Optimum training sequences for wireless systems
View Patent ↗In various embodiments, techniques are provided to determine channel characteristics of various communication systems such as OFDM systems or systems using a plurality of transmit antennas by using various sets of training symbols that produce zero cross-correlation energy. Channel communication can accordingly be simplified as the zero cross-correlation property allows for channel estimation without a matrix inversion.
1. An apparatus for communicating, comprising:
a first transmit device that transmits a set of first training symbols; and
a second transmit device that transmits a set of second training symbols;
wherein a cross-correlation estimate between the set of first training symbols and the set of second training symbols is essentially zero, whereby a channel estimation is achieved without performing a matrix inversion;
wherein the set of second training symbols is substantially identical to the set of first training symbols with a phase shift;
wherein the set of second training symbols is related to the set of first training symbols according to:
t 2 [n,k]=t 1 [n,k]W K −kl o ,
where t 1 [n, K] is the set of first training symbols, t 2 [n, k] is the set of second training symbols and
W
K
-
k
l
o
=
exp
(
-
j
2
π
k
l
0
K
)
,
where n is an Orthogonal Frequency Division Multiplexing (OFDM) block, k is an OFDM sub-band, K is a total number of OFDM sub-bands and l o is a reference frequency.
2. An apparatus for communicating, comprising:
a receive device that receives at least a set of first training symbols transmitted by a first transmit device and a set of second training symbols transmitted by a second transmit device; and
an estimator that estimates at least a first channel related to the first transmit device based on at least the set of first training symbols;
wherein a cross-correlation estimate between the set of first training symbols and the set of second training symbols is essentially zero, whereby a channel estimation is achieved without performing a matrix inversion;
wherein the estimator further estimates the first channel based on at least the set of second training symbols;
wherein the estimator estimates the first channel without using a matrix inversion;
wherein the set of second training symbols is substantially identical to the set of first training symbols with a phase shift;
wherein the set of second training symbols is related to the set of first training symbols according to:
t 2 [n,k]=t 1 [n,k]W K −kl o ,
where t 1 [n, k] is the set of first training symbols, t 2 [n, k] is the set of second training symbols and
W
K
-
k
l
o
=
exp
(
-
j
2
π
k
l
0
K
)
,
where n is an Orthogonal Frequency Division Multiplexing (OFDM) block, k is an OFOM sub-band, K is a total number of OFDM sub-bands and l o is a reference frequency.