CN115361091A - Downlink mixed broadcast unicast transmission method based on multi-user superposition transmission technology - Google Patents
Downlink mixed broadcast unicast transmission method based on multi-user superposition transmission technology Download PDFInfo
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- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
- H04L1/0009—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the channel coding
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
- H04L1/0002—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate
- H04L1/0003—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate by switching between different modulation schemes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
- H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
- H04L1/0026—Transmission of channel quality indication
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- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/06—Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
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Abstract
The invention discloses a downlink mixed broadcast unicast transmission method based on a multi-user superposition transmission technology, which comprises the following steps: a base station acquires channel state information of a broadcast service from a cell edge user and determines a broadcast service coding modulation scheme according to the channel state information; a base station selects a hot spot service area in a cell, and selects a unicast service with proper channel conditions from the hot spot service area to be transmitted in a superposition manner with the broadcast service; and the base station carries out non-orthogonal multiplexing on the unicast service and the broadcast service to obtain a composite service, determines a code modulation scheme of the composite service according to the channel quality information fed back by the unicast service user, and replaces the code modulation scheme of the broadcast service with the code modulation scheme of the composite service. The invention can provide additional unicast service for the system on the premise of not influencing the coverage performance of the broadcast service, and improve the overall transmission efficiency of the unicast service.
Description
Technical Field
The invention relates to the technical field of digital information transmission, in particular to a downlink hybrid broadcast unicast transmission method based on a multi-user superposition transmission technology.
Background
Cellular communication networks face an explosive growth in traffic demand, and multimedia services such as high definition video are particularly significant. Since video services often have the characteristic of high contact ratio among wide-area users, that is, a small amount of hot content is requested by a large number of users at the same time, the conventional unicast transmission method inevitably faces the problems of insufficient bandwidth and network congestion, and pushing the content in a broadcast manner can effectively alleviate the problem. For this reason, in Rel-17 release of 5G, 3GPP has performed a research on a 5G NR (global 5G standard based on a brand new air interface design of OFDM) multimedia broadcast multicast service (MBS) system based on a Single Cell Point To multipoint (SC-PTM) technology, in order To realize coverage of a broadcast service To a handheld terminal. It still faces problems such as the inability to efficiently support wide area tower broadcasts; in order to ensure deep coverage of a cell, the frequency spectrum efficiency of the mobile phone broadcasting service is low; in the physical layer transmission technology, deep interleaving is lacked, and coded modulation is not optimized for a multi-service broadcast channel.
The spectrum is an important strategic resource, and in order to fully utilize the 700M gold band, it is necessary to improve the spectrum efficiency of the 5G MBS system. Compared with the orthogonal multiplexing technology, the non-orthogonal multiplexing technology can obviously improve the spectrum efficiency of the system under the asymmetric service scene, and the broadcast service and unicast service multiplexing is obviously an asymmetric service scene. Hybrid broadcast unicast transmission based on non-orthogonal multiplexing has recently received a lot of attention.
In LTE-related proposals, non-orthogonal multiplexing transmission of downlink based on superposition coding has been widely studied and is referred to as a multi-user superposition transmission (MUST) technique. The MUST (Multiuser superposition transmission) technology is divided into three types, wherein the first type is that constellation symbols of QAM (quadrature amplitude modulation) at a sending end are directly superposed; the second type is a non-linear superposition with Gray mapped composite constellations; the third category is flexible bit segmentation based on Gray mapped QAM complex constellations.
The existing hybrid broadcast unicast transmission scheme based on non-orthogonal multiplexing adopts a method of directly superimposing at the transmitting end and performing SIC (Successive interference cancellation) at the receiving end. However, SIC brings a great computational burden and processing delay to unicast users, and when time-frequency long interleaving is adopted for broadcast services, the delay caused by SIC is more significant. And when a plurality of orthogonally multiplexed unicast services and broadcast services are orthogonally multiplexed, each unicast user faces the problem and does not meet the requirement of 5G on low delay. When the receiving end adopts independent de-mapping and single-stage decoding (namely, SIC is not carried out), direct superposition is compared with nonlinear superposition, and the nonlinear superposition based on the Gray mapping composite constellation is more suitable for a low-complexity and low-delay receiving scheme without SIC because the composite constellation is not Gray mapping and can cause larger BICM capacity loss. Meanwhile, the existing solution does not consider the support of unicast service Adaptive Modulation and Coding (AMC), and when the unicast service is adaptive, how to ensure that the coverage of the broadcast service is not affected is also a problem to be considered.
Thus, there is a need for improvements and enhancements in the art.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a method for transmitting a downlink hybrid broadcast unicast based on a multi-user superposition transmission technique, aiming at the above-mentioned defects in the prior art.
In a first aspect, the present invention provides a method for transmitting a downlink hybrid broadcast unicast based on a multi-user superposition transmission technology, where the method includes:
a base station acquires channel state information of a broadcast service from a cell edge user and determines a broadcast service coding modulation scheme according to the channel state information;
a base station selects a hot spot service area in a cell, and selects a unicast service with proper channel conditions from the hot spot service area to be transmitted in a superposition manner with the broadcast service;
and the base station carries out non-orthogonal multiplexing on the unicast service and the broadcast service to obtain a composite service, determines a code modulation scheme of the composite service according to the channel quality information fed back by the unicast service user, and replaces the code modulation scheme of the broadcast service with the code modulation scheme of the composite service.
In one implementation, the method for the base station to obtain channel state information of a broadcast service from a cell edge user and determine a broadcast service coding modulation scheme according to the channel state information includes:
a base station sends a channel state reference signal to a cell edge user;
the cell edge user carries out channel estimation according to the channel state reference signal and feeds back the signal state information of the broadcast service to the base station, wherein the channel state information comprises a receiving signal-to-noise ratio;
and the base station selects a proper broadcast service coding modulation scheme according to the signal state information, wherein the broadcast service coding modulation scheme comprises an effective constellation mapping order and a channel coding code rate.
In one implementation manner, the base station selects a hotspot service area in a cell, and selects a unicast service with appropriate channel conditions from the hotspot service area to be transmitted in an overlapping manner with the broadcast service, including:
a base station selects a hot spot service area in a cell;
and the base station sorts the channel state information of the unicast service users in the selected hotspot service area according to the channel state information fed back by the unicast service users in the cell, and selects the unicast service with proper channel conditions to be transmitted in a superposition manner with the broadcast service.
In one implementation, the determining the coded modulation scheme of the composite service according to the channel quality value fed back by the unicast service user includes:
a unicast service user periodically measures channel quality information, maps the channel quality information into a CQI value and reports the CQI value to a base station;
the base station selects a target code modulation scheme corresponding to the CQI value from preset code modulation schemes according to the CQI value, and takes the target code modulation scheme as the code modulation scheme of the composite service, wherein the code modulation scheme of the composite service comprises the following steps: the order of the composite constellation mapping and the channel coding rate.
In one implementation manner, the selecting, by the base station, a target coded modulation scheme corresponding to the CQI value from preset coded modulation schemes according to the CQI value includes:
the base station determines a receiving signal-to-noise ratio range corresponding to the CQI value according to the CQI value;
and determining a target code modulation scheme corresponding to the receiving signal-to-noise ratio range from the preset code modulation schemes according to the receiving signal-to-noise ratio range.
In one implementation, the method further comprises:
and the base station informs the unicast service user of the coded modulation scheme channel control information of the composite service.
In a second aspect, an embodiment of the present invention further provides a downlink hybrid broadcast and unicast transmission system based on a multi-user superposition transmission technology, where the system includes: a base station and a cell, the base station comprising:
the broadcast service analysis module is used for acquiring channel state information of a broadcast service from a cell edge user and determining a broadcast service coding modulation scheme according to the channel state information;
the unicast service determining module is used for selecting a hotspot service area in a cell, and selecting unicast service with proper channel conditions from the hotspot service area to be transmitted in a superposition manner with the broadcast service;
and the code modulation scheme determining module is used for carrying out non-orthogonal multiplexing on the unicast service and the broadcast service to obtain a composite service, determining a code modulation scheme of the composite service according to the channel quality information fed back by the unicast service user, and replacing the code modulation scheme of the broadcast service with the code modulation scheme of the composite service.
In one implementation, the broadcast service analysis module includes:
a signal sending unit, configured to send a channel state reference signal to a cell edge user by a base station;
a state receiving unit, configured to perform channel estimation for a cell edge user according to the channel state reference signal, and feed back signal state information of the broadcast service to the base station, where the channel state information includes a received signal-to-noise ratio;
and the scheme determining unit is used for selecting a proper broadcast service coding modulation scheme by the base station according to the signal state information, wherein the broadcast service coding modulation scheme comprises an effective constellation mapping order and a channel coding code rate.
In one implementation, the unicast traffic determination module includes:
a base station selects a hot spot service area in a cell;
and the base station sorts the channel state information of the unicast service users in the selected hotspot service area according to the channel state information fed back by the unicast service users in the cell, and selects the unicast service with proper channel conditions to be transmitted in a superposition manner with the broadcast service.
In one implementation, the code modulation scheme determining module includes:
a CQI value determining unit, configured to periodically measure channel quality information by a unicast service user, and map the channel quality information into a CQI value to report the CQI value to a base station;
a scheme selecting unit, configured to select, by the base station according to the CQI value, a target coded modulation scheme corresponding to the CQI value from preset coded modulation schemes, and use the target coded modulation scheme as a coded modulation scheme of the composite service, where the coded modulation scheme of the composite service includes: the order of the composite constellation mapping and the channel coding rate.
In one implementation, the scheme selecting unit includes:
a signal-to-noise ratio range determining subunit, configured to determine, by the base station according to the CQI value, a received signal-to-noise ratio range corresponding to the CQI value;
and the target scheme determining subunit is used for determining a target code modulation scheme corresponding to the receiving signal-to-noise ratio range from the preset code modulation schemes according to the receiving signal-to-noise ratio range.
In one implementation, the base station further includes:
and the information informing module is used for informing the unicast service user of the coded modulation scheme channel control information of the composite service.
In a third aspect, an embodiment of the present invention further provides a base station, where the base station includes a memory, a processor, and a downlink hybrid broadcast and unicast transmission program based on a multi-user superposition transmission technology, where the downlink hybrid broadcast and unicast transmission program is stored in the memory and can be executed on the processor, and when the processor executes the downlink hybrid broadcast and unicast transmission program based on the multi-user superposition transmission technology, the step of implementing the downlink hybrid broadcast and unicast transmission method based on the multi-user superposition transmission technology according to any one of the above schemes is implemented.
Has the advantages that: compared with the prior art, the invention provides a downlink mixed broadcast unicast transmission method based on a multi-user superposition transmission technology. Then, the base station selects a hot spot service area in the cell, and selects unicast service with proper channel conditions from the hot spot service area to be superposed and transmitted with the broadcast service. And finally, the base station carries out non-orthogonal multiplexing on the unicast service and the broadcast service to obtain a composite service, determines a code modulation scheme of the composite service according to the channel quality information fed back by the unicast service user, and replaces the code modulation scheme of the broadcast service with the code modulation scheme of the composite service. The base station of the invention can self-adaptively adjust the coding modulation scheme of the composite service according to the feedback of the non-orthogonal multiplexing unicast user, provide additional unicast service for the system on the premise of not influencing the coverage performance of the broadcast service, and improve the overall transmission efficiency of the unicast service.
Drawings
Fig. 1 is a flowchart of a specific implementation of a downlink hybrid broadcast and unicast transmission method based on a multi-user superposition transmission technology according to an embodiment of the present invention.
Fig. 2 shows the channel capacity of different bits of Gray-256-QAM in AWGN channel.
Fig. 3 is a schematic diagram of an equivalent complex constellation mapping set (16, 64, 256 order NU-QAM).
Fig. 4 is a schematic diagram of channel capacity of broadcast services under different constellation mappings in an equivalent composite constellation mapping set.
Fig. 5 is a schematic diagram of channel capacity of unicast traffic under different constellation mappings in an equivalent composite constellation mapping set.
Fig. 6 is a diagram of a constellation limited reachable capacity bound.
Fig. 7 is a schematic diagram of the SFN architecture of the present invention.
Fig. 8 is a functional schematic diagram of a downlink hybrid broadcast and unicast transmitting apparatus based on a multi-user superposition transmission technology according to an embodiment of the present invention.
Fig. 9 is a schematic block diagram of a base station according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and effects of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The embodiment provides a downlink hybrid broadcast and unicast transmission method based on a multi-user superposition transmission technology, and the method comprises the steps that firstly, a base station acquires channel state information of a broadcast service from a cell edge user, and determines a broadcast service coding modulation scheme according to the channel state information. Then, the base station selects a hot spot service area in the cell, and selects the unicast service with proper channel condition from the hot spot service area to be superposed with the broadcast service for transmission. And finally, the base station carries out non-orthogonal multiplexing on the unicast service and the broadcast service to obtain a composite service, determines a code modulation scheme of the composite service according to the channel quality information fed back by the unicast service user, and replaces the code modulation scheme of the broadcast service with the code modulation scheme of the composite service. The base station of this embodiment can adaptively adjust the code modulation scheme of the composite service according to the feedback of the non-orthogonal multiplexed unicast user, provide additional unicast service for the system on the premise of not affecting the broadcast service coverage performance, and improve the overall transmission efficiency of the unicast service.
Exemplary method
In specific implementation, as shown in fig. 1, the method for transmitting a downlink hybrid broadcast and unicast based on a multi-user superposition transmission technology in this embodiment includes the following steps:
step S100, the base station obtains the channel state information of the broadcast service from the cell edge user, and determines the broadcast service coding modulation scheme according to the channel state information.
In this embodiment, the transmission mode of the broadcast service may be adjusted according to the channel state information of the broadcast service of the edge user of the cell, so that the base station first obtains the channel state information of the broadcast service from the edge user of the cell, and then determines the broadcast service coding modulation scheme according to the channel state information, that is, obtains the transmission mode of the broadcast service. Compared with the traditional single-layer multimedia broadcasting system with a fixed transmission mode, the adjustment of the transmission mode of the embodiment can improve the spectrum efficiency of the broadcasting channel.
In an implementation manner, the step S100 specifically includes the following steps:
step S101, a base station sends a channel state reference signal to a cell edge user;
step S102, the cell edge user carries out channel estimation according to the channel state reference signal and feeds back the signal state information of the broadcast service to the base station, wherein the channel state information comprises a receiving signal-to-noise ratio;
step S103, the base station selects a proper broadcast service coding modulation scheme according to the signal state information, wherein the broadcast service coding modulation scheme comprises an effective constellation mapping order and a channel coding code rate.
Specifically, a base station firstly sends a channel state reference signal to a cell edge user, and then selects a suitable broadcast service coding modulation scheme according to channel state information such as a receiving signal-to-noise ratio of cell edge broadcast service, wherein the broadcast service coding modulation scheme comprises an equivalent constellation mapping order and a channel coding code rate. The equivalent constellation mapping order here means that if the composite constellation mapping order is M, mb bits are carried, where Mb1= log 2 M1 bits are used for transmission of the broadcast service, and then M1 is the equivalent constellation mapping order of the broadcast service.
When selecting a broadcast service coding modulation scheme, for a fixed-mode multimedia broadcast system, if a transmission mode is selected according to the worst channel condition in the covered area, the spectrum efficiency is low and channel resources are wasted. One solution is to select the appropriate transmission mode based on the channel conditions in the coverage area. For example, in rainy, snowy and windy weather, the channel condition is poor, and the base station selects the most robust transmission mode, namely the combination of low-order constellation mapping and low coding code rate; and when the weather condition is good, the channel condition is good, and the broadcast service terminal in the coverage area has a better receiving signal-to-noise ratio, the base station selects the combination of the high-order equivalent constellation mapping and the high coding code rate.
The meaning of the equivalent constellation mapping order is that if the composite constellation mapping order is M, mb bits are carried, where Mb1= log 2 M1 bits are used for transmission of the broadcast service, and then M1 is the equivalent constellation mapping order of the broadcast service. One broadcast service transmission mode, i.e., the equivalent constellation mapping order and the coding rate, corresponds to one equivalent composite constellation mapping group. The equivalence here has two layers, one is that the composite constellations use Mb1 bits for broadcast services; second, these composite constellation mappingsThe sum of the mutual information of Mb1 bits mapped for broadcast traffic has the same signal-to-noise threshold at the transmission rate of the selected mode. Any one of the set of equivalent composite constellation mappings is equivalent for transmission of the broadcast service in the selected mode. The reason why a set of equivalent complex constellation mapping sets with different orders is designed for a broadcast service transmission mode is that after the broadcast service transmission mode is selected, the unicast service superimposed on the broadcast service has a need for adaptively selecting a coding modulation scheme.
After the transmission mode of the broadcast service is selected, an M-order composite constellation mapping chart carrying Mb bits can be selected from an equivalent constellation mapping group corresponding to the transmission mode of the selected broadcast service according to the requirement of the unicast service. Different bits in a higher order composite constellation tend to exhibit Unequal Error Protection (UEP) characteristics, i.e., the reliability or transmission capability of different bits is different. Fig. 2 shows the channel capacity versus signal-to-noise ratio for 8 bits in the Gray-256-QAM constellation mapping, and it can be seen that these 8 bits exhibit 4 different error protection capabilities. Since the reception threshold for broadcast traffic is significantly lower than for unicast traffic, the most robust Mb1 of the Mb bits should be selected for broadcast traffic. From the mutual information point of view, mb1 bits with the largest bit channel capacity at the corresponding received signal-to-noise threshold should be selected. It is worth noting that for Mb1=2, the two bits determining the quadrant position in the composite constellation tend to be the most robust bits. As shown in fig. 2, bit 0 and bit 1 are two bits that determine the quadrant in Gray-256-QAM, and both bits are more reliable than the rest of the bits in the entire snr range.
For example, the cell covered by a certain period of time has poor channel conditions due to bad weather conditions, so the base station selects the most robust broadcast service transmission mode, that is, the equivalent constellation mapping order is 4, and the code rate is 1/2. At this time, an equivalent composite constellation mapping group is determined, and a composite constellation mapping map is selected according to the requirement of the superposed unicast service. Those two bits of the composite constellation that define the quadrant are used for broadcast traffic transmission and the remaining bits are used for transmission of the superimposed unicast traffic.
In order to correctly demodulate the information of the broadcast service at the broadcast service receiving end, the base station needs to inform the broadcast service terminal of the MCS of the composite service in a control signaling manner, including composite constellation mapping, bit positions allocated to the broadcast service in the composite constellation mapping, and channel coding code rate of the broadcast service.
Step S200, the base station selects a hot spot service area in the cell, and selects a unicast service with proper channel conditions from the hot spot service area to be transmitted in a superposition mode with the broadcast service.
Specifically, the step S200 includes the steps of:
step S201, a base station selects a hot spot service area in a cell;
step S202, the base station sequences the channel state information of the unicast service users in the selected hotspot service area according to the channel state information fed back by the unicast service users in the cell, and selects the unicast service with proper channel conditions to be transmitted in a superposition manner with the broadcast service.
Specifically, the base station of this embodiment first selects a hot spot service area in a cell, and a unicast user in the hot spot service area has a higher unicast traffic demand. The base station adjusts relevant parameters such as a transmitting antenna directional diagram and the like, so that higher antenna gain is achieved in the direction of the hot spot service area. In order to fully excavate the performance gain brought by the superposition coding, the base station sequences the channel state information of the unicast users in the selected hotspot service area, selects the unicast service with proper channel conditions to be superposed and transmitted with the original broadcast service, and provides additional unicast transmission capability for the system on the premise of not influencing the coverage of the broadcast service.
Step S300, the base station carries out non-orthogonal multiplexing on the unicast service and the broadcast service to obtain a composite service, determines a code modulation scheme of the composite service according to channel quality information fed back by a unicast service user, and replaces the code modulation scheme of the broadcast service with the code modulation scheme of the composite service.
In one implementation, the step S300 includes the following steps:
step S301, a unicast service user periodically measures channel quality information, maps the channel quality information into a CQI value and reports the CQI value to a base station;
step S302, the base station selects a target code modulation scheme corresponding to the CQI value from preset code modulation schemes according to the CQI value, and takes the target code modulation scheme as the code modulation scheme of the composite service, wherein the code modulation scheme of the composite service comprises: the order of the composite constellation mapping and the channel coding code rate.
In the existing cellular mobile communication network, the unicast service adopts Adaptive Modulation and Coding (AMC) technology to match the link throughput with the time-varying channel characteristics, so that the BLER is lower than a certain threshold. In order to guarantee the service quality of the unicast service users, the scheme provided by the embodiment also supports AMC. Specifically, the unicast service user periodically measures the downlink quality (i.e., channel quality information), and maps the Channel quality information into a CQI (Channel quality indicator) value to be fed back to the base station. And each CQI value corresponds to a receiving signal-to-noise ratio range, and the base station determines the receiving signal-to-noise ratio range corresponding to the CQI value according to the CQI value. And then according to the receiving signal-to-noise ratio range, selecting a target coding modulation scheme corresponding to the receiving signal-to-noise ratio range from preset coding modulation schemes, and using the target coding modulation scheme as the coding modulation scheme of the composite service, wherein the target coding modulation scheme comprises the order of composite constellation mapping and the channel coding code rate. Finally, the base station informs the unicast service user of the selected code modulation scheme of the composite service through the channel control information.
Specifically, after the transmission mode of the broadcast service is determined (the switching frequency of the transmission mode of the broadcast service is generally much lower than the frequency of AMC of the unicast service), a group of composite constellation maps with different orders but equivalent to the current broadcast service mode can be used for selecting the unicast service. For example, when the broadcast service mode is selected to have an equivalent constellation mapping order of 4, a code rate of 5/6, and a received signal-to-noise ratio threshold of 5dB, an equivalent complex constellation mapping group meeting the requirements may be a group of complex constellation mappings shown in fig. 3.
Fig. 4 shows the variation of channel capacity with signal-to-noise ratio for broadcast services under several composite constellations as described in fig. 3, and it can be seen that these several composite constellation mappings are equivalent for the selected broadcast service transmission mode. Fig. 5 shows the variation curve of the channel capacity of the unicast service with the signal-to-noise ratio under several composite constellations described in fig. 3, and the base station selects an appropriate target coding modulation scheme according to the CQI (each CQI corresponds to a received signal-to-noise ratio range) fed back by the unicast service user. When the signal-to-noise ratio range of the unicast service user is 10-15 dB, NU-16-QAM and a proper coding code rate are selected; and when the signal-to-noise ratio of the unicast service user ranges from 25 dB to 30dB, NU-256-QAM and a proper coding code rate are selected.
This embodiment illustrates that the composite constellation obtained by nonlinear superposition of uniform QAM constellations according to a certain power ratio based on the MUST-Type2 has a large gap from the reachable capacity bound at some system operating points, and this gap can be reduced by optimizing the composite constellation, thereby further improving the spectral efficiency of the system.
Suppose that the mapping order of the broadcast service equivalent constellation is 4, the code rate is 1/2, the threshold of the signal-to-noise ratio is 5dB, and the receiving signal-to-noise ratio of the unicast service user is 15dB. Fig. 6 plots the achievable capacity domain when different composite constellations are used (the capacity bounds at time division multiplexing and at gaussian input are also given for comparison), and it can be seen that the composite constellation obtained based on the non-linear superposition of uniform QAM constellations can provide a transmission rate of about 3.0bit/symbol for unicast service at a received signal-to-noise ratio of 15dB. And the APSK constellation map is used as a composite constellation map, and certain optimization is performed under the transmission mode of the selected broadcast service and the signal to noise ratio of unicast service reception, so that certain forming gain and better multi-user superposition gain can be provided. Fig. 6 also shows the reachable capacity of the non-uniform APSK composite constellation mapping obtained by optimization for the current embodiment, and it can be seen that the optimized composite constellation mapping can provide a higher transmission rate of about 3.2 bits/symbol for the unicast service on the premise of not affecting the coverage of the broadcast service (when the reachable capacity is compared, the receiving end assumes that independent demapping and single-stage decoding are adopted).
In another implementation, this embodiment may also adopt a Single Frequency Network (SFN) networking scheme, where broadcast services transmitted by base stations of different cells are completely the same signal, and each base station may multiplex unicast services in each cell on the same broadcast signal, and although viewed from a composite signal, the requirement of the single frequency network on the same frequency and same signal is broken, because (equivalent) power of the base layer broadcast service is often significantly higher than (equivalent) power of the multiplexed enhancement layer unicast service, the base layer broadcast service may be regarded as noise introduced by a receiving end, so that the present invention may be extended to an SFN architecture, as shown in fig. 7.
In summary, the transmission mode of the broadcast service in this embodiment may be adjusted according to the channel condition, that is, the broadcast service is selected according to the channel state information such as the received signal-to-noise ratio of the broadcast service fed back by the cell edge user. Compared with a broadcasting system with a fixed transmission mode, the method can obtain higher spectral efficiency of the broadcasting service. The embodiment can also enable the multiplexed unicast users to have higher receiving signal-to-noise ratio by adjusting the relevant parameters of the transmitting antenna directional diagram so as to obtain higher superposition coding gain. In this embodiment, the broadcast service and the unicast service are multiplexed by using a nonlinear superposition method, which is specifically represented by performing bit division on a Gray-mapped composite constellation diagram, and allocating bit subchannels with unequal error protection to the broadcast and unicast services with large channel condition difference. Compared with the existing broadcast-unicast hybrid transmission scheme, the embodiment considers the support of unicast service AMC, namely, a group of equivalent constellation mapping groups is designed for each supported broadcast service transmission mode by introducing the concept of the equivalent constellation mapping groups, and the selection of composite constellation mapping can be performed according to the channel condition of a unicast user under the condition of transparency to the broadcast service.
Exemplary System
Based on the above embodiments, the present invention provides a downlink hybrid broadcast unicast transmission system based on a multi-user superposition transmission technology, where the system includes: a base station and a cell. As shown in fig. 8, the base station includes: a broadcast service analysis module 10, a unicast service determination module 20 and a coded modulation scheme determination module 30. Specifically, the broadcast service analysis module 10 is configured to obtain channel state information of a broadcast service from a cell edge user, and determine a broadcast service coding modulation scheme according to the channel state information. The unicast service determining module 20 is configured to select a hot spot service area in a cell, and select a unicast service with a suitable channel condition from the hot spot service area to be transmitted in an overlapping manner with the broadcast service. The code modulation scheme determining module 30 is configured to perform non-orthogonal multiplexing on the unicast service and the broadcast service to obtain a composite service, determine a code modulation scheme of the composite service according to channel quality information fed back by a unicast service user, and replace the code modulation scheme of the broadcast service with the code modulation scheme of the composite service.
In one implementation, the broadcast service analysis module includes:
a signal sending unit, configured to send a channel state reference signal to a cell edge user by a base station;
a state receiving unit, configured to perform channel estimation for a cell edge user according to the channel state reference signal, and feed back signal state information of the broadcast service to the base station, where the channel state information includes a received signal-to-noise ratio;
and the scheme determining unit is used for selecting a proper broadcast service coding modulation scheme by the base station according to the signal state information, wherein the broadcast service coding modulation scheme comprises an effective constellation mapping order and a channel coding code rate.
In one implementation, the unicast traffic determination module includes:
a base station selects a hot spot service area in a cell;
and the base station sorts the channel state information of the unicast service users in the selected hotspot service area according to the channel state information fed back by the unicast service users in the cell, and selects the unicast service with proper channel conditions to be transmitted in a superposition manner with the broadcast service.
In one implementation, the code modulation scheme determining module includes:
a CQI value determining unit, configured to periodically measure channel quality information by a unicast service user, map the channel quality information into a CQI value, and report the CQI value to a base station;
a scheme selecting unit, configured to select, by the base station according to the CQI value, a target coded modulation scheme corresponding to the CQI value from preset coded modulation schemes, and use the target coded modulation scheme as a coded modulation scheme of the composite service, where the coded modulation scheme of the composite service includes: the order of the composite constellation mapping and the channel coding code rate.
In one implementation, the scheme selecting unit includes:
a signal-to-noise ratio range determining subunit, configured to determine, by the base station, a received signal-to-noise ratio range corresponding to the CQI value according to the CQI value;
and the target scheme determining subunit is used for determining a target code modulation scheme corresponding to the receiving signal-to-noise ratio range from the preset code modulation schemes according to the receiving signal-to-noise ratio range.
In one implementation, the base station further includes:
and the information informing module is used for informing the unicast service user of the coded modulation scheme channel control information of the composite service.
The working principle of each module in the downlink hybrid broadcast and unicast transmission apparatus based on the multi-user superposition transmission technology in this embodiment is the same as the principle of each step in the foregoing method embodiment, and details are not described here.
Based on the above embodiments, the present invention further provides a base station, and a schematic block diagram of the base station may be as shown in fig. 9. The base station may include one or more processors 100 (only one shown in fig. 9), a memory 101, and a computer program 102 stored in the memory 101 and executable on the one or more processors 100, for example, a program for a down-mix broadcast-unicast transmission based on a multi-user superposition transmission technique. The steps in method embodiments for downlink hybrid broadcast-unicast transmission based on a multi-user superposition transmission technique may be implemented by one or more processors 100 executing computer program 102. Alternatively, the one or more processors 100, when executing the computer program 102, may implement the functions of the modules/units in the apparatus embodiment of the downlink hybrid broadcast-unicast transmission based on the multi-user superposition transmission technology, which is not limited herein.
In one embodiment, the Processor 100 may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic device, discrete hardware component, or the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
In one embodiment, the storage 101 may be an internal storage unit of the electronic device, such as a hard disk or a memory of the electronic device. The memory 101 may also be an external storage device of the electronic device, such as a plug-in hard disk, a Smart Memory Card (SMC), a Secure Digital (SD) card, a flash memory card (flash card), and the like provided on the electronic device. Further, the memory 101 may also include both an internal storage unit and an external storage device of the electronic device. The memory 101 is used for storing computer programs and other programs and data required by the base station. The memory 101 may also be used to temporarily store data that has been output or is to be output.
It will be understood by those skilled in the art that the block diagram of fig. 9 is a block diagram of only a portion of the structure associated with the inventive arrangements and is not intended to limit the base stations to which the inventive arrangements may be applied, and that a particular base station may include more or less components than those shown, or may combine certain components, or have a different arrangement of components.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above may be implemented by hardware that is instructed by a computer program, and the computer program may be stored in a non-volatile computer-readable storage medium, and when executed, may include the processes of the embodiments of the methods described above. Any reference to memory, storage, operational databases, or other media used in embodiments provided herein may include non-volatile and/or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically Programmable ROM (EPROM), electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms such as Static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double-rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous Link DRAM (SLDRAM), rambus (Rambus) direct RAM (RDRAM), direct Rambus Dynamic RAM (DRDRAM), and Rambus Dynamic RAM (RDRAM).
In summary, the present invention discloses a downlink hybrid broadcast unicast transmission method based on a multi-user superposition transmission technology, wherein the method comprises: a base station acquires channel state information of a broadcast service from a cell edge user and determines a broadcast service coding modulation scheme according to the channel state information; a base station selects a hot spot service area in a cell, and selects a unicast service with proper channel conditions from the hot spot service area to be transmitted in a superposition manner with the broadcast service; and the base station carries out non-orthogonal multiplexing on the unicast service and the broadcast service to obtain a composite service, determines a code modulation scheme of the composite service according to the channel quality information fed back by the unicast service user, and replaces the code modulation scheme of the broadcast service with the code modulation scheme of the composite service. The invention can provide additional unicast service for the system on the premise of not influencing the coverage performance of the broadcast service, and improve the overall transmission efficiency of the unicast service.
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.
Claims (13)
1. A downlink hybrid broadcast unicast transmission method based on a multi-user superposition transmission technology is characterized by comprising the following steps:
a base station acquires channel state information of a broadcast service from a cell edge user and determines a broadcast service coding modulation scheme according to the channel state information;
a base station selects a hot spot service area in a cell, and selects a unicast service with proper channel conditions from the hot spot service area to be transmitted in a superposition manner with the broadcast service;
and the base station carries out non-orthogonal multiplexing on the unicast service and the broadcast service to obtain a composite service, determines a code modulation scheme of the composite service according to the channel quality information fed back by the unicast service user, and replaces the code modulation scheme of the broadcast service with the code modulation scheme of the composite service.
2. The method as claimed in claim 1, wherein the base station obtains channel state information of broadcast service from cell edge users and determines a broadcast service coding modulation scheme according to the channel state information, and the method comprises:
a base station sends a channel state reference signal to a cell edge user;
the cell edge user carries out channel estimation according to the channel state reference signal and feeds back the signal state information of the broadcast service to the base station, wherein the channel state information comprises a receiving signal-to-noise ratio;
and the base station selects a proper broadcast service coding modulation scheme according to the signal state information, wherein the broadcast service coding modulation scheme comprises an effective constellation mapping order and a channel coding code rate.
3. The method according to claim 1, wherein the base station selects a hot spot service area in a cell, and selects a unicast service with a suitable channel condition from the hot spot service area to perform the superposition transmission with the broadcast service, and the method comprises:
the base station selects a hot spot service area in a cell;
and the base station sorts the channel state information of the unicast service users in the selected hotspot service area according to the channel state information fed back by the unicast service users in the cell, and selects the unicast service with proper channel conditions to be transmitted in a superposition manner with the broadcast service.
4. The method according to claim 3, wherein the determining the coded modulation scheme of the composite service according to the channel quality value fed back by the unicast service user comprises:
a unicast service user periodically measures channel quality information, maps the channel quality information into a CQI value and reports the CQI value to a base station;
the base station selects a target code modulation scheme corresponding to the CQI value from preset code modulation schemes according to the CQI value, and takes the target code modulation scheme as the code modulation scheme of the composite service, wherein the code modulation scheme of the composite service comprises the following steps: the order of the composite constellation mapping and the channel coding rate.
5. The method according to claim 4, wherein the selecting, by the base station, the target modulation and coding scheme corresponding to the CQI value from preset modulation and coding schemes according to the CQI value comprises:
the base station determines a receiving signal-to-noise ratio range corresponding to the CQI value according to the CQI value;
and determining a target code modulation scheme corresponding to the receiving signal-to-noise ratio range from the preset code modulation schemes according to the receiving signal-to-noise ratio range.
6. The method according to claim 1, further comprising:
and the base station informs the unicast service user of the coded modulation scheme channel control information of the composite service.
7. A downlink hybrid broadcast and unicast transmission system based on a multi-user superposition transmission technology, comprising: a base station and a cell, the base station comprising:
the broadcast service analysis module is used for acquiring channel state information of a broadcast service from a cell edge user and determining a broadcast service coding modulation scheme according to the channel state information;
the unicast service determining module is used for selecting a hotspot service area in a cell, and selecting unicast service with proper channel conditions from the hotspot service area to be transmitted in a superposition manner with the broadcast service;
and the code modulation scheme determining module is used for carrying out non-orthogonal multiplexing on the unicast service and the broadcast service to obtain a composite service, determining a code modulation scheme of the composite service according to the channel quality information fed back by the unicast service user, and replacing the code modulation scheme of the broadcast service with the code modulation scheme of the composite service.
8. The system according to claim 7, wherein the broadcast service analyzing module comprises:
a signal sending unit, configured to send a channel state reference signal to a cell edge user by a base station;
a state receiving unit, configured to perform channel estimation for a cell edge user according to the channel state reference signal, and feed back signal state information of the broadcast service to the base station, where the channel state information includes a received signal-to-noise ratio;
and the scheme determining unit is used for selecting a proper broadcast service coding modulation scheme by the base station according to the signal state information, wherein the broadcast service coding modulation scheme comprises an effective constellation mapping order and a channel coding code rate.
9. The system according to claim 7, wherein the unicast service determination module comprises:
a base station selects a hot spot service area in a cell;
and the base station sorts the channel state information of the unicast service users in the selected hotspot service area according to the channel state information fed back by the unicast service users in the cell, and selects the unicast service with proper channel conditions to be transmitted in a superposition manner with the broadcast service.
10. The system according to claim 9, wherein the code modulation scheme determining module comprises:
a CQI value determining unit, configured to periodically measure channel quality information by a unicast service user, and map the channel quality information into a CQI value to report the CQI value to a base station;
a scheme selecting unit, configured to select, by the base station according to the CQI value, a target coded modulation scheme corresponding to the CQI value from preset coded modulation schemes, and use the target coded modulation scheme as a coded modulation scheme of the composite service, where the coded modulation scheme of the composite service includes: the order of the composite constellation mapping and the channel coding rate.
11. The system according to claim 10, wherein the scheme selecting unit comprises:
a signal-to-noise ratio range determining subunit, configured to determine, by the base station according to the CQI value, a received signal-to-noise ratio range corresponding to the CQI value;
and the target scheme determining subunit is used for determining a target code modulation scheme corresponding to the receiving signal-to-noise ratio range from the preset code modulation schemes according to the receiving signal-to-noise ratio range.
12. The downlink hybrid broadcast-unicast transmission system based on the multi-user superposition transmission technique according to claim 7, wherein said base station further comprises:
and the information informing module is used for informing the unicast service user of the coded modulation scheme channel control information of the composite service.
13. A base station, characterized in that the base station comprises a memory, a processor and a program for hybrid downlink broadcast and unicast transmission based on the multiuser superposition transmission technique, which is stored in the memory and can be executed on the processor, and when the processor executes the program for hybrid downlink broadcast and unicast transmission based on the multiuser superposition transmission technique, the steps of the method for hybrid downlink broadcast and unicast transmission based on the multiuser superposition transmission technique according to any one of claims 1 to 6 are implemented.
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