Why We Are Choosing COFDM for Brazil
Summary
Brazilian broadcast engineer Fernando Bittencourt argues that COFDM is the superior modulation standard for Brazil's DTV transition, citing extensive field tests in São Paulo that revealed 8VSB's critical multipath failures and inability to support portable or mobile reception. Brazil's projected cable penetration growth makes spectrum flexibility for mobile services — only achievable with COFDM — the decisive factor over ATSC.
0Exclusive Report From Brazil's Fernando Bittencourt
WHY WE ARE CHOOSING COFDM FOR BRAZIL
By Fernando Bittencourt
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Dear Dale,
Thank you for the mass amount of information about the US current DTV situation. We have done an extensive study for the introduction of DTV in Brazil. Probably our lab and field tests are the the most complete and deep analysis comparing the existing systems ATSC, DVB (Europe) and ISDB (Japanese) ever done. All the procedures were previously approved by each of the "contenders". According to our tests results, clearly the COFDM is more appropriate to be adopted for a terrestrial transmission, due to its inherent robustness to multipath. The conceptual analysis is: Cable penetration is growing fast in Brazil. Deregulation has started in the country and in a few years, cable TV operators are going to compete with Telecom Companies offering the same services at a lower and lower costs in a bigger and bigger pipe to the home( gigabits may be ). TV, INTERNET,  VOICE, MULTIMIDA INTEREACTIVE, all together in the same pipe. Today we have a 10% cable penetration. In 10 years we may have 80% to 90% cable penetration in the majors cities.As strong content providers, the Brazilian broadcasters are going to be with their programs in HDTV or not in the cable's "bouquet". We don't need a "must carry". They need us to sell their cable subscriptions. What then will we need the spectrum for? We will need the spectrum to offer some complement to the cable. We have to do something that the cable is not able to do; Television and other multimidia services for portables and mobiles! The ATSC, with 8 VSB modulation with fixed 19 Mbps payload, is not able in the foreseeable future to offer portable and mobile. Currently it is not even close to the desirable performance using fixed rooftop antenas! In the Sao Paulo tests, we found an average 20% of "no signal". We think that in a real life, with multiple antennas facing different transmitter sites, the percentage "no signal" will be higher than 20%. All the ATSC "yes signal" reception were extremely critical! Any change in the direction of the antenna, the signal broke down. We have compared three generations of the 8 VSB chips, including all of the miracle chips, with almost two years of difference in the development between the first and the third. We found minor improvement in their performance. Almost nothing! The main failure in the 8VSB is the difficult in dealing with multipaths, that is inherent to any off-air reception. The only advantage of 8VSB over COFDM is the performance in the Carrier to Noise figure-- 15 db for ATSC and 19 db for COFDM -- which in the field tests showed better performance in sites too far (40 km or so) from the transmitters, useless for our Brazilian commercial broadcast model. Theoretically it is possible to have 100% coverage with the COFDM systems, managing the amount of transmitters in the same frequency (adding gap fillers) or reducing the payload. If the choice is HDTV, the current performance of 8k COFDM is much better than 8VSB for both indoor reception and rooftop antennas. If the choice is portable and mobile, only 2KCOFDM offers this possibility. ATSC does not offer this possibility and it seems to be years and millions of dollars in chip development behind . If you look into our test report, the best performance, by far, is the ISDB-T COFDM proposal. The biggest problem for us in adopting the ISDB-T is the fact that Japan is schedule to start the terrestrial transmission only in 2003 .  The flexibility that COFDM systems offer to the broadcasters for competing in the new "wireless world" in our point of view is absolutely important for keeping them in the market. |
 Location: Eastern South America, bordering the Atlantic Ocean Area: total area: 8,511,965 sq km land area: 8,456,510 sq km comparative area: slightly smaller than the US note: includes Arquipelago de Fernando de Noronha, Atol das Rocas, Ilha da Trindade, Ilhas Martin Vaz, and Penedos de Sao Pedro e Sao Paulo Land boundaries: total 14,691 km, Argentina 1,224 km, Bolivia 3,400 km, Colombia 1,643 km, French Guiana 673 km, Guyana 1,119 km, Paraguay 1,290 km, Peru 1,560 km, Suriname 597 km, Uruguay 985 km, Venezuela 2,200 km Coastline: 7,491 km Terrain: mostly flat to rolling lowlands in north; some plains, hills, mountains, and narrow coastal belt largest country in South America; shares common boundaries with every South American country except Chile and Ecuador  |
