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IOSR Journal of Electronics and Communication Engineering (IOSR-JECE

e-ISSN: 2278-2834,p- ISSN: 2278-8735.Volume 9, Issue 2, Ver. VIII (Mar - Apr. 2014), PP 15-24

Feedback Alarm and Its Troubleshooting For Improvement of
Microwave Link
Mohd Aamirullah Inamdar and Dr.Sayyad Ajij D
Department of Electronics & Communication Engineering, MIT Aurangabad-431028.

Abstract: Initially NEC (Name of company) Microwave manufacturing, Japan is introduced briefly and then
various parameters to establish microwave link is discussed then proposed system is explained. The flow chart
to reduce the time of doing troubleshooting is explain. The main objective is to reduce the call drop of TATA
DOCOMO and to overcome the drop if occur within short duration of time. There exists limited literature on
NEC microwave, especially with regard to acknowledgments and troubleshooting. The working of NEC
microwave, classification & tools on the basis of the NEC equipment used in TATA DOCOMO & flow chart to
reduced the time is described. According to different types they produce different acknowledgment and
depending upon the acknowledgment the troubleshooting strategy changes.
Index Terms: Troubleshooting, O&M report, Acknowledgment,Proposed system

I. Introduction
A. Introduction

Today wireless technology is used in many applications well integrated into our everyday life. Planning a
good, stable and reliable microwave network can be quite challenging. Careful planning and detailed
analysis is required for a microwave radio system before the equipment can be installed. A poorly
designed path can result in periodic system outages, resulting in increased system latency, decreased
throughput, or worst case, a complete failure of the system. It is generally agreed that a microwave signal
is a signal whose fundamental frequency is between 300 MHz and 300 GHz (1 GHz = 109 Hz)[1,7].
In terms of wavelength, a microwave signal has a wavelength between 0.1 cm and 100 cm A The
waveguide is a hollow mechanical structure that permits propagation of microwave signals from one point to
another with the least possible loss. most commonly used waveguides are those having a rectangular form.
There are, however, a variety of rectangular waveguides, each being identified according to its internal
dimensions. Each type of waveguide allows microwave propagation within a particular frequency band [2].
Discussing all the acknowledgment present in working link of NEC microwave and there trouble shooting

B. Classification Of NEC Microwave:
1. SDH(Synchronous Digital Hierarchy)
2. PDH (Plesuchronous Digital Hierarchy)
SDH: Pasolink+ STM1, Pasolink Neoi
PDH: Pasolink CPV, Pasolink V4.

C. Tools:
The following tools are used in NEC Microwave
1) Software Tools
2) Hardware Tools 15 | Page

The PNMSj is used for the observation of all the types of NEC microwave from the 16 | Page . At the receive end. Figure 2. Note that the difference in FSL between a 15 GHz link and a 18 GHz link is always about 1 dB. Free space loss (FSL). Figure 2. The details are as follows. the receiver demodulate the received signal and decode it and generate the original message. modulate the signal and then over the channel. the details are as follows  IDU  ODU  Antenna IDU (In door Unit):-It is used for the assigning the frequency. ODU (Out Door Unit):-It is used for the allowing the different frequency and power for getting the maximum receiving power. The Transmitter is basically responsible for encoding the message and then this encoded message is multiplied by carrier frequency i. regardless of the distance. It is of two types upper band & lower band. the upper band is having more TX frequency then the TX of lower and the RX of upper is the TX of lower and vice versa. II. LCT for STD is used for commissioning of NEOi IDU and LCT for CPV is used for commissioning of NEO/ic IDU. Minimal distortion at the receiver end is referred as a good communication property [3]. www. measured in dB.2 shows the formula to calculate FSL and what the theoretical loss would be at sample distances. Free Space Loss As signals spread out from a radiating source.e. As this occurs. power to ODU for microwave link. since at any appreciable distance all antennas look like a point source radiator. Working Principle: The Transmitter converts the source message into an electrical signal.  PNMT  PNMTj  LCT for STD  LCT for CPV  PNMSj The PNMT is used for the commissioning of Passo+/Passo V4 IDU.1 working of NEC microwave B. It is also used for observing the alarms in working Link. 2)Hardware Tools:-Three hardware are used in this. System Modeling A. the strength of that signal gets weaker. Microwave radio Link Design Following parameters should be considered for planning microwave radio link[11]. and specifies how much the signal has weakened over a given distance. Feedback Alarm and Its Troubleshooting For Improvement of Microwave Link 1)Software Tools:. PNMTj is used for observing the alarms of NEOi/Neo/ic in working link. The type of antenna used has no effect on FSL.iosrjournals.Four software’s are used for commissioning of different types of NEC microwave and one software is used for observing all the sites from the server. Antenna:-It act as transmitter which can transmit and receive the microwave signals. the energy is spread out over a larger surface area.

Antennas achieve gain simply by focusing RF energy. The area that the signal spreads out into is called the Fresnel zone (pronounced fra-nell). Effective Isotropic Radiated Power Effective isotropic radiated power (EIRP) is the actual RF power as measured in the main lobe (or focal point) of an antenna. As with FSL.3 – Fresnel Zone Receive Signal Level Receive signal level is the actual received signal level (usually measured in negative dBm) presented to the antenna port of a radio receiver from a remote transmitter. If there is an obstacle in the Fresnel zone.2 – Free Space Loss (FSL) Fresnel Zone Radio waves travel in a straight line. Figure 2. If this gain is compared with an isotropic (no gain) radiator. If the gain is measured against a standard dipole antenna. Receiver Sensitivity Receiver sensitivity is the weakest RF signal level (usually measured in negative dBm) that a radio needs receive in order to demodulate and decode a packet of data without errors. Since it is a power level. Feedback Alarm and Its Troubleshooting For Improvement of Microwave Link Figure 2.3 illustrates how the Fresnel zone is fattest in the middle. the smaller the Fresnel zone. It is measured in dBm. part of the radio signal will be diffracted or bent away from the straight-line path. It is equal to the sum of the transmit power into the antenna (in dBm) added to the dBi gain of the 17 | Page . The thickness or radius of the Fresnel zone depends on the frequency of the signal — the higher the frequency. Figure 2. this refraction will reduce the amount of RF energy reaching the receive antenna. the result is measured in www. Watts or milliWatts and does not include the signal loss of the coax cable or the gain of the antenna. Antenna Gain Antenna gain is the ratio of how much an antenna boosts the RF signal over a specified low-gain radiator.‖ They spread out the farther they get from the radiating source — like ripples from a rock thrown into a pond.iosrjournals. it is measured in dBi. it is measured in dBd. The practical effect is that on a point-to-point radio link. But the energy of radio waves is not ―pencil thin. unless something refracts or reflects them. Note that gain applies to both transmit and receive signals.[6] Transmit Power The transmit power is the RF power coming out of the antenna port of a transmitter. the antennas used have no effect on the Fresnel zone.

org 18 | Page .6 – Signal-to-Noise Ratio (SNR) System Operating Margin System operating margin (SOM) is the difference (measured in dB) between the nominal signal level received at one end of a radio link and the signal level required by that radio to assure that a packet of data is decoded without error (see Figure 2. So even a ―clear‖ link might have 80-foot trees in the way that could block the signal. SOM is the difference between the signal received and the radio’s specified receiver’s sensitivity. Feedback Alarm and Its Troubleshooting For Improvement of Microwave Link dBm. But even if your Fresnel zone is partially blocked. but at least 60 percent of the first Fresnel zone clear of obstructions as well. Figure 2. if one at all. The longer the distance. Figure 2.4 – Effective Isotropic Radiated Power (EIRP) Figure 2. how can you know if you will have a good link or not? How much gain do your antennas need to have? Figure 2. since it does not show trees or buildings. In other words. no line-of-site — and attempt to set up a link anyway. then you will get a lower signal level on the distant end than expected — even if you can literally ―see‖ the other antenna in the distance. SOM is also referred to as link margin or fade margin. You will likely not have a reliable link.5 – System Operating Margin (SOM) Multipath Interference When signals arrive at a remote antenna after being reflected off the ground or refracted back to earth www. A clear path on paper is not a guarantee that your link will work. the first thing to do is to verify that it will have not only clear line of sight.5). the more important this is. an RF path analysis should be done. it is still possible to get a link. If the Fresnel zone is blocked. provided that your system was designed to have a strong signal at the other end of the link. You could be wasting your time and money if you ignore Fresnel zone issues — or worse yet. [9] First Step in Planning a Link Whether your link is point-to-point or point-to-multipoint.4 shows how +24 dBm of power (250 mW) can be ―boosted‖ to +48 dBm or 64 Watts of radiated power.iosrjournals. There are many software packages available that have terrain data and can create a path profile from a set of latitude/longitude coordinates. But these programs can only indicate for certain if a link will not work due to terrain obstruction. In planning long-range microwave links where you are not sure that you have unobstructed line-of-site and clear Fresnel zone. But assuming that you do have clear line-of-site and 60 percent of the first Fresnel zone clear (or nearly clear).

FSL + RX Antenna Gain – Coax Cable Loss Compute the difference between the received signal and the radio’s receiver sensitivity to determine the SOM. we can test various system designs and scenarios to see how much fade margin (or ―safety cushion‖) our link will theoretically have. subtract the coax cable loss (1 dB). It also graphically shows how the SNR is computed. Then subtract the FSL (137 dB). To calculate SOM in the example. and add the transmit antenna gain (24 dBi). Figure 2 . they will subtract (or add) to the main signal and cause the received signal to be weaker (or stronger) throughout the day. Figure 2.e. start with the transmit power (+24 dBm).org 19 | Page . The SNR is really the only thing receiver demodulators really care about. add the receiver antenna gain (24 dBi).6 illustrates that weaker signals are larger negative numbers. Feedback Alarm and Its Troubleshooting For Improvement of Microwave Link from the sky (sometimes called ducting). the absolute level of the signal or noise is not critical..11]: EIRP = TX Power . Signal-to-Noise Ratio Signal-to-noise ratio (SNR) is the ratio (usually measured in dB) between the signal level received and the noise floor level for that particular signal. should external amplifiers be used? Or given your fixed base station antenna with a pre-set gain. Unless the noise floor is extremely high. Proposed system 1) Controlling power of IDU by sensing water drop 2) Control of Diesel Generator(DG) by using auxiliary port of IDU 3) Adding cooling fan 4) Status of alarms on Mobile by sending SMS 1) Block Diagram of controlling power of IDU www. subtract the coax cable loss (1dB) and you get the signal reaching the receiver: RX Signal = EIRP .4 GHz. In this example.iosrjournals. This gives you the effective isotropic radiated power[5.7 Sample System Operating Margin (SOM) Calculation much coax cable loss is too much? If your link is at 2. the received signal is –67 dBm and the receiver’s sensitivity is –90 dBm giving a theoretical SOM of 23 dB C. they are in each others’ main lobe). Figure 2. how far can you reach with the different types of client antennas? And which clients will need amplification? Why Perform an SOM Calculation? By doing an SOM calculation. It presumes that the antennas are aimed at each other properly (i.Coax Cable Loss + TX Antenna Gain.7 illustrates a sample SOM calculation on a point-to-point link.

iosrjournals. 3) Adding two cooling fan for avoiding the problem of high temperature.8 Power controlling unit 1) First sensing water drop on the surface of the IDU. connecting the alarm cable to the auxiliary port of the IDU. when AC power cutoff alarm cable send the signal to the auxiliary port of the IDU and the it will power ON the DG. the output of the water drop sensor is connected to the relay as a input. and power of IDU is connected to IDU through relay (NC terminal) and RC 20 | Page . To perform all this operation I am using 16 bit AVR & GSM modem. thus when water falls on the surface of the sensor it gives input to the relay hence coil of relay becomes active and it power off the IDU. Figure 2.9 Circuit Diagram of proposed system www. Feedback Alarm and Its Troubleshooting For Improvement of Microwave Link Figure 2. when water drop sensor sense water is not falling it does not gives any output and hence relays NC terminal becomes active and hence 2) Control of Diesel Generator by using auxiliary port of IDU. 4) Which alarms are generate are send on mobile to take the design of which troubleshooting methods to be used for it to take action fast against it to reduced the troubleshooting time.

because many operators are using NEC equipment In microwave that’s why it will be helpful to all the operators. First stage (Start-A) are written to avoid the call drops. then there is Chance that the bit error rate will need to be considered. a transmission might have a BER of 10 to the minus 6.1 shows the general flow chart. B. Flowchart for Reducing time of troubleshooting Figure:-3. out of 1.1 Flow chart of trouble shooting Method.[5. The following no of operators are using NEC  TATA DOCOMO  Reliance  Idea  Airtel  Aircel Only Vodafone and BSNL is not using this equipment they are using NOKIA.000. Acknowledgment And their troubleshooting Methods 1) Description(Figure 3. For example. one bit was in 21 | Page . Figure 3. usually expressed as ten to a negative power. the main aim of this flow chart is to reduce the call drops of any operators.2) In this four alarms is generated. Feedback Alarm and Its Troubleshooting For Improvement of Microwave Link III. then the bit error rate will be very small .6] www. The definition of bit error rate can be translated into a simple formula: BER = number of errors / total number of bits sent If the medium between the transmitter and receiver is good and the signal to noise ratio is high.iosrjournals.000 bits transmitted. details are as follows a) EARLY WARNING b) FRAME ID c) LOF d) HIGH BER Bit Error Rate (BER) is the percentage of bits that have errors relative to the total number of bits received in a transmission. but it will be helpful for nokia employee also for their troubleshooting method [4]. near about four operators are dependent on TATA that’s why it is more useful for TATA. meaning that. and if drop occurs how to overcome the drop within very small time spectrum. which can be used for any equipment(Other then NEC) & for any operator(Other then TATA). Description of Acknowledgment. from second stage (A-End) if call drop occurs how to overcome that drop is mention. Performance Analysis A.possibly insignificant and having no noticeable effect on the overall system However if noise can be detected.

in LOF when we transmit signal does not reach at the receiver end and return to the transmitter. The power failure may occurs due to following reasons  MCB Trip  NO Power Supply  IDU Faulty If MCB is Trip:-Then either change the MCB or repair the MCB If No power Supply:-Make the arrangement of power supply 22 | Page . LOF(Loss Of frame):-when any tree. any other radio.3) In this following alarm are observed a) RX Level b) LOF c) STM-1(1)(DMR) d) TCN-RX LEV-15min RX Level:-This alarm is generated when receiving level decreases from its limit. High BER:-when signal to noise ratio decreases it tends to increase in BER and due to increase in bit error rate high BER is generated. disconnect power supply at one end and check the RX level at other end and vice versa. it generates early warning alarm and a increment of BER results in following alarms  Low BER  High BER  DEM Alarm Frame ID:. At the starting stage of BER. Feedback Alarm and Its Troubleshooting For Improvement of Microwave Link Early Warning:. 2) Description(Figure 3. it is notified that the continuous increment in BER creates complications in link. Figure 3. LOF:-when there is any frame loss takes place then this alarm will appear. building.This alarm is generated due to the increase in Bit Error Rate(BER).2 Acknowledgment 1 Troubleshooting When all this alarm comes together then it means there is a major chance of interference or misalignment (To check whether interference exist or not. Troubleshooting When all this alarm comes together then it means there is a major chance of power failure at far end.iosrjournals. STM-1(1)(DMR):-when there is no transmission through optical port then this alarm will appear.(It is the application which is inserted by NEC to avoid the interference in between the two link) This alarm is generated when there is mismatch of frame ID between the two sites of single link. etc comes in between the two microwave of single link then this alarm will appear. if RX level is coming in the range of -99 to -80 dbm at both the end then there is no interference) If Interference:-we need to change the frequency & frame ID at both the end If misalignment:-We need to make the proper alignment at both the ends. TCN-RX LEV-15min:-when the RX level reduces from their limit after 15 mints this alarm will appear.

no control of DG.4 lacks 23 | Page .11 the same link failures occurs two time to avoid this proposed system is developed and I am sure if we used the proposed system then the numbers of breakdown will be reduced. Report of Breakdown Maintenance Activity carried out Table 4. D. In each sites we can see the troubleshooting is done within 30 minutes. the report shows the details of 12 link failures and the details of date and time of link failure. Feedback Alarm and Its Troubleshooting For Improvement of Microwave Link If IDU faulty:-please check the power card if not working change the power card and if it may creating problem the changed the complete IDU. no problem of high temperature. And in SrNo:8. Figure 3. 7 Disadvantages No cooling fans hence Temperature The size is big. easily available.1 Breakdown Report Table 4.7cm*6.7cm 48. DG can be control with IDU and troubleshooting time is reduced because system is work on SMS. cost is increased. small size No power fluctuations.9cm*18. no sms circuits into the new system.1 shows the breakdown report of maintenance carried out at tata docomo Aurangabad.9 & 10. when we reached the site and when site was restored. if equipment problem. power card faulty because of become faulty then we need to transfer all the heavy rain.5 lacks 4 Troubleshooting time Larger then proposed system Less then the existing system 5 Availability Easily available in market Need to manufacture 6 Advantages Low price.7cm*3.3 Acknowledgment C.iosrjournals. Comparison of existing system and proposed system Sr No Existing system Proposed system Parameters 1 Cost of single IDU 25000 30000 2 L*H*B 48.4cm 3 Total cost of link 2. indicator to troubleshoot online www.9cm*18.

[6]. Prentice. Feedback Alarm and Its Troubleshooting For Improvement of Microwave Link IV. Molinaro. April 2003. ―Tools For Microwave Radio Communications System Design‖.Hall. Practical telecommunications and wireless communications for business AvEdwin Wright. Md. ―Fundamentals of Radio Link Engineering‖. by providing the proper troubleshooting command action with respective to the feedback error signal. [3]. McGraw-Hill [7]. Due to minimization of microwave error signal we can improve the quality of microwave signal and reducing the call dropping between caller and callee. Telecom Regulatory Authority of India. “Wireless Communications & Networks”. Frank Jimene. Carlos Evangelista. www. we have reduced the microwave acknowledgement with the particular alarm at particular frame. References [1]. [10]. Deon Reynders [Online Book].org 24 | Page . L Bermudez.iosrjournals.ydi. William Stalling. [2].2005 [8]. 1999. [5]. F. Website of NEC www. Paulo Carvalho. 2nd ed. Rakib Al Mahmud. Abdullah Jr. J. May 2010. Microwave Engineering. H. Website of ceragaon [11]. [9]. Conclusion By the sanctity of caller and callee voice information. ―Analysis And Planning Microwave Link To Established Efficient Wireless Communications‖. ―Basic Path Considerations For A Microwave Link‖. EM Clarity White Paper. Japan. [4]. September 2009. 1957. Luis. Sanjeeva Gupta.