Coexistence of multiple air interface side-links on a channel

Various arrangements for using multiple air interfaces on a frequency channel for side-link communications are presented. A first indication of a first time-window of a first resource pool may be transmitted by a first air interface system. A second indication of a second time-window of a second resource pool may be transmitted by a second air interface system. Side-link communications may be performed using the first air interface during only the first time-window of the first resource pool. Side-link communications may be performed using the second air interface during only the second time-window of the second resource pool.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No. 16/277,116, entitled “Coexistence of Multiple Air Interface Side-links on Adjacent Channels”, filed on the same day as this application, the entire disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND

Typically, air interface communication protocols, such as 4G LTE and 5G NR are used to communicate between user equipment (UE) and a cellular network base station. However, side-link and device to device (or ProSe) communication is also possible. In side-link communications, vehicle UE communicates with another instance of vehicle UE, either directly or with the assistance of a base station. Similarly, other forms of UE can perform device to device (D2D) or ProSe communication directly or via a base station. Such direct communication may be useful if there is data that would be useful to transmit to particular instances of UE that are in the immediate vicinity of a transmitting UE.

While such side-link communications may be beneficial in certain instances, not all UE may use the same air interface communication protocol. Therefore, the ability of various instances of UE to coexist may result in significant inefficiencies, such as different frequency channels being needed to be allocated to each air interface.

SUMMARY

Various embodiments are described related to a method for using multiple air interfaces on a frequency channel for side-link communications. In some embodiments, a method for using multiple air interfaces on a frequency channel for side-link communications is described. The method may include determining, by an air interface coordination management server system, an allocation of a system resource pool among multiple different air interfaces such that a first air interface may be assigned a first time-window of a frequency channel of the system resource pool and a second air interface may be assigned a second time-window of the frequency channel of the system resource pool. The first time-window and the second time-window may not overlap. The method may include transmitting a first indication of the first time-window of the system resource pool to a first air interface system. The method may include transmitting a second indication of the second time-window of the system resource pool to a second air interface system. The method may include transmitting, by the first air interface system, a first indication of the first time-window of the system resource pool to a first set of user equipment using the first air interface. The method may include transmitting, by the second air interface system, a second indication of the second time-window of the system resource pool to a second set of user equipment using the second air interface. The method may include performing, by the first set of user equipment, side-link communications using the first air interface during only the first time-window of the system resource pool. The method may include performing, by the second set of user equipment, side-link communications using the second air interface during only the second time-window of the system resource pool.

Embodiments of such a method may include one or more of the following features: the first air interface may be a 4G LTE air interface. The second air interface may be a 5G NR air interface. The first air interface may use a first subcarrier spacing and the second air interface may use a second subcarrier spacing that may be different from the first subcarrier spacing. The side-link communications may be selected from a group consisting of vehicle to vehicle communications, vehicle to infrastructure communications, and vehicle to pedestrian communications. The side-link communications may include basic safety messages (BSMs). Each BSM may include: vehicle size data, position data, speed data, heading data, acceleration data, and brake system status data. The method may further include receiving, by the air interface coordination management server system, one or more reports of communication traffic on the first time-window, the second time-window, or both. The method may further include re-determining, by the air interface coordination management server system, the allocation of the system resource pool among multiple different air interfaces based on the one or more reports of communication traffic. The system resource pool may periodically repeat. The method may further include transmitting, by the second air interface system, an indication of a subcarrier spacing to be used during the second time-window of the system resource pool to the second set of user equipment using the second air interface. No indication of subcarrier spacing may be transmitted to the first set of user equipment using the first air interface. Subcarrier spacing of the second air interface may be variable but subcarrier spacing of the first air interface may be fixed.

In some embodiments, a system that uses multiple air interfaces on a frequency channel for side-link communications is described. The system may include an air interface coordination management server system that may determine an allocation of a system resource pool among multiple different air interfaces such that a first air interface may be assigned a first resource pool having a first time-window of a frequency channel and a second air interface may be assigned a second resource pool having a second time-window of the frequency channel. The system may include a first air interface system that may receive an indication of the first time-window from the air interface coordination management server system and may transmit the indication of the first time-window to a first plurality of user equipment that may communicate using the first air interface. The system may include a second air interface system that may receive an indication of the second time-window from the air interface coordination management server system and may transmit the indication of the second time-window to a second plurality of user equipment that may communicate using the second air interface. The system may include the first plurality of user equipment that may perform side-link communications using the first air interface during only the first time-window of the first resource pool. The system may include the second plurality of user equipment that may perform side-link communications using the second air interface during only the second time-window of the second resource pool.

Embodiments of such a system may include one or more of the following features: The first air interface may be a 4G LTE air interface. The second air interface may be a 5G NR air interface. The side-link communications may be selected from a group consisting of vehicle to vehicle communications, vehicle to infrastructure communications, and vehicle to pedestrian communications. The side-link communications may include basic safety messages (BSMs). Subcarrier spacing of the second air interface may be variable but subcarrier spacing of the first air interface may be fixed.

In some embodiments, a vehicle system that uses multiple air interfaces on a frequency channel for side-link communications is described. The system may include a first air interface component that may perform side-link communications using a first air interface. The system may include a second air interface component that may perform side-link communications using a second air interface. The system may include a vehicle systems interface. The system may include one or more processors configured to receive one or more resource pool allocation messages via the first air interface component, the second air interface component, or both. The one or more resource pool allocation messages may allocate a system resource pool among multiple different air interfaces such that the first air interface may be assigned a first resource pool having a first-time-window of a frequency channel and the second air interface may be assigned a second resource pool having second time-window of the frequency channel. The system may schedule a first side-link communication using the first air interface component and the first air interface during the first time-window on the frequency channel. The system may schedule a second side-link communication using the second air interface component and the second air interface during the second time-window on the frequency channel. The system may perform the first side-link communication during the first time-window on the frequency channel. The first side-link communication may use data obtained from the vehicle systems interface. The system may perform the second side-link communication during the second time-window on the frequency channel. The second side-link communication may use data obtained from the vehicle systems interface.

DETAILED DESCRIPTION OF THE INVENTION

Various air interfaces describe the ability of UE to communicate using side-links. A side-link can refer to a direct wireless communication between two instances of vehicle UE with or without using a cellular network base station. Such a side-link may be autonomous (radio resources are chosen for the side-link communication without scheduling from the base-station), or scheduled by the base-station (the base-station assigns the resources for the communication and the UEs receive messages indicating as such). Vehicle communication systems may be built into a vehicle (e.g., car, truck, motorcycle, scooter, train, boat, tram, subway, etc.). Typically, such as defined by 3GPP, side-link communications refer to vehicle-to-vehicle (V2V) side-link communications; however, other forms of communication may also be considered a form of side-link communication, such as vehicle-to-infrastructure (V2I) side-link communications and vehicle-to-pedestrian (V2P) communications. Infrastructure UE may be installed at various pieces of infrastructure, such as brides, roadways, highways, traffic lights, buildings, parking facilities, etc. Pedestrian communication systems may include mobile devices, such as smartphones, that a pedestrian may carry on his body.

Such side-link communications may allow for safety information to be quickly and efficiently exchanged between UE located in the vicinity of each other. For example, side-link communications may typically be performed over distances of 1000 feet or less. Such side-link communications may involve basic safety messages (BSMs) being transmitted and received via side-link communications. BSMs may include data such as: a timestamp; position (latitude, longitude, elevation); speed; heading; acceleration; brake system status; vehicle size; steering wheel angle; positional accuracy; braking history; path prediction; throttle position; vehicle mass; trailer weight; vehicle type; vehicle description; anti-lock brake system (ABS) status; traction control status; stability control status; differential GPS; lights status; wiper status; brake level; coefficient of friction; rain type; air temperature; air pressure; vehicle identification; cargo weight; and GPS status. Such data may be transmitted via a side-link using an air interface to other instances of UE in the immediate vicinity.

In order to successfully communicate using a side-link communication, the same air interface needs to be used by the transmitting UE and the receiving UE. For example, side-link communications may use 4G LTE (Long Term Evolution) as the air interface communication protocol or may use 5G NR (New Radio) as the air interface communication protocol. An instance of user equipment may, for example, be able to communicate: using only 4G LTE; using only 5G NR; or using both air interface communication protocols. It can be expected that 5G NR UE will be compatible with 4G LTE. Other air interface communication protocols may also be possible.

Side-links performed using air interfaces that use different communication protocols (such as 4G LTE and 5G NR) may be performed using the same frequency channel. Since different air interface communication protocols are incompatible, interference is possible. For example, different air interface communication protocols may use different subcarrier spacing; thus, interference could result due to the lack of orthogonality if both air interfaces were used for communication on the same resource pool. As a specific example, 4G LTE only uses 15 KHz subcarrier spacing; however, 5G NR uses multiple different subcarrier spacings (15 KHz, 30 KHz, 60 KHz, etc.) to be used. However, multiple air interface communication protocols can share a same frequency channel for side-link communications as detailed herein by the frequency channel being subdivided based on time.

FIG. 1illustrates multiple resource pools that are configured to allow for coexistence of multiple air interfaces on the same channel. A system resource pool100can be subdivided in the frequency domain into various subcarriers having various subcarrier spacings. System resource pool100may also be defined over a period of time. After the period of time, a new system resource pool may be present, allowing for periodic repetition of system resource pool100.

System resource pool100is divided, based on time, into a first air interface side-link resource pool110and a second air interface side-link resource pool120. For example, the first air interface may be 4G LTE and the second air interface may be 5G NR. First air interface side-link resource pool110and second air interface side-link resource pool120each include the entire frequency channel. First air interface side-link resource pool110occurs over first time period111and second air interface side-link resource pool120occurs over second time period121. The first time period111and the second time period121can be adjacent, but do not overlap. The relative duration of first air interface side-link resource pool110and second air interface side-link resource pool120may be varied based on the measured or expected amount of traffic using each air interface communication protocol. As seen inFIG. 1, first time period111is shorter in duration than second time period121. Therefore, it can be expected that fewer side-link communications using the first air interface have previously been present or are expected to be present than via the second air interface. In other embodiments, a predefined fixed allocation of system resource pool100may be performed between the first air interface and the second air interface.

Even though first air interface side-link resource pool110and second air interface side-link resource pool120are part of the same frequency channel, since time division of system resource pool100is used, different subcarrier spacing or the same subcarrier spacing may be used for each pool without interference. For example, if the first air interface is 4G LTE, the subcarrier spacing can only be at 15 kHz. If the second air interface is 5G NR, the subcarrier spacing may be set to either, for example, 15 kHz, 30 kHz, 60 kHz in a first frequency range (FR1) or 60 kHz or 120 kHz in a second frequency range (FR2). To change the subcarrier spacing, side-link resource pool120may need to be reconfigured.

Each instance of UE may receive data that indicates how system resource pool100is apportioned. Therefore, a UE can schedule side-link communications during first time period111if the first air interface is to be used or during second time period121if the second air interface is to be used. While the illustrated example illustrates system resource pool100being divided into more than two resource pools to accommodate more than two air interface communication protocols.

FIG. 2illustrates a system200that uses multiple air interfaces for side-link communications using a resource pool. System200may include: coordination management system210; first air interface control system220; second air interface control system230; base station222; base station232; pedestrian UE250(which is represented onFIG. 2as a pedestrian holding a UE); vehicles240(240-1,240-2,240-3); and infrastructure260.

Coordination manager system210can represent one or more server systems that can either statically, semi-statically or dynamically subdivide side-link resource pools (e.g., system resource pool100) into one or more resource pools for different air interfaces. Coordination manager system210may be operated by a particular cellular network provider or may be used to coordinate resource pools across multiple cellular network service providers. If coordination manager system210is operated by a particular cellular network provider, it may be in communication with a master coordination system that communicates with coordination manager systems operated by multiple cellular network providers or coordination manager system210may communicate with coordination manager systems operated by other cellular service providers such that the side-link resource pools are divided consistently across service providers in a given geographic region (thus allowing for communication among UE of different service providers). Coordination manager system210may assign a portion of a resource pool to each air interface.

In some embodiments, a static amount of resource pool is assigned to each air interface. A static amount of resource pool may be assigned once and remain fixed. In a semi-static arrangement, the semi-static amount may be occasionally or periodically reassessed, such as daily or weekly. For example, half of a resource pool may be assigned to a first air interface and the second half of the resource pool may be assigned to the second air interface. In some embodiments, a dynamic amount of resource pool is assigned to each air interface. In such embodiments, coordination manager system210may have a traffic analysis system212. Traffic analysis system212, which may be special-purpose computer hardware or a software process executed by coordination manager system210, may receive indications of side-link traffic. Based on analyzing the amount of side-link traffic or the amount of collisions in side-link traffic, coordination manager system210may adjust the allocation of the amount of resource pools that are assigned to each air interface. For example, if a large amount of side-link traffic is present using a first air interface but a relatively little amount of side-link traffic is present using a second air interface, allocation of resource pools may be adjusted such that the first air interface is allocated a greater portion of each resource pool. Such an adjustment may occur on a geographic basis; that is, certain geographic regions may see one air interface being allocated a greater portion of each resource pool while another geographic region may see a different air interface being allocated a greater portion of each resource pool.

Coordination manager system210may communicate with first air interface control system220and second air interface control system230. First air interface control system220and second air interface control system230can represent control systems that are part of wireless networks that use different air interface communication protocols. By way of example, first air interface control system220may use 4G LTE as its air interface communication protocol and second air interface control system230may use 5G NR as its air interface communication protocol. First air interface control system220and second air interface control system230may receive indications of the time window of side-link resource pools that are allocated to the air interface used by the particular control system. The time window available for use for side-link communications for each particular air interface may be communicated by the control system, through a base station, to each instance of UE with which the base station is in communication. For example, first air interface control system220may transmit an indication of the time window of each resource pool during which side-link communication using the first air interface is permitted via base station222to instances of UE that communicate using the first air interface and are in communication with base station222. Similarly, for example, second air interface control system230may transmit an indication of the time window of each resource pool during which side-link communication using the second air interface is permitted via base station232to instances of UE that communicate using the second air interface and are in communication with base station232. In other embodiments, the indication may include more information, such as indicating the particular air interface that is allocated to each time window within each resource pool. Therefore, in such embodiments, a UE that communicates using multiple air interfaces could determine when it can transmit a side-link communication using the second air interface based on an indication received from first air interface control system220through base station222.

In system200, for example, the first air interface may be 4G LTE. In such an embodiment, base station222may be an eNodeB. First air interface control system220may be part of the enhanced packet core (EPC) of the 4G LTE network or may be incorporated as part of the eNodeB. The second air interface may be 5G NR. In such an embodiment, base station232may be a gNodeB. Second air interface control system230may be part of the core 5G network or may be incorporated as part of the gNodeB.

In system200, pedestrian UE250, vehicle240-3, vehicle240-2, and vehicle240-1communicate using the first air interface; vehicle240-1, and infrastructure260communicate using the second air interface. Pedestrian UE250communicates with base station222via wireless link270; vehicle240-3communicates with base station222via wireless link271; vehicle240-2communicates with base station222via wireless link272; and vehicle240-1communicates with base station222via wireless link279. Vehicle240-1communicates with base station232via wireless link275; vehicle240-2communicates with base station232via wireless link280; and infrastructure260communicates with base station232via wireless link276. In system200, side-link communications may be in the form of broadcast messages or messages transmitted to specific other instance of UE in the vicinity. Various side-link communications are present: side-link273(which is vehicle-to-pedestrian); side-link278(which is vehicle-to-vehicle); and side-link274(which is vehicle-to-vehicle). In some embodiments, another form of direct or indirect communication may be present, such as side-link277(which is vehicle-to-infrastructure).

Side-link273may be performed using the first air interface using the portion of resources for side-links assigned to the first air interface, such as first air interface side-link resource pool110. Side-link278may also be performed using the first air interface using the portion of the resources for side-links assigned to the first air interface. However, vehicle240-2may have UE that is also capable of communicating using the second air interface. Side-link274may be performed using the second air interface using the portion of resources for side-links assigned to the second air interface, such as second air interface side-link resource pool120. Side-link277may also be performed using the second air interface using the portion of resources for side-links assigned to the second air interface. In some embodiments, data about side-link communications may be reported back to first air interface control system220, second air interface control system230, or both. Such data about side-link communications may indicate: 1) that such side-link transmissions have occurred; and/or 2) that side-link transmission collisions occurred. Such data may be reported back to coordination manager system210for use by traffic analysis system212.

FIG. 3illustrates an embodiment of a vehicle system300that can communicate using multiple air interfaces using a same resource for side-links. An embodiment of vehicle system300may be present on vehicle240-1and240-2. On vehicle240-3, an embodiment of vehicle system300may present that does not include second air interface component330. Vehicle system300can include: vehicle processing system310; first air interface component320; second air interface component330; vehicle systems interface340; and vehicle systems350(which can include GPS module352, steering system354, braking system356, and fixed vehicle datastore358).

Vehicle processing system310may include one or more special-purpose or general-purpose processors. Such special-purpose processors may include processors that are specifically designed to perform the functions detailed herein. Such special-purpose processors may be ASICs (application-specific integrated circuits) or FPGAs (field-programmable gate arrays) which are general-purpose components that are physically and electrically configured to perform the functions detailed herein. Such general-purpose processors may execute special-purpose software that is stored using one or more non-transitory processor-readable mediums, such as random access memory (RAM), flash memory, a hard disk drive (HDD), or a solid state drive (SSD). The various components of vehicle processing system310may be implemented using such special- or general-purpose processors.

Vehicle processing system310may be in communication with first air interface component320, second air interface component330, or both. First air interface component320may transmit and receive data with a cellular network that uses the first air interface and may perform side-link communications with other instances of UE that communicate using the first air interface. Second air interface component330may transmit and receive data with a cellular network that uses the second air interface and may perform side-link communications with other instances of UE that communicate using the second air interface. In some examples, first air interface component320communicates using 4G LTE and second air interface component communicates using 5G LTE. It should be understood that in other embodiments a greater number (or fewer number) of air interface components may be present.

Vehicle processing system310may store side-link resource pool allocation data received via first air interface component320, second air interface component330, or both in air interface configuration data314. This data may be accessed by side-link communication scheduler316to determine which portion of a resource pool has been allocated for side-link communications in the air interface that is to be used for the side-link communication. Side-link communication scheduler316may cause the side-link communication to be transmitted as one or more packets during one or more appropriate sub-pools across one or more side-link communication resource pools.

Vehicle data compiler and analyzer312may: 1) receive and format data obtained from vehicle systems interface340for transmission in the form of one or more messages, such as BSMs; and 2) interpret messages, such as BSMs, received from other instances of UE via side-link communications. Vehicle systems interface340may collect data from various vehicle systems350. For example, such vehicle systems can include: GPS module352(e.g., location, elevation, position accuracy); steering system354(e.g., steering angle); braking system356(e.g., whether or not engaged, amount of braking); and fixed vehicle datastore358(e.g., data about the vehicle that does not regularly change, such as vehicle type, vehicle description, etc.). In some embodiments, vehicle systems350may communicate directly with vehicle processing system310. In other embodiments, other vehicle systems may provide data for inclusion in BSMs or other forms of data transmissions via side-links.

BSMs or other types of messages may be broadcast via side-link communications or may be transmitted to particular other instances of UE. In a broadcast form, any instance of UE in the vicinity (within reception range) that communicates using the air interface used to transmit the side-link communication may be able to receive the side-link communication to determine where the instance of UE is located. In an embodiment such as illustrated of vehicle system300, both first air interface component320and second air interface component330may be used to transmit similar data as side-link communications using different air interfaces and the assigned sub-pools of resource pools.

Similar systems to vehicle system300may be present in pedestrian UE and infrastructure UE to transmit via side-link transmissions the position and state of the instance of UE and to receive and analyze side-link communications received from other instances of UE.

Various methods may be performed using the systems detailed inFIGS. 2 and 3and the resource pool allocation detailed in relation toFIG. 1.FIG. 4illustrates an embodiment of a method400for using multiple air interfaces on a same resource pool for side-link communications. Method400may be performed using at least some components of system200ofFIG. 2. In other embodiments, method400may be performed using a system other than system200ofFIG. 2.

At block405, a determination that a system resource pool is to be divided up between multiple air interfaces may be made. In some embodiments, this determination may not be necessary because the resource pools are always allocated among multiple air interfaces. In other embodiments, a system, such as a coordination manager system, may determine that based on various parameters, such as the instances of user equipment in a particular region, that resource pools available for site links are to be allocated among multiple air interfaces. While more than two air interfaces may be used in conjunction with a resource pool for single frequency channel, the remainder of the example of method400assumes that the resource pool is being allocated for two air interfaces. For example, the first air interface may be 4G LTE and the secondary interface may be 5G NR.

At block410, a determination may be made about how resource pools are to be allocated among multiple air interfaces. The allocation may be based on a time window of the entire frequency channel of the resource pool being assigned to each air interface. Therefore, the greater the percent that the time window is of the entire resource pool, the greater the available bandwidth for transmitting side-link messages using the associated air interface. The determination of block410may be performed by a coordination manager system. The determination may be based on the determined or expected amount of side-link traffic using each air interface among which the system resource pool is being allocated.

At block415, an indication may be provided to a first air interface system of a time-window for side-link resource pools that has been allocated to the first air interface. The indication may indicate a start time and end time of the time-window of each resource pool. Similarly, at block420, an indication may be provided to a second air interface system of a second, non-overlapping time-window for side-link resource pools that has been allocated to the second air interface. The indication may indicate a start time and end time of the second time-window of each resource pool. These indications may be provided by the coordination manager system. The duration of each time-window may be based on the determination of block410.

At block425, an indication of the first time-window of the resource pools that are allocated for side-link transmissions using the first air interface may be transmitted to UE that is communicating with the first air interface system. Such an indication may be transmitted in only a particular geographic region or in certain cells of the cellular network. In response to the indication, each UE which receives the message may update stored air interface configuration data that is stored locally. In an example in which the first air interface is 4G LTE, no indication of a subcarrier spacing may be transmitted since subcarrier spacing for side-link communications may be fixed. At block430, an indication of the second time-window of the resource pools that are allocated for side-link transmissions using the second air interface may be transmitted to UE that is communicating with the second air interface system. Such an indication may be transmitted in only a particular geographic region or in certain cells of the cellular network. In response to the indication, each UE which receives the message may update stored air interface configuration data that is stored locally. In an example in which the second air interface is 5G NR, an indication of subcarrier spacing may also be transmitted since subcarrier spacing for 5G NR side-link communications may be variable based on the network configuration. Therefore, the subcarrier spacing of the second pool may differ

At block435, side-link communications may be performed directly between UE using the first time-window for the first air interface and the second time-window for the second air interface. By using different time-windows of each resource pool, different air interfaces can use the same frequency channel. Side-link communications may be sent in the form of a broadcast message that can be received directly by multiple instances of UE located within communication range or may be sent as a message addressed to a particular instance of UE. At block440, in some embodiments, side-link communication messages or collisions may be reported back via the first air interface system, the second air interface system, or both such that the allocation of the resource pool can be adjusted to better accommodate the side-link communication traffic.

While method400is focused on actions that are taken at a system level, method500is focused on actions performed by an instance of UE, such as a vehicle-based system.FIG. 5illustrates an embodiment of a method500for a vehicle system using multiple air interfaces on a same resource pool for side-link communications. Method500may be performed using vehicle system300. Method500may alternatively be performed using some alternate form of UE.

At block505, an instance of UE may receive one or more resource pool allocation messages. A resource pool allocation message may indicate a time window within side-link system resource pools allocated to the air interface particular corresponding to the air interface system from which the message was received. Alternatively, the resource pool allocation message may indicate how the resource pool is allocated as a whole. (Thus, it may be possible for an instance of UE to receive a resource pool message via a first air interface and send a side-link communication using a second air interface during the correct pool assigned to the second air interface.)

At block510, based on the received one or more resource pool allocation messages, a side-link communication message may be scheduled for transmission using the first air interface during a first time-window or first resource pool assigned to the first air interface. Similarly, if the UE also has an air interface component that communicates using the second air interface, At block515, based on the received one or more resource pool allocation messages, a different side-link communication message may be scheduled for transmission using the second air interface during a second time-window or second resource pool assigned to the second air interface. Therefore, while the first side-link message and the second side-link message may contain the same or similar data, they may be sent using different protocols and carrier spacing during the appropriate assigned resource pool time-windows. At block520and525, the first side-link communication and the second side-link communication may be transmitted. At block520, the first side-link communication may be transmitted using the first air interface to a first UE using a first subcarrier spacing during the first time-window. At block525, the second side-link communication may be transmitted using the second air interface to a second UE using a second subcarrier spacing during the second time-window.

While method500is directed to transmitting side-link messages, a similar scheduled arrangement can also be used for receiving side-link messages. That is, during the pool or time-window assigned to the first air interface, side-link messages in the first air interface communication protocol are listened for and received on the frequency channel; and during the second pool or second time-window assigned to the second air interface, side-link messages in the second air interface communication protocol are listened for and received on the frequency channel.

In the example of method500, the UE communicates using both air interfaces. If UE uses the second air interface, it may be backwards compatible to use the first air interface. In other embodiments, some instances of UE may exclusively use the first air interface or the second air interface. In other embodiments, a greater number of air interfaces may be used and the resource pool may be further subdivided to accommodate more than two air interfaces.