Abstract
Directional modulation (DM) has been proposed as a technique to enhance physical layer security of wireless transmissions. In DM, the improvement of security is achieved by increasing the transmitted power in such a way that the bit error rate (BER) is degraded in the observation angles out of the desired secure direction. The performance of DM in terms of BER is typically evaluated by transmitting a stream of symbols for every observation angle, but this approach can be time consuming. In this communication, we propose an approach to evaluate, accurately and efficiently, the BER of dynamic DM (DDM) for standard modulation schemes. Several DDM configurations will be tested to illustrate the benefits and limitations of the evaluation method. The proposed approach is also used to present a non-iterative DDM synthesis with restrictions in the BER response.
Highlights
In wireless transmissions, the absence of a physical boundary that limits the wave propagation makes transmitted information highly vulnerable to interception by potential eavesdroppers [1]
SNRav(φ) in the side lobes and the information beam width cannot be adjusted independently. This strategy is inefficient in terms of power efficiency of DDM (PEDDM), since artificial noise is transmitted along some directions, such as the radiation nulls of the conventional radiation pattern, where no information is sent
We continue to use the synthesis method of [19], but we set the artificial noise to constant magnitude and random phase, as proposed in [16,23,24], so that PEDDM can be adjusted based on (8)
Summary
The absence of a physical boundary that limits the wave propagation makes transmitted information highly vulnerable to interception by potential eavesdroppers [1]. The relentless growth of computational power is making it possible to break ciphers that were considered virtually unbreakable in the past [3] In this sense, an additional level of security will be achieved if encryption is performed in the physical layer where the raw interchange of information takes place. Physical layer security (PLS) exploits intrinsic characteristics of the wireless channel to limit the amount of information that can be extracted at bit level by a potential eavesdropper [4]. DM is typically based on antenna arrays that generate multiple transmission radiation patterns These radiation patterns are chosen to produce the desired constellation in the selected secure observation angle and, at the same time, a distorted or noisy version of the constellation in the other observation angles [8]. DM is termed static (SDM) when the distortion does not change with time and dynamic (DDM) when the distortion changes at the symbol rate [9]
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