Method for estimating the bit error rate in a radio receiver and corresponding radio receiver
View Patent ↗In a radio receiver, an equalizer generates reliability information in the form of soft decision information indicating probabilities that a data symbol received by the radio receiver is based on a specific transmitted value. A bit error rate estimator obtains bit error rate information regarding the bit error rate of the received signal, corresponding to the received data symbols, by evaluating the reliability information.
1. A method for estimating the bit error rate in a radio receiver, which comprises:
with an equalizer in a radio receiver, generating reliability information indicating probabilities that a data symbol received by the radio receiver via a radio channel is based on a specific transmitted value;
generating the reliability information as soft decision information;
with a bit error rate estimator, evaluating the reliability information to obtain bit error rate information regarding a bit error rate of a received signal corresponding to received data symbols; and
quantizing the soft decision information into K quantization levels, determining a symbol error rate information item for a corresponding quantization level of each quantized soft decision information item, and dependent thereon, calculating the bit error rate information p for a complete burst in accordance with a formula:
p
=
∑
k
=
0
K
-
1
(
n
k
p
k
)
∑
k
=
0
K
-
1
n
k
where K denotes a number of the quantization levels, n k denotes a number of estimated symbols in a quantization level k, and p k denotes a symbol error rate of the quantization level k.
2. The method according to claim 1 , which comprises: calculating the symbol error rate p k of the quantization level k from quantized soft decision information q k of the quantization level k in accordance with a formula:
p
k
=
1
1
+
exp
(
q
k
)
.
3. The method according to claim 2 , which comprises:
determining the soft decision information q in accordance with a formula:
q
=
ln
P1
P2
where P 1 indicates a probability that a received data symbol is based on a first transmitted value, and P 2 indicates a probability that a received data symbol is based on a second transmitted value;
approximating the probability P 1 by a path metric of a first path of a trellis diagram that describes the radio channel, the first path being a path of the trellis diagram that has a first transmitted value with a best path metric at a specific instant; and
approximating the probability P 2 by a path metric of a second path of the trellis diagram, the second path being a path of the trellis diagram that has a second transmitted value with a best path metric at the specific instant.
4. The method according to claim 1 , which comprises:
determining the soft decision information q in accordance with a formula:
q
=
ln
P1
P2
where P 1 indicates a probability that a received data symbol is based on a first transmitted value, and P 2 indicates a probability that a received data symbol is based on a second transmitted value;
approximating the probability P 1 by a path metric of a first path of a trellis diagram that describes the radio channel, the first path being a path of the trellis diagram that has a first transmitted value with a best path metric at a specific instant; and
approximating the probability P 2 by a path metric of a second path of the trellis diagram, the second path being a path of the trellis diagram that has a second transmitted value with a best path metric at the specific instant.
5. The method according to claim 4 , which comprises:
approximating ln(P 1 ) by MOP/2σ 2 and approximating ln(P 2 ) by MZP/2σ 2 , where MOP denotes the path metric of the first path of the trellis diagram and MZP denotes the path metric of the second path of the trellis diagram, and σ 2 denotes a noise power that is superposed on the received signal along the radio channel.
6. The method according to claim 5 , which comprises:
approximating the soft decision information q using a formula:
q
=
C
MOP
-
MZP
2
σ
2
where C represents a scaling constant; and
subsequently quantizing the soft decision information q into the K quantization levels.
7. A radio receiver, comprising:
an equalizer for equalizing a radio signal received via a radio channel and for generating reliability information indicating probabilities that a received data symbol is based on a specific transmitted value; and
a bit error rate estimator for evaluating the reliability information supplied by said equalizer to obtain bit error rate information p regarding a bit error rate of a received signal corresponding to received data symbols;
said equalizer generating the reliability information as soft decision information; and
said bit error rate estimator quantizing the soft decision information into a plurality of quantization levels, determining a symbol error rate information item for a corresponding quantization level from each quantized soft decision information item, and in a manner dependent thereon, calculating the bit error rate information p for a complete burst in accordance with a formula:
p
=
∑
k
=
0
K
-
1
n
k
p
k
∑
k
=
0
K
-
1
n
k
where K denotes a number of the quantization levels, n k denotes a number of estimated symbols in a quantization level k, and p k denotes a symbol error rate of the quantization level k.
8. The radio receiver according to claim 7 , comprising:
a deinterleaver;
said bit error rate estimator connected between said equalizer and said deinterleaver.
9. The radio receiver according to claim 7 , wherein said bit error rate estimator is configured for:
calculating the symbol error rate p k of the quantization level k from quantized soft decision information q k of the quantization level k in accordance with a formula:
p
k
=
1
1
+
exp
(
q
k
)
.
10. The radio receiver according to claim 7 , wherein said bit error rate estimator is configured for:
determining the soft decision information q in accordance with a formula:
q
=
ln
P1
P2
where P 1 indicates a probability that a received data symbol is based on a first transmitted value, and P 2 indicates a probability that a received data symbol is based on a second transmitted value;
approximating the probability P 1 by a path metric of a first path of a trellis diagram that describes the radio channel, the first path being a path of the trellis diagram that has a first transmitted value with a best path metric at a specific instant; and
approximating the probability P 2 by a path metric of a second path of the trellis diagram, the second path being a path of the trellis diagram that has a second transmitted value with a best path metric at the specific instant.
11. The radio receiver according to claim 7 , wherein said bit error rate estimator is configured for:
approximating ln(P 1 ) by MOP/2σ 2 and approximating ln(P 2 ) by MZP/2σ 2 , where MOP denotes the path metric of the first path of the trellis diagram and MZP denotes the path metric of the second path of the trellis diagram, and σ 2 denotes a noise power that is superposed on the received signal along the radio channel.
12. The radio receiver according to claim 7 , wherein said bit error rate estimator is configured for:
approximating the soft decision information q using a formula:
q
=
C
MOP
-
MZP
2
σ
2
where C represents a scaling constant; and
subsequently quantizing the soft decision information q into the K quantization levels.