Field

The present application relates to a method, apparatus, and computer program and in particular but not exclusively to methods, apparatus, and computer programs related to narrowband internet of things (NB-loT) based communications.

Background

A communication system can be seen as a facility that enables communication sessions between two or more entities such as user terminals, base stations and/or other nodes by providing carriers between the various entities involved in the communications path. A communication system can be provided for example by means of a communication network and one or more compatible communication devices. The communication sessions may comprise, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and/or content data and so on. Non-limiting examples of services provided comprise two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

In a wireless communication system at least a part of a communication session between at least two stations occurs over a wireless link. Examples of wireless systems comprise public land mobile networks (PLMN), satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). The wireless systems can typically be divided into cells, and are therefore often referred to as cellular systems.

A user can access the communication system by means of an appropriate communication device or terminal. A communication device of a user is often referred to as user equipment (UE) or mobile station (MS). A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by a station, for example a base station of a cell, and transmit and/or receive communications on the carrier.

The communication system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and/or parameters which shall be used for the connection are also typically defined. An example of attempts to solve the problems associated with the increased demands for capacity is an architecture that is known as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. The LTE is being standardized by the 3rd Generation Partnership Project (3GPP). The various development stages of the 3GPP LTE specifications are referred to as releases. Certain releases of 3GPP LTE (e.g., LTE Rel-1 1 , LTE Rel-12, LTE Rel-13) are targeted towards LTE-Advanced (LTE- A). LTE-A is directed towards extending and optimising the 3GPP LTE radio access technologies. Another proposed communication system is a 5G network or a communication network which comprises enhancements for machine type communications or to support services for the Internet of Things. The deployed communication technologies of e.g., 3GPP GSM (Global Mobile System) and EGPRS (Edge Global Packet Radio System) or 3GPP LTE, may be enhanced to satisfy the specific requirements of the loT services and their related user equipments or mobile stations, known as loT devices. Those loT devices may communicate via the radio link of the communication network to the service provider/server

Summary

In a first aspect there is provided a method for configuring an access node to operate within a time division duplex communications system between the access node and at least one user equipment, the method comprising configuring at the access node a subframe structure for a frame of the time division duplex communications system by: defining at least one first type subframe period comprising a defined number of downlink subframes for communication from the access node to the at least one user equipment; defining at least one second type subframe period comprising a defined number of uplink subframes for communication from the at least one user equipment to the access node; and defining at least one third type subframe period, wherein the third type subframe period is located succeeding one of the at least one first type subframe period and proceeding one of the at least one second type subframe period, the third type subframe period comprising a downlink part for communication from the access node to the at least one user equipment, a guard part and an uplink part for communication from the access node to the at least one user equipment, wherein the third type subframe period is two or more subframes in length and the downlink part of the third type subframe period increases downlink resources for communication from the access node to the at least one user equipment within the frame.

The time division duplex communications system may be a narrowband internet of things time division duplex communications system co-located with a long term evolution communications system network, and wherein defining the first special subframe period may comprise: defining the third type subframe period downlink part such that it does not interfere with a long term evolution communications system time division duplex uplink subframe for communication from a neighbouring or co-located user equipment to a co-located or neighbouring access node; and defining the third type subframe period uplink part such that it does not interfere with a long term evolution communications system time division duplex downlink subframe for communication from the co-located or neighbouring access node to the neighbouring or co-located user equipment.

Defining at least one third type subframe period may comprise defining at the access node the downlink part of the third type subframe period at least 1 1 orthogonal frequency division multiplexed symbols in length.

Defining at least one third type subframe period may comprise mapping at the access node at least one of: a narrowband primary synchronisation sequence; a narrowband secondary synchronisation sequence; a narrowband physical broadcast channel; a narrowband physical downlink shared channel; a narrowband physical downlink control channel; and a narrowband system information block, to the downlink part of the third type subframe period.

Defining at the access node at least one first type subframe period may comprise defining a first first type subframe period and a second first type subframe period, defining at the access node at least one second type subframe period may comprise defining a first second type subframe period and a second second type subframe period; defining at the access node at least one third type subframe period may comprise defining a first third type subframe period and a second third type subframe period, wherein the configuring at the access node a subframe structure for a frame of the time division duplex communications system may further comprise defining at the access node the frame of the time division duplex communications system in the format and order of: a first first type subframe period of one subframe length comprising a mapping of a narrowband primary synchronisation sequence; a first third type subframe period of two subframes length with a downlink part comprising a mapping of a narrowband physical broadcast channel; a first second type subframe period of two subframes length; a second first type subframe period of one subframe length comprising a mapping of a narrowband physical downlink shared channel and a narrowband physical downlink control channel; second third type subframe period of two subframes length with a downlink part comprising a mapping of a narrowband secondary synchronisation sequence and a narrowband system information block; second second type subframe period of two subframes length.

Defining at the access node at least one first type subframe period may comprise defining a first first type subframe period and a second first type subframe period, defining at the access node at least one second type subframe period may comprise defining a first second type subframe period and a second second type subframe period; defining at the access node at least one third type subframe period may comprise defining a first third type subframe period and a second third type subframe period, wherein the configuring at the access node a subframe structure for a frame of the time division duplex communications system may further comprise defining at the access node the frame of the time division duplex communications system in the format and order of: a first first type subframe period of one subframe length comprising a mapping of a narrowband primary synchronisation sequence; a first third type subframe period of two subframes length with a downlink part comprising a mapping of any downlink channel; a first second type subframe period of two subframes length; a second first type subframe period of one subframe length comprising a mapping of a narrowband physical downlink shared channel and a narrowband physical downlink control channel; second third type subframe period of two subframes length with a downlink part comprising a mapping of any downlink channel; second second type subframe period of two subframes length.

Defining at the access node at least one third type subframe period may further comprise mapping at the access node the uplink part to a narrowband physical random access channel.

Defining at the access node at least one third type subframe period may comprise mapping at the access node at least one of: a narrowband primary synchronisation sequence for the at least one user equipment and a narrowband secondary synchronisation sequence for the at least one user equipment to the downlink part of the third type subframe period and defining at least one first type subframe period comprising a defined number of downlink subframes comprises mapping the other of the narrowband primary synchronisation sequence for the at least one user equipment and a narrowband secondary synchronisation sequence for the at least one user equipment to the downlink subframes, wherein the distance within the frame between the narrowband primary synchronisation sequence and the narrowband secondary synchronisation sequence is configured to indicate the narrowband time division duplex communications system is operating in an extended special subframe mode.

The frame is associated with a first physical resource block, and the method may further comprise configuring at the access node a second subframe structure for a frame for a second physical resource block associated with the first physical resource block by: defining for the second physical resource block at least one first type subframe period which may comprise a defined number of downlink subframes for communication from the access node to the at least one user equipment; defining for the second physical resource block at least one second type subframe period which may comprise a defined number of uplink subframes for communication from the at least one user equipment to the access node; and defining for the second physical resource block at least one third type subframe period, wherein the third type subframe period may be located succeeding one of the at least one first type subframe period and proceeding one of the at least one second type subframe period, the third type subframe period comprising a downlink part for communication from the access node to the at least one user equipment, a guard part and an uplink part for communication from the access node to the at least one user equipment, wherein the third type subframe period may be two or more subframes in length and the downlink part of the third type subframe period increases downlink resources for communication from the access node to the at least one user equipment within the frame for the second physical resource block.

There may be provided a method comprising: configuring a long term evolution access node with a long term evolution time division duplex cell frame structure comprising a long term evolution special subframe configuration; and configuring the access node subframe structure for a frame of the time division duplex communications system as discussed herein, for one or more narrowband internet of things carriers associated with the long term evolution access node.

Configuring the access node subframe structure for a frame of the time division duplex communications system may be further based on the long term evolution special subframe configuration.

According to a second aspect there is provided an access node configured to implement a time division duplex communications system between the access node and at least one user equipment, the access node to configure a subframe structure for a frame of the time division duplex communications system, is configured to: define at least one first type subframe period comprising a defined number of downlink subframes for communication from the access node to the at least one user equipment; define at least one second type subframe period comprising a defined number of uplink subframes for communication from the at least one user equipment to the access node; and define at least one third type subframe period, wherein the third type subframe period is located succeeding one of the at least one first type subframe period and proceeding one of the at least one second type subframe period, the third type subframe period comprising a downlink part for communication from the access node to the at least one user equipment, a guard part and an uplink part for communication from the access node to the at least one user equipment, wherein the third type subframe period is two or more subframes in length and the downlink part of the third type subframe period increases downlink resources for communication from the access node to the at least one user equipment within the frame.

The time division duplex communications system may be a narrowband internet of things time division duplex communications system co-located with a long term evolution communications system network which may comprise at least one further access node co- located with or neighbouring the access node, and wherein the access node configured to define the first special subframe period may be configured to: define the third type subframe period downlink part such that it does not interfere with a long term evolution communications system time division duplex uplink subframe for communication from a neighbouring or co- located user equipment to the co-located or neighbouring access node; and define the third type subframe period uplink part such that it does not interfere with a long term evolution communications system time division duplex downlink subframe for communication from the co-located or neighbouring access node to the neighbouring or co-located user equipment.

The access node configured to define at least one third type subframe period may be further configured to define the downlink part of the third type subframe period at least 1 1 orthogonal frequency division multiplexed symbols in length.

The access node configured to define at least one third type subframe period may be further configured to map at least one of: a narrowband primary synchronisation sequence; a narrowband secondary synchronisation sequence; a narrowband physical broadcast channel; a narrowband physical downlink shared channel; a narrowband physical downlink control channel; and a narrowband system information block, to the downlink part of the third type subframe period.

The access node configured to: define at the access node at least one first type subframe period may be configured to define a first first type subframe period and a second first type subframe period; define at least one second type subframe period may be configured to define a first second type subframe period and a second second type subframe period; define at the access node at least one third type subframe period may be configured to define a first third type subframe period and a second third type subframe period, wherein the access node configured to configure a subframe structure for a frame may be further configured to define the frame format and order of: a first first type subframe period of one subframe length comprising a mapping of a narrowband primary synchronisation sequence; a first third type subframe period of two subframes length with a downlink part comprising a mapping of a narrowband physical broadcast channel; a first second type subframe period of two subframes length; a second first type subframe period of one subframe length comprising a mapping of a narrowband physical downlink shared channel and a narrowband physical downlink control channel; second third type subframe period of two subframes length with a downlink part comprising a mapping of a narrowband secondary synchronisation sequence and a narrowband system information block; and second second type subframe period of two subframes length.

The access node configured to: define at the access node at least one first type subframe period may be configured to define a first first type subframe period and a second first type subframe period; define at least one second type subframe period may be configured to define a first second type subframe period and a second second type subframe period; define at the access node at least one third type subframe period may be configured to define a first third type subframe period and a second third type subframe period, wherein the access node configured to configure a subframe structure for a frame may be further configured to define the frame format and order of: a first first type subframe period of one subframe length comprising a mapping of a narrowband primary synchronisation sequence; a first third type subframe period of two subframes length with a downlink part comprising a mapping of any downlink channel; a first second type subframe period of two subframes length; a second first type subframe period of one subframe length comprising a mapping of a narrowband physical downlink shared channel and a narrowband physical downlink control channel; second third type subframe period of two subframes length with a downlink part comprising a mapping of any downlink channel; and second second type subframe period of two subframes length.

The access node configured to define at least one third type subframe period may be further configured to map the uplink part to a narrowband physical random access channel.

The access node configured to define at least one third type subframe period may be configured to map at least one of: a narrowband primary synchronisation sequence for the at least one user equipment and a narrowband secondary synchronisation sequence for the at least one user equipment to the downlink part of the third type subframe period and the access node configured to define at least one first type subframe period comprising a defined number of downlink subframes may be configured to map the other of the narrowband primary synchronisation sequence for the at least one user equipment and a narrowband secondary synchronisation sequence for the at least one user equipment to the downlink subframes, wherein the distance within the frame between the narrowband primary synchronisation sequence and the narrowband secondary synchronisation sequence is configured to indicate the narrowband time division duplex communications system is operating in an extended special subframe mode.

The frame may be associated with a first physical resource block, and the access node may be further configured to configure a second subframe structure for a second physical resource block frame which may be associated with the first physical resource block the access node may be further configured to: define for the second physical resource block at least one first type subframe period comprising a defined number of downlink subframes for communication from the access node to the at least one user equipment; define for the second physical resource block at least one second type subframe period comprising a defined number of uplink subframes for communication from the at least one user equipment to the access node; and define for the second physical resource block at least one third type subframe period, wherein the third type subframe period is located succeeding one of the at least one first type subframe period and proceeding one of the at least one second type subframe period, the third type subframe period comprising a downlink part for communication from the access node to the at least one user equipment, a guard part and an uplink part for communication from the access node to the at least one user equipment, wherein the third type subframe period is two or more subframes in length and the downlink part of the third type subframe period increases downlink resources for communication from the access node to the at least one user equipment within the frame for the second physical resource block.

According to a further aspect there is provided a method comprising: receiving, at a user equipment, at least one frame of a time division duplex communications system between an access node and the user equipment; determining the distance within the frame between a narrowband primary synchronisation sequence and a narrowband secondary synchronisation sequence; determining the frame is an extended special subframe frame based on the determined distance.

A system may comprise: a long term evolution access node with a long term evolution time division duplex cell frame structure configured to configure a long term evolution access node comprising a long term evolution special subframe configuration; and an access node as discussed herien, wherein configuring the access node subframe structure for a frame of the time division duplex communications system may be for one or more narrowband internet of things carriers associated with the long term evolution access node.

The access node may be configured to configure the access node subframe structure for a frame of the time division duplex communications system based on the long term evolution special subframe configuration

According to another aspect there is provided an apparatus configured to: receive at least one frame of a time division duplex communications system between an access node and the apparatus; determine the distance within the frame between a narrowband primary synchronisation sequence and a narrowband secondary synchronisation sequence; and determine the frame is an extended special subframe frame based on the determined distance.

The time division duplex communications system may be one of: an inband deployed narrowband time division duplex communications system; and a guardband deployed narrowband time division duplex communications system.

In another aspect there is provided a computer program embodied on a non-transitory computer-readable storage medium, the computer program comprising program code for providing any of the above methods.

In another aspect there is provided a computer program product for a computer, comprising software code portions for performing the steps of any of the previous methods, when said product is run.

A computer program comprising program code means adapted to perform the method(s) may be provided. The computer program may be stored and/or otherwise embodied by means of a carrier medium. In the above, many different embodiments have been described. It should be appreciated that further embodiments may be provided by the combination of any two or more of the embodiments described above.

In the above, many different embodiments have been described. It should be appreciated that further embodiments may be provided by the combination of any two or more of the embodiments described above.

Description of Figures

Embodiments will now be described, by way of example only, with reference to the accompanying Figures in which:

Figure 1 shows a schematic diagram of an example communication system comprising a base station and a plurality of communication devices;

Figure 2a shows a schematic diagram of an example mobile communication device;

Figure 2b shows a schematic diagram of an example control apparatus;

Figure 3a shows an example table of known narrow band internet of things (NB-loT) uplink/downlink (UL/DL) time division duplex (TDD) configurations;

Figure 3b shows an example table of known available downlink subframes according to the known narrow band internet of things (NB-loT) uplink/downlink (UL/DL) time division duplex (TDD) configurations shown in Figure 3a;

Figure 4 shows a schematic diagram illustrating an extended special subframe configuration according to some embodiments;

Figure 5 shows a table showing the length in orthogonal frequency division modulation symbols within the extended special subframe configuration shown in Figure 4; and

Figure 6 shows a schematic diagram illustrating an example frame configuration showing an extended special subframe with common control information mapping according to some embodiments.

Detailed description

Before explaining in detail the examples, certain general principles of a wireless communication system and mobile communication devices are briefly explained with reference to Figures 1 , 2a and 2b to assist in understanding the technology underlying the described examples.

In a wireless communication system 100, such as that shown in Figure 1 , mobile communication devices or user equipment (UE) 102, 104, 105 are provided wireless access via at least one base station or similar wireless transmitting and/or receiving node or point. Base stations (BTS, NodeB (NB), enhanced NodeB (eNB) are typically controlled by at least one appropriate controller apparatus, so as to enable operation thereof and management of mobile communication devices in communication with the base stations. The controller apparatus may be located in a radio access network (e.g. wireless communication system 100) or in a core network (CN) (not shown) and may be implemented as one central apparatus or its functionality may be distributed over several apparatus. The controller apparatus may be part of the base station and/or provided by a separate entity such as a Radio Network Controller (RNC). In Figure 1 control apparatus 108 and 109 are shown to control the respective macro level base stations 106 and 107. The control apparatus of a base station can be interconnected with other control entities. The control apparatus is typically provided with memory capacity and at least one data processor. The control apparatus and functions may be distributed between a plurality of control units. In some systems, the control apparatus may additionally or alternatively be provided in a radio network controller controller or a base station controller (BSC).

LTE systems may however be considered to have a so-called "flat" architecture, without the provision of RNCs; rather the (e)NB is in communication with a system architecture evolution gateway (SAE-GW) and a mobility management entity (MME), which entities may also be pooled meaning that a plurality of these nodes may serve a plurality (set) of (e)NBs. Each UE is served by only one MME and/or S-GW at a time and the (e)NB keeps track of current association. SAE-GW is a "high-level" user plane core network element in LTE, which may consist of the S-GW and the P-GW (serving gateway and packet data network gateway, respectively). The functionalities of the S-GW and P-GW are separated and they are not required to be co-located.

In Figure 1 base stations 106 and 107 are shown as connected to a wider communications network 1 13 via gateway 1 12. A further gateway function may be provided to connect to another network.

The smaller base stations 1 16, 1 18 and 120 may also be connected to the network 1 13, for example by a separate gateway function and/or via the controllers of the macro level stations. The base stations 1 16, 1 18 and 120 may be pico or femto level base stations or the like. In the example, stations 1 16 and 1 18 are connected via a gateway 1 1 1 whilst station 120 connects via the controller apparatus 108. In some embodiments, the smaller stations may not be provided. Smaller base stations 1 16, 1 18 and 120 may be part of a second network, for example WLAN and may be WLAN APs.

A possible mobile communication device will now be described in more detail with reference to Figure 2a showing a schematic, partially sectioned view of a communication device 200. Such a communication device is often referred to as user equipment (UE), mobile station (MS) or terminal. An appropriate mobile communication device may be provided by any device capable of sending and receiving radio signals. Non-limiting examples comprise a mobile station (MS) or mobile device such as a mobile phone or what is known as a 'smart phone', a computer provided with a wireless interface card or other wireless interface facility (e.g., USB dongle), personal data assistant (PDA) or a tablet provided with wireless communication capabilities, an loT device or any combinations of these or the like. The term "mobile station", may also cover any such device configured for movement, e.g. a mobile loT device. A mobile communication device may provide, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on. Users may thus be offered and provided numerous services via their communication devices. Non-limiting examples of these services comprise two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. Users may also be provided broadcast or multicast data. Non- limiting examples of the content comprise downloads, television and radio programs, videos, advertisements, various alerts and other information.

The mobile device 200 may receive signals over an air or radio interface 207 via appropriate apparatus for receiving (e.g., a receiver) and may transmit signals via appropriate apparatus for transmitting radio signals (e.g., a transmitter). In Figure 2a transceiver apparatus is designated schematically by block 206. The transceiver apparatus 206 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

A mobile device is typically provided with at least one data processing entity 201 , at least one memory 202 and other possible components 203 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 204. The user may control the operation of the mobile device by means of a suitable user interface such as key pad 205, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 208, a speaker and a microphone can be also provided. Furthermore, a mobile communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto.

Figure 2b shows an example of a control apparatus for a communication system, for example to be coupled to and/or for controlling a station of an access system, such as a RAN node, e.g. a base station, (e)node B or 5G AP, a central unit of a cloud architecture or a node of a core network such as an MME or S-GW, a scheduling entity, or a server or host. The method may be implanted in a single control apparatus or across more than one control apparatus. The control apparatus may be integrated with or external to a node or module of a core network or RAN. In some embodiments, base stations comprise a separate control apparatus unit or module. In other embodiments, the control apparatus can be another network element such as a radio network controller or a spectrum controller. In some embodiments, each base station may have such a control apparatus as well as a control apparatus being provided in a radio network controller. The control apparatus 250 can be arranged to provide control on communications in the service area of the system. The control apparatus 250 comprises at least one memory 251 , at least one data processing unit 252, 253 and an input/output interface 254. Via the interface the control apparatus can be coupled to a receiver and a transmitter of the base station. The receiver and/or the transmitter may be implemented as a radio front end or a remote radio head. For example the control apparatus 250 or processor 251 can be configured to execute an appropriate software code to provide the control functions.

The communication devices 102, 104, 105 may access the communication system based on various access techniques, such as code division multiple access (CDMA), or wideband CDMA (WCDMA). Other non-limiting examples comprise time division multiple access (TDMA), frequency division multiple access (FDMA) and various schemes thereof such as the interleaved frequency division multiple access (IFDMA), single carrier frequency division multiple access (SC-FDMA) and orthogonal frequency division multiple access (OFDMA), space division multiple access (SDMA) and so on. Signalling mechanisms and procedures, which may enable a device to address in-device coexistence (IDC) issues caused by multiple transceivers, may be provided with help from the LTE network. The multiple transceivers may be configured for providing radio access to different radio technologies.

An example of wireless communication systems are architectures standardized by the 3rd Generation Partnership Project (3GPP). A latest 3GPP based development is often referred to as the long term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. The various development stages of the 3GPP specifications are referred to as releases. More recent developments of the LTE are often referred to as LTE Advanced (LTE-A). The LTE employs a mobile network architecture known as the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). Base stations or access nodes of such systems are known as evolved or enhanced Node Bs (eNBs) and provide E-UTRAN features such as user plane Packet Data Convergence/Radio Link Control/Medium Access Control/Physical layer protocol (PDCP/RLC/MAC/PHY) and control plane Radio Resource Control (RRC) protocol terminations towards the communication devices. Other examples of a radio access system comprise those provided by base stations of systems that are based on technologies such as wireless local area network (WLAN) and/or WiMax (Worldwide Interoperability for Microwave Access). A base station can provide coverage for an entire cell or similar radio service area. Machine type communication is expected to provide significant growth opportunities in the 3GPP ecosystem. Of various applications of Machine type communication (MTC) or loT (Internet of things), and/or cellular IOT (CIOT), one application may be the deployment of low cost low throughput devices in extended coverage conditions. This application may be suitable for sensors or smart meters deployed in basement or indoor coverage conditions.

Support of ultra low complexity Internet of Things in cellular networks is introduced in 3GPP Rel-13. The key objectives of the Cellular loT for low complexity devices are increased battery life time, extended coverage and support of massive number of devices per cell. An example of a technology introduced in 3GPP which work in narrow spectrum of 200 kHz is narrowband Internet of things (NB-loT).

Enhancing the functionality of NB-loT is a goal many are attempting to achieve. For example support for NB-loT time division duplex (TDD) communications, which is required for some specific operator deployments where only TDD deployments are possible, has been recently been agreed. Moreover without implementing a NB-loT functionality extended for TDD configuration it is not possible to introduce support for loT wherever a LTE-TDD network is deployed.

The uplink/downlink (UL/DL) Configuration for LTE-TDD defines a subframe allocation for uplink and downlink within a radio frame of 10 msec. In the current configurations a special subframe S is introduced whenever the transmission switches from downlink D to uplink U. The special subframe S provides the guard period for an UE to receive the last downlink symbol and switch to uplink and start transmission earlier so that the uplink signal reaches an eNB at the next UL subframe. The guard period also provides protection from downlink interference from neighbouring cells with a larger propagation delay to the next uplink transmissions.

For example with respect to Figure 3a is shown a table which lists the possible UL/DL configurations each having different number of subframes allocated for uplink and downlink. The table shows a first column 301 of the UL/DL configuration value (0 to 6), a second column 303 defining the DL to UL switch point periodicity (either 5ms or 10ms), a third column 305 which shows for the subframes 0 to 9 whether the configuration defines the subframe as an downlink (D), uplink (U) or special (S) subframe. According to such configurations a minimum number of DL subframes is 2 (configuration 0) and maximum number of DL subframes is 8 (configuration 5).

As per the frame mapping for NB-loT frequency division duplex (FDD) configurations a Primary Synchronization Signal is mapped onto subframe 5 in every radio frame, a Secondary Synchronization Signal is mapped onto subframe 9 in every even numbered radio frame, the broadcast channel (NPBCH) is mapped onto subframe 0. Furthermore the narrowband-system information block 1 , NB-SIB1 , which provides information on cell access and selection and other system information block scheduling is scheduled on subframe 4 with the repetitions as indicated in NPBCH with periodicity of 1280 msec. Furthermore narrowband physical downlink control channel (NPDCCH) / narrowband physical downlink shared channel (NPDSCH) transmission happens in the remaining subframes. Narrowband physical uplink shared channel (NPUSCH) and Narrowband physical random access channel (NPRACH) transmission happens in all uplink subframes.

In order to conserve energy a UE operating in such a communications system is configured to operate in a discontinuous transmission/reception where the UE may switch off the transceiver for periods of time and enter an idle mode. For an idle-mode UE to synchronise to the network and enter into state where it is ready for transmission, it needs to receive and determine a narrowband primary synchronisation sequence (NPSS), narrowband secondary synchronisation sequence (NSSS), narrowband physical broadcast channel (NPBCH) and narrowband-system information block 1 (NB-SIB1 ) transmissions in the carrier. For some UL/DL configurations the available DL subframes are not sufficient to map all of these transmissions. Moreover, additional resources are required for NPDCCH transmission which is essential for data transmission. Due to these restrictions, it is not possible to deploy NB-loT as in-band deployment where LTE-TDD has such UL/DL configurations.

For example Figure 3b shows a table providing the available downlink subframes for every radio frame for each of the UL-DL configurations shown in Figure 3a. The table furthermore identifies that the downlink resources for configuration 0 and configuration 6 are not sufficient to map the downlink common control channels of NB-loT.

The concept as discussed hereafter is the provision of suitable apparatus configuration and methods which enable resource mapping for common control channels of NB-loT for TDD configurations which have limited downlink resources per radio frame, such as shown in Figure 3b when deployed as inband deployment having UL/DL configurations 0 and 6.

In some embodiments the concept as discussed above can be achieved by a NB-loT TDD based system comprising an extended special subframe which spans across two subframes. This extended special subframe has an increased number of downlink symbols within the special subframe. These additional downlink symbols can therefore be used to map any of common control channel elements to be transferred to the UE in order that the UE is able to operate in a discontinuous reception/transmission mode. In some embodiments extended special subframe configuration is where the downlink transmission in the subframe is extended up to 12 symbols allowing more downlink resources.

This may be further implemented in some embodiments by a single carrier deployment without extended special subframe where the NPSS and NSSS are mapped to DL subframes SFO and SF5 whereas in the single carrier deployment with extended special subframe NSSS is mapped to the extended special subframe starting at SF6. In such embodiments a UE may be configured to identify the extended special subframe configuration based on the placement of NPSS and NSSS within radio frame. The NB-loT TDD cell in some embodiments is thus configured to send the NPSS and NSSS in specific subframes whose location is different from a defined NB-IOT FDD system so that UE can identify the cell as NB-loT TDD. Alternately in some embodiments a NB-loT TDD cell may be configured to use different NPSS or NSSS cover codes so that UE can identify the cell as NB-loT TDD.

Furthermore in some embodiments a NPRACH format is defined where the transmission can be fit into the uplink symbols of the extended special subframe.

In some further embodiments this may alternatively be achieved where the NPSS and NSSS signals are only sent in the primary carrier along with the additional control channel which contains the carrier on which NPBCH and other system information are scheduled.

In some further embodiments the primary carrier may be configured to only send NPSS and NSSS signals along with NPBCH channel when the narrowband master information block (NB-MIB) and which comprises the contents of NPBCH indicates the physical resource block (PRB) or carrier on which narrowband secondary information blocks (NB-SIBs) are scheduled and also the subframe assigned for the NB-SIB. This approach may be called the dual anchor physical resource block embodiments.

In some embodiments the NB-loT TDD cell is configured to send NPSS and NSSS at different subframes in the anchor PRB when the anchor PRB only transmit NPSS and NSSS.

In such embodiments the NB-MIB indicates the use of extended special subframe in the cell so that UE can use the extended special subframe for its operation after NBPCH acquisition itself.

By implementing such embodiments in NB-loT TDD deployment is possible to deploy inband NB-loT variants in existing LTE networks where the LTE-TDD uses UL/DL configurations which have limited downlink resources for mapping common control channels and also traffic channel operations (NPDCCH/NPDSCH). The extended special subframe option furthermore converts one special-subframe+uplink subframe to an extended special subframe allowing more downlink resources in the extended special subframe.

With respect to the extended special subframe embodiments Figure 4 shows an example extended special subframe for narrowband loT communications. The first part 501 shows the un-extended special subframe 506 which is preceded by a downlink subframe 510 and succeeded by an uplink subframe 514. The second part 503 shows the extended subframe 516 which is two subframes in length and which is preceded by a downlink subframe 520 and succeeded by an uplink subframe 514.

The structure of the un-extended and extended special subframes is similar in that the special subframe (unextended and extended) comprises a downlink (DPT) part 51 1 , 521 , which is followed by a guard (GP) part 512, 522 and which is further followed by an uplink (UPT) part 513, 523. In the extended special subframe the downlink part 521 , guard part 522 and uplink part 523 are all extended when compared to the un-extended special subframe respective downlink part 51 1 , guard part 512 and uplink part 513.

The above configuration is applicable when NB-loT TDD is deployed as in-band or guardband deployment with LTE-TDD. The LTE-TDD implementation may employ UL/DL configuration 0 which has only 2 DL subframes. For such configurations, the NB-loT can use this modified special subframe which spans across 2 subframes as indicated in Figure 4.

In these embodiments, the downlink pilot timeslot (DwPTS) symbols are extended for a longer duration, until one symbol before the start of uplink pilot timeslot (UpPTS) in the corresponding LTE Frame. This allows the ramp down of downlink transmission of NB-loT prior to reception in the LTE cell to avoid uplink interference at LTE cell. With this option, assuming special subframe configuration 0 for LTE, the downlink pilot timeslot (DwPTS) can be extended to 12 OFDM symbols in the first subframe (SF) of the extended special subframe. This length is sufficient for mapping the narrowband primary synchronisation sequence (NPSS)/narrowband secondary synchronisation sequence (NSSS), for which the minimum length is 1 1 OFDM symbols. The guard period in the extended special subframe can be made as long as the guard period in the LTE special subframe in order to meet the design requirements.

The extended special subframe can be used in the LTE inband deployments where the LTE transmission uses UL/DL configurations which have at least 2 UL subframes following the special subframe. In these cases the extended special subframe on inband NB-loT TDD does not impact the downlink transmission on LTE for the DL transmissions.

The extended special subframe configurations for different guard periods is shown in the table shown in Figure 5. Figure 5 specifically shows a first column of an extended special subframe configuration number (0 to 8) and columns of the length in OFDM symbols (for a normal CP) for the extended downlink pilot timeslot (DwPTS-Extended) 603, the guard period 605 and the extended uplink pilot timeslot (UpPTS-Extended) 607. In the examples shown in Figure 6 The DwPTS-extended is always fixed to be at least 1 1 OFDM symbols so that NPSS /NSSS can be transmitted in these symbols. The number of UpPTS-extended symbols may then vary depending on the guard period (GP) length. These additional uplink symbols can be used for NPUSCH or for any new uplink control channels in future. With the DwPTS of NB- IOT restricted to 1 1 symbols, it is expected to ramp down well before the LTE-TDD reception on UpPTS starts.

If the extended special subframe is configured for UL/DL configuration 0, the common channel mapping to DL and special subframes can be inserted into the subframe structure as shown in Figure 6 and as described as follows (if NPBCH is also required in the same PRB):

NPSS is mapped to DL subframe 651 SF0 610; The first extended special subframe 653a (SF1 +SF2) comprises a DL part 611 which may be used for NPBCH, a guard period 613 and UL part 615;

UL 655 subframes SF3 617, SF4 619;

NPDSCH and NPDCCH are mapped to DL subframe 651 SF5 621 ;

The second extended special subframe 653b (SF6+SF7) comprises a DL part 623 which can be used for NSSS and NB-SIB1 , a guard period 625 and UL part 627;

UL 655 subframes SF8 631 , SF9 633.

With this configuration it is possible to map all the downlink control channels within a single carrier without impacting the system acquisition time (time to acquire NPBCH). The time taken for system information acquisition may be increased in this configuration as NB-SIB1 is scheduled only every odd radio frames multiplexed with NSSS.

Furthermore in some embodiments the uplink symbols of UpPTS (for example UL parts 615 and 627) can be combined with the next uplink subframe to map NPUSCH channel.

In some embodiments the uplink symbols of the extended special subframe (for example within UL parts 615 and 627) can also be used for NPRACH transmissions. For example, single tone NPRACH of 15KHz with symbol group of 3 symbols which contain 1 CP and 2 symbols can be transmitted 2 times with frequency hopping for configurations which have 6 or 8 uplink symbols. For other configurations the same symbol group can be transmitted 4 times with frequency hopping.

In some embodiments the UE may be configured to determine the NPSS position at the first subframe (SFO), the NSSS position at the seventh subframe (SF6) within the special subframe and the distance between of them as 6 subframe periods. Having determined these the UE may be configured to determine that the system is employing NB-loT-TDD Anchoring where the NSSS is mapped to an extended special subframe and the NPBCH is located in the sixth subframe (SF5).

It is also noted herein that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

It is expected that NB-loT is likely to be deployed in one of the PRB of LTE system bandwidth. Thus it is expected that LTE and NB-loT cells may be co-located in most cases. For inband operation with LTE, NB-loT should align its UL/DL configuration to the LTE system to avoid Cross Line Interference (UL to DL.DL to UL) between these two cells.

In other words where the LTE system uses UL/DL configuration 0: this configuration have only 2 DL Subframes per radio frame. DL/UL ratio is therefore 2/6. (DL SF/UL SF). For Inband deployment same configuration is applicable for NB-loT.

In some UL/DL configurations the NB-loT would require more DL resources for mapping common channels and this changing of a UL/DL configurations will require change of the UL/DL configuration at the LTE also. This would therefore impact on LTE resource utilization.

The concepts introduced above to increase the available DL symbols within the special subframe with a corresponding reduction in next UL subframe in order to increase the DL resources per radio frame changes the DL/UL ratio from 2 to 4. With this DL/UL ratio of NB- loT increases to 4/4 without changing LTE part.

The extended special subframe can therefore increases the DL resources for NB-loT for inband operation having limited DL resources. It is a mechanism where two LTE based RAT co-located uses may have different UL/DL ratios without impacting the CLI between them.

In contrast the secondary anchor carrier examples where there is a mechanism to redirect the UE to other carriers to check for common control channels, there the DL resource per NB-IOT carrier is unchanged.

In NB-loT in-band deployment, anchor and non-anchor NB-loT carriers are associated with the same LTE cell. When TDD is used on the LTE cell, a special subframe consisting of DwPTS/GP/UpPTS must be configured for both LTE and NB-loT. The concepts introduced above allow NB-loT carriers to use different special subframe configuration than the associated LTE cell. The special subframe configuration for NB-loT, however, must be based on the special subframe configuration for LTE. For example, the number of symbols used for DwPTS period of NB-loT should be smaller than the number of symbols used for DwPTS and GP of LTE. In another example, the number of symbols used for GP period of NB-loT should be equal to or larger than the number of symbols used for GP period of LTE.

In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects of the invention may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The embodiments of this invention may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware. Computer software or program, also called program product, including software routines, applets and/or macros, may be stored in any apparatus-readable data storage medium and they comprise program instructions to perform particular tasks. A computer program product may comprise one or more computer- executable components which, when the program is run, are configured to carry out embodiments. The one or more computer-executable components may be at least one software code or portions of it.

Further in this regard it should be noted that any blocks of the logic flow as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD. The physical media is a non-transitory media.

The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may comprise one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), FPGA, gate level circuits and processors based on multi core processor architecture, as non-limiting examples.

Embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

The foregoing description has provided by way of non-limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention as defined in the appended claims. Indeed there is a further embodiment comprising a combination of one or more embodiments with any of the other embodiments previously discussed.