Implementation of Coded OFDM and IDMA in 4G

The 4G wireless networks are being developed to make use of the latest developments in wireless technology domain. These networks are envisioned to offer higher bandwidths, up to 100 Mbps, global roaming, and network scalability. Coded OFDM, a combination of orthogonal frequency division multiplexing (OFDM) and code division multiple access (CDMA) has been considered as an efficient technique due to its bandwidth efficiency, frequency diversity, high throughput and immunity to channel dispersion. Low Density Parity Check (LDPC) codes are used for Coded OFDM transmission due to its simple iterative decoding and excellent performance which results in high throughput. Interleave Division Multiple Access (IDMA) fulfils the design objectives of bandwidth and power efficiency, link adaptation with respect to data rate, data reliability, quality of service, and service provisioning, low-complexity transceivers, and ability to operate on frequency selective and fast-fading channels. In this paper, the salient features as well as the important technological advancements being incorporated in 4G wireless networks are described. The improvement of optimized LDPC-coded OFDMA system shows an improvement in performance gain in terms of Frame Error Rate (FER) for more than 1dB as compared to other coded OFDM techniques. More improvements can be obtained by using Variable Spreading Factor Orthogonal Frequency and Code Division Multiple Access (VSF-OFCDMA) and optimizing the placement of the information bits in LDPC codes.