CN1145384C - Array transmitting method and equipment for broad-band radio communication system - Google Patents

Abstract

The present invention discloses an array transmitting method used for a broadband wireless communication system and a device. When a reception signal-to-noise ratio is increased as much as possible by the method, a mobile station is guaranteed to be capable of obtaining sufficient time diversity gain according to the estimation to the angle and the average gain of a channel during upstream reception and the reasonable adjustment of the weight values of transmitted wave beams in each direction. The device comprises an upstream multi-path separation module, a parameter estimation module of an upstream channel, a downstream weight generating module, a downstream digital-to-analog converter and a downstream transmitting module. The present invention is suitable for channel environments of the expansion of any angles. In addition, the present invention has the advantages of simple calculation and easy realization.

Description

The array transmitting method that is used for system of broadband wireless communication

The present invention relates to system of broadband wireless communication, more specifically refer to a kind of array transmitting method that is used for system of broadband wireless communication.

Intelligent antenna technology is adjusted antenna pattern in real time by the weights that change array antenna, the gain of enhancing on the direction of subscriber signal, thereby improve subscriber signal intensity in the wireless communication system effectively, reduce interference each other, improve systematic function at aspects such as coverage, the availability of frequency spectrum and capacity.Array antenna is mounted in the base station in the common wireless communication system, and travelling carriage can only have an antenna, and therefore carrying out wave beam formation in the base station to transmitting is the effective ways that improve down link (base station is to travelling carriage) performance.

All beam-forming technologies all are to finish on the basis of channel estimating.Just can therefrom extract channel response when the base station receives through the mobile station signal of dissemination channel and finish uplink beam formation, but downlink wave beam is formed on signal through before the dissemination channel, does not comprise the information of channel in the at this moment processed signal.Can think that in the system of time division duplex the channel response of up-downgoing is identical and directly utilize up estimated result.In frequency division duplex system since uplink and downlink works on different frequencies, the transient response of up-downgoing channel is independent, can not directly estimate be used for downlink wave beam to the up channel response and form.But this moment some the slow variable elements in the channel, for example direction of arrival and average gain etc. remain identical.These that can utilize that up array received signal estimates become channel parameter slowly to be finished downlink wave beam and forms.Common method is the direction (it has reflected the strongest direction of channel gain) that estimates up received signal average power maximum, adjusts weight of downgoing emission and makes downlink wave beam point to this direction.This based on the angle estimation approach have calculate simple, realize the advantage that is easy to, be widely used in the antenna system.

In wide-band communication system, receiver can be isolated the multipath signal that different time arrives, and utilizes the characteristic that declines between the multipath signal independently to carry out time diversity and receives and can effectively suppress decline, and signal quality is obviously improved.The angle spread of channel hour (asking for an interview shown in Figure 1), point to channel gain the wave beam of strong direction covered contiguous multipath direction simultaneously, can provide enough diversity gains for travelling carriage simultaneously improving signal to noise ratio.But the angle spread of working as channel is bigger, when the angle between the multipath differs big, situation among Fig. 2 appears, the strongest gain direction of beam position, the concentration of energy that transmits is on a footpath, and the signal in other footpath is suppressed by wave beam, though at this moment the signal to noise ratio of travelling carriage received signal reaches maximum, but owing to received only a footpath signal, the decline of travelling carriage suppresses ability drop.If make antenna pattern form peak value as shown in Figure 3 on several multipath directions this moment, can guarantee that then travelling carriage obtains strong time diversity gain, but, may cause the travelling carriage received signal to noise ratio to descend because signal energy is dispersed on several directions.Therefore, the snr gain or the diversity gain that improve base station transmit signals individually are not best bets, and optimal transmit weights should be trading off between snr gain and time diversity gain.

, the objective of the invention is for this reason, propose a kind of array transmitting method that is used for system of broadband wireless communication at the problems referred to above so that the base station to the weighting that transmits after, snr gain and diversity gain that travelling carriage receives reach optimum efficiency.

To achieve these goals, the present invention adopts following array transmitting method,

This method may further comprise the steps:

A, up receiving array signal is carried out multipath separate, estimate gain and angle parameter of each footpath channel then;

B, isolated each footpath select a footpath of average gain maximum in channel, be called most powerful path;

C, set a gain threshold, select the multipath of the gain inequality of all and most powerful path less than this gain threshold;

D, set an angle thresholding again, the angle parameter of all multipaths that will select from step c compares in twos, if the difference of certain two footpath angle parameter is less than the angle thresholding of setting, then remove the little footpath of gain, the difference of angle parameter is all greater than the angle threshold multi-path of setting between each footpath of finally selecting;

E, according to the aerial array flow pattern of base station and after steps d selected each the footpath angle generate one group of steering vector;

F, this group steering vector is obtained Launch Right after according to each directly gain weighted sum and normalization, utilize this weights adjustment will transmit signal amplitude and phase place on each antenna, launch by antenna after passing through digital-to-analogue conversion again.

The span of described gain threshold is-3～-8dB.

Described angle thresholding at array beams 3dB width to value between the 5dB width.

In the launching technique of invention, up receiving array signal is carried out multipath separate, estimate the gain and the angle parameter of each footpath channel then; Isolated each footpath select a footpath of average gain maximum in channel, set a gain and angle thresholding, the gain inequality of selecting all and most powerful path compares in twos less than the angle parameter of the multipath of this gain threshold and all multipaths of selecting, and the difference of angle parameter is all greater than the angle threshold multi-path of setting between each footpath of finally selecting; Angle according to selected each footpath of the aerial array flow pattern of base station generates one group of steering vector; This group steering vector is obtained Launch Right after according to each directly gain weighted sum and normalization, utilize this weights adjustment will transmit signal amplitude and phase place on each antenna, launch by antenna after passing through digital-to-analogue conversion again.Therefore, launching technique of the present invention is applicable to the channel circumstance of any angle spread, can improve the snr gain and the diversity gain of base station transmit signals with taking into account, performance improves 1.5dB than most powerful path method when angle spread is big, this method can obviously be better than at present the method for strong direction of only selective channel gain in wide-angle expansion environment neutrality, and has and calculate advantage simple, that be easy to realize.

Below in conjunction with drawings and Examples, method of the present invention is done one explains:

Fig. 1-Fig. 3 is respectively the channels transmit wave beam schematic diagram of formed different angles between base station and the travelling carriage.

Fig. 4 is an emitter structural principle schematic diagram of the present invention.

Suppose that channel has M multipath that separates, the signal that then up base station receives can be expressed as

$x\left(t\right)=\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{h}_m(t-{\mathrm{\τ}}_m)s(t-{\mathrm{\τ}}_m)\stackrel{\→}{a}\left({\mathrm{\θ}}_m\right)+i\left(t\right)+n\left(t\right)----\left(1\right)$

Wherein s (t) is that the user transmits, h _m(t) be m footpath channel response.Usually each footpath signal all is to be formed by stacking h by the signal that many time delays differ very little _m(t) be a Gaussian random process, can define its standard deviation h _mBe the average gain of channel,, can estimate, and hypothesis is constant in analysis time with the average of channel gain in a period of time because average gain is the slowly varying function of time. Be the array flow pattern of array antenna, it is by the element number of array and the placement location decision of array antenna.

It is the array response of l footpath direction.I (t) disturbs for the cochannel that other user in the system causes, and n (t) is a white noise.

In broadband system, if the delay inequality between each multipath greater than the inverse of signal bandwidth, then receiver can come out the Signal Separation of different delay, adopts channel estimation technique can obtain the average gain h in each footpath respectively _mWith angle θ _m, then descending power can generate according to these parameters and known array flow pattern.

Therefore, the array transmitting method that the present invention is used for system of broadband wireless communication during according to up the reception to the angle of each footpath channel and the estimation of average gain, select relevant multipath, and generate one group of steering vector according to the gain and the angle of selected multipath channel, again steering vector weighted sum and the normalization that is generated is obtained the Launch Right of launching beam on all directions, by signal amplitude and the phase place that Launch Right adjustment will be launched, go out by transmission antennas transmit through after the digital-to-analogue conversion again.

Above-mentioned array transmitting method of the present invention further may further comprise the steps:

A, up receiving array signal is carried out multipath separate, estimate gain and angle parameter of each footpath channel then;

B, isolated each footpath select a footpath of average gain maximum in channel, be called most powerful path;

C, set a gain threshold, select the multipath of the gain inequality of all and most powerful path less than this gain threshold;

D, set an angle thresholding again, the angle parameter of all multipaths that will select from step c compares in twos, if the difference of certain two footpath angle parameter is less than the angle thresholding of setting, then remove the little footpath of gain, the difference of angle parameter is greater than the multipath of the angle thresholding of setting between each footpath of finally selecting;

E, according to the aerial array flow pattern of base station and after steps d selected each the footpath angle generate one group of steering vector;

F, this group steering vector is obtained Launch Right after according to each directly gain weighted sum and normalization, utilize this weights adjustment will transmit signal amplitude and phase place on each antenna, launch by antenna after passing through digital-to-analogue conversion again.

The span of described gain threshold is-3～-8dB.

Described angle thresholding at array beams 3dB width to value between the 5dB width.

See also shown in Figure 4, array emitter of the present invention comprises up multipath separation module 101, up channel parameter Estimation module 102, descending power generation module 103, descending digital to analog converter 104, downlink module 105, multiplier 106, the digital signal of up reception resolves into multipath signal through multipath separation module 101, the gain and the angle parameter of 102 pairs of each footpath signals of up channel parameter Estimation module are estimated, descending power generation module 103 utilizes each footpath channel parameter to form weight of downgoing emission, and downlink digital signal and weight of downgoing emission are changed through digital to analog converter 104 and downlink module 105 laggard line number moulds respectively after multiplier 106 conjugate multiplication and sent to the space by bay.

The number of described up channel parameter Estimation module 102 is identical with the multipath number;

The quantity of described downlink module 105 is identical with the quantity of bay.

As channel parameter estimation module 102 comprised 102_1,102_2 ... 102_m unit; Descending digital to analog converter 104 comprised 104_1,104_2 ... 104_n unit; Downlink module 105_1, a 105_2...105_n unit, wherein n bay quantity.

In Fig. 4, send into the angle θ that estimates each footpath among channel estimation module 102_1～102_m respectively through multipath separation module 101 generation M footpath multipath signals from the up receiving array signal of desired user _mWith average gain h _mEstimated result is sent into descending power generation module 103, generate after the downlink array weights conjugation with downlink digital signal Di through multiplier 106 multiply each other its amplitude of adjustment and phase place, the n road array signal of generation produces the downlink analog signals through the digital to analog converter 104 and the transmitter module 105 of each passage of aerial array respectively.

Wherein, descending power generation module 103 utilizes the direction of up each multipath channel and average gain estimated result to generate weights, downstream signal is weighted emission, and descending power generation module is the key modules of emitter of the present invention, and the processing procedure of this module is described below:

Suppose the up M of a searching multipath, their angle and gain are provided by the uplink channel estimation module.

So,

Descending power generation module 103 is at first therefrom selected a footpath of average gain maximum;

Set a gain threshold, select all and most powerful path gain inequality multipath less than this thresholding;

Set an angle thresholding, relatively select all and most powerful path gain inequality parameter in twos, if certain two footpath differential seat angle less than the angle thresholding, then removes the little footpath of gain less than the multipath of gain threshold.Finally obtain s bar multipath, parameter is designated as [θ ₁, h ₁], [θ ₂, h ₂] ..., [θ _s, h _s], wherein gain inequality is less than gain threshold between each footpath, and differential seat angle is then greater than the angle thresholding.

After the situation of known antenna array flow pattern, generate one group of steering vector according to the angle of selecting each footpath: $\stackrel{\→}{a}\left({\mathrm{\θ}}_0\right),\stackrel{\→}{a}\left({\mathrm{\θ}}_2\right),...,\stackrel{\→}{a}\left({\mathrm{\θ}}_s\right),$ With each weighted sum that directly gains: $\stackrel{\‾}{w}=\underset{i=1}{\overset{s}{\mathrm{\Σ}}}{\stackrel{\‾}{h}}_i\stackrel{\→}{a}\left({\mathrm{\θ}}_i\right),$ Export after the renormalization

${\stackrel{\‾}{w}}_{\mathrm{out}}=\stackrel{\‾}{w}/{\left|\right|\stackrel{\→}{w}\left|\right|}_2.$

The power that descending power generation module 103 is generated is assigned to the downlink energy on each footpath direction of selecting in the gain ratio.

Need to prove that adopting the advantage of method and apparatus of the present invention is to provide better diversity gain for travelling carriage.But emitted energy divides breaking up that the signal to noise ratio of travelling carriage received signal is descended to some extent, therefore determining a footpath whether to participate in that downlink wave beam forms is equilibrium between diversity gain and signal to noise ratio, if the gain in certain footpath is lower, transmit and also decrease along this energy that directly arrives travelling carriage, the signal to noise ratio that causes is thus decreased arrow just may offset its contribution to diversity, and such multipath just is unsuitable for participating in downlink wave beam and forms.Therefore in descending power generation module, be provided with gain threshold remove gain little (with the most powerful path gain inequality greater than thresholding) multipath.Its estimated value do not need to provide the absolute value of channel gain by the visible channel estimation module of operation finished of power generation module, as long as can reflect correctly that the relativeness of each footpath channel gain is just passable.In addition, usually smart antenna array element number can be not a lot, and wave beam always has certain width, travelling carriage can receive the multipath signal of wave beam in covering, so in descending power generation module the angle thresholding is set, removes angle and differ more weak footpath less than thresholding.Thereby, by analysis with emulation show gain threshold be made as-3～-3dB to 5dB width that 8dB, angle thresholding are made as array beams is advisable.

In the WCDMA system, the inventive method shows through the result of emulation, and is when channel angle is expanded less than 15 °, identical with the performance of selecting the most powerful path method; When angle spread during greater than 15 °, under the same bit error rate condition, with the required transmit signal power of method of the present invention than selecting the low 1.5db of strong routing method.

In sum, the descending power generation method among the present invention has excellent adaptability to the variation of channel circumstance.For the low-angle extended channel, all multipaths concentrate on when one very low-angle or the gain on certain direction are very strong, the downlink wave beam that the present invention forms with select the most powerful path method identical, the signal to noise ratio of maximum is provided for travelling carriage.When angle spread is big, exist gain quite and the multipath that differs greatly with angle, the downlink wave beam that the present invention forms is dispersed in signal energy on several stronger multipath directions in proportion, for travelling carriage provides better diversity gain.This moment, systematic function obviously was better than selecting at present the most powerful path method.

Claims (3)

1, a kind of array transmitting method that is used for system of broadband wireless communication is characterized in that,

This method may further comprise the steps:

A, up receiving array signal is carried out multipath separate, estimate gain and angle parameter of each footpath channel then;

B, isolated each footpath select a footpath of average gain maximum in channel, be called most powerful path;

C, set a gain threshold, select the multipath of the gain inequality of all and most powerful path less than this gain threshold;

D, set an angle thresholding again, the angle parameter of all multipaths that will select from step c compares in twos, if the difference of certain two footpath angle parameter is less than the angle thresholding of setting, then remove the little footpath of gain, the difference of angle parameter is all greater than the angle threshold multi-path of setting between each footpath of finally selecting;

E, according to the aerial array flow pattern of base station and after steps d selected each the footpath angle generate one group of steering vector;

F, this group steering vector is obtained Launch Right after according to each directly gain weighted sum and normalization, utilize this weights adjustment will transmit signal amplitude and phase place on each antenna, launch by antenna after passing through digital-to-analogue conversion again.

2, array transmitting method according to claim 1 is characterized in that: the span of described gain threshold is-3～-8dB.

3, array transmitting method according to claim 1 is characterized in that: described angle thresholding at array beams 3dB width to value between the 5dB width.