CN116015412A - Discontinuous communication method of satellite mobile communication system - Google Patents
Discontinuous communication method of satellite mobile communication system Download PDFInfo
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Abstract
The invention discloses a discontinuous communication method of a satellite mobile communication system, which comprises the following steps: in a satellite mobile communication system based on GMR-1 standard, DKAB burst format and transmission mode are improved, and time-frequency synchronization between a terminal and a network is realized by utilizing unique words borne by DKAB and the phase difference of two KAB bursts; the voice activation control mechanism between the terminal and the network is designed to realize the voice activation control process including the voice activation control under the same network in the inactive state, the voice activation control from other networks to the satellite network in the inactive state, and the voice activation control process from the satellite network to other networks in the inactive state. When the signal-to-noise ratio of the link is low, the invention can utilize the improved DKAB channel to maintain the synchronization with the satellite network, thereby solving the problem that the DKAB is difficult to maintain the communication link for a long time.
Description
Technical Field
The invention relates to the technical field of satellite mobile communication systems, in particular to a discontinuous communication method of a satellite mobile communication system.
Background
The satellite mobile communication system is used as extension and supplement of ground cellular mobile communication, is mainly used for communication and emergency communication in remote areas, and well solves the problem that the coverage capability of the ground cellular mobile communication system in remote areas and sea areas is limited. In general, a typical satellite mobile communication system is composed of GEO/LEO satellites, satellite terminals/mobile earth stations, gateway stations GW, and operation control systems, and can provide services such as in-network telephone, short message, internet surfing, fax, etc. for users, and through interconnection with PSTN, PLMN, internet, global service interconnection is realized. Figure 1 shows a block diagram of the elements of a satellite mobile communication system based on the GMR-1 standard.
Generally, 60% of the time is in a voice silence state during a call, if only a small amount of information such as background noise characteristics and power control information is transmitted in the voice silence state, not only interference between co-frequency beams is reduced, but also system power is greatly saved, and the concurrency number of system users is improved.
In GMR-1 communication standard, the system also adopts a similar technology, when the party in conversation is in silence state, after the voice codec detects silence state, the network is notified to enter discontinuous transmission mode through fast feedback signaling, and silence frame SID is sent, however, due to the difference of transmission link condition with ground mobile communication, satellite terminal still needs to send DKAB burst per frame to maintain link synchronization between terminal and network. In order to reduce the transmitting power, DKAB carries a small amount of bit information such as background noise and power control, a double keep-alive burst design is adopted, the two keep-alive bursts are included, the interval between the bursts is about half of the burst length, the two bursts respectively carry N bits of power control and background noise characteristic information, and because DKAB only carries a small amount of data symbols, the accuracy of timing estimation is poor, especially when Es/N0 is smaller than 0.5 dB. Furthermore, only the air interface standard is given in the GMR-1 standard, and how the network side implements the voice activation scheme is not given.
In a satellite mobile communication system based on GMR-1 standard, the accuracy of timing estimation is poor because DKAB carries a small number of data symbols, especially when Es/N0 is less than 0.5dB, it is difficult for a user to track the satellite network using DKAB. In addition, users silence for a long time during communication, and it is difficult to maintain a communication link using DKAB bursts, and practical tests have found that the communication link can be maintained only when 16% and 84% of the probability of DACCH and DKAB occurring during communication. Therefore, there is a need to further improve DKAB synchronization performance.
Disclosure of Invention
The invention aims to provide a discontinuous communication method of a satellite mobile communication system, which can utilize a DKAB tracking satellite network and has good DKAB synchronization performance when the symbol signal-to-noise ratio is low.
The technical solution for realizing the purpose of the invention is as follows: a discontinuous communication method of a satellite mobile communication system, comprising the steps of:
step 1, performing discontinuous transmission by using an improved discontinuous transmission method;
step 2, synchronizing DKAB channel time and frequency;
and 3, performing voice activation control between the terminal and the network.
Compared with the prior art, the invention has the remarkable advantages that: (1) The method solves the problem that the DKAB can not maintain the communication link for a long time in the communication process of a user because the system power is not increased, and solves the control process under the voice activation of the satellite network; (2) The existing DKAB burst format is improved, background noise characteristic information carried by the DKAB is transmitted periodically by the NT3 channel, the DKAB channel only carries unique words and power control information, the sliding correlation technology based on the unique words is adopted to obtain accurate timing, the phase difference of two KAB bursts is used for calculating frequency offset on the basis, the DKAB can be used for tracking a satellite network when the signal-to-noise ratio of symbols is low, and the DKAB synchronization performance is good.
Drawings
Fig. 1 is a schematic diagram of a typical satellite communication system network.
Fig. 2 is a flow chart of a discontinuous communication method of a satellite mobile communication system according to the present invention.
Fig. 3 is a schematic diagram of the structure of the DKAB burst format in the present invention.
Fig. 4 is a schematic diagram of a structure of a terminal receiving window in the present invention.
Fig. 5 is a schematic flow chart of a voice activation control process in the same network in an inactive state in the present invention.
Fig. 6 is a flow chart of the satellite network to other network voice activation control process in the inactive state of the present invention.
Fig. 7 is a flow chart of the other network to satellite network voice activation control process in the inactive state of the present invention.
Detailed Description
Referring to fig. 2, the discontinuous communication method of the satellite mobile communication system of the present invention comprises the following steps:
step 1, performing discontinuous transmission by using an improved discontinuous transmission method;
step 2, synchronizing DKAB channel time and frequency;
and 3, performing voice activation control between the terminal and the network.
As a specific example, the improved discontinuous transmission method described in step 1 is specifically as follows:
in a satellite mobile communication system based on the GMR-1 standard, background noise characteristic information carried by a DKAB is transmitted periodically by a NT3 channel, and the DKAB channel only carries unique words and power control information.
As a specific example, the discontinuous transmission is performed by using the improved discontinuous transmission method described in step 1, specifically as follows:
step 1.1, when a voice coder/decoder continuously detects that n frames of voice data are background noise, if n is more than or equal to 4, generating SID_first normal voice frames, wherein the voice frames bear normal voice coding data;
step 1.2, after a sender detects an SID_first voice frame, entering a discontinuous transmission stage, carrying the SID_first voice frame by using a normal DTCH channel, generating a DKAB burst according to a p value allocated to a user by a gateway station, and scheduling the DTCH channel of the discontinuous transmission stage;
step 1.3, the voice coder-decoder generates a SID_UPDATE frame carrying background noise characteristic information in the n+1st frame or each DTCH period, and gives the SID_first frame to a transmitting end; the voice coder-decoder generates a occupying data packet to be processed by a transmitting end in other frame periods of a discontinuous transmission stage;
step 1.4, the sender performs different treatments according to the voice frame type, when the voice frame is a SID_UPDATE frame, the sender waits for DTCH channel time of discontinuous transmission stage to send the SID_UPDATE frame; immediately generating a DKAB burst after the voice frame is a space occupying data packet, wherein the first KAB of the DKAB burst is filled with 8-bit unique words, and the second KAB is filled with 8-bit power control words;
and 1.5, when the voice coder and decoder detects that the voice data arrives, generating a real voice data SPEECH frame, and delivering the real voice data SPEECH frame to a transmitting end, wherein the transmitting end carries the SPEECH data on a DTCH channel.
As a specific example, the period T of the DTCH channel in step 1.2 DTCH Set to an integer multiple of the p maximum length in DKAB, the Interval KAB Interval between bursts in step 1.4 is half the length of the DKAB burst.
As a specific example, the DKAB channel time and frequency synchronization described in step 2 is specifically as follows:
the accurate timing is obtained by adopting a sliding correlation technique based on unique words, and the frequency offset is calculated by utilizing the phase difference of two KAB bursts on the basis.
As a specific example, the DKAB channel time and frequency synchronization described in step 2 includes the following steps:
step 2.1, in the set receiving window { RxWin ] Start ,RxWin End Sliding correlation is carried out on the internal unique word sequence stored locally, and IFFT operation is carried out after 0 is complemented on the local unique word sequence;
step 2.2, respectively performing sliding correlation with the down-sampled signals, wherein the position of the maximum value of the correlation peak is the initial coarse synchronization position;
the modulus square formula of the cross-correlation function is:
wherein s is * (N) represents a conjugate operation, N FFT Representing the number of sampling points, r (n) representing the downsampled signal in the receive window, s (n) being the locally stored unique word signal, d being the starting instant;
performing a correlation operation at each moment to obtain a coarse synchronization position
The method comprises the following steps:
step 2.3, the system is according to
Adjusting system timing, and locating the position of the first KAB according to p;
and 2.4, because the two KABs adopt a differential modulation mode, estimating frequency offset by calculating the phase difference of the two KAB bursts, and synchronizing the time and the frequency of the DKAB channel according to the frequency offset.
As a specific example, the voice activation control between the terminal and the network in step 3 includes a voice activation control procedure in the same network in the inactive state, a voice activation control procedure from other networks to the satellite network in the inactive state, and a voice activation control procedure from the satellite network to other networks in the inactive state.
As a specific example, the voice activation control process under the same network in the inactive state includes the following steps:
step 3.1.1, the calling and called satellite terminals allocate p values for forming DKAB burst and DTCH transmission during voice activation to the terminals by the gateway station during the calling process;
step 3.1.2, the voice coder-decoder of the calling terminal detects that continuous n frames are monitored to be in a non-voice activation state, if n is more than or equal to 4, a discontinuous transmission stage is started in an n+1st frame, an effective voice frame SID_first is generated and is sent to a gateway station through a physical layer DTCH channel, meanwhile, the calling terminal enters a discontinuous transmission state, and the voice coder-decoder generates background noise bits to wait for transmission;
step 3.1.3, after receiving the voice frame, the core network media gateway of the gateway station confirms that the terminal enters a voice activation state, and forwards the SID_first voice frame to the called terminal, and the core network sets the calling terminal in a silence stage;
step 3.1.4, after receiving SID_first, the called terminal enters a continuous receiving DKAB state, waits for receiving DKAB burst of each frame, and continuously adjusts time and frequency in the process of receiving the burst;
step 3.1.5, the calling terminal continuously transmits DKAB burst, the gateway station access network generates a occupied bit data packet after receiving DKAB burst, and transmits the occupied bit data packet to the core network, and a voice data channel between the core network and the access network of the calling user is maintained; the core network forwards the data to the access network where the called user is located, and the access network generates DKAB burst after receiving the occupying data packet and sends the DKAB burst to the called user so as to maintain a downlink channel from the access network to the called user;
step 3.1.6, when the DTCH channel sending time of the calling terminal arrives, the generated SID_UPDATE used for bearing the background noise characteristic bit is sent to the gateway station through the DTCH channel, after the gateway station core network media gateway receives the SID_UPDATE frame, the SID_UPDATE frame is forwarded to the access network where the called terminal is located, and the access network packages the SID_UPDATE voice frame into a DTCH burst and sends the DTCH burst;
and 3.1.7, in the discontinuous transmission stage, when the calling terminal suddenly detects the voice of the user in a certain frame, interrupting the discontinuous transmission process and entering a voice activation state, and immediately transmitting the valid voice frame data to the gateway station through a service channel DTCH in the frame.
As a specific example, the other network-to-satellite network voice activation control procedure in the inactive state includes the following steps:
step 3.2.1, during the calling process, the gateway station allocates a p value for forming DKAB burst and DTCH transmission during voice activation for the satellite terminal;
step 3.2.2, the continuous n frames of the satellite terminal voice coder/decoder are monitored to be in a non-voice activated state, if n is more than or equal to 4, a discontinuous transmission stage is started in the n+1st frame, an effective voice frame SID_first is generated and is sent to a gateway station through a physical layer DTCH channel, meanwhile, the satellite terminal enters a discontinuous transmission state, and the voice coder/decoder generates background noise bits to wait for transmission;
step 3.2.3, after the core network media gateway of the gateway station receives the voice frame, confirming that the terminal enters a voice activation state, encoding the SID_first voice frame into silence voice data of other networks and forwarding the silence voice data, wherein the core network sets the satellite terminal in a silence stage;
step 3.2.4, the satellite terminal continuously transmits DKAB burst, the gateway station access network generates a occupied bit data packet after receiving the DKAB burst and transmits the occupied bit data packet to the core network, a voice data channel between the core network and the access network of a calling user is maintained, and the core network transmits silence voice data generated last time;
3.2.5, when the DTCH channel sending time of the satellite terminal comes, sending the generated SID_UPDATE for bearing the background noise characteristic bits to a gateway station through the DTCH channel, and after the gateway station core network media gateway receives the SID_UPDATE frame, updating and forwarding the silence voice data according to the background noise characteristic parameters in the SID_UPDATE frame;
and 3.2.6, in the discontinuous transmission stage, when the calling terminal suddenly detects the voice of the user in a certain frame, interrupting the discontinuous transmission process and entering a voice activation state, and when the frame immediately transmits the valid voice frame data to the gateway station through a service channel DTCH channel, the gateway station codes the voice data of the satellite terminal into voice frames recognizable by other networks.
As a specific example, the satellite network to other network voice activation control process in the inactive state includes the following steps:
step 3.3.1, when the core network media gateway monitors that voice frames sent by other network users are in a non-voice activation state through continuous n frames of a voice coder-decoder, starting a discontinuous transmission stage at an n+1st frame, generating an effective voice frame SID_first and forwarding the effective voice frame SID_first to an access network;
step 3.3.2, after receiving the SID_first frame, the access network immediately transmits the SID_first frame to the satellite terminal through a physical layer DTCH channel, and simultaneously enters a discontinuous transmission state;
step 3.3.3, the core network media gateway generates SID_UPDATE through the voice coder-decoder in the next frame, and waits for the sending time of the DTCH after the access network detects the voice frame through forwarding the access network where the satellite terminal is located;
step 3.3.4, the core network media gateway continuously detects voice frames sent by other network users through a voice coder-decoder, generates occupied data packets and sends the occupied data packets to the access network, and the access network generates DKAB bursts and sends the DKAB bursts after detecting the occupied data packets;
step 3.3.5, the core network media gateway generates background noise characteristics once every SID_UPDATE period and forms SID_UPDATE, and forwards the SID_UPDATE to the access network, and the access network transmits the SID_UPDATE when the transmission opportunity of the DTCH arrives;
and 3.3.6, after detecting that the speech frames of other network users contain speaking voices, the core network media gateway enters a voice activation state, generates normal speech frames and forwards the normal speech frames to the access network, and the access network immediately forwards the normal speech frames to the users through a DTCH channel.
The invention will be described in further detail with reference to the drawings and the specific examples.
Examples
1. Improved discontinuous transmission procedure
In a satellite mobile communication system based on the GMR-1 standard, since DKAB carries a small number of data symbols per frame, if background noise characteristic information bits are transmitted through DKAB, the transmission time is about 1.04s, and if the frame length is 40ms, 26 frames are required to transmit a complete SID information frame, which indicates that the SID frame has low real-time requirements. Because DKAB bears a small amount of data symbols, when the signal-to-noise ratio is low (Es/N0 is smaller than 0.5 dB), the accuracy of timing estimation is poor, and the network is still required to continuously adjust the uplink timing of the satellite terminal through DACCH channel closed loop.
Therefore, in order to keep the communication link between the satellite terminal and the network synchronous during voice activation, reduce the frequency of closed loop time-frequency adjustment of the system and improve the reliability of silence frame transmission, the invention transmits the background noise characteristic information carried by DKAB to the NT3 channel for periodic transmission, and the DKAB channel only carries unique words and power control information.
In this embodiment, background noise characteristic information carried by DKAB is sent to NT3 channel for periodic transmission, and DKAB channel only carries unique words and power control information, and meanwhile, the improved discontinuous transmission process is shown in fig. 2, which specifically includes the following steps:
(1) When the voice coder-decoder continuously detects that n frames (n is more than or equal to 4) of voice data are background noise, immediately generating SID_first normal voice frames, wherein the voice frames bear normal voice coding data;
(2) After detecting the SID_first voice frame, the transmitting end enters a discontinuous transmission stage, and utilizes a normal DTCH channel to bear the SID_first voice frame, and simultaneously generates a DKAB burst according to a p value distributed by a gateway station for a user, and schedules the DTCH channel in the discontinuous transmission stage;
(3) The voice coder-decoder generates a SID_UPDATE frame carrying background noise characteristic information in the n+1st frame or each DTCH period, and gives the SID_UPDATE frame to a transmitting end in the SID_first frame; the voice coder-decoder generates a occupying data packet to be processed by a transmitting end in other frame periods of a discontinuous transmission stage;
(4) The transmitting end performs different treatments according to the voice frame type, and when the voice frame is an SID_UPDATE frame, the transmitting end waits for DTCH channel time of a discontinuous transmission stage to transmit the SID_UPDATE frame; immediately after the voice frame is a placeholder packet, a DKAB burst is generated, as shown in fig. 3, with the first KAB of the DKAB burst filling the 8-bit unique word and the second KAB filling the 8-bit power control word.
(5) The SPEECH codec, upon detecting the arrival of SPEECH data, immediately generates a SPEECH frame of real SPEECH data and delivers the SPEECH frame to the transmitting end, which carries the SPEECH data on the DTCH channel.
In general, the DTCH period T DTCH Is set as an integer multiple of the p maximum length in DKAB, and is found by test that when T DTCH When the signal is 2*p, the timeliness of the transmission of background noise information can be ensured, the downlink transmission times of the DACCH can be reduced while the stability of a communication link is maintained, and the power of the signal is obviously superior to that of a burst format adopting GMR-1. The Interval between bursts (KAB Interval) is about half of the DKAB burst length, and the two KAB burst length determines the accuracy of the frequency error estimation, and if the KAB burst distance is insufficient, ambiguity in the phase difference estimation may occur.
2. DKAB channel time and frequency synchronization procedure
In a certain receiving window { RxWin } start ,RxWin End Sliding correlations with the locally stored unique word sequence within the window, as shown in fig. 4, p is the window's most intermediate position.
Firstly, the local unique word sequence is subjected to IFFT operation after being complemented with 0, and then the local unique word sequence is respectively subjected to sliding correlation with the downsampled signals, wherein the position of the maximum value of the correlation peak is the initial coarse synchronization position. The modulus square of the cross-correlation function is given by the following formula.
Wherein s is * (N represents a conjugate operation, N FFT Representing the number of sampling points. r (n represents the downsampled signal in the receive window, s (n is the locally stored unique word signal, d is the starting time, and each time is correlated to obtain the coarse synchronization position)
The method comprises the following steps:
at the same time, the system is according to
The system timing is adjusted and the position of the first KAB is located according to p. Since the two KABs use differential modulation, the frequency offset can be estimated by calculating the phase difference of the two KAB bursts.
3. Voice activation control flow between terminal and network
Because of the difference between the voice activation flow and the voice activation flow of the ground mobile communication, the voice activation control and the voice activation flow of the network side need to be slightly modified, and the voice activation control and the voice activation flow mainly comprise two processes of voice processing under the same network in an inactive state and voice processing under heterogeneous networks in an inactive state. The method comprises the following steps:
(1) Inactive state voice under the same network
1) During the calling process of the calling and called satellite terminals, the gateway station distributes p values for forming DKAB burst and DTCH transmission during voice activation for the terminals;
2) When the continuous n (n is more than or equal to 4) frame monitoring of the calling terminal is in a non-voice activation state, in the non-continuous transmission stage of the n+1st frame, an effective voice frame SID_first is generated and is sent to a gateway station through a physical layer DTCH channel, meanwhile, the calling terminal enters a non-continuous transmission state, and the voice codec generates background noise bits to wait for transmission.
3) After receiving the voice frame, the core network media gateway of the gateway station confirms that the terminal enters a voice activation state and forwards the SID_first voice frame to the called terminal, and the core network sets the calling terminal to be in a silence stage;
4) After receiving the SID_first, the called terminal enters a continuous receiving DKAB state, waits for receiving DKAB burst of each frame, and continuously adjusts time and frequency in the process of receiving the burst;
5) The calling terminal continuously sends DKAB burst, the gateway station access network generates a occupying data packet to be forwarded to the core network after receiving the DKAB burst, and a voice data channel between the core network and the access network of the calling user is maintained. The core network forwards the data to the access network where the called user is located, and the access network generates DKAB burst after receiving the occupying data packet and sends the DKAB burst to the called user so as to maintain a downlink channel from the access network to the called user;
6) When the DTCH channel of the calling terminal sends the time, the generated SID_UPDATE (used for bearing the background noise characteristic bit) is sent to the gateway station through the DTCH channel. After receiving SID_UPDATE frame, media gateway of core network of gateway station forwards the frame to access network where called terminal is located.
7) In the discontinuous transmission stage, when the calling terminal suddenly detects the voice of the user in a certain frame, the discontinuous transmission process is interrupted and the voice activation state is entered, and the effective voice frame data is immediately transmitted to the gateway station through a service channel DTCH channel in the frame.
Fig. 5 is a schematic diagram of a voice interaction process in an inactive state in the same network.
(2) Voice under different networks in inactive state
1) During a call, the gateway station allocates a p value for the satellite terminal for forming a DKAB burst and DTCH transmission during voice activation;
2) The continuous n (n is more than or equal to 4) frame monitoring of the satellite terminal voice coder is in a non-voice activation state, then in the non-continuous transmission stage of the n+1st frame, an effective voice frame SID_first is generated and sent to the gateway station through a physical layer DTCH channel, meanwhile, the satellite terminal enters a non-continuous transmission state, and the voice coder generates background noise bits to wait for transmission.
3) After receiving the voice frame, the core network media gateway of the gateway station confirms that the terminal enters a voice activation state, codes the SID_first voice frame into silence voice data of other networks and forwards the silence voice data, and the core network sets the satellite terminal in a silence stage;
4) The satellite terminal continuously transmits DKAB burst, and the gateway station access network generates a occupied data packet to be forwarded to the core network after receiving the DKAB burst, so as to maintain a voice data channel between the core network and the access network for the calling user. The core network transmits the silence voice data generated last time;
5) When the DTCH channel of the satellite terminal sends the opportunity, the generated SID_UPDATE (used for bearing the background noise characteristic bit) is sent to the gateway station through the DTCH channel. After receiving the SID_UPDATE frame, the gateway station core network media gateway UPDATEs and forwards the silent voice data according to the background noise characteristic parameters in the SID_UPDATE frame;
6) In the discontinuous transmission stage, when the calling terminal suddenly detects the voice of a user in a certain frame, the discontinuous transmission process is interrupted and the voice activation state is entered, and the effective voice frame data is immediately transmitted to the gateway station through a service channel DTCH channel in the frame, and the gateway station encodes the voice data of the satellite terminal into voice frames recognizable by other networks.
Fig. 6 is a flow chart of satellite network terminal to other network voice inactivity processing.
7) When the core network media gateway monitors that voice frames sent by other network users are in a non-voice activation state through continuous n frames of a voice coder/decoder, starting a discontinuous transmission stage at an n+1st frame, generating an effective voice frame SID_first and forwarding the effective voice frame SID_first to an access network;
8) After receiving the SID_first frame, the access network immediately transmits the SID_first frame to the satellite terminal through a physical layer DTCH channel, and simultaneously enters a discontinuous transmission state;
9) The core network media gateway generates SID_UPDATE through a voice coder/decoder in the next frame, and waits for the sending time of the DTCH after the access network detects the voice frame through forwarding the access network where the satellite terminal is located;
10 Then, the core network media gateway continuously detects voice frames sent by other network users through the voice coder-decoder, generates occupied data packets and sends the occupied data packets to the access network, and the access network generates DKAB burst and sends the DKAB burst after detecting the occupied data packets;
11 The core network media gateway generates background noise characteristics once every SID_UPDATE period and forms SID_UPDATE, and forwards the SID_UPDATE to the access network, and the access network sends the SID_UPDATE when the sending time of the DTCH arrives;
12 After detecting that the speech frames of other network users contain speaking voices, the core network media gateway enters a voice activation state, generates normal speech frames and forwards the normal speech frames to the access network, and the access network immediately forwards the normal speech frames to the users through a DTCH channel.
Fig. 7 is a flowchart of the inactive state processing of the other network voice-to-satellite network terminal.
The invention improves the existing DKAB burst format, transmits the background noise characteristic information carried by DKAB to the NT3 channel for periodic transmission, and the DKAB channel only carries unique words and power control information, obtains accurate timing by adopting a sliding correlation technique based on the unique words, and calculates frequency offset by utilizing the phase difference of two KAB bursts on the basis. In addition, because of the difference between the voice activation flow and the voice activation flow of the ground mobile communication, the voice activation control and the voice activation flow of the network side are improved, and the processing procedures of voice under the same network in the inactive state, voice from other networks to the satellite network in the inactive state, satellite network to other networks in the inactive state and the like are provided.
The invention solves the problems that a user is silent for a long time in the communication process and the DKAB can not maintain a communication link for a long time without increasing the system power, and solves the control process under the voice activation of a satellite network.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (10)
1. A method of discontinuous communication in a satellite mobile communication system, comprising the steps of:
step 1, performing discontinuous transmission by using an improved discontinuous transmission method;
step 2, synchronizing DKAB channel time and frequency;
and 3, performing voice activation control between the terminal and the network.
2. The method for discontinuous transmission of a satellite mobile communication system according to claim 1, wherein the improved discontinuous transmission method according to step 1 is specifically as follows:
in a satellite mobile communication system based on the GMR-1 standard, background noise characteristic information carried by a DKAB is transmitted periodically by a NT3 channel, and the DKAB channel only carries unique words and power control information.
3. The method for discontinuous transmission according to claim 2, wherein the discontinuous transmission is performed by using the modified discontinuous transmission method in step 1, specifically comprising the steps of:
step 1.1, when a voice coder/decoder continuously detects that n frames of voice data are background noise, if n is more than or equal to 4, generating SID_first normal voice frames, wherein the voice frames bear normal voice coding data;
step 1.2, after a sender detects an SID_first voice frame, entering a discontinuous transmission stage, carrying the SID_first voice frame by using a normal DTCH channel, generating a DKAB burst according to a p value allocated to a user by a gateway station, and scheduling the DTCH channel of the discontinuous transmission stage;
step 1.3, the voice coder-decoder generates a SID_UPDATE frame carrying background noise characteristic information in the n+1st frame or each DTCH period, and gives the SID_first frame to a transmitting end; the voice coder-decoder generates a occupying data packet to be processed by a transmitting end in other frame periods of a discontinuous transmission stage;
step 1.4, the sender performs different treatments according to the voice frame type, when the voice frame is a SID_UPDATE frame, the sender waits for DTCH channel time of discontinuous transmission stage to send the SID_UPDATE frame; immediately generating a DKAB burst after the voice frame is a space occupying data packet, wherein the first KAB of the DKAB burst is filled with 8-bit unique words, and the second KAB is filled with 8-bit power control words;
and 1.5, when the voice coder and decoder detects that the voice data arrives, generating a real voice data SPEECH frame, and delivering the real voice data SPEECH frame to a transmitting end, wherein the transmitting end carries the SPEECH data on a DTCH channel.
4. A satellite mobile communications system discontinuous communications method according to claim 3 and wherein the period T of the DTCH channel in step 1.2 DTCH Set to an integer multiple of the p maximum length in DKAB, the Interval KAB Interval between bursts in step 1.4 is half the length of the DKAB burst.
5. The discontinuous communication method according to claim 1, wherein the step 2 of performing DKAB channel time and frequency synchronization is specifically as follows:
the accurate timing is obtained by adopting a sliding correlation technique based on unique words, and the frequency offset is calculated by utilizing the phase difference of two KAB bursts on the basis.
6. The discontinuous communication method according to claim 5, wherein the step 2 of performing DKAB channel time and frequency synchronization comprises the steps of:
step 2.1, at the set receptionWindow { RxWin Start ,RxWin End Sliding correlation is carried out on the internal unique word sequence stored locally, and IFFT operation is carried out after 0 is complemented on the local unique word sequence;
step 2.2, respectively performing sliding correlation with the down-sampled signals, wherein the position of the maximum value of the correlation peak is the initial coarse synchronization position;
the modulus square formula of the cross-correlation function is:
wherein s is * (N) represents a conjugate operation, N FFT Representing the number of sampling points, r (n) representing the downsampled signal in the receive window, s (n) being the locally stored unique word signal, d being the starting instant;
performing a correlation operation at each moment to obtain a coarse synchronization position
The method comprises the following steps:
step 2.3, the system is according to
Adjusting system timing, and locating the position of the first KAB according to p;
and 2.4, because the two KABs adopt a differential modulation mode, estimating frequency offset by calculating the phase difference of the two KAB bursts, and synchronizing the time and the frequency of the DKAB channel according to the frequency offset.
7. The method according to claim 1, wherein the voice activation control between the terminal and the network in step 3 includes a voice activation control procedure in the same network in the inactive state, a voice activation control procedure from other networks to the satellite network in the inactive state, and a voice activation control procedure from the satellite network to other networks in the inactive state.
8. The method for discontinuous communication of satellite mobile communication system according to claim 7, wherein said voice activation control process under the same network in the inactive state comprises the steps of:
step 3.1.1, the calling and called satellite terminals allocate p values for forming DKAB burst and DTCH transmission during voice activation to the terminals by the gateway station during the calling process;
step 3.1.2, the voice coder-decoder of the calling terminal detects that continuous n frames are monitored to be in a non-voice activation state, if n is more than or equal to 4, a discontinuous transmission stage is started in an n+1st frame, an effective voice frame SID_first is generated and is sent to a gateway station through a physical layer DTCH channel, meanwhile, the calling terminal enters a discontinuous transmission state, and the voice coder-decoder generates background noise bits to wait for transmission;
step 3.1.3, after receiving the voice frame, the core network media gateway of the gateway station confirms that the terminal enters a voice activation state, and forwards the SID_first voice frame to the called terminal, and the core network sets the calling terminal in a silence stage;
step 3.1.4, after receiving SID_first, the called terminal enters a continuous receiving DKAB state, waits for receiving DKAB burst of each frame, and continuously adjusts time and frequency in the process of receiving the burst;
step 3.1.5, the calling terminal continuously transmits DKAB burst, the gateway station access network generates a occupied bit data packet after receiving DKAB burst, and transmits the occupied bit data packet to the core network, and a voice data channel between the core network and the access network of the calling user is maintained; the core network forwards the data to the access network where the called user is located, and the access network generates DKAB burst after receiving the occupying data packet and sends the DKAB burst to the called user so as to maintain a downlink channel from the access network to the called user;
step 3.1.6, when the DTCH channel sending time of the calling terminal arrives, the generated SID_UPDATE used for bearing the background noise characteristic bit is sent to the gateway station through the DTCH channel, after the gateway station core network media gateway receives the SID_UPDATE frame, the SID_UPDATE frame is forwarded to the access network where the called terminal is located, and the access network packages the SID_UPDATE voice frame into a DTCH burst and sends the DTCH burst;
and 3.1.7, in the discontinuous transmission stage, when the calling terminal suddenly detects the voice of the user in a certain frame, interrupting the discontinuous transmission process and entering a voice activation state, and immediately transmitting the valid voice frame data to the gateway station through a service channel DTCH in the frame.
9. The method for discontinuous communication of a satellite mobile communication system according to claim 7, wherein the other network-to-satellite network voice activation control process in the inactive state comprises the steps of:
step 3.2.1, during the calling process, the gateway station allocates a p value for forming DKAB burst and DTCH transmission during voice activation for the satellite terminal;
step 3.2.2, the continuous n frames of the satellite terminal voice coder/decoder are monitored to be in a non-voice activated state, if n is more than or equal to 4, a discontinuous transmission stage is started in the n+1st frame, an effective voice frame SID_first is generated and is sent to a gateway station through a physical layer DTCH channel, meanwhile, the satellite terminal enters a discontinuous transmission state, and the voice coder/decoder generates background noise bits to wait for transmission;
step 3.2.3, after the core network media gateway of the gateway station receives the voice frame, confirming that the terminal enters a voice activation state, encoding the SID_first voice frame into silence voice data of other networks and forwarding the silence voice data, wherein the core network sets the satellite terminal in a silence stage;
step 3.2.4, the satellite terminal continuously transmits DKAB burst, the gateway station access network generates a occupied bit data packet after receiving the DKAB burst and transmits the occupied bit data packet to the core network, a voice data channel between the core network and the access network of a calling user is maintained, and the core network transmits silence voice data generated last time;
3.2.5, when the DTCH channel sending time of the satellite terminal comes, sending the generated SID_UPDATE for bearing the background noise characteristic bits to a gateway station through the DTCH channel, and after the gateway station core network media gateway receives the SID_UPDATE frame, updating and forwarding the silence voice data according to the background noise characteristic parameters in the SID_UPDATE frame;
and 3.2.6, in the discontinuous transmission stage, when the calling terminal suddenly detects the voice of the user in a certain frame, interrupting the discontinuous transmission process and entering a voice activation state, and when the frame immediately transmits the valid voice frame data to the gateway station through a service channel DTCH channel, the gateway station codes the voice data of the satellite terminal into voice frames recognizable by other networks.
10. The method for discontinuous communication of a satellite mobile communication system according to claim 7, wherein the satellite network to other network voice activation control process in the inactive state comprises the steps of:
step 3.3.1, when the core network media gateway monitors that voice frames sent by other network users are in a non-voice activation state through continuous n frames of a voice coder-decoder, starting a discontinuous transmission stage at an n+1st frame, generating an effective voice frame SID_first and forwarding the effective voice frame SID_first to an access network;
step 3.3.2, after receiving the SID_first frame, the access network immediately transmits the SID_first frame to the satellite terminal through a physical layer DTCH channel, and simultaneously enters a discontinuous transmission state;
step 3.3.3, the core network media gateway generates SID_UPDATE through the voice coder-decoder in the next frame, and waits for the sending time of the DTCH after the access network detects the voice frame through forwarding the access network where the satellite terminal is located;
step 3.3.4, the core network media gateway continuously detects voice frames sent by other network users through a voice coder-decoder, generates occupied data packets and sends the occupied data packets to the access network, and the access network generates DKAB bursts and sends the DKAB bursts after detecting the occupied data packets;
step 3.3.5, the core network media gateway generates background noise characteristics once every SID_UPDATE period and forms SID_UPDATE, and forwards the SID_UPDATE to the access network, and the access network transmits the SID_UPDATE when the transmission opportunity of the DTCH arrives;
and 3.3.6, after detecting that the speech frames of other network users contain speaking voices, the core network media gateway enters a voice activation state, generates normal speech frames and forwards the normal speech frames to the access network, and the access network immediately forwards the normal speech frames to the users through a DTCH channel.
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