Performance of TTI Bundling for VoIP In EUTRAN TDD Mode

The long term evolution (LTE) of 3GPP radio-access technology aims to develop a framework towards a high-data-rate, low-latency and packet-optimized radio access technology: Evolved Universal Terrestrial Radio Access Networks (E-UTRAN). However, low terminal transmission power, short TTI length and long HARQ RTT give a critical problem on LTE TDD UL performance in a coverage-limited scenario. To solve coverage problem, this paper presents an effective coverage enhancement mechanism called TTI bundling to enhance uplink VoIP performance in LTE TDD mode. HARQ design for different TDD configurations is discussed with TTI bundling. Performance evaluation for TTI bundling with VoIP traffic is carried out by system simulation, and the impact from different bundling options with different bundle size and packet delay budget is investigated. The simulation analysis proves that with proper bundle size and suitable packet delay budget setting, TTI bundling can enhance the coverage performance for LTE TDD effectively.