JPH02137530A - Communication system - Google Patents

Abstract

PURPOSE: To obtain the promptness of a slot in a simple constitution by realizing simultaneous communication through a digital radio telephone system between a base station and a subscriber's station through a prescribed channel having plural continuously repeating time slots. CONSTITUTION: A base station 10 including a central station terminal 12 and a remote radio terminal 14 is made correspond to plural subscriber's stations 42. In this case, each span trunk 28 is provided with time slots multiplexed by each multiplexer 30. Then, the multiplexer 30 extracts data from the trunk 28, and distributes the data through a power amplifier 40 to a transmitter/ receiver circuit network 38 and a channel module 36 in a circuit conductive state. At this time, a central station terminal 16 controls both a converter 20 and a remote radio terminal station 14, and processes a request from a subscriber for setting a desired transmission path between the subscriber's terminal station 42 and a central station 22.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention provides a method for transmitting and receiving information to a base station by means of an RF channel in a manner that enables simultaneous communication with subscriber stations through a predetermined channel having a number of consecutively repeating time slots. The present invention relates to a wireless digital telephone system communicating with a plurality of subscriber stations connected to the base station, with particular time slots being assigned to particular subscriber stations.

[Summary of the invention]

The present invention provides a system for communicating with a plurality of subscriber stations connected to a base station by an RF channel in such a manner that the subscriber stations can communicate simultaneously through a predetermined channel having a number of consecutively repeating time slots. The present invention relates to a wireless digital telephone system that includes a base station and in which particular time slots are assigned to particular subscriber stations. The present invention provides an apparatus for automatically changing both frequency or time slot configuration in the event of input of additional subscriber units that go off hook or in the event of modulation changes, frequency channel interference, equipment defects, etc. The modification device preferably includes a remote connection processing unit and a switch responsive to control signals from the remote connection processing unit by physically connecting selected ports in the communication circuit to selected slots. A replacement unit in the form of a concentrator is included. Control signals are provided in response to status messages received at the remote connection processor.

The present invention relates to wireless digital telephony communication systems, and more particularly to systems that automatically adjust the system to compensate for undesirable effects during operation such as frequency interference, attenuation, link quality degradation, and equipment defects. It relates to devices in the system.

The present invention can now be utilized in systems such as those disclosed in U.S. Patent Application No. 713,925 filed March 20, 1985, issued June 23, 1987 as U.S. Patent No. 4,675,863. . Such systems include a base station and a plurality of subscriber stations connected to the base station through an RF channel. This system provides communication between a subscriber station and an external communications network having multiple ports. The base station allows simultaneous communication between multiple ports and subscriber stations over a predetermined communication channel having a number of consecutively repeating time slots, each predetermined time slot being connected to a predetermined subscriber station. Contains assigned communication circuits. This system includes a central office terminal (COT) equipped with a remote access radio processing unit (RPU) that directs communication between a time slot assigned to a given subscriber station and a given port, and a central office terminal (COT) equipped with a remote access radio processing unit (RPU) that directs communication between a time slot assigned to a given subscriber station and a given port; Contains a switch to connect to. A switch, preferably a concentrator of the type fully described hereinafter, receives information from the RPU by physically connecting selected ports to selected communication channel time slots assigned to a given subscriber station. includes a switch responsive to a control signal.

The communication circuit includes a baseband control channel (B CC
) includes a plurality of channel control units (CCUs) that connect assigned communication channel time slots to corresponding subscriber stations in response to command signals communicated to the CCUs by RPUs at . These command signals are responsive to status messages provided to the RPU at the BCC to indicate communication channel time slots and subscriber station usage status. The assigned communication channel time slots are connected to corresponding subscriber stations by the assigned time slots within the assigned radio frequency (RF) channels. The BCC is provided from the RPU to each CCU via a separate line. Control commands and status messages are sent via predetermined RF
Communication occurs between the CCU and subscriber stations on radio control channels (RCCs) that are assigned to predetermined time slots of the channel.

[Problem to be solved by the invention]

It is a principal object of the present invention to provide frequency and slot agility that overcomes the transmission difficulties between a base station and its associated subscriber unit. The objective is to provide the same functionality in a relatively simple and inexpensive manner.

〔Example〕

Various other objects and related advantages of the present invention will become readily apparent from the following detailed description when read in conjunction with the accompanying drawings.

Acronym Combination Terminology BCC: Base Band Control Channel BER: Bit φ Error Rate CCT': Channel Control Task CCU: Channel Control Unit CO: Central Office COT: Central Office Terminal CRC: Cyclic Redundancy Check DBM: Data 1 Base tatami module LQ: Link quality MF: Malfunction MPM: Message processing module MTU: Master timing φ unit MUX: Multiplexer PCM: Pulse code modulation RCC: Radio control channel RF: Radio frequency RPU: Radio processing unit RRT: Remote Wireless terminal SCT: Subscriber control task 5 DLC: Synchronous data link control 8 bar: Scheduler module VCU: Voice codec ◆Unit Referring to the drawings in which similar reference characters represent similar parts, FIG. , a base station generally indicated at 10 including a central office terminal (COT) indicated generally at 12 and a remote radio terminal (RRT) indicated generally at 14. C0TI2 has a wireless processing unit (R) connected to the exchange unit 20 via the interface 18.
PU) 16 are included. The switch is preferably in the form of a concentrator, such as a Model R1218C Digital Image Concentrator equipped with switches currently available from ITT Corporation of New York, NY, USA.

The exchange 20 connects the central office (
Co) is in circuit communication with 22, and echo canceler 2
6 and a plurality of span trunks 28 to a master timing unit (MTU) within remote wireless terminal 14.
Multiple units connected to 32 and multiplexer (MUX)
30 are also in circuit communication state. Each span trunk 28
has a plurality of multiplexed time slots provided by its respective MUX 30.

A baseband control channel (BCC) 34, which occupies one of the time slots on one of span trunks 28, provides communication between MUX 30 and channel module 36.

Each MUX30 has 24 pulse code modulation (PCM)
It is embodied in a modular card that can handle up to 23 simultaneous circuits or 23 PCM simultaneous circuits plus BCC. MUX
operates to retrieve data from span trunk 28 and distribute the data via power amplifier 40 to channel modules 36 in circuit communication with transceiver circuitry 38.

The RPU 16 provides ultimate control of both the switch 20 and the RRP 140, and provides subscriber control for establishing the desired transmission path between the subscriber station, generally designated 42, and the central office (Co) 22. Act to process the request.

Each subscriber station 42 may include a single subscriber unit, dual subscriber units, or multiple subscriber units. FIG. 2 shows a single subscriber unit that also includes a transceiver 50 connected between an antenna 52 and a modem 54 in circuit communication with a codec 56 for encoding or decoding signals to a subscriber set 58. It shows. In FIG. 3, an antenna 60, a transceiver 6
2. Modemuro 4 and codec 66 are buffer 68
The same general type of unit is shown except that it includes a dual subscriber unit in circuit communication with separate subscriber sets 72 and 74 via and 70.

In the dual subscriber unit of FIG. 3, when two conversations are transmitted and received in one slot, the transceiver
, modems and codecs can be single reversible elements that only perform one set of operations at a time, eg, transmitting and receiving on each line. Additionally, no duplexer is required since the only duplication that occurs since the units are not transmitting and receiving at the same time is through buffers 68 and 70 which are connected to the interface circuitry (not shown) to the subscriber set.

FIG. 4 shows a generally 8-channel antenna connected to an antenna 82 and multiple single subscriber units 84a, 84b, 84n
A single subscriber multiplex system is shown including combining, unrolling, and duplexing circuitry designated 0.0. Each subscriber unit is 86a, 86b and 86
connected to the individual subscriber sets indicated in n.

FIG. 5 shows that network 88 connects dual subscriber units 90.92.
94, etc., each of the type shown in FIG.
2 and for dual subscriber unit 94 104
4 shows a multiplex system of the same type as that shown in FIG. 4, except that it is connected to individual dual subscriber sets at points 1 and 106.

During a conversation, (a) multiple subscriber configuration, (b) modulation change, (C
A number of problems can arise due to various factors that can be grouped together, such as a) avoidance of interference and (d) equipment deficiencies of individual channels.

FIG. 6 shows an example of an RPU matrix in which the various subscribers are represented by letters A through G, the horizontal columns represent frequencies, and the vertical rows represent slots. The number rlJ is “
rOJ represents "in use", and rOJ represents "not in use". In this matrix, only the transmit slots need to be stored (as shown) since the receive slots are always offset by two slots.

During operation, it often happens that all four slots of a particular frequency are occupied by various subscribers.

For example, assume there is one dual subscriber unit and the other units are single subscriber units.

In the case of dual subscriber units, it is necessary that the one dual subscriber be in adjacent slots.

If one subscriber of two dual subscribers occupies a particular frequency and slot while the other slot on a particular frequency is occupied by the other single subscriber; If the other subscriber of two dual subscribers has to connect off-hook for the purpose of making a call or because the incoming call must be routed from the central office to that subscriber. If so, a single subscriber in an adjacent slot of that frequency must move to another frequency and/or slot to make room for the second subscriber of the two dual subscribers. Or, the first dual subscriber occupying a particular frequency and slot must move to another available frequency in an adjacent slot. In this situation, the RPU acts to set up the current connection and store it in its memory, so it can determine where in the matrix the transfer can take place.

Transfers of the above types will be made in the following format:

For example, if the first subscriber of a dual subscriber is currently transmitting slot 1
Assume that the receiver is in a frequency conversation state within (reception slot 3). When the second subscriber of a dual subscriber goes off hook, an alert signal (one bit) is sent back to the base station as part of the control bits sent in addition to the conversation. The alert bit is detected within channel module 26, which in turn passes the message along a reverse conversation path or along separate paths via MUX 30, span trunk 28, switch 20, and interface 18. Send it back to RPU16. Conversely, the central office (Co) 22
The input signal from the switch 20 and the interface 18
and reaches RPU16.

For example, if any signal originates from a set off-hook or from a central station, the base station will Dual subscriber second to connect
Slots must be available to subscribers. If it is possible to move the first dual subscriber from frequency channel D to G, this is less preferred since two empty adjacent slots on the same frequency are often not available. In any case, it is at least easy to move an adjacent single subscriber unit from frequency D1 slot 2 to a different frequency. In the illustrated example, an adjacent subscriber could move into any one of the eight open slots. Since a single subscriber being moved does not require adjacent slots for transmitting or receiving, if this movement is done only in frequency (e.g. from channel D to K or G), then while the slot is not in use, can be achieved and is therefore glitchless. If changes are made in both slot and frequency, one of the transmitted data
The value of one slot is doubled or lost.

An analog situation exists with multiple single unit subscribers as in FIG. Since each unit is equipped with a complete set of elements, more than one unit can transmit at a time. In fact, it is preferred that all transmissions be simultaneous and all receptions be simultaneous in order to prevent front end overload of the receiver. Therefore, the sixth
In the matrix shown, two subscribers are on frequency B
and occupies slot 1 on D and call setup is required for a third subscriber, RPU 16 must assign the third subscriber to slot 1 on either frequency F or G. .

If the system is that of FIG. 5 and there are a number of dual subscriber units, the first subscriber of each pair of dual subscribers must be in the same slot, but each pair on a different frequency. The second subscriber must be in an adjacent slot on the same frequency as its respective first subscriber.

The RPU in the above situation operates at each time interval to set up the current connection state and stores those connections in its memory. Therefore, it is possible to determine where within the matrix a transfer can take place at any given time.

In all of the above situations involving slot and frequency allocation in a multi-subscriber situation, the stimulus for the change occurs outside the base station (either from the central station or from the subscriber set). In the following situations, including modulation changes due to attenuation or interference avoidance or changes due to equipment defects, the stimulus is generated or detected at the base station itself.

In the base station, each channel module 36 includes a channel control unit (CCU), as shown in FIG.
) 110 and a modem 112, each connected to a voice codec unit (VCU) 114 by separate compressed data links 116 and control state links 118. The VCU is a pulse code modulation (PCM) data
is interfaced to MUX 30 by channel 120, while the CCU provides synchronous data link control (
SDLC) 122 interfaces with MUX 30.

A number of buffers (not shown) are associated with various elements. In that regard, each channel module has a link quality (LQ) that measures the difference in received phase errors.
As well as buffers, an AGC buffer for each slot is included.

Additionally, the vCU is equipped with a bit-time error rate (BER) buffer. A cyclic redundancy check (CRC) is sent as part of each speech coded burst that provides a BER count to the BER buffer.

For purposes of the present invention, a high AGC level means that a high signal level is being received and the receive gain is low. Conversely, a low AGC level indicates a low received signal level and a large receive gain. This AGC level is used to indicate whether signal degradation is due to signal attenuation or whether interference is present. Since the AGC level is based on the sum of the signals that interfere with the transmitted signal, interference is indicated by a high AGC level. In either case the modification is done by modulation changes. As will be explained more fully hereinafter, each channel module 36 includes a modem capable of transmitting and receiving voice slots with 16 or 4 phase modulation. In 4-phase modulation, there are only half as many bits passing per symbol as in 166-phase modulation, but the bit ratio is the same. Therefore, when 4-phase modulation is used, two adjacent slots are combined into one long slot as shown in the matrix of FIG. Contains the same number of bits that occur within the slot.

For example, if a dual subscriber system is operating, BE
If R increases above a threshold (e.g. 0.1%) or LQ decreases below a threshold (e.g. 6 degrees), the contents of the corresponding buffer are device) is reported to the RPU via the interface link. The RPU then sends control signals back to the control module via the same link for the purpose of changing from 16-phase operation to 4-phase operation. At the same time, if two subscribers are currently operating on the same frequency in adjacent slots, one of the subscribers is changed to another frequency in the manner described above.

If the AGC level is still at a high level for that particular subscriber after the modulation level is changed in the manner described above, the reason for the low BER and LQ is assumed to be interference rather than transmission attenuation. A
The output of all the GC buffers is reported to the RPU which determines which frequency (if any) has a low AGC level and then the RPU switches from the high AGC level frequency to the low AGC level frequency for that subscriber. Start changing the frequency. This acts to eliminate interference if it exists.

The base station also has switchboards (concentrators), spans, trunks,
A malfunction function (MF) buffer is provided that provides the operational status of each link in the base station chain, including the MUX, channel modules, power amplifiers, and transceivers. If the MF buffer detects a malfunction or equipment defect, a signal is sent to the RPU indicating which frequencies are involved. Upon receiving this MF multiplier signal, the RPU initiates a frequency (and slot, if necessary) change for each conversation currently occurring (if any) on the affected channel.

The RPU 18 is a primary element that controls frequency channel and slot allocation, and its overall structure is shown in FIG. This is a database module (DBM) 132
and a message processing module (MPM) 130 connected to a scheduler module (SM) 134. The MPM consists of a channel control unit (CCU) 110 and a subscriber control task (CT) located outside the RPU.
Similar to 136, it controls all interference between the SM and DBM within the RPU. The CCU is located within the channel module 36 as shown in FIG. 7, while the FCT is in circuit communication with the subscriber station.

In operation, e.g. link quality (LQ) during a call.
When the value falls below a predetermined level, the RPU sends the message to BCT.
128, at which point BCT 128 communicates with MPM 122.

The MPM then (a) sends a signal to the DM 124 to check for available channels, and (b) checks with the scheduler-Φ module 126 for schedule control and timing. (The scheduler module operates to arrange the messages it receives in the order in which they are received.) If there are channels available, the M
The PM sends a message back to the SCT to reconfigure the matrix to move the call to an available channel. If no channel is available, the call is kept on the same channel.

During a call, if all four slots are occupied, but due to interference on a particular frequency it is necessary to move all subscribers to other frequencies with the same individual slots, then the following sequence arise. RPU
sends a message to the SCT requesting a frequency change when excited by a decrease in link quality. The SCT forwards the message to the Channel Control Task (CCT) located at the subscriber station for frequency change processing and also to the MPM located at the base station for allocation of available CCU channels.
communicate with. The MPM sends a signal to the DBM confirming the available channels and also checks with the scheduler module to obtain the time position in the schedule. If there are channels available, the MPM sends a message back to the SCT to reconfigure the channel location.

If there are no channels available, the SCT sends a busy signal to the RPU and no changes are made.

FIG. 9 shows the RCC protocol. RPU 16 is in communication with CCUIIO and modem 112. At the subscriber station, the 5CT 136 is connected to the C
It is in communication with C0138. The RCC protocol has two layers: a data link layer 142 and a packet layer 14.
It consists of 4. The data link layer is the physical link between parts, while the packet layer consists of the messages sent on this physical link. The data link layer is also responsible for error detection, word synchronization and framing, and collision detection and resolution (content collisions for the same time slot on the same RF channel).

Referring to FIG. 9 - As an example, the RPU processes two paths of the protocol. In the first protocol, RP
The U sends a message to the base station's CCU requesting a modulation change. In the second protocol, the RPU sends a message to the SCT requesting a frequency change. In the third protocol, the SCT sends a message back to the RPU indicating that all channel frequencies are occupied.

In another example, the RPU sends a message protocol to the SCT requesting a channel frequency change. This message initiates two functions. First, the message requests that the SCT at the subscriber station obtain a route to another frequency from the RCC. The SCT communicates with the CCT here and there. The CCT then searches for a channel and, if it finds an available slot and frequency, switches to that channel. In the second function,
In the message protocol, the SCT calls the central office to wait for a connection.

During a conversation, if the link quality falls below a certain level, the RPU
forwards this information to the CCU and requests a change in modulation level. CCU sends RP via MUX through 5CLC link
Confirm this message to U.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a base station utilized in the present invention, with connected subscriber stations generally shown; FIG. 2 is a block diagram of a single subscriber unit embodying the present invention; FIG. 3 is a block diagram of a dual subscriber unit embodying the present invention; FIG. 4 is a block diagram of a multiple single subscriber unit embodying the present invention; FIG. 5 is a block diagram of a multiple single subscriber unit embodying the present invention; FIG. 6 is a block diagram of a number of dual subscriber units embodying the invention; FIG. 7 is a block diagram of a wireless processing unit matrix embodying the invention; FIG. FIG. 8 is a block diagram of a radio processing unit and its connecting elements embodying the present invention; FIG. 9 is a functional diagram showing communication layers between a base station and a subscriber station. 10: Base station 42: Subscriber station 1, Indication of the case 2, Title of the invention 3, Relationship with the amended person's patent application No. 1984-284050 Communication system case Patent applicant's address Pennsylvania, United States of America 191
02 100 North Towninteeth Street, Philadelphia Name International Mobil Machines Corporation Representative Stephen Vye, Abramson Nationality United States 4 Agent Kimraya Otsuka Building 6, 1-18-19 Shinbashi, Minato-ku, Tokyo
Subject of amendment (1) “Patent applicant column” of the application (2) Copy of specification (3) Power of attorney

Claims (1)

Claims: 1. A communication system comprising a plurality of subscriber stations in RF communication with a base station having a plurality of consecutively repeating time slots, the subscriber stations transmitting selected RF channels in response to control command signals. A communication system comprising apparatus for connecting to a corresponding subscriber station, the command signal being responsive to a status message indicating usage of the time slot in relation to the subscriber station. 2. The communication system of claim 1, wherein the control command signals and status messages are communicated to the subscriber station over a wireless control channel assigned for a selected time slot of a selected RF channel. 3. The communication system of claim 1, wherein said control commands and status messages are transmitted to said subscriber station by a wireless processing unit in communication with both a central station and said base station. 4. A communication system comprising a base station in communication with a central station and a subscriber station connected to said base station by an RF channel, said base station having a plurality of continuously repeating time slots. frequency channels, the time slots and frequency channels are selectively assignable to the subscriber station, and the input line of an additional subscriber or a base station is connected to a subscriber station in communication with the base station. A communication system includes an assigning device for selectively assigning time slots and frequency channels to one of the subscriber stations in response to attenuation of transmissions between the subscriber stations. 5. The communication system of claim 4, wherein the assignment device makes the assignment in response to transmission impairments due to modulation changes, frequency channels, interferences, or equipment defects. 6. The communication system of claim 4, wherein there are a number of single subscriber stations communicating with the assigning device. 7. There are a number of dual subscriber stations in communication with said assigning device, each subscriber of each pair of dual subscribers being assigned separately by said assigning device to adjacent slots in a selected frequency channel; 5. The communication system according to claim 4, wherein the communication system is enabled. 8. A communication system comprising a base station communicating with a central station and a plurality of subscriber stations via an RF channel, said base station having a plurality of continuously repeating time slots and a plurality of frequency channels, allocating time slots and frequency channels to selected subscribers by allocating selected empty slots in selected frequency channels to occupied slots in the memory matrix according to their adjacency, said allocation depending on additional subscriber input lines; or in response to stimuli caused by transmission degradation between the base station and the subscriber. 9. The method of claim 8, wherein the transmission impairment is caused by modulation changes, frequency channel interference, or equipment defects. 10. Claim 8, wherein said assignment occurs during a conversation between subscribers.
Method described.