Patent Description:
Long Term Evolution (LTE) networks require seamless connectivity between User Equipments (UEs) and Evolved Node Base Stations (eNBs) irrespective of UE speed. This seamless connectivity is achieved via handover of active connection of a UE by a Serving Base Station (SBS) to an appropriate Neighbouring Base Station (NBS). The handover of a UE is network controlled and is initiated by the SBS with the help from the UE. The SBS decides on a target NBS to handover the UE based on the UE's reported measurement of coverage signal for various NBSs.

For a smooth handover to a target NBS, the SBS maintains neighbour relation information regarding the NBSs of the SBS. However, an outdated neighbour relation information may lead to severe call drops and performance degradation after a UE handover. Thus, for a successful UE handover, in conventional systems, the SBS maintains a Neighbour Relation Table (NRT) that includes a list of NBSs for the SBS. However, as these conventional systems do not add NBS into the NRT based on their suitability for a handover, they end up including non-prospective NBSs in the NRT, while failing to include prospective NBSs, thereby resulting is an ineffective UE handover.

<CIT> relates to techniques for improved allocation of network resources and improved signal strength/quality in a mobile communication network using geolocation and handover management. <CIT> relates to neighbor cell list creation and management for femtocells and other access points.

<CIT> relates to managing a neighbor cell list using handover statistical information, including excluding from a handover target cells with poor handover performance. IN <NUM>/CHE/<NUM> relates to methods and systems for X2 link management in wireless communications networks.

According to aspects of the claimed invention, there are provided a method of neighbor relation management in a wireless broadband network, a Serving Base Station for neighbor relation management in a wireless broadband network, and a computer-readable storage medium as respectively set out in claims <NUM>, <NUM>, and <NUM>.

In particular, the present invention is based on the embodiments disclosed below with reference to <FIG> and <FIG>. Additional embodiments, aspects and examples other than those defined are disclosed for illustrative purposes.

In one embodiment, a method neighbor relation management in a wireless broadband network is disclosed. The method includes dynamically selecting, by a Serving Base Station (SBS), a set of signal measurement reports from a plurality of signal measurement reports received within a predefined time interval based on at least one of: a location of origin of each of the plurality of signal measurement reports, and variation of signal quality of each of the plurality of signal measurement reports with respect to an average signal quality associated with the plurality of signal measurement reports; sampling, by the SBS, signal level values of a plurality of configured Neighboring Base Stations (NBSs) and at least one new NBS, from the set of signal measurement reports, for a predefined sampling time period, wherein the signal level values of the at least one new NBS are greater than a predefined threshold for the predefined sampling time period, and wherein the set of signal measurement reports comprises signal measurement reports corresponding to the plurality of configured NBSs and the at least one new NBS; and computing, by the SBS, a retention factor for each of the plurality of configured NBSs and each of the at least one new NBS, in response to sampling the signal level values.

In another embodiment, an SBS for neighbor relation management in a wireless broadband network is disclosed. The SBS includes a processor and a memory communicatively coupled to the processor, wherein the memory stores processor instructions, which, on execution, causes the processor to dynamically select a set of signal measurement reports from a plurality of signal measurement reports received within a predefined time interval based on at least one of: a location of origin of each of the plurality of signal measurement reports, and variation of signal quality of each of the plurality of signal measurement reports with respect to an average signal quality associated with the plurality of signal measurement reports; sample signal level values of a plurality of configured NBSs and at least one new NBS, from the set of signal measurement reports, for a predefined sampling time period, wherein the signal level values of the at least one new NBS are greater than a predefined threshold for the predefined sampling time period, and wherein the set of signal measurement reports comprises signal measurement reports corresponding to the plurality of configured NBSs and the at least one new NBS; and compute a retention factor for each of the plurality of configured NBSs and each of the at least one new NBS, in response to sampling the signal level values.

In yet another embodiment, a computer-readable storage medium having stored thereon, a set of computer-executable instructions for causing a computer comprising one or more processors to perform steps comprising: dynamically selecting, by an SBS, a set of signal measurement reports from a plurality of signal measurement reports received within a predefined time interval based on at least one of: a location of origin of each of the plurality of signal measurement reports, and variation of signal quality of each of the plurality of signal measurement reports with respect to an average signal quality associated with the plurality of signal measurement reports; sampling, by the SBS, signal level values of a plurality of configured NBSs and at least one new NBS, from the set of signal measurement reports, for a predefined sampling time period, wherein the signal level values of the at least one new NBS are greater than a predefined threshold for the predefined sampling time period, and wherein the set of signal measurement reports comprises signal measurement reports corresponding to the plurality of configured NBSs and the at least one new NBS; and computing, by the SBS, a retention factor for each of the plurality of configured NBSs and each of the at least one new NBS, in response to sampling the signal level values.

The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles.

Additional illustrative embodiments are listed below. In one embodiment, an exemplary wireless broadband network <NUM> in which various embodiments may function is illustrated in <FIG>. The wireless broadband network <NUM> may be a Long Term Evolution (LTE) network that includes an Evolved Node Base station (eNB) <NUM>, an eNB <NUM>, an eNB <NUM>, an eNB <NUM>, an eNB <NUM>, an eNB <NUM>, an eNB <NUM>, an eNB <NUM>, an eNB <NUM>, and an eNB <NUM>. It will be apparent to a person skilled in the art that the number of eNBs in the wireless broadband network <NUM> is not limited to those depicted in <FIG>. One of the eNBs acts as a Serving Base Station (SBS) for one or more User Equipments (UEs) and other eNBs act as Neighboring Base Stations (NBSs) to the SBS. In the wireless broadband network <NUM>, the eNB <NUM> is the SBS and each of the eNBs <NUM>-<NUM> act as NBSs. The eNB <NUM> has a coverage area <NUM> and communicates wirelessly with a UE <NUM>, a UE <NUM>, and a UE <NUM> that are associated with eNB <NUM>. It will be apparent to a person skilled in the art that the number of UEs associated with the eNB <NUM> is not limited to those depicted in <FIG>. Examples of a UE may include but are not limited to a cell phone, a smart phone, a tablet, a phablet, and a laptop.

With regard to the NBSs, each of the eNBs <NUM> - <NUM> has a coverage area within which they communicate with UEs that are associated with them. These coverage areas and UEs have not been depicted in <FIG> for ease of explanation. The eNBs <NUM>-<NUM> collectively form the evolved UMTS Terrestrial Radio Access Network (E-UTRAN) for the wireless broadband network <NUM>.

Each of the eNBs <NUM>-<NUM> wirelessly communicate with a respective Mobility Management Entity (MME) or a Serving Gateway (S-GW) using an S1 interface. Each MME or S-GW further communicate with a Packet Data Network Gateway (PDN-GW) through an S5 interface, which connects the wireless broadband network <NUM> with the Internet through an SGi link. Each of the MME, S-GW, or PDN-GW are not shown in <FIG>.

It will be apparent to a person skilled in the art that the wireless broadband network <NUM> is not limited to an LTE network and may include, but is not limited to, Worldwide Interoperability for Microwave Access (WiMAX), Code Division Multiple Access (CDMA), Enhanced Data rates for GSM Evolution (EDGE), High Speed Packet Access (HSPA), GSM EDGE Radio Access Network (GERAN), a UMTS Terrestrial Radio Access Network (UTRAN), an Evolved-UTRAN (E-UTRAN), and/or an improved E-UTRAN. It will be further apparent to a person skilled in the art that for a wireless communication network other than LTE, network components and parameters associated with that wireless communication network will be used. Also, the description below describes an LTE network for purposes of example, and LTE terminologies are used in much of the description below. However, as stated above the techniques are applicable beyond the LTE networks.

Referring now to <FIG>, a block diagram for communication amongst various components of a management subsystem <NUM> in an eNB is illustrated, in accordance with an embodiment. The management subsystem <NUM> is responsible for system level management of co-channel interference, radio resources, and other radio transmission characteristics in the eNB. The management subsystem <NUM> includes a processing module <NUM> and a memory block <NUM>.

The processing module <NUM> may be a single processor with multiple partitions or independent processors working in a group to perform the desired functionalities. To this end, the processing module <NUM> includes a configuration handler module <NUM> and a radio resource management module <NUM>. The configuration handler module <NUM> handles overall configuration of the eNB and performs various functions that may include, but are not limited to, receiving configuration data from an Operation and Maintenance (OAM) module (not shown in <FIG>) through an OAM interface and storing them in the memory block <NUM> at start up, bringing up the control subsystem, the data subsystem, and the radio subsystem (not shown in <FIG>), and configuring them using the configuration data. The configuration handler module <NUM> may also receive reconfiguration data from the OAM module to reconfigure the control subsystem, the data subsystem, and the radio subsystem. Additionally, the configuration handler module <NUM> updates feedback, via the OAM interface, to the OAM module to enable it to perform any change in the configuration data.

Radio resource management module <NUM> takes management decision to efficiently run the eNB and interfaces with the OAM module through the configuration handler module <NUM>. Additionally, the radio resource management module <NUM> interfaces with the control subsystem via an MSS-CSS interface. The MSS-CSS interface is used between the management subsystem <NUM> and the control subsystem to send control instruction and configuration data to the control subsystem and to receive system level measurement data from the control subsystem. In an example, the MSS-CSS interface is additionally used to carry performance parameters, for example, a traffic load at NBSs, interference level at NBSs, and handover failure rate associated with NBSs. These performance parameters are in addition to the performance parameters that are carried by the MSS-CSS interface in compliance with the applicable standard.

Radio resource management module <NUM> performs various functions through a Self-Organized Network (SON) module <NUM>, an admission control module <NUM>, a power control module <NUM>, a handover control module <NUM>, and an interference control module <NUM>. The SON module <NUM> performs various functions to (re)organize the eNB in a dynamically changing network topology. The decision to (re)organize is taken based on the configuration data and measurement data stored in the memory block <NUM>. These functions may include, but are not limited to Physical Cell Identity (PCI) self-configuration and/or self-optimization, Automatic Neighbor Relation (ANR) management, X2 link auto creation, cell outage detection, cell coverage optimization, and/or collecting live measurement metrics to send feedback to the OAM module about current network conditions. The SON module <NUM> preforms additional functionalities that are further explained in conjunction with <FIG>.

The admission control module <NUM> analyzes the current network load and UE capability to allow the UE connectivity into the wireless broadband network. The power control module <NUM> analyzes different network condition to decide on the transmission power to be used by the eNB and the handover control module <NUM> analyzes measurement data for different NBSs to decide on a target NBS for handover of a UE. To reduce interference from various NBSs, the interference control module <NUM> analyzes the measurement data for different NBSs and reconfigures the eNB.

To store the measurement data, configuration data, and performance parameters, the memory block <NUM> includes a volatile memory <NUM> and a non-volatile memory <NUM>. The volatile memory <NUM> stores system level measurement data provided by the control subsystem. The system level measurement data includes different measurement metrics collected from UEs and calculated by the control subsystem, the data subsystem, and the radio subsystem. Thus data is used by the radio resource management module <NUM> to monitor the prevalent radio network condition in order to take radio network management decisions.

The non-volatile memory <NUM> stores configuration data received from the OAM module. The processing module <NUM> accesses this data from the non-volatile memory <NUM> to configure the control subsystem, the data subsystem, and the radio subsystem through the MSS-CSS interface. The configuration data is also used for configuration, updating existing configuration, and instantiation of the eNB. A portion of the non-volatile memory <NUM> may persist across system-start-up cycles.

Referring now to <FIG>, a block diagram depicting various modules of the SON module <NUM> within the management subsystem <NUM> is illustrated, in accordance with an embodiment. In addition to other modules (not shown in <FIG>) required by the applicable standard, the SON module <NUM> includes a neighbor relation management module <NUM> that further includes a neighbor ranking module <NUM>, a Neighbor Relation Table (NRT) <NUM> that includes a list of NBSs, and a NRT management module <NUM> that updates or modifies the NRT <NUM> and extracts information related to NBSs.

The neighbor ranking module <NUM> stores configuration data that is required by the other modules within the SON module <NUM>. The neighbor ranking module <NUM> also receives a plurality of signal measurement reports from a plurality of UEs and determines ranks for the NBSs for which the plurality of signal measurement reports are received. To this end, the neighbor ranking module <NUM> further includes a configuration module <NUM>, a parameter collection module <NUM>, and a rank determination module <NUM>.

The configuration module <NUM> stores the configuration data that it receives from the configuration handler module <NUM>. The configuration data includes, but is not limited to the maximum number of NBS entries in the NRT <NUM>, i.e., M, a default NBSs list (for example, <NBR1, NBR2, NBR3. NBRm>, where m ≤ M, a predefined sampling time period to sample signal for NBSs (which may be represented as: τSample), a threshold for the predefined sampling time period (which may be represented as: δINFLECTION_TH), gradient threshold for a signal level time gradient (which may be represented as: σth), and/or a threshold for a retention factor computed for an NBS. The computation of the retention factor for an NBS is explained in detail in conjunction with <FIG>. This configuration data is used by the parameter collection module <NUM>, the rank determination module <NUM>, and the NRT management module <NUM>.

The parameter collection module <NUM> receives signal measurement reports and performance indicators for the NBSs from the configuration module <NUM> and subsequently stores them. The performance indicators include, but are not limited to, an inactivity timer (γ), a traffic load at the neighbor (υ), an interference level (χ), and/or a Handover failure rate (ω). Further, the aforementioned performance indicators may be used to determine the retention factor. A signal measurement report received from a UE includes, but is not limited to, one or more of a measured signal level value between the UE and the SBS, measured signal level values between the UE and NBSs configured with the SBS, and/or measured signal level values between the UE and newly detected NBSs.

Based on the signal measurement reports, the configuration data, and the performance indicators, the rank determination module <NUM> computes a retention factor for a plurality of the configured NBSs and one or more new NBSs. Thereafter, the rank determination module <NUM>, via the NRT management module <NUM>, updates the NRT <NUM> with the newly detected NBSs and retention factors for each NBSs in NRT <NUM>. The computation of the retention factor for an NBS is explained in detail in conjunction with <FIG>. Thereafter, the rank determination module <NUM> ranks the NBSs listed in the NRT <NUM> based on the values of the retention factors. Based on these rankings, the NRT management module <NUM> removes one or more NBSs from the NRT <NUM>, when the NRT <NUM> is full. The handover control module <NUM> uses the rankings updated in the NRT <NUM> to decide which NBS should be used to handover a UE. This is further explained in detail in conjunction with <FIG>, <FIG>, and <FIG>.

As a result, the system discussed above enables a time based assessment of the measured signal levels of NBSs, such that, only prospective NBSs are added into the NRT. As there is an upper number limit for adding NBSs into the NRT, the effective management of the NRT by removal of least prospective NBSs, when the NRT is full, leads to preemption of NBSs. Moreover, as prospective NBSs in the NRT are ordered based on their suitability ranking for a handover, issues of unsuccessful handovers and call drops for UEs are resolved.

Referring now to <FIG>, a flowchart of a method for neighbor relation management in a wireless broadband network is illustrated, in accordance with an embodiment. In the wireless broadband network, the SBS receives a plurality of signal measurement reports from a plurality of UEs that are associated with the SBS. These plurality of signal measurement reports may be sent periodically by associated UEs to the SBS after a predefined time interval or in response to a request from the SBS. The plurality of signal measurement reports are associated with a plurality of NBSs of the SBS. By way of an example, the eNB <NUM> receives signal measurement reports from each of the UE <NUM>, UE <NUM>, and UE <NUM>. These signal measurement reports are associated with one or more of the eNBs <NUM>-<NUM>. Based on their respective locations, the UE <NUM> may send signal measurement reports associated with the eNB <NUM>, the UE <NUM> may send signal measurement reports associated with each of the eNB <NUM>, eNB <NUM>, and eNB <NUM>, and the UE <NUM> may send signal measurement reports associated with the eNB <NUM> and eNB <NUM>. A signal measurement report received for an NBS includes details associated with the quality of the signal received from the NBS. The quality of the signal may, for example, be measured using a parameter that may include, but is not limited to, Reference Signal Received Power (RSRP), Signal to Noise Ratio (SNR), Received Signal Strength Indicator (RSSI), Channel Quality Indicator (CQI), and/or Reference Signal Received Quality (RSRQ).

The plurality of signal measurement reports are received for the NBSs that are already configured with the SBSs, i.e., configured NBSs, and for the NBSs that are not already configured with the SBS, i.e., new NBSs. A Neighbor Relation Table (NRT) at the SBS would already include one or more configured NBSs, based on the maximum number of NBSs defined for the NRT (for example, <NUM> NBSs). The NRT, at this time, may not include new NBSs, which may be later added to the NRT as elaborated further. By way of an example, an NRT for the eNB <NUM> may be represented by table <NUM> given below, when the already configured NBSs for the eNB <NUM> include the eNBs <NUM>-<NUM>. The eNBs <NUM> - <NUM> are new NBSs which are not yet configured with the eNB <NUM> and thus not included in the NRT.

The SBS, at step <NUM>, dynamically selects from the plurality of signal measurement reports, a set of signal measurement reports that were received within a predefined time interval. The predefined time interval for selecting the set of signal measurement reports may be defined by an administrator and may be reconfigured based on handover performance for increased efficiency of the UE handover. A signal measurement report in the set may be selected based on a location of origin of the signal measurement reports, i.e., location of the UE sending the signal measurement report. Additionally, for selecting the signal measurement report, variation of signal quality of the signal measurement report with respect to an average signal quality associated with the plurality of signal measurement reports is also considered. In other words, the signal measurement report is included in the set by the SBS, when the signal quality associated with the signal measurement report is greater than the average signal quality computed for the plurality of signal measurement reports. This is further explained in conjunction with <FIG> and <FIG>.

At step <NUM>, using the set of signal measurement reports, the SBS, samples signal level values of a plurality of configured NBSs for a predefined sampling time period. The predefined sampling time period may be represented as τSample. The SBS, at step <NUM>, also samples signal level values for one or more new NBSs that have signal level values greater than a predefined threshold for the predefined sampling time period. The predefined threshold may be represented as δINFLECTION_TH. The set of signal measurement reports includes signal measurement reports for the plurality of configured NBSs and the one or more new NBSs. In other words, NBSs for which the set of signal measurement reports was received, include the plurality of configured NBSs and the one or more new NBSs.

After sampling the signal values for the predefined sampling time period, a signal level time gradient is determined for each of the plurality of configured NBSs and the one or more new NBSs using a regression technique. A signal level time gradient for an NBS is determined based on a relationship modelled by the SBS between measured signal level value for the NBS and a time period required to measure that signal level value. This is further explained in detail in conjunction with <FIG> and <FIG>.

In response to sampling the signal level values, the SBS, at step <NUM> computes a retention factor for each of the plurality of configured NBSs and each of the one or more new NBSs. The retention factor for an NBS is a preferably a value that reflects or represents ability of the NBS to become a target NBS for handover of the UE. The retention factor for an NBS may be computed based on a signal level time gradient for the NBS. The retention factor is also computed based on inactivity time associated with the NBS, which is the time period during which no measured signal level is reported by any UE for that NBS. Additionally, the retention factor is computed using the handover failure rate experienced by the NBS, traffic load at the NBS, and interference level at the NBS, which may be computed as the average level of downlink interference experienced from the NBS by one or more UEs.

In an exemplary embodiment, a retention factor for an NBS may be computed using the equation (<NUM>) given below: <MAT> where,.

In addition to computing retention factors for each of the plurality of configured NBSs and the one or more new NBSs, the SBS also computes retention factors for each NBS that is included in the NRT. In an embodiment, the NBSs present in the NRT may be the same as the plurality of configured NBSs. In this case, by computing the retention factors for the plurality of configured NBSs, the SBS also exhausts the NBSs in the NRT. In another embodiment, the plurality of configured NBSs may be a subset of the NBSs included in the NRT. In this case, after computing the retention factors for the plurality of configured NBSs, the SBS computes retention factors for the NBSs in the NRT that were not included in the plurality of configured NBSs. This is further explained in detail in conjunction with <FIG> and <FIG>.

Based on the retention factors computed for the NBSs in the NRT, the SBS ranks each of the NBSs in the NRT, such that, the NBS that has the highest retention factor in the NRT is assigned the highest rank and the NBS that has the lowest retention factor in the NRT is assigned the lowest rank. Based on the ranking of the NBSs in the NRT, the SBS determines a relative rank for one or more NBSs that are not already present in the NRT. The one or more NBSs, for which the relative rank is determined, may be the same as the one or more new NBSs.

By way of an example, referring back to the NRT of table <NUM>, when ranks have been determined for each of the eNBs <NUM>-<NUM>, the relative ranks are determined for the new NBSs, i.e., the eNBs <NUM>-<NUM>, based on the ranks assigned to each of the eNBs <NUM>-<NUM>. In an embodiment, the one or more NBSs, for which the relative rank is determined, are a subset of the plurality of configured NBSs. The one or more NBSs are temporarily updated to the NRT based on their relative ranking. The NRT may be pruned later in order to keep the total number of NBSs in conformance with the maximum number of NBSs allowed to be retained in the NRT. The rankings, thus assigned by the SBS are used to perform handover of one or more of the plurality of UEs associated with the SBS to one or more NBSs included in the NRT. This is further explained in detail in conjunction with <FIG> and <FIG>.

Referring now to <FIG> and <FIG>, a flowchart of a method for performing UE handover in a wireless broadband network based on neighbor relation management is illustrated, in accordance with an embodiment. After the plurality of signal measurement reports have been received by the SBS from the plurality of UEs associated with the SBS, the SBS, at step <NUM>, determines a sample set of signal measurement reports within a predefined time interval from the plurality of signal measurement reports. The sample set is determined based on the average of signal quality associated with the plurality of signal measurement reports. In other words, only those signal measurement reports are included in the sample set, for which the signal quality measured within the predefined time interval is greater than the average of signal quality associated with the plurality of signal measurement reports.

Thereafter, the SBS, at step <NUM>, compares each of the plurality of signal measurement reports with the sample set of signal measurement reports based on the location of origin (i.e., the location of UEs sending these reports) and variation of signal quality from the average signal quality associated with the sample set, to select a set of signal measurement reports. In other words, the signal quality for each signal measurement report in the set is greater than the average of signal quality associated with the sample set.

Once the set of signal measurement reports has been selected, the SBS, at step <NUM>, samples signal level values of a plurality of configured NBSs and one or more NBSs from the set of signal measurement reports for a predefined sampling time period. The predefined sampling time period may be represented as τSample. The SBS samples signal level values only for those new NBSs that have signal level values greater than a predefined threshold, for the predefined sampling time period. This has been explained in detail in conjunction with <FIG>. At step <NUM>, the SBS computes a signal level time gradient for each of the plurality of configured NBSs and each of the one or more NBSs using a regression technique. In an embodiment, a linear regression is used to determine a linear relationship of the sampled signal level values versus time for each of the plurality of configured NBSs and each of the one or more NBSs. In an exemplary embodiment, the linear relation for an NBS may be represented using equation (<NUM>) given below: <MAT> where,.

In the above the equation, m is the slope of the linear relationship and it depicts the rate at which signal level value changes with respect to time for the NBS. A positive signal level time gradient indicates that the signal level value changes at a positive rate, while a negative signal level time gradient indicates that the signal level value changes at a negative rate. Thereafter, at step <NUM>, the SBS computes a retention factor for each of the plurality of configured NBSs and each of the one or more NBSs, based on one or more of an associated signal level time gradient, inactivity time, handover failure rate, traffic load at the NBS, and/or interference level. The SBS also computes retention factor for each NBS included in the NRT and updates the NRT with values of these retention factors. This has been explained in detail in conjunction with <FIG>.

By way of an example, with reference to the NRT of table <NUM>, eNB <NUM> may compute the retention factors for NBSs in the NRT as given in table <NUM> and the retention factors for other new NBSs as given in table <NUM>.

At step <NUM>, the SBS ranks NBSs listed within its NRT based on the retention factors computed for these NBSs. As discussed in <FIG>, at this point, the NRT would only include NBSs that are already configured with the SBS. In continuation of the example above and referring back to the table <NUM>, the eNB <NUM> (SBS) assigns a rank to each of the eNBs <NUM>-<NUM> based on the retention factors computed for them. This assignment of ranks is depicted by table <NUM> given below:.

At step <NUM>, the SBS determines a relative rank for one or more NBSs not already present in the NRT. These one or more NBSs may be a part of the plurality of configured NBSs or the one or more new NBSs. In continuation of the example above, based on the retention factors as depicted in the table <NUM> and the ranks assigned in the table <NUM>, the eNB <NUM> determines relative ranks for eNBs <NUM>-<NUM> and modifies the rank assigned to the NBSs in the NRT. This is depicted in table <NUM> given below:.

Thereafter, at step <NUM>, the SBS temporarily updates the NRT by adding the one or more NBSs into the NRT, such that the signal level time gradient for each of the one or more NBSs is greater than a gradient threshold, i.e., σth. The NBSs that are temporarily updated in the NRT may be marked with a potential NBS flag/tag. In continuation of the example above, the signal level time gradient for each of the new NBSs, i.e., the eNBs <NUM>-<NUM>, is greater than the gradient threshold, thus the NRT of table <NUM> is updated to include the eNBs <NUM>-<NUM>. Once the NRT has been temporarily updated, the SBS performs a check, at step <NUM>, to determine whether the total number of NBSs in the NRT is greater than a threshold number for the NRT. The maximum number of NBSs that can be included in an NRT, can be based on the standard, such as <NUM> in 3GPP TS <NUM> V8. <NUM>, however, an administrator may set the threshold number to be lower than <NUM>.

If the total number of NBSs in the NRT, after being temporarily updated, is greater than the threshold number, SBS, at step <NUM>, removes one or more low ranked NBSs from the NRT. In continuation of the example above, the threshold number of NBSs for the NRT may be fixed at <NUM>. As the total number of NBSs in the NRT after being temporarily updated is <NUM>, two NBSs that have the lowest ranks are removed from the temporarily updated NRT. Referring back to table <NUM>, as the eNB <NUM> has <NUM>th rank and the eNB <NUM> has <NUM>th rank, both these eNBs are removed from the temporarily updated NRT. As a result, the NRT is permanently updated.

Thereafter, at step <NUM>, the SBS performs handover of one or more of the plurality of UEs to one or more NBSs selected from one of the plurality of configured NBSs or the one or more new NBSs that are included in the permanently updated NRT. These one or more NBSs are selected based on the ranks assigned to the NBSs in the NRT. In continuation of the example given above, as the eNB <NUM> is assigned the <NUM>st rank in the NRT, handover of a UE from the eNB <NUM> to the eNB <NUM> is performed. Based on the handover performance associated with the handover of the one or more UEs, the SBS, at step <NUM>, reconfigures the predefined time interval and the predefined sampling time period. Referring back to step <NUM>, if the total number of NBSs in the NRT after being temporarily updated is less than or equal to the threshold number, the control moves to step <NUM>.

As a result, the methods discussed above enable a time based assessment of the measured signal levels of NBSs, such that, only the prospective NBSs are added into the NRT. As there is an upper number limit for adding NBSs into the NRT, the effective management of the NRT by removal of the least prospective NBSs, when the NRT is full, leads to preemption of the NBSs. Moreover, since the prospective NBSs in the NRT are ordered based on their suitability ranking for a handover, issues of unsuccessful handovers and call drops for UEs are resolved.

<FIG> is a block diagram of an exemplary computer system for implementing various embodiments. A computer system <NUM> may include a central processing unit ("CPU" or "processor") <NUM>. The processor <NUM> may include at least one data processor for executing program components for executing user or system-generated requests. A user may include a person, a person using a device such as such as those included in this disclosure, or a device itself. The processor may include specialized processing units such as integrated system (bus) controllers, memory management control units, floating point units, graphics processing units, digital signal processing units, etc. The processor may include a microprocessor, such as AMD Athlon, Duron or Opteron, ARM's application, embedded or secure processors, IBM PowerPC, Intel's Core, Itanium, Xeon, Celeron or other line of processors, etc. The processor <NUM> may be implemented using a mainframe, distributed processor, multi-core, parallel, grid, or other architectures. Some embodiments may utilize embedded technologies like application-specific integrated circuits (ASICs), digital signal processors (DSPs), Field Programmable Gate Arrays (FPGAs), etc..

The processor <NUM> may be disposed in communication with one or more input/output (I/O) devices via an I/O interface <NUM>. The I/O interface <NUM> may employ communication protocols/methods such as, without limitation, audio, analog, digital, monoaural, RCA, stereo, IEEE-<NUM>, serial bus, universal serial bus (USB), infrared, PS/<NUM>, BNC, coaxial, component, composite, digital visual interface (DVI), high-definition multimedia interface (HDMI), RF antennas, S-Video, VGA, IEEE <NUM>. n /b/g/n/x, Bluetooth, cellular (e.g., code-division multiple access (CDMA), high-speed packet access (HSPA+), global system for mobile communications (GSM), long-term evolution (LTE), WiMax, or the like, etc..

Using the I/O interface <NUM>, the computer system <NUM> may communicate with one or more I/O devices. For example, an input device <NUM> may be an antenna, keyboard, mouse, joystick, (infrared) remote control, camera, card reader, fax machine, dongle, biometric reader, microphone, touch screen, touchpad, trackball, sensor (e.g., accelerometer, light sensor, GPS, gyroscope, proximity sensor, or the like), stylus, scanner, storage device, transceiver, video device/source, visors, etc. An output device <NUM> may be a printer, fax machine, video display (e.g., cathode ray tube (CRT), liquid crystal display (LCD), light-emitting diode (LED), plasma, or the like), audio speaker, etc. In some embodiments, a transceiver <NUM> may be disposed in connection with the processor <NUM>. The transceiver <NUM> may facilitate various types of wireless transmission or reception. For example, the transceiver <NUM> may include an antenna operatively connected to a transceiver chip (e.g., Texas Instruments WiLink WL1283, Broadcom BCM4750IUB8, Infineon Technologies X-Gold <NUM>-PMB9800, or the like), providing IEEE <NUM>. 11a/b/g/n, Bluetooth, FM, global positioning system (GPS), <NUM>/<NUM> HSDPA/HSUPA communications, etc..

In some embodiments, the processor <NUM> may be disposed in communication with a communication network <NUM> via a network interface <NUM>. The network interface <NUM> may communicate with the communication network <NUM>. The network interface <NUM> may employ connection protocols including, without limitation, direct connect, Ethernet (e.g., twisted pair <NUM>/<NUM>/<NUM> Base T), transmission control protocol/internet protocol (TCP/IP), token ring, IEEE <NUM>. 11a/b/g/n/x, etc. The communication network <NUM> may include, without limitation, a direct interconnection, local area network (LAN), wide area network (WAN), wireless network (e.g., using Wireless Application Protocol), the Internet, etc. Using the network interface <NUM> and communication network <NUM>, the computer system <NUM> may communicate with the devices <NUM>, <NUM>, and <NUM>. These devices may include, without limitation, personal computer(s), server(s), fax machines, printers, scanners, various mobile devices such as cellular telephones, smartphones (e.g., Apple iPhone, Blackberry, Android-based phones, etc.), tablet computers, eBook readers (Amazon Kindle, Nook, etc.), laptop computers, notebooks, gaming consoles (Microsoft Xbox, Nintendo DS, Sony PlayStation, etc.), or the like. In some embodiments, computer system <NUM> may itself embody one or more of these devices.

In some embodiments, the processor <NUM> may be disposed in communication with one or more memory devices (e.g., RAM <NUM>, ROM <NUM>, etc.) via a storage interface <NUM>. The storage interface <NUM> may connect to memory <NUM> including, without limitation, memory drives, removable disc drives, etc., employing connection protocols such as serial advanced technology attachment (SATA), integrated drive electronics (IDE), IEEE-<NUM>, universal serial bus (USB), fiber channel, small computer systems interface (SCSI), etc. The memory drives may further include a drum, magnetic disc drive, magneto-optical drive, optical drive, redundant array of independent discs (RAID), solid-state memory devices, solid-state drives, etc..

The memory <NUM> may store a collection of program or database components, including, without limitation, an operating system <NUM>, a user interface <NUM>, a web browser <NUM>, a mail server <NUM>, a mail client <NUM>, a user/application data <NUM> (e.g., any data variables or data records discussed in this disclosure), etc. The operating system <NUM> may facilitate resource management and operation of the computer system <NUM>. Examples of the operating system <NUM> include, without limitation, Apple Macintosh OS X, Unix, Unix-like system distributions (e.g., Berkeley Software Distribution (BSD), FreeBSD, NetBSD, OpenBSD, etc.), Linux distributions (e.g., Red Hat, Ubuntu, Kubuntu, etc.), IBM OS/<NUM>, Microsoft Windows (XP, Vista/<NUM>/<NUM>, etc.), Apple iOS, Google Android, Blackberry OS, or the like. The user interface <NUM> may facilitate display, execution, interaction, manipulation, or operation of program components through textual or graphical facilities. For example, user interfaces may provide computer interaction interface elements on a display system operatively connected to the computer system <NUM>, such as cursors, icons, check boxes, menus, scrollers, windows, widgets, etc. Graphical user interfaces (GUIs) may be employed, including, without limitation, Apple Macintosh operating systems' Aqua, IBM OS/<NUM>, Microsoft Windows (e.g., Aero, Metro, etc.), Unix X-Windows, web interface libraries (e.g., ActiveX, Java, Javascript, AJAX, HTML, Adobe Flash, etc.), or the like.

In some embodiments, the computer system <NUM> may implement the web browser <NUM> as a stored program component. The web browser <NUM> may be a hypertext viewing application, such as Microsoft Internet Explorer, Google Chrome, Mozilla Firefox, Apple Safari, etc. Secure web browsing may be provided using HTTPS (secure hypertext transport protocol), secure sockets layer (SSL), Transport Layer Security (TLS), etc. Web browsers may utilize facilities such as AJAX, DHTML, Adobe Flash, JavaScript, Java, application programming interfaces (APIs), etc. In some embodiments, the computer system <NUM> may implement the mail server <NUM> as a stored program component. The mail server <NUM> may be an Internet mail server such as Microsoft Exchange, or the like. The mail server may utilize facilities such as ASP, ActiveX, ANSI C++/C#, Microsoft. NET, CGI scripts, Java, JavaScript, PERL, PHP, Python, WebObjects, etc. The mail server may utilize communication protocols such as internet message access protocol (IMAP), messaging application programming interface (MAPI), Microsoft Exchange, post office protocol (POP), simple mail transfer protocol (SMTP), or the like. In some embodiments, the computer system <NUM> may implement the mail client <NUM> as a stored program component. The mail client <NUM> may be a mail viewing application, such as Apple Mail, Microsoft Entourage, Microsoft Outlook, Mozilla Thunderbird, etc..

In some embodiments, the computer system <NUM> may store the user/application data <NUM>, such as the data, variables, records, etc. as described in this disclosure. Such databases may be implemented as fault-tolerant, relational, scalable, secure databases such as Oracle or Sybase. Alternatively, such databases may be implemented using standardized data structures, such as an array, hash, linked list, struct, structured text file (e.g., XML), table, or as object-oriented databases (e.g., using ObjectStore, Poet, Zope, etc.). Such databases may be consolidated or distributed, sometimes among the various computer systems discussed above in this disclosure. It is to be understood that the structure and operation of the any computer or database component may be combined, consolidated, or distributed in any working combination.

It will be appreciated that, for clarity purposes, the above description has described embodiments with reference to different functional units and processors. However, it will be apparent that any suitable distribution of functionality between different functional units, processors or domains may be alternatively used. For example, functionality illustrated to be performed by separate processors or controllers may be performed by the same processor or controller. Hence, references to specific functional units are only to be seen as references to suitable means for providing the described functionality, rather than indicative of a strict logical or physical structure or organization.

Various embodiments disclose methods and systems for neighbor relation management in wireless broadband networks. The method and system enable a time based assessment of the measured signal levels of NBSs, such that, only prospective NBSs are added into the NRT. As there is an upper number limit for adding the NBSs into the NRT, the effectively management of the NRT by removal of the least prospective NBSs, when the NRT is full, leads to preemption of the NBSs. Moreover, as the prospective NBSs in the NRT are ordered based on their suitability ranking for a handover, issues of unsuccessful handovers and call drops for UEs are resolved.

The specification has described methods and systems for neighbor relation management in wireless broadband networks.

Claim 1:
A method of neighbor relation management in a wireless broadband network (<NUM>), the method being performed by a Serving Base Station, SBS (<NUM>), and comprising:
dynamically selecting (<NUM>) a set of signal measurement reports from a plurality of signal measurement reports received within a predefined time interval from a plurality of user equipments, UEs, associated with the SBS, each signal measuring report including a level of a signal received by corresponding one of said plurality of UEs from a corresponding Neighboring Base Station, NBS (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) among a plurality of NBSs, wherein said plurality of NBSs includes a plurality of configured NBSs comprised in a Neighboring Relation Table, NRT (<NUM>), within the SBS and at least one new NBS which is not comprised in the NRT, and wherein the step of dynamically selecting is based on at least one of: a location of origin of each of the plurality of signal measurement reports, and a comparison of the signal level of each of the plurality of signal measurement reports with respect to an average signal level associated with the plurality of signal measurement reports;
sampling (<NUM>; <NUM>) the dynamically selected set of signal measurement reports for a predefined sampling period to obtain sampled signal level values of the plurality of configured NBSs (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>), and to obtain, for the at least one new NBS (<NUM>, <NUM>, <NUM>, <NUM>) sampled signal level values which are greater than a predefined threshold;
computing (<NUM>) based on the sampled signal level values, a signal level time gradient for each of the plurality of configured NBSs and for each of the at least one new NBS, wherein for each of said NBSs the signal level time gradient is computed (<NUM>) using a regression technique based on a relationship modelled by the SBS between the measured signal level value associated with the NBS and a time at which the signal level value is measured; and
computing (<NUM>; <NUM>) a retention factor for each of the plurality of configured NBSs (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) and for each of the at least one new NBS (<NUM>, <NUM>, <NUM>, <NUM>) based on the respective computed signal level time gradient, wherein for each of said NBSs the retention factor of a NBS is a value that represents an ability of the NBS to become a target NBS for handover of a User Equipment, UE, from said SBS.