1. A Time Domain Equalizer for Channel Shortening in Project 802.16m SDD Document Number: S802.16m-07/199 Date Submitted: November 12, 2007 Source: Chun Fang Lee, Yuan Pin Lin, Fan-Shuo Tseng, Chieh Yuan Ho, Chung-Hsien Hsu, Ta-Sung Lee, Yu-Ted Su, Wen-Rong Wu, Kai-Ten Feng, Ching Yao Huang, NCTU/MediaTek Inc., 1001 Ta Hsueh Road, Hsinchu, Taiwan 300, ROC Pei-Kai Liao (pk.liao@mediatek.com), I-Kang Fu (IKang.Fu@gmail.com) and Paul Cheng (paul.cheng@mediatek.com)pk.liao@mediatek.comIKang.Fu@gmail.compaul.cheng@mediatek.com MediaTek Inc. No. 1 Dusing Rd. 1 Hsinchu Science Park Hsinchu City 300 Taiwan. Venue: Atlanta, GA Base Contribution: IEEE C802.16m-07/199 Purpose: Propose TGm SDD to have a section “Time domain equalizer (TEQ)”. Notice: This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.16. Patent Policy: The contributor is familiar with the IEEE-SA Patent Policy and Procedures: and.http://standards.ieee.org/guides/bylaws/sect6-7.html#6http://standards.ieee.org/guides/opman/sect6.html#6.3 Further information is located at and.http://standards.ieee.org/board/pat/pat-material.htmlhttp://standards.ieee.org/board/pat S802.16m-07/199

2. Introduction Motivation –A cyclic prefix (CP) is required to add in front of an OFDM / OFDMA symbol. to have the circular convolution property, to avoid the intersymbol interference (ISI) due to the channel delay spread (CDS). –In some scenarios, the length of the channel impulse response (CIR) may exceed the CP range, residual ISI is induced, the system performance is degraded. Purpose –The technique is further extended as the time domain equalizer (TEQ) to shorten the CIR into the CP range. –Propose to enable this functionality in IEEE 802.16m system

3. System Model In an OFDM / OFDMA system, CP is added to each symbol in the transmitter side. If the CDS of a channel is larger than the CP size, then the severe ISI is induced. TEQ is proposed to put in the receiver side to shorten the CDS of the channel. A typical OFDM system model for the TEQ design

4. Time Domain Equalizer Only Limited computations are involved in calculating the TEQ parameters. The performance of the system with TEQs is superior to that of system without TEQ, especially on the channel with long CDS.

5. Proposed Texts in the Table of Content x.y Time domain equalizer (TEQ) [A cyclic prefix (CP) is added in front of an OFDM / OFDMA symbol to avoid the intersymbol interference (ISI). In some scenarios, the length of the channel delay spread (CDS) will exceed the CP range. When it happens, the ISI is induced and the system performance is degraded. To put a TEQ in front of the FFT module is a simple way such that the CIR can be shortened in the receiver side. Hence, the system performance can be improved significantly.]