JP2899805B2 - Communications system - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to wireless digital telephone systems, and in particular, to the connection between a base station and a plurality of subscriber stations by means of an RF channel, each of which comprises a number of successively repeated time slots. The present invention relates to a wireless digital telephone system for allocating a specific time slot to a specific subscriber station via a plurality of predetermined frequency channels having a function of enabling simultaneous communication.

SUMMARY OF THE INVENTION The present invention is directed to a frequency configuration, time slot configuration, or the like when a new off-hook subscriber unit is added or when modulation switching, interference between frequency channels, equipment malfunctions, and the like occur. Means for automatically switching between the two. The switching means preferably includes a remote connection processing unit and switching means responsive to a control signal from the remote connection processing unit by physically connecting a selected port in the communication circuit to a selected time slot. A replacement unit in the form of a device. The control signal is provided in response to a status message received by the remote connection processor.

The present invention relates to wireless digital telephone type communication systems, and more particularly, to automatically adjust such communication systems to compensate for adverse effects during operation, such as frequency channel interference, fading, link quality degradation and equipment malfunction. About the means.

The present invention can be used in a communication system according to the present applicant disclosed in Japanese Patent Application Laid-Open No. 61-218297 on September 21, 1986 (corresponding to U.S. Pat. No. 4,675,863 issued on June 23, 1987). The system disclosed in that publication includes a base station and a plurality of subscriber stations connected to the base station via an RF channel. The system allows communication between the subscriber stations and an external communication network with multiple ports. The base station simultaneously communicates between a plurality of ports and the plurality of subscriber stations by allocating predetermined time slots to predetermined subscriber stations via predetermined frequency channels having a large number of sequentially repeated time slots. Communication circuit that enables The system includes a central office terminal (COT) having a remote connection processing unit (RPU) for directing communication between an assigned time slot to a predetermined subscriber station and a predetermined port, and connecting the communication circuit to the port. And an exchange. This switch, preferably comprised of a concentrator of the type described below, responds to control signals from the RPU by physically connecting the selected port to a selected communication channel time slot assigned to a given subscriber station. Including switches.

The communication circuit responds to a command signal transmitted by the RPU to the CCU via the baseband control channel (BCC), and transmits the allocated frequency channels and time slots to the corresponding subscriber stations by a plurality of channel control units ( CCU). These command signals are generated in response to status messages provided to the RPU via the BCC to indicate the frequency channel / time slot and the usage status of the subscriber station. An assigned frequency channel / time slot is connected to a corresponding subscriber station by an assigned time slot in an assigned radio frequency (RF) channel. The BCC is connected by lines separately connected from the RPU to each of the CCUs. Control commands and status messages are exchanged between the CCU and the subscriber station via a radio control channel (RCC) assigned to a given time slot of a given RF channel.

SUMMARY OF THE INVENTION It is a primary object of the present invention to provide a rapid switching of frequency and time slots to overcome signal transmission difficulties between a base pole and its associated subscriber unit. Is to do. Another object of the present invention is to provide the above-described switching speed relatively simply and at low cost.

Examples Other objects and advantages of the present invention will become apparent from the following detailed description, which proceeds with reference to the accompanying drawings.

Abbreviations used in this specification: BCC: Baseband control channel BER: Bit error rate CCT: Channel control task CCU: Channel control unit CO: Central office COT: Central office terminal CRC: Cyclic code check DBM: Database Module LQ: Link quality MF: Malfunction MPM: Message processing module MTU: Master timing device MUX: Multiplexer PCM: Pulse code modulation RCC: Radio control channel RF: Radio frequency RPU: Remote connection processor device RRT: Remote radio terminal SCT: Join User control task SDLC: Synchronous data link control SM: Scheduler module VCU: Voice codec Referring to the drawings showing the same parts with the same reference numbers,
FIG. 1 shows a base station indicated generally at 10 including a central office terminal (COT) indicated generally at 12 and a remote radio terminal (RRT) indicated generally at 14. The COT 12 includes a remote connection processor unit (RPU) 16 connected to a switching unit 20 via an interface 18. Switching unit 20 is preferably formed from a concentrator, such as a 1218C "digital image signal concentrator with switch, available from ITT, New York, NY.

The switching unit 20 is connected to a central office (CO) 22 via a plurality of two-wire lines 24 and a master timing unit in a remote radio terminal (RRT) 14 via an echo canceller 26 and a plurality of span trunks 28. A plurality of multiplexers (MUX) 30 connected to the (MTU) 32 are also connected. Trunk 28
Has a plurality of multiplexing time slots formed by the respective MUXs 30. The baseband control channel (BCC) 34 occupying one of the time slots on one of the trunks 28 is M
Enables signal transfer between the UX 30 and the channel module 36.

Each MUX 30 is configured in a modular card that can handle up to 24 pulse code modulation (PCM) signal transmission lines or up to 23 PCM signal transmission lines and the BCC. These MUXs 30 receive data from trunk 28 and pass them through power amplifier 40, respectively, to transceiver network 38.
To the channel module 36 connected to.

The RPU 16 controls both the switching unit (concentrator) 20 and the RRT 14 and processes a subscriber's call request for setting up a desired transmission path between the subscriber station 42 and the central office (CO) 22.

The subscriber station 42 may be a single telephone type having a single telephone, a two telephone type having two telephones, or a multiple telephone type having a large number of telephones. Second
The figure shows a single telephone-type unit including a transceiver 50 connected between an antenna 52 and a modem 54 connected to a codec 56 that decodes input and output signals to and from a telephone 58.
FIG. 3 is similar to that of FIG. 2 except that it comprises a two-telephone type unit in which an antenna 60, a transceiver 62, a modem 64 and a coding 66 are connected to separate telephones 72 and 74 via buffers 68 and 70. The same device is shown.

In the two-phone type unit shown in FIG. 3, when transmitting and receiving a two-way call via one time slot, the transmitting / receiving device 50, the modem 54, and the codec 66 simply perform a pair of transmitting / receiving operations simultaneously on each line. It can be composed of one reversible element. Further, since the two-phone type unit does not transmit and receive at the same time, a duplexer is not required.
That is, duplication only occurs through buffers 68 and 70 connected to the telephone interface circuit (not shown).

FIG. 4 shows a single telephone multiplex system including an antenna 82 and a coupled evolved duplex network 80 connected to a number of single telephone type units 84a, 84b, 84n. Each subscriber unit is connected to a telephone 86a, 86b and 86n, respectively.

FIG. 5 shows a multiplexing system similar to that shown in FIG. 4, in which a network 88 has the same configuration as that shown in FIG. 3 and two telephones 96 and 98 are two telephones. In the mold unit 90, the telephones 100 and 102 are unit 92
The only difference is that the telephones 104 and 106 are connected to the unit 94, respectively.

During a call, (a) multi-phone configuration, (b) modulation switching,
Problems can occur due to various factors such as (c) interference avoidance and (d) malfunction of the equipment of each channel.

FIG. 6 shows an example in which subscribers A to G are displayed in an RPU matrix in which frequencies are represented by horizontal columns and time slots are represented by vertical rows. The number “1” indicates “in use”, and “0” indicates “free”. In this matrix, the receive slots are always offset by two time slots, so only the transmit slots need be stored (as shown).

In operation, it is frequently the case that various subscribers occupy all four time slots of a particular frequency. For example, assume that there is one two-phone type unit and the other units are of a single subscriber type. In the case of a two-telephone type unit, two telephones belonging to the unit must be accommodated in adjacent time slots. One of the two telephones is assigned a particular frequency and time slot and the other time slot of that frequency is assigned to the other telephone, and the other of the two telephones goes off-hook to place a call. If a connection is required to receive an incoming call from the central office, the single telephone in the adjacent time slot of that frequency is moved to another frequency or time slot, and the other telephone of the two telephones is moved. One of the two telephones which has been accommodated or has been assigned a specific frequency and time slot needs to be moved to another frequency which has room in an adjacent time slot. In that state, the RPU sets up the current connections and stores those connections in the RPU's internal memory, and thus can determine possible destinations in the matrix.

The above transfer is performed as follows. Here, it is assumed that, for example, the first telephone of the two telephones is talking on the transmission slot 1 (reception slot 3) of frequency D. When the second of the two telephones goes off-hook, an alert signal (one bit) is returned to the base station as part of the control bits transmitted in addition to the call. The alert bit is detected in the channel module 36, and in response to this detection, the channel module 36
0, the call path is returned to the RPU 16 via the trunk 28, the exchange 20, and the interface 18 in a reverse direction or another route. Conversely, an incoming signal from the central office (CO) 22 is sent to the RPU 16 via the exchange 20 and the interface 18.

If either a signal from the off-hook telephone or a signal from the central office occurs, a slot is assigned to the second of the two telephones and assigned to the first of the two telephones. The connection to the base station must be made in the slot adjacent to the occupied slot. Although it is possible to move the first of the two telephones from the frequency channel D to the frequency channel G, it is unlikely that two empty slots adjacent to each other will occur in the same frequency channel, so that the frequency channel movement is Not preferred. Either way, it is easier to move the assigned slot to an adjacent single subscriber unit from frequency D slot 2 to a different frequency. In the illustrated example, the slot allocated to the adjacent subscriber unit can be moved to any one of eight empty slots. Since the assigned slot to the single telephone type unit to be moved does not require an adjacent slot for transmission and reception, this movement is performed only by frequency (for example,
From frequency channel D to frequency channel K or G
H), the movement is achievable while the slot is vacant and therefore can be glitch-free. When the movement is performed in both the slot and the frequency, one slot of the transmission data is duplicated or lost.

A similar situation occurs with a subscriber station having a plurality of single telephone type units as shown in FIG. In this example,
Since each of the units comprises a complete combination of functional elements, two or more units can transmit simultaneously. Preferably, all transmissions are performed simultaneously and all receptions are performed simultaneously to prevent leading edge overload of the receiver. Thus, in the matrix of FIG. 6, if two subscriber units are assigned slot 1 of frequency channels B and D, and if there is a call setup request to a third subscriber unit, RPU 16 will have its third The subscriber must hit slot 1 at either frequency F or G.

If the system is of the type shown in FIG. 5, that is to say with a number of two-phone units,
The first telephone of each pair of telephones must be assigned the same slot at a different frequency, and the second telephone of each pair of the telephones must be assigned adjacent slots at the same frequency as the first telephone. .

In the case described above, the RPU sets up connections for each required time and stores those connections in its memory. Therefore,
The transfer destination in the matrix can be determined at any time.

Channel frequency / time slot assignment in the above system including multiple telephone units is made in response to signals from outside the base station (from the central office or from the telephone). In the situations described below with fluctuations due to fading or anti-interference modulation switching or equipment malfunction, the control signal is generated at the base station or detected at the base station.

Each channel module 36 in the base station comprises a channel control unit (CCU) 110 and a modem 112, as shown in FIG. 7, which components are voice codec via a control state link 118 and a compressed data link 116, respectively. The device (VCU) 114 is connected. The VCU 114 is connected to the MUX 30 using a pulse code modulation (PCM) data channel 120 as an interface, while the CCU 114 is connected to the MUX 30 using a synchronous data link control line (SDLC) 122 as an interface.

A number of buffers (not shown) are associated with the various components described above. That is, each channel module includes an AGC buffer for each slot and a link quality (LQ) buffer for detecting variations in receive transport errors. VCU 114 also includes a bit error rate (BER) buffer. A cyclic code check (CR) as part of the coded burst from each call that supplies the BER value to the BER buffer
C) Send.

In connection with the above objectives, a high AGC level means receiving at a high signal level and having a low receiver gain. Conversely, low
The AGC level indicates that the signal is received at a low signal level and the receiver gain is large. The AGC level is used to indicate whether the signal degradation is due to fading or whether there is interference. Since the AGC level is based on the sum of the transmitted signal and the interfering signal, the interference is displayed at a high AGC level. In any case, the correction can be made by switching the modulation. In this regard, the channel
Each of the modules 36 includes a modem capable of transmitting and receiving signals via voice slots with 16 or 4 phase modulation as described below. In four-phase modulation, the number of transmission bits per symbol is half that in 16-phase modulation, but the bit repetition frequency is the same. Therefore, when four-phase modulation is used, two adjacent slots are combined into one long slot as shown in the matrix of FIG.
The number of bits per slot should be the same as in the case of phase phase modulation.

For example, if the BER exceeds a predetermined threshold (for example, 0.1%) or the LQ falls below a predetermined threshold (for example, 6 degrees) during the operation of the two-phone type subscriber unit, the contents of the corresponding buffer are stored in the MUX30-span. Sent to RPU 16 via trunk 28-concentrator link. In response to the signal, the RPU 16 returns a control signal for switching from 16-phase modulation to 4-phase modulation to the control module via the same link. At the same time, if two adjacent slots at the same frequency have been allocated to two subscribers, one of the subscribers is switched to another frequency in the manner described above.

If the AGC level is still high for that particular subscriber after switching the modulation level, i.e. the number of modulation phases, as described above, it is assumed that the poorer BER and LQ values are due to interference rather than fading. It is. In that case, the output of the entire AGC buffer is transmitted to the RPU 16, based on which the RPU 16 determines at which frequency the AGC level is low and increases the frequency assigned to that subscriber to the high AG
Switch from C level frequency to low AGC level frequency. If there is interference, it is canceled by this frequency switching.

The base station 10 includes a switching unit or concentrator 20, a span trunk 28, a MUX 30, a channel module 36,
It includes a malfunction (MF) buffer that indicates the operation state of each link in the base station connection path including the power amplifier 40 and the transmission / reception device 38. If the MF buffer detects a malfunction or equipment failure, it sends a signal to the RPU 16 indicating which frequency channel is affected. When this MF signal is received, R
PU 16 initiates frequency switching (and slot switching if necessary) for ongoing calls (if any) on the affected frequency channel.

The RPU 16 is an important component for controlling the allocation of frequency channels and slots, and its general configuration is shown in FIG. The RPU 16 has a database module (DBM) 132 and a scheduler module (SM) 134
And a message processing module (MPM) 130 connected to. The MPM 130 controls all interfaces between the SM 134 and the DBM 132 in the RPU 16 and also controls the interface between the channel control unit (CCU) 110 and the subscriber control task (SCT) 136 outside the RPU. I do. The CCU 110 is located in the channel control module 36 of FIG. 7, and the SCT 136 is connected to the subscriber station.

If, for example, the link quality (LQ) falls below a predetermined level during a call, the RPU 16 sends a message to the SCT 136, and as a result, the SCT 136 exchanges signals with the MPM 130. MPM 130 (a) sends signal to DM 132 to identify available frequency channels, and (b) checks SM 134 for schedule control and timing control (SM acts to arrange received messages in the order received) ). If there is an available frequency channel, MPM 130 sends a message back to SCT 136 to reconstruct the matrix for movement to that available frequency channel. If no channel is available, the call is kept on the same frequency channel.

During a call, if all four subscriber stations need to be moved to the same slot on another frequency, even though all four slots are occupied, the following procedure is followed. That is, when the RPU 16 is activated due to a decrease in link quality (LQ), the RPU 16 sends a frequency switching request message to the SCT1.
Send to 36. The SCT 136 transfers the message to a channel control task (CCT) located in the subscriber station for frequency switching processing, and also exchanges signals with the base station MPM to allocate available CCU channels. This MPM sends a signal to identify available frequency channels to DBM1
Send to 32 and check SM134 to get time position in schedule. If there is an available channel, MPM 130 returns a message to SCT 136 to reconfigure the channel position. If no channels are available, SCT 136 sends a busy signal to RPU 16 and does not switch.

FIG. 9 shows the RCC protocol. RPU16 at base station
Is connected to the CCU 110 and the modem 112. At the subscriber station, the SCT 136 exchanges signals with the CCT 138 with the modem 140. The RCC protocol consists of two layers, a data link layer 142 and a packet layer 144. The data link layer is the physical link between the parts, while the packet layer contains the messages sent over this physical link. The data link layer is responsible for error detection, word synchronization, frame synchronization, and collision detection (contention for the same time slot on the same RF channel).

Referring to FIG. 9, there is shown an example in which the RPU 16 processes two paths of the protocol. In the first protocol, RPU16
Sends a modulation switching request message to the CCU 110 of the base station.
In the second protocol, the RPU 16 sends a frequency switching request message to the SCT 136. In the third protocol, the SCT 136 sends a message indicating that all channels have been allocated to the RPU 1
Return to 6.

In another example, RPU 16 sends a channel frequency switch request message to SCT 136. This message initiates two functions. First, the message requests that the subscriber station's SCT 136 obtain a route from the RCC to another frequency. The SCT 136 then exchanges signals with the CCU 110. Next, when the CCU searches for a frequency channel and detects an available frequency / slot, it switches to that frequency / slot. Another feature is a message
Call SCT136 to the central office and wait for connection.

If the link quality (LQ) falls below a predetermined level during a call, the RPU 16 sends this information to the CCU 110 to request a change in modulation level. CCU 110 acknowledges receipt of this message to RPU 16 via the SDLC link and MUX.

[Brief description of the drawings]

FIG. 1 is a block diagram of a base station used in the present invention,
FIG. 2 is a block diagram schematically showing a subscriber station to be connected, FIG. 2 is a block diagram of a single telephone type subscriber unit embodying the present invention, and FIG. 3 is a two telephone type subscriber embodying the present invention. FIG. 4 is a block diagram of a single telephone multiple connection subscriber unit embodying the present invention, FIG. 5 is a block diagram of a dual telephone multiple connection subscriber unit embodying the present invention, FIG. FIG. 6 shows a remote connection processor (RP) embodying the present invention.
FIG. 7 is a block diagram showing details of a channel module used in the present invention, FIG. 8 is a block diagram of a wireless processing unit embodying the present invention and a connection element thereof, and FIG. 2 is a functional illustration showing layers of signal exchange between a base station and a subscriber station. (Explanation of symbols) 10: Base station 12: Central office terminal (COT) 14: Remote radio terminal (RRT) 16: Remote processing unit (RPU) 18: Concentrator / RPU interface 20: Concentrator (switching unit) 22: Central office 30: Multiplexer (MUX) 32: Backbone timing unit 34: Baseband control channel (BCC) 36: Channel module 38: Transceiver 40: Power amplifier 42: Subscriber station 110: Channel control unit (CCU) 112, 140: Modem 114: Voice codec (VCU) 130: Message processing module (MPM) 132: Database module (DBM) 134: Schedule module (SM) 136: Subscriber control task (SCT) 138: Channel control task ( CCT)

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Chamlong Deing Deal, Wood Hay Van Road, 19154 Philadelphia, PA 3516 (56) References JP-A-63-187739 (JP, A) JP-A-59 -158138 (JP, A) JP-A-55-120235 (JP, A)

Claims (11)

(57) [Claims] 1. A communication system having a base station in communication with a central office and connected to a plurality of subscriber stations via repetitive time slots and a plurality of frequency channels, wherein the time slots and the frequency channels are in communication. A call request from another subscriber in a multi-telephone configuration or a call with the base station, wherein at least one of the allocated time slots and frequency channels is selectively assignable to the subscriber station; A communication system including an assignment means for selectively reassigning individual subscribers in response to signal transmission degradation between the subscriber stations. 2. The method according to claim 1, wherein said allocating means allocates said time slot and said frequency channel in response to said signal transmission deterioration caused by at least one of modulation switching, frequency channel interference and device malfunction. Item 2. The communication system according to Item 1. 3. A system comprising a plurality of dual-telephone subscriber stations each of which conducts at least one call controlled by said allocating means, each of said two telephones being adjacent to a time slot of a selected frequency channel. 2. The communication system according to claim 1, wherein said communication means can be separately assigned by said assignment means. 4. The communication system according to claim 1, wherein said allocating means performs allocation to said subscriber station according to a predetermined allocation table. 5. The communication system according to claim 1, wherein said time slot and said frequency channel to which said subscriber station is reassigned are in an idle state. 6. A communication system including a base station and a plurality of subscriber stations capable of communicating with each other and communicating with an external communication network having a plurality of ports, wherein the base station comprises: Switching means for connecting to said port of the network; and connecting to said switching means via a base station control channel;
The status of the time slot and the frequency channel is continuously monitored, and the port and the subscriber are connected via the time slot and the frequency channel individually assigned to each subscriber station in response to the monitoring result of each of the time slots. A remote connection processor for completing the connection with the subscriber station to the switching means, comprising a memory for storing the status of the connection at each time interval, thereby enabling a time slot to the subscriber station during a call, Enables the reassignment of frequency channels from time to time, with one subscriber station being assigned to one subscriber station from one time slot in the selected frequency channel to another time slot or to another time slot in another frequency channel. And a remote connection processor that allows for selective movement on a per-service basis. 7. The time slot and the frequency channel to which the subscriber station moves are idle.
A communication system as described. 8. A base station in communication with a central office and in communication with a plurality of subscriber stations via radio frequency (RF) channels, that is, a base station having a number of sequentially repeating time slots and a plurality of frequency channels. Reallocating time slots and frequency channels to a selected subscriber station during a call in a communication system comprising the steps of: Holding in memory and selectively reassigning selected time slots that are idle or in use in the selected frequency channel to selected subscriber units in accordance with an assignment routine. In response to a call request by another subscriber in a multi-telephone configuration or with the base station. A reassignment process performed by deterioration of signal transmission to / from the subscriber station. 9. A communication system for wireless communication between a base station transmitting and receiving a user data stream via a number of successive repetition time slots and a plurality of subscriber stations in communication with the base station. , A unique combination of radio frequency channels and time slots can be individually assigned to each subscriber station by the assignment means for forming said wireless communication between said base station and said subscriber station, In a communication system, each of which modulates with one of said user data streams, the time slot and frequency channel of said first subscriber station are allocated by said allocating means to the first subscriber station during the course of a user call. Individual reassignment moves the first subscriber station from an original time slot to another time slot.
This is possible by reassigning from an original frequency channel to another frequency channel or from an originally assigned frequency channel and time slot to another frequency channel and time slot, wherein the reassignment is performed by the base station and its associated The response is made in response to a degradation of communication with the first subscriber station of the other party or a call request of another subscriber in a multi-telephone configuration, and due to the degradation of the communication or in response to the call request. Other subscriber stations that have already been assigned a time slot and / or frequency channel and are currently speaking are assigned to another time slot and / or frequency channel for use of the certain time slot and / or frequency channel. A communication system that can be individually reassigned. 10. The communication system according to claim 1, wherein said reallocation is performed in response to said signal transmission degradation. 11. Assigning the subscriber station to a base station capable of communicating with a telephone station and communicating with a plurality of subscriber stations via a radio frequency (RF) channel, ie, a selected free time slot of a selected frequency channel. In a communication system comprising a base station having a number of successively repetitive time slots and a plurality of frequency channels that can be assigned to a selected subscriber station, the assignment of time slots and frequency channels to the selected subscriber station is By assigning the subscriber station to the selected idle time slot of the selected frequency channel according to the adjacency with the busy time slot in the memory matrix;
A method wherein the assignment is made in response to a call request from another subscriber in a multi-telephone configuration and / or signal transmission degradation between the base station and the subscriber station.