1. “AUTOMATIC SWITCHOVER OF E1 LINK
IN CASE OF FAILURE”
Bachelor of Engineering
( Electronics and Telecommunication Engineering )
Submitted by: -
Ms.Shreya Chakrabarti
Ms.Snehal Karpe
Ms.Anubha Bhimsaria
Ms.Dipali Kare
Under the guidance of:-
Prof. Mrs Geeta Devurkar
Mr.D.B Drode
Department of Electronics and Telecommunication Engineering
Dr. D. Y. Patil Group’s
Ramrao Adik Institute of Technology
2. Nerul, Navi Mumbai – 400706
OCT– 2009 to MAY-2010
“AUTOMATIC SWITCHOVER OF E1 LINK
IN CASE OF FAILURE”
Bachelor of Engineering
( Electronics & Tele-Communication Engineering )
Submitted by
Ms.Shreya Chakrabarti
Ms. Snehal Karpe
Ms. Anubha Bhimsaria
Ms. Dipali Kare
Under the guidance of
Prof. Geeta Devurkar
Department of Electronics & Tele-Communication Engineering
Dr. D. Y. Patil Group’s
Ramrao Adik Institute of Technology
Nerul, Navi Mumbai – 400706
3. (University of Mumbai)
OCT– 2009
RAMRAO ADIK INSTITUTE OF
TECHNOLOGY
NERUL, NAVI MUMBAI
CERTIFICATE
This is to certify that
Ms.Shreya Chakrabarti
Ms.Snehal Karpe
Ms.Anubha Bhimsaria
Ms.Dipali Kare
has satisfactorily completed the requirements of the PROJECT ‘A’
entitled
“Automatic switchover of E1 link in case of failure”
as prescribed by the University of Mumbai Under the guidance of
Prof.Geeta Devurkar
Project Guide
Prof.Geeta Devurkar Prof.R.H.Khade Dr. S. R. Devane
Project-coordinator H.O.D Principal
6. ACKNOWLEDGEMENT
We take this opportunity to express our gratitude which was given to us to
Successfully complete our project in Department of Research And
Development, MTNL,Navi Mumbai. It will always remain an enriching
experience which we will always cherish.
Firstly, we would like to thank our guide Mr.D.B. Drode the person
without whom this project would never have materialized. We are really
indebted him for providing us direction and support and sparing his
precious time for our project.
Our special thanks to Prof .Mrs.Geeta Deverkar our college internal guide
And project coordinator,Head of Department Mr.R.H Khade, Department of
Electronics And Telecommunications at RAIT ,Nerul for their valuable
guidance and regular assessment of the progress made by us in our project.
6
7. ABSTRACT
Our Project is basically automatic switch over of E1 link to the standby link, in
the case of failure of working E1 link so as to keep the BTS radiating and provide
mobile coverage. The name of the project itself indicates the process of
automation. The Project is implemented in MTNL Mumbai’s Dolphin GSM
network.
E1 is the link which connects the BTS to BSC .In order to keep the BTS
radiating so as to provide Mobile network, the E1 link has to be maintained
regularly. In the case of any failure of E1 link the BTS will fail thereby affecting
the mobile network in the area.
This will not only deprive the people in that area from the usage of their mobiles
but will affect the mobile service provider in the form of revenue loss.
In order to overcome the issues faced above, we have developed our project so
as to switchover the working E1 link to standby E1 link in the case of any failure
automatically.
Our project will not only provide solution to the mobile operators, but will also
provide uninterrupted mobile services to the mobile customers in the case of any
failures.
Introduction
7
8. PROBLEM DEFINITION
In order to keep the BTS radiating so as to provide Mobile network, the E1 link
has to be maintained regularly. In the case of any failure of E1 link the BTS will
fail thereby affecting the mobile network in the area.
It would be quite unfortunate if any fault occurs in this E1 link after office hours,
then the site engineer will have to rush to the site so as to restore the fault in the
E1 link, but if the fault in the E1 link occurs at odd hours may be at midnight,
then it would not be possible for an engineer to reach the site at that hour which
will in turn affect the mobile network
in the area. The fault in that particular area will be restored only after 8 to 10
hours. This will not only deprive the people in that area from the usage of their
mobiles but will affect the mobile service provider in the form of revenue loss.
In order to overcome the issues faced above, we have developed our project so as
to switchover the working E1 link to standby E1 link in the case of any failure
automatically.
Our project will not only provide solution to the mobile operators, but will also
provide uninterrupted mobile services to the mobile customers in the case of any
failures.
Literature survey:
8
9. Automatic switchover of E1 link in the case of
failure.
We are going to implement our project in the MTNL Mumbai’s Dolphin GS M
network. The name of the project itself indicates the process of automation. It is
basically automatic switch over of E1 link to the standby link, in the case of
failure of working E1 link so as to keep the BTS radiating and provide mobile
coverage.
E1 LINK:
E1 link is the 2Mbps PCM link.
Structure of E1 link:
0 1 2 3 4 1
6
3
1
E1 link consists of 32 Time slots/Channels this ranges from TS0 to TS31.
TS0 is exclusively used for synchronisation and is known as FAS (Frame
alignment synchronisation).
TS16 is exclusively used for signaling.
The remaining 30 time slots/ Channels are used for carrying traffic i.e. speech.
The bit rate of each time slot/Channels is 64 Kbps.
The total rate of an E1 link is therefore 64 * 32 = 2048 Kbps i.e. 2 Mbps.
Thus the E1 link is also known as 2Mb link.
By taking in to consideration the above information we will develop a circuitry so
as to manage the automatic switchover of the 2Mb E1 links in the case of failure.
9
10. STUDY AND ANALYSIS
GSM is Global systems for Mobile communication. It operates in bands 900 &
1800.
Frequencies in 900 bands:
890 MHz – 915 MHz --------- Uplink frequencies.
935 MHz – 960 MHz --------- Downlink frequencies.
Frequencies in 1800 band:
1710MHz – 1785 MHz --------- Uplink frequencies.
1805MHz – 1880 MHz --------- Downlink frequencies.
10
11. GSM Architecture
MS-Mobile System MSC - Mobile switching centre
BTS- Base Transceiver station VLR – Visitor location register
BSC-Base Station controller HLR – Home location register
EIR- Equipment Identity registers AUC – Authentication centre
HLR
AUC
EIR
VLR
TRX
OTHER
MSC
OTHER
MSC
VLR
UmUm
A bisA bis AA
BB
CC
DD
EE
FF
HH
GG
MS (User)
MSC
BTS
BASE STATION SUB-
SYSTEM (BSS) SWITCHING SUB-SYSTEM
(NSS)
OMC /
NMC
BSC
O & M SUB-SYSTEM
(OSS)
11
12. GSM system consists of three major interconnected sub
systems
1. Base station Subsystem
• Mobile station (MS)
• Base Transceiver Station (BTS)
• Base Station Controllers (BSC)
2. Network Switching Subsystem
• Mobile Switching Centre (MSC)
• Home Location Register (HLR)
• Visitor Location Register (VLR)
• Authentication centre (AU)
3. Operation & Maintenance Support Subsystem
• Operation Maintenance Centres (OMC)
12
13. Base station subsystem
The base station subsystem (BSS) is the section of a traditional cellular
telephone network which is responsible for handling traffic and signaling between
a mobile phone and the network switching subsystem. The BSS carries out
transcoding of speech channels, allocation of radio channels to mobile phones,
paging, quality management of transmission and reception over the air interface
and many other tasks related to the radio network.
The base transceiver station, or BTS, contains the equipment for transmitting and
receiving radio signals (transceivers), antennas, and equipment for encrypting and
decrypting communications with the base station controller (BSC). Typically a
BTS for anything other than a Pico cell will have several transceivers (TRXs)
which allow it to serve several different frequencies and different sectors of the
cell (in the case of sectorised base stations). A BTS is controlled by a parent BSC
via the base station control function (BCF).The BCF is implemented as a
discrete unit or even incorporated in a TRX in compact base stations. The BCF
provides an operations and maintenance (O&M) connection to the network
management system (NMS), and manages operational states of each TRX, as well
as software handling and alarm collection.
The functions of a BTS vary depending on the cellular technology used and the
cellular telephone provider. There are vendors in which the BTS is a plain
transceiver which receives information from the MS (mobile station) through the
Um (air interface) and then converts it to a TDM ("PCM") based interface, the
Abis interface, and sends it towards the BSC. There are vendors which build their
BTSs so the information is preprocessed, target cell lists are generated and even
intracell handover (HO) can be fully handled. The advantage in this case is fewer
loads on the expensive Abis interface.
The BTSs are equipped with radios that are able to modulate layer 1 of interface
Um; for GSM 2G+ the modulation type is GMSK, while for EDGE-enabled
networks it is GMSK and 8-PSK.
Antenna combiners are implemented to use the same antenna for several TRXs
(carriers); the more TRXs are combined the greater the combiner loss will be. Up
to 8:1 combiners are found in micro and pico cells only.
Frequency hopping is often used to increase overall BTS performance; this
involves the rapid switching of voice traffic between TRXs in a sector. A hopping
sequence is followed by the TRXs and handsets using the sector. Several hopping
13
14. sequences are available, and the sequence in use for a particular cell is continually
broadcast by that cell so that it is known to the handsets.
A TRX transmits and receives according to the GSM standards, which specify
eight TDMA timeslots per radio frequency. A TRX may lose some of this
capacity as some information is required to be broadcast to handsets in the area
that the BTS serves. This information allows the handsets to identify the network
and gain access to it. This signaling makes use of a channel known as the
broadcast control channel (BCCH).
The base station controller (BSC) provides, classically, the intelligence behind the
BTSs. Typically a BSC has tens or even hundreds of BTSs under its control. The
BSC handles allocation of radio channels, receives measurements from the mobile
phones, controls handovers from BTS to BTS (except in the case of an inter-BSC
handover in which case control is in part the responsibility of the anchor MSC). A
key function of the BSC is to act as a concentrator where many different low
capacity connections to BTSs (with relatively low utilisation) become reduced to
a smaller number of connections towards the mobile switching center (MSC)
(with a high level of utilization). Overall, this means that networks are often
structured to have many BSCs distributed into regions near their BTSs which are
then connected to large centralized MSC sites.
The BSC is undoubtedly the most robust element in the BSS as it is not only a
BTS controller but, for some vendors, a full switching center, as well as an SS7
node with connections to the MSC and serving GPRS support node (SGSN)
(when using GPRS). It also provides all the required data to the operation support
subsystem (OSS) as well as to the performance measuring centers.
A BSC is often based on a distributed computing architecture, with redundancy
applied to critical functional units to ensure availability in the event of fault
conditions. Redundancy often extends beyond the BSC equipment itself and is
commonly used in the power supplies and in the transmission equipment
providing the A-ter interface to PCU.
The databases for all the sites, including information such as carrier frequencies,
frequency hopping lists, power reduction levels, receiving levels for cell border
calculation, are stored in the BSC. This data is obtained directly from radio
planning engineering which involves modeling of the signal propagation as well
as traffic projections.
Base transceiver station
14
15. A base transceiver station or cell site (BTS) is a piece of equipment that
facilitates wireless communication between user equipment (UE) and a network.
UEs are devices like mobile phones (handsets), WLL phones, computers with
wireless internet connectivity, WiFi and WiMAX gadgets etc. The network can be
that of any of the wireless communication technologies like GSM, CDMA, WLL,
WAN, WiFi, WiMAX etc. BTS is also referred to as the radio base station
(RBS), node B (in 3G Networks) or, simply, the base station (BS). For discussion
of the LTE standard the abbreviation eNB for enhanced node B is widely used.
A GSM BTS network is made up of three subsystems: • The Mobile Station
(MS) • The Base Station subsystem (BSS) – comprising a BSC and several BTSs
• The Network and Switching Subsystem (NSS) – comprising an MSC and
associated registers.
Though the term BTS can be applicable to any of the wireless communication
standards, it is generally and commonly associated with mobile communication
technologies like GSM and CDMA. In this regard, a BTS forms part of the base
station subsystem (BSS) developments for system management. It may also have
equipment for encrypting and decrypting communications, spectrum filtering
tools (band pass filters) etc. antennas may also be considered as components of
BTS in general sense as they facilitate the functioning of BTS. Typically a BTS
will have several transceivers (TRXs) which allow it to serve several different
frequencies and different sectors of the cell (in the case of sectorised base
stations). A BTS is controlled by a parent base station controller via the base
station control function (BCF). The BCF is implemented as a discrete unit or even
incorporated in a TRX in compact base stations. The BCF provides an operations
and maintenance (O&M) connection to the network management system (NMS),
and manages operational states of each TRX, as well as software handling and
alarm collection. The basic structure and functions of the BTS remains the same
regardless of the wireless technologies.
In GSM architecture BTS is the one which provides coverage to the
area in which it is located. BTS is BASE TRANSCEIVER STATION. BTS is
connected to MSC via BSC through 2Mbps E1 link. This E1 interface which
connects the BTS to BSC is termed as Abis link. All the necessary interfaces are
shown in the figure above.
15
16. E1 Link.
An E1 link operates over two separate sets of wires, usually twisted pair cable. A
nominal 3 Volt peak signal is encoded with pulses using a method that avoids
long periods without polarity changes. The line data rate is 2.048 Mbit/s (full
duplex, i.e. 2.048 Mbit/s downstream and 2.048 Mbit/s upstream) which is split
into 32 timeslots, each being allocated 8 bits in turn. Thus each timeslot sends and
receives an 8-bit sample 8000 times per second (8 x 8000 x 32 = 2,048,000). This
is ideal for voice telephone calls where the voice is sampled into an 8 bit number
at that data rate and reconstructed at the other end. The timeslots are numbered
from 0 to 31.
One timeslot (TS0) is reserved for framing purposes, and alternately transmits a
fixed pattern. This allows the receiver to lock onto the start of each frame and
match up each channel in turn. The standards allow for a full Cyclic Redundancy
Check to be performed across all bits transmitted in each frame, to detect if the
circuit is losing bits (information), but this is not always used.
One timeslot (TS16) is often reserved for signalling purposes, to control call setup
and teardown according to one of several standard telecommunications protocols.
This includes Channel Associated Signaling (CAS) where a set of bits is used to
replicate opening and closing the circuit (as if picking up the telephone receiver
and pulsing digits on a rotary phone), or using tone signalling which is passed
through on the voice circuits themselves. More recent systems used Common
Channel Signaling (CCS) such as ISDN or Signalling System 7 (SS7) which send
short encoded messages with more information about the call including caller ID,
type of transmission required etc. ISDN is often used between the local telephone
exchange and business premises, whilst SS7 is almost exclusively used between
exchanges and operators. SS7 can handle up to 4096 circuits per signalling
channel[citation needed]
, thus allowing slightly more efficient use of the overall
transmission bandwidth (for example: uses 31 voice channels on an E1).
Unlike the earlier T-carrier systems developed in North America, all 8 bits of each
sample are available for each call. This allows the E1 systems to be used equally
well for circuit switch data calls, without risking the loss of any information.
While the original CEPT standard G.703 specifies several options for the physical
transmission, almost exclusively HDB3 format is used.
16
17. Hierarchy levels
The PDH based on the E0 signal rate is designed so that each higher level can
multiplex a set of lower level signals. Framed E1 is designed to carry 30 E0 data
channels + 1 signalling channel, all other levels are designed to carry 4 signals
from the level below. Because of the necessity for overhead bits, and justification
bits to account for rate differences between sections of the network, each
subsequent level has a capacity greater than would be expected from simply
multiplying the lower level signal rate (so for example E2 is 8.448 Mbit/s and not
8.192 Mbit/s as one might expect when multiplying the E1 rate by 4).
Note, because bit interleaving is used, it is very difficult to demultiplex low level
tributaries directly, requiring equipment to individually demultiplex every single
level down to the one that is required.
Signal Rate
E0 64 kbit/s
E1 2.048 Mbit/s
E2 8.448 Mbit/s
E3 34.368 Mbit/s
E4 139.264 Mbit/s
17
18. Mobile switching center (MSC)
Description
The mobile switching center (MSC) is the primary service delivery node for
GSM, responsible for handling voice calls and SMS as well as other services
(such as conference calls, FAX and circuit switched data). The MSC sets up and
releases the end-to-end connection, handles mobility and hand-over requirements
during the call and takes care of charging and real time pre-paid account
monitoring.
In the GSM mobile phone system, in contrast with earlier analogue services, fax
and data information is sent directly digitally encoded to the MSC. Only at the
MSC is this re-coded into an "analogue" signal (although actually this will almost
certainly mean sound encoded digitally as PCM signal in a 64-kbit/s timeslot,
known as a DS0 in America).
There are various different names for MSCs in different contexts which reflects
their complex role in the network, all of these terms though could refer to the
same MSC, but doing different things at different times.
The gateway MSC (G-MSC) is the MSC that determines which visited MSC the
subscriber who is being called is currently located. It also interfaces with the
PSTN. All mobile to mobile calls and PSTN to mobile calls are routed through a
G-MSC. The term is only valid in the context of one call since any MSC may
provide both the gateway function and the Visited MSC function, however, some
manufacturers design dedicated high capacity MSCs which do not have any BSSs
connected to them. These MSCs will then be the Gateway MSC for many of the
calls they handle.
The visited MSC (V-MSC) is the MSC where a customer is currently located.
The VLR associated with this MSC will have the subscriber's data in it.
18
20. BLOCK DIAGRAM DESCRIPTION
• The system uses microcontroller to handle the above system.
• Microcontroller 89C51 which is a 16 bit processor is used to handle the
above specified MTNL’S control room which controls and supervises the
various incoming lines.
• In case of failure in the discussed system the microcontroller automatically
switches to the alternate.
• The automatic switching system uses ADC to detect the status of the links.
• The output of the ADC is given to the peripheral port interface(PPI) for
interfacing purpose.
• The oscillator IC 555 is used to provide clock to ADC.
• The power supply and voltage regulator are used to provide a stable and
suitable voltage level to the various blocks of the system.
• The amplifier blocks are used to amplify the levels obtained from the link
status blocks and thus provide the suitable level to the ADC for the proper
status detection of the link blocks.
• Serial interface is provided to the status Indicator via the RS232 which
increases the interfacing capability the status indicator used here displays
the status of the links i.e. operational or failed conditions of the links to the
processor.
• The various External Memories such as RAM ,ROM, EPROM are used
depending upon their accessing speeds and storage limits by the
Microcontroller for storage of numerous data during Switching operation.
• The relay networks carry out the entire mechanism of switchover in case
of failure of the links.
• Thus the automatic switching is successfully carried out.
20
21. COMPONENTS DESCRIPTION:
ADC0808/ADC0809
8-Bit μP Compatible A/D Converters with 8-Channel
Multiplexer
General Description
The ADC0808, ADC0809 data acquisition component is a monolithic CMOS
device with an 8-bit analog-to-digital converter, 8-channel multiplexer and
microprocessor compatible control logic. The 8-bit A/D converter uses successive
approximation as the conversion technique. The converter features a high
impedance chopper stabilized comparator, a 256R voltage divider with analog
switch tree and a successive approximation register. The 8-channel multiplexer
can directly access any of 8-single-ended analog signals. The device eliminates
the need for external zero and full-scale adjustments. Easy interfacing to
microprocessors is provided by the latched and decoded multiplexer address
inputs and latched TTL TRI-STATE® outputs.
The design of the ADC0808, ADC0809 has been optimized by incorporating the
most desirable aspects of several A/D conversion techniques. The ADC0808,
ADC0809 offers high speed, high accuracy, minimal temperature dependence,
excellent long-term accuracy and repeatability, and consumes minimal power.
These features make this device ideally suited to applications from process and
machine control to
Consumer and automotive applications. For 16-channel multiplexer with common
output (sample/hold port) see ADC0816 data sheet.
21
22. Features
• Operates ratio metrically or with 5 VDC or analog span
Adjusted voltage reference
• No zero or full-scale adjust required
• 8-channel multiplexer with address logic
• 0V to 5V input range with single 5V power supply
• Outputs meet TTL voltage level specifications
• Standard hermetic or molded 28-pin DIP package
• 28-pin molded chip carrier package
• ADC0808 equivalent to MM74C949
• ADC0809 equivalent to MM74C949-1
Key Specifications
• Resolution 8 Bits
• Total Unadjusted Error ±1⁄2 LSB and ±1 LSB
• Single Supply 5 VDC
• Low Power 15 mW
• Conversion Time 100 μs
22
25. 8-Bit Microcontroller with 4K Bytes Flash
AT89C51
Features
• Compatible with MCS-51™ Products
• 4K Bytes of In-System Reprogrammable Flash Memory
– Endurance: 1,000 Write/Erase Cycles
• Fully Static Operation: 0 Hz to 24 MHz
• Three-Level Program Memory Lock
• 128 x 8-Bit Internal RAM
• 32 Programmable I/O Lines
• Two 16-Bit Timer/Counters
• Six Interrupt Sources
• Programmable Serial Channel
• Low Power Idle and Power Down Modes
Description
The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer
with 4K
Bytes of Flash Programmable and Erasable Read Only Memory (PEROM). The
Device is manufactured using Atmel’s high density nonvolatile memory
technology
and is compatible with the industry standard MCS-51™ instruction set and
pinout. The
On-chip Flash allows the program memory to be reprogrammed in-system or by a
conventional
Nonvolatile memory programmer. By combining a versatile 8-bit CPU with
Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer
which
Provides a highly flexible and cost effective solution to many embedded control
applications.
The AT89C51 provides the following standard features: 4K bytes of Flash, 128
bytes of RAM, 32 I/O lines, two 16-bit timer/counters, five vector two-level
interrupt architecture, a full duplex serial port, and on-chip oscillator and clock
circuitry. In addition, the AT89C51 is designed with static logic
For operation down to zero frequency and supports two software selectable power
saving modes. The Idle Mode stops the CPU while allowing the RAM,
timer/counters, serial port and interrupt system to continue functioning. The
25
26. Power down Mode saves the RAM contents but freezes the oscillator disabling all
other chip functions until the next hardware reset
26
29. REGULATOR IC 7805
The linear regulator is the basic building block of nearly every power supply used
in
Electronics. The IC linear regulator is so easy to use that it is virtually foolproof,
and
So inexpensive that it is usually one of the cheapest components in an electronic
Assembly.
Linear Voltage Regulator Operation
Introduction
Every electronic circuit is designed to operate off of some supply voltage, which
is
Usually assumed to be constant. A voltage regulator provides this constant DC
Output voltage and contains circuitry that continuously holds the output voltage at
the
Design value regardless of changes in load current or input voltage (this assumes
That the load current and input voltage is within the specified operating range for
The part).
The Basic Linear Regulator
A linear regulator operates by using a voltage-controlled current source to force a
Fixed voltage to appear at the regulator output terminal.
The control circuitry must monitor (sense) the output voltage, and adjust
the current
source (as required by the load) to hold the output voltage at the desired
value. The
29
30. design limit of the current source defines the maximum load current the
regulator
can source and still maintain regulation.
The output voltage is controlled using a feedback loop, which requires
some type of
compensation to assure loop stability. Most linear regulators have built-in
compensation, and are completely stable without external components.
Some
regulators (like Low-Dropout types), do require some external capacitance
connected from the output lead to ground to assure regulator stability.
Another characteristic of any linear regulator is that it requires a finite
amount of time
to "correct" the output voltage after a change in load current demand.
This "time lag"
defines the characteristic called transient response, which is a measure
of how fast
the regulator returns to steady-state conditions after a load change.
Selecting the Best Regulator For Your Application
The best choice for a specific application can be determined by evaluating the
Requirements such as:
• Maximum Load Current
• Type of Input Voltage Source (Battery or AC)
• Output Voltage Precision (Tolerance)
• Quiescent (Idling) Current
• Special Features (Shutdown Pin, Error Flag, etc.)
30
31. RS-232 INTERFACE
A standard serial interfacing for PC, RS232C, requires negative logic, i.e., logic
'1' is -3V to -12V and logic '0' is +3V to +12V. To convert a TTL logic, say, TxD
and RxD pins of the uC chips, thus need a converter chip. A MAX232 chip has
long been using in many uC boards. It provides 2-channel RS232C port and
requires external 10uF capacitors. Carefully check the polarity of capacitor when
soldering the board. A DS275, however, no need external capacitor and smaller.
Either circuit can be used without any problems.
The RS-232 interface with presupposes a common ground between the DTE and
DCE. This is a reasonable assumption when a short cable connects the DTE to the
DCE, but longer lines and connections between devices that may be on different
electrical busses with different grounds, this may not be true.
RS232 data is bi-polar.... +3 TO +12 volts indicates an "ON or 0-state (SPACE)
condition" while A -3 to -12 volts indicates an "OFF" 1-state (MARK)
condition.... Modern computer equipment ignores the negative level and accepts a
zero voltage level as the "OFF" state. In fact, the "ON" state may be achieved
with lesser positive potential. This means circuits powered by 5 VDC are capable
of driving RS232 circuits directly, however, the overall range
The output signal level usually swings between +12V and -12V. The "dead area"
between +3v and -3v is designed to absorb line noise. In the various RS-232-like
definitions this dead area may vary. For instance, the definition for V.10 has a
dead area from +0.3v to -0.3v. Many receivers designed for RS-232 are sensitive
to differentials of 1v or less.
This can cause problems when using pin powered widgets - line drivers,
converters, modems etc. These type of units need enough voltage & current to
power them self's up. Typical URART (the RS-232 I/O chip) allows up to 50ma
per output pin - so if the device needs 70ma to run we would need to use at least 2
pins for power. Some devices are very efficient and only require one pin (some
times the Transmit or DTR pin) to be high - in the "SPACE" state while idle.
An RS-232 port can supply only limited power to another device. The number of
output lines, the type of interface driver IC, and the state of the output lines are
important considerations.
The types of driver ICs used in serial ports can be divided into three general
categories:
31
32. • Drivers which require plus (+) and minus (-) voltage power supplies such
as the 1488 series of interface integrated circuits. (Most desktop and tower
PCs use this type of driver.)
• Low power drivers which require one +5 volt power supply. This type of
driver has an internal charge pump for voltage conversion. (Many
industrial microprocessor controls use this type of driver.)
• Low voltage (3.3 v) and low power drivers which meet the EIA-562
Standard. (Used on notebooks and laptops.)
Data is transmitted and received on pins 2 and 3 respectively. Data Set Ready
(DSR) is an indication from the Data Set (i.e., the modem or DSU/CSU) that it is
on. Similarly, DTR indicates to the Data Set that the DTE is on. Data Carrier
Detect (DCD) indicates that a good carrier is being received from the remote
modem.
Pins 4 RTS (Request To Send - from the transmitting computer) and 5 CTS (Clear
To Send - from the Data set) are used to control. In most Asynchronous situations,
RTS and CTS are constantly on throughout the communication session. However
where the DTE is connected to a multipoint line, RTS is used to turn carrier on
the modem on and off. On a multipoint line, it's imperative that only one station is
transmitting at a time (because they share the return phone pair). When a station
wants to transmit, it raises RTS. The modem turns on carrier, typically waits a
few milliseconds for carrier to stabilize, and then raises CTS. The DTE transmits
when it sees CTS up. When the station has finished its transmission, it drops RTS
and the modem drops CTS and carrier together.
Clock signals (pins 15, 17, & 24) are only used for synchronous communications.
The modem or DSU extracts the clock from the data stream and provides a steady
clock signal to the DTE. Note that the transmit and receive clock signals do not
have to be the same, or even at the same baud rate. that the RS232 signal may be
transmitted/received may be dramatically reduced. RS-232 is simple,
universal, well understood and supported but it has some serious
shortcomings as a data interface. The standards to 256kbps or less and line
lengths of 15M (50 ft) or less but today we see high speed ports on our home
PC running very high speeds and with high quality cable maxim distance has
increased greatly. The rule of thumb for the length a data cable depends on
speed of the data, quality of the cable.
32
34. PROGRAMMING LOGIC:
C PROGRAM:
#include <graphics.h>
#include <stdlib.h>
#include <conio.h>
#include <time.h>
#include <stdio.h>
#include <dos.h>
#include <bios.h>
#define COM1 0
#define COM_INIT 0
#define COM_SEND 1
#define COM_RECEIVE 2
#define COM_STATUS 3
static unsigned int data[]={18,81,34,102,23,56,78,24,0xff};
//array for set value
static unsigned int data21[]={0x0,0x0,0x0,0x0,0x0,0x0};
// o/p from embedded
int i;
short int data1;
34
35. unsigned char z,c;
void main()
{
int graphdriver = DETECT;
int graphmode=1 ;
initgraph (&graphdriver,&graphmode,"e:TCBGI");
clearviewport();
settextstyle(TRIPLEX_FONT,HORIZ_DIR,5);
setcolor(12);
outtextxy(45,90," AUTOMATIC SWITCH OVER ");
outtextxy(70,210," OF LINK ");
getch();
clearviewport();
settextstyle(TRIPLEX_FONT,HORIZ_DIR,3);
setcolor(13);
outtextxy(100,70,"P R O J E C T ");
outtextxy(100,100," BY ");
outtextxy(100,130,"Miss ANUBHA BHIMSARIA ");
outtextxy(100,160,"Miss SNEHAL KARPE");
outtextxy(100,190,"Miss SHREYA CHAKRABARTI");
35
44. SOFTWARE DESCRIPTION:
• “intigraph”:
It is placed under the library GRAPHICS.h. It is used to initialize the
graphics system by loading the graphics driver from the disk(or validating
the registerd driver), thus putting the system into graphics mode.It also
resets all graphics settings.
• “closegraph”:
It shuts down the graphics mode and restore the screen in to the mode it
was before “intigraph”.The “closegraph” deallocates all the memory
allocated by the graph system.
• “setviewport”:
It sets the current viewport of the graphics output.The viewport corners all
absolute screen co-ordinates by(left,top) and (right,bottom).In addition to
a clip parameter is provided to determine whether the drawings are clipped
at the current viewpoint boundries.If clip is non-zero, all drawings will be
clipped to the current viewport.
• “clearviewport”:
It clears the current viewport.It erases the viewport and moves the current
position(CP) to home(0,0) relative to the viewport.
• “setcolor” & “getcolor”:
“setcolor” sets the current drawing color while “getcolor” returns the
current drawing color.By selecting a drawing color one can pass either the
color number or the eqvivalent color name.
44
45. • “gotoxy”:
“gotoxy” moves the cursor o the given position in the current text
window.If the co-ordinates are invalid the call to the gotoxy is ignored.
• “inport” “inportb”, “outport”, “outportb”:
“inport” reads a word from a hardware port.
“inportb” reads a byte from a hardware port.
“outport” outputs a word to hardware port.
“outportb” outputs a byte to hardware port.
• “outtext”, “outtextxy”:
“outtext” displays a string in the viewport(graphics mode).
“outtextxy” displays a string at the specific location(graphics mode).
• getch”, “getche”:
“getch” gets a character from console but does not echo to the screen.
“getche”gets a character from console and echoes to the screen.
45
46. MICROCONTROLLER PROGRAM:
_x0 bit p1.4
_x1 bit p1.5
_x2 bit p1.6
_x3 bit p1.7
_a bit p1.0
_b bit p1.1
_c bit p1.2
_stc bit p1.3
; PCON = 0x0 ;
mov PCON,#0;
; SCON = 0x50 ;
mov SCON,#50H;
; TMOD = 0x20 ;
mov TMOD,#20H
; TCON = 0x40 ;
mov TCON,#40H
; TH1 = 0xfd ;
46
57. djnz r1,backk1
ljmp back
delay_ms:mov r3,a
bq3: mov r4,#2
bq2: mov r7,#ffh
bq1: djnz r7,bq1
djnz r4,bq2
djnz r3,bq3
ret
getchar:
jnb ri,getchar
mov a,sbuf
clr ri
ret
trans:
mov sbuf ,a
back: jnb ti,back
clr ti
ret
57
58. FLOWCHART/ALGORITHM:
(PC)
START
INITIATE SERIAL COMMUNICATION
COMPORT AT 9600 BAUD RATE.
ENABLE TX/RX
SET VALUES OF NETWORK SWITCH
STATUS
TRANSMIT USING COMPORT ALL THE
VALUES OF SET NETWORK PARAMETER
READ STATUS OF THE SWITCH USING
RS232 STANDARD PROTOCOL
DISPLAY THE STATUS OF THE SWITCH.
STOP
58
59. FLOWCHART/ALGORITHM:
(MICROCONTROLLER)
START
INITIATE TIMER1
INITIATE SERIAL COMMUNICATION AT 9600 BAUD
RATE, 1 STOP, 1 START, 8 BIT DATA FORMAT.
READ DATA FROM THE PC H/W i.e SET VALUES
READ PARAMETERS VALUE DFROM THE NETWORK
COMPARE WITH THE SET VALUES
ACTIVATE STANDBY NETWORK IN CASE OF A
FAILURE.
REPEAT FOR ALL NETWORK LINKS
STOP
59
60. PROJECT ADVANTAGES AND DISADVANTAGES
ADVANTAGES:
• It is very useful in real-time applications such as ATM services and in
share trading where a delay of even few seconds can cause huge revenue
losses.
• It can be used by service engineers for maintenance purposes.
• It allows a fast switchover than manual.
• Since the process is very fast customers are not left in inconvenience for a
long time.
• Customer inconvenience is avoided and they get better service.
DISADVANTAGES:
• The device requires DC power supply so in case of failure of the DC
power supply the system will fail, even when there is no failure of the
links.
• Automatic switchover will not take place in case there is a failure at the
main base stations they will need manual attention.
• It does not give us the exact location where the failure has occurred the
faults can be detected only through the OMC.
60
61. CONCLUSION:-
• Thus it is concluded that the present MTNL system used for switching
can be improved by using the AUTOMATIC SWITCHOVER OF E1
LINK system.
• It can also be concluded that it is comparatively a low cost project as
compared to its huge advantages and the very low amount of
inconvenience it will cause to the service engineers as well as the
customers.
61
62. FUTURE SCOPE:-
• Although this is an external portable device, it can be built in the RF
tester unit.
• This increases the flexibility and efficiency of the system as the inbuilt
RF tester unit does not need to be connected externally, as well our
device requires very less space in the system.
62
63. BIBLIOGRAPHY:-
• Wireless communication-By Theodore S.Rappaport
• Data Communication and Networking-By Frouzan
• Google and Yahoo search engines
• MTNL research papers
• ATMEL and other datasheets for the IC information.
63
