BACKGROUND OF THE INVENTION

IoT devices may include physical devices, vehicles, buildings and other items having embedded therein electronics, software, sensors, actuators, or the like as well as network connectivity that enable these devices to collect and exchange data across an existing network infrastructure.FIG. 1is a schematic representation of an example of such a network infrastructure, like a wireless communication system including a plurality of base stations eNB1to eNB5, each serving a specific area surrounding the base station schematically represented by the respective cells1001to1005. The base stations are provided to serve users within a cell. A user may be a stationary device or a mobile device. Further, the wireless communication system may be accessed by IoT devices which connect to a base station or to a user.FIG. 1shows an exemplary view of only five cells, however, the wireless communication system may include more such cells.FIG. 1shows two users UE1and UE2, also referred to as user equipment (UE), that are in cell1002and that are served by base station eNB2. Another user UE3is shown in cell1004which is served by base station eNB4. The arrows102,1022and1023schematically represent uplink/downlink connections for transmitting data from a user UE1, UE2and UE3to the base stations eNB2, eNB4or for transmitting data from the base stations eNB2, eNB4to the users UE1, UE2, UE3. Further,FIG. 1shows two IoT devices1041and1042in cell1004, which may be stationary or mobile devices. The IoT device1041accesses the wireless communication system via the base station eNB4to receive and transmit data as schematically represented by arrow1051. The IoT device1042accesses the wireless communication system via the user UE3as is schematically represented by arrow1052.

The wireless communication system may be any single-tone or multicarrier system based on frequency-division multiplexing, like the orthogonal frequency-division multiplexing (OFDM) system, the orthogonal frequency-division multiple access (OFDMA) system defined by the LTE standard, or any other IFFT-based signal with or without CP, e.g. DFT-s-OFDM. Other waveforms, like non-orthogonal waveforms for multiple access, e.g. filter-bank multicarrier (FBMC), may be used.

Standard LTE devices, like the users UE1, UE2, UE3, operate within a first bandwidth, and the IoT devices1041and1042operate within a second bandwidth which is narrower than the first bandwidth. The second bandwidth may be defined in accordance with the NB-IoT enhancement of the LTE Rel. 13 standard, referred to in the following also as NB-IoT. A wireless communication system operating in accordance with the LTE standard may have a system bandwidth of 1.4 MHz, 3.0 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz or aggregated system bandwidth consisting of any combination of these, and the bandwidth in accordance with the NB-IoT enhancement of the LTE Rel. 13 standard may be by 200 kHz.

An OFDMA system for data transmission may include an OFDMA-based physical resource grid which comprises plurality of physical resource blocks (PRBs) each defined by 12 subcarriers by 7 OFDM symbols and including a set of resource elements to which various physical channels and physical signals are mapped. A resource element is made up of one symbol in the time domain and one subcarrier in the frequency domain. For example, in accordance with the LTE standard a system bandwidth of 1.4 MHz includes 6 PRBs, and the 200 kHz bandwidth in accordance with the NB-IoT enhancement of the LTE Rel. 13 standard includes 1 PRB. In accordance with LTE and NB-IoT, the physical channels may include the physical downlink shared channel (PDSCH) including user specific data, also referred to as downlink payload data, the physical broadcast channel (PBCH) including for example the master information block (MIB) or the system information block (SIB), the physical downlink control channel (PDCCH) including for example the downlink control information (DCI), etc. The physical signals may comprise reference signals (RS), synchronization signals and the like. The LTE resource grid comprises a 10 ms frame in the time domain having a certain bandwidth in the frequency domain, e.g. 1.4 MHz. The frame has 10 subframes of 1 ms length, and each subframe includes two slots of 6 or 7 OFDM symbols depending on the cyclic prefix (CP) length.

FIG. 2shows an exemplary LTE OFDMA-based subframe with two antenna ports for different selected Tx antenna ports. The subframe includes two resource blocks (RB) each made up of one slot of the subframe and 12 subcarriers in the frequency domain. The subcarriers in the frequency domain are shown as subcarrier 0 to subcarrier 11, and in the time domain, each slot includes 7 OFDM symbols, e.g. in the slot 0 OFDM symbols 0 to 6 and in slot 1 OFDM symbols 7 to 13. The white boxes106represent resource elements allocated to the PDSCH including the payload or user data, also referred to a payload region. The resource elements for the physical control channels (including non-payload or non-user data), also referred to the control region, are represented by the hatched boxes108. In accordance with examples, resource elements108may be allocated to the PDCCH, to the physical control format indicator channel (PCFICH), and to the physical hybrid ARQ indicator channel (PHICH). The cross-hatched boxes110represent resource elements which are allocated to the RS that may be used for the channel estimation. The black boxes112represent unused resources in the current antenna port that may correspond to RSs in another antenna port. The resource elements108,110,112allocated to the physical control channels and to the physical reference signals are not evenly distributed over time. More specifically, in slot 0 of the subframe the resource elements associated with the symbol 0 and the symbol 1 are allocated to the physical control channels or to the physical reference signals, no resource elements in the symbols 0 and 1 are allocated to payload data. The resource elements associated with symbol 4 in slot 0 as well as the resource elements associated with symbols 7 and 11 in slot 1 of the subframe are allocated in part to the physical control channels or to the physical reference signals. The white resource elements shown inFIG. 2may include symbols associated with payload data or user data and in the slot 0 for symbols 2, 3, 5 and 6, all resource elements106may be allocated to payload data, while less resource elements106are allocated to payload data in symbol 4 of slot 0, and no resource element is allocated to payload data in symbols 0 and 1. In slot 1 the resource elements associated with symbols 8, 9, 10, 12 and 13 are all allocated to payload data, while for symbols 7 and 11 less resource elements are allocated to payload data.

FIG. 3shows an example for time units that may be used for the downlink in accordance with the NB-IoT. As mentioned above, NB-IoT may operate within a 200 kHz bandwidth, which corresponds to 12 subcarriers or 1 physical resource block (PRB) in frequency domain. The downlink may be based on orthogonal frequency division multiple access (OFDMA) and may have the same subcarrier spacing, the same OFDM symbol duration, the same slot format, the same slot duration, and the same subframe duration as defined by the LTE standard. The uplink may be based on SC-FDMA (Single Carrier Frequency Division Multiple Access) including a single-tone transmission per user equipment, as a special case of SC-FDMA. In addition, PAPR (Peak-to-Average Power Ratio) reduction techniques may be considered for a multi-tone transmission. Due to the fact that the NB-IoT system bandwidth is only one sixth of the smallest LTE bandwidth (e.g. 6 PRBs for a 1.4 MHz bandwidth system), time units referred to as “M-frame” and “M-subframe” are introduced.FIG. 3shows a NB-IoT radio frame referred as M-frame and having a length of 60 ms. Each M-frame includes 10 M-subframes200each having a duration of 6 ms. Each M-subframe comprises 6 consecutive subframes202, each subframe having a length of 1 ms. Each subframe202has a structure as shown inFIG. 2and includes two slots204, each slot including 7 symbols206, each symbol including the actual signal and a cyclic prefix.

FIG. 4(a)shows an example of the first three M-subframes2000,2001and2002of the M-frame ofFIG. 3. In a M-subframe, the minimum scheduling unit is 1 PRB (1 ms×180 kHz). Hence, up to 6 users or devices may be scheduled in one of the M-subframes (one user per subframe). Following the principle of LTE, a transport block is mapped to the scheduling units (PRBs) assigned to the user in one M-subframe. Unlike LTE, which spreads the scheduling units, e.g. 6 PRBs in a 1.4 MHz bandwidth system, in the frequency dimension, NB-IoT applies a time expansion approach to spread the scheduling units in time dimension.FIG. 4(a)further shows how NB-IoT resource elements are mapped to the respective LTE downlink physical channels and physical signals. In a similar was as LTE also NB-IoT may include the following LTE physical channels:M-PBCH: including broadcast of system informationM-PDSCH: including downlink UE data and control informationM-PDCCH: including downlink control information, for example scheduling informationM-PSCH: including the primary synchronization signal (PSS) and the secondary synchronization signal (SSS) used to obtain time and frequency synchronization with the wireless communication network.

Each of the M-subframes includes 6 subframes2020to2025having a structure similar to that described above with reference toFIG. 2. The LTE physical channels and physical signals are distributed as depicted inFIG. 4(a). Each of the subframes2020to2025in the first M-subframe2000includes at the beginning resource elements defined by the first OFDM symbol and the 12 subcarriers which are mapped to the M-PDCCH. Each subframe may further include resource elements mapped to the M-PBCH, to the M-PDSCH, as well as resource elements mapped to the reference signals CRS. The second M-subframe2001also includes 6 subframes2020to2025, each subframe including resource elements at the first OFDM symbol mapped to the M-PDCCH. Further, each of the subframes includes resource elements mapped to the reference signals CRS. In subframes2020,2021,2023,2024and2025substantially all of the resource elements are mapped to the M-PDSCH, except for those resource elements mapped to M-PDCCH and the mapped to the reference signals CRS. In the subframe2022substantially all resource elements are mapped to the M-PSCH including the secondary and primary synchronization signals, except for those resource elements mapped to M-PDCCH and the mapped to the reference signals CRS. In the third M-subframe2002also 6 subframes2020to2025are provided all including resource elements being mapped to the M-PDSCH, except for those resource elements mapped to M-PDCCH and the mapped to the reference signals CRS. The remaining M-subframes2003to2009forming the M-frame shown inFIG. 3are not shown inFIG. 4(a).FIG. 4(b)shows all M-subframes2000to2009of a M-frame. M-subframes2004,2005,2007and2009have the same structure as the third M-subframe2022, i.e., include, besides the control information in the first resource elements and the reference signals only resource elements mapped to the M-PDSCH. M-subframes2003,2006and2008have substantially the same structure as the second M-subframe2001, except that in M-subframes2003and2008the primary and secondary synchronization signals are in the last subframe2025.

Thus, in the above example, in the first M-frame2009the resource elements are mapped to the M-PBCH, however no resource elements are mapped or allocated to the M-PBCH in second and third M-subframes2021and2022. The primary and secondary synchronization signals PSS and SSS of the M-PSCH are transmitted in the second, fourth, seventh and ninth M-subframes2001,2003,2006and2008but not in first M-subframe2009and also not in any of the M-subframes2002,2004,2005,2007and2009following the second M-subframe2001. In the M-subframes2001,2003,2006and2008the PSS and SSS are arranged in continuous OFDM symbols (see the symbols206inFIG. 4(b)). The M-PDCCH is distributed across the M-subframes, more specifically in the example ofFIG. 4(a)andFIG. 4(b), resource elements at the first OFDM symbol in each M-subframe are mapped to the M-PDCCH. To avoid buffering of M-PDSCH symbols while receiving M-PDCCH symbols, a forward scheduling method may be used for NB-IoT, and the M-PDCCH scheduling information given in a M-subframe may be applicable to M-PDSCH that starts at least one M-subframe later.

Three operating modes for NB-IoT are now described with reference toFIG. 5, namely the in-band LTE operation mode, the standalone GSM operation mode, and the LTE guard band operation mode.FIG. 5is a schematic representation of the different operating modes in accordance with NB-IoT, also referred to as the NB-IoT.FIG. 5(a)shows the in-band LTE operation mode in accordance with which a NB-IoT carrier or frequency band300, also referred to as a NB-IoT channel, is deployed within the LTE carrier or frequency band301.FIG. 5(b)shows the standalone GSM operation mode placing the NB-IoT frequency band300among a plurality of GSM carriers302. The NB-IoT frequency band300is separated by a guard band from the GSM carriers.FIG. 5(c)shows the LTE guard band operation mode, in accordance with which the NB-IoT carrier300is placed in one of the LTE guard bands provided at both ends of the carrier of the standard LTE.

A receiver operating in accordance with NB-IoT, for example a stationary or mobile IoT device or another LTE legacy user, needs to establish a connection with a wireless communication network, like the one depicted inFIG. 1, to receive or send information. For setting up the connection to the network, the receiver is tuned to listen to the NB-IoT frequency band to find the primary synchronization signal PSS and the secondary synchronization signal SSS which allow the receiver to synchronize on a subframe level and to obtain a physical layer cell identity group number. Following this synchronization procedure, the receiver will proceed to read system information, e.g. from the master information block (MIB) provided in the M-PBCH.FIG. 6shows the distribution of the M-subframes including information for establishing a connection over a plurality of M-frames. The first M-subframes2009are provided at the beginning of each M-frame, followed by the second M-subframes2001. When listening to a radio signal transmitted in the NB-IoT frequency band or on the NB-IoT channel, PSS and SSS are received on average every 15 ms, and occur 4 times within a 60 ms M-frame (seeFIG. 3andFIG. 4). The system information is transported in parts of every M-subframe 0 in each M-frame via M-PBCH every 60 ms, which has a transmission time interval (TTI) of 240 ms. Thus, establishing a connection of a receiver, like an IoT device, operating in accordance with NB-IoT may be delayed as the remaining M-subframes2002to2009do not include any resource elements mapped to connection and system information. Also, when serving a plurality of IoT devices, the 6 PRBs in the M-frame need to be shared among the IoT devices which may lead to further delays when receiving/transmitting data. Thus, synchronization, random access and activity time when connecting and transmitting on a NB-IoT channel or a NB-IoT frequency band may be quite high. Further, even when using more than one NB-IoT channel or NB-IoT frequency band, for example, for increasing the number of IoT devices to be served, each of the channels has the same structure.

SUMMARY

One embodiment may have a receiver, wherein the receiver is configured to receive and process a radio signal, the radio signal including at least a first frequency band and a second frequency band, the first frequency band including a first signal, the second frequency band including a second signal, and each of the first signal and the second signal including a plurality of frames, each frame having a plurality of subframes, wherein one or more of the subframes of the first signal includes connecting information allowing a receiver to establish a connection with a wireless communication system, wherein all of the subframes of the second signal are free of any connecting information so that a receiver listening to the second signal cannot set up a connection with the wireless communication system, and wherein the receiver is configured to establish the connection with the wireless communication system using the connecting information, and, after having established the connection with the wireless communication system and responsive to band information indicating the second frequency band, to operate in the second frequency band.

According to another embodiment, a radio signal may have: at least a first frequency band and a second frequency band, the first frequency band including a first signal, the second frequency band including a second signal, and each of the first signal and the second signal including a plurality of frames, each frame having a plurality of subframes, wherein one or more of the subframes of the first signal includes connecting information allowing a receiver to establish a connection with a wireless communication system, and wherein all of the subframes of the second signal are free of any connecting information so that a receiver listening to the second signal cannot set up a connection with the wireless communication system.

Another embodiment may have a transmitter, wherein the transmitter is configured to transmit a radio signal, the radio signal including at least a first frequency band and a second frequency band, the first frequency band including a first signal, the second frequency band including a second signal, and each of the first signal and the second signal including a plurality of frames, each frame having a plurality of subframes, wherein one or more of the subframes of the first signal includes connecting information allowing a receiver to establish a connection with a wireless communication system, and wherein all of the subframes of the second signal are free of any connecting information so that a receiver listening to the second signal cannot set up a connection with the wireless communication system.

According to another embodiment, a wireless communication system may have: an inventive receiver and an inventive transmitter.

According to another embodiment, a method may have the steps of: receiving and processing, by a receiver of a wireless communication system, a radio signal, the radio signal including at least a first frequency band and a second frequency band, the first frequency band including a first signal, the second frequency band including a second signal, and each of the first signal and the second signal including a plurality of frames, each frame having a plurality of subframes, wherein one or more of the subframes of the first signal includes connecting information allowing a receiver to establish a connection with a wireless communication system, and wherein all of the subframes of the second signal are free of any connecting information so that a receiver listening to the second signal cannot set up a connection with the wireless communication system, establishing a connection of the receiver with the wireless communication system using the connecting information, and after having established the connection with the wireless communication system, operating the receiver in the second frequency band responsive to band information indicating the second frequency band.

According to another embodiment, a method may have the steps of: transmitting, by a transmitter of a wireless communication system, a radio signal, the radio signal including at least a first frequency band and a second frequency band, the first frequency band including a first signal, the second frequency band including a second signal, and each of the first signal and the second signal including a plurality of frames, each frame having a plurality of subframes, wherein one or more of the subframes of the first signal includes connecting information allowing a receiver to establish a connection with a wireless communication system, and wherein all of the subframes of the second signal are free of any connecting information so that a receiver listening to the second signal cannot set up a connection with the wireless communication system.

According to another embodiment, a method may have the steps of: transmitting, by a transmitter of a wireless communication device, a radio signal, the radio signal including at least a first frequency band and a second frequency band, the first frequency band including a first signal, the second frequency band including a second signal, and each of the first signal and the second signal including a plurality of frames, each frame having a plurality of subframes, wherein one or more of the subframes of the first signal includes connecting information allowing a receiver to establish a connection with a wireless communication system, and wherein all of the subframes of the second signal are free of any connecting information so that the receiver listening to the second signal cannot set up a connection with the wireless communication system, receiving and processing, by a receiver of the wireless communication system, the radio signal, establishing a connection of the receiver with the wireless communication system using the connecting information, and after having established the connection with the wireless communication system, operating the receiver in the second frequency band responsive to band information indicating the second frequency band.

According to another embodiment, a non-transitory computer program product including a computer readable medium storing instructions which, when executed on a computer, perform the inventive methods.

