RU2237366C2 - Communication system and method for assigning time intervals and frequency channels - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: system has plurality of subscriber stations and base station, all connected through radio-frequency channels so as to ensure simultaneous communications with subscriber stations over assigned channel that has multiple sequentially repetitive time intervals assigned to specific subscriber stations. System also has means for varying frequency and/or configuration of time intervals used in case of impaired transfer characteristics due to modulation change, noise, and additional subscriber stations connected to system.

EFFECT: enhanced frequency control speed.

10 cl, 9 dwg

Description

The present invention relates to digital communication systems and is associated with discrete telephone radiocommunication systems, where the base station communicates with a plurality of subscriber stations connected via radio frequency channels so that simultaneous communication with subscriber stations can be performed on a given channel having multiple successively repeating time intervals, moreover, specific time intervals are assigned to specific subscriber stations.

The invention also relates to a method for assigning time slots and frequency channels to selected subscribers.

From US No. 47777633, a digital communication system is known including a base station comprising a central terminal connected to a radio terminal by connecting lines, and a central communication point connected to a central terminal comprising a radio processing unit, connected via an interface to a switch connected via echo cancellers to connecting lines and the radio terminal contains multiplexers connected to connecting lines and corresponding channel nodes, which through the corresponding power amplifiers with dinene with a transmitter-receiver unit connected to the antenna, while the channel nodes contain a speech codec connected to a modem and a control unit connected to a corresponding multiplexer, as well as subscriber stations containing a subscriber control unit connected to a channel control unit, which is connected via a modem connected to the antenna.

The same publication discloses a method for assigning time intervals and frequency channels to selected subscribers by assigning selected free intervals in selected frequency channels in accordance with their contiguity to occupied intervals in a memory matrix in a digital communication system containing a base station that communicates with a central communication center and through radio frequency channels with many subscriber stations, while the base station has many sequentially repeating time intervals and frequency channels.

However, the known technical solutions do not allow for rapid frequency and time interval tuning to overcome transmission difficulties between the base station and associated subscriber stations.

The objective of the present invention is to create a digital communication system that provides fast frequency and time interval adjustment to overcome any difficulties in transmissions between the base station and associated subscriber stations.

Another objective of the present invention is the implementation of the above adjustment in a relatively simple and inexpensive way.

These problems are solved by the digital communication system proposed in the present invention and by the method of assigning time intervals and frequency channels to selected subscribers.

In accordance with the invention, in a digital communication system, the radio processing unit of the central terminal comprises a message processing unit, as well as a program compilation unit and a database unit connected to it.

In a preferred embodiment of the invention, the message processing unit, the program composing unit and the database unit are the means of selectively assigning time intervals and frequency channels to any of the subscriber stations in response to either connecting an additional subscriber line, or to a degradation of transmission between the base station and subscriber station communication between them.

Moreover, communication with subscriber stations is established preferably by means of control command signals and status messages via a radio-controlled channel assigned to a selected time interval of a selected frequency channel.

Control command signals and status messages are transmitted to the subscriber stations, preferably by means of a radio processing unit, which communicates with both the central communication point and the base station.

It should be noted that the means of appropriation carry out their operations preferably in response to transmission degradation caused by a change in modulation, interference in the frequency channel or equipment malfunction.

Many single subscriber stations communicating with the assignment means may be provided.

A plurality of dual subscriber stations may also be provided that communicate with the assignment means, with each subscriber of each pair of double subscribers being individually assigned an adjacent interval in a selected frequency channel by means of said assignment means.

In accordance with the invention, the assignment method is caused either by connecting additional subscribers to the line, or by a degradation in transmission between the base station and the subscribers.

At the same time, transmission degradation is caused either by a change in modulation, or by interference from the frequency channel, or a malfunction of the equipment.

Moreover, assignments occur during negotiations between subscribers.

All other aspects and corresponding advantages of the present invention will be apparent from the following description, which is illustrated by drawings, where:

figure 1 presents a block diagram of a base station used in the present invention (connected subscriber stations are shown in General),

figure 2 is a block diagram of one subscriber station used in the present invention,

figure 3 is a block diagram of a dual subscriber station used in the present invention,

4 is a block diagram of a plurality of single subscriber stations used in the present invention,

5 is a block diagram of a plurality of dual subscriber stations used in the present invention,

figure 6 shows the matrix of the block radio processing used in the present invention,

7 is a block diagram illustrating a channel node used in the present invention,

on Fig is a block diagram of a radio processing unit and its connecting elements used in the present invention,

Fig.9 is a functional illustration showing the levels of communication between the base and subscriber stations.

For a clearer understanding of the invention, the following is a list of abbreviations used in the description and in the above drawings.

PCHMS frequency band of modulating signals.

BER is the bit error rate.

ZUK task control channel.

UUK channel control device.

DSP is the central point of contact.

TPP terminal of the central point.

TsKIK cyclic control using redundant codes.

Bbd block database.

KS communication quality.

BN fault buffer.

BOS message processing unit.

GTU is the main timing device.

MGTS multiplexer.

PCM pulse code modulation.

KRU radio control channel.

RF radio frequency.

BRO radio processing unit.

DRT remote radio terminal.

ZUA job subscriber management.

SLPD synchronous data line.

BSP block of compilation of programs.

USDG voice encryption-decryption device.

In the drawings, like symbols refer to like parts.

1 shows a base station 10, which includes a central terminal 12 of a central point (TP) and a remote radio terminal 14 (DRT). The TCP 12 includes a radio processing unit (BRO) 16 connected via an interface 18 to the switch 20. It is preferable that the switch be in the form of a hub, for example a model 1218 C digital image concentrator equipped with a switch, currently manufactured by ITT, New York, USA .

The switch 20 is in a circuit with a central communication point 22 (DSP), connecting to it with a plurality of two-conductor external lines 24, and is also connected through echo cancellers 26 and a plurality of connecting lines 28 with a plurality of multiplexers (MPS) 30 connected to the main timing device (GTU) 32 in the remote radio terminal 14. Each of the connecting lines 28 carries a plurality of multiplex slots in the time intervals provided by the corresponding MPS 30. The control channel 34 of the frequency band of the modulating signals (FMS), occupying one of the time slots on one of the connecting lines 28, provides communication between the IPU 30 and the channel 36 nodes.

Each MPS 30 is included in a modular card that is capable of controlling a maximum of 24 simultaneous pulse code modulation (PCM) circuits or 23 simultaneous PCM circuits plus FMS. During their operation, the MPS extract data from the line and distribute it over the channel nodes 36, which are in circuit with the network of the transmitting and receiving unit 38, connecting to it through a power amplifier 40.

BRO 16 carries out final control over both the switch (hub) 20 and the DRT 14 and processes the requests of subscribers to establish the desired transmission chain between the subscriber stations 42 and the central point 22 of the communication (DSP).

Each of the subscriber stations 42 may include either a single subscriber station, or a dual subscriber station, or a plurality of subscriber stations. Figure 2 shows a single subscriber station, consisting of a transceiver 50 connected between the antenna 52 and the modem 54, which is in circuit with a codec 56, encrypting and decrypting the signals coming to the subscriber unit 58 or from it. Figure 3 shows the same general type of subscriber station, except that it includes a dual subscriber station, in which the antenna 60, transceiver 62, modem 64, and codec 66 are connected to separate subscriber units 72, 74, respectively, through buffers 68 and 70.

In the dual subscriber station of FIG. 3, when two conversations are transmitted and received in the same interval, the transceiver, modem and codec can be single reversible elements that only need to perform one set of operations at a specific time, for example, transmit or receive on each line. Moreover, since the subscriber station never receives and transmits at the same time, no duplexer is required because duplication occurs only through buffers 68 and 70, which are connected to an interface circuit (not shown) for subscriber installations.

Figure 4 shows a communication system consisting of many single subscriber stations, which includes a network 80 Association, deployment and duplexing, connected to the antenna 82 and to many single subscriber stations 84a, 84b, 84n. Each subscriber station is connected to a respective subscriber unit 86a, 86b, and 86n.

Fig. 5 shows the same type of communication system as in Fig. 4, except that the network 88 is connected to dual subscriber stations 90, 92, 94, etc., the type of which is shown in Fig. 3; these stations are connected to the corresponding dual subscriber units, designated 96, 98 (for station 90), 100 and 102 (for station 92), 104 and 106 (for station 94).

During the conversation, some problems may arise due to various reasons, which can usually be classified as follows: (a) multi-subscriber configuration, (b) modulation change, (c) interference suppression, (d) malfunction of the equipment of a separate channel.

Figure 6 shows an example of a matrix BRO 16, where different subscribers are indicated by the letters A-G, and the horizontal rows represent the frequencies, and the vertical columns represent the intervals. The number “1” means “used”, and “0” means “not used”. In this matrix, it is only necessary to store transmission intervals (as shown), since the receiving intervals are always shifted by 2.

During operation, it often happens that all four intervals of a certain frequency are occupied by different subscribers. Assume, for example, that there is one dual subscriber station, while the other subscriber stations are single. In the case of a dual subscriber station, it is necessary that the two dual subscribers are in adjacent intervals. If one of the two dual subscribers occupies a specific frequency and a specific interval, while the other intervals in this frequency are occupied by other single subscribers, and if the other of the two dual subscribers requires a connection, because either he picked up the phone to make a call, or he needs to send an incoming call from the central point, then either a single subscriber in an adjacent interval of this frequency needs to be moved to another frequency and / or to another interval to make room for the second of two double subscribers Or the first dual subscriber occupying a specific frequency and a specific interval to be moved to another frequency where there is an adjacent interval. In this situation, the BRO 16 establishes the current connections and stores them in its memory and therefore can determine where the transfer can be made inside the matrix.

The aforementioned type of transmission is as follows: suppose, for example, that the first of the dual subscribers is currently engaged in a conversation at a frequency D in transmission interval 1 (reception interval 3). When the second of the double parties picks up, the base station 10 sends a warning signal (one bit) as part of the control bits transmitted in addition to the conversation. A warning signal is detected in the channel node 36, which then sends a message to the BRO 16 through the MPTS 30, trunk 28, switch 20 and interface 18 either through the reverse talk circuit or through a separate circuit. And, on the contrary, the incoming signal from the central point of communication 22 (DSP) is routed through the switch 20 and interface 18 to the BRO 16.

In the event of any signal, for example, from a hands-free installation or from a central point, the interval must be made available to the second of the dual subscribers to connect to the base station in the interval adjacent to the first of the dual subscribers already in use. Although it is possible to move the first double subscriber from frequency channel D to frequency channel G, this is a less preferable step, since two empty adjacent slots at the same frequency are often not available. In any case, it is easier to move the neighboring single subscriber station from frequency D, interval 2 to another frequency. In the above example, the neighboring subscriber can be transferred to any of eight open intervals. Since the roaming single subscriber does not need adjacent intervals for transmission and reception, then if the movement is done only in frequency (for example, from channel D to channels B or G), it can be performed when the interval is not used, that is, without failures. If you change both the interval and frequency, then the transmitted data for one interval is either duplicated or lost.

A similar situation exists with many single subscriber stations shown in figure 4. Since each station has a complete set of elements, several stations can transmit simultaneously. Indeed, it is preferable that all stations transmit and receive at the same time, since this prevents overloading the leading edge of the transmitter. As a result, in the matrix of FIG. 6, if two subscribers occupy interval I at frequencies B and D and a call is required for the third subscriber, then BRO 16 must assign the third subscriber to interval I at frequencies F and G.

When the system is represented by the configuration shown in FIG. 5, where there are many double subscriber stations, the first subscribers from each pair of double subscribers should be at the same intervals, but at different frequencies, while the second subscribers from each pair should be at adjacent intervals at the same frequencies as their respective first subscribers.

BRO 16 in the above situations establishes current connections in each time interval and stores them in memory. Therefore, it can at any time determine where the transfer can be made within the matrix.

In all the above situations, when you have to take care of the assignment of intervals and frequencies in multi-subscriber configurations, the change trigger is outside the base station (the initiative comes from a central point or subscriber unit). In the following situations, which encompass a change in modulation due to fading or damping of interference or a change due to a malfunction of equipment, the driver is located or is detected in the base station itself.

In the base station 10, each channel node 36, as shown in Fig. 7, includes a channel management device (CCM) 110 and a modem 112, each of which is connected to a voice encryption-decryption device (USDG) 114 via a corresponding compressed data transmission line 116 and control state transmission lines 118. USDG 114 is interfaced with the MPS 30 via the pulse-code modulation (PCM) data channels 120, while the CMD is coupled to the MPS 30 by controlling the synchronous data line 122 (SLPD).

A number of buffers (not shown) are associated with various elements. In this regard, each data module contains an automatic gain control (AGC) buffer for each interval, as well as a communication quality buffer (CC), which measures the difference in the received phase error. In addition, a USDG with a bit error rate (BER) buffer is provided. As part of each data packet of the encoded conversation, cyclic control information is transmitted using redundant codes (CCIC), which issue the BER to the BER buffer.

For these purposes, a high AGC level means that a high signal level is being received, and the receiver gain is small. On the contrary, a low AGC level means a low level of the received signal and a large gain of the receiver. This AGC level is used to show that signal degradation occurs either due to fading or due to interference. The effect of interference is indicated by a higher AGC level because the AGC level is based on the sum of the transmitted signals and any interference signals. In any case, correction can be done by changing the modulation. In this regard, as will be shown in more detail below, each channel node 36 contains a modem that can transmit and receive at voice intervals using either 16- or 4-phase modulation. In 4-phase modulation, a symbol accounts for only half of the bits transmitted in 16-phase modulation, but the bit rate is the same. Therefore, when 4-phase modulation is used, two adjacent intervals are combined, as shown in the matrix of FIG. 6, into one extended interval containing the same number of bits per extended interval that would have been in the interval during the 16-phase operation.

When, for example, the dual-subscriber system is operating, either when the BER increases above a certain threshold (for example, 0.1%), or when the SC decreases below a certain threshold (for example, 6 degrees), the contents of the corresponding buffers are transmitted to the BRO through a communication line MPS-line-switch (hub) -interface. After that, the BRO sends back to the control node a control signal along the same circuit in order to change the operation from 16-phase to 4-phase. At the same time, if at the current time in adjacent intervals at the same frequency two subscribers are working, one of the subscribers is transferred to the other frequency as described above.

If, after changing the modulation level in the above manner, the AGC level remains high for a given subscriber, it is assumed that the cause of the wrong BER and SC is interference, not transmission fading. The contents of the outputs of all AGC buffers are transmitted to the BRO, which determines which frequencies (if any) have a low AGC level, and the BRO then starts for this subscriber to change the frequency with a high AGC level to a frequency having a low AGC level. This eliminates interference, if any.

The base station is also equipped with fault buffers (BN), which give the operational status of each communication line in the base station circuit, including the switch (hub), trunk, MPS, channel node, power amplifier, transmitter and receiver. If the BN buffer recognizes a malfunction or malfunction of the equipment, a signal is sent to the BRO indicating what frequency is affected. Upon receipt of this signal BN, BRO begin to change the frequency (and, if necessary, the interval) for each conversation (if any) that takes place at the moment on the current channel.

BRO 16 is the primary control element for the assignment of frequency channels and intervals, its general structure is shown in Fig. 8. The radio processing unit 16 comprises a message processing unit (BOS) 130 associated with the database unit 132 (BDB) and the program compilation unit (BSP) 134. BOS 130 controls the entire interface between the BSP and the BBB within the BRO, as well as the channel control device (CC) 110 and the subscriber control task (CAM) block 136, which are located outside the BRO. AMC 110 is located inside the channel node 36, as shown in Fig.7, and block 136 ZUA is connected to the subscriber stations.

If in operation, for example, during a call, the communication quality (CC) drops below a predetermined level, BRO 16 initiates sending a message to block 136 of the memory, which then communicates with BOS 130. Then BOS: (a) sends a signal to BDB 132 for identification the available channel and (b) checks with the BSP 134 the control and timing of the distribution, which serves to organize the messages it receives in the order they are received. If a channel is available, the BOC sends a message to block ZUA 136 to reconfigure the matrix in order to move the call to the available channel. If there is no channel, the call is held on the same channel.

If during a call all four intervals are busy, but due to interference at a certain frequency, it is necessary to transfer all subscribers to another frequency with the same corresponding intervals, the following sequence occurs: BRO, excited by a decrease in communication quality, sends a message to block 136 of the memory requesting a change in frequency. Block 136 ZUA sends a message to the task of channel management (ZUK), located at the subscriber station, for processing frequency changes, and also communicates with the BOC at the base station to distribute the available channel UUK. Next, the biofeedback sends a signal to the BDB in order to identify the available channel, and also checks with block 134 compiling programs to obtain time in the schedule. If the channel is available, the biofeedback sends a message to the block 136 of the RAM, in order to reconfigure the position of the channel. If there is no channel, block 136 ZUA sends a busy signal to the BRO, and no changes are made.

Figure 9 shows the protocol of the radio control channel (KRU). The BRO 16 communicates with the CCM 110 and the modem 112. At the subscriber station, the ZUA block 136 communicates with the ZUK block 138, which is provided for the modem 140. The switchgear protocol consists of two levels: the data communication level 142 and the packet level 144. The data communication level is physical link between the parts, and the packet layer covers messages that are transmitted on this physical link. The data communication layer is responsible for detecting errors, word synchronization and frame formation, collision detection and resolution (conflict rivalry for the same time interval on one radio frequency channel).

For an example, we turn again to Fig. 9. The BRO processes two protocol chains; in the first protocol, the BRO sends a message to the CAM in the base station to request a modulation change. In the second protocol, the BRO sends a message to the memory unit 136 to request a frequency change. In the third protocol, the memory unit 136 sends a message to the BRO to indicate that all channel frequencies are busy.

In another example, the BRO sends a message protocol to the memory unit 136 to request a change in the channel frequency. This message initiates two functions: first, the message requires that the memory at the subscriber station receive from the switchgear a path to a different frequency. Following this, the ZUA is associated with block 138 ZUK. Then the ZUK searches for channels, and when it finds free intervals and frequency, it switches to them. In the second function, the message protocol causes the memory to call the central point to go into standby mode for the purpose of connection.

If during a call the communication quality falls below a predetermined level, the BRO sends this information to the CAM and requests a change in the modulation level. UUK confirms this message through the communication line SLPD (via the MMS to the BRO).

Claims (10)

1. A digital communication system comprising a base station (10) comprising a central terminal (12) connected to a radio terminal (14) by connecting lines (28), as well as a central communication point (22) connected to a central terminal (12) comprising a radio processing unit (16) connected via an interface (18) to a switch (20) connected via echo cancellers (26) to connecting lines (28), and the radio terminal (14) contains multiplexers (30) connected to connecting lines (28) and corresponding channel nodes (36), which, through the corresponding power amplifiers (40) are connected to a transmitter-receiver unit (38) connected to the antenna, while the channel nodes (36) contain a speech codec connected to a modem and a control unit connected to the corresponding multiplexer, as well as subscriber stations (42), comprising a subscriber control unit connected to a channel control unit that is connected via an modem to an antenna, characterized in that the radio processing unit (16) of the central terminal (12) contains a message processing unit (130), as well as a compilation unit (134) connected to it prog frames and block (132) of the database. 2. The digital communication system according to claim 1, characterized in that the message processing unit (130), program compilation unit (134) and database unit (132) are means for selectively assigning time intervals and frequency channels to any of the subscriber stations (42) in response to either connecting an additional subscriber to the line, or to a degradation of transmission between the base station (10) and the subscriber station (42) during communication between them. 3. A digital communication system according to claim 2, characterized in that communication with subscriber stations (42) is established by means of control command signals and status messages via a radio-controlled channel assigned to the selected time interval of the selected frequency channel. 4. The digital communication system according to claim 3, characterized in that the control command signals and status messages are transmitted to the subscriber stations (42) using the radio processing unit (16), which communicates with both the central communication point (22) and the base station (10). 5. The digital communication system according to claim 2, characterized in that the assignment means perform their operations in response to transmission degradation caused by a change in modulation, interference in the frequency channel, or equipment malfunction. 6. The digital communication system according to claim 2, characterized in that there are many single subscriber stations that communicate with the means of assignment. 7. The digital communication system according to claim 2, characterized in that there are many double subscriber stations that communicate with the assignment means, each subscriber of each pair of double subscribers is individually assigned an adjacent interval in the selected frequency channel by means of the indicated assignment means. 8. The method of assigning time intervals and frequency channels to selected subscribers by assigning selected free intervals to selected frequency channels in accordance with their contiguity to occupied intervals in a memory matrix in a digital communication system containing a base station (10) that communicates with a central point (22 ) communication and through radio frequency channels with many subscriber stations (42), while the base station (10) has many successively repeating time intervals and frequency channels, distinguishing Take care that the assignment is caused either by connecting additional subscribers to the line, or by a deterioration in the transmission between the base station and the subscribers. 9. The method according to claim 8, characterized in that the degradation of the transmission is caused either by a change in modulation, or by interference from the frequency channel, or a malfunction of the equipment. 10. The method according to claim 8, characterized in that the assignment occurs during negotiations between subscribers.

Images