WO2013060807A2

WO2013060807A2 - Cell selection based on biasing for uplink-centric ues

Info

Publication number: WO2013060807A2
Application number: PCT/EP2012/071199
Authority: WO
Inventors: Nitin MANGALVEDHE; Rapeepat Ratasuk
Original assignee: Nokia Siemens Networks Oy
Priority date: 2011-10-26
Filing date: 2012-10-26
Publication date: 2013-05-02
Also published as: WO2013060807A3; EP2772092A2

Abstract

A method includes communicating from a cell to user equipment a biasing parameter to be used by the user equipment to select and attach to a cell for uplink-centric communications with the selected cell. User equipment that receive the biasing parameter may (e.g., if preconfigured to use the parameter) select and attach to one of a number of cells for uplink-centric communications based on the biasing parameter. Another method includes determining at a cell user equipment that have uplink-centric communications, calculating a biasing parameter for uplink-centric communications, sending the calculated biasing parameter to neighbor cell(s), and receiving a corresponding biasing parameter from each of the neighbor cell(s). For the user equipment that were determined to have uplink-centric communications, the user equipment are handed over from the cell to one of the neighbor cell(s) based on the calculated and the received biasing parameters. Apparatus, software, and program products are also disclosed.

Description

Title

Cell Selection Based on Biasing for Uplink-Centric UEs

TECHNICAL FIELD

[0001] This invention relates generally to radio access networks and, more specifically, relates to cell selection in radio access networks.

BACKGROUND

[0002] 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.

[0003] Wireless traffic volumes are dramatically outstripping macro-cellular capability. Having multiple smaller cell coverage areas (called zone eNB access points or remote radio units, home eNBs, femto cells, pico-cells, remote radio heads, or additional names) controlled by a single controller (which might be called zone eNB controller, central control unit, home eNB Gateway, eNB gateway, or additional names) is anticipated to be a potential solution to this problem. For instance, a macro-cell might provide coverage based on a higher power output over a larger area, where there are multiple smaller cells (with correspondingly smaller power output) within this larger coverage area. The smaller cells might be controlled by a single controller. Such a configuration may be referred to as a heterogeneous network (HetNet), although HetNet may also refer to any combination of larger and smaller cells with overlapping coverage. In this manner, users within the smaller cells share data resources amongst a smaller set of users and typically the HetNet configuration can provide higher capacity and a faster network overall.

[0004] In a HetNet environment, cell selection process is in favor of the best downlink cell. That is, a user equipment (a wireless device) connected to the HetNet performs downlink measurements from the various cells within the HetNet and typically selects and attaches to the cell having the best downlink measurement. This typical scenario may not be the best scenario for all user equipment in the environment.

[0005] Similar problems may exist in wireless systems in general. For instance, if there is a mixture of macro- and micro- cells with different transmission powers, a user equipment will typically connect to the macro-cell based on the higher transmission power of the macro-cell. That is, the user equipment performs downlink measurements from the various micro-cells (and the macro cell) and selects and attaches to the cell having the best downlink measurement. The best measurement in many instances is the macro cell. This typical scenario may not be the best scenario for all user equipment in the environment. SUMMARY

[0006] This section contains examples of possible implementations and is not meant to be limiting.

[0007] In an exemplary embodiment, a method includes communicating wirelessly from a cell to user equipment a biasing parameter to be used by the user equipment to select and attach to a cell for uplink-centric communications with the selected cell.

[0008] A further exemplary embodiment is a computer program comprising program code for executing the method of the previous paragraph. Another exemplary embodiment is 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.

[0009] 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: communicating wirelessly from a cell to user equipment a biasing parameter to be used by the user equipment to select and attach to a cell for uplink-centric communications with the selected cell.

[0010] Another exemplary embodiment is an apparatus that comprises means for communicating wirelessly from a cell to user equipment a biasing parameter to be used by the user equipment to select and attach to a cell for uplink-centric communications with the selected cell.

[0011] An exemplary computer program product includes a computer-readable medium bearing computer program code embodied therein for use with a computer, the computer program code including: code for communicating wirelessly from a cell to user equipment a biasing parameter to be used by the user equipment to select and attach to a cell for uplink-centric communications with the selected cell.

[0012] In another exemplary embodiment, a method is disclosed that includes receiving wirelessly at a user equipment a biasing parameter for uplink-centric

communications from individual ones of a plurality of cells, and selecting and attaching to one of the plurality of cells for uplink-centric communications based on the received biasing parameter. [0013] An additional exemplary embodiment is a computer program comprising program code for executing the method of the previous paragraph. Another exemplary embodiment is 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.

[0014] 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: receiving wirelessly at a user equipment a biasing parameter for uplink-centric communications from individual ones of a plurality of cells; and selecting and attaching to one of the plurality of cells for uplink-centric communications based on the received biasing parameter.

[0015] An exemplary computer program product includes a computer-readable medium bearing computer program code embodied therein for use with a computer, the computer program code including: code for receiving wirelessly at a user equipment a biasing parameter for uplink-centric communications from individual ones of a plurality of cells; and code for selecting and attaching to one of the plurality of cells for uplink-centric communications based on the received biasing parameter.

[0016] Yet another exemplary embodiment is a method comprising: determining, at a cell able to wirelessly communicate with user equipment, user equipment that have uplink-centric communications; calculating a biasing parameter for uplink-centric communications; sending the calculated biasing parameter to one or more neighbor cells; receiving a corresponding biasing parameter from each of the one or more neighbor cells; and for the user equipment that were determined to have uplink-centric communications, handing over the user equipment from the cell to one of the one or more neighbor cells based on at least the calculated biasing parameter, the received biasing parameters, and handover measurement reports from the user equipment for each of the cell and the one or more neighbor cells.

[0017] A further exemplary embodiment is a computer program comprising program code for executing the method of the previous paragraph. Another exemplary embodiment is 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.

[0018] 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: determining, at a cell able to wirelessly communicate with user equipment, user equipment that have uplink-centric

communications; calculating a biasing parameter for uplink-centric communications;

sending the calculated biasing parameter to one or more neighbor cells; receiving a corresponding biasing parameter from each of the one or more neighbor cells; and for the user equipment that were determined to have uplink-centric communications, handing over the user equipment from the cell to one of the one or more neighbor cells based on at least the calculated biasing parameter, the received biasing parameters, and handover measurement reports from the user equipment for each of the cell and the one or more neighbor cells.

[0019] An exemplary computer program product includes a computer-readable medium bearing computer program code embodied therein for use with a computer, the computer program code including: determining, at a cell able to wirelessly communicate with user equipment, user equipment that have uplink-centric communications; calculating a biasing parameter for uplink-centric communications; sending the calculated biasing parameter to one or more neighbor cells; receiving a corresponding biasing parameter from each of the one or more neighbor cells; and for the user equipment that were determined to have uplink-centric communications, handing over the user equipment from the cell to one of the one or more neighbor cells based on at least the calculated biasing parameter, the received biasing parameters, and handover measurement reports from the user equipment for each of the cell and the one or more neighbor cells.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In the attached Drawing Figures:

[0021] FIG. 1 is a diagram of a heterogeneous network (HetNet) used to illustrate cell selection.

[0022] FIG. 2 is a block diagram of an exemplary system in which the exemplary embodiments may be practiced.

[0023] FIG. 3 is a table of exemplary uplink user throughput gain for configuration

4a.

[0024] FIG. 4 is a table of exemplary uplink user throughput gain for configuration

4b.

[0025] FIG. 5 is an exemplary method performed by a cell (e.g., performed by a base station such as an eNB in the cell) for cell selection based on biasing for uplink- centric user equipment. [0026] FIG. 6 is an exemplary method performed by a user equipment for cell selection based on biasing for uplink-centric user equipment.

[0027] FIG. 7 is another exemplary method performed by a cell (e.g., performed by a base station such as an eNB in the cell) for cell selection based on biasing for uplink- centric user equipment.

DETAILED DESCRIPTION OF THE DRAWINGS

[0028] Before proceeding with description of exemplary embodiments, it is helpful at this point to describe certain communication systems, since "releases" of these systems are referenced below. The specification of a communication system known as evolved UTRAN (E-UTRAN, also referred to as UTRAN-LTE, universal terrestrial radio access network-long term evolution, or as E-UTRA) is currently nearing completion within the 3GPP (third generation partnership project). One specification of interest is 3GPP TS (technical standard) 36.300, V8.12.0 (2010-04), "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Access Network (E-UTRAN); Overall description; Stage 2 (Release 8)". This system may be referred to for convenience as LTE Rel-8 (which also contains 3G HSPA, third generation high speed packet access, and its improvements). In general, the set of specifications given generally as 3GPP TS 36.xyz (e.g., 36.21 1 , 36.31 1 , 36.312, etc.) may be seen as describing the Release 8 LTE system. Release 9 (Rel-9) versions of these specifications have been published, including 3GPP TS 36.300, V9.7.0 (201 1 -3). Release 10 (Rel-10) versions of these specifications have also been published, including 3GPP TS 36.300, V10.4.0 (201 1-06). Work on Rel- 1 1 is ongoing and should be finished sometime in 2012 for RAN1 (physical layer). Rel-12 work has not started as of the drafting of this disclosure, but studies are currently proceeding for what will be included in Rel-12. Thus, there are multiple releases of communication systems for user equipment (e.g., wireless devices communicating at least over cellular frequencies), and these releases contain describe implementation details for user equipment and the communication systems.

[0029] Currently, low-cost user equipment for machine-type communications (MTC) are being studied in RAN1 as part of, e.g., release 12 (Rel-12). Machine-type communications are also referred to as Machine-to-Machine (M2M) communications. One characteristic of machine-to-machine (M2M) UEs is that traffic is mostly in the uplink direction. However, due to the large difference in transmission power and antenna gain for macro-cells versus smaller cells (for instance), the best downlink cell may not be the best uplink cell. It is proposed herein that a biasing parameter to be used for MTC UEs in order to be attached to the best uplink cell for those UEs.

[0030] More specifically, in a heterogeneous network, a mixture of, e.g., macro- cells, pico-cells, femto-cells, and relay cells are deployed. Typically, the macro-cell enjoys a 25-30 dB gain in downlink (DL, from a base station to a user equipment) signal strength (e.g., RSRP, reference symbol received power) compared to the DL signal strength of a low-power node such as pico-cell, femto-cell, or relay cell for the same path loss, due to the high transmit power and antenna gain of the macro-cell. A user equipment (UE) will attach to the best DL cell. However, the best DL cell may not be the best UL (uplink, from a user equipment to a base station) cell due to the power bias toward the macro-cell (as described in more detail below). For Machine-to-Machine (M2M) or machine-type communication (MTC), traffic is mostly in the uplink direction. MTC UE examples include UEs for video surveillance, traffic monitoring, and real-time sensing. MTC communication can require high uplink data rate and generally smaller downlink data rate compared to the uplink data rate. These M2M/MTC UEs are best served by the best UL cell, not the best DL cell.

[0031] FIG. 1 shows a typical heterogeneous deployment with an overlay macro- cell 230-1 (a coverage area created, e.g., by eNB 220-1 shown in FIG. 2) and underlay pico-cell (a coverage area created, e.g., by eNB 220-2 shown in FIG. 2). The power of the macro-cell is 46 dBm (decibels (dB) of measured power referenced to one milliwatt (mW)) with an antenna gain of 17 dBi (decibel isotropic), while the pico-cell transmission power is only 30 dBm with antenna gain of 5 dBi. For a typical user, cell attachment will be based on the best downlink cell since in general traffic is downlink-centric. In this case, the UE will attach to the macro-cell even though its pathloss from the macro-cell is 15 dB worse than to the pico-cell. For MTC traffic and other traffic with mostly uplink data (called

"uplink-centric" herein), this is not the optimal cell selection method. For instance, uplink performance is degraded due to the larger path loss to the macro-cell. Also, in this example, the UE will generate large amount of interference to the pico-cell. These problems are improved by use of the exemplary embodiments described below.

[0032] Additional description of solutions to the problems are described after a system into which the exemplary embodiments may be used is described. Turning to FIG. 2, this figure shows a block diagram of an exemplary system in which the exemplary embodiments may be practiced. In FIG. 2, a UE 1 10 is in wireless communication with a radio network 100. The user equipment 1 10 includes one or more processors 120, one or more memories 125, and one or more transceivers 130 interconnected through one or more buses 127. The one or more transceivers 130 are connected to one or more antennas 128. The one or more memories 125 include computer program code 123. The one or more memories 125 and the computer program code 123 are configured to, with the one or more processors 120, cause the user equipment 1 10 to perform one or more of the operations as described herein. The UE 1 10 communicates with eNB 220-1 via link A (e.g., eNB 220-1 could be the base station for the macro-cell 230-1 in FIG. 1 ) and communicates with eNB 220-2 via link B (e.g., eNB 220-2 could be the base station for the pico-cell 230-2 shown in FIG. 1 ). Although only two base stations are shown in FIG. 2, this is merely exemplary, and more than two base stations may suitably be used.

[0033] The radio network 100 includes two eNBs 220-1 , 220-2 in this example. Each eNB 220 includes one or more processors 150, one or more memories 155, one or more network interfaces (N/W l/F(s)) 161 , and one or more transceivers 160

interconnected through one or more buses 157. 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 one or more memories 155 and the computer program code 153 are configured to, with the one or more processors 150, cause a corresponding one of the eNBs 220 to perform one or more of the operations as described herein. The one or more network interfaces 161 communicate over a network such as the network 175. The eNBs 220 communicate using, e.g., network 175. The network 175 may be wired or wireless or both and may implement, e.g., an X2 interface.

[0034] The computer readable memories 125 and 155 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 and 150 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.

[0035] In general, the various embodiments of the user equipment 1 10 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.

[0036] As described above, for MTC UEs and other uplink-centric UEs, traffic is mostly in the uplink direction with very little downlink traffic. In addition, downlink traffic in general is addressed to a group of MTC UEs and may be best served using broadcast services (e.g., using MBSFN, multi-media broadcast over a single frequency network, transmissions). As a result, MTC UEs (and other uplink-centric UEs) may not be best served when they connect to the strongest downlink cell. Instead, the MTC UEs should attach to the best uplink cell. This can be performed in several ways:

[0037] 1 ) A biasing parameter is implemented on the cells for MTC UEs. This is similar to the factor being introduced to offload UEs from the over-lay to the under-lay and also for UEs to attach to relay cells. However, in this case, the biasing parameter is used for MTC UEs to attach to the best cell in terms of uplink performance. This will require some knowledge of the power and gain difference between cells which can be obtained as part of network planning or higher-layer self-optimization procedure.

[0038] 2) The serving cell can compute the pathloss and received power difference between the serving cell and neighboring cells as reported by the UEs as part of handover measurement. The serving cells can then handoff the MTC UEs to the best uplink cells. This will require some knowledge of the power and gain difference between cells which can be obtained as part of network planning or higher-layer self-optimization procedure. This procedure will incur some overhead as handovers are needed. Since MTC UEs will generally be in an idle state and will perform cell selection as part of connection establishment every time uplink data are sent, this can introduce significant overhead and delay.

[0039] 3) A modified UE attachment procedure is implemented so that the MTC

UEs will attach to the best uplink cell. However, the UE will need knowledge of the power and gain difference between cells. This is not possible prior to attachment unless this knowledge is provided or preconfigured in the UEs as part of an advanced network planning.

[0040] 4) MTC UEs are preconfigured to attach only to certain cells. This requires extensive planning and does not guarantee attachment to the best uplink serving cell. Furthermore, for MTC UEs with mobility (e.g., vehicular telemetry), this will not work.

[0041] Consequently, it is proposed that a biasing parameter be implemented on the cells for MTC UEs due to the simplicity in implementation of the biasing parameter and having the network in control of the process. Rel-12 and pre-Rel-12 (e.g., Rel-8/9) communications are handled differently. First, exemplary embodiments for Rel-12 communications are described, and then exemplary embodiments for pre-Rel-12 (e.g., Rel-8/9) communications are described.

[0042] For Rel-12 communications, at the eNB, the biasing parameter could be part of a PHY broadcast parameter, similar to the factor being used to offload traffic or for relay attachment. However, the biasing factor will typically only apply to MTC UEs (i.e., UEs that are preconfigured to apply this factor). On the UE side, MTC UEs will be preconfigured to receive this parameter and thus would be required to apply this parameter in the cell selection procedure. Non- MTC UEs can choose to ignore this parameter but may take the parameter into consideration in the cell selection procedure as well.

[0043] In an example, each cell broadcasts an MTC selection biasing parameter, T-II M2M, for MTC user equipment. During a cell selection process, an MTC UE adds a value of the biasing parameter from each cell to its DL measurements and attaches to the cell with the highest adjusted value. The biasing parameter is determined to adjust the relative bias for selection of cells so that MTC UEs select a cell having a better pathloss in uplink for data transmissions than the pathloss for other potential cells. The biasing parameter, T-II M2M, is determined from several factors and can be updated slowly. As an example, the biasing parameter may be determined and updated based on one or more of the following system parameters:

1 ) Relative Effective Isotropic Radiated Power (EIRP) differences among cells. For instance, the biasing parameter is determined to adjust the relative bias for selection of cells so that MTC UEs select a cell having a better pathloss in uplink for data transmissions than the pathloss for other potential cells. The downlink EI RP difference may be between a measured EIRP of a cell and a reference value, e.g., set by an operator and sent to/received by an eNB. The biasing parameter may be adjusted, e.g., inversely proportional to the difference in downlink EIRP. For example, if the reference value is the EI RP of the macro-cell, the EI RP of a pico-cell would be lower than the reference value, which means the difference between the EI RP of the pico-cell and the reference value would be negative.

2) Resource utilization factor (e.g. the average percentage of resource blocks being used over time) - bias is inversely proportional to resource utilization factor; the higher the resource utilization, the lower the bias.

3) UL/DL traffic ratio in the cell - bias is proportional to UL/DL data traffic ratio. 4) MTC traffic priority - bias is used to balance MTC traffic with other types of traffic (e.g., voice over Internet protocol, VoIP; file transfer protocol, FTP; hypertext transfer protocol, HTTP); if the bias is increased, then MTC traffic is emphasized.

5) System load (e.g., number of active M2M and other UEs) - bias is inversely proportional to the system load; the higher the system load, the lower the bias.

6) Average MCS (modulation and coding scheme) level - bias is proportional to the average UL MCS level for all UEs in the cell.

[0044] For example, the biasing parameter can be initialized as follows:

T-II M2M = 0 for macro-cell, T-II _M2M > 0 for pico-cell,

and the adaptation of the biasing parameter is performed using the following exemplary equation:

^l M2M,k(i+1 ) = ai_M2M,k(i) + $II *MI N(1 , ain¾,n*(¾,n-$IWn)) dB (decibels), where n = 1 , 2, N are the N relevant system metrics (described above in one or more of the examples (1 )-(6)) of cell k and T-ll _ref,n are reference values of the system metrics, a_k,n are weighting factors, τ-ΙΙ _η represents summation over n terms, and τ-ΙΙ is an adaptation step-size parameter. The τ-ΙΙ is what is often called a step-size parameter. This parameter limits the change in biasing parameter, i.e., the step-size parameter determines the maximum step size. If it is desirable to have the biasing parameter react slowly to the system changes, then the step-size parameter can be set to a small value. The MI N() function also helps to limit the change in biasing parameter per iteration.

[0045] It is noted that although macro-cells and pico-cells are described above, there may be other adjustments for other cells. For instance, femto-cells may have an initialization different from (or the same as) the macro-cells and pico-cells and their own set of relevant system parameters. Furthermore, the relevant system parameters may vary between cells (e.g., a macro-cell may implement different relevant system

parameters implemented by a pico-cell).

[0046] In the Rel-12 exemplary versions, each pico-cell independently calculates and updates the biasing parameter according to the exemplary equation given above. Note that all the factors in the equation pertain to that cell alone. This biasing parameter is broadcast to M2M UEs, which incorporate the parameters into their measurements when determining to which cell to attach. There is no need for cells to share this biasing parameter or coordinate in any manner, although sharing the parameter is not restricted.

[0047] Uplink performance results using 3GPP Case 1 and heterogeneous simulation configurations 4a and 4b are shown in FIGS. 3 and 4, respectively, using simulation assumptions in 3GPP TR 36.814, "E-UTRA; Further Advancements for E- UTRA Physical Layer Aspects", v9.0.0, 2010-03. Configurations 4a and 4b are UE dropping configurations specified for system simulations. These are described in Table A.2.1.1.2-4 of TR 36.814. Pages 59-69 of 3GPP TR 36.814 include Tables A.2.1.2-1 through A.2.1.2-8. In configuration 4a, 3GPP Case 1 is 500m (meters) ISD (inter-site distance), 30 MTC UEs per macro-cell, with two UEs placed near each pico-cell, and the remaining UEs placed randomly within the macro-cell. In configuration 4b, 3GPP Case 1 is 500m ISD, 30 MTC UEs per macro-cell, with 20 UEs placed near pico-cells, and 10 UEs placed randomly within the macro-cell. From the results, it is seen that the gain increases as the number of pico-cells increases due to more users being attached to the pico-cells.

[0048] Turning now to FIG. 5, this figure is an exemplary method performed by a cell 230 (e.g., performed by a base station such as an eNB 220 in the cell 230) for cell selection based on biasing for uplink-centric user equipment. For instance, eNB 220-1 in FIG. 2 may perform the blocks of FIG. 5 by executing computer program code 153-1 on processor(s) 150-1 , which causes the eNB 220-1 to perform the blocks. In block 510, the cell 230 calculates a biasing parameter for uplink-centric communications. Uplink-centric communications are those that are primarily uplink-based (e.g., relative to downlink communications). More specifically, the following are several examples one can use to define uplink-centric communications (or correspondingly an uplink-centric UE):

[0049] 1. Based on the number of scheduled subframes. For a given time period, divide the number of scheduled new uplink subframes by the number of new downlink subframes. If the ratio is greater than a threshold (e.g., 4.0), then declare the UE as uplink-centric and its communications as uplink-centric.

[0050] 2. Based on the number of data requests (e.g., initiations) by the UE. The eNB has information about whether the UE or the network is initiating transmission and can collect this information. One can use a ratio computed over a time period again like in Example 1 to define an uplink-centric UE and its communications as uplink-centric.

[0051] 3. Based on explicit classification by the operator. Here the operator can just classify some UEs as uplink-centric (similar to how MTC/M2M UEs will be classified). Here having to define uplink-centric is circumvented and it will be up to the operator to use the operator's own criteria.

[0052] The biasing parameter is to be used by user equipment 1 10 having uplink- centric communications to select and attach to a cell 230 for communications with the selected cell. The uplink-centric user equipment are those supporting machine-type communications and, e.g., especially those specifically preconfigured to use the biasing parameter and to have uplink-centric communications (e.g., machine-type

communications) with the eNB 220. Calculating the biasing parameter is described in detail above, e.g., in relation to the examples (1 ) to (6) and the adaptation equation presented above. In block 520, the cell wirelessly communicates the biasing parameter for the uplink-centric communications to the uplink-centric user equipment 1 10. In one example, the communication includes broadcasting the biasing parameter (e.g., such that all user equipment in the cell receive the biasing parameter).

[0053] Concerning actions taken by the user equipment 1 10, FIG. 6 is an exemplary method performed by a user equipment 1 10 for cell selection based on biasing for uplink-centric user equipment. For example, the user equipment 1 10 may perform the actions in FIG. 6 by executing the computer program code 123 on the processor(s) 120. In block 610, the user equipment 1 10 receives an indication of a biasing parameter for uplink-centric communications from individual ones of a multitude of cells 230. For instance, the user equipment 1 10 can receive the biasing parameter from each of the eN Bs 220 (each of which creates a suitable cell 230). In block 620, the user equipment 1 10 selects and attaches to one of the multitude of cells 230 for uplink-centric

communications based on the received biasing parameters. Illustratively, as described above, the user equipment 1 10 can apply the received biasing parameter to

corresponding ones of the downlink measurements for the cells 230, and then select the cell having the highest result and attaching to that cell.

[0054] The previous description involved techniques for Rel-12 and later communications. For previous releases (e.g., Rel-8 and Rel-9), the user equipment would likely ignore the biasing parameter and would not therefore use the biasing parameter for cell selection and attachment. That is, for these user equipment, the concept of biasing is not supported, so an uplink-centric (e.g., MTC) UE will initially select the strongest cell based solely on DL measurements.

[0055] In this case, the biasing parameter T-II _M2M is calculated by each cell and exchanged to other neighbor cells in, e.g., a neighbor list. Each cell will implement the bias internally and handoff uplink-centric (e.g., MTC) UEs with uplink-heavy traffic to another cell based on UE handover measurement reports and the known internal biases of nearby cells.

[0056] For example, a macro-cell maintains τ-ΙΙ_Μ2Μ,ι , T-II _M2M,₂ , T-II _M2M,3 for 3 pico-cells in the area. Together with UE RSRP measurements from those cells, the macro-cell decides whether to handoff to pico-cells. Each pico-cell also does the same calculation so UEs are not handed back to the macro-cell. That is, a cell adds a value of the biasing parameter for itself and its neighbor cells to UE RSRP measurements and selects the cell with the highest adjusted value. The cell then hands off the UE to the selected cell (if the selected cell is not the cell performing the addition and selection). Biasing parameter adaptation may be performed as previously described. [0057] Whether a UE is uplink-centric may be identified based on, e.g., a unique ID (identification) provisioned by the operators (e.g., operators may be told the M2M IDs so the operators know which UEs are M2M, or the operators can reserve a certain block of IDs for M2M UEs), or a traffic pattern observed by a scheduler at the eNB of that user equipment's traffic pattern (e.g., larger uplink traffic than downlink traffic). As previously suggested, the term "uplink-centric" is used herein to mean that a UE has mostly uplink data to transmit. The amount of uplink data compared to the amount of downlink data may be used as criteria to determine an uplink-centric UE, as can, e.g., the number of uplink data packets compared to downlink data packets. Typically, an uplink-centric UE will have significantly more uplink than downlink transmission.

[0058] Turning now to FIG. 7, FIG. 7 is another exemplary method performed by a cell (e.g., performed by a base station such as an eNB in the cell) for cell selection based on biasing for uplink-centric user equipment. The example of FIG. 7 is performed, e.g., by a base station such as an eNB 220. In block 710, the base station determines user equipment that have uplink-centric communications. Such a determination could be performed, as described above, by using a unique ID identifying a user equipment 1 10 as an MTC user equipment, or by examining uplink and downlink traffic patterns for a user equipment and making the uplink-centric communication determination based thereon. In block 720, the base station calculates a biasing parameter for uplink-centric

communications. Exemplary calculations of the biasing parameter are described in detail above, e.g., in relation to the examples (1 ) to (6) and the adaptation equation presented above.

[0059] Blocks 730-740 are an example of an exchanging process, where the cell and its cells (e.g., in a neighbor cell list for the cell) exchange calculated bias parameters. In block 730, the base station sends the calculated biasing parameter to one or more neighbor cells. For instance, the eNB 220-1 could send its calculated biasing parameter to eNB 220-2. In block 740, the base station receives a corresponding biasing parameter from each of the one or more neighbor cells. As an example, the eNB 220-1 could receive a calculated biasing parameter from eNB 220-2. In block 750, the base station, for the user equipment that were determined to have uplink-centric communications, hands over the user equipment from the cell to one of the one or more neighbor cells based on at least the calculated biasing parameter and the received biasing parameters. Illustratively, the base station can apply the received biasing parameter to corresponding ones of handover measurement reports (made by the user equipment and sent to the base station) for neighbor cells 230 and compare these adjusted values with a value of its calculated biasing parameter and its handover measurement report (made by the user equipment and sent to the base station). If one of the adjusted values from the neighbor cells is greater than the adjusted value from the base station, the base station then selects the neighbor cell 230 having the highest adjusted value and hands off the user equipment 1 10 to that neighbor cell 230.

[0060] As indicated hereinabove, the following exemplary embodiments are disclosed. 1. A method, including: communicating wirelessly from a cell to uplink-centric user equipment a biasing parameter to be used by the uplink-centric user equipment to select and attach to a cell for uplink-centric communications with the selected cell.

[0061] 2. The method of item 1 , wherein the cell derives the biasing parameter by calculating the biasing parameter based on a system parameter of a difference between a downlink effective isotropic radiated power for each cell and a reference value.

[0062] 3. The method of item 2, further comprising the uplink-centric user equipment receiving the reference value.

[0063] 4. The method of item 2, wherein the biasing parameter is inversely proportional to the difference in the downlink effective isotropic radiated power.

[0064] 5. The method of any one of items 1 to 4, wherein the cell derives the biasing parameter by calculating the biasing parameter based on a system parameter of a resource utilization factor.

[0065] 6. The method of item 5, wherein calculating is performed so that the biasing parameter is inversely proportional to the resource utilization factor.

[0066] 7. The method of any one of items 1 to 6, wherein the cell derives the biasing parameter by calculating the biasing parameter based on a system parameter of a traffic ratio between uplink and downlink data traffic between the cell and the uplink-centric user equipment.

[0067] 8. The method of item 7, wherein calculating is performed so that the biasing parameter is proportional to the traffic ratio.

[0068] 9. The method of any one of items 1 to 8, wherein the cell derives the biasing parameter by calculating the biasing parameter based on a system parameter of a traffic priority for machine traffic relative to other types of traffic.

[0069] 10. The method of any one of items 1 to 9, wherein the cell derives the biasing parameter by calculating the biasing parameter based on a system parameter of a system load of the cell.

[0070] 1 1 . The method of item 10, wherein calculating is performed so that the biasing parameter is proportional to the system load. [0071] 12. The method of any one of items 1 to 1 1 , wherein the cell derives the biasing parameter by calculating the biasing parameter based on a system parameter of average modulation and coding scheme level used for transmitting data in uplink from the uplink-centric user equipment to the cell.

[0072] 13. The method of item 12, wherein calculating is performed so that the biasing parameter is proportional to the average modulation and coding scheme level.

[0073] 14. The method of any one of items 1 to 13, wherein the biasing parameter is initialized based on a type of the cell relative to other types of cells, and wherein the biasing parameter is adapted per the following equation:

Τ½2Μ(Ι+1 )

+ | xMI N(1 , _nx dB (decibels), where τ-ΙΙ _n, n = 1 , 2, N are N system metrics of the cell, are reference values of the system metrics, a_n are weighting factors, τ-ΙΙ_η represents summation over n terms, τ-ΙΙ is an adaptation step-size parameter, and N is one or more.

[0074] 15. The method of any one of the preceding items, wherein only those user equipment preconfigured to use the biasing parameter are uplink-centric user equipment that use the biasing parameter to select and attach to a cell for uplink-centric communications with the selected cell, and wherein other user equipment not

preconfigured to use the biasing parameter are not uplink-centric user equipment and do not use the biasing parameter to select and attach to a cell.

[0075] 16. The method of any one of the preceding items, wherein

communicating wirelessly further comprises broadcasting the biasing parameter to the uplink-centric user equipment.

[0076] 17. The method of any one of the preceding items, wherein at least one of the uplink-centric user equipment performs uplink-centric communications that are machine-type communications with the selected cell.

[0077] 18. A method, comprising: receiving wirelessly at an uplink-centric user equipment a biasing parameter for uplink-centric communications from individual ones of a plurality of cells; and selecting and attaching to one of the plurality of cells for uplink- centric communications based on the received biasing parameters.

[0078] 19. The method of item 18, wherein: selecting further comprises: for each of the plurality of cells, adding a corresponding biasing parameter to a value of a corresponding downlink measurement for the cell to create an adjusted value; and selecting a cell based on which one of the plurality of cells has a corresponding highest adjusted value; and attaching further comprises attaching to the selected cell.

[0079] 20. The method of item 18, further comprising sending data in uplink to the selected cell. [0080] 21 . The method of item 18, further comprising determining whether the user equipment is preconfigured to use the biasing parameter for uplink-centric

communications, and performing adding, selecting, and attaching are performed only in response to determining the user equipment is preconfigured to use the biasing parameter for uplink-centric communications.

[0081] 22. The method of any one of items 18 to 21 , wherein the user equipment performs uplink-centric communications that are machine-type

communications with the attached-to cell.

[0082] 23. A method, comprising:

[0083] determining, at a cell able to wirelessly communicate with user equipment, user equipment that have uplink-centric communications; calculating a biasing parameter for uplink-centric communications; sending the calculated biasing parameter to one or more neighbor cells; receiving a corresponding biasing parameter from each of the one or more neighbor cells; and for the user equipment that were determined to have uplink- centric communications, handing over the user equipment from the cell to one of the one or more neighbor cells based on at least the calculated biasing parameter and the received biasing parameters.

[0084] 24. The method of item 23, wherein handing over further comprises handing over user equipment from the cell to one of the one or more neighbor cells based on at least the calculated biasing parameter, the received biasing parameters, and handover measurement reports from the user equipment for each of the cell and the one or more neighbor cells.

[0085] 25. The method of item 24, wherein the handing over further comprises:

[0086] for each of the cell and the one or more neighbor cells, adding a

corresponding biasing parameter to a value of a corresponding handover measurement report for the cell to create an adjusted value; selecting a cell based on which one of the plurality of cells has a corresponding highest adjusted value; and in response to the selected cell being one of the one or more neighbor cells, handing over the user equipment from the cell to the selected one of the one or more neighbor cells.

[0087] 26. The method of item 23, wherein determining user equipment that have uplink-centric communications further comprises determining the user equipment have uplink-centric communications based on unique identification provided for the user equipment.

[0088] 27. The method of item 23, wherein determining user equipment that have uplink-centric communications further comprises determining the user equipment have uplink-centric communications based on traffic patterns of the user equipment. [0089] 28. The method of item 27, wherein determining the traffic patterns of the user equipment further comprise a predetermined significantly higher amount of uplink traffic as compared to downlink traffic for the user equipment determined to have uplink- centric communications.

[0090] 29. The method of any one of items 23 to 28, wherein calculating a biasing parameter further comprises calculating the biasing parameter by any one of the methods from items 2 to 14.

[0091] 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 FIG. 2. A computer-readable medium may comprise a computer- readable storage medium (e.g., memories 125, 155 or other device) that may be any media or means that can contain or store the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer.

[0092] 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.

[0093] 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.

[0094] 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.

Claims

CLAIMS What is claimed is:

1. A method, comprising:

communicating wirelessly from a cell to user equipment a biasing parameter to be used by the user equipment to select and attach to a cell for uplink-centric communications with the selected cell.

2. The method of claim 1 , wherein the cell derives the biasing parameter by

calculating the biasing parameter based on a system metric of a difference between a downlink effective isotropic radiated power for each cell and a reference value.

3. The method of claim 2, further comprising the user equipment receiving the

reference value.

4. The method of claim 2, wherein the biasing parameter is inversely proportional to the difference in the downlink effective isotropic radiated power.

5. The method of any one of claims 1 to 4, wherein the cell derives the biasing

parameter by calculating the biasing parameter based on a system metric of a resource utilization factor for the cell.

6. The method of claim 5, wherein calculating is performed so that the biasing

parameter is inversely proportional to the resource utilization factor.

7. The method of any one of claims 1 to 6, wherein the cell derives the biasing

parameter by calculating the biasing parameter based on a system metric of a traffic ratio between uplink and downlink data traffic between the cell and the user equipment.

8. The method of claim 7, wherein calculating is performed so that the biasing parameter is proportional to the traffic ratio.

The method of any one of claims 1 to 8, wherein the cell derives the biasing parameter by calculating the biasing parameter based on a system parameter of traffic priority for machine traffic relative to other types of traffic.

The method of any one of claims 1 to 9, wherein the cell derives the biasing parameter by calculating the biasing parameter based on a system metric of a system load of the cell.

1 1 . The method of claim 10, wherein calculating is performed so that the biasing parameter is proportional to the system load. 12. The method of any one of claims 1 to 1 1 , wherein the cell derives the biasing parameter by calculating the biasing parameter based on a system metric of average modulation and coding scheme level used for transmitting data in uplink from the user equipment to the cell.

The method of claim 12, wherein calculating is performed so that the biasing parameter is proportional to the average modulation and coding scheme level.

The method of any one of claims 1 to 13, wherein the biasing parameter is initialized based on a type of the cell relative to other types of cells, and wherein the biasing parameter is adapted per the following equation:

M2M(I+ 1 ) = $\ M2M(I) + $\ xMI N(1 , ¾\„¾\„x(¾\„-¾ _ref,_n)) d B (decibels),

where τ-ΙΙ _n, n = 1 , 2, N are N system metrics of the cell, -ll_ref,_n are reference values of the system parameters, a_n are weighting factors, τ-ΙΙ_η represents summation over n terms, τ-ΙΙ is an adaptation step-size parameter, and N is one or more.

The method of any one of the preceding claims, wherein only those user equipment preconfigured to use the biasing parameter are user equipment that use the biasing parameter to select and attach to a cell for uplink-centric communications with the selected cell, and wherein other user equipment not preconfigured to use the biasing parameter do not use the biasing parameter to select and attach to a cell.

The method of any one of the preceding claims, wherein communicating wirelessly further comprises broadcasting the biasing parameter to the user equipment.

The method of any one of the preceding claims, wherein at least one of the user equipment performs uplink-centric communications that are machine-type communications with the selected cell.

An apparatus comprising:

one or more processors; and

one or more memories including computer program code,

the one or more memories and the computer program code configured, with the one or more processors, to cause the apparatus to perform at least the following:

An apparatus comprising:

means for communicating wirelessly from a cell to user equipment a biasing

parameter to be used by the user equipment to select and attach to a cell for uplink-centric communications with the selected cell.

A method, comprising:

receiving wirelessly at a user equipment a biasing parameter for uplink-centric communications from individual ones of a plurality of cells; and

selecting and attaching to one of the plurality of cells for uplink-centric

communications based on the received biasing parameter.

The method of claim 20, wherein:

selecting further comprises:

for each of the plurality of cells, adding a corresponding biasing parameter to a value of a corresponding downlink measurement for the cell to create an adjusted value; and selecting a cell based on which one of the plurality of cells has a corresponding highest adjusted value; and

attaching further comprises attaching to the selected cell.

The method of claim 20, further comprising sending data in uplink to the selected cell.

The method of claim 20, further comprising determining whether the user equipment is preconfigured to use the biasing parameter for uplink-centric communications, and performing adding, selecting, and attaching are performed only in response to determining the user equipment is preconfigured to use the biasing parameter for uplink-centric communications.

The method of any one of claims 20 to 23, wherein the user equipment performs uplink-centric communications that are machine-type communications with the attached-to cell.

An apparatus, comprising:

one or more processors; and

one or more memories including computer program code,

selecting and attaching to one of the plurality of cells for uplink-centric

communications based on the received biasing parameters.

An apparatus, comprising:

means for receiving wirelessly at a user equipment a biasing parameter for uplink- centric communications from individual ones of a plurality of cells; and means for selecting and attaching to one of the plurality of cells for uplink-centric communications based on the received biasing parameters.

27. A method, comprising:

determining, at a cell able to wirelessly communicate with user equipment, user equipment that have uplink-centric communications;

calculating a biasing parameter for uplink-centric communications;

sending the calculated biasing parameter to one or more neighbor cells;

receiving a corresponding biasing parameter from each of the one or more

neighbor cells; and

for the user equipment that were determined to have uplink-centric

communications, handing over the user equipment from the cell to one of the one or more neighbor cells based on at least the calculated biasing parameter, the received biasing parameters, and handover measurement reports from the user equipment for each of the cell and the one or more neighbor cells.

The method of claim 27, wherein the handing over further comprises:

for each of the cell and the one or more neighbor cells, adding a corresponding biasing parameter to a value of a corresponding handover measurement report for the cell to create an adjusted value;

selecting a cell based on which one of the plurality of cells has a corresponding highest adjusted value; and

in response to the selected cell being one of the one or more neighbor cells,

handing over the user equipment from the cell to the selected one of the one or more neighbor cells.

29. The method of claim 27, wherein determining user equipment that have uplink- centric communications further comprises determining the user equipment have uplink-centric communications based on unique identification provided for the user equipment.

30. The method of claim 27, wherein determining user equipment that have uplink- centric communications further comprises determining the user equipment have uplink-centric communications based on traffic patterns of the user equipment.

31 . The method of claim 30, wherein determining the traffic patterns of the user

equipment further comprise a predetermined significantly higher amount of uplink traffic as compared to downlink traffic for the user equipment determined to have uplink-centric communications.

The method of any one of claims 27 to 31 , wherein calculating a biasing parameter further comprises calculating the biasing parameter by any one of the methods from claims 2 to 14.

An apparatus, comprising:

one or more processors; and

one or more memories including computer program code,

calculating a biasing parameter for uplink-centric communications;

sending the calculated biasing parameter to one or more neighbor cells;

receiving a corresponding biasing parameter from each of the one or more

neighbor cells; and

for the user equipment that were determined to have uplink-centric

34. An apparatus, comprising:

means for determining, at a cell able to wirelessly communicate with user

equipment, user equipment that have uplink-centric communications;

means for calculating a biasing parameter for uplink-centric communications; means for sending the calculated biasing parameter to one or more neighbor cells; means for receiving a corresponding biasing parameter from each of the one or more neighbor cells; and

means, for the user equipment that were determined to have uplink-centric

communications, for handing over the user equipment from the cell to one of the one or more neighbor cells based on at least the calculated biasing parameter, the received biasing parameters, and handover measurement reports from the user equipment for each of the cell and the one or more neighbor cells.

35. A computer program comprising program code for executing the method according to any of claims 1 to 17, 20 to 24, or 27 to 32.

36. The computer program according to claim 35, 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.