MIMO pre-equalization and DFE for high-speed off-chip communication

In this contribution, we present a multiple-input multiple-output (MIMO) transceiver scheme for high-speed chip-to-chip communication over low-cost electrical interconnects. Linear MIMO pre-equalization at the transmitter is combined with decision feedback equalization (DFE) at the receiver to counteract the adverse effect of inter symbol interference (ISI) and crosstalk (XT). Considering an energy constraint at the transmit side, we derive elegant closed-form expressions for the equalization filters under a minimum mean square error (MMSE) criterion. Numerical analysis shows that the combination of linear MIMO pre-equalization and MIMO DFE allows to significantly improve the reliability of future high-speed off-chip communication

Application of MIMO DF equalization to high-speed off-chip communication

In this contribution, we present a multiple-input multiple-output (MIMO) equalizer with decision feedback (DF) for high-speed chip-to-chip communication. We derive an elegant closed-form expression for the minimum mean square error (MMSE) equalization filters and show that the application of MIMO DF equalization (DFE) allows to significantly improve the reliability of high-speed communication over low-cost electrical interconnects

MIMO Equalization for Multi-Gbit/s Access Nodes Affected by Manufacturing Tolerances

While the requirements for delivering high throughputs increase exponentially with every generation of access node hardware, the device cost is of primary concern. As a result, multiple- input multiple-output (MIMO) equalization, which has been shown to facilitate multi-Gbit/s communication over low-cost parallel electrical interconnects, is emerging as an attractive high- speed interconnect solution for next-generation access nodes. Because of the high operating frequencies, however, the transfer functions of the on- and off-chip interconnects become highly susceptible to manufacturing tolerances (MTs); hence, the equalization filters must be adjusted to the specific channel realization to achieve optimal performance, which involves a high implementation and computational complexity. Considering that the MTs are usually limited, we propose a robust low-complexity transceiver consisting of a fixed MIMO linear pre-equalizer (which avoids the need for feeding back the channel state information to the transmitter), with either a fixed or adjustable MIMO decision- feedback equalizer (DFE). For a specific chip-to- chip interconnect operating at 75 Gbit/s per line and a 26 dB signal-to-noise ratio, we show that the resulting bit error rate does not exceed 10^(-12) for MTs up to 10.5% (fixed DFE) and 17.7% (adjustable DFE) of the nominal line width

Temporal and spatial combining for 5G mmWave small cells

This chapter proposes the combination of temporal processing through Rake combining based on direct sequence-spread spectrum (DS-SS), and multiple antenna beamforming or antenna spatial diversity as a possible physical layer access technique for fifth generation (5G) small cell base stations (SBS) operating in the millimetre wave (mmWave) frequencies. Unlike earlier works in the literature aimed at previous generation wireless, the use of the beamforming is presented as operating in the radio frequency (RF) domain, rather than the baseband domain, to minimise power expenditure as a more suitable method for 5G small cells. Some potential limitations associated with massive multiple input-multiple output (MIMO) for small cells are discussed relating to the likely limitation on available antennas and resultant beamwidth. Rather than relying, solely, on expensive and potentially power hungry massive MIMO (which in the case of a SBS for indoor use will be limited by a physically small form factor) the use of a limited number of antennas, complimented with Rake combining, or antenna diversity is given consideration for short distance indoor communications for both the SBS) and user equipment (UE). The proposal’s aim is twofold: to solve eroded path loss due to the effective antenna aperture reduction and to satisfy sensitivity to blockages and multipath dispersion in indoor, small coverage area base stations. Two candidate architectures are proposed. With higher data rates, more rigorous analysis of circuit power and its effect on energy efficiency (EE) is provided. A detailed investigation is provided into the likely design and signal processing requirements. Finally, the proposed architectures are compared to current fourth generation long term evolution (LTE) MIMO technologies for their anticipated power consumption and EE

On Partial Response Signaling for MIMO Equalization on Multi-Gbit/s Electrical Interconnects

Because of its ability to deal with intersymbol interference (ISI) and crosstalk (XT) over mutually coupled electrical interconnects, multiple-input multiple-output (MIMO) decision feedback equalization (DFE) has proven to be a promising low-cost solution for achieving multi-Gbit/s wireline communication on- and off-chip. However, not only does the channel become very sensitive to manufacturing tolerances at very high symbol rates, the latency in the feedback loop becomes prohibitively large as well. Whereas the former issue has been addressed by adopting a stochastic MIMO approach where (part of) the equalization filters depend on the channel statistics rather than on the actual channel, we tackle in this paper the latency issue by setting to zero the first N taps of the feedback filters. Moreover, we show that precoded partial response (PR) signaling can improve the performance of the resulting scheme, although the achieved gain is smaller than in the case of single-input single-output (SISO) equalization

SGD Frequency-Domain Space-Frequency Semiblind Multiuser Receiver with an Adaptive Optimal Mixing Parameter

A novel stochastic gradient descent frequency-domain (FD) space-frequency (SF) semiblind multiuser receiver with an adaptive optimal mixing parameter is proposed to improve performance of FD semiblind multiuser receivers with a fixed mixing parameters and reduces computational complexity of suboptimal FD semiblind multiuser receivers in SFBC downlink MIMO MC-CDMA systems where various numbers of users exist. The receiver exploits an adaptive mixing parameter to mix information ratio between the training-based mode and the blind-based mode. Analytical results prove that the optimal mixing parameter value relies on power and number of active loaded users existing in the system. Computer simulation results show that when the mixing parameter is adapted closely to the optimal mixing parameter value, the performance of the receiver outperforms existing FD SF adaptive step-size (AS) LMS semiblind based with a fixed mixing parameter and conventional FD SF AS-LMS training-based multiuser receivers in the MSE, SER and signal to interference plus noise ratio in both static and dynamic environments