Embodiment
Below in conjunction with accompanying drawing specific embodiments of the invention are described.Need to prove that at this present invention is not limited to the following examples, the following examples are exemplary explanation, for example, below us with down channel as specific embodiment, promptly be that example illustrates, but device and method of the present invention also can be used in the base station with the terminal installation.In each accompanying drawing of the present invention, identical module is used identical Reference numeral in addition.
With reference to figure 1, Fig. 1 is the channel model of down channel:
In down channel, the base station sends K user's data vector d
(k), k=1...K wherein, K is a maximum number of user, like this, the receiver receiving end signal can be expressed as:
r(t)=Ad+n(t) (1)
Wherein: A is a sytem matrix, and d is the user data vector, here
d=(d
(1),d
(2),...,d
(k),)
T (2)
N (t) is an additive white Gaussian noise, and n (t)=σ
2I.
In this model, matrix A can be regarded two-part synthetic C as
kAnd H
h, wherein comprised specific user's signature waveform C
(k)And channel impulse response (CIR), h
K
So A=H
hC
k(3)
Then receiving end signal is:
r=Ad+σ
2I=H
hC
kd+σ
2I (4)
Here, σ
2Be variance, I is a unit vector.
Introduce the adaptive channel estimation method based on the expectation intermediate code of constructing of the present invention below in detail.Same as above, we only describe the adaptive channel estimation method and the device of down channel at this.
In the TD-SCDMA communication system, use intermediate code as pilot signal, intermediate code can be used as the channel estimating signal and is used for time synchronized and detects and adjust.
In the TD-SCDMA system, the intermediate code of descending time slot is to use same basic midamble code (Basic midamble), according to the stack sequence of number of users through different time shift (MO) formations.In same sub-district, use identical basic midamble code's sequence with each user on the carrier wave, each user has different time delays.Terminal can be known the number of users that this sub-district has according to the intermediate code of the downstream signal that receives.But in terminal equipment, estimate if only adopt basic midamble code to carry out adaptive channel as desired signal, then owing to the intermediate code of this desired value with reality falls far short, so the convergence of calculating is slower, the result of calculation poor performance.But because in the descending time slot of the base station of launching, what its intermediate code was partly launched is a stack with basic midamble code of specific time shift feature, therefore, we are in the estimation of down channel is estimated, according to TD-SCDMA technology standard and different user number, construct an intermediate code sequence according to basic midamble code according to certain rule at portable terminal, and with its reference signal as sef-adapting filter, the synchronous intermediate code that receives is carried out self adaptation estimates, with this self adaptation results estimated then as channel estimation results.
From two parts this scheme principle is described below:
At first, structure intermediate code sequence:
The method of structure expectation intermediate code sequence signal is:
Wherein M (n) is 128 basic midamble codes, a
iBe the weight coefficient to different user, i Δ n has represented the different time offset information of different user in intermediate code, and n represents time-domain sampling, and N represents number of users.This formula shows that the desired signal of being constructed (intermediate code) comes from the time shift of basic midamble code through number of users, obtains through weighting.
The structure of concrete expectation intermediate code is seen accompanying drawing 2, Fig. 2 is the block diagram of the adaptive channel estimation unit of first embodiment of the invention, in this basic apparatus structure, two modules have been comprised, as shown in Figure 2, modules A is the constructing module 10 of expectation intermediate code, and it uses the basic mode of constant amplitude weighted superposition as the structure intermediate code.Module B is an adaptive channel estimation module 20, modules A with the sequence of constant amplitude weighted superposition as reference signal input adaptive estimation module 20.
The channel estimating that sef-adapting filter is realized is described below.Module 20 is the sef-adapting filter module as shown in Figure 2, and this is the self adaptation realization module of a Weiner filter, and input signal is received signal and reference signal.Wherein reference signal comes from the intermediate code constructing module.At first calculate the error vector of the intermediate code and the reference signal of input signal, rely on descent algorithm to make error convergence, send into the FIR filter, set the tap coefficient h1 (n) and the h1 (m) of this filter, just can obtain estimation channel according to this error vector.Simultaneously this result is compared with the intermediate code of constructing as input signal again, error vector is sent into computing module, obtain the estimation to channel once more, this operation is through circulation several times, just can obtain the channel estimating of comparison, can be used for signal reconstruction and carry out joint-detection near true value.
The algorithm that adopts in this sef-adapting filter can be MMSE (least-mean-square error algorithm) and LMS (Least Mean Square lowest mean square) algorithm, and for example use the LMS algorithm to realize: the descent algorithm of filter is: ω (n)=ω (n-1)+μ (n) x (n) e (n)
Wherein μ (n) upgrades step-length for iteration, and x (n) is an input signal, and n is an iterative times, and ω (n) is the filter coefficient of the n time iteration, and e (n) is output in the error of the actual output of filter for expectation.
The following describes enforcement the preferred embodiments of the present invention.
First embodiment
Still with reference to figure 2, as can be seen from Figure 2, this adaptive channel estimation unit comprises: the constructing module 10 and the adaptive channel estimation module 20 of expectation intermediate code, and wherein the intermediate code constructing module comprises: basic midamble code unit 11 is used to generate basic intermediate code; Weighting squarer 12 is used for being weighted according to the basic midamble code of input; Intermediate code structural unit 13 is used for the weighting intermediate code based on input, constructs intermediate code according to number of users.Described adaptive channel estimation module 20 comprises: FIR filter h
1(n) 21, MMSE/LMS descent algorithm unit 22 and subtracter 23 are at first imported subtracter with the intermediate code of the input signal that receives with the structure intermediate code that constructing module 10 generates, and calculate its error vector, error vector is imported descent algorithm unit 22, with FIR and the h that calculates
1(n) send into the FIR filter, obtain the estimation of a channel, then subtracter 23 is imported in the estimation of this channel again, repeat the above-mentioned computational process that relatively reaches, just can obtain the actual estimated value that approaches down channel, then the result be sent into joint-detection unit 31, just can carry out joint-detection.
The performing step of first embodiment of the invention is described below in conjunction with the flow chart of Fig. 5:
Step S51. at first each tap coefficient of the h1 of initialization FIR filter (n) is 1;
Step S52. intermediate code constructing module 10 is determined the side-play amount of basic midamble code according to number of users, according to etc. the amplitude weighted superposition intermediate code sequence that obtains to construct, the input adaptive estimation module;
Step S53. receives the signal of a time slot;
Step S54. gets the input of the intermediate code partial data of received signal as the self adaptation estimation module, and carries out subtraction with the intermediate code sequence of being constructed, and obtains error amount;
Step S55. sends this error amount into the descent algorithm unit, calculates h1 (n), the i.e. filter coefficient of LMS algorithm according to the LMS algorithm;
Step S56. determines whether described calculating restrains, if do not restrain then enter step S58;
The estimated value of step S57. delivery channel;
Step S58. is according to h1 (n), during the intermediate code of received signal in, redefine the tap coefficient of filter, and turn back to step S54.
Need to prove that at this adaptive channel estimation module can also be used existing other algorithms, as MMSE (least mean-square error) or RLS etc.
Second embodiment
Figure 3 shows that the another kind of implementation of down channel estimation unit, wherein the adaptive channel estimation module is a kind of self adaptation paranorm version, but included module and unit and shown in Figure 2 basic identical, the step of being carried out is also identical with embodiment.Therefore, at this structure of various piece and concrete implementation procedure are described no longer.
The 3rd embodiment
The 3rd embodiment realizes example of the present invention for the parameter of adjusting constructing module according to the correlated results of output signal and basic midamble code dynamically.
With reference to figure 4, Fig. 4 is the block diagram of the adaptive channel estimation unit of third embodiment of the invention, as can be seen from Figure 4, can make the parameter (fingerbreadth value weighting etc.) of the sign indicating number constructing module that ins all sorts of ways between centering carry out real-time adjustment to obtain more performance.
With reference to figure 4, as can be seen from Figure 4, the channel self-adapting estimation unit of present embodiment and the channel self-adapting estimation unit of first embodiment are basic identical, difference is that the intermediate code constructing module 10 of present embodiment comprises a correlator 14, the output signal that this correlator 14 can make filter 21 and basic midamble code do slide relevant, the weighting multiplier is adjusted in the i.e. output that obtains according to sef-adapting filter, the intermediate code that basic midamble code is constructed by intermediate code structural unit 13 according to weighted value more approaches the intermediate code of real down channel, even also can accelerate arithmetic speed, restrain quickly to obtain the channel estimating of down channel.This slip stepping amount is a chip-level, can be that also 1,2,4 or 8 samplings at interval.
Flow chart below with reference to accompanying drawing 6 specifically describes job step of the present invention:
Step S61. at first each tap coefficient of the h1 of initialization FIR filter (n) is 1;
Step S62. intermediate code constructing module is determined the side-play amount of basic midamble code according to number of users, according to etc. the amplitude weighted superposition intermediate code sequence that obtains to construct, the input adaptive estimation module;
Step S63. receives the signal of a time slot;
Step S64. gets the input of the intermediate code partial data of received signal as the self adaptation estimation module, and carries out subtraction with the intermediate code sequence of being constructed, and obtains error amount;
Step S65. sends this error amount into the descent algorithm unit, calculates h1 (n), the i.e. filter coefficient of LMS algorithm according to the LMS algorithm;
Step S66. determines whether described calculating restrains, if do not restrain then enter step S68 and S69;
The estimated value of step S67. delivery channel;
Step S68. is according to h1 (n), during the intermediate code of received signal in, redefine the tap coefficient of filter, and turn back to step S63;
Step S69. is according to h1 (n), does in chip-level and basic midamble code and slides relevantly, obtains constructing the estimator of weighted value required in the intermediate code module, and returns step S64;
Step S70. to basic midamble code delay time weighting and the summation, construct new intermediate code, and return step S63.
As mentioned above, doing in filtering output signal and basic midamble code sequence and to slide when relevant, in order to obtain the relevant output of corresponding time domain, is to accelerate arithmetic speed, this relevant can carrying out at chip-level, and slip stepping amount can be 1,2,4 or 8 samplings interval.
In addition, according to the mould value of time domain correlated results on the different time delay point of each user as weight coefficient, to basic midamble code delay time weighting and summation, the reference signal that obtains constructing is stored in the reference signal memory (not providing) as the reference signal of upgrading.
Need to prove that at this though method and apparatus of the present invention uses at down channel, this method and apparatus can be used in up channel equally, that is to say, this device not only can use in terminal, and can use in the base station.
In sum, description of the invention, describe in detail and above-mentioned accompanying drawing be not be used for limiting of the present invention.To those skilled in the art, under instruction of the present invention, can carry out various corresponding modification and can not exceed the spirit and scope of the present invention, but this variation should be included within claim of the present invention and the equivalent scope thereof.