Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-11-16
2001-11-13
Urban, Edward F. (Department: 2746)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C342S357490, C342S451000
Reexamination Certificate
active
06317602
ABSTRACT:
BACKGROUND OF THE INVENTION
Signal processing methods which determine the time-of-arrival of signals are well known. It is known to read frequency modulated coded signals and to determine a time of arrival of these signals to the time resolution given by the inverse of the bandwidth of the signal. To date, no signal processing methods and apparatuses have been described which can improve upon this resolution by analysing the signal in terms of its composite components.
Packet switching networks are known such as modacom and Mobitex. These networks are exclusively operated as messaging networks and they operate according to a structured protocol in which remote units request transmission windows to communicate with the nearest processing base station. The transmitted data packets are of very short duration and each comprises identification code information identifying the unit from which the message was sent. To date, no methods have been proposed to analyse the signals transmitted by remote units operating in accordance with said packet switching networks and thus provide a positioning capability to the packet switching network's messaging capability.
Conventional networks determine the approximate location of GSM telephones and personal message pagers to the resolution of a cell based upon the signal strength of their transmissions. Communication channels are allocated to that base station which receives the strongest signal from the transmitting unit. Conventional networks do not process signals to determine the location of transmitting units to a high resolution.
Furthermore, no signal processing system is presently available which serves to analyse a discrete signal in terms of its composite components and thereby greatly improve upon the bandwidth limitation on the determination of the time-of-arrival of the signal whereby a coded signal can be determined to a time resolution given by the inverse of the bandwidth. Moreover, no signal processing system of this type is known which also serves to determine the position of a remote transmitting unit by differential comparison of the time-of-arrival of the signal at a plurality of receivers in such a simple and effective manner as herein proposed
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a novel signal processing system which serves to provide a highly accurate measure of the time of arrival of a discrete coded signal comprising composite component attributes.
It is a further object of the present invention to provide such a signal processing system method and apparatus which is both efficient and effective in its processing algorithm.
It is a further object of the present invention to provide the means to make use of a differential time measurement technique which is applicable for positioning purposes by gathering information from a plurality of receivers that analyse either a discrete coded signal such as that transmitted according to the protocol of a packet switching network, wherein said signal comprises component parts, or a continuously transmitted coded signal comprising composite component parts.
It is a further object of the present invention to provide a signal-processing system comprising a time-measurement technique that is applicable to the transmission protocol of a packet switching network such as that used by the paged area network as described in U.S. Pat. No. 5,051,741 (Wesby).
BRIEF SUMMARY OF THE INVENTION
Certain of the foregoing and related objects are readily-attained according to the present invention by the provision of a signal processing system which includes the means to receive a discretely transmitted coded signal at one or more receiving means such as that transmitted is according to the protocol of a packet switching network wherein the signal is composed of composite parts which may comprise a frequency modulated signal ramp of increasing amplitude from zero to a maximum followed by a frequency modulated data stream of digital bits.
1. The invention of the signal processing system relates to a method and apparatus for determining the time of arrival of a coded signal.
2. More particularly, it relates to a signal processing method and apparatus to determine the arrival of a discrete coded signal comprising differing composite components such as signals used for transmitting data over a data bus operating according to the protocol of a packet switching network.
3. Furthermore, the invention relates to a signal processing method and apparatus for identifying discrete components of a transmitted coded signal for determining the time-of-arrival of this coded signal.
4. Furthermore, the system relates to a method for comparing the difference in time of arrival of a signal at a number of receiving stations wherein the signal may comprise a discrete coded signal such as that used in packet switching networks or a continuously transmitted signal comprising differing component parts which can be readily identifiable by the receiving means.
Alternatively the signal may comprise a continuously transmitted signal which includes a train of composite signal components such that the arrival of the is coded signal can be time-determined relative to one of these components.
Alternatively and including the above examples, the signal may be transmitted using one or more of any transmission mediums including any possible encoding.
In all cases, the receiver divides the signal into its component parts and recognises the components of the signal. In the particular case of a discrete coded signal transmitted according to the protocol of a packet switching network, the receiver tracks the arrival of the signal as it traces a frequency-modulated bandwidth-limited ramp, increasing in amplitude up to the maximum operational amplitude, which is frequency modulated according to known data modulation principles with a specified bandwidth about a carrier frequency.
Furthermore, the receiver identifies the rate of change of the amplitude of the signal as it increases up to a maximum amplitude.
Furthermore, the receiver stores the transmitted coded signal and analyses it subsequent to storage. Furthermore the receiver provides a highly accurate timing reference such that the time of arrival of the transmitted coded signal may be determined to a very high time-resolution.
A master station communicates with the network of receiving stations to determine which of the receiving stations has determined a time-of-arrival of a coded signal transmitted from a remote transmitter.
The invention relates to using the analogue part of a signal containing coded information, whatever the form, in order to determine the time-of-arrival of this signal, regardless of the carrier frequency, the coding of the signal (PSK, FSK, etc.) and regardless of the data contained in the signal. The method according to the invention is applicable to all signals whose characteristics are known.
Furthermore, the master station communicates periodically with each of the plurality of receiving stations to determine the exact difference in time between the master station's own timing means and each receiver's timing means in order that the master station is able to combine time-of-arrival information from different receivers wherein each receiver has its own unique time reference.
Furthermore, each received coded signal, transmitted from a remote transmitter, whose time-of-arrival is determined by one of each of a plurality of receivers spaced throughout an area from within which said signal is transmitted, is processed by a master station which receives said encoded time-of-arrival information from each of the plurality of receivers which received the said coded transmission and combines said information differentially, knowing the relative positions of each of the receivers, and knowing the difference in time between the master station's own timing means and each of the receiver's timing means such that the master station may determine a position from which the transmission was sent rela
Merchant & Gould P.C.
Nokia Telecommunications Oy
Urban Edward F.
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