The long-term evolution (LTE) is the newly adopted technology to offer enhanced capacity and coverage for current mobility networks, which experience a constant traffic increase and skyrocketing bandwidth demands. This new cellular communication system, built upon a redesigned physical layer and based on an orthogonal frequency division multiple access (OFDMA) modulation, features robust performance in challenging multipath environments and substantially improves the performance of the wireless channel in terms of bits per second per Hertz (bps/Hz). Nevertheless, as all wireless systems, LTE is vulnerable to radio jamming attacks. Such threats have security implications especially in the case of next-generation emergency response communication systems based on LTE technologies. This proof of concept paper overviews a series of new effective attacks (smart jamming) that extend the range and effectiveness of basic radio jamming. Based on these new threats, a series of new potential security research directions are introduced, aiming to enhance the resiliency of LTE networks against such attacks. A spread-spectrum modulation of the main downlink broadcast channels is combined with a scrambling of the radio resource allocation of the uplink control channels and an advanced system information message encryption scheme. Despite the challenging implementation on commercial networks, which would require inclusion of these solutions in future releases of the LTE standard, the security solutions could strongly enhance the security of LTE-based national emergency response communication systems.

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The performance of a noncoherent serial acquisition technique is evaluated for direct-sequence spread-spectrum packet communications. The acquisition technique that is considered uses threshold crossing of a matched-filter output to detect a fixed-length preamble at the start of each packet. The analysis accounts for frequency mismatch between the transmitter and the receiver due to oscillator inaccuracies and mobility-induced Doppler shifts. It also accounts for the effects of automatic gain control (AGC) in the receiver. The role of the AGC system in determining the acquisition performance is examined. In addition, selection of the optimal acquisition threshold is considered, and a simple method for selection of a good suboptimal threshold is presented. It is shown that use of this threshold results in performance close to that obtained with the optimal threshold over a wide range of channels.

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