Cronologia: Padrões de rede sem fio
Autor: Lukas Amorim | Publicado: 2012-03-02T14:37:00-03:00

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Padrões
de rede sem fio

Cronologia

1955: o Federal Communications
     Commission (FCC), órgão americano responsável pela regulamentação do
     uso do espectro de frequências, autorizou o uso de três faixas de
     frequência;
1990: o Institute of
     Electrical and Electronics Engineers (IEEE) instaurou um comitê para
     definição de um padrão para conectividade sem fio;
1997: após sete anos de pesquisa
     e desenvolvimento, o comitê de padronização da IEEE aprovou o padrão IEEE
     802.11; nessa versão inicial, as taxas de transmissão nominais atingiam 1
     e 2 Mbps;
1999: foram aprovados os padrões
     IEEE 802.11b e 802.11a, que usam as frequências de 2,4 e 5&nbsp;GHz e são
     capazes de atingir taxas nominais de transmissão de 11 e 54 Mbps,
     respectivamente. O padrão 802.11b, apesar de atingir taxas de transmissão
     menores, ganhou fatias maiores de mercado do que 802.11a; as razões para
     isso foram basicamente duas: primeiro, as interfaces 802.11b eram mais
     baratas do que as 802.11a e, segundo, as implementações de 802.11b foram
     lançadas no mercado antes do que as implementações de 802.11a. Além disso,
     nesse ano foi criada a Wireless Ethernet Compatibility Alliance
     (WECA), que se organizou com o objetivo de garantir a interoperabilidade
     entre dispositivos de diferentes fabricantes;
2000: surgiram os primeiros hot
     spots, que são áreas públicas onde é possível acessar a Internet por
     meio das redes IEEE 802.11. A WECA lançou o selo Wireless Fidelity
     (Wi-Fi) para testar a adesão dos fabricantes dos produtos às especificações;
     mais tarde o termo Wi-Fi tornou-se um sinônimo de uso abrangente das
     tecnologias IEEE 802.11;
2001: a companhia americana de
     cafeterias Starbucks implementou hot spots em sua rede de lojas. Os
     pesquisadores Scott Fluhrer, Itsik Mantin e Adi Shamir demonstraram que o
     protocolo de segurança Wired Equivalent Privacy (WEP) é inseguro;
2002: a WECA passou a se chamar
     Wi-Fi Alliance (WFA) e lançou o protocolo Wi-Fi Protected Access
     (WPA) em substituição ao protocolo WEP;
2003: o comitê de padronização da
     IEEE aprovou o padrão IEEE 802.11g que, assim como 802.11b, trabalha na
     frequência de 2,4&nbsp;GHz, mas alcança até 54 Mbps de taxa nominal de
     transmissão. Aprovou também, sob a sigla IEEE 802.11f, a recomendação de
     práticas para implementação de handoff;
2004: a especificação 802.11i
     aumentou consideravelmente a segurança, definindo melhores procedimentos
     para autenticação, autorização e criptografia;
2005: foi aprovada a
     especificação 802.11e, agregando qualidade de serviço (QoS) às redes IEEE
     802.11. Foram lançados comercialmente os primeiros pontos de acesso
     trazendo pré-implementações da especificação IEEE 802.11e;
2006: surgiram as
     pré-implementações do padrão 802.11n, que usa múltiplas antenas para
     transmissão e recepção, Multiple-Input Multiple-Output (MIMO),
     atingindo taxa nominal de transmissão de até 600 Mbps.
2009: foi aprovada a versão final
     da especificação 802.11n.