Joint receiver for DS-CDMA/TDMA signals using complex multirate filter bank

This paper discusses the problem of coexistence of DS-CDMA (direct sequence code division multiplex access) and TDMA (time division multiple access) s ystems where their signals are transmitted in the same frequency band. The DS-CDMA signal is robust against narrowband interference, but there is a li mit to its immunity against interference. This paper proposes, from such a viewpoint, a method using a complex multirate filter bank, as a way to reje ct TDMA signals, which act as narrowband interference to the DS-CDMA signal , in the coexistence system. By the proposed method, a notch filter can be composed with an arbitrary frequency resolution at an arbitrary frequency, by constructing the complex version of the conventional multirate filter ba nk. It is shown that, by eliminating the TDMA signal by the proposed method , the bit error rate of the DS-CDMA signal is improved, indicating that the proposed system is useful in the coexistence problem. (C) 1999 Scripta Tec hnica.