an antenna array for sending the precoding index and the encoded cqi value over a feedback channel to a transmitter for use in generating the transmission profile, where the encoded cqi value is used to control transmission over the transmission channel from the transmitter to the receiver.
A method for generating a transmission profile for a multiple input multiple output (MIMO) transmission channel, comprising
- quantizing a first precoding value from a precoder matrix that corresponds to estimated channel state information for the transmission channel, thereby forming a precoder index;
- encoding a feedback value into an encoded feedback value to indicate a number of spatial streams to be used during transmission of a data signal sent over the transmission channel, where the feedback value comprises a power control value or a channel quality indicator value;
- and
- sending the precoder index and the encoded feedback value over a feedback channel to a transmitter for use in controlling transmission over the transmission channel from the transmitter to a receiver by specifying the number of spatial streams to be used during transmission.
Dependencies are inferred from the claim text.