CN102104948A - Downlink transmission method and device in distributed multiple input multiple output system - Google Patents
Downlink transmission method and device in distributed multiple input multiple output system Download PDFInfo
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- CN102104948A CN102104948A CN2009102012820A CN200910201282A CN102104948A CN 102104948 A CN102104948 A CN 102104948A CN 2009102012820 A CN2009102012820 A CN 2009102012820A CN 200910201282 A CN200910201282 A CN 200910201282A CN 102104948 A CN102104948 A CN 102104948A
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Abstract
The present invention relates to a downlink transmission method in a distributed multiple input multiple output (MIMO) system, comprising the following steps of: (a) selecting antennae in the system to obtain transmission vector matrixes of all users; and (b) distributing smallest power factor for each user in order to minimize the total transmission power of the system on the premise of ensuring the transmission quality. The downlink transmission method and the device in the distributed multiple input multiple output system have the advantages of improving the error rate performance of a multiple-base station multiple-user MIMO system and reducing the transmission power.
Description
[technical field]
The present invention relates to the communication network technology field, relate in particular to downlink transmission method and device in a kind of distributed MIMO system.
[background technology]
Along with mobile communication subscriber quantity constantly increases, a base station of traditional type makes that to a plurality of user's communications the capacity problem of system is more and more outstanding, and spaced antenna (DA, distributed antenna) system is considered to very competitive alternative with its large coverage, less characteristics such as switching.Have the notion of a kind of distributed multiple-input and multiple-output (MIMO) in the prior art, promptly the antenna of many base stations constitutes distributed multiaerial system, and constitutes distributed mimo system between many antennas of user.Many antennas for the base station end, owing to the correlation that exists between antenna and because different path fading, can make the channel of some antenna be in the deep fading, in order under the prerequisite that does not reduce power system capacity, to reduce the complexity of system, improve the efficient of transmission, need select the antenna in the system. for the situation that common single base station has, existing at present documents, but also do not carry out day line options and all antennas are carried out unified allotment for many antennas of many base stations.
The shortcoming of prior art is,
(1) in existing distributed MIMO system, the antenna of many base stations constitutes distributed many antennas, because the situation of base station and user's dimensional orientation, all antennas that are not the base station all are the second best in quality to user's channel, if the antenna of bad channel quality participates in the emission meeting in consumed power, and is less to the communication contribution of system.
What (2) all consider in the existing method is that the antenna that is positioned at the base station is incoherent situation, and in fact the antenna in same base station can have certain correlation, and this correlation can influence the utilization to diversity in the communication.
(3) existing method has been discussed the power system capacity under the different channels fade condition and how have been utilized channel information that descending beam shaping vector is optimized during for downlink transfer, but does not take into account how to make total consumed power minimum of system under the condition that satisfies the system transmissions performance.
[summary of the invention]
Technical problem to be solved by this invention is, downlink transmission method and device in a kind of distributed MIMO system are provided, to distributed MIMO multi-user system, it when downlink transfer the effect that obtains good space division multiplexing, not only considered the difference of the different base station that different spatial caused to the channel quality between the user, and considered that existing correlation is to the situation that influences of channel capacity between many antennas of same base station deployment, when obtaining the precoding vectors of downlink transfer optimum, can when satisfying telex network, reduce the total transmitting power of system by selection to different base station antenna in many base stations, by to the selection of antenna and scheduling between different base station in the system, can select to have the strongest channel to different user, the reliability of communication is improved.
In order to address the above problem, the invention provides the downlink transmission method in a kind of distributed MIMO system, comprise the steps: that (a) selects the antenna in the described system, to obtain each user's used for vector transfer matrix; (b) under the prerequisite that guarantees transmission quality,, make total transmitting power of system reduce to minimum by for each user distributes the minimal power factor.
As optional technical scheme, described step (a) further comprises: (a1) select a certain user, the channel matrix of each base station to this user decomposed; (a2) select several the strongest in the characteristic sub-channel of each base station to this user channels to constitute user's used for vector transfer; (a3) the still non-selected user of another in the selective system, repeating step (a1) with (a2), to obtain each user's used for vector transfer matrix; (a4) transmission matrix to all users of being obtained carries out orthogonalization to eliminate common-channel interference.
As optional technical scheme, described step (b) further comprises: (b1) be respectively each user and select the strongest characteristic sub-channel of transmission signals in all subchannels that it had; (b2) under the prerequisite that guarantees transmission quality, determine power partition coefficient according to the characteristic value of determined each subchannel.
The present invention further provides the downlink transfer device in a kind of distributed MIMO system, comprised as lower module: Antenna Selection Module is used for the antenna of described system is selected, to obtain each user's used for vector transfer matrix; The power division module by for each user distributes the minimal power factor, makes total transmitting power of system reduce to minimum.
As optional technical scheme, described Antenna Selection Module further comprises as lower unit: resolving cell, be used to select a certain user, and the channel matrix of each base station to this user decomposed; Selected cell selects several the strongest in the characteristic sub-channel of each base station to this user channels to constitute user's used for vector transfer; The user travels through the unit, is used for another still non-selected user of selective system, repeats to implement resolving cell and selected cell, to obtain each user's used for vector transfer matrix; The orthogonalization unit is used for all users' of being obtained transmission matrix is carried out orthogonalization to eliminate common-channel interference.
As optional technical scheme, described power division module further comprises as lower unit: the subchannel selected cell is respectively each user and selects the strongest characteristic sub-channel of transmission signals in all subchannel that it had; The distribution coefficient computing unit is determined power partition coefficient according to the characteristic value of determined each subchannel.
The invention has the advantages that the bit error rate performance that has improved the multi-BS (base station) multi-user mimo system, reduce emitted power, specifically:
1, provides in the distributed MIMO system that many antenna for base station constitute system of selection to antenna for base station
In the distributed MIMO system that the many antennas by many antennas in many base stations and user constitute, consider between the antenna of same base station and have certain correlation, simultaneously because with respect to a fixing user, the residing dimensional orientation difference of different base station, even dimensional orientation is identical, can be not identical to user's channel quality yet.The antenna of different base station is lumped together many antennas of regarding an equivalent base station as, when the many antennas with the user constitute mimo system, in order to improve the efficient of emission, the selection problem that has an antenna, by selection to equivalent base station end antenna, choose the wherein measured subchannel of matter, can when the information of transmitting does not effectively reduce power system capacity, reduce the consumption of system emission power.
2, under the situation of the selection of finishing antenna, under the condition of given transmission quality, emitted power is minimized.
If the quality of transmission is certain, by selection to antenna, can select all to have stronger channel to each user, like this when finishing given transmission, under the situation that number of symbols of Chuan Songing and modulation system are fixed, can select to use top-quality those subchannels in all subchannels if desired.Obtain at user side just can reduce of the consumption of base station end under the situation of the identical quality of reception to power.
3, can improve the transmission rate of system effectively.
Single base station to the pretreated process of multi-user's emission in, total number of characters that the base station end can transmit has been subjected to the restriction of the set antenna number in single base station, but when the antenna of a plurality of base stations can be unified selection and during scheduling, at first the base station end to the number of transmit antennas purpose restriction removed; At this moment, under the situation that user side can effectively be decoded, can pass some data more, thereby total transmission rate of system is improved.
4, the scheduling of the many speed of multi-user is more flexible with distribution.
Owing to be the downlink transfer of the many antennas in many base stations to the multi-user, by selection, can there be more surplus to allow between the multi-user, to dispatch to base station end antenna, can distribute the subchannel of varying number at the situation of the channel of different user and demand; And if transmission quality one regularly, good user has some subchannels more can also to make channel quality, higher transmission rate is arranged, and the user of bad channel quality distributes some subchannels less.Equally, under condition with given transmission quality, if limit the gross power of emission again, can also be in the scheduling of carrying out between different users on the power division.
[description of drawings]
Accompanying drawing 1 is depicted as the implementation step schematic diagram of the embodiment of the downlink transmission method in the distributed MIMO system of the present invention;
Accompanying drawing 2 is depicted as the structural representation of the embodiment of the downlink transfer device in the distributed MIMO system of the present invention.
[embodiment]
Elaborate below in conjunction with the embodiment of accompanying drawing to downlink transmission method in the distributed MIMO system provided by the invention and device.
Provide the embodiment of the downlink transmission method in the distributed MIMO system of the present invention at first in conjunction with the accompanying drawings.Accompanying drawing 1 is depicted as the implementation step schematic diagram of this embodiment, comprising: step S11, select a certain user, and the channel matrix of each base station to this user decomposed; Step S12 selects several the strongest in the characteristic sub-channel of each base station to this user channels to constitute user's used for vector transfer; The still non-selected user of step S13, another in the selective system, repeating step S11 and S12 are to obtain each user's used for vector transfer matrix; Step S14 carries out orthogonalization to eliminate common-channel interference to all users' of being obtained transmission matrix; Step S21 is respectively each user and selects the strongest characteristic sub-channel of transmission signals in all subchannel that it had; Step S22 determines power partition coefficient according to the characteristic value of determined each subchannel.
Step S11 to S14 in the said method may be summarized to be " antenna in the described system being selected; to obtain each user's used for vector transfer matrix ", also can realize the above-mentioned operation that obtains each user's used for vector transfer matrix by other similar methods in other embodiment.
Specifically, K base station arranged in the supposing the system, there is N each base station
kIndividual antenna, total M user, each user has N
mIndividual antenna.Between many base stations hypothesis obtained good synchronously, and obtained each user's channel information at the base station end.When a certain specific user being carried out day line options, at first the channel matrix of different base station to this user's interchannel decomposed, choose wherein the strongest subchannel, in conjunction with different base stations this user is chosen given subchannel number.User to other selects then, determines each user's used for vector transfer matrix A
mInterference when transmitting for eliminating base station down between different user is to different used for vector transfer matrix A
mBetween carry out orthogonalized processing, after orthogonalization process is finished, again to the used for vector transfer matrix A
mEach row carry out normalization, obtain each final user pre-coding matrix.
In the distributed MIMO system that the many antennas by many antennas in many base stations and user constitute, consider between the antenna of same base station and have certain correlation, simultaneously because with respect to a fixing user, the residing dimensional orientation difference of different base station, even dimensional orientation is identical, can be not identical to user's channel quality yet.The antenna of different base station is lumped together many antennas of regarding an equivalent base station as, when the many antennas with the user constitute mimo system, in order to improve the efficient of emission, the selection problem that has an antenna, by selection to equivalent base station end antenna, choose the wherein measured subchannel of matter, can when the information of transmitting does not effectively reduce power system capacity, reduce the consumption of system emission power.
Above-mentioned steps S21 and S22 may be summarized to be " under the prerequisite that guarantees transmission quality, by for each user distributes the minimal power factor, making total transmitting power of system reduce to minimum ".In other embodiment, also can realize the above-mentioned operation that minimizes transmitting power by other similar methods.
Specifically, transmission quality one timing when user side, under the condition of given transmission rate, in order to make the transmitting power minimum of base station end, need in the subchannel that different user had, select, select wherein the strongest characteristic sub-channel, the size according to the characteristic value of each characteristic sub-channel is satisfying under the prerequisite of given transmission quality then, determines suitable power partition coefficient.Owing to all be, so just can under the condition that guarantees transmission quality, make transmitting power minimum total in the system in the minimal power factor of guaranteeing to choose under the situation of communication quality concerning each user.
If establish the L that distributes to m user
nThe power of individual subchannel is P
Mn, the transmitting power of system minimizes and can be described as under the then given Signal to Interference plus Noise Ratio condition:
If the quality of transmission is certain, by selection to antenna, can select all to have stronger channel to each user, like this when finishing given transmission, under the situation that number of symbols of Chuan Songing and modulation system are fixed, can select to use top-quality those subchannels in all subchannels if desired.Obtain at user side just can reduce of the consumption of base station end under the situation of the identical quality of reception to power.
The described method of this embodiment can improve the transmission rate of system effectively.Single base station to the pretreated process of multi-user's emission in, total number of characters that the base station end can transmit has been subjected to the restriction of the set antenna number in single base station, but when the antenna of a plurality of base stations can be unified selection and during scheduling, at first the base station end to the number of transmit antennas purpose restriction removed; At this moment, under the situation that user side can effectively be decoded, can pass some data more, thereby total transmission rate of system is improved.
The described method of this embodiment can also make the scheduling of the many speed of multi-user more flexible with distribution.Owing to be the downlink transfer of the many antennas in many base stations to the multi-user, by selection, can there be more surplus to allow between the multi-user, to dispatch to base station end antenna, can distribute the subchannel of varying number at the situation of the channel of different user and demand; And if transmission quality one regularly, good user has some subchannels more can also to make channel quality, higher transmission rate is arranged, and the user of bad channel quality distributes some subchannels less.Equally, under condition with given transmission quality, if limit the gross power of emission again, can also be in the scheduling of carrying out between different users on the power division.
Next provide the embodiment of the downlink transfer device in the distributed MIMO system of the present invention in conjunction with the accompanying drawings.
Be the structural representation of the described device of this embodiment shown in the accompanying drawing 2, comprise as lower module: Antenna Selection Module 210 is used for the antenna of described system is selected, to obtain each user's used for vector transfer matrix; Power division module 220 by for each user distributes the minimal power factor, makes total transmitting power of system reduce to minimum.
Described Antenna Selection Module 210 further comprises as lower unit: resolving cell 211, be used to select a certain user, and the channel matrix of each base station to this user decomposed; Selected cell 212 selects several the strongest in the characteristic sub-channel of each base station to this user channels to constitute user's used for vector transfer; The user travels through unit 213, is used for another still non-selected user of selective system, repeats to implement resolving cell and selected cell, to obtain each user's used for vector transfer matrix; Orthogonalization unit 214 is used for all users' of being obtained transmission matrix is carried out orthogonalization to eliminate common-channel interference.
Described power division module 220 further comprises as lower unit: subchannel selected cell 221 is respectively each user and selects the strongest characteristic sub-channel of transmission signals in all subchannel that it had; Distribution coefficient computing unit 222 is determined power partition coefficient according to the characteristic value of determined each subchannel.
More than each module and the operation principle of unit and the content that correlation each other please refer to previous embodiment, repeat no more herein.
The above only is a preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.
Claims (6)
1. the downlink transmission method in the distributed MIMO system is characterized in that, comprises the steps:
(a) antenna in the described system is selected, to obtain each user's used for vector transfer matrix;
(b) under the prerequisite that guarantees transmission quality,, make total transmitting power of system reduce to minimum by for each user distributes the minimal power factor.
2. method according to claim 1 is characterized in that, described step (a) further comprises:
(a1) select a certain user, the channel matrix of each base station to this user decomposed;
(a2) select several the strongest in the characteristic sub-channel of each base station to this user channels to constitute user's used for vector transfer;
(a3) the still non-selected user of another in the selective system, repeating step (a1) with (a2), to obtain each user's used for vector transfer matrix;
(a4) transmission matrix to all users of being obtained carries out orthogonalization to eliminate common-channel interference.
3. method according to claim 1 is characterized in that, described step (b) further comprises:
(b1) be respectively each user and in all subchannels that it had, select the strongest characteristic sub-channel of transmission signals;
(b2) under the prerequisite that guarantees transmission quality, determine power partition coefficient according to the characteristic value of determined each subchannel.
4. the downlink transfer device in the distributed MIMO system is characterized in that, comprises as lower module:
Antenna Selection Module is used for the antenna of described system is selected, to obtain each user's used for vector transfer matrix;
The power division module under the prerequisite that guarantees transmission quality, by for each user distributes the minimal power factor, makes total transmitting power of system reduce to minimum.
5. device according to claim 4 is characterized in that, described Antenna Selection Module further comprises as lower unit:
Resolving cell is used to select a certain user, and the channel matrix of each base station to this user decomposed;
Selected cell selects several the strongest in the characteristic sub-channel of each base station to this user channels to constitute user's used for vector transfer;
The user travels through the unit, is used for another still non-selected user of selective system, repeats to implement resolving cell and selected cell, to obtain each user's used for vector transfer matrix;
The orthogonalization unit is used for all users' of being obtained transmission matrix is carried out orthogonalization to eliminate common-channel interference.
6. device according to claim 4 is characterized in that, described power division module further comprises as lower unit:
The subchannel selected cell is respectively each user and selects the strongest characteristic sub-channel of transmission signals in all subchannel that it had;
The distribution coefficient computing unit is determined power partition coefficient according to the characteristic value of determined each subchannel.
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| US20080299981A1 (en) * | 2007-05-31 | 2008-12-04 | Foschini Gerard J | Method of coordinated wireless downlink transmission |
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| CN101123461A (en) * | 2002-02-19 | 2008-02-13 | 高通股份有限公司 | Power control for partial channel-state information (CSI) multiple-input, multiple-output (MIMO) systems |
| US20080299981A1 (en) * | 2007-05-31 | 2008-12-04 | Foschini Gerard J | Method of coordinated wireless downlink transmission |
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Application publication date: 20110622 |