Transmit power allocation in wireless backhaul networks

Abstract

There is provided techniques for assigning transmit power settings to links in a wireless backhaul network. A method comprises obtaining channel and interference information of links in the wireless backhaul network, a capacity demand per link, and a priority metric of the links within each subnetwork. The priority metric of each of the links indicates a relative priority compared to the other links. The method comprises computing, per each given subnetwork, a capacity allocation per link within said given subnetwork. The capacity allocation per link is iteratively computed based on the capacity demand per link and the priority metric of the links. The capacity allocation per link within said given subnetwork is computed by iteratively decreasing the capacity demands in priority order until a signal-to-interference-plus-noise criterion for the capacity allocation and the channel and interference information, is fulfilled for all the links within said given subnetwork. The method comprises instructing the links to apply transmit power settings corresponding to the computed capacity allocations.

Description

[0001] TRANSMIT POWER ALLOCATION

[0002] IN WIRELESS BACKHAUL NETWORKS TECHNICAL FIELD

[0003] Embodiments presented herein relate to a method, a network controller, a computer program, and a computer program product for assigning transmit power settings to links in a wireless backhaul network.

[0004] BACKGROUND

[0005] Wireless backhaul networks support mobile and fixed communication infrastructure by providing wireless connectivity between base stations and core network elements. The demand for data transmission in such wireless backhaul networks is increasing, for example due to the proliferation of high-capacity services and the growing number of connected devices. As the volume of data traffic continues to grow, efficient utilization of the available spectrum is essential to ensure network reliability and performance.

[0006] The spectrum allocated for backhaul transmission is inherently limited, necessitating the adoption of techniques that enhance spectral efficiency. Various technologies have been developed to optimize spectrum utilization, such as multiple-input multiple-output (MIMO) techniques, increased frequency reuse, multi-carrier transmission, and multi-band operation. These technologies enable more efficient use of the available spectrum whilst maintaining network performance and mitigating interference.

[0007] Traditionally, wireless backhaul networks are planned and deployed in a manner that minimizes or eliminates interference between links. This is typically achieved by employing directional antennas with low side-lobe levels and by assigning distinct frequency channels to adjacent links. By carefully managing frequency allocations and antenna patterns, interference can be minimized, thereby ensuring stable and high-capacity communication links.

[0008] However, in scenarios where high frequency reuse is implemented, multiple links within the same geographical area may operate on identical frequency channels. This results in a network environment where interference between neighboring links is more prevalent. The transmitted signal from one link can interfere with adjacent links, thereby impacting their capacity and overall network performance. The interference effects may propagate through multiple links, leading to a chain reaction where one link degrades the performance of another, which in turn affects additional links in the network. Managing such interference is a challenge in high-frequency reuse backhaul networks, as it requires careful coordination of transmission parameters to maintain service quality.Power control mechanisms are commonly employed in wireless backhaul networks to set transmission power levels based on operational requirements. However, some power control mechanisms do not necessarily account for real-time variations in network traffic conditions. More advanced approaches incorporate dynamic adjustments to transmission power and adaptive coding and modulation (ACM) schemes to match the instantaneous traffic demand. By adjusting transmission parameters in response to traffic variations, these approaches can improve spectral efficiency and reduce unnecessary power emissions.

[0009] To meet the growing traffic demand in the links will need more bandwidth. With more bandwidth comes risks of interference between links since links need to reuse frequency channels more densely, and also because the available spectrum is limited. In more detail, in high-frequency reuse wireless backhaul networks, increased spectrum utilization leads to a higher risk of interference between links. In scenarios such as universal frequency reuse, links operating on the same frequency channels may experience significant interference from neighboring transmissions, affecting link capacity and overall network performance. While transmission power control mechanisms can adjust output power based on traffic demand, uncoordinated adjustments may lead to power fluctuations, where links alternately increase and decrease power in response to interference. For example, any given link cannot just increase its power to meet its traffic demand, because there is a risk of reducing the capacity for other links, due to additional interference. In turn this may lead to power rushes when links start to interfere with each other. This can result in network instability and reduced spectral efficiency. One challenge in wireless backhaul networks is therefore to ensure that links can adapt to varying traffic demands without negatively impacting neighboring links due to excessive interference.

[0010] WO2O24188447A1 relates to selection of a frequency channel reuse scheme and transmit powers for a fixed wireless network.

[0011] However, there is still a need for interference management to maintain network performance in dense deployments, where frequency reuse is necessary to accommodate growing traffic demands within the constraints of limited spectrum availability.

[0012] SUMMARY

[0013] An object of embodiments herein is to address the above issues and to enable network performance to be maintained even in dense wireless backhaul network deployments.

[0014] According to a first aspect there is presented a method for assigning transmit power settings to links in a wireless backhaul network. The links belong to at least one interference isolated subnetwork. All the links within each subnetwork use a common frequency channel. The method is performed by a network controller. The method comprises obtaining channel andinterference information of links in the wireless backhaul network, a capacity demand per link, and a priority metric of the links within each subnetwork. The priority metric of each of the links indicates a relative priority compared to the other links. The method comprises computing, per each given subnetwork, a capacity allocation per link within said given subnetwork. The capacity allocation per link is iteratively computed based on the capacity demand per link and the priority metric of the links. The capacity allocation per link within said given subnetwork is computed by iteratively decreasing the capacity demands in priority order until a signal-to-interference-plus-noise criterion for the capacity allocation and the channel and interference information, is fulfilled for all the links within said given subnetwork. The method comprises instructing the links to apply transmit power settings corresponding to the computed capacity allocations.

[0015] According to a second aspect there is presented a network controller for assigning transmit power settings to links in a wireless backhaul network. The links belong to at least one interference isolated subnetwork. All the links within each subnetwork use a common frequency channel. The network controller comprises processing circuitiy. The processing circuitiy is configured to cause the network controller to obtain channel and interference information of links in the wireless backhaul network, a capacity demand per link, and a priority metric of the links within each subnetwork. The priority metric of each of the links indicates a relative priority compared to the other links. The processing circuitry is configured to cause the network controller to compute, per each given subnetwork, a capacity allocation per link within said given subnetwork. The capacity allocation per link is iteratively computed based on the capacity demand per link and the priority metric of the links. The capacity allocation per link within said given subnetwork is computed by iteratively decreasing the capacity demands in priority order until a signal-to-interference-plus-noise criterion for the capacity allocation and the channel and interference information, is fulfilled for all the links within said given subnetwork. The processing circuitiy is configured to cause the network controller to instruct the links to apply transmit power settings corresponding to the computed capacity allocations.

[0016] According to a third aspect there is presented a computer program for assigning transmit power settings to links in a wireless backhaul network. The links belong to at least one interference isolated subnetwork. All the links within each subnetwork use a common frequency channel. The computer program comprises computer code which, when run on processing circuitiy of a network controller, causes the network controller to perform actions. One action comprises the network controller to obtain channel and interference information of links in the wireless backhaul network, a capacity demand per link, and a priority metric of the links within each subnetwork. The priority metric of each of the links indicates a relative priority compared to the other links. One action comprises the network controller to compute, per each given subnetwork, a capacity allocation per link within said given subnetwork. The capacity allocationper link is iteratively computed based on the capacity demand per link and the priority metric of the links. The capacity allocation per link within said given subnetwork is computed by iteratively decreasing the capacity demands in priority order until a signal-to-interference-plus-noise criterion for the capacity allocation and the channel and interference information, is fulfilled for all the links within said given subnetwork. One action comprises the network controller to instruct the links to apply transmit power settings corresponding to the computed capacity allocations.

[0017] According to a fourth aspect there is presented a computer program product comprising a computer program according to the third aspect and a computer readable storage medium on which the computer program is stored. The computer readable storage medium could be a non-transitory computer readable storage medium.

[0018] Advantageously, these aspects enable high priority links to be less congested, without causing unnecessary power rushes. In turn, this may thus reduce the total output power consumption of the links in the wireless backhaul network.

[0019] Advantageously, according to these aspects, traffic does not need to be monitored and classified. Instead, the network controller obtains a priority metric for each link, where this priority metric is then used for computing the capacity allocation per link.

[0020] In some embodiments, the priority metric for a given link may be related to a link quality of service for that given link (e.g., northbound, geographical location, etc.).

[0021] In some embodiments, the priority metric is obtained during deployment of the links.

[0022] In some embodiments, the prioiy metric is updated based on buffer sizes of the links.

[0023] Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings.

[0024] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, module, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, module, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which:

[0026] Fig. i is a schematic diagram illustrating a wireless backhaul network according to embodiments;

[0027] Fig. 2 is a flowchart of methods according to embodiments;

[0028] Fig.3 schematically illustrates rate regions for a two-link scenario according to an embodiment; Fig. 4 is a signaling diagram of a method according to an embodiment;

[0029] Fig.5 is a flowchart of a method according to an embodiment;

[0030] Fig. 6 is a signaling diagram of a method according to an embodiment;

[0031] Fig. 7 is a flowchart of a method according to an embodiment;

[0032] Fig. 8 is a schematic diagram showing structural units of a network controller according to an embodiment; and

[0033] Fig. 9 shows one example of a computer program product comprising computer readable storage medium according to an embodiment.

[0034] DETAILED DESCRIPTION

[0035] The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the inventive concept are shown. This inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description. Any step or feature illustrated by dashed lines should be regarded as optional.

[0036] As noted above, there is a need for interference management to maintain network performance in dense deployments, where frequency reuse is necessary to accommodate growing traffic demands within the constraints of limited spectrum availability.

[0037] In further detail, current interference management technologies do not take into account that different links may have different needs and priorities from a higher-level network performance perspective. Using current interference management technologies, this may cause links to startcompeting for capacity in an uncontrolled way. Current interference management technologies thus do not enable a supervised way of controlling links that compete for capacity.

[0038] Consider a wireless backhaul network. Without loss of generality, it is assumed that the wireless backhaul network has a single network operator. In case two or more network operators share a common wireless backhaul network, each network operator may typically have their own block of unique spectrum available for their respective operation, and thus the herein disclosed embodiments are applicable per each individual network operator. In Fig. i is illustrated an example of such a wireless backhaul network too. A link 120 in the wireless backhaul network too is defined as a transmitter and receiver using a single carrier frequency in a single direction. All links in the wireless backhaul network too have been assigned to a subnetwork. In this respect, all subnetworks 110a, nob, 110c are isolated from each other from an interference point of view. In other words, it is only links within the same subnetwork 110a, nob, noc that may interfere with each other. In the example wireless backhaul network too there are three such subnetworks noa, nob, noc. The subnetworks noa, nob, noc are non-overlapping. Each link thus belongs to exactly one of the subnetworks noa, nob, noc. Further, although three subnetworks noa, nob, noc are illustrated in Fig. 1, the wireless backhaul network too may comprise any number of subnetworks, and thus in one example, all links are part of one and the same subnetwork. Also, there may be different number of links in the subnetworks, and the number of links may vaiy from one subnetwork to another. However, in general terms, it may be assumed that there are at least two links in each of the subnetworks.

[0039] There can be different ways to assign the links to the different subnetworks such that all subnetworks noa, nob, noc are isolated from each other from an interference point of view. According to one non-limiting example, preambles are transmitted from the transmitted to the receiver. Such preambles can be used to compute the interference levels between links. If the interference level between any two links exceeds a pre-defined threshold, then the links are allocated to the same subnetwork. As a non-limiting and illustrative example, the interference level may pertain to a worst case scenario, e.g., where the interferer is transmitting with its maximum power. All subnetworks are isolated from each other from an interference point of view. In other words, it is only links within the same subnetwork that may interfere with each other and compete for capacity.

[0040] A network controller 130 is operatively connected to all links in the subnetworks noa, nob, noc. In this respect, there may be either one network controller 130 per each individual subnetwork, or one network controller 130 common for two or more subnetworks noa, nob, noc. It is thus possible to have a respective network controller 130 for each subnetwork noa, nob, noc, but also to have a single network controller 130 that can manage multiple subnetworks noa, nob, noc, as in Fig. 1. The network controller 130 can be implemented inone of the link nodes (transmitter or receiver), or in a separate node. The network controller 130 could also be implement as a virtualized function in a cloud environment.

[0041] In general terms, the network controller 130 is configured to manage all links within a subnetwork 110a, nob, 110c. In more detail, the network controller 130 is configured to manage the interference in a supervised way at the subnetwork level. The network controller 130 is therefore configured to obtain (acquire, fetch, collect, or receive) and use knowledge of traffic demands, priorities, modulation and coding scheme (MCS) order, channels and interference channels, etc., within the subnetwork 110a, nob, 110c. It is therefore assumed that the network controller 130 has access to a digital representation of the subnetwork 110a, nob, noc. This implies that the network controller 130 has knowledge of the channels of the links, power and noise levels (or at least thresholds), interference channels between the transmitter of one link and the receiver of another link, link capacity demands, link priorities, etc. Static parts of this information (e.g., noise levels) may be programmed in the network controller 130 during planning phase, whilst dynamically changing information (e.g., channel and interference channel state information, capacity demand, etc.) can be sent frequently to the network controller 130 from the links in the subnetwork 110a, nob, 110c. Here, link priorities may be either static or dynamic. For example, initial link priorities may be programmed in a planning phase and then be dynamically updated during an operating phase.

[0042] In general terms, each link 120 may have a maximum allowed transmit power value. This value can come from hardware capabilities as well as regulatory requirements. Further, each link 120 may also have a minimum allowed transmit power value. This value can come due to hardware limitations. In this respect, the maximum and the minimum transmit power values may differ from one link to the next. Any information about the maximum and minimum allowed transmit power values may therefore also be assumed to be known at the network controller 130.

[0043] Further, with respect to dynamically changing information, each link 120 may continuously, periodically, or based on events, update the network controller 130 about its own traffic demand. Traffic demand prediction can be performed at link level based on instantaneous and historical traffic measurements by using standard statistical prediction methods and is beyond the scope of the present disclosure. Each link may also measure the channel quality between its transmitter and every other receiver within its own subnetwork 110a, nob, 110c, where the channel qualities can be computed by using preambles in accordance with what has be disclosed above. This information can also be sent to the network controller 130.

[0044] Based on all this information, the network controller 130 can calculate, or predict, the MCS order allocation for each link 120 at subnetwork level. This MCS order may differ from the MCS order reported form each link. How to handle such situations will be disclosed below. In any case, since it is assumed that there is no interference between links in different subnetworks, thecalculations, or predictions, of MCS order for each link 120 within a subnetwork can be performed independently for each subnetwork.

[0045] At least some of the herein disclosed embodiments are based on that the network controller 130 computes power setting based on a priority metric of the links within a given subnetwork and instructs the links to use the computed power settings. Different examples of priority metrics can here be used. Below will be disclosed two non-limiting examples of priority metrics, namely prioritization based on modulation priority numbers and prioritization based on link priority numbers.

[0046] Fig. 2 is a flowchart illustrating embodiments of methods for assigning transmit power settings to links 120 in a wireless backhaul network too. In some examples, the links 120 are microwave links. As already disclosed with respect to Fig. 1, each link 120 in the wireless backhaul network too is defined as a transmitter and receiver using a single carrier frequency in a single direction. The links 120 belong to at least one interference isolated subnetwork noa:noc. In this respect, by being interference isolated is meant that a given subnetwork noa:noc does not yield any interference outside the given subnetwork noa:noc, or at least that the interference outside the given subnetwork 110a: 110c is below some interference threshold. For example, in case there are at least two subnetworks noa:noc, the at least two subnetworks noa:noc are isolated from each other with respect to interference. All the links 120 within each subnetwork 110a: 110c use a common frequency channel. The methods are performed by the network controller 130. The methods are advantageously provided as computer programs.

[0047] S102: The network controller 130 obtains channel and interference information of links 120 in the wireless backhaul network too, a capacity demand per link 120, and a priority metric of the links 120 within each subnetwork noa:noc. The priority metric of each of the links 120 indicates a relative priority compared to the other links 120. For example, the priority metric of a given link 120 may pertains to the link quality of that given link 120.

[0048] The priority metrics of the links 120 may either be obtained from the links 120 themselves or from an operations, administration, and management (0AM) system of the wireless backhaul network too. Further, the priority metrics may be obtained during deployment of the links 120 and / or updated based on the different buffer sizes of the links 120.

[0049] S104: The network controller 130 computes, per each given subnetwork noa:noc, a capacity allocation per link 120 within the given subnetwork 110a: 110c.

[0050] The capacity allocation per link 120 is iteratively computed based on the capacity demand per link 120 and the priority metric of the links 120.The capacity allocation per link 120 within the given subnetwork noa:noc is computed by iteratively decreasing the capacity demands in priority order until a signal-to-interference-plus-noise (SIN) criterion for the capacity allocation and the channel and interference information, is fulfilled for all the links 120 within the given subnetwork noa:noc.

[0051] The capacity allocation per link 120 may, when computing the capacity allocation, be represented by an MCS order per link 120. In this way, the network controller 130 may, as part of computing the capacity allocation per link 120 test possible MCS orders for the link 120 and eventually select MCS orders for which the SIN criterion is fulfilled for all the links 120 within the given subnetwork 110a: 110c.

[0052] S106: The network controller 130 instructs the links 120 to apply transmit power settings corresponding to the computed capacity allocations.

[0053] In this way, if it is not possible for all links to fulfill their traffic demand (e.g., where the MCS order as calculated, or predicted, by the network controller 130 is not the same as the MCS order reported form each link), the network controller 130 performs prioritization between links in accordance with the herein disclosed embodiments. Reference is here made to Fig. 3. Fig.3 schematically illustrates rate regions in a two-link scenario (i.e. , a subnetwork with two links; Link 1 and Link 2) where different rate and priority combinations have been marked by circles. All feasible operating points are inside the shaded area. In this example, because the shaded area is not rectangular, it is infeasible for both links to have peak capacity at the same time. The task of the network controller 130 is then, for the given priority metric, to decide on a feasible operating point, as defined in terms of power settings, and communicate this operating point to the two links in the subnetwork. Different ways for selecting the operating point will be disclosed below.

[0054] Each of the links 120 may be associated with a minimum allowed capacity allocation. The capacity allocation for a given link 120 may not be further decreased than the minimum allowed capacity allocation for the given link 120.

[0055] As disclosed above, the network controller 130 is configured to obtain and use knowledge of traffic demand, priorities, MCS order, channels and interference channels, etc., within the subnetwork 110a, nob, 110c. Hence, in some embodiments, the channel and interference information of the of links 120 pertains to interference channels between the links 120. Further, in some aspects, the network controller 130 is configured to obtain the pathloss matrix or the channel coefficients, for example the channel coefficient between the transmitter and the receiver of the same link (i.e., the pathloss of every link), and / or the channel coefficient between the transmitter and the receiver of different links (i.e., the interference). Further, the network controller 130 may be configured to obtain the thermal noise level at the receiver of each of thelinks, the required signal-to-interference-plus-noise ratio to achieve eveiy MCS for each link, and the maximum and minimum possible transmit power values of each link.

[0056] A first particular embodiment for assigning transmit power settings to links 120 in a wireless backhaul network too based on at least some of the above disclosed embodiments will now be disclosed in detail with parallel references to the signaling diagram of Fig. 4 and the flowchart of Fig.5.

[0057] In this embodiment, the priority metric of the links 120 is represented by a priority list for each of the links 120, with priority numbers assigned to different MCS orders, and the link 120 that according to the priority number has lowest priority in the subnetwork 110a: 110c has its capacity demand adjusted first. In further detail, the link 120 that according to the priority number has lowest priority in the subnetwork 110a: 110c may have its MCS order lowered until either the SIN criterion is fulfilled (which, as disclosed above, takes into consideration all links 120) or there is another link 120 in the given subnetwork noa:noc that, according to its priority number, has lower priority in the subnetwork 110a: 110c.

[0058] In this embodiment it is assumed that priority numbers are assigned to various MCS orders of each of the links. An example of this for two links (Link 1 and Link 2), where the MCS order is represented by modulation only, is provided in Table 1. Lowest possible priority is denoted by priority number 1. Thus, a link MCS with modulation priority number N has priority over a link MCS with modulation priority number smaller than N. In this example, Link 1 represents a high priority link and Link 2 represents a low priority link.

[0059]

[0060] Table 1: Example of modulation priority numbers for different modulations two different links.An algorithm performed by the network controller 130 for assigning transmit power settings to links 120 in a wireless backhaul network 100 based on such priority numbers will be disclosed next. For non-limiting and illustrative purposes the algorithm is disclosed with reference to a two-link example, where each link is assigned a priority list with priority numbers for each modulation as in Table 1, and hence where there is one high priority link and one low priority link.

[0061] S201: The network controller 130 obtains a respective capacity demand for each link.

[0062] S202: The capacity demand of each link is mapped to a required SIN ratio (SINR). This required SINR corresponds to the SINR needed at the receiver of each link to be able to operate at the demanded capacity.

[0063] S203: The corresponding transmit power for each link is computed, e.g., based on traffic-aware power save principles. Links for which the required SINR could not be fulfilled are marked. As an example, the transmit power can be computed based on traffic-aware power save principles as follows. Sub-step 1: assume initial transmit power values. Sub-step 2: calculate the SINR for the assumed transmit power values. Sub-step 3: add the difference between the obtained SNIR and the required SINR to the transmit power values and clip the transmit power values to the maximum and minimum limits to obtain updated transmit power values. Sub-step 4: if the updated transmit power values are close to the transmit power values just before the update, the procedure is terminated. Otherwise, the procedure is continued again from sub-step 2. After running the procedure, the links for which the required SNIR could not be fulfilled are marked.

[0064] If the required SINR can be fulfilled for all links then the capacity demands are feasible, and the network controller 130 communicates to each link which transmit power that it is allowed to use. Step S204 is entered in case one or more links have been marked.

[0065] S204: For each given marked link, all links that interfere with the given marked link, are found. These are links that cause a raise in interference over noise larger than a threshold, e.g., according to

[0066] lOlogio >

[0067]

[0068] where llnis the interference from link n towards link I, given by lln= Hln■ Pn, where N;is the thermal noise at link I, and Th is some threshold in decibel scale. Further, Hlnis the channel gain between the transmitter of link n and the receiver of link I, and Pnis the transmit power of link n. A marked link and links that interfere with this marked link forms a group of links,referred to a marked group of links, where link capacities need to be lowered. Each marked group of links is then processed as in step S205.

[0069] S205: Each link has a modulation priority number for each modulation, as in Table 1. In the marked group of links (i.e., the group of all marked links), the modulation (and thus the corresponding required capacity) for the link with lowest priority (as given by the highest modulation priority number) is reduced using Table 1. For example, assume that Link 1 and Link 2 constitute a marked group of links. Assume further that both Link 1 and Link 2 has reported modulation 16 QAM. Then, for Link 2, the modulation is reduced first to 16 QAM(s) where it is again evaluated if the required SINR can be fulfilled for Link 1 and Link 2. If not, the modulation for Link 2 is further reduced to 4 QAM. If the required SINR still cannot be fulfilled for Link 1 and Link 2, then, since 3 <7, the modulation for Link 1 is reduced to 16 QAM(s) where it is again evaluated if the required SINR can be fulfilled for Link 1 and Link 2, etc. In this way, the required capacity, and thereby the required SINR, can be iteratively reduced. The links are un-marked once allowable modulation orders have been found for all links in the marked group of links.

[0070] S206: Once there are no more marked links, the power settings corresponding to the resulting modulations are communicated to the links.

[0071] There could be different ways to assign priorities to different MCS orders of a link. One way is to give a committed rate, i.e., a low rate that should be fulfilled with high availability) a high priority (i.e., a low modulation priority number) and to give its peak rate a lower priority (i.e., a high modulation priority number). A high priority of a committed rate may guarantee that important control information, synchronization information, and high-priority services are transported without congestion over the links. Peak rates occur more rarely and can therefore be assigned lower priority without significant risk of congestions.

[0072] A second particular embodiment for assigning transmit power settings to links 120 in a wireless backhaul network too based on at least some of the above disclosed embodiments will now be disclosed in detail with parallel references to the signaling diagram of Fig. 6 and the flowchart of Fig. 7.

[0073] In this embodiment, the link 120 with lowest priority, as given by the priority metric of the links 120, in the subnetwork noa:noc has its capacity demand adjusted first. In further detail, the links 120 are ordered from lowest priority to highest priority, and the capacity allocation in each iteration is adjusted for the link 120 with lowest priority out of all links 120 not already having had their capacity allocation adjusted. The link 120 with lowest priority has its MCS order lowered until either the SIN criterion is fulfilled or an MCS order corresponding to a minimum allowed transmit power setting is reached for the link 120. When the SIN criterion is fulfilled,the MCS order is increased at least for the link 120 with highest priority among the links 120 for which the MCS order was lowered, conditioned that the SIN criterion is still fulfilled.

[0074] In this embodiment, transmit power is allocated to each individual link whilst maintaining the link priority requirements and MCS demands. The network controller 130 is therefore assumed to, or regular basis, obtain the priority needed for each link. The priority for each link can be represented as a real number wbreferred to as link priority numbers, taking a value in some predefined range. The priority can be a measure of congestion at the link, a predetermined value based on how north bound the link is, or a combination of these. To measure the congestion of a link, the percentage occupancy of the various queues in the link can be measured. It may further be assumed that there is a minimum MCS order to be supported by each link, and that the network controller 130 is aware of this information.

[0075] An algorithm performed by the network controller 130 for assigning transmit power settings to links 120 in a wireless backhaul network too based on such link priority numbers will be disclosed next. According to this algorithm, the network controller 130 allocates transmit powers to satisfy the MCS demands and the link priority numbers for the links in a given subnetwork 110a, nob, 110c. For illustrative purposes, the algorithm is described as two routines. However, it is understood that the algorithm can be implemented as a single routine as well. The first routine describes how to check for feasibility of given MCS demands. The second routine handles the case when the MCS demands are not feasible. This second routine is executed by the network controller 130 to assign power settings to the individual links.

[0076] The first routine will be disclosed next.

[0077] S301: The network controller 130 obtains a respective MCS demand for each link and converts the MCS demands to SINR values SINffy, SINR2one for each link.

[0078] S302: The network controller 130 seeks a solution to a linear programming (LP) problem forcing to satisfy the SINR constraints and the power limits simultaneously. In one example, the linear programming problem is formulated as

[0079]

[0080] subject to

[0081] >

[0082]

[0083] P1min,i < — P11 < — P1max,iwhere Pj denotes the transmit power value of the i-th link, where Hjj denotes the channel coefficient between the transmitter of j-th link and the receiver of i-th link. In general terms, the objective to be maximized can be any linear function of the transmit power value allocations. Different algorithms are available for solving such a linear programming problem depending on factors such as problem size, structure, and computational efficiency. Some non-limiting examples are the simplex method, the dual simplex method, interior-point methods, the revised simplex method, the network simplex method, branch and bound, and the cutting plane method.

[0084] S303: In case the network controller 130 indeed finds a solution to the linear programming problem, a list of the transmit power values, representing power settings, are returned.

[0085] S304: In case the network controller 130 does not find a solution to the linear programming problem, the MCS demands cannot be satisfied, and the output from the first routine is information, e.g., represented by a flag being set, that the assignment is infeasible.

[0086] The second routine will be disclosed next.

[0087] S305: All links are assigned their demanded MCS. If this assignment is feasible, as can be determined according to the first routine, then the resulting power settings are sent to the links. S306: In case the assignment is infeasible, the link with lowest link priority among the unprocessed links is selected.

[0088] S307: The MCS order of the selected link is reduced, one step at a time, whilst checking for feasibility (using the first routine), until the assignment is feasible or the link minimum MCS order of that link is reached.

[0089] S308: It is checked whether step S307 resulted in a feasible assignment or not. If a feasible assignment was reached, then step S312 is entered. Else, step S309 is entered.

[0090] S309: The MCS of the selected link is set as the minimum MCS order for this link, and the link is marked as processed.

[0091] S310: It is checked whether all the links are marked as processed or not. If yes, step S311 is entered, and else step S306 is entered again for selection of a new link.

[0092] S311: The minimum MCS order has been reached for all links and thus a feasible MCS demand point cannot be found.

[0093] S312: The processed link with highest priority is selected.S313:The MCS order for the selected link is increase one iteration step at a time and the feasibility is checked using the first routine for each iteration step, until an infeasible assignment is reached, or the demanded MCS for this link is reached.

[0094] S314: If an infeasible MCS order was reached for the selected link, the MCS order is given by the MCS order for the previous iteration step. Else, the MCS order is given by the MCS order for the last iteration step. The link is marked as post-processed only if an infeasible assignment or the demanded MCS is reached.

[0095] S315: If there are any more processed links, step S312 is entered. Else, step S316 is entered. S316: The network controller 130 has computed an MCS order and transmit power assignment for the links where high priority links get their demanded MCS and low priority links gets at least minimum MCS order. The power settings corresponding to the computed MCS order communicated to the links.

[0096] The herein disclosed methods may be executed at regular time intervals in the wireless backhaul network too. A typical time interval can be anywhere in the order of sub-seconds to minutes. With longer time intervals, each of the links may have an MCS demand that corresponds to the maximum expected MCS demand in the following time interval. In that way, the link can prepare itself for worst case capacity requirements. The links may enable power savings by using traffic-aware power savings to further adjust for reduced MCS demand. With longer time intervals, each link may autonomously control its own output power by using localized traffic-aware power savings between updates. However, if the time interval is very short implying veiy fast updates, then the network controller 130 may be regarded as performing centralized traffic-aware power savings.

[0097] Fig. 8 schematically illustrates, in terms of a number of structural units, the components of a network controller 800 according to an embodiment. Processing circuitry 810 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 910 (as in Fig. 9), e.g. in the form of a storage medium 830. The processing circuitry 810 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

[0098] Particularly, the processing circuitry 810 is configured to cause the network controller 800 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 830 may store the set of operations, and the processing circuitry 810 may be configured to retrieve the set of operations from the storage medium 830 to cause the network controller 800 toperform the set of operations. The set of operations may be provided as a set of executable instructions.

[0099] Thus the processing circuitiy 8io is thereby arranged to execute methods as herein disclosed. The storage medium 830 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memoiy, solid state memory or even remotely mounted memoiy. The network controller 800 may further comprise a communications (comm.) interface 820 at least configured for communications with other entities, functions, nodes, and devices, such as the links 120 in Fig. 1. As such the communications interface 820 may comprise one or more transmitters and receivers, comprising analogue and digital components. The processing circuitry 810 controls the general operation of the network controller 800 e.g. by sending data and control signals to the communications interface 820 and the storage medium 830, by receiving data and reports from the communications interface 820, and by retrieving data and instructions from the storage medium 830. Other components, as well as the related functionality, of the network controller 800 are omitted in order not to obscure the concepts presented herein.

[0100] The network controller 800 may be provided as a standalone device or as a part of at least one further device. For example, the network controller 800 may be provided in a node of a radio access network, in an integrated access and backhaul network node, or in one of the links 120. Alternatively, functionality of the network controller 800 may be distributed between at least two devices, or nodes. These at least two nodes, or devices, may either be part of the same network part or may be spread between at least two such network parts. In general terms, instructions that are required to be performed in real time may be performed in a device, or node, operatively closer to the subnetworks than instructions that are not required to be performed in real time. A first portion of the instructions performed by the network controller 800 may be executed in a first device, and a second portion of the of the instructions performed by the network controller 800 may be executed in a second device; the herein disclosed embodiments are not limited to any particular number of devices on which the instructions performed by the network controller 800 may be executed. Hence, the methods according to the herein disclosed embodiments are suitable to be performed by a network controller 800 residing in a cloud computational environment. Therefore, although a single processing circuitry 810 is illustrated in Fig. 8 the processing circuitry 810 may be distributed among a plurality of devices, or nodes. The same applies to the computer program 920 of Fig. 9.

[0101] Fig. 9 shows one example of a computer program product 910 comprising computer readable storage medium 930. On this computer readable storage medium 930, a computer program 920 can be stored, which computer program 920 can cause the processing circuitry 810 and thereto operatively coupled entities and devices, such as the communications interface 820 and thestorage medium 830, to execute methods according to embodiments described herein. The computer program 920 and / or computer program product 910 may thus provide means for performing any steps as herein disclosed.

[0102] In the example of Fig. 9, the computer program product 910 is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product 910 could also be embodied as a memory, such as a random access memory (RAM), a read-only memoiy (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM) and more particularly as a non-volatile storage medium of a device in an external memoiy such as a USB (Universal Serial Bus) memory or a Flash memory, such as a compact Flash memoiy. Thus, while the computer program 920 is here schematically shown as a track on the depicted optical disk, the computer program 920 can be stored in any way which is suitable for the computer program product 910.

[0103] The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.

Claims

CLAIMS1. A method for assigning transmit power settings to links (120) in a wireless backhaul network (100), wherein the links (120) belong to at least one interference isolated subnetwork (noa:iioc), wherein all the links (120) within each subnetwork (noa:iioc) use a common frequency channel, wherein the method is performed by a network controller (130, 800), and wherein the method comprises:obtaining (S102) channel and interference information of links (120) in the wireless backhaul network (100), a capacity demand per link (120), and a priority metric of the links (120) within each subnetwork (noa:iioc), wherein the priority metric of each of the links (120) indicates a relative priority compared to the other links (120);computing (S104), per each given subnetwork (noa:iioc), a capacity allocation per link (120) within said given subnetwork (110a: 110c),wherein the capacity allocation per link (120) is iteratively computed based on the capacity demand per link (120) and the priority metric of the links (120), and wherein the capacity allocation per link (120) within said given subnetwork (noa:noc) is computed by iteratively decreasing the capacity demands in priority order until a signal-to-interference-plus-noise criterion for the capacity allocation and the channel and interference information, is fulfilled for all the links (120) within said given subnetwork (noa:noc); andinstructing (S106) the links (120) to apply transmit power settings corresponding to the computed capacity allocations.

2. The method according to any claim 1, wherein the channel and interference information of the of links (120) pertains to interference channels between the links (120).

3. The method according to any preceding claim, wherein the capacity allocation per link (120) when computing the capacity allocation is represented by a modulation and coding scheme order per link (120).

4. The method according to any preceding claim, wherein each of the links (120) is associated with a minimum allowed capacity allocation, and wherein the capacity allocation for a given link (120) is not further decreased than the minimum allowed capacity allocation for said given link (120).

5. The method according to any preceding claim, wherein the priority metric of the links (120) is represented by one priority list per each of the links (120), with priority numbersassigned to different modulation and coding scheme orders, and wherein the link (120) that according to the priority number has lowest priority in said subnetwork (noa:noc) has its capacity demand adjusted first.

6. The method according to claim 5, wherein the link (120) that according to the priority number has lowest priority in said subnetwork (noa:noc) has its modulation and coding scheme order lowered until either the signal-to-interference-plus-noise criterion is fulfilled or there is another link (120) in said given subnetwork (110a: 110c) that, according to its priority number, has lower priority in said subnetwork (noa:noc).

7. The method according to any of claims 1 to 4, wherein the link (120) with lowest priority, as given by the priority metric of the links (120), in said subnetwork (noa:noc) has its capacity demand adjusted first.

8. The method according to claim 7, wherein the links (120) are ordered from lowest priority to highest priority, wherein the capacity allocation in each iteration is adjusted for the link (120) with lowest priority out of all links (120) not already having had their capacity allocation adjusted.

9. The method according to claim 8, wherein the link (120) with lowest priority has its modulation and coding scheme order lowered until either the signal-to-interference-plus-noise criterion is fulfilled or a modulation and coding scheme order corresponding to a minimum allowed transmit power setting is reached for said link (120).

10. The method according to claim 9, wherein, when the signal-to-interference-plus-noise criterion is fulfilled, the modulation and coding scheme order is increased at least for the link (120) with highest priority among the links (120) for which the modulation and coding scheme order was lowered, conditioned that the signal-to-interference-plus-noise criterion is still fulfilled.

11. The method according to any preceding claim, wherein there are at least two subnetworks (noa:noc), and wherein the at least two subnetworks (noa:noc) are isolated from each other with respect to interference.

12. The method according to any preceding claim, wherein the priority metrics of the links (120) are obtained from the links (120) and / or obtained during deployment of the links (120).

13. The method according to any preceding claim, wherein the priority metric of each link pertains to link quality.14- The method according to any preceding claim, wherein the links (120) are microwave links.

15. A network controller (130, 800) for assigning transmit power settings to links (120) in a wireless backhaul network (too), wherein the links (120) belong to at least one interference isolated subnetwork (110a: 110c), wherein all the links (120) within each subnetwork (110a: 110c) use a common frequency channel, the network controller (130, 800) comprising processing circuitiy (810), the processing circuitiy being configured to cause the network controller (130, 800) to:obtain channel and interference information of links (120) in the wireless backhaul network (too), a capacity demand per link (120), and a priority metric of the links (120) within each subnetwork (noa:noc), wherein the priority metric of each of the links (120) indicates a relative priority compared to the other links (120);compute, per each given subnetwork (noa:noc), a capacity allocation per link (120) within said given subnetwork (110a: 110c),wherein the capacity allocation per link (120) is iteratively computed based on the capacity demand per link (120) and the priority metric of the links (120), and wherein the capacity allocation per link (120) within said given subnetwork (noa:noc) is computed by iteratively decreasing the capacity demands in priority order until a signal-to-interference-plus-noise criterion for the capacity allocation and the channel and interference information, is fulfilled for all the links (120) within said given subnetwork (noa:noc); andinstruct the links (120) to apply transmit power settings corresponding to the computed capacity allocations.

16. The network controller (130, 800) according to claim 15, further being configured to perform the method according to any of claims 2 to 14.

17. A computer program (920) for assigning transmit power settings to links (120) in a wireless backhaul network (too), wherein the links (120) belong to at least one interference isolated subnetwork (110a: 110c), wherein all the links (120) within each subnetwork (110a: 110c) use a common frequency channel, the computer program comprising computer code which, when run on processing circuitiy (810) of a network controller (130, 800), causes the network controller (130, 800) to:obtain (S102) channel and interference information of links (120) in the wireless backhaul network (100), a capacity demand per link (120), and a priority metric of the links (120) within each subnetwork (noa:iioc), wherein the priority metric of each of the links (120) indicates a relative priority compared to the other links (120);compute (S104), per each given subnetwork (noa:iioc), a capacity allocation per link (120) within said given subnetwork (110a: 110c),wherein the capacity allocation per link (120) is iteratively computed based on the capacity demand per link (120) and the priority metric of the links (120), and wherein the capacity allocation per link (120) within said given subnetwork (noa:iioc) is computed by iteratively decreasing the capacity demands in priority order until a signal-to-interference-plus-noise criterion for the capacity allocation and the channel and interference information, is fulfilled for all the links (120) within said given subnetwork (noa:iioc); andinstruct (S106) the links (120) to apply transmit power settings corresponding to the computed capacity allocations.

18. A computer program product (910) comprising a computer program (920) according to claim 17, and a computer readable storage medium (930) on which the computer program is stored.

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