DESCRIPTION OF THE DRAWINGS

Figure 1 shows a view of context-aware spectrum coordination according to the state of the art. Figure 2 shows an example of architecture on which the present invention is applicable.

Figure 3 describes a procedure to dynamically select MAC profiles according to the present invention.

Figure 4 shows an example of MAC profile configuration according to the present invention.

Figure 5 shows an example of equivalence between MAC profiles associated with different radio access technologies.

Figure 6 shows an example of application of the present invention to groups of devices.

Figure 7 shows an example of application of the present invention in a vehicular environment.

Figure 8 shows example radio transmissions according to two MAC profiles.

Figure 9 shows an example of optimization of MAC profile configuration over a given geographic area.

DESCRIPTION OF THE INVENTION

Background on radio environment maps

A radio environment map (REM), representing a dynamic radio environment, can be used to help decision-making processing in many radio applications and systems such as self- configuration, self-optimization and self-healing of radio networks, dynamic radio planning or dynamic spectrum sharing.

The REM can be designed as a database containing information of the radio environment (e.g., RF signal strength, RF path loss or RF interference level), in space, time and frequency dimensions. The REM builds its radio environment using information retrieved from radio network topology deployment, radio node configuration and field measurements. The radio environment map is then computed over space, time and frequency dimensions using advanced radio propagation environment models.

The REM can be viewable e.g. through a GIS interface (Geographic Information System) to reveal the space, time and frequency dimensions of the information.

Background on context-aware spectrum sharing

In order to maximize usage of spectrum, new models have been defined, which enable to share spectrum among multiple users. In some of those models, licenses related to spectrum usage may be associated with priorities and contexts specifying when those licenses are applicable. Those licenses may allow users to have exclusive use of spectrum or allow users to share spectrum with other users.

When a user has a license allowing exclusive use of spectrum, users that may interfere with this user and whose license indicate a lower priority are not allowed to use spectrum.

When multiple users over a given geographic area have licenses allowing shared use of spectrum on the same frequency, no mechanism currently exist to adjust the amount of spectrum allocated to those users according to their priority and the estimated amount of interferences among them.

The present invention addresses this issue and provides a method to prioritize access to shared spectrum among devices operating within a given geographical area, owned by licensed users with different priorities, using identical or different radio access technologies, capable to send and/or receive radio signals on the same frequency, by selecting and configuring a MAC profile at each device according to its priority and the estimated amount of interferences with other devices.

This method may be characterized by the following operations: i. sorting MAC profiles of a given radio access technology according to their efficiency, each MAC profile consisting of a set of parameters associated with a given MAC protocol,

ii. defining equivalence between MAC profiles of different radio access technologies, wherein two MAC profiles are equivalent when the impact of interferences caused by a device configured with any of those MAC profiles on other devices is the same, iii. selecting a MAC profile for each device according to the priority of its licensed user, its context, and the allowed amount of interferences on other devices,

iv. configuring each device with the selected MAC profile.

Figure 1 shows a view of context-aware spectrum coordination according to the state of the art.

In this figure, licensed users are connected to a context-aware spectrum management engine. The context-aware spectrum management engine determines spectrum availability information (describing the conditions to access spectrum such as the allowed frequencies, the allowed bandwidth and the allowed maximum transmission power) of a given user based on:

- the context of this user,

- the spectrum usage requirements provided by this user,

- the license of this user,

spectrum usage of users who may be interfered by this user or who may interfere on this user.

A user may consist of a single device or of a multiplicity of devices accessing spectrum according to the same spectrum availability information. Devices referred to throughout the present invention may consist of user terminals or radio base stations, and may be part of a cellular network or of a mesh network. In addition some or all devices may be able to communicate using d2d (device-to-device) communication and/or to act as relays to provide connectivity to other devices. The context of each user is regularly provided by users to the context-aware spectrum management engine, for example at pre-defined intervals or whenever changes to their context are identified.

MAC (Medium Access Control) profile definition

A MAC profile consists of a set of parameters associated with a given MAC protocol and a given radio access technology.

The value of those parameters may have an impact on spectrum usage and on the efficiency of the protocol, such as the throughput and/or the delay to access the medium. MAC profiles within a given radio access technology may therefore be ranked according to the level of efficiency they provide (for example based on the throughput and/ or the delay to access the medium), or based on their level of spectrum occupancy.

MAC profiles may contain different parameters depending on the radio access technology (e.g. wi-fi, multeFire, LTE-TDD, LTE-FDD) and/or on the type of devices (e.g., user equipment, base station, Machine Type Communication (MTC) device, Narrowband IoT (NB-IoT) device).

All or a subset of the following parameters may be used, for example, to create a MAC profile: - an inter-frame interval, indicating the time during which a device must wait after a transmission before initiating another transmission,

a back-off timer, determining the time during which a device must wait after failing to access the medium before attempting to access the medium again,

a UL (uplink) frame duration,

- a DL (downlink) frame duration,

a number of UL subframes within each frame. This parameter is applicable, for example to a MAC profile to be configured at a base station, and indicates, for a given frame, how many subframes are allocated to uplink.

a number of DL subframes within each frame. This parameter is applicable, for example to a MAC profile to be configured at a base station, and indicates, for a given frame, how many subframes are allocated to downlink.

a number of interlaces over which the transmission bandwidth is divided. Increasing the number of interlaces enables to spread the transmission power over the spectrum and therefore reduce the power spectrum density. Equivalence between MAC profiles associated with different radio access technologies may be determined based on the spectrum utilization of each MAC profile. Figure 5 shows an example of equivalence between MAC profiles associated with different radio access technologies.

In Figure 5, the MAC profile 2 of radio access technology A is equivalent to the MAC profile of the MAC profile 3 of radio access technology B.

The level of efficiency of a given MAC profile may be determined by theoretical means, or by experimental means.

Equivalence between MAC profiles of different radio access technologies may be determined through theoretical means, through simulation, and/or by testing devices configured with those MAC profiles and identifying the level of efficiency at those devices.

Two MAC profiles are equivalent when the impact of interferences caused by a device configured with any of those MAC profiles on other devices is the same.

One method to determine whether two MAC profiles 1 and 2 are equivalent could be, for example, to verify whether the quality of service on a device A interfered by radio transmissions originating from a device 2 is identical when this device B is configured and transmitting using MAC profile and when this device B is configured and transmitting using MAC profile 2.

Figure 8 shows an example radio transmissions according to two MAC profiles.

In this example, MAC profile 1 and MAC profile 2 are defined by only 2 parameters (UL frame duration and inter- frame interval).

White rectangles indicate UL transmissions over time from a device configured with the corresponding MAC profile.

This figure shows that MAC profile 2 is more efficient than MAC profile 1 since more data can be sent and received over the same period of time.

Architecture for MAC profile configuration

Figure 2 shows an example of architecture on which the present invention is applicable. In this architecture, a spectrum management engine is responsible for determining spectrum availability information of each user.

This spectrum management engine is connected to the following elements: a radio environment map (REM), used to estimate radio propagation and identify interferences among users,

- a database containing the licenses of each user,

a database containing the current context of each user,

a database containing information associated with MAC profiles.

The text shown in bold in this figure highlights the inventive aspects of the present invention compared to prior art. In addition to determining the frequency, the bandwidth and the transmission power allowed for each user, as described in prior art, the context-aware spectrum management engine is capable of selecting a MAC profile to be configured by each user, and to provide each user with this selected MAC profile (for example within the spectrum availability information). In the example shown in Figure 2, user 2, located at latitude x and longitude y, is requesting authorization to transmit at a maximum transmission power of 30 dBm, at frequency 2340 MHz.

Upon receiving this request, the spectrum management engine first retrieves license conditions of user 2, based on the context provided by user 2.

The spectrum management engine then determines, based on the current context of all users, their licenses conditions, and their current use of spectrum, the MAC profile to be used by user 2, and provides the MAC profile identifier (MAC profile 1 in this example) to user 2.

User 2 then configures the device or the multiplicity of devices associated with user 2 with the provided MAC profile. A timing parameter (for example, an absolute date and time or a countdown in seconds) may also be provided by the spectrum management engine, indicating to the user when the MAC profile shall be activated.

In addition, the spectrum management engine identifies whether some updated spectrum availability information needs to be provided to other users as a result of the request originating from user 2. In this example, spectrum availability information of user 1 is updated.

Alternative architectures The architecture shown in Figure 2 is centralized.

In an alternative architecture, the context-aware spectrum management engine may be distributed within each device. In such alternative, each device could autonomously determine its MAC profile, based on its current context license conditions and estimated mutual interferences with nearby devices computed using a radio environment map (REM) embedded within each device. Device-to-device communication could for example be used to retrieve information from nearby devices required to determine the MAC profile according to the present invention.

In an hybrid alternative, some functionalities of the context-aware spectrum management engine may be performed within a centralized server, such as the estimation of interferences among devices, while the selection of the MAC profile may be performed by users based on the estimation of interferences among users, received from the centralized server.

In summary, each device may autonomously, or through a centralized entity acting on behalf of each device, or in a distributed manner across the device and one or multiple remote entities, determine its MAC profile. MAC profile selection

Figure 3 describes a procedure to dynamically reconfigure MAC profiles according to the present invention. This procedure may, for example, be applied by the spectrum management engine described in Figure 2, over a set of users allowed to access spectrum on the same frequency within a given geographic area, each user being associated with one or multiple devices. It may be executed whenever a user provides an updated context or updated spectrum usage requirements to the context-aware management service.

At the first step of the procedure, the MAC profile associated with each user is initialized with the MAC profile associated with the highest level of efficiency.

At the second step, the set of users (UserHPset) having the highest priority (MaxP) is identified. This can be performed by checking the current applicable license conditions of each user. For example, the Licence 1 in Figure 6 indicates a priority set to 2, while the License 2 indicates a priority set to 1.

If there is no user whose priority is lower than MaxP, the procedure stops. The spectrum management engine may then configure users with the MAC profile determined according to the procedure. This configuration can be performed by sending the identifier of the MAC profile (for example as part of the spectrum availability information, as shown in Figure 2) to each user.

At step three, for each user X in the set of users UserHPset, the set of users (UserlFset) interfering with this user X and having a priority lower than user X is identified.

At step four, the MAC profile associated with each user Y in the set of users UserlFset is updated according to the level of interference of user Y on user X.

The rank of the MAC profile updated on a given user Y during step 4 shall be lower or equal to the rank of the MAC profile of user X and to the rank of the MAC profile currently assigned to user Y.

A set of pre-defined threshold interferences values may be associated with a set of interference handicap levels (IHL) to be subtracted from the MAC profile rank of user X to determine the MAC profile rank of user Y.

For example, if the level of interferences of user Y on user X is below a first threshold, the MAC profile ranked just below the current MAC profile of user X may be selected for user Y. If the level of interference of user Y on user X is below a second threshold higher than the first threshold, the MAC profile ranked 2 levels below the current MAC profile of user X may be selected for user Y.

The procedure is then executed again from step 2, with a highest priority (MaxP) decremented by 1. The procedure stops when no user has a priority lower than the highest priority (MaxP).

MAC profile selection on a set of users can be summarized as follows: i. initializing each user with the MAC profile associated with the highest level of efficiency,

ii. identifying the set of users having the highest priority,

iii. for each given user in the set of users identified in step ii, identifying users whose devices interfere with the devices of this given user,

iv. updating the MAC profile of each of the users identified in step iii according to the level of interference generated on said given highest priority user, v. excluding the users having the highest priority, and repeating this procedure from step ii, until the remaining set of users is empty.

Figure 4 shows an example of MAC profile configuration resulting from the procedure described in Figure 3.

In this figure, six users, with current priorities ranging from 1 to 3 (labeled PI to P3) are shown. Four MAC profiles are assumed to be available, from MAC P l to MAC P 4.

The circle around a given device indicates the zone over which the signal strength from transmissions originating from this device is above a pre-defined threshold. The zone over which circles are overlapping indicates the area where devices are interfering with each other's transmissions.

Other criteria may be used to determine interference levels between devices. For example, instead of overlapping coverage areas, the signal strength of a transmissions from a device A at the antenna of a device B may be used as a criterion to determine whether device A is interfering with device B.

In Figure 4, user 1 and user 2 do not interfere with any device. Therefore, according to the procedure described in Figure 3, user 1 and user 2 are configured with the most efficient MAC profile (MAC P 4).

On the other hand, user 3 and user 4 are configured with less efficient MAC profiles since they interfere with users who have a higher priority. User 3 is interfering with user 5, whose priority is higher. Similarly, user 4 is interfering with user 6, whose priority is higher.

The MAC profile associated with user 3 (MAC P 3) his only 1 rank lower than the MAC profile of user 5 because the level of interference from user 3 on user 5 is low, as illustrated by the small overlapping area between the circle around user 3 and the circle around user 5.

The MAC profile associated with user 4 is two ranks below the MAC profile of user 6 because the level of interference from user 4 on user 6 is high, as illustrated by the wide overlapping area between the circle around user 4 and the circle around user 6.

Thresholds values may be defined in order to determine, for a given overlapping area size between the circles associated with two devices, whether interferences among those devices are low or high.

MAC profile configuration on groups of devices

Figure 6 shows an example of application of the present invention to users associated with groups of devices.

In this example, two groups of devices are shown. Each group is associated with a license (labeled LI or 12) indicating a priority. For each group, a controller is assumed to be connected to the spectrum management engine and assumed to be capable of configuring a MAC profile at each device.

Devices from group 2 (labeled G2) may interfere with devices from group 1 (labeled Gl), as shown by the overlapping dotted lines around the each group. The priority of group 2 is lower than the priority of group 1. As a result, the MAC profile configured for group 2 is lower than the MAC profile of group 1. This MAC profile (MAC P 3) is configured at each device belonging to group 2. Similarly, the MAC profile MAC P 4 is configured at each device belonging to group 1.

MAC profile configuration in a vehicular environment

Figure 7 shows an example of application of the present invention within the context of vehicle to vehicle communication.

In this example, a high-priority vehicle connected to a spectrum management engine is accessing spectrum on a given frequency for an emergency.

Devices located nearby this high-priority vehicle (colored in white in the figure) and using this given frequency reconfigure their devices with a lower MAC profile (labeled MAC_P_1), in order to limit interferences with the high-priority vehicle.

This reconfiguration may be performed autonomously by vehicles, for example using a spectrum management engine located within vehicles and by detecting devices located in the vicinity, or by connecting to a remote spectrum management engine.

MAC profile configuration optimization

The efficiency of MAC profiles may depend on the radio environment. For example, in case of a high density of devices, it may be more efficient to increase the back-off timer in order to reduce collisions.

A change in the radio environment over a given geographic area may be computed using a radio environment map.

Upon detecting a change in the radio environment, the spectrum management engine may simultaneously modify the MAC profile configured at each device over a given geographic area for optimization purposes, while maintaining the same difference between the ranks of MAC profiles configured at each device.

Figure 9 shows an example of optimization of MAC profile configuration upon detecting that the radio environment is degrading (for example based on reports from devices or based on the density of devices). In this example, all MAC profiles are decreased from 1 level. For example, User 3 is configured with MAC profile 3 before reconfiguration and with MAC profile 2 after reconfiguration.

This enables to maintain fairness among users according to their priorities, while configuring the most efficient MAC profiles according to the surrounding radio environment.