Table 4 Application specific comparison of angular DM techniques
From: Directional modulation techniques for secure wireless communication: a comprehensive survey
S.no | Description | Applications |
|---|---|---|
Spatial angular DM | ||
1 | Switched-phased array architectures: ASM [49,50,51, 53,54,55], SPA [58, 59], SAH [60], LSA [61] [62], demonstration of 71 GHz secure link [65] | Switched-phased array DM architectures are well-suited for secure angular point-to-point wireless communication. Low-complexity and ease of implementation are two major advantages |
2 | Cryptography-inspired analysis of DM [22] [56], and cryptographic array optimization of ASM [57] | Focussed on cryptographic analysis and optimization of DM arrays. SLL optimization is shown to be ineffective. The need for an integrated security approach for PLS techniques is emphasized |
3 | Fourier network based circular array for DM [63] | It provides an added advantage of secure beamsteering along two angular directions, i.e. along elevation and azimuth, for more precise and secure transmission at the expense of increased complexity |
4 | DM using retrodirective antenna array [64] | Feasible for more than one user positioned along different angular directions, providing multi-directional security |
5 | Recommended for single antenna based point-to-point secure angular directional communication. Requires switching control circuitry of varactors and switches placed in the near-field of antenna | |
6 | Multiple antenna arrays based positional modulation [68, 69] | Multiple antenna arrays positioned at different angular directions are required. Overcomes the issue of security breach in case eavesdropper is spatially close to legitimate user, but at the expense of higher complexity. Not feasible for situations in which multiple arrays cannot be placed at multiple spatial positions |
7 | Intelligent reflecting surfaces for multipath DM [70] | Intelligent reflecting surfaces are used to create multipath transmission. Suited for multipath DM applications |
Temporal angular DM | ||
8 | Antenna array is modulated with respect to sub-slots of time. Major advantage is that hardware level changes in conventional phased array transmitter architecture are not required | |
9 | Proposed for angular directional security of OFDM transmitter [83], and antenna level multi-carrier TMA [84] | |
Frequency angular DM | ||
10 | Random sub-carrier selection for DM [85] | Secures OFDM architecture with respect to angular transmission |
11 | DFT-based multi-directional DM [86] | Provides multi-directional secure OFDM transmission capability |
Phase angular DM | ||
12 | Secures transmission by phase control of antenna array. Major drawback is compromised directivity due to misalignment of array phases | |
13 | Dual-beam phased array [90] | Uses two beams for directional transmission of data symbols. Provides better security than phased array transmitter with reduced antenna elements |
Polarization Angular DM | ||
14 | Transmission is both directionally secure and polarization sensitive. Useful for dual-polarized secure satellite applications | |