Disclosure of Invention
In order to solve the problems, the invention discloses a super-dense network small station dormancy method based on channel and queue sensing, which describes the balance problem of system energy consumption and time delay as the problem of minimizing a system cost function, and makes a channel and queue sensing base station dormancy strategy under the condition that user service and channel state dynamically change.
Existing base station dormancy techniques select a base station to be turned off based on user traffic awareness or channel conditions. We have found that the user delay in the system is not only related to the traffic but also to the channel conditions. The larger the traffic is, the longer the user queue waiting time is, and meanwhile, the better the channel state between the user and the base station is, the smaller the user transmission delay is.
Based on the method, the optimal base station dormancy ratio is calculated firstly, the number of base stations to be dormant is calculated according to the base station dormancy ratio, namely, the number of the base stations to be closed under the condition of meeting the user time delay characteristic is determined. Secondly, considering the average queue length of each base station and the average transmission rate obtained by the user associated with the base station, arranging the small stations in an ascending order according to the product of the average queue length and the average transmission rate obtained by the user, and sequentially selecting the base stations to be closed according to the order, thereby reducing the energy consumption of the system.
In order to achieve the purpose, the invention provides the following technical scheme:
a super-dense network small station sleeping method based on channel and queue sensing comprises the following steps:
step 1, collecting network information
Measuring the total number N of users, macro stations, small stations and gateways in the areau、Nm、Ns、NgObtaining the distribution density lambda of the gateway, the macro station, the small station and the user in the areag,λm,λsAnd λu;
When the user flow reaches the meeting berth process, counting the user flow use condition in a period of time to obtain the user flow arrival rate lambda and the average bit size l of each packet;
obtaining the bandwidth W of the backhaul link of the small station wireless deployed in the areabWireless access bandwidth W adopted by macro stationmWireless access bandwidth W adopted by small stationsMacro station transmission power PmtSmall station transmission power PstGateway transmission power Pgt;
Recording the average energy consumption of each gateway
Average energy consumption of sleeping small stations
Energy consumption of macro and small station static links
And
obtaining a path loss coefficient alpha in a wireless channel by using a channel estimation method;
determining offset value A of user associated to small station according to network operation conditionbLoad-dependent energy consumption factor Δ p for macro and small stationsmAnd Δ psThe values of a signal-to-interference ratio threshold beta, a weight factor omega, an iterative search step length delta, iterative search accuracy xi, a time interval T and a time length T are determined according to needs;
all macro stations are in an activated state;
the base station dormancy ratio of the small station is marked as theta, and the initial value theta of the base station dormancy ratio0The optimal sleep ratio is determined according to the network operation condition*The value of the base station dormancy ratio in the nth iteration process is thetan;
And 2, iterating according to a gradient descent method, wherein the initial value of the iteration number is n-0, and calculating the sleep ratio theta-theta of the base station during the nth iteration
nAverage packet delay for macro and small station users
And
and average time delay of the whole network
Firstly, the probability Pr of the user connecting to the small station is calculatedSUE(θ)
The gateway, the macro station and the small station are M/G/1 queues, so the time delay of a user comprises transmission time delay and queuing time delay;
the user is divided into two parts: the first part is a user connected with the macro station, and the second part is a user connected with the small station;
average time delay for user connected with macro station
Including average transmission delay for the delay of the radio access link
And average queuing delay
Namely, it is
Calculated by the following formula:
Wherein the content of the first and second substances,
represents an average transmission rate obtained when a user accesses the macro station;
and
the average transmission probability of the macro station and the small station is obtained by the following two equations through a dichotomy:
in the above formula, the first and second carbon atoms are,
for the users accessing the small station, the average time delay of each packet is the average time delay of the wireless access link
And wireless backhaul link average delay
Summing; likewise, the access link average delay
And wireless backhaul link average delay
Also respectively comprise average transmission time delay
And average queuing delay
Namely, it is
Wherein the content of the first and second substances,
calculated by the following formula:
wherein the content of the first and second substances,
the average transmission rate of the wireless transmission link for the small station user,
representing the average transmission rate of the backhaul link from the gateway to the small station;
calculated by the following formula:
wherein the content of the first and second substances,the average transmission probability for a gateway is calculated by:
thereby obtaining the average time delay of the network
The following formula:
step 3, calculating the sleep ratio theta of the current base station by the following formula
nLower system average energy consumption
And a cost function F (θ):
and 4, solving the current nth iteration through the following formula, wherein the sleep proportion theta of the cost function F (theta) to the base station is theta
nDerivative function of
Wherein the content of the first and second substances,
and 5, updating the base station sleep ratio theta, wherein the base station sleep ratio theta is equal to theta in the n +1 th iterationn+1Updated by the following equation:
step 6, judging that the whole network cost function F (theta) is F (theta) under the current base station dormancy ration) Whether a minimum point is reached; when F (theta)n+1)-F(θn) When the value is less than ξ, the optimal point is reached, and the step 8 is executed to quit the iteration process; otherwiseExecuting step 7;
and 7: updating the current iteration number n +1, and executing the step 2-6;
and 8: quitting the iteration process to obtain the optimal sleep proportion theta of the base station*;
And step 9: making theta equal to 0, namely all the small stations are in an activated state, and updating the user connection state; counting the queue lengths of all the small stations and the average transmission rate of users at a time interval T, and further calculating the average queue length and the average transmission rate in the time length T;
step 10: arranging the small stations in an ascending order according to the product of the average queue length of each small station and the average transmission rate of the user;
step 11: obtaining the optimal dormancy ratio theta according to the step 8*Calculating the number N of base stations to be dormantoff=[θ*Ns];
Step 12: closing the top N in sequence according to the small station sequence obtained in the step 10offAnd (5) a small station.
Specifically, the minimum value of the base station sleep ratio θ of the small station in step 1 is θmin0, maximum value θmax=1。
Specifically, the average transmission rate obtained when the user accesses the macro station in step 2
Average transmission rate of wireless transmission link of small station user
Average transmission rate of backhaul link from gateway to small station
And (4) solving according to a shannon formula.
Compared with the prior art, the invention has the following advantages and beneficial effects:
the base station dormancy method provided by the invention aims at the super-dense heterogeneous network, and the base station dormancy strategy is executed by collecting data traffic and combining the channel state between the base station and the user, so that the method is well suitable for an actual system, can bring better performance gain than the traditional method, and obviously reduces the energy consumption of the system under the condition of ensuring the time delay characteristic of the user. Compared with the existing business perception and channel perception base station dormancy scheme, the method can fully utilize the business change and channel information of the small station, select the base station set to be dormant, and flexibly control the balance problem between the energy saving of the system and the service quality of the user.
Detailed Description
The technical solutions provided by the present invention will be described in detail below with reference to specific examples, and it should be understood that the following specific embodiments are only illustrative of the present invention and are not intended to limit the scope of the present invention.
The invention relates to a method for solving the problem of energy consumption and time delay balance, which is based on the point of energy consumption and time delay balance and corresponds to the problem of minimizing the cost function of a system. The operator may select a particular tradeoff factor based on the relative importance of energy savings and user quality of service to determine the number of base stations to hibernate.
According to the invention, the flow model of the user is considered to meet the Poisson arrival process, the time delay and the energy consumption of the wireless access network and the backhaul network are firstly analyzed according to the M/G/1 queuing model, the minimum value point of the cost function corresponding to the energy consumption and time delay balance problem is solved by iteration through a gradient descent method, the optimal base station dormancy proportion of the system is obtained, and then the set of the optimal dormancy base stations is selected according to the optimal base station dormancy proportion, so that the energy consumption of the system is minimized under the condition that the service quality of the user is ensured.
Specifically, the ultra-dense network small station sleep method based on channel and queue sensing, as shown in fig. 1, includes the following steps:
step 1: collecting network information
The operator measures the total number of users, macro stations, small stations and gateways in the area and respectively records the total number as N
u,N
m,N
s,N
gThereby obtaining the regionDistribution density lambda of gateway, macro station, small station and user in domain
g,λ
m,λ
sAnd λ
u. When the user traffic reaches the destination, the operator counts the user traffic usage within a period of time (the time can be set according to the situation) to obtain the user traffic arrival rate λ and the average bit size l of each packet. Obtaining the backhaul link bandwidth W of the small station wireless deployed in the area through an operator
bWireless access bandwidth W adopted by macro station
mWireless access bandwidth W adopted by small station
sMacro station transmission power P
mtSmall station transmission power P
stGateway transmission power P
gt. The operator records the average energy consumption of each gateway
Average energy consumption P of sleeping small stations
SEnergy consumption of static links of macro and small stations
And
and obtaining the path loss coefficient alpha in the wireless channel by using a channel estimation method. Offset value A for user association to small station
bLoad-dependent energy consumption factor Δ p for macro and small stations
mAnd Δ p
sThe values of the signal-to-interference ratio threshold beta, the weight factor omega, the iterative search step length delta, the iterative search accuracy xi, the time interval T and the time length T are automatically determined by an operator according to the network operation condition. All macro stations are all in an active state.
The sleep ratio of the base station of the small station is recorded as theta, and the minimum value of the sleep ratio is thetamin0, maximum value θ max1. Initial value theta of base station sleep ratio0The optimum sleep ratio is theta which is determined by an operator according to the network running condition*. The initial value of the iteration times is n-0, and the value of the dormancy proportion of the base station in the nth iteration process is thetan。
Then, the optimal base station dormancy proportion theta is solved by iteration according to a gradient descent method*。
Step 2: in the nth iteration, the dormancy ratio theta at the base station is calculated
nThen, the average packet delay of the macro station and the small station users are respectively recorded as
And
and average time delay of the whole network
Firstly, the probability Pr of the user connecting to the small station is calculatedSUE(θ)
The gateway, the macro station and the small station are M/G/1 queues, so the time delay of the user comprises transmission time delay and queuing time delay. Average transmission time delay of users
And average queuing delay
Respectively expressed as:
here, the
The average transmission rate is expressed and can be obtained by a shannon formula. P represents the average transmission probability, the average transmission probability of the macro and the small stations, respectively
And
the following conditions are respectively satisfied:
where x denotes an integral variable, with no practical physical meaning.
The average transmission probability in the current traffic state can be obtained from equations (4) and (5) by using the dichotomy
And
the user is divided into two parts: the first part is users connected with the macro station, and the second part is users connected with the small station. Average time delay for user connected with macro station
Including average transmission delay for the delay of the radio access link
And average queuing delay
Namely, it is
According to the formulas (2) and (3), the following results are obtained
Here, the
The average transmission rate obtained when the user accesses the macro station can be obtained according to the shannon formula.
For the users accessing the small station, the average time delay of each packet is the average time delay of the wireless access link
And wireless backhaul link average delay
And (4) summing. Likewise, the access link average delay
And wireless backhaul link average delay
Also respectively comprise average transmission time delay
And average queuing delay
Namely, it is
Similarly, from equation (2) can be derived
Here, the first and second liquid crystal display panels are,
the average transmission rate of the wireless transmission link for the small station user,
representing the average transmission rate of the gateway-to-small-station backhaul link.
And
can be obtained according to the Shannon formula.
From equation (3) can be obtained
Is the average transmission probability of the gateway,
thereby obtaining the average time delay of the network
And step 3: calculating the dormancy ratio theta of the current base station
nLower system average energy consumption
And a cost function F (theta)
Here, the value of the weighting factor ω is determined by the operator according to the network operation condition.
And 4, step 4: when the current nth iteration is solved, the sleep proportion theta of the cost function F (theta) relative to the base station is thetanDerivative function of
Here, the
And 5: updating the base station dormancy ratio theta, and when the (n + 1) th iteration is performed, the base station dormancy ratio theta is equal to thetan+1Is updated to
Here, the value of the iterative search step δ is determined by the operator according to the network operation conditions.
Step 6: under the condition of judging the dormancy ratio of the current base station, the cost function F (theta) of the whole network is equal to F (theta)n) Whether the minimum point is reached: when F (theta)n+1)-F(θn) When the value is less than ξ, the optimal point is reached, and the step 8 is executed to quit the iteration process; otherwise, step 7 is performed. Here, the value of the iterative search accuracy ξ is determined by the operator depending on the network operating conditions.
And 7: and updating the current iteration number n +1 and executing the step 2-6.
And 8: quitting the iteration process to obtain the optimal sleep proportion theta of the base station*。
And step 9: let θ be 0, i.e. all the small stations are in active state, and update the user connection state. The operator determines the time length T and the time interval T according to the network operation condition, counts the queue lengths of all the small stations and the average transmission rate of the users in the time interval T, and further calculates the average queue length and the average transmission rate in the time length T.
Step 10: the small stations are arranged in ascending order according to the product of the average queue length of each small station and the average transmission rate of the user.
Step 11: obtaining the optimal dormancy ratio theta according to the step 8*Calculating the number N of base stations to be dormantoff=[θ*Ns]。
Step 12: closing the top N in sequence according to the small station sequence obtained in the step 10offAnd (5) a small station.
The technical means disclosed in the invention scheme are not limited to the technical means disclosed in the above embodiments, but also include the technical scheme formed by any combination of the above technical features. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and such improvements and modifications are also considered to be within the scope of the present invention.