Estimation of the time-varying paramets characterizing the wireless channels in cellular systems

我的主要研究目标，是提出一个有效的迭代估计模块的无线信道系数和相关参数（信噪比，最大多普勒频移，时间和频率偏移，角扩展，K因子与视线（LOS），LOS多普勒频移，.）在未来更高数据速度的蜂窝网络中。我将集中我的努力，使用OFDM的宽带系统，即使许多开发的估计算法预计将适用于，此外，一个窄带信道的假设是适当的系统。虽然大多数研究集中在特定的参数，同时使用简化的假设，其他参数，我们的最终目标将是开发一个完整的估计模块，能够估计信道及其参数在实际条件下。因此，估计器必须充分执行非恒定包络调制和有色干扰场景。所开发的模块将依赖于导频符号的存在，并且将评估各种导频分配和信令策略，这将需要针对多址接入（将研究OFDMA、TDMA和混合版本）、智能天线（波束成形、空间复用等）和链路自适应策略的类型进行定制。将考虑时分双工（TDD）和频分双工（FDD）两者，并且利用可能的上行链路/下行链路信道对称性。将研究递归或类似涡轮的方法，以获得相对较低复杂度的全局估计模块。此外，由于我们观察到的GPS使能的蜂窝终端的扩散，我将调查的可能性，通过利用各种发射机/接收机的位置/速度/轨迹的可能的知识（与适当的信令），增强信道参数估计过程。算法设计将首先基于链路级性能，但将基于在模拟器上进行的多用户多蜂窝系统级性能评估进行微调，该模拟器将需要用适当的简化假设来构造。还将审议执行方面的问题。

My main research objective, is to propose an efficient iterative estimation module for the wireless channel coefficients and associated parameters (SNR, maximum Doppler shift, time and frequency offsets, angular spread, K-factor associated with the line-of-sight (LOS) , LOS Doppler shift,...) in future high data speed cellular networks. I will focus my efforts on wideband systems that use OFDM, even if many of the developed estimation algorithms are expected to be applicable, in addition, to systems for which a narrowband channel assumption is appropriate. While most studies focus on specific parameters while using simplifying assumptions for other parameters, our ultimate goals will be to develop a full estimation module capable of estimating the channel and its parameters under practical conditions. The estimators will therefore have to perform adequately with non-constant envelope modulation and with colored interference scenarios. The developed module will rely on the presence of pilot symbols, and various pilot allocation and signaling strategies will be evaluated, which will need to be tailored to the type of multi-access (OFDMA, TDMA and hybrid versions will be studied), smart antenna (beamforming, spatial multiplexing, etc) and link adaptation strategies. Both time division duplex (TDD) and frequency division duplex (FDD) will be considered, and possible uplink/downlink channel symmetry exploited. Recursive or turbo-like approaches will be studied to obtain a global estimation module of relatively low complexity. Furthermore, since we observe a proliferation of GPS-enabled cellular terminals, I will investigate the possibility of enhancing the channel parameters estimation process by exploiting the possible knowledge (with the appropriate signaling) of the position/speed/trajectory of the various transmitters/receivers. The algorithmic designs will first be based on the link-level performance, but will be fine-tuned based on a multi-user multi-cellular system-level performance evaluations conducted on a simulator that will need to be constructed with appropriate simplifying assumptions. Implementation aspects will also be considered.