Telefonaktiebolaget Lm Ericsson (publ)

Optis Wireless Technology, LLC

Lars-Erik Jonsson

Krister Svanbro

Ghyslain Pelletier

Mikael Degermark

Hans Hannu

Anders Furuskär

Ingemar Johansson

Jim Sundqvist

Vicknesan Ayadurai

Stefan Hakansson

Zsolt Haraszti

Zolt Haraszti

A unit () performs a compression operation or a decompression operation with respect to information for transmission in packets over a wireless link (). The transmission over the wireless link is such that the packets may become reordered from a transmission sequence. The compression operation and the decompression operation involve a tradeoff of robustness and reordering depth. The robustness is an indicator of a degree of information loss over the link tolerated by the compression operation and the decompression operation; the reordering depth is a degree of packet reordering tolerated by the compression operation and the decompression operation. The unit dynamically adjusts the tradeoff of the robustness and the reordering depth in accordance with characteristics of the link. In an example embodiment, the information upon which the compression operation and the decompression operation is performed is sequence number information of a packet header.

Dynamic robust header compression

A technique for compressing header information to produce a compressed header portion of a data packet to be transmitted across a communication channel includes generating a checksum from the header information, and providing the checksum as the compressed header portion.

Robust header compression in packet communications

A method for improving the use of a secure reference principle in a header compression scheme over a channel that admits reordering of packets between a compressor and a decompressor includes transmitting a first plurality of non-context updating packets between a compressor and a decompressor over the channel and, in response to a context update, transmitting a second plurality of context-updating packets between the compressor and the decompressor over the channel. The number of packets in the second plurality is greater than or equal to a maximum possible reordering that packets can experience on the channel between the compressor and the decompressor.

Methods for increased tolerance against packet reordering for the secure reference principle in robust header compression

The invention relates to header compression in packet-based communication systems. A mechanism that allows a compressor to reject a request for an undesirable mode change is proposed. The compressor indicates to the decompressor that the mode change request is being ignored, whereafter the decompressor may abort the initiated mode transition, with the understanding that the compressor has valid reasons to refuse it. The compressor preferably determines whether the rejection succeeded by link monitoring, and in case of a successful rejection, the compressor remains in its current mode. A preferred embodiment performs explicit rejection signaling through a mode change rejection message with a redefined mode value. The rejection signaling of the invention makes it possible for a compressor to disable the transition to a particular mode and enables implementations with only a subset of all modes.

Header compression method

In a system for transmitting packets over a link between a compressor and a decompressor, a method is provided for implicit packet type identification. A set of implicit packet transmission characteristics including at least first and second characteristics is selected, and the compressor is operated to assign the first and second transmission characteristics to packets of first and second packet types, respectively. The decompressor is operated to detect transmission characteristics of packets received by the decompressor, and to thereby identify a received packet as being either a first or second packet type. Usefully, header free packets comprise one of the packet types.

Implicit packet type identification

Systems and methods are provided for Internet Protocol (IP) based communication systems without using a complete Internet Protocol stack on both sides of a communication link. Various exemplary embodiments include communication of audio information over a wireless transmission channel to a wireless terminal from a network that includes transmission of audio information using voice over Internet Protocol (VoIP). A first communication system and method may include a wireless terminal having a dedicated audio application that includes processing for header compression and decompression. A second communication system and method may include a wireless terminal and a network device (e.g., a network transmitter/receiver terminal), each containing at least a portion of an Internet Protocol stack, and the network device may include a header modification means that may reduce or eliminate the header from VoIP packets it will send to the wireless terminal.

Systems and methods for VoIP wireless terminals

In packet communications that utilize header compression/decompression, relatively fast and reliable header compression context updates can be accomplished with relatively low overhead by: sending anticipatory context update requests before decompressor context invalidation is detected; sending redundant context update requests; and sending redundant context updates. Transmission parameters associated with both context update requests and context updates can be controlled appropriately to improve their chances for delivery, and needless context update requests can be identified and ignored at the header compression side.

Efficient header compression context update in packet communications

In packet communications that employ header compression/decompression, the computational complexity of checksum generation can be reduced by re-using static checksum information associated with header bits that do not change from header to header. The static checksum information can be used together with information about header bits that do change from header to header, in order to generate a desired checksum. The checksum can then be used to verify a reconstructed header produced from a compressed header by a header decompressor.

Re-use of static checksum information in header compression/decompression applications

In packet communication paths that include header compression, header fields of packets to be communicated are altered. The alteration of the header fields does not disturb their functionality, and is transparent to the header compression scheme of the packet communication path. The altered header fields are provided for compression by the header compression scheme, resulting in improved performance of the header compression scheme. Performance improvements can also be achieved in packet communication paths that do not use header compression, by violating the integrity of header fields in packets to be transmitted over the packet communication path.

Manipulating header fields for improved performance in packet communications

Techniques are provided for efficiently compressing and reconstructing the time stamp value of a real time communications packet whose time stamp value does not fall within a normally expected sequence of time stamp values. A first part of the time stamp value is selected by the header compressor and transmitted. A second part of the time stamp value is estimated by the header decompressor based on elapsed time between receipt of consecutive packets. The header decompressor combines the second part with the first part received from the header compressor to produce a reconstructed time stamp value.

Estimation of time stamps in real-time packet communications

A method and apparatus for replacing a transport layer header error detection code and a header compression algorithm error detection code with a one error detection code. The replacement error detection code covers both the transport layer header and the transport layer payload. Such an arrangement reduces the amount of as-is or uncompressed information transmitted, thereby reducing the required bandwidth. The replacement error detection code is subsequently used to verify the correctness of both the reconstructed header and the payload.

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Lulea, Sweden

Lars-Erik Jonsson