DIRECT COMMUNICATION BETWEEN MOBILE RADIO COMMUNICATION DEVICES
WIPO Patent Application WO/
The present invention provides for a wireless communications method and related system and wireless terminal devices arranged for communication between first (304, 404) and second (306, 408) wireless terminal devices by way of direct communication, for example by way of a D2D link in a network environment, the method and system and, as appropriate, devices, being arranged to provide for the delivery of link-quality parameter information from at least one of the two terminal devices to the network for communications interaction by the network with communication between for the two terminals in direct communication.
Inventors:
PANAITOPOL, Dorin (The Imperium Imperial Way, Reading, Berkshire, RG20TD, GB)
Application Number:
Publication Date:
10/02/2014
Filing Date:
12/27/2013
Export Citation:
NEC CORPORATION (7-1 Shiba 5-chome, Minato-ku Tokyo, 01, 10880, JP)
International Classes:
H04W92/18; H04W28/18; H04W52/38
View Patent Images:
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Domestic Patent References:
Other References:
INTEL: "ProSe Use Case for Unidirectional D2D Communication", 3GPP TSG-SA WG1 MEETING #57 SL- February -02-17), pages 1 - 3, XP, Retrieved from the Internet
TEXAS INSTRUMENTS: "Scenarios and Requirements for Device to Device Proximity Services", 3GPP TSG-RAN WG1 MEETING #72 RL- February -02-01), pages 1 - 2, XP, Retrieved from the Internet
See also references of EP
Attorney, Agent or Firm:
IEIRI, Takeshi (HIBIKI IP Law Firm, Asahi Bldg. 10th Floor 3-33-8, Tsuruya-cho, Kanagawa-ku, Yokohama-sh, Kanagawa 35, 22108, JP)
A wireless communications method for communication between first and second wireless terminal devices arranged to communicate by direct communication by way of a direct link in a network environment, the method including the step of delivering direct link-quality parameter information from at least one of the two terminal devices to the network for interaction by the network with communication between the two terminals in direct
communication.
A method as claimed in Claim 1, wherein the said interaction by the network comprises network control of communication between the first and second terminal devices. [Claim 3]
A method as claimed in Claim 2, wherein the network control comprises at least one of control and/or resource allocation and/or transmission parameters.
A method as claimed in Claim 3, wherein the network control exerts control for at least one of increasing, decreasing or setting a range, maximum or other imposed value.
A method as claimed in Claim 2,3 or 4, wherein said at least one wireless terminal delivers a signal to the network comprising an indication of quality of wireless direct link between the first and second terminals, and the said wireless terminal further receives a wireless command signal for control of the link-quality parameter in response to the command signal.
A method as claimed in any of Claims 1 to 5, wherein the network control is provided by way of a control loop.
A method as claimed in Claim 6, wherein the said control loop comprises a slow outer loop.
A method as claimed in Claim 1, wherein the said interaction by the network comprises a network planning procedure.
A method as claimed in Claim 8, wherein the said interaction by the network is for the purpose of Minimization of Drive Tests.
[Claim 10]
A method as claimed in any of Claims 1 to 9, wherein at least one of the first and second terminal devices comprises a mobile radio communications network User Equipment. [Claim 11]
A method as claimed in any of Claims 1 to 10, and comprising a device to device communications method.
[Claim 12]
A method as claimed in any of Claims 1 to 9 wherein at least one of the terminal devices comprises a Low Power Node.
[Claim 13]
A method as claimed in any of Claims 1 to 12, wherein the said direct link-quality parameter information comprises terminal device transmission information.
[Claim 14]
A method as claimed in any of Claims 1 to 13, wherein the said direct link-quality parameter information comprises terminal reception information.
[Claim 15]
A method as claimed in any of Claims 1 to 14, wherein the said direct linkquality parameter information comprises Quality of Service statistics. [Claim 16]
A method of operation within a wireless communications terminal device arranged for direct communication with a further wireless communications terminal device by way of a direct link in a network environment, the method including the step of delivering link-quality parameter information from the said wireless communications terminal device to the network for interaction by the network with communication between the terminals in the said direct communication.
[Claim 17]
A method as claimed in Claim 16, wherein the said wireless communications terminal device delivers a signal to the network comprising an indication of quality of wireless link between the first and second terminals, and the said wireless communications terminal further receives a wireless command signal for control of the link quality parameter in response to the command signal.
[Claim 18]
A method as claimed in Claim 16 or 17, wherein the said wireless communications tenninal device comprises a Low Power Node. [Claim 19]
A method as claimed in Claim 16 or 17, wherein the said wireless communications terminal device comprises a mobile radio communications network User Equipment.
[Claim 20]
A method as claimed in any of Claims 16 to 19, wherein the said link- quality parameter information comprises at least one of terminal device transmission information and terminal device reception information.
[Claim 21]
A method as claimed in any of Claims 16 to 19, wherein the said link- quality parameter information comprises Quality of Service statistics.
[Claim 22]
A method as claimed in any of Claims 1 to 21, wherein device to device communication is provided by way of a 3GPP air interface.
[Claim 23]
A method as claimed in any of Claims 1 to 21, wherein the device to device communication is provided by non-3 GPP technology.
[Claim 24]
A method as claimed in Claim 23, wherein the device to device communication is provided by way one of a WiFi, FlashLinkQ, WiMax or Bluetooth link.
[Claim 25]
A wireless communications system comprising first and second wireless terminal devices arranged for direct communication by way of a link in a network environment, the system being arranged for delivery of link-quality parameter information from at least one of the two terminal devices to the network for interaction by the network with the communication between the said first and second wireless terminal devices in direct communication.
[Claim 26]
A system as claimed in Claim 25, wherein the said communications interaction by the network comprises network control of communication between the first and second terminal devices.
[Claim 27]
A system as claimed in Claim 26, wherein the network control comprises at least one of power control and/or resource allocation.
[Claim 28]
A system as claimed in Claim 26 or 27, wherein the said at least one wireless terminal device is arranged to deliver a signal to the network comprising an indication of quality of wireless link between the first and second terminals, and the said at least one wireless terminal is further arranged to receive a wireless command signal for control of the link-quality parameter in response to the command signal.
[Claim 29] A system as claimed in Claim 26, 27 or 28, wherein the network includes at least one base station connected to a Mobile Management Entity, the Mobile Management Entity being arranged for control of the direct communication.
[Claim 30]
A system as claimed in any of Claims 25, 26, 27 , 28 or 29, wherein the network control is provided by way of a control loop.
[Claim 31]
A system as claimed in Claim 30, wherein the said control loop comprises a slow outer loop.
[Claim 32]
A system as claimed in Claim 25, wherein the said interaction by the network comprises a network planning procedure.
[Claim 33]
A system as claimed in Claim 32, wherein the said interaction by the network is for the purpose of Minimization of Drive Tests.
[Claim 34]
A system as claimed in any of Claims 25 to 33, wherein at least one of the first and second terminal devices comprises a mobile radio communications network User Equipment.
[Claim 35]
A system as claimed in any of Claims 25 to 34, and arranged for device to device communication.
[Claim 36]
A system as claimed in any of Claims 25 to 35, wherein at least one of the terminal devices comprises a Low Power Node.
[Claim 37]
A system as claimed in any of Claims 25 to 36, wherein the said link-quality parameter information comprises terminal device transmission information.
[Claim 38]
A system as claimed in any of Claims 25 to 37, wherein the said link- quality parameter information comprises terminal reception information.
[Claim 39]
A system as claimed in any of Claims 25 to 38, wherein the said link- quality parameter information comprises Quality of Service statistics.
[Claim 40]
A wireless communications terminal device arranged for direct communication with a further wireless communications terminal device by way of a link in a network environment, the said wireless communications terminal device being arranged to deliver link-quality parameter information to the network for interaction by the network with the said direct communication.
[Claim 41]
A terminal device as claimed in Claim 40 and arranged to deliver a signal to the network comprising an indication of quality of wireless link between the first and second terminals, and further arranged to receive a wireless command signal for control of the link-quality parameter in response to the command signal.
[Claim 42]
A terminal device as claimed in Claims 40 or 41, and comprising a Low Power Node.
[Claim 43]
A terminal device as claimed in Claim 40 or 41, and comprising a mobile radio communications network User Equipment. [Claim 44]
A terminal device as claimed in any of Claims 40 to 43, wherein the said link-quality parameter information comprises at least one of terminal device transmission information or terminal device reception information. [Claim 45]
A terminal device as claimed in any of Claims 40 to 44, wherein the said link quality parameter information comprises Quality of Service statistics. [Claim 46]
A terminal device as claimed in any of Claims 40 to 45, and arranged for device to device communication.
Description:
DESCRIPTION
Title of Invention
DIRECT COMMUNICATION BETWEEN MOBILE RADIO COMMUNICATION DEVICES
Technical Field
The present invention relates to a direct communication link between two wireless terminals, such as mobile radio communication devices, and in particular to such devices performing Device to Device (D2D) communication.
Background Art
It is currently provided that two wireless terminals, examples of which according to several modern communications standards are referred to as a number of User Equipment (UE) can communicate with one another directly by means of D2D communication, and which of course is provided in addition to normal network connectivity. It has been suggested that valuable services could be provided by Third Generation Partnership Project (3 GPP) wireless communication systems based on UEs being in proximity to each other. Such services could include Public Safety services and non-Public- Safety services that potentially would be of interest to operators and users.
For example, 3 GPP technical report RP- 122009, by Huawei and HiSilicon is entitled "Evaluation requirements for D2D", 3 GPP publication FS_ProSe, TR 22.803, and SP-120456 - MoU between TETRA & Critical Communications Association (TCCA) & the National Public Safety Telecommunications Council), and SI -121247 (TCCA).
Also, 3 GPP publication Rl-130133 (ZTE- "Evaluation methodology for D2D discovery") proposes that D2D-based proximity services (D2D ProSe) could be realized within or without 3 GPP Long-term Evolution (LTE) network coverage, and in both cases detection signals would be used by UEs for D2D proximity direct discovery without position information.
There is currently a need for improvements relating to three technical aspects of D2D communications: D2D communication and signalling (including PHY and MAC layers, control layer and protocol design); and mitigation of the effects of noise and interference. Discussions below are concerned mainly with the last two of these technical aspects.
The physical environment in which wireless communication terminals are located changes over time. This can be due to changes in position, interference from other base stations or other terminals, power of received signals, distance between terminals, multipath attenuation etc. Also, D2D communication may affect cellular communication by interference of a signal used in the direct (D2D) communication link with signal(s) used in the ce and/or a D2D communication link may affect other D2D communication links by interference of a signal used in the direct (D2D) communication link with signal(s) used in such other D2D communication links.
Currently, the direct link (D2D link) between two terminals is established and maintained by means of signals transmitted between the two terminals and control of the quality of the direct link between the terminals is disadvantageously limited.
The present invention seeks to provide for wireless communications methods and related communications systems and terminal devices having advantages over known such methods, systems and terminals.
Citation List
Non Patent Literature
NPL 1: "Evaluation requirements for D2D" 3 GPP technical report RP- 122009, by Huawei and HiSilicon.
NPL 2.-3GPP publication FS ProSe.
NPL 3:3GPP publication TR 22.803.
NPL 4:3GPP publication SP- 120456.
NPL 5:3GPP publication Sl-121247 (TCCA).
NPL 6:3GPP publication Rl-130133 ZTE- "Evaluation methodology for D2D discovery" NPL 7:3GPP publication TR 36.932.
Summary of Invention
Technical Problem [0010]
Currently, the direct link (D2D link) between two terminals is established and maintained by means of signals transmitted between the two terminals and control of the quality of the direct link between the terminals is disadvantageously limited.
Solution to Problem
According to one aspect of the invention there is provided a wireless communications method for communication between first and second wireless terminal devices arranged to communicate by direct communication by way of a direct link in a network environment, the method including the step of delivering direct-link-quality parameter information from at least one of the two terminal devices to the network for interaction by the network with
communication between the two terminals in direct communication.
The invention can advantageously employ the sending of device to device
measurements/statistics associated with one link and one wireless terminal device in an efficient manner to the network for handling.
The said interaction by the network be employed as required but in particular can comprise network control of communication between the first and second terminal devices, or for example can comprise network planning procedures such as for the purpose of Minimization of Drive Tests.
The said terminal device can comprise any appropriate device such as a wireless network UE, or for example a Low Power Node.
Further, the link-quality parameter information can comprise terminal device
transmission information and /or terminal device reception information.
Also, the said link-quality parameter information comprises Quality of Service statistics.
According to another aspect of the present invention there is provided a method of operation within a wireless communications terminal device arranged for direct communication with a further wireless communications terminal device by way of a link in a network environment, the method including the step of delivering link-quality parameter information from the said wireless communications terminal device to the network for interaction by the network with communication between the terminals in the said direct communication.
As will be appreciated, the said wireless communications terminal device can be arranged to deliver a signal in accordance with the general wireless communications method outlined above.
Further, all aspects of the present invention can involve communication provided by way of a 3 GPP air interface, or alternatively provided by non-3 GPP technology such as, or example, but not limited to, a Wi-Fi, FlashLinkQ, WiMax or Bluetooth link.
According to yet a further aspect of the present invention, there is provided a wireless communications system comprising first and second wireless terminal devices arranged for direct communication by way of a link in a network environment, the system being arranged for delivery of link-quality parameter information from at least one of the two terminal devices to the network for interaction by the network with the communication between the said first and second wireless terminal devices in direct communication.
The system can be arranged to operate in accordance with any one or more of the features of the methods defined and described herein.
That is, in particular, in the system the said at least one wireless terminal device can be arranged to deliver a signal to the network comprising an indication of quality of wireless link between the first and second terminals, and the said at least one wireless terminal is further arranged to receive a wireless command signal for control of the link-quality perimeter in response to the command signal.
Advantageously, the network control can provided by way of a closed control loop, which, if required, can comprise a slow outer loop. The control loop can also allow for the collection of current Tx/Tx parameters and, if required, give a maximum, range or some other target limit.
According to still a further aspect of the present invention there is provided a wireless communications terminal device arranged for direct communication with a further wireless communications terminal device by way of a link in a network environment, the said wireless communications terminal device being arranged to deliver link-quality parameter information to the network for interaction by the network with the said direct communication.
Again, the operability of such a device can be consistent with one or more of the features of the system and methods outlined above.
In particular the present invention finds particular use within a D2D communications environment.
The invention advantageously identifies that D2D power control and or resource allocation and/or other transmission and reception parameters (such as coding scheme, number of retransmissions, etc.) can be performed by a cellular wireless network, and doing so can reduce interference to other user and/or a number of network equipment by controlling signals transmitted in a D2D link.
As will therefore be appreciated, the invention proposes that control of the quality of a direct communication link between two wireless terminals be achieved by way of part of a communication network connected to at least one of the two wireless terminals. Accordingly, in a general sense, apparatus, systems and methods disclosed herein are arranged to allow for network control of the quality of the direct link.
Also, it should be appreciated that link-quality parameters can be Tx (e.g power) and Rx (e.g. BLER). In particular Quality is not to be considered only QoS, because Tx power is not a QoS parameter. For the control "slow" loop, not only current values (power, BLER,
retransmissions) but also control values (generally speaking a target, a max, a range etc) should advantageously be sent.
Further, the commands or the measurement reports can be triggered, or event based, or periodical.
The above and further features and aspects of the invention and are explained in more detail, by way of illustration only, in the following detailed description of embodiments of the invention and with reference to the accompanying drawings.
Advantageous Effects of Invention
The present invention can provide for wireless communications methods and related communications systems and terminal devices having advantages over known such methods, systems and terminals.
Brief Description of Drawings
Fig. 1 is a simplified representation of a network arrangement of a base station and plural wireless com
Fig. 2 is a simplified representation of a network arrangement of plural wireless communication terminals which can each transmit a beacon signal for indic [Fig. 3]
Fig. 3 is a simplified schematic representation of a base station in communication with a wireless terminal, and another wireless terminal which is out of coverage [Fig. 4]
Fig. 4 is a simplified schematic representation of a base station in communication with a wireless terminal, and another wireless terminal which is out of coverage of the base station but within coverage of
Fig. 5 is a simple diagram showing different possible combinations of inputs and outputs of an algorithm for controlling a link quality parameter of a D2D link via a base
Fig. 6 is a respective flow diagram illustrating the algorithm at a high level according to respective possible i
Fig. 7 is a respective flow diagram illustrating the algorithm at a high level according to respective possible i
[Fig. 8] Fig. 8 is a respective flow diagram illustrating the algorithm at a high level according to respective possible i
Fig. 9 is an example of a Message Sequence Chart (MSC) for control of a quality link parameter of an Intra-Cell D2D link.
Fig. 10 is an envisaged Message Sequence Chart (MSC) for control of a quality link parameter of an Inter-Cell D2D
Fig. 11 is an envisaged Message Sequence Chart (MSC) for control of a quality link parameter of an Out-of-Coverage D2D link, where one of the wireless terminals is out of covera
Fig. 12 is a graph showing how number of retransmissions can affect BLER & SINR; [Fig. 13]
Fig. 13 is a time/frequency grid representing an example of MCS & RE (Resource Element) resource allocation performed by an eNB under good si
Fig. 14 is a time/frequency grid representing an example of MCS & RE (Resource Element) resource allocation performed by an eNB under poor si
Fig. 15 is a flow diagram representing a further arrangeme
Fig. 16 illustrates an embodiment that includes the use of a so-called Low Power N [Fig. 17]
Fig. 17 illustrates an alternative embodiment to that of Fig. 16;
Fig. 18 is a schematic representation of a UE emb
Fig. 19 is a schematic representation of a UE according to a further asp
Fig. 20 is a schematic representation of a network node according to a further embodiment of the invention. Description of Embodiments
Turning first to Fig. 1, there is provided a simplified representation of part of a cellular mobile radio communications network including a base station 102 of a cell and arranged to communicate with at least one of plural wireless communication terminals 104, 106 of the type commonly referred to as User Equipment (UE) and which can each transmit a beacon signal 108 for indicating their presence and can also receive and detect such a beacon signal 108 and thereby discover nearby wireless terminals. In this example, UEs 104 are in communication with the base station 102, but UEs 106 may not be in communication with the base station. In particular in this illustrated example, the UE 104 shown left of base station 102 is a legacy device, whereas the UE 104 to the right of the base station 102 is capable of measuring/receiving a beacon from one of the other UEs 106 as noted. Both of the aforementioned UEs 104 and 106 comprise enhanced UEs having potential use for UE-R transmission and D2D purposes.
Fig. 2 is a simplified representation of plural wireless communication terminals 106 spaced from one another but proximal to each other, which can each transmit a beacon signal 108 for indicating their presence and can receive and detect such a beacon 108 and thereby discover nearby wireless terminals 106. In this example, the terminals perform discovery without interacting with a base station and independent of receiving any signal from a base station.
Possible scenarios are now explained with reference to Fig. 3 and Fig. 4, in which an aspect of the present invention can be employed. In particular, detail regarding the use of the link quality measurements/ statistics is provided further below.
Fig. 3 is a simplified schematic representation of a cellular network arrangement employing a base station 302 and which is in communication with UE 304. Another UE 306 is illustrated and which is out of coverage of the base station 302, that is UE 306 cannot establish or maintain a communication link with the base station 302 because the physical environment of the link is adverse, for example the distance to the base station, and thus the path attenuation between the base station and UE 306 is so large that UE 306 cannot receive and decode a signal transmitted by the base station 302, or vice versa.
In this scenario, where one 306 of the UEs is out-of-coverage, UE 304 can nevertheless perform Device-to-Device (D2D) communication with the out-of-service UE 306 under network control, because the network control can take place through, or via, UE 304 by means of signalling between the wireless terminal 304 and the base station 302.
Fig. 4 is another simplified schematic representation of a cellular network arrangement (inter-cell D2D scenario) including a base station 402 in communication with a UE 404.
Another UE 408 is illustrated which is out of coverage of the base station 402. However, UE 408 is within coverage of another base station 403. The two base stations 402, 403 are in communication with each other via a network connection as indicated by double-ended arrow 410, and in this manner the two base stations 402, 403 can therefore provide a connection between the two UEs 404, 408 by way of the network connection 410. In the figure, the network connection 410 is via an 'X2 interface' directly between the base stations. However, the connection could equally be via another network entity common to the base stations 402, 403. For example, the base stations may both be connected to a common mobility management entity (MME) and in such a scenario D2D control would be performed by the MME.
In this inter-cell D2D scenario, the UE 404 can initiate and control D2D communication with UE 408 under network control. Furthermore, UE 408 can initiate and control D2D
communication with UE 404 under network control, because the network control can be achieved by way of UE 408 and base station 403.
Thus, one of the UEs initiates and controls the D2D link in order to communicate with the other UE via the D2D link and to maintain good or acceptable communication under different D2D link conditions, without interfering unduly with other UEs or network equipment with which it not in communication. The UE achieves this whilst not consuming more resources than required, such resources including power consumption of the UE, and resource block(s) (RB) used by the UE.
In another arrangement (comprising an intra-cell D2D scenario, not illustrated), similar to that shown in Fig. 4, each of the two UEs could be within coverage of the same base station 402 which can then provide a connection between the two terminals 404, 408 without routing any signal from either of the wireless terminals via the network to another base station. In this further arrangement, and comprising an "intra-cell" scenario, either UE 404 or UE 408 can initiate and control the D2D communication.
[0043] According to this intra-cell scenario, according to one variant both of the two UEs are within coverage of, and may be controlled by, the same base station e.g. eNB. Example signalling for this variant is illustrated in Fig. 9, which is described in further detail below.
According to another variant of the intra-cell scenario, only one of the UEs is controlled by the base station. Operation of this other variant would be similar to that of the arrangement illustrated in Fig. 3, and example signalling according to this other variant is illustrated in Fig. 11, which is described in further detail below.
Fig. 5 is a schematic diagram showing different possible combinations and alternatives, with respect to inputs and outputs of the algorithm ("ALGO"). With reference to Fig. 3 and Fig. 4, the diagram in Fig. 5 shows different possible inputs and outputs of the algorithm when the algorithm is used by the wireless terminal 304, 404 (UE1) to control, via a "slow outer loop", a direct wireless link between the wireless terminal 304, 404 and the other wireless terminal 306, 408 (UE2), via the wireless terminal 304, 404. With reference to Fig. 4, the same diagram of Fig. 5 applies to using the link control algorithm to control, via a "slow outer loop", the direct wireless link between the wireless terminal 408 and the other wireless terminal 404 (UEl) via the other wireless terminal 408.
D2D link quality measurements and/or statistics may include transmission (Tx) and reception (Rx) D2D statistics of two devices (wireless terminals) involved in communications via a D2D link, and may be sent to the network for the purposes of network control of the D2D wireless link and/or MDT (Minimization of Drive Tests).
During MDT tests, the network obtains performance statistics during a so-called 'drive test' during which a UE is used as a testing means while it is deployed in one or more locations in the network coverage area. The one or more locations typically include multiple locations along a drive route along which the UE is transported for example in a vehicle.
Control of the D2D link by the network is possible because the network has a global view of the status of various devices in the network. For example for the inter-cell scenario described above in relation to Fig. 4, the base station 402 knows when UE resending information is redundant and affects Quality of Link (QoL) of D2D and the base station 402 can therefore decide which link is bad and how to control UEl transmission (Tx) and UE2 reception (Rx). Similarly, for intra-cell scenario the base station controls both UEl and UE2 transmissions (Tx) and reception (Rx). This would be also the case for an out-of-coverage scenario.
On the other hand, and if required, the statistics can optionally be reported only for MDT usage (e.g. network planning). In this case the network does not need to send control commands, but it will use such statistics for (further) planning purposes.
The "Fast" Inner Loop and "Slow" Outer Loop can be used together for control of one or more D2D quality-of-link parameter. The principle of such a double-loop is as follows:
a "slow" loop is used for D2D resource allocation, and also transmission and reception parameters under network control and
a "fast" loop is used for link adaptation of D2D to radio conditions which could be limited to the allocated resources provided by the first "slow" loop.
The "slow" loop takes much longer than the "fast" loop and has some limits imposed upon it by the network via control signalling from the network. The slow loop imposes a limit, or a target, of allocated resources. For example, the slow loop can set a maximum power level (MAX PWR) and the fast loop can adapt in response to the maximum power level that has been set by the slow loop. The slow loop determines or computes a transmit power for a UE to use for transmitting a D2D signal to the other UE.
The slow loop can, in addition to or instead of specifying a maximum transmit power, specify a range of values, or a target value, or a maximum value, for one or more other parameters associated with the D2D link, for example a modulation scheme, a maximum modulation order, a maximum number of retransmissions, etc.
The slow loop is used to obtain, and relay to the network, information/statistics regarding the D2D link, and to send one or more messages from the network to the UE, the one or more messages including a range of values, or a target value, or a maximum value, as described above in relation to transmit power control, for one or more link quality-determining parameters such as order of modulation and others.
On the other hand, the fast loop can adapt the wireless link to changes in the physical environment (e.g. path loss) and can for example use less power than the power that the slow loop determines.
In use of the invention, the "Slow" Outer Loop can be used to control the quality of link parameter without any use of a "Fast" Inner Loop. Equally the combination of "Fast" Inner Loop and "Slow" Outer Loop may be used.
Commands that may be sent through or via the "fast" inner loop, and which may be considered to be D2D commands, include: modulation (or Modulation Coding Scheme MCS); and number of retransmissions to UE1 or UE2.
Commands that may be sent through or via the "slow" outer loop, and which may be considered to be network commands, may include: resource allocation (e.g. Modulation (MCS) & RBs) and transmission and
maximum allowed power information such as MAX UE1/UE2 D2D power or range of UE1 UE2 D2D power or TARGET UE1 UE2 D2D MAX # of Retransmissions of UE 1 /UE2, Move D2D Link to network command.
Power Control and resource allocation are performed by the network because (as explained above): D2D communication may affect classic cellular communication (in Uplink or in Downlink) and/or D2D communication between a pair of UEs. D2D communication may therefore also affect other D2D communication between another pair of UEs.
Evaluation of delay/latency for the "slow" outer-loop and the "fast" inner-loop has resulted in the following values of various parameters:
- A total of 40-50 ms is used for the <> outer-loop.
- 10 ms detection time of UE 1 by UE2
- 10 ms reporting time (through RRC)
- 10 ms decision time (in eNB)
10 ms command time (through RRC)A total of 10 ms is normally required for the <> inner-loop.
If however the slow loop is controlled by the MME rather than by the eNB, the time necessary for slow loop control is even longer and the above timing values could be at least in the order of 20ms longer.
The "slow" outer-loop can be justified such as Increase/ Decrease D2D resources and therefore can be dealt only through the network control. Only the network can determine whether to increase or decrease resource allocation because the network is arranged to reduce, or maintain below a limit, interference from D2D devices (and D2D communications) to other D2D devices (and D2D communications) and/or other a number of typical user equipment UE network equipment such as eNBs.
It follows that the network can perform control of a D2D link by using the slow outer loop to control the fast inner loop. The slow outer loop provides constraints for the fast inner loop, the fast inner loop being more adaptive in its response to physical changes of the D2D link.
The "slow" outer-loop therefore provides a means for the network to control the power and resource allocation and transmission and reception parameters for a D2D communication link. Such resource allocation may include one or more of position of resources in the time-frequency grid (such as those illustrated in Fig. 13 and Fig. 14), modulation, number of antennas, number of retransmissions, coding scheme, and several other parameters.
Two UEs involved in D2D communication under network control are arranged to send quality-of-service (QoS) measurements or statistics to the network. The physical environment changes over time (i.e., position, interference from other cells or other users, power, distance between D2D devices etc., as discussed earlier above) and the network can be arranged to control a D2D communication link with respect to these physical changes.
The following statistics (or any combination of them) for network resource allocation ("Slow" Outer-Loop) can be used for the purposes of controlling a D2D communication link.
Transmission (Tx) Statistics of UEl (or UE2) transmitting to UE2 (or UEl), can be transmitted by UEl (or UE2) to the network and can include one or more of the following:
Number of retransmissions "# of retransmissions"; UEl Tx power (or UE2); current Modulation and Coding Scheme (MCS); D2D Link ID (identity of the D2D link); Transmission Mode, TM (if the network doesn't have means to know it); and other information e.g. Channel State
Information CSI such as CQI (such as coding rate, modulation index and resulted channel efficiency that can be supported), number of antennas, multipath conditions, Precoding Matrix Indicator (PMI), Rank Indicator (RI), Precoding Type Indicator (PTI) etc.
[0066] Reception (Rx) Statistics obtained by UE2 (or UE1) transmitted by UE1 (or UE2), and sent by UE2 (or UE1) to the network, can include one or more of: number of NACKs / number of rec number of NACKs / number of received RB; number of ACKs / number of received RB; Block Error Rate (BLER), Packet Error Rates (PER) or Bit Error Rates (BER) or Frame Error Rate (FER); and optionally Reference Signal Received Power (RSRP) or Reference Signal Received Quality (RSRQ) levels of reception from UE1 (or UE2).
As should be clear from the following, Transmission (Tx) statistics without Reception (Rx) statistics may not be sufficient for controlling the link quality of a D2D communication link, and similarly Reception (Rx) statistics without Transmission (Tx) statistics may not be sufficient for controlling the link quality.
These statistics may be useful for the "Slow" Outer-Loop (UE1 to eNB to UE2 & vice versa), the "Slow" Outer-Loop being used for allocation of network resource.
Tx statistics and/or Rx statistics may be sent by a wireless terminal to a network base station to which the wireless terminal is connected, when the wireless terminal (e.g. UE1) is connected to another wireless terminal (e.g. UE2) via a direct (in this case D2D) wireless communications link between the wireless terminals. Depending on the statistics, the base station sends a command signal to the wireless terminal for the purpose of controlling a quality link parameter of the direct wireless communications link.
UE1 Tx statistics may be sent when UE1 resends information to UE2 because UE2 is in a high interference region or because UE1 Tx power is low or modulation is of high order or because UE1 does not receive ACK because UE1 is in a high-interference region.
UE2 Rx statistics may be sent when UE2 does not receive information from UE1 because UE2 is in high interference region or UE1 power is low or modulation is of high order.
Based on these statistics the network can determine one or more of whether: the link from UE1 to UE2 is bad/ the link UE2 to UE1 is bad/ the bi-directional
communication between UE1 and UE2 is bad/ and UE1 and/or UE2 are in a high
interference position.
[0073] The network can further send a command signal to perform one or more of: increase/decrease the Target (Maximum) # Retransmissions of UE1, UE2
increase/decrease the power of UE1, UE2 change the D2D modulation scheme of UE1, UE2 or both from 64QAM/QPSK for example to QPSK/64QAM (adaptive modulation):
64QAM-&QPSK if link is bad and QPSK-&64Q AM route back to the network the D2D communication: UE1 will communicate with UE2 change the resource allocated to D2D (e.g. orthogonal resource or other).
As explained briefly above, Tx statistics without Rx statistics may not be sufficient, and vice versa. It has been found that that these statistics may be useful for the "Slow" Outer-Loop (UE1 to eNB to UE2 & viceversa), the "Slow" Outer-Loop dealing with network resource allocation and transmission and reception parameters control.
Figs. 6 to 8 are respective flow diagrams illustrating the algorithm at a high level according to three respective possible implementation schemes.
Reasoning for the following proposed algorithms (alternatives) is as follows:
- The maximum number of retransmissions ("MAX # of Retransmission") may be performed first or second (see Fig. 5 and the associated portion of the description below);
- MCS & RB allocation may be performed first or second (see Fig. 5 and the
associated portion of the description below) on the basis that MCS & RB Allocation have less impac
- Power (PWR) assignment may be the option before the last option, on the basis that D2D power control should change not too frequently, in order to reduce interference to other D2D users or t
- The <> command may be treated as the last option in case nothing else works (please also see the alternative in the alternatives section).
With reference to each of Fig. 6 to Fig. 8, for simplification purposes the following part of the description refers to a "slow" outer loop algorithm for a direct link between wireless terminal 404 and the other wireless terminal 408, via the wireless terminal 404. It should be appreciated that this would also be applicable to control D2D terminal 408 to terminal 404 via terminal 408, and would also be applicable for out-of-coverage and intra-cell scenarios. [0078]
Also it should be appreciated that Fig. 6 to Fig. 9 are equally applicable to both UEl and UE2 control if UEl is inverted with respect to UE2.
Fig. 6 is a flow diagram illustrating the algorithm at a high level implemented at a network level e.g. a base station, or. an eNB or MME.
At step 601 the algorithm begins.
At step 602 a determination is made, as to whether the block error rate (BLER) of the D2D link, measured in UE2, is greater than a threshold value (Thr).
When the determination in step 602 is negative (NO), in step 603, the algorithm does not proceed further since there is no further action to perform.
When the determination in step 602 is positive (YES), in step 604 a further
determination is made as to whether the number of retransmissions is less than or equal to a specified maximum number of retransmissions.
When the determination in step 604 is negative (NO), the algorithm moves to step 605, described further below.
When the determination in step 604 is positive (YES), in step 606 the network decides to change the UEl modulation and coding scheme (MCS) and change the resource block (RB) allocation, and the algorithm then moves on to step 607.
In step 607, a further determination is made as to whether the order of the MCS currently set (according to step 606) is below a minimum or above a maximum specified order, and cannot be decreased or increased anymore, or the RB allocation that was changed in step 606 cannot be implemented due possibly to all resources having already been allocated to other users in direct communication (if the RB allocation that was changed was increased), or other users in legacy communication, through the network or e.g. for eNB communication.
When the determination in step 607 is positive (YES), the algorithm can moves to step 611, described further below, which is the first step in a first alternative of the algorithm, or alternatively can end at step 611.
When the determination in step 607 is negative (NO), the algorithm moves to step 608, in which the network transmits a control signal intended for UEl , the control signal comprising a command indicating that UEl should or is allowed to increase the order of the MCS by a specified decrement below, or increment above, the value currently set and/or to allocate more RBs or less RBs or different RBs and/or which RBs.
Thus, the control signal indicates that UEl should or is allowed to change the value of a parameter related to the quality of a D2D link between UEl and UE2, this parameter being the possibly changed MCS order.
The algorithm then moves back to step 602.
Step 611, mentioned above, itself comprises the initial step in the remainder of the first alternative of the algorithm. In step 612, a determination is made, as to whether the number of retransmissions is less than or equal to a specified maximum number of retransmissions.
When the determination in step 612 is negative (NO), in step 613 the algorithm does not proceed further since there is no further action to perform.
When the determination in step 612 is positive (YES), in step 614 a further
determination is made as to whether the block error rate (BLER) of the D2D link between UEl and UE2, measured in UE2, is greater than a threshold value (Thr).
When the determination in step 614 is negative (NO), the algorithm moves to step 615, in which the algorithm does not proceed further since there is no further action to perform.
When the determination in step 614 is positive (YES), in step 616 the network decides to increase the maximum number of retransmissions by a specified increment, and the algorithm then moves on to step 617.
In step 617, a further determination is made as to whether the maximum number of retransmissions can be increased any further than the present number. The determination will depend on delay constraints and system constraints which are checked by the network for example with respect to the service type. As a possible alternative, this aspect could be implemented at the UE side particularly, for example, if the UE changes service type wherein delay and system constraints could change. For example, if D2D changes the service from data to video streaming where less delay is required, or as another example upon a change from data to voice.
When the determination in step 617 is positive (YES), the algorithm moves to step 618, in which the network transmits a control signal intended for UEl , the control signal comprising a command indicating that UEl should or is allowed to increase, by a specified increment relative to the present value, the maximum number of retransmissions via the D2D link between UEl and UE2.
The algorithm then moves back to step 612.
When the determination in step 617 is negative (NO), the algorithm ends in step 619. Optionally, at step 619, the process continues at step 701 of Fig. 7, or indeed can start at this location.
Fig. 7 is a flow diagram illustrating another variant of the algorithm at a high level implemented at a network level e.g. a base station or an eNB or a MME.
This part of the algorithm commences at step 701.
In step 702 a determination is made, as to whether the currently set maximum number of retransmissions is less than or equal to a specified maximum number of retransmissions.
When the determination in step 702 is negative (NO), in step 703, the algorithm does not proceed further since there is no further action to perform.
When the determination in step 702 is positive (YES), in step 704 a further
determination is made as to whether the estimated current block error rate (BLER) of the D2D link, measured in UE2, is greater than a threshold value (Thr). [0105]
When the determination in step 704 is negative (NO), the algorithm moves to step 705, in which the network decides to reduce UE maximum number of retransmissions by a specified decrement below the currently set value. The algorithm then moves to step 708 which is described further below.
When the determination in step 704 is positive (YES), in step 706 the network decides to increases UEl's maximum number of retransmissions by a specified increment above the currently set value. The algorithm then moves to step 707.
In step 707, a further determination is made as to whether the maximum number of retransmissions can be further increased.
When the determination in step 707 is positive (YES), the algorithm moves to step 708 for transmitting a command.
In step 708, which is reached when the determination in step 707 is positive (YES), the network transmits a control signal intended for UEl, the control signal comprising a command indicating that UEl should increase, or be allowed to increase, the maximum number of retransmissions by a specified increment above the value currently set.
Thus, the control signal, which can be an increase, decrease or imposed value, indicates that UEl should change the value of a parameter related to the quality of a D2D link between UEl and UE2, this parameter being the maximum number of retransmissions.
The algorithm then moves back to step 702.
When the determination in step 707 is negative (NO), the algorithm moves to step 711 which is the first step of this alternative of the algorithm.
In step 712, a determination is made as to whether the block error rate (BLER) of the D2D link between UEl and UE2, measured in UE2, is greater than a threshold value (Thr).
When the determination in step 712 is negative (NO), in step 713 the algorithm does not proceed further since there is no further action to perform. [0114]
When the determination in step 712 is positive (YES), the algorithm moves onto step 714.
In step 714 a further determination is made as to whether the transmit power of UE1 currently set is less than an allowed maximum value (MAX PWR).
When the determination in step 714 is positive (YES), the algorithm moves to step 715, in which the algorithm does not proceed further since there is no further action to perform.
When the determination in step 714 is negative (NO) because the power is equal to, ro very close to, the maximum value, in step 716 the maximum allowed transmit power is increased by a specified increment, and the algorithm then moves on to step 717.
In step 717, a further determination is made as to whether the maximum allowed transmit power is limited. When it is limited, it cannot be increased any further than the present value. The determination will depend on interference constraints to other D2D or other legacy UE or network equipment This can readily be checked by the network which knows all of the environmental characteristics since it is constantly receiving measurement from devices/eNBs etc. The network can also impose power constraints if the UE does not have sufficient energy or wants to conserve UE energy.
When the determination in step 717 is negative (NO), the algorithm moves to step 718 (requiring the sending of a command which can be an increase, a decrease or an imposed value), in which the network transmits a control signal intended for UE1 , the control signal comprising a command indicating that UE1 should increase, by a specified increment relative to the present value, the maximum allowed transmit power of UE 1.
The algorithm then moves back to step 712.
When the determination in step 717 is positive (YES), the algorithm ends. Optionally at step 719, the process continues at step 801 of Fig. 8, which could also comprise the start of this further aspect of the algorithm.
[0122] Fig. 8 is a flow diagram illustrating another variant of the algorithm at a high level implemented at a network level e.g. a base station or an eNB, or MME.
In this variant the algorithm begins at 801 which can be the second step of the first or second alternative.
In step 802 a determination is made, as to whether the estimated current block error rate (BLER) of the D2D link, measured in UE2, is greater than a threshold value (Thr).
When the determination in step 802 is negative (NO), in step 803, the algorithm does not proceed further since there is no further action to perform.
When the determination in step 802 is positive (YES), in step 804 a further
determination is made as to whether the currently set value of UEl transmit power is less than a maximum allowed transmit power at which UEl should transmit.
When the determination in step 804 is positive (YES), the algorithm moves to step 805, in which the network decides to reduce UEl 's maximum allowed transmit power by a specified decrement below the currently set value. The algorithm then moves to step 808 which sends a command from the network to the UE as described further below.
When the determination in step 804 is negative (NO), in step 806 the network decides to increase UEl 's maximum allowed transmit power by a specified increment above the currently set value. The algorithm then moves to step 807.
In step 807, a further determination is made as to whether the maximum allowed transmit power can be further increased.
When the determination in step 807 is negative (NO), the algorithm moves to step 808. In step 808, which is reached when the determination in step 807 is negative (NO) the network transmits a control signal intended for UEl, the control signal comprising a command indicating that UEl should increase the maximum allowed transmit power by a specified increment above the value currently set.
The algorithm then moves back to step 802. [0131]
When the determination in step 807 is positive (YES), the algorithm moves to step 811 which is the next step in this part of the algorithm.
From step 811, the algorithm moves onto step 812, although alternatively could start at this step.
In step 812, a determination is made as to whether the estimated current block error rate (BLER) of the D2D link, measured in UE2, is greater than a threshold value (Thr).
When the determination in step 812 is negative (NO), the algorithm terminates in step 813, as there is no further action to perform.
When the determination in step 812 is positive (YES), the algorithm moves onto step 814.
In step 814, the network decides to transmit a control signal to UE1 comprising a command to move the D2D link to the network, or only to UE1. The algorithm then moves onto step 815.
In step 815, the networktransmits a control signal for UE1 comprising a command for UE1 and/or UE2 for the commanded UE(s) to move to the network.
In step 819, the algorithm ends.
Referring back to Fig. 5, it was noted that the UE2 inputs Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ) are optional. With regard to the algorithm of Figs. 6 to 8 however, possible adoption could be as follows. A further loop could be introduced based on either a comparison with an RSRP target or RSRQ target, or a comparison with minimum RSRP or RSRQ values noted. Alternatively, the noted condition UE2 BLER &Thr could be replaced withUE2 RSRP or RSRQ&Thr.
Figs. 9 to 11 illustrate Message Sequence Charts (MSC) for different scenarios. In Figs. 9 to 11, information regarding the Modulation Coding Scheme (MCS) has been removed for the sake of clarity and conciseness. UE1 and UE2 communicate with one another via a direct wireless link (D2D link).
Fig. 9 is an example of a Message Sequence Chart (MSC) for control of a quality link parameter of an Intra-Cell D2D link.
Fig. 10 is an example of a Message Sequence Chart (MSC) for control of a quality link parameter of an Inter-Cell D2D link.
Fig. 11 is an example of a Message Sequence Chart (MSC) for control of a quality link parameter of an Out-of-Coverage D2D link, where one of the wireless terminals is out of coverage of a base station, as shown in Fig. 3 (306).
In each of Figs. 9 to 11, signalling messages are shown which are transmitted between a UE (UEl) 902,
involved in a D2D link and another UE (UE2) 904,
also involved in the D2D link. Signalling is also shown that occurs between the respective UEs (UEl, UE2) and a first eNodeB (eNBl) 906, . Additionally, for the inter-cell scenario shown in Fig. 10, signalling is shown to and from a second eNodeB (eNB2) 1008.
While the aforementioned drawings relate to a scenario in which UEl configuration occurs in a serial manner before UE2 configuration, in practice it is also possible and applicable that the configuration of UE2 could occur in a serial manner before that of UEl, or indeed both configurations could occur in parallel. Equally, the invention also provides that only one configuration might occur per D2D link.
Such options and alternatives are also applicable when the network acts to stop the connection. That is UE2's connection could be stopped before that of UEl, or indeed both connections could be stopped in parallel. Equally, the invention also provides that the network sends only a single message to both UEs (message per D2D link) to stop D2D communication.
Fig. 12 is a graph of BLER or PER versus different required signal-to-interference and noise ratio (SINR) for different numbers of retransmissions, showing how number of retransmissions can affect BLER & SINR. Each Retransmission improves SINR quality but increases communication delay & may require more resources to be allocated.
[0147] The uppermost curve 1202 is a graph of BLER or PER versus SINR for a first retransmission, the next curve 1204 is a graph of BLER or PER versus SINR for a second retransmission, the next curve 1206 is a graph of BLER or PER versus SINR for a third retransmission, and the lowermost curve 1208 is a graph of BLER or PER versus SINR for a fourth retransmission.
Fig. 13 is a time/frequency grid representing an example of MCS & RE (Resource Element) resource allocation performed by an eNB, and representative of experimentation performed within the context of the invention under good signal path conditions (providing a low error rate). In the figure, time is represented on the horizontal axis from left to right and frequency is represented on the vertical axis, and each small rectangle represents a resource element of a resource block. Resource elements 1302, labelled NP, are allocated to network pilot signals, resource elements 1304, labelled D2D, are allocated to D2D co and resource elements 1306, labelled OC, are allocated to other communications signals.
Initially only two resource elements were allocated for D2D communication using 64QAM (2A6 =& a 64QAM symbol has 6 bits of information) in the time/frequency grid.
Note that current 3 GPP standards only allows resource allocation by allocating whole resource blocks, each block comprising 12 subcarriers, 7 symbols for normal cyclic prefix (CP) configuration, or 6 symbols for Extended CP configuration. The current 3 GPP standards do not provide for resource allocation by Resource Element, respective Resource Elements being represented by respective individual rectangles in Fig. 13 and Fig. 14.
Fig. 14 is another time/frequency grid representing an example of MCS & RE
(Resource Element) resource allocation performed by an eNB, according to further
experimentation, but under poor signal path conditions (causing high initial error rate). The eNB had initially allocated a higher modulation scheme, 64QAM, when the link quality was good. Because of the subsequent poor link quality, the eNB then allocated a lower modulation scheme because a QPSK-modulated signal is much more resistant to noise and interference than a 64QAM-modulated signal.
However, a penalty of using QPSK is that a QPSK symbol has only two bits of information and is therefore three times more resource-consuming than 64QAM (it uses three times as many bits of information). Therefore, three times as many resource elements are used as in the case of good signal conditions. This represents a potential problem.
In this poor-signal situation, the resource allocation is performed by the network insofar as the network should ensure that such decision is not taken at the UE which could interfere with other UEs or network equipment. The network must allow such allocation to the UE, in order to ensure that the UE does not interfere with other equipment (UE and/or network equipment). This can be because if the modulation scheme were not changed to a lower order, it would be necessary to increase the transmit power to a level that would cause such interference with other equipment. Also, if nearby RBs or Resource Elements (REs) are already busy, the network has to decide which extra RBs or REs to allocate when going from 64QAM to QPSK.
In the figure, a group 1405 of six resource elements are allocated to the D2D link, as compared to the two resource elements 1302 allocated in Fig. 13.
The invention alleviates this problem by ensuring that the link quality remains good. Fig. 15 is a flow diagram representing an algorithm that may be used in addition to one or more of the algorithms described above, for example in relation to Fig. 5 to Fig. 8. For example, according to a variation of the algorithm illustrated in Fig. 6, when the determination in step 602 is negative, instead of carrying out the step 603, the algorithm illustrated in Fig. 15 may be executed, and then the algorithm illustrated in Fig. 6 would return to the beginning step 601. That is, the algorithm starts at 1501 and then proceeds to a determination at 1502 of whether BER or PER UE2 ,is higher than THr. If so, it proceeds to 1504 for a decrease of retransmissions of UEl, or use of a higher modulation scheme. If at 1502 it is determined that BER or PER UE2 is not less than Thr, then it proceeds to 1503 to increase retransmissions of UEl or a change in modulation scheme.
Fig. 16 illustrates an embodiment that includes the use of a so-called "Low Power Node" (LPN) 1602 instead of a user equipment (UE) for communicating via a D2D link 1604 with a UE 1606. A Macro eNB 1604 communicates, using a Radio Resource Management (RRM) entity 1608, with a Mobility Management Entity (MME) 1610 and also with the Low Power Node 1602. In this embodiment, the LPN 1602 can function in the same way as one (304; 404) of the two UEs (304, 306; 404, 408) functions, as described above for example in relation to Fig. 3 and Fig. 4, in order to transmit D2D link quality data to the network. Equally, the LPN can function in the same way as one (304; 404) of the two UEs functions, as described above, to control the link quality. In the embodiment shown in Fig. 16, the Radio Resource Management (RRM) entity 1608 is a centralized RRM.
According to an embodiment, the interface 1612 between a Macro eNB and the LPN is similar to, but not identical to, a so-called "X2 interface" that is used between base stations. It is envisaged that the LPN 1602 may have functionality that is similar to that of a base station entity. The arrows
in Fig. 16 represent control signalling which is controlled by means of the Radio Resource Management (RRM) entity 1608 of the network. Also arrow 1616 represents interface between MeNB 1604 and UE 1606.
Fig. 17 illustrates another embodiment similar to that shown in Fig. 16. In the embodiment shown in Fig. 17, the Radio Resource Management (RRM) entity 1708 is a distributed RRM with single Radio Resource Control protocol.
The Low Power Node (LPN) 1602 may be a device or entity that is largely in accordance with the 3GPP document TR 36.932, which states:
"A low-power node generally means a node whose Tx power is lower than macro node and BS classes, for example Pico and Femto eNB are both applicable. Small cell enhancements for E-UTRA and E-UTRAN will focus on additional functionalities for c
enhanced performance in hotspot areas for indoor and outdoor using low power nodes. "
Use of the LPN would allow increase of the coverage of the Macro eNB, which is another possible scenario in RAN2. Also the use of LPN is a possible scenario for use in RAN2 SCE (Small Cells Enhancements).
Another envisaged embodiment comprises at least one UE-Relay (UE-R) which is a UE with relaying capability. The UE-R may relay information to another UE-Relay or to the eNB. Thus, the UE Relay can act in the same way at one (304; 404) of the two UEs (304, 306; 404, 408) functions, as described above for example in relation to Fig. 3 and Fig. 4, in order to transmit D2D link quality data. Equally, the UE-Relay can function in the same way as one (304; 404) of the two UEs functions, as described above, to control the link quality.
[0162] This embodiment would be able to function in a similar way to the embodiment described above in relation to Fig. 3 (out-of-coverage case) but the out-of-coverage UE could also perform data communication with the network through the (one or more) UE-R, for example by means of either a single UE-R or a multi-hop transmission through multiple UE-Rs.
The claims, the above detailed description and the accompanying drawings together provide a technical teaching that makes it possible to put the inventive subject matter into practice.
The subject matter of the invention provides for a wireless terminal sending D2D measurements associated with one link and one wireless terminal.
The subject matter of the invention can also provide for a wireless terminal sending an indication of the type of D2D measurements which it sends.
The subject matter of the invention can also provide for the use of a double-loop comprising a "slow" loop for resource allocation, and transmission and reception parameters, and another, "fast" loop for link adaptation to radio conditions in the limit of the allocated resource allocation by the slow loop. As an example, the outer loop can set the maximum power to lOOmW and the faster loop adapts to this constraint, e.g. 99mW if the environment is bad, or to lOmW if the environment is good enough. This serves to prevent the UEl transmitting to another UE2 with a power higher than the network allows.
However, with an alternative command, when eNB instead configures a target, the UE can increase and decrease the value around this imposed target (it can be below and above but converging to the target).
The slow loop imposes a limit of allocated resources and transmission and reception parameters. For example, the slow loop may set maximum power}