WO2015096027A1

WO2015096027A1 - Method and apparatus for transmission mode selection

Info

Publication number: WO2015096027A1
Application number: PCT/CN2013/090315
Authority: WO
Inventors: Ming Lei; Dalin Zhu; Mingxin ZHOU; Lingyang Song
Original assignee: Nec Corporation
Priority date: 2013-12-24
Filing date: 2013-12-24
Publication date: 2015-07-02

Abstract

A method and an apparatus for a first node in a wireless communication system are provided. The first node is in a bi-direction communication with a second node. Both the first node and the second node are equipped with at least two antennas. Each antenna is configurable for transmission or reception. The method comprises: obtaining channel state information about communication channels between the first node and the second node and self interference channel state information of each of the first node and the second node; selecting a transmission mode which optimizes communication performance of the bi-direction communication, based on the obtained information, from a group consisted of at least a time division duplex (TDD) multiple-input multiple-output (MIMO) mode and a plurality of full duplex (FD) modes with different antenna configurations; and configuring antennas according to the selected transmission mode.

Description

METHOD AND APPARATUS FOR TRANSMISSION MODE SELECTION

TECHNICAL FIELD [0001] Embodiments herein generally relate to wireless communications, and more particularly to a method, an apparatus, a node, and a computer readable storage medium for selecting a transmission mode for bi-direction communications.

BACKGROUND

[0002] This section introduces aspects that may facilitate a better understanding of the disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.

[0003] In Multiple-Input Multiple-Output (MIMO) wireless communication systems, both of the transmitting node and the receiving node use a plurality of antennas or antenna arrays to provide a rich diversity and a large communication capacity. Spatial Multiplexing (SM) is an important technique to improve the spectrum efficiency for MIMO systems. In spatial multiplexing, a high rate signal is split into multiple lower rate streams and each stream is transmitted from a different transmit antenna in the same frequency channel. If these signals arrive at the receiver antenna array with sufficiently different spatial signatures and the receiver has accurate Channel State Information (CSI), it can separate these streams into (almost) parallel channels. Spatial multiplexing is a very powerful technique for increasing channel capacity at higher signal-to-noise ratios (SNR). The performance is enhanced with the number of the antennas.

[0004] However, in a practical MIMO channel, spatial correlation exists between the signals transmitted by or received at different antennas, when the antennas are not sufficiently separated due to the small size of the communication device, or it lacks scattering. Large spatial correlation will influence spatial multiplexing, thereby degrading the performance of the MIMO systems.

[0005] Conventional wireless communication systems adopt Time Division Duplex

(TDD) or Frequency Division Duplex (FDD) to implement bi-direction communications. TDD or FDD can also be used in MIMO systems. TDD and FDD require dividing time or frequency resources into orthogonal portions for corresponding transmission and reception.

[0006] By means of the plurality of antennas or antenna arrays equipped at the transmitting node and the receiving node, Full duplex (FD), which allows a communication node to perform transmission and reception at the same frequency band and in the same time interval, is possible in MIMO systems. FD has the potential to double the spectrum efficiency compared with TDD and FDD.

[0007] Due to the close proximity of a communication node's transmit antenna to its receive antenna, the self interference is large and thus unavoidable. However, many self interference cancellation methods have been proposed to make it feasible by exploiting various combinations of antenna cancellation, radio frequency (RF) cancellation, and baseband signal cancellation. In a practical FD system, the residual self interference still exists due to imperfect interference cancellation capability, and thus limits the performance of FD.

SUMMARY

[0008] To address one or more of the above concerns, it would be desirable in the art to provide an optimized transmission mode for bi-direction communications in MIMO systems.

[0009] In a first aspect, a method for a first node in a wireless communication system is provided. The first node is in a bi-direction communication with a second node. Both the first node and the second node are equipped with at least two antennas. Each antenna is configurable for transmission or reception. The method comprises: obtaining channel state information about communication channels between the first node and the second node and self interference channel state information of each of the first node and the second node; selecting a transmission mode which optimizes communication performance of the bi-direction communication, based on the obtained information, from a group consisted of at least a time division duplex (TDD) multiple-input multiple-output (MIMO) mode and a plurality of full duplex (FD) modes with different antenna configurations; and configuring antennas according to the selected transmission mode.

[0010] In some embodiments, the selecting a transmission mode which optimizes communication performance of the bi-direction communication may comprise selecting a transmission mode which maximizes a sum rate of the bi-direction communication.

[0011] In some other embodiments, the selecting a transmission mode which optimizes communication performance of the bi-direction communication may comprise selecting a transmission mode which minimizes a parameter relating to a symbol error rate (SER) of the bi-direction communication, such as the instantaneous sum SER.

[0012] In some further embodiments, the obtaining may comprise: estimating the channel state information by measuring the communication channels between the first node and the second node; estimating the self interference channel state information by measuring the self interference channel of the first node; and receiving, from the second node, the self interference channel state information of the second node.

[0013] In some further embodiments, the configuring antennas according to the selected transmission mode may comprise: configuring the antennas of the first node; and informing the second node of the selected transmission mode for configuring the antennas of the second node.

[0014] In some further embodiments, the method may further comprise: triggering the obtaining, the selecting, and the configuring, in response that an elapsed time since the last obtaining of the channel state information and the self interference channel state information is above a threshold. The threshold is determined as the minimum coherent time among a coherent time of the communication channels between the first node and the second node and a coherent time of respective self interference channel of each of the first node and the second node.

[0015] In some embodiments, the first node is an access point or a user equipment.

[0016] In some embodiments, the self interference channel state information is residual self interference channel state information after self interference cancellation.

[0017] In a second aspect, an apparatus for a first node in a wireless communication system is provided to implement various embodiments of the method of the first aspect of the disclosure herein. The first node is in a bi-direction communication with a second node. Both the first node and the second node are equipped with at least two antennas. Each antenna is configurable for transmission or reception. The apparatus comprises: an obtaining unit, configured to obtain channel state information about communication channels between the first node and the second node and self interference channel state information of each of the first node and the second node; a selecting unit, configured to select a transmission mode which optimizes communication performance of the bi-direction communication, based on the obtained information, from a group consisted of at least a time division duplex (TDD) multiple -input multiple-output (MIMO) mode and a plurality of full duplex (FD) modes with different antenna configurations; and a configuring unit, configured to configure antennas according to the selected transmission mode.

[0018] In a third aspect, an apparatus for a first node in a wireless communication system is provided to implement various embodiments of the method of the first aspect of the disclosure herein. The first node is in a bi-direction communication with a second node. Both the first node and the second node are equipped with at least two antennas. Each antenna is configurable for transmission or reception. The apparatus comprises at least one processor and at least one memory including computer program code. The memory and the computer program code are configured to cause the apparatus to perform embodiments of the method of the first aspect of the disclosure herein.

[0019] In a fourth aspect, a non-transitory computer-readable storage media having computer program code stored thereon is provided. The computer program code is configured to, when executed, cause an apparatus to perform actions in the method according to the first aspect as above described.

[0020] In a fifth aspect, a computer program product is provided, which, comprises at least one computer readable storage medium having a computer readable program code portion stored thereon. The computer readable program code portion comprises program code instructions for performing embodiments of the method of the first aspect of the disclosure herein.

[0021] With particular embodiments of the techniques described in this specification, a transmission mode for bi-direction communications between two nodes can be selected adaptively, which can optimize communication performance of the bi-direction communications .

[0022] Other features and advantages of the embodiments of the present invention will also be understood from the following description of specific embodiments when read in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other aspects, features, and benefits of various embodiments herein will become more fully apparent, by way of example, from the following detailed description and the accompanying drawings, in which:

[0024] FIG. 1 illustrates an exemplary scenario where embodiments disclosed herein can be implemented;

[0025] FIG. 2 illustrates a signal flow of a method for selecting a transmission mode according to embodiments herein;

[0026] FIG. 3 illustrates an exemplary flowchart of a method for selecting a transmission mode according to embodiments herein; [0027] FIG. 4 illustrates possible transmission modes according to one embodiment herein;

[0028] FIG. 5 illustrates a schematic block diagram of an apparatus that may be configured to practice the exemplary embodiments herein; and

[0029] FIG. 6 illustrates a simplified block diagram of a node that is suitable for use in practicing exemplary embodiments herein.

[0030] Like reference numbers and designations in the various drawings indicate like elements. DETAILED DESCRIPTION

[0031] Hereinafter, the principle and spirit of the present disclosure will be described with reference to the illustrative embodiments. It should be understood, all these embodiments are given merely for the skilled in the art to better understand and further practice the present disclosure, but not for limiting the scope of the present disclosure. For example, features illustrated or described as part of one embodiment may be used with another embodiment to yield still a further embodiment. In the interest of clarity, not all features of an actual implementation are described in this specification.

[0032] In the following description, a communication node is an entity in wireless communications and can be any of an access point (AP) and a terminal. The terminal can be a user equipment (UE), a mobile station (MS), a cellular phone, a smart phone, a computer, or a multimedia system equipped with communication function. Please be noted that, the terms "user terminal" and "user equipment" can be used interchangeable hereinafter.

[0033] While embodiments are described below in the context of a LTE type cellular network for illustrative purposes, those skilled in the art will recognize that the embodiments disclosed herein can also be applied to various other types of wireless communication networks.

[0034] With reference to Fig. 1, an example of wireless communication network environment 100 where embodiments disclosed herein may be implemented is shown. As illustrated in Fig. 1, in the wireless communication network environment 100, there may be a first node 101 and a second node 102 communicating with each other in a bi-direction communication. Each of the first node 101 and the second node 102 is equipped with at least two antennas, and each antenna is configurable for transmission or reception. Various transmission modes may be employed for the bi-direction communication, such as Spatial Multiplexing TDD mode, and Full Duplex (FD) mode.

[0035] In some embodiments, in the bi-direction communication system, the first node may be for example an access point (AP) and the second node may be a user terminal or a user equipment. In some other embodiments, both the first node and the second node may be user terminals.

[0036] Inventors note that, when the two nodes in a bi-direction communication are far away from each other, the power of the signal of interest is relatively small. Moreover, when the capability of self interference cancellation is not good in some frequency band, the self interference is large at that frequency. In such cases, the performance (e.g., the sum rate) of the bi-direction communication in an FD mode can be greatly degraded by the low signal to interference ratio (SIR), due to large residual self interference or small signal of interest. In the other hand, when the antennas are not sufficiently separated due to the small size of the communication device, or it lacks scattering, for example in an indoor environment, the performance of the bi-direction communication in a MIMO mode, e.g., a TDD MIMO mode, will be greatly degraded.

[0037] In view of the above, according to embodiments herein, by using such multiple antenna structure, a mechanism for selecting a transmission mode can be employed to combat the limitation of low SIR or large spatial correlation, thereby improving the communication performance of the bi-direction communications, such as increasing the sum rate or decreasing the instantaneous sum symbol error rate. More particularly, when the SIR is small, a TDD MIMO mode can be selected to accomplish the bi-direction communication between the two nodes, while a FD mode is a better selection with high spatial correlation which limits the performance, e.g., the sum rate of spatial multiplexing.

[0038] FIG. 2 illustrates a signal flow of a method for selecting a transmission mode according to embodiments herein.

[0039] As shown in FIG. 2, the bi-direction communication system may comprise two nodes, the first node 101 and the second node 102. In some embodiments, the first node 101 may be an access point (AP) and the second node 102 may be a user equipment. In such case, preferably, the first node 101 is a master node for hosting the selection of a transmission mode. In some other embodiments, both the first node and the second node may be user equipments, and either of them may be the master node for hosting the selection of a transmission mode. In the example shown in FIG. 2, without loss of generality, the first node 101 plays the role of a master and the second node 102 plays the role of a slave.

[0040] The selection of a transmission mode may be performed at various stages, such as at the initiation of the bi-direction communication, or during the procedure of the bi-direction communication. Moreover, the selection of a transmission mode may be triggered by a variety of reasons.

[0041] In a preferred embodiment, the selection may be performed periodically with a period of a minimum coherent time Tmin. The minimum coherent time Tmin can be determined as the minimum value among a coherent time of the communication channels between the first node 101 and the second node 102 and a coherent time of respective self interference channel of each of the first node 101 and the second node 102.

[0042] In some other embodiments, the selection may be performed in response to a certain event occurring. For example, such an event may be the sum rate dropping below a threshold, or the sum symbol error rate (SER) increasing above a threshold, or the outage probability increasing above a threshold.

[0043] Upon determining that the selection of a transmission mode should be performed, at block SI 10, the first node 101 measures the communication channels e.g. in a TDD MIMO mode, between the first node 101 and the second node 102, in order to estimate the channel state information of the communication channels.

[0044] In addition, the first node 101 measures the self interference channel in a full duplex (FD) mode at the first node 101, in order to estimate the self interference channel information of the first node 101. In embodiments disclosed, in an FD mode, each antenna can be selectively configured for transmission or reception. Thus, there may be various patterns of antenna configuration in an FD mode. Alternatively, such an FD mode can be referred to as an FD mode with antenna selection, or a plurality of FD modes with different antenna configurations. Self interference channels in various patterns of the FD mode will be measured. In some embodiments, a self interference cancellation method may be employed to cancel the self interference. In such cases, the measured self interference channel is the residual self interference channel after self interference cancellation.

[0045] Meanwhile, at block S210, the second node 102 measures the self interference channel in a full duplex (FD) mode at the second node 102, in order to estimate the self interference channel information of the second node 102. Similarly, self interference channels in various patterns of the FD mode will be measured, and in some embodiments, the measured self interference channel is the residual self interference channel after self interference cancellation. The measurement at the second node 102 may be performed periodically or upon request. As mentioned previously, the selection of a transmission mode may be performed periodically with a period of a minimum coherent time Tmin. In such an embodiment, the second node 102 can be configured to measure and estimate the self interference channel information of the second node 102 periodically based on the minimum coherent time Tmin. In some other embodiments, the second node 102 can perform the measurement and estimation upon receiving a request from the first node 101.

[0046] The measurement of a channel is well known in the art, for example, through the use of a training sequence or a pilot signal. Also, the estimation of channel state information is well known in the art, such as through maximum likelihood (ML), least square (LS) or other criteria.

[0047] Then, as indicated by the signaling S211, the second node 102 sends the self interference channel information to the first node 101.

[0048] At block SI 20, having obtained the channel state information about the communication channels between the first node 101 and the second node 102 and self interference channel state information of each of the first node 101 and the second node 102, the first node 101 can select a transmission mode based on the obtained information. A transmission mode which optimizes communication performance of the bi-direction communication can be selected from a group consisted of at least a TDD MIMO mode and a plurality of FD modes with different antenna configurations.

[0049] In some embodiments, a transmission mode which maximizes a sum rate of the bi-direction communication may be selected. In some other embodiments, a transmission mode which minimizes a parameter relating to a symbol error rate (SER) of the bi-direction communication, such as an instantaneous sum SER, may be selected. The detailed description will be described later.

[0050] Having selected a transmission mode for the bi-direction communication, at block SI 30, the first node 101 could configure antennas for communications according to the selected transmission mode. More particularly, the first node 101 could configure its own antennas according to the selected transmission mode. Further, the first node 101 could inform the second node 102 of the selected transmission mode, as indicated by the signaling S 131 , such that the second node 102 could configure its antennas according to the informed selected transmission mode at block S220.

[0051] Finally, at block S140, the first node 101 and the second node 102 could perform the bi-direction communication with the selected transmission mode.

[0052] In some embodiments, in response that an elapsed time t since the last obtaining of the channel state information and the self interference channel state information is above a threshold, e.g., the minimum coherent time Tmin, the procedure for selecting a transmission mode can be performed again. In other words, those steps shown in FIG. 2 are triggered again. In this way, the system can always select the transmission mode with better performance.

[0053] FIG. 3 illustrates an exemplary flowchart of a method for selecting a transmission mode at a master node, e.g., the first node 101 shown in FIG. 2, according to embodiments herein.

[0054] In some embodiments, optionally, at block S310, a minimum coherent time

Tmin can be estimated. The minimum coherent time Tmin can be determined as the minimum value among a coherent time of the communication channels between the first node 101 and the second node 102 and a coherent time of respective self interference channel of each of the first node 101 and the second node 102. For example, a coherent time of a channel can be defined as a maximum time period during which the variety of the channel is within a predefined range. In other words, if the variety of the channel changes a lot, e.g., exceeding a threshold, then there is less correlation between the previous channel and the current channel, and thus the channel should be measured again. Such embodiments are more suitable for a slow fading channel.

[0055] At block S320, the first node 101 obtains channel state information about communication channels between the first node 101 and the second node 102 and self interference channel state information of each node. More particularly, the channel state information about communication channels between the first node and the second node can be estimated by measuring the communication channels between the first node and the second node in a TDD MIMO mode. The self interference channel state information of the first node can be estimated by measuring the self interference channel of the first node in a plurality of FD mode with different antenna configurations. The self interference channel state information of the second node can be received from the second node.

[0056] At block S330, the first node 101 can select a transmission mode which optimizes communication performance of the bi-direction communication, based on the obtained channel state information. The transmission mode can be selected from a group consisted of at least a TDD MIMO mode and a plurality of FD modes with different antenna configurations. The TDD MIMO can be a SM TDD MIMO mode or some other TDD MIMO mode, such as Space Time Block Code (STBC). In some embodiments, a transmission mode which maximizes a sum rate of the bi-direction communication may be selected. In some other embodiments, a transmission mode which minimizes a parameter relating to a symbol error rate (SER) of the bi-direction communication, such as an instantaneous sum SER, may be selected.

[0057] At block S340, having selected the transmission mode, the first node 101 can configure antennas and use the selected transmission mode for bi-direction communication with the second node 102. The first node 101 could configure its own antennas for communications according to the selected transmission mode. Further, the first node 101 could inform the second node 102 of the selected transmission mode, such that the second node 102 could configure its antennas according to the informed selected transmission mode. Then, the first node 101 and the second node 102 could perform the bi-direction communication with the selected transmission mode.

[0058] In some further embodiments, at optional step S350, the first node 101 could determine whether an elapsed time t since the last obtaining of the channel state information and the self interference channel information is above a threshold, e.g., the minimum coherent time Tmin. If it is determined that the elapsed time t is larger than Tmin, then the method can go back to block S320, thereby the obtaining, the selecting and the configuration can be triggered again. In some embodiments, a timer or a counter can be used to monitor the elapsed time.

[0059] Descriptions above thus have described method for selecting a transmission mode for a bi-direction communication according to embodiments disclosed herein. In the following, the criteria for selecting a transmission mode which optimizes communication performance of the bi-direction will be detailed with reference to some examples.

[0060] FIG. 4 illustrates possible transmission modes according to one embodiment herein. In the example shown in FIG. 4, each of the first node and the second node is configured with two antennas for the purpose of simplicity. The skilled in the art should appreciate that, the nodes could be configured with more than two antennas, and the principle of selecting a transmission mode can be applied accordingly.

[0061] Moreover, in the shown example, the transmission mode is selected from a group consisted of a TDD SM mode and a plurality of FD modes with different antenna configurations. The skilled in the art should appreciate that, some other MIMO modes such as STBC can be included in the group of transmission modes.

[0062] As shown in FGI. 4, the left part illustrates a TDD SM mode. The top left diagram shows an antenna configuration in a first time slot in the TDD SM mode, where the two antennas of the first node is configured for transmission, and the two antennas of the second node is configured for reception. The bottom left diagram shows an antenna configuration in a second time slot in the TDD SM mode, where the two antennas of the first node is configured for reception, and the two antennas of the second node is configured for transmission. In this way, bi-direction communication can be supported via time division multiplexing.

[0063] The middle and right parts of FIG. 4 illustrates four FD modes. In each FD mode, in each of the first node and the second node, one antenna is configured for transmission, and the other antenna is configured for reception. Thus, there are four combinations of antennas as shown in FIG. 4. In other words, each antenna's function is not fixed. In addition, in each FD mode, the self interference channels in each node are also depicted by dotted lines.

[0064] Generally speaking, the selection of a transmission mode is executed by comparing communication performance of the bi-direction communication under various transmission modes. The communication performance can be the instantaneous sum rate, the instantaneous sum SER, or the outage probability, etc.

[0065] In one embodiment, the selection may be based on the instantaneous sum rate, which can be expressed as:

P = argmax{¾ (1)

i=l,2,3,4,5

where arg max stands for the argument of the maximum, that is to say, the set of points of the given argument for which the given function attains its maximum value, and SR; represents the sum rate under various transmission mode.

For SM TDD mode,

_M ^ ,o e<{/ ₊ ™» } (2)

Where SRi and SRSM represent the sum rate in the SM TDD mode, H represents the channel matrix for the communication channel between the first node and the second node, H^H represents Hermitian Transpose of the channel matrix H, I is a unitary matrix, Ps is the transmission power of the node, and det(A) represents the determinant of a matrix A. In this example, we assume the transmission power in each node is equal to Ps.

For FD mode,

SR_j = SR_FD__AS __l = (3)

where j = 2,3,4,5

Where SR_j and SRFD-ASJ-I represent the sum rate in the (j-1 )-th pattern in the FD mode as shown in FIG. 4; η is the interference cancellation factor; σ_η ² is the noise power; H^ represents the channel from the first node to the second node in the (k)-th pattern of the FD mode; H_{SI l} represents the residual self interference channel of the first node; and Ps is the transmission power of the node. Also, in this example, we assume the transmission power in each node is equal to Ps.

[0066] In another embodiment, the selection may be based on the instantaneous sum SER, which can be expressed as: P = arg mm{SER_i (4)

i=l,2,3,4,5

where arg min stands for the argument of the minimum, that is to say, the set of points of the given argument for which the given function attains its minimum value, and SERi represents the sum SER under various transmission mode.

For SM TDD mode,

SER₁ = SER_SM = e(VH ) + e( bi) (5)

Where SER i and SERSM represent the sum SER in the SM TDD mode. The channel matrix for the communication channel between the first node and the second node can be represented by H. In the example shown in FIG. 4, H is a 2x2 matrix. The eigen value of H is given by ,λ₂ , which can be obtained by Singular Value Decomposition (SVD). Q( ) represents Q function,

1

Q(a) = ,— e ² dy , b is a constant determined by the modulation format. For example, b=2 for binary phase shift keying (BPSK).

For FD mode,

Where SER; and SER FD ^■ASJ-l represent the sum SER in the (j-l)-th pattern in the FD mode as shown in FIG. 4, j = 2,3,4,5 ; η is the interference cancellation factor; σ_η is the noise power; HS₂ represents the channel from the first node to the second node in the (k)-th pattern of the FD mode; H_{SI l} represents the residual self interference channel of the first node; and Ps is the transmission power of the node. Also, in this example, we assume the transmission power in each node is equal to Ps.

[0067] Although the above embodiments are described in the case of each node equipped with two antennas, the principle may be applied in the case of each node equipped with more than two antennas. In such cases, in order to reduce the amount of calculation, algorithms such as Greedy algorithm may be used to select the transmission mode, instead of traversing all the transmission modes as described in FIG. 4.

[0068] FIG. 5 illustrates a schematic block diagram of an apparatus that may be configured to practice the exemplary embodiments herein. The apparatus may be configured for a first node (such as an access node, or a user terminal) in a wireless communication system to implement various embodiments of the method disclosed herein. The first node is in a bi-direction communication with a second node. Both the first node and the second node are equipped with at least two antennas. Each antenna is configurable for transmission or reception.

[0069] As shown in FIG. 5, the apparatus 500 comprises: an obtaining unit 510, a selecting unit 520, and a configuring unit 530.

[0070] The obtaining unit 510 is configured to obtain channel state information about communication channels between the first node and the second node and self interference channel state information of each of the first node and the second node.

[0071] In some embodiments, the obtaining unit 510 may comprise: a first estimating unit 511, configured to estimate the channel state information by measuring the communication channels between the first node and the second node; a second estimating unit 512, configured to estimate the self interference channel state information by measuring the self interference channel of the first node; and a receiving unit 513, configured to receive, from the second node, the self interference channel state information of the second node.

[0072] The selecting unit 520 is configured to select a transmission mode which optimizes communication performance of the bi-direction communication, based on the obtained information, from a group consisted of at least a time division duplex (TDD) multiple -input multiple-output (MIMO) mode and a plurality of full duplex (FD) modes with different antenna configurations.

[0073] In some embodiments, the selecting unit 520 may be configured to select a transmission mode which optimizes communication performance of the bi-direction communication by selecting a transmission mode which maximizes a sum rate of the bi-direction communication. In some other embodiments, the selecting unit 520 may be configured to select a transmission mode which optimizes communication performance of the bi-direction communication by selecting a transmission mode which minimizes a parameter relating to a symbol error rate of the bi-direction communication, such as an instantaneous sum SER.

[0074] The configuring unit 530 is configured to configure antennas according to the selected transmission mode. The configuring unit 530 may be configured to configure antennas according to the selected transmission mode by: configuring the antennas of the first node; and informing the second node of the selected transmission mode for configuring the antennas of the second node.

[0075] The apparatus 500 may further comprise a trigger unit 540. The trigger unit 540 may be configured to trigger the obtaining unit 510, the selecting unit 520, and the configuring unit 530, in response that an elapsed time since the last obtaining by the obtaining unit 510 of the channel state information and the self interference channel state information is above a threshold. The threshold can be the minimum coherent time Tmin as described above, which is determined as the minimum coherent time among a coherent time of the communication channels between the first node and the second node and a coherent time of respective self interference channel of each of the first node and the second node.

[0076] It should be understood, the units 510-540 contained in the apparatus 500 are configured for practicing exemplary embodiments herein. Thus, the operations and features described above with respect to FIGs. 2-3 also apply to the apparatus 500 and the units/modules therein, and the detailed description thereof is omitted here

[0077] FIG. 6 illustrates a simplified block diagram of a node that is suitable for use in practicing exemplary embodiments herein. The node 600 may be a node at the network side, for example, an access node, for a node at the user side, for example, a user terminal.

[0078] As shown in FIG. 6, the node 600 includes a data processor (DP) 601, a memory (MEM) 602 coupled to the DP 601, a suitable RF transmitter TX and receiver RX 604 coupled to the DP 601, and a communication interface 605 coupled to the DP 601. The MEM 602 stores a program (PROG) 603. The TX/RX 604 is for bidirectional wireless communications. Note that the TX/RX 604 has at least two antennas to facilitate communication, though only one is illustrated in the figure. The communication interface 605 may represent any interface that is necessary for communication with other network elements. The entity 600 may be coupled via a data path to one or more external networks or systems, such as the internet, for example.

[0079] The PROG 603 is assumed to include program instructions that, when executed by the associated DP 601, enable the node 600 to operate in accordance with the exemplary embodiments of this disclosure, as discussed herein with the methods in FIGs. 2-3. For example, the PROG 603 and the DP 601 may embody the selecting unit 520 to perform the respective function. The TX RX 604 may embody the obtaining unit 610 to perform the function of obtaining channel state information.

[0080] The embodiments herein may be implemented by computer software executable by the DP 601 of the node 600, or by hardware, or by a combination of software and hardware.

[0081] The MEM 602 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. While only one MEM is shown in the node 600, there may be several physically distinct memory units in the node 600. The DP 601 may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non limiting examples. The node 600 may have multiple processors, such as for example an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

[0082] Exemplary embodiments herein have been described above with reference to block diagrams and flowchart illustrations of methods, apparatuses (i.e., systems). It will be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, respectively, can be implemented by various means including computer program instructions. These computer program instructions may be loaded onto a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions which execute on the computer or other programmable data processing apparatus create means for implementing the functions specified in the flowchart block or blocks.

[0083] The foregoing computer program instructions can be, for example, sub-routines and/or functions. A computer program product in one embodiment comprises at least one computer readable storage medium, on which the foregoing computer program instructions are stored. The computer readable storage medium can be, for example, an optical compact disk or an electronic memory device like a RAM (random access memory) or a ROM (read only memory).

[0084] While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any implementation or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular implementations. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

[0085] It should also be noted that the above described embodiments are given for describing rather than limiting the disclosure, and it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the disclosure as those skilled in the art readily understand. Such modifications and variations are considered to be within the scope of the disclosure and the appended claims. The protection scope of the disclosure is defined by the accompanying claims. In addition, any of the reference numerals in the claims should not be interpreted as a limitation to the claims. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The indefinite article "a" or "an" preceding an element or step does not exclude the presence of a plurality of such elements or steps.

Claims

WHAT IS CLAIMED IS:

1. A method for a first node in a wireless communication system, wherein said first node is in a bi-direction communication with a second node, both the first node and the second node are equipped with at least two antennas, and each antenna is configurable for transmission or reception, said method comprising:

obtaining channel state information about communication channels between the first node and the second node and self interference channel state information of each of the first node and the second node;

selecting a transmission mode which optimizes communication performance of the bi-direction communication, based on the obtained information, from a group consisted of at least a time division duplex (TDD) multiple-input multiple-output (MIMO) mode and a plurality of full duplex (FD) modes with different antenna configurations; and

configuring antennas according to the selected transmission mode.

2. The method of claim 1, wherein said selecting a transmission mode which optimizes communication performance of the bi-direction communication comprises selecting a transmission mode which maximizes a sum rate of the bi-direction communication.

3. The method of claim 1, wherein said selecting a transmission mode which optimizes communication performance of the bi-direction communication comprises selecting a transmission mode which minimizes a sum symbol error rate of the bi-direction communication.

4. The method of any of claims 1-3, wherein said obtaining comprises:

estimating the channel state information by measuring the communication channels between the first node and the second node;

estimating the self interference channel state information by measuring the self interference channel of the first node; and

receiving, from the second node, the self interference channel state information of the second node.

5. The method of any of claims 1-4, wherein said configuring antennas according to the selected transmission mode comprises:

configuring the antennas of the first node; and informing the second node of the selected transmission mode for configuring the antennas of the second node.

6. The method of any of claims 1-5, wherein said method further comprises:

triggering said obtaining, said selecting, and said configuring, in response that an elapsed time since the last obtaining of said channel state information and said self interference channel state information is above a threshold, wherein said threshold is determined as the minimum coherent time among a coherent time of the communication channels between the first node and the second node and a coherent time of respective self interference channel of each of the first node and the second node.

7. The method of any of claims 1-6, wherein said first node is an access point or a user equipment.

8. The method of any of claims 1-7, wherein said self interference channel state information is residual self interference channel state information after self interference cancellation.

9. An apparatus for a first node in a wireless communication system, wherein said first node is in a bi-direction communication with a second node, both the first node and the second node are equipped with at least two antennas, and each antenna is configurable for transmission or reception, said apparatus comprising:

an obtaining unit, configured to obtain channel state information about communication channels between the first node and the second node and self interference channel state information of each of the first node and the second node;

a selecting unit, configured to select a transmission mode which optimizes communication performance of the bi-direction communication, based on the obtained information, from a group consisted of at least a time division duplex (TDD) multiple-input multiple-output (MIMO) mode and a plurality of full duplex (FD) modes with different antenna configurations; and

a configuring unit, configured to configure antennas according to the selected transmission mode.

10. The apparatus of claim 9, wherein said selecting unit is configured to select a transmission mode which optimizes communication performance of the bi-direction communication by selecting a transmission mode which maximizes a sum rate of the bi-direction communication.

11. The apparatus of claim 9, wherein said selecting unit is configured to select a transmission mode which optimizes communication performance of the bi-direction communication by selecting a transmission mode which minimizes a sum symbol error rate of the bi-direction communication.

12. The apparatus of any of claims 9-11, wherein said obtaining unit comprises:

a first estimating unit, configured to estimate the channel state information by measuring the communication channels between the first node and the second node;

a second estimating unit, configured to estimate the self interference channel state information by measuring the self interference channel of the first node; and

a receiving unit, configured to receive, from the second node, the self interference channel state information of the second node.

13. The apparatus of any of claims 9-12, wherein said configuring unit is configured to configure antennas according to the selected transmission mode by:

configuring the antennas of the first node; and

informing the second node of the selected transmission mode for configuring the antennas of the second node.

14. The apparatus of any of claims 9-13, wherein said apparatus further comprises: a trigger unit, configured to trigger said obtaining unit, said selecting unit, and said configuring unit, in response that an elapsed time since the last obtaining by said obtaining unit of said channel state information and said self interference channel state information is above a threshold, wherein said threshold is determined as the minimum coherent time among a coherent time of the communication channels between the first node and the second node and a coherent time of respective self interference channel of each of the first node and the second node.

15. The apparatus of any of claims 9-14, wherein said first node is an access point or a user equipment.

16. The apparatus of any of claims 9-15, wherein said self interference channel state information is residual self interference channel state information after self interference cancellation.