Abstract: The invention relates to a method and apparatus for transmitting and receiving video data arranged in data frames forming a data stream. Each frame has assigned a priority level. Once a data frame has been transmitted through an unreliable channel and has not been received at the receiver, the priority level of the missing data frame is compared with a priority threshold value, and is then retransmitted if its priority level is greater than the priority threshold value. The retransmission decision is performed either at the transmitting or at the receiving side. According to a preferred embodiment, the priority level of any data frame to be transmitted is compared with the threshold value. The priority decision may involve the calculation of the priority threshold value based on a measurement of the available channel bandwidths and eventually on the bit rate of previously sent frames. The retransmission decision further may include an estimation of the arrival time of the data frame to be retransmitted.

Abstract: The invention relates to a method and apparatus for transmitting and receiving video data arranged in data frames forming a data stream. Each frame has assigned a priority level. Once a data frame has been transmitted through an unreliable channel and has not been received at the receiver, the priority level of the missing data frame is compared with a priority threshold value, and is then retransmitted if its priority level is greater than the priority threshold value. The retransmission decision is performed either at the transmitting or at the receiving side. According to a preferred embodiment, the priority level of any data frame to be transmitted is compared with the threshold value. The priority decision may involve the calculation of the priority threshold value based on a measurement of the available channel bandwidths and eventually on the bit rate of previously sent frames. The retransmission decision further may include an estimation of the arrival time of the data frame to be retransmitted.

Abstract: A method of transmitting data packets, in particular of real-time or near-real-time data over internet protocol (IP) networks using a real-time protocol (RTP) for media data products and a real-time control protocol (RTCP) for control data packets. Each protocol is allocated a fraction of the available transmission bandwidth. The method comprises the steps of measuring relevant characteristics of the network link, calculating from this measurement an optimized RTCP bandwidth and transmitting control data packets using the optimized RTCP bandwidth.

Abstract: The radio control section 205 notifies a transmission rate that can be currently set up out of the radio channel transmission rates to the transmission rate decision section 207. The buffer monitoring section 208 monitors an amount of media data stored in the media reception buffer 209 and when the amount of media data stored exceeds a threshold, the buffer monitoring section 208 notifies it to the transmission rate decision section 207. When information on the radio channel transmission rate from the radio control section 205 shows that the radio channel transmission rate is well within the capacity and when monitoring information from the buffer monitoring section 208 shows that the amount of data stored in the media reception buffer 209 does not exceed a threshold, the transmission rate decision section 207 outputs a request for increasing the transmission rate of the media data to the control signal transmission/reception section 206.

Abstract: When an amount of stored media data exceeds a threshold, the media reception buffer 209 outputs a signal indicating the fact to the radio control section 205. When the radio control section 205 receives a signal indicating that the amount of media data has exceeded the threshold from the media reception buffer 209, the radio control section 205 instructs the initial buffering condition decision section 207 to decrease the data reception rate. The media reception rate decision section 208 decides the media-specific rate and outputs it to the initial buffering condition decision section 207. The initial buffering condition decision section 207 decides the buffering time and rate based on the media-specific rate input from the media reception rate decision section 208. This makes it possible to shorten the time required to store data in the storage section before starting data play back and shorten the time after requesting the server to send data until the data is played back.

Abstract: The invention relates to a method and apparatus for transmitting and receiving video data arranged in data frames forming a data stream. Each frame has assigned a priority level. Once a data frame has been transmitted through an unreliable channel and has not been received at the receiver, the priority level of the missing data frame is compared with a priority threshold value, and is then retransmitted if its priority level is greater than the priority threshold value. The retransmission decision is performed either at the transmitting or at the receiving side. According to a preferred embodiment, the priority level of any data frame to be transmitted is compared with the threshold value. The priority decision may involve the calculation of the priority threshold value based on a measurement of the available channel bandwidths and eventually on the bit rate of previously sent frames. The retransmission decision further may include an estimation of the arrival time of the data frame to be retransmitted.

Abstract: A data transmission apparatus for sequentially transmitting data in units of packets each containing transmission data to the receiving end, comprises: a reception unit for receiving the transmission data as an input signal; a packet formation unit for receiving the transmission data received, and forming an uncompressed packet in which predetermined transmission data is stored as uncompressed data, and a compressed packet in which at least a portion of transmission data that follows the predetermined transmission data is compressed and stored as compressed data; a reference information management unit for holding and managing, as reference information, information relating to the uncompressed packet formed by the packet formation unit; and a transmission unit for transmitting the respective packets formed by the packet formation unit, as a transmission signal, to the receiving end.

Abstract: A data transmission apparatus for sequentially transmitting data in units of packets each containing transmission data to the receiving end, comprises: a reception unit for receiving the transmission data as an input signal; a packet formation unit for receiving the transmission data received, and forming an uncompressed packet in which predetermined transmission data is stored as uncompressed data, and a compressed packet in which at least a portion of transmission data that follows the predetermined transmission data is compressed and stored as compressed data; a reference information management unit for holding and managing, as reference information, information relating to the uncompressed packet formed by the packet formation unit; and a transmission unit for transmitting the respective packets formed by the packet formation unit, as a transmission signal, to the receiving end.

Abstract: The invention relates to a method and apparatus for transmitting and receiving video data arranged in data frames forming a data stream. Each frame has assigned a priority level. Once a data frame has been transmitted through an unreliable channel and has not been received at the receiver, the priority level of the missing data frame is compared with a priority threshold value, and is then retransmitted if its priority level is greater than the priority threshold value. The retransmission decision is performed either at the transmitting or at the receiving side. According to a preferred embodiment, the priority level of any data frame to be transmitted is compared with the threshold value. The priority decision may involve the calculation of the priority threshold value based on a measurement of the available channel bandwidths and eventually on the bit rate of previously sent frames. The retransmission decision further may include an estimation of the arrival time of the data frame to be retransmitted.

Abstract: A method of incrementing a receiver-initiated sending rate of data packets transmitted from a sender over a network receiver using Transport Control Protocol (TCP) comprising the step of sending an acknowledgement for received data packets from the receiver to the sender, wherein said acknowledgement contains an advertised window indicating the allowed sending bit rate and the step of increasing the advertised window by a maximum of one segment size per acknowledgement.

Abstract: A method of performing Round Trip Time (RTT) measurement in a data packet receiver using a Transmission Control Protocol (TCP) for communication via a network with a sender, said method comprising the steps of sending an acknowledgement for a currently received data packet to the sender, measuring a first time instant when sending the acknowledgement, triggering at the sender the transmission of an expected data-packet, measuring a second time instant when the expected data packet is received, and calculating the round-trip time based on the measured first and second time instants.

Abstract: Method, transmitter and system for transmitting compressed header data in a packet stream from a transmitter to a receiver, the header data including a header data item, wherein the method comprises estimating a time period needed for performing a re-initialization process for reinitializing a value of said header data item, determining a time for starting the re-initialization process, the determined time being based on the estimated time period and starting the re-initialization process at the determined time.

Abstract: A method of transmitting data packets, in particular of real-time or near-real-time data over internet protocol (IP) networks using a real-time protocol (RTP) for media data products and a real-time control protocol (RTCP) for control data packets. Each protocol is allocated a fraction of the available transmission bandwidth. The method comprises the steps of measuring relevant characteristics of the network link, calculating from this measurement an optimized RTCP bandwidth and transmitting control data packets using the optimized RTCP bandwidth.

Abstract: A method of transmitting data packets, in particular a real-time or near-real-time data over an internet protocol (IP) network using a real-time protocol (RTP) for media data packets and a real-time control protocol (RTCP) for control data packets. Each protocol is allocated a fraction of the available transmission bandwidth. The method comprises the steps of determining the needed RTCP bandwidth based on known link parameters for an individual media session, transmitting control data packets using the needed RTCP bandwidth and transmitting media data packets using the remainder of the available bandwidth.

Abstract: The present invention provides a method and apparatus for distinguishing between congestion and corruption losses during the transmission of data packets. The packet lost distinction is based on the evaluation of an error detection/correction code of each data packet and by detecting sequence numbers.

Abstract: SN examine section 101 monitors transmission data by way of monitoring an SN per packet, compares the SN in a packet that is to be transmitted with the SN in an immediately preceding packet, and outputs the comparison result to CID selection section 102 with transmission data. CID selection section 102 selects a CID based on the comparison result output from SN examination section 101 and appends the CID to the transmission data, and outputs the transmission data to header compression section 104. CRC bit calculation section 103 calculates a CRC bit from the header information. Header compression section 104 determines on a header compression format, compresses a header that contains an SN and a CRC bit, and connects the header with transmission data and transmit this to transmission section 106. Transmission packet storing section 105 that stores transmitted packets.

Abstract: When a received packet contains static information and a CRC section 104 detects an error, the static information alone will be read from a buffer 106 and replace the static information of the received packet. A header reproduction section 107 once again reproduces a header, and upon this reproduced header the CRC section 104 performs CRC. If a bit error is detected, the received packet will be discarded. If no error is detected, determining that the bit error was in the static information portion in the header of the received packet, the packet in which the static information has been replaced will be output as a received packet.

Abstract: The invention relates to a method and apparatus for transmitting data packets over a channel wherein the data packets have compressed headers. After compressing a header using a context, a number of consecutive update packets are transmitted, each containing data indicating said context. According to the invention, the channel quality is determined and the number of update packets is set accordingly. The channel quality may be determined by measuring the block error rate or the signal-to-noise ratio. Alternatively, the channel quality may be estimated by evaluating whether a NACK message has been received. The total number of update and non-update packets transmitted during a context update phase may be set according to the Round Trip Time. The number of non-update packets may further be determined based on codec properties. The invention may advantageously be used over unreliable, e.g. wireless, channels.

Abstract: The invention relates to a method and apparatus for transmitting data packets in a packet stream wherein the data packets have compressed headers. Update packets containing data indicating the context used in compressing the headers, and non-update packets are transmitted. According to the invention, an irregular change of the packet stream is detected and at least one packet stream parameter is obtained. Dependent on the determined packet stream parameter, either an extended update packet or an extended non-update packet is transmitted where the extended packets include information about the irregular change. The invention further includes estimating the packet stream parameter and applying a safety factor.

Abstract: The invention relates to a method and apparatus for transmitting and receiving video data arranged in data frames forming a data stream. Each frame has assigned a priority level. Once a data frame has been transmitted through an unreliable channel and has not been received at the receiver, the priority level of the missing data frame is compared with a priority threshold value, and is then retransmitted if its priority level is greater than the priority threshold value. The retransmission decision is performed either at the transmitting or at the receiving side. According to a preferred embodiment, the priority level of any data frame to be transmitted is compared with the threshold value. The priority decision may involve the calculation of the priority threshold value based on a measurement of the available channel bandwidths and eventually on the bit rate of previously sent frames. The retransmission decision further may include an estimation of the arrival time of the data frame to be retransmitted.