Realizing up and downlink subcarrier allocation in Orthogonal Frequency Division Duplex (OFDD) Systems

In this paper we describe a new method for multi-carrier systems that allows the allocation of different subcarriers to their up and downlinks. Techniques utilizing such subcarrier allocation have already been used in some cooperation and resource allocation algorithms for multiuser Orthogonal Frequency Division Multiple Access (OFDMA) as well as in Orthogonal Frequency Division Duplexing (OFDD). Therefore it is useful to investigate methods that can enable them. In this work we focus on the physical feasibility of the system since the radio impairments and system imperfections are the key challenges that need to be addressed. In particular we propose a baseband echo cancellation approach to mitigate the interference between the up and downlink subcarriers. An iterative echo canceller is utilized at the receiver, with the reference samples obtained from the output of the transmit power amplifier. The system performance in terms of output signal to interference and noise ratio (SINR) and bit error rate (BER) is evaluated by computer simulations based on the configuration of 802.11a/g systems.