阅读说明：本技术 一种基于自适应的卫星链路功率控制方法 (Satellite link power control method based on self-adaption ) 是由 关庆阳 吴双 于 2021-10-29 设计创作，主要内容包括：本发明提供一种基于自适应的卫星链路功率控制方法,首先用户终端进行发射功率初始化；然后星上根据上行用户终端的导频信号,计算每个用户功率变化量,通过控制信道传递用户功率变化指令；最后用户根据星上的功率控制指令调整功率变化,并且估计路径损耗以调整用户的发射功率；本发明方法不仅有效补偿了路径损耗、衰落,而且在满足正常通信质量的前提下降低了功率损耗,不依赖于具体的信道环境,对于不同的接入环境可以降低接入用户的功率损失,有效提高低轨卫星上行链路用户的接入。(The invention provides a satellite link power control method based on self-adaptation, firstly, a user terminal initializes the transmitting power; then, calculating the power variation of each user on the satellite according to the pilot signal of the uplink user terminal, and transmitting a user power variation instruction through a control channel; finally, the user adjusts the power change according to the on-satellite power control instruction, and estimates the path loss to adjust the transmitting power of the user; the method not only effectively compensates path loss and fading, but also reduces power loss on the premise of meeting normal communication quality, does not depend on specific channel environment, can reduce power loss of access users for different access environments, and effectively improves access of low-earth orbit satellite uplink users.)

1. An adaptive-based satellite link power control method, comprising:

step 1: initializing the transmitting power by the user terminal;

step 2: calculating the power variation of each user according to the data frame power of the mobile user received by the low-orbit satellite, and transmitting a user power variation instruction through a control channel;

and step 3: adjusting power variation according to the received power variation command, estimating path loss by using formula (1) to adjust transmitting power P of user_PC：

In the formula, P_maxMaximum total transmitted power, R, for the user_minPreventing users with good channel conditions from transmitting at lower power, L, for minimum power reduction_x-ileTransmitting the percentage of users for the maximum power, wherein alpha is a balance parameter of poor channel conditions and good channel conditions; p_LPath loss for the downlink of the user terminal and the low earth orbit satellite; delta_TFIs the offset of the transport format; delta_TPCIncreasing or decreasing the power of the satellite control command received by the user; p_LThe path loss between the user and the access low earth orbit satellite.

2. The adaptive-based satellite link power control method according to claim 1, wherein the step 2 comprises:

step 2.1: the low earth orbit satellite receives the data frame power of the mobile user;

step 2.2: calculating a power control issuing instruction of the satellite-borne equipment:

p_i(n+1)＝I_i[P(n)] (2)

wherein P (n) is the power value of the nth received user on the satellite, p_i(n +1) is the power of the (n +1) th transmission of the ith user, I_i[·]For the ith power control function,

wherein the content of the first and second substances,for receiving power of mobile terminal, p^*Is a threshold for power; alpha (n) is the step size of the nth multi-user power control change, and is defined as

Wherein, p (n-1) is the power value of the user received at the (n-1) th time on the satellite, and the issued power change command tpc (n) is expressed as:

wherein, TPC (n) takes the value of-1 or 0 or 1; 1 represents that the user terminal increases the transmitting power, 1 represents that the user terminal reduces the transmitting power, and 0 represents that the user terminal keeps transmitting with the original power;

step 2.3: effective omnidirectional radiation power EIRP of user terminal_{Terminal device}Comprises the following steps:

EIRP_{terminal device}＝P+L_p+L_a+L_y-G_r (5)

Where P is the minimum signal power detection threshold on the satellite and L_pIs free space loss; l is_aIs the power loss caused by natural disasters; l is_yIs the system reserve loss to overcome the multipath shadow effect, G_rIs the satellite receive antenna gain.

3. The adaptive-based satellite link power control method according to claim 1, wherein Δ in step 3 is_TPCSpecific values were determined as follows:

when TPC (n) is equal to-1, if the power of the data frame received in the last iteration is smaller than the lower limit value of the threshold, controlling the transmitting end of the mobile user to increase the transmitting power of one step; otherwise, controlling the transmitting end of the mobile user to increase the transmitting power of Q step lengths;

when TPC (n) is 0, keeping the transmission power of the user terminal unchanged;

when TPC (n) is 1, if the power of the data frame received in the last iteration is larger than the upper limit value of the threshold, controlling the transmitting end of the mobile user to reduce the transmitting power of one step; otherwise, controlling the transmitting end of the mobile user to reduce the transmitting power of Q steps.

Technical Field

The invention relates to the technical field of satellite communication, in particular to a satellite link power control method based on self-adaptation.

Background

Aiming at an uplink of a low earth orbit satellite communication system, on the premise that a user establishes a communication link, the transmitting power needs to be reduced to ensure the power utilization rate of the system; but due to the high speed movement of the low earth orbit satellite relative to the ground, and the power loss caused by the frequent switching of the beam and the multi-path fading of the channel, higher requirements are put on the power control of the uplink user terminal. Therefore, the user power control of the low-earth orbit satellite communication system is more complicated, and the power control algorithm of many terrestrial wireless communication systems (CDMA transmission systems for short) adopting the code division multiple access CDMA technology cannot be directly used in the low-earth orbit satellite communication system. At present, there are relatively few power control methods for low-earth orbit satellite mobile communication systems, and the following are some common methods.

The first method is that aiming at the low orbit satellite communication system, different power control algorithms are adopted according to different speed services. The algorithm takes the satellite spot beam coverage users as targets, and classifies the users in the coverage range according to different signal-to-interference ratios of satellite service users. When the user terminal is located near the beam coverage center area, the satellite transmits data service at a higher rate; while when the user is near the beam coverage boundary, the satellite transmits data traffic at a lower rate. The algorithm is based on the premise that the position of the user terminal can be obtained by measuring signal power, signal round-trip delay, satellite elevation angle and a navigation system, but in practical situations, the position of the user in a beam is difficult to determine.

And secondly, providing a self-adaptive power control algorithm aiming at different rain attenuation models in the satellite communication system. The algorithm abstracts a rain attenuation model into a logarithmic normal distribution function; similarly, in order to reduce the influence of rainfall attenuation on the satellite signal transmission quality caused by the Ka band, a method for adding a correction parameter in each power control period is provided, and different correction parameters are selected according to different control periods so as to improve the compensation precision of the rainfall attenuation of the uplink.

And thirdly, aiming at the uplink of the satellite communication system of the Ka waveband, in order to reduce the influence of rain attenuation, the rainfall attenuation is summarized into an autoregressive moving average model, and the rainfall attenuation value of the uplink is predicted by the user terminal according to the measured downlink rainfall attenuation value, so that the power control precision is improved.

And fourthly, analyzing the power control schemes of fixed step length, variable step length and self-adaptive step length aiming at the low-orbit satellite CDMA transmission system, and providing a power control scheme of variable step length of compressed coding. Also for the low orbit satellite CDMA transmission system, an open loop power control scheme is provided, and a power control error cost function is given. A single step power control scheme is provided for a low earth orbit satellite CDMA transmission system by combining signal detection of a receiving end.

A fifth method, a self-adaptive power control scheme is used for overcoming the long-distance transmission and large-scale fading of a satellite channel, and meanwhile, the influence of a normal logarithmic distribution model and a Rice channel fading model on the power control scheme is considered; on the basis, the related document adopts a power control scheme of Turbo coding to obtain higher receiving gain. For the low-earth-orbit satellite uplink, in order to ensure the access performance of the user terminal, an appropriate power control scheme is also required to meet the user service quality requirement of the system.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a satellite link power control method based on self-adaptation, which comprises the following steps:

step 1: initializing the transmitting power by the user terminal;

step 2: calculating the power variation of each user according to the data frame power of the mobile user received by the low-orbit satellite, and transmitting a user power variation instruction through a control channel;

and step 3: adjusting power variation according to the received power variation command, estimating path loss by using formula (1) to adjust transmitting power P of user_PC：

In the formula, P_maxMaximum total transmitted power, R, for the user_minPreventing users with good channel conditions from transmitting at lower power, L, for minimum power reduction_x-ileTransmitting the percentage of users for the maximum power, wherein alpha is a balance parameter of poor channel conditions and good channel conditions; p_LPath loss for the downlink of the user terminal and the low earth orbit satellite; delta_TFIs the offset of the transport format; delta_TPCIncreasing or decreasing the power of the satellite control command received by the user; p_LFor subscriber and access to low earth orbit satellite。

The step 2 comprises the following steps:

step 2.1: the low earth orbit satellite receives the data frame power of the mobile user;

step 2.2: calculating a power control issuing instruction of the satellite-borne equipment:

p_i(n+1)＝I_i[P(n)] (2)

wherein P (n) is the power value of the nth received user on the satellite, p_i(n +1) is the power of the (n +1) th transmission of the ith user, I_i[·]For the ith power control function,

wherein the content of the first and second substances,for receiving power of mobile terminal, p^*Is a threshold for power; alpha (n) is the step size of the nth multi-user power control change, and is defined as

Wherein, p (n-1) is the power value of the user received at the (n-1) th time on the satellite, and the issued power change command tpc (n) is expressed as:

wherein, TPC (n) takes the value of-1 or 0 or 1; 1 represents that the user terminal increases the transmitting power, 1 represents that the user terminal reduces the transmitting power, and 0 represents that the user terminal keeps transmitting with the original power;

step 2.3: effective omnidirectional radiation power EIRP of user terminal_{Terminal device}Comprises the following steps:

EIRP_{terminal device}＝P+L_p+L_a+L_y-G_r (5)

Where P is the minimum signal power detection threshold on the satellite and L_pIs free space loss; l is_aIs the power loss caused by natural disasters; l is_yIs the system reserve loss to overcome the multipath shadow effect, G_rIs the satellite receive antenna gain.

Delta in said step 3_TPCSpecific values were determined as follows:

when TPC (n) is equal to-1, if the power of the data frame received in the last iteration is smaller than the lower limit value of the threshold, controlling the transmitting end of the mobile user to increase the transmitting power of one step; otherwise, controlling the transmitting end of the mobile user to increase the transmitting power of Q step lengths;

when TPC (n) is 0, keeping the transmission power of the user terminal unchanged;

when TPC (n) is 1, if the power of the data frame received in the last iteration is larger than the upper limit value of the threshold, controlling the transmitting end of the mobile user to reduce the transmitting power of one step; otherwise, controlling the transmitting end of the mobile user to reduce the transmitting power of Q steps.

The invention has the beneficial effects that:

the invention has proposed a satellite link power control method based on self-adaptation, carry on the initialization of transmitting power at first in the user terminal; then, calculating the power variation of each user on the satellite according to the pilot signal of the uplink user terminal, and transmitting a user power variation instruction through a control channel; finally, the user adjusts the power change according to the on-satellite power control instruction, and estimates the path loss to adjust the transmitting power of the user; the method not only effectively compensates path loss and fading, but also reduces power loss on the premise of meeting normal communication quality, does not depend on specific channel environment, can reduce power loss of access users for different access environments, and effectively improves access of low-earth orbit satellite uplink users.

Drawings

FIG. 1 is a flow chart of a method for adaptive-based satellite link power control according to the present invention;

fig. 2 is a user power control scheme in conjunction with on-satellite power detection in accordance with the present invention.

Detailed Description

The invention is further described with reference to the following figures and specific examples.

For the uplink of the low-earth-orbit satellite, signals are affected by free space loss, rain attenuation, channel multipath attenuation and the like in the transmission process, so that the level of user signals received by the low-earth-orbit satellite has large fluctuation, and the signal receiving performance is affected. Therefore, power control of uplink users not only needs to compensate for the path loss and fading of the channel to ensure the establishment of the link, but also needs to reduce power loss on the premise of satisfying normal communication quality.

As shown in fig. 2, for the power detection of the low-orbit satellite user, the user power control scheme combining the satellite power detection may dynamically adjust the power control command according to the signal power and the detection threshold value in order to effectively transmit the power control command. The detection threshold may be set by estimating the access user pilot signal for the uplink. And when the received user power is in the dynamic threshold value detected by the satellite power, issuing a power control command. When the power of the user received by the satellite is smaller than the lower limit of the acceptable dynamic threshold, the satellite informs the user terminal of needing to increase the transmitting power through a downlink control channel; if the power of the previous received signal is still smaller than the lower limit of the dynamic threshold, continuously sending a plurality of instructions for increasing the user sending power to the user on the satellite; otherwise, an instruction for increasing the user transmission power is sent once. When the power of the user received by the satellite-borne equipment is greater than the upper limit of the acceptable dynamic threshold and the power sent by the mobile terminal for the previous time is still greater than the upper limit of the dynamic threshold, continuously sending a plurality of instructions for reducing the user sending power to the user on the satellite; otherwise, an instruction for reducing the user transmission power is sent once.

The power control principle of the satellite link is designed as follows:

s1: initializing the transmitting power of a user terminal;

s2: calculating the power variation of each user on the satellite according to the pilot signal of the uplink user terminal, and transmitting a user power variation instruction through a control channel;

s3: the user adjusts the power variation according to the on-satellite power control commands and estimates the path loss to adjust the user's transmit power.

Based on the above principle, the method for controlling power of a satellite link based on adaptation, as shown in fig. 1, includes:

step 1: the user terminal initializes the transmitting power according to the formula (1);

step 2: calculating the power variation of each user according to the data frame power of the mobile user received by the low-orbit satellite, and transmitting a user power variation instruction through a control channel; the method comprises the following steps:

step 2.1: the low earth orbit satellite receives the data frame power of the mobile user;

step 2.2: the low earth orbit satellite adjusts the transmitting power of the user by detecting the user access power and the downlink control channel to ensure that the satellite receives the user signal to meet the power detection range, and the power control issuing instruction of the satellite-borne equipment is represented as follows:

p_i(n+1)＝I_i[P(n)] (2)

wherein P (n) is the power value of the nth received user on the satellite, p_i(n +1) is the power of the (n +1) th transmission of the ith user, I_i[·]For the ith power control function,

wherein, it is madeDefined as the value of the power change of the user terminal,for receiving power of mobile terminal, p^*Is a threshold for power; alpha (n) is the step size of the nth multi-user power control change, and is defined as

Wherein, p (n-1) is the user power value received on the satellite (n-1) times, and the issued power change command tpc (n) is expressed as:

wherein, TPC (n) takes the value of-1 or 0 or 1; 1 represents that the user terminal increases the transmitting power, 1 represents that the user terminal reduces the transmitting power, and 0 represents that the user terminal keeps transmitting with the original power;

for the uplink on the low earth orbit satellite, the minimum power threshold for detecting user access by the satellite-borne device can be determined by the following formula, and can be expressed as

P＝kRB(C/N)_u

Wherein k is Boltzmann constant (1.38054 × 10)^-23Joules/K, -228.6dBW/K Hz), R is the equivalent noise temperature of the satellite-borne receiver, B is the bandwidth of the satellite-borne receiver, (C/N)_uIs the carrier-to-noise ratio of the uplink. When the bandwidth and the noise temperature are determined, the minimum signal power detection threshold P on the satellite can be calculated.

Step 2.3: user terminal transmitting effective omnidirectional radiation power EIRP_{Terminal device}Comprises the following steps:

EIRP_{terminal device}＝P+L_p+L_a+L_y-G_r (5)

Where P is the minimum signal power detection threshold on the satellite and L_pIs a function of free space loss, satellite orbit height and elevation; l is_aIs power loss caused by natural disasters (cloud, rain, etc.); l is_yIs the system reserve loss to overcome the multipath shadow effect, G_rIs the satellite receive antenna gain.

The user terminal needs to control the transmitting power by combining the satellite power control instruction. For a low-orbit broadband satellite mobile communication system, although the complexity is low, the accuracy of an open-loop power control scheme is poor, the condition that the interference of beam internal users and beam edge users is different is not considered, and the open-loop power control scheme is not suitable for terminal power control of a satellite; although the power control method of partial path loss compensation is improved to some extent, the scheme cannot accurately control the power of the ue due to the limitation of the open-loop power control scheme. For a low earth orbit satellite system, due to resource limitation, a mobile user terminal needs to receive an adjustment instruction on a satellite, and needs to analyze the path loss of an uplink through a downlink along with the high-speed movement of the satellite, and determine appropriate transmission power to ensure that a communication link is established. The power control method is improved, and the power control method of the access user terminal of the low-orbit broadband satellite mobile communication system is provided as follows

Wherein the content of the first and second substances,the user selects proper transmitting power according to the self condition;

and step 3: adjusting power variation according to the received power variation command, estimating path loss by using formula (1) to adjust transmitting power P of user_PC：

In the formula, P_maxMaximum total transmitted power, R, for the user_minPreventing users with good channel conditions from transmitting at lower power, L, for minimum power reduction_x-ileTransmitting the percentage of users for the maximum power, wherein alpha is a balance parameter of poor channel conditions and good channel conditions; p_LPath loss for the downlink of the user terminal and the low earth orbit satellite; delta_TFIs the offset of the transport format; delta_TPCIncreasing or decreasing the power of the satellite control command received by the user; p_LThe path loss between the user and the access low earth orbit satellite.

Wherein, Delta_TPCSpecific values were determined as follows:

when TPC (n) is equal to-1, if the power of the data frame received in the last iteration is smaller than the lower limit value of the threshold, controlling the transmitting end of the mobile user to increase the transmitting power of one step; otherwise, controlling the transmitting end of the mobile user to increase the transmitting power of Q step lengths;

when TPC (n) is 0, keeping the transmission power of the user terminal unchanged;

when TPC (n) is 1, if the power of the data frame received in the last iteration is larger than the upper limit value of the threshold, controlling the transmitting end of the mobile user to reduce the transmitting power of one step; otherwise, controlling the transmitting end of the mobile user to reduce the transmitting power of Q steps.

Aiming at the user power control of the uplink of the low-orbit broadband satellite, the invention firstly provides a user power control scheme combining the on-satellite power detection, and the scheme is divided into the power detection of the satellite for the access user terminal and the user power control; the proposed power control scheme is not specific to a specific channel environment, can reduce the power loss of an access user for different access environments, and effectively improves the access of an uplink user of a low-earth orbit satellite.