CN115734252A - Cognitive wireless power supply network optimization method based on backscatter relay transmission - Google Patents
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Abstract
本发明公开了一种基于反向散射中继传输的认知无线供能网络优化方法,将认知无线供能网络的工作时隙分为中继阶段、反向散射数据传输阶段和能量捕获数据传输阶段,在中继阶段主发射机发送数据给主接收机,反向散射单元发射机采用反向散射模式中继主用户数据给主接收机,能量捕获单元发射机进行能量捕获;在反向散射数据传输阶段,主发射机发送数据给主接收机,反向散射单元发射机采用反向散射模式发送数据给反向散射接收机,能量捕获单元发射机进行能量捕获;在能量捕获数据传输阶段,主发射机休眠,能量捕获单元发射机利用捕获的能量传输数据给能量捕获接收机。本发明优化了各个阶段的持续时间,提高了数据传输的吞吐量。
The invention discloses a cognitive wireless energy supply network optimization method based on backscatter relay transmission, which divides the working time slot of the cognitive wireless energy supply network into a relay stage, a backscatter data transmission stage and energy capture data In the transmission phase, in the relay phase, the main transmitter sends data to the main receiver, the backscatter unit transmitter uses the backscatter mode to relay the main user data to the main receiver, and the energy capture unit transmitter performs energy capture; In the scatter data transmission stage, the main transmitter sends data to the main receiver, the backscatter unit transmitter uses the backscatter mode to send data to the backscatter receiver, and the energy capture unit transmitter performs energy capture; in the energy capture data transmission stage , the main transmitter is dormant, and the energy harvesting unit transmitter uses the captured energy to transmit data to the energy harvesting receiver. The invention optimizes the duration of each stage and improves the throughput of data transmission.
Description
技术领域technical field
本申请属于认知无线供能通信技术领域,尤其涉及一种基于反向散射中继传输的认知无线供能网络优化方法。The present application belongs to the technical field of cognitive wireless power supply communication, and in particular relates to a cognitive wireless power supply network optimization method based on backscatter relay transmission.
背景技术Background technique
在认知无线供能网络中,通常包含主用户和次级用户。主用户拥有频谱的授权,可以随时接入频谱。次级用户没有授权频谱,只能在授权频谱空闲时段伺机接入授权频谱。主用户通常有恒定的电源供电,例如电视、手机等。次级用户通常没有固定的电源供能,因此需要从周围环境中捕获能量,并将捕获到的能量存储到次级用户的可充电电池中。次级用户存储的能量供其在传输数据时使用。In a cognitive wireless power supply network, there are usually primary users and secondary users. The primary user has spectrum authorization and can access the spectrum at any time. Secondary users do not have licensed spectrum and can only opportunistically access the licensed spectrum during the idle period of the licensed spectrum. Primary users usually have a constant power supply, such as TV, mobile phone, etc. Secondary users usually do not have a fixed source of energy, so energy needs to be captured from the surrounding environment and stored in the secondary user's rechargeable battery. The energy stored by the secondary user is used when transmitting data.
此外,近年来反向散射技术由于其功耗低,已经在认知无线供能网络中得到广泛的研究。配备反向散射单元的设备可以通过反向散射网络中的射频信号来传输自己的数据,也可以做为反向散射中继设备,通过反向散射来进行中继。In addition, backscatter technology has been extensively studied in cognitive wireless powering networks due to its low power consumption in recent years. A device equipped with a backscatter unit can transmit its own data through the radio frequency signal in the backscatter network, or it can be used as a backscatter relay device to relay through backscatter.
在该网络中,如何分配次级用户何时进行反向散射中继、能量捕获和次级数据传输,以及分配多长时间给次级用户进行反向散射中继、能量捕获和次级数据传输以实现网络吞吐量最大化是需要考虑的主要问题。In this network, how to allocate when secondary users perform backscatter relay, energy harvesting, and secondary data transmission, and how long to allocate to secondary users for backscatter relay, energy harvesting, and secondary data transmission To maximize network throughput is the main issue that needs to be considered.
发明内容Contents of the invention
为了提升现有基于反向散射中继的认知无线供能网络中的吞吐量,本申请的目的是提供一种基于反向散射中继传输的认知无线供能网络吞吐量优化方法。该方法通过次级用户中继主用户数据,有效解决了网络的吞吐量最大化问题,提升了网络的频谱利用率,并且采用能量捕获技术和反向散射技术大大节省了网络的能耗。In order to improve the throughput of the existing cognitive wireless power supply network based on backscatter relay, the purpose of this application is to provide a throughput optimization method of the cognitive wireless power supply network based on backscatter relay transmission. This method relays primary user data through secondary users, effectively solves the problem of network throughput maximization, improves network spectrum utilization, and uses energy harvesting technology and backscattering technology to greatly save network energy consumption.
为了实现上述目的,本申请的技术方案如下:In order to achieve the above object, the technical scheme of the present application is as follows:
一种基于反向散射中继传输的认知无线供能网络优化方法,所述认知无线供能网络包括对应主用户的主发射机和主接收机,以及对应第一次级用户的配备能量捕获单元的次级发射机和能量捕获接收机,以及对应第二次级用户的配备反向散射单元的次级发射机和反向散射接收机,所述基于反向散射中继传输的认知无线供能网络优化方法,包括:A cognitive wireless energy supply network optimization method based on backscatter relay transmission, the cognitive wireless energy supply network includes a main transmitter and a main receiver corresponding to the main user, and an equipped energy corresponding to the first secondary user The secondary transmitter and energy harvesting receiver of the acquisition unit, and the secondary transmitter and backscatter receiver equipped with the backscatter unit corresponding to the second secondary user, said knowledge based on backscatter relay transmission A method for optimizing a wireless energy supply network, including:
将所述认知无线供能网络的工作时隙分为中继阶段、反向散射数据传输阶段和能量捕获数据传输阶段;Dividing the working time slots of the cognitive wireless energy supply network into a relay stage, a backscatter data transmission stage and an energy harvesting data transmission stage;
其中,在中继阶段主发射机发送数据给主接收机,配备反向散射单元的次级发射机采用反向散射模式中继主用户数据给主接收机,配备能量捕获单元的次级发射机进行能量捕获;Among them, in the relay stage, the main transmitter sends data to the main receiver, the secondary transmitter equipped with backscatter unit adopts the backscatter mode to relay the primary user data to the main receiver, and the secondary transmitter equipped with energy harvesting unit perform energy capture;
在反向散射数据传输阶段,主发射机发送数据给主接收机,配备反向散射单元的次级发射机采用反向散射模式发送数据给反向散射接收机,配备能量捕获单元的次级发射机进行能量捕获;In the backscatter data transmission phase, the primary transmitter sends data to the primary receiver, the secondary transmitter equipped with a backscatter unit sends data to the backscatter receiver in backscatter mode, and the secondary transmitter equipped with an energy harvesting unit machine for energy capture;
在能量捕获数据传输阶段,主发射机休眠,配备能量捕获单元的次级发射机利用捕获的能量传输数据给能量捕获接收机。In the energy harvesting data transmission stage, the primary transmitter is dormant, and the secondary transmitter equipped with an energy harvesting unit uses the captured energy to transmit data to the energy harvesting receiver.
进一步的,所述基于反向散射中继传输的认知无线供能网络优化方法,还包括:Further, the cognitive wireless power supply network optimization method based on backscatter relay transmission also includes:
将中继阶段、反向散射数据传输阶段和能量捕获数据传输阶段的持续时间分别表 示为:,和,在满足主用户目标吞吐量的前提下,以实现次级用户的总吞吐量最大化为 目标构建优化模型: Denote the durations of the relay phase, the backscatter data transmission phase, and the energy harvesting data transmission phase as: , and , under the premise of satisfying the target throughput of the primary user, an optimization model is constructed with the goal of maximizing the total throughput of the secondary user :
; ;
满足如下约束条件:;; Satisfy the following constraints: ; ;
其中,表示在能量捕获数据传输阶段,第个配备能量捕获单元的次级发射机产 生的吞吐量,表示在反向散射数据传输阶段,第个配备反向散射单元的次级发射机产 生的吞吐量,M表示配备反向散射单元的次级发射机数量,N表示配备能量捕获单元的次级 发射机数量,;表示在能量捕获数据传输阶段,第个配备能量捕获单 元的次级发射机被分配到的时间; in, Indicates that in the energy harvesting data transmission stage, the first Throughput produced by secondary transmitters equipped with energy harvesting units, Indicates that in the backscatter data transmission stage, the first Throughput produced by secondary transmitters equipped with backscatter elements, M is the number of secondary transmitters equipped with backscatter elements, N is the number of secondary transmitters equipped with energy harvesting elements, ; Indicates that in the energy harvesting data transmission stage, the first The time at which secondary transmitters equipped with energy harvesting units are assigned;
,表示在能量捕获数据传输阶段,第个配备能量捕获单 元的次级发射机产生的吞吐量; , which means that in the stage of energy harvesting data transmission, the first Throughput produced by secondary transmitters equipped with energy harvesting units;
,表示在反向散射数据传输阶段,第个配备反向散 射单元的次级发射机产生的吞吐量,反向散射系数,表示主发射机的发射功率; , which means that in the backscatter data transmission stage, the first Throughput produced by secondary transmitters equipped with backscatter elements, backscatter coefficient, Indicates the transmit power of the main transmitter;
,表示在中继阶段,主接收机处实现的吞 吐量; , represents the throughput achieved at the master receiver during the relay phase;
,表示在反向散射数据传输阶段,主接收机处实现的吞 吐量; , represents the throughput achieved at the main receiver during the backscatter data transmission phase;
表示主用户在每个时隙内的目标吞吐量; Indicates the target throughput of the primary user in each time slot;
表示信道带宽; Indicates the channel bandwidth;
表示环境噪声功率; Indicates the ambient noise power;
,表示第个配备能量捕获单元的次级发射机在授权频谱忙碌 时捕获到的能量,表示能量捕获效率; , indicating the first The energy captured by a secondary transmitter equipped with an energy harvesting unit when the licensed spectrum is busy, Indicates the energy capture efficiency;
表示从第个配备能量捕获单元的次级发射机到能量捕获接收机的信道增益; means from the The channel gain from a secondary transmitter equipped with an energy harvesting unit to an energy harvesting receiver;
表示从第个配备反向散射单元的次级发射机到反向散射接收机的信道增益; means from the channel gain from a secondary transmitter equipped with a backscatter unit to a backscatter receiver;
表示从主发射机到第个配备反向散射单元的次级发射机的信道增益; Indicates from the main transmitter to the second channel gain of a secondary transmitter equipped with backscatter elements;
表示从主发射机到第个配备能量捕获单元的次级发射机的信道增益; Indicates from the main transmitter to the second The channel gain of a secondary transmitter equipped with an energy harvesting unit;
表示从第个配备反向散射单元的次级发射机到主接收机的信道增益; means from the channel gain from a secondary transmitter equipped with a backscatter unit to the primary receiver;
表示从主发射机到主接收机的信道增益; Indicates the channel gain from the main transmitter to the main receiver;
求解优化模型的最优解,得到中继阶段、反向散射数据传输阶段和能量捕获数据传输阶段的持续时间。The optimal solution of the optimized model is solved for the duration of the relay phase, the backscatter data transmission phase, and the energy harvesting data transmission phase.
进一步的,所述求解优化模型的最优解,包括:Further, said solving the optimal solution of the optimization model includes:
将优化变量转化为,带入到优化模型,得到优化模型: will optimize the variable Converted to , into the optimization model to obtain the optimization model :
; ;
列出的拉格朗日函数,如下: list The Lagrange function of is as follows:
其中:in:
; ;
; ;
; ;
,为拉格朗日乘子; , is the Lagrangian multiplier;
通过对拉格朗日函数求关于的一阶偏导数,令该一阶偏导数为零,得到的表达 式,如下: By finding the Lagrangian function about The first-order partial derivative of , let the first-order partial derivative be zero, get The expression of is as follows:
; (1) ; (1)
其中表示若,则,否则,; in express if ,but ,otherwise, ;
通过对拉格朗日函数求关于一阶偏导数,令该一阶偏导数为零,得的表达式, 如下:By finding the Lagrangian function about The first-order partial derivative, let the first-order partial derivative be zero, get The expression of is as follows:
其中; in ;
拉格朗日乘子更新的表达式,如下:The expression of Lagrange multiplier update is as follows:
; (3) ; (3)
; (4) ;(4)
然后求解优化模型,包括: Then solve the optimization model ,include:
步骤4.1:设置初始化,的值,并且都大于等于0,初始化迭代次数; Step 4.1: Setup initialization , value, and are greater than or equal to 0, the number of initialization iterations ;
步骤4.2:判断超过N,若否,则采用二分搜索算法更新,通过固定,的 值,,然后跳到步骤4.2;否则,跳到步骤4.3; Step 4.2: Judgment Exceeds N, if not, use binary search algorithm to update , fixed by , the value of , then skip to step 4.2; otherwise, skip to step 4.3;
步骤4.3:通过固定基于公式(1)更新的值; Step 4.3: Fix by Update based on formula (1) value;
步骤4.4:通过固定,基于公式(3)更新; Step 4.4: Fix by , Update based on formula (3) ;
步骤4.5:通过固定,基于公式(4)更新; Step 4.5: Fix by , Update based on formula (4) ;
步骤4.6:判断所有的变量是否收敛,若是,则跳到步骤4.7;否则,跳到步骤4.2;Step 4.6: Judging whether all variables are convergent, if so, skip to step 4.7; otherwise, skip to step 4.2;
步骤4.7:输出最优解,最优解。 Step 4.7: Output the optimal solution ,Optimal solution .
进一步的,所述采用二分搜索算法更新,包括: Further, the update using the binary search algorithm ,include:
步骤3.1:输入一个上界值,设置下界值,将替代带入到拉格朗日函数 对的一阶偏导数中,得到解; Step 3.1: Enter an upper bound value , set the lower bound value ,Will replace into the Lagrange function pair In the first partial derivative of , the solution is obtained ;
步骤3.2:设置循环次数为,初始值为1,判断解是否小于,为一个很小的数, 若是,则跳到步骤3.5,否则跳到步骤3.3,; Step 3.2: Set the number of cycles to , the initial value is 1, and the judgment solution Is it less than , is a very small number, if so, go to step 3.5, otherwise go to step 3.3, ;
步骤3.3:判断是否大于0,若是,则,否则,; Step 3.3: Judgment Is it greater than 0, if so, then ,otherwise, ;
步骤3.4:将替代带入到拉格朗日函数对的一阶偏导数中,得到解,跳到 步骤3.2; Step 3.4: Put replace into the Lagrange function pair In the first partial derivative of , the solution is obtained , skip to step 3.2;
步骤3.5:此时得到的为的解。Step 3.5: At this point get for solution.
本申请技术方案,考虑在认知无线供能网络中,配备反向散射单元的发射机采用反向散射模式中继主用户数据,然后传输自己的数据,配备能量捕获单元的发射机进行射频能量捕获,然后使用捕获到的能量进行数据传输。通过优化中继、能量捕获以及数据传输的时间使得次级用户的总吞吐量最大化,从而提升网络的频谱利用率和能量效率。在此处,考虑的前提是主用户在一个时隙内需要满足其目标吞吐量,主用户空闲时,次级用户才能接入授权频谱。然后,通过对总吞吐量问题的单调性分析,将问题进行转化,并证明其是一个凸优化问题,再对其拉格朗日函数求偏导,以及采用二分搜索算法求得优化变化得表达式,再将问题用最优解迭代算法求解。从而保证主用户在满足其目标吞吐量的前提下,实现次级用户总吞吐量的最大化。The technical solution of this application considers that in the cognitive wireless energy supply network, the transmitter equipped with the backscattering unit uses the backscattering mode to relay the primary user data, and then transmits its own data, and the transmitter equipped with the energy capture unit performs radio frequency energy capture, and then use the captured energy for data transmission. By optimizing the time of relay, energy capture and data transmission, the total throughput of secondary users is maximized, thereby improving the spectrum utilization and energy efficiency of the network. Here, the premise considered is that the primary user needs to meet its target throughput within a time slot, and the secondary user can access the licensed spectrum only when the primary user is idle. Then, through the monotonic analysis of the total throughput problem, the problem is transformed, and it is proved that it is a convex optimization problem, and then the partial derivative of its Lagrangian function is obtained, and the expression of the optimization change is obtained by using the binary search algorithm formula, and then solve the problem with the optimal solution iterative algorithm. In this way, it is ensured that the primary user can maximize the total throughput of the secondary user under the premise of satisfying its target throughput.
附图说明Description of drawings
图1为本申请认知无线供能网络在中级阶段示意图;Figure 1 is a schematic diagram of the cognitive wireless energy supply network of the present application at the intermediate stage;
图2为本申请认知无线供能网络在反向散射数据传输阶段示意图;Figure 2 is a schematic diagram of the cognitive wireless energy supply network of the present application in the backscatter data transmission stage;
图3为本申请认知无线供能网络在能量捕获数据传输阶段示意图;FIG. 3 is a schematic diagram of the cognitive wireless energy supply network in the energy capture data transmission stage of the present application;
图4为本申请实施例单个时隙划分示意图。FIG. 4 is a schematic diagram of division of a single time slot according to an embodiment of the present application.
具体实施方式Detailed ways
为了使本申请的目的、技术方案及优点更加清楚明白,以下结合附图及实施例,对本申请进行进一步详细说明。应当理解,此处描述的具体实施例仅用以解释本申请,并不用于限定本申请。In order to make the purpose, technical solution and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present application, not to limit the present application.
如图1至图3所示,基于反向散射中继传输的认知无线供能网络主用户包括一个主发射机、一个主接收机。次级用户又分为两种,一种次级用户包括N个配备能量捕获单元的次级发射机(称为能量捕获单元发射机)和一个次级接收机(能量捕获接收机),能量捕获接收机只负责接收能量捕获单元发射机的数据;另一种次级用户包括M个配备反向散射单元的次级发射机(称为反向散射单元发射机)和一个次级接收机(反向散射接收机),反向散射接收机只负责接收反向散射单元发射机的数据。As shown in Figures 1 to 3, the main user of the cognitive wireless power supply network based on backscatter relay transmission includes a main transmitter and a main receiver. Secondary users are divided into two types. One secondary user includes N secondary transmitters equipped with energy harvesting units (called energy harvesting unit transmitters) and a secondary receiver (energy harvesting receiver). Energy harvesting The receiver is only responsible for receiving data from the energy harvesting unit transmitter; another secondary user includes M secondary transmitters equipped with backscatter units (called backscatter unit transmitters) and a secondary receiver (reverse backscatter receiver), the backscatter receiver is only responsible for receiving the data from the backscatter unit transmitter.
在一个实施例中,基于反向散射中继传输的认知无线供能网络优化方法,包括:In one embodiment, the cognitive wireless power supply network optimization method based on backscatter relay transmission includes:
将所述认知无线供能网络的工作时隙分为中继阶段、反向散射数据传输阶段和能量捕获数据传输阶段;Dividing the working time slots of the cognitive wireless energy supply network into a relay stage, a backscatter data transmission stage and an energy harvesting data transmission stage;
其中,在中继阶段主发射机发送数据给主接收机,配备反向散射单元的次级发射机采用反向散射模式中继主用户数据给主接收机,配备能量捕获单元的次级发射机进行能量捕获;Among them, in the relay stage, the main transmitter sends data to the main receiver, the secondary transmitter equipped with backscatter unit adopts the backscatter mode to relay the primary user data to the main receiver, and the secondary transmitter equipped with energy harvesting unit perform energy capture;
在反向散射数据传输阶段,主发射机发送数据给主接收机,配备反向散射单元的次级发射机采用反向散射模式发送数据给反向散射接收机,配备能量捕获单元的次级发射机进行能量捕获;In the backscatter data transmission phase, the primary transmitter sends data to the primary receiver, the secondary transmitter equipped with a backscatter unit sends data to the backscatter receiver in backscatter mode, and the secondary transmitter equipped with an energy harvesting unit machine for energy capture;
在能量捕获数据传输阶段,主发射机休眠,配备能量捕获单元的次级发射机利用捕获的能量传输数据给能量捕获接收机。In the energy harvesting data transmission stage, the primary transmitter is dormant, and the secondary transmitter equipped with an energy harvesting unit uses the captured energy to transmit data to the energy harvesting receiver.
具体的,如图1至图3所示,中继阶段:Specifically, as shown in Figures 1 to 3, the relay stage:
主发射机发送数据给主接收机,即频谱忙碌。M个配备反向散射单元的次级发射机采用反向散射模式中继主用户数据给主接收机。N个配备能量捕获单元的次级发射机进行能量捕获。The main transmitter sends data to the main receiver, ie the spectrum is busy. M secondary transmitters equipped with backscatter units relay primary user data to the primary receiver in backscatter mode. Energy harvesting is performed by N secondary transmitters equipped with energy harvesting units.
反向散射数据传输阶段,授权频谱处于忙碌,主发射机发送数据给主接收机。M个配备反向散射单元的次级发射机采用反向散射模式发送数据给反向散射接收机。N个只配备能量捕获单元的次级发射机进行能量捕获。In the phase of backscatter data transmission, the licensed spectrum is busy, and the main transmitter sends data to the main receiver. M secondary transmitters equipped with backscatter units transmit data to backscatter receivers in backscatter mode. N secondary transmitters equipped with only energy harvesting units perform energy harvesting.
由于配备反向散射单元的次级发射机中继主发射机的数据,因此主发射机可以提前满足其在一个时隙内的目标吞吐量。Since the secondary transmitter equipped with a backscatter unit relays the data from the primary transmitter, the primary transmitter can meet its target throughput in one slot ahead of time.
而在能量捕获数据传输阶段,授权频谱处于空闲,主发射机休眠。N个配备能量捕获单元的次级发射机利用捕获的能量传输数据给能量捕获接收机。In the phase of energy harvesting data transmission, the licensed spectrum is idle and the main transmitter is dormant. N secondary transmitters equipped with energy harvesting units utilize the captured energy to transmit data to an energy harvesting receiver.
本实施例中继阶段、反向散射数据传输阶段和能量捕获数据传输阶段的持续时间 分别表示为:,和,如图4所示。由于中继阶段持续时间的增加会使得主用户更快地 满足目标吞吐量,授权频谱处于忙碌的时间减少,反向散射数据传输阶段减少,因此配备 能量捕获单元的次级发射机捕获能量的时间减少。,和之间存在折衷,需要进行优化 来得到时间分配的最优比例。 In this embodiment, the durations of the relay stage, the backscatter data transmission stage and the energy capture data transmission stage are respectively expressed as: , and ,As shown in Figure 4. Due to the relay phase duration The increase of λ will allow the primary user to meet the target throughput faster, the licensed spectrum is busy for less time, and the backscatter data transmission phase Reduced, and therefore less time for secondary transmitters equipped with energy harvesting units to capture energy. , and There is a trade-off between and needs to be optimized to get the optimal ratio of time allocation.
在一个具体的实施例中,所述基于反向散射中继传输的认知无线供能网络优化方法,还包括:In a specific embodiment, the cognitive wireless power supply network optimization method based on backscatter relay transmission further includes:
步骤F1、将中继阶段、反向散射数据传输阶段和能量捕获数据传输阶段的持续时 间分别表示为:,和,在满足主用户目标吞吐量的前提下,以实现次级用户的总吞吐量 最大化为目标构建优化模型: In step F1, the durations of the relay phase, the backscatter data transmission phase and the energy capture data transmission phase are respectively expressed as: , and , under the premise of satisfying the target throughput of the primary user, an optimization model is constructed with the goal of maximizing the total throughput of the secondary user :
其中,表示在能量捕获数据传输阶段,第个配备能量捕获单元的次级发射机产 生的吞吐量,表示在反向散射数据传输阶段,第个配备反向散射单元的次级发射机产 生的吞吐量,M表示配备反向散射单元的次级发射机数量,N表示配备能量捕获单元的次级 发射机数量。 in, Indicates that in the energy harvesting data transmission stage, the first Throughput produced by secondary transmitters equipped with energy harvesting units, Indicates that in the backscatter data transmission stage, the first where M is the number of secondary transmitters equipped with backscatter elements, and N is the number of secondary transmitters equipped with energy harvesting elements.
本实施例中,在满足主用户目标吞吐量的前提下,通过联合优化中继阶段,反向 散射数据传输阶段和能量捕获数据传输阶段的持续时间,实现次级用户的总吞吐量最 大化。 In this embodiment, under the premise of meeting the target throughput of the primary user, the relay stage is jointly optimized , the backscatter data transmission stage and the duration of the energy harvesting data transfer phase , to maximize the total throughput of secondary users.
在反向散射数据传输阶段,M个配备反向散射单元的次级发射机采用反向散射模 式发送数据给反向散射接收机,包括:M个配备反向散射单元的次级发射机被分配到相同的 时长传输数据,即。 In the backscatter data transmission phase, M secondary transmitters equipped with backscatter units transmit data to the backscatter receiver in the backscatter mode, including: M secondary transmitters equipped with backscatter units are allocated to transmit data for the same duration, ie .
在能量捕获数据传输阶段,N个只配备能量捕获单元的次级发射机利用捕获的能 量传输数据给能量捕获接收机,包括:N个配备能量捕获单元的次级发射机以时分多址 (Time Division Multiple Access,TDMA)的方式传输数据。每个发射机被分配到的时间表 示为:。In the energy harvesting data transmission stage, N secondary transmitters equipped with energy harvesting units use the captured energy to transmit data to energy harvesting receivers, including: N secondary transmitters equipped with energy harvesting units in time division multiple access (Time Division Multiple Access, TDMA) to transmit data. The times to which each transmitter is assigned are expressed as: .
实现次级用户的总吞吐量最大化,被表述为以下数学优化模型:Maximizing the total throughput of secondary users is expressed as the following mathematical optimization model:
本实施例优化模型的约束条件:,。 待优化的变量:。 The constraints of the optimization model in this embodiment: , . Variables to optimize: .
上述优化模型中,各个参数说明如下:In the above optimization model, each parameter is described as follows:
:中继阶段的持续时间,单位是秒; : The duration of the relay phase, in seconds;
:反向散射数据传输的持续时间,单位是秒; : Duration of backscatter data transmission, in seconds;
:能量捕获数据传输阶段的持续时间,单位是秒; : The duration of the energy harvesting data transmission phase, in seconds;
:在能量捕获数据传输阶段,第个配备能量捕获单元的次级发射机被分配到的 时间,单位是秒; : In the energy harvesting data transmission phase, the first The time, in seconds, that a secondary transmitter equipped with an energy harvesting unit is assigned;
:在能量捕获数据传输阶段,第个配备能量捕获单元的 次级发射机产生的吞吐量,单位是比特每秒; : In the energy harvesting data transmission phase, the first Throughput produced by secondary transmitters equipped with energy harvesting units, in bits per second;
:在反向散射数据传输阶段,第个配备反向散射单 元的次级发射机产生的吞吐量,单位是比特每秒,反向散射系数,表示主发射机的发射 功率; : In the backscatter data transmission stage, the first Throughput produced by secondary transmitters equipped with backscatter elements in bits per second, backscatter coefficient, Indicates the transmit power of the main transmitter;
:在中继阶段,主接收机处实现的吞吐 量,单位是比特每秒; : In the relay phase, the throughput achieved at the main receiver, in bits per second;
: 在反向散射数据传输阶段,主接收机处实现的吞吐 量,单位是比特每秒; : The throughput achieved at the main receiver during the backscatter data transmission phase, in bits per second;
:主用户在每个时隙内的目标吞吐量,单位是比特每秒; : The target throughput of the primary user in each time slot, in bits per second;
:信道带宽,单位是赫兹; : Channel bandwidth, unit is Hz;
:环境噪声功率,单位是瓦; : ambient noise power, in watts;
:第个配备能量捕获单元的次级发射机在授权频谱忙碌时捕 获到的能量,单位是焦耳; : No. The energy captured by a secondary transmitter equipped with an energy harvesting unit when the licensed spectrum is busy, in joules;
:能量捕获效率; : energy capture efficiency;
:从第个配备能量捕获单元的次级发射机到能量捕获接收机的信道增益; : from the The channel gain from a secondary transmitter equipped with an energy harvesting unit to an energy harvesting receiver;
:从第个配备反向散射单元的次级发射机到反向散射接收机的信道增益; : from the channel gain from a secondary transmitter equipped with a backscatter unit to a backscatter receiver;
:从主发射机到第个配备反向散射单元的次级发射机的信道增益; : From the main transmitter to the second channel gain of a secondary transmitter equipped with backscatter elements;
:从主发射机到第个配备能量捕获单元的次级发射机的信道增益; : From the main transmitter to the second The channel gain of a secondary transmitter equipped with an energy harvesting unit;
:从第个配备反向散射单元的次级发射机到主接收机的信道增益; : from the channel gain from a secondary transmitter equipped with a backscatter unit to the primary receiver;
:从主发射机到主接收机的信道增益。 : channel gain from main transmitter to main receiver.
本实施例中,约束条件说明如下:In this embodiment, the constraints are described as follows:
:本实施例将一个时隙的长度归一化为1秒,三个阶段的时间 之和不超过一个时隙的长度。对于其他长度的时隙,本申请提供的方法仍然适用,只需按照 时隙长度等比例得到三个阶段的时长即可; : In this embodiment, the length of one time slot is normalized to 1 second, and the sum of the times of the three stages does not exceed the length of one time slot. For time slots of other lengths, the method provided by this application is still applicable, and it is only necessary to obtain the duration of the three stages in proportion to the length of the time slot;
:每个阶段的持续时间非负; : the duration of each stage is non-negative;
:在每个时隙中,主用户的吞吐量至少要满足目标吞吐量。 : In each time slot, the throughput of the primary user must at least meet the target throughput.
步骤F2、求解优化模型的最优解,得到中继阶段、反向散射数据传输阶段和能量捕获数据传输阶段的持续时间。Step F2, solving the optimal solution of the optimization model to obtain the duration of the relay phase, the backscatter data transmission phase and the energy capture data transmission phase.
本实施例通过对问题分别求关于,和的一阶偏导和二阶偏导,并且列出其 海森(Hessian)矩阵,发现该海森矩阵为半负定,因此可以得到问题是一个凸优化问题。 In this embodiment, the ask questions about , and The first-order partial derivative and second-order partial derivative of , and list its Hessian matrix, it is found that the Hessian matrix is semi-negative definite, so we can get The problem is a convex optimization problem.
假设问题的最优解为时,约束满足。 suppose The optimal solution to the problem is When the constraint satisfies .
假设问题的可行解为,且。 suppose The feasible solution to the problem is ,and .
由于问题关于的偏导数大于0,使得可行解求得的吞吐量大于最优解的吞吐 量,这与最优解相矛盾。 because question about The partial derivative of is greater than 0, so that the throughput obtained by the feasible solution is greater than that of the optimal solution, which contradicts the optimal solution.
因而,通过上述结论问题取得最优解时,约束满足。此时优 化变量转化为。 Therefore, through the above conclusion When the problem is optimally solved, the constraints satisfy . Optimize variables at this time Converted to .
基于上述证明,问题转化为问题,如下: Based on the above proof, The problem turns into Questions are as follows:
其中,约束条件为:Among them, the constraints are:
转化为待优化的变量为:, Transformed into variables to be optimized are: ,
由于问题为凸优化问题,因此问题也为凸优化问题。 because The problem is a convex optimization problem, so The problem is also a convex optimization problem.
求解时,列出问题的拉格朗日函数,如下: When solving, list The Lagrangian function of the problem is as follows:
。 .
下面对拉格朗日函数中的各个参数进行说明,如下:The parameters in the Lagrangian function are described below, as follows:
; ;
; ;
; ;
:拉格朗日乘子。 : Lagrangian multiplier.
通过对拉格朗日函数求关于的一阶偏导数,令该一阶偏导数为零,可得的表达 式,如下: By finding the Lagrangian function about The first-order partial derivative of , let the first-order partial derivative be zero, we can get The expression of is as follows:
; (1) ; (1)
其中表示若,则,否则,。 in express if ,but ,otherwise, .
通过对拉格朗日函数求关于一阶偏导数,令该一阶偏导数为零,可得的表达 式,如下: By finding the Lagrangian function about The first-order partial derivative, let the first-order partial derivative be zero, we can get The expression of is as follows:
其中,发现该一阶偏导数是单调递减的,并由于超越函数很难得到的闭式表达式,因此采用二分搜索算法来求解。 in , it is found that the first-order partial derivative is monotonically decreasing, and due to the transcendental function it is difficult to obtain The closed-form expression of , so the binary search algorithm is used to solve .
拉格朗日乘子更新的表达式,如下:The expression of Lagrange multiplier update is as follows:
其中表示迭代次数,,为更新步长。 in represents the number of iterations, , is the update step.
本实施例问题的解决思路如下:首先将转化为问题;其次,由于 为凸优化问题,因此问题也为凸优化问题。为求解问题,提出最优解迭代算法来解决; 通过块坐标下降法和梯度下降法分别更新待优化变量和拉格朗日乘子,直到待优化变量和 拉格朗日乘子都收敛,从而解得,,即的全局最优解。 This example The solution to the problem is as follows: firstly, the Converted to problems; secondly, due to is a convex optimization problem, so The problem is also a convex optimization problem. to solve The optimal solution iterative algorithm is proposed to solve the problem; the variables to be optimized and the Lagrangian multipliers are updated respectively by the block coordinate descent method and the gradient descent method until the variables to be optimized and the Lagrange multipliers converge, so that the solution is obtained , ,Right now global optimal solution.
本实施例对于求解问题采用最优解迭代算法,步骤如下: This example solves for The optimal solution iteration algorithm is used for the problem, and the steps are as follows:
步骤4.1:设置初始化,的值,并且都大于等于0,初始化迭代次数。 Step 4.1: Setup initialization , value, and are greater than or equal to 0, the number of initialization iterations .
步骤4.2:判断超过N,若否,则采用二分搜索算法更新,通过固定,的 值,,然后跳到步骤4.2。否则,跳到步骤4.3。 Step 4.2: Judgment Exceeds N, if not, use binary search algorithm to update , fixed by , the value of , then skip to step 4.2. Otherwise, skip to step 4.3.
步骤4.3:通过固定基于公式(1)更新的值。 Step 4.3: Fix by Update based on formula (1) value.
步骤4.4:通过固定,基于公式(3)更新。 Step 4.4: Fix by , Update based on formula (3) .
步骤4.5:通过固定,基于公式(4)更新。 Step 4.5: Fix by , Update based on formula (4) .
步骤4.6:判断所有的变量是否收敛,若是,则跳到步骤4.7;否则,跳到步骤4.2。Step 4.6: Judge whether all variables are converged, if yes, go to step 4.7; otherwise, go to step 4.2.
步骤4.7:输出最优解,最优解。 Step 4.7: Output the optimal solution ,Optimal solution .
其中,对于求解采用的二分搜索算法,步骤如下: Among them, for solving The binary search algorithm used, the steps are as follows:
步骤3.1:输入一个上界值,设置下界值,将替代带入到拉格朗日函数 对的一阶偏导数中,得到解; Step 3.1: Enter an upper bound value , set the lower bound value ,Will replace into the Lagrange function pair In the first partial derivative of , the solution is obtained ;
步骤3.2:设置循环次数为,初始值为1,判断解是否小于,为一个很小的数, 若是,则跳到步骤3.5,否则跳到步骤3.3,; Step 3.2: Set the number of cycles to , the initial value is 1, and the judgment solution Is it less than , is a very small number, if so, go to step 3.5, otherwise go to step 3.3, ;
步骤3.3:判断是否大于0,若是,则,否则,; Step 3.3: Judgment Is it greater than 0, if so, then ,otherwise, ;
步骤3.4:将替代带入到拉格朗日函数对的一阶偏导数中,得到解,跳到 步骤3.2; Step 3.4: Put replace into the Lagrange function pair In the first partial derivative of , the solution is obtained , skip to step 3.2;
步骤3.5:此时得到的为的解。 Step 3.5: At this point get for solution.
以上所述实施例仅表达了本申请的几种实施方式,其描述较为具体和详细,但并不能因此而理解为对发明专利范围的限制。应当指出的是,对于本领域的普通技术人员来说,在不脱离本申请构思的前提下,还可以做出若干变形和改进,这些都属于本申请的保护范围。因此,本申请专利的保护范围应以所附权利要求为准。The above-mentioned embodiments only represent several implementation modes of the present application, and the description thereof is relatively specific and detailed, but it should not be construed as limiting the scope of the patent for the invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the scope of protection of the patent application should be based on the appended claims.
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