FR3092460A1 - Estimation of the risk for a CBSD of being unauthorized to transmit on a channel near an activated DPA - Google Patents

Abstract

Estimation of the risk for a CBSD of being unauthorized to transmit on a channel near an activated DPA Method for determining the risk, for a CBSD of being unauthorized to transmit on a given channel, when a DPA located in the vicinity of this CBSD is active.

Description

Estimation of the risk for a CBSD to be unauthorized to transmit on a channel near an activated DPA

The shows the architecture of the CBRS (“Citizens Broadband Radio Service”) according to the state of the art.

The shows an example of deployment of CBSDs in the vicinity of DPAs (“Dynamic Protection Areas”).

The shows the exchanges between a CBSD and an SAS to obtain an authorization to issue, or "grant", in accordance with the state of the art.

The describes the steps for ordering a list of channels according to the risk of interference, in accordance with the present invention.

The describes in more detail the procedure of [Fig.4], including a possible criterion for evaluating the channels.

The shows an example of the SAS indicating the available channels, ordered according to the risk of interference, in accordance with the present invention.

The shows an example in which a channel is considered unusable (according to step 4.A of the procedure described [Fig.4]), for a given CBSD, when the DPAs are activated.

The shows an example where the risk of interference on a given c-channel and a given CBSD is minimal.

The describes the exchanges allowing the SAS to provide alternative channels in response to a grant request.

DESCRIPTION OF THE INVENTION

State of the art on CBRS (Citizens Broadband Radio Service)

CBRS is a service defined by the FCC regulatory authority (“Federal Communications Commission”, document 15-47) allowing frequency sharing on the 3.5 GHz band between three priority levels, or 3 thirds:

- primary users (or priority users),

- PAL secondary users (Priority Access Licensees),

- third party GAA (General Authorized Access) users.

The Wireless Innovation Forum defines the architecture and protocols of the CBRS service, in accordance with FCC requirements.

The shows the architecture of the CBRS service. A centralized SAS (“Spectrum Access System”) server controls the access and use of the spectrum of fixed radio base stations called CBSDs (Citizens Broadband Radio Service Devices) connected to this SAS server. These CBSDs can be connected directly to the SAS server (as illustrated by "CBSD 4" in [Fig.1]), or indirectly through a Proxy Server (SP) connected to CBSDs.

Server Proxy (SP) is also called Domain Proxy (DP) in the context of the CBRS service.

The protocol between the SAS server and CBSDs or between the SAS server and an SP makes it possible to control the channels used by the CBSDs for radio transmission and/or reception, as well as the maximum authorized transmission power.

Before starting to transmit on a contiguous set of channels, a CBSD must ask the SAS for a transmission authorization or "grant", using the message "grant Request", indicating a maximum transmission power.

If a CBSD is located in the vicinity of a primary user, and the channels of the "grant" overlap with this primary user, the SAS cannot authorize this grant without first ensuring that the aggregation of the emissions of the grants current, associated with other CBSDs, and of this new grant does not exceed the authorized threshold.

DPA “Dynamic Protection Areas” are an example of areas associated with a primary user. These zones have the particularity of being able to be activated or deactivated depending on whether or not the primary user is present.

The presence of a primary user can be detected using sensors near these DPAs and transmitted to the SAS. A DPA can also be activated by a primary user via, for example, a web portal. When a DPA is active, the aggregation of interference from CBSDs must not exceed a predefined threshold associated with this DPA.

In the event that a SAS does not have information on the status of a DPA, it considers that the DPA is active.

The shows an example deployment of CBSDs in the vicinity of DPAs.

When a DPA is activated on a given channel, the total interference caused by the “grants” of the CBSDs operating on this channel must not exceed a predefined threshold, at any point of this DPA.

At regular intervals (for example daily), the SAS determines, at each DPA point (with a predefined granularity, for example every 50 meters), the list of grants, called "move list", to be suspended so that the aggregation of the remaining grants (not present in the "move list") does not exceed the only predefined one associated with this DPA.

This process, carried out at regular intervals, is called CPAS (“Coordinated Periodic Activities among SASes”). Other operations are carried out during this process, not relevant for the description of the present invention.

The “move list” associated with a DPA consists of the union of all the “move lists” calculated at each of the points of this DPA.

The procedure for calculating a move list is described in requirement "R2-SGN-24" of the document "WINNF-TS-0112-CBRS Operational and Functional Requirements" published by the Wireless Innovation Forum.

For example in the , the DPA 3 consists of two points P1 and P2 to be protected.

It is assumed that all CBSDs in the figure have a grant on the same channel (eg 3550-3560 MHz).

Each CBSD is connected to an SAS. There may be several SASes controlling different CBSDs deployed in the same geographical area. In this case, the SASes must exchange, during the CPAS, the "grants" that they control, so that each SAS is able to calculate the aggregate interference of all the CBSDs at a given point.

The "move lists" at each point of the DPA 3 are made up of the CBSDs indicated in bold on the .

In P1, the "move list" associated with the 3550-3560 MHz channel is made up of CBSD 2 and CBSD 3.

In P2, the "move list" associated with the 3550-3560 MHz channel is made up of CBSD 5, CBSD 4 and CBSD 3.

The "move list" associated with DPA 3 on the 3550-3560 MHz channel is the union of the "move lists" calculated for each point of this DPA and is therefore made up of the following CBSDs: CBSD 5, CBSD 2, CBSD 3, CBSD 4.

When DPA 3 is activated, only CBSD 1, not present in the “move list” will be authorized to transmit on the 3550-3560 MHz channel.

The shows the exchanges between a CBSD and a SAS to obtain a grant in accordance with the state of the art.

It is assumed that CBSD 2 is located in the vicinity of DPA 1. It is assumed that DPA 1 is activated on the “3640-3650 MHz” channel.

Sending the “registration request” message allows the CBSD to provide the SAS with its installation parameters (such as its location and its maximum transmission power). This information will be used by the SAS to determine the interference of this CBSD at a given point in the territory.

Sending the "grant request" message allows the CBSD to indicate to the SAS the channels on which it is requesting authorization to operate, as well as the transmission power.

In this example, the SAS sends the response SUCCESS, indicating that the grant is accepted. However, the CBSD cannot yet issue on this grant. Indeed, a CBSD is only authorized to transmit upon receipt of a “hearbeat response” message containing the “SUCCESS” response.

For each grant, the CBSD then sends a "hearbeat request" message at regular intervals.

According to the state of the art, the SAS automatically adds the grant to the "move list" of each DPA channel impacted by the grant, pending the next CPAS. So, in this example, because DPA 1 is activated on one of the channels associated with the grant, the SAS sends the response SUSPENDED_GRANT, indicating that the CBSD is not authorized to transmit.

During the next CPAS, the SAS recalculates the “move list” associated with DPA 1. If the grant requested by CBSD 2 is not included in the move list, CBSD 2 will be authorized to transmit. Otherwise, CBSD 2 will continue to be suspended as long as the DPA is active.

This mechanism, although correctly protecting the DPAs from interference, results in an underutilization of the spectrum. In particular, when a DPA is always activated (or considered to be activated, for example when a SAS is unable to know the status of a DPA), CBSD 2 will be suspended the next day (and the days) if it is in the "move list" of a DPA at the end of the next CPAS (and the CPAS of the following days), while other channels may be available for this CBSD.

Description of the present invention

The present invention describes a method for determining the risk, for a CBSD, of being unauthorized to transmit on a given channel, when a DPA located in the vicinity of this CBSD is active.

• par une CBSD, pour choisir les canaux à inclure dans une demande de « grant ».
• par le SAS, pour indiquer à une CBSD les canaux recommandés (par exemple lors d’une réponse à un message « grant request » ou lors d’une réponse à un message « heartbeat request »).

This information on the risk, for a given channel, of being unauthorized can be used:

• by a CBSD, to choose the channels to be included in a grant request.
• by the SAS, to indicate to a CBSD the recommended channels (for example when replying to a “grant request” message or when replying to a “heartbeat request” message).

The describes the steps for determining the risk, for a CBSD, of being unauthorized to transmit on a given channel, when a DPA located in the vicinity of this CBSD is active.

Description of steps 1 to 4 to determine the risk, for a CBSD, of being unauthorized to transmit on a given channel

In step 1, the list of DPA points impacted by CBSD is identified. A CBSD impacts a DPA point if it is located at a distance from this point less than the neighborhood distance associated with this DPA.

Steps 2 to 4 are then carried out for each “c” channel on which a CBSD is likely to transmit (in the case of CBRS, the channels are 10 MHz, from 3550 MHz to 3700 MHz).

In step 2, the "Interference_Risk(c)" variable is initialized to 0. At the end of the procedure described , the higher the value of this variable, the higher the risk for this CBSD to be suspended on channel “c”.

Steps 3 and 4 are carried out on each point “p” of the DPA to be protected on channel “c”.

During step 3, the interference generated by CBSD at point “p” and for channel “c” (I_CBSD_p_c) is calculated using a radio propagation algorithm (for example ITM). This calculation takes into account:

- the location of the CBSD,

- the maximum transmission power of the CBSD (“maxEIRP”),

- its antenna height,

- the CBSD antenna gain in the direction of the point to be protected,

- the terrain (for example the nature of the terrain and its elevation) between the CBSD and the point considered.

This step 3 can only be performed once for all the channels because the radio propagation varies little from one channel to another.

During step 4, a channel exclusion condition, based on the I_CBSD_p_c value calculated during step 3, is evaluated. An example of a channel exclusion condition is described in .

If the channel exclusion condition is satisfied, the channel is considered unusable by the CBSD (case 4.A) when the DPAs are active.

Otherwise, the “Interference_Risk(c)” variable, whose value expresses the risk for a CBSD of being suspended when a DPA located close to this CBSD is activated, is increased according to the I_CBSD_p_c value. An example of updating this variable is described in .

At the end of this procedure, the higher the value of the "Interference_Risk(c)" variable is for a given channel "c", the greater the risk, for the CBSD evaluated during this procedure, of being unauthorized to transmit on this "c" channel is high.

Alternatively, steps 3 and 4 are performed on a predefined subset N of points (for example the N DPA points closest to the CBSD considered).

Alternatively, the “Interference_Risk(c)” variable is increased or weighted proportionally to the following value: [I_CBSD_p_c –DPA_Threshold]. This makes it possible to take into account the fact that the closer a “grant” is to exceeding the authorized threshold on a DPA, the higher the risk for this “grant” of being unauthorized when this DPA is active.

Alternatively, the "Interference_Risk(c)" variable is increased or weighted inversely proportional to the number of grants not present in the "move list" associated with point "p" and channel "c", and whose interference at point "p" is greater than the value I_CBSD_p_c. This makes it possible to take into account the fact that these grants will be the first to be included in the "move list" in the event of interference being exceeded during a next CPAS and thus to free up an additional margin of interference for the other "grants ".

Example of channel endpoint and variable update " Interference_Risk(c) »

• un exemple de critère possible d’évaluation des canaux,
• un exemple de mise à jour de la variable « Interference_Risk(c) ».

The further describes the procedure of [Fig.4] including:

• an example of a possible channel evaluation criterion,
• an example of updating the “Interference_Risk(c)” variable.

In this example, the channel exclusion condition (c), evaluated in step 4, is as follows:

If the calculated value I_CBSD_p_c is greater than the interference threshold authorized for this DPA (“DPA_Threshold”) for the DPA associated with point “p”, this channel is considered as not usable (step 4.A) when this DPA is active.

This exclusion criterion is based on the fact that whatever the activity of the other CBSDs located nearby, this CBSD cannot be authorized to transmit on this channel "c", assuming that it uses its maximum power. transmission "maxEIRP".

In this example, the update of the “ Interference_Risk(c)” variable is as follows:

If the I_CBSD_p_c value is greater than the “Max_Current_Interference_p_c” value (previously initialized as described below), the “Interference_Risk(c)” variable is incremented.

Initialization of the Max_Current_Interference_p_c parameter:

• ce « grant » est non présent dans la « move list » associée à ce point « p » et ce canal « c », calculée durant le CPAS, et,
• ce « grant » est celui qui interfère le plus sur ce point « p », parmi tous les « grants » à la fois opérant sur le canal c et non présents dans cette « move list ».

The “Max_Current_Interference_p_c” parameter, used during step 4.B of the , is initialized during each CPAS, at each point “p” of DPA and for each channel “c”. This parameter contains the value of the interference at point "p" of the grant satisfying the following conditions:

• this "grant" is not present in the "move list" associated with this point "p" and this channel "c", calculated during the CPAS, and,
• this “grant” is the one that interferes the most on this point “p”, among all the “grants” both operating on channel c and not present in this “move list”.

If during the CPAS, after calculating a "move list", there is no "grant" satisfying these conditions, the "Max_Current_Interference_p_c" parameter is initialized to the value "DPA_Threshold".

Sorting of the available channels according to the risk of interference, when processing a “spectrum inquiry request” message

The shows an example of the SAS indicating the available channels, ordered according to the risk of interference, in accordance with the present invention.

The CBSD provides, in the "spectrum inquiry request" message, the minimum frequency and the maximum frequency of the channels for which information on the risk of interference is requested (respectively 3600 MHz and 3650 MHz in this example).

The SAS executes the procedure described in , for each channel requested, using the maximum transmission power of the CBSD as the “maxEIRP” value.

The SAS then provides, using the "spectrum inquiry response" message, the list of channels sorted by order of risk of interference, omitting the channels excluded during the procedure described in .

In this example, the channels [3600-3610] and [3610-3620] were excluded during the procedure described in [Fig.4]. The channel on which CBSD is least likely to be suspended when activating a DPA is channel [3620-3630], followed by channel [3640-3650] and finally channel [3630-3640] .

Alternatively, the procedure described in is executed several times, by varying the “maxEIRP” parameter over a set of values less than or equal to the maximum value supported by the CBSD.

For each channel, the most optimal "maxEIRP" value among all these "maxEIRP" values (for example the highest "maxEIRP" value for which the channel is not excluded during the procedure of the ) is then included in a new parameter of the “spectrum inquiry request” message.

Example of exceeding the authorized interference threshold

The shows an example in which a channel is excluded (according to step 4.A of the procedure described [Fig.4]), for a given CBSD.

In this example, CBSD impacts DPA 3 and DPA 4. The black dots indicate locations where the interference caused by CBSD is above the allowable threshold.

It is assumed that the maximum EIRP value of CBSD is 47 dBm / 10 MHz.

The interference at P1 is calculated as follows:

CBSD_EIRP–CBSD_Pathloss=47–104=-57dBm/10MHz

Where “CBSD_Pathloss” is the path loss between CBSD and point P1.

-57 dBm being greater than -144 dBm, the interference threshold is considered by SAS to be exceeded by CBSD.

Example of CBSD with minimal risk of interference

The shows an example where the risk of interference on a given “c” channel and a given CBSD is minimal according to the evaluation criteria described in [Fig.5].

In this example, the CBSD considered - CBSD 6 - is located in the vicinity of DPA 3 and DPA 4.

To simplify, we only consider the interference at two points P1 and P2.

• les CBSDs 1 à 5 ont obtenu un « grant » sur le canal c considéré dans cet exemple.
• les CBSDs causant des interférences sur le point P1, sont les suivantes, par ordre décroissant d’interférence : CBSD 1, CBSD 4, CBSD 3, CBSD 2.
• les CBSDs causant des interférences sur le point P2, sont les suivantes, par ordre décroissant d’interférence : CBSD 4, CBSD 1, CBSD 3, CBSD 5.

We suppose that :

• CBSDs 1 to 5 have obtained a “grant” on channel c considered in this example.
• the CBSDs causing interference on point P1 are as follows, in decreasing order of interference: CBSD 1, CBSD 4, CBSD 3, CBSD 2.
• the CBSDs causing interference on point P2 are as follows, in decreasing order of interference: CBSD 4, CBSD 1, CBSD 3, CBSD 5.

The "move list" in P1 calculated during the last CPAS consists of CBSD 1 and CBSD 4. The CBSD authorized to transmit on channel c and generating the most interference in P1 is CBSD 3 (among all the CBSDs authorized to transmit on this channel).

The value of Max_Current_Interference_p_c describes for point P1 is therefore the interference of the “grant” of CBSD 3 at point P1.

The "move list" in P2 calculated during the last CPAS consists of CBSD 4. The CBSD authorized to transmit on channel "c" and generating the most interference in P2 is CBSD 1 (among all the CBSDs authorized to transmit on this channel).

The value of Max_Current_Interference_p_c describes for point P2 is therefore the interference of the “grant” of CBSD 1 at point P2.

It is assumed that the interference at P1 of CBSD 6 is lower than that of CBSD 3.

It is assumed that the interference at P2 of CBSD 6 is lower than that of CBSD 1.

As a result, when performing the procedure described in , the value of the “Interference_Risk(c)” variable will be zero (step 4.B will not be executed for any DPA point).

The risk for CBSD 6 of being unauthorized to transmit on channel "c" when DPA 3 or DPA 4 is active is therefore minimal.

Identification of alternative channels when processing a “grant request” message

The describes the exchanges allowing the SAS to provide alternative channels in response to a grant request.

• la valeur « maxEIRP » est la valeur demandée par la CBSD pour ce grant et fournie dans le message « grant request ».

On receipt of a "grant request" message, the SAS evaluates the channels in accordance with the procedure described , with the following details:

• the “maxEIRP” value is the value requested by the CBSD for this grant and provided in the “grant request” message.

In this example, one of the channels [3630-3640] is excluded during the described procedure [Fig.4]. This grant cannot therefore be accepted.

The value of the "Interference_Risk" variable associated with each channel can be used by the SAS as a criterion for selecting alternative channels, in addition to other criteria, such as the channels used by other CBSDs deployed in the same geographical area, or even the presence of priority users in the vicinity of the CBSD.

In this example, the SAS identifies channels [3650-3660] and [3660-3670] as having a lower risk of being suspended, and provides these channels in the "grant response" message.

Application of the invention in the event that several "grants" are requested between two CPAS.

In the event that a grant is accepted for a given CBSD, this grant is temporarily added (until the next CPAS), for each channel of the grant, to the "move list" of each DPA point impacted by this grant.

If another CBSD sends a “grant request” message or a “spectrum inquiry request” message before the execution of the next CPAS, each “move list” thus updated is used in the procedure described in to evaluate the channels.

Claims (9)

A method for determining the risk, for a CBSD, of being unauthorized to transmit on a given "c" channel, when a DPA located in the vicinity of this CBSD is active, characterized by the following operations:

1. Identification of DPA points located at a distance from the CBSD less than the neighborhood distance associated with this DPA,
2. For each point “p” of DPA identified in i:
   1. Calculation of the interference called I_CBSD_p_c generated by the CBSD at point “p”.
   2. Evaluation of an exclusion criterion for channel "c", based on the interference I_CBSD_p_c calculated in 1.
   3. In the case where this criterion for exclusion of the channel “c” evaluated in 2 is satisfied, marking of the channel “c” as not usable by the CBSD.
   4. In the event that this exclusion criterion of channel "c" evaluated in 2 is not satisfied, update of the risk estimate "Interference_Risk(c)" for the CBSD to be unauthorized on this channel "c" when a DPA is active.

The method according to claim 1 characterized in that said criterion for exclusion of the channel "c" considered is satisfied when the interference I_CBSD_p_c calculated by the CBSD at at least one point of DPA is greater than the authorized interference threshold DPA_Threshold associated with this DPA. The method according to claims 1 to 2, characterized in that the updating of the estimation of the interference risk "Interference_Risk(c)" consists in incrementing this risk, each time the interference calculated for the said CBSD in one point "p" of given DPA is greater than the maximum interference caused by a "grant" at this point "p" among all the "grants" authorized on this channel "c" and not present in the "move list" associated with this point "p" and this channel "c" previously calculated in accordance with the state of the art. The method according to claims 1 to 3, characterized in that only the N closest DPA points to said CBSD are taken into account, where N is a pre-defined value. The method according to claims 1 to 4, characterized in that the estimation of the interference risk "Interference_Risk(c)" is evaluated on receipt of a "spectrum inquiry request" message, and the list of channels is then sorted according to the decreasing order of the “Interference_Risk(c)” value associated with each channel “c” then included in the “spectum inquiry response” message. The method according to claims 1 to 5, characterized in that the estimation of the interference risk "Interference_Risk(c)" is evaluated on receipt of a "spectrum inquiry request" message, several times, by varying the parameter "maxEIRP", and in which the resulting optimal "maxEIRP" value, for each channel, is included in the "spectum inquiry response" message. The method according to claims 1 to 6, characterized in that the interference risk estimate "Interference_Risk(c)" is evaluated on receipt of a "grant request" message and in which the interference risk estimate interference "Interference_Risk(c)" is used as a criterion to determine the channels included in the "grant response" message. The method according to claims 1 to 7, characterized in that the estimation of the interference risk “Interference_Risk(c)” is increased or weighted proportionally to the following value: [I_CBSD_p_c –DPA_Threshold]. The method according to claims 1 to 8, characterized in that the estimation of the interference risk "Interference_Risk(c)" is increased or weighted inversely proportional to the number of "grants" not present in the associated "move list" at point "p" and channel "c", and whose interference at point "p" is greater than the value I_CBSD_p_c.