WO2016113472A1

WO2016113472A1 - A solution for device-to-device communication

Info

Publication number: WO2016113472A1
Application number: PCT/FI2016/050020
Authority: WO
Inventors: Kalle RUTTIK; Nicolas MALM; Olav Tirkkonen; Riku Jäntti
Original assignee: Aalto-Korkeakoulusäätiö
Priority date: 2015-01-16
Filing date: 2016-01-18
Publication date: 2016-07-21

Abstract

The invention relates to a method for controlling device-to-device communication between a first wireless terminal (110) and a second wireless terminal (120) by a base station (130). The method comprising: receiving (210) a request for a device-to-device communication resource from at least one of the wireless terminals (110, 120) over a communication link, allocating (220) at least a first communication resource being primarily used in the device-to-device communication and at least one second communication resource being secondarily used in the device-to-device communication, informing (230) at least the allocated first communication resource, and maintaining (240) the established communication link for transmitting information comprising at least data representing a state of an established communication channel on the allocated first communication resource. The invention also relates to a base station (130).

Description

A solution for device-to-device communication

TECHNICAL FIELD

The invention concerns in general the technical field of mobile communications. More particularly, the invention concerns radio resource management in a device-to-device communication.

BACKGROUND

A traditional way of communication between two wireless terminals in a cellular radio network is that each wireless terminal communicates with a serving base station of the radio network by sending uplink radio signals to the base station as well as receiving downlink radio signals from the base station. The serving base station may be different for each wireless terminal or the same if both wireless terminals reside within an area i.e. in a cell which the base station in question serves.

Another traditional approach of communication is that the two wireless terminals are directly coupled to each other with a radio link, such as Bluetooth. This kind of arrangement enables direct communication without any control or involvement by any other network element. Typically, no specific radio spectrums are allocated for this kind of direct communication and they have to operate in ISM band. Lately, techniques have been developed to enable the wireless terminals in a radio network to communicate with each other directly, but at least partly controlled by the radio network and using frequency spectrum of the network, such that each wireless terminal receives and decodes the radio signals that are transmitted from the other wireless terminal. In other words, the communication may take place directly between the two wireless terminals without the radio signals being communicated over the radio network via one or more base stations. In this kind of case, the serving base station allocates radio resources, e.g. defined by time and/or frequency, which the wireless terminals are allowed to use in the direct communication. Such direct radio communication between two wireless devices is commonly referred to as Device-to-Device, D2D, communication. The D2D communication is assumed to provide some advantages over the traditional ways of communicating. At least some of them are decreased latency and increased reliability. However, the D2D communication has also challenges and some of them are next discussed by referring to Figure 1 . In Figure 1 wireless terminals being involved in D2D communication are referred with 1 10 and 120. A further wireless terminal that communicates at the same time with a base station 130 is referred with 140. In this example, the D2D communication and the communication between the wireless terminal 140 and the base station 130 happen in the same band, but in different time-frequency resources as is typically the situation. Scheduling of transmissions may happen both in time, and in frequency. For sake of clarity it is here assumed that time is divided into slots, and frequency in blocks for the transmission purposes. Due to non-ideal transmit and receive filters, there is interference between simultaneous transmissions. Especially within the system bandwidth, only digital filtering is often used, so that interference levels may be rather high in adjacent frequency blocks. In conventional cellular transmissions, the transmission powers both in downlink and uplink are controlled in such a manner that the received powers on adjacent frequency blocks are rather similar. Thus, if e.g. the further wireless terminal 140 transmits in uplink slot where D2D communication happens, there is interference from the D2D transmission to the cellular communication and from the cellular transmission to the D2D connection. Further, the further wireless terminal 140 and the D2D wireless terminals 1 10, 120, and sometimes even the base station 130 may be mobile. Due to mobility, the relative distances between the cellular interferer, i.e. the further wireless terminal and the interference victim - a D2D receiver - may change. As a consequence the interference caused by cellular transmission on the resources allocated for reliable D2D communication may increase, and render reliable D2D communication impossible. In worst case, a cellular interferer may come so close to a D2D receiver that the receiver is blocked. In this case, the wanted D2D transmission would be compromised by quantization noise.

In addition to user mobility, changes in interference may be due to directional transmissions of the cellular transmission. Different levels of interference may be targeted towards the direction where the D2D receiver is. This may change according to the user scheduled for cellular communication in a resource.

Hence, there is need to mitigate the above described problems due to interference especially for D2D communication.

SUMMARY The following presents a simplified summary in order to provide basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention.

An objective of the invention is to present a method and a base station for controlling device-to-device communication. Another objective of the invention is that the method and the base station enable management of radio resource in device-to-device communication area.

The objectives of the invention are reached by a method and base station as defined by the respective independent claims.

According to a first aspect, a method for controlling device-to-device communication between a first wireless terminal and a second wireless terminal by a base station is provided wherein the method comprising: receiving, in the base station, a request for a device-to-device communication resource from at least one of the wireless terminals over a communication link established between the at least one wireless terminal and the base station; allocating, by the base station, at least a first communication resource being primarily used in the device-to-device communication between the first wireless terminal and the second wireless terminal and at least one second communication resource being secondarily used in the device-to-device communication between the first wireless terminal and the second wireless terminal; informing, by the base station, at least one of the wireless terminals at least on the allocated first communication resource; and maintaining the established communication link between the at least one wireless terminal and the base station for transmitting information comprising at least data representing a state of an established communication channel on the allocated first communication resource between the first wireless terminal and the second wireless terminal.

The allocation of the one or more communication resources may comprise a step of selecting the first and the at least one second communication resource at least partly on basis of channel measurement information received from at least one wireless terminal in the context of the request.

The data representing a state of the established communication channel on the allocated first communication resource may comprise at least one of the following: quality data of the communication channel on the allocated first communication resource, signal strength data of adjacent communication resources to the allocated first communication resource, data describing interference experienced on the allocated first communication channel.

The information may further comprise data representing a state of the communication channel on each at least one second communication resource, wherein the data comprises at least one of the following: quality data of the communication channel on the at least one second communication resource, signal strength data of adjacent communication resources to each of the at least one second communication resource, data describing interference experienced on the at least one second communication channel. The method may further comprise: generating a prediction of interference on basis of the signal strength data of adjacent communication resources at least to the first communication resource.

The method may also comprise: instructing, by the base station, a further wireless terminal identified as a source of the interference to reduce power used in transmission in response to detection that the generated prediction of the interference exceeds a threshold.

In response to a detection that the generated prediction of the interference exceeds a threshold the method may further comprise one of the following: scheduling, by the base station, a further wireless terminal identified as a source of the interference to another time slot; reallocating a further wireless terminal identified as a source of the interference to another time slot.

Alternatively or in addition, the method may further comprise: monitoring if the quality data of the communication channel on the allocated first communication resource changes over a threshold, and in response to a detection that the quality data changes over the threshold, instructing, by transmitting a control signal over the communication link, the first wireless terminal and the second wireless terminal to perform a switchover from the first communication resource to at least one of the identified second communication resources. According to a second aspect, a base station for controlling device-to-device communication between a first wireless terminal and a second wireless terminal is provided wherein the base station comprises at least one processor; at least one memory including computer program code; and wherein the at least on memory and the computer program code configured to, with the at least one processor, cause the base station to perform: receive a request for a device-to-device communication resource from at least one of the wireless terminals over a communication link established between the at least one wireless terminal and the base station; allocate at least a first communication resource being primarily used in the device-to-device communication between the first wireless terminal and the second wireless terminal and at least one second communication resource being secondarily used in the device-to-device communication between the first wireless terminal and the second wireless terminal; inform at least one of the wireless terminals at least on the allocated first communication resource; and maintain the established communication link between the at least one wireless terminal and the base station for transmitting information comprising at least data representing a state of an established communication channel on the allocated first communication resource between the first wireless terminal and the second wireless terminal. The base station may be configured to perform the allocation of the one or more communication resources so that it comprises a step of selecting the first and the at least one second communication resource at least partly on basis of channel measurement information received from at least one wireless terminal in the context of the request. The base station may be configured to receive, the data representing a state of the established communication channel on the allocated first communication resource, at least one of the following: quality data of the communication channel on the allocated first communication resource, signal strength data of adjacent communication resources to the allocated first communication resource, data describing interference experienced on the allocated first communication channel.

The base station may also be further configured to receive information, as data representing a state of the communication channel on each at least one second communication resource, at least one of the following: quality data of the communication channel on the at least one second communication resource, signal strength data of adjacent communication resources to each of the at least one second communication resource, data describing interference experienced on the at least one second communication channel. Moreover, the base station may be configured to generate a prediction of interference on basis of the signal strength data of adjacent communication resources at least to the first communication resource.

The base station may further be configured to instruct a further wireless terminal identified as a source of the interference to reduce power used in transmission in response to detection that the generated prediction of the interference exceeds a threshold.

The base station may also be configured to, in response to a detection that the generated prediction of the interference exceeds a threshold, to perform at least one of the following: schedule a further wireless terminal identified as a source of the interference to another time slot; reallocate a further wireless terminal identified as a source of the interference to another time slot.

Alternatively or in addition, the base station may further be configured to: monitor if the quality data of the communication channel on the allocated first communication resource changes over a threshold, and in response to a detection that the quality data changes over the threshold, instruct, by transmitting a control signal over the communication link, the first wireless terminal and the second wireless terminal to perform a switchover from the first communication resource to at least one of the identified second communication resources.

Various exemplifying and non-limiting embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying and non-limiting embodiments when read in connection with the accompanying drawings.

The verbs "to comprise" and "to include" are used in this document as open limitations that neither exclude nor require the existence of unrecited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does not exclude a plurality.

BRIEF DESCRIPTION OF FIGURES

The embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings.

Figure 1 illustrates schematically an example of a communication environment in D2D communication.

Figure 2 illustrates schematically an example of a method according to an embodiment of the invention. Figure 3 illustrates schematically an example of an operation performed by a base station according to an embodiment of the invention.

Figure 4 illustrates schematically another example of an operation performed by a base station according to another embodiment of the invention.

Figure 5 illustrates schematically a still further example of an operation performed by a base station according to a still further embodiment of the invention.

Figure 6 illustrates schematically an example of a base station according to an embodiment of the invention.

DESCRIPTION OF THE EXEMPLIFYING EMBODIMENTS The specific examples provided in the description given below should not be construed as limiting the scope and/or the applicability of the appended claims. Lists and groups of examples provided in the description given below are not exhaustive unless otherwise explicitly stated.

The term "wireless terminal" is used in this disclosure to represent any wireless communication entity capable of radio communication with a cellular radio network including receiving and sending radio signals. Furthermore, the wireless terminals in this context are capable of establishing a device-to-device (D2D) connection with each other in a manner as will be described. Some non- limiting examples of the wireless terminals are mobile phones, tablets, laptop computers, modems, and so on. The wireless terminals may need a subscriber identity module in accessing to the cellular radio network.

Further, the term "base station", sometimes also referred to as a network node, radio node, e-NodeB, eNB, NB, base transceiver station, etc., represents in this context any node of a cellular radio network that is arranged to communicate radio signals with wireless terminals. The base station described here may, without limitation, be a so- called macro base station or a low power base station such as a micro, pico, femto being involved at least in radio resource management operations in a cellular radio network as well as capable of participating to D2D communication to the extent as will be described. The solution according to the present invention will now be described by referring to Figure 1 and any further figures, as will be described. The present invention relates to a solution for controlling device-to-device communication between a first wireless terminal 1 10 and a second wireless terminal 120. The controlling is at least partly performed by a base station as will be described. Additionally, there may reside one or more further wireless terminals 140 in the environment which may request to utilize or may utilize communication services provided by the base station 130. For sake of clarity, the further wireless terminals 140 are not involved as such to the D2D communication between the wireless terminals 1 10 and 120. Moreover, the term control of the device-to-device communication shall be understood in a broad manner covering control operations that may be performed towards at least one of the wireless terminals 1 10, 120 being involved in the device-to-device communication but also control operations that may be performed towards other entities, such that the further wireless terminal(s) 140 and other network node(s) if any. The present invention does not take any standpoint to an initial stage, how the wireless terminals 1 10, 120 willing to establish D2D communication have found each other, and even negotiated somehow on an establishment of the D2D communication. The starting point here is that the wireless terminals 1 10, 120 have recognized a need to establish a D2D communication.

Figure 2 illustrates schematically an example of a method according to an embodiment of the invention. In the method device-to-device communication between the first wireless terminal 1 10 and the second wireless terminal 120 is controlled by a base station 130. The method may start from a receipt 210 of a request in the base station 130. The request comprises an indication of a need for a device-to-device communication resource. The communication resource in this context refers to time-frequency resource whose allocation is at least partly managed by the base station either directly or indirectly. As a non- limiting example of the communication resource one may mention a physical layer resource blocks in LTE (Long Term Evolution) system. The request for the communication resource may be transmitted by either of the wireless terminals 1 10, 120, or by both, using any type of signaling. For example, a modified cellular uplink resource request format may be used. The signal may carry an identifier indicating that a specific connection is requested. The specific connection may e.g. refer to a reliable connection, or connection arrangement, that is requested from the base station 130. The identifier may indicate directly or indirectly that the specific connection is requested. An example of an indirect identifier may be an identifier, e.g. a Radio Network Temporary Identifier (RNTI), from a specific subspace of identifiers that are reserved for users, or terminals with subscription, allowed receiving the reliable D2D connection. Such identifiers may e.g. be negotiated by higher layer protocols. Correspondingly, an example of a direct identifier, or explicit identifier, may be an identifier residing in a specific control channel format of the request for reliable D2D communication. This may e.g. be implemented in one dedicated bit. Furthermore, the utilization of the direct and indirect identifiers may be combined in some manner. For example, for users with an identifier from a part of identifier space allowed reliable D2D, a specific information element, or a bit, in a control channel indicates a desire for reliable D2D resources. For users with identifiers outside of this space, the meaning of this information element, or bit, may be different, or it may be a dummy bit for such users. As mentioned at least one of the wireless terminals 1 10, 120 may request the time-frequency resource by connecting to the base station 130 and by providing an identifier in the request as described. The base station 130 may collect channel measurements information from one or more wireless terminals 1 10, 120 and may allocate 220 resources. According to an embodiment of the invention the base station 130 may be configured to allocate at least a first communication resource being primarily used in the device-to-device communication between the first wireless terminal 1 10 and the second wireless terminal 120 and at least one second communication resource being secondarily used in the device-to-device communication between the first wireless terminal 1 10 and the second wireless terminal 120. The selection of the first and the at least one second communication resource may be performed at least partly on basis of channel measurement information received from at least one wireless terminal in the context of the request i.e. together with the request or with a separate signaling. Advantageously, the allocation process avoids resources in time slots where sporadic high power transmissions may appear. Such sporadic channels include - but are not limited - to random access channel where other users can have uncontrollably high power. Further, the allocation process may be arranged also to avoid system information channels. Hence, the base station may be configured to avoid communication resources that overlap in time with system channels so that no interruptions are caused in the connection between the wireless terminals.

In response to the allocation of the first and at least one second communication resource the base station 130 may inform the allocated first communication resource to at least one of the wireless terminals 1 10, 120. In some embodiment of the invention the base station 130 may information both the allocated first communication resource but also the at least one second communication resource to at least one of the wireless terminals 1 10, 120. The informing may be performed by base station 130 to the both wireless terminals 1 10, 120 when the base station 130 is aware of both parties intended to take part in the D2D communication. Alternatively, the base station 130 may deliver the information to only one of the wireless terminals 1 10, 120. In such a case, the wireless terminal 1 10, 120 receiving the information from the base station 130 may be configured to deliver, e.g. by signaling, the information to the other wireless terminal 1 10, 120. The delivery of information may e.g. be performed by a signaling channel either directly between the wireless terminals 1 10, 120, or indirectly through a network node, such as the base station 130, for example.

According to an embodiment of the invention a signaling protocol may be utilized for requesting and informing on a grant of resource allocation for the D2D connection. Furthermore, the signaling protocol may be used for transmitting other information, such as information relating to a state of a communication channel and controlling information. The information may be sent over the signaling connection periodically, in response to events or upon request from BS. The communication link, i.e. the signaling connection, is referred with 150 in Figure 1 .

Furthermore, the embodiment of the invention as illustrated in Figure 2 comprises a step of maintaining 240 the established communication link 150 between the at least one wireless terminal 1 10, 120 and the base station 130. The communication link may be used for transmitting information comprising at least data representing a state of an established communication channel between the first wireless terminal 1 10 and the second wireless terminal 120 on the allocated first communication resource.

As mentioned above the method enables transmission of information comprising data representing a state of the established communication channel by maintaining the communication link 150 as described. The data representing a state of the established communication channel on the allocated first communication resource may comprise at least one of the following: quality data of the communication channel on the allocated first communication resource, signal strength data of adjacent communication resources to the allocated first communication resource, data describing interference experienced on the allocated first communication channel. Moreover, according to some embodiment of the invention the information may further comprise data representing a state of the communication channel on each at least one second communication resource, wherein the data comprises at least one of the following: quality data of the communication channel on the at least one second communication resource, signal strength data of adjacent communication resources to each of the at least one second communication resource, data describing interference experienced on the at least one second communication channel. The aim is to generate and gather information in the base station on the state of the radio environment within an area.

More specifically, the wireless terminals 1 10, 120 may be configured to measure interference at the allocated resource or resources. The measurements may be used for predicting the interference trend in those communication resources. The trend prediction may be used by BS 130 for preemptively avoiding interference increase from other users using the same time-frequency resources. The measurement performed on the wanted channel may be a Channel Quality Indicator (CQI), indicating the usability of the channel in terms of a signal-to-interference -plus-noise ratio, or a maximum achievable transmission rate. Alternatively, it may be a Reference Signal Received Power (RSRP) measurement, as examples.

The measurements may also cover signal measurements on adjacent communication resources, or other resources in the same time slot as the active D2D communication. The measurements may be based on a received Signal Strength Indicator (RSSI). For a RSSI measurement, the measuring wireless terminals 1 10, 120 may not need to know any characteristics of the potentially interfering transmitter, which may, e.g., be a further wireless terminal 140 transmitting in the resource 301 . If the identity of the interferer is known, at least on the level of a reference signal, or pilot/scrambling sequence used, a RSSI measurement may be supplemented or replaced by a RSRP measurement. The adjacent resource may be immediately adjacent to the scheduled resource i.e. the communication resource in use, or it may be any block of frequency within the same operational band in the same time slot as the communication resource in use.

The adjacent resource measurements may be used for identifying the trend of interference generation on those resources. The predicted interference level change may be used by base station 130 and the wireless terminals 1 10, 120 involved in D2D communication for taking preemptive link protection measures.

The same set of measurements may also be utilized to detect and predict changes in the channel conditions e.g. due to mobility or changes in the environment. In that case it may be beneficial to measure both CQI and RSRP on the wanted channel.

The prediction of the interference trend may be partially performed in the D2D subsystem and partially in the base station, for example. The wireless terminals 1 10, 120 involved in the D2D communication, or at least one of them, may report measurement values (or increasing interference indicators) to the base station 130. For predicting and reporting the interference, predefined thresholds may be used by the wireless terminals 1 10, 120, or thresholds configured by higher layers. Wireless terminal 1 10, 120 CQI and adjacent channels signal levels (e.g. RSSIs), or threshold overflow indicators, may be reported by the at least one of the wireless terminals 1 10, 120 periodically, upon request by base station 130, or in an event based manner. In the latter method, a trigger for reporting would be an observed trend in increased received power on adjacent channels, and/or deteriorating CQI, e.g. observed by crossing a threshold. Preferably, a measurement report indicating increased interference indicates the frame/subframe and frequency resource block where growing interference was observed. Results from multiple adjacent blocks (203) may be aggregated for reporting. For this, signaling methods known in the art, based on bit maps, binary trees, maximum and or minimum values and differences, relative or absolute resource indications, and so on, may be used. As said the wireless terminals 1 10, 120 being the parties in device-to-device communication may inform the base station 130 of interference trends on adjacent frequency resources at least to the one communication resource that is in use, but possibly also for any secondary communication resource if the information on the secondary communication resource is provided to at least one of the wireless terminals 1 10, 120. The base station knows scheduling information in the network. According to an embodiment of the invention, the base station may couple the scheduling information with the interference change/overflow indications received from the wireless terminal or wireless terminals 1 10, 120. Based on the information of frame and frequency resource block in such an indication, the base station 130 may identify a further wireless terminal 140 potentially causing problems to the D2D communication. Problems may be caused by a further wireless terminal 140 transmitting in uplink moving closer to a D2D communication party 1 10, 120, or a further wireless terminal 140 transmitting in downlink receiving highly directive transmission from the base station 130 being scheduled in an adjacent resource, or the movement of such a further wireless terminal 140 causing base station 130 downlink beamforming to change so that an interfering beam is pointed towards a D2D party 1 10, 120. Although this transmission would be on an adjacent resource block, there may be interference leaking to the D2D communication resource due to imperfect filtering.

As already discussed, one advantage of the present invention is that it enables at least one wireless terminal 1 10, 120 being involved in the D2D communication to measure interference from/to unidentified transmitters, such as further wireless terminals 140. Generic measurements may be used. By reporting an indication of the interference, and the time/frequency resource where it was measured the base station 130 may use its scheduling information to find from which further wireless terminal 140 this transmission is from (in uplink) or to (in downlink). This enables the base station 130 to initiate operations to mitigate the interference to the D2D connection, as will next be described by referring to Figures 3, 4 and 5. Further, according to an embodiment of the invention the base station 130 may be configured to initiate control actions by means of which it is possible, at least partially, avoid interference caused at least to the communication channel used in device-to-device communication.

According to a first embodiment the base station 130 is configured to control transmission power of the at least one further wireless terminal 140. In other words, the base station 130 may control transmission power used in one or more adjacent communication resources. This is illustrated schematically in Figure 3 that discloses the time-frequency communication resource allocation at certain instant of time. The D2D communication resource is referred with 310 and the communication resource used for communication between a further wireless terminal 140 and a base station 130 is referred with 320. In response to RSSI measurement, for example, the base station 130 may conclude that the communication resource reserved for the further wireless terminal 140 causes interference to the D2D communication resource which further wireless terminal is identified e.g. in the manner as described. As a result, the base station 130 may apply power control and may instruct (arrow in Figure 3) the interfering further wireless terminal 140 to reduce the power in its resource 330.

In another non-limiting embodiment, as illustrated schematically in Figure 4, the base station may schedule the potentially harmful further wireless terminal 140 in another time slot in further communication, or reallocate the further wireless terminal 140 to another time slot, if the further wireless terminal 140 has a semi-persistent type of resource allocation. This is illustrated in Figure 4 wherein the communication resource 320 of the further wireless terminal 140 is scheduled in another time slot (referred with 420 in Figure 4). In case of reallocation the base station 130 may identify which further wireless terminal 140 was using the adjacent resource 320 during the reported or identified increased interference event, and reschedules the further wireless terminal 140 to use a communication resource 410. The new resource may be selected in a manner to reduce the interference to primary D2D time-frequency communication resource 310, and potentially also to the secondary communication resource (not illustrated in Figure 4), either by being at a sufficient frequency separation, or orthogonal in time domain. The advantage of this embodiment is that if the proposed D2D method is used in a LTE or LTE-type system, where most cellular traffic is scheduled on a subframe-by- subframe basis, such a scheduling in other resources would be completely transparent to the potentially interfering further wireless terminal and would not mix with other Radio Resource Management algorithms, such as power control. Figure 5 illustrates schematically a solution for reallocating the D2D communication to at least one second communication resource 510 allocated for the D2D communication in response to the original request. In this embodiment at least one of the wireless terminals 1 10, 120 being involved in D2D communication may be configured to continuously measure and exchange channel quality information (CQI). If a sudden change in link quality in initial communication resource 310 is observed, the wireless terminals 1 10, 120 being involved in the D2D communication may be switched to use the second communication resource 510, or one of the second communication resources, pre-allocated for the D2D communication in the method step 220. After the reallocation the previously standby resource 510 becomes primary time-frequency communication resource 310. The original primary communication may be released (referred with 520 on resource allocation scheme on right in Figure 5). Alternatively, it may be switched to be the secondary communication resource for a time being and it is monitored if the interference of it gets smaller. Furthermore, after switching the wireless terminals 1 10, 120 being involved in D2D communication have time to inform the base station 130 of changed conditions and may initiate actions for improving the conditions in initial communication resource 520, especially if it is kept reserved. Alternatively or in addition, acquisition of at least one new secondary time-frequency resource may be initiated e.g. with a request towards the base station 130. It is worthwhile to mention that the secondary communication resource may also be utilized for time-frequency diversity transmission.

Figure 6 illustrates schematically a base station 130 according to one or more embodiments herein for controlling device-to-device communication between a first wireless terminal 1 10 and a second wireless terminal 120 in a manner as described in the context of describing the embodiments and aspects of the method.

The base station 130 comprises one or more processors 610, one or more memories 620 and one or more communication interfaces 630 which entities may be at least communicatively coupled to each other with e.g. a data bus. The communication interface 630 comprise necessary hardware for communication with the wireless terminals 1 10, 120, 140 as well as any network nodes residing in an access network or in core network. The communication interface may be at least partly controlled by the one or more processors 610 e.g. by executing portions of computer program code stored in the one or more memories 620, and in such manner enable the communication of the base station with the wireless terminals 1 10, 120, 140.

Furthermore, the base station 130 may be configured to receive a request for a device-to-device communication resource from at least one of the wireless terminals 1 10, 120 over a communication link established between the at least one wireless terminal 1 10, 120 and the communication interface 630 of the base station 130. The processor 610 may be configured to allocate at least a first communication resource being primarily used in the device-to-device communication between the first wireless terminal 1 10 and the second wireless terminal 120 and at least one second communication resource being secondarily used in the device-to-device communication between the first wireless terminal 1 10 and the second wireless terminal 120. Furthermore, the base station 130 may be configured to inform, over the communication interface 630, at least one of the wireless terminals 1 10, 120 on the allocated first communication resource. The base station 130 may also be configured to maintain the established communication link between the at least one wireless terminal 1 10, 120 and the base station 130 for transmitting information comprising at least data representing a state of an established communication channel on the allocated first communication resource between the first wireless terminal 1 10 and the second wireless terminal 120.

The base station may also be configured, e.g. by executing portions of computer program code stored in the memory 620 by the processor 610, to perform the other steps and processes as described in the context of the method description above. The specific examples provided in the description given above should not be construed as limiting the applicability and/or the interpretation of the appended claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.

Claims

WHAT IS CLAIMED IS:

1 . A method for controlling device-to-device communication between a first wireless terminal (1 10) and a second wireless terminal (120) by a base station (130), the method comprising: - receiving (210), in the base station (130), a request for a device-to-device communication resource from at least one of the wireless terminals (1 10, 120) over a communication link established between the at least one wireless terminal (1 10, 120) and the base station (130),

- allocating (220), by the base station (130), at least a first communication resource being primarily used in the device-to-device communication between the first wireless terminal (1 10) and the second wireless terminal (120) and at least one second communication resource being secondarily used in the device-to-device communication between the first wireless terminal (1 10) and the second wireless terminal (120), - informing (230), by the base station (130), at least one of the wireless terminals (1 10, 120) at least on the allocated first communication resource, and

- maintaining (240) the established communication link between the at least one wireless terminal (1 10, 120) and the base station (130) for transmitting information comprising at least data representing a state of an established communication channel on the allocated first communication resource between the first wireless terminal (1 10) and the second wireless terminal (120).

2. The method as claimed in claim 1 , wherein the allocation of the one or more communication resources comprises a step of selecting the first and the at least one second communication resource at least partly on basis of channel measurement information received from at least one wireless terminal (1 10, 120) in the context of the request.

3. The method of any of the preceding claims, wherein the data representing a state of the established communication channel on the allocated first communication resource comprises at least one of the following: quality data of the communication channel on the allocated first communication resource, signal strength data of adjacent communication resources to the allocated first communication resource, data describing interference experienced on the allocated first communication channel.

4. The method as claimed in claim 3, wherein the information further comprises data representing a state of the communication channel on each at least one second communication resource, wherein the data comprises at least one of the following: quality data of the communication channel on the at least one second communication resource, signal strength data of adjacent communication resources to each of the at least one second communication resource, data describing interference experienced on the at least one second communication channel.

5. The method as claimed in one of the claims 3 or 4, wherein the method further comprises: generating a prediction of interference on basis of the signal strength data of adjacent communication resources at least to the first communication resource.

6. The method as claimed in claim 5, wherein the method further comprises: instructing, by the base station (130), a further wireless terminal (140) identified as a source of the interference to reduce power used in transmission in response to detection that the generated prediction of the interference exceeds a threshold.

7. The method as claimed in claim 5, wherein in response to a detection that the generated prediction of the interference exceeds a threshold the method further comprises one of the following: scheduling, by the base station, a further wireless terminal (140) identified as a source of the interference to another time slot; reallocating a further wireless terminal (140) identified as a source of the interference to another time slot.

8. The method as claimed in claim 3, wherein the method further comprises:

- monitoring if the quality data of the communication channel on the allocated first communication resource changes over a threshold, and

- in response to a detection that the quality data changes over the threshold, instructing, by transmitting a control signal over the communication link, the first wireless terminal (1 10) and the second wireless terminal (120) to perform a switchover from the first communication resource to at least one of the identified second communication resources.

9. A base station (130) for controlling device-to-device communication between a first wireless terminal (1 10) and a second wireless terminal (120), the base station comprising at least one processor (610); at least one memory (620) including computer program code; the at least on memory (620) and the computer program code configured to, with the at least one processor, cause the base station (130) to perform: receive a request for a device-to-device communication resource from at least one of the wireless terminals (1 10, 120) over a communication link established between the at least one wireless terminal (1 10, 120) and the base station (130), allocate at least a first communication resource being primarily used in the device-to-device communication between the first wireless terminal (1 10) and the second wireless terminal (120) and at least one second communication resource being secondarily used in the device-to-device communication between the first wireless terminal (1 10) and the second wireless terminal (120), inform at least one of the wireless terminals (1 10, 120) at least on the allocated first communication resource, and maintain the established communication link between the at least one wireless terminal (1 10, 120) and the base station (130) for transmitting information comprising at least data representing a state of an established communication channel on the allocated first communication resource between the first wireless terminal (1 10) and the second wireless terminal (120).

10. The base station (130) as claimed in claim 9, wherein the base station (130) is configured to perform the allocation of the one or more communication resources so that it comprises a step of selecting the first and the at least one second communication resource at least partly on basis of channel measurement information received from at least one wireless terminal (1 10, 120) in the context of the request.

1 1 . The base station (130) as claimed in any of the claims 9-10, wherein the base station (130) is configured to receive, the data representing a state of the established communication channel on the allocated first communication resource, at least one of the following: quality data of the communication channel on the allocated first communication resource, signal strength data of adjacent communication resources to the allocated first communication resource, data describing interference experienced on the allocated first communication channel.

12. The base station (130) as claimed in claim 1 1 , wherein the base station (130) is further configured to receive information, as data representing a state of the communication channel on each at least one second communication resource, at least one of the following: quality data of the communication channel on the at least one second communication resource, signal strength data of adjacent communication resources to each of the at least one second communication resource, data describing interference experienced on the at least one second communication channel.

13. The base station (130) as claimed in any of the claims 1 1 or 12, wherein the base station (130) is further configured to generate a prediction of interference on basis of the signal strength data of adjacent communication resources at least to the first communication resource.

14. The base station (130) as claimed in claim 13, wherein the base station (130) is further configured to instruct a further wireless terminal (140) identified as a source of the interference to reduce power used in transmission in response to detection that the generated prediction of the interference exceeds a threshold.

15. The base station (130) as claimed in claim 13, wherein the base station (130) is configured to, in response to a detection that the generated prediction of the interference exceeds a threshold, to perform at least one of the following: schedule a further wireless terminal (140) identified as a source of the interference to another time slot; reallocate a further wireless terminal (140) identified as a source of the interference to another time slot.

16. The base station (130) as claimed in claim 1 1 , wherein the base station is further configured to:

- monitor if the quality data of the communication channel on the allocated first communication resource changes over a threshold, and

- in response to a detection that the quality data changes over the threshold, instruct, by transmitting a control signal over the communication link, the first wireless terminal (1 10) and the second wireless terminal (120) to perform a switchover from the first communication resource to at least one of the identified second communication resources.