Inside GNSS Media & Research

NOV-DEC 2017

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Page 58 of 67 N O V E M B E R / D E C E M B E R 2 0 1 7 Inside GNSS 59 as compared to a GNSS-based localiza- tion, there are several terrestrial entities involved in a non-GNSS localization, as seen in the "Terrestrial positioning sys- tem" block from Figure 1. First, an LSP should offer an entirely soware or a hybrid soware-hardware solution to the user for his/her position- ing. For example, a mobile application for indoor positioning can be down- loaded from a certain server. Alternately, a dedicated positioning hardware solu- tion can be installed in a shopping mall (based on WLAN, Bluetooth Low Ener- gy BLE, LED, etc.) and users visiting that particular shopping mall can download the application that uses the dedicated infrastructure. The LBSP is the one offering the services to the user, such as finding an item on a shelf in a super- market, or finding the cheapest offers for nearby restaurants, etc. e LSP and LBSP are typically distinct entities, and, in order to preserve the users' privacy, they might interact through the help of a third entity, called an Anonymizer. is is done in order to not send the user's position in clear from one server to another. e last entity in the chain is, of course, the user mobile device, on which the positioning application is running. e position can be computed in two ways: • network-centric approach, when the LSP computes the user's position and sends it to the user, or • mobile-centric approach (J. H. Lee), when the LSP only sends some of the information to the user (e.g., training databases, maps, etc.), and the user device computes its final position based on the signals in range and the information received from the net- work. Clearly, the second approach more successfully preserves location-privacy than the first one. As mentioned earlier, hybrid GNSS positioning systems combine several positioning systems, thus they also incorporate the vulnerabilities of these positioning systems. In a hybrid posi- tioning system aggregation, pre- and post-processing of data can a lmost arbitrarily be divided between LSP and user device as long they are able to share (intermediate) results. ese exchanges of information can potentially suffer breaches of location privacy. Analogous to loose and tight GNSS/INS coupling in other hybrid GNSS systems, either posi- tions or other features derived from the signals are used to yield a more robust solution. ese features are oen ranges or RSS, but any feature unique to a cer- tain location could be used. e location privacy vulnerabilities of hybrid GNSS systems depend on the data used by the non-GNSS positioning system, i.e., ranges or RSS, and whether the data is fused on the device or on the network by the LSP. Data that is missing at the fusion center must be transmit- ted to it. Data fusion on the user device reduces communication and is typically the better choice from a privacy point of view. Non-GNSS Localization In recent years, we have witnessed the advent of the IoT. Terrestrial IoT can have positioning capabilities either based on the signal strength of pow- ers measured at the receiver side or as intrinsic to a certain IoT standard, such as 5G positioning (A. Dammann et alia; M. Koivisto et alia) or LoRa positioning (B. Ray). WLAN is currently the most widespread non-GNSS localization tech- nology in IoT and it is typically based on RSS measurements. Cellular technolo- gies are also gaining prominence in the IoT positioning field. e legacy cellu- lar systems (2G and 3G) do not explic- itly support positioning signals in their standards, but they do have positioning capabilities based, for example, on cell– ID (i.e., positioning of the device inside the coverage areas of the heard trans- mitters), RSS, time of arrival (TOA), or time difference of arrival (TDOA). In 4G cellular systems or LTE, the Positioning Reference Signals (PRS) have been intro- duced to support TDOA-based position- ing. e 5G emerging cellular concept is based on the assumption of very dense Access Nodes (AN), e.g., even down to 5-10 meters average distances between the AN, and very large bandwidths (e.g., trend to move towards mmWave com- munications, where the spectrum is still scarcely used or unused). ese two fea- tures strongly support the capacity of achieving highly accurate positioning and tracking through, for example, com- binations of TOA, TDOA, and Angle of Arrival (AOA) solutions. The privacy threats in 5G will likely be related more to the attacks during channel transmis- sion rather than to unsecure or mali- cious ANs, as the security in 5G has been actively addressed, deeply thought- out and optimized. Another category of emerging com- munication systems with potential sup- port for positioning is the terrestrial IoT category. For instance, Low Power Wide Area Network (LPWAN) standards such as LoRa, NarrowBand IoT (NB-IoT), enhanced Machine Type Communi- cation (eMTC) or Sigfox, which were incipiently devoted to IoT communica- tions, can also be used for IoT position- ing. ese technologies are also affected with the security threats of typical cel- lular and non-GNSS based localization systems. e main threats of IoT positioning techniques relate to attacks performed on the IoT sensor itself instead of the localization ser vice. In this context, t he IoT sensor suf fers from similar threats as most non-GNSS localiza- tion techniques, which are node-based localization solutions. Finally, in het- erogeneous IoT sensor networks, as the hybrid positioning techniques are applied in a control unit and not in the device itself by means of soware, the security breach produced by this so- ware is circumvented. It is supposed that the control unit is already pro- tected against attacks which may jeop- ardize the security and privacy of the sensor or user. More aspects related to hybrid and non-GNSS localization are discussed later. Passive Positioning Concept The current literature includes a dual definition of "passive positioning." e two definitions, used with opposite meanings, are given below: 1. "Passive" from the user's point of view: the user terminal is passive, meaning that it does not send any positioning information to the net- work; the terminal only receives

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