CA1186426A - System of transmitting information between a central station and sub-stations - Google Patents
System of transmitting information between a central station and sub-stationsInfo
- Publication number
- CA1186426A CA1186426A CA000398702A CA398702A CA1186426A CA 1186426 A CA1186426 A CA 1186426A CA 000398702 A CA000398702 A CA 000398702A CA 398702 A CA398702 A CA 398702A CA 1186426 A CA1186426 A CA 1186426A
- Authority
- CA
- Canada
- Prior art keywords
- sub
- stations
- central station
- delay
- transmission
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
- H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
- H04B7/2662—Arrangements for Wireless System Synchronisation
- H04B7/2671—Arrangements for Wireless Time-Division Multiple Access [TDMA] System Synchronisation
- H04B7/2678—Time synchronisation
- H04B7/2687—Inter base stations synchronisation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
- H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
- H04B7/2662—Arrangements for Wireless System Synchronisation
- H04B7/2671—Arrangements for Wireless Time-Division Multiple Access [TDMA] System Synchronisation
- H04B7/2678—Time synchronisation
- H04B7/2687—Inter base stations synchronisation
- H04B7/269—Master/slave synchronisation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
- H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
- H04B7/2662—Arrangements for Wireless System Synchronisation
- H04B7/2671—Arrangements for Wireless Time-Division Multiple Access [TDMA] System Synchronisation
- H04B7/2678—Time synchronisation
- H04B7/2687—Inter base stations synchronisation
- H04B7/2693—Centralised synchronisation, i.e. using external universal time reference, e.g. by using a global positioning system [GPS] or by distributing time reference over the wireline network
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0635—Clock or time synchronisation in a network
- H04J3/0682—Clock or time synchronisation in a network by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
Abstract
ABSTRACT:
The system for transmitting information between a central station (SP) and sub-stations (SS1, SS2, SS3) operates, for the transmission from the sub-stations to the central station in accordance with a method (TDMA
method) which consists in providing time slots in each of which only one sub-station can transmit, the arrangement of these time slots being determined by a synchronizing signal transmitted via a link from the central station to the sub-stations; this system is characterized in that it comprises at the sub-station ends delay adjustment means (MR1, MR2, MR3 ...) so as to ensure that the transmission from the sub-stations will be properly situated in the time slots assigned to them, while at the central station end it comprises means (MMR) for measuring the transmis-sion delay between the sub-stations and the central station and in that the said link between the central station and the sub-stations has for its function to transmit, inter alia, the delay measurement information while the means (PR1, PR2, PR3) receiving the said measure-ment information provided in the sub-stations are used to act on the said adjusting means. Used in systems using the time division multiple access.
The system for transmitting information between a central station (SP) and sub-stations (SS1, SS2, SS3) operates, for the transmission from the sub-stations to the central station in accordance with a method (TDMA
method) which consists in providing time slots in each of which only one sub-station can transmit, the arrangement of these time slots being determined by a synchronizing signal transmitted via a link from the central station to the sub-stations; this system is characterized in that it comprises at the sub-station ends delay adjustment means (MR1, MR2, MR3 ...) so as to ensure that the transmission from the sub-stations will be properly situated in the time slots assigned to them, while at the central station end it comprises means (MMR) for measuring the transmis-sion delay between the sub-stations and the central station and in that the said link between the central station and the sub-stations has for its function to transmit, inter alia, the delay measurement information while the means (PR1, PR2, PR3) receiving the said measure-ment information provided in the sub-stations are used to act on the said adjusting means. Used in systems using the time division multiple access.
Description
PHF 81.530 The present invention relates to a system of transmitting information between a central station and sub-stations operating, for transmission in the direction from the sub~stations to the central station, in accor dance with a method t~DM~ method) which consists in pro viding tirne slots in each of which only one sub-station can transmit, the disposition of these time slots being determined by a synchronizing signal conveyed in a link in the direction from the main station to the sub-stations.
Transmission systems using the TDMA method(time division multiple access) are well known in the transmission technique utilizing satellitesO U.S. Patent 4,117,267 which issued on September 26, 1978 and assigned to International Standard Electric Corporation describes such a system.
In the systems which operate in accordance with the TDMA method, the synchronization problems are of par-ticular importance~ Sub-stations rnust not transmit ln overlapping time slots. To solve this probl~m, the above-mentioned patent describes a firs-t measure which consists in the provision of comparatively important time margins between each time slot and a second measure which, so as to reduce these time margins somewhat, consists in calcu-lating a time shift for the tran~mission of the substation as a function of their position~; these sub-stations, in this case aircrafts~ moving along predeter-mined paths.
The present invention proposes a transmission system as described in the opening paragraph for which the time margins are reduced and which does not have the problem that tirne shifts, must be calculated.
For that purpose such a system is characterized in that it comprises,at the side of the sub stations, delay PHF ~1,530 2 1202~1982 adjustment means to ensure that tha transmission from the sub-stations is properly located in the time slots assigned to them7 in that it cornprises at the central station end means to measure the transmission delays between 5 the sub-stations and the central station~ in that the said ~ from the central station to the sub stations is arranged for transmitting inter alia inform~tion about the measured delay and in that means for receiving the said measurement provided in the sub-stations are used to act on lO the said adjusting means.
Thus 5 in accordance with the invention the time shift to be effe~ted for the transmission from the sub~
stations is no longer calculated but may be measured continuouslyl The time margins may then be reduced to a ~5 considerable e~tent.
The following description given by way of e~ample with referance to the accompanying drawings will make it better understood how the invention can be put into effect.
Fig. 1 shows a circuit diagram of a s~stem in accordance with the invention, Fig, 2 is a diagram showing -the organi~ation of the links between the central station and the sub-stations on the one hand and between the sub-s-tations and the 25 ccntral station on the other hancl~ as well as some signals prescnt within the measuring circuit comprised in a central station wl1ose circuit diagram is shown in Fig~ 3.
Fig, 3 shows in detail the circui-t diagram of a central station in accordance with the inven-tionO
Fig~ ~ shows in detail the circuit diagram of a sub-station in accordance with the invention, Fig~ 5 shows a variant of the embodirnent of a sub-station in accordance with the inven-tion, ~ he s~stem shown in Fig~ 1 is formed by a 35 central station SP and sub-stations SSI7 SS27 SS35,o ~he central station SP has a terminal IEP for receiving the information intended -to be transmitted to the sub-stations PMF 81.530 3 1 2~2~1982 SS1, SS2, SS3 7 , . ~ and a terminal ISP for ma~ing the information coming from these sub-stations available;
these sub-sta-tions SS1 9 SS29 SS3 are provided in a corres-ponding manner with respec-tive terminals IE19 IE2, IE3,.~.
5 f`or receiving the information intended for the central station and terminals IS1, IS2, IS3 for ma~ing the inforrna-tion coming from the central station available.
The station SP transmits information to the sub-stations SSi~ SS2, SS3, . . via a radio channel by means of its transmitting aerlal AEPo To receive this informa-tiOIl, the sub-stations SSI~ SS2 T SS3 9, . . have recei.ving aerials ARl~ AR2~ AR3~ ... and to transmit information to the central station the~ have transmitting aerials ~E1, A~2 7 AE3, while the central station has one aerial ARP to 5 receive the last-mentioned information. The sub-stations SS1~ SS2~ SS3l ... comprise a receiving portion PR1 7 PR29 PR3~ respectively connected between the aeri.al AR2 and the terminal IS1 for the first station, between the aerial AR2 and the terminal IS2 for the second sta-tion, 20 and between the aerial AR3 and the terrninal IS3 for the third station~ and comprises a -transmission portion PE1, PE2 a.nd PE3 connectecl between the terminal IE1 and the aerial A~1 for the first station, between the terminal I~2 an(l the aerial ~E2 I`or t:he second station and hetween tne 25 terminal IF3 and thc aeria.l AE3 for the third station.
The central station SI' comprises a translni.ssion portion PEP connected between the terminal IEP and the aerial AEP
and a transmission portion PRP connected be-tween the aerial ARP and the terminal ISP~
The transmission of information from -the central station to -the sub-sta-tions is ef`fected in. accordance with a conventional time division multiplex method; the organi-zation of this multiplex system is shown at line a of ~ig~ 20 In the described example f`ourty-four frames T~O
35 TR1~ TR2 ~ .., TR43 are used, the orgranization of` these frame~ is not shown in detail, as it is not relevant for the wnderstanding of the invention. The assembl~ of` these ~rames TRO, TR1~ .. TR~3 f`orms a multi-frame, In -this PHF 81~530 4 12,2.1982 multi-frame~ to identify the individual ~rames, a synchronization word SY is placed in a time interval in :~ame TROo The transmissioll o~' information f'rom the sub stations to the central stati~n is ef~ected in time slots GR0~ GR1~ ... GRlO~ each slot being capable of containing a pac~et of 52 bytes (see line b in Fig. 2). ~ach o~ these sub~stations SS19 SS29 SS3 3 0.O can transmit information in one o~ the time slots GR0 to ~R9 and in addition ser~ice (on housekeeping) information in the time slot The time slots GR0~ GR1~ GR2~ ~,, GR10 are organized in frames TGR0, TGR1~ 0.. to ensure that each time slot GR10 is assigned in turn to a sub-sta-tion SS1 15 SS2, ... There are sixty four frames of this type. To identify these frames a word ~FrG is pro~ided in the time slot GR10 of frame TGR0.
According to the invention the system comprises at the sub-stations SS19 SS25 SS3~ ~.. end means to adjus-t 20 the delay MR1, ~R2~ MR3 to ensure that the transmission ~rom the sub-stations will be accuratel~ situated in the time slots assigned to them~ while at the centra:L station end it comprises means M~rR for measuring the transmisslon delays of the su.b-stations and l.n the mul-tiplex li~k con.nec-ting the central station to the s-wb-statiorLs there are time intervals ID f`or tran~smittirLg the del.ay measurement (see line a o~ Figr 2), while receiving means provided in the sub-stations are used to act on the said adJusting means~
To measure this delay9 each sub-station transmits in t~e centre of the time slot GRI0 assigned to it a word ~R whose use will be further explained in the further course of this descrip-tionO
Fig~ 3 shows by way of example a circui-t 5 diagram of' an embodiment of` a central station which is par-t of' a syste~ in accoraance with the inventiona The aerial A~P is connected to the oUtp~Lt of a P~IF ~1~530 5 12.2.1982 transmitter 10 in order that the data appliecl to its input 11 will be transmitted on a f`irst carrier frequency. This input 11 is connected to the output of a multiple~er 15 having -three inputs one of which is connected to the -terminal IEP~ whose second input permanently receives the information representing the worcl SY and whose third input is connected to the output of a R~M (random access memory); denoted by reference numeral 20. The inputs of -this memory are connected to the outputs of a delay measuring circuit CMR which, in this example9 in essence forms the delay measurement means l~MR, this circuit is connected to the output of a radio recei~rer 50~ w~ich is connected to an aerial ARP ~hich. receives the information con~eyed at a second carrier f'requency of a ~alue diffe-rent from the ~alue of the first carrier frequenc~l A clock recovery circuit 52 provides the rate of the data at the output of the receiver 50~ The data and the rate are gi~en on the one hand to the terminals ISP and on the other hand to the delay measure1nent circuit c~m.
This delay measuring circuit CMR comprises a shift regicter 60 whose data input is connected to theoutput of the receiver 50 and whose shift signal input is connected to the o-utput of the circuit 52. ~ decocLer circuit 61 produces an acti~e signal (a "O") w:hen the word MRn mentioned abo~e is contained in this register 60, This circu:it c-~m comprises also two bistable trigger circuits of the RS type, 63 and 65, Ths input S for acljus-ting the bistable trigger circuit 63 to -the "1" state is connected to the output of an OR gate 679 an input of 30 which is connected to the output of the decoder 61. The output of the decoder 61 is inter alia connected to the input S of the bi.stable -trigger circuit 65. The inputs R
o~ the bistable trigger circuits 63 and 65 are connected to a wire DGR and the second input of the gate 67 is connec ted to a wire SR~ The outputs Q of the ~istable trigger circuits 63 and 65 are connec-ted to the inputs of the memor-y 20 ~ the respecti~e wires F1 and ~2~ These wires PHF 81~530 6 12~2~1982 SR~ DGR lead ~rom a time base BT (in partic ~ r control circuit 74). This time base comprises a reference oscil-lator 70 which controls the transmission control circuit 72 and -the receiving control circuit 74 The transmission control circuit 72 de-termines all the time intarvals of the multiplex frame used for the transmission in the direction from the central station to the sub-sta-tions and particularly controls the multiple~er 15 so as to ensure that the information at the terminal IEP th.e synchroni~
zing word SY and the delay information ID will be trans-mitted in the time interval assigned to them. ~-t the central station the time slots GR0~ GR1~ o~ GRI0 are e~pected and actually received when the system functions properly9 at the instants which are rigidly bound up wi-th the transmitted multiplex signals in the central station-substations liIik~ Thus~ having reference to Fig. 2 the time slots GR0~ GR-I are received during the transmission of the frames TR0 to TR3 for GR0~ and TR4 to TR7 ~or GRl~
the time slots GR10 are received during the transmission 20 of the ~rarnes TR~0 to TRL~3. Over a wire assembly ~DL the transmissi.o:n control circuit 72 supplies an adclress code to the addressing inpu-t AD of the rnemory 20 so as to ensure -that the information IE will be written into the memory 20 and will be -transmitted in adequate time inter-25 val.c. for reception by the relevant sub-stations Over a wire assen1bly ADW the receiving control circui-t 74 applies an address code to the addressing input ~D of the rnemory 20 so as to ensure that the delay information available on the wires Sl and S2 will be registered in the .nemory in the 30 address corresponding to the relevant sub-stations~ Via the wire DGR the circuit 74 supplies a pulse which is shown in line c o~ Fig 2 and which corresponds to the beginning of the time slot GR10. ~ia the wire SR it also supplies a window pulse which is shown in line d of this 35 same Figure 2 and whose width corresponds to the ~uration of a ~ew binar~ elernents which i~orrn the word ~ R, the centre of this pulsa corresponds to the end of the word ~IF 8l.530 7 12.2.1982 MRR. ~inally, via the wire FSR3 t~e circuit 74 supplies a pulse which is shown at line e o~ Fig.2, This pulse is produced at the end o~ the window pulse and is applied to the circuit controlling writing into the memory 20 to register the information available on the wires F-l and F20 It i5 now possible to explain how the ~easuring circuit C~ functions.
Before the appearance of the pulse on t'he wire DGR~ the address code on the assembly ADlr corresponds to the number of one o~ -the frames TRG0~ TR1~ .~. and as a result thereof correspondsto one of the relevant sub-stations SS19 SSZ, .,. by measuring the delay; the pulse which appears ~n the wire DGR adjus-ts the bistable trigger ~5 circuit 63 and 65 to the "0" state; the logic signals trabsmitted via the wires F1 and F2 have for each of these wires the respective logic values; "0" and "0"~ It is therefore sufficient to examine the following three cases, The first case relates to the fact that the 20 transmission from the sub-stations is adaquately shifted in the time 7 for e~ample with an accu~acy of ~ 0l5 'binary element; in this case the word ~R~ is clecoded by the decoder- 61 at an instant loca-ted within the winclow pulse of wire SR~ the gate 6'7 whic'h is opene~ by the signa] from 25 WiI'O SR transnlits the decoding signal o~`-the decoder 61 to adjl:~t the bistable trigger circuit 63 to the "'1" state.
~'ha bistable trigger circuit 65 is also adjusted to the "1" state by this decoding signal. So t'he first case is characterlzed by logic signals having -the value "1"
30 and "1"~ which are transmitted via the wires F1 and F2 respectively.
The second case relates to the fact that the transmission ~rom the su:b-sta-tion is advancecl in the -time The word MRP is dacoded before the window pulse has been 35 produced, which reswlts in that the bistable trigger circui-t 65 is adjusted to tha "1" state and that the bistable trigger circui-t 63 ramains in the "0" state while PHF 81.530 8 12.201982 the gate 67 has not been able to transmit the decoding signa.l to the decoder 61. So this second case is charac-teriæed b~ logic signals ha.ving a value "0" and "1", which are transmit-ted via the wires F1 and F2, respectively.
The third case relates to the fact that the transmission ~'rom the sub~stations is delayed in the time, In this last case, when the writing pulse is produced on the wire FSR? the decoding signal not having appeared, the bistable trigger circuits 63 and 65 remain in the "0" stateO The ~gic signals on the wires F1 and F2 then have the respective values "0" and "0".
Thus, the signal on the wire F1 indicates whether the transmission ~rom the relevant sub-station is adequately shi~-ted or not shifted in the time~ while in the case where this transmission is not adequately shifted, the signal on the wire F2 indicates whether said transmis-sion is delayed or advancedO
Figo L~ is a detailed representation of the portions of the sub-station SS1 which are in accordance with the invention. The other s~ tions have identical constructions, Ths mouth of Ihe aerial AR1 is connec-tecl to the input of a radio receiver 100 which at its output restitutes the data which were transmitted at the sai.d first carrier frequency. ~ rate recovery circuit 102 applios signals to a demulti-ple~er 104 so as to ensure that it wil:L supply at its terminal IS1 the proper data to the load device and at the wires FR1 and FR2 the statcs of the wires F1 and F2 to the central station corresponding to the relevant sub-stations~ The wires FR1 and FR2 are connected to indicator lamps L1 and L2 which indicate the states of -the wires FR1 and FR2~ The rate recovery circuit also applies its signal to a counter 1 o6 9 The outputs of this coun-ter are connected to the inputs of an adder l10 ~or digital signals. The furth.er inputs of this adder are connected to switches CLl, CL2, CL3~ ,,. by means of which a variable bi.nary number can be displayed~ depending on the position of these switches. Thus7 the number at the ~ ~ ~9~77r7~ 7 PHF 8~730 9 12.2.1~82 output of the adder varies and all this occurs as if the assembly formed by the counter 106, the adder 110 and the switches CL1, CL2, CL3, ... behaves as one single coun-ter whose content can be shiftecl as a function of the position of the switches. A comparator 120 wllich compares the number available at the output of the adder 110 withthe content of a register 122 containing the time slots (GrO to GrlO) in ~lich th.e sub-station SS1 must transmit supplies a signal which authorizes the -transmission9 In -this Figure 5 the OlltpUt signal of the comparator 120 is applied to a radio transmitter 125 transmitti.ng in accor~
dance with the second carrier frequency~ the output o:f this transmitter is connected to the input of the aerial AE1 while its input is connected to the output of a multi-ple~er 130 an input o.f which is connected to the terminalIE1 and whose other input permanently receives the word ~RR.
The control of this multiplexer is effected from the cir-cuit 102 in accordance with cus-tomary procedures 90 tha-t it is not necessary to describe it here. The switches 20 CL1, CL3, CL2 are operated by an operato:r who observes the lamps L1 and L2; as these lamps indicate the direction i~
which -the shift must approximately 'be effected by manipula-ting the switches CL1, CL2, CL3 7 , ., the operator will ad~ust t:he delay to be ef~ected in -the transmission so ~5 as to ensure tha-t -this transmission will be adequatel-y shifted in the time.
Fig 5 shows a varian-t of an arrangement by means of which it is possible to effec-t this -time s'hift automati.cally9 instead of manually by a human opera.tor~
30 The swi-tches CL19 CL29 CL3, .~ are replaced by a two-way counter 2009 whose input for putting the counter in the up-coun-ting and the down-coun-ting positions i9 connec-ted to the wire FR2, while the clock input is connected to the output of a monostable circuit 220 havlng a period which is comparable to the total duration of the frames TRGO, TRG43, triggering of this monosta'hle circui.t being ensured by the signal present on the wire FR1 whi.ch indi~
PHF 81.530 10 12.2.1982 cates a poor fre~uellcr shift. Thus~ in some steps~ the sub-station is shifted in the -time and the content o~ the two-way counter 200 is ~ixed as o-therwise no signal would be present on the wires FRl and FR2~
~5
Transmission systems using the TDMA method(time division multiple access) are well known in the transmission technique utilizing satellitesO U.S. Patent 4,117,267 which issued on September 26, 1978 and assigned to International Standard Electric Corporation describes such a system.
In the systems which operate in accordance with the TDMA method, the synchronization problems are of par-ticular importance~ Sub-stations rnust not transmit ln overlapping time slots. To solve this probl~m, the above-mentioned patent describes a firs-t measure which consists in the provision of comparatively important time margins between each time slot and a second measure which, so as to reduce these time margins somewhat, consists in calcu-lating a time shift for the tran~mission of the substation as a function of their position~; these sub-stations, in this case aircrafts~ moving along predeter-mined paths.
The present invention proposes a transmission system as described in the opening paragraph for which the time margins are reduced and which does not have the problem that tirne shifts, must be calculated.
For that purpose such a system is characterized in that it comprises,at the side of the sub stations, delay PHF ~1,530 2 1202~1982 adjustment means to ensure that tha transmission from the sub-stations is properly located in the time slots assigned to them7 in that it cornprises at the central station end means to measure the transmission delays between 5 the sub-stations and the central station~ in that the said ~ from the central station to the sub stations is arranged for transmitting inter alia inform~tion about the measured delay and in that means for receiving the said measurement provided in the sub-stations are used to act on lO the said adjusting means.
Thus 5 in accordance with the invention the time shift to be effe~ted for the transmission from the sub~
stations is no longer calculated but may be measured continuouslyl The time margins may then be reduced to a ~5 considerable e~tent.
The following description given by way of e~ample with referance to the accompanying drawings will make it better understood how the invention can be put into effect.
Fig. 1 shows a circuit diagram of a s~stem in accordance with the invention, Fig, 2 is a diagram showing -the organi~ation of the links between the central station and the sub-stations on the one hand and between the sub-s-tations and the 25 ccntral station on the other hancl~ as well as some signals prescnt within the measuring circuit comprised in a central station wl1ose circuit diagram is shown in Fig~ 3.
Fig, 3 shows in detail the circui-t diagram of a central station in accordance with the inven-tionO
Fig~ ~ shows in detail the circuit diagram of a sub-station in accordance with the invention, Fig~ 5 shows a variant of the embodirnent of a sub-station in accordance with the inven-tion, ~ he s~stem shown in Fig~ 1 is formed by a 35 central station SP and sub-stations SSI7 SS27 SS35,o ~he central station SP has a terminal IEP for receiving the information intended -to be transmitted to the sub-stations PMF 81.530 3 1 2~2~1982 SS1, SS2, SS3 7 , . ~ and a terminal ISP for ma~ing the information coming from these sub-stations available;
these sub-sta-tions SS1 9 SS29 SS3 are provided in a corres-ponding manner with respec-tive terminals IE19 IE2, IE3,.~.
5 f`or receiving the information intended for the central station and terminals IS1, IS2, IS3 for ma~ing the inforrna-tion coming from the central station available.
The station SP transmits information to the sub-stations SSi~ SS2, SS3, . . via a radio channel by means of its transmitting aerlal AEPo To receive this informa-tiOIl, the sub-stations SSI~ SS2 T SS3 9, . . have recei.ving aerials ARl~ AR2~ AR3~ ... and to transmit information to the central station the~ have transmitting aerials ~E1, A~2 7 AE3, while the central station has one aerial ARP to 5 receive the last-mentioned information. The sub-stations SS1~ SS2~ SS3l ... comprise a receiving portion PR1 7 PR29 PR3~ respectively connected between the aeri.al AR2 and the terminal IS1 for the first station, between the aerial AR2 and the terminal IS2 for the second sta-tion, 20 and between the aerial AR3 and the terrninal IS3 for the third station~ and comprises a -transmission portion PE1, PE2 a.nd PE3 connectecl between the terminal IE1 and the aerial A~1 for the first station, between the terminal I~2 an(l the aerial ~E2 I`or t:he second station and hetween tne 25 terminal IF3 and thc aeria.l AE3 for the third station.
The central station SI' comprises a translni.ssion portion PEP connected between the terminal IEP and the aerial AEP
and a transmission portion PRP connected be-tween the aerial ARP and the terminal ISP~
The transmission of information from -the central station to -the sub-sta-tions is ef`fected in. accordance with a conventional time division multiplex method; the organi-zation of this multiplex system is shown at line a of ~ig~ 20 In the described example f`ourty-four frames T~O
35 TR1~ TR2 ~ .., TR43 are used, the orgranization of` these frame~ is not shown in detail, as it is not relevant for the wnderstanding of the invention. The assembl~ of` these ~rames TRO, TR1~ .. TR~3 f`orms a multi-frame, In -this PHF 81~530 4 12,2.1982 multi-frame~ to identify the individual ~rames, a synchronization word SY is placed in a time interval in :~ame TROo The transmissioll o~' information f'rom the sub stations to the central stati~n is ef~ected in time slots GR0~ GR1~ ... GRlO~ each slot being capable of containing a pac~et of 52 bytes (see line b in Fig. 2). ~ach o~ these sub~stations SS19 SS29 SS3 3 0.O can transmit information in one o~ the time slots GR0 to ~R9 and in addition ser~ice (on housekeeping) information in the time slot The time slots GR0~ GR1~ GR2~ ~,, GR10 are organized in frames TGR0, TGR1~ 0.. to ensure that each time slot GR10 is assigned in turn to a sub-sta-tion SS1 15 SS2, ... There are sixty four frames of this type. To identify these frames a word ~FrG is pro~ided in the time slot GR10 of frame TGR0.
According to the invention the system comprises at the sub-stations SS19 SS25 SS3~ ~.. end means to adjus-t 20 the delay MR1, ~R2~ MR3 to ensure that the transmission ~rom the sub-stations will be accuratel~ situated in the time slots assigned to them~ while at the centra:L station end it comprises means M~rR for measuring the transmisslon delays of the su.b-stations and l.n the mul-tiplex li~k con.nec-ting the central station to the s-wb-statiorLs there are time intervals ID f`or tran~smittirLg the del.ay measurement (see line a o~ Figr 2), while receiving means provided in the sub-stations are used to act on the said adJusting means~
To measure this delay9 each sub-station transmits in t~e centre of the time slot GRI0 assigned to it a word ~R whose use will be further explained in the further course of this descrip-tionO
Fig~ 3 shows by way of example a circui-t 5 diagram of' an embodiment of` a central station which is par-t of' a syste~ in accoraance with the inventiona The aerial A~P is connected to the oUtp~Lt of a P~IF ~1~530 5 12.2.1982 transmitter 10 in order that the data appliecl to its input 11 will be transmitted on a f`irst carrier frequency. This input 11 is connected to the output of a multiple~er 15 having -three inputs one of which is connected to the -terminal IEP~ whose second input permanently receives the information representing the worcl SY and whose third input is connected to the output of a R~M (random access memory); denoted by reference numeral 20. The inputs of -this memory are connected to the outputs of a delay measuring circuit CMR which, in this example9 in essence forms the delay measurement means l~MR, this circuit is connected to the output of a radio recei~rer 50~ w~ich is connected to an aerial ARP ~hich. receives the information con~eyed at a second carrier f'requency of a ~alue diffe-rent from the ~alue of the first carrier frequenc~l A clock recovery circuit 52 provides the rate of the data at the output of the receiver 50~ The data and the rate are gi~en on the one hand to the terminals ISP and on the other hand to the delay measure1nent circuit c~m.
This delay measuring circuit CMR comprises a shift regicter 60 whose data input is connected to theoutput of the receiver 50 and whose shift signal input is connected to the o-utput of the circuit 52. ~ decocLer circuit 61 produces an acti~e signal (a "O") w:hen the word MRn mentioned abo~e is contained in this register 60, This circu:it c-~m comprises also two bistable trigger circuits of the RS type, 63 and 65, Ths input S for acljus-ting the bistable trigger circuit 63 to -the "1" state is connected to the output of an OR gate 679 an input of 30 which is connected to the output of the decoder 61. The output of the decoder 61 is inter alia connected to the input S of the bi.stable -trigger circuit 65. The inputs R
o~ the bistable trigger circuits 63 and 65 are connected to a wire DGR and the second input of the gate 67 is connec ted to a wire SR~ The outputs Q of the ~istable trigger circuits 63 and 65 are connec-ted to the inputs of the memor-y 20 ~ the respecti~e wires F1 and ~2~ These wires PHF 81~530 6 12~2~1982 SR~ DGR lead ~rom a time base BT (in partic ~ r control circuit 74). This time base comprises a reference oscil-lator 70 which controls the transmission control circuit 72 and -the receiving control circuit 74 The transmission control circuit 72 de-termines all the time intarvals of the multiplex frame used for the transmission in the direction from the central station to the sub-sta-tions and particularly controls the multiple~er 15 so as to ensure that the information at the terminal IEP th.e synchroni~
zing word SY and the delay information ID will be trans-mitted in the time interval assigned to them. ~-t the central station the time slots GR0~ GR1~ o~ GRI0 are e~pected and actually received when the system functions properly9 at the instants which are rigidly bound up wi-th the transmitted multiplex signals in the central station-substations liIik~ Thus~ having reference to Fig. 2 the time slots GR0~ GR-I are received during the transmission of the frames TR0 to TR3 for GR0~ and TR4 to TR7 ~or GRl~
the time slots GR10 are received during the transmission 20 of the ~rarnes TR~0 to TRL~3. Over a wire assembly ~DL the transmissi.o:n control circuit 72 supplies an adclress code to the addressing inpu-t AD of the rnemory 20 so as to ensure -that the information IE will be written into the memory 20 and will be -transmitted in adequate time inter-25 val.c. for reception by the relevant sub-stations Over a wire assen1bly ADW the receiving control circui-t 74 applies an address code to the addressing input ~D of the rnemory 20 so as to ensure that the delay information available on the wires Sl and S2 will be registered in the .nemory in the 30 address corresponding to the relevant sub-stations~ Via the wire DGR the circuit 74 supplies a pulse which is shown in line c o~ Fig 2 and which corresponds to the beginning of the time slot GR10. ~ia the wire SR it also supplies a window pulse which is shown in line d of this 35 same Figure 2 and whose width corresponds to the ~uration of a ~ew binar~ elernents which i~orrn the word ~ R, the centre of this pulsa corresponds to the end of the word ~IF 8l.530 7 12.2.1982 MRR. ~inally, via the wire FSR3 t~e circuit 74 supplies a pulse which is shown at line e o~ Fig.2, This pulse is produced at the end o~ the window pulse and is applied to the circuit controlling writing into the memory 20 to register the information available on the wires F-l and F20 It i5 now possible to explain how the ~easuring circuit C~ functions.
Before the appearance of the pulse on t'he wire DGR~ the address code on the assembly ADlr corresponds to the number of one o~ -the frames TRG0~ TR1~ .~. and as a result thereof correspondsto one of the relevant sub-stations SS19 SSZ, .,. by measuring the delay; the pulse which appears ~n the wire DGR adjus-ts the bistable trigger ~5 circuit 63 and 65 to the "0" state; the logic signals trabsmitted via the wires F1 and F2 have for each of these wires the respective logic values; "0" and "0"~ It is therefore sufficient to examine the following three cases, The first case relates to the fact that the 20 transmission from the sub-stations is adaquately shifted in the time 7 for e~ample with an accu~acy of ~ 0l5 'binary element; in this case the word ~R~ is clecoded by the decoder- 61 at an instant loca-ted within the winclow pulse of wire SR~ the gate 6'7 whic'h is opene~ by the signa] from 25 WiI'O SR transnlits the decoding signal o~`-the decoder 61 to adjl:~t the bistable trigger circuit 63 to the "'1" state.
~'ha bistable trigger circuit 65 is also adjusted to the "1" state by this decoding signal. So t'he first case is characterlzed by logic signals having -the value "1"
30 and "1"~ which are transmitted via the wires F1 and F2 respectively.
The second case relates to the fact that the transmission ~rom the su:b-sta-tion is advancecl in the -time The word MRP is dacoded before the window pulse has been 35 produced, which reswlts in that the bistable trigger circui-t 65 is adjusted to tha "1" state and that the bistable trigger circui-t 63 ramains in the "0" state while PHF 81.530 8 12.201982 the gate 67 has not been able to transmit the decoding signa.l to the decoder 61. So this second case is charac-teriæed b~ logic signals ha.ving a value "0" and "1", which are transmit-ted via the wires F1 and F2, respectively.
The third case relates to the fact that the transmission ~'rom the sub~stations is delayed in the time, In this last case, when the writing pulse is produced on the wire FSR? the decoding signal not having appeared, the bistable trigger circuits 63 and 65 remain in the "0" stateO The ~gic signals on the wires F1 and F2 then have the respective values "0" and "0".
Thus, the signal on the wire F1 indicates whether the transmission ~rom the relevant sub-station is adequately shi~-ted or not shifted in the time~ while in the case where this transmission is not adequately shifted, the signal on the wire F2 indicates whether said transmis-sion is delayed or advancedO
Figo L~ is a detailed representation of the portions of the sub-station SS1 which are in accordance with the invention. The other s~ tions have identical constructions, Ths mouth of Ihe aerial AR1 is connec-tecl to the input of a radio receiver 100 which at its output restitutes the data which were transmitted at the sai.d first carrier frequency. ~ rate recovery circuit 102 applios signals to a demulti-ple~er 104 so as to ensure that it wil:L supply at its terminal IS1 the proper data to the load device and at the wires FR1 and FR2 the statcs of the wires F1 and F2 to the central station corresponding to the relevant sub-stations~ The wires FR1 and FR2 are connected to indicator lamps L1 and L2 which indicate the states of -the wires FR1 and FR2~ The rate recovery circuit also applies its signal to a counter 1 o6 9 The outputs of this coun-ter are connected to the inputs of an adder l10 ~or digital signals. The furth.er inputs of this adder are connected to switches CLl, CL2, CL3~ ,,. by means of which a variable bi.nary number can be displayed~ depending on the position of these switches. Thus7 the number at the ~ ~ ~9~77r7~ 7 PHF 8~730 9 12.2.1~82 output of the adder varies and all this occurs as if the assembly formed by the counter 106, the adder 110 and the switches CL1, CL2, CL3, ... behaves as one single coun-ter whose content can be shiftecl as a function of the position of the switches. A comparator 120 wllich compares the number available at the output of the adder 110 withthe content of a register 122 containing the time slots (GrO to GrlO) in ~lich th.e sub-station SS1 must transmit supplies a signal which authorizes the -transmission9 In -this Figure 5 the OlltpUt signal of the comparator 120 is applied to a radio transmitter 125 transmitti.ng in accor~
dance with the second carrier frequency~ the output o:f this transmitter is connected to the input of the aerial AE1 while its input is connected to the output of a multi-ple~er 130 an input o.f which is connected to the terminalIE1 and whose other input permanently receives the word ~RR.
The control of this multiplexer is effected from the cir-cuit 102 in accordance with cus-tomary procedures 90 tha-t it is not necessary to describe it here. The switches 20 CL1, CL3, CL2 are operated by an operato:r who observes the lamps L1 and L2; as these lamps indicate the direction i~
which -the shift must approximately 'be effected by manipula-ting the switches CL1, CL2, CL3 7 , ., the operator will ad~ust t:he delay to be ef~ected in -the transmission so ~5 as to ensure tha-t -this transmission will be adequatel-y shifted in the time.
Fig 5 shows a varian-t of an arrangement by means of which it is possible to effec-t this -time s'hift automati.cally9 instead of manually by a human opera.tor~
30 The swi-tches CL19 CL29 CL3, .~ are replaced by a two-way counter 2009 whose input for putting the counter in the up-coun-ting and the down-coun-ting positions i9 connec-ted to the wire FR2, while the clock input is connected to the output of a monostable circuit 220 havlng a period which is comparable to the total duration of the frames TRGO, TRG43, triggering of this monosta'hle circui.t being ensured by the signal present on the wire FR1 whi.ch indi~
PHF 81.530 10 12.2.1982 cates a poor fre~uellcr shift. Thus~ in some steps~ the sub-station is shifted in the -time and the content o~ the two-way counter 200 is ~ixed as o-therwise no signal would be present on the wires FRl and FR2~
~5
Claims (5)
1. A system for transmitting information between a central station and a plurality of sub-stations operating, for transmission in the direction from the sub-stations to the central station in accordance with a determined method consisting of providing time slots in each of which only one sub-station can transmit, the disposition of these time slots being determined by a synchronizing signal transmitted in a link fro the central station to the sub-stations, the system being characterized in that the system comprises delay adjusting means at each of the sub-stations to ensure that the transmission from the sub-stations will be properly situated in the time slots assigned to them, and means at the central station for measuring the transmission delays between the sub-stations and the central station, that the said link between the central station and the sub-stations comprising means is provided (intervals ID) to transmit delay measurement information while the means receiving the said measurement information (arranged) in the sub-stations comprises means controlling said adjusting means.
2. A system for transmitting information in accord-ance with Claim 1, characterized in that the link between the central station and the sub-stations comprises a time-division multiplex link in which time intervals are provided for transmitting the delay measurement information.
3. A transmission system as claimed in Claim 1 or Claim 2, characterized in that the sub-stations include a generator for generating a predetermined word in a given time interval in the link accomplished by said determined method, while at the central station end the means for measuring the delays are comprises of a decoding circuit for decoding said word which cooperates with a delay measuring circuit connected to determine the delay between the output signal of the decoding circuit and a locally generated sig-nal which determines the instant of the expected appearance of the said output signal.
4. A transmission system as claimed in Claim 1 or Claim 2, characterized in that the delay adjustment means comprise manually operable switches while the receiving means comprise indicator lamps connected to indicate the direction in which the delay must be effected to correct time shift errors.
5. A transmission system as claimed in Claim 1, 2 or 3, characterized in that the receiving means are coupled to the adjusting means in order to effect the time shift automatically.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8105633 | 1981-03-20 | ||
| FR8105633A FR2502426A1 (en) | 1981-03-20 | 1981-03-20 | SYSTEM FOR TRANSMITTING INFORMATION BETWEEN A MAIN STATION AND SECONDARY STATIONS OPERATING IN ACCORDANCE WITH A TDMA METHOD |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1186426A true CA1186426A (en) | 1985-04-30 |
Family
ID=9256477
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000398702A Expired CA1186426A (en) | 1981-03-20 | 1982-03-18 | System of transmitting information between a central station and sub-stations |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US4472802A (en) |
| AU (1) | AU557246B2 (en) |
| BR (1) | BR8201464A (en) |
| CA (1) | CA1186426A (en) |
| DE (1) | DE3209381A1 (en) |
| FR (1) | FR2502426A1 (en) |
| GB (1) | GB2095516B (en) |
| ZA (1) | ZA821225B (en) |
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- 1981-03-20 FR FR8105633A patent/FR2502426A1/en active Granted
-
1982
- 1982-02-24 ZA ZA821225A patent/ZA821225B/en unknown
- 1982-03-15 DE DE19823209381 patent/DE3209381A1/en active Granted
- 1982-03-16 US US06/358,753 patent/US4472802A/en not_active Expired - Lifetime
- 1982-03-17 GB GB8207811A patent/GB2095516B/en not_active Expired
- 1982-03-17 BR BR8201464A patent/BR8201464A/en unknown
- 1982-03-17 AU AU81604/82A patent/AU557246B2/en not_active Expired
- 1982-03-18 CA CA000398702A patent/CA1186426A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| BR8201464A (en) | 1983-02-01 |
| ZA821225B (en) | 1983-09-28 |
| GB2095516B (en) | 1985-08-14 |
| AU8160482A (en) | 1982-09-23 |
| FR2502426B1 (en) | 1984-07-27 |
| FR2502426A1 (en) | 1982-09-24 |
| DE3209381A1 (en) | 1982-11-18 |
| US4472802A (en) | 1984-09-18 |
| GB2095516A (en) | 1982-09-29 |
| DE3209381C2 (en) | 1991-11-07 |
| AU557246B2 (en) | 1986-12-11 |
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