WO2016015782A1

WO2016015782A1 - Sub-band allocation signaling in a non-contiguous multi-carrier communication system

Info

Publication number: WO2016015782A1
Application number: PCT/EP2014/066635
Authority: WO
Inventors: Martin Fuhrwerk; Christoph Thein; Jurgen Peissig; Malte Schellmann; Zhao ZHAO
Original assignee: Huawei Technologies Duesseldorf Gmbh
Priority date: 2014-08-01
Filing date: 2014-08-01
Publication date: 2016-02-04

Abstract

The invention relates to methods for signaling sub-band allocation information on a carrier having plural sub-bands forming a fragmented spectrum. Furthermore, the invention also relates to implementations of such methods in hardware and/or software. Special synchronization sequences are used for signaling the sub-band allocation in a non-contiguous multi-carrier mobile communication system to the terminals. According to different embodiments the synchronization sequence is detected by means of auto-correlation followed by cross-correlation to thereby establish synchronization and simultaneously detect the signaled sub-band allocation.

Description

Sub-Band Allocation Signaling in a

Non-Contiguous Multi-Carrier Communication System

TECHNICAL FIELD

The invention relates to methods for signaling sub-band allocation information on a carrier having plural sub-bands forming a fragmented spectrum. Furthermore, the invention also relates to implementations of such methods in hardware and/or software.

BACKGROUND

The regulatory permission of flexible spectrum sharing for white spaces (WS) in the ultrahigh frequency (UHF) bands in conjunction with the need for a high spectral efficiency led to the proposal of non-contiguous multi-carrier (NC-MC) transmission schemes. NC-MC systems allow access to fragmented spectrum bands. Pilot preambles used for synchronization need to be adapted to the accessible parts of the spectrum and can no longer be defined with a fixed spectrum allocation.

Since accessible spectrum bands may be dynamically changing, it may not easily be possible to establish a control channel where information on the current bandwidth allocation may be transmitted prior to setting up a transmission, as it is done in currently applied wireless systems (LTE - bandwidth in Physical Broadcast Channel, PBCH).

A problem may occur in the context of dynamic/shared spectrum access and inter-operator sharing scenarios. As noted above, NC-MC allows access to any type of fragmented spectrum. A user communicating with a base station in a fragmented spectrum band needs to know the details of the spectrum parts that have been allocated for signal transmission. This information can be also referred to as an "allocation vector", which the base station signals to the terminal(s).

Common allocation vector signaling strategies may encounter the following issues: - In spectrum sharing scenarios, the spectrum may be highly fragmented, resulting in the impossibility to predict which parts of the spectrum may be used or not. Hence, it is difficult to define a dedicated signaling channel (control channel) with a fixed allocation in the spectrum band in advance.

- A dedicated out-of-band channel for signaling requires a dedicated spectrum resource solely used for signaling purposes. Supporting this additional spectrum band comes at the cost of additional hardware complexity and may reduce spectral efficiency.

- In case of using sensing on receiver side, the following drawbacks may be encountered:

- Energy detection cannot distinguish between different coexisting systems,

- Feature detection suffers from noise uncertainty and spans long time durations, resulting in an increase of the system latency,

- Synchronization and demodulation has a high system complexity and may not work conveniently without any knowledge of the allocation vector.

Furthermore, considering synchronization in dynamic/shared spectrum access and inter- operator sharing scenarios, state-of-the-art synchronization solutions in time domain are challenging if not impossible, as the following drawbacks can be encountered:

- Failure to synchronize, in case other users/interfering signals exhibit higher signal power than the wanted signal at the receiver.

- Additional pre-filtering of time domain signal stream comes at higher costs and leads to distortion of the signal, depending of the filter parameters.

- Time domain synchronization generally needs more preamble symbols, leading to a penalty in spectral efficiency.

- In the uplink at the base station each user needs to have one processing branch consisting of an interference rejection filter and the metric, which scales the costs of synchronization linearly with the number of users.

SUMMARY One object is to suggest mechanisms that allow terminals of a non-contiguous multi-carrier mobile communication system to detect, which of the sub-bands that form the spread spectrum of the multi-carrier mobile communication system are used for communication. Furthermore, it is another object to suggest such mechanisms that provide high reliability in detecting which of the sub-bands of the non-contiguous multi-carrier mobile communication system are used for communication and/or that can be implemented with low resource utilization and/or signaling overhead. A first aspect of the invention provides a method for signaling information on a carrier having plural sub-bands forming a fragmented spectrum, the method comprising the following steps performed by a terminal of a non-contiguous multi-carrier mobile communication system: auto-correlating respective signals received in the sub-bands, to detect whether a predetermined periodically transmitted synchronization sequence is present in one or more of the received signals; in case a synchronization sequence is present in the one or more received signals, matching the synchronization sequence to one of multiple candidate synchronization sequences by cross-correlation, respectively; wherein the respective candidate synchronization sequences are indicative of one or more sub-bands employed for data communication in the non-contiguous multi-carrier mobile communication system; and determining the one or more sub-bands employed for data communication in the noncontiguous multi-carrier mobile communication system based on the matched candidate synchronization sequence.

The first aspect relates to using "special" synchronization sequences that are indicative of the one or more sub-bands that are employed by a non-contiguous multi-carrier mobile communication system for the communication of data. Accordingly, for a given combination of one or more sub-bands utilized for data communication, there is a corresponding synchronization sequence. The synchronization sequences may thus be considered to indicate an allocation vector or sub-band allocation in terms of indicating the sub-band(s) out of the available candidate sub-bands that are to be used for communication.

By detecting such "special" synchronization sequence in one or more of the sub-bands of a multi-carrier mobile communication system, a terminal is capable of detecting a given combination of one or more sub-bands utilized for data communication, i.e. the allocation vector. Furthermore, in some more detailed implementation forms, a terminal can employ auto-correlation of a received signal for the detection of a synchronization sequence and may thereafter confirm the one or more of the sub-bands yielded by the detected synchronization sequence by cross-correlation of the received signal with the "special" synchronization sequences. Furthermore, it should be noted that the synchronization sequence does not need to be transmitted on all sub-bands that are utilized for data communication due to the synchronization sequence indicating the sub-bands of the multi-carrier communication system employed for communication. Optionally, the synchronization sequence may indicate the sub-band(s) and/or resources in the sub-band(s) in which control channel is provided. Hence, the synchronization sequence may thus enable not only the signaling of the sub-band allocation, but may additionally or alternatively indicate location of the control channel in the sub-bands. The control channel may be for example used to signal control information on the resource allocation to a terminal or group of terminals, but the control channel may also carry other information relevant for the configuration and/or control of the communication system.

A second aspect of the invention provides a method for signaling information on a carrier having plural sub-bands forming a fragmented spectrum, the method comprising the following steps performed by a terminal of a non-contiguous multi-carrier mobile communication system: receiving respective signals in each of the sub-bands of the noncontiguous multi-carrier mobile communication system; auto-correlating the received signals, to detect whether a predetermined periodically transmitted synchronization sequence is present in the received signals in the sub-bands of the carrier; in case the synchronization sequence is present in the signals, confirming the detection of the synchronization sequence by cross-correlating the synchronization sequence with a predefined synchronization sequence stored in the terminal; synchronizing with a frame structure in the one or more sub-bands employed for data communication by means of the synchronization sequence, wherein each frame comprises at least one resource block; and receiving a resource block in each of the sub-bands of the non-contiguous multi-carrier mobile communication system, wherein at least one of the resource blocks comprises control information on the resource allocation in one or more sub-bands for data communication to the terminal.

The second aspect relates to an alternative to the first aspect outlined above. In this second aspect, a synchronization sequence is transmitted in each of the sub-bands that have been selected for data communication. In this second aspect, the sub-band allocation or allocation vector may thus be inherent to the sub-bands on which the synchronization sequence is signaled. Either the synchronization sequence is transmitted in each of these sub-bands or one single synchronization sequence is spread across all the sub-bands that have been selected for data communication. The correct detection of the synchronization sequence can be confirmed by the terminal by means of cross-correlation.

In case the synchronization sequence is spread across the sub-bands, only one predefined synchronization sequence could be provided, as the spreading of the synchronization sequence across the sub-bands and the following cross-correlation may provide sufficient robustness, e.g. with respect to noise and interference distortions, to the signaling scheme. In this case, no cross-correlation for confirming the sub-band allocation may be implemented, but the sub-band allocation may be confirmed in a separate control channel. In both cases of spreading of the synchronization sequence across the sub-bands or repeating the synchronization sequence in the sub-bands, in order to improve the robustness of this signaling scheme, "special" synchronization sequences that are indicative of the one or more sub-bands may be predefined. In this latter case, the synchronization sequences thus also yield different allocation vectors or sub-band allocations, respectively. Hence, the synchronization sequence transmitted in each of these sub-bands or the synchronization sequence spread across all the sub-bands that have been selected for data communication may allow the terminal to confirm the sub-band allocation.

Further, according to the second aspect, upon synchronization with the frame structure on the respective sub-bands carrying the synchronization sequence, the terminal may further receive control information within a resource block of a frame. The control information may be considered part of information signaled in a control channel. This control information may only be present in one of the sub-bands carrying the synchronization sequence; it is however also possible to signal the control information in multiple or all sub-bands carrying the synchronization sequence. The control information may be used to signal for example information on the resource allocation in one or more sub-bands for data communication to a terminal or group of terminals, or could be alternatively used to indicate the location of a control channel in the sub-bands for signaling resource allocation information and optionally further information for controlling or configuring the communication system.

Implementation forms of the first and second aspect do not require a dedicated signaling (control) channel on which the sub-band allocation is signaled, since the sub-band allocation vector can be embedded into the synchronization sequence. Compared to blind detection methods, detection quality of sub-band allocation may be improved since additional embedded information in the synchronization sequence(s) can be exploited.

It is noted that in the first aspect and second aspect, the synchronization sequence could be also referred to as a preamble or midamble within the frame structure of the received signal. Moreover the synchronization sequences may also be referred to pilots, pilot sequences or pilot symbols. The first aspect of the invention provides a method for signaling information on a carrier having plural sub-bands forming a fragmented spectrum, wherein the sub-bands can be considered to form a set of available resources that can be used for communication in a noncontiguous multi-carrier mobile communication system. Herein, a terminal performs an auto- correlation to respective signals received in the sub-bands of a non-contiguous multi-carrier mobile communication system. This allows the terminal to detect whether a predetermined periodically transmitted synchronization sequence is present in a received signal or not. In case the synchronization sequence is present in a received signal, the synchronization sequence is matched to one of multiple candidate synchronization sequences. This matching by the terminal may for example be achieved by cross-correlation. The respective candidate synchronization sequences are each indicative of the one or more sub-bands employed for data communication in the non-contiguous multi-carrier mobile communication system. Accordingly, by finding the matching candidate synchronization sequence the terminal can determine the one or more sub-bands employed for data communication in the non- contiguous multi-carrier mobile communication system.

In a further implementation form of the first aspect, the method comprises synchronizing with a frame structure on the one or more sub-bands employed for data communication by means of the synchronization sequence.

According to a further implementation form of the first or second aspect, in the time domain, the signals transmitted in the one or more sub-bands employed for data communication are transmitted in frames. Each frame may be subdivided in resource blocks and wherein at least one resource block in each frame comprises the synchronization sequence.

In a further implementation form of the first aspect, the same synchronization sequence is transmitted in some of or in each of the sub-bands employed for data communication. As the synchronization sequence is indicative of the sub-bands that are to be used for communication, there is no need to transmit the synchronization sequence in all sub-bands that are to be used for communication. Yet, doing so may also be advantageous, as this may improve the robustness of the signaling scheme: Assuming that the terminal receives the synchronization sequence in all sub-bands that are to be used for communication, the terminal may confirm the sub-band selection yielded by the particular synchronization sequence based on the sub-bands on which the synchronization sequence is received. In some implementation forms of the first or second aspect, the synchronization sequence and the yielded sub-bands for communication may apply to all terminals in the communication system. Alternatively, in another implementation form of the first or second aspect, the synchronization sequence is further indicative of an allocation of the one or more sub-bands to a terminal. This would allow signaling different sub-band selections for communication to individual terminal. In a further alternative implementation form of the first or second aspect, the different sub-band selections for communication may be signaled to groups of terminals. For example, the synchronization sequence could further indicate a service class or user class to which the respective sub-bands used for data communication are allocated. Accordingly, the signaled sub-band allocation would apply to terminals user class, or terminals that use services of a particular service class. Notably, also grouping criteria may be defined.

In a further implementation form of the first or second aspect, the synchronization sequence may further indicate control information of the non-contiguous multi-carrier mobile communication system. For instance, in one exemplary implementation form, the control information could indicate the sub-band and/or spectral and temporal allocation of a control channel or signaling channel, which is used to transmit resource allocation information to the terminals.

In a further implementation form of the first or second aspect, the auto-correlation of signals received by the terminal in the respective sub-bands may be performed in the frequency domain. Alternatively, the auto-correlation could also be performed in the time domain for a given signal in a sub-band.

The second aspect of the invention relates to a method for signaling information on a carrier having plural sub-bands forming a fragmented spectrum. The method comprises the following steps performed by a terminal of the non-contiguous multi-carrier mobile communication system: The terminal receives respective signals in each of the sub-bands of the noncontiguous multi-carrier mobile communication system and auto-correlates the received signals. The auto-correlation allows the terminal to detect whether a predetermined periodically transmitted synchronization sequence is present in the received signals in the sub- bands of the carrier. In case the synchronization sequence is present in the signals, the terminal may next confirm the detection of the synchronization sequence by cross-correlating the synchronization sequence with a predefined synchronization sequence stored in the terminal. According to the method, the terminal further synchronizes with a frame structure in the one or more sub-bands employed for data communication by means of the synchronization sequence, wherein each frame comprises at least one resource block, and receives a resource block in each of the sub-bands of the non-contiguous multi-carrier mobile communication system, wherein at least one of the resource blocks comprises control information on the resource allocation in one or more sub-bands for data communication to the terminal or a group of terminals.

In a further implementation form of this second aspect, the synchronization sequence may be spread across the sub-bands used for data communication, and the cross-correlation comprises cross-correlating the detected synchronization sequence with respective candidate synchronization sequences each of which is indicative of one or more sub-bands employed for data communication in the non-contiguous multi-carrier mobile communication system. For example, in one exemplary implementation, the candidate synchronization sequences each have bit sequences corresponding to the respective sub-bands of the non-contiguous multi- carrier mobile communication system, and a respective bit sequence corresponding to unused sub-band is zero.

According to a further implementation form of the first or second aspect, the synchronization sequence and the control information may be comprised in a same resource block or distinct resource blocks. According to a further implementation form of the first or second aspect, the detected synchronization sequence is indicative of a sub-band allocation of one or more sub-bands employed for data communication in the non-contiguous multi-carrier mobile communication system, and the method further comprises decoding said control information. In a more specific implementation of this implementation form, the decoding of the control information may for example use a code or decoding parameters specific to the sub-band allocation indicated by the detected synchronization sequence.

According to a further implementation form of the first or second aspect, the method performed by the terminal comprises individually decoding each of the resource blocks to obtain decoded control information. In an alternative implementation form of the first or second aspect, the terminal jointly decodes the resource blocks to obtain decoded control information. A third aspect of the invention relates to the operation of a base station (The operation can also be performed by another apparatus in the radio access network (RAN) or core network (CN)).

The third aspect of the invention provides a method for signaling information on a carrier having plural sub-bands forming a fragmented spectrum, wherein the sub-bands are available for communication in a non-contiguous multi-carrier mobile communication system, the method comprising the following steps performed by a base station of the non-contiguous multi-carrier mobile communication system: determining one or more sub-bands for use for communication in the non-contiguous multi-carrier mobile communication system; providing multiple candidate synchronization sequences indicative of respective combinations of one or more sub-bands employed for data communication in the non-contiguous multi-carrier mobile communication system; selecting, from the multiple candidate synchronization sequences, the candidate synchronization sequence indicative of the determined one or more sub-bands; and periodically transmitting the selected synchronization sequence in a signal within one or more of the sub-bands.

The method of this third aspect is a method for signaling information on a carrier having plural sub-bands forming a fragmented spectrum. The sub-bands are available for communication in a non-contiguous multi-carrier mobile communication system. A base station of the non-contiguous multi-carrier mobile communication system determines one or more sub-bands for use for communication in the non-contiguous multi-carrier mobile communication system. It is noted that "determines" also encompasses that the base station receives a selection of one or more sub-bands for use for communication in the noncontiguous multi-carrier mobile communication system from another RAN or CN entity of the communication system. The base station is further provided with multiple candidate synchronization sequences. The synchronization sequences are indicative of respective combinations of one or more sub- bands employed for data communication in the non-contiguous multi-carrier mobile communication system. The base station selects, from the multiple candidate synchronization sequences, the candidate synchronization sequence indicative of the determined one or more sub-bands and periodically transmits the selected synchronization sequence in a signal within one or more of the sub-bands. In a first implementation form of the method according to the third aspect, the determined one or more sub-bands for use for communication in the non-contiguous multi-carrier mobile communication system are determined for one single terminal, a group of terminals or all terminals of the non-contiguous multi-carrier mobile communication system. In a second implementation form of the method according to the third aspect as such or according to the first implementation form of the third aspect, in the time domain, the signals transmitted in the one or more sub-bands employed for data communication are transmitted in frames, wherein each frame is subdivided in resource blocks and wherein at least one resource block in each frame comprises the selected synchronization sequence. In a third implementation form of the method according to the third aspect as such or according to any of the previous implementation forms of the third aspect, the same selected synchronization sequence is transmitted in some of or in each of the sub-bands employed for data communication.

In a fourth implementation form of the method according to the third aspect as such or according to any of the previous implementation forms of the third aspect, the selected synchronization sequence is further indicative of an allocation of the determined one or more sub-bands to one terminal.

In a fifth implementation form of the method according to the third aspect as such or according to any of the previous implementation forms of the third aspect, the selected synchronization sequence further indicates a service class or user class to which the respective sub-bands used for data communication are allocated.

In a sixth implementation form of the method according to the third aspect as such or according to any of the previous implementation forms of the third aspect, the selected synchronization sequence further indicates control information of the non-contiguous multi- carrier mobile communication system.

In a seventh implementation form of the method according to the sixth implementation form of the third aspect, the control information may indicate the sub-band and/or spectral and temporal allocation of a control channel, which is used to transmit resource allocation information to the terminals. In an eighth implementation form of the method according to the third aspect as such or according to any of the previous implementation forms of the third aspect, the selected synchronization sequence is transmitted in all sub-bands that have been determined for use for communication in the non-contiguous multi-carrier mobile communication system. For example, the synchronization sequence could be repeated in each of the sub-bands that have been determined for use for communication or a single synchronization sequence may be spread across the sub-bands that have been determined for use for communication.

A fourth aspect of the invention, which refers to an exemplary implementation of the first aspect, relates to a terminal for use in a non-contiguous multi-carrier mobile communication system in which information is transmitted on a carrier having plural sub-bands forming a fragmented spectrum. The terminal comprises a storage unit configured to store multiple candidate synchronization sequences, each being indicative of the one or more sub-bands employed for data communication in the non-contiguous multi-carrier mobile communication system. Further, the terminal has also a receiver unit configured to receive respective signals in the sub-bands and an auto-correlation unit configured to auto-correlate the received signals, to detect one or more received signals comprising a predetermined periodically transmitted synchronization sequence. The terminal further comprises a processing unit configured to match the synchronization sequence to one of said candidate synchronization sequences by cross-correlation to confirm the one or more sub-bands being used for data communication in the non-contiguous multi-carrier mobile communication system.

A fifth aspect of the invention, which refers to an exemplary implementation of the second aspect, relates to a terminal for use in a non-contiguous multi-carrier mobile communication system information in which information is transmitted on a carrier having plural sub-bands forming a fragmented spectrum. The terminal comprises a receiver unit configured to receive respective signals in each of the sub-bands of the non-contiguous multi-carrier mobile communication system, and an auto-correlation unit configured to auto-correlate the received signals, to detect whether a predetermined periodically transmitted synchronization sequence is present in the received signals in the sub-bands of the carrier. The terminal further comprises a processing unit configured to confirm the detection of the synchronization sequence by cross-correlating the synchronization sequence with a predefined synchronization sequence stored in the terminal, in case the synchronization sequence is present in the signals. The terminal may also have a synchronization unit configured to synchronize with a frame structure in the one or more sub-bands employed for data communication by means of the synchronization sequence, wherein each frame comprises at least one resource block. Further, the terminal's receiver unit may be configured to receive a resource block in each of the sub- bands of the non-contiguous multi-carrier mobile communication system, wherein at least one of the resource blocks comprises control information on the resource allocation in one or more sub-bands for data communication to the terminal.

An implementation form of the fourth or fifth aspect relates to a terminal configured to perform the steps of the method for signaling information on a carrier having plural sub-bands forming a fragmented spectrum according to one of the various implementation forms described herein. A sixth aspect of the invention relates to a base station for use in a non-contiguous multi- carrier mobile communication system in which information is signaled on a carrier having plural sub-bands forming a fragmented spectrum. The base station comprises a processing unit configured to determine one or more sub-bands for use for communication in the noncontiguous multi-carrier mobile communication system and a storage unit configured to store multiple candidate synchronization sequences indicative of respective combinations of one or more sub-bands employed for data communication in the non-contiguous multi-carrier mobile communication system. The processing unit is configured to select, from the multiple candidate synchronization sequences, the candidate synchronization sequence indicative of the determined one or more sub-bands. Furthermore, the base station also comprises a transmitter unit configured to periodically transmit the selected synchronization sequence in a signal within one or more of the sub-bands.

An implementation form of the sixth aspect relates to a base station configured to perform the steps of the method for signaling information on a carrier having plural sub-bands forming a fragmented spectrum according to one of the various implementation forms described herein. A seventh aspect of the invention, which refers to an exemplary implementation of the first aspect, provides a computer-readable medium storing instructions that, when executed by a processing unit of a terminal, the terminal being suitable for use in non-contiguous multi- carrier mobile communication system in which information is transmitted on a carrier having plural sub-bands forming a fragmented spectrum, cause the terminal to perform the following: auto-correlating respective signals received in the sub-bands, to detect whether a predetermined periodically transmitted synchronization sequence is present in one or more of the received signals; in case a synchronization sequence is present in the one or more received signals, matching the synchronization sequence to one of multiple candidate synchronization sequences by cross-correlation, respectively; wherein the respective candidate synchronization sequences are indicative of one or more sub-bands employed for data communication in the non-contiguous multi-carrier mobile communication system; and determining the one or more sub-bands employed for data communication in the noncontiguous multi-carrier mobile communication system based on the matched candidate synchronization sequence.

An eighth aspect of the invention, which refers to an exemplary implementation of the second aspect, provides a computer-readable medium storing instructions that, when executed by a processing unit of a terminal, the terminal being suitable for use in a non-contiguous multi- carrier mobile communication system in which information is transmitted on a carrier having plural sub-bands forming a fragmented spectrum, cause the terminal to perform the following: receiving respective signals in each of the sub-bands of the non-contiguous multi-carrier mobile communication system; auto-correlating the received signals, to detect whether a predetermined periodically transmitted synchronization sequence is present in the received signals in the sub-bands of the carrier; in case the synchronization sequence is present in the signals, confirming the detection of the synchronization sequence by cross-correlating the synchronization sequence with a predefined synchronization sequence stored in the terminal; synchronizing with a frame structure in the one or more sub-bands employed for data communication by means of the synchronization sequence, wherein each frame comprises at least one resource block; and receiving a resource block in each of the sub-bands of the noncontiguous multi-carrier mobile communication system, wherein at least one of the resource blocks comprises control information on the resource allocation in one or more sub-bands for data communication to the terminal. An implementation form of the seventh or eighth aspect relates to a computer-readable medium, further storing instructions that, when executed on said processing unit, cause the terminal to perform the steps of the method for signaling information on a carrier having plural sub-bands forming a fragmented spectrum according to one of the various implementation forms described herein. A ninth aspect of the invention provides a computer-readable medium storing instructions that, when executed by a processing unit of a base station, the base station being suitable for use in non-contiguous multi-carrier mobile communication system in which information is transmitted on a carrier having plural sub-bands forming a fragmented spectrum, cause the base station to perform the following: determining one or more sub-bands for use for communication in the non-contiguous multi-carrier mobile communication system; providing multiple candidate synchronization sequences indicative of respective combinations of one or more sub-bands employed for data communication in the non-contiguous multi-carrier mobile communication system; selecting, from the multiple candidate synchronization sequences, the candidate synchronization sequence indicative of the determined one or more sub-bands; and periodically transmitting the selected synchronization sequence in a signal within one or more of the sub-bands. An implementation form of the ninth aspect relates to another computer-readable medium storing instructions that, when executed on said processing unit, cause the base station to perform the steps of the method for signaling information on a carrier having plural sub-bands forming a fragmented spectrum according to one of the various implementation forms described herein. BRIEF DESCRIPTION OF DRAWINGS

In the following embodiments of the invention are described in more detail in reference to the attached figures and drawings. Similar or corresponding details in the figures are marked with the same reference numerals.

Fig. 1 shows an exemplary preamble implementation in accordance with an embodiment of the invention,

Fig. 2 shows an exemplary flow chart of a method for signaling information on a carrier having plural sub-bands forming a fragmented spectrum in accordance with an embodiment of the invention,

Fig. 3 illustrates the synchronization sequence structure according to the preamble design in a multi-user scenario in accordance with an embodiment of the invention,

Fig. 4 illustrates the synchronization sequence structure according to the midamble design in a multi-user scenario in accordance with an embodiment of the invention, Fig. 5 shows an exemplary flow chart of a method for signaling information on a carrier having plural sub-bands forming a fragmented spectrum in accordance with an embodiment of the invention,

Fig. 6 shows another exemplary flow chart of a method for signaling information on a carrier having plural sub-bands forming a fragmented spectrum in accordance with an embodiment of the invention,

Fig. 7 illustrates the synchronization sequence structure in a multi-user scenario in accordance with an embodiment of the invention,

Fig. 8 shows multi-user spectrum sharing in an LTE macro cell according to an embodiment of the invention,

Fig. 9 shows a terminal according to an embodiment of the invention, and

Fig. 10 shows a base station according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

The following paragraphs will describe various implementations and embodiments of the invention.

As noted above, embodiments of the invention use "special" synchronization sequences that are indicative of an allocation vector, which signals the sub-band allocation in a noncontiguous multi-carrier (NC-MC) mobile communication system. The sub-band allocation corresponds to an indication of those sub-bands within the spread spectrum that are employed for the communication of data. Accordingly, for a given combination of one or more sub- bands utilized for data communication, there is a corresponding synchronization sequence.

The proposed synchronization sequence(s) can be either placed at the beginning of the transmission burst (called "preamble") or placed in the middle of the transmission burst (called "midamble").

By detecting such "special" synchronization sequence in one or more of the sub-bands of a multi-carrier mobile communication system, a terminal is capable of detecting a given combination of one or more sub-bands utilized for data communication, i.e. the allocation vector. Furthermore, a terminal can employ auto-correlation of a received signal for the detection of a synchronization sequence in the frequency domain. Only if auto-correlation yields a periodicity in the signal that could be caused by a synchronization sequence, the terminal may further process the received signal and may confirm the sub-bands allocation yielded by the detected synchronization sequence, for example by performing a cross- correlation of the received signal with the "special" synchronization sequences.

Generally, one can assume that the terminals receive a (time domain) signal on a given carrier over the entire bandwidth/band covered by their receiving circuitry. In FDM system, the receiving circuitry typically form blocks of samples that are processed. For example, the processed blocks could have a predefined number of samples that are assumed to correspond to an OFDM symbol block. The block length needs to be long enough to cover the synchronization sequence.

In processing one block of symbols, the terminals may transform this time domain signal into the frequency domain, e.g. by means of a FFT, DCT or the like, to thereby obtain a time-and- frequency resolution of the signal. In this time-and-frequency representation the individual sub-band signals can be distinguished in terms of frequency and time. Commonly, the sub- band signals are partitioned in frames in the time domain, and cover the sub-carriers belonging to the sub-band in the time domain. A time-frequency block in such structure is commonly referred to a resource block. A resource block may consist of plural modulation symbols logically ordered on respective sub-carriers of the respective sub-band, and time slots within a frame in the time domain.

For example, when considering for exemplary purposes an implementation in an OQAM- OFDM communication system, a resource block is formed by a set of OQAM symbols spanning the sub-carriers of the sub-band in frequency domain and the slots of the frame in the time domain. The preamble may consist of a certain number of consecutive real OQAM symbols, whereby at maximum each n^th subcarrier and symbol are used to transmit preamble symbols to reduce the OQAM-OFDM inherent interference (n > 1, e.g. n= 2 or n=3). The last OQAM-OFDM symbol of the preamble may optionally contain auxiliary pilots to reduce the interference inflicted by the following payload. An exemplary preamble implementation is depicted in Fig. 1. For a midamble design, one additional real OQAM-OFDM symbol containing auxiliary pilots could be inserted directly before the midamble symbols to counteract the interference inflicted by preceding payload. The auto-correlation of the sub-band signals described herein may be performed in the frequency domain using a fixed offset. The offset depends on the periodicity in the symbols of the sub-band signal. For example in the preamble implementation of Fig. 1, the offset used in the auto-correlation for the sub-band signal would be two. Generally, a periodic design of the synchronization sequence in the frequency domain, as for example proposed in Fig. 1, implies a periodicity of the corresponding time domain signal. Accordingly, the presence of a synchronization sequence may also be detected by a receiver (terminal) by auto-correlation of the sub-band signal in the time domain, i.e. after filtering to separate the signals in the frequency domain. Furthermore, it should be noted that the synchronization sequence does not need to be transmitted in all sub-bands that are utilized for data communication due to the synchronization sequence indicating the sub-bands allocation. Hence, no dedicated signaling channel for signaling the sub-band allocation needs to be allocated in advance.

The auto-correlation of the sub-band signals allows the terminal to perform an initial "coarse" synchronization. The cross-correlation with the candidate synchronization sequences in subsequent step allows the terminal a further "finer" synchronization, providing reliable results even in strong in-band interference or non-contiguous spectrum allocation scenarios.

The different synchronization sequences may have similar auto-correlation properties, e.g. to facilitate frame detection, and good cross-correlation properties, e.g. to facilitate sequence detection. The synchronization based on auto-correlation and cross-correlation may improve the robustness against in-band interference during the separation of different users/interference or similar frequency localized signals.

In another embodiment of the invention, a synchronization sequence is transmitted in each of the sub-bands that have been selected for data communication. In this embodiment, the sub- band allocation or allocation vector may thus be inherent to the sub-bands on which the synchronization sequence is signaled. Also in this embodiment, the synchronization sequence may be implemented as a preamble or midamble within a transmission burst.

The synchronization sequence may for example be transmitted either in each of these sub- bands, or alternatively one synchronization sequence is spread across all the sub-bands that have been selected for data communication. The correct detection of the synchronization sequence can be confirmed by the terminal by means of cross-correlation. In case the synchronization sequence is spread across the sub-bands, only one predefined synchronization sequence could be provided, as the spreading of the synchronization sequence across the sub-bands and the following cross-correlation may provide sufficient robustness to the signaling scheme. In this case, no cross-correlation for confirming the sub- band allocation is used, but the sub-band allocation may be confirmed in a separate control channel.

In both cases of spreading of the synchronization sequence across the sub-bands or repeating the synchronization sequence in the sub-bands, in order to improve the robustness of this signaling scheme, "special" synchronization sequences that are indicative of the one or more sub-bands may be predefined. In this latter case, the synchronization sequences thus also yield different allocation vectors or sub-band allocations, respectively. Hence, the synchronization sequence transmitted in each of these sub-bands or the synchronization sequence spread across all the sub-bands that have been selected for data communication may allow the terminal to confirm the sub-band allocation. Further, according to an embodiment of the invention, upon synchronization with the frame structure on the respective sub-bands carrying the synchronization sequence, the terminal may further receive control information within a resource block of a frame. This control information may only be present in one of the sub-bands carrying the synchronization sequence; it is however also possible to signal the control information in multiple or all sub- bands carrying the synchronization sequence. The control information may be used to signal for example information on the resource allocation in one or more sub-bands for data communication to a terminal or group of terminals.

The synchronization sequences may be for example predefined or computable for each terminal, for groups of terminals or all terminals. Accordingly, this facilitates signaling the sub-band allocation per terminal (user), group of terminals (multiple users) or for all terminals (all users) in the communication system. For this purpose the different synchronization sequences could be for example structures according to a predefined scheme: A first portion thereof may be for example address the sub-band allocation to one terminal, a group of terminals, or all terminals, while a second portion of the synchronization sequences comprises the sub-band allocation vector. The first portion may for example be generated by the base station by using respective terminal IDs and/or group IDs. Similarly, the second portion of a synchronization sequence could be generated for example based on bit-maps indicating the respective sub-band allocations.

Accordingly, different sets of synchronization sequences may be predefined and stored in the terminals, or can be generated by the terminals for determining the sub-band allocation from signaled synchronization sequences. Furthermore, the terminals may check the received signals from comprising a synchronization sequence of one of the sets of synchronization sequences. The sets could be for example correspond to synchronization sequences yielding per user sub-band allocations, per group of users sub-band allocations, or sub-band allocations for all terminals. In the following, more detailed embodiments of the invention will be described in further detail. It is assumed in the following that the communication system is a NC-MC mobile communication system. In the frequency domain, the NC-MC communication system has a spread spectrum formed by a given number of sub-channels. Advantageously, the subchannels have equal bandwidth, but this is not necessarily required. For example, sub- channels could also have bandwidths of integer multiples of a minimum bandwidth. In the time domain, it can be assumed that resources are partitioned in frames. A frame in the time domain and a sub-band in the frequency domain form a resource block. The resource blocks in one sub-band can be assumed to have equal size. If the sub-bands have equal bandwidth, the resource blocks may also have equal size across all sub-bands. The resource blocks on distinct sub-bands of the NC-MC communication system may be time aligned in the time domain, but again this is not necessarily required. The general resource block structure on the air interface is assumed to be known to the terminals and the base stations.

It is noted that most of these embodiments are based on a synchronization scheme as proposed in C. Thein et al.,„Frequency-Domain Processing for Synchronization and Channel Estimation in OQAM-OFDM Systems", Proceedings on the IEEE 14^th Workshop on Signal Processing Advances in Wireless Communications (SPAWC), June 2013, which is incorporated herein by reference, or as discussed in the applicant's co-pending patent application PCT/EP2013/062442, which is also incorporated herein by reference.

Fig. 2 shows an exemplary flow chart of a method for signaling sub-block allocation information on a carrier having plural sub-bands forming a fragmented spectrum in accordance with an embodiment of the invention. The flow chart will be explained in connection with Fig. 3 and Fig. 4. Fig. 3 illustrates the synchronization sequence structure according to the preamble design in a multi-user scenario. Fig. 4 illustrates the synchronization sequence structure according to the midamble design in a multi-user scenario.

A terminal in the NC-MC mobile communication system receives 201 respective signals of one or more of the sub-bands of the NC-MC mobile communication system. In principle, it would be possible to define a subset of sub-bands of all available sub-bands in the NC-MC mobile communication system, and the terminal processes signals in the sub-bands of the predetermined subset. Alternatively, the terminal may process signals on all sub-bands defined in the NC-MC mobile communication system. Here it is assumed that sub-band signals si are received on sub-bands SBi, where i = 1 , . .. , k , i.e. signals are received on k sub-bands, where k>l . It is noted that the following steps 202-212 are only illustrative and essentially describe iterations through the sub-band signals Si to determine a sub-band allocation vector yielding the sub-bands that are allocated for data communication. Steps 205, 206, 207, 209, and 210 show another iteration through the predefined set of synchronization sequences sync_j , where j= 1 , 1 , i.e. there are 1 synchronization sequences. The variables i and j are used to describe the iterations, but the iterations could also be performed in parallel for all signals ¾ or all synchronization sequences syn respectively.

The terminal performs 203 auto-correlation of the sub-band signals ¾ to determine 204, whether the signal ¾ is periodic or not. Prior to the auto-correlation, the signal received by the receiving circuitry of the terminal may be subjected to a frequency transformation, in order to obtain a time-and-frequency resolution in which the individual signals Si of the individual sub- bands SBi are defined (not shown in Fig. 2). Auto-correlation may be performed in the frequency domain or time domain as outlined above. If the sub-band signal ¾ is not periodic, the terminal checks the next signal (steps 211 , 212). If the sub-band signal s_t is periodic, this yields the presence of a synchronization sequence in sub-band signal ¾, and the terminal synchronizes to the frame structure on the sub-band SB; and further iterates 205, 206, 207 through the synchronization sequences to try finding a synchronization sequence sync_j matching the periodic signal portion of in sub-band signal Si.

For this, the terminal cross-correlates the sub-band signal Si with the synchronization sequences until a matching synchronization sequence sync_j is found. It is noted again that the terminal may not necessarily perform such iteration sequentially, but it is likewise possible to check for a matching synchronization sequence sync_j out of the available synchronization sequences in parallel. The synchronization sequence sync_j yielding a maximum in cross- correlation is determined 207 to be the matching synchronization sequence synq and the sub- band allocation inherent to this matching synchronization sequence sync_j is determined 208 to be the sub-band allocation signaled to the terminal.

Further, it is noted that due to noise and other transmission effects, it is also possible that a sub-band signal Si is found to be periodic, but no synchronization sequence is found therein. Furthermore, it is also feasible to cross-correlate a sub-band signal ¾ with all predefined synchronization sequences and to select the synchronization sequence sync_j exhibiting the largest maximum in the cross-correlation and being above a given threshold as the matching sequence. The examples of Figs. 3 and 4 exemplarily assume a OQAM-OFDM communication system, in which the channel on the carrier is divided into 9 sub-bands (or blocks) indexed k = 1 , . .. ,9 within the frequency domain and in individual frames in the time domain. Further, it is noted that in the example of Figs. 3 and 4, the sub-bands with block indices 5 and 8 are used by other systems, and the other sub-bands carry synchronization sequences, i.e. the respective synchronization sequence symbols within the respective blocks.

Each physical resource in one frame and on a given sub-band can be considered to form a resource block (RB). Considering the terminal's operation discussed in connection with Fig. 2, the terminal might thus process sub-band signals Si on all or a subset of the 9 sub-bands and may perform auto-correlation and cross-correlation as described above for each of the signals Si. As noted above, Fig. 3 assumes for exemplary purposes that the synchronization sequence is a preamble defined in at least some of the symbols (synchronization sequence symbols) of a resource block, while Fig. 4 assumes for exemplary purposes that the synchronization sequence is a midamble defined in at least some of the symbols (synchronization sequence symbols) of a resource block. In the examples of Figs. 3 and 4, sub-band allocations are signaled per user.

User 1 (synch sequence user 1 and data user 1) is assigned to available sub-bands 2, 3, 6 and 9, and user 2 (synch sequence user 2 and data user 2) is assigned to available sub-bands 1 , 4, and 7. The remaining blocks are assumed to be allocated by other systems operating in the same band. In the examples of Figs. 3 and 4, it can be assumed that the users (terminals) monitor all sub-bands 1 to 9 and check signals (step 201 , Fig. 2) of all 9 sub-bands for the presence of a synchronization sequence yielding a sub-band allocation vector. Furthermore, the synchronization sequence indicative of the sub-band allocation to the respective users is signaled in all sub-bands allocated to the particular user.

The control channel for signaling e.g. resource allocation information to the terminals may for example be located in the sub-band having the lowest or highest sub-band index, or its location may be somehow inherent to the sub-band allocation.

Although signaling the synchronization sequence indicative of the sub-band allocation to the respective users in one of the sub-bands would be sufficient, the robustness against detection failures, e.g. due to noise, can be improved, if the synchronization sequence indicative of the sub-band allocation to the respective users is signaled on more than one sub-band. This also allows confirming the sub-band allocation at the terminal (see dotted arrow in Fig. 2), in that the terminal continues checking other signals of other sub-bands even if a synchronization sequence has been successfully detected in a given sub-band.

For implementing the described scheme, the frequency domain based synchronization technique used in the publication by C. Thein et al. mentioned above can be applied. After successfully detecting the frame by auto-correlating the received signals in each of the resource blocks, the cross-correlation with the candidate sequences can be given by the following mathematical expression:

Y_k Received sequence at subcarrier k (within the RB)

Ψ Set of subcarriers used in resource block

K Total number of subcarriers spanning the signal bandwidth of the non-contiguous multi-carrier system

S Candidate sync sequence

S_k k-th element of candidate Sync sequence

S Detected Sync sequence

τ Candidate timing offset to be tested (from a given set of candidates)

τ Detected timing offset

Fig. 5 shows another exemplary flow chart of a method for signaling sub-block allocation information on a carrier having plural sub-bands forming a fragmented spectrum in accordance with an embodiment of the invention. In this embodiment, the synchronization sequence is not repeated in the respective sub-band signals but is spread across the sub-band signals of all sub-bands allocated to the terminal(s). A terminal in the NC-MC mobile communication system receives 201 sub-band signals of one or more of the sub-bands of the NC-MC mobile communication system. Similar to Fig. 2, it is possible to define a subset of sub-bands of all available sub-bands in the NC-MC mobile communication system, and the terminal processes signals in the sub-bands of the predetermined subset. Alternatively, the terminal may process signals on all sub-bands defined in the NC-MC mobile communication system. Here it is assumed that sub-band signals si are received on sub-bands SBi, where i = 1 , . .. , k , i.e. signals are received on k sub-bands, where k>l . The terminal performs 203 auto-correlation of the sub-band signals ¾ to determine 204, whether the signal ¾ is periodic or not. Prior to the auto-correlation, the signal received by the receiving circuitry of the terminal may be subjected to a frequency transformation, in order to obtain a time-and-frequency resolution in which the individual signals Si of the individual sub- bands SBj are defined (not shown in Fig. 2). Auto-correlation may be performed in the frequency domain or time domain as outlined above. If the sub-band signal ¾ is not periodic, the terminal checks the next signal (steps 211 , 212).

If the sub-band signal Si is periodic, this yields the presence of a portion of the synchronization sequence in sub-band signal The terminal may synchronize to the frame structure on the sub-band SBi and further marks 501 the sub-band SBi as a sub-band in which a portion of the synchronization sequence has likely been found. Then the terminal processes the sub-band signal Si of the next sub-band (steps 211 , 212). It is noted that the processing of the sub-bands may also be performed in parallel or partially in parallel, instead of sequentially as indicated in Fig. 5.

Once all sub-bands SBi to SB_k have been processed, all sub-band signals ¾ of all sub-bands SBi are concatenated 502 into a combined signal sc. The combined signal sc should comprise the synchronization sequence. To detect the synchronization sequence, the terminal cross- correlates 503 the combined signal sc with the synchronization sequences until a matching synchronization sequence sync_j is found. It is noted that the terminal may not necessarily perform such iteration sequentially, but it is likewise possible to check for a matching synchronization sequence sync_j out of the available synchronization sequences in parallel. The synchronization sequence sync_j yielding a maximum in cross-correlation with the combined signal sc is determined 207 to be the matching synchronization sequence synq and the sub- band allocation inherent to this matching synchronization sequence synq is determined 208 to be the sub-band allocation signaled to the terminal.

Similar to the procedure in Fig. 2 due to noise and other transmission effects it is possible that a sub-band signal Si is found to be periodic, but no portion of a synchronization sequence is found therein, or vice versa. Accordingly, Fig. 6 shows another alternative embodiment of the invention and provides an exemplary flow chart of a method for signaling sub-block allocation information on a carrier having plural sub-bands forming a fragmented spectrum. In comparison to the embodiment of Fig. 5, the terminal concatenates 601 the sub-band signals ¾ of all sub-bands SBi into a combined signal sc (similar to step 502 in Fig. 5) and performs 602 the auto-correlation on this combined signal sc- If the combined signal sc shows some periodicity, the terminal next continues with cross-correlation 503, similar to Fig. 5.

In the embodiments described in connection with Figs. 5 and 6 above, due to the spreading of the synchronization sequence across the sub-bands used for communication, the synchronization sequence may only indicate a general sub-band allocation for all terminals, which is however not necessarily corresponding to the sub-band allocation to individual terminals or groups of terminals. Accordingly, additional control information may be transmitted in addition to the synchronization sequence within a frame. Such additional control information could be for example considered to form a codeword vector. The additional control information may inform individual terminals or groups of terminal for example, on the location of a control channel, or a resource allocation in the sub-bands.

Fig. 7 illustrates a synchronization sequence structure in a multi-user scenario in accordance with an embodiment of the invention. Similar to Figs. 3 and 4, an OQAM-OFDM communication system is exemplarily assumed, in which the channel on the carrier is divided into 9 sub-bands (or blocks) indexed k = 1,...,9 within the frequency domain and in individual frames in the time domain. Further it is noted that in the example of Figs. 3 and 4, the sub- bands with block indices 5 and 8 are used by other systems.

The synchronization sequence structure shows a synchronization sequence which is spread over all sub-bands used for communication, and additional control information signaled in individual sub-bands to individual terminals (user 1, user 2). The synchronization sequence spread over all sub-bands used for communication is referred to as a full band Sync sequence in Fig. 7 and is carried in the sub-band with block indices 1 to 4, 6, 7 and 9. The terminal can establish synchronization with the frame structure and determine the general sub-band allocation for all terminals using, for example, the procedures of Figs. 5 and 6, and may then detect the additional control information contained in the successively transmitted codewords or codeword vectors as exemplarily shown in Fig. 7, providing information on the user- specific allocation of each sub-band (codeword user 1, codeword user 2). The codewords may carry this information in form of a unique sequence per block indicating the block(s) assigned to a user (or group of users), or alternatively in form of a modulated and channel coded word indicating the block(s) assigned to a user. In the latter case, it is possible to decode the blocks either independently, or to combine for the decoding to benefit from the joint coding gain.

The principles of the invention described in various embodiments herein above may be for example employed in multi-user spectrum sharing in an LTE macro cell, as for example exemplified in Fig. 8. A Macro BS with a macro-cell is transmitting to MUE 1 (user 1) on fragmented spectrum resources, which have been granted after a request to the White Space database. The used spectrum is non-contiguous, and it is assumed that the spectrum hole in between the used band is occupied by another user MUE 2 (user 2) using contiguous spectrum. Using the invention, the receiver of user 1 could for example detect and utilize the available spectrum resources during the synchronization process performed in the frequency domain and thus set up the transmission link and enable the successful transmission over fragmented frequency resources.

A further embodiment provides a terminal 900 as exemplarily shown in Fig. 9. The terminal 900 may be configured to implement the embodiments of the invention described herein. The terminal 900 may be a mobile terminal, e.g. a cellular phone, a PDC, smart-phone, tablet computer etc. The terminal comprises a transceiver 910, which has a transmitter 911 and a receiver 912. The receiver 912 comprises receiver circuitry and is configured to receive signals over the air. As explained before, the receiver 912 could receive a signal via antenna(s) 905 on a carrier over the entire bandwidths supported by the receiver circuitry. Furthermore, the receiver 912 may provide demodulation and decoding functionality to terminal 900. Transmitter 911 may provide encoder and modulation functionality to the terminal 900. Additionally, the terminal 900 could be equipped with a display 902 and a keyboard 903 to facilitate control of the terminal 900 by a user. The terminal 900 further comprises a processor 901 configured to transform the received (time domain) signal into the frequency domain, so as to obtain a time-and-frequency representation of the signal, in which the individual sub-band signals can be processed. The processor 901 may be further used to perform the auto-correlation of the sub-band signals and the cross-correlation for finding the matching synchronization sequence, as discussed herein above.

The terminal 900 may also comprise a memory 904 in which the individual synchronization sequences for use in cross correlation may be stored. Furthermore, the memory 904 may also store additional information that yield the sub-band allocation associated with each of the synchronization sequences.

Another embodiment relates to a base station 1000 as exemplarily shown in Fig. 10. Base station 1000 is configured to implement the embodiments of the invention described herein. The base station has a processor 1001 that can determine one or more sub-bands for use for communication in the non-contiguous multi-carrier mobile communication system. The memory 1002 stores multiple candidate synchronization sequences indicative of respective combinations of one or more sub-bands employed for data communication in the noncontiguous multi-carrier mobile communication system. Processor 1101 is also configured to select, from the multiple candidate synchronization sequences, the candidate synchronization sequence indicative of the determined one or more sub-bands. The base station 1000 may optionally have further wired and/or wireless network interface 1003 to support e.g. alternative wired or wireless access technologies, or to connect the base station 1000 to the core network of the communication system. The base station 1000 comprises a transceiver 1010, which has a transmitter 1011 and a receiver 1012. The transceiver 1010 is coupled to antenna(s) 1005 for reception and transmission of signals via an air interface. Further, using antenna(s) 1005, the transmitter 1011 periodically transmits the selected synchronization sequence in a signal within one or more of the sub-bands. Although the invention has been described in the context of a method, it is clear that the invention also represents a description of the corresponding apparatus suitably adapted to perform such method. In such apparatus a (functional or tangible) block may correspond to one or more method step or a feature of a method step. Analogously, the invention described in the context of a corresponding block or item or feature of a corresponding apparatus may also correspond to individual method steps of a corresponding method. Furthermore, the methods described herein may also be executed by (or using) a hardware apparatus, like processor(s), microprocessor(s), a programmable computer or an electronic circuit. Some one or more of the most important method steps may be executed by such an apparatus. Where an apparatus has been described herein in terms of functional blocks, it should be further understood that those elements of the apparatus may be fully or partly implemented in hardware elements/circuitry. Individual hardware, like processor(s) or microprocessor(s), etc., may be used to implement the functionality of one or more elements of the apparatus.

In addition, where information or data is to be stored in the process of implementing a method step of functional element of an apparatus in hardware, the apparatus may comprise memory or storage medium, which may be communicatably coupled to one or more hardware elements/circuitry of the apparatus.

It is also contemplated implementing the embodiments of the invention in in hardware or in software or a combination thereof. This may be using a digital storage medium, for example a floppy disk, a DVD, a Blu-Ray, a CD, a ROM, a PROM, an EPROM, an EEPROM or a FLASH memory, having electronically readable control signals or instructions stored thereon, which cooperate (or are capable of cooperating) with a programmable computer system such that the respective method is performed. A data carrier may be provided which has electronically readable control signals or instructions, which are capable of cooperating with a programmable computer system, such that the method described herein is performed.

It is also contemplated implementing the embodiments of the invention in the form of a computer program product with a program code, the program code being operative for performing the method when the computer program product runs on a computer. The program code may be stored on a machine readable carrier. The above described is merely illustrative, and it is understood that modifications and variations of the arrangements and the details described herein will be apparent to others skilled in the art. It is the intent, therefore, that the invention is limited only by the scope of the impending claims and not by the specific details presented by way of description and explanation above.

Claims

1. A method for signaling information on a carrier having plural sub-bands forming a fragmented spectrum, the method comprising the following steps performed by a terminal of a non-contiguous multi-carrier mobile communication system: auto-correlating respective signals received in the sub-bands, to detect whether a predetermined periodically transmitted synchronization sequence is present in one or more of the received signals; in case a synchronization sequence is present in the one or more received signals, matching the synchronization sequence to one of multiple candidate synchronization sequences by cross-correlation, respectively; wherein the respective candidate synchronization sequences are indicative of one or more sub-bands employed for data communication in the non-contiguous multi- carrier mobile communication system; and determining the one or more sub-bands employed for data communication in the non-contiguous multi-carrier mobile communication system based on the matched candidate synchronization sequence.

2. The method according to claim 1, wherein the same synchronization sequence is received in some of or in each of the sub-bands employed for data communication.

3. The method according to claim 1 or 2, wherein the synchronization sequence is further indicative of an allocation of the one or more sub-bands to the terminal.

4. The method according to one of claims 1 to 3, wherein the synchronization sequence further indicates a service class or user class to which the respective sub- bands used for data communication are allocated.

5. The method according to one of claims 1 to 4, wherein the synchronization sequence further indicates control information of the non-contiguous multi-carrier mobile communication system.

The method according to claim 5, wherein the control information indicates the sub-band and/or spectral and temporal allocation of a control channel, which is used to transmit resource allocation information to the terminals.

A method for signaling information on a carrier having plural sub-bands forming a fragmented spectrum, the method comprising the following steps performed by a terminal of a non-contiguous multi-carrier mobile communication system: receiving respective signals in each of the sub-bands of the non-contiguous multi- carrier mobile communication system; auto-correlating the received signals, to detect whether a predetermined periodically transmitted synchronization sequence is present in the received signals in the sub-bands of the carrier; in case the synchronization sequence is present in the signals, confirming the detection of the synchronization sequence by cross-correlating the synchronization sequence with a predefined synchronization sequence stored in the terminal; synchronizing with a frame structure in the one or more sub-bands employed for data communication by means of the synchronization sequence, wherein each frame comprises at least one resource block; and receiving a resource block in each of the sub-bands of the non-contiguous multi- carrier mobile communication system, wherein at least one of the resource blocks comprises control information on the resource allocation in one or more sub-bands for data communication to the terminal.

The method according to claim 7, wherein the synchronization sequence is spread across the sub-bands used for data communication, and the cross-correlation comprises cross-correlating the detected synchronization sequence with respective candidate synchronization sequences each of which is indicative of one or more sub-bands employed for data communication in the non-contiguous multi-carrier mobile communication system.

The method according to claim 8, wherein the candidate synchronization sequences each have bit sequences corresponding to the respective sub-bands of the non-contiguous multi-carrier mobile communication system, and a respective bit sequence corresponding to unused sub-band is zero.

10. The method according to one of claims 7 to 9, wherein the synchronization sequence and the control information are comprised in distinct resource blocks.

11. A method for signaling information on a carrier having plural sub-bands forming a fragmented spectrum, wherein the sub-bands are available for communication in a non-contiguous multi-carrier mobile communication system, the method comprising the following steps performed by a base station of the non-contiguous multi-carrier mobile communication system: determining one or more sub-bands for use for communication in the noncontiguous multi-carrier mobile communication system; providing multiple candidate synchronization sequences indicative of respective combinations of one or more sub-bands employed for data communication in the non-contiguous multi-carrier mobile communication system; selecting, from the multiple candidate synchronization sequences, the candidate synchronization sequence indicative of the determined one or more sub-bands; and periodically transmitting the selected synchronization sequence in a signal within one or more of the sub-bands.

12. A terminal for use in a non-contiguous multi-carrier mobile communication system in which information is transmitted on a carrier having plural sub-bands forming a fragmented spectrum, the terminal comprising: a storage unit configured to store multiple candidate synchronization sequences, each being indicative of the one or more sub-bands employed for data communication in the non-contiguous multi-carrier mobile communication system; a receiver unit configured to receive respective signals in the sub-bands; an auto-correlation unit configured to auto-correlate the received signals, to detect one or more received signals comprising a predetermined periodically transmitted synchronization sequence; and a processing unit configured to match the synchronization sequence to one of said candidate synchronization sequences by cross-correlation to confirm the one or more sub-bands being used for data communication in the non-contiguous multi- carrier mobile communication system.

A terminal for use in a non-contiguous multi-carrier mobile communication system information in which information is transmitted on a carrier having plural sub-bands forming a fragmented spectrum, the terminal comprising: a receiver unit configured to receive respective signals in each of the sub-bands of the non-contiguous multi-carrier mobile communication system; an auto-correlation unit configured to auto-correlate the received signals, to detect whether a predetermined periodically transmitted synchronization sequence is present in the received signals in the sub-bands of the carrier; a processing unit configured to confirm the detection of the synchronization sequence by cross-correlating the synchronization sequence with a predefined synchronization sequence stored in the terminal, in case the synchronization sequence is present in the signals; and a synchronization unit configured to synchronize with a frame structure in the one or more sub-bands employed for data communication by means of the synchronization sequence, wherein each frame comprises at least one resource block; wherein the receiver unit is configured to receive a resource block in each of the sub-bands of the non-contiguous multi-carrier mobile communication system, wherein at least one of the resource blocks comprises control information on the resource allocation in one or more sub-bands for data communication to the terminal.

14. A base station for use in a non-contiguous multi-carrier mobile communication system in which information is signaled on a carrier having plural sub-bands forming a fragmented spectrum, the base station comprising: a processing unit configured to determine one or more sub-bands for use for communication in the non-contiguous multi-carrier mobile communication system; a storage unit configured to store multiple candidate synchronization sequences indicative of respective combinations of one or more sub-bands employed for data communication in the non-contiguous multi-carrier mobile communication system; wherein the processing unit is configured to select, from the multiple candidate synchronization sequences, the candidate synchronization sequence indicative of the determined one or more sub-bands; and a transmitter unit configured to periodically transmit the selected synchronization sequence in a signal within one or more of the sub-bands.

15. A computer-readable medium storing instructions that, when executed by a processing unit of an apparatus, the apparatus being suitable for use in a noncontiguous multi-carrier mobile communication system in which information is transmitted on a carrier having plural sub-bands forming a fragmented spectrum, cause the apparatus to perform the steps of the method according to one of claims 1 to 11.