Patent Description:
In cellular wireless networks, inter-cell interference (ICI) imposes significant limitations on the performance of wireless links between access nodes and wireless devices. General characteristics of intercell interference include:.

Strong ICI can seriously degrade cell performance by reducing the data rate that can be achieved between the host access node and wireless devices. Thus, many existing works introduce different means to mitigate or cancel ICI.

<CIT> describes a technique for assigning transceiver devices to transmission resources for inter-cell interference coordination in a heterogeneous cellular communication network. The network comprises a first cell layer having a first cell associated with a first transmission resource and a second cell layer having a second cell associated with a second transmission resource disjunctive from the first transmission resource. In a method implementation, the technique comprises performing a first selection procedure to select a first set of transceiver devices served in the first cell based on the potential of causing interference to transceiver devices served in the second cell, performing a second selection procedure to select a second set of transceiver devices served in the second cell based on the potential of being sensitive to interference from transceiver devices served in the first cell, and assigning the first set of transceiver devices to the first transmission resource and the second set of transceiver devices to the second transmission resource.

<CIT> presents a method and an apparatus of triggering an inter cell interference coordination (ICIC) mechanism in a wireless network. For example, the disclosure presents a method for identifying a pilot pollution metric and determining when a pilot pollution condition based at least on the pilot pollution metric is satisfied. In addition, such as an example method may include triggering an ICIC mechanism when the pilot pollution condition is satisfied. As such, triggering an ICIC mechanism in a wireless network may be achieved.

<CIT> describes methods and apparatus for mitigating intercell interference in wireless communication systems utilizing substantially the same operating frequency band across multiple neighboring coverage areas. The operating frequency band may be shared across multiple neighboring or otherwise adjacent cells, such as in a frequency reuse one configuration. The wireless communication system can synchronize one or more resource allocation regions or zones across the multiple base stations, and can coordinate a permutation type within each resource allocation zone. The base stations can coordinate a pilot configuration in each of a plurality of coordinated resource allocation regions. Subscriber stations can be assigned resources in a coordinated resource allocation region based on interference levels. A subscriber station can determine a channel estimate for each of multiple base stations in the coordinated resource allocation region to mitigate interference.

<CIT> Discloses an inter-cell interference mitigation method using a spatial covariance matrix (SCM) estimation method in a multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) communication system for mitigating interference between asynchronous cells. The inter-cell interference mitigation method includes extracting a reference symbol (RS) of a received OFDM symbol and performing channel estimation, estimating an initial SCM using the RS signal and the channel estimation result, applying time-domain sinc type weighting to the initial SCM and applying an SCM, and demodulating a data symbol with mitigated inter-cell interference using the channel estimation result and the estimated SCM. By applying time-domain sinc type weighting to SCM estimation, it is possible to reduce an SCM estimation error occurring due to a spectral leakage induced by an abrupt change in a signal at a border point between an effective sub carrier zone and a guard band zone, and a simple design of a moving average filter form for a frequency domain signal can be made instead of frequency-time-frequency domain transformation using an inverse fast Fourier transform (IFFT) and fast Fourier transfer (FFT).

<CIT> discloses an intercell interference suppression method based on channel coherence multi-subscriber dispatching, specifically comprising the following steps: first of all, determining the activated user collection in the cooperative multi-point transmission mode CoMP, performing the multi-user dispatching for the activated user collection, selecting the user collection having the least channel coherence with channel coherence dispatching standard as the final CoMP transmission user collection, and designing a block diagonal pre-coding array by the system based on the channel state information of various users in the CoMP transmission user collection to eliminate the interference between users and perform multiple base station cooperative combined transmission for the user. The method is suitable for multi-cell multi-user MIMO system, thereby giving better attention to both the system performance and the complexity, effectively inhibiting the interference between cells, improving user performance at the cell edge and enhancing the overall system capacity.

<CIT> discloses a method for suppressing the interference of cofrequency network through scheduling. The method comprises the following steps: firstly sorting or ranking by each cell according to the latent interference state of the subscriber in the cell to other cell; and then scheduling by each cell according to the sorting and ranking of the subscriber to obtain the purposes of suppression or elimination to the co-channel interference. The method provided by the invention can effectively reduce the co-channel interference in a wireless communication system and increases the efficiency of frequency spectrum thereby further increasing the coverage and flow capacity of the system.

The methods described in <CIT>, <CIT> and <CIT> coordinate interference among cells, whereas <CIT>, <CIT> and <CIT> employ spatial separation techniques to mitigate ICI. All of these techniques suffer a limitation, in that they employ a reactive procedure in which interference is detected, quantized, and then evaluated to implement a mitigation strategy. This implies that that inter-cell interference, and its consequential impacts on system performance, must be present before the prior art techniques can be implemented.

Techniques that overcome at least some limitations of the prior art are desired.

<CIT> discloses a method for receiving downlink data in a wireless communication system supporting <NUM> QAM, comprising the steps of: receiving setting information for power back-off, receiving downlink data transmitted on the basis of the setting information for power back-off, and demodulating the downlink data received on the basis of the setting information for power back-off, wherein the setting information for power back-off is information related to at least one of whether to apply the power back-off, a reduced amount of power of the downlink data by the power back-off, a frame index to which the power back-off is applied, a subframe index and a resource to which the power back-off is applied.

Document <NPL>, aims at minimizing the total transmitted power based on getting the benefit from available but unused PRBs.

According to the present disclosure, a method, an access node and a non-transitory computer-readable medium according to the independent claims are provided. Developments are set forth in the dependent claims.

The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain principles of the disclosure.

At least some of the following abbreviations and terms may be used in this disclosure.

Wireless Device: As used herein, a "wireless device" is any type of device that has access to (i.e., is served by) a cellular communications network by wirelessly transmitting (and/or receiving) signals to (and/or from) a radio access node.

Cell: As used herein, a "cell" is a combination of radio resources (such as, for example, antenna port allocation, time and frequency) that a wireless device may use to exchange radio signals with a radio access node, which may be referred to as a host node or a serving node of the cell. However, it is important to note that beams may be used instead of cells, particularly with respect to <NUM> NR. As such, it should be appreciated that the techniques described herein are equally applicable to both cells and beams.

Note that references in this disclosure to various technical standards (such as <NPL>) and <NPL>), for example) should be understood to refer to the specific version(s) of such standard(s) that is(were) current at the time the present application was filed, and may also refer to applicable counterparts and successors of such versions.

The description herein focuses on a 3GPP cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPP terminology is oftentimes used.

<FIG> illustrates one example of a cellular communications network <NUM> in which embodiments of the present disclosure may be implemented. In the embodiments described herein, the cellular communications network <NUM> is a Public Land Mobility Network (PLMN) conforming to one or more of the LTE, <NUM>, <NUM> and <NUM> NR standards, or their successors. In the illustrated example, the cellular communications network <NUM> includes a (Radio) Access Network ((R)AN) <NUM> comprising base stations <NUM>-<NUM> and <NUM>-<NUM> controlling radio communications with wireless devices <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>,<NUM>-<NUM> within corresponding macro cells <NUM>-<NUM> and <NUM>-<NUM>. Each macro cell <NUM> may be defined by any suitable combination of geography, frequency, Radio Access Technology (RAT) and modulation scheme.

Base stations <NUM> can be any type of network access device capable of establishing radio connection(s) with one or more wireless devices <NUM> within a respective coverage area of the base station <NUM> or low power node <NUM>, and further configured to forward subscriber traffic between the core network <NUM> and the one or more wireless devices <NUM>. An important feature of a base station <NUM> is that it is configured with both a radio interface configured to send and receive radio signals to and from a wireless device <NUM>, and a network interface configured to exchange electronic and/or optical signals with the core network <NUM>. Examples of base stations <NUM> and low power nodes <NUM> include: Evolved Node B (eNB) systems (known, for example, in the 3GPP standards): Wireless Local Area Network (WLAN) access points (known, for example from IEEE <NUM> standards) or the like. In some contexts, a base station <NUM> may be referred to as an access point (AP) regardless of the Radio Access Technology (RAT) that it supports.

In the present disclosure, base stations <NUM> and low power nodes <NUM> may be generically referred to a radio transmitters or transmission points.

The illustrated (R)AN <NUM> also includes small cells <NUM>-<NUM> through <NUM>-<NUM>, within which radio communication can be controlled by corresponding low power nodes <NUM>-<NUM> through <NUM>-<NUM>. As with the macro cells <NUM>, each small cell may be defined by any suitable combination of geography, frequency, Radio Access Technology (RAT) and modulation scheme. As with the base stations <NUM>, a low power node <NUM> can be any type of network access device capable of establishing radio connection(s) with one or more wireless devices <NUM> within a respective coverage area of the low power node <NUM>, and further configured to forward subscriber traffic between the core network <NUM> and the one or more wireless devices <NUM>. An important feature of a low power node <NUM> is that it is configured with both a radio interface configured to send and receive radio signals to and from a wireless device <NUM>, and a network interface configured to exchange electronic and/or optical signals with the core network <NUM>. In some embodiments, a low power node <NUM> may be connected to the core network <NUM> by a direct connection, such as an optical cable. In other embodiments, a low power node <NUM> may be connected to the core network <NUM> by an indirect connection, such as via a radio or optical fiber link to a base station <NUM>. Examples of low power nodes <NUM> include: Remote Radio Heads (RRHs) connected to a base station or a network router (not shown): WLAN access points or the like. In some contexts, a low power node <NUM> may be referred to as an access point (AP) regardless of the specific Radio Access Technology (RAT) that it supports.

Notably, while not illustrated, a particular small cell <NUM> may alternatively be controlled by a base station <NUM>, for example using a beam-forming technique. In such cases, the particular small cell <NUM> will not be associated with a respective low power node <NUM> per se. Rather, the particular small cell <NUM> will be associated with a respective set of parameters implemented in the base station <NUM>. In this disclosure, the term "cell" is used to refer to a defined combination of parameters (such as geography, frequency, Radio Access Technology (RAT), modulation scheme, identifiers and the like) that can be used by a wireless device <NUM> to access communication services of the network <NUM>. The term "cell" does not imply any particular parameter values, or any particular physical configuration of devices needed to enable a wireless device <NUM> to access those communication services.

Wireless devices <NUM> can be any type of device capable of sending and receiving radio signals to and from a base station <NUM> and/or low power node <NUM>. Examples of wireless device <NUM> include cellular phones, Personal Data Assistants (PDAs), mobile computers, Internet of Things (IoT) devices, autonomous vehicle controllers, and the like. In some contexts, a wireless device <NUM> may be referred to as a User Equipment (UE) or a mobile device.

In some embodiments, the macro cells <NUM>-<NUM> and <NUM>-<NUM> may overlap each other, and may also overlap one or more small cells <NUM>. For example, a particular macro cell <NUM>-<NUM> may be one macro cell <NUM> among a plurality of macro cells covering a common geographical region and having a common RAT and modulation scheme, but using respective different frequencies and/or AP identifiers. In such cases, a wireless device <NUM> located within a region covered by two or more overlapping cells <NUM>, <NUM> may send and receive radio signals to and from each of the corresponding base stations <NUM> and/or low power nodes <NUM>.

In the illustrated example, the (R)AN <NUM> is connected to a Core Network (CN) <NUM>, which may also be referred to as Evolved Core Network (ECN) or Evolved Packet Core (EPC). The CN <NUM> includes (or, equivalently, is connected to) one or more servers <NUM> configured to provide networking services such as, for example, Network Functions (NFs) described in 3GPP TS <NUM> V15. <NUM> (<NUM>-<NUM>) "System Architecture for the <NUM> System" and its successors. The CN <NUM> also includes one or more gateway (GW) nodes <NUM> configured to connect the CN <NUM> to a packet data network (DN) <NUM> such as, for example, the internet. A gateway node <NUM> may be referred to as a packet gateway (PGW) and/or a serving gateway (SGW). The DN <NUM> may provide communications services to support end-to-end communications between wireless devices <NUM> and one or more application servers (ASs) <NUM> configured to exchange data packet flows with the wireless devices <NUM> via the CN <NUM> and (R)AN <NUM>. In some contexts, an application server (AS) <NUM> may also be referred to as a host server.

In some contexts, an end-to-end signal path between an AS <NUM> and one or more wireless devices <NUM> may be referred to as an Over-The-Top (OTT) connection. Similarly, a communication service that employs signal transmission between an AS <NUM> and one or more wireless devices <NUM> may be referred to as an OTT service.

It should be appreciated that the separation between the CN <NUM> and the DN <NUM> can be purely logical, in order to simplify understanding of their respective roles. In particular, the CN <NUM> is primarily focused on providing wireless device access services and supporting wireless device mobility. On the other hand, the DN <NUM> is primarily focused on providing end-to-end communications, particularly across network domains. However, it will be appreciated that both the CN <NUM> and the DN <NUM> can be implemented on common physical network infrastructure, if desired.

<FIG> is a block diagram schematically illustrating a communications system <NUM> including a computing device <NUM> usable in embodiments of the present invention. In various embodiments, any or all of the base stations <NUM> or <NUM>, wireless devices <NUM>, core network servers <NUM> or gateways <NUM> and data network servers <NUM> may be implemented using systems and principles in accordance with the computing device <NUM>. It may also be appreciated that any or all of the elements of the network <NUM> may be virtualized using techniques known in the art or developed in the future, in which case the functions of any or all the base stations <NUM> or <NUM>, core network servers <NUM> or gateways <NUM>, and/or any or all of the network functions <NUM>-<NUM> may be implemented by suitable software executing within a computing device <NUM> or within a data center (non shown) composed of multiple computing devices <NUM>.

In the example of <FIG>, the communications system <NUM> generally includes computing device <NUM> connected to one or more networks <NUM> and one or more radio units <NUM>. The computing device <NUM> includes one or more processors <NUM>, a memory <NUM>, one or more network interfaces <NUM>. The processors <NUM> may be provided as any suitable combination of Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), or the like. Similarly, the memory <NUM> may be provided as any suitable combination of Random Access Memory (RAM), Read Only Memory (ROM) and mass storage technologies such as magnetic or optical disc storage or the like. The network interfaces <NUM> enable signaling between the computing device <NUM> and the networks <NUM>, such as the Core Network <NUM>, the data network <NUM>, or a private domain network such as a data center (not shown).

Each radio unit <NUM> typically includes at least one transmitter (Tx) <NUM> and at least one receiver (Rx) <NUM> coupled to one or more antennas <NUM>. In the example of <FIG>, the radio unit(s) <NUM> is(are) shown as being external to the computing device <NUM> and connected to the computing device <NUM> via a suitable physical connection (such as a copper cable or an optical cable). In the example of <FIG>, the radio unit(s) <NUM> is(are) shown as being connected to computing device <NUM> via a network <NUM> and a network interface <NUM>. In still other embodiments, the radio unit(s) <NUM> and optionally also the antenna(s) <NUM> may be integrated together with the computing device <NUM>.

The one or more processors <NUM> operate to provide functions of the computing device <NUM>. Typically, these function(s) are implemented as software applications (APPs) <NUM> or modules that are stored in the memory <NUM>, for example, and executed by the one or more processors <NUM>. In some embodiments, one or more software applications or modules <NUM> may execute within a secure run-time environment (RTE) <NUM> maintained by an operating system (not shown) of the computing device <NUM>.

It may be appreciated that specific embodiments may exclude one or more of the elements illustrated in <FIG>. For example, a computing device <NUM> configured to implement a wireless device <NUM> may incorporate one or more processors <NUM>, a memory <NUM>, and one or more radio units <NUM>, but may exclude a network interface <NUM>. Conversely, a computing device <NUM> configured to implement a server <NUM> or <NUM> may include one or more processors <NUM>, a memory <NUM>, and one or more network interfaces <NUM>, but may exclude radio units <NUM>. A computing device <NUM> configured to implement a base station <NUM> or <NUM>, on the other hand, will normally include one or more processors <NUM>, a memory <NUM>, and both radio units <NUM> and network interfaces <NUM>.

<FIG> is a block diagram schematically illustrating an example architecture for network element virtualization usable in embodiments of the present invention. It is contemplated that the network elements may be physically implemented using one or more computers, data storage devices and routers (any or all of which may be constructed in accordance with the system <NUM> described above with reference to <FIG>) interconnected together and executing suitable software to perform its intended functions. Those of ordinary skill will recognize that there are many suitable combinations of hardware and software that may be used for this purpose, which are either known in the art or may be developed in the future. For this reason, a FIG. showing physical hardware components and connections is not included herein.

As maybe seen in <FIG>, the illustrated architecture <NUM> generally comprises hosting infrastructure <NUM>, a virtualization layer <NUM> and an Application Platform Services layer <NUM>. The hosting infrastructure <NUM> comprises physical hardware resources provided by the infrastructure on which the architecture <NUM> is being implemented. These physical hardware resources may include any or all of the processors <NUM>, memory <NUM>, network interfaces <NUM> and radio units <NUM> described above with reference to <FIG>, and may also include traffic forwarding and routing hardware <NUM>. The virtualization layer <NUM> presents an abstraction of the hardware resources <NUM> to the Application Platform Services layer <NUM>. The specific details of this abstraction will depend on the requirements of the applications <NUM> being hosted by the Application Platform Services layer <NUM>. Thus, for example, an APP <NUM> that provides traffic forwarding functions may be presented with an abstraction of the hardware resources <NUM> (e.g. processor(s) <NUM>, memory <NUM> and traffic forwarding hardware <NUM>) that simplifies the implementation of traffic forwarding policies. Similarly, an application that provides data storage functions may be presented with an abstraction of the hardware resources <NUM> (e.g. processor(s) <NUM> and memory <NUM>) that facilitates the storage and retrieval of data (for example using Lightweight Directory Access Protocol - LDAP).

The application platform <NUM> provides the capabilities for hosting applications. In some embodiments, the application platform <NUM> supports a flexible and efficient multi-tenancy run-time and hosting environment for applications <NUM> by providing Infrastructure as a Service (laaS) facilities. In operation, the application platform <NUM> may provide a security and resource "sandbox" for each application <NUM> being hosted by the platform <NUM>. Each "sandbox" may be implemented as a Virtual Machine (VM) image <NUM> that may include an appropriate operating system and controlled access to (virtualized) hardware resources <NUM>. Alternatively, each "sandbox" may be implemented as a container <NUM> that may include appropriate virtual memory and controlled access to host operating system and (virtualized) hardware resources <NUM>. The application platform <NUM> may also provide a set of middleware application services and infrastructure services to the applications <NUM> hosted on the application platform <NUM>, as will be described in greater detail below.

Applications <NUM> from vendors, service providers, and third-parties may be deployed and executed within a respective Virtual Machine <NUM>. For example, PCF <NUM> may be implemented by means of one or more applications <NUM> hosted on the application platform <NUM> as described above. Communication between applications <NUM> and services of the application platform <NUM> may conveniently be designed according to the principles of Service-Oriented Architecture (SOA) known in the art.

Communication services <NUM> may allow applications <NUM> to communicate with the application platform <NUM> (through pre-defined Application Programming Interfaces (APIs) for example) and with each other (for example through a servicespecific API).

A Service registry <NUM> may provide visibility of the services available on the server <NUM>. In addition, the service registry <NUM> may present service availability (e.g. status of the service) together with the related interfaces and versions. This may be used by applications <NUM> to discover and locate the end-points for the services they require, and to publish their own service end-point for other applications to use.

Network Information Services (NIS) <NUM> may provide applications <NUM> with low-level network information pertaining to a network service instance or one or more PDU sessions, for example. For example, the information provided by NIS <NUM> may be used by an application <NUM> to calculate and present relevant data (such as: cell-ID, location of the subscriber, cell load and throughput guidance) to other network functions, any or all of which may themselves to implemented by applications <NUM> executing in respective VMs <NUM>.

A Traffic Off-Load Function (TOF) service <NUM> may prioritize traffic, and route selected, policy-based, data streams to and from applications <NUM>.

<FIG> illustrates an example resource grid <NUM> usable in the network of <FIG>. The illustrated resource grid consists of a time-frequency division of radio resources that may be used for scheduling of data transmissions between radio access nodes <NUM>, <NUM> and UEs <NUM>. As may be seen in <FIG>, the total system bandwidth is divided (in the frequency dimension) into a set of physical resource blocks (PRBs) <NUM>. In <NUM> NR networks, the total system bandwidth may be into N=<NUM> or more PRBs <NUM>. Each physical resource block (PRB) may be further sub-divided (in the frequency dimension) into a set of sub-carriers on a defined frequency spacing. For example, a PRB <NUM> may be subdivided into <NUM> sub-carriers on a <NUM> spacing. In the illustrated example, <NUM> OFDM symbols are transmitted within a slot having a defined period, such as 1mSec. for example. Each time-frequency location within the resource grid is referred to as a resource element (RE). Two successive slots may be taken together to form a sub-frame comprising 12x14=<NUM> REs, which can be allocated as required to enable transmission of control channel signals, synchronization signals, cell-specific reference signals, UE-specific reference signals and data signals destined for UEs.

Those skilled in the art will appreciate that wireless signals are transmitted between a radio access node <NUM>,<NUM> and the wireless devices <NUM> using radio resources which are scheduled according to one or more scheduling algorithms. A scheduler may be provided in the radio access node <NUM>,<NUM> or logically coupled to the radio access node for this purpose. As used herein, the term "radio resources" refers to any available resource or combination of available resources which can be used to transmit wireless signals, such as frequency (e.g. one or more frequency channels or sub-channels), time (e.g. one or more frames, sub-frames, slots, etc) or codes (e.g. as used for code-division multiplexing).

Thus, for downlink communications (i.e. from the radio access node <NUM>,<NUM> to the wireless devices <NUM>), a pool of available radio resources is distributed for transmissions to the wireless devices <NUM> according to a scheduling algorithm. Various scheduling algorithms are known in the art, and the present disclosure is not limited in that respect. Suitable examples include round robin, fair queuing, proportionally fair scheduling and maximum throughput.

Those skilled in the art will appreciate that the output power of a radio access node varies as a function of the resources it uses for transmissions. For example, when the radio access node is scheduled to transmit using a relatively large amount of resources at any one time (e.g. a relatively large number of frequencies), the output power of that radio access node will also be relatively high. Conversely, when the radio access node is scheduled to transmit using relatively few resources at any one time, the output power of that radio access node will be relatively low.

As noted above, strong ICI can seriously degrade cell performance by reducing the data rate that can be achieved between the host access node and wireless devices. Thus, many existing works introduce different means to mitigate or cancel ICI. Known prior art techniques suffer a limitation in that they employ a reactive procedure in which interference is detected, quantized, and then evaluated to implement a mitigation strategy. This implies that that inter-cell interference, and its consequential impacts on system performance, must be present before the prior art techniques can be implemented.

In modern wireless networks, it frequently occurs that PRBs are only partially scheduled for carrying data traffic, such that at least some PRBs remain unscheduled at any given time. For example, partial scheduling of PRBs can occur under any combination of the following conditions:.

<FIG> is a block diagram illustrating an example communication system <NUM> in LTE <NUM> and NR <NUM>. The illustrated example communication system <NUM> includes an Access Node <NUM> and UEs <NUM>. The Access Node <NUM> may be implemented as a computing device <NUM> or an application <NUM> executing in a computing device <NUM> or a virtual machine <NUM> or container <NUM>. In the illustrated example, the Access node <NUM> includes higher layers <NUM>, one or more data buffe4rs <NUM>, a radio resources scheduler <NUM> and a physical layer <NUM> which includes one or more antennas <NUM>. The Higher Layers (HL) <NUM> send and receive data and control signaling to and from lower layers of the protocol stack, and in particular the data buffer(s) <NUM> and radio resource scheduler <NUM>. The data buffers <NUM> store downlink data being transmitted to the UEs <NUM>, and also uplink data received from the UEs <NUM>. The radio resource scheduler <NUM> allocates radio resources to each UE. According to the allocation results, the data buffer <NUM> forwards downlink data to the physical layer (PHY) <NUM>, which transmits the downlink data to the appropriate UE <NUM>. The PHY <NUM> also measures various channel parameters and reports measurement results to the scheduler <NUM> for use as input arguments to scheduling algorithms.

In practical networks, many UEs require only small data packets. For example, in a network in which a large number of UEs (such as Internet of Things, loT, devices) that only require small data packets, such as the likelihood of un-scheduled PRBs at any given time is relatively high.

Systems and methods are disclosed herein that exploit partial scheduling of PRBs to pre-emptively suppress inter-cell interference (ICI). If desired, conventional techniques may also be used to mitigate any residual ICI, but in such cases the performance requirements of the conventional techniques can be relaxed because the amount of ICI that remains to be mitigated is reduced by the operation of the methods disclosed herein.

Referring to the flow-chart of <FIG>, in very general terms, when the system PRBs are partially scheduled (at <NUM>) (or, equivalently, at least some PRBs are not scheduled for data traffic), ICI can be pre-emptively suppressed by diluting (at <NUM>) downlink data traffic flows over one or more of the un-scheduled PRBs, and reducing (at <NUM>) the transmission power of the scheduled PRBs. This approach reduces the power spectral density (PSD) of physical downlink shared channel (PDSCH) transmissions from the access node, which in turn reduces ICI in neighboring cells. In addition, dilution of downlink data traffic flows increases frequency diversity, which in turn improves decoding robustness against ICI from neighboring cells. An advantage of this approach is that it does not rely on measured ICI. Rather, ICI is pre-emptively suppressed based on the data traffic demand of each UE at any particular time and the physical characteristics of each wireless link.

In order to better understand aspects of the present disclosure, it is useful to consider the Shannon formula. <MAT> where r: is the information bit rate (or data rate) achieved in a given PRB; B is the bandwidth of the PRB; p is the transmission power; and g is the channel gain to noise ratio.

This formula can be rearranged as: <MAT> from which it can be seen that the power is an exponential function in the rate. Thus, for two different data rates, r<NUM> and r<NUM>, the corresponding transmission powers p<NUM> and p<NUM> will be: <MAT> <MAT>.

For an incremental increase in data rate Δ, the corresponding transmission powers <MAT> and <MAT> will be: <MAT>.

For the case where r<NUM> < r<NUM>, then it can be seen that <MAT>.

This means that for a given data rate increment Δ, a larger power increase is required for a higher base rate r. Put another way, for a given total data rate between the access node <NUM> and a UE <NUM>, a lower total transmission power is achieved by scheduling a larger number of lower-power PRBs than by using a smaller number of higher-power PRBs. This means that when the channel quality is symmetric for a UE, it is beneficial to employ more PRBs instead of more power in each PRB to achieve a given data rate.

Accordingly, it is possible to reduce the transmission power of each PRB scheduled for a given UE, by minimizing the data rate in each scheduled PRB. When the traffic to/from the UE in question is diluted across previously un-scheduled PRBs, the data rate in each PRB scheduled for the UE can be reduced by reducing the modulation and coding scheme (MCS) associated with that UE. Furthermore, the benefits of this approach can be maximized by concentrating on the UE(s) with the highest base MCS values.

<FIG> is a flow-chart illustrating an example embodiment in which an access node <NUM> transmits downlink traffic to a set of I (an integer) UEs <NUM> (each of which may be denoted as UEj, j=<NUM>. I) and initially at least one unscheduled PDSCH PRB. Referring to <FIG>, the example method includes the following steps, which may be executing iteratively until the number of remaining unscheduled PRBs has been reduced to a desired value, such as zero, for example. The example method of <FIG> includes the following steps:.

For example, <FIG> illustrates an example iterative algorithm for determining a new MCS value for the UEj, which may be denoted as newMCSj. In the example of <FIG>, the new MCS value (newMCSj) is selected such that a change in the transport block size is minimized. This approach is beneficial in that it reduces changes in buffering requirements of downlink traffic destined for the UEj. However, it will be appreciated that alternative algorithms for selecting newMCSj may be used, if desired. The example method of <FIG> includes the following steps:.

As noted above, the iterative process of <FIG> terminates when the candidate MSC value, MCSj(n) is below a predetermined threshold, which may, for example, reflect a minimum allowable SINR of the PDSCH. When this happens, the values newMCS; and newTBS; will respectively contain new MCS and TBS values that can be assigned to PDSCH for the selected UEj while minimizing any change in the TBS, and thus also minimizing any change to buffering of downlink traffic destined for the UEj. Accordingly, the values newMCS; and newTBS; may be allocated (at <NUM>) to the PDSCH for the selected UEj.

Returning to <FIG>, Once the new (reduced) value of MCS has been found (at <NUM>, and <FIG>), the process may return to step <NUM> for selection of a next unscheduled PRB, if any.

While processes in the figures may show a particular order of operations performed by certain embodiments of the present disclosure, it should be understood that such order is representative, and that alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc..

Claim 1:
A method performed by an access node (<NUM>; <NUM>) of a wireless communication network, the access node (<NUM>; <NUM>) configured to transmit downlink traffic to a plurality of user equipments, UEs, (<NUM>) in a coverage area of the access node (<NUM>; <NUM>), the method comprising:
detecting (<NUM>) at least one unscheduled physical resource block, PRB;
diluting (<NUM>) downlink traffic across the at least one unscheduled PRB; and
reducing (<NUM>) transmission power of scheduled PRBs,
wherein diluting downlink traffic across the at least one unscheduled PRB comprises:
selecting (<NUM>) one UE (<NUM>) from among the plurality of UEs (<NUM>); and
scheduling a selected one unscheduled PRB for downlink traffic destined for the selected UE (<NUM>),
wherein selecting one UE (<NUM>) from among the plurality of UEs comprises selecting a UE (<NUM>) having a highest modulation and coding scheme, MCS, value among the plurality of UEs (<NUM>),
wherein reducing (<NUM>) transmission power of scheduled PRBs comprises reducing the MCS value allocated to the selected UE (<NUM>).