HK1222970B - Mitigation of traffic congestion in dual connectivity systems - Google Patents

Description

Alleviate traffic congestion in dual-connection systems

Related applications

This application claims the benefit of U.S. Provisional Patent Application Serial No. 61/883,127 (Docket No. P61192Z), filed March 26, 2013, the entire specification of which is hereby incorporated by reference herein in its entirety for any reason. This application also claims the benefit of U.S. Non-Provisional Patent Application Serial No. 14/317,900 (Docket No. P66310), filed June 27, 2014, the entire specification of which is hereby incorporated by reference herein in its entirety for any reason.

Background Art

Wireless mobile communication technology uses various standards and protocols to transmit data between nodes (e.g., transmission stations) and wireless devices (e.g., mobile devices). Some wireless devices use orthogonal frequency division multiple access (OFDMA) in downlink (DL) transmissions and single-carrier frequency division multiple access (SC-FDMA) in uplink (UL) transmissions. Standards and protocols that use orthogonal frequency division multiplexing (OFDM) for signal transmission include the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE), the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standards (e.g., 802.16e, 802.16m) (commonly referred to as WiMAX (Worldwide Interoperability for Microwave Access) by industry groups), and the IEEE 802.11 standard (commonly referred to as WiFi by industry groups).

In a 3GPP radio access network (RAN) LTE system, a node may be a combination of an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (also commonly referred to as an evolved Node B, enhanced Node B, eNodeB, or eNB) and a Radio Network Controller (RNC), which communicates with wireless devices, referred to as user equipment (UE). Downlink (DL) transmissions may be communications from a node (e.g., an eNodeB) to a wireless device (e.g., a UE), and uplink (UL) transmissions may be communications from a wireless device to a node.

In a homogeneous network, a node (also known as a macro node) can provide basic wireless coverage to wireless devices in a cell. A cell can be an area in which a wireless device can operate to communicate with a macro node. Heterogeneous networks (HetNets) can be used to handle the increased traffic load on macro nodes due to the increased use and functionality of wireless devices. A HetNet can include a layer of planned high-power macro nodes (or macro eNBs) that overlaps with multiple layers of lower-power nodes (small eNBs, micro eNBs, pico eNBs, femto eNBs, or home eNBs) that can be deployed within the coverage area (cell) of the macro cell in a poorly planned or even completely uncoordinated manner. Lower-power nodes (LPNs) are often referred to as "low-power nodes," small nodes, or small cells.

In LTE, data can be transmitted from the eNodeB to the UE via the Physical Downlink Shared Channel (PDSCH). The Physical Uplink Control Channel (PUCCH) can be used to confirm that the data has been received. The downlink channel and the downlink channel, or uplink transmission or downlink transmission, can use time division duplexing (TDD) or frequency division duplexing (FDD).

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the present disclosure will become apparent from the following detailed description taken in conjunction with the accompanying drawings, which together illustrate features of the present disclosure by way of example; and wherein:

1A-1E illustrate a dual connectivity architecture according to an example;

FIG1F illustrates an architecture of a user equipment (UE) operable to support dual connectivity, according to an example;

FIG2 illustrates a conventional user plane Packet Data Convergence Protocol (PDCP) layer according to an example;

FIG3A illustrates a Packet Data Convergence Protocol (PDCP) layer in a primary evolved Node B (MeNB) according to an example;

FIG3B illustrates a Packet Data Convergence Protocol (PDCP) layer in a user equipment (UE) according to an example;

FIG4 depicts functionality of computer circuitry of a primary evolved Node B (MeNB) operable to alleviate traffic congestion, according to an example;

FIG5 depicts a flow chart of a method for alleviating traffic congestion according to an example;

FIG6 depicts functionality of computer circuitry of a primary evolved Node B (MeNB) operable to alleviate traffic congestion, according to an example;

FIG7 shows a diagram of a wireless device (eg, UE) according to an example.

Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. However, it will be understood that no limitation of the scope of the invention is intended thereby.

DETAILED DESCRIPTION

Before disclosing and describing the present invention, it should be understood that the present invention is not limited to the specific structures, processing steps, signaling protocols and exchanges, or materials disclosed herein, but is extended to its equivalents recognized by those skilled in the relevant art. It should also be understood that the terms used herein are only used for the purpose of describing specific examples and are not intended to be limiting. The same reference numerals in different figures represent the same elements. The sequence numbers provided in the flowcharts and processes are provided for the purpose of clearly illustrating the steps and operations, and this does not necessarily indicate a specific order or sequence.

Example Embodiments

The following provides a preliminary overview of the technology embodiments, and further describes the specified technology embodiments. This preliminary summary is intended to help readers understand the technology more quickly, and is not intended to identify the key features or essential features of the technology nor to limit the scope of the claimed subject matter.

In 3GPP LTE Release 12.0, a user equipment (UE) can be connected to more than one cellular base station simultaneously. For example, a UE can be connected to a primary evolved Node B (MeNB) and simultaneously connected to at least one secondary evolved Node B (SeNB). When a UE is connected to two cells, the UE can receive data bearers from both cells substantially simultaneously. Multiple bearers can be sent to the UE based on where the S1-U terminates and where the bearer is split. In one example, the S1-U can be terminated at the MeNB, and the bearer split can be performed at the Packet Data Convergence Protocol layer in the MeNB.

Figure 1A shows an example of a dual-connectivity architecture of a primary evolved Node B (MeNB) and a secondary evolved Node B (SeNB). S1-U can be terminated at the MeNB, and bearer separation can occur at the MeNB. In addition, for separated bearers, independent radio link control (RLC) may exist in the MeNB and SeNB. The MeNB can be connected to the evolved packet core (EPC) via the S1 interface. For example, the MeNB can be connected to the serving gateway (S-GW) or the mobility management entity (MME) via the S1 interface. The MeNB may include a PDCP layer, an RLC layer, and a media access channel (MAC) layer. The SeNB may include an RLC layer and a MAC layer. The MeNB can receive data and/or control information from a higher layer (e.g., an IP layer or an application layer) at the PDCP layer. In one example, data or control information can be transmitted from the PDCP layer in the MeNB to the RLC layer and MAC layer in the MeNB. In addition, data or control information can be transmitted from the PDCP layer in the MeNB to the RLC layer in the SeNB via the X2 interface.

Figure 1B shows another example of a dual-connectivity architecture of a primary evolved Node B (MeNB) and a secondary evolved Node B (SeNB). S1-U can be terminated at the SeNB, and both the SeNB and the MeNB can include independent packet data convergence protocols (PDCPs), i.e., no bearer separation. The MeNB and the SeNB can be connected to the evolved packet core (EPC) via the S1 interface. For example, the MeNB and the SeNB can be connected to the serving gateway (S-GW) or the mobility management entity (MME) via the S1 interface. The MeNB can include a PDCP layer, a radio link control (RLC) layer, and a media access channel (MAC) layer. In addition, the SeNB can include a separate PDCP layer, an RLC layer, and a MAC layer. The PDCP layer in the MeNB can receive data or control information from a higher layer, and the PDCP layer in the SeNB can receive data or control information from a higher layer.

Figure 1C shows another example of a dual-connectivity architecture of a primary evolved Node B (MeNB) and a secondary evolved Node B (SeNB). S1-U can be terminated at the MeNB, and bearer separation can occur at the MeNB. In addition, for separated bearers, a master-slave radio link control (RLC) may exist in the MeNB and SeNB. The MeNB can be connected to the evolved packet core (EPC) via the S1 interface. For example, the MeNB can be connected to the serving gateway (S-GW) or the mobility management entity (MME) via the S1 interface. The MeNB may include a PDCP layer, an RLC layer, and a media access channel (MAC) layer. The SeNB may include an RLC layer and a MAC layer. The MeNB can receive data and/or control information from a higher layer (e.g., an IP layer or an application layer) at the PDCP layer. In one example, data or control information can be transmitted from the PDCP layer in the MeNB to the RLC layer and MAC layer in the MeNB. In addition, data or control information can be transmitted from the RLC layer in the MeNB to the RLC layer in the SeNB via the X2 interface.

Figure 1D shows another example of a dual-connectivity architecture of a primary evolved Node B (MeNB) and a secondary evolved Node B (SeNB). S1-U can be terminated at the MeNB and no bearer splitting occurs at the MeNB. In addition, there may be an independent radio link control (RLC) at the SeNB. The MeNB can be connected to the evolved packet core (EPC) via the S1 interface. For example, the MeNB can be connected to the serving gateway (S-GW) or the mobility management entity (MME) via the S1 interface. The MeNB may include a PDCP layer, an RLC layer, and a media access channel (MAC) layer. The SeNB may include an RLC layer and a MAC layer. The MeNB can receive data and/or control information from a higher layer (e.g., an IP layer or an application layer) at the PDCP layer. In one example, data or control information can be transmitted from the PDCP layer in the MeNB to the RLC layer and MAC layer in the MeNB. In addition, data or control information can be transmitted from the PDCP layer in the MeNB to the RLC layer in the SeNB via the X2 interface.

Figure 1E shows another example of a dual-connectivity architecture of a primary evolved Node B (MeNB) and a secondary evolved Node B (SeNB). S1-U can be terminated at the MeNB and no bearer splitting occurs at the MeNB. In addition, there may be a master-slave radio link control (RLC) for the SeNB bearer. The MeNB can be connected to the evolved packet core (EPC) via the S1 interface. For example, the MeNB can be connected to the serving gateway (S-GW) or the mobility management entity (MME) via the S1 interface. The MeNB may include a PDCP layer, an RLC layer, and a media access channel (MAC) layer. The SeNB may include an RLC layer and a MAC layer. The MeNB can receive data and/or control information from a higher layer (e.g., an IP layer or an application layer) at the PDCP layer. In one example, data or control information can be transmitted from the PDCP layer in the MeNB to the RLC layer and MAC layer in the MeNB. In addition, data or control information can be transmitted from the RLC layer in the MeNB to the RLC layer in the SeNB via the X2 interface.

The dual connectivity architecture depicted in Figures 1A-1E is further discussed in 3GPP Technical Review (TR) 36.842 version 12.0.0.

FIG1F illustrates an exemplary architecture of a user equipment (UE). The UE may be configured to communicate with a primary evolved Node B (MeNB) and a secondary evolved Node B (SeNB) in a dual-connectivity architecture. The UE may include a PDCP layer, an RLC layer, and a MAC layer. The PDCP layer in the UE may receive data and/or control information from the MeNB. Additionally, the PDCP layer in the UE may receive data and/or control information from the SeNB. In one example, data or control information may be transmitted from the PDCP layer in the UE to lower layers in the UE (e.g., the RLC layer and the MAC layer).

In one configuration, the PDCP layer in the MeNB can receive packets (e.g., PDCP SDU packets or PDCP PDU packets) in the downlink from higher layers. The higher layers may include the IP layer or application layer in the MeNB. The PDCP layer can temporarily store the packets in a retransmission buffer. In other words, the packets can be temporarily stored in the retransmission buffer until they are ready to be transmitted in the downlink to the UE or SeNB. For example, the packets in the retransmission buffer can be transmitted from the MeNB to the UE via the MeNB radio link. As another example, the packets in the retransmission buffer can be transmitted from the MeNB to the SeNB via the SeNB radio link.

In one example, the retransmission buffer may have a limited capacity. Therefore, the retransmission buffer may discard some packets based on a discard timer. In other words, if a packet has been in the retransmission buffer for a predetermined period of time, the packet may be cleared to make room in the retransmission buffer for additional packets.

When the retransmission buffer is full with packets, a potential overflow in the downlink can be detected at the retransmission buffer. In other words, the number of packets in the retransmission buffer may be approaching a certain maximum value. Alternatively, when the reordering buffer is full with packets, a potential overflow in the uplink can be detected at the reordering buffer. The potential overflow may be caused by delays or capacity limitations in the X2 interface between the MeNB and SeNB, the MeNB radio link between the MeNB and the UE, and/or the SeNB radio link between the SeNB and the UE. In other words, when delays or capacity limitations prevent packets from being delivered to the UE and/or SeNB, packets are suspended in the retransmission buffer. In another example, packets are suspended in the retransmission buffer due to problems in the RLC layer or MAC layer of the SeNB.

When a packet remains in the retransmission buffer for a period exceeding a discard timer (e.g., due to delay or capacity limitations), the packet can be removed from the retransmission buffer. However, some packets in the retransmission buffer may not necessarily be cleared. In other words, these packets need to be transmitted to the UE, but due to delay or capacity limitations, the time these packets remain in the retransmission buffer exceeds the discard timer. Therefore, the discard timer can be extended based on the type of traffic associated with the packet. Thus, clearing the retransmission buffer due to slow delivery of packets to the UE and/or SeNB can be avoided. For example, when the packet is associated with delay-tolerant traffic (i.e., no time limit), the discard timer can be extended. On the other hand, when the packet is associated with delay-sensitive traffic (e.g., Voice over Internet Protocol (VoIP) or video streaming), the discard timer may not be extended. Therefore, when the packet is associated with delay-tolerant traffic, the packet in the retransmission buffer may not be quickly discarded (i.e., the discard timer is extended). Instead, when the packet is associated with delay-sensitive traffic, the packet in the retransmission buffer may be discarded according to the discard timer.

In one example, the PDCP mechanism in the UE and MeNB is based on a COUNT to prevent replay attacks. The COUNT can be maintained at the UE and MeNB and incremented for each PDCP PDU transmitted. To provide robustness against lost packets, the least significant bit of the COUNT is rounded up to serve as the PDCP sequence number (SN). The length of the PDCP SN can be increased to multiple bits, thereby extending the discard timer in the retransmission buffer.

In one configuration, due to the delay of the X2 connection, the number of packets (PDCP SDU packets or PDCP PDU packets) in the retransmission buffer in the PDCP layer of the MeNB may increase. For example, the X2 connection between the MeNB and the SeNB may experience delays or capacity limitations, and thus cause packets to be suspended in the retransmission buffer of the MeNB. The PDCP layer in the MeNB can discard one or more packets to alleviate potential overflow at the retransmission buffer. In addition, the PDCP layer in the MeNB can discard one or more packets in the retransmission buffer to instruct the upper layer (e.g., the Internet Protocol (IP) layer or the application layer) to slow down the rate at which packets are transmitted to the PDCP layer in the MeNB. In other words, the discarding of packets at the retransmission buffer can indicate an overflow buffer state to the IP layer, and in response, the IP layer will send fewer packets to the PDCP layer in the MeNB. Therefore, the number of packets stored in the retransmission buffer can be reduced, so that overflow at the retransmission buffer can be avoided.

Additionally, when the DL discard timer expires at the MeNB, some PDCP packets in the retransmission buffer have already been sent as PDCP PDUs to the RLC layer and to lower layers of the MeNB. For example, when the DL discard timer expires, there are five PDCP packets (e.g., A, B, C, D, and E) in the retransmission buffer. Packets A and B may have been sent to the RLC layer, but ACKs have not yet been received. If packets A and B are discarded, the UE may be notified of the discarded packets.

When the PDCP layer of the MeNB discards one or more packets from the retransmission buffer, the PDCP layer in the UE does not know which packets were discarded. However, when the UE does not receive a packet from the MeNB on time, the UE can be sure that the packet is delayed, the packet is lost in the air, and/or the packet will be retransmitted from the MeNB to the UE. Therefore, the UE does not have to wait for the packet without realizing that the packet has been discarded at the MeNB. In one configuration, the PDCP layer in the MeNB can send a list of packets (e.g., PDCP PDUs) to the PDCP layer in the UE, where the list of packets indicates the packets discarded at the MeNB. In addition, the list of packets can include an identifier associated with each discarded packet. As an example, when the UE reassembles the packets, the UE may already know that packets X and Y were discarded at the MeNB and that the UE should not wait for these packets to arrive at the UE. Therefore, the list of packets enables the UE to distinguish between discarded packets and delayed packets.

In one configuration, the PDCP layer in the MeNB may receive multiple packets from a higher layer (e.g., the IP layer or the application layer). The PDCP layer in the MeNB may calculate a downlink separation ratio (i.e., the percentage of packets served directly to the UE using the MeNB link, and the percentage of packets served to the UE via the SeNB using the SeNB link). As an example, the PDCP layer in the MeNB may receive 10 packets. The PDCP layer may push 6 of the 10 packets (i.e., 60%) to the UE via the SeNB, and the remaining 4 packets (i.e., 40%) may be pushed down to the UE via the MeNB link. In other words, a 60/40 relationship may describe the downlink separation ratio at the PDCP in the MeNB. When the retransmission buffer in the MeNB (e.g., due to delays in the X2 interface, delays in the MeNB radio link, delays in the SeNB radio link) approaches a predetermined capacity, the MeNB may recalculate the downlink separation ratio in order to reduce the amount of time to deliver packets to the UE.

As an example, the number of packets in the retransmission buffer may steadily increase, and it is known that the X2 connection between the MeNB and the SeNB is about to be delayed and distorted. Therefore, to optimize the packet flow to the UE, the MeNB may change the 60/40 split ratio to 10/90. In other words, the PDCP layer in the MeNB may push 1 of 10 packets (i.e., 10%) to the UE via the SeNB, and the remaining 9 packets (i.e., 90%) may be pushed down to the UE over the MeNB link. Therefore, when the X2 connection between the MeNB and the SeNB is delayed, the MeNB may send fewer packets to the UE via the SeNB and more packets directly to the UE.

In one configuration, the PDCP layer in the UE may further include a retransmission buffer. The retransmission buffer may temporarily store packets to be transmitted to the SeNB and/or MeNB. In the uplink, the discard timer associated with the retransmission buffer may be extended based on the traffic type associated with the packet. For example, when the packet is associated with delay-tolerant traffic (i.e., no time limit), the discard timer may be extended. On the other hand, when the packet is associated with delay-sensitive traffic (e.g., Voice over Internet Protocol (VoIP) or video streaming), the discard timer may not be extended. Therefore, when the discard timer is extended at the UE, early clearing of packets in the retransmission buffer due to capacity and delay limitations in the link (e.g., MeNB radio link, SeNB radio link) may be avoided.

In one example, a retransmission buffer in the PDCP layer of the UE may drop one or more packets. In the uplink, when an overflow is about to occur at the retransmission buffer, the retransmission buffer may drop packets. The dropping of packets may indicate an overflow buffer status to the IP layer, which may cause the IP layer and the application layer to reduce the data rate to the retransmission buffer. In other words, when the IP layer recognizes a potential overflow at the retransmission buffer, the IP layer may send fewer packets to the retransmission buffer. The PDCP layer in the UE sends a packet list to the PDCP layer in the MeNB, where the packet list includes packets dropped at the UE. Therefore, the MeNB can identify which packets are dropped at the UE and which packets are delayed at the UE.

Additionally, when the DL discard timer expires at the UE, some PDCP packets in the retransmission buffer have already been sent as PDCP PDUs to the RLC layer and to lower layers of the UE. For example, when the DL discard timer expires, there are five PDCP packets (e.g., A, B, C, D, and E) in the retransmission buffer. Packets A and B may have been sent to the RLC layer, but ACKs have not yet been received. If packets A and B are discarded, the MeNB can be notified of the discarded packets A and B.

In one configuration, in response to detecting a potential overflow in a retransmission buffer in a UE, the UE may send a buffer status and/or a request for a modified uplink (UL) separation ratio to the PDCP layer in the MeNB. As an example, in the uplink, the PDCP layer in the UE may send 50% of packets to the MeNB via the MeNB radio link and 50% of packets to the SeNB via the SeNB radio link. However, the SeNB radio link may be congested, causing packets to be transmitted via the SeNB radio link to be suspended in the retransmission buffer. The PDCP layer in the MeNB may determine a modified UL separation ratio and send the modified UL separation ratio to the UE. The UE may send packets to the MeNB and SeNB based on the modified UL separation ratio. For example, the PDCP layer in the UE may send 80% of packets to the MeNB via the MeNB radio link and 20% of packets to the SeNB via the SeNB radio link based on the modified UL separation ratio. In other words, the UE may send fewer packets to the SeNB due to latency in the SeNB radio link. When the delay is substantially eliminated, the UE may again request the MeNB to modify the UL separation ratio.

Figure 2 shows a conventional user plane packet data convergence protocol (PDCP) layer. In one example, the PDCP layer may be in a primary evolved Node B (MeNB). In the downlink, the PDCP layer in the MeNB may receive PDCP service data units (SDUs) from higher layers (e.g., the IP layer or the application layer). The PDCP SDUs may be stored in a retransmission buffer at the PDCP layer in the MeNB. A numbering function may be applied to the PDCP SDUs. The PDCP layer may perform head-end compression using the Robust Header Compression (ROHC) protocol defined by the IETF (Internet Engineering Task Force), which may result in compressed PDCP SDUs. Encryption may be applied to the compressed PDCP SDUs, and a PDCP header may be added. In addition, the PDCP SDUs may be converted into PDCP packet data units (PDUs). For example, the PDCP PDUs may be transmitted to the UE in the downlink.

In the uplink, the PDCP layer in the MeNB can receive PDCP PDUs from the UE (directly or via the SeNB). The PDCP header in the PDCP PDU can be processed and the COUNT can be determined. The PDCP PDU timer (referred to as COUNT) can be used as input to the security algorithm. During the radio resource control (RRC) connection, the COUNT value is incremented for each PDCP PDU. COUNT has a length of 32 bits, allowing for an acceptable duration of the RRC connection. During the RRC connection, the COUNT value is maintained at the MeNB by timing each PDCP PDU received. Decryption can be applied to the PDCP PDU. The PDCP layer can perform head-end decompression and store the PDCP PDU in a reordering buffer. In addition, the PDCP PDU can be converted into a PDCP SDU. The PDCP SDU can be transmitted from the PDCP layer to higher layers in the MeNB (e.g., the IP layer or application layer) in the uplink. In other words, the PDCP SDU can be arranged in the correct order before the PDCP PDU is sent to the IP layer.

Figure 3A shows the new user plane packet data convergence protocol (PDCP) layer in the main evolved Node B (MeNB). In the downlink, the PDCP SDU can be received from the higher layer in the MeNB at the retransmission buffer. The numbering function can be applied to the PDCP SDU. The PDCP layer can perform header compression using the ROHC protocol, which can result in a compressed PDCP SDU. Encryption can be applied to the compressed PDCP SDU. In addition, the PDCP SDU can be converted into a PDCP PDU. Bearer separation may occur after encryption is performed. In other words, bearer separation may refer to the ability to separate bearers on multiple eNBs in dual connectivity. Bearer separation can be performed based on a separation ratio. Based on the separation ratio, the first part of the PDCP PDU can become an M-PDCP PDU, and the second part of the PDCP PDU can become an S-PDCP PDU. A first PDCP header can be added to the M-PDCP PDU, and a second PDCP header can be added to the S-PDCP PDU. The MeNB can transmit the M-PDCP PDU to the UE via the MeNB radio link. In addition, the MeNB may transmit the S-PDCP PDU to the SeNB via the X2 interface, wherein the SeNB may transmit the S-PDCP PDU to the UE via the SeNB radio link.

In the uplink, the PDCP layer in the MeNB may receive an M-PDCP PDU from a lower layer in the MeNB. In addition, the PDCP layer may receive an S-PDCP PDU from a lower layer in the MeNB. The PDCP layer in the MeNB may process the PDCP header of the M-PDCP PDU. In addition, the PDCP layer in the MeNB may process the PDCP header of the S-PDCP PDU. The PDCP layer may merge bearers and determine a COUNT. In other words, the M-PDCP PDU and the S-PDCP PDU may be merged into a PDCP PDU. The PDCP PDU may be converted into a PDCP SDU. Decryption may be applied to the PDCP SDU. The PDCP layer may perform ROHC decompression and store the PDCP SDU in a reordering buffer, where the reordering buffer assembles the PDCP SDU in the correct order. The PDCP SDU may be transmitted from the PDCP layer to a higher layer in the MeNB (e.g., an IP layer or an application layer) in the uplink.

Figure 3B shows a new user plane packet data convergence protocol (PDCP) layer in a user equipment (UE). In the downlink, a PDCP SDU can be received from a higher layer at the PDCP layer in the UE and stored in a retransmission buffer. A numbering function can be applied to the PDCP SDU. The PDCP layer can perform head-end compression using the ROHC protocol, which can result in a compressed PDCP SDU. Encryption can be applied to the compressed PDCP SDU. In addition, the PDCP SDU can be converted into a PDCP PDU. Bearer separation may occur after encryption is performed. Bearer separation can be performed based on a separation ratio, where the separation ratio is determined by the MeNB. Based on the separation ratio, the first part of the PDCP PDU can become an M-PDCP PDU, and the second part of the PDCP PDU can become an S-PDCP PDU. The UE can transmit the M-PDCP PDU to the primary evolved Node B (MeNB) via the MeNB radio link. In addition, the UE can transmit the S-PDCP PDU to the secondary evolved Node B (SeNB) via the SeNB radio link.

In the uplink, the PDCP layer in the UE may receive an M-PDCP PDU from a lower layer in the UE. In addition, the PDCP layer in the UE may receive an S-PDCP PDU from a lower layer in the UE. The PDCP layer in the UE may merge bearers and determine a COUNT. In other words, the M-PDCP PDU and the S-PDCP PDU may be merged into a PDCP PDU. The PDCP PDU may be converted into a PDCP SDU. Decryption may be applied to the PDCP SDU. The PDCP layer may perform ROHC decompression and store the PDCP SDU in a reordering buffer, where the reordering buffer assembles the PDCP SDU in the correct order. In the uplink, the PDCP SDU may be transmitted from the PDCP layer to a higher layer in the UE.

Another example provides functionality 400 of computer circuitry of a master evolved Node B (MeNB) operable to alleviate traffic congestion, as shown in the flowchart of FIG4 . The functionality may be implemented as a method, or the functionality may be executed as instructions on a machine, wherein the instructions are included on at least one computer-readable medium or a non-transitory machine-readable storage medium. The computer circuitry may be configured to: identify discarded service data unit (SDU) packets in a retransmission buffer of a packet data convergence protocol (PDCP) layer of the MeNB, as shown in block 410. The computer circuitry may be configured to: create a list of discarded packet data unit (PDU) packets at the PDCP layer of the MeNB, wherein the discarded PDU packets are associated with the SDU packets, as shown in block 420. The computer circuitry may be configured to: send the list of discarded PDU packets from the PDCP layer of the MeNB to the PDCP layer of a user equipment (UE) to enable the UE to distinguish between delayed PDU packets and discarded PDU packets, as shown in block 430.

In one example, discarding the PDU packet can indicate an overflow buffer condition to the Internet Protocol (IP) layer, wherein the IP layer reduces the packet rate to the PDCP layer at the MeNB in response to the overflow buffer condition. In another example, the PDU packet is discarded in response to detecting a potential overflow at the MeNB's retransmission buffer. In another example, the potential overflow is due to delay or capacity limitations on at least one of the following: an X2 link between the MeNB and a secondary evolved NodeB (SeNB), a radio link between the MeNB and a UE, or a radio link between the SeNB and a UE.

In one example, the computer circuitry may be further configured to: when a potential overflow occurs at a retransmission buffer, recalculate a downlink (DL) separation ratio, the DL separation ratio defining a first percentage of PDU packets to be sent to the UE via the SeNB and a second percentage of PDU packets to be sent directly to the UE. Additionally, the computer circuitry may be further configured to: detect a potential overflow at a retransmission buffer of the MeNB, wherein SDU packets are stored in the retransmission buffer for retransmission in the downlink to one of the UE or a secondary evolved NodeB (SeNB); detect a traffic type associated with the SDU packets; and extend a discard timer at the retransmission buffer based in part on the traffic type associated with the SDU packets to avoid premature clearing of the SDU packets at the retransmission buffer.

In one example, the computer circuitry may be further configured to extend a discard timer at the retransmission buffer when the traffic type associated with the SDU packet is delay-tolerant traffic. Additionally, the computer circuitry may be further configured to not extend the discard timer at the retransmission buffer when the traffic type associated with the SDU packet is delay-sensitive traffic. In one configuration, extending the discard timer at the retransmission buffer includes increasing the length of a Packet Data Convergence Protocol Sequence Number (PDCP SN) to include multiple least significant bits. Additionally, the computer circuitry may be further configured to communicate with a secondary evolved Node B (SeNB) via an X2 link in a dual-connectivity architecture.

Another example provides a method 500 for mitigating traffic congestion, as shown in the flowchart of FIG5 . The method can be executed as instructions on a machine, wherein the instructions are included on at least one computer-readable medium or a non-transitory machine-readable storage medium. The method includes the following operations: detecting a potential overflow at a retransmission buffer of a packet data convergence protocol (PDCP) layer of a user equipment (UE), wherein packet data units (PDU packets) are stored in the retransmission buffer for retransmission in a downlink to one of a primary evolved Node B (MeNB) or a secondary evolved Node B (SeNB), as shown in block 510 . The method may include the following operations: detecting a traffic type associated with the PDU packets, as shown in block 520 . The method may include the following operations: extending a discard timer at the retransmission buffer based in part on the traffic type associated with the PDU packets to avoid premature clearing of the PDU packets from the retransmission buffer, as shown in block 530 .

In one example, the method may include extending a discard timer at the retransmission buffer when the traffic type associated with the PDU packet is delay-tolerant traffic. Additionally, the method may include not extending a discard timer at the retransmission buffer when the traffic type associated with the PDU packet is delay-sensitive traffic.

In one example, the method may include: identifying a service data unit (SDU) packet discarded in a retransmission buffer of a PDCP layer of a UE, wherein the SDU packet is discarded in response to detecting a potential overflow at the retransmission buffer; creating a list of discarded packet data unit (PDU) packets at the PDCP layer of the UE, wherein the discarded PDU packets are associated with the SDU packets; and sending the list of discarded PDU packets from the PDCP layer of the UE to the PDCP layer of the MeNB to enable the MeNB to distinguish between delayed PDU packets and discarded PDU packets. In one configuration, the discarded PDU packets indicate an overflow buffer status to an Internet Protocol (IP) layer to reduce a packet rate to the PDCP layer at the UE.

In one example, the method may include dropping PDU packets due to delay or capacity limitations on at least one of: an X2 link between the MeNB and the SeNB, a radio link between the MeNB and the UE, or a radio link between the SeNB and the UE. Additionally, the method may include dropping PDU packets to indicate a buffer status to an Internet Protocol (IP) layer, wherein the IP layer reduces a packet rate to a PDCP layer at the UE in response to the overflow buffer status. In one aspect, the method may include requesting a modified uplink (UL) separation ratio from the MeNB when a potential overflow occurs at a retransmission buffer of the UE. In one configuration method, the UE includes an antenna, a touch-sensitive display screen, a speaker, a microphone, a graphics processor, an application processor, internal memory, or a non-volatile memory port.

Another example provides functionality 600 of computer circuitry of a primary evolved Node B (MeNB) operable to alleviate traffic congestion, as shown in the flowchart of FIG6 . The functionality may be implemented as a method, or the functionality may be executed as instructions on a machine, where the instructions are embodied on at least one computer-readable medium or a non-transitory machine-readable storage medium. The computer circuitry may be configured to determine that a number of packets stored in a retransmission buffer at the MeNB exceeds a selected threshold level, as shown in block 610. The computer circuitry may be configured to adjust a downlink (DL) separation ratio for packets in the retransmission buffer, where the packets are to be sent to a secondary evolved Node B (SeNB) or directly from the MeNB to a user equipment (UE), as shown in block 620. The computer circuitry may also be configured to separate bearers in the PDCP layer of the MeNB based on the adjusted DL separation ratio, such that the UE and the SeNB receive packets in the retransmission buffer from the MeNB according to the adjusted DL separation ratio.

In one configuration, the retransmission buffer is at a Packet Data Convergence Protocol (PDCP) layer of the MeNB. In one example, the computer circuitry may be further configured to adjust a DL separation ratio for packets in the retransmission buffer in response to a delay or capacity limitation detected on an X2 link between the MeNB and the SeNB.

Figure 7 provides an example diagram of a wireless device (e.g., a user equipment (UE), a mobile station (MS), a mobile wireless device, a mobile communication device, a tablet, a mobile phone, or other types of wireless devices). The wireless device may include one or more antennas configured to communicate with a node, macro node, low power node (LPN), or transmission station (e.g., a base station (BS), an evolved Node B (eNB), a baseband unit (BBU), a remote radio head (RRH), a remote radio equipment (RRE), a relay station (RS), a radio equipment (RE), or other types of wireless wide area network (WWAN) access points). The wireless device may be configured to communicate using at least one wireless communication standard, including 3GPP LTE, WiMAX, High Speed Packet Access (HSPA), Bluetooth, and Wi-Fi. The wireless device may use a separate antenna for each wireless communication standard or a shared antenna for multiple wireless communication standards. The wireless device may communicate in a wireless local area network (WLAN), a wireless personal area network (WPAN), and/or a WWAN.

FIG7 also provides an illustration of a microphone and one or more speakers that can be used for audio input and output from the wireless device. The display screen can be a liquid crystal display (LCD) screen, or other types of display screens (e.g., organic light emitting diode (OLED) displays). The display screen can be configured as a touch screen. The touch screen can use capacitive touch screen technology, resistive touch screen technology, or other types of touch screen technology. An application processor and a graphics processor can be coupled to internal memory to provide processing and display capabilities. A non-volatile memory port can also be used to provide data input/output options to the user. The non-volatile memory port can also be used to expand the memory capacity of the wireless device. A keyboard can be integrated with the wireless device, or a keyboard can be wirelessly connected to the wireless device to provide additional user input. A touch screen can also be used to provide a virtual keyboard.

Various technologies or some aspects or parts thereof can be in the form of program codes (i.e., instructions) embedded in tangible media (e.g., floppy disks, CD-ROMs, hard drives, non-transient computer-readable storage media, or any other machine-readable storage media), wherein when the program code is loaded into a machine (e.g., a computer) and is run by the machine, the machine becomes a device for implementing various technologies. Circuits can include hardware, firmware, program codes, executable code, computer instructions, and/or software. Non-transient computer-readable storage media can be computer-readable storage media that does not include signals. In the case where the program code runs on a programmable computer, a computing device can include a processor, a storage medium readable by the processor (including volatile and non-volatile memory and/or storage element), at least one input device, and at least one output device. Volatile and non-volatile memory and/or storage element can be RAM, EPROM, flash drive, optical drive, magnetic hard drive, or other media for storing electronic data. Nodes and mobile devices can also include a transceiver module, a timer module, a processing module, and/or a clock module or a timer module. One or more programs that can implement or utilize the various technologies described herein can use application programming interfaces (APIs), reusable controls, etc. Such programs can be implemented in high-level procedural or object-oriented programming languages to communicate with a computer system. However, the program(s) can be implemented in component or machine language as needed. In any case, the language can be a compiled language or an interpreted language and combined with a hardware implementation.

It should be understood that many of the functional units described in this specification are labeled as modules to emphasize the independence of their implementation. For example, a module can be implemented as a hardware circuit comprising conventional VLSI circuits or gate arrays, off-the-shelf semiconductors (e.g., logic chips, transistors, or other discrete components). A module can also be implemented in a programmable hardware device (e.g., a field programmable gate array, programmable array logic, a programmable logic device, etc.).

Module can also be implemented in the software that is run by various types of processors.The module of the executable code of being identified can for example comprise one or more physical blocks or logical blocks of computer instructions, and it can for example be organized as object, program, or function.Yet the executable property of being identified module does not need to be physically located together, but can comprise the different instructions that are stored in different locations, and when these different instructions that are stored in different locations are logically combined together, it comprises this module and realizes the purpose that this module is stated.

In fact, the module of executable code can be a single instruction or many instructions, and can even be distributed on several different code segments across several storage devices and between different programs.Similarly, operational data can be identified and illustrated in this article in module, and can be embedded in and organized into the data structure of any appropriate type in any suitable form.Operational data can be collected as a single data set, or can be distributed in different locations (comprising on different storage devices), and can only exist as the electronic signal on system or network at least in part.Module can be active or passive, comprises the agent that can be operated to perform desired function.

References throughout this specification to an "example" are intended to refer to a particular feature, structure, or characteristic described in connection with the example as included in at least one embodiment of the present invention. Thus, the appearances of the phrase "in an example" in various places throughout this specification are not necessarily all referring to the same embodiment.

As used herein, for convenience, multiple items, structural elements, constituent elements, and/or materials can be presented in a general list. However, these lists should be understood as if each member in the list is independently identified as a separate and unique member. Therefore, based on its presentation in a general group without the need for contrary instructions, the independent members in such a list should not be interpreted as the de facto equivalence of any other member of the same list. In addition, various embodiments and examples of the present invention can be referred to together with the replacement of its various components herein. It should be understood that such embodiments, examples and replacements are not interpreted as de facto equivalence to each other, but are considered to be independent and autonomous representations of the present invention.

Moreover, described features, structures, or characteristics can be combined in any appropriate manner in one or more embodiments. In the following description, a large amount of specific details (such as, the example of layout, distance, network example, etc.) are provided to provide a thorough understanding of embodiments of the present invention. However, those skilled in the art will recognize that the present invention can be implemented without the need for one or more of these specific details, or other methods, components, layouts, etc. are utilized to implement the present invention. In other examples, in order to avoid blurring various aspects of the present invention, well-known structures, materials, or operations are not shown or described in detail.

Although the foregoing examples are illustrative of the principles of the present invention in one or more specific applications, it will be apparent to those skilled in the art that numerous modifications in form, use, and details of implementation may be made without departing from the concepts and principles of the present invention and without requiring practice of the inventor. Therefore, it is not intended that the present invention be limited except as set forth in the appended claims.

Claims (18)

1. A major evolved Node B (MeNB) for mitigating traffic congestion, having computer circuitry configured to: Identify Service Data Unit (SDU) packets that have been dropped in the retransmission buffer of the Packet Data Convergence Protocol (PDCP) layer of the MeNB; A list of discarded Packet Data Unit (PDU) packets is created at the PDCP layer of the MeNB, wherein the discarded PDU packets are associated with SDU packets; and The list of dropped PDU packets is sent from the MeNB's PDCP layer to the UE's PDCP layer, enabling the UE to distinguish between delayed and dropped PDU packets. Specifically, the PDU packets are discarded to indicate an overflow buffer state to the Internet Protocol (IP) layer, and the IP layer reduces the packet rate of the PDCP layer at the MeNB in response to the overflow buffer state. 2. The MeNB of claim 1, wherein the PDU packet is dropped in response to a potential overflow detected in the retransmission buffer of the MeNB. 3. The MeNB of claim 2, wherein the potential overflow is due to latency or capacity limitations on at least one of the following: the X2 link between the MeNB and the secondary evolved Node B (SeNB), the radio link between the MeNB and the UE, or the radio link between the SeNB and the UE. 4. The MeNB of claim 2, wherein the computer circuitry is further configured to: when the potential overflow occurs at the retransmission buffer, recalculate the downlink DL separation ratio, the DL separation ratio defining a first percentage of PDU packets to be transmitted to the UE via the secondary evolved Node B, i.e., the SeNB, and a second percentage of PDU packets to be transmitted directly to the UE. 5. The MeNB as claimed in claim 1, wherein the computer circuitry is further configured to: Detect potential overflows in the retransmission buffer of the MeNB, where SDU packets are stored in the retransmission buffer for retransmission to the UE or one of the Secondary Evolved Node B (SeNB) in the downlink; Detect the traffic type associated with the SDU packet; and The drop timer at the retransmission buffer is extended in part based on the traffic type associated with the SDU packet in order to avoid premature clearing of the SDU packet at the retransmission buffer. 6. The MeNB of claim 5, wherein the computer circuitry is further configured to extend the drop timer at the retransmission buffer when the traffic type associated with the SDU packet is delay-tolerant traffic. 7. The MeNB of claim 5, wherein the computer circuitry is further configured to: not extend the drop timer at the retransmission buffer when the traffic type associated with the SDU packet is delay-sensitive traffic. 8. The MeNB of claim 5, wherein extending the drop timer at the retransmission buffer includes increasing the length of the packet data aggregation protocol sequence number to include a plurality of least significant bits. 9. The MeNB of claim 1, wherein the computer circuitry is further configured to communicate with the secondary evolved Node B, i.e., the SeNB, via an X2 link in a dual-connectivity architecture. 10. A method for alleviating traffic congestion, the method comprising: Identify Service Data Unit (SDU) packets that have been dropped in the retransmission buffer of the Packet Data Convergence Protocol (PDCP) layer of the primary evolved Node B (MeNB). A list of discarded Packet Data Unit (PDU) packets is created at the PDCP layer of the MeNB, wherein the discarded PDU packets are associated with SDU packets; and The list of dropped PDU packets is sent from the MeNB's PDCP layer to the UE's PDCP layer, enabling the UE to distinguish between delayed and dropped PDU packets. Specifically, the PDU packets are discarded to indicate an overflow buffer state to the Internet Protocol (IP) layer, and the IP layer reduces the packet rate of the PDCP layer at the MeNB in response to the overflow buffer state. 11. The method of claim 10, wherein the PDU packet is dropped in response to a potential overflow detected at the retransmission buffer of the MeNB. 12. The method of claim 11, wherein the potential overflow is due to latency or capacity limitations on at least one of the following: the X2 link between the MeNB and the secondary evolved Node B (SeNB), the radio link between the MeNB and the UE, or the radio link between the SeNB and the UE. 13. The method of claim 11, further comprising: When the potential overflow occurs at the retransmission buffer, the downlink DL separation ratio is recalculated. The DL separation ratio defines a first percentage of PDU packets that will be sent to the UE via the Secondary Evolved Node B (SeNB) and a second percentage of PDU packets that will be sent directly to the UE. 14. The method of claim 10, further comprising: Detect potential overflows in the retransmission buffer of the MeNB, where SDU packets are stored in the retransmission buffer for retransmission to the UE or one of the Secondary Evolved Node B (SeNB) in the downlink; Detect the traffic type associated with the SDU packet; and The drop timer at the retransmission buffer is extended in part based on the traffic type associated with the SDU packet in order to avoid premature clearing of the SDU packet at the retransmission buffer. 15. The method of claim 14, further comprising: extending the drop timer at the retransmission buffer when the traffic type associated with the SDU packet is delay-tolerant traffic. 16. The method of claim 14, further comprising: not extending the drop timer at the retransmission buffer when the traffic type associated with the SDU packet is delay-sensitive traffic. 17. The method of claim 14, wherein extending the drop timer at the retransmission buffer includes increasing the length of the packet data convergence protocol sequence number to include a plurality of least significant bits. 18. The method of claim 10, wherein the MeNB is configured to communicate with the secondary evolved Node B, i.e., the SeNB, via an X2 link in a dual-connectivity architecture.