Patent Publication Number: US-11665691-B2

Title: Communications devices and methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is based on PCT filing PCT/EP2017/081501, filed Dec. 5, 2017, which claims priority to EP 17150482.2, filed Jan. 5, 2017, the entire contents of each are incorporated herein by reference. 
     BACKGROUND 
     Field of Disclosure 
     The present disclosure relates to communications devices which are configured to transmit data to and receive data from infrastructure equipment of a wireless communications network, in accordance with at least one of a first radio access technology, RAT, and a second RAT. 
     Description of Related Art 
     The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention. 
     Third and fourth generation mobile telecommunication systems, such as those based on the Third Generation Project Partnership (3GPP) defined Universal Mobile Telecommunications Standard (UMTS) and Long Term Evolution (LTE) architecture are able to support more sophisticated services than simple voice and messaging services offered by previous generations of mobile telecommunication systems. For example, with the improved radio interface and enhanced data rates provided by LTE systems, a user is able to enjoy high data rate applications such as mobile video streaming and mobile video conferencing that would previously only have been available via a fixed line data connection. The demand to deploy third and fourth generation networks is therefore strong and the coverage area of these networks, i.e. geographic locations where access to the networks is possible, is expected to increase rapidly. However, whilst fourth generation networks can support communications at high data rate and low latencies from devices such as smart phones and tablet computers, it is expected that future wireless communications networks, will be expected to efficiently support communications with a much wider range of devices associated with a wider range of data traffic profiles, for example including reduced complexity devices, machine type communication devices, high resolution video displays and virtual reality headsets. Some of these different types of devices may be deployed in very large numbers, for example low complexity devices for supporting the “The Internet of Things”, and may typically be associated with the transmissions of relatively small amounts of data with relatively high latency tolerance, whereas other types of device, for example supporting high-definition video streaming, may be associated with transmissions of relatively large amounts of data with relatively low latency tolerance. 
     There is therefore expected to be a desire for future wireless communications networks, which may be referred to as 5G or new radio access technology (which may be denoted new RAT or, simply, NR) networks, to support efficiently connectivity for a wide range of devices associated with different applications with different characteristic data traffic profiles, resulting in different devices having different operating characteristics and/or requirements. 
     The introduction of new radio access technology (RAT) systems/networks therefore gives rise to new opportunities as well as challenges. One such challenge is how initially deploy new RAT systems, particularly when LTE systems will still be widespread. 
     SUMMARY OF THE DISCLOSURE 
     Embodiments of the present technique can provide methods which relate to communicating in a wireless telecommunications system comprising a communications device and one or more infrastructure equipment, wherein the communications device is configured to transmit signals to and receive signals from the infrastructure equipment via a first wireless access interface in accordance with a first radio access technology, RAT, and to transmit signals to and receive signals from the infrastructure equipment via a second wireless access interface in accordance with a second RAT, the second RAT being different to the first RAT. 
     In a first embodiment, the method comprises receiving, at the communications device via the first wireless access interface, control signalling from one of the infrastructure equipment, the control signalling comprising an indication of first communications resources to be used by the communications device to transmit/receive signals representing data to/from the one of the infrastructure equipment via the second wireless access interface, and transmitting, from the communications device, the signals representing data to and/or receiving, at the communications device, the signals representing data from, using the first communications resources, the one of the infrastructure equipment via the second wireless access interface. 
     In a second embodiment, the method comprises transmitting, by the communications device via the first wireless access interface, control signalling to one of the infrastructure equipment, the control signalling comprising physical uplink control information to be used by the one of the infrastructure equipment, the physical uplink control information relating to the second RAT. 
     Embodiments of the present technique, which further relate to communications devices, methods of operating communications devices, and circuitry for communications devices, may provide ways in which complexity of initial deployment of NR systems may be reduced, allowing for wider, faster and cheaper deployment of such systems. 
     It is known in prior art systems, such as that disclosed in [1], that NR uplink control information (UCI) can be transmitted in uplink resources used for LTE in order to indicate the status of NR transmissions, where the NR UCI is coded according to NR transmission formats. However, embodiments of the present technique relate to the transmission of new inter-RAT downlink control information (DCI) and inter-RAT UCI that can be transmitted using LTE transmission formats in order to indicate the status of NR transmissions. 
     Respective aspects and features of the present disclosure are defined in the appended claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the present technology. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein like reference numerals designate identical or corresponding parts throughout the several views, and wherein: 
         FIG.  1    is a schematic block diagram of a first wireless communications system with architectural components corresponding to that of a conventional LTE-based network; 
         FIG.  2    is a schematic block diagram of a second wireless communications system with architectural components corresponding to that of an example enhanced new radio (NR) or 5G network; 
         FIG.  3    shows an example of how LTE and NR transmissions may be differentiated between using time division multiplexing (TDM); 
         FIG.  4    shows an example of how LTE and NR transmissions may be differentiated between using frequency division multiplexing (FDM); 
         FIG.  5    shows an example of a multicast-broadcast single-frequency network (MBSFN) subframe used to support a LTE/NR coexistence; 
         FIG.  6    is a part schematic representation, part message flow diagram of communications between a communications device and an infrastructure equipment of a wireless communications network in accordance with embodiments of the present technique; 
         FIG.  7    shows an example of an inter-RAT downlink control information (i-RAT DCI) allocating NR-physical downlink shared channel (NR-PDSCH) resources to a UE in accordance with embodiments of the present technique; 
         FIG.  8    shows an example of multiple i-RAT DCIs allocating NR-PDSCH resources and LTE-PDSCH resources in accordance with embodiments of the present technique; 
         FIG.  9    shows an example of i-RAT DCI in LTE MBSFN subframes in accordance with embodiments of the present technique; 
         FIG.  10    shows an example of the scheduling of NR-PDSCH resources in non-MBSFN subframes and MBSFN subframes in accordance with embodiments of the present technique; and 
         FIG.  11    shows an example of the allocation of NR-PDSCH resources using either an i-RAT DIC in the LTE control channel region or an NR-DCI in the NR control channel region in accordance with embodiments of the present technique. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     LTE Technology (4G) 
       FIG.  1    provides a schematic diagram illustrating some basic functionality of a mobile telecommunications network/system operating in accordance with LTE principles and which may be adapted to implement embodiments of the disclosure as described further below. Various elements of  FIG.  1    and their respective modes of operation are well-known and defined in the relevant standards administered by the 3GPP (RTM) body, and also described in many books on the subject, for example, Holma H. and Toskala A [2]. 
     The network  100  includes a plurality of base stations  101  connected to a core network  102 . Each base station provides a coverage area  103  (i.e. a cell) within which data can be communicated to and from communications devices  104 . Data is transmitted from base stations  101  to communications devices  104  within their respective coverage areas  103  via a radio downlink. Data is transmitted from communications devices  104  to the base stations  101  via a radio uplink. The uplink and downlink communications are made using radio resources that are licensed for exclusive use by the operator of the network  100 . The core network  102  routes data to and from the communications devices  104  via the respective base stations  101  and provides functions such as authentication, mobility management, charging and so on. 
     Wireless communications systems such as those arranged in accordance with the 3GPP defined Long Term Evolution (LTE) architecture use an orthogonal frequency division modulation (OFDM) based interface for the radio downlink (so-called OFDMA) and a single carrier frequency division multiple access scheme (SC-FDMA) on the radio uplink. 
     New Radio Access Technology (5G) 
     As mentioned above, the embodiments of the present invention can find application with advanced wireless communications systems such as those referred to as 5G or New Radio (NR) Access Technology. New Radio Access Technology (RAT) has been proposed in [3] to develop a new RAT for the next generation wireless communication system, i.e. 5G, and in 3GPP a Study Item (SI) on NR has been agreed [4] in order to study and develop the new RAT. The new RAT is expected to operate in a large range of frequencies, from hundreds of MHz to 100 GHz and it is expected to cover a broad range of use cases. The use cases that are considered under this SI include:
         Enhanced Mobile Broadband (eMBB)   Massive Machine Type Communications (mMTC)   Ultra Reliable &amp; Low Latency Communications (URLLC)       

     The aim of 5G is not only mobile connectivity for people, but to provide ubiquitous connectivity for any type of device and any type of application that would benefit from being connected. Many requirements and use-cases are still being discussed, but amongst those are:
         Low latency   High data rates   Millimetre wave spectrum use   High density of network nodes (e.g. small cell and relay nodes)   Large system capacity   Large numbers of devices (e.g. MTC devices/Internet of Things devices)   High reliability (e.g. for vehicle safety applications, such as self-driving cars)   Low device cost and energy consumption   Flexible spectrum usage   Flexible mobility       

     An example configuration of a wireless communications network which uses some of the terminology proposed for NR and 5G is shown in  FIG.  2   . In  FIG.  2    a plurality of transmission and reception points (TRP)  210  are connected to distributed control units (DU)  220 ,  230  by a connection interface represented as a line  203 . Each of the transmitter receiver points (TRP)  210  is arranged to transmit and receive signals via a wireless access interface within a radio frequency bandwidth available to the wireless communications network. Thus within a range for performing radio communications via the wireless access interface, each of the TRP  210 , forms a cell of the wireless communications network as represented by a dashed line  208 . As such wireless communications devices  104  which are within a radio communications range provided by the cells  210  can transmit and receive signals to and from the TRP  210  via the wireless access interface. Each of the distributed control units  220 ,  230  are connected to a coordinating unit (CU)  214  via an interface  216 . The CU  214  is then connected to the a core network  217  which may contain all other functions required for communicating data to and from the wireless communications devices and the core network  217  may be connected to other networks  218 . 
     The elements of the wireless access network shown in  FIG.  2    may operate in a similar way to corresponding elements of an LTE network such as that shown in  FIG.  1   . It will be appreciated that operational aspects of the telecommunications network represented in  FIG.  2   , and of other networks discussed herein in accordance with embodiments of the disclosure, which are not specifically described (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be implemented in accordance with any known techniques, for example according to currently used approaches for implementing such operational aspects of wireless telecommunications systems, e.g. in accordance with the relevant standards. 
     The TRPs  210  of  FIG.  2    may in part have a corresponding functionality to a base station or eNodeB  101  of an LTE network, and so the terms TRP and eNodeB in the following description are interchangeable. Base stations, which are an example of radio network infrastructure equipment, may also be referred to as transceiver stations/NodeBs/eNodeBs (eNBs)/gNodeBs (gNBs), and so forth. Similarly the communications devices  104  may have a functionality corresponding to devices know for operation with an LTE network and may also be referred to as mobile stations, user equipment (UE), user terminal, terminal device, mobile radio, communications device, and so forth. It will be appreciated therefore that operational aspects of a new RAT network (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be different to those known from LTE or other known mobile telecommunications standards. However, it will also be appreciated that each of the core network component, base stations and terminal devices of a new RAT network will be functionally similar to, respectively, the core network component, base stations and terminal devices of an LTE wireless communications network. 
     At least for initial deployment, NR and LTE are expected to coexist. Coexistence can be implemented using the same frequency resources but NR and LTE are differentiated using time division multiplexing (TDM). For example, NR may use LTE multicast-broadcast single frequency network (MBSFN) subframes, where there are up to a maximum of six LTE MBSFN subframes in each radio frame, as shown in  FIG.  3   . As shown in  FIG.  3   , six LTE MBSFN subframes  302  (subframes 1, 2, 3, 6, 7, 8) are used for NR transmissions, and the remaining subframes  304  are used for LTE transmissions. Another implementation is to use separate frequency resources and implement NR as a secondary carrier in a multi-carrier operation. Here, LTE uses one frequency carrier  402  and NR uses another frequency carrier  404  as shown in  FIG.  4   . 
     It will be appreciated that an MBSFN subframe consists of an LTE control region and a blank region. The LTE control region contains LTE control channels (e.g. physical downlink control channel (PDCCH), physical hybrid-ARQ indicator channel (PHICH)) and cell-specific reference signals (CRS). The blank region is not modulated. The reason for having an LTE control channel region in the MBSFN subframe is to allow the gNodeB to signal to the UE the following:
         PHICH provides ACK/NACK information related to previous uplink transmissions from the UE.   PDCCH is used for indicating uplink allocations to the UE. The gNodeB signals a PDCCH to the UE to assign a physical uplink shared channel (PUSCH) in a future subframe. The PUSCH is transmitted in a future subframe and is not impacted by MBSFN transmissions (since PUSCH is an uplink transmission, not a downlink transmission). Note that the UE monitors for “PDCCH indicating uplink allocations” by performing blind decoding for downlink control information (DCI) format 0 or DCI format 4.   PDCCH for indicating transmit power control commands to the UE. Note that the UE monitors for these by blind decoding for DCI formats 3 or 3A.       

     However, the LTE UE does not monitor for PDCCH indicating downlink allocations to the UE in an MBSFN subframe. In LTE, there is a rule that states that the PDCCH allocating downlink resources to the UE in subframe ‘n’ relates to a PDSCH in subframe ‘n’. Since there is no PDSCH region in MBSFN subframes, it is evident that there is no point in the UE monitoring PDCCH for downlink allocations in MBSFN subframes. As such, the UE does not need to blind decode for DCI formats 1-&gt;2C in MBSFN subframes. 
     When NR occupies an MBSFN subframe (as discussed above, for example with reference to the subframes  302  in  FIG.  3   ), the NR transmission does not occupy the LTE control channel region.  FIG.  5    shows the structure of an MBSFN subframe used to transmit NR. The subframe consists of an LTE control channel region  502  occupying OFDM symbols 0 and 1. The LTE control channel region  502  also contains LTE CRS  504 . The NR region of the subframe occupies OFDM symbols 2 to 13 (where the OFDM symbol duration is defined with reference to LTE), and comprises an NR control channel region  512  and an NR data region  514 . The NR region can implement a different numerology to the numerology of the LTE region. It is evident that if an NR UE is to be scheduled in an MBSFN subframe, such as the one shown in  FIG.  5   , there is inefficiency in that the NR control channel occupies NR resources, even though the LTE control channel may not be used to serve LTE UEs. As can be seen in  FIG.  5   , an LTE DCI  506  in the LTE control channel region (e.g. DCI format 0) may allocate LTE PUSCH  508  in a future subframe and an NR DCI  516  in the NR control channel region  512  allocating NR PDSCH  518  in the NR data region  514  in the same subframe. 
     NR-LTE coexistence may serve UEs that are only capable of LTE or only capable of NR (i.e. LTE UEs occupy LTE portions of the resource, such as subframes  304  in  FIG.  3    and NR UEs occupy NR portions of the resource, such as subframes  302  in  FIG.  3   ). It is also expected that some UEs may be both LTE and NR capable and hence some inter-working between NR and LTE would be beneficial for such UEs. 
     It is well understood that it is inefficient from a statistical multiplexing perspective to dedicate some fixed resource for one type of UE and dedicate some other fixed resource for another type of UE. Consider for example, the frame structure of  FIG.  3   . If data arrives for an LTE UE in subframe 1, that data cannot be scheduled to the LTE UE, even if there are no NR UEs active in subframe 1; the UE can only be scheduled in subframe 4, at which time there may be other LTE UEs that need to be served. 
     In [5] it is proposed that LTE can be further evolved to allow higher degree of adaptation/flexibility in time/frequency for enhanced NR-LTE inter-working. Embodiments of the present technique are related to methods for NR-LTE inter-working. Embodiments of the present technique are related to the concept of a master RAT, or anchor carrier. The master RAT/anchor carrier is the base RAT technology that the cell operates on. Downlink control channel signaling is carried on the master RAT. In  FIG.  3   , LTE is the master RAT and the NR system is inserted into the LTE frame structure. However, as would be appreciated by those skilled in the art, embodiments of the present technique could equally apply to either NR or LTE as the master RAT. 
     Inter-RAT Scheduling for NR-LTE Interworking 
     Embodiments of the present technique introduce a new Inter-RAT Downlink Control Information (i-RAT DCI) that enables one RAT, for example LTE, to schedule resources in another RAT, for example NR. The i-RAT DCI can be carried by LTE physical channels such as PDCCH or EPDCCH (i.e. in LTE transmissions). When the i-RAT DCI schedules a downlink transmission in the NR resource an NR-PDSCH is used to carry the data to the UE. Similarly when the i-RAT DCI schedules an uplink grant in the NR resource, the UE will transmit a NR-PUSCH to the network. Although it is expected that the LTE to be the anchor carrier or the master RAT, in some embodiments of the present technique, the i-RAT DCI can also be carried by a NR-PDCCH. 
     A first embodiment of the present technique is described with relation to  FIG.  6   .  FIG.  6    illustrates a method of communicating in a wireless telecommunications system  600  comprising a communications device  601  and one or more infrastructure equipment  611 , which each comprise a transmitter (or transmitter circuitry)  602 ,  612 , a receiver (or receiver circuitry)  604 ,  614  and a controller (or controller circuitry  606 ,  616 . Each of the controllers  606 ,  616  may be, for example, a microprocessor, a CPU, or a dedicated chipset, etc. The communications device  601  is configured to transmit signals to and receive signals from the infrastructure equipment  611  via a first wireless access interface  620  in accordance with a first radio access technology, RAT, and to transmit signals to and receive signals from the infrastructure equipment  611  via a second wireless access interface  630  in accordance with a second RAT, the second RAT being different to the first RAT. The method comprises receiving  640 , at the communications device  601  via the first wireless access interface  620 , control signalling from one of the infrastructure equipment  611 , the control signalling comprising an indication of first communications resources to be used by the communications device  601  to transmit/receive signals representing data to/from the one of the infrastructure equipment  611  via the second wireless access interface  630 , and transmitting  650 , from the communications device  601 , the signals representing data to and/or receiving, at the communications device  601 , the signals representing data from, using the first communications resources, the one of the infrastructure equipment  611  via the second wireless access interface  630 . In other words, in an example relating to the first embodiment of the present technique, the i-RAT DCI transmits downlink and/or uplink grants to schedule NR resources in the downlink or uplink respectively. 
     Operation according to the first embodiment of the present technique as shown in  FIG.  6    is shown in further detail in  FIG.  7   .  FIG.  7    is adapted from the subframe structure illustrated in  FIG.  5   , and similarly shows an LTE DCI  706  allocating an LTE PUSCH  708  to a UE using the LTE control channel region  702 , which may also contain LTE CRS  704 . Although this is known in prior art systems,  FIG.  7    also shows an i-RAT DCI  720  in the LTE control channel region  702  allocating an NR-PDSCH  718  to a UE in the NR data region  714 . Such a structure provides various advantages when compared to that shown in  FIG.  5   . In particular, a single control channel region is sufficient to support both LTE and NR UEs, and a separate NR control channel region is not required in the subframe. 
     In an example relating to the first embodiment of the present technique, the i-RAT DCI can also schedule downlink and/or uplink grants for LTE resources in addition to NR resources. When the i-RAT DCI schedules downlink or uplink in LTE resources the LTE PDSCH and LTE PUSCH are used. When the i-RAT DCI schedules downlink or uplink in NR resources the NR-PDSCH and NR-PUSCH are used. This example has the advantage that only a single DCI format is used for NR-LTE capable UE, such that the UE does not need to monitor two kinds of control region. This example is also useful for NR-LTE multi-carrier operation where the i-RAT DCI can provide a single grant that schedules resources in the LTE and NR resources. In other words, in this example, the method comprises receiving, at the communications device via the first wireless access interface, second control signalling from the one of the infrastructure equipment, the second control signalling comprising an indication of second communications resources to be used by the communications device to transmit/receive signals representing data to/from the one of the infrastructure equipment via the first wireless access interface. 
     Such an example is illustrated in  FIG.  8   , which shows an arrangement where a carrier has an NR region  810  and an LTE region  800 . The NR region  810  is frequency multiplexed with the LTE region  800  and the NR region  810  does not have its own control channel.  FIG.  8    shows a first UE being allocated LTE PDSCH  808  in the LTE region  800  using an i-RAT DCI  806  in the LTE control channel region  802 , which also comprises LTE CRS  804 . The first UE interprets the allocation as being an allocation of LTE PDSCH  808  since the resources allocated to the UE (PRBs 20-&gt;35 inclusive) are within the LTE region  800  (PRBs 0-&gt;49 inclusive). 
       FIG.  8    also shows a second UE being allocated NR PDSCH  818  in the NR region  810  using an i-RAT DCI  816  in the LTE control channel region  802 . The second UE interprets the allocation as being an allocation of NR PDSCH  818  since the resources allocated to the UE (PRBs 60-&gt;69 inclusive) are within the NR region  810  (PRBs 50-&gt;74 inclusive). The second UE also interprets the NR PDSCH  818  allocation as occupying OFDM symbols 0-&gt;13 inclusive, since the NR region  810  has been defined in this case to not have an NR control channel region. In contrast, the first UE interprets the LTE PDSCH allocation  808  as occupying OFDM symbols 2-&gt;13 inclusive, since it is known to the first UE that the LTE control channel region  802  occupies OFDM symbols 0 and 1. 
     In embodiments of the present technique, NR and LTE may be differentiated using frequency division multiplexing (FDM) or by time division multiplexing (TDM). In other words, the first communications resources comprise first frequency sub-bands and the second communications resources comprise second frequency sub-bands, the first frequency sub-bands being separated in frequency from the second frequency sub-bands, or the first communications resources comprise first temporal units and the second communications resources comprise second temporal units, the first temporal units being separated in time from the second temporal units. 
     In an example where the NR and LTE are differentiated using TDM, the i-RAT DCI is transmitted using LTE PDCCH  902  in the MBSFN subframes  904  as shown in  FIG.  9   , where the maximum number of MBSFN subframes (i.e. six) are configured. In this example, a LTE only UE would not decode the PDCCH for a downlink allocation in MBSFN subframes whilst a NR capable or LTE and NR capable UE would blind decode for a PDCCH for a downlink allocation using an i-RAT DCI. It should be appreciated there may not be any NR scheduling in these MBSFN subframes. It should also be appreciated that in MBSFN subframes, an LTE UE would monitor for LTE PDDCH carrying DCI allocating uplink resources and PHICH. In other words, in this example, the method comprises receiving, at the communications device via the first wireless access interface, downlink control information from one of the infrastructure equipment, and, if the communications device is a communications device capable of transmitting signals to and receiving signals from the infrastructure equipment via the second wireless access interface, decoding, at the communications device, the downlink control information. In this instance, and in embodiments of the present technique, the term “decoding” means blind decoding. Blind decoding is a term of art in relation to wireless telecommunications systems, and is a process which depends on making a number of decoding attempts on PDCCH candidate locations for a number of defined DCI formats. As such, those skilled in the art would differentiate between the steps of receiving the DCI, and decoding it. 
     In an example where NR and LTE are differentiated using TDM, the i-RAT DCI can schedule NR resources in non-MBSFN subframes. Here the i-RAT DCI indicates the presence of LTE CRS so that the UE processing the NR signal would avoid (e.g. rate match or puncture) these LTE CRS.  FIG.  10    shows the operation of this example. In a non-MBSFN subframe  1000 , the UE is allocated NR-PDSCH in the NR data region  1008  and the i-RAT DCI  1006  in the LTE control channel region  1002  indicates to the UE that this NR-PDSCH allocation contains CRS  1004 . In an MBSFN subframe  1010 , the UE is allocated NR-PDSCH  1018  and the i-RAT DCI  1016  in the LTE control channel region  1002  indicates to the UE that this NR-PDSCH  1018  allocation does not contain CRS  1004 . In other words, in this example, the method comprises receiving, at the communications device, with the control signalling, if the first temporal units are temporal units of a multicast-broadcast, single-frequency network, MBSFN, an indication that the first communications resources comprise no cell-specific reference signals, or receiving, at the communications device, with the control signalling, if the first temporal units are not temporal units of a MBSFN, an indication that the first communications resources comprise one or more cell-specific reference signals. 
     It should be appreciated that, in other examples of embodiments of the present technique, the UE can implicitly determine whether the NR PDSCH allocation contains CRS or not. The NR UE may be informed of which subframes contain CRS and which subframes don&#39;t (e.g. an NR SIB carries information on which subframes are MBSFN subframes and which subframes are non-MBSFN subframes). The UE then decodes the NR-PDSCH using the implicitly derived knowledge of whether the subframe contains CRS or not. 
     In an example, the UE can be allocated with either the i-RAT DCI in the LTE control channel region or with the NR DCI in the NR control channel region, for the case where both an LTE control channel region and an NR control channel region are active in the subframe. For example, in an MBSFN subframe containing NR, the UE can be allocated either with an i-RAT DCI in the LTE control channel region or with an NR DCI in the NR control channel region. There are various options for the decoding of the i-RAT DCI and the NR DCI:
         The UE blind decodes for both the i-RAT DCI in the LTE control channel region and the NR DCI in the NR control channel region. In other words, where the control signalling is first control signalling, the method comprises receiving, at the communications device via the second wireless access interface, second control signalling from one of the infrastructure equipment, the second control signalling comprising an indication of the first communications resources, and attempting to decode, at the communications device, each of the first control signalling and the second control signalling to identify the first communications resources.   A Broadcast Control Channel (BCCH) in the NR section of the subframe indicates whether the full NR control channel region exists. If it exists, the UE decodes for the NR DCI in the NR control channel region (and also potentially for the i-RAT DCI in the LTE control channel region). In other words, where the control signalling is first control signalling, the method comprises receiving, at the communications device via the second wireless access interface, second control signalling from one of the infrastructure equipment, the second control signalling comprising an indication of the first communications resources, determining, by the communications device, whether the second control signalling comprises, in a broadcast control channel region, an indication that a full control channel region in accordance with the second RAT exists, and attempting to decode, at the communications device, the second control signalling to identify the first communications resources. The method may also comprise attempting to decode, at the communications device, the first control signalling in addition to the second control signalling.   A radio network temporary identifier, or RNTI, (NRCE-RNTI—“NR control exists RNTI”) is used in the LTE control channel region to indicate that the NR control channel region exists. If it exists, the UE decodes for the NR DCI in the NR control channel region (and also potentially for the i-RAT DCI in the LTE control channel region). In other words, where the control signalling is first control signalling, the method comprises receiving, at the communications device via the second wireless access interface, second control signalling from one of the infrastructure equipment, the second control signalling comprising an indication of the first communications resources, determining, by the communications device, whether the first control signalling comprises a radio network temporary identifier, RNTI, indicating that a full control channel region in accordance with the second RAT exists, and attempting to decode, at the communications device, the second control signalling to identify the first communications resources. The method may also comprise attempting to decode, at the communications device, the first control signalling in addition to the second control signalling.       

     Operation of this example is shown in  FIG.  11   .  FIG.  11    shows an NR UE that can be allocated with NR PDSCH  1108  either using an i-RAT DCI  1106  in the LTE control channel region  1102 , which may also include LTE CRS  1104 , or an NR DCI  1116  in the NR control channel region  1112 . The UE decodes  1120  both the i-RAT DCI  1106  and the NR DCI  1116 . The number of blind decoding candidates of the UE can be split between the i-RAT DCI  1106  and the NR DCI  1116  (for example the UE may have sixteen blind decoding candidates in total, where eight of these candidates are applied to the i-RAT DCI  1106  and eight of these candidates are applied to the NR DCI  1116 ). Based on both the i-RAT DCI  1106  candidates and NR DCI  1116  candidates, the UE determines its NR PDSCH  1108  allocation and proceeds to decode that allocation. This example provides more statistical multiplexing opportunities when there are many NR UEs that need to be multiplexed in the NR region  1114  of an MBSFN subframe, since the NR PDSCH  1108  may be allocated either by the NR control channel region  1112  or the LTE control channel region  1102 . 
     In a second embodiment of the present technique, an inter-RAT Uplink Control Information (i-RAT UCI) is also introduced. Similarly to the i-RAT DCI, the i-RAT UCI carries physical uplink control information for NR using the LTE PUCCH or LTE PUSCH. UCI carried by the i-RAT UCI includes HARQ ACK/NACK for NR-PDSCH, CSI, CQI, PMI for NR transmissions. In other words, the second embodiment of the present technique relates to a method of communicating in a wireless telecommunications system comprising a communications device and one or more infrastructure equipment, wherein the communications device is configured to transmit signals to and receive signals from the infrastructure equipment via a first wireless access interface in accordance with a first radio access technology, RAT, and to transmit signals to and receive signals from the infrastructure equipment via a second wireless access interface in accordance with a second RAT, the second RAT being different to the first RAT, the method comprising transmitting, by the communications device via the first wireless access interface, control signalling to one of the infrastructure equipment, the control signalling comprising physical uplink control information to be used by the one of the infrastructure equipment, the physical uplink control information relating to the second RAT. 
     In an example, where NR and LTE are differentiated using TDM, the i-RAT UCI also carries uplink reference signals (SRS) for channel sounding purposes at the gNodeB. In other words, this example relates to the second embodiment of the present technique, wherein the first wireless access interface is divided into first temporal units and the second wireless access interface is divided into second temporal units, the first temporal units being separated in time from the second temporal units, and wherein the control signalling further comprises a sounding reference signal to be used by the one of the infrastructure equipment to estimate a quality of the second wireless access interface. 
     There is a significant amount of engineering development work required to introduce a new RAT, such as NR. An advantage of using i-RAT DCI and i-RAT UCI carried by LTE physical channels such as PDCCH/EPDCCH and PUCCH is that the UE and gNodeB in the initial stage can avoid implementing NR control channels, since there may be very little reuse of engineering design between the NR and LTE control channels (for example, the LTE control channels are based on tail-biting convolutional codes (TBCCs), whereas the NR control channels are based on polar codes). This would reduce complexity in initial deployment of NR systems, allowing for wider, faster and cheaper deployment of such systems. 
     The following numbered paragraphs provide further example aspects and features of the present technique: 
     Paragraph 1. A method of communicating in a wireless telecommunications system comprising a communications device and one or more infrastructure equipment, wherein the communications device is configured to transmit signals to and receive signals from the infrastructure equipment via a first wireless access interface in accordance with a first radio access technology, RAT, and to transmit signals to and receive signals from the infrastructure equipment via a second wireless access interface in accordance with a second RAT, the second RAT being different to the first RAT, the method comprising
         receiving, at the communications device via the first wireless access interface, control signalling from one of the infrastructure equipment, the control signalling comprising an indication of first communications resources to be used by the communications device to transmit/receive signals representing data to/from the one of the infrastructure equipment via the second wireless access interface, and   transmitting, from the communications device, the signals representing data to and/or receiving, at the communications device, the signals representing data from, using the first communications resources, the one of the infrastructure equipment via the second wireless access interface.       

     Paragraph 2. A method according to Paragraph 1, comprising
         receiving, at the communications device via the first wireless access interface, second control signalling from the one of the infrastructure equipment, the second control signalling comprising an indication of second communications resources to be used by the communications device to transmit/receive signals representing data to/from the one of the infrastructure equipment via the first wireless access interface.       

     Paragraph 3. A method according to Paragraph 2, wherein the first communications resources comprise first frequency sub-bands and the second communications resources comprise second frequency sub-bands, the first frequency sub-bands being separated in frequency from the second frequency sub-bands. 
     Paragraph 4. A method according to Paragraph 2, wherein the first communications resources comprise first temporal units and the second communications resources comprise second temporal units, the first temporal units being separated in time from the second temporal units. 
     Paragraph 5. A method according to Paragraph 4, comprising
         receiving, at the communications device via the first wireless access interface, downlink control information from one of the infrastructure equipment, and, if the communications device is a communications device capable of transmitting signals to and receiving signals from the infrastructure equipment via the second wireless access interface,   decoding, at the communications device, the downlink control information.       

     Paragraph 6. A method according to Paragraph 4, comprising
         receiving, at the communications device, with the control signalling, if the first temporal units are temporal units of a multicast-broadcast, single-frequency network, MBSFN, an indication that the first communications resources comprise no cell-specific reference signals, or   receiving, at the communications device, with the control signalling, if the first temporal units are not temporal units of a MBSFN, an indication that the first communications resources comprise one or more cell-specific reference signals.       

     Paragraph 7. A method according to any of Paragraphs 1 to 6, the control signalling being first control signalling, the method comprising
         receiving, at the communications device via the second wireless access interface, second control signalling from one of the infrastructure equipment, the second control signalling comprising an indication of the first communications resources, and   attempting to decode, at the communications device, each of the first control signalling and the second control signalling to identify the first communications resources.       

     Paragraph 8. A method according to any of Paragraphs 1 to 7, the control signalling being first control signalling, the method comprising
         receiving, at the communications device via the second wireless access interface, second control signalling from one of the infrastructure equipment, the second control signalling comprising an indication of the first communications resources,   determining, by the communications device, whether the first communications resources comprise, in a broadcast control channel region, an indication that a full control channel region in accordance with the second RAT exists, and   attempting to decode, at the communications device, the second control signalling to identify the first communications resources.       

     Paragraph 9. A method according to any of Paragraphs 1 to 8, the control signalling being first control signalling, the method comprising
         receiving, at the communications device via the second wireless access interface, second control signalling from one of the infrastructure equipment, the second control signalling comprising an indication of the first communications resources,   determining, by the communications device, whether the first control signalling comprises a radio network temporary identifier, RNTI, indicating that a full control channel region in accordance with the second RAT exists, and   attempting to decode, at the communications device, the second control signalling to identify the first communications resources.       

     Paragraph 10. A method according to Paragraph 8 or Paragraph 9, comprising
         attempting to decode, at the communications device, the first control signalling in addition to the second control signalling.       

     Paragraph 11. A communications device configured to communicate with a wireless telecommunications network comprising one or more infrastructure equipment, the communications device comprising
         transmitter circuitry configured to transmit signals to the infrastructure equipment via a first wireless access interface in accordance with a first radio access technology, RAT, and to transmit signals to the infrastructure equipment via a second wireless access interface in accordance with a second RAT, the second RAT being different to the first RAT,   receiver circuitry configured to receive signals from the infrastructure equipment via the first wireless access interface in accordance with the first RAT, and to receive signals from the infrastructure equipment via the second wireless access interface in accordance with the second RAT, and   controller circuitry configured to control the transmitter circuitry to transmit the signals and to control the receiver circuitry to receive the signals, the controller circuitry being configured in combination with the transmitter circuitry and the receiver circuitry   to receive via the first wireless access interface control signalling from one of the infrastructure equipment, the control signalling comprising an indication of first communications resources to be used by the communications device to transmit/receive signals representing data to/from the one of the infrastructure equipment via the second wireless access interface, and   to transmit the signals representing data to and/or to receive the signals representing data from, using the first communications resources, the one of the infrastructure equipment via the second wireless access interface.       

     Paragraph 12. A method of operating a communications device in a wireless telecommunications system comprising one or more infrastructure equipment, wherein the communications device is configured to transmit signals to and receive signals from the infrastructure equipment via a first wireless access interface in accordance with a first radio access technology, RAT, and to transmit signals to and receive signals from the infrastructure equipment via a second wireless access interface in accordance with a second RAT, the second RAT being different to the first RAT, the method comprising
         receiving via the first wireless access interface control signalling from one of the infrastructure equipment, the control signalling comprising an indication of first communications resources to be used by the communications device to transmit/receive signals representing data to/from the one of the infrastructure equipment via the second wireless access interface, and   transmitting the signals representing data to and/or receiving the signals representing data from, using the first communications resources, the one of the infrastructure equipment via the second wireless access interface.       

     Paragraph 13. Circuitry for a communications device configured to communicate with a wireless telecommunications network comprising one or more infrastructure equipment, the communications device comprising
         transmitter circuitry configured to transmit signals to the infrastructure equipment via a first wireless access interface in accordance with a first radio access technology, RAT, and to transmit signals to the infrastructure equipment via a second wireless access interface in accordance with a second RAT, the second RAT being different to the first RAT,   receiver circuitry configured to receive signals from the infrastructure equipment via the first wireless access interface in accordance with the first RAT, and to receive signals from the infrastructure equipment via the second wireless access interface in accordance with the second RAT, and   controller circuitry configured to control the transmitter circuitry to transmit the signals and to control the receiver circuitry to receive the signals, the controller circuitry being configured in combination with the transmitter circuitry and the receiver circuitry   to receive via the first wireless access interface control signalling from one of the infrastructure equipment, the control signalling comprising an indication of first communications resources to be used by the communications device to transmit/receive signals representing data to/from the one of the infrastructure equipment via the second wireless access interface, and   to transmit the signals representing data to and/or to receive the signals representing data from, using the first communications resources, the one of the infrastructure equipment via the second wireless access interface.       

     Paragraph 14. A method of communicating in a wireless telecommunications system comprising a communications device and one or more infrastructure equipment, wherein the communications device is configured to transmit signals to and receive signals from the infrastructure equipment via a first wireless access interface in accordance with a first radio access technology, RAT, and to transmit signals to and receive signals from the infrastructure equipment via a second wireless access interface in accordance with a second RAT, the second RAT being different to the first RAT, the method comprising
         transmitting, by the communications device via the first wireless access interface, control signalling to one of the infrastructure equipment, the control signalling comprising physical uplink control information to be used by the one of the infrastructure equipment, the physical uplink control information relating to the second RAT.       

     Paragraph 15. A method according to Paragraph 14, wherein the first wireless access interface is divided into first temporal units and the second wireless access interface is divided into second temporal units, the first temporal units being separated in time from the second temporal units, and wherein the control signalling further comprises a sounding reference signal to be used by the one of the infrastructure equipment to estimate a quality of the second wireless access interface. 
     Paragraph 16. A communications device configured to communicate with a wireless telecommunications network comprising one or more infrastructure equipment, the communications device comprising
         transmitter circuitry configured to transmit signals to the infrastructure equipment via a first wireless access interface in accordance with a first radio access technology, RAT, and to transmit signals to the infrastructure equipment via a second wireless access interface in accordance with a second RAT, the second RAT being different to the first RAT,   receiver circuitry configured to receive signals from the infrastructure equipment via the first wireless access interface in accordance with the first RAT, and to receive signals from the infrastructure equipment via the second wireless access interface in accordance with the second RAT, and   controller circuitry configured to control the transmitter circuitry to transmit the signals and to control the receiver circuitry to receive the signals, the controller circuitry being configured in combination with the transmitter circuitry and the receiver circuitry,   to transmit via the first wireless access interface control signalling to one of the infrastructure equipment, the control signalling comprising physical uplink control information to be used by the one of the infrastructure equipment, the physical uplink control information relating to the second RAT.       

     Paragraph 17. A method of operating a communications device in a wireless telecommunications system comprising one or more infrastructure equipment, wherein the communications device is configured to transmit signals to and receive signals from the infrastructure equipment via a first wireless access interface in accordance with a first radio access technology, RAT, and to transmit signals to and receive signals from the infrastructure equipment via a second wireless access interface in accordance with a second RAT, the second RAT being different to the first RAT, the method comprising
         transmitting via the first wireless access interface control signalling to one of the infrastructure equipment, the control signalling comprising physical uplink control information to be used by the one of the infrastructure equipment, the physical uplink control information relating to the second RAT.       

     Paragraph 18. Circuitry for a communications device configured to communicate with a wireless telecommunications network comprising one or more infrastructure equipment, the communications device comprising
         transmitter circuitry configured to transmit signals to the infrastructure equipment via a first wireless access interface in accordance with a first radio access technology, RAT, and to transmit signals to the infrastructure equipment via a second wireless access interface in accordance with a second RAT, the second RAT being different to the first RAT,   receiver circuitry configured to receive signals from the infrastructure equipment via the first wireless access interface in accordance with the first RAT, and to receive signals from the infrastructure equipment via the second wireless access interface in accordance with the second RAT, and   controller circuitry configured to control the transmitter circuitry to transmit the signals and to control the receiver circuitry to receive the signals, the controller circuitry being configured in combination with the transmitter circuitry and the receiver circuitry,   to transmit via the first wireless access interface control signalling to one of the infrastructure equipment, the control signalling comprising physical uplink control information to be used by the one of the infrastructure equipment, the physical uplink control information relating to the second RAT.       

     Numerous modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced otherwise than as specifically described herein. 
     In so far as embodiments of the disclosure have been described as being implemented, at least in part, by software-controlled data processing apparatus, it will be appreciated that a non-transitory machine-readable medium carrying such software, such as an optical disk, a magnetic disk, semiconductor memory or the like, is also considered to represent an embodiment of the present disclosure. 
     It will be appreciated that the above description for clarity has described embodiments with reference to different functional units, circuitry and/or processors. However, it will be apparent that any suitable distribution of functionality between different functional units, circuitry and/or processors may be used without detracting from the embodiments. 
     Described embodiments may be implemented in any suitable form including hardware, software, firmware or any combination of these. Described embodiments may optionally be implemented at least partly as computer software running on one or more data processors and/or digital signal processors. The elements and components of any embodiment may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the disclosed embodiments may be implemented in a single unit or may be physically and functionally distributed between different units, circuitry and/or processors. 
     Although the present disclosure has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in any manner suitable to implement the technique. 
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     [2] LTE for UMTS: OFDMA and SC-FDMA Based Radio Access, Harris Holma and Antti Toskala, Wiley 2009, ISBN 978-0-470-99401-6. 
     [3] RP-151621, “New Work Item: NarrowBand IOT NB-IOT,” Qualcomm, RAN #69. 
     [4] RP-160671, “New SID Proposal: Study on New Radio Access Technology,” NTT DOCOMO, RAN #71. 
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