EP2243227A1 - Communication by return pathway from a terminal to a transmitter for reducing in particular interference between beams from the transmitter - Google Patents

Communication by return pathway from a terminal to a transmitter for reducing in particular interference between beams from the transmitter

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Publication number
EP2243227A1
EP2243227A1 EP20080867695 EP08867695A EP2243227A1 EP 2243227 A1 EP2243227 A1 EP 2243227A1 EP 20080867695 EP20080867695 EP 20080867695 EP 08867695 A EP08867695 A EP 08867695A EP 2243227 A1 EP2243227 A1 EP 2243227A1
Authority
EP
European Patent Office
Prior art keywords
transmitter
beams
terminal
number
active
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP20080867695
Other languages
German (de)
French (fr)
Inventor
Thomas Salzer
Marios Kountouris
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Orange SA
Original Assignee
France Telecom SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to FR0850020 priority Critical
Application filed by France Telecom SA filed Critical France Telecom SA
Priority to PCT/FR2008/052293 priority patent/WO2009083680A1/en
Publication of EP2243227A1 publication Critical patent/EP2243227A1/en
Application status is Withdrawn legal-status Critical

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Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/02Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413MIMO systems
    • H04B7/0417Feedback systems
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/02Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413MIMO systems
    • H04B7/0452Multi-user MIMO systems

Abstract

The invention relates to a communication by return pathway from a terminal to a transmitter for reducing in particular interference between beams from the transmitter. A telecommunication system comprises a transmitter designed to render simultaneously active a first number of beams (Fl, F2, F3), in the guise of the resources for a plurality of user terminals. Within the sense of the invention, each terminal: calculates, while taking account of interference noise, at least one second preferred, number, of beams to be rendered simultaneously active by the transmitter, and sends to the transmitter, through the return pathway, an indication of this second preferred number, among information about the quality of reception. On its side, the transmitter (BS) can then adjust the first number of beams to be rendered active, as a function of the returns from the terminals, for a next burst.

Description

Communication return channel from a terminal to a particular transmitter to reduce interference between beams from the transmitter

The present invention relates to a communication on a return path from a terminal to a transmitter associated with a telecommunication network, to inform the transmitter about the quality of data reception by the terminal.

He referred in particular a communication (or "metric") that would fit the mode of transmission in such a multiple access system spatial distribution or "SDMA" (for "Space Division Multiple Access"). Such a system is characterized by the use of multiple antennas (technique known as "MIMO" for "Multiple Input Multiple Output") upon issue to generate beams that may be allocated to different user terminals. Thus, a transmitter (e.g. a base station in a cellular network) may comprise a plurality of antennas generating a set of beams that can be allocated to one or more terminals. Thus, a transmitter having M antennas can generate a maximum of M beams simultaneously. However, in practice, as discussed below, a K, less than or equal to M beam is generated, particularly to avoid interference between beams on a single channel to a user terminal.

The use of multiple antennas to serve multiple users (SDMA system) through a plurality of beams, is one of the latest standards for mobile radio networks, such as the E-LJTRAN standard described in particular in 3GPP TS 36.212, Release 8.0.0 - "Physical Channels and Modulation (Release 8)".

The invention is subsequently presented in a pure SDMA system, but it can also be applied in a hybrid system combining SDMA technique with other multiple access technique. In order to serve a plurality of terminals (e.g., over M terminals), it can in particular be provided to serve K terminals at a time t, then K other terminals at a time t + 1, etc. Alternatively, it may be provided to serve K terminals in a frequency band F, K and other terminals to a frequency band F + l, etc. Thus, the invention can be applied in a hybrid system combining the SDMA technique, including TDMA (for "Time Division Multiple Access") if it is decided to allocate resources by time slots, or OFDM or FDMA (for "frequency Division Multiple Access") if it is decided to allocate resources by separate frequency bands, or CDMA (for "Code Division Multiple Access") or otherwise, since a path back is used to refine the choice of transmission parameters.

Indeed, the invention relates to the allocation of beams users "downlink" where transmission mode configuration (number of beams, modulation, coding, guidance beams, etc.) is usually determined using information brought by an upstream channel (from the terminals to the transmitter), said upstream channel being referred to as "return path" (or "feedback").

However, this return path is very costly in terms of throughput. It is best to find a compromise between the quality of the information obtained from this feedback and the amount of information sent. In an SDMA system where the choice of resource allocation depends on the information on the expected reception quality for a large number of user terminals and a large number of beams, the amount of information sent on the return channel can become quickly prohibitive. A reduction of this amount would involve the implementation of a technique less efficient allocation of resources.

So the technical state of the art are intended to reduce the amount of information on the return path while enabling the use of an allocation algorithm and connection configuration (called "Link configuration") that is as efficient as possible. The choice of the number of active beams simultaneously according to the prior art is generally carried out at the base station, only, which is the disadvantage that the base station does not know the impact of interference beam quality of the link to the user terminal. There are many methods of feedback to inform the base station of the impact of the interference, but this information is given retrospectively and require, in any case, an amount of feedback often prohibitive. However, no additional feedback on the impact of the interference, the base station is generally required to forward a fixed number of beams in parallel to enable a terminal to evaluate the impact of interference and estimate the quality reliably link. Such a fixed configuration of the number of beams, however, is not optimal for certain user terminals, according to the channel state.

Referring indeed to Figure 1 there is shown a multiple access system with spatial distribution or "SDMA" (for "Space Division Multiple Access"). The multiple antennas at the transmitter (e.g. a base station BS) are used to generate beams Fl, F2, F3 representing the distinct resources that can be allocated to different terminals Tl, T2, T3, T4. The number of separate beams which can be generated simultaneously is typically equal to the number of antennas that includes the base station, this number being denoted M below (with M = 3 in the example of Figure 1). In principle, the maximum number of terminals that can be served simultaneously is also Mr.

A group of M antennas can generate a plurality of sets of M distinct beams. The optimum choice of one of these sets depends on the relative position of terminals that are to be served simultaneously and the state of their radio channels.

A feature of a SDMA system is that the orthogonality of the resource is not secured, which creates interference between the signals transmitted on different beams at the terminal of a receiver. To reduce this interference, it is recommended to make a choice of a group of beams (in transmission mode) that will be suitable for a choice of a group of terminals to serve simultaneously.

As an example to illustrate this, the base station BS in Figure 1 has three antennas and could therefore serve three of the four terminals simultaneously present. Comparing all beams created by the antenna array of the base station with the channel status of the user terminals (these channels are here defined only by their position), it includes the compromise must be find. First, the base station BS to choose between T3 and T4 user terminals which are both covered by the beam F3 but can not be served simultaneously. One possible choice would be to serve the user terminal Tl with the beam Fl, the terminal T2 with the beam F2, and the terminal T3 with the beam F3.

However, the user terminal T2 is located between the beams F2 and F3, which means that receives the two beams with the same quality. Therefore, signals transmitted with the F2 and F3 beams arrive at the terminal T2 of the receiver with a similar power, which generates strong interference. Signal quality, if it were transmitted on the beam F2, is not assured.

Knowing that a signal transmitted on the beam F2 also creates some interference to user terminals Tl and T3, the use of the beam F2 is not optimal with respect to the terminal configurations shown here by their respective positions. So the best choice for the system would save the power needed to serve the T2 user and does serve, however, that Tl and T3 users. Then, the T2 and T4 users may be served with another set of beams, eg beams F2 and F3 directed otherwise.

then it will be understood from this example that the optimal number of active beam for transmission, which is K-2 in this example of Figure 1, is not necessarily the maximum number M of beams that the transmitter is capable of producing simultaneously (with M = 3 in the example of Figure 1), due to the interference that may be generated by a maximum number M of active beams simultaneously.

However, the transmitter BS has no prior knowledge of the exact state channel user terminals at the time of issue and in particular on the interference generated on such channels by the beam allocation and mode of selected transmission. It is difficult for him to choose: the transmission mode, that is to say the set of beams and the number K of active beams simultaneously, and the allocation of beams to each user terminal.

The present invention improves the situation.

It proposes for this purpose a telecommunication method in a system comprising at least one transmitter arranged to make active simultaneously a first number of beams, as a resource for a plurality of user terminals, wherein the user terminals receive, through said bundles, telecommunication data.

At least one of the terminals transmits to the transmitter, by return path, an indication of at least one second preferred number of beams to make active simultaneously by the transmitter.

Note that the second preferred number is unique to the terminal, in that it results, for example the calculation of the terminal alone, or it is for example determined by the terminal, only on the basis of prerecorded information in this latest. It is transmitted to the sender for possible consideration by the latter in particular to adjust the number of beams to make active simultaneously. However, the number of active beams made does not necessarily correspond to the preferred number of beams by a terminal.

This second preferred number is calculated by the terminal, preferably taking into account an interference noise.

Thus, it will be taken into account in this calculation interference that may result from the simultaneous reception of multiple beams from a single terminal, e.g., via estimating a signal to interference plus noise. Moreover, in a particular embodiment, we seek to maximize the estimated throughput that can provide the transmitter to all the terminals, wherein estimating the throughput is a function of the signal to noise interference over supra. A terminal can then determine the preferred number of beams as the number of beams maximizing the estimate of the overall flow.

It is therefore proposed to require the terminal an indication of its preferred transmission (typically the number of beams tolerated in parallel). This indication of the terminal as to its preferred transmission mode can then define a particular metric used on the terminal return path to the base station to inform the base station of this preferred embodiment.

Thus, the invention proposes to build a terminal for the latter determines its preferred mode of transmission, which may be a new definition of metrics used on the way back to inform the issuer. This metric can, for example, be part of a set of metrics feedback (or "feedback" below) allows the base station to operate in order to optimize overall throughput served to all user terminals while ensuring a satisfactory quality of service for each user terminal. A typical set of metrics may consist of: an index of the preferred beam by the terminal (an integer, for example), - a receiving quality value in this beam, a transmission mode indicator (e.g., an integer or a binary number indicating the preferred number of beams, according to possible embodiments of the invention).

However, the invention is not limited to the application of such metrics. It is possible to provide eg feedback on the transmission mode indicator by fixing a priori, at the base station, the beam used for a given user or determining the preferred beam by other means that the return path (e.g., an estimate by the base station in the uplink). It is therefore possible to provide a metric in which any of the information conveyed by the other metrics above could be available immediately to the base station without the need to return devices.

Other features and advantages of the invention will appear on examining the detailed description below and the attached drawings, in addition to Figure 1 illustrating resource allocation in a SDMA system described above: the 2 schematically illustrates the processing by the transmitter of the information provided by the terminals on the return path, Figure 3 schematically illustrates the steps of a method according to the invention.

2 shows an exemplary block diagram implemented within the meaning of the invention, by a base station. The base station is equipped with M antennas and can transmit a maximum of M flow of information to the user terminals. however the M antennas generate K distinct beams simultaneously, where K ≤ M to avoid interference between beams. It is assumed here that a separate beam corresponds immediately to a served terminal. Can alternatively be provided that multiple beams can be used by a single terminal, which can be done in practice, for example according to the state of the radio channel and if the terminal, in turn, has a sufficient number of antennas For the reception.

The set of beams used simultaneously for transmission is denoted by Ω = {w | , ..., w A.}. Although the implementation of the invention is not of course limited to such an embodiment, therefore makes the assumption that K ≤ M.

The set Ω is then composed of K vectors of length M, denoted by W n = {w v ..., w M].

Each vector w ,, thus represents a separate beam and has M complex coefficients (as components), these coefficients corresponding in practice to the weights applied to each antenna branch for generating a beam ,, w. In the example shown in Figure 2, the base station receives a terminal information about the quality of link Q to optimize the S21 treatment of modulation and coding for the terminal as well as information on a preferred beam w f pre finally optimize the S22 control beams antennas Antl ... ANTM. Within the meaning of the invention, the preferred base station further receives from the terminal a number of beams K prej to optimize the K number of beams to be transmitted.

More particularly, to generate the set of K beams, the allocation to the user terminals and perform the "link adaptation" (which is to select an optimum modulation and coding processing in step S21), the base station receives and interprets such information transmitted to it on the way back from a user terminal. These may be, for example, two types of information as described above: a first information pre w f of the preferred beams or by the terminal, which may thus depend on the position of the terminal with respect to the base station and / or the state of the radio channel, a second information Q on the quality of the radio link achievable in the preferred beams or by the terminal, then the second information for deciding the effective allocation of a beam to a user and perform link adaptation.

For example, the first information may be the index of a preferred vector in a set of vectors known by the terminal and the base station. This set can be defined by a dictionary (or "code book"), shared between the base station and the terminal. the base station can be provided as an alternative that can independently change the beam and transmit drivers on each beam to allow each terminal to identify them.

The size of the overall set of beams that can be generated by the base station (taking into account in particular the various possible forms of beams) is generally greater than or equal to the previously set number M and this assembly will be noted in the following Ω = {w,, ...} ^^ with N ≥ M (and in particular with TV = M in the aforementioned case of transmitting pilot in each beam as shown above). Note that all of Ω actually transmitted beams can then be a subset of the set Ω. It will be understood that the base station can freely steer or refine the K beams of the set Ω from the feedback received from the terminals, by performing his choice overall Ω 'TV opportunities beams.

The received second information can usually be based on an estimate, at the terminal, the signal-to interference plus noise ratio (SINR or for "Signal to Interference plus Noise Ratio"). This estimate will be described later to a particular embodiment of the invention. Feedback in itself can be carried out for example according to the process disclosed in the document FR-2 893 468.

For the purposes of the invention, it is proposed to associate a third type of information. This additional information indicates to the base station how many other streams (beams) the user terminal can tolerate in parallel with the current flow of information. This information is advantageously quantified and its quantification is based on an estimate of the impact of interference from other bundles on the quality of its existing radio link. The value assigned in feedback on this third information may be an integer or be a single bit, according to embodiments described below.

In what follows, we consider that each terminal explicitly knows the vectors of the set Ω. The base station may transmit such a pilot signal on each antenna allowing the terminal to estimate a complex coefficient h m representing the effect of the mobile radio channel between each antenna of the base station and the terminal of the receiving antenna. The radio channel between the base station and the terminal can thus be represented by a vector h = {/ ?, ..., h m, ..., h Vf). As indicated above, the terminal can alternatively have multiple receive antennas. Furthermore, alternatively or additionally, the radio channel can be described by a number of complex coefficients of both, such as in the case of a frequency selective channel. In these embodiments, the channel is described by a matrix (rather than a single vector h) and the following expressions given in the embodiment where it affects a single vector h to a channel, can be adapted appropriately. It is therefore understood that the invention is not limited to the assignment of a single vector to a channel.

From the estimate of the channel vector h and the knowledge of the set Ω 'of the beams, the terminal may estimate the quality of radio link to each of the beams under the assumption of a transmission mode using a set Ω is a subset of the set Ω '. Here one formula also assumes that the same power is allocated to all beams. However, it may be provided to adapt the following expression in the case of a variant in which the allowance in power is not homogeneous.

According to the above assumption, the signal-to interference plus noise ratio (SINR) for a w ,, given beam can be written as follows:

SINR (Vf n, Ω), n = l, ..., N, where σ represents the inverse of signal to noise ratio (ie the ratio between receiver noise power and the useful signal received by the terminal) and K is the cardinality of the set Ω. In addition, the notation h.vv (denotes the scalar product between the column vector h and the column vector W 1, is therefore hw = h? W (.

It should be noted that according to the definition of this metric, the terminal must make an assumption about the set Ω that will actually be selected by the base station, the set Ω is therefore unknown to the terminal when it estimates its quality reception. Therefore, the terminal can not accurately calculate the interference portion (first term of the denominator).

However, it shows that it is possible to estimate the SINR in a w beam (given with the only knowledge K size of the set Ω, the vector h and the overall set Ω. We may at this effect usefully refer to the document:

"Efficient Metrics for Scheduling in MIMO Broadcast Channels with Limited

Feedback ", Mr. Kountouris, R. Francisco, Gesbert D., D. Slock T. Salzer, in Proceedings IEEE ICASSP, Hawaii, USA (April 2007).

We can then choose here an estimate of the form:

SINR (W k, K) = k = l, ..., K, (1)

This estimate is satisfactory under the assumption that the base station selects a set of orthogonal vectors Ω (or approximately orthogonal). This precaution is in any way desirable to reduce interference between the transmitted beams simultaneously. The selection algorithm of the base station beams therefore generally seeks to achieve such a configuration.

The function C (K, M, σ 2) in the relation (1) above is used to estimate the impact of the interference with the other beams, with preferably single hypothesis as the number K of beams transmitted simultaneously. This is a generally non-linear and configurable function. It can be optimized based on the knowledge available at the terminal, for example the mode of adaptation and selection of the beams at the base station. It is therefore possible for the terminal to select, among all the vectors of the set Ω ', a preferred beam, represented by the vector w pιef given by an expression of the type: w = argmax pref Ω, | hw (/ | ( that is to say the vector w n from the overall set Ω 'which has the greatest scalar product in absolute value with the channel vector h). in other words, the preferred vector \ v p, ef is therefore that which advantageously maximizes the projection on the channel vector h.

The index k of this vector (with W ^ = vtprej) in the overall set Ω 'represents one of the feedback elements to the base station. It should be noted that the terminal may also determine a plurality of beams with an order of preference and to inform the base station as a succession of data values ​​in that order of preference.

In a second step, the terminal determines its preferred transmission mode. Here we consider the K beams simultaneously generated are likely to create more or less strong interference with the beam served to a given user. As it is desired to minimize interference for all users served

(As discussed above with reference to Figure 1), thus determines the number K as the optimal number of beams tolerated in parallel for each user.

Of course, a terminal prefer to be served without interference from other beams served concurrently with his. In this case (ideal if we can just consider that KI to calculate SINR), its SINR written simply as follows: lh.w,

SINR (Vf pιet, I) = σ

From this ratio value SINR, the terminal may estimate the flow rate that the base station is able to transmit in this configuration, this flow rate being denoted by R (w pιet 1). Generally, the terminal has for this purpose a correspondence table enabling it to associate a flow rate SINR. It may also, by approximation from the Shannon limit, calculating the flow rate as follows:

* (w PM Glog D = (l + SINR (w pref, l)), where G is a constant of the system which depends in particular on the available frequency band and other parameters known by the terminal. It is then the maximum flow rate that can be provided to the terminal if it is selected by the base station.

However, the terminal may estimate its flow rate for the transmission of K beams in parallel in the same manner, with:

R (Yf ^, K) = Glog (l + SINR (Yf ^ n K))

hw A where w, = w and <9 hw = arccos A '

In the base station, it is best to serve multiple users simultaneously to maximize overall system throughput. The fact of serving a user terminal increases more interference and therefore reduces the user rate. Usually, the base station can not estimate a priori the impact of the interference created on the quality of user connections because it knows that their preferred beam w ptej but not their channel vector h.

An embodiment of the invention then proposes to calculate the optimum configuration at the terminal through an approximation of the system throughput. To this end, an approximation of a homogeneous network is made, where each user is served with the same speed. The total flow therefore represents only the flow per user multiplied by the number K. This assumption is only used for the calculation of the optimal mode of transmission, but does not limit the scope of application of the invention.

The terminal can then find its optimal K pιef configuration as follows:

K pιe = argmax (*: R χ (yv pιef, K)) (2) λ = l, 2, .M

This number will then be transmitted over the return channel and allow the base station to serve the user terminal as a preferred mode, which maximizes speed and taking into account the overall system including also the other terminals.

In practice, it is often useful not to report the number K pre / in itself but simply report in binary mode if the terminal can not tolerate or other users in parallel with it. The terminal can therefore choose between a configuration K = I and M = K and report his preference by a single feedback bit.

It should be noted that, in the case where K = M, the function C (K, M, σ 2) is trivial and equation (1) is written:

SINR (W k, K)

schematically shown in Figure 3 the main steps of the method hereinbefore in one embodiment.

As indicated above, the transmitter BS transmits to the terminal the pilot signals enabling the terminal to estimate the coefficients h \, ..., h \ f each representing a radio channel between a transmitter antenna and the terminal (or antenna of the terminal). From these coefficients h \, ..., h, y, the terminal is able to set up in step S31 the vector h representative of the overall channel between the transmitter and the terminal. The beam preferred by this terminal is determined based on the vector h representative of the overall channel. It is recalled that the preferred beam is represented by a beam vector w pre f having, among the overall set of possible beams Ω ', the greater scalar product, in absolute value, with the vector h representative of the overall channel. In fact, according to equation (1) given above, this preferred beam represented by the vector w pre maximizes f, among the set of possible beams Ω ', the signal to interference plus noise ratio, estimated based on the channel vector h in step S32 of Figure 3 and denoted SINR (h) in this figure 3. the maximum search SINR (h), knowing the channel vector h, giving, at the end of step S32 of Figure 3, the vector of the preferred beam w pre f.

In broad terms, it is then understood that the terminal determines the preferred beam w pre / maximizing among a set of possible beams Ω ', an estimate of the signal to interference plus noise ratio SINR (wy t / K). In particular, the beam preferred by the pre f w terminal is determined based on a global channel (vector h) between the beams from the transmitter and the terminal, the global channel h is estimated from information transmitted by the transmitter to the terminal on the coefficients h \ values, ..., h \ ι each representing a channel between a beam from the transmitter and the terminal.

At the next step S33, the terminal deduces, from equation (2) given above, the preferred number of K beams pre f defined from this equation (2), as the number of beams to make assets to maximize the overall throughput, denoted KXR (w preβ K), the transmitter is capable of transmitting to all the terminals. It is recalled that the overall throughput KXR (pre w f, K) is estimated based on the signal to interference plus noise K).

It is also recalled that the signal to interference plus noise ratio SINR (My 6 /., K) is estimated by calculating a function C (K, M, σ 2), inverse variation of the ratio SlNR (w pre f, K) and depending on at least: the number of active beam K, a maximum number of beams M that the transmitter can make simultaneously active and which is generally equal to the number of antennas at the transmitter, and σ 2 ratio a sound reception and the power of the useful signal received by the terminal, and this noise power can be measured by the terminal.

Once the pιej K value determined, the latter may for example be encoded, in step S34, a single bit indicating that the terminal: tolerates only one active beam, or can tolerate a maximum number M of beams assets. At the next step S35, the value of the preferred number K pιe f and encoded on a bit in the example described, is transmitted to the transmitter via the return channel, possibly with an indication of the preferred beam represented by the vector w p / ef and a Q value representing the quality of the radio link.

It should be noted that the steps illustrated in Figure 3 are implemented by the same entity communicating, ie the user terminal. As such, the present invention also relates to such a terminal comprising means for implementing the above method before (e.g. a memory and / or work, and a processor). The present invention also provides a computer program to be executed by such a processor.

However, the invention is not limited, of course, to the embodiment illustrated in Figure 3. Moreover, in turn, the transmitter BS can adjust the number K of active beams made at least according to the indications of preferred numbers of K beams pιe f, provided by the user terminals. As a purely illustrative example, a base station may not be used immediately indicating terminal (particularly in the embodiment where the preferred number K pte f is coded on a single bit) that do not tolerate the issue of too many bundles. This terminal can be used in a next salvo, for example in a TDMA transmission mode, combined with a SDMA mode. As such, the present invention also provides such a transmitter BS, then comprising means (e.g. even a storage memory and / or work, and a processor) to adjust the K number of beams made active at least according to the indications by the terminals for their preferred number of pre K f beams. The present invention also provides a computer program to be executed by such a processor.

The present invention further relates to a telecommunication system including at least one terminal within the meaning of the invention and a transmitter for the purposes of the invention. In an advantageous embodiment, such a system may be a multiple access system spatial distribution or "SDMA".

The present invention also relates the metric itself, for transmitting to the base station indicating the preferred number of beams K pre /. As such, it is then a signal transmitted by return path from a terminal to a transmitter having the information on the reception quality of telecommunications data, and in particular the preferred number of K f pre beams.

Thus, it is proposed to be specified by a user terminal his favorite mode of transmission. In particular, the terminal transmits to the transmitter on the return channel an indication of the number K pre f he prefers, to make beams simultaneously active by the transmitter. It is then proposed a metric associated feedback. The implementation of the invention has the following advantages: - the choice of mode of transmission is from the terminal and requires no additional feedback to inform the issuer of the impact of interference between beams on the quality of the link, the only knowledge required for the terminal is the overall set of beams that can generate the base station - no knowledge about the channels of the other user terminals and allocation decisions is needed, the metric feedback to the choice of mode is somewhat complex. It can be an integer or just a single bit.

Claims

claims
1. A method of telecommunication in a system comprising at least one transmitter (BS) arranged to make active simultaneously a first number (K) of bundles, as a resource for a plurality of user terminals, wherein the user terminals (Tl, T2 , T3, T4) received by said beams, telecommunications data, characterized in that at least one of the terminals transmits to the transmitter, by return path, an indication of at least one second preferred number (K pre f) beams (K f pre) to be active simultaneously by the transmitter.
2. Method according to claim 1, characterized in that said second preferred number (K pre j) is calculated by said terminal taking into account an interference noise.
3. The method of claim 1, characterized in that said terminal:
- considers an overall (KXR (w pre f, K)) that the transmitter is capable of transmitting to all terminals,
- and determines said second preferred number of beams (K f pre) as the number of beams to make assets to maximize the estimate of said overall throughput.
4. A method according to claim 3, characterized in that said terminal estimates said overall flow rate to maximize (KXR (w pre f, K)) based on a signal to interference plus noise ratio K)).
5. A method according to claim 4, characterized in that the signal to interference plus noise K)) is estimated by calculating a function (C [KM (y 2), inverse variation of said ratio, and depending at least:
- the number of active beams (K), - a maximum number of beams (M) that the transmitter can make simultaneously active,
- and a ratio (σ 2) between the sound receiving and the power of the useful signal received by the terminal, measured by the terminal.
6. A method according to claim 1, characterized in that said indication of the second preferred number (K pιe j), transmitted to the transmitter by the return channel, is encoded on one bit indicating that a terminal: tolerates that a single active beam, or - can tolerate a maximum number (M) active beam.
7. A method of telecommunication in a system comprising at least one transmitter (BS) arranged to make active simultaneously a first number (K) of bundles, as a resource for a plurality of user terminals, wherein the transmitter (BS) transmits to the user terminals by said beams, telecommunication data, characterized in that the transmitter adjusts said first number (K) of bundles rendered active at least as a function of an indication of a second preferred number (K pιej) of to make simultaneously active beams transmitted by at least one of said terminals on said return path.
8. Terminal for a telecommunication system comprising at least one transmitter arranged to make active simultaneously a first number (K) of bundles, as a resource for a plurality of user terminals, characterized in that it comprises means for implementation of the method according to one of claims 1 to 6.
9. A computer program comprising instructions for implementing the method according to claim 1 when that program is executed by a processor.
10. A transmitter for a telecommunications system wherein said transmitter is arranged to make active at the same first number (K) of bundles, as a resource for a plurality of user terminals, characterized in that it comprises means for implementation of the method according to claim 7.
1 1. A computer program comprising instructions for implementing the method according to claim 7 when the program is executed by a processor.
12. Telecommunication system comprising at least one terminal according to claim 8 and at least one transmitter according to claim 10.
13. Signal transmitted by return path by at least one terminal to a transmitter in a telecommunication system wherein the transmitter is arranged to make active at the same first number (K) of bundles, as a resource for a plurality of terminals users, the transmitter (BS) transmitting to the user terminals (Tl, T2, T3, T4), by said beams, telecommunications data, characterized in that the signal comprises an indication of a second preferred number of beams (K pre j) to be active simultaneously by the transmitter.
EP20080867695 2008-01-03 2008-12-12 Communication by return pathway from a terminal to a transmitter for reducing in particular interference between beams from the transmitter Withdrawn EP2243227A1 (en)

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PCT/FR2008/052293 WO2009083680A1 (en) 2008-01-03 2008-12-12 Communication by return pathway from a terminal to a transmitter for reducing in particular interference between beams from the transmitter

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