JPH1155313A - Path designation method for radio base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fast and flexibly change a path against the variance of traffic and radio quality and also to significantly improve the delay time and throughtput by measuring the inter-radio link delay time and changing the path according to the sum of the measured delay time and the delay time caused at an adjacent radio station and covering up to a wired base station. SOLUTION: Every radio base station WR measures the delay time to its adjacent station for each transmission of a radio packet. A station WR 25 measures the delay time Δ (25, 26) to its host station WR 26 every time a radio packet is sent to a wired base station WJ. Then the station WR 25 adds delay time Dwj (26) described in an adjacent base station list to the time Δ (25, 26) and then notifies its adjacent base station of Δ (25, 26) + Dwj (26) when the above addition value of delay times is larger or smaller than the prescribed upper or lower limit threshold respectively. Thus, every station WR updates its path to another where the delay time is minimized to the station WJ.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio network for performing two-way communication between radio base stations as shown in FIG. The present invention relates to a method for dynamically, autonomously dispersing, and efficiently setting a route for a station.

[0002]

2. Description of the Related Art In a wireless network having a plurality of wireless base stations, there are two methods for determining a route of a wireless packet between the wireless base stations. One is a method in which each wireless base station records a route to a wireless base station of a transmission partner as a route information table and transmits a wireless packet according to the route information table (“The DARPA Packet R”).
adio Network Protocols, "J
OHN JUBIN etc). The optimum route is always determined by independently and simultaneously transmitting the route information table of each wireless base station. The routing information table describes the wireless base station to be transmitted next and the number of relays (the number of hops) in order to transmit a wireless packet to the target wireless base station, and the route is determined so that the number of hops is minimized. Is done.

FIG. 2 is a diagram for explaining the method. 11
Reference numerals 15 to 15 indicate wireless base stations, and 10 indicates a wireless link. When the radio base station 11 transmits to the radio base station 15, the route is determined so as to minimize the number of hops, so that 11-13-15 is selected as the route. Each wireless base station has a route information table for determining routes to all the wireless base stations, and transmits wireless packets based on the route information table. The route information table of the wireless base station 11 is shown in Table 1.

[0004]

[Table 1]

[0005] The routing information table is broadcast to adjacent base stations by radio packets at predetermined time intervals.
By the broadcast transmission of the route information table, the route information table of each wireless base station is updated, and the optimum route is determined.

As another method for determining an optimum route, a method of recording geographical information of another radio base station in each radio base station and determining a route based on the geographical information (US Pat. No. 4,939,726). ). In this method, a route is determined based on geographical information such as the latitude and longitude of a target wireless base station. The wireless base station that has received the wireless packet transmits the wireless packet so as to be closer to the target wireless base station.

The geographic information of the radio base station shown in FIG. 2 can be represented in Table 2 using, for example, coordinates.

[0008]

[Table 2]

When the wireless base station 11 transmits a wireless packet to the wireless base station 15, the wireless base station 11
Then, based on the geographical information of other wireless base stations, it is determined that the wireless packet should be transmitted to the wireless base station 13 next.

[0010]

Among the conventional route determination methods, the former method of determining a route based on a route information table increases the size of the route information table as the number of wireless base stations increases. In addition, a route information table is broadcast from each wireless base station to change the route information. The fact that a large amount of information for determining a route in a wireless space is transmitted as a wireless packet leads to a reduction in the use efficiency of a wireless section, resulting in deterioration of traffic and delay time characteristics.

In the latter method of recording geographical information in a radio base station, a new radio base station is installed, removed, moved, etc. every time the position of the radio base station is changed. The geographic information needs to be updated, and the geographic information of the target base station needs to be known in some way.

[0012] Both methods have little flexibility with respect to fluctuations in traffic and radio quality, and have large delay time and throughput degradation with respect to fluctuations in traffic and radio quality.

The present invention has been made in view of the above-described problems, and in transmitting and receiving wireless packets in a wireless network, an optimal path for traffic and wireless quality fluctuations does not increase without increasing the number of wireless packets used for determining a path. The purpose is to make a decision.

[0014]

According to the invention, the above-mentioned object is solved by the means described in the claims.

That is, according to the first aspect of the present invention, when each wireless base station transmits data to the next wireless base station in the form of a wireless packet, the next wireless base station receives the wireless packet accurately after receiving the wireless packet. Measure the delay time until the time when it is completed, and if the delay time exceeds the predetermined upper threshold,
And calculating the total delay time from the wireless base station to the wireless base station for communication when the value falls below a predetermined lower threshold, notifying the adjacent wireless base station of the total delay time, and receiving the total delay time. The base station selects a route with the smallest total delay time from the total delay time to the communication target wireless base station obtained from the surrounding wireless base station before, determines the route to the communication target wireless base station, and determines the route. Is a route determination method of notifying an adjacent wireless base station of the total delay time to a wireless base station for communication when the is changed.

According to the present invention, a delay time between wireless links is measured, and a route is updated based on a sum of the measured delay time and a delay time obtained from an adjacent wireless base station to a wireless base station for communication. It is different from the conventional method.

Due to this difference, the route can be changed at high speed and flexibly with respect to the fluctuation of the traffic and the radio quality, and the radio packet transmission of the entire radio network can be performed efficiently.

[0018]

Embodiments of the present invention will be described with reference to the embodiment of FIG. 3 and a flowchart of FIG. The system of FIG. 1 is used as a wireless communication network. The user's wireless packet is relayed through the wireless base station, reaches the wireless base station connected to the wired network, and is sent from there to the wired network.

A method for determining a route from a wireless base station to a wireless base station (called a wired base station) connected to a wired network will be described. In FIG. 3, reference numerals 21 and 22 denote wired base stations (WJ: Wi).
release Junction, 23 to 27 are wireless base stations (WR: Wireless Router), 3
0 is a wireless link, and 31 is a wired network.

In the radio link, a delay time is determined for each direction. The delay time includes a processing time in the wireless base station, a retransmission time of a wireless packet, and a propagation time. The delay time of each wireless link is from when the WR receives a wireless packet to when it is confirmed that the next WR and WJ have correctly received the wireless packet (FIG. 5). Where the wireless base station or a wired base station (referred to as base station) from n ₁ to the base station n ₂ delay time until the radio packet reaches delta (n _1, n ₂₎
And

First, each WR knows, as an initial condition, a route with the shortest delay time to the WJ with respect to traffic, radio quality, and the like at that point in time. Time [D _WJ (n)]
n is an adjacent base station]. Each WR has an adjacent base station table (NRT) in which the delay time D _{WJ is stored.}
(N) is noted. For example, it is assumed that the delay time of each wireless link is described in Table 3.

[0022]

[Table 3]

Table 4 shows the NRT of the WR25 from the initial conditions.

[0024]

[Table 4]

The WR 25 determines a route having the smallest D _WJ (n) than the NRT. The WR 25 sends a packet to the WR 26 from the NRT in order to transmit a wireless packet to the WJ. At this time, WR26 is set to an upper base station (WRn) of WR25.
_up ). Considering other WRs in the same way,
24-25-26-22, 27-22, and 23-21 are the three routes that minimize the delay time to the WJ.
Transmission and reception of wireless packets are performed on two routes.

Each WR measures a delay time with an adjacent base station every time a wireless packet is transmitted (S1-1).
Each time the WR 25 transmits a wireless packet to the WJ, the WR 25 measures a delay time Δ (25, 26) with the WR 26 as an upper base station. The WR 25 adds D _WJ (26) written on the NRT to the measured Δ (25, 26), and when the value exceeds the upper limit threshold (δ _up (25)), or -determined lower threshold _{(δ do wn (25))} Δ to the adjacent base station when it falls below the (25,26) + D notifies the _WJ (26) (S1-2). Here, the upper limit threshold δ of the WR 25
_{Assuming that up} (25) is 3, Δ (25, 26) becomes 1 to 3 in Table 3 due to an increase in traffic, deterioration of radio quality, and the like.
And rise to Δ (25, 26) measured at this time
And the sum Δ (25, 2) of D _WJ (26) written in the NRT
6) + D _WJ (26) changes from 2 to 4, and δ _up (25) =
Since Δ3 has exceeded 3, Δ (25, 26) + D _WJ (26) is subtracted from WR24 and WR27 excluding WR26 which is an upper-level base station.
(S1-3).

From WR25, Δ (25, 26) + D _WJ (2
WR 24 notified of 6) is Δ (25, 26) + D
_WJ (26) = D _WJ (25) is written in the NRT of WR24 (S1-5). Table 5 shows the NRT of the WR 24 at this time.

[0028]

[Table 5]

The next most D _WJ small neighbor base station a new upper base station and (n _'up) from NRT (S1-6).
From Table 5, the upper base station has n ' _up = 23. The upper base station of WR24 is originally WR25 from Table 3, and has been changed to WR23 by this update (S1-
7), WR 24 measures Δ (24, 23), and WR2 which is an adjacent base station other than WR23 which is a new higher-order base station.
5 is notified of Δ (24, 23) + D _WJ (23) (S1
-8).

Similarly to the WR 24, the WR 27 updates the route based on the notification from the WR 25.

According to the above-described method, each WR can be updated to the route having the shortest delay time to the WJ.

FIG. 6 shows a delay time-throughput characteristic when uniform traffic in a service area changes to non-uniform traffic. FIG. 7 shows the system model and the traffic model, and Table 6 shows various simulation conditions.

[0033]

[Table 6]

In the conventional method, the shortest route is determined based on the number of relay base stations and the geographical distance. Since the system model evaluated in this computer simulation is grid-like, the route determined by the conventional method is uniquely fixed and has the least number of relays irrespective of traffic distribution and fluctuations in radio quality. . As can be seen from the figure, the present invention can improve the throughput that satisfies the average delay time 600 standardized by the slot length of the radio packet by 0.1 in a state where the traffic is uneven, by 0.1.

[0035]

As described above, according to the present invention,
Compared with the conventional method, the traffic is measured by measuring the delay time between the wireless links and updating the route by the sum of the measured delay time and the delay time from the adjacent wireless base station to the wired base station. There is an advantage that the route can be changed quickly and flexibly with respect to the fluctuation of the radio quality, and the delay time and the throughput can be greatly improved.

Further, since the determination is made only by the delay time from the adjacent base station to the wired base station, the amount of calculation for determining the route can be reduced, and the broadcast transmission of the route information is not performed. There is an advantage that the use efficiency of the wireless space does not deteriorate due to the route control.

[Brief description of the drawings]

FIG. 1 is a diagram showing a use form of the present invention.

FIG. 2 is a diagram for explaining a conventional method.

FIG. 3 is a diagram illustrating an example.

FIG. 4 is a diagram illustrating a route determination flow of a wireless base station.

FIG. 5 is a diagram for explaining the definition of a delay time.

FIG. 6 is a diagram illustrating simulation results of delay time-throughput characteristics.

FIG. 7 is a diagram showing a simulation evaluation system.

Continuation of front page (72) Inventor Toshinori Tanaka 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] In a wireless network having a plurality of wireless base stations and transmitting and receiving data by wireless packets between wireless base stations, a route for relaying wireless packets transmitted and received between wireless base stations is determined. In the method, when each wireless base station transmits data to the next wireless base station in a wireless packet, the delay time from when the wireless packet is received to when the next wireless base station can correctly receive the wireless packet. When the delay time exceeds a predetermined upper threshold, and when the delay falls below a predetermined lower threshold, the total delay time from the wireless base station to the wireless base station for communication is calculated and the adjacent The wireless base station that has notified the wireless base station and received the total delay time determines the most among the total delay times from the surrounding wireless base station to the wireless base station for communication obtained from the surrounding wireless base station before. A route with a small total delay time is selected and determined as a route to the wireless base station for communication. When the route is changed, the total delay time to the wireless base station for communication is notified to an adjacent wireless base station, and the notification is made. A radio base station routing method, wherein the received radio base station stores the contents of the notification.