Automatically measures and reports in the system
in the state of the water, the data long-distance transmission is the
essential link. In recent years moved the company the
technological development and its the data service 商业?
application, caused the GPRS means of communication into to be
possible in the hydrology data transmission application. Through
analyzes the GPRS application principle, carries on the network design
and the application methods design, and through the maintenance test,
obtains using the GPRS network carries on the water information news
is effective, also is feasible.
Environment: Communications channel GPRS RTU minute
center
1. forewords
Automatically measures and reports the system and in the
flood prevention command system water friendship center project in the
construction hydrology, the data long-distance transmission is the
essential link, the national flood prevention command system is
composed by four subsystems: (1) foundation data acquisition
system and hydrologic survey facility improvement; (2) data
communication subsystem, (3) computer and its network construction;
(4) guards against floods consults the service support program.
The data communication subsystem duty is extremely explicit, is
must transmit the open country scene telemetered data to a minute
center.
Realized the long range data transmission means of communication
already to have many has planted, they mainly were: The
ultrashort wave communication, the short-wave communication, the wired
PSTN correspondence, the GSM correspondence (is divided SMS and the
GPRS two ways), CDMA, the optical fiber communications ofc as well as
the satellite communication (contain many kinds of satellites channel)
and so on. Progresses by leaps and bounds along with the male
net correspondence enterprise develops, but also further will appear
the recent data service communication way.
After in May, 2002, China moved the GPRS network to enter
商业?the practical stage, thus has provided the use country my
father net transmission state of the water data another method for us.
This means of communication in hydrology data transmission
application.
2. GPRS outline
1 GPRS application principle
GPRS (General Packet Radio Service) the general grouping
wireless service is one kind based on the data packet wireless
communication service. Theoretically it will cause the
communication speed continuously to rise from 56 Kbps to 114Kbps, also
the support computer and the mobile subscriber will continue the
connection. GPRS is based on the GSM network, in theoretically,
the GPRS data packet communication service expenditure exchanges the
service station flower the electric circuit the expense to have to be
less than, its communications channel is sharing, is only needing time
only then has the data packet transmission production, therefore must
save very many resources compared to the use special-purpose
connection. The GPRS mobile subscriber may visit own as
necessary hypothesized private network (VPN), but is not each time all
needs the digit dialing to access the net, thus provides the simpler
application service for the user.
GPRS is according to the GSM standard definition wrapped gift
swap agreement, but fast turns on the data network. It has
realized "on-line forever" between the mobile termination and the
network the connection, the network capacity only has in the reality
carries on time the transmission only then is taken. The GPRS
true speed typical value is slower than the theoretical velocity, lies
between 14.4~43.2 kbps (about a line of asymmetrical speed) about.
GPRS will be a standard which the first realization mobile
interned turns on immediately, also is steps to the 3G/UMTS process.
Uses moves the GPRS technology to carry on the network data
transfer, the expense is low, the easy to operate, the region limit,
is not advantageous for the service development, has the very good
development tendency, from SMS to GPRS to future 3G, will be road of
the one kind of more economical convenient communication, will be
allowed the skeleton more widespread correspondence network, to
realize the nimble information network transmission.
GPRS is based on the data grouping transmission, can provide
continuously the uninterrupted data communication service, has
compared to the SMS better data transfer speed and the ability, also
can throughout on-line, the correspondence expense is defers to the
actual transmission the data byte to carry on the settlement, the
operating cost is low.
2 GPRS transmission data characteristic
(1) the relative GSM digit dialing way electric circuit
exchange data transfer way, GPRS groups the exchange technology, has
"is high speed" and "on-line" merit.
(2) except the speed in superiority, GPRS also has "on-line" the
characteristic, namely user as necessary with network maintenance
relation. Has when the data transfer on transmits and accepts
the data on the wireless channel, does not have the data transfer, the
terminal to enter one kind of "the accurate dormancy" condition,
releases wireless frequency channel which uses for other user uses, by
now between the network and the user also maintained in one logical
the connection, when the user transmitted once more, the handset to
the network requested immediately the wireless frequency channel used
for to transmit the data, did not need the frequent digit dialing.
(3) the GPRS data transmission is bidirectional, also may
transmit the batch data, applies to the hydrology said also may
realize solid state stored datum wireless downloading, this
characteristic is the ultrashort wave, the GSM short note, PSTN as
well as the satellite message center cannot substitute.
3 GPRS network design
3.1 networks and the central station GPRS data turn on
the method
According to the hydrology data transmission application
characteristic, we move GPRS to China which provides to turn on the
method to carry on the generalized analysis, considered the natural
price compared to with the usability, the experimental system data
turned on chooses has selected the application method in the water
friendship center which GPRS wireless Modem carried on turns on,
established own for the user wireless VPN special-purpose data
networking, provided each kind of speed high grade, the transparent
data transmission permanent or the semi-permanent special-purpose
communication link, in the remote telemetering end, the hydrology data
transmission realized through GPRS wireless DDN. Wireless DDN
uses the GPRS migration data communication network composition the
digital data transmission network, is extremely suits dispersers open
country environmental condition difference the system, also suits the
use environment.
After the user applied for GPRS special-purpose VPN, according
to moves the operation business to assign for the data central Modem
net in the fixed IP address, the data central with 遥测?realizes
the multi- spots through wireless GPRS Modem to the central data
communication, the remote 遥测?basis disposes in data central
network IP address and data central establishment data channel.
This kind turns on the method the merit is:
(1) the data carries on the communication in own VPN special
net, the outside terminal or the pitch point cannot enter, the data
security is good.
(2) the data carries on the communication in own VPN special
net, also has guaranteed the data transmission timeliness.
(3) turns on the cost is only 1/3 which the DDN special line
turns on. The expense has reduces, the flexibility has the
enhancement, does not need the construction construction.
(4) uses the band width between 40 - 80K, the communication
performance has been able to satisfy the state of the water text of a
telegram data transmission request.
(5) the center 接入?or 遥测?may tie up settled in net
fixed IP, occasionally falls the line to be allowed again to continue
on the automatic line, cannot lose the central end the address.
GPRS state of the water telemetering network principle
3.2 GPRS band width estimate
If the water friendship center system has 50
telemeterings stands, each station from the newspaper telemetered data
package is 20 bytes, stands the data stream is only 200bit, 50
stations are 10K bit, if requests in 2s completely to transmit
finished, it takes the band width approximately is 5 kbps, if requests
in 1s completely to transmit finished, it takes the band width
approximately is 10 kbps, is smaller than the central end actual
transmission band width. Moreover, the hydrology data
transmission certainly is not all carries on every time, in fact the
hydrology telemetry system takes the band width is narrower.
The far-end 遥测?is the area GPRS actual transmission band
width generally to be bigger than 40k, because the state of the water
telemeters the stand the distributed characteristic, in a 基站 scope
the stand number is extremely limited, therefore in the open country
stand data the biography is completely does not have the question.
In 3.3 data passes on
Each hydrology 遥测?gathering system needs the
data, will pack after the data conversion and the data delivers the
GPRS module, the GPRS module basis realizes the definition APN
connection way to pack the good data to increase the partial redundant
code and the verification code and transforms suits the network data
packet signal which will transmit on the wireless link. After
motion company bureau end special-purpose APN receives the signal
transparently to transmit the water friendship center.
Under 3.4 orders passes on
Similarly, because is the transparent transmission, the
water friendship center may order, and so on to pass to the far-end
遥测?establishment parameter passes to telemeters the stand, thus
the realization data long-distance reads takes with 遥测?the
operational parameter long-distance establishment.
3. GPRS application method
We in 遥测?center dispose GPRS wireless DTU, the
central station use GPRS wireless Modem. In has the GPRS signal
cover the place network station construction, actually uses GPRS to
carry on the long range data transmission.
1 GPRS wireless DTU module selection
The GPRS terminal uses conforms to industrial
application standard GPRS wireless DTU/GPRS module GF-2008w.
The DTU/GPRS connection module is section specially for needs
the wireless data transmission protocol dtp switch which the wireless
data transmitting equipment develops. DTU/GPRS has realized the
wireless GSM agreement stack transformation, does not need with it
connected terminal device supports the GMS agreement handling ability,
when the data transmission only to need, through the string mouth to
the DTU/GPRS transmission string mouth form data, DTU/GPRS can
automatically add on the GSM wireless correspondence the agreement,
transforms the string mouth data packet the GSM wireless
correspondence the agreement data packet, data transmission to goal
main engine; Simultaneously opposite party main engine the data
which transmits through wireless GSM after the DTU/GPRS agreement
transformation, also passes on by the transparent string mouth data
mode for the central station state of the water workstation main
engine. So long as provides the RS-232 connection the equipment
all to be allowed to realize the wireless GSM data transmission
through DTU/GPRS. The terminal device and DTU/GPRS alternately
uses the simple string mouth package form, all GSM agreement stack
agreement all completes the transformation by DTU/GPRS. Realizes
the wireless data transmission function through DTU/GPRS.
Module characteristic as follows:
(1) completed the GSM agreement stack to transform;
(2) realizes the string mouth transparent wireless data
transmission;
(3) supports the GSM data packet exchange;
(4) supports the GSM900/DCS1800/PCS1900MHZ three frequency bands
networks;
(5) through the FTA test, may supply two times of developments;
(6) uses the CLASS 10 wireless modules, the high speed
transmission, stable is reliable.
Technical parameter as follows:
(1) connection type: RS232 connection
(2) works the frequency band:
GSM900/DCS1800/PCS1900
(3) receiving sensitivity: -104dbm
(4) emissive power: CLASS4 (2W) /EGSM900;
CLASS1 (1W) /DCS1800 CLASS1 (1W) /PCS1900
(5) frequency error: <=0.1ppm
(6) conforms to ETSI GSM the Phase 2+ standard
(7) GPRS Class 2-10
(8) code scheme: CS1-CS4
(9) conforms to the SMG31bis technology standard
(10) supports the A5/1&A5/5 encryption algorithm
Outside setting at module DC voltage input scope width
(+5~26VDC), operating temperature: -20~65 ? humidity scope:
0~95%, the non- condensation satisfies the complex application
environment, the easy to operate, nimble, reliable, the volume small,
the power loss is low, suitablly inserts the type use.
2 GPRS the wireless DTU module telemeters in terminal RTU in the
state of the water to insert the design
2.1 hardware designs
The hardware system based on the YDH-1A hydrology
telemetring terminal equipment, the YDH-1A telemetering number passes
on terminal RTU is the general purpose equipment which controls by the
microprocessor, because uses pulls out inserts the type template
structure to become the distributional terminal type, according to the
need which applies may compose the different type. With the aid
of the YDH-1A correspondence control template, module carries on the
control using the template on RS-232 hardware connection to GPRS the
wireless DTU, completes the data long-distance receiving and
dispatching task.
2.2.2 software designs
The telemetering number passes on the terminal GPRS data
transmission flow
3 GPRS application experiment
3.1 tests the place choice and the experimental
technique
Can measure and report in the system construction for
GPRS in the national hydrology to obtain the application and the
promotion, provides the advanced data transmission method for the
system construction to prepare for technology, we chose in the
Guangdong Province Huizhou city carry on the GPRS network really to
move the experiment, moved the VPN special-purpose hypothesized net
through Guangdong which provided to carry on the water literary
journal high water GPRS transmission, confirmed the GPRS transmission
state of the water the feasibility and the usability.
Attends experimental the hydrology to telemeter the stand to
elect in the A place (station number 10) and the B place (station
number 11). The water friendship center is located in the C
place hydrology sub-bureau.
The experimental technique is in the A place (10), the B place
(11) constructs GPRS to telemeter the stand, each station
establishment is 1h fixed time from the newspaper, the rainfall 1mm
increase from 报以 and the water level 1cm increase from the
newspaper, the central station 24h opening machine receive text of a
telegram.
In order to guarantee the correspondence quality, first needs to
guarantee the stand installment quality, if the stand signals strength
not high outside, then uses lengthens the antenna to improve the
effect, simultaneously also can save the power loss. The antenna
does not permit the level laying aside, must be vertical the laying
aside.
遥测?the use solar cell board and the import exempts the
maintenance accumulator cell combination to provide RTU and the GPRS
DTU power source.
After the experiment ended withdraws the information from the
computer database to carry on the statistics and the analysis.
3.2 experimental results
After the experiment ended, through database recording
text of a telegram data statistical analysis, result as follows:
(1) transmits when extends generally between 1~3s.
(2) 1h fixed time from the newspaper text of a telegram
integrity, does not have a flaw.
(3) the water level rainfall increase newspaper text of a
telegram is normal.
3.3 experiences and enlightenment
(1) according to the hydrology data transmission
service actual need and hydrology text of a telegram timeliness, the
central station must have in the true significance "on-line" the
function, the concrete realization method is the central station
should have the automatic maintenance to wireless Modem the function.
(2) in order to guarantee the hydrology text of a telegram data
transmission is surefire, central end software should have the receive
data confirmation and to 遥测?the transmission receipt feedback
mechanism. If 遥测?has not received the central station in
the stipulation time the receipt, 遥测?should carry on makes an
after-event report, like this may prevent in the GPRS data
transmission has the possibility to occur makes a fraudulent switch
the phenomenon.
(3) because the GPRS channel is bidirectional, therefore may on
pass on besides 遥测?the data, but also may realize the center to
the remote RTU long-distance establishment and the control, another
important characteristic is may realize wireless long-distance reads
takes the data which 遥测?the solid state saves, this function is
other correspondences is not easy to achieve, should positively
develop the use.
4. conclusions
According to the national flood prevention command
system construction instruction book request, the reference former
hydrology automatically measures and reports the system the
construction experience below, may draw the conclusion:
(1) has the country my father net to be allowed the use, do not
have to construct own as far as possible special net;
(2) has the wireless channel to be possible to help the use, do
not have to use the wired channel. These two principles may
enormously enhance the system long-term movement the reliability.
The experimental result indicated, automatically measures and
reports the system and in the national flood prevention command system
data communication transmission subsystem in the hydrology introduces
the GPRS data communication method not only is effective, also is
feasible. Along with the future 3G time arrival, the
technological development which the modern communication same water
conservation enterprise will unify hastens obviously.
Reference:
The SL61-2003 hydrology automatically measures and reports the
system technology standard (S)
"GF-2008W Instruction for use" Beijing fine duplicate
joyful company
Picks from the Ministry of Water Conservation Nanjing
water conservation hydrology Institute of Automation
More details please register: Http://www.gfdtu.com/info/200719/200719150841.shtml |
