EP1749377A1 - Reservierungssteuerung für virtuelle kanäle - Google Patents

Reservierungssteuerung für virtuelle kanäle

Info

Publication number
EP1749377A1
EP1749377A1 EP04739322A EP04739322A EP1749377A1 EP 1749377 A1 EP1749377 A1 EP 1749377A1 EP 04739322 A EP04739322 A EP 04739322A EP 04739322 A EP04739322 A EP 04739322A EP 1749377 A1 EP1749377 A1 EP 1749377A1
Authority
EP
European Patent Office
Prior art keywords
node
destination node
virtual channel
transmission
control message
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP04739322A
Other languages
English (en)
French (fr)
Inventor
Emma Carlson
Holger Karl
Christian Prehofer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NTT Docomo Inc
Original Assignee
NTT Docomo Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by NTT Docomo Inc filed Critical NTT Docomo Inc
Publication of EP1749377A1 publication Critical patent/EP1749377A1/de
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access, e.g. scheduled or random access
    • H04W74/08—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access]
    • H04W74/0808—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access] using carrier sensing, e.g. as in CSMA
    • H04W74/0816—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access] using carrier sensing, e.g. as in CSMA carrier sensing with collision avoidance
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W48/00—Access restriction; Network selection; Access point selection
    • H04W48/08—Access restriction or access information delivery, e.g. discovery data delivery
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W8/00—Network data management
    • H04W8/22—Processing or transfer of terminal data, e.g. status or physical capabilities
    • H04W8/24—Transfer of terminal data
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/18—Self-organising networks, e.g. ad-hoc networks or sensor networks

Definitions

  • the present invention relates ' to a reservation of resources for a virtual channel in a wireless network.
  • Wireless communication networks are becoming increasingly popular and co-exist with or may even replace traditional wireline communication networks .
  • Wireless networks enable users to wirelessly transmit information to other users, such as for a telephone conversation between users of telephone terminals or a data communication between computing devices .
  • a mobile telephone is one type of wireless communication device which is widely used in voice and/or data communications.
  • a mobile computer may be used as a wireless communication device and may be enabled to connect to a wireless communication network for data transmissions and/or for assisting voice communications.
  • Wireless communication networks include mobile communication networks, such as networks according to the GSM (Global System for Mobile Communications) standard, UMTS (Universal Mobile Telephone System) and similar.
  • GSM Global System for Mobile Communications
  • UMTS Universal Mobile Telephone System
  • a further type of wireless communication network is a wireless network with distributed medium access, i.e., a network without a central control facility for managing resources, etc. While many types of -wireless communication networks employ a central control facility, wireless networks, with distributed medium access control use a decentralized access to communication resources, essentially allowing the individual participants of the network to negotiate access to resources among one another.
  • An ad-hoc communications network may be configured as a wireless network with distributed medium access control, constituting a network with dynamic behaviour and composition, where an availability of resources and for example a coverage area depends on the participating network elements or nodes.
  • An ad- hoc network may consist of a plurality of wireless devices using a wireless interface for exchanging data, such as packet data or continuous streams of data.
  • Each wireless device may serve as a communication node, being responsible for forwarding data on behalf of other communication devices and may at the same time be running user applications on behalf of a user of the communication device, such as communication services.
  • Various kinds of ad-hoc networks exist, including networks allowing mobile nodes, i.e., networks wherein mobile devices can freely move within at least a coverage area of the network, even during an ongoing communication.
  • Another kind of ad-hoc network is allowing fixed wireless nodes, i.e.
  • ad- hoc networks may rely on packetized data transfer, or on direct communication links or any kind of connection-less 1inks .
  • a communication path is established through a number of communication devices or network nodes participating in the relaying of the data between the two communicating parties, i.e., nodes relay information or data packets on behalf of other nodes.
  • This approach is termed multi-hopping and allows advantages such as a better reuse of resources of the network, and a decrease of a transmit power of the system, since the individual "hops" between nodes only involve a short distance which can be covered without requiring large transmission power.
  • a network in accordance with the IEEE 802.11 or another wireless communication network standard may provide for a distributed access control to use communication resources wherein, if a communication device wants to transmit a chunk of information or data packet on a transmission path covering a plurality of nodes of the network, it first contents for access. The contention for access may be made at each of the participating nodes in order to establish a virtual channel for data transfer between the individual nodes of the network.
  • a virtual channel may be established between a source node and a destination node and channel data may be transmitted from the source node to the destination node via the resources specified for the virtual channel.
  • nodes in the vicinity of the nodes handling the data transfer for the virtual channel may also be engaged in the transmission of data on behalf of other users or virtual channel and may not be aware of the resources specified for the virtual channel. Therefore, the transmissions of surrounding nodes may disturb or interfere with the transmissions of data via the virtual channel and a transmission quality of the virtual channel may deteriorate or the virtual channel may be interrupted.
  • This object of the invention is solved by a method of virtual channel reservation in a wireless network, including: receiving, at a destination node, channel data, transmitted over a virtual channel established between a source node and the destination node, using transmission resources specified prior to the transmission of channel data; and transmitting, after the transmission resources for the virtual channel are specified, a reservation control message from the destination node, the reservation control message including information on the specified transmission resources, for informing any surrounding nodes of the use of the specified transmission resources.
  • the destination node may use the reservation control message to inform any surrounding node of the fact that the transmission resources specified for the virtual channel between the source node and the destination node are in use .
  • the transmission resources specified for the virtual channel include at least one of time periods for transmission, a transmission frequency and a transmission code to be used for receiving channel data at the destination node.
  • the transmission resources specified for the virtual channel may include information on at least one of the duration of a time period, a repetition of a time period and a time reference for reception of channel data at the destination node.
  • the reservation control message may include information on transmission resources used between the source node and at least one transmit node handling the virtual channel. Accordingly, the destination node may not only inform surrounding nodes on transmission resources specified for the reception of channel data from the source node at the destination node, but may also include information on preceding sections of the virtual channel, i.e. between a transmit node and the source node .
  • the reservation control message may include information on at least one of: a time slot, a frequency, routing update information; a frequency channel; a transmit power; a link quality; a network load; and a network congestion.
  • the reservation control message includes an instruction for any surrounding node to modify its transmission based on information of the reservation control message or an instruction for requesting any surrounding nodes to avoid a transmission of data using the specified transmission resources.
  • the destination node may use the reservation control message to instruct surrounding nodes to avoid use of the specified resources or at least modification of the use of the specified resources, e.g., until an acceptable reception of the data at the destination node can be assured.
  • the transmission of the reservation control message is scheduled independent from the transmission of channel data from the source node to the destination node. Further, the reservation control message may be transmitted by avoiding use of the transmission resources specified for the virtual channel. Still further, the reservation control message may be transmitted repeatedly from the destination node.
  • the reservation control message is transmitted depending on an interference level determined at the destination node.
  • the destination node may determine presence of a surrounding node, and may transmit the reservation control message, when a surrounding node is determined.
  • the destination node may determine the presence of the surrounding node by detecting the transmission activity of the surrounding node and/or a transmission activity of the surrounding node using the specified transmission resources.
  • the reservation control message is transmitted depending on a load of the network.
  • the method includes determining motion of the destination node and the reservation control message is transmitted, if the destination node is determined to be moving.
  • the reservation control message is included into an acknowledgement message transmitted from the destination node to the source node or a transmit node to acknowledge reception of channel data.
  • the destination node is a terminating node of the virtual channel which does not transmit channel data via an air interface.
  • the destination node may further transmit channel data to an additional node forming part of the virtual channel and may transmit the reservation control message as a refresh message.
  • a program may be provided having instructions adapted to make a data processing device execute any of the above operations.
  • a computer readable medium may have embodied therein a program, wherein the program is to make a data processing device execute any of the above operations.
  • a computer program product maybe provided comprising the computer readable medium.
  • a destination node in a wireless network for virtual channel reservation including: a receiver for receiving channel data transmitted over a virtual channel established between a source node and the destination node, using transmission resources specified prior to the transmission of channel data; and a transmitter for transmitting, after specification of the transmission resources for the virtual channel, a reservation control message from the destination node, the reservation control message including information on the specified transmission resources, for informing any surrounding nodes of the use of the specified transmission resources .
  • Fig. 1 illustrates elements of a wireless network for virtual channel reservation according to an embodiment of the invention
  • Fig. 2 illustrates operations of a method for virtual channel reservation in a wireless network according to an embodiment of the invention
  • Fig. 3 illustrates elements of a wireless network for virtual channel reservation, particularly illustrating a transmission of data via a virtual channel and the transmission of a reservation control message according to an embodiment of the invention
  • Fig. 4 illustrates operations of a method for virtual channel reservation and a wireless network according to another embodiment of the invention, particularly illustrating operations at a source node, a destination node and a surrounding node;
  • Fig. 5 illustrates elements of a wireless network for virtual channel reservation according to another embodiment of the invention, particularly illustrating a transmission of virtual channel data and the reservation control message;
  • Fig. 6 illustrates operations of a method for virtual channel reservation in a wireless network according to another embodiment of the invention, particularly illustrating the scheduling of transmission of the reservation control message;
  • Fig. 7 illustrates operations of a method for virtual channel reservation in a wireless network according to another embodiment of the invention, particularly illustrating transmitting the reservation control message based on an interference level determined at the destination node;
  • Fig. 8 illustrates operations of a method for virtual channel reservation in a wireless network according to another embodiment of the invention, particularly illustrating transmitting the reservation control message based on the determination of presence of a surrounding node;
  • Fig. 9. illustrates elements of a wireless network for virtual channel reservation according to another embodiment of the invention, particularly outlining elements of the destination node in an alternative.
  • Fig. 1 illustrates elements of a wireless network for virtual channel reservation, particularly illustrating a destination node 100, a source node 110 and a surrounding node 120.
  • a virtual channel is assumed to be established between the source node 110 and the destination node 100, illustrated at 150.
  • data are transmitted from the source node 110 to the destination node 100.
  • the destination node 100 includes a receiver 102 for receiving channel data transmitted over the virtual channel 150 established between the source node 110 and the destination node ' 120 using the transmission resources specified prior to the transmission of the channel dat . Further, the destination node 100 includes a transmitter 101 for transmitting, after the transmission resources for the virtual channel are specified, a reservation control message, indicated at 151, from the destination node, the reservation control message including information on the specified transmission resources, and is intended to inform any surrounding node such as the surrounding node 120 of the use of the specified transmission resources of the virtual channel . Based on the reservation control message any surrounding nodes may modify their own transmissions so that a transmission of channel data via the virtual channel to the destination node is improved.
  • the destination node 100 is receiving or desires to receive data via the virtual channel 150 from the source node 110.
  • the virtual channel data are transmitted from the source node to the destination node using transmission resources specified generally prior to actually commencing transmission of the channel data.
  • the transmission resources may have been negotiated between the source node and the destination node at an earlier point in time and upon actual transmission of virtual channel data the destination node will be set up to receive the channel data using the specified transmission resources .
  • This scheme of transmitting virtual channel data from the source node 110 to the destination node 100 will generally work well as long as the destination node can properly receive the virtual channel data from the source node.
  • the surrounding nodes may not be aware of the established virtual channel 150 between the source node and the destination node and may be not be aware of the fact that certain transmission resources have been specified or negotiated between the source node and the destination node for use in transmitting channel data via the virtual channel .
  • the surrounding node may by itself receive and transmit information in the wireless network as illustrated by the arrows 121, disregarding the virtual channel established between the source node and the destination node.
  • the surrounding node may perform its own transmissions in the wireless network, for example in connection with the transmission of data via other virtual channels, using transmission resources which differ from the transmission resources specified for the virtual channel 150 between the source node 110 and the destination node 100 in which case a problem at the destination node 100 should not occur.
  • the surrounding node 120 may schedule its own transmissions using transmission resources which at least overlap with the transmission resources specified for the virtual channel between the source node and the destination node, but the use of the transmission resources at the surrounding node may be such that a proper reception at the destination node of virtual channel data transmitted via the virtual channel from the source node is not disturbed or negatively effected, for example if a transmission power at the surrounding node is at a sufficiently low level, in which case a problem at the destination node 100 should also not occur.
  • problems occur in cases where the surrounding node 120 schedules its own transmissions using transmission resources at least overlapping with the transmission resources specified for the virtual channel 150 between the source node 110 and the destination node 100 in a way which disturbs the reception of the virtual channel data at the destination node.
  • radio signals from the surrounding node 120 could propagate and arrive at the destination node 100 in a way that a proper or sufficiently correct reception of the virtual channel data via the virtual channel 150 at the destination node 100 becomes impossible.
  • the surrounding node 120 may be unaware of the fact its own transmissions disturb the reception of virtual channel data at the destination node for various reasons.
  • the surrounding node 120 may be unaware of the virtual channel 150 and the transmission resources specified for this virtual channel, as the surrounding node 120 may not have participated in the reservation process of transmission resources or may not have overheard any communication between nodes in view of the reservation of transmission resources for the virtual channel 150.
  • the surrounding node may have moved into or may be introduced the vicinity of the destination node at a later point in time or the destination node may have moved into the vicinity of the surrounding node during ongoing communications via the virtual channel.
  • the surrounding node 120 may be located in a distance from the source node 110 which makes it impossible for the surrounding node 120 to read any virtual channel information transmitted from the source node 110 via the virtual channel 150 towards the destination node 100.
  • the source node 110 transmits the virtual channel data via the virtual channel 150 with a certain transmission power which makes the virtual channel data readable by any receiver within a certain region 160, which in a simple case may be a circle with a radius Rvc, indicated at 152.
  • the surrounding node 120 is located outside the circle 160, the surrounding node is unaware of any transmissions concerning the virtual channel 150.
  • the surrounding node 120 may be able to listen to the virtual channel data transmission via the virtual channel 150 from the surrounding node to the destination node, and may gain information on the transmission resources specified for the virtual channel 150.
  • the surrounding node 120 As the surrounding node 120 is positioned comparatively far away from the source node 110, transmissions from the surrounding node 120 may not negatively effect any reception at the source node 110, e.g. of virtual channel data transmitted via another portion of the virtual channel towards the destination node, e.g. via a virtual channel portion 154 illustrated in Fig. 1.
  • the surrounding node As schematically illustrated in Fig. 1, the surrounding node is located in comparatively close distance to the destination node 100, and therefore, transmissions at the surrounding node 120 can potentially interfere with the reception of virtual channel data at the destination node 100.
  • the destination node 100 may not perform any transmission activity in connection with the transmission or reception of virtual channel data via the virtual channel 150, which could be used by the surrounding node 120 to gain information on the transmission resources specified for the virtual channel 150. Accordingly, even if the surrounding node 120 is in close proximity to the destination node 100, as illustrated in Fig. 1, it may be unaware of the specification of transmission resources for the virtual channel 150, and thus unaware of the reception activity at the destination node 100.
  • the destination node 100 can make use of the reservation control message indicated at 151 in Fig. 1 for informing any -surrounding nodes in the vicinity of the destination node 100 on the transmission resources specified for the virtual channel 150.
  • the reservation control message will be transmitted from the destination node 100 with a certain transmission power so that the reservation control message is readable by a receiver within a certain reception region, which is in the simplest case a circle as indicated at 161.
  • a certain reception region which is in the simplest case a circle as indicated at 161.
  • all nodes such as the surrounding node 120 located inside the region 161, or within a certain radial distance from the destination node 100, as indicated at 153, will be in the position to. read the information of the reservation control message and may appropriately act on it, for example by avoiding use of the specified transmission resources or modifying its own transmissions based on the information of the reservation control message.
  • the transmission resources specified for the virtual channel 150 between the source node 110 and the destination node 100 and notified in the reservation control message may include any kind of radio transmission recourses usable for transmitting information between a transmitter and a receiver using radio signals.
  • the transmission resources specified for the virtual channel may include at least one of time periods for transmission, a transmission frequency or a transmission code to be used for receiving channel data at the destination node.
  • the transmission resources specified for the virtual channel may include information on at least one of the duration of a time period, a repetition of a time period and a time reference for reception of channel data at the destination node.
  • the reservation control message including information on the specified transmission resources, can be received at surrounding nodes, and the information of the reservation control message can be used to e.g. avoid a certain time period, transmission frequency or code for transmissions at the ' surrounding node, or the information of the reservation control message may be used to modify the transmission at the surrounding node 120, e.g. by lowering a transmission power or similar.
  • the destination node may transmit the reservation control message without specifically targeting a particular destination node, i.e., the destination node may transmit the reservation control message in a broadcast fashion, to be received by any surrounding node potentially located within a receiving distance of the reservation control message.
  • the destination node targets a particular surrounding node, e.g. by including an identifier of the surrounding node into the reservation control message.
  • the wireless network illustrated in Fig. 1 may be any kind of wireless network, such as a GSM, UMTS or other kind of wireless network. Further, the wireless network may be any other kind of wireless network with time-based access schemes, frequency-based access schemes or code-based access schemes, or combinations thereof. Moreover, the wireless network may be a network for distributed medium access control, and may for example operate according to the IEEE 802.11 standard, and/or may constitute a wireless ad-hoc network with distributed medium access control .
  • the wireless network may be a network for packetized transmission of data between network nodes and/or may -include data streams pertaining to certain virtual channels .
  • the wireless network shown in Fig. 1 may be a standalone network or may be integrated into any existing ' wireless communication network, including mobile communication network operating in accordance with the GSM standard, UMTS standard or any other communication standard.
  • Fig. 1 only illustrates three network nodes of the wireless network, it is understood that a far larger number of network nodes may be present.
  • the size and shape of the wireless network may change depending on the participating nodes of the network, and it is possible that nodes dynamically enter the wireless network or leave the wireless network.
  • a transmission path between the source node and the destination node for carrying the virtual channel includes further intermediate network nodes and/or transmission facilities of other networks, such as wireline communication networks, other wireless mobile communication networks, etc.
  • the destination node 100 may be any kind of device suitable for transmitting, receiving and/or relay information in the wireless network, such as a wireless telephone, a wireless computing device and similar.
  • the destination node 100 includes the receiver 101 for receiving channel data transmitted over the virtual channel between the source node and the destination node using the specified transmission resources, and further, the destination node includes the transmitter for transmitting the reservation control message including information on the specified transmission resources.
  • the transmitter and receiver may cooperate or form part of a processing element and a memory and suitable further components for enabling the transmission and reception of information to other nodes of the network via an air interface.
  • the destination node includes a memory for storing sequences of instructions which, when loaded to a processor, make the processor execute the functionality of the transmitter 101 and the receiver 102, as detailed above.
  • the transmitter and receiver may be realized as dedicated hardware or combinations of software and hardware approaches.
  • the destination node may receive and/or transmit information and association with an application executed at the destination node, such as a communication application, or any other computer application, including text processing applications, imaging applications and similar. Further, the destination node may also be involved in forwarding data received from another network node of the wireless network (not illustrated in Fig. 1) and accordingly the destination node may receive/transmit data on its own behalf or may relay information on the behalf of another device.
  • the destination node may be terminating node, i.e., may be the last node of the network involved in radio transmissions of virtual channel data. The received data may be handled or processed locally, or may be transmitted further via wireline connections .
  • the destination node may also transmit the virtual channel data using radio signals to still another node of the network, in which case the destination node relays virtual channel data received from the source node to another node of the network.
  • the destination node includes a receiver for receiving channel data transmitted over a virtual channel established between a source node and the destination node, using transmission resources specified prior to the transmission of channel data; and a transmitter for transmitting, after specification of the transmission resources for the virtual channel, a reservation control message from the destination node, the reservation control message including information on the specified transmission resources, for informing any surrounding nodes of the use of the specified transmission resources.
  • the transmitter schedules transmission of the reservation control message independent from the transmission of channel data from the source node to the destination node, and/or the transmitter may transmit the reservation control message by avoiding use of the transmission resources specified for the virtual channel .
  • the transmitter may repeatedly transmit reservation control message or may transmit the reservation control message depending on an interference level determined at the destination node.
  • the receiver determines presence of a surrounding node and transmits the reservation control message, when a surrounding node is determined. For example the receiver determines the presence of the surrounding node by detecting a transmission activity of the surrounding node or a transmission activity of the surrounding node using the specified transmission resources.
  • the transmitter may transmit the reservation control message depending on a load of the network.
  • the destination node includes means for determining motion of the destination node and the transmitter transmits the reservation control message if the destination node is determined to be moving.
  • the source node 110 can generally have a similar construction as the destination node, i.e., may also be any kind of wireless device, including a wireless telephone or computing device. Further, the source node preferably has means to transmit virtual channel data via the virtual channel 150 towards the destination node 100, as detailed above.
  • the source node 110 may be the source of the data for transmission towards the destination node, or may constitute a transmit node of the network for relaying virtual channel data received from another node via another portion of the virtual channel, indicated at 154.
  • the source node 110 in the shown embodiment of Fig. 1 assumes the functionality of a source of virtual channel data transmitted via the virtual channel 150 towards the destination node 100
  • the source node may at the same time have also the functionality described with regard to the destination node 100, i.e., in other examples the source node 110 may constitute a destination node.
  • the destination node 100 shown in Fig. 1 is described as a destination of virtual channel data received from the source node 110, the destination nodes 100 in other examples may also assume functionality of a source node, i.e., as a source of virtual channel data to be transmitted via a virtual channel to a destination node.
  • the surrounding node 120 shown in Fig. 1 may also be any kind of device suitable for transmitting, receiving and/or relaying information in the wireless network, similar to the destination node and source node, such as a wireless telephone, a wireless computing device and similar.
  • the source node may be involved in transmissions to and from other network nodes of the wireless network, as indicated by the arrow 121 in Fig. 1 and has means to receive the reservation control message 151 from the destination node 100. Further, the destination node has means to analyse the reservation control message from the destination node, in order to obtain information on the transmission resources specified for the virtual channel.
  • the surrounding node 120 may modify its own ' transmissions so as to avoid the transmission resources specified in the reservation control message, or may modify its own transmissions, e.g. by reducing a transmission power, so that the reception of virtual channel data at the destination node 100 is not any longer disturbed.
  • the virtual channel established between the source node 110 and the destination node 100 may be a uni-directional virtual channel, i.e., for transmission of virtual channel data from the source node to the destination node, but may also be a bi-directional channel, with also transmissions from the destination node to the source node.
  • the transmission resources will preferably be negotiated prior to the actual data transmission.
  • the source node and the destination node or any other entity of the wireless network may participate in negotiating resources for the virtual channel between the source node and the destination node.
  • the virtual channel will preferably be maintained as long as data need to be transmitted from the source node to the destination node and be only released thereafter.
  • the transmission resources for the virtual channel may be negotiated before the actual data transmission and the reservation control message may be advantageously used by the destination node to inform any potential surrounding nodes in the vicinity of the destination node of the specified transmission resources, even at a later point in time during transmission of data via the virtual channel, i.e., after lapse of substantial amount of time since a reservation of the transmission resources.
  • the channel data transmitted over the virtual channel may include any kind of data such as control data for controlling the virtual channel or other network operations and/or user data, e.g. user data including audio or video data or data pertaining to an application such as email data, text data, etc.
  • a virtual channel as understood in the context of this application is any link between the two elements of the wireless network for transmitting data.
  • the expression 'virtual' is uses as the channel will from the view point of the participants such as the source node and the destination node be a fixed link but not on the physical level. On the physical level the channel may use dedicated time slots, frequencies, codes or combinations thereof.
  • Fig. 2 illustrates operations for virtual channel reservation in a wireless network according to another embodiment of the invention, particularly outlining operations at a source node and a destination node.
  • the operations of Fig. 2 may be carried out using the elements of the wireless network shown in Fig. 1, however, Fig. 2 is not limited thereto.
  • the source node of Fig. 2 may be any node of the wireless network shown in Fig. 1, for example the source node 110 of the virtual channel, and the destination node may be any node of the wireless network of Fig. 1, such as the destination node 100 shown in Fig. 1.
  • a first operation 201 the source node transmits channel data over a virtual channel established between the source node and the destination node.
  • the transmission in operation 201 will use transmission resources specified for * the virtual channel between the source node and the destination node at an earlier point in time.
  • the resources for the virtual channel may be negotiated between the source node and the destination node beforehand, i.e., before data transmissions of virtual channel data.
  • the source node or destination node may generate a virtual channel request, requesting the allocation of transmission . resources and may send this reservation request along a transmission path between the source node and the destination node.
  • the transmission path between the source node and the destination node may be a direct one, i.e., without any intermediate nodes or devices, with the destination node receiving radio signals transmitted from the source node, or, the virtual channel may include further devices placed in the transmission path from the source node to the destination node, such as further network nodes of the wireless network. Further, for channel reservation, the virtual channel request may be received at the destination node, which in response thereto will try to determine and/or allocate the requested resources for transmission. If there are any intermediate nodes between the source node and the destination node, the virtual channel request may also trigger reservation of the requested resources at the intermediate node or nodes .
  • the destination node may return a virtual channel response towards the source node as a virtual channel confirmation.
  • each of the participating nodes of the virtual channel may return an acknowledgement or a virtual channel confirmation to further intermediate nodes, the destination node and/or the source node, indicating availability and/or reservation of the requested resources at the respective node.
  • the respective node could notify all remaining nodes along the communication path for the virtual channel, e.g. using a negative acknowledgement, so that further reservation operations can be terminated and alternate resources be requested.
  • the virtual channel confirmation may indicate the availability and/or allocation of the requested transmission resources for the virtual channel, and, after receiving the virtual channel confirmation, the source node may use the allocated resources for transmitting virtual channel data from the source node to the destination node along the virtual channel, e.g. as indicated at 151 in Fig. 1.
  • reservation scheme for reserving transmission resources for the virtual channel is an example only and that any other kind of virtual channel reservation for reserving transmission resources can be used.
  • the channel data transmitted from the source node are received, using the transmission resources specified for the virtual channel prior to the transmission of the channel data, as outlined in an example above. For example, if the transmission resources pertain to a certain frequency, time period or code or combinations thereof, the destination node will use a receiver set to the specified timing, frequency or code, in order to receive the channel data.
  • Fig. 2 illustrates an operation 202 a reception of the channel data
  • this does not necessarily indicate that the channel data can be successfully read or analysed at the destination node, in case a reception operation is disturbed by transmission activities at a surrounding node located in the vicinity of the destination node.
  • the destination node may only attempt to receive the channel data using the specified transmission resources, but may not necessarily succeed in doing so.
  • the destination node in an attempt to improve the reception or make the reception of channel data at the destination node possible, transmits, in an operation 203 a reservation control message, including information about the transmission resources specified for the virtual channel, i.e. the specified transmission resources.
  • the reservation control message is intended to inform any potentially existence surrounding node regarding use of the specified transmission resources, so that any surrounding node may appropriately schedule or re-schedule its own transmissions, respecting the specified transmission resources of the reservation control message.
  • the destination node uses the reservation control message to distribute information on e.g. a desired reception timing, such as a time slot or reception time period, and/or a desired reception frequency and/or a desired code for a reception at the destination node. And, the surrounding nodes can schedule their own transmissions to avoid these time periods and/or frequencies and/or codes for transmission during the required reception intervals at the destination node. The destination node can therefore properly receive the channel data via the virtual channel established between the source node and the destination node.
  • Fig. 3 illustrates elements of a wireless network, particularly illustrating nodes along a transmission path of a virtual channel .
  • Fig. 3 illustrates a destination node 100, such as the destination node 100 shown in Fig. 1. Further, Fig. 3 illustrates a source node 110, such as the source node 110 shown in Fig. 1. Still further, Fig. 3 illustrates a transmit node 300 inbetween the source node 110 and the destination node 100.
  • a virtual channel, indicated at 350 is established between the source node 110 and the destination node lOOvia the transmit node 300,.
  • the virtual channel 350 is follows a communication path involving the transmit node 300, the source node and the destination node.
  • the virtual channel is used for transmitting virtual channel data towards the destination node, as noted with regard to previous embodiments.
  • the virtual channel, shown in Fig. 3 is illustrated at a uni-directional virtual channel, i.e., for transmission of data only towards the destination node, however, in other embodiments the virtual channel may be bidirectional, i.e., also for transmission of virtual channel data from the destination node via the transmit node to the source node and possibly towards other nodes of the network.
  • the virtual channel illustrated in Fig. 3 is following a path from the source node 110 via the transmit node 300 to the destination node 100 and thus is composed of two partitions 351 and 352, with the virtual channel partition 351 being established between the source node 110 and the transmit node 300, and the second virtual channel partition 352 being established between the transmit node 300 and the destination node 100.
  • Each of the virtual channel partitions 351 and 352 will use certain transmission resources specified for the respective virtual channel partition, the resources being for example specified or negotiated beforehand between the transmit node, the source node and the destination node.
  • the resources for the virtual channel partition 352 between the source node and the destination node may involve anyone or a combination of an allocation of a time period, a frequency, ' a code or any other kind of resources which can be used for a transmission from the source node to the destination node.
  • the resources for the virtual channel partition 351 between the transmit node and the source node may also involve anyone or a combination of a time period, a frequency or code or any other transmission resource . for radio transmission.
  • the resources for both virtual channel partitions 351 and 352 are selected such that transmissions via the individual sections of the virtual channel do not disturb one another, as known in the art.
  • the source node 110 may transmit a virtual channel request over a transmission path including the transmit node 300 towards the destination node 100.
  • the transmit node 300 and the destination node may allocate transmission resources for the virtual channel and may return a clearance message towards the source node 110.
  • the source node 110 may transmit virtual channel data using the allocated transmission resources towards the destination node 100.
  • the transmission resources of the virtual channel 350 between the source node 110, the transmit node and the destination node may be negotiated using the above scheme or any other scheme for reserving resources for a virtual channel.
  • the virtual channel request may include a request for a repeating time period or time slot for a transmission from the source node towards the destination node, the repeating time period specifying a time period to be used by the transmit node, the source node and the destination node for transmitting/receiving data over a transmission carrier.
  • the repeating time period can consist of a number of time slots of networks with time-based access schemes or may specify any other kind of time period for the virtual channel .
  • the time slots for the first virtual channel partition 351 may be the same or may differ from the time slots for the second virtual channel partition 352.
  • the time period requested for allocation of the virtual channel may repeat periodically, such as every 20ms for the duration of 1 ms or any other repetition rate and duration. Alternatively, the repeating time period may be repeated in regular intervals, for example if the virtual channel requires a higher data rate at one point in time and a lower data rate at another point in time.
  • the virtual channel request may advantageously include a reservation information pertaining to at least one of the duration of the requested time period, the repetition frequency or period of the time period and/or a time reference.
  • This time reference can facilitate synchronisation of transmission between the individual nodes of the wireless network, such as the transmit node, the source node and destination node and/or further nodes of the network.
  • the wireless network lacks a central control facility, such as a wireless network with distributed medium access control, there may be no overall valid time reference available in the network. Therefore, including a time reference into the virtual channel can be used by all participating nodes, i.e., the transmit node, the source node and the destination node shown in Fig.
  • the time reference can for example be related to the start of a transmission for the virtual channel or could relate to any other event at the transmit node, the destination node or the source node or any other element of the wireless network.
  • the time reference can then be used to synchronize internal clocks at the nodes of the network, particularly the nodes participating in the virtual channel .
  • the clocks of the participating nodes or any other node of the network may be synchronized using the periodic transmissions of the virtual channel.
  • the virtual channel used for synchronizing clocks may be constituted by the virtual channel to be established, as outlined above, or may pertain to any other virtual channel, including periodic transmissions of a virtual channel solely for the purpose of synchronizing clocks of nodes of the wireless network.
  • the transmission resources requested for the virtual channel may include a transmission frequency, e.g. in a frequency-based access approached.
  • This frequency may be one of a plurality of transmission frequencies available in the wireless network or a portion of a bandwidth available for communications in the wireless network.
  • the transmission resources requested in the virtual channel may pertain to access code in a network, such as in a CDMA network (Code Division Multiple Access Network) .
  • the virtual channel request could request allocation of one or a plurality of codes or spreading codes for the transmission of data between the transmit nodes, the source node and the destination node.
  • the specified transmission resources for the virtual channel can include a combination of a time period, a transmission frequency and a transmission code.
  • the wireless network may be a multi-hop wireless network, such as an ad-hoc network, or may form part of a cellular network. Therefore, while the established virtual channel 350 may use the same specified transmission resources along the entire communication path from the source node to the destination node, it is also possible that different resources are specified or made available for different portions of the transmission path, e.g. a first type of transmission resource may be specified for the first virtual channel partition 351 from the source node to the transmit node and a second type of transmission resources may be specified for the second virtual channel partition 352 between the transmit node and the destination node.
  • a first type of transmission resource may be specified for the first virtual channel partition 351 from the source node to the transmit node
  • a second type of transmission resources may be specified for the second virtual channel partition 352 between the transmit node and the destination node.
  • the reservation information of resources of the virtual channel may be transmitted in association or combination with messages or data packets according to a communication protocol used in the wireless network, such as according to the IEEE 802.11 standard.
  • the reservation information may be included into user data fields or specifically provided fields for data frames transmitted in a network, in which case the exchange of reservation information can be simplified and make use of existing resources of the network.
  • reservation information transmitted in the wireless network separately or in association or combination with existing messages can be used to spread reservation information on allocated resources or specified resources for the virtual channel to participating nodes of the network, including further nodes not involved in the virtual channel .
  • each node receiving the reservation information may maintain information- on occupied or available resources of the network or a portion of the network and therefore interfering transmissions originating from different nodes can be reduced.
  • any nodes of the network not being informed of the specified transmission resources such as the surrounding node 120 located too far away from the source node 110 in order to receive information on the specified transmission resources, may not respect the specified transmission resources, i.e., may not try to avoid use of the specified transmission resources and may therefore disturb receptions at the destination node.
  • the destination node 100 shown in Fig. 3 is enabled to transmit a reservation control message, indicated at 354 in Fig. 3.
  • the reservation control message includes information on the transmission resources specified for the virtual channel 350, e.g. to inform any surrounding node on the use of the specified transmission resources for the virtual channel 350.
  • the reservation control message includes information on the transmission resources specified for the virtual channel partition 352 between the transmit node 110 and the destination node 100, i.e., on any time periods, frequencies or codes used for the transmissions, as noted above .
  • the reservation control message 354 may include further information on the virtual channel 350, such as regarding resources specified for the virtual cannel partition 351 between the source node 310 and the transmit node 110, i.e., on any time period, frequency or code specified for virtual channel data transmission, as noted above.
  • resources specified for the virtual cannel partition 351 between the source node 310 and the transmit node 110 i.e., on any time period, frequency or code specified for virtual channel data transmission, as noted above.
  • One of the reasons for including such information into the reservation control message is to also inform the potential surrounding nodes on resources for use between the source node and the transmit node, as the surrounding nodes may not be aware of the correspondingly specified transmission resources between the source node and the transmit node and transmission from the surrounding nodes may also disturb reception of virtual channel data at the transmit node 300.
  • a surrounding node may also not be aware of the resources used for reception at the transmit node 300, as it may not be able to read any correspondingly transmitted information from the source node 110, and as the transmit node 300may not itself transmit any information regarding the transmission resources specified for reception of virtual channel data at the transmit node 300.
  • the reservation control message 354 may include a time stamp or time information which may be used by the surrounding node or nodes for synchronizing clocks, in order to be enabled to properly schedule transmissions or modify transmissions .
  • the reservation control message may include time slot information, e.g. available or preferred time slots may be indicated in this information so that the nodes of the virtual channel and also the surrounding nodes can adopt or change their transmission, respectively.
  • the reservation control message may also include information on a frequency used for transmitting information from the destination node to the source node or vice versa to specify a frequency. This frequency may be preferred in a subsequent transmission due to changes in the network such as moving surrounding nodes transmitting on a similar frequency.
  • the reservation control message may include routing update information in order to inform the nodes of the virtual channel of other routing possibilities or changes. For example, a node in the virtual channel might have to be replaced by another node due to low power or other problems. Therefore, a back up routing option could be used by the virtual channel. These routing changes also may have to be indicated to the surrounding nodes that they do not interfere with the updated virtual channel.
  • the reservation control message may include information on a frequency channel used for the virtual channel.
  • the reservation control message may also include information on a required transmit power for transmitting information from the source node to the destination node and/or for transmitting information from the transmit node to the source node, in order to notify surrounding nodes of the required power levels.
  • the surrounding nodes may appropriately consider modifying their own transmission in order to support proper transmission of data pertaining to the virtual channel.
  • the surrounding nodes may also appropriately schedule their own transmissions, in order to reduce an overall transmission power required in the network, in order to reduce interference levels and optimise the throughput of the network.
  • the reservation control message may include information on a link quality of the link or virtual channel partition between the source node and the destination node and/or the transmit node and the source node.
  • a transmit node may use the information on the link quality to modify its own transmissions in order to improve the quality of the virtual channel between the transmit node and the destination node, until an acceptable level is reached.
  • the reservation control message may include information on a network load and/or a network congestion, in order to enable the surrounding nodes to appropriately schedule their own transmissions .
  • the reservation control message may be transmitted repeatedly in certain time intervals or transmission of the reservation control message may be triggered based on certain events.
  • the resources specified for the virtual channel are modified during the life time of the virtual channel, i.e. during a first period of time first specified resources are used for the virtual channel and during a second period of time second specified resources are used for the virtual channel.
  • These first and second specified resources may be negotiated prior or during ongoing communications through the virtual channel, e.g. upon certain events during the life time of the virtual channel the resources specified for the virtual channel may be modified from the first to the second specified resources, for example, if a required band width of the virtual channel changes, e.g. from voice data to video data or similar.
  • the reservation control messages transmitted prior to switching the resources from the first specified resources to the second specified resources will include information on the first specified resources and after switching to the second specified resources the reservation control messages transmitted from the destination node will include information on the second sr.
  • the reservation control messages may also include information specifying the conditions for switching between the first specified resources and the second specified resources such as a switching timing etc.
  • Fig. 3 illustrates a virtual channel terminating at the destination node 100
  • the virtual channel 350 may extend beyond the destination node 100, e.g. via radio signals to another node of the wireless network or via a wire bound connection to another device.
  • Fig. 4 a further embodiment of the invention will be described with regard to Fig. 4.
  • Fig. 4 illustrates operations of a method for virtual channel reservation in a wireless network, particularly illustrating operations at a source node, a destination node and a surrounding node .
  • Fig. 4 may be carried out using the elements of the wireless network shown in Fig. 1 or 3 , however, Fig. 4 is not limited thereto. Further, in Fig. 4 it is assumed that a virtual channel is established between the source node and the destination node, such as the virtual channel 150 established between the source node 110 and the destination node 100 of Fig. 1. Further, it is assumed that transmission resources for this virtual channel have been assigned or negotiated prior to the transmission of data from the source node to the destination node.
  • a first operation 301 the source node transmits channel data over the virtual channel to work the destination node.
  • Operation 301 may be as outlined with regard to previous embodiments . With the channel data transmitted via the virtual channel using the transmission resources specified for the virtual channel .
  • the destination node in an operation 302 the channel data are received using the specified transmission resources, as for example outlined with regard to previous embodiments . If for example the specified transmission resources include a repeating time slot, the destination node will receive or attempt to receive channel data using this specified time slot.
  • Operations 301 and 302 may form part of an ongoing data transmission between the source node and the destination node, for example using data packets or a stream of channel data of the virtual channel .
  • the destination node transmits a reservation control message including information on the specified transmission resources.
  • the transmission of the reservation control message may be scheduled fully independent from the transmission of channel data between the source node and the destination node.
  • the destination node transmits the reservation control message depending on a condition or state of the virtual channel between the source node and the destination node, e.g. a quality of the received data of the virtual channel of the destination node.
  • the destination node may trigger the transmission of the reservation control message on detecting a deterioration of the received data of the virtual channel beyond a certain point .
  • the transmission of the reservation control message will be a broadcast type transmission, without a . specified recipient in the reservation control message.
  • the reservation control message is therefore targeted for any additional or surrounding' nodes with able to receive the reservation control message from the destination node.
  • a surrounding node such as the surrounding node 120 of Fig. 1, is considered to receive the reservation control message in an operation 304.
  • the surrounding node analyses the reservation control message, in order to gain information on the specified transmission resources of the virtual channel .
  • the surrounding node may execute an optional operation 305 for synchronizing clocks at the destination node and the surrounding node, to facilitate adapting transmissions at the surrounding node.
  • the synchronization of clocks may be performed based on the time reference of the reservation control message or, the reservation control message may trigger the surrounding node to obtain a time reference information e.g. from a central clock of the system.
  • the surrounding node now having knowledge about the resources specified for the transmission of virtual channel data from the source node to the destination node, can modify its own transmission based on this information. Based on the information of the reservation control message the surrounding node may be instructed to modify its own transmission so that a transmission of data from the surrounding node using the specified transmission resources is avoided. For example, if the reservation control message indicates a time slot specified for the virtual channel, the surrounding node can avoid use of this particular time slot.
  • the surrounding node may modify its own transmissions based on the information of the reservation control message in an extend that the reception of channel data at the destination node is not disturbed beyond a certain level. For example, the surrounding node may lower its own transmissions during or for the specified transmission resources of the virtual channel or may assume any other measure to enable improvement of a reception of virtual channel data at the destination node. For example the surrounding node may lower its own transmission rate, change a number of time slots used, etc.
  • the adjustment of .the use of transmission resources at the surrounding node in view of an improvement of a reception of virtual channel data that the destination node may involve additional communications between the destination node and the surrounding node, including for example an indication transmitted from the surrounding node to the destination node that the use of transmission resources at the surrounding node has been modified and a confirmation from the destination node towards the surrounding node, whether the modification was suitable for achieving a desired improvement of the reception at the destination node of virtual , channel data.
  • the source node may transmit further channel data over the virtual channel to the destination node, where it is received in an operation 308.
  • the operation 308 may be followed by further transmissions of the reservation control message, e.g. if reception problems persist, or based on any other scheme.
  • the reservation control message transmitted in operation 303 may be received at an arbitrary number of surrounding nodes and therefore an arbitrary number of surrounding nodes may be instructed to modify their own transmissions on the basis of the information of the reservation control message.
  • the reservation control message may thus be generally used in the system to spread information on the status of communications, e.g. signal quality, frequency channels etc, allowing nodes to adjust their own transmission to better use the overall resources of the system.
  • Fig. 5 illustrates elements of a wireless network for virtual channel reservation, particularly illustrating a transmission of the reservation control message and virtual channel data between the individual nodes of the wireless network.
  • Fig. 5 shows a destination node 100, a source node 110 and an additional node 510 in communication with the source node.
  • the additional node 510 is arranged to transmit virtual channel data towards the source node 110 and the source node 110 is arranged to transmit virtual channel data to the destination node 100, as noted with regard to previous embodiments .
  • the source node therefore may be viewed as an intermediate node in Fig. 5 as regards traffic from the additional node, but it will still constitute the source of any traffic between the source node and the destination node.
  • Transmissions at the individual nodes will be carried out using a certain transmission power, and therefore the messages transmitted from the individual nodes will be spread over a certain area.
  • a transmission from one node of the network using a certain transmission power may be readable i.e. its content may be derived, within a certain reading zone. In other words, within the reading zone the content of a message transmitted from the respective node can be derived.
  • transmission activity at a certain node will be detectable in a certain sensing zone, the sensing zone always being larger than the reading zone of the node.
  • Fig. 5 illustrates such reading zones and sensing zones as outlined above.
  • the source node 110 has a reading zone 550 being, of course, dimensioned such that transmissions from the source node pertaining to the virtual channel data can be fully received at the destination node 100.
  • the source node 110 has a sensing zone 551, wherein nodes can detect transmission activity at the source node.
  • the additional node 510 has a reading zone 552 dimensioned such that the source node 110 can receive all data transmitted via the virtual channel from the transmit node 332 to the source node 110.
  • the transmit node 330 has a sensing zone 553.
  • nodes within the reading zone of a node may also obtain information on transmission resources specified for a virtual channel, such as outlined with regard to the previous embodiments.
  • the source node could include into messages containing virtual channel data for the destination node also information pertaining to the specified resources for the virtual channel .
  • the destination node 100 in this particular embodiment is assumed to be a terminating node, i.e. virtual channel data are received at the destination node but not transmitted any further. Accordingly the destination node does not have a reading zone in association with the transmission of channel data and the combined reading zones of the nodes of the virtual channel, i.e. the addition node 300, the source node 110 and the destination node 100 form a shape which is large in the area of the transmit node and the source node, but with the destination node possibly lying within a boundary portion of the combined reading zone in which surrounding nodes could learn about the resources used for the virtual channel .
  • surrounding nodes present sven in the direct neighbourhood of the destination node which are not aware of any reception operations at the destination node pertaining to reception of virtual channel data from the source node and these surrounding nodes may interfere with or disturb reception operations at the destination node.
  • the destination node 100 transmits a reservation control message with a certain transmission power which can be read in a certain reading zone 554, i.e. a zone wherein the content of the reservation control message can be fully detected.
  • a certain reading zone 554 i.e. a zone wherein the content of the reservation control message can be fully detected.
  • the destination node has no other means for notifying surrounding nodes, e.g. if the destination node only receives data from the source node via the virtual channel but does not return any data to the source node, the actively transmitted reservation control message can be used to advantageously inform surrounding nodes .
  • Fig. 5 further illustrates for surrounding nodes 500, 501, 502 and 503.
  • surrounding nodes 550 and 501 are positioned within the reading zone of 554 of the reservation control message originating from the destination node 100. Accordingly, based on the reception of the reservation control message the surrounding nodes 501 and 500 can schedule their own transmissions such that a reception of virtual channel data at the destination node is not disturbed or overly impaired, as outlined with regard to previous embodiments.
  • the surrounding node 502 shown in Fig. 5 is located outside the reading zone 554 of the .reservation control message from the destination node, and therefore will not be informed of the transmission resources specified for the virtual channel through the reservation control message. However, as the surrounding node 502 is assumed to be in a large enough distance from the destination node 100, the surrounding node 502 can continue scheduling its own transmissions without considering transmission of virtual channel data between the source node and the destination node.
  • the surrounding node 503 is located within the reading zone 550 of the source node 110, albeit being located outside the reading zone 554 of the reservation control message transmitted from the destination node. Accordingly, while the surrounding node 503 is unable to receive the reservation control message, as it is within the reading zone 550 of the source node 110, it may derive information on the virtual channel resources from information received with the virtual channel data transmitted from the source node to the destination node. Presuming that the virtual channel information transmitted from the source node to the destination node includes information on the resources used for transmitting the data, the surrounding node 503 may schedule its own transmissions so that a reception using the specified resources of the virtual channel at the destination node is not disturbed. A reception of information regarding the virtual channel is illustrated in Fig. 5 at reference numeral 555.
  • the destination node has been illustrated as a terminating node, i.e. the destination node is assumed to only receive virtual channel data.
  • the destination node transmits virtual channel data via a further portion of the virtual channel towards another node of the network.
  • the destination node receives virtual channel data and transmits virtual channel data as a transmit node of the network.
  • the destination node 100 may broadcast or transmit the reservation control message as in previous embodiments, as a refresh message, to inform any node in the vicinity, i.e., any surrounding node in the vicinity of the destination node regarding use of the specified resources of the virtual channel.
  • the reservation control message in this case may be transmitted in addition to information pertaining to the use of resources for the transmission of channel data transmitted in association with the virtual channel data, transmitted from the destination node.
  • the refresh message can be used to synchronize clocks at the nodes of the system to avoid erroneous transmissions and collisions.
  • Fig. 6 illustrates operations of virtual channel reservation in a wireless network at a destination node and in particular scheduling transmission of the reservation message.
  • the operations shown in Fig. 6 may be carried out using the destination node shown in Fig. 1, however, the embodiment of Fig. 6 is not limited thereto.
  • a first operation 601 at the destination node such as the destination node 100 of Fig. 1, the destination node receives or tries to receive, depending on the surrounding radio communication traffic, channel data over the virtual channel, using specified transmission resources described in detail above .
  • the transmission of a reservation control message is scheduled independent from the reception of channel data from the source node 110 of Fig. 1, wherein the scheduling may be performed by the transmitter 101.
  • the transmission is handled by processes or hardware elements which are unrelated to processes or hardware elements for handling the reception and/or transmission of channel data through the virtual channel .
  • the process or hardware elements for handling the transmission of the reservation control message may use predetermined timings or predetermined events for scheduling the transmission of the reservation control message as will be discussed further below.
  • the destination node 100 is therefore able to transmit the reservation control message described previously without being triggered by an intended transmission or by a received data stream or data packet associated with the virtual channel.
  • the type of transmission resource of the reservation control message may be independent of the transmission resources used by the virtual channel .
  • the destination node may transmit the reservation control message using specific time periods or time slots, while the virtual channel uses a transmission frequency or a transmission code or vice versa.
  • the reservation control message can be transmitted repeatedly, for example in certain intervals, certain time patterns or with a specific periodicity, which can be dynamically changed according to the network configuration, such as load and mobility. For example, if network traffic is low and the node is not very active in transmitting data, the intervals, in which the reservation control messages are transmitted might be longer than in the case of a very active node and high network traffic, where collision of data is likely to occur.
  • the transmission of the reservation control message is scheduled depending on a predetermined event, such as after switching on the destination node or upon a certain instruction or command input at the destination node, or at a predetermined time and date, which may be set in the destination node using a timer, for example, if a specific data download via the virtual channel is scheduled for a certain time of day.
  • the transmission of a reservation control message is triggered by surrounding transmissions.
  • the destination node or any other node handling the virtual channel generates the reservation control message when they overhear a transmission from a new neighbouring node that cannot yet have received information about the transmission about the reservation. Then, if a node of the virtual channel wants to communicate with other nodes in the virtual channel, it might inform the surrounding nodes thereof. Therefore, it might be decided that the transmitter schedules to transmit the reservation control message, which is then transmitted prior to the communication in the virtual channel. This case will also be discussed in detail in the following figures.
  • the reservation control message can be transmitted by avoiding use of the transmission resources specified for the virtual channel so that the transmission resources of the reservation control message and the virtual channel are different. For example, when the transmission resources for the virtual channel include time periods for transmission, the reservation control message can then be transmitted in different time periods by the transmitter 101. Similarly, if a certain transmission frequency or frequency band is used by the virtual channel as a transmission resource, the reservation control message can be transmitted at a different frequency or frequency band. These considerations also apply to using a transmission code to be used for receiving channel data at the destination node 100.
  • the transmitter 101 may transmit a reservation control message at specific time periods or specific time slots, when a virtual channel uses a transmission frequency or a transmission code or vice versa. Still further, transmission resources may be mixed or combined so that for example a transmission code may be used in specific time slots.
  • the reservation control message can be combined with an acknowledgement message transmitted from the destination node by the transmitter.
  • Such an acknowledgement message might acknowledge the reception of channel data and can be transmitted to the source node or the transmit node of Fig. 3.
  • a virtual channel reservation mechanism can successfully repair a reservation chain or virtual channel that is broken due to mobility or nodes that are switching off, since a feedback mechanism of the working state of the nodes is thereby provided. For example, it might be determined that a node is inactive or not present anymore, if the node does not respond anymore for a specific time.
  • Transmission of the acknowledgement message can be followed by a transmission of a reserved data packet or stream. Further, it may be necessary to combine a reservation control message only with some of the acknowledgements, which can be changed dynamically depending e.g. on network traffic or load.
  • Another option is to combine the reservation control message with the signalling of a handshake mechanism, such as combining or including it in a Request-to-Send message from a transmitting node or/and the Clear-to-Send message transmitted from a receiving node. Similar messages are also commonly used in establishing the virtual channel for example and therefore have to be transmitted anyway.
  • acknowledgement messages might also acknowledge inquiries from other surrounding nodes also interested in knowing the presence and transmission resources of other nodes in the wireless network so that collisions can be avoided.
  • Fig. 7 illustrates operations of a method for virtual channel reservation in the wireless network according to another embodiment of the invention, particularly illustrating transmitting the reservation control message based on an interference level determined at the destination node.
  • the operations shown in Fig. 7 may be carried out using the destination node shown in Fig. 1, however, the embodiment of Fig. 7 is not limited thereto.
  • nodes When nodes communicate with each other they constantly transmit data. Therefore, the communication of the surrounding node 120 with any other node can potentially interfere with the reception of virtual channel data at the destination node 100.
  • the destination node 100 when the destination node 100 is the node terminating the virtual channel, the destination node 100 may not transmit data via the virtual channel but largely receive data via virtual channel 150 and it is impossible for the surrounding node 120 to know about its existence and the transmission resources specified for the virtual channel 150. Therefore, the surrounding node carries on transmitting data, which also reaches the destination node 100 interfering with virtual channel data if the same transmission resources are used.
  • the destination node 100 and the surrounding node might use the same time slots so that the receiver 102 not only receives data over the virtual channel but also unwanted data from the surrounding node.
  • the destination node it would be advantageous for the destination node to be able to inform the surrounding nodes of its presence and transmission resources if surrounding nodes are transmitting data that interferes with virtual channel data.
  • the destination node receives or tries to receive channel data over the virtual channel, using specified transmission resources in operation 701.
  • the receiver 102 determines an interference level of reception at the destination node 100.
  • the interference level is a measure of the radio communication traffic received at the destination node using the same transmission resources but the signals are not expected by or directly addressed to the destination node. Therefore, the reception of data e.g. from a virtual channel is disturbed, since the different transmissions are overlapping .
  • These transmissions creating the interference level can be caused, for example, by surrounding nodes 120 transmitting and receiving data and operating by using the same or similar transmission resources as the destination node 100 and the virtual channel 150 linked to the destination node 100. Therefore, the communications of the surrounding nodes might strongly influence the quality of radio communication between the nodes of the virtual channel, and in particular the reception of data at the destination node, since collisions might occur .
  • the receiver 102 of the destination node 100 may listen to the transmission in the network and analyse the transmission messages, in order to determine an interference level .
  • the cause might be interference from other data transmissions using the same transmission resources. Therefore, the level of disturbance and eventually the data quality might constitute a direct indication of the interference level.
  • another way of measuring interference is determining the amount of surrounding nodes based upon the presence of different identifiers corresponding to each of the surrounding nodes and their approximate transmission activity. These identifiers might be present in each transmission of a node and then might be exchanged in the network from neighbouring nodes or nodes of the virtual channel to update the number and identity of the nodes present in the wireless network.
  • the information about active nodes in a network, their identity, transmission activity, position etc. might be distributed in the wireless network and passed to nodes in the neighbourhood or might be stored centrally in a storage unit being accessible by nodes requesting information about the wireless network. This information might then be used to determine or calculate a possible interference level for different regions in the wireless network.
  • the surrounding node might be informed of the interference level by surrounding nodes, which already have measured it or received this information from another source, such as the above discussed storage unit.
  • interference levels are usually different for different nodes.
  • assumptions about the interference level detected at the destination node can be made from the information of nodes closely spaced to the destination node.
  • the interference level is compared to a threshold value, which can be preset for a certain node or might be dynamically changeable, depending on the quality and type of service desired.
  • the threshold value might be changed based on a certain priority included in the received data transmission indicating important data, such as data needed for configuration of a device to run a specific application. Further, considering video telephony, it might be desirable to have a high quality of service with a large throughput of data so that real time transmission of voice and images can be obtained.
  • the decision is "no" indicating that the interference level is below a threshold, the flow returns to the beginning and restarts the determination process with operation 701. If, however, the interference level is above a threshold value and the decision in operation 703 is "yes", the flow moves forward to operation 704.
  • the transmitter of the destination node transmits a reservation control message, which can be received by a surrounding node. Furthermore, the reservation control message is transmitted without any needed reply, meaning that no acknowledgement of the reception at the surrounding node has to be sent from a surrounding node to the destination node, which decreases signalling between nodes and overhead in the wireless network.
  • the reservation control message can also be transmitted depending on a load of the wireless network. This load can be a measure of the utilization of the network indicating the available capacity for additional data transmission.
  • the load might be determined similarly to the interference level by the radio communication traffic in the environment of the destination node or the destination node might be simply informed by other nodes or through the virtual channel of the load and activity in the wireless network.
  • the interference level using information about the number, identity and activity of the nodes present in the network can give a good indication of the load of the network, however, the load is more or less constant from node to node .
  • GPS Global Positioning System
  • a GPS receiver can be integrated in a means for determining motion, which might be included in the destination node. Similar to the decision in operation 703 and the operation 704, a reservation control message can be transmitted, when a decision is made that the destination node is moving.
  • Fig. 8 illustrates operations of a method of virtual channel reservation in a wireless network according to another embodiment of the invention, particularly illustrating operations to determine if other surrounding nodes are present.
  • the operations shown in Fig. 8 may be carried out using the destination node shown in Fig. 1, however, the embodiment of Fig. 8 is not limited thereto.
  • the presence of a surrounding node might cause similar problems.
  • nodes When nodes are active and communicate with each other they constantly transmit data, which can cause reception problems at the destination node 100 of the virtual channel 150.
  • detecting the presence of an inactive node or a moving node not yet in a certain communication area, namely a certain vicinity of the destination node such as the reception region 161 might also potentially cause collisions, since the node can start transmitting anytime.
  • the destination node receives or tries to receive channel data of the virtual channel, using specified transmission resources as described above in a previous embodiment .
  • the presence of a surrounding node is determined at the destination node.
  • the presence of a surrounding node can be determined, for example, by radio signals transmitted from a surrounding node, namely its transmission activity. This can be detected by the receiver 102 of the destination node 100 so that the destination node is informed about the existence of surrounding nodes .
  • different surrounding nodes can be detected by different identifiers included in the radio traffic generated by the nodes discussed above so that the signals of the radio traffic can be associated to individual nodes.
  • the presence of a surrounding node and its identifier might be communicated to the destination node by other nodes including the nodes of the virtual channel, updating the nodes in the wireless network of changes in the network.
  • These updates might also be performed by the base stations of the network, which know the number and activity of the nodes based on their signalling in the communication area of the base station so that they can keep track of changes in the network and might be able to quickly inform other nodes about changes and likely developments. For example, nodes, which were previously switched off might be activated again and then contribute to the communication traffic or interference level of the network. Further, it is possible that a node previously located outside of the communication area of the destination node moves now inside of it, which can be easily determined by the base stations by extrapolating the previous direction of travel of that node. Therefore, it is important to constantly keep track of the nodes in the network.
  • the procedure decides whether a surrounding node is present. If in operation 803 the decision is "no", indicating that there is no surrounding node present, the flow returns to the beginning of the procedure before operation 801 and restarts the determination process. If, however, the decision is "yes”, indicating that at least one surrounding node is present, the procedure moves forward to operation 805. In an operation 805, the surrounding node transmits a reservation control message based on the presence of a surrounding node to inform surrounding nodes of its presence and its intent to communicate, using specified transmission resources.
  • an alternative operation 804 might be included in the flow, which determines if the surrounding node uses the specified transmission resources of the destination node 100.
  • the procedure moves forward to operation 805, in which a reservation control message 151 is transmitted by the transmitter 101 to inform the surrounding nodes of the destination node 100.
  • a transmission resource previously used by a surrounding node can be changed in time so that a previously non-interfering node might cause interference at another point in time. Therefore, a continuous update of the information about the surrounding no ' des is necessary to make sure that possible collisions are prevented at an early stage .
  • Fig. 9 illustrates elements of a wireless network for virtual channel reservation according to another embodiment of the invention, and particularly focuses on elements of the destination node, such as the destination node 900 shown in the previous embodiments.
  • Fig. 9 the functionality of the receiver and transmitter of the destination node are realised by a receive and a transmit unit 901, a processing unit 902 and a memory 903.
  • the receive and transmit unit 901 is provided for receiving a virtual channel data via a virtual channel from a source node, and for transmitting a reservation control message towards surrounding nodes of the destination node. Additionally, the receive and transmit unit 901 may be provided for transmitting virtual channel data towards a still further node of the network, in which case the destination node 900 constitutes a transmit node for relaying virtual channel data between a source and a destination.
  • the destination node 900 may also provide for a wireline connection towards an additional node or device of the wireless network or any other destination device, e.g. to carry the virtual channel data received from the source node towards their intended destination.
  • the destination node 900 may be provided with a suitable reproduction or display means for reproducing, displaying or otherwise handling virtual channel data received from the source node.
  • the destination node 900 may be arranged to display the video information on a display associated with the destination node 900.
  • the memory unit 903 of the destination node may store coded instructions which, when executed on the processing unit 1002, realise at least part of the functionality of the receiver and transmitter of the destination node as outlined with regard to previous embodiments.
  • processing unit and memory may be used for handling further functionality of the destination node, such as further communication processes, service applications for users and similar.
  • any of the above functionality of the destination node described with regard to the embodiments may be realized by means of a processing element or computing device executing corresponding coded instructions. Further, the functionality of the destination node described with regard to the embodiments may be realized at least partially in software and hardware .
  • a program may be provided having instructions adapted to make a data processing device or devices execute any of the above operations.
  • a computer-readable medium may be provided having a program embodied thereon, where the program is to make a computer or a system of data processing devices to execute functions or operations of the features and elements of the above-described examples.
  • a computer-readable medium can be a magnetic or optical or other tangible medium on which a program is recorded, but can also be a signal, e.g. analog or digital, electronic, magnetic or optical, in which the program is embodied for transmission.
  • a computer program product may comprise the computer readable medium.
  • a destination node including a processor and a memory for storing program sections for execution on the processor.
  • the program sections including a code section containing instructions to receive channel data transmitted over a virtual channel established between a source node and the destination node, using transmission resources specified prior to the transmission of channel data; and a code section containing instructions to receive transmit, after specification of the transmission resources for the virtual channel, a reservation control message including information on the specified transmission resources, for informing any surrounding nodes of the use of the specified transmission resources.
  • the program may include a code section containing instructions to schedule transmission of the reservation control message independent from the transmission of channel data from the source node to the destination node.
  • the program may include a code section containing instructions to transmit the reservation control message by avoiding use of the transmission resources specified for the virtual channel .
  • the program may include a code section containing instructions to repeatedly transmit reservation control message .
  • the program may include a code section containing instructions to transmit the reservation control message depending on an interference level determined at the destination node.
  • the program may include a code section containing instructions to determine presence of a surrounding node and wherein the transmitter is adapted to transmit the reservation control message, when a surrounding node is determined.
  • the program may include a code section containing instructions to determine the presence of the surrounding node by detecting a transmission activity of the surrounding node .
  • the program may include a code sectipn containing instructions to determine the presence of the surrounding node by detecting a transmission activity of the surrounding node using the specified transmission resources.
  • the program may include a code section containing instructions to transmit the reservation control message depending on a load of the network.
  • the program may include a code section containing instructions to determine motion of the destination node and a code section containing instructions to transmit the reservation control message if the destination node is determined to be moving.
  • the program may ' include a code section containing instructions to transmit channel data to an additional node forming part of the virtual channel and a code section containing instructions to transmit the reservation control message as a refresh message.
EP04739322A 2004-05-24 2004-05-24 Reservierungssteuerung für virtuelle kanäle Withdrawn EP1749377A1 (de)

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US8340027B2 (en) 2006-08-07 2012-12-25 Qualcomm Incorporated Monitor period for asynchronous wireless communication
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