WO2013081628A1

WO2013081628A1 - Wireless communication system and its method, and device and program used for same

Info

Publication number: WO2013081628A1
Application number: PCT/US2011/063035
Authority: WO
Inventors: Yumi TANI; Dipankar Raychaudhuri; Shweta JAIN
Original assignee: Nec Corporation; Rutgers, The State University Of New Jersey
Priority date: 2011-12-02
Filing date: 2011-12-02
Publication date: 2013-06-06

Abstract

In a multi-hop communication network system, each route for each source and destination pair is purposely established to share the routing paths which are already used for the other traffic flows in order that the area which suffers from interference is localized. These shared paths are selected based on the interference index of nodes which are the transmitter and receiver over a wireless link, bandwidth availability which shows the traffic occupancy of the wireless bandwidth, and quality requirement of the traffic flow.

Description

WIRELESS COMMUNICATION SYSTEM AND ITS METHOD, AND DEVICE AND

PROGRAM USED FOR SAME

BACKGROUND

1. Field

[01] The present invention relates to a wireless multi hop network control technique and system, and more particularly to a routing scheme technology for a wireless multi hop network, device and system that enable a total network utilization and network capacity of number of flows to be larger than that with conventional routing protocols.

2. Related Art

[02] Wireless multi hop networks have been an attractive network concept such as in tactical networks, sensor networks, M2M, and so on. However, they are still not viable yet, because the communication quality is worse than wired networks in terms of lower bandwidth, longer delay, and larger packet loss ratios. These three parameters are affected by packet errors which are caused by the packet collision and buffer overflows, which easily occur in the wireless network. This is generated by nodes' wireless radio. These collisions and buffer overflow can be considered as "wireless interference." The three types of wireless interference are defined here. They are "access failure collision," "hidden node collision, and "exposed node overflow."

[03] Whether the wireless interferences occur or not depends on the node position of the transmitter and receiver node in terms of wireless coverage. In general, the

transmission range of wireless communication is inside a circle where the transmitter node is in the center as illustrated in Figure 1. The shape of range is not limited to a circle, and it depends on the design of the antenna. In the case where the receiver node is in the

transmission range and there are no bit rates, the wireless packet frame reaches the receiver node. The radius of the range depends on the wireless signal power. For a larger signal power, the range becomes larger, and vice versa.

[04] The frame collisions from two nodes occur under the following conditions. Let us consider two node pairs which are transmitter and receiver nodes of a wireless frame. The collision occurs when one or both receivers are in the overlapped wireless coverage of the two transmitter nodes as seen in Figure 1 , and the two nodes transmit frames simultaneously. In the case where both of the two transmitter nodes are in the overlapped area as shown in the left hand figure in Fig. 3, multiple access (MAC) protocols can be used to avoid them. Access failure collision is defined to be a collision in the case that failure of the MAC protocol of both of the two transmitter nodes and one or both of the receiver nodes in the overlapped transmission range. The example of MAC protocol is CSMA/CA, which is specified in IEEE 802.11 for wireless LAN. Actually, CSMA/CA has the possibility of failures because the multiple nodes send the packet at the randomly selected timing. The possibility of failure increases when the number of transmitter nodes increases.

[05] In the case where both of the two transmitter nodes are out of the range for each other, the collisions occur more often. In general, a transmitter senses the wireless channel when it has a frame to send. If the transmitter detects a signal power, it gives up transmitting the frame because a different node is transmitting a frame. Then the transmitter waits for the end of transition from the other node by sensing the signal power. The power is detected by nodes in the transmission range of the other node, which is transmitting a frame. However, if the two transmitter nodes are out of range each other, each transmitter node is not able to detect the signal of the other transmitter. The hidden node collision occurs when one or both receiver nodes are in the overlapped range of two transmitter nodes and the two transmitter nodes are transmitting a frame simultaneously. [06] To reduce this possibility of the above two collisions, the concept of carrier sense range (CS range) is deployed in the current wireless network systems such as wireless LANs. The CS range is larger than the transmission range, and the range depends on the CS threshold of wireless signal power. At the signal around the CS threshold, it can be detected as channel busy because a different node is transmitting a frame. Consider an example that node 1 is transmitting frames. When the other nodes which are in CS range, but out of the transmission range of node 1, senses the signal between transmission and CS threshold, and the media is considered to be busy. The node position is defined as the "exposed position of node 1." Those exposed nodes cannot transmit any frames when node 1 is transmitting a frame. In other words, the nodes in the exposed position of node 1 are blocked from transmitting and receiving frames. The continuously channel busy causes a buffer overflow at the node in the exposed node position. It is obvious that the buffer overflow results in a burst packet loss.

[07] Each type of interference has different event probabilities. When the two transmitters are in the overlapped wireless range, the collision occurs at less probability as long as MAC protocol works well. However, a more serious case is exposed node position. If the receiver is in the exposed node position, hidden node collision occurs more often. If a transmitter node is in exposed node position, the exposed node overflow also occurs more often. From this observation, node position is an important factor to reduce interference.

[08] In order to reduce the packet loss due to wireless interference, one of the most important techniques to avoid interference is routing mechanism which determines the nodes which are forwarding traffic data packets between a source and destination pair. This means that the routing mechanism enables one to distribute the traffic to nodes in the safe region, such as out of wireless range of the other transmitting nodes, out of exposed node regions, and out of a hidden node region. As a result, one can avoid the effects of interference which are frame collisions and buffer overflows. If one can assign the forwarding nodes in proper positions, the route selection enables network-wide traffic load balance.

[09] The conventional routing protocol in a wireless ad hoc network such as Ad hoc on demand distance vector (AODV) and optimized link state routing (OLSR) attempts to establish the better route which has the minimum cost. In the case that interference is selected as a cost, less interference route is selected from unused routes. Then the next traffic also attempts to select a route which has the lowest interference possible. Thus, when looking at this situation at the node level, traffic is distributed at nodes which are in random positions as a result of routing based on individual nodes' requirements. The problem occurs when traffic is increased, which is a degradation of a network utilization. When the total traffic load becomes close to a network capacity due to an increase in number of flows, each node suffers from interference of other nodes on the different flows. The packet loss caused by

interference corresponds to a reduction of network utilization.

[10] Thereupon, the present invention has been accomplished in consideration of the above-mentioned problems, and an object thereof lays in a point that providing routing protocols which manage the multiple routes to decrease the packet loss due to interference which results in reduction of network capacity.

SUMMARY OF THE INVENTION

[11] Exemplary implementations of the present invention address at least the above problems and/or disadvantages and other disadvantages not described above. Also, the present invention is not required to overcome the disadvantages described above, and an exemplary implementation of the present invention may not overcome any of the problems listed above.

[12] An embodiment of the present invention a wireless communication network system in which routes for multiple pairs of source and destination nodes for sending traffic data packets consist of more than one intermediate node, the multi hop wireless communication network includes a wireless communication function unit that acquires route information associated with an intermediate node, which is an intermediate node in other active routes; and a routing function unit that selects a route which contains intermediate nodes that are also in other active routes; wherein the wireless communication function unit acquires route quality information associated with a route and a required route quality; and wherein the routing function unit selects a route with a highest quality when there are more than route which have a route quality that is higher than the required quality.

[13] Another feature is that the routing function unit selects a route which has a lowest interference when there are no routes which have a route quality that is higher than said required quality.

[14] Another feature is that interference information along the route is associated with a position of the node which consists of a route and the position is based on wireless range of other nodes on an active route.

[15] Another feature is that the quality information of a route is associated with the available bandwidth which remains other than occupied by data packets, hop count, and interference, and the quality information of a route is used to select a route which satisfies the requirement of traffic flow.

[16] Another feature is that a node which selects a route is a source or destination node of traffic flow with regard to advertised information about the quality of the route and the required quality of route from traffic flow.

[17] Another feature is that a node which selects a route is the third party node, which is different from a source or destination node of traffic flow, with regard to advertised information about the quality of a route and the required quality of route from traffic flow. [18] Another feature is that the route information about interference, nodes on an active route, and quality of the route is advertised by using routing protocol of Ad hoc on demand distance vector (AODV).

[19] Another feature is that the route information of quality is advertised by using routing protocol of Optimized Link state routing (OLSR).

[20] Another embodiment of the present invention is a method of selecting a route in wireless communication network system in which routes for multiple pairs of source and destination nodes for sending traffic data packets consist of more than one intermediate node, wherein the method includes: acquiring route information associated with an intermediate node, which is an intermediate node in other active routes; selecting a route which contains intermediate nodes that are also in other active routes; acquiring route quality information associated with a route and a required route quality; and selecting a route with a highest quality when there are more than route which have a route quality that is higher than the required quality.

[21] Another feature of the method is selecting a route which has a lowest interference when there are no routes which have a route quality that is higher than the required quality.

[22] Another feature of the method is that interference information along the route is associated with a position of the node which consists of a route and the position is based on wireless range of other nodes on an active route.

[23] Another feature of the method is that the quality information of a route is associated with the available bandwidth which remains other than occupied by data packets, hop count, and interference, and the quality information of a route is used to select a route which satisfies the requirement of traffic flow. [24] Another feature of the method is that a node which selects a route is a source or destination node of traffic flow with regard to advertised information about the quality of the route and the required quality of route from traffic flow.

[25] Another feature of the method is that a node which selects a route is the third party node, which is different from a source or destination node of traffic flow, with regard to advertised information about the quality of a route and the required quality of route from traffic flow.

[26] Another feature of the method is that the route information about interference, nodes on an active route, and quality of the route is advertised by using routing protocol of Ad hoc on demand distance vector (AODV).

[27] Another feature of the method is that the route information of quality is advertised by using routing protocol of Optimized Link state routing (OLSR).

[28] A reason for a first effect is that the routing scheme uses information of the interference degree at each node in a network from other nodes which currently have traffic to forward, and decides the route which avoids the interference from the nodes on the other routes.

[29] A second effect of the present invention lies in a point that the fairness among flows and routes can be reduced.

[30] A reason for a second effect is that routing scheme uses information of traffic requirement of each flow and bandwidth availability for each route, and decides the route which satisfies the traffic requirement.

BRIEF DESCRIPTION OF THE DRAWINGS

[31] Fig. 1 is a view illustrating a wireless multi hop network system configuration in embodiments of the present invention. [32] Fig. 2 is a view illustrating a configuration of a wireless node device in the first embodiment of the present invention.

[33] Fig. 3 is a view illustrating a classification of wireless interference in these embodiments of the present invention.

[34] Fig. 4 is a flowchart illustrating an operation of selecting algorithm of the routes in the first embodiment of the present invention.

[35] Fig. 5 is a view illustrating expected routes in the first embodiment of the present invention.

[36] Fig. 6 is a view illustrating a configuration of a wireless node device in the second embodiment of the present invention.

[37] Fig. 7 is a view illustrating threshold definitions of signal power in Tx and CS ranges in the present invention.

[38] Fig. 8 is a view illustrating a configuration of wireless node device of the third embodiment of the present invention.

[39] Fig. 9 contains tables showing each node pair of source and destination at a node device. The entry in a table show the candidate of route and the interference index, bandwidth availability, traffic node, and hop count.

[40] Fig. 10 is a table of a list of the counts of node for each position, tx and exposed position in the first embodiment of the present invention.

[41] Fig. 11 is a table of the candidate of routes and their interference index, bandwidth availability and number of traffic node, and hop count along the route in the first embodiment of the present invention.

[42] Fig. 12 is a table showing an example of a routing table. DETAILED DESCRIPTION

[43] The following detailed description is provided to assist the reader in gaining a comprehensive understanding of the methods, apparatuses and/or systems described herein. Various changes, modifications, and equivalents of the systems, apparatuses and/or methods described herein will suggest themselves to those of ordinary skill in the art. Descriptions of well-known functions and structures are omitted to enhance clarity and conciseness.

[44] First Embodiment. A first embodiment of the present invention will be explained in details by making a reference to the accompanied drawings. This embodiment is the present prevention combined with the routing protocol, AODV. Any routing protocols can be applied for this operation. In this embodiment, AODV as one of reactive routings in wireless multi-hop network is introduced, but any other reactive routings such as dynamic source routing (DSR) can be used.

[45] Fig. 1 is a view illustrating one example of a configuration of the wireless network control system in the embodiment of the present invention. Referring to Fig. 1 , the wireless network control system in the embodiment includes a wireless node device 101 that can communicate with other nodes in the same network which are out of the transmission range of a wireless node device 101 and requires one or more than one nodes which forwards packets from and to a wireless node device 101. When node 101 has a frame to transmit a wireless frame, the range where the wireless frame is reachable is shown as transmission range (Tx range). The range where the transmitted wireless makes wireless channel busy is shown as carrier sense range (CS range). The nodes in CS range detect the signal which is larger power than carrier sense threshold (CS threshold), and the signal is notified that a wireless frames is being transmitted from the other node as illustrated in Fig. 7. Node 102 and 103 are in the range of Tx range. Nodes inside the Tx range are defined to be "Tx nodes" of node 101. Whereas, nodes in CS range but out of the Tx range such as 103 to are defined to be "exposed nodes" of node 101.

[46] Fig. 2 is a view illustrating a configuration of the wireless node devices

101-135 relating to the present invention. The node devices 101-135 include a wireless communication function unit S101 which deals with all the wireless frames to be transmitted and received. Further, the wireless network node devices 101-135 includes a routing function unit (S102) and an application function unit S103, too. Application function unit S103 in the present invention, which becomes an interface between a communication network and an end user of the device or application software, is a function unit for inputting/outputting a reception/transmission packet, and signifies, for example, a web application and a voice application. Routing function unit SI 02 in the present invention, which plays a role in advertised its own link conditions by sending routing messages and decision of the route for each source and destination pair. The route is constructed by making a routing table at each node in which each entry contains a destination of the route and the next hop node to forwarding packets to. Consider an example where node 101 receives a packet from node 103 and the destination of the packet is node 109. The route to node 109 is assumed to be already established. Node 109 checks its own routing table shown in Figure 12, and finds the next hop node in the entry of the destination node 109 which is written in a header of a received packet. Node 101 notices the next hop for node 109 is node 102. Then, the node forwards the received packet to node 102. The routing protocol specifies the procedures to advertise the link condition, discover the routes, select the best route, and recover from route failures.

[47] Three modules are added in a conventional routing function unit SI 02 and in a wireless communication function unit S101. The first is a function unit of interference calculation SI 04 in wireless communication unit S101. This function unit calculates the interference index and reports the index to information storage unit SI 05 in routing function unit SI 02. The interference index calculation module SI 04 sniffs wireless frames, knows if the node itself is a tx or CS node of other nodes, or outside. Then the function unit SI 04 counts the number of those nodes. In this instance, consider an example of the table in Figure 10 for node 101, which is used to count the numbers of exposed and tx nodes at node 101 in Figure 1. This table is constructed by sniffing data or ACK frames. A new entry is inserted when the node sniffs a frame from the new transmitter node. Node 101 receives frames from node 109, 102, and 104 which are on the path of route 1 and are sending data frames. A sniffed frame is a frame of which the receiver of the frame is not node 101. In this case, node 101 receives a data frame from node 102, a new entry with tx node bit set is inserted. At this entry, tx node is set because the data frame receiving at node 101 means that the node 101 is a tx node of node 102. Then, the flag which shows if the entry is effective is also set. The updated time of the entry is written in time. When an ACK control frame from node 109 reaches to node 101, a new entry for 109 is inserted and a CS node bit is set. CS range bit shows the node is in the CS range of the entry node. The transmission power of control frames such as ACK and management frames such as a beacon are higher than data frame in order to reach at receiver more correctly. And the transmission range tends to be the same with CS range. Hence, the ACK. The current time is written in the field of time. But the flag is not set yet, because node 101 is waiting for sniffing a data frame from node 109. Node 101 needs to judge if node 101 is a tx node or exposed node of node 109. After waiting for 0.5 seconds, node 101 judges that. If the node receives some data frames, the tx node field is set and flag is also set for the entry to be valid. But in this case traffic data frames from node 109 cannot reach to node 101. Hence, node 101 never receives a data frame from 109, and the flag is set for the entry to be valid. This entry shows the node 101 is an exposed node of node 109. The third entry for node 104 shows the node 101 is waiting for data frames from 104 and node 101 hasn't judged if node 101 is an exposed node or a tx node of node 104. Hence, the flag field is not set and this means this entry is invalid. The network and traffic condition are not constant, thus the status of the flag also varies. Therefore, the time field is confirmed for each entry.

[48] Based on the table in Figure 10, the number of nodes which makes the node tx and exposed node of is counted, respectively. The counted results are used to calculate interference index I. The interference index I, which is a degree of interference, is as follows:

[49] I = a Nexposed+ P N_te

[50] Here, N_eXposed is the number of around nodes which counting node is exposed of. Ntx is the number of nodes which counting node is tx node of. In case of Table 1, N_eXposed is 1 , and Ntx is also 1. When Ntx is larger, the possibility of access failure collision becomes higher. Similarly, For larger number of N_ex_Posed , the possibility of hidden node collision and exposed buffer overflow becomes higher, a and β are weight parameters for each count, which can be the ratio of degree of interference of access failure collisions to exposed buffer overflow and hidden node collision They could be constant or time-varying. In general, an effect of exposed buffer overflow and hidden node collision is more serious than an access failure collision, because MAC protocol is designed to avoid the collisions of packets from two nodes in overlapped Tx range of each other. An example of a setting of a and β is 0.8 and 0.2, respectively. The point here is for nodes to be able to estimate an interference degree based on actual traffic flows.

[51 ] One more new unit is information storage unit S 105 in routing function unit

SI 02, which stores information related to interference index, traffic node, and bandwidth availability. The storage unit is divided to two regions, route information and node status information. The table in Figure 11 shows an example of route information stored in information storage unit SI 05. This is a table for a destination node. Route information is stored when the node is the destination node and receives request (RREQ) messages in order to judge a better route. Interference index can be the average or/and total value of nodes on the path. The bandwidth availability is the remaining bandwidth which can be available to a new route besides occupation by existing traffic flows. The available bandwidth is advertised from each node along the route on the header of RREQ. The value which a destination gets is a minimum value of available bandwidth which can be a bottleneck link. If this value is over a traffic load for new flow, the route is not selected. In a field of traffic node, the number of traffic nodes on the active route is recorded. An Active route denotes the route which is used for a traffic flow. This number corresponds to a number of links which can be shared with existing routes. The route with larger number of traffic nodes can share the longer path with other routes. The field of hop count is the number of hops from source node of the route. This field can be copied from header filed of RREQ. Each node which forwards RREQs increments this counts by 1. The count which the destination node gets is the hop length from source and destination node. This field is the performance which denotes the quality of the route. In many cases, the hop count is used to measure the route performance. However, the hop counts can be replaced with arbitrary parameters. For example, packet delay of the route between source and destination is also used in many cases. The mixture of various costs which are power consumption, node failure probability, and interference index is also applicable such as in a sensor network. Thus, hop counts here denote the route quality parameter if the route is established in order to maximize only the flow quality, such as throughput, delays, and delivery ratio.

[52] In the node status information area in information storage unit SI 05, the own node status of interference index, bandwidth availability, and traffic node is stored. The information is used when the node receives and forwards request message (RREQ) as an intermediate node in order to advertise the information along a route. [53] Next, the entirety of the operation by each wireless node device in the case where a wireless node 110 receives a traffic data frame from an application based on Fig. 5 will be explained. The explanation begins with a case of a traffic flow which starts first as shown in Fig. 5. For the first flow, flowl, the source and destination is marked as node SI and Dl in Fig. 5. For the first traffic flow, a route is established with a conventional routing protocol, AODV. As a precondition, the established route, route 1, is the path node S 1-118- 119-120-D1. This route is chosen because of the minimum hop count. Then the second flow, flow2, starts at another source S2 to a destination D2. The ideal route for flow2, route2, is S2-116- Sl-118-119-120-D1-112-D2. When route 2 is compared with route 1, it can be seen that the two routes share the path partially, Sl-118-119-120-D 1. A route 2 with common path is intentionally selected.

[54] The sharing path enables two routes to avoid interfering with each other.

Sharing path denotes that the nodes which are forwarding traffic data packets are localized in limited area. The limitation helps the nodes avoid the area where the nodes are affected by wireless interference. The interference is major causes of packet loss as mentioned above. Hence, the shared path enables the wireless networks to increase in network capacity which means the increased bandwidth utilization even if the number of flows is increased.

[55] EXAMPLE 1

[56] Next, the explanation of a detailed operation for the route establishment based on path and traffic flow information will be discussed by referring to Figure 5. The explanation begins with a route established for flow2. The routel for flow 1 is assumed to be already established.

[57] As in the conventional AODV protocol, S2, a source node, floods route request (R EQ) messages to every node in the network. In addition to conventional header field of RREQ in AODV, the information of interference with other flows, available information, and traffic node is added. A source node of traffic flows sets those new fields to be blank when the source node floods the message. Nodes which received R EQ update the header information of RREQ with their own node information before forwarding it. The nodes add their own interference index value to the value in the received header field and updates it. The interference index is available from function unit of interference calculation (SI 04). Regarding bandwidth availability, the forwarding nodes obtain the value from wireless communication function unit (SI 01) and compare their own values with the received values. If its own value is less than the received value, it updates it with its own availability. A lower bandwidth availability denotes that the bandwidth availability in RREQ advertises the minimum bandwidth availability on the route in order to avoid a route with bottleneck link which has no room in the bandwidth. For the number of traffic nodes, the number is incremented by 1 when the node is an intermediate node of other routes. The number of traffic nodes corresponds to the length of the sharing path. A larger number of traffic nodes means that it is a better route to be shared with others.

[58] The destination nodes of traffic flow receive more than one RREQ message with information along the routes. An algorithm to select the best route by using advertised information is shown in the flowchart in figure 4. The routing function unit (SI 02) in a destination node after receiving multiple request messages from the same source node of a traffic flow has the table which lists routes for source node S2 as shown in the table in Figure 11. The table is stored in information storage unit (SI 05). Each entry denotes path information for each route which is obtained from request messages (RREQs). The next hop, interference index, bandwidth availability, and traffic node field are defined as a next hop on the route to the source node S2, the summation of interference index along the path, a number of nodes which are forwarding traffic data packets, respectively. The number of traffic nodes corresponds to the length of the path which is actually shared by multiple flows. [59] An algorithm to select a route from the list in Figure 11 is shown is detailed here with the flowchart in figure 4. In the table in figure 11 four routes are listed as shown in Fig. 5. The selection is performed at a function unit of shared node decision (SI 06), which can be a microprocessor or computer or other computing device. Each value in a circle in Figure 5 is interference index at each node. The main scheme is to filter the listed routes in order to remove routes which don't meet the requirements for sharing paths with other routes (F 101-103). In the case where there are no shared path route to match the condition, such as due to no room in bandwidth and too long of a route, a new shared path route with the lowest interference is selected for the traffic flows which starts later.

[60] First of all, to find the best shared path, bandwidth availability is compared to a required bandwidth c₂ for traffic flow, flow2 (F 101) in order to avoid the total traffic at the shared path over the capacity. In this case, all routes match this condition. In the next step, the portion of number of traffic nodes related to the total number of nodes on the path is checked (F102). A large portion is better, because that the traffic load can be localized at a shared node, and the region which suffers from interference can be limited. In this example, the threshold portion is 0.5. However, only the first route in the table in figure 11 meets this condition. The other routes aren't candidates shared path routes. The portion can be changed due to required route quality and status of network. Then the average of interference index for every node on the path is compared with a threshold F_thresh (F103). The first route satisfies this condition, too. After these three checks, one route is selected as the shared path route. If there is more than one shared path route (F104), the route with the highest quality (F105), such as the lowest hop count, and the lowest interference index is selected. In this example, only one route passes the criteria, and the first route is automatically selected as a shared path. If there are no routes which satisfies those three conditions, the route which has the lowest interference is selected as the new shared path route (F107 and 108). In this example, the third route would be selected as the new route, because the interference index is the lowest, zero.

[61] Second Embodiment. A second embodiment will be explained.

[62] The second embodiment differs from the first embodiment in that another calculation method to detect interference index is used. The method measures the busy time in wireless media, which means that the signal power level reflects the node position based on the wireless range of adjacent nodes. The different operations from a first embodiment will be mainly described.

[63] Fig. 6 is a view illustrating a configuration of the wireless node devices

101-135 relating to the present invention. A difference from the first embodiment is that the function unit of interference calculation SI 04 is replaced with a function unit of signal power and bandwidth utilization detecton S201. The function unit of signal power and bandwidth utilization detection S201 tracks the business of the wireless media for two levels of signal power, which are above the tx threshold and between cs and tx threshold. As shown in Figure 7, they are called Tx power and exposed power, respectively. The power which is lower than cx threshold is not detected, and is recognized as the wireless media being idle. The power detection enables each node to estimate the degree of interference based on the position of the wireless range of other nodes. The interference index is calculated as follows:

[64] I = Pexposed + βρΐχ

[65] Pexposed t_exposed / T

[66] _Ptx = ttx / T

[67] Here, T is the time period to measure the wireless media. t_tx and t_ex_Posed are the measured time of the exposed power and tx power. Therefore, ptx and p_ex_Posed are the ratio of tx and exposed power signal during T. a and β are weight parameters for each power level. p_tx show the degree of the collision as the result of CSMA/CA failures. On the other hand, Pexposed shows the degree the collision due to a hidden node, and overflow due to an exposed node. The interference index is advertised in the header of RREQ and the operations after this are as same with the first embodiment.

[68] Third Embodiment. A third embodiment will be explained. This embodiment is based on different routing protocol, OLSR. OLSR is the representative one of link state routing protocols in wireless networks. However, the other proactive routings such as DSDV and TORA can be applied to this. This is also the embodiment in the case where information about all of the nodes and links can be obtained. The different operations and configurations from a first embodiment are described here. The network system and a configuration of the wireless node devices are same with other embodiments. The operations of collecting information about interference, traffic flow, and existing traffic, shared node path is also the same as in the first and second embodiments. The difference from other embodiments is an operation to advertise the information about interference, traffic, and available bandwidth. In conventional OLSR, every node in the network advertises its own connectivity information by flooding TC (Topology Control) messages to every node in overall the network.

Additionally, a third embodiment puts information about interference, traffic, and, available bandwidth in TC messages.

[69] As shown in Figure 8, the wireless node device has a function unit of connected reroute calculation S301, which is a unit for conventional OLSR. In conventional OLSR, the unit finds the shortest path route for each source and destination pair by calculation from connectivity information of each node. The different operation is to find more than one routes for each arbitrary source and destination pair, and to construct a table for each source and destination pair as shown Figure 9. In that table, interference index, bandwidth availability, number of traffic nodes, and hop counts are described. These tables compare the routes with each other and select the best route. For node 1 and 2 pair, the route is selected by using a flow chart as described in Fig. 7. If the node itself is one of the nodes on the path, the routing table is updated. In OLSR, each node forwards packets by referring to this routing table. The table in figure 12 is an example of the routing table. For a different pair, node 3 and 4, another table tl02 is constructed. In this case, the route in the second entry is selected, and the node itself is not one of the nodes on the path. Then, the routing table is not updated.

[70] In this embodiment, all nodes perform the same calculations based on the same information. Instead of calculation at each node, a server node can perform these calculations by correcting the same information from each node in the network.

[71] The foregoing exemplary embodiments are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. Also, the description of the exemplary embodiments of the present invention is intended to be illustrative, and not to limit the scope of the claims, and many alternatives, modifications, and variations will be apparent to those skilled in the art.

Claims

LISTING OF CLAIMS What is claimed is:

1. A wireless communication network system in which routes for multiple pairs of source and destination nodes for sending traffic data packets consist of more than one intermediate node, said multi hop wireless communication network comprising:

a wireless communication function unit that acquires route information associated with an intermediate node, which is an intermediate node in other active routes; and

a routing function unit that selects a route which contains intermediate nodes that are also in other active routes;

wherein said wireless communication function unit acquires route quality information associated with a route and a required route quality; and

wherein said routing function unit selects a route with a highest quality when there are more than route which have a route quality that is higher than said required quality.

2. The wireless communication network system according to claim 1, wherein said routing function unit selects a route which has a lowest interference when there are no routes which have a route quality that is higher than said required quality.

3. The wireless communication system according to claim 2, wherein said interference information along the route is associated with a position of the node which consists of a route and the position is based on wireless range of other nodes on an active route.

4. The wireless communication system according to claim 1, wherein said quality information of a route is associated with the available bandwidth which remains other than occupied by data packets, hop count, and interference, and

said quality information of a route is used to select a route which satisfies the requirement of traffic flow.

5. The wireless communication system according to claim 2, wherein said quality information of a route is associated with the available bandwidth which remains other than occupied by data packets, hop count, and interference, and

6. The wireless communication network system according to claim 1, wherein a node which selects a route is a source or destination node of traffic flow with regard to advertised information about the quality of the route and said required quality of route from traffic flow.

7. The wireless communication network system according to claim 2, wherein a node which selects a route is a source or destination node of traffic flow with regard to advertised information about the quality of the route and said required quality of route from traffic flow.

8. The wireless network communication system according to claim 1, wherein a node which selects a route is the third party node, which is different from a source or destination node of traffic flow, with regard to advertised information about the quality of a route and said required quality of route from traffic flow.

9. The wireless network communication system according to claim 2, wherein ί node which selects a route is the third party node, which is different from a source or destination node of traffic flow, with regard to advertised information about the quality of a route and said required quality of route from traffic flow.

10. The wireless network communication system according to claim 1, wherein said route information about interference, nodes on an active route, and quality of the route advertised by using routing protocol of Ad hoc on demand distance vector (AODV).

11. The wireless network communication system according to claim 2, wherein said route information about interference, nodes on an active route, and quality of the route advertised by using routing protocol of Ad hoc on demand distance vector (AODV).

12. The wireless network communication system according to claim 1, wherein said route information of quality is advertised by using routing protocol of Optimized Link state routing (OLSR).

13. The wireless network communication system according to claim 2, wherein said route information of quality is advertised by using routing protocol of Optimized Link state routing (OLSR).

14. A method of selecting a route in wireless communication network system in which routes for multiple pairs of source and destination nodes for sending traffic data packets consist of more than one intermediate node, said method comprising:

acquiring route information associated with an intermediate node, which is an intermediate node in other active routes;

selecting a route which contains intermediate nodes that are also in other active routes;

acquiring route quality information associated with a route and a required route quality; and

selecting a route with a highest quality when there are more than route which have a route quality that is higher than said required quality.

15. The method according to claim 14, further comprising selecting a route which has a lowest interference when there are no routes which have a route quality that is higher than said required quality.

16. The method according to claim 15, wherein said interference information along the route is associated with a position of the node which consists of a route and the position is based on wireless range of other nodes on an active route.

17. The method according to claim 14, wherein said quality information of a route is associated with the available bandwidth which remains other than occupied by data packets, hop count, and interference, and

18. The method according to claim 15, wherein said quality information of a route is associated with the available bandwidth which remains other than occupied by data packets, hop count, and interference, and

19. The method according to claim 14, wherein a node which selects a route is a source or destination node of traffic flow with regard to advertised information about the quality of the route and said required quality of route from traffic flow.

20. The method according to claim 15, wherein a node which selects a route is a source or destination node of traffic flow with regard to advertised information about the quality of the route and said required quality of route from traffic flow.

21. The method according to claim 14, wherein a node which selects a route is the third party node, which is different from a source or destination node of traffic flow, with regard to advertised information about the quality of a route and said required quality of route from traffic flow.

22. The method according to claim 15, wherein a node which selects a route is the third party node, which is different from a source or destination node of traffic flow, with regard to advertised information about the quality of a route and said required quality of route from traffic flow.

23. The method according to claim 14, wherein said route information about interference, nodes on an active route, and quality of the route is advertised by using routing protocol of Ad hoc on demand distance vector (AODV).

24. The method according to claim 15, wherein said route information about interference, nodes on an active route, and quality of the route is advertised by using routing protocol of Ad hoc on demand distance vector (AODV).

25. The method according to claim 14, wherein said route information of quality is advertised by using routing protocol of Optimized Link state routing (OLSR).

26. The method according to claim 15, wherein said route information of quality is advertised by using routing protocol of Optimized Link state routing (OLSR).