CN101141235B - Interference canceling method for co-frequency co-time slot duplexing - Google Patents

Abstract

The utility model provides a interference clearance technique, so that the up-down-going link of the wireless communication can run via the same frequency and the time-slot, so as to improve the rate of spectrum utilization. When the up-down-going channel is under the common frequency and the time-slot, the down link will interfere the up-link, namely, the base station receiver in the sub-zone is interfered by the base station transmitter of the sub-zone and the base station transmitter of the adjoining sub-zone. The utility model delivers the undesired signals to the receiver through the wired communication. The receiver is arranged with a signal preprocessing unit, so as to remove the transmitter signal interference in the radio frequency. Such signal interference is from the air interface. In addition, the utility model provides an aerial distribution rule to reduce the direct interference of the transmitter to the receiver. The interference clearance method is suitable to the duplex system with the common frequency and time-slot, so as to greatly reduce the frequency resources and time resources.

Description

A kind of interference elimination method that is applicable to co-frequency co-time slot duplexing

Technical field

The present invention relates to a kind of new interference elimination method, it belongs to wireless communication field.

Background technology

A basic task of wireless communication system is the communication link of setting up between wireless terminal and the base station.The transmission of data is divided into both direction, is passed the link of past wireless terminal direction by the base station that is:, is called down link; Pass toward the link of base station direction by wireless terminal, be called up link.The system that can realize the uplink and downlink transfer of data is called duplex system.Existing duplex system has Frequency Division Duplexing (FDD) and tdd systems.Different frequency transmission is up, downlink data has been isolated the uplink and downlink interference among links thereby frequency division duplex system adopts.Tdd systems uses same frequency, but that different time-gap transmits is up to isolate, the interference between the down link.Above-mentioned two kinds of duplex method have been sacrificed frequency resource and time resource respectively in isolating the uplink and downlink link.

If the uplink and downlink channel adopts same frequency and same slot transmission, spectrum efficiency can improve greatly.In order to realize this purpose, need set up a kind of effective interference cancellation techniques.

Summary of the invention

The objective of the invention is to propose a kind ofly to be applicable to frequently, uplink and downlink interference among links technology for eliminating and a kind of antenna of avoiding directly disturbing of slot duplexing lay method simultaneously.

Basic thought of the present invention is to utilize wired connection (for example: independent microwave channel) interference signal is delivered to receiver, cancel out each other with the interference signal in the air interface.Its technical scheme is as described below:

1. uplink channel interference removing method

Adopting with in the slot duplexing system frequently and simultaneously, up link passes the signal of wireless terminal toward the base station, and interference at this moment is mainly from the interference to this base station receiver of this cell base station transmitter and adjacent cell base station transmitter signal.

Ignore thermal noise and disturb, the signal that this cell base station receiver receives is transmit (up link) and this cell base station transmitter and an adjacent cell base station transmitter signal sum of wireless terminal:

$X\left(t\right)=\underset{i=1}{\overset{N_D}{\mathrm{\Σ}}}{h}_i\left(t\right)\⊗x_i\left(t\right)+\underset{d}{\mathrm{\Σ}}{h}_d\left(t\right)\⊗y_d\left(t\right)---\left(1\right)$

X in the following formula (t) is the received signal of base station, x _i(t) be the signal of i wireless terminal emission in this sub-district, y _d(t) be the signal of d jamming transmitter emission.First on equal sign the right transmits for wireless terminal; Second is the base station interference transmitter signal; Convolution in the expression mathematical operation; h _iAnd h _dThe channel response function of representing i mobile phone and d base station transmitter air interface respectively.Second on the right in the formula (1) is the interference from air interface.Here defining above-mentioned base station transmitter is jamming transmitter.

In order to eliminate above-mentioned interference from air interface, we are provided with a Signal Pretreatment unit (system as shown in Figure 1) at traditional receiver place.Between Signal Pretreatment unit and jamming transmitter, set up an independent signal interface channel, i.e. a wired connection.Utilize this wired connection that the jamming transmitter signal is directly sent into the Signal Pretreatment unit, make it and cancel out each other from the interference signal of air interface.

Because wire message way and jamming transmitter air interlace channel generally exist than big-difference, so need to be provided with a channel simulator in the Signal Pretreatment unit.Channel simulator can at first be estimated the opposite number of the channel parameter between local receiver and the jamming transmitter, and this channel estimation methods can use any existing channel estimation methods, as: least mean-square error (MMSE) estimation that pilot tone is auxiliary etc.The signal that channel simulator utilizes the estimated value of this channel parameter opposite number and the jamming transmitter that sends by wire message way sends recovers the opposite number of the interference signal that receiver end receives, then in adder unit subsequently with the received signal addition, can eliminate the interference of jamming transmitter.Channel simulator also can be estimated the channel parameter between local receiver and the jamming transmitter, the jamming transmitter signal mode that utilizes this channel parameter estimation value that wired connection is sent is drawn up the aerial interference signal that receiver is received, the signal that receiver receives deducts the output signal of channel simulator, has promptly eliminated the interference of jamming transmitter.

The estimation of the opposite number of the interference signal of above-mentioned channel simulator can realize (see figure 2) by an auto-adaptive fir filter.When air interlace channel was single footpath channel, the FIR filter can replace with the multiplier of a single tap.

Consider automatic gain control (AGC) performance of receiver, the restriction of analog digital conversion figure place, above-mentioned Signal Pretreatment unit should at first be arranged in the radio circuit.If eliminate fully inadequately, the digital signal pretreatment unit of an identical operation principle then is set again, on baseband signal, further eliminate.

2. antenna lays method

Laying of jamming transmitter and receiver antenna is another main points of the present invention, in real system, as far as possible receiver antenna be positioned on the jamming transmitter aerial radiation minimal point position, thus the received power of reduction jamming transmitter signal.

Fig. 3 has provided the example under the jamming transmitter situation very near apart from receiver, i.e. a sending and receiving antenna in same sub-district.In two whip antennas shown in Figure 3, the dual-mode antenna vertical arrangement, top is transmitter antenna, is receiver antenna below.According to the radiation theorem as can be known: receiver antenna is in the azimuth of transmitter antenna zero radiation.Therefore, under the hypothesis that does not have reflected wave to exist, transmitter is zero to the interference of receiver.Under the situation that reflection be can not ignore, lay the interference of having avoided direct wave owing to this, so still can reduce interference power effectively, reduce the work load of the described Signal Pretreatment of last joint unit.

When the transmitting and receiving antenna and work simultaneously an of base station, because two antenna distances are closer, transmitting antenna has constituted a powerful interference source of this base station receiver usually.As mentioned above, the antenna of the application of the invention lays method, just can effectively reduce this interference, even also have remaining interference, utilizes foregoing interference elimination method, can also further eliminate remaining interference.Interference elimination method of the present invention is applicable to the co-frequency co-time slot duplexing system, can save frequency resource and time resource greatly.

Description of drawings

Fig. 1 is an inter base station interference removing method schematic diagram;

Fig. 2 is a FIR filter construction schematic diagram;

Fig. 3 is the sending and receiving antenna arrangement method schematic diagram in the same sub-district.

Embodiment

Below in conjunction with accompanying drawing the present invention is illustrated in further detail, but the scope that does not limit the present invention in any way.

Exemplify system as shown in Figure 1, the key of implementing above-mentioned interference cancellation techniques is the filter parameter that accurately obtains in the channel simulator, the jamming transmitter signal that will send by wired connection by channel simulator be transformed to air interface on interference signal approximate consistent, thereby utilize subtraction, interference signal in the receiver signal is eliminated as much as possible fully.The method that obtains channel parameter can be: set up equally spaced special narrow time slot by system protocol on time domain earlier, in these special time slots, all these sub-district wireless terminal stop signal emissions, the adjacent interference transmitter also stops emission signal except that the jamming transmitter that will estimate channel, the interference that utilizes signal that reception antenna receives and wire message way to send transmits, just can estimate channel parameter, then, use the same method other jamming transmitters are carried out channel estimating.

The ground that is without loss of generality, we at first narrate the method for eliminating the 1st base station interference transmitter, promptly eliminate second distracter when d=1 in formula (1) the right.At first, receiver utilizes a kind of existing channel estimation methods to estimate the opposite number of the 1st jamming transmitter to the channel parameter between the local receiver, i.e. estimated value h ₁' (t) be right-h ₁(t) estimation.

Then with h ₁' (t) with the y that transmits of first jamming transmitter that sends by wire message way ₁(t) do convolution, promptly obtained the output signal of channel simulator.The output that the output of channel simulator and receiver signal input adder unit are obtained and be:

$Z_1\left(t\right)=\underset{i=1}{\overset{N_D}{\mathrm{\&Sigma;}}}{h}_i\left(t\right)\&CircleTimes;x_i\left(t\right)+\underset{d\&NotEqual;1}{\mathrm{\&Sigma;}}{h}_d\left(t\right)\&CircleTimes;y_d\left(t\right)+h_1\left(t\right)\&CircleTimes;y_1\left(t\right)+{\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="H061B3054420060927E000012.png"\; state="\{\{state\}\}">h</figure-callout>}}_1^{\&prime;}\left(t\right)\&CircleTimes;y_1\left(t\right)---\left(2\right)$

We are split as two of d ≠ 1 and d=1 with second on formula (1) the right, and the 4th on following formula the right is the channel simulator output signal.For last two sums in feasible (2) formula the right are zero, we can adopt following method.

The design system agreement, on time domain, set up equally spaced special narrow time slot, in these special time slots, all these sub-district wireless terminal stop signal emissions, the adjacent interference transmitter also stops emission signal except that first jamming transmitter, with signal and the addition of channel simulator output signal that this moment, receiver received, and separate following equation:

$h_1\left(t\right)\&CircleTimes;y_1\left(t\right)+{{\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="H061B3054420060927E000012.png"\; state="\{\{state\}\}">h</figure-callout>}}_1}^{\&prime;}\left(t\right)\&CircleTimes;y_1\left(t\right)=0---\left(3\right)$

Obtain: h ₁' (t)=-h ₁(t).

With (t) substitution of h ' (2) formula that (3) solve, then interference eliminated is finished.At this moment the adder unit output signal is:

$Z_1\left(t\right)=\underset{i=1}{\overset{N_D}{\mathrm{\&Sigma;}}}{h}_i\left(t\right)\&CircleTimes;x_i\left(t\right)+\underset{d\&NotEqual;1}{\mathrm{\&Sigma;}}{h}_d\left(t\right)\&CircleTimes;y_d\left(t\right)---\left(4\right)$

In actual conditions, because the randomness of noise jamming and channel variation, we can only obtain the approximate solution of (3) formula usually.That is:

$h_1\left(t\right)\&CircleTimes;y\left(t\right)+{{\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="H061B3054420060927E000012.png"\; state="\{\{state\}\}">h</figure-callout>}}_1}^{\&prime;}\left(t\right)\&CircleTimes;y\left(t\right)={\mathrm{\&delta;}}_1\left(t\right)---\left(5\right)$

δ in the following formula ₁(t) be the random function of a t variation in time, be referred to as residual interference here.

Therefore, the adder unit output signal is:

$Z_1\left(t\right)=\underset{i=1}{\overset{N_D}{\mathrm{\&Sigma;}}}{h}_i\left(t\right)\&CircleTimes;x_i\left(t\right)+\underset{d\&NotEqual;1}{\mathrm{\&Sigma;}}{h}_d\left(t\right)\&CircleTimes;y_d\left(t\right)+{\mathrm{\&delta;}}_1\left(t\right)---\left(6\right)$

The rest may be inferred, and we can eliminate the interference signal of the 2nd jamming transmitter, the 3rd jamming transmitter ... so the interference up to eliminating the adjacent interference transmitter obtains at last:

$Z\left(t\right)=\underset{i=1}{\overset{N_D}{\mathrm{\&Sigma;}}}{h}_i\left(t\right){\&CircleTimes;x}_i\left(t\right)+\mathrm{\&delta;}\left(t\right)---\left(7\right)$

In order to suppress the influence of residual interference, we can be used for the CDMA spread spectrum modulation of uplink and downlink signal (being referred to as code division duplex), that is: x _i(t) and y _d(t) all adopt the spreading code modulation.

Can obtain the signal-to-jamming ratio gain of the highest 12-15dB to (7) formula despreading, thereby effectively overcome the influence of residual interference.

In addition, the present invention is to eliminate the basic functional principle that a base station interference is the example summary.This method is suitable for the situation of many base station interference.At last, point out that above-mentioned principle is applicable to the interference eliminated of mobile phone self up-downgoing channel fully.Therefore no longer repeat.

Claims (7)

1. interference elimination method that is used for the co-frequency co-time slot duplexing system, a Signal Pretreatment unit is set at the receiver place, utilize wired connection that the jamming transmitter signal is transferred to this pretreatment unit and carry out signal processing, make it and cancel out each other from the jamming transmitter signal of air interface, wherein said jamming transmitter comprises this cell base station and adjacent cell base station transmitter, it is characterized in that described Signal Pretreatment unit is arranged on the radio circuit.

2. interference elimination method as claimed in claim 1, it is characterized in that, channel simulator of described Signal Pretreatment unit by using is at first estimated the channel parameter between receiver and the jamming transmitter or the opposite number of channel parameter, utilize the estimated value of this channel parameter or its opposite number then and recover interference signal or its opposite number that receiver is received by the jamming transmitter signal that wire message way sends, subtract each other or addition with received signal subsequently, can eliminate the interference of jamming transmitter.

3. interference elimination method as claimed in claim 2 is characterized in that, described channel simulator adopts the auxiliary least mean-square error method of estimation of pilot tone to carry out channel estimating.

4. interference elimination method as claimed in claim 2, it is characterized in that, the method that described channel simulator carries out channel estimating is: set up equally spaced special narrow time slot by system protocol on time domain earlier, in these special time slots, all these sub-district wireless terminal stop signal emissions, the adjacent interference transmitter also stops emission signal except that the jamming transmitter that will estimate channel, the interference that utilizes signal that reception antenna receives and wire message way to send transmits, just can estimate channel parameter, then, use the same method other jamming transmitters are carried out channel estimating.

5. interference elimination method as claimed in claim 2 is characterized in that, described channel simulator is auto-adaptive fir filter or single tap multiplier.

6. interference elimination method as claimed in claim 1 is characterized in that, as much as possible receiver antenna is positioned on the jamming transmitter aerial radiation minimal point position.

7. interference elimination method as claimed in claim 6 with the dual-mode antenna vertical arrangement of same base station, is a transmitter antenna above, is receiver antenna below.

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