Multiplex communications – Communication over free space – Combining or distributing information via time channels
Reexamination Certificate
1999-11-19
2001-05-08
Kizou, Hassan (Department: 2662)
Multiplex communications
Communication over free space
Combining or distributing information via time channels
C370S400000, C370S468000, C455S450000
Reexamination Certificate
active
06229802
ABSTRACT:
BACKGROUND OF INVENTION
The invention relates to packet-switched transmission of calls in a situation where the packets have to queue for forwarding, and particularly to packet-switched transmission of calls toward base stations on circuits between a telecommunication network and base stations in a mobile telephone system where a call is forwarded as data packets at even intervals.
In most digital mobile telephone systems the carrier wave of the radio path is divided between several users by using, for example, a TDMA (Time Division Multiple Access) or CDMA (Code Division Multiple Access) method. The common feature of the methods is that a different channel is allocated for each call, and that the call is divided into call packets of a certain length and the packets are transferred on different channels in successive frames transmitted on the carrier wave of the radio path. A frame comprises several channels. In order for a packet to arrive in time at the appropriate frame, the packet has to arrive in time at the base station. In the TDMA method, where a frame consists of time channels that are successive with respect to time, a call packet has to arrive at the base station in time so that it can be transmitted on the correct time channel.
In a packet-switched network the arrival rate and the order of arrival of the packets vary in the network node, for example, with the load of the network nodes encountered on the way, whereby packets arrive in random order, for example, at the network node located before the base station transmitting onto the radio path. The previously known network nodes transmit packets to the base station in the same order in which they arrive at the network node. The order of arrival may not be the appropriate order of transmission in view of the forwarding of the packets from the base station: the call packets must be transmitted onto the radio path at an even rate in the order of channels in accordance with the radio path protocol. The same disadvantageous situation may also arise when the network node transmitting the packets is connected to the rest of the network at a higher rate than the network node receiving the packets is connected to the transmitting network node. The packets will then have to queue at the network node for access to a lower-rate connection, and they are forwarded to the receiving network node in the random order of arrival.
BRIEF DESCRIPTION OF INVENTION
The object of the invention is to solve the above problem and to provide a method that notably reduces the risk of a packet not arriving in time. The method of the invention, in which packets are transmitted from a first node to a second node, is characterized by defining, on the basis of the resource allocation situation of the second node, the order of transmission in which the packets associated with different data transmission connections are to be sent from the first node to the second node; sending the first node a control signal that indicates the order of transmission of the second node; and transmitting the packets associated with the different data transmission connections from the first node to the second node in said order of transmission, until a new control signal is received.
The invention also relates to a method which is characterized by defining, on the basis of the resource allocation situation of the second node, the data transmission connection associated with the packet needed next in the second node; sending the first node a control signal that indicates the data transmission connection associated with the packet to be transmitted next to the second node; and transmitting the packet associated with said data transmission connection from the first node to the second node.
The invention also relates to a network node to which the methods of the invention can be applied. The network node comprises reception means for receiving packets, said reception means being arranged to identify the data transmission connection associated with the packet; transmission means for transmitting the packets toward a destination address; identification means for identifying the destination address and the data transmission connection associated with the packet; and a buffer for buffering the received packets. The network node is characterized by further comprising processing means for receiving a control signal from the data transmission network, said control signal comprising information on the data transmission connection of the packet to be sent next toward a defined destination address; and transmission control means for selecting, in response to the information contained in the control signal, the packet to be sent next to the destination address.
The invention further relates to a packet-switched data transmission system which utilizes wireless data transmission and in which the methods and network node of the invention can be used. The data transmission system comprises at least one base station for transmitting packets on a wireless transmission path, on which a different channel is allocated for each data transmission connection; channel management means for managing the setup, maintenance and set-down of the wireless data transmission connections and for allocating channels for the data transmission connections and for deallocating the channels; and a transmission network for transmitting packets, said network comprising at least one node for transmitting packets to a base station, the node comprising a buffer for buffering the packets to be sent, and the node being arranged to identify, upon receiving the packet, the data transmission connection associated with the packet from the identification data contained in the packet. The data transmission system is characterized in that the channel management means comprise control means for generating a control signal and for transmitting it to the node, the control signal containing information on the data transmission connection of the packet to be sent next to the base station, and the node comprising at least one transmission control means for retrieving packets from the buffer to transmit them to the base station, the transmission control means being arranged to select the packet to be sent next to the base station from the buffer of the node in response to the control signal.
The invention is based on the idea that a network node receives, for example, from a receiving node, information indicating which packet the receiving node wants to receive next, and retrieves the packet indicated by the information from the group of packets waiting for transmission, whereby it is possible to ensure that all the packets arrive in time. The advantage achieved with the invention is that the receiving network node receives exactly the packet it needs to forward. For example, a base station transmitting onto the radio path receives the packet it needs to transmit onto the radio path and the packet will not be late for the transmission slot. Also, the quality of the speech connection remains good. The invention also has the advantage that the delay of the transmission onto the radio path covers the waiting delay in the node and thus need not be taken into account when the transmission delays are calculated. These advantages are achieved both when the order of transmission based on the resource allocation situation of the receiving node is followed continuously and when it is followed one packet at a time.
In a preferred embodiment of the invention, the channel allocation information of the base station is stored in the network node as the order of transmission, which will be followed cyclically. When the channel allocation information changes, the order of transmission will be revised to be in line with the new information. The advantage achieved is that the amount of signalling is reduced in the network, as control signals are transmitted only when the situation changes and as the control signal contains more information. The receiving node, such as a base station, however, receives the packets in the appropriate order.
In a second
Altera Law Group LLC
Ho Duc
Kizou Hassan
Nokia Networks Oy
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