Enhancements of Positioning for IoT Devices

Abstract

The aim of this thesis work is to find novel method(s), which enhance the performance of the existing Observed Time Difference of Arrival (OTDOA) positioning technique for Internet of Thing (IoT) devices introduced in Third Generation Partnership Project (3GPP) standard release 14. In this thesis work, NarrowBand IoT (NB-IoT) positioning is considered as the baseline. The scope includes the investigation on positioning reference signal (PRS), including modifying/replacing the current sequence generation by mathematical derivations, and modifying PRS configuration (e.g. increasing the density, new time/frequency resource grid).

Moreover, different correlator designs at the receiver side (either operating in time or frequency domain) have been analyzed in terms of performance and complexity. In addition, we also investigate the impact of PRS transmission extension either in time domain by sending multiple subframes or in frequency domain by utilizing more spectrum resources (using more Physical Resource Blocks(PRBs)).
Our results show that the current NB-IoT PRS resource mapping is already well designed. The newly suggested sequences and resource time/frequency grids influence the correlation properties which in turn affect the positioning accuracies. Increasing the number of resources for PRS transmission in time/frequency results in positioning accuracy improvements. Different sequences for PRS can lead to performance improvements with the cost of implementation complexity, and design flexibility. In addition, optimizing the original gold sequence shows a consistent good performance gain.

Popular Abstract

The Internet of Things (IoT) is a technology that allows the connectivity of smart devices and items to the Internet. IoT is becoming an increasingly growing topic since it has been estimated that billions of devices will be connected to the internet by 2025. The strong growth in IoT market will trigger a revolutionary in many industries, such as healthcare, agriculture, automotive, safety and security. Thus, our daily life will be significantly affected by the development of this technology in the future. However, IoT will allow endless connections to take place which will open a door of many challenges such as strict requirements of devices power consumption, cost and complexity. Due to its wide range of applications, a lot of new standards have emerged to support IoT integration. Narrowband IoT (NB-IoT) is one of the newest cellular technologies which connects many low-cost devices in severe coverage situations with a lower power consumption and a longer battery lifetime.
In 3rd Generation Partnership Project (3GPP) release 14, positioning feature has been introduced to NB-IoT which will allow the location of devices to be determined by using the transmitted positioning reference signal (PRS) at the base-station side. This positioning technique is known as Observed Time Difference of Arrival (OTDOA), because the device position can be obtained by measuring the time of arrival of multiple signals from multiple base-stations. Then device position can be estimated by measuring the difference between the time of arrivals. Nevertheless, it is a quite challenging task to implement OTDOA in NB-IoT devices, due to the constraint of low cost and the strict power consumption requirements. Furthermore, extreme coverage conditions are expected for NB-IoT devices that affect received signal levels which in turn influences the positioning accuracy.
In this thesis, an OTDOA positioning simulation platform has been built. Several approaches have been implemented at transmitter side with an objective of improving positioning accuracy. The methods include generating various types of sequences, changing the original sequence mapping, and proposing new designs of the time-frequency resource grid in the system.It is shown that the current standard is well designed and has a good positioning performance. A lot of ideas have been implemented within this thesis scope, which lead to adequate accuracy under certain circumstances with acceptable complexity. For future work, more investigation of new sequences can be conducted to be used instead of the current standard. In addition, advanced low power receiver algorithms can be considered.

• author: Odetalla, Hatem and Tian, Guoda
• supervisor: Fredrik Tufvesson
• organization: Department of Electrical and Information Technology
• alternative title: IoT Positioning
• course: EITM02 20172
• year: 2018
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Internet of Things, IoT, NB-IoT, Narrowband IoT, Positioning, OTDOA, PRS, Positioning Reference Signal
• report number: LU/LTH-EIT 2018-647
• language: English
• id: 8949966
• date added to LUP: 2018-06-19 15:01:36
• date last changed: 2018-06-19 15:01:36