Latency reducing techniques for control channel decoding
Introduced here are techniques for reducing the latency at a terminal device. In particular, for reducing the latency of detecting the downlink control information (DCI) in a downlink signal such as the physical downlink control channel (PDCCH) signal. The techniques include determining a probability of each aggregation level of the control channel elements (CCE) in a signal carrying the DCI. The probability can be based on the packet error rate (PER) of the signal. The PER can vary based on factors such as the signal to noise ratio (SNR) and/or the fading measurements. Further, the probability can depend on the reception history of the terminal device. Based on these factors, the terminal device can decode the CCEs in an order indicative of the probability of the corresponding aggregation levels carrying the DCI.
1 . A method for reducing latency, comprising:
receiving, at a terminal, a physical downlink control channel (PDCCH) signal, the PDCCH signal comprising a plurality of groups of control channel elements (CCEs),
wherein each group of CCEs is associated with an aggregation level (AL) of a plurality of aggregation levels;
determining, by the terminal, based on a packet error rate (PER), a probability of downlink control information (DCI) being present at each aggregation level of the plurality of aggregation levels; and
decoding, by the terminal, the groups of CCEs in an order, wherein the order is based on the probability of the DCI being present at each aggregation level,
wherein the PER is based on any of the signal to noise ratio (SNR) of the PDCCH signal, a fading measurement of the PDCCH signal, or any combination thereof.
2 . The method of claim 1 , wherein the PER and the SNR are inversely related, and wherein the PER and the fading measurement are directly related.
3 . The method of claim 1 , wherein the fading measurement is based on any of a delay caused by Doppler shift, frequency selectivity, or any combination thereof.
4 . The method of claim 1 , wherein the probability is further based on a reception history of the terminal; wherein the reception history is indicative of an aggregation level of previously received DCI.
5 . The method of claim 1 , wherein the order is from a highest probability to a lowest probability.
6 . The method of claim 1 , wherein one or more CCEs are associated with the same aggregation level, the method further comprising:
decoding the one or more CCEs based on a sequence in which the one or more CCEs were received by the terminal.
7 . The method of claim 1 , wherein the aggregation level is indicative of a number of CCEs used to transmit the DCI.
8 . The method of claim 1 , wherein the terminal is operating in Long Term Evolution (LTE) technology, and wherein decoding the plurality of CCEs further comprising:
applying Viterbi decoding algorithms.
9 . The method of claim 1 , wherein the terminal is operating New Radio (NR) technology, and wherein decoding the plurality of CCEs further comprising:
applying Polar decoding algorithms.
10 . The method of claim 1 , further comprising:
in response to decoding a given CCE including the DCI, determining whether the DCI is valid based on results of an error check.
11 . The method of claim 10 , wherein performing the error check comprises:
performing a cyclic redundancy check (CRC) to detect changes in the DCI.
12 . The method of claim 10 , further comprising:
in response to determining that the DCI is not valid, discarding the DCI and decoding remaining CCEs of the plurality of CCEs or decoding the given CCE with a different aggregation level.
13 . A method for reducing latency, comprising:
transmitting, by a network node, a physical downlink control channel (PDCCH) signal, the PDCCH signal comprising a plurality of groups of control channel elements (CCEs),
wherein each group of CCEs is associated with an aggregation level (AL) of a plurality of aggregation levels;
causing, by the network node, based on a packet error rate (PER), determination of a probability of downlink control information (DCI) being present at each aggregation level of the plurality of aggregation levels; and
causing, by the network node, decoding of the groups of CCEs in an order, wherein the order is based on the probability of the DCI being present at each aggregation level,
wherein the PER is based on any of the signal to noise ratio (SNR) of the PDCCH signal, a fading measurement of the PDCCH signal, or any combination thereof.
14 . The method of claim 13 , wherein the probability is further based on a transmission history of the network node.
15 . The method of claim 13 , wherein the order is from a highest probability to a lowest probability.
16 . The method of claim 13 , wherein the PDCCH signal is transmitted to a terminal device.
17 . A system comprising:
a receiver through which to receive, a physical downlink control channel (PDCCH) signal, the PDCCH signal comprising a plurality of groups of control channel elements (CCEs),
wherein each group of CCEs is associated with an aggregation level of a plurality of aggregation levels;
a processor configured to:
determine, based on a packet error rate (PER), a probability of downlink control information (DCI) being present at each aggregation level of the plurality of aggregation levels; and
decode the groups of CCEs in an order, wherein the order is based on the probability of the DCI being present at each aggregation level,
wherein the PER is based on any of the signal to noise ratio (SNR) of the PDCCH signal, a fading measurement of the PDCCH signal, or any combination thereof.
18 . The method of claim 5 , wherein the aggregation level with the highest probability is determined as
a
l
1
=
arg
min
al
(
per
a
l
<=
per
target
)
,
and the order is determined as al 1 , al 1 *2, . . . , max AL, al 1 /2, . . . , 1, where p target is a target PER and per al is the PER of each respective aggregation level of the plurality of aggregation levels.