WO2018042295A1

WO2018042295A1 - Npbch design and decoding for nb-iot-u

Info

Publication number: WO2018042295A1
Application number: PCT/IB2017/055108
Authority: WO
Inventors: Xingqin LIN; Cagatay Capar; Jung-Fu Cheng; Havish Koorapaty; Amitav Mukherjee; Yi-Pin Eric Wang
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2016-09-01
Filing date: 2017-08-24
Publication date: 2018-03-08

Abstract

Systems and methods relating to transmission of a physical broadcast channel in a cellular communications network are disclosed. In some embodiments, a method of operation of a radio access node in a cellular communications network comprises transmitting, on a carrier, a broadcast channel using frequency hopping. In some embodiments, the carrier is a Narrowband Internet-of-Things (NB-IoT) carrier. Further, in some embodiments, the broadcast channel is a NB-IoT Physical Broadcast Channel in unlicensed spectrum (NPBCH-U). In some embodiments, the carrier is in an unlicensed frequency band.

Description

NPBCH DESIGN AND DECODING FOR NB-loT-U

Related Applications

[0001 ] This application claims the benefit of provisional patent application serial number 62/382,493, filed September 1 , 2016, the disclosure of which is hereby incorporated herein by reference in its entirety.

Technical Field

[0002] The present disclosure relates to the Internet of Things (loT) and, more particularly to a broadcast channel in Narrowband loT (NB-loT).

Background

[0003] The Internet of Things (loT) is a vision for the future world where everything that can benefit from a connection will be connected. Cellular technologies are being developed or evolved to play an indispensable role in the loT world, particularly Machine Type Communication (MTC). MTC is

characterized by lower demands on data rates than, for example, mobile broadband, but with higher requirements on, e.g., low cost device design, better coverage, and ability to operate for years on batteries without charging or replacing the batteries. To meet the loT design objectives, Third Generation Partnership Project (3GPP) has standardized Narrowband loT (NB-loT) in Release (Rel) 13 that has a system bandwidth of 180 kilohertz (kHz) and targets improved coverage, long battery life, low complexity communication design, and network capacity that are sufficient for supporting a massive number of devices.

[0004] To further increase the market impact of NB-loT, extending its deployment mode to unlicensed band operation is being considered. For example, in the United States, the 915 megahertz (MHz) and 2.4 gigahertz (GHz) Industrial, Scientific, and Medical (ISM) bands may be considered.

However, an unlicensed band has specific regulations to ensure different systems can co-exist in the band with good performance and fairness. This requires certain modifications of Rel-13 NB-loT for it to comply with the regulations. In the aforementioned United States ISM bands, it is

advantageous to adopt frequency hopping so that a transmitter can transmit at a higher power level without Power Spectral Density (PSD) limitation or requiring Listen-Before-Talk (LBT).

[0005] In NB-loT, two synchronization signals, Narrowband Primary

Synchronization Signal (NPSS) and Narrowband Secondary Synchronization Signal (NSSS), are transmitted periodically to allow the User Equipment device (UE) to search as well as to synchronize timing and frequency with the network. This is illustrated in Figure 1 .

[0006] In NB-loT, a Master Information Block (MIB) containing the essential system information for initial access to a cell is carried on a Narrowband Physical Broadcast Channel (NPBCH). NPBCH design in Rel-13 NB-loT is illustrated in Figure 2.

[0007] The NPBCH Transmission Time Interval (TTI) is 640 milliseconds (ms), and the transmissions occur in subframe 0 in each radio frame. In subframe 0, NPBCH occupies all the Orthogonal Frequency Division Multiplexing (OFDM) symbols except for the first three OFDM symbols. The NPBCH structure has taken into account the following in-band deployment constraints.

1 . NPBCH uses subframe 0, avoiding collision with Long Term Evolution

(LTE) Multicast Broadcast Single Frequency Network (MBSFN) that may occur in subframes 1 , 2, 3, 6, 7, and 8.

2. NPBCH symbols avoid collision with LTE Physical Control Format

Indicator Channel (PCFICH), Physical Hybrid Automatic Repeat Request (HARQ) Indicator Channel (PHICH), and Physical Downlink Control

Channel (PDCCH) that may use up to the first three OFDM symbols in a subframe (for >1 .4 MHz LTE bandwidth).

3. After cell search, the NB-loT UE does not know the LTE Cell-Specific

Reference Symbol (CRS) values (though it can derive their positions from a cell Identifier (ID) obtained in the cell search). To enable channel estimation and coherent demodulation of NPBCH, new Narrowband Reference Symbols (NRSs) are defined.

4. NPBCH symbols avoid collision with all LTE CRSs (up to four antenna ports). As noted above, after the cell search, the LTE CRS positions are known to the UE, though the exact values are not known.

[0008] With the 640 ms TTI, there are eight blocks of NPBCH. Each block is masked with a unique scrambling code, mapped to a subframe that is repetitively transmitted in subframe 0 in each radio frame in an 80 ms block. Further, NPBCH supports transmission with either one or two antenna ports. When two antenna ports are used, the Space Frequency Block Code (SFBC) is used to encode a pair of NPBCH symbols to produce a pair of SFBC encoded symbols, which are mapped to a pair of resource elements. Thus, the UE has to perform 16 NPBCH decoding attempts, i.e., two NPBCH decoding attempts for the two transmission schemes (i.e., one antenna port and two antenna ports) for each of the eight blocks of NPBCH. After a successful NPBCH decoding, the UE acquires the timing information within the 640 ms TTI of NPBCH. This means that the six Least Significant Bits (LSBs) of the System Frame Number (SFN) need not be included in the system information block.

[0009] The detailed description of NPBCH can be found in Section 10.2.4 in 3GPP Technical Specification (TS) 36.21 1 V13.2.0.

Summary

[0010] Systems and methods relating to transmission of a physical broadcast channel in a cellular communications network are disclosed. In some

embodiments, a method of operation of a radio access node in a cellular communications network comprises transmitting, on a carrier, a broadcast channel using frequency hopping. In some embodiments, the carrier is a Narrowband Internet-of-Things (NB-loT) carrier. Further, in some embodiments, the broadcast channel is a NB-loT Physical Broadcast Channel in unlicensed spectrum (NPBCH-U). In some embodiments, the carrier is in an unlicensed frequency band. [0011 ] In some embodiments, the broadcast channel comprises a plurality of blocks scrambled with a plurality of scrambling codes such that each block is scrambled with a different scrambling code. The broadcast channel has a respective Transmission Time Interval (TTI) that is greater than a dwell time on a frequency hopping channel such that the broadcast channel is divided into two or more portions transmitted on two or more frequency hopping channels, respectively, where each portion of the two or more portions of the broadcast channel comprises a different subset of the plurality of blocks of the broadcast channel. Transmitting the broadcast channel using frequency hopping comprises transmitting the broadcast channel such that, for each portion of the two or more portions of the broadcast channel, a subset of the plurality of scrambling codes utilized for the subset of the plurality of blocks in the portion of the broadcast channel is a function of a frequency hopping channel index of the respective frequency hopping channel.

[0012] In some embodiments, the broadcast channel comprises a plurality of blocks, and the broadcast channel has a respective TTI that is greater than a dwell time on a frequency hopping channel such that the broadcast channel is divided into two or more portions transmitted on two or more frequency hopping channels, respectively, where each portion of the two or more portions of the broadcast channel comprises a different subset of the plurality of blocks of the broadcast channel. Transmitting the broadcast channel using frequency hopping comprises transmitting the broadcast channel such that, for each portion of the two or more portions of the broadcast channel, a set of scrambling codes utilized for the subset of the plurality of blocks in the portion of the broadcast channel is the same as that utilized for the subset of the plurality of blocks in each other portion of the broadcast channel.

[0013] In some embodiments, the broadcast channel comprises a plurality of blocks scrambled with a plurality of scrambling codes such that each block is scrambled with a different scrambling code, and the broadcast channel has a respective TTI that is equal to a dwell time on a frequency hopping channel. [0014] In some embodiments, the carrier is either in a guard band of a Long Term Evolution (LTE) carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that broadcast channel symbols are mapped to resource elements normally reserved for LTE Cell-Specific Reference Symbols (CRSs).

[0015] In some embodiments, the carrier is a NB-loT carrier either in a guard band of an LTE carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that broadcast channel symbols are mapped to all resource elements other than those reserved for NB-loT reference symbols.

[0016] In some embodiments, the carrier is a NB-loT carrier either in a guard band of an LTE carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that NB-loT reference symbols are repeated in resource elements normally reserved for LTE CRS.

[0017] In some embodiments, the broadcast channel supports up to at least four antenna ports.

[0018] Embodiments of a radio access node for a cellular communications network are also disclosed. In some embodiments, a radio access node for a cellular communications network is adapted to transmit, on a carrier, a broadcast channel using frequency hopping.

[0019] In some embodiments, a radio access node for a cellular

communications network comprises at least one processor and memory comprising instructions executable by the at least one processor whereby the radio access node is operable to transmit, via an associated radio unit(s), a broadcast channel on a carrier using frequency hopping.

[0020] In some embodiments, a radio access node for a cellular

communications network comprises a transmitting module operable to transmit, via an associated radio unit(s), a broadcast channel on a carrier using frequency hopping. [0021 ] Embodiments of a method of operation of a wireless device in a cellular communications network are also disclosed. In some embodiments, a method of operation of a wireless device in a cellular communications network comprises decoding a broadcast channel transmitted on a carrier using frequency hopping. In some embodiments, the carrier is a NB-loT carrier. In some embodiments, the broadcast channel is a NPBCH-U. In some

embodiments, the carrier is in an unlicensed frequency band.

[0022] In some embodiments, the broadcast channel comprises a plurality of blocks scrambled with a plurality of scrambling codes such that each block is scrambled with a different scrambling code. The broadcast channel has a respective TTI that is greater than a dwell time on a frequency hopping channel such that the broadcast channel is divided into two or more portions transmitted on two or more frequency hopping channels, respectively, where each portion of the two or more portions of the broadcast channel comprises a different subset of the plurality of blocks of the broadcast channel. Decoding the broadcast channel comprises determining, for at least one portion of the two or more portions of the broadcast channel, a subset of the plurality of scrambling codes utilized for the subset of the plurality of blocks in the portion of the broadcast channel based on a frequency hopping channel index of the respective frequency hopping channel.

[0023] In some embodiments, the broadcast channel comprises a plurality of blocks, and the broadcast channel has a respective TTI that is greater than a dwell time on a frequency hopping channel such that the broadcast channel is divided into two or more portions transmitted on two or more frequency hopping channels, respectively, where each portion of the two or more portions of the broadcast channel comprises a different subset of the plurality of blocks of the broadcast channel. Decoding the broadcast channel comprises, for at least one portion of the two or more portions of the broadcast channel, decoding the portion of the broadcast channel utilizing a set of scrambling codes that is the same as that utilized for each other portion of the broadcast channel.

[0024] In some embodiments, the broadcast channel comprises a plurality of blocks scrambled with a plurality of scrambling codes such that each block is scrambled with a different scrambling code, and the broadcast channel has a respective TTI that is equal to a dwell time on a frequency hopping channel.

[0025] In some embodiments, the carrier is either in a guard band of an LTE carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that broadcast channel symbols are mapped to resource elements normally reserved for LTE CRS.

[0026] In some embodiments, the carrier is a NB-loT carrier either in a guard band of an LTE carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that broadcast channel symbols are mapped to all resource elements other than those reserved for NB-loT reference symbols.

[0027] In some embodiments, the carrier is a NB-loT carrier either in a guard band of an LTE carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that NB-loT reference symbols are repeated in resource elements normally reserved for LTE CRS.

[0028] In some embodiments, the broadcast channel supports up to at least four antenna ports.

[0029] Embodiments of a wireless device for a cellular communications network are also disclosed. In some embodiments, a wireless device for a cellular communications network is adapted to decode a broadcast channel transmitted on a carrier using frequency hopping.

[0030] In some embodiments, a wireless device for a cellular communications network comprises at least one transceiver, at least one processor, and memory comprising instructions executable by the at least one processor whereby the wireless device is operable to decode a broadcast channel transmitted on a carrier using frequency hopping.

[0031] In some embodiments, a wireless device for a cellular communications network comprises a decoding module operable to decode a broadcast channel transmitted on a carrier using frequency hopping. [0032] Other embodiments are also disclosed. In some embodiments, a method of operation of a radio access node in a cellular communications network comprises transmitting, on a carrier, a NB-loT broadcast channel, wherein a resource element to resource grid mapping for the broadcast channel is such that: broadcast channel symbols are mapped to resource elements normally reserved for LTE CRS; broadcast channel symbols are mapped to all resource elements other than those reserved for NB-loT reference symbols; and/or NB-loT reference symbols are repeated in resource elements normally reserved for LTE CRS.

[0033] In some embodiments, a method of operation of a wireless device in a cellular communications network comprises decoding, on a carrier, a NB-loT broadcast channel, wherein a resource element to resource grid mapping for the broadcast channel is such that: broadcast channel symbols are mapped to resource elements normally reserved for LTE CRS; broadcast channel symbols are mapped to all resource elements other than those reserved for NB-loT reference symbols; and/or NB-loT reference symbols are repeated in resource elements normally reserved for LTE CRS.

Brief Description of the Drawings

[0034] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

[0035] Figure 1 illustrates a Narrowband Primary Synchronization Signal (NPSS) and a Narrowband Secondary Synchronization Signal (NSSS) for Narrowband Internet of Things (NB-loT);

[0036] Figure 2 illustrates Narrowband Physical Broadcast Channel (NPBCH) design in Long Term Evolution (LTE) Release (Rel) 13 NB-loT;

[0037] Figure 3 illustrates an example of channel definition suitable for NB-loT in the United States 902-928 megahertz (MHz) Industrial, Scientific, and Medical (ISM) band; [0038] Figure 4 illustrates an example of channel definition suitable for NB-loT in the United States 2.4-2.4835 gigahertz (GHz) ISM band;

[0039] Figure 5 illustrates when NPBCH in unlicensed spectrum (NPBCH-U) is designed to be the same as NPBCH except the scrambling aspect according to one embodiment of the present disclosure;

[0040] Figure 6 illustrates when NPBCH-U is designed by tailoring 640 millisecond (ms) NPBCH Transmission Time Interval (TTI) to 320 ms dwell time on a hopping channel according to one embodiment of the present disclosure;

[0041 ] Figure 7 illustrates when NPBCH-U symbols do not avoid collision with all LTE Cell-Specific Reference Symbols (CRSs) and are mapped to the resource elements corresponding to the LTE CRS as well according to one embodiment of the present disclosure;

[0042] Figure 8 illustrates when NPBCH-U symbols do not avoid collision with all LTE CRSs as well as LTE Physical Control Format Indicator Channel (PCFICH), Physical Hybrid Automatic Repeat Request (HARQ) Indicator

Channel (PHICH), and Physical Downlink Control Channel (PDCCH) that may use up to the first three Orthogonal Frequency Division Multiplexing (OFDM) symbols according to one embodiment of the present disclosure;

[0043] Figure 9 illustrates one example of a cellular communications network, or more generally a wireless communications system, in which embodiments of the present disclosure may be implemented;

[0044] Figure 10 illustrates the operation of a radio access node (e.g., a base station such as an enhanced or evolved Node B (eNB)) and a wireless device (e.g., a User Equipment device (UE)) according to some embodiments of the present disclosure;

[0045] Figures 1 1 through 13 illustrate example embodiments of a radio access node; and

[0046] Figures 14 and 15 illustrate example embodiments of a wireless device. Detailed Description

[0047] The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.

[0048] Radio Node: As used herein, a "radio node" is either a radio access node or a wireless device.

[0049] Radio Access Node: As used herein, a "radio access node" is any node in a radio access network of a cellular communications network that operates to wirelessly transmit and/or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., an enhanced or evolved Node B (eNB) in a Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) network), a high-power or macro base station, a low-power base station (e.g., a micro base station, a pico base station, a home eNB, or the like), and a relay node.

[0050] Core Network Node: As used herein, a "core network node" is any type of node in a Core Network (CN). Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a Packet Data Network (PDN) Gateway (P-GW), a Service Capability Exposure Function (SCEF), or the like.

[0051] Wireless Device: As used herein, a "wireless device" is any type of device that has access to (i.e., is served by) a cellular communications network by wirelessly transmitting and/or receiving signals to a radio access node(s). Some examples of a wireless device include, but are not limited to, a User Equipment device (UE) in a 3GPP network and a Machine Type Communication (MTC) device. [0052] Network Node: As used herein, a "network node" is any node that is either part of the radio access network or the CN of a cellular communications network/system.

[0053] Note that the description given herein focuses on a 3GPP cellular communications system and, as such, 3GPP LTE terminology or terminology similar to 3GPP LTE terminology is oftentimes used. However, the concepts disclosed herein are not limited to LTE or a 3GPP system.

[0054] Note that, in the description herein, reference may be made to the term "cell;" however, particularly with respect to Fifth Generation (5G) concepts, beams may be used instead of cells and, as such, it is important to note that the concepts described herein are equally applicable to both cells and beams.

[0055] Narrowband Internet of Things (NB-loT) is a radio access technology introduced in 3GPP Release (Rel) 13 targeting specifically the Internet of Things (loT) and MTC use cases. It has a system bandwidth of 180 kilohertz (kHz) and achieves improved coverage, long battery life, and network capacity that is sufficient for supporting a massive number of devices. It further allows low complexity communication design and facilitates low UE module cost.

[0056] Currently, extending NB-loT deployment to unlicensed band operation is being considered. For example, in the United States, the 915 megahertz (MHz) and 2.4 gigahertz (GHz) Industrial, Scientific, and Medical (ISM) bands may be considered. The 915 MHz ISM band in the United States spans over 902-926 MHz, and the 2.4 GHz ISM band starts from 2.4 GHz to 2.4835 GHz. However, an unlicensed band has specific regulations to ensure different systems can co-exist in the band with good performance and fairness. This requires certain modifications of Rel-13 NB-loT for it to comply with the regulations. In the aforementioned United States ISM bands, it is

[0057] The Federal Communications Commission (FCC) regulations state that a transmitter transmitting a signal of 20 decibels (dB) bandwidth smaller than 250 kHz may use 36 decibel-milliwatts (dBm) Equivalent Isotropically Radiated Power (El PR) if hopping over 50 (or greater) and 75 (or greater) frequency channels in the 915 MHz and 2.4 GHz ISM bands, respectively (FCC Part 15, Section 247). Figure 3 shows an example of channel definition suitable for NB-loT in the United States 902-928 MHz ISM band. Each channel occupies 250 kHz bandwidth. There are 50 uplink channels and 50 downlink channels. Figure 4 shows an example of channel definition suitable for NB-loT in the United States 2.4-2.4835 GHz ISM band. Each channel occupies 250 kHz bandwidth. There are 160 uplink channels and 160 downlink channels.

[0058] In the discussion below, N is the number of hopping channels. FCC regulations further state that the average dwell time on any of the hopping channels needs to be lower than 1/N (FCC Part 15, Section 247).

[0059] The hopping pattern may be a repetitive one based on a hopping pattern Q in a hopping cycle that consists of N hopping channels.

Q = ( (0), /(l) f(N - 1)), f(i) 6 {0 N - 1} where each hopping channel is represented by an integer from 0 to N - 1. The hopping pattern Q is essentially a shuffling operation to the N hopping channels indexed from 0 to N - 1 such that the system hops to each channel exactly once in a hopping cycle.

[0060] The dwell time on a hopping channel is an important design parameter that trades off many factors. For example, long dwell time may facilitate initial acquisition and cell search procedure for the UE at the cost of possibly increased mutual interfering time when two cells/systems are using the same channel in unlicensed bands.

[0061 ] The existing Narrowband Physical Broadcast Channel (NPBCH) design and/or decoding are not tailored to NB-loT deployment in unlicensed bands.

[0062] The present disclosure proposes methods of optimizing NPBCH design and reducing NPBCH decoding complexity for deploying NB-loT in unlicensed bands with frequency hopping. [0063] Some advantages of some embodiments of the present disclosure are as follows. NPBCH decoding complexity can be reduced by exploiting the frequency hopping pattern designed for NB-loT in unlicensed bands. For an example of 320 milliseconds (ms) dwell time on a hopping channel, the decoding complexity can be reduced by -50%. Reducing the length of scrambling code used in NPBCH may lead to advantages such as reduced memory requirement and lower complexity. Adapting NPBCH Transmission Time Interval (TTI) to the hopping design of NB-loT in unlicensed bands may facilitate the UE's acquisition of Master Information Block (MIB). Optimizing resource element mapping in NPBCH for NB-loT in unlicensed bands may improve the efficiency of radio resource usage.

[0064] To differentiate from Rel-13 NB-loT, a suffix "U" is added when the version of NB-loT with frequency hopping that can be used for unlicensed band operation is described. For example, NB-loT-U represents such a system, and Narrowband Physical Broadcast Channel in unlicensed spectrum (NPBCH-U) is the physical broadcast channel of NB-loT-U. It should be further noted the teaching of NB-loT with frequency hopping herein can be applied to other licensed or shared spectrums.

[0065] The present disclosure describes how NPBCH design or decoding can be optimized for NB-loT deployment in unlicensed bands. For

concreteness, the dwell time on a hopping channel is assumed to be 320 ms in describing the following embodiments. Depending on the adopted hopping pattern for NB-loT-U, the ideas may apply to other dwell time values.

[0066] In a first embodiment, NPBCH-U is designed to be the same as NPBCH. However, the UE utilizes the hopping pattern of NB-loT-U to reduce the number of decoding attempts of NPBCH-U.

[0067] The UE obtains the knowledge of the hopping pattern before NPBCH decoding and thus can determine the timing boundaries of 320 ms. One non- limiting exemplary embodiment to obtain said hopping pattern and timing boundaries is by receiving the synchronization signals (Narrowband Primary Synchronization Signal (NPSS) and Narrowband Secondary Synchronization Signal (NSSS)) from the network. Another non-limiting exemplary embodiment to obtain said hopping pattern by the UE is reading from the UE's internal storage.

[0068] Based on the hopping pattern knowledge, the UE knows the index i of the hopping channel f i) used in any 320 ms hopping duration. Based on whether the index i is an even or odd number, the UE knows the associated 320 ms of the hopping channel contains the first or the second half of NPBCH- U. With the following inverse mapping

the UE knows that the associated time lies in the n-th half internal of 640 ms NPBCH-U TTI. Recall that there are eight scrambling codes used in NPBCH-U, with each being applied to an 80 ms interval. If n = 0, the UE can determine that the scrambling codes used are the first four scrambling codes. If n = 1, the UE can determine that the scrambling codes used are the last four scrambling codes. Therefore, with the knowledge of hopping pattern, the UE only needs to perform eight (four scrambling codes x two transmission schemes) NPBCH-U decoding attempts, instead of 16 decoding attempts in the case of not exploiting the knowledge of hopping pattern.

[0069] This embodiment is applicable to other dwell times t_D that can divide the NPBCH-U TTI of 640 ms evenly. As another non-limiting embodiment with dwell time t_D = 160 ms, the inverse mapping n =

gives values in the range of 0, 1 , 2, and 3. Based on the calculated value n, the UE knows the associated time lies in the n-th quarter interval of 640 ms

NPBCH-U TTI. Then, as described above, the UE can determine the

scrambling codes used for the n-th segment of the 640 ms NPBCH-U TTI and use the determined scrambling codes for decoding the NPBCH-U.

[0070] In a second embodiment, NPBCH-U is designed to be the same as NPBCH except for the scrambling aspect. [0071 ] Assuming 320 ms dwell time on each hopping channel, it is clear from the description of the first embodiment that the hopping pattern design helps determine timing boundaries of 320 ms. In particular, the UE knows the associated time lies in the first or second half of the 640 ms TTI. Therefore, the same set of scrambling codes can be used across the two 320 ms intervals while still enabling the UE to acquire timing concept in 640 ms TTI. In other words, the scrambling sequence for NPBCH-U shall be initialized in radio frames fulfilling u_j mod32 = 0, where n_f is radio frame number.

[0072] Figure 5 gives an illustration of the second embodiment. As illustrated, scrambling codes 0, 1 , 2, and 3 are used in the first half of the 640 ms NPBCH-U TTI, and the same scrambling codes 0, 1 , 2, and 3 are again used in the second half of the 640 ms NPBCH-U TTI.

[0073] In a third embodiment, NPBCH-U is designed by tailoring 640 ms NPBCH TTI to 320 ms dwell time on a hopping channel.

[0074] Specifically, the NPBCH-U TTI is 320 ms, and there are four blocks of NPBCH-U. Each block is masked with a unique scrambling code, mapped to a subframe that is repetitively transmitted in subframe 0 in each radio frame in an 80 ms block. Assuming that NPBCH-U supports transmission with either one or two antenna ports, the UE needs to perform eight NPBCH-U decoding attempts. After a successful NPBCH-U decoding, the UE acquires the timing information within the 320 ms TTI of NPBCH-U.

[0075] As in the first embodiment, the hopping pattern design helps determine timing boundaries of 320 ms. In particular, the UE knows the associated time lies in the first or second half of every 640 ms time interval. This means that the six Least Significant Bits (LSBs) of the System Frame

Number (SFN) need not be included in the system information block in NB-loT-U. Since the remaining bits of the SFN do not change across a pair of 320 ms TTIs, the two NPBCH-U transmissions can be considered as two repetitions (i.e., two repetitions of the 4 scrambled blocks), assuming that the other MIB bits also do not change across a pair of 320 ms TTIs.

[0076] Figure 6 gives an illustration of the third embodiment. [0077] In the first, second, and third embodiments, it has been assumed that resource element mapping to the resource grid for NPBCH-U is the same as NPBCH, as illustrated in Figure 2. NPBCH has been designed to enable the possibility of deploying NB-loT inside a LTE carrier by replacing one LTE physical resource block for an NB-loT carrier. In particular, as described in the Background section above, NPBCH symbols avoid collision with LTE Physical Control Format Indicator Channel (PCFICH), Physical Hybrid Automatic Repeat Request (HARQ) Indicator Channel (PHICH), and Physical Downlink Control Channel (PDCCH) that may use up to the first three Orthogonal Frequency Division Multiplexing (OFDM) symbols in a subframe (for >1 .4 MHz LTE bandwidth). NPBCH symbols also avoid collision with all LTE Cell-Specific Reference Symbols (CRSs) (up to four antenna ports).

[0078] If in-band deployment is not targeted for NB-loT-U, the resource element mapping for NPBCH-U may be changed without concerning legacy LTE signals.

[0079] In a first aspect of a fourth embodiment, NPBCH-U symbols do not avoid collision with all LTE CRSs and are mapped to the resource elements corresponding to the LTE CRS as well. Figure 7 gives an illustration of the first aspect of the fourth embodiment.

[0080] In a second aspect of a fourth embodiment, NPBCH-U symbols do not avoid collision with all LTE CRSs as well as LTE PCFICH, PHICH, and PDCCH that may use up to the first three OFDM symbols. In other words, NPBCH-U symbols are mapped to all the available resource elements in a subframe except those reserved for NB-loT reference symbols. Figure 8 gives an illustration of the second aspect of the fourth embodiment.

[0081 ] In a third aspect of the fourth embodiment, the Narrowband Reference Symbols (NRSs) are repeated in LTE CRS symbol positions. One non-limiting example is to repeat NRS port 0 symbols in the LTE CRS port 0 positions and NRS port 1 symbols in the LTE CRS port 1 . A subset of NRS port 0 symbols is repeated in the LTE CRS port 2 positions and a subset of NRS port 1 symbols is repeated is repeated in the LTE CRS port 3 positions. [0082] In a fourth aspect of the fourth embodiment, it is further noted that the above aspects of the fourth embodiment can be combined. One non-limiting example is to repeat NRS port 0 symbols in the LTE CRS port 0 positions and NRS port 1 symbols in the LTE CRS port 1 . The rest of the not-yet-used symbols in the first three OFDM symbols as well as those for LTE CRS port 2 and 3 are used by the NPBCH-U.

[0083] In a fifth aspect of the fourth embodiment, NPBCH-U is extended to support up to four antenna ports. For example, CRS port 0 is mapped to NPBCH-U port 2 and CRS port 1 is mapped to NPBCH-U port 3. For example, symbols of CRS port 0 are used for estimating the channel coefficients of NPBCH-U port 2 and symbols of CRS port 1 are used for estimating the channel coefficients of NPBCH-U port 3. The data symbols are still encoded using Space Frequency Block Code (SFBC). However, frequency or time- switch diversity can be used to map the SFBC encoded symbols across four NPBCH-U ports. For example, some of the resource pairs can be transmitted by NPBCH-U ports 0 and 1 , and the remaining resource pairs can be

transmitted by NPBCH-U ports 2 and 3.

[0084] Note that the fourth embodiment, including the first through fifth aspects of the fourth embodiment, is not a parallel embodiment to the first through third embodiments described above. Instead, the fourth embodiment can be combined with any of the first through third embodiments by replacing the underlying resource mapping pattern to form a new embodiment.

[0085] Figure 9 illustrates one example of a cellular communications network 10, or more generally a wireless communications system, in which embodiments of the present disclosure may be implemented. The cellular communications network 10 includes a radio access network, where the radio access network includes a number of radio access nodes 12 (e.g., base stations such as eNBs) serving corresponding cells 14. The radio access nodes 12 provide radio access to wireless devices 16 (e.g., LTE UEs, MTC devices, Machine-to-Machine (M2M) devices, etc.) within the cells 14. The radio access nodes 12 are capable of communicating with the wireless devices 16 along with any additional elements suitable to support communication between wireless communication devices or between a wireless communication device and another communication device (such as a landline telephone). The radio access nodes 12 are connected to a core network 18.

[0086] As discussed herein, the radio access node 12 operates to transmit, and the wireless device 16 operates to decode, a NPBCH-U having a design in accordance with any of the first through fourth embodiments described above. Note that while the NPBCH-U is the focus the embodiments described herein, the concepts disclosed herein can be utilized for any similar physical broadcast channel (i.e., is not necessarily limited to NB-loT, but may be utilized for other similar technologies in which frequency hopping is utilized for transmission of the physical broadcast channel).

[0087] Figure 10 illustrates the operation of a radio access node 12 (e.g., a base station such as an eNB) and a wireless device 16 (e.g., a UE) according to some embodiments of the present disclosure. In general, the radio access node 12 and the wireless device 16 can operate to provide the functionality of the eNB and the UE, respectively, according to any of the first through fourth

embodiments described above. As illustrated, the wireless device 16 obtains the frequency hopping pattern utilized by the radio access node 12 for transmission of the NPBCH-U (step 100). As discussed above, the wireless device 16 obtains the frequency hopping pattern in any suitable manner such as, e.g., by receiving the synchronization signals (NPSS and NSSS) from the network or by reading the frequency hopping pattern from internal storage at the wireless device 16.

[0088] The radio access node 12 transmits the NPBCH-U using the frequency hopping pattern (step 102). As discussed above, in the first embodiment, the NPBCH-U (or more generally the broadcast channel) includes multiple blocks scrambled with multiple scrambling codes, respectively, such that each block is scrambled with a different scrambling code. The NPBCH-U (or more generally the broadcast channel) has a respective TTI that is greater than a dwell time on a frequency hopping channel such that the broadcast channel is divided into two or more portions transmitted on two or more frequency hopping channels, respectively. Each portion of the broadcast control channel includes a different subset of the blocks of the broadcast control channel. The radio access node 12 transmits the NPBCH-U (or more generally the broadcast channel) using frequency hopping such that, for each portion of the broadcast channel, a subset of the scrambling codes utilized for the subset of the blocks in the portion of the broadcast channel is a function of a frequency hopping channel index of the respective frequency hopping channel. As an example as discussed above, in some embodiments, the NPBCH-U TTI is 640 ms where eight different scrambling codes are used for the eight 80 ms blocks of the NPBCH-U TTI.

[0089] As discussed above, in the second embodiment, the NPBCH-U (or more generally the broadcast channel) includes multiple blocks scrambled with multiple scrambling codes, respectively, such that each block is scrambled with a different scrambling code. The NPBCH-U (or more generally the broadcast channel) has a respective TTI that is greater than a dwell time on a frequency hopping channel such that the broadcast channel is divided into two or more portions transmitted on two or more frequency hopping channels, respectively. Each portion of the broadcast control channel includes a different subset of the blocks of the broadcast control channel. The radio access node 12 transmits the NPBCH-U (or more generally the broadcast channel) using frequency hopping such that, for each portion of the broadcast channel, a set of scrambling codes utilized for the subset of the blocks in the portion of the broadcast channel is the same as that utilized for the subset of the blocks in each other portion of the broadcast channel. As an example as described above, the NPBCH-U TTI is 640 ms where the same four scrambling codes are used for the four 80 ms blocks of the NPBCH-U in each 320 ms half of the NPBCH-U TTI.

[0090] In some other embodiments, the NPBCH-U TTI is tailored to the desired dwell time on a hopping channel, which may be 320 ms, as described above.

[0091 ] Still further, in some embodiments, the NPBCH-U uses the same resource element mapping to resource grid as that used for NPBCH, e.g., as defined in 3GPP Technical Specification (TS) 36.21 1 V13.2.0. In other embodiments, the NPBCH-U uses a different resource element mapping to resource grid that, e.g., maps NPBCH-U symbols to resource elements corresponding to LTE CRS, maps NPBCH-U symbols to all resource elements in the subframe other than those used for NB-loT reference symbols, repeats NRS symbols in LTE CRS symbol positions, and/or is extended to support up to four antenna ports.

[0092] The wireless device 16 decodes the NPBCH-U, as described above (step 104). In some embodiments, portions of the NPBCH-U are transmitted on different frequency hopping channels. As discussed above, in the first embodiment, the NPBCH-U (or more generally the broadcast channel) includes multiple blocks scrambled with multiple scrambling codes, respectively, such that each block is scrambled with a different scrambling code. The NPBCH-U (or more generally the broadcast channel) has a respective TTI that is greater than a dwell time on a frequency hopping channel such that the broadcast channel is divided into two or more portions transmitted on two or more frequency hopping channels, respectively. Each portion of the broadcast control channel includes a different subset of the blocks of the broadcast control channel. In order to decode the NPBCH-U (or more generally the broadcast channel), the wireless device 16 determines, for one or at least one portion of the broadcast channel, a subset of the scrambling codes utilized for the subset of the plurality of blocks in the portion of the broadcast channel based on a frequency hopping channel index of the respective frequency hopping channel. The wireless device 16 then decodes the portion of the NPBCH-U (or more generally the broadcast channel), or more specifically the NPBCH-U blocks in the portion, using the determined scrambling codes. As an example as described above, in some embodiments, the NPBCH-U uses eight different scrambling codes for the eight 80 ms blocks of the NPBCH-U. For one or at least one portion of the NPBCH-U, the wireless device 16 determines which scrambling codes to use for decoding that portion of the NPBCH-U based on the frequency hopping channel index for the respective frequency hopping channel (e.g., determines which of two sets of scrambling codes to use for decoding based on whether the frequency channel hopping index is even or odd). The wireless device 16 then decodes the portion(s) of the NPBCH-U using the determined subset of the scrambling codes for that portion(s).

[0093] As discussed above, in the second embodiment, the NPBCH-U (or more generally the broadcast channel) includes multiple blocks scrambled with multiple scrambling codes, respectively, such that each block is scrambled with a different scrambling code. The NPBCH-U (or more generally the broadcast channel) has a respective TTI that is greater than a dwell time on a frequency hopping channel such that the broadcast channel is divided into two or more portions transmitted on two or more frequency hopping channels, respectively. Each portion of the broadcast control channel includes a different subset of the blocks of the broadcast control channel. In order to decode the NPBCH-U (or more generally the broadcast channel), for one or at least one of the portions of the NPBCH-U, the wireless device 16 decodes the portion of the NPBCH-U using a set of scrambling codes that is the same as that utilized in each other portion of the NPBCH-U. As an example as described above, in some embodiments, the NPBCH-U uses the same four scrambling codes for the four 80 ms blocks in each half of the NPBCH-U, and the wireless device 16 decodes the NPBCH-U accordingly.

[0094] In some other embodiments, the NPBCH-U TTI is tailored to the desired dwell time on a hopping channel, which may be 320 ms, as described above, and the wireless device 16 decodes the NPBCH-U accordingly.

[0095] In some embodiments, the wireless device 16 obtains system information (e.g., MIB) from the decoded NPBCH-U and uses the system information e.g., in the conventional manner (step 106).

[0096] Figure 1 1 is a schematic block diagram of the radio access node 12 according to some embodiments of the present disclosure. As illustrated, the radio access node 12 includes a control system 20 that includes one or more processors 22 (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and/or the like), memory 24, and a network interface 26. In addition, the radio access node 12 includes one or more radio units 28 that each includes one or more transmitters 30 and one or more receivers 32 coupled to one or more antennas 34. In some embodiments, the radio unit(s) 28 is external to the control system 20 and connected to the control system 20 via, e.g., a wired connection (e.g., an optical cable). However, in some other embodiments, the radio unit(s) 28 and potentially the antenna(s) 34 are integrated together with the control system 20. The one or more processors 22 operate to provide one or more functions of a radio access node 12 as described herein. In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory 24 and executed by the one or more processors 22.

[0097] Figure 12 is a schematic block diagram that illustrates a virtualized embodiment of the radio access node 12 according to some embodiments of the present disclosure. This discussion is equally applicable to other types of network nodes. Further, other types of network nodes may have similar virtualized architectures.

[0098] As used herein, a "virtualized" radio access node 12 is an

implementation of the radio access node 12 in which at least a portion of the functionality of the radio access node 12 is implemented as a virtual

component(s) (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)). As illustrated, in this example, the radio access node 12 includes the control system 20 (optional) that includes the one or more processors 22 (e.g., CPUs, ASICs, FPGAs, and/or the like), the memory 24, and the network interface 26 and the one or more radio units 28 that each includes the one or more transmitters 30 and the one or more receivers 32 coupled to the one or more antennas 34, as described above. The control system 20 is connected to the radio unit(s) 28 via, for example, an optical cable or the like. The control system 20 is connected to one or more processing nodes 36 coupled to or included as part of a network(s) 38 via the network interface 26. Each processing node 36 includes one or more processors 40 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 42, and a network interface 44. [0099] In this example, functions 46 of the radio access node 12 described herein are implemented at the one or more processing nodes 36 or distributed across the control system 20 and the one or more processing nodes 36 in any desired manner. In some particular embodiments, some or all of the functions 46 of the radio access node 12 described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) 36. As will be appreciated by one of ordinary skill in the art, additional signaling or communication between the processing node(s) 36 and the control system 20 is used in order to carry out at least some of the desired functions 46. Notably, in some embodiments, the control system 20 may not be included, in which case the radio unit(s) 28 communicate directly with the processing node(s) 36 via an appropriate network interface(s).

[0100] In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of a radio access node 12 or a node (e.g., a processing node 36) implementing one or more of the functions 46 of the radio access node 12 in a virtual environment according to any of the embodiments described herein is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

[0101] Figure 13 is a schematic block diagram of the radio access node 12 according to some other embodiments of the present disclosure. The radio access node 12 includes one or more modules 48, each of which is implemented in software. The module(s) 48 provide the functionality of the radio access node 12 described herein. For example, the module(s) 48 include a transmitting module 48 that operates to transmit, e.g., NPBCH-U according one of the embodiments described herein. This discussion is equally applicable to the processing node 36 of Figure 12 where the modules 48 may be implemented at one of the processing nodes 36 or distributed across multiple processing nodes 36 and/or distributed across the processing node(s) 36 and the control system 20.

[0102] Figure 14 is a schematic block diagram of a wireless device 16 according to some embodiments of the present disclosure. As illustrated, the wireless device 16 includes one or more processors 50 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 52, and one or more transceivers 54 each including one or more transmitters 56 and one or more receivers 58 coupled to one or more antennas 60. In some embodiments, the functionality of the wireless device 16 described above may be fully or partially implemented in software that is, e.g., stored in the memory 52 and executed by the processor(s) 50.

[0103] In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of the wireless device 16 according to any of the embodiments described herein is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

[0104] Figure 15 is a schematic block diagram of the wireless device 16 according to some other embodiments of the present disclosure. The wireless device 16 includes one or more modules 62, each of which is implemented in software. The module(s) 62 provide the functionality of the wireless device 16 described herein. For example, the module(s) 62 may include a decoding module 62 that operates to decode, e.g., a NPBCH-U according to any one of the embodiments described herein.

[0105] While not being limited thereto, some example embodiments of the present disclosure are provided below.

[0106] Embodiment 1 : A method of operation of a radio access node (12) in a cellular communications network (10), comprising: transmitting (102), on a carrier, a broadcast channel using frequency hopping. [0107] Embodiment 2: The method of embodiment 1 wherein the carrier is a NB-loT carrier.

[0108] Embodiment s: The method of embodiment 2 wherein the broadcast channel is a NPBCH-U.

[0109] Embodiment 4: The method of any one of embodiments 1 to 3 wherein the carrier is in an unlicensed frequency band.

[0110] Embodiment 5: The method of any one of embodiments 1 to 4 wherein: the broadcast channel comprises a plurality of blocks scrambled with a plurality of scrambling codes such that each block is scrambled with a different scrambling code; the broadcast channel has a respective TTI that is greater than a dwell time on a frequency hopping channel such that the broadcast channel is divided into two or more portions transmitted on two or more frequency hopping channels, respectively, where each portion of the two or more portions of the broadcast control channel comprises a different subset of the plurality of blocks of the broadcast control channel; and transmitting (102) the broadcast channel using frequency hopping comprises transmitting (102) the broadcast channel such that, for each portion of the two or more portions of the broadcast channel, a subset of the plurality of scrambling codes utilized for the subset of the plurality of blocks in the portion of the broadcast channel is a function of a frequency hopping channel index of the respective frequency hopping channel.

[0111 ] Embodiment 6: The method of any one of embodiments 1 to 4 wherein: the broadcast channel comprises a plurality of blocks; the broadcast channel has a respective TTI that is greater than a dwell time on a frequency hopping channel such that the broadcast channel is divided into two or more portions transmitted on two or more frequency hopping channels, respectively, where each portion of the two or more portions of the broadcast control channel comprises a different subset of the plurality of blocks of the broadcast control channel; and transmitting (102) the broadcast channel using frequency hopping comprises transmitting (102) the broadcast channel such that, for each portion of the two or more portions of the broadcast channel, a set of scrambling codes utilized for the subset of the plurality of blocks in the portion of the broadcast channel is the same as that utilized for the subset of the plurality of blocks in each other portion of the broadcast channel.

[0112] Embodiment 7: The method of any one of embodiments 1 to 4 wherein: the broadcast channel comprises a plurality of blocks scrambled with a plurality of scrambling codes such that each block is scrambled with a different scrambling code; and the broadcast channel has a respective TTI that is equal to a dwell time on a frequency hopping channel.

[0113] Embodiment 8: The method of any one of embodiments 1 to 7 wherein the carrier is either in a guard band of an LTE carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that broadcast channel symbols are mapped to resource elements normally reserved for LTE CRS.

[0114] Embodiment 9: The method of any one of embodiments 1 to 7 wherein the carrier is a NB-loT carrier either in a guard band of an LTE carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that broadcast channel symbols are mapped to all resource elements other than those reserved for NB-loT reference symbols.

[0115] Embodiment 10: The method of any one of embodiments 1 to 7 wherein the carrier is a NB-loT carrier either in a guard band of an LTE carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that NRS are repeated in LTE CRS symbol positions.

[0116] Embodiment 1 1 : The method of any one of embodiments 1 to 7 wherein broadcast channel supports up to at least four antenna ports.

[0117] Embodiment 12: A radio access node (12) for a cellular

communications network (10), the radio access node (12) adapted to: transmit, on a carrier, a broadcast channel using frequency hopping.

[0118] Embodiment 13: The radio access node (12) of embodiment 12 wherein the radio access node (12) is further adapted to operate according to the method of any one of embodiments 2 to 1 1 . [0119] Embodiment 14: A radio access node (12) for a cellular

communications network (10), comprising: at least one processor (22, 40); and memory (24, 42) comprising instructions executable by the at least one processor (22, 40) whereby the radio access node (12) is operable to transmit, via an associated radio unit(s) (28), a broadcast channel on a carrier using frequency hopping.

[0120] Embodiment 15: A radio access node (12) for a cellular

communications network (10), comprising a transmitting module (48) operable to transmit, via an associated radio unit(s), a broadcast channel on a carrier using frequency hopping.

[0121 ] Embodiment 16: A method of operation of a wireless device (16) in a cellular communications network (10), comprising: decoding (104) a broadcast channel transmitted on a carrier using frequency hopping.

[0122] Embodiment 17: The method of embodiment 16 wherein the carrier is a NB-loT carrier.

[0123] Embodiment 18: The method of embodiment 17 wherein the broadcast channel is a NPBCH-U.

[0124] Embodiment 19: The method of any one of embodiments 16 to 18 wherein the carrier is in an unlicensed frequency band.

[0125] Embodiment 20: The method of any one of embodiments 16 to 19 wherein: the broadcast channel comprises a plurality of blocks scrambled with a plurality of scrambling codes such that each block is scrambled with a different scrambling code; the broadcast channel has a respective TTI that is greater than a dwell time on a frequency hopping channel such that the broadcast channel is divided into two or more portions transmitted on two or more frequency hopping channels, respectively, where each portion of the two or more portions of the broadcast control channel comprises a different subset of the plurality of blocks of the broadcast control channel; and decoding (104) the broadcast channel comprises determining, for each portion of the two or more portions of the broadcast channel, a subset of the plurality of scrambling codes utilized for the subset of the plurality of blocks in the portion of the broadcast channel based on a frequency hopping channel index of the respective frequency hopping channel.

[0126] Embodiment 21 : The method of any one of embodiments 16 to 19 wherein: the broadcast channel comprises a plurality of blocks; the broadcast channel has a respective TTI that is greater than a dwell time on a frequency hopping channel such that the broadcast channel is divided into two or more portions transmitted on two or more frequency hopping channels, respectively, where each portion of the two or more portions of the broadcast control channel comprises a different subset of the plurality of blocks of the broadcast control channel; and decoding (104) the broadcast channel comprises, for each portion of the two or more portions of the broadcast channel, decoding (104) the portion of the broadcast channel utilizing a set of scrambling codes that is the same as that utilized for decoding each other portion of the broadcast channel.

[0127] Embodiment 22: The method of any one of embodiments 16 to 19 wherein: the broadcast channel comprises a plurality of blocks scrambled with a plurality of scrambling codes such that each block is scrambled with a different scrambling code; and the broadcast channel has a respective TTI that is equal to a dwell time on a frequency hopping channel.

[0128] Embodiment 23: The method of any one of embodiments 16 to 22 wherein the carrier is either in a guard band of an LTE carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that broadcast channel symbols are mapped to resource elements normally reserved for LTE CRS.

[0129] Embodiment 24: The method of any one of embodiments 16 to 22 wherein the carrier is a NB-loT carrier either in a guard band of an LTE carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that broadcast channel symbols are mapped to all resource elements other than those reserved for NB-loT reference symbols.

[0130] Embodiment 25: The method of any one of embodiments 16 to 22 wherein the carrier is a NB-loT carrier either in a guard band of an LTE carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that NRS are repeated in LTE CRS symbol positions.

[0131 ] Embodiment 26: The method of any one of embodiments 16 to 22 wherein broadcast channel supports up to at least four antenna ports.

[0132] Embodiment 27: A wireless device (16) in a cellular communications network (10), the wireless device (16) adapted to: decode (104) a broadcast channel transmitted on a carrier using frequency hopping.

[0133] Embodiment 28: The wireless device (16) of embodiment 27 wherein the wireless device (16) is further adapted to operate according to the method of any one of embodiments 17 to 26.

[0134] Embodiment 29: A wireless device (16) for a cellular communications network (10), comprising: at least one transceiver (54); at least one processor (50); and memory (52) comprising instructions executable by the at least one processor (50) whereby the wireless device (16) is operable to decode a broadcast channel transmitted on a carrier using frequency hopping.

[0135] Embodiment 30: A decoding (104) a broadcast channel transmitted on a carrier using frequency hopping for a cellular communications network (10), comprising: a decoding module (62) operable to decode a broadcast channel transmitted on a carrier using frequency hopping.

[0136] The following acronyms are used throughout this disclosure.

• 3GPP Third Generation Partnership Project

• 5G Fifth Generation

• ASIC Application Specific Integrated Circuit

• CN Core Network

• CPU Central Processing Unit

• CRS Cell-Specific Reference Symbol

• dB Decibel

• dBm Decibel-Milliwatt

• EIPR Equivalent Isotropically Radiated Power

• eNB Enhanced or Evolved Node B FCC Federal Communications Commission

FPGA Field Programmable Gate Array

GHz Gigahertz

HARQ Hybrid Automatic Repeat Request

ID Identifier

loT Internet of Things

ISM Industrial, Scientific, and Medical

kHz Kilohertz

LBT Listen-Before-Talk

LSB Least Significant Bit

LTE Long Term Evolution

M2M Machine-to-Machine

MBSFN Multicast Broadcast Single Frequency Network

MHz Megahertz

MIB Master Information Block

MME Mobility Management Entity

ms Millisecond

MTC Machine Type Communication

NB-loT Narrowband Internet of Things

NPBCH Narrowband Physical Broadcast Channel

NPBCH-U Narrowband Physical Broadcast Channel in

Unlicensed Spectrum

NPSS Narrowband Primary Synchronization Signal

NRS Narrowband Reference Symbol

NSSS Narrowband Secondary Synchronization Signal

OFDM Orthogonal Frequency Division Multiplexing

PCFICH Physical Control Format Indicator Channel

PDCCH Physical Downlink Control Channel

PDN Packet Data Network

P-GW Packet Data Network Gateway • PHICH Physical Hybrid Automatic Repeat Request Indicator

Channel

• PSD Power Spectral Density

• Rel Release

• SCEF Service Capability Exposure Function

• SFBC Space Frequency Block Code

• SFN System Frame Number

• TS Technical Specification

• TTI Transmission Time Interval

• UE User Equipment

[0137] Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.

Claims

Claims What is claimed is:

1 . A method of operation of a radio access node (12) in a cellular

communications network (10), comprising:

transmitting (102), on a carrier, a broadcast channel using frequency hopping.

2. The method of claim 1 wherein the carrier is a Narrowband Internet of Things, NB-loT, carrier.

3. The method of claim 2 wherein the broadcast channel is a Narrowband Physical Broadcast Channel in unlicensed spectrum, NPBCH-U.

4. The method of any one of claims 1 to 3 wherein the carrier is in an unlicensed frequency band.

5. The method of any one of claims 1 to 4 wherein:

the broadcast channel comprises a plurality of blocks scrambled with a plurality of scrambling codes such that each block is scrambled with a different scrambling code;

the broadcast channel has a respective Transmission Time Interval, TTI, that is greater than a dwell time on a frequency hopping channel such that the broadcast channel is divided into two or more portions transmitted on two or more frequency hopping channels, respectively, where each portion of the two or more portions of the broadcast channel comprises a different subset of the plurality of blocks of the broadcast channel; and

transmitting (102) the broadcast channel using frequency hopping comprises transmitting (102) the broadcast channel such that, for each portion of the two or more portions of the broadcast channel, a subset of the plurality of scrambling codes utilized for the subset of the plurality of blocks in the portion of the broadcast channel is a function of a frequency hopping channel index of the respective frequency hopping channel.

6. The method of any one of claims 1 to 4 wherein:

the broadcast channel comprises a plurality of blocks;

transmitting (102) the broadcast channel using frequency hopping comprises transmitting (102) the broadcast channel such that, for each portion of the two or more portions of the broadcast channel, a set of scrambling codes utilized for the subset of the plurality of blocks in the portion of the broadcast channel is the same as that utilized for the subset of the plurality of blocks in each other portion of the broadcast channel.

7. The method of any one of claims 1 to 4 wherein:

the broadcast channel comprises a plurality of blocks scrambled with a plurality of scrambling codes such that each block is scrambled with a different scrambling code; and

the broadcast channel has a respective Transmission Time Interval, TTI, that is equal to a dwell time on a frequency hopping channel.

8. The method of any one of claims 1 to 7 wherein the carrier is either in a guard band of a Long Term Evolution, LTE, carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that broadcast channel symbols are mapped to resource elements normally reserved for LTE Cell-Specific Reference Symbols, CRSs.

9. The method of any one of claims 1 to 7 wherein the carrier is a NB-loT carrier either in a guard band of a Long Term Evolution, LTE, carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that broadcast channel symbols are mapped to all resource elements other than those reserved for NB-loT reference symbols.

10. The method of any one of claims 1 to 7 wherein the carrier is a NB-loT carrier either in a guard band of a Long Term Evolution, LTE, carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that NB-loT reference symbols are repeated in resource elements normally reserved for LTE Cell-Specific Reference Symbols, CRSs.

1 1 . The method of any one of claims 1 to 7 wherein the broadcast channel supports up to at least four antenna ports.

12. A radio access node (12) for a cellular communications network (10), the radio access node (12) adapted to:

transmit, on a carrier, a broadcast channel using frequency hopping.

13. The radio access node (12) of claim 12 wherein the radio access node (12) is further adapted to operate according to the method of any one of claims 2 to 1 1 .

14. A radio access node (12) for a cellular communications network (10), comprising:

at least one processor (22, 40); and

memory (24, 42) comprising instructions executable by the at least one processor (24, 42) whereby the radio access node (12) is operable to:

transmit, via an associated radio unit(s) (28), a broadcast channel on a carrier using frequency hopping.

15. A radio access node (12) for a cellular communications network (10), comprising:

a transmitting module (48) operable to transmit, via an associated radio unit(s), a broadcast channel on a carrier using frequency hopping.

16. A method of operation of a wireless device (16) in a cellular

communications network (10), comprising:

decoding (104) a broadcast channel transmitted on a carrier using frequency hopping.

17. The method of claim 16 wherein the carrier is a Narrowband Internet of Things, NB-loT, carrier.

18. The method of claim 17 wherein the broadcast channel is a Narrowband Physical Broadcast Channel in unlicensed spectrum, NPBCH-U.

19. The method of any one of claims 16 to 18 wherein the carrier is in an unlicensed frequency band.

20. The method of any one of claims 16 to 19 wherein:

the broadcast channel has a respective Transmission Time Interval, TTI, that is greater than a dwell time on a frequency hopping channel such that the broadcast channel is divided into two or more portions transmitted on two or more frequency hopping channels, respectively, where each portion of the two or more portions of the broadcast channel comprises a different subset of the plurality of blocks of the broadcast channel; and decoding (104) the broadcast channel comprises determining, for at least one portion of the two or more portions of the broadcast channel, a subset of the plurality of scrambling codes utilized for the subset of the plurality of blocks in the portion of the broadcast channel based on a frequency hopping channel index of the respective frequency hopping channel.

21 . The method of any one of claims 16 to 19 wherein:

the broadcast channel comprises a plurality of blocks;

decoding (104) the broadcast channel comprises, for at least one portion of the two or more portions of the broadcast channel, decoding (104) the portion of the broadcast channel utilizing a set of scrambling codes that is the same as that utilized for each other portion of the broadcast channel.

22. The method of any one of claims 16 to 19 wherein:

23. The method of any one of claims 16 to 22 wherein the carrier is either in a guard band of a Long Term Evolution, LTE, carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that broadcast channel symbols are mapped to resource elements normally reserved for LTE Cell-Specific Reference Symbols, CRSs.

24. The method of any one of claims 16 to 22 wherein the carrier is a NB-loT carrier either in a guard band of a Long Term Evolution, LTE, carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that broadcast channel symbols are mapped to all resource elements other than those reserved for NB-loT reference symbols.

25. The method of any one of claims 16 to 22 wherein the carrier is a NB-loT carrier either in a guard band of a Long Term Evolution, LTE, carrier or in an unlicensed frequency band, and a resource element to resource grid mapping for the broadcast channel is such that NB-loT reference symbols are repeated in resource elements normally reserved for LTE Cell-Specific Reference Symbols, CRSs.

26. The method of any one of claims 16 to 22 wherein the broadcast channel supports up to at least four antenna ports.

27. A wireless device (16) for a cellular communications network (10), the wireless device (16) adapted to:

decode (104) a broadcast channel transmitted on a carrier using frequency hopping.

28. The wireless device (16) of claim 27 wherein the wireless device (16) is further adapted to operate according to the method of any one of claims 17 to 26.

29. A wireless device (16) for a cellular communications network (10), comprising:

at least one transceiver (54);

at least one processor (50); and

memory (52) comprising instructions executable by the at least one processor (50) whereby the wireless device (16) is operable to: decode a broadcast channel transmitted on a carrier using frequency hopping.

30. A wireless device (16) for a cellular communications network (10), comprising:

a decoding module (62) operable to decode a broadcast channel transmitted on a carrier using frequency hopping.

31 . A method of operation of a radio access node (12) in a cellular communications network (10), comprising:

transmitting (102), on a carrier, a Narrowband Internet of Things, NB-loT, broadcast channel, wherein a resource element to resource grid mapping for the broadcast channel is such that:

broadcast channel symbols are mapped to resource elements normally reserved for Long Term Evolution, LTE, Cell-Specific Reference Symbols, CRSs;

broadcast channel symbols are mapped to all resource elements other than those reserved for NB-loT reference symbols; and/or

NB-loT reference symbols are repeated in resource elements normally reserved for LTE CRS.

32. A method of operation of a wireless device (16) in a cellular

communications network (10), comprising:

decoding (104), on a carrier, a Narrowband Internet of Things, NB-loT, broadcast channel, wherein a resource element to resource grid mapping for the broadcast channel is such that:

broadcast channel symbols are mapped to all resource elements other than those reserved for NB-loT reference symbols; and/or NB-loT reference symbols are repeated in resource elements normally reserved for LTE CRS.