CN102065032A - Mobile communication system and method based on high altitude platform semi-regeneration signal processing - Google Patents

Abstract

The invention discloses a mobile communication system based on high-altitude platform semi-regenerative signal processing, which mainly solves the contradiction problem between limited resources of the existing high-altitude platform and large user capacity. It includes a high-altitude platform, a ground gateway, and a user terminal; the high-altitude platform performs regenerative processing or semi-regenerative processing after receiving an uplink signal and constructs a downlink signal for transmission; the radio frequency components, user interface, baseband rate, and frequency band of the user terminal are all related to the ground TD - The user terminals in the SCDMA system are the same to achieve partial compatibility with the TD-SCDMA system; the users of the high-altitude platform realize the interconnection with the users in the ground TD-SCDMA system through the high-speed data transmission link between the ground gateway and the high-altitude platform Intercommunication; under limited high-altitude platform resources, the system can maximize the supported user capacity, provide real-time voice and multimedia services with good QoS guarantee, and can be used to build a low-complexity high-altitude platform cellular network mobile communication system located in the stratosphere .

Description

Mobile communication system and method based on high-altitude platform semi-regenerative signal processing

technical field

The invention belongs to the technical field of communication and relates to data transmission and exchange, in particular to a high-altitude platform-based mobile communication system, which can be used to construct a low-complexity high-altitude platform cellular network mobile communication system located in the stratosphere.

Background technique

The wireless communication system based on the high-altitude platform is a new type of communication system that is currently in the research stage in the world. The carriers of high-altitude platforms mainly include tethered balloons and airships. The height of the former is generally below 10Km, and the latter is generally located in the stratosphere at an altitude of 20Km to 50Km. The air in the stratosphere is thin, its density is about a few percent of sea level, and its buoyancy is very small, but the airflow is relatively stable and the wind shear is small. It is an ideal airspace for deploying high-altitude hovering airships.

Compared with the distance from the geostationary satellite to the ground, the distance from the stratospheric platform to the ground is shortened to 1/1700, so its transmission delay is relatively shortened to 1/1700, and the free space attenuation is relatively reduced by 64.6dB, which is very conducive to the miniaturization of communication terminals and broadband. Compared with the terrestrial cellular network mobile communication system, although the transmission distance of the cellular network mobile communication system based on the stratospheric platform is increased by more than ten times, its channel condition is much better than that of the terrestrial cellular network system, and its link attenuation is about 20dB/ 10 times range, while the link attenuation of the ground cellular network system is 50dB/10 times range, so if the terminal in the high-altitude platform system has the same transmission power as the terminal of the ground TD-SCDMA system, then without considering the antenna gain , such terminal transmission power is completely suitable for the high-altitude platform system. In terms of antenna gain, the high-altitude platform system can obtain a gain of 20-30dB by using a multi-beam antenna, which is equivalent to the gain of the smart antenna technology of the ground TD-SCDMA system. Combining the two factors of signal attenuation and antenna gain, it can be seen that the power level of the ground TD-SCDMA system terminal is completely suitable for the high-altitude platform system. This feature provides a basic guarantee for the partial compatibility of the two systems. The high-altitude platform is not only suitable for cities as an effective supplement to the ground mobile communication system, but also can be used in areas where the ground mobile communication system is inconvenient to deploy, such as oceans and mountainous areas, and can also be quickly transferred to battlefield areas or areas where natural disasters occur (such as floods, mountains, etc.) fire) monitoring and communication. In the long run, the high-altitude platform communication system may become the third wireless mobile communication system besides the ground mobile communication system and the satellite communication system.

The mobile communication system supported by the platform has significant advantages over the terrestrial cellular network mobile communication system in terms of mobility and wide-area coverage, and is also significantly better than the satellite mobile communication network in terms of construction cost and service quality. The development prospect has received extensive attention at home and abroad. At present, countries and regions such as Japan, the United States, and Europe have conducted more research on high-altitude platform communication systems. Japan plans to cover the entire territory of the country with dozens of high-altitude platforms to realize high-altitude wireless communication systems. The U.S. company Sky Station International suggested using more than 200 high-altitude platforms to form a network around the world, forming an aerial Internet, accommodating 1.5 billion telephone users, and realizing low-cost global communication. There have been many achievements in research in this field, and some international norms have been formed in the allocation of frequency resources and the positioning of service types. The system working in the Ka frequency band mainly supports broadband wireless access of fixed stations, and the system working in the S frequency band The system is compatible with the third generation (3G) cellular network mobile communication system, and these two types of services have formed a consensus. The applicant is aiming at the latter situation, and considering that my country's 3G mobile communication mainly adopts the TD-SCDMA international standard with independent intellectual property rights, so it is as compatible as possible with the TD-SCDMA international standard.

At present, the development of the mobile communication system based on the high-altitude platform, except that the technology of the high-altitude platform carrier itself has not yet completely broken through, from the perspective of communication equipment and communication system, it mainly faces three problems:

1) There is a contradiction between the limited resources of the high-altitude platform and the large demand for system communication capacity;

2) How to be compatible with the ground mobile communication system;

3) How to ensure the service quality of the system.

Due to the wide coverage of the mobile communication system supported by the high-altitude platform, the demand for communication capacity is large. Multi-beam antenna technology must be used to achieve a large user capacity. For example, 7,000 users can communicate at the same time under the coverage of 100 beams. If the user data in each beam is demodulated and decoded, it is actually equivalent to moving a large number of base stations to the high-altitude platform. At this time, the volume, weight and power consumption of multiple base stations will inevitably affect the payload of the high-altitude platform. Very high requirements are placed on power and power supply capabilities. In this case, there is a contradiction between the limited resources on the platform and the large demand for user capacity, and it is the main contradiction. It is the core topic and main difficulty of research in this field.

The important application goal of the high-altitude platform mobile communication system is to supplement the geographical coverage of the 3G terrestrial cellular network mobile communication system. Therefore, its terminals must be compatible or partially compatible with the existing terrestrial mobile communication network in order to truly exert its benefits. This compatibility is another difficulty encountered by the high-altitude platform system, because compared with the ground cellular network, the transmission distance of the user link in the high-altitude platform mobile communication system is much larger, and link budget and transmission delay will become problems.

The coverage of the high-altitude platform mobile communication system is quite large, and it needs to have the ability to support a large number of users for communication. Among the services it supports, real-time voice and real-time video services may occupy a large proportion. Therefore, large-scale user data exchange must be performed on the high-altitude platform, and at the same time, it must be able to meet the real-time requirements of the service, that is, provide quality of service QoS guarantee. If the packet switching technology is used, due to the non-uniformity of the switching path, it will cause a large delay and jitter, so that it cannot provide better QoS guarantee for real-time services.

Contents of the invention

Aiming at the above three problems, the present invention proposes a cellular network mobile communication system based on high-altitude platform semi-regenerative signal processing to support high-reliability communication of a large number of users in a high-altitude platform environment with limited resources, so that limited platform resources The supported user capacity is maximized, and it is partially compatible with the international standard of the 3G TD-SCDMA mobile communication system in terms of system, while providing good QoS guarantee for real-time voice and multimedia services.

In order to achieve the above object, the present invention is based on a high-altitude platform semi-regenerative signal processing cellular network mobile communication system, including: a high-altitude platform located in the stratosphere, one or more ground gateways and user terminals on the ground; the high-altitude platform includes A set of radio frequency intermediate frequency equipment used to form N ground cellular network cells and multi-beam antennas on the platform. The radio frequency intermediate frequency equipment is connected with N uplink signal receiving and processing modules, N downlink signal sending and processing modules, and a sample point circuit switching module And a network management control module, and also includes a signaling despreading demodulation decoding module, a signaling coding modulation module, a gateway information receiving and processing module, a gateway information sending and processing module, N≥200, wherein:

The radio frequency components and user interface of the user terminal are the same as those of the user terminal in the terrestrial TD-SCDMA system, and its baseband rate is the same as that of the terrestrial TD-SCDMA system, and uses the same frequency band as the terrestrial TD-SCDMA system, ensuring that the user terminal Can be connected to the terrestrial TD-SCDMA system to achieve partial compatibility with the international standard of the TD-SCDMA third-generation mobile communication system;

As a transit node, the ground gateway has a high-speed data transmission link between it and the high-altitude platform. Users within the coverage of the high-altitude platform communication system and users in the ground TD-SCDMA system outside the system communicate with each other through the high-speed data transmission link. Data and signaling are exchanged over the road to realize the interconnection between the high-altitude platform and the ground TD-SCDMA system.

The signaling despreading, demodulation and decoding module, the network management control module and the signaling coding and modulation module on the high-altitude platform are sequentially connected to form a signaling processing and network control management center to realize the interpretation of signaling information, Execution and construction.

The uplink signal receiving and processing module includes:

Orthogonal sampling A/D conversion unit, which is used to perform analog/digital conversion on the received signal and send the converted digital signal to the synchronization control, power control and related despreading unit;

The synchronization control unit estimates the synchronization time of the digital signal from the orthogonal sampling A/D conversion unit, obtains the synchronization time deviation of the user terminal and adjusts it, and realizes the closed-loop synchronization control;

The power control unit estimates the power level of the digital signal from the orthogonal sampling A/D conversion unit, obtains and adjusts the power level deviation of the user terminal, and realizes closed-loop power control;

The correlation despreading unit uses a semi-regenerative signal processing method to process the digital signal from the orthogonal sampling A/D conversion unit, that is, only performs correlation despreading and RAKE combination on the synchronous CDMA signals sent by each user to obtain the Soft decision quantities, and output these soft decision quantities to the sample point circuit switching module for exchange and further transmission.

The sample point circuit switching module adopts program-controlled circuit switching, under the control of signaling, switches the symbol soft decision quantity of each user from the uplink signal receiving and processing module, and adopts a basic high-speed switching clock for non-spread spectrum signals, Instead, a low-speed switching clock derated by the spreading factor is used for spread-spectrum signals.

The downlink signal processing module is composed of a multiplexing unit and a quadrature amplitude modulation unit, and the multiplexing unit performs subframe interleaving and time-division multiplexing on downlink signals sent to the same beam and each user in the same frequency band. The multi-channel signals are multiplexed, and the multiplexed signals are sent to the quadrature amplitude modulation unit to be modulated to the carrier frequency and then sent downwards.

In order to achieve the above object, the present invention is based on the cellular network mobile communication method of high-altitude platform semi-regenerative signal processing, including:

(1) The sending steps of the user terminal on the voice code channel of the uplink time slot:

1a) The user terminal performs 1/2 convolution coding and quaternary phase shift keying QPSK modulation on the original voice bits within 20ms to obtain 96 user voice modulation symbols;

1b) spreading the obtained user voice modulation symbols with a Gold sequence with a length of 31 as a spreading code to obtain 2976 spreading symbols;

1c) dividing the obtained spread spectrum symbols into time slots to obtain 4 spread spectrum symbol blocks with a length of 744 chips;

1d) each spreading symbol block is divided into two sections of equal length, and a Gold sequence with a length of 63 is added as a midamble code in the middle of the two sections to form an uplink time slot sequence to be sent with a length of 822 chips;

1e) Carrying out waveform shaping and D/A conversion on the sequence to be sent in the uplink time slot;

(2) The receiving steps of the high-altitude platform on the voice code channel of the uplink timeslot:

2a) The high-altitude platform performs orthogonal down-conversion, analog/digital A/D conversion and matched filtering on the received voice signal to obtain the digital signal of the uplink voice;

2b) Extract the midamble code in the uplink voice digitized signal, perform synchronization time estimation and power level estimation, and send the estimated synchronization time deviation information and power level deviation information to the network management control module to generate downlink signaling; Speech spread spectrum data in the voice digitized signal, and perform semi-regenerative processing on the voice spread spectrum data to obtain the soft information point of the user's voice symbol;

2c) Send the obtained voice symbol soft information point to the sample point circuit switching module for switching;

(3) The sending steps of the high-altitude platform in the downlink voice time slot:

3a) The high-altitude platform performs TDM multiplexing on the voice symbol soft information points of multiple users output by the sample point circuit switching, and adds a Gold sequence with a length of 63 as a midamble code to form a downlink time slot waiting sequence;

3b) Carrying out waveform shaping and D/A conversion on the sequence to be transmitted in the downlink time slot;

(4) The receiving steps of the user terminal in the downlink voice time slot:

4a) The user terminal performs orthogonal down-conversion, A/D conversion and matched filtering on the received signal of the downlink voice time slot to obtain a digitized signal of the downlink voice;

4b) extracting the midamble code in the downlink voice digitized signal for downlink synchronization and channel state estimation;

4c) equalizing the speech symbols in the downlink speech digitized signal according to the estimated channel state information CSI;

4d) Demodulate and decode the equalized speech symbols to obtain original speech information.

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

(1) Since the present invention adopts a semi-regenerative signal processing method, it only despreads the user's uplink transmission signal without performing demodulation and decoding, which greatly reduces the complexity of the system processing equipment, and satisfies the communication needs of large-scale users. At the same time, it effectively reduces the resource requirements of high-altitude platform communication system processing equipment. Under the same platform resource conditions, the number of users that can be supported is more than 2.5 times the number of users of conventional demodulation and decoding schemes, which solves the problem of high-altitude platform resource constraints and user capacity. There is a great contradiction between the needs.

(2) The present invention uses the same frequency band as the terrestrial TD-SCDMA cellular network system, and the radio frequency components and the user interface of the user terminal can be compatible with the terrestrial TD-SCDMA system terminal, and the baseband rate is the baseband rate of the terrestrial TD-SCDMA cellular network system Equal, when there is TD-SCDMA cellular network system signal coverage in the area where user terminal is located, can access ground TD-SCDMA network; Simultaneously because user terminal of the present invention is on the single-mode user terminal of ground TD-SCDMA cellular network system, The dual-mode user terminal with only part of the baseband processing function added, most of the hardware of the user terminal can be used in the high-altitude platform system and the ground TD-SCDMA cellular network system at the same time, so compared with the single-mode user terminal, the complexity of the dual-mode terminal The increase is very limited, but it can be switched between the two systems, so that the high-altitude platform system is partially compatible with the existing ground TD-SCDMA cellular network system.

(3) On the high-altitude platform, the QoS of the voice and multimedia real-time services is fully guaranteed due to the use of the sample point circuit switching module to program-controlled switching of the soft-decision multiple sample point values of each symbol of each user; and for higher-speed data transmission, due to A connection-oriented switching transmission mode is adopted, so that QoS guarantee can be well provided for broadband data services.

(4) Since the high-altitude platform only performs despreading without demodulation and decoding, the coding and modulation methods of the ground terminal will not have any impact on the processing method of the high-altitude platform, so that the ground terminal can flexibly change the coding and modulation according to actual needs In this way, the application flexibility is greatly enhanced.

Description of drawings

Fig. 1 is a schematic diagram of the composition of the system of the present invention;

Fig. 2 is the 15M different frequency networking structural diagram of the system of the present invention;

Fig. 3 is a schematic diagram of the system TDD frame structure of the present invention;

Fig. 4 is a schematic structural diagram of the uplink and downlink guard interval time slot GAP in the system frame of the present invention;

Fig. 5 is a schematic diagram of the structure of the downlink synchronization time slot DwPTS in the system frame of the present invention;

Fig. 6 is a schematic diagram of the structure of the uplink synchronization time slot UpPTS in the system frame of the present invention;

Fig. 7 is a schematic diagram of the conventional time slot structure in the system frame of the present invention;

Fig. 8 is the flow chart that the inventive method carries out semi-regenerative processing to speech signal;

Fig. 9 is the sending flow chart of the user terminal on the voice code channel of the uplink time slot when the method of the present invention performs semi-regenerative processing on the voice signal;

Fig. 10 is the receiving flowchart of the high-altitude platform on the uplink time slot voice code channel when the method of the present invention carries out semi-regenerative processing to the voice signal;

Fig. 11 is the high-altitude platform transmission flowchart in the downlink voice time slot when the method of the present invention carries out semi-regenerative processing to the voice signal;

Fig. 12 is a flow chart of user terminal reception in downlink voice time slots when the method of the present invention performs semi-regenerative processing on voice signals;

Fig. 13 is a flow chart of sending the user terminal on the signaling code channel of the uplink time slot when the method of the present invention performs regenerative processing on the signaling signal;

Fig. 14 is the receiving flow chart of the high-altitude platform on the uplink time slot signaling code channel when the method of the present invention performs regenerative processing on the signaling signal;

Fig. 15 is a flow chart of high-altitude platform transmission in downlink signaling time slot Ts0 when the method of the present invention performs regenerative processing on signaling signals;

Fig. 16 is a flow chart of user terminal reception in downlink signaling time slot Ts0 when the method of the present invention performs regenerative processing on signaling signals;

Fig. 17 is the sending flowchart of the high-altitude platform when the method of the present invention simultaneously sends the signaling symbol and the voice symbol soft information point in the Ts0 time slot;

Fig. 18 is a flow chart of receiving by the user terminal when the method of the present invention simultaneously transmits signaling symbols and voice symbol soft information points in Ts0 time slot.

Fig. 19 is a flow chart of terminal transmission when the method of the present invention transmits 144Kbps non-voice information uplink;

Fig. 20 is a flow chart of the terminal sending during the uplink transmission of 384Kbps non-voice information in the method of the present invention;

Fig. 21 is a flow chart of terminal transmission when the method of the present invention transmits non-voice information uplink at 1.92Mbps;

Fig. 22 is a flow chart of high-altitude platform reception during high-speed non-voice information uplink transmission in the method of the present invention;

Fig. 23 is a flow chart of high-altitude platform transmission during the downlink transmission of high-speed non-voice information in the method of the present invention;

Fig. 24 is a flow chart of user terminal reception during high-speed non-voice information downlink transmission in the method of the present invention.

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

Detailed ways

The present invention relates to a high-altitude platform broadband mobile communication system based on semi-regenerative signal processing and sample point circuit switching and a high-altitude platform broadband mobile communication method based on semi-regenerative signal processing and sample point circuit switching. The system uses a semi-regenerative signal processing method And sample point circuit switching technology reduces the complexity of the high-altitude platform, and uses the same frequency band as the ground TD-SCDMA system, which is compatible with the ground TD-SCDMA system and is used to support large-capacity users in the resource-constrained high-altitude platform environment Communication and provide QoS guarantee for real-time services; this method includes regenerative processing of signaling information and semi-regenerative processing of voice information and non-voice information other than signaling, specifically described as follows:

1. System overview

Referring to Fig. 1, the cellular network mobile communication system based on the semi-regenerative signal processing of the high-altitude platform in this embodiment, its communication system is partially compatible with the international standard of the TD-SCDMA third-generation mobile communication system, and uses the same technology as the ground TD-SCDMA system frequency band, the baseband rate is equal to the baseband rate of the terrestrial TD-SCDMA system; the system includes a high-altitude platform located in the stratosphere, one or more ground gateways and user terminals on the ground; the high-altitude platform includes a set for forming N ground The radio frequency intermediate frequency equipment of the multi-beam antenna on the cellular network cell and the platform, the radio frequency intermediate frequency equipment is connected with N uplink signal receiving and processing modules, N downlink signal sending and processing modules, a sample point circuit switching module and a network management control module, At the same time, it also includes a signaling despreading, demodulating and decoding module, a signaling encoding and modulating module, a gateway information receiving and processing module, and a gateway information sending and processing module. in:

Described user terminal, its radio frequency component and user interface are all the same as the user terminal in the terrestrial time division duplex-synchronous code division multiple access TD-SCDMA system, and its baseband rate is the same as the baseband rate of the terrestrial TD-SCDMA system, and uses The same frequency band as the terrestrial TD-SCDMA system ensures that user terminals can access the terrestrial TD-SCDMA system to achieve partial compatibility with the international standard of the TD-SCDMA third-generation mobile communication system. When the terminal of the high-altitude platform system leaves the coverage of the high-altitude platform and enters the coverage of the ground TD-SCDMA system, it can access the ground TD-SCDMA system. When the coverage of the high-altitude platform system and the ground TD-SCDMA system overlap, appropriate measures should be taken to avoid the mutual influence of the two systems. User terminals in the overlapping coverage area can choose to access the ground TD-SCDMA system or the high-altitude platform system. The user terminal can communicate with users who are also within the coverage of the high-altitude platform through the high-altitude platform, and can also communicate with the ground 3G cellular network system through the high-altitude platform and ground gateway, so as to realize communication with users outside the coverage area.

The ground gateway, as a transfer node, is provided with a high-speed data transmission link between the high-altitude platform, and the link can work in the Ka frequency band. Users within the coverage of the high-altitude platform communication system and users in the ground TD-SCDMA system outside the system exchange data and signaling through high-speed data transmission links to realize the interconnection between the high-altitude platform and the ground TD-SCDMA system .

The above-mentioned high-altitude platform has a total of 200 beams on it, corresponding to 200 cells on the ground. Each beam includes three frequency points, and each frequency point supports up to 23 voice users. In this way, 200 beams can support nearly 14,000 voice users at the same time. voice users.

The uplink signal receiving and processing module is composed of an orthogonal sampling A/D conversion unit, a frequency division demultiplexing processing unit and a synchronous correlation despreading unit, and is used to perform semi-regenerative processing on the received voice information to obtain the voice symbol software Information point.

The sample point circuit switching module adopts program-controlled circuit switching and is a TST switching structure. Under the control of signaling, the voice symbol soft information points obtained by the semi-regenerative processing of the uplink signal receiving and processing module are regenerated by the gateway information receiving and processing module. The phonetic symbols obtained by formula processing are exchanged.

The downlink signal processing module is composed of a time division frequency division multiplexing unit and a quadrature amplitude modulation unit, and is used for multiplexing and modulating the voice symbols and soft information points of the voice symbols and downlink signaling symbols sent downlink.

The signaling despreading demodulation decoding module is composed of an orthogonal sampling A/D conversion unit, a frequency division demultiplexing unit, a synchronous correlation despreading unit and a demodulation decoding unit, and is used to receive and regenerate uplink signaling information.

The network management control module is composed of a central processing unit CPU and a protocol stack running on it, and is used for interpreting and executing received signaling information and constructing new downlink signaling as required.

The signaling encoding and modulating module is composed of an encoding and modulating unit, and is used for encoding and modulating the downlink signaling constructed by the network management control module to form downlink signaling symbols.

The gateway information receiving and processing module is composed of a radio frequency intermediate frequency device, an orthogonal sampling A/D conversion unit, a frequency division demultiplexing unit, and a demodulation and decoding unit, and is used for receiving and regeneratively processing information from the ground gateway. The processed data symbols are sent to the sample point circuit switching module for switching, and the processed signaling information is sent to the network management control module for subsequent processing.

The gateway information sending and processing module is composed of a coding modulation unit, a frequency division multiplexing unit, a D/A conversion unit and an intermediate frequency radio frequency unit, and is used for coding, modulating, multiplexing and sending the information to be sent to the ground gateway.

After the high-altitude platform receives the uplink signal sent by each user terminal through the multi-beam antenna and radio frequency intermediate frequency equipment, the signaling signal is sent to the signaling despreading demodulation and decoding module for regenerative processing to restore the uplink signaling information; The signal is sent to the uplink signal receiving and processing module for semi-regenerative processing to obtain the soft information point of the voice symbol; then the soft information point of the voice signal is sent to the sample point circuit switching module for switching, and then the soft information point of the voice symbol output by the exchange is sent to To the downlink signal transmission processing module for multiplexing processing and downlink transmission through the intermediate frequency radio frequency equipment; and the signaling information obtained by the regenerative processing of the signaling despreading, demodulation and decoding module is sent to the network management control module, managed by the network The control module identifies, executes, and constructs new downlink signaling information. The downlink signaling information is sent to the signaling coding and modulation module for coding and modulation, and then sent to the downlink signal transmission processing module for multiplexing and downlink transmission through the intermediate frequency radio frequency device; The communication between the user terminal in the system and the user in the ground cellular network mobile communication system is carried out through the ground gateway and its equipment for data transmission with the high-altitude platform. The gateway information receiving and processing module on the high-altitude platform is responsible for regenerative processing of the information sent by the ground gateway uplink, and then sends the processed signaling information to the network management control module for subsequent processing, and sends the processed user data to the sample point circuit switching module for switching and subsequent processing. The information output by the sampling circuit switching module to be sent to the ground gateway is coded and modulated by the gateway information sending processing module and sent downlink. The data link between the ground gateway and the high-altitude platform can use Ka-band microwave transmission; the user's information exchange on the high-altitude platform is carried out under the control of the network management control module.

The system uses TDD duplex mode, and its frame structure is similar to the ground TD-SCDMA system frame structure, which is divided into 7 regular time slots and 3 special time slots. The three special time slots are downlink synchronization time slot DwPTS, uplink and downlink guard interval GP and uplink synchronization time slot UpPTS. The conventional time slots include uplink time slots and downlink time slots. The multiple access method used in the uplink time slots is synchronous CDMA, and the multiplexing method of the downlink time slots is time division multiplexing TDM.

Among the 7 regular time slots of the system frame, the first time slot Ts0 is fixed for downlink transmission, while the second time slot Ts1 is fixed for uplink transmission, and the remaining 5 regular time slots can be used for both uplink transmission and for downlink transmission. When a time slot is used for uplink transmission, a time slot can accommodate up to 4 different spread spectrum code channels, supporting 4 users for uplink transmission at the same time. Designate a fixed code channel in the time slot Ts1 as the uplink signaling code channel, so if the five conventional time slots Ts2-Ts6 are used as the uplink time slot, together with the three spreading code channels in Ts1 except the signaling code channel , there are a total of 23 uplink spreading code channels, which can support simultaneous uplink transmission of 23 users, and at this time, Ts0 is used to simultaneously transmit downlink signaling and exchanged symbol soft information points.

After the user joins the network, the downlink synchronization is obtained by monitoring the downlink synchronization time slot DwPTS. If the user needs to perform uplink transmission, the uplink synchronization sequence should be sent in the uplink synchronization time slot first to initiate the uplink initial synchronization process. The high-altitude platform obtains the user's synchronization time adjustment information and power level adjustment information through the detection of the uplink synchronization sequence. The corresponding downlink signaling is constructed according to the information and sent to the user terminal in the downlink broadcast signaling, and the user terminal adjusts the synchronization time according to the signaling information to obtain the uplink initial synchronization. The maintenance of uplink synchronization is realized through the midamble code in the uplink time slot. The user places the midamble code in the middle of the two pieces of spread spectrum data in the uplink time slot. The high-altitude platform obtains the user's synchronization time adjustment information and power by detecting the midamble code. level adjustment information and inform the user terminal of the information in the downlink broadcast signaling, and the user terminal makes corresponding adjustments according to the information to maintain uplink synchronization.

The user's uplink data symbol sequence is divided into two sections of equal length after being spread by their respective spreading codes, and each section has a length of 372. Put the user's midamble code in the middle of the two sections of spreading data to form an uplink time slot and send it to the high-altitude platform send.

After receiving the uplink spread spectrum data superimposed by multiple users, the high-altitude platform obtains the uplink channel state information UL-CSI of each user by detecting the respective midamble codes of the users; Correlation despreading and RAKE merging are carried out, and the symbolic soft information points output by merging are directly sent to the sample point circuit switching module on the platform for switching without judgment.

The soft information points of user symbols are exchanged by the circuit switching module of the high-altitude platform and sent to the downlink transmission processing module of the high-altitude platform for downlink TDM multiplexing. The multiplexing position in the time slot. Since the data for downlink transmission is the user soft information point after despreading, and the downlink transmission is not spread, the time slot resources occupied by the downlink transmission can be greatly reduced compared with the uplink transmission.

After receiving the downlink time slot sent by the high-altitude platform, the terminal obtains accurate downlink synchronization according to the midamble code in the middle of the time slot, and estimates the downlink channel state information DL-CSI; The soft information point of the user symbol; finally, judgment, demodulation and decoding are performed to restore the original transmission data.

In addition to supporting voice information transmission, the system can also support non-voice information transmission. Non-speech information is divided into low-rate non-speech information and high-rate non-speech information according to its rate. When low-rate non-voice information is transmitted, the uplink time slot uses the same spread spectrum mechanism as that used for voice information transmission. Users can occupy multiple code channels in multiple time slots, and the data transmission rate can be increased or decreased at a granularity of 4.8Kbps. When a user occupies all available 23 uplink spreading code channels, the highest transmission rate can be obtained is 110.4Kbps; the supported rate for high-speed non-voice information transmission is a set of preset values, and the user terminal can choose according to its own needs Appropriate data transfer rate. The uplink time slot does not use the spread spectrum mechanism during high-speed non-voice information transmission, and each time slot is occupied by a single user. In order to support high-speed non-speech information transmission, an advanced coding and modulation scheme is required, so low-density parity-check code LDPC is used for coding at this time, and the modulation method varies according to the rate. When performing non-voice information transmission, resource allocation is also based on code channels or/and time slots. It is also necessary to first use signaling information to perform connection establishment operations, making non-voice information transmission a connection-oriented operation, so it can be used for real-time video Provide good QoS guarantee for other services.

Since the transmission process of low-rate non-speech information is similar to that of speech information, the sample point circuit switching module on the high-altitude platform can also be used to exchange low-speed data. The exchange process is the same as the exchange process of symbolic soft information points of speech information. For the transmission of high-speed non-speech information, since the spread spectrum operation is not performed, the symbol soft information points are not obtained through correlation despreading, but are obtained by sampling the received signal at symbol intervals, so the symbol soft information points are obtained at this time When the point circuit is switched, its switching clock rate should be increased compared with the switching clock rate of voice information transmission and low-speed non-voice information transmission, and the increased multiple is equal to the length of the spreading code. During implementation, the switching clock rate during the exchange of high-speed non-voice information can be used as the basic working clock rate of the circuit switch, and high-speed non-voice information is exchanged according to this basic working clock rate, while voice information or low-speed non-voice information is When exchanging, the basic operating clock rate should be reduced according to the spread spectrum multiple as the exchange clock rate.

When transmitting voice information and low-rate non-voice information, since the uplink transmission uses the spread spectrum mechanism, but the downlink transmission does not use the spread spectrum mechanism, the time slot resources occupied by the uplink and downlink are asymmetrical, and the time slot occupied by the uplink transmission The resources are larger than the time slot resources occupied by downlink transmission. When performing high-speed non-voice information transmission, the uplink and downlink transmissions do not use the spread spectrum mechanism, so the time slot resources occupied by the uplink and downlink transmissions are symmetrical.

2. System network planning

Referring to Fig. 2, the cellular network mobile communication system based on the high-altitude platform semi-regenerative signal processing in this embodiment adopts a 15M inter-frequency networking mode. The terminal of the system can be compatible with the RF unit of the terrestrial TD-SCDMA system terminal, so the system needs to select the same frequency band as the terrestrial TD-SCDMA system, and the specific frequency point should be selected according to the actual application. For example, if the high-altitude platform system and the ground TD-SCDMA system have no overlapping coverage areas, you can choose any frequency point in this frequency band; if the high-altitude platform system and the ground TD-SCDMA system have overlapping coverage areas, take appropriate measures to Avoid mutual interference between the two systems. The high-altitude platform system terminal in the repeated coverage area can choose to access the ground TD-SCDMA system or the high-altitude platform system. The system occupies a frequency band of 15MHz bandwidth from 2010 to 2025MHz, which is divided into 9 frequency bands with a bandwidth of 1.6M. The center frequencies are: f1=2010.8MHz, f2=2012.4MHz, f3=2014.0MHz, f4=2015.8MHz, f5=2017.4 MHz, f6=2019.0MHz, f7=2020.8MHz; f8=2022.4MHz, f9=2024.0MHz.

3. System frame structure

Referring to FIG. 3 , the frame structure of the system described in this embodiment adopts TDD mode, and the length of one frame is 5 ms, including 7 regular time slots and 3 special time slots. In order to be compatible with the radio frequency part of TD-SCDMA, the baseband rate of this system, that is, the chip rate after spreading the uplink time slot is also 1.28Mcps, and the downlink time slot is not spread, but its symbol rate is also 1.28Msps. In this way, the symbol length of the downlink time slot is equal to the chip length of the uplink time slot, and Tc is used to represent the basic symbol length. Such a 5ms frame lasts for 6400 Tc in total.

Referring to Fig. 4, the length of the uplink and downlink guard interval GP of this system is 390Tc. If the height of the high-altitude platform is 20Km and the elevation angle of the edge users is 30°, the distance between the farthest user and the high-altitude platform is 40.19Km, and the coverage of a single high-altitude platform communication system is 3781.13Km ² . The length of the uplink and downlink guard interval required at this time is about 345Tc, which is the minimum length that satisfies the conditions, and the guard interval greater than or equal to this length can meet the system requirements.

Referring to Figure 5, the structure of the uplink synchronization time slot UpPTS of this system is similar to that of the UpPTS time slot in the frame structure of the terrestrial TD-SCDMA system. It is also composed of an uplink synchronization sequence with a length of 128Tc plus a guard interval Gap with a length of 32Tc Different SYNC-UL distinguishes different user terminals UE during the access process.

Referring to Figure 6, the structure of the downlink synchronization time slot DwPTS of this system is similar to that of the DwPTS time slot in the frame structure of the terrestrial TD-SCDMA system. Since the inter-frequency networking mode is adopted, it is not necessary to use different SYNC-DLs to distinguish adjacent beams. Putting the DwPTS in a separate time slot facilitates the user terminal UE to realize downlink synchronization through this time slot, and also reduces interference to other downlink signals.

In addition to the three special time slots of uplink and downlink protection time slots GP, DwPTS and UpPTS, there are seven regular time slots in the system frame, of which the first regular time slot Ts0 is fixed for downlink transmission, and the second regular time slot Ts1 is fixedly used for uplink transmission, and the remaining five regular time slots Ts2-Ts6 can be used for both uplink and downlink. When the regular time slot is used for the uplink direction, each regular uplink time slot can provide 4 CDMA code channels supporting 4.8Kbps voice transmission, and the code channels are distinguished by a balanced Gold sequence with a length of 31.

Referring to FIG. 7, each regular time slot is composed of a data part, a midamble part and a guard interval. The data part is divided into two sections, the length of each section is 372Tc, which is obtained by 31-fold spread spectrum of 12 modulation symbols. The Midamble code part is a Gold sequence with a length of 63, which is used for uplink synchronization control and power control. The high-altitude platform estimates the user's synchronization time and power level by detecting the midamble code, and then constructs synchronization time adjustment information and power level adjustment information based on the estimated value, and broadcasts these information to each user through downlink signaling. The synchronization time adjustment information received by the frame adjusts the transmission time of the next frame to achieve closed-loop synchronization; at the same time, according to the received power level adjustment information, the transmission power is adjusted to achieve closed-loop power control.

The voice information sent in the uplink time slot of this system needs to use the Gold sequence with a length of 31 for direct sequence spread spectrum, while the downlink sent from the high-altitude platform to the ground terminal is the symbol soft information point obtained by despreading, so The frequency band utilization rate of the downlink is much greater than the frequency band utilization rate of the uplink, so less system resources can be allocated to the downlink and more system resources can be allocated to the uplink so as to realize full utilization of system resources. Because in the regular time slots, Ts0 is fixedly used for downlink transmission, and Ts1 is fixedly used for uplink transmission. Refer to the design method of TD-SCDMA, use Ts0 to send the downlink signaling information of the system, and use one of the four code channels in the Ts1 time slot to send the uplink signaling information. Among the remaining five regular time slots Ts2-Ts6, Ts6 can be set as a downlink time slot, and the remaining time slots can be set as uplink time slots. In this way, there are 5 uplink time slots in total, and 20 uplink code channels can be provided. Excluding one uplink signaling code channel in Ts1, a total of 19 channels of 4.8Kbps uplink voice transmission can be supported. The conventional time slot Ts6 is used as a downlink time slot, and can transmit 744 symbol samples output by despreading. Since 19 channels of uplink voice transmission can obtain 19*24=456 symbol soft information points after despreading and outputting in one frame, it is completely sufficient to use conventional time slot Ts6 for downlink voice transmission. In this way, the system frame structure can support 19 users to communicate at the same time, and the user capacity is relatively close to the number of users supported by the frame structure of the terrestrial TD-SCDMA system. In special cases, Ts0 can even be used to transmit downlink voice information and downlink signaling information, while conventional time slots Ts1-Ts6 are used to transmit uplink voice information, so that the system frame structure can accommodate 23 users, and the system user capacity has reached The number of users supported by the frame structure of the TD-SCDMA international standard. At this time, 552 symbol resources are used in the Ts0 time slot to transmit the exchanged symbol soft information points, and the remaining 192 symbol resources are used to transmit downlink signaling information. So totally doable.

4. Semi-regenerative processing of voice information

Referring to Figure 8, the semi-regenerative processing of voice information includes the following:

Step 1, the user terminal sends an uplink voice signal on the voice code channel in the uplink time slot;

Step 2. The high-altitude platform receives the uplink voice signal on the voice code channel in the uplink time slot and sends the processed symbolic soft information point to the sample point circuit switching module for switching;

Step 3, the high-altitude platform sends the downlink voice signal in the downlink voice time slot;

Step 4, for the terminal to receive the downlink voice signal in the downlink voice time slot;

Referring to Figure 9, the specific implementation of step 1 is as follows:

1a) The user terminal adds 8 frame quality indication bits and 8 coding tail bits to the 80 original speech bits within 20 ms to form a 96-bit data block with a corresponding data rate of 4.8 Kbps. The 96-bit The data block is 1/2 convolutionally encoded to form 192 coded bits, and then QPSK modulated to form 96 user voice modulation symbols;

1b) spreading the obtained user voice modulation symbols with a Gold sequence with a length of 31 as a spreading code to obtain 2976 spreading symbols;

1c) dividing the obtained spread spectrum symbols into time slots to obtain 4 spread spectrum symbol blocks with a length of 744 chips;

1d) Divide each spread spectrum symbol block into two sections of equal length, add a Gold sequence with a length of 63 as a midamble code in the middle of the two sections, obtain a symbol sequence with a length of 807, and then add a sequence with a length of 15 at the end of the symbol sequence The guard interval Gap is used to form an uplink time slot waiting sequence with a length of 822 chips, and the baseband rate of the waiting sequence is 1.28Mcps;

1e) performing waveform shaping and D/A conversion on the sequence to be transmitted in the uplink time slot, and then orthogonal up-conversion and frequency transmission.

Referring to Figure 10, the specific implementation of step 2 is as follows:

2a) The high-altitude platform performs orthogonal down-conversion, analog/digital A/D conversion and matched filtering on the received voice signal to obtain the digital signal of the uplink voice;

2b) Extract the midamble code in the uplink voice digital signal, perform synchronization time estimation and power level estimation, and send the estimated synchronization time deviation information and power level deviation information to the network management control module to generate downlink signaling; simultaneously extract uplink Speech spread spectrum data in the voice digital signal, and semi-regenerative processing is performed on the voice spread spectrum data, that is, the voice spread spectrum data is only despread without demodulation and decoding, and the user's 24 voice symbol soft Information point;

2c) sending the voice symbol soft information point to the sample point circuit switching module for switching;

Referring to Figure 11, the specific implementation of step 3 is as follows:

3a) The high-altitude platform performs TDM multiplexing on the voice symbol soft information points of multiple users output by the sample point circuit switching, adds a Gold sequence with a length of 63 as a midamble code, and adds a guard interval Gap with a length of 15 to form Downlink time slot waiting sequence;

3b) Carrying out waveform shaping and D/A conversion on the sequence to be transmitted in the downlink time slot;

Referring to Figure 12, the specific implementation of step 4 is as follows:

4a) The user terminal performs orthogonal down-conversion, A/D conversion and matched filtering on the received signal of the downlink voice time slot to obtain a digital signal of the downlink voice;

4b) extracting the midamble code in the downlink voice digital signal for downlink synchronization and channel state estimation;

4c) equalizing the speech symbols in the downlink speech digital signal according to the estimated channel state information CSI;

4d) Demodulate and decode the equalized speech symbols to obtain original speech information.

5. Regenerative processing of signaling signals

The regenerative processing of signaling signals includes processing at the sending end of the user terminal on the signaling code channel of the uplink time slot, processing at the receiving end of the high-altitude platform on the signaling code channel of the uplink time slot, processing at the sending end of the high-altitude platform on the downlink signaling time slot and downlink Receiver processing of signaling slots for user terminals.

Referring to Figure 13, on the uplink time slot signaling code channel, the user terminal generates 80 signaling bits every 20 ms, plus 8 frame quality indicator bits and 8 coding tail bits to form a data block with a length of 96 bits. The data rate is 4.8Kbps; then the 96-bit data block is 1/2 convolutionally encoded to form 192 coded bits; then the 192 coded bits are QPSK modulated to form 96 symbols, and the length of the signaling code channel is The Gold sequence of 31 spreads to form 2976 chips; it is then divided into fixed time slots Ts1 in four consecutive frames for transmission, and 744 signaling spreading chips are sent in each time slot, and these 744 signaling are spread The chip is divided into two sections of equal length, a Gold sequence with a length of 63 is added in the middle as a midamble, and a guard interval Gap with a length of 15 is added after the second signaling spreading code segment to form a sequence consisting of 822 chips For the sequence to be sent, the baseband rate is 1.28Mcps; finally, after waveform shaping and D/A conversion, the quadrature up-conversion is sent.

Referring to Figure 14, on the uplink time slot signaling code channel, after the high-altitude platform receives the signal of the uplink signaling code channel, it first performs orthogonal down-conversion, A/D conversion and matched filtering to obtain the uplink signaling digital signal; then extracts The midamble in the uplink signaling digital signal is processed to determine the user's synchronization time adjustment information and power level adjustment information and output these information to the network management control module to generate corresponding downlink control signaling; then the platform extracts the uplink signaling digital signal Signaling spread spectrum data in the signal is despread, demodulated and decoded, and the uplink signaling information is recovered and sent to the network management control module for subsequent processing.

Referring to Figure 15, in the downlink signaling time slot, the high-altitude platform transmitting end performs TDM multiplexing on the signaling symbols output by the signaling coding and modulation module; then adds a Gold sequence with a length of 63 as a midamble code and adds a length of A guard interval Gap of 15 forms a downlink signaling time slot to-be-sent sequence; finally, waveform shaping is performed on the downlink signaling time-slot to-be-sent sequence, followed by D/A conversion and orthogonal up-conversion transmission.

Referring to Fig. 16, in the downlink signaling time slot, the user terminal first performs orthogonal down-conversion, A/D conversion and matched filtering on the received signal of the downlink signaling time slot to obtain the digital signal of the downlink signaling; then, The user terminal extracts the midamble code in the downlink signaling digital signal for downlink synchronization and channel state estimation, and equalizes the signaling symbols in the downlink signaling digital signal according to the estimated channel state information CSI; finally, the equalized signaling Symbols are demodulated and decoded to restore the original signaling information.

6. Processing when voice signal and signaling signal are sent simultaneously in downlink time slot Ts0

The downlink time slot Ts0 is a regular time slot fixed for downlink transmission in the system frame. The time slot can be used solely for the transmission of downlink signaling information, or can be used for the transmission of downlink voice signals and downlink signaling signals simultaneously. The processing when the voice signal and the signaling signal are simultaneously transmitted in the downlink time slot Ts0 includes processing at the sending end of the high-altitude platform and processing at the receiving end of the user terminal.

Referring to Figure 17, when the voice signal and the signaling signal are simultaneously transmitted in the downlink time slot Ts0, the high-altitude platform first performs time-division multiplexing on the soft information points of the signaling symbol and the voice symbol; then adds midamble code and guard interval Gap; finally performs waveform Shaping, D/A conversion, and quadrature up-conversion transmission.

Referring to Figure 18, when the voice signal and signaling signal are simultaneously transmitted in the downlink time slot Ts0, the user terminal first performs orthogonal down-conversion, A/D conversion, and matched filtering on the received signaling signal and voice signal; then extracts the midamble Carry out downlink synchronization and channel estimation; finally perform channel equalization, demodulation and decoding on downlink signaling data and voice data to restore the original signaling information and voice information.

7. Processing of non-voice information

In addition to supporting voice information transmission, the system also supports non-voice information transmission at different rates. When Ts1-Ts6 are all used as uplink time slots, except for one signaling code channel in Ts1, the uplink can provide 23 spreading code channels, so for non-speech information greater than 4.8Kbps but less than 23×4.8=110.4Kbps , it can occupy multiple uplink spreading code channels to realize variable rate data transmission, and the rate change granularity is 4.8Kbps.

For higher rate non-speech information transmission, since there is no support for more spread spectrum code channels, the use of spread spectrum schemes can no longer meet the requirements. High-speed non-speech information transmission is carried out by using low-density parity-check code LDPC with extremely high error correction capability and high-order modulation to replace the spread-spectrum scheme. Set three rate levels for high-speed non-voice information transmission: 144Kbps, 384Kbps and 1.92Mbps.

Referring to Figure 19, for 144Kbps high-speed non-speech information transmission, the sender on the uplink generates 1440*4=5760 bits within 40ms, fills the tail with 1394 padding bits 0 to 7154 bits, and generates 8176 bits through 7/8LDPC encoding Coded bits, since the first 7154 bits of the LDPC coded bits are the original uncoded bits, 736 of the 1394 padding bits added to the tail of the first 7154 bits of the coded bits can be deleted to obtain 7440 coded bits; then these 7440 coded bits The bits are QPSK modulated to 3720 symbols, which are divided into 5 time slots for transmission, and each time slot transmits 744 symbols; then the 744 symbols are divided into two sections of equal length, and midamble is added between the two sections. A guard interval Gap is added at the end of the second section to form a waiting sequence with a length of 822; finally, waveform shaping, D/A conversion, and upconversion are performed on the waiting sequence for transmission.

Since there are 8 frames in 40ms, if the uplink and downlink resources are allocated symmetrically, the number of time slots available in a single uplink or downlink direction is 24, and 6 time slots are selected for transmission among the 24 time slots. In this way, the remaining time slots support at least three other 144Kbps users for high-speed non-voice information transmission, or for voice information transmission.

Referring to Figure 20, for 384Kbps high-speed non-speech information transmission, the sending end on the uplink generates 3840*5=19200 bits within 50ms, and adds 2262 0 to 21462 bits at the end; it is further divided into 3 lengths of 7154 bit segment, 7/8 LDPC encoding is performed on each segment to generate 3 encoded bit segments with a length of 8176. Since the first 7154 bits of the LDPC encoded bit end are the original uncoded bits, the last encoded bit segment can be The first 7154 bits of the first 7154 bits are filled with 2262 filling bits 0 and 2208 are deleted to obtain 22320 coded bits; then the 22320 coded bits are QPSK modulated to obtain 11160 symbols, which are divided into 15 time slots for transmission, each The time slot transmits 744 symbols; then the 744 symbols are divided into two sections of equal length, midamble is added between the two sections and a guard interval Gap is added at the end of the second section to form a waiting sequence with a length of 822; finally The sequence to be sent is subjected to waveform shaping, D/A conversion, and then up-conversion transmission.

Since there are 10 frames within 50 ms, if the uplink and downlink resources are allocated symmetrically, the number of time slots available in a single uplink or downlink direction is 30, and 15 time slots are selected on average for transmission within the 30 time slots. In this way, the remaining time slots can support another 384Kbps user for high-speed non-voice information transmission, or for voice information transmission.

Referring to Figure 21, for 1.92Mbps high-speed non-speech information transmission, the sending end on the uplink generates 76800 bits within 40ms, and fills 1894 bits from 0 to 78694 at the end; it is further divided into 11 bit segments with a length of 7154, Perform 7/8LDPC encoding on each segment to generate 11 coded bit segments with a length of 8176. Since the first 7154 bits of the LDPC coded bit end are the original uncoded bits, the tail of the first 7154 bits of the last coded bit segment can be supplemented 656 of the 1894 stuffing bits 0 are deleted, and 1238 are reserved, so that a total of 89280 coded bits are formed; then 32QAM modulation is performed on the 89280 coded bits to obtain 17856 symbols, which are transmitted in 24 time slots, and each time slot The slot transmits 744 symbols; then these 744 symbols are divided into two sections of equal length, midamble is added between the two sections and a guard interval Gap is added at the end of the second section to form a sequence to be sent with a length of 822; finally The sequence to be sent is subjected to waveform shaping, D/A conversion, and then up-converted for transmission.

Since there are 8 frames in 40 ms, if the uplink and downlink resources are allocated symmetrically, the number of time slots available in a single uplink or downlink direction is 24, which can meet the transmission requirements.

Referring to Figure 22, when high-speed non-voice information is transmitted uplink at 144Kbps, 384Kbps, and 1.92Mbps, the high-altitude platform first performs quadrature down-conversion, A/D conversion, and matched filtering on the received high-speed non-voice signals to obtain high-speed non-voice digital signals. signal; then extract the midamble code in the high-speed non-voice information to calculate the synchronization time deviation information and power level deviation information, and output these information to the network management control module to generate corresponding downlink control signaling; then the high-speed non-voice digital The non-speech symbols in the signal are sampled at symbol intervals to obtain the soft information points of each symbol and sent to the switching module for subsequent switching.

Referring to Figure 23, during the downlink transmission of high-speed non-speech information, the high-altitude platform first adds midamble codes and guard interval Gap to the high-speed non-speech symbol soft information points output by sample point circuit switching; then performs waveform shaping, D/A conversion and quadrature Up-conversion transmission.

Referring to Figure 24, during the downlink transmission of high-speed non-speech information, the user terminal first performs orthogonal down-conversion, A/D conversion, and matched filtering on the received high-speed non-speech signal; then extracts the midamble code for downlink synchronization and estimates the channel state Information; then channel equalization; finally demodulation and decoding to obtain the original non-speech information.

It should be noted that the above-mentioned embodiments are preferred examples, and the present invention is not limited to the above-mentioned embodiments. On the basis of utilizing the principles and technical solutions of the present invention, those skilled in the art can make simple adjustments or replacements. Should belong to the protection scope of the present invention.

Claims (10)

1. A mobile communication system based on high-altitude platform semi-regenerative signal processing, comprising: a high-altitude platform located in the stratosphere, one or more ground gateways and user terminals on the ground; the high-altitude platform includes a set for forming N The radio frequency intermediate frequency equipment of a ground cellular network cell and a multi-beam antenna on the platform, the radio frequency intermediate frequency equipment is connected with N uplink signal receiving and processing modules, N downlink signal sending and processing modules, a sampling point circuit switching module and a network management control module The module also includes a signaling despreading and demodulating module, a signaling encoding and modulating module, a gateway information receiving and processing module, and a gateway information sending and processing module, N≥200, characterized in that: The radio frequency components and user interface of the user terminal are the same as the user terminal in the terrestrial time division duplex-synchronous code division multiple access TD-SCDMA system. The same frequency band as the SCDMA system ensures that user terminals can access the terrestrial TD-SCDMA system to achieve partial compatibility with the international standard of the TD-SCDMA third-generation mobile communication system; As a transit node, the ground gateway has a high-speed data transmission link between it and the high-altitude platform. Users within the coverage of the high-altitude platform communication system and users in the ground TD-SCDMA system outside the system communicate with each other through the high-speed data transmission link. Data and signaling are exchanged over the road to realize the interconnection between the high-altitude platform and the ground TD-SCDMA system. 2. The cellular network mobile communication system as claimed in claim 1, wherein the signaling despreading demodulation decoding module, the network management control module and the signaling coding and modulation module on the high-altitude platform are connected in sequence to form a signaling Processing and network control management center to enable interpretation, execution and construction of signaling information. 3. cellular network mobile communication system as claimed in claim 1, is characterized in that, uplink signal receiving processing module comprises: Orthogonal sampling analog/digital A/D conversion unit for analog/digital conversion of the received signal and sending the converted digital signal to the synchronization control, power control and related despreading unit; The synchronization control unit estimates the synchronization time of the digital signal from the orthogonal sampling A/D conversion unit, obtains the synchronization time deviation of the user terminal and adjusts it, and realizes the closed-loop synchronization control; The power control unit estimates the power level of the digital signal from the orthogonal sampling A/D conversion unit, obtains and adjusts the power level deviation of the user terminal, and realizes closed-loop power control; The correlation despreading unit uses a semi-regenerative signal processing method to process the digital signal from the orthogonal sampling A/D conversion unit, that is, the synchronous code division multiple access CDMA signal sent by each user only performs correlation despreading and Rake combination, The soft decision quantities of each symbol are obtained, and these soft decision quantities are output to the sample point circuit exchange module for exchange and further transmission. 4. cellular network mobile communication system as claimed in claim 1, it is characterized in that, sample point circuit switching module adopts program-controlled circuit switching, under the control of signaling, to the sign soft decision quantity of each user from uplink signal receiving processing module Switching is performed with a basic high-speed switching clock for non-spread-spectrum signals and a low-speed switching clock that is reduced by the spreading factor for spread-spectrum signals. 5. The cellular network mobile communication system as claimed in claim 1, wherein the downlink signal processing module is composed of a multiplexing unit and a quadrature amplitude modulation unit, and the multiplexing unit is time-division multiplexed by subframe interleaving The method multiplexes the multiple signals sent by the downlink to the same beam and each user in the same frequency band, and sends the multiplexed signals to the quadrature amplitude modulation unit to be modulated to the carrier frequency and then sent downwards. 6. cellular network mobile communication system as claimed in claim 1, is characterized in that, described user terminal is on the single-mode user terminal of terrestrial TD-SCDMA system, only increases the dual-mode user terminal of part baseband processing function , in order to meet the requirements of high-altitude platform system and ground TD-SCDMA system at the same time. 7. A cellular network mobile communication method based on high-altitude platform semi-regenerative signal processing, including carrying out regenerative processing to signaling information, and carrying out non-regenerative processing to non-voice information and voice information, characterized in that the voice information Non-regenerative processing includes: (1) The sending steps of the user terminal on the voice code channel of the uplink time slot: 1a) The user terminal performs 1/2 convolution coding and quaternary phase shift keying QPSK modulation on the original voice bits within 20ms to obtain 96 user voice modulation symbols; 1b) spreading the obtained user voice modulation symbols with a Gold sequence with a length of 31 as a spreading code to obtain 2976 spreading symbols; 1c) dividing the obtained spread spectrum symbols into time slots to obtain 4 spread spectrum symbol blocks with a length of 744 chips; 1d) Divide each spread spectrum symbol block into two sections of equal length, add a Gold sequence with a length of 63 as a midamble code in the middle of the two sections, obtain a symbol sequence with a length of 807, and then add a sequence with a length of 15 at the end of the symbol sequence Guard interval Gap, to form an uplink time slot waiting sequence with a length of 822 chips; 1e) Carrying out waveform shaping and D/A conversion on the sequence to be sent in the uplink time slot; (2) The receiving steps of the high-altitude platform on the voice code channel of the uplink timeslot: 2a) The high-altitude platform performs orthogonal down-conversion, analog/digital A/D conversion and matched filtering on the received voice signal to obtain the digital signal of the uplink voice; 2b) Extract the midamble code in the uplink voice digital signal, perform synchronization time estimation and power level estimation, and send the estimated synchronization time deviation information and power level deviation information to the network management control module to generate downlink signaling; simultaneously extract uplink Speech spread spectrum data in the voice digital signal, and perform semi-regenerative processing on the voice spread spectrum data to obtain the user's voice symbol soft information point; 2c) sending the voice symbol soft information point to the sample point circuit switching module for switching; (3) The sending steps of the high-altitude platform in the downlink voice time slot: 3a) The high-altitude platform performs TDM multiplexing on the voice symbol soft information points of multiple users output by the sample point circuit switching, adds a Gold sequence with a length of 63 as a midamble code, and adds a guard interval Gap with a length of 15 to form Downlink time slot waiting sequence; 3b) Carrying out waveform shaping and D/A conversion on the sequence to be transmitted in the downlink time slot; (4) The receiving steps of the user terminal in the downlink voice time slot: 4a) The user terminal performs orthogonal down-conversion, A/D conversion and matched filtering on the received signal of the downlink voice time slot to obtain a digital signal of the downlink voice; 4b) extracting the midamble code in the downlink voice digital signal for downlink synchronization and channel state estimation; 4c) equalizing the speech symbols in the downlink speech digital signal according to the estimated channel state information CSI; 4d) Demodulate and decode the equalized speech symbols to obtain original speech information. 8. The cellular network mobile communication method based on high-altitude platform semi-regenerative signal processing as claimed in claim 7, wherein step 2b) described voice spread spectrum data is carried out semi-regenerative formula processing, refers to voice spread spectrum data is carried out Correlation despreading and Rake are combined to obtain soft information points of speech symbols. 9. The cellular network mobile communication method based on high-altitude platform semi-regenerative signal processing as claimed in claim 7, wherein non-regenerative processing is carried out to non-voice information, which is divided into low-speed non-voice information and high-speed non-voice information; Low-speed non-voice information is transmitted using the above-mentioned voice code channel; high-speed non-voice information has three typical rates: 144kbps, 384kbps and 1.92Mbps, using LDPC coding and high-order modulation mechanisms to support the transmission of these three high-speed non-voice information , the non-regenerative processing of these three types of high-speed non-speech information includes: A. The sending steps of the user terminal in the uplink time slot: (A1) The user terminal adds coding padding tail bits to the original data bit block generated within a specific time and performs LDPC coding at a code rate of 7/8, then deletes redundant bits of a specific length and modulates to obtain a modulation symbol block; (A2) segmenting the modulation symbol block according to the length of the time slot to obtain a specific number of modulation symbol sub-blocks with a length of 744; (A3) Divide each modulation symbol sub-block into two sections of equal length, add a Gold sequence with a length of 63 as a midamble code in the middle of the two sections, obtain a symbol sequence with a length of 807, and then add a length of 15 to the end of the sequence The guard interval Gap forms a waiting sequence with a length of 822; (A4) Carry out waveform shaping and D/A conversion on the sequence to be transmitted, and send it with orthogonal up-conversion frequency; B. The receiving steps of the high-altitude platform in the uplink time slot: (B1) Carry out orthogonal down-conversion, A/D conversion and matched filtering to the received high-speed non-speech signal to obtain a high-speed non-speech digital signal; (B2) extract the midamble code from the obtained high-speed non-speech digital signal to estimate the synchronization time, and send the estimated synchronization time deviation information to the network management control module to generate corresponding downlink control signaling; The speech digital signal is sampled at the symbol rate to obtain non-speech symbol soft information points; (B3) sending the non-speech symbol soft information point to the sample point circuit switching module for switching; C. The sending steps of the high-altitude platform in the downlink time slot: (C1) The high-altitude platform extracts the non-speech symbol soft information point of the sample point circuit switching output, then adds a Gold sequence with a length of 63 as a midamble code and adds a guard interval Gap with a length of 15 to form a downlink time slot waiting sequence; (C2) Carrying out waveform shaping and D/A conversion on the sequence to be sent in the downlink time slot; D. The receiving steps of the user terminal in the downlink time slot: (D1) The user terminal performs orthogonal down-conversion, A/D conversion and matched filtering on the received downlink high-speed non-speech signal to obtain a downlink high-speed non-speech digital signal; (D2) extracting the midamble code in the downlink high-speed non-speech digital signal to carry out downlink synchronization and channel state estimation; (D3) equalizing the non-speech symbols in the downlink high-speed non-speech digital signal according to the estimated channel state information CSI; (D4) Demodulate and decode the equalized non-speech symbols to obtain original information. 10. The cellular network mobile communication method based on high-altitude platform semi-regenerative signal processing as claimed in claim 9, wherein the specific time described in step A1 corresponds to these three rates of 144kbps, 384kbps and 1.92Mbps respectively 40ms, 50ms and 40ms; The length of described original data bit block is corresponding to these three kinds of rates of 144kbps, 384kbps and 1.92Mbps and is respectively 5760, 19200 and 76800; The length of described coding filling tail bit is corresponding to 144kbps, 384kbps and These three kinds of rates of 1.92Mbps are respectively 1394, 2262 and 1894; The specific length corresponding to these three kinds of rates of 144kbps, 384kbps and 1.92Mbps are respectively 736, 2208 and 656; The modulation symbol subblock described in step A2 The numbers correspond to 5, 15 and 24 for the three rates of 144kbps, 384kbps and 1.92Mbps respectively.

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