Abstract-In this paper we present detailed profiling results and identify the time critical algorithms of the Long Term Evolution (LTE) layer 2 (L2) protocol processing on an ARM based mobile hardware platform. Furthermore, we investigate the applicability of a single ARM processor combined with a traditional hardware acceleration concept for the significantly increased computational demands in LTE and future mobile devices. A virtual prototyping approach is adopted in order to simulate a state-of-the-art mobile phone platform which is based on an ARM1176 core. Moreover a physical layer and base station emulator is implemented that allows for protocol investigations on transport block level at different transmission conditions . By simulating LTE data rates of 100 Mbit/s and beyond, we measure the execution times in a protocol stack model which is compliant to 3GPP Rel.8 specifications and comprises the most processing intensive downlink (DL) part of the LTE L2 data plane. We show that the computing power of a single embedded processor at reasonable clock frequencies is not enough to cope with the L2 requirements of next generation mobile devices. Thereby, Robust Header Compression (ROHC) processing is identified as the major time critical software algorithm, demanding half of the entire L2 DL execution time. Finally, we illustrate that a conventional hardware acceleration approach for the encryption algorithms fails to offer the performance required by LTE and future mobile phones.

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In this paper, we present different acceleration concepts for the Robust Header Compression version 2 (ROHCv2) algorithms in Long Term Evolution (LTE) handsets. First, we explore the potential performance improvements and energy savings by adopting scratchpad memories at various sizes. Second, dedicated hardware accelerators with different data transfer modes are compared in terms of processing speed and energy efficiency on system level. By applying a virtual prototyping methodology with a proprietary filter module, we are able to investigate these two approaches within a state-of-the-art ARM based mobile phone platform at real software loads. Additionally, combined measurements of the execution time together with an estimation of the energy, that is consumed in the memory and the bus architecture, are performed. With reasonably dimensioned scratchpad memories (16 kB for instructions and data respectively), maximum speedups and energy savings both of approximately 60 % are achieved depending on the cache sizes in the embedded processor. Even better performance, especially in combination with big caches, is reached with a dedicated ROHCv2 hardware accelerator supporting the processing of several packets at once in a so called list mode. Compared to the pure software case, the execution time and the energy consumption are both improved by up to 80 % at small caches and still amount to more than 40 % and almost 30 % at big caches, respectively.

In this paper we present an efficient software im plementation of the Advanced Encryption Standard (AES) used in the confidentiality algorithm of the Long Term Evolution (LTE) protocol. Our implementation is based on slicing and merging the bytes of several data blocks to exploit processor's architecture width for multi-block encryption. In addition, an appropriate lookup table and data organization in memory are applied, combined with media processing instructions in order to enhance the performance of AES in embedded environments.Other optimized software implementations from literature are also explored and evaluated in comparison to the proposed implementation with respect to processing throughput and energy consumption using a multi-core based mobile phone platform.Simulation results show that the proposed implementation is the fastest among other implementations and achieves improvements in performance up to 69 % while providing S9 % of energy savings. Moreover, the presented implementation is scalable for multi-core execution. When running on two cores, it fulfills the LTE data rate of 100 Mbitls and extends energy savings to 68%, leading to a total of 13 times improvement in energy efficiency. I. I NTRODUCTIONThe speed of data transfer in mobile networks is continu ously increasing, reaching up to 100 Mbitls in the upcoming Long Term Evolution (LTE) standard. Security in cellular communication systems is based on cryptographic algorithms to encrypt and decrypt user data. These algorithms are com putationally expensive and require relatively long execution times. A former performance analysis of the LTE protocol stack in [1] identified ciphering as a time critical function. Thus providing an efficient ciphering implementation has a great impact on overall system performance. The energy consumption of software plays also a vital role in mobile devices due to its limited battery capacity.Ciphering algorithms in mobile handsets are typically ac celerated by dedicated hardware. Software implementations, however, enable sharing of computing resources between ci phering and other communication functionalities. In addition, it provides flexibility needed to support multiple cellular stan dards using different ciphering schemes. However, software implementations are relatively slow and therefore have to be efficient enough in order to fulfill the required timing constraints while consuming lowest energy possible. In this paper we introduce a novel software implementation of the confidentiality algorithm used in the LTE standard. The pro posed implementation exploits the processor architecture width to perform several ciphering operations simultaneously. As 978-1-61284-486-2/111$26.00 ©2011 IEEE embedded multi-core processors are expected to be deployed in future mobile devices [2], we also investigate how further speedups can be obtained by using multi-core processing. Fi nally, our implementation is evaluated against other optimized implementations from literature with respect to processing throughput and energy c...