JPH11261535A - Time-division communications system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a time division system capable of highly efficiently transmitting even the data of a long sentence as plural packet data without degrading the reception rate by setting the transmission intervals of a plurality of packets at every repetition to be not shorter than an electrolytic intensity fluctuation period by phasing. SOLUTION: One main frame is constituted of 64 sub-frames and the respective frames are transmitted from the left to the right in the Fig. in order from the smallest number. The respective frames are constituted of three control slots, C1, C2 and C3 and following 1024 slots. Data 260 bits for one packet are allocated to the respective slots. The main frame is repetitively transmitted and the packets are continuously transmitted. In such a case, a plurality of packets are repetitively transmitted for plural times, and the transmission intervals of a plurality of packets at every repetition are set to be not shorter than an electrolytic intensity fluctuation period by phasing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time division communication system (HSDS: High Speed Data System) for performing data transmission services such as paging, road traffic information or various information services using FM subcarriers. Used
The present invention relates to a communication system of a plurality of packets in which relatively long data is divided into a plurality of packets and transmitted and received. Publicly known material: Broadcasting technology May issue 1994 attached.

[0002]

2. Description of the Related Art FIG. 1 shows a conventional transmission frame structure of the HSDS system. One main frame is composed of 64 sub-frames, and each sub-frame is transmitted from left to right in the figure in the order of the slot having the smaller number. Each subframe has three control slots, C1, C2, C3, followed by 10
It consists of 24 slots, and 260 bits of data for one packet are allocated to each slot. In the case of the HSDS method, the bit rate is a transmission rate of 19 k bits per second, so that one sub-frame is transmitted for about 14 msec to transmit one packet of data included in one slot. Is transmitted in about 14 seconds, and one mainframe is transmitted in about 15 minutes. This main frame is repeatedly transmitted, and continuous packets are transmitted. Here, a slot refers to each unit time on the time axis to be received by the receiver, and a packet refers to unit data (usually 260 bits) consisting of a fixed bit included in each slot. Point to. Normally, one packet of data is included in one slot time unit.

Conventionally, data transmission based on one packet (single packet) has been performed, and a transmission service of a 16-digit numerical display or a fixed text such as "CALL HOME" or "CALL OFFICE" has been provided to a wristwatch type receiver. I was In this case, the receiver side receives the slot of the number determined every 8 sub-frames, and if the slot contains a bit indicating that the data is its own, this data is reproduced. Was displayed on the display.
Each data is repeatedly transmitted three times to improve the reception accuracy.

In recent years, long-length data has been transmitted in data transmission such as paging, and not only numbers but also characters and other transmission services have been provided.

[0005]

When transmitting a plurality of packet data (multi-packets) using the frame structure of the HSDS system, the following transmission systems are conceivable.

First, the transmitting side divides data into a plurality of packet data. When the data is long, the number of packets increases, and when the data is short, the data is transmitted with a small number of packets. When transmitting these packets, one packet of data is usually prepared in a slot of a predetermined number transmitted every 8 sub-frames as conventionally used, and the receiver itself is included in this data. , And a plurality of slot numbers including a plurality of packets described below. The receiver intermittently receives a plurality of sequentially designated slots based on the data, combines the data, reproduces long data, and displays the data on a display.

However, in an area where the electric field strength fluctuates due to the influence of fading due to multipaths or the like, when transmitting long data, the transmission period becomes long, and the problem is that a part of the data is likely to be lost. Have. Also, if the number of times of transmission of the same data is increased in order to improve the reception rate, the accumulated reception time is required for a long time to receive the same data, resulting in a decrease in subscriber capacity and a decrease in the battery life of the receiver, There is also a problem that. Preferably, regardless of the presence or absence of multipath in a field in which data is transmitted, it is desirable that information transmission with a shorter arrival time and less errors be performed more efficiently.

An object of the present invention is to solve these problems, and an object of the present invention is to provide a time-division communication system which does not reduce the reception rate even when long data is transmitted as a plurality of packet data, with high efficiency. There.

[0009]

In order to solve the above-mentioned problems, the present invention provides the following: 1) A transmitter continuously transmits packets of a predetermined number of bits, and a receiver determines a packet among the transmitted packets. In a time-division communication system designed to periodically receive packets of a given number, a plurality of packets are repeatedly transmitted a plurality of times, respectively, and the transmission interval of the plurality of packets at each repetition is changed by electric field strength fluctuation due to fading in radio frequency The period is set so as not to be shorter.

2) In a communication system in which a transmitter continuously transmits packets of a predetermined number of bits and a receiver periodically receives a packet of a predetermined number among the transmitted packets. , A plurality of packets are repeatedly transmitted a plurality of times, respectively, and transmission intervals of the plurality of packets at each repetition are time intervals that are not the same.

3) In a communication system in which a transmitter continuously transmits packets of a predetermined number of bits and a receiver periodically receives a packet of a predetermined number among the transmitted packets. , A plurality of packets are repeatedly transmitted a plurality of times, and transmission is first performed at a shorter interval among time intervals in which the transmission intervals of the plurality of packets are not the same for each repetition.

4) In a communication system in which a transmitter continuously transmits packets of a predetermined number of bits and a receiver periodically receives a packet of a predetermined number among the transmitted packets. , A plurality of packets are repeatedly transmitted a plurality of times, and transmission is performed sequentially from transmission at a shorter interval among unequal transmission intervals of the plurality of packets at each repetition.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an HSDS transmission frame structure used in the present invention. One mainframe has 64 su
Each frame is transmitted from left to right in the figure in ascending order of the number. Each frame is composed of three control slots, C1, C2, and C3, followed by 1024 slots, and each slot is assigned 260 bits of data for one packet. In the case of the HSDS system, the bit rate is a transmission rate of 19 kbits per second, so that one sub-frame is transmitted for about 14 ms in order to transmit one packet of data included in one slot. Is transmitted in about 14 seconds, and one mainframe is transmitted in about 15 minutes. This main frame is repeatedly transmitted, and continuous packets are transmitted.

[0015] However, in FIG.
Are expressed small in the middle part. Also, slot, fram
Due to the limitations of the notation, only a part of the number of e was described.

Conventionally, when a single packet is received, one slot is received approximately every 112 seconds, with each 8 sub-frame as a reception repetition period. That is, in FIG.
When receiving a single packet, the receiver configured to receive the data of the slot number n (the slot of B) of the sub-frame of the n-th sub-frame has the n-th slot of the M + 8-th sub-frame ( C slot) to receive. Similarly, M + 16th s
The order is the n-th (D slot) of the ub-frame. Here, when a plurality of packets (multi-packets) are received, for example, first, the slot B is received, and this data includes data indicating that the data is the receiver's own data, and the following plurality of packets. And a plurality of slot numbers. Based on this data, the receiver receives a plurality of subsequent slots indicated by oblique lines to the right in the figure. Next, the C slot is received, and thereafter, a plurality of subsequent slots indicated by oblique lines to the right in the figure are received. Further, it receives the D slot, and similarly receives a plurality of subsequent slots indicated by oblique lines. Here, for the sake of simplicity, a description will be given assuming that four additional packets are received in the same sub-frame.

These four additional packets are transmitted at the same slot interval k for simplicity. That is, the first additional packet is included in the (n + k) th slot,
The third is the n + 2kth, the third is the n + 3kth, and the fourth is the n + 4k
Is th. If the value of k is to be transmitted in a short time, the smaller the value, the faster the data can be transmitted. Also, if all additional packets are transmitted within 8 sub-frames even if it is set large, the basic reception cycle can be reduced.
Additional packets can be received within 112 seconds.

Here, considering the effect of fading due to multipath, it is assumed that, in the publicly known document “Telecommunications Technology Council Report Advisory No. 25, the technical conditions of signals that can be superimposed on FM broadcast waves, Technical conditions concerning FM teletext broadcasting system described in section 3-5-1, which describes general multipath fading. Fig. 3-5-1 shows the simulation results of fading in the FM frequency band. Figure 3-5-1
When the fluctuation of the electric field strength in the upper stage is evaluated, it is considered that the electric field strength fluctuates (an instantaneous decrease in the electric field strength) three times in about 1 second on average. The electric field strength reduction period (burst length) is shown in the figure.
As shown in 3-5-2, it depends on the speed of the moving object, but when the slow case is considered as the worst case, it is considered to be about 1200 bits and about 75 ms.

Publicly known document “Telecommunications Technology Council Report Consultation No.
No. 25, the technical conditions of signals that can be superimposed on FM broadcast radio waves, of the technical conditions for FM teletext broadcasting system premised on reception by mobiles "and the HSDS system of the present invention are 16 kbps and 19 kbps Although the bit rate is slightly different from the above, the conditions of multipath fading in the FM band are considered to be almost the same, so the values read from Fig. 3-5-1 and Fig. 3-5-2 are used as representative values and the HSDS method The relationship between multi-packet reception and fading in is described with reference to FIG.

In FIG. 2, the horizontal axis represents the time axis in seconds. The hatched portion on the right side of the MB (multi pass burst) indicates a period (burst period) during which the electric field intensity is reduced by the multi-pass. This value is the representative value described above, with an average frequency of three times per second, and a length corresponding to about 75 ms per time. The packet transmitted during this period becomes an error due to the decrease in the electric field strength, and the receiver cannot reproduce it as data. In the figure, four transmission states E, F, G, and H are shown in the vertical direction, and another transmission state I is shown below the MB. It is assumed that the time of the first packet matches each transmission state.

E indicates the transmission state of a single packet,
F, G, and H represent transmission states when the transmission interval of each packet transmitted from the second onward is shorter than the period (burst period) of the period in which the electric field strength is reduced due to multipath (burst period). Further, I represents a transmission state when the transmission interval is almost the same as the period (burst period) period of the electric field strength reduction due to multipath.

In FIG. 2, rectangles on the horizontal axes of E, F, G, H, and I represent one packet to be transmitted, and hatched lines indicate that the packet is in error. That is, a packet overlapping on the time axis with each burst period shown on the horizontal axis of the MB indicates that the data cannot be reproduced due to the influence of the decrease in the electric field intensity, resulting in an error. In F, three out of five transmitted packets have an error, and in G, two out of five packets have an error. Similarly, in H, two of the five packets have an error. It is presumed that errors are likely to occur in multi-packet or long message transmission in fields affected by multi-path, for example, in urban areas.

On the other hand, in the case of I, the transmission interval of the multipacket is substantially the same as MB. In this case, none of the five packets has an error. This state does not change even if the packet transmission interval is doubled in I. From the above, it is considered that the possibility of an error in multi-packet reception is lower when the transmission interval of the multi-packet is shorter than the burst period and when the transmission interval is not shorter. In fact, the burst period indicated by MB in FIG. 2 is about 75 ms, and its cycle is equivalent to 330 ms. Therefore, I indicates that transmission is performed at intervals of about 24 slots. This interval may be an integral multiple of 24 slots. If this is represented by a multi-packet following FIG. 1B, the value of k representing the second slot following B is preferably 24 or an integer multiple thereof.

In the present embodiment, the FM wave (from 76 MHz to 90 M in Japan)
Hz, 87.4 MHz to 108 MHz overseas), but the same applies to the period (burst period) of the electric field strength reduction period (burst period) due to multipath at other frequencies when using other frequencies. I can say.

Next, another embodiment of the present invention will be described.

In FIG. 1, it is assumed that the same multi-packet data is transmitted a plurality of times. First time B followed by
Four packets are transmitted, and the same packet data is transmitted a second time to C and the subsequent slot indicated by diagonal lines. Further, the same packet data is transmitted to D and the hatched slot following it. By doing so, the same data can be transmitted and received three times, and the reception rate can be improved. Here, in three transmissions, the transmission cycle is B,
Set a different cycle for C and D. In the first embodiment described above.
The transmission cycle of every 24 slots is set at the representative value of the period (burst period) of the electric field strength reduction due to multipath in the FM band, but since this period actually has a certain amount of fluctuation, it is fixed to a constant value. Preferably, a plurality of cycles are set. That is, transmission is performed such that transmission intervals (periods) are not the same as indicated by B, C, D and a plurality of subsequent slots. In this case, if the period (burst period) of the decrease in the electric field strength due to the multipath fluctuates, the period shorter than 24 slots and the longer period may be combined so as to correspond to the period when the period is shorter or longer than 24 slots. preferable. For example, in B, the transmission cycle k is 12
Slots: 24 slots for C, 32 slots for D.

Alternatively, in B, C, and D, the intervals may be 12 slots, 120 slots, and 240 slots, respectively. These values can be set to optimum values in a real system in a multipath situation of an actual service area rather than theoretical values.

When a plurality of packet transmissions are performed at a plurality of transmission periods, when the packet transmission period is set to be long, it is preferable to perform transmission at short transmission intervals first in order to shorten the reception delay time. In this case, if the area is not affected by the multipath, the transmission of a short cycle can be received without error, so that the effect is large.

[0029]

As described above, according to the present invention, in an area where the electric field strength is constantly reduced due to the influence of the fading due to the multipath, the data composed of a plurality of packets can be transmitted a plurality of times. A communication method with a high reception probability can be provided.

2) The reception delay time can be relatively shortened.

By achieving the above 1) and 2), 3) the number of times of repeated transmission and reception can be reduced, and as a result, the current consumption for receiving by the receiver can be reduced, and the battery life can be reduced. Can be lengthened.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a transmission format of an HSDS system in an embodiment of the present invention.

FIG. 2 is a schematic diagram of a multiple-packet transmission scheme showing a relationship between a multiple-packet transmission interval and a period (burst period) period of a decrease in electric field intensity due to multipath in an embodiment of the present invention.

[Explanation of symbols]

slot C0: control slot C0 slot C1: control slot C1 slot C2: control slot C2 slot 0 to slot 1023: general information slot sub-frame 0 to sub-frame 63: control slot C0
To C2 and a general information slot slot 0 to slot 1023 T slot: 1 slot time T sub-frame: 1 sub-frame time T master-frame: 1 master frame time A: Single packet AB: Packet B and a plurality following it Packet C: Packet C followed by multiple packets D: Packet D followed by multiple packets E: Single packet EF: Packet F followed by multiple packets G: Packet G followed by multiple packets H: Packet H Followed by multiple packets I: Packet I followed by multiple packets MB: Field strength reduction period due to multipath (burst period)

Claims (4)

[Claims] 1. A time-division communication in which a transmitter continuously transmits packets of a predetermined number of bits and a receiver periodically receives a packet of a predetermined number among the transmitted packets. A communication method, wherein a plurality of packets are repeatedly transmitted a plurality of times, and a transmission interval of the plurality of packets at each repetition is set so as not to be shorter than an electric field strength fluctuation period due to fading in a radio frequency. 2. A communication system in which a transmitter continuously transmits packets of a predetermined number of bits and a receiver periodically receives a packet of a predetermined number among the transmitted packets. A plurality of packets are repeatedly transmitted a plurality of times, respectively, and the transmission intervals of the plurality of packets at each repetition are not the same time intervals. 3. The communication method according to claim 2, wherein transmission is performed first at a shorter interval among time intervals at which transmission intervals of a plurality of packets for each repetition are not the same. 4. The communication system according to claim 2, wherein transmission is performed sequentially from transmission at a shorter interval among transmission intervals at which transmission intervals of a plurality of packets for each repetition are not the same.