Configurable and Scalable Turbo Decoder for 4G Wireless Receivers

Configurable and Scalable Turbo Decoder for 4G Wireless Receivers

Yang Sun, Joseph R. Cavallaro, Yuming Zhu, Manish Goel
Copyright: © 2010 |Pages: 22
DOI: 10.4018/978-1-61520-674-2.ch027
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The increasing requirements of high data rates and quality of service (QoS) in fourth-generation (4G) wireless communication require the implementation of practical capacity approaching codes. In this chapter, the application of Turbo coding schemes that have recently been adopted in the IEEE 802.16e WiMax standard and 3GPP Long Term Evolution (LTE) standard are reviewed. In order to process several 4G wireless standards with a common hardware module, a reconfigurable and scalable Turbo decoder architecture is presented. A parallel Turbo decoding scheme with scalable parallelism tailored to the target throughput is applied to support high data rates in 4G applications. High-level decoding parallelism is achieved by employing contention-free interleavers. A multi-banked memory structure and routing network among memories and MAP decoders are designed to operate at full speed with parallel interleavers. A new on-line address generation technique is introduced to support multiple Turbo interleaving patterns, which avoids the interleaver address memory that is typically necessary in the traditional designs. Design trade-offs in terms of area and power efficiency are analyzed for different parallelism and clock frequency goals.
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The Turbo code (Berrou et al., 1993; Berrou et al., 1996) has become one of the most important research topics in coding theory since its discovery in 1993. The astounding performance of Turbo code has attracted a great deal of interest in the research activity in the area of iterative error correction codes. Due to its excellent error correction performance, many communication standards have chosen Turbo codes as the Forward Error Correction (FEC) codes, such as CDMA-2000, W-CDMA, DVB-RCS, HSDPA, UMTS, IEEE 802.16e WiMax, and 3GPP LTE. Turbo codes can be categorized into two classes: binary Turbo codes and non-binary Turbo codes. For example, Turbo codes in CDMA, HSDPA, UMTS and 3GPP LTE are binary types of Turbo codes, whereas Turbo codes in IEEE 802.16e and DVB-RCS are double-binary types of Turbo codes. Table 1 summarizes some of the Turbo codes in practice (Berrou, 2003). As we can see, there are many similarities between the Turbo codes employed in different standards. This motivates the design of a unified and flexible Turbo decoder which can support multiple standards. Without loss of generality, we will mainly focus on the Turbo codes defined in 3GPP LTE and WiMax in the following analysis. Note that these analyses can be applied to other systems directly because the encoder polynomials are same.

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