Radio Frequency Spectrum in NepalPrinter-friendly version |
It's a limited natural resource, writes Jagdish Lekhak, a telecom engineer with NTC.
A radio wave is an electromagnetic wave propagated by an antenna. Radio waves have different frequencies, and by tuning a radio receiver to a specific frequency you can pick up a specific signal.
When you listen to a radio station and the announcer says, "You are listening to 96.1 FM" what the announcer means is that you are listening to a radio station broadcasting an FM radio signal at a frequency of 96.1 MHz. MHz means "millions of cycles per second," so "96.1 MHz" means that the transmitter at the radio station is oscillating at a frequency of 96,100,000 cycles per second. Your FM (frequency modulated) radio can tune in to that specific frequency and give you clear reception of that station. All FM radio stations transmit in a band of frequencies between 88 MHz and 108 MHz. This band of the radio spectrum is used for no other purpose but FM radio broadcasts.
In the same way, AM radio is confined to a band from 535 kilohertz to 1,700 kilohertz (kilo meaning "thousands," so 535,000 to 1,700,000 cycles per second).
Common radio frequency bands include the following:
The system of frequency allocation is fairly archaic, and tradition dictates much of its design. The lower frequencies are allocated to the oldest services, such as maritime communication and navigation, aeronautical communication and navigation, and AM radio. Many regions of the spectrum, such as those devoted to radio navigation, have been technologically supplanted (in this case by GPS, the global positioning system, a satellite- based global navigation system). Huge portions of the spectrum are wasted on television broadcasts, and even more have been recently allocated to allow for 535 kHz - 1.6 MHz: AM Radio stations.
• 535 kHz - 1.6 MHz: AM Radio stations.
• 54 MHz - 72 MHz: Television (channels 2-4).
• 76 MHz - 88 MHz: Television (channels 5-6).
• 88 MHz - 108 MHz: FM radio.
• 174 MHz - 216 MHz: Television (channels 7-13).
• 470 MHz - 806 MHz: Television (channels 14-69).
What is funny is that every wireless technology you can imagine has its own little band. There are hundreds of them! For example:
• Garage door openers, alarm systems, etc. -Around 40 MHz
• Standard cordless phones: Bands from 40 to 50 MHz
• Radio controlled airplanes: Around 72 MHz, which is different from...
• Radio controlled cars: Around 75 MHz
• Air traffic control radar: 960 to 1,215 MHz
• Global Positioning System: 1,227 and 1,575 MHz
The system of frequency allocation is fairly archaic, and tradition dictates much of its design. The lower frequencies are allocated to the oldest services, such as maritime communication and navigation, aeronautical communication and navigation, and AM radio. Many regions of the spectrum, such as those devoted to radio navigation, have been technologically supplanted (in this case by GPS, the global positioning system, a satellite- based global navigation system). Huge portions of the spectrum are wasted on television broadcasts, and even more have been recently allocated to allow for simultaneous digital and analog transmission during a transition phase to an all digital television system. But it is difficult to reclaim these regions of the spectrum because residual uses remain. Partly as a consequence, it has become extremely difficult to find unused radio spectrum for new services. Cellular telephony, for example, has undoubtedly had its growth constrained by the shortage of available bandwidth. Hence radio frequency spectrum is a limited resource.
Cellular mobile communication is one of the major branches of wireless communication which gives mobility and service to the user. The main technologies that are currently being used are GSM (Global System for Mobile) and CDMA (Code Division Multiple Access).GSM technology works in the frequency bands of 900MHz and 1800MHz while CDMA technology works in 800MHz. In Nepal, NTC and Ncell have adopted GSM system, while Sky phone use CDMA technology.
Although both GSM and CDMA divide their available frequency band into channels, the main difference between these two technologies is GSM uses certain number of frequency channels in a cell and each user get their own frequency channel, while CDMA uses only one frequency channel in a cell with proper allocation of PN (pseudo-random) code to each user. PN code is a special set of numbers which is mixed with the modulated signal during transmission and transmitted message can be decoded only with the same PN code.
Spectrum can neither be created nor be destroyed.
It is the use of spectrum, which can be regulated so as to maximize its usage, given its capabilities and constraints. Thus, the process of spectrum management or radio regulation is different from other regulations in general parlance. An evaluation of the interference potential to and from a new station is an integral part of radio regulatory mechanism requiring an in-depth analysis services. Since the 1930s, spectrum was assigned through administrative licensing. Limited by technology, signal interference was once considered as a major problem of spectrum use. Therefore, exclusive licensing was established to protect licensees' signals. This former practice of discrete bands licensed to groups of similar services is giving way, in many countries, to a "spectrum auction" model that is intended to speed technological innovation and improve the efficiency of spectrum use. During the experimental process of spectrum assignment, other approaches have also been carried out, namely, lotteries, unlicensed access and privatization of spectrum.
The electromagnetic spectrum is in demand, not only for traditional uses but also for traditional uses such as broadcasting but also, increasingly, for new forms of mobile communications. How should governments decide who has right to use the spectrum? Four methods have been used:
● Administrative process
● First come first served
Out of four methods auction works better than of technical characteristics of the station and its environment.
● Are transparent and fair
● Generate revenue for the government
● Assigns licenses to firms quickly and economically
However, as for Nepal, above methods of spectrum allocation might not be suitable for all the operators
operating wireless communications. Hence some variable spectrum pricing/mixed spectrum pricing would be better to be employed rather employing a fixed pricing. It could be a matter of debate and NTA( Nepal Telecommunication Authority) should look upon this matter.
As spectrum is a scarce resource, its equitable allotment for systems using different technologies seems to be the solution. The government while formulating its spectrum policy should try to create a flexible and technology neutral regime to allow new technologies equal access to spectrum. Also try to bring about transparency and openness in the spectrum allotment process so that this scarce natural resource (radio frequency) is put to it optimal use in a more efficient manner.
The author is associated with the Nepal Telecommunication Corporation. The original article is from 8th Annaul Souvenir of NTC.