Innovative method and apparatus for transmitting data packets over a communication link that is shared by multiple users
|623 - Abstract:|
|Many variants exist on the basic ALOHA broadcasting protocol which transmits data packets at random intervals until acknowledgement of reception has been received. Most variants require strict synchronization by all participants so that time slots for packet transmissions do not overlap, or use spread spectrum broadcasts to create transmission redundancy. The technology offered here improves the efficiency of a communication link by relaxing synchronization and avoiding spread spectrum techniques. License agreements are sought.|
The protocol described here transmits data packets in the form of virtual frames that span a known number of time slots, which in turn have a known duration. Two or more time slots within each frame contain the same broadcast information of interest, separated by a time interval that is included as metadata in both slots. Partial loss of a data replica can in most cases be compensated immediately by the receiver by isolating the missing data from another replica. The interval between the two or more replicas within the frame is quasi-randomly chosen by the transmitter, independently from other transmitters that share the same communication channel. There is no need for strict time slot synchronization between transmitters or for spread-spectrum redundancy, which simplifies design and removes various limitations of synchronized protocols, such as limited range due to signal travel delays that interfere with the synchronization. Nonetheless, the basic structure of frames consisting of slots is preserved, which elegantly maintains compatibility with the existing broadcast protocol CRSDA and associated hardware. Statistical probabilities of packet collisions are demonstrably smaller than in existing protocols, while the method also allows for a trade-off between redundancy and channel occupation, by increasing or reducing the number of data replicas within the virtual frame.
The technology also describes an efficient method for receiving and reconstructing data that is transmitted according to this protocol, and describes a communication layout in which multiple transmitters and receivers can share the same digital broadcast channel under the proposed protocol.
Innovations and advantages
The innovation lies in a clever redundancy of transmitted data that has an excellent chance of avoiding data collisions with interlaced transmissions from other users, because the intervals between the interlaced data packets will almost always be different for different receivers. This greatly improves the chance that data packets arrive without more repetitions than the automatically provided redundancy of the frames themselves.
The key advantages are:
- For a given combination of simultaneous users and transmitted data, channel occupation is reduced, so that more users can be handled within the same limits of the communication channel
- Time synchronization between simultaneous users of the channel is not necessary, which greatly simplifies the overall communication layout and reduces hardware cost. It also reduces the metadata overhead on the communication channel, contributing to larger capacity.
- Because of the various simplifications, the cost of hardware involved with the communication can be reduced in comparison to earlier generation protocols.
Domain of application
The proposed communication protocol and system are specifically suitable for radio communication but can also have applications in computer network environments or similar in which multiple users share a single communication bus or other medium.
It is only relevant to communication systems with low duty cycles, i.e. short data bursts interlaced with larger periods of silence.
Last update: 3 December 2014