CN106937256A - A kind of cooperation multicast transmission method based on non-orthogonal multiple access technology - Google Patents

Abstract

The invention discloses a kind of cooperation multicast transmission method based on non-orthogonal multiple access technology, its step is：S1, base station construction unicast user Candidate SetS2, base station is from Candidate SetThe middle optimal unicast user d of selection_n*With multicast users while access network；S3, base station sending signal S_BST () gives all-multicast user and optimal unicast user d_n*；S4, unicast user d_n*Receive S_BSMulticast users signal S is first decoded after (t)₀T (), turns S5 if being successfully decoded, otherwise turn S6；S5, unicast user d_n*By successive interference cancellation techniques from S_BSS is removed in (t)₀T () decodes desired signal S afterwards₁T () and retransmitting multi-casting subscriber signal, multicast users merge the signal with the signal received from base station after receiving forward signal, decoding desired signal S₀(t)；S6, unicast user d_n*(multicast users) are respectively directly from signal S_BSItself desired signal S is decoded in (t)₁(t)(S₀(t)).The present invention can effectively improve the anti-interruption performance of multi-casting communication, for unicast user provides transmission opportunity, lift spectrum efficiency, can be used for multimedia multicast transmission system.

Description

A Coordinated Multicast Transmission Method Based on Non-orthogonal Multiple Access Technology

technical field

The invention relates to the field of wireless communication, in particular to a cooperative multicast transmission method based on non-orthogonal multiple access technology.

Background technique

The development of wireless communication services and mobile terminal applications has brought about a blowout growth in data traffic, which has increased people's demand for spectrum resources. As a new type of wireless service, wireless multicast transmission utilizes the broadcast characteristics of wireless channels, and regards all users who have the same demand for specific resources during the transmission process as a multicast group, and delivers the same information to all multicast users at the same time. It is a wireless service with high spectrum efficiency and can be widely used in communication scenarios such as video on demand, video conferencing, and multimedia education.

In wireless multicast transmission, due to the need to ensure the transmission quality of multiple users at the same time, the system performance is usually limited by the reception quality of the user with the worst channel gain. In wireless multicast networks, cooperative relay technology can effectively combat channel fading Improve the transmission performance of the multicast system. At present, the research on wireless cooperative multicast transmission technology has obtained certain papers, patents and other related achievements. In 2013, I-H.Lee et al. proposed an optimal multicast relay selection scheme in "IEEE Communications Letters" ("International Institute of Electrical and Electronics Engineers Communication Letters"), which can enable the cooperative multicast system to obtain the maximum diversity gain and improve system reliability. However, this solution requires the global instantaneous channel state information of the entire system, the system complexity is high and the overhead is high, and with the increase of system users, the transmission reliability of the system will deteriorate. In 2015, L Yang et al. proposed a cooperative multicast scheme based on optimal user forwarding in "IEEE Transactions on Vehicular Technology" ("International Institute of Electrical and Electronics Engineers Vehicle Technology Transactions"). In this scheme, the system selects the best user to act as a relay from the multicast users who successfully decode, and forwards information to the multicast users who fail to decode. The scheme can achieve full diversity gain, and the order of diversity gain is equal to the number of multicast users, indicating that the reliability of the scheme improves with the increase of the number of users, and overcomes the fact that the reliability of optimal relay forwarding cooperative multicast increases with the number of users and exacerbated defects. However, most of the nodes participating in the cooperation in the existing cooperative multicast technology are specially deployed relays or multicast users in the network, and the application flexibility is low. In addition, the common requirements of communication network users are not considered Individual data transmission requirements to differentiated users are not suitable for general networks where multicast users and unicast users coexist.

On the other hand, as a means of information multiple access, non-orthogonal multiple access technology can greatly improve the spectrum utilization efficiency of the increasingly scarce available spectrum resources. Transmit on channels with overlapping domain/code domains, and provide multiple users with differentiated wireless services on the same wireless resource at the same time, which can significantly improve system spectrum efficiency and user access capabilities, reduce user scheduling signaling overhead, and shorten access time. delay and reduce terminal energy consumption. As a core candidate technology for future communications and 5G communications, it has been widely recognized by domestic and foreign industries.

Contents of the invention

Aiming at the deficiencies in the existing cooperative multicast technology mentioned above, and taking advantage of the high spectrum efficiency and huge application potential brought by the orthogonal multiple access technology, this paper aims to propose a non-orthogonal multiple access technology based on The cooperative multicast transmission method, through the non-orthogonal multiple access technology, the multicast user information and the unicast user information are superimposed and transmitted in the power domain, which can provide unicast users in the system during the multicast transmission process. Access opportunities greatly improve the spectrum utilization of the network. While satisfying the common information needs of multiple users and the needs of individual users, the reliability of multicast user transmission is improved by utilizing the diversity gain brought by multiple users.

In order to achieve the above object, the present invention takes the following technical solutions:

A cooperative multicast transmission method based on non-orthogonal multiple access technology, including a base station, N unicast users and M multicast users, wherein the unicast users serve as cooperative relays to assist the base station in forwarding data to the multicast users, Each method execution contains at most 2 transmission time units.

A cooperative multicast transmission method based on non-orthogonal multiple access technology, the network includes a base station, N unicast users and M multicast users, wherein the unicast users serve as cooperative relays to assist the base station to multicast Broadcasting user carries out data forwarding; It is characterized in that, described method comprises the following steps:

S1. The base station arranges the channel gains between the unicast users and the base station in ascending order as |f ₁ | ² <...<|f _n | ² <...<|f _N | ² , where |f _n | ² means After the nth channel gain value is sorted in ascending order, the base station selects the unicast user corresponding to the largest q channel gain values as the candidate unicast user according to the sorting result and the unicast user candidate set base q preset by the system, and constructs Unicast User Candidate Set where d _n is the unicast user whose channel gain is |f _n | ² ;

S2, the base station selects from the unicast user candidate set Select an optimal unicast user d _n* and multicast user to access at the same time, and use the unicast user d _n* as a cooperative relay to assist the base station to forward multicast user information;

S3, the base station processes the original information required by the multicast user and unicast user d _n* , and constructs the transmission signal S _BS (t), which includes the multicast user signal S ₀ (t) and the unicast user signal S ₁ (t);

S4, in the unit transmission unit, the base station broadcasts the signal S _BS (t) to the unicast user d _n* and all multicast users, and the unicast user d _n* first decodes the multicast user after receiving the signal S _BS (t) Signal S ₀ (t), if it can be successfully decoded, it will go to S5, if it cannot be successfully decoded, it will go to S6;

S5, after the unicast user d _n* removes the multicast user signal S ₀ (t) from the received signal S _BS (t) through serial interference cancellation technology, decodes its own desired signal S ₁ (t), in addition, the unicast user d _n* re-encode and modulate the obtained multicast user information to generate a unit power signal containing multicast user information and forward the signal to all multicast users within the next transmission unit Multicast user p _m , (m∈{1,...,M}) receives the forwarded signal decoding the signal after combining it with the signal S _BS (t) from the base station;

S6, the unicast user d _n* directly decodes its desired signal S ₁ (t) from the received signal S _BS (t), and the multicast user p _m directly _decodes the multicast user signal S ₀ ( t).

Furthermore, the acquisition of the channel gain between the unicast user and the base station by the base station is that the base station broadcasts a training sequence to the unicast user, and each unicast user measures the instantaneous channel gain between itself and the base station according to the training sequence, and feeds back the measurement result to the base station.

Further, the specific method of step S2 is as follows:

S21, in the candidate set The unicast user d _n in the method obtains the channel gain |h _{n, m} | ² between itself and the multicast user p _m , (m∈{1,...,M}) by using the method described in claim 2;

S22, in the candidate set The unicast users d _n in will feed back the obtained channel gains |h _n,m | ² to the base station;

S23, for each unicast user d _n to multicast user p _m has a "minimum channel gain value", denoted as The base station selects a unicast user d _n* with the largest "minimum channel gain value" from all unicast users in the candidate set as the best unicast user, and the process can be expressed as:

Through this criterion, the channel gain of the worst forwarding link of the unicast user can be maximized;

S24, the base station broadcasts the selection result to each unicast user.

Further, the specific method of step S3 is as follows:

S31, the base station encodes and modulates the original information required by the multicast user and the unicast user d _n* respectively, and constructs corresponding unit power signals S ₀ (t) and S ₁ (t);

S32. The base station allocates the available transmission power P _BS between the signals S ₀ (t) and S ₁ (t) according to the preset power allocation ratio. Specifically, the base station allocates the transmission power to the signal S ₀ (t) as a ₀ P _BS , allocate transmission power for signal S ₁ (t) as a ₁ P _BS , where a ₀ and a ₁ are preset power allocation factors, and satisfy a ₀ +a ₁ =1;

S33, the base station superimposes the two signals after power allocation to generate a transmission signal S _BS (t), which can be expressed as:

Further, the specific method of step S4 is as follows:

S41, after the base station transmits the signal S _BS (t) through the wireless channel, unicast the received signal of the user d _n* Can be expressed as:

The received signal of multicast user p _m is:

in, with denote the white noise at the unicast user d _n* and the multicast user p _m respectively, f _n* and g _m denote the complex Gaussian channel between the base station to the unicast user d _n* and the base station to the multicast user p _m respectively, Take the modulus value of f _n* and g _m and then square it, that is, |f _n* | ² and |g _m | ² represent the channel gain value between the base station and the unicast user d _n* and the base station to the multicast user p _m ;

S42, the unicast user d _n* decodes the multicast user signal, and the corresponding decoding SINR Can be expressed as:

S43, when decoding SINR If it is greater than the predetermined decoding threshold γ _th , it is judged that the decoding of the unicast user d _n* is successful, otherwise it is judged that the decoding fails.

Further, the specific method of step S5 is as follows:

S51, after the unicast user d _n* removes the multicast user signal through the serial interference cancellation technology, a new received signal is obtained And carry out the decoding of its own desired signal, and the corresponding decoding signal-to-noise ratio Can be expressed as:

S52, the unicast user d _n* re-encodes and modulates the acquired multicast user information to generate a unit power signal containing the multicast user information and forward the information to all multicast users with a preset power P _d ;

S53, the multicast user p _m receives the information forwarded by the unicast user d _n* , and compares the signal with the received signal Carry out the maximum ratio combination, and the combined signal-to-interference-noise ratio Expressed as:

Further, the specific method of step S6 is as follows:

S61, the unicast user d _n* receives the signal directly from Decoding the desired signal S ₁ (t) in middle, the signal-to-interference-noise ratio at this time Expressed as:

S62, the multicast user p _m directly receives the signal from Decoding the expected signal S ₀ (t), the SINR at this time Expressed as:

The present invention has the following advantages:

1. The present invention introduces the cooperative relay technology into the wireless multicast system, and selects unicast users for cooperative transmission, so that the multicast users can obtain diversity gain, effectively resist channel fading, and improve the transmission efficiency and transmission reliability of the multicast network ;

2. The present invention superimposes and transmits different data information through non-orthogonal multiple access technology. While serving multicast users, it provides access opportunities for unicast users and provides incentives for them to become cooperative relays. Compared with the traditional multicast transmission, the utilization rate of the spectrum is further improved. Each unicast user also decodes the multicast user signal in the process of decoding the desired signal, which can become a natural cooperative node of the multicast user, providing cooperative multicast Greater freedom;

3. The selection strategy of cooperative unicast users based on the unicast user candidate set proposed by the present invention not only takes into account the transmission quality of multicast users, but also ensures that the unicast users who access the network have higher The quality of communication transmission ensures the fairness of transmission between multicast users and unicast users.

Description of drawings

Fig. 1 is the model diagram of the cooperative multicast system that the present invention uses;

Fig. 2 is the realization general flowchart of the present invention;

Fig. 3 is the performance figure that the outage probability of the present invention changes with system transmission power;

Fig. 4 is a trade-off diagram of diversity gain between unicast users and multicast users in the present invention.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution, and provides detailed implementation and specific operation process, but the protection scope of the present invention is not limited to the present invention. Example.

As shown in Figure 1, the wireless multicast network used in the present invention includes a base station, N unicast users and M multicast users, wherein the unicast users serve as cooperative relays to assist the base station in forwarding data to the multicast users, Each method execution contains at most 2 transmission time units.

As shown in Figure 2, the implementation steps of the present invention are as follows:

A cooperative multicast transmission method based on non-orthogonal multiple access technology, the network includes a base station, N unicast users and M multicast users, wherein the unicast users serve as cooperative relays to assist the base station to multicast Broadcasting user carries out data forwarding; It is characterized in that, described method comprises the following steps:

S1. The base station arranges the channel gains between the unicast users and the base station in ascending order as |f ₁ | ² <...<|f _n | ² <...<|f _N | ² , where |f _n | ² means After the nth channel gain value is sorted in ascending order, the base station selects the unicast user corresponding to the largest q channel gain values as the candidate unicast user according to the sorting result and the unicast user candidate set base q preset by the system, and constructs Unicast User Candidate Set where d _n is the unicast user whose channel gain is |f _n | ² ;

S2, the base station selects from the unicast user candidate set Select an optimal unicast user d _n* and multicast user to access at the same time, and use the unicast user d _n* as a cooperative relay to assist the base station to forward multicast user information;

S3, the base station processes the original information required by the multicast user and unicast user d _n* , and constructs the transmission signal S _BS (t), which includes the multicast user signal S ₀ (t) and the unicast user signal S ₁ (t);

S4, in the unit transmission unit, the base station broadcasts the signal S _BS (t) to the unicast user d _n* and all multicast users, and the unicast user d _n* first decodes the multicast user after receiving the signal S _BS (t) Signal S ₀ (t), if it can be successfully decoded, it will go to S5, if it cannot be successfully decoded, it will go to S6;

S5, after the unicast user d _n* removes the multicast user signal S ₀ (t) from the received signal S _BS (t) through serial interference cancellation technology, decodes its own desired signal S ₁ (t), in addition, the unicast user d _n* re-encode and modulate the obtained multicast user information to generate a unit power signal containing multicast user information and forward the signal to all multicast users within the next transmission unit Multicast user p _m , (m∈{1,...,M}) receives the forwarded signal decoding the signal after combining it with the signal S _BS (t) from the base station;

S6, the unicast user d _n* directly decodes its desired signal S ₁ (t) from the received signal S _BS (t), and the multicast user p _m directly _decodes the multicast user signal S ₀ ( t).

In this embodiment, the acquisition of the channel gain between the unicast user and the base station by the base station is that the base station broadcasts a training sequence to the unicast user, and each unicast user measures the instantaneous channel gain between itself and the base station according to the training sequence, and the measured The results are fed back to the base station.

In this embodiment, the specific method of step S2 is as follows:

S21, in the candidate set The unicast user d _n in the method obtains the channel gain |h _{n, m} | ² between itself and the multicast user p _m , (m∈{1,...,M}) by using the method described in claim 2;

S22, in the candidate set The unicast users d _n in will feed back the obtained channel gains |h _n,m | ² to the base station;

S23, for each unicast user d _n to multicast user p _m has a "minimum channel gain value", denoted as The base station selects a unicast user d _n* with the largest "minimum channel gain value" from all unicast users in the candidate set as the best unicast user, and the process can be expressed as:

Through this criterion, the channel gain of the worst forwarding link of the unicast user can be maximized;

S24, the base station broadcasts the selection result to each unicast user.

In this embodiment, the specific method of step S3 is as follows:

S31, the base station encodes and modulates the original information required by the multicast user and the unicast user d _n* respectively, and constructs corresponding unit power signals S ₀ (t) and S ₁ (t);

S32. The base station allocates the available transmission power P _BS between the signals S ₀ (t) and S ₁ (t) according to the preset power allocation ratio. Specifically, the base station allocates the transmission power to the signal S ₀ (t) as a ₀ P _BS , allocate transmission power for signal S ₁ (t) as a ₁ P _BS , where a ₀ and a ₁ are preset power allocation factors, and satisfy a ₀ +a ₁ =1;

S33, the base station superimposes the two signals after power allocation to generate a transmission signal S _BS (t), which can be expressed as:

In this embodiment, the specific method of step S4 is as follows:

S41, after the base station transmits the signal S _BS (t) through the wireless channel, unicast the received signal of the user d _n* Can be expressed as:

The received signal of multicast user p _m is:

in, with denote the white noise at the unicast user d _n* and the multicast user p _m respectively, f _n* and g _m denote the complex Gaussian channel between the base station to the unicast user d _n* and the base station to the multicast user p _m respectively, Take the modulus value of f _n* and g _m and then square it, that is, |f _n* | ² and |g _m | ² represent the channel gain value between the base station and the unicast user d _n* and the base station to the multicast user p _m ;

S42, the unicast user d _n* decodes the multicast user signal, and the corresponding decoding SINR Can be expressed as:

S43, when decoding SINR If it is greater than the predetermined decoding threshold γ _th , it is judged that the decoding of the unicast user d _n* is successful, otherwise it is judged that the decoding fails.

In this embodiment, the specific method of step S5 is as follows:

S51, after the unicast user d _n* removes the multicast user signal through the serial interference cancellation technology, a new received signal is obtained And carry out the decoding of its own desired signal, and the corresponding decoding signal-to-noise ratio Can be expressed as:

S52, the unicast user d _n* re-encodes and modulates the acquired multicast user information to generate a unit power signal containing the multicast user information and forward the information to all multicast users with a preset power P _d ;

S53, the multicast user p _m receives the information forwarded by the unicast user d _n* , and compares the signal with the received signal Carry out the maximum ratio combination, and the combined signal-to-interference-noise ratio Expressed as:

In this embodiment, the specific method of step S6 is as follows:

S61, the unicast user d _n* receives the signal directly from Decoding the desired signal S ₁ (t) in middle, the signal-to-interference-noise ratio at this time Expressed as:

S62, the multicast user p _m directly receives the signal from Decoding the expected signal S ₀ (t), the SINR at this time Expressed as:

The performance of the present invention will be further described below in combination with simulation experiments.

FIG. 3 shows the performance diagram of the variation of the outage probability with the transmission power of the system according to the present invention. It can be seen from the figure that as the system transmit power increases, the system outage probability also decreases. Compared with traditional non-cooperative transmission, the present invention can achieve lower interruption probability and has higher transmission reliability.

Figure 4 shows the trade-off curves of diversity gain between unicast users and multicast users. It can be seen from the figure that there is a certain interaction between the performance of unicast users and multicast users. In actual transmission, the size of the base q of the unicast user candidate set can be adjusted according to the actual system indicators, so that the multicast users and unicast Broadcasting users all meet their own transmission reliability requirements.

For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and ideas, and all these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims (7)

1. A cooperative multicast transmission method based on non-orthogonal multiple access technology, comprising a base station, N unicast users and M multicast users in the network, wherein the unicast users assist the base station as a cooperative relay Carry out data forwarding to multicast user; It is characterized in that, described method comprises the following steps: S1. The base station arranges the channel gains between the unicast users and the base station in ascending order as |f ₁ | ² <...<|f _n | ² <...<|f _N | ² , where |f _n | ² means After the nth channel gain value is sorted in ascending order, the base station selects the unicast user corresponding to the largest q channel gain values as the candidate unicast user according to the sorting result and the unicast user candidate set base q preset by the system, and constructs Unicast User Candidate Set where d _n is the unicast user whose channel gain is |f _n | ² ; S2, the base station selects from the unicast user candidate set Select an optimal unicast user d _n* and multicast user to access at the same time, and use the unicast user d _n* as a cooperative relay to assist the base station to forward multicast user information; S3, the base station processes the original information required by the multicast user and unicast user d _n* , and constructs the transmission signal S _BS (t), which includes the multicast user signal S ₀ (t) and the unicast user signal S ₁ (t); S4, in the unit transmission unit, the base station broadcasts the signal S _BS (t) to the unicast user d _n* and all multicast users, and the unicast user d _n* first decodes the multicast user after receiving the signal S _BS (t) Signal S ₀ (t), if it can be successfully decoded, it will go to S5, if it cannot be successfully decoded, it will go to S6; S5, after the unicast user d _n* removes the multicast user signal S ₀ (t) from the received signal S _BS (t) through serial interference cancellation technology, decodes its own desired signal S ₁ (t), in addition, the unicast user d _n* re-encode and modulate the obtained multicast user information to generate a unit power signal containing multicast user information and forward the signal to all multicast users within the next transmission unit Multicast user p _m , (m∈{1,...,M}) receives the forwarded signal decoding the signal after combining it with the signal S _BS (t) from the base station; S6, the unicast user d _n* directly decodes its desired signal S ₁ (t) from the received signal S _BS (t), and the multicast user p _m directly _decodes the multicast user signal S ₀ ( t). 2. the non-orthogonal multiple access technology-based cooperative multicast transmission method according to claim 1, is characterized in that, the acquisition of the channel gain between the unicast user and the base station by the base station is by the base station to the unicast user The training sequence is broadcast, and each unicast user measures the instantaneous channel gain between itself and the base station according to the training sequence, and feeds back the measurement result to the base station. 3. The coordinated multicast transmission method based on non-orthogonal multiple access technology according to claim 1, wherein the specific method of step S2 is as follows: S21, in the candidate set The unicast user d _n in the method obtains the channel gain |h _{n, m} | ² between itself and the multicast user p _m , (m∈{1,...,M}) by using the method described in claim 2; S22, in the candidate set The unicast users d _n in will feed back the obtained channel gains |h _n,m | ² to the base station; S23, for each unicast user d _n to multicast user p _m has a "minimum channel gain value", denoted as The base station selects a unicast user d _n* with the largest "minimum channel gain value" from all unicast users in the candidate set as the best unicast user, and the process can be expressed as: Through this criterion, the channel gain of the worst forwarding link of the unicast user can be maximized; S24, the base station broadcasts the selection result to each unicast user. 4. The coordinated multicast transmission method based on non-orthogonal multiple access technology according to claim 1, wherein the specific method of step S3 is as follows: S31, the base station encodes and modulates the original information required by the multicast user and the unicast user d _n * respectively, and constructs corresponding unit power signals S ₀ (t) and S ₁ (t); S32. The base station allocates the available transmission power P _BS between the signals S ₀ (t) and S ₁ (t) according to the preset power allocation ratio. Specifically, the base station allocates the transmission power to the signal S ₀ (t) as a ₀ P _BS , allocate transmission power for signal S ₁ (t) as a ₁ P _BS , where a ₀ and a ₁ are preset power allocation factors, and satisfy a ₀ +a ₁ =1; S33, the base station superimposes the two signals after power allocation to generate a transmission signal S _BS (t), which can be expressed as: 5. The coordinated multicast transmission method based on non-orthogonal multiple access technology according to claim 1, wherein the specific method of step S4 is as follows: S41, after the base station sends the signal S _BS (t) through the wireless channel, the received signal of the user d _n * is unicast Can be expressed as: The received signal of multicast user p _m is: in, with denote the white noise at the unicast user d _n * and multicast user pm respectively, f _n * and gm denote the complex Gaussian channel between the base station to the unicast user d _n * and the base station to the multicast user p _m respectively, for f _n* and g _m take the modulus value and then square, that is, |f _n* | ² and |g _m | ² represent the channel gain value between the base station and the unicast user d _n* and the base station to the multicast user p _m ; S42, the unicast user d _n* decodes the multicast user signal, and the corresponding decoding SINR Can be expressed as: S43, when decoding SINR If it is greater than the predetermined decoding threshold γ _th , it is judged that the decoding of the unicast user d _n* is successful, otherwise it is judged that the decoding fails. 6. The coordinated multicast transmission method based on non-orthogonal multiple access technology according to claim 1, wherein the specific method of step S5 is as follows: S51, after the unicast user d _n* removes the multicast user signal through the serial interference cancellation technology, a new received signal is obtained And carry out the decoding of its own desired signal, and the corresponding decoding signal-to-noise ratio Can be expressed as: S52, the unicast user d _n* re-encodes and modulates the acquired multicast user information to generate a unit power signal containing the multicast user information and forward the information to all multicast users with a preset power P _d ; S53, the multicast user p _m receives the information forwarded by the unicast user d _n* , and compares the signal with the received signal Carry out the maximum ratio combination, and the combined signal-to-interference-noise ratio Expressed as: . 7. The coordinated multicast transmission method based on non-orthogonal multiple access technology according to claim 1, wherein the specific method of step S6 is as follows: S61, the unicast user d _n* receives the signal directly from Decoding the desired signal S ₁ (t) in middle, the signal-to-interference-noise ratio at this time Expressed as: S62, the multicast user p _m directly receives the signal from Decoding the expected signal S ₀ (t), the SINR at this time Expressed as: