Low Complexity Time-Concatenated Turbo Equalization for Block Transmission Without Guard Interval: Part 1 - The Concept

This paper proposes a novel time-concatenated turbo equalization technique, chained turbo equalization (CHATUE), that allows block transmission systems to eliminate the guard interval (GI), while achieving excellent performance. The proposed CHATUE algorithm connects turbo equalizers neighboring in time, so that they exchange information about their inter-block-interference components in the form of a posteriori log-likelihood ratio. The latest version of the low complexity sub-optimal turbo equalization technique for block-wise single carrier transmission, frequency domain soft cancellation and minimum mean squared error, is fully exploited in developing the CHATUE algorithm. Results of extrinsic information transfer chart analysis as well as a series of bit-error rate (BER) simulations show that excellent performances can be achieved without imposing heavy computational burden in multipath-rich (quasi-static) block Rayleigh fading channels. It is shown that, if the information bit-rate is kept identical (because it may be unpreferable for the industry to change the frame structure), the CHATUE algorithm achieves lower BER than that with block transmission with GI, because lower rate (strong) code for error protection can be used by utilizing the time-duration made available by eliminating the GI. In addition, by combining the proposed structure with a simple rate-1 doped accumulator, further BER improvement exhibiting clear turbo cliff can be achieved. A sister paper (a Part-2 paper) applies the proposed CHATUE algorithm to single carrier frequency division multiple access systems Hui et al. (Wirel Pers Commun, 2011). This work was supported in part by SANYO Electric Co., Ltd. and in part by the (Kinki) Mobile Wireless Center. K. Anwar (B) · T. Matsumoto School of Information Science, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan e-mail: [email protected] T. Matsumoto Center for Wireless Communication, University of Oulu, 90014 Oulu, Finland e-mail: [email protected]; [email protected]