JP4032032B2 - Bandwidth allocation apparatus and bandwidth allocation method in data transmission system - Google Patents

Description

  The present invention relates to a bandwidth allocation apparatus and bandwidth allocation method in a data transmission system that performs bidirectional data communication between a base station and a plurality of subscriber stations using a time division multiple access scheme.

One base station fixed at a certain location that receives all data from the opposite device to all subordinate subscriber stations, and a plurality of subscriber stations each connected to a terminal and fixed at another certain location Has been proposed a data transmission system called a fixed wireless access system that performs two-way data communication using a time-division multiple access method using a communication frame of a fixed bandwidth (fixed length) (Patent Documents 1, 2, and 3).
In Patent Document 1, one communication is performed according to the amount of data transmitted from a base station to a plurality of subscriber stations (downlink data amount) and the amount of data transmitted from a plurality of subscriber stations to the base station (upstream data amount). A bandwidth control method is described in which the bandwidth of the uplink and downlink in the frame is dynamically changed to efficiently use the bandwidth of the communication frame without waste.

  Patent Document 2 discloses already-transmitted data that may be transmitted between a time point at which the amount of data accumulated for a subscriber station is measured in a base station and a scheduling time point at which a bandwidth is allocated. Describes a data transmission apparatus that prevents a bandwidth from being allocated and similarly uses a communication frame efficiently without waste.

  Further, in Patent Document 3, a guaranteed bandwidth (also referred to as a minimum guaranteed bandwidth) set for each subscriber station is grasped, and a priority and a guaranteed bandwidth are set for each subscriber station. For the set subscriber stations (also referred to as special subscriber stations), priority is given to band allocation in the communication frame, and subscriber stations that are not set with guaranteed bands (also referred to as general subscriber stations). Has proposed a time scheduling method in which a surplus bandwidth is allocated fairly after the priority bandwidth allocation is completed. A general subscriber station for which no guaranteed bandwidth is set has the same meaning as a subscriber station for which the guaranteed bandwidth “0” is set.

  In this time scheduling method, first, a guaranteed bandwidth is set for a subscriber station and given a priority. In this case, the sum of the guaranteed bandwidths to be set does not exceed the allocatable bandwidth in the communication frame.

  FIG. 9 shows an example of guaranteed bandwidth setting assignment (also referred to as assignment). In this example, among the subscriber stations WT1 to WT8, the guaranteed bandwidth “0” for the subscriber stations WT1, 2, 5, and 7, hereinafter, the guaranteed bandwidth “3” for the subscriber station WT3, and the subscriber station WT4. The guaranteed bandwidth “8” is assigned to the subscriber station WT6, the guaranteed bandwidth “4” is assigned to the subscriber station WT6, and the guaranteed bandwidth “2” is assigned to the subscriber station WT8. The priority is given in descending order of the guaranteed bandwidth of the subscriber stations WT4, WT6, WT3, WT8, WT1, 2, 5, and 7. In this example, it is assumed that the allocatable bandwidth in the communication frame is set to 46 [Mbps], for example.

  Second, a table is created in which the guaranteed bandwidth of each subscriber station and the requested bandwidth of each subscriber station are arranged as data in order of priority. That is, as shown in FIG. 10, from the left side, a table is created in which subscriber stations WT4, 6, 3, 8, 1, 2, 5, and 7 are arranged in descending order of guaranteed bandwidth.

  Third, bandwidth allocation is performed in descending order of priority. In this case, the special subscriber station in which the guaranteed bandwidth is set assigns the lower bandwidth by comparing the set guaranteed bandwidth with the requested bandwidth requested by the special subscriber station itself.

  Fourth, when the assignment to one subscriber station is completed, the assignment is made to the subscriber station with the next highest priority.

  Thereafter, the above third and fourth procedures are repeated to continue allocation until there is no bandwidth that can be allocated.

  FIG. 10 shows an example of the result of assigning guaranteed bandwidths in order of priority in this way. The numerical value in the graph indicates the number of laps (also called the number of rounds). In the first lap, all the guaranteed bands set for the subscriber stations WT4, 6, 3 and 8 are allocated, and the remaining bands below. As for (shared band), a predetermined band (also referred to as a unit band), here 2 [Mbps] is allocated to each of the subscriber stations WT1, 2, 5, and 7. In the second round, band “8” is allocated to subscriber station WT4, band “4” is allocated to WT6, band “3” is allocated to WT3, and band “2” is allocated to WT8, 1, and 2.

  FIG. 11 shows a guaranteed bandwidth allocation technique according to still another technique (Patent Document 4). In the example of the allocation technique in FIG. 11, the guaranteed bandwidth is allocated for the guaranteed bandwidth, and the remaining shared bandwidth is allocated fairly by all the subscriber stations WT1 to WT7.

JP 2003-274446 A JP 2003-234715 A JP 2003-101574 A JP 2003-23450 A

  However, as described in Patent Document 3 or Patent Document 4, after the guaranteed bandwidth is allocated, the remaining shared bandwidth is allocated as shown in the graphs of FIG. 10 and FIG. There is a problem that there is a large difference in the total bandwidth between the special subscriber station and the general subscriber station.

  The present invention has been made in consideration of such problems, and not only the guaranteed bandwidth but also the shared bandwidth is allocated to the special subscriber station, and all subscriber stations are irrelevant to the guaranteed bandwidth. An object of the present invention is to provide a bandwidth allocating device and a bandwidth allocating method in a data transmission system that can allocate a shared bandwidth so as to increase the fairness.

  The bandwidth allocating device according to the present invention includes upper and lower data included in a communication frame of a certain length used in a data transmission system for performing bidirectional data communication between one base station and a plurality of subscriber stations by a time division multiple access method. In a bandwidth allocating apparatus for allocating bandwidth to a region, means for identifying a special subscriber station for which a guaranteed bandwidth is set and a general subscriber station for which a guaranteed bandwidth is not set, and bandwidth allocation included in the communication frame are possible Band allocating means for allocating bands to the upper and lower data areas, wherein the band allocating means refers to the identification means for the band allocable upper and lower data areas included in the communication frame, and the special subscriber station After the guaranteed bandwidth is allocated, the surplus shared bandwidth is allocated to the general subscriber station in a round-robin manner for each predetermined bandwidth. Wherein if it exceeds the guaranteed bandwidth of the special subscriber station, wherein also characterized in that to resume the allocation for a particular subscriber station (the invention according to claim 1).

  According to the present invention, the bandwidth allocating means refers to the identification means for the upper and lower data areas that can be allocated in the communication frame, and after assigning the guaranteed bandwidth to the special subscriber station, Allocating to a general subscriber station in a round-robin manner for a predetermined bandwidth, and if the allocation by round robin exceeds the guaranteed bandwidth of the special subscriber station, the allocation is also resumed for the special subscriber station. Therefore, the shared bandwidth is allocated as a whole so that the disparity is reduced, and a higher fairness can be allocated. By changing the bandwidth of each of the upper and lower data areas for each communication frame according to the required bandwidth, the use of the upper and lower data areas in the communication frame can be effectively avoided by avoiding unnecessary use of the bandwidth in the communication frame. Can be used.

  Furthermore, it has request band detection means for detecting a request band for each subscriber station, and when the band allocation means allocates a guaranteed band to the special subscriber station, the request band of the special subscriber station After the requested bandwidth is allocated if the bandwidth is below the guaranteed bandwidth of the subscriber station, or after the guaranteed bandwidth is allocated if the requested bandwidth of the special subscriber station exceeds the guaranteed bandwidth of the special subscriber station The surplus shared band is allocated to a general subscriber station in a round robin manner for each predetermined band, and when the allocation by round robin exceeds the allocated band to the special subscriber station, the special subscriber station By resuming the allocation to the station, when the required bandwidth of the special subscriber station is equal to or less than the guaranteed bandwidth, the shared bandwidth increases by the difference, so the bandwidth allocation to the general subscriber station increases, Overall data transmission system The bandwidth of the communication frame and can be efficiently used effectively (the invention described in claim 2).

  In this case, the guaranteed bandwidth is set individually for each of the upper and lower data areas, and the sum of the guaranteed bands set for all the special subscriber stations exceeds the bandwidth of the assignable upper and lower data areas included in one communication frame. By setting so that there is no finer bandwidth, fine bandwidth allocation and guaranteed bandwidth can be ensured (the invention according to claim 3).

  In addition, after the bandwidth allocation unit resumes the allocation to the special subscriber station, the bandwidth is allocated to all of the upper and lower data areas to which the bandwidth can be allocated or when the bandwidth required for all the subscriber stations is exhausted. All the communication frames can be efficiently used by assigning all the subscriber stations by a predetermined number of bands in a round robin manner (the invention according to claim 4).

  Also, the allocation method of the present invention is an upper and lower frame included in a communication frame of a fixed length used in a data transmission system that performs bidirectional data communication between one base station and a plurality of subscriber stations by a time division multiple access method. In the bandwidth allocation method for the data area, a guaranteed bandwidth allocation process for allocating a guaranteed bandwidth to a special subscriber station for which a guaranteed bandwidth is set, and a guaranteed bandwidth for the upper and lower data areas that can be allocated included in the communication frame After that, the shared band first allocation process for allocating a surplus shared band to a general subscriber station for which a guaranteed band is not set by a predetermined number of rounds in a round robin manner, and allocation by round robin are performed by the special subscriber station. And a shared bandwidth second allocation process for resuming allocation to the special subscriber station when the guaranteed bandwidth is exceeded (claim 5). Of the invention).

  According to the present invention, after the guaranteed bandwidth is allocated to the special subscriber station in which the guaranteed bandwidth is set for the upper and lower data areas that can be allocated in the communication frame by the guaranteed bandwidth allocation process, the shared bandwidth first allocation is performed. The shared band remaining by the process is allocated to the general subscriber station for which the guaranteed band is not set by a round robin method for each predetermined band, and the allocation by the round robin in the second shared band allocation process is the guaranteed band of the special subscriber station. When the number exceeds the limit, the allocation is resumed for the special subscriber station. For this reason, the shared bandwidth as a whole is allocated so that the disparity is reduced, and a higher sense of fairness can be allocated. In addition, each band of the upper and lower data areas is changed for each communication frame according to the requested band, thereby avoiding waste of band use in the communication frame and making the bands of the upper and lower data areas in the communication frame effective. Can be used. Even in this case, when the guaranteed bandwidth is allocated to the special subscriber station for which the guaranteed bandwidth is set, if the required bandwidth of the special subscriber station is less than the guaranteed bandwidth, the requested bandwidth is allocated to the special subscriber station. Thereafter, a shared band first allocation process is performed.

  According to the present invention, it is possible to guarantee the bandwidth according to the requested bandwidth without wasting the bandwidth even for the special subscriber station, and when the requested bandwidth exceeds the guaranteed bandwidth, the shared bandwidth is allocated and shared. Since the bandwidth is allocated so as to reduce the disparity as a whole, the shared bandwidth can be allocated so that the fairness is higher in all subscriber stations regardless of the guaranteed bandwidth.

  More specifically, the guaranteed bandwidth is set when the total guaranteed bandwidth guaranteed by the special subscriber station is small, or when there is a lot of free space in the shared bandwidth due to a small number of general subscriber stations. Special subscriber stations can be allocated a bandwidth that is greater than the guaranteed bandwidth, and all subscriber stations (special subscriber stations + general subscriber stations) can allocate bandwidth fairly regardless of whether or not the guaranteed bandwidth is set. It can be performed. In addition, even if the shared bandwidth decreases due to an increase in the number of subscriber stations, the special subscriber station set as the guaranteed bandwidth guarantees the guaranteed bandwidth according to the requested bandwidth (number of bandwidth requests) as the minimum guaranteed bandwidth. As a result, it is possible to guarantee the bandwidth for effective use of the bandwidth.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an overall configuration of a radio communication system 10 to which a band allocation device and a band allocation method according to an embodiment of the present invention are applied.

  The wireless communication system 10 is used as a P-MP (Point to Multi-Point) type that provides a fixed wireless access service to a plurality of subscribers.

  The wireless communication system 10 basically includes a base station 11 fixed to a building or a utility pole, and bidirectional communication with the fixed base station 11 via a transmission line 15 of a wireless line. A plurality of subscriber stations 21 (1) to 21 (3) (representatively referred to as subscriber stations 21) disposed in a company or at home.

  A wireless channel is established through wireless communication between the antenna 12 of the base station 11 and the antennas 22 (1) to 22 (3) (typically referred to as the antenna 22) of the plurality of subscriber stations 21.

  Each subscriber station 21 is connected to terminals 20 (1) to 20 (3) (typically referred to as terminals 20) such as personal computers by wire or wirelessly. Each terminal 20 and each subscriber station 21 can be integrated. On the other hand, the base station 11 is mainly wired and is connected to each of the opposing devices 14 (1) to 14 (3) (typically the opposing devices 14) of the terminals 20 (1) to 20 (3) via the network 13. Connected).

  Each subscriber station 21 can access the network 13 via the radio line and the base station 11. As the network 13, an IP (Internet Protocol) network connected to the opposite device 14 such as a WWW (World Wide Web) server can be used. Further, the counter device 14 is not limited to a server, but also includes a subscriber station (not shown) of another base station connected via another base station (not shown).

  For communication between the base station 11 and a plurality of subscriber stations 21, bidirectional data communication employing a TDD (Time Division Duplex) / TDMA (Time Division multiple Access) method, a so-called time division multiple access method is possible. It is. In this case, a common radio frequency, for example, a 26 [GHz] band is allocated between the base station 11 and the plurality of subscriber stations 21, and the base station 11 and the plurality of subscriber stations are different depending on the time slot to be used. Efficient and congestion-free communication with 21 is possible.

  For communication between the base station 11 and the plurality of subscriber stations 21, an FDD / TDMA system, which will be described later, can be adopted instead of the TDD / TDMA system. In either case of the TDD / TDMA system or the FDD / TDMA system, the downlink direction is the TDM (Time Division Multiplex) system, and the uplink direction is the TDMA system. In either case, the time division multiple access system is used. Is adopted.

  FIG. 2 shows a configuration of a radio frame (communication frame) based on the TDD scheme for performing communication between a plurality of subscriber stations 21 and the base station 11. The period of one radio frame (one communication frame) is selected to be a fixed period, for example, 1 [ms], etc., from about 1 to 10 [ms]. As the period of one radio frame, a shorter period or a longer period can be selected in relation to hardware or the like.

  One radio frame includes a downlink area, an uplink area, and a guard time TS16. The downlink region includes a downlink header region TS11 and a downlink data region TS12. The uplink area includes a DMF (Delay Measurement Frame) area TS13, a slot request area TS14, and uplink data, which are time zones for commands and the like related to the measurement of the propagation delay between the base station 11 and each subscriber station 21 and the authentication process. Region TS15.

  In the downlink area of one radio frame, the downlink header area TS11 includes a preamble area TS17 for generating a reception synchronization signal for each radio frame, a base station number area TS18, a frame position designation area TS19, and DMF transmission permission. And a command area TS20 including a control command such as a command related to the authentication process, and a slot allocation area TS21.

  In the downlink region of one radio frame, the remaining downlink data region TS12 is divided into a plurality of time slots, and a fixed downlink packet (also simply referred to as a packet) Pd is assigned to each. Each downlink fixed length packet Pd includes a subscriber station number Pd1, control information Pd2 such as adjacent packet presence / absence information, fixed length data Pd3 which is actual data, and an error detection code Pd4.

  In the uplink region of one radio frame, the uplink data region TS15 is divided into a plurality of time slots, and an uplink fixed length packet (also simply referred to as a packet) Pu is allocated to each. Each uplink fixed length packet Pu is composed of guard time Pu1, preamble Pu2, subscriber station number Pu3, control information Pu4 including adjacent packet presence / absence information, etc., fixed length data Pu5 which is actual data, and error detection code Pu6. ing.

  Note that the configurations of the upper and lower data areas TS12 and TS15 are common to the TDD / TDMA system and the FDD / TDMA system.

  In addition, the total number of time slots (bandwidth) of the upper and lower data areas TS12 and TS15 constituting one radio frame is constant, but according to the number of slot requests (bandwidth request), the time slot ( The number of time slots (bandwidth) in the upstream data area TS15 and the downstream data area TS12 can be dynamically changed during so-called scheduling.

The data length of one downlink fixed length packet Pd or one uplink fixed length packet Pu is selected as, for example, 64 bytes or 128 bytes. In this embodiment, 128 bytes are selected. Accordingly, the bandwidth that can be allocated to one time slot is about 128 [bytes] × 8/10 ⁻³ [SEC] ≈1 [Mbps].

  FIG. 3 shows a wireless communication system 10 showing configurations of a subscriber station 21 and a base station 11 as an example. In FIG. 3, the antennas 12 and 22 shown in FIG. 1, the transceiver circuit (high frequency circuit) connected to the antennas 12 and 22, and the modulation / demodulation circuit connected to the transmission / reception circuit are not shown.

  The subscriber station 21 basically includes a TDD-TDM / TDMA (TDD / TDMA) control circuit 52 connected to a modem circuit (not shown), a communication interface circuit 53 connected to the terminal 20, and a downlink reception buffer. 61, an upstream transmission buffer 62, and a packet number measuring unit 63.

  The packet number measuring unit 63 periodically measures the number of packets stored in the uplink transmission buffer 62 of each subscriber station 21 for each period of one radio frame, and uses this as information of the uplink slot request 71 for TDD / TDMA control. This is transmitted to the circuit 52. The slot request 71 information is notified from the TDD / TDMA control circuit 52 to the base station 11 through the transmission line 15 in the time zone of the slot request area TS14 of one radio frame in FIG. 2 as schematically shown in FIG. Is done.

  The base station (slot allocating device) 11 basically includes a TDD-TDM / TDMA (TDD / TDMA) control circuit 152 connected to a modem circuit (not shown), a communication interface circuit 153 connected to the network 13, and a slot. An allocation unit (band allocation unit) 54, a reception buffer 64 for each uplink subscriber station, a transmission buffer 65 for each downlink subscriber station, a packet number measurement unit 66, and a guaranteed bandwidth table (identification unit) 68 for each subscriber station are provided. .

  The packet number measurement unit 66 periodically measures the number of packets for each subscriber station 21 stored in the transmission buffer 65 for each downlink subscriber station for each period of one radio frame, and assigns this as a slot assignment request 73 as a slot allocation. Transmitted to the unit 54. The TDD / TDMA control circuit 152 extracts the information of the uplink slot request 71 of each subscriber station 21 notified in the time slot of the slot request area TS14 of one radio frame in FIG. 2 and transmits it to the slot allocation unit 54.

  The slot allocation unit 54 performs scheduling based on the information of the downlink slot request 73 and the uplink slot request 71 corresponding to the number of packets for each subscriber station 21, determines the information of the slot allocation 72, and the TDD / TDMA control circuit 152 is notified.

  The time slot allocation (bandwidth allocation) in the uplink direction for each subscriber station 21 is notified in the time slot of the slot allocation area TS21 in one radio frame in FIG.

  The wireless communication system 10 to which one embodiment of the present invention is applied is basically configured as described above. Next, in order to facilitate understanding of this embodiment, first, a slot is used. Details of the allocation process (bandwidth allocation process) are omitted. The general overall operation will be described. The detailed operation by the slot allocation unit 54 will be described in this order.

A. General Overall Operation When data is transmitted from the terminal 20 to the opposite device 14, randomly generated variable length data such as an ether frame supplied from the terminal 20 to the subscriber station 21 is stored in the subscriber. The communication interface circuit 53 of the station 21 divides the packet into uplink fixed length packets Pu. At this time, the communication interface circuit 53 further adds control information Pu4 including error recombination information such as adjacent packet presence information, error detection code Pu6, etc. to each uplink fixed length packet Pu, and temporarily stores it in the uplink transmission buffer 62. Is done.

  Each uplink fixed-length packet Pu is a slot (bandwidth) according to the contents of the slot allocation area TS21 from the base station 11 in response to an uplink slot request (requested bandwidth) 71 based on the amount stored in the uplink transmission buffer 62 from the subscriber station 21. Are transmitted from the uplink transmission buffer 62 from each subscriber station 21 functioning as a transmission side device through the TTD / TDMA control circuit 52, an antenna (not shown), and the transmission line 15 of the wireless line. In FIG. 3, the uplink slot request 71 is schematically depicted in parallel with the transmission line 15 for convenience of understanding, but actually, the uplink slot request 71 is included in the slot request area TS14 in the radio frame. 15 is transmitted.

  On the base station 11 functioning as a receiving side device, each uplink fixed length packet Pu received through the TDD / TDMA control circuit 152, such as an antenna (not shown), is temporarily stored in the receiving buffer 64 for each uplink subscriber station. Based on the control information Pu4 and the like, the communication interface circuit 153 detects the presence or absence of a packet loss. If there is no packet loss, the packet is recombined and the recombined frame is sent as data to the opposite device 14 through the network 13. Is output.

  On the other hand, when data is to be transmitted from the opposite device 14 to the terminal 20, the same applies to the data supplied from the opposite device 14 to the base station 11 through the network 13, but in this case, it functions as a transmission side device. Is divided into downlink fixed-length packets Pd by the communication interface circuit 153 of the base station 11, and re-synthesizing information such as adjacent packet presence / absence information is added to each downlink fixed-length packet Pd as control information Pd2. It is transmitted to the subscriber station 21 that functions as a receiving side device through the transmission buffer 65 for each station, the TDD / TDMA control circuit 152, the antenna, etc., and the transmission path 15, and temporarily stored in the downlink reception buffer 61 of the subscriber station 21 .

  The received and stored downlink fixed length packet Pd is detected by the communication interface circuit 53 of the corresponding subscriber station 21 based on the control information Pd2, and recombined if there is no packet loss. And transmitted to the terminal 20.

  The above description is the general overall operation of the wireless communication system 10.

  Next, B. A detailed slot (bandwidth) allocation operation of the slot allocation unit 54 functioning as slot allocation means (control means) of the base station (slot allocation apparatus) 11 will be described with reference to the flowchart of FIG.

B. Detailed Slot (Bandwidth) Allocation Operation In this case, a subscriber station guaranteed bandwidth table 68 is created in advance with the subscriber station 21 as an index. Here, it is assumed that the setting is made as shown in FIG. 9, for example. That is, as shown in FIG. 5, the subscriber station guaranteed bandwidth table 68 functioning as an identification means is, for example, that a subscriber operating the subscriber station 21 informs the owner / manager operating the base station 11 in advance. A guaranteed bandwidth contract is made by paying a special fee, and a guaranteed subscriber bandwidth is set according to the special fee 21 {= WT (Wireless Terminal) 3: 3 [Mbps], WT4: 8 [Mbps], WT6 : 4 [Mbps], WT8: 2 [Mbps]}, and no guaranteed bandwidth (in other words, guaranteed bandwidth is set to “0 [Mbps]”), general subscription allowed to be used The person station 21 {= WT 1, 2, 5, 7} is a identifiable table. Note that the guaranteed uplink bandwidth and the guaranteed downlink bandwidth are set in the subscriber station guaranteed bandwidth table 68, but the slot (bandwidth) allocation process is the same for both uplink and downlink, so the subscriber station shown in FIG. In each guaranteed bandwidth table 68, in order to avoid complexity, the setting of the downlink guaranteed bandwidth is omitted. The uplink guaranteed bandwidth and the downlink guaranteed bandwidth can be set to different values for each special subscriber station based on the guaranteed bandwidth contract or the like.

  Therefore, first, in step S1, the slot allocation unit 54 obtains an uplink slot request (requested bandwidth) 71 for each subscriber station 21 (WT1 to WT8) from the TDD / TDMA control circuit 152 and also measures the number of packets. 63, a downlink slot request (requested bandwidth) 73 for each subscriber station 21 (WT1 to WT8) is acquired. 4 is the slot allocation unit 54, and therefore, in the following steps, the control entity is omitted as necessary.

  Next, in step S2, an uplink guaranteed bandwidth allocation process is performed. In this case, the subscriber station guaranteed bandwidth table 68 is referred to, and first, allocation is performed to the special subscriber stations 21 (WTs 3, 4, 6, 8) for which the guaranteed bandwidth is set. At this time, the set guaranteed bandwidth is compared with the requested bandwidth of the special subscriber station 21 (WT 3, 4, 6, 8) according to the uplink slot request 71, and the smaller bandwidth is allocated.

  That is, when “guaranteed bandwidth ≧ requested bandwidth”, “requested bandwidth” is assigned. As a result, it is possible to use a portion that is not required even as guaranteed as a shared band. If “guaranteed bandwidth <required bandwidth”, “guaranteed bandwidth” is allocated. As a result, a minimum guaranteed bandwidth is allocated. As a result of the processing in step S2, as shown in FIG. 9, the guaranteed bandwidth “3” for the special subscriber station 21 (WT 3, 4, 6, 8) corresponding to the guaranteed bandwidth table 68 for each subscriber station. “8”, “4”, “2” [Mbps] are assigned.

  Next, in step S3, downlink guaranteed bandwidth allocation processing is performed. This allocation process is the same as the uplink guaranteed bandwidth allocation process. That is, the guaranteed bandwidth table 68 for each subscriber station is referred to, and allocation is performed to the special subscriber station 21 for which the guaranteed bandwidth is set. At this time, the set guaranteed bandwidth and the requested bandwidth to the special subscriber station 21 by the downlink slot request 73 are compared, and the smaller bandwidth is allocated.

  That is, when “guaranteed bandwidth ≧ requested bandwidth”, “requested bandwidth” is assigned. As a result, it is possible to use a portion that is not required even as guaranteed as a shared band. If “guaranteed bandwidth <required bandwidth”, “guaranteed bandwidth” is allocated. As a result, a minimum guaranteed bandwidth is allocated.

  Next, in step S4, the shared band is calculated and the upper and lower bands are distributed. In this case, in steps S2 and S3, the total data band, that is, the total number of time slots (bandwidth) in the uplink data area TS15 and the number of time slots (bandwidth) in the downlink data area TS12 in one radio frame is determined. A bandwidth obtained by subtracting the allocated bandwidth (the bandwidth that is smaller of the guaranteed bandwidth or the requested bandwidth) is set as the shared bandwidth.

  Then, considering the upper and lower slot requests 71 and 73, the shared band is distributed to the upstream band (the number of time slots in the upstream data area TS15) and the downstream band (the number of time slots in the downstream data area TS12). In this way, the length (bandwidth) of one radio frame does not change, but the lengths of the downlink and uplink areas dynamically expand and contract for each radio frame, and one radio frame is wasted. Can be used efficiently. Bandwidth allocation is performed for the uplink shared band and the downlink shared band thus determined as described below.

  With regard to the dynamic distribution of the upper and lower bands in step S4, various bands are indicated by a symbol W **, and an example will be described. The total bandwidth of the remaining upper and lower data areas TS15 and TS12 that become the shared bandwidth (Wp) is distributed at a predetermined ratio (5: 5, 6: 4, 7: 3, etc.), and the shared bandwidth that has been distributed is Reference bands (upstream reference band Wru and downstream reference band Wrd) are used.

  A shared band Wp is allocated based on the upper and lower reference bands Wru and Wrd and the upper and lower total request band (upstream total request band Wsu and downlink total request band Wsd) which is the sum of the upper and lower request bands in each subscriber station 21. . That is, when the total uplink request bandwidth Wsu exceeds the uplink reference bandwidth Wru and the downlink total request bandwidth Wsd exceeds the downlink reference bandwidth Wrd (Wsu> Wru and Wsd> Wrd), or the uplink total request bandwidth Wsu is uplink If the total required bandwidth Wsd below the reference band Wru and below the downlink reference band Wrd (Wsu <Wru and Wsd <Wrd), the upper and lower shared bands Wp are distributed as they are in the upper and lower reference bands Wru and Wrd. (If the shared band Wp is composed of the upstream shared band Wpu and the downstream shared band Wpd, Wp = Wpu + Wpd, and in this case, Wpu = Wru and Wpd = Wrd are distributed.)

  Next, when only the total downlink requested bandwidth Wsd exceeds the downlink reference bandwidth Wrd (Wsd> Wrd), the uplink total requested bandwidth Wsu is set as the uplink shared bandwidth (Wpu = Wsu), and the remaining bandwidth (Wp−Wsu). Are distributed to the downstream shared band Wpd. When only the total uplink request bandwidth Wsu exceeds the uplink reference bandwidth Wru (Wsu> Wru), the downlink total request bandwidth Wsd is set as the downlink shared bandwidth (Wpd = Wsd), and the remaining bandwidth (Wp−Wsd). Are distributed to the upstream shared band Wpu. In this way, the bandwidth of each subscriber station 21 is allocated to the dynamically distributed upper and lower shared bands Wpu, Wpd as described below. In the following, since it becomes complicated, the code W ** representing the band is used as necessary.

  First, in step S5, the uplink shared band of one radio frame is assigned by the round robin method. Hereinafter, the subscriber station 21 is changed to a subscriber station N (N is a station number corresponding to the above-mentioned WT number, N = 1 to 8) or a subscriber station WTN (N = 1 to 8) as necessary. explain.

  In step S5a, whether or not there is a request band (remaining request band) that has not been allocated for the subscriber station N is confirmed based on the uplink slot request 71 and the allocation results thus far.

  If the requested bandwidth exists, in step S5b, the guaranteed bandwidth of the subscriber station N (in this embodiment, the guaranteed bandwidth of the subscriber station N is N = 1 → 0, as can be seen from FIG. 9 or FIG. N = 2 → 0, N = 3 → 3, N = 4 → 8, N = 5 → 0, N = 6 → 4, N = 7 → 0, N = 8 → 2). If it is smaller, in step S5c, a shared band for a predetermined band (unit band) is allocated. In this embodiment, the predetermined bandwidth is one packet corresponding to the uplink fixed length packet Pu, and one time slot for sending one uplink fixed length packet Pu is allocated in the uplink data region TS15. Here, it is assumed that the predetermined band (unit band) is 1 [Mbps].

  Actually, in step S5b, since one unit band is allocated by one allocation, the minimum allocated band in the first round after the allocation of all the subscriber stations 21 of the general subscriber station is the unit band “1”. Thus, the minimum allocated bandwidth in the second round after all allocation of the general subscriber station 21 is completed is the unit bandwidth “2”. That is, the number of laps and the minimum allocated bandwidth are the same value. Accordingly, in the determination in step S5b, it is determined whether or not the subscriber station N is smaller than the minimum allocated bandwidth, that is, the allocated number of laps.

  Therefore, in step S5c, when the band allocated to the subscriber station N is the minimum allocated band, a new unit band is allocated. In other words, general subscriber stations WT1, 2, 5, and 7 for which no guaranteed bandwidth is set are allocated by one unit band by a round robin method (shared band first allocation process), and allocation by round robin is special. When the guaranteed bandwidth of the subscriber station WT3, 4, 6, 8 is exceeded, the allocation is resumed for the special subscriber station WT3, 4, 6, 8 (shared bandwidth second allocation process).

  Next, in step S5d, the station number of the subscriber station N is incremented {the process proceeds to the assignment of the subscriber station N (N = N + 1) of the next station number. }.

  In step S5e, it is determined whether or not the station number of the subscriber station N to be assigned next exceeds the maximum subscriber station number Nmax (Nmax = 8 in this embodiment), and if so, it is shown in step S5f. Thus, the station number of the subscriber station N is returned to “1”. At this time, in step S5g, the number of round robin rounds, that is, the number of assigned rounds is increased by 1 (number of rounds of assigned rounds + 1).

  Next, in step S5h, it is determined whether the requested bandwidth (remaining required bandwidth) of all the subscriber stations N has become zero or whether the allocatable shared bandwidth (remaining shared bandwidth) has become zero. If it is not zero, the uplink shared band allocation after step S5a is continued. If it is determined in step S5h that the allocatable shared bandwidth becomes zero during the allocation of the shared bandwidth, the remaining required bandwidth of all the subscriber stations 21 at that time is stored, and the stored remaining bandwidth is stored. The requested bandwidth is assigned to the shared bandwidth of the next radio frame.

  After the uplink shared band allocation process in step S5 is completed in this way, in step S6, the downlink shared band allocation process is performed in the same manner as the uplink shared band allocation process.

  The shared band allocation process in step S5 described above will be described more specifically with reference to FIGS.

  As shown in FIG. 6, after the guaranteed bandwidth allocation in step S2, the shared bandwidth is allocated in land robin in order from the subscriber station WT1 (N = 1) in step S5 (white number allocation 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12) for the special subscriber stations WT3, 4, 6, and 8 to which the guaranteed bandwidth is allocated. In this case, the shared band is not allocated until the number of times of allocation is two. However, in the “allocation 13” for the third allocation cycle, the round robin cycle count, in other words, the normal allocation bandwidth (normal allocation count) exceeds the guaranteed bandwidth “2” of the subscriber station WT8. For “13”, the allocation is resumed also for the special subscriber station WT8 that allocates the guaranteed bandwidth.

  FIG. 7 shows the result of assigning the guaranteed bandwidth (17) and the shared bandwidth (29) to all the time slots (46 in this embodiment) of the uplink data region TS15 in the uplink region of one radio frame. Yes. It can be seen that the bandwidth allocation is equal as long as the guaranteed bandwidth does not exceed the normal allocation bandwidth for one subscriber station 21. Note that it is understood that the allocation of the shared band of the uplink data region TS15 of the next radio frame is performed by the subscriber station WT5 because the guaranteed band is set in the subscriber station WT4. .

  6 and FIG. 7 generally, the bandwidths already assigned to the subscriber stations 21 in the order of the station numbers of the subscriber stations 21 with respect to the dynamically distributed uplink shared bandwidth Wpu (existing bandwidths). Bandwidth of the subscriber station 21 having the smallest allocation (allocated bandwidth) among all the subscriber stations 21 (excluding the subscriber station 21) holding the allocated bandwidth) and the requested bandwidth (remaining requested bandwidth) In comparison with (already allocated bandwidth), if the bandwidth already allocated to the subscriber station 21 is less than the bandwidth of the smallest subscriber station 21, the subscriber station 21 is assigned one unit bandwidth. If the bandwidth already assigned to the subscriber station 21 is greater than the bandwidth of the smallest subscriber station 21, the bandwidth is not assigned to the subscriber station 21 and the next station number is assigned. The subscriber station 21 is assigned. In this way, when the allocation order reaches the subscriber station WT8 having the largest subscriber station number, the allocation process is repeated by returning to the subscriber station WT1 having the smallest subscriber station number. Further, when all the uplink total request bandwidth Wsu is allocated, or when all allocated bandwidths are allocated, the next station number N of the subscriber station 21 allocated last is stored, and slot allocation in the next communication frame is stored. (Bandwidth allocation) is started from the subscriber station 21 next to the stored station number N. After the uplink slot allocation (bandwidth allocation) is completed, slot allocation (bandwidth allocation) similar to the uplink is performed on the downlink shared band Wpd.

  The above description is the detailed operation of the slot (bandwidth) allocation process.

  This embodiment can also be applied to the FDD system. In the FDD system, the TDD / TDMA control circuit 52 is replaced with the FDD-TDM / TDMA control circuit in the subscriber station 21, and the base station 11 The TDD / TDMA control circuit 152 is replaced with an FDD-TDM / TDMA control circuit (FIGS. 10 and 11 of Patent Document 1).

  FIG. 8 shows the configuration of an FDD radio frame. As is clear from FIG. 2 and FIG. 8, in the TDD scheme, the radio frame is divided in series on the time axis using the same frequency in the downlink and uplink. In the FDD scheme, different frequencies are assigned to the downlink and uplink, and the time axis is configured in parallel.

  Here, the downlink data area in the downlink radio frame shown in FIG. 8 has the same configuration as the downlink fixed length packet Pd shown in the downlink data area TS12 of FIG.

  Similarly, the uplink data area in the uplink radio frame shown in FIG. 8 has the same configuration as the uplink fixed length packet Pu shown in the uplink data area TS15 in FIG.

  For this reason, in the FDD system, similar to the TDD system, the same processing based on the flowchart of FIG. 6 and the sequence shown in FIG. 7 can be performed.

  As described above, according to the above-described embodiment, the slot allocating unit 54 functioning as the band allocating unit serves as the identification unit for the upper and lower data areas TS12 and TS15 that can be allocated to the band included in the radio frame. Refer to the guaranteed bandwidth table 68 for each subscriber station. After the guaranteed bandwidth is allocated to the special subscriber stations WT3, 4, 6 and 8, the surplus shared bandwidth is allocated to the general subscriber stations WT1, 2, 5 and 7 by one unit band in a round robin manner. , The allocation by round robin exceeded the guaranteed bandwidth of the special subscriber station WT3, 4, 6, 8 (first, first, the guaranteed bandwidth allocation exceeds the guaranteed bandwidth "2" of the special subscriber station WT8) .), The allocation is resumed for the special subscriber stations WT3, 4, 6, 8 (in this embodiment, the allocation is resumed in the order of the special subscriber stations WT8, 3, 6, 4). Therefore, the shared band is allocated so that the disparity is reduced as a whole (see FIG. 7), and a higher sense of fairness can be allocated. Note that the upper and lower data areas TS12 and TS15 are changed for each radio frame according to the required band, thereby avoiding waste of band use in the radio frame, and the upper and lower data areas in the radio frame. The bands of TS12 and TS15 can be used effectively.

  Further, by providing packet number measuring units 63 and 66 as request bandwidth detecting means for detecting the requested bandwidth for each subscriber station 21, the slot allocation unit 54 guarantees the special subscriber stations WT 3, 4, 6 and 8. When the bandwidth is allocated, if the required bandwidth of the special subscriber station WT3, 4, 6, 8 is equal to or less than the guaranteed bandwidth of the special subscriber station WT3, 4, 6, 8; Or, if the required bandwidth of the special subscriber station WT3, 4, 6, 8 exceeds the guaranteed bandwidth of the special subscriber station WT3, 4, 6, 8 Are allocated to the general subscriber stations WT1, 2, 5 and 7 in a unit of one unit band in a round robin manner (shared band first allocation process), and the allocation by the round robin is performed by the special subscriber stations WT3, 4, 6, 8 already allocated bandwidth (guaranteed bandwidth or If the bandwidth is exceeded, whichever is smaller), the special subscriber station WT3 is resumed by allocating to the special subscriber station WT3, 4, 6, 8 (shared bandwidth second allocation process). When the requested bandwidth of 4, 6, 8 is equal to or less than the guaranteed bandwidth, the shared bandwidth becomes larger by the difference, so that bandwidth allocation to the general subscriber stations WT1, 2, 5, 7 increases, and the wireless communication system As a whole, the bandwidth of the radio frame can be effectively used without waste.

  The present invention is not limited to the above-described embodiments, and can be applied to, for example, a bidirectional optical line in which a base station and a subscriber station are connected by an optical fiber, instead of a wireless line as a transmission line. Of course, various configurations can be adopted without departing from the gist of the present invention.

1 is a configuration diagram of a wireless communication system to which an embodiment of the present invention is applied. It is a block diagram of a TDD radio frame. It is a block diagram of the radio | wireless communications system which shows the abbreviate | omitted structure of the subscriber station and base station of this embodiment. It is a flowchart for time slot allocation processing explanation. It is explanatory drawing of a guarantee zone | band table for every subscriber station. It is explanatory drawing which shows the state in the middle of the band allocation process which concerns on this embodiment. It is explanatory drawing which shows the final allocation result of the band allocation process which concerns on this embodiment. It is a block diagram of the radio | wireless frame of a FDD system. It is explanatory drawing which shows the allocation result of the guarantee band with respect to a subscriber station. It is explanatory drawing which shows the final allocation result of the band allocation process which concerns on a prior art. It is explanatory drawing which shows the final allocation result of the band allocation process which concerns on another prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Wireless communication system 11 ... Base station (bandwidth allocation device)
21 ... Subscriber station 54 ... Slot allocation unit (bandwidth allocation means)
68 ... Guaranteed bandwidth table for each subscriber station (identification means)
WT3, 4, 6, 8 ... Special subscriber station WT1, 2, 5, 7 ... General subscriber station

Claims (5)

Bandwidth allocation for allocating bandwidth to upper and lower data areas included in a fixed-length communication frame used in a data transmission system that performs bidirectional data communication between a base station and a plurality of subscriber stations using a time division multiple access method In the device
Discriminating means between a special subscriber station for which a guaranteed band is set and a general subscriber station for which no guaranteed band is set, and band allocating means for allocating a band to upper and lower data areas which can be allocated to a band included in the communication frame And
The bandwidth allocating means refers to the identification means for the upper and lower data areas to which bandwidth can be allocated included in the communication frame, and after assigning a guaranteed bandwidth to the special subscriber station, the remaining shared bandwidth is The subscriber station is allocated in a round-robin manner for each predetermined band, and if the allocation by the round robin exceeds the guaranteed bandwidth of the special subscriber station, the allocation to the special subscriber station is resumed. A characteristic bandwidth allocation device. The bandwidth allocation device according to claim 1, wherein
Furthermore, it has request band detection means for detecting the request band for each subscriber station,
When the bandwidth allocation means allocates a guaranteed bandwidth to the special subscriber station, if the requested bandwidth of the special subscriber station is less than or equal to the guaranteed bandwidth of the special subscriber station, Or, when the required bandwidth of the special subscriber station exceeds the guaranteed bandwidth of the special subscriber station, after assigning the guaranteed bandwidth, the remaining shared bandwidth is sent to the general subscriber station by the round robin method for each predetermined bandwidth. When the allocation by round robin exceeds the allocated bandwidth to the special subscriber station, the allocation is also resumed for the special subscriber station. The bandwidth allocation device according to claim 1 or 2,
The guaranteed bandwidth is individually set for each of the upper and lower data areas,
A bandwidth allocating device, characterized in that a total sum of guaranteed bandwidths set for all special subscriber stations is set so as not to exceed a bandwidth of allocatable upper and lower data areas included in one communication frame. The bandwidth allocation device according to any one of claims 1 to 3,
The bandwidth allocating means restarts allocating the surplus shared bandwidth to the special subscriber station and then allocates bandwidth to all of the upper and lower data areas to which bandwidth can be allocated or the bandwidth required for all subscriber stations. A bandwidth allocating device that allocates a predetermined bandwidth to all subscriber stations in a round-robin manner when there is no more data. Bandwidth allocation for allocating bandwidth to upper and lower data areas included in a fixed-length communication frame used in a data transmission system that performs bidirectional data communication between a base station and a plurality of subscriber stations using a time division multiple access method In the method
A guaranteed bandwidth allocation process for allocating a guaranteed bandwidth to a special subscriber station for which a guaranteed bandwidth is set for the allocatable upper and lower data areas included in the communication frame;
A first shared band allocation process for allocating a surplus shared band to a general subscriber station for which a guaranteed band is not set by a predetermined amount in a round robin manner after allocating the guaranteed band;
And a shared bandwidth second allocation process for resuming allocation to the special subscriber station when the round robin allocation exceeds the guaranteed bandwidth of the special subscriber station. Method.

Images