WO2014117344A1

WO2014117344A1 - Methods, apparatuses, and systems for frequency planning

Info

Publication number: WO2014117344A1
Application number: PCT/CN2013/071150
Authority: WO
Inventors: Feifeng QIN
Original assignee: Nokia Siemens Networks Oy
Priority date: 2013-01-30
Filing date: 2013-01-30
Publication date: 2014-08-07

Abstract

Frequency planning may be used in various communication systems. For example, communication systems that are configured for wireless communication with terminal devices may benefit from frequency planning. More particularly, certain implementations of long term evolution (LTE) of the third generation partnership project (3GPP) may benefit from frequency planning methods, apparatuses, and systems. For example, a method may include dividing frequency resources available for a plurality of sectors into a plurality of carriers. The method may also include selecting at least one edge frequency carrier and at least one center frequency carrier for a sector of the plurality of sectors.

Description

METHODS, APPARATUSES, AND SYSTEMS FOR FREQUENCY

PLANNING

BACKGROUND:

Field:

[0001] Frequency planning may be used in various communication systems. For example, communication systems that are configured for wireless communication with terminal devices may benefit from frequency planning. More particularly, certain implementations of long term evolution (LTE) of the third generation partnership project (3 GPP) may benefit from frequency planning methods, apparatuses, and systems.

Description of the Related Art:

[0002] A major topology used in macro site LTE network planning is N-sector structure, where N is typically 3. In LTE network planning, frequency planning is used to deploy a frequency carrier (FC) for each sector.

[0003] Figure 1 illustrates a three-sector structure for an LTE macro network. As shown in Figure 1, the macro structure 100 can include three sectors, labeled Sector 0, Sector 1 , and Sector 2, clustered outward from a center point. A device at the center point can radiate, shown as arrows, into each of the sectors.

[0004] The frequency carrier (FC) planning includes the configurations of the frequency carrier reusing (FRU) factor and their power spectrum density (PSD), based on which, LTE network planners should also define the related rules for load balancing between frequency carriers, as well as for handover in order to support continuous coverage.

[0005] Figure 2 illustrates two approaches to frequency planning. As shown in Figure 2, there are two typical approaches for frequency planning for LTE network: same frequency networking and different frequency networking.

[0006] Same frequency networking shares one frequency carrier (FC), as the frequency reuse factor is 1 (FRU1), for each sector of the same macro site as shown in a first macro structure 210 on the left side of Figure 2. As illustrated, each sector is operating using F0. On the other hand, different frequency networking uses respectively N (typically 3) FCs for each sector of a single macro site, as the frequency reuse factor is N (FRU-N, for example, FRU3), as shown in a second macro structure 220 on the right hand side of Figure 2. The different patterning in the different sectors where FRU = 3, illustrates that different FCs are used, respectively F0, Fl, and F2.

[0007] If there is one set of spectrum resource which could be divided into N FCs, FRUl method could configure all of the frequency carriers for each individual sector, while FRU-N can configure only one FC for each sector.

[0008] In these two methods it is common for each sector to configure the same power spectrum density for all FCs. These two methods show opposite effects in the LTE network.

[0009] FRUl has an effect with respect to frequency resource usage, namely that each sector can fully use the whole frequency resource. However, due to the same frequency being used in all sectors, same frequency interference would also be an effect in the LTE network, especially in the edge area.

[0010] FRU-N method may avoid same frequency interference in the edge area because frequencies in different sectors are different from one another, at least within a macro-cell. However, frequency resource may be under-used in an FRU-N.

[001 1] Inter-cell interference coordination (ICIC) is one intra-frequency approach that can be used to address one frequency carrier approaches in an LTE network. Figure 3 illustrates an inter-cell interference coordination method.

[0012] As shown in Figure 3, three different cell types having three different power profiles can be tiled over an area of a network 300. As illustrated, there are three cell types, type 1, type 2, and type 3, corresponding to Sectors 1, 2, and 3, respectively, having the power density functions illustrated. However, ICIC is only valid in one frequency carrier. Moreover, ICIC does not address how to schedule subcarriers within one frequency carrier for physical downlink shared channel (PDSCH) or physical uplink shared channel (PUSCH) of LTE. As illustrated, multiple macro-cells can be considered, with the cells of the center-most macro-cell labeled in Figure 3.

[0013] As illustrated at right, the power spectral density for Sector 1 can be a function that is different from the function for Sector 2 and Sector 3. The varying power functions in Sectors 1, 2, and 3 can have higher peaks 310 and lower peaks 320 that may be at different places from one another.

[0014] ICIC emphasizes different power spectral density (PSD) configurations among the subcarriers of one frequency carrier. Moreover, ICIC cannot conventionally plan multiple frequency carriers from different frequency bands, for example, band 38 and band 39. Furthermore, ICIC may strongly limit the physical resource block (PRB) scheduling rules in one FC for one sector. Indeed, the ICIC approach cannot conventionally be used for common channel and control channel of LTE.

SUMMARY:

[0015] According to certain embodiments, a method includes dividing frequency resources available for a plurality of sectors into a plurality of carriers. The method also includes selecting at least one edge frequency carrier and at least one center frequency carrier for a sector of the plurality of sectors.

[0016] In accordance with certain embodiments, an apparatus includes at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to divide frequency resources available for a plurality of sectors into a plurality of carriers. The at least one memory and the computer program code are also configured to, with the at least one processor, cause the apparatus at least to select at least one edge frequency carrier and at least one center frequency carrier for a sector of the plurality of sectors.

[0017] An apparatus, in certain embodiments, includes dividing means for dividing frequency resources available for a plurality of sectors into a plurality 5 of carriers. The apparatus also includes selecting means for selecting at least one edge frequency carrier and at least one center frequency carrier for a sector of the plurality of sectors.

[0018] A non-transitory computer-readable medium is, in certain embodiments, encoded with instructions that, when executed in hardware, perform a process, l o The process includes dividing frequency resources available for a plurality of sectors into a plurality of carriers. The process also includes selecting at least one edge frequency carrier and at least one center frequency carrier for a sector of the plurality of sectors.

BRIEF DESCRIPTION OF THE DRAWINGS:

[0019] For proper understanding of the invention, reference should be made to the accompanying drawings, wherein:

[0020] Figure 1 illustrates a three-sector structure for an LTE macro network.

[0021] Figure 2 illustrates two approaches to frequency planning.

[0022] Figure 3 illustrates an inter-cell interference coordination method.

[0023] Figure4 illustrates frequency carrier planning and power spectral density setting according to certain embodiments.

[0024] Figure 5 illustrates load balancing in own sector according to certain embodiments.

[0025] Figure 6 illustrates an inter-sector handover procedure according to certain embodiments.

[0026] Figure 7 illustrates a combined procedure of migration and handover to a target sector, according to certain embodiments.

[0027] Figure 8 illustrates a general flow of load balancing and handover functions according to certain embodiments.

[0028] Figure 9 illustrates simulation assumptions for a simulation of certain embodiments.

[0029] Figure 10 illustrates simulation result curves for simulations of certain embodiments.

[0030] Figure 11 illustrates a 40MHz of band38, according to certain embodiments.

[0031] Figure 12 illustrates a 30MHz of band39, according to certain embodiments.

[0032] Figure 13 illustrates a method according to certain embodiments of the invention.

[0033] Figure 14 illustrates a system according to certain embodiments of the invention.

DETAILED DESCRIPTION:

[0034] Certain embodiments can address edge performance and frequency usage efficiency, thereby appropriating the benefits of the approaches of FRU1 and FRU-N. Moreover, certain embodiments attempt to realize interference cancellation for all physical (PHY) downlink channels of LTE, which could ensure performance for all procedures, especially in the edge area.

[0035] Thus, certain embodiments attempt to provide both edge performance and frequency usage efficiency. Technical aspects of certain embodiments include frequency carrier planning methods, power spectrum density (PSD) setting, rule designing for load balancing (LB) in inter-FC of own sector, and rule designing for a handover (HO) procedure.

[0036] In a frequency carrier planning method according to certain embodiments, there may be more than N, which typically is 3, carriers available in frequency spectrum resource, no matter which frequency bands they are from. Moreover, each carrier may be used by all sectors. Each carrier may be working as edge FC in only one of these sectors, and as center FC in other sectors.

[0037] If working as edge FC, this carrier may be preferentially for, but not strictly limited to, use for edge areas. If working as center FC, the FC is limited to use for only center area of those sectors. The edge FC(s) can be different frequency carrier(s) to each other in all sectors.

[0038] In power spectrum density (PSD) setting according to certain embodiments, the PSD setting for a given FC may be different in different sectors. It may be configured with higher PSD when this FC is working as edge FC in one sector, while it may correspondingly be configured with lower PSD when it is working as center FC in other sectors.

[0039] Figure 4 illustrates frequency carrier planning and power spectral density setting according to certain embodiments. As shown in Figure 4, for a given set of frequency resources 410, frequency carrier planning 420 can first be performed to arrive at a set of N frequency carriers 430, in this case three frequency carriers designated f0, fl, and £2. Then PSD setting 440 can be performed, with an edge frequency carrier 450 being given greater power spectral density when it is an edge frequency carrier than when it is a center frequency carrier 460, and each sector having a different edge frequency carrier.

[0040] In designing for load balancing (LB) in inter-FC of own sector according to certain embodiments, those user equipment (UE) with worse performance may be triggered to migrate to the edge FC for the sector. Those UE with better performance can stay in the edge FC or migrate to the center FC, which may depend on a current load balancing design.

[0041] Figure 5 illustrates load balancing in own sector according to certain embodiments. As shown in Figure 5 on the left side at 510, when a channel quality indicator (CQI) is below a threshold, a user equipment can be migrated to an edge frequency carrier, which may have a higher CQI. Likewise, as shown on the right side of Figure 5 at 520, when a center carrier frequency experiences a high load, a user equipment may be migrated to a center frequency carrier that has a low load. These may be examples of load balancing within a single sector, rather than of load balancing amongst different sectors. However, in some cases these same principles can be applied to a plurality of sectors of a macro-cell, particularly in areas where sectors have significant overlap of coverage.

[0042] In rule designing for handover (HO) procedure according to certain embodiments, those UEs waiting for handover to a neighboring sector can stay in an edge FC. Moreover, the edge FC of target sector can be the FC that is used to admit those handover UE. In other words, in certain embodiments inter-sector handovers can be performed as inter-FC handover in respective edge FCs, and handovers can be limited to this category of handover, thereby avoiding using center FCs for inter-sector handovers.

[0043] Figure 6 illustrates an inter-sector handover procedure according to certain embodiments. As shown, the handover may be from an edge frequency carrier in a current service sector 610 to an edge frequency carrier in a neighboring sector 620. Because the different sectors have different edge frequency carriers, the handover can include a change of frequency carrier for the user equipment.

[0044] Figure 7 illustrates a combined procedure of migration and handover to a target sector, according to certain embodiments. As shown in Figure 7, from left to right, in a source sector there can be movement between frequency carriers for the purposes of load balancing. For example, a user equipment can migrate between a center frequency 710 and an edge frequency 720. However, when an intra-sector handover is to occur, there may be weak CQI of the radio channel in a handover zone of a same frequency layer, so a handover that stays on the same frequency can be avoided or limited. Instead, the user equipment can first be handed from a center frequency carrier 710 to an edge frequency carrier 720 of the source sector. Then the user equipment can be handed over from an edge frequency carrier 720 of the source sector to an edge frequency carrier 730 of the target sector. Thus, the edge frequencies 720, 730 can serve as special frequency carriers that bridge a crossing chasm. Outside the inter-sector handover zone, a better CQI may be available on a center carrier frequency 740 in the target cell, or for other reasons the user equipment may be load balanced between the center frequency carrier(s) 740 and the edge frequency carrier 730. These intra-sector inter-frequency handovers may have a higher success probability, due, for example, to the better cover of center frequencies in a central portion of a sector.

[0045] The above described embodiments can be implemented in various ways in a wireless communication system such as, for example, an LTE network.

[0046] Frequency carrier planning, according to certain embodiments, can in implementation, include such features as setting frequency carriers of one operator by dividing the frequency spectrum resource and defining edge FC and center FC used respectively for each sector.

[0047] Power setting, in accordance with certain embodiments, can include, in implementation, configuring different PSD for a particular FC when the FC is working as an edge FC in one sector than from when the FC is working as a center FC(s) in other sectors, and the whole PSD setting can be limited within the capability of an evolved Node B (eNB), base station, or other access point.

[0048] Intra-sector Load balance (LB) rules can, in implementation, include features such as setting the measurement channel quality indicator (CQI), e.g. signal to interference ratio (SIR) or reference signal received quality (RSRQ), defining trigger event and related up and down thresholds for the measurement CQI, the eNB migrating those UE with worse CQI than down-threshold from center FC to edge FC, and, when the UE has better CQI than up-threshold, the eNB migrating the UE from edge FC to center FC within own sector.

[0049] Handover procedure in implementation in certain embodiments can include setting the channel quality indicator (CQI) to measure, e.g. SIR or reference signal received power (RSRP), and can also include triggering, by the service or serving eNB, the UE to handover out from edge FC of source sector to the edge FC of target sector to achieve better measurement CQI.

[0050] Figure 8 illustrates a general flow of load balancing and handover functions according to certain embodiments. As shown in Figure 8, at 810, a user equipment (UE) can report channel quality using a channel quality indicator (CQI) to, for example, an eNB.

[0051] The eNB can determine, at 820, whether the UE is currently using an edge frequency carrier. If it is not, at 830, the eNB can determine whether the UE has a CQI with a value below a threshold. If not, then the UE can continue to periodically report CQI at 810, and so on. If the UE has a CQI with a value below a threshold, at 860, the eNB can migrate the UE to an edge FC, and the UE can return to periodically reporting CQI at 810.

[0052] The threshold can be a value of CQI that is selected by, for example, a network planner to ensure a minimum channel quality. The value of the threshold may depend on a variety of factors including, for example, the number of edge FCs available. Moreover, the value of the threshold can be dynamic, depending on the load of the edge FCs. For example, the threshold can be SIR = 0 dB or SIR = 2 dB, as illustrated in Figure 10 and discussed below.

[0053] Referring to Figure 8, if it is determined at 820 that the UE is currently using an edge frequency carrier, then at 850 if CQI has a value above a threshold, at 880 the eNB can migrate the UE to a center frequency carrier and the UE can return to reporting CQI periodically at 810.

[0054] If it is determined at 850 that the CQI value is not above the threshold, then at 840 it can be determined whether a CQI value of a serving sector plus an offset is less than a CQI value of a target sector. If so, then the eNB can, at 870, hand the UE off to the target sector, which is a neighbor sector, and the UE can continue to periodically report CQI at 810. If the CQI value of a serving sector plus an offset is not less than a CQI value of a target sector, then the UE can simply continue to periodically report CQI at 810.

[0055] Certain embodiments may have various benefits and/or advantages, although such benefits and/or advantages are not mandatory for all embodiments. For example, certain embodiments can permit an LTE network to more fully use all available frequency spectrum resource. Moreover, certain embodiments may provide better CQI, which may improve edge performance.

[0056] Moreover, certain embodiments may be used for multiple FCs from different frequency bands. Furthermore, in certain embodiments, a different PSD configuration for one FC in different sectors can simply depend on whether it would be edge FC or center FC.

[0057] Certain embodiments of the present invention can be running functionally co-existent with an otherwise conventional network that employs typical frequency planning methods, such as FRU-1 or FRU-N.

[0058] Certain embodiments may not affect the scheduler within each FC. Moreover, certain embodiments can be used both in LTE or LTE-Advanced (LTE- A).

[0059] Figure 9 illustrates simulation assumptions for a simulation of certain embodiments. As shown in Figure 9, an edge frequency carrier 910 can be different in each sector and the center frequency carriers 920 can be 3 dB lower in power spectral density than the edge frequency carriers. For example, Sector 0 can have fO as edge frequency and fl and f2 as center frequencies. The power spectral density value for f0 can be 3 dB greater than the power spectral density value for fl and f2. It is not necessary that each center frequency carrier have the same power spectral density value. In Sector 1, the edge frequency can be fl, which is illustrated as having a power spectral density value that is 3 dB greater than the power spectral density value for the center frequency carriers, f0 and f2. Furthermore, as illustrated, in Sector 2 f0 and fl are the center frequency carriers and have a power spectral density that is 3 dB less than the power spectral density of f2, the edge frequency carrier for this sector. This figure also illustrates that certain embodiments may make an LTE network fully use all the frequency spectrum resource. [0060] Figure 10 illustrates simulation result curves for simulations of certain embodiments. As shown in Figure 10, the curves corresponding to raw signal to interference ratio (SIR) and enhanced SIR demonstrate that certain embodiments may significantly enhance the edge performance of an LTE network. For example, when the ratio of signal to interference plus noise (SINR) is greater than 5 dB, the cumulative distribution function (CDF) for enhanced SIR is higher than the raw SIR or the edge SIR.

[0061] The left hand side of Figure 10 illustrates a case where the SIR threshold is set to 0 dB, and the right hand side illustrates a case where the SIR threshold is set to 2 dB. As shown on the left side, the power (PW) offset can be enhanced 3 dB in either case.

[0062] Figure 1 1 illustrates a 40MHz spectrum of band38, according to certain embodiments. As shown in Figure 11, the frequency resources can be divided into three frequency carriers, namely a 20 MHz block and two 10 MHz blocks for each sector. For example, from left to right Sector 1 includes a twenty MHz block and then two 10 MHz blocks, the second of which is the edge frequency carrier and has 3 dB more of power spectral density than the other frequency carriers. Similarly, from left to right Sector 2 includes a twenty MHz block and then two 10 MHz blocks, the first of which is the edge frequency carrier and has 3 dB more of power spectral density than the other frequency carriers. Finally, in Sector 3 from left to right there are two 10 MHz blocks followed by a 20 MHz blocks, with the second of the two 10 MHz blocks being the edge frequency carrier. Thus, a different 10 MHz block for each sector can be designated as an edge frequency carrier. Moreover, it should be noted that it is not necessary that every part of the available spectrum be used specifically as an edge frequency carrier. In Figure 1 1 , the leftmost 10 MHz of the frequency resources is not used as an edge frequency carrier in any sector. As in Figures 4 and 9, the larger size of the edge frequency carriers illustrates that they may have more power. However, it is not necessary that the power differential be 3 dB, as other power differentials are also permitted.

[0063] Figure 12 illustrates a 30MHz spectrum of band39, according to certain embodiments. As shown in Figure 12, the sectors do not necessarily need to have the same number of divisions of the frequency resources. As illustrated, Sector 2 has three groups of frequency resources, whereas Sectors 1 and 2 have only two groups of frequency resources. In each case, a different 10 MHz block for each sector can be designated as an edge frequency carrier. In Sector 1 , the leftmost 10 MHz is the edge frequency carrier; in Sector 2, the centermost 10 MHz is the edge frequency carrier; and in Sector 3, the leftmost 10 MHz is the edge frequency carrier. As in Figures 4, 9, and 1 1, the larger size of the edge frequency carriers illustrates that they may have more power. However, it is not necessary that the power differential be 3 dB, as other power differentials are also permitted.

[0064] Accordingly, certain embodiments can take the opposite advantages of two planning methods, such as FRU1 and FRU-N. Certain embodiments plan multiple frequency carriers in each site with cooperated power configuration. With the help of dedicated rules in both load balancing and handover, the network may avoid performance accidents in an edge area, such as accidents caused by same frequency interference.

[0065] More particularly, the features of certain embodiments include frequency carrier planning, in which N, which is more than one and may be three, frequency carriers are available for each sector of LTE network, no matter which frequency band these FCs are from. Moreover, each sector can differently configure one of the FCs as edge FC, and another one of them as a center FC.

[0066] Furthermore, the features of certain embodiments can include power setting in which when a FC is used as an edge FC in a service sector, the FC is configured with higher PSD than the PSD for the same FC in other neighbor sectors.

[0067] Moreover, the features of certain embodiments can include intra-sector load balance rules, such as that those UE with worse performance are migrated to an edge FC and those UE waiting for handover are migrated to an edge FC.

[0068] Likewise, the features of certain embodiments can include handover rules, such as that those UEs engaged in handover should start the handover from an own edge FC and that these UEs should be accepted by an edge FC of a target sector.

[0069] Other features in addition to the above are also possible, particularly with respect to designs for reconnection and cell reselection procedures. For example, when an idle UE moves into an intra-frequency handover zone where there is low CQI, careful configuration for cell priority and offset can be employed to avoid inopportunely involving the UE in reconnection and cell reselection procedures.

[0070] Figure 13 illustrates a method according to certain embodiments. The method may be performed by a network element such as, for example, an eNode B. As shown in Figure 13, the method includes, at 1310, dividing frequency resources available for a plurality of sectors into a plurality of carriers. The method also includes, at 1320, selecting at least one edge frequency carrier and at least one center frequency carrier for a sector of the plurality of sectors. The method can further include, at 1330, operating a wireless network based on the selected at least one edge frequency carrier and at least one center frequency carrier.

[0071] The selecting can include selecting, for each sector of a group of sectors in a macro-cell, at least one unique edge frequency carrier. In other words, each sector of the macro-cell can have an edge frequency carrier that no neighboring sector has.

[0072] The method can further include, at 1340, limiting use of a center frequency carrier for a particular sector to a central area of that sector. In other words, the center frequency carrier can have a specific geographic limitation. This can be achieved through power control, as discussed below. [0073] The method can additionally include, at 1350, performing power spectral density control based on whether a carrier is selected to be an edge frequency carrier or a center frequency carrier. For example, when the carrier is selected to be an edge frequency carrier the carrier is assigned a higher power spectral density than when the carrier is selected to be a center frequency carrier.

[0074] The method can also include, at 1360, applying intra-sector load balancing based on whether a carrier is selected to be an edge frequency carrier or a center frequency carrier. For example, the load balancing can include migrating a user equipment to an edge frequency carrier when the user equipment is experiencing performance below a predetermined threshold. The load balancing can also include migrating a user equipment to a center frequency carrier when the user equipment is experiencing performance above a predetermined threshold.

[0075] The method can further include, at 1370, applying inter-sector handover based on whether a carrier is selected to be an edge frequency carrier or a center frequency carrier. The handover can include migrating a user equipment from a center frequency carrier to an edge frequency carrier when the user equipment is awaiting inter-sector handover. The applying the inter-sector handover can include permitting handing over only between edge carrier frequencies of the source sector and target sector.

[0076] Figure 14 illustrates a system according to certain embodiments of the invention. In one embodiment, a system may comprise several devices, such as, for example, access point 1410 (such as an eNode B) and user equipment 1420 (such as a mobile phone, tablet computer, or personal digital assistant).

The system may comprise two or more access points or two or more user equipment, although only one of each is shown for the purposes of illustration.

Each of these devices may comprise at least one processor, respectively indicated as 1414 and 1424. At least one memory may be provided in each device, and indicated as 1415 and 1425, respectively. The memory may comprise computer program instructions or computer code contained therein. One or more transceiver 1416 and 1426 may be provided, and each device may also comprise an antenna, respectively illustrated as 1417 and 1427. Although only one antenna each is shown, many antennas and multiple antenna elements may be provided to each of the devices. Other configurations of these devices, for example, may be provided. For example, access point 1410 and user equipment 1420 may be additionally configured for wired communication, in addition to wireless communication, and in such a case antennas 1417 and 1427 may illustrate any form of communication hardware, without being limited to merely an antenna.

[0077] Transceivers 1416 and 1426 may each, independently, be a transmitter, a receiver, or both a transmitter and a receiver, or a unit or device that may be configured both for transmission and reception.

[0078] Processors 1414 and 1424 may be embodied by any computational or data processing device, such as a central processing unit (CPU), application specific integrated circuit (ASIC), or comparable device. The processors may be implemented as a single controller, or a plurality of controllers or processors.

[0079] Memories 1415 and 1425 may independently be any suitable storage device, such as a non-transitory computer-readable medium. A hard disk drive (HDD), random access memory (RAM), flash memory, or other suitable memory may be used. The memories may be combined on a single integrated circuit as the processor, or may be separate therefrom. Furthermore, the computer program instructions may be stored in the memory and which may be processed by the processors can be any suitable form of computer program code, for example, a compiled or interpreted computer program written in any suitable programming language.

[0080] The memory and the computer program instructions may be configured, with the processor for the particular device, to cause a hardware apparatus such as access point 1410 and user equipment 1420, to perform any of the processes described above (see, for example, Figures 4-13). Therefore, in certain embodiments, a non-transitory computer-readable medium may be encoded with computer instructions that, when executed in hardware, may perform a process such as one of the processes described herein. Alternatively, certain embodiments of the invention may be performed entirely in hardware.

[0081] Furthermore, although Figure 14 illustrates a system including a access point 1410 and a user equipment 1420, embodiments of the invention may be applicable to other configurations, and configurations involving additional elements, as illustrated and discussed herein. For example, multiple user equipment devices and multiple access points may be present, or other nodes providing similar functionality, such as relays which may receive data from an access point and forward the data to a UE and may implement both functionality of a UE and functionality of the access point.

[0082] One having ordinary skill in the art will readily understand that the invention as discussed above may be practiced with steps in a different order, and/or with hardware elements in configurations which are different than those which are disclosed. Therefore, although the invention has been described based upon these preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of the invention. In order to determine the metes and bounds of the invention, therefore, reference should be made to the appended claims.

[0083] Glossary

[0084] LTE long term evolution

[0085] FC frequency carrier

[0086] FRU frequency reuse

[0087] PSD power spectrum density [0088] ICIC inter-cell interference coordination [0089] UE user

[0090] CQI channel quality indicator

[0091] LB load balance

[0092] HO handover

[0093] KPI key performance indicator

Claims

WHAT IS CLAIED IS:

1. A method, comprising:

dividing frequency resources available for a plurality of sectors into a plurality of carriers; and

5 selecting at least one edge frequency carrier and at least one center frequency carrier for a sector of the plurality of sectors.

2. The method of claim 1, wherein the selecting comprises selecting, for each sector of a group of sectors in a macro-cell, at least one unique edge l o frequency carrier.

3. The method of claim 1, further comprising:

limiting use of a center frequency carrier for a particular sector to a central area of that sector.

15

4. The method of claim 1, further comprising:

performing power spectral density control based on whether a selected to be an edge frequency carrier or a center frequency carrier.

20 5. The method of claim 4, wherein when the carrier is selected to be an edge frequency carrier the carrier is assigned a higher power spectral density than when the carrier is selected to be a center frequency carrier.

6. The method of claim 1, further comprising:

applying intra-sector load balancing based on whether a selected to be an edge frequency carrier or a center frequency carrier.

7. The method of claim 6, wherein the load balancing comprises migrating a user equipment to an edge frequency carrier when the user equipment is experiencing performance below a predetermined threshold.

8. The method of claim 6, wherein the load balancing comprises migrating a user equipment to a center frequency carrier when the user

5 equipment is experiencing performance above a predetermined threshold.

9. The method of claim 1, further comprising:

applying inter-sector handover based on whether a carrier is selected to be an edge frequency carrier or a center frequency carrier.

o

10. The method of claim 9, wherein the handover comprises migrating a user equipment from a center frequency carrier to an edge frequency carrier when the user equipment is awaiting inter-sector handover.

11. The method of claim 9, wherein the applying the inter-sector handover comprises permitting handing over only between edge carrier frequencies of the source sector and the target sector.

12. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to divide frequency resources available for a plurality of sectors into a plurality of carriers; and

select at least one edge frequency carrier and at least one center frequency carrier for a sector of the plurality of sectors.

13. The apparatus of claim 12, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to select by selecting, for each sector of a group of sectors in a macro-cell, at least one unique edge frequency carrier.

14. The apparatus of claim 12, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to limit use of a center frequency carrier for a particular sector to a central area of that sector.

15. The apparatus of claim 12, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to perform power spectral density control based on whether a carrier is selected to be an edge frequency carrier or a center frequency carrier.

16. The apparatus of claim 15, wherein when the carrier is selected to be an edge frequency carrier the carrier is assigned a higher power spectral density than when the carrier is selected to be a center frequency carrier.

17. The apparatus of claim 12, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to apply intra-sector load balancing based on whether a carrier is selected to be an edge frequency carrier or a center frequency carrier.

18. The apparatus of claim 17, wherein the load balancing comprises migrating a user equipment to an edge frequency carrier when the user equipment is experiencing performance below a predetermined threshold.

19. The apparatus of claim 17, wherein the load balancing comprises migrating a user equipment to a center frequency carrier when the user equipment is experiencing performance above a predetermined threshold.

20. The apparatus of claim 12, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to apply inter-sector handover based on whether a carrier is selected to be an edge frequency carrier or a center frequency carrier.

21. The apparatus of claim 20, wherein the handover comprises migrating a user equipment from a center frequency carrier to an edge frequency carrier when the user equipment is awaiting inter-sector handover.

22. The apparatus of claim 20, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to apply the inter-sector handover by permitting handing over only between edge carrier frequencies of the source sector and target sector.

23. An apparatus, comprising:

dividing means for dividing frequency resources available for a plurality of sectors into a plurality of carriers; and

selecting means for selecting at least one edge frequency carrier and at least one center frequency carrier for a sector of the plurality of sectors.

24. The apparatus of claim 23, wherein the selecting comprises selecting, for each sector of a group of sectors in a macro-cell, at least one unique edge frequency carrier.

25. The apparatus of claim 23, further comprising: limiting means for limiting use of a center frequency carrier for a particular sector to a central area of that sector.

26. The apparatus of claim 23, further comprising:

control means for performing power spectral density control based on whether a carrier is selected to be an edge frequency carrier or a center frequency carrier.

27. The apparatus of claim 26, wherein when the carrier is selected to be an edge frequency carrier the carrier is assigned a higher power spectral density than when the carrier is selected to be a center frequency carrier.

28. The apparatus of claim 23, further comprising:

balancing means for applying intra-sector load balancing based on whether a carrier is selected to be an edge frequency carrier or a center frequency carrier.

29. The apparatus of claim 28, wherein the load balancing comprises migrating a user equipment to an edge frequency carrier when the user equipment is experiencing performance below a predetermined threshold.

30. The apparatus of claim 28, wherein the load balancing comprises migrating a user equipment to a center frequency carrier when the user equipment is experiencing performance above a predetermined threshold.

31. The apparatus of claim 23, further comprising:

handover means for applying inter-sector handover based on whether a carrier is selected to be an edge frequency carrier or a center frequency carrier.

32. The apparatus of claim 31, wherein the handover comprises migrating a user equipment from a center frequency carrier to an edge frequency carrier when the user equipment is awaiting inter-sector handover.

33. The apparatus of claim 31, wherein the applying the inter-sector handover comprises permitting handing over only between edge carrier frequencies of the source sector and target sector.

34. A non- transitory computer-readable medium encoded with instructions that, when executed in hardware, perform a process, the process comprising the method according to any of claims 1-11.