CN110247694B - Decoding forwarding-based satellite communication and satellite television signal IP fusion relay method - Google Patents
Decoding forwarding-based satellite communication and satellite television signal IP fusion relay method Download PDFInfo
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- CN110247694B CN110247694B CN201910513715.XA CN201910513715A CN110247694B CN 110247694 B CN110247694 B CN 110247694B CN 201910513715 A CN201910513715 A CN 201910513715A CN 110247694 B CN110247694 B CN 110247694B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/155—Ground-based stations
- H04B7/15507—Relay station based processing for cell extension or control of coverage area
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/1851—Systems using a satellite or space-based relay
- H04B7/18515—Transmission equipment in satellites or space-based relays
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/1851—Systems using a satellite or space-based relay
- H04B7/18517—Transmission equipment in earth stations
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/20—Adaptations for transmission via a GHz frequency band, e.g. via satellite
Abstract
The invention discloses a decoding forwarding-based satellite communication and satellite television signal IP fusion relay method, which comprises a satellite television signal access unit, a satellite communication signal access unit, a relay unit and a terminal unit; the satellite television signal access unit and the satellite communication signal access unit are connected with the relay unit through the switch; the working mode of the method is explained in detail. The invention has the following effects: 1. compared with a transparent forwarding scheme, the effect of satellite television signal relaying can be obviously improved; 2. the satellite television signal is relayed by a decoding and forwarding method based on the LTE technology, and can be deeply fused with a satellite communication signal relay scheme realized by the decoding and forwarding method based on the LTE; 3. the satellite television and the satellite communication signals are relayed by a decoding and forwarding method based on the LTE technology, and when tunnel relay equipment of the ground mobile network exists in a tunnel region, the putting amount of new equipment can be reduced, so that the access cost of the satellite network in the region covered by the existing ground mobile network is further reduced, and the waste of public resources is reduced.
Description
Technical Field
The invention relates to a decoding forwarding-based satellite communication and satellite television signal IP fusion relay method.
Background
High-speed rail has become the most common trip mode at present, and the mileage of high-speed rail in China reaches 3.8 kilometers by 2025. At present, a high-speed rail mobile internet system capable of greatly improving passenger riding experience is mainly realized based on a ground mobile network, and a high-speed rail mobile internet system realized based on satellite communication has no mature application case at present.
In a high-speed rail mobile interconnection system based on a ground mobile network, the defects of high network construction cost (a base station needs to be established every few hundred meters), frequent cell switching, complex network optimization and the like exist. In the aspect of network coverage, in wide areas of the middle and the west or mountainous areas, the city density is low, and the return on investment of network construction is greatly reduced. Due to the difference of the ground mobile network standards of various countries and the difference of the current situation of network construction, the practical difficulty is caused for the application of the high-speed rail mobile internet system in a wider area. The satellite-based high-speed rail mobile interconnection system can well solve the difficulties, does not depend on complicated network construction on the ground, can greatly reduce the investment cost no matter in the vast middle and western regions or leaves the country, and accelerates the wide application of the high-speed rail mobile interconnection system. On the other hand, with the rapid development of high-throughput satellites, the satellite-based internet can solve the problem of bandwidth limitation of the existing satellites, and the application of the satellite-based high-speed rail mobile internet system is greatly promoted.
Like a ground mobile network, a satellite-based high-speed rail mobile internet system also needs to solve the problem that satellite signals are shielded in special areas such as tunnels, bridges, moats, canyons and the like. At present, for the relay problem of Satellite signals in special scenes (especially tunnels), the prior literature mainly focuses on the research of the Gap Filler technology, especially the Gap Filler technology based on DVB-S/S2/S2x (Digital Video Broadcasting-Satellite/2/2x) standard. The research contents show that the relay technology based on DVB-S/S2 is seriously influenced by multipath, and although the problem can be partially solved by introducing DVB-RCS/T (Digital Video Broadcasting-Return Channel via Satellite/Terrestrial) technology based on OFDM (orthogonal Frequency Division multiplexing) technology, the research contents only exist in a simulation level and are not shown in a real object.
Disclosure of Invention
The invention provides a method for carrying out IP fusion relay transmission on satellite communication signals and satellite television signals, which can realize simultaneous relay of the satellite communication signals and the satellite television signals under the condition of limited bandwidth. Compared with the existing satellite television signal transparent forwarding method, the satellite television signal relay method based on decoding forwarding provided by the invention can obviously improve the relay quality of the satellite television signal (the television is smoother). The satellite television signal and the satellite communication signal are relayed by a decoding and forwarding method, so that the development cost of relay equipment can be further reduced.
The purpose of the invention is realized by the following technical scheme:
the decoding forwarding-based satellite communication and satellite television signal IP fusion relay method comprises a satellite television signal access unit, a satellite communication signal access unit, a relay unit and a terminal unit; the satellite television signal access unit and the satellite communication signal access unit are connected with the relay unit through the switch;
the satellite television signal access unit comprises a satellite television signal receiving antenna, a radio frequency front end, a Sat-IP gateway and a transcoding server; after receiving the Satellite signal and converting the signal to an L-band intermediate frequency signal by the radio frequency front end, the Satellite signal receiving antenna firstly decodes the Satellite signal of DVB-S2 standard or ABS-S (Advanced Broadcasting System-Satellite) standard by the Sat-IP gateway and converts the decoded Satellite signal into an IP program stream of MPEG2 format; sending the IP program stream in the MPEG2 format into a transcoding server for data compression to obtain the IP program stream in the H.264/H.265 format;
the satellite communication signal access unit comprises a satellite communication terminal communication antenna, a radio frequency front end and a modem; the satellite central station modulates the needed internet content by the satellite modem and transmits the modulated internet content to the communication satellite through the radio frequency front end and the antenna of the central station; after the satellite communication signal is received by the satellite communication terminal antenna and is converted into an L-waveband intermediate frequency signal through the radio frequency front end, the satellite communication signal is demodulated into IP data through the satellite modem and is transmitted to the switchboard;
for the return link, the exchanger transmits information to the modem and the radio frequency front end, the signal is transmitted to the communication satellite through the satellite communication terminal antenna, the communication satellite transmits the signal to the satellite central station antenna, and the signal is transmitted to the internet through the radio frequency front end and the modem in sequence;
after the satellite communication IP data and the satellite television IP program stream are accessed to the switch, relaying is carried out through an LTE channel;
for a downlink, the relay unit firstly re-modulates IP data into an LTE radio frequency signal through an LTE base station digital board, then couples the LTE radio frequency signal into a near-end machine digital board of the relay remote unit, converts the LTE radio frequency signal into an optical signal and then remotely transmits the optical signal to the indoor unit through an optical fiber; in the indoor unit, firstly, an optical signal is restored into an LTE radio frequency signal through a remote terminal digital board of an optical fiber remote, then the LTE radio frequency signal is amplified through a power amplifier, and the amplified radio frequency signal is output to a leaky cable for wireless coverage;
for the uplink, after receiving the uplink LTE radio frequency signal, the indoor unit amplifies the signal by the low noise amplifier and sends the signal to the remote terminal digital board of the optical fiber remote, where the LTE uplink radio frequency signal is converted into an optical signal and then is remote to the outdoor unit by the optical fiber. In the outdoor unit, the optical signal is restored to an LTE radio frequency signal through a near-end digital board which is pulled far by an optical fiber, and then the optical signal is coupled into an LTE base station digital board, and the LTE signal is decoded into uplink satellite communication IP data.
Preferably, the IP program stream in the MPEG2 format is sent to the transcoding server for data compression to become the IP program stream in the H.264/H.265 format.
Preferably, a coupler and a power divider are arranged between the LTE substrate digital board and the near-end digital board. Preferably, the indoor unit is a tunnel relay indoor unit, and the outdoor unit is a tunnel relay outdoor unit, so as to meet the tunnel communication requirement.
Preferably, the terminal unit is an in-vehicle unit.
Preferably, in the vehicle-mounted unit, the satellite signal and the satellite signal are firstly recovered into IP data, and then converted into a WI-FI signal through the router after being recovered into the IP data, so that wireless coverage in the vehicle is realized.
Preferably, the access of the onboard unit is divided into three parts: accessing a relay signal in a tunnel, accessing a satellite television signal outside the tunnel, and accessing a satellite communication signal outside the tunnel;
for the access part of the relay signal in the tunnel: firstly, receiving a wireless LTE radio frequency signal through a tunnel relay signal vehicle-mounted receiving and transmitting antenna, then recovering IP data of a satellite communication signal and an IP program stream of a satellite television signal through an LTE modulation and demodulation terminal, and then sending the IP data and the IP program stream into a soft switching server;
access to out-of-tunnel satellite television signals: when the train is outside the tunnel, the satellite television live broadcast signal can be directly received through the vehicle satellite television signal receiving antenna, and is accessed to the soft switching server after being subjected to IP processing through the Sat-IP gateway and the transcoding server;
access to out-of-tunnel satellite communication signals: and the satellite communication outside the tunnel is received and transmitted through a vehicle-mounted satellite communication signal receiving and transmitting antenna, and for a receiving link, after the antenna receives a signal, satellite communication data is decomposed into IP data through a satellite communication terminal and then is sent to the soft switching server.
As a preferred mode, outside the tunnel, the soft handover server can receive the television IP program stream from the satellite television signal access unit outside the tunnel and the communication IP data of the satellite communication signal access unit outside the tunnel, and the soft handover server directly sends the television IP program stream and the communication IP data to the router to convert the television IP program stream and the communication IP data into WI-FI signals and then realizes wireless coverage inside the vehicle;
in the tunnel, the soft switching server can receive the television IP program stream and the communication IP data from the relay signal access unit in the tunnel, send the television IP program stream and the communication IP data to the router to be converted into WI-FI signals, and then realize wireless coverage in the vehicle;
when a train enters the tunnel from the outside of the tunnel or drives to the outside of the tunnel from the inside of the tunnel, switching between a relay system in the tunnel and a communication or television access system outside the tunnel exists;
under the current relay mode, for satellite communication, because the communication is carried out with people or objects at a far end, two systems in a tunnel and outside the tunnel only play a role of relay, data sources are at the far end, and the soft switching between the data sources can be automatically realized directly through the routing addressing of a network layer; for the satellite television signals, the relay system in the tunnel and the satellite television signal access system outside the tunnel respectively provide program sources independently, and when the communication terminal wants to continuously watch the television signals inside and outside the tunnel, the soft switching is realized by software deployed in a soft switching server.
As a preferred mode, the relay device is implemented based on an LTE technology, and signals of the relay device are LTE signals of 1.4G and 1.8G frequency bands;
the outfield environment is built as follows: the leakage cable is erected along the rail and divided into 3 sections, and each section is 100 m. And a digital optical fiber relay remote terminal is deployed at the starting end of each section of the leaky cable, the output of the remote terminal is connected to the leaky cable, and the signal is radiated out through the leaky cable. The satellite signal access subsystem, the digital optical fiber relay near-end machine, the LTE base station with the frequency band of 1.8GHz, the LTE base station with the frequency band of 1.4G, the Sat-IP gateway and the transcoding server are all arranged in a cabinet at one end of the leaky cable. The satellite signal access subsystem receives satellite signals, and after satellite signals are processed through a Sat-IP gateway and a transcoding server, compressed television program IP data streams are accessed to the input end of an LTE (Long term evolution) base station through an exchanger; for the satellite communication signals, IP data output by the satellite modem is also connected to the input end of the LTE base station through the switch. The LTE radio frequency signal output by the LTE base station is accessed to the digital optical fiber relay near-end machine, and after the LTE radio frequency signal is converted into an optical signal, the optical signal is respectively accessed to 3 digital optical fiber relay far-end machines through optical fiber remote.
The invention has the beneficial effects that:
1. satellite television signals are relayed by a decoding and forwarding method based on an LTE technology, compared with a transparent forwarding scheme, the effect of satellite television signal relaying can be obviously improved, televisions are smoother, during implementation, a relatively obvious mosaic phenomenon exists in transparent forwarding, and no mosaic phenomenon exists in the whole process of decoding and forwarding;
2. the satellite television signal is relayed by a decoding and forwarding method based on the LTE technology, and can be deeply fused with a satellite communication signal relay scheme realized by the LTE decoding and forwarding method, so that the complexity of relay equipment is simplified, and the development cost of the relay equipment is reduced;
3. the satellite television and the satellite communication signals are relayed by a decoding and forwarding method based on the LTE technology, and when tunnel relay equipment of a ground mobile network exists in a tunnel region, under the condition that conditions permit, leaky cables and LTE related equipment can be shared with the ground mobile network, so that the putting amount of new equipment can be reduced, the access cost of the satellite network in the region covered by the existing ground mobile network is further reduced, and the waste of public resources is reduced.
Drawings
Fig. 1 is a schematic diagram of a satellite television signal IP access relay unit;
fig. 2 is a schematic diagram of a satellite television signal relaying method based on LTE decoding and forwarding;
fig. 3 is a schematic diagram of a satellite communication signal relaying method based on LTE decoding and forwarding;
fig. 4 is a schematic diagram of an IP convergence relay method based on decoding and forwarding for a satellite link and a satellite link;
FIG. 5 is a schematic diagram of the internal components of a relay unit of the fusion relay method;
fig. 6 is a schematic diagram of the internal components of the on-board unit of the fusion relay method.
Detailed Description
The technical solutions of the present invention are further described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the following.
As shown in fig. 4, based on the decoding and forwarding satellite communication and satellite television signal IP fusion relay method, the satellite link decoding and forwarding relay method and the satellite link decoding and forwarding relay method are subjected to IP fusion, and at least one LTE decoding and forwarding channel is provided on a physical channel;
the system comprises a satellite television signal access unit, a satellite communication signal access unit, a relay unit and a terminal unit; the satellite television signal access unit and the satellite communication signal access unit are connected with the relay unit through the switch;
as shown in fig. 2, the satellite television signal access unit includes a satellite television signal receiving antenna, a radio frequency front end, a Sat-IP gateway and a transcoding server; after receiving a Satellite signal and performing frequency conversion to an L-waveband intermediate frequency signal through a radio frequency front end, a Satellite signal receiving antenna firstly decodes the Satellite signal of DVB-S2 standard or ABS-S (Advanced Broadcasting System-Satellite) standard through a Sat-IP gateway and converts the Satellite signal into an IP program stream of an MPEG2 format (the data volume of a single set of standard definition television program stream is about 4Mbps, and the data volume of a single set of high definition television program stream can reach 8 Mbps); sending the IP program stream in the MPEG2 format into a transcoding server for data compression to obtain the IP program stream in the H.264/H.265 format;
as shown in fig. 3, the satellite signal access unit includes a satellite communication terminal communication antenna, a radio frequency front end and a modem; the satellite communication signal relay is a bidirectional link so as to realize bidirectional communication between the vehicle-mounted user and the Internet user; for a forward link, a satellite central station modulates internet contents (web pages, files, voice, videos and the like) required by a vehicle-mounted user through a satellite modem and transmits the modulated internet contents to a communication satellite through a radio frequency front end and an antenna of the central station; at the tunnel end, the satellite communication signal is received by the satellite communication antenna, converted into an L-band intermediate frequency signal through the radio frequency front end in a frequency conversion mode, demodulated into IP data through the satellite modem and transmitted to the switchboard; after the satellite communication signal enters the tunnel relay outdoor unit, the processes of signal conversion, relay zoom-out and wireless coverage in the high-speed rail are consistent with the related processes of the satellite television signal, and are not described again here.
For a return link (from a vehicle-mounted user to a far-end internet end), the exchanger transmits information to the modem and the radio frequency front end, signals are transmitted to a communication satellite through a satellite communication terminal communication antenna (or a communication signal receiving and transmitting antenna), the communication satellite transmits the signals to a satellite central station antenna, and the signals are transmitted to the internet through the radio frequency front end and the modem in sequence; the whole process is reverse to that of the forward link.
After the satellite communication IP data and the satellite television IP program stream are accessed to the switch, the satellite communication IP data and the satellite television IP program stream can be freely relayed through the two LTE channels;
for a downlink, the relay unit firstly re-modulates IP data into an LTE radio frequency signal through an LTE base station digital board, then couples the LTE radio frequency signal into a near-end machine digital board of the relay remote unit, converts the LTE radio frequency signal into an optical signal and then remotely transmits the optical signal to the indoor unit through an optical fiber; in the indoor unit, firstly, an optical signal is restored to an LTE radio frequency signal through a remote terminal digital board of an optical fiber remote, then the LTE radio frequency signal is amplified through a Power Amplifier (PA), and the amplified radio frequency signal is output to a leaky cable for wireless coverage;
for the uplink (only the uplink is required), contrary to the downlink, after receiving the uplink LTE radio frequency signal, the indoor unit amplifies the signal by a Low Noise Amplifier (LNA) and sends the amplified signal to a remote digital board for fiber-optic remote, where the LTE uplink radio frequency signal is converted into an optical signal, and then the optical signal is sent to the outdoor unit through the fiber-optic remote. In the outdoor unit, the optical signal is restored to an LTE radio frequency signal through a near-end digital board which is pulled far by an optical fiber, and then the optical signal is coupled into an LTE base station digital board, and the LTE signal is decoded into uplink satellite communication IP data. And finally, the relay unit sends the uplink satellite communication IP data to the satellite communication signal access unit for transmission. When the scheme is implemented, the relay unit adopts 2 paths of LTE channels, and in the actual use process, 1 path, 2 paths or even multiple paths of LTE channels can be selected for construction according to actual requirements and construction conditions.
In a preferred embodiment, in order to reduce the occupation of relay channel by a single set of programs, an IP program stream in MPEG2 format is sent to a transcoding server for data compression to become an IP program stream in H.264/H.265 format.
At present, for standard definition programs, the data amount of a single set of programs can be compressed to about 700kbps, high-speed moving pictures can also be compressed to about 1Mbps (h.264 output, and h.265 output can save 1 time of bandwidth to within 500kbps, but the cost is higher), and high-definition programs can be compressed to within 2 Mbps. And the transcoding server transmits the IP program stream with smaller data volume after transcoding into the LTE base station of the relay unit for subsequent processing, so that relay bandwidth resources can be greatly saved.
In a preferred embodiment, a coupler and a power divider are arranged between the LTE substrate digital board and the near-end digital board, and the internal structure of a specific relay unit is as shown in fig. 5.
In a preferred embodiment, the indoor units are tunnel relay indoor units and the outdoor units are tunnel relay outdoor units to meet the requirements of tunnel communication.
In a preferred embodiment, the terminal unit is an on-board unit.
In a preferred embodiment, at the vehicle-mounted unit, the satellite signal and the satellite signal are firstly recovered into IP data, and then converted into a WI-FI signal through the router after being recovered into the IP data, so that the wireless coverage in the vehicle is realized.
In a preferred embodiment, as shown in fig. 6, the access of the onboard unit is divided into three parts: accessing a relay signal in a tunnel, accessing a satellite television signal outside the tunnel, and accessing a satellite communication signal outside the tunnel;
for the access part of the relay signal in the tunnel: firstly, receiving a wireless LTE radio frequency signal through a tunnel relay signal vehicle-mounted receiving and transmitting antenna, then recovering IP data of a satellite communication signal and an IP program stream of a satellite television signal through LTE modulation and demodulation terminals (2 LTE modulation and demodulation terminals in the figure correspond to two paths of LTE signals in a relay unit respectively), and then sending the IP data and the IP program stream into a soft switching server;
access to out-of-tunnel satellite television signals: when the train is outside the tunnel, the satellite television live broadcast signal can be directly received through the vehicle satellite television signal receiving antenna, and is accessed to the soft switching server after being subjected to IP processing through the Sat-IP gateway and the transcoding server;
access to out-of-tunnel satellite communication signals: and the satellite communication outside the tunnel is received and transmitted through a vehicle-mounted satellite communication signal receiving and transmitting antenna, and for a receiving link, after the antenna receives a signal, satellite communication data is decomposed into IP data through a satellite communication terminal and then is sent to the soft switching server. The satellite television signal and satellite communication signal relay system realized based on the decoding forwarding relay method and the existing vehicle-mounted television and communication system can realize soft switching based on an IP method, so that newly developed equipment can be more conveniently fused with the existing high-speed rail vehicle-mounted equipment, and the access cost is reduced.
In a preferred embodiment, outside the tunnel, the soft handover server can receive the television IP program stream from the satellite television signal access unit outside the tunnel and the communication IP data of the satellite communication signal access unit outside the tunnel, and the soft handover server directly sends the television IP program stream and the communication IP data to the router to be converted into WI-FI signals and then realizes wireless coverage inside the vehicle;
in the tunnel, the soft switching server can receive the television IP program stream and the communication IP data from the relay signal access unit in the tunnel, send the television IP program stream and the communication IP data to the router to be converted into WI-FI signals, and then realize wireless coverage in the vehicle;
when a train enters the tunnel from the outside of the tunnel or drives to the outside of the tunnel from the inside of the tunnel, switching between a relay system in the tunnel and a communication or television access system outside the tunnel exists;
in the current relay mode, for satellite communication, because passenger communication is carried out with people or objects at a far end, two systems in a tunnel and outside the tunnel only play a role of relay, data sources are at the far end, and soft switching between the systems can be automatically realized directly through routing addressing of a network layer without special switching software; for the satellite television signals, the relay system in the tunnel and the satellite television signal access system outside the tunnel respectively provide program sources independently, and when a passenger wants to continuously watch the television signals inside and outside the tunnel (without manual input switching), the soft switching needs to be realized through software deployed in a soft switching server.
In a preferred embodiment, the relay device is implemented based on the LTE technology, and signals of the relay device are LTE signals of 1.4G and 1.8G frequency bands;
the outfield environment is built as follows: the leakage cable is erected along the rail and divided into 3 sections, and each section is 100 m. And a digital optical fiber relay remote terminal is deployed at the starting end of each section of the leaky cable, the output of the remote terminal is connected to the leaky cable, and the signal is radiated out through the leaky cable. The satellite signal access subsystem, the digital optical fiber relay near-end machine, the LTE base station with the frequency band of 1.8GHz, the LTE base station with the frequency band of 1.4G, the Sat-IP gateway and the transcoding server are all arranged in a cabinet at one end of the leaky cable. The satellite signal access subsystem receives satellite signals, and after satellite signals are processed through a Sat-IP gateway and a transcoding server, compressed television program IP data streams are accessed to the input end of an LTE (Long term evolution) base station through an exchanger; for the satellite communication signals, IP data output by the satellite modem is also connected to the input end of the LTE base station through the switch. The LTE radio frequency signal output by the LTE base station is accessed to the digital optical fiber relay near-end machine, and after the LTE radio frequency signal is converted into an optical signal, the optical signal is respectively accessed to 3 digital optical fiber relay far-end machines through optical fiber remote.
During testing, the test vehicle runs along a leaky cable or is stationary at a certain position, signals are accessed through the vehicle-mounted antenna, the vehicle-mounted LTE receiving terminal demodulates data and then converts the data into WI-FI signals through the router to wirelessly cover the vehicle, and the mobile terminal in the vehicle watches satellite live television and achieves internet connection through connecting the WI-FI signals.
In the whole relay system, two LTE channels (20MHz bandwidth) are equivalently used for data transmission under the condition of a single antenna, and experiments show that the total downlink throughput rate is about 80Mbps and the total uplink throughput rate is about 14Mbps in the vehicle moving process.
For communication signals, the verification of the whole satellite communication link (through testing the throughput rate) is carried out by leasing satellite resources with the bandwidth of 2 MHz. During the test, the satellite communication adopts TDMA system, QPSK modulation and 3/4 code rate Turbo channel coding, the roll-off coefficient is 0.2, and the theoretical reachable rate of the system is R under the condition of 2MHz bandwidth resourceb2 × 0.8 × 2 × 3/4 is 2.4 Mbps. Through satellite communication relay channel tests of the system, the peak value of the throughput rate can reach 2.2Mbps no matter a test vehicle is in a moving or static condition, and no matter a forward link (from a satellite central station to the test vehicle) or a return link (from the test vehicle to the satellite central station), and the average value is about 2 Mbps.
For the television signal, after the IP processing is performed in the manner shown in fig. 1, the single set of standard definition television program stream is compressed (output h.264 format), the simple picture throughput rate is about 750kbps, and the moving picture throughput rate is about 1.2 Mbps. During the experiment, the situation that 8 sets of television programs are simultaneously relayed is tested, and the occupied throughput rate is about 9.9 Mbps.
The invention mainly comprises the following steps:
1. the invention firstly provides a satellite television signal relay method based on decoding and forwarding, and a schematic diagram of the satellite television signal relay method is shown in figure 2;
2. based on the satellite television signal decoding and forwarding relay method, an IP fusion relay method based on decoding and forwarding of both satellite communication signals and satellite television signals is provided for a high-speed rail tunnel scene, and a schematic diagram is shown in FIG. 4;
3. based on the above IP convergence relay method in which both the satellite communication signal and the satellite television signal are decoded and forwarded, a soft handover method based on IP routing with the existing vehicle television and communication system is proposed, and a schematic diagram is shown in fig. 6;
4. in the relay method for decoding and forwarding the satellite television Signal, the most critical point is in the process of IP access conversion of the satellite television Signal, as shown in fig. 1, after the satellite television receiving antenna receives the radio frequency Signal and converts the radio frequency Signal into an intermediate frequency Signal through a radio frequency front end, the intermediate frequency television Signal is decoded into an IP program stream in an MPEG2(Moving Picture Experts Group-2) format through a Sat-IP (satellite Signal to IP Data transform) gateway, the IP program stream in the MPEG2 format is transcoded into an IP program stream in an h.264 or h.265 format through a transcoding server, the Data volume of the transcoded IP program stream is greatly reduced, the Data volume occupying about 4Mbps of a single program before transcoding is converted into the Data volume of about 1Mbps after transcoding, and the transcoded IP program stream is sent to an LTE base station for relay transmission;
5. in the IP fusion relay method based on decoding and forwarding of the satellite communication signals and the satellite television signals, the first key point is that after the satellite communication signals and the satellite television signals are subjected to IP access, relay sections all adopt a relay technology based on LTE and digital optical fiber remote, a relay channel is shared, and the cost of relay equipment is saved; the second key point is that the relay section adopts double LTE channels, so that the relay capability of the relay section of the whole system is improved, and the capability of expanding to more LTE channels is realized; the third key point is that the satellite communication signal and the satellite television signal are accessed to the router after being accessed to the IP, and then are accessed to the two LTE channels through the router, so that flexible distribution of data volume in the two LTE channels is realized, and deep fusion of the satellite communication signal and the satellite television signal is realized in a routing manner, so that the bandwidth utilization rate of the relay channel is improved, and related contents are shown in fig. 5.
In the research of the team, the relay forwarding of the satellite television signals is carried out in a transparent forwarding mode, the relay forwarding of the satellite communication signals is carried out in a decoding forwarding mode, and the function of simultaneously relaying the satellite television signals and the satellite communication signals in a tunnel is basically realized. In order to further improve the relay effect of satellite television signals, reduce the cost of relay equipment and facilitate the realization of IP access of satellite televisions, the invention provides a new solution for decoding and forwarding and performing deep fusion on the basis of an LTE (Long Term evolution) technology for the problem of simultaneous relay of satellite television signals and satellite communication signals in scenes such as tunnels.
The invention provides an IP (Internet protocol) fusion relay method of satellite communication signals and satellite television signals based on a decoding and forwarding technology, which aims to provide relay coverage of satellite communication and satellite television signals when high-speed rails pass through weak coverage areas of wireless signals such as tunnels, bridges, moats, canyons and the like so as to ensure that the high-speed rails have continuous satellite communication connection and satellite television playing capacity in the whole operation process. Based on the scheme, the application of satellite communication and satellite television in the field of high-speed rail mobile interconnection can be greatly promoted. Meanwhile, the related technology of the scheme can also be popularized and applied to other mobile scenes, such as highway tunnel scenes.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, it should be noted that any modifications, equivalents and improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (8)
1. The decoding forwarding-based satellite communication and satellite television signal IP fusion relay method is characterized in that: the system comprises a satellite television signal access unit, a satellite communication signal access unit, a relay unit and a terminal unit; the satellite television signal access unit and the satellite communication signal access unit are connected with the relay unit through the switch;
the satellite television signal access unit comprises a satellite television signal receiving antenna, a radio frequency front end, a Sat-IP gateway and a transcoding server; after receiving the satellite signal and converting the satellite signal into an L-waveband intermediate frequency signal through the radio frequency front end, the satellite signal receiving antenna firstly decodes the satellite signal of the DVB-S2 standard or ABS-S standard through a Sat-IP gateway and converts the satellite signal into an IP program stream in an MPEG2 format; sending the IP program stream in the MPEG2 format into a transcoding server for data compression to obtain the IP program stream in the H.264/H.265 format;
the satellite communication signal access unit comprises a satellite communication terminal communication antenna, a radio frequency front end and a modem; the satellite signal relay is a bidirectional link; for a forward link, a satellite central station modulates required internet content through a satellite modem and transmits the modulated internet content to a communication satellite through a central station radio frequency front end and an antenna; after the satellite communication signal is received by the satellite communication terminal antenna and is converted into an L-waveband intermediate frequency signal through the radio frequency front end, the satellite communication signal is demodulated into IP data through the satellite modem and is transmitted to the switchboard;
for the return link, the exchanger transmits information to the modem and the radio frequency front end, the signal is transmitted to the communication satellite through the satellite communication terminal antenna, the communication satellite transmits the signal to the satellite central station antenna, and the signal is transmitted to the internet through the radio frequency front end and the modem in sequence;
after the satellite communication IP data and the satellite television IP program stream are accessed to the switch, relaying is carried out through an LTE channel;
for a downlink, the relay unit firstly re-modulates IP data into an LTE radio frequency signal through an LTE base station digital board, then couples the LTE radio frequency signal into a near-end machine digital board of the relay remote unit, converts the LTE radio frequency signal into an optical signal and then remotely transmits the optical signal to the indoor unit through an optical fiber; in the indoor unit, firstly, an optical signal is restored into an LTE radio frequency signal through a remote terminal digital board of an optical fiber remote, then the LTE radio frequency signal is amplified through a power amplifier, and the amplified radio frequency signal is output to a leaky cable for wireless coverage;
for an uplink, after receiving an uplink LTE radio frequency signal, the indoor unit amplifies the signal through a low noise amplifier and sends the signal to a remote terminal digital board of an optical fiber remote unit, and after the LTE uplink radio frequency signal is converted into an optical signal, the optical fiber remote unit sends the optical signal to the outdoor unit; in the outdoor unit, the optical signal is restored to an LTE radio frequency signal through a near-end digital board which is pulled far by an optical fiber, and then the optical signal is coupled into an LTE base station digital board, and the LTE signal is decoded into uplink satellite communication IP data.
2. The decoding forwarding-based satellite communication and satellite television signal IP convergence relaying method according to claim 1, characterized in that: and a coupler and a power divider are arranged between the LTE substrate digital board and the near-end machine digital board.
3. The decoding forwarding-based satellite communication and satellite television signal IP convergence relaying method according to claim 1, characterized in that: the indoor unit is a tunnel relay indoor unit, and the outdoor unit is a tunnel relay outdoor unit so as to meet the tunnel communication requirement.
4. The decoding forwarding-based satellite communication and satellite television signal IP convergence relaying method according to claim 3, characterized in that: the terminal unit is an on-board unit.
5. The decoding forwarding-based satellite communication and satellite television signal IP convergence relaying method of claim 4, wherein: at the vehicle-mounted unit, the satellite television signal and the satellite communication signal are firstly recovered into IP data, and then converted into WI-FI signals through the router after being recovered into the IP data, so that the wireless coverage in the vehicle is realized.
6. The decoding forwarding-based satellite communication and satellite television signal IP convergence relaying method of claim 5, wherein: the access of the on-board unit is divided into three parts: accessing a relay signal in a tunnel, accessing a satellite television signal outside the tunnel, and accessing a satellite communication signal outside the tunnel;
for the access part of the relay signal in the tunnel: firstly, receiving a wireless LTE radio frequency signal through a tunnel relay signal vehicle-mounted receiving and transmitting antenna, then recovering IP data of a satellite communication signal and an IP program stream of a satellite television signal through an LTE modulation and demodulation terminal, and then sending the IP data and the IP program stream into a soft switching server;
access to out-of-tunnel satellite television signals: when the train is outside the tunnel, the satellite television live broadcast signal can be directly received through the vehicle satellite television signal receiving antenna, and is accessed to the soft switching server after being subjected to IP processing through the Sat-IP gateway and the transcoding server;
access to out-of-tunnel satellite communication signals: and the satellite communication outside the tunnel is received and transmitted through a vehicle-mounted satellite communication signal receiving and transmitting antenna, and for a receiving link, after the antenna receives a signal, satellite communication data is decomposed into IP data through a satellite communication terminal and then is sent to the soft switching server.
7. The decode-and-forward-based satellite communication and satellite television signal IP convergence relaying method of claim 6, wherein:
outside the tunnel, the soft switching server can receive the television IP program stream from the satellite television signal access unit outside the tunnel and the communication IP data of the satellite communication signal access unit outside the tunnel, and the soft switching server directly sends the television IP program stream and the communication IP data to the router to be converted into WI-FI signals and then realizes wireless coverage inside the vehicle;
in the tunnel, the soft switching server can receive the television IP program stream and the communication IP data from the relay signal access unit in the tunnel, send the television IP program stream and the communication IP data to the router to be converted into WI-FI signals, and then realize wireless coverage in the vehicle;
when a train enters the tunnel from the outside of the tunnel or drives to the outside of the tunnel from the inside of the tunnel, switching between a relay system in the tunnel and a communication or television access system outside the tunnel exists;
for satellite communication, the soft switching is automatically realized through the routing addressing of a network layer; for satellite television signals, soft handoff is implemented by software deployed in a soft handoff server.
8. The decoding forwarding-based satellite communication and satellite television signal IP convergence relaying method according to any one of claims 1 to 7, characterized by:
the relay equipment is realized based on an LTE technology, and signals of the relay equipment are LTE signals of 1.4G and 1.8G frequency bands;
the outfield environment is built as follows: the leakage cable is erected along the rail and divided into 3 sections, and each section is 100 m; deploying a digital optical fiber relay remote terminal at the starting end of each section of leaky cable, connecting the output of the remote terminal to the leaky cable, and radiating signals through the leaky cable; the satellite signal access subsystem, the digital optical fiber relay near-end machine, the LTE base station with the frequency band of 1.8GHz, the LTE base station with the frequency band of 1.4G, the Sat-IP gateway and the transcoding server are all arranged in a cabinet at one end of the leaky cable; the satellite signal access subsystem receives satellite signals, and after satellite signals are processed through a Sat-IP gateway and a transcoding server, compressed television program IP data streams are accessed to the input end of an LTE (Long term evolution) base station through an exchanger; for the satellite communication signals, IP data output by the satellite modem is also accessed to the input end of the LTE base station through the switch; the LTE radio frequency signal output by the LTE base station is accessed to the digital optical fiber relay near-end machine, and after the LTE radio frequency signal is converted into an optical signal, the optical signal is respectively accessed to 3 digital optical fiber relay far-end machines through optical fiber remote.
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| CN112822733B (en) * | 2020-12-31 | 2023-08-01 | 上海擎昆信息科技有限公司 | Network access method, user equipment and storage medium for tunnels along line |
| CN113099190B (en) * | 2021-05-12 | 2022-04-08 | 华中科技大学 | IP service convergence communication system and communication method based on DTMB and communication-in-motion |
| CN114111895A (en) * | 2021-11-12 | 2022-03-01 | 中国电子科技集团公司第二十九研究所 | Device and method for sharing electronic instrument |
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