CN111092643B - Delay CSIT interference alignment method under MISO-BC by utilizing cache - Google Patents
Delay CSIT interference alignment method under MISO-BC by utilizing cache Download PDFInfo
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
- H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
- H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
- H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
- H04B7/0621—Feedback content
- H04B7/0626—Channel coefficients, e.g. channel state information [CSI]
Abstract
A delay CSIT interference alignment method under MISO-BC utilizing buffer memory, the base station sends the second order signal vector constructed by the linear combination method, judges the number of the p order signal vector of the selected user by judging whether the highest order p of the signal vector generated by the base station is equal to the total number of the users, the base station sends the signal vector belonging to the selected user set and the signal vector belonging to the whole user to the user, so that the invention can be applied to the condition that the number of the p order signal vector of the selected user set is different under the MISO-BC of multiple users, and the application range is expanded; on the other hand, the total number of the base station antennas which need to be used in the invention is less than the total number of the user antennas, thus saving the antenna resources of the base station.
Description
Technical Field
The invention belongs to the technical field of communication, and further relates to a method for delaying the interference alignment of channel state information CSIT (channel state information at transmitter) at a transmitter by using a buffered multiple input single output broadcast channel MISO-BC (multiple input single output broadcast channel) in the technical field of wireless communication. The invention can be used for a multi-input single-output downlink broadcast channel BC (broadcast channel) from a base station to a user, which consists of the base station and a plurality of users, and achieves the aim of interference alignment by designing the placement mode of cache contents and signal vectors transmitted by the base station on the premise that the channel state information obtained by the base station has delay and each user has a cache with equal size.
Background
It is difficult for a transmitter in communication to obtain instantaneous channel state information from a wireless communication system because the channel state information at the transmitter is generally fed back to the transmitter after channel estimation by a receiver, thereby causing a delay of the channel state information at the transmitter. Conventional interference alignment techniques rely on instantaneous transmitter-site channel state information to design precoding matrices that are not applicable in cases where the transmitter-site channel state information is delayed.
The patent document "delayed CSIT interference alignment method for multi-cell MIMO-IMAC" (publication number: 107566018A, application number: 201710783405.0) applied by the university of west ampere electronics technology discloses a delayed CSIT interference alignment method for multi-cell MIMO-IMAC. The method comprises the following implementation steps: setting parameters of a MIMO-IMAC system of a multi-input multi-output multi-user access channel; selecting a transmission strategy used by a user for transmitting symbols to a base station and the number of used time slots according to system parameters, and segmenting the time slots; after the strategy is selected, selecting a user of a specific cell to transmit the same type of signal vector in each stage except the last stage, and keeping users of other cells silent; selecting two different cells in each time slot of the last stage, wherein users of the two cells design a sending signal vector by using delayed channel state information CSIT at a transmitter and send the designed sending signal vector at the same time; the base station eliminates interference to obtain an interference-free received signal vector, and interference alignment is realized. The method has the disadvantages that the type of the transmitted signal vector is single, and the CSIT interference alignment of the channel state information at the delayed transmitter can be realized only in a simple scene.
Zhang and p.elia in its published paper "Fundamental Limits of Cache-air Wireless BC: interactive of Coded-Caching and CSIT Feedback" (IEEE Transactions on Information Theory 2017, 63 (5): 3142) propose a transmission method using mixed channel state Information (including channel state Information at delayed transmitters and part of channel state Information at current transmitters) under a broadcast channel using a buffer. The method comprises the following implementation steps: the first step is to divide the file into subfiles which are stored in the user's cache according to a specific style. And a second step, in which the transmission process is divided into a plurality of stages, and signals are transmitted in a specific manner in the first stage, wherein the transmission manner adopts a zero forcing method and needs to utilize the same number of antennas as the total number of the user antennas. The base station then generates a next-stage transmission signal using the mixed channel state information at the transmitter. And thirdly, transmitting the signal generated in the previous stage in a specific mode, and generating the transmission signal in the next stage by the base station by using the mixed channel state information at the transmitter. And fourthly, repeating the third step until the order of the transmitted signals is the same as the total number of the users, and the base station finishes transmitting the signals generated in the last stage and does not generate higher-order signals any more. The method has the disadvantages that the method is only suitable for the condition that the total number of the base station antennas is equal to the total number of the user antennas, and is not suitable for the condition that the total number of the base station antennas is less than the total number of the user antennas.
Disclosure of Invention
The present invention is directed to provide a method for aligning channel state information CSIT (channel state information at transmitter) interference at a delayed transmitter under a buffered mimo broadcast channel MISO-BC, aiming at implementing the delayed CSIT interference alignment under the MISO-BC system of multiple users and improving the degree of freedom of the MISO-BC system.
The specific idea for realizing the purpose of the invention is to set MISO-BC system parameters and the cache content of a user, construct a second-order signal vector transmitted by a base station by a linear combination method according to the cache content of the user and a required file, and then judge whether a third-order signal vector is generated; if so, the base station generates a third-order signal vector by using channel state information CSIT at the delay transmitter; dividing users into different sets, constructing a transmitting signal vector of each set by the base station according to the number of third-order signals in a third-order signal vector generated by the base station and transmitting the transmitting signal vectors, then determining whether to generate a higher-order signal vector according to the difference of the signal vectors transmitted by the base station, and iteratively transmitting the signal vectors constructed by the base station in such a way; finally, the user uses the interference cancellation method to eliminate the interference.
In order to achieve the purpose, the main steps of the invention are as follows:
(1) setting cache content:
dividing each file of N files contained in a base station side database into J sub-files with equal size and mutual disjunction, and configuring 1 antenna and 1 buffer for each user; each user caches the subfiles according to rules; one subfile of each file in the database at the base station side is stored in the user buffer, the number of the subfile is the same as the user number, L represents the total number of users, L is larger than 1, the value of N is equal to the total number of users L, and the value of J is equal to the total number of users L;
(2) the base station sends a second-order signal vector constructed by a linear combination method to the user:
(2a) transmitting second order signal vectors to users at base station
Selecting two users from all users according to a polling method in each time slot; wherein, B represents the total number of symbols contained in each file in the base station side database, and B is L2-L, L representing the total number of users;
(2b) summing symbols at the same position in 2 sub-files required by the user selected from each time slot to form a second-order signal;
(2c) sequentially combining the L-1 second-order signals with the same number of antennas configured by the base station according to the sequence of the second-order signals to form a second-order signal vector transmitted by the base station;
(2d) The base station sends the second-order signal vector to the user;
(3) judging whether the total number of the users is equal to 2, if so, executing a step (21); otherwise, executing the step (4);
(4) generating time slot combination of a base station transmitting a second-order signal vector to a user:
transmitting second-order signal vectors from base station to user
In each time slot, arbitrarily taking three different time slots to form a time slot combination to obtain
A time slot combination;
(5) the base station selects a time slot combination, and generates a third-order signal by using channel state information CSIT at a delay transmitter:
(5a) randomly selecting a time slot combination which is different from the previously selected time slot combination from all the time slot combinations;
(5b) judging whether all users in three time slots contained in the selected time slot combination contain three different users or not; if yes, forming the three users into a user set and then executing the step (5 c); otherwise, executing the step (5 a);
(5c) the base station receives the channel state information CSIT at the delayed transmitter fed back by the user and utilizes a formula
Constructing signals received by unselected users of each time slot in three time slots contained in the selected time slot combination; wherein, ymSignals, h, representing reception of unselected users in the m-th time slotmChannel vectors representing the m-th slot unselected users, T represents the transpose operation, x mRepresenting a signal vector transmitted by the base station at the mth time slot;
(5d) the base station constructs a third-order signal vector by using a formula u-kv; wherein u represents a third order signal vector constructed by the base station, the third order signal in the third order signal vector belongs to a user set in the selected time slot combination, k represents a second order signal coefficient matrix artificially set in the base station,
v represents a signal vector formed by signals received by three unselected users in three time slots contained in the selected time slot combination according to the time slot serial number;
(6) determining the transmission of a second order signal vector to a user at a base station
Whether all time slot combinations are selected in each time slot or not, if so,after generating a third-order signal vector of each time slot combination, the base station sets the value of the highest order p of the signal vector to be 3 and then executes the step (7); otherwise, executing the step (5);
(7) judging whether the value of the highest order p of the signal vector is equal to the total number of users, if so, executing the step (8); otherwise, executing step (9);
(8) the base station sends the highest order signal vector to the user:
in each time slot that the base station sends the highest order signal vector to the user, the base station sequentially takes out 1 p order signal and L-2 zeros according to the order of the p order signal in the p order signal vector to form a highest order signal vector, and the base station sends the signal vector to the user; after all the highest-order signal vectors are sent by the base station, executing the step (21);
(9) Generating a user set:
selecting users with the same number as the highest order p of a signal vector from all users of a multi-input single-output broadcast channel MISO-BC system as a user set to obtain the users together
A set of individual users; wherein! Representing a factorial operation;
(10) selecting a user set:
randomly selecting a user set different from the previously selected user set from all the user sets;
(11) determining whether the number of p-order signal vectors of the selected user set is less than
If yes, executing step (12); otherwise, executing step (14);
(12) the base station sends signal vectors belonging to all users to the users:
in each time slot of the signal vector which belongs to all users and is sent to the users by the base station, the base station sequentially takes out 1 p-order signal and L-2 zeros according to the position of the p-order signal in the p-order signal vector to form a signal vector which belongs to all users, and the base station sends the signal vector to the users; executing step (16) after all signal vectors belonging to all users are transmitted by the base station;
(13) judging whether all user sets in the multiple-input single-output broadcast channel MISO-BC system are selected or not, and if so, executing the step (21); otherwise, executing step (10);
(14) Dividing the number of p-order signal vectors of the selected set of users by
Obtaining a quotient q and a remainder z; if the remainder z is equal to 0, performing step (15); otherwise, executing step (16);
(15) the base station sends to the users the signal vectors belonging to the selected set of users:
in each time slot that the base station sends a signal vector belonging to the selected user set to the user, the base station sequentially takes out L-p order signals and p-1 zeros according to the order of the p order signals in the p order signal vector to form a signal vector belonging to the selected user set, and the base station sends the signal vector to the user; after all signal vectors belonging to the selected user set are transmitted by the base station, executing the step (17);
(16) the base station sends to the users the signal vectors belonging to the selected set of users and the signal vectors belonging to all users:
in each time slot of the first q time slots of q + z time slots for which the base station sends signal vectors belonging to all users and signal vectors belonging to all users to the users, the base station sequentially takes out L-p signals and p-1 zeros according to the order of the p signals in the p signal vectors to form a signal vector belonging to a selected user set, and the base station sends the signal vector to the users; in each time slot of the last z time slots of q + z time slots for which the base station sends signal vectors belonging to all users and signal vectors belonging to all users to the users, the base station sequentially takes out 1 p-order signal and L-2 zeros to form a signal vector belonging to all users according to the order of the p-order signal in the p-order signal vector, and the base station sends the signal vector to the users; executing step (17) after the signal vectors belonging to all users and the signal vectors belonging to all users are all transmitted by the base station;
(17) Judging whether all user sets in the multiple-input single-output broadcast channel MISO-BC system are selected or not, if so, executing the step (18); otherwise, executing step (10);
(18) generating a slot combination of multicast slots for base station transmit signal vectors:
arbitrary p +1 different time slots in the multicast time slot of the signal vector sent by the base station form a time slot combination, and the time slots are generated together
A time slot combination; wherein! Representing a factorial operation;
(19) the base station selects a time slot combination, and generates a p +1 order signal vector by using channel state information CSIT at a delay transmitter:
(19a) randomly selecting a combination different from the previously selected time slot combination from all time slot combinations;
(19b) judging whether all users in p +1 time slots contained in the selected combination contain p +1 different users or not; if yes, the step (19c) is executed after the p +1 users form a user set; otherwise, executing step (19 a);
(19c) the base station receives the channel state information CSIT at the delay transmitter fed back by the user and utilizes a formula
Constructing signals received by unselected users of each time slot in p +1 time slots contained in the selected combination; wherein, ymSignal representing reception of unselected users in the m-th time slot, h mChannel vectors representing the m-th slot unselected users, T represents the transpose operation, xmRepresenting a signal vector transmitted by the base station at the mth time slot;
(19d) the base station constructs a p +1 order signal vector by using a formula o-rs; wherein, o represents a p +1 order signal vector constructed by the base station, the p +1 order signal in the p +1 order signal vector belongs to a user set in a selected time slot combination, r represents a p order signal coefficient matrix artificially set in the base station, r ═ E f, E represents a unit matrix of p rows and p columns, f represents a column vector of p rows and 1 columns with the first element of 1 and other elements of 0, and s represents a signal vector formed by signals received by p +1 unselected users according to time slot numbers in p +1 time slots contained in the selected combination;
(20) judging whether all time slot combinations are selected in the multicast time slots of the signal vectors sent by the base station, if so, adding 1 to the value of the highest order p of the signal vectors generated by the base station and then executing the step (7); otherwise, executing step (18);
(21) interference received by a user is eliminated:
each user of the multiple-input single-output broadcast channel MISO-BC system multiplies the symbol of the sub-file in the buffer of the user and the signal received by the user in the time slot with the order of the signal vector less than p sent by the base station by the corresponding coefficient in the signal received by the user in the time slot with the order of the signal vector sent by the base station to the user to generate an interference signal; and subtracting the generated interference signal from the signal received by the user in the time slot in which the base station sends the p-order signal vector to the user to obtain the signal after interference elimination.
Compared with the prior art, the invention has the following advantages:
first, the present invention judges the number of p-order signal vectors of a selected user by judging whether the highest order p of the signal vectors generated by a base station is equal to the total number of users, the base station sends the signal vectors belonging to a selected user set and the signal vectors belonging to all users to the users, so that the signal vectors transmitted by different base stations are flexibly constructed under the condition that the number of the p-order signal vectors of the selected user set is different, and the problems that the type of the transmitted signal vectors is single in the prior art and the alignment of the channel state information CSIT interference at a delay transmitter can be realized only under a simple scene are overcome, so that the present invention is applicable to the condition that the number of the p-order signal vectors of the selected user set is different under the condition of multi-input single-output MISO-BC of multiple users, and the application range is expanded.
Secondly, the base station sends the second-order signal vector constructed by the linear combination method, so that the total number of the base station antennas required to be used is reduced, the defect that the communication resources of the antennas are wasted because the total number of the base station antennas required to be used is greater than or equal to the total number of the user antennas in the prior art is overcome, the method is suitable for the condition that the total number of the base station antennas is less than the total number of the user antennas, and the antenna resources of the base station are saved.
Drawings
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a graph showing the results of a simulation experiment according to the present invention.
Detailed Description
The present invention is described in further detail below with reference to the attached drawings.
The specific steps of the present invention will be described in further detail with reference to fig. 1.
Dividing each file of N-3 files contained in a base station side database into 3 sub-files with equal size and without mutual intersection, and configuring 1 antenna and 1 buffer for each user; each user caches the subfiles according to rules; the 3 files contained in the base station side database are W1、W2、W3By WnRepresenting the nth file in the database; in a file W1For example, W1The file is divided into 3 sub-files (W)1)1、(W1)2、(W1)3(ii) a Wherein (W)1)1 Presentation document W 11 st sub-file, (W)1)2 Presentation document W 12 nd sub-file, (W)1)3Presentation document W1The 3 rd sub-file of (1); one subfile of each file in the database at the base station side is stored in the user buffer, the number of the subfile is the same as the user number, and L is 3 to represent the total number of users; the base station side database is a file database connected with the base station through an optical fiber, and the information type contained in each file in the database is one of four types, namely image, video, sound and character. The user is connected with the base station through a wireless network, and the user needs to take the database file through the transmitter; the user has global instantaneous channel state information, and the base station has channel state information at the transmitter with a time slot delay CSIT; the channel being time-varying, the channel of the next time slot The state is different from the channel state of the time slot; the rule means that the subfiles of each file are numbered from small to large, one subfile is sequentially extracted from the subfiles of each file according to the number, and all the subfiles with the same number form a subfile set; numbering each subfile set from small to large, and numbering the user from small to large; and putting the subfiles with the same number as the user in all the subfile sets into the buffer of the user. RxjDenotes the jth user, with 1 st user Rx1For example, Rx1Has a sub-file (W) placed in the buffer1)1、(W2)1、(W3)1(ii) a At this time, the user does not specify which file of the base station side database the user needs.
And 2, the base station sends the second-order signal vector constructed by the linear combination method to the user.
And step 2, summing the symbols at the same position in the 2 sub-files required by the selected user in each time slot to form a second-order signal. For example, the user selected in the 1 st slot is Rx1、Rx2，Rx1Has subfiles (W) in the buffer2)1The subfile is Rx 2What is needed; because of Rx2The file of the requirement is W2And Rx are2Has subfiles (W) in the buffer2)2Also, a subfile (W) is required2)1、(W2)3Therefore Rx1Sub-file (W) in the buffer of (2)2)1Is Rx2On demand; similarly, Rx2Has subfiles (W) in the buffer1)2The subfile is Rx1Is required. a (1) represents a 1 st second-order signal, and a (1) ═ W1)2,1+(W2)1,1(ii) a Wherein (W)1)2,1Representation subfile (W)1)21 st symbol, (W)2)1,1Representation subfile (W)2)1The 1 st symbol of (1).
And step 3, sequentially combining the second-order signals with the same number of L-1-2 antennas configured by the base station according to the sequence of the second-order signals to form a second-order signal vector transmitted by the base station. Taking the 1 st time slot as an example, since the number of antennas of the base station is L-1 ═ 2, the second-order signals a (1) and a (2) are taken out, and the vector of the signals transmitted by the base station is [ a (1) a (2)]T(ii) a Where a (1) represents the 1 st second-order signal, a (2) represents the 2 nd second-order signal, and T represents transposition.
And step 4, the base station sends the second-order signal vector to the user.
And 4, generating a time slot combination for sending the second-order signal vector to the user by the base station.
Transmitting second-order signal vectors from base station to user 
Randomly selecting three different time slots in each time slot to form a time slot combination, and obtaining the time slots in total
And (4) combining time slots. In this embodiment, the generated slot combination is { 1 st slot, 2 nd slot, 3 rd slot }.
And step 5, the base station selects a time slot combination and generates a third-order signal by using the channel state information CSIT at the delay transmitter.
And step 1, randomly selecting a time slot combination which is different from the previously selected time slot combination from all the time slot combinations.
b(1)＝y1+y3，
b(2)＝y2。
And 8, the base station sends the highest-order signal vector to the user.
In each time slot that the base station sends the highest order signal vector to the user, the base station sequentially takes out 1 p order signal and L-2 zeros according to the order of the p order signal in the p order signal vector to form a highest order signal vector, and the base station sends the signal vector to the user; after all the highest order signal vectors are transmitted by the base station, step 21 is performed. In this embodiment, the base station generates only one third-order signal vector, which includes the third-order signals b (1) and b (2); in the 1 st time slot of the p-order signal vector of the selected user set sent to the user by the base station, the signal vector constructed by the base station is [ b (1) 0% ]T(ii) a In the 1 st time slot of the p-order signal vector of the selected user set sent to the users by the base station, the signal vector constructed by the base station is [ b (2)0 [ ]]T。
And 9, generating a user set.
Selecting users with the same number as the highest order p of a signal vector from all users of a multi-input single-output broadcast channel MISO-BC system as a user set to obtain the users together
A set of individual users; wherein! Indicating a factorial operation.
And 10, selecting a user set.
Randomly selecting one user set different from the previously selected user set from all the user sets.
Step 11, judging whether the number of the p-order signal vectors of the selected user set is less than or equal to
If yes, go to step 12; otherwise, step 14 is performed. When the number of the p-order signal vectors of the selected user set is less than
Meaning that the number of p-order signal vectors of the selected set of users is insufficient, which affects the base station's construction of the transmitted signal vectorsThe method.
Step 12, the base station sends signal vectors belonging to all users to the users.
In each time slot of the signal vector which belongs to all users and is sent to the users by the base station, the base station sequentially takes out 1 p-order signal and L-2 zeros according to the position of the p-order signal in the p-order signal vector to form a signal vector which belongs to all users, and the base station sends the signal vector to the users; after all the signal vectors belonging to all the users are transmitted by the base station, step 16 is executed.
Step 13, judging whether all user sets in the multiple-input single-output broadcast channel MISO-BC system are selected, if so, executing step 21; otherwise, step 10 is performed.
Step 14, dividing the number of p-order signal vectors of the selected user set by
Obtaining a quotient q and a remainder z; if the remainder z is equal to 0, go to step 15; otherwise, step 16 is performed. So that the number of p-order signal vectors of the selected user set is divided by
Because these p-order signal vectors are divided into two parts, the p-order signal vectors of different parts being used for signal vectors transmitted by base stations constructed in different ways.
Step 15, the base station sends the signal vector belonging to the selected user set to the user.
In each time slot that the base station sends a signal vector belonging to the selected user set to the user, the base station sequentially takes out L-p order signals and p-1 zeros according to the order of the p order signals in the p order signal vector to form a signal vector belonging to the selected user set, and the base station sends the signal vector to the user; after all signal vectors belonging to the selected user set are transmitted by the base station, step 17 is performed.
Step 16, the base station sends the signal vectors belonging to the selected user set and the signal vectors belonging to all users to the users.
In each time slot of the first q time slots of q + z time slots for which the base station sends signal vectors belonging to all users and signal vectors belonging to all users to the users, the base station sequentially takes out L-p signals and p-1 zeros according to the order of the p signals in the p signal vectors to form a signal vector belonging to a selected user set, and the base station sends the signal vector to the users; in each time slot of the last z time slots of q + z time slots for which the base station sends signal vectors belonging to all users and signal vectors belonging to all users to the users, the base station sequentially takes out 1 p-order signal and L-2 zeros to form a signal vector belonging to all users according to the order of the p-order signal in the p-order signal vector, and the base station sends the signal vector to the users; after all the signal vectors belonging to all the users and the signal vectors belonging to all the users are transmitted by the base station, step 17 is executed.
Step 17, judging whether all user sets in the multiple-input single-output broadcast channel MISO-BC system are selected, if so, executing step 18; otherwise, step 10 is performed.
Step 18, generating a time slot combination of the multicast time slots of the base station transmitting signal vectors.
Arbitrary p +1 different time slots in the multicast time slot of the signal vector sent by the base station form a time slot combination, and the time slots are generated together 
A time slot combination; wherein! Representing a factorial operation; the multicast slots for transmitting the signal vectors from the base station refer to the slots used by the base station to transmit the signal vectors belonging to the selected user set to the users in step 15 for each user set and the first q slots of q + z slots for transmitting the signal vectors belonging to the selected user set and the signal vectors belonging to the entire users to the users in step 16.
Step 19, the base station selects a time slot combination, and generates a p +1 order signal vector by using the channel state information CSIT at the delay transmitter.
In step 1, a combination different from the previously selected time slot combination is randomly selected from all time slot combinations.
Step 20, judging whether all time slot combinations are selected in the multicast time slots of the signal vectors sent by the base station, if so, adding 1 to the value of the highest order p of the signal vectors generated by the base station, and then executing step 7; otherwise, go to step 18; the multicast slots for transmitting the signal vectors from the base station refer to the slots used by the base station to transmit the signal vectors belonging to the selected user set to the users in step 15 for each user set and the first q slots of q + z slots for transmitting the signal vectors belonging to the selected user set and the signal vectors belonging to the entire users to the users in step 16.
And step 21, eliminating the interference received by the user.
Each user of the multiple-input single-output broadcast channel MISO-BC system multiplies the symbol of the sub-file in the buffer of the user and the signal received by the user in the time slot with the order of the signal vector less than p sent by the base station by the corresponding coefficient in the signal received by the user in the time slot with the order of the signal vector sent by the base station to the user to generate an interference signal; and subtracting the generated interference signal from the signal received by the user in the time slot in which the base station sends the p-order signal vector to the user to obtain the signal after interference elimination.
The effect of the present invention is further explained by combining the simulation experiment as follows:
1. simulation experiment conditions are as follows:
the hardware platform of the simulation experiment of the invention is as follows: the processor is an Intel i 75930 k CPU, the main frequency is 3.5GHz, and the memory is 16 GB.
The software of the simulation experiment of the invention is as follows: windows 10 operating system and Matlab R2018b emulation software.
2. Simulation content and result analysis:
in the simulation experiment, the applicant utilizes Matlab R2018b simulation software to simulate a multi-input multi-output broadcast channel MISO-BC system in a programming mode, and the multi-input multi-output broadcast channel MISO-BC system comprises a file database, a plurality of users and a base station. The file database size is 10GB, in which 20 video files of mp4 type of 500MB size are configured. Each user simulated in the system is respectively configured with 1 antenna and 1 buffer.
The simulation experiment of the invention adopts the method of the invention and a prior art (delay CSIT interference alignment method) to carry out 9 transmission experiments on files in a file database simulated in a MISO-BC system, the number of users simulated in each simulation experiment is 2, 3, 4, 5, 6, 7, 8, 9 and 10 in sequence, the number of antennas configured in a base station simulated in each simulation experiment is 1, 2, 3, 4, 5, 6, 7, 8 and 9 in sequence, the number of files transmitted in each simulation experiment is the same as the number of users, and the total freedom degree of the MISO-BC system when the number of users is 2, 3, 4, 5, 6, 7, 8 and 9 and 10 respectively is obtained.
In the simulation experiment, one prior art adopted refers to:
the delayed CSIT interference alignment method is that m.a.maddah-Ali and d.tse are assigned in "complex stator channel state Information is static very useful, IEEE Transactions on Information Theory 2012, 58 (7): 4418-4431 ", the method for aligning channel state information interference at a delayed transmitter is abbreviated as a delayed CSIT interference alignment method.
The total degrees of freedom of different MISO-BC systems obtained by performing 9 times of experiments respectively by using two methods in the simulation experiment of the invention are plotted as a curve, as shown in FIG. 2.
The abscissa in fig. 2 represents the number of users in the MISO-BC system, the ordinate represents the total degree of freedom of the MISO-BC system, the curve marked with squares represents the curve of the simulation result using the prior art delayed CSIT interference alignment method, and the curve marked with circles represents the curve of the simulation result using the method of the present invention.
As can be seen from the two simulation curves in fig. 2, the total degree of freedom of the MISO-BC system increases linearly as the number of users increases. When the number of users is 2, 3, 4, 5, 6, 7, 8, 9 and 10 respectively, the total degree of freedom of the MISO-BC system obtained by the method is higher than that of the MISO-BC system obtained by the delayed CSIT interference alignment method.
Simulation experiment results show that under the condition that the number of users is the same, the total degree of freedom of the MISO-BC system obtained by the method is higher than that of the MISO-BC system obtained by the delay CSIT interference alignment method; the method of the invention is a high-efficiency data transmission method.
Claims (8)
1. A delayed CSIT interference alignment method under MISO-BC using buffer memory is characterized in that a base station in a multiple input single output broadcast channel MISO-BC system transmits a second order signal vector constructed by a linear combination method to users, judges whether the highest order p of the signal vector generated by the base station is equal to the total number of users, judges the number of the p order signal vectors of a selected user set, and the base station transmits the signal vectors belonging to the selected user set and the signal vectors belonging to all the users to the users, the method comprises the following steps:
(1) Setting cache content:
dividing each file of N files contained in a base station side database into J sub-files with equal size and mutual disjunction, and configuring 1 antenna and 1 buffer for each user; each user caches the subfiles according to rules; one subfile of each file in the database at the base station side is stored in the user buffer, the number of the subfile is the same as the user number, L represents the total number of users, L is larger than 1, the value of N is equal to the total number of users L, and the value of J is equal to the total number of users L;
(2) the base station sends a second-order signal vector constructed by a linear combination method to the user:
(2a) transmitting second order signal vectors to users at base station
Selecting two users from all users according to a polling method in each time slot; wherein, B represents the total number of symbols contained in each file in the base station side database, and B is L2-L, L representing the total number of users;
(2b) summing symbols at the same position in 2 sub-files required by the user selected from each time slot to form a second-order signal;
(2c) sequentially combining the L-1 second-order signals with the same number of antennas configured by the base station according to the sequence of the second-order signals to form a second-order signal vector transmitted by the base station;
(2d) The base station sends the second-order signal vector to the user;
(3) judging whether the total number of the users is equal to 2, if so, executing a step (21); otherwise, executing the step (4);
(4) generating time slot combination of a base station transmitting a second-order signal vector to a user:
transmitting second-order signal vectors from base station to user
In each time slot, arbitrarily taking three different time slots to form a time slot combination to obtain
A time slot combination;
(5) the base station selects a time slot combination, and generates a third-order signal by using channel state information CSIT at a delay transmitter:
(5a) randomly selecting a time slot combination which is different from the previously selected time slot combination from all the time slot combinations;
(5b) judging whether all users in three time slots contained in the selected time slot combination contain three different users or not; if yes, forming the three users into a user set and then executing the step (5 c); otherwise, executing the step (5 a);
(5c) the base station receives the channel state information CSIT at the delayed transmitter fed back by the user and utilizes a formula
Constructing signals received by unselected users of each time slot in three time slots contained in the selected time slot combination; wherein, ymSignals, h, representing reception of unselected users in the m-th time slotmChannel vectors representing unselected users in the mth slot, T represents a transpose operation, x mRepresenting a signal vector transmitted by the base station at the mth time slot;
(5d) the base station constructs a third-order signal vector by using a formula u-kv; wherein u represents a third order signal vector constructed by the base station, the third order signal in the third order signal vector belongs to a user set in the selected time slot combination, k represents a second order signal coefficient matrix artificially set in the base station,
v represents a signal vector formed by signals received by three unselected users in three time slots contained in the selected time slot combination according to the time slot serial number;
(6) determining a second order signal vector to be transmitted to a user at a base stationIs/are as follows
Whether all time slot combinations are selected in each time slot or not is judged, if yes, the base station generates a third-order signal vector of each time slot combination, and then the value of the highest order p of the signal vector is set to be 3 and then the step (7) is executed; otherwise, executing the step (5);
(7) judging whether the value of the highest order p of the signal vector is equal to the total number of users, if so, executing the step (8); otherwise, executing step (9);
(8) the base station sends the highest order signal vector to the user:
in each time slot that the base station sends the highest order signal vector to the user, the base station sequentially takes out 1 p order signal and L-2 zeros according to the order of the p order signal in the p order signal vector to form a highest order signal vector, and the base station sends the signal vector to the user; after all the highest-order signal vectors are sent by the base station, executing the step (21);
(9) Generating a user set:
selecting users with the same number as the highest order p of a signal vector from all users of a multi-input single-output broadcast channel MISO-BC system as a user set to obtain the users together
A set of individual users; wherein! Representing a factorial operation;
(10) selecting a user set:
randomly selecting a user set different from the previously selected user set from all the user sets;
(11) determining whether the number of p-order signal vectors of the selected user set is less than
If yes, executing step (12); otherwise, executing step (14);
(12) the base station sends signal vectors belonging to all users to the users:
in each time slot of the signal vector which belongs to all users and is sent to the users by the base station, the base station sequentially takes out 1 p-order signal and L-2 zeros according to the position of the p-order signal in the p-order signal vector to form a signal vector which belongs to all users, and the base station sends the signal vector to the users; executing step (16) after all signal vectors belonging to all users are transmitted by the base station;
(13) judging whether all user sets in the multiple-input single-output broadcast channel MISO-BC system are selected or not, and if so, executing the step (21); otherwise, executing step (10);
(14) Dividing the number of p-order signal vectors of the selected set of users by
Obtaining a quotient q and a remainder z; if the remainder z is equal to 0, executing step (15); otherwise, executing step (16);
(15) the base station sends to the users the signal vectors belonging to the selected set of users:
in each time slot that the base station sends a signal vector belonging to the selected user set to the user, the base station sequentially takes out L-p order signals and p-1 zeros according to the order of the p order signals in the p order signal vector to form a signal vector belonging to the selected user set, and the base station sends the signal vector to the user; after all signal vectors belonging to the selected user set are transmitted by the base station, executing the step (17);
(16) the base station sends to the users the signal vectors belonging to the selected set of users and the signal vectors belonging to all users:
in each time slot of the first q time slots of q + z time slots for which the base station sends signal vectors belonging to all users and signal vectors belonging to all users to the users, the base station sequentially takes out L-p signals and p-1 zeros according to the order of the p signals in the p signal vectors to form a signal vector belonging to a selected user set, and the base station sends the signal vector to the users; in each time slot of the last z time slots of q + z time slots for which the base station sends signal vectors belonging to all users and signal vectors belonging to all users to the users, the base station sequentially takes out 1 p-order signal and L-2 zeros to form a signal vector belonging to all users according to the order of the p-order signal in the p-order signal vector, and the base station sends the signal vector to the users; executing step (17) after the signal vectors belonging to all users and the signal vectors belonging to all users are all transmitted by the base station;
(17) Judging whether all user sets in the multiple-input single-output broadcast channel MISO-BC system are selected or not, if so, executing the step (18); otherwise, executing step (10);
(18) generating a slot combination of multicast slots for base station transmit signal vectors:
arbitrary p +1 different time slots in the multicast time slot of the signal vector sent by the base station form a time slot combination, and the time slots are generated together
A time slot combination; wherein! Representing a factorial operation;
(19) the base station selects a time slot combination, and generates a p +1 order signal vector by using channel state information CSIT at a delay transmitter:
(19a) randomly selecting a combination different from the previously selected time slot combination from all time slot combinations;
(19b) judging whether all users in p +1 time slots contained in the selected combination contain p +1 different users or not; if yes, the step (19c) is executed after the p +1 users form a user set; otherwise, executing step (19 a);
(19c) the base station receives the channel state information CSIT at the delayed transmitter fed back by the user and utilizes a formula
Constructing signals received by unselected users of each time slot in p +1 time slots contained in the selected combination; wherein, ymSignals, h, representing reception of unselected users in the m-th time slot mChannel vectors representing unselected users in the mth slot, T represents a transpose operation, xmRepresenting a signal vector transmitted by the base station at the mth time slot;
(19d) the base station constructs a p +1 order signal vector by using a formula o-rs; wherein, o represents a p +1 order signal vector constructed by the base station, the p +1 order signal in the p +1 order signal vector belongs to a user set in a selected time slot combination, r represents a p order signal coefficient matrix artificially set in the base station, r ═ E f, E represents a unit matrix of p rows and p columns, f represents a column vector of p rows and 1 columns with the first element of 1 and other elements of 0, and s represents a signal vector formed by signals received by p +1 unselected users according to time slot numbers in p +1 time slots contained in the selected combination;
(20) judging whether all time slot combinations are selected in the multicast time slots of the signal vectors sent by the base station, if so, adding 1 to the value of the highest order p of the signal vectors generated by the base station and then executing the step (7); otherwise, executing step (18);
(21) interference received by a user is eliminated:
each user of the multiple-input single-output broadcast channel MISO-BC system multiplies the symbol of the sub-file in the buffer of the user and the signal received by the user in the time slot with the order of the signal vector less than p sent by the base station by the corresponding coefficient in the signal received by the user in the time slot with the order of the signal vector sent by the base station to the user to generate an interference signal; and subtracting the generated interference signal from the signal received by the user in the time slot in which the base station sends the p-order signal vector to the user to obtain the signal after interference elimination.
2. The method for delaying CSIT interference alignment under MISO-BC using buffer of claim 1, wherein the database at the base station side in step (1) and step (2a) is a file database connected to the base station through an optical fiber, and each file in the database contains information of one of four types, i.e. image, video, sound and text.
3. The method for delaying CSIT interference alignment under MISO-BC using cache according to claim 1, wherein the rule in step (1) is that the subfiles of each file are numbered from small to large, one subfile is sequentially extracted from the subfiles of each file according to the number, and all the subfiles with the same number are combined into one subfile set; numbering each subfile set from small to large, and numbering the user from small to large; and putting the subfiles with the same number as the user in all the subfile sets into the buffer of the user.
4. The method for delaying CSIT interference alignment under MISO-BC using cache according to claim 1, wherein the polling in step (2a) is performed by selecting users in turn in each time slot, randomly selecting two users from all users each time, and determining whether there are two users of the selected users that are the same as the previously selected users; if yes, randomly selecting two users from all users again in the time slot until the selected user is different from the previous selected user by one user; if two users different from the previously selected user in one user can not be selected, the previously selected user is changed into the unselected user, and two users are randomly selected again from all the users in the time slot until the selected user is different from the previously selected user in one user.
5. The MISO-BC delay-less CSIT interference alignment method using buffer storage according to claim 1, wherein the symbol in step (2a), step (2b) and step (21) is a point mapped onto a constellation diagram by a digital modulation method from information bits in a file, and is a basic unit constituting the file.
6. The method of claim 1, wherein the step (5c) and the step (5d) of delaying the CSIT interference alignment under MISO-BC using buffering indicate that the non-selected user is transmitting a second-order signal to the user at the base station
Three different selected users are in three time slots contained in each time slot combination selected in the time slots, two of the users are selected in each time slot of the three selected time slots, and the rest users are unselected users.
7. The method for delayed CSIT interference alignment under MISO-BC using buffering according to claim 1, wherein the multicast slots for transmitting signal vectors from the base station in step (18) and step (20) refer to the slots used by the base station to transmit signal vectors belonging to the selected user set to users in step (15) for each user set and the first q slots of q + z slots for transmitting signal vectors belonging to the selected user set and signal vectors belonging to all users to users in step (16).
8. The method of claim 1, wherein the delayed CSIT interference alignment under MISO-BC using buffering is performed in step (19c) and step (19d), and wherein the non-selected users are p +1 different selected users in p +1 slots included in each slot combination of the multicast slot for transmitting the signal vector by the base station, p users are included in the selected user set in each slot of the selected p +1 slots, and the remaining one user is the non-selected user.
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