Back to results
US 9,001,641 B2Granted
Sounding reference signal processing for LTE
AssigneeTexas Instruments Incorporated
InventorsPierre Bertrand, Anthony Ekpenyong
Life of this patent
Estimating the term…
Abstract
A wireless communication receiver including a serial to parallel converter receiving an radio frequency signal, a fast Fourier transform device connected to said serial to parallel converter converting NFFT corresponding serial signals into a frequency domain; an EZC root sequence unit generating a set of root sequence signals; an element-by-element multiply unit forming a set of products including a product of each of said frequency domain signals from said fast Fourier transform device and a corresponding root sequence signal, an NSRS-length IDFT unit performing a group cyclic-shift de-multiplexing of the products and a discrete Fourier transform unit converting connected cyclic shift de-multiplexing signals back to frequency-domain.
Claims12
A wireless communication receiver comprising;
- a serial-to-parallel converter receiving a time sample sequence and generating parallel signals;
- a fast Fourier transform (FFT device connected to said serial-to-parallel converter and converting said signals from a time domain into a frequency domain;
- an Extended Zadoff-Chu (EZC) root sequence unit generating a set of root sequence signals;
- an element-by-element multiply unit connected to said FFT device and said EZC root sequence unit, said element-by-element multiply unit forming a set of products Y including a product of each of said frequency domain signals from said FFT device and a complex conjugate of one of said corresponding root sequence signals X;
- an Inverse Discrete Fourier Transform (IDFT) unit connected to said element-by-element multiply unit performing a group cyclic-shift de-multiplexing of said products to compute an impulse response for each multiplexed channel;
- and
- a discrete Fourier transform unit connected to said IDFT unit to convert said impulse responses back to frequency domain.
4 more elements
A wireless communication receiver comprising;
- a serial-to-parallel converter receiving a time sample sequence and generating parallel signals;
- a fast Fourier transform (FFT) device connected to said serial-to-parallel converter and converting said signals from a time domain into a frequency domain;
- an Extended Zadoff-Chu (EZC) root sequence unit generating a set of root sequence signals;
- an element-by-element multiply unit connected to said FFT device and said EZC root sequence unit, said element-by-element multiply unit forming a set of products Y including a product of each of said frequency domain signals from said FFT device and a complex conjugate of one of said corresponding root sequence signals X;
- an Inverse Discrete Fourier Transform (IDFT) unit connected to said element-by-element multiply unit performing a group cyclic-shift de-multiplexing of said products to compute an impulse response for each multiplexed channel, wherein said group cyclic shift de-multiplexing performed by said discrete Fourier transform unit includes:
- Y=FNSRSNFFT(r)
- y=FNSRS−1diag(X*YT)
- where:
- Y is the frequency domain product of an element-wise multiplication, r is the received time sample sequence, y is the time domain product of an element-wise multiplication, FNSRS N FFT is a NSRS by NFFT matrix corresponding to NFFT -point FFT and NSRS sub-carriers de-mapping, X is the expected root sequence;
- and FNSRS is a NNSRS by NSRS matrix, thereby producing for each Sounding Reference Signal (SRS) comb a concatenated Channel Impulse Response (CIR) sequence y of all received wireless users multiplexed on a same root sequence;
- and
- a discrete Fourier transform unit connected to said IDFT unit to convert said impulse responses back to frequency domain.
9 more elements
A wireless communication receiver comprising:
- a serial-to-parallel converter receiving a time sample sequence and generating parallel signals;
- a fast Fourier transform (FFT) device connected to said serial-to-parallel converter and converting said signals from a time domain into a frequency domain;
- an Extended Zadoff-Chi (EZC) root sequence unit generating a set of root sequence signals;
- an element-by-element multiply unit connected to said FFT device and said EZC root sequence unit, said element-by-element multiply unit forming a set of products Y including a product of each of said frequency domain signals from said FFT device and a complex conjugate of one said corresponding root sequence signals X;
- an Inverse Discrete Fourier Transform (IDFT) unit connected to said element-by-element multiply unit performing a group cyclic-shift de-multiplexing of said products to compute an impulse response for each multiplexed channel, wherein said group cyclic shift de-multiplexing performed by said discrete Fourier transform unit includes:
- yu=(0, . . . , 0, yn1(u), yn2(u), . . . , ynL(u), 0, . . . , 0)T
- Ĥ=FNSRSyN
- where:
- y is the time domain product of an element-wise multiplication, FNSRS is a NSRS by NSRS matrix corresponding to NSRS-point DFT;
- and n1(U), . . . , nL (U) are the samples defining the cyclic shift window of user u, involving zeroing-out the remaining samples outside the cyclic shift window of user u and ĤN is the channel estimate across frequency chunk c produced by the last stage NSRS-length DFT-based frequency interpolation;
- and
- a discrete Fourier transform unit connected to said IDFT unit to convert said impulse responses back to frequency domain.
9 more elements
A wireless communication receiver comprising;
- a serial-to-parallel converter receiving a time sample sequence and generating parallel signals;
- a fast Fourier transform (FFT) device connected to said serial-to-parallel converter and converting said signals from a time domain into a frequency domain;
- an Extended Zadoff-Chu (EZC) root sequence unit generating a set of root sequence signals;
- an element-by-element multiply unit connected to said FFT device and said EZC root sequence unit, said element-by-element multiply unit forming a set of products Y including a product of each of said frequency domain signals from said FFT device and a complex conjugate of one of said corresponding root sequence signals X:
- an Inverse Discrete Fourier Transform (IDFT) unit connected to said element-by-element multiply unit performing a grog cyclic-shift de-multiplexing of said products to compute an impulse response for each multiplexed channel,
- a non-biased per-antenna per-sub-carrier channel gain estimator performing
- Ĝ0(a)=|Ĥ(a)|2−{circumflex over (σ)}N2
- where:
- Ĝ0(a)is the channel gain estimate per sub-carrier per antenna, Ĥ(a) is the channel estimate {circumflex over (σ)}N2 an estimate of the noise variance σN2=a2σH2, involving estimating and removing the noise variance;
- and
- a discrete Fourier transform unit connected to said IDFT unit to convert said impulse responses back to frequency domain.
8 more elements
A wireless communication receiver comprising:
- a serial-to-parallel converter receiving a time sample sequence and generating parallel signals;
- a fast Fourier transform (FFT) device connected to said serial-to-parallel converter and converting said signals from a time domain into a frequency domain;
- an Extended Zadoff-Chu (EZC) root sequence unit generating a set of root sequence signals;
- an element multiply unit connected to said FFT device and said EZC root sequence unit, said element-by-element multiply unit forming a set of products Y including a product of each of said frequency domain signals from said FFT device and a complex conjugate of one of said corresponding root sequence signals X;
- an Inverse Discrete Fourier Transform (IDFT) unit connected to said element-by-element multiply unit performing a group cyclic-shift de-multiplexing of said products to compute an impulse response for each multiplexed channel,
- a non-biased per-antenna per-sub-carrier channel gain estimator performing
- Ĝ0(a)=|Ĥ(a)|2−{circumflex over (σ)}N2
- where:
- Ĝ0(a) is the channel gain estimate per sub-carrier per antenna, Ĥ(a)is the channel estimate, {circumflex over (σ)}N2 is an estimate of the noise variance σN2=a2σH2, involving estimating and removing the noise variance, and
- wherein said gain estimator includes a negative gain avoidance by applying a simple clipping threshold of 0.01 according to
- ĜClip(a)=max{|Ĥ(a)|2−{circumflex over (σ)}N2;
- Gfloor}
- where:
- ĜClip(a) is the channel gain estimate per sub-carrier per antenna, Ĥ(a) is the channel estimate, {circumflex over (σ)}N2 is an estimate of the noise variance σN2=a2σH2 and Gfloor is the clipping threshold;
- and
- a discrete Fourier transform unit connected to said IDFT unit to convert said impulse responses back to frequency domain.
13 more elements
A wireless communication Sounding Reference Signal (SRS) receiver comprising:
- a serial to parallel converter receiving a radio frequency signal and generating NFFT corresponding parallel signals;
- a fast Fourier transform device connected to said serial to parallel converter receiving said NFFT corresponding parallel signals and converting said NFFT corresponding serial signals from a time domain into a frequency domain;
- a EZC root sequence unit generating a set of root sequence signals;
- an element-by-element multiply unit connected to said fast Fourier transform device and said EZC root sequence unit, said element-by-element multiply unit forming a set of products including a product of each of said frequency domain signals from said fast Fourier transform device and a corresponding root sequence signal;
- an NSRS-length IDFF unit connected to said element-by-element multiply unit performing a group cyclic-shift de-multiplexing of said products employing a sounding reference symbol Orthogonal Frequency Division Multiplexing Orthogonal Frequency Division Multiple Access symbol structure and a Constant Amplitude Zero Auto-Correlation sequence to compute an impulse response for each multiplexed channel through a frequency-domain computed periodic correlation;
- and
- a discrete Fourier transform unit connected to said IDFT unit and receiving cyclic shift de-multiplexing signals to convert them back to frequency-domain
- a timing offset estimator combining the amplitude delay profiles across antennas from the concatenated delay profiles sequence y and searching for the highest peak in the user's timing offset window according to:
- {
- i
- ^
- u
- =
- arg
-
-
- max
- i
-
- {
- p
- i
- }
- ;
- i
- ∈
- I
- τ
- ,
- u
- ;
- p
- i
- =
- ∑
- a
- =
- 1
- A
-
-
-
- y
- i
- ,
- a
-
- 2
- τ
- ^
- u
- =
- (
- i
- ^
- u
- -
- C
- u
- )
-
- T
- S
- where:
- A is the number of antenna;
- Cu is the cyclic shift of user u;
- TS is the sampling period of sequence y;
- and Iτ,u is the timing offset window of user u, defined as:
- {
- I
- τ
- ,
- u
- =
- {
- -
- N
- early
- ,
- …
-
- ,
- -
- 1
- ,
- 0
- ,
- 1
- ,
- …
-
- ,
- N
- late
- }
- N
- early
- =
- ⌈
- max
-
- (
- 0.5
-
-
- µs
- ,
- τ
- max
- )
- /
- T
- S
- ⌉
- N
- late
- =
- ⌈
- [
- W
- M
- +
- max
-
- (
- 0.5
-
-
- µs
- ,
- τ
- max
- )
- ]
- /
- T
- S
- ⌉
- W
- M
- =
- min
-
- (
- 1
-
-
- µs
- ,
- τ
- )
- where:
- Iτ,u(Nearly+1)=0 coincides with the first sample of the cyclic shift window of user U;
- ±τmax is the maximum expected timing error;
- WM is the main energy region within the user delay spread;
- and τis the delay spread of the user;
- and
- a discrete Fourier transform unit connected to said IDFT unit to convert said products back to frequency-domain.
155 more elements
Dependencies are inferred from the claim text.