Equaliser

Abstract: Equalisation of a communication channel is achieved through use of a Wiener filter frequency response mechanism that operates to transform at least a portion of a data stream generated from a plurality of space time coded (STC) symbol streams received from a plurality of transmit antenna elements into a packet spectrum. A training sequence for a channel through which the symbol streams have been sent is also transformed to a channel impulse response spectrum in order to assess the channel impulse response for the channel. The packet spectrum is equalised with the channel impulse response spectrum to produce an equalised packet spectrum in the transform domain. This is then converted into a time domain equalised data stream for recovery of originally transmitted information.

Abstract: Currently, 3GPP standardizes an evolved UTRAN (E-UTRAN) within the Release 8 Long Term Evolution (LTE) project. Targets include higher spectral efficiency, lower latency, higher peak data rate when compared to previous 3GPP air interfaces. The air interface of E-UTRAN is based on OFDMA and MIMO in downlink and on SCFDMA in uplink Main challenges for a terminal implementation include efficient realization of the inner receiver, especially for channel estimation and equalisation, and the outer receiver including a turbo decoder which needs to handle data rates of up to 75 Mbps per spatial MIMO stream. We show that the inner receiver can nicely and straightforwardly be parallelized due to frequency domain processing. In addition to the computational complexity of even a simple linear equaliser, one of the challenges is an efficient implementation considering necessary flexibility for different MIMO modes, power consumption and silicon area. This paper will briefly overview the current LTE standard, highlight a functional data flow through the single entities of an LTE terminal and elaborate more on possible first implementation details, including sample algorithms and first complexity estimates.

Abstract: A transversal filter (TF) and a decision feedback equaliser (DFE) have been manufactured as integrated electronic circuits in SiGe technology suitable for 10 Gbit/s operation. Using these devices, electrical equalisers for implementation in optical receivers have been realised and the reduction in penalty induced by polarisation mode dispersion (PMD) has been experimentally analysed. A device consisting of the concatenation of a TF and DFE exhibits the lowest residual penalty, < 3 dB for a PMD with a differential group delay of < 80 ps.