Antenna Subset Modulation for secure millimeter-wave wireless communication

Abstract

The small carrier wavelength at millimeter-wave (mm-Wave) frequencies allows the possibility of implementing a large number of antennas on a single chip. This work uses the potential of large antenna arrays at these frequencies to develop a low-complexity directional modulation technique: Antenna Subset Modulation (ASM) for point-to-point secure wireless communication. The main idea in ASM is to communicate information by modulating the far-field radiation pattern of the array at the symbol rate. By driving only a subset of antennas and changing the subset used for each symbol transmission the far-field pattern is modulated. Two techniques for implementing antenna subset selection are proposed. The first technique is simple where the antenna subset to be used is selected at random for every symbol transmission. While randomly switching antenna subsets does not affect the symbol modulation for a desired receiver along the main lobe direction, it effectively randomizes the amplitude and phase of the received symbol for an eavesdropper along a sidelobe. Using a simplified statistical model for random antenna v subset selection, an expression for the average symbol error rate (SER) is derived as a function of observation angle for linear arrays. To overcome the problem of large peak sidelobe level in random antenna subset switching, an optimized antenna subset selection procedure based on simulated annealing is then discussed. Finally, numerical results comparing the average SER performance of the proposed techniques against conventional array transmission are presented. While both methods produce a narrower information beam-width in the desired direction, the optimized antenna subset selection technique is shown to offer better security and array performance.vi

Silent Antenna Hopping Transmission Technique for Secure Millimeter-Wave Wireless Communication

“…In recent years, mm-wave has attracted more attention due to its inherent advantages such as very wide bandwidth, licensefree spectrum. Another key advantage is the ability to co-locate large numbers of antennas in a small space [1]- [3], thanks to the significant decrease in wavelength at these frequencies; for example 64 antennas can be co-located in a single die [4]. Conversely, mm-wave propagation is subject to a large path loss, thus the non-line-of-sight signals are very weak, and the scattering is less significant.…”

“…The authors in [4] and [16] proposed solutions to protect signal copies that are emitted from the side-lobes from eavesdropping processes via distorting the signal constellation. In [16], [17] and [18] a phased-array transmitter is used to perform Directional Modulation (DM).…”

“…Physical-layer security can be implemented with various techniques [12] such as beam-steering, jamming, or a combination of the two. In beam-steering techniques, the transmitter aims to steer the main lobe towards the desired destination, and steer the null towards the direction of the unintended users [4], [13]- [15].…”

Directional modulation far‐field pattern separation synthesis approach

“…Later it was discovered that by imposing baseband signals directly onto the beam-forming networks, for example, variable RF phase shifters and attenuators [3][4][5], or the antenna radiators [6] in an actively driven antenna array, signal transmissions with direction-dependent modulation formats could be achieved. Another two novel types of DM structures, named by the authors as antenna subset modulation [9] or four-dimensional (4D) antenna arrays [10,11] and Fourier lens DM arrays [12,13], have also been described.…”

“…Directional modulation (DM) technology, as a promising physical layer security means for wireless communication in free space, has attracted extensive research in recent years [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Different to conventional wireless transmitters, which broadcast identical copies of information into the whole space, DM-enabled transmitters have the capability of scrambling information formats, that is, the received constellation patterns in IQ space, along every spatial directions other than a pre-specified communication direction where no distortion will occur.…”