This paper presents a systematic approach to modeling and simulating an OFDM transceiver for wireless LAN using SystemC. On the one hand, it shows the problems associated with using pure untimed dataflow models, suggesting different solutions for circumventing them and add run-time control features to modules. On the other hand, it proposes a method for modeling latency (add timing information) with minimal overhead on the model complexity. For both the timed and the untimed dataflow models, two approaches to transferring data between modules are presented: sample-based and symbol-based, which results in four possible modeling scenarios.
I. INTRODUCTIONConsidering the scarcity of the wireless spectrum, high efficiency communication standards are becoming a necessity in all wireless fields: LAN, WAN, PAN, and broadcasting. The orthogonal frequency-division multiple-access (OFDM) modulation scheme, in conjunction with powerful source coding, proved to be extremely robust and spectrally efficient. An increasing number of standards adopting OFDM emerge nowadays, which creates the need for a more systematic design methodology of such systems, which promotes reusability of components and consistency of modeling. The present paper aims to present some solutions and guidelines for the functional modeling of an OFDM physical layer (PHY) communication chain.In order to illustrate our ideas, we have chosen a real application, a transceiver for the OFDM-based IEEE 802.11a wireless LAN standard. However, the insights presented here are also applicable to other standards employing OFDM, for wireless networking, such as 802.11g (LAN) [1], 802.15 (PAN), 802.16 (WiMAX MAN), as well as for broadcasting, like DVB [2], DAB, and DRM. As description methodology, we have selected SystemC [3][4] because it is free, it simulates relatively fast and allows modules described at different levels of abstraction to coexist, which makes it ideal for architectural exploration and refinement.The paper begins with a short overview of the 802.11a standard, with emphasis on those features which are of special interest for modeling the transceiver chain. We spend then most of the paper with describing the modeling of the chain using a sample-based untimed dataflow approach. A special attention is given to embedding control information in a pure dataflow simulation using control flags that accompany data tokens, targeted specifically to OFDM systems. A discussion on functional modeling for maximum reusability is presented in the next section, by separating the functionality of a module from the communication with other modules.We then go on to present a flexible method for adding clocks and timing information to the modules (latencies), with minimal impact on the model complexity. If the modeling style from the previous section is used, most of the code from the untimed models can be reused. Furthermore, in order to increase the simulation speed, a symbol-based approach (both untimed and timed) is presented in the next section, which complements the ...
