David L. Mills. A Computer-Controlled LORAN-C Receiver for Precision Timekeeping. Technical Report 92-3-1, Department of Electrical and Computer Engineering, University of Delaware, March 1992.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....clocks is #. The value of the parameter # must be known by all nodes in the network, and for temporal leashes, generally must be on the order of a few microseconds or even hundreds of nanoseconds. This level of time synchronization can be achieved now with offthe shelf hardware based on LORAN C [28], WWVB [29] or GPS [9, 42] although such hardware is not currently a common part of wireless network nodes, it can be deployed in networks today and is expected to become more widely utilized in future systems at reduced expense, size, weight, and power consumption. In addition, the time ....

....longer than the nominal range of the radio, or any other range that might be specified. Sufficiently tight clock synchronization can be achieved in a wireless LAN using commercial GPS receivers [42] and wireless MAN technology could be sufficiently time synchronized using either GPS or LORAN C [28] radio signals. A MAC layer protocol using TIK efficiently protects against replay, spoofing, and wormhole attacks, and ensures strong freshness. TIK is implementable with current technologies, and does not require significant additional processing overhead at the MAC layer, since the ....

David L. Mills. A Computer-Controlled LORAN-C Receiver for Precision Timekeeping. Technical Report 92-3-1, Department of Electrical and Computer Engineering, University of Delaware, Newark, DE, March 1992.

....We assume that all nodes in the ad hoc network have synchronized clocks within a maximum bound between any two nodes clocks of A. The value of the parameter A must be known by all nodes in the network. Though this time synchronization can be maintained with off the shelf hardware based on LORAN C [58], WWVB [59] or GPS [ 18, 87] it is currently not a common part of ad hoc network nodes, and the time synchronization signal itself may be subject to attack [23] Stable time sources such as microcomputer compensated crystal oscillators [8] can provide sub second accuracy for several months. ....

David L. Mills. A computer-controlled LORAN-C receiver for precision timekeeping. Technical Report 92-3-1, Department of Electrical and Computer Engineering, University of Delaware, March 1992.

....value of the parameter # must be known by all nodes in the network. For the purpos of this paper, # must be very small; generally on the order of a few microseconds or even hundreds of nanoseconds. This level of time synchronization can be achieved now with off the shelf hardware based on LORAN C [28], WWVB [29] or GPS [9, 46] although such hardware is not currently a common part of ad hoc network nodes, it can be deployed in ad hoc networks today and is expected to become more widely utilized in future systems at reduced expense, size, weight, and power consumption. In addition, the time ....

....longer than the nominal range of the radio, or any other range that might be specified. Sufficiently tight time synchronization can be achieved in a wireless LAN using commercial GPS receivers [46] and wireless MAN technology could be sufficiently time synchronized using either GPS or LORAN C [28] radio signals. A MAC using TIK efficiently protects against replay, spoofing, and wormhole attacks, and ensures strong freshness. TIK is implementable with current technologies, and does not require significant additional processing at the MAC layer, since the authentication of each packet can ....

David L. Mills. A Computer-Controlled LORAN-C Receiver for Precision Timekeeping. Technical Report 92-3-1, Department of Electrical and Computer Engineering, University of Delaware, March 1992.

....fails to utilize the redundancy of multiple processors, and increases contention for the host processor. On the other hand, synchronizing independent computer clocks is a difficult process at best [MO85] Methods for hardware synchronization to UTC (via WWV short wave broadcasts, or Loran [Mil92] and GPS positioning systems [Cla95] are not commercially available. Their construction is complicated by variable atmospheric propagation delays and government restrictions. Instead, synchronization is accomplished through the exchange of timestamps among multiples machines over the network. ....

....because most workstations have no well behaved reference clock for comparison. It is easy to draw a timeline like Figure 1. 1, but to create that precise picture of reality requires a precision time source, plus the software and hardware to interface it to the CPU in a deterministic manner [Mil92]. This study also investigates techniques for detecting instability and estimating accuracy without a precision time source. 1.4.2 Measurement techn iques The second study emphasizes the use of ansynchronous clocks to order events occurring on several processors, and to measure the intervals ....

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Mills, D.L. A Computer--controlled Loran--C Receiver for Precision Timekeeping. Electrical Engineering Department Report, University of Delaware, 92-3-1, March 1992.

....problem because most workstations have no well behaved reference clock for comparison. It is easy to draw a timeline like Figure 1, but to create that precise picture of reality requires a precision time source, plus the software and hardware to interface it to the CPU in a deterministic manner [Mil92]. Section 3 of this paper describes techniques for detecting instability and estimating accuracy without a precision time source. Section 4 describes three approaches to getting the required functionality for experimental studies of operating systems. Large scale instabilities induced by time ....

Mills, D.L. "A Computer--controlled Loran--C Receiver for Precision Timekeeping." Electrical Engineering Department Report 92-3-1, Univ. of Delaware, March 1992, 63 pp.

....designs have appeared in the open literature [9 12] although many designs are commercial and unpublished. Culver s 1986 paper [13] gives a review of receiver architectures which were prevalent at that date. Most modern receivers, e.g. the design by Inmos [9, 10] and the timing receiver by Mills [11], process the received RF signal directly, by synchronous sampling. Receivers of this type typically track a standard zero crossing, which is usually the one at t = 30 s. They typically take one sample each pulse, i.e. 16m samples in each 2G period, where m is the number of stations in the ....

....is not required. The software component is simple. The program comprises about 50 pages of C code, which includes a real time scheduler and all necessary support routines. The DSP code which implements the software component of figure 2 comprises only six pages. By contrast, Mills s software [11] has about 30 pages of C code (excluding comments) but relies on the services of an underlying operating system for scheduling, input and output, and mathematical routines. The size of the Inmos [9, 10] program is not known; but it is a stand alone Occam [20] program, and a direct size comparison ....

David L. Mills, A computer-controlled Loran-C receiver for precision timekeeping, Electrical Engineering Department report 92-3-1, University of Delaware (March 1992). -- 20 --

....problem because most workstations have no well behaved reference clock for comparison. It is easy to draw a timeline like Figure 1, but to create that precise picture of reality requires a precision time source, plus the software and hardware to interface it to the CPU in a deterministic manner [Mil92]. Section 3 of this paper describes techniques for detecting instability and estimating accuracy without a precision time source. 6 Section 4 describes three approaches to getting the required functionality for experimental studies of operating systems. Large scale instabilities induced by time ....

Mills, D.L. A computer--controlled Loran--C receiver for precision timekeeping. Electrical Engineering Department Report 92-3-1, Univ. of Delaware, March 1992, 63 pp.

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David L. Mills. A Computer-Controlled LORAN-C Receiver for Precision Timekeeping. Technical Report 92-3-1, Department of Electrical and Computer Engineering, University of Delaware, March 1992.

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