The patent's assignee for patent number 8645786 is
News editors obtained the following quote from the background information supplied by the inventors: "Field of the Invention
"The invention concerns a decoding method and a telecommunication device for performing that method.
"Often for a better decoding result several transmissions of the same data packet are combined. Combining data packets is already known for communication systems where packet transmission is employed. One example of such a transmission system is the so called E-DCH scheme (E-DCH: Enhanced Dedicated Channel, basically an improvement of the existing UMTS uplink channel) which is right now being standardized as an enhancement of the UMTS system (UMTS: Universal Mobile Telecommunication System).
"The outlines of the E-DCH scheme can be found in the 3 GPP RAN 1 technical report TR 25.896 v2.0.0 'Feasibility Study for Enhanced Uplink for UTRA FDD (Release 6)', R1-040392,
"This scheme is designed to make use of a HARQ (HARQ: Hybrid ARQ, Hybrid Automatic Repeat reQuest) scheme. In this scheme packets are transmitted, and if they are not received correctly, a retransmission is transmitted upon receipt of a negative confirmation of the receiver, a so called 'not acknowledge' (NACK) If the receipt has been correct a positive confirmation is sent, the so called 'acknowledge' (ACK). In the case of more than one transmission of the same data packet, at the receiver both the initial transmission and the retransmission is used for decoding the packet. Therein 'soft bit decisions' making use of the information of both data packets is used. This means, that to every bit of the data packet of transmission or retransmission a quantity is assigned which is correlated with the probability, whether the bit is 1 or 0. The decoding is then done considering both quantities.
"This gives a better performance, as if only the retransmission would be used without regarding previous transmissions (hybrid ARQ with selection combining).
"In order to a proper function of this scheme as explained above, it should be ensured, that both received transmissions actually relate to the same transmitted (higher layer) packet i.e. both transmissions are derived from the same information content, the same 'higher layer' packet (but may be transmitted using different packets on layer 1). Layer refers here to the OSI (Open System Interconnection) model. Due to transmission properties, which are considered in layer 1, the representation of information for a certain application, the application itself being taken care of in a higher layer) may be different for transmission and retransmission.
"There are several ways to ensure this: one is a so called synchronous retransmission protocol. In this protocol a retransmission is sent at a fixed time interval after the initial transmission or also the previous retransmission, if more than one retransmission is foreseen. In this way the receiver knows at which times it can expect retransmissions of a given packet.
"However, the receiver still does not know, whether two transmissions at compatible times actually relate to the same packet, or whether already the transmission of a new packet has been started. This is in particular the case if the receiver is not able to receive all packets but misses some, e.g. due to interference. If the transmission employs soft handover (SHO), that means that more than one receiver tries to receive the packets, it may well be that one receiver has not been able to receive a packet, but another receiver has been able to do so and acknowledged the packet. In this case a new packet can be transmitted next. The receiver which did not receive the first packet has no knowledge on the acknowledgement send by the other receiver and therefore must now somehow recognize that this new packet cannot be combined with any previously received packets.
"In respect of the E-DCH a soft handover takes place, e.g. if a terminal, which has established a data connection with a first base station approaches a second base station. In a transition phase there is a connection to both base stations, in order to ensure a smooth or soft transition when going from one cell, governed by the first base station to the second cell, governed by the second base station.
"For an easy recognition, it is further possible to introduce a so called Retransmission Sequence Number (RSN) or retransmission counter:
"This counter is reset (e.g. to 0) if a new data packet is transmitted, and it is incremented with each retransmission. If the receiver compares the difference in RSN with the difference in time (taking into consideration the synchronous retransmission protocol and the known time difference between retransmission), the receiver can combine the receptions if the differences in time an RSN match and not combine them if the differences do not match.
"It is a problem according to the state of the art, that the value range of the RSN is at least as large as the maximum number of possible retransmissions: Typically if a packet cannot be transmitted with a maximum number of retransmission this packet is dropped and the next packet is transmitted. The maximum number of possible retransmissions can be quite high. This can cause an excessive amount of signaling information, as the RSN has to be transmitted with every packet transmission and retransmission."
As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventors' summary information for this patent: "Based on this state of the art, it is therefore an object of the invention to provide a possibility of improving a transmission of data packets, wherein a retransmission of data packets is foreseen.
"It is a further task of the presented invention to present an improved retransmission method.
"This object is achieved by what is disclosed in the independent claims. Advantageous embodiments are subject of the dependent claims.
"According to the invention a data packet is transmitted from a sender to a receiver. In the data packet information is contained, which is represented by bit sequence. For transmission this bit sequence is transformed into a redundancy version, that is one out of more possible representations suited for transmission. In case the receiver does not receive the data packet correctly, it sends a confirmation, e.g. a
"This selection has the advantage that the selection of the redundancy version can be done taking into account the transmission properties, e.g. whether the receiver has previous versions of the data packets which it can use for decoding. Thus better decoding results can be achieved. At the same time no or only little additional effort is performed for additional signaling.
"Further aspects and criteria of the selection of the redundancy version are detailed in the description of embodiments and Figures.
"The present invention gives also an enhancement of the 'Retransmission Sequence Number' (RSN) concept, which allows reducing the value range of RSN while still allowing it to be used to determine which packets to combine, at least for most cases, in particular in those cases where the number of retransmissions does not exceed the maximum value of the RSN. The first and/or the second retransmission numbers according to this application can be designed to be a 'Retransmission Sequence Number' according to the previous description.
"There may now be some cases where the receiver can now no longer tell whether packets have to be combined, but these cases are rare enough and will not severely harm the performance. It is more valuable to reduce the number of bits needed to encode the RSN, say from 3 bits to 2 bits, which gives a significant reduction of the resources needed to transmit this 'overhead' information along with the packet data.
"Further advantages and embodiments are detailed in the following with reference to a drawing FIGURE."
For additional information on this patent, see:
Keywords for this news article include: Telecommunications, Clinical Trials and Studies,
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