CN115865161A - Flexible rate division multiple access method - Google Patents
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- CN115865161A CN115865161A CN202211509839.9A CN202211509839A CN115865161A CN 115865161 A CN115865161 A CN 115865161A CN 202211509839 A CN202211509839 A CN 202211509839A CN 115865161 A CN115865161 A CN 115865161A
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Abstract
The invention discloses a flexible rate division multiple access method. Different from a common rate division multiple access system, the method considers flexibly selecting partial users to adopt rate division, avoids the problem that the rate is limited by the worst user channel caused by forcing all users to carry out rate division, and can effectively improve the effective throughput of the system. In addition, the invention considers the more practical situation of limited packet length and can effectively improve the effective throughput of the system. Based on the method, the invention designs a flexible rate division multiple access method aiming at a multi-user multi-antenna system of a downlink.
Description
Technical Field
The invention relates to the technical field of wireless communication, in particular to a flexible rate division multiple access method.
Background
With the increasing amount of data transmission, the conventional Orthogonal Multiple Access (OMA) method is gradually unable to meet the requirements of future communication systems, and various new Multiple Access schemes have been proposed. In a multi-antenna system, space Division Multiple Access (SDMA) is the most commonly used, but in an overloaded system where the number of users is greater than the number of transmission antennas, the performance of SDMA may be greatly degraded due to severe interference. Non-Orthogonal Multiple Access (NOMA) is another new Multiple Access candidate, NOMA may allow Multiple users to occupy the same Orthogonal time-frequency resource block, and thus may accommodate more users than conventional OMA, but in a multi-antenna system, NOMA may result in inefficient utilization of space-dimensional resources and may result in extremely high complexity.
Rate-Splitting Multiple Access (RSMA) is a new multi-Access scheme that is widely focused on, and at a transmitting end of a downlink system, signals of all users are split and recombined into a public data stream and a plurality of private data streams, at a receiving end, all users decode the public data stream first, then, the users solve corresponding private data streams through Successive Interference Cancellation (SIC), and finally, signals of each user are obtained through recombining the public data stream and the private data streams. Through the division and recombination of user signals, RSMA can flexibly adjust the interference among users, thereby obtaining higher spectral efficiency and freedom degree than NOMA and SDMA. In addition, the RSMA can simultaneously support a large number of users with different quality of service requirements, and is more robust to different network bearers and imperfect channel information.
However, in current protocol studies on RSMA, there are two general assumptions: one is to assume that all users adopt rate segmentation, at this time, all users must decode the common data stream, the data rate of the common data stream is limited to the user with the worst channel quality, and the advantages of RSMA cannot be fully embodied; the second assumption is that the packet length is infinite, since most of the current RSMA scheme research adopts shannon capacity formula, and the shannon capacity formula is based on the assumption of infinite packet length, which is much different from the real system. These two assumptions lead to the current schemes for RSMA not being able to flexibly select users for rate splitting, and the schemes are not practical and have poor performance.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a flexible rate segmentation multiple access method, which can flexibly select part of users to adopt rate segmentation, and effectively improve the overall effective throughput of the system.
In order to solve the above technical problem, the present invention provides a flexible rate segmentation multiple access method, which comprises the following steps:
(1) And sequentially processing target data streams of all users according to a user selection scheme: and (3) if the user adopts the rate division, skipping to execute the step (2), and if the user does not adopt the rate division, skipping to execute the step (3). And (4) skipping to the step (4) after all users are executed.
(2) The target data stream of the user is divided into a public part and a private part, and the private part is also the private data stream of the user. And (4) skipping to execute the step (1).
(3) The user has no public data stream part, and the target data stream is a private data stream. And (4) skipping and executing the step (1).
(4) The common part of all users adopting rate division is combined into a common data stream.
(5) Carrying out beam forming on a user signal: and after the public data stream and the private data streams of all the users are respectively multiplied by the beam forming vector, all the signals are superposed and transmitted by the base station.
(6) Decoding is performed for all users in turn: if the user adopts rate segmentation, skipping to execute the step (7); and (4) if the user does not adopt the rate division, skipping to execute the step (8). Until all users decode.
(7) The user first takes all private data streams as interference, decodes public data streams from received signals, and separates public parts of the user from the decoded public data streams; then, subtracting a part corresponding to the public data stream from the received signal, and decoding the private part of the user according to the subtracted signal; and recombining the public part and the private part of the user obtained by decoding to obtain the target data stream of the user. And (6) jumping and executing.
(8) The user directly decodes the private data stream, i.e. the target data stream of the user, from the received signal using all other data streams as interference. And (6) jumping and executing.
Preferably, in step (4), the data transmission rate of the common data stream is equal to the sum of the data transmission rates of the common part of all the users adopting rate division.
Preferably, in step (1), the specific operation of optimizing the user selection scheme is as follows:
and (1-1) randomly generating a user selection scheme and calculating the effective throughput of the system corresponding to the user selection scheme.
(1-2) randomly selecting a user and changing the user selection scheme, namely: if the user originally adopts rate segmentation, the user does not adopt rate segmentation after the change; if the user does not originally adopt rate segmentation, the user adopts rate segmentation after the change.
(1-3) calculating the effective throughput of the system after the user selection scheme is changed.
And (1-4) judging whether the effective throughput of the system after the user selection scheme is changed is larger than that of the system before the user selection scheme is changed. If yes, executing the step (1-5); if not, executing the step (1-6).
(1-5) approving the change of the user selection scheme in this step (1-2). And (5) jumping to execute the step (1-7).
(1-6) not approving the change of the user selection scheme in this step (1-2), and returning the user selection scheme to the scheme before this change.
(1-7) judging whether changing the indication variable of any user can not improve the effective throughput of the system. If yes, executing (1-8); if not, skipping to execute the step (1-2).
(1-8) outputting the user selection scheme.
Preferably, in steps (1-1) and (1-3), the system goodput is calculated by considering the limited packet length of the system, and the system goodput is determined by the packet length, the user channel coefficient, the data transmission rate, the user selection scheme and the beam forming vector.
The invention has the beneficial effects that: the rate division multiple access method provided by the invention can flexibly select partial users to carry out rate division, avoids the problem that the rate is limited by the worst user channel caused by forcing all users to carry out rate division, and can improve the effective throughput of the system; the rate division multiple access method provided by the invention can improve the effective throughput of the system by considering the condition of the limited packet length close to the reality.
Drawings
Fig. 1 is a schematic signal flow diagram of a transmitting end according to the present invention.
Fig. 2 is a schematic diagram of a signal flow at a receiving end according to the present invention.
Fig. 3 is a flow chart illustrating the optimization of user selection schemes, data transmission rates, and beamforming vectors in an embodiment of the present invention.
Fig. 4 is a diagram showing the comparison of the system effective throughput of the flexible RSMA proposed by the present invention with the conventional RSMA, SDMA and NOMA for different users.
Fig. 5 is a schematic diagram showing the comparison of the system goodput of the flexible RSMA proposed by the present invention with the conventional RSMA, SDMA and NOMA under different base station antenna numbers.
Detailed Description
The following describes a flexible rate division multiple access method proposed by the present invention in detail with reference to a system embodiment of K users. As shown in fig. 3, the method comprises the following steps:
(1) In a downlink system, a base station end is provided with N t The antenna is a single antenna for K users, and the users are marked as K = {1, \8230;, K }.
(2) The beamforming vectors, data transmission rates, and user selection schemes are optimized. The user selection scheme is a: = { a = k I k belongs to k, where a k E {0,1} is an indicator variable of user k, a k =0 denotes that user k does not employ rate splitting, a k =1 indicates that user k employs rate splitting.
(3) According to a user selection scheme, the following operations are sequentially performed on users K = 1. And (5) if the user k adopts the rate division, skipping to execute the step (4), and if the user k does not adopt the rate division, skipping to execute the step (5). And (6) jumping to the execution step after all users are executed.
(4) Target data stream s for user k k Divided into common parts s k，c And a private part s k，p Common part according to an optimized data transmission rate schemeData transmission rate of R k，c The data transmission rate of the private part (i.e. the private data stream of user k) is R k，p . And (4) jumping to execute the step (3).
(5) User k has no public data stream part, the target data stream is private data stream s k，p According to the optimized data transmission rate scheme, the data transmission rate is R k，p . And (4) jumping to execute the step (3).
(6) Merging the common data portions of all users using rate splitting into a common data stream s c 。
(7) And performing beamforming on the signals according to the optimized beamforming vector: base station end transmitting signal x = w c s c +∑ k∈κ w k，p s k，p Wherein w is c Beamforming vectors, w, for common data streams k，p Beamforming vectors for private data streams of respective users.
(8) Decoding is performed on users K =1,., K in turn: the received signal of user k is
Wherein h is k Is the channel vector of user k, z k Noise for user k is mean 0, variance @>
Is additive white gaussian noise. If the user k adopts rate segmentation, skipping to execute the step (9); and if the user k does not adopt the rate division, skipping to execute the step (10). Until all users decode.
(9) User k first treats all private data streams as interference, from y k Decoding a common data stream s c The decoding result is recorded as
Freed up from which the common part of the user k is separated>
Then from y k Minus the common data stream->
The corresponding portion is taken>
According to>
Decoding private section +for user k>
The decoded common part->
And a private section +>
Recombining to obtain the target data stream of the user k>
And (8) jumping to execute the step.
(10) User k takes all other data streams as interference, directly from y k Decoding private data stream
I.e. the target data stream of subscriber k->
And (8) jumping and executing. />
In step (2), the specific operations of optimizing the beamforming vector, the data transmission rate and the user selection scheme are as follows:
(2-1) parameter initialization: initializing optimal system goodput T * : =0; initializing the original system goodput T (old) : =0; initialization iteration number t: and =0.
(2-2) randomly generating a user selection scheme
The superscript (0) indicates the number of iterations.
(2-3) updating user selection scheme a (new) ：＝a (t) . Updating indicator variables for user k
Wherein, k: = mod (t, K) +1.
(2-4) optimizing the beam forming vector and the data transmission rate to obtain the effective throughput T of the system (new) 。
(2-5) determining whether T is present (new) ＞T (old) . If yes, executing (2-6); if not, executing (2-7).
(2-6) update of T (old) ：＝T (new) And a (t+1) ：＝a (new) (ii) a If T (new) ＞T * Then, T is updated * ＝T (new) . Jump execution (2-8).
(2-7) keeping the indicator variable unchanged, i.e. a (t+1) ：＝a (t) 。
(2-8) judging whether changing the indication variable of any user can not improve the effective throughput of the system. If yes, executing (2-9); if not, jumping to execute (2-3).
(2-9) outputting the optimal user selection scheme a (t) Corresponding system goodput, beamforming vector, and data transmission rate.
In step (2-4), the specific operations of optimizing the beamforming vector and the data transmission rate are as follows:
(2-4-1) parameter initialization: initialization iteration number q: =0, error margin δ 2 Is greater than 0. Initializing system goodput T (0) ：＝0。
(2-4-2) setting initial beamforming vectors for common data streams
Setting an initial beamforming vector ∈ κ for all users k ∈ κ's private data streams>
Wherein P is total transmission power, 1 is N t A vector of all 1's of dimensions.
(2-4-3) updating q: = q +1.
(2-4-4) optimizing a data transmission rate, comprising: optimizing the data transmission rate R of the private part for all users k，p (ii) a Optimizing data transmission rate R of common part for user using rate division k，c 。
(2-4-5) optimizing the beamforming vector.
(2-4-6) calculating System goodput T (q) 。
(2-4-7) judgment: if T (q) -T (q-1) |≤δ 2 Then executing the step (2-4-8); if T (q) -T (q-1) |＞δ 2 And jumping to execute the step (2-4-3).
(2-4-8) output beamforming vector, data transmission rate, system goodput T (q) 。
In steps (2-4) and (2-4-6), the formula for calculating the goodput of the system is as follows,
wherein R is c ＝∑ k∈κ a k R k，c Is the sum of the rates of the common part information of the users using rate segmentation, L is the code block length, γ k，c Is the signal to interference plus noise ratio of the common part of the user by adopting rate division:
γ k，p is the signal to interference plus noise ratio of the private part of the user:
in the step (2-4-4), the specific operation of optimizing the private part data transmission rate is as follows: for any user k ∈ k, the optimal data transmission rate of the private part is calculated by the following formula:
wherein the content of the first and second substances,
is the equation phi k，p (x) Solution of =0, equation Φ k，p (x) Is composed of
In the step (2-4-4), the specific operation of optimizing the data transmission rate of the common part is as follows:
(2-4-4-1) parameter initialization: setting the error margin delta 3 Initialization iteration number t: and =0.
(2-4-4-2) Note that all the user sets using rate splitting are κ 1 For all users employing rate splitting, k ∈ k 1 Initialization of
(2-4-4-3) update t: = t +1;
(2-4-4-4) update
Wherein the content of the first and second substances,
is the equation phi k，c (x) Solution of =0, equation Φ k，c (x) Is composed of
(2-4-4-5) judging: if it is
Performing step (2-4-4-6); if it is
The jump executes step (2-4-4-3).
(2-4-4-6) outputting the optimal common part data transmission rate
In the step (2-4-5), the specific operation of optimizing the beamforming vector is as follows:
(2-4-5-1) parameter initialization: initialization penalty factor eta, growth factor beta 2 > 1, error margin delta 4 (ii) a Initialization iteration number n: =0.
(2-4-5-2) defining a parameter vector v = [ v = i，c ，i∈κ 1 ，v k，p ，k∈κ] T And is initialized to v (0) 。
(2-4-5-3) defining a beamforming matrix W c And W k，p The set of beamforming matrices is W = { W = { (W) c ，W k， p | k ∈ κ }, and is initialized to W (0) 。
(2-4-5-4) for a given v (n) And W (n) Solving the optimization problem to obtain v (n+1) And W (n+1 ) The value of (c).
(2-4-5-5) updating n: = n +1 and η: = beta 2 η。
(2-4-5-6) judging: if W (n) -W (n-1) ||≤δ 4 Then executing the step (2-4-5-7); if W | | (n) -W (n-1) ||＞δ 4 And skipping to execute the step (2-4-5-4).
(2-4-5-7) adding W (n) Beam forming matrix W in c And W k，p Respectively decomposing the characteristic roots, and respectively recording the maximum characteristic root as lambda c And λ k，p Its corresponding feature vector is q c And q is k，p Outputting beamforming vectors
And
in the step (2-4-5-4), the specific operation of solving the optimization problem is as follows:
(2-4-5-4-1) defining a set of relaxation variables τ = { τ = { (4-5-4-1) i，c ，τ k，p |i∈κ 1 ，k∈κ}
(2-4-5-4-2) for a given v (n) And W (n) And solving the following convex-down optimization problem through a CVX tool bag:
log 2 (1+v k，p )+τ k，p ≥R k，p ，k∈κ
wherein the content of the first and second substances,
for the channel matrix of user k, the function->
Is defined as
Function I i，c (W)＝∑ j∈κ tr(H i W j，p )，i∈κ 1 Function I k，p (W)＝(1-a k )tr(H k W c )+∑ j∈κ\{k} tr(H k W j，p )，k∈κ。
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Claims (4)
1. A flexible rate split multiple access method, comprising the steps of:
(1) And sequentially processing target data streams of all users according to a user selection scheme: if the user adopts rate division, skipping to execute the step (2), and if the user does not adopt rate division, skipping to execute the step (3); after all users are executed, skipping to execute the step (4);
(2) Dividing the target data stream of the user into a public part and a private part, wherein the private part is also the private data stream of the user; skipping to execute the step (1);
(3) The user has no public data stream part, and the target data stream is a private data stream; skipping to execute the step (1);
(4) Merging the common parts of all users adopting rate division into a common data stream;
(5) Carrying out beam forming on a user signal: respectively multiplying the public data stream and the private data streams of all users by the beam forming vector, and then superposing all signals to be sent by a base station;
(6) Decoding is performed for all users in turn: if the user adopts the rate segmentation, executing the step (7); if the user does not adopt the rate division, skipping to execute the step (8); until all users finish decoding;
(7) The user firstly takes all private data streams as interference, decodes public data streams from received signals, and separates public parts of the user from the decoded public data streams; then, subtracting a part corresponding to the public data stream from the received signal, and decoding the private part of the user according to the subtracted signal; recombining the public part and the private part of the user obtained by decoding to obtain a target data stream of the user; a jump execution step (6);
(8) The user directly decodes the private data stream from the received signal by taking all other data streams as interference, namely the target data stream of the user; and (6) jumping and executing.
2. The flexible rate division multiple access method of claim 1 wherein in step (4), the data transmission rate of the common data stream is equal to the sum of the data transmission rates of the common portions of all users employing rate division.
3. The flexible rate split multiple access method of claim 1 wherein in step (1), the specific operations for optimizing the user selection scheme are as follows:
(1-1) randomly generating a user selection scheme, and calculating the effective throughput of a system corresponding to the user selection scheme;
(1-2) randomly selecting a user and changing the user selection scheme, namely: if the user originally adopts rate segmentation, the user does not adopt rate segmentation after the change; if the user does not adopt the rate segmentation originally, the user adopts the rate segmentation after the change;
(1-3) calculating a system goodput after changing the user selection scheme;
(1-4) judging whether the effective throughput of the system after the user selection scheme is changed is larger than that before the user selection scheme is changed; if yes, executing the step (1-5); if not, executing the step (1-6);
(1-5) approving the change of the user selection scheme in this step (1-2); skipping to execute the step (1-7);
(1-6) disapproving of the change of the user selection scheme in this step (1-2), and returning the user selection scheme to the scheme before this change;
(1-7) judging whether the effective throughput of the system cannot be improved by changing the indication variable of any user; if yes, executing (1-8); if not, skipping to execute the step (1-2);
(1-8) outputting the user selection scheme.
4. The flexible rate split multiple access method of claim 3 wherein in steps (1-1) and (1-3), the system goodput is calculated considering the limited packet length condition of the system, and the system goodput is determined by the packet length, the user channel coefficients, the data transmission rate, the user selection scheme, and the beamforming vector.
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