CN101951658A - Mobile self-networking Internet gateway routing selection method based on path quality perception - Google Patents

Abstract

The invention relates to a route quality-aware mobile ad hoc network Internet gateway route selection method. The 802.11MAC layer carrier sense mechanism is used to estimate the remaining available bandwidth of the link, and the path quality information is integrated into a multi-objective routing criterion by weighting: Metric = α · MBR + β · PDR + γ · NQR. The node that needs to discover the gateway initiates a gateway routing request. The routing request counts the path quality information of each path along the way. The node selects the route with the largest Metric as the default route to the gateway and maintains it. Simulation results show that the invention can provide mobile nodes with optimal Internet interconnection performance, meet the QoS requirements of interconnection services, and maintain reasonable control overhead.

Description

A Route Selection Method for Internet Gateways in Mobile Ad Hoc Networks Based on Path Quality Awareness

technical field

The invention belongs to a method for Internet gateway routing selection in the field of wireless network communication technology, in particular to a method for Internet gateway routing selection based on path quality perception for Mobile Ad Hoc Network (MANET), which utilizes cross-layer design ideas to estimate The remaining available bandwidth of the link, and the method of selecting the route to the Internet gateway by calculating the gateway route selection criterion.

Background technique

In recent years, the rapid development of the communication field has brought people into an unprecedented information age. The rapid development of mobile communication has changed people's lives drastically and has become a highlight of network services. As several important fields of modern communication technology, wireless local area network WLAN, wireless metropolitan area network Wimax, and traditional GSM, CDMA telephone network meet people's needs from different angles. However, from the perspective of network structure, the above-mentioned network is only a single star-shaped network connection, and the communication between mobile nodes must pass through fixed nodes. This model requires permanent fixed facilities, and for some special areas, such as the sea , deserts, cities and battlefields damaged by earthquakes, etc., the above-mentioned mobile communication network cannot meet the requirements, which requires a special network that can temporarily and quickly automatically form a network, and mobile nodes can directly exchange information through wireless links. The emergence of a new mobile multi-hop network - mobile ad hoc network has solved this problem.

The mobile ad hoc network is composed of a group of mobile terminal nodes with wireless communication transceivers, and has self-organizing, self-recovery, self-adaptive multi-hop temporary non-central network. The network does not rely on infrastructure such as base stations, and all nodes operate in a distributed manner. At any time, nodes form an arbitrary network topology through wireless channels. In the MANET network, each node assumes two roles of host and router at the same time, and the control of the entire network is distributed through various nodes. As a router, a node needs to run relevant routing protocols, perform common routing operations such as route discovery and route maintenance, and need to forward packets for received packets whose destination is not its own. MANET can provide a communication support environment without or inconveniently utilizing the existing network infrastructure, thus broadening the application environment of mobile communication networks.

The characteristics of mobile ad hoc network can be summarized as the following points:

(1) Multi-hop routing. Due to the limitation of the node's transmission power, the range of the node is limited. When communicating with nodes outside its coverage, it needs to be forwarded by the intermediate node, that is, it needs to go through multiple hops. The multi-hop routing in the MANET network is completed by ordinary nodes, not by dedicated routing devices (such as routers).

(2) Dynamic network topology. Nodes are connected through wireless channels to form an arbitrary mesh topology. The connection between nodes is due to the departure of nodes and the arrival of new nodes, as well as the arbitrary movement of nodes, plus the change of the transmission power of the wireless sending device and the dynamics of the wireless channel. Under the influence of comprehensive factors such as characteristics, the network topology may undergo drastic dynamic changes, and such changes are unpredictable.

(3) Portability of the mobile terminal. Mobile terminals are characterized by portability, lightness and dexterity, and are extremely convenient for network relocation, but they also have inherent defects, such as limited energy, small memory, low CPU processing capacity, and high cost. Mobile nodes are generally powered by batteries with limited energy, so how to efficiently use the battery energy of nodes and prolong the survival time of nodes and the survival time of the entire network has become a very prominent problem.

(4) Limited wireless transmission bandwidth. Due to the physical characteristics of the wireless channel itself, the network bandwidth it can provide is much lower than that of the wired channel. In addition, considering factors such as collisions, signal attenuation, noise interference, and inter-channel interference caused by competition for shared wireless channels, the actual bandwidth available to nodes is far less than the theoretical bandwidth value.

(5) Distributed control. All network behaviors in the MANET network, including topology discovery and message delivery, must be completed by the nodes themselves. That is to say, the routing function must be integrated in the mobile node, and there is no centralized network center control point similar to the base station, so it is a distributed control network.

(6) There may be a one-way wireless channel. Since the transmission power of each node is different, the signal propagation range is also different, there may be a situation where A can hear B, but B cannot hear A.

(7) Bandwidth is limited. The capacity of a wireless link is much lower than that of a wired link, and the actual capacity is lower due to noise, fading, and interference.

These characteristics make the shortest route from the source to the destination node of the fixed wired network generally difficult to be directly applied to the MANET network. At this time, the quality of the variable wireless link is an important factor that must be considered, and the network should be able to change the route adaptively. to mitigate the effects of these factors.

With the increasing demands of MANETs for Internet real-time services and the continuous development of mobile terminal technologies, the interconnection between MANETs and the Internet has gradually become a research hotspot in the industry. Bearing Internet services needs to pay more attention to network load balancing and QoS guarantee, and the Internet gateway located at the edge of the mobile ad hoc network, while serving as a bridge connecting heterogeneous networks, has also become a potential load bottleneck. Therefore, discovering and selecting an available gateway with a lower load has become a key issue that needs to be considered when the mobile ad hoc network accesses the Internet. Due to the special access network attributes, the problem of congestion control is particularly prominent. Most of the existing access mechanisms are based on the minimum hop count criterion, which cannot perceive the path quality to meet the user's QoS requirements and transmission fairness, and the interconnection performance is not ideal.

Contents of the invention

The purpose of the present invention is to provide a kind of quality situation of link and gateway routing selection to combine, aim at the routing selection method that provides QoS guarantee for Mobile Ad hoc Network (MobileAd hoc Network, MANET) Internet gateway discovery.

In order to achieve the above object, the present invention estimates the remaining available bandwidth of the link according to the cross-layer design idea, and introduces the gateway routing selection criterion function to select the route from the source node to the Internet gateway in the mobile ad hoc network, taking into account the remaining bandwidth of the link. Based on various factors such as available bandwidth, delivery rate and queue load, a feasible path quality state model is discussed, which is the gateway routing selection criterion based on cross-layer design, and a path quality perception and cross-layer design based on A routing selection method for Internet gateways in mobile ad hoc networks.

Concrete steps of the present invention are:

Step 1: Select the gateway routing selection criterion based on path quality perception:

Metric＝α·MBR+β·PDR+γ·NQR (1)

Define the path minimum bandwidth availability ratio MBR:

$\mathrm{<span\; class="notranslate">\; MBR</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Bw</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; Bw</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span>{<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; Bw</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; Bw</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Define path cumulative delivery rate PDR:

$\mathrm{<span\; class="notranslate">\; PDR</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Pi;</span>}}}\mathrm{<span\; class="notranslate">\; pdr</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Define path minimum queue remaining load availability ratio NQR:

$\mathrm{<span\; class="notranslate">\; NQR</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; ,</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; ,</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Where n is the path length, Bw _i is the remaining available bandwidth of node i, and B is the basic data bandwidth; pdr(i, i+1) represents the delivery rate from node i to node i+1; q _i represents the load queue of node i length, Q _i is the cache size of node i; α, β, γ are weighting factors, and α, β, γ≥0, α+β+γ=1.

The second step: estimation method of remaining available bandwidth based on cross-layer design

The remaining available bandwidth is estimated by using the carrier sense mechanism of the 802.11MAC layer combined with the Network Allocation Vector (NAV) field of the MAC frame header. The duty-to-idle ratio of the node channel, that is, the channel idleness is approximately proportional to the average remaining bandwidth available for the channel. Define the remaining bandwidth estimation expression:

${\mathrm{<span\; class="notranslate">\; Bw</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; kB</span>}\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}<span\; class="notranslate">\; -</span>\underset{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; NAV</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; DIFS</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; back</span>}{\mathrm{<span\; class="notranslate">\; ff</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Among them, B represents the average bandwidth of the link; Δ represents the measurement period; NAV _j is the NAV value of the neighbor nodes of node i within Δ; DIFS is the DCF interframe interval; Backoff _i is the value of the backoff counter of node i. Due to the characteristics of IEEE802.11, under the influence of the back-off strategy, the available bandwidth of the node cannot reach the theoretical limit, so the correction factor k is set to 0.89.

Step 3: Choose the method of routing to the Internet gateway

All nodes in the mobile ad hoc network perform on-demand route discovery, and maintain the route to the gateway as the default route. Nodes without a default route need to initiate a gateway routing request if they have Internet service requirements. The path quality information field is expanded in the gateway routing request packet, including path minimum bandwidth availability ratio MBR, path cumulative delivery ratio PDR, path minimum queue remaining load availability ratio NQR, and gateway selection criterion Metric. The gateway routing request records the path quality information of each link along the way. After receiving the gateway routing request, the gateway calculates the gateway selection criterion Metric according to (1) according to the path quality, and adds the Metric to the gateway routing reply packet, and Unicast the Gateway Route Reply packet back to the source node. From the received L route reply records from the same or different gateways, the source node selects the route with the largest Metric value as the default route to the gateway, and saves the rest of the gateway route reply records.

The fourth step: the method of maintaining the default route

When the default route maintained by the source node to the gateway node fails or the communication path breaks, the source node selects the route with the largest Metric value as the default route from the remaining response request records, and switches the gateway if necessary. If the selection still fails to communicate normally, the source node re-initiates the gateway routing request.

Simulation results show that the invention can establish an optimal communication path between the mobile ad hoc network node and the Internet gateway, effectively improve the packet delivery rate, reduce the average transmission delay, improve network interconnection performance, and reduce routing overhead.

Description of drawings

Accompanying drawing 1 is the flow chart of gateway routing discovery process of the present invention, accompanying drawing 2 is the format of gateway routing request packet of the present invention, and accompanying drawing 3 is the format of gateway routing reply packet of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and test examples, but this embodiment should not be construed as limiting the present invention.

1. Gateway routing selection criteria based on path quality perception

Suppose the path length is n, the remaining available bandwidth of node i is Bw _i , and the basic data bandwidth is B; pdr(i, i+1) represents the delivery rate from node i to node i+1; q _i represents the load queue of node i length, Q _i is the cache size of node i, and the following three path quality information indicators are defined at the same time:

Define the path minimum bandwidth availability ratio MBR:

$\mathrm{<span\; class="notranslate">\; MBR</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Bw</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; Bw</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span>{<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; Bw</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; Bw</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; B</span>}}$

Define path cumulative delivery rate PDR:

$\mathrm{<span\; class="notranslate">\; PDR</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Pi;</span>}}}\mathrm{<span\; class="notranslate">\; pdr</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Define path minimum queue remaining load availability ratio NQR:

$\mathrm{<span\; class="notranslate">\; NQR</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; ,</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; ,</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; )</span>$

Then the gateway routing selection criterion based on path quality perception is:

Metric＝α·MBR+β·PDR+γ·NQR

α, β, γ are weighting factors, and α, β, γ≥0, α+β+γ=1. Nodes can estimate the remaining bandwidth availability rate based on the information provided by the MAC layer, and count the delivery rate and queue remaining load availability rate at the network layer, and integrate them into gateway routing selection criteria through weighting to better reflect the path quality status.

2. Remaining available bandwidth estimation method based on cross-layer design

The remaining available bandwidth is estimated by using the carrier sense mechanism of the 802.11MAC layer combined with the Network Allocation Vector (NAV) field of the MAC frame header. The duty-to-idle ratio of the node channel, that is, the channel idleness is approximately proportional to the average remaining bandwidth available for the channel. Suppose the average bandwidth of the link is B, the measurement period is Δ, the NAV value of the neighbor nodes of node i within Δ is NAV _j , the DCF interframe interval is DIFS, and the backoff counter value of node i is Backoff _i , then the remaining bandwidth estimation The expression is:

${\mathrm{<span\; class="notranslate">\; Bw</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; kB</span>}\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}<span\; class="notranslate">\; -</span>\underset{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; NAV</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; DIFS</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; back</span>}{\mathrm{<span\; class="notranslate">\; ff</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}$

Due to the characteristics of IEEE802.11, under the influence of the back-off strategy, the available bandwidth of the node cannot reach the theoretical limit, so the correction factor k is set to 0.89.

3. Choose the method of routing to the Internet gateway

After introducing the gateway routing criterion, this method requires each source node in the mobile ad hoc network to record path quality information in the appropriate packet format field (as shown in Figure 2 and Figure 3). When the source node needs a route to the gateway node When routing, this method starts the gateway route discovery process. When a node receives a gateway route request, as shown in Figure 1, this method processes the route request according to the following steps:

A. Start the gateway route discovery process;

B. broadcast a gateway routing request packet containing path quality information;

C. When the intermediate node receives the request packet, if the packet has been processed by the node, it will destroy the request packet and no longer forward it;

D. Otherwise, if the intermediate node is in an overloaded state, the request packet will be destroyed and not forwarded;

E. Otherwise, update the path quality information in the request packet according to the information provided by the MAC layer of this node and the network layer, set up a reverse route to the previous hop node, and continue to forward the request packet;

F. If the node is a gateway node, update the path quality information in the request packet, calculate Metric according to (1), and add the path quality information and Metric to the gateway routing reply packet;

G. Return the gateway routing reply packet to the source node by unicast;

H. If the source node does not receive L routing replies, it will continue to receive until L routing replies are received;

1. After the source node receives L route replies, select the route with the largest Metric as the default route to the gateway, this gateway is its default gateway, and save the remaining gateway route reply records simultaneously;

J. End the gateway route discovery process.

The unique ID number is used to determine each gateway routing request packet, and the gateway routing request packet is continuously forwarded in the network until it is received by the destination node. If this gateway discovery fails, add 1 to the gateway route request packet ID number to continue to initiate the next gateway discovery. If the route to the gateway is still not found after accumulating a certain number of times, it is considered that the node cannot establish an Internet connection.

4. How to maintain the default route

Compared with wired networks, wireless networks are relatively less stable due to their inherent characteristics. 802.11 utilizes MAC (Medium Access Control) layer-by-item acknowledgment to provide early detection and retransmission of lost and damaged data packets. If the MAC layer reflects that the transmission problem cannot be repaired, the node sends a path error packet to the source node, and the source node tries to select the route with the largest Metric value as the default route from the remaining response request records, and needs to switch the gateway if necessary. If the selection still fails to communicate normally, the source node re-initiates the gateway routing request.

The content not described in detail in this specification is the prior art known to those skilled in the art.

Claims (2)

1. A mobile ad hoc network Internet gateway route selection method based on path quality perception, its concrete steps are: the first step: select the gateway route selection criterion based on path quality perception: Metric＝α·MBR+β·PDR+γ·NQR (1) Define the path minimum bandwidth availability ratio MBR: $\mathrm{<span\; class="notranslate">\; MBR</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Bw</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; Bw</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; Bw</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; Bw</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$ Define path cumulative delivery rate PDR: $\mathrm{<span\; class="notranslate">\; PDR</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Pi;</span>}}}\mathrm{<span\; class="notranslate">\; pdr</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$ Define path minimum queue remaining load availability ratio NQR: $\mathrm{<span\; class="notranslate">\; NQR</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; ,</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; ,</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$ Where n is the path length, Bw _i is the remaining available bandwidth of node i, and B is the basic data bandwidth; pdr(i, i+1) represents the delivery rate from node i to node i+1; q _i represents the load queue of node i length, Q _i is the cache size of node i; α, β, γ are weighting factors, and α, β, γ≥0, α+β+γ=1. The second step: estimation method of remaining available bandwidth based on cross-layer design The remaining available bandwidth is estimated by using the carrier sense mechanism of the 802.11MAC layer combined with the Network Allocation Vector (NAV) field of the MAC frame header. The node channel duty-to-idle ratio, that is, the channel idleness is approximately proportional to the available average remaining bandwidth of the channel. Define the remaining bandwidth estimation expression: ${\mathrm{<span\; class="notranslate">\; Bw</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; kB</span>}\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}<span\; class="notranslate">\; -</span>\underset{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; NA</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; DIFS</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Bac</span>}{\mathrm{<span\; class="notranslate">\; koff</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$ Among them, B represents the average bandwidth of the link; Δ represents the measurement period; NAV _j is the NAV value of the neighbor nodes of node i within Δ; DIFS is the DCF interframe interval; Backoff _i is the value of the backoff counter of node i. Due to the characteristics of IEEE802.11, under the influence of the back-off strategy, the available bandwidth of the node cannot reach the theoretical limit, so the correction factor k is set to 0.89. Step 3: Choose the method of routing to the Internet gateway All nodes in the mobile ad hoc network perform on-demand route discovery, and maintain the route to the gateway as the default route. Nodes without a default route need to initiate a gateway routing request if they have Internet service requirements. The path quality information field is expanded in the gateway routing request packet, including path minimum bandwidth availability ratio MBR, path cumulative delivery ratio PDR, path minimum queue remaining load availability ratio NQR, and gateway selection criterion Metric. The gateway routing request records the path quality information of each link along the way. After receiving the gateway routing request, the gateway calculates the gateway selection criterion Metric according to (1) according to the path quality, and adds the Metric to the gateway routing reply packet, and Unicast the Gateway Route Reply packet back to the source node. From the received L route reply records from the same or different gateways, the source node selects the route with the largest Metric value as the default route to the gateway, and saves the rest of the gateway route reply records. The fourth step: the method of maintaining the default route When the default route maintained by the source node to the gateway node fails or the communication path breaks, the source node selects the route with the largest Metric value as the default route from the remaining response request records, and switches the gateway if necessary. If the selection still fails to communicate normally, the source node re-initiates the gateway routing request. 2. a kind of mobile ad hoc network Internet gateway route selection method based on path quality perception and cross-layer design as claimed in claim 1, is characterized in that: after introducing gateway route selection criterion, this method requires each mobile ad hoc network The source node in the network can record the path quality information in the appropriate packet format field. When the source node needs a route to the gateway node, this method starts the gateway route discovery process. When the node receives the gateway route request, the method is as follows Steps to handle routing requests: A. Start the gateway route discovery process; B. broadcast a gateway routing request packet containing path quality information; C. When the intermediate node receives the request packet, if the packet has been forwarded by the node, it will destroy the request packet and no longer forward it; D. Otherwise, if the intermediate node is in an overloaded state, the request packet will be destroyed and not forwarded; E. Otherwise, update the path quality information in the request packet according to the information provided by the MAC layer of this node and the network layer, set up a reverse route to the previous hop node, and continue to forward the request packet; F. If the node is a gateway node, update the path quality information in the request packet, calculate Metric according to (1), and add the path quality information and Metric to the gateway routing reply packet; G. Return the gateway routing reply packet to the source node by unicast; H. If the source node does not receive L routing replies, it will continue to receive until L routing replies are received; 1. After the source node receives L route replies, select the route with the largest Metric as the default route to the gateway, this gateway is its default gateway, and save the remaining gateway route reply records simultaneously; J. End the gateway route discovery process.

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