Patent Application
20130301629
1. Field of the Invention
This invention relates to a communication apparatus, a method of communication, and a program executing a process for communication, which are preferably applicable to, for example, a wireless LAN (Local Area Network) system for data communication.
2. Description of Related Art
Conventionally, in wireless communication in which a predetermined transmission unit of packets are collectively transmitted, it is general that a structure of packet information of each transmission unit is determined in advance and the packet information is added to each packet to be transmitted.
On the other hand, in a rate variable transmission method for a general wireless communication system, it is known that transmission is carried out by a mechanism called fall back at a possible highest rate. When an error occurs, the transmission rate is decreased to a predetermined transmission rate for re-transmission.
In a rate variable control method for these wireless communication systems, there was proposed one in which header information includes rate information regarding a modulation process of a payload portion on the basis of a predetermined frame format. In the method, in a case where the header information can be decoded, a desired payload portion is decoded at a rate that is changed to the rate of the modulation process.
Here, in the conventional wireless communication system, a possible transmission rate is substantially determined in accordance with a bandwidth of a signal used in the wireless communication.
That is, in a certain wireless communication system, since a data rate for transmitting an application is substantially determined in accordance with its bandwidth. For example, an IEEE (The Institute of Electrical and Electronics Engineers) 802.11b-compliant wireless communication system has been designed to use a data rate of several megabits/sec and an IEEE 802.11a-compliant wireless communication system has been designed to use a data rate of tens megabits/sec.
Therefore, a fragment process and a frame structure, optimized for each wireless communication system, are specially prepared as a unique structure for each system.
The MAC header of this wireless communication system includes information such as a packet type, a transmission source station ID, a transmission destination station ID, a relay station ID, a B/E flag, a sequence number, and a data length (Length).
In such an existing wireless communication system, the MAC header information is formed in which information pieces of address information such as a destination and a transmission source, a sequence number, a data length, and presence and absence of a fragment are mixed.
In the figure, a MAC header includes a Frame Control (two Octets), a PN ID (two Octets), a Destination DEV ID (one Octet), a Source DEV ID (one Octet), a Fragmentation Control (three Octets), and a Stream Index (one Octet).
This case features that all address information pieces are represented by a DEV ID (device identifier). Further, contents of a predetermined fragment process are represented by a predetermined bit at a Fragmentation control field. In addition to the MAC header, a Frame Body (variable length) as a data payload and an FCS (4 Octets) for error detection constitutes a frame. Though it is not shown between the MAC header and the MAC frame in the figure, a header check sequence (HCS) may be further provided.
The MAC header includes a Frame Control (two Octets), a Duration ID (two Octets), an Address 1 (six Octets), an Address 2 (six Octets), an Address 3 (six Octets), a Sequence Control (two Octets), and an Address 4 (six Octets). In addition, a frame body (0-2312 Octets) as a data payload and FCS (four Octets) are also included therein.
Address fields of the Address 1 to the Address 4 in this configuration are occasionally assigned to a source address, a destination address, or the like, if necessary. Further, sequence number information and the like are described at the Sequence Control field.
In this fragment structure, a predetermined MSDU is divided into four fragments, namely, Fragment 0 to Fragment 3. A MAC header and a CRC (Cyclic Redundancy Check) are added to each fragment. It is understood that, when the fragmentation process is executed, MAC header information is attached to each fragment.
It is also understood that even if such a data frame format is adopted, a sequence number and fragment information of a data payload are necessary for each sequence, but the reception destination address information and the transmission source address information and the like are commonly used.
The Patent Document 1 cited below discloses an example of such a header structure.
[Patent Document 1]
Japanese Patent Application Publication No. Hei 10-247942
As described above, in the related art frame format, the MAC headers are generally multiplexed as they are. Thus, there is a problem that redundant fields such as address information exist at the MAC header more than the necessity.
Further, in a case where a predetermined transmission unit of packets are transmitted collectively, the same information such as address information is included as header information during transmission at each packet. Thus, there is a problem that such header information becomes redundant.
In view of the problem described above, the present invention provides effective packet construction suitable for a case of employing a communication system such as a wireless LAN system.
According to an aspect of the present invention, in a case of wireless communication with another communication apparatus through a predetermined wireless communication network, overhead information defined at a media access control layer is divided into a first header including data necessary for common access control and a second header including data necessary for each payload, in which address information is added to the first header including the data necessary for the common access control, and the generated headers are added to transmission data for transmission.
For example, in a case of forming a physical burst (PHY burst) with a plurality of data payloads combined into one, this structure provides a frame configuration without useless repetition of the address information.
According to the present invention, overhead information defined in a MAC layer is formed with a single piece of common MAC header information and a sub-MAC header in a frame structure. This efficiently provides a data frame and a corresponding control information frame.
In addition, in a case of transmitting a plurality of data payloads in the form of a single frame (burst), only the sub-MAC header is added to each payload, which results in configuration of a frame with minimum requirement parameters.
Further, since a frame is formed with portions (a PHY header and the common MAC header) transmitted at a known fixed transmission rate and the other portions (the sub-MAC header and the data payload) transmitted at a variable transmission rate, in a case where a plurality of frames are sequentially connected to form a frame, a transmission frame can be provided with compression for overlapped information in the MAC header information.
In addition, since the address information is described at the common MAC header, and its error detection code is added thereto, only the information of which address can be correctly decoded is instantaneously obtained.
Still furthermore, length information and a sequence number of the data payload length, a sequence number, and fragment information are added to the sub-MAC header, so that the information in the common MAC header is allowed to include only minimum requirement information.
Furthermore, at the PHY header, rate information used for the data payload is informed, so that a margin can be provided for a time interval from when the rate is specified until the rate is actually changed.
In addition, fragmentation process in which the data payload formed using the sub-MAC header is fragmented at a predetermined length provides a suitable frame structure for cases using various ARQ methods.
Since the description of the fragment unit at the common MAC header prevents the error from affecting the later part, even in a case where there is an error in the data, thus providing a frame structure efficient, for example, for the selectively repeat ARQ.
Forming the common MAC headers in the same configuration between a control information frame and a data frame provides easy multiplexing, so that a single burst can be simply formed.
Forming the control information frame in the predetermined common MAC header structure makes multiplexing a plurality of control information frames easy, so that a single burst can be simply formed.
The object and features of the present invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawings and the same or corresponding elements or parts are designated with like references throughout the drawings in which:
An embodiment of the present embodiment will be described below with reference to
This embodiment assumes that a propagation path of communication is wireless and that a network is formed among a plurality of apparatuses with a single transmission medium (a link is not divided with frequency channels). However, if a plurality of frequency channels exist as a transmission medium, the same result can be achieved also. Further, the communication assumed in this embodiment is a stored and forward type traffic in which information is transmitted in a packet unit. Further, the network according to this embodiment is an ad hoc network in which there is no control station for controlling overall stations in the network. However, the present invention is applicable to a network including a control station, as mentioned later.
In
The communication apparatus 1 exits in an area communicable with the adjacent communication apparatuses 2, 3, and 7.
The communication apparatus 2 exits at in area communicable with the adjacent communication apparatuses 1 and 3.
The communication apparatus 3 exits in an area communicable with the adjacent communication apparatuses 1, 2, and 5.
The communication apparatus 4 exits in an area communicable with the adjacent communication apparatus 5.
The communication apparatus 5 exits in an area communicable with the adjacent communication apparatuses 3, 4, and 6.
The communication apparatus 6 exits in an area communicable with the adjacent communication apparatus 5.
The communication apparatus 7 exits in an area communicable with the adjacent communication apparatus 1.
In this embodiment, each communication apparatus performs an access control process in which one wireless transmission path is time-divisionally used with consideration of influence among the communication apparatus and the adjacent other communication apparatuses.
The wireless communication apparatus further includes a central control section 10 for unitedly effecting control of both a sequential information transmission and reception process and an access control of the transmission path. The wireless communication apparatus further includes a burst generation section 13 for generating a frame burst from the transmission data as a processing section executing transmission process under the control of the central control section 10, a common header information and control information generation section 14 for generating a common MAC header information and control information, and a wireless transmission section 16 for transmitting these information. The burst generation section 13 of the present example includes a sub-header generation section 13a for generating sub-header information in a predetermined unit. A preamble specified by a preamble insertion section 17 is inserted into a packet to be transmitted by the wireless transmission section 16.
The wireless communication apparatus further includes, as a processing section for a reception process under the control by the central control section 10, a wireless reception section 20 receiving an reception signal, a common header information/control information analyzing section 21 for analyzing the common header information and the control information in the signal received by the wireless reception section 20, and a burst analyzing section 22. Reception in the wireless reception section 20 is executed at a timing depending the detection of a preamble in a preamble detection section 19.
Transmission process in the wireless transmission section 16 and reception process in the wireless reception section 20 are performed at a timing under control of an access control section 15, respectively. The wireless transmission section 16 executes a modulation process, for example, for an Ultra Wideband (UWB) signal on a signal to be transmitted. The wireless reception section 20 executes a demodulation process, for example, for the Ultra Wideband (UWB) signal on a received signal and supplies demodulated data to a later stage of a circuit. An antenna 18 for transmitting and receiving a wireless signal is coupled to the wireless transmission section and the wireless reception section 20. Here, it is also possible to prepare individual antennas for the transmission and the reception, respectively. Further, it is also possible to prepare a plurality of antennas to provide so-called diversity reception.
A common header information/control information analyzing section 21 extracts a common header section from the received signal and analyzes it. The burst analyzing section 22 analyzes the structure of a received data burst from the received common header information. The burst analyzing section further includes a sub-header analyzing section 22a for analyzing sub-headers in the received data burst. The burst analyzing section 22 recognizes the data received in a sub-header unit and includes an ACK information generation section for generating ACK information indicative of the reception confirmation. An information storing section 24 is further coupled to the central control section 10, as storing regions of the information storing section 24, an access control information storing section 24a and a rate information storing section 24b necessary for constituting the burst.
The above description is made with an example of the UWB system as a wireless communication system. However, it is also possible to use other various communication systems applicable, for example, to a wireless LAN, and suitable for communication having a relative near field communication. More specifically, as a system other than the UWB system, the OFDM (Orthogonal Frequency Division Multiplex) method, the CDMA (Code Division Multiple Access) method, and the like are applicable.
Next, transmission conditions at the wireless communication apparatuses in the network of this example will be described with reference to
In this example, the transmission source apparatus transmits a request to send RTS to the reception destination apparatus. After a lapse of a predetermined interval SIFS, the reception destination apparatus returns a confirmation notice CTS to the transmission source apparatus. After a lapse of a predetermined interval SIFS, the transmission source apparatus transmits a data frame to the reception destination apparatus. After a lapse of a predetermined interval SIFS, the reception destination apparatus returns an acknowledge ACK to the transmission source apparatus.
The preamble includes a predetermined known sequence common among all wireless communication apparatuses and is provided for synchronization of data in an asynchronous data communication.
The PHY header used in a process in the physical layer includes sections of: a frame type (eight bits) indicative of the type of the frame in the data frame (burst) (frame type: eight bits); data of a total data length of the burst (total data length: twelve bits); data of a setting rate for the data payload section (four bits); duration of the data frame (burst) (duration: six bits); and a parity bits (parity: two bits). These numbers of bits are only examples, and the setting rate data for the data payload section is also indicative of a transmission rate of the sub-MAC header.
The MAC header is a header necessary for access control within the network and is divided into a common MAC header and a sub-MAC header in this example. The common MAC header includes sections of: an address of a reception apparatus (reception address: six bytes); an address of a transmission apparatus (transmission address: six bytes); a frame type indicative of the type of this MAC frame (frame type: one byte); a type of ARQ requested for the confirmation of receiving the data (ARQ type: one byte); a fragment size of the data payload (fragment size: two bytes); and a header check sequence (HCS: four bytes). Here, the numbers of bytes are only examples.
The sub-MAC header includes sections of: a payload length (payload data length: two bytes); a sequence number (one byte); and a sequence number in a case of fragmentation (fragment sequence number: one byte). The numbers of bytes herein are only examples. If necessary, it is also possible to add a header check sequence (HCS: four bytes) (not shown) for detecting an error at the sub-MAC header.
There are ARQ types usable for this wireless communication system such as a Stop-and-Wait ARQ (SW-ARQ), a Go-Back N ARQ (GBN-ARQ), and a selective repeat ARQ (SR-ARQ).
Each data payload is controlled with each sequence number (sequence #1, #2, #3) described in the sub-MAC header, has a data length represented by the payload data length in the sub-MAC header, and has the frame check sequence (FCS) thereafter for error detection and error correction.
This enables the transmission in which data frames directed to the same destination are efficiently combined into one burst.
The data payload in a sequence, herein, the sequence #1, is divided into fragments (three parts in this example) on the basis of the Fragment Size information and each part is dealt as one data payload.
To each data payload, a sub-MAC header (SMH) and a frame check sequence (FCS) are added to enable error detection and error correction, so that a resending control is provided at this fragment unit.
In this example, because only the last payload has a length less than the fragment size, the Payload Length in the sub-MAC header for the fragment #3 indicates this.
The ACK frame shown in
The ACK frame includes sections of: an address of a reception apparatus (reception address: six bytes); an address of a transmission apparatus (transmission address: six bytes), a frame type indicative of the type of this MAC frame (frame type: one byte); an ACK sequence number (ACK sequence); bit map information (ACK bit map: two bytes) indicative of received parts in a case of fragmenting the ACK sequence; and a header check sequence (HCS: four bytes) for error checking the ACK frame. Here, the numbers of bytes are only examples.
The RTS frame shown in
The RTS frame includes sections of: an address of a reception apparatus (reception address: six bytes); an address of a transmission apparatus (transmission address: six bytes); a frame type indicative of the type of this MAC frame (frame type: one byte); an amount of the queued data to be transmitted (queuing size: two byte); a not-defined region for future extension (one byte); and a header check sequence (HCS: four bytes) for error checking the RTS frame.
The CTS frame shown in
The CTS frame includes sections of: an address of a reception apparatus (reception address: six bytes); an address of a transmission apparatus (transmission address: six bytes); a frame type indicative of the type of this MAC frame (frame type: one byte); rate information (available rate: one byte); a not-defined region for future extension (one byte); and a header check sequence (HCS: four bytes) for error-checking the CTS frame.
In this example, subsequent to a preamble and a PHY header, as a control information frame, an RTS frame is arranged. The RTS frame has the structure, for example, shown in
In the example shown in
Next, a process for the communication operation by the central control section 10 in each wireless communication apparatus within the network will be described with reference to flow charts shown in
If the wireless transmission is possible, a header setting process is executed (step S3) and the processing returns to step S1. If the transmission is impossible, the processing directly returns to step S1.
If the data is not received in step S1, it is judged whether there is transmission-waiting data (step S4). If there is transmission-waiting data, a transmission activation process is executed (step S5). After this, the processing returns to step S1.
In step S4, if there is no transmission-waiting data, it is judged whether the wireless communication operation is necessary (step S6). If the wireless communication operation is necessary, the wireless communication operation is executed (step S7) and then, the processing returns to step S1. Further, in step S6, if the wireless communication operation is unnecessary, the processing directly returns step S1.
Next, with reference to the flow chart in
Next, the sub-MAC header is set using the sequence number, the information of the fragmentation process, a data length, and the like (step S15). The data is set as transmission-waiting data (step S16), and the processing returns to the main routine.
Next, with reference to the flow chart shown in
When the transmission right is acquired, the RTS frame of which setting has been done is transmitted (step S23). Further, to receive the CTS transmitted from the reception destination apparatus just after this, a setting is made (step S24) for its own reception region just after the transmission. Then, the processing terminates the sequential processes and returns to the main routine.
Next, with reference to the flow chart in
Further, the common MAC header is received and the data is stored (step S35). It is confirmed whether the signal is directed to this apparatus with reference to the address information (step S36). In the step S36, when the Preamble cannot be detected and when the signal is not directed to this apparatus, the processing returns to the step S31 to repeat this operation. In the step S36, when the signal is directed to this apparatus, it is judged which type of the frame is transmitted with reference to the frame type information in the common MAC header.
In a case where it is determined that the type of the frame is a data frame (step S37), the rate for the data payload is set (step S38) with the rate information stored in step S34. Next, a reception process for the data payload is carried out (step S39). Further, in accordance with success or fail in the reception of the data, AKC information is generated (step S40). A replying process of the ACK is carried out just after the reception (step S41), and the processing terminates the sequential processes and returns to the main routine.
In a case where it is determined that the frame is not a data frame in the step S37, it is judged whether or not the frame is an RTS frame (step S42). In a case where an RTS frame is received, in accordance with the receiving condition of the RTS frame, an available transmission rate is set for the data section (step S43). Further, the transmission source of the RTS frame is set to the reception destination address, and with these pieces of information, settings are made for the CTS frame (step S44). Just after this, a replying process of the CTS is performed in Step S45. Next, the receiving region of the data is set in step S46, and the processing terminates the sequential processes and returns to the main routine.
In a case where it is determined that the frame is not an RTS frame in the step S42, it is judged whether or not the frame is a CTS frame (step S47). If the CTS frame corresponding to the RTS frame transmission from this apparatus is received, the rate information described at the common MAC header is referred (step S48). With the stored data, the setting is made for the data burst (step S49), and an actual data transmission process is performed (step S50). Further, the reception region of the ACK is set (step S51), and the processing terminates the sequential process and returns to the main routine.
In a case where it is determined that the frame is not a CTS frame in the step S47, it is judged whether or not the frame is an ACK frame (step S52). If an ACK frame is received, it is judged whether or not there is a re-transmission request from the ACK information (step S53). If there is a re-transmission request, the data to be re-transmitted is acquired (step S54), and a setting is made to deal with the data as transmission-waiting data (step S55). The processing terminates the sequential processes and returns to the main routine.
When it is without the setting interval of the reception region in step S31, when any ACK is not received in step S52, and when re-transmission is unnecessary in step S53, the processing terminates sequential processes and returns to the main routine.
The above embodiment is described with an example of a special communication apparatus for transmission and reception shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| P2003-139547 | May 2003 | JP | national |
This application is a continuation of U.S. application Ser. No. 12/781,370, filed on May 17, 2010, which is a continuation of U.S. application Ser. No. 10/834,798, filed on Apr. 29, 2004, which is based on Japanese Priority Document JP 2003-139547, filed in the Japanese Patent Office on May 16, 2003, the disclosures of which are being incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12781370 | May 2010 | US |
| Child | 13941952 | US | |
| Parent | 10834798 | Apr 2004 | US |
| Child | 12781370 | US |
