Pierre Bertrand

Channel Gain Estimation from Sounding Reference Signal in LTE

3G Long Term Evolution (LTE) technology aims at addressing the increasing demand for mobile multimedia services in high user density areas. Channel aware scheduling across wide system bandwidth is one of the key techniques enabling this goal. The Sounding Reference Signal (SRS) in uplink comes in support of this feature as its main purpose is to allow the LTE Base Station (eNodeB) estimating the UL channel of the users across the scheduling bandwidth. Therefore, SRS channel and channel gain estimators are important functions that can drive the overall performance of the system. In this paper, we study such estimation algorithms and show that SRS noise variance estimation is necessary to deliver a non-biased channel gain estimation. We suggest to provision a cyclic shift of the SRS for this purpose and show simulation results validating the performance of the proposed scheme.

Frequency Offset Estimation in 3G LTE

3G Long Term Evolution (LTE) technology aims at addressing the increasing demand for mobile multimedia services in high user density areas while maintaining good performance in extreme channel conditions such as high mobility of High Speed Trains. This paper focuses on the latter aspect and compares different algorithms for the uplink frequency offset estimation in LTE Base Stations (eNodeB). A frequency-domain maximum-likelihood based solution is proposed, taking profit of the available interference-free OFDM symbols de-mapped (or de-multiplexed) at the output of the FFT of an OFDMA multi-user receiver. It is shown to outperform the state-of-the-art CP correlation approach on both link-level performance and complexity aspects.

Link Adaptation Control in LTE Uplink

Long Term Evolution (LTE) technology aims at addressing the increasing demand for mobile multimedia services in high user density areas. Channel aware scheduling across wide system bandwidth is one of the key techniques enabling this goal. To this end, the LTE scheduler heavily relies on an accurate and robust Link Adaptation (LA) function for predicting the best modulation and coding scheme (MCS) of a user. In this paper, we complement the popular block error rate (BLER) based LA with a scheme maximizing the throughput without BLER constraint and show that it indeed optimizes the spectral efficiency performance. We also describe a sub-optimal UL scheduler providing a good performance/complexity trade-off between a low-complexity basic scheduler and the optimal, but impractical complexity-wise.

NLOS Backhaul PHY Optimized for Small Cells

The evolution to denser radio access network (RAN) with small cells in cluttered urban environments increases the need for wireless non-line-of-sight (NLOS) backhaul. A novel NLOS backhaul solution is designed that is optimized for coexistence with TD-LTE radio access. The NLOS backhaul solution is based on TD-LTE air-interface for fast development but with critical modifications and improvements to meet all the technical requirements of wireless backhaul. The system is targeted for unprecedented 10 bits/s/Hz spectral efficiency through 256-QAM, concatenated turbo and Reed-Solomon (RS) coding, and 2x2 MIMO techniques. This paper discusses the key design concepts of the air-interface with simulation results in NLOS channels.