CN1150712C - Down link receiving method for cancelling interference of common down channel before despreading - Google Patents

Abstract

The present invention relates to a downlink receiving method for counteracting common channel interference in code division multiple access (CDMA) communication. The receiving method of the present invention has the fundamental principle that a contribution item of a common interference channel in a signal is subtracted when the required channel receives the signal; the difference signal is used as the judgment base of the transmission information of the required channel. The removal of the common interference channel item is carried out before the required channel is de-spread. The method of the present invention can enhance the receiving performance of required signals, and consequently enhance the performance of the whole system. The method of the present invention is applied to the down CDMA receiving mode.

Description

The down link receiving method that counteracting downstream common channel disturbs before the despreading

(1) technical field:

The invention belongs to code division multiple access (CDMA) communications field, comprise cellular mobile communication and fixed wireless access.

The present invention relates to offset the down link receive mode that common signal channel disturbs, is the descending receive mode of a kind of brand-new cdma communication, and this receive mode can almost need not to increase under the situation of implementation complexity, improves the receptivity of required channel.

(2) background technology:

Any cdma communication system is in order to guide subscriber board work or in order to improve efficiency of transmission, to be bound at descending adding some public control and CTCH Common Traffic Channels.In the WCDMA standard of 3G (Third Generation) Moblie 3GPP, descending basic/auxiliary-Common Control Channel, continuous pilot channel, master/auxiliary-synchronizing channel, the DSCH Downlink Shared Channel etc. of just having.For CDMA2000 similar common down channel is arranged also.

Though the adding of common down channel makes subscriber board can make things convenient for access network efficiently in the CDMA communication, also brought multiple access to disturb simultaneously to other downlink traffic channel.Even descending employing synchronized orthogonal coding mode is distinguished these channels, but because the influence of multipath effect, this interference still can exist.And the power of common signal channel is often all more intense, so this interference has ill effect to the reception of Traffic Channel.

(3) summary of the invention:

The object of the present invention is to provide the descending receive mode of a kind of new CDMA, can improve the performance of the existing descending reception of CDMA effectively.

Down channel is meant in the present invention: the code channel that is mail to the certain information of carrying that the different spreading codes of the usefulness of travelling carriage distinguish by the base station.In the present invention, down channel is divided into required channel, common interference channel and other channel three kinds.Required channel is exactly some channels that subscriber board is receiving at present, and not getting rid of is common signal channel.The common downlink interference channel is meant the common downlink channel except required channel.The present invention suppose before the despreading of common downlink interference channel or after the despreading signal can be by part in advance known and estimation obtain, this had both comprised can obtain its data and spreading code, also comprises the position and the channel complex gain that can obtain its footpath.

The precondition of method of reseptance of the present invention is:

(1) carrier synchronization and timing are set up synchronously

The footpath timing position of the descending common interference channel that (2) will offset and its corresponding complex gain have been estimated to obtain

The spreading code of the descending common interference channel that (3) will offset is known in advance or detect and to obtain

The symbol of the descending common interference channel that (4) will offset is known in advance or estimate to obtain.

These preconditions can obtain by known or existing classical way estimation in advance.

Method of reseptance basic step of the present invention is: under the situation that above-mentioned precondition has possessed

(1) the descending common interference channel that selection will be offset from all common down channels;

(2) at the some descending common interference channels that will offset in (1),, then to selecting to known symbols spread scrambling;

(3) at the descending common interference channel in (2), in its all possible footpath, select the footpath that will offset, then result in (2) is constituted signal behind the spread spectrum in a plurality of footpaths to these complex gains that directly multiply by them;

(4) at the descending common interference channel in (2), by different timing position directly the results added in (3) is merged, so just estimate that obtaining this descending common interference channel disturbs the reconstruct item to received signal;

(5) all adopt (2), (3), (4) step structure interference reconstruct item to received signal at each descending common interference channel in (1), then these merging of time alignment additions have as a result just been constructed all the descending common interference channels that will offset and in received signal, disturbed the reconstruct item;

(6) when receiving, required channel deducts all common interference channel disturbance reconstruct items in (5) with the input received signal;

(7) do conventional relevant despreading with the difference signal in (6) as the despreading input signal of required channel.

In sum, essential characteristic of the present invention is:

In received signal, deduct the common interference channel contribution item of the not despreading of structure, then this difference signal is done conventional despreading as the input signal of required channel despreading.

The inventive method need illustrate following some:

(1) only offsets the common signal channel distracter, and do not consider dedicated channel.

(2) origin cause of formation of common signal channel distracter no matter, for example: no matter be that multipath makes so or because sign indicating number is non-orthogonal, as long as it has formed interference to required channel.

(3) which kind of is no matter to the obtain manner of complex gain, symbol and the spreading code of common signal channel distracter.

(4) no matter whether the common signal channel distracter receives just at the same time.Certainly more convenient to the counteracting of the common signal channel distracter that receives simultaneously.

(5) can offset part common signal channel distracter, also can offset whole common signal channel distracters.

(6) for the counteracting of a plurality of common signal channels, no matter offsetting step is to offset one by one, offset or disposable whole counteracting in batches.

Beneficial effect of the present invention: meaning of the present invention is to improve the quality of reception of required down channel.For subscriber board, because some common signal channel is always in stopping to receive, the information of common signal channel can be estimated to obtain in passing, adds the implementation complexity of subscriber board so this performance improves very to reduce.

(4) description of drawings:

Fig. 1 is the method for reseptance framework schematic diagram that single footpath counteracting downstream common channel disturbs.Wherein: k is the number of the common down channel that will offset;

A is an input signal;

Spreading code for the common down channel distracter;

c _EchSpreading code for required channel;

For the common down channel data symbol that will offset is adjudicated the estimated value that gets from the relevant despreading of received signal;

Channel gain valuation for the descending common signal channel contribution item that will offset;

By the mark cinder of being resided expands the back mark;

A be with

Or c _EchDigital correlator for local code;

B be to

Or c _EchFor getting the sign bit hard decision, the digital correlator of local code output result gets the information symbol estimated value Directly will with

Or c _EchDigital correlator for local code; Output delivery as a result obtains the channel gain estimation

${\hat{g}}_{\mathrm{cl}\·\·\·\·\·\·}{\hat{g}}_{\mathrm{ck}};$

C is to the spreading code spread spectrum of information symbol with this common signal channel;

D is the time alignment delayer, is used for the common interference channel time of input signal and structure is aimed at.

(5) embodiment:

Specific embodiments of the invention will be described in detail as follows in conjunction with Fig. 1.

Fig. 1 has described the distracter that method of reseptance that single footpath counteracting downstream common channel disturbs is only offset a footpath of common interference channel.

Method step is as follows:

(1) each common interference channel that will offset is implemented despreading;

(2) obtain the information symbol valuation and the complex gain estimated value of each common interference channel;

(3) with the information symbol value with its corresponding spreading code spread spectrum;

(4) channel gain takes advantage of the result of (3) to rebuild signal after these common interference channel spread;

(5) time alignment deducts signal behind the common signal channel spread spectrum of these reconstructions from received signal, just obtains the signal before the desired signal despreading.

Protection of the present invention is not subjected to the restriction of Fig. 1 feature that embodiment describes, and comprises other distortion and the change in claims scope.

Claims (1)

1. the down link receiving method that counteracting downstream common channel disturbs before the despreading is characterized in that according to the following steps flow process:

(1) the descending common interference channel that selection will be offset from all common down channels;

(2) at the some descending common interference channels that will offset in (1),, then to selecting to known symbols spread scrambling;

(3) at the descending common interference channel in (2), in its all possible footpath, select the footpath that will offset, then result in (2) is constituted signal behind the spread spectrum in a plurality of footpaths to these complex gains that directly multiply by them;

(4) at the descending common interference channel in (2), by different timing position directly the results added in (3) is merged, so just estimate that obtaining this descending common interference channel disturbs the reconstruct item to received signal;

(5) all adopt (2), (3), (4) step structure interference reconstruct item to received signal at each descending common interference channel in (1), then these merging of time alignment additions have as a result just been constructed all the descending common interference channels that will offset and in received signal, disturbed the reconstruct item;

(6) when receiving, required channel deducts all common interference channel disturbance reconstruct items in (5) with the input received signal;

(7) do conventional relevant despreading with the difference signal in (6) as the despreading input signal of required channel.