Impulse ultra-wideband radio communication system
View Patent ↗A method and apparatus are provided for implementing an impulse ultra-wideband communications system which combines the technique of transmitted reference (TR) with a code-sifted reference scheme that separates the reference and the data pulses with a sequence of codes such as a subset of Walsh codes. The combination of the two techniques in ultra-wideband (UWB) radio systems removes the wideband delay elements required by conventional TR UWB systems. The invention provides a system with no analog carriers and lower complexities than other UWB systems, and which has better performances, higher tolerance to nonlinearity, and larger capacities.
1. A method of transmitting and receiving information bits in an ultra-wideband (UWB) radio communication system, comprising:
encoding a reference bit and at least one information bit using shifting codes;
modulating a series of ultra-wideband UWB pulses with modulation amplitudes determined from the encoded reference bit and the at least one encoded information bit;
transmitting the modulated series of UWB pulses as a signal;
receiving the signal; and
decoding the received signal using detection codes.
2. The method of claim 1 wherein modulating a series of wideband pulses with modulation amplitudes comprises:
determining the modulation amplitudes by summing the encoded bits into a sequence of modulating amplitudes; and
modulating the amplitude of the series of UWB pulses using the absolute value of the modulating amplitudes.
3. The method of claim 1 wherein decoding the received signal comprises:
generating a series of signal values by squaring and integrating over time the signal; and
recovering the information bits from the series of signal values.
4. The method of claim 3 wherein recovering the information bits from the series of signal values comprises:
correlating the series of signal values with a series of detection codes; and
determining the information bits from the correlation results.
5. The method of claim 4 wherein encoding at least one information bit comprises directly encoding at least one information bit.
6. The method of claim 5 wherein determining the information bits from the correlation results comprises determining each information bit as the sign of a respective one of the correlation results.
7. The method of claim 6 wherein the shifting codes c k and the detection codes {tilde over (c)} k are Walsh codes satisfying the rules
{tilde over (c)} k =c 0 c k , ∀k ε{1, 2 , . . . , M }, and
c 1 c n ≠{tilde over (c)} k , ∀k,l,n ε{1, 2 , . . . , M},
where M is the number of information bits in a group, and k, l, and n are integer indices.
8. The method of claim 4 wherein determining the information bits from the correlation results comprises determining which information bits {circumflex over (b)} jk yield a maximum value of
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where j is a group number of information bits, M is the number of information bits within the group, k identifies an information bit within the group, and n and l are indices identifying a particular one of the detection codes used to generate a particular one {tilde over (r)} ln of the correlation results.
9. The method of claim 8 wherein encoding at least one information bit comprises:
generating processed information bits d jk as
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where b jl is a raw information bit, j is a group number of information bits, M is the number of information bits within the group, k identifies an information bit within the group, and l is a summation index; and
encoding the processed information bits.
10. The method of claim 9 wherein the shifting codes c l and the detection codes {tilde over (c)} ln are Walsh codes satisfying the rules
{tilde over (c)} ln =c 1 c n , ∀l ε{0, 1 , . . . , M −1} and ∀ nε{l +1 , l +2 , . . . M }, and
{tilde over (c)} ln ≠{tilde over (c)} pq except l=p and n=q, ∀l, p ε{0, 1, . . . , M −1} and ∀ n,q ε{1, 2 , . . . , M},
where M is the number of information bits in a group, and l, n, p, and q are integer indices.
11. An ultra-wideband (UWB) radio communication system comprising:
means for generating a series of UWB pulses containing an encoded reference bit and at least one encoded information bit;
a transmitter having an antenna for transmitting the UWB pulses as a signal;
a receiver having an antenna for receiving the signal; and
means for decoding the signal to recover the at least one information bit,
wherein the means for generating the series of UWB pulses comprise means for encoding the reference bit and the at least one information bit with a series of shifting codes; means for summing the encoded bits into a sequence of modulating amplitudes; and means for modulating the amplitude of a series of UWB pulses using the absolute value of the modulating amplitudes.
12. The UWB radio communication system of claim 11 wherein the means for decoding the signal comprise:
means for squaring and integrating over time the signal to generate a series of signal values;
an information bit detection unit for recovering the information bits from the series of signal values.
13. The UWB radio communication system of claim 12 wherein the information bit detection unit comprises:
means for correlating the series of signal values with a series of detection codes; and
means for determining the information bits from the correlation results.
14. The UWB radio communication system of claim 13 wherein the means for encoding the at least one information bit comprise means for directly encoding the at least one information bit.
15. The UWB radio communication system of claim 14 wherein the means for determining the information bits from the correlation results comprise determining each information bit as the sign of a respective one of the correlation results.
16. The UWB radio communication system of claim 15 wherein the shifting codes c k and the detection codes {tilde over (c)} k are Walsh codes satisfying the rules
{tilde over (c)} k =c 0 c k , ∀k ε{1, 2 , . . . , M }, and
c 1 c n ≠{tilde over (c)} k , ∀k,l,n ε{1, 2 , . . . , M},
where M is the number of information bits in a group, and k, l, and n are integer indices.
17. The UWB radio communication system of claim 15 wherein the shifting codes c l and the detection codes {tilde over (c)} ln are Walsh codes satisfying the rules
{tilde over (c)} ln =c 1 c n , ∀l ε{0, 1 , . . . M −1} and ∀ nε{l +1, l+2 , . . . M }, and
{tilde over (c)} ln ≠{tilde over (c)} pq except l=p and n=q, ∀l, p ε{0, 1 , . . . , M −1} and ∀ n,q ε{1, 2 , . . . , M},
where M is the number of information bits in a group, and l, n, p, and q are integer indices.
18. The UWB radio communication system of claim 12 wherein the means for determining the information bits from the correlation results comprise determining which information bits {circumflex over (b)} jk yield a maximum value of
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l
=
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M
-
1
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=
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+
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M
r
~
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n
b
^
jk
,
where j is a group number of information bits, M is the number of information bits within the group, k identifies an information bit within the group, and n and l are indices identifying a particular one of the detection codes used to generate a particular one {tilde over (r)} ln of the correlation results.