The invention is based on a priority application EP 07 291 057.3 which is hereby incorporated by reference.
The invention relates to a wireless transmission of a single packet flow, and more particularly without limitation to a method of wireless transmission of a single packet flow, to a network element, to a wireless terminal, and to a computer program product adapted to perform the method in accordance with the invention.
A connection between a terminal and a network element of a wireless communication network is generally established via an air interface. The air interface can for example be compliant with the IEEE 802.16 standard. The functions of a protocol can be divided into a series of layers in accordance with the open systems interconnection reference model (OSI model), starting on the applications layer up to the air interface. One of these layers is the so called data link layer.
One of the main tasks of the link layer includes establishing a logical link connection between a transmitter and a receiver and using an identification number to identify the logical connections. The sub-layer responsible for controlling this traffic on the communications channel used by different network devices is called the Media Access Network (MAC).
There are different types of logical connections between network elements. One of the most common is the unicast mode that sends information packets to a single destination, setting up independent connections and copying the information from end-to-end to every user that requires it. The extreme opposite is the broadcasting mode, which uses the network capabilities to send information to all destinations without congesting the network capacity, using either broadcast channels or different routing methods. A more controlled approach is reached using the multicast mode, as it transports the packets to a group of destinations simultaneously, delivering the message over each link of the network only once and creating copies only when the links to the destinations split. All mentioned methods use in general a single transmitter to send the information to one or more users. If it is necessary to transmit simultaneously a message from different transmitters, there is a commonly technique known as simulcast. In this case, there is a transmission area covered by several transmitters or network elements. One of the disadvantages of this type of connections in standards as IEEE 802.16 is that the connection mode is established at the beginning of the connection, before the delivery of the packet flow, leading to a congestion of the network or to a waste of network resources.
There is therefore a need for a method of establishing wireless multiple connections in a communication network, an improved component of the wireless communication network, an improved terminal, and a computer program product that is adapted for performing the method in accordance with the invention.
The present invention provides a method for wireless transmission of a single packet flow from a network element. The method comprises establishing a first logical connection to a first wireless terminal for transmission of said single packet flow, determining at least one traffic parameter, establishing at least a second logical connection to the wireless terminal depending on said traffic parameter, for transmission of said single packet flow and transmitting the single packet flow using at least one of the first and second logical connections to the wireless terminal.
The method in accordance with the invention is particularly advantageous as by establishing simultaneous connections for a single packet flow between the transmitter and a receiver, it allows performing more advanced processing and handling to deliver the given single packet flow. For example, it is possible to switch from a type of connection to the other based on the reception quality and transmission speed, or to handle specific packets of the single packet flow in different ways. The network is then able for example to adapt the transmission of packets based on service priorities or based on changes in the geographical position of the mobile.
In accordance with an embodiment of the invention, the first logical connection corresponds to a unicast connection, the second logical connection corresponds to a multicast connection for transmission to a plurality of wireless terminals including the first wireless terminal and the at least one traffic parameter corresponds to a number of the plurality of wireless terminals. This method further comprises selecting one of the first and second logical connections for transmission of the single packet flow to the wireless terminal, depending on the number of the plurality of wireless terminals.
In accordance with an embodiment of the invention, a first plurality of logical connections including the first logical connection correspond to a plurality of unicast connections for transmission to a plurality of wireless terminals including the first wireless terminal, the second logical connection corresponds to a multicast connection for transmission to the plurality of wireless terminals including the first wireless terminal and the at least one traffic parameter corresponds to a number of the plurality of wireless terminals. This method further comprises selecting one of the first and second logical connections for transmission of the single packet flow to the plurality of wireless terminals including the first wireless terminal, depending on the number of the plurality of wireless terminals. This method allows adapting the transmission to the changes in the characteristics of the network elements, allowing a more efficient use of the network resources. Another advantage is that the connection mode can be switched at the beginning or during the transmission of the packet flow, using a dynamic creation of logical connections.
In accordance with an embodiment of the invention, the first logical connection corresponds to a simulcast connection for transmission to a plurality of wireless terminals including the first wireless terminal inside a predefined transmission area, the second logical connection corresponds to a unicast connection, the at least one traffic parameter corresponds to a first wireless terminal location. This method further comprises selecting the unicast connections for transmission of the single packet flow, if the first wireless terminal location is not inside the predefined transmission area. One of the advantages of the method is that the terminal receives a continuous packet flow independent of its geographical location and using the best adapted connection mode to obtain a good reception quality without wasting network resources.
In accordance with an embodiment of the invention, the first logical connection and the second logical connection correspond to unicast connections to the first wireless terminal, the at least one traffic parameter correspond to a packet parameter. This method further comprises selecting on a per packet basis one or more of the unicast connections for transmission of the single packet flow to the first wireless terminal, depending on the traffic parameter. This embodiment is particularly advantageous as it allows setting two logical connections with different characteristics, sending each packet based on its specific packet parameters and improving the reception quality on the receiver side. This one or more packet parameters could be e.g. a packet priority or the type of packets. According to the inventor, this embodiment is especially useful during congestion periods of the wireless network.
In accordance with an embodiment of the invention, the wireless transmission is compliant with the WiMAX standard and the logical connection is identified with a connection ID (CID).
In another aspect, the invention relates to a wireless terminal that comprises means for establishing a first logical connection from a network element, means for establishing a second logical connection from the network element, means for receiving a packet flow of a first and second logical connection from the network element, and means for associating data packets received over the at least first and second logical connection with the single packet flow.
In accordance with an embodiment the invention relates to a network element that comprises means for establishing a first logical connection to a first wireless terminal, means for determining at least one traffic parameter, means for establishing at least a second logical connection to the first wireless terminal depending on the traffic parameter, and means for transmitting the single packet flow using at least one of the first and second logical connections to the wireless terminal.
In another aspect the invention relates to a computer program product comprising computer executable instructions, wherein the instructions are adapted to perform the steps of: establishing a first logical connection to a wireless terminal, determining at least one traffic parameter, establishing an at least second logical connection to the wireless terminal depending on the traffic parameter, and transmitting the single packet flow using at least one of the first and second logical connections to the wireless terminal.
In another aspect the invention relates to a computer program product in a wireless terminal comprising computer executable instructions, wherein the instructions are adapted to perform the steps of: establishing first logical connection from a network element, establishing second logical connection from the network element, receiving a packet flow over at least one of the first and second logical connections from the network element, and associating data packets received over at least one of the first and second logical connections with the single packet flow.
In the following preferred embodiments of the invention are described in greater detail by way of example only making reference to the drawings in which:
The network element 102 establishes a first logical connection 113 with the wireless terminal 103 for transmission of the single packet flow 104. Once this first logical connection 113 has been established, the detection unit 107 determines at least one traffic parameter 109. Depending on the result of the traffic parameter 109, a second logical connection 114 may the established and the scheduler 106 will transmit the single packet flow 104 to the wireless terminal 103, using at least one of the first and second logical connections 113, 114. Alternatively, the second logical connection 114 can be established simultaneously with the first logical connection 113 at the beginning of the transmission of the single packet flow 104. The network element 102 may select at least one of the first and second logical connections for transmission of the single packet flow 104 to the wireless terminal 103, depending on the traffic parameters 109. On the wireless terminal 103 side, the selector 110 associates data packets 115 received over the at least first and second logical connections 113,114 with the single packet flow 104.
One of the advantages of the invention is that, allowing a dynamic connection switch between the at least two connections, the network adapts better to the channel characteristics, the service provided or the required priorities of the transmission, improving the overall network performance and resources usage, as well as the quality of the reception in the wireless terminal. If the wireless communication network 101 uses for example the IEEE 802.16 standard, then the network may identify the logical connections using the Connection ID (CID). All CIDs may be transmitted using frames compliant with IEEE 802.16. The header of the frames contains a DL-MAP informing the wireless terminals of which CIDs are carried in the specific frame. The network element or base station creates several connections (CIDs) sending to the terminal (or mobile station) the 802.16 DSx messages (DSa, DSc and DSd) and informing the mobile terminal to use the same packet classification rule for the CIDs with the same packet flow. The DSa message further informs which CIDs are associated to the mobile station. Once the mobile station receives a frame, it can now learn from the frame header (DL_MAP) if one (or more) of its associated CIDs are transported in the frame.
The traffic parameter 109 can be the number of wireless terminals where the single packet flow 104 is transmitted to. If the number of wireless terminals is below a predefined amount, a unicast connection will be established between the network element 102 and each of the wireless terminals, as the unicast delivers an optimum resources usage for the number of users. If the number of wireless terminals is increased to another predefined amount, a multicast connection to the wireless terminals is established as it improves the efficiency of the resources usage. When both logical connections are established between the network element 102 and the wireless terminal 103, both connections are kept active, so if the number of wireless terminals changes, the network element can switch again to transmit the single packet flow 104 using a suitable connection mode.
If for example an element of the network requires a connection with a wireless terminal 403 for transmission of the single packet flow 104, the network element 102 establishes a unicast connection 404. Then, the network element may establish a multicast connection 302 with the wireless terminal 403 as an alternative medium of transmission. Alternatively, the network element may wait for the detection unit 107 to detect, for example, at least three wireless terminals to establish the multicast connection 302. The transmission of the single packet flow 104 uses the unicast connection 404. When a request for a connection to a second wireless terminal 405 is completed, a second unicast connection 406 is established. The wireless terminal 405 is informed by the network element 102 about the multicast connection 302. The multicast connection 302 remains active but without transmitting the single packet flow 104. If a third wireless terminal 407 requires the establishment of a connection with the network element 102, then a unicast connection 408 is established and the wireless terminal 408 is informed about the multicast connection 302. When the traffic parameter reaches the predetermined value of, for example, three wireless terminals requesting the single packet flow 104, the detection unit 107 informs the scheduler 106 and it starts transmitting the single packet flow 104 using the multicast connection 302, in order to improve the efficiency of the resources usage within the wireless communication network. Alternatively, the multicast connection 302 may need to be established prior to the transmission of the packet flow 104.
If the wireless communication network 101 requires a plurality of network elements 501 to transmit the single packet flow 104 to the predefined transmission area 503, the plurality of network elements 501 establishes a simulcast transmission of the single packet flow to the predefined transmission area 503. The plurality of wireless terminals 502 will receive the single packet flow if they are located within the predefined transmission area. If for example the first wireless terminal 103 moves outside the predefined transmission area 503, the communication established with the network elements 501 may be dropped. In this case, a network element can establish a unicast connection 504 to the wireless terminal 103 that is located outside the predefined transmission area 503, while keeping the established logical simulcast connection in case that it returns to the predefined transmission area. The advantage of this aspect of the invention is that the user of a wireless terminal will receive a continuous stream of single packet flow when they are, for example, using a TV channel service.
If for example the single packet flow represents a video stream as H.264, MPEG-4, MPEG-2, or H.263, these are usually composed of three types of packets: I, P and B. According to the inventor, in order to improve the quality of the reception during congestion periods, it is recommended to transmit the I and B packets over for example the unicast connection 601 with good error protection (e.g. FEC or H-ARQ) and robust modulation (e.g. QPSK 3/4), while the B frames can be transmitted over the second unicast connection 602 with less robust modulation (e.g. QPSK 3/4) and coding, and with faster data transmission rate. The scheduler 106 will decide, on a per packet basis, which packets should be transmitted over the more secure connection and which packets should be delivered to a less robust but faster transmission. The detection unit 106 that determines the traffic parameter 109 can decide, based on the parameters of the packet, over which connection it should be sent to. One of the advantages of the embodiment is that the at least two logical connections 601,602 can be established with different transmission characteristics, using different modulation orders, modulation types, error protections or coding schemes, allowing different speeds and robust transmissions. Therefore, the packets will be sent over the logical connection that is best adapted to packet parameters and the service characteristics.
Number | Date | Country | Kind |
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07291057.3 | Aug 2007 | EP | regional |