Matthias Kamuf

Successive interference cancellation techniques for LTE downlink

Successive interference cancellation (SIC) is a well-known technique for mitigating interference. For multiple-layer reception, hard-decision SIC with perfect per-layer rate control has been proven to be a capacity-achieving scheme. In practice, however, due to imperfect rate control and signaling constraints, there is a potential for certain variants of SIC techniques to achieve better performance than the conventional hard-decision SIC approach. In this paper, the benefits of various SIC techniques are studied. We show that a soft SIC scheme that passes information iteratively between equalizer, demodulator, and decoder enhances MIMO reception in downlink LTE.

Modification of SOVA-Based Algorithms for Efficient Hardware Implementation

In this paper, a modified soft-output Viterbi algorithm (SOVA) is presented to enable efficent hardware implementation. The forward-only processing of the SOVA has an inherent lower latency than forward-backward algorithms such as BCJR and its offsprings, which are commonly used in iterative decoders. Thus, SOVA-based architectures require less parallelization and therefore hardware for the same data throughput. A simplification is proposed to the Battail rule (BR) SOVA to approximate the concurrent path reliability values with the corresponding metric differences. This simplified BR-SOVA (SB-SOVA) performs close to max-log-MAP. Furthermore, a novel hybrid decoding architecture is proposed that combines the simplicity of the original Hagenauer rule and the performance-preserving properties of the SB-SOVA to trade implementation complexity for decoding performance. The hybrid approach is evaluated with practical link-level simulations of the downlink data channel in LTE Rel-8.