Symmetrical double-sided two-way ranging

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Symmetrical Double-Sided Two-Way Ranging

In radio technology, symmetrical double-sided two-way ranging (SDS-TWR) is a ranging method that uses two delays that naturally occur in signal transmission to determine the range between two stations: [1]

Radio Technology of using radio waves to carry information

Radio is the technology of signaling or communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves, and received by a radio receiver connected to another antenna. Radio is very widely used in modern technology, in radio communication, radar, radio navigation, remote control, remote sensing and other applications. In radio communication, used in radio and television broadcasting, cell phones, two-way radios, wireless networking and satellite communication among numerous other uses, radio waves are used to carry information across space from a transmitter to a receiver, by modulating the radio signal in the transmitter. In radar, used to locate and track objects like aircraft, ships, spacecraft and missiles, a beam of radio waves emitted by a radar transmitter reflects off the target object, and the reflected waves reveal the object's location. In radio navigation systems such as GPS and VOR, a mobile receiver receives radio signals from navigational radio beacons whose position is known, and by precisely measuring the arrival time of the radio waves the receiver can calculate its position on Earth. In wireless remote control devices like drones, garage door openers, and keyless entry systems, radio signals transmitted from a controller device control the actions of a remote device.

Rangefinder device for determining the distance to an object; device that measures distance from the observer to a target, in a process called ranging

A rangefinder is a device that measures distance from the observer to a target, in a process called ranging.

Signal varying physical quantity that conveys information

In communication systems, signal processing, and electrical engineering, a signal is a function that "conveys information about the behavior or attributes of some phenomenon". In its most common usage, in electronics and telecommunication, this is a time varying voltage, current or electromagnetic wave used to carry information. A signal may also be defined as an "observable change in a quantifiable entity". In the physical world, any quantity exhibiting variation in time or variation in space is potentially a signal that might provide information on the status of a physical system, or convey a message between observers, among other possibilities. The IEEE Transactions on Signal Processing states that the term "signal" includes audio, video, speech, image, communication, geophysical, sonar, radar, medical and musical signals. In a later effort of redefining a signal, anything that is only a function of space, such as an image, is excluded from the category of signals. Also, it is stated that a signal may or may not contain any information.

Contents

This method is called symmetrical double-sided two-way ranging, because:

The Transmission Control Protocol (TCP) is one of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, the entire suite is commonly referred to as TCP/IP. TCP provides reliable, ordered, and error-checked delivery of a stream of octets (bytes) between applications running on hosts communicating via an IP network. Major internet applications such as the World Wide Web, email, remote administration, and file transfer rely on TCP. Applications that do not require reliable data stream service may use the User Datagram Protocol (UDP), which provides a connectionless datagram service that emphasizes reduced latency over reliability.

Signal propagation delay

A special type of packet (test packets) is transmitted from station A (node A) to station B (node B). As time the packet travels through space per meter is known (from physical laws), the difference in time from when it was sent from the transmitter and received at the receiver can be calculated. This time delay is known as the signal propagation delay.

Transmitter Electronic device that emits radio waves

In electronics and telecommunications a transmitter or radio transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves.

Radio receiver radio device for receiving radio waves and converting them to a useful signal

In radio communications, a radio receiver, also known as a receiver, wireless or simply radio is an electronic device that receives radio waves and converts the information carried by them to a usable form. It is used with an antenna. The antenna intercepts radio waves and converts them to tiny alternating currents which are applied to the receiver, and the receiver extracts the desired information. The receiver uses electronic filters to separate the desired radio frequency signal from all the other signals picked up by the antenna, an electronic amplifier to increase the power of the signal for further processing, and finally recovers the desired information through demodulation.

Processing delay

Station A now expects an acknowledgement from Station B. A station takes a known amount of time to process the incoming test packet, generate an acknowledgement (ack packet), and prepare it for transmission. The sum of time taken to process this acknowledgement is known as processing delay.

In data networking, telecommunications, and computer buses, an acknowledgement (ACK) is a signal that is passed between communicating processes, computers, or devices to signify acknowledgement, or receipt of message, as part of a communications protocol. The negative-acknowledgement signal is sent to reject a previously received message, or to indicate some kind of error. Acknowledgements and negative acknowledgements inform a sender of the receiver's state so that it can adjust its own state accordingly.

In a network based on packet switching, processing delay is the time it takes routers to process the packet header. Processing delay is a key component in network delay.

Calculating the range

The acknowledgement sent back to station A includes in its header those two delay values – the signal propagation delay and the processing delay. A further signal propagation delay can be calculated by Station A on the received acknowledgement, even as this delay was calculated on the test packet. These three values can then be used by an algorithm to calculate the range between these two stations.

Propagation delay is the length of time taken for the quantity of interest to reach its destination. It can relate to networking, electronics or physics.

Algorithm An unambiguous specification of how to solve a class of problems

In mathematics and computer science, an algorithm is a set of instructions, typically to solve a class of problems or perform a computation. Algorithms are unambiguous specifications for performing calculation, data processing, automated reasoning, and other tasks.

Verifying the range calculation

To verify that the range calculation was accurate, the same procedure is repeated by station B sending a test packet to station A and station A sending an acknowledgement to station B. At the end of this procedure, two range values are determined and an average of the two can be used to achieve a fairly accurate distance measurement between these two stations.

See also

Related Research Articles

IEEE 802.11 set of media access control (MAC) and physical layer (PHY) specifications

IEEE 802.11 is part of the IEEE 802 set of LAN protocols, and specifies the set of media access control (MAC) and physical layer (PHY) protocols for implementing wireless local area network (WLAN) Wi-Fi computer communication in various frequencies, including but not limited to 2.4, 5, and 60 GHz frequency bands.

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In telecommunications, the round-trip delay time (RTD) or round-trip time (RTT) is the length of time it takes for a signal to be sent plus the length of time it takes for an acknowledgement of that signal to be received. This time delay includes the propagation times for the paths between the two communication endpoints.

Communication channel physical transmission medium such as a wire, or logical connection

A communication channel or simply channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used to convey an information signal, for example a digital bit stream, from one or several senders to one or several receivers. A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second.

Hidden node problem Problem in wireless networking

In wireless networking, the hidden node problem or hidden terminal problem occurs when a node can communicate with a wireless access point (AP), but cannot directly communicate with other nodes that are communicating with that AP. This leads to difficulties in medium access control sublayer since multiple nodes can send data packets to the AP simultaneously, which creates interference at the AP resulting in neither packet getting through.

RTS/CTS is the optional mechanism used by the 802.11 wireless networking protocol to reduce frame collisions introduced by the hidden node problem. Originally the protocol fixed the exposed node problem as well, but modern RTS/CTS includes ACKs and does not solve the exposed node problem.

In data communications, flow control is the process of managing the rate of data transmission between two nodes to prevent a fast sender from overwhelming a slow receiver. It provides a mechanism for the receiver to control the transmission speed, so that the receiving node is not overwhelmed with data from transmitting node. Flow control should be distinguished from congestion control, which is used for controlling the flow of data when congestion has actually occurred. Flow control mechanisms can be classified by whether or not the receiving node sends feedback to the sending node.

Transmission Control Protocol (TCP) uses a network congestion-avoidance algorithm that includes various aspects of an additive increase/multiplicative decrease (AIMD) scheme, with other schemes such as slow start and congestion window to achieve congestion avoidance. The TCP congestion-avoidance algorithm is the primary basis for congestion control in the Internet. Per the end-to-end principle, congestion control is largely a function of internet hosts, not the network itself. There are several variations and versions of the algorithm implemented in protocol stacks of operating systems of computers that connect to the Internet.

Radiolocating is the process of finding the location of something through the use of radio waves. It generally refers to passive uses, particularly radar—as well as detecting buried cables, water mains, and other public utilities. It is similar to radionavigation, but radiolocation usually refers to passively finding a distant object rather than actively one's own position. Both are types of radiodetermination. Radiolocation is also used in real-time locating systems (RTLS) for tracking valuable assets.

Multilateration is a navigation and surveillance technique based on the measurement of the times of arrival (TOAs) of energy waves having a known propagation speed. The time origin for the TOAs is arbitrary. For surveillance, a subject of interest – in cooperative surveillance, often a vehicle – transmits to multiple receiving stations having synchronized 'clocks'. For navigation, multiple synchronized stations transmit to a user receiver. To find the coordinates of a user in n dimensions, at least n + 1 TOAs must be measured. Multilateration systems are also called hyperbolic systems, for reasons discussed below.

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PowWow Power Optimized Hardware and Software FrameWork for Wireless Motes

PowWow is a wireless sensor network (WSN) mote developed by the Cairn team of IRISA/INRIA. The platform is currently based on IEEE 802.15.4 standard radio transceiver and on an MSP430 microprocessor. Unlike other available mote systems, PowWow offers specific features for a very-high energy efficiency:

References

  1. ↑ IEEE Standard 802.15.4a: Part 15.4: Wireless Medium Access Control (MAC) and Physical Layer (PHY) specifications for low-rate wireless personal area networks (WPANs) Amendment 1: Add Alternate PHYs
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