Dynamic TDMA slot assignment in ad hoc networks

AINA 2003Akimitsu KANZAKI, Toshiaki UEMUKAI, Takahiro HARA, Shojiro NISHIO

Outline

Related work Proposed protocol Simulation Conclusion Future work

Related work - USAP

USAP: a unifying dynamic distributed multichannel TDMA slot assignment protocol [96 MILCOM]

Related work - USAP

Related work - USAP The first slot in each frame is reserved to tra

nsmit control packet (NMOP) NMOP

STi(s) : node i transmits a data packet to its neighbors in slot s

SRi(s) : i receives a data packet from one of its neighbors in sl

ot s NTi(s) :

nod ei has neighbors which transmit data packets to their neighbors in slot s

Related work - USAP

When a new node joins the network, it firstly collects NMOPs by listening the network channel for a cycle

All nodes in the network, N and M should be large enough As a result, the channel utilization usually

becomes low

Related work - USAP multiple access

USAP multiple access: dynamic resource allocation for mobile multihop multichannel wireless networking

[99 MILCOM]

Related work - USAP multiple access

Related work - USAP multiple access

The frame length is a power of 2. The channel utilization is still low.

Proposed protocol – frame format

The frame length in our protocol is set as a power of 2.

The first slot in the frame is reserved for new nodes to transmit control packets.

Data packet Frame length

Proposed protocol – Slot assignment

Requesting the information on slot assignment in the contention area Listen the channel for a certain period Send REQ packet in the first slot next frame Neighbors send its and its neighbor slot

information in its assigned slot by INF packet

Frame length Slot information

Proposed protocol – Slot assignment

Setting the frame length and grasping slot assignment The new node adopts the maximum frame

length among all nodes in the contention area

Proposed protocol – Slot assignment

Selecting an assigned slot Getting an unassigned slot (GU)

Proposed protocol – Slot assignment

Selecting an assigned slot Releasing multiple assigned slots (RMA)

Proposed protocol – Slot assignment

Selecting an assigned slot Doubling the frame (DF)

Proposed protocol – Slot assignment

Announcement and Confirmation After selecting a slot assigned to itself, the

new node sends a SUG to its neighbors which contains information on the frame length and the assigned slot.

When a neighbor receives this packet, it updates its slot assignment information.

If the frame length of the neighbor is different from that in SUG, its frame length is changed in the same way in there

Neighbors send REP to confirm

Proposed protocol – Conflict and solution

Proposed protocol – Conflict and solution

Proposed protocol – Conflict and solution

Proposed protocol – Conflict and solution

Simulation - environment

Do not move New node appears at a random

position No new node appears until slot

assignment 2 node to 50 node

Simulation - result

Simulation - result

Simulation - result

Conclusion

Proposed a TDMA slot assignment protocol to improve the channel utilization.

Avoids the increase of unassigned slots by minimizing the frame length of each node.

Future work

Our protocol can enlarge the frame length, but cannot minify it.