Multiplier Free Filter Bank Based Concept for Blocker Detection in LTE Systems Thomas Schlechter Institute of Networked and Embedded Systems Klagenfurt University 9020 Klagenfurt, Austria Email: thomas.schlechter@ieee.org c 2011 IEEE. Personal use of this material is per- mitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. T. Schlechter, ”Multiplier free filter bank based concept for blocker detection in LTE systems,” in Proc. Conf. Design and Architectures for Signal and Image Process. (DASIP 2011), Tampere, Finland, Nov. 2011, pp. 291-297. http://dx.doi.org/10.1109/DASIP.2011.6136893 Abstract— Power efficiency is an important issue in mobile communication systems. Especially for mobile user equipments, the energy budget, limited by a battery, has to be treated carefully. Despite this fact, quite an amount of energy is wasted in todays user equipments, as analog and digital frontend in communication systems are engineered for extracting the wanted signal from a spectral environment defined in the corresponding communication standards with their extremely tough requirements. In a real receiving process those requirements can typically be considered as dramatically less critical. Capturing the environmental transmission conditions and adapting the receiver architecture to the actual needs allows to save energy during the receiving process. An efficient architecture being able to fulfill this task for a typical Long Term Evolution scenario is desired and introduced in this paper. The development of a suitable filterchain is described and a complexity comparison to Fast Fourier Transformation based methods is given. I. I NTRODUCTION Recently, research on Cognitive Radio (CR) has gained great interest. The concept of CR, e.g. de- scribed in [1], allows the user equipment (UE) to scan its relevant environment with respect to instantaneous spectrum allocation. In the original context of CR this information is used for efficient spectrum usage by different UEs using various radio access technologies. However, this concept can be used beyond. Considering a UE providing Long Term Evolution (LTE) functionality, knowledge about the environmental spectral composition is extremely valuable for the design of the receive path [2, 3]. The main idea is as follows: if the UE detects many interferences to the wanted signal, then both the analog and digital frontend (AFE/DFE) of the receive path have to provide full performance, e.g. highly linear amplifiers, filters of high order, etc. In the remainder of this paper this interferences will be called blockers. Full performance of the AFE and DFE results in high energy consumption of the UE. If, on the other hand, there are only few blockers present, which additionally contain little energy, the receive path does not have to run in full performance mode, resulting in power saving. A concept handling this task for the Universal Mobile Telecommunications System test case has been described in [4], while this paper introduces a concept for efficient spectral estimation for a typical LTE scenario. The con- cept presented here is optimized to the LTE specification, while approaches for a more general implementation are described in [5]. The Matlab simulation environment im- plementing the given approach is described in [6], while a hardware-software co-simulation approach based on a FPGA board has been given in [7]. Section II describes the initial conditions and worst case scenario the UE has to cope with to clarify the motivation of building a spectrum sensing filter chain. Section III introduces and discusses different approaches of DFE based interference detection. Section IV provides simulation results and complexity estimates using the method described in [8] for specific implemented filter chains.