JPH01300721A - Tdma radio communication system - Google Patents

Abstract

PURPOSE:To prevent wrong synchronization of an adjustment station to one reference station even when the reference station stops transmission by repeatedly using the same time slot between base stations which are separated from each other longer than the distance at which no mutual interference takes place between the base stations and, at the same time, adding an identify signal only between each base station. CONSTITUTION:Two systems (a) and (b) are respectively constituted of base stations A and A' (reference stations) which become references when time slots are synchronized to each other and base stations B and B' (adjustment stations) which make the time slots synchronous to each other by adjusting the transmitting timing of the time slots. The systems (a) and (b) are not interfered from each other, but can receive signals from each other. Identify signals A and B are respectively added to the time slots transmitted from the base stations A and B and identification signals A' and B' are respectively added to the time slots transmitted from the base stations A' and B'. When the base station A stops the transmission at the normal time slot assigned to its own station, the adjustment station B receives the time slot of the base station A' instead of the base station A, but, since the the identification not is A, but A', phase synchronism cannot be monitored and, therefore, the synchronized state is not disturbed by wrong phase adjustment.

Description

[Detailed description of the invention] [Industrial application field] INDUSTRIAL APPLICATION This invention is utilized for a digital wireless communication system.

The present invention places base stations in each of a plurality of wireless zones,
The present invention relates to a TDMA communication method in which each base station transmits a burst signal in a time-divisional manner in individual time slots through a common radio channel.

The present invention monitors synchronization loss between time slots transmitted from base stations, and the base station that has lost synchronization re-establishes phase synchronization by adjusting the amount of delay in signal transmission timing. In communication systems, the same time slot is repeatedly used between base stations that are separated by a distance that does not cause interference, and each base station is given a different identification code, thereby improving frequency usage efficiency. In addition, the adjustment station is designed to prevent the coordination station from falling into false synchronization even if one reference station stops transmitting.

[Conventional technology]

TDM in which multiple base stations alternately transmit time slots
In method A, if the transmission timings between base stations are not synchronized, interference will occur between time slots, making it impossible to receive signals.

For this reason, each time slot is provided with an identification code for the transmitting base station, and each base station measures the time difference between each time slot, monitors the phase synchronization shift, and if a phase synchronization shift occurs, that base station transmits. A method for automatically adjusting the phase is known.

In this way, if we increase the number of time slots assigned to each base station as we increase the number of base stations, the transmission period of each time slot will become longer and the measurement time for monitoring the phase synchronization of each base station will decrease. As the time length increases, the transmission intervals of the transmission information from other base stations also become longer.

FIG. 3 is a diagram showing an example of the configuration of the TDMA wireless communication system. This example represents two systems (a) and (b) that are at a certain distance from each other, and in each system, base station A or A' is set as a reference station, and another base station is set as a coordination station. This shows a mode in which stations B or B' operate synchronously. Furthermore, in this example, the time slots of the two systems (a) and (b) are synchronized with each other. FIG. 4 is a block diagram showing a main part of the apparatus for each of the systems shown in FIG. FIG. 5 is a time chart of this system.

Here, a case will be described in which the adjustment station B adjusts the phase to the reference station. In Fig. 5, the time slots transmitted from each base station have identification codes A and B for base stations A and A'.
An identification code B is added to each of base station B and B'.
Then, the receiver receives these time slots and transmits them to base stations A and A' and base station B, ! :B' time slots are received in a combined manner. Base station A' seen from base station B
and B' are far away compared to base stations A and B, and the reception levels of base stations A and B have a sufficient signal-to-noise ratio (D/U) with respect to the reception levels of base stations A' and B'. It's taken. Therefore, coordinating station B receives its own time slot from the reference station, and the time difference TAB between the detection timings of the detection circuits for identification codes A and B can be measured by a timer. In a synchronized state as shown in FIG. 5, this TAB is approximately equal to the time slot length T.

FIG. 6 shows an adjustment method when out-of-synchronization occurs.

The transmission timing of base station B is advanced by ΔT. For this reason, some interference occurs between the time slots of base stations A and B, but this does not extend to the identification codes, so the time difference between the detection timings of identification codes A and B is T.
AB can be measured, which is TA! 1=T−ΔT. In this case, the control unit of base station B can automatically calculate the difference T TAB = ΔT from the time difference T at the time of synchronization and add ΔT to the delay circuit to return to the synchronized state as shown in Fig. 3. can.

[Problem that the invention seeks to solve]

Next, considering the operation of base station B when base station A stops transmitting for some reason, the signal-to-noise ratio (D/
U) is considered to be sufficient, but the arrangement is not such that the absolute reception level of the interference layer is lowered below the reception limit. Therefore, when base station A stops transmitting time slots, coordination station B replaces base station A with base station A.
There is a possibility that the station receives the time slot of ', and also receives the time slot of its own station normally.

In this case, the reception timing of the identification code A of the reference station A' measured by the adjustment station B will have an error corresponding to the distance propagation delay, resulting in a problem of incorrect phase adjustment.

Although the case of the adjustment station B has been described above, the adjustment station B' also achieves phase synchronization with the reference station A' through exactly the same operation, and a similar problem occurs.

In a TDMA system in which a plurality of base stations transmit time slots alternately, the present invention provides a system for transmitting time slots even if that base station stops transmitting when there is another base station that uses the same time slot. It is an object of the present invention to provide a TDMA phase synchronization system in which a regulating station serving as a reference station does not perform erroneous phase adjustment.

[Means for solving problems]

The present invention uses the same time slot for base stations separated beyond a distance that does not cause interference with each other, and even when the same time slot is used, the identification code is different for each base station. It is characterized by using

[Effect]

Base stations that are separated by a distance that does not cause interference with each other can be operated using the same time slot. Therefore, it is possible to improve the efficiency of using radio waves.

Furthermore, if a base station operating as a reference station using the same time slot stops transmitting, a coordinating station performing phase synchronization according to that reference station may Even if a signal from a reference station of another system using P2a is received, it is possible to avoid erroneous synchronization with the reference station P2a due to the different identification codes.

〔Example〕

FIG. 1 is a block diagram of an embodiment of the present invention. In this example, base stations A and A serve as the reference for synchronizing between time slots for two systems (a) and
' (base station) and base stations B and B' (coordination station) that adjust and synchronize the transmission timing of time slots.
shows the configuration of The two systems (a) and (tora) are located slightly apart and do not interfere with each other, but can receive signals from the other system.

FIG. 2 shows a time chart of time slots transmitted synchronously from base stations A and A' and B and B'.

In the embodiment of the present invention shown in FIG. 1, the identification code detected at the adjustment station B' is different from the identification code detected at the adjustment station B'. As shown in Figure 2, base stations A and B
Identification codes A and B are added to the time slots transmitted from the base stations A' and B', respectively, and identification codes A' and B' are added to the time slots transmitted from the base stations A' and B'.

Here, a case will be described in which the adjustment station B is phase-synchronized with the reference station. At base station B, each time slot is received by a receiver, and the time slots of base stations A and A' and base stations B and B' are combined and received. Base station A' or B' as seen from base station B is far away compared to base station A or B, and the reception level of base station A or B is the same as that of base station A.
A sufficient signal-to-noise ratio (
D/U) is removed. Therefore, coordinating station B receives the time slots of reference station A and local station B, and there is a time difference TAX1 between the detection timings of the detection circuits of identification codes A and B.
is measured by a timer, and phase synchronization is monitored and adjusted in the same way as in the prior art.

Next, consider the operation of base station B when base station A stops transmission for some reason. In this embodiment, as in the prior art described above, when the absolute reception level of the interfering station is equal to or higher than the reception limit and base station A stops transmitting in the regular time slot assigned to it, the coordinating station B On behalf of base station A, it receives the same time slot Δ'. However, the identification code at this time is not A but A', so
Adjustment station BLy in FIG. 1) The detection circuit for identification code A cannot detect the identification code in the time slots of base stations A and A'. For this reason, phase synchronization cannot be monitored, but the synchronization state will not be disturbed due to incorrect phase adjustment.

〔Effect of the invention〕

As explained above, in the present invention, frequency utilization efficiency is improved by using the same time slot, and since different identification codes are assigned to base stations that use the same time slot, the same time slot is used. Even if a base station where another base station exists stops transmitting, a coordinating station that uses that base station as a reference station will not make incorrect phase adjustments.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention. FIG. 2 is a time chart during phase synchronization in the embodiment of the present invention. Figure 3 is an example of time slot repeat arrangement. FIG. 4 is a block diagram of a conventional TDMA phase synchronization system. FIG. 5 is a time chart during phase synchronization in the conventional TDMA phase synchronization method. FIG. 6 is a time chart of an out-of-synchronization state in the TDMA phase synchronization method. Patent Applicant Nippon Telegraph and Telephone Corporation-5-Agent Patent Attorney Nao Takashi Ide M 1 Figure 5 = T-4 Iris 2 times (b) Iris 3 ro

Claims (1)

[Claims] 1. One base station among a plurality of base stations is designated as a reference station, the other base station is designated as a coordination station, and the burst signal transmitted by the reference station is used as a reference for each coordination station. Each coordinating station transmits a burst signal in the set time slot, each burst signal has an identification code that identifies the transmitting base station, and each coordinating station uses the time slot of the reference station and the time slot of its own station. In the TDMA wireless communication system, which monitors base stations based on the time difference between their identification codes and automatically adjusts their own station's transmission time slot to the set time slot, base stations that are separated by a distance that does not cause mutual interference A TDMA wireless communication system is characterized in that the same time slot is used, and even when the same time slot is used, different identification codes are used for each base station.