System and method for smart broadcast for multicast communication over IP-based TDMA networks

Abstract

A system, process, and method are described that increase the reliability of packet delivery while reducing end-to-end delay and power consumption in low-power wireless networks. Packets are forwarded during transmission time slots using link layer broadcast transmission. A preset number of retransmission time slots are provided for retransmitting packets. To reduce energy consumption for a receiver, the receiver can enter a sleep mode after receiving packets for the remaining retransmission time slots.

Description

[Technical field]

[0001] The field of the invention is multicast communications, such as for use in on-board wireless sensor networks, the Internet of Things, home automation, and low power devices. [Background technology]

[0002] The following description contains information that may be useful in understanding the present invention. It is not admitted that any of the information provided herein is prior art or relevant to the present claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Currently, there is an increasing demand for new applications of Wireless Sensor Networks (WSNs). One exemplary area of ​​application relates to in-flight communications, particularly for aircraft. As aircraft systems become more and more connected, additional sensors are utilized in aircraft to determine the status and health of seats, electronics, and other components. With the demand for these increasing new applications, it is useful to connect WSNs to the Internet by Internet Protocol (IP) addressing, and particularly by Internet Protocol version 6 (IPv6) and future protocols, to achieve all IP communications and thus interoperability.

[0004] However, current standards, including IEEE 802.15.4, do not natively support multicasting. Instead, algorithms have been developed that utilize link-layer unicast or link-layer broadcast transmissions to achieve IP multicasting. One of the main differences between unicast and broadcast modes of communication is reliability. With unicast transmission, the sender receives an acknowledgment from the destination upon successful delivery of the packet. Broadcast communication, however, does not offer this feature.

[0005] In link-layer unicast transmission, duplicates need to be generated for each subscriber and delivered to every subscriber individually, which consumes both time and energy. On the other hand, in link-layer broadcast transmission, a packet is sent out once to every subscriber and no duplicates are generated. Therefore, link-layer broadcast transmission saves energy and end-to-end delay compared to link-layer unicast transmission, especially in the case of multiple subscribers. However, broadcast communication has reliability problems.

[0006] For example, Bidirectional Multicast RPL Forwarding (BMRF) has been implemented using link layer unicast and broadcast transmissions based on the number of involved subscribers. A more detailed description of BMRF can be found in the article "BMRF: Bidirectional Multicast RPL Forwarding" by Lorente et al., published by Ad Hoc Networks in 2017.

[0007] BMRF allows multicast packets to traverse both up and down the RPL tree. An example of BMRF is shown in Figure 1. Unlike Enhanced Stateless Multicast RPL Forwarding (ESMRF) below, multicast packets do not need to traverse all the way to the root. All motes (sensors) in the network are aware of the topology. Thus, multicast sources can be anywhere in the network. BMRF shows improvements in energy consumption, radio transmission, and end-to-end delay compared to previous algorithms. The idea is to choose between unicast and broadcast at the link layer based on the number of children involved and the duty cycle ratio.

[0008] BMRF is at a disadvantage because it uses the ContikiMAC algorithm for its radio duty cycle (RDC) and has IEEE 802.15.4 with carrier sense multiple access (CSMA) as its physical and media access control (MAC) layers. CSMA is generally non-deterministic. BMRF may also incur additional delays required to avoid collisions, such as when waiting for a clear channel if link layer broadcasts are used. In addition, bandwidth and energy are wasted when there are few children involved. BMRF is also prone to cross-technology interference with various other technologies, such as cordless phones, Wi-Fi, Zegbee, Bluetooth, and microwave ovens using the 2.4 GHz Industrial, Scientific, and Medical (ISM) band.

[0009] Others make use of the Multicast Protocol for Low-Power And Lossy Networks (MPL), described in Kelsey et al., Multicast Protocol For Low-Power And Lossy Networks (MPL), published by the IETF in 2016. MPL involves controlled network-wide flooding managed by a Trickle timer. Trickle is an effective periodic propagation mechanism for state information. See Levis et al., Trickle: A Self regulating Algorithm For Code Propagation And Maintenance In Wireless Sensor Networks, Proceedings of the First USENIX / ACM Symposium on Networked Systems Design and Implementation, and Levis et al., The Trickle Algorithm, Technical Report of the IETF, Fremont, CA, 2011, USA: RFC6206.

[0010] In MPL, all motes (sensors) in the network receive multicast packets, whether they are interested in the packet or not. Each mote (sensor) then disseminates the multicast packet to its neighbors. These multicast packets need to be buffered to keep track of whether a particular multicast packet has been received before. To help ensure that packets are received by all motes, a trickle timer is used to schedule periodic retransmission of these buffered packets.

[0011] MPL is disadvantageous in terms of both energy and bandwidth efficiency. Due to the controlled flooding of packets throughout the network, all motes (sensors) in the network receive multicast packets which increases communication overhead. Control packets also need to be regularly disseminated throughout the network to keep track of the buffering state. This further adds to the communication overhead. Motes (sensors) also need to maintain two trickle timers to handle buffered packets and control messages. This increases the overall complexity, code size, and memory requirements.

[0012] Since all of the packets are buffered, the transmission takes up a lot of memory, which can be problematic because motes (sensors) generally have limited memory, limiting the number of packets that can be buffered and directly impacting the efficiency of MPL.

[0013] Another example is Stateless Multicast RPL Forwarding (SMRF), which is described in Oikonomou et al., "Stateless Multicast Forwarding With RPL In 6LoWPAN Sensor Networks," In Pervasive Computing and Communications Workshops, 2012 IEEE International Conference on Pervasive Computing and Communications (PERCOM Workshops), 2012, and "IPV6 Multicast Forwarding In RPL-Based Wireless Sensor Networks," Oikonomou et al., Wireless Personal Communications, 2013. As shown in Figure 2, SMRF only supports downstream traffic because it enforces a preferred parent check before accepting a message. Therefore, the source of the multicast communication is limited to the root of the RPL tree. In other words, other motes (sensors) in the low power and lossy network (LLN) cannot be the source.

[0014] To avoid collisions, the receiving mote (sensor) must wait an additional period before it can forward the message. This results in a large end-to-end delay. Furthermore, when the number of interested children is small, link-layer broadcast transmission may not be the most efficient approach in terms of energy. Many uninterested children will receive the multicast message.

[0015] A further example is ESMRF, described in "ESMRF: Enhanced Stateless Multicast RPL Forwarding For IPV6-Based Low-Power And Lossy Networks" by Fadeel et al., published in Proceedings of the 2015 Workshop on IoT Challenges in Mobile and Industrial Systems, 2015. As shown in Figure 3, ESMRF is disadvantageous because multicast packets must traverse all paths to the root, even if the DODAG tree is large and even if the multicast source and its associated group members are close to each other. This reduces communication efficiency. The structure also creates a bottleneck at the DODAG root, especially when the DODAG tree consists of hundreds of nodes. This may also create a single point of failure at the DODAG root.

[0016] All publications identified in this specification are incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. In the event that the definition and use of a term in an incorporated reference is inconsistent with or contrasts with the definition of the term provided herein, the definition of the term provided herein shall apply and the definition of the term in the reference shall not apply.

[0017] Therefore, a need remains for a system and method for multicast communication over low power wireless networks that limits the possibility of duplicate packets while conserving bandwidth and energy. Summary of the Invention

[0018] The subject matter of the present invention provides apparatus, systems and methods by which a low power wireless personal area network (6LoWPAN) using IPv6 address space may be implemented to overcome the above-identified problems that arise when scaling device addressing. To improve communication efficiency, bandwidth and energy usage, the systems and methods described herein utilize multicast forwarding techniques that reduce communication overhead.

[0019] Generally, multicast communication utilizes unicast transmission at layer 3 (L3) or broadcast transmission at link layer (L2). In low power wireless personal area networks, the protocol at link layer (L2) is IEEE802.15.4, and the protocol at network layer (L3) adopts IPv6.

[0020] Although the systems and methods described herein are described in the context of the IEEE 802.15.4 protocol, it is understood that it is contemplated that the systems and methods described herein may be used with later evolved protocols in which relocation of transmissions to subscribers of a multicast group is possible to reduce end-to-end delay.

[0021] The main difference between unicast and broadcast transmission is reliability. In unicast transmission, the sender receives an acknowledgment from the destination when the packet is successfully delivered. However, broadcast communication does not provide this feature. In terms of multicast communication, in case of link-layer unicast transmission, duplicates need to be generated for each of the subscribers and delivered to all the subscribers individually. This consumes both time and energy. On the other hand, in link-layer broadcast transmission, the packet is sent out once to all the subscribers. No duplicates are generated, it is a single transmission. Therefore, compared to link-layer unicast transmission, especially in case of multiple subscribers, link-layer broadcast transmission saves a lot of energy and has much smaller end-to-end delay. However, as mentioned before, broadcast communication has reliability problems.

[0022] The preferred embodiment utilizes a modified BMRF algorithm that provides the ability to choose between link layer unicast and broadcast communications. Time Slotted Channel Hopping (TSCH) is utilized at the Media Access Control (MAC) layer instead of CSMA / CA used by the BMRF to provide a deterministic solution, reduce end-to-end delays, and reduce or eliminate cross-technology interference.

[0023] To improve the reliability of link-layer broadcast transmission, time division multiple access (TDMA) can be used to provide broadcast retransmission. Thus, instead of a single transmission, as is common in link-layer unicast transmission, a packet is retransmitted multiple times. Since there is no acknowledgement in broadcast transmission, a packet is always retransmitted multiple times. However, for energy saving, in the case of a receiver, once a packet is successfully received in broadcast mode, the remaining time slots where broadcast retransmissions may be received are set to sleep mode. Thus, on the receiver side, the mote goes into sleep mode right after receiving the very first packet, and subsequent retransmissions are ignored.

[0024] The subject matter described herein has a variety of applications. In an aircraft environment, for example, on-board sensors can be divided into separate multicast groups. In such an environment, the galleys can form a first multicast group, each seating class can form a separate multicast group, and on-board carts can be formed as separate multicast groups.

[0025] Multicast groups can also be formed based on application, for example oxygen mask release in a passenger service unit can form a separate group.

[0026] Various objects, features, aspects and advantages of the present subject matter will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings, in which like reference numerals represent like components. [Brief description of the drawings]

[0027] [Figure 1] 13 is a flow chart for packet forwarding using bidirectional multicast RPL forwarding. [Diagram 2] 1 is a flowchart for packet forwarding using stateless multicast RPL forwarding. [Diagram 3] 1 is a flow chart for packet forwarding using enhanced stateless multicast RPL forwarding. [Figure 4] 4 is a flow chart of one embodiment of a method for forwarding packets using broadcast transmission. [Diagram 5] 2 is a flow chart of one embodiment of a method for transmission of packets from a source. [Figure 6] 4 is a flow chart of one embodiment of a method for receiving a packet. [Figure 7] FIG. 1 is a diagram showing an example of a conventional broadcast transmission method. [Figure 8] FIG. 1 illustrates an example of an embodiment of a smart broadcast transmission method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Throughout the following description, reference may be made to an access point, router, server, service, interface, portal, platform, or other system formed from a computing device. It is recognized that use of such terms is considered to represent one or more computing devices having one or more processors configured to execute software instructions stored on a computer-readable tangible non-transitory medium. For example, an access point or router may have a processor including one or more cores and a non-transitory computer-readable storage medium, where a program is stored on the medium to perform an action or perform a programmed rule, response, or function.

[0029] The following description provides a number of exemplary embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, the inventive subject matter is considered to include any other remaining combinations of A, B, C, or D, even if not expressly disclosed.

[0030] The following systems, processes and methods are provided for power saving in wireless communication networks, where packet receivers can enter a sleep mode in which they do not receive retransmitted packets to reduce power consumption. The inventive broadcast transmission algorithm overcomes the difficulties faced by traditional broadcast modes and addresses the needs of wireless sensors for low power and lossy networks. It substantially reduces end-to-end delays while reducing energy needs compared to the above unicast modes and previous research efforts.

[0031] 4 illustrates an exemplary process for forwarding a packet. As shown, a node (node ​​and mote are used interchangeably herein to denote devices in a wireless sensor network) receives a packet whose destination is a multicast group. It is also determined whether the packet was received from a preferred parent.

[0032] If a packet is received from a preferred parent, the multicast group is checked to see if it is listed in the routing table. If so, the packet is forwarded downstream using link-layer unicast or broadcast transmission based on the number of children. The mote is then checked to see if it is a member of the multicast group. If the multicast group is not listed in the routing table, the packet is not forwarded and the mote is checked to see if it is a member of the multicast group.

[0033] If the mote is a member of the multicast group, the packet is delivered to the network stack and the packet is accepted, otherwise the packet is dropped.

[0034] If the packet was not received from the preferred parent, then a check is made to see if the packet arrived from below in the RPL tree (i.e., was it received from a link-layer unicast transmission). If so, then a check is made to see if the multicast group is listed in the routing table. If not, the packet is dropped.

[0035] If the multicast group is listed in the routing table, the packet is forwarded downstream using link-layer unicast, except to children (from which the packet was received). Then it is checked whether the mote is the root of the RPL. If so, it is checked whether the mote is a member of the multicast group. If it is not, the packet is forwarded upstream to the preferred parent.

[0036] If the mote is a member of the multicast group, the packet is delivered to the network stack and the packet is accepted, otherwise the packet is dropped.

[0037] In FIG. 5, one embodiment of a smart broadcast transmission method or process is shown. This embodiment is preferably performed on a low-power wireless personal area network using time division multiple access (TDMA). In such an embodiment, it is assumed that one device, which may be, for example, an access point or other device, periodically transmits a beacon frame. The beacon frame provides a timing structure by dividing time into superframes. This allows motes to synchronize with the beacon and know when the transmission and retransmission slots occur. Each superframe preferably includes a transmission (broadcast) slot, such as the one shown in FIG. 8, and a preset number of retransmission slots.

[0038] Time slots in TDMA can be classified according to function. There are time slots that are new time slots especially for sending and receiving broadcast retransmissions. For the sender, these time slots are always used for retransmissions. However, for energy saving, for the receiver, once a packet is successfully received by broadcast transmission, the remaining time slots where broadcast retransmissions can be received are set to sleep mode. Thus, on the receiver side, the mote goes into sleep mode just after receiving its first packet and subsequent retransmissions are ignored. By adding multiple retransmissions for broadcast mode, the probability that the packet will be successfully received at the destination is increased. This combined with the reduced end-to-end delay of broadcast transmission makes it superior to the previous concept above.

[0039] In contemplated systems, processes and methods, received packets are forwarded (transmitted) to one or more recipients, and preferably to multiple motes, using link-layer broadcast transmission.

[0040] The same packet is then forwarded using link-layer broadcast transmission on retransmission time slots to one or more recipients until the total number of transmissions of the packet to the one or more recipients is equal to a preset integer. The number of retransmission slots can be between 1 and 10, more preferably, for example, between 4 and 6. Although the particular number is likely to vary depending on one or more of the number of recipients, the importance of the packet, the network topology, etc. Once the last retransmission slot has been used, the process is complete.

[0041] As shown in Figure 6, each receiver of a packet is configured to wait for a broadcast packet from the sender on a known time slot for transmission and retransmission. If the packet is not received, the receiver checks whether the packet has been received on a retransmission slot. This process continues until either (i) the last retransmission slot for the packet, or (ii) the packet is received, whichever occurs first.

[0042] With a time division into TDMA time slots feature such as that shown in Figure 8, if a packet is received before the last retransmission slot, the receiver sets the subsequent retransmission slots for reception of broadcast retransmissions for that packet to sleep mode. Thus, on the receiver side, the mote goes into sleep mode right after receiving its very first packet, and subsequent retransmissions are ignored. This advantageously reduces energy consumption.

[0043] The inventive concept is further illustrated by comparing FIG. 7 with FIG. In the conventional broadcast method shown in Figure 7, a packet is transmitted to multiple motes in a single time slot. Broadcast transmission typically significantly reduces end-to-end delay and energy consumption, especially where there are a large number of receivers. However, compared to unicast transmission, broadcast transmission generally has low reliability because, unlike in unicast transmission, receivers do not provide acknowledgment when they receive a packet.

[0044] In one test, the inventors found a packet delivery ratio (PDR) of 100% in unicast transmission compared to 8% PDR in broadcast transmission. However, the end-to-end delay in the case of broadcast transmission was about 30% less than the end-to-end delay of unicast transmission. In addition to this, the number of radio transmissions was twice as much as in the unicast transmission example. This indicates an increase in energy consumption.

[0045] The system, method and process enable retransmission of packets in link layer broadcast transmissions to improve the reliability of broadcast transmissions. Because broadcast transmissions do not have an acknowledgement feature, the sender always retransmits packets multiple times to increase reliability. By retransmitting packets, the reliability of broadcast transmissions is significantly improved and has been shown to be comparable to that of unicast mode. In particular, the inventors found a PDR of 99% in broadcast transmissions compared to a PDR of 100% for unicast transmissions.

[0046] Even if the sender always retransmits a packet multiple times regardless of whether the packet is successfully delivered, the number of over-the-air transmissions is still less than the number of unicast transmissions in the case of multiple multicast subscribers. Preferably, the number of transmissions in a broadcast transmission is limited to a fixed value compared to a conventional broadcast transmission. Also, this number remains the same regardless of the number of subscribers.

[0047] As used herein, unless the context dictates otherwise, the term "coupled to" is intended to include both direct coupling (the two elements that are coupled to each other are in contact with each other) and indirect coupling (one or more additional elements are positioned between the two elements). Thus, the terms "coupled to" and "coupled with" are used synonymously.

[0048] In some embodiments, the numbers expressing properties such as amounts of ingredients, concentrations, reaction conditions, and the like, used to describe and claim certain embodiments of the present invention are understood to be modified in some cases by the term "about". Thus, in some embodiments, the numerical parameters set forth in the specification and appended claims are approximations that may vary depending on the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters are interpreted in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the present invention are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as practicable. The numerical values ​​presented in some embodiments of the present invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0049] Unless the context dictates to the contrary, all ranges set forth herein are to be understood to be inclusive of their endpoints, and open-ended ranges are to be understood to include only commercially feasible values. Similarly, all lists of values ​​are to be considered to include intermediate values, unless the context dictates to the contrary.

[0050] As used in the description and throughout the claims that follow, "a," "an," and "the" include plural references unless the context clearly indicates otherwise. Also, as used in the description, "in" includes "in" and "on," unless the context clearly indicates otherwise.

[0051] The recitation of ranges of values ​​herein is merely intended to serve as a shorthand method of individually referring to each separate value falling within the range. Unless otherwise indicated herein, each individual value with a range is incorporated herein as if it were individually set forth herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or made clear by context. Any and all examples provided for specific embodiments herein, or the use of exemplary language (e.g., "etc.") are intended only to better illustrate the invention, and are not intended to limit the scope of the invention as otherwise claimed. No language in this specification should be construed as indicating any non-claimed element necessary to the practice of the invention.

[0052] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limiting. Each group member may be referenced and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group may be included in or deleted from a group for reasons of convenience and / or patentability. When such inclusion or deletion occurs, the specification is deemed to include the modified group and thus fulfills all Markush-style group descriptions used in the appended claims.

[0053] It will be apparent to those skilled in the art that many more modifications beyond those already described are possible without departing from the inventive concepts herein. Accordingly, the inventive subject matter is not to be limited except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms shall be interpreted in the broadest possible manner consistent with the context. In particular, the terms "comprises" and "comprising" shall be construed to refer to elements, components, or steps in a non-exclusive manner, indicating that the referenced element, component, or step may be present, utilized, or combined with other elements, components, or steps not expressly referenced. When a claim of the specification refers to one or more selected from the group consisting of A, B, C.... and N, the sentence shall be construed to require only one element from the group, and not A and N, or B and N, etc.

Claims

1. A program stored on a non-transitory computer readable storage medium, the program, when executed by one or more processors of a router, performs the following operations for multicast communication on an IP network, the role of the router being capable of being assumed by any mote that is part of a network topology, the operations comprising: receiving a packet at a mote; transmitting the packet to one or more recipients using a link-layer broadcast transmission; retransmitting the packet to the one or more receivers using the link-layer broadcast transmission until a total number of transmissions of the packet to the one or more receivers is equal to a preset integer, each of the one or more receivers having a set of time slots during which the packet may be received; and upon receipt of the packet by one of the one or more receivers that received the transmitted packet using the link layer broadcast transmission, scheduling each of the remaining time slots for receiving retransmissions of the packet into a sleep mode for that receiver.

2. The operation includes: determining if the origin of the received packet having a multicast group address of a multicast group is a preferred parent of the mote; If the origin is the preferred parent, the mote checks whether the multicast group address is listed in the mote's routing table; the mote forwarding the packet downstream using link-layer unicast transmission or the link-layer broadcast transmission depending on the number of children only if the multicast group address is listed in the routing table; after determining if the multicast group address is listed in the routing table, the mote checks if the mote is a member of the multicast group; 2. The program of claim 1, further comprising: if the mote determines that it is the member of the multicast group, accepting the packet.

3. The operation includes: If the origin is not the preferred parent, the mote checks if the packet was received from below; if the mote determines that the packet was received from below, the mote determines if the multicast group address is listed in the routing table; if the mote determines that the packet was not received from below, dropping the packet; if the multicast group address is listed in the routing table, the mote forwards the packet downstream using link-layer unicast transmission, but does not forward the packet to any child from which it was received; determining, using the mote, whether the mote is the root of a network topology; If the mote is the root of the network topology, determining if the mote is a member of the packet's multicast group; 3. The method of claim 2, further comprising: if the mote is not the root of the network topology, forwarding the packet upstream to the preferred parent.

4. The operation includes:

4. The program of claim 3, further comprising: accepting the packet if the mote is the member of the multicast group; and dropping the packet if the mote is not the member of the multicast group.

5. 2. The program of claim 1, wherein a greater value of the predetermined threshold number of time slots corresponds to a greater reliability of each of the one or more recipients receiving the packet.

6. The program of claim 1 , wherein the transmission occurs over a low power wireless personal area network.

7. The program of claim 1 , wherein the transmission and reception of the packets utilizes time division multiple access.

8. 1. A system configured for multicast communication over an IP network between motes, comprising: A first mote having a processor with one or more cores and a memory, configured to receive packets and to transmit the packets to one or more recipients using a link-layer broadcast transmission; a first mote further configured to retransmit the packet to the one or more recipients using the link-layer broadcast transmission until a total number of retransmissions of the packet to the one or more recipients is equal to a preset integer; a second mote among the one or more receivers that received the transmitted packet using the link-layer broadcast transmission, the second mote configured upon receipt to receive the packet from the first mote and to schedule any remaining time slots in a sleep mode for receiving retransmissions of the packet.

9. The first moat determining if the origin of the received packet having a multicast group address of a multicast group is a preferred parent of the first mote; If the origin is the preferred parent, the first mote checks whether the multicast group address is listed in the first mote's routing table; the first mote forwarding the packet downstream using link-layer unicast transmission or the link-layer broadcast transmission depending on the number of children only if the multicast group address is listed in the routing table; after determining if the multicast group address is listed in the routing table, the first mote checks if the first mote is a member of the multicast group; 9. The system of claim 8, further configured to: accept the packet if the first mote determines that the first mote is the member of the multicast group.

10. The first moat if the origin is not the preferred parent, checking if the packet was received from below; if the packet is received from below, determining whether the multicast group address is listed in the routing table; dropping the packet if the packet was not received from below; if the multicast group address is listed in the routing table, sending the packet downstream using the link-layer unicast transmission, but not forwarding the packet to the child from which it was received; determining if the mote is a root of a network topology; If the mote is the root of the network topology, determining if the mote is a member of the packet's multicast group; 10. The system of claim 9, further configured to: if the mote is not the root of the network topology, then sending the packet upstream to the preferred parent.

11. The first moat 11. The system of claim 10, further configured to: accept the packet if the mote is the member of the multicast group; and drop the packet if the mote is not the member of the multicast group.

12. The system of claim 8 , wherein the predetermined threshold number of time slots is greater than or equal to four and less than or equal to six.

13. The system of claim 8 , wherein the transmission occurs over a low power wireless personal area network.

14. 10. The system of claim 8, wherein the transmission and reception of packets utilizes time division multiple access.

15. A method for multicast communication over an IP network using a mote, comprising: receiving a packet at a mote; transmitting the packet to one or more recipients using a link-layer broadcast transmission; retransmitting the packet to one or more receivers using the link-layer broadcast transmission until a total number of transmissions of the packet to the one or more receivers is equal to a preset integer, each of the one or more receivers having a set of time slots during which the packet is available to be received; and upon receipt of the packet by one of the one or more receivers that received the transmitted packet using the link-layer broadcast transmission, scheduling each of the remaining time slots for receiving retransmissions of the packet into a sleep mode for that receiver.

16. The method of claim 15 , wherein the predetermined threshold number of time slots is greater than or equal to four and less than or equal to six.

17. 16. The method of claim 15, wherein the transmission occurs over a low power wireless personal area network.

18. The method of claim 15 , wherein the transmission and reception of packets utilizes time division multiple access.

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