Patent Description:
It has been discussed in the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) standard that Discovery Reference Signals (DRS), also referred as discovery signal, could be used for Radio Resource Management (RRM) measurement as well as synchronisation in the topic of Licensed Assisted Access (LAA). LAA is sometimes also referred to as Licensed-Assisted Carrier Aggregation and concerns aggregation of a carrier wherein a primary cell is using a licensed spectrum to deliver critical information and guaranteed Quality of Service, and an unlicensed spectrum to opportunistically boost the transmitted data rate. The DRS detection is expected to be on one-shot basis.

In e.g. LTE Evolved UMTS Terrestrial Radio Access (E-UTRA), OFDM is used in the downlink; i.e. from a cell site to a User Equipment (UE). OFDM is a frequency-division multiplexing scheme used as a digital multi-carrier modulation method. A large number of closely spaced orthogonal sub-carrier signals are used to carry data on several parallel data streams or channels.

For synchronisation purpose, the current synchronisation signal design for DRS with one length-<NUM> Primary Synchronisation Signal (PSS) sequence and one length-<NUM> Secondary Synchronisation Signal (SSS) sequence is not sufficient to support one-shot synchronisation in a low serving cell Signal-to-Noise Ratio (SNR) condition, e.g. SNR of -3dB. Typically, the User Equipment (UE) according to previously known synchronisation signalling schemes need to detect the synchronisation signals successfully in multiple occasions in such a SNR condition. For DRS detection, the synchronisation signals shall satisfy one shot DRS measurement in a neighbour cell SNR condition, e.g. SNR of -6dB. Therefore current DRS synchronisation signal design has to be enhanced in terms of performance.

Further, one key feature of LTE PSS is to enable low-complex receiver implementations which needs a symmetry property of the signal in the time domain.

In a first prior art, the Licensed-Assisted Access (LAA) e-NodeB (eNB) transmits LAA DRS as in the form of Rel-<NUM> DRS, which consists of one PSS sequence, one SSS sequence, antenna port <NUM> CRS and potentially Channel State Information Reference Signal (CSI-RS), if configured.

In a second prior art, the LAA eNB repeats multiple synchronisation sequences in the frequency domain, e.g. the PSS and/ or SSS sequence is repeated in the entire transmission bandwidth of the LAA system.

However, the disadvantages of these prior arts can be summarised; firstly, DRS detection based on one shot is not ensured if a Long Term Evolution (LTE) Release <NUM> DRS is reused for LAA.

Secondly, it has not been shown that how multiple synchronisation sequence shall be mapped in the frequency domain to achieve good detection performance as well as low complex receiver implementations.

The problem is how a transmitter such as e.g. an LAA eNB, transmits an OFDM symbol comprising multiple synchronisation sequences which provides good performance while also facilitates low complexity of the receiver.

It would thus be desired to provide a solution on how to map multiple synchronisation sequences to the OFDM symbol to achieve better synchronisation performance and low complex receiver implementations.

<CIT> discloses that a common reference signal is transmitted in a subframe configured to receive the common reference signal and/or a fixed subframe predefined to receive the common reference signal, from among a plurality of subframes within a frame. In the present invention, the common reference signal is transmitted in every subframe within a legacy frame duration. However, the common reference signal is transmitted in said configured subframe and/or said fixed subframe within a frame duration which is not a legacy frame duration.

<CIT> discloses a method for investigating a signal in an OFDMA transmission. The method comprises receiving the OFDMA transmission and obtaining a resource grid comprising resource elements of the transmission; determining a set of pairs of the resource elements, wherein the resource elements of the pair are disjoint; correlating, for each resource element, the received signal with a possible transmitted signal; sorting the results according to the pairs of the resource elements; for each pair, comparing the results of the pair; determining a statistical test value based on the sum of the comparisons; and processing the statistical test value to obtain an investigation output about the signal.

<CIT> discloses a universal mapping of resource elements (REs) to enhanced resource element groups (eREG) that applies to both the PDCCH and PDSCH regions.

It is therefore an object to obviate at least some of the above mentioned disadvantages and to improve the performance in a wireless communication system.

This and other objects are achieved by the features of the appended independent claims.

The scope of protection of the present invention is set out by the appended claims.

According to a first aspect, a processor is provided, configured to map at least two synchronisation signal sequences to a respective set of resource elements of one OFDM symbol, wherein there is at least one intermediate resource element between each pair of adjacent sets of resource elements; and the at least two synchronisation signal sequences comprises Primary Synchronisation Signals, PSS, Secondary Synchronisation Signals, SSS, or a combination thereof.

Thanks to the presented concept of introducing one or more intermediate resource elements between the synchronisation signal sequences, wherein no synchronisation signal sequences are transmitted, the respective adjacent synchronisation signal sequence becomes distributed in the frequency domain, increasing frequency diversity. The adjacent sets of resource elements are adjacent in the frequency domain, not in the time domain as all resource elements of the OFDM symbol are located at the same time period. Thereby a good robustness in case of frequency error is achieved. Furthermore, by establishing a frequency symmetry property of the synchronisation signal sequences, low complexity implementation at the receiver side is ensured.

In a first possible implementation of the processor according to the first aspect, the processor may be configured to disallow transmission of a Physical Downlink Shared Channel (PDSCH), a Cell-specific Reference Signal (CRS) and/ or a Channel State Information Reference Signal (CSI-RS) in the at least one intermediate resource element between each pair of adjacent sets of resource elements.

Thereby, by avoiding to transmit any of the enumerated channels/ signals, the frequency domain symmetry property of the synchronisation signal sequences is ensured and the thus the synchronisation signal time symmetry is maintained, enabling low-complex receiver implementation.

In a second possible implementation of the processor according to the first aspect, or the first possible implementation of the processor according to the first aspect, the processor may be configured to disallow transmission of any signal or channel in the at least one intermediate resource element between each pair of adjacent sets of resource elements.

By not transmitting any signals at all in the at least one intermediate resource element between each pair of adjacent sets of resource elements, each component synchronisation signal sequence will suffer less interference from the adjacent carriers and thus becomes easier to detect for the receiver, especially in the case one individual filter is used for one respective component synchronisation signal sequence.

In a third possible implementation of the processor according to the first aspect, or any previous possible implementation of the processor according to the first aspect, the processor may be configured to map the at least two synchronisation signal sequences to the respective set of resource elements of the OFDM symbol, wherein there are at least five resource elements between each pair of adjacent sets of resource elements.

By putting at least five resource elements between each pair of adjacent sets of resource elements, the detection of the respective synchronisation signal sequence by the receiver is further facilitated as the respective sets of resource elements are clearly distinguishable, which especially helpful to reuse a LTE release <NUM> synchronisation signal based filter implementation as the same empty resource elements are maintained. Also, the robustness in case of frequency error is further enhanced.

In a fourth possible implementation of the processor according to the first aspect, or any previous possible implementation of the processor according to the first aspect, the processor may be configured to map the at least two synchronisation signal sequences, to the respective set of resource elements of the OFDM symbol, wherein delta<NUM> is smaller than delta<NUM>, and:.

By introducing a first frequency gap delta<NUM> between the adjacent pairs of synchronisation signal sequences, and a second frequency gap delta<NUM> in other resource elements within the OFDM symbol wherein no synchronisation signal sequences are mapped, wherein delta<NUM> is smaller than delta<NUM>, thereby introducing different gap lengths between the synchronisation signal sequences and between the edge synchronisation signal sequence and the band edge or the PRB edge containing synchronisation signal sequences, maximum frequency diversity is ensured while a similar guard band for each individual synchronisation signal sequence is provided.

In a fifth possible implementation of the processor according to the first aspect, or any previous possible implementation of the processor according to the first aspect, the processor may be configured to map the at least two synchronisation signal sequences with the same number of synchronisation signal sequences for at least two different transmission bandwidth values.

Thereby the same repetition factor for the synchronisation signal sequences could be used for different bandwidth options such as e.g. <NUM> and <NUM>. By applying the same repetition factor, same or similar synchronisation performance can be achieved for different bandwidth options, which allows an efficient usage of the time frequency resource especially for a large bandwidth system.

In a sixth possible implementation of the processor according to the first aspect, or any previous possible implementation of the processor according to the first aspect, the processor may be configured to map the at least two synchronisation signal sequences, to the respective set of resource elements of the OFDM symbol, wherein delta<NUM> is the same for at least two different transmission bandwidth values, where
delta<NUM> = k<NUM> - k<NUM>; k<NUM> is the lowest frequency index of the resource elements, and k<NUM> is the highest frequency index of the resource elements.

Thereby, a bandwidth independent transmitter and receiver implementation can be achieved and thus further reduce the implementation complexity.

In a seventh possible implementation of the processor according to the first aspect, or any previous possible implementation of the processor according to the first aspect, there are another set of resource elements of the OFDM symbol used for transmission of at least one of the following: a PDSCH, a CRS or a CSI-RS.

By utilising frequency resources of the OFDM symbol, not used neither for synchronisation signal sequences, nor for any intermediate frequency gaps, for transmitting reference signals or data channels such as e.g. PDSCH, CRS or CSI-RS, further functionality and advantages such as better spectrum efficiency and/ or better measurement performance are achieved.

In an eight possible implementation of the processor according to the first aspect, or any previous possible implementation of the processor according to the first aspect, the processor may be configured to map each of the at least two synchronisation signal sequences to <NUM> resource elements.

Thereby, e.g. a LTE release-<NUM> synchronisation signal sequence may be reused, advantageous in terms of low specification and implementation impact.

In a ninth possible implementation of the processor according to the first aspect, or any previous possible implementation of the processor according to the first aspect, the processor may be configured to communicate by aggregation of a carrier in a licensed frequency spectrum and a carrier in an unlicensed frequency spectrum.

Thereby further specifications are provided, leading to additional advantages in an LAA environment.

In a tenth possible implementation of the processor according to the first aspect, or any previous possible implementation of the processor according to the first aspect, the processor may be configured to map the same number of intermediate resource elements between each pair of adjacent sets of resource elements in the OFDM symbol.

By dedicating the same number of intermediate resource elements between each of the adjacent sets of resource elements, implementation both at transmitter side and receiver side is simplified. Additionally, a frequency gap of the same size is ensured for each pair of adjacent synchronisation signal sequences, which helps to implement the filters with a same pass band.

In an eleventh possible implementation of the processor according to the first aspect, or any previous possible implementation of the processor according to the first aspect, the processor may be configured to map the at least two synchronisation signal sequences, to the respective set of resource elements of the OFDM symbol, wherein there are an even number of intermediate resource elements between at least one pair of adjacent resource elements when there are an even number of synchronisation signal sequences mapped to the OFDM symbol.

Thereby it allows to map two adjacent synchronisation signal sequences around the Direct Current (DC) subcarrier with an even number of intermediate resource elements in between, which helps to maintain the frequency symmetry of the synchronisation signals sequence around the DC carrier.

According to a second aspect, a method is provided to be performed by a processor according to the first aspect. The method comprises mapping each of the synchronisation signal sequences to a respective set of resource elements of the OFDM symbol, wherein there is at least one intermediate resource element between each pair of adjacent sets of resource elements. elements; and the at least two synchronisation signal sequences comprises Primary Synchronisation Signals, PSS, Secondary Synchronisation Signals, SSS, or a combination thereof.

In a first possible implementation of the method according to the second aspect, transmission of a PDSCH, a CRS and/ or a CSI-RS may be disallowed in the at least one intermediate resource element between each pair of adjacent sets of resource elements.

In a second possible implementation of the method according to the second aspect, or the first possible implementation of the method according to the second aspect, transmission of any signal or channel at all in the at least one intermediate resource element between each pair of adjacent sets of resource elements may be disallowed.

In a third possible implementation of the method according to the second aspect, or any previous possible implementation thereof, the method may comprise mapping the at least two synchronisation signal sequences to the respective set of resource elements of the OFDM symbol, wherein there are at least five intermediate resource elements between each pair of adjacent sets of resource elements.

In a fourth possible implementation of the method according to the second aspect, or any previous possible implementation thereof, the method may further comprise mapping the at least two synchronisation signal sequences, to the respective set of resource elements of the OFDM symbol, wherein delta<NUM> is smaller than delta<NUM>, and:.

In a fifth possible implementation of the method according to the second aspect, or any previous possible implementation thereof, the method may also comprise mapping the at least two synchronisation signal sequences with the same number of synchronisation signal sequences for at least two different transmission bandwidth values.

In a sixth possible implementation of the method according to the second aspect, or any previous possible implementation thereof, the method may also comprise mapping the at least two synchronisation signal sequences, to the respective set of resource elements of the OFDM symbol, wherein delta<NUM> is the same for at least two different transmission bandwidth values, where
delta<NUM> = k<NUM> - k<NUM>; k<NUM> is the lowest frequency index of the resource elements, and k<NUM> is the highest frequency index of the resource elements.

In a seventh possible implementation of the method according to the second aspect, or any previous possible implementation thereof, the method may further comprise utilising another set of resource elements of the OFDM symbol used for transmission of at least one of the following: a PDSCH, a CRS or a CSI-RS.

In an eight possible implementation of the method according to the second aspect, or any previous possible implementation thereof, the method may further comprise mapping each of the at least two synchronisation signal sequences to <NUM> resource elements.

In a ninth possible implementation of the method according to the second aspect, or any previous possible implementation thereof, the method may further comprise aggregating a carrier in a licensed frequency spectrum and a carrier in an unlicensed frequency spectrum.

In a tenth possible implementation of the method according to the second aspect, or any previous possible implementation thereof, the method may comprise mapping the same number of resource elements between each pair of adjacent sets of resource elements in the OFDM symbol.

In an eleventh possible implementation of the method according to the second aspect, or any previous possible implementation thereof, the method may comprise mapping the at least two synchronisation signal sequences, to the respective set of resource elements of the OFDM symbol, wherein there are an even number of intermediate resource elements between at least one pair of adjacent resource elements when there are an even number of synchronisation signal sequences mapped to the OFDM symbol.

According to a third aspect, a computer program is provided, comprising program code for performing a method according to the second aspect, or any possible implementation of the method according to the second aspect, for mapping at least two synchronisation signal sequences to a respective set of resource elements of the OFDM symbol, when the computer program is performed on a processor according to the first aspect, or any possible implementation of the processor according to the first aspect.

Thereby advantages are achieved, corresponding with the previously described advantages of the first and second aspects.

According to a fourth aspect, a transmitter is provided, for transmitting the OFDM symbol comprising at least two synchronisation signal sequences. The transmitter comprises a processor according to the first aspect, or any possible implementation of the processor according to the first aspect. Further the transmitter also comprises a transmitting circuit, configured to transmit the OFDM symbol comprising the multiple synchronisation signal sequences to a receiver.

According to a fifth aspect, a second processor is provided. The second processor is configured to de-map at least two synchronisation signal sequences from a respective set of resource elements of the OFDM symbol, wherein there is at least one intermediate resource element between each pair of adjacent sets of resource elements, wherein the at least two synchronisation signal sequences have been mapped to the respective set of resource elements of the OFDM symbol by a processor according to the first aspect, or any possible implementation thereof.

According to a sixth aspect, a method is provided, to be performed by a processor according to the fifth aspect. The method comprises detecting each of the synchronisation signal sequences to a respective set of resource elements of the OFDM symbol, wherein there is at least one intermediate resource element between each pair of adjacent sets of resource elements, wherein the at least two synchronisation signal sequences have been mapped to the respective set of resource elements of the OFDM symbol by a processor according to the first aspect, or any possible implementation thereof.

According to a seventh aspect, a computer program is provided, comprising program code for performing a method according to the sixth aspect, for detecting at least two synchronisation signal sequences to a respective set of resource elements of the OFDM symbol, when the computer program is performed on a processor according to the fifth aspect.

According to an eight aspect, a receiver is provided, for receiving the OFDM symbol comprising at least two synchronisation signal sequences. The receiver comprises a processor according to the fifth aspect. Further the receiver also comprises a receiving circuit, configured to receive the OFDM symbol comprising the multiple synchronisation signal sequences from a transmitter according to the fourth aspect.

Thereby advantages are achieved, corresponding with the previously described advantages of the first and second aspects. Thus an improved performance within a wireless communication system is provided.

Other objects, advantages and novel features of the aspects of the invention will become apparent from the following detailed description.

Various embodiments are described in more detail with reference to attached drawings in which:.

Embodiments of the invention described herein are defined as a processor and a method in a processor, which may be put into practice in the embodiments described below. These embodiments may, however, be exemplified and realised in many different forms and are not to be limited to the examples set forth herein; rather, these illustrative examples of embodiments are provided so that this disclosure will be thorough and complete.

Still other objects and features may become apparent from the following detailed description, considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the herein disclosed embodiments, for which reference is to be made to the appended claims. Further, the drawings are not necessarily drawn to scale and, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.

<FIG> is a schematic illustration over a wireless communication system <NUM> comprising a transmitter <NUM> communicating with a receiver <NUM>.

The transmitter <NUM> and the receiver <NUM> may be configured for LAA communication, i.e. to aggregate a primary cell, using licensed spectrum, to deliver critical information and guaranteed Quality of Service, and a co-located secondary cell, using unlicensed spectrum, to opportunistically boost data rate on a best effort basis.

Such primary cell may at least partly be based on e.g. 3GPP LTE, LTE-Advanced, LTE fourth generation mobile broadband standard, Evolved Universal Terrestrial Radio Access Network (E-UTRAN), etc. The secondary cell may be based on e.g. LTE, WiFi or any other non-licensed communication technology, just to mention some few options.

The expressions "wireless communication network", "wireless communication system" and/ or "cellular telecommunication system" may within the technological context of this disclosure sometimes be utilised interchangeably.

In the illustrated wireless communication system <NUM>, the transmitter <NUM> comprises a radio network node and the receiver <NUM> comprises a UE, wherein the radio network node may be serving one or more cells.

The purpose of the illustration in <FIG> is to provide a simplified, general overview of the methods and nodes, such as the transmitter <NUM> and receiver <NUM> herein described, and the functionalities involved.

The transmitter <NUM> may according to some embodiments be referred to as e.g. a radio network node, a base station, a NodeB, an eNodeB, a base transceiver station, an Access Point Base Station, a base station router, a Radio Base Stations (RBS), a macro base station, a micro base station, a pico base station, a femto base station, a Home eNodeB, a sensor, a beacon device, a relay node, a repeater or any other network node configured for communication with the receiver <NUM> over a wireless interface, depending e.g. of the radio access technology and terminology used.

Sometimes, the expression "cell" may be used for denoting the radio network node itself. However, the cell may also in normal terminology be used for the geographical area where radio coverage is provided by the radio network node at a base station site. One radio network node, situated on the base station site, may serve one or several cells. The radio network nodes may communicate over the air interface operating on radio frequencies with any UE within range of the respective radio network node.

The receiver <NUM> may correspondingly, in some embodiments, be represented by e.g. a UE, a wireless communication terminal, a mobile cellular phone, a Personal Digital Assistant (PDA), a wireless platform, a mobile station, a portable communication device, a laptop, a computer, a wireless terminal acting as a relay, a relay node, a mobile relay, a Customer Premises Equipment (CPE), a Fixed Wireless Access (FWA) nodes or any other kind of device configured to communicate wirelessly with the transmitter <NUM>, according to different embodiments and different vocabulary used. The receiver <NUM> in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/ or data, via the radio access network, with another entity, such as another UE or a server.

The transmitter <NUM> is configured to transmit radio signals comprising information to be received by the receiver <NUM>. Correspondingly, the receiver <NUM> is configured to receive radio signals comprising information transmitted by the transmitter <NUM>.

The illustrated network setting of one receiver <NUM> and one transmitter <NUM> in <FIG>, is to be regarded as non-limiting examples of different embodiments only. The wireless communication system <NUM> may comprise any other number and/ or combination of transmitters <NUM> and/ or receiver/s <NUM>, although only one instance of a receiver <NUM> and a transmitter <NUM>, respectively, are illustrated in <FIG>, for clarity reasons. A plurality of receivers <NUM> and transmitters <NUM> may further be involved in some embodiments.

Thus whenever "one" or "a/ an" receiver <NUM> and/ or transmitter <NUM> is referred to in the present context, a plurality of receivers <NUM> and/ or transmitter <NUM> may be involved, according to some embodiments.

The transmitter <NUM> is configured for using Orthogonal Frequency Division Multiplexing (OFDM) for the downlink transmission, i.e. from the transmitter <NUM> to the receiver <NUM> to transmit data over many narrow band careers of <NUM> each instead of spreading one signal over the complete <NUM> career bandwidth i.e. OFDM uses a large number of narrow sub-carriers for multi-carrier transmission to carry data. OFDM is a frequency-division multiplexing scheme used as a digital multi-carrier modulation method. The basic downlink physical resource can be seen as a time-frequency grid as illustrated in <FIG>.

Multiple synchronisation signal sequences are mapped to the resource elements in a distributed way, i.e. there is at least one resource element between two adjacent frequency regions comprising synchronisation signal sequences, wherein no synchronisation signal sequences are mapped. Specifically, the LAA transmitter <NUM>, such as e.g. LAA eNB, may transmit the OFDM symbol with multiple synchronisation signal sequences wherein each synchronisation signal sequence is mapped to a number of resource elements. Further there is at least one intermediate resource element between the resource elements of the two different component, adjacent, synchronisation signal sequences. The adjacent sets of resource elements as discussed in this disclosure are adjacent in the frequency domain, not in the time domain as all resource elements of the OFDM symbol are located at the same time period.

The at least one intermediate resource element between the two different component, adjacent, synchronisation signal sequences thus may form a frequency gap, distinguishing the respective synchronisation signal sequences in the frequency domain.

Also, nothing may be transmitted in the intermediate resource elements within the frequency gap according to some embodiments, e.g. no Cell-specific Reference Signal (CRS), no Physical Downlink Shared Channel (PDSCH), no Channel State Information Reference Signal (CSI-RS) nor any other physical channel or signal.

The advantages herewith comprise increased frequency diversity, good robustness in case of frequency error, time symmetry property of the signal as well as simple receiver <NUM> complexity.

Furthermore the frequency region of the multiple synchronisation signal sequences may in some embodiments be as wide as possible at least for the smallest bandwidth option. Specifically there may be an edge gap between the entire frequency region mapped by multiple synchronisation signal sequences and the band edge. The edge gap may be smaller than the gap between the resource elements of the two different component synchronisation signal sequences in some embodiments. This may maximise or at least increase the frequency diversity gain as well as maintain similar guard band for each individual synchronisation signal sequences.

The transmitter <NUM> further, in some embodiments may use a unique pattern of synchronisation signals in different transmission bandwidth options. Thereby, receiver complexity is reduced while offering a sufficient synchronisation performance.

Further the transmitter <NUM>, which may be an LAA device, transmits the OFDM symbol with multiple synchronisation signal sequences such as PSS and/ or SSS sequences as well as CRS in some embodiments. Multiple synchronisation signal sequences may be located around the central frequency of the transmission band, while CRS (or similar reference signals) may only be transmitted outside of the synchronisation signal sequences frequency region.

<FIG> illustrates a time-frequency resource grid <NUM> comprising resource elements <NUM>. The resource element <NUM> is the smallest time-frequency entity that can be used for transmission, which may convey a complex-valued modulation symbol on a subcarrier <NUM>. A Resource Block (RB) comprises a set of resource elements <NUM>, i.e. a set of time-frequency resources, and may be of <NUM> duration (or <NUM> OFDM symbols <NUM>) and <NUM> bandwidth (or <NUM> subcarriers <NUM> with <NUM> spacing) in some embodiments.

The transmission bandwidth of the system <NUM> may be e.g. <NUM>, <NUM>, <NUM>, <NUM> or similar, may be divided into a set of resource blocks. Typical carrier bandwidths may correspond to e.g. <NUM>, <NUM>, <NUM> and/ or <NUM> resource blocks in different embodiments. Each transmission of user data on the PDSCH may be performed over <NUM> duration, which is also referred to as a subframe, on one or several resource blocks. A radio frame comprises <NUM> subframes, or alternatively <NUM> slots of <NUM> length (enumerated from <NUM> to <NUM>).

In one embodiment, the transmitter <NUM> may transmit an OFDM symbol <NUM> comprising multiple component synchronisation signal sequences in a DRS subframe, wherein different component synchronisation signal sequences are mapped in a distributed way, i.e. there is a frequency gap between two different component synchronisation signal sequences mapped adjacently, and wherein neither any PDSCH, Cell-specific Reference Signal (CRS), Channel State Information Reference Signal (CSI-RS) may be mapped in the intermediate resource elements of the frequency gap, in some embodiments. In some embodiments, nothing may be mapped in the intermediate resource elements of the frequency gap, as will be further discussed and explained in conjunction with presentation of <FIG>, <FIG>, <FIG>.

In LTE, the time-continuous signal <MAT> on antenna port p in OFDM symbol l in a downlink slot is defined by: <MAT> for <NUM> ≤ t < (NCP,+ N)×Ts where <MAT> and <MAT>, Ts = <NUM>/(<NUM>*<NUM>)second <MAT> and <MAT> is related to the system bandwidth, e.g. <NUM> for <NUM> bandwidth, <NUM> for <NUM> bandwidth. The variable N equals <NUM> for Δf = <NUM> subcarrier spacing and <NUM> for Δf = <NUM> subcarrier spacing. <MAT> is the modulated symbol or value mapped to the resource elements (k, l) on antenna p. The OFDM symbols <NUM> in a slot shall be transmitted in increasing order of l, starting with l = <NUM> , where OFDM symbol l > <NUM> starts at time <MAT> within the slot. The value of NCP,l is given in Table <NUM>. As the focus herein is put on the transmission on one antenna port, the antenna port p may be omitted for simplicity.

The synchronisation signal sequence such as e.g. Primary Synchronisation Signal (PSS) may be generated in order to enable low-complex receiver implementations. The sequence d(n) used for the synchronisation signal sequence may be generated from a frequency-domain Zadoff-Chu sequence according to: <MAT> where the Zadoff-Chu root sequence index u is chosen from <NUM>, <NUM>, <NUM>.

Without loss of generality, consider the following representation of a sampled OFDM symbol <NUM> (without cyclic prefix and no frequency error) with multiple synchronisation signal sequences mapped <MAT> <MAT> where Hu are the Fourier coefficients of the OFDM symbol <NUM> to which multiple synchronisation signal sequences are mapped.

<FIG> illustrates the OFDM symbol <NUM> wherein multiple, i.e. at least two, synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> are mapped to the resource elements <NUM> using localised mapping and distributed mapping, respectively.

There are basically two means to map the at least two synchronisation signal sequences to one OFDM symbol <NUM>, i.e. localised or distributed way. An example of mapping with a first synchronisation signal sequence <NUM>-<NUM> and a second synchronisation signal sequence <NUM>-<NUM> (the root index u is the same and omitted for simplicity) is illustrated in <FIG>, wherein the gap <NUM> comprises zero intermediate resource elements <NUM> in localised mapping and any arbitrary number of intermediate resource elements <NUM> exceeding zero in distributed mapping, such as e.g. at least one intermediate resource element <NUM> and/ or at least five intermediate resource elements <NUM> in some embodiments (non-limited examples). Thus the first synchronisation signal sequence <NUM>-<NUM> and the second synchronisation signal sequence <NUM>-<NUM> are mapped to two respective sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>.

One advantage of the distributed mapping is that it provides frequency diversity. If one component synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM> mapped to one partial frequency resource is in a deep fading, another component synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM> mapped to a different frequency resource located distributed may still be able to provide reliable performance as the fading condition might be dramatically different, due to the frequency gap <NUM> and the at least one intermediate resource element <NUM> held therein.

If there is a carrier frequency offset, a sampled OFDM symbol <NUM> can be: <MAT> where Δf<NUM> is the carrier frequency offset.

The synchronisation signal sequence detection may in some embodiments be done by matched filtering: <MAT>.

Since multiple synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> are mapped to one OFDM symbol <NUM>, one detection implementation may utilise multiple matched filters for the legacy synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM>. For each component synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, a corresponding bandpass filter with the associated pass band may be used. As the bandpass filter is practically not ideal and subject to the implementation, one component synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM> with localised mapping will experience interference from the adjacent subcarriers <NUM> which are mapped by one other component synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM>. Therefore distributed mapping is advantageous as there is no or less interference from other synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM>.

One other detection implementation is using only one long matched filter related to multiple synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>. Performance evaluation is done assuming different frequency offset for localised mapping and distributed mapping, as further illustrated in <FIG>.

<FIG> is a diagram illustrating an auto-correlation value ρ(<NUM>) as dependent on the frequency offset, or gap <NUM> between two adjacent synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, i.e. the number of intermediate resource elements <NUM> between two adjacent synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>.

The auto-correlation value ρ(<NUM>) is given in <FIG>, where the simulated bandwidth of LTE signal is <NUM> with a transmission bandwidth of <NUM> PRB, the root index u = <NUM>, Δf = <NUM> and Δf<NUM> is <NUM>. The two adjacent synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> are mapped to resource element with frequency index [<NUM>, <NUM>,. , <NUM>, <NUM> delta +,. , <NUM>+ delta, <NUM>+ delta,. , <NUM>+ delta], where delta is the size of the frequency gap <NUM>, i.e. a non-negative integer specifying the number of intermediate resource elements <NUM> between the two adjacent synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>. It can be observed from the evaluation results that there is a gain in case of carrier frequency offset <NUM> when distributed mapping is used instead of localised mapping; i.e. by providing at least one intermediate resource element <NUM> in the frequency gap <NUM>.

It may be noted that the at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> mapped to one OFDM symbol <NUM> in a distributed way also may comprise one implementation that more than one group of synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> are mapped with a frequency gap <NUM>, where a group of synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> may comprise more than one synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM> and be mapped in a localised way (i.e. there is no frequency gap <NUM> between two adjacent synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> within the group). In this way, the mapping may be seen as a combination of localised and distributed mapping which also provides the advantages of increased frequency diversity, less interference from the adjacent synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM> according to some embodiments.

It may be noted that various different embodiments may apply to at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> mapped to one OFDM symbol <NUM>, which could be multiple PSS sequences <NUM>-<NUM>, <NUM>-<NUM>, multiple SSS sequences <NUM>-<NUM>, <NUM>-<NUM>, and/ or a combination of at least one PSS sequence <NUM>-<NUM>, <NUM>-<NUM> and at least one SSS sequence <NUM>-<NUM>, <NUM>-<NUM> in different embodiments.

As at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> are mapped in the resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> distributed in the frequency domain, one further issue is that what to be transmitted in the frequency gap <NUM>. If this OFDM symbol <NUM> with at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> is part of DRS, the OFDM symbol <NUM> may comprise PDSCH and/ or CRS in some embodiments.

One key feature of LTE PSS is that it is generated in order to enable low-complex receiver implementations which results in a time symmetry property, i.e. su(n) = s(N - n). It has been shown that a time symmetry property can be achieved if a frequency symmetry property around the DC subcarrier <NUM> is achieved, i.e. Hu(n) = Hu(-n) = Hu(N - n). The time symmetry property according to some embodiments ensures low-complex receiver implementations. One bandpass filter with the central frequency within the frequency gap <NUM> between two adjacent component PSS sequences <NUM>-<NUM>, <NUM>-<NUM> can be used to extract the frequency elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> associated with the multiplexed PSS sequence <NUM>-<NUM>, <NUM>-<NUM> in some embodiments.

In LTE, CRS are mapped to one resource element in every six resource elements in an OFDM symbol <NUM> containing CRS, where which of resource elements <NUM> in a group of six resource elements is used is dependent on <MAT> is the cell identity. This causes the uncertainty of the mapping during the frequency gap <NUM> in case CRS is introduced. In addition, the CRS sequence is generated from the cell ID, which again causes the uncertainty of the signal transmitted during the frequency gap <NUM> at the intermediate at least one resource element <NUM>. Furthermore, as CRS sequence and the mapping to the resource elements <NUM> do not satisfy the frequency domain symmetry property, it will not be able to achieve low-complex receiver implementation. Therefore CRS may not be transmitted in the frequency gap <NUM> according to some embodiments. Similar observations related to PDSCH generation holds for PDSCH. Therefore PDSCH may not be transmitted in the frequency gap <NUM> in some embodiments, for achieving low-complex receiver implementation.

It would therefore be beneficial not to map CRS or PDSCH in the intermediate resource elements <NUM> of the frequency gap <NUM>. The resource elements <NUM> in the frequency gap <NUM> may in some embodiments be left un-modulated (e.g. the same as the DC subcarrier <NUM>), which provides the advantages of easy implementation, less inter-carrier interference in case of a frequency offset <NUM> while also maintaining the time domain symmetry. It would according to some alternative embodiments be possible to transmit some type of sequences in the frequency gap <NUM> which satisfies the time symmetry of the compound resulting signal, at the cost of additional complexity of transmitting new signals and the use of the power.

For the distrusted mapping, there are M component synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> multiplexed in one OFDM symbol <NUM>.

If M is an odd integer exceeding <NUM>, one example of mapping is given in <FIG> assuming M=<NUM>, where the central component synchronisation signal sequence <NUM>-<NUM> is mapped like in LTE, i.e. mapped to <NUM> successively indexed resource elements <NUM> around the DC carrier <NUM>, while each of the other two component synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> are mapped to <NUM> resource elements <NUM> with the central resource element <NUM> un-modulated. The frequency gaps <NUM>-<NUM>, <NUM>-<NUM> between each of the side component synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> and the central component synchronisation signal sequence <NUM>-<NUM> may be the same to ensure the side component synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> are mapped in the frequency domain symmetrically. This is advantageous as it ensures the time symmetry of the synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and also allows a multi-step detection, where in the first step a legacy compatible synchronisation signal sequence detection of low complexity can be used and the second step of using multiple synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> can be used if the first step is not able to provide sufficient performance.

In case M is an even integer, i.e., an even number of component synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> are multiplexed in one OFDM symbol <NUM>, one example of mapping is given in <FIG> assuming M=<NUM>, where each of the two component synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> are mapped to <NUM> resource elements <NUM> with the central resource element <NUM> un-modulated. The frequency gap <NUM> between the adjacent synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM> in case M><NUM> (still being an even integer) may be set to equal size in some embodiments to ensure the synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-M are mapped in the frequency domain symmetrically. The frequency gap <NUM> may contain an even number of resource elements <NUM>, i.e. the difference between the highest frequency index of the resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> for one synchronisation signal sequence <NUM>-<NUM> and the lowest frequency index of the resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> for an adjacent synchronisation signal sequence <NUM>-<NUM> is even. This is advantageous as it ensures the time symmetry of the synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-M, while also being able to provide frequency diversity.

<FIG> is a block diagram illustrating four component synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> mapped to resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> using distributed mapping to a <NUM> LAA cell, according to an embodiment.

The synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and the intermediate frequency gaps <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> are situated in an inner frequency range <NUM>, which also may be referred to as delta<NUM>.

To map multiple synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-M in one OFDM symbol <NUM>, an edge gap <NUM>-<NUM>, <NUM>-<NUM> of zero length or a length of integer resource elements may be defined between the edge synchronisation signal sequences <NUM>-<NUM>, <NUM>-M and the band edge <NUM>-<NUM>, <NUM>-<NUM> or the nearest Physical Resource Block (PRB) edge. One example mapping is given in <FIG>, where <NUM> synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> are mapped to one OFDM symbol <NUM> in a <NUM> LAA cell, the frequency gap <NUM> is the gap between two adjacent synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and the edge gap <NUM>-<NUM>, <NUM>-<NUM> is the gap between the edge synchronisation signal sequences <NUM>-<NUM>, <NUM>-M and the band edge <NUM>-<NUM>, <NUM>-<NUM> or the nearest PRB edge. It may be noted that LTE techniques only uses the transmission bandwidth in a system bandwidth to allow some guard band, e.g. <NUM> PRB transmission bandwidth in <NUM> system. Even when the edge gap <NUM>-<NUM>, <NUM>-<NUM> is set to zero, the guard band at the band edge is <NUM> (or slightly less in case DC subcarrier <NUM> is considered). Therefore, the edge gap <NUM>-<NUM>, <NUM>-<NUM> may be set smaller than the frequency gap <NUM> to ensure maximum frequency diversity and similar guard band for each individual synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>.

In some embodiments, the edge gaps <NUM>-<NUM>, <NUM>-<NUM> may be set to zero while the frequency gaps <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be set to <NUM> resource elements <NUM>, i.e. <NUM> component synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be mapped to frequency elements {k+(<NUM>,. , <NUM>, <NUM>,. , <NUM>)}, {k+(<NUM>,. , <NUM>, <NUM>,. ,<NUM>)}, {k+(<NUM>,. , <NUM>, <NUM>,. , <NUM>)}, {k+(<NUM>,. , <NUM>, <NUM>,. , <NUM>)}, where k is non-negative integer, and k+<NUM> is no greater than the highest frequency index of all the resource elements <NUM>.

It may be mentioned that the edge gaps <NUM>-<NUM>, <NUM>-<NUM> may be set to the same or different values in different embodiments. Also the frequency gaps <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be set to the same, or different values, i.e. comprising the same, or different numbers of intermediate resource elements <NUM> in different embodiments.

In one embodiment, the edge gaps <NUM>-<NUM>, <NUM>-<NUM> may be set to k1 while the frequency gaps <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be set to k2 resource elements <NUM>. Thus four component synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> are mapped to frequency elements {k1+(<NUM>,. , <NUM>, <NUM>,. , <NUM>)}, {k1+k2+(<NUM>,. , <NUM>, <NUM>,. ,<NUM>)}, {k1+<NUM>*k2+(<NUM>,. , <NUM>, <NUM>,. , <NUM>)}, {k1+<NUM>*k2+(<NUM>,. , <NUM>, <NUM>,. , <NUM>)}, where k2>k1>=<NUM>, and k1 is the gap <NUM>-<NUM> between the lowest frequency resource element index of transmission band (i.e. <NUM>) and the lowest frequency resource element index mapped by the synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, or the gap between the lowest frequency resource element index mapped by the synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and the nearest PRB edge not mapped by the synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>.

In one embodiment, the transmitter <NUM>, e.g. an LAA eNB, may transmit the OFDM symbol <NUM> comprising multiple component synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> in a DRS subframe, where CRS is also transmitted in the same OFDM symbol <NUM>. Multiple component synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be mapped to resource elements <NUM> around the DC subcarrier <NUM>, which may be referred to as inner frequency range, while CRS may be mapped to resource elements <NUM> outside of the inner frequency range, which may be referred to as outer frequency range. In addition, there may be a wireless system with different LAA eNBs using different bandwidth options. The same repetition factor for synchronisation signal sequence repetition is used for different bandwidth options. Within the inner frequency range, the mapping to the resource elements <NUM> may be the same for different bandwidth options in some embodiments.

LAA may support multiple bandwidth options, such as e.g. <NUM>, <NUM>, <NUM> and/ or <NUM>, in some non-limiting examples. If synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> are repeated in the frequency domain, In a given SNR condition, the detection performance of could be approximately determined by the frequency multiplexing gain, i.e. how many times the synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> are repeated, also referred as repetition factor. Given a repetition factor is used for a small bandwidth LAA cell, e.g. <NUM>, the same repetition factor may be sufficient by a large bandwidth cell, <NUM>. In addition, the frequency pattern may be the same to reduce the receiver detection complexity, i.e. the receiver <NUM> is able to use the same synchronisation signal sequence detection algorithm for different LAA bandwidths.

To make use of the frequency resource also for other purpose, such as e.g. various signal strength measurements like Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), Receive Strength Signal Indicator (RSSI), CRS can be added in the frequency domain, as in <FIG>. As already explained, CRS may not be expected to exist/ be transmitted within the synchronisation signal sequence frequency region in some embodiments. It may however exist in the frequency region outside of the synchronisation signal sequence frequency region in some embodiments, where the synchronisation signal sequence frequency region can be understood as the frequency range between the lowest indexed resource element <NUM> carrying the synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and the highest indexed resource element <NUM> carrying the synchronisation signal sequence <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>.

To maintain similar guard band for different bandwidth options, an LAA system <NUM> with larger bandwidth may blank some or several resource elements <NUM>, i.e. not to be used by CRS. As explained above, the guard band of LAA <NUM> could be up to around <NUM> even when synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> are mapped to the transmission band edge PRE. For a <NUM> system, the transmitter <NUM> may blank several resource elements <NUM> to achieve some guard band for synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> (e.g. PSS/ SSS sequences), as in a <NUM> system. Therefore the edge gaps <NUM>-<NUM>, <NUM>-<NUM> may be larger than zero for at least a certain bandwidth option, i.e. there are a positive integer number of resource elements <NUM> not mapped by CRS between the closest resource element <NUM> mapped by synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and CRS, in some embodiments.

Thus any, some or all of a PDSCH, a CRS or a CSI-RS may be mapped to a set of resource elements <NUM>-<NUM>, <NUM>-<NUM> of the OFDM symbol <NUM>, wherein no synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> are mapped.

<FIG> is a flow chart illustrating embodiments of a method <NUM> in a processor.

The processor may be comprised e.g. in a transmitter <NUM>, configured for transmitting the OFDM symbol <NUM> comprising multiple synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> to be received by a receiver <NUM>. Such transmitter <NUM> may comprise a network node such an LAA eNodeB while the receiver <NUM> may comprise a UE in some embodiments. The transmitter <NUM> and the receiver <NUM> may be comprised in a wireless communication network <NUM>. Such wireless communication network <NUM> may be based on LAA.

The method <NUM> comprises the subsequent action <NUM>.

Action <NUM> comprises mapping each of the synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> to a respective set of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> of the OFDM symbol <NUM>, wherein there is at least one intermediate resource element <NUM> between each pair of adjacent sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>.

The adjacent sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> are adjacent in the frequency domain, not in the time domain as all resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> of the OFDM symbol <NUM> are located at the same time period.

According to some embodiments, no PDSCH, CRS and/ or CSI-RS is allowed to be transmitted in the at least one intermediate resource element <NUM> between each pair of adjacent sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>.

According to some embodiments, no reference signal at all is allowed to be transmitted in the at least one intermediate resource element <NUM> between each pair of adjacent sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>.

According to some embodiments, no signal and/ or channel at all is allowed to be transmitted in the at least one intermediate resource element <NUM> between each pair of adjacent sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>.

In some further embodiments, the mapping of the at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> to the respective set of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> of the OFDM symbol <NUM> may be made, wherein there are at least five resource elements <NUM> between each pair of adjacent sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>. It may be noted that although only one synchronisation signal sequence is mapped to one OFDM symbol <NUM> for LTE release <NUM>, the mapping is done is a way that a length-<NUM> synchronisation signal sequence is mapped to <NUM> resource elements, resulting <NUM> resource elements not mapped by synchronisation signal for each side. This may be especially helpful to reuse a LTE release <NUM> synchronisation signal based filter implementation as the same empty resource elements are maintained.

Furthermore according to some embodiments, delta<NUM> <NUM>-<NUM>, <NUM>-<NUM> may be smaller than delta<NUM> <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, wherein delta<NUM> <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> is the number of resource elements <NUM> between at least one pair of adjacent sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>; and
delta<NUM> (<NUM>-<NUM>, <NUM>-<NUM>) is derived from one of the following:.

According to some embodiments, the mapping of the at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be made with the same number of synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> for at least two different transmission bandwidth values like e.g. <NUM> and <NUM>.

In some additional embodiments, the mapping may be made such that wherein delta<NUM> <NUM> is the same for at least two different transmission bandwidth values, where delta<NUM> = k<NUM> - k<NUM>; k<NUM> is the lowest frequency index of said resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>, and k<NUM> is the highest frequency index of said resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>.

Furthermore, according to some embodiments, another set of resource elements <NUM>-<NUM>, <NUM>-<NUM> of the OFDM symbol <NUM> may be used for transmission of at least one of the following: a PDSCH; a CRS; a CSI-RS.

According to some alternative embodiments, each of the at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be mapped to <NUM> resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>.

In some further embodiments, the method <NUM> may comprise aggregation of a carrier in a licensed frequency spectrum and a carrier in an unlicensed frequency spectrum. Also the at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may comprise PSS, SSS, or a combination thereof.

According to some embodiments, the same number of intermediate resource elements <NUM> between each pair of adjacent sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> may be mapped in the OFDM symbol <NUM>.

Further in case there are an even number of resource elements <NUM> between at least one pair of adjacent resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> when there are an even number of synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> mapped to the OFDM symbol <NUM>, according to some embodiments.

<FIG> illustrates an embodiment of a transmitter <NUM>, comprising a processor <NUM>. The processor <NUM> is configured to map at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> to a respective set of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> of the OFDM symbol <NUM>, wherein there is at least one intermediate resource element <NUM> between each pair of adjacent sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>, by performing the previously described method <NUM> according to action <NUM>.

The processor <NUM> may also be configured to disallow transmission of PDSCH, CRS and/ or
CSI-RS in the at least one intermediate resource element <NUM> between each pair of adjacent sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>.

In some embodiments, the processor <NUM> may be configured to disallow transmission of any signal or channel at all in the at least one intermediate resource element <NUM> between each pair of adjacent sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>.

The processor <NUM> may additionally be configured to map the at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> to the respective set of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> of the OFDM symbol <NUM>, wherein there are at least five resource elements <NUM> between each pair of adjacent sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>.

Further, the processor <NUM> may be configured to map the at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, to the respective set of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> of the OFDM symbol <NUM> such that delta<NUM> <NUM>-<NUM>, <NUM>-<NUM> may be smaller than delta<NUM> <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, wherein delta<NUM> <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> is the number of resource elements <NUM> between at least one pair of adjacent sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>; and
delta<NUM> (<NUM>-<NUM>, <NUM>-<NUM>) is derived from one of the following:.

Furthermore the processor <NUM> in addition, according to some embodiments, may be configured to map the at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be made with the same number of synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> for at least two different transmission bandwidth values like e.g. <NUM> and <NUM>.

In addition the processor <NUM> may be configured to map the at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> such that wherein delta<NUM> <NUM> is the same for at least two different transmission bandwidth values, where delta<NUM> = k<NUM> - k<NUM>; k<NUM> is the lowest frequency index of said resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>, and k<NUM> is the highest frequency index of said resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>.

Also the processor <NUM> may be configured to utilise another set of resource elements <NUM>-<NUM>, <NUM>-<NUM> of the OFDM symbol <NUM> for transmission of at least one of the following: a PDSCH; a CRS; a CSI-RS.

The processor <NUM> may further be configured to map each of the at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> to <NUM> resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>.

In some further embodiments, the processor <NUM> may further be configured to aggregate a carrier in a licensed frequency spectrum and a carrier in an unlicensed frequency spectrum. Also the at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may comprise PSS, SSS, or a combination thereof.

According to some embodiments, the processor <NUM> may be configured to map the same number of intermediate resource elements <NUM> between each pair of adjacent sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> in the OFDM symbol <NUM>.

Further the processor <NUM> may be configured to map the at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, to the respective set of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> of the OFDM symbol <NUM>, wherein there are an even number of resource elements <NUM> between at least one pair of adjacent resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> when there are an even number of synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> mapped to the OFDM symbol <NUM>.

Such processor <NUM> may comprise one or more instances of a processing circuit, i.e. a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The herein utilised expression "processor" may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones enumerated above.

The transmitter <NUM> also comprises a transmitting circuit <NUM>, configured to transmit the OFDM symbol <NUM> comprising the multiple synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> to a receiver <NUM>.

Furthermore the transmitter <NUM> also may comprise a receiving circuit <NUM> in some embodiments, for receiving wireless signalling.

The method <NUM> comprising the action <NUM> may be implemented through the one or more processors <NUM> in the transmitter <NUM> together with computer program product for performing the functions of the action <NUM>.

Thus a computer program comprising program code for performing the method <NUM> according to any embodiment of action <NUM>, may be performed when the computer program is loaded in the processor <NUM>.

The computer program product mentioned above may be provided for instance in the form of a data carrier carrying computer program code for performing at least some of the actions <NUM> according to some embodiments when being loaded into the processor <NUM>. The data carrier may be, e.g., a hard disk, a CD ROM disc, a memory stick, an optical storage device, a magnetic storage device or any other appropriate medium such as a disk or tape that may hold machine readable data in a non-transitory manner. The computer program product may furthermore be provided as computer program code on a server and downloaded to the transmitter <NUM>, e.g., over an Internet or an intranet connection.

<FIG> discloses a receiver <NUM> for receiving the OFDM symbol <NUM> comprising multiple, i.e. at least two, synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> from the transmitter <NUM>.

The receiver <NUM> comprises a receiving circuit <NUM>, configured to receive the OFDM symbol <NUM> comprising the multiple synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> from a transmitter <NUM>.

The receiver <NUM> further comprises a processor <NUM>. The processor <NUM> is configured to detect at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> from a respective set of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> of the OFDM symbol <NUM>, wherein there is at least one resource element <NUM> between each pair of adjacent sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>, wherein the at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> have been mapped to the respective set of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> of the OFDM symbol <NUM> by a processor <NUM> in a transmitter <NUM>.

Furthermore, the receiver <NUM> may comprise a transmitting circuit <NUM>, configured to transmit wireless signals.

Furthermore, the processor <NUM> may perform a method for detecting at least two synchronisation signal sequences <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> from a respective set of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM> of the OFDM symbol <NUM>, wherein there is at least one resource element <NUM> between each pair of adjacent sets of resource elements <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-<NUM>.

The terminology used in the description of the embodiments as illustrated in the accompanying drawings is not intended to be limiting of the described methods <NUM>, <NUM> and/ or transmitter <NUM> and/ or receiver <NUM>. Various changes, substitutions and/ or alterations may be made, without departing from the invention as defined by the appended claims.

Claim 1:
A processor (<NUM>) configured to:
map at least two synchronisation signal sequences (<NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>) to a respective set of resource elements (<NUM>-<NUM>, <NUM>-<NUM>, ..., <NUM>-<NUM>) of an Orthogonal Frequency-Division Multiplexing, OFDM, symbol (<NUM>), and
there is at least one resource element (<NUM>) between each pair of adjacent sets of resource elements (<NUM>-<NUM>, <NUM>-<NUM>, ..., <NUM>-<NUM>); and
the at least two synchronization signal sequences are multiple Primary Synchronisation Signal, PSS, sequences, multiple Secondary Synchronisation Signal, SSS, sequences, or a combination of at least one PSS sequence and at least one SSS sequence.