EXIT Charts for System Design and Analysis

Abstract

Abstract-Near-capacity performance may be achieved with the aid of iterative decoding, where extrinsic soft information is exchanged between the constituent decoders in order to improve the attainable system performance. Extrinsic Information Transfer (EXIT) charts constitute a powerful semi-analytical tool used for analysing and designing iteratively decoded systems. In this tutorial, we commence by providing a rudimentary overview of the iterative decoding principle and the concept of soft information exchange. We then elaborate on the concept of EXIT charts using three iteratively decoded prototype systems as design examples. We conclude by illustrating further applications of EXIT charts, including near-capacity designs, the concept of irregular codes and the design of modulation schemes.

EXIT Chart Aided Convergence Analysis of Recursive Soft <inline-formula> <tex-math notation="LaTeX">$m$</tex-math> </inline-formula>-Sequence Initial Acquisition in Nakagami-m Fading Channels

“…• In Section III we conceive a new EXIT chart tool [3], relying on soft decision feedback for improving the performance of the system as compared to the hard decision approach, which is achieved at the cost of a modest increase in complexity [6]. The correlation of chips inherent in the m-sequences is exploited for maximizing the Mutual Information (MI).…”

“…The concept of EXtrinsic Information Transfer (EXIT) charts was introduced by Brink [3,12] as a powerful tool of analysing the convergence behaviour of iteratively decoded systems. Explicitly, the EXIT chart is capable of predicting the specific SNR value, at which a vanishingly low Bit Error Ratio (BER) can be achieved.…”

“…In this contribution, we calculate the MI between the transmitted chips and the associated extrinsic LLRs by using the time-averaging method, hence we may use the LLR-based MI metric online [3].…”

“…Hence the information transmission over the channel should be as bandwidth-efficient as possible [1,2]. Fortunately, the performance of wireless systems can be enhanced using iterative decoding, where extrinsic soft information is exchanged between the constituent receiver components [3]. The increased tele-traffic has led to the development of new enabling techniques operating at increased millimetre wave carrier frequencies, where more bandwidth is available for small cells [1,2].…”

Unity-Rate Codes Maximize the Normalized Throughput of ON–OFF Keying Visible Light Communication

“…We demonstrate that the URC is capable of ensuring a dimming level of 50%. We quantify the benefits of the proposed 4B6B and URC aided VLC schemes by invoking the 17-subcode IRregular Convolutional Code (IRCC) of [6] as the outer decoding component, whose weighting coefficients are optimized using EXtrinsic information Transfer (EXIT) charts [7]. It is demonstrated that the 4B6B and URC aided VLC systems designed offer higher throughput than their BMC aided counterpart.…”