JPH0145256B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for establishing initial synchronization in a time division multidirectional communication network formed by a large number of scattered slave stations and one common master station.

FIG. 1 is a diagram illustrating a time division multidirectional communication network according to the present invention. In the figure, the master station simultaneously emits multiplexed PCM signals in multiple directions on the time axis t, and each slave station 1, 2, ..., n receives its own PCM signal from among the PCM signals transmitted from the master station. quota 1,
2,...,n only are extracted and received. In FIG. 1, Fsb ₁ and Fsb ₂ indicate subframes of slave station 1 and slave station 2, respectively. Each slave station 1, 2, ..., n also transmits a signal to the master station in the time slot assigned to it and with corrections made to the signal propagation delay time. The signals arrive in the order in which they were sent.

That is, in the master station, the signals 1, 2, . . . , n received from the respective slave stations do not overlap and are arranged in an orderly manner on the time axis. This can be done if each slave station synchronizes with the frame bits included in the master station transmission signal and transmits in its own station's assigned time slot and by correcting the signal propagation delay time between the master stations using a delay equalizer. At the station, as shown in Figure 1, signals 1,
2,...,n can be received in an orderly manner in the order of transmission.

FIG. 2 shows details of the above description.
In FIG. 2, a indicates a master station transmission signal, and each slave station 1, 2, . . . , n receives a continuous signal having a frame length F. FIG. 2b shows the received signal of the slave station 1, and this signal arrives with a delay of the signal propagation delay time between the master station and the slave station. FIG. 2c shows the transmission signal of the slave station 1, and the delay time Δα is determined so that the master station can receive the signals from each slave station in an orderly manner as shown in FIG. 2d. By the way, the determination of the transmission time from the slave station is calculated based on the frame synchronization signal sent from the master station, and this is used as the reference for all times.

FIG. 4a is a diagram of a transmission frame sent from the master station to the slave station, in which a frame synchronization signal FS is added before the data signal destined for slave station 1. FIG. 4b shows a subframe configuration for the slave station 1, where a ₁ is a random signal, b ₁ is a frame synchronization signal, and c ₁ is a data section. FIG. 4c shows a subframe signal for another slave station, in which case a ₁ ', b ₁ ' are random signals, and c' is a data signal. FIG. 4d shows the subframe structure of slave station n, and the meanings of a _o , b _o , and c _o are the same as in FIG. 4 c.

Now, in an actual line, if the line between a certain slave station is disconnected due to fading or the like as shown in Figure 3, for example, when slave station 2 cannot establish a synchronization signal from the master station, the slave station Disables transmission from to the master station. The reason for this is to prevent the master station from influencing other stations. Next, in order to detect and establish a synchronization signal, the synchronization is completed with the carrier wave and the clock signal, and only after the frame synchronization signal is detected.

However, since the line is disconnected due to fading or the like when the S/N of the line is very low, it takes several frames of time to establish synchronization. Therefore, once the line is disconnected, it will take time to restore the line if the S/N is poor.

SUMMARY OF THE INVENTION An object of the present invention is to provide an initial synchronization system in a time-division multidirectional communication network that allows initial synchronization to be established at high speed in order to eliminate such drawbacks.

According to the present invention, multiplexed PCM signals are emitted from the master station in multiple directions on the time axis, and each slave station 1,
2,...,n, the PCM sent from the master station
Of the signals, only the portions 1, 2, ..., n allocated to the local station are extracted and received, and each slave station synchronizes with the frame bits included in the signal transmitted by the master station and performs communication between the slave station and the master station during the time period allocated to the slave station. In a time-division multidirectional communication network in which the signal propagation delay time is adjusted and transmitted so that the signals from each slave station arrive at the master station in the order in which they were transmitted, the subframes from the master station to each slave station are usually does not insert the carrier wave regeneration signal and the clock regeneration signal, but inserts the carrier wave regeneration signal and the clock regeneration signal in the subframe for the slave station where the line is disconnected in the continuous signal to each slave station. An initial synchronization method for time-division multidirectional communication networks is proposed, which is characterized by speeding up the establishment of synchronization.

The method according to the present invention will be explained in detail below using embodiments.

Usually, in this type of multi-directional communication system, a synchronous detection method is often used as the detection method in consideration of line quality. In this case, the signal configuration from the slave station to the master station is as shown in FIG. In the figure, a _c is a carrier wave regeneration signal, a _B is a clock regeneration signal, b is a station identification and auxiliary signal or a PN signal, and c is a data or PN signal. However, in general, it is not necessary to insert a carrier wave and a clock reproduction signal from the master station to the slave station as shown in FIG. Therefore, only data is sent from the master station.If the child station sends the above signals and data, the uplink and downlink transmission capacity differs, causing problems in the design of lines and radio equipment.Usually, an additional signal is added to the data from the master station to frame the data. The length is the same for both the top and bottom.

When a carrier wave and a clock recovery signal are inserted into the signal from the master station, the data of the carrier wave recovery signal does not change, so the data divisions are not known, and the phase of the clock signal shifts, resulting in loss of synchronization, and the phase of the clock recovery signal frequently changes. This signal is not suitable for carrier wave regeneration. Therefore, if carrier wave regeneration and clock regeneration have already been established, and these regeneration signals are received, it will be even more inconvenient.

Taking these into consideration, the present invention changes the signal configuration from the master station to the slave station at the time of initial synchronization and resynchronization as shown in FIG. When a slave station's line is disconnected (including initial synchronization), the synchronization time is shortened by inserting a carrier wave and a clock reproduction signal into the signal to the slave station. In FIG. 8, a ₁ ~a _o , b ₁ ~ _bo and c ₁ ~c _o
is composed as follows.

From slave station to master station a ₁ to a _o : Carrier wave and clock regeneration signal b ₁ to b _o : Station identification signal and auxiliary signal c ₁ to c _o : Data From master station to slave station a ₁ to _{a o} : Carrier wave and clock regeneration signal (when asynchronous) PN signal (when synchronous) b ₁ : Frame synchronous signal b ₂ ~ _{b o} : PN signal (regardless of synchronous or asynchronous) c ₁ ~ c _o : Data (regardless of synchronous or asynchronous) In other words, if there is no line disconnection, a _o and b _o are inserted as PN signals in front of each data as shown in Fig. 4d.
Next, if the line between the slave stations is disconnected, the fourth
The carrier wave and clock recovery times can be shortened by inserting the carrier wave and clock recovery signals into the ao or synchronization section of FIG. _d .

Note that the signal from the master station includes a frame synchronization signal as shown in FIG. 4, and its length is required to be a specific length as shown in FIG. In FIG. 7, the horizontal axis shows the frame synchronization signal length, the vertical axis shows the probability of occurrence, curve A shows the pseudo synchronization probability, and curve B shows the probability that the signal cannot be detected. That is, if a frame synchronization signal that is too long is used, false synchronization probability can be prevented, but the frame synchronization signal cannot be detected. Therefore, the length of the frame synchronization signal is not changed.

As described above in detail, according to the method according to the present invention, initial synchronization can be easily made fast and stable by changing the contents of the additional bits when the line is disconnected.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a time-division multidirectional communication network to which the system according to the present invention is applied, FIG. 2 is an explanatory diagram of transmission and reception signals used in the communication network of FIG. 1, and FIG. 4 and 5 are diagrams showing transmission frames used in the method according to the present invention, and FIGS. 6 and 7 are diagrams showing clock signal phase shift and frame synchronization, respectively. FIG. 8 is a chart showing limitations on signal length, and is a diagram showing a transmission/reception frame structure in the system according to the present invention. In the figure, F is a frame, FS is a frame synchronization signal, a _C is a carrier wave recovery signal, a _B is a clock recovery signal, b is a station identification and auxiliary signal or PN signal, c is a data PN signal, and a ₁ to _{a o} are Carrier wave and clock recovery signal or PN signal, b ₁ is frame synchronization signal or station identification signal and auxiliary signal, b ₂ ~
b _o indicates a PN signal, data, reproduction signal, station identification signal and auxiliary signal.

Claims (1)

[Claims] 1 Multiplexed on the time axis from the master station
Emit PCM signals in multiple directions, and each slave station 1, 2,...
At n, only the own-station assigned portions 1, 2, ..., n are extracted and received from the PCM signals transmitted from the master station, and each slave station transmits its own station in synchronization with the frame bits included in the master station transmission signal. In a time-division multidirectional communication network in which signals are transmitted by adjusting the signal propagation delay time between the master station and the master station during the allocated time period, and the signals from each slave station arrive at the master station in the order in which they were transmitted, the master station Normally, carrier wave regeneration signals and clock recovery signals are not inserted in the subframes from 1 to each slave station, but carrier wave recovery signals are inserted into the subframes for slave stations where the line in the continuous signal to each slave station is disconnected. An initial synchronization method in a time division multidirectional communication network that is characterized by speeding up the establishment of synchronization by inserting a signal and a clock regeneration signal.