Design of Fixed-Point Processing Based Turbo Codes Using Extrinsic Information Transfer Charts

The operand-width specifications in fixed-point hardware implementations of turbo code decoders is an important design issue, since this governs the trade-off between the decoder's performance and its complexity, cost, area and energy consumption. The investigation of this issue would be extremely time-consuming in the conventional approach, which relies upon Monte-Carlo simulation based Bit Error Ratio (BER) analysis. In this paper, we propose a generic design method, which uses EXtrinsic Information Transfer (EXIT) chart analysis to simplify this design process. Our method is not only an order of magnitude faster than the conventional Monte-Carlo simulation based approach, but also offers deeper insights into why performance degradations are imposed by insufficient operand-width specifications. The benefits of our generic method are demonstrated in the context of a turbo decoder, allowing accurate specifications to be obtained and compared to those suggested by previous works

Energy-efficient design and implementation of turbo codes for wireless sensor network

The objective of this thesis is to apply near Shannon limit Error-Correcting Codes (ECCs), particularly the turbo-like codes, to energy-constrained wireless devices, for the purpose of extending their lifetime. Conventionally, sophisticated ECCs are applied to applications, such as mobile telephone networks or satellite television networks, to facilitate long range and high throughput wireless communication. For low power applications, such as Wireless Sensor Networks (WSNs), these ECCs were considered due to their high decoder complexities. In particular, the energy efficiency of the sensor nodes in WSNs is one of the most important factors in their design. The processing energy consumption required by high complexity ECCs decoders is a significant drawback, which impacts upon the overall energy consumption of the system. However, as Integrated Circuit (IC) processing technology is scaled down, the processing energy consumed by hardware resources reduces exponentially. As a result, near Shannon limit ECCs have recently begun to be considered for use in WSNs to reduce the transmission energy consumption [1,2]. However, to ensure that the transmission energy consumption reduction granted by the employed ECC makes a positive improvement on the overall energy efficiency of the system, the processing energy consumption must still be carefully considered.The main subject of this thesis is to optimise the design of turbo codes at both an algorithmic and a hardware implementation level for WSN scenarios. The communication requirements of the target WSN applications, such as communication distance, channel throughput, network scale, transmission frequency, network topology, etc, are investigated. Those requirements are important factors for designing a channel coding system. Especially when energy resources are limited, the trade-off between the requirements placed on different parameters must be carefully considered, in order to minimise the overall energy consumption. Moreover, based on this investigation, the advantages of employing near Shannon limit ECCs in WSNs are discussed. Low complexity and energy-efficient hardware implementations of the ECC decoders are essential for the target applications