Method operable to determine a signal to noise ratio gap between selection combining and maximal ratio combining for an arbitrary number of diversity branches
The present invention provides a method of quantifying a signal to noise ratio (SNR) gap between diversity combining schemes that are operable to process multi-path wireless communications for an arbitrary number of diversity branches. The method determines the gap in a without the need to determine or know the SNR for each individual diversity combining scheme. This involves determining the number of diversity branches associated with the multi-path wireless communication and the receiver used to process the multi-path wireless communication. The SNR gap may then be expressed as the term 10log 10 L!/L where L is the number of diversity branches.
1 . A method for quantifying a signal to noise ratio (SNR) gap for an arbitrary number of diversity branches between at least two diversity combining schemes that are operable to process a multipath wireless communication, the method comprising:
determining a number of diversity branches, L, associated with the multipath wireless communication;
determining a first diversity combining scheme SNR associated with the number of diversity branches;
determining a second diversity combining scheme SNR associated with the number of diversity branches; and
quantifying a difference between the first diversity combining scheme SNR and second diversity combining scheme SNR.
2 . The method of claim 1 , wherein:
the first diversity combining scheme comprises selection combining (SC); and
the second diversity combining scheme comprises maximal ratio combining (MRC).
3 . The method of claim 2 , wherein:
an MRC bit error rate (BER)
BER
(
Pe
mrc
)
≈
(
2
L
-
1
L
)
(
1
4
c
)
L
;
and
an
SC
BER
(
Pe
sc
)
≈
(
2
L
-
1
)
!!
2
L
+
1
c
L
,
wherein
c
=
1
Γ
,
and Γ is an average SNR per diversity branch.
4 . The method of claim 3 , wherein the difference between the first diversity combining scheme SNR and second diversity combining scheme SNR for the number of diversity branches is about
10
L
log
10
L
!
.
5 . The method of claim 4 , wherein the multipath wireless communication conforms to a wireless communication standard or variant of the wireless communication standard selected from the group consisting of:
Code Division Multiple Access (CDMA);
Global System for Mobile communications (GSM);
Time Division Multiple Access (TDMA); and
Orthogonal Frequency Division Multiplexing (OFDM).
6 . The method of claim 1 , further comprising:
determining an actual SNR associated with the multipath wireless communication, and wherein a given BER is a maximum BER operable to support wireless communications;
comparing the actual SNR with the first diversity combining scheme SNR associated with the given BER;
comparing the actual SNR with the second diversity combining scheme SNR associated with the given BER;
selecting the first diversity combining scheme to process the multipath wireless communication when the first diversity combining scheme SNR compares favorable to the actual SNR; and
selecting the second diversity combining scheme to process the multipath communication when the first diversity combining scheme SNR compares unfavorable to the actual SNR.
7 . A method of selecting a diversity combining scheme used to process a multipath communication, comprising:
determining an acceptable bit error rate (BER);
determining a signal to noise ratio (SNR) associated with the multipath communication;
determining a number of diversity branches, L, associated with the multipath communication;
determining a first diversity combining scheme BER, wherein the first diversity combining scheme BER is a function of an inverse of the SNR to an L th order;
determining a second diversity combining scheme BER, wherein the second diversity combining scheme BER is a function of an inverse of the SNR to an L th order;
comparing the acceptable BER to the first diversity combining scheme BER and second diversity combining scheme BER;
selecting the first diversity combining scheme to process the multipath communication when the first diversity combining scheme BER compares favorable to the acceptable BER; and
selecting the second diversity combining scheme to process the multipath communication when the first diversity combining scheme BER compares unfavorable to the acceptable BER.
8 . The method of claim 7 , wherein:
the first diversity combining scheme comprises selection combining (SC); and
the second diversity combining scheme comprises maximal ratio combining (MRC).
9 . The method of claim 8 , wherein:
the
MRC
BER
(
Pe
mrc
)
≈
(
2
L
-
1
L
)
(
1
4
c
)
L
;
and
the
SC
BER
(
Pe
sc
)
≈
(
2
L
-
1
)
!!
2
L
+
1
c
L
,
wherein
c
=
1
Γ
,
and Γ is an average SNR per diversity branch.
10 . The method of claim 9 , wherein the difference between the first diversity combining scheme SNR and second diversity combining scheme SNR for the given BER is about
10
L
log
10
L
!
.
11 . The method of claim 4 , wherein the multipath wireless communication conforms to a wireless communication standard or variant of the wireless communication standard selected from the group consisting of:
Code Division Multiple Access (CDMA);
Global System for Mobile communications (GSM);
Time Division Multiple Access (TDMA); and
Orthogonal Frequency Division Multiplexing (OFDM).
12 . A method of processing a multipath wireless communication, comprising:
receiving the multipath wireless communication, wherein a number of diversity branches, L, are associated with the received multipath wireless communication;
determining a signal to noise ratio (SNR) associated with the received multipath wireless communication;
determining a first diversity combining scheme BER, wherein the first diversity combining scheme BER is a function of an inverse of the SNR to an L th order;
determining a second diversity combining scheme BER, wherein the second diversity combining scheme BER is a function of an inverse of the SNR to an L th order;
comparing an acceptable BER to the first diversity combining scheme BER and second diversity combining scheme BER;
selecting the first diversity combining scheme to process the multipath communication when the first diversity combining scheme BER compares favorable to the acceptable BER;
selecting the second diversity combining scheme to process the multipath communication when the first diversity combining scheme BER compares unfavorable to the acceptable BER;
applying the selected diversity combining scheme to the received multipath communication to produce a combined signal;
down converting the combined signal to produce a baseband signal; and
processing the baseband signal to produce a data block.
13 . The method of claim 12 , wherein:
the first diversity scheme comprises selection combining (SC); and
the second diversity scheme comprises maximal ratio combining (MRC).
14 . The method of claim 13 , wherein:
the
MRC
BER
(
Pe
mrc
)
≈
(
2
L
-
1
L
)
(
1
4
c
)
L
;
and
the
SC
BER
(
Pe
sc
)
≈
(
2
L
-
1
)
!!
2
L
+
1
c
L
,
wherein
c
=
1
Γ
,
and Γ is an average SNR per diversity branch.
15 . The method of claim 14 , wherein the difference between the first diversity scheme SNR and second diversity scheme SNR for the given BER is about
10
L
log
10
L
!
.
16 . The method of claim 15 , wherein the multipath wireless communication conforms to a wireless communication standard or variant of the wireless communication standard selected from the group consisting of:
Code Division Multiple Access (CDMA);
Global System for Mobile communications (GSM);
Time Division Multiple Access (TDMA); and
Orthogonal Frequency Division Multiplexing (OFDM).
17 . A wireless terminal operable to select a diversity combining scheme to process a received multipath communication, comprising:
a Radio Frequency (RF) front end, wherein, the RF front end is operable to:
determine a signal to noise ratio (SNR) associated with the multipath communication;
determine a number of diversity branches, L, associated with the multipath communication;
determine a first diversity scheme BER, wherein the first diversity scheme BER is a function of an inverse of the SNR to an L th order;
determine a second diversity scheme BER, wherein the second diversity scheme BER is a function of an inverse of the SNR to an L th order;
compare a required BER to the first diversity scheme BER and second diversity scheme BER;
select the first diversity scheme to process the multipath communication when the first diversity scheme BER compares favorable to the required BER;
select the second diversity scheme to process the multipath communication when the first diversity scheme BER compares unfavorable to the required BER;
apply the selected diversity combining scheme to the multipath communication to produce a combined signal;
down convert the combined signal to produce a baseband signal; and
a baseband processor communicatively coupled to the RF front end, wherein the baseband processor is operable to process the baseband signal to produce a data block.
18 . The wireless terminal of claim 17 , wherein the RF front end further comprises a rake receiver, and wherein the number of diversity branches, L, is determined by a number of fingers within the rake receiver.
19 . The wireless terminal of claim 17 , wherein the first diversity scheme BER compares favorably to the required BER corresponds to the first diversity scheme BER not exceeding a threshold BER value, and wherein the first diversity scheme BER compares unfavorably to the required BER corresponds to the first diversity scheme BER exceeding a threshold BER value.
20 . The wireless terminal of claim 19 , wherein the threshold BER value is based on a Coding Scheme of the multipath communication.
21 . The wireless terminal of claim 20 , wherein:
the first diversity scheme comprises selection combining (SC); and
the second diversity scheme comprises maximal ratio combining (MRC).
22 . The wireless terminal of claim 21 , wherein:
the
MRC
BER
(
Pe
mrc
)
≈
(
2
L
-
1
L
)
(
1
4
c
)
L
;
and the
SC
BER
(
Pe
sc
)
≈
(
2
L
-
1
)
!!
2
L
+
1
c
L
,
wherein
c
=
1
Γ
,
and Γ is an average SNR per diversity branch.
23 . The wireless terminal of claim 22 , wherein the difference between the first diversity scheme SNR and second diversity scheme SNR for the given BER is about
10
L
log
10
L
!
.
24 . The wireless terminal of claim 23 , wherein the multipath wireless communication conforms to a wireless communication standard or variant of the wireless communication standard selected from the group consisting of:
Code Division Multiple Access (CDMA);
Global System for Mobile communications (GSM);
Time Division Multiple Access (TDMA); and
Orthogonal Frequency Division Multiplexing (OFDM).