RRNS-ConvolutionaI Concatenated Coded OFDM Wireless Communication System with a Direct Analog-to-Residue Converter

A novel approach for direct analog-to-residue conversion is presented in this chap/er using the most popular sigma-della analog-to-digital converter. This converter provides high resolulion. high conversion speed and a low cost for implementation. The non-positional nature (~f RNS makes it suitable for fault-toleranl architectures. The error detection and correction properties (?f Redundant Residue Number System (RRNS) are obtained by introducing few redundant moduli that are relatively prime to the non-redundant moduli. An RRNS-Convolutional concatenated coding (RCCC,) scheme for OFDM wireless communication system is presented to improve the !!.ystem performance under different operating conditions. An important step in the Residue Number System (RNS) based signal processing is the conversion of signal into residue domain. The forward and reverse conversion circuitries are complex for a general moduli set and limits the applications of RNS. Many researchers have explored efficient methods for forward and reverse conversions [Radhakrishnan et aI. The analog-to-residue conversion usually involves two steps. The analog signal is first converted to digital signal by analog-to-digital converter, then to residue fonn by a binary-to-residue converter. Several implementations of this conversion have been presented for various goals; one of the implementations is by a direct conversion from an analog input to residue fonn. The direct analog-to-residue (AIR) converters operating at Nyquist rate available in literature are detailed in the following section. A novel approach for analog-to-residue conversion is presented in this research using the most popular sigma-delta analog-to-digital converter (SO-ADC). In this approach, the front end is the same as in traditional SO-ADC that uses sigma-delta modulator with appropriate dynamic range and the filtering is done by a filter implemented using RNS arithmetic. Hence, the natural output of the filter is an RNS representation of the input signal. The existing Nyquist rate AIR converters include a multiple-residue flash converter, successive approximation based AIR converter and iterative flash AIR converter. Nyquist rate AJR converters are practically implemented 84 only up to 10-12 bits of resolution due to component matching and circuit nonidealities. Mandyam and Stouraitis presented a direct analog-to-residue conversion that uses flash ADC, PLA, latches, code converter, buffers and XOR gates as shown in Figure 4.1 [Mandyam and Stouraitis, 1990]. A converter of n-bits resolution requires (2n-1) comparators and 2 n resistors. Bj is the quotient which represents the base value in a flash converter and Xi is the residue. The comparators are grouped into (M / m r) groups with mr outputs …