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Continental J. Engineering Sciences 7 (1): 24 - 35, 2012 ISSN: 2141 – 4068 © Wilolud Journals, 2012 http://www.wiloludjournal.com Printed in Nigeria doi:10.5707/cjengsci.2012.7.1.24.35

SPECTRUM PLANNING, MANAGEMENT AND MONITORING IN NIGERIA TELECOMMUNICATION INDUSTRY (RADIO AND TELEVISION)

Kamalu U.A., Dike J.N. and Anyakora N.N. Department of Electrical/Electronic Engineering, University of Portharcourt, Reiver State, Nigeria

ABSTRACT In Nigeria, analogue television broadcasting is carried out in the VHF and the UHF bands. The VHF band has 12 channels while the UHF has 49 channels, both totaling 61 channels. The National Television Authority, NTA, which is the national television broadcasting carrier, operates mostly in the VHF with at least one television broadcasting station in each of the 36 States and the nation’s capital city. In addition to the spectrum demand, each State has its own television broadcasting station vis-à-vis the numerous cable television existing in the country. Hence, availability of sufficient spectrum to satisfy the ever-increasing demand is a big issue in the analogue domain. However, spectrum management in radio and television is less stringent with good planning and monitoring of frequency in radio and television broadcasting since each of the television channels carrying only one analogue television program will be capable of supporting more than one program. Considering the importance of radio and television communication, it is important to discuss the present usage of the radio and television broadcast spectrum and the savings in spectrum expected. One important benefit planning, management and monitoring is spectrum use efficiency. This paper reviews the limitations and problems of terrestrial analogue television and radio broadcasting in respect of spectrum; and the benefits that emerges from good spectrum planning through allocation of different transmit powers and antenna heights. KEYWORDS: Television, Radio, Spectrum, Management, frequency.

INTRODUCTION Electromagnetic spectrum is the frequency and wavelength of electromagnetic radiation. It is a unique natural resource shared by various types of services which is free from depletion but subject to congestion through use. If left unplanned, spectrum congestion can lead to harmful interference and hinder users from getting the best these services have to offer. Different spectrum bands offer different physical characteristics. Higher frequencies do not carry signals as far and do not penetrate buildings as easily, and lower frequencies have capacity limitations and create more interference. The UHF spectrum is particularly attractive because it is located between 200MHz and 1GHz offering an optimal balance between transmission capacity and distance coverage, [CEC, 2007]. New services competing for the VHF and UHF band include mobile television, digital television, and wireless broadband and enhanced phone services. The need to accommodate an ever-increasing number of users and offer bandwidth-rich applications using a limited spectrum challenges the system designer to continuously search for solutions that use the spectrum more efficiently. The transmission of signals in space as applicable to radio and television brings to mind the role of electromagnetism. Radio and television broadcast involves electromagnetic wave propagation; the phenomenon of electromagnetic energy propagating in the form of waves of the coupled electric and magnetic field intensity vectors. In Nigeria, the VHF and UHF frequency bands of the electromagnetic spectrum are mainly occupied by television services, while radio broadcasting is transmitted in the low frequency, medium frequency and high frequency bands. Presently, television broadcasting is analogue however; the government has announced a deadline of 2012 for the transition to digital. The released spectrum is known as the “digital dividend”. The digital dividend is a unique opportunity to meet the fast growing demand for wireless communication services. However, its benefit can only be fully reaped if proper planning is made, ahead of time, for the use of the

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Kamalu U.A et al.,: Continental J. Engineering Sciences 7 (1): 24 - 35, 2012 released spectrum. Due to the increase in spectrum congestion and the high field strength required for television reception, radio and television broadcast network planning is more challenging than analogue television transmission broadcast. This means that the impact on existing analogue services needs to be closely examined. Therefore, it is important to manage the allocated spectrum for these services to ensure that radio and television broadcast stations do not interfere in signal transmission since the allocated operating frequencies of these broadcast stations lie very close to each other within a given area of coverage. This paper discusses the present usage of the radio and television spectrum band by analogue television services in Nigeria. It estimates the dividend resulting from planning, monitoring and management of the available spectrum. Specifically, this paper will:

(1) Analyze the allocation of frequencies to radio and television stations in Nigeria (2) Determine the transmit power, transmitting antenna heights of the radio and television stations in

Nigeria. (3) Solve the problem of signal interference in both radio and television broadcast in Nigeria through the

use of differences in transmit power and antenna heights. RADIO SPECTRUM Radio waves have the longest wavelengths in the electromagnetic spectrum. These waves can be longer than a football field or as short as a football. Radio waves do more than just bring music to your radio. They also carry signals for your television and cellular phones. The antennae on your television set receive the signal, in the form of electromagnetic waves, which is broadcasted from the television station. It is displayed on your television screen. Because radio waves are larger than optical waves, radio telescopes work differently than telescopes that we use for visible light (optical telescopes). Radio telescopes are dishes made out of conducting metal that reflect radio waves to a focus point. Because the wavelengths of radio light are so large, a radio telescope must be physically larger than an optical telescope to be able to make images of comparable clarity. For example, the NTA radio telescope, which has a dish 64 meters wide, cannot give us any clearer an image than a small backyard telescope! In order to make better and more clear (or higher resolution) radio images, radio astronomers often combine several smaller telescopes, or receiving dishes, into an array. Together, the dishes can act as one large telescope whose size equals the total area occupied by the array [Burns et al, 2004]. The radio spectrum lies at the lower end of the electromagnetic spectrum, which includes other categories of electromagnetic radiation such as infra-red, optical light and ultra-violet (see Figure 1). Electromagnetic waves are characterised by either: • Frequency, i.e. the number of sinusoidal oscillations, or “cycles” per second, usually specified in Hertz (Hz)

where 1 Hz = 1 cycle per second, or • Wavelength, i.e. the distance traversed by 1 cycle of a electromagnetic wave in free space (all

electromagnetic radiation travels at a constant speed of 300,000 km/sec in free space)[Burns et al, 2004] •

Figure 1: The Electromagnetic Spectrum

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Kamalu U.A et al.,: Continental J. Engineering Sciences 7 (1): 24 - 35, 2012 REVIEW OF THE EXISTENCE OF RADIO AND TELEVISION IN NIGERIA The radio spectrum is generally considered to lie within the frequency range 3kHz to 3,000GHz, which corresponds to wavelengths between 100km and 0.1mm. Within this range, blocks of spectrum have been designated over the years for various applications, such as broadcasting, fixed or mobile communications. Note that frequencies above 300GHz are currently unallocated, largely due to the lack of current technology to harness such frequencies for effective radio communication. The radio spectrum is further sub-divided into the following categories, each of which has distinct characteristics that make it suitable for particular applications. RADIO Radio broadcasting began in Nigeria on December 19, 1932 when a medium frequency (MF) band repeater station of the British Broadcasting Corporation was set up in Lagos operating at 375kHz. To listen to radio, one had to subscribe, and be given a loudspeaker cabled right to the station and hung in the house. The excitement that greeted this rudimentary development was illustrated by the fact that within a year, subscribers to loudspeakers outnumbered the available loudspeakers [Ojebode and Akinleye, 2004]. And in 1933, radio broadcasting was introduced into Nigeria as a form of distribution system. The Post & Telegraph received and re- transmitted via the wire system of BBC News, which was later called Radio Diffusion system transmitting at 375 KHz. In 1939, a station was opened in Ibadan operating at 328kHz; Kano Station was commissioned in 1949 while between 1945 to 1949 radio stations and their operating frequencies had been opened in towns like Kaduna (301kHz), Enugu (325kHz), Abeokuta (388kHz), Ijebu-Ode (315kHz), Jos (426kHz), Zaria (355kHz), Calabar (405kHz) and Port-Harcourt (542kHz) as relay stations [Fadeyi, 2004]. The Nigerian Broadcasting Services (NBS) which was established on April 1, 1951, later transformed into the Nigerian Broadcasting Corporation (NBC), licensed by the Federal Ministry of Information under the NBC Act No. 39 of 1956 [Okpanachi, 2008. By 1st January, 1962, Voice of Nigeria (VON) was launched as the International Service of Radio Nigeria covering West Africa, East Central & Southern Africa, North Africa & other parts of the world. VON was later excised from Radio Nigeria on January 5, 1990. The 1st FM in Nigeria was commissioned on April 22, 1977. It was known then as Radio Nigeria 2 (now Metro FM) (97.6MHz) [Okpanachi, 2008]. A year later when NBC was reorganised, the state stations were handed over to State Governments while NBC was left with only Lagos, Ibadan, Enugu & Kaduna which became Federal Radio Corporation of Nigeria (FRCN). In 2000, FRCN was directed by the Federal Government of Nigeria to operate FM Stations at various State capitals. Although, the Partial Commercialisation of FRCN came up in 1992 which means FRCN was to be free from government support with a take-off grant that would equip FRCN for commercialisation. Decree no. 38 of 1992 gave birth to National Broadcasting Commission, which regulates broadcasting in Nigeria. But before this time, the federal ministry of information with the assistance of the federal ministry of communication was allocating licenses and frequencies to the radio and television stations. With the deregulation of broadcasting in Nigeria, FRCN ceased to benefit from the monopoly of radio broadcasting. TELEVISION Television broadcasting in Nigeria started with the initiative of the first Western Region Premier, Chief Obafemi Awolowo who on October 31, 1959 launched television broadcasting at Ibadan the headquarters of the region to operate from channel 12 VHF. The western Region Government went into partnership with the Overseas Rediffusion Limited. The Western Nigeria Radiovision Service Limited was created with the responsibility of radio and television broadcasting under one management. A small transmitter of 500 watts power was mounted on Mapo Hill in Ibadan and another at Abafon near Ikorodu. The television (channel 10 VHF) was licensed by the Federal Ministry of Information to disseminate information and entertain viewers. The radio and TV stations in the Western Region pioneered commercial broadcasting in Nigeria to supplement government subvention.

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Kamalu U.A et al.,: Continental J. Engineering Sciences 7 (1): 24 - 35, 2012 In 1962, the Western region government took full control of the Western Nigeria Broadcasting Service/Western Nigeria TV by buying over all the shares held by the Overseas Rediffusion Ltd. In the same year, the Nigeria television Service was born in Lagos with the radio corporation of America (RCA) and the National Broadcasting Company International Limited managing the station. But the management was eventually handed over to Reverend Victor Badejo, who was then the acting Director General of the NBC as Nigerian Television Service NTS. The NTS later changed its name to NBC/TV [NBC, 2011]. Today, Nigeria has thirty six states with each aspiring to set up her own television station. The federal government is also making efforts to establish a branch of NTA in each state. In 1976, television stations started beaming colour programmes thus, however, opened in the history of TV broadcasting in Nigeria. The Federal Military Government of Nigeria under General Olusegun Obasanjo took over the television stations in Nigeria in 1978 and changed its name to Nigeria Television Authority (NTA) [Ndanusa, 2006]. All TV stations are made to beam network programmes. A new chapter was opened in the history of Nigeria broadcasting in 1992. The federal government under General Ibrahim Babangida deregulated the broadcast industry by granting license to private individuals and organizations to set up radio and television broadcasting stations. As at today, there are over thirty private owned stations. In 1992 the National Broadcasting Commission (NBC) was established to monitor and regulate broadcasting on a national basis. One goal of the organization is to open up the industry to the marketplace paradigm. Both foreign and domestic participation is sought [CBN, 2004]. There were two government controlled television broadcast stations in Nigeria in 1999 and fourteen licenses to operate private television stations. The nation has eighty two AM radio stations and thirty five FM stations. There are eleven short-wave stations in Nigeria. Throughout the country there are 23.5 million radios and 6.9 million television sets [Ojebode and Akinleye, 2004]. SPECTRUM PLANNING, MANAGEMENT AND MONITORING IN NIGERIA Planning for Spectrum Use, or simply Spectrum Planning, is done to ensure that the spectrum resource is used to the fullest extent possible. Spectrum managers need to take into account the changing needs of society and secure opportunities that match existing demands with new ones through innovative uses of technology. At the national level, plans and technical standards for spectrum use are created to ensure that applications of technology are done in a consistent manner and that interference is reduced to acceptable levels. This paper adopts the use of different transmit power and antenna heights for each operating radio and television broadcast station in minimizing signal interference. The radio spectrum for frequency modulation (FM) has a bandwidth of 20MHz (88MHz to 108MHz) of the planned spectrum [Gbenga-Ilori and Ibiyemi, 2010b]. At the regional and international level, agreements are formed amongst nations for spectrum use and technical specifications to aid coordination of services globally. Spectrum planning has the objective of forecasting future requirements of spectrum and methods for adjusting spectrum use over time. These planning activities result in spectrum use standards to establish the target map for future spectrum use and the paths taken to get there. For enhanced signal broadcast in Nigeria, while the Nigeria Broadcasting Commission allocates licences to radio and television stations, it is important to also allocate different antenna heights and transmit power. This difference in antenna heights and transmit power will indeed reduce the difference in received signal strength of a coverage area; its strict application shows that the problem of interference is minimized to the least [Gbenga-Ilori and Ibiyemi, 2010a]. Technical standards provide the rules of the road and govern which types of equipment can operate under specific operating conditions. Monitoring is the act of watching/listening to the activities of broadcast stations by officers of the NBC to ensure that what the stations do not go against the law. This is implemented through the monitoring officers across the country. Monitoring is therefore done to obtain detailed information on the technical or operational characteristics of radio systems. The spectrum manager will monitor radio equipment to determine conformity with applicable standards. This can be done as part of an equipment certification process where measurements can be taken and recorded and then used in analyzing the compatibility of radio systems -Electromagnetic Compatibility (EMC).

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Kamalu U.A et al.,: Continental J. Engineering Sciences 7 (1): 24 - 35, 2012

Figure 2: Transmit power Vs Antenna height of radio transmission in North Central

Figure 3: Transmit power Vs Antenna height of radio transmission in south south.

Figure 4: Transmit power Versus Antenna height of radio transmission in south west

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Kamalu U.A et al.,: Continental J. Engineering Sciences 7 (1): 24 - 35, 2012

Figure 5: Transmit power Versus Antenna height of radio transmission in south east

Figure 6: Transmit power Versus Antenna height of radio transmission in north east and north west

Figure 7: Transmit power versus frequency of radio transmission in north central

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Kamalu U.A et al.,: Continental J. Engineering Sciences 7 (1): 24 - 35, 2012

Figure 8: Transmit power versus frequency of radio transmission in south south

Figure 9: Transmit power versus frequency of radio transmission in south east

Figure 10: Transmit power versus frequency of radio transmission in Lagos state

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Kamalu U.A et al.,: Continental J. Engineering Sciences 7 (1): 24 - 35, 2012

Figure 11: Transmit power versus frequency of radio transmission in south west

Figure 12: Transmit power versus frequency of radio transmission in north east and north west

NUMBER OF TELEVISION STATIONS

0

1

2

3

4

5

6

7

8

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67

CHANNEL

NO

OF

TV

ST

AT

ION

S

NUMBER OF TELEVISIONSTATIONS

Figure 13: Present number of analogue terrestrial television stations in Nigeria

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Kamalu U.A et al.,: Continental J. Engineering Sciences 7 (1): 24 - 35, 2012

Figure 14: Channel versus Transmit frequency of terrestrial television stations in Nigeria

Minimizing Interference in Radio Broadcast in Nigeria The main motivation for managing radio spectrum has been interference oriented. To minimize interference across different applications, most frequency bands have in all countries been allocated to certain uses (e.g. aeronautical, maritime, defence, broadcasting, etc.). Much of spectrum management involves overseeing that frequencies are being used by the correct applications. Additionally, interference between different users within a frequency band also needs to be managed. Radio-based communications systems, unlike wired communications, involve signals being transmitted and received that travel at least a significant portion of their path in free space. This is clearly an essential characteristic in certain applications such as mobile phones, satellite communications, and broadcasting. The main disadvantage however is that transmission over free space means that stray signals from one radio communications system can easily interfere with the proper reception of another. Interference is unavoidable and ever present. The impact of excessive interference ranges from simple inconvenience to individual users to, on occasions, the undermining of the commercial viability of networks suffering interference. At the very extreme, it can have ‘safety of life’ implications, for example where radio systems used by the emergency services suffer interference. Furthermore radio signals do not respect national borders. Thus, if not properly managed, signals emanating from one country can unduly interfere with systems in other countries. Transmit Power The power of transmission of a radio transmitter is one of the factors that help to minimize interference in radio broadcast. It is usually made to be high enough to ‘push back’ the incoming signal from the next available radio transmitter, transmitting at a nearly same frequency. Figure 2 shows the transmit power and the transmitting antenna heights in the North central geographical zone of Nigeria. Radio stations broadcasting in this zone which have the same transmitting antenna heights are made to transmit at different transmit powers of 38.6dBm, 39.9dBm, 41.2dBm, 42.1dBm 42.3dBm, 43.1dBm, 43.2dBm, 43.6dBm and 44.0dBm and the radio broadcast stations made to be far from each other with different operating frequencies. Figure 3 is the transmit power distribution in the South South geographical zone in Nigeria. With a transmitting antenna height of 60 meters, the transmit powers are distributed such that the radio broadcast stations can transmit without interfering with the signals of each other and when they have the same antenna height of 45 meters the difference in the transmitter power will prevent the broadcast stations from interfering with each other. Figure 4 shows the variation in the transmit power and the transmitting antenna heights for radio broadcast stations in south west geographical zone of Nigeria. From the research conducted in the course of this paper, it is observed that Lagos state has the highest number of radio and television broadcast stations in the country, as such, emphasis is made on the frequency allocation; transmit power allocation and transmitting antenna heights. Most radio stations in this state has assigned frequencies very close to each other

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Kamalu U.A et al.,: Continental J. Engineering Sciences 7 (1): 24 - 35, 2012 as such there is high level of interference , so what can reduce the interference depends largely on the transmit power and the transmitting antenna heights. Figures 5 and 6 show the transmit powers and the transmitting antenna heights in the south east and north east and north west geographical zones of Nigeria. It is observed that these three zones have fewer number of radio broadcast stations as compared to south west. Therefore, there is less problem of interference, but the transmit powers are more widely spaced since few stations share the available spectrum. Frequency Allocation Difference in operating frequencies is another factor that makes radio stations not to interfere in signal transmission. Each radio broadcast station has a frequency assigned to it by the Nigeria broadcasting commission (NBC). Figure 7 shows the frequencies of transmission of radio broadcast stations in north central geographical zone in Nigeria. It can be seen that majority of the radio broadcast stations has frequencies between 92MHz and 102MHz even when the radio spectrum for frequency modulation is between 88MHz and 108MHz. To minimize the effect of interference, these broadcasts stations must be assigned different transmit powers which determine the areas of coverage each broadcast station can be received by the receivers. Figure 8 shows the frequency allocation in South South of Nigeria. In figure 8, two radio broadcast stations having the same transmit powers have frequencies of 95.5MHz and 96.1MHz, to ensure that there is less interference; there antenna heights are 45 meters and 60 meters respectively as shown in figure 3. Figures 9 and 10 show the frequency distribution of the different radio broadcast stations in the south east geographical zone of Nigeria and Lagos state. Lagos state has the highest density of broadcast stations in Nigeria, as such emphasis is laid on transmit power and antenna heights since some of the stations have frequencies very close to each other. It can be seen that majority of the broadcast stations has transmit powers of 42.1dBm, but varying operating frequencies. Figures 11 and 12 are the operating frequencies and the transmit powers of radio broadcast stations in south west and north east and north west respectively. The North East and North West have fewer radio broadcast stations, so it’s very easy to manage the allocation of operating frequencies to the broadcasters. In figure 12, it can be seen that the frequencies are sparsely distributed and even if they have the same transmit power, the level of interference is very much minimized unlike the case of south west in which their operating frequencies are close to each other. Minimizing Interference in Television Broadcast in Nigeria Transmitting Band Allocation Figure 13 shows the number of analogue television stations present in each VHF and UHF channel in Nigeria. The figure shows that channel 10 and channel 6 has the highest television stations nationwide. Also some stations has more than one channel, such as NTA Bauchi which has channels 5, 6 and 7 and NTA Lokoja which has channels 7, 8 and 37. These television stations must operate with distinct operating frequencies despite the use of the same channel of transmission. To ensure good picture quality during transmission of signals, it is imperative to assign different frequencies to the audio and video signals. For instance NTA Portharcourt has 210.25MHz for video and 215.75MHz for audio. It is believed that this practice can reduce the problem of raster and interference. Frequency and Channel Allocations The broadcasting organisation of Nigeria by its objective assigns frequencies and channels to all television stations in the country; it is observed that majority of the television stations lie in the VHF band as such their frequencies lie between 170MHz and 225MHz as shown in figure 14 The effect of this cluster of frequencies is indeed responsible to the high level of interference experienced in the country today. If some of these channels are allocated frequencies in the UHF band, the problem of interference will be very minimal using high transmitting power and increasing the height of the transmitting antennas in broadcasting. It is therefore important that frequency allocations should be spread evenly in the VHF and UHF bands since it will be the only means of spacing the frequencies of transmission. In figure 14, it can be seen that the television stations in the UHF band are well spaced because UHF has wider spectrum of allocation.

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Kamalu U.A et al.,: Continental J. Engineering Sciences 7 (1): 24 - 35, 2012 CONCLUSION Based on the review, it can be concluded that: The transmit power of each radio and television broadcast stations should be made high enough to ‘push-out’ all incoming signals from nearby broadcasting stations. The efficiency of a radio or television broadcast station depends largely on planning, monitoring and the management of the station. Nigeria being a country with geographical size of 923,768 square kilometers (both land and sea), will be difficult to implement a pure single frequency network (SFN). This is because the presence of SFN transmitters and gap-fillers produces a significantly more critical multipath propagation environment, introducing "artificial echoes" of high amplitude and long delay. These artificial echoes are superimposed on the natural echoes. The delay spread of the artificial echoes is proportional to the transmitter distance, and it is determined by the transmitter network geometry. RECOMMENDATION Based on the above results obtained, it can be observed that adequate planning and monitoring has the potential to adequately improve the efficiency of the radio and television broadcast stations in Nigeria as well as remove the problem of interference in broadcasting.

Deploying technologies in the radio spectrum is a complex decision that takes many different factors into account. Technology design, efficient use of bandwidth, availability of spectrum for alternative deployment options, the cost of acquiring spectrum, end-user demand, availability of receiver equipment, investment in infrastructure and many other technical and market conditions have to be examined to make an appropriate judgment. The scope for new services to be made available in many parts of the spectrum is exciting. But that adds to the challenges facing those responsible for national spectrum planning. Further research work could be aimed at reducing the effect of rain and atmospheric humidity. There should be incorporated the use of satellite communication in broadcasting. REFERENCES Akinleye, L. and Ojebode, A (2004): World communication and information imbalance: the domestic dimension of Topical issues in communication arts and sciences, II: 15-24 BON: Broadcasting Organisation of Nigeria (2008): Spectrum Planning and Management in Nigeria. http://www.bon.org.ng: Visited 20 Oct, 2011 Burns, J., Marks, P., LeBorgne, F. and Rudd, R. (2004): Study on Spectrum Management in the field of Broadcasting: Implications of Digital Switchover for Spectrum Management, DG Information Society, 2004 (2): 5-6 CBN: Central Bank of Nigeria (2004) Nigeria: National Economic Empowerment and Development Strategy NEEDS. http://www.cenbank.org/OUT/PUBLICATIONS/GUIDELINES/RD/2004/PDF Accessed 17 Oct, 2011 Commission of the European Communities (2007): Reaping the Benefits of Digital Dividend in Europe: A Common Approach to the Use of the Spectrum Released by Digital Switchover, COM (2007) 700 Final, 1-10. Fadeyi, I. O (2004): Location as a factor in stations' compliance with programming regulations, A project of Department of Communication and Language Arts, University of Ibadan, Nigeria Gbenga-Ilori, A.O. and Ibiyemi, T.S. (2010b): Nigeria Broadcast Spectrum usage in the Analogue and Digital Domains, S.doc, (3): 1-3 Gbenga-Ilori, A.O. and Ibiyemi, T.S. (2010a): Network Configuration for Efficient Spectrum use: cost implication for Nigeria, S.doc, (3): 3-5

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Kamalu U.A et al.,: Continental J. Engineering Sciences 7 (1): 24 - 35, 2012 NBC: Nigeria Broadcasting Commission (2011): Broadcasting Policy. http//www.nbc.org.ng visited 21 December, 2011. Ndanusa, J. N (2006): Standardisation and national economic development, Ibadan: University of Ibadan Postgraduate School Okpanachi, M. S. O., 2008: Radio Development: The case of radio Nigeria: A Paper for Presentation at the 2008 Commonwealth Broadcasting, Association Conference, 2008: 3-5 Received for Publication: 29/01/12 Accepted for Publication: 12/03/12 Corresponding author Anyakora N.N. Department of Electrical/Electronic Engineering, University of Portharcourt, Nigeria E-mail: anyakorandidi@yahoo.com