CN104219748B - A kind of energy-conservation and user scheduling method of large-scale and multiple users mimo system - Google Patents

Abstract

The invention relates to a method for energy saving and user scheduling of a large-scale multi-user MIMO system, which is characterized in that the method uses a base station and user equipment to accurately calculate the required uplink power and downlink power according to the state of the base station end and the state of the user equipment end, and perform uplink and downlink data The transmission specifically includes uplink energy-saving scheduling and downlink energy-saving scheduling. Compared with the prior art, the present invention has the advantages of low computational complexity and the like.

Description

A Method of Energy Saving and User Scheduling for Massive Multi-User MIMO System

technical field

The invention relates to a user scheduling method of a MIMO system, in particular to a method for energy saving and user scheduling of a massive multi-user MIMO system.

Background technique

In massive multi-user MIMO systems, how to perform low-complexity user scheduling to achieve energy saving is an urgent problem to be solved. Currently there is no user scheduling and power saving method specifically for massive multi-user MIMO systems, using conventional user scheduling and power control methods in massive multi-user MIMO systems will bring unnecessary execution overhead and fail to achieve optimal energy utilization efficiency.

Contents of the invention

The object of the present invention is to provide a method for energy saving and user scheduling of a massive multi-user MIMO system in order to overcome the above-mentioned defects in the prior art.

The purpose of the present invention can be achieved through the following technical solutions:

A method for energy saving and user scheduling of a massive multi-user MIMO system. The method uses a base station and user equipment to accurately calculate the required user terminal transmit power and downlink power according to the state of the base station end and the state of the user equipment end and perform data transmission, specifically including uplink Link energy-saving scheduling and downlink energy-saving scheduling.

The uplink energy-saving scheduling includes the following steps:

101) The base station notifies the user equipment of the number of antennas and noise power of the base station;

102) The user equipment side obtains the channel gain through the reverse link measurement and determines the target value of the uplink signal-to-noise ratio required for transmission;

103) The user equipment side calculates the required user terminal transmit power p _UE,k in the uplink transmission:

in: is the noise power at the base station of the user equipment, is the target value of the uplink signal-to-noise ratio, M is the number of antennas at the base station, is the channel gain;

104) The user equipment side uses the calculated transmit power of the user terminal to perform uplink transmission.

The downlink energy-saving scheduling includes the following steps:

201) The user equipment notifies the base station of the noise power of the user equipment;

202) The base station obtains the channel gain through the reverse link measurement and determines the target value of the downlink signal-to-noise ratio to be achieved;

203) The base station calculates the downlink power required to support the downlink transmission of user equipment k

in; is the downlink signal-to-noise ratio target value, is the noise power at the user equipment, is the channel gain, and M is the number of antennas at the base station;

204) The base station sums the downlink power required to support all active users, if the sum is greater than the transmit power of the base station, then perform step 205), if the sum is less than or equal to the transmit power of the base station, then perform step 206);

205) The base station selects k user equipments to simultaneously obtain the service according to the selection criteria;

206) All active users are served.

The sum of the downlink powers of the k user equipments selected in step 205) is smaller than the transmit power of the base station.

The user equipment UE has only one antenna.

The selection criteria include maximizing the comprehensive rate and maximizing the number of service objects.

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

1) The problem of energy saving in massive multi-user MIMO systems is realized.

2) The computational complexity is low.

Description of drawings

FIG. 1 is a flow chart of the uplink energy saving method of the present invention;

Fig. 2 is a flow chart of the downlink energy saving method of the present invention;

Fig. 3 is a schematic structural diagram of the device of the present invention.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is carried out on the premise of the technical solution of the present invention, and detailed implementation and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

An energy saving and user scheduling method for a massive multi-user MIMO system. The present invention performs user power control for uplink and user scheduling for downlink, both of which aim at energy saving.

The method uses the base station and the user equipment to accurately calculate the required user terminal transmit power and downlink power according to the state of the base station and the user equipment and perform data transmission, specifically including uplink energy-saving scheduling and downlink energy-saving scheduling.

For the uplink, use M to represent the number of antennas of the base station, and use _hUL,k to represent the M×1 vector channel of user k, then the signal received by the base station is:

where x _{UL, k} is the user's symbol carrying the message, E(|x _{UL, k} | ² )=1, n _BS represents the additive white noise of the base station, and the variance is

Because the matched filter detection method is best used in massive multi-user MIMO systems,

So the uplink SINR of user k is:

Uplink energy saving: when M is large and M>>K,

According to the law of large numbers, when M is large,

When M is large

Therefore, if p _UE,k is a constant relative to M, then as increases, ρ _UE,k →+∞, but the SINR does not need to be infinite. In order to ensure the requirements of transmission quality, we can set p _{UE, k} decreases linearly with the decrease of M, that is:

Among them, c _k is a coefficient that has nothing to do with M. Substituting the above formula into the formula of ρ _{UE, k} , when M is very large, we can get:

To successfully decode the transmitted data and meet the QoS index of user k, it is required

in is the SINR threshold of user k. For a given SINR threshold of user k c _k needs to meet:

For the UE energy saving problem and to meet the transmission requirements, we can set:

in where the base station is known, is known at the UE, and the UE's It has been measured through the reverse link, so the transmit power of the UE is:

where M is known at the base station.

Uplink user scheduling: According to the ρ _UL,k expression, it can be seen that when the number of antennas in the base station is large and M>>K, the multi-user interference in the uplink can be ignored, so all active users can be scheduled simultaneously on the uplink Send data on the road.

As shown in Figure 1, uplink energy-saving scheduling includes the following steps:

101) The base station notifies the user equipment of the number of antennas and noise power of the base station;

102) The user equipment side obtains the channel gain through the reverse link measurement and determines the signal-to-noise ratio target value required for transmission, which is determined by user requirements and is a known quantity;

103) The user equipment side calculates the required user terminal transmit power p _UE,k in the uplink transmission:

in: is the noise power at the base station of the user equipment, is the target value of the uplink signal-to-noise ratio, M is the number of antennas at the base station, is the channel gain;

104) The user equipment side uses the calculated transmit power of the user terminal to perform uplink transmission.

Use f _{BS, k} and h _{DL, k} to denote the M×1 precoding vector of user data transmission and the vector channel corresponding to 1×M, and the signal received by user k is:

y _{UE, k} = h _{DL, k} f _{BS, k} x _{DL, k} + Σ _{k'≠ k} h _{DL, k} f _{BS, k'} x _{DL, k'} + n _{UE, k}

where x _{DL, k} is the symbol of the message carried by user k, E(|x _{DL, k} | ² )=1 and n _{UE, k} is the additive white noise of UE, and the variance is

Because in massive MIMO TDD systems, it is recommended to use combined beamforming precoding, namely:

where is the allocated power of the data stream of user k, and the received signal of user k is:

and

Therefore, the downlink SINR of user k is:

When M is large and M>>K:

According to the law of large numbers and reason:

therefore

In order to be able to successfully decode the transmitted data and meet the QoS index of user k, we need to meet the following requirements

Where ρ _DL,k is the SINR threshold of user k, and the allocated power of user k must satisfy:

Use P _BS,max to represent the maximum transmission power of the base station, and the transmission power limit of the base station is:

∑p _{BS, k ≤} P _{BS, max} .

Downlink user selection and power allocation: Assuming there are K ₁ active users, the required power allocation for user k can be calculated according to the following formula:

Where M is a known number at the base station, In base station settings, measured at the base station, UE representation is required, if

Then according to the selection criteria such as maximizing the comprehensive rate, the conditions are met:

K users of can obtain the service at the same time, and the corresponding allocated power of user k is

Downlink energy saving: if there are K users and

Then the allocated power for each user is and using the UE expressed It can be seen that the transmit power of the base station is smaller than P _BS,max , which means that the transmit power of the base station is saved.

As shown in Figure 2, downlink energy-saving scheduling includes the following steps:

201) The user equipment notifies the base station of the noise power of the user equipment;

202) The base station obtains the channel gain through the reverse link measurement and determines the target value of the received signal-to-noise ratio to be achieved;

203) The base station calculates the downlink power required to support the downlink transmission of user equipment k

in: Downlink SNR target value, is the noise power at the user equipment, is the channel gain, and M is the number of antennas at the base station;

204) The base station sums the downlink power required to support all active users, if the sum is greater than the transmit power of the base station, then perform step 205), if the sum is less than or equal to the transmit power of the base station, then perform step 206);

205) The base station selects k user equipments to simultaneously obtain services according to selection criteria such as maximization of comprehensive rate;

206) All active users are served.

The sum of the downlink powers of the k user equipments selected in step 205) is smaller than the transmit power of the base station.

In a specific scenario, assuming that in a time-division duplex cellular system, a UE roams into a cell with a large number of antennas installed in the base station, the UE will find that the cell is in the massive MIMO working mode during the access process , the number of antennas M and the noise level of the base station are sent to the UE through a cell message, and the message is also broadcast to all UEs in the cell.

Uplink: If the UE has multiple antennas, it will use the main eigenvector for transmission and use the main eigenvector as the precoding vector. The UE estimates the channel variance through the reverse link and adjust the transmit power to p _UE,k :

in:

obtained from the base station, Set by the UE according to the requirements of the uplink data flow.

Downlink: Each UE communicates the noise level Sent to the base station, which calculates the required power allocation for each user flow

in Included in the UE-specific message of the response, Set by the base station according to the transmission quality requirements, M is a known quantity at the base station, and is estimated by the base station through the reverse link. If there are K ₁ active UEs and the sum of the downlink power required by the base station to support K ₁ active users is greater than the transmit power of the base station, then according to selection criteria such as maximizing the comprehensive rate, the base station selects K users that meet the conditions ( The sum of the downlink power of these K users is not greater than the transmit power of the base station), and the data streams of K users are precoded by combining beamforming, and the corresponding power is allocated to each user data stream, and all precoded data streams are sent at the same time flow. If the sum of the downlink power required by the K1 active users is not greater _than the transmit power of the base station, then the power allocation of each user data stream is:

Therefore, the transmit power of the base station is:

This means that the power saving of the base station transmit power has been achieved.

Claims (5)

1. A method for energy saving and user scheduling of a massive multi-user MIMO system, characterized in that the method uses the base station and the user equipment to accurately calculate the required user terminal transmit power and downlink power according to the state of the base station and the state of the user equipment, and perform Data transmission, specifically including uplink energy-saving scheduling and downlink energy-saving scheduling; The uplink energy-saving scheduling includes the following steps: 101) The base station notifies the user equipment of the number of antennas and the noise power of the base station, 102) The user equipment side obtains the channel gain through the reverse link measurement and determines the uplink signal-to-noise ratio target value required for transmission, 103) The user equipment side calculates the required user terminal transmit power p _UE,k in the uplink transmission: <mrow><msub><mi>p</mi><mrow><mi>U</mi><mi>E</mi><mo>,</mo><mi>k</mi></mrow></msub><mo>=</mo><mfrac><mrow><msubsup><mi>&amp;sigma;</mi><mrow><mi>B</mi><mi>S</mi></mrow><mn>2</mn></msubsup><msub><mover><mi>&amp;rho;</mi><mo>&amp;OverBar;</mo></mi>mover><mrow><mi>U</mi><mi>L</mi><mo>,</mo><mi>k</mi></mrow></msub></mrow><mrow><msubsup><mi>M&amp;sigma;</mi><mrow><mi>h</mi><mo>,</mo><mi>k</mi></mrow><mn>2</mn></msubsup></mrow></mfrac></mrow> in: is the noise power at the base station of the user equipment, is the target value of the uplink signal-to-noise ratio, M is the number of antennas at the base station, is the channel gain, 104) The user equipment side uses the calculated transmit power of the user terminal to perform uplink transmission. 2. The energy-saving and user scheduling method of a massive multi-user MIMO system according to claim 1, wherein the downlink energy-saving scheduling comprises the following steps: 201) The user equipment notifies the base station of the noise power of the user equipment; 202) The base station obtains the channel gain through the reverse link measurement and determines the target value of the downlink signal-to-noise ratio to be achieved; 203) The base station calculates the downlink power required to support the downlink transmission of user equipment k <mrow><msub><mover><mi>p</mi><mo>&amp;OverBar;</mo></mover><mrow><mi>B</mi><mi>S</mi><mo>,</mo><mi>k</mi></mrow></msub><mo>=</mo><mfrac><mrow><msub><mover><mi>p</mi><mo>&amp;OverBar;</mo></mover><mrow><mi>D</mi><mi>L</mi><mo>,</mo><mi>k</mi></mrow></msub><msubsup><mi>&amp;sigma;</mi><mrow><mi>U</mi><mi>E</mi><mo>,</mi>mo><mi>k</mi></mrow><mn>2</mn></msubsup></mrow><mrow><msubsup><mi>M&amp;sigma;</mi><mrow><mi>h</mi><mo>,</mo><mi>k</mi></mrow><mn>2</mn></msubsup></mrow></mfrac></mrow>mrow> in: is the downlink SNR target value, is the noise power at the user equipment, is the channel gain, and M is the number of antennas at the base station; 204) The base station sums the downlink power required to support all active users, if the sum is greater than the transmit power of the base station, then perform step 205), if the sum is less than or equal to the transmit power of the base station, then perform step 206); 205) The base station selects k user equipments to simultaneously obtain the service according to the selection criteria; 206) All active users are served. 3. The energy-saving and user scheduling method of a massive multi-user MIMO system according to claim 2, wherein the sum of the downlink powers of the k user equipments selected in the step 205) is less than the transmit power of the base station . 4. The method for energy saving and user scheduling of a massive multi-user MIMO system according to claim 2, wherein the user equipment UE has only one antenna. 5 . The method for energy saving and user scheduling of a massive multi-user MIMO system according to claim 2 , wherein the selection criteria include maximizing the comprehensive rate and maximizing the number of service objects. 6 .