FIELD OF INVENTION

The present invention relates to Mobile Ad-Hoc Network (MANET). More particularly, the present invention relates to a method of providing fast multicast subscriptions for MANET.

BACKGROUND

Mobile Ad-Hoc Network (MANET) provides instantaneous connection between mobile nodes and mobile networks. The implementation of MANET has been further extended to Vehicular Ad-Hoc Networks (VANET) which allows vehicles to communicate with each other to transmit data through the ad-hoc basis. In the case of VANET, often, the connection between two vehicles lasts no more than a second, or less. Often, it is difficult to maintain and establish a successful transmission during such short time period.

FIG. 1 illustrates a typical multicast operation of a MANET that includes two simplified networks, i.e. mobile network A and mobile network B. The mobile network

A includes a mobile device 101 and a router 102. Similarly, the mobile network B too includes a mobile device 111 and a router 112. At step 120, the mobile network A and the mobile network B are not connected to each other. At. step 121, the mobile network

A and the mobile network B are attempting to establish communication through the routers 102, 112. Once connected, the mobile device 101 performs a multicast announcement to the router 102 at step 122. At step 123, the router 102 forwards the multicast announcement to the connected router 112. In step 124, the mobile device 111 receives the multicast announcement from the mobile device 101 through the router 112. In step 125, the mobile device 111 subscribe to the multicast stream through the router 112. In step 126, the subscription is forwarded from the router 112 to the router 102. In step 127, the multicast subscription reaches the mobile device 101 to initiate the multicast streaming. In step 128, the mobile device 101 sends the multicast stream to the router 102, and in step 129, the multicast stream is forwarded to the router 112. In step 130, the mobile device 111 receives the multicast stream through the network under the multicast protocol. Such multicast connection between the two networks works generally fine in a MANET. However, such multicast protocol may face challenge in VANET when the time period allowable for establishing the connecting is short.

US issued patent no. 7,333,026 discloses a collaborative multicast for dissemination of information in vehicular ad-hoc networks. It uses multicast protocol to share information in VANET through a mesh network by nominating one of the collaborating vehicles to broadcast a subsequent vehicle communication message, thus synchronizing and retaining the low latency over relatively long-distance multi-hop packet routes.

US issued patent no. 7,330,736 discloses a method and apparatus for reduced energy communication in an ad-hoc network. The proposed method and apparatus attempt to save energy during communication sessions between vehicles. SUMMARY

In one aspect of the present invention, there is provided a method of multicast streaming between two mobile networks forming a mobile ad-hoc network (MANET), each networks having a mobile device (201 ,21 1) and a router (202,212) The method comprises multicast streaming data from a sender device (201) through a sender router (202) without the presence of a recipient device (21 1); subscribing to a multicast stream by the recipient device (211) through a recipient router (212) without the presence of the sender device (201); establishing a connection between the sender router (202) and the recipient router (212); sending the subscription from the recipient device (211) to the sender device (201) once the two routers (202,212) are connected; transmitting the data from the sender device (201) to the recipient device (21 1). The multicast streaming of the MANET may be carried out without any multicast announcement.

In one embodiment, the method further comprises verifying a source address of the received data to avoid multicast loop back.

In another embodiment, the multicast streaming is carried out by the sender device (201) without specifying receiver and the subscription by the recipient device is carried without specifying a sender or source address.

During multicast streaming and prior to connection between the routers (202,212), the sender router (202) may drop multicast packets.

In a further embodiment, a pre-assigned multicast address is used by the sender device (201) and the recipient device (21 1) for the multicast streaming and the subscription The routers can be acted as a proxy to stream data.

In yet a further embodiment, the MANET is VANET. In another aspect of the present invention, there is provided a multicast streaming system for communicating with another for data exchange and sharing via a MANET. The system comprises a mobile device (201,21 1) operable to send multicast stream as a sender device and subscribe to a multicast stream as a recipient device; and a router (202,212) operable to route transmission of another multicast streaming system. The multicast streaming is established upon connections between two routers of the multicast streaming system, without any multicast announcement.

In one embodiment, the system is operable to verify a source address of the received data to avoid multicast loop back.

In another embodiment, the multicast streaming is carried out without specifying receiver and the subscription is carried out without specifying a sender or source address. During multicast streaming and prior to connection between routers (202,212), the router (202) may drop multicast packets. In yet a further embodiment, a pre-assigned multicast address is used by the mobile device for multicast streaming and the subscription. The router may be acted as a proxy to stream data.

In yet a further embodiment, wherein the MANET is VANET. BRIEF DESCRIPTION OF DRAWINGS

This invention will be described by way of non-limiting embodiments of the present invention, with reference to the accompanying drawings, in which

FIG. 1 illustrates a typical operation of a MANET that includes two simplified networks; and

FIG. 2 illustrates operations of a simplified MANET in accordance with one embodiment of the present invention.

DETAILED DESCRIPTIONS

In line with the above summary, the following description of a number of specific and alternative embodiments is provided to understand the inventive features of the present invention. It shall be apparent to one skilled in the art, however that this invention may be practiced without such specific details. Some of the details may not be described at length so as not to obscure the invention. For ease of reference, common reference numerals will be used throughout the figures when referring to the same or similar features common to the figures.

FIG. 2 illustrates operations of a simplified MANET in accordance with one embodiment of the present invention. The operations have significantly speed up information exchanges between nodes within the MANET. Speeding up the transmission process is particularly useful for MANET that requires fast transmissions, such as VANET. The MANET provided herewith includes two networks i.e. a mobile network A and a mobile network B, for simplifying the illustrations only, not limitation. It is understood to the skilled person that the present invention is applicable and implementable to a more sophisticated MANET that involves more data networks. The MANET uses multicast as a carrier protocol for information exchanges. In the present embodiment, the sender of data stream can continuously stream information without having to define the receiver for the transmissions.

The mobile network A is a sender network that includes a sender device 201 and a router 202, and the mobile network B is a recipient network that includes a recipient device 211 and a router 212. In step 220, the sender device 201 starts multicast data stream through the router 202 among the MANET. The data stream is multicast without having to specify receiver of the data stream. At the same time, the recipient device 211 continuously sends multicasts subscriptions through the router 212 of the mobile network B. Similarly, the recipient device 211 subscribes to a multicast stream without having to specify any sender or source address for the multicast stream. During which, when there is no-connectivity, the router 202 of the mobile network A drops the multicast packets received from the sender device 201. In step 221, the router 202 of the mobile network A connects with the router 212 of the mobile network B. The connection usually occurs, when both mobile networks A and B are in a range of the wireless coverage, for example. In step 222, the multicast subscription from the recipient device 211 of the mobile network B is transmitted to sender device 201 through the router 202 of the mobile network A. In step 223, once the recipient device 211 is subscribed to the sender device 201, the multicast packet (from the sender device 201) is re-streamed to the router 212 through the router 202 and thereafter in step 224 to the recipient device 211. Once the multicast streaming is initiated, both router 202 and the router 212 verify the source address of receiving multicast packets to ensure that the respective multicast stream is not forwarded back to the sender device causing a looping.

In the above embodiment, the auto subscription by the recipient device 211 allows the multicast streaming to be carried out without the need to wait for session announcement from the sender device 201. By performing this auto subscription method, the receiver can start receiving information at the instant the connection is established, which saves a lot of time.

As depicted in the figures above, it is clearly shown that the whole process is reduced more than half by implementing the method as proposed by the present invention. In one embodiment, the multicast streaming uses one pre-assigned multicast address for all mobile network.

In another embodiment, the routers 202, 212 act as proxy multicast sender/receiver to re-stream the packets to a next hop when the sender device 201 and the recipient device 211 belong to different mobile networks. Such configuration allows the routers to act as proxies for the multicast streaming without a need to specify address of the sender device 201 as required under Source Specific Multicast (SSM) protocol, which the recipient device 211 would otherwise required to wait till it receives the sender device's streaming announcement before the address can be retrieved. When the routers act as the proxies for the multicast streaming, the packets are treated as sending within a local network, so that the recipient device 211 is virtually receiving multicast packets from sender device 201, but in actual fact, it is received from the router 212.

In a further embodiment, the sender device 201 streams out continuously with a specific multicast address with/without the presence of a receiver device. On the other hand, the receiver device 211 is adapted to continuously subscribe to a specific multicast address even there is no sender device subscribing.

In yet a further embodiment, the routers drop multicast packets when the source address is detected to belong to a local network to avoid looping.

With the embodiments of the present invention described above, multicast protocol steaming is sped up for information sharing, thereby saving time during communication sessions between the networks.

Depending on the hardware used, the process proposed by the invention may be suitable to implement on MANET with minimal hopping, rather than long range multi- hop hierarchical connection. One example of MANET that includes minimal hopping is VANET.

While specific embodiments have been described and illustrated, it is understood that many changes, modifications, variations and combinations thereof could be made to the present invention without departing from the scope of the invention.