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

The area that the signal spreads out into is called the Fresnel zone (pronounced fra-nell). If this gain is compared with an isotropic (no gain) radiator. If there is an obstacle in the Fresnel zone. But the energy of radio waves is not ―pencil thin. unless something refracts or reflects them. Since it is a power level. part of the radio signal will be diffracted or bent away from the straight-line path. it is measured in dBd. this refraction will reduce the amount of RF energy reaching the receive antenna. Figure 2. The thickness or radius of the Fresnel zone depends on the frequency of the signal — the higher the frequency. Note that gain applies to both transmit and receive signals. the result is measured in www.3 illustrates how the Fresnel zone is fattest in the middle. 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. Antennas achieve gain simply by focusing RF energy. As with FSL. the smaller the Fresnel zone. Antenna Gain Antenna gain is the ratio of how much an antenna boosts the RF signal over a specified low-gain radiator.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. the antennas used have no effect on the Fresnel zone. Feedback Alarm and Its Troubleshooting For Improvement of Microwave Link Figure 2. Figure 2. it is measured in dBi.[6] Transmit Power The transmit power is the RF power coming out of the antenna port of a transmitter. 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.‖ They spread out the farther they get from the radiating source — like ripples from a rock thrown into a pond. It is equal to the sum of the transmit power into the antenna (in dBm) added to the dBi gain of the 17 | Page . It is measured in dBm.iosrjournals. If the gain is measured against a standard dipole antenna. The practical effect is that on a point-to-point radio link. Watts or milliWatts and does not include the signal loss of the coax cable or the gain of the antenna.2 – Free Space Loss (FSL) Fresnel Zone Radio waves travel in a straight line.

an RF path analysis should be done. SOM is also referred to as link margin or fade margin. but at least 60 percent of the first Fresnel zone clear of obstructions as well.5). In planning long-range microwave links where you are not sure that you have unobstructed line-of-site and clear Fresnel zone. Figure 2. But even if your Fresnel zone is partially blocked. since it does not show trees or buildings. But assuming that you do have clear line-of-site and 60 percent of the first Fresnel zone clear (or nearly clear). You could be wasting your time and money if you ignore Fresnel zone issues — or worse yet. the first thing to do is to verify that it will have not only clear line of sight. no line-of-site — and attempt to set up a link anyway. if one at all.iosrjournals. In other words. But these programs can only indicate for certain if a link will not work due to terrain obstruction. A clear path on paper is not a guarantee that your link will work. [9] First Step in Planning a Link Whether your link is point-to-point or point-to-multipoint. how can you know if you will have a good link or not? How much gain do your antennas need to have? Figure 18 | Page . There are many software packages available that have terrain data and can create a path profile from a set of latitude/longitude coordinates. 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. Figure 2.6 – 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 2.4 shows how +24 dBm of power (250 mW) can be ―boosted‖ to +48 dBm or 64 Watts of radiated power. SOM is the difference between the signal received and the radio’s specified receiver’s sensitivity.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. the more important this is.4 – Effective Isotropic Radiated Power (EIRP) Figure 2. provided that your system was designed to have a strong signal at the other end of the link. it is still possible to get a link. Feedback Alarm and Its Troubleshooting For Improvement of Microwave Link dBm. So even a ―clear‖ link might have 80-foot trees in the way that could block the signal. You will likely not have a reliable link. The longer the distance. If the Fresnel zone is blocked.

add the receiver antenna gain (24 dBi).4 GHz. To calculate SOM in the example.6 illustrates that weaker signals are larger negative numbers.7 illustrates a sample SOM calculation on a point-to-point link. Figure 2. Figure 2. The SNR is really the only thing receiver demodulators really care about. the received signal is –67 dBm and the receiver’s sensitivity is –90 dBm giving a theoretical SOM of 23 dB C. In this example. they will subtract (or add) to the main signal and cause the received signal to be weaker (or stronger) throughout the day. This gives you the effective isotropic radiated power[5. start with the transmit power (+24 dBm).e. and add the transmit antenna gain (24 dBi).FSL + RX Antenna Gain – Coax Cable Loss Compute the difference between the received signal and the radio’s receiver sensitivity to determine the SOM. subtract the coax cable loss (1 dB). Figure 2 . It presumes that the antennas are aimed at each other properly (i. the absolute level of the signal or noise is not critical. they are in each others’ main lobe). 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.7 Sample System Operating Margin (SOM) Calculation much coax cable loss is too much? If your link is at 2. Unless the noise floor is extremely high. should external amplifiers be used? Or given your fixed base station antenna with a pre-set gain. subtract the coax cable loss (1dB) and you get the signal reaching the receiver: RX Signal = EIRP . It also graphically shows how the SNR is computed.iosrjournals. 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. Then subtract the FSL (137 dB).. Feedback Alarm and Its Troubleshooting For Improvement of Microwave Link from the sky (sometimes called ducting).11]: EIRP = TX Power .Coax Cable Loss + TX Antenna Gain. 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. we can test various system designs and scenarios to see how much fade margin (or ―safety cushion‖) our link will theoretically 19 | Page .

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 . 3) Adding two cooling fan for avoiding the problem of high temperature. connecting the alarm cable to the auxiliary port of the 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. Feedback Alarm and Its Troubleshooting For Improvement of Microwave Link Figure 2. 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. To perform all this operation I am using 16 bit AVR & GSM modem.8 Power controlling unit 1) First sensing water drop on the surface of the IDU.9 Circuit Diagram of proposed system www. when AC power cutoff alarm cable send the signal to the auxiliary port of the IDU and the it will power ON the DG. 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.iosrjournals.

usually expressed as ten to a negative power.2) In this four alarms is generated. because many operators are using NEC equipment In microwave that’s why it will be helpful to all the operators. then there is Chance that the bit error rate will need to be considered. Acknowledgment And their troubleshooting Methods 1) Description(Figure 3. then the bit error rate will be very small . meaning that. a transmission might have a BER of 10 to the minus 6. but it will be helpful for nokia employee also for their troubleshooting method [4]. Flowchart for Reducing time of troubleshooting Figure:-3. the main aim of this flow chart is to reduce the call drops of any operators. Figure 3. out of 1.000 bits transmitted. one bit was in error. 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 21 | Page .possibly insignificant and having no noticeable effect on the overall system However if noise can be detected.1 shows the general flow chart. First stage (Start-A) are written to avoid the call drops.6] www. 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. near about four operators are dependent on TATA that’s why it is more useful for TATA. and if drop occurs how to overcome the drop within very small time spectrum. from second stage (A-End) if call drop occurs how to overcome that drop is mention.1 Flow chart of trouble shooting Method.iosrjournals.[5. Description of Acknowledgment.000. 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. Feedback Alarm and Its Troubleshooting For Improvement of Microwave Link III. B. which can be used for any equipment(Other then NEC) & for any operator(Other then TATA). For example. Performance Analysis A.

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. it generates early warning alarm and a increment of BER results in following alarms  Low BER  High BER  DEM Alarm Frame ID:.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.iosrjournals. it is notified that the continuous increment in BER creates complications in link. 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. At the starting stage of BER. Figure 3. LOF:-when there is any frame loss takes place then this alarm will appear.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. etc comes in between the two microwave of single link then this alarm will appear. disconnect power supply at one end and check the RX level at other end and vice 22 | Page .(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.This alarm is generated due to the increase in Bit Error Rate(BER). Feedback Alarm and Its Troubleshooting For Improvement of Microwave Link Early Warning:. Troubleshooting When all this alarm comes together then it means there is a major chance of power failure at far end. LOF(Loss Of frame):-when any tree. STM-1(1)(DMR):-when there is no transmission through optical port then this alarm will appear. 2) Description(Figure 3. TCN-RX LEV-15min:-when the RX level reduces from their limit after 15 mints this alarm will appear. 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 www. building. any other radio. in LOF when we transmit signal does not reach at the receiver end and return to the transmitter.

iosrjournals.1 shows the breakdown report of maintenance carried out at tata docomo Aurangabad. 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. DG can be control with IDU and troubleshooting time is reduced because system is work on SMS.9cm*18. Figure 3. easily available. cost is increased. no control of DG. D. no sms circuits into the new system. Report of Breakdown Maintenance Activity carried out Table 4. the report shows the details of 12 link failures and the details of date and time of link failure.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.7cm*6. 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.1 Breakdown Report Table 4.4 lacks 2.7cm*3.4cm 3 Total cost of link 2. when we reached the site and when site was restored.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. In each sites we can see the troubleshooting is done within 30 minutes.9cm*18.9 & 10. small size No power fluctuations. indicator to troubleshoot online www. And in 23 | Page . no problem of high temperature.7cm 48. power card faulty because of become faulty then we need to transfer all the heavy rain. 7 Disadvantages No cooling fans hence Temperature The size is big.3 Acknowledgment C. if equipment problem.

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