CN103391163B - A kind of CBTC data using distributed fountain codes send and method of reseptance and system - Google Patents
A kind of CBTC data using distributed fountain codes send and method of reseptance and system Download PDFInfo
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Abstract
The invention discloses a kind of CBTC car ground data transmission method using distributed fountain codes and system.This system includes the parts such as ground distributor cloth fountain codes coder, vehicle-carrying distribution fountain codes coder, after the data of CBTC control centre both can be encoded by ground distributor cloth fountain codes coder, it is transferred to optic_fiber intelligent skin, packet from optic_fiber intelligent skin can also be carried out virtual trunk and decode, the data reduced after decoding are transferred to CBTC control centre；The packet being received from vehicle-mounted dual-mode antenna both can be carried out virtual trunk and decode by vehicle-carrying distribution fountain codes coder, the data reduced after decoding are transferred to Vehicle Controller, after the data that Vehicle Controller transmits can also being encoded, sent by the vehicle-mounted dual-mode antenna of the headstock tailstock.The present invention can be used for the data transmission of car ground, and solution CBTC handover interrupts, utilization rate of equipment and installations is low, decode process needs the deficiency of at least one road partial data.
Description
Technical field
The present invention relates to data communication technology field, particularly relate to the distributed fountain of a kind of employing
The CBTC data of code send and method of reseptance and system.
Background technology
In modern railway transportation system, based on communication train control system
(Communication-Based Train Control, CBTC) becomes the car-ground communications field
The focus of research.CBTC can carry out two-way, even between the train run at high speed and ground
Continuous, large-capacity data transmission.
CBTC by Moving Block Technology in UMT shorten interval, improve train operational efficiency and
The motility of system.In CBTC system, Vehicle Controller (Vehicle Onboard
Controller, VOBC) carry out locomotive velocity measuring and location on one's own initiative, positional information is passed through nothing
Line channel is sent to trackside zone controller (Zone Controller, ZC).ZC is responsible for tracking
The all of train of circuit also calculates mobile authorization (Movement Authority, MA) for train,
The movable block forming train is interval (Moving B1ock), and prevents any other train from entering
Enter.Vehicle Controller controls the current state of train by receiving the MA order of ZC,
And guaranteeing in the case of any least favorable, train will not overshoot distance and target velocity.
As it is shown in figure 1, CBTC system mainly includes Vehicle Controller, zone controller, meter
Calculation machine interlocking (Computer Interlocking, CI), train automatic monitoring system
(Automatic Train Supervision, ATS), data storage cell (Database
Storage Unit, DSU) and data transmission system (Data Communication System,
DCS)。
Under wireless propagation environment, multipath fading, Doppler effect and due to sleety weather
Produced interference all will affect the electric field intensity of receiving terminal, bring error code, therefore, car-ground
Error protection in radio communication is most important.
In CBTC system, car-ground communication work is completed by data transmission system.Data pass
Communication system realizes the two-way information interaction between CBTC system ground installation and car ground equipment, is
The core of CBTC system.Data transmission system specifically includes that ground backbone network, wireless trackside connect
Access point, in-vehicle wireless device.
In order to solve the communication disruption caused due to handover, CBTC data communication system makes
With a whole set of redundancy structure, independent parallel works.Increase the system structure such as Fig. 2 after redundancy
Shown in, wherein AP11 and AP12 is installed on the same position that track is other, AP21 and AP22
Being installed on the same position that track is other, two antennas corresponding for AP on same position are respectively
Towards two different directions, respectively with front and back two last vehicle of train and the wireless device association of head,
Two AP forward identical communication message, AP11 and AP21 data are by the first exchange
Machine and the first optic_fiber intelligent skin connect, AP12 and AP22 data pass through the second switch and second
Optic_fiber intelligent skin connects, as long as the control equipment on ground control centre or train receives
Any one AP sends the complete message of coming, and can be achieved with transmitting normally.
By using redundancy structure can improve the reliability of CBTC system, but redundancy structure
Cause high buying and operation cost.This method there is also limitation simultaneously, when single
When network transmission goes wrong, redundancy structure is used to can ensure that CBTC system can be used；But
When two network transmission go wrong simultaneously, the CBTC system using redundancy structure is same
Unavailable.
The concept of digital fountain code is proposed in 1998 by Luby the earliest, so-called digital fountain
The concept of code refers to regard a fountain, nothing as by constantly encoding the process sending code word
Poor endless ground outwards water spray drips.Receiving terminal is then similar to the water tumbler of a water receiving.Due to each code word
Independent random, every block codewords all comprises information source information, and receiving terminal is not relevant for receiving
Be " where dripping ".So through erasure channel, deleting the arbitrary portion of coding information,
Do not interfere with other symbolic information and participate in decoding.Fountain codes is initially erasure channel and designs.
Along with deepening continuously of fountain codes theoretical research, find that fountain codes almost can be at various channels
The communication performance of lower lifting system.
Luby proposed the fountain codes LT code that the first is the most feasible in 2002.Its
After, in order to solve the shortcomings such as LT code decoding space-time is fixing, Shokrollahi et al. is at LT
Code coding/decoding time aspect has done further improvement, and improved novel fountain codes is named
For Raptor code, it is achieved that the coding and decoding performance of near ideal.
Ahlswede of Hong Kong Chinese University et al. proposed network code first in 2000
(Network Coding, NC) this concept.The via node of network code is applied not only to
Route relaying, carries out coded combination to the information from different links simultaneously, thus improves biography
Defeated efficiency.Network code can be effectively increased network throughput and improve network performance, but
Because there is no strong encoding mechanism, cause decoding under normal circumstances extremely difficult.And spray
Spring code is because having the existence of its degree distribution, so decoding complexity ratio is relatively low.Network code and
Fountain codes is all stochastic linear code, substantially communicates at mathematics.Wherein network code exists
Packet is asked for linearly combining by via node, fountain codes in an encoding process, by letter
Source symbol asks for XOR to obtain coded identification.Network code and fountain codes are blended permissible
Increase effective code length of fountain codes, thus improve the transmission performance of coding.It is possible not only to greatly
Increase network throughput, also make the computation complexity of decoding end be substantially reduced simultaneously.
Distributed fountain codes mainly has a following two realization approach:
1, Puducheri et al. propose distributed LT code (Distributed LT codes,
DLT).It is the evolution to LT code, many sub-coded combinations form.DLT code is to LT
Code decomposes, and carries out encoding and carrying out different to these coded identifications by multiple information source node
Or operate and reach.The system structure of DLT code includes multiple information source node, secondary saltus step, list
Individual destination node.This method can be that decoding end provides satisfied healthy and strong orphan's degree distribution
The coded identification sequence of (Robust Soliton Distribution, RSD) (adopt by information source
Being distributed with degree of deconvoluting, via node has selection XOR).The shortcoming of this method is this
Method, for the change of the number of signal sources and sensitivity thereof, once has information source node add or exit whole
Individual system, in system, the cataloged procedure of all information source node all must be revised therewith.Additionally,
DLT algorithm is not particularly suited for a fairly large number of situation of information source node, and all of information source node
All must know in system have how many information source node in real time actually.
2, the soliton-like that Andrew et al. proposed in 2011 is without rate code (Soliton-Like
Rateless Coding, SLRC).Fountain codes can preferably be encoded by it with Y-type network
Combine.The advantage of SLRC is that it can tolerate that transmission network is left in the midway of information source node,
Or have information source node midway to add transmission network.In SLRC, each information source node all uses standard
Healthy and strong orphan's degree distribution encodes, and each information source node requires no knowledge about remaining information source node
State.The decoding overheads of SLRC reduces 5% than DLT code.
By the calibration technologies such as fountain codes technology and CRC or FEC erasure techniques are combined,
So that wireless channel is converted to erasure channel.Simultaneously because after fountain codes encodes,
Receiving terminal have only to the correct coding symbol quantity that receives than legacy data symbol quantity relatively
Can be carried out decoding more, the order of the coded identification that decoding process receives without consideration,
Without automatic request for repetition and the reliable of data be can ensure that for corrupted or lost data symbol
Property.Therefore technical characterstic based on fountain codes, uses it for data transmission between car ground and can enter
One step promotes the performance of CBTC system.
Summary of the invention
The technical problem to be solved in the present invention is: how to solve existing CBTC handover interrupt,
Need that utilization rate of equipment and installations in redundant system, CBTC data transmission system is low, decoding process needs
The deficiency of at least one road partial data.
In order to solve prior art problem, the embodiment of the invention discloses a kind of employing distributed
The car-ground data of CBTC of fountain codes send and the system of reception, including CBTC control centre, core
Heart switch, ground distributor cloth fountain codes coder, ground distributor cloth fountain codes coding and decoding
Device, the first optic_fiber intelligent skin, the second optic_fiber intelligent skin, the first switch, the second switch,
Forward direction trackside dual-mode antenna, backward trackside dual-mode antenna, headstock dual-mode antenna, the tailstock are received and dispatched
Antenna, vehicle-carrying distribution fountain codes coder and Vehicle Controller, CBTC control centre leads to
Cross core switch and ground distributor cloth fountain codes coder one end connects, ground distributor cloth
The fountain codes coder other end connects the first optic_fiber intelligent skin and the second optic_fiber intelligent skin one
End, the first optic_fiber intelligent skin other end by the first switch with after communicate with headstock
Connecting to trackside dual-mode antenna, the second optic_fiber intelligent skin other end passes through the second switch and use
It is connected in the forward direction trackside dual-mode antenna communicated with the tailstock, ground distributor cloth fountain codes coding and decoding
Device both can will carry out void from the packet of the first optic_fiber intelligent skin, the second optic_fiber intelligent skin
Intend relaying and decode, the data reduced after decoding are transferred to CBTC control centre, it is also possible to
After the data of CBTC control centre are encoded, be transferred to the first optic_fiber intelligent skin, second
Optic_fiber intelligent skin；Vehicle-carrying distribution fountain codes coder is positioned on train, vehicle-carrying distribution
Fountain codes coder one end and headstock dual-mode antenna, tailstock dual-mode antenna connect, vehicle-mounted point
The cloth fountain codes coder other end and Vehicle Controller connect, vehicle-carrying distribution fountain codes
Coder both can by being received from headstock dual-mode antenna, the packet of tailstock dual-mode antenna enters
Row virtual trunk also decodes, and the data reduced after decoding are transferred to Vehicle Controller, it is possible to
After encoding with the data that Vehicle Controller is transmitted, by headstock dual-mode antenna, the tailstock
Dual-mode antenna sends.
The embodiment of the invention also discloses a kind of car-ground number of CBTC using distributed fountain codes
According to transmission method.Data side is sent to Vehicle Controller including a kind of ground control centre
Method, comprises the following steps:
The information being defeated by approach train to be passed is carried out subpackage packing and obtains data by control centre
Bag, sends data packets to be positioned at the ground distributor cloth fountain codes coder of control centre；
The fountain codes encoder in the ground distributor cloth fountain codes coder data to receiving
Bag carries out fountain codes coding, and the packet after packet is considered the source symbol of fountain codes coding,
Fountain codes encoder produces the coded identification data coming from same source character subset continually
Bag；
Error correction in ground distributor cloth fountain codes coder or entangle and delete coder with packet
For unit, the coded identification data bag coming from same source assemble of symbol is encoded, concurrently
Send coded identification data bag to trackside positioning transceiving antenna, sent to train by wireless channel
Vehicle Controller；
If control centre receives the feedback letter that the data message that Vehicle Controller sends receives
Number then carry out sending or waiting new task instruction of next data information；If not receiving anti-
Coded identification data bag after feedback signal then continues error correction or erasure code transmits continually
To trackside positioning transceiving antenna, until data are sent.
The embodiment of the invention also discloses a kind of Vehicle Controller and receive ground control centre data
Method, comprise the following steps:
The dual-mode antenna at train two ends receives the data from trackside positioning transceiving antenna respectively,
Data membership received by the reception antenna at train two ends is in same source symbol set not
With coded identification subset, the most both can overlap, it is also possible to separate, two volumes
Code sign subset sum must be complete or collected works；
The coded identification data bag received is transferred to ground distributor by the dual-mode antenna at train two ends
The error correction of cloth fountain codes coder or entangle and delete decoder, error correction or entangle and delete decoder docking
The packet received carries out completeness check, carries out error correction and is maybe entered by the packet comprising mistake
Row is deleted, and sends accurate packet to virtual trunk nodes encoding device；
Virtual trunk nodes encoding device uses the via node defined in distributed fountain codes to calculate
The data received directly are forwarded by method selectively, or by two paths of data XOR
It is forwarded to after process in caching；
The vehicle-carrying distribution fountain codes coder fountain codes coded data to storing in the buffer
Bag decodes, if the coded data packet quantity in Huan Cun is slightly larger than the data of former subpackage packing
Former data message just can be reduced by bag quantity with decoding success, the data letter after reduction
Breath transmission is to Vehicle Controller；If negligible amounts in Huan Cun, continue to coded data packet,
And the packet received from each antenna does not differentiates between order, do not mind the packet loss of transmitting procedure；
Vehicle Controller, after receiving data message, sends confirmation signal and receives to trackside orientation
Send out antenna, represent that this task completes；Otherwise, this confirmation signal is not sent.
The embodiment of the invention also discloses a kind of Vehicle Controller control centre earthward and send number
According to method, comprise the following steps:
The information being defeated by control centre to be passed is carried out subpackage packing and obtains data by Vehicle Controller
Bag, sends data packets to the vehicle-carrying distribution fountain codes coder being positioned on train；
The fountain codes encoder in the vehicle-carrying distribution fountain codes coder data to receiving
Bag carries out fountain codes coding, and the packet after packet is considered the source symbol of fountain codes coding,
Fountain codes encoder produces the coded identification data coming from same source character subset continually
Bag；
In vehicle-carrying distribution fountain codes coder, error correction or erasure code device are with packet as list
The coded identification data bag coming from same source assemble of symbol is encoded by position, passes through headstock
Coded identification data bag after error correction or erasure code is transmitted by the tailstock two antennas continually
To trackside positioning transceiving antenna, sent to control with optic_fiber intelligent skin by each layer switch
The heart；
If Vehicle Controller receives the feedback letter that the data message that control centre sends receives
Number then carry out sending or waiting new task instruction of next data information；If not receiving anti-
Feedback signal then continues through two dual-mode antennas of the headstock tailstock by the volume after error correction or erasure code
Code sign packet transmits continually to trackside positioning transceiving antenna, continues transmission and is not fully complete
Data message.
The embodiment of the invention also discloses a kind of ground control centre and receive Vehicle Controller data
Method, comprise the following steps:
Trackside positioning transceiving antenna receives the data transmitted from train, trackside positioning transceiving sky
Data membership received by line in the different coding character subset of same source symbol set,
The most both can overlap, it is also possible to separate, two coded identification subset sums must
Must be complete or collected works；
The coded identification data bag received is transferred to each layer switch by optic_fiber intelligent skin
The error correction of ground distributor cloth fountain codes coder or entangle and delete decoder, error correction or entangle and delete decoding
The device packet to receiving carries out error checking and correction, and error correction maybe will comprise the data symbol of mistake
Delete, accurate packet is sent to virtual trunk nodes encoding device；
Virtual trunk nodes encoding device uses the via node defined in distributed fountain codes to calculate
The data received directly are forwarded by method selectively, or by two paths of data XOR
It is forwarded to after process in caching；
The ground distributor cloth fountain codes coder fountain codes coded data to storing in the buffer
Bag decodes, if the coded data packet quantity in Huan Cun is slightly larger than the data of former subpackage packing
Former data message just can be reduced by bag quantity with decoding success, the data letter after reduction
Breath transmission is to control centre；If negligible amounts in Huan Cun, continue to coded data packet, and
The packet received from each antenna does not differentiates between order, does not minds the packet loss of transmitting procedure；
Control centre, after receiving data message, sends confirmation signal to approach train, table
Show that this task completes；Otherwise, this confirmation signal is not sent.
Use the having the beneficial effect that of the car-ground data transmission method of CBTC of distributed fountain codes
1) the distributed car-ground data of fountain codes CBTC are used to transmit, control centre and vehicle-mounted control
Device processed can carry out unified decoded operation to the information from different transmission networks.At two sets
Data that transmission network obtains and imperfect time, if the part that two set transmission networks receive
Data can cover whole source symbol, and decoder still can work as usual.With needs extremely
The redundancy structure CBTC system of a few road partial data is compared, and improves availability.
2) using distributed fountain codes, CBTC data transmission system car-ground communicated whole
Without being equipped with redundance unit in journey, so that it may eliminate interruption and time delay that handover procedure causes,
Eliminate sham cut and change the possibility causing communication disruption.
3) using distributed fountain codes, CBTC system can save stand-by equipment, reduces system
Cost.
4) by distributed fountain codes and error correction, entangle and delete coder and be combined, can be by any nothing
Line channel is converted to erasure channel.The impact of data can be led to by decline with Doppler frequency shift
Cross probability of erasure to change.The car-ground data transfer of CBTC becomes under binary erasure channel
Fountain codes coding and decoding process, bit error rate can be made to be reduced to, and fountain codes can reach 10-6
To 10-8The order of magnitude.
Accompanying drawing explanation
When considered in conjunction with the accompanying drawings, by referring to detailed description below, it is possible to more completely more
Understand well the present invention and easily learn the advantage that many of which is adjoint, but described herein
Accompanying drawing be used for providing a further understanding of the present invention, constitute the part of the present invention, this
The schematic description and description of invention is used for explaining the present invention, is not intended that the present invention
Improper restriction, wherein:
Fig. 1 is for the structure chart of CBTC in prior art.
Fig. 2 is the CBTC data transmission system schematic diagram for using redundancy structure in prior art.
Fig. 3 is CBTC handover schematic diagram.
Fig. 4 is that the CBTC data transmission system using distributed fountain codes in detailed description of the invention is illustrated
Figure.
Fig. 5 is distributed fountain coder workflow in detailed description of the invention.
Fig. 6 is distributed fountain decoder workflow in detailed description of the invention.
Fig. 7 is that the CBTC data transmission system using distributed fountain codes in detailed description of the invention works
Flow process.
Fig. 8 is the network topology model in the specific embodiment of the invention.
Fig. 9 is the CBTC data transmission system using distributed fountain codes in the specific embodiment of the invention
System transmission performance analogous diagram.
Figure 10 is CBTC data communication system handover schematic diagram.
Figure 11 is CBTC data communication system transmission under switching in the specific embodiment of the invention
Performance simulation figure.
Detailed description of the invention
Illustrate with reference to-11 pairs of embodiments of the invention of Fig. 1.
Understandable, below in conjunction with the accompanying drawings for enabling above-mentioned purpose, feature and advantage to become apparent from
The present invention is further detailed explanation with detailed description of the invention.
Fig. 3 is the schematic diagram of CBTC handover.Figure includes three community Z1、Z2、Z3。
Using traditional approach, train by this section, is positioned at the antenna of headstock and the tailstock from bottom to top
Respectively carry out twice handover.Every time switching is required for carrying out turning of main equipment and stand-by equipment
Change, totally four times.Using the distributed car-ground data of fountain codes CBTC to transmit, train need not
It is equipped with the interruption that two complete equipments cause with reply handover.
Train travels from bottom to top, the method using the present invention, experiences following process:
1) train driving is at community Z1, it is positioned at headstock and communicates with BS1 with the antenna of the tailstock.This
Time, transmission network is Y-type network.
2) at community Z1、Z2Between Zone switched in, headstock antenna receive from BS1
Signal with BS2.Along with train travels from bottom to top, from the signal of BS1 by path
The impact of decline gradually dies down, and the signal from BS2 gradually becomes strong.First train head enters
Row handover.Meanwhile, tailstock antenna is still in community Z1In, and protect with BS1
Keep steady and determine transmission.Transmission network is deteriorated to point to point network by Y-type network.
3) the train tailstock sails community Z into1、Z2Between Zone switched in, need to carry out more district and cut
When changing, headstock antenna completes handover work, and sets up stable communication biography with BS2
Defeated.
4) antenna of the tailstock completes handover, and transmission network is become again Y type by point to point network
Network.
5) train sails community Z into2, process afterwards repeats above step, repeats no more.
Use the car-ground data transmission system of CBTC of distributed fountain codes in handover only
Experience transport network topology structure change procedure, will not produce interruption.
Fig. 4 is the system schematic of the present invention, wherein at CBTC control centre 100 and train
Vehicle-mounted part 200 be each provided with a set of have entangle delete function ground distributor cloth fountain codes compile
Decoder 3 and vehicle-carrying distribution fountain codes coder 14, fountain codes compiling in this embodiment
The front end of code device is entangled and is deleted coder and be illustrated as a example by CRC.The vehicle-mounted part of train is joined
A standby vehicle-carrying distribution fountain codes coder 14.Vehicle-carrying distribution fountain codes coder
14 are connected with headstock dual-mode antenna 12 and tailstock dual-mode antenna 13.Vehicle-carrying distribution fountain codes
Coder 14 both can will be received from positioning transceiving antenna headstock dual-mode antenna 12 and orientation
The packet of dual-mode antenna tailstock dual-mode antenna 13 carries out virtual trunk and decodes, after decoding
The data of reduction are transferred to Vehicle Controller 15, it is also possible to the number transmitted by Vehicle Controller 15
After encoding, sent by headstock dual-mode antenna 12 and tailstock dual-mode antenna 13.
It is equipped with a ground connecting the control centre 1 core switch 2 front end with backbone network
Distributed fountain codes coder 3.Ground distributor cloth fountain codes coder 3 and the first optical fiber
Backbone network 4 is connected with the second optic_fiber intelligent skin 5.Ground distributor cloth fountain codes coder 3
Both can will carry out from the packet of the first optic_fiber intelligent skin 4 and the second optic_fiber intelligent skin 5
Virtual trunk also decodes, and the data reduced after decoding are transferred to control centre 1, it is also possible to will
After the data of control centre 1 encode, it is transferred to the first optic_fiber intelligent skin 4 and the second light
Fine backbone network 5.
In the present embodiment, ground distributor cloth fountain codes coder 3 and vehicle-carrying distribution fountain
CODEC 14 structure is identical.Fig. 5, Fig. 6 give in the embodiment of the present invention and adopt
The workflow of distributed fountain codes coder.Distributed fountain codes coder
Coding and decoding function are realized by the algorithm that two sets are independent.This patent combines coding and decoding
These two functions are described in detail by process.
As it is shown in figure 5, in cataloged procedure, distributed fountain codes encoder obtains letter from front end
Source data (S31).The form of information source number packet according to this inputs distributed fountain codes encoder.
If information source data are not packed by subpackage, information source data will be carried out by distributed fountain codes encoder
Packet, obtains information source packet (S32).In encoder, CRC encoder is with packet as list
Position carries out encoding (S33), sends to fountain codes encoder and carry out fountain codes coding after CRC coding
(S34), so far the cataloged procedure of fountain codes has i.e. been accused.
As shown in Figure 6, during decoding, distributed fountain codes decoder is first to reception
To each circuit-switched data bag carry out CRC check (S41) respectively.Only accorded with by the coding of verification
Number just can send to virtual trunk nodes encoding device, otherwise, be deleted (S42).Empty
Intend via node encoder and use the via node algorithm of SLRC, selectively to coded identification
Carry out forwarding or XOR summation process (S43).After being re-encoded by virtual trunk nodes encoding device
Packet be delivered to the buffer area of fountain codes decoder, fountain codes decoder is receiving
Start after sufficient amount of coded identification to decode (S44), restore initial data (S45).
Fig. 7 gives the workflow of the CBTC data transmission system using distributed fountain codes
Journey.Fig. 7 both can be used to describe CBTC control centre and sends the mistake of data to Vehicle Controller
Journey, it is also possible to be used for describing Vehicle Controller and send the process of data to CBTC control centre.
According to Fig. 7, first send the angle of data to Vehicle Controller with CBTC control centre,
The running of whole system is illustrated:
1, in the heart the information being defeated by approach train to be passed is carried out subpackage packing in the controlling,
In this embodiment, former data are distributed into 12 packets and send to the ground being positioned at control centre
EDS maps formula fountain codes coder (S51).
2, fountain codes coder in ground distributor cloth fountain codes coder is to receiving
Packet carries out LT coding, and the packet after packet is considered the source symbol of fountain codes coding.
In the present embodiment, after 12 source symbol codings, obtain 16 coded identifications data bag (S52).
3, in ground distributor cloth fountain codes coder, CRC coder is carried out in units of bag
Coding (can encode in units of multiple packets in implementation process), CRC encodes
After, data packet number is still 16.After CRC is encoded by distributed fountain codes coder
Packet is transferred to two unjacketed optical fiber backbone networks (S53).
4, the coded identification data bag transmission after CRC is encoded by optic_fiber intelligent skin is to two set tracksides
Positioning transceiving antenna (S54).In the T moment, train is passed through trackside positioning transceiving antenna, position
Dual-mode antenna in train two ends receives coded identification data bag X respectively1With X2(S55).
As it is shown in fig. 7, Vehicle Controller receives the data that CBTC control centre sends, whole
The running of system is described below:
1, the positioning transceiving antenna at train two ends is by coded identification data bag X1With X2It is transferred to car
Carry the CRC coder of distributed fountain codes coder.CRC coder is to receiving
Packet carries out CRC check, deletes, the data symbol comprising mistake by accurate
Packet sends to virtual trunk nodes encoding device (S61).
2, virtual trunk nodes encoding device according to following rule to coded identification data bag X1With X2
Carry out virtual trunk (wherein the numerical value of λ is set) (S62):
A) according to being uniformly distributed generating random variable U on (0,1).If
(deg[X1]=1 ∨ 2) ∧ (deg [X2]=1 ∨ 2) and U≤λ, retain X the most at random1Or X2In one, another
Individual abandon.
If b) deg [X1]=1 ∨ deg [X1]=2 and U≤λ, then directly by X1Forward, Y=X1。
If c) deg [X2]=1 ∨ deg [X2]=2 and U≤λ, then directly by X2Forward, Y=X2。
If d) conditions above is all unsatisfactory for,
Y is the re-encoding symbol data bag obtained after virtual trunk.Virtual trunk can be by soft
Part realizes.
3, the re-encoding symbol Y quilt that the T moment is obtained by vehicle-carrying distribution fountain codes coder
Store in caching (S63), now, add 15 packets stored before, in caching
Preserve 16 packets, possess the condition of decoding success.Carry out LT decoding (S64),
These 16 packets are together carried out fountain codes decoding and restore former data (S65) by decoder.
4, the data obtained after reduction are sent to vehicle-mounted by vehicle-carrying distribution fountain codes coder
Controller.
5, the message that Vehicle Controller transmission confirmation current data is sent is to control centre,
Inform that current task completes, be ready for the transmission of next round data or to carry out other regulation dynamic
Make.Current task terminates.
Below according to Fig. 7, with Vehicle Controller to the angle of CBTC control centre transmission information,
The running of whole system is illustrated:
According to Fig. 7, first send the angle of data to CBTC control centre with Vehicle Controller,
The running of whole system is illustrated:
1, Vehicle Controller carries out testing the speed and positioning of train on one's own initiative, the position letter that will obtain
Breath carries out subpackage packing, and in this embodiment, former data are distributed into 12 packets and send
To vehicle-carrying distribution fountain codes coder (S51).
2, fountain codes coder in vehicle-carrying distribution fountain codes coder is to receiving
Packet carries out LT coding, and the packet after packet is considered the source symbol of fountain codes coding.
In the present embodiment, after 12 source symbol codings, obtain 16 coded identifications data bag (S52).
3, in vehicle-carrying distribution fountain codes coder, CRC coder is carried out in units of bag
Coding (can encode in units of multiple packets in implementation process), CRC encodes
After, data packet number is still 16.After CRC is encoded by distributed fountain codes coder
Packet is transferred to the dual-mode antenna (S53) at train two ends.
4, the coded identification data bag after CRC is encoded by the dual-mode antenna at train two ends transmits extremely
Two sets trackside positioning transceiving antenna (S54).In the T moment, train is passed through trackside positioning transceiving
Antenna, the trackside positioning transceiving antenna near train two ends is respectively received coded identification data
Bag X1With X2(S55).
As it is shown in fig. 7, CBTC control centre receives the data that Vehicle Controller sends, whole
The running of system is described below:
1, trackside positioning transceiving antenna is by coded identification data bag X1With X2By switches at different levels
And optic_fiber intelligent skin is transferred to the CRC coder of ground distributor cloth fountain codes coder.
The CRC coder packet to receiving carries out CRC check, will comprise the data symbols of mistake
Number delete, accurate packet is sent to virtual trunk nodes encoding device
(S61).
2, virtual trunk nodes encoding device according to following rule to coded identification data bag X1With X2
Carry out virtual trunk (wherein the numerical value of λ is set) (S62):
A) according to being uniformly distributed generating random variable U on (0,1).If
(deg[X1]=1 ∨ 2) ∧ (deg [X2]=1 ∨ 2) and U≤λ, retain X the most at random1Or X2In one, another
Individual abandon.
If b) deg [X1]=1 ∨ deg [X1]=2 and U≤λ, then directly by X1Forward, Y=X1。
If c) deg [X2]=1 ∨ deg [X2]=2 and U≤λ, then directly by X2Forward, Y=X2。
If d) conditions above is all unsatisfactory for,
Y is the re-encoding symbol data bag obtained after virtual trunk.Virtual trunk can be by soft
Part realizes.
3, the re-encoding symbol Y that the T moment is obtained by distributed fountain codes coder is stored
In caching (S63), now, add 15 packets stored before, in caching
Preserve 16 packets, possess the condition of decoding success.Carry out LT decoding (S64),
These 16 packets are together carried out fountain codes decoding and restore former data (S65) by decoder.
4, the data obtained after reduction are sent to control by ground distributor cloth fountain codes coder
Center.
5, the message that control centre's transmission confirmation current data is sent is to train, informs and works as
Front task completes, and is ready for the transmission of next round data or carries out other compulsory exercise.When
Front task terminates.
Fig. 8 gives the network topology model of the embodiment of the present invention.The embodiment of the present invention is by base
Emulate in this model.Topological model includes two information source node S1、S2, information source saves
Point transmits the data of equal length, two information source node by via node N to destination node T
In coded data set be the subset of total data.Via node only connects in single time slot
Receive the single encoded symbol from each information source node.The data received are carried out by via node
Limited process, and it is transmitted to destination node.For such a Y-type network, Ke Yitong
Cross following two mode data are transmitted:
1, two information source node S1、S2Use different LT codes, independently at its data subsetIn respective information is encoded, generate coded identificationVia node uses time-multiplexed mode, forwards at odd-times time slot
From S1Data, forward from S at even-times time slot2Data.
2, two information source node S1、S2Use different LT codes, independently at its data subsetIn respective information is encoded, generate coded identificationVia node is to being received from node S1、S2Symbol re-encode, raw
Become coded identification { Yr: t=0 ... 0, N-1} and be transferred to destination node.
First kind of way is parallel decoding scheme, and system transfers is inefficient.Use existing
Redundancy structure CBTC data transmission system directly use fountain codes be equivalent to have employed parallel
Decoding scheme.The second way have employed fountain codes and network coding technique, at via node
Process data further to improve system effectiveness.
Fig. 9 is that the CBTC data transmission system transmission performance using distributed fountain codes emulates.
Emulation is carried out in the network shown in a Fig. 8.Whole system to transmit 2000 information source symbols
Number.When using DLT code, cataloged procedure uses degree of deconvoluting distribution, when using SLRC code,
Employing parameter is Ωrs(1000,0.03,0.5) healthy and strong orphan's degree distribution.Impact and sky due to channel
Between the difference of position, in the most extreme case, the data that two reception antennas receive are divided
Not covering the 50% of total data, under traditional transmission means, two antennas all fail
Receive total data meaning bust this.This extreme case is by two separate letters
Source node emulates, and the coded identification of two information source node transmissions is all by diverse 1000
Source symbol coding obtains.Via node is respectively adopted the via node of DLT code and SLRC code
Algorithm relays.Re-encoding data transmission after relaying decodes to destination node.Imitative
Really rerun 2000 times.
By simulation result it can be seen that headstock and tailstock antenna receive full detail respectively
50%, use the distributed fountain codes still can be successfully decoded.And use distributed fountain codes
Time the performance of transmission performance redundancy structure to be substantially better than parallel decoding scheme.To fountain codes
Use parallel decoding, between two set LT codes, there is no interference.Distributed fountain codes then can make
Must be at receiving terminal, coded identification all comes from one and same coding process, can give play to spray
Spring code code length is the longest, the advantage that performance is more excellent.Distributed fountain codes is used to have only to redundancy knot
Under structure parallel decoding scheme, the decoding overheads of 2/3rds just can reach identical performance (mistake
Bit rate is 10-6The order of magnitude).
Figure 10 gives the system structure that CBTC data communication system occurs relaying switching.?
In the case of this, an antenna is owing to switching over operation, it is impossible to normally work.Use distribution
The CBTC data transmission system of formula fountain codes is transformed to unicast form.
Figure 11 gives CBTC data communication system to be occurred, when relaying switches, using distributed
The transmission performance of fountain codes.In order to tackle handover case, the distributed spray of application claims
Spring code must have good toleration to the unexpected off-line of information source node.This extremely
In the case of carry out the performance comparison of two kinds of distributed fountain codes.Comparing result shows, DLT code exists
CBTC data communication system occurs during relaying switching unavailable.And SLRC code is to information source node
Off-line has good toleration, uses the distributed fountain codes decoding process of SLRC code only to need
Receive be equivalent to the data of information source length 1.5 times just can be with 100% decoding success.
Although the foregoing describe the detailed description of the invention of the present invention, but those skilled in the art
Member should be appreciated that these detailed description of the invention are merely illustrative of, those skilled in the art
In the case of without departing from the principle of the present invention and essence, can be to said method and system
Details carries out various omissions, substitutions and changes.Such as, merge said method step, thus
Substantially identical function is performed to realize substantially identical result then according to substantially identical method
Belong to the scope of the present invention.Therefore, the scope of the present invention is only limited by the claims that follow.
Claims (5)
1. the car-ground data of CBTC using distributed fountain codes send and the system of reception, and it is special
Levy and be: include CBTC control centre, core switch, the compiling of ground distributor cloth fountain codes
Code device, the first optic_fiber intelligent skin, the second optic_fiber intelligent skin, the first switch, the second exchange
Machine, forward direction trackside dual-mode antenna, backward trackside dual-mode antenna, headstock dual-mode antenna, the tailstock
Dual-mode antenna, vehicle-carrying distribution fountain codes coder and Vehicle Controller, during CBTC controls
The heart is connected by core switch and ground distributor cloth fountain codes coder one end, ground distributor
The cloth fountain codes coder other end connects the first optic_fiber intelligent skin and the second optic_fiber intelligent skin
One end, the first optic_fiber intelligent skin other end by the first switch with for communicating with headstock
Backward trackside dual-mode antenna connects, the second optic_fiber intelligent skin other end by the second switch and
Forward direction trackside dual-mode antenna for communicating with the tailstock is connected, and ground distributor cloth fountain codes compiles
Code device both can will be carried out from the packet of the first optic_fiber intelligent skin, the second optic_fiber intelligent skin
Virtual trunk also decodes, and the data reduced after decoding are transferred to CBTC control centre, it is possible to
After encoding with the data by CBTC control centre, be transferred to the first optic_fiber intelligent skin,
Two optic_fiber intelligent skin；Vehicle-carrying distribution fountain codes coder is positioned on train, vehicle-mounted distribution
Formula fountain codes coder one end and headstock dual-mode antenna, tailstock dual-mode antenna connect, vehicle-mounted
The distributed fountain codes coder other end and Vehicle Controller connect, vehicle-carrying distribution fountain
CODEC both can will be received from headstock dual-mode antenna, the packet of tailstock dual-mode antenna
Carry out virtual trunk and decode, the data reduced after decoding are transferred to Vehicle Controller, also
After the data that Vehicle Controller transmits can being encoded, by headstock dual-mode antenna and car
Tail dual-mode antenna sends.
2. the car-ground data of CBTC based on the distributed fountain codes of employing described in claim 1
Send the method that the ground control centre with the system of reception sends data to Vehicle Controller, its
It is characterised by: comprise the following steps:
Control centre, by the information subpackage packing being defeated by approach train to be passed, obtains packet, by number
Send to the ground distributor cloth fountain codes coder being positioned at control centre according to bag；
The packet received is entered by the fountain codes encoder in ground distributor cloth fountain codes coder
Row fountain codes encodes, and the packet after packet is considered the source symbol of fountain codes coding, spray
Spring code coder produces coded identification data bag continually；
Error correction in ground distributor cloth fountain codes coder or entangle and delete coder with packet as list
Coded identification data bag is encoded by position, and sends coding symbol number according to bag to trackside orientation
Dual-mode antenna, sends the Vehicle Controller to train by wireless channel；
If control centre receives the feedback signal that the data message that Vehicle Controller sends receives,
Then carry out sending or waiting new task instruction of next data information；If not receiving feedback
Signal, then the coded identification data bag after continuing error correction or erasure code transmits continually
To trackside positioning transceiving antenna, until data are sent.
3. the car-ground data of CBTC based on the distributed fountain codes of employing described in claim 1
Sending the method that the Vehicle Controller with the system of reception receives ground control centre data, it is special
Levy and be: comprise the following steps:
The dual-mode antenna at train two ends receives the data from trackside positioning transceiving antenna, train respectively
Data membership received by the dual-mode antenna at two ends is in the different volumes of same source symbol set
Code sign subset, the most both can overlap, it is also possible to separate, two coding symbols
Work song collection sum must be complete or collected works；
The coded identification data bag received is transferred to vehicle-carrying distribution by the dual-mode antenna at train two ends
The error correction of fountain codes coder or entangle and delete decoder, error correction or entangle and delete decoder to receiving
Packet carry out completeness check, carry out error correction and maybe the packet comprising mistake deleted
Remove, accurate packet is sent to virtual trunk nodes encoding device；
Virtual trunk nodes encoding device uses the via node algorithm defined in distributed fountain codes, has
Selectively the data received directly are forwarded, or by after the process of two paths of data XOR
It is forwarded in caching；
The fountain codes coded data packet stored in the buffer is entered by vehicle-carrying distribution fountain codes coder
Row decoding, if the coded data packet quantity in Huan Cun is slightly larger than the number-of-packet of former subpackage packing
Former data message just can be reduced by amount with decoding success, and the data message after reduction passes
Transport to Vehicle Controller；If negligible amounts in Huan Cun, continue to coded data packet, and from
The packet that each antenna receives does not differentiates between order, does not minds the packet loss of transmitting procedure；
Vehicle Controller, after receiving data message, sends confirmation signal to trackside positioning transceiving sky
Line, represents that this task completes；Otherwise, this confirmation signal is not sent.
4. the car-ground data of CBTC based on the distributed fountain codes of employing described in claim 1
Send the method that the Vehicle Controller control centre earthward with the system of reception sends data, its
It is characterised by: comprise the following steps:
The information being defeated by control centre to be passed is carried out subpackage packing and obtains packet by Vehicle Controller,
Send data packets to the vehicle-carrying distribution fountain codes coder being positioned on train；
The packet received is entered by the fountain codes encoder in vehicle-carrying distribution fountain codes coder
Row fountain codes encodes, and the packet after packet is considered the source symbol of fountain codes coding, spray
Spring code coder produces coded identification data bag continually；
In vehicle-carrying distribution fountain codes coder, error correction or erasure code device are right in units of packet
Coded identification data bag encodes, and error correction or entangle is deleted by headstock, tailstock dual-mode antenna
Coded identification data bag after coding transmits continually to trackside positioning transceiving antenna, then leads to
Cross each layer switch to send to control centre with optic_fiber intelligent skin；
If Vehicle Controller receives the feedback signal that the data message that control centre sends receives,
Carry out sending or waiting new task instruction of next data information；If not receiving feedback letter
Number then continue through headstock, tailstock dual-mode antenna by the coded identification after error correction or erasure code
Packet transmits continually to trackside positioning transceiving antenna, continues to send the data being not fully complete
Information.
5. the car-ground data of CBTC based on the distributed fountain codes of employing described in claim 1
Sending the method that the ground control centre with the system of reception receives Vehicle Controller data, it is special
Levy and be: comprise the following steps:
Trackside positioning transceiving antenna receives the data that train transmits, and trackside positioning transceiving antenna is received
The data membership arrived, in the different coding character subset of same source symbol set, the most both may be used
To overlap, it is also possible to separate, two coded identification subset sums must be complete or collected works；
The coded identification data bag received is transferred to ground by optic_fiber intelligent skin and each layer switch
The error correction of distributed fountain codes coder or entangle and delete decoder, error correction or entangle and delete decoder pair
The packet received carries out error checking and correction, and the data symbol comprising mistake is maybe carried out by error correction
Delete, accurate packet is sent to virtual trunk nodes encoding device；
Virtual trunk nodes encoding device uses the via node algorithm defined in distributed fountain codes, has
Selectively the data received directly are forwarded, or by after the process of two paths of data XOR
It is forwarded in caching；
The fountain codes coded data packet stored in the buffer is entered by ground distributor cloth fountain codes coder
Row decoding, if the coded data packet quantity in Huan Cun is slightly larger than the number-of-packet of former subpackage packing
Former data message just can be reduced by amount with decoding success, and the data message after reduction passes
Transport to control centre；If negligible amounts in Huan Cun, continue to coded data packet, and from respectively
The packet that individual antenna receives does not differentiates between order, does not minds the packet loss of transmitting procedure；
Control centre is after receiving data message, and transmission confirmation signal, to approach train, represents this
Task completes；Otherwise, this confirmation signal is not sent.
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| CN103716134B (en) * | 2013-11-21 | 2016-08-24 | 浙江大学 | The coding method of cumulative fountain codes is spent under feedback condition |
| CN110022544B (en) * | 2018-01-09 | 2020-11-06 | 比亚迪股份有限公司 | Vehicle-ground wireless comprehensive bearing system and method based on LTE-U |
| CN109649437B (en) * | 2018-12-31 | 2021-04-27 | 河南思维自动化设备股份有限公司 | Railway station computer interlocking information transmission method and system |
| US11332173B2 (en) | 2019-10-11 | 2022-05-17 | Progress Rail Services Corporation | Train control with centralized and edge processing handovers |
| CN111277365B (en) * | 2020-01-16 | 2022-07-26 | 北京同有飞骥科技股份有限公司 | Fountain code-based self-adaptive distributed data storage method and system |
| CN112486037B (en) * | 2020-12-09 | 2023-08-18 | 友道科技有限公司 | Communication matching method and system for train and regional controller in CBTC simulation system |
| CN112804232B (en) * | 2021-01-13 | 2021-10-26 | 中国电子科技集团公司第十五研究所 | Fountain code network beacon-based tracing method and device |
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