COMMUNICATION SYSTEM, A SLAVE NODE, A ROUTE MAKING METHOD AND A PROGRAM

• US 20120320781A1
• Filed: 02/23/2011
• Published: 12/20/2012
• Est. Priority Date: 02/23/2010
• Status: Active Grant

• Current Assignee: Kyushu University
• Original Assignee: Kyushu University
• Inventors: Furukawa, Hiroshi, Jin, Guangri
• Granted Patent: US 8,693,366 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• CPC Class Codes: H04W 40/08 based on transmission power
• CPC Class Codes: H04W 40/14 based on stability
• CPC Class Codes: H04W 40/24 Connectivity information management, e.g. connectivity discovery or connectivity update
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Provided are a communication system and the like capable of making a stable relay route even when a propagation channel is fluctuated by the fluctuation of RSSI. For making a tree-type communication route whose root is a core node, each slave node, after the reception of the latest reset routing packet from a node, judges if the transmission source node should be the parent of the tree-type structure based on the sequential average of the reception power of n routing packets received from the same transmission source node. As the reception power is log-normally distributed in general, an asymptotically stable relay route can be obtained, especially by using the sequential average.

Claims

1. A communication system, comprising:

a core node that connects to a backbone network; and

a plurality of slave nodes that connect to the core node with wireless communication directly or via another slave node,

wherein the core node transmits, to one of the slave nodes, a reset routing packet for instructing the slave node to initialize a communication route from the core node to the slave node itself, and afterwards, a plurality of normal routing packets for instructing the slave node to construct a communication route from the core node to the slave node itself;

the slave node includes;

an own route evaluation value storing unit that stores an own route evaluation value which is an evaluation value of a communication route from the core node to the slave node itself;

an uplink forwarding target storing unit that stores an uplink forwarding target information which shows an uplink forwarding target node which is a first node on a communication route from the slave node itself to the core node; and

a route making processing unit that decides a communication route from the core node to the slave node itself, when receiving the reset routing packet and n (n is a counting number) of the normal routing packets from a single transmission source node, after judging whether to replace the uplink forwarding target node by the transmission source node;

the route making processing unit includes;

a reception power evaluation value calculating unit that calculates a reception power evaluation value which is an evaluation value of reception power between the slave node itself and the transmission source node, based on reception power of an n-th normal routing packet received;

a new accumulated route evaluation value calculating unit that calculates a new accumulated route evaluation value which is an evaluation value of a communication route that the n-th normal routing packet received has gone through, based on an evaluation value of a relay route from the core node to the transmission source node and on the reception power evaluation value; and

a route making processing unit that, if the new accumulated route evaluation value is smaller than the own route evaluation value, makes the uplink forwarding target storing unit store a transmission source node of the normal routing packet as a new uplink forwarding target node, and makes the own route evaluation value storing unit store the accumulated route evaluation value as a new own route evaluation value for a route making processing; and

the reception power evaluation unit, if n equals to or is larger than two, calculates a reception power evaluation value which is an evaluation value of a reception power between the slave node itself and the transmission source node, based not only on a reception power of the n-th normal routing packet received but also on a part of or all of reception power of the reset routing packet and/or the normal routing packet separately received.

2. The communication system of claim 1,

wherein the reception power evaluation value calculating unit calculates a reception power evaluation value A_n which is an evaluation value of a reception power R_n of the n-th normal routing packet received, setting a default value a constant or a reception power of the reset routing packet, based on an equation (eq1) with α

_n and β

_n (α

_n and β

_n are functions of n, α

_n is not identically

     0), and

[Equation 1]

A_nα

_n×

A_n-1+β

_n×

R_n. 

 

(eq1)

3. The communication system of claim 2,

wherein in the equation (eq1),

A₁=R₁;

and

if n equals to or is larger than two, α

_n=(n−

1)/n and β

_n=1/n.

4. The communication system of claim 2,

wherein in the equation (eq1), α

_n and/or β

_n is a constant.

5. A slave node that connects to a core node with wireless communication directly or via another slave node, comprising:

an own route evaluation value storing unit that stores an own route evaluation value which is an evaluation value of a communication route from the core node to the slave node itself;

an uplink forwarding target storing unit that stores an uplink forwarding target information which shows an uplink forwarding target node which is a first node on a communication route from the slave node itself to the core node; and

a route making processing unit that decides a communication route from the core node to the slave node itself, when receiving a reset routing packet for instructing the slave node to initialize a communication route from the core node to the slave node itself, from the core node, and n (n is a counting number) of normal routing packets for instructing the slave node to construct a communication route from the core node to the slave node itself, from a single transmission source node, after judging whether to replace the uplink forwarding target node by the transmission source node,

wherein the route making processing unit includes;

a reception power evaluation value calculating unit that calculates a reception power evaluation value A_n which is an evaluation value of a reception power R_n of an n-th normal routing packet received, by calculating a sequential average of a reception power of the reset routing packet and n of received normal routing packets or by calculating a sequential average of received normal routing packets;

a new accumulated route evaluation value calculating unit that calculates a new accumulated route evaluation value which is an evaluation value of a communication route that the n-th normal routing packet received has gone through, based on an evaluation value of a relay route from the core node to the transmission source node and on the reception power evaluation value; and

a route making processing unit that, if the new accumulated route evaluation value is smaller than the own route evaluation value, makes the uplink forwarding target storing unit store a transmission source node of the normal routing packet as a new uplink forwarding target node, and makes the own route evaluation value storing unit store the accumulated route evaluation value as a new own route evaluation value for a route making processing.

7. A program capable of causing a computer to function as a slave node of claim 5.

6. A route making method for a communication system including a core node that connects to a backbone network and a plurality of slave nodes that connect to the core node with wireless communication directly or via another slave node,

wherein each of the slave nodes includes:

an own route evaluation value storing unit that stores an own route evaluation value which is an evaluation value of a communication route from the core node to the slave node itself;

an uplink forwarding target storing unit that stores an uplink forwarding target information which shows an uplink forwarding target node which is a first node on a communication route from the slave node itself to the core node; and

a neighbor node storing unit that stores a combination of a node which is capable of transmit or receive a packet with the slave node itself and a reception power evaluation value which is an evaluation value of a reception power of packet transmission with the node;

the method comprising;

initializing including transmitting, by the core node, a reset routing packet for instructing the slave node to initialize a communication route from the core node to the slave node itself, and, by an initialization unit of the slave node which received the reset routing packet, judging whether the slave node has received the reset routing packet for the first time, and if received for the first time, transmitting the same reset routing packet to nodes stored in the neighbor node storing unit, deleting information stored in the neighbor node storing unit, and setting the own route evaluation value a maximum value; and

route making including;

transmitting, by the core node, a plurality of normal routing packets for instructing the slave node to construct a communication route from the core node to the slave node itself with their transmission order specified;

and by a reception power evaluation value calculating unit in the slave node which received the normal routing packet,

if a transmission source node of the received normal routing packet is not stored in the neighbor node storing unit, calculating a reception power evaluation value which is an evaluation value of a reception power between the slave node itself and the transmission source node based on a reception power of the normal routing packet and making the neighbor node storing unit store a combination of the transmission source node and the reception power evaluation value;

if a transmission source node of the received normal routing packet is stored in the neighbor node storing unit, calculating a new reception power evaluation value not only based on a reception power of the normal routing packet but also on the reception power evaluation value stored in the neighbor node storing unit, and making the neighbor node storing unit store a combination of the transmission source node and a new reception power evaluation value;

judging, by a new round processing unit, whether the received normal routing packet is the normal routing packet received for the first time or not based on the transmission order, and setting the new own route evaluation value a maximum value if received for the first time;

calculating, by a new accumulated route evaluation value calculating unit, a new accumulated route evaluation value which is an evaluation value of a communication route that the normal routing packet has gone through, based on an evaluation value of a relay route from the core node to the transmission source node and on the reception power evaluation value; and

if the new accumulated route evaluation value is smaller than the own route evaluation value, making, by a route making processing unit, the uplink forwarding target storing unit store a transmission source node of the normal routing packet as a new uplink forwarding target node, making the own route evaluation value storing unit store the accumulated route evaluation value as a new own route evaluation value for a route making processing, and deciding a communication route from the core node to the slave node itself by transmitting a new own route evaluation value to a node stored in the neighbor node storing unit.