Method for triggering RLC layer retransmissionTechnical Field
The present invention relates to.
Background
With the development of wireless mobile communication technology, people put higher and higher demands on high speed, low delay and low cost. The lte (long Term evolution) project has been generated in such a context, pursuing higher peak rates and shorter transmission delays.
The main performance goals of the LTE project include: the peak rate of 100Mbps downlink and 50Mbps uplink can be provided in the 20MHz frequency spectrum bandwidth, the performance of cell edge users is improved, and the cell capacity is improved; the system delay is reduced, the one-way transmission delay inside the user plane is lower than 5ms, the transition time of the control plane from the sleep state to the active state is lower than 50ms, and the transition time from the residence state to the active state is less than 100 ms; cell coverage of 100Km radius is supported; the method can provide access service of more than 100kbps for 350Km/h high-speed mobile users; supporting paired or unpaired spectrum; supporting variable bandwidth, up to 20M bandwidth.
The LTE adopts a single-layer flat full IP network structure of an access network formed by NodeB on the network architecture, and the structure is favorable for simplifying the network and reducing the delay, thereby realizing the requirements of low time delay, low complexity and low cost. LTE reduces RNC nodes compared to traditional 3GPP access networks. The eNB not only has the functions of the original NodeB, but also can complete most of the functions of the original RNC, including a physical layer, an MAC layer, an RRC, scheduling, access control, bearer control, access mobility management, and the like. Node bs and Node bs are directly interconnected by using a Mesh (Mesh) method, which is also a significant modification of the original UTRAN structure. Approaching the typical IP broadband network architecture.
In physical layer technology, LTE adopts advanced radio transmission technologies such as ofdm (orthogonal Frequency division multiplexing), mimo (Multiple Input Multiple output), and channel-based link adaptive scheduling and interference coordination technologies. Further improving the speed of the user and the throughput of the cell, and improving the performance of the edge of the cell.
With the development of wireless communication technology and the further desire for low latency and high rate, new technologies are introduced in LTE-a phase, such as carrier aggregation ca (carrier aggregation), Relay technology, coordinated multipoint (comp), and Enhanced Inter-cell interference (eICIC) wireless technologies.
The 5GHz spectrum is an unlicensed spectrum, and an LAA (License Assisted Access) technology is proposed in order to make the potential of the unused 5GHz band to be utilized, so that an operator can obtain more capacity from the unlicensed band. I.e. carrier aggregation between unlicensed and unlicensed spectrum, and the Pcell is located in the licensed spectrum. But LAA should satisfy fair coexistence with WIFI systems and other operator LAA cells during use. The unlicensed spectrum usage employs lbt (listen before talk) mechanism and is transmitted non-continuously for a defined time.
In an LAA cell, due to the introduction of an LBT mechanism and discontinuous transmission within a limited time, an eNB cannot guarantee that resources can be always used for transmission during data transmission, and for a HARQ (hybrid automatic Repeat request) process, a current standard specifies that retransmission and initial transmission are completed in the same HARQ. Therefore, for HARQ retransmission, resources may not be available for retransmission for a long time, which causes a problem in rlc (radio Link control).
For AM (Acknowledged mode) mode: the manner of triggering RLC layer retransmission, e.g., HARQ layer up to maximum retransmission times, or receiving RLC layer NACK feedback. For the receiving side, a reordering timer is provided, if the reordering timer is overtime, NACK is considered, and the NACK is fed back to the sending end.
For um (uucknowleded mode) mode: RLC retransmission is not triggered, but a receiving end has a reordering timer, and the receiving end does not wait for retransmission after the reordering timer is passed. Even if the air interface retransmits, the data is discarded as useless data, and air interface resources are wasted. So for UM mode there may be only one initial transmission without HARQ retransmission opportunities.
Disclosure of Invention
In view of the above problems, the present invention provides a method for triggering RLC layer retransmission, including: and in the HARQ transmission process, the sending end informs the RLC layer to retransmit the data if a preset condition is met.
Preferably, the predetermined condition is: the HARQ initial transmission is in error, no HARQ retransmission is successful within the predetermined time T1, and/or the number of HARQ retransmissions reaches a predetermined threshold.
Further, the predetermined time T1 is less than the receiving-end reordering timer duration.
Preferably, the method further comprises the following steps: and if the HARQ primary transmission receiving end feeds back NACK, immediately informing the RLC layer to retransmit the data.
Preferably, the method further comprises the following steps: after the sending end RLC layer stores the sent data in the memory for a preset time T2, the stored data is deleted no matter whether RLC transmission is successful or not.
Preferably, the transmitting end is an LAA cell; the transmitting end RLC is in the UM mode.
The invention ensures that the UM mode RLC data can be transferred to the RLC layer for retransmission when no HARQ retransmission chance exists or the HARQ retransmission chance is very little. Therefore, the transmission success probability of the data packet sent by the LAA cell under the UM mode is improved, and the user experience is improved.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments; it should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a method for triggering RLC layer retransmission, which comprises the following steps: and in the HARQ transmission process, the sending end informs the RLC layer to retransmit the data if a preset condition is met.
Preferably, the predetermined condition is: the HARQ initial transmission is in error, no HARQ retransmission is successful within the predetermined time T1, and/or the number of HARQ retransmissions reaches a predetermined threshold.
Further, the predetermined time T1 is less than the receiving-end reordering timer duration.
Preferably, the method further comprises the following steps: and if the HARQ primary transmission receiving end feeds back NACK, immediately informing the RLC layer to retransmit the data.
Preferably, the method further comprises the following steps: after the sending end RLC layer stores the sent data in the memory for a preset time T2, the stored data is deleted no matter whether RLC transmission is successful or not.
Preferably, the transmitting end is an LAA cell; the transmitting end RLC is in the UM mode.
The invention ensures that the UM mode RLC data can be transferred to the RLC layer for retransmission when no HARQ retransmission chance exists or the HARQ retransmission chance is very little. Therefore, the transmission success probability of the data packet sent by the LAA cell under the UM mode is improved, and the user experience is improved.
Example (b): taking the LAA cell as an example, the RLC is in UM mode.
Step 1: for UM mode RLC, a timer T2 is started when one RLC PDU is sent to the bottom layer. And stores the data in memory.
Step 2: if the timer exceeds T2, the RLC PDUs in memory are deleted.
Step 3 a: after receiving the RLC PDU, the MAC layer of the LAA cell performs HARQ transmission, starts a timer T1, counts the number of times the packet is transmitted by HARQ, or both.
If T1 times out or the number of HARQ transmissions reaches a threshold N, the RLC layer is notified to retransmit the RLC pdu.
Or,
and step 3 b: and after receiving the RLC PDU, the MAC layer of the LAA cell performs HARQ initial transmission, and if the HARQ initial transmission feeds back NACK, the MAC layer is immediately informed to retransmit the RLC PDU.
Those of ordinary skill in the art will understand that: all or part of the steps for implementing the method embodiments may be implemented by hardware related to program instructions, and the program may be stored in a computer readable storage medium, and when executed, the program performs the steps including the method embodiments; and the aforementioned storage medium includes: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.