I. Introduction
In Cellular mobile communications systems like the Global System for Mobile Communications (GSM), cochannel interference from cells using the same frequencies as the considered cell (frequency reuse) is an important capacity limiting factor. For systems with a low frequency reuse factor corresponding to high system capacity, cancellation of cochannel interference at the receiver is necessary in order to obtain a good performance. In case of multiple receive anten-nas, solutions for cochannel interference cancellation are well known [1]. However, in most cases, antenna diversity is only available at the base station but not at the mobile terminal due to cost and size limitations. Hence, for downlink transmission, single antenna interference cancellation (SAIC) algorithms are required. In this letter, a novel SAIC algorithm referred to as mono interference cancellation (MIC) is introduced which is applicable to general real-valued modulation formats and in particular to the Gaussian minimum-shift keying (GMSK) modulation used in GSM which can be well approximated by filtered binary phase-shift keying (BPSK). The proposed MIC algorithm, cf. also [2], employs complex-valued filtering and projection and is followed by trellis-based equalization. The required operations are well suited for a low-complexity software implementation. It is demonstrated that MIC has advantages compared to other SAIC algorithms proposed in literature, e.g. [3], [4].