Disclosure of Invention
In order to solve the above-mentioned problems in the prior art, the present invention provides a joint resource allocation method that minimizes the weighted delay energy. The technical problems to be solved by the invention are realized by the following technical scheme:
The invention provides a joint resource allocation method for minimizing weighted delay energy, which is applied to an MEC server in a system of mixing NOMA-MEC, and comprises the following steps:
S1, acquiring time delay requirements of users in a coverage area, and dividing the users into sensitive user groups and non-sensitive user groups according to the time delay requirements;
s2, adding virtual users into the sensitive user group so that the number of the members of the sensitive user group is the same as that of the members of the non-sensitive user group, and combining the members of the sensitive user group with the members of the non-sensitive user group to form a plurality of different ST units;
Wherein each sub-channel resource can only be invoked by one ST element;
S3, respectively creating three initial matching lists for recording unmatched sensitive users, unmatched non-sensitive users and unmatched sub-channel resources;
S4, taking the distribution power of each member of each ST unit as a variable, taking the minimum weighted delay energy of each ST unit under each sub-channel resource as a constraint problem, calculating the weighted delay energy of each ST unit under each sub-channel resource, sequencing the weighted delay energy from small to large, and forming a preference list of the channel resource by the sequenced weighted delay energy;
S5, aiming at any unmatched sub-channel resource in the initial matching list, trying to match ST units from the best preference to the worst preference according to the sequence of weighted delay energy recorded in the preference list, if the unmatched sub-channel resource is successfully matched with the ST units, deleting corresponding records from the three initial matching lists, and if the worst preference is not successfully matched, carrying out matching cut-off;
s6, obtaining the minimum weighted delay energy result of the matching result of the ST unit and the sub-channel resource according to the matching result of the ST unit and the sub-channel resource.
The invention has the beneficial effects that:
The invention provides a joint resource allocation method for minimizing weighted delay energy, which comprehensively considers a NOMA user clustering strategy, scheduling inter-cluster frequency band allocation and controlling intra-cluster power allocation, groups users through delay requirements, further uses the allocation power of the users as a variable and the minimized weighted delay energy as a constraint problem to obtain the weighted energy of each ST unit under sub-channel resources. And then, matching the ST unit with the sub-channel resources through multiple iterations, and finding out the most suitable resource allocation according to the delay requirement by each user after the matching is completed, so as to realize the optimal resource allocation. Compared with the prior art, the method and the device have the advantages of resource saving, higher resource allocation efficiency, accurate resource allocation and higher user experience.
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but embodiments of the present invention are not limited thereto.
The joint resource allocation method for minimizing the weighted delay energy is applied to an MEC server in a system of mixing NOMA-MEC. As shown in fig. 1, the system includes 1 MEC server, M sensitive users and N non-sensitive users, and K sub-channel resources. The system is characterized in that each user has a calculation task to be unloaded, the MEC server can acquire channel information and user information to be used as the basis of strategy scheduling, each sub-channel resource can only be used by one ST unit, and the calculation time of the calculation task at the MEC server and the time returned by the calculation result are ignored.
As shown in fig. 2, the joint resource allocation method for minimizing weighted delay energy provided by the present invention includes:
S1, acquiring time delay requirements of users in a coverage area, and dividing the users into sensitive user groups and non-sensitive user groups according to the time delay requirements;
Wherein the sensitive user group and the non-sensitive user group are respectively marked as Us＝{us1,us2,...,usN}、Ut＝{ut1,ut2,...,utN}; sensitive group user numbers are marked as M, and the non-sensitive group user numbers are marked as N, wherein M is less than or equal to N.
S2, adding virtual users into the sensitive user group so that the number of the members of the sensitive user group is the same as that of the members of the non-sensitive user group, and combining the members of the sensitive user group with the members of the non-sensitive user group to form a plurality of different ST units;
The method comprises the steps of receiving a sub-channel resource, wherein each sub-channel resource can only be called by one ST unit, adding N-M virtual users in a sensitive user group, and combining N sensitive users and N non-sensitive users in a network to form N multiplied by N different ST units. For the purpose of describing the proposed matching algorithm, a user group consisting of 1 sensitive user and 1 non-sensitive user is defined as 1ST element. Note that ST units are not independent, as they may contain the same sensitive or non-sensitive users.
S3, respectively creating three initial matching lists for recording unmatched sensitive users, unmatched non-sensitive users and unmatched sub-channel resources;
specifically, S3 includes:
S31, taking each sub-channel resource as an unmatched sub-channel resource, and generating an initial matching list for recording the unmatched sub-channel resources;
s32, taking the non-sensitive user corresponding to each ST unit as a non-matched non-sensitive user, and generating an initial matching list for recording the non-matched non-sensitive users;
S33, taking the sensitive user corresponding to each ST unit as an unmatched sensitive user, and generating an initial matching list for recording the unmatched sensitive users.
It should be noted that the three initial matching lists are SUmatchlist,TUmatchlist,SCmatchlist to record a flag of whether each of the sensitive user, the non-sensitive user, and the subchannel match, and default that all members and subchannel resources are not matched at the initial time.
S4, taking the distribution power of each member of each ST unit as a variable, taking the minimum weighted delay energy of each ST unit under each sub-channel resource as an objective function, calculating the weighted delay energy of each ST unit under each sub-channel resource, sequencing the weighted delay energy from small to large, and forming a preference list of the channel resource by the sequenced weighted delay energy;
Specifically, S4 includes:
S41, taking the allocated power Psi of the sensitive user usi and the allocated power Ptj of the non-sensitive user utj in each ST unit as variables;
S42, taking the weighted delay energy DETij of each ST unit under each sub-channel resource as an objective function, taking the minimized objective function as a constraint problem, calculating the weighted delay energy of each ST unit under each sub-channel resource under the constraint condition, sequencing the weighted delay energy from small to large, and forming a preference list of the channel resource by the sequenced weighted delay energy.
When the MEC device receives the NOMA signal, the SIC receiver will demodulate, and the channel gains of the sensitive user usi and the non-sensitive user utj and the base station on channel k can be expressed as hi,k and gj,k. In the SIC demodulation stage, we choose to demodulate the delay insensitive user utj before demodulating the sensitive user usi. It is thus apparent that there are two phases of the data offloading process for user utj, one being the NOMA transfer phase of the shared channel with user usi, and the OMA transfer phase being entered after the offloading of the computing tasks by user usi is completed. Thus, the two data transfer rates of the NOMA transfer phase and the OMA transfer phase exist for user utj throughout the data transfer process, expressed as:
For user usi, its data transmission rate can be expressed as:
Wherein Bk denotes the bandwidth of channel k and Psi、Ptj denotes user usi、utj in NOMA phase, respectively
For an ST element, the total time of its data transmission process can be divided into NOMA transmission phase and OMA transmission phase, expressed as:
where Dsi、Dtj represents the amount of data that the user usi、utj task offloads, the total time can be expressed as:
τij＝τNOMA+τOMA
the energy consumed in the whole process can be expressed as two phases, and the total energy consumed is:
Eij＝(Psi+Ptj)×τNOMA+Ptj×τOMA
The weighted delay energy can be expressed as:
DETij＝c1τij+c2Eij
Where c= (c1,c2) is a weighting coefficient, the constraint problem can be expressed as:
Constraint problem:
constraint conditions:
C1:τNOMA≤Tsi
C2:τNOMA+τOMA≤Ttj
C3:0≤Psi≤Pmax
C4:0≤Ptj≤Pmax
the objective function is as follows:
delta is the standard deviation of noise, alpha is an artificial parameter introduced for simplifying the expression, and the value of the artificial parameter can be expressed as follows:
It can be seen that the objective function is not convex and the optimization variables are highly coupled. To simplify the optimization process, the optimization problem is transformed as follows, which can be obtained according to known conditions:
wherein:
after transformation, the objective function can be simplified as:
wherein:
S5, aiming at any unmatched sub-channel resource in the initial matching list, trying to match ST units from the best preference to the worst preference according to the sequence of weighted delay energy recorded in the preference list, if the unmatched sub-channel resource is successfully matched with the ST units, deleting corresponding records from the three initial matching lists, and if the worst preference is not successfully matched, carrying out matching cut-off;
specifically, referring to fig. 3, s5 includes:
S51, in each iteration process, aiming at any unmatched subchannel resource k in the initial matching list, sending a matching request from a rejected ST unit in the previous iteration process according to the descending order recorded by the preference list;
s52, if the member of the ST unit receiving the matching request never receives any quotation before the current iteration, temporarily matching any unmatched sub-channel resource k with the ST unit;
S53, if at least one member usi or utj of the ST unit is matched with the sub-channel resource before the current iteration, further judging whether the non-matched sub-channel resource is optimally matched with the ST unit;
S54, if the unmatched sub-channel resource and the ST unit are optimally matched in S53, the sub-channel resource k preempts the ST unit and matches with the ST unit so as to lead the ST unit to reject the previous matching, and an alpha type blocking triplet formed by the ST unit and the sub-channel resource is obtained;
S55, if the unmatched sub-channel resource in S53 is not optimally matched with the ST unit, sending a matching request to the next ST unit of the ST unit, and executing S52 to S55;
S56, eliminating the matched ST units and sub-channel resources from the initial matching table, and re-recording the preempted ST units in the initial matching table;
and S57, repeating S51 to S56 in each iteration process until all ST units are matched, or ending the iteration until the last ST unit, and obtaining a matching result of the ST unit and the sub-channel resource.
S6, obtaining the minimum weighted delay energy result of the matching result of the ST unit and the sub-channel resource according to the matching result of the ST unit and the sub-channel resource.
Referring to fig. 3, from the start of the best preference, that is, the start of the ST with the smallest weighted delay energy until the end of the last ST, it is determined whether the first ST unit is occupied, if otherwise, it is determined that the unmatched sub-channel resource and the ST unit form the best match, then the users and sub-channel resources corresponding to the best match in the three initial matching lists are deleted, if any user exists in the first ST unit, it is further determined whether the unmatched sub-channel resource and the ST unit are the best match, if yes, the ST unit is preempted and an alpha-type blocking triplet is formed with the ST unit, and the preempted sub-channel resource is put back into the initial matching list, if the unmatched sub-channel resource and the ST unit are not the best match, then the ST unit is abandoned, the next ST unit is applied to be accessed until the last ST unit is blocked, and the matching result of the ST unit and the sub-channel resource is obtained.
Furthermore, each ST element temporarily retaining the subchannel k offers is not yet ready to actually accept the offer (match) because it still has the right to select a better offer in the next iteration if other subchannels are also proposed to it. When no sub-channels send an application to the ST element, this means that all sub-channels either match the ST element or are rejected by all ST elements, and the iteration stops.
Referring to fig. 4, fig. 4 is a graph of system weighted delay energy versus sensitive user delay for the present application. As can be seen from fig. 4, the weighted delay energy gradually increases with the increase of the time delay of the sensitive user in the conventional scheme, and the weighted delay energy obviously decreases with the increase of the time delay of the sensitive user in the application. Therefore, compared with the prior art, the method and the device have better resource allocation and higher user experience.
The invention provides a joint resource allocation method for minimizing weighted delay energy, which comprehensively considers a NOMA user clustering strategy, scheduling inter-cluster frequency band allocation and controlling intra-cluster power allocation, groups users through delay requirements, further uses the allocation power of the users as a variable and the minimized weighted delay energy as a constraint problem to obtain the weighted energy of each ST unit under sub-channel resources. And then, matching the ST unit with the sub-channel resources through multiple iterations, and finding out the most suitable resource allocation according to the delay requirement by each user after the matching is completed, so as to realize the optimal resource allocation. Compared with the prior art, the method and the device have the advantages of resource saving, higher resource allocation efficiency, accurate resource allocation and higher user experience.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
Although the application is described herein in connection with various embodiments, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed application, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the "a" or "an" does not exclude a plurality.
The foregoing is a further detailed description of the invention in connection with the preferred embodiments, and it is not intended that the invention be limited to the specific embodiments described. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the invention, and these should be considered to be within the scope of the invention.