CN101877594A - Receiver algorithm for mobile communication random access introduction burst - Google Patents

Abstract

The invention provides a high-performance receiver algorithm for mobile communication random access introduction burst. The algorithm performs channel estimation by using the characteristics of an introduction sequence (Zadoff-Chu sequence) per se which is sent from a mobile terminal in a random access process and applies channel information to an interference elimination mechanism, so that the problem that a base station is interfered by the introduction of a neighboring cell when receiving the introduction burst sequence of the cell can be effectively solved. In addition, when the base station is not interfered by the introduction burst of the neighboring cell, the random access detection performance cannot be reduced due to the algorithm, and the complexity is also lower.

Description

A kind of receiver algorithm of mobile communication random access introduction burst

Technical field

The present invention relates to general data communication system, relating in particular to is the method that the E-UTRAN uplink random inserts the receiver structure of introduction burst sequence and utilizes this sequence to carry out channel estimating and detect by interference eliminated improvement random access introduction burst.

Background technology

Random Access Channel (RACH) is used for the E-UTRA up link, and it informs that network mobile terminal will have data to transmit, and makes the base station can detect the timing of portable terminal.There is multiple orthogonal sequence to make and after the base station successfully receives random access introduction burst, can sends a confirmation by a plurality of portable terminals access network simultaneously.

Insert subframe at random and mainly form, as shown in Figure 1 by introduction sequence with good correlation.Selecting for use of this sequence need be satisfied following three conditions: good autocorrelation performance makes base station Estimated Time of Arrival accurately; Good their cross correlation makes the base station can accurately estimate the asynchronous sequence that arrives different the time; Good their cross correlation makes that the synchronizing sequence cross-correlation that arrives the base station simultaneously is 0.

Summary of the invention

The receiver algorithm of a kind of high performance mobile communication random access introduction burst of the present invention.This algorithm has utilized the characteristic of the introduction sequence that portable terminal sent in random access procedure itself to carry out channel estimating, and channel information applied in the interference cancellation mechanisms, can effectively solve the base station and when receiving this sub-district introduction burst sequence, be subjected to the neighbor cell introduction and disturb this problem.

Utilized the correlation properties of random access introduction burst sequence (Zadoff-Chu sequence), carried out time domain channel and estimate; Detect the access introduction burst sequence of this sub-district and neighbor cell simultaneously at the base station receiving terminal, the channel information that utilizes channel estimating to go out carries out disturbance reconstruction to the access introduction burst sequence of neighbor cell, and deletes before the detection of next stage.

The auto-correlation of sequence is the length of sequence; With the cross-correlation between family sequence is 0; The mould of the cross-correlation between different race's sequence square be sequence length.

Described time-domain channel estimating method, be meant by utilizing the correlation of Zadoff-Chu sequence, after having detected the introduction sequence of neighbor cell, sequence and the introduction sequence that detects are carried out related operation to the received signal, thus estimate the neighbor cell introduction burst amplitude, phase place and the time delay of time domain channel of process.

Described interference cancellation mechanisms, it is characterized in that receiver detects interference signal, and simulate the decay that it is subjected to after by channel by the channel parameter that channel estimating obtains, part with this disturbance reconstruction deducts after former received signal again, make that the contained amount of information of former received signal is bigger, the possibility that detects information improves.

Described interference cancellation mechanisms is with the different of interference eliminated of symbol level: because the default channel parameter is constant in a time domain scope that inserts subframe at random, then only need be that unit makes interference eliminated with the sequence.Can reduce algorithm complex greatly like this.

Described disturbance reconstruction method is characterized in that: by channel magnitude (plural number has comprised phase place) and the time delay that channel estimating obtains, can obtain the signal of the multipath fading stack that the neighbor cell interference signal obtains after by channel.

Description of drawings

Fig. 1 is for inserting subframe and corresponding introduction at random;

The schematic diagram that Fig. 2 disturbs for the sub-district random access introduction burst;

Shown in Figure 3 is random access introduction burst interference cancellation receiver system.

Embodiment

Random Access Channel (RACH) is used for the E-UTRA up link, and it informs that network mobile terminal will have data to transmit, and makes the base station can detect the timing of portable terminal.There is multiple orthogonal sequence to make and after the base station successfully receives random access introduction burst, can sends a confirmation by a plurality of portable terminals access network simultaneously.

Insert subframe at random and mainly form, as shown in Figure 1 by introduction sequence with good correlation.Selecting for use of this sequence need be satisfied following three conditions: good autocorrelation performance makes base station Estimated Time of Arrival accurately; Good their cross correlation makes the base station can accurately estimate the asynchronous sequence that arrives different the time; Good their cross correlation makes that the synchronizing sequence cross-correlation that arrives the base station simultaneously is 0.

Cyclic shift Zadoff-Chu sequence has above-mentioned characteristic, will be applied in the introduction burst sequence that E-UTRAN inserts at random.Make with the cyclic shift Zadoff-Chu that prime length is N (CS-ZC) sequence is suc as formula (1)

$s_{r,i}\left(k\right)=\exp (-j\frac{2\mathrm{\πr}}{N}\{\left[(k+\mathrm{i\Δ})\mathrm{mod}N\right][(k+\mathrm{i\Δ})\mathrm{mod}N+1]/2+q\left[(k+\mathrm{i\Δ})\mathrm{mod}N\right]\left\}\right)---\left(1\right)$

I=0 in the formula, 1 ... m-1, k=0,1 ... N-1, r represent the family number of sequence, it is a positive integer, and relatively prime with N, the time span of Δ indication cycle displacement is a positive integer, m is illustrated in the number of certain next family sequence of condition of Δ cycle, and promptly m is that the N/ Δ rounds downwards. can make parameter q=0.

What adopt on the introduction burst sequence allocation of sub-district is the method for mixing the sequence of choosing of the same clan and different race, the sequence (r difference) that promptly different cell allocation is not of the same clan, the sequence of the corresponding family in each sub-district.In the process that receives random access introduction burst, the base station may be subjected to disturbing and disturbing from different race's sequence of neighbor cell from the same family sequence in the same sub-district, as shown in Figure 2.

Mainly contain two indexs for the evaluation that inserts receiver performance at random: false alarm rate (false alarm probability) and loss (miss detection probability).False alarm rate is meant that working as travelling carriage does not send introduction, has but detected the probability of this introduction.Loss refers to send introduction when some travelling carriages, does not but detect the probability of this introduction.

Good random access introduction burst sequence and receiving algorithm thereof should be able to satisfy lower false alarm rate and loss simultaneously, and common measure is a size of investigating loss under certain false alarm rate condition.

In inserting at random, the collision problem of introduction burst need cause concern.When the base station receiving terminal received the introduction burst of this sub-district and neighbor cell simultaneously, it was differentiated and the ability of this sub-district introduction of timing will descend significantly.Therefore we have introduced interference cancellation mechanisms in the introduction receiver that inserts at random, carry out channel estimating and rebuild interference signal by the special nature of ZadOff-Chu sequence, again it is deleted from received signal, improve the detectability of base station this sub-district introduction burst.

The core component of traditional random access introduction burst receiver is a matched filter banks.Receiver is made the signal received and possible introduction burst sequence relevant one by one, obtains correlation peak by the correlation of this code word, sets thresholding and thinks current introduction burst sequence if surpass.The output of matched filter as the formula (2),

$\mathrm{\λ}\left(m\right)=\frac{{\left|\frac{1}{\sqrt{N}}\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}{r}_n{r}_{(n+m)\mathrm{mod}N}^{*}\right|}^2}{{\mathrm{\σ}}^2}---\left(2\right)$

R represents the sequence that receives in the following formula.N represents the length of sequence, if in detection window scope D, detected λ (m)＞TH, and m ∈ [0, D-1], TH represents detection threshold, then thinks to detect this sequence.Threshold T H is determined by false alarm rate, makes the false alarm rate of unique sequence reach 0.1%.σ ²The power of expression noise and interference.

Yet if the base station is subjected to when receiving the introduction burst of this sub-district disturbing from the collision of neighbor cell introduction burst simultaneously, then because the introduction burst sequence of different districts is based on the Zadoff-Chu sequence of (r difference) not of the same clan, the cross-correlation performance is relatively poor, can cause loss higher.Therefore we have adopted interference delete mechanism to eliminate the interference of neighbor cell.

As shown in Figure 3, expression two-stage interference eliminated introduction detects.The signal that receives is obtained a series of introductions by matched filter, again the introduction that is obtained is divided into groups by family.Select detected prominent introduction by power detector,, it is carried out signal reconstruction and eliminate entering the next stage interference eliminated and detecting if not the introduction (different race's introduction) of this sub-district if the introduction of this sub-district thinks that then its judgement is correct.(need to utilize channel parameter in the process of signal reconstruction, in view of the sensitiveness that inserts at random time delay, we utilize the good correlation of Zadoff-Chu sequence to carry out channel estimating, and complexity is low.) afterwards, received signal deducts and detects the introduction sequence that just can detect this sub-district more accurately again by matched filter banks again after different race disturbs.

Owing to enter the signal difference that matched filter detects at every turn, the thresholding of employing is also different, and requiring detection threshold to each matched filter of each grade all must satisfy false alarm rate is 0.1%.

Fig. 1 is for inserting subframe and corresponding introduction at random, and we select for use the ZadOff-Chu sequence structure as introduction burst.UE transmits introduction in the access subframe at random of k * 0.5ms.Need enough guard time T _GPGuarantee that the time delay in the uplink can not pollute the data of consecutive frame.CP is a Cyclic Prefix.

The schematic diagram that Fig. 2 disturbs for the sub-district random access introduction burst, the user of each sub-district will use the random access introduction burst with the Zadoff-Chu sequence structure one-tenth of gang.The Zadoff-Chu sequence that the user of different districts uses belongs to not of the same clan.The A sub-district may be subjected to the influence of the introduction burst of neighbor cell when receiving the random access introduction burst that this community user sends to.Because the correlation of Zadoff-Chu sequence not of the same clan is relatively poor, the influence of this interference is bigger.

Shown in Figure 3 is random access introduction burst interference cancellation receiver system, below with an example explanation:

Be without loss of generality, that establish place, base station cell allocation is the r of family ₁The introduction burst sequence.Suppose that this base station of a certain moment receives 2 introductions simultaneously, sequence S is from the r of family ₁(this sub-district), sequence T is from the r of family ₂(neighbor cell).

The input r of receiver can use formula (3) expression,

$r=\underset{k\∈F_B}{\mathrm{\Σ}}{h}_{1,k}{S}_k+\underset{k\∈F_B}{\mathrm{\Σ}}{h}_{2,k}{T}_k+n---\left(3\right)$

F in the following formula _BThe set of each footpath time delay time of expression channel, { h _{1, k}, h _{2, k}Representing S and T introduction sequence time domain channel parameter respectively at the multidiameter fading channel that passes through, k represents time delay, can think that channel is constant in the whole introduction burst transport process of a frame.N represents gaussian additive noise altogether.

Detection algorithm following steps, purpose are in order to reduce the loss of S sequence (this sub-district introduction burst):

Allow received signal r pass through the matched filter banks (matched filter is by shown in the formula (2)) of S sequence and T sequence respectively.

If the matched filter banks of S sequence can be to the r response (correlation surpasses thresholding) that receives, then judgement detects S, detects to stop, and can determine its time of advent by the detected time.

If the matched filter banks of S sequence can not detect the T sequence to make interference delete again to the r response (correlation is lower than thresholding) that receives:

If the matched filter banks of T sequence can not then be judged omission S sequence to the r response that receives, detect termination.

By the matched filter banks of T sequence, if can respond, then detect T, and the output c (m) of record matched filter

$c\left(m\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}{r}_n{T}_{(n+m)\mathrm{mod}N}^{*}---\left(4\right)$

M ∈ in the formula (4) [0, D-1], D is the scope of detection window, N is a sequence length.

Channel estimating is made in output by the T matched filter banks.

Formula (3) is launched and can be got

$r=S_0{h}_1^1+S_1{h}_{\mathrm{1,2}}+...+S_{p-1}{h}_{1,p}+...+T_0{h}_{\mathrm{2,1}}+T_1{h}_{\mathrm{2,2}}+...+T_{p-1}{h}_{2,p}+n---\left(5\right)$

Wherein p represents channel maximum delay length.The subscript of S and T is represented the figure place (multidiameter) of its right cyclic shift.

Because Zadoff-Chu sequence auto-correlation is N, be 0 with the cross-correlation of family sequence, the computing of formula (3) is carried out at formula (5) two ends, the left and right sides, the channel magnitude that we can adjudicate the T sequence is (ignoring Gaussian noise):

${\hat{h}}_{2,m}\≈\frac{c\left(m\right)}{N}---\left(6\right)$

Reconstruct interference by channel parameter and the sequence T of different race

Carrying out interference eliminated obtains

r′＝r-I (8)

Bring r ' into S sequences match filter detection once more, method is with step 1.

By the interference eliminated to other sub-district different race sequences, feasible random access introduction burst loss to this sub-district introduction sequence reduces.

Claims (7)

1. the receiver algorithm of a high performance mobile communication random access introduction burst.This algorithm has utilized the characteristic of the introduction sequence that portable terminal sent in random access procedure itself to carry out channel estimating, and channel information applied in the interference cancellation mechanisms, can effectively solve the base station and when receiving this sub-district introduction burst sequence, be subjected to the neighbor cell introduction and disturb this problem.

2. the receiver algorithm of the high performance mobile communication random access introduction burst described in claim 1 is characterized in that: utilized the correlation properties of random access introduction burst sequence (Zadoff-Chu sequence), carried out time domain channel and estimate; Detect the access introduction burst sequence of this sub-district and neighbor cell simultaneously at the base station receiving terminal, the channel information that utilizes channel estimating to go out carries out disturbance reconstruction to the access introduction burst sequence of neighbor cell, and deletes before the detection of next stage.

3. the correlation properties of the introduction burst sequence described in claim 2 (Zadoff-Chu sequence) mainly comprise: the auto-correlation of sequence is the length of sequence; With the cross-correlation between family sequence is 0; The mould of the cross-correlation between different race's sequence square be sequence length.

4. the time-domain channel estimating method described in claim 2, be meant by utilizing the correlation of Zadoff-Chu sequence, after having detected the introduction sequence of neighbor cell, sequence and the introduction sequence that detects are carried out related operation to the received signal, thus estimate the neighbor cell introduction burst amplitude, phase place and the time delay of time domain channel of process.

5. the interference cancellation mechanisms described in claim 1, it is characterized in that receiver detects interference signal, and simulate the decay that it is subjected to after by channel by the channel parameter that channel estimating obtains, part with this disturbance reconstruction deducts after former received signal again, make that the contained amount of information of former received signal is bigger, the possibility that detects information improves.

6. the interference cancellation mechanisms described in claim 5 is with the different of interference eliminated of symbol level: because the default channel parameter is constant in a time domain scope that inserts subframe at random, then only need be that unit makes interference eliminated with the sequence.Can reduce algorithm complex greatly like this.

7. the disturbance reconstruction method described in claim 5 is characterized in that: by channel magnitude (plural number has comprised phase place) and the time delay that channel estimating obtains, can obtain the signal of the multipath fading stack that the neighbor cell interference signal obtains after by channel.

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