Patent Application
20080239975
This disclosure is generally directed to data communication systems and more particularly to systems and methods for handling message collisions.
Conventional data communication systems typically use a shared medium such as, for example, a wireless network. A receiver may receive messages from two or more transmitters simultaneously. Such occurrences are generally referred to as “collisions”. Although conventional systems typically can detect whether a collision has occurred, such systems are not able to decode colliding messages. In addition, conventional systems fail to enumerate multiple messages.
There is therefore a need for a system and method to handle message collisions in a data communication system. In particular, there is a need for improved receivers and transmitters to accommodate handling message collisions.
This disclosure provides a system and method for handling message collisions in a data communication system. This disclosure also provides a system and method for handling message collisions in a receiver and in a transmitter.
According to one embodiment of the present disclosure, a receiver sorts the symbols into separate sequences by grouping together symbols having similar time of arrival. In other words, each periodic sequence of symbols represents the signal from a distinct transmitter. In addition, receiver retains the sequences with sufficiently reliable symbol detection, for example, when 75% of the symbols in a sequence are detected with sufficient quality. Receiver 102 then ranks the received messages by received signal level and decodes the messages from transmitters 101 with highest received signal level.
In still another embodiment, the present disclosure provides a collision handling receiver for use in a data communication network. The receiver includes a matched filter to detect symbols from an input signal. The receiver also includes a mechanism to sort the symbols into separate sequences based on their respective times of arrival and a decoders to decode the sorted symbol sequences.
In yet another embodiment, the present disclosure provides a method of handling collisions in a receiver for use in a data communication network. The method includes receiving input signals originally transmitted with independent pseudo-random delays and detecting qualified symbol sequences from the input signals. The method also includes a mechanism to sort the symbols into separate sequences based on their respective times of arrival. The method further includes retaining the sequences with sufficient signal quality and ranking the retained sequences by received signal strength. The method still further includes decoding the input signals with the highest received signal strength.
Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions and claims.
For a more complete understanding of this disclosure and its features, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:
The present disclosure provides a system and method of handling message collisions in a data communication system.
Although only four transmitters 101 are shown in
Receiver 102 detects symbols using a matched filter, as later described herein in conjunction with
At receiver 102, the input signal is passed through a matched filter. The matched filter output is analyzed to produce an adaptive detection threshold. Local energy peaks above the detection threshold are sorted by their respective time of arrivals. The sorted symbol sequences are then ranked by signal level and assigned to separate decoders for decoding.
In one embodiment, receiver 102 receives the input signal in step 201 and passes each signal through a matched filter in step 202. In step 203 receiver 102 detects each qualified symbol as it arrives and notes the signal strength and time of arrival of each symbol, i.e., modulo T, where T is one symbol period, using the peak detector in step 204. It should be understood that qualified symbols are typically those with sufficient received signal strength and relatively high signal to noise ratios, although any suitable symbol may be used in accordance with the present disclosure.
In one embodiment, local energy peaks above detection threshold are sorted by their respective time of arrivals in step 204. Receiver 102 sorts the symbols into separate sequences by grouping together symbols having similar time of arrival in step 205. In other words, each periodic sequence of symbols preferably represents the signal from a distinct transmitter 101.
In addition, receiver 102 retains the sequences with sufficiently reliable symbol detection, for example, when 75% of the symbols in a sequence are detected with sufficient quality. In step 206, receiver 102 then ranks the retained sequences from transmitter 101 by their respective received signal strengths or levels. Receiver 102 also decodes the messages from transmitters 101 with highest received signal level according to one embodiment of the present disclosure.
Referring now to
In particular,
It should be understood that in one embodiment, the present disclosure provides receivers that are capable of decoding multiple messages received simultaneously. In addition, it should also be understood that the transmitters may be instructed to transmit each message with a pseudo-random delay ranging from zero to one symbol period.
In one embodiment, the present disclosure may be used in various applications for handling message collisions including, for example, applications in which bandwidth may be dynamically allocated according to the traffic requirements. In addition, application in accordance with the present disclosure may enable dynamic traffic estimation which can be used to control network traffic.
Accordingly, the present disclosure provides a system and method of handling message collisions in a data communication system. The present disclosure is not limited to wireless networks, but may be used in any suitable shared medium. In addition, the present disclosure may be used in conjunction with other wireless devices (e.g., mobile stations, conventional cell phones, PCS handsets, personal digital assistant (PDA) handsets, portable computers, telemetry devices, mobile stations, cell phones, wireless laptops, personal data assistants, wireless digital signal processors, etc.), including fixed wireless terminals (e.g., a machine monitor with wireless capability).
It may be advantageous to set forth definitions of certain words and phrases used in this patent document. The term “couple” and its derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with one another. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and/or. The phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like.
While this disclosure has described certain embodiments and generally associated methods, alterations and permutations of these embodiments and methods will be apparent to those skilled in the art. Accordingly, the above description of example embodiments does not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure, as defined by the following claims.
