Satellite user capacity measuring and calculating method

Abstract

The invention provides a satellite user capacity measuring and calculating method. The satellite user capacity measuring and calculating method comprises the following steps: measuring and calculating the user capacity when the uplink bandwidth of each beam is limited, the user capacity when the uplink power is limited, the user capacity when the downlink bandwidth is limited and the user capacity when the downlink power is limited; the smaller value of the user capacity when the uplink bandwidth is limited and the user capacity when the uplink power is limited is taken as the single-beam uplink user capacity; and taking the smaller value of the user capacity when the downlink bandwidth is limited and the user capacity when the downlink power is limited as the single-beam downlink user capacity. According to the method, the influence of the power in the uplink and downlink of the satellite on the estimation of the user capacity of the satellite system is considered, so that the measurement and calculation result of the user capacity is more accurate and better conforms to the actual satellite operation condition, and a satellite resource manager can accurately evaluate the current satellite resource use condition and the residual available satellite communication resources; and satellite communication resources are better planned and allocated, so that each satellite user can obtain high-quality satellite communication service.

Description

Technical Field

[0001] This invention belongs to the field of satellite user capacity assessment technology, and specifically relates to a method for calculating satellite user capacity. Background Technology

[0002] With the rapid development of new technologies and applications in recent years, the demand for satellite communication has been increasing, leading to a rise in the number of satellite communication users and a wide variety of services. At the same time, the increase in satellite users has also resulted in channel congestion, decreased communication quality, and frequent satellite communication interference incidents, which in severe cases can even cause communication outages.

[0003] Satellite systems are resource-constrained systems, and maximizing the utilization of limited satellite resources is a crucial issue that satellite resource management must address. Calculating satellite user capacity provides an important reference for satellite resource management. Accurately calculating satellite user capacity and reasonably assessing current satellite resource usage helps in better planning and allocating satellite communication resources, providing users with truly usable satellite communication resources.

[0004] Calculating satellite user capacity involves a vast array of parameters, especially with the continuous emergence of new technologies and an increasing number of factors to consider, such as the bandwidth allocated to the satellite, the technology system used by the satellite, the satellite power, and the anti-interference performance of the satellite terminal. How to accurately calculate the capacity of various types of satellite users that meet their communication quality requirements based on different scenarios is a problem that needs to be addressed.

[0005] Current methods for calculating the user capacity of communication satellites typically involve dividing the frequency band in the frequency domain, dividing it into multiple time slots in the time domain, or combining both frequency and time domain dimensions for block calculation.

[0006] Current methods primarily involve segmenting the satellite system in both the frequency and time domains based on its modulation scheme. ① In FDMA (Frequency Division Multiple Access) technology, the system bandwidth is divided into multiple non-overlapping sub-bands, each representing a channel. The number of channels, or user capacity, can be calculated based on parameters such as the system's total bandwidth, channel isolation bandwidth, and single-channel information rate. ② In TDMA (Time Division Multiple Access) technology, the transmission time is periodically divided into non-overlapping time slots, with each channel corresponding to one time slot. These time slots are then allocated to different users. The number of channels supported by the system, or user capacity, can be calculated based on parameters such as the system's information rate and frame structure. ③ Combining TDMA and FDMA modes, segmentation is performed in both the frequency and time domains, such as... Figure 2 Each block corresponds to one channel, and the user capacity can be calculated based on the number of channels in this allocation mode.

[0007] Current technologies calculate satellite user capacity by simple segmentation in the frequency and time domains, without considering power. In reality, a satellite system is a power-constrained system, and this power limitation significantly impacts the calculation of user capacity. Although the system allocates channels to each user using a time-frequency block model, the power limitations of the satellite system actually cannot support so many users communicating simultaneously. Therefore, the calculation results of existing technologies have a low degree of consistency with actual satellite communication scenarios. Summary of the Invention

[0008] In view of the shortcomings of the existing technology, the present invention provides a method for calculating satellite user capacity, which can effectively solve the above problems.

[0009] The technical solution adopted in this invention is as follows:

[0010] This invention provides a method for calculating satellite user capacity, comprising the following steps:

[0011] Step S1: Obtain the basic parameters of the communication satellite system and the basic parameters of the satellite user terminal;

[0012] Step S2: Analyze the basic parameters of the communication satellite system and extract the performance parameters of a single satellite beam;

[0013] Step S3: Based on the performance parameters of a single satellite beam and the basic parameters of the satellite user terminal, calculate the user capacity when uplink bandwidth is limited, the user capacity when uplink power is limited, the user capacity when downlink bandwidth is limited, and the user capacity when downlink power is limited for each beam; take the smaller value between the user capacity when uplink bandwidth is limited and the user capacity when uplink power is limited as the uplink user capacity of a single beam; take the smaller value between the user capacity when downlink bandwidth is limited and the user capacity when downlink power is limited as the downlink user capacity of a single beam.

[0014] Step S4: The uplink user capacity of each beam is summed to obtain the total uplink user capacity of the communication satellite system; the downlink user capacity of each beam is summed to obtain the total downlink user capacity of the communication satellite system.

[0015] Preferably, in step S3, if the communication satellite system is a Frequency Division Multiple Access (FDMA) system, the calculation methods for user capacity when the uplink bandwidth of each beam is limited and user capacity when the downlink bandwidth is limited are the same, including the following steps:

[0016] Step A1, Channel bandwidth B ch The expression is given by formula (1):

[0017]

[0018] Among them: B ch R is the channel bandwidth; α is the roll-off factor of the receiver filter; B R is the symbol rate of a single channel; b M represents the information rate of a single channel; M is the modulation level.

[0019] Step A2, the number of channels N for each beam in a frequency division multiple access (FDMA) system under bandwidth constraints. B The expression is formula (2):

[0020]

[0021] Where: B is the bandwidth of the Frequency Division Multiple Access (FDMA) system; B g Guard interval between channels;

[0022] Step A3: Substitute formula (1) into formula (2) to obtain formula (3):

[0023]

[0024] Step A4: Using formula (3), calculate the number of channels N when the uplink bandwidth of each beam is limited. B This refers to the user capacity when the uplink bandwidth of each beam is limited; using formula (3), the number of channels N when the downlink bandwidth of each beam is limited is calculated. B This refers to the user capacity when the downlink bandwidth of each beam is limited.

[0025] Preferably, in step S3, if the communication satellite system is a Time Division Multiple Access (TDMA) system, the calculation methods for user capacity when the uplink bandwidth of each beam is limited and user capacity when the downlink bandwidth is limited are the same, including the following steps:

[0026] Step B1: Using formula (4), calculate the reference voice channel capacity N of each beam in the Time Division Multiple Access (TDMA) system. TDMA ;

[0027]

[0028] in:

[0029] Reference voice channel bit rate r c Calculate using formula (5):

[0030] r c =64kbps (5)

[0031] Available information bit rate r i Calculate using formula (6):

[0032] r i =r T -N r (r r +r g )-N t (r P +r g (6)

[0033] r r Reference burst bit rate; r g : Guard time bit rate; r P Preamble bit rate; N r : Number of reference stations; N t : Number of sudden business disruptions;

[0034] r T The total TDMA bit rate is calculated using formula (7):

[0035]

[0036] M is the modulation order; α is the roll-off factor of the receiving filter; B ch Channel bandwidth;

[0037] Step B2, the reference voice channel capacity N for each beam in the Time Division Multiple Access (TDMA) system. TDMA This refers to the user capacity when the uplink bandwidth of each beam in a Time Division Multiple Access (TDMA) system is limited, and the user capacity when the downlink bandwidth of each beam is limited.

[0038] Preferably, in step S3, if the communication satellite system is a Code Division Multiple Access (CDMA) system, the calculation methods for user capacity when the uplink bandwidth of each beam is limited and user capacity when the downlink bandwidth is limited are the same, including the following steps:

[0039] Step C1, assume the total power of all interfering signals in the CDMA system channel is J; if the total number of signal sources transmitted in the channel is N. c Each source has a carrier power of c, and only one source is the desired signal, while the others N c If -1 is an interference signal, then:

[0040] J = (N c -1)c (8)

[0041] Step C2, total noise power density n t Represented as formula (9):

[0042]

[0043] Where: n0 is the thermal noise power density, nj b is the power density of the interference noise. rf For the spreading bandwidth; since c = e b r b e b and r b Let the bit energy and bit rate be respectively; therefore, we get formula (10):

[0044]

[0045] Based on formula (10), we can transform it to obtain formula (11):

[0046]

[0047] make Given the spread spectrum processing gain of the CDMA system, we obtain formula (12):

[0048]

[0049] Due to the second term of formula (12) of the CDMA system Since it is much greater than 1, simplifying formula (12) yields formula (13):

[0050]

[0051] Step C3: Using formula (13), the total number of information sources N in the Code Division Multiple Access (CDMA) system is obtained. c This refers to the user capacity when the uplink bandwidth of a Code Division Multiple Access (CDMA) system is limited, and the user capacity when the downlink bandwidth is limited.

[0052] Preferably, in step S3, the calculation method for user capacity when the uplink power of each beam is limited is the same for frequency division multiple access (FDMA), time division multiple access (TDMA), and code division multiple access (CDMA) systems, including the following steps:

[0053] Step D1: When the satellite transponder receives signals from multiple carriers on the ground, the total power flux density reaching the satellite must be less than or equal to the saturation power flux density of the satellite transponder. Therefore, in the uplink, the satellite transponder operating on multiple carriers is power-limited and must satisfy formula (14):

[0054] N×pfd≤Φ (14)

[0055] Where: pfd is the power flux density; N is the number of carriers arriving at the satellite transponder; Φ is the saturation power flux density of the satellite transponder;

[0056] Step D2, express formula (14) in decibel form to obtain formula (15):

[0057]

[0058] Among them: EIRP U For a single satellite user terminal, EIRP is the transmitted Equivalent Isotropic Radiated Power; L is the link loss; λ is the wavelength; [Φ] dB This is the decibel representation of the saturation power flux density of a satellite transponder.

[0059] Step D3: Calculate the maximum value of the number of carriers N reaching the satellite transponder that satisfies formula (15), and use it as the user capacity when the uplink power of each beam in the frequency division multiple access (FDMA) system, time division multiple access (TDMA) system, and code division multiple access (CDMA) system is limited.

[0060] Preferably, in step S3, for both Frequency Division Multiple Access (FDMA) and Code Division Multiple Access (CDMA) systems, the method for calculating user capacity when downlink power of each beam is limited is the same, including the following steps:

[0061] Step E1, for both Frequency Division Multiple Access (FDMA) and Code Division Multiple Access (CDMA) systems, the downlink carrier noise power spectral density is expressed in decibels as formula (16):

[0062]

[0063] Where: C is the carrier power in decibels; N0 is the noise power spectral density; G / T is the receiver system quality factor; L is the link loss; K is the logarithmic form of the Boltzmann constant;

[0064] Step E2, since the carrier power c = e b r b e b and r b Let c = e be the bit energy and bit rate, respectively. b r b Expressed in decibels as C=E b +R b E b and R b e b and r b Logarithmic form; then we get the bit rate R in decibels when downlink power is limited, as shown in formula (17). b :

[0065]

[0066] Equation (17) shows that the downlink transmission bit rate of frequency division multiple access (FDMA) and code division multiple access (CDMA) systems is limited, and the corresponding satellite user capacity is also limited.

[0067] Step E3: For both Frequency Division Multiple Access (FDMA) and Code Division Multiple Access (CDMA) systems, multiple carriers share a satellite transponder; the carrier-to-noise ratio (CNR) of a single carrier under the condition of satisfying the bit error rate is (c / n0). t , For the energy noise density per bit, we get formula (18):

[0068]

[0069] Step E4, according to formula (18), the carrier-to-noise ratio required for each carrier, expressed in decibels, is obtained as follows:

[0070]

[0071] in: The carrier-to-noise ratio required for each carrier, expressed in decibels; To achieve the required bit error rate threshold R B Data bit rate is expressed in decibels; Margin is the link headroom.

[0072] Step E5, Total Carrier-to-Noise Ratio (C / N0) on the Link T and the carrier-to-noise ratio required per carrier, expressed in decibels. It has relation (20):

[0073]

[0074] Where: N P This represents the number of carriers that the link can support.

[0075] Step E6, express relation (20) as:

[0076]

[0077] Step E7: According to formula (21), the number of carriers N that the link can support is obtained. P This refers to the user capacity of frequency division multiple access (FDMA) and code division multiple access (CDMA) systems when the downlink power of each beam is limited.

[0078] Preferably, in step S3, the method for calculating the user capacity when the downlink power of each beam is limited in a Time Division Multiple Access (TDMA) system includes the following steps:

[0079] Step F1: For a Time Division Multiple Access (TDMA) system, the bit rate R, expressed in decibels, is obtained using formula (17) when the downlink power of each beam in the TDMA system is limited. b ;

[0080] Step F2, set the bit rate R b Convert the total TDMA bit rate r according to equation (22). T :

[0081]

[0082] Step F3, set the total TDMA bit rate r T Substituting into formula (6), we obtain the available information bit rate r. i Then, the reference voice channel capacity N of each beam in the time division multiple access (TDMA) system is calculated using formula (4). TDMA This refers to the user capacity when the downlink power of each beam in a Time Division Multiple Access (TDMA) system is limited.

[0083] The method for calculating satellite user capacity provided by this invention has the following advantages:

[0084] This invention, based on traditional frequency and time domain slicing, considers the impact of satellite uplink and downlink power on satellite system user capacity estimation, making the user capacity calculation results more accurate and more in line with the actual satellite operation. This helps satellite resource managers to accurately assess the current satellite resource usage and remaining available satellite communication resources, better plan and allocate satellite communication resources, and ensure that every satellite user can receive high-quality satellite communication services. Attached Figure Description

[0085] Figure 1 A schematic diagram of a method for calculating satellite user capacity provided by the present invention;

[0086] Figure 2 This is a schematic diagram illustrating the principle of segmentation in both the frequency and time domains for both TDMA and FDMA modes. Detailed Implementation

[0087] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the invention.

[0088] The abbreviations and key terms of this invention are defined as follows:

[0089] TDMA: Time Division Multiple Access

[0090] FDMA: Frequency Division Multiple Access

[0091] CDMA: Code Division Multiple Access

[0092] Saturated power flux density: The power flux density required by the satellite receiving antenna when the satellite transponder produces maximum saturated output power.

[0093] To improve the accuracy of satellite system user capacity assessment, this invention analyzes the characteristics of satellite channels under three technical systems: TDMA, FDMA, and CDMA. Besides considering that bandwidth limits the improvement of satellite user capacity, it innovatively takes into account that satellites are power-constrained systems and provides a detailed analysis of the power limitations of satellite uplink and downlink. By combining parameters such as satellite system bandwidth, transmit power, information rate, coding scheme, modulation scheme, technical system, transponder saturation power flux density, and earth station bit error rate requirements, the uplink and downlink satellite user capacity of the three technical systems are derived. This method is closer to the actual operation of satellite systems, yields more accurate assessment results, and greatly enhances support for satellite resource management.

[0094] In current wireless communication systems, satellite user capacity is primarily constrained by two physical conditions: bandwidth limitation and power limitation. To overcome bandwidth limitations, multiple access methods such as FDMA, TDMA, and CDMA are widely used in practical satellite systems, further increasing satellite user capacity. Due to differences in communication systems and specific application technologies, the methods for estimating satellite user capacity also vary.

[0095] The most commonly used multiple access methods for satellites are frequency division multiple access (FDMA), code division multiple access (CDMA), and time division multiple access (TDMA).

[0096] FDMA was the first commercially available multiple access technology. In this multiple access method, the system bandwidth is divided into multiple non-overlapping subbands. Different links modulate their respective signals onto the corresponding subbands via transmitters. The receiver then demodulates the useful information from different subbands using appropriate filters. A link can occupy one or more channels depending on the service type. The advantages of FDMA are its mature technology and simple ground terminal and application terminal equipment; the disadvantage is that when multiple subcarriers share a satellite transponder, it can cause satellite transponder saturation, resulting in low satellite transponder power and bandwidth utilization. This is due to intermodulation interference caused by the nonlinearity of the power amplifier.

[0097] TDMA (Time-Divided DMA) divides the transmission time into non-overlapping time slots, with one repetition period called a frame. Each channel corresponds to one time slot, and time selection (time gate) is used to separate channels. Different links can use the same frequency in different time slots, and a link can occupy one or more channels depending on the service type.

[0098] CDMA systems overcome frequency band limitations to some extent by using orthogonal pseudo-random codes. Channels are distinguished based on the quasi-orthogonality of the communication signal waveforms in the time domain. Each channel is assigned a wideband, mutually quasi-orthogonal address code, broadening the baseband signal spectrum for transmission. The receiver uses a matched filter or correlator corresponding to the address code in the time domain to extract the baseband signal. Cells can use the same frequency, facilitating system expansion, and links can be randomly accessed, allowing for flexible network configuration. However, in CDMA systems, the system capacity ceiling depends primarily on interference from other links; therefore, CDMA is an interference-constrained system.

[0099] This invention, based on traditional frequency and time domain slicing, considers the impact of satellite uplink and downlink power on satellite system user capacity estimation, making the user capacity calculation results more accurate and more in line with the actual satellite operation. This helps satellite resource managers to accurately assess the current satellite resource usage and remaining available satellite communication resources, better plan and allocate satellite communication resources, and ensure that every satellite user can receive high-quality satellite communication services.

[0100] like Figure 1 As shown, the present invention provides a method for calculating satellite user capacity, comprising the following steps:

[0101] Step S1: Obtain the basic parameters of the communication satellite system and the basic parameters of the satellite user terminal;

[0102] Step S2: Analyze the basic parameters of the communication satellite system and extract the performance parameters of a single satellite beam;

[0103] Step S3: Based on the performance parameters of a single satellite beam and the basic parameters of the satellite user terminal, calculate the user capacity when uplink bandwidth is limited, the user capacity when uplink power is limited, the user capacity when downlink bandwidth is limited, and the user capacity when downlink power is limited for each beam; take the smaller value between the user capacity when uplink bandwidth is limited and the user capacity when uplink power is limited as the uplink user capacity of a single beam; take the smaller value between the user capacity when downlink bandwidth is limited and the user capacity when downlink power is limited as the downlink user capacity of a single beam.

[0104] Step S4: The uplink user capacity of each beam is summed to obtain the total uplink user capacity of the communication satellite system; the downlink user capacity of each beam is summed to obtain the total downlink user capacity of the communication satellite system.

[0105] The following is a detailed description of step S3 of the present invention:

[0106] (I) Situations where uplink and downlink bandwidth are limited in Frequency Division Multiple Access (FDMA) systems

[0107] If the communication satellite system is a Frequency Division Multiple Access (FDMA) system, the calculation methods for the user capacity when the uplink bandwidth of each beam is limited and the user capacity when the downlink bandwidth is limited are the same, including the following steps:

[0108] Step A1, Channel bandwidth B ch The expression is given by formula (1):

[0109]

[0110] Among them: B ch R is the channel bandwidth; α is the roll-off factor of the receiver filter; B R is the symbol rate of a single channel; b M represents the information rate of a single channel; M is the modulation level.

[0111] Step A2, the number of channels N for each beam in a frequency division multiple access (FDMA) system under bandwidth constraints. B The expression is formula (2):

[0112]

[0113] Where: B is the bandwidth of the Frequency Division Multiple Access (FDMA) system; B g Guard interval between channels;

[0114] Step A3: Substitute formula (1) into formula (2) to obtain formula (3):

[0115]

[0116] Step A4: Using formula (3), calculate the number of channels N when the uplink bandwidth of each beam is limited. B This refers to the user capacity when the uplink bandwidth of each beam is limited; using formula (3), the number of channels N when the downlink bandwidth of each beam is limited is calculated. B This refers to the user capacity when the downlink bandwidth of each beam is limited.

[0117] (II) Situations where uplink and downlink bandwidth are limited in Time Division Multiple Access (TDMA) systems

[0118] If the communication satellite system is a Time Division Multiple Access (TDMA) system, the calculation methods for the user capacity when the uplink bandwidth of each beam is limited and the user capacity when the downlink bandwidth is limited are the same, including the following steps:

[0119] Step B1: Using formula (4), calculate the reference voice channel capacity N of each beam in the Time Division Multiple Access (TDMA) system.TDMA ;

[0120]

[0121] in:

[0122] Reference voice channel bit rate r c Calculate using formula (5):

[0123] r c =64kbps (5)

[0124] Available information bit rate r i Calculate using formula (6):

[0125] r i =r T -N r (r r +r g )-N t (r P +r g (6)

[0126] r r Reference burst bit rate; r g : Guard time bit rate; r P Preamble bit rate; N r : Number of reference stations; N t : Number of sudden business disruptions;

[0127] r T The total TDMA bit rate is calculated using formula (7):

[0128]

[0129] M is the modulation order; α is the roll-off factor of the receiving filter; B ch Channel bandwidth;

[0130] Step B2, the reference voice channel capacity N for each beam in the Time Division Multiple Access (TDMA) system. TDMA This refers to the user capacity when the uplink bandwidth of each beam in a Time Division Multiple Access (TDMA) system is limited, and the user capacity when the downlink bandwidth of each beam is limited.

[0131] (III) Uplink and downlink bandwidth limited scenarios in CDMA systems

[0132] If the communication satellite system is a Code Division Multiple Access (CDMA) system, the calculation methods for the user capacity when the uplink bandwidth of each beam is limited and the user capacity when the downlink bandwidth is limited are the same, including the following steps:

[0133] CDMA user capacity defines the maximum number of channels that can be accommodated in a CDMA system for acceptable signal recovery. This signal recovery requires the energy-noise density per bit necessary for the system to achieve a specified bit error rate.

[0134] Step C1, assume the total power of all interfering signals in the CDMA system channel is J; if the total number of signal sources transmitted in the channel is N. c Each source has a carrier power of c, and only one source is the desired signal, while the others N c If -1 is an interference signal, then:

[0135] J = (N c -1)c (8)

[0136] Step C2, total noise power density n t Represented as formula (9):

[0137]

[0138] Where: n0 is the thermal noise power density, n j b is the power density of the interference noise. rf For the spreading bandwidth; since c = e b r b e b and r b Let the bit energy and bit rate be respectively; therefore, we get formula (10):

[0139]

[0140] Based on formula (10), we can transform it to obtain formula (11):

[0141]

[0142] make Given the spread spectrum processing gain of the CDMA system, we obtain formula (12):

[0143]

[0144] Due to the second term of formula (12) of the CDMA system Since it is much greater than 1, simplifying formula (12) yields formula (13):

[0145]

[0146] Step C3: Using formula (13), the total number of information sources N in the Code Division Multiple Access (CDMA) system is obtained. c This refers to the user capacity when the uplink bandwidth of a Code Division Multiple Access (CDMA) system is limited, and the user capacity when the downlink bandwidth is limited.

[0147] In a CDMA system, this user capacity specifies the maximum number of channels that can be accommodated. If this is a voice-data channel system, additional capacity can be achieved by applying voice activation factors or voice compression techniques.

[0148] (iv) Uplink power limitation in frequency division multiple access (FDMA), time division multiple access (TDMA), and code division multiple access (CDMA) systems

[0149] For Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), and Code Division Multiple Access (CDMA) systems, the calculation method for user capacity when uplink power of each beam is limited is the same, including the following steps:

[0150] Step D1: When the satellite transponder receives signals from multiple carriers on the ground, the total power flux density reaching the satellite must be less than or equal to the saturation power flux density of the satellite transponder. Therefore, in the uplink, the satellite transponder operating on multiple carriers is power-limited and must satisfy formula (14):

[0151] N×pfd≤Φ (14)

[0152] Where: pfd is the power flux density; N is the number of carriers arriving at the satellite transponder; Φ is the saturation power flux density of the satellite transponder;

[0153] That is, the total power flux density of N carriers arriving at the satellite transponder must be less than the transponder's saturation power flux density Φ;

[0154] Step D2, express formula (14) in decibel form to obtain formula (15):

[0155]

[0156] Among them: EIRP U For a single satellite user terminal, EIRP is the transmitted Equivalent Isotropic Radiated Power; L is the link loss; λ is the wavelength; [Φ] dB This is the decibel representation of the saturation power flux density of a satellite transponder.

[0157] Step D3: Calculate the maximum value of the number of carriers N reaching the satellite transponder that satisfies formula (15), and use it as the user capacity when the uplink power of each beam in the frequency division multiple access (FDMA) system, time division multiple access (TDMA) system, and code division multiple access (CDMA) system is limited.

[0158] (v) Downlink power limitation in frequency division multiple access (FDMA) and code division multiple access (CDMA) systems

[0159] For both Frequency Division Multiple Access (FDMA) and Code Division Multiple Access (CDMA) systems, the calculation method for user capacity when downlink power of each beam is limited is the same, including the following steps:

[0160] Ground user terminals receive downlink signals from satellites. To meet bit error rate (BER) requirements, the receiver needs a certain carrier-to-noise power spectral density ratio (CNR) for each downlink carrier. Due to the limited overall EIRP of the satellite, an increase in the number of carriers (users) inevitably leads to a decrease in the CNR per carrier. Power limitation occurs when the EIRP is insufficient to meet the CNR requirements. When the number of users increases to a certain extent, the reduced CNR prevents the receiver from meeting its BER requirements, which is considered unacceptable.

[0161] Step E1, for both Frequency Division Multiple Access (FDMA) and Code Division Multiple Access (CDMA) systems, the downlink carrier noise power spectral density is expressed in decibels as formula (16):

[0162]

[0163] Where: C is the carrier power in decibels; N0 is the noise power spectral density; G / T is the receiver system quality factor; L is the link loss; K is the logarithmic form of the Boltzmann constant;

[0164] Step E2, since the carrier power c = e b r b e b and r b Let c = e be the bit energy and bit rate, respectively. b r b Expressed in decibels as C=E b +R b E b and R b e b and r b Logarithmic form; then we get the bit rate R in decibels when downlink power is limited, as shown in formula (17). b :

[0165]

[0166] Equation (17) shows that the downlink transmission bit rate of frequency division multiple access (FDMA) and code division multiple access (CDMA) systems is limited, and the corresponding satellite user capacity is also limited.

[0167] Step E3: For both Frequency Division Multiple Access (FDMA) and Code Division Multiple Access (CDMA) systems, multiple carriers share a satellite transponder; the carrier-to-noise ratio (CNR) of a single carrier under the condition of satisfying the bit error rate is (c / n0). t , For the energy noise density per bit, we get formula (18):

[0168]

[0169] Step E4, according to formula (18), the carrier-to-noise ratio required for each carrier, expressed in decibels, is obtained as follows:

[0170]

[0171] in: The carrier-to-noise ratio required for each carrier, expressed in decibels; To achieve the required bit error rate threshold R B The data bit rate is expressed in decibels; Margin is the link headroom, typically 1-2 dB.

[0172] Total carrier-to-noise ratio (C / N0) on the RF link T This can be calculated from the link. The single-carrier carrier-to-noise ratio (C / N0) is... t Compared to the total carrier-to-noise ratio (C / N0) on the RF link. T A comparison is made to determine the number of carriers N that can be supported. P See step E5 for details.

[0173] Step E5, Total Carrier-to-Noise Ratio (C / N0) on the Link T and the carrier-to-noise ratio required per carrier, expressed in decibels. It has relation (20):

[0174]

[0175] Where: N P This represents the number of carriers that the link can support.

[0176] Step E6, express relation (20) as:

[0177]

[0178] Step E7: According to formula (21), the number of carriers N that the link can support is obtained. P This refers to the user capacity of frequency division multiple access (FDMA) and code division multiple access (CDMA) systems when the downlink power of each beam is limited.

[0179] (vi) Downlink power limitation in Time Division Multiple Access (TDMA) systems

[0180] In a TDMA system, only one carrier uses the transponder at any given time, and there is no multi-carrier scenario. However, the transmission bit rate is limited by the satellite power.

[0181] For a Time Division Multiple Access (TDMA) system, the method for calculating the user capacity when the downlink power of each beam is limited includes the following steps:

[0182] Step F1: For a Time Division Multiple Access (TDMA) system, the bit rate R, expressed in decibels, is obtained using formula (17) when the downlink power of each beam in the TDMA system is limited. b ;

[0183] Step F2, set the bit rate R b Convert the total TDMA bit rate r according to equation (22). T :

[0184]

[0185] Step F3, set the total TDMA bit rate r T Substituting into formula (6), we obtain the available information bit rate r. i Then, the reference voice channel capacity N of each beam in the time division multiple access (TDMA) system is calculated using formula (4). TDMA This refers to the user capacity when the downlink power of each beam in a Time Division Multiple Access (TDMA) system is limited.

[0186] In summary, this invention considers the impact of satellite uplink and downlink power on the estimation of satellite system user capacity, making the calculation results of user capacity more accurate and more in line with the actual satellite operation. This helps satellite resource managers to accurately assess the current satellite resource usage and remaining available satellite communication resources, better plan and allocate satellite communication resources, and ensure that every satellite user can receive high-quality satellite communication services.

[0187] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for calculating satellite user capacity, characterized in that, Includes the following steps: Step S1: Obtain the basic parameters of the communication satellite system and the basic parameters of the satellite user terminal; Step S2: Analyze the basic parameters of the communication satellite system and extract the performance parameters of a single satellite beam; Step S3: Based on the performance parameters of a single satellite beam and the basic parameters of the satellite user terminal, calculate the user capacity when the uplink bandwidth is limited, the user capacity when the uplink power is limited, the user capacity when the downlink bandwidth is limited, and the user capacity when the downlink power is limited for each beam. The smaller value between the user capacity under uplink bandwidth limitation and the user capacity under uplink power limitation is taken as the single-beam uplink user capacity. The smaller value between the user capacity under downlink bandwidth limitation and the user capacity under downlink power limitation is taken as the single-beam downlink user capacity. Step S4: The uplink user capacity of each single beam is summed to obtain the total uplink user capacity of the communication satellite system. The downlink user capacity of each beam is summed to obtain the total downlink user capacity of the communication satellite system.

2. The method for calculating satellite user capacity according to claim 1, characterized in that, In step S3, if the communication satellite system is a Frequency Division Multiple Access (FDMA) system, the calculation methods for user capacity when the uplink bandwidth of each beam is limited and user capacity when the downlink bandwidth is limited are the same, including the following steps: Step A1, Channel bandwidth B ch The expression is given by formula (1): Among them: B ch R is the channel bandwidth; α is the roll-off factor of the receiver filter; B R is the symbol rate of a single channel; b M represents the information rate of a single channel; M is the modulation level. Step A2, the number of channels N for each beam in a frequency division multiple access (FDMA) system under bandwidth constraints. B The expression is formula (2): Where: B is the bandwidth of the Frequency Division Multiple Access (FDMA) system; B g Guard interval between channels; Step A3: Substitute formula (1) into formula (2) to obtain formula (3): Step A4: Using formula (3), calculate the number of channels N when the uplink bandwidth of each beam is limited. B This refers to the user capacity when the uplink bandwidth of each beam is limited; using formula (3), the number of channels N when the downlink bandwidth of each beam is limited is calculated. B This refers to the user capacity when the downlink bandwidth of each beam is limited.

3. The method for calculating satellite user capacity according to claim 1, characterized in that, In step S3, if the communication satellite system is a Time Division Multiple Access (TDMA) system, the calculation methods for user capacity when the uplink bandwidth of each beam is limited and user capacity when the downlink bandwidth is limited are the same, including the following steps: Step B1: Using formula (4), calculate the reference voice channel capacity N of each beam in the Time Division Multiple Access (TDMA) system. TDMA ; in: Reference voice channel bit rate r c Calculate using formula (5): r c =64kbps (5) Available information bit rate r i Calculate using formula (6): r i =r T -N r (r r +r g )-N t (r P +r g ) (6) r r Reference burst bit rate; r g : Guard time bit rate; r P Preamble bit rate; N r : Number of reference stations; N t : Number of sudden business disruptions; r T The total TDMA bit rate is calculated using formula (7): M is the modulation order; α is the roll-off factor of the receiving filter; B ch Channel bandwidth; Step B2, the reference voice channel capacity N for each beam in the Time Division Multiple Access (TDMA) system. TDMA This refers to the user capacity when the uplink bandwidth of each beam in a Time Division Multiple Access (TDMA) system is limited, and the user capacity when the downlink bandwidth of each beam is limited.

4. The method for calculating satellite user capacity according to claim 1, characterized in that, In step S3, if the communication satellite system is a Code Division Multiple Access (CDMA) system, the calculation methods for user capacity when the uplink bandwidth of each beam is limited and user capacity when the downlink bandwidth is limited are the same, including the following steps: Step C1, assume the total power of all interfering signals in the CDMA system channel is J; if the total number of signal sources transmitted in the channel is N. c Each source has a carrier power of c, and only one source is the desired signal, while the others N c If -1 is an interference signal, then: J=(N c -1)c (8) Step C2, total noise power density n t Represented as formula (9): Where: n0 is the thermal noise power density, n j b is the power density of the interference noise. rf For the spreading bandwidth; since c = e b r b e b and r b Let the bit energy and bit rate be respectively; therefore, we get formula (10): Based on formula (10), we can transform it to obtain formula (11): make Given the spread spectrum processing gain of the CDMA system, we obtain formula (12): Due to the second term of formula (12) of the CDMA system Since it is much greater than 1, simplifying formula (12) yields formula (13): Step C3: Using formula (13), the total number of information sources N in the Code Division Multiple Access (CDMA) system is obtained. c This refers to the user capacity when the uplink bandwidth of a Code Division Multiple Access (CDMA) system is limited, and the user capacity when the downlink bandwidth is limited.

5. The method for calculating satellite user capacity according to claim 1, characterized in that, In step S3, the calculation method for user capacity when the uplink power of each beam is limited is the same for frequency division multiple access (FDMA), time division multiple access (TDMA), and code division multiple access (CDMA) systems, including the following steps: Step D1: When the satellite transponder receives signals from multiple carriers on the ground, the total power flux density reaching the satellite must be less than or equal to the saturation power flux density of the satellite transponder. Therefore, in the uplink, the satellite transponder operating on multiple carriers is power-limited and must satisfy formula (14): N×pfd≤Φ (14) Where: pfd is the power flux density; N is the number of carriers arriving at the satellite transponder; Φ is the saturation power flux density of the satellite transponder; Step D2, express formula (14) in decibel form to obtain formula (15): Among them: EIRP U For a single satellite user terminal, EIRP is the transmitted Equivalent Isotropic Radiated Power; L is the link loss; λ is the wavelength; [Φ] dB This is the decibel representation of the saturation power flux density of a satellite transponder. Step D3: Calculate the maximum value of the number of carriers N reaching the satellite transponder that satisfies formula (15), and use it as the user capacity when the uplink power of each beam in the frequency division multiple access (FDMA) system, time division multiple access (TDMA) system, and code division multiple access (CDMA) system is limited.

6. The method for calculating satellite user capacity according to claim 3, characterized in that, In step S3, the calculation method for user capacity when downlink power of each beam is limited is the same for both Frequency Division Multiple Access (FDMA) and Code Division Multiple Access (CDMA) systems, including the following steps: Step E1, for both Frequency Division Multiple Access (FDMA) and Code Division Multiple Access (CDMA) systems, the downlink carrier noise power spectral density is expressed in decibels as formula (16): Where: C is the carrier power in decibels; N0 is the noise power spectral density; G / T is the receiver system quality factor; L is the link loss; K is the logarithmic form of the Boltzmann constant; Step E2, since the carrier power c = e b r b e b and r b Let c = e be the bit energy and bit rate, respectively. b r b Expressed in decibels as C=E b +R b E b and R b e b and r b Logarithmic form; then we get the bit rate R in decibels when downlink power is limited, as shown in formula (17). b : Equation (17) shows that the downlink transmission bit rate of frequency division multiple access (FDMA) and code division multiple access (CDMA) systems is limited, and the corresponding satellite user capacity is also limited. Step E3: For both Frequency Division Multiple Access (FDMA) and Code Division Multiple Access (CDMA) systems, multiple carriers share a satellite transponder; the carrier-to-noise ratio (CNR) of a single carrier under the condition of satisfying the bit error rate is (c / n0). t , For the energy noise density per bit, we get formula (18): Step E4, according to formula (18), the carrier-to-noise ratio required for each carrier, expressed in decibels, is obtained as follows: in: The carrier-to-noise ratio required for each carrier, expressed in decibels; To achieve the required bit error rate threshold R B Data bit rate is expressed in decibels; Margin is the link headroom. Step E5, Total Carrier-to-Noise Ratio (C / N0) on the Link T and the carrier-to-noise ratio required per carrier, expressed in decibels. It has relation (20): Where: N P This represents the number of carriers that the link can support. Step E6, express relation (20) as: Step E7: According to formula (21), the number of carriers N that the link can support is obtained. P This refers to the user capacity of frequency division multiple access (FDMA) and code division multiple access (CDMA) systems when the downlink power of each beam is limited.

7. The method for calculating satellite user capacity according to claim 6, characterized in that, In step S3, the method for calculating the user capacity when the downlink power of each beam is limited in a Time Division Multiple Access (TDMA) system includes the following steps: Step F1: For a Time Division Multiple Access (TDMA) system, the bit rate R, expressed in decibels, is obtained using formula (17) when the downlink power of each beam in the TDMA system is limited. b ; Step F2, set the bit rate R b Convert the total TDMA bit rate r according to equation (22). T : Step F3, set the total TDMA bit rate r T Substituting into formula (6), we obtain the available information bit rate r. i Then, the reference voice channel capacity N of each beam in the time division multiple access (TDMA) system is calculated using formula (4). TDMA This refers to the user capacity when the downlink power of each beam in a Time Division Multiple Access (TDMA) system is limited.

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