Carrier priority order determination for energy saving

Abstract

This invention provides method of operating a controller in a wireless telecommunications network, the wireless telecommunications network comprising one or more access points configured to communicate via a plurality of carriers in which the plurality of carriers are cumulatively switched from an inactive mode to an active mode according to a carrier priority order, the method comprising the steps of: obtaining data indicating a forecast demand for a time period; determining a carrier configuration of a first candidate carrier priority order to meet the forecast demand for the time period, the carrier configuration complying with the first candidate carrier priority order; estimating an energy consumption of the first candidate carrier priority order with the determined carrier configuration; and causing configuration of the one or more access points to use the first candidate carrier priority order based on the estimated energy consumption of the candidate carrier priority order.

Description

[0001] A36147

[0002] WIRELESS TELECOMMUNICATIONS NETWORK

[0003] Field of the Invention

[0004] The present invention relates to a wireless telecommunications network and a method

[0005] 5 in the wireless telecommunications network.

[0006] Background

[0007] An access point in a wireless telecommunications network may have an overlapping coverage area with another access point. Furthermore, an access point may communicate using a plurality of carriers, wherein the carriers have an overlapping coverage area. The provision of multiple access points or carriers in these overlapping coverage areas increases capacity in that area, allowing the wireless telecommunications network to serve more users and / or provide improved Quality of Service (QoS).

[0008] 15

[0009] Summary of the Invention

[0010] According to a first aspect of the invention, there is provided a method of operating a controller in a wireless telecommunications network, the wireless telecommunications network comprising one or more access points configured to communicate via a plurality

[0011] 20 of carriers in which the plurality of carriers are cumulatively switched from an inactive mode to an active mode according to a carrier priority order, the method comprising the steps of: obtaining data indicating a forecast demand for a time period; determining a carrier configuration of a first candidate carrier priority order to meet the forecast demand for the time period, the carrier configuration complying with the first candidate carrier

[0012] 25 priority order; estimating an energy consumption of the first candidate carrier priority order with the determined carrier configuration; and causing configuration of the one or more access points to use the first candidate carrier priority order based on the estimated energy consumption of the candidate carrier priority order.

[0013] The method may further comprise the steps of: determining a carrier configuration of a second candidate carrier priority order to meet the forecast demand for the time period, the carrier configuration complying with the second candidate carrier priority order; and estimating an energy consumption of the second candidate carrier priority order with the determined carrier configuration, wherein the step of causing configuration of the one or

[0014] 35 more access points to use the first candidate carrier priority order is based on the A36147 estimated energy consumption of the first candidate carrier priority order being lower than the estimated energy consumption of the second candidate carrier priority order.

[0015] The method may further comprise the steps of: estimating a signalling requirement of

[0016] 5 the first candidate carrier priority order with the determined carrier configuration; and determining that the signalling requirement for the first candidate carrier priority order with the determined carrier configuration is met by the signalling capacity of the first candidate carrier priority order with the determined carrier configuration.

[0017] The signalling requirement of the first candidate carrier priority order with the determined carrier configuration may be based on an estimation of one or more user transfers and user attaches triggered by the first candidate carrier priority order with the determined carrier configuration.

[0018] 15 The time period may include a plurality of segments, the step of determining the carrier configuration of the first candidate carrier priority order may comprise determining the carrier configuration of the first candidate carrier priority order for each segment of the plurality of segments to meet the forecast demand for that segment of the plurality of segments, and the step of estimating the energy consumption of the first candidate

[0019] 20 carrier priority order may comprise estimating the energy consumption of the first candidate carrier priority order for each segment of the plurality of segments with the determined carrier configuration for that segment of the plurality of segments.

[0020] The or each candidate carrier priority order may be defined as an ordered set in which

[0021] 25 each element identifies a carrier, and the carrier configuration of the candidate carrier priority order comprises n elements of the ordered set, whereby if n=1 , the determined carrier configuration of the candidate carrier priority order comprises the first element of the ordered set, and if n>1 , the determined carrier configuration of the candidate carrier priority order comprises the first element of the ordered set up to and including the n-th element of the ordered set.

[0022] The carrier configuration may comprise at least one active carrier, the access point being configured to communicate using the at least one active carrier, the at least one active carrier being the n elements of the ordered set.

[0023] 35 A36147

[0024] The carrier configuration may comprise a coverage carrier and at least one capacity carrier, the access point being configured to communicate using the coverage carrier and zero, one or more capacity carriers. The coverage carrier may be the first element of the ordered set. Alternatively, each element of the ordered set may identify a capacity

[0025] 5 carrier, whereby n is a non-negative integer.

[0026] According to a second aspect of the invention, there is provided a wireless telecommunications network comprising: one or more access points; and a controller configured to implement the steps of the method of the first aspect of the invention.

[0027] 10

[0028] The one or more access points may comprise at least one of a group comprising a singlecarrier access point and a multi-carrier access point.

[0029] According to a third aspect of the invention, there is provided a computer program

[0030] 15 comprising instructions which, when the program is executed by a controller, cause the controller to carry out the steps of the method of the first aspect of the invention. The computer program may be stored on a computer readable carrier medium.

[0031] In a further aspect, there is provided a method in a wireless telecommunications network,

[0032] 20 the wireless telecommunications network comprising one or more access points configured to communicate via a plurality of carriers, the method comprising the steps of: obtaining data indicating a forecast demand for a time period; determining a carrier configuration of a first candidate carrier priority order to meet the forecast demand for the time period, the carrier configuration complying with the first candidate carrier priority

[0033] 25 order; estimating an energy consumption of the first candidate carrier priority order with the determined carrier configuration; and causing configuration of the one or more access points to use the first candidate carrier priority order based on the estimated energy consumption of the candidate carrier priority order.

[0034] 30 Brief Description of the Figures

[0035] In order that the present invention may be better understood, embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings in which:

[0036] 35 Figure 1 is a schematic diagram of a first wireless telecommunications network; A36147

[0037] Figure 2 is a schematic diagram of a first access point of the network of Figure 1 ;

[0038] Figure 3 is a graph illustrating a first scenario of forecast demand in the network of Figure 1 implementing a first candidate carrier priority order;

[0039] Figure 4 is a graph illustrating the first scenario of forecast demand in the network of

[0040] 5 Figure 1 implementing a second candidate carrier priority order;

[0041] Figure 5 is a flow diagram illustrating a first method;

[0042] Figure 6 is a graph illustrating a second scenario of forecast demand in the network of Figure 1 implementing the first candidate carrier priority order;

[0043] Figure 7 is a graph illustrating the second scenario of forecast demand in the network of Figure 1 implementing the second candidate carrier priority order;

[0044] Figure 8 is a graph illustrating a third scenario of forecast demand in the network of Figure 1 implementing the first candidate carrier priority order;

[0045] Figure 9 is a graph illustrating the third scenario of forecast demand in the network of Figure 1 implementing the second candidate carrier priority order;

[0046] 15 Figure 10 is a graph illustrating a fourth scenario of forecast demand in the network of Figure 1 implementing the first candidate carrier priority order;

[0047] Figure 11 is a graph illustrating the fourth scenario of forecast demand in the network of Figure 1 implementing the second candidate carrier priority order;

[0048] Figure 12 is a schematic diagram of a second wireless telecommunications network;

[0049] 20 Figure 13 is a graph illustrating a fifth scenario of forecast demand in the network of Figure 12 implementing a first candidate carrier priority order;

[0050] Figure 14 is a graph illustrating the fifth scenario of forecast demand in the network of Figure 12 implementing a second candidate carrier priority order; and

[0051] Figure 15 is a flow diagram illustrating a second method.

[0052] 25

[0053] Detailed Description

[0054] A first wireless telecommunications network 100 is shown in Figure 1 . The first wireless telecommunications network 100 comprises a first access point 110 and a plurality of User Equipment (UE) (collectively 120).

[0055] Figure 2 is a schematic diagram of the first access point 110, illustrating a first communications interface 111 , a processor 113, memory 115, and a second communications interface 117, all connected via a communications bus 119. The first communications interface 111 is connected to one or more antenna configured to

[0056] 35 transmit a plurality of carriers (collectively 130), in which a carrier is a specific frequency A36147 or range of frequencies allocated for communication between the first access point 110 and the plurality of UE 120. The second communications interface 117 is a backhaul connection to a core network (now shown).

[0057] 5 In this example, the plurality of carriers 130 includes a coverage carrier 130-1 , a first capacity carrier 130-2 and a second capacity carrier 130-3. The coverage areas of each carrier of the plurality of carriers are at least partially overlapping. The plurality of UE 120 are positioned in the overlapping coverage area of the plurality of carriers such that each UE may be served by one or more of the plurality of carriers.

[0058] The plurality of carriers 130 each have a capacity for serving the plurality of UE 120. That is, the coverage carrier 130-1 has a particular capacity (based on a bandwidth of e.g. 10MHz), the first capacity carrier 130-2 has a particular capacity (based on a bandwidth of e.g. 15MHz) and the second capacity carrier 130-3 has a particular capacity

[0059] 15 (based on a bandwidth of e.g. 5MHz). The overall capacity of the first access point 110 is the sum of the respective capacities of each carrier of the plurality of carriers 130.

[0060] In this example, the capacity carriers 130-2, 130-3 of the plurality of carriers 130 may be switched between an inactive mode (also known as “energy saving mode”) and an active

[0061] 20 mode. When operating in the active mode, the capacity carrier is available such that the first access point 110 can communicate with the plurality of UE 120 via that active capacity carrier and the capacity of that active capacity carrier contributes to the overall capacity of the first access point 110. In contrast, when operating in the inactive mode, the capacity carrier is unavailable such that the first access point 110 does not

[0062] 25 communicate with any UE 120 via that inactive capacity carrier and the capacity of that inactive capacity carrier does not contribute to the overall capacity of the first access point 110. The plurality of capacity carriers 130 are therefore selectively switched between the inactive and active modes so as to balance energy saving and overall capacity.

[0063] The first access point 110 implements a priority order for the capacity carriers, such that the capacity carriers are switched from their respective inactive mode to their respective active mode cumulatively in the priority order. If the priority order is {first capacity carrier 130-2, second capacity carrier 130-3}, then (in an example scenario in which the first

[0064] 35 access point 110 initially communicates using the coverage carrier 130-1 only such that A36147 the first and second capacity carriers 130-2, 130-3 are in inactive mode), the first access point 110 may switch the capacity carriers to active mode in the following manner:

[0065] 1. first capacity carrier 130-2, and then,

[0066] 2. both the first and second capacity carriers 130-2, 130-3 (as the capacity carriers

[0067] 5 are switched on cumulatively - i.e. stacked - such that the second capacity carrier 130-3 is only switched to active mode once the first capacity carrier 130- 2 is already in active mode).

[0068] If the priority order is {second capacity carrier 130-3, first capacity carrier 130-2}, then (in the same example scenario in which the first access point 110 initially communicates using the coverage carrier 130-1 only such that the first and second capacity carriers 130-2, 130-3 are in inactive mode), the first access point 110 may switch the capacity carriers to active mode in the following manner:

[0069] 1. second capacity carrier 130-3, and then,

[0070] 15 2. both the first and second capacity carriers 130-2, 130-3 (that is, the first capacity carrier 130-2 is only switched to active mode once the second capacity carrier 130-3 is already in active mode).

[0071] Demand in the wireless telecommunications network 100 is a sum of the demand of each

[0072] 20 UE of the plurality of UE 120 and typically fluctuates over time. Demand in the wireless telecommunications network 100 may also be forecast for a future time period, such as by using one or more of the methods described in Applicant’s co-filed European patent application number 24202174.9, hereby incorporated by reference, or “Traffic Forecasting for Mobile Networks with Multiplicative Seasonal ARIMA Models” Jia Guo et al., The Ninth International Conference on Electronic Measurement & Instruments. The processor 113 of the first access point 110 is configured to implement one or more of these forecasting tools so as to forecast demand for a time period. This forecast demand is stored in memory 115 and used in the methods described below.

[0073] 30 A first method will now be described with reference to Figures 3 to 11. Figure 3 illustrates a first scenario of forecast demand for a first time period, overlaid with the overall capacity of the first access point 110 using a first candidate priority order {first capacity carrier 130-2, second capacity carrier 130-3}. Figure 4 illustrates the first scenario of forecast demand for the first time period overlaid with the overall capacity of the first access point A36147

[0074] 110 using a second candidate priority order {second capacity carrier 130-3, first capacity carrier 130-2}.

[0075] Figure 5 is a flow chart illustrating the first method. In a first step (S101), the processor

[0076] 5 113 of the first access point 110 retrieves the forecast demand of the first scenario for the first time period from memory 115.

[0077] In step S103, the processor 113 determines, for each candidate priority order, a cumulative energy consumption for the first time period. This may be achieved by:

[0078] 1) Dividing the first time period into a plurality of segments,

[0079] 2) Determining, for each segment, a carrier configuration of the first access point such that the overall capacity of the first access point 110 using the carrier configuration satisfies the forecast demand in that segment, the carrier configuration complying with the candidate priority order,

[0080] 15 3) Estimating, for each segment, the energy consumption of the carrier configuration determined in step S103-2, and

[0081] 4) Estimating the cumulative energy consumption for the first time period as the sum of the energy consumptions for each segment estimated in step S103-3.

[0082] 20 As noted above, the priority order indicates the order in which capacity carriers are cumulatively switched from inactive mode to active mode. In step S103-2 above, the carrier configuration must comply with the candidate priority order. In other words, if the candidate priority order is defined as a tuple (i.e. an ordered set) in which each element identifies a capacity carrier, then any capacity carriers of the carrier configuration identified in step S103-2 are a subset of the candidate priority order comprising each capacity carrier from the 1stelement up to and including the n-th element, such that the overall capacity of the first access point 110 satisfies the forecast demand in that segment. Furthermore, step S103-2 may determine that only the coverage carrier is required to satisfy the forecast demand in that segment, such that no capacity carriers

[0083] 30 are required. Therefore, step S103-2 may be defined as:

[0084] 1. Select a candidate carrier configuration of the first access point 110 for the current iteration, n (n being a non-negative integer), the candidate carrier configuration for the current iteration comprising the coverage carrier and n capacity carriers of the candidate priority order, whereby A36147 a. If n=0, the candidate carrier configuration does not comprise any capacity carriers of the candidate priority order, b. If n=1 , the candidate carrier configuration comprises the 1stcapacity carrier of the candidate priority order, and

[0085] 5 c. If n>1 , the candidate carrier configuration comprises each capacity carrier from the 1stelement to the n-th element of the candidate priority order; and

[0086] 2. Determine whether the overall capacity of the first access point 110 using the candidate carrier configuration for the current iteration satisfies the forecast demand in that segment, and a. If so, return the candidate carrier configuration of the first access point 110 for the current iteration as the determined carrier configuration; or b. It not, return to step S103-2-1 to select a further candidate carrier configuration in which n is increased by 1.

[0087] 15

[0088] In sub-step S103-3, the energy consumption of the carrier configuration is estimated. Generally, the energy consumption of each carrier is a function of its bandwidth, such that the first capacity carrier 130-2 having a 15MHz bandwidth consumes more energy that the second capacity carrier 130-3 having a 5MHz bandwidth. The energy

[0089] 20 consumption of each carrier may be determined from previous measurements of the carrier. These measurements may be correlated with characteristics of the first access point 110 and / or conditions of the wireless telecommunications network 100, such as current demand, hardware components, number of users, services offered, and types of users, such that the energy consumption may be determined based on previous

[0090] 25 measurements of the carrier in the same or similar conditions. Furthermore, the energy consumption may be determined based on previous measurements of another carrier in with the same or similar characteristics or in the same or similar conditions.

[0091] In step S105, the processor 113 determines the priority order for the first access point 110 during the first time period as the candidate priority order having the lowest cumulative energy consumption as determined in step S103.

[0092] In step S107, the processor 113 configures the first communications interface 111 so as to use the priority order, as determined in step S105, for the first time period.

[0093] 35 A36147

[0094] Figures 3 and 4 illustrate the cumulative energy consumption for the first time period for the first and second candidate priority orders, in which the non-patterned sections indicate that the carrier is in active mode and the patterned sections indicate that the carrier is in inactive mode. The forecast demand between segments txand tyis greater

[0095] 5 than 10MHz and rises to a peak of 16MHz. As shown in Figure 3, the overall capacity of the first access point 110 satisfies this forecast demand between segments txand tyby using the coverage carrier 130-1 and the first capacity carrier 130-2, such that the second capacity carrier 130-3 remains in inactive mode for the first time period. As shown in Figure 4, the overall capacity of the first access point 110 does not satisfy the forecast demand for the entirety of the time period between segments txand tywhen using the coverage carrier 130-1 and the second capacity carrier 130-3, such that the first capacity carrier 130-2 must also be activated whilst the forecast demand is above 15MHz. The cumulative energy consumption for the first time period for the first candidate priority order, as represented by the total area of the non-patterned sections

[0096] 15 of all carriers in Figure 3, is less than the cumulative energy consumption for the first time period for the second candidate priority order, as represented by the total area of the non-patterned sections of all carriers in Figure 4. The first candidate priority order is therefore selected as the priority order for the first access point 110 for the first time period.

[0097] 20

[0098] Figures 6 and 7 illustrate a second scenario of forecast demand for the first time period in which the forecast demand follows a similar pattern but, between segments txand ty, is greater than 10MHz and rises to a peak of 14MHz. Figure 6 illustrates the first candidate priority order in which the overall capacity of the first access point 110 satisfies

[0099] 25 the forecast demand between segments txand tywhen using the coverage carrier 130-1 and the first capacity carrier 130-2 (that is, the second capacity carrier 130-3 is in inactive mode between segments txand ty). Similarly, Figure 7 illustrates the second candidate priority order in which the overall capacity of the first access point 110 satisfies the forecast demand between segments txand tywhen using the coverage carrier 130-1 and the second capacity carrier 130-3 (that is, the first capacity carrier 130-2 is in inactive mode between segments txand ty). As the energy consumption of the second capacity carrier 130-3 is less than the energy consumption of the first capacity carrier 130-2, then the second candidate priority order has the lowest cumulative energy consumption. The second candidate priority order is therefore selected as the priority order for the first

[0100] 35 access point 110 for the first time period in this second scenario. A36147

[0101] Figures 8 and 9 illustrate a third scenario of forecast demand for the first time period in which the forecast demand is between 10MHz and 15MHz between segments txand ta, is between 15MHz and 16MHz between taand tb, and is between 10MHz and 15MHz

[0102] 5 between segments tb and ty. The forecast demand therefore rises above 15MHz for a shorter proportion of the first time period (relative to the first scenario). Figure 8 illustrates the first candidate priority order in which the overall capacity of the first access point 110 satisfies the forecast demand between segments txand tywhen using the coverage carrier 130-1 and the first capacity carrier 130-2 (that is, the second capacity carrier 130- 3 is in inactive mode between segments txand ty). Similarly, Figure 9 illustrates the second candidate priority order in which the overall capacity of the first access point 110 satisfies the forecast demand between segments txand ta when using the coverage carrier 130-1 and the second capacity carrier 130-3 (that is, the first capacity carrier 130- 2 is in inactive mode between segments txand ta), the overall capacity of the first access

[0103] 15 point 110 satisfies the forecast demand between segments taand tb when using the coverage carrier 130-1 , the first capacity carrier 130-2 and the second capacity carrier 130-3, and the overall capacity of the first access point 110 satisfies the forecast demand between segments tband tywhen using the coverage carrier 130-1 and the second capacity carrier 130-3. The cumulative energy consumption of the second candidate

[0104] 20 carrier order (as represented by the non-patterned areas of Figure 9) is less than the cumulative energy consumption of the first candidate carrier order (as represented by the non-patterned areas of Figure 8), despite the first candidate carrier order requiring fewer capacity carriers to be active during the first time period. The second candidate priority order is therefore selected as the priority order for the first access point 110 for

[0105] 25 the first time period in this third scenario.

[0106] Figures 10 and 11 illustrate a fourth scenario of forecast demand for the first time period, which follows a similar pattern to the third scenario above but has a 14MHz peak (that is, the forecast demand is greater than 10MHz and less than 15MHz between segments txand ty). Figure 10 illustrates the first candidate priority order in which the overall capacity of the first access point 110 satisfies the forecast demand between segments txand tywhen using the coverage carrier 130-1 and the first capacity carrier 130-2 (that is, the second capacity carrier 130-3 is in inactive mode between segments txand ty). Similarly, Figure 11 illustrates the second candidate priority order in which the overall

[0107] 35 capacity of the first access point 110 satisfies the forecast demand between segments tx A36147 and tywhen using the coverage carrier 130-1 and the second capacity carrier 130-3 (that is, the first capacity carrier 130-2 is in inactive mode between segments txand ty). The cumulative energy consumption of the second candidate carrier order (as represented by the non-patterned areas of Figure 11) is less than the cumulative energy consumption

[0108] 5 of the first candidate carrier order (as represented by the non-patterned areas of Figure 10). The second candidate priority order is therefore selected as the priority order for the first access point 110 for the first time period in this fourth scenario.

[0109] A second wireless telecommunications network 200 is shown in Figure 12. The second telecommunications network is the same as the first wireless telecommunications network 100 described above except that the first access point 110 is configured to communicate via a plurality of carriers comprising a coverage carrier 130-1 , a first capacity carrier 130-1 (having a 15MHz bandwidth), a second capacity carrier 130-2 (having a 5MHz bandwidth), a third capacity carrier 130-3 (having a 5MHz bandwidth)

[0110] 15 and a fourth capacity carrier 130-4 (having a 5MHz bandwidth). The same reference numerals are used to refer to components of the second wireless telecommunications network 200.

[0111] A second method will now be described with reference to Figures 13 to 15. Figure 13

[0112] 20 illustrates a fifth scenario of forecast demand for the first time period overlaid with a first candidate priority order of the second method {first capacity carrier 130-2, second capacity carrier 130-3, third capacity carrier 130-4, fourth capacity carrier 130-5}. The forecast demand includes a steep increase in demand at segment tx(from less than 10MHz to 14MHz) and a steep decrease in demand at segment ty(from 14MHx to less than 10MHz). Figure 14 illustrates the fifth scenario of forecast demand for the first time period overlaid with a second candidate priority order of the second method {second capacity carrier 130-3, third capacity carrier 130-4, fourth capacity carrier 130-5, first capacity carrier 130-2.

[0113] 30 Figure 15 is a flow chart illustrating the second method. In a first step (S201), the processor 113 of the first access point 110 retrieves the forecast demand of the fifth scenario for the first time period from memory 115. A36147

[0114] In step S203, the processor 113 determines, for each candidate priority order, a cumulative energy consumption for the first time period. This may be achieved in the same manner as described above in step S103 for the first method.

[0115] 5 In step S205, the processor 113 estimates the additional signalling required for each segment of each candidate priority order over the first time period. This may be achieved by estimating, for each segment of the first time period, how many user transfers and / or user attaches are triggered by the change in the carrier configuration of the current segment of the first time period relative to the carrier configuration of the previous segment of the first time period. The additional signalling requirement may be quantified as a function of these user transfers and / or user attaches, such as by the amount of control signalling of a serving carrier and the amount of control signalling of a target carrier in any handover.

[0116] 15 As noted above, Figure 13 illustrates the fifth scenario of forecast demand for the first time period overlaid with the first candidate priority order of the second method {first capacity carrier 130-2, second capacity carrier 130-3, third capacity carrier 130-4, fourth capacity carrier 130-5}. The overall capacity of the first access point 110 satisfies the forecast demand during segments txand tywhen using the coverage carrier 130-1 and

[0117] 20 the first capacity carrier 130-2 only. In step S205, the processor 113 estimates the additional signalling required for segment txof the first time period for the first candidate priority order based on the how many user transfers and / or user attaches are triggered by the change in the carrier configuration of the first candidate priority order of segment txof the first time period (when the carrier configuration comprises the coverage carrier

[0118] 25 130-1 and the first capacity carrier 130-2 only) relative to the carrier configuration of the first candidate priority order in the previous segment tx-i of the first time period (when the carrier configuration comprises the coverage carrier 130-1 only). The processor 113 also estimates the additional signalling required for each other segment for this first candidate priority order, including at segment ty+i of the first time period (when the carrier configuration comprises the coverage carrier 130-1 only) relative to the carrier configuration in the previous segment tyof the first time period (when the carrier configuration comprises the coverage carrier 130-1 and first capacity carrier 130-2 only).

[0119] Figure 14 illustrates a fifth scenario of forecast demand for the first time period overlaid

[0120] 35 with the second candidate priority order of the second method {second capacity carrier A36147

[0121] 130-3, third capacity carrier 130-4, fourth capacity carrier 130-5, first capacity carrier 130-2}. The overall capacity of the first access point 110 satisfies the forecast demand during segments txand tywhen using the coverage carrier 130-1 and the second, third and fourth capacity carriers 130-3, 130-4, 130-5. In step S205, the processor 113

[0122] 5 estimates the additional signalling required for segment txof the second candidate priority order based on the how many user transfers and / or user attaches are triggered by the change in the carrier configuration of the second candidate priority order at segment tx(when the carrier configuration comprises the coverage carrier 130-1 and the second, third and fourth capacity carriers 130-3, 130-4, 130-5) relative to the carrier configuration in the previous segment tx-i (when the carrier configuration comprises the coverage carrier 130-1 only). The processor 113 also estimates the additional signalling required for each other segment for this second candidate priority order, including at segment ty+i of the first time period (when the carrier configuration comprises the coverage carrier 130-1 only) relative to the carrier configuration in the previous segment

[0123] 15 tyof the first time period (when the carrier configuration comprises the coverage carrier 130-1 and the second, third and fourth capacity carriers 130-3, 130-4, 130-5).

[0124] In step S207, the processor 113 determines, for each candidate priority order, whether the additional signalling requirement for each segment of the time period is less than the

[0125] 20 signalling capacity of the active carriers of the carrier configuration in the segment of the time period.

[0126] In the example shown in Figure 13, the additional signalling requirement of segment txis greater than the signalling capacity of the active carriers in segment txdue to the number

[0127] 25 of user transfers and / or attaches from the coverage carrier 130-1 to the first capacity carrier 130-2. In the example shown in Figure 14, the additional signalling requirement of all segments, including at segment tx, is less than the signalling capacity of the active segments in each segment. By comparing segment txof Figures 13 and 14, the additional signalling requirement must be within the signalling capacity of the first capacity carrier 130-2 in Figure 13 whereas the additional signalling requirement must be within the signalling capacity of the second, third and fourth capacity carriers 130-3, 130-4, 130-5 in Figure 14. Accordingly, if the fifth scenario involves a sufficient number of users such that the change in carrier configuration at segment txtriggers a certain number of user transfers and / or attaches, then the additional signalling requirement for

[0128] 35 segment txmay exceed the signalling capacity of the active carriers of the carrier A36147 configuration of the first candidate carrier order (the coverage carrier 130-1 and first capacity carrier 130-2), whereas the additional signalling requirement for segment txmay be within the signalling capacity of the active carriers of the carrier configuration of the second candidate carrier order (the coverage carrier 130-1 and the second, third and

[0129] 5 fourth capacity carriers 130-3, 130-4, 130-5). It is noted that, if the number of users is relatively low, then the additional signalling requirement for segment txmay be within the signalling capacity of the active carriers of the carrier configuration of the first candidate carrier order.

[0130] 10 In step S209, the processor 113 determines the priority order for the first access point 110 for the first time period as the candidate priority order having a signalling capacity the satisfies the additional signalling requirements over the first time period (as determined in steps S205 and S207) that has the lowest cumulative energy consumption (as determined in step S203).

[0131] 15

[0132] In step S211 , the processor 113 configures the first communications interface 111 so as to use the priority order, as determined in step S209, for the first time period.

[0133] The first and second wireless telecommunications networks 100, 200 utilise a first base

[0134] 20 station 110 having a plurality of carriers 130. However, the skilled person will understand that the first and second methods may also apply to a wireless telecommunications network utilising a plurality of single-carrier access points (additionally or alternatively to the multi-carrier access point) having overlapping coverage areas. The first and second method may therefore be implemented by a controller external to the access point,

[0135] 25 especially when controlling a plurality of single-carrier access points.

[0136] The first and second wireless telecommunications networks 100, 200 above use a coverage carrier and zero, one or more capacity carriers. However, the skilled person will understand that the above methods apply more generally such that the first access

[0137] 30 point 110 communicates using one or more carriers and these one or more carriers have a priority order. The first element of the priority order may be considered the coverage carrier (which may always be active), and all further elements of the priority order may be considered the one or more capacity carriers that may be selectively switched between active and inactive modes.

[0138] 35 In the first and second wireless telecommunications networks 100, 200, each carrier may be independently and selectively switched between active and inactive mode. The skilled person will understand that a subset of two or more carriers of the plurality of carriers may not be independently switched between active and inactive mode, such that

[0139] 5 they may only be switched between modes at the same time (e.g. when those carriers share one or more of the same hardware components, such as antenna or power amplifier). The first and second methods may still be applied to these carriers by identifying them as a group.

[0140] The skilled person will also understand that is non-essential that the methods above are used in the context of a cellular telecommunications network. The methods may also be used in any form of wireless telecommunications network, including wireless local area networks, wireless wide area networks and wireless personal area networks, whereby access points and / or carriers may be switched between an active mode and an inactive

[0141] 15 mode.

[0142] The skilled person will also understand that the above methods may be used to determine if a single candidate priority order should be used or not. For example, the energy consumption of the candidate priority order may be determined and compared to a threshold to determine whether than candidate priority order should be implemented or not.

[0143] The skilled person will also understand that the segmentation of the time period is non- essential but produces a dynamic carrier configuration that is tailored to the forecast

[0144] 25 demand.

[0145] The skilled person will understand that any combination of features is possible within the scope of the invention, as claimed.

Claims

A36147CLAIMS1. A method of operating a controller in a wireless telecommunications network, the wireless telecommunications network comprising one or more access points5 configured to communicate via a plurality of carriers in which the plurality of carriers are cumulatively switched from an inactive mode to an active mode according to a carrier priority order, the method comprising the steps of: obtaining data indicating a forecast demand for a time period; determining a carrier configuration of a first candidate carrier priority order to10 meet the forecast demand for the time period, the carrier configuration complying with the first candidate carrier priority order; estimating an energy consumption of the first candidate carrier priority order with the determined carrier configuration; and causing configuration of the one or more access points to use the first15 candidate carrier priority order based on the estimated energy consumption of the candidate carrier priority order.

2. A method as claimed in Claim 1 , further comprising the steps of: determining a carrier configuration of a second candidate carrier priority order to20 meet the forecast demand for the time period, the carrier configuration complying with the second candidate carrier priority order; and estimating an energy consumption of the second candidate carrier priority order with the determined carrier configuration, wherein the step of causing configuration of the one or more access points to25 use the first candidate carrier priority order is based on the estimated energy consumption of the first candidate carrier priority order being lower than the estimated energy consumption of the second candidate carrier priority order.

3. A method as claimed in Claim 1 or Claim 2, further comprising the steps of:30 estimating a signalling requirement of the first candidate carrier priority order with the determined carrier configuration; and determining that the signalling requirement for the first candidate carrier priority order with the determined carrier configuration is met by the signalling capacity of the first candidate carrier priority order with the determined carrier configuration.35A361474. A method as claimed in Claim 3, wherein the signalling requirement of the first candidate carrier priority order with the determined carrier configuration is based on an estimation of one or more user transfers and user attaches triggered by the first candidate carrier priority order with the determined carrier configuration.

55. A method as claimed in any one of the preceding claims, wherein: the time period includes a plurality of segments, the step of determining the carrier configuration of the first candidate carrier priority order comprises determining the carrier configuration of the first candidate carrier priority order for each segment of the plurality of segments to meet the forecast demand for that segment of the plurality of segments, and the step of estimating the energy consumption of the first candidate carrier priority order comprises estimating the energy consumption of the first candidate carrier priority order for each segment of the plurality of segments with the determined carrier15 configuration for that segment of the plurality of segments.

6. A wireless telecommunications network comprising: one or more access points; and a controller configured to implement the steps of the method of any one of20 Claims 1 to 5.

7. A wireless telecommunications network as claimed in Claim 6, wherein the one or more access points comprise at least one of a group comprising a single-carrier access point and a multi-carrier access point.

8. A computer program comprising instructions which, when the program is executed by a controller, cause the controller to carry out the steps of any one of Claims 1 to 5.30 9. A computer readable carrier medium comprising the computer program of Claim 8.

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