Systems And Methods For Allocating Timeslots For Unicast Transmissions
Systems and methods are described for reducing an end-to-end latency occurring in link layer unicast transmissions by shifting the timeslots in the super frame of the TDMA mode based on membership to a multicast group. In this manner, transmission to all of the multicast subscribers occupy adjacent timeslots, which results in an optimization of slot allocation and improvement of the end-to-end latency for multicast communication.
1 . A method for reducing end-to-end latency using link layer unicast transmission in a network, comprising:
providing a router having a processor and memory, wherein the role of the router can be taken up by any mote that is part of the network topology;
dynamically allocating timeslots of a time division multiple access (TDMA) super frame for transmission from a mote A to a set of motes, such that transmission to each of the motes is allocated a distinct timeslot, wherein the set of motes comprises a first mote, a second mote, and a third mote;
wherein the first mote, second mote and third mote are each members of a first multicast group;
wherein mote A is allocated a first timeslot for transmission to the first mote;
the router reallocating a second timeslot for transmission from mote A to the second mote based on a membership of the second mote to the first multicast group, wherein the reallocated second timeslot is shifted such that the second timeslot is adjacent to the first timeslot; and
the router reallocating a third timeslot for transmission from mote A to the third mote based on a membership of the third mote to the first multicast group, wherein the reallocated third timeslot is shifted such that the third timeslot is adjacent to the second timeslot.
2 . The method of claim 1 , wherein the router wirelessly communicates using a TDMA (Time Division Multiple Access) based protocol.
3 . The method of claim 1 , wherein the router dynamically allocates the timeslots and reallocates the second and third timeslots.
4 . The method of claim 1 , wherein the router wirelessly communicates over a low-power wireless personal area network.
5 . The method of claim 1 , further comprising:
the router receiving a packet;
determining whether the packet has a multicast group address that is a preferred parent using the processor;
if the origin is the preferred parent, the router checking whether the multicast group address is listed in a routing table of the router;
if the origin is not the preferred parent, dropping the packet;
only if the multicast group address is listed in the routing table, the router forwarding the packet downward using the link layer unicast transmission as a function of the number of children;
after determining whether the multicast group address is listed in the routing table, the router checking whether the first node is a member of the multicast group; and
if the router determines that the first node is the member of the multicast group, delivering the packet upward.
6 . The method of claim 5 , further comprising:
if the origin is not the preferred parent, the router checking whether the packet was received from below;
if the router determines the packet was received from below, the router determining whether the multicast group address is listed in the routing table;
if the router determines the packet was not received from below, dropping the packet; and
if the multicast group address is listed in the routing table, the router forwarding the packet downward using a link layer unicast transmission, but not forwarding the packet to the child from which the packet was received.
7 . A router, comprising:
a processor; and
a control thread stored on a non-transitory computer readable medium;
wherein the processor and control thread enable a transceiver module at a beginning of a slot of a time division multiple access (TDMA) super frame;
wherein the processor dynamically allocates a timeslot for transmission to each of a set of motes for link layer unicast transmission using a first protocol;
wherein the processor determines whether each of the motes of the set is a member of a first multicast group; and
the router shifting an allocated timeslot for transmission to each of the motes of the set that is a member of the first multicast group, such that each timeslot for transmission to each of the members of the first multicast group is shifted to be adjacent to another of the timeslots.
8 . The router of claim 7 , further comprising:
wherein the processor determines whether each of the motes of the set is a member of a second multicast group; and
the router shifting an allocated timeslot for transmission to each of the motes of the set that is a member of the second multicast group, such that each timeslot for transmission to each of the members of the second multicast group are shifted to be adjacent to another of the timeslots allocated for transmission to members of the second multicast group.
9 . The router of claim 7 , wherein the first protocol comprises an IEEE 802.15.4 protocol.
10 . The router of claim 7 , wherein the processor defines a structure of the super frame based on IEEE 802.15.4 according to a topology of a wireless sensor network comprising the set of motes.
11 . The router of claim 7 , further comprising:
determining whether each of the motes of the set has data to send by timestamping each packet received from a first sensor during the allocated one of the TDMA super frame timeslots.
12 . The router of claim 7 , wherein the router wirelessly communicates over a low-power wireless personal area network.
13 . A program stored in non-transitory computer-readable storage medium, wherein the program executes the following operations for multicast communication over an IP network when the program is executed by one or more processors of a router, the operations comprising:
dynamically allocating timeslots of a time division multiple access (TDMA) super frame for transmission from a first mote to a second mote and from the first mote to a third mote, wherein each transmission is allocated a distinct timeslot;
wherein transmission from the first mote to the second mote is allocated a first timeslot, and wherein the second mote is a member of a first multicast group;
determining if the third mote is a member of the first multicast group;
if the third mote is the member of the first multicast group, reallocating a second timeslot allocated for transmission to the third mote based on a membership of the third mote to the first multicast group, wherein the reallocated second timeslot is shifted such that the second timeslot is adjacent to the first timeslot.
14 . The program of claim 13 , further comprising:
dynamically allocating a third timeslot of the TDMA super frame for transmission from the first mote to a fourth mote;
determining if the fourth mote is a member of the first multicast group;
if the fourth mote is the member of the first multicast group, reallocating the third timeslot based on a membership of the fourth mote to the first multicast group, wherein the reallocated third timeslot is shifted such that the third timeslot is adjacent to the second timeslot.
15 . The program of claim 13 , wherein the motes wirelessly communicate using an Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 protocol.
16 . The program of claim 13 , wherein the motes wirelessly communicate over a low-power wireless personal area network.