Low complexity link adaptatation for LTE/LTE-A uplink with a turbo receiver
View Patent ↗An inventive method for link adaptation for an LTE/LTE-A uplink with a turbo SIC receiver includes the steps of determining a precoding matrix index PMI and rank index RI selection for an LTE/LTE-A uplink when precoding of the uplink is enabled, responsive to channel state information of a subcarrier in the uplink; determining a decoding order for codewords in the uplink i) when the precoding of the uplink is not enabled and ii) if needed when the precoding of the uplink is enabled; performing modulation and coding scheme MCS assignment for the uplink based on a hard decision successive interference cancellation SIC rule (without intra-CW cancellation) or a partial hard decision successive interference cancellation SIC rule (with intra-CW cancellation), responsive to the determined PMI and RI selection; and influencing data transmission in the uplink responsive to the MCS assignment for detection by a turbo SIC receiver.
1. A method for link adaptation for an LTE/LTE-A uplink with a turbo SIC receiver, said method comprising the steps of:
determining a precoding matrix index PMI and rank index RI selection for an LTE/LTE-A uplink when precoding of said uplink is enabled, responsive to channel state information of a subcarrier in said uplink;
determining a decoding order for codewords in said uplink i) when said precoding of said uplink is not enabled and ii) if needed when said precoding of said uplink is enabled;
performing modulation and coding scheme MCS assignment for said uplink based on a hard decision successive interference cancellation SIC rule without intra-codeword CW cancelation or a partial hard decision SIC rule with intra-CW cancellation, responsive to said determined PMI and RI selection; and
influencing data transmission in said uplink for detection by a turbo successive interference cancellation SIC receiver, responsive to said MCS assignment.
2. The method of claim 1 , wherein said determining a PMI and RI selection comprises a per-layer signal-to-noise-interference-ratio SINR determination for finding a PMI for each respective rank of said RI.
3. The method of claim 1 , wherein said performing MCS assignment on said uplink comprising determining a linear minimum mean-square error LMMSE for a first decoded codeword in said uplink influencing said MCS for said first decoded codeword and determining a secondary user SINR for a second decoded codeword in said uplink for influencing said MCS for said second decoded codeword.
4. The method of claim 1 , wherein said rank index RI is optimized according to
RI
=
arg
max
R
∈
[
1
,
…
,
R
max
]
v
(
R
)
,
where R is a given rank, ν(R) is a weighted sum metric assuming sub-band PMIs and R max denotes a maximum supported rank.
5. The method of claim 4 , wherein said weighted sum metric comprises
v
(
R
)
=
∑
r
=
1
R
φ
(
r
)
log
2
(
1
+
SINR
(
r
)
)
,
where SINR (r) is a post-discrete Fourier transform DFT SINR of an r-th layer and φ(r) denotes a layer-dependent weighting factor.
6. The method of claim 1 , wherein for a wideband said precoding a wideband precoding matrix index PMI for R-layer transmission comprises
PMI
=
arg
max
q
∈
[
1
,
…
,
Q
]
∑
r
=
1
R
φ
(
r
)
log
2
(
1
+
SINR
q
(
r
)
)
,
where R is a given rank, SINR q (r) denotes a wideband post-DFT SINR for an r-th layer upon selecting a q-th precoding matrix, and φ(r) denotes a layer-dependent weighting factor.
7. The method of claim 1 , wherein said step of determining a PMI and RI selection comprises obtaining a per codeword SINR, for a rank R=2 (2-layer) transmission per codeword SINR being a per layer SINR because of a on-to-one codeword-to-layer mapping relationship and for a rank R>2, per codeword SINR being obtainable based on a codeword-to-layer mapping relationship.
8. The method of claim 1 , wherein said step of performing modulation and coding scheme MCS assignment for said uplink comprises choosing for a first decoded codeword in said uplink a largest MCS index i* that a minimum mean square MMSE SINR can support and choosing for a second decoded codeword in said uplink a largest MCS index j* that SU SINR can support.
9. The method of claim 8 , wherein said step of performing modulation and coding scheme MCS assignment comprises determining a linear minimum square error LMMSE SINR for a first decoded codeword in said uplink and determining a single user SU SINR for a second decoded codeword in said uplink.
10. The method of claim 8 , wherein said largest MCS index i* is given by i*=max i s.t. γ mmse (1) ≧SINR thr1 (i); and said largest MCS index j* is given by j*=max s.t. γ su (2) ≧SINR thr2 (j); where SINR thr1 and SINR thr2 are respectively SINR threshold vectors for said first decoded codeword and said second decoded codeword respective MCS assignments.
11. The method of claim 8 , said step of performing modulation and coding scheme MCS assignment for said uplink comprises obtaining two SINR threshold vectors for said MCS assignment with one SINR threshold vector being a minimum SINR level that ensures a target BLER=0.1 for said MCS with a first index and another SINR threshold vector denoting an SINR value at a transition point such that said MCS with said first index maximizing effective throughput for all SINRs in a predetermined range.
12. A method for link adaptation for an LTE/LTE-A uplink with a turbo SIC receiver, said method comprising the steps of:
i) determining a precoding matrix index PMI and rank index RI selection for an LTE/LTE-A uplink when precoding of said uplink is enabled, responsive to channel state information of a subcarrier in said uplink, said PMI and RI being determinable for both sub-band precoding and wideband precoding with codeword decoding being jointly determinable with PMI and RI selection;
ii) determining a decoding order for codewords in said uplink a) when said precoding of said uplink is not enabled and b) if needed when said precoding of said uplink is enabled, responsive to step i), said decoding order being one of enforced from an upper layer by a scheduler or determined on-the-fly, in case of a proportional fairness said scheduler an ordering being to set said decoding order as a reverse order of weights of said proportional fairness or said decoding order being jointly determined with said determining of said PMI and rank selection;
iii) selecting modulation and coding scheme MCS indices on said uplink according to a hard decision successive interference cancellation signal-to-interference-noise-ratio SIC SINR or a partial hard decision SIC SINR, responsive to step ii), for a codeword in said uplink decoded first, said MCS being assigned according to its minimum mean square error MMSE-SINR and for a codeword decoded second, said MCS being assigned according to its single-user SINR; and
iv) conveying said MCS indices to scheduling at a base station of said uplink for being applied to data transmission in said uplink.