BACKGROUND

A cellular wireless network typically includes a number of access nodes that are configured to provide wireless coverage areas, such as cells and cell sectors, 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. 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 cellular network 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 network could operate in accordance with a particular radio access technology (RAT), with communications from the access nodes to UEs defining a downlink or forward link and communications from the UEs to the access nodes 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 can facilitate mobile broadband service using technologies such as orthogonal frequency division multiplexing (OFDM) and multiple input multiple output (MIMO). And most recently, the industry is now exploring developments in “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 provide coverage on one or more radio frequency (RF) carriers, each of which could be frequency division duplex (FDD), defining 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. Each such frequency channel could be defined as a specific range of frequency having a bandwidth and a center frequency and thus extending from a low-end frequency to a high-end frequency.

Further, on the downlink and uplink, the air interface on each carrier could be configured in a specific manner to define physical resources for carrying information (e.g., user-plane data and control-plane signaling) wirelessly between the access node and UEs.

In a non-limiting example implementation, for instance, the air interface on each carrier could be divided over time into frames, transmission time intervals (TTIs) (e.g., 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, with each resource element spanning a respective symbol time segment and occupying a respective subcarrier, and the subcarrier of each resource element could be modulated to carry information. Further, each TTI may be defined by subframes. In each TTI, the resource elements on the downlink and uplink of the example air interface could be grouped to define physical resource blocks (PRBs) that could be allocated as needed to carry data between the access node and served UEs.

In addition, certain resource elements on the example air interface could be designated for special use. For instance, on the downlink, certain resource elements could be set aside to define a downlink control region for carrying control signaling from the access node to UEs, certain resource elements could be designated to carry broadcast synchronization signals that UEs could detect as an indication of coverage on the carrier and to establish frame timing, and certain resource elements could be designated to carry a reference signal that UEs could measure to determine coverage strength, among other possibilities. And on the uplink, certain resource elements could be set aside to define an uplink control region for carrying control signaling from UEs to the access node, and certain resource elements could be designated to carry uplink reference signals or the like that could be used to evaluate uplink signal communications, among other possibilities.

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 could then coordinate setup for the UE of one or more bearers extending between the UE and a core-network gateway that provides transport-network connectivity.

Once the UE is so connected and registered with the example network, 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.

For instance, with the air interface described above, when packet data for the UE arrives at the core network from a transport network, the data could flow to the access node, and the access node could buffer the data, pending transmission of the data to the UE. The access node could then schedule and allocate downlink PRBs in an upcoming TTI for carrying at least a portion of the data, defining a transport block, to the UE. And the access node could then transmit to the UE in the downlink control channel of that subframe a Downlink Control Information (DCI) message that designates the allocated PRBs, and the access node could accordingly transmit the transport block to the UE in those designated PRBs.

For each such downlink transmission, the UE could then determine if the UE received the transport block successfully. For instance, the transmission could carry a cyclic redundancy check (CRC) value computed based on the transport block, and the UE could compute a CRC based on the received transport block and determine whether its computed CRC matches that carried by the transmission. If the UE receives the transmission and determines that the CRC matches or otherwise that the UE received the transport block successfully, then the UE could transmit to the access node a positive acknowledgement (ACK) control message, and the access node could then proceed with transmission of a next transport block (if any) to the UE. Whereas, if the UE did not receive the transmission or determined that the CRC did not match and thus that there was an error in the received transport block, then the UE could transmit to the access node a negative acknowledgement (NACK), in response to which the access node could attempt the transmission again.

Likewise, when the UE has data to transmit on the transport network, the UE could buffer the data, pending transmission of the data to the access node, and the UE could transmit to the access node a scheduling request that carries a buffer status report (BSR) indicating the quantity of data that the UE has buffered for transmission. The access node could then allocate uplink PRBs in an upcoming TTI to carry a transport block of the data from the UE and could transmit to the UE, in the downlink channel of a preceding subframe, a DCI message that designates those upcoming PRBs. And the UE could then accordingly transmit the transport block to the access node in the designated PRBs.

As with downlink transmission, for each transport block that the UE transmits to the access node, the access node could determine if the transport block arrived successfully, based on a CRC analysis. And if the access node received the transmission successfully, then the access node could transmit to the UE an ACK and could schedule a next uplink transmission from the UE. Whereas, if the access node did not receive the transmission successfully, then the access node could transmit to the UE a NACK, and the UE could attempt re-transmission to the access node.

Normally, the UE may transmit data in one subframe corresponding to a TTI, and then wait to receive a NACK or ACK response before re-transmitting the data or transmitting additional data. This re-transmission process may give rise to a delay as the UE waits for the response. In order to reduce the delay associated with re-transmitting data, a representative RAT could support a bundling option for data transmissions. A possible bundling option for data transmissions could be to repeatedly transmit data in multiple consecutive TTIs, referred to as TTI bundling. When TTI bundling is used, the UE automatically transmits the data repeatedly in multiple consecutive TTIs and then waits to receive a NACK or ACK response for that group of transmissions. In this way, the UE can transmit multiple instances of the data, which allows for more robust reception of the data, but without the delay that would be associated with the UE transmitting the data multiple times and waiting for a NACK or ACK response after each transmission.

As an access node serves a UE on a given carrier, the bandwidth of the carrier may also define an effective limit on the peak rate of data communication between the access node and the UE, as the bandwidth would define only a limited number of air-interface resources (e.g., PRBs) per TTI that could be allocated for use to carry data communications. Further, the data rate available on the carrier could also be limited by the access node serving multiple UEs at once on the carrier, with the access node allocating PRBs per TTI among the various served UEs.

One way to help overcome this per-carrier data rate limitation is to have an access node serve a UE on multiple carriers at once, providing the UE with “carrier-aggregation” service. With carrier-aggregation service, multiple carriers from either contiguous frequency bands or non-contiguous frequency bands are aggregated together as “component carriers” to increase the overall bandwidth available per subframe by providing more air-interface resources on which the access node can schedule uplink and downlink communication. In a representative carrier-aggregation implementation, one of the UE's serving carriers is deemed a primary component carrier or primary cell (PCell), while each other of the UE's serving carriers is deemed a secondary component carrier or secondary cell (SCell).

In practice, the UE's PCell could function as the anchor for carrying key control signaling between the UE and the access node, such as scheduling requests and DCI messaging for instance. Further, the UE's PCell might be used for both downlink and uplink service of the UE, while each SCell in the UE's connection might be used for just downlink service of the UE, to help increase the UE's peak downlink data rate.

With the above arrangement, a UE might engage in various forms of communication, an example of which for present purposes is voice over packet (VOP) call communication. VOP-call communication involves communication of voice-call audio in a sequence of Internet Protocol (IP) packets. For an end-to-end VOP call, for instance, a device at one end of a VOP call could receive a user's voice audio (e.g., speech or other voice-band audio), digitize the voice audio using a voice codec to produce a digital bit stream, encode the bit stream to compress it for transmission, packetize the encoded bit stream into a sequence of voice packets, and transmit the voice packets to another device. And on receipt, the other device could then de-packetize the encoded bit stream, decode the bit stream, and convert the bit stream to analog audio output using a voice codec for playout to another user. Further, typical VOP systems provide silence voice packets as filler or natural background noise at times during the call when there is no talking.

In a representative wireless communication system, the voice codec outputs a new voice frame approximately every 20 milliseconds. Given the rate of output, the voice frames should be transmitted from one device to another device in a timely manner in order to prevent problems on receipt such as receiving the voice frames out of order. However, a heavy load on the carrier may pose an issue for voice packet transmission.

In some instances, due to a heavy load of data being transmitted on the carrier, voice packet transmission may fail. Packets that are not successfully transmitted to their destination are referred to as dropped packets. Packets may be dropped as the result of congestion on the carrier, e.g., if there is low PRB availability. For example, an access node may have insufficient air-interface resources available to carry the packet in a timely manner. When there are insufficient air-interface resources on a carrier, the voice packets may be buffered for too long awaiting available PRBs and may therefore be dropped, e.g. per a packet-drop timer. Thus voice packets may not be transmitted. Other examples may exist as well.

Dropped voice packets could result in the loss of voice communication due to the failure to transmit digitized audio on the uplink and/or the downlink. This loss of communication is known as voice muting. When voice muting occurs, a user may not receive a portion of audio sent as a voice packet. Thus, voice muting may negatively affect user-experience.

The present disclosure provides a mechanism that could help address the problem of voice muting. The mechanism could detect a high rate of muting on an uplink and/or a downlink of a carrier in a system in which an access node operates on the carrier. In response to detecting that at least a threshold high rate of voice muting is occurring, the access node could take action to limit PRB utilization on the carrier, so as to help reduce the rate of voice muting. For example, the access node could responsively limit an extent to which the access node provides a resource-intensive service on or with the carrier, such as by imposing a maximum limit on the number of UEs that the access node would serve concurrently with the resource-intensive service on the carrier.

Without limitation, for instance, resource-intensive services may include providing TTI bundling on the carrier and/or using the carrier as an SCell for carrier-aggregation service. Because these services take up a large amount of available resources for data transmission, they may contribute to the high rate of voice muting on a carrier. Thus, limiting the use of these services when faced with a high rate of voice muting may help to lower the rate of voice muting.

These as well as other aspects, advantages and alternatives will become apparent to those reading the following description, with reference where appropriate to the accompanying drawings. Further, it should be understood that the discussion in this overview and elsewhere in this document is provided by way of example only and that numerous variations are possible.

