WO2012120379A1 - Procédé et appareil pour la formation de faisceau au moyen de la maximisation du débit de données - Google Patents

Procédé et appareil pour la formation de faisceau au moyen de la maximisation du débit de données Download PDF

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Publication number
WO2012120379A1
WO2012120379A1 PCT/IB2012/000600 IB2012000600W WO2012120379A1 WO 2012120379 A1 WO2012120379 A1 WO 2012120379A1 IB 2012000600 W IB2012000600 W IB 2012000600W WO 2012120379 A1 WO2012120379 A1 WO 2012120379A1
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Prior art keywords
user
beamforming
users
transmitting
data rate
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PCT/IB2012/000600
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English (en)
Inventor
Zhenning Shi
Yajuan Luo
Daqing Gu
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France Telecom
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Publication of WO2012120379A1 publication Critical patent/WO2012120379A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0452—Multi-user MIMO systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming

Definitions

  • the invention relates to wireless communication systems, and more particularly to the precoding of data to be transmitted in a multiuser multi-input multi-output (MIMO) wireless communication system.
  • MIMO multi-input multi-output
  • multiuser MIMO downlink transmissions multiple users are served at the same time on the same channel.
  • the suppression of co-channel interference can be achieved by using properly configured precoders at the transmitter side, in other words by choosing carefully beamforming vectors, or precoding weights, before the transmission of the signal to multiple users.
  • the beamforming vectors are chosen optimally in order to maximize the output signal to interference plus noise ratio (SINR) for each user.
  • SINR output signal to interference plus noise ratio
  • Another scheme consist in using a leakage based criterion to design the transmit beamforming vectors, where a leakage parameter refers to the interference caused by the signal intended for a desired user to other co-channel users. Such a leakage parameter is thus a measure of how much signal power leaks into other users.
  • the corresponding performance criterion to be maximized is the signal to leakage and noise ratio (SLNR) for all users simultaneously.
  • SLNR signal to leakage and noise ratio
  • the beamforming vector of a user is projected in the null space spanned by the channel of its co-channel users to eliminate the interference.
  • all of the above-mentioned schemes present a certain number of drawbacks.
  • the optimal precoding vector of a user needs to be determined jointly with those of co-channel users. This in turn leads to a multi-dimensional optimization problem that involves SINR metrics and corresponding precoding vectors of all users. No closed form solutions are available due to the complexity and coupled nature of the resulting optimization problem.
  • SLNR is an arbitrarily defined metric, which is not directly related to performance metric, e.g., throughput, of the user or its co-channel users. For this reason, a precoding vector determined according to SLNR criterion may outweigh the user performance compared to its co-channel counterparts, or, on the other hand, outweigh the interference generated by users to co-channel users.
  • precoding schemes using zero-forcing beamforming eliminates the co- channel interference at the cost of increasing the noise.
  • zero-forcing schemes impose a restriction on the number of antennas. Indeed, the number of transmit antennas at the base station is required to be larger than the sum of receive antennas of all users. This condition is necessary in order to provide enough degrees of freedom for the zero-forcing solution to force the co-channel interference to zero at each user.
  • the object of the present invention is to propose a sum-throughput maximizing beamforming approach for the precoding scheme in Ml MO systems.
  • it is proposed to achieve the optimal sum throughput in a progressive or iterative manner, by maximizing the net sum data rate gain introduced by a user introduced to the MU-MIMO channel.
  • the present invention proposes a method of transmitting a signal carrying data in a multiple-input multiple-output communication system involving a plurality of users, this method comprising the steps of:
  • determining at least one beamforming vector for at least one of these users precoding the data in accordance with the beamforming vector prior to the transmission of the signal from a plurality of transmitting antennas of a transmitting apparatus;
  • the beamforming vector is determined for this user by computing the beamforming vector which maximizes the difference between the sum data rate throughput achieved by this user and at least one other user and the sum data rate throughput achieved by the at least one other user without said user.
  • a plurality of beamforming vectors are progressively determined respectively for each one of the plurality of users, and the determination step consists in a progressive determination step A(i) which comprises the steps, performed for each user of the plurality of users of selecting one of these users and computing a beamforming vector for the selected user which maximizes the difference between the sum data rate throughput achieved by the selected user and users belonging to a beamforming user set and the sum data rate throughput achieved by users belonging to said beamforming user set without the selected user.
  • the selected user is selected among users of plurality of users which do not belong to the beamforming user set, and the method further comprises adding the selected user to the beamforming user after the computing step.
  • each progressive determination step is followed by the verification of at least a first condition, the beamforming determination being interrupted if the first condition is not verified, wherein this first condition comprises the condition that the number of computed beamforming vectors is less than the number of transmitting antennas of the transmitting apparatus.
  • the first condition further comprises that the number of computed beamforming vectors is less than the number of users multiplied by the number of receiving antennas per user in the communication system.
  • a second condition is verified during the verification step, this second condition being that the difference between the sum data rate throughput achieved by said user and at least one other user and the sum data rate throughput achieved by said at least one other user without said user is positive.
  • the computed beamforming vector is obtained by computing the eigenvector corresponding to the largest eigenvalue of an optimisation matrix depending on the matrixes of the covariance of interference received by the users, the channel matrixes and the computed beamforming vector with respect to the users.
  • this optimisation matrix M is defined according to the following equation:
  • G k H ⁇ R ⁇ H k , wherein H k is the channel matrix with respect to the k-th user ;
  • the determination step comprises, prior to the computation step, an initial calculation step comprising the following steps: based on the computation of MRT beamforming vectors for a plurality of users of the set, the selection of a first user whose MRT beamforming maximizes the receive power;
  • the progressive determination step is performed for each user of the plurality of users and, for each user, the determination step further comprises, prior to the computation step, an initial computation step comprising the steps of computing a MRT beamforming vector for said user and defining the beamforming user set as comprising only said user.
  • the determination step is repeated iteratively a predetermined number of times.
  • the determination step is repeated iteratively until the value of a metric parameter > depending on the matrixes of the covariance of interference received by the users and the channel matrixes and computed beamforming vectors with respect to the users, is less than a system-defined threshold £ tes3 ⁇ 4oM .
  • the metric parameter ⁇ 1 ⁇ is defined according to the following equation:
  • the present invention further proposes a transmitting apparatus for transmitting a signal carrying data, comprising:
  • a precoding module connected to the plurality of antennas and configured to precode the data by using at least one beamforming vector
  • a beamforming controller module connected to the precoding module and configured to determine said at least one beamforming vector
  • the apparatus is adapted to perform the above-mentioned method of transmitting a signal carrying.
  • the present invention also proposes a multiple-input multiple-output communication system comprising the above-mentioned transmitting apparatus for transmitting a signal carrying data according and at least one receiving apparatus with a plurality of receiving antennas.
  • the present invention further proposes a computer program comprising instruction codes for implementing the beamforming determination step of the above- mentioned method of transmitting a signal carrying data, when loaded and run on processing means of a beamforming controller module.
  • FIG. 1 represents a simplified wireless communication system which illustrates the principle of the invention
  • FIG. 2 represents the steps of the method of transmitting a signal carrying data that is the subject of the present invention
  • FIG. 3A shows a modelized block diagram of a typical multi-user MIMO system
  • FIG. 3B illustrates schematically a transmitting apparatus for transmitting signal carrying data according to the present invention
  • FIG. 4A illustrates a first embodiment of the beamforming determination step of the method according to the present invention
  • FIG. 4B illustrates an embodiment of the initial determination step of the first embodiment of the beamforming determination step according to the present invention
  • FIG. 5A shows simulated curves of various data rate achieved with data layers determined at different scheduling stages for a four-user MIMO system, when using the above-mentioned RAMP scheme according to the present invention
  • FIG. 5B shows simulated curves representing the achieved net gain ratio AGNR for data streams precoded at different iteration stages of the above- mentioned RAMP scheme according to the present invention
  • FIG. 5F shows a simulated curve of the sum data rate throughput achieved with the multi-iteration precoding of this embodiment of the method according to the present invention, for a MIMO system involving 4 users;
  • FIG. 6B and 6C show simulated curves of the distribution of the relative exponent of net gain difference ⁇ ⁇ over iterations for different signal-to-noise ratios, respectively.
  • Figure 1 represents a simplified wireless communication system which illustrates the principle of the invention.
  • FIG. 1 The upper part of figure 1 shows the cell of a wireless system with only two co- channel users ui and u 2 , which achieve individual data rate throughputs r ll k and r 2l k , respectively.
  • the back slash in the subscript of these data rate throughputs parameters denotes that these data rate are achieved without the presence of any third user Uk-
  • the present invention seeks to maximize the sum throughput gain of all three users, when compared to the previous situation with only two users, which is given by the following equation:
  • the first part r k is the individual data rate throughput (or gain) realized by the third user Uk and the second part, (r x - r l/ k ) + (r 2 - r 2/ k ) , is the gain caused to co-channel users ui and u 2 by the introduction of user Uk.
  • the beamforming vector optimization for user Uk, consists of maximizing the sum of these two parts such that the total sum data rate throughput is maximized.
  • Figure 2 represents a flow diagram of the steps of the method of transmitting a signal carrying data that is the subject of the invention.
  • Such a method is performed in a multiple-input multiple-output (MIMO) communication system involving a plurality of K users U i , ... ,u k , ... ,u K and a transmitting apparatus having N t transmitting antennas.
  • This method comprises first a beamforming determination step A wherein beamforming vector(s) w k are determined respectively for one or more user(s) belonging to this user set L tot .
  • the determination of the beamforming vector w k for a user u k of the set Uot comprises the step of computing the beamforming vector w k which maximizes the sum throughput gain S corresponding to the difference between, on the one hand, the sum data rate throughput U achieved by this user u k and one or more other user(s) of the user set L to t, and, on the other hand, the sum data rate throughput achieved by these one or more other users of the user set L tot without said user u k .
  • the beamforming vector w k for user u k is thus the beamforming vector which maximizes the equation :
  • the data to be transmitted are precoded, during a precoding step B, in accordance with the beamforming vector(s) which have been determined during step A.
  • a signal carrying on the precoded data can be transmitted, during a transmission step C, from the plurality of antennas of the transmitting apparatus towards the users U-I -UK.
  • the maximization of the sum throughput gain S can be reformulated as follows, with reference to figure 3A which shows a modelized block diagram of a typical multi-user MIMO system.
  • the received signal for user u k can be expressed by the following (N r x 1 ) receiving vector y k :
  • H fc is the (N r x N t ) channel matrix. Assuming that transmit power is uniformly distributed among the users, the transmitted waveform can be expressed as:
  • the Covariance Matrix R k of the interferences affecting user u k can be then defined as follows:
  • a beamforming user set L of users which comprises users of L to t which are properly configured, i.e. which are already associated with a beamforming vector.
  • ⁇ is the data rate for user ui.
  • the beamforming vector w k for user Uk is obtained by computing the beamforming vector w pt which maximizes the sum data rate throughput gain introduced by the user u k , in other words which solves the following equation:
  • both data rate r k and data rate throughput gains r ! - r 1/k ,l ⁇ k can be reformulated in terms of w k .
  • the former is readily obtained by employing the Shannon capacity formula for the link of user u k as:
  • the beamforming vector w k that maximizes the above-mentioned ratio Q k in (14) is actually the generalized eigenvector corresponding to the maximum eigenvalue of the two matrixes (i + Gj and fl + ⁇ z
  • the optimal beamforming vector w k for user u k is given by:
  • Formula (15) shows that the optimal beamforming vector w° k pt depends on matrixes G k and , which are determined by the channel state information and selected precoders of users ui.
  • the joint multi-user beamforming problem naturally lends itself to a progressive solution: given the user beamforming set L determined in the previous stage, the algorithm maximizes the sum throughput for an enlarged beamforming user set L comprising the former beamforming set and a newly added user Uk by determining the precoder weights for the new user with the formula (15).
  • the method of the present invention can bee seen as being a rate-maximizing progressive (RAMP) beamforming method.
  • RAMP rate-maximizing progressive
  • Figure 3B illustrates schematically a transmitting apparatus for transmitting signal carrying data according to the present invention.
  • the transmitting apparatus Tx comprises a channel encoder module ENCOD, a modulator module MOD, a precoder module PRECOD, a modulation and coding scheme (MCS) controller MCS_CTRL, a beamforming controller BM_CTRL, a channel information controller Hk_CTRL and N t transmitting antennas.
  • ENCOD channel encoder module
  • MOD modulator module
  • PRECOD precoder module
  • MCS_CTRL modulation and coding scheme
  • BM_CTRL beamforming controller
  • Hk_CTRL channel information controller
  • Such a transmitting apparatus Tx can be used in a multiple-input multiple-output (MIMO) communication system comprising this transmitting apparatus and one or more receiving apparatus, belonging to users Ui ,...,u K and having a plurality of receiving antennas.
  • MIMO multiple-input multiple-output
  • signals to be transmitted to the receiving users are input in the respective channel encoders ENCOD-i, ...,ENCOD Nt in the encoder module ENCOD, where they are encoded with an associated method before being transmitted to the respective modulators MOD-i ,...,MOD Nt in the modulator module MOD, where they are modulated by data streams in order to output complex symbols.
  • the channel information controller Hk_CTRL receives channel information and transmit this channel information to the MCS controller MCS_CTRL and the beamforming controller BM_CTRL.
  • the MCS controller MCS_CTRL controls the encoding process of the signal in the channel encoders ENCOD-i, ...,ENCOD Nt , as well as the modulation process of the encoded signal by data in the modulators MOD-i ,...,MOD Nt , depending on the received channel information.
  • the beamforming controller BM_CTRL on its side, calculates transmission beam vectors to be applied for each antennas by their respective beamforming modules BF-i, ...,BF Nt using, among others, the received channel information.
  • the beamforming controller comprises processing means which carry out the beamforming determination step A described previously, and discussed in more details hereafter, in order to determine the beamforming vectors w k to be used in association with the signal and data scheduled for the users.
  • the processing means can carry out these steps by running instruction codes of a computer program loaded in memory means of the beamforming controller BM_CTRL.
  • the beamforming modules BF-i ,...,BF Nt use this beamforming vectors to beam-from the complex symbol outputted by the respective modulators MODi , ...,MOD N t, before that the resulting signals are transmitted by the N t transmitting antennas to the users.
  • RAMP Rate-Maximizing Precoding
  • Figure 4A illustrates a first embodiment of the beamforming determination step of the method according to the present invention.
  • the determination of beamforming vectors is realized by progressively repeating beamforming determination steps A(i) for each one of a plurality of data stream (i.e. layers) to be scheduled to one or more users of a set Ltot of users.
  • a beamforming user set L is also defined.
  • Such a beamforming user set L comprises all the users of the global set Uot for which a beamforming vector has already been computed.
  • An index i may also be introduced here, such an index i being initialized at the zero value and incremented each time a beamforming vector is computed, indicating thus the number of beamforming determination steps A(i) progressively performed at one stage.
  • the beamforming determination step A(i) comprises the selection (sub-step A1 (i)) of one user u k among the set of users L tot .
  • the optimal beamforming vector w k is determined (sub-step A3(i)) for this user u k , by computing a beamforming vector for the selected user which maximizes the difference between the sum data rate throughput U achieved by the selected user u k and users belonging to the beamforming user set L and the sum data rate throughput U /k achieved by users belonging to said beamforming user set L without the selected user u k .
  • this beamforming vector can be obtained by computing the eigenvector corresponding to the largest eigenvalue of an optimisation matrix depending on the matrixes of the covariance of interference received by the users and the channel matrixes with respect to the users.
  • such an optimisation matrix M can be defined as M I + GJ wherein:
  • Ai is a matrix defined as: A,
  • the user u k is added (sub-step A5(i)) to the beamforming user set L, in order to indicate that an optimal beamforming vector has been allocated to this user u k .
  • the user u k already belongs to the beamforming user set L (because it has already been allocated previously another beamforming vector), such a sub-step can be ignored.
  • the sub-steps A1 (i) to A5(i) are repeated, for a plurality of data streams to be scheduled to one or more users, the index i being incremented for each occurrence of the beamforming determination step A(i).
  • the same user u k can be selected several times during different beamforming steps A(i), allowing spatial diversity to be better utilized.
  • the selection of a user u k among the users of the user set L tot is limited to users which do not belong to the beamforming user set L, in order to avoid the same user to be scheduled twice for different data streams.
  • the sub-steps A1 (i) to A5(i) are repeated (and the index i is incremented for each occurrence of the beamforming determination step A(i)), until one or more conditions are not verified during a verification step A7(i).
  • step A7(i) if one or more condition is not verified, the beamforming determination process A is interrupted and the method proceed further directly to precoding step B with the computed beamforming vectors w-i, ...,w k which have been already computed at that stage.
  • a first condition, to be verified during step A7(i) concerns the number i of already allocated computed beamforming vectors, in other words the number of scheduled data streams (i.e. of layers).
  • This first condition may comprise the condition that the number i of computed beamforming vectors is less than the number N t of transmitting antennas in the MIMO communication system.
  • the beamforming determination process A interrupts when a number of scheduled data streams (i.e. of layers) reaches the number of transmitting antennas.
  • the first condition may further comprise the condition that the number i of computed beamforming vectors is less than the number K of users multiplied by the number N r of receiving antennas per user in the MIMO communication system.
  • the progressive beamforming determination steps A(i) are carried out repeatedly as long as the condition i ⁇ min(N t ,K * N r ) is fulfilled.
  • a second additional condition can be set on the repetition of the beamforming determination steps, in order to possibly interrupt the progressive process if it occurs that the addition of a user u k causes a too large degradation to the other users' throughput.
  • the progressive determination steps can be stopped if the sum gain throughput corresponding to the difference between the sum data rate throughput U achieved by the selected user u k (for which the beamforming vector has just been computed) and users belonging to the beamforming user set L and the sum data rate throughput U /k achieved by users belonging to said beamforming user set L without the selected user u k is negative.
  • the second condition, to be verified during verification step A7(i) can then be defined as a condition that the difference between, on the one hand, the sum data rate throughput U achieved by the user u k and one or more user(s) of the beamforming user set L and, on the other hand, the sum data rate throughput achieved by these one or more user(s) of the beamforming user set L without this user u k is positive.
  • the ratio of the exponent of the sum data rate gain Q k should always be larger than one. Otherwise the rate loss caused by user u k to other users outweighs the achievable data rate of user u k , and this user u k should not be considered for transmission.
  • the process should be stopped and the user u k should not be allocated any beamforming vector.
  • Figure 4B illustrates an embodiment of the initial determination step A(1 ) of the first embodiment of the beamforming determination step according to the present invention.
  • the selection of the first user u k i cannot be based on other co-channel users' beamforming vectors.
  • the first iterative determination step A(1 ) can be based on the computation of a maximal ratio transmission (MRT) beamforming vector.
  • the selection sub-step A1 (1 ) consists in selecting the user u k whose MRT beamforming vector w kjM RT results in the maximum receive power, in order for the iterative beamforming determination to achieve the best performance.
  • MRT beamforming vectors W ⁇ MRT ⁇ - ⁇ W ⁇ MRT are computed for each of the K users in the user set L tot (as shown in figure 4B with the incrementation of the index j).
  • the user u k i whose MRT beamforming vector achieves the maximum receive power is selected first.
  • the user u k i is the user for which the following equation applies:
  • the beamforming determination for users scheduled in early stages of the determination step A do not take into account the influence to the users scheduled in the later stages. In some cases, this may lead to the introduction of excessive interference to later-scheduled data streams.
  • the beamforming vectors are computed follows with the RAMP scheme: opt
  • Figure 5A shows simulation curves of various data rate achieved with data layers determined at different scheduling stages for a four-user MIMO system, when using the above-mentioned RAMP scheme according to the present invention.
  • a block fading channel is employed such that channel state between blocks are assumed to be uncorrelated, while within one block, the entries in the channel state matrix are i.i.d. distributed complex Gaussian.
  • ANGR achieved net gain ratio
  • Figure 5B shows simulated curves representing the achieved net gain ratio AGNR for data streams precoded at different iteration stages of the above-mentioned RAMP scheme according to the present invention.
  • degenerating AGNR for data streams scheduled in the first stage indicates that the precoding for early-stage data streams may be suboptimal, because it introduces interference to later-stage layers and may not achieve the maximum net sum throughput.
  • Figure 5C describes another embodiment of the beamforming determination step according to the present invention, which takes into consideration this issue.
  • the beamforming determination is performed in n iterations, where n>2, while in each iteration the i-th user's beamforming vector is updated using the current beamforming vectors of the entire user set L tot , in order to mitigate the issue discussed in the previous section.
  • a precoding scheme can be thus designated as being an iterative precoding scheme, with a fixed scheduling (of n iterations).
  • the beamforming determination step A' comprises thus a first beamforming determination sub-step A1 ' wherein the beamforming vector ⁇ w ⁇ 'j ⁇ are determined for the K users of the global set L to t.
  • a beamforming group determination sub-step A2' is performed, which comprises K beamforming determination sub-steps A3' carried on for each i-th user, wherein the beamforming vector is updated as a function of the currently determined beamforming vectors of the other users.
  • each user Ui, W; 2) is calculated based on the currently determined beamforming vectors of all the other users.
  • the repetition of sub-step A3' for each user is designated, in figure 5C, by the incrementation of the index i until its value reaches the number K of users.
  • the beamforming group determination sub-step A2' is then iteratively repeated (n- 1 ) times, as shown in figure 5C with the incrementation of the index j until its value reaches the number n of scheduling layers.
  • FIG. 5D shows that most of the gain is achieved with two iterations.
  • the iterative precoding scheme illustrated in figure 5C can significantly improve the sum data rate throughput for SNR > 15dB.
  • a metric parameter ⁇ ⁇ is defined in order to assess the convergence of the method.
  • This metric parameter ⁇ 1 ⁇ can then be compared with a system-defined threshold theshou in order to determine whether to stop, or not, the iterative processing.
  • the beamforming determination is performed in multiple iterations, wherein in each iteration the i-th user's beamforming vector is updated using the current beamforming vectors of the user set L, similarly to the determination performed in figure 5C.
  • the number of iterations is not fixed, but varies according to the convergence of the beamforming vectors towards their optimal values.
  • Such a precoding scheme can be thus designated as being an iterative precoding scheme with a dynamic scheduling.
  • the initial beamforming determination sub-step A1 " and the iterative beamforming group determination sub-steps A2" are similar to sub-steps A1 ' and A2' discussed previously.
  • the metric parameter ⁇ 1 ⁇ is determined (sub-step A5") by computing equation (21 ).
  • the computed metric parameter ⁇ 1 ⁇ is thereafter compared with the system-defined threshold ⁇ ⁇ in order to decide if it is necessary to carry out another round of beamforming determination, or if the beamforming vectors are sufficiently close to their optimal values.
  • the end of the iterative process is not triggered by reaching a specific number of iterations, but by checking if a sufficient degree of convergence with optimal values has been reached.
  • the convergence is considered as being achieved and the beamforming determination process can stop at this j-th iteration.
  • the hereby obtained beamforming vectors can then be used for precoding the data to be transmitted to the users.
  • Figure 6D shows a simulated curve of the sum data rate throughput for such an iterative precoding scheme with dynamic scheduling.
  • the iterative precoding scheme with dynamic scheduling also outperforms other advanced precoding schemes, such as BD-schemes and SLNR-schemes.
  • Figure 6E shows simulated distribution curves of the relative ENG difference achieved by the iterative precoding scheme with dynamic scheduling at different SNR. This figure 6E demonstrates a more converged performance when compared to the RAMP scheme and the iterative decoding with fixed schedule scheme.
  • the invention also covers a computer program product stored on a storage medium for execution by a computer or by a dedicated invocation call server as described in association with the abovementioned figure 13, particularly noteworthy in that this computer program product includes instructions making it possible to execute the method according to figures 5a, 5b, 10a et seq., previously described in the description.

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Abstract

La présente invention a trait à un procédé d'émission d'un signal transportant des données dans un système de communication entrée multiple sortie multiple (MIMO) qui implique une pluralité d'utilisateurs, ledit procédé comprenant : la détermination (A) d'au moins un vecteur de formation de faisceau pour au moins un desdits utilisateurs ; et le précodage (B) desdites données selon le vecteur de formation de faisceau avant la transmission (C) du signal à partir d'une pluralité d'antennes d'émission appartenant à un appareil d'émission. Ledit vecteur de formation de faisceau est déterminé pour ledit utilisateur (uk) grâce au calcul du vecteur de formation de faisceau (wk) qui maximise la différence entre la somme des débits (U) atteints par ledit utilisateur (uk) et au moins un autre utilisateur (u1, u2) et la somme des débits atteints par le ou les autres utilisateurs (u1, u2) sans ledit utilisateur. La présente invention se rapporte également à un appareil d'émission permettant de mettre en œuvre ce procédé, et à un système de communication entrée multiple sortie multiple (MIMO) comprenant un tel système.
PCT/IB2012/000600 2011-03-10 2012-03-09 Procédé et appareil pour la formation de faisceau au moyen de la maximisation du débit de données WO2012120379A1 (fr)

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