Publication Date


Document Type


First Advisor

Tahernezhadi, Mansour

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Electrical Engineering


Telephone--Emergency reporting systems; Telephone; Wireless; Spread spectrum communications


This thesis proposes a frequency hopping spread spectrum (FHSS) signaling system as the basis for a wireless 911 system. The proposed 911 wireless system has the advantages of (i) working independently of the telephone network, (ii) allowing people to get help while outdoors and away from a telephone, (iii) being able to get police, fire and/or medical help with a press of a button, (iv) getting help without the need to talk, (v) transmitting your position quickly to the 911 emergency services, (vi) providing immunity from fake callers and other users and (vii) being small and lightweight. The proposed wireless 911 system works independently of local 911 systems that use the wired telephone network and present statewide *911 using the cellular telephone network. The proposed system brings additional capabilities lacking in these systems. The proposed system uses FHSS technology and transmits the user's location, personal identification number and an emergency code to the 911 receiver. The proposed system overcomes the near-far problem that plagues code division multiple access (CDMA) systems. The system incorporates minimum shift keying (MSK) modulation, providing a high signal-to-noise ratio (SNR) data transmission and bi-phase shift keying (BPSK) modulation for determining position. The total system requires a transmitter for each user, three remote relays and a receiver. Each relay receives the distress signal, up converts the signal to a different frequency and retransmits the signal to the receiver. The receiver locks on to the original distress signal, creates a timing reference from the BPSK signal and decodes the MSK data. With separate circuits, the receiver locks on to each relay signal. The receiver calculates the time delay between the distress signal received directly from the transmitter and the distress signal received through each relay. Knowing the location of each relay, the receiver calculates the position of the transmitter through triangulation within a meter.


Includes bibliographical references (pages [78]-79)


xii, 98 pages




Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type