JP2997856B2 - Time division wireless communication system - Google Patents

Abstract

PURPOSE:To decide a phase of a frame operated stably even under a complicated propagation condition. CONSTITUTION:When a radio station sending a radio wave is in existence (step 101), plural radio stations are operated in the subordinate synchronization with a radio station with higher priority or a radio station in subordinate synchronization with the higher priority radio station (step 107) and when no radio station sending the radio wave is in existence, the wait time reaching the subordinate state is reduced more in response to the higher priority (step 101).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time-division wireless communication system for a plurality of wireless stations to share one frequency by time-division multiple access.

[0002]

2. Description of the Related Art As is well known, a cellular radio system is shown in FIG. 4 as an ellipse in FIG. 4 in a range of propagation attenuation in which radio stations indicated by symbols A to G can communicate with its own station. A wireless zone, and a service area by combining a plurality of zones. In such a case, since radio waves leaking out of a zone cause interference to other zones, it is necessary to avoid accessing at the same timing with each other.

Heretofore, this type of timing determination has been performed by so-called autonomous distributed control, in which the control is left to the terminal part of the system. FIG. 5A shows an initial state of the timing determination. The frame phase of the time slot of the wireless station A has already been determined, and transmission has started. The next wireless station B and wireless station C determine the timing for any time slots B and C that do not overlap with wireless station A. FIG. 5B shows the final state of the timing decision by such a method.

An algorithm for realizing such an operation is considered to be a mutual synchronization method which is determined in consideration of the strength of radio waves of another station that can be received by the own station, the amount of timing deviation, and the propagation delay between wireless stations. I have. According to such a method, when each wireless station determines a time slot position at the same time, a result of converging with 100 control times was obtained (for example, Akaiwa et al .: Autonomous base station in TDMA cellular system). Mutual synchronization method, IEICE technical report, A.P90-116 / RCS90-46,199
0) It is considered that the synchronization of the entire system can be simplified and high frequency use efficiency can be achieved by autonomous decentralization.

[0005]

However, in such a conventional method, there is a fading due to irregular reflection of a vehicle or the like, shadowing or absorption of a human body in an actual propagation path. There is always a problem with good focusing characteristics and stability under various environmental conditions.
Further, in actual operation, re-establishing mutual synchronization every time a wireless station unit is replaced has a problem of impairing the serviceability of the system, such as a temporary interruption of communication.

The present invention has been made in view of such a situation, and provides a means for determining a frame phase which operates stably even under complicated propagation conditions and has good maintainability.

[0007]

In order to solve such a problem, a first aspect of the present invention is to set priorities for determining a frame phase among a plurality of radio stations in advance, and the plurality of radio stations have higher priorities. The wireless station operates in a state of being dependently synchronized with a wireless station having a higher wireless station or a wireless station that is dependently synchronized with the wireless station, and the waiting time until the slave station becomes dependent becomes shorter in accordance with the priority. According to a second aspect of the present invention, in the first aspect, the priority of the wireless station or the state of subordinate synchronization is determined based on the transmission cycle of the wireless station or the amplitude modulation of the transmission signal.

[0008]

When there is a radio station emitting radio waves (step 101), a plurality of radio stations operate in a state of being subordinately synchronized with a radio station having a higher priority or a radio station being subordinately synchronized with the radio station. When there is no radio station emitting radio waves (step 107), the operation is performed so that the waiting time to reach the subordinate state becomes shorter in accordance with the priority order (step 101).

[0009]

FIG. 1 shows an example of a control algorithm according to the present invention. First, in the initial state, as shown in step 100, the presence or absence of another wireless station that has already transmitted radio waves is detected around the wireless station that is about to transmit. If the radio wave of another radio station cannot be received, as shown in step 101, the radio station with the higher priority is short-time and the radio with the lower priority is determined by the preset priority of the radio station. The station waits for a long time before performing step 1
As shown at 02, the radio station waits for a time to confirm that another radio station does not emit a radio wave, and transmits a radio wave with its own timing determined as shown at step 103.

On the other hand, when the radio wave of another wireless station is detected, as shown in step 105, it is subordinately synchronized with the wireless station having the highest priority. After that, Step 106
As shown in (1), when a radio station with a higher priority is generated in the vicinity, an operation dependent on the radio station is always repeated as shown in step 107. In this method, it is necessary to take countermeasures when radio waves of other radio stations cannot be received in the initial state.This is to prevent radio stations from starting up independently at the same time due to power failure recovery, etc. Processing such as giving a randomized waiting time for each time is conceivable.

FIG. 2 shows a means for indicating the priority order or the dependent synchronization state of the radio station according to the second aspect. First, in FIG. 2A, the priority is made to correspond to the bit of the digital signal to be transmitted. This signal is composed of a preamble part for synchronizing a burst signal, a unique word part (UW), an identification ID of a radio station, and an information part. Some bits in the information portion include information such as the slave synchronization of the wireless station as shown in FIG. 2A, that is, the slave synchronization state, the priority of the slave synchronization target, and the time after entering the slave synchronization state. Contains information to represent. Using this, each wireless station can select a wireless station to be subjected to slave synchronization.

FIG. 2B shows the priority by changing the periodically transmitted frame period shown in satin, and FIG. 2C shows the amplitude modulation of the burst signal transmitted in satin. Are superimposed and modulated, and in either case, FIG.
Even in the case where the received signal level is lower than that of the method (a) and decoding as a digital signal cannot be performed sufficiently well, it is possible to obtain information on the priority or the dependent synchronization state.

FIG. 3 shows an operation example when a plurality of radio stations form a mutual synchronization system by the above method. In the figure, ◎ indicates the synchronization reference station with the highest synchronization priority, ● indicates a radio station that is dependently synchronized with the synchronization reference station, * indicates a radio station that determines independent synchronization, and Δ indicates that synchronization is determined independently. A wireless station that is subordinately synchronized with a certain wireless station, and △ indicates a wireless station that is not transmitting a signal.

First, in FIG. 3A showing the initial state, only the synchronization reference station 局 determines the time slot, and the other radio stations are not in the synchronization state and do not transmit signals. In the next state diagram 3 (b), a wireless station .circle-solid. Around the synchronization reference station is subordinate to the synchronization state, for example, by means of claim 2.

Further, in FIG. 3 (c), the radio stations near the synchronization reference station sequentially enter the synchronization state. On the other hand, since the radio station * cannot receive the radio station signal to be subjected to the subordinate synchronization, it becomes independent. , And starts transmitting signals, and a wireless station 属 that is dependently synchronized appears. However, since the speed of the synchronization with the synchronization reference station is quickly reported, FIG.
Then, the number of wireless stations ● that perform slave synchronization of the synchronization reference station rapidly increases, while the number of wireless stations 属 that slave dependently determine the synchronization independently of each other is slow.

Further, in FIG. 3 (e), all the radio stations determine the time slot and transmit a signal, but the radio stations dependent on the synchronization reference station independently synchronize with the radio station * which is independently determined to synchronize. Became to surround the bureau. Since the radio stations are given the property of subordinately synchronizing with the synchronization reference station preferentially, all the radio stations eventually become dependent on the synchronization reference station as shown in FIGS. 3 (f) and 3 (g). All time slots are filled without gaps, and the frequency utilization efficiency is improved.

[0017]

As described above, according to the present invention, in determining the time slot between the radio stations, the time slot determination centering on the synchronous reference station is performed stably and quickly centering on the higher-ranking station. Even when time-division multiple access is introduced into public communication or the like that requires high reliability, good serviceability can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a control algorithm showing one embodiment of the present invention.

FIG. 2 is an example of a transmission signal of a wireless station

FIG. 3 is a diagram illustrating an operation example of wireless station synchronization;

FIG. 4 is a diagram showing an example of a wireless zone configuration.

FIG. 5 is a diagram showing a timing decision instruction of a time slot.

[Explanation of symbols]

A to G radio stations ◎ The synchronization reference station with the highest synchronization priority ● The radio station that is subordinate to the synchronization reference station * The radio station that determines independent synchronization ◆ The subordinate synchronization is performed by the radio station that determines synchronization independently Radio station that does not transmit Radio stations that do not transmit signals

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-63-115499 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 7/26 H04Q 7/00-7 / 38

Claims (2)

(57) [Claims] 1. A time division wireless communication system in which a plurality of wireless stations transmit burst signals at a predetermined frame cycle at one frequency, and the plurality of wireless stations autonomously determine the phase of the frame cycle. The priorities of frame phase determination are set in advance among the plurality of wireless stations, and the plurality of wireless stations are dependently synchronized with a wireless station having a higher priority or a wireless station that is dependently synchronized with the wireless station. A time-division wireless communication system characterized in that the waiting time to operate and to become dependent depends on the priority. 2. The time division wireless communication system according to claim 1, wherein the priority of the wireless station or the state of the subordinate synchronization is determined based on the transmission cycle of the wireless station or the amplitude modulation of the transmission signal.