COMMUNICATION NETWORKS

FIELD OF THE INVENTION

The present invention generally relates to direct device-to-device (D2D) communications integrated into a cellular network, for example LTE (long-term evolution)/LTE-A cellular network specified in 3GPP (3rd Generation Partnership Project). More specifically, the invention relates to an interference suppression mechanism in communication networks.

BACKGROUND

At present, there are mainly two kinds of separate network scenarios, cellular network and ad-hoc network. In a cellular network, a user equipment (UE) goes through a bases station (BS) for communication with another UE. However in an ad-hoc network, a UE communicates with another UE directly because of the direct traffic (or by relaying). In a cellular network mode, traffics usually go through a centralized controller such as an evolved Node B (eNB), even if a source and a destination are close to each other. The main benefit of such operation is the easy resource control and interference control, but an obvious drawback is the inefficient resource utilization, for example, double resources would be required for the cellular network mode compared to the direct transmission when two users are close each other.

So in future, in order to achieve the best system throughput, the launched radio network would probably be in a multiple networks scenario. A hybrid network is shown in Fig. 1 as an example. One UE (such as UE 101) can choose either a cellular mode 110 or a direct device-to-device (D2D) transmission mode 120 to get a high total system performance. Such scenario is also a hot topic in 3 GPP LTE- A work to enhance the system performance.

Basically, in such hybrid scenario, the critical problems are mainly from the resource sharing and interference situation. For example, one of critical interference situations exists when the cellular uplink (UL) spectrum is reused by D2D users. Therefore, it is desirable to propose some corresponding solutions to perform interference measurement and suppression in a hybrid network.

SUMMARY

According to a first aspect of the present invention, there is provided a method comprising: broadcasting resource information of a control channel by a network node, wherein device-to-device user equipments execute device-to-device handshaking on the control channel according to the resource information; receiving measurement information reported by one or more cellular user equipments, wherein by measuring device-to-device handshaking signals transmitted on the control channel, the one or more cellular user equipments detect that there is at least one victim device-to-device user equipment nearby; and sending a scheduling message generated based at least partly on the measurement information.

According to a second aspect of the present invention, there is provided a method comprising: performing by a device-to-device user equipment a registration with a network node; obtaining resource information of a control channel which is broadcasted by the network node; and executing device-to-device handshaking on the control channel according to the resource information, wherein device-to-device handshaking signals transmitted on the control channel are measured by cellular user equipments.

According further to the second aspect of the present invention, the method may further comprise: receiving a scheduling message from the network node; and managing resources for interference avoidance according to the scheduling message. According to a third aspect of the present invention, there is provided a method comprising: obtaining resource information of a control channel from a network node by a cellular user equipment, wherein device-to-device user equipments execute device-to-device handshaking on the control channel according to the resource information; detecting whether there is at least one victim device-to-device user equipment nearby by measuring device-to-device handshaking signals transmitted on the control channel; and reporting measurement information to the network node, when detecting that there is the at least one victim device-to-device user equipment nearby.

According to a fourth aspect of the present invention, there is provided a network node comprising: broadcasting means for broadcasting resource information of a control channel, wherein device-to-device user equipments execute device-to-device handshaking on the control channel according to the resource information; receiving means for receiving measurement information reported by one or more cellular user equipments, wherein by measuring device-to-device handshaking signals transmitted on the control channel, the one or more cellular user equipments detect that there is at least one victim device-to-device user equipment nearby; and sending means for sending a scheduling message generated based at least partly on the measurement information.

According to a fifth aspect of the present invention, there is provided an apparatus comprising: performing means for performing a registration with a network node; obtaining means for obtaining resource information of a control channel which is broadcasted by the network node; and executing means for executing device-to-device handshaking on the control channel according to the resource information, wherein device-to-device handshaking signals transmitted on the control channel are measured by cellular user equipments.

According further to the fifth aspect of the present invention, the apparatus may further comprise: receiving means for receiving a scheduling message from the network node; and managing means for managing resources for interference avoidance according to the scheduling message.

According to a sixth aspect of the present invention, there is provided an apparatus comprising: obtaining means for obtaining resource information of a control channel from a network node, wherein device-to-device user equipments execute device-to-device handshaking on the control channel according to the resource information; detecting means for detecting whether there is at least one victim device-to-device user equipment nearby by measuring device-to-device handshaking signals transmitted on the control channel; and reporting means for reporting measurement information to the network node, when detecting that there is the at least one victim device-to-device user equipment nearby.

According to a seventh aspect of the present invention, there is provided a computer program product comprising a computer-readable medium bearing computer program code embodied therein for use with a computer, the computer program code comprising: code for broadcasting resource information of a control channel by a network node, wherein device-to-device user equipments execute device-to-device handshaking on the control channel according to the resource information; code for receiving measurement information reported by one or more cellular user equipments, wherein by measuring device-to-device handshaking signals transmitted on the control channel, the one or more cellular user equipments detect that there is at least one victim device-to-device user equipment nearby; and code for sending a scheduling message generated based at least partly on the measurement information.

According to an eighth aspect of the present invention, there is provided a computer program product comprising a computer-readable medium bearing computer program code embodied therein for use with a computer, the computer program code comprising: code for performing by a device-to-device user equipment a registration with a network node; code for obtaining resource information of a control channel which is broadcasted by the network node; and code for executing device-to-device handshaking on the control channel according to the resource information, wherein device-to-device handshaking signals transmitted on the control channel are measured by cellular user equipments.

According to a ninth aspect of the present invention, there is provided a computer program product comprising a computer-readable medium bearing computer program code embodied therein for use with a computer, the computer program code comprising: code for obtaining resource information of a control channel from a network node by a cellular user equipment, wherein device-to-device user equipments execute device-to-device handshaking on the control channel according to the resource information; code for detecting whether there is at least one victim device-to-device user equipment nearby, by measuring device-to-device handshaking signals transmitted on the control channel; and code for reporting measurement information to the network node, when detecting that there is the at least one victim device-to-device user equipment nearby.

In exemplary embodiments of the present invention, the provided methods, network node, device-to-device user equipment, cellular user equipment, apparatus and computer program product can realize effective resource reuse in a hybrid network and avoid near-far interference in an autonomous D2D operation.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention itself, the preferable mode of use and further objectives are best understood by reference to the following detailed description of the embodiments when read in conjunction with the accompanying drawings, in which:

Fig.1 shows schematically a structure of a hybrid network; Fig.2 illustrates schematically near-far interference (from cellular users to D2D users) in the cellular UL spectrum;

Fig.3 shows an example of a Common Control Channel (CCCH) definition in a downlink (DL) spectrum in accordance with embodiments of the present invention;

Fig.4 A is a flowchart illustrating a method for interference avoidance in accordance with an embodiment of the present invention;

Fig.4B is a flowchart illustrating a method for interference avoidance in accordance with another embodiment of the present invention;

Fig.4C is a flowchart illustrating a method for interference avoidance in accordance with another embodiment of the present invention;

Fig.5 shows schematically different user locations and operations in a hybrid network in accordance with an embodiment of the present invention;

Fig.6 shows schematically a procedure of near-far interference suppression in the cellular UL spectrum in accordance with an embodiment of the present invention;

Fig.7 A is a block diagram schematically illustrating a network node in accordance with embodiments of the present invention;

Fig.7B is a block diagram schematically illustrating a D2D UE in accordance with embodiments of the present invention; and

Fig.7C is a block diagram schematically illustrating a cellular UE in accordance with embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the present invention are described in detail with reference to the accompanying drawings. Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present invention should be or are in any single embodiment of the invention. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Furthermore, the described features, advantages, and characteristics of the invention may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the invention may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the invention.

In a hybrid D2D and cellular network, since D2D users work autonomously and fully share frequency resources with cellular users, sometimes there is near-far interference from the cellular users to D2D user pairs. The addressed problems are illustrated in Fig. 2, where in a dash circle, cellular UE1 may have serious near-far interference to D2D user pair UE3-UE4 if they are sharing the same frequency resources. Whereas the interference from UE2 may be neglectable due to the long distance between D2D user pair UE3-UE4 and UE2 even they are using the same resources. For D2D user pair UE7-UE8 which is in another cell, cellular UE2 may generate inter-cell interference to this D2D user pair.

Besides, in most 3G (3rd Generation) and B3G (Beyond 3rd Generation) systems, a BS (or similar device such as Node B and eNB) allocates resources to cellular UEs in a dynamic way (for example, 1ms Transmission Time Interval (TTI) based), which means that the resource allocation can not be predicted accurately by the accumulated knowledge. Therefore, it is hard to implement blind interference avoidance methods, and the blind interference avoidance methods can not work well without any resource allocation knowledge of cellular users. Thus, there is a need for some new methods to deal with resource allocation and interference avoidance issues by utilizing network peculiarity of the hybrid network.

In a Worldwide Interoperability for Microwave Access (Wimax)-like system, there is one solution to avoid the interference from cellular users to D2D user pairs. In this solution, by decoding an allocation table, a D2D user can measure interference and do radio resource management (RRM) effectively. However, such scheme would require a Wimax-like allocation table so that the D2D user can decode this allocation table to get resource allocation information of other users. Thus in a non- Wimax-like system (such as a LTE system), it is a bit hard to use this solution.

Another solution directed to interference measurements for D2D communications is to measure interference from other UEs based on a list of UEs given by an eNB. A D2D UE reports the measurement to the eNB. The eNB may schedule cellular users on resources with low interference from and to D2D groups. However, there are two constraints on this solution. First, it requires an eNB to broadcast Radio Network Temporary Identifier (RNTI) information. Second, it may not solve the inter-cell interference problem efficiently since a D2D UE can only detect the interference according to the RNTIs broadcasted by the eNB.

Further, some methods of controlling the interference produced by D2D communications are proposed, in which cellular UEs are able to distinguish D2D signals and may report to a BS if the interference becomes excessive. Unfortunately, such method is not able to handle the interference from/to neighbor cell's D2D users.

Thus, it is desirable to design a mechanism to perform resource allocation and achieve good interference avoidance in an ad hoc and LTE like hybrid network, which mechanism can realize resource reusing, avoid near-far interference in an autonomous D2D operation and deal with inter-cell interference in a multi-cell scenario.

An interference avoidance mechanism, aiming at avoiding the harmful interference from cellular UEs to D2D transmissions is proposed in the present invention. Fig.4A is a flowchart illustrating a method for interference avoidance in accordance with an embodiment of the present invention. This method can be performed at a network node in a hybrid D2D and cellular network, where D2D UEs working in an autonomous mode can share/reuse the UL spectrum of a cellular system with cellular UEs, and the eNB-assisted autonomous D2D transmission is employed in this system. With this method, a network node (such as a BS, Node B, eNB and etc.) can coordinate D2D and cellular transmissions on the same band even if D2D users may not be in the same cell as cellular users.

In step 412, the network node broadcasts resource information of a control channel, on which control channel D2D UEs execute D2D handshaking according to the resource information. In an exemplary embodiment, the control channel may comprise a Common Control Channel (CCCH), a dedicated control channel or the like. The control channel can be in Frequency Division Multiple Access/Time Division Multiple Access/Code Division Multiple Access (FDMA/TDMA/CDMA) mode, and can be expressed with a mathematic expression such as CCCH (f, t) in the case of FDMA/TDMA, where f denotes the frequency domain and t for the time domain.

The resource information (used resources) of a D2D control channel may be included in broadcasting system information (for example, System Information Block SIB1 or SIB2) to let all users know this information. As an example, the resource allocation information of the control channel may be broadcasted in the whole cell by the network node through a Physical Broadcast Channel (PBCH) or granted over a Physical Downlink Control Channel (PDCCH). In an exemplary embodiment, the resource information comprises indication of whether the control channel is located in a UL spectrum or a DL spectrum, and identifiers and/or positions of physical resource blocks (PRBs) assigned for the control channel. This information can be dynamically changed, for example in terms of system status.

One example for a CCCH definition is shown in Fig.3, in which two ways of configurations are provided. In way-1, some PRBs are always reserved over the whole time duration, while in way-2, some PRBs are reserved in some distributed TTI only. Thus, when the network node broadcasts the reserved resource of a D2D CCCH in the broadcasting channel, all cellular UEs and D2D UEs can know the information of the D2D CCCH, which may comprise indication of whether it is located in a UL spectrum or a DL spectrum, which and how many PRBs will be used for the D2D CCCH, and/or in which TTIs these PRBs are located.

With the resource information from the network node, D2D UEs can perform a handshaking procedure on the control channel, for example by using a Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme or any other suitable schemes. For a D2D UE, handshaking signals transmitted during its D2D handshaking procedure may carry at least one of the following information: identifier of a cell in which this D2D UE registered, identifier of the D2D UE, and D2D transmission power.

Referring Fig.4A again, in step 414, the network node receives measurement information reported by one or more cellular UEs, wherein by measuring D2D handshaking signals transmitted on the control channel, the one or more cellular UEs detect that there is at least one victim D2D UE nearby. Here, victim D2D UEs refer to those potentially experiencing near-far interference from the cellular UEs nearby. In an exemplary embodiment, the received measurement information may comprise identifier of the reporting cellular UE and at least one of the following: a position of this reporting cellular US, and identification information of one or more victim D2D UEs detected by the reporting cellular UE. For example, identification information of a victim D2D UE may comprise identifier of a cell (such as an identity of a cell/Cell-ID) in which the victim D2D UE registered, identifier of the victim D2D UE and etc.

Then in step 416, the network node sends a scheduling message generated based at least partly on the received measurement information. In terms of the reported information from cellular UEs, the network node can classify the cellular UEs into two different groups: "non-near-far-risk" and "near-far-risk". Cellular UEs of "non-near-far-risk" are far away from D2D UEs so they may not interfere with D2D transmissions. However, cellular UEs of "near-far-risk" are near to D2D UEs and they could have large near-far interference when they use the same frequency resources with the D2D UEs. In an exemplary embodiment, the network node may broadcast the allocated frequency resources of all the "near-far-risk" cellular UEs on a defined channel, after the network node has made RRM decision for cellular users. D2D UEs may receive such information in the defined channel.

According to exemplary embodiments, the scheduling message may comprise identifiers of prohibited resources, which indicate resources allocated to the "near-far-risk" cellular UEs, respectively. Corresponding to each of the identifiers of the prohibited resources, the scheduling message may further comprise at least one of the following: identifiers of one or more D2D UEs registered with the network node which are forbidden to use respective prohibited resource, and a position of a cellular UE to which the respective prohibited resource is allocated.

Actually, D2D UEs (for example, edge D2D UE7-UE8 shown in Fig.2) may experience interference from a cellular UE (UE2 in Fig.2) in a different cell. Thus, upon receiving the measurement report from cellular UEs, for example by the defined specific signaling, a network node can check if the reported victim D2D UE is from own cell or neighbor cell by its Cell-ID at first. If the reported victim D2D UE belongs to a cell served by the network node, then the network node can broadcast "prohibited frequency resources plus corresponding IDs of D2D UEs" or "position information plus allocated frequency resources of cellular UEs", for example. Then D2D UEs can use such information to do autonomous RRM for interference avoidance. If the reported victim D2D UE does not belong to the network node's own cell, then the network node may, for example, avoid scheduling the reporting cellular UEs during the D2D communication of this victim D2D UE. This can be implemented by predefining the allowed TTIs for D2D data transmissions and exchanging such information via an X2 interface among neighboring network nodes. Alternatively, if the reported victim D2D UE is located or registered in another different cell, several neighboring network nodes can do coordination to get the agreed D2D resources via an X2 interface, and a proper neighboring network node will tell this cell edge D2D UE the agreed resources for example by PDCCH.

Thus, according to exemplary embodiments, when an identifier of at least one edge D2D UE which is registered with another network node exists in the measurement information, the network node can either enable avoidance of scheduling at least one cellular UE reporting the at least one edge D2D UE during D2D transmissions of the at least one edge D2D UE, or make an agreement on allowable resources with at least one neighboring network node. Then the at least one edge D2D UE can be informed of the allowable resources by its serving network node.

Moreover, a UE category based mechanism for Release 8 (R'8) backward compatibility is also considered in the present invention. A network node such as eNB can know UE's capability (for example, is it R'8, R'9, or R' lO or later release?) and do corresponding scheduling to separate them. For instance, the eNB may broadcast identification information of resources used by R'8 users to a D2D pair to avoid reusing the resources, and/or may employ Time Division Multiplexing (TDM) between the R'8 users and the D2D pair.

Fig.4B is a flowchart illustrating a method for interference avoidance in accordance with another embodiment of the present invention. This method can be applied at a D2D UE in a hybrid D2D and cellular network. In this hybrid network, D2D users work in an autonomous mode, and a CSMA/CA type Media Access Control (MAC) protocol can be applied for D2D transmissions, which means a control channel such as a dedicated common control channel (CCCH) can be used for a D2D handshaking procedure where RTS/CTS (Request to Send/ Clear to Send) signals are transmitted to facilitate RRM and D2D data transmissions.

In step 422, the D2D UE performs a registration with a network node. This network node has the same functionality as that of the network node described in connection with Fig.4 A. In an embodiment, the registration may comprise getting from the network node at least one of: an identifier of a cell served by the network node, an identifier of the D2D UE, and fractional power control parameters used by the cell. Optionally, the registration may comprise informing the network node of the D2D UE's capability. Therefore, by registering in one cell, a D2D UE can get some essential information from an eNB, for example, Cell-ID of the anchored cell, the allocated C-RNTI (Cell Radio Network Temporary Identifier), fractional power control parameters used by this cell and etc. Otherwise, a D2D UE can inform an eNB of the D2D UE's capability such as UE category including the maximum transmission power. Because the D2D UEs' power setting can follow the fractional power control in a LTE system, the interference from D2D users to cellular users can be avoided efficiently. Then the key problem in interference issues is how to avoid interference from the cellular users to the D2D users.

When registered in one cell served by the network node, the D2D UE can obtain resource information of a control channel broadcasted by the network node, as shown in step 424. As mentioned before, the control channel can be used for signaling between D2D UEs to achieve handshake. All the D2D UEs can easily find the resources allocated for D2D control channels, which are reliable enough since they are not interfered by cellular or D2D data transmissions. It is noted that since a D2D UE also has the capability to communicate with a network node such as eNB of a cellular network, the D2D signaling and data transmission can follow the same frame structure as the cellular system.

In an exemplary embodiment, a D2D pair may use the control channel such as CCCH to claim a set of dedicated resources for D2D communications within the D2D community in a contentious way using a RTS/CTS based mechanism, for example. RTS is a data transmission request from a transmitting UE in a D2D pair (Tx D UE), and CTS is a response from a receiving UE in the D2D pair (Rx D UE). As an example, RTS and the corresponding CTS may share the same CCCH frequency resource in the time domain, for instance, CTS can be transmitted in the first slot of one TTI whereas RTS on the second slot.

If D2D CCCH is located in the DL spectrum and D2D data was transmitted in the UL spectrum. Then considering the channel difference between CCCH transmission using a DL carrier and DTCH (Data Transmission Channel) transmission in a UL carrier, the power offset between them can be applied to ensure the similar coverage of CCCH and DTCH. For example, the power offset may be propagation difference between them. In the mean while, the Signal-to-Interference Ratio (SIR) requirement difference, which is caused by different modulation and coding scheme (MCS) selections of CCCH and DTCH, also can be taken into account.

According to the obtained resource information, in step 426, the D2D UE executes D2D handshaking on the control channel, and D2D handshaking signals transmitted on this channel can be measured by cellular UEs. In an exemplary embodiment, the D2D handshaking signals carry at least one of: identifier of the serving cell, identifier of the D2D UE, and D2D transmission power. For example, Cell-ID and C-RNTI may be carried in RTS/CTS messages (on D2D CCCH) to identify D2D users. Then a cellular user can report the accurate information about the potential victim D2D UEs. Furthermore, the D2D transmission power could be included in RTS/CTS messages for pathloss estimation. This is impossible or complicated in the network controlled D2D mode, since there is no such kind of dedicated CCCH channel for the channel contention in a broadcasting way.

Optionally, the D2D UE may receive a scheduling message from its serving network node, and manage resources for interference avoidance according to the scheduling message. Similar to the scheduling message illustrated in connection with Fig.4 A, the scheduling message received by the D2D UE may comprise identifiers of prohibited resources, and corresponding to each of the identifiers of the prohibited resources, the scheduling message may further comprise at least one of the following: identifiers of one or more D2D UEs registered with the network node which are forbidden to use respective prohibited resource, and a position of a cellular UE to which the respective prohibited resource is allocated.

According to exemplary embodiments, when a D2D UE finds that its identifier exists in the scheduling message, or that it is near to at least one of the cellular UEs indicated in the scheduling message, the D2D UE would not use the corresponding prohibited resources to transmit D2D data. Alternatively, the scheduling message may comprise allowable resources which are agreed by several neighboring network nodes for this D2D UE.

Corresponding to operations of the methods described in connection with Fig.4A and Fig.4B, a flowchart shown in Fig.4C illustrates a method for interference avoidance in accordance with still another embodiment of the present invention. The method can be applied at a cellular UE in a hybrid network. In step 432, the cellular UE obtains resource information of a control channel from a network node. As mentioned before, D2D UEs execute D2D handshaking on this control channel, according to the resource information which indicates whether the control channel is located in a UL spectrum or a DL spectrum, as well as identifiers and/or positions of PRBs assigned for the control channel.

According to the obtained resource information, the cellular UE detects whether there is at least one victim D2D UE nearby by measuring D2D handshaking signals transmitted on the control channel, as shown in step 434. When detecting that there is at least one victim D2D UE nearby, the cellular UE reports measurement information to the network node in step 436. In an exemplary embodiment, the measurement information comprises identifier the cellular UE. When the power of at least one of D2D handshaking signals monitored by the cellular UE is larger than a first predefined threshold, the measurement information may further comprise a position of this cellular UE. Alternatively, when the power of at least one of D2D handshaking signals monitored by the cellular UE is larger than a second predefined threshold, the cellular UE receives and decodes the at least one D2D handshaking signal to identify the corresponding victim D2D UE. In this case, the measurement information may further comprise at least one of the following: a position of the cellular UE, and identification information of the at least one victim D2D UE (such as a Cell-ID and an identifier for the victim D2D UE).

For example, the cellular user can monitor the victim D2D users by blindly decoding the reserved D2D CCCH and/or by measuring the power level of D2D CCCH which is operating, for example, in a broadcasting mode with some predefined MCS and frequency resources. If CCCH is decodable, then decoding on CCCH transmissions can clearly know the interferers without any mistake caused by the possible interference from other cells' D2D transmissions or some in-band emission from nearby users.

According to the foregoing description, it can be seen that one of advantages of the invention is that a cellular user can perform interference measurement by blindly decoding D2D control channel and/or detecting D2D control channel's power level regardless of the same or neighbor cell's D2D users. The schematic flow chart diagrams described above are generally set forth as logical flow chart diagrams. As such, the depicted order and labeled steps are indicative of specific embodiments of the presented methods. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the illustrated methods. Additionally, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown.

Fig.5 shows schematically different user locations and operations in a hybrid network in accordance with an embodiment of the present invention. In the hybrid network shown in Fig.5, a network node such as eNB 501 can decide D2D CCCH resources in terms of the D2D load and other system information. When D2D UEs such as D2D pair#l and D2D pair#2 do interactions via CCCH, cellular users can monitor the CCCH channel and report measurement results to the eNB 501 (as illustrated in Fig.5). If a cellular user can hear CCCH information, then it means the cellular user is near to some D2D pairs, so the possibility of near-far interference to the D2D pairs exists. Cellular users may report measurement information by means of two methods depending on measurement results. As an example, if the D2D CCCH is not decodable, a cellular user may report his position information to indicate that there are D2D pairs nearby. However, if a cellular UE can blindly decode the D2D CCCH successfully according to the predefined MCS and frequency resource information used on CCCH, it may report the victim D2D UE's Cell-ID, C-RNTI to the eNB, for example by the new defined signaling. Additionally or alternatively, the cellular UE may report its position information to the eNB in this case.

The eNB 501 can schedule cellular users or control D2D users in its cell with at least one of the following methods by broadcasting or PDCCH signaling:

a) scheduling the reporting cellular user by stopping victim D2D transmissions (for instance, applying a TDM scheme to the cellular user and victim D2D users). For example, PDCCH signaling with D2D RNTI and 1 bit information can be used to disable victim D2D users' transmissions; b) scheduling the reporting cellular user by prohibiting D2D transmissions from using the same resource allocated to this cellular user (for instance, applying a FDM scheme to the cellular user and victim D2D users). For example, PDCCH signaling with D2D RNTI and prohibited PRBs information can be sent to the victim D2D users;

c) not scheduling the reporting cellular user for data transmission if victim D2D users are located in another different cell (in this case, the allowed TTIs for D2D data transmissions may be predefined and exchanged via an X2 interface among neighboring eNB); or d) if victim D2D users are located in another different cell, several neighboring eNBs can do coordination to get the agreed D2D resources via an X2 interface, and then a neighboring eNB serving the another different cell can tell these victim D2D users (cell edge D2D users) the agreed resources by PDCCH signaling.

It is noted that R'8 backward compatibility seems very important when more advanced methods (such as D2D features) are introduced in a future system. Actually, it is easy to implement some methods for R'8 backward compatibility as well. For example, an eNB can know a UE's capability (Is it R'8, R'9, or R' lO or later release?) and do corresponding scheduling to separate different UEs. Then the eNB can broadcast information of resources used by R'8 users to D2D pairs to avoid reusing the resources. Alternatively, a TDM scheme can be employed between R'8 users and D2D pairs. By such way, the D2D CCCH also can be located at a UL spectrum for R'9 or later release. While R'8 users can use scheduling schemes described above to avoid interference for fully backward compatibility. Fig.6 shows schematically a procedure of near-far interference suppression in the cellular UL spectrum in accordance with an embodiment of the present invention. In order to implement eNB-assisted autonomous D2D transmissions in the addressed hybrid D2D and cellular network, an interference avoidance mechanism is proposed, aiming at avoiding the harmful interference from cellular UEs to D2D UEs. This mechanism involves a procedure on how to schedule/reschedule the cellular and D2D resources, where a signal transmitted on a common control channel (such as CCCH) is used as a reference signal for detecting the interference level by cellular users. The used resources of the D2D CCCH can be dynamically decided and allocated by a broadcasting channel. Through measuring the D2D CCCH by cellular users and broadcasting the prohibited resources by an eNB or PDCCH signaling, resource reusing can be realized and near-far interference can be avoided in an autonomous D2D operation. Thus, with this mechanism, a near-far interference problem when using D2D transmissions in the cellular UL spectrum, as well as variable interference problems for a multi-cell scenario can be eliminated effectively.

Here C UE and D UE are used to denote a cellular UE and a D2D UE, respectively. The procedure of interference suppression is illustrated in Fig.6, where Tx D UE and Rx D UE refer to a D2D UE sending data and a D2D UE receiving data in a D2D pair, respectively. As shown in Fig.6, an eNB broadcasts the reserved resource (such as time and frequency, which frequency band, and the like) of D2D CCCH in a broadcasting channel (step 601). Then all cellular UEs and D2D UEs can obtain information of the D2D CCCH. The D2D UEs (Tx D UE and Rx D UE) may perform a handshaking procedure on the D2D CCCH, for example, by using a CSMA/CA scheme (step 602). While the cellular UEs (C_UE1 and C_UE2) can listen to the D2D CCCH periodically to monitor whether some D2D UEs are near to them (step 602). Two options could be used to achieve this measurement:

Solution#l : Cellular UEs only monitor the power of CCCH regularly, but do not decode the signal of CCCH. In this solution, cellular UEs need to listen to CCCH for a defined period to decide nearby D2D pairs accurately. Here a first threshold for power/interference is used to identify whether there are D2D UEs nearby. For example, if the monitored power of a signal on CCCH is larger/higher than the first threshold, then the corresponding D2D UE transmitting this signal may be considered as a victim D2D UE. The first threshold can be configured by a network semi-statically or dynamically. To reduce the impact of in-band emission, cellular UEs can ignore the CCCH measurement results in the TTIs when there is very high receiving power in other PRBs, or try to subtract the effect of in-band emission from the CCCH receiving power.

Solution#2: Cellular UEs first monitor the power of CCCH regularly and in case that the power of CCCH is larger/higher than a second threshold for power/interference, the cellular UEs can receive signals on the CCCH and decode the signals to find identifiers such as IDs of victim D2D UEs. The second threshold, which also can be configured by a network semi-statically or dynamically, may have the same or difference value with the first threshold. By doing so, the cellular UEs can know which D2D UEs are near to them and then report these D2D UEs' identifiers to the eNB. It is noted that in this case, the information of RTS/CTS during D2D handshaking includes identifiers of D2D UEs (for example, Cell-ID + C-RNTI).

Thus, the interference situation can be reported from cellular users to the corresponding eNB (step 603). For example, cellular UEs may report their collected information to the eNB in a dedicated channel. According to different measurement results detected by the cellular UEs, there may be two reporting formats:

Solution#3 : Cellular UEs may report their position information (for example, when a Global Positioning System (GPS) available) to an eNB when they detected serious D2D CCCH interference (see Table 1). In this option, cellular UEs and D2D UEs both can know their position information. This is not a big problem considering mounting a GPS device in a cell phone is so popular nowadays.

Table 1. Interference map in an eNB based on reporting of Solution#3

where Al and Bl are geographical coordinates of a cellular UE denoted by C UEl, and A2 and B2 are geographical coordinates of a cellular UE denoted by C UE2.

Solution#4: Cellular UEs may report the detected D2D UEs' IDs to an eNB when they detected serious D2D CCCH interference (see Table 2).

Table 2. Interference map in an eNB based on reporting of Solution#4

II ) ol ^* el lular I J H i D of i r ) i n -;

C UEl D UEl

D UE2

C UE2 D UE3

where D UEl and D UE2 respectively represent identifiers of D2D UEs which potentially experience interference from a cellular UE denoted by C UEl, and D UE3 represents identifier of a D2D UE which potentially experiences interference from a cellular UE denoted by C UE2. Thus, according to Table 2, the eNB can know that C UEl is near to D UEl and D UE2 and may have high interference to the D2D transmission between D UEl and D UE2. Optionally, a cellular UE may report the corresponding Cell-ID of a detected D2D UE to the eNB, in addition to the D2D UE's ID, so that the eNB can check whether the detected D2D UE belongs to its own cell.

Alternatively, the cellular UE may report both its position information and the detected D2D UE's ID to the eNB if it detected serious D2D CCCH interference. In this case, an interference map (not shown) in the eNB may be generated, for example, by combining Table 1 and Table 2.

According to an exemplary embodiment, in order for reducing the signaling overhead, only those cellular UEs receiving the higher CCCH power may report measurement results to their respective serving eNBs. The reported measurement results can be Time Division Multiplexing/Frequency Division Multiplexing/Code Division Multiplexing (TDM/FDM/CDM) on a dedicated channel, for example. The principle of the solutions is predicting the potential interference of cellular users to nearby D2D users. If the interference measurement is not enough for the prediction because the D2D power level may be quite different from the cellular UE's power, the predicted interference could be derived as below:

Resulted_Interference_fromCellularUEtoD2DUE

= CellularUEPower - (D2D_CCCH_Power - ReceviedPowerlnCellularUE) .

Thus, the D2D transmission power information (D2D_CCCH_Power) is required and can be included in CCCH signals. In case that the reported measurement results comprise identification information of at least one victim D2D UE, the victim D2D UE's RNTI and its Cell-ID need to be transmitted in CCCH signals. However, sometimes the CCCH signals may not be decodable, and in such case a position based method may be used.

In a multi-cellular network scenario, inter-cell interference from neighboring cells may occur especially when D2D UEs are at the edge of a given cell. To overcome such interference, a TDM scheme is proposed. When a cellular UE measures a D2D CCCH signal beyond the predefined threshold, it may report to its eNB. The eNB may check if this D2D UE is in its cell (for example by checking the D2D UE's ID or position information). If the eNB found that the D2D UE is not in its cell, it may stop scheduling the reporting cellular UE during D2D transmissions. Or if the D2D UE (for example from a cell edge D2D pair) is located in another different cell, several neighboring eNBs can do coordination to get the agreed D2D resources via an X2 interface, and then the cell edge D2D pair can be informed by its serving eNB of the agreed resources by PDCCH, as an example.

With the measurement results reported from cellular UEs, an eNB can make a RRM decision for cellular UEs in a cell served by this eNB (as shown in Fig.6). Then, the eNB broadcasts information of the allocated resources (such as frequency, time and the like) of all the "near-far-risk" cellular UEs on a defined channel (step 604). D2D UEs can receive such information in the defined channel. Depending on different measuring and reporting solutions described above, the broadcasting information of the eNB can be classified as follows:

Solution#5 : An eNB broadcasts prohibited resources plus IDs of D2D UEs (see Table 3). Then a D2D UE may have knowledge of which resources it is prohibited from reusing, according to the broadcasting information.

Table 3. Broadcasting format of Solution#5

I ^{) " )} ui : ID Prohibit d Resources

D UE1 PRB 1

PRB 15

D UE2 PRB 4

D UE3 None

In this solution, cellular UEs which detected victim D2D UEs have the competence to decode D2D CCCH signals for obtaining identification information (such as IDs, RNTIs and etc.) of the victim D2D UEs. It may not a big problem to know the RNTI information in a future IMT-A network.

Solution#6: An eNB broadcasts the position information and allocated resources of cellular UEs (see Table 4). Then a D2D UE can use such information to avoid reusing those resources at the specific location. Table 4. Broadcasting format of Solution#6

In Solution#6, the D2D UE also knows the position of itself, so it can reuse the resources with a distant cellular UE and avoid interference from a near cellular UE. Here, RNTIs of D2D UEs are not needed to be detected, and security and reusing efficiency can be guaranteed.

For example, the eNB can broadcast the scheduling information in advance of a fixed TTI, such as in advance of 4TTI with the cellular UL grant information. In this way, D2D signaling and data transmissions follow the same frame structure as that of the UL of a cellular network, so the time relationship could be well defined to let D2D UEs know that which resource may be utilized through the handshake and competition procedure (RTS/CTS) at the specific time.

With the scheduling information received from the eNB, the D2D UE can make a D2D RRM decision (step 605) and start the D2D transmission utilizing the permitted resources.

Fig.7 A is a block diagram schematically illustrating a network node 710 in accordance with embodiments of the present invention. The network node 710 such as BS, Node B, eNB or the like, may comprise various means and/or components for implementing functions of the foregoing steps and methods in Fig.4A. Particularly, the network node 710 comprises broadcasting means 711, receiving means 712, and sending means 713, as shown in Fig.7 A. Alternatively, the network node 710 also may comprise a transceiver (not shown) for sending and/or receiving signals and messages to/from a UE, and a processor (not shown) for processing these signals and messages. The components and elements comprised in the network node 710 may be coupled to each other by a variety of communication links and/or interfaces.

In an exemplary embodiment, the broadcasting means 711 broadcasts resource information of a control channel such as CCCH, and according to the resource information (which can be dynamically changed by the network node 710), D2D UEs can execute D2D handshaking on this control channel. As mentioned previously, the resource information may comprise indication of whether the control channel is located in an uplink spectrum or a downlink spectrum, as well as identifiers and/or positions of PRBs assigned for the control channel. For example, a D2D CCCH can be defined in a DL spectrum although D2D data is transmitted in a UL spectrum. The used resources of the D2D CCCH can be dynamically decided and allocated by the network node via a broadcasting channel. When one or more cellular UEs detected at least one victim D2D UE by measuring D2D handshaking signals transmitted on the control channel, the receiving means 712 receives measurement information from the one or more cellular UEs. Then a scheduling message is generated based at least partly on the measurement information and sent by the sending means 713 of the network node 710. As described before, there are many feasible schemes for implementing interference reporting and signaling scheduling message, which can be used for different network situations and competence cases.

As an example, the scheduling message may comprise identifiers of prohibited resources, and corresponding to each of the identifiers of the prohibited resources, the scheduling message may further comprise at least one of the following: identifiers of one or more D2D UEs registered with the network node 710 which are forbidden to use respective prohibited resource, and a position of a cellular UE to which the respective prohibited resource is allocated. When an edge D2D UE which is registered with another network node is reported, the network node 710 may avoid scheduling the reporting cellular UE during D2D transmissions of this edge D2D UE, or make an agreement on allowable resources for this edge D2D UE with at least one neighboring network node.

Fig.7B is a block diagram schematically illustrating a D2D UE 720 in accordance with embodiments of the present invention. The D2D UE 720 may be a mobile terminal, a wireless device, a portable computer and any other suitable user device which is capable of performing D2D transmissions. The D2D UE 720 may comprise various means and/or components for implementing functions of the foregoing steps and methods in Fig.4B. Particularly, as shown in Fig.7B, the D2D UE 720 comprises performing means 721, obtaining means 722 and executing means 723.

In an exemplary embodiment, the D2D UE 720 registers in a cell by utilizing the performing means 721 which performs a registration with a network node serving this cell. Upon registration, the D2D UE 720 can get at least one of: an identifier of this cell, an identifier for this D2D UE, and fractional power control parameters used by the cell. Then, the obtaining means 722 obtains resource information of a control channel broadcasted by this network node, and according to the resource information, the executing means 723 executes D2D handshaking on the control channel. For example, D2D handshaking signals transmitted on the control channel can carry at least one of: the identifier of the cell, the identifier of the D2D UE, and D2D transmission power.

Optionally, the D2D UE 720 may further comprise receiving means (not shown) for receiving a scheduling message from the network node, and managing means (not shown) for managing resources for interference avoidance according to the scheduling message. When the D2D UE found that its identifier exists in the scheduling message, or it is near to at least one of the cellular UEs indicated in the scheduling message, the D2D UE would not use the corresponding prohibited resources to transmit D2D data.

Fig.7C is a block diagram schematically illustrating a cellular UE 730 in accordance with embodiments of the present invention. The cellular UE 730 may be a mobile terminal, a wireless device, a portable computer and the like. The cellular UE 730 may comprise various means and/or components for implementing functions of the foregoing steps and methods in Fig.4C. Particularly, as shown in Fig.7C, the cellular UE 730 comprises obtaining means 731, detecting means 732 and reporting means 733.

In an exemplary embodiment, the obtaining means 731 obtains resource information of a control channel from a network node. Since D2D UEs execute D2D handshaking on the control channel according to the resource information, the detecting means 732 of the cellular UE 730 can detect whether there is at least one victim D2D UE nearby, by measuring D2D handshaking signals transmitted on the control channel. When the monitored power of at least one of D2D handshaking signals is larger than a first predefined threshold, the cellular UE 730 adds its identifier and position into measurement information. According to another embodiment, the cellular UE 730 is able to decode signals on the control channel. In this case, when the monitored power of at least one of D2D handshaking signals is larger than a second predefined threshold, the cellular UE 730 receives and decodes the at least one D2D handshaking signal to identify at least one victim D2D UE, and adds its identifier and at least one of the following information into the measurement results: a position of the cellular UE 730, and identification information of the at least one victim D2D UE. Then, the reporting means 733 of the cellular UE 730 reports the generated measurement information to the network node. It is noted that D2D users in neighbor cells also can be protected from the cellular users' interference efficiently because a cellular UE do not make a difference between D2D UEs in its own cell and in neighbor cells when monitoring signals on the control channel.

Those skilled in the art will realize that the network node 710, the D2D UE 720 and the cellular UE 730 may comprise other functional means and/or modules not shown. According to an embodiment of the present invention, the foregoing and additional means and/or modules comprised in the network node 710, the D2D UE 720 and the cellular UE 730 can be implemented as a software block or a hardware block or a combination thereof. Furthermore, these means and/or modules can be implemented as a separate block or can be combined with any other standard block or it can be split into several blocks according to their functionality.

According to exemplary embodiments, a D2D control channel can be in either a FDD DL or UL spectrum. For example, by using D2D CCCH in a DL spectrum, backward compatibility can be got to some extent. In this case, cellular UEs can measure CCCH in the DL spectrum. Optionally, cellular UEs also can decode CCCH to get identification information of D2D UEs. A cellular UE can report the measured information (such as, used PRBs, ID for a neighboring D2D pair, location information) to its serving eNB. The approach, in which the victim's information is reported from the interferer, provides benefits to a hybrid network. In addition, inter-cell interference problem in D2D communications is also solved.

The present invention can be realized in hardware, software, firmware or a combination thereof. The present invention also can be embodied in a computer program product, which comprises all the features enabling the implementation of the methods and devices or modules described herein, and when being loaded into a computer system or a processing device, is able to carry out these methods or constitute the functional means/modules in the apparatuses or devices according to embodiments of the present invention. For example, a program of the computer program product may be loadable into a memory of the processing device. The computer program product may comprise a computer-readable medium on which software code portions for performing the methods, apparatus, devices and/or modules of the present invention are stored.

Although specific embodiments of the invention have been disclosed, those having ordinary skill in the art will understand that changes can be made to the specific embodiments without departing from the spirit and scope of the invention. The scope of the invention is not to be restricted therefore to the specific embodiments, and it is intended that the appended claims cover any and all such applications, modifications, and embodiments within the scope of the present invention.