This invention relates generally to wireless communication and, more specifically, relates to distribution of UEs in wireless networks.
This section is intended to provide a background or context to the invention disclosed below. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise explicitly indicated herein, what is described in this section is not prior art to the description in this application and is not admitted to be prior art by inclusion in this section. Acronyms used in the specification and/or drawings are defined below, prior to the claims.
Over the past year due to rapid growth in data traffic, operators are deploying additional LTE carriers to maintain and/or improve user experience. These new carriers can overlay the original carriers and provide improved bandwidth, which improves user experience. One way of conceptualizing this type of system is through the use of layers, which are mapped to a cell and include frequency and possibly other characteristics (such as radio access technologies) to distinguish between the layers. In such multi-band radio access deployment using one or various technologies, there is a need to distribute UEs in a geographical area across overlying layers to maximize the use of the entire available spectrum.
One commercially deployed approach to distribute the UEs is to load balance without additional RRC signaling messages based, e.g., on operator configured thresholds or a round robin mechanism during the release of the UE as it is being transitioned to idle mode. This technique works well when multiple frequencies are deployed in the same band, as each of the frequencies have similar coverage. As an example, the frequency band referred to as number 18 in EUTRAN may have downlink EUTRAN frequencies of 860 MHz, 875 MHz. These would have similar coverage areas, which may be considered to be an area over which a UE can connect to a base station using the particular frequency range.
There are certain problems, described below, which may occur when attempting to distribute the UEs, e.g., to perform load balancing at the time of transitioning UEs to idle mode.
This section contains examples of possible implementations and is not meant to be limiting.
A method includes selecting, from a set of overlaying cells using one or more radio access technologies and a plurality of different frequencies and whose coverage areas for the cells in the set partially or completely overlay each other, a reduced set of overlaying cells to provide access to user equipment, wherein the selection is based on location of the user equipment within the overlaying cells and estimates of coverage areas of the overlaying cells. The method further includes performing distribution of user equipment across the selected overlaying cells based on a desired statistical distribution for the user equipment across the cells in the reduced set of cells, wherein the desired statistical distribution takes into account the one or more radio access technologies and the plurality of different frequencies.
An additional exemplary embodiment includes a computer program, comprising code for performing the method of the previous paragraph, when the computer program is run on a processor. The computer program according to this paragraph, wherein the computer program is a computer program product comprising a computer-readable medium bearing computer program code embodied therein for use with a computer.
An exemplary apparatus includes one or more processors and one or more memories including computer program code. The one or more memories and the computer program code are configured to, with the one or more processors, cause the apparatus to perform at least the following: selecting, from a set of overlaying cells using one or more radio access technologies and a plurality of different frequencies and whose coverage areas for the cells in the set partially or completely overlay each other, a reduced set of overlaying cells to provide access to user equipment, wherein the selection is based on location of the user equipment within the overlaying cells and estimates of coverage areas of the overlaying cells; and performing distribution of user equipment across the selected overlaying cells based on a desired statistical distribution for the user equipment across the cells in the reduced set of cells, wherein the desired statistical distribution takes into account the one or more radio access technologies and the plurality of different frequencies.
An exemplary computer program product includes a computer-readable storage medium bearing computer program code embodied therein for use with a computer. The computer program code includes: code for selecting, from a set of overlaying cells using one or more radio access technologies and a plurality of different frequencies and whose coverage areas for the cells in the set partially or completely overlay each other, a reduced set of overlaying cells to provide access to user equipment, wherein the selection is based on location of the user equipment within the overlaying cells and estimates of coverage areas of the overlaying cells; and code for performing distribution of user equipment across the selected overlaying cells based on a desired statistical distribution for the user equipment across the cells in the reduced set of cells, wherein the desired statistical distribution takes into account the one or more radio access technologies and the plurality of different frequencies.
Another exemplary embodiment is an apparatus comprising: means for selecting, from a set of overlaying cells using one or more radio access technologies and a plurality of different frequencies and whose coverage areas for the cells in the set partially or completely overlay each other, a reduced set of overlaying cells to provide access to user equipment, wherein the selection is based on location of the user equipment within the overlaying cells and estimates of coverage areas of the overlaying cells; and means for performing distribution of user equipment across the selected overlaying cells based on a desired statistical distribution for the user equipment across the cells in the reduced set of cells, wherein the desired statistical distribution takes into account the one or more radio access technologies and the plurality of different frequencies.
In the attached Drawing Figures:
As indicated above, there are certain problems, which may occur when attempting to distribute the UEs at the time of transitioning to idle mode. These problems and example solutions are presented after a system into which examples of embodiments may be used is described.
Turning to
The base station 170 is a network node that provides access by wireless devices such as the UE 110 to the wireless network 100. The base station 170 may be an eNB supporting LTE systems or another radio access network supporting other systems such as legacy 3GPP systems or some combination of these. For instance, the base station 170 could include base transceiver station/NodeB and/or RNC functionality. For ease of reference, the base station 170 is considered to be an eNB with the ability to be in deployments such as legacy 3GPP and LTE systems.
The eNB 170 includes one or more processors 152, one or more memories 155, one or more network interfaces (N/W I/F(s)) 161, and one or more transceivers 160 interconnected through one or more buses 157. Each of the one or more transceivers 160 includes a receiver, Rx, 162 and a transmitter, Tx, 163. The one or more transceivers 160 are connected to one or more antennas 158. The one or more memories 155 include computer program code 153.
The eNB 170 includes a distribution module 150 that performs distribution (e.g., load balancing) of UEs at the time of transitioning to idle mode. The module 150 may therefore be considered to be a distributing UEs at the time of transitioning to idle mode module 150. For ease of reference, this module will be referred to as the distribution module 150. The distribution module 150 comprises one of or both parts 150-1 and/or 150-2, which may be implemented in a number of ways. The distribution module 150 may be implemented in hardware as module 150-1, such as being implemented as part of the one or more processors 152. The distribution module 150-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, the distribution module 150 may be implemented as load balancing mode module 150-2, which is implemented as computer program code 153 and is executed by the one or more processors 152. For instance, the one or more memories 155 and the computer program code 153 are configured to, with the one or more processors 152, cause the eNB 170 to perform one or more of the operations as described herein. The one or more network interfaces 161 communicate over a network such as via the links 176 and 131. Two or more eNBs 170 communicate using, e.g., link 176. The link 176 may be wired or wireless or both and may implement, e.g., an X2 interface.
It is noted that description herein indicates that “cells” perform functions, but it should be clear that the eNB that forms the cell will perform the functions. A cell makes up part of an eNB. That is, there can be multiple cells per eNB. For instance, there could be three cells for a single eNB carrier frequency and associated bandwidth, each cell covering one-third of a 360 degree area so that the single eNB's coverage area covers an approximate oval or circle. Furthermore, each cell can correspond to a single carrier and an eNB may use multiple carriers. So if there are three 120 degree cells per carrier and two carriers, then the eNB has a total of six cells.
The one or more buses 157 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, wireless channels, and the like. For example, the one or more transceivers 160 may be implemented as a remote radio head (RRH) 195, with the other elements of the eNB 170 being physically in a different location from the RRH, and the one or more buses 157 could be implemented in part as fiber optic cable to connect the other elements of the eNB 170 to the RRH 195.
The wireless network 100 may include a network control element (NCE) 190 that may include MME/SGW functionality, and which provides connectivity with a further network, such as a telephone network and/or a data communications network (e.g., the Internet). The eNB 170 is coupled via a link 131 to the NCE 190. The link 131 may be implemented as, e.g., an SI interface. The NCE 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N/W I/F(s)) 180, interconnected through one or more buses 185. The one or more memories 171 include computer program code 173. The one or more memories 171 and the computer program code 173 are configured to, with the one or more processors 175, cause the NCE 190 to perform one or more operations.
The wireless network 100 may implement network virtualization, which is the process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network. Network virtualization involves platform virtualization, often combined with resource virtualization. Network virtualization is categorized as either external, combining many networks, or parts of networks, into a virtual unit, or internal, providing network-like functionality to software containers on a single system. Note that the virtualized entities that result from the network virtualization are still implemented, at some level, using hardware such as processors 152 or 175 and memories 155 and 171, and also such virtualized entities create technical effects.
The computer readable memories 125, 155, and 171 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The processors 120, 152, and 175 may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples.
In general, the various embodiments of the user equipment 110 can include, but are not limited to, cellular telephones such as smart phones, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, tablets with wireless communication capabilities, as well as portable units or terminals that incorporate combinations of such functions.
Turning to
Overlapping cells will have areas where there is coverage overlap from both cells and areas where only a subset of the cells provides coverage. In this example, there are locations 260-1 and 260-2 where the angle of arrival (AoA) criteria are not met and location 270 where the timing advance (TA) criteria are not met. As indicated by reference 280, both the AoA and the TA criteria are met in the overlap area. The UE 110 has an AoA 285 that does meet the AoA criteria. The UE 110 also has a timing advance (TA) 290 that does not meet timing advance criteria, as illustrated by reference 270. As both criteria are not met, the UE is considered not in the cell coverage overlap area.
Also shown is an access distance 250, which is a distance from the eNB 170 to the UE 110 at a point at which the UE is accessing the radio network. The AoA (usually azimuth) in an angle from which a signal arrives relative to a reference angle of an antenna array.
As stated above, there are certain problems, which may occur at the time of attempting to distribute the UEs at a time of transitioning to idle mode. For example, in a multi-band, multi-frequency deployment, the cell coverage area 210 differs based on the band used as can be seen in the propagation model of
The load balancing UEs at the time of transitioning to idle mode approach works well when the overlying cells have the same coverage. It has been observed in the commercial deployment that the UEs are unevenly distributed in a multi-band multi-frequency deployment due to the difference in cell coverage. This is illustrated by
Thus, the load balancing UEs at the time of transitioning to idle mode approach used in a multi-band multi-frequency deployment does not meet the objective of load balancing, as the UE access distribution does not reflect the factors provisioned by the operator. To overcome this, the following methods have been attempted.
Method 1. In this method, an operator artificially biases the operator-provisionable distribution factors in such a way that the desired distribution is achieved. In particular, in this method, a weighted round-robin scheme to select the target layer (e.g., frequency and corresponding cell) to which a UE shall be released with dedicated cell re-selection priority. The ratio of UEs for which the load balancing at the time of transitioning to idle mode is applied is controlled by operator-provisioned settings. The operator provisions the weighting factor used for each configured intra-LTE and inter-RAT cell re-selection target. At the time of sending RRC: RRC Connection Release message to the UE, the serving cell determines based on operator-provisioned factors which overlaying layer should be given the highest priority. The target layer selection is based on the weights and the round robin scheme, thus the operator can distribute UEs in a geographical area across the overlaying layers.
For example, in a typical operator scenario with a low and high band LTE deployment with equal bandwidth and capacity, the operator desires to achieve a 50:50 distribution across the layers. But, due to unequal coverage between high and low bands, the distribution factors have to be provisioned such that higher factor of UEs are sent from low band to high band. This increases the number of UEs on the high band, decreases the utilization of low band and increases the utilization on the high band to match the utilization of the low band. In this approach, the biased weighting factor is applied to all UEs in the low band. This adversely impacts the UEs on the lower band, where there is no overlaying high band coverage. In the areas where the higher frequency band coverage is not available, the UEs fail to access the higher band and re-acquire the lower band. This adversely affects the battery life of the UE (estimated at about 6-10 percent) due to unproductive inter-frequency cell reselections. Further, during the reselection window, the UE is unavailable for data traffic.
More particularly, the plots in
Method 2). An alternative method is to perform inter-frequency measurement at the UE 110 to determine which cells are providing access at its location prior to determining the target carrier and corresponding cell for load balancing UEs at the time of transitioning to idle mode. The enhanced approach would be for the eNB to determine the layers which are available for the UE at the location of the UE. This can be achieved by performing the measurement of the overlaying inter-frequency layers before releasing the UE. Based on the UE measurement report, the eNB acts to send the UE to a target layer which is available at the UE location. If there is no overlaying frequency available, then the UE will stay in the serving carrier.
This approach leads to N+1 RRC messages (N is the number of overlying frequencies) to and from the UE before release. This approach can help in achieving the desired UE distribution, but it has the following possible disadvantages:
So, solutions which address the above short comings are needed.
The examples herein propose examples of algorithms and devices for performing the algorithms to enhance the Method 1 load balancing UEs at the time of transitioning to idle mode solution. The enhancement in an example embodiment is based on the eNB 170 considering the following factors at the time of making a decision to release the UE:
1) UE access distance 250 within the cell site. This can be derived, for instance, using UE Rx-Tx difference information and the Angle of Arrival (AoA) measurements available for the UE at the eNB. Other possible techniques for determining access distances are described below.
2) Access coverage distances 240 of each of the overlying band classes. This can be based on an operator-provisioned data structure 600 as shown in Table 1 (see
With overlapping layers in an area, one example of an implementation is to have an effective distribution of UEs across these layers such that the UEs are accessing on different layers at the desired percentage factors. Each overlaying layer is associated with a unique cell, and the serving cell is the cell to which the UE is connected for service. In this method, the serving cell determines which layer the UE should be sent to so that the distribution of UEs in an area across overlaying layers is maintained.
It is noted that the data such as in
An alternative approach to the coverage distances 650 is for the eNB 170 to self-learn the coverage details based on access distances 250 and the distances at which inter-frequency handovers are attempted from a high frequency band cell to a lower frequency band cell for coverage reasons. These coverage distances are shown as coverage distance histogram 658. In the self-learning approach, it is possible in an exemplary embodiment that SON-based procedures will be used to perform the following:
In the example of
In addition to access distances 250, the angle of arrival can be also added as a decision metric. The angle of arrival for the operator-provisioned coverage angles of arrival 655 and the SON-derived angles of arrival histogram 657 are examples of this. If a UE is within the range of angles (e.g., 20-100 degrees for Cell IDs A and B), then the UE may be assigned to one of the cells having a cell ID A or B; if the UE is outside this range of angles, the UE is not assigned to one of the cells having the cell ID A or B. The references 660 and 670 are described below.
The examples herein are not limited to a single radio access technology such as E-UTRAN. Another possibility, for instance, for the tables 600-1 and 600-2 is illustrated by
The following example of an algorithm is proposed to enhance the load balancing UEs at the time of transitioning to idle mode. This example will be described in part through reference to
In response to a determination the UE should be released for distributing UEs at the time of transitioning to idle mode, the eNB 170 will determine the access distance 250 and possibly the angle of arrival 285 for the UE. The eNB 170 may use the UE Rx-Tx timing difference information monitored for each UE to determine the access distance 250, in an exemplary embodiment. Thus, in block 710, the eNB 170 determines whether it is time to release a UE for distributing UEs at the time of transitioning to idle mode. For instance, the eNB 170 could detect inactivity for the UE or an MME could initiate the release of the UE. If not (block 710=No), the eNB 170 waits (e.g., by returning to block 710) until it is time to release a UE.
If it is time to release the UE for distributing (e.g., load balancing) UEs at the time of transitioning to idle mode (block 710=Yes), the eNB 170 in block 720 determines the access distance 250 (e.g., and angle of arrival 285) for the UE 110.
Based on the UE's current access distance 250, the eNB 170 filters out the overlying frequencies, e.g., which do not provide reliable access at this access distance. The eNB 170 may use the data structure 600 described above for this process, although the invention is not limited to this data structure. This allows the eNB 170 to identify the candidate layers (e.g., frequencies(s) and corresponding cells) which have reliable coverage at the UE's current access distance. When both the operator-provisioned details (see coverage distance 650 of
More specifically, in block 730, the eNB, based on the access distance 250 (e.g., and/or angle of arrival) for the UE and the coverage distances 240 (or 650 or 658) for the cells, will filter cells in a set of cells to determine a reduced set of cells. The coverage area profile 695, which is one or both of the coverage distances 240 (or 650 or 658) and/or the angles of arrival 655 and 657, may be used in block 730. Note that the cells in the original set are a set of cells that partially or completely overlie each other. For instance,
Block 730 characterizes this process as using cells (such as using cell IDs 610 in
Using the data structure 600-1 of
The distributing the UEs at the time of transitioning to idle mode is performed on the reduced set 670 rather than all the overlying carriers and their corresponding cells in the original set 660. Thus, in block 750, the eNB 170 performs distributing the UEs at the time of transitioning to idle mode for the UE based on the reduced set 670 of cells. Such distributing may be performed using many different techniques such as (block 760) load balancing techniques including, for instance, round robin load balancing (where the cells are selected in a circular order, e.g., 1, 2, 3, then 1, 2, 3 again). In block 770, the eNB 170 can release the UE 110 to a selected one of the cells in the reduced set of cells for distributing UEs at the time of transitioning to idle mode. When UE is released by the eNB, the eNB could specify the frequencies the UE can idle on and also set the priorities for different frequencies. Then the UE will use the information provided by eNB and reselect a frequency. The UE is released when the UE is in connected mode. Due to inactivity, the eNB could release the UE. As another example, the MME also could initiate the release of the UE.
Note that an eNB 170 can share each coverage area profile of a cell across overlaying cells for the base station. That is, if the single eNB 170 creates multiple overlaying cells, the coverage area profiles 690 (with coverage areas 650/658 and/or angles of arrival 655/657) may be shared across the overlaying cells. In another example, multiple base stations may create the multiple overlaying cells and the base station(s) may share each coverage area profile 690 of a cell across these multiple base stations. That is, one specific base station may share its coverage area profiles 695 with other base stations, and those base stations may share their coverage area profiles 695 with the specific base station.
The example charts described below show the benefit of the proposed examples and the set of UEs where the negative impact can be prevented. These charts are derived from field data on UEs access on high and low bands.
In
The examples of embodiments herein may be used by legacy 3GPP and LTE operators. Both macro and small cell deployment will benefit from the examples. An exemplary embodiment proposes inclusion of access distances and potentially angle of arrival to make a decision on a suitable candidate set of overlying carriers. In addition, GPS based location can be used to get the UE's current location accurately, but such an approach does add additional signaling to the UE and may not be available in all areas. Alternatively, the CQI measurements reported from the UE can be also used to get a distance estimate.
The embodiments provide one or more of the following benefits and technical effects over existing solutions:
Examples of possible embodiments include the following. A method, comprising: selecting, from a set of overlaying cells using one or more radio access technologies and a plurality of different frequencies and whose coverage areas for the cells in the set partially or completely overlay each other, a reduced set of overlaying cells to provide access to user equipment, wherein the selection is based on location of the user equipment within the overlaying cells and estimates of coverage areas of the overlaying cells; and performing distribution of user equipment across the selected overlaying cells based on a desired statistical distribution for the user equipment across the cells in the reduced set of cells, wherein the desired statistical distribution takes into account the one or more radio access technologies and the plurality of different frequencies.
Another example includes the method of the previous paragraph, wherein performing distribution of user equipment across overlaying cells further comprises selecting one of the cells in the reduced set of the cells and moving the user equipment to the selected cell. Another example is the method of this paragraph, wherein performing distribution of user equipment further comprises selecting one of the cells in the reduced set of the cells based on a share of user equipment to be distributed to each cell in the set of cells and moving the user equipment to the selected cell.
A further example includes the methods of the previous paragraphs, wherein each estimated coverage area is defined in part by a corresponding access distance range and selecting cells further comprises of determining an access distance for the user equipment and using the cells which have access distance range indicating that the cells are able to provide access for the user equipment based upon the determined access distance.
Another example is the method of the previous paragraph, wherein each estimated coverage area is defined in part by a corresponding range for angles of arrival for a cell and wherein selecting further comprises determining an angle of arrival of the user equipment and using the cells which have ranges for angles of arrival indicating the cells can provide access for the user equipment based upon the determined angle of arrival.
Another example is the method of the previous paragraph, wherein each estimate of the coverage area of each cell is derived based on stored measurement data of user equipment distance and of angle of arrival during access in the cell and handover traffic by the user equipment in the cell.
Another example is the method of the previous paragraph, further comprising sharing information defining a coverage area for a cell across overlaying cells for a base station. A further example is the method of the previous paragraph, further comprising sharing information defining a coverage area of a cell across multiple base stations each of which has at least one of the overlaying cells.
Another example is the methods of the previous three paragraphs, further comprising determining one or both of access distance or angle of arrival for the user equipment by using one or more of the following: reception-transmission difference information for the user equipment; global positioning system information received from the user equipment; channel quality information measurements reported from the user equipment; or phase measurement at the base station antenna.
A further example includes the methods of the previous paragraphs, wherein the selecting the reduced set of overlaying cells and the performing distribution are performed during a process resulting in transitioning the user equipment to an idle mode.
Another example is an apparatus comprising means for performing any of the methods of the previous paragraphs. For instance, the apparatus could comprise: means for selecting, from a set of overlaying cells using one or more radio access technologies and a plurality of different frequencies and whose coverage areas for the cells in the set partially or completely overlay each other, a reduced set of overlaying cells to provide access to user equipment, wherein the selection is based on location of the user equipment within the overlaying cells and estimates of coverage areas of the overlaying cells; and means for performing distribution of user equipment across the selected overlaying cells based on a desired statistical distribution for the user equipment across the cells in the reduced set of cells, wherein the desired statistical distribution takes into account the one or more radio access technologies and the plurality of different frequencies.
An exemplary apparatus includes one or more processors and one or more memories including computer program code. The one or more memories and the computer program code are configured to, with the one or more processors, cause the apparatus to perform any of the methods of the previous paragraphs.
Embodiments herein may be implemented in software (executed by one or more processors), hardware (e.g., an application specific integrated circuit), or a combination of software and hardware. In an example embodiment, the software (e.g., application logic, an instruction set) is maintained on any one of various conventional computer-readable media. In the context of this document, a “computer-readable medium” may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer, with one example of a computer described and depicted, e.g., in
If desired, the different functions discussed herein may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the above-described functions may be optional or may be combined.
Although various aspects of the invention are set out in the independent claims, other aspects of the invention comprise other combinations of features from the described embodiments and/or the dependent claims with the features of the independent claims, and not solely the combinations explicitly set out in the claims.
It is also noted herein that while the above describes example embodiments of the invention, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended claims.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:
2G second generation
3G third generation
3GPP third generation partnership project
AoA angle of arrival
BTS base transceiver station
CQI channel quality information
CDMA code-division multiple access
DL downlink (from base station to UE)
eNB or eNodeB base station, evolved Node B (e.g., LTE base station)
EUTRAN evolved universal terrestrial radio access network
GHZ giga-Hertz
ID identification
GPS global positioning system
km kilometers
LTE long term evolution
MHz mega-Hertz
MME mobility management entity
NCE network control element
RAT radio access technology
Rel release
RF radio frequency
RNC radio network control
RRC radio resource control
Rx reception or receiver
SGW serving gateway
SON self-organizing network
TA timing advance
TS technical specification
Tx transmission or transmitter
UE user equipment (e.g., a mobile wireless device)
UL uplink (from UE to base station)