BACKGROUND

A typical wireless communication system includes a number of access nodes that are configured to provide coverage in which user equipment devices (UEs) such as cell phones, tablet computers, machine-type-communication devices, tracking devices, embedded wireless modules, and/or other wirelessly equipped communication devices (whether or not user operated), can operate. Further, each access node could be coupled with a core network that provides connectivity with various application servers and/or transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a UE within coverage of the system could engage in air-interface communication with an access node and could thereby communicate via the access node with various application servers and other entities.

Such a system could operate in accordance with a particular radio access technology (RAT), with communications from an access node to UEs defining a downlink or forward link and communications from the UEs to the access node defining an uplink or reverse link.

Over the years, the industry has developed various generations of RATs, in a continuous effort to increase available data rate and quality of service for end users. These generations have ranged from “1G,” which used simple analog frequency modulation to facilitate basic voice-call service, to “4G”— such as Long Term Evolution (LTE), which facilitates mobile broadband service using technologies such as orthogonal frequency division multiplexing (OFDM) and multiple input multiple output (MIMO). And recently, the industry has completed initial specifications for “5G” and particularly “5G NR” (5G New Radio), which may use a scalable OFDM air interface, advanced channel coding, massive MIMO, beamforming, and/or other features, to support higher data rates and countless applications, such as mission-critical services, enhanced mobile broadband, and massive Internet of Things (IoT).

In accordance with the RAT, each access node could be configured to provide coverage and service on one or more radio-frequency (RF) carriers. Each such carrier could be frequency division duplex (FDD), with separate frequency channels for downlink and uplink communication, or time division duplex (TDD), with a single frequency channel multiplexed over time between downlink and uplink use. And each such frequency channel could be defined as a specific range of frequency (e.g., in RF spectrum) having a bandwidth (width in frequency) and a center frequency and thus extending from a low-end frequency to a high-end frequency.

Further each carrier could be defined within an industry standard frequency band, by its frequency channel(s) being defined within the frequency band. Examples of such frequency bands include (i) bands 2, 4, 12, 25, 26, 66, 71, and 85, supporting FDD carriers (ii) band 41, supporting TDD carriers, and (iii) bands n258, n260, and n261, supporting FDD and TDD carriers, among numerous other possibilities.

On the downlink and uplink, the air interface provided by an access node on a given carrier could be configured in a specific manner to define physical resources for carrying information wirelessly between the access node and UEs.

Without limitation, for instance, the air interface could be divided over time into a continuum of frames, subframes, and symbol time segments, and over frequency into subcarriers that could be modulated to carry data. The example air interface could thus define an array of time-frequency resource elements each being at a respective symbol time segment and subcarrier, and the subcarrier of each resource element could be modulated to carry data. Further, in each subframe or other transmission time interval, the resource elements on the downlink and uplink could be grouped to define physical resource blocks (PRBs) that the access node could allocate as needed to carry data between the access node and served UEs.

In addition, certain resource elements on the example air interface could be reserved for special purposes. For instance, on the downlink, certain resource elements could be reserved to carry reference signals or the like that UEs could measure in order to determine coverage strength, and other resource elements could be reserved to carry other control signaling such as PRB-scheduling directives and acknowledgement messaging from the access node to UEs. And on the uplink, certain resource elements could be reserved to carry random-access signaling from UEs to the access node, and other resource elements could be reserved to carry other control signaling such as PRB-scheduling requests, acknowledgement messaging, and channel-quality reports from UEs to the access node.

OVERVIEW

When a UE enters into coverage of an example network, the UE could detect threshold strong coverage of an access node on a particular carrier (e.g., a threshold strong reference signal broadcast by the access node on that carrier) and could then engage in random-access and connection signaling, such as Radio Resource Control (RRC) signaling, with the access node to establish an RRC connection or the like through which the access node will then serve the UE on the carrier.

Further, if the UE is not already registered for service with the core network, the UE could transmit to the access node an attach request, which the access node could forward to a core-network controller for processing. And the core-network controller and access node could then coordinate setup for the UE of a bearer extending between the UE and a core-network gateway that provides transport-network connectivity, with the bearer including a data radio bearer portion extending between the UE and the access node an access-bearer portion extending between the access node and the gateway.

Once the UE is so connected and registered, the access node could then serve the UE in a connected mode on the carrier, managing downlink air-interface communication of packet data to the UE and uplink air-interface communication of packet data from the UE.

With the example air interface described above, for instance, when packet data for the UE arrives at the core network from a transport network, the data could flow over the UE's access bearer to the UE's serving access node, and the access node could then schedule and provide transmission of that data to the UE on particular downlink PRBs of the carrier. Likewise, when the UE has data to transmit on the transport network, the UE could transmit a scheduling request to the access node, the access node could responsively schedule transmission of that data from the UE on particular uplink PRBs of the carrier, and the UE could accordingly transmit the data to the access node for forwarding over the UE's access bearer and through the core network to the transport network.

When the industry advances from one generation of wireless technology to the next, or in other scenarios, networks and UEs may also support dual-connectivity service, where a UE is served on multiple co-existing connections, perhaps according to different respective RATs.

For instance, a network could include a first access node configured to provide coverage and service according to a first RAT and a second access node configured to provide overlapping coverage and service according to a second RAT, and a UE positioned concurrently within coverage of both the first and second access nodes could have a first radio configured to engage in service according to the first RAT and a second radio configured to engage in service according to the second RAT. With this arrangement, the UE may be able to establish a first air-interface connection with the first access node according to the first RAT and a second air-interface connection with the second access node according to the second RAT, and the access nodes may then concurrently serve the UE over those connections according to their respective RATs.

Such dual connectivity (or “non-standalone” (NSA) connectivity) could help facilitate increased peak data-rate of communications, by multiplexing the UE's communications across the multiple air-interface connections. Further or alternatively, dual connectivity may provide other benefits compared with serving a UE on a single connection (as “standalone” (SA) connectivity).

In a representative dual-connectivity implementation, one of the access nodes could operate as a master node (MN), responsible for coordinating setup, management, and teardown of dual-connectivity service for the UE and functioning as an anchor point for RRC signaling and core-network control signaling related to the dual-connected UE. And each of one or more other access nodes could operate as a secondary node (SN) mainly to provide additional connectivity and increased aggregate bandwidth for the UE.

When a UE that supports dual-connectivity service enters into coverage of such a system, the UE could initially scan for and detect coverage of a first-RAT access node on a first-RAT carrier and engage in signaling to establish a first-RAT connection between the UE and that access node on that carrier as discussed above. And perhaps having determined from profile data that the UE is dual-connectivity-capable, the UE's serving access node, acting as an MN, could then engage in a process to set up dual connectivity for the UE.

In an example dual-connectivity setup process, the MN could first determine a second-RAT carrier on which to establish for the UE a second-RAT connection between the UE and the second-RAT access node that would serve as an SN. And the MN could then engage in signaling with the core-network controller, with the SN, and with the UE, to establish for the UE the second-RAT connection on that second-RAT carrier.

Further, the MN could coordinate bearer connectivity for the UE via the SN, to enable a portion of the UE's packet-data flow to be served by the MN concurrently with another portion of the UE's packet-data flow being served by the SN. For instance, the MN could engage in signaling to transfer the UE's access bearer from being between the MN and the gateway to instead being between the SN and the gateway, and a leg of the bearer could extend between the MN and the SN. That way, when the core network has data destined to the UE, that data would flow to the SN, (i) the SN could transmit a portion of the data over the UE's second-RAT connection to the UE, and (ii) the SN could send another portion of the data to the MN, which the MN would transmit over the UE's first-RAT connection to the UE. And when the UE has data to transmit, (i) the UE could transmit a portion of the data over the UE's second-RAT connection to the SN, which the SN would forward into the core network, and (ii) the UE could transmit another portion of the data over the UE's first-RAT connection to the MN, the MN could send to the SN and the SN could forward into the core network. Other bearer arrangements are possible as well.

With these first-RAT and second-RAT connections and bearer connectivity established for the UE, the MN and SN could then serve the UE with packet-data communications on their respective connections with the UE, each in the manner discussed above, for instance with a portion of data flowing over the UE's first-RAT connection between the UE and the MN concurrently with another portion of the data flowing over the UE's second-RAT connection between the UE and the SN.

In a representative system, the access nodes that could function as MN and SN for dual-connectivity service of one or more such UEs could regularly engage in inter-access-node data communications with each other. For instance, the access nodes could regularly engage in user-plane communications, such as transfer of UE data as discussed above, and control-plane communications such as interface-management signaling, mobility-management signaling, load reporting, and secondary-connection usage reporting, among others.

These communications could occur on one or more preconfigured inter-access-node interfaces, such as industry standard X2 and/or Xn interfaces or other virtual packet tunnels, through physical communication paths between the access nodes. For instance, if the access nodes are collocated with each other at a common cell site, they could communicate with each other on a preconfigured X2 interface and/or Xn interface through a local cell site router or other local connection mechanism. Or if the access nodes are separately located, they could communicate with each other on a preconfigured X2 interface and/or Xn interface through respective local routers and perhaps one or more intervening networks or other connections.

Unfortunately, however, these access nodes, interfaces, and/or physical communication paths may support up to only a limited quantity of inter-access-node communication per unit time—possibly due to maximum bit rates of network ports and physical connection media, processing restrictions, configuration settings, and/or other factors. And as a result, at times of heavy load, the access nodes may experience delays in communicating with each other. And particularly with respect to transfer of UE data, but also for other communications, such delay could be problematic, possibly giving rise to user-experience issues.

The present disclosure provides a mechanism to help address this.

In accordance with the disclosure, a computing system will monitor a total extent of data communication that flows between a pair of access nodes, and the computing system will use that monitored total extent of data communication as a basis to control a rate of periodic control-plane messaging between the access nodes. Namely, when the total extent of data communication between the access nodes is, or is likely to be, relatively high, the computing system could set a relatively long period for such control-plane messaging, so that the control-plane messaging would occur less often. Whereas, when the total extent of data communication between the access nodes is, or is likely to be, relatively low, the computing system could set a relatively short period for the control-plane messaging (perhaps a default period), so that the control-plane messaging would occur more often.

In an example implementation, the periodic control-plane messaging between the access nodes could be secondary-connection usage reporting for one or more UEs served with dual connectivity, where one of the access nodes, as SN, periodically reports to the other access node, as MN, a volume of data served by the SN (perhaps for the MN to report to the core network for accounting, or other purposes). With this implementation, the SN could be configured to operate with a usage-reporting rate set to a default rate, defining a default time interval between each such usage report that the SN sends to the MN. Upon detecting that the total extent of data communication between the SN and MN is at least as high as a predefined threshold that is deemed to represent high load, the computing system could then responsively decrease the SN's usage-reporting rate from the default rate to a reduced rate, thus increasing the time interval between each such usage report from the default time interval to a longer time interval.

Using the total extent of data communication between the access nodes as a basis to control the rate of this or other such periodic control-plane signaling between the access nodes may help to avoid or reduce the likelihood of an overload situation that could give rise to the delay issue noted above.

These as well as other aspects, advantages, and alternatives will become apparent to those of ordinary skill in the art by reading the following detailed description, with reference where appropriate to the accompanying drawings. Further, it should be understood that the descriptions provided in this overview and below are intended to illustrate the invention by way of example only and not by way of limitation.

