JP4137083B2 - Wireless data communication method and system - Google Patents

Description

  The present invention relates to a wireless data communication method and system, and more particularly, to a wireless data communication method and system suitable for P-MP wireless data communication.

  Non-Patent Document 1 defines a standard for high-speed wireless data communication (IEEE802.16). The IEEE802.16 physical layer supports single carrier, OFDM (Orthogonal Frequency Division Multiplexing) and OFDMA (Orthogonal Frequency Division Multiple Access) as modulation schemes. Hereinafter, a wireless data communication method compliant with IEEE802.16 will be described by taking as an example a case where OFDM is used as a modulation method.

  IEEE 802.16 defines P-MP (point-to-multipoint) as one of the communication modes. In this P-MP, BS (radio base station) transmits and receives all SS (subscriber terminals). Scheduling opportunities enables efficient communication and guaranteed quality of service (QoS).

  FIG. 16 is a diagram illustrating an example of an OFDM frame configuration in the P-MP scheme, and is included in the broadcast message field in the first DL (downlink) burst following the preamble and FCH (Frame Control Header). Scheduling information is stored in the MAP message.

  In this scheduling information, downlink slot information and uplink slot information to be assigned to each SS are stored, and the SS receives these pieces of information to determine when the data for itself arrives and You can know when to send data. Hereinafter, the MAP message included in the broadcast message field in the first DL burst following the FCH is simply expressed as a MAP message.

  Each BS is given a 48-bit unique identifier called Base Station ID (BSID), and the SS identifies each BS by BSID. The upper 24 bits of the BSID identify the business operator, and each BS is identified by the lower 24 bits within the same business operator.

  FIG. 17 is a diagram showing a frame structure of a MAC (Media Access Control) header defined by IEEE 802.16. A connection ID for uniquely identifying a connection is given to each connection. A space for this connection ID is prepared in the MAC header of IEEE802.16, and BS and SS identify a packet by this connection ID.

  The SS performs a process called ranging in order to adjust the transmission / reception timing and transmission power with the BS when joining the network and periodically after joining. When joining the network, ranging is performed during the initial ranging period assigned by the BS. The initial ranging period is contention-based, and the SS transmits an RNG-REQ (ranging request) message to the BS during this period. The BS that has received the RNG-REQ, if SS adjustment is necessary, information such as transmission output, frequency, transmission timing, etc. RNG-RSP with ranging continuation notification (Ranging Status = continue in RNG-RSP) Register to the (ranging response) message and respond to the SS.

  The SS that has received the ranging continuation notification RNG-RSP adjusts the transmission output, frequency, and transmission timing, and then transmits the RNG-REQ to the BS again in the initial ranging period allocated from the BS to the SS. When the transmission output of the SS satisfies a preset value, the BS returns an RNG-RSP with a ranging success notification (Ranging Status = success in the RNG-RSP) to the SS.

  Such ranging ends when an RNG-RSP accompanied by a ranging success notification is received by the SS. The ranging performed after the SS participates in the network is performed in the same initial ranging period as in the network participation or the initial ranging period allocated for the SS.

The BS transmits data to the SS using a burst profile described in “Downlink Operational Burst Profile” of RNG-RSP. SS transmits data to BS using burst profile described in UIUC of UL-MAP. The burst profile described in UIUC of this UL-MAP is specified by BS. Here, the burst profile is a parameter set such as a modulation scheme or FEC code type.
IEEE Standard for Local and metropolitan area networks-Part 16: Air Interface for Fixed Broadband Wireless Access Systems, IEEE 802.16 -2004, Oct, 2004.

  In wireless data communication, there is a dead zone where the SS cannot communicate with the BS even though the SS is in the service area due to the influence of radio wave attenuation caused by shielding by obstacles located between the transmitting and receiving antennas. In order to perform high-speed wireless data communication, it is necessary to use a high frequency. However, since the wavelength is short and the straightness of radio waves increases, it is expected that the dead zone will increase. As a method of eliminating such dead zones, it is conceivable to install a relay station between BS and SS.

  However, when a relay station is added to the P-MP wireless data communication system, communication opportunities for ranging requests and bandwidth requests are indirectly transmitted to subscriber terminals that communicate directly with the radio base station via the relay station. When compared with subscriber terminals that communicate with each other, inequality occurs. That is, a subscriber terminal that performs indirect communication requires a communication opportunity that the relay station requests from the relay station and a communication opportunity that the relay station further requests from the radio base station. It will be disadvantageous.

  An object of the present invention is to solve the above-described problems of the prior art and in a P-MP wireless data communication, a subscriber terminal that communicates directly with a wireless base station and a subscriber that communicates indirectly via a relay station It is an object to provide a radio communication system and a communication direction thereof in which communication opportunities are given equally to terminals.

In order to achieve the above-described object, the present invention provides a P-MP wireless data communication method in which a plurality of subscriber terminals are accommodated in one wireless base station, wherein the wireless base station and each subscriber terminal are connected to each other. A relay station for relaying communication is provided, and the following means are further included.
(1) The relay station includes a procedure for receiving a communication opportunity request message from a subscriber terminal, and a procedure for the relay station to transfer the request message to a radio base station. Receiving a request message from the relay station, receiving a request message from the relay station, and returning a response message notifying a communication opportunity assigned to the request source to the request message, Individual communication opportunities are assigned to the subscriber terminal and the relay station.
(2) The communication opportunity assigned to the subscriber terminal is contention-based, and the communication opportunity assigned to the relay station is not contention-based.
(3) The communication opportunity assigned to the relay station is dynamically set based on the amount of data transmitted and received between the relay station and the radio base station.

According to the present invention, the following effects are achieved.
(1) In P-MP wireless data communication, individual communication opportunities are assigned to subscriber terminals and relay stations that can directly communicate with the radio base station, and both do not compete with each other. It will be given equally.
(2) While the communication opportunity assigned from the radio base station to the subscriber terminal is contention-based, the communication opportunity assigned from the radio base station to the relay station is not contention-based. As long as the user terminal can communicate with the relay station, it can reliably communicate with the radio base station.
(3) Since the communication opportunity assigned to the relay station is dynamically set based on the amount of data transmitted and received between the relay station and the radio base station, it is possible to accommodate subscriber terminals of relay stations with a large number of accommodated terminals. Communication opportunities are given equally to subscriber terminals of relay stations with a small number of terminals.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a network configuration to which a P-MP wireless data communication method according to the present invention is applied. Subscriber terminals SS1 and SS2 are located within the radio wave coverage of a wireless base station BS. So you can communicate directly with the BS. On the other hand, since the subscriber terminals SS3 and SS4 are located outside the BS radio wave reachable range, they communicate with the BS via the relay station RS located within the BS radio wave reachable range.

  FIG. 2 is a diagram showing a frame structure of a MAC header attached to a packet transmitted / received in the present embodiment, and is compliant with a frame structure of a MAC header (FIG. 17) defined by IEEE802.16. . In this embodiment, one of the reserved bits of the MAC header is used for encapsulation (encap bit), and when this bit is “1”, it is assumed that MAC encapsulation is performed. When this bit is “0”, it is the same as the IEEE 802.16 MAC header.

  FIG. 3 is a diagram illustrating an OFDM frame configuration according to the present embodiment. Compared with the OFDM frame configuration (FIG. 16) defined by IEEE 802.16, the initial ranging period for RS is included in the uplink subframe. And a BW (bandwidth) request period, and a remaining message count notification period for each RS to notify the BS of the remaining message count. These periods are not contention-based, but each RS-dedicated band defined in UL-MAP. FIG. 4 shows an example of UL-MAP IE (Information Element) in UL-MAP in this case. In the example of FIG. 4, an initial ranging period is allocated for RS1 for a length of 11110 symbols from time t1. Here, the BS gives each RS a CID for initial ranging and a CID for BW request.

  The SS under either BS or RS makes a ranging request and a bandwidth request according to IEEE802.16 in a contention period assigned by the BS. The RS that has received the RNG-REQ and the bandwidth request from the SS encapsulates the message in the RS initial ranging period and BW request period allocated from the BS and transmits (transfers) the message to the BS. Further, the number of messages transferred from all subordinate SSs is transmitted to the BS during the remaining message count notification period. Here, since each period during which the RS transmits the RNG-REQ, the bandwidth request, and the number of messages is not contention-based, it can be delivered to the BS without causing packet collision.

  Next, the operation of this embodiment will be described with reference to the flowcharts of FIGS. 5 and 6 and the time chart of FIG. In the present embodiment, the subscriber station SS that can directly communicate with the base station BS without going through the relay station RS operates in accordance with IEEE 802.16, and thus the description thereof is omitted.

  FIG. 5 is a flowchart showing the RNG-REQ message reception process in the relay station RS. The RS transmits the RNG-REQ message transmitted by the subscriber station SS3 to perform the ranging process with the RS in step S101. If it receives, it will progress to step S102. In step S102, it is determined whether or not the entry of the transmission source (SS3) of the received RNG-REQ message is registered in its own management table. If not registered, the process proceeds to step S103, and parameters such as received power are registered in the management table in association with the address of SS3. In step S104, the received RNG-REQ message is encapsulated with a MAC header destined for the BS and transmitted in the initial ranging period for the RS. The BW request message received from SS3 is similarly encapsulated and transmitted to the BS during the RS BW request period.

  In step S105, the number of messages received from all the SSs under control of the RS is totaled, and this is reported as the remaining message number to the BS during the remaining message number notification period. In the BS, the amount of data transmitted / received between the BS and RS is predicted based on the number of remaining messages notified from each RS, and the communication slot allocated to each RS is dynamically determined based on the prediction result. That is, more communication slots are allocated to an RS having a large amount of data. In this embodiment, the amount of data transmitted / received between the BS and RS is represented by the number of remaining messages, but may be represented by the total number of SSs under the RS.

  FIG. 8 is a diagram schematically illustrating how the RNG-REQ message transmitted from SS3 is encapsulated in RS and transferred to base station BS. In RS, the RNG-REQ message received from SS3 is transmitted. The transmission source is the local station (RS), and the encap bit is encapsulated with the MAC header set to “1” and transmitted to the BS.

  In this embodiment, the SS3 that has transmitted the RNG-REQ message determines whether the receiving party is an RS or a BS. If the receiving party is a BS, the first reference time Tref1 is set in the retransmission timer T1. If the reception partner is RS, a second reference time Tref2 longer than the first reference time Tref1 is set in the retransmission timer T1. Then, after the RNG-REQ message is transmitted, the RNG-REQ message is retransmitted when the retransmission timer T1 times out before the RNG-RSP message as a response to the RNG-REQ message is received.

  FIG. 6 is a flowchart showing message reception processing in the base station BS. When the BS receives the RNG-REQ message relayed by the RS in step S201, whether or not the message is encapsulated in step S202. Is determined with reference to the encap bit of the MAC header. Here, since the encap bit is set to “1” and it is determined that it is encapsulated, the process proceeds to step S203. In step S203, the capsule is released. In step S204, it is determined whether or not the encapsulated message is RNG-REQ. Here, since it is determined as an RNG-REQ message, the process proceeds to step S205.

  In step S205, the CID of the SS3 is created. In step S206, parameters such as “MAC address”, “CID”, and “connection destination” are registered in the management table. In step S207, an RNG-RSP message that is a response to the RNG-REQ message is created. In step S208, a destination MAC header corresponding to SS3 and a relay MAC header corresponding to RS are created. In step S209, the RNG-RSP message provided with the destination MAC header is encapsulated with the relay MAC header and transmitted to the RS.

  FIG. 9 is a diagram showing an example of the management table created for managing each SS in the BS, in which the MAC address and connection destination (@) of each SS are registered. In the case of SS3, an RS address is registered as the connection destination @.

  FIG. 10 is a diagram schematically showing a state in which an RNG-RSP message encapsulated from a BS is decapsulated by RS and transferred to SS3. From the BS, the destination MAC address is SS3. The RNG-RSP message to which the header is attached is encapsulated with a MAC header in which the destination is RS and the encap bit is set to “1”, and is transmitted.

  Returning to FIG. 5, when the RS receives the encapsulated RNG-RSP message in step S106, the RS decapsulates in step S107, and in step S108, the transmission output measured when the RNG-REQ message is received from SS3. In addition to the RNG-RSP message, TLV (Type / Length / Value) and the like for adjusting the frequency are transmitted to SS3. In step S109, a ranging process is executed with SS3. In step S110, a ranging message (RNG-INFO) is transmitted to the BS.

  FIG. 11 is a diagram showing a configuration of RNG-INFO used in the present invention, and RNG-INFO includes a downlink burst profile and an uplink burst profile adopted between RS-SS. .

  Returning to FIG. 6, when the RNG-INFO is received in step S210, the BS proceeds to step S211 and an SS3 entry is added to the management table as shown in FIG.

  FIG. 13 is a diagram showing the contents of the management table created by the BS in the network configuration shown in FIG. 1. For the subscriber stations SS1 and SS2 located within the radio wave reachable range, the connection destinations are shown. While the own address (BS) is registered as @, for the subscriber stations SS3 and SS4 located outside the radio wave coverage, the relay station address (RS) is registered as the connection destination @ Has been.

  When the RS receives an RNG-REQ message from an SS whose entry is already registered in the management table in step S102 in FIG. 5, the process proceeds to step S116, and whether parameters such as a burst profile registered in the message have been changed. It is determined whether or not. If the change is confirmed, the process proceeds to step S117, and the changed burst profile is registered in the RNG-INFO message and transmitted to the BS. In step S118, RNG-RSP is returned to the SS.

  FIG. 14 is a flowchart illustrating a procedure in which a BS that has received a message addressed to an SS transfers the message to the SS. When the BS receives a message addressed to the SS in step S301, the management table is updated in step S302. Is searched. In step S303, based on the search result, it is determined whether the SS is under RS. If SS is not under RS, but can communicate directly with BS, it shifts to normal processing. On the other hand, if SS is under RS, the process proceeds to step S304.

  In step S304, a DL-MAP to be transmitted to the SS is created prior to data transmission. FIG. 15 is a diagram illustrating an example of a DL-MAP created in the present embodiment, and the BS refers to the management table and refers to the DL-MAP along the burst profile between BS-RS and RS-SS3. Create IE. That is, the time (t2−t1) for transmission to the RS is calculated from the modulation scheme adopted between the BS and the RS. On the other hand, the time (t4−t3) for RS to transmit to SS3 is calculated from the modulation scheme adopted between RS and SS3. This DL-MAP is encapsulated and transmitted in step S305.

  The present invention has been described above with reference to preferred embodiments. However, the present invention is not necessarily limited to the above-described embodiments, and various changes can be made without departing from the concept of the present invention.

1 is a diagram showing a network configuration to which a P-MP wireless data communication method according to the present invention is applied. FIG. It is the figure which showed the frame structure of the MAC header provided to a transmission / reception packet in this invention. FIG. 3 is a diagram showing an OFDM frame configuration in the present invention. It is the figure which showed an example of UL-MAP IE (Information Element) in UL-MAP. 5 is a flowchart showing RNG-REQ message reception processing in a relay station. It is the flowchart which showed the message reception process in a base station. 3 is a time chart showing the operation of the present invention. It is the figure which showed typically a mode that the RNG-REQ message transmitted from the subscriber station was encapsulated by the relay station and transferred to the base station. It is the figure which showed an example of the management table produced in order to manage each subscriber terminal in a base station. It is the figure which showed typically a mode that the RNG-RSP message encapsulated and transmitted from the base station is decapsulated by the relay station and transferred to the subscriber terminal. It is the figure which showed the structure of RNG-INFO used by this invention. It is the figure which showed an example of the management table of a base station. It is the figure which showed an example of the management table of a base station. It is the flowchart which showed the procedure in which the base station which received the message addressed to a subscriber terminal transfers the said message to a subscriber terminal. It is the figure which showed an example of DL-MAP created in this invention. [Fig. 3] Fig. 3 is a diagram illustrating an example of an OFDM frame configuration in the P-MP scheme. FIG. 3 is a diagram illustrating a frame structure of a MAC header defined by IEEE 802.16.

Explanation of symbols

BS ... Radio base station
RS ... Relay station
SS: Subscriber terminal

Claims (12)

In a P-MP wireless data communication method in which a plurality of subscriber terminals are accommodated in one wireless base station,
A plurality of relay stations for relaying communication between the radio base station and each subscriber terminal,
A procedure in which a radio base station assigns each relay station a unique communication opportunity without a communication collision for relaying a request message received by the relay station from a subscriber terminal at a communication opportunity with a communication collision;
Each relay station relays a request message received from the subscriber terminal at a communication opportunity with a communication collision to a radio base station using the unique communication opportunity assigned to the own station;
Based on the request message received from each relay station by the radio base station, each relay station is assigned with more communication opportunities to a relay station having a large amount of data to be transmitted to and received from the radio base station. wireless data communication method and a procedure for determining a communication opportunity, characterized in containing Mukoto to be assigned to. The wireless data communication method according to claim 1, wherein the request message includes a ranging request and a bandwidth request . 3. The wireless data communication method according to claim 1 , wherein the request message includes the number of messages transferred from all subordinate subscriber terminals . Communication opportunity assigned to the relay station, either the relay station of claims 1, characterized in that it is dynamically set on the basis of the data amount of each subscriber terminal for relaying a radio base station 3 The wireless data communication method described.   The data amount of the subscriber terminal relayed by the relay station to the radio base station is represented by the number of messages from the subscriber terminal relayed from the relay station to the radio base station. Wireless data communication method.   5. The wireless data communication method according to claim 4, wherein the data amount of the subscriber terminal relayed by the relay station to the wireless base station is represented by the number of subscriber terminals under the relay station. In a P-MP wireless data communication system in which a plurality of subscriber terminals are accommodated in one wireless base station,
A plurality of relay stations for relaying communication between the radio base station and each subscriber terminal,
Means for assigning a unique communication opportunity without a communication collision for relaying a request message received by the relay base station from a subscriber terminal at a communication opportunity with a communication collision to each relay station by the radio base station;
Means for each relay station to relay a request message received at a communication opportunity with a communication collision from the subscriber terminal to the radio base station using the unique communication opportunity assigned to the own station;
Based on the request message received from each relay station by the radio base station, each relay station is assigned with more communication opportunities to a relay station having a large amount of data to be transmitted to and received from the radio base station. Means for determining a communication opportunity to be assigned to the wireless data communication system. The wireless data communication system according to claim 7, wherein the request message includes a ranging request and a bandwidth request . The wireless data communication system according to claim 7 or 8, wherein the request message includes the number of messages transferred from all subordinate subscriber terminals. Communication opportunity assigned to the relay station, to any one of the relay stations claims 7, characterized in that it is dynamically set on the basis of the data amount of each subscriber terminal for relaying a radio base station 9 The wireless data communication system described.   The data amount of a subscriber terminal relayed by the relay station to a radio base station is represented by the number of messages from the subscriber terminal relayed from the relay station to the radio base station. Wireless data communication system.   The wireless data communication system according to claim 10, wherein the data amount of the subscriber terminal relayed by the relay station to the wireless base station is represented by the number of subscriber terminals under the relay station.

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