CN1179251A - Method and apparatus for processing burst signals in a telecommunication system - Google Patents
Method and apparatus for processing burst signals in a telecommunication system Download PDFInfo
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- CN1179251A CN1179251A CN 96192624 CN96192624A CN1179251A CN 1179251 A CN1179251 A CN 1179251A CN 96192624 CN96192624 CN 96192624 CN 96192624 A CN96192624 A CN 96192624A CN 1179251 A CN1179251 A CN 1179251A
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Abstract
A control unit (102) efficiently decodes burst signal transmissions in a TDMA-based telecommunication system (100) by decimating down the number of samples requiring processing during symbol detection. The control unit (102) includes a sampling receiver (304) that inputs burst signals from cable access units, converts them to a pair of baseband quadrature signals, I and Q. The sampling receiver (304) also includes an A/D converter (314) that samples the I and Q signals at preferably four times the symbol rate. A digital signal processor circuit (306) produces a timing error signal for substantially all of the samples. The digital processor circuit (306) also accumulates a timing error sum for each of the four samples. The processor circuit (306) selects the optimum sample as the sample between the samples having the largest positive and negative error sums. The processor circuit (306) also includes a pi /4-DQPSK differential detector that processes the optimum sample of each symbol for symbol detection.
Description
The present invention relates to common telecommunication system, especially the processing of the burst signals that transmits in the telecommunication system.
Signal and/or information that some telecommunication system scheme requires to send from afar arrive another place in a time slot of being scheduled to.For example, telecommunication system that uses time division multiple access (TDMA) require the burst information that sends from a dispensing device receiving system predetermined/known time slot is received.In the system based on TDMA, a plurality of isolated users are shared a transmission medium by get one or more pieces time slots in limiting time.
TDMA is to use a kind of conventional method of transmitting in order to control information in such as the basic telecommunication facility of line telecommunications system.The basic telecommunication facility of line telecommunications system has the line concentration center of the various nodes of a service usually, and each branch road end at this line concentration center has one or more nodes.Branch road is optical cable normally.Optical cable leads to a distribution system that is connected by coaxial cable, extends to such as family isolated users such as enterprise again.Often be divided into some manageable subsystems (be as radius 20 kilometers subsystem) at the distribution system of particular branches one end, these subsystems are nodes independently.Node generally includes one or more user access points so that each user and line telecommunications system are coupled together.
The control unit at line concentration center is responsible for the automatic route of reception of each user's signal and burst information, thereby must be from user there received signal in predetermined time slot.Information is sent to control unit as burst information usually in predetermined time slot.Therefore, the control unit signal that must can analysis user transmit is just with information extraction from the signal that is received.These analyses are included in the timing of determining signal in the time slot, detect the burst information that comprises the some code elements that embody transmission information, and (being symbol detection), and the burst information decoding become detected code element.These are analyzed needs very strong disposal ability.
People are that many effort have been made in the requirement of satisfying the high strength processing of tdma system.For example, U.S. Patent number is 4937841, Chuang etc., carrier wave recovery in the radio tdma system is proposed, this method is stored half of code element then and is carried out the correlation demodulation with two two/parts of received signal by input symbols is sampled with the sampling rate of 16 samples of each code element.The method of Chuang is enough for resembling the lower transmission systems of symbol-rate such as radio, and for higher telecommunication systems of symbol-rate such as all wired systems as the aforementioned, his solution is then powerless.
Say that further though the line telecommunications system is used for the transmission of TV signal traditionally, and they needing to be used for the bidirectional communication scheme that higher symbol-rate suit to operate more at present.Can be thereby need with the system and method based on TDMA of signal between the each several part of the symbol-rate processing telecommunication system higher than radio system.
Fig. 1 is to use the structure diagram of the telecommunication system of wire communication facility;
Fig. 2 is a sample flow sequential chart of the initial burst information that receives of control unit of telecommunication system shown in Figure 1;
Fig. 3 is the structured flowchart of the preferred line control unit of telecommunication system shown in Figure 1;
Fig. 4 is a flow chart, the processing procedure of the high-efficiency decoding that the burst information that the line control unit of its key diagram 3 sends the subscriber unit in the telecommunication system shown in Figure 1 carries out.
On the whole, the present invention provides method and apparatus for the efficient processing of the burst signals that transmits in the telecommunication system based on TDMA.More precisely, method and apparatus of the present invention is particularly useful for using the efficient processing based on burst signals in the TDMA telecommunication system of wire communication facility.
According to principle of the present invention, we provide the method and apparatus based on the TDMA transmission of efficiently handling burst signals with higher symbol-rate.Complicated burst (comprise noise and be positioned at the signal message in predetermined time slot window somewhere) stores.Treatment circuit gives burst information regularly, detects the code element in the burst information and burst information is decoded into data and further handle for line control unit.Treatment circuit is efficiently handled the burst signals that control unit receives, thereby keeps the symbol-rate of per second 368K code element.
Can more detailed understanding principle of the present invention by accompanying drawing.Fig. 1 has shown and has been the structure diagram of the wire communication facility of two-way communication configuration (as the layout of the transmitted in both directions of call or computer data).According to Fig. 1, telecommunication system 100 comprises a line control unit 102 (CCU).Line control unit 102 is used for the reception and the automatic route of the signal (or information) of whole system 100, and carries out other system management function.
Extend some branch roads 104,106,108 and 110 from line control unit 102 (being the line concentration center).The first-selected optical cable of these branch roads is a medium.Branch road 104-110 also can be according to specific application scenario, and network topology and system requirements are selected other suitable transmission medium, such as the coaxial cable of low consumption.Branch road 104-110 is as the backbone of telecommunication system 100, and this point is obviously for those skilled in the art.
Among the optical fiber branch road 104-110 each is led to a specific distribution system 112,114,116 or 118 respectively.Each distribution system among the 112-118 all is arranged in corresponding one end of branch road 104-110.Every branch road reality ends at distributing point 120,122 respectively, in 124,126 one.Usually distribution system 112-118 by coaxial cable but not optical cable form.They distribute the signal that debouches each user (demonstrated in three line access units among the figure, but should be appreciated that in fact each user can have a line access unit in the distributed line system) by line access unit 121.
Having shown among the figure that different representative of some of distribution system 112-118 is configured to illustrate can use different configurations.For example, distribution system 112 is ring-types, and distribution system 114 and 116 is different wire layout.Thereby the present invention does not limit distribution system and selects specific configuration.
Except distribution system, line control unit 102 also can link to each other with other telecommunication system by gateway.For example, the branch road of telling from line control unit 102 128 links to each other with public switched telephone network (PSTN) 130.Branch road 128 can be the optical cable similar to 104-110, or other suitable transmission medium of knowing of technical staff.Therefore, telecommunication system 100 can insert all various common communication networks and various gateway such as PSTN130 by 128 circuits.
By among the distribution system 112-118 any one, between control unit 102 and each line access unit 121 transmission data a representational example as shown in Figure 2.The signal 202 that is received by control unit 102 comprises eight burst information 204-218.Each burst information is sent by different access unit 121 usually, and all in a predetermined time slot calibration window (shown in dotted line among the figure 220) by complete reception.Distance between any two 220 dotted lines is represented single time slot calibration window.The burst information that receives in Fig. 2 display time slot window B0-B7.
Each burst information in each time slot is made up of some code elements that comprise the digital information of transmission.In the line telecommunications system, preferred 120 code elements of time slot window B0-B7 wide (i.e. 240 bits), and actual window length can change under the prerequisite that does not break away from principle of the present invention and spirit.In addition, known in the communication technology is that the length of actual burst information is shorter than length of window usually, to adapt to the minor variations in the transmission.For this reason, a kind of preferred embodiment of the present invention has 112 code elements long for burst information 204-218, and each window allows the variation of eight code elements.
Pass shown in 224 as boundary 222, the burst information 204-218 of reception has varying strength level and phase place discontinuous in control unit 102.This be since send that user's access unit 121 of burst information is positioned at different positions in network and on the code element level asynchronous due to.The variation of amplitude in a preferred embodiment may be up to 26 decibels, this in fact be since each line access unit different with distance between control unit due to.The variation of amplitude and phase place adds the relative short cycle of burst information, requires all processing of burst information (112 code element) in succession relatively independently, and each burst information is all set up new symbol timing.These all are the requirements of necessity of system, and method of the present invention can be carried out necessary processing fully.
Fig. 3 shows the details of the control unit 102 that has embodied the principle of the invention.Control unit 102 is connected in line access unit 121 by branch road 302.Branch road is arbitrary of branch road 112-118 or the branch road that does not draw in addition that links to each other with telecommunication system 100 in the representative graph 1 only.Branch road 302 links to each other with the sampling receiver 304 of control unit 102 inside that link to each other.Digital signal processor (DSP) circuit 306 and processor storage 308 are also included within the control unit 102.In the preferred embodiment of the present invention, DSP circuit 306 comprises one group of DSP (shown in dotted line 310), undertakes the Processing tasks of control unit 102 jointly.DSP also can regard as and comprise the timing error testing circuit, and summation circuit is estimated circuit and symbol detection circuit.The effect of these circuit is described below.
The operation of preferred control unit 102 is described with flow chart Fig. 4.In step 402, burst information is imported into sampling receiver 304.During step 404, the sampling receiver carries out filtering to the received signal, and filtered signal is converted into the I of quantification, Q signal, and I, Q signal changes into digital signal and is stored in buffer storage 316 by mould/number conversion circuit.The present invention allows mould in the step 404/number conversion speed to reach four times of sample rate and performance does not have substantial reduction.
For improving the performance of telecommunication system 100, preferably adopt paired A/D converter 314 and two-port RAM 316 alternately to store odd number and even number burst information.For example, B0, B2, B4, the B6 burst information is stored in even number RAM, and B1, B3, B5, the B7 burst information is stored in odd number RAM.Such odd even configuration adds that the two DSP in the DSP circuit 306 provide performance relatively reliably for control unit 102.This point has more detailed description below.
In step 406, each independently burst information (be burst B
0-B
7In one) from the buffering memory 316 transfer to processor storage 308.At step 408 (shown in the empty frame of Fig. 4), 306 pairs of burst informations of sampling fully of DSP circuit carry out the symbol timing signal and recover.Each code element that is stored in a particular burst information of processor storage 308 is sampled four times by A/D converter 314.Symbol timing step 408 comprises step 410-418, determines which time in four samplings is sampled as optimum for all code elements of given burst information.
Step 410-414 is a cyclic process, successively each code element that is written into burst information is handled (except that first code element as following more detailed explanation).In step 410, to the signal of timing error of each generation in four sampled signals of selected code element.Because timing error calculates and depends on previous sampled signal, thereby first code element of each burst information is not carried out timing error calculating.Signal of timing error is preferably by following formula decision:
E
n=Y
I(r-2) [Y
I(r)-Y
I(r-4)]+Y
Q(r-2) [Y
Q(r)-Y
Q(r-4)] wherein n determines which of four sampled signals be current sampled signal be, on behalf of current sampled signal, Y (r) (comprise I, the Q orthogonal signalling), Y (r-2) represents the sampled signal of half code element back, the current sampled signal of the previous code element of Y (r-4) representative.Step 412 pair four signal of timing error add up.Step 414 judges whether all code elements have all been carried out the processing of signal of timing error.If be untreated code element in addition, then return step 410; Otherwise entering step 416 proceeds to handle.
In step 418, processor 306 determines in four timing errors and the signal maximum negative value of error and which which have the maximum difference of correcting errors is arranged; Based on these values, processor 306 is selected optimum sampled signal from four sampled signals during step 418, promptly select the sampled signal between two definite sampled signals of step 416.For example, if the sampled signal of n=2 has maximum negative definite time error (expression is significantly adjusted regularly) and n=4 sampled signal that maximum positive timing error (expression is significantly adjusted regularly) is arranged to the right left, it is optimum that 306 of processors are selected the sampled signal of n=3.
This selection course is carried out in mould 4 modes.For example, if the sampled signal of n=4 has maximum negative definite time error, and the sampled signal of n=2 has maximum positive timing error, and 306 sampled signals of selecting n=1 of processor are as optimum.In this kind mode, between 1 to No. 4 sampled signal, carry out wraparound and handle.Otherwise, except search the most just and the sample signal of the most negative error, and in these values, select outside the desired sample signal; Another scheme is simply to find out maximum negative definite time error signal, selects next high sampled signal as optimum in mould 4 modes then.Under the situation of high noise levels or low signal-to-noise ratio, this sample signal selection mode is optimum on statistics.
Consistent with principle of the present invention, owing to have only selecteed sampled signal to be used for symbol detection, the mode of selection optional sampling signal has alleviated the subsequent treatment burden of control unit 102 greatly.Thereby, though burst information comprises 480 compound sampled signals, have only wherein 120 to be used for symbol detection.In addition, preferred embodiment only requires that initial sampling carries out with four times of symbol-rate.Thereby, in the tdma system of routine, 8 one group (B
0-B
7) with the several burst informations that continue mutually of number time slot (as time slot 2) all from same access unit.Have only first of continuous burst information of time slot 2 in succession to need each code element to adopt sample four times, this is because can determine optimum sampling (for the signal from specific access unit) by first burst information.Therefore, the present invention has further alleviated the processing burden, has increased information throughput.
In case selected the optimum sampling signal in step 408, control unit 102 continues to handle the burst information after the sampling so that the code element in the burst information is detected and decodes.In step 420, processor 306 preferably uses the PI/4-DQPSK difference detector that the sampled signal of 120 selections is carried out Differential Detection.Use Differential Detection to offset phase error greatly, difference detector is information extraction from received signal, eliminates noise from signal significantly.Those of skill in the art will appreciate that input is ripe technically, under the prerequisite that does not break away from principle of the present invention and spirit, can implement various trace routines in the processing procedure of step 420.In case detect code element, processor 306 carries out being decoded for further processed by control unit 102 then synchronously to code element in step 422.
Should understand the aforesaid just explanation of the principle of the invention, under the prerequisite that does not break away from the scope of the invention and spirit, can make various modifications by those skilled in the art.For example, line telecommunications system shown in Figure 1 uses PSTN to link to each other with the local exchange telephone system, and also available other connected mode of this system directly links to each other with other line telecommunications system or remote service supplier.
Claims (10)
1. method of handling the burst in the telecommunication system, it is included in the decoding of the burst signals that transmits between access unit and control unit in the telecommunication system.The method includes the steps of:
Control unit receives burst signals at the predetermined time slot window, and the predetermined length of burst signals is less than the length of time slot window.Each burst signals comprises some code elements;
By burst signals is converted burst to digital signal with certain sampling rate sampling, each code element is with regard to the sampled signal representative of available predetermined number.
Digital signal is written into memory;
Each sampled signal for all code elements in the burst signals produces a signal of timing error;
Signal of timing error to each sampled signal adds up, thus be in the sampled signal of predetermined number each produce a timing error and;
Check timing error and, select the maximum positive and negative timing error of tool and sampled signal;
On the basis of checking step results, select the optional sampling signal;
By the optional sampling Signal Processing to each code element, detected symbol from burst signals.
2. in the method for claim 1, the time slot length of window is 120 code elements.
3. in the method for claim 2, the predetermined length of burst signals is 112 code elements.
4. in the method for claim 1, sampling rate is four times of symbol-rate.
5. in the method for claim 4, conversion of signals may further comprise the steps with being written into:
Make the digital signal of the burst signals of even number by mould/number conversion circuit generation even number with certain sampling rate;
Make the digital signal of the burst signals of odd number by mould/number conversion circuit generation odd number with certain sampling rate;
The odd number digital signal is written into the double-port random incoming memory;
The even number digital signal is written into the double-port random incoming memory;
6. in the claim 5, the generation of digital signal and to add up be to be carried out by first and second digital signal processors.The first digital signal processor processes odd number digital signal; And the second digital signal processor processes even number digital signal.
7. the method for handling burst signals in the telecommunication system comprises the timing of decision based on code element in the burst signals transmission between line access unit on the customer location of TDMA telecommunication system and the line control unit.Method comprises following steps:
Digital signal after the sampling is written into memory, and this sampled signal has the code element of predetermined number, and each code element is by the sampled signal representative of predetermined number;
Each sampled signal to the digital signal after the sampling produces a signal of timing error;
To the signal of timing error of each sampled signal produce a timing error and;
Estimate timing error and from the sampled signal of predetermined number, select the optimum sampling signal.
8. in the claim 7, the predetermined number of sampled signal is four.
9. in the claim 7, evaluation comprises the following steps:
Define the positive peak timing error and sampled signal;
Define the negative peak timing error and sampled signal;
Between the sampling letter that abovementioned steps is determined, select a sampled signal.
10. the device of handling burst signals in the telecommunication system comprises a control unit, and it is used for comprising that based on the telecommunication system of TDMA a plurality of access units are sent to control unit to burst information in predetermined time slot window.Each burst information has the code element of predetermined number.Control unit comprises:
The sampling receiving circuit is connected at least one access unit, is used to receive burst information;
Change-over circuit is connected in the sampling receiver, with predetermined sampling rate burst information is converted to sampled signal
Memory is connected in change-over circuit, the store sample signal;
The timing error testing circuit is to signal of timing error of all sampled signals generations of each burst information;
Summation circuit carries out the summation of correspondence to the signal of timing error of each burst;
Estimate circuit, handle timing error and, determine the optimum sampling signal of each burst information;
The symbol detection circuit is removed noise from burst information, extract wherein code element information.The symbol detection circuit is for each code element is carried out choosing of optional sampling signal.
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| Application Number | Priority Date | Filing Date | Title |
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| CN 96192624 CN1179251A (en) | 1996-01-17 | 1996-12-21 | Method and apparatus for processing burst signals in a telecommunication system |
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| US08/583,736 | 1996-01-17 | ||
| CN 96192624 CN1179251A (en) | 1996-01-17 | 1996-12-21 | Method and apparatus for processing burst signals in a telecommunication system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102045081A (en) * | 2009-10-14 | 2011-05-04 | 上海摩波彼克半导体有限公司 | Method for storing and optimizing sampling data of baseband receiving part in GSM (Global System for Mobile Communication) mobile communication terminal |
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1996
- 1996-12-21 CN CN 96192624 patent/CN1179251A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102045081A (en) * | 2009-10-14 | 2011-05-04 | 上海摩波彼克半导体有限公司 | Method for storing and optimizing sampling data of baseband receiving part in GSM (Global System for Mobile Communication) mobile communication terminal |
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