Method and apparatus for efficient determination of channel estimate and baud frequency offset estimate
View Patent ↗A method and apparatus for obtaining a channel estimate and a baud frequency offset estimate for a communications channel in a communications system. The communications system has a transmitter for transmitting to a receiver over the communications channel signals representing data appended to a preamble signal. The preamble signal is provided as a periodic plurality of preamble sequences, each preamble sequence being generated in accordance with: 1 32 ∑ k = 0 15 b k b mod ( k + n , 16 ) * = { 1 , n = 0 0 , n ≠ 0 . A signal representing the periodic plurality of preamble sequences is sent by a transmitter over the communications channel to a receiver and is received at the receiver as a received signal. The received signal is processed to determine from the received signal both a channel estimate in accordance with: h ^ = 1 64 B H ( y 1 + y 2 ) , wherein B represents a matrix of preamble symbol values, upsampled by four and zero-filled, and y 1 and y 2 are column vectors of received samples, and a baud frequency offset estimate Δf b in accordance with: S = ∑ k = 0 63 y k y k + 64 * Δ f b ≅ real ( S ) · f b imag ( S ) · f c · 32 π , wherein f b is a baud frequency and f c is a center frequency of the transmission signal.
1. A single-carrier propagated signal comprising:
a preamble segment having a periodic plurality of preamble sequences, each preamble sequence containing 16 b symbols generated in accordance with:
1
32
∑
k
=
0
15
b
k
b
mod
(
k
+
n
,
16
)
*
=
{
1
,
n
=
0
0
,
n
≠
0
;
the 16 b symbols belonging to a 4-quadrature amplitude modulation constellation, a quadrature phase shift keying modulation constellation, or a carrierless amplitude modulation/phase modulation constellation; and
a data segment appended to the preamble,
the single-carrier propagated signal being transmittable from a transmitter to a receiver over a communications channel.
2. The propagated signal of claim 1 , wherein the preamble segment has a three preamble sequence of periodic plurality of preamble sequences.
3. The propagated signal of claim 1 , wherein the preamble segment has a four preamble sequence of periodic plurality of preamble sequences.
4. The propagated signal of claim 1 , wherein the communications channel is a telephone line.
5. The propagated signal of claim 1 , wherein the communications channel is an alternating current power line.