CN113613321B - LTE-U system carrier power distribution method facing throughput demand - Google Patents

Abstract

The invention discloses a method for allocating carrier power of an LTE-U system oriented to throughput requirements, comprising the following steps: (1) adaptively adjusting the CSAT cycle LTE-U ON/OFF duty cycle; (2) performing minimum power allocation; (3) Perform upper limit power allocation. The present invention can effectively guarantee the fairness of the coexistence of the LTE-U system in the unlicensed frequency band and the WiFi system, and under the premise of meeting the transmission power limit of the base station in the unlicensed frequency band and the throughput requirements of LTE-U users, comprehensively consider the channel quality on different carriers and the LTE The difference in channel occupancy time of the ‑U system periodically adjusts the transmission power allocation of the base station on different carriers, effectively improving the total throughput of the LTE‑U system.

Description

A carrier power allocation method for LTE-U system oriented to throughput requirements

technical field

The invention relates to the technical field of co-existence of LTE-U system and WiFi system in unlicensed frequency bands in mobile communication, in particular to a carrier power allocation method of LTE-U system oriented to throughput requirements.

Background technique

There are a large number of available spectrum resources in the unlicensed frequency bands commonly used in the world, which have not been fully utilized. If the cellular network is allowed to transmit data in the unlicensed frequency band, the pressure on the licensed frequency band will be alleviated, the capacity of the cellular network will be significantly improved, and the spectrum utilization rate of the unlicensed frequency band will be greatly improved. Therefore, the industry has begun to study the development and utilization of unlicensed frequency bands. In 2013, Qualcomm, Ericsson, Huawei, etc. formally proposed the concept of "LTE-Unlicensed (LTE-U)" in the wireless access network standardization conference RAN#62 organized by 3GPP. A key challenge of the LTE-U technology is to ensure the friendly coexistence of the LTE system and the existing wireless communication systems in the unlicensed frequency band, such as the WiFi system in the 5GHz frequency band. The LTE system and the WiFi system use completely different channel access mechanisms. Compared with the WiFi system, the channel access mechanism adopted by the LTE system is somewhat aggressive. If the LTE system is directly deployed in an unlicensed frequency band, it will seriously affect the transmission of the WiFi system. Therefore, a reasonable channel access mechanism needs to be adopted on each carrier in the coexistence network to coordinate the transmission of the two systems, so as to ensure that the performance of the WiFi system will not be seriously affected.

On the basis of ensuring the coexistence fairness of the LTE-U system and the WiFi system, in order to further improve the total throughput of the LTE-U system, it is necessary to meet the transmission power limit of the base station in the unlicensed frequency band and the throughput requirements of LTE-U users. Consider comprehensively the differences in channel quality on different carriers and the channel occupation time of the LTE-U system. In the coexistence network of LTE-U and WiFi in the unlicensed band, the total throughput of the LTE-U system and the signal-to-noise ratio (SNR) on each carrier, channel gain and channel occupation time of the LTE-U system on each carrier Relevant, where the channel gain depends on factors such as path loss and channel fading, and the channel gain of different carriers is different. With the dynamic arrival and departure of users in the network, the channel occupation time of the LTE-U system on each carrier will also change accordingly. In addition, due to the regulatory requirements of the unlicensed frequency band, in order to minimize the interference to other coexisting systems in the unlicensed frequency band, the total transmission power of the LTE-U base station on the unlicensed frequency band and the transmission power on a single carrier have upper limits limit. At the same time, it is also necessary to consider that LTE-U users on each carrier in the coexistence network have specific throughput requirements. Therefore, in order to improve the total throughput of the LTE-U system on the premise of ensuring the throughput requirements of LTE-U users, it is necessary to study the carrier power allocation problem of the LTE-U system oriented to the throughput requirements.

Contents of the invention

The object of the present invention is to provide a method for allocating carrier power of an LTE-U system oriented to throughput requirements in order to solve the above problems. This method can effectively guarantee the fairness of the coexistence of the LTE-U system in the unlicensed frequency band and the WiFi system. Under the premise of meeting the transmission power limit of the base station in the unlicensed frequency band and the throughput requirements of LTE-U users, the channel quality on different carriers and the LTE - U system channel occupation time differences, periodically adjust the transmission power allocation of the base station on different carriers, effectively improving the total throughput of the LTE-U system.

In order to achieve the above object, the present invention adopts a method for allocating carrier power of an LTE-U system oriented to throughput requirements, comprising the following steps:

(1) Adaptively adjust the LTE-U ON/OFF duty cycle of the CSAT cycle: Before the end of each CSAT cycle, after all LTE-U users in the coexistence network complete the carrier selection, according to the need for service on each carrier in the next CSAT cycle The number of users, that is, the sum of the number of users who have not yet completed transmission in the current cycle and the number of users newly allocated to the carrier, adjust the duty cycle of LTE-U ON/OFF on different carriers in the next CSAT working cycle;

(2) Perform the lowest power allocation: After determining the LTE-U ON duty cycle on each carrier in the next CSAT period, combined with information such as channel quality on different carriers, the base station on different carriers in the next CSAT period The transmission power is redistributed; in order to ensure the total throughput requirements of LTE-U users on each carrier, the LTE-U base station has the lowest power requirement on a single carrier in the unlicensed frequency band, that is, the lower limit of transmission power; firstly, the water injection algorithm is used for each Carriers carry out initial power allocation. If the initial power allocation value of a single carrier is lower than the minimum power requirement of the carrier, the minimum power allocation is performed on the carrier; by performing the minimum power allocation, the power allocated to all carriers is guaranteed to meet the minimum power requirement. ;

(3) Perform upper limit power allocation: After the minimum power allocation is completed, in order to meet the regulatory requirements of the unlicensed frequency band, the power allocation needs to consider the upper limit of the transmission power of the LTE-U base station on a single carrier in the unlicensed frequency band. If the initial power allocation value of a single carrier exceeds the transmission power upper limit of the carrier, the upper limit power allocation is performed on the carrier; through the implementation of the upper limit power allocation, it is ensured that the power allocated to all carriers does not exceed the transmission power upper limit. After the upper limit power allocation is completed, the power allocated to all carriers is between the minimum power requirement of the carrier and the transmission power upper limit range, and at this time, all carriers have obtained power allocation that meets the constraint conditions.

In the method of the present invention, in steps (1)-(3), a converged network architecture based on network virtualization technology between the LTE-U system and the WiFi system is used to share information between the LTE-U system and the WiFi system, It is conducive to the realization of friendly coexistence and reasonable and efficient resource allocation of unlicensed frequency band LTE-U system and WiFi system. The converged network architecture is described as follows:

An LTE-U subsystem and multiple WiFi subsystems coexist in an unlicensed frequency band. In this coexistence network, the LTE-U subsystem consists of a base station BS and several uniformly distributed users UE, and each LTE-U user has a specific throughput requirement. Each WiFi subsystem consists of an AP and several uniformly distributed user STAs. It is assumed that there are N orthogonal component carriers (Component Carriers, CCs) in the unlicensed frequency band, denoted as CC ₁ , CC ₂ , . . . , CC _N . Each CC can be shared by an LTE-U system and a WiFi system. Each WiFi AP uses a carrier. In order to avoid serious co-channel interference due to geographical proximity, it is further assumed that different WiFi APs use different carriers, so the mutual interference between different WiFi APs can be ignored. An LTE-U BS can use all N carriers to serve LTE-U users. The downlink transmission of the LTE-U system adopts the OFDMA channel access mechanism centrally scheduled by the base station to allocate time-frequency resources to users; the WiFi system adopts the 802.11n contention-based CSMA/CA channel access mechanism, and users access channels in a competitive manner. On each carrier, the F-CSAT mechanism based on time division multiplexing is used to coordinate the coexistence of the two systems.

This method adopts the integrated network architecture of LTE-U system and WiFi system based on network virtualization technology, and virtualizes the physical entities LTE-U BS and WiFi AP in the LTE-U system and WiFi system into corresponding virtual network entities vBS respectively. (virtual BS) and vAP (virtual AP), manage virtual entities through software-defined network (Software Defined Network, SDN) technology. The LTE-U BS virtual entity (vBS) and the WiFi AP virtual entity (vAP) are uniformly controlled by an SDN controller, and receive the load intensity of the wireless access network side, user throughput requirements and Channel status and other information. In the case that all users in the coexistence network complete carrier selection before the end of each CSAT period, LTE-U needs to base on the number of users that need to be served on each carrier in the next CSAT period, for LTE-U on different carriers in the next CSAT period. U ON/OFF duty cycle is adjusted. After determining the LTE-U ON/OFF duty cycle on each carrier, combined with information such as channel quality on different carriers, the next CSAT cycle base station on different carriers Transmit power is redistributed. Therefore, it is necessary for the virtual entities to communicate the received information, based on which the carrier power allocation is performed, and the total throughput of the LTE-U system is improved on the premise of meeting the throughput requirements of LTE-U users.

In the method step (2) and step (3) of the present invention, the water injection algorithm is adopted to allocate initial power for each carrier under the premise of satisfying the total transmission power limit of the LTE-U base station, and the specific process is:

LTE-U用户数目为

LTE-U系统独自占用第i个成分载波时能够获得的系统吞吐量为

每个载波上的LTE-U ON占空比为

每个载波上基站的传输功率为P_i。在这样的情况下，可得出LTE-U系统在N个正交成分载波上能够获得的总吞吐量R_total为：Assuming that there are N orthogonal component carriers on the unlicensed frequency band of the coexistence network, denoted as CC ₁ , CC ₂ , ..., CC _N , the frequency bandwidth of each component carrier is B _i , the channel gain is h _i , i=1, 2,...,N. At the beginning of a CSAT period, the number of WiFi users that the i-th carrier needs to serve is

The number of LTE-U users is

The system throughput that can be obtained when the LTE-U system occupies the i-th component carrier alone is

The LTE-U ON duty cycle on each carrier is

The transmission power of the base station on each carrier is _Pi . In such a case, it can be concluded that the total throughput R _total that the LTE-U system can obtain on N orthogonal component carriers is:

where N ₀ represents the additive white Gaussian noise power spectral density on each carrier CC _i .

然后对下一个CSAT周期基站在不同载波上的传输功率进行重新分配，以最大化LTE-U系统的总吞吐量，即：In the carrier power allocation problem of LTE-U system, the difference of channel quality and channel occupancy time of LTE-U system on each carrier in the coexistence network is considered. Before the end of each CSAT period, when all users in the coexistence network have completed carrier selection, first determine the LTE-U ON duty cycle on each carrier in the next CSAT period

Then redistribute the transmission power of the base station on different carriers in the next CSAT cycle to maximize the total throughput of the LTE-U system, namely:

Restrictions:

Formula (5) can be expressed as:

LTE-U基站在单个载波上的传输功率需要满足其最低传输功率需求。Among them, the inequality (3) indicates that the total transmission power of the LTE-U base station is limited to P _total , and the inequality (4) indicates that in order to meet the regulatory requirements of the unlicensed frequency band, the upper limit of the transmission power allowed by the LTE-U base station on a single carrier in the unlicensed frequency band is P _max , Inequality (6) expresses that in order to guarantee the total throughput requirement of LTE-U users on each carrier

The transmission power of an LTE-U base station on a single carrier needs to meet its minimum transmission power requirements.

In order to maximize the total throughput of the LTE-U system, it is necessary to make full use of the total transmission power of the LTE-U base station for transmission within the limit; therefore, the objective function (2) should satisfy the inequality (3) when obtaining the optimal solution:

First, considering only the total transmission power limitation of the LTE-U base station, the initial power allocation on each carrier is solved by adopting the Lagrangian multiplier method and applying the KKT condition. To do this, construct the corresponding Lagrange function:

Where λ represents the Lagrangian multiplier, and the following KKT conditions can be obtained:

Therefore, it can be concluded that the transmission power allocated to the i-th carrier is:

为正，则为该载波分配功率；否则，不为该载波分配功率，即该载波的P_i为0；由于通过式(10)求解得到的功率分配不一定满足式(4)和式(6)中单个载波的最低传输功率需求和传输功率上限，将其作为初始功率分配。Wherein [x] ⁺ ＝max(0, x); formula (10) expresses: if a certain carrier

is positive, the power is allocated to the carrier; otherwise, no power is allocated to the carrier, that is, the P _i of the carrier is 0; since the power allocation obtained by solving formula (10) does not necessarily satisfy formula (4) and formula (6 ) in the minimum transmission power requirement and transmission power upper limit of a single carrier, which is used as the initial power allocation.

The traditional water filling algorithm is used to solve the Lagrangian multiplier λ in formula (10) and the initial power allocation P _i of the LTE-U system; formula (10) is equivalent to:

相等，某个载波能否获得功率分配取决于

的大小。实际中可能存在一些载波CC_i，其

和h_i很小，以至于

对于这些载波，将不为其分配功率，即这些载波的P_i为0；对于其它满足

的载波，将为其分配功率。采用

表示最终获得功率分配的载波的集合，将式(10)代入式(7)中可得到：All carriers are assumed to have the same bandwidth. For the same λ, all carriers’

are equal, whether a carrier can get power allocation depends on

the size of. In practice, there may be some carriers CC _i , whose

and h _i are so small that

For these carriers, no power will be allocated to them, that is, the _Pi of these carriers is 0; for other

of the carriers for which power will be allocated. use

Represents the set of carriers that finally obtain power allocation, and substituting Equation (10) into Equation (7) can be obtained:

It can be solved that λ is:

为此，采用注水算法通过反复迭代以确定哪些载波因

而没有获得功率分配以及最终哪些载波获得功率分配；在此基础上，求解λ的最终值，并为

中的载波进行初始功率分配。According to equation (13), solving the Lagrangian multiplier λ needs to determine the set of carriers that finally obtain power allocation

To this end, the water injection algorithm is used to determine which carrier factors are

Without getting the power allocation and which carriers finally get the power allocation; on this basis, solve the final value of λ, and give

Carriers in the initial power allocation.

The main steps of the water injection algorithm are as follows:

a) initialization

b) Solve the current λ according to formula (13), namely:

中的载波根据

降序排列，并选取

最大的载波

c) will

The carrier in the

Sort in descending order and select

Maximum carrier

则此时

中所有载波的P_i均为正值，当前的λ为最终值，为

中的每一个载波分配相应功率，即设置：

否则，此时载波

的

为负值或零，则不为载波

分配功率，即设置：

并将载波

移出

然后转到步骤b)。d) if

then at this time

The P _i of all carriers in are positive, and the current λ is the final value, which is

Each carrier in is allocated corresponding power, that is, setting:

Otherwise, at this time the carrier

of

Negative or zero, not carrier

Allocate power, i.e. set:

and place the carrier

move out

Then go to step b).

In step (2) of the method of the present invention, the minimum power allocation is performed to ensure that the power allocated to all carriers meets the minimum power requirement. The specific process is:

In order to ensure the total throughput requirements of LTE-U users on each carrier, LTE-U base stations have the lowest power requirements on a single carrier in the unlicensed frequency band; If the value is lower than the minimum power requirement of the carrier, the minimum power allocation is performed on the carrier, and the specific steps are as follows:

a) Initialize the set of carriers representing power to be allocated

中所有载波进行初始功率分配，每个载波上获得的功率分配为

b) Use the water injection algorithm to

Initial power allocation is performed on all carriers in , and the power allocation obtained on each carrier is

中每个载波获得的初始功率分配P_i与该载波的最低功率需求进行比较；c) in turn

The initial power allocation P _i obtained by each carrier in is compared with the minimum power requirement of the carrier;

设置为该载波的最低功率需求，同时将总传输功率P_total减少

然后将载波CC_i移出待分配载波集合

If P _i of carrier CC _i is less than its minimum power requirement, then the

Set to the minimum power requirement for that carrier while reducing the total transmit power P _total

Then move the carrier CC _i out of the carrier set to be allocated

中所有载波完成一轮最低功率分配之后，若该轮分配过程中有载波完成功率分配被移出

则转到步骤b)；否则，最低功率分配完成。d) right

After all carriers complete a round of minimum power allocation, if any carrier completes power allocation during this round of allocation, it will be removed

Then go to step b); otherwise, the minimum power allocation is complete.

In step (3) of the method of the present invention, upper limit power allocation is performed to ensure that the power allocated to all carriers does not exceed the upper limit of transmission power. The specific process is:

In order to meet the regulatory requirements of the unlicensed frequency band, the power allocation needs to consider the upper limit of the transmission power of the LTE-U base station on a single carrier in the unlicensed frequency band; The upper limit power allocation, the specific steps are as follows:

中所有载波进行初始功率分配，每个载波上获得的功率分配为

a) Water injection algorithm is used to complete the lowest power allocation

Initial power allocation is performed on all carriers in , and the power allocation obtained on each carrier is

中每个载波获得的初始功率分配P_i与该载波的传输功率上限P_max进行比较；若载波CC_i的P_i超过其传输功率上限P_max，则将

设置为该载波的传输功率上限，同时将总传输功率P_total减少

然后将载波CC_i移出待分配载波集合

b) in turn

The initial power allocation P _i obtained by each carrier in CC i is compared with the transmission power upper limit P _max of the carrier; if the P _i of the carrier CC _i exceeds its transmission power upper limit P _max , then the

Set as the upper limit of the transmission power of the carrier, and at the same time reduce the total transmission power P _total

Then move the carrier CC _i out of the carrier set to be allocated

中所有载波完成一轮上限功率分配之后，若该轮分配过程中有载波完成功率分配被移出

转到步骤a)；否则，上限功率分配完成。c) right

After all carriers complete a round of upper limit power allocation, if a carrier completes power allocation during this round of allocation, it will be removed

Go to step a); otherwise, capped power allocation is complete.

中剩余载波的功率分配值

均在载波的最低功率需求和传输功率上限范围之间，此时所有载波都获得了满足约束条件的功率分配。After the upper limit power allocation is completed,

The power allocation value of the remaining carriers in

are between the minimum power requirement of the carrier and the upper limit of the transmission power, and at this time all the carriers have obtained the power allocation that satisfies the constraints.

Beneficial effect

Compared with the prior art, the present invention has the following advantages:

1) The present invention takes into account the dynamics of the LTE-U and WiFi coexistence network status and the differences of different carriers, and cannot simply allocate the same transmission power for the base station on all carriers, but needs to be based on the channel quality and LTE-U on different carriers. The difference in channel occupancy time of the U system periodically adjusts the transmission power allocation of the base station on different carriers, effectively improving the total throughput of the LTE-U system.

2) A method for allocating carrier power in an LTE-U system oriented to throughput requirements provided by the present invention can solve the problem of allocating carrier power in an LTE-U system in an unlicensed frequency band. This method can effectively guarantee the fairness of the coexistence of the LTE-U system in the unlicensed frequency band and the WiFi system. Under the premise of meeting the transmission power limit of the base station in the unlicensed frequency band and the throughput requirements of LTE-U users, the channel quality on different carriers and the LTE - U system channel occupation time differences, periodically adjust the transmission power allocation of the base station on different carriers, effectively improving the total throughput of the LTE-U system.

Description of drawings

Figure 1: Schematic flow diagram of the LTE-U system carrier power allocation method for throughput requirements;

Figure 2: Schematic diagram of LTE-U and WiFi coexistence network scenario based on converged network architecture;

Figure 3: Schematic flow chart of the minimum power allocation steps;

Figure 4: Schematic flow chart of the capped power allocation steps.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings. The present invention provides a kind of LTE-U system carrier power allocation method oriented to throughput demand, as shown in Figure 1, implement according to the following steps:

(1) Adaptively adjust the LTE-U ON/OFF duty cycle of the CSAT cycle: Before the end of each CSAT cycle, after all LTE-U users in the coexistence network complete the carrier selection, according to the need for service on each carrier in the next CSAT cycle The number of users, that is, the sum of the number of users who have not yet completed transmission in the current cycle and the number of users newly allocated to the carrier, adjusts the LTE-U ON/OFF duty cycle on different carriers in the next CSAT working cycle.

This method adopts an LTE-U system and WiFi system fusion network architecture based on network virtualization technology, and one LTE-U subsystem and multiple WiFi subsystems coexist in an unlicensed frequency band, as shown in FIG. 2 . In this coexistence network, the LTE-U subsystem consists of a base station BS and several uniformly distributed users UE, and each LTE-U user has a specific throughput requirement. Each WiFi subsystem consists of an AP and several uniformly distributed user STAs. It is assumed that there are N orthogonal component carriers (Component Carriers, CCs) in the unlicensed frequency band, denoted as CC ₁ , CC ₂ , . . . , CC _N . Each CC can be shared by an LTE-U system and a WiFi system. Each WiFi AP uses a carrier. In order to avoid serious co-channel interference due to geographical proximity, it is further assumed that different WiFi APs use different carriers, so the mutual interference between different WiFi APs can be ignored. An LTE-U BS can use all N carriers to serve LTE-U users. The downlink transmission of the LTE-U system adopts the OFDMA channel access mechanism centrally scheduled by the base station to allocate time-frequency resources to users; the WiFi system adopts the 802.11n contention-based CSMA/CA channel access mechanism, and users access channels in a competitive manner. On each carrier, the F-CSAT mechanism based on time division multiplexing is used to coordinate the coexistence of the two systems.

The physical entities LTE-U BS and WiFi AP in the LTE-U system and WiFi system are respectively virtualized into corresponding virtualized network entities vBS (virtual BS) and vAP (virtual AP), through Software Defined Network (SoftwareDefined Network, SDN ) technology to manage virtual entities. The LTE-U BS virtual entity (vBS) and the WiFi AP virtual entity (vAP) are uniformly controlled by an SDN controller, and receive the load intensity of the wireless access network side, user throughput requirements and Channel status and other information. In the case that all users in the coexistence network complete carrier selection before the end of each CSAT period, LTE-U needs to base on the number of users that need to be served on each carrier in the next CSAT period, for LTE-U on different carriers in the next CSAT period. U ON/OFF duty cycle is adjusted. After determining the LTE-U ON/OFF duty cycle on each carrier, combined with information such as channel quality on different carriers, the next CSAT cycle base station on different carriers Transmit power is redistributed. Therefore, it is necessary for the virtual entities to communicate the received information, based on which the carrier power allocation is performed, and the total throughput of the LTE-U system is improved on the premise of meeting the throughput requirements of LTE-U users.

(2) Perform the lowest power allocation: After determining the LTE-U ON duty cycle on each carrier in the next CSAT cycle, combined with information such as channel quality on different carriers, the base station on different carriers in the next CSAT cycle Transmit power is redistributed. In order to guarantee the total throughput requirements of LTE-U users on each carrier, the LTE-U base station has the lowest power requirement on a single carrier in the unlicensed frequency band, that is, the lower limit of transmission power. First, the water filling algorithm is used to allocate initial power for each carrier. If the initial power allocation value of a single carrier is lower than the minimum power requirement of the carrier, the minimum power allocation is performed for the carrier. By performing the minimum power allocation, it is ensured that the power allocated to all carriers meets the minimum power requirement.

LTE-U用户数目为

LTE-U系统独自占用第i个成分载波时能够获得的系统吞吐量为

每个载波上的LTE-U ON占空比为

每个载波上基站的传输功率为P_i。在这样的情况下，可得出LTE-U系统在N个正交成分载波上能够获得的总吞吐量R_total为：Assuming that there are N orthogonal component carriers on the unlicensed frequency band of the coexistence network, denoted as CC ₁ , CC ₂ , ..., CC _N , the frequency bandwidth of each component carrier is B _i , the channel gain is h _i , i=1, 2,...,N. At the beginning of a CSAT period, the number of WiFi users that the i-th carrier needs to serve is

The number of LTE-U users is

The system throughput that can be obtained when the LTE-U system occupies the i-th component carrier alone is

The LTE-U ON duty cycle on each carrier is

The transmission power of the base station on each carrier is _Pi . In such a case, it can be concluded that the total throughput R _total that the LTE-U system can obtain on N orthogonal component carriers is:

where N ₀ represents the additive white Gaussian noise power spectral density on each carrier CC _i .

然后对下一个CSAT周期基站在不同载波上的传输功率进行重新分配，以最大化LTE-U系统的总吞吐量，即：In the carrier power allocation problem of LTE-U system, the difference of channel quality and channel occupancy time of LTE-U system on each carrier in the coexistence network is considered. Before the end of each CSAT period, when all users in the coexistence network have completed carrier selection, first determine the LTE-U ON duty cycle on each carrier in the next CSAT period

Then redistribute the transmission power of the base station on different carriers in the next CSAT cycle to maximize the total throughput of the LTE-U system, namely:

Restrictions:

Formula (5) can be expressed as:

LTE-U基站在单个载波上的传输功率需要满足其最低传输功率需求。Among them, the inequality (3) indicates that the total transmission power of the LTE-U base station is limited to P _total , and the inequality (4) indicates that in order to meet the regulatory requirements of the unlicensed frequency band, the upper limit of the transmission power allowed by the LTE-U base station on a single carrier in the unlicensed frequency band is P _max , Inequality (6) expresses that in order to guarantee the total throughput requirement of LTE-U users on each carrier

The transmission power of an LTE-U base station on a single carrier needs to meet its minimum transmission power requirements.

In order to maximize the total throughput of the LTE-U system, it is necessary to make full use of the total transmission power of the LTE-U base station for transmission within the limit; therefore, the objective function (2) should satisfy the inequality (3) when obtaining the optimal solution:

First, considering only the total transmission power limitation of the LTE-U base station, the initial power allocation on each carrier is solved by adopting the Lagrangian multiplier method and applying the KKT condition. To do this, construct the corresponding Lagrange function:

Where λ represents the Lagrangian multiplier, and the following KKT conditions can be obtained:

Therefore, it can be concluded that the transmission power allocated to the i-th carrier is:

为正，则为该载波分配功率；否则，不为该载波分配功率，即该载波的P_i为0；由于通过式(10)求解得到的功率分配不一定满足式(4)和式(6)中单个载波的最低传输功率需求和传输功率上限，将其作为初始功率分配。Wherein [x] ⁺ ＝max(0, x); formula (10) expresses: if a certain carrier

is positive, the power is allocated to the carrier; otherwise, no power is allocated to the carrier, that is, the P _i of the carrier is 0; since the power allocation obtained by solving formula (10) does not necessarily satisfy formula (4) and formula (6 ) in the minimum transmission power requirement and transmission power upper limit of a single carrier, which is used as the initial power allocation.

The traditional water filling algorithm is used to solve the Lagrangian multiplier λ in formula (10) and the initial power allocation P _i of the LTE-U system; formula (10) is equivalent to:

相等，某个载波能否获得功率分配取决于

的大小。实际中可能存在一些载波CC_i，其

和h_i很小，以至于

对于这些载波，将不为其分配功率，即这些载波的P_i为0；对于其它满足

的载波，将为其分配功率。采用

表示最终获得功率分配的载波的集合，将式(10)代入式(7)中可得到：All carriers are assumed to have the same bandwidth. For the same λ, all carriers’

are equal, whether a carrier can get power allocation depends on

the size of. In practice, there may be some carriers CC _i , whose

and h _i are so small that

For these carriers, no power will be allocated to them, that is, the _Pi of these carriers is 0; for other

of the carriers for which power will be allocated. use

Represents the set of carriers that finally obtain power allocation, and substituting Equation (10) into Equation (7) can be obtained:

It can be solved that λ is:

为此，采用注水算法通过反复迭代以确定哪些载波因

而没有获得功率分配以及最终哪些载波获得功率分配；在此基础上，求解λ的最终值，并为

中的载波进行初始功率分配。According to equation (13), solving the Lagrangian multiplier λ needs to determine the set of carriers that finally obtain power allocation

To this end, the water injection algorithm is used to determine which carrier factors are

Without getting the power allocation and which carriers finally get the power allocation; on this basis, solve the final value of λ, and give

Carriers in the initial power allocation.

The main steps of the water injection algorithm are as follows:

a) initialization

b) Solve the current λ according to formula (13), namely:

中的载波根据

降序排列，并选取

最大的载波

c) will

The carrier in the

Sort in descending order and select

Maximum carrier

则此时

中所有载波的P_i均为正值，当前的λ为最终值，为

中的每一个载波分配相应功率，即设置：

否则，此时载波

的

为负值或零，则不为载波

分配功率，即设置：

并将载波

移出

然后转到步骤b)。d) if

then at this time

The P _i of all carriers in are positive, and the current λ is the final value, which is

Each carrier in is allocated corresponding power, that is, setting:

Otherwise, at this time the carrier

of

Negative or zero, not carrier

Allocate power, i.e. set:

and place the carrier

move out

Then go to step b).

In order to ensure the total throughput requirements of LTE-U users on each carrier, LTE-U base stations have the lowest power requirements on a single carrier in the unlicensed frequency band; If the value is lower than the minimum power requirement of the carrier, the minimum power allocation is performed for the carrier. The specific steps of minimum power allocation are shown in Figure 3 and described as follows:

a) Initialize the set of carriers representing power to be allocated

中所有载波进行初始功率分配，每个载波上获得的功率分配为

b) Use the water injection algorithm to

Initial power allocation is performed on all carriers in , and the power allocation obtained on each carrier is

中每个载波获得的初始功率分配P_i与该载波的最低功率需求进行比较；若载波CC_i的P_i小于其最低功率需求，则将

设置为该载波的最低功率需求，同时将总传输功率P_total减少

然后将载波CC_i移出待分配载波集合

c) in turn

The initial power allocation P _i obtained by each carrier in CC i is compared with the minimum power requirement of the carrier; if the P _i of the carrier CC _i is less than its minimum power requirement, then the

Set to the minimum power requirement for that carrier while reducing the total transmit power P _total

Then move the carrier CC _i out of the carrier set to be allocated

中所有载波完成一轮最低功率分配之后，若该轮分配过程中有载波完成功率分配被移出

则转到步骤b)；否则，最低功率分配完成。d) right

After all carriers complete a round of minimum power allocation, if any carrier completes power allocation during this round of allocation, it will be removed

Then go to step b); otherwise, the minimum power allocation is complete.

(3) Perform upper limit power allocation: After the minimum power allocation is completed, in order to meet the regulatory requirements of the unlicensed frequency band, it is necessary to consider the upper limit of the transmission power of the LTE-U base station on a single carrier in the unlicensed frequency band. If the initial power allocation value of a single carrier exceeds the transmission power upper limit of the carrier, the upper limit power allocation is performed on the carrier. By implementing upper limit power allocation, it is guaranteed that the power allocated to all carriers does not exceed the transmission power upper limit. After the upper limit power allocation is completed, the power allocated to all carriers is between the minimum power requirement of the carrier and the transmission power upper limit range, and at this time, all carriers have obtained power allocation that meets the constraint conditions.

In order to meet the regulatory requirements of the unlicensed frequency band, the power allocation needs to consider the upper limit of the transmission power of the LTE-U base station on a single carrier in the unlicensed frequency band; Capped power allocation. The specific steps of upper limit power allocation are shown in Figure 4 and described as follows:

中所有载波进行初始功率分配，每个载波上获得的功率分配为

a) Water injection algorithm is used to complete the lowest power allocation

Initial power allocation is performed on all carriers in , and the power allocation obtained on each carrier is

中每个载波获得的初始功率分配P_i与该载波的传输功率上限P_max进行比较；若载波CC_i的P_i超过其传输功率上限P_max，则将

设置为该载波的传输功率上限，同时将总传输功率P_total减少

然后将载波CC_i移出待分配载波集合

b) in turn

The initial power allocation P _i obtained by each carrier in CC i is compared with the transmission power upper limit P _max of the carrier; if the P _i of the carrier CC _i exceeds its transmission power upper limit P _max , then the

Set as the upper limit of the transmission power of the carrier, and at the same time reduce the total transmission power P _total

Then move the carrier CC _i out of the carrier set to be allocated

中所有载波完成一轮上限功率分配之后，若该轮分配过程中有载波完成功率分配被移出

转到步骤a)；否则，上限功率分配完成。c1 is right

After all carriers complete a round of upper limit power allocation, if a carrier completes power allocation during this round of allocation, it will be removed

Go to step a); otherwise, capped power allocation is complete.

中剩余载波的功率分配值

均在载波的最低功率需求和传输功率上限范围之间，此时所有载波都获得了满足约束条件的功率分配。After the upper limit power allocation is completed,

The power allocation value of the remaining carriers in

are between the minimum power requirement of the carrier and the upper limit of the transmission power, and at this time all the carriers have obtained the power allocation that satisfies the constraints.

Claims (4)

1. a kind of LTE-U system carrier power allocation method facing throughput demand, it is characterized in that: this carrier power allocation method comprises the following steps: (1) Adaptively adjust the LTE-U ON/OFF duty cycle of the CSAT cycle: Before the end of each CSAT cycle, after all LTE-U users in the coexistence network complete the carrier selection, according to the need for service on each carrier in the next CSAT cycle The number of users, that is, the sum of the number of users who have not yet completed transmission in the current cycle and the number of users newly allocated to the carrier, adjust the duty cycle of LTE-U ON/OFF on different carriers in the next CSAT working cycle; (2) Perform the lowest power allocation: After determining the LTE-U ON duty cycle on each carrier in the next CSAT cycle, combined with the channel quality on different carriers, the transmission power of the base station on different carriers in the next CSAT cycle Reallocate; in order to ensure the total throughput requirements of LTE-U users on each carrier, LTE-U base stations have the lowest power requirements on a single carrier in the unlicensed frequency band, that is, the lower limit of transmission power; first use the water injection algorithm for each carrier Initial power allocation, if the initial power allocation value of a single carrier is lower than the minimum power requirement of the carrier, the minimum power allocation is performed on the carrier; by performing the minimum power allocation, it is ensured that the power allocated to all carriers meets the minimum power requirement; (3) Perform upper limit power allocation: After the minimum power allocation is completed, in order to meet the regulatory requirements of the unlicensed frequency band, it is necessary to consider the upper limit of the transmission power of the LTE-U base station on a single carrier in the unlicensed frequency band; if the value of the initial power allocation of a single carrier exceeds If the upper limit of the transmission power of the carrier is determined, the upper limit power allocation will be performed on the carrier; through the implementation of the upper limit power allocation, it is ensured that the power allocated to all carriers does not exceed the upper limit of transmission power; after the upper limit power allocation is completed, the power allocated to all carriers Between the carrier's minimum power requirement and the transmission power upper limit range, all carriers have obtained power allocation satisfying the constraints; In steps (1)-(3), a converged network architecture based on network virtualization technology between the LTE-U system and the WiFi system is used to share information between the LTE-U system and the WiFi system, which is conducive to the realization of unauthorized The frequency band LTE-U system and WiFi system coexist friendly and allocate resources reasonably and efficiently; the converged network architecture is described as follows: An LTE-U subsystem and multiple WiFi subsystems coexist in the unlicensed frequency band; in this coexistence network, the LTE-U subsystem consists of a base station BS and several uniformly distributed user UEs, and each LTE-U user has a throughput Requirements; each WiFi subsystem consists of an AP and several evenly distributed user STAs; assuming that there are N orthogonal component carriers in the unlicensed frequency band, which are represented as CC ₁ , CC ₂ ,..., CC _N ; each CC can Shared by LTE-U system and a WiFi system; each WiFiAP uses a carrier, and different WiFiAPs use different carriers; LTE-U BS can use all N carriers to provide services for LTE-U users; LTE-U system downlink The transmission adopts the OFDMA channel access mechanism centrally scheduled by the base station to allocate time-frequency resources for users; the WiFi system adopts the 802.11n contention-based CSMA/CA channel access mechanism, and users access the channel in a competitive manner; each carrier adopts The F-CSAT mechanism based on time division multiplexing coordinates the coexistence of the two systems; Virtualize the physical entities LTE-U BS and WiFi AP in the LTE-U system and WiFi system into corresponding virtualized network entities vBS and vAP respectively, and manage the virtual entities through software-defined network technology; LTE-U BS virtualization The network entity vBS and WiFiAP virtualized network entity vAP are uniformly controlled by an SDN controller, which receives the load intensity of the wireless access network side, user throughput requirements and channel status from the LTE-U BS and WiFi AP physical entities; in each CSAT When all users in the coexistence network complete carrier selection before the end of the cycle, LTE-U needs to turn ON/OFF LTE-U on different carriers in the next CSAT cycle according to the number of users to be served on each carrier in the next CSAT cycle The duty cycle is adjusted. After determining the LTE-U ON/OFF duty cycle on each carrier, combined with the channel quality on different carriers, the transmission power of the base station on different carriers in the next CSAT period is redistributed; Therefore, it is necessary to communicate the received information between virtualized network entities, based on which carrier power allocation is performed, and the total throughput of the LTE-U system is improved on the premise of meeting the throughput requirements of LTE-U users; In steps (2)-(3), the water injection algorithm is used to carry out initial power allocation for each carrier under the condition that the total transmission power of the LTE-U base station is satisfied, and the specific process is as follows: Assuming that there are N orthogonal component carriers on the unlicensed frequency band of the coexistence network, denoted as CC ₁ , CC ₂ ,..., CC _N , the frequency bandwidth of each component carrier is _Bi , and the channel gain is h _i , i=1, 2,...,N; at the beginning of a CSAT period, the number of WiFi users that the i-th carrier needs to serve is

The number of LTE-U users is

The system throughput that can be obtained when the LTE-U system occupies the i-th component carrier alone is

The LTE-U ON duty cycle on each carrier is

The transmission power of the base station on each carrier is _Pi ; in this case, the total throughput R _total that the LTE-U system can obtain on N orthogonal component carriers is:

where _N0 represents the additive white Gaussian noise power spectral density on each carrier CC _i ; In the carrier power allocation problem of LTE-U system, consider the difference of channel quality on each carrier in the coexistence network and the channel occupancy time of LTE-U system; before the end of each CSAT cycle, all users in the coexistence network complete carrier selection In the case of , first determine the LTE-U ON duty cycle on each carrier in the next CSAT cycle

Then redistribute the transmission power of the base station on different carriers in the next CSAT cycle to maximize the total throughput of the LTE-U system, namely:

Restrictions:

Formula (5) is expressed as:

Among them, the inequality (3) indicates that the total transmission power of the LTE-U base station is limited to P _total , and the inequality (4) indicates that in order to meet the regulatory requirements of the unlicensed frequency band, the upper limit of the transmission power allowed by the LTE-U base station on a single carrier in the unlicensed frequency band is P _max , Inequality (6) expresses that in order to guarantee the total throughput requirement of LTE-U users on each carrier

The transmission power of the LTE-U base station on a single carrier needs to meet its minimum transmission power requirements; In order to maximize the total throughput of the LTE-U system, it is necessary to make full use of the total transmission power of the LTE-U base station for transmission within the limit; therefore, the objective function (2) should satisfy the inequality (3) when obtaining the optimal solution:

First, only the total transmission power limitation of the LTE-U base station is considered, and the initial power allocation on each carrier is solved by adopting the Lagrangian multiplier method and applying the KKT condition; for this, the corresponding Lagrangian function is constructed:

where λ represents the Lagrangian multiplier, leading to the following KKT conditions:

Therefore, the transmission power assigned to the i-th carrier is obtained as:

Wherein [x] ⁺ ＝max(0,x); Equation (10) expresses: if a certain carrier

is positive, the power is allocated to the carrier; otherwise, no power is allocated to the carrier, that is, the P _i of the carrier is 0; since the power allocation obtained by solving formula (10) does not necessarily satisfy formula (4) and formula (6 ) in the minimum transmission power requirement and transmission power upper limit of a single carrier, which is used as the initial power allocation; The traditional water filling algorithm is used to solve the Lagrangian multiplier λ in formula (10) and the initial power allocation P _i of the LTE-U system; formula (10) is equivalent to:

Assuming that the bandwidth of all carriers is the same; for the same λ, the bandwidth of all carriers

are equal, whether a carrier can get power allocation depends on

the size; for satisfying

No power will be allocated to the carriers that meet the conditions, that is, the _Pi of these carriers is 0; for other

conditional carrier, power will be allocated to it; using

Represents the set of carriers that finally obtain power allocation, and substitute equation (10) into equation (7) to get:

The solution for λ is:

According to equation (13), solving the Lagrangian multiplier λ needs to determine the set of carriers that finally obtain power allocation

To this end, the water injection algorithm is used to determine which carrier factors are

Without getting the power allocation and which carriers finally get the power allocation; on this basis, solve the final value of λ, and give

Carriers in the initial power allocation. 2. the LTE-U system carrier power allocation method facing throughput demand as claimed in claim 1, is characterized in that, the step of described water filling algorithm is as follows: a) initialization

b) Solve the current λ according to formula (13), namely:

c) will

The carrier in the

Sort in descending order and select

Maximum carrier

d) if

then at this time

The P _i of all carriers in are positive, and the current λ is the final value, which is

Each carrier in is allocated corresponding power, that is, setting:

Otherwise, at this time the carrier

of

for Negative or zero, not carrier

Allocate power, i.e. set:

and place the carrier

move out

Then go to step b). 3. The LTE-U system carrier power allocation method facing throughput requirements as claimed in claim 1, wherein in step (2), the lowest power allocation is performed to ensure that the allocated power of all carriers meets the minimum power requirement , the specific process is: In order to ensure the total throughput requirements of LTE-U users on each carrier, LTE-U base stations have the lowest power requirements on a single carrier in the unlicensed frequency band; If the value is lower than the minimum power requirement of the carrier, the minimum power allocation is performed on the carrier, and the specific steps are as follows: a) Initialize the set of carriers representing power to be allocated

b) Use the water injection algorithm to

Initial power allocation is performed on all carriers in , and the power allocation obtained on each carrier is

c) in turn

The initial power allocation P _i obtained by each carrier in is compared with the minimum power requirement of the carrier; If P _i of carrier CC _i is less than its minimum power requirement, then the

Set to the minimum power requirement for that carrier while reducing the total transmit power P _total

Then move the carrier CC _i out of the carrier set to be allocated

d) right

After all carriers complete a round of minimum power allocation, if any carrier completes power allocation during this round of allocation, it will be removed

Then go to step b); otherwise, the minimum power allocation is complete. 4. the LTE-U system carrier power allocation method facing throughput demand as claimed in claim 1, is characterized in that, in step (3), carries out upper limit power allocation, guarantees that the power that all carriers are allocated does not exceed transmission power The upper limit, the specific process is: In order to meet the regulatory requirements of the unlicensed frequency band, the power allocation needs to consider the upper limit of the transmission power of the LTE-U base station on a single carrier in the unlicensed frequency band; The upper limit power allocation, the specific steps are as follows: a) Water injection algorithm is used to complete the lowest power allocation

Initial power allocation is performed on all carriers in , and the power allocation obtained on each carrier is

b) in turn

The initial power allocation P _i obtained by each carrier in CC i is compared with the transmission power upper limit P _max of the carrier; if the P _i of the carrier CC _i exceeds its transmission power upper limit P _max , then the

Set as the upper limit of the transmission power of the carrier, and at the same time reduce the total transmission power P _total

Then move the carrier CC _i out of the carrier set to be allocated

c) right

After all carriers complete a round of upper limit power allocation, if a carrier completes power allocation during this round of allocation, it will be removed

Go to step a); otherwise, upper limit power allocation is completed; d) After the upper limit power distribution is completed,

The power allocation value of the remaining carriers in

are between the minimum power requirement of the carrier and the upper limit of the transmission power, and at this time all the carriers have obtained the power allocation that satisfies the constraints.

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