2 research outputs found
Learning-Based Adaptive Transmission for Limited Feedback Multiuser MIMO-OFDM
Performing link adaptation in a multiantenna and multiuser system is
challenging because of the coupling between precoding, user selection, spatial
mode selection and use of limited feedback about the channel. The problem is
exacerbated by the difficulty of selecting the proper modulation and coding
scheme when using orthogonal frequency division multiplexing (OFDM). This paper
presents a data-driven approach to link adaptation for multiuser multiple input
mulitple output (MIMO) OFDM systems. A machine learning classifier is used to
select the modulation and coding scheme, taking as input the SNR values in the
different subcarriers and spatial streams. A new approximation is developed to
estimate the unknown interuser interference due to the use of limited feedback.
This approximation allows to obtain SNR information at the transmitter with a
minimum communication overhead. A greedy algorithm is used to perform spatial
mode and user selection with affordable complexity, without resorting to an
exhaustive search. The proposed adaptation is studied in the context of the
IEEE 802.11ac standard, and is shown to schedule users and adjust the
transmission parameters to the channel conditions as well as to the rate of the
feedback channel
Practical Link Adaptation Algorithm with Power Density Offsets for 5G Uplink Channels
This letter proposes a pragmatic link adaptation algorithm considering power
density offsets (PDOs) for next-generation uplink wireless channels. The
proposed algorithm consists of PDO calculation between a physical uplink shared
channel and its associated sounding reference signal, key channel state metric
generation, and modulation and coding scheme (MCS) adaptation with respect to
the PDO. Scaling is applied to estimated channel matrices based on multiple
reference PDO points to generate corresponding reference mutual information
(MI) values, followed by interpolation or extrapolation to obtain the adapted
MI and ultimately MCS. The proposed algorithm has low complexity in terms of
hardware implementation, while yielding satisfactory block error rates and
throughput for a wide range of PDOs as shown by simulation results.Comment: 5 pages, 4 figure