Patent Description:
Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in the present disclosure and are not admitted to be prior art by the inclusion in this section.

To manage increased traffic on mobile networks, some mobile network traffic can be accommodated through the use of small cells. A small cell is typically provided through a low-powered radio access node that operates in licensed and unlicensed spectrums. These low-powered radio access nodes have a transmission power that is less than that of a macro node or other high-powered cellular base station. For example, the range of such low-powered radio access nodes is often between ten (<NUM>) meters to two (<NUM>) kilometers, whereas the range of a macro node might be several tens of kilometers.

The low-powered radio access nodes that are to provide small cells may be embodied in a number of different systems. A common low-powered radio access node is a femtocell cellular base station. A femtocell connects to a service provider's network through a broadband connection (e.g., cable or digital subscriber line), thereby allowing that service provider to extend service coverage indoors or at a cell edge where network access might otherwise be limited. Other common small cells include, among others, picocells and microcells. In order to realize the increased service coverage and/or network capacity provided by a small cell, a user equipment ("UE") operating on the network may be served by that small cell.

<CIT> discloses a system having a pilot channel for transmitting a pilot signal and reference symbol is used for the mobile station to estimate the channel or measure the channel quality indicator (CQI). Also, the pilot channel is used for a mobile station to identify the cell to which the mobile station belongs by using the cell group information acquired through the primary synchronization channel and the secondary synchronization channel and the frame time information of the cell. For this purpose, the pilot channel is generated based on a random sequence commonly allocated to the cell group and an orthogonal sequence allocated to the cell. That is, in order to identify the cell to which the mobile station belongs, the mobile station searches for the random sequence that corresponds to the cell group found in the secondary synchronization channel and the orthogonal sequence that is allocated to the cell and thereby identifies the corresponding cell.

<CIT> discloses a method of transmitting an aggregated measurement report to a network in an Evolved Universal Mobile Telecommunications System (E-UMTS) evolved from the Universal Mobile Telecommunications System (UMTS) or a Long Term Evolution (LTE) system.

<CIT> discloses a discovery reference signal designed for coordinated multipoint operations in heterogeneous networks. Techniques are disclosed that include receiving distinct discovery reference signals (RSs) transmitted from a plurality of different transmission points involved in coordinated multipoint (CoMP) operations with the UE, calculating path loss estimations for each of the transmission points based on the distinct discovery RSs, and performing a random access channel (RACH) procedure with a transmission power level set based on the path loss estimations.

<CIT> discloses a wireless communication system and method using distributed antennas. A physical channel and reference signal (RS) transmission/reception method for downlink and uplink communication using a plurality of points is provided for a case in which the plurality of points have different physical cell identities (PCIs), or in a wireless communication environment using distributed antennas in which the plurality of points belong to the same cell and have the same PCI. Also, a method of transmitting a physical channel and an RS in an uplink and a downlink by introducing a virtual cell identity (VCI) is provided. Further, a cooperative transmission method using a plurality of points is provided, so that communication efficiency of a wireless communication system using distributed antennas can be improved.

The article "<NPL> discloses algorithms and results for both initial and target cell search scenarios for the wideband CDMA standard.

The embodiments described herein are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements.

In the following detailed description, reference is made to the accompanying drawings which form a part hereof wherein like numerals designate like parts throughout, and in which is shown by way of illustration embodiments that may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of embodiments is defined by the appended claims and their equivalents. Various operations may be described as multiple discrete actions or operations in turn, in a manner that is most helpful in understanding the claimed subject matter. However, the order of description should not be construed as to imply that these operations are necessarily order dependent. In particular, these operations may not be performed in the order of presentation. Operations described may be performed in a different order than the described embodiment. Various additional operations may be performed and/or described operations may be omitted in additional embodiments.

For the purposes of the present disclosure, the phrases "A or "B" and "A and/or B" mean (A), (B), or (A and B). For the purposes of the present disclosure, the phrase "A, B, and/or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C).

As used herein, the terms "module" and/or "logic" may refer to, be part of, or include an Application Specific Integrated Circuit ("ASIC"), an electronic circuit, a processor (shared, dedicated, or group) and/or memory (shared, dedicated, or group) that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.

<FIG> illustrates an exemplary wireless communication network <NUM>, according to one embodiment. The wireless communication network <NUM> (hereinafter "network <NUM>") may be an access network of a 3rd Generation Partnership Project ("3GPP") long-term evolution ("LTE") network such as evolved universal mobile telecommunication system ("UMTS") terrestrial radio access network ("E-UTRAN"). The network <NUM> features, among other elements, a relatively high-power base station, such as an evolved Node B ("eNB") <NUM>, that is to provide a wireless macro cell <NUM>. This wireless macro cell <NUM> provided by the eNB <NUM> may operate on a first frequency F1.

To serve a user equipment ("UE") <NUM> and otherwise administrate and/or manage wireless communication in the network <NUM>, the eNB <NUM> includes processing circuitry <NUM> and transceiver circuitry <NUM>. The processing circuitry <NUM> is adapted to perform various tasks in the network <NUM>, including, but not limited to, providing a wireless cell that is to serve the UE <NUM>, generating base and orthogonal sequences, and/or generating conjugate sequences from at least one of base sequences and orthogonal sequences. The transceiver circuitry <NUM> is adapted to transmit data to and receive data from low-powered radio access nodes <NUM> and/or the UE <NUM>; for example, the transceiver circuitry <NUM> may cause a base and/or orthogonal sequence to be transmitted to a low-powered radio access node <NUM>.

In the network <NUM>, the UE <NUM> is to connect with the eNB <NUM> where the UE is within the wireless macro cell <NUM>. The UE <NUM> may be any device adapted to connect with the eNB <NUM> according to, for example, the 3GPP specification, such as a hand-held telephone, a laptop computer, or other similar device equipped with a mobile broadband adapter. According to the embodiment, the UE <NUM> may be adapted to administrate one or more tasks in the network <NUM>, including mobility management, call control, session management, and identity management.

To process data, communicate with the eNB <NUM> and/or the nodes <NUM>, or otherwise function in the network <NUM>, the UE <NUM> includes but is not limited to, processing circuitry <NUM>, measurement circuitry <NUM>, communication circuitry <NUM>, and transceiver circuitry <NUM>. The processing circuitry <NUM> is adapted to perform a plurality of tasks for the UE <NUM>, such as detecting physical signals (e.g., discovery signals, primary synchronization signals, secondary synchronization signals, and/or reference signals) transmitted by one or both of the eNB <NUM> and the nodes <NUM>, identifying the identities of one or more cells <NUM>, <NUM> (e.g., a physical layer cell identity and/or a global cell identity), reading information blocks (e.g., master information blocks and/or system information blocks) so that the UE <NUM> may camp on a cell <NUM>, <NUM> and/or performing RRM tasks. The measurement circuitry <NUM> is adapted to perform RRM measurements associated with the eNB <NUM> and/or a node <NUM>. Finally, the transceiver circuitry <NUM> is adapted to send data to and receive data (e.g., measured RRM metric values, cell identities, physical signals, etc.) from the eNB <NUM>, a node <NUM>, or another data source/recipient.

Also included in the wireless network environment <NUM> is a plurality of low-powered radio access nodes <NUM>. The plurality of low-powered radio access nodes <NUM> are to provide a plurality of small cells <NUM>. According to the embodiment, the plurality of small cells <NUM> may include one or more of a femtocell, picocell, microcell, remote radio head ("RRH"), or essentially any similar cell having a range of about less than two (<NUM>) kilometers ("km"). The small cells <NUM> may operate on a second frequency F2 that is different than the first frequency F1 (although the two frequencies may be the same in alternative embodiments). In this arrangement, the UE may be provided both macro-layer and local-node layer coverage. With the benefit of such coverage, the bandwidth and/or network reliability (e.g., near the edge of macro cell <NUM>) may be increased for the UE <NUM> through such as data offloading, carrier aggregation, and other similar technologies. In the illustrated embodiment, the range of the macro cell <NUM> may be insufficient to reach each small cell <NUM> of the plurality, and therefore not all of the plurality of small cells <NUM> have macro-layer coverage.

To efficiently serve the UE <NUM> in the network <NUM> while concurrently conserving resources (e.g., power) and mitigating intercellular interference, a node <NUM> may include processing circuitry <NUM>, transceiver circuitry <NUM>, and storage circuitry <NUM>. The processing circuitry <NUM> may be adapted to perform various tasks in the network <NUM>, including, but not limited to, providing a wireless cell that is to serve the UE <NUM>, generating base and orthogonal sequences, and/or generating conjugate sequences from at least one of base sequences and orthogonal sequences. The transceiver circuitry <NUM> may be adapted to transmit data to and receive data from the eNB <NUM> and/or the UE <NUM>; for example, the transceiver circuitry <NUM> may receive a base and/or orthogonal sequence or a conjugate thereof from the eNB <NUM>. In one embodiment, the transceiver circuitry <NUM> is adapted to transmit a discovery signal (e.g., a signal that includes one or both of a base sequence and orthogonal sequence or a conjugate thereof) to the UE <NUM>. Such a discovery signal may be transmitted with a relatively long periodicity to conserve power of a node <NUM> and reduce interference with signals broadcast by another node <NUM>.

Turning now to <FIG>, a conceptual block diagram depicts discovery signals for small cell clusters in a wireless network environment. In the wireless network environment <NUM>, an eNB <NUM> is to provide a wireless macro cell <NUM> adapted to serve one or more UE(s) <NUM> (which may be embodiments of the eNB <NUM> and the UE <NUM> of <FIG>, respectively). Additionally, the wireless network environment <NUM> may include a plurality of low-powered radio access nodes <NUM> (e.g., the nodes <NUM>) which may be adapted to provide small cell coverage that is complementary to or outside of the coverage of the macro cell <NUM>. Groups of nodes 215a-c may be proximate to one another in the wireless network environment <NUM> so that overlay or extended coverage may be provided in small cell clusters 220a-c. The small cell clusters 220a-c may offer resources for mobile data offloading, carrier aggregation, extended coverage, or carrier service outside the macro cell <NUM>.

Inherently, nodes <NUM> in a small cell cluster <NUM> are collocated in the wireless network environment <NUM> and, therefore, signals transmitted by a first node 215a may interfere with signals transmitted by a second node 215a that is collocated with the first node 215a in a small cell cluster 220a. This interference may be particularly problematic in instances in which nodes <NUM> perpetually transmit signals - e.g., all nodes 215b in a small cell cluster 220b are adapted to transmit always-on physical signals. Furthermore, always-on signal transmission may be resource intensive for a node <NUM> and/or UE <NUM> (e.g., through the power consumed by constantly transmitting and receiving physical signals, respectively).

To mitigate signal interference between nodes <NUM> in a small cell cluster <NUM> as well as conserve resources at a node <NUM> and/or UE <NUM>, a node <NUM> may be adapted to transmit a discovery signal <NUM>. Where a UE <NUM> is within range of a node <NUM>, that UE <NUM> may receive a discovery signal <NUM> from that node <NUM> and determine (e.g., either alone or in combination with the eNB <NUM>) whether to join a small cell provided by that node <NUM>. Subsequently, the UE <NUM> may join a small cell provided by a node <NUM> and receive transmissions from the node <NUM> that is then serving the UE <NUM> (e.g., by issuing a request to the node <NUM> for broadcast transmission so that the UE may perform cellular synchronization).

A discovery signal <NUM> may operate on a new carrier type so that, for example, cell-specific or other common reference signals may be omitted. A discovery signal <NUM> transmitted by a node <NUM> may feature further optimizations to reduce interference and/or conserve resources, such as, for example, a higher time density of the discovery signal <NUM> within a short time period (e.g., subframe) to improve detection by a UE <NUM> and/or a relatively long periodicity to conserve transmission power at the transmitting node <NUM> as well as reception power at the receiving UE <NUM>.

In some embodiments, a discovery signal <NUM> may include identifying information. For example, a discovery signal <NUM> may include a signature and/or sequence (e.g., a base and/or orthogonal sequence) to distinguish a small cell <NUM> in a cluster <NUM> of small cells and/or distinguish a first small cell cluster 220a from a second small cell cluster 220b. The inclusion of a signature and/or sequence in a discovery signal <NUM> may resolve issues of physical layer cell identity ("PCI") confusion and/or collision at one or both of the eNB <NUM> and a UE <NUM> where the eNB <NUM> and/or UE <NUM> is, for example, measuring and/or reporting Radio Resource Management ("RRM") metric values for a small cell provided by a node <NUM>. In the context of wireless networking, PCI confusion describes an environment in which a first small cell provided by a first node 215a within a first small cell cluster 220a is identified with the same PCI as that of a second small cell provided by a second node 215b within a second small cell cluster 220b. Although a UE <NUM> may receive physical signals (not shown) from both nodes 215a, 215b and report measurement values to the eNB <NUM> for the cells provided by those nodes 215a, 215b, the eNB <NUM> may be unable to differentiate between measurement values reported for the first cell provided by the first node 215a and the second cell provided by the second node 215b based on a PCI reported with the measurement values (because the UE <NUM> may report different sets of measurement values but each set may be associated with the same PCI). PCI collision, however, refers to an environment in which a UE cannot distinguish between two neighboring cells provided by two collocated nodes 215a because those neighboring cells use the same PCI.

Now with reference to <FIG>, a flow diagram depicts a method <NUM> for detecting a small cell based on a discovery signal by a UE. The method <NUM> may be performed by a UE, such as the UE <NUM> in the network <NUM> shown in <FIG>. While <FIG> illustrates a plurality of sequential operations, one of ordinary skill would understand that one or more operations of the method <NUM> may be transposed and/or performed contemporaneously. The method <NUM> may be performed in a wireless network environment by a UE served by a macro cell. In another embodiment, the method <NUM> may be performed for handover between cells.

Beginning first with operation <NUM>, the method <NUM> may include receiving a discovery signal from a node associated with a cell (e.g., a small cell). The first synchronization signal may be broadcast by the cell in the downlink direction. A UE in which the method <NUM> is performed may scan the frequency spectrum and tune transceiver circuitry of the UE to a frequency (or band) at which a plurality of radio frames is transmitted. At that frequency, the UE may receive and decode a discovery signal transmitted by a node, such as a node that is collocated with at least one other node to form a cell cluster (e.g., a cluster of small cells).

In the embodiment of the present invention the discovery signal includes at least two sequences: (<NUM>) a base sequence and (<NUM>) an orthogonal sequence. The base sequence may be, for example, a Zadoff-Chu sequence or a pseudorandom sequence. In connection with the base sequence, the method <NUM> includes an operation <NUM> of identifying an identity of a cluster that includes a cell associated with the node that transmitted the received discovery signal. A UE and/or an eNB providing a macro cell that serves the UE may distinguish nodes providing cells in a first cluster from nodes in a second cluster based on the base sequence. Accordingly, the UE and/or eNB may avoid PCI confusion and/or collision by identifying a cell cluster based on the base sequence.

In conjunction with identifying a cluster of cells, the cell that transmitted the received discovery signal may be identified within the cluster, as illustrated at operation <NUM>. According to the embodiment, the identity of the cell may be all or part of a PCI or a global cell identity. A UE may identify the cell within the cluster of cells using the orthogonal sequence included in the discovery signal. The orthogonal sequence may be, for example, a code division multiplexed ("CDM") sequence (e.g., time/frequency domain cyclic shifts, Walsh codes, density functional theory codes, etc.), a frequency division multiplexed ("FDM") sequence (e.g., different subcarrier or subcarrier group allocation), or a time division multiplexed ("TDM") sequence (e.g., different time units). In some embodiments, identifying both the cell cluster based on the base sequence and the cell within the cluster prevents PCI confusion and/or collision.

With the cell identified, the method <NUM> includes the subsequent operation <NUM> of measuring at least one measurement of a metric value. This measurement is to be performed for radio resource management ("RRM") so that radio transmission characteristics of the cell that transmitted the discovery signal can be observed. In one embodiment, a UE may perform cellular synchronization using primary and secondary synchronization signals transmitted by the node after the UE has received the discovery signal transmitted by the node. The UE may measure RRM metric values including, but not limited to, reference signal received power ("RSRP") and/or reference signal received quality ("RSRQ").

In the embodiment of the present invention the subsequent operations <NUM>-<NUM> of the method <NUM> may be contingent upon the radio resource control ("RRC") state of the UE receiving the discovery signal. Following the reception of the discovery signal, the UE establishs an RRC connection with the transmitting (and identified) node. In the RRC connected state with the node, the one or more measured RRM metric value(s) may be transmitted from the UE to an eNB (e.g., an eNB providing a macro cell to the UE and having a coverage area that includes the identified node). Further, the UE may be adapted to transmit the identity (e.g., PCI) corresponding to the identified cell. This eNB may be, for example, responsible for handover of the UE to another serving cell.

In some embodiments, the UE may report one or more measured RRM metric value(s) in response to an event and/or at an interval (e.g., a predetermined interval). In the embodiment of the present invention the UE is to report a measured RRM metric value in response to determining a relationship of a measured RRM metric value to a threshold. For example, if the measured RRM metric value exceeds a threshold, then the UE reports the measured RRM metric value as a consequence of that relationship.

Conversely, the UE that is to receive the discovery signal may not establish an RRC connection with the identified cell. In this RRC idle state, the method <NUM> includes the operation <NUM> of comparing the measured RRM metric value to a threshold. The threshold may be predetermined in the UE and/or may be received from an eNB. If the measured RRM metric value fulfills a condition for cell selection or reselection (based on the relationship of the RRM metric value to the threshold), then the UE may camp on the identified cell, as illustrated at operation <NUM>. In some embodiments, the UE may camp on the identified cell by reading one or both of the master information block and a system information block (e.g., the system information block type <NUM>), which are transmitted in the downlink direction from the identified node to the UE.

With reference to <FIG>, a flow diagram depicts a method <NUM> for transmitting a sequence to a UE, in accordance with some embodiments. The method <NUM> may be performed by a node, such as a low-powered radio access node <NUM> and/or the eNB <NUM> in the network <NUM> shown in <FIG>. While <FIG> illustrates a plurality of sequential operations, one of ordinary skill would understand that one or more operations of the method <NUM> may be transposed and/or performed contemporaneously.

Beginning first with operation <NUM>, the method <NUM> includes an operation of providing a wireless cell that is to serve a UE in a wireless network environment. Depending upon the embodiment of the node in which the method <NUM> is performed, the cell provided by the node may be, for example, a macro cell or a small cell. In embodiments in which the wireless cell is a small cell, the small cell may be included in a cluster of small cells. In other embodiments in which the wireless cell is a macro cell, the macro cell may include overlay coverage from a cluster of small cells.

So that a UE and/or eNB may suitably identify the wireless cell provided by the node, the node may be associated with a base sequence that is uniform for all collocated cells (e.g., all cells that comprise a cell cluster). In some embodiments, this sequence is generated at the node providing the wireless cell, as illustrated at operation <NUM>. In other embodiments, however, operation <NUM> is absent. In such embodiments, the base sequence may be, for example, preconfigured (e.g., hardcoded) at the node, received at the node from an eNB that is adapted to centrally manage the nodes in the cell cluster, configured through backhaul exchange, or configured through a self-organizing network ("SON").

Regardless of the location at which the base sequence is generated, the base sequence may be generated as, for example, a Zadoff-Chu sequence or a pseudorandom sequence (e.g., a Gold sequence). For example, the base sequence may be a vector that is generated according to the function <MAT> c(<NUM> + <NUM>)), m = <NUM>,<NUM>,. ; where cinit=f(u<NUM>, NCP, and/or ns), ns:slot number, and <MAT>. A pseudorandom sequence may be defined by a length-<NUM> Gold sequence. The output sequence of c(n) of length MPN, where n=<NUM>, <NUM>,. , MPN-<NUM> may be defined by c(n) = ((x<NUM>(n + Nc) + x<NUM>(n + Nc)) mod <NUM>; x<NUM>(n + <NUM>) = ((x<NUM>(n + <NUM>) + x<NUM>(n)) mod <NUM>; and x<NUM>(n + <NUM>) = ((x<NUM>(n + <NUM>) + x<NUM>(n + <NUM>) + x<NUM>(n)) mod <NUM>; where Nc=<NUM> and the first m-sequence is initialized with x<NUM>(<NUM>) = <NUM>, x<NUM>(n) = <NUM>, n = <NUM>,<NUM>,. The initialization of the second m-sequence is denoted by <MAT> with the value depending on the application of the sequence.

In addition to the operation <NUM> for generating a uniform (e.g., base) sequence, the method <NUM> may include an operation <NUM> for generating a unique sequence that is to distinguish the cell from another cell in the cell cluster (which may have the same uniform sequence). This unique sequence may be an orthogonal sequence. In some embodiments, operation <NUM> is omitted. In such embodiments, the unique sequence may be, for example, preconfigured (e.g., hardcoded) at the node, received at the node from an eNB that is adapted to centrally manage the nodes in the cell cluster, configured through backhaul exchange, configured through a SON. In another embodiment, a unique sequence is entirely absent, and therefore only the uniform sequence is associated with the node providing the cell.

Similar to the uniform sequence, the unique (e.g., orthogonal) sequence may be generated according to one or more algorithms regardless of the location at which the sequence is generated. In one embodiment the unique sequence, represented as a vector Wu<NUM>, may be generated as a phase rotational sequence or cyclic shift sequence (e.g., a CDM sequence or a variant thereof). In such an embodiment, Wu<NUM> may be generated according to the formula <MAT>. In another embodiment, Wu<NUM> may be generated as a FDM sequence. Here, Wu<NUM> may be generated according to the formula <MAT>; in case the number of orthogonal sequences in an orthogonal frequency-division multiplexing ("OFDM") symbol is six (<NUM>). In a third embodiment, Wu<NUM> may be generated as a TDM sequence according to the formula <MAT>; in case the number of orthogonal sequences is six (<NUM>) (n. , a valued time index may be, for example, an OFDM symbol or subframe index). In even another embodiment, Wu<NUM> may be a hybrid of two or more of CDM, FDM, and TDM sequences.

As illustrated, the method <NUM> includes the operation <NUM> of transmitting the uniform (e.g., base) sequence to the UE. In one embodiment, the uniform sequence is transmitted specifically to the UE (e.g., using beamforming). In other embodiments, however, the uniform sequence may be broadcast so that the uniform sequence is detectable by a plurality of UEs that are within a coverage area of the transmitting node. Also at operation <NUM>, the unique (e.g., orthogonal) sequence may be transmitted to the UE.

The uniform sequence may be included in a discovery signal that operates on a new carrier type. In one embodiment of operation <NUM>, the uniform sequence and the unique sequence are transmitted to the UE in a discovery signal. For example, if the uniform sequence is a first vector Bu<NUM> and the unique sequence is a second vector Wu<NUM>, then the discovery signal may include a vector du = du<NUM>,<NUM> = Bu<NUM> ⊗ Wu<NUM>, where ⊗ represents element-by-element multiplication. The discovery signal may be then be transmitted so that cells (e.g., small cells) and clusters of cells (e.g., small cell clusters) may be detected and/or differentiated in a wireless network environment so that issues related to, for example, PCI confusion and/or collision may be avoided.

Now with respect to <FIG>, a flow diagram depicts a method <NUM> for transmitting a sequence to a UE, in accordance with some embodiments. The method <NUM> may be performed by a node, such as a low-powered radio access node <NUM> and/or the eNB <NUM> in the network <NUM> shown in <FIG>. While <FIG> illustrates a plurality of sequential operations, one of ordinary skill would understand that one or more operations of the method <NUM> may be transposed and/or performed contemporaneously.

The number of available sequences that a node may include in, for example, a discovery signal may be finite. Thus, the number of available sequences may be increased by a conjugate operation (e.g., complex conjugate), assuming the original (e.g., base and/or orthogonal) sequence that is to be conjugated is a polyphase sequence consisting of in-phase and quadrature. To take advantage of these additional sequences, the method <NUM> may include an operation <NUM> for conjugating an original sequence to generate a conjugated sequence. For example, a base sequence may be generated according to the function <MAT>. The number of available sequences may be doubled by generating sequences Bu<NUM>(m) = <MAT>. In another embodiment, the conjugated sequence may be based on an existing signal, such as common reference signal ("CRS"), positioning reference signal ("PRS"), or demodulation reference signal ("DM RS"). The formulas used to generate such reference signals may be conjugated in a manner analogous to that described for the base sequence.

In some embodiments, operation <NUM> is omitted. In such embodiments, the unique sequence may be, for example, preconfigured (e.g., hardcoded) at the node, received at the node from an eNB that is adapted to centrally manage the nodes in the cell cluster, configured through backhaul exchange, configured through a SON.

In one embodiment, the method <NUM> may include an operation <NUM> for storing the conjugated sequence so that the conjugated sequence may be accessed at a later time. This operation <NUM> may include storing a conjugated sequence in non-volatile storage, such as a mass storage device. Accordingly, the conjugated sequence may be persistently accessible, even where power or other services required for a node are interrupted.

With a conjugated sequence, an operation <NUM> of transmitting the conjugated sequence to a UE may be included in the method <NUM>. In one embodiment, the conjugated sequence is transmitted to a specific UE (e.g., using beamforming). In other embodiments, however, the uniform sequence may be broadcast so that the uniform sequence is detectable by a plurality of UEs that are within a coverage area of the transmitting node.

The conjugated sequence may be included in a discovery signal that operates on a new carrier type and is discontinuously transmitted with a relatively long periodicity - e.g., the transmitting node does not always broadcast signals, but broadcasts the discovery signal on the order of hundreds of milliseconds. The conjugated sequence may be used by a receiving UE to distinguish cell providers in a wireless networking environment. In one embodiment, the conjugated sequence is transmitted from a low-powered radio access node while the original sequence is transmitted from an eNB so that a small cell is separately identifiable from a macro cell, respectively. In another embodiment, the original sequence and the conjugated sequence are allocated to collocated nodes comprising a cell cluster so that a first cell cluster is distinguishable from other cell clusters. For example, the pair of the original sequence and the conjugated sequence may be used as a base sequence in a discovery signal. In a third embodiment, the original sequence and the conjugated sequence are allocated to a single node so that node is identifiably separate from all other nodes, such as other nodes that are proximate to the transmitting node in a cell cluster. In even another embodiment, a first original sequence is uniform for all nodes in a cell cluster (e.g., a base sequence), while a plurality of conjugated sequences generated from a plurality of original sequences may distinguish the nodes within that cell cluster.

Turning now to <FIG>, a flow diagram is shown illustrating an embodiment of a method <NUM> for detecting cells by a UE in a wireless network environment. The method <NUM> may be performed by a UE, such as the UE <NUM> in the network <NUM> shown in <FIG>. While <FIG> illustrates a plurality of sequential operations, one of ordinary skill would understand that one or more operations of the method <NUM> may be transposed and/or performed contemporaneously.

At operation <NUM>, the method <NUM> begins with the receiving of a first sequence from at least one of a low-powered radio access node and an eNB. Both the low-powered node and the eNB may be adapted to provide respective cells to a UE. In one embodiment, the first sequence is received by the UE in a signal, such as a discovery signal, transmitted by a node. The discovery signal may be received by the UE so that is able to identify and/or distinguish a cell which provides coverage to the UE.

As described above, the range of sequences available to be transmitted by cells in a wireless network environment may be appreciably increased (e.g., doubled) where the conjugates of a first set of sequences are used. Accordingly, the method <NUM> includes an operation <NUM> for receiving a conjugate of the first sequence from at least one of the low-powered node and the eNB. Depending upon the embodiment, the conjugate sequence may be received by the UE in a signal (e.g., a discovery signal) transmitted from a single node. For example, a low-powered radio access node may transmit a discovery signal that includes both the first sequence and the conjugate sequence. The UE may detect this discovery signal and, consequently, receive both the first sequence and the conjugate sequence. Alternatively, the first sequence and the conjugate sequence may be received as part of two signals transmitted by two different nodes. For example, an eNB may transmit the first sequence in a physical signal, while a low-powered radio access node may transmit the conjugate sequence. According to more embodiments, the UE will receive both the first sequence and the conjugate sequence; however, the source node(s) may vary.

At operation <NUM>, the method <NUM> proceeds with detecting a cell provided by at least one of the low-powered radio access node and the eNB. A UE may be adapted to detect a cell provided by a node based on at least one of the first sequence and the conjugate sequence. For example, the UE may be served by a macro cell provided by an eNB, and the eNB may transmit the first sequence. The UE may be adapted to receive a discovery signal from a low-powered node (e.g., a node with coverage overlaying the macro cell) and detect a small cell provided by that low-powered node based on a conjugate of the first sequence that is included in the discovery signal. In another embodiment, the low-powered radio access node transmits both the first sequence and the conjugate sequence. The UE may detect and/or identify a cell or a cell cluster that includes the cell based on this sequence pair. Based on the first sequence and the conjugate sequence, the UE (and/or an eNB with which the UE is to interact) may efficiently detect and/or identify as well as mitigate PCI confusion and/or collision.

With respect to <FIG>, a block diagram illustrates an example computing device <NUM>, in accordance with various embodiments. The eNB <NUM>, low-powered radio access node <NUM>, and/or UE <NUM> of <FIG> and described herein may be implemented on a computing device such as computing device <NUM>. The computing device <NUM> may include a number of components, one or more processor <NUM> and at least one communication chips <NUM>. Depending upon the embodiment, one or more of the enumerated components may comprise "circuitry" of the computing device <NUM>, such as processing circuitry, measurement circuitry, storage circuitry, transceiver circuitry, and the like. In various embodiments, the one or more processor(s) <NUM> each may be a processor core. In various embodiments, the at least one communication chips <NUM> may be physically and electrically coupled with the one or more processor <NUM>. In further implementations, the communication chips <NUM> may be part of the one or more processor <NUM>. In various embodiments, the computing device <NUM> may include a printed circuit board ("PCB") <NUM>. For these embodiments, the one or more processors <NUM> and communication chip <NUM> may be disposed thereon. In alternate embodiments, the various components may be coupled without the employment of the PCB <NUM>.

Depending upon its applications, the computing device <NUM> may include other components that may or may not be physically and electrically coupled with the PCB <NUM>. These other components include, but are not limited to, volatile memory (e.g., dynamic random access memory <NUM>, also referred to as "DRAM"), non-volatile memory (e.g., read only memory <NUM>, also referred to as "ROM"), flash memory <NUM>, an input/output controller <NUM>, a digital signal processor (not shown), a crypto processor (not shown), a graphics processor <NUM>, one or more antenna(s) <NUM>, a display (not shown), a touch screen display <NUM>, a touch screen controller <NUM>, a battery <NUM>, an audio codec (not shown), a video code (not shown), a global positioning system ("GPS") or other satellite navigation device <NUM>, a compass <NUM>, an accelerometer (not shown), a gyroscope (not shown), a speaker <NUM>, a camera <NUM>, one or more sensors <NUM> (e.g., a barometer, Geiger counter, thermometer, viscometer, rheometer, altimeter, or other sensor that may be found in various manufacturing environments or used in other applications), a mass storage device (e.g., a hard disk drive, s solid state drive, compact disk and drive, digital versatile disk and drive, etc.) (not shown), and the like. In various embodiments, the processor <NUM> may be integrated on the same die with other components to form a system on a chip ("SOC").

In various embodiments, volatile memory (e.g., DRAM <NUM>), non-volatile memory (e.g., ROM <NUM>), flash memory <NUM>, and the mass storage device (not shown) may include programming instructions configured to enable the computing device <NUM>, in response to the execution by one or more process <NUM>, to practice all or selected aspects of the data exchanges and methods described herein, depending on the embodiment of the computing device <NUM> used to implement such data exchanges and methods. More specifically, one or more of the memory components (e.g., DRAM <NUM>, ROM <NUM>, flash memory <NUM>, and the mass storage device) may include temporal and/or persistent copies of instructions that, when executed by one or more processors <NUM>, enable the computing device <NUM> to operate one or more modules <NUM> configured to practice all or selected aspects of the data exchanges and method described herein, depending on the embodiment of the computing device <NUM> used to implement such data exchanges and methods.

The communication chips <NUM> may enable wired and/or wireless communications for the transfer of data to and from the computing device <NUM>. The term "wireless" and its derivatives may be used to describe circuits, devices, systems, methods, techniques, communication channels, etc., that may communicate data through the use of modulated electromagnetic radiation through a non-solid medium. The communication chips <NUM> may implement any of a number of wireless standards or protocols, including but not limited to Long Term Evolution ("LTE"), LTE Advanced ("LTE-A"), Institute of Electrical and Electronics Engineers ("IEEE") <NUM>, General Packet Radio Service ("GPRS"), Evolution Data Optimized ("Ev-DO"), Evolved High Speed Packet Access ("HSPA+"), Evolved High Speed Downlink Packet Access ("HSDPA+"), Evolved High Speed Uplink Packet Access ("HSUPA+"), Global System for Mobile Communications ("GSM"), Enhanced Data Rates for GSM Evolution ("EDGE"), Code Division Multiple Access ("CDMA"), Time Division Multiple Access ("TDMA"), Digital Enhanced Cordless Telecommunications ("DECT"), Bluetooth, derivatives thereof, as well as other wireless protocols that are designated as <NUM>, <NUM>, <NUM>, and beyond. The computing device <NUM> may include a plurality of communication chips <NUM> adapted to perform different communication functions. For example, a first communication chip <NUM> may be dedicated to shorter range wireless communications, such as Wi-Fi and Bluetooth, whereas a second communication chip <NUM> may be dedicated to longer range wireless communications, such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, LTE-A, Ev-DO, and the like.

In various implementations, the computing device <NUM> may be a laptop, netbook, a notebook computer, an ultrabook computer, a smart phone, a computing tablet, a personal digital assistant ("PDA"), an ultra mobile personal computer, a mobile phone, a desktop computer, a server, a printer, a scanner, a monitor, a set-top box, an entertainment control unit (e.g., a gaming console), a digital camera, a portable digital media player, a digital video recorder, and the like. In further embodiments, the computing device <NUM> may be another other electronic device that processes data.

Some portions of the preceding detailed description have been presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory.

Embodiments described herein also relate to an apparatus for performing the illustrated operations. Such a computer program is stored in a non-transitory computer readable medium. A machine-readable medium includes any mechanism for storing information in a form readable by a machine (e.g., a computer). For example, a machine-readable (e.g., computer-readable) medium includes a machine (e.g., a computer) readable storage medium (e.g., read only memory ("ROM"), random access memory ("RAM"), magnetic disk storage media, optical storage media, flash memory devices).

Claim 1:
An apparatus to be implemented in a user equipment, UE, (<NUM>) residing in a cell (<NUM>) included in a cell cluster, the apparatus comprising:
transceiver circuitry (<NUM>) configured to receive a discovery signal from a node (<NUM>) associated with the cell (<NUM>), the discovery signal to include a base sequence that distinguishes the cell cluster that includes the cell (<NUM>) from other cell clusters and an orthogonal sequence that distinguishes the cell (<NUM>) from other cells in the cell cluster that includes the cell (<NUM>), wherein the base sequence is a Zadoff-Chu sequence or a pseudo-random sequence; and
processing circuitry (<NUM>), communicatively coupled with the transceiver circuitry (<NUM>), and configured to determine an identity of the cell cluster that includes the cell (<NUM>) based on the base sequence and to determine an identity of the cell (<NUM>) based on the orthogonal sequence; and
measurement circuitry (<NUM>), communicatively coupled with the transceiver circuitry (<NUM>), to measure a Radio Resource Management, RRM, metric value associated with the cell (<NUM>);
wherein the transceiver circuitry (<NUM>) is further to transmit the measured RRM metric value to an eNB (<NUM>) that is to serve the UE (<NUM>) where a Radio Resource Control, RRC, state of the UE (<NUM>) is connected, and the processing circuitry (<NUM>) is further to compare the measured RRM metric value with a threshold value where a RRC state of the UE (<NUM>) is idle, the comparison to the threshold value enabling the UE to determine whether to camp on the cell.