Multiplex communications – Communication over free space – Repeater
Reexamination Certificate
2000-05-11
2001-10-16
Ton, Dang (Department: 2661)
Multiplex communications
Communication over free space
Repeater
C370S310000
Reexamination Certificate
active
06304559
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to digital wireless communications and more particularly to a protocol for use between radio transceivers and repeaters as well as between radio transceivers and radio transceivers.
BACKGROUND OF THE INVENTION
Wireless communications are well known. Such systems as walkie talkies, CB radios, and cellular telephones utilize wireless communications to facilitate point-to-point communications between individuals at different locations.
Such wireless communications systems typically utilize well known half duplex or talk-then-listen radio methodology wherein a user can listen to an incoming communication, or can speak, but not both simultaneously. Such half duplex wireless communication systems use either a push button control or the like or alternatively use a voice operated switch (VOX) to change the mode of the transceiver from receive to transmit.
While such contemporary wireless communication systems have generally been suitable for their intended purposes, they possess the inherent deficiency of requiring explicit actuation of the transmit mode via such a manually operated or automatic switch and also suffer from the inherent deficiency of not permitting an incoming communication when the transceiver is in the transmit mode. Of course, requiring an operator to manually actuate the transmit mode, typically via a push button switch, necessitates that the operator use a hand (or possibly a foot) to key the microphone. Such explicit operation of the transceiver is not only a distraction, but may also be extremely undesirable in instances where the operator's hands (and possibly feet) are otherwise occupied. For example, tank drivers, aircraft pilots, helicopter pilots, etc., particularly when engaged in demanding maneuvers, may not be able to perform such manipulations, or may do so only at the risk of neglecting some other task which requires immediate attention.
Voice operated switches have been developed in an attempt to mitigate the problems associated with manually operated half duplex transceivers. However, such voice operated switches introduce an altogether new set of problems. Such problems include the operation of a voice operated switch in a high noise environment and the necessity of properly adjusting the sensitivity of the voice operated switch in such a high noise environment. As those skilled in the art will appreciate, high levels of ambient noise frequently result in the undesirable and inadvertent keying or actuation of the voice operated switch, such that no actual voice transmission is broadcast and the transceiver is prevented from accepting incoming transmissions.
Also, the user of such a voice operated switch in a high noise environment must speak louder than normal, so as to actuate even a properly adjusted voice operated switch. Such loud speaking can be fatiguing and may even result in hoarseness or other voice-related problems.
Regardless of what type of half duplex transceiver is utilized (manually actuated or VOX), another problem associated with such half duplex systems is the inadvertent keying thereof. Manually operated switches have an undesirable tendency to stick in the actuated position, thereby resulting in constant transmission and the inability to receive broadcasts from other transceivers. Thus, the operator who has such a stuck key can not even be notified by other individuals, who are listening to the inadvertent broadcast, that his key is stuck in the actuator position, since the individual who has the stuck key is incapable of receiving broadcasts due to half duplex operation of the transceiver. Further, as discussed above, voice operated switches may become inadvertently actuated due to high ambient noise levels.
As such, it is clear that a full duplex transceiver for point-to-point communications would be desirable.
Wire intercoms are also well known. Frequently, such intercoms are configured such that a plurality of users may talk simultaneously with respect to one another and each user may talk while listening to the conversations of a plurality of users. Thus, conversations via such wired intercoms tend to be much more natural than those taking place via wireless, half-duplex wireless communication systems.
It would further be desirable to provide intercom-like operation of the radio transceivers, such that they are capable of receiving a plurality of separate transmissions simultaneously, while the user is speaking. In this manner, each transceiver will pick up the broadcast of all other transceivers so as to provide a much more natural means for communication.
It would further be desirable to provide a comprehensive communications system which integrates wireless communications with wired intercom communications, such that persons utilizing a wired communications system, such as that of a tank, aircraft, helicopter, etc., may readily communicate among one another, and may also, simultaneously if desired, communicate with persons who are not part of the wired intercom system.
SUMMARY OF THE INVENTION
The present invention specifically addresses and alleviates the above-mentioned deficiencies associated with the prior art. More particularly, the present invention comprises a method for implementing a time division multiple access protocol for digital communications between a personal communication unit (PCU) which comprises a radio transceiver and a universal adapter interface (UAI) which comprises a repeater, or between one PCU and another PCU, or between one UAI and another UAI.
The method comprises the steps of dividing a communication into a plurality of frames having a predetermined length of time, and dividing each frame into a plurality of downlink slots, each downlink slot for containing a transmission from the repeater to the receiver and a plurality of uplink slots, each uplink slot for containing a transmission from the transceiver to the repeater or to another PCU. After the communication has been formatted according to the protocol of the present invention, it is transmitted.
The step of receiving the communication may comprise either receiving a voice communication or receiving a data communication.
The step of dividing the communication into at least one frame preferably comprises dividing the communication into at least one frame having a length of approximately 5.12 milliseconds. Those skilled in the art will appreciate that various other time periods are likewise suitable.
The steps of dividing each frame into a plurality of downlink slots and a plurality of uplink slots comprises dividing each frame into a plurality of paired downlink and uplink slots having corresponding indices.
According to the preferred embodiment of the present invention, a Medium Access Control (MAC) algorithm is used to provide fair access to available uplink slots.
A radio transceiver accesses an available uplink slot to transmit information to the repeater. Similarly, the repeater uses a corresponding downlink slot to transmit information to that particular radio transceiver. In this manner, the uplink slots and the downlink slots are tied to one another, preferably via a common indexing scheme.
According to the preferred embodiment of the present invention, a downlink slot D
0
is provided. The repeater transmits information to those radio transceivers that do not have an uplink slot via downlink slot D
0
.
A frame gap is preferably formed intermediate adjacent frames to prevent adjacent frames from overlapping due to clock inaccuracies. The frame gap also facilitates synthesizer re-programming in a frequency hopping spread spectrum system.
The step of dividing each frame into a plurality of downlink slots and a plurality of uplink slots preferably comprise dividing each frame into downlink and uplink slots comprising: a bit synchronization field; a slot synchronization field for radio acquisition; a header field for control information; a data field for digital audio and digital data information; a CRC field for error detection; and a slot gap field for accommodatin
Jacklin William Edward
Stratmoen Scott Alan
Anderson Terry J.
Hoch, Jr Karl J.
Northrop Grumman Corporation
Pizarro Ricardo M.
Ton Dang
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