CN101272226A - Indoor-overlapping multi-input multi-output system and method of TD-SCDMA system - Google Patents

Abstract

A multi-input multi-output system indoor covered in a time diversion synchronous code division multiple access system comprises a user terminal and a base station; the user terminal is provided with an independent weak double-antenna; the system is collocated to be that two channels are mixed to cover a certain area together to an indoor covering environment; the channels keep independent with each other; the system adopts a multi-input multi-output mode of 2 multiplied by 2; the invention also discloses a multi-input multi-output method applied in the system; the base station evaluates the situation of a user business throughput under the space diversity and the space multiplexing modes and self-adaptively respectively switches an upstream link and a downstream link into a mode with a higher throughput speed evaluation value; thereby integrating the advantages of the existing two multi-input multi-output modes and simultaneously avoiding the defects of the two multi-input multi-output modes when the two multi-input multi-output modes are independently used in a TD-SCDMA system, thus remarkably improving the business capacity.

Description

The multi-input multi-output system of the indoor covering of TDS-CDMA system and method

Technical field

The present invention relates to TD SDMA (TD-SCDMA) system, relate in particular to the system and method for using multiple-input and multiple-output (MIMO) technology in the TD-SCDMA system chambers that adopts smart antenna, covering.

Background technology

The MIMO technology is the popular research field of moving communicating field in recent years, and it is characterised in that transmitting set and receiver all introduced many antennas.With respect to the traditional single output of single input (SISO) system, mimo system obtains the very big lifting of power system capacity by space diversity reception to communicate or space multiplexing technique.Many single outputs of input (MISO) and single many outputs of input (SIMO) are two kinds of special shapes of MIMO, and promptly an end at communication link adopts many antennas, and the other end still adopts single antenna.

The main flow scheme that covers in the existing TD-SCDMA system chambers is to adopt the distributed covering of multichannel.With the distributed example (follow-up as do not do specified otherwise then do not give tacit consent to 8 passages) that is covered as of 8 passages, base-station node (Node B) adopts 8 independently distributed passages, one group of ceiling mount antenna of each passage band independently covers certain zone (for example certain floor of office building), having only between the different passages is very little overlapping covered to guarantee to cover (for example staircase) continuously, and user terminal (UE) generally adopts single antenna, therefore, communication link in Node B and the sub-district between UE is the SISO mode fully.

For other 3G (Third Generation) Moblie (3G) systems that adopt the CDMA mode, the spreading rate of TD-SCDMA system is lower, so the multi-path resolved rate of receiver is relatively poor, and the rake gain is remarkable not as other 3G systems.Especially in indoor environment, because the expansion of the time delay of channel is very narrow, may obtain the rake gain hardly, so this just introduces space diversity gain by the MIMO mode and has stayed very big performance and improve the space for follow-up.

Certainly, the MIMO technology merges the average that improves signal to noise ratio except the space diversity mode by asthenia and high specific, dwindle variance, thereby beyond the lifting on the acquisition capacity, can also pass through spatial multiplexing mode, utilize the independence of different antennae channel to set up a plurality of spatial sub-channels and come the raising capacity, famous BLAST (layering when Bell Laboratory is empty) technical scheme that Here it is.In theory, the power-carrying of spatial multiplexing mode is that the lifting along with antenna number is linear lifting, but not the relation of the logarithm lifting under the space diversity mode.

But, this dual mode (space diversity mode, spatial multiplexing mode) of existing MIMO technology is not perfect solution, uses in covering in the TD-SCDMA system chambers separately then to possess following pluses and minuses separately:

1.TD-SCDMA the advantage of using MIMO space diversity mode is in the indoor covering:

A) performance gain is more sane, the problem of the degree of freedom deficiency that causes at strong LOS environment can not occur under the spatial multiplexing mode;

B) under low signal-to-noise ratio, by diversity and merge capacity lifting that the improving gain signal to noise ratio brings than the multiplexing height of space delamination.

2.TD-SCDMA the shortcoming of using MIMO space diversity mode is in the indoor covering: better in some channel independence, capacity is not as the MIMO spatial multiplexing mode under the scene of interference also not serious (signal to noise ratio is higher).

3.TD-SCDMA the advantage of using MIMO spatial multiplexing mode is in the indoor covering: better in some channel independence, capacity promotes very big under the scene of interference also not serious (signal to noise ratio is higher).

4.TD-SCDMA the shortcoming of using MIMO spatial multiplexing mode is in the indoor covering: at strong LOS environment, the limited situation of the degree of freedom can appear in the Data Detection of descending UE side, cause Node B must close the emission of certain passage, this is a very big loss for power system capacity.

And in the indoor covering of TD-SCDMA system using MIMO technique especially spatial multiplex scheme possess advantage, this shows:

1. the adjacent area interference of indoor covering is very little, exists the outdoor macro honeycomb multi-plot joint to detect the problem of the degree of freedom hardly;

2. indoor environment is because specular scattering is numerous and angle spread is big, so the probability that the LOS footpath definitely is dominant is smaller.

Therefore, in existing TD-SCDMA system chambers, cover in using MIMO technique (especially spatial multiplexing mode) will promote the up-downgoing throughput greatly.And the TD-SCDMA system is as a kind of 3G system of smooth evolution backward that supports, the pursuit that improves for the data service throughput is to exist forever.

Summary of the invention

Technical problem to be solved by this invention provides a kind of system and method based on using MIMO technique in the covering in the TD-SCDMA system chambers of covering of mixed distribution formula and ADAPTIVE MIXED space collection multiplexing technology, thereby increases substantially the up-downgoing business throughput of overlay environment in the TD-SCDMA system chambers.

The main contents of technical solution of the present invention are as follows:

The multi-input multi-output system of the indoor covering of a kind of TDS-CDMA system, comprise user terminal and base station, it is characterized in that described TDS-CDMA system is configured to two passages to indoor overlay environment and mixes common certain zone that covers, and keeps independent between the described passage; Two antennas of described user terminal configuration form independent weak double antenna; The binary channels that any a pair of mixing of the different antennae of described user terminal and described base station covers is all distributed different basic Midamble sign indicating numbers, or all distributes the difference skew of same basic Midamble sign indicating number; Described TDS-CDMA system adopts 2 * 2 multiple-input and multiple-output modes.

Described two passages mix the summation that common its size of zone that covers equals existing two passage independence overlay areas.

A kind of multiple-input multiple-output method that is applied in the said system may further comprise the steps:

(1) uplink channel estimation is carried out in the base station, and by the described uplink channel estimation channel relevancy between the channel relevancy between the real-time assessment base station receiving terminal antenna and the user terminal transmitting terminal antenna as a result, if both channel relevancies are all less than default thresholding, then enter step (2), otherwise its uplink downlink is switched to the space diversity mode;

(2) real-time assessment is carried out to up and/or the customer service throughput rate of down link under space diversity mode and spatial multiplexing mode in the base station, and up and/or down link are switched to the higher mode of throughput rate assessed value.

Described base station is carried out real-time assessment for the customer service throughput rate of up link and comprised: the base station is according to the uplink channel estimation result, and, respectively the customer service throughput rate under upstream space diversity mode and the upstream space multiplex mode is carried out real-time assessment in conjunction with the interference measurement results of each reception antenna.

Described base station is carried out real-time assessment for the customer service throughput rate of down link and comprised: user terminal carries out the signal power measurement of two transmitting antennas of descending two reception antenna respective base station and the interference power of two reception antennas is measured, and give the base station with described measurement feedback, real-time assessment is carried out to the customer service throughput rate under descending space diversity mode and the descending spatial multiplexing mode respectively according to the described measurement result that user terminal fed back in the base station.

Adopt the mimo system and the method that cover in the TD-SCDMA system chambers based on covering of mixed distribution formula and ADAPTIVE MIXED space collection multiplexing technology of the present invention, having improved the interior distribution of existing TD-SCDMA system chambers does not greatly almost have the deficiency of spatial domain diversity gain, merged the advantage of existing MIMO space diversity mode and spatial multiplexing mode to greatest extent, the shortcoming that has faced when having avoided both in the TD-SCDMA system, to use separately simultaneously, minimum with system and hardware structure (especially at network side) is changed cost, has exchanged significant capacity for and has improved.

Description of drawings

Fig. 1 is the switch decision flow chart of adaptive MIMO space diversity mode and spatial multiplexing mode in the TD-SCDMA indoor covering system of the present invention.

Embodiment

Increase a stand-alone antenna in the UE side, form independent weak double antenna; Changing the existing indoor overlay environment single channel of TD-SCDMA, independently to cover certain zone be that two passages mix the common certain zone (annotate: mixing overlay area size equals to have now the summation of two passage independence overlay areas) that covers, so onesize overlay area, the total number of channels of existing system remains unchanged.All passages remain independently, and the different ceiling mount antennas that promptly belong to two passages will guarantee its weak independence (this point is obviously accomplished indoor being easy to) on the distance of position; Therefore mixed the zone that covers arbitrary by binary channels, formed 2 * 2MIMO mode.UE side different antennae is distributed the difference skew (perhaps distributing different basic Midamble sign indicating numbers) of same basic Midamble sign indicating number; Similarly, the binary channels of any a pair of mixing covering of Node B side all will distribute the difference of same basic Midamble sign indicating number to be offset (perhaps distributing different basic Midamble sign indicating numbers).

Node B is according to the adaptive switching of carrying out MIMO space diversity mode and spatial multiplexing mode of following criterion:

The channel relevancy of assessment receiving terminal (Node B) antenna when 1.Node B passes through the uplink channel estimation fructufy and the channel relevancy of transmitting terminal (UE) antenna, the higher space diversity mode that then switches to of the Antenna Correlation of any end, two correlation assessments of then carrying out follow-up criterion all on the low side;

2.Node B is according to the uplink channel estimation result, and in conjunction with the interference measurement results of each reception antenna, respectively the customer service throughput rate under upstream space diversity mode and the upstream space multiplex mode is carried out real-time assessment, and up link is switched to the higher mode of throughput rate assessed value;

3.UE signal power measurements with corresponding Node B two transmitting antennas of descending two reception antennas (2 * 2), interference power measurement result together with two reception antennas feeds back to Node B with certain form, Node B carries out real-time assessment to the customer service throughput rate under descending space diversity mode and the descending spatial multiplexing mode respectively, and down link is switched to the higher mode of throughput rate assessed value.

For the space diversity mode, transmitting terminal is that transmit diversity, receiving terminal are receive diversity.It (is that weight of downgoing emission generates by uplink channel estimation that the weights of uplink and downlink transmit diversity (wave beam forming) can generate based on the channel estimating that opposite link is obtained, up emission value is estimated to generate by down channel), can certainly adopt the mode of mutual feedback to obtain.The receiver of uplink and downlink merges (becoming 2 * 1 by 2 * 2) for the channel impulse response of different transmit antennas on same reception antenna, adopts the joint-detection mode under the double antenna to carry out subsequent treatment then.

For spatial multiplexing mode, antenna rate controlled (PARC) mode of pursuing that uplink and downlink transmitting terminal different antennae emission different pieces of information, the modulation of every antenna and coded system (MCS) adopt similar 3GPP TR25.867 technical documentation to mention is determined; The NodeB receiver is included the data of UE different transmit antennas in two antenna combined detection system equations, and the detection of carrying out each independent signal uniformly separates; Vice versa.

Notice that the foregoing invention content can expand to UE stand-alone antenna number fully similarly greater than 2 situation, this moment system side to mix the common autonomous channel number that covers also consistent with the number of UE stand-alone antenna.

In addition, thought of the present invention not merely is confined to the range of application of indoor covering, can also extend in the outdoor distributed covering scene to go.

Be that example is specifically introduced the execution mode that the several committed steps in the foregoing invention content may adopt with descending high speed business below, but thought of the present invention is not confined on these details execution modes, any employing thought of the present invention but adopt other equivalent details execution modes should be considered yet and adopted the present invention program.

A kind of assessment mode example of Node B and UE antenna channel correlation

If

Be that up Node B m root reception antenna is received the channel impulse response sequence of also passing through the thresholding reprocessing after the channel estimating of user (UE) i n transmit antennas, 2 * 2 total channel impulse responses of this user can be write as matrix so

$H_i=\left[\begin{array}{cc}{\hat{h}}_i^{\left(\mathrm{1,1}\right)}& {\hat{h}}_i^{\left(\mathrm{1,2}\right)}\\ {\hat{h}}_i^{\left(\mathrm{2,1}\right)}& {\hat{h}}_i^{\left(\mathrm{2,2}\right)}\end{array}\right]---\left(1\right)$

Therefore, the Node B aerial signal spatial correlation matrix of user i correspondence is:

$R_{i,\mathrm{NB}}=H_i\·{H_i}^H=\left[\begin{array}{cc}{r}_{\mathrm{1,1},\mathrm{NB}}& r_{\mathrm{1,2},\mathrm{NB}}\\ r_{\mathrm{2,1},\mathrm{NB}}& r_{\mathrm{2,2},\mathrm{NB}}\end{array}\right]---\left(2\right)$

Equally, the UE aerial signal spatial correlation matrix of user i correspondence is:

$R_{i,\mathrm{UE}}={H_i}^H\·H_i=\left[\begin{array}{cc}{r}_{\mathrm{1,1},\mathrm{UE}}& r_{\mathrm{1,2},\mathrm{UE}}\\ r_{\mathrm{2,1},\mathrm{UE}}& r_{\mathrm{2,2},\mathrm{UE}}\end{array}\right]---\left(3\right)$

A kind of simple Node B two antenna coefficient correlations or UE two antenna coefficient correlations can be done as giving a definition:

${\mathrm{\ρ}}_{i,\mathrm{NB}}=\frac{2\·\left|r_{\mathrm{1,2},\mathrm{NB}}\right|}{r_{\mathrm{1,1},\mathrm{NB}}+r_{\mathrm{2,2},\mathrm{NB}}}---\left(4\right)$

${\mathrm{\ρ}}_{i,\mathrm{UE}}=\frac{2\·\left|r_{\mathrm{1,2},\mathrm{UE}}\right|}{r_{\mathrm{1,1},\mathrm{UE}}+r_{\mathrm{2,2},\mathrm{UE}}}---\left(5\right)$

If the Node B antenna coefficient correlation ρ that calculates _{I, NB}With UE antenna coefficient correlation ρ _{I, UE}In have one then user i switch to the space diversity mode greater than predefined certain threshold value, otherwise carry out the assessment of follow-up criterion.

Above-mentioned antenna submatrix coefficient correlation ρ _{I, NB}And ρ _{I, UE}Calculating can also calculate according to the mode of mean value, principle is similar.

A kind of assessment example of user's downlink business throughput and modulation coding mode (MCS) under space diversity mode and the spatial multiplexing mode

Definition $P_i=\left[\begin{array}{cc}{P}_i\left(\mathrm{1,1}\right)& P_i\left(\mathrm{1,2}\right)\\ P_i\left(\mathrm{2,1}\right)& P_i\left(\mathrm{2,2}\right)\end{array}\right]$ Be the descending received power matrix of user i, wherein P _i(m, n) m the received signal power measurement result of Node B antenna emission data on n root UE reception antenna of expression; Definition I=[I (1) I (2)] be the interference power measurement result on two antennas of UE (only consider can not disturbed removing method curb residual interference).

The space diversity mode

Total carrier/interface ratio (C/I) approximate evaluation after the down receiving signal double antenna merges is:

${\left(\frac{C}{I}\right)}_i=\frac{{(\sqrt{P_i\left(\mathrm{1,1}\right)}+\sqrt{P_i\left(\mathrm{2,1}\right)})}^2}{I\left(1\right)}+\frac{{(\sqrt{P_i\left(\mathrm{1,2}\right)}+\sqrt{P_i\left(\mathrm{2,2}\right)})}^2}{I\left(2\right)}---\left(6\right)$

Then according to different MCS in above-mentioned carrier/interface ratio

Under the Block Error Rate index, calculate the highest Block Error Rate restriction (for example 10%) condition, the MCS of business throughput maximum with and corresponding throughput index.

Spatial multiplexing mode

Node B antenna 1 transmits and in the total carrier/interface ratio of descending received signal (C/I) approximate evaluation is:

${\left(\frac{C}{I}\right)}_{i,1}=\frac{P_i\left(\mathrm{1,1}\right)}{I\left(1\right)}+\frac{P_i\left(\mathrm{1,2}\right)}{I\left(2\right)}---\left(7\right)$

Node B antenna 2 transmits and in the total carrier/interface ratio of descending received signal (C/I) approximate evaluation is:

${\left(\frac{C}{I}\right)}_{i,2}=\frac{P_i\left(\mathrm{2,1}\right)}{I\left(1\right)}+\frac{P_i\left(\mathrm{2,2}\right)}{I\left(2\right)}---\left(8\right)$

Then according to different MCS in above-mentioned carrier/interface ratio

With Under the Block Error Rate index, calculate the highest Block Error Rate restriction (for example 10%) condition respectively, transmitting antenna 1 and transmitting antenna 2 separately the maximum corresponding MCS of throughput with and corresponding throughput index, at last with the throughput sum of two transmitting antennas as the total throughput of this user.

After having provided the embodiment of top 3 committed steps, provide whole handoff procedure at the adaptive space diversity and the spatial multiplexing mode of arbitrary user i down link referring now to Fig. 1:

Step 1:Node B carries out up 8 * 2 channel estimating, comprises that this cell channel is estimated and adjacent cell channel is estimated;

Step 2:Node B if correlation is higher than a certain default thresholding, then switches to the space diversity mode with its down link, end switch decision process at the channel relevancy that user i assesses two submatrixs; Otherwise enter step 3;

Step 3: user i carries out descending 2 * 2 channel estimating, comprises that this cell channel is estimated and adjacent cell channel is estimated;

Step 4: the degree of freedom situation that user i detects descending multi-plot joint is assessed and is fed back to Node B;

Step 5:UE carries out 2 * 2 received signal power measurements, and the measurement of two reception antenna interference powers, and above-mentioned measurement result is fed back to Node B with certain form;

Does step 6:Node B judge according to the feedback result of step 4 whether adopt the degree of freedom that descending multi-plot joint detects after the spatial multiplexing mode enough? if not enough, then its down link is switched to the space diversity mode, finish the switch decision process; Otherwise enter step 7;

Step 7:Node B estimates the throughput of descending space diversity mode and spatial multiplexing mode respectively according to the feedback result of step 5, and finally switches on the big MIMO mode of throughput.

Node B down transmission diversity (beam shaping) weights under the space diversity mode generate

Behind the using MIMO technique, the weights of Node B down transmission diversity (wave beam forming) need be considered the factor that UE side diversity antenna merges, with maximum receiving signal power is example, because the antenna of UE side merge make signal be form with power in stack, so the optimization criterion of wave beam forming should guarantee UE two antenna receiving signal power sum maximums.

If user i transmitting antenna 1 is R at the signal space correlation matrix that Node B receiving terminal forms _{I, 1}, transmitting antenna 2 is R at the signal space correlation matrix that Node B receiving terminal forms _{I, 2}, transmit diversity (beam shaping) weight w then _iShould for:

$w_i=\underset{w_i}{\arg }\max ({w_i}^H\·(R_{i,1}+R_{i,2})\·w_i)---\left(9\right)$

So down transmission diversity weight w of user i _iDesirable value should be square formation (R _{I, 1}+ R _{I, 2}) eigenvalue of maximum characteristic of correspondence vector.

The embodiment of uplink service and downlink business are identical, do not repeat them here.

Claims (7)

1. the multi-input multi-output system of the indoor covering of TDS-CDMA system, comprise user terminal and base station, it is characterized in that described TDS-CDMA system is configured to two passages to indoor overlay environment and mixes common certain zone that covers, and keeps independent between the described passage; Two antennas of described user terminal configuration form independent weak double antenna; The binary channels that any a pair of mixing of the different antennae of described user terminal and described base station covers is all distributed different basic Midamble sign indicating numbers, or all distributes the difference skew of same basic Midamble sign indicating number; Described TDS-CDMA system adopts 2 * 2 multiple-input and multiple-output modes.

2. the multi-input multi-output system of the indoor covering of TDS-CDMA system as claimed in claim 1 is characterized in that, described two passages mix the summation that common its size of zone that covers equals existing two passage independence overlay areas.

3. multiple-input multiple-output method that is applied in the system according to claim 1 may further comprise the steps:

(1) uplink channel estimation is carried out in the base station, and by the described uplink channel estimation channel relevancy between the channel relevancy between the real-time assessment base station receiving terminal antenna and the user terminal transmitting terminal antenna as a result, if both channel relevancies are all less than default thresholding, then enter step (2), otherwise its uplink downlink is switched to the space diversity mode;

(2) real-time assessment is carried out to up and/or the customer service throughput rate of down link under space diversity mode and spatial multiplexing mode in the base station, and up and/or down link are switched to the higher mode of throughput rate assessed value.

4. multiple-input multiple-output method as claimed in claim 3, it is characterized in that, described base station is carried out real-time assessment for the customer service throughput rate of up link and comprised: the base station is according to the uplink channel estimation result, and, respectively the customer service throughput rate under upstream space diversity mode and the upstream space multiplex mode is carried out real-time assessment in conjunction with the interference measurement results of each reception antenna.

5. multiple-input multiple-output method as claimed in claim 3, it is characterized in that, described base station is carried out real-time assessment for the customer service throughput rate of down link and comprised: user terminal carries out the signal power measurement of two transmitting antennas of descending two reception antenna respective base station and the interference power of two reception antennas is measured, and give the base station with described measurement feedback, real-time assessment is carried out to the customer service throughput rate under descending space diversity mode and the descending spatial multiplexing mode respectively according to the described measurement result that user terminal fed back in the base station.

6. multiple-input multiple-output method as claimed in claim 3, it is characterized in that, described space diversity mode is: transmitting terminal is that transmit diversity, receiving terminal are receive diversity, on/channel estimating that the weights of down transmission diversity wave beam forming obtain based on opposite link generates, be that weight of downgoing emission generates by uplink channel estimation, up emission value is estimated to generate by down channel, perhaps adopts the mode of feeding back mutually to obtain; On/descending receiver merges for the channel impulse response of different transmit antennas on same reception antenna, adopts the joint-detection mode under the double antenna to handle then.

7. multiple-input multiple-output method as claimed in claim 3, it is characterized in that, described spatial multiplexing mode is: on/downlink end different antennae emission different pieces of information, the modulation of every antenna and coded system adopt by antenna rate controlled mode to be determined, base station receiver is included the data of user terminal different transmit antennas in two antenna combined detection system equations, and the unified detection of carrying out each independent signal separates.

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