WPR.3 - Adaptive coding/modulation for the wireless channel

Objectives

Adaptive Modulation and Coding (AMC) techniques address the problem of proper real-time adjustment of transceiver parameters, based on the environmental and operational conditions for better spectral utilization. WPR.3 objective is primarily the development of AMC algorithms to achieve the goals posed by the new data services and application requirements of current and evolving standards; additionally, to analyze the implementation aspects of such algorithms and give architectural guidelines based on a comprehensive complexity/performance trade-off analysis.

Description of work

Work is segregated into three tasks, based on the target system of each effort.

Task TR3.1: AMC for Multi-carrier systems

The goal of this task is to examine and propose new AMC algorithms in terms of complexity and performance for the evolving multi-carrier based standards. The first step towards that goal is the adoption of a model description of the link-level performance of a system, capable to support emerging MIMO coded multi-carrier standards (e.g. WiMax, LTE-Advanced). This modelling effort will target a description that compromises between simplicity (thus cost-effective implementation) and accuracy. It will incorporate different MIMO options, channel estimation noise, feedback delay and ICI noise (due to Doppler, phase noise, residual frequency offset) and interference. Based on that model AMC algorithms will be designed and assessed.

The research effort in this task includes AMC techniques for bit-interleaved coded OFDM (BIC-OFDM) wireless systems, and the modelling of hybrid automatic repeat request (HARQ) protocols for AMC design purposes. AMC methods for emerging non-orthogonal multi-carrier technologies (e.g. filtered multi-tone schemes or generalized non-orthogonal multi-carrier modulations) will also be investigated. Besides the classic optimization goals, advanced research on goodput maximization will also be performed. The goodput is the bit rate related to successfully transmitted bits, and contains in a way a compromise between bit rate and bit error rate. This task will also examine the effect of channel estimation errors on AMC performance.

Main players: IASA, UCL, PUT, BILKENT, CNIT, RWTH, CNRS

Task TR3.2: AMC for Continuous Phase Modulation systems

The main goal of this task is to investigate adaptivity techniques for coded CPM systems and to propose new spectrally efficient coded-CPM schemes to be used in adaptive CPM systems. As a first step, CPM schemes will be evaluated in terms of achievable spectral efficiency and decoding complexity. Receiver algorithms featuring different complexity-efficiency trade-offs will be studied. Then, coded-CPM schemes will be investigated starting from the chosen modulation schemes and sets of modulation-coding configurations enabling accurate adaptation to channel conditions will be proposed. The following step will consist in the study of adaptation algorithms employing such sets of modulation-coding configurations. Multi-user frequency-division multiplexing (FDM) CPM systems with tight carrier frequency spacing will be studied and suitable low-complexity multi-user receivers will be proposed. Adaptation algorithms for such scenario will be studied, their complexity will be evaluated and their performance assessed through simulation

Main players: CNIT, PUT

Task TR3.3: AMC for Coherent QAM modulation

The goal of this task is to analyze adaptive wireless systems under a framework that enables to capture main aspects affecting the performance (small-scale and large-scale fading, noise, coding and modulation techniques, non-ideal channel estimation, diversity techniques, power control, interference, etc.) and to obtain sensitivity of the performance to system parameters. Starting from simple cases such as single-carrier systems, and proper definition of performance metrics and fundamental limits, we aim to learn some lessons possibly generalized and useful for the design of more complex systems. This would enable the system design considering the trade-off between performance and complexity taking all the aspects above mentioned into account. In non-ideal conditions (e.g., practical channel estimation) this task will cover: definition of metrics; performance behaviour and bounds; utility-based strategies for AMC; adaptive communications in different channels; adaptive modulation and space-time coding.

Main players: CNIT, IASA, UCL, PUT