LLR calculation for LDPC coded SCBT in 60 GHz WPAN

The single-carrier block transmission（SCBT）,a.k.a.,single-carrier frequency-domain equalization（SC-FDE）,is being considered as an option technique for the wireless personal area network（WPAN） operating at 60 GHz.It is found that for residential environment,in non-line-of-sight（NLOS） multi-path channels,the SCBT is much more effective to combat the inter-symbol interference（ISI） compared with orthogonal frequency division multiplexing（OFDM）.Low-density parity-check（LDPC） codes are a class of linear block codes which provide near capacity performance on a large collection of data transmission and storage channels while simultaneously admitting implementable decoders.To facilitate using LDPC codes for SCBT system,a new log-likelihood ratio（LLR） calculation method is proposed based on pilot symbols（PS）.Golay Sequences whose sum autocorrelation has a unique peak and zero sidelobe are used for creating the PS.The position and length of the PS are not fixed in the data blocks.The simulation results show that the proposed method can significantly improve the LDPC decoding performance in SCBT system.This is very promising to support ultra high-data-rate wireless transmission.

Partial channel information feedback mechanism for FFR-based multi-channel systems

This article puts forward a partial channel state information （CSI） feedback scheme for fractional frequency reuse （FFR）-based orthogonal frequency division multiple access （OFDMA） systems. Efficient CSI feedback strategy plays an important role in opportunistic scheduling because base station （BS） can employ adaptive modulation and coding （AMC） technique to adaptively change transmission rates according to CSI feedback, and therefore the spectrum efficiency can be improved significantly. On the other hand, FFR is a simple but effective technique to improve the throughput of users at cell edge. To exploit opportunistic scheduling in FFR-based OFDMA systems, both users and spectrum are divided into multiple groups in this article, and specific feedback pattern is designed for each user group on each spectrum sub-band. Simulations results prove that the proposed algorithm can reduce the feedback load significantly, while maintain nearly the same performance as the system with full feedback.

Generalized analysis model for fractional frequency reuse

Fractional frequency reuse （FFR） is an effective technique to mitigate co-channel interference in orthogonal frequency division multiple access （OFDMA）-based broadband cellular systems.In this paper,we present a generalized model for FFR under which all existing FFR schemes can be considered as its special cases.Additionally,quality factor has been proposed to indicate the quality of the subband.An interesting conclusion can be drawn that,as the power ratio in FFR is adjusted continuously,the corresponding quality factor varies smoothly.Subsequently,simulation is conducted based on worldwide interoperability for microwave access （WiMAX）,and the result agrees well with our theoretical analysis.Finally,an effective range for power ratio is presented,which is very instructive to practical system design.