WO2020025111A1

WO2020025111A1 - Method for transmitting data utilising distributed resource allocation

Info

Publication number: WO2020025111A1
Application number: PCT/EP2018/070759
Authority: WO
Inventors: Ricardo BLASCO SERRANO; Stefano Sorrentino; Wanlu Sun
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2018-07-31
Filing date: 2018-07-31
Publication date: 2020-02-06

Abstract

A method, in a wireless device (50), for transmitting data utilizing distributed resource allocation. The method comprises selecting (410) a first antenna configuration for a transmission of first data, the first antenna configuration being one of a plurality of possible antenna configurations for the wireless device. The method further comprises performing (420) distributed resource allocation for selecting a radio resource for transmission of the first data, using at least one distributed resource allocation parameter value that is maintained independently by the wireless device for the first antenna configuration, relative to others of the possible antenna configurations.

Description

METHOD FOR TRANSMITTING DATA UTILISING DISTRIBUTED RESOURCE ALLOCATION

TECHNICAL FIELD

The present application is related to the allocation of transmission resources for multi antenna data transmission. BACKGROUND

Release 12 of the 3^rd Generation Partnership Project (3GPP) standards for Long-Term

Evolution (LTE) wireless networks have been extended to provide support for several device-to-device (D2D) features targeting both commercial and Public Safety applications. Some of these features, which are referred to in the LTE context as "sidelink" features, relate to device discovery, where devices are able to sense the proximity of another device and associated applications by broadcasting and detecting discovery messages that carry device and application identities. Another application enabled by these specification extensions consists of direct communication over physical channels terminated directly between devices. See, for example, 3GPP TS 36.331 V12.17.0 (2018-07-08). One of the potential extensions for the device-to-device work in 3GPP is the support of V2x communication, which includes any combination of direct communication between vehicles, pedestrians and infrastructure. (V2x may be understood as standing for "vehicle-to- anything-you-can-imagine.") V2x communication may take advantage of a network infrastructure, e.g., an LTE radio access network (RAN) infrastructure, when available, but at least basic V2x connectivity should be possible even in case of lack of coverage. Providing an LTE-based V2x interface is expected to be economically advantageous because of the LTE economies of scale, and will enable tighter integration between communications with the network infrastructure (vehicle-to-infrastructure, or V2I), communications between vehicles and pedestrians (V2P), and vehicle-to-vehicle (V2V) communications, as compared to using a dedicated V2x technology. Figure 1 illustrates various V2x scenarios that may be apply within the context of an LTE-based network.

V2x communications may carry both non-safety and safety information, where each of the applications and services may be associated with specific requirements sets, e.g., in terms of latency, reliability, capacity, etc. With regards to messages related to road safety, the European Telecommunications Standards Institute (ETSI) has defined two types: the Co operative Awareness Message (CAM) and the Decentralized Environmental Notification Message (DENM). The CAM message is intended to enable vehicles, including emergency vehicles, to notify their presence and other relevant parameters in a broadcast fashion. Such messages target other vehicles, pedestrians, and infrastructure, and are handled by their applications. CAM message also serves as active assistance to safety driving for normal traffic. The availability of a CAM message is indicatively checked for every 100ms, yielding a maximum detection latency requirement of no more than 100 milliseconds for most messages. However, the latency requirement for pre-crash sensing warning is 50 milliseconds. The DENM message is event-triggered, such as by braking. The availability of a DENM message is also checked for every 100 milliseconds, and the requirement of maximum latency is 100 milliseconds. The package size for CAM and DENM message varies from 100+ to 800+ bytes, with the typical size being around 300 bytes. The message is supposed to be detected by all vehicles in proximity.

The Society of Automotive Engineers (SAE) has also defined the Basic Safety Message (BSM) for Dedicated Short-Range Communications (DSRC), with various messages sizes defined. According to the importance and urgency of the messages, the BSMs are further classified by the SAE definitions into different priorities.

In Rel-12 a new resource allocation mode for D2D communications was introduced. This resource allocation mode allows UEs to autonomously select the resources for their transmissions. A new distributed resource allocation mode specifically for V2V

communications is being introduced in Release 14 of the 3GPP specifications. Distributed resource allocation is necessary in scenarios when there is no cellular coverage or when centralized resource allocation is otherwise not possible or practical, e.g., due to complexity considerations. Although distributed resource allocation is quite new to 3GPP, it has a long use history in IEEE standards.

For the purposes of the present disclosure, the term "distributed resource allocation" refers to a procedure or process whereby a wireless device autonomously selects a resource for transmission of control and/or data to other wireless devices, from among resources shared by the wireless device and peer wireless devices. This includes processes whereby the wireless device makes a final decision to use a transmission resource from among a group of transmission resources that have been predefined or pre-designated for selection or selective use by the wireless device. The term "distributed resource allocation protocol" simply refers to a standardized or otherwise widely known or agreed procedure for distributed resource allocation.

Following are descriptions of several distributed resource allocation protocols. It will be appreciated that there are others, as well as variants of these particular examples.

A first example is the well-known Aloha protocol, which is a simple distributed resource allocation protocol with many variations. In its simplest form, the procedure followed by a user equipment (UE) or other wireless device for accessing the channel using Aloha is the following:

1. The UE transmits a data packet and awaits an acknowledgement response for a certain time Tack- a. If a positive acknowledgement response is received, the UE waits for a new packet to be transmitted, and then starts again from Step 1. b. If a negative acknowledgement response is received or no response is

received within T_ack, the UE assumes that the packet was not correctly received, e.g., due to a collision. Consequently, the UE defers the retransmission of the packet for a certain time using a timer. The timer is initially set to Tbackoff, which is a randomly generated value within a predefined range. Once the timer has expired, the UE starts again at Step 1 and retransmits the packet.

Note that a UE following the Aloha protocol can only process the transmission of one packet at a time. That is, if a UE is in the process of transmitting a first packet (i.e., it is following the procedure outlined above) and a second packet arrives at the transmitter buffer, the UE will not start the process to transmit the latter until it has finished transmitting the former. In particular, if the UE has deferred the transmission of the first packet (i.e., it is in Step lb) and the second packet arrives during the back-off time, the transmission procedure for the second packet will not start immediately.

A second example of a distributed resource allocation protocol is the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol. CSMA/CA is a widely used distributed resource allocation protocol, for example in the IEEE 802.11 series of standards. With some simplifications, the procedure followed by a UE for accessing the channel using CSMA/CA is the following:

1. To transmit a new packet, the UE first needs to sense the transmission medium. If it detects an ongoing transmission, then it defers the new transmission for a certain time using a timer. The timer is initially set to Tbackoff which is a randomly generated value between 1 and T_Contention_window, measured in time units (e.g., in steps of 8 microseconds). If it does not detect an ongoing transmission, then the UE proceeds to Step 3.

2. Whenever the UE senses the transmission medium as idle, it decrements the counter. If the UE senses the medium as busy, it does not decrement the counter. The UE proceeds to Step 3 whenever the counter reaches 0.

3. The UE transmits the packet and awaits an acknowledgement response for a certain time T_aCk. a. If a positive acknowledgement response is received, the UE resets Tcontention_window to some default value, waits for a new packet to be transmitted, and then starts again from Step 1. b. If a negative acknowledgement response is received or no response is

received within T_aCk, the UE assumes that the packet was not correctly received, e.g., due to a collision. Consequently, the UE increments

Tcontention_window and defers the retransmission of the packet for a certain time using a timer. The timer is initially set to Tbackoff which is a randomly generated value between 1 and T_Contention_window (using the updated value) measured in time units (e.g., in steps of 8 microseconds). The UE continues the retransmission of the packet from Step 2.

Note that a UE using CSMA/CA can only process the transmission of one packet at a time. That is, if a UE is in the process of transmitting a first packet (i.e., it is following the procedure outlined above) and a second packet arrives at the transmitter buffer, the UE will not start the process to transmit the latter until it has finished transmitting the former. In particular, if the UE has deferred the transmission of the first packet and the second packet arrives during the back-off time, the transmission procedure for the second packet will not start immediately. Note also that the CSMA/CA protocol may define a maximum number of retransmission attempts for a given packet.

A third example of distributed resource allocation is the distributed resource allocation protocol for LTE Release 14/15 sidelink (SL) mode 4 transmissions. In Release 14 and 15 of the 3GPP standards for sidelink communications, the distributed resource allocation mechanism referred to within 3GPP as mode 4 is based on two functionalities: semi- persistent transmission and sensing-based resource allocation.

Semi-persistent transmission is a type of transmission in which the UE sending a message notifies receivers in the area about its intention to transmit using certain time-frequency resources at a later point in time. For example, a UE transmitting at time T informs the receivers that it will transmit using the same frequency resources at time T+100 milliseconds. This is called resource reservation or resource booking and is especially suitable for the type of vehicular applications targeted by LTE Release 14/15, which rely on the periodic transmission of packets.

Semi-persistent transmission allows a UE to predict the utilization of the radio resources in the future. That is, by listening to the current transmissions of other UEs, it also obtains information about potential future transmissions. This information can be used by the UE to avoid collisions when selecting its own resources. Specifically, a UE predicts the future utilization of the radio resources by reading received booking messages and then schedules its current transmission to avoid using the same resources. This is known as sensing-based resource selection.

The sensing-based resource selection scheme specified in Rel-14 includes the following three key steps. · Step a: All the resources are considered available.

• Step b: The UE excludes resources at least based on scheduling assignment (SA) decoding and additional conditions. A resource is excluded if it is indicated or reserved by a decoded SA and the PHY Sidelink ThShared Channel (PSSCH) reference signal received power (RSRP) in the associated data resources is above a threshold.

• Step c: The UE measures and ranks the remaining PSSCH resources based on

received signal strength indicator (RSSI) measurement and selects a subset for transmission. The subset is the set of candidate resources with the lowest total received energy. The size of the subset is, e.g., 20%, of the total resources within the selection window.

SUMMARY

Wireless networks and wireless devices will increasingly use multiple antennas for transmission, which allows for the selective use of directional transmission, i.e., the focusing of broadcasted energy during a transmission into a specific region of transmission space. Directional transmission improves transmission by ensuring that the power to the intended receiver(s) is larger than in the case the signal is broadcasted in an

omnidirectional way. In addition, it minimizes the interference created to other parts of the space on which there are no intended receiver(s).

Existing distributed resource allocation protocols, however, do not fully exploit the spatial advantages that are possible with directional transmission. The reason is that the distributed resource allocation protocol does not distinguish the different parts of the transmission space. Embodiments of the techniques and apparatuses disclosed herein address this problem by providing for distributed resource allocation procedures that explicitly take into account the availability of multiple antenna configurations at the transmitting device. Some of the methods detailed below, for example, provide for the adapting of transmission

parameters independently, for each of multiple specific antenna configurations, in response to transmissions received and measurements performed by the device, in some cases using the corresponding antenna configuration. These parameters are later used for transmission using the respective antenna configuration. The techniques described herein thereby enable distributed resource allocation with efficient spatial reutilization of radio resources, which in turn results in increased system capacity.

Embodiments disclosed herein include an example method, as implemented in a wireless device, for transmitting data utilizing distributed resource allocation. This example method includes selecting a first antenna configuration for a transmission of first data, where this first antenna configuration is one of a plurality of possible antenna configurations for the wireless device. In some embodiments, selecting this first antenna configuration is based on one or more radio measurements or based on one or more received messages. In some of these embodiments, the radio measurements are performed or the messages are received using this same first antenna configuration; in other embodiments, some or all of the measurements may be performed with or messages received via a different antenna configuration. The example method further includes performing distributed resource allocation for selecting a radio resource for transmission of the first data, using at least one distributed resource allocation parameter value that is maintained independently by the wireless device for the first antenna configuration, relative to others of the possible antenna configurations.

Other embodiments include a wireless device for transmitting data utilizing distributed resource allocation, where the wireless device is adapted to select a first antenna configuration for a transmission of first data, the first antenna configuration being one of a plurality of possible antenna configurations for the wireless device, and to perform distributed resource allocation for selecting a radio resource for transmission of the first data, using at least one distributed resource allocation parameter value that is maintained independently by the wireless device for the first antenna configuration, relative to others of the possible antenna configurations.

Other embodiments include computer program, computer program products, carrier carrying computer instructions and computer-readable media comprising instructions which when executed on a computer cause the computer to behave corresponding to the above methods. Variations of all of these example embodiments are described in the detailed description that follows.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 illustrates various V2X scenarios in a LTE network environment. Fig. 2 illustrates an example device-to-device (D2D) scenario for illustrating features and advantages of the presently disclosed techniques.

Fig. 3 is an example method according to some of the presently disclosed techniques.

Fig. 4 is a process flow diagram illustrating another example method according to several disclosed embodiments. Fig. 5 illustrates a wireless device according to some embodiments.

Fig. 6 illustrates a virtual apparatus according to some embodiments.

DETAILED DESCRIPTION

As noted above, directional transmission consists of focusing the energy broadcasted during a transmission into a specific area of the space. Directional transmission improves transmission by ensuring that the power to the intended receiver(s) is larger than in the case the signal is broadcasted in an omnidirectional way. In addition, it minimizes the interference created to other parts of the space on which there are no intended receiver(s). Directional transmission is usually implemented using multiple antennas (i.e., beamforming), or using directional antennas (i.e., antennas with a directional pattern), or a combination of both.

Multiple antennas and distributed resource allocation have been used together in different communication standards, as well as in commercial products. By using beamformed or directional transmission, the capacity of the communication systems is increased. The reason is that power is only broadcasted in the direction of the intended receiver(s), thus increasing the received useful power, reducing undesired interference, and improving the efficiency of the distributed resource allocation, for example when applying or comparing with protocols like Aloha or CSMA/CA.

However, the simple combination of multiple antennas and existing distributed resource allocation does not fully exploit the spatial advantages that are possible with directional transmission. The reason is that distributed resource allocation protocols do not distinguish the different parts of the space. For example, from the point of view of a given UE, a certain adjacent area may be crowded by many UEs, whereas few UEs may be present in the rest of the adjacent area.

Consider, for example, the scenario in Figure 2. From the point of view of UE1, the concentration of UEs in one quadrant (shaded) is much higher than in the other three quadrants (unshaded). This means that transmission traffic to UEs in that quadrant is more likely to suffer collisions. These collisions will force UE1 to adjust its transmission behavior (e.g., defer retransmission, use increased congestion window, etc.), even for transmissions that are directionally transmitted towards UEs in other quadrants and that are thus less likely to have an impact on UEs in the crowded quadrant. These adjustments to UEl's behavior will result in less efficient communications with UEs in other quadrants, e.g., with UE6.ln short, it can be seen that using a distributed resource allocation protocol that is oblivious to the differences in traffic for the different parts of the space (e.g., directions) results in reduced system efficiency.

Embodiments of the techniques and apparatuses disclosed herein address this problem by providing for distributed resource allocation procedures that explicitly take into account the availability of multiple antenna configurations at the transmitting device. Some of the methods detailed below, for example, provide for the adapting of transmission

parameters independently, for each of multiple specific antenna configurations, in response to transmissions received and measurements performed by the device, in some cases using the corresponding antenna configuration. These parameters are later used for transmission using the respective antenna configuration. This provides a number of significant advantages when compared to applying the previously described distributed allocation protocols to the transmission resources as a whole. For example, transmission buffers may be reduced, thus saving memory capacity. Latency and throughput are increased due to the reduced buffering and more efficient use of the available resources. The techniques described herein thereby enable distributed resource allocation with efficient spatial reutilization of radio resources, which in turn results in increased system capacity.

Among the various embodiments described herein are methods for selecting radio resources in a distributed fashion. That is, selection of the radio resources is performed by the UEs instead of a central node (e.g., eNB). These methods may be especially beneficial for D2D or V2V UEs, but may also be used by other devices and/or in other contexts, e.g., by eNBs (3GPP terminology for LTE base stations) serving a Licensed-Assisted Access (LAA) -like carrier on unlicensed spectrum. The techniques described herein may be applied to devices operating within an LTE network, in an NR network (the 5G network under development by the 3GPP), as well as in WiFi networks.

Several of these methods comprise some or all of the following steps, which are illustrated in Figure 3.

1. (Optional) In a first step, shown at block 310 in Figure 3, the UE defines or is provided with definitions for multiple antenna configurations for

transmission/reception.

2. In a second step, shown at block 320, the UE receives a transmission (e.g., message or signal) or performs a measurement. This may involve the use of a particular one of the antenna configurations (e.g., one of the ones defined in Step 1 ), such as an antenna configuration having a particular directionality, and/or may involve a measurement or signal received using an omnidirectional antenna configuration (for reception). Based on the measurement/received signal, the UE infers something about at least one antenna configuration, e.g., the antenna configuration used for receiving the signal or for performing the measurement.

The UE may learn, for example, how busy the medium is in a certain direction. 3. In a third step, shown at block 330 of Figure 3, the UE selects or adjusts some parameter related to transmission/reception with a particular antenna

configuration. This may be the antenna configuration used in Step 2, but this is not necessarily the case in all embodiments. This selection or adjustment may be based on the measurement performed or the transmission received in Step 2.

4. In a fourth step, shown at block 340, the UE performs a transmission using the parameter selected or adjusted in Step 3.

In the context of the present disclosure, the term "antenna configuration" should be understood in a general sense, referring to such things as the number of used antennas and their placements, polarizations of the used antennas, directivity of each antenna element (i.e., the directional pattern of each antenna element), coefficients applied to antenna elements (i.e., beamforming), number and choice of antennas or antenna ports, and so on. It may also be associated with the space covered by a certain antenna configuration or some other spatial or spatial characteristic (one or more beams, beamforming vectors, etc.).

In the context of the steps described above (e.g., Steps 3 and 4), the transmission parameters may include transmit power, back-off time, contention window size, power thresholds (e.g., sensitivity threshold), energy thresholds (e.g., sensitivity threshold), modulation, coding rate, coding scheme, number of retransmissions, bandwidth, minimum or maximum transmission duration, the size of candidate resources within resource selection, transmission precoder/beamformer, transmission mode (e.g., unicast, multicast, or broadcast), transmission path (e.g., direct sidelink or UE-to-base station link), etc.

Consider, for example, how the general approach described above might be applied in an Aloha context, so as to provide Aloha with space awareness. Referring back to Figure 2, assume that UE1 can divide the area around it into four quadrants, corresponding to four antenna configurations available for UE1 to use for transmissions, where each of these antenna configurations focuses transmission energy into one of these quadrants. It will be appreciated, of course, that the differences between these configurations may involve multiple parameters and/or choices of antennas, antenna elements, etc. According to the presently disclosed techniques, UE1 may be configured to independently execute the Aloha protocol for each of these antenna configurations, and thus, for each of these quadrants. In other words, UE1 maintains an independent set of Aloha-related parameters, such as back-off timers, and can thus make separate and independent resource allocation/selection decisions for each antenna configuration.

For example, referring once more to Figure 2, transmissions from UE1 to UE2 take place in the quadrant with high UE density and they are often subject to collisions. Consequently, UE1 often has to back-off and retransmit the packet when communicating with UE2.

However, transmissions from UE1 to UE6 take place in a quadrant with low UE density and are seldom subject to collisions. By executing the Aloha protocol independently, with respect to the two different antenna configurations directed towards UE2 and UE6, UE1 may be able to transmit to UE6 even while it is backing off a transmission to UE2 due to packet collisions in the busy quadrant. This is because the back-off process is operated independently for each antenna configuration, and thus for each region of the space surrounding UE1.

In some examples separate distributed resource allocation instances are implemented for each antenna configuration. For each resource allocation instance the resource allocation parameters and resource allocation "states" being maintained or operated on

independently from the other resource allocation instances. In some examples separate resource allocation protocols and/or protocol instances may be employed for different antenna configurations.

Similar results can be expected when applying these techniques to the CSMA/CA protocol. Again referring to Figure 2, UE1 may consider independent transmissions with independent back-off counters and independent contention windows for each of the antenna

configurations corresponding to the four quadrants surrounding it. Again, transmissions from UE1 to UE2 take place in the quadrant with high UE density and they are often subject to collisions. Consequently, UE1 often uses a large contention window when transmitting to UE2. However, transmissions from UE1 to UE6 take place in a quadrant with low UE density and are seldom subject to collisions. Consequently, UE1 may transmit to UE6 even while it is backing off a transmission to UE2 due to packet collisions in the busy quadrant. In addition, UE1 may use a smaller contention window when transmitting to UE6, compared to the contention window being used simultaneously for transmission to UE2.

More generally, then, having multiple antenna configurations available for transmissions may result in independent channel access procedures for each of the configurations. For example, consider the case in which a UE is in the process of transmitting a first packet (i.e., it is following the procedure outlined above) using a first antenna configuration. At this point, a second packet arrives at the transmitter buffer for transmission using a second (different) antenna configuration, e.g., an antenna configuration that directs the

transmission in a direction or in a spatial dimension different from that used for the transmission of the first packet. The UE may go ahead and process the transmission of the second packet independently of whether it has finished the procedure for first packet or not. In particular, if the UE has deferred the transmission of the first packet and the second packet arrives during the back-off time, the transmission procedure for the second packet may start immediately. Depending on the capabilities of the UE, the actual transmissions may or may not happen simultaneously.

Consider the following variation of the LTE release 14/15 distributed resource allocation protocol, as used by UE1 in Figure 2. Once more, UE1 divides the area around it in 4 quadrants, corresponding to the four areas into which it can focus its transmissions. Each of these areas corresponds to an antenna configuration for transmission/reception. Once again, it should be noted that that the word "configuration" as used herein should be understood here in a general sense. For example, this configuration may include multiple alternative antenna settings, as described above. For each of the configurations, and hence for each of the areas, the UE considers independent transmissions with independent back off counters and independent contention windows.

Transmissions from UE1 to UE2 take place in the quadrant with high UE density and they are often subject to collisions. Consequently, for latency-critical transmissions, UE1 can use a higher threshold for RSRP measurement or an increased size of subset selection after RSSI measurement (e.g., more than 20% resources within the selection window,). On the other hand, transmissions from UE1 to UE6 take place in a quadrant with low UE density and are seldom subject to collisions. Consequently, to further improve transmission reliability, UE1 may transmit to UE6 using a lower threshold for RSRP measurement. Thus, in this example, at least the RSRP thresholds used for excluding/including resources for potential use are maintained independently, for multiple antenna configurations.

With these and other example applications of the techniques disclosed herein in mind, the process illustrated in Figure 3 and described in general terms above may be considered in more detail, beginning with step 1, as shown at block 310.

Above, this step was referred to as optional. This step is optional in the sense that, in some embodiments, the multiple antenna configurations are part of the specification and/or are hard-coded in the UE. In others, they may be part of a pre-configuration or a configuration provided to the wireless device by a network node (e.g., eNB). That is, the UE may not necessarily define the antenna configurations itself but may instead receive them or be programmed with them.

In some embodiments, the multiple antenna configurations relate to accessing multiple parts of the space. For example, antenna configuration 1 may correspond to transmissions in region 1 of the space surrounding the UE (according to some partition), antenna configuration 2 may correspond to transmissions in region 2 of the space, etc. In some embodiments, an antenna configuration corresponds to one or several beams. That is, the UE uses one of the beams when transmitting/receiving with the selected configuration. Similarly, an antenna configuration may correspond to one or more antenna factors (i.e., multipliers) or a range of antenna factors. In some embodiments, an antenna configuration corresponds to a multiantenna scheme (sometimes referred to as a transmission mode in the specification).

In some embodiments, Step 1 is performed only once, before the first transmission. In some embodiments, Step 1 may be performed regularly, e.g., every N transmissions or every T seconds. In some embodiments, Step 1 is only performed when triggered internally, e.g., when the UE has changed its position and/or orientation significantly compared to the last time when Step 1 was performed, or when triggered externally, e.g., by a network node. In some embodiments, the transmission parameters associated with some or all antenna configurations are reset to default values every time Step 1 is performed. Step 2, as shown at block 320 of Figure 3, is considered next. In some embodiments, the UE selects an antenna configuration for performing a measurement or receiving a signal or message based on the estimated/known position of a receiver or set of receivers to which the UE wants to transmit a signal or message. For example, the UE may select an antenna beam that is appropriate for transmitting to or receiving from a specific UE. In some embodiments, the UE selects this antenna configuration based on some received signals or messages (or absence of received signals or messages). For example, the UE may decide to transmit in a direction from which it does not receive any signal, or in a direction in which it does not expect to create significant interference to ongoing transmissions.

In some embodiments, the UE selects the antenna configuration based on a message received from another network node (e.g., an eNB). In some embodiments, the UE receives a transmission of control information, e.g., ACK/NACK messages, channel-state-information (CSI) reports, etc. In other embodiments, the UE receives a transmission of data (e.g., a data channel). In other embodiments, the UE performs a measurement of energy, e.g., a

Received Signal Strength Indicator (RSSI) measurement or a Reference Signal Received Power (RSRP) measurement, or a resource utilization measurement such as a channel-busy ratio (CBR) measurement.

At step 3, as shown at block 330 of Figure 3, the UE selects or adjusts some parameter related to transmission/reception with a particular antenna configuration. This may be the same antenna configuration used for performing measurements or receiving

signals/measurements in step 2, in some embodiments, but may be different. Where it is different, this antenna configuration may be chosen according to any of the mechanisms discussed above, in various embodiments.

In some embodiments, the UE adjusts some parameters and/or the transmission strategy or procedure, relative to this antenna configuration, in response to receiving a positive feedback response (ACK message). For example, upon the reception of an ACK message, the UE may assume that its previous transmission was successful. In response to this, it may decide to modify some random-access parameters (e.g., reducing the size of the contention window, etc.) or some other transmission parameters (e.g., reducing the transmission power, increasing the coding rate, etc.). In another example, upon the reception of an ACK message, the UE may switch to a more aggressive transmission strategy for the corresponding antenna configuration.

In some embodiments, the UE adjusts some parameters in response to not receiving a positive feedback response, e.g., if no response is received or if a negative feedback response, or NACK, is received. For example, if a first UE does not receive an ACK message for a message transmitted according to a particular antenna configuration, it may assume that its previous transmission collided with a transmission by a second UE. Consequently, the first UE may decide to modify some random-access parameters for that antenna configuration, e.g., using a random back-off window, increasing the size of the contention window, etc., and/or some other transmission parameter, such as transmission power, coding rate, etc. In another example, after not receiving the ACK message, the UE may switch to a more conservative transmission strategy for the corresponding antenna configuration.

In some embodiments, the UE adjusts some parameters in response to the channel state information (CSI) report (e.g., a CQJ report) sent from other UEs. The CSI report can take into account both link quality of the desired transmission(s) and the interference situation experienced at the intended receiver(s). The CSI report can also include the interference situation that the desired transmission may incur to other UEs.

In some embodiments, the UE selects radio resources based on a procedure that uses the received signal (e.g., a reservation notification in sidelink control information) or the performed measurement (e.g., received power or energy, RSRP, RSSI, CBR, etc.).

In some embodiments, different transmission strategies or procedures may be selected or adapted (e.g., Aloha or CSMA/CA, different transmission modes, etc.) responsive to the received transmission or the performed measurement. For example, if the utilization of the channel is perceived to be low, a more aggressive transmission scheme may be used than if the utilization is perceived to be high.

In step 4, as shown at block 340 of Figure 3, the UE performs a transmission using the parameter selected or adjusted in Step 3, in conjunction with the corresponding antenna configuration. In some embodiments, the transmission is performed in the part of the space associated with the antenna configuration, for example, using directional antennas or multiple antennas (i.e., beamforming). Similarly, the transmission may be performed with a beam associated with the antenna configuration. In some embodiments, the transmission may take place using resources selected in Step 3. Figure 4 is a process flow diagram illustrating an example method, as implemented in a wireless device, for transmitting data utilizing distributed resource allocation. The illustrated method corresponds to several embodiments of the presently disclosed techniques.

As shown at block 410, the method includes selecting a first antenna configuration for a transmission of first data, where this first antenna configuration is one of a plurality of possible antenna configurations for the wireless device. In some embodiments, these possible antenna configurations for the wireless device differ from one another according to at least one of any of the following: a number of antennas used for transmission; a polarization of one or more antennas used for transmission; and an effective antenna pattern for antennas used for transmission. The effective antenna pattern for a given antenna configuration may correspond to or result from the directivity of each of one or more antennas or elements (i.e., a directional pattern of each antenna or antenna element), coefficients applied to antenna elements (i.e., beamforming coefficients), for example, and will often correspond to a particular coverage area or region, differing at least in part from the coverage area or region for another antenna configuration. In some embodiments, for example, each of the plurality of antenna configurations corresponds to a beam or a set of beams.

In some embodiments, selecting this first antenna configuration is based on one or more radio measurements or based on one or more received messages. In some of these embodiments, the radio measurements are performed or the messages are received using this same first antenna configuration; in other embodiments, some or all of the

measurements may be performed with or messages received via a different antenna configuration.

As shown at block 420, the illustrated method further includes performing distributed resource allocation for selecting a radio resource for transmission of the first data, using at least one distributed resource allocation parameter value that is maintained independently by the wireless device for the first antenna configuration, relative to others of the possible antenna configurations. Note that the phrase "selecting a radio resource," as used herein, may refer to the selection of a particular radio resource (e.g., a time, frequency, or spatial resource, or a combination of any of these) from multiple radio resources generally available to or allocated to the wireless device. The phrase "selecting a radio resource" may also refer to a decision, by the wireless device, to either transmit or refrain from

transmitting at a particular time, e.g., according to a listen-before-talk (LBT) protocol.

Performing distributed resource allocation may comprise executing a distributed resource allocation protocol. Executing a distributed resource allocation protocol may comprise executing all or only parts of the protocol. The embodiments disclosed herein are independent of the type of distributed resource allocation protocol or the extent with which an implementation complies with such a protocol. In various embodiments, the distributed resource allocation parameter value discussed above may be any one of the following parameters for a distributed resource allocation protocol: a back-off time; a contention window size; a power threshold or energy threshold for sensing resource occupancy; a minimum or maximum transmission duration; a size of candidate resources for resource selection according to the distributed resource allocation protocol. Of course, while block 420 only refers to a single distributed resource allocation parameter value, several distributed resource allocation parameters may be maintained independently for each of several antenna configurations, in some embodiments of the presently disclosed

techniques.

Examples of the distributed resource allocation protocol include, but are not limited to, an Aloha-based protocol and a carrier-sense multiple access with collision avoidance

(CSMA/CA) protocol. In some embodiments, performing distributed resource allocation may comprise excluding one or more resources from a set of resources shared by the wireless device and peer wireless devices, based on decoding one or more messages scheduling or reserving resource usage by peer wireless devices, and selecting a resource for transmission of the first data from among the remaining ones of the set of resources, after said excluding, wherein said selecting is based on signal strength measurements for one or more of the resources. A distributed resource allocation protocol defined for Release 13/14 of the LTE specifications may be used, for example.

The approach illustrated in blocks 410 and 420 of Figure 4 facilitates the independent use of the distributed resource allocation (or the independent use of one or each of several different resource allocation protocols) for each of several antenna configurations. This independent use may include embodiments or instances where the protocol (or protocols) are executed at the same time. (Here, "the same time" means that the protocols at least partly overlap in time.) Thus, as discussed above in some of the detailed examples, distributed resource allocation protocols may be executed at the same time for data transmissions corresponding to two different antenna configurations, e.g., for transmissions to two different wireless devices.

The independent use of the distributed resource allocation (or the independent use of one or each of several different resource allocation protocols) for a second antenna

configuration is shown in blocks 430 and 440 of Figure 4, which are illustrated with a dashed outline to indicate that these steps are not present in every embodiment or instance of the method. As shown at block 430, the method, in these embodiments, includes the step of selecting a second antenna configuration for a transmission of second data, the second antenna configuration being one of a plurality of possible antenna configurations for the wireless device and differing from the first antenna configuration. As shown at block 440, the method in these embodiments further includes performing distributed resource allocation for selecting a radio resource for transmission of the second data, using at least one distributed resource allocation parameter value that is maintained independently by the wireless device for the second antenna configuration, relative to the first antenna configuration. In some embodiments, for example, the first data and second data are targeted to first and second receiving devices, respectively, and wherein the selecting of the second antenna configuration is based on an estimated direction for the second receiving device.

As suggested above, performing distributed resource allocation for selecting the radio resource for transmission of the second data may overlap in time with the distributed resource allocation for selecting the radio resource for transmission of the first data. Thus, for example, executing the distributed resource allocation for transmission of the second data may comprise transmitting the second data while transmission of the first data is still pending, e.g., as a consequence of performing distributed resource allocation for transmission of the first data.

Other embodiments of the presently disclosed techniques include wireless devices adapted to carry out any one or more of the techniques described herein. Such a wireless device, for example, may be adapted to select a first antenna configuration for a transmission of first data, the first antenna configuration being one of a plurality of possible antenna

configurations for the wireless device, and may be further adapted to perform distributed resource allocation for selecting a radio resource for transmission of the first data, using at least one distributed resource allocation parameter value that is maintained independently by the wireless device for the first antenna configuration, relative to others of the possible antenna configurations. The wireless device may be further adapted according to any of the various details and variations discussed above.

Figure 5 illustrates an example wireless device 50 for transmitting data utilizing distributed resource allocation, according to several embodiments of the presently disclosed techniques. This wireless device may be a UE and/or a D2D device, or other end user terminal, in various embodiments, but could also be an access node, such as an eNodeB or other base station, in others. Wireless device 50 comprises a radio transceiver 52, which is configured to communicate with one or more other devices, e.g., via a D2D or V2x link, or via an uplink or downlink. In the illustrated example, wireless device 50 comprises four antenna elements, which provide for directional/beam-formed transmissions. Other antenna arrangements are possible, of course.

Wireless device 50 further comprises a processing circuit 54, which in turn comprises a processor 56 (e.g., a microprocessor, microcontroller, digital signal processor, or the like) and a memory 58. Memory 58 may store program instructions for execution by processor 56, in some embodiments, where the program instructions are configured to cause the processor to execute all or parts of a method according to any of the methods described herein, including the methods illustrated in Figure 4. More generally, however, the techniques described herein may be implemented by a processing circuit using digital logic alone or any combination of digital logic and a processor or processors executing program instructions stored in a memory.

Regardless of its specific implementation, processing circuit 54 is operatively coupled to radio transceiver 52 and controls its operation, and is configured to select a first antenna configuration for a transmission of first data, the first antenna configuration being one of a plurality of possible antenna configurations for the wireless device. The processing circuit 54 is further configured to perform distributed resource allocation for selecting a radio resource for transmission of the first data, using at least one distributed resource allocation parameter value that is maintained independently by the wireless device for the first antenna configuration, relative to others of the possible antenna configurations.

In some embodiments, processing circuit 54 and, thereby, wireless device 50, are configured to select the first antenna configuration based on one or more radio measurements or based on one or more received messages. In some embodiments, the processing circuit 54 and wireless device are configured to perform the radio measurements or receive the messages using this same first antenna configuration.

As above, the plurality of possible antenna configurations for the wireless device differ from one another according to at least one of any of the following: a number of antennas used for transmission; a polarization of one or more antennas used for transmission; and an effective antenna pattern for antennas used for transmission. In some embodiments, each of the plurality of antenna configurations corresponds to a beam or a set of beams.

In some embodiments, the distributed resource allocation parameter value corresponds to one of the following: a back-off time; a contention window size; a power threshold or energy threshold for sensing resource occupancy; a minimum or maximum transmission duration; and a size of candidate resources for resource selection. In various embodiments, the distributed resource allocation is performed according to one of: an Aloha-based protocol; and a carrier-sense multiple access with collision avoidance (CSMA/CA) protocol.

In some embodiments, the distributed resource allocation may comprise the steps of excluding one or more resources from a set of resources shared by the wireless device and peer wireless devices, based on decoding one or more messages scheduling or reserving resource usage by peer wireless devices, and selecting a resource for transmission of the first data from among the remaining ones of the set of resources, after said excluding, wherein said selecting is based on signal strength measurements for one or more of the resources - the wireless device 50 in these steps is therefore configured to carry out these steps, as part of the distributed resource allocation.

In some embodiments, the processing circuit 54, and thereby the wireless device 50, is configured to select a second antenna configuration for a transmission of second data, the second antenna configuration being one of a plurality of possible antenna configurations for the wireless device and differing from the first antenna configuration. The processing circuit 54 in these embodiments is further configured to perform distributed resource allocation for selecting a radio resource for transmission of the second data, using at least one distributed resource allocation parameter value that is maintained independently by the wireless device for the second antenna configuration, relative to the first antenna configuration. The first data and second data may be targeted to first and second receiving devices, respectively, and the processing circuit 54 and wireless device 50 may be configured to select the second antenna configuration based on an estimated direction for the second receiving device. In some embodiments, the processing circuit 54 and wireless device 50 are configured to transmit the second data while transmission of the first data is still pending, e.g., as a consequence of performing distributed resource allocation for transmission of the first data.

Figure 6 illustrates an example virtual apparatus 60 for transmitting data utilizing distributed resource allocation, according to several embodiments of the presently disclosed techniques. The apparatus 60 comprises a transceiver module 62, which comprises instructions to communicate with one or more other devices, e.g., via a D2D or V2x link, or via an uplink or downlink.

Apparatus 60 further comprises a selection module 64, which comprises instructions to select a first antenna configuration for a transmission of first data, the first antenna configuration being one of a plurality of possible antenna configurations for the wireless device. The apparatus 60 further comprises an execution module 66 which comprises instructions to perform distributed resource allocation for selecting a radio resource for transmission of the first data, using at least one distributed resource allocation parameter value that is maintained independently by the wireless device for the first antenna configuration, relative to others of the possible antenna configurations.

In some embodiments, the selection module 64 comprises instructions to select the first antenna configuration based on one or more radio measurements or based on one or more received messages. In some embodiments, the selection module 64 comprises instructions to perform the radio measurements or receive the messages using this same first antenna configuration.

In some embodiments, the distributed resource allocation parameter value corresponds to one of the following: a back-off time; a contention window size; a power threshold or energy threshold for sensing resource occupancy; a minimum or maximum transmission duration; and a size of candidate resources for resource selection. In various embodiments, the distributed resource allocation protocol is performed according to one of: an Aloha- based protocol; and a carrier-sense multiple access with collision avoidance (CSMA/CA) protocol. In some embodiments, the distributed resource allocation may comprise the steps of excluding one or more resources from a set of resources shared by the wireless device and peer wireless devices, based on decoding one or more messages scheduling or reserving resource usage by peer wireless devices, and selecting a resource for transmission of the first data from among the remaining ones of the set of resources, after said excluding, wherein said selecting is based on signal strength measurements for one or more of the resources - the execution module 66 may comprise instructions to carry out these steps, as part of the distributed resource allocation.

In some embodiments, the selection module 64 comprises instructions to select a second antenna configuration for a transmission of second data, the second antenna configuration being one of a plurality of possible antenna configurations for the wireless device and differing from the first antenna configuration. The execution module 66 in these

embodiments comprises instructions to perform the distributed resource allocation for selecting a radio resource for transmission of the second data, using at least one distributed resource allocation parameter value that is maintained independently by the wireless device for the second antenna configuration, relative to the first antenna configuration. The first data and second data may be targeted to first and second receiving devices, respectively, and the selection module 64 comprises instructions to select the second antenna configuration based on an estimated direction for the second receiving device. In some embodiments, the transceiver module 62 comprises instructions to transmit the second data while transmission of the first data is still pending, e.g., as a consequence of performing distributed resource allocation for transmission of the first data.

It will be appreciated that the inventive techniques and apparatuses disclosed herein are not limited to any of the specific example configurations or example embodiments described above. Other embodiments, for instance, include computer programs 59 or computer program products such as a computer-readable storage medium 58 in the form of a memory, or a carrier carrying instructions, comprising program instructions for execution by a wireless device configured to transmit data utilizing distributed resource allocation, where the program instructions are configured so as to cause the wireless device to carry out one or more of the techniques disclosed herein, e.g., to select a first antenna configuration for a transmission of first data, the first antenna configuration being one of a plurality of possible antenna configurations for the wireless device, and to perform distributed resource allocation for selecting a radio resource for transmission of the first data, using at least one distributed resource allocation parameter value that is maintained independently by the wireless device for the first antenna configuration, relative to others of the possible antenna configurations. Other embodiments include computer-readable media, including non-transitory media, that carry or otherwise store such a computer program product. Likewise, embodiments comprising computer programs, computer program products, computer-readable media or a carrier carrying instructions, comprising computer program instructions are envisaged, which when executed on a computer, cause the computer to perform one or more of the techniques disclosed herein. It will be appreciated that the detailed discussion above and the appended claims relate to techniques for distributed resource allocation using directional transmission. These techniques allow a wireless device to independently adapt transmission for different antenna configurations. In this way, transmission with those configurations that are exposed to high loads (e.g., in directions with many users) are treated independently of those configurations that are expose to lower loads (e.g., in directions with fewer users). This independent configuration results in better utilization of the radio resources because only those constraints that are relevant for a specific antenna configuration are considered.

Claims

1. A method, performed by a wireless device, for transmitting data utilizing distributed resource allocation, the method comprising:

selecting (410) a first antenna configuration for a transmission of first data, the first antenna configuration being one of a plurality of possible antenna configurations for the wireless device;

performing (420) distributed resource allocation for selecting a radio resource for transmission of the first data, using at least one distributed resource allocation parameter value that is maintained independently by the wireless device for the first antenna configuration, relative to others of the possible antenna configurations.

2. The method of claim 1, wherein the plurality of possible antenna configurations for the wireless device differ from one another according to at least one of any of the following: a number of antennas used for transmission;

a polarization of one or more antennas used for transmission; and

an effective antenna pattern for antennas used for transmission.

3. The method of claim 2, wherein each of the plurality of antenna configurations corresponds to a beam or a set of beams.

4. The method of any one of claims 1-3, wherein selecting (410) the first antenna configuration is based on one or more radio measurements or based on one or more received messages.

5. The method of claim 4, wherein the radio measurements are performed or the messages are received using the first antenna configuration.

6. The method of any one of claims 1-5, wherein the distributed resource allocation parameter value corresponds to one of the following:

a back-off time;

a contention window size; a power threshold or energy threshold for sensing resource occupancy; a minimum or maximum transmission duration;

a size of candidate resources for resource selection.

7. The method of any one of claims 1-6, wherein the distributed resource allocation is performing according to one of:

an Aloha-based protocol; and

a carrier-sense multiple access with collision avoidance (CSMA/CA) protocol.

8. The method of any one of claims 1-6, wherein performing (420) distributed resource allocation comprises:

excluding one or more resources from a set of resources shared by the wireless device and peer wireless devices, based on decoding one or more messages scheduling or reserving resource usage by peer wireless devices; and selecting a resource for transmission of the first data from among the remaining ones of the set of resources, after said excluding, wherein said selecting is based on signal strength measurements for one or more of the resources.

9. The method of any one of claims 1-8, wherein the method further comprises:

selecting (430) a second antenna configuration for a transmission of second data, the second antenna configuration being one of a plurality of possible antenna configurations for the wireless device and differing from the first antenna configuration;

performing (440) distributed resource allocation for selecting a radio resource for transmission of the second data, using at least one distributed resource allocation parameter value that is maintained independently by the wireless device for the second antenna configuration, relative to the first antenna configuration.

10. The method of claim 9, wherein the first data and second data are targeted to first and second receiving devices, respectively, and wherein the selecting of the second antenna configuration is based on an estimated direction for the second receiving device.

11. The method of claim 9 or 10, wherein performing (440) distributed resource allocation for transmission of the second data comprises transmitting the second data while transmission of the first data is still pending as a consequence of the performing distributed resource allocation for transmission of the first data.

12. A wireless device (50) for transmitting data utilizing distributed resource allocation, wherein the wireless device (50) is adapted to:

select a first antenna configuration for a transmission of first data, the first antenna configuration being one of a plurality of possible antenna configurations for the wireless device;

perform distributed resource allocation for selecting a radio resource for

transmission of the first data, using at least one distributed resource allocation parameter value that is maintained independently by the wireless device for the first antenna configuration, relative to others of the possible antenna configurations.

13. The wireless device (50) of claim 12, wherein the plurality of possible antenna configurations for the wireless device (50) differ from one another according to at least one of any of the following:

a number of antennas used for transmission;

a polarization of one or more antennas used for transmission; and

an effective antenna pattern for antennas used for transmission.

14. The wireless device (50) of claim 13, wherein each of the plurality of antenna configurations corresponds to a beam or a set of beams.

15. The wireless device (50) of any one of claims 12-14, wherein the distributed resource allocation parameter value corresponds to one of the following:

a back-off time;

a contention window size;

a power threshold or energy threshold for sensing resource occupancy; a minimum or maximum transmission duration;

a size of candidate resources for resource selection.

16. The wireless device (50) of any one of claims 12-15, wherein the distributed resource allocation is performed according to one of:

an Aloha-based protocol; and

a carrier-sense multiple access with collision avoidance (CSMA/CA) protocol.

17. The wireless device (50) of any one of claims 12-15, wherein the distributed resource allocation comprises:

18. The wireless device (50) of any one of claims 12-17, wherein the wireless device (50) is further adapted to:

select a second antenna configuration for a transmission of second data, the second antenna configuration being one of a plurality of possible antenna configurations for the wireless device and differing from the first antenna configuration;

perform distributed resource allocation for selecting a radio resource for

transmission of the second data, using at least one distributed resource allocation parameter value that is maintained independently by the wireless device for the second antenna configuration, relative to the first antenna configuration.

19. The wireless device (50) of claim 18, wherein the first data and second data are targeted to first and second receiving devices, respectively, and wherein the wireless device is adapted to select the second antenna configuration based on an estimated direction for the second receiving device.

20. The wireless device (50) of claim 18 or 19, wherein the wireless device (50) is adapted to transmit the second data while transmission of the first data is still pending as a

consequence of the performing distributed resource allocation for transmission of the first data.

21. The wireless device (50) of any one of claims 12-20, wherein the wireless device (50) is adapted to select the first antenna configuration based on one or more radio measurements or based on one or more received messages.

22. The wireless device (50) of claim 21, wherein the wireless device (50) is adapted to perform the radio measurements or receive the messages using the first antenna configuration.

23. A wireless device (50) configured to transmit data utilizing distributed resource allocation, the wireless device (50) comprising:

a radio transceiver (52) configured to transmit to and receive from one or more

other wireless devices;

a processing circuit (54) operatively coupled to the radio transceiver and configured to control the radio transceiver (52) and to:

perform distributed resource allocation for selecting a radio resource for transmission of the first data, using at least one distributed resource allocation parameter value that is maintained independently by the wireless device for the first antenna configuration, relative to others of the possible antenna configurations.

24. The wireless device (50) of claim 23, wherein the processing circuit (54) comprises a processor (56) and a memory (58) operatively coupled to the processor (56) and comprising program instructions for execution by the processor (56), whereby the processing circuit (54) is configured to select the first antenna configuration and perform distributed resource allocation.

25. The wireless device (50) of claim 23 or 24, wherein the processing circuit (54) is configured to carry out a method according to any one of claims 1-11.

26. A computer program (59), computer program product or computer-readable storage medium (58), comprising program instructions or carrier carrying program instructions for execution by a wireless device configured to transmit data utilizing distributed resource allocation, wherein the program instructions are configured so as to cause the wireless device to: