EP0954936A1

EP0954936A1 - Method for providing uplinks in a radiomessaging network, radiomessaging network and network radio terminal, for implementing the method

Info

Publication number: EP0954936A1
Application number: EP98903110A
Authority: EP
Inventors: Laurent Zibell
Original assignee: Sagem SA
Current assignee: Sagem SA
Priority date: 1997-01-24
Filing date: 1998-01-23
Publication date: 1999-11-10
Also published as: CN1249884A; WO1998033341A1; FR2758933B1; FR2758933A1

Abstract

The invention concerns a method for providing uplinks in a radiomessaging network comprising at least one base station (4), for transmitting radio messages to a plurality of radio terminal transceivers (1, 2), and at least a base station for receiving messages coming from the terminals (1, 2). The method consists in: allocating to each terminal (1; 2) a set of specific attributes including: a transmitting frequency, selected from a predetermined group, a transmitting time interval, of a predetermined time frame, and a coding word; synchronising among them the terminal (1, 2) time frames (C); and identifying the terminals (1, 2) at the receiving station (4) by their attributes.

Description

Method for establishing uplinks in a paging network, this paging network and radio terminal of the network, for the implementation of the method.

A paging network includes base stations, each providing radio coverage, in downlink channels, of a specific area of the territory benefiting from the paging service.

To transmit a written message to the bearer of a network radio terminal, the person transmitting the message orally transmits it by telephone to an operator of a radio network operating center and the latter transmits by radio the characters forming the message as well as the identity number of the receiving terminal. Only the terminal with this identity accepts the message to display it on its screen.

It is therefore a simple transmission of a message in real time. In particular, the possible action that the bearer of the terminal will take in response to the information displayed escapes the network completely, for lack of an uplink to the station. This action can for example be to provide in return, to the correspondent sending the message, a simple acknowledgment of good reception or even a response to the content of the message. This return call is made today by means of a telephone network.

Such bidirectional communication therefore requires a downlink network and an uplink network, which is not very user-friendly and often results in a loss of time, to access a terminal of the telephone network, and an increased expense, often for providing only a response. 'an acknowledgment of receipt.

To overcome the drawback mentioned above, it has been envisaged to provide the terminals with a radio transmitter thus providing an uplink to the base station. One can think of transforming the messaging terminals almost into radiotelephony terminals, having the transmission range desired to reach the base station. However, we are leaving the field of messaging, with much higher costs and a very limited energy autonomy.

If we remain in the field of messaging terminals, the need to preserve their autonomy in energy limits their admissible transmitting power. However, to be able to be detected on reception by the base station, the binary signals (bits) transmitted on the uplinks by the terminals must exceed the minimum threshold of energy sensitivity of the station.

The energy of a bit transmitted by a terminal is proportional to the level, or power, of transmission and to the duration of this bit. The energy of the received bit corresponds to that of the transmitted bit, obviously reduced by the transmission attenuation, increasing with the required range.

In the present case, the maximum transmission power of the uplink being limited, only a relatively long duration of transmission of each bit would make it possible to transmit sufficient energy to compensate, compared to the sensitivity threshold in reception of the station , the attenuation of radio propagation between any point in the station area and the latter. However, such a reduction in the uplink speed would waste radio resources during busy time and is therefore excluded, given the number of terminals and bits to be transmitted by each, if only for identity terminals which answer various calls and which extend over tens of bits.

The minimum speed to be ensured thus limits the range of the uplink to a distance insufficient to ensure the connection with the station from any point in the downlink area that it covers. It is then necessary to plan to subdivide this descending zone into ascending sub-zones each comprising a receiving station. In existing networks, the calculation shows that a few dozen receiving stations would be required per zone. In short, the second network for uplink, or return, is prohibitively expensive.

The present invention aims to reduce this second network, of uplink channels, used to transmit a response, or even spontaneously a message, to a receiving station.

To this end, the invention relates first of all to a method for establishing uplinks in a paging network comprising at least one base station, for transmitting messages by radio broadcast to a plurality of radio transmitter-receiver terminals. , and at least one base station for radio reception of messages from the terminals, method characterized in that:

- each terminal is allocated a specific set of attributes including:

. a transmission frequency, chosen from a determined group,. a transmission time interval, of a determined time frame, and

. a coding word,

the time frames of the terminals are synchronized with one another, and

- the terminals are identified at the receiving station by their attributes.

Thus, a terminal transmits its identity in implicit form since its transmission frequency and the time interval used allow, on reception, to make a first selection in all of the terminals. The coding word makes it possible to remove the remaining uncertainty. It can be a code word sent "next to" the message but, preferably, it is a word used to code the message, therefore fused with it and therefore not requiring a specific transmission. As it is the set, or the combination, of these three attributes which determines the identity of the terminal, each of these attributes can therefore be common to several terminals and thus have only a limited number of possible values, this which simplifies reception analysis. The invention also relates to a paging network comprising at least one base station for transmitting by radio broadcast to a plurality of radio transmitter-receiver terminals, and at least one base station for receiving radio messages from the terminals. , characterized in that the terminals each comprise transmitting means arranged to comply with attributes allocated to the terminal, comprising:

- a transmission frequency, chosen from a determined group,

- a transmission time interval, of a determined time frame, and

a coding word to be transmitted, with the message, in said time interval, and the receiving station comprises:

- a table for identifying the terminals by said attributes.

Finally, the invention relates to a paging terminal, comprising radio transmission-reception means for communicating with a base station of a paging network, characterized in that

the radio means are arranged to be adjusted on a transmission frequency, chosen from a determined group,

- a time base is provided for defining, in a time frame, a time interval allocated to the terminal,

- means of data entry are provided and

- Sequencing means, controlled by the time base, are provided, arranged to read memory means containing a coding word allocated to the terminal, and to cooperate with the input means.

The invention will be better understood using the following description of a preferred embodiment of a paging network with upward and downward tracks according to the invention, with reference to the figures of the appended drawing, in which:

FIG. 1 diagrammatically represents the network, with a station and two terminals,

FIG. 2 illustrates a group of transmission frequencies F distributed between the terminals,

FIG. 3 represents a time frame regulating the transmissions of the terminals, FIG. 4 represents a coding word used during the transmission of a message by a terminal,

FIG. 5 is a block diagram of the terminal, and

- Figure 6 is a block diagram of the receiving part of the station.

The paging network of FIG. 1 comprises a plurality of N terminals 1, 2 for radio transmission and reception and a base station 4 which, in this example, integrates the transmission and reception functions, that is to say - say ensuring radio coverage (3) for both the uplink and downlink.

As the invention relates to the upward paths, a detailed description concerning the downward paths is omitted for the sake of clarity of the description.

Each of the N terminals 1, 2 is allocated a trilogy of attributes: frequency (fig. 2), time interval (fig. 3) and coding word

(fig- 4).

FIG. 2 shows a group of eight determined frequencies fi (i: integer from 0 to 7) here provided.

FIG. 3 illustrates, as a function of time t, two successive time frames T, here comprising only four time intervals ITO, IT1, IT2 and IT3, for the sake of clarity.

Figure 4 illustrates the coding word CD. In this example, the coding word CD defines both a code word C, or bit pattern, and a delay Rk of the start of this pattern C with respect to the start of the time interval in which it is used, here ITO. The bit pattern C is here common to a subgroup of the N terminals 1, 2, just as the delay Rk is in fact common to another subgroup of the N terminals 1, 2. We can therefore have four attributes but here, for convenience, the bit pattern C is common to all the N terminals 1, 2, so that there remain three attributes: frequency fi, time interval ITj, delay Rk; provision could also have been made for the coding word CD to contain only one pattern C, chosen from among several, and no delay Rk.

Figure 5 is a block diagram of terminal 1.

A radio receiver 11, controlling circuits, not shown, for storing and displaying downlink messages, synchronizes a time base 12 with frame synchronization pulses (T) transmitted here by the station 4.

In this example, the attributes of terminal 1 are downloaded, which makes it possible to modify them if necessary and, moreover, avoids any manual adjustment. To this end, the receiver 11 supplies three memories 17, 18, 19 to store there the three attributes, respectively the frequency fi, the time interval ITj and the coding word CD. The validation of the above memorizations implements a memory circuit 20, containing an identity word specific to the terminal 1 considered here, in order to unlock a comparator-door control circuit 21. The circuit 21 allows access to the memories 17 to 19 when a received message address (11), associated with the attributes to be downloaded, corresponds to the identity of the terminal 1.

The time base 12 receives from memory 18 the time interval number ITj allocated to the terminal 1 and, by reference to the successive T frames which it generates, it supplies clock signals H during only the time interval ITj assigned. A sequencer circuit 13 is then activated by the clock H to transmit an uplink message, by command of a radio transmitter 15. The memory 17 controls, therefore according to the allocated attribute, the frequency carrier of an adjustable oscillator 16 controlling the transmitter 15. The third attribute, coding word CD of the memory 19, is used to adjust the sequencer 13, as explained below.

The sequencer 13 cooperates with a data entry keyboard 14, used to enter a response to a received message or even to transmit an uplink message, independently of any reception of a downlink message. In the case of a response, it can be a single bit of acknowledgment.

The bits of a message sent by the terminal 1 are here transmitted by coding by means of a determined code word C, common here to all the N terminals 1, 2. The principle of this coding will be explained, before describing the corresponding circuits.

Each bit of a message sent by the terminal 1 is sent in the form of the code word C here representing 2047 code moments. It will be recalled that a code moment, or Baud, corresponds to an elementary duration of modulation during which the latter remains unchanged. The transmitted signal keeps a constant level, or a constant phase or frequency, depending on the type of modulation. A transmitted bit is therefore here represented by a pattern C of elementary moments whose sequence of values is determined. Depending on whether the bit is 0 or 1, these values are inverted or not.

As indicated, the delay Rk introduces a logical phase shift of the code word C, by a certain number of periods of the clock H, delay Rk which is not the same for all the terminals 1, 2, although it may be common to several, if they differ in their two other attributes. On reception, the station 4 searches in each time interval ITj for the pattern C, or signature, above, in direct or complementary representation, with all the possible delays Rk. The pattern C has a length producing sufficient redundancy to successfully carry out such a search despite the overlaps that may occur between the emissions originating from several terminals 1, 2. The sequencer 13 comprises a set 131 of shift registers supplied by the clock H, providing the determined sequence C of 2047 pseudo-random bits used for coding the message. These registers 131 are associated with loopback gates like 132, here exclusive OR, which apply to an upstream input a logical combination of outputs downstream from the registers 131, in order to confer the pseudo-random character to the sequence C, which facilitates reception recognition.

The sequence C of bits at the output of the registers 131 is applied to an exclusive OR gate 134, reading the state of the keyboard 14 through a buffer memory 135 written byte by byte, gate 134 which controls the transmitter 15. The memory 135 is read bit by bit every 2047 clock periods H, at each start of time interval ITj, that is to say that the bit read controls the inversion or not of the 2047 bits of the sequence C, as explained upper.

The setting in the initial state of the sequence C with the desired delay Rk is carried out under the control of the time base 12. A comparator 133 receives from the latter signals Qi representing the state of frequency dividers, advancing with the clock H from the start of each frame T, and, by comparison with the content of the memory 19, commands at the instant indicated by the latter (Rk) the parallel forcing of the registers 131 in a predetermined state, the even for all the terminals 1, 2. The sequence at the output of the registers 131 is therefore delayed by the specified number, or allocated to the terminal 1, by clock periods H corresponding to the delay Rk. C The sequence repeats itself and is therefore ^'provided with a frame T constantly to the next, in the allotted time interval ITJ. In this example, the sequence C has a cycle time equal to the duration of a time interval ITj. Taking into account the delay Rk, the registers 131 first supply, in each of the time intervals ITO here allocated, the end of the pattern C (unused at the end of the interval ITO of the previous frame T) and then continue with the supply of the beginning of motif C. FIG. 6 schematically represents the reception circuits of station 4. It comprises a set 41 with eight channels of i = 8 receivers in parallel tuned respectively to the eight frequencies fi. Each receiver of the assembly 41 supplies a circuit 43, which is specific to it, for extracting the patterns C of 2047 moments indicated above. To this end, a time base 40 supplies a clock signal H1, similar to the signal H, to a generator 42 of pseudo-random sequence, similar to the circuits 131, 132. The generator 42 serves as a time reference for fixing the offsets throughout the network of terminals, that is to say that the delays Rk are defined relative to its state. The time base 40 also generates the T frames and controls, by radio channels not shown downlink, the transmission of the frame synchronization signals from the terminals 1, 2. In the circuit 43, a circuit 432 with adjustable delay makes it possible to find the pattern C according to the various possible delays Rk. In practice, it may be a serial / parallel register supplied by the circuit 42 and read by a set of multiplexers making it possible to scan its various outputs, therefore to modify the delay Rk. The circuit 432 supplies a circuit 434 for recognizing the patterns C received, direct and inverted, and for determining the delay Rk of each. The detection of the pattern C, direct or complemented moment by moment, provides the value of the message information bit M which it carries.

A memory 46 contains a triple table comprising, for each terminal 1, 2 of the network, the three attributes which have been allocated to it: frequency fi, time interval ITj, coding word CD (here only Rk). It has three (groups of) read addressing entries for the three attributes above, respectively. Thus, the time base 40 applies to it time interval signals ITj, here 3 bits, to identify the eight time intervals.

Each of eight circuits as 43 additionally applies to memory 46, when a recognition of a coding word C occurs, a value representing the detected delay Rk and a value representing the rank i of the circuit 43 considered, that is to say ie the frequency fi. To manage the access restrictions to memory 46, each circuit as 43 controls, by one bit, a specific input, among eight inputs of increasing priority, of a priority encoder circuit 44 providing at output a three-bit code word representing the address or rank i of the input activated in addition high priority. 74,147 and 74,148 family circuits produced by TEXAS INSTRUMENTS INC. are suitable for this purpose.

The circuit 44 controls a multiplexer circuit 45 with several output channels, reading the value Rk supplied by the channel (43) considered, to read the memory 46 in read mode.

As will be understood, the intersection of the three subsets determined by the detected value of each of the three attributes comprises only one terminal ID identity like 1 and 2, except in the case where an addressing of a subgroup is desired.

Having identified the terminal 1, 2 calling among the N in service, the detected bit M is routed, by a multiplexer 47 at i = 8 channels, from the circuit 43 considered to a memory 48 to be associated with this identity ID. The following bits, upon receipt of the following C patterns, are stored with the first to reconstruct the message.

It is understood that the network of uplink channels can be distinct from that of the downlink channels and that in particular the synchronization of the frames is carried out by a broadcast transmitter different from that of a paging station.

Claims

1.- Method for establishing uplinks in a paging network comprising at least one base station (4), for transmitting messages by radio broadcast to a plurality of radio transceiver terminals (1, 2), and at least one radio reception base station for messages from the terminals (1, 2), method characterized in that:

- each terminal (1; 2) is allocated a specific set of attributes including:

. a transmission frequency (fi), chosen from a determined group,. a transmission time interval, (ITj) of a determined time frame (T), and. a coding word (CD), the time frames (T) of the terminals (1, 2) are synchronized with each other, and

- the terminals (1, 2) are identified at the reception station (4) by their attributes.

2.- Method according to claim 1, wherein the messages are coded by the coding word (CD).

3.- Method according to claim 2, wherein the coding of the message is carried out by a time shift (Rk), chosen from several, of the coding word (C D).

4.- Paging network comprising at least one base station (4), for transmission by radio broadcast to a plurality of radio transmitter-receiver terminals (1, 2), and at least one receiving base station (4) radio message from the terminals (1, 2), characterized in that the terminals (1, 2) each comprise transmitting means arranged to comply with attributes allocated to the terminal (1; 2), comprising:

- a transmission frequency (16, 17), chosen from a determined group, - a transmission time interval (12, 18), of a determined time frame, and

- a coding word (19) to be transmitted, with the message, in said time interval, and the receiving station (4) comprises:

- A table (46) for identifying the terminals (1, 2) by said attributes.

5.- Paging terminal, comprising radio transmission-reception means (11, 15, 16, 17) for communicating with a base station (4) of a paging network, characterized by the fact than

the radio means are arranged (16, 17) to be adjusted on a transmission frequency, chosen from a determined group,

- there is a time base (12) arranged to define, in a time frame, a time interval allocated to the terminal,

- Means (14) for data entry are provided and

- sequencing means (13) are provided, controlled by the time base (12), arranged to read memory means (19) containing a coding word allocated to the terminal (1; 2), and to cooperate with the means of seizure (14).

6. Terminal according to claim 5, in which the sequencing means (13) comprise coding means (131, 132, 134) arranged to control the transmission means (15).