FR2684508A1 - TELEPHONE ARRAY TELECOMMUNICATIONS SYSTEM PROVIDING ACCELERATED ACCESS PROCEDURES, AND ASSOCIATED METHOD. - Google Patents

Abstract

A telephone backhaul telecommunications system is provided which includes a central station (11) and a remote unit (10) having means for communicating over a TDMA link. Predetermined signaling slots (channel 1) and predetermined traffic slots (channels 2 to 5) are provided for the respective transmission of signaling information and traffic information from the central station to the remote unit while that predetermined signaling slots and predetermined traffic slots are provided for the respective communication of signaling information and traffic information from the remote unit to the central station during relatively busy traffic. The invention enables the remote unit to transmit signaling information, for example an ALOHA access request, on a slice of traffic (for example channel 5) during relatively low traffic and, at the central station, to to receive the signaling information during the traffic slice and to treat this information as signaling information.

Description

1 2684508

  The present invention relates to telecommunications systems using telephone lines, which communicate over a time division multiple access channel, as well as an access method in such a system and a

  remote unit capable of communicating on such a system.

  A typical protocol for establishing communications, or calls, in a time division multiple access or multiple access system

  temporal, (TDMA) is illustrated in Figures 1 and 2.

  In Figure 1, the incoming (incoming) transmissions of a remote unit

  requesting data (mobile or portable) to a central unit appear on the left side, outward (outgoing) transmissions to the requesting unit and a requested unit appear in the center, and incoming transmissions from the requested unit appears on the right side The user of the requesting unit presses the "talk" button, or altemat button, (P Mf) or performs some other action in order to start the transmission The unit remote requester issues an access instruction "ALOHA" over a signaling time interval, or slice The central unit receives this instruction, in

  acknowledges receipt and issues an "AHOY" instruction to the requesting unit

  The function of the AHOY instruction is to check that the requested unit is free before attempting to establish communication. This operation is not

  essential and, therefore, is indicated by a dashed line.

  The requested unit acknowledges receipt of this instruction during the next signaling section The central unit receives the acknowledgment of receipt and, during the next signaling section, transmits to the requesting unit, on the outgoing channel, a "TRANSMIT Ti E ON TRACK" instruction as well as the indication of the traffic channel (conversation) to be used After that, the requesting unit transmits on

this traffic lane.

  The letters on the right side of Figure 1 refer to

  events shown in Figure 2.

  In FIG. 2, the sequence of events is further illustrated in terms of outgoing (outward) and inbound (incoming) links arranged on different frequencies and divided into slices. By way of illustration, there are

  five slices of traffic or conversation, ("channels") for each slice of signal

  reading ("channel") The channels are numbered from 1 to 6 Channel 1 is the signaling channel Each section has a duration of 15 ms A "frame" includes 6 sections and has a duration of 90 ms There is a small offset appearing between the

  incoming frame and outgoing frame, as is typical in the operating

  is lying. The user presses his PIT button at instant A The next incoming signaling segment is at instant B In this period of time, the requesting unit issues its access request ALOHA The central unit acknowledges receipt at instant C, the requested unit acknowledges receipt at instant D, and the central unit emits the TRANSMIT ON TRACK instruction at instant E In the case where the channel is channel 2, the requesting unit transmits the signal of traffic at time F There is a total delay of 240 ms between the pressing of the PIT button and the start of

the show.

  This access delay is undesirable and is particularly annoying when traffic is reduced. Under reduced traffic conditions, a user is very likely to obtain immediate access to the channel.

  less patient than when he knows or suspects that traffic is loaded.

  According to the invention, there is provided a method of accessing a telecommunications system by telephone lines comprising a central station and a remote unit having means for communicating via a TDMA channel, the method comprising the following operations: providing slices of predetermined signaling and predetermined traffic slices for the respective transmission of signaling information and traffic information from the central station to the remote unit, and providing predetermined signaling slices and predetermined traffic slices in view of the respective communication of signaling information and traffic information from the remote unit to the

  central station during relatively busy traffic.

  The invention aims to enable the remote unit to transmit information

  signaling on a slice of traffic during a relatively traffic

  reduces and provides a means contained in the central station for receiving information

  signaling signals during the traffic segment and for processing information

  as signaling information.

  The invention also provides a telecommunications system by

  telephone routes, comprising a central station and at least one remote unit

  designed to communicate via a TDMA channel The remote unit is intended to transmit signaling information, for example a request for access to

  one lane, on a slice of traffic during relatively reduced traffic, and the sta-

  This central function is intended to receive this information during the traffic segment and to treat the information as signaling information, for example by sending an acknowledgment of receipt and by initiating an acceptance of access request.

one way.

  The central station can initiate an acceptance of access request to

  a channel using signaling signals using signal sections

  The advantage of the invention is that, under reduced traffic conditions, the remote unit does not have to wait for the next signaling section before transmitting its

request for access to a track.

  The remote unit preferably has means for over-

  take care of the instructions for acceptance of a channel access request intended for other remote units and to keep a record of the identifications of the accepted channels In this way, the remote unit can send information

  signaling on an unassigned traffic lane.

  The following description, intended to illustrate the invention, aims

  to give a better understanding of its characteristics and advantages; they are based on the appended drawings, in which: FIG. 1 shows an exchange of instructions between a remote unit and a central unit during the access procedure to a channel, according to the prior art; FIG. 2 shows the typical division of the incoming (inbound) and outward (outbound) channels in a TDMA route telecommunications system, according to the prior art; FIG. 3 shows the incoming and outgoing links of a TDMA telecommunications system according to the preferred embodiment of the invention; and Figure 4 shows a remote unit according to the embodiment

preferred of the invention.

  We have already described Figures 1 and 2 in relation to the prior art

  We will now describe, by way of example, a preferred embodiment

  of the invention, in connection with Figures 3 and 4.

  In Figure 3, a communication establishment protocol is shown.

  TDMA indications which includes two telecommunications links working on different frequencies, which are separated for example by 25 k Hz The outgoing link, going from a central unit to distant units, is illustrated by the sequence of time slots 30 L ' other bond is represented by the sequence

  time slots 31 In each link, time is divided into frames

  taking 6 time slices, where the first slice is a signaling slice

  tion ("channel") and slices 2 to 6 are traffic slices ("channels") Each slice has a duration of 15 ms A frame of 6 slices has a duration of ms.

  According to the preferred embodiment of the invention, a communication

  The user of a remote unit presses his FIT button (or performs an equivalent action requesting transmission) and the remote unit immediately issues an ALOHA access instruction on the first

  available channel (signaling or traffic) The way in which the unit removes

  gnée ensures that channels are free is described below This transmission of an ALOHA access instruction is represented by traffic channel 5 "shaded" immediately following the actuation of the PIT button The central unit receives this access instruction ALOHA and, in the first available slot (traffic or signaling), the central unit issues an acknowledgment instruction and an AHOY instruction (C) In the example of FIG. 3, those -these are issued on the

  signaling channel (outgoing channel 1).

  The requested unit sends its acknowledgment of receipt in the first available time slot (traffic or signaling), which, in the example shown, is on the signaling slot (incoming channel 1) The reasons why the requested unit "knows" that the range is available are the same as

  for the requesting unit and are described below.

  The central unit issues the "TRANSMIT ON TRACK" instruction in

  the first available tranche, which, in the case shown, is the outgoing channel 3.

  The central unit instructs the requested unit to switch to a selected channel which, if all the channels are free and are not subject to any other condition, may be the channel corresponding to the time slot immediately

next, incoming channel 3.

  The total time between pressing the PIT button and accessing the traffic lane is, in the example shown, 75 ms. Although this is a "best case" scenario, there is a notable reduction, compared to the 240 ms corresponding to the worst case of the typical system of the technique

anterior.

  Each remote unit monitors the outgoing link and receives and decodes the instructions addressed to the other remote units. When the unit transmits a TRANSMIT ON TRACK instruction, a remote unit recognizes this instruction and takes note of the channel which has been accepted (even if the instruction is not intended for the remote unit considered) In this way, the remote unit can build a record of the channels whose assignment has been accepted and of the channels which remain free. It is said that a channel becomes free either at the receipt of a "clear the lane" instruction, that is, in a system where there is no such instruction, the recognition of a characteristic of no traffic on this time slot The characteristic of no traffic is an unmodulated carrier, a "free" signal, or a complete absence of carrier (depending on the design of the transmitter), but this can be any characteristic of no traffic

  known in the prior art.

  As general traffic on a lane increases, the benefit from

  the invention diminishes Thus, when four out of five of the traffic lanes are used

  pées, the improvement provided by the invention is significantly reduced.

  Referring to FIG. 4, which shows in detail a remote unit 10 The remote unit comprises an antenna 40 connected to a duplexer 41, itself connected to a high frequency (RF) reception circuit 42 and to a

  RF transmission circuit 43 The reception circuit 42 is connected to a converter

  analog-digital (A / D) 44 and the transmission circuit 43 is connected to a

  digital / analog converter D / A 45 The converters 44 and 45 cons-

  respectively the input and output of a digital signal processing device which performs certain functions, as illustrated in the figure. Thus, a demodulator 46, a modulator 47, a device 48 for formatting the channels are provided, a search table 49, an error coder 50 for the channels, and a speech coder 51 The speech coder 51 is connected to an A / D converter 52 to allow bidirectional connection to a handset The speech coder 51 and converter 52 can of course be replaced in a

  telecommunications applying to data.

  The remote unit communicates with a central unit 11.

  When the remote unit (a mobile or portable transceiver has

  switched on, it starts to receive broadcasts from the station

  tion and synchronizes with the bursts received from the central station

  trale This is done by means of a synchronization word received from the central station at the start of each frame or each time slot These signals are received via the RF reception circuit 42, are demodulated in the demodulator 46 and are identified in the device 48 for formatting the channels using a synchronization algorithm, as is well known in the art.

  technical The unit remains in a "free" mode where the reception circuit 42 is active.

  The unit receives, demodulates and decodes the signaling information received from the central unit in the signaling time slots In this information, there are instructions for accepting a channel access request which are intended for other users of the geographic area So, for example, the unit

  n 20 can receive a "TRANSMIT ON TRACK 2" instruction

  truction is identified and, in lookup table 49, a flag is set to indicate that channel 2 has been allocated and is busy Lookup table 49 has a flag element for each of the five traffic lanes When traffic loads and as more channels are assigned, these channel assignment instructions are stored in Table 49 When the system uses "clear channel" instructions, the receipt of a "clear channel" instruction causes the erasure, in table 49, of the flag relating to this lane When instructions are not used "clear the lane", that is to say when a lane is freed by simple cessation of the transmission, the flag bit contained in table 49

  is cleared when the unit no longer detects traffic in this time slot.

  In a short time after powering up, the unit will have

  acquired a knowledge of the traffic taking place on the tracks, and this will be emma-

fueled in table 49.

  As another possibility of monitoring the "TRANSMIT ON TRACK" instructions, the unit can simply detect whether or not traffic exists on the respective tracks. This makes it possible to construct the

  information on the existence of traffic.

  To build table 49, it is possible to use various combinations

  sounds of lane assignment and lane clearance instructions and traffic measurements.

  When the user presses the PIT button (not shown), the

  positive 48 for formatting the channels search in table 49 in order to find

  a free channel The format 48 device composes a telegram with trans-

  switch to the central station, which starts with a synchronization word and com-

  carries an ALOHA access request instruction The formatting device

  48 delivers this telegram to modulator 47 at the start of the first tranche

  on an unused traffic lane, according to the indications provided by the

  table 49 The telegram is sent to the transmitter circuit 43, which is switched on.

  at the appropriate time, and the telegram is sent via

antenna 40.

  The central station, which is the station providing channel request acceptances and receiving channel release instructions, is informed of the

  when there is no traffic in a given time slot The station cen-

  traie maintains a similar search table for the pathways and their affecta-

tions.

  The operation of the central station is as follows: The central station

  trale is ready to receive an ALOHA access request from any of the units located in the geographic area.

  receives the ALOHA access request (and if we assume that there was no colli-

  sions, that is to say that no other unit at the same time transmits, by the same time slot, an access request ALOHA), it receives the telegram, decodes from it identity of the unit requesting access and, during the immediately following signaling time slot (section 1 in FIG. 3), issues a

  acknowledgment of receipt and an AHOY message identifying the unit requested.

  Mobile or portable unit receives acknowledgment and message

  AHOY and issues its own acknowledgment of receipt in the time slot available

  next target (traffic or signaling) The procedure continues as

described above.

  As traffic increases, the units rely more and more on the predefined signaling channel to send signaling signals until the channels are saturated, and then, there are no other traffic channels available to assign and all other signaling information is issued

  on the respective incoming or outgoing signaling channel.

  When two distant units transmit simultaneously and in order to interfere with each other ALOHA access requests at the same time in the same time slot and with a signal intensity such that it is not possible to reconstitute at least one of the two signals, there is a collision and at least one of the two units must try again The system of the preferred embodiment of the invention reduces the probability of collisions, since the emission of

  signaling is not obliged to stick to the same signaling path.

  It will be understood that a remote unit according to the embodiment pre-

  bere of the invention can communicate with another remote unit which performs all its signaling work on the signaling channel (according to the typical system of the prior art) The reduction in access time is not so

  important, but there is still a significant reduction in it.

  It will also be understood that it is not essential that the central unit is designed to transmit signaling signals on the signaling channels and the traffic lanes In a system where the central unit transmits signaling messages only on the signaling channel, there will nevertheless be a significant reduction in access time since the requesting unit will not have to wait for the next incoming signaling time slot to issue its ALOHA access instruction. proportion of eas, using a free traffic lane, it will issue its request for ALOHA access in time for the central unit to receive the request and transmit its acknowledgment of receipt and its message

  AHOY in the outgoing signaling time slot immediately following.

  This alone can already bring a reduced access time to a value of the order of ms in the example described, even if the following signaling operations

  must be carried out on the signaling track.

  Of course, those skilled in the art will be able to imagine, from the

  process and system whose description has just been given simply

  illustrative and in no way limitative, various variants and modifications not coming out

of the scope of the invention.

Claims (9)

  1 Access method in a telecommunications system by telephone lines comprising a central station (11) and a remote unit (10) which have means for communicating on a TDMA link, comprising the following operations: providing predetermined signaling slots and slices of   predetermined traffic for the respective transmission of signaling information   readout and traffic information from the central station to the remote unit during relatively busy traffic; providing predetermined signaling slots and predetermined traffic slots for the respective communication of signaling information and traffic information from the remote unit to the central station during relatively busy traffic; characterized by the following operations: allowing the remote unit to transmit signaling information on a slice of traffic during relatively reduced traffic;   receive signaling information in the central station during   in the traffic slice and treat the information as traffic information signage.   2 Compressed telephone route telecommunications system   nant a central station (11) and at least one remote unit (10) designed to communicate on a TDMA channel, characterized in that:   the remote unit has means for transmitting information   signaling mations on a signaling section during related traffic   charged and to send signaling information selectively on   a signaling section or a section of traffic during related traffic   tively reduced, and the central station has means for receiving this information during the traffic slice and for processing this information as signaling information.   3 System according to claim 2, characterized in that the central station comprises means making it possible to transmit an acknowledgment of receipt and to launch an acceptance of request for access to a channel in response to the reception of   signaling information on the traffic section.   4 System according to claim 2 or 3, characterized in that the means contained in the remote unit and used to transmit signaling information comprise means serving to transmit a request for access to a way.   5 System according to any one of claims 2 to 4, character-   in that the central station includes means for transmitting an instruction to accept a request for access to a channel on a slice of traffic   during relatively reduced traffic.   6 System according to any one of claims 2 to 5, character-   that the remote unit has means (49) for monitoring the instructions for accepting a channel access request which are addressed to other remote units, for keeping a record of the identifications of the channels thus affected and therefore to identify time slices that do not are not assigned to traffic.   7 Remote unit (10) used for communication on a communication system   radio telecommunications by telephone routes, including a central station   trale (11) and at least one remote unit designed to communicate on a multiple   channel reality comprising a plurality of traffic channels and at least one predetermined signaling channel, where each channel comprises a sequence of sections   times interleaved with time slots from other channels, said unit   being characterized by: means (49) for monitoring the use of the channels by other remote units; means for transmitting signaling information on a traffic channel which has been determined not to be used; means for transmitting signaling information on the traffic channel thus determined when there is no unused traffic channel of which   the time slot appears before the time slot of the pre-   determined. 8 remote unit according to claim 7, characterized in that the   means for monitoring the use of the channels include means   putting to identify instructions for accepting access request to a channel   which are addressed to other remote units.   9 remote unit according to claim 7 or 8, o the means for monitoring the use of the channels include means for identifying   channel clearing instructions that are sent to other remote units.   il Remote unit according to claim 7, 8 or 9, characterized in that the means used to monitor the use of the channels comprise means   to identify radio activity on the track.