Throughput of Hybrid ARQ Types for UTRA TDD mode

A throughput analysis of ARQ Types I and II-III based on simulations for unconstrained delay data (UDD) services is presented. We emphasise differences between Types I and II and consider Types II and III as minor variants of the same scheme which we call “Type II-III” for the purpose at hand. For this contribution, a subset of the protocol on Layers 1-3 for UMTS terrestrial radio access (UTRA) time division duplex (TDD) mode is simulated for a single cell. Both user traffic and signalling messages suffer from path-loss, fading, and interference in the model. Interference due to traffic in neighbouring cells is also taken in to account through the “actual value interface”. Results are obtained for downlink traffic for various code-rates and interleaving schemes. The available results include capacity, signalling overhead, the distribution of the number of retransmissions, and PDU delay. It is shown that Type II-III greatly outperforms Type I for the cases “UDD 2048 Pico” and “UDD 384 Micro” in terms of capacity and the number of retransmissions. Although, the benefit of using Type II-III over Type I becomes smaller at lower bit rates it is still significant. This is exemplified by simulation results for the case “UDD 8 Micro”. We conclude that Hybrid ARQ Type II-III outperforms Type I for all UDD services between 8 kb/s and 2 Mb/s for UTRA TDD mode