Dual carrier modulator for a multiband OFDM UWB transceiver
View Patent ↗A Dual Carrier Modulator (DCM) for a Multiband OFDM (Orthogonal Frequency Division Multiplexing) Transceiver of a Ultra Wide Band (UWB) wireless personal access network transmitting OFDM modulated symbols is provided, wherein each OFDM symbol is modulated by a predetermined number of encoded bits. The Dual Carrier Modulator comprises a grouping unit for grouping N CBPS encoded bits of a serial bit stream into bit groups each having a predetermined number of bits. The Dual Carrier Modulator also comprises a mapping unit for mapping each bit group received from said grouping unit to complex symbols using an orthogonal transform. The Dual Carrier Modulator further comprises a reordering unit for reordering the complex symbols mapped by said mapping unit. Each complex symbol is provided to modulate a corresponding data tone of an OFDM symbol.
1. A dual carrier modulator (DCM) for a multiband orthogonal frequency division multiplexing (OFDM) transceiver of an ultra wide band (UWB) wireless network transmitting OFDM modulated symbols, wherein each OFDM symbol is modulated by a first predetermined number (N CBPS ) of encoded bits, said dual carrier modulator comprising:
(a) a grouping unit configured to group the N CBPS encoded bits of a serial bit stream into bit groups each having a second predetermined number (m) of bits;
(b) a mapping unit configured to map each bit group received from said grouping unit to complex symbols (y); and
(c) a reordering unit configured to reorder the complex symbols (y) mapped by said mapping unit, wherein each complex symbol (y) is provided to modulate a corresponding data tone of an OFDM symbol;
wherein the first predetermined number is two hundred (N CBPS =200) and the second predetermined number is four (m =4), such that the grouping unit groups two hundred encoded bits to bit groups each having four bits;
wherein the mapping unit maps bit groups each having four bits respectively to two complex symbols (y n ; y n+NCBPS/4 ) to generate N CBPS /2 complex symbols (y 0 . . . y NCBPS /2) for modulating one N CBPS /2 data tones of an OFDM symbol;
wherein the mapping unit ( 1 - 2 ) comprises:
a first mapping stage for mapping unipolar bit values of the encoded bits within each bit group to bipolar bit values, and
a second mapping stage which provides an orthogonal 2×2 mapping of two complex numbers composed of the 4 bipolar bits into two complex symbols; and
wherein the orthogonal 2×2 mapping is defined by the equation:
(
y
n
y
n
+
50
)
=
1
b
2
+
1
(
1
b
b
-
1
)
(
x
a
(
n
)
j
x
a
(
n
)
+
50
x
a
(
n
)
+
1
j
x
a
(
n
)
+
51
)
wherein
n
=
0
,
1
…
49
a
(
n
)
=
{
2
n
n
=
0
,
1
,
2
,
…
24
2
n
+
50
n
=
25
,
26
,
…
49
wherein b is a constant.
2. The dual carrier modulator of claim 1 , wherein the mapping unit is formed by a look-up-table stored in a memory.
3. The dual Carrier Modulator according to claim 1 , wherein the look-up-table stored in said memory is given as follows:
Input
Output (y)
X 1
X 2
Re (y n )
Re (y n+50 )
1
1
K · (1 + b)
K · 1 + b)
1
0
K · (1 − b)
K · 1 + b)
0
1
K · (−1 + b)
K · (−1 − b)
0
0
K · (−1 − b)
K · (1 − b)
Input
Output (y)
X 3
X 4
Im (y n )
Im (y n+50 )
1
1
K · (1 + b)
K · (−1 + b)
1
0
K · (1 − b)
K · (1 + b)
0
1
K · (−1 + b)
K · (−1 − b)
0
0
K · (−1 − b)
K · (1 − b)
wherein
K
=
1
b
2
+
1
is a real constant.
4. The dual carrier modulator of claim 3 , wherein the constant b is two (b=2).
5. The dual carrier modulator of claim 1 , wherein the constant b is two(b=2).