JOHANNESBURG, South Africa-Wireless local loop (WLL) is currently the most popular access technology to supply basic voice connectivity to subscribers in the rural areas of many African nations. It is an expensive option and difficult to implement, but offers the most effective way of reaching rural areas. With the Internet revolution, however, carriers realize that providing voice circuits alone through WLL systems is insufficient and broadband data connectivity is a necessity.
New technologies and standards are being tested to fulfill this need and provide the most economically feasible solution for both small- and large-scale applications. There are already well over 20 CDMA- and PHS-based solutions being offered. TETRA is also being tested as a possible solution for WLL.
Suppliers are offering a range of performance, features and, most importantly, radio frequencies.
Robin Goodwin, regional director, Sub-Saharan Africa for Simoco International, believes that TETRA can be highly efficient at using the available spectrum because of the small radio channel allocations. “The cost to rural users would be far less than that of a specially designed single purpose system,” he said.
Analog CT-2 systems are by no means dead in Africa. Statistics provided by Pyramid Research, based on estimates of subscribers connected as of December 1998, show CT-2 serves well over 30 percent of the total WLL subscribers in Africa. DECT follows with 24 percent; AMPS has 15 percent; TDMA, 14 percent; GSM, 10 percent; PHS, 6 percent; and CDMA, 1 percent.
But as Africa joins the telecommunications revolution with the vision of introducing voice and data access to the most rural areas, this pattern is likely to change. African countries are searching for new, realistic solutions to fulfill this need.
WLL in Sudan
One African country determined to choose the right WLL solution is Sudan. The country is one of the largest in Africa in terms of geographical area, but is mainly rural with several villages at distances ranging from 7 to 50 kilometers from populated areas and several isolated villages, which are hundreds of kilometers from main population centers.
The main operator, Sudatel, trialed a variety of mixed and merged technologies and tested their technical problems before selecting what it considered to be the right technology.
“There are five types of combined technologies currently being tested in Sudan. These include WLL (TDMA, CDMA, ETACS and DECT), VSAT, Inmarsat-Mini M and TDMA, as well as the combined wireless/wired (WW) systems, besides the rural exchanges of capacities of less than 600 lines,” explained Ibrahim Eisa El Baigawi, Sudatel’s transmission technologies manager.
The Sudosat satellite network, which is part of the domestic/national backbone, is also used for access to some isolated villages. A GSM system was tested to service rural and remote sites, but proved to be too expensive.
A WW MARS system from Alcatel was installed around the three major cities of Atbara, Karima and Dongola. The maximum capacity in each network is 320 subscribers.
Together with Motorola, Sudatel agreed in 1995 to install a WLL trial system in Greater Khartoum using ETACS and operating in the 800/900 MHz frequency band. The analog system has a capacity of 500 subscribers, with no switching facility, and its base station is connected through subscriber lines to a Siemens switch in Khartoum South. The system, which can provide coverage within a radius of 50 kilometers, was then moved to provide telephone service to the suburban areas around Khartoum.
In 1998, Sudatel and Granger Telecom agreed to a TDMA/CD1000 WLL trial system in Shendi. Granger Telecom’s CD1000S has a switching facility, and its capacity ranges from 300 to 496 subscribers. The system operates in the 800-900 MHz frequency band, supporting the ETACS air interface. Depending on the carrier’s evaluation of the system, a deal of about eight additional stations could be concluded.
The first CDMA/CD2000 WLL system, with 300 lines, was recently implemented by Granger Telecom in the Free Zone in Port Sudan.
“As the lines went into operation only in August 1999, it is premature to evaluate the system,” said El Baigawi. The CD2000 system planned for later this year for Greater Khartoum will offer 8,000 lines, and three more sites are possible in the future.
A DECT system from Siemens is currently under trial in Khartoum, and other technologies such as VSAT and Inmarsat-Mini M are in an experimental phase. Presently, eight stations have been installed, and another offer of about 200 VSAT terminals is under discussion. Installing WLL to supplement VSATs could also be a possibility in the near future.
“As it emerged from all the trials of different technologies conducted in Sudan, certain serious challenges will have to be met before WLL systems can be confidently used on the African continent,” said El Baigawi.
The problem that will determine the future of WLL is power supply in rural areas, where electricity is not currently available.
“Yet WLL technology is still the most [feasible] and economic to use provided the technology has to be capable of providing (a) wide range of services complying with the needs for building the global information infrastructure,” he added.
