Method and system for radio-location determination

• US 6,459,704 B1
• Filed: 08/12/1997
• Issued: 10/01/2002
• Est. Priority Date: 08/12/1997
• Status: Expired due to Term

• Current Assignee: USA Mobility Wireless, Inc. (Spok Holdings, Inc.)
• Original Assignee: Spectrum Tracking Systems, Inc. (5th Element Tracking LLC)
• Inventors: Jandrell, Louis H. M.
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): Tsegaye, Saba
• Application Number:
  US08/910,066
• Time in Patent Office: 1,876 Days
• Field of Search: 370/252, 370/343, 370/344, 370/349, 370/387, 370/445, 370/447, 370/462, 370/480, 370/448, 370/497, 370/338, 375/202, 375/132, 375/130, 435/67.1, 435/67.3, 435/67.6
• US Class Current: 370/445
• CPC Class Codes: G01S 2205/06 Emergency
• CPC Class Codes: G01S 5/02 using radio waves using satellite radio beacon systems for determining position G01S19/00
• CPC Class Codes: G08B 25/007 Details of data content structure of message packets; data protocols
• CPC Class Codes: G08B 25/016 Personal emergency signalling and security systems emergency non-personal manually actuated alarm activators G08B25/12
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 74/0875 with assigned priorities based access

Abstract

A method for prioritizing multiple access to a communication channel for the transmission of packets from a plurality of devices on the communication channel. It comprises the steps of once a packet is ready to be transmitted over a communications channel, sensing if a channel is idle, waiting for a predetermined (prioritizing) time after sensing the channel is idle and then transmitting the packet only if the channel is sensed to still be clear at the end of that (prioritizing) time. A scheme is also described for applying an efficient frequency hopping technique to the method for use on congested, shared radio-bands requiring spread spectrum techniques for access to the band.

Claims

1. A frequency hopping spread spectrum method for communicating a message, the steps comprising the following steps in the sequence set forth:

A) assigning a priority to the message;

B) selecting a frequency and setting a timer to a hop interval and starting the timer;

C) sensing a channel at the selected frequency;

D) waiting an interval based on the priority of the message, restarting the process at step B) whenever the timer expires and the channel has not been clear for the interval, wherein a new frequency is selected and the timer is restarted;

E) transmitting the message if the selected frequency is still clear;

F) waiting until an occurrence of at least one of an acknowledgment is received and the timer expires; and

G) repeating steps B) through F) when at least one of the message was not transmitted in step E) and the acknowledgment was not received in step F) occurs, wherein a different frequency is selected each time step B) is repeated.

2. The frequency hopping spread spectrum method for communicating a message, as in claim 1, wherein the frequency is selected randomly.

3. The frequency hopping spread spectrum method for communicating a message, as in claim 1, wherein the frequency is selected from a predefined table.

4. The frequency hopping spread spectrum method for communicating a message, as in claim 1, the sensing step further comprises selecting another frequency and resetting the timer to the hop interval when the channel is busy and the timer has expired.

5. The frequency hopping spread spectrum method for communicating a message, as in claim 4, wherein the another frequency is selected randomly.

6. The frequency hopping spread spectrum method for communicating a message, as in claim 4, wherein the another frequency is selected from a predefined table.

7. The frequency hopping spread spectrum method for communicating a message, as in claim 1, further comprising, providing feedback indicating that the message was received.

8. The frequency hopping spread spectrum method for communicating a message, as in claim 1, wherein the another frequency is selected randomly.

9. The frequency hopping spread spectrum method for communicating a message, as in claim 1, wherein the another frequency is selected from a predefined table.

10. The frequency hopping spread spectrum method for communicating a message, as in claim 1, wherein the selected frequency is in the 902-928 MHz ISM band.

11. The frequency hopping spread spectrum method for communicating a message, as in claim 1, wherein the selected frequency is chosen from a set at least of fifty pre-selected frequencies.

12. The frequency hopping spread spectrum method for communicating a message, as in claim 1, wherein the message is a data packet, the data packet comprising:

a) a bit synch and timing preamble;

b) a checksum;

c) an opcode;

d) a repeat count and hop count filed;

e) a transmitter identifier field.

13. An apparatus for transmitting a message using frequency hopping spread spectrum, comprising:

communication means for communicating a message and sensing a channel at a selected frequency;

signal processing means operatively coupled to the communication means, the signal processing means programmed to perform the following functions in the sequence set forth;

a) assigning a priority to a message,

b) selecting a frequency and setting a timer to a hop interval and starting the timer

c) receiving from the sensing means, the availability of the channel, the signal processing means selecting a new frequency if the channel is unavailable and the timer expired;

d) waiting an interval based on the priority of the message and receiving from the sensing means the availability of the channel, the signal processing means selecting a new frequency and resetting the timer when the channel is unavailable and the timer has expired; and

,

e) causing the transmission means to send the message if the channel is clear;

f) waiting for an acknowledgment to the message;

g) repeating steps b) through f) when at least one of the message is not sent in step e) and the acknowledgment is not received in step f), wherein a new frequency is selected and the timer is restarted each time step b) is repeated.

14. Computer readable instructions on a computer readable medium, consisting of:

A) computer readable instructions for assigning a priority to the message;

B) computer readable instructions for selecting a frequency, setting a timer to a hop interval and starting the timer;

C) computer readable instructions for receiving sensing data for a channel at the selected frequency;

D) computer readable instructions for waiting an interval based on the priority of the message, wherein a new frequency is selected and the timer is restarted when the timer has expired and the channel has not been available for a time period at least equal to the interval;

E) computer readable instructions for transmitting the message if the channel is still clear;

F) computer readable instructions for waiting until an occurrence of at least one of an acknowledgment is received and the timer expires; and

G) computer readable instructions for repeating steps B) through F) upon the occurrence of at least one of the message not being sent in step E) and an acknowledgment is not