KR101706965B1 - Communication method using outdated channel state information in g-cell, k-user cellular network - Google Patents

Abstract

In the network environment composed of the G-cell and the K-user, the terminal and the base stations transmit and receive data symbols for G time intervals, and transmit and receive a reconfiguration signal for one additional time interval. Communication method.

Description

Technical Field [0001] The present invention relates to a communication method using outdated channel state information in a G-cell, a K-user cellular network, and a communication method using outdated channel state information in a G-

The present invention is related to a method for communicating with a terminal and a base station using outdated channel state information in a cellular network environment in which G cells exist and K users exist in each cell.

Interference is one of the major causes of reducing performance in a wireless network environment. This interference problem occurs mainly in a multi-user environment where there are many transmission-reception pairs. This is because the transmission signals simultaneously transmitted from the respective transmission terminals are transmitted not only to the target reception terminal but also to the non-intended receivers. Interference Alignment (IA) technology has received much attention as a potential solution to this interference problem. The interference alignment technique was originally developed under a model of an interference channel between an X-channel and a K-user, and has been developed for a practically-relevant network model related to various real situations. Interference sorting techniques have been developed that achieve nearly the same performance as DoF (degree of freedom) performance in an interference-free situation, especially under cellular network conditions.

Although these interference alignment techniques contribute to increase the communication capacity, there are a number of problems to be applied to the actual environment. One of them is that the transmitter must know the current channel state information (CSI) precisely. In a conventional FDD (Frequency Division Duplex) communication system, such channel information is normally obtained by receiving feedback from a receiving end to a transmitting end, and further delay is required to receive feedback. Therefore, in the conventional communication system, the interference alignment technique is applied based on the predicted channel information after predicting the current channel information based on the outdated channel state information (outdated CSI). However, in fast-fading scenarios where the channel environment changes rapidly, the current channel state may be completely different from the predicted channel state from the feedback. In this case, the method of predicting the current channel state is to improve the communication capacity It will fail.

However, it has been found that communication capacity can be improved even with outdated channel state information in a multi-antenna broadcast channel. That is, it is known that in a fast-fading environment in which a channel environment changes rapidly, even if the channel information fed back from the receiver is completely different from the current channel state, the communication efficiency can be improved by using such channel information. If the communication performance is improved as compared with the case where there is no channel information in such an extreme situation, the efficiency of communication can be improved in any environment by using the delayed outbound channel information.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the efficiency of communication by using delayed out- put channel information.

It is still another object of the present invention to achieve an improvement in communication efficiency even in a network environment in which the number of terminals and cells changes.

Yet another object of the present invention is to obtain a higher DoF gain than the DoF in the case where the outdated channel information is not used.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the invention to the particular form disclosed. ≪ / RTI >

According to an aspect of the present invention,

1 < / RTI > time period constituting the first time period together with the 1-2 time period,

Transmitting different data symbols for each time slot to a first base station, receiving a feedback signal comprising channel information for transmitted data symbols,

During the first-second time period, which is composed of time slots,

Transmitting a linear combination of a plurality of data symbols for each time slot to a first base station, interrupting transmission of data for a second time period to a Gth time period, and

And transmitting the generated reconstructed signal based on the feedback signal during the (G + 1) -th time period consisting of the number of time slots.

The step of transmitting the reconfiguration signal may comprise the steps of:

Lt; RTI ID = 0.0 > time slots. ≪ / RTI >

The step of transmitting the reconfiguration signal comprises:

It is possible to transmit the reconfiguration signal together with the first terminal included in any one of the G-1 cells except for the first cell in each of the time slots.

During the 1-1 time period, other terminals located in the first cell

During a time slot

RTI ID = 0.0 > 1 < / RTI > time slots

And transmitting the sum of the different data symbols to the first base station.

Can be performed repeatedly.

During the first-second time interval, the other terminals located in the first cell are in the G time slots

The process of transmitting a linear combination of the data symbols for each time slot to the first base station and stopping the transmission of data for the next G time slots,

Can be performed repeatedly.

According to another aspect of the present invention,

A first terminal located in the first cell for every time slot during a first time interval constituting the first time interval together with the first time interval,

Receiving from the second terminal and the third terminal located in the first cell during the first time interval,

During a time slot

Lt; RTI ID = 0.0 > 1 < / RTI > timeslots

The process of receiving the sum of the different data symbols

Repeating the steps one by one,

For each of the time slots, from the first terminal

Receiving a linear combination of a plurality of data symbols,

From one of the second terminal and the third terminal

Receiving a linear combination of a plurality of data symbols in each time slot, receiving signals transmitted by terminals located in the second through Gth cells as interference signals during a second time period to a G time period,

Receiving a reconfiguration signal for each time slot from a terminal and a first terminal belonging to any one of the second cell to the G-th cell during a (G + 1) th time interval consisting of time slots, And decoding the received data symbols during a first time interval.

The communication method may further include receiving a feedback signal including channel information for received signals during a 1-1 time period, and the reconfiguration signal may be generated based on the feedback signal.

The communication method includes performing a nulling process on signals received in a first time interval using signals received in a first time interval and transmitting data generated through a nulling process to first side information and storing the received information as side information.

The communication method may further include generating second side information related to only one terminal by performing a nulling process on the first side information using the reconfiguration signal received in the G + 1 time period.

The step of receiving the reconstructing signal comprises the steps of:

Lt; RTI ID = 0.0 > time slot, < / RTI >

According to the embodiments of the present invention, the following effects can be expected.

First, higher communication efficiency can be secured by utilizing the delayed out- put channel information.

Second, the performance can be improved even in a situation where the channel environment changes rapidly, so that it is possible to improve the performance that is robust against changes in the network environment, compared to the case in which the outdated channel information is not used.

Third, as the number of cells increases, higher performance increases and the total communication capacity can be increased.

The effects obtainable in the embodiments of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be obtained from the description of the embodiments of the present invention described below by those skilled in the art Can be clearly understood and understood. In other words, undesirable effects of implementing the present invention can also be obtained by those skilled in the art from the embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. It is to be understood, however, that the technical features of the present invention are not limited to the specific drawings, and the features disclosed in the drawings may be combined with each other to constitute a new embodiment. Reference numerals in the drawings refer to structural elements.
1 is a diagram illustrating an uplink channel model of a G-cell and a K-user associated with the present invention.
2 is a diagram showing a structure of a time interval related to an embodiment of the present invention.
3 is a diagram illustrating a method for a terminal to communicate using outdated channel state information in accordance with an embodiment of the present invention.
4 is a diagram illustrating a method by which a base station communicates using outdated channel state information in accordance with an embodiment of the present invention.
5 is a diagram showing a configuration of a terminal and a base station according to an embodiment of the present invention.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. Also, in certain cases, there may be a term selected arbitrarily by the applicant, in which case the meaning thereof will be described in detail in the description of the corresponding invention. Therefore, the term used in the present invention should be defined based on the meaning of the term, not on the name of a simple term, but on the entire contents of the present invention.

The following embodiments are a combination of elements and features of the present invention in a predetermined form. Each component or characteristic may be considered optional unless otherwise expressly stated. Each component or feature may be implemented in a form that is not combined with other components or features. In addition, some of the elements and / or features may be combined to form an embodiment of the present invention. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of certain embodiments may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments.

In the description of the drawings, there is no description of procedures or steps that may obscure the gist of the present invention, nor is any description of steps or steps that can be understood by those skilled in the art.

Throughout the specification, when an element is referred to as " comprising " or " including ", it is meant that the element does not exclude other elements, do. In addition, the term " "... Quot ;, " module " and the like refer to a unit for processing at least one function or operation, which may be implemented by hardware, software, or a combination of hardware and software. Also, the terms " a or ", " one ", " the ", and the like are synonyms in the context of describing the invention (particularly in the context of the following claims) May be used in a sense including both singular and plural, unless the context clearly dictates otherwise.

The embodiments of the present invention have been described herein with reference to a data transmission / reception relationship between a base station and a mobile station. Here, the base station is meaningful as a terminal node of a network that directly communicates with a mobile station. The specific operation described herein as performed by the base station may be performed by an upper node of the base station, as the case may be.

That is, various operations performed for communication with a mobile station in a network consisting of a plurality of network nodes including a base station may be performed by a base station or other network nodes other than the base station. The term 'base station' may be replaced by terms such as a fixed station, a Node B, an eNode B, an Advanced Base Station (ABS), or an access point.

Also, a 'Mobile Station (MS)' may be a user equipment (UE), a subscriber station (SS), a mobile subscriber station (MSS), a mobile terminal, an advanced mobile station The term " terminal "

Also, the transmitting end refers to a fixed and / or mobile node providing data service or voice service, and the receiving end means a fixed and / or mobile node receiving data service or voice service. Therefore, in the uplink, the mobile station may be the transmitting end and the base station may be the receiving end. Similarly, in a downlink, a mobile station may be a receiving end and a base station may be a transmitting end.

Further, an indication that a device performs communication with a " cell " may mean that the device transmits and receives signals with the base station of the corresponding cell. That is, although a practical object to which a device transmits and receives a signal may be a specific base station, it may be described as transmitting and receiving signals with a cell formed by a specific base station for convenience of description. Similarly, the description 'macro cell' and / or 'small cell' may mean specific coverage, and may also refer to a 'macro cell supporting a macro cell' and / or a 'small cell supporting a small cell' Base station '.

Embodiments of the present invention may be supported by standard documents disclosed in at least one of IEEE 802.xx systems, 3GPP systems, 3GPP LTE systems and 3GPP2 systems, which are wireless access systems. That is, self-explaining steps or parts not described in the embodiments of the present invention can be described with reference to the documents.

In addition, all terms disclosed in this document may be described by the standard document. In particular, embodiments of the present invention may be supported by one or more of the standard documents P802.16e-2004, P802.16e-2005, P802.16.1, P802.16p, and P802.16.1b, which are standard documents of the IEEE 802.16 system have.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following detailed description, together with the accompanying drawings, is intended to illustrate exemplary embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced.

In addition, the specific terminology used in the embodiments of the present invention is provided to help understanding of the present invention, and the use of such specific terminology can be changed into other forms without departing from the technical idea of the present invention.

1 is a diagram illustrating an uplink channel model of a G-cell and a K-user associated with the present invention.

The channel model shown in FIG. 1 illustrates a situation of uplink communication in which there are K users in each of G (G is three or more) cells. In a simple embodiment, there is shown a case where there are three users in each cell (i.e., K = 3). It is assumed that the user terminal (transmitting end) and the base station (receiving end) each have one antenna. Users of cell 1, cell 2, ..., and cell G transmit an uplink signal to base station 1, base station 2, ..., and base station G, respectively, and each base station receives an interference signal .

For example, the base station 1 receives a preference signal (shown by a solid line) from a user 1, a user 2, and a user 3 located in a cell 1, and simultaneously receives a preference signal from a user 1, a user 2, And receives a signal transmitted to the base station 2 as an interference signal (shown by a dotted line). Similarly, the base station 1 receives a signal transmitted from the user 1, the user 2, and the user 3 located in the cell G to the base station G as an interference signal.

Similarly to the case where the base station 1 receives the preference signal and the interference signal together, the base station 2 to the base station G also receive the preference signal and the interference signal together. That is, while the base station 2 receives a preference signal from users located in the cell 2, the base station 2 receives an uplink signal from users located in other cells as an interference signal. The interference signal is received by overhearing the uplink signal to the neighboring base stations located adjacent to the base station.

Hereinafter, a communication method in which each base station processes the received signal using the outdated channel information in the G-cell and K-user scenarios shown in FIG. 1, thereby achieving one or more DoFs will be described. The proposed communication method is performed by a series of time intervals, and each time interval is represented by a phase. A phase, which means a predetermined time period, is composed of two subphases, and each subphase is composed of a plurality of time slots. A time slot means a time unit in which one data symbol is transmitted, and a phase and a sub phase are composed of two or more time slots. A data symbol means a unit of data transmission. Hereinafter, phases 1-1 and 1-2 denote subphases for phase 1, respectively. That is, Phase 1 - 1 refers to Subphase 1 of Phase 1, and Phase 1 - 2 refers to Subphase 2 of Phase 1.

First, a scenario of a G-cell and a 3-user will be described as an example for explaining a scenario of a G-cell and a K-user. The G-cell, K-user scenario can be understood by extending the case of the G-cell, 3-user scenario and will be described in detail later.

2 is a diagram showing a structure of a time interval related to an embodiment of the present invention. As described above, the series of communication methods operate in a cycle of one G + 1 phase from Phase 1 (first time interval) to Phase G + 1 (G + 1 time interval). Phase 1, on the other hand, consists of sub-phase 1 and sub-phase 2. (2G-1) time slots are repeated (2G-1)

Lt; / RTI > time slots. Subphase 2 is repeated (G-1) times with (2G) time slots,

Lt; / RTI > time slots.

Phase 2 to Phase G are the same as Phase 1

Lt; RTI ID = 0.0 > G + 1 < / RTI >

Lt; / RTI > time slots. Therefore, a series of operation processes according to the proposed communication method are executed

Lt; / RTI > time slots. Hereinafter, how the proposed communication method operates for each phase will be described in detail, and three terminals for each cell will be described as an example.

First, phase 1-1 (i.e., sub-phase 1 of phase 1)

And one time slot. In phase 1-1, as shown in FIG. 2

The number of timeslot units is

Times, and each

The operation of each time slot unit will be described.

On the other hand, only the terminals belonging to the cell 1 transmit the uplink signal in the entire phase 1 comprising the phases 1-1 and 1-2, and the terminals belonging to the remaining cells 2 to G do not transmit any data.

In phase 1-1, a user terminal (hereinafter referred to as terminal) 1 of cell 1 transmits 2G-1 data symbols during a 2G-1 time slot. 2G-1 data symbols are transmitted once for every 2G-1 time slots. At the same time, the terminal 2 and the terminal 3 of the cell 1 transmit 2G-2 data symbols (in every time slot) during the preceding 2G-2 time slots in the 2G-1 time slots and transmit And transmits a sum of 2G-2 data symbols. The data symbols transmitted by the UEs in Phase 1-1 are summarized as Equation (1) below.

In the equation (1), the top line represents each time slot, the second line represents data symbols transmitted by the terminal 1, and the third line and the fourth line represent data symbols transmitted by the terminal 2 and the terminal 3, respectively. On the other hand, in Equation (1)

Denotes a data symbol transmitted by the j-user of the i-th cell,

Superscripts < / RTI > represent time slots in which each data symbol is transmitted.

On the other hand, data symbols transmitted in each time slot of phase 1 are multiplied by a channel coefficient and received by base stations. That is, the base station 1 receives a signal transmitted by the terminals 1, 2, and 3 as a preference signal, and the base station 2 to the base station G receive the same signal as an interference signal. Taking the time slot 1 of the phase 1-1 as an example, a signal received by each base station can be expressed by the following equation (2).

In Equation 2,

Denotes a channel coefficient for a data symbol transmitted from the j-th terminal of the i-th cell to the k-th base station in the time slot t (1 in this example).

On the other hand, the number of data symbols received by the base station 1 of the cell 1 in the phase 1 - 1 is 2G-1, 2G-2 * 2 received from the terminal 1, -1) + 2 * (2G-2). The number of linear equations received by base station 1 during a 2G-1 time slot of phase 1-1 is 2G-1, and to decode all data symbols received in the first 2G-1 time slot of phase 1-1, 2G-2) equations are additionally required.

Meanwhile, the signals received by the base station k other than the base station 1 during the first 2G-1 time slot of the phase 1-1 are expressed by Equation (3) below.

Equation (3) can be expressed as Equation (4) below using a determinant.

In Equation 4,

A precoder vector,

Denotes a vector of data symbols.

On the other hand, in the first 2G-1 time slot of phase 1-1, terminal 2 and terminal 3 of cell 1 transmit the sum of data symbols previously transmitted in the last time slot. Accordingly, other base stations other than the Node B 1 can generate a null space vector for the interference signals received during the 2G-1 time slot. Other base stations can then remove components for terminal 2 and terminal 3 from the received interference signal by applying a null space vector to the interfering signal. This process is called a nulling process, and information generated through a nulling process is referred to as side information. Each of the base stations stores the side information generated through the nulling process and Equation (5) below represents the null space vector generated by the base station k excluding the base station 1

.

The base station k can generate the side information from which the components related to the terminal 2 or 3 are removed, as shown in Equation (6) below, by multiplying the interference signal described in Equation (4) by a null space vector.

In Equation (6), the first side information is the side information from which the component for the terminal 2 is removed, and the second side information is the side information from which the component for the terminal 3 is removed. Accordingly, each base station generates and stores two pieces of side information. The above-described process is performed using interference signals at each of the G-1 base stations except for the base station 1.

In Equation 6,

Denotes side information stored in the base station k and required by the base station i. E.g,

Represents side information stored in the base station k and required for the base station 1 to decode the received signal,

Represents the side information stored in the base station k and required for the base station 2 to decode the received signal. The side information required by a particular base station means additional equations required for decoding the data symbols as described above.

In Equation (6)

Is an expression composed of components for the terminal 1 and the terminal 3. Equation 6

The component for terminal 1 (

) And the component (

) Can be expressed as Equation (7) below.

Similarly to the process of deriving Equation (7), Equation (6)

Is composed of components for the terminal 1 and the terminal 2,

The component for terminal 1 (

) And the component (

), The following equation (8) can be derived.

At this time, as described in Equations (7) and (8)

,

,

,

(G-1) are provided to the base station 1, the base station 1 obtains an equation sufficient to decode the data symbols received in the first 2G-1 timeslot. Prior to describing the process for transmitting this information to the base station 1, the following description will be made with respect to the phase 1-1.

The operation performed in the first time slot of 2G-1 in the above-mentioned Phase 1-1 has been described. As shown in FIG. 2, this series of processes is repeated a total of 2G-1 times during Phase 1-1. Since the base stations except for the base station 1 generate 2 pieces of side information for each 2G-1 time slots, when 2G-1 time slots are repeatedly performed 2G-1 times in total, each base station (excluding the base station 1) (2G-1) pieces of side information.

Next, phase 1-2 (sub-phase 2 of phase 1) will be described. Prior to describing the phases 1-2, the terminals can receive feedback from the base station about the signal transmitted by the terminals themselves. Accordingly, the UEs can know the information on the channel coefficients of the data symbols transmitted from the feedback signal. Based on the information on the channel coefficients, the UEs can reconstruct a signal possessed by the BS only and related to itself, and can transmit the reconstructed signal to the base station of the cell in which the UE is located.

As described above, the base station 1 stores the side information from which the components for the terminal 2 are removed and the side information from which the components for the terminal 3 are removed. Since the side information from which the components for the terminal 2 are removed consists only of components for the terminal 1 and components for the terminal 3, the base station 1 desires to separate and acquire the components for the two terminals.

Thus, in phase 1-2, terminal 1 of cell 1 is in the first G time slot

For each time slot. ≪ tb >< TABLE > At the same time, the terminal 3 of the cell 1 waits for the first G time slot

Lt; / RTI > every time slot.

G linear combinations from terminal 1 and terminal 3 arrive at each base station during a G time slot. At this time, the base station 2 has the side information for the terminal 1 and the terminal 3 generated in the phase 1-1. Accordingly, the base station 2 can generate G side information related to only the UE 1 and G side information related to only the UE 3 through the nulling process for the received linear combinations during the G time slot. The remaining base stations other than the base station 1 and the base station 2 can generate one side information related to only the terminal 1 through the nulling process for the linear combinations transmitted by the terminal 3.

Similar processes are also performed by the terminal 1 and the terminal 2. That is, during the next G time slots,

Lt; / RTI > every time slot. At the same time, the terminal 2 transmits

Lt; / RTI > every time slot. Through this process, the base station 2 generates G side information associated only with the terminal 1 and G side information associated with only the terminal 2, respectively. In addition, other base stations except for the base station 1 and the base station 2 additionally generate and store side information related to only the terminal 1 one by one.

Thus, the process of the base station 2 generating the side information related to only one terminal is performed through the 2G time slot. Similarly, a similar procedure is performed for the base station 3 to the base station G, so that a total of 2G * (G-1) time slots is required. That is, in Phase 1 - 2, two terminals (terminal 1 and another terminal) of cell 1 transmit linear combinations during a G time slot, and two terminals of cell 1 (terminal 1 and another terminal) Lt; / RTI > This 2G timeslot-based process is repeated a total of G-1 times, and a total of 2G * (G-1) time slots is required in the phase 1-2.

According to the above-described procedure, phase 1 consisting of phase 1-1 and phase 1-2 is performed. In phase 1, the UEs belonging to cell 1 transmit data symbols and reconstructed signals. Phase 2 to Phase G are then performed. In Phase 2 to Phase G, a process similar to that performed in Phase 1 is performed in Cell 2 to Cell G. Specifically, in phase 2, terminals belonging to cell 2 perform phase 2-1 and phase 2-2, and in phase G, terminals belonging to cell G perform phases G-1 and G-2.

Next, the phase G + 1 will be described. In the phase G + 1, a process of using the side information related to only one terminal generated from each of the subphases (phase 1-2, phase 2-2,?, Phase G-2) of phase 1 to phase G is performed .

Phase G + 1 is composed of a total of G * (3G-2) * (G-1) time slots, and terminals 1 of two cells out of G cells transmit a reconfiguration signal for each time slot. The reconstructed signal transmitted in phase G + 1 is side information related only to each terminal 1 itself. The terminal 1 can acquire information on the channel coefficient as it receives feedback from the base station and can reconstruct a signal related to itself.

On the other hand, an arbitrary base station i receives a reconfiguration signal from the terminal 1 of the cell i and also receives a reconfiguration signal from the terminal 1 belonging to another cell j in the same time slot as an interference signal. At this time, the base station i already stores the side information associated only with the terminal 1 of the cell j. Therefore, the base station i can extract only the preference signal from the terminal 1 of the cell i by using the reconfiguration signal received from the cell j and the side information held by the cell j.

Similarly, when the UEs 1 of the cell i, k transmit a reconfiguration signal in another time slot, the base station i transmits a reconfiguration signal received as an interference signal from the UE 1 of the cell k to the side 1 Processed with information and removed. Thus, base station i is able to obtain additional equations related only to terminal 1 of cell i.

2 reconstructed signals are transmitted to the base station in each time slot of phase G + 1, and the user terminals transmit 2G * (3G-2) * (G-1) -1) < / RTI > time slots. Therefore, two pieces of side information in two base stations of all base stations are processed together with the reconstruction signal for each time slot. As the side information and the reconfiguration signal are processed together, each base station acquires additional equations related only to terminals located in its own cell.

As a result, the side information held by each of the G total base stations is all processed in the phase G + 1, and the G total base stations transmit (2G-1) + 2 * (2G-2) Lt; / RTI > and decodes all data symbols.

In conclusion, through Phase 1 through Phase G + 1,

Lt; / RTI > time slots. The number of data symbols decoded in the entire phase is

Dog. Therefore, the DoF obtained through the above-described series of processes becomes (6G-5) / {2G-1 + (4G-4) (5G-2) / (8G-4)}.

In the above, the G-cell 3-user case has been described and extended to the general case of K-user. A total of G + 1 phases are also performed for the K-user case. Phase 1 is transmitted only by the terminals of cell 1, and similarly in phase G, transmission by only terminals of cell G is performed. The difference from the 3-user case is that each phase in Phase 1 to Phase G is composed of G-1 subphases. That is, Phase 1 is composed of Phase 1-1, Phase 1-2, ..., Phase 1- (K-1).

Subphase 1 of phase 1 is transmitted to terminals of cell 1 for data symbols to be transmitted to base station 1, that is, a preference signal. In the sub-phase 1, the base stations other than the base station of the cell 1 overhear the signal transmitted by the terminals of the cell 1 to receive the interference signal. When the sub-phase 1 ends, base stations other than the base station 1 null the symbols of one terminal and store the side information composed only of symbols of K-1 terminals.

In sub-phase 2, symbols for using the side information generated in sub-phase 1 are transmitted. In sub-phase 2, components related to only one terminal are further nulled in the side information generated in sub-phase 1, and side information for K-2 terminals is stored. Sub-phase 3 then stores side information for the K-3 terminals through an additional nulling process. In this manner, the components for one terminal are sequentially removed for each subphase, and in the last subphase K-1, components for one terminal are nullified from side information having only components for two terminals.

When phase 1 composed of K-1 subphases ends in this manner, phase 2, phase 3, ..., phase G is performed. Phase 2 to Phase G are performed similarly to Phase 1, and data transmission is performed by the terminals belonging to cells 2 to G, respectively.

Finally, in the phase G + 1, as described in the G-cell 3-user case, in order to use the side information for only one terminal generated from the phase 1 to the phase G, the two terminals 1 transmit an additional reconfiguration signal . As the UEs 1 of two cells transmit a reconfiguration signal for each time slot, two additional equations are generated in two base stations. Each base station acquires a number of equations that can finally decode all the data symbols through phase G + 1 and decodes all data symbols.

In an FDD system in which the channel condition changes rapidly, the channel information received through the feedback may be outdated (i.e., outdated) information completely independent of the current channel. (6G-5) / {2G-1 + (4G-4) (5G-2) / (8G-4) using the outdated channel information, even in this extreme case, } Can be achieved. This value is greater than 1, which is the DoF when the transmitter does not have any channel information. Also, as the number of G cells increases, the DoF gain increases and the communication capacity of the entire communication system increases.

3 is a diagram illustrating a method for a terminal to communicate using outdated channel state information in accordance with an embodiment of the present invention. 3, a description will be made of a series of processes in which the terminal 1, terminal 2, and terminal 3 located in a specific cell (cell 1) operate in the embodiment described with reference to FIG.

As described above, since the terminals 1, 2, and 3 in the cell operate in different ways within the same time interval, the operation process of the terminals is separately shown and described. 3 shows the operation flow of the terminal 1, the flow chart shown in the middle of FIG. 3 shows the operation flow of the terminal 2, and the flow chart shown on the right shows the operation flow of the terminal 3, respectively.

First, when the first time interval (phase 1) starts, only the terminals located in the cell 1 transmit data in the first time interval. The terminals located in the remaining cells do not transmit data. The terminal 1 of the cell 1 transmits 2G-1 data symbols to the base station 1 during the first 2G-1 time slots of the 1-1 time period (i.e., phase 1-1) (S312). At the same time, during the first 2G-1 time slots, the terminal 2 and the terminal 3 transmit 2G-2 data symbols to the base stations 2 and 3, respectively, and the sum of the data symbols transmitted in the last 1 time slot is transmitted to the base stations 2 and 3 (S314, S316).

Although not explicitly shown, each of the terminals receives a feedback signal from the base station 1 for data symbols transmitted during 2G-1 time slots. The feedback signal may include channel coefficient information for each data symbol transmitted by the UEs.

Subsequently, the UE repeats the process of 2G-1 timeslots in total 2G-1 times (S320). That is, the terminals 1, 2, and 3 perform the processes of S312, S314, and S316, respectively, 2G-2 times,

RTI ID = 0.0 > time slots. ≪ / RTI > When all of the above processes are performed, the 1-1 time period (sub-phase 1 of phase 1) ends.

In the first-second time period (sub-phase 2 of phase 1), as described above with reference to FIG. 2, the two terminals located in the cell transmit data. First, the terminal 1 transmits a linear combination of 2G-1 data symbols to the base station 1 during the first G time slots of the first-second time interval (S332). At the same time, the terminal 3 transmits a linear combination of G-1 data symbols to the base station 1 during the same G timeslots (S336). At this time, the terminal 2 of the cell 1 stops the data transmission and does not perform any operation (S334).

Subsequently, during the next G time slots of the first-second time period, the terminal 1 similarly transmits a linear combination of 2G-1 data symbols to the base station 1 (S342). At this time, the terminal 2 transmits a linear combination of G-1 data symbols to the base station 1 (S344), and the terminal 3 stops transmitting data during the previous G time slots (S346).

In this way, a series of processes during the 2G time slots is repeated G-1 times (S350). That is, the terminal 1 to the terminal 3 additionally perform the processes of S332 to S346 G-2 times,

1 < / RTI > On the other hand, the linear combination of the data symbols transmitted by the UEs in the first-second time period may be a reconstructed signal generated based on the feedback signal received from the base station. That is, as the UE receives the feedback signal, the UEs can know the channel coefficient information of the data symbols transmitted by the UE, and can reconstruct the signals transmitted by the UEs based on the channel coefficient information and transmit the reconstructed signals to the base station.

The first time period (i.e., phase 1) is terminated as the first-time period and the first-second time period end. Then, the second time period to the Gth time period are performed. In each time period, the processes described above with reference to FIG. 3 are similarly performed symmetrically (S362, S364, and S366). That is, the UEs located in the cell 2 transmit data in the second time interval and the UEs located in the cell G transmit the data in the Gth time interval.

If all the processes from the first time period to the G time period are performed, the last G + 1 time period is performed. The (G + 1) th time period

And a reconfiguration signal is transmitted to the base stations from two terminals in each time slot (S370). At this time, the terminals 1 of each cell transmit data in the G + 1 time interval. For example, the terminal 1 of the cell 1 and the terminal 1 of the cell 2 transmit data in one time slot. As another example, the terminal 1 of the cell 2 and the terminal 1 of the cell 3 or the terminal 1 of the cell G-1 and the terminal 1 of the cell G respectively transmit a reconfiguration signal to the base station.

The UEs other than the UEs 1 that transmit data in the (G + 1) th time interval do not transmit data, and no data is transmitted in the cells other than the cell to which the UEs 1 transmitting the data belong. Since two reconfiguration signals are transmitted to the base stations for each time slot,

Data symbols are transmitted to the base station.

4 is a diagram illustrating a method by which a base station communicates using outdated channel state information in accordance with an embodiment of the present invention. In FIG. 3, a series of processes according to the exemplary embodiment is described in the context of a terminal. On the other hand, in FIG. 4, the description will be made in the context of a base station, and will be described in the context of the base station 1 of the cell 1 in which the terminal 1, the terminal 2, and the terminal 3 are located.

First, the base station receives data symbols from the terminals of cell 1 during a 1-1 time interval. In the first 2G-1 time slot of the 1-1 time slot, the base station receives the data symbols every time slot from the terminal 1 of the cell 1 (S412). At the same time, the base station receives data symbols from each of the 2G-2 time slots from the terminal 2 and the terminal 3 of the cell 1 every time slot, and receives the sum of 2G-2 data symbols in the last time slot (S414). That is, in the first 2G-1 time slot of the 1-1 time slot, the base station operates to correspond to the operations of the terminals described in S312, S314, and S316 of FIG.

Subsequently, the base station transmits a feedback signal for the signals received in S412 and S414 to each of the terminals (S420). This feedback signal may include information of the channel coefficients for the received data symbols.

After transmitting the feedback signal, the base station generates and stores side information through a nulling process on the signals received in S412 and S414 (S425). The side information generated in S425 is information composed only of components related to the two terminals. This side information is generated by performing a nulling process on the components of the terminal 2 or the terminal 3 in the data symbols received from the three terminals in S412 and S414. For example, the side information in the case where nulling is performed for the terminal 2 is composed only of the components for the terminal 1 and the terminal 3, and the side information in the case where nulling is performed for the terminal 3 is the component for the terminal 1 and the terminal 2 .

Side information is stored, the base station repeatedly performs the processes of S412 to S425 in total 2G-1 times. That is, by performing the process performed during the time slot of 2G-1 additionally 2G-2 times,

And a 1-1 time section composed of time slots is performed.

Subsequently, in the first-second time interval, the base station receives signals from the two terminals in the cell during the first G time slots. First, the base station receives a linear combination of 2G-1 data symbols from the terminal 1 every time slot (S432), and the base station receives a linear combination of G-1 data symbols from the terminal 3 every time slot S434). As described above, the terminal 2 does not transmit any data during the G time slot.

The base station can separately generate the side information for the terminal 1 and the side information for the terminal 3 using the received linear combination, and stores the two side information, respectively (S440).

Similarly, during the next G timeslot, the base station receives a linear combination of 2G-1 data symbols from terminal 1 every time slot (S442), and transmits G-1 data from terminal 2 while terminal 3 is not transmitting data A linear combination of symbols is received for each time slot (S444).

Subsequently, the base station separately generates and stores the side information for the terminal 1 and the terminal 2 (S450). The base station performs the operation during this 2G time slot more than G-2 times,

The first time interval consisting of time slots is performed, and thus all the first time intervals are ended (S460).

Subsequently, a process similar to the first time period is performed symmetrically in the second time period to the Gth time period (S470). That is, the BSs receive data from the UEs belonging to the cell 2 to the cell G, and store the side information through the nulling process.

When all the processes up to the Gth time interval are completed, the base station receives a reconfiguration signal from the two terminals 1 in the (G + 1) -th time interval (S480). The (G + 1) th time period

Slots, and two terminals 1 located in different cells in each time slot transmit a reconfiguration signal.

The base station 1 receives the reconfiguration signal transmitted by the terminal 1 of the cell 1 and the reconfiguration signal transmitted by the terminal 1 of the other cell as the preference signal and the interference signal, respectively. The base station 1 can extract a component related to only one terminal from the side information stored therein using the reconstruction signal received in the (G + 1) -th time interval. Since two UEs 1 transmit a reconfiguration signal for each time slot, two related components are generated for only one UE in the entire BS.

When the reconfiguration signals are received through all time slots of the (G + 1) th time slot, the base stations have an equation sufficient to decode the received data symbols and decode the received signals accordingly (S490).

As described above, the operation of each terminal and the base station has been described by taking the network environment of the G-cell 3-user as an example. The procedure of this process can be extended to the network environment of the G-cell K- have. In the case of a G-cell K-user, each phase is composed of K-1 subphases, and the components related to one terminal are sequentially nulled in each subphase.

5 is a diagram showing a configuration of a terminal and a base station according to an embodiment of the present invention.

5, the terminal 100 and the base station 200 may include radio frequency (RF) units 110 and 210, processors 120 and 220, and memories 130 and 230, respectively. Although FIG. 5 shows only a 1: 1 communication environment between the terminal 100 and the base station 200, a communication environment can be established between a plurality of terminals and a plurality of base stations. In addition, the base station 200 shown in FIG. 5 can be applied to both the macro cell base station and the small cell base station.

Each of the RF units 110 and 210 may include transmitters 112 and 212 and receive units 114 and 214, respectively. The transmitter 112 and the receiver 114 of the terminal 100 are configured to transmit and receive signals to and from the base station 200 and other terminals and the processor 120 is operatively connected to the transmitter 112 and the receiver 114, And controls transmission and reception of signals between the transmitting unit 112 and the receiving unit 114 with other devices. In addition, the processor 120 performs various processes on a signal to be transmitted, and then transmits the processed signal to the transmitting unit 112, and performs processing on the signal received by the receiving unit 114.

The processor 120 may store information contained in the exchanged message in the memory 130 if necessary. With this structure, the terminal 100 can perform the methods of various embodiments of the present invention described above.

The transmitting unit 212 and the receiving unit 214 of the base station 200 are configured to transmit and receive signals with other base stations and terminals and the processor 220 is functionally connected to the transmitting unit 212 and the receiving unit 214, The control unit 212 and the receiving unit 214 may control the process of transmitting and receiving signals with other devices. In addition, the processor 220 may perform various processes on a signal to be transmitted, transmit the signal to the transmitter 212, and process the signal received by the receiver 214. If desired, the processor 220 may store the information contained in the exchanged message in the memory 230. Having such a structure, the base station 200 can perform the methods of various embodiments described above.

The processors 120 and 220 of the terminal 100 and the base station 200 respectively instruct (for example, control, adjust, manage, etc.) the operation of the terminal 100 and the base station 200. Each of the processors 120, 220 may be coupled with memories 130, 230 that store program codes and data. The memories 130 and 230 are coupled to the processors 120 and 220 to store operating systems, applications, and general files.

The processors 120 and 220 of the present invention may also be referred to as a controller, a microcontroller, a microprocessor, a microcomputer, or the like. Meanwhile, the processors 120 and 220 may be implemented by hardware or firmware, software, or a combination thereof. (DSP), digital signal processing devices (DSPDs), programmable logic devices (PLDs), and the like may be used to implement embodiments of the present invention using hardware, , Field programmable gate arrays (FPGAs), and the like may be provided in the processors 120 and 220.

On the other hand, the above-described method can be implemented in a general-purpose digital computer that can be created as a program that can be executed in a computer and operates the program using a computer-readable medium. Further, the structure of the data used in the above-described method can be recorded on a computer-readable medium through various means. Program storage devices that may be used to describe a storage device including executable computer code for carrying out the various methods of the present invention should not be understood to include transient objects such as carrier waves or signals do. The computer readable medium includes a storage medium such as a magnetic storage medium (e.g., ROM, floppy disk, hard disk, etc.), optical reading medium (e.g., CD ROM, DVD, etc.).

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed methods should be considered in an illustrative rather than a restrictive sense. It is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims (10)

A method for a first terminal located in a first cell to communicate using outdated channel state information in a network environment composed of G cells (G is an integer of 3 or more) where three terminals are located,

1 < / RTI > time period constituting the first time period together with the 1-2 time period,

Transmitting different data symbols for each time slot to the first base station;
Receiving a feedback signal including channel information for the transmitted data symbols;
Transmitting a linear combination of 2G-1 data symbols to the first base station every time slot during the first-second time period, which is composed of 2G * (G-1) time slots;
Stopping the transmission of the data for the second time period to the Gth time period; And
And transmitting to the first base station a reconfiguration signal generated based on the feedback signal during a (G + 1) -th time period comprising G * (3G-2) * (G- Communication method. The method according to claim 1,
Wherein the step of transmitting the reconfiguration signal comprises transmitting the reconfiguration signal during 2 * (3G-2) * (G-1) time slots during the (G + 1) th time interval. 3. The method of claim 2,
Wherein the step of transmitting the reconfiguration signal comprises the steps of: transmitting a reconfiguration signal to a first terminal included in any one of the G-1 cells excluding the first cell in each of the 2 * (3G-2) * (G-1) And transmit the reconfiguration signal together. The method according to claim 1,
During the first time interval, the other terminals located in the first cell transmit 2G-2 different data symbols to the first base station during 2G-2 time slots, And transmitting the sum of -2 different data symbols to the first base station in a total of 2G-1 times. The method according to claim 1,
During the first-second time interval, the other terminals located in the first cell transmit a linear combination of G-1 data symbols during G time slots to the first base station for each time slot, And repeats the process of interrupting the transmission of data during the slot by repeating a total of G-1 times. A method for a first base station located in a first cell to communicate using outdated channel state information in a network environment composed of G cells (G is an integer of 3 or more) in which three terminals are located,

A first terminal located in the first cell and a second terminal located in the first cell for every time slot during a first time interval constituting a first time interval together with a first-

Receiving different data symbols;
2G-2 different data symbols are received from the second terminal and the third terminal located in the first cell during the 1 < st > -th time interval for 2G-2 time slots, 2G-repeating the process of receiving the sum of two different data symbols in total 2G-1 times;
Receiving a linear combination of 2G-1 data symbols from the first terminal for each time slot during the first-second time interval, which is composed of 2G * (G-1) time slots;
Receiving in each time slot a linear combination of G-1 data symbols from any one of the second terminal and the third terminal for every G time slots in the first-second time interval;
Receiving signals transmitted by terminals located in the second through Gth cells as interference signals during a second time period to a Gth time period;
(G + 1) -th time interval consisting of G * (3G-2) * (G-1) time slots, a terminal belonging to any one of the second cell to the G- Receiving a reconfiguration signal for each slot; And
And decoding the received data symbols during the first time interval based on the interference signal and the reconfiguration signal. The method according to claim 6,
The communication method may further include receiving a feedback signal including channel information on signals received during the 1-1 time period,
Wherein the reconfiguration signal is generated based on the feedback signal. The method according to claim 6,
The communication method includes:
A nulling process is performed on the signals received in the first-time period using the signals received in the first-time period, the data generated through the nulling process is referred to as first side information side information. < Desc / Clms Page number 13 > 9. The method of claim 8,
The communication method includes:
Further comprising generating a second side information associated with only one terminal by performing a nulling process on the first side information using the reconfiguration signal received in the G + 1 time interval . The method according to claim 6,
Wherein receiving the reconfiguration signal comprises receiving a reconfiguration signal from the first terminal during 2 * (3G-2) * (G-1) time slots in the (G + 1) th time interval.

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