>Foreword
The coal mine gas accident is in the coal mine
safety in production has the frequency to be high, the harm degree big
main accident source. Completes the coal mine safety in
production supervisory work, solves the coal mine gas hidden danger
realizes a coal mine safety in production condition radical change for
the better key link, is one of national coal mine security supervision
bureau current deployment key work. The implementation unified
"the coal safe supervisory system" has the extremely vital
significance to the coal mine safety in production long-term peace and
good government.
General coal mine geographical position remote, terrain complex,
uses has the wire to construct invests in a big way, network wiring
difficult, uses way 覆盖�lowly and so on microwave, the
transmitting range is limited. Wireless has 布网 is nimble
quickly, the comparatively quicker transmission speed characteristic,
may take the wireless network the coal mine safe supervisory system
very good solution.
GPRS and CDMA 1X wireless network synopsis
At present, based on the GPRS/CDMA wireless data
transmission service widely in the motion work, the industry control,
the long-distance telemetering and so on the various application,
network operation business China moves GPRS and the association passes
CDMA respectively to have its characteristic.
GPRS (General Packet Radio Service, general wireless grouping
service) took second-generation mobile communication technology GSM to
third generation mobile communication (3G) the transition technology,
was Corporation as early as proposes by English BT Cellnet in 1993,
was GSM Phase2+ (in 1997) one of standard realization contents, was
one kind based on the GSM migration integrated data service, provided
the motion grouping face the user IP or the X.25 connection.
GPRS is a new network which superimposes in the existing GSM
network foundation, simultaneously increases some hardware equipment
on the network equipment, and promoted to original software, has
formed a new network logic entity. GPRS can end-to-end provide,
the macrozonality wireless IP connection to the user. Popularly
speaking, GPRS is a wireless high speed data transmission technology,
it take groups the exchange technology as the foundation, the user may
use each kind of high speed data service through GPRS under the motion
condition, including receives and dispatches E-mail, carries on the
Internet browsing, chats immediately and so on.
GPRS system use existing GSM wireless network. GPRS and
GSM altogether use same 基站 and the frequency spectrum resources,
only was increased some hardware equipment and the software promotion
in the existing GSM network foundation. Therefore, realizes GSM
to promote is extremely easy to GPRS, also China moves with the aid of
the original GSM network, therefore the GPRS cover is extremely broad.
At present China moves the GPRS network to cover national all
provinces, the municipality, the autonomous region, the network
spreads more than 240 cities.
CDMA is code minute sites English condenses (Code Division
Multiple Access), it is one kind of new wireless communication which
develops in the digital technology branch - wide frequency
communication. The CDMA technology principle is based on the
wide frequency technology, soon must transmit has the certain signal
band width information data, far is bigger than the signal band width
with a band width the high speed pseudo-random code to carry on the
modulation, makes the prime number to expand according to the signal
band width, again passes through the carrier modulation concurrently
to deliver. The receiving end use quite same not less than
pseudo-random code, makes correlation processing with the receive band
width signal, changes into the wide band signal the original
information data the narrow band signal is the solution expands,
realizes the data transmission.
The CDMA technology standardization has experienced several
stages. IS95 is a standard which in the CDMAONE series standard
first issued, truly obtains the widespread application in the whole
world the first CDMA standard is IS95A, this standard supports the 8K
code voice service. When ITU solicits the third generation
mobile communication wireless candidate technology to the various
countries, IS95 because just obtains the commercial success, the
American TR45 standard committee not very many energy will put on in
the third generation standard research, but will be diligently is
completing IS95B the standard.
Under the ITU request, proposed in the same year the CDMA2000
third generation standard, namely CDMA2000 1X and 3X (1X represents an
its carrier time to the IS95A band width, 3X represents its carrier
three time to the IS95A band width) under, 3X divides into the line
directly to expand the spectrum and three carriers two ways,
afterwards directly expanded scores the CDMA2000 part and WCDMA has
carried on the fusion, therefore present CDMA2000 on only includes
CDMA2000 1X and three carriers way 3X in fact.
CDMA 1X is refers to the CDMA 2,000 first stage (speed to be
higher than IS95, is lower than 2Mbit/s), may support 308kbit/s the
data transmission, the network part introduction grouping exchange,
supports moves the IP service. Is one kind of new bearer service
which system develops in existing CDMA on the IS95, the goal is the
CDMA user provides groups the IP form the data service.
CDMA based on the wide frequency technology, takes is the
brand-new 800M frequency band (GSM takes is the 900M frequency band),
therefore cannot directly promote on the original GSM equipment.
At present, China Unicom through the second phased projects
construction, has carried on the network optimization and the
promotion to the CDMA network, the network from the IS95 promotion is
the CDMA1X network; Simultaneously completes covers national 31
provinces (autonomous region, municipality) the wireless data
networking.
Coal mine safe supervisory system introduction
The coal mine will gather each kind of security
data from the mine shaft to compile to the ground monitoring center,
through GPRS/CDMA the 1X wireless network transmission to the wireless
hub LAS equipment, will transmit the place coal monitoring center and
the higher authority again through the special line safely supervises
the department. In order to guarantee the network security,
establishes in the existing physical network foundation based on L2TP
the agreement VPN logic hypothesized special network, realizes the
coal mine and the place coal monitoring center safe correspondence.
The ground monitoring center carries forward to GPRS/CDMA
through the assignment special-purpose VPN account number by the digit
dialing way the 1X network, authenticates the server (AAA) and the
coal security supervision bureau authenticates the server (Radius) to
complete together wireless carries forward to the coal mine user the
authentication and the warning power. The coal mine user
establishes the VPN special-purpose communication channel after the
authentication and the warning power in the coal mine and between the
coal security supervision bureau. Through the VPN network
establishment hypothesized special-purpose correspondence channel, the
coal monitoring center and the higher authority safely supervise the
department to be possible the real-time monitoring coal mine safety in
production data.
Coal mine safe supervisory system
The coal monitoring center and other office
computer passable bureau territory work networks, various higher
authorities safely have supervised the department passable
macrozonality work network visit coal place coal monitoring center the
information issue system, carries on the coal mine safety in
production the information inquiry, the statistics and the analysis.
System constituent
The wireless network coal mine safe supervisory
system mainly by three major part is composed: Ground monitoring
center, wireless data transmission network platform, coal monitoring
administrative center system.
Ground monitoring center: By monitors the main engine, the
transmission connection, the UPS, the wireless router, the color
printer, monitors software, the substation, the wind speed sensor, the
temperature sensor, the carbon monoxide sensor, the equipment opens
stops the sensor, the smog sensor, the gas sensor, far moves the
switch and so on to be composed.
Wireless data transmission network platform: At present
domestic wireless male net, like GPRS, CDMA 1X network platform.
Coal monitoring administrative center system: Network
communication server, real-time database server and user control
operation contact surface and so on. 
The coal mine safe monitoring stand develops the plain
structure drawing
Coal mine safe supervisory system block diagram
System superiority
The system invests, the network convenience slightly
nimble, the transmission speed quick, is easy to maintain.
Summary
Using the GPRS/CDMA network digital data service,
with the aid of the great electricity company's CDMA/GPRS
communication product, will be able smoothly to complete the coal mine
to produce the scene safe monitoring information transmission, in
anticipation to manage, reduces the gas to the coal mine the harm
degree, ceases contrary mining, violates regulations the work,
violates the labor discipline the phenomenon, reduces the coal mine
accident the occurrence positive function.
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