In February 1997, Telecomunicacoes Brasileiras S/A (Telebras) invited all major WLL system manufacturers to test their systems in Brazil. The planned trials will enable TelebrasNBrazil’s state-run telecommunications monopolyNto set a national standard for WLL system deployments. Attracted not only by the enormous market opportunity that Brazil represents, 16 companies signed agreements with 13 of the 26 Brazilian regional operating companies to trial a range of technologies in different frequency bands (see Table 1).

Scheduled to conclude in early 1998, the extensive testing program of the Telebras Research & Development department is evaluating equally and comprehensively all the technologies presented (see Table 1), covering every aspect of system performance. If ever there were a chance for PHS to demonstrate its worth N this is it!
While trials are not complete, early results indicate strong advantages for PHS-based systems, such as ArrayComm’s IntelliWavea system, over competing approaches such as DECT. As seen elsewhere around the world, applying cellular technology to WLL system requirements has noteworthy shortcomings.

PHS-WLL Solution
Two types of cell stations, one with 360-degree coverage and the other with 120-degree sectorized coverage, were installed.
Interface to the PSTN is made via 2 Mbps connections to the ZTX-610 switch manufactured in Brazil.

Provisional Results and Comments to Date
Most of the trials are in the 1.9 GHz frequency band (see Table 1), with some testing in the 3.5 GHz band. At this point, it appears that the preferred frequency band will be in the 1.9 GHz range, most likely the 1910-1930 MHz portion separating the PCS upper and lower bands.
PHS currently operates up to 1918 MHz, and ArrayComm’s IntelliWave system requires only 10 MHz of bandwidth to serve the entire country including Sao Paulo’s 16 million inhabitants.

The performance of the IntelliWave PHS system installed at Joao Pessoa, Paraiba has exceeded expectations of Telecomunicacoes da Paraiba S.A. (TELPA), the Telebras operating company, and attracted interest from the Telebras R&D department, which previously believed PHS coverage to be less than one kilometer. ArrayComm’s demonstration of 64 Kbps service using two time slots has further increased the chances for PHS to become the specification for WLL systems in Brazil. Other notable differences with DECT-based systems included data transmission speeds and other basic service issues listed below (Fig. 1).
Other technologies tested by Telebras are believed not to have given the required voice quality necessary for a WLL system. Though there have been significant improvements in digital voice techniques, 13 Kbps still does perform adequately for fixed applications, and there is an increasing awareness that attempting to adapt a high-mobility system for fixed applications is akin to putting a square peg in a round hole.
An important difference between a system designed for WLL and a high-mobility cellular system is its billing facility. In a true WLL approach such as the IntelliWave system, billing is handled by the incumbent operator’s system without difficult reconciliation between two billing platforms. In comparison, the CDMA system installed with Telecomunicacoes de Minas Gerais (TELEMIG) in Belo Horizonte includes not only CDMA fixed wireless terminals and base stations but also a switching center that performs billing and database functions and provides a trunked interface to the PSTN. The additional cost of such a switching center to a WLL system, combined with the headache of reconciling two separate billing systems, clearly shows the disadvantage of a mobile switching center.

Positive Outlook For PHS-WLL Solutions in Brazil

With voice quality practically equal to that of copper wiresNand at lower installation and maintenance costsNthere is great interest in today’s wireless technology. Telebras’ extensive testing has satisfied them that wireless is a viable option, and commercial orders for WLL systems are anticipated for as early as Q1 1998. With the pending privatization of Telebras, the operating companies are attempting to increase their installed base as quickly as possible to enhance their valuation by potential investors. Wire lines take too long to implement in time for this privatization (expected by November 1998), making this a very promising year for WLL suppliers to Brazil. The November 26, 1997 notice from TELERJ gives some indication of the potential: “The Rio de Janeiro state telecommunication company, TELERJ, plans on investing USD$2.5 billion during the period 1997-1999 as a part of the investment program created in 1996. TELERJ intends to triple the telecommunication infrastructure in the state, focusing on the number of available telephone lines.”

This article was kindly contributed by ArrayComm Inc.