A two-satellite terminal downlink transmission method with partial time slot resource flexible occupation

Abstract

The application discloses a two-satellite terminal downlink transmission method of partially time slot resource flexible occupation, and aims at improving the time slot resource utilization rate of a downlink service channel of a satellite communication system based on a TDM transmission system. The method allocates each downlink transmission time slot of the satellite communication system based on the TDM system to two satellite terminals with gain difference of receiving antennas, and the signals of the two satellite terminals are superposed at the satellite end and then are transmitted downward; when the satellite terminal with larger receiving antenna gain receives the downlink signal, a serial interference cancellation method is used to correctly demodulate the effective signal. Meanwhile, the time slot length is dynamically adjusted to meet different service transmission requirements.

Description

Technical Field

[0001] This invention belongs to the field of satellite communication downlink transmission technology, and particularly relates to a method for downlink transmission between two satellite terminals that flexibly utilizes some time slot resources. Background Technology

[0002] In satellite communication downlink technology, to support multiple satellite terminal applications, the downlink service channel is often divided into multiple time slots or frequency bands. Satellite terminals occupy different time slot / frequency band resource blocks to receive the required downlink information. Since time slot / frequency band resources are limited within a certain time period or bandwidth, when the resources are full, the satellite communication network cannot allocate service channel resources to too many terminals, causing these satellite terminals to be unable to receive downlink information in a timely manner.

[0003] In satellite downlink based on TDM, existing technologies generally use one satellite to one satellite terminal to transmit information, resulting in low utilization of service channel resources. Summary of the Invention

[0004] In view of this, the present invention proposes a two-satellite terminal downlink transmission method for flexibly occupying part of the time slot resources, aiming to improve the utilization rate of satellite downlink service channels based on the TDM system.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0006] A method for flexible use of partial time slot resources in a two-satellite terminal downlink transmission is proposed, used for transmitting signals from one satellite to two satellite terminals. The satellite orbital altitude is d, the downlink carrier wavelength is λ, and the satellite transmit antenna gain is G. s The steps include:

[0007] (1) Each satellite terminal reports its own receiving antenna gain G and satellite terminal noise power N0 obtained through power estimation to the satellite via the signaling channel, and obtains the downlink channel coefficient h of each satellite terminal according to the formula:

[0008]

[0009] (2) The satellite's onboard network controller selects a first satellite terminal and a second satellite terminal with receiving antenna gains of G1 and G2, respectively. The satellite's processing payload allocates downlink signal power P1 and P2 to the first and second satellite terminals. 0 < β < 1; G1 and G2 satisfy the following relationship:

[0010]

[0011] Wherein, Φ2 is the demodulation threshold required by the second satellite terminal. Delta Phi is the acceptable signal-to-noise ratio deterioration of the received signal of the first satellite terminal caused by the second satellite terminal:

[0012]

[0013] h1 is the downlink channel coefficient of the first satellite terminal, and h2 is the downlink channel coefficient of the second satellite terminal.

[0014] (3) The satellite selects the time slot length τ, and allocates the first satellite terminal and the second satellite terminal in the downlink same-frequency resource block with the time slot length τ; the selection of τ satisfies the following relationship:

[0015]

[0016] (4) The satellite superimposes the downlink signal s1 of the first satellite terminal and the downlink signal s2 of the second satellite terminal, obtains the superimposed signal s1+s2, and then transmits;

[0017] (5) After the first satellite terminal receives the superimposed signal, the first satellite terminal directly demodulates s1 to obtain the corresponding effective signal;

[0018] (6) After the second satellite terminal receives the superimposed signal, the second satellite terminal first demodulates s1, then eliminates s1, and then demodulates s2 to obtain the corresponding effective signal.

[0019] Compared with the background art, the present application has the following advantages:

[0020] 1. The present application can allocate two satellite terminals satisfying the receiving antenna gain condition on the same part of the downlink service channel time slot resource, thereby improving the time slot resource utilization rate.

[0021] 2. The present application at least doubles the number of satellite terminals that can be carried by the service channel, which helps to improve the resource utilization rate of the TDM downlink service channel. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a comparison diagram of the time slot allocation of the two-satellite-terminal downlink service channel based on the TDM system and the partial time slot flexible occupation system. DETAILED DESCRIPTION

[0023] The present application will be described in detail below with reference to the accompanying drawings.

[0024] A two-satellite-terminal downlink transmission method of partial time slot resource flexible occupation, Figure 1 The utilization of the time slot resource of the two-satellite-terminal downlink service channel based on the traditional TDM system and the two-satellite-terminal downlink service channel time slot resource utilization based on the partial time slot resource system proposed by the present application are given.

[0025] This method transmits information simultaneously from one satellite to two satellite terminals, where the satellite orbital altitude is d, the downlink carrier wavelength is λ, and the satellite transmit antenna gain is G. s The method specifically includes the following steps:

[0026] (1) Each satellite terminal reports its own receiving antenna gain G and satellite terminal noise power N0 obtained through power estimation to the satellite via the signaling channel, and obtains the downlink channel coefficient h of each satellite terminal according to the formula:

[0027]

[0028] (2) The satellite's onboard network controller selects a first satellite terminal and a second satellite terminal with receiving antenna gains of G1 and G2, respectively. The satellite's processing payload allocates downlink signal power P1 and P2 to the first and second satellite terminals. 0 < β < 1; G1 and G2 satisfy the following relationship:

[0029]

[0030] Wherein, Φ2 is the demodulation threshold required by the second satellite terminal. ΔΦ is the acceptable signal-to-noise ratio degradation caused by the second satellite terminal to the first satellite terminal:

[0031]

[0032] h1 is the downlink channel coefficient of the first satellite terminal, and h2 is the downlink channel coefficient of the second satellite terminal;

[0033] (3) The satellite selects a time slot length τ and simultaneously allocates the first satellite terminal and the second satellite terminal in the downlink co-frequency resource block with a time slot length of τ; the selection of τ satisfies the following relationship:

[0034]

[0035] (4) The satellite superimposes the downlink signal s1 from the first satellite terminal and the downlink signal s2 from the second satellite terminal to obtain signal s1+s2, and then transmits it. The received signal of signal s1+s2 after passing through a channel with coefficient h1 to the first satellite terminal can be calculated as y1 = h1(s1+s2) + n, and the received signal of signal s1+s2 after passing through a channel with coefficient h2 to the second satellite terminal can be calculated as y2 = h2(s1+s2) + n. Here, n is the receiver noise of the first and second satellite terminals; the downlink channels of the first and second satellite terminals can be calculated as follows: and

[0036] (5) After receiving the signal, the first satellite terminal directly demodulates s1 to obtain the corresponding valid signal. The demodulated signal-to-interference-plus-noise ratio (SIR) on the first satellite terminal side is calculated as follows:

[0037] (6) After receiving the signal, the second satellite terminal first demodulates s1, and the demodulated signal-to-interference-plus-noise ratio is calculated as follows: Next, after eliminating s1, s2 is demodulated to obtain the corresponding effective signal. The demodulation signal-to-noise ratio is calculated as follows:

[0038] The principle for selecting the first satellite terminal and the second satellite terminal in step (2) is as follows:

[0039] 1) Calculate the acceptable SINR degradation caused by the second satellite terminal to the first satellite terminal as ΔΦ, then...

[0040] 2) The signal power of the second satellite terminal is calculated as follows:

[0041] 3) Assuming the demodulation threshold required by the second satellite terminal is Φ2, then we have

[0042] 4) The receiving antenna gain of the first and second satellite terminals selected in step (2) needs to meet the following requirements.

[0043] In step (3), the principle for determining the time slot length τ is as follows:

[0044] 1) The downlink achievable transmission rate of s1 is calculated as follows:

[0045]

[0046] The downlink achievable transmission rate of s2 is calculated as follows:

[0047]

[0048] 2) The total downlink traffic volume achievable within a time slot of length τ is calculated as follows:

[0049]

[0050] 3) In the TDM system, if the system allocates half a time slot to the first satellite terminal and half a time slot to the second satellite terminal per unit time, then the downlink traffic that the two satellite terminals can achieve per unit time based on the TDM system is:

[0051]

[0052] 4) The downlink achievable traffic gain of the transmission system with flexible time slot allocation compared to the TDM system is:

[0053]

[0054] 5) While ensuring ΔR>0, the time slot length τ can be flexibly adjusted to obtain the required downlink transmission rates for the first and second satellite terminals.

[0055] In summary, this invention allocates each downlink transmission time slot in a TDM-based satellite communication system to two satellite terminals with different receiving antenna gains. The signals from these two satellite terminals are superimposed at the satellite end before being transmitted downlink. When the satellite terminal with the larger receiving antenna gain receives the downlink signal, a serial interference cancellation method is used to correctly demodulate the effective signal. Simultaneously, the time slot length is dynamically adjusted to meet the transmission requirements of different service volumes.

Claims

1. A method for downlink transmission between two satellite terminals with flexible use of partial time slot resources, characterized in that, This is used for transmitting signals from one satellite to two satellite terminals. The satellite's orbital altitude is d, the downlink carrier wavelength is λ, and the satellite transmit antenna gain is G. s ; Includes the following steps: (1) Each satellite terminal reports its own receiving antenna gain G and satellite terminal noise power N0 obtained through power estimation to the satellite via the signaling channel, and obtains the downlink channel coefficient h of each satellite terminal according to the formula: (2) The satellite's onboard network controller selects a first satellite terminal and a second satellite terminal with receiving antenna gains of G1 and G2, respectively. The satellite's processing payload allocates downlink signal power P1 and P2 to the first and second satellite terminals. 0 < β < 1; G1 and G2 satisfy the following relationship: G2≥ Φ2(G1 2 G s (λ / (4πd)) 2 P1-ΔΦN0G1); Wherein, Φ2 is the demodulation threshold required by the second satellite terminal. ΔΦ is the acceptable signal-to-noise ratio degradation caused by the second satellite terminal to the first satellite terminal: h1 is the downlink channel coefficient of the first satellite terminal, and h2 is the downlink channel coefficient of the second satellite terminal; (3) The satellite selects a time slot length τ and simultaneously allocates the first satellite terminal and the second satellite terminal in the downlink co-frequency resource block with a time slot length of τ; the selection of τ satisfies the following relationship: (4) The satellite superimposes the downlink signal s1 from the first satellite terminal and the downlink signal s2 from the second satellite terminal to obtain the superimposed signal s1+s2 and then transmits it. (5) After receiving the superimposed signal, the first satellite terminal directly demodulates s1 to obtain the corresponding effective signal; (6) After receiving the superimposed signal, the second satellite terminal first demodulates s1, then eliminates s1 and demodulates s2 to obtain the corresponding effective signal.

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