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Wednesday, October 11, 2006

Internet access: Efficacy of C-band

Features of the week:

Various frequency bands exist through the satellite including C-band. REMMY NWEKE in this report examines the efficacy of C-band for a developing nation like Nigeria.

Enterprising youngman who is an Information and Communications Technologies (ICT) enthusiast, Mr. Ejike Umunnaekwe, believes in the usefulness of modern technologies and does not want to be left out in any form; be it knowledge or applications.

So he engaged a Very Small Aperture Terminal (VSAT) solution provider who came to his office, mounted a satellite dish at the back of the building, brought in some other installations identified as downlinks and uplinks modem.

VSAT, defined as a computer term and a small earth station for satellite transmission by TheFreeDictionary.com, while another online encyclopaedia, Whatis.com says VSAT is a satellite communications system that offers a number of advantages over terrestrial alternatives.

The solution was serving him as he described it “very well” until the ground began to get wet in the middle of the year, then disruption crept in and he began to experience all manner of data loss by the day, as well as hardware device errors and so on.

The Internet, no doubt has been very instrumental to the progress of being a part of today’s history globally, yet there seems to be seasons for downturn, which happens from time to time.

But the period when the Internet mostly records an increase in the downturn, according to our investigation is during the rainy seasons, also referred to as change of weather, especially if the deployment was structured on satellite tool like the Very Small Aperture Terminal (VSAT).

At first instance, it would report on the screen “Bad Gateway,” informing the subscriber that the enhancement client proxy could not communicate with the server proxy.

The reason automatically generated is that connection is lost and “If you contact your satellite service provider because of this message, please include a copy of the receiver log ‘recv.log’ otherwise known as log file.

Persistence would give you the report that there is a bad gateway due to the inability of the enhancement client proxy to communicate with the server proxy, indicating, “An outstanding acknowledge protocol data unit (pdu) was not received in time probably due to high User Datagram Protocol (udp) data loss.”

In some other instances the system would inform the subscriber that the page could not be displayed as “The page you are looking for is currently unavailable. The web site might be experiencing technical difficulties, or you may need to adjust your browser settings.”

Yet in other cases the systems generated message would read thus; “Please try the following by clicking on the ‘Refresh button,’ or try again later and if you typed the page address in the address bar, make sure that it is spelled correctly. To check your connection settings, click the tools menu, and then click Internet options. On the connections tab, click settings. The settings should match those provided by your local area network (LAN) administrator or Internet Service Provider (ISP).”

It would further advise that you check to see if your Internet connection settings are being detected, just as “You can set Microsoft Windows to examine your network and automatically discover network connection settings - if your network administrator has enabled this setting.”

Thereafter, it would request that the subscriber clicks the tools menu, and then on the Internet options and connections tab, click LAN settings, select automatically detect settings, before clicking OK. Underscoring that some sites require 128-bit connection security.

However, it would ask to click the help menu and then ‘About Internet Explorer’ to determine what strength security you have installed. “If you are trying to reach a secure site, make sure your security settings can support it. Click the tools menu, and then click Internet options.”

The system also states that on the ‘advanced tab,’ the user should scroll to the security section and check settings, counseling that the subscriber clicks back button to try another link, mostly when it could not find server or Domain Name System (DNS) error via the Internet explorer.

At the opening of the fourth hub by a Lagos-based satellite solution company, Direct-On PC, the Managing Director, Mr. Munish Sharma, noted that the hub hosted in the United States, would reinforce the firm’s strategies for its market share in the sub-region and precisely in Nigeria.

He disclosed that the hub, based on Hughes Network Systems (HNS) technology, is the most advanced platform Digital Video Broadcasting-Standard 2 (DVB/S2), a pioneer of VSAT technology.

Mr. Sharma also noted that the launch positions DOPC as truly a pioneer of Ku-band VSAT, explaining that DVB/S2 technology is the most recent technology that has just got introduced in Europe and United States, “And we’re bringing the same in Africa, thus, ensuring that Nigeria is at par with any leading nations.”

This, he said, gives DoPC high bandwidth efficiency by approximated 30 per cent, which the company intends to avail to its customers so as to provide them with high Internet bandwidths at low price.

The new platform, he also said, comes with the Associated Computer Machinery (ACM) enabled KU band, that withstands rains.

“All existing KU band VSAT’s will cut off and loose its link while ACM available with, DVBS-2 adjusts the VSAT during rain, so as to speedy up slow connectivity and keep the link alive,” he said.

Founder of Jidaw.com and Nigerian online enterpreneur, Mr. Jide Awe, opined that VSAT systems operate in the Ku-band and C-band frequencies, but usually, C-band suffers less from rain attenuation, whereas it requires larger size antennas.

He stressed that though small antennas are now being produced for C-band, even as Ku-band uses smaller size antennas, but suffers from rain fade.

However, history has it that C band is the original frequency allocation for communications satellites.

According to the TechFAQ, C band uses 3.7-4.2 Gega Hertz (GHz) for the downlink and 5.925 – 6.425 GHz for its uplink, stressing that the lower frequencies used by C band perform better under adverse weather conditions than the ku-band or ka-band frequencies.

Whereas the Universal Mobile Telephone System, www.umtsworld.com, indicated that there are actually three core operating bands between Tx and Rx frequency separation, namely band 1 in this case is 190 Mega Hertz (MHz); band 2 is on 80 MHz and band 3 could be located on 95 Mhz.

C-band, therefore, requires the use of a large dish to be able to have a wider reach, just as it has variants in band frequencies that were approved for use in various parts of the world including Africa. These include what some experts classified as ‘slight variations,’ that is, between transmitting (Tx) and receiving (Rx) frequencies respectively, whilst the band cuts across as extended C-band, super extended C-band, InSat C-band, Palapa C-band, Russian C-band and IMT C-band.

C band is one of the label for three portions of the electromagnetic spectrum, including Ku and Ka bands, used in different ways as outlined by the Institute of Electrical and Electronics Engineers (IEEE). C band is also known as “compromise” band and is a portion of the spectrum in the microwave range of frequencies, ranging from 4 to 8 GHz and an electronic and electrical standard defined by the IEEE.

Primarily used for satellite communications, normally downlink 3.7 – 4.2 GHz, (LOF 5.150 GHz, uplink 5.9 – 6.4 GHz), usually via twenty-four 36 MHz-wide transponders on board a satellite. Most C band satellites serving North America use linear polarization, while those serving other continents such as Africa and via particularly Intelsat satellites use circular polarization, in line with Wikipedia online, http://en.wikipedia.org/wiki/IEEE.

Experts at www.Argospress.com corroborated that C band is a band of frequencies used for terrestrial radio relay and satellite transmissions in satellite communications and is commonly called 6/4 GHz to demonstrate that the uplink frequencies are about 6 GHz and the downlink is in the neighbourhood of 4 GHz and could be located between 5.925-6.425 GHz for uplinks and 3.7-4.2 GHz for downlinks.

They also noted that communications equipment for C band is rather cheap due to its akin to the terrestrial microwave, troposcatter and radar apparatus developed some decades ago as well as is the known first branch of the spectrum to be applied extensively to satellite communications.

Still, it is the most widely used due to the low cost and wide availability of components, even as each C-band satellite covers about 500 MHz of bandwidth with a number of 36-MHz transponders, while 72-MHz transponders also exist.

Unfortunately, in this part of the world there seems to be lots of rain most of the time unpredictably. This does not give the service providers the impetus to even place outage calculators on their website to enable customers using their satellite-based services like VSAT to adjust to the time.

As matter of fact, investigations conducted showed that during the rainy seasons most ISPs suffer drastic reduction in patronage and investment for bigger ISPs who buy services in bulk and retail to the smaller ones.

On the other hand, C band is reputed as a lower frequency than Ku band, as such, it requires a much larger dish than ku band; you need at least a 7 foot dish (2 meters) and Ku band, at least, a 2-3 foot (.8 meter) dish.

While we look forward to hosting the four-day West Africa Satellite Communications summit at the federal capital territory (FCT) Abuja, it is relevant that the authorities including the Global VSAT Forum (GVF) examine the root for localised solution to this kind of occurrence so as to increase the accessibility of the Internet in this part of the world, known for its unassumed backwardness in almost everything including technologies (ICT) sector are of the opinion that it is high time political office seekers came up with what they called an ICT agenda for the nation.

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1 comment:

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