JPH11177572A - Communication controller, terminal equipment, system and method for data communication using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively utilize a channel by disconnecting a terminal at the time of moving out from a service area in a radio data transmitting system. SOLUTION: FCI(Free Channel Information) is periodically transmitted from a communication controller (PD) and a terminal (SD) outputs CR(channel Request) at the time of looking at it (SD1-1). When CR competes, it is adjusted by a p-persistence algorithm. When CR is recognized, a token TK is given (PD-3) to transmit data, On the other hand, when an idle token IDLE is transmitted, CR can be outputted. BS periodically transmits a token and the terminal responds to it (ND: No Data to transmitte). When no response is made, the token is repeated (PD-6, 9) but when no response is made twice, BS disconnects (DC: Disconnect) the terminal (PD-10).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a communication control device, a terminal device, a data communication system and a data communication method using the same, used in a wireless transmission system.
More specifically, the present invention relates to a channel sharing protocol that enables the use of the same channel while avoiding collision when there are a plurality of clients.

[0002]

BACKGROUND OF THE INVENTION Rapid developments have been seen in wireless communications over the last decade. This movement in wireless communications is driven by attractive features such as flexibility, increased portability, reduced wiring complexity, and ease of installation. These benefits from wireless systems have also led to rapid development in the field of wireless local area networks (LANs).

[0003] On the other hand, an increase in demand for wireless communication has further led to a shortage of frequencies (spectrum) which is inherently limited. As described above, there is a demand for more efficient use of a short-lived spectrum. Also, when many users want to transmit on one channel at the same time, a conflict occurs. Therefore, there must be a procedure for how much available channel capacity to allocate to users. These procedures consist of multiple access protocol rules that each user follows when accessing a common channel (see R. Rom, M. Sidi, Multiple Access P).
rotocls Performance and Analysis, Springer-Verlag
New York Inc., 1990).

[0004] To fulfill the demands for wireless LANs, consider a point-to-point communication network.
The system is intended to be used mostly as an Internet browser, but can also be used for email and games. All personal stations (Person
al Station: PS) is the base station (Base Stat)
ion: BS). Since we are talking about wireless systems, the lack of spectrum must be considered. This shortage limits the number of personal stations (PS) that can access the channel at the same time. At the same time, the problems faced by collisions between channel accesses must be considered. As collisions increase, the efficiency of the system decreases.

[0005] Therefore, standardization in IEEE802.11 (international standard for wireless LAN) is made to satisfy the requirements of wireless data networks. Carrier sensing multiple access (CSMA / CA) with collision avoidance is a protocol adopted by IEEE 802.11. (Reference: W. Diep
Straten, G.A. Ennis, P .; Belan
ger, "Distributed Foundat
ion wireless Medium Accesses
s Control ", IEEE p802.11-
93/190, R.A. White, M.A. Dema
nge, K .; Doss, F.C. Vook, "
A complete description of
Frame Prioritization ina
CSMA / CA MAC Protocol ”, I
EEE p802.11-93 / 208, T.E. S. H
o, K. C. Chen, "Performance
Analysis of IEEE 802.11 C
SMA / CA Medium Access Cont
rol Protocol ”, PIMRC'96,
Taipei, Taiwan, pp. 407-41
0, October 15-18)

[0006]

Here, the basic channel access method uses a MAC (Media Access).
Control-level acknowledged p-persistence CSMA. CSMA is a network access method used to control access to a network in a shared network topology such as Ethernet. The CSMA protocol requires a personal station (PS) to listen before speaking. Before starting to speak, the personal station (PS) must determine that the channel is free. If the channel is busy, the personal station (PS) has to wait until the channel is free.

A device connected to a network cable performs a listen (carrier detection) before transmission. Multiple access (MA) indicates that many devices can connect to a network formed by a single cable. When the network is clear, all devices have equal access to use the network.
Thus, if multiple stations attempt to access the cable simultaneously, a "collision" will occur. The method to avoid this is CSMA / CA. CSMA / CA, as collision avoidance (CA), avoids collisions by signaling each node's intention before performing the actual transmission. That is, CS
Using MA / CA requires extra overhead and inevitably reduces performance.

Further, there are the following prior arts similar to this kind of technology, but none of them is superior to CSMA / CA.

Japanese Patent Publication No. 8-500227 describes "Method and Apparatus for Reducing Contention and Possibility of Improper Allocation of Resources in Packet Transmission System".
This technique is a method of determining a re-request using two timers for the purpose of avoiding double allocation for an access request and reducing unnecessary re-requests.

Japanese Patent Application Laid-Open No. 9-172446 describes "Multi-bus LAN and wireless LAN". This technology is
In a system having two random access buses and a time-division bus, this is a method in which an access request is made on the random access bus and the slot length of the time-division bus is changed accordingly (variable length slot) to increase the overall transmission efficiency. .

JP-A-8-251187 describes a "wireless communication system". This technology is a collision detection method and a distributed control method in a system in which a random access CSMA / CD is applied to a wireless channel.

Japanese Patent Application Laid-Open No. Hei 8-212373 describes a "local network". This technique is a method of increasing the efficiency of the entire system by exchanging bus load information on a station having a plurality of network buses.

The present invention has been made to solve the above problems, and provides a communication control device, a terminal device, a data communication system and a data communication method using the same, which have higher performance than CSMA / CA. With the goal.

[0014]

SUMMARY OF THE INVENTION The present invention is directed to a data transmission system including a first device for controlling communication and a plurality of second devices, which are wirelessly transmitted through a channel that allows a plurality of second devices at the same time. A data communication method for performing data communication, wherein the in-channel free information receiving step in which the second device receives in-channel free information transmitted by the first device and indicating that the channel is not full, Said second who is going to receive the allocation of
A channel request step in which the device issues a channel request; a designation information receiving step of receiving designation information transmitted by the first device in response to the channel request; and the second device receiving the designation information transmits data. And a data transmission step.

The in-channel free information is, for example, an idle token. The channel request is, for example, CR (Channel
Request). The designation information is, for example, a token.

The present invention includes a contention adjusting step of adjusting by a p-persistence algorithm when a plurality of second devices simultaneously issue a channel request in the channel requesting step.

According to the present invention, in response to the channel request,
If there is no data to be transmitted when the designation information transmitted by the first device is received, the second device includes a transmission data absence information transmitting step of transmitting transmission data absence information.

The transmission data absence information is, for example, ND (No D
ata to transmitte).

According to the present invention, the specified information is repeatedly transmitted after the channel request is made, and the specified second device responds to the transmission.

According to the present invention, the first device repeatedly transmits the designated information a predetermined number of times when there is no response from the designated second device.

According to the present invention, the transmission of the specified information repeatedly for a predetermined number of times can be performed even when the specified second apparatus does not respond even after repeating the predetermined number of times. The first device is the designated second
This cancels the device designation.

This makes it possible to distinguish between a communicable terminal and a non-communicable terminal. For example, by disconnecting a non-communicable terminal, the channel can be effectively used.

The present invention is characterized in that, when the plurality of channels exist, the second device receives channel information transmitted by the first device and indicating a vacant channel, and the second device receives the channel information based on the channel information. No. 2
A channel selection step for the device to select a channel.

According to the present invention, the channel information is transmitted simultaneously on the plurality of channels at predetermined intervals.

In the present invention, the first device includes a memory in which a table including a plurality of shortened addresses is stored in advance, and in the channel requesting step, the second device transmits its own address information together with the channel request. ,
The first device stores the address information sent from the second device in a predetermined position of the table, transmits a corresponding shortened address, and when the second device transmits the shortened address, The first device converts the shortened address to the original address based on the table and transmits the converted address to the outside.

According to the present invention, in the channel request step, there is provided a contention adjustment step of performing adjustment when a plurality of second devices simultaneously issue a channel request, and in the contention adjustment step, a channel request is not recognized. For the two devices, the first device sets another vacant channel in a reserved state, and transmits to the second device that the reservation information of the another channel can be allocated by another channel and the reservation information of the another channel. It is.

The present invention relates to a data communication system that includes a first device for controlling communication and a plurality of second devices, and simultaneously performs data communication wirelessly through a channel that allows the plurality of second devices. The first device transmits in-channel vacancy information indicating that the channel is not full, the second device receives the in-channel vacancy information, and the second device attempts to receive the channel assignment. The device issues a channel request and, in response to said channel request,
The first device transmits designation information to the second device, and the second device that has received the designation information transmits data.

[0028] In the present invention, the first device may further perform adjustment when a plurality of second devices simultaneously issue a channel request, and may perform the second process when the channel request is not recognized.
For the device, the first device sets another vacant channel in a reserved state, and transmits to the second device the reservation information of the another channel that can be allocated by another channel and the other channel. is there.

The present invention is used in a data transmission system including a communication control device for controlling communication and a plurality of terminal devices to perform wireless data communication through a channel that permits a plurality of terminal devices at the same time. A communication control unit, which transmits in-channel free information indicating that the channel is not full, and transmits designation information in response to a channel request from the terminal device; And a radio receiving unit for receiving a channel request issued by the terminal device to be transmitted.

According to the present invention, the communication control device includes a memory in which a table including a plurality of shortened addresses is stored in advance, and the communication control device stores the address information sent from the terminal device at a predetermined position in the table. And the corresponding shortened address is transmitted, and when the terminal device transmits the shortened address, the shortened address is converted to the original address based on the table and then transmitted to the outside.

According to the present invention, when there are a plurality of the channels, the radio transmitting unit transmits channel information indicating a vacant channel.

The channel information is, for example, FCI (Free Chan)
nel Information).

The present invention is used in a data transmission system including a communication control device for controlling communication and a plurality of terminal devices to perform wireless data communication through a channel that allows a plurality of terminal devices at the same time. A terminal device, which is transmitted by the communication control device and receives in-channel free information indicating that the channel is not full, and in response to a channel request issued by itself,
A wireless receiving unit that receives designation information transmitted by the communication control device; and a wireless transmission that issues the channel request when trying to receive the channel assignment and transmits data when receiving the designation information. Unit.

According to the present invention, when there are a plurality of the channels, the radio receiving section receives channel information transmitted from a communication control device and selects a channel based on the channel information.

The present invention relates to a new channel sharing protocol. This protocol uses a p-persistence algorithm to access the channel or token for fair channel sharing. Token passing is controlled by a base station (BS). If the channel is not full (not crow
ded), the user can join the channel. Channel idle information is provided by an idle token from the base station (BS). The numerical evaluation of the protocol is given in terms of load G and throughput S. Numerical evaluation is also based on Carrier Sense Multiple Access / Collision Av.
oidance: Compared to that of the CSMA / CA) protocol.
When the number of channels is 3 or more, the method of the present invention uses CSMA / CA
Better.

The features of the present invention are, for example, as follows.

(1) The base station (BS) transmits a token for permitting data transmission to a specific terminal. There was no concept of BS in the wired transmission system.

(2) When the maximum number of terminals are not connected to the base station (BS), the BS transmits an idle token for notifying the connection timing to terminals not connected to the system at a predetermined timing.

(3) When the terminal permitted to transmit has no data to send, the terminal transmits a token indicating no data to the BS.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 of the Invention 1. Overview An embodiment of the present invention will be described with reference to the drawings. The present invention provides a new channel sharing protocol (CS
P). To solve the collision problem faced by multiple access protocols during channel access, the proposed method uses p-persistence (pp) similar to carrier sense multiple access with collision avoidance (CSMA / CA).
ersistence). High data rates are not required, as the main purpose of the system is for internet access and e-mail transmission. Thus, frequency division multiple access / time division duplex (Frequency Division Multiple Access)
Access / Time Division Duplex (FDMA / TDD) is used for simultaneous channel access by several personal stations (PS). This large (but limited) number of personal stations (PS)
Channels can be used. However, more personal stations (PSs) than allocated are unable to use the channel.

For more efficient use of the channel, the channel sharing protocol (CSP) of the present invention is used.
Uses tokens so that several personal stations (PS) can join one channel. Although the number of personal stations (PS) per channel is fixed, the channel can be used efficiently by using tokens.

[0042] Each of the personal station in p- sustained algorithm (PS) are given the value p _p between 0 and 1. Before transmission, the personal station (PS) generates a random value p between 0 and 1. when p is greater than p _p, personal station (PS) can send. Once the personal station (PS) has been assigned a channel, it is given a token number. The personal station (PS) waits for a token number transmitted by the base station (BS). Once the correct token has been received, the personal station (PS) can begin transmitting.

FIGS. 1 and 2 schematically show the flow of the above processing.

FIG. 1 is a flowchart of the processing of the base station. Upon receiving the channel request, a token is assigned to the personal station (S100). Since the personal station transmits either data or no transmission data, the base station receives this and changes the processing according to the received content (S10).
1). When data is received, the process proceeds to step S102, and when no data is received, the process proceeds to step S104.
Proceed to. When data is received, ARQ (Automatic
est for Repetition) procedure (S10
3) After receiving the channel release signal (S104), transmit the next token.

FIG. 2 is a flowchart of the processing of the personal station. A random p-persistence value between 0 and 1 is obtained (S110). FCI (Free Channel Informatio
n) is received (S111). The FCI periodically (eg, 1
Broadcast (broadcast to all PSs) from BS every second). It is determined from the FCI whether the channel can be used (S112). If the channel can be used, step S11
3. The process of S114 is performed, and when it is not usable, the processes of steps S115, S116, and S117 are performed. When usable, any channel is selected and a random number between 0 and 1 is generated (S113). Random numbers and p- obtained in S110
The duration values are compared, and if (random number)> (p-persistence value), a channel request is transmitted, a token is received and transmission is started, and the ARQ procedure is continuously performed (S118). On the other hand, when it is not usable, any channel is selected (S115). It is determined whether or not the channel is full (S116). If the channel is full, the process is terminated. If not, an idle signal is received (S117), a channel request is transmitted, a token is received and transmission is performed. Start and ARQ
The procedure is continued (S118).

The method of selecting which free channel to use from the information obtained from the FCI includes the following method in addition to the above random access.

1. For all channels, it is determined whether each channel is full (Crowded), and channels that are full are excluded.

2. Next, with respect to the remaining channels, the number of the contained PSs is one and searched and extracted. A channel is selected from the extracted channels by random access.

3. If the number of accommodated PSs cannot extract one channel, the number of accommodated PSs retrieves and extracts two channels. A channel is selected from the extracted channels by random access.

4. Thereafter, similarly, the process is repeated up to the limit value while adding the number of stored PSs.

The reason why the base station assigns a token to a PS is as follows. In a wireless transmission system, a personal station may move and move out of a service area, or communication may be temporarily disabled due to fading, noise, or the like. Such a situation does not occur in a wired manner. To solve this problem specific to wireless transmission systems, the base station must constantly monitor whether the personal station is currently in a communicable state. In the embodiment of the present invention, this is realized by assigning a token and using an idle token.

When the data transmission is completed, a channel release signal is transmitted (S119), and the process ends.

The above is the outline of the channel sharing protocol (CSP) of the present invention, which will be described later in detail.
In addition, detailed performance studies on the throughput S and the load G were performed, and will be described later. The numerical result of the CSP of the present invention is C
Compared to that of SMA / CA.

2. System Model Here, a point-point network structure is considered.
This system is considered to be used mainly as an Internet browser, but can also be applied to e-mail, games, etc. FIG. 11 shows this system configuration diagram. There is one base station (BS) and can communicate with several personal stations (PS) wirelessly. The base station (BS) is connected to a wired LAN, and the personal station (PS) can access all Internet-based services through the base station (BS). The connection between the personal station (PS) and the base station (BS) is wireless.

Each personal station is, for example, a personal computer provided with a wireless communication device.
The base station is, for example, a personal computer or a workstation, and includes a wireless communication device and a communication connection device for connecting to an external network. The protocol described below is mainly processed by the wireless communication device, but may be processed by a personal computer or a workstation.

FDMA / TDD can be considered as multiple access and double transmission. A fixed number of personal stations (P
S) is allowed to communicate on each channel. The base station (BS) transmits free channel information (Free Channel Information: FCI) at fixed intervals. FIG. 3 shows transmission of FCI by the base station (BS) in each channel. In FIG. 3, N
There are a number of channels, and one first device (corresponding to a base station) manages them, and transmits FCI for a free channel. One channel can be assigned n second devices (corresponding to personal stations). After all, a total of N * n second devices are allowed. Arrows from the second device indicate channel selection.

3. Channel Sharing Protocol Each personal station (PS) is given a token number. When the personal station (PS) finishes transmitting, the token is sent to the next personal station (PS)
Proceed to. This passing of the token continues until the last personal station (PS) transmits data, after which the token proceeds to the first personal station (PS). When the number of personal stations (PS) in a channel is small, the channel is available and the first token sent is an idle token. When the personal station (PS) receives the idle token, it can send a channel request to the base station (BS). When there is no personal station (PS) transmitting data, the token is circulating between the personal stations (PS) in the channel.

Only the basic idea of the p-persistence algorithm is used in the method of the invention. Each personal station (PS) are given probability value p _p. When the personal station (PS) wants to transmit, it generates a random value between zero and one. When this value is larger than p _p, personal station (P
S) starts transmission, otherwise waits for FCI or idle token and repeats this step again.

3.1 Terms Used Idle: Idle is a state of transmission. Occurs when there is no personal station (PS) transmitting.

[0060] crowded: Each channel can have up to n personal stations (PS). A channel is said to be full when n personal stations (PS) are already using one channel.

Free channel: "crowded"
The "not" channel is called a free channel.

Fragments: the term fragment is always IP
Means a packet fragment.

3.2 Channel Sharing Protocol
(CSP) When a personal station (PS) is switched on, the probability equal to _pp is
(PS). The personal station (PS) waits for FCI from the base station (BS). The FCI contains token information for all channels. After receiving the FCI, the personal station (PS) randomly selects one free channel and waits for an idle token. Then p-
The persistence algorithm is used to start the transmission.
This can prevent a collision between two personal stations (PS) trying to access the same channel at the same time.

When all the channels are busy, the personal station (PS) randomly selects one channel and checks the FCI. FCI is Base Station (BS)
Not only does it pass through the field to the personal station (PS) that communicates with it, but also informs whether the channel is full or not, and whether the channel is idle or idle. If the channel is full, the personal station (PS) selects another channel and checks the token again on that channel. When the channel is not full, the personal station (PS)
Checks if the channel is idle.

As long as the channel is idle, the personal station (PS) starts transmitting to the base station (BS) based on the p-persistence algorithm. The first transmission informs the base station (BS) of the presence of the personal station (PS). The base station (BS) increases the number of personal stations (PS) of the channel by one and gives the personal station (PS) the number of the token.

3.3 Channel Sharing Protocol
(CSP) Example A single channel with multiple personal stations (PS) trying to access the channel is described. Up to four personal stations per channel
(PS) is allowed and no collision occurs. After each personal station (PS) receives the idle token,
Send a channel request to the base station (BS). Some personal stations (PS) receive free channel information and idle tokens, but according to p-persistence, they cannot access that channel at the same time,
Avoid collisions. According to this example, PS5 cannot access the channel. Thus, a failure in access results in a significant delay in data transmission.
Each channel requests the receipt of an acknowledgment (ACK) from the base station (BS) along with the token number assigned to the personal station (PS). When the personal station (PS) completes the data transmission (for example, PS1), it transmits no data available to the base station (BS), and then notifies the base station (BS) that the next token will be transmitted.

To better understand the channel sharing protocol (CSP) of the present invention, an example will be given.

FIG. 9 shows an example of the channel sharing protocol (CSP) of the present invention. First device (Preliminar
y Communication Device: PD) transmits FCI (PD-1), returns ACK (Token 1) in response to the channel request (PD-2), and transmits Token 1 when the channel is not full (PD- 3) Data transmission / reception is performed according to the ARQ procedure (PD-4), and ACK (token 2) is returned in response to the SD2 channel request (PD-5). ACK (token 3) is returned in response to the SD3 channel request (PD-
7) In response to the SD4 channel request, ACK (Token 4, full channel) is returned (PD-8). After this,
In order to confirm the connection status of SD1 to SD4 for which connection has been permitted, corresponding tokens TK1 to TK4 are transmitted. On the other hand, each SD returns no data ND.

On the other hand, the second device (Secondary Communication
Device: SD) No. 1 transmits a transmission channel request because the random number generated by receiving the FCI (PD-1) is (random number)> (p-persistent value) (SD1-1) Send data. When data transmission is completed, a channel release without transmission data is transmitted (SD1-2). After that, the token T of PD
In response to K1, SD1 sends no data ND to PD. This is because, as described above, the PD determines whether the SD is in a communicable state and manages the system.

The other second device (No. 2) receives the idle token IDLE generated by the no data ND (SD1-2) of SD1 and transmitted by the PD, and generates a channel request CR.
Data is transmitted, and after transmission is completed, no data ND is returned.

Further, another second device (No. 3) is an FCI (PD-
Since the random number generated in response to 1) is (random number) <(p-persistent value), the transmission channel request is not transmitted (SD3-1).
Wait for the next FCI or idle token.

Further, the other second device (No. 5) has the FCI (PD-
In response to 1), this channel was selected, but it cannot be transmitted because the generated random number was (random number) <(p-persistent value) (SD5-1). After receiving FCI again, the same channel was selected, but it could not be transmitted (SD5-
2). Eventually, SD5 could not join this channel.

The other second device (No. 4) is activated and initialized (SD4-1).

In the example of FIG. 9, up to four
Indicates when SD is allowed. The PD transmits the FCI periodically (at one-second intervals). On the other hand, after SD4 is connected (P
D-8 or later), because this channel is full, SD-1 to S
No idle token is sent unless one of the D-4s releases the channel. On the other hand, four tokens TK1 to TK
4 is periodically transmitted from the PD.

FIG. 9 shows an example in which there is no connection error. The next timing chart when there is a connection error is shown in FIG. In FIG. 10, the operations of the portions denoted by the same reference numerals as those in FIG. 9 are the same. However, in FIG. 10, it is assumed that communication becomes impossible for some reason after the SD-2 transmits the channel request CR (this is unlikely to occur in a wired manner). PD returns ACK to the channel request CR of SD2 and sends token TK2. However, SD-2 cannot return no data ND. In such a case, in order to assure certainty, the PD is given a predetermined number of times (eg,
Times) Send TK2 repeatedly. However, in the case of FIG. 10, there is still no response. In the embodiment of the present invention, the token is transmitted once again (not necessarily a total of two tries). That is, after PD-6, the token TK2 is transmitted five times again in PD-9. If there is still no response,
The PD notifies the disconnection of SD-2 (DC-2). According to such a procedure, the terminal that has become unable to communicate can be disconnected to effectively use the channel, and the procedure is carefully performed to prevent the terminal from being carelessly disconnected.

FIG. 8 is a state transition diagram summarizing the above description.

3.4 Detailed Flowchart FIGS. 4 and 5 show detailed flowcharts of the PD corresponding to FIGS. 9 and 10, and FIG. 6 shows a detailed flowchart of the SD.
And FIG.

Referring to FIG. 4 and FIG. The token is initialized to idle and the FCI is transmitted (S50). If the FCI times out, the FCI is transmitted again (S51), and the token is transmitted (S53). No transmission data (ND) / Data reception (DATA) / Transmission data to PS / None / Channel request (CR)
It is determined which of the signals has been received (S54).

When there is no transmission data (ND), it is determined whether or not the token is the last token (S57). If so, an idle token is transmitted (S59). Otherwise, the token number is increased by one. (S58).

When data or data to the PS is received, a data reception procedure is performed (S55). Thereafter, it is determined whether a channel release request has been received (S56), and if so, the process proceeds to step S57, and if not, the process proceeds to step S57.
Return to 51.

For a channel request, a free token
Assign to SD address, return ACK of channel request, SD
Returns the token number (S64). Next, it is determined whether the token number is the same as the maximum number of SDs allowed per channel (for example, four) (S65), and if so, the channel is set to be crowded in the FCI and the token (S66). To step S57, otherwise directly to step S57.

If there is nothing, it is determined whether or not the maximum number of tokens (for example, five times) have been transmitted (S60). If not, the process returns to step S51 to repeat the processing. (Eg, twice) is checked (S61). If so, the token is a free token, that is, there is no SD using the token (S62).
Proceed to. Otherwise, the token transmission cycle is increased by 1 (S63), and the process proceeds to step S57.

Referring to FIG. 6 and FIG. The p-persistence value is set (S1), and the FCI is received.
When there is no FCI being transmitted, it waits for an FCI (S2). It is checked whether there is any available free channel other than the interfering channel (S3).

When there are available free channels,
A channel is randomly selected (S4), and it is checked whether there is too much interference in the channel (S5). If so, the channel number is stored in the memory as the interfering channel (S7), and the process returns to step S2. . Otherwise, a random number between 0 and 1 is generated (S6), and whether (generated random number)> (p-persistent value) is checked (S8), and if so, a channel request is transmitted to the BS. (S15), otherwise step S2
Return to

When there is no available free channel,
A channel is randomly selected (S9), and it is determined whether the channel is full (S10). If so, the process returns to step S2. Otherwise, check if the channel is idle (S11),
If so, proceed directly to step S13; otherwise, wait until a channel idle signal is received (S12), generate a random number between 0 and 1 (S13), (generated random number)> (p-persistent value) Is checked (S14), and if so, a channel request is sent to the BS (S15); otherwise, step S2
Return to

After transmitting the channel request in step S15, it is determined whether an ACK and a token number for the channel request have been received (S16).
And if so, store the token number in memory,
Wait for a token from PD (S17, S18). Next, it is determined whether the token waiting time has passed (S19). If so, the process returns to step S2. If not, it is determined whether the message is a disconnection message from the PD (S20). If so, the process returns to step S2. Otherwise, it is determined whether a token has been received from the PD (S21), and if so, it checks whether or not it has the data to be transmitted (S22). If not, it returns no data to be transmitted (S27). For example, data transmission is started (S23).
Check whether there is no transmission data (S24), and if so, continue data transmission (S26). If no, check whether there is data (IP packet) to send (S25), and if so, continue data transmission (S26). If not, return no transmission data to the PD (S27) and wait for a token from the PD again (S18).

3.5 Format FIG. 12 shows an example of a format according to the embodiment of the present invention. The format of FIG. 12 is data / channel
Used as U-frames / tokens such as ACK, no data ND, and disconnect DC / tokens TK, ACK, NACK, and other empty frames. The 2-bit frame ID of the first data indicates the type of the frame, and ND (No Data to Transmit) indicates the type of the U-frame. The third control field (Control
Field) indicates what has been transmitted, and the fourth control field indicates what has been received.

FIG. 13 shows an example of the format of the FCI.

4. Throughput Analysis The channel throughput of the channel sharing protocol (CSP) of the present invention can be written as equation (1).

[0090]

(Equation 1)

Here, S is the channel throughput, U is the expected use time, B is the expected busy time, and I is the expected idle time.

The expected use time is a time during which the channel is continuously used. Since no interference or errors are taken into account in this analysis, data transmission is always successful. Thus, the probability that a channel will be used is the probability that a personal station (PS) has data to receive and transmit a token. The probability that the personal station (PS) will receive the token is

[0093]

(Equation 2)

When the i-th personal station (PS) is 1
The probability of being in one channel is

[0095]

(Equation 3)

Here, N is a personal station (PS)
, M is the number of channels, n is the number of personal stations (PS) allowed per channel, and pp is the _p -persistence value (between 0 and 1) given to each personal station (PS). .

The expected number of personal stations (PS)

[0098]

(Equation 4)

Assuming that the IP packet arrival has a Poisson distribution, the probability that the IP packet arrives at one user is

[0100]

(Equation 5)

Here, T is the time slot for TDD and p is the arrival rate related to the number of IP packets. The probability of using k channels is

[0102]

(Equation 6)

Here, G = gT is a load.

The expected number of used channels at T (ms) is

[0105]

(Equation 7)

Similarly, the expected number of busy channels in time slot T is the sum of the expected number of collision channels and the expected number of used channels. The probability that there is a collision on one channel is greater than two personal stations
With (PS) to select the same channel, the probability to obtain a large random number than p _p. Collision probability is 1 minus (probability any PS do not select a channel) minus (the probability that a single user obtaining a large random number than p _p with selecting a channel).

[0107]

(Equation 8)

The probability that there is a collision on the k channel is

[0109]

(Equation 9)

Knowing the probability of collision occurring on the k channel,
The expected number of channels where collisions occur can be written as:

[0111]

(Equation 10)

The expected number of busy channels can be written as follows.

[0113]

[Equation 11]

The expected number of idle channels in time slot T is calculated. One personal station (PS)
When one token arrives, one channel is idle and this personal station (PS) has no data to send. Given that the arrival of data is Poisson distribution, the probability of not being given any data arrival is

[0115]

(Equation 12)

Using equation (4), the probability that all channels are idle is given by:

[0117]

(Equation 13)

Therefore, the probability that the k channels are idle is given by:

[0119]

[Equation 14]

The expected value is given as follows.

[0121]

(Equation 15)

If all the channels are idle, the throughput is 0. If the channels are not idle, the throughput is the ratio between the used channel and the busy channel.
Thus, the throughput for the Channel Sharing Protocol (CSP) can be written as:

[0123]

(Equation 16)

Equations (7), (11) and (15) are replaced by equation (1).
By substituting into 6), the throughput can be written as follows.

[0125]

[Equation 17]

5. Numerical results The channel sharing protocol (CS
The numerical results of P) for T = 10 ms are shown.

To deal with collisions, the p-persistence algorithm is used by the Channel Sharing Protocol (CSP). The value p _p is a very important factor. For small _pp , the probability of collision increases and the delay in transmission increases. When p _p is large, a delay in channel access is increased. Proper selection of the value of _pp is important for the proper functioning of the Channel Sharing Protocol (CSP). FIG. 14 shows the result when the value of _pp is changed.

FIG. 14 shows the relationship between the throughput and the load of the channel sharing protocol (CSP) having 17 channels. 68PS and 4PS per channel, a: p
_{p = 0.9, b: p p} = 0.8, c: p p = 0.5, d:
p _p = 0.1. These results clearly indicate better performance for higher values of _pp . This is because this value increases as the number of collisions decreases. The rest of the results occur for p _p = 0.8.

FIG. 15 shows a comparison result having CSMA / CA. FIG. 15 shows a relationship between throughput and load in comparison of a channel sharing protocol (CSP) having CSMA / CA. Here, a: CSMA / CA, b: CSP, 2 channels 20PS
And 10 PS (per channel), c: CSP, 3 channels 30 PS and 10 PS (per channel), d: CSP, 10
Channels, 100PS and 10PS (per channel). CS
AM / CA results are for N = 10, contention window = 0.4 * Pkt_Time. Where Pkt_T
ime = 20. This result clearly shows that the larger the number of channels in the channel sharing protocol (CSP) of the present invention, the better the performance compared to CSMA / CA.

FIG. 16 shows the result when the number of personal stations (PS) per channel is changed. FIG.
Shows the relationship between throughput and load for 17 channels.
These results show that the number of personal stations (PS) per channel has no effect on the performance of the channel sharing protocol (CSP) of the present invention.

As described above, the performance of the method of the present invention is measured in terms of throughput and load, and the numerical results show that the channel sharing protocol (CSP) of the present invention is used.
, When changing the load for high p- persistent _{(p p} = 0.8,0.9), as high as 0.9, most realize constant throughput. If the number of channels is 3 or more, the channel sharing protocol (CSP) of the present invention is C
Better than SMA / CA. The performance of the channel sharing protocol (CSP) of the present invention improves as the number of channels increases. Personal station on one channel
Channel sharing protocol (CS
Has no effect on the performance of P). Thus, the method of the present invention can realize effective use of the spectrum.

Embodiment 2 of the Invention It is assumed that the first embodiment is applied to the Internet. Conventional TCP / IP
In the communication protocol, as the identification information of the communication partner,
IP Address (32 bits) or MAC Address (48 bits) is used. These addresses are managed to be the only value in the world. LAN (Local Area Ne
10Mbps like twork) and WAN (Wide Area Network)
In a system having the above transmission rate, these address lengths can be ignored. At a connection point of a wide area network such as the Internet or a WAN, by using these addresses, packet information (these addresses are included in the packet) can be routed or transmitted to a communication partner.

However, in a communication protocol of a short-range wireless transmission system having a transmission rate of about 64 to 128 kbps per channel connected to a LAN or WAN by TCP / IP,
The bit length cannot be ignored if the address or MAC address is used as it is as the identification information.

Therefore, by assigning a short address of several bits to about 8 bits corresponding to the IP address or the MAC address and being unique in the system (for example, in the system of FIG. 11), the effective transmission rate is increased. Think about improving.

More specifically, the following procedure is performed.

(1) The base station (BS or PD) manages all short addresses available in the system. The number of short addresses depends on each system.

(2) The wireless device (PS or SD) that has made a communication request selects an arbitrary channel, and uses its own MAC address as additional information to transmit a channel assignment request CR from that channel.
Send

(3) Upon receiving the channel assignment request, the base station selects an unassigned short address from all the short addresses and associates it with the received MAC address. The base station has a memory for this purpose, prepares a table of a plurality of short addresses in advance, and associates the MAC address with any of these. The short address is transmitted as additional information of the channel assignment response.

(4) Thereafter, the base station and the wireless device can use the assigned short address during communication.

FIG. 17 shows an example of the format of the channel busy / idle management data. FIG. 18 shows the format of the channel status management data. FIG. 19 shows an example of a channel assignment request frame structure. FIG. 20 shows an example of a channel assignment response frame structure. According to FIGS. 17 to 20, an 8-bit “00000001” short address is assigned to a 48-bit MAC address.

As described above, according to Embodiment 2 of the present invention, a long data string such as TCP / IP packet data is divided and transmitted on a channel having a relatively low transmission rate such as a wireless transmission system. If the original IP address or
Using a MAC address can solve the problem that the division loss increases and the effective transmission rate decreases.

Embodiment 3 of the Invention The first embodiment of the present invention employs the p-persistence algorithm to prevent collision. By the way, the terminal that could not be connected in the p-connection algorithm searches for a free channel again. Collisions may occur again in this channel. For example, when there are channel requests from three terminals at the same time, the remaining two terminals to which no channel has been assigned may compete again. In this case, the same processing is repeated, resulting in waste and time delay.

Therefore, it is considered that unnecessary waiting time can be reduced by allocating all channels and resources to terminals requesting communication in real time.

More specifically, the following procedure is performed.

(1) The base station manages the free / busy information (FCI) and all short addresses of all channels available in the system.

(2) The wireless device that has made a communication request selects an arbitrary channel from the idle channels, and transmits a channel assignment request for the channel using its own MAC address as additional information.

(3) Upon receiving the channel request, the base station
An unassigned short address is selected from all the short addresses and associated with the received MAC address. If the specified channel cannot be allocated, another vacant channel is set in the reserved state, and the reserved channel information and the indication of the possible allocation in another channel are transmitted as additional information of the channel allocation response.

(4) Upon receiving the channel assignment response, the wireless terminal switches the transmission / reception channel to the designated channel, and transmits a channel assignment request from the channel with its own MAC address as additional information.

(5) Upon receiving the channel assignment request, if the MAC address of the reserved channel matches the MAC address of the additional information of the channel assignment request, the base station transmits the short address as the additional information of the channel assignment response.

(6) Thereafter, the base station and the radio device can use the assigned short address during communication.

As described above, according to the third embodiment of the present invention, even if an access contention or the like occurs for a certain channel, if another channel in the system is empty, the wireless terminal that has lost the access contention Communication can be started without generating an invalid delay time.

Incidentally, in order to construct a more efficient wireless transmission system, all the inventions of the above-described first to third embodiments may be combined.

In the present specification, means does not necessarily mean physical means, but also includes a case where the function of each means is realized by software.
Further, the function of one unit may be realized by two or more physical units, or the function of two or more units may be realized by one physical unit.

[Brief description of the drawings]

FIG. 1 is a schematic flowchart of the operation of a base station (BS) according to Embodiment 1 of the present invention.

FIG. 2 is a schematic flowchart of an operation of the personal station (PS) according to the first embodiment of the present invention.

FIG. 3 is a conceptual diagram of a wireless transmission system according to the first embodiment of the present invention.

FIG. 4 is a detailed flowchart of an operation of the base station (BS) according to the first embodiment of the present invention.

FIG. 5 is a detailed flowchart of the operation of the base station (BS) according to the first embodiment of the present invention (continued).

FIG. 6 is a detailed flowchart of an operation of the personal station (PS) according to the first embodiment of the present invention.

FIG. 7 is a detailed flowchart of the operation of the personal station (PS) according to the first embodiment of the present invention (continued).

FIG. 8 is a state transition diagram of the channel sharing protocol according to the first embodiment of the present invention.

FIG. 9 is a timing chart illustrating channel access and token transmission according to the first embodiment of the present invention.

FIG. 10 is a timing chart for explaining an operation when an error occurs in the first embodiment of the present invention.

FIG. 11 is a schematic configuration diagram of a wireless transmission system.

FIG. 12 is an example of a format according to the first embodiment of the present invention.

FIG. 13 is an example of a format of free channel information (FCI) according to the first embodiment of the present invention.

FIG. 14 is a diagram showing throughput versus load characteristics in the channel sharing protocol according to the first embodiment of the present invention.

FIG. 15 is a diagram showing a throughput versus load characteristic comparing the channel sharing protocol according to the first embodiment of the present invention with a collision carrier sensing multiple access / avoidance function (CSMA / CA).

FIG. 16 is a diagram illustrating throughput versus load characteristics when the number of personal stations per channel is changed in the channel sharing protocol according to the first embodiment of the present invention.

FIG. 17 shows an example of a format of channel busy / idle management data according to the second embodiment of the present invention.

FIG. 18 shows a format of channel status management data according to the second embodiment of the present invention.

FIG. 19 shows an example of a channel assignment request frame structure according to the second embodiment of the present invention.

FIG. 20 shows an example of a channel assignment response frame structure according to the second embodiment of the present invention.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Isao Tonegawa 2-12-7 Hatchobori, Chuo-ku, Tokyo Inside Uniden Corporation

Claims (17)

[Claims] In a data transmission system including a first device for controlling communication and a plurality of second devices, data communication for wirelessly performing data communication through a channel allowing a plurality of second devices at the same time. A method for receiving in-channel vacancy information transmitted by the first device and indicating that the channel is not full, wherein the second device receives in-channel vacancy information; and A channel requesting step in which the second device issues a channel request; a designation information receiving step of receiving designation information transmitted by the first device in response to the channel request; and And a data transmitting step of transmitting the data. 2. The method according to claim 1, further comprising the step of: adjusting a contention by a p-persistence algorithm when a plurality of second devices simultaneously issue a channel request. Data communication method described. 3. In response to the channel request, when receiving designation information transmitted by the first device, if there is no data to be transmitted, the second device transmits transmission data absence information. 2. The data communication method according to claim 1, further comprising a transmission data absence information transmitting step. 4. The data communication method according to claim 1, wherein, after the channel request is made, the designated information is repeatedly transmitted, and the designated second device responds to the designated information. 5. The apparatus according to claim 4, wherein the first device repeatedly transmits the designated information a predetermined number of times when there is no response from the designated second device.
The data communication method described in 1. 6. The method according to claim 1, further comprising: transmitting the specified information repeatedly a predetermined number of times, even after repeating the predetermined number of times, when there is no response from the specified second device. The data communication method according to claim 5, wherein the device cancels the designation of the designated second device. 7. A channel information step in which when the plurality of channels are present, the second device receives channel information transmitted by the first device and indicating a vacant channel, the second device based on the channel information. 2. The data communication method according to claim 1, further comprising a channel selecting step of selecting a channel by the device. 8. The data communication method according to claim 7, wherein the channel information is transmitted simultaneously on the plurality of channels at predetermined intervals. 9. The first device includes a memory in which a table including a plurality of shortened addresses is stored in advance, and in the channel requesting step, the second device includes:
The first device transmits its own address information together with the channel request, the first device stores the address information sent from the second device in a predetermined position of the table, and transmits a corresponding shortened address, 2. The data communication method according to claim 1, wherein when the device transmits the shortened address, the first device converts the shortened address to an original address based on the table and transmits the converted address to the outside. 10. The channel requesting step,
A contention adjustment step of performing adjustment when a plurality of second devices simultaneously issue a channel request, wherein in the contention adjustment step, the first device is different from the second device for which no channel request was granted. Vacant channels are reserved, and the reservation information of the other channels can be assigned to another channel.
The data communication method according to claim 1, wherein the data is transmitted to two devices. 11. A data communication system, comprising: a first device for controlling communication; and a plurality of second devices, wherein the data communication system wirelessly performs data communication through a channel that simultaneously allows the plurality of second devices. The first device transmits in-channel vacancy information indicating that the channel is not full, the second device receives the vacancy information in the channel, and the second device, which is about to receive the channel assignment, A data communication system, wherein the first device transmits designation information to the second device in response to the channel request, and the second device receiving the designation information transmits data. . 12. The first device further adjusts when a plurality of second devices issue a channel request at the same time, and adjusts the first device with respect to a second device for which no channel request has been granted. 12. The method according to claim 11, wherein another reserved channel is set in a reserved state, and that another channel can be allocated, and reservation information of the another channel is transmitted to the second device. Data communication system. 13. A data transmission system including a communication control device for controlling communication and a plurality of terminal devices, the communication control being used for wirelessly performing data communication through a channel allowing a plurality of terminal devices at the same time. A device, which transmits in-channel free information indicating that the channel is not full, and transmits a designated information in response to a channel request from the terminal device, and receives the channel assignment. And a wireless receiving unit for receiving a channel request issued by the terminal device. 14. The communication control device includes a memory in which a table including a plurality of shortened addresses is stored in advance, and the communication control device stores address information sent from the terminal device at a predetermined position in the table. And transmitting the corresponding shortened address, and when the terminal device transmits the shortened address, converting the shortened address to the original address based on the table and then transmitting the converted address to the outside. Item 14. The communication control device according to item 13. 15. When there are a plurality of said channels,
14. The communication control device according to claim 13, wherein the wireless transmission unit transmits channel information indicating a vacant channel. 16. In a data transmission system including a communication control device for controlling communication and a plurality of terminal devices, a terminal device used for wirelessly performing data communication through a channel allowing a plurality of terminal devices at the same time. And receiving in-channel free information indicating that the channel is not full and receiving designation information transmitted by the communication control device in response to a channel request issued by the communication control device. A terminal device comprising: a wireless receiving unit; and a wireless transmitting unit that, when trying to receive the channel assignment, issues the channel request and transmits data when receiving the designation information. . 17. When there are a plurality of said channels,
17. The terminal device according to claim 16, wherein the wireless reception unit receives channel information transmitted from a communication control device, and selects a channel based on the channel information.