CN113381801B

CN113381801B - GMR-1-based signaling setting method for narrow-band communication system of low-orbit satellite

Info

Publication number: CN113381801B
Application number: CN202110715505.6A
Authority: CN
Inventors: 丁亚南; 鲍峰; 陆天爱; 刘剑锋
Original assignee: Nanjing Panda Handa Technology Co Ltd
Current assignee: Nanjing Panda Handa Technology Co Ltd
Priority date: 2021-06-28
Filing date: 2021-06-28
Publication date: 2022-06-28
Anticipated expiration: 2041-06-28
Also published as: CN113381801A

Abstract

The invention discloses a GMR-1-based signaling setting method for a low-orbit satellite narrow-band communication system, which redefines a service channel burst format and a channel associated link control signaling aiming at the channel associated signaling in a service channel, sets an enhanced service channel burst format and an enhanced channel associated control signaling, and is used for adjusting and continuously switching the time-frequency offset of a link in real time so as to deal with the changed link characteristics. While the service data is loaded, the channel associated control coding data is added to transmit the real-time link control information, and simultaneously, the unique word in the GMR-1 is replaced by the synchronous code with longer length; in addition, on the time slot of the service channel, switching access burst is added; the link control command LCC has a fixed length of 32 bits, and comprises an LCC type of 3 bits and an LCC content of 29 bits. The invention can adjust and continuously switch the time frequency offset of the link in real time so as to deal with the link characteristics which change rapidly.

Description

GMR-1-based signaling setting method for narrow-band communication system of low-orbit satellite

Technical Field

The invention belongs to the technical field of low-orbit narrow-band communication systems, and particularly relates to a GMR-1-based signaling setting method for a low-orbit satellite narrow-band communication system.

Background

The low-orbit narrow-band satellite communication system is a satellite communication system for forwarding signals through a low-orbit constellation, is different from a broadband satellite communication system, and a user link of the low-orbit narrow-band satellite communication system mainly works in an L, S frequency band and can support a miniaturized portable terminal. Currently, low orbit constellation satellite communication systems built in the world mainly include Iridium, GlobalStar and the like, and China mainly includes systems such as rainbow clouds and swan gooses. Generally, a low orbit constellation satellite communication system is composed of three parts, i.e., a low orbit constellation, a gateway station, and a user terminal, as shown in fig. 1, (1) the low orbit constellation: the low orbit constellation is composed of a plurality of LEO satellites distributed on the same orbit at different heights, each satellite realizes efficient utilization of user link spectrum resources through multi-beam, all satellites in the constellation are interconnected through inter-satellite links, and the satellites are responsible for maintaining inter-satellite links among themselves and feeder links among gateway stations and system control sections, as shown in fig. 2. (2) A gateway station: the gateway station is used as an important component of the low-earth constellation satellite communication system, completes the functions of satellite load management, service processing, network management, operation management, service settlement and the like of the low-earth constellation satellite communication system, and is also responsible for interconnection and intercommunication between the low-earth constellation satellite communication system and ground systems such as PSTN, PLMN and the like. (3) The user terminal: the user terminal is composed of various handheld, portable and vehicle-mounted terminals distributed in the coverage range of the low-orbit constellation wave beam, the terminals are portals and application platforms of a user access low-orbit constellation satellite communication system and are used for establishing data transmission links between the user and the satellite, and each terminal has switching capacity among the wave beams, between the satellites and among the gateways and can provide continuous service for the user.

In order to evaluate the dynamic characteristics of the feed link signals, an iridium satellite constellation satellite system simulation scene is constructed by using the STK, and the dynamic characteristics of the electrical receiving signals are simulated by taking a place in Beijing as reference electricity. 1) Frequency dynamics of the signal: from the simulation of fig. 3 and fig. 4, it can be known that the user link signal doppler is up to 50KHz, the signal change rate is 0.45KHz/s, and the signal has high dynamic characteristics relative to the signal bandwidth adopted by the low-track narrow band. 2) Time delay characteristic of the signal: since the constellation satellite moves at a high speed relative to the ground, the dynamic characteristic of the signal frequency of the user link is introduced, and the change of the propagation delay of the user link is caused at the same time, and a simulation diagram of the change of the delay of the feeder link when the satellite and the gateway station are visible is given in fig. 5. According to the simulation diagram, due to the change of the propagation distance of the feeder link introduced by the motion of the constellation satellite relative to the gateway station, the propagation delay of the user link is regularly changed within the range of 2.6-8.6 ms, and the estimated maximum time change rate is 0.025 ms/s. From analyzing the time delay and frequency variation of the user link, in the terminal communication process, the uplink timing and frequency of the terminal need to be continuously adjusted to ensure synchronization with the network side.

GMR-1 is a narrow-band GSO satellite mobile communication standard established by ETSI, and the working frequency band is L/S. The standard is derived from the 3GPP series terrestrial digital cellular standard GSM and supports access to the GSM/UMTS core network. ACeS, SkyTerra, TerreStar, and Thuraya all use GMR-1 series standards. The GMR-1 system is composed of elements such as a satellite, an Earth mobile station MES (Mobile Earth station), a gateway station GS (gateway station) and a satellite operation center SOC (satellite operation center), and the GMR-1 system provides GSM basic services such as voice, data transmission, fax, point-to-point short message service, and cell broadcast short message service and value-added service between a mobile user and a fixed user. Worldwide interconnections are possible with GMR-1 systems via public and private switched telecommunications networks such as the Public Switched Telephone Network (PSTN), the Public Land Mobile Network (PLMN), and a block diagram of the elements of the GMR-1 system is shown in fig. 6. GMR-1 defines three traffic channels and associated dedicated control channels as shown in table 1. The special control channel is not only used for service management and control signaling transmission such as service establishment and release, but also used for signaling transmission such as time frequency offset adjustment, switching and service control in the service process, in the service communication process, FACCH is realized by occupying time slot resources of the service channel, which often has certain influence on service transmission, SACCH is realized by the service channel along the way, the rate is low, and in GMR-1 standard, bits coded by SACCH are transmitted by 20 continuous service channels.

TABLE 1 GMR-1 traffic channel and dedicated control channel definitions

In an actual system, a Gateway Station (GS) continuously measures time-frequency offset information of a user terminal (user terminal) uplink service channel, and when the offset reaches a certain threshold, a time-frequency offset adjustment instruction is immediately sent to a terminal through a channel associated channel FACCH, and the instruction adjustment is gradual, so that the time-frequency offset of terminal uplink sending can be ensured to be in a receiving window of the gateway station through gradual adjustment of a plurality of continuous frames.

In a low-orbit satellite communication system, a terminal is rapidly switched in different beams of the same satellite and among different satellites due to the high-speed movement of a low orbit relative to the ground, and the GMR-1 standard facing the GSO satellite mobile communication cannot meet the requirement of the rapid switching of the low-orbit satellite communication system.

In a low-earth satellite communication system, because a low earth moves at a high speed relative to the ground, in a service communication process, the time-frequency bias change rate of a satellite-ground transmission link is high, a user service channel is switched continuously, a certain control signaling needs to be transmitted in order to deal with the problems of high dynamic link change and service channel switching, and the GMR-1 standard facing the GSO satellite mobile communication cannot meet the transmission control requirement of the low earth service channel.

Disclosure of Invention

The invention aims to provide a GMR-1-based low-orbit satellite narrow-band communication system signaling transmission method,

the technical solution for realizing the purpose of the invention is as follows: a GMR-1-based signaling setting method for a low-orbit satellite narrow-band communication system is characterized in that redefinition is carried out on a service channel burst format and a channel associated link control signaling aiming at a channel associated signaling in a service channel, and an enhanced service channel burst format and an enhanced channel associated control signaling are set and used for adjusting and continuously switching the time frequency offset of a link in real time so as to deal with the changed link characteristics.

Further, an enhanced traffic channel burst format is set, specifically:

while the service data is loaded, the channel associated control coding data is added to transmit the real-time link control information, and simultaneously, the unique word in the GMR-1 is replaced by the synchronous code with longer length; in addition, a handover access burst is added on the traffic channel slot.

Further, an enhanced associated control signaling is set, which specifically includes:

the Link Control Command (LCC) is a channel associated control signaling channel, shares time-frequency resources with a service channel, and is positioned in front of service coding information; the link control command has a fixed length of 32 bits, and comprises an LCC type of 3 bits and an LCC content of 29 bits, wherein the LCC type comprises synchronization, position, measurement and handover, 0 represents a synchronization command, 1 represents terminal position information, 2 represents terminal measurement signaling, 3 represents a handover command, 4 represents handover access, and 5 represents handover completion.

Further, when the LCC is a synchronous command, the field definitions of the LCC contents are as shown in table 1:

TABLE 1 LCC Sync Command content

Parameter(s)	Number of bits	Function(s)
			Status	1	Synchronous state, 0 for synchronized and 1 for unsynchronized
Time Offset
		14	In the service process, the timing deviation of the uplink channel
Frequece Offset
		12	In the service process, the frequency deviation of the uplink channel
Reserved				2	Retention

The synchronous command is used for adjusting uplink sending timing and frequency by the terminal, the network measures according to the uplink transmission burst signal of the terminal, when the frequency deviation reaches a set threshold value when the terminal is in uplink, the network sends the synchronous command to the terminal, reports the current uplink synchronous state and the time frequency deviation of the terminal, and can also respond to a switching access command sent by the terminal in uplink; the command is only a downlink associated channel.

Further, when the LCC is the terminal location information, the definition of each field of the LCC content is shown in table 2:

TABLE 2 LCC location information content

Parameter(s)	Number of bits	Function(s)
			Relative Latitude	13	Difference between terminal relative latitude and common reference point
Relative Longitude	14	Difference between terminal relative longitude, and common reference point
			Reserved	2	Retention

The terminal position information command is used for the terminal to report the latitude and longitude information of the terminal at regular time, and the network makes a switching decision according to the terminal position information; the command is only an uplink associated channel, and the terminal acquires positioning information according to the GPS or the Beidou and reports the positioning information to the network after compression.

Further, when the LCC is a handover command, the field definitions of the LCC contents are shown in table 3:

TABLE 3 LCC Handover Command content

Parameter(s)	Number of bits	Function(s)
			TX Time Slot	5	Transmission timeslot numbering
TX ARFCN	8	Transmitting carrier frequency number
			RX Time Slot	5	Receiving time slot numbering
RX ARFCN	8	Receiving carrier frequency number
			Reserved	3	Retention

The switching command is that the network initiates a switching control instruction to the terminal, and the terminal switches to the related channel of the next beam or another channel of the same beam according to the switching command.

Further, when the LCC is switched access, the field definitions of the LCC contents are shown in table 4:

TABLE 4 LCC handover Access content

Parameter(s)	Number of bits	Function(s)
			Retry Counter	5	Number of handover access retries
S-RNTI	20	Terminal access network communication identifier
			RRC Establishment Cause	4	Reason for connection establishment

The switching access instruction is used for dealing with an asynchronous switching scene, a terminal uplink cannot keep synchronization with a gateway station, and the signaling adopts a burst structure the same as a random access burst and occupies an uplink service time slot; the signaling is only uplink signaling.

Further, when the LCC is switched, the LCC has no content; the switching command is completed by the terminal notifying the network that the switching is completed, and the terminal sends the switching completion command on the switched channel.

Compared with the prior art, the invention has the following remarkable advantages: (1) the capacity of channel associated signaling in a service channel in the GMR-1 standard is enhanced, and redefinition is carried out on a service channel burst format and channel associated link control signaling, so that the time-frequency offset of a link can be adjusted and continuously switched in real time to deal with the characteristics of the link which changes rapidly; (2) an enhanced channel associated channel signaling mechanism is adopted, and the signaling transmission problem is solved through channel associated transmission synchronization, switching, position and other information.

Drawings

Fig. 1 is a schematic diagram of a low earth orbit constellation satellite communication system.

Fig. 2 is a diagram of a low-orbit constellation.

Fig. 3 is a diagram illustrating doppler shift of a subscriber link signal in beijing.

Fig. 4 is a diagram illustrating the change rate of the doppler shift of the user link signal in beijing.

Fig. 5 is a graph of the variation of the propagation distance of the user link in beijing.

FIG. 6 is a schematic diagram of the composition of a GMR-1 system.

Fig. 7 is a diagram of a TCH3 burst structure.

Fig. 8 is a diagram of an enhanced channel burst structure in a high dynamic environment.

Fig. 9 is a diagram of a handover access burst structure.

Detailed Description

At present, the industry does not make a narrow-band satellite mobile communication protocol standard meeting the LEO link requirements, and the Iridium satellite is adaptively modified to adapt to the link characteristics of low-earth-orbit users on the basis of a ground mobile communication protocol standard GSM, so as to finally form a communication system meeting the Iridium satellite link requirements. The invention designs a signaling design mode meeting the communication link characteristics of the low earth orbit satellite based on GMR-1.

The invention relates to a GMR-1-based low-orbit satellite narrow-band communication system signaling setting method, which is used for redefining a service channel burst format and a channel associated link control signaling aiming at the channel associated signaling in a service channel, and setting an enhanced service channel burst format and an enhanced channel associated control signaling for adjusting and continuously switching the time frequency offset of a link in real time so as to cope with the changed link characteristics.

Further, an enhanced traffic channel burst format is set, specifically:

while the service data is loaded, the channel associated control coding data is added to transmit the real-time link control information, and simultaneously the unique word in the GMR-1 is replaced by a synchronization code with longer length; in addition, a handover access burst is added on the traffic channel slot.

Further, an enhanced associated control signaling is set, specifically as follows:

the link control command, namely LCC, is a channel associated control signaling channel, shares time-frequency resources with a service channel and is positioned in front of service coding information; the link control command has a fixed length of 32 bits, and comprises an LCC type of 3 bits and an LCC content of 29 bits, wherein the LCC type comprises synchronization, position, measurement and switching, wherein 0 represents a synchronization command, 1 represents terminal position information, 2 represents terminal measurement signaling, 3 represents a switching command, 4 represents switching access, and 5 represents switching completion.

Further, when the LCC is a synchronous command, the field definitions of the LCC contents are shown in table 1:

TABLE 1 LCC Sync Command content

The synchronous command is used for adjusting uplink sending timing and frequency by the terminal, the network measures according to the uplink sending burst signal of the terminal, when the frequency deviation reaches a set threshold value when the terminal is in uplink, the network sends the synchronous command to the terminal, reports the current uplink synchronous state and the time frequency deviation of the terminal, and can also respond to a switching access command sent by the terminal in uplink; the command is only the downlink associated channel.

TABLE 2 LCC location information content

Further, when the LCC is a handover command, the definition of each field of the LCC content is shown in table 3:

TABLE 3 LCC Handover Command content

Parameter(s)	Number of bits	Function(s)
			TXTime Slot	5	Transmission timeslot numbering
TX ARFCN	8	Sending carrier frequency numbers
			RX Time Slot	5	Receive timeslot numbering
RX ARFCN	8	Receiving carrier frequency number
			Reserved	3	Retention

TABLE 4 LCC handover Access content

The present invention will be described in further detail with reference to specific examples.

Examples

In the GMR-1 standard, considering that the power of the channel may change greatly due to the change of the occlusion and the pointing direction of the handheld terminal, the power control bit associated with the channel is added to the traffic channel designs such as TCH3, TCH6 and TCH9 to control the channel transmit-receive gain in real time, thereby implementing link adaptation. The change of the link time frequency offset can only be adjusted through a special control channel FACCH corresponding to a service channel, and when the change of the link time frequency offset of the GSO is small, the influence of occupying service channel resources on the service channel is small.

However, when the link changes greatly, such as in a low-track communication system, it is clear that GMR-1 is not designed to meet the application requirements due to the continuous adjustment required to meet the traffic channel conditions. Therefore, the invention enhances the capability of channel associated signaling in the traffic channel in GMR-1 standard, redefines the traffic channel burst format and the channel associated link control signaling (LCC), and can adjust and continuously switch the time-frequency offset of the link in real time to deal with the rapidly changing link characteristics, as follows

(1) Enhanced traffic channel burst format

Taking TCH3 as an example here, the burst format definition of TCH3 in the GMR-1 standard is shown in fig. 7.

The burst format of the fast associated channel FACCH3 corresponding to the TCH3 channel is consistent with the burst structure of the TCH3, and it can be seen that the unique word with basic synchronization capability only occupies 5% of load, and the synchronization performance of the unique word is far lower than that of a synchronization code, and for this reason, the channel burst structure needs to be redesigned for a high dynamic environment, as shown in fig. 8. While carrying the service data, adding the channel associated control coding data to transmit the real-time link control information, and simultaneously replacing the unique word in the GMR-1 with a synchronization code with a longer length.

In some scenarios, such as inter-satellite handover, there may be uplink non-synchronization situations, and to cope with this situation, a handover access burst is added over the traffic channel time slot, similar to the random access burst in GMR-1, as shown in fig. 9.

(2) Enhanced associated control signaling

A Link Control Command (LCC) is a channel associated Control signaling channel, and shares a time frequency resource with a traffic channel, and is located before the traffic coding information. The link control command has a fixed length of 32 bits, and includes two parts including a LCC type of 3 bits, a LCC content of 29 bits, and the like, where the LCC type includes synchronization, location, measurement, handover, and the like, where 0 represents a synchronization command, 1 represents terminal location information, 2 represents terminal measurement signaling, 3 represents a handover command, 4 represents handover access, and 5 represents handover completion.

When the LCC is a synchronous command, the LCC content fields are defined as shown in the following table. The synchronous command is mainly used for adjusting uplink sending timing and frequency by the terminal, the network measures according to the uplink sending burst signal of the terminal, when the frequency deviation reaches a certain threshold value when the terminal is in uplink, the synchronous command is sent to the terminal, the current uplink synchronous state and the time frequency deviation of the terminal are reported, and the synchronous command can also respond to a switching access command sent by the terminal in uplink. The command is only a downlink associated channel.

TABLE 1.1 LCC Sync Command content

Parameter(s)	Number of bits	Function(s)	Remarks for note
				Status	1	Synchronous state, 0 for synchronized and 1 for unsynchronized
Time Offset	14	In the service process, the timing deviation of the uplink channel
				Frequece Offset	12	In the service process, the frequency deviation of the uplink channel
Reserved	2	Retention

When the LCC is location information, the definition of each field of the LCC content is shown in the following table. The position information command is mainly used for the terminal to report the latitude and longitude information of the terminal at regular time, and the network makes a switching decision according to the position information of the terminal. The command is only an uplink associated channel, and the terminal acquires positioning information according to the GPS or the Beidou and reports the positioning information to the network after compression.

TABLE 1.2 LCC location information content

When the LCC is a handover command, the LCC content fields are defined as shown in the following table. The handover Command (handover Command) is a handover control Command initiated by the network to the terminal, and the terminal is switched to the related channel of the next beam or another channel of the same beam according to the handover Command.

TABLE 1.3 LCC Handover Command content

Parameter(s)	Number of bits	Function(s)	Remarks for note
				TX Time Slot	5	Transmission timeslot numbering
TX ARFCN	8	Sending carrier frequency numbers
				RX TimeSlot
	5	Receiving time slot numbering
				RX ARFCN	8	Receiving carrier frequency number
Reserved	3	Retention

When the LCC is Handover Access (Handover Access), the respective fields of the LCC contents are defined as shown in the following table. The command is mainly used for dealing with asynchronous switching scenes, a terminal uplink cannot keep synchronization with a gateway station, and the signaling adopts a burst structure the same as a random access burst and occupies an uplink service time slot. The signaling is only uplink signaling.

TABLE 1.4 LCC Handover Access content

Parameter(s)	Number of bits	Function(s)	Remarks to note
				Retry Counter	5	Number of handover access retries
S-RNTI	20	Terminal access network communication identification
				RRC Establishment Cause	4	Reason for connection establishment

When the LCC is the switching command, the LCC has no content. The switching command is completed by the terminal notifying the network that the switching is completed, and the terminal sends the switching completion command on the switched channel.

The invention enhances the channel associated signaling capability in the service channel in GMR-1 standard, redefines the service channel burst format and the channel associated link control signaling, and can adjust and continuously switch the time frequency offset of the link in real time to deal with the fast-changing link characteristics.

Claims

1. A GMR-1-based signaling setting method for a narrow-band communication system of a low-orbit satellite is characterized in that a channel associated signaling in a service channel is redefined on a service channel burst format and a channel associated link control signaling, and an enhanced service channel burst format and an enhanced channel associated control signaling are set and used for adjusting and continuously switching a time-frequency offset of a link in real time so as to deal with the changed link characteristics;

setting an enhanced service channel burst format, specifically:

while the service data is loaded, the channel associated control coding data is added to transmit the real-time link control information, and simultaneously the unique word in the GMR-1 is replaced by a synchronization code with longer length; in addition, on the time slot of the service channel, switching access burst is added;

Setting an enhanced associated control signaling, specifically as follows:

the Link Control Command (LCC) is a channel associated control signaling channel, shares time-frequency resources with a service channel, and is positioned in front of service coding information; the link control command has a fixed length of 32 bits, and comprises an LCC type of 3 bits and an LCC content of 29 bits, wherein the LCC type comprises synchronization, position, measurement and switching, wherein 0 represents a synchronization command, 1 represents terminal position information, 2 represents terminal measurement signaling, 3 represents a switching command, 4 represents switching access, and 5 represents switching completion.

2. The GMR-1 based signaling setup method for the narrow band communication system of the low earth orbit satellite according to claim 1, wherein when the LCC is the synchronization command, the LCC content fields are defined as shown in Table 1:

TABLE 1 LCC Sync Command content

3. The GMR-1 based signaling setting method for the low earth orbit satellite narrow-band communication system of claim 1, wherein when LCC is terminal location information, the LCC content fields are defined as shown in Table 2:

TABLE 2 LCC location information content

The terminal position information command is used for regularly reporting the latitude and longitude information of the terminal by the terminal, and the network makes a switching decision according to the terminal position information; the command is only an uplink associated channel, and the terminal acquires positioning information according to the GPS or the Beidou and reports the positioning information to the network after compression.

4. The GMR-1 based signaling setup method for the narrow band communication system of the low earth orbit satellite according to claim 1, wherein when the LCC is a handover command, the LCC content fields are defined as shown in Table 3:

TABLE 3 LCC Handover Command content

5. The GMR-1 based signaling setup method for low earth orbit satellite narrow band communication system according to claim 1, wherein when LCC is switched access, the LCC content fields are defined as shown in Table 4:

TABLE 4 LCC handover Access content

6. The GMR-1 based low earth orbit satellite narrowband communication system signaling setup method of claim 1, wherein when the LCC is handover complete, the LCC has no content; the switching command is completed by the terminal notifying the network that the switching is completed, and the terminal sends a switching completion command on the switched channel.