Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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.
To facilitate understanding of the method provided in the embodiment of the present invention, a resource allocation method for downlink data transmission in the prior art is first described.
First, the concepts of cqi (channel Quality indicator), MCS (Modulation and Coding Scheme), and TBS (Transmit Block Size) are introduced.
The LTE physical shared channel (PDSCH) supports three coding schemes: QPSK, 16QAM, and 64QAM, different coding schemes require different channel conditions, and the higher the coding scheme (QPSK <16QAM <64QAM), the better the dependent channel conditions. Since downlink scheduling is performed by the eNodeB, and the eNodeB does not know how the downlink channel condition is, the UE needs to report the channel condition, that is, report the CQI. The CQI is mainly used to make order selection, i.e. to map the MCS according to the CQI (essentially to determine the IMCS, i.e. the index of the MCS). Specifically, the 4-bit reported CQI is converted into a 5-bit format with a sequence number of 0 to 31, wherein 29 to 31 are reserved, and the converted result is the IMCS. This process of converting from 5 bits to 4 bits involves some specific conversion algorithms, which are prior art and will not be described herein. After the IMCS is determined. The ITBS (index of TBS) may then be determined from the mapping of IMCS to ITBS in table 1. The corresponding TBSize of different ITBSs is different. For example, if the IMCS is 28 and the ITBS is 26 according to the CQI, then one PRB maximum TB Size is 712 bits; if the IMCS is determined to be 22 and the ITBS is determined to be 20 according to the CQI, one PRB maximum TB Size is 452 bits. That is, the order of the MCS, TBS and TB Size are all uniquely corresponding.
TABLE 1MCS to TBS mapping relationship
As can be seen from the above description, the ITBS is different, and the maximum TBSize of one PRB is also different, that is, the TBS determines the air interface capacity. Referring to fig. 1, if it is to be ensured that an RTP voice packet is completely transmitted in one scheduling, the information capacity that can be carried by the PRB resources allocated to this scheduling must be greater than or equal to the information size of a user RTP packet (that is, a downlink voice data packet to be transmitted), but the minimum unit for scheduling air interface resources for a user by LTE is RB, that is, the number of PRB resources allocated to the user must be an integer multiple of RB, and the packet size of the user RTP packet has a certain randomness, so that the possibility that all PRBs are just filled with information carried by the RTP packet is small, and therefore, a certain padding is required to be filled. Padding is done to ensure that transport block sizes are consistent, and padding is actually redundant information for the user.
As is clear from the above description, the order of the MCS determines the code modulation scheme, and thus the interference rejection of the signal. In a high-speed scenario, a problem of voice quality degradation of VoLTE caused by rapid fluctuation of a user terminal signal exists, and therefore, in order to enhance the capability of the terminal against rapid signal fluctuation in the high-speed scenario, it is desirable that, when the terminal performs VoLTE service, the terminal performs data coding of an air interface with a lower MCS order relative to that of data service. However, the terminal unlimitedly reduces the MCS order to perform air interface data modulation, which may cause the maximum TB Size of one PRB to be correspondingly reduced, and further cause the air interface capacity to be reduced, and cannot carry voice data packets. Therefore, in a scenario of a high-speed railway with a large number of simultaneous online users, the unlimited reduction of MCS will affect the overall performance of the network.
Based on this, in a first aspect, an embodiment of the present invention provides a method for improving voice quality of TD-LTE VoLTE, which is applied to a network device, as shown in fig. 2, and includes:
s101, acquiring a Channel Quality Indicator (CQI) reported by a user;
s102, determining a modulation and coding strategy MCS and a transport block size TBS required by sending downlink data according to the CQI; determining the number of Resource Blocks (RBs) allocated to downlink according to the size of a VoLTE voice packet to be sent in downlink, MCS and TBS;
s103, judging whether a target TBS meeting preset conditions exists or not, wherein the preset conditions are as follows: under the condition that the number of RBs is kept unchanged, the VoLTE voice packet to be sent can be borne, and the order of the MCS is reduced; if yes, re-determining the MCS according to the target TBS;
and S104, transmitting the VoLTE voice packet according to the target TBS and the re-determined MCS.
In the method provided by the embodiment of the present invention, after primarily determining an MCS and a TBS according to a CQI, a network side device (e.g., a base station) can perform secondary order selection on the MCS, and can select the TBS that can carry a VoLTE voice packet to be sent and can reduce the order of the MCS under the condition of keeping the number of RBs unchanged (i.e., ensuring that the capacity of an air interface is unchanged), so that the purpose of reducing the order of the MCS is achieved while ensuring that data can be normally received and sent, the signal interference resistance of the data packet is improved, and the VoLTE voice quality is improved.
The high-speed scene here refers to a scene in which the user is moving at a high speed, for example, the user is in a running high-speed rail or a car. The manner in which step S102 determines MCS and TBS according to CQI is described in detail in the foregoing, and is not described herein again.
In addition, the preset condition that the target TBS satisfies in step S103 here may further be: and under the condition that the number of RBs is kept unchanged, the VoLTE voice packet to be sent can be carried, and the order of the MCS is reduced to be as low as possible. Therefore, the anti-interference capability of signals can be improved as much as possible on the premise of ensuring normal conversation, and the VOLTE voice quality is improved.
The method provided by the embodiment of the present invention is exemplified by taking an example that a 872-bits high-definition voice packet needs to be sent in the downlink, and a CQI mapping ITBS reported by a user is 26 and an IMCS is 28 for transmission.
According to the method provided by the embodiment of the invention, after the method is applied, the secondary selection of the MCS can be performed according to the situation, the number of allocated PRBs is kept unchanged, and the MCS is reduced as much as possible. Table 1 lookup may be used to obtain that when the ITBS is 20, the TBS corresponding to 2 PRBs is 904, which is enough to carry 872bits of higher layer data, and only padding of 32bits is needed, so that TBS is 20, which is the target TBS, and the corresponding IMCS is 22. Compared with the prior IMCS (international mobile communication system) ═ 28, the MCS reduction is realized, and the VOLTE voice quality is improved.
After applying the optimization method in a high-speed rail scene, observing the empty packet loss rate of the VOLTE service, wherein: the downlink packet loss rate of the VOLTE voice service is reduced from 0.172% to 0.082%, and the amplitude is reduced by 52.33%; the uplink packet loss rate of the VOLTE voice service is reduced from 0.49% to 0.40%, and the amplitude is reduced by 20%; the voice quality improvement effect on VOLTE is obvious.
In addition, it is understood that the method provided by the embodiment of the present invention may further include:
and S105, if the target TBS does not exist, transmitting the VoLTE voice packet according to the current MCS and TBS.
That is, if the MCS level cannot be reduced any more, and the speech packet cannot be carried any more, the speech packet is also transmitted at the originally determined MCS and TBS.
For high speed motion scenes, there are other factors that affect voice communication in addition to the problems described above. For example, in a high-speed rail scene, the penetration loss of a bullet train body is large, and along with the incident angle of a signal and the immobility of the riding position of a user, the difference of the received signal strength of the users at different positions in the same carriage is large, so that the coverage of part of the users is weak, and the problem is more obvious particularly when the users pass through scenes such as a tunnel. When a user performs VOLTE voice service at a position with weak coverage, the problem that an RTP packet cannot be correctly received by an opposite terminal occurs due to poor quality of a wireless link, and the RTP packet needs to be retransmitted at the moment.
For downlink, after i TTIs from the initial transmission, the UE feeds back ACK/NACK, and retransmits at least k TTIs after receiving NACK feedback (k > 4 in TDD system). The interval between the initial transmission and the retransmission is different under different subframe ratios, and under the condition that the current uplink and downlink subframe ratio is SA2, the interval between the initial transmission and the retransmission is between 8 subframes and 12 subframes, and between 8ms and 12 ms. For uplink, the position and MCS of the RB resource for retransmission are completely consistent with those of initial transmission, that is, the reselection data is sent at the same time after 10 subframes, and the initial transmission and reselection delay is 10 ms.
As can be seen from the above description, after an RTP packet is not correctly received by an opposite end, a time interval between retransmission data and initial transmission data is within 16ms, the current operating speed of the high-speed rail is about 300KM, and within 16ms, a high-speed rail user only moves 1.3 meters, that is, within a short time of 16ms, the position of the high-speed rail user is almost unchanged, so at the time of retransmission, the quality of a wireless link of the user is almost the same as that of the wireless link at the time of initial transmission, and the opposite end cannot correctly receive the packet at the time of initial transmission, if the same quality of the wireless link is still adopted for modulation at the same MCS order as that of the initial transmission at the time of retransmission, the probability that the retransmission packet is correctly received by the opposite end is small.
Based on this, the method provided by the embodiment of the present invention may further include:
s106, when the VoLTE voice packet is not correctly received by the user terminal and is retransmitted, reducing the order of the VoLTE voice packet on the basis of the current MCS, and determining the TBS corresponding to the MCS after the order reduction and the RB number required by transmitting the VoLTE voice packet;
and S107, retransmitting the VoLTE voice packet according to the newly determined RB number, MCS and TBS.
Specifically, the conventional LTE general retransmission scheduling procedure is as follows:
1. the eNodeB sends initial transmission data to the UE on the PDSCH;
2. the eNodeB waits for ACK fed back by the UE after the UE correctly receives the data;
3. and if the eNodeB successfully receives the ACK, the eNodeB transmits the subsequent data, and if the ACK is not received or the NACK is received, the eNodeB retransmits the data by using the MCS order and the RB resource number which are the same as those of the initial transmission.
After the optimization method provided by the embodiment of the present invention is used, when the VOLTE data packet is retransmitted, the MCS selection order is reduced, and the RB number is increased for retransmission, and a specific process may be as shown in fig. 3, including:
1. the ENODEB sends initial transmission data to the UE on the PDSCH;
2. the ENODEB waits for ACK fed back by the UE after the UE correctly receives the data;
3. if the ENODEB successfully receives the ACK, the transmission of subsequent data is carried out; if no ACK or NACK is received, the MCS order is reduced (for example, one order can be reduced) on the basis of the original MCS, the number of RBs required after the reduction is calculated, and the data is retransmitted.
That is to say, when the VOLTE service is retransmitted because the data packet is not correctly received by the peer end, the RB resource is added to the user, and the MCS order of the user is reduced at the same time to perform retransmission, so that the probability that the retransmitted packet is correctly received by the peer end can be greatly improved after the MCS order is reduced to perform retransmission under the same radio link quality.
In addition, the method provided by the embodiment of the present invention may also improve the VoLTE voice quality in a high speed scene from other angles, and specifically may include:
and S108, when the current service type is determined to be VoLTE service, the RANK1 mode is fixedly used for downlink data transmission.
Specifically, there are 7 downlink transmission modes of LTE, i.e., TM1 to TM4 and TM6 to TM8, and MIMO schemes in the transmission modes include single antenna transmission, transmit diversity, space division multiplexing, and Beamforming. The various transmission modes are detailed in table 1.
TABLE 1LTE Downlink Transmission modes
The transmission mode of the base station can be configured into two schemes:
(1) transmission mode adaptation. In this configuration, the terminal can switch between transmission modes, such as between TM3 and TM8, according to a change in wireless environment.
(2) The transmission mode is fixed. The base station is configured to fix a transmission mode, and the terminal can only use the transmission mode to perform air interface data transmission.
The two MIMO schemes, namely closed-loop spatial multiplexing and Beamforming, may lose the performance of the network, and therefore, for a high-speed scenario, only two MIMO schemes, namely open-loop spatial multiplexing and transmit diversity, may be used, corresponding to the transmission mode TM3, and therefore, the transmission mode of the current high-speed network is configured as the fixed TM3 mode, that is, the above-mentioned mode (2) is adopted.
Fixed TM3 mode, there may be two MIMO schemes RANK1 (transmit diversity) and RANK2 (open loop spatial multiplexing). RANK1 has better air interface demodulation performance, but the air interface efficiency is lower; the RANK2 air interface has higher efficiency, but the demodulation performance of the air interface is poorer, and the packet loss rate of the air interface is higher than that of the RANK 1. When the base station configures a fixed TM3 mode, the terminal may adaptively use a RANK1 or RANK2 mode according to a difference in wireless environment.
As shown in fig. 4, for LTE data services in the prior art, the higher the downlink rate, the better the user perception. Because the air interface efficiency is high in RANK2 mode, it is desirable to use RANK2 for data transmission as much as possible (e.g., the midpoint user in fig. 4), and to use RANK1 for data transmission only when the radio link is severely degraded (e.g., the far-end user in fig. 4).
However, in the process of the invention creation, the inventor finds that, for VOLTE voice service, the requirement on the downlink rate is low, and the requirement on voice quality perception is high, and for the mid-point user in fig. 4, if the RANK2 mode is used, the air interface packet loss rate is high, and voice quality is perceived to be affected.
Therefore, the method provided in the embodiment of the present invention considers the requirement of high quality requirement of the air interface of the VOLTE service, and as shown in fig. 5, after identifying that the user performs the VOLTE service, the VOLTE service is transmitted by using the RANK1 mode, so that the packet loss rate can be effectively reduced. And for data service, the original scheme is still adopted and self-adaptive adjustment is carried out according to the wireless environment. Therefore, the VOLTE voice service can be adjusted in a targeted manner, and the VOLTE voice quality is improved.
In a second aspect, an embodiment of the present invention provides another apparatus for improving voice quality of TD-LTE VoLTE, which is applied to a network device side, and as shown in fig. 6, the apparatus includes:
a receiving unit 601, configured to obtain a channel quality indicator CQI reported by a user;
a resource allocation unit 602, configured to determine, according to the CQI, a modulation and coding strategy MCS and a transport block size TBS required for sending downlink data; determining the number of Resource Blocks (RBs) allocated to downlink according to the size of a VoLTE voice packet to be sent in downlink, MCS and TBS;
a secondary rank selection unit 603, configured to determine whether there is a target TBS that meets preset conditions, where the preset conditions are: under the condition that the number of RBs is kept unchanged, the VoLTE voice packet to be sent can be borne, and the order of the MCS is reduced; if yes, re-determining the MCS according to the target TBS;
a sending unit 604, configured to send a VoLTE voice packet according to the target TBS and the re-determined MCS.
In some embodiments, the sending unit 604 is further configured to:
and if the target TBS does not exist, transmitting the VoLTE voice packet according to the current MCS and the TBS.
In some embodiments, the secondary order selecting unit 603 is further configured to, when the VoLTE voice packet is not correctly received by the user terminal and is retransmitted, reduce the order of the VoLTE voice packet based on the current MCS, and determine the TBS corresponding to the reduced MCS and the number of RBs required for transmitting the VoLTE voice packet;
and the sending unit is further configured to retransmit the VoLTE voice packet according to the re-determined RB number, MCS, and TBS.
In some embodiments, the apparatus further comprises:
a mode selecting unit 605, configured to perform downlink data transmission by using the RANK1 mode when the current service type is determined to be the VoLTE service.
Since the voice quality improving apparatus for TD-LTE introduced in the second aspect is an apparatus capable of executing the voice quality improving method for TD-LTE in the embodiment of the present invention, based on the voice quality improving method for TD-LTE introduced in the embodiment of the present invention, a person skilled in the art can understand a specific implementation manner and various variations of the voice quality improving apparatus for TD-LTE in the embodiment, and therefore, how the voice quality improving apparatus for TD-LTE realizes the voice quality improving method for TD-LTE in the embodiment of the present invention is not described in detail herein. As long as those skilled in the art implement the apparatus used in the method for improving the VoLTE voice quality of TD-LTE in the embodiment of the present invention, the apparatus is within the scope of the present application.
Fig. 7 shows a block diagram of a network device according to an embodiment of the present invention.
Referring to fig. 7, the network side device includes: a processor (processor)701, a memory (memory)702, and a bus 703;
the processor 701 and the memory 702 complete communication with each other through the bus 703.
The processor 701 is configured to call the program instructions in the memory 702 to execute the method provided in the first embodiment.
Embodiments of the present invention also disclose a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium, where the computer program includes program instructions, and when the program instructions are executed by a computer, the computer is capable of executing the method provided in the foregoing first aspect embodiment.
Embodiments of the present invention further provide a non-transitory computer-readable storage medium, which stores computer instructions, where the computer instructions cause the computer to perform the method provided in the foregoing first aspect.
In the description provided herein, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
Similarly, it should be appreciated that in the foregoing description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. However, the disclosed method should not be interpreted as reflecting an intention that: that the invention as claimed requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.
Those skilled in the art will appreciate that the modules in the device in an embodiment may be adaptively changed and disposed in one or more devices different from the embodiment. The modules or units or components of the embodiments may be combined into one module or unit or component, and furthermore they may be divided into a plurality of sub-modules or sub-units or sub-components. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and all of the processes or elements of any method or apparatus so disclosed, may be combined in any combination, except combinations where at least some of such features and/or processes or elements are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.
Furthermore, those skilled in the art will appreciate that while some embodiments herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the following claims, any of the claimed embodiments may be used in any combination.
Some component embodiments of the invention may be implemented in hardware, or in software modules running on one or more processors, or in a combination thereof. Those skilled in the art will appreciate that a microprocessor or Digital Signal Processor (DSP) may be used in practice to implement some or all of the functionality of some or all of the components of a gateway, proxy server, system according to embodiments of the present invention. The present invention may also be embodied as apparatus or device programs (e.g., computer programs and computer program products) for performing a portion or all of the methods described herein. Such programs implementing the present invention may be stored on computer-readable media or may be in the form of one or more signals. Such a signal may be downloaded from an internet website or provided on a carrier signal or in any other form.
It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The usage of the words first, second and third, etcetera do not indicate any ordering. These words may be interpreted as names.