CN1012548B - Apparatus and method for obtaining frequency agility in digital communication system - Google Patents

Abstract

The present invention relates to a communication system which comprises a plurality of subscriber boards and a frequency or time slot transition device, wherein the subscriber boards carry out RF communication with a base station which has a plurality of time slots sequentially repeated, and each time slot is allocated to a specified subscriber board; the frequency or time slot transition device is used for overcoming transmission distortion caused by modulation variation, frequency channel interference, equipment fault, etc. or caused by the fact that other subscribers go into an on-line state.

Description

Apparatus and method for obtaining frequency agility in digital communication system

The present invention relates to wireless digital telephone system, wherein, a plurality of subscriber boards that base station connects through the RF channel with it communicate, and its mode is to communicate by letter with a plurality of subscriber boards simultaneously through an allocated channel, this channel has and a plurality ofly sequentially repeats time slot, and particular time-slot is specified in particular subscriber station.

Wireless digital telephone system involved in the present invention comprises a base station that communicates through RF channel and a plurality of subscriber boards that connect with it, its communication mode is to communicate with subscriber board simultaneously through an allocated channel, this channel has and a plurality ofly sequentially repeats time slot, and particular time-slot is assigned to particular subscriber station.Under the situation that other subscriber unit off-hooks enter, or because modulation variation, when channel interference, equipment fault or similar incidents caused sending the quality reduction, device provided by the present invention can change frequency or time slot configuration automatically, or two all change.This conversion equipment comprises a long-range processing unit and the switch of continuing, preferably the form with concentrator realizes, this switch comprises a switch, it is by physically being connected in a selected time slot with the selected port in the telecommunication circuit, makes switch can respond control signal from long-range connection processing device.The state information that is received according to long-range connection processing device provides control signal.

The present invention relates to the communication system of wireless digital telephone type, refer more particularly to this device in the system, it can adjust this system automatically, with the harmful effect that occurs during the compensation work, and for example frequency interferences, decline, link-quality deterioration and equipment fault etc.

Disclosed system on the U.S. Patent application serial number 713,925 that the present invention can be applicable to submit on March 20th, 1985, the patent No. of its promulgation is 4,675,863, the promulgation date is on June 23rd, 1987.This system comprises a base station and is connected in a plurality of subscriber boards of base station by the RF channel.It provides the communication that reaches between the subscriber board with the external communication networking with a plurality of ports.This base station comprises a telecommunication circuit, is used to make that the communication channel through an appointment communicates simultaneously between a plurality of ports and the subscriber board; This channel has and a plurality ofly sequentially repeats time slot, and predetermined time slot is assigned to predesignated subscriber's platform respectively.This system comprises a main exchange terminal (COT), the long-range radio that continues wherein is housed handles device (RPU), is used to make between the time slot that is assigned to a particular subscriber station and the particular channel communicate; It also is equipped with a switch, is used for telecommunication circuit is connected with port.That class concentrator that described switch preferably hereinafter will describe in detail, it comprises a switch, this switching response is from the control signal that RPU sends, and a selected port physically is connected in be assigned to the selected communication channel time slot of particular subscriber station.

Telecommunication circuit comprises a plurality of channel control apparatus (CCUs), and these devices pass to the command signal of CCU according to RPU through base band control channel (BCC), with the communication channel time slot and the corresponding subscriber board coupling of appointment.These command signals offer RPU according to state information through BCC, to indicate the user mode of communication channel time slot and subscriber board.Specified communication channel time slot is arranged in by one specifies the particular time-slot of radio frequency (RF) channel to be coupled in corresponding subscriber board.BCC is that the circuit through being connected to RPU offers each CCU's.The radio control channel (RCC) of control command and the state information predetermined time slot through being assigned to predetermined RF channel is transmitted between CCU and subscriber board.

Main purpose of the present invention provides the fast change of frequency and time slot, to overcome between base station and the subscriber unit relevant with it hell and high water when the transmission.Another object of the present invention is to provide above-mentioned fast change function with quite simple and inexpensive manner.

Various other purpose of the present invention and advantage thereof will be done detailed description according to following accompanying drawing, wherein:

Fig. 1 is the block diagram of the used base station of the present invention, and the subscriber board that is connected is also made indication.

Fig. 2 is a block diagram of implementing Single Subscriber Unit of the present invention.

Fig. 3 is a block diagram of implementing dual user of the present invention unit.

Fig. 4 is a block diagram of implementing a plurality of Single Subscriber Units of the present invention.

Fig. 5 is a block diagram of implementing a plurality of dual user of the present invention unit.

Fig. 6 implements radio of the present invention to handle the device matrix.

Fig. 7 is the more detailed block diagram of the used channel module of the present invention.

Fig. 8 implements the block diagram that radio of the present invention is handled device and Connection Element thereof.

The block diagram of Fig. 9 has functionally been represented the communication layers between base station and the subscriber board.

Among the figure:

BBC base band control channel

The BER error rate

CCT channel control task

The CCU channel control apparatus

The CO main exchange

COT main exchange terminal

The CRC cyclic redundancy check (CRC)

The DBM database module

The LQ link-quality

The MF fault

The MPM message processing module

The MTU timing master device

The MUX multiplexer

PCM pulse code decoding modulation

The RCC radio control channel

The RF radio frequency

The RPU radio is handled device

RRT long distance wireless electric terminals

SCT user's control task

The control of SDLC synchronous data-link

The SM scheduler module

VCU voice signal code device

The XMIT transmitter

The REC receiver

With reference to accompanying drawing, wherein identical part indicates identical reference marks, Figure 1 shows that a base station, and with 10 signs, it comprises that a label is 12 main exchange terminal (COT), and label is 14 long distance wireless electric terminals (RRT).COT12 comprises a radio processing device (RPU) 16, and it is coupled to switch 20 by interface 18.This switch is the concentrator formula preferably, for example adopts " Model 1218C " the digital image concentrator that has a change over switch, and it can be provided by ITT Corp. of New York, United States New York.

Interchanger 20 is connected with main exchange (CO) 22 by a plurality of pairs of outside lines 24, and be connected on a plurality of multiplexer (MUX) 30 through Echo Canceller 26 and a plurality of span trunk line 28, these modulators are coupled in the timing master device (MTU) 32 in the long distance wireless electric terminals 14.Every span trunk line 28 is loaded with the time slot of a plurality of multiplexer MUX30 modulation by separately.Base band control channel (BCC) 34 provides the communication between MUX30 and the channel module 36, and it occupies a time slot of a trunk line in the span trunk line 28.

Each makes standard package plate (MUX) 30 can handle 24 pulse code modulation (pcm)s circuit simultaneously, or 23 PCM while circuit add BCC.MUX obtains data from trunk line 28, and it is distributed to channel module 36, and module 36 is connected with transceiver network 38 by power amplifier 40.

16 pairs of interchanger (concentrators) 20 of RPU and RRT14 have basic controlling, and the process user requirement, so that set up required path between subscriber board 42 and main exchange (CO) 22.

Each subscriber board 42 can have a Single Subscriber Unit, a dual user unit, or a multi-user unit.Single Subscriber Unit shown in Figure 2 comprises a transceiver 50 that is coupled between antenna 52 and the modulator-demodulator 54, and modulator-demodulator 54 is connected with the coder-decoder 56 of encoding for the signal of subscriber board 58 receptions or transmission or decipher.In Fig. 3, except above-mentioned identical plain edition unit, it also comprises a dual user unit, and wherein antenna 60, wireless set 62, and modulator-demodulator 64 is connected with 74 with the subscriber board 72 that separates with 70 by buffer 68 with coder-decoder 66.

In the dual user unit of Fig. 3, if in a time slot, send and receive two sessions, wireless set then, modulator-demodulator and coder-decoder can be the reversible parts of list that can only once carry out a phone operation, promptly send or receive through every line.Further, owing to this unit receives simultaneously never and sends, thereby do not need duplexer, because repeat only to take place by buffer 68 and 70, these buffers are connected in the interface circuit (not shown) of subscriber board.

Figure 4 shows that single user's redundant system, it comprises tandem, expansion and duplex network 80, is coupled in antenna 82 and a plurality of Single Subscriber Unit 84a, 84b, 84n.Each subscriber unit is coupled to separately subscriber board 86a, 86b and a 86n.

Fig. 5 is except having the redundant system identical with Fig. 4, and network 88 is coupled to dual user unit 90,92,94 or the like, its type as shown in Figure 3, each unit is coupled to other dual user platform of branch, for example, 96 and 98 order units 90,100 and 102 order units 92, and 104 and 106 order units 94.

During session, because following factor may produce some problems: (a) multi-user distributes, and (b) modulation variation (c) is disturbed and (d) equipment fault of each channel.

Fig. 6 has showed the example of a RPU matrix, and wherein each user represents that with alphabetical A to G horizontal line is represented frequency, and vertical row is represented time slot.Numeral " 1 " expression " use " and " 0 " expression " use ".In this matrix, because receiving slot always departs from 2 time slots, so have only sending time slots to need storage.

When operation, all 4 situations that time slot is taken by different user of characteristic frequency often take place.Suppose for example to have a dual user unit and other are Single Subscriber Units.Under the dual user cell cases, be necessary to make dual user to take adjacent time slot.Other time slots of this frequency are shared by other single users if one of two dual user have taken a specific frequency and time slot, and if another of two dual user needs to connect (because he off-hook call out or call out the circuit that enters him from main exchange); Then any the single user in the adjacent time-slots of this frequency must transfer to another frequency and/or time slot, offer an opportunity with the second party of thinking two dual user, perhaps the characteristic frequency that takies of first dual user and time slot must move on to adjacent time-slots can with another frequency get on.In this case, RPU moves to set up existing connection and they are kept in its memory, therefore, can determine which transmitter in the matrix can work.

The transmitter of above type is realized in the following manner: the first party of for example supposing dual user at that time with frequency D at sending time slots 1(receiving slot 3) in carry out session connection, when the second party off-hook of dual user, an alarm signal (one) sends back to the part of base station as the control bit that sends except that session, the alarm position is detected in channel module 36, by channel module 36 information is passed through MUX30 then, span trunk line 28, interchanger 20 and interface 18 are along oppositely a session path or a separate paths are transmitted back to RPU16.Otherwise the signal that main exchange (CO) 22 is sent here is via interchanger 20 and interface 18 to RPU16.

In case off hook signal for example occurs or from the signal of main exchange, the second party that is necessary for dual user is selected a time slot for use and has been used base station in the adjacent time-slots of time slot so that it is linked the dual user first party.When may with first dual user when frequency D moves to G,, being not the best so shift because two vacant adjacent time-slots of same frequency are not always available.Under any circumstance, at least easily with adjacent Single Subscriber Unit from frequency D, time slot 2 is transferred to a different frequency.In the example shown, neighboring user can be transferred among any one in eight open slots, because the single user who is transferred need not adjacent time-slots and sends and receive, if only in frequency, shift (as from channel D to B or G), then can the time spent finish at time slot, therefore can not go wrong, if change in time slot and frequency, a time slot width that then sends data will be repeated or lose.

Analogue also exists in the multiple connection Single Subscriber Unit, as Fig. 4.Because there is one group of complete unit each unit, so once can send one more than the unit.In fact, preferably send simultaneously and receive simultaneously, to prevent the receiver front end overload.Therefore, in Fig. 6 matrix, if two CUs the time slot 1 on frequency B and the D, and the calling of setting up requires third party, then RPU16 must be assigned to the 3rd user to the time slot on frequency F or the G 1.

In the system of Fig. 5 and under the situation of multiple connection dual user unit, first user of every pair of dual user must be in the same time slot of different frequency, and second user of every pair of dual user must be in the adjacent time-slots of user's same frequency separately.

Under these conditions, RPU located to cause current connection in each time interval, and in its memory it was stored, and therefore, can determine at any time can affectedly to transmit in the matrix.

In all above-mentioned conditions, what addressed is the time slot under multi-user's situation and the distribution of frequency, and the factor that changes is (from main exchange or the subscriber board) that occurs in outside the base station.In following because decline or disturb the modulation variation cause, or, detect from the changing factor of base station own because equipment fault brings under the situation of variation.

In base station, as shown in Figure 7, each channel module 36 comprises 110 and modulator-demodulators 112 of a channel control apparatus (CCU), and the packed data link 116 that they pass through separately respectively links to each other with voice signal coding-decoding apparatus (VCU) 114 with state of a control link 118.VCU is connected to MUX30 by pulse code modulated (PCM) data channel 120, and CCU links MUX30 by synchronous data-link control (SDLC) 122.

A plurality of buffer (not shown) are associated with each parts, and in this regard, each channel module contains an AGC buffer that is used for each time slot, and link-quality (LQ) buffer of the difference of the pulse error that receives of measurement.In addition, VCU also is furnished with a bit error rate (BER) buffer, and Cyclic Redundancy Check will send as the coded pulse group's of each session a part, thereby provides BER counting for the BER buffer.

For this purpose, high AGC level means and receives high level signal and receiver gain is less, otherwise, low level AGC signal indicating receiver gain is big and received a low level signal, this AGC signal level is used to point out that whether signal is owing to its decline has produced distortion, or not having to disturb exists, and higher AGC level is pointed out to disturb, and this is to send signal and any interference signal sum because the AGC level depends on.In two kinds of examples, can revise by modulation variation.At this on the one hand, with clearer discussion, each channel module 36 contains a modulator-demodulator as following, and it can be by 16 mutually or 4 phase modulation transmissions and receive the speech gap.4 mutually in the modulation figure place passed through of each symbol only 16 pass through in the modulation mutually 1/2, but bit rate is consistent.Therefore, when adopting 4 to modulate mutually, two adjacent time-slots shown in the matrix among Fig. 6 are combined into the time slot of a prolongation, and the situation of the figure place that it comprised and 16 phase operating periods is identical.

For example, when a dual user system works, if BER surpasses a certain threshold values (as 0.1%) or LQ is lower than a certain threshold values (as 6 degree), then the content in the respective buffer is reported to RPU by MUX-main line-interchanger (concentrator)-interface link.Therefore RPU is returned to control module by same connection with a control signal, thereby switches to 4 operations mutually mutually with 16.Meanwhile, if two users work on the adjacent time-slots of same frequency simultaneously, one of them user will be switched to another frequency in the above described manner.

If after modulation level changes in the above described manner, the AGC level still is higher than a specific user, infers that then it is to disturb but not the transmission decline that BER and LQ become bad reason.The output of all AGC buffers determines that by it which frequency (if the words that have) has a low AGC level all to RPU report, then, by RPU this user's frequency for a change is low AGC level from high AGC level.This move has been eliminated the interference that may exist.

Base station also has fault (MF) buffer, it provides the operating state of each link in the base station link, this base chain of stations comprises telephone switchboard (concentrator), the span trunk line, MUX, channel module, power amplifier, transmitter and receiver if the MF buffer detects fault or equipment breakdown, will have a signal to be sent to RPU, point out related frequency, in case receive this MF signal, RPU just carries out frequency (if necessary, also time slot) to simultaneous each session (if present) on the affected channel and switches.

RPU18 is the main element of control frequency passage and time slot allocation, and its universal architecture as shown in Figure 8.It comprises a message processing module (MPM) 130, and it links to each other with scheduler module (SM) 134 with database module (DBM) 132.MPM manages SM and the total interface between the DBM in RPU and the channel control apparatus (CCU) 110 and is positioned at the outer user's control task (SCT) 136 of RPU.CCU is positioned within the channel module 36, and as shown in Figure 7, SCT then links to each other with subscriber board.

When operation, if be reduced to a frequency levels under (for example when calling out) link-quality (LQ), then RPU is sent to SCT136 with information, and therefore it communicate by letter with MPM130.MPM (a) then send a signal to DBM132, to discern an available channel, (b) by be responsible for arranging control and scheduler module 134 regularly test (this scheduler module be used to arrange received in proper order by it information).If there is a channel to use, then MPM sends a message back to SCT, so that form matrix again this calling is passed on this available channel.If no available channel then keeps this calling in former channel.

If all four time slots are all occupied in calling procedure, but because a characteristic frequency is disturbed, must move all users when having another frequency of time slot equally separately, to carry out in the following order: when RPU is driven by low-quality link, it will send message to ask conversion frequency to SCT, this SCT sends to the channel control task (CCT) that is positioned at the subscriber board place so that carry out frequency conversion process with this message, and distributes the base station place of available CCU channel to communicate by letter with MPM at one.This MPM send a signal to DBM discerning an available channel, and carry out verification in timetable, to obtain a time location by scheduler module.If an available channel arranged, then MPM with an information back to SCT to form this channel position again.If do not have available channel, SCT to send one " hurrying " signal to RPU, and no change takes place.

Fig. 9 shows the RCC scheme, and RPU16 communicates by letter with modulator-demodulator 112 with CCU110.At the subscriber board place, SCT136 communicates by letter with the CCT138 that is furnished with modulator-demodulator 140, the RCC agreement comprises two-layer, a data link layer 142 and a packet layer 144, data link layer is the physical link between the parts, and packet layer is included in the information of passing through on this physical link, and data link layer is responsible for error-detecting, synchronous and the framing of word, (contradiction of the same time slot on same RF channel is striven unexpectedly to detect and eliminate conflict.）

Referring to Fig. 9, as an example, RPU handles the agreement of two paths: in first agreement, the CCU request that RPU delivers to base station with message changes modulation, in second agreement, RPU delivers to the SCT request with an information and changes frequency, and in the 3rd agreement, it is all occupied to indicate all channel frequencys that SCT turns back to RPU with information.

In another example, RPU delivers to SCT with the conversion of request channel frequency with an information protocol, and this information has two functions: at first, it asks the SCT at subscriber board place to obtain a route from RCC to another frequency.Therefore this SCT communicates by letter with CCT, and CCT searches for channel then, and exchanges when an available time slot and frequency occurring, and in its second function, information protocol makes SCT called telephone general bureau prepare to connect.

If the link-quality during session is lower than predetermined level, then RPU sends information to CCU and request conversion modulation level.CCU confirms that by MUX this information arrives RPU via synchronous data link control link.

Claims (9)

1, communication system, it comprises a plurality ofly carries out the subscriber board that RF communicates by letter with base station, described base station has repetition time slot and a plurality of frequency channel of a plurality of orders, described time slot and frequency channel are distributed to described subscriber board selectively, it is characterized in that described system also comprises: respond a control command signal, the selected communication time slot in the selected RF channel is coupled to the coupling device of corresponding subscriber board, described command signal is in response to the state information that shows relevant time slot user mode with described subscriber board; And, be used to respond entering or the bad change of transmission when base station and subscriber board communication and distribute the distributor of time slot and frequency channel selectively into arbitrary subscriber board of another user.

2, according to the described system of claim 1, wherein said control command signal and state information are given described subscriber board by a radio control channel transfer, and this passage is the selected time slot of selected RF channel.

3, according to the described system of claim 1, wherein said control command and state information are handled device by a radio that communicates with main exchange and base station and are sent to described subscriber board.

4, system according to claim 1, wherein said distributor is according to modulation variation, the bad change of transmission that frequency channel disturbs or equipment fault causes and distributing.

5,, wherein, there are a plurality of single subscriber boards and described distributor to communicate according to the described system of claim 1.

6, according to the described system of claim 1, wherein, there are a plurality of dual user platforms to communicate by letter with described distributor, each user of every pair of dual user platform can distribute to an adjacent time-slots of selecting in the frequency channel respectively by described distributor.

7, in having a communication system with the main exchange and the base station of communicating by letter with a plurality of subscriber boards by the RF channel, this base station has a plurality of time slot and a plurality of frequency channels that sequentially repeat, the method of time slot and frequency channel being distributed to selected user is: distribute selected vacant time slot in selected frequency channel, for described user according to the situation that occupied time slot in a storage matrix adjoins, described assignment response in other users enter or base station and user between the variation that causes of transmission distortion.

8, according to the described method of claim 7, wherein, transmitting distortion is by modulation variation, what frequency channel disturbed or equipment fault causes.

9, according to the described method of claim 7, wherein, described distribution occurs between two users in the conversation procedure.

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