Beacon scheduling method in multi-hop ad-hoc networks
A beacon scheduling method in multi-hop ad-hoc communications is provided. This method can prevent overhead in a manner that a base station (BS) transmits beacon slot information to a carrier sense multiple access (CSMA)/collision avoidance (CA) node (CN) and a gateway (GW) through contention-free time division multiple access (TDMA) communications at initial clustering, the CN and the GW performs a sequential clustering to forward the beacon slot information to a cluster head (CH), the CH aggregates joining messages from nodes and assigns non-colliding beacon slots to the nodes, and the GW uses a beacon slot frame of a beacon transmission period (BTP) used by its selected CH in a beacon reply period (BRP) as well. Accordingly, the CH does not need to separately perform the initialization to elect the beacon slot, and the GW also does not require a separate initialization to select the beacon relay slot.
1. A beacon scheduling method in a multi-hop ad-hoc network, comprising:
(a) transmitting an advertisement message to initial nodes (INs);
(b) receiving respective joining messages from each of the INs; and
(c) assigning non-colliding beacon slots based on the respective joining messages,
wherein the advertisement message is transmitted from one of a base station (BS) and a cluster head (CH) to each of the INs,
wherein, before said operation (c), an IN which is assigned one of the beacon slots becomes one of a gateway (GW), a cluster head (CH), and an ordinary node (ON),
wherein, when the CH assigns a frame of a beacon transmission period (BTP) to the GW as a first beacon slot, the GW uses a same frame of a beacon relay period (BRP) as the frame of the BTP, as a second beacon slot.
2. The beacon scheduling method of claim 1 , wherein the respective joining messages comprise information relating to at least one of a node identifier (ID), a status and a beacon slot.
3. The beacon scheduling method of claim 1 , wherein said operation (c) comprises assigning beacon slots of a beacon transmission period (BTP) using contention-free time division multiple access (TDMA) communications.
4. The beacon scheduling method of claim 1 , wherein, when an IN is previously assigned a beacon slot, said operation (b) comprises receiving respective joining messages containing information relating to the previous beacon slot.
5. The beacon scheduling method of claim 4 , wherein said operation (c) comprises selecting a beacon slot which does not collide with the previous beacon slot.
6. The beacon scheduling method of claim 1 , wherein, when a base station (BS) assigns a frame of the BTP to the CH as a beacon slot, the CH assigns one of the GW and the ON another frame of the BTP which does not collide with the frame of the BTP.
7. The beacon scheduling method of claim 1 , wherein a sequential clustering is carried out in a manner that a base station (BS) sends beacon slot information to the GW in a frame of a beacon transmission period (BTP), the GW forwards the beacon slot information to the CH in a frame of a beacon relay period (BRP), and the CH forwards the beacon slot information to another GW in another frame of the BTP.
8. The beacon scheduling method of claim 7 , wherein said another GW forwards the beacon slot information to another CH in another frame of the BRP which is the same as said another frame of the BTP.