Broadband Indoor Wireless System with In-cell Frequency Reuse Based on Sectored Antennas *
نویسندگان
چکیده
Resumo: Neste artigo investiga-se urn novo sistema de multiplo acesso para comunica~Oes sem fio de banda larga em interiores utilizando antenas setorizadas. 0 que 0 difere de outros sistemas previamente propostos, que tambem utilizam antenas setorizadas, e a sua capacidade de reusar frequencias em setores distintos da microcelula : terminais portateis 10 calizados em setores distintos da microcelula podem compar tilhar 0 mesmo espectro de frequencia se a nivel de interfe rcncia mutua for aceitavel. Porem, isto requer uma cuidadosa programa~ao das transmissoes a fim de evitar interferencias destrutivas. A program~ao Gtima, a que maximiza 0 nt1mero de pacotes transmitidos por quadro, se encontra na classe de problemas NP-completos para a caso de tres ou mais trans missoes simultiineas. Como este tipo de problema nao pode ser resolvido em tempo real, propOe-se urn algoritmo sub 6timo chamado "First Fit Algorithm". 0 problema IS estudado experimentalmente para 0 caso em que a microcelula e divi dida em dez setores (setoriza~ao de nivel dez). Urn modelo estatistico de propaga~ao por carninhos multiplos e utilizado para estender os resultados para outros niveis de setoriza~ao. o sistema proposto pode proporcionar urn grande incremento na capacidade da microcelula. Por exemplo, enquanto os sis temas previamente propostos podem transmitir somente urn pacote de informa~ao par vez, este novo sistema e capaz de transmitir, em media, perto de tres pacotes simultaneamente. Este resultado e valido para urn nive! de interfercncia mutua maximo de 10 dB com setoriza~iio de nivel dez em urn am biente interno com paredes divisorias feitas com blocos de concreto. Abstract: This paper investigates a new multiple ac cess system for broadband indoor wireless communications based on sectored antennas. Unlike previous sectored an tenna indoor systems, this system incorporates the capability of reusing spectrum in different antenna sectors of the base station. It is shown that portable terminals located in different sectors of the indoor microcell may transmit/receive simul taneous data packets on the same frequency if their mutual interference is below a threshold level (or capture threshold) that guarantees an acceptable packet error rate. However, this requires careful scheduling of packet transmissions in order to avoid transmitting packets that would jam each other dur ing the same time slot. When trying to transmit more than two packets per time slot, the optimum scheduling problem, the one that maximizes the number of packets transmitted per
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