GB2537623A - Content delivery over D2D links - Google Patents

Abstract

A content delivery method employing a plurality of transient device-to-device, D2D, links among User Equipments, UEs, (10, 12, 14, 16) in the vicinity of a content-seeking UE (11) and which locally cache desired content. To obtain the desired content, successive D2D links are initiated by the content-seeking UE (11) with initial guidance from a central Femto network controller (50). The central Femto network controller (50) identifies possible D2D content donor UEs in the vicinity of the content-seeking UE (11) and indicates a probability of successfully obtaining the content through UE-orchestrated content delivery using multiple D2D links. A user then decides whether to attempt UE-orchestrated content delivery or whether to obtain the content in another way, for example directly from a root server through the core network. Requested content may be divided into a plurality of segments, wherein at least one segment is obtained from each of the D2D links. Addresses the problem with public access small cell networks wherein users are highly mobile and D2D links may be transient in nature and therefore a single D2D links will not be sufficient to deliver large file size content such as HD video.

Description

Content Delivery Civet' D20 Links, rteid of the invention The present invention relates to wireless communication networks, for example networks com.piiant with the 3GPF Long Term Evolution (LTE) and 3GPF LTE-A (L.TE-Advanced) groups of wireless communication standards, including so-called "40" standards and also future "50" standards; and more particularly to content delivery using so-called D20 (Device-to-Device) links under control of such networks,

Background of the Invention

Within the context of a cellular wireless communication network in which terminals (UEs) normally communicate via base stations (BSs), 3GPP has proposed the use of licensed spectrum for direct, peer-to-peer communication between terminals, Figure 1 shows the basic principle, in which UEs 10 and 11 are initially in communication with a network node in the Form of a BS 20 as shown in Figure 1(a). Mutual discovery of these UEs 10 and 11 in proximity to each other, as indicated by the waves emanating from UEs 10 and 11 in Figure 1(a), leads to direct communication between those UEs as shown in Figure 1(b). Discovery and communications between devices that are in proximity is studied under the general umbrella of Proximity Services, and is also colloquially referred to as Device-to-Device (D2D) communication..

In D20 communication, it is not necessary for every UE to maintain a direct data path with the BS 20. In the case of UE 12 in Figure 1(b) for example, the data path may be via UE 10 with which UE 11 is in 02D communication, Thus, 020 involves LIEs acting as relays or "donors" for other UEs, at least for user data. in Fig, 1(b), UE 10 is referred to as a "donor UE" for the "recipient LIE" 11: user data for downloading to the UE 11 is transmitted by base station 20 to UE 10 and relayed from UE 10 to UE 11 over the 020 link. The result is a mixed network comprising 02D wireless links and cellular wireless links between UEs and base stations.

A mixed network such as this is illustrated in Figure 2. As indicated in the Figure, UEs 10 -15 can be of various types such as mobile phones, laptop computers and PDAs or tablet computers. A LIE 10 in the form of a mobile phone has a wifeless link with 03 20, whilst another DE. 12 in the form of PDA anti a further li.10 14 in ihe form of a laptop corn/tater also have winnings links with BS 20. UF_ 10 has a 02n link with DE 11, as in Figure 1(b), and D2D links with other LiEs aisrt, thereby acting as donor UE for these t.PEs. Likewise, 00 12 is a donor ti0 for other DE's such as UE 13, and DE 14 is a donor DE for other LJEs such as UE 15.

Meanwhile, the BS 20 is connected to a backbone network (core network) for connecting the base station to a root or main server 40 representing a source of user data, and which may be on the Internet. A controller 50 manages LlEs' connections with base stations, and is at least aware of their D2D links if any, Since at least some of the UEs are mobile, the controller 50 is also involved in handove,rs of UEs between base stations, and possibly also '020 handovers" in which a UE exchanges one D2D link for another.

The precise manner in which D2D communication is conducted is not essential to the invention to be described; however, the term generally implies communication using the same RAT as the cellular network and on spectrum available to the network operator. Therefore, the D2D links may be managed by the network to avoid interference between devices in D2D mode and conventional transmissions between UEs and BSs, for example by reserving specific resources (time periods and/or frequencies) for D2D communication. An alternative scenario is where UEs directly communicate using a different RAT (such as \MEI, IEEE802.11, in particular so-called VViFi Direc(). Even in this case it may be possible for the central network controller to exert some form of control.

Thus. D2D can be used to carry user data instead of, or in addition to, a UE's conventional wireless link with a BS. Normally the base station will continue to maintain control paths to each of the UEs. The effort in 3GPP is currently focused on D2D communication between terminals (or UEs) which are 'under continuous network control, and are under 3GPP network coverage".

Henceforth any use of D2D for a data path (or part of a data path) will be referred to as a "D2D link", The conventional wireless links between UEs and a BS will be referred to as "the cellular network" where necessary for clarity, or more generally as "the network". References to "the network' also include higher-layer network entities including the controller 50 in Figure 2, where appropriate.

The above discussion has referred to llEs in the form of mobile phones, laptop computers and PDAs or tablets. operated by human users. However, a wireless communication system may also be used for i,,orctiilled Machine "Type commuolitatirat (0170), wheie (\ITC; is a t[.,Frn of tiara common cation which involves one or more entities that do not necessarily need human interaction. Entitles involved in MIC, henceforth referteri to as VIC devices, are also to be considered as a kind of UP except where the context demands otherwise. Applications MTO devices include fleet management, smart metering, product tracking, home automation, e-health, etc. MTC devices are often in fixed locations, in contrast to the mobile devices of human users.

Meanwhile, in an attempt to deai with fast-growing demands for user data, the conventional base station infrastructure is being augmented by the addition of so-called "small cells", providing a "small cell network" (SON), The general term SCN covers a range of radio network design concepts which are all based on the idea of deploying BSS much smaller than the traditional, "Macro" base stations to offer extended coverage (to indoor area or coverage hole areas of the existing Macro cells) or to provide additional capacity to meet high demand, such as in places where users congregate. Small cells target at a coverage radius of 20-150m and radiate at low power (0.01-10VV). Possible deployment scenarios include public indoor and outdoor with public or closed access, residential and enterprise environments. In this sense, SCNs comprise iow-power Micro, Pico and Femto cells, overlaid on the Macro cells, As an addition to the above mentioned central network controller. SCNs may have a SON (Self Organizing Network) controller.

Henceforth, the term "Feroto cell" is used to denote any kind of small cell, and "Fernto node" or "FeNB' to cover any kind of small c.eli base station_ The term "Femto network' will be used to 2rr denote a SCN providing Femto cells (and/or other small cells) in the same vicinity and serving a limited area such as an office building or shopping mall for example. The term "Femto network controller" will be used to denote a local controller of the SON (such as a SON controller as just noted).

Increasingly, user data consists of specificitems (data files) of content downloaded or streamed to the terminal for consumption of the user. particularly video and web pages. Such downloading/streaming conventionally involves transfer of content from a source (such as server 40 in Figure 2) over the backbone network to a base station, which leads to duplicate access of content from the backbone network or other servers. As demand increases, simple densification nth/ the oroces controller, in rermw of ltitude of hancovers for popular content at the edge of the network o being developed The van/ extreme form of edge caching can be caching in t search devices themselves. The content can then be distributed through emerging technologies like D2D and WIFi direct. The LIE device caching not only eases the bottlenecks on the backbone network; and the load upon the main or root servers storing the content, but also eases the demand for radio access resources.

Thus, content caching at UEs and sharing through D2D (or WiFi Direct) provides a potential solution. However, the problem with public access small cell networks is that the users are highly mobile and any possible D2D links will be only transient in nature; hence a single D2D link will not be sufficient to deliver the full content, particularly for large file sizes such as are required for high-definition video. At present, if a D2D link fails, the content delivery has to be started all over again because there is no mechanism for linking multiple D2D connections. There needs to he some mechanism to make use of multiple D2D links and synchronize the content delivery.

A central controller-orchestrated solution possible, as proposed in the applicant's co-pending UK patent application no. 1500690.1; however, this incurs a significant signalling overhead on the network, It would be desirable to make use of multiple 02D links for content delivery without incurring such a significant signalling overhead.

ention According to a first aspect of the present invention, there previded a terminal for use in a wireless network and equipped for device-to-device, D2D, wireless communication with other terminals in its vicinity, comprising: input means for receiving, from a user, an instruction to obtain requested content; requesting means for transmitting a corresponding content request to the network; receiving means for receiving information from the network in response to the content request; and managing means for, when if is determined based on the receive-al information to employ 020 communication far content delivery, esfablishing o plurality of 020 iinks with other terminals for obtaining the requested content, the managing means arranged to establish the 02D links without further guidance torn the network.

The above-defined terminal is referred to subsequently as a content-seekino or requesting terminal. In general it can be any wireless terminal capable of obtaining content requested by (and preferably reproducing the content to) a user. The term "content" covers arty kind of tile(s) capable of being consumed (e.g. viewed, read or listened to) by a user of the terminal, including videos, music and other audio files, e-books, games, Web pages, data files and so forth.

The received information, based on which the managing means determines to employ D2D communication for content delivery, may include a likelihood estimate of success in obtaining the requested content.

The wireless network may be a Femto network. in which case the information is received from a Femto network controller or a central content manager.

The input means may be further arranged to receive a decision from the user to employ 02D communication for the content delivery, The managing means can be arranged to divide the requested content into a plurality of segments and to obtain at least one segment from each of the D2D links. In one embodiment, the managing means maintains one 020 fink at a time, continuing with a D2D link for as long as the link remains viable to transfer segments of the requested content and then to establish a fresh D2E) link to obtain at least one further segment.

As a precaution to avoid unnecessarily transferring content which may no longer be required, the requesting terminal may, after arranging content delivery of one segment (typically the first segment in the series) confirm that the content is still needed (for example by monitoring whether a media player application is still running) before repeating the identifying and instructing for any further segments.

According to a second aspect of the present invention, there is provided a control entity in a rc...,cSve, a content request from a cententiseeifing terminal; on the bas a of the content specified in the request, identify potential donor terminals for the requested content; estimate a likelihood of content del aery to the conten -seeking terminal being possible by use of multiple 020 links; and notify the content-seeking terminal of the calculated likelihood.

The control entity may estimate said likelihood based on information includingi terminals being served in the wireless network and locations of such terminals; content stored in the terminals; and movements of the terminals.

The control entity may be in the form of a Fernto network controller or a central content manager, the terminals being terminals of a Femto network. The central content manager may be provided for the Fiemto network or for a number of Femto networks and/or conventional wireless networks.

According to a third aspect of the present iovention, there is provided a method of content delivery via device-to-device, D2D, links of terminals in a wireless network comprising: at a control entity of the wireless network: receiving a content request from a content-seeking terminal and identifying potential donor terminals for the requested content; and estimating a likelihood of content delivery being possible by use of multiple 020 links and notifying the content-seeking terminal of the likelihood; and at the content-seeking terminal: deciding on the basis of the received likelihood whether to employ D20 links to obtain the requested content and, if so, establishing multiple 02D links with donor terminals to obtain the requested content, the requesting terminal managing the establishment of the D2D links without further involvement of the network controller.

As already mentioned, the requested content is preferably divided into a plurality of segments and the content-seeking terminal obtains at least one segment from each of the 020 links.

The 020 llnke are preferably successive, the content-seeking terminal malotoining ore 020 link for as long as the D2D links remains viable to transfer segments of the requested content and the content-seeking telnlirla then e.sioNishing a fresh 020 link to obtain at least one further segment.

in the above method, the control entity ma oentify potential donor terminals for the requested content based on information including: terminals being served by the network controller and locations of such terminals; ci content stored in the terminals; and movements of the terminals.

The terminals may be terminals in a Femto network, in which case the control entity is a Femto network controller or a central content manager.

The control entity may provide to the content-seeking terminal, as an alternative to employing D20 links to obtain the requested content, an option to select at least one further mode of obtaining the requested content and to indicate an expected time taken in each mode. for example content delivery from a core network linked to the wireless netwotk, and/or content delivery via 020 links managed externally to the content-seeking terminal.

According to a fu her aspect of the present invention, there is provided software in the form of program code which when executed by a processor of a wireless terminal in a wireless network. causes the terminal to perform the steps of; receiving a request for specified content from a user of the terminal and transmitting a corresponding content request to the network; receiving from the network an estimate of a likelihood of delivery of the specified content being possible by use of multiple D2D links; 0bt3iningadecisinnbasedUponthereCeiVed|ik |ih0ndofvvh ernp|Cy[)2OliDkS likelihood to obtain the specified content and, if so, establishing, without further involvement of the network, multiple D2D links with donor terminals to obtain the specified content, Such software may be recorded on a computer-readable medium, or it may, for example, be in the form of a signal such as a downicadable data signal provided from an Internet website, or it may he in any other form.

Thus, We corititintese.ekinci, terminal orchestrates multipie D20 links;n order to obtain the requested content. The item of requested content is considered as a series of segments, and for each segment in turn the terminal uses D2D communication to obtain the segment from a donor terminal. Usualty, multiple 02D links will be needed to complete the content delivery. These D2D links will normally he (but are not necessarily) consecutive, the content seeking terminal waiting for successful delivery of an earlier one or more segments in the series before identifying a 02D link for a next one or more segments.

The "donor terminal' referred to above is a terminal which holds the requested content (or at least a segment thereof needing delivery), which has opted-in to transfer such content to another terminal if required, and which is in a suitable location to perform 020 communication with the content-seeking terminal. The network controller can identify such donor terminals and provide initial guidance to the content-seeking terminal.

It is not necessary to establish a different D2D link for each segment in the series: an existing link can continue to be used for as long as it remains suitable, Thus, the content-seeking terminal can determine, on the basis or the iink information and the movement information, whether a device-to-device wireless link already instructed is adequate to transfer the next segrnent(s) of the series, A fresh D2D link will be needed if an existing link is no longer via' le due to, for example, the content-seeking terminal going out of range of the existing donor terminal, Therefore, preferably, the content-seeking terminal is further arranged to, upon determining that the deviceto-device link is not adequate, form a new device-to-device link with another donor terminal in order to transfer the next segment(s).

In doing so, the content-seeking terminal may predict which other terminal it is likely to become proximate to, based on the movement information. Thus, preferably, the content-seeking terminal is arranged to process the movement information to predict its movement relative to other terminals, when identifying another donor terminal, When the current 132D link starts becoming weaker, the content-seeking terminal has to start booking tnir new donor ins; tor obtaining the remaining content. ming content-seeking terminsi will start to transmit messages in this regard, trying to iratiath new id2D Preferably, the controiler is arrang to store information about the content held in each terminal by recording a content ID associated with each item of content held by the terminal, Normally, each donor terminal will hold the whole item of content (in other words, every segment in the senes), but individual segments may also be tracked using a sub-ID In this invention, the central controller plays merely a supportive role to the D2D communications. It will provide an indication to the requesting user about the potential number of donor devices in the vicinity and the likelihood of success for the obtaining content with this UE-centric orchestration mode.

The donor terminals need not all have human users; rather, it may be possible to take advantage of content stored in MTC devices. Thus, in one embodiment the identifying comprises identifying a machine-type communication device as a donor terminal. Such a device may either be one already present in a wireless communication system for another purpose, or alternatively it may be deployed in the system deliberately at least partly for the purpose of content delivery, In general, and unless there is a clear intention to the contrary, features described with respect to one embodiment of the invention may be applied equally and in any combination to any other embodiment, even if such a combination is not explicitly mentioned or described herein.

As is evident from the foregoing, the present invention involves signal transmissions between base stations and terminals in a wireless communication system, A base station may take any form suitable for transmitting and receiving such signals. It is envisaged that the base stations will typically take the form proposed for implementation in the 3GPP LTE and 3GPP LTE-A groups of standards, and may therefore be described as an eNodeB (eNB) (which term also embraces Femto eNB or FeNB) as appropriate in different situations. However, subject to the functional requirements of the invention, some or all base stations may take any other form suitable for transmitting and receiving signals from user equipments.

Similarly, in the present invention, each terminal may take any form suitable for transmitting and receiving signals from base au:Aliens. For example, the tor imira may cake the form of a subscriber station, nr a mobile station (MS), or any other suitabie fixed-oosibon or movable form, For the purpose of visualising the inveritiort, it may be convenient to imagine the terminal as a mobile handset (and in many instances at least some el the terminals will comprise mobile handsets), however no limitation whatsoever is to he implied from this. For example, at least some of the donor terminals may be machine-type communication /NM devices such vending machines; smart meters and the like.

To summarise, and in contrast to the solution proposed by the applicant in UK patent application no. 1500690.1. embodiments of the present invention hand the management ot D2D links to the content-seeking terminal, thereby reducing the control overhead and signalling load of the Femto network, but with less certainty of completing the content delivery compared with a fully-centralised solution. On the other hand, the content delivery is more assured than would be the case if the content-seeking terminal was left to establish the D2D links entirely alone without any guidance from a network controller/content manager.

Brief Description of the Drawings

Reference is made, by way of example only, to the accompanying drawings in which: Figure 1(a) schematically illustrates cony tonal wireless cellular communication and Figure 1(b) illustrates D2D communication; Figure 2 shows a mixed network with wireless cellular links and D2 n Figure 3 shows the principle of content delivery employed in the present invention; Figure 4 is a flowchart of a content delivery proce an embodiment of the present in tion; Figure 5 is a block diagram illustrating an example of a central Feint() network controller to which the invention may be applied; Figure 6 is a block diagram illustrating an example of a terminal to which the invention may be applied; and Figure 7 is a lock dagram inns atava an example of a base station to which the invention may be applied.

Detailed Description

Small cell networks will continue to flourish in the 5G era., specially covering public access spaces like transport hubs and shopping malls, With the trends towards SON (Software Defined Networking) and NFV (Network Functions Virtualization), the physical Femto nodes wili become processor-and memory-light, thin devices. The processing and control of the networks will move to centralized controllers/managers, much like the SON controllers discussed in 4G. On the other hand, it is expected that IJEs will continue to possess more and more functionality, processing power and memory. These developments tally well with the model of UE caching and content distribution (through D2D), with some guidance from the network, Embodiments of the present invention therefore give to UEs (below, 'content-seeking UEs") the task of orchestrating --that is, managing and synchronizing -the content delivery through the D2D links within a local Femto network. In this process, the content-seeking tiE is given initial assistance by the Femto network controller (or alternatively a content manager as explained below). However, the subsequent management ("orchestrating") of D2D links is left to the content-seeking UE itself.

Thus, a locally-managed but centrally-assisted process is proposed for performing content delivery within a localized Femto network. The Ferrite network will physically cover locations like a shopping malt or a train station, with a large number of transient users. The area of such a Femto network is typically much smaller than one covered with a Macro cell. A Fernto network controller exists at the level of the control functions of the Femto network.

In such a Femto network, a large proportion of the data traffic will be multimedia content which is viewed (or consumed) by users on their mobile devices. A typical example would be a video clip which the user views on a display of the device, and the following description will refer to a "video" and 'viewing" by way of examples of "content' and "consuming" respectively. It should be understood, however, that many other forms of content may be delivered by the technique proposed here, including music and other audio files. eshooks, games. Web pages, data flies and so forth in any case, it can be assumed that there is at least one data file which contains the requested content and which is capable of being divided into parts or "segments" as referred to later, it can be further assumed that af a given time, certain items of content are more popular than others, For example the latest hit record or a video of a current sports event way be, if only for a short time, requested by many users and therefore cached in many user devices. Embodiments of the present invention make use of this phenomenon in order to deliver content locally from UEs in the vicinity which already store the requested content. As noted earlier, a typical Femto cell network is quite localized, covering R limited physical area like a shopping mall or a train station, with UEs in proximity close enough to initiate D2D links, albeit only temporarily.

Many of the above types of content will be capable of being accessed (reproduced) even before the whole file has been transferred to the content-seeking UE. For example, a video clip may start to be viewed front the beginning after a certain amount of the file has been stored in a buffer of the user's mobile device, even while subsequent parts of the We are still being transferred..

Suppose that a user of a mobile device (henceforth called a "content-seeking UE'") wishes to access some item of content on the device. As is normally the case, the content-seeking UF will request content from the network (higher layers). The request, received initially at a Fernto base station to which the UE is connected, is passed by the base station to higher-layer entities in the network. The network will push down the request to the Femto network controller. This controller maintains an up tc date list of the donor UEs in the Femto network, and the details of content (including freshness) they have cached. The Femto network controller examines the content request and checks whether there are enough donor UEs in the vicinity of the content-seeking UE to provided the requested content through D2D links. The controller can take into account the speeds and directions of movement of the content-seeking UE and the potential donor UEs, and estimate a likelihood of the content being delivered through the UEorchestrated multiple D2D connections. The Femto controller passes on this likelihood value to the content-seeking UE, allowing the user to decide which option is best to take. The user can weigh up the cost benefits of using this option as against other options which may be available, roe conten:, c n, qya core network in unvenb addition, the technique pr=oposed in UK patent application no. 00690.1 may;onie deirvery D2D Inks but s d by controller or a content manager. The cost, but reliability of successful deny, ssiyely for each option of core network delivery, centrally-orchestrated D20 delivery and LIE-orchestrated content delivery.

Therefore, the user's decision on which option to take up may depend on the user's situation at the time. If the desired content is not time-critical and the user is intending to spend more time within the Femto network, he or she may choose to use the option provided in embodiments of the present invention, namely UE-orchestrated content delivery. For example, if the user is relaxing in a coffee shop in a shopping mall or transport hub, and wants to watch a music video he or she may opt to select the UE-orchestrated content delivery option, even if the QoS guarantee is low. In the centrally-orchestrated technique proposed in UK patent application no. 1500690.1, delivery is virtually guaranteed either through D2D links or, in their absence, using normal (FeNB to UE) communication. However the control signalling required to achieve this is higher and this will be reflected in a higher cost charged to the user. Therefore, a user who is in a hurry to receive local weather information for example, may choose to select centrally-orchestrated content delivery.

In embodiments of the present invention, the Femto network controller Involved only in the initial stage to inform the user of the likelihood (possibly as a probability value) of the content being sourced by UE-orchestrated content delivery. if the user decides to take up this option, their UE then broadcasts content request messages to other UEs in the vicinity, in order to discover donor UEs and then establish D20 links. The UE may be assisted in this by the controller informing the UE (e.g. along with the likelihood value) of a suitable other UE with which to establish a first 02D link, Thereafter, however, the UE has to discover other UEs and establish links autonomously.

Content delivery an then commence over a 02D link so established. In the prior art, successful content delivery via D2D requires that one D2D link remain stable for the length of time needed to transfer the requested content, but this is not necessary in the present invention.

If this 02D link breaks or) before the full content has been transferred (for example owing to mobiiity of the respective itlEs), the content:seeking will then discover-another donor LIE and source the remaining part (e.g., a next segment or segments) of the content Re. it should be noted, however, that deperkling on the gate buffet raie and consumption rate, the UE may not need an immediate physical handover from one donor LIE to another, Assuming that the user has already started to view the requested content and that there is sufficient buffered content in the content-seeking LIE" the content-seeking UE need not immediately connect to another donor UE, but has some time to spare before the next content segment becomes necessary, If should also be noted that delivery of the full content (e.g. the whole of a video file) in a single D2D connection is not always necessary, because many items of content (such as video dips) download on mobile devices are not viewed in their entirety by a user but rather, are abandoned part-way through. It is therefore a waste of resources and energy to buffer extensively large content. The buffer should contain only the right amount of content to enable the user to view (or consume) the content without disruption. Also the D2D link quality may not always be as good as the FeNB UE link quality, so the data rates on the D2D link can be low. This dictates that only a limited amount of data be transferred within a single D20 iink.

EnoU0din\en\a(d1hepnesentiMvenh0nre|yooUEobeiAgwiUi0gkloffercOntSn\t0o| he|UEGin their vicinity, -to be precise, it is assumed that users of those UEs have opted in to content sharing (which can he incentivized as explained later). The Femto network controiler maintains an up-to-date list of UEs currently within the Femto network and which are available to cache and share content through D2D. The Femto network controller will also possess knowledge of the details of the content (content ID,. its freshness etc) each such UE is caching. Normally, it can be assumed that a tiE stores the whole of an item of content (e.g., the whole of a video from start to finish), typically because the user of that UE has downloaded it for their own use, Further, the Fernto network controller will hold a register of donor UEs, their content and their current locations, so the controller can provide an accurate estimate of success probability for content seeking UE-orchestrated D2D attempts. In this way, the Femto network controller is better informed than any content-seeking UE can be regarding the availability of content on other devices in the vicinity, and on the likelihood of success in content delivery via D2D, and can provide guidance to the content-seeking UE at the start of the content delivery process. It should be noted that the Femto network controller only has a function of providing initial guidance to the content-seeking DE: it does not itself manage the content delivery, nor does it provide content est)" a network caching eiement Content is labelled with a content lD, tnis may locates. URL, on the internet cif an original source (main or root server) where the content can be found, with additional indexing for versions of the content. A content request, inciuding a content ID, is received at the base station (Femto eNB) and passed, via higher network layers, to the central Femto network controller. The Fernto network controller identifies the item of content being asked for" based on the ID, analyses the content availability and decides whether or not D2D links can be used for the content delivery to the requesting LIE Preferably, both UEs and the central Femto network controller employ a common ID for the content, so the Femto network controller can track this easily, If there are different IDs for the same content being used by different services or applications, the Femto network controller uses a matching table to cross-reference the different IDs. A version number or date of modification of the file may be added as an indication of "freshness" of the content.

Certain LiEs in the network have opted to become 'donor 1,M's' and reveal the content they are willing to donor, to the Femto network controller. The cached content of each participating UE is refreshed periodically to take account of newer versions of the content becoming available at the original source. In this way.; the Femto network controller knows the content each donor LiE is holding. By identifying donor LIEs with the same content cached in the vicinity of the content seeking UE, the Femto network controller can judge the probability of the content-seeking UE being able to source the requested content over D2D links, and notify the content-seeking UE accordingly_ Here, 'in the vicinity' means within range to establish D2D radio connectivity. Depending on LIF transmit power, this can be 100m or more in free space. in the more typical indoor Femto ceil environments, the range will be rather less but there may be a dense population of users, so there is a good chance of D2D based content transfer being possible.

The principle of the invention will now be explained in more detail by referring to Figure 3.

Femto nodes 21-28 form a Femto network of overlapping small sells, and are connected to a Trento natl./5W controdier 50. For sirrickliky" connecrfichs /4 the Ferrite codes to the backbone network and content server 40 are not shown. As shown, there are many UEs-in proximity to one another, as wcuid be the case for example in a /away station or shopping malt Each temto cell could correspond, for example, to one retail unit or pubk area in a shopping malt UEs 10, 11, 12, 14 and 16 are connected to the femto nodes 21 -28 (at least tor control purposes) and may also form 02D links with one another. UE is a c.ontent-seeking (requesting or recipient) LJE, Le. a LIE the user of which wishes to access certain content. The content-seeking LIE 11 may be assumed to be connected to the network via a FeNB; in the example shown this would initially be FeNB 22. UEs 10, 12, 14 and 16 are the donor UEs employed by the content-seeking UE 11 to obtain the content, and each has a communication range for D2D as indicated by the shaded ellipse. For simplicity, only one D2D link at a time is used in this example.

The logical connections from the Femto nodes 21-28 to the Femto network controller 50 are shown in black solid lines. The dash-dot lines with arrow ends show signalling between the Femto network controller 50, and the UEs; through the Fernto eNBs. For the purposes of the present invention; with respect to signalling between controller 50 and the FeNBs. only signalling between the Femto network controller 50 and the FeNE3 22 is required, The content deliven,i from the donor UEs is shown as black dotted arrows, along the path of the recipient UE 10's movement.

The content-seeking UE 1 is assumed to be mobile, with a direction of movement shown by the broad arrow. Of course, any of the other LIEs (including donor UEs 12, 14) may also be mobile; in different directions, but for clarity such movements are not shown in the Figure. On receipt of a content request from content-seeking UE 11; the Femto network controller 50 notifies the content-seeking UE 11 (via the FeNB 22) of the likelihood of obtaining the content hy UE-orchestrated content delivery, which option is accepted by the user. The controller 50 may further recommend a specific other UE with which to establish an initial D2D link (and the likelihood value may be conditional on the content-seeking UE 11 making this link). At this point, communication (with respect to the particular content de(ivery) between the content-seeking UE 11 and the controller 50 ceases, and the content-seeking LIE 11 has to discover donor UEs to obtain the content.

The content-seeking UE establishes D20 links with a succession cif donor tiEs along its path of movement in the example shown, initially the content-seek ng UE 11 starts to receive the requested content from UE 10 over an initial D2D link (which may have been recommended by the contraries). This content delivery continues for a while as the content-seeking UE 11 moves, until the strength of its 020 connection with UE 10 begins to decrease beyond a point where the D2D link is no longer stable. Although not directly relevant to the present invention, it may be noted that whilst employing the 020 link for content delivery, the content-seeking UE 11 maintains a wireless link with a femto node (initially, femto node 22) for exchanging controi signalling.

If the initial D2D link is no longer viable for content delivery, the content-seeking UE 11 must establish a connection with another donor UE 12, from which a further part of the requested content (i.e., a further one or more segments) can be obtained. As shown by the shaded circles in Figure 3, some of the coverage areas of donor UEs have gaps in between; in other words physical continuity of D2D links is not assured. Thus, UE-orchestrated content delivery is likely to be prolonged and less assured, compared;with other available modes of content delivery. As already mentioned however, this need not be a problem since data buffered in the content-seeking UE 11 may be sufficient to compensate for any gaps in the connectivity. Even if the buffered data is not sufficient, the user may be able to tolerate some pauses or freezing in the content -in other words a low.(..)oS -if the UE-orchestrated content delivery mode is financiaily attractive (for example, free of charge).

At a later point in its travel, content-seeking UE 11 is no iortger in range of donor UE 12 and it establishes a 020 link to a further donor UE 14. Eventually this connection too is no longer useful and the content-seeking UE 11 replaces the D2D link to UE 14 with one to UE 16. It may he assumed that the D2D link with DE 14 is sufficient to complete the transfer of the content, or alternatively that the user has abandoned viewing the content by this time such that further D2D links are not necessary, 3C Whilst the above process of changing from one D2D link to another resembles the handover between cells in a conventional cellular network, it should be noted that a "handover in the sense of a seamless transition is not essential The content delivery is packet based so the content delivery is "granular" in the sense of being divided into packets (or even bigger chuglosisegmento comprising multiple packets -see belong, to facilitate continuation of the content. Panpfer, By buffering coptem the content-seeking 11, a is sufficient that the content delivery, interrupted by an existing D2D becomind lost or unstable, can be resumed without a long deiay, in this way, the ooptentiseeking UE 11 can repfoduce to the user ibie content received so far, whilst a suitable source for the remainder of the content is sought. Thus. in the present invention, a logical tomi of a D20 hangover is sufficient, which need not require the physical contiguity of the D2D Meanwhile, the content-seeking UE 11 as it travels in the direction indicated in Figure 3, may be handed over for control purposes from one FeNB 22 to another FeNB 23 or 25 and sc on, but this is not of relevance for the content delivery process.

As just mentioned, the content delivery is packet-based and packets may furthermore be grouped into "segments', the entire item of content to be delivered being broken down into a convenient number of segments. For example in the case of a movie download, the requested content may be notionally divided into, say, a hundred segments of roughly equal size in terms of data size and/or duration when played back. This allows a possibly very large file, which would be unfeasible to transfer at present by one 020 link, to be delivered.

The segment size or number can be determined in various ways. Preferably, this is decided at the Femto network controller since this is the entity in the wireless network best able to judge a suitable segmentation for the current conditions in the Fernto network. The Feint° network controller 50 will look at the (average) signal strengths of the 020 links and the times available for a single link, and decide on the segment sizes. it can be as small as a few dozen packets or as large as few tnousands of packets. A policy on size of the segments can he set for the specific Femto network, at the Femto network controller level or higher. Thus, in this example the Femto network controller 50 informs the content-seeking UE 11 of how to segment the requested content.

Alternatively, however, the segmentation may be determined at a higher level in the network, at the content-seeking UE 11.0r even set in the system specification, By dividing the task of content delivery on the basis of segments, the content-seeking UE 11 can also deal with the case where the user interrupts accessing the content for some reason.

The UE records up to whet segment the content was delivereitt if the user requests the content agads tne UE can orchestrate the content to no delaterem start!ng from the ptent where the delivery was interrupted.

The preceding paragraphs concern dkpwrigeading of a file, but similar considerations would apply in the case of streaming, where the aim is not to store an entire file in the recipient LIE but to transfer enough of the content at one time to aliow uninterrupted v ewing and/or fistening.

A flow chart describing a content delivery method none ernbodime p sent inven, is shown in Figure 4. The process begins at S10.

At 511, the Femto network controller 50 receives a content request from a content-seeking UE 11 (referred to in the flowchart as "recipient UE") That is, the UE transmits a content request to its current serving Femto cell, or more precisely to the FeNB. The FeNB, being a "thin'. device, simply passes the content request up the network to higher layers capable of interpreting it, The content request thus finds its way to the Femto network controller 50. The content request includes the content ID referred to earlier, such as a URL on the World Wide Web where the content can he found.

Meanwhile, the network (the Femto eNBs) supply the Femte network controller with other information including the locations of each of the tiEs currently active in the Femto network, including the content-seeking UE 1(. Further, the Femto network controlier maintains against each UE (or at least, each UE which has opted-in to being a donor UE) a record of content held by that LIE. It can normally be assumed that in each potential donor UE, the whole of the 2-$ requested content is available, but that the donor LJE can transmit segments individually.

In step 512, the Femto network congener 50 checks which LiEs have the requested content and assesses which UEs are suitable to act as donor UEs for the content-seeking UE 11, bearing in mind the respective locations and relative motions of the LiEs. The Femto network controller only performs this process with UEs who opt to be donors, so this factor need not be checked again.

Next (S13) he controller calculates the likelihood of UE-crchestrated content rieliv ry being successful, and informs the recipient UE accordingly, via the FeN6.

in step 814, the UE. (or more precisely, the human user of the LiE) act des whether or not to accept the UE-orchesthated content delivery opt:on. The user indicates their choice via a user interface of the recipient liJE (e.g., a keyboard or toughs-Teen). If the user's choice is Yes, the flow proceeds to step 515, fVleanwhile, if the resuit of the decision in S14 is No, the process according to the present invention is not employed and instead (step 522) the content-seeking UE. '11 obtains the desired content in another way, for example through direct content delivery via the cellular network.

in 315 the recipient UE discovers a donor LIE and establishes a D2D connection with that UE.

This process occurs automatically without involving the user The content delivery phase of the operation can now commence. As already mentioned, the content requested is nationally divided into multiple segments for management purposes. In the form of the algorithm described below, the segments are considered one at a time, but alternatively more than one segment may be considered together. As already mentioned, the segmentation (in other words the sizes and/or s(art-end points of the segments within the file) is known to both the requesting and donor UEs, for example by being notified from the Femto network controller 5G.

Starting with a first segment (316), the donor UF. transfers the current segment to the recipient UE (517). Preferably, each segment successfully delivered is acknowledged by the recipient 11E_ At 317, after delivery of the current segment, the recipient UE checks whether the 02D link is still viable, or it is breaking up (fading, or unstable) Signal strength of the D2D link is an indication of this as already mentioned. Alternatively, or in addition, the recipient OE may detect that the current segment was not successfully receive& The recipient UE keeps track of which segments have been successfully received, and which remain to be delivered.

Following a determination in 318 that the existing D2D link is breaking up (518, Yes), the recipient UE discovers a new donor UE in step S19 and establishes a D2D link with this UE. This would correspond, for example, to the switch from UE10 to UE 12 in Figure 3 Again, the recipient UE is configured to perform this switch automatically without the user being involved (or even aware of the switch). if the link rs not breaking up (S)18, No) it can continue to be used any case, b k of further segments are delivered (step 8201 and is is cliecked vidriethei content deliveor is complete in £21. If the content has been transferred entirely then the process ends (823). otherwise flow returns to before £17 for the next segment.

in £21, 'is content delivery complete? can cover both the actual completion or the abandonment of the content consumption by the user. In either case, the recipient LIE will be aware of the fact, Though not essential to the process, the content-seeking UE 11 may inform the network (via a FeNIE3) of completion cif the content delivery as an aid to the controller 50 to monitor success of UE orchestrated content delivery attempts, allowing refinement of its future guidance to attempts by other UEs.

To summarise the above, the essence of the algorithm is that once a content-seeking UE 11 opts for UE-orchestrated content delivery, the controller (and the other entities in the network) will keep a hands-off approach. The content-seeking UE 11 is in full control to discover donor UEs and initiate D2D sessions with them, A benefit of this approach is the elimination of the signalling overhead from the network side, needed to manage D2D delivery in the applicants previous proposal. This benefit to the network can be reflected in lower (or no) data charges for the recipient UE when using this mode. Any charge levied would be for providing the estimated chance of success and likely time taken, rather than for the content delivery as such. If content delivery fails for any reason, the UE will have the option to receive the content through the normal core network delivery mode (this is not shown in Figure 3), The likelihood value referred to above can be a simple probability estimate, but also can include an estimate of the time expected to be required for the UE to obtain the requested content through UE-orchestrated content delivery. Such a detailed estimate may help the user to decide how quickly he or she wants the content and decide cn the best option to take. In generating the time estimate, the controller (or content manager) looks at the file size of the requested content and the quality of the possible D2D links the content-seeking UE 11 is likely to establish, This estimate can also be given as a range of time values (shortest time n the best case scenario to the longest time in the worst-case scenario).

Expected enhancements in 40 and 50 systems will facilitate the ability of mobile handsets to estabflsh multiple LCD llnks in the cfartner described above. For example., urE Release 12 includes 02D-based proximity services.

A key benefit of the approach described above is hat the more popular an item of content, the bigger is the advantage to be gained from reducing duplicated traffic in the hackhaul and reducing the load on the root/main content servers. A content request from a LIE will gO to the content server, which will proxy to the local Ferrito network controller or content manager, which in turn will proxy to the local cache/content source (as indicated above) to deliver the content Another embodiment aims to entice some of the users to become donors within the network. For the method of the invention to be feasible, it is important that there be donor UEs available to deliver the requested content. As an inducement to become donors, the donor UEs may be given some incentive such as obtaining UE-orchestrated content delivery free of charge.

Other measures can be taken to improve the availability of content via D2D, For example, if a user is employed as shop workers at the shopping mall or the transport hub, they are likely to spend a far greater amount of time than the average customer or passenger within the Femto network. Such users (identified through the time spent within the network) can be given more incentives to allow their devices to act as donor LiEs in the present solution. f heir monthly data allowances can be increased, or newer phones can be offered at cheaper prices, for example.

In a further embodiment, availability of popular content is enhanced by taking advantage of storage capacity available in MTC devices. As already mentioned, such devices are often provided in locations where users congregate; for example, MTC devices in the form of vending machines may be located in a public area of an office block. They may be mains-powered and always-on, and thus may be very useful for content delivery to users passing in their vicinity. MTC devices may also have a wired internet connection; allowing transfer of popular content from the original content servers without burdening the wireless network.

In one variation of this embodiment, existing MTC devices, already provided for other purposes, are employed opportunistically. taking advantage of spare storage capacity to cache popular content in return for some kind of reward or incentive to the owner of the MTC device.

another variation, additional WC devices are deployed for the primary purpose of storing popular contest, in this case the range of content made avaiiabie can be potent:gib! paha iarge For example in a public area such as a train station, the network operator could deploy a M C device having a wired (or fibre) Internet connection, iscal hard-disk based storage., and a Eifi2D capability, allowing popular content to be pushed to the device and later made available io a requesting terminal via 02D.

Figure 5 is a block diagram illustrating an example of a central Femto network controller 50 to which the present invention may be applied. The Femto network controller may be provided in the form of a conventional computer connected (via the backbone network) to the Femto network. A communications interface 502 of the central Ferrite) network controller 50 deals with communications to and from the femto network. A processor 504 is programmed or otherwise configured to perform the various functions described above, such as calculating the likelihood of content delivery via D2D links. A Table 506 is maintained by the processor to record details of donor LlEs and their cached content, as well as the state of connections between UEs, in particular D2D links of the content-seeking UE 11 with other UEs. Locations of all UEs in the femto network, and their states (such as 'active" oi "standby') are further information stored in the central Femto network controller.

Figure 6 is a block diagram illustrating an example of a term nal 10 to which the present invention may be applied, The terminal 10 may include any type of device which may he used in a wireless communication system described above and may include cellular (or cell) phones (including smartphones), personal digital assistants (PDAs) with mobile communication capabilities, laptops or computer systems with mobile communication components, and/or MTC devices as discussed earlier, The terminal 10 includes transmitter/receiver unit(s) 804 connected to at!east one antenna 802 (together defining a communication unit) and a controller 806 having access to memory in the form of a storage medium 808. The controller may be, for example, a microprocessor, digital signal processor (DSP), ASIC, FPGA, or other logic circuitry programmed or otherwise configured to perform the various functions described above, such as initiating a D2D link with another UE and monitoring progress of the content delivery. For example, the various functions described above may be embodied in the form of a computer program stored in the storage medium 808 and executed by the controller 804, The storage medium 808, or another storage medium, stores the content cached by the UE. The same or another storage medium may alsc be used as the buffer for content being consumed by the user. The transmissionlrecept on unit 804 is arranged, under control of the Daueoller 806, to send annnYen!EttqueSti0theUe(mock, neceiw6hroU1th6Detw/nrkthegUidaoc6frOrnfheFra8bj network controller and so forth as discussed previously.

Figure. '7 is a bettick diagram illustrating an example of a base station 20 (F"el\tB) to which the present invention may be applied. The base station includes transmitterlreceiver unit(s) 904 connected to at least one antenna 902 (together defining a communication unit) and a controller 906. The controller may be, for example, microprocessor, digital signal processor (DSP), ASIC, FT)GA" or other logic circuitry programmed or otheiwise configured to perform various functions such as performing resource allocation (under network control) for the UEs which it serves. For example, the various functions described above may be embodied in the form of a computer program stored in the storage medium 908 and executed by the controller 906: The transmission/reception unit 904 is responsible for receiving a content request from a content-seeking UE, transmitting signalling for UEs from higher layers including the Femto network controller and so on under control of the controller 906.

To summarise, embodiments of the present invention provide a content delivery method employing transient 020 links among LIEs 10, 11, 12 14 in the vicinity of a content-seeking UE 11 and which locally cache desired content. To obtain the desired content, successive D2D links are initiated by the content-seeking UE 11 with initial guidance from a central Fernto network controller 50. The central Femto network controller 50 identifies possible 020 content donor LJEs in the vicinity of the content-seeking UE 11 and indicates a probability of successfully obtaining the content through UE-orchestrated content delivery. A user then decides whether to attempt LIE-orchestrated content delivery or whether to obtain the content in another way, for example directly from a root server through the core network. in the case of UE-orchestrated content delivery, the content-seeking UE 11 handles the establishing of the necessary D2D links automatically.

The use of a central Fent° network controller to guide the content-seeking UE 11 in establishing D2D links is a novel feature of the present invention. As noted before, the concepts of UE caching and transfers of content through D2D are not new in themselves. What is novel is usage of the transient D2D links for content transfer and executing the content transfer through multiple, coordinated D20 links as orchestrated (managed) by the content-seeking UE 11.

D2D iniandovere have been discussed before, as a physical layer problem, By contrast:, embodiments of the present invention provide a content management sc Jtion, in which the Fernto network contrail& dgmarity keiitke tor the availability of content in donor UEs to execute a logical handovet between UEs.

One novel feature of embodiments is the manner in which. the 020 links are initiated and how (at least logically) handover is sought arid executed. There are some solutions in the prior art, where 02D handover is considered as a physical layer problem, just as an inter-eNB handover.

If the UE could find another UE. with good radio links the handover is executed. But in the present invention, it is considered as a content layer problem. The central controller of the (Femto) network seeks a donor UE to continue the content delivery, from the point of (buffered) content termination from the previous D2D link. The physical D2D handover can be discontinuous in this sense, but the connectivity in the sense of content provision should be continuous.

Various modifications are possible within the scope of the present invention.

Whilst the above description referred to 020 links within the context cf a Ferfito network, the presence of a Femto network is not essential. The present invention can be applied also to links within a Macro cell. References to "Ferntc network' are to read as covering any kind of SON.

As mentioned earlier, "020' is oeneraily understood as meaning wireless communication using the same RAT as the cellular network and on licensed spectrum available to the network operator, However, the present invention can also he applied to other types of short-range wireless technology between UEs" including Wi-Fi lin particular WiFi Direct) and VVPAN technologies including B/uetooth (IEEE 802.15), so long as the Femto network controller is able to guide the UEs' usage of these technologies.

Above, reference was made to the Fernto network controller as the entity which assists the content-seekino UE 11 at the start of the content delivery process" In one variation, a separate entity is provided which is in charge of managing content delivery generally in the Femto network. In contrast to the conventional Femto network controller having many different functions, this content manager focuses only on the actions for content delivery to a requesting be!a this variation, it is the content manager which evaluates Lhh locations and movements of the content-seeking UE 11 and potential donor LtEsi and which provides a likelihood value for obtaining content through his option to the content-seeking UE 11. Such a content manager can also be responsible for handling centraiiyaorchestrated content delivery; this an available option made available, As a further variation; it is possible to nj out the content manager role also in the root/main content server.

In a further variation, although the content-seeking UE 11 is left to establish D2D links without network assistance, it does not necessarily establish a next D2D link with the closest donor UE available. The content-seeking UE 11 may be configured to take into account its direction and rate of movement in order to select as the next donor UE, a UE which the content-seeking UE 11 is approaching even if this is not the closest potential donor at the time the selection is made.

The content-seeking UE 11 may be assumed to be aware of its own movement through monitoring of received signal strengths, having a receiver for a satellite-positioning system or other known techniques.

The example was given above of users in a shopping mall or transport hub, and in such a case there is a natural lirnit on the extent of the Fernto network to be controlled, as well as a reasonable presumption that 020 links among LiEs are possible. In the case of a more extensive network, the Fernto network controller or content manager could notionally divide up the network into sub-regions for which the number of users is more manageable, and D2D links are feasible.

Reference was made above to transferring content in segments with an Initiar * n 0i being followed by "subsequent" segments. This is a convenient way to break down the problem, particularly for content such as video and/or audio which has a duration in time and can be consumed starting from the beginning. It will be apparent, however; that it is not essential to deliver segments in any particular order. So long as segments can be identified in some way; they can be transferred to the content-seeking UE 11 in any arbitrary order and re-assembled there for consumption by the user.

The method described above considered one D2D link at a time for simplicity. However, it may he gossege for the reoBnent HE to arrange coulifole sunt.litangous D2D links from iffferent donor DEs, employing different timelfrequency resources to avoid interference. By keeping track of which segments have oeen successfuliy roc:en::4 the redtAent DE can avoid duplication of segments.

in the above description, it was assumed that any LIE. holding the requested content, which is opted-in to act as a donor and which is in range of the c,oritent-seeking UE II, may be chosen to become a donor UE. However, other factors may also be taken into account such as how recently, or how often the potential donor has already transferred content to a content-seeking UE 11, and/or the power supply or battery state of the potential donor UE, Where necessary, such additional factors would be notified to the content-seeking UE 11 at the start of the process (step S13 in Figure 3). In this regard, devices of shop workers which may be plugged into a charger, or MTC devices having a mains power supply, may be especially useful since power consumption is not a constraint.

was also assumed above that the donor UE already hoids the stored content owing to the user of that UE having requested it. This is not essential, however. In return for a suitable incentive (such as an extra data allowance or credit against network charges), a donor LIE may accept content which has not specifically been requested by the user but which it is useful for the Feinto network controller to have made available by that LIE. In the case of the shop worker referred to earlier for example, he/she may not have the Iime or inclination to watch a sports video, but their mobile phone may be valuable as a donor UE by remaining in roughly the same place for an extended period. In this case, the content chosen to push to the donor IJE would be content which either is already frequently-requested or which can be predicted to be popular based on past experience. In the embodiment employing MTC devices as discussed above, the choice of which content to store in the MTC device wouid he made in the same way.

In the method described above with respect to Figure 4, the user made the decision to select the UE-orchestrated content delivery mode or not after the UE received likelihood information from the Femto network controller. However, this is not essential. The recipient UE may be configured to select the UE-orchestrated content delivery automatically whenever preset conditions are met, such as the probability of success exceeding a user-seiected threshold value, and/or the expected time being within a user-selected limit time.

mdoslirlai appliciablige Embodiments of the present invention nun improve efficiency in a wireless communication network by reducing the need for content delivery to take piece via the ceilular network and via retrieval of content over a backbone network, instead taking advantage of content already held by nearby LJEs. By employing successive 02D links with the nearby LlEs. a possibly large content file can be delivered,

Claims (7)

1. CLAIMSA terminal for use in a wireless network and equipped for deviceSomievice, L.14 0, wireless communication wlth other terminals in its Ws:Inlay: comprising: input means for receiving, from a user, an instruction to obtain requested content; requesting means for transmitting a corresponding content request to the network; receiving means for receiving information from the network in response to the content request; and managing means for, when it is determined based cn the received information to employ 02D communication for content delivery, establishing a plurality of 02D links with other terminals for obtaining the requested content, ihe managing means arranged to establish the D2D links without further guidance from the network.
2. 2. The terminal according to claim 1 wherein the received information, based on which the managing means determines to employ D2D communication for content delivery, includes a likelihood estimate of success in obtaining the requested content.
3. The terminal according to claim 1 or 2 wherein the wireless network is a F'emto network and the information is received from a Femto network controller or a central content manager.
4. 4, The terminal according to claim 1, 2 or 3 wherein the input means is further arranged to receive a decision from the user to employ 02D communication for the content delivery.
5. The terminal according to any preceding claim wherein the managing means is arranged to divide the requested content into a plurality of segments and to obtain at least one segment from each of the D20 links.
6. 6. The terminal according to claim 5 wherein the managing means is arranged to maintain one D2D link at a time, continuing with a D2D!ink for as long as the link remains viable to transfer segments of the requested content and then to establish a fresh D2D link to obtain at least one further segment.
7. 7. The terminal according to claim 6 wherein the managing means is arranged, prior to establishing a fresh D2D!ink, to check that the requested content is still required by the user, ei control entity in a wireless network, cooriffyieed to: receive a content request from a conteneseekew terminal; on the basis of the content specified in the request, identify potential donor terminals for the requested content; estimate a likelihood of content defivery to the cootentrseeking terminal being possible by use of multiple 020 Links; and notify the content-seeking terminal of the calculated likeiihood.9. The control end b/ according to claim 8 further configured to estimate said likelihood based on information including: terminals being served in the wireless network and locations of such terminals; content stored in the terminals; and movements of the terminals.10. The control entity according to claim 8 or 9 in the form of a Femto network controller or a central content manager, the terminals being terminals of a Femto network.11. A method of content delivery via device-to-device, D2D, links of terminals in a wireless network comprising: at a control entity of the wireless network: receiving a content request from a content-seeking terminal and identifying potential donor terminals for the requested content; and estimating a likelihood of content delivery being possible by use of multiple 020 links and notifying the content-seeking terminal of the likelihood; and at the content-seeking terminal: deciding on the basis of the received iikelihoo whether to employ 020 links to obtain the requested content and, if so, establishing multiple D2D links with donor terminals to obtain the requested content, the requesting terminal managing the establishment of the D2D links without further. involvement of the network controller.12. The method according to claim 11 wherein the requested conte. divided into a plurality of segments and the content-seeking terminal obtains at least one segment from each of the 070 lirik.s 13. The method according to claim 12 wherein the D2D:inks are successive, the content-seeking terminal maiMaining one 020 link for as tong as the D2D links remains viabie transfer segments of the requested content and the conteriteseeking terminal then establishing a fresh D2D link to obtain at least one further segment.14. The method according to claim 13 wherein prior to establishing a fresh 020!ink the content-seeking terminal checks that the requested content is still required by a user of the content-seeking terminal.15. The method according to any of claims 11 to 14 wherein the control entity identifies potential donor terminals for the requested content based on information including: terminals being served by the network controller and locations of such terminals; content stored in the terminals; and movements of the terminals.16. The method according to any of claims 11 to 15 wherein the terminals are terminals n a Fernto network and the control entity is a Femtc network controller or a central content manager 17.. The method according to any of claims 11 to 16 further comprising the control entity providing to the content-seekina terminal, as an alternative to employing D2D links to obtain the requested content, at least one further mode of obtaining the requested content and indicating an expected time taken in each mode.18. The method according to claim 17 wherein the at least one further mode n content delivery from a core network linked to the wireless network.19. The method according to claim 17 or 18 wherein the at least one further mode includes content delivery via D2D links managed externally to the content-seeking terminal.20. Software in the form of program code which when executed by a processor of a wireless terminal in a wireless network, causes the terminal to perform the steps of: receiving a request for specified content from a user of the terminal and transmitting a corresponding content request to the network: receiving from the network an estimate of a likelihood of delivery of the specified content being possible by use of multiple 02D links; obtaining a decision based upon he received likelihood of whether to employ D2D links to obtain the specified content and, if so, estabiishing, without further involvement of the network, multiple D20 links with donor terminals to obtain the specified content.