CN113613321B - LTE-U system carrier power distribution method facing throughput demand - Google Patents
LTE-U system carrier power distribution method facing throughput demand Download PDFInfo
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- CN113613321B CN113613321B CN202110894211.4A CN202110894211A CN113613321B CN 113613321 B CN113613321 B CN 113613321B CN 202110894211 A CN202110894211 A CN 202110894211A CN 113613321 B CN113613321 B CN 113613321B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/18—TPC being performed according to specific parameters
- H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters
- H04W52/241—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/18—TPC being performed according to specific parameters
- H04W52/28—TPC being performed according to specific parameters using user profile, e.g. mobile speed, priority or network state, e.g. standby, idle or non transmission
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- H—ELECTRICITY
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- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/30—TPC using constraints in the total amount of available transmission power
- H04W52/34—TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
- H04W52/346—TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading distributing total power among users or channels
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Abstract
The invention discloses a LTE-U system carrier power distribution method facing throughput demand, which comprises the following steps: (1) adaptively adjusting the LTE-U ON/OFF duty ratio of a CSAT period; (2) performing a minimum power allocation; and (3) performing upper limit power allocation. The invention can effectively ensure the fairness of coexistence of the LTE-U system and the WiFi system in the unlicensed frequency band, comprehensively considers the difference between the channel quality on different carriers and the occupation time of the channel of the LTE-U system on the premise of meeting the transmission power limit of the base station in the unlicensed frequency band and the throughput requirement of the LTE-U user, periodically adjusts the transmission power distribution of the base station on different carriers, and effectively improves the total throughput of the LTE-U system.
Description
Technical Field
The invention relates to the technical field of coexistence of unlicensed frequency bands of an LTE-U system and a WiFi system in mobile communication, in particular to a method for allocating carrier power of the LTE-U system facing throughput requirements.
Background
The unlicensed frequency band in general use worldwide has a lot of available spectrum resources that are not fully utilized. If the cellular network is allowed to transmit data in the unauthorized frequency band, the pressure of the authorized frequency band can be relieved, the capacity of the cellular network is obviously improved, and the frequency spectrum utilization rate of the unauthorized frequency band is greatly improved. Therefore, the industry has begun to research the development and utilization of unlicensed frequency bands. In 2013, a concept of "LTE-Unlicensed (LTE-U)" was formally proposed in radio access network standardization meeting RAN #62 held by the 3GPP organization, such as high-pass, ericsson, and huacheng. One key challenge of LTE-U technology is the need to ensure friendly coexistence of LTE systems with existing wireless communication systems in unlicensed bands, such as WiFi systems in the 5GHz band. LTE systems and WiFi systems employ distinct channel access mechanisms. Compared with a WiFi system, a channel access mechanism adopted by the LTE system has certain aggressiveness, and if the LTE system is directly deployed in an unauthorized frequency band, serious influence is caused on transmission of the WiFi system. Therefore, a reasonable channel access mechanism needs to be adopted on each carrier wave in the coexisting network to coordinate the transmission of the two systems, and the performance of the WiFi system is not seriously influenced.
On the basis of ensuring coexistence fairness of an LTE-U system and a WiFi system, on the premise of meeting transmission power limit of an unauthorized frequency band base station and throughput requirements of LTE-U users, the difference between channel quality on different carriers and the occupation time of channels of the LTE-U system needs to be comprehensively considered in order to further improve the total throughput of the LTE-U system. In the unlicensed band LTE-U and WiFi coexisting network, the total throughput of the LTE-U system is related to the signal-to-noise ratio (SNR) on each carrier, the channel gain and the channel occupation time of the LTE-U system on each carrier, wherein the channel gain depends on the factors of path loss, channel fading and the like, and the channel gains of different carriers are different. As users in the network dynamically arrive and leave, the channel occupancy time of the LTE-U system on each carrier may also vary. In addition, due to the regulatory requirement of the unlicensed frequency band, in order to reduce the interference to other coexisting systems of the unlicensed frequency band as much as possible, the total transmission power of the LTE-U base station on the unlicensed frequency band and the transmission power of the LTE-U base station on a single carrier both have upper limit limits. At the same time, it is also necessary to consider that LTE-U users on each carrier in a coexisting network have specific throughput requirements. Therefore, in order to improve the total throughput of the LTE-U system on the premise of guaranteeing the throughput requirement of the LTE-U user, it is necessary to research the problem of carrier power allocation of the LTE-U system facing the throughput requirement.
Disclosure of Invention
The invention aims to provide an LTE-U system carrier power distribution method facing throughput requirements to solve the problems. The method can effectively guarantee the fairness of coexistence of the LTE-U system and the WiFi system in the unlicensed frequency band, comprehensively considers the differences of the channel quality on different carriers and the occupation time of the LTE-U system channel on the premise of meeting the limitation of the transmission power of the base station in the unlicensed frequency band and the throughput requirement of the LTE-U user, periodically adjusts the transmission power distribution of the base station on different carriers, and effectively improves 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 facing throughput requirements, comprising the following steps:
(1) Adaptively adjusting the LTE-U ON/OFF duty ratio of a CSAT period: before each CSAT period is finished, after all LTE-U users in the coexisting network complete carrier selection, according to the number of users needing service ON each carrier in the next CSAT period, namely the sum of the number of users which have not finished transmission in the current period and the number of users newly distributed to the carrier, the ON/OFF duty ratio of the LTE-U ON different carriers in the next CSAT working period is adjusted;
(2) Performing a minimum power allocation: after the LTE-U ON duty ratio of each carrier wave in the next CSAT period is determined, the transmission power of the base station in the next CSAT period ON different carrier waves is redistributed by combining information such as channel quality ON different carrier waves; in order to guarantee the total throughput requirement of an LTE-U user on each carrier, the LTE-U base station has the lowest power requirement, namely the lower limit of transmission power, on a single carrier of an unauthorized frequency band; firstly, performing initial power distribution on each carrier by adopting a water injection algorithm, and performing minimum power distribution on the carrier if the initial power distribution value of a single carrier is lower than the minimum power requirement of the carrier; by executing minimum power distribution, the distributed power of all carriers is guaranteed to meet the minimum power requirement;
(3) Performing upper limit power allocation: after the minimum power allocation is completed, in order to meet the supervision requirement 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 wave of the unlicensed frequency band. If the value of the initial power allocation of a single carrier exceeds the upper limit of the transmission power of the carrier, performing upper limit power allocation on the carrier; and by executing upper limit power distribution, the distributed power of all the carriers is ensured not to exceed the upper limit of the transmission power. After the upper limit power distribution is completed, the power distributed to all the carriers is between the lowest power requirement of the carriers and the upper limit range of the transmission power, and all the carriers obtain the power distribution meeting the constraint condition at the moment.
In the method, in the steps (1) to (3), a network architecture integrating the LTE-U system and the WiFi system based on the network virtualization technology is adopted to share information between the LTE-U system and the WiFi system, so that the method is favorable for realizing friendly coexistence and reasonable and efficient resource allocation of the LTE-U system and the WiFi system in the unauthorized frequency band. The converged network architecture is described as follows:
an LTE-U subsystem and a plurality of WiFi subsystems coexist in an unlicensed frequency band. In the coexisting network, an LTE-U subsystem consists of a base station BS and a plurality of uniformly distributed user UEs, and each LTE-U user has a specific throughput requirement. Each WiFi subsystem consists of one AP and several evenly distributed user STAs. The unlicensed frequency band is assumed to have N orthogonal Component Carriers (CCs), which are denoted as CCs 1 ，CC 2 ，…，CC N . Each CC may be shared by the LTE-U system and one WiFi system. Each WiFi AP uses one carrier, and in order to avoid serious co-channel interference due to geographical proximity, it is further assumed that different WiFi APs use different carriers, so that mutual interference between different WiFi APs can be ignored. The LTE-U BS may use all N carriers to serve LTE-U users. Downlink transmission of the LTE-U system adopts an OFDMA channel access mechanism of base station centralized scheduling to distribute time-frequency resources for users; the WiFi system adopts an 802.11n CSMA/CA channel access mechanism based on competition, and users access the channel in a competition mode. And an F-CSAT mechanism based on time division multiplexing is adopted on each carrier wave to coordinate the coexistence of the two systems.
The method adopts a Network architecture of fusing an LTE-U system and a WiFi system based on a Network virtualization technology, respectively virtualizes physical entities in the LTE-U system and the WiFi system, namely an LTE-U BS and a WiFi AP, into a corresponding virtualized Network entity vBS (virtual BS) and a virtual AP (virtual AP), and manages the virtual entities through a 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 information such as load intensity, user throughput demand and channel state of a wireless access network side is received from the LTE-U BS and the WiFi AP physical entity. Under the condition that all users in the coexisting network complete carrier selection before each CSAT period is finished, the LTE-U needs to adjust the ON/OFF duty ratio of the LTE-U ON different carriers of the next CSAT working period according to the number of users needing service ON each carrier of the next CSAT period, and after the ON/OFF duty ratio of the LTE-U ON each carrier is determined, the transmission power of the base station ON different carriers of the next CSAT period is redistributed by combining information such as channel quality ON different carriers. Therefore, the received information needs to be communicated among the virtual entities, and carrier power allocation is performed according to the received information, so that the total throughput of the LTE-U system is improved on the premise of meeting the throughput requirement of the LTE-U user.
In the steps (2) and (3), the method of the invention adopts a water injection algorithm to distribute initial power for each carrier on the premise of meeting the limitation of the total transmission power of the LTE-U base station, and the specific process is as follows:
suppose there are N orthogonal component carriers, respectively denoted as CC, on the unlicensed band of the coexisting network 1 ，CC 2 ，…，CC N The bandwidth of each component carrier is B i Channel gain of h i I =1,2, \ 8230;, N. At the beginning of a CSAT period, the number of WiFi users to be served by the ith carrier is
The number of LTE-U users is
The system throughput obtained when the LTE-U system occupies the ith component carrier by itself is
LTE-U ON duty cycle ON each carrier of
The transmission power of the base station on each carrier is P i . In this case, the total throughput R that can be obtained by the LTE-U system on the N orthogonal component carriers can be obtained total Comprises the following steps:
wherein N is 0 Represents each carrier CC i Additive white gaussian noise power spectral density.
In the problem of carrier power distribution of an LTE-U system, the difference between the channel quality on each carrier in a coexisting network and the occupation time of the channel of the LTE-U system is considered. Before each CSAT period is finished, under the condition that all users in the coexisting network finish carrier selection, the LTE-U ON duty ratio ON each carrier in the next CSAT period is firstly determined
And then, the transmission power of the base station on different carriers in the next CSAT period is redistributed to maximize the total throughput of the LTE-U system, namely:
constraint conditions are as follows:
equation (5) can be expressed by deformation:
wherein inequality (3) represents that the total transmission power limit of the LTE-U base station is P total Inequality (4) indicates that in order to meet the regulatory requirement of the unlicensed frequency band, the upper limit of the allowed transmission power of the LTE-U base station on a single carrier wave of the unlicensed frequency band is P max Inequality (6) represents the total demand for throughput to guarantee 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, the total transmission power of the LTE-U base station needs to be fully utilized within a limited range for transmission; therefore, the objective function (2) should satisfy the inequality (3) when obtaining the optimal solution:
firstly, only the total transmission power limit of an LTE-U base station is considered, and the initial power distribution on each carrier wave is solved by adopting a Lagrange multiplier method and applying a KKT condition. To this end, a corresponding lagrangian function is constructed:
where λ represents the lagrange multiplier, the following KKT condition can be derived:
therefore, the transmission power allocated to the ith carrier can be found as:
wherein [ x ]] + = max (0, x); the formula (10) represents: if a certain carrier wave
If the carrier is positive, allocating power to the carrier; otherwise, no power is allocated to the carrier, i.e. P for the carrier i Is 0; since the power allocation obtained by solving equation (10) does not necessarily satisfy the minimum transmission power requirement and the upper transmission power limit of the single carrier in equations (4) and (6), it is taken as the initial power allocation.
Solving Lagrange multiplier lambda in formula (10) and initial power distribution P of LTE-U system by adopting traditional water filling algorithm i (ii) a Formula (10) is equivalent to:
it is assumed that the bandwidth of all carriers is the same. For the same lambda, all carriers
Equality, whether a certain carrier can achieve power division depends on
The size of (2). In practice there may be some carrier CCs i Which is
And h i Is so small that
For these carriers, no power will be allocated to them, i.e. P for these carriers i Is 0; for other satisfaction
Will be allocated power. By using
The set of carriers representing the final power allocation is obtained by substituting equation (10) for equation (7):
can be solved to obtain λ:
according to the formula (13), solving the Lagrange multiplier lambda needs to determine the set of carriers which finally obtain power distribution
To this end, a water-filling algorithm is used to determine which carrier factors by iterative iterations
Without obtaining power allocation and ultimately which carriers obtain power allocation; on the basis of this, the final value of λ is solved and is
The carrier of (1) performs initial power allocation.
The water filling algorithm mainly comprises the following steps:
a) Initialization
b) The current λ is solved according to equation (13), i.e.:
c) Will be provided with
According to the carrier wave
Sorting in descending order and selecting
Maximum carrier wave
d) If it is
Then this time
P of all carriers in i Are all positive values, the current lambda is the final value, is
Each carrier in (2) allocates a respective power, i.e. setting:
otherwise, the carrier wave at this time
Is/are as follows
Negative or zero, then not carrier
Allocating power, i.e. setting:
and will carry the carrier wave
Removal of
And then go to step b).
In step (2), the method of the present invention executes the lowest power allocation to ensure that the power allocated to all carriers meets the lowest power requirement, and the specific process is as follows:
in order to guarantee the total throughput requirement of the LTE-U users on each carrier, the LTE-U base station has the lowest power requirement on a single carrier of an unauthorized frequency band; firstly, allocating initial power to each carrier by a water injection algorithm, and if the value of the initial power allocation of a single carrier is lower than the minimum power requirement of the carrier, performing minimum power allocation on the carrier, wherein the specific steps are as follows:
a) Initializing a set of carriers representing power to be allocated
b) Using water-filling algorithm pair
The initial power distribution is carried out on all the carriers, and the power distribution obtained on each carrier is
c) In turn will
Initial power allocation P obtained per carrier i Comparing to the lowest power requirement for the carrier;
if carrier CC i P of i Less than its minimum power requirement, then
Set to the minimum power requirement for that carrier, while setting the total transmit power P total Reduce the number of
Then CC carrier i Removal ofSet of carriers to be allocated
d) When is paired with
After all carriers finish a round of lowest power distribution, if the carrier finish power distribution is shifted out in the distribution process of the round
Go to step b); otherwise, the lowest power allocation is complete.
In step (3), the method of the present invention executes upper limit power distribution to ensure that the power distributed to all carriers does not exceed the transmission power upper limit, and the specific process is as follows:
in order to meet the supervision requirement of an unlicensed frequency band, the upper limit of the transmission power of the LTE-U base station on a single carrier wave of the unlicensed frequency band needs to be considered in power distribution; if the value of the initial power allocation of a single carrier exceeds the upper limit of the transmission power of the carrier, performing upper limit power allocation on the carrier, and specifically comprising the following steps:
a) Using water-filling algorithms for minimum power allocation
The initial power distribution is carried out on all the carriers, and the power distribution obtained on each carrier is
b) In turn will
Initial power allocation P obtained for each carrier i Upper limit of transmission power P with the carrier max Comparing; if carrier CC i P of i Exceeds its upper transmission power limit P max Then will be
Setting the upper limit of the transmission power of the carrier wave and simultaneously setting the total transmission power P total Reduction of
Then CC carrier i Moving out a set of carriers to be allocated
c) When is to
After completing one round of upper limit power distribution of all carriers, if the carrier completion power distribution is shifted out in the round of distribution process
Go to step a); otherwise, the upper power allocation is complete.
After the upper limit power allocation is completed,
power allocation value of medium remaining carrier
Are both between the minimum power requirement of the carriers and the upper limit range of the transmission power, and all carriers have power allocation meeting the constraint condition.
Advantageous effects
Compared with the prior art, the invention has the following advantages:
1) The invention considers the dynamic of the LTE-U and WiFi coexisting network state and the difference of different carriers, can not simply distribute the same transmission power to the base station on all the carriers, but needs to periodically adjust the transmission power distribution of the base station on different carriers according to the channel quality on different carriers and the difference of the channel occupation time of the LTE-U system, thereby effectively improving the total throughput of the LTE-U system.
2) The LTE-U system carrier power distribution method facing the throughput demand can solve the problem of carrier power distribution of an unlicensed frequency band LTE-U system. The method can effectively guarantee the fairness of coexistence of the LTE-U system and the WiFi system in the unlicensed frequency band, comprehensively considers the differences of the channel quality on different carriers and the occupation time of the LTE-U system channel on the premise of meeting the limitation of the transmission power of the base station in the unlicensed frequency band and the throughput requirement of the LTE-U user, periodically adjusts the transmission power distribution of the base station on different carriers, and effectively improves the total throughput of the LTE-U system.
Drawings
FIG. 1: a flow diagram of a LTE-U system carrier power distribution method facing throughput requirements;
FIG. 2: an LTE-U and WiFi coexisting network scene schematic diagram based on a converged network architecture;
FIG. 3: a flow chart of a lowest power distribution step;
FIG. 4 is a schematic view of: the upper limit power allocation step is a schematic flow chart.
Detailed Description
The present invention will be further described with reference to the accompanying drawings. The invention provides a method for allocating LTE-U system carrier power facing throughput demand, which is implemented according to the following steps as shown in figure 1:
(1) Adaptively adjusting the LTE-U ON/OFF duty ratio of a CSAT period: before each CSAT period is finished, after all LTE-U users in the coexisting network complete carrier selection, the LTE-U ON/OFF duty ratio ON different carriers of the next CSAT working period is adjusted according to the number of users needing service ON each carrier of the next CSAT period, namely the sum of the number of users which have not finished transmission in the current period and the number of users newly distributed to the carrier.
The method adopts a network architecture integrating an LTE-U system and a WiFi system based on a network virtualization technology, and an LTE-U subsystem and a plurality of WiFi subsystems coexist in an unauthorized frequency band, as shown in figure 2. In the coexisting network, an LTE-U subsystem consists of a base station BS and a plurality of uniformly distributed user UEs, and each LTE-U user has a specific throughput requirement. Each WiFi subsystem consists of one AP and several evenly distributed user STAs. Assuming unlicensed frequenciesThe segment has N orthogonal Component Carriers (CCs), which are denoted as CC 1 ，CC 2 ，…，CC N . Each CC may be shared by the LTE-U system and one WiFi system. Each WiFi AP uses one carrier, and in order to avoid severe co-channel interference due to geographical proximity, it is further assumed that different WiFi APs use different carriers, so mutual interference between different WiFi APs can be ignored. The LTE-U BS may use all N carriers to serve LTE-U users. Downlink transmission of the LTE-U system adopts an OFDMA channel access mechanism of base station centralized scheduling to distribute time-frequency resources for users; the WiFi system adopts an 802.11n CSMA/CA channel access mechanism based on competition, and users access the channel in a competition mode. And an F-CSAT mechanism based on time division multiplexing is adopted on each carrier wave to coordinate the coexistence of the two systems.
Physical entities in an LTE-U system and a WiFi system, namely an LTE-U BS and a WiFi AP, are virtualized into corresponding virtualized Network entities, namely a virtual BS and a virtual AP, respectively, and the virtual entities are managed through 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 information such as load intensity, user throughput demand and channel state of a wireless access network side is received from the LTE-U BS and the WiFi AP physical entity. Under the condition that all users in the coexisting network complete carrier selection before each CSAT period is finished, the LTE-U needs to adjust the LTE-U ON/OFF duty ratio ON different carriers of the next CSAT working period according to the number of users needing service ON each carrier of the next CSAT period, and after the LTE-U ON/OFF duty ratio ON each carrier is determined, the transmission power of the base station ON different carriers of the next CSAT period is redistributed by combining information such as channel quality ON different carriers. Therefore, the received information needs to be communicated between the virtual entities, so that the carrier power distribution is performed, and the total throughput of the LTE-U system is improved on the premise of meeting the throughput requirement of the LTE-U user.
(2) Performing a minimum power allocation: after the LTE-U ON duty ratio of each carrier wave in the next CSAT period is determined, the transmission power of the base station in the next CSAT period ON different carrier waves is redistributed by combining information such as channel quality ON different carrier waves. In order to guarantee the total throughput requirement of the LTE-U users on each carrier, the LTE-U base station has the lowest power requirement, namely the lower limit of transmission power, on a single carrier in an unauthorized frequency band. Firstly, a water filling algorithm is adopted to carry out initial power distribution on each carrier, and if the value of the initial power distribution of a single carrier is lower than the minimum power requirement of the carrier, the minimum power distribution is carried out on the carrier. And by executing the minimum power allocation, the allocated power of all the carriers is ensured to meet the minimum power requirement.
Suppose there are N orthogonal component carriers, denoted as CC, on the unlicensed band of the coexisting network 1 ，CC 2 ，…，CC N The frequency bandwidth of each component carrier is B i Channel gain of h i I =1,2, \ 8230;, N. At the beginning of a CSAT period, the number of WiFi users to be served by the ith carrier is
The number of LTE-U users is
The system throughput obtained when the LTE-U system occupies the ith component carrier by itself is
LTE-U ON duty cycle ON each carrier of
Transmission power of base station P on each carrier i . In this case, the total throughput R that can be obtained by the LTE-U system on the N orthogonal component carriers can be obtained total Comprises the following steps:
wherein N is 0 Denotes each carrier CC i Additive white gaussian noise power spectrumAnd (4) degree.
In the problem of carrier power distribution of an LTE-U system, the difference between the channel quality on each carrier in a coexisting network and the occupation time of the channel of the LTE-U system is considered. Before each CSAT period is finished, under the condition that all users finish carrier selection in the coexisting network, the LTE-U ON duty ratio ON each carrier in the next CSAT period is determined firstly
And then, the transmission power of the base station on different carriers in the next CSAT period is redistributed to maximize the total throughput of the LTE-U system, namely:
constraint conditions are as follows:
equation (5) can be expressed by deformation:
wherein inequality (3) represents that the total transmission power limit of the LTE-U base station is P total Inequality (4) indicates that in order to meet the regulatory requirement of the unlicensed frequency band, the upper limit of the allowed transmission power of the LTE-U base station on a single carrier wave of the unlicensed frequency band is P max Inequality (6) represents the total demand for throughput to guarantee 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, the total transmission power of the LTE-U base station needs to be fully utilized within a limited range for transmission; therefore, the objective function (2) should satisfy the inequality (3) when obtaining the optimal solution:
firstly, only the total transmission power limit of an LTE-U base station is considered, and the initial power distribution on each carrier wave is solved by adopting a Lagrange multiplier method and applying a KKT condition. To this end, the corresponding lagrangian function is constructed:
where λ represents the lagrange multiplier, the following KKT condition can be derived:
therefore, the transmission power allocated to the ith carrier can be found as:
wherein [ x ]] + = max (0, x); the formula (10) represents: if a certain carrier wave
If the carrier is positive, allocating power to the carrier; otherwise, no power is allocated to the carrier, i.e. P for the carrier i Is 0; since the power distribution obtained by solving equation (10) does not necessarily satisfy the singles in equations (4) and (6)The lowest transmission power requirement and the upper transmission power limit of each carrier are used as initial power allocation.
Solving Lagrange multiplier lambda in formula (10) and initial power distribution P of LTE-U system by adopting traditional water filling algorithm i (ii) a Equation (10) is equivalent to:
it is assumed that the bandwidth of all carriers is the same. For the same lambda, all carriers
Equality, whether a certain carrier can achieve power division depends on
The size of (2). There may be some carrier CCs in practice i Which is
And h i Is so small that
For these carriers, no power will be allocated to them, i.e. P for these carriers i Is 0; for other satisfaction
Will be allocated power. By using
The set of carriers representing the final power allocation is obtained by substituting equation (10) for equation (7):
can be solved to obtain λ:
according to equation (13), solving the lagrangian multiplier λ requires determining the set of carriers that ultimately obtain power allocation
To this end, a water-filling algorithm is used to determine which carrier factors by iterative iterations
Without obtaining a power allocation and ultimately which carriers obtain a power allocation; on this basis, the final value of λ is solved and
the carrier in (1) performs initial power allocation.
The water filling algorithm mainly comprises the following steps:
a) Initialization
b) The current λ is solved according to equation (13), i.e.:
c) Will be provided with
According to the carrier wave in
Sorting in descending order and selecting
Maximum carrier wave
d) If it is
Then this time
P of all carriers in i All positive values, the current lambda is the final value, which is
Each carrier in (2) allocates a respective power, i.e. setting:
otherwise, the carrier wave at this time
Is/are as follows
Negative or zero, then not carrier
Allocating power, i.e. setting:
and will carry the carrier wave
Removal of
And then go to step b).
In order to guarantee the total throughput requirement of an LTE-U user on each carrier, the LTE-U base station has the lowest power requirement on a single carrier of an unauthorized frequency band; the method comprises the steps that initial power is distributed to each carrier through a water filling algorithm, and if the value of the initial power distribution of a single carrier is lower than the minimum power requirement of the carrier, the minimum power distribution is carried out on the carrier. The specific steps of the lowest power allocation are shown in fig. 3 and described as follows:
a) Initializing a set of carriers representing power to be allocated
b) Using water-filling algorithm pair
The initial power distribution is carried out on all the carriers, and the power distribution obtained on each carrier is
c) In turn will
Initial power allocation P obtained for each carrier i Comparing to the lowest power requirement for the carrier; if carrier CC i P of i Less than its minimum power requirement, will
Set to the minimum power requirement for that carrier, while setting the total transmit power P total Reduce the number of
Then CC is carried i Moving out the set of carriers to be allocated
d) When is paired with
After all carriers finish a round of lowest power distribution, if the carrier finish power distribution is shifted out in the distribution process of the round
Go to step b); otherwise, the lowest power allocation is complete.
(3) Performing upper limit power allocation: after the minimum power allocation is completed, in order to meet the supervision requirement of the unlicensed frequency band, the upper limit of the transmission power of the LTE-U base station on a single carrier wave of the unlicensed frequency band needs to be considered. And if the value of the initial power allocation of the single carrier exceeds the upper limit of the transmission power of the carrier, performing upper limit power allocation on the carrier. And by executing upper limit power distribution, the distributed power of all the carriers is ensured not to exceed the upper limit of the transmission power. After the upper limit power allocation is completed, the power allocated to all the carriers is between the lowest power requirement of the carriers and the upper limit range of the transmission power, and all the carriers obtain the power allocation meeting the constraint condition at this time.
In order to meet the supervision requirement of the unauthorized frequency band, the transmission power upper limit of the LTE-U base station on a single carrier wave of the unauthorized frequency band needs to be considered in power distribution; and if the value of the initial power allocation of the single carrier exceeds the upper limit of the transmission power of the carrier, performing upper limit power allocation on the carrier. The specific steps of the upper limit power allocation are shown in fig. 4 and described as follows:
a) Using water-filling algorithms for minimum power allocation
The initial power distribution is carried out on all the carriers, and the power distribution obtained on each carrier is
b) In turn will
Initial power allocation P obtained per carrier i Upper limit of transmission power P with the carrier max Comparing; if carrier CC i P of i Exceeds its upper limit of transmission power P max Then will be
Setting the upper limit of the transmission power of the carrier wave and simultaneously setting the total transmission power P total Reduction of
Then CC is carried i Moving out the set of carriers to be allocated
c1 when being paired
After completing one round of upper limit power distribution of all carriers, if the carrier completion power distribution is shifted out in the round of distribution process
Go to step a); otherwise, the upper power allocation is complete.
After the upper power allocation is completed,
power allocation value of medium remaining carrier
Are both between the minimum power requirement of the carriers and the upper limit range of the transmission power, and all carriers have power allocation meeting the constraint condition.
Claims (4)
1. A LTE-U system carrier power distribution method facing throughput demand is characterized in that: the carrier power distribution method comprises the following steps:
(1) Adaptively adjusting the LTE-U ON/OFF duty ratio of a CSAT period: before each CSAT period is finished, after all LTE-U users in the coexisting network complete carrier selection, according to the number of users needing service ON each carrier in the next CSAT period, namely the sum of the number of users which have not finished transmission in the current period and the number of users newly distributed to the carrier, the ON/OFF duty ratio of the LTE-U ON different carriers in the next CSAT working period is adjusted;
(2) Performing a minimum power allocation: after the LTE-U ON duty ratio of each carrier wave in the next CSAT period is determined, the transmission power of the base station in the next CSAT period ON different carrier waves is redistributed by combining the channel quality ON different carrier waves; in order to guarantee the total throughput requirement of the LTE-U users on each carrier, the LTE-U base station has the lowest power requirement, namely the lower limit of transmission power, on a single carrier in an unauthorized frequency band; firstly, performing initial power distribution on each carrier by adopting a water injection algorithm, and performing minimum power distribution on the carrier if the initial power distribution value of a single carrier is lower than the minimum power requirement of the carrier; by executing minimum power distribution, the distributed power of all carriers is guaranteed to meet the minimum power requirement;
(3) Performing upper limit power allocation: after the lowest power allocation is completed, in order to meet the supervision requirement of the unauthorized frequency band, the upper limit of the transmission power of the LTE-U base station on a single carrier wave of the unauthorized frequency band needs to be considered; if the value of the initial power allocation of a single carrier exceeds the upper limit of the transmission power of the carrier, performing upper limit power allocation on the carrier; by executing upper limit power distribution, ensuring that the power distributed by all carriers does not exceed the upper limit of transmission power; after the upper limit power distribution is finished, the power distributed to all the carriers is between the lowest power requirement of the carriers and the upper limit range of the transmission power, and all the carriers obtain the power distribution meeting the constraint condition at the moment;
in the steps (1) - (3), a network architecture integrating the LTE-U system and the WiFi system based on a network virtualization technology is adopted to share information between the LTE-U system and the WiFi system, so that the LTE-U system and the WiFi system in an unauthorized frequency band can coexist friendly and reasonably and efficiently can be distributed; the converged network architecture is described as follows:
an LTE-U subsystem and a plurality of WiFi subsystems coexist in an unauthorized frequency band; in the coexisting network, an LTE-U subsystem consists of a base station BS and a plurality of user UEs which are uniformly distributed, and each LTE-U user has throughput requirements; each WiFi subsystem consists of an AP and a plurality of user STAs which are uniformly distributed; assume that the unlicensed band has N orthogonal component carriers, denoted CC 1 ,CC 2 ,…,CC N (ii) a Each CC may be shared by LTE-U systems and one WiFi system; each wifi ap uses one carrier, and different wifi aps use different carriers; the LTE-U BS can use all N carriers to provide service for the LTE-U user; under LTE-U systemThe line transmission adopts an OFDMA channel access mechanism of base station centralized scheduling to distribute time-frequency resources for users; the WiFi system adopts an 802.11n CSMA/CA channel access mechanism based on competition, and users access a channel in a competition mode; an F-CSAT mechanism based on time division multiplexing is adopted on each carrier wave to coordinate coexistence of the two systems;
respectively virtualizing physical entities LTE-U BS and WiFi AP in an LTE-U system and a WiFi system into corresponding virtualized network entities vBS and vAP, and managing the virtual entities through a software defined network technology; the LTE-U BS virtual network entity vBS and the WiFiAP virtual network entity vAP are uniformly controlled by an SDN controller, and the load intensity, the user throughput demand and the channel state of a wireless access network side are received from the LTE-U BS and the WiFi AP physical entity; under the condition that all users in the coexisting network complete carrier selection before each CSAT period is finished, the LTE-U needs to adjust the LTE-U ON/OFF duty ratio ON different carriers of the next CSAT working period according to the number of users needing service ON each carrier of the next CSAT period, and after the LTE-U ON/OFF duty ratio ON each carrier is determined, the transmission power of the base station ON different carriers of the next CSAT period is redistributed by combining the channel quality ON different carriers; therefore, the received information needs to be communicated among the virtualized network entities, and the carrier power distribution is carried out according to the information, so that the total throughput of the LTE-U system is improved on the premise of meeting the throughput requirement of an LTE-U user;
in the steps (2) - (3), a water injection algorithm is adopted to perform initial power distribution on each carrier under the condition of meeting the limitation of the total transmission power of the LTE-U base station, and the specific process is as follows:
suppose there are N orthogonal component carriers, denoted as CC, on the unlicensed band of the coexisting network 1 ,CC 2 ,…,CC N The frequency bandwidth of each component carrier is B i Channel gain of h i I =1,2, \ 8230;, N; at the beginning of a CSAT period, the number of WiFi users to be served by the ith carrier is
Number of LTE-U users is
The system throughput obtained when the LTE-U system occupies the ith component carrier by itself is
LTE-U ON duty cycle ON each carrier of
The transmission power of the base station on each carrier is P i (ii) a In such a case, the total throughput R that can be obtained by the LTE-U system on the N orthogonal component carriers is obtained total Comprises the following steps:
wherein, N 0 Denotes each carrier CC i Additive white gaussian noise power spectral density;
in the problem of carrier power distribution of an LTE-U system, the difference between the channel quality on each carrier in a coexisting network and the occupied time of a channel of the LTE-U system is considered; before each CSAT period is finished, under the condition that all users in the coexisting network finish carrier selection, the LTE-U ON duty ratio ON each carrier in the next CSAT period is firstly determined
And then, the transmission power of the base station on different carriers in the next CSAT period is redistributed to maximize the total throughput of the LTE-U system, namely:
constraint conditions are as follows:
equation (5) is expressed by deformation:
wherein inequality (3) represents that the total transmission power limit of the LTE-U base station is P total Inequality (4) indicates that in order to meet the supervision requirement of the unlicensed frequency band, the upper limit of the allowed transmission power of the LTE-U base station on the single carrier wave of the unlicensed frequency band is P max Inequality (6) represents the total demand for throughput to guarantee LTE-U users on each carrier
The transmission power of the LTE-U base station on a single carrier needs to meet the requirement of the LTE-U base station on the lowest transmission power;
in order to maximize the total throughput of the LTE-U system, the total transmission power of the LTE-U base station needs to be fully utilized within a limited range for transmission; therefore, the objective function (2) should satisfy the inequality (3) when obtaining the optimal solution:
firstly, only considering the total transmission power limit of an LTE-U base station, and solving initial power distribution on each carrier by adopting a Lagrange multiplier method and applying a KKT condition; to this end, the corresponding lagrangian function is constructed:
where λ represents the lagrange multiplier, the following KKT condition results:
therefore, the transmission power allocated to the ith carrier is obtained as:
wherein [ x ]] + = max (0, x); the formula (10) represents: if a certain carrier wave
If the carrier is positive, allocating power to the carrier; otherwise, no power is allocated to the carrier, i.e. P for the carrier i Is 0; the power allocation obtained by solving the equation (10) does not necessarily satisfy the minimum transmission power requirement and the upper transmission power limit of a single carrier in the equations (4) and (6), and is taken as the initial power allocation;
solving Lagrange multiplier lambda in formula (10) and initial power distribution P of LTE-U system by adopting traditional water filling algorithm i (ii) a Equation (10) is equivalent to:
assuming that the bandwidths of all carriers are the same; for the same lambda, all carriers
Equality, whether a certain carrier can achieve power division depends on
The size of (d); for the satisfaction of
Carriers of the condition for which no power is to be allocated, i.e. P for these carriers i Is 0; for other satisfaction
A conditional carrier for which power is to be allocated; by using
The set of carriers for which power allocation is finally obtained is represented by equation (10) in equation (7):
the solution λ is:
according to equation (13), solving the lagrangian multiplier λ requires determining the set of carriers that ultimately obtain power allocation
To this end, a water-filling algorithm is used to determine which carrier factors by iterative iteration
Without obtaining a power allocation and ultimately which carriers obtain a power allocation; on this basis, the final value of λ is solved and
the carrier of (1) performs initial power allocation.
2. The method for LTE-U system carrier power allocation for throughput-oriented requirements according to claim 1, wherein the step of the water-filling algorithm is as follows:
a) Initialization
b) The current λ is solved according to equation (13), i.e.:
c) Will be provided with
According to the carrier wave
Sorting in descending order and selecting
Maximum carrier wave
d) If it is
Then this time
P of all carriers in i Are all positive values, the current lambda is the final value, is
Each carrier of which is assigned a phasePower, i.e. settings:
otherwise, the carrier wave at this time
Is/are as follows
Is composed of
Negative or zero, then not carrier
Allocating power, i.e. setting:
and will carry the carrier wave
Removal of
And then go to step b).
3. The method for allocating carrier power to LTE-U system facing throughput requirement according to claim 1, wherein in step (2), minimum power allocation is performed to ensure that the allocated power of all carriers meets the minimum power requirement, and the specific process is as follows:
in order to guarantee the total throughput requirement of the LTE-U users on each carrier, the LTE-U base station has the lowest power requirement on a single carrier of an unauthorized frequency band; firstly, allocating initial power to each carrier by a water injection algorithm, and if the value of the initial power allocation of a single carrier is lower than the minimum power requirement of the carrier, performing minimum power allocation on the carrier, wherein the specific steps are as follows:
a) Initializing a set of carriers representing power to be allocated
b) Using water-filling algorithm pair
The initial power distribution is carried out on all the carriers, and the power distribution obtained on each carrier is
c) In turn will
Initial power allocation P obtained per carrier i Comparing to the lowest power requirement for the carrier;
if carrier CC i P of i Less than its minimum power requirement, will
Set to the minimum power requirement for that carrier, while setting the total transmit power P total Reduction of
Then CC carrier i Moving out a set of carriers to be allocated
d) When is paired with
After all carriers finish a round of lowest power distribution, if the carrier finish power distribution is shifted out in the distribution process of the round
Go to step b); otherwise, the lowest power allocation is complete.
4. The method for allocating carrier power to LTE-U system facing throughput requirement of claim 1, wherein in step (3), the upper limit power allocation is performed to ensure that the allocated power of all carriers does not exceed the upper limit of transmission power, and the specific process is as follows:
in order to meet the supervision requirement of an unlicensed frequency band, the upper limit of the transmission power of the LTE-U base station on a single carrier wave of the unlicensed frequency band needs to be considered in power distribution; if the value of the initial power allocation of a single carrier exceeds the upper limit of the transmission power of the carrier, performing upper limit power allocation on the carrier, and specifically comprising the following steps:
a) Using water-filling algorithms for minimum power allocation
All the carriers are initially allocated with power, and the power obtained on each carrier is allocated as
b) In turn will
Initial power allocation P obtained per carrier i Upper limit of transmission power P with the carrier max Comparing; if carrier CC i P of i Exceeds its upper transmission power limit P max Then will be
Setting the upper limit of the transmission power of the carrier wave and simultaneously setting the total transmission power P total Reduce the number of
Then CC is carried i Moving out the set of carriers to be allocated
c) When is to
After completing one round of upper limit power distribution of all carriers, if the carrier completion power distribution is shifted out in the round of distribution process
Go to step a); otherwise, completing the upper limit power distribution;
d) After the upper limit power allocation is completed,
power allocation value of medium remaining carrier
Are both between the minimum power requirement of the carriers and the upper limit range of the transmission power, and all carriers have power allocation meeting the constraint condition.
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