TWI440343B - Wireless base station, communication terminal, communication processing method, and program - Google Patents

Description

Wireless base station device, communication terminal device, communication processing method, and program

The present invention relates to a wireless base station apparatus, a communication terminal, a communication processing method, and a program for causing a computer to execute the method.

OFDM (Orthogonal Frequency Division Multiplexing) wireless communication is a multiple carrier method in which a data per user is serially converted and transmitted in a wide communication band. Since the signals are orthogonal to each other, the frequency band can be made narrower than for FDM communication. Such OFDM communication can communicate at high speed due to multi-carrier transmission, but on the other hand, the influence of inter-symbol interference becomes a problem because the bit or symbol period is shortened.

In OFDM communication, in order to avoid the influence of inter-symbol interference, a guard segment is attached to the front end of the data. Figure 1 illustrates the guard section.

As shown in FIG. 1, a guard segment is added to each data symbol in the fixed-frame communication frame to avoid inter-symbol interference caused by the delayed wave. The protection zone copies the fixed section after the data symbol to the front end section. Inter-symbol interference can be avoided by attaching a guard segment to the material.

However, since the guard section has a small capacity, it is equivalent to a loss from the viewpoint of the entire system, and extending the guard section to a necessary level or more will become a cause of a decrease in the transmission capacity. Therefore, there are various proposals as a method of changing the length of the guard section.

An example of the proposal is disclosed in Japanese Laid-Open Patent Publication No. 2006-352786 (hereinafter referred to as Patent Document 1). Patent Document 1 discloses that the amount of delay spread of each mobile station is considered and the mobile station is classified, and the frequency is allocated to each mobile station in a predetermined time slot for each mobile station classified. Delay spread refers to the temporal fluctuation (distribution) of the propagation delay time between the mobile station and the base station. Further, Patent Document 1 discloses that it is associated with a distribution of mobile stations in an area, and a mobile station having a different reception delay spread is allocated to a time slot having an appropriate guard section length.

In the method disclosed in Patent Document 1, it is determined that the delay spread per mobile station, and A total of three types are added by the symbol of the guard section with the shorter delay spread, the symbol of the guard section with the average delay spread, and the symbol of the guard section with the longer delay spread. Symbols form a communication frame.

Fig. 2 is a communication processing method of a related art.

2 shows the length of the guard section (GI), that is, the frame when the GI length is fixed, and the frame of the method disclosed in Patent Document 1. Referring to Fig. 2, when the GI length is fixed and the method disclosed in Patent Document 1 is used, if the communication frame is constituted by the same symbol number, the method disclosed in Patent Document 1 can be shortened compared to when the GI length is fixed. The advantages of the long message frame.

In mobile communication using a mobile object such as a vehicle, a train, or a ship, unlike a fixed communication such as a relay station or a television broadcast, the propagation environment changes constantly, and thus a problem described later occurs in such a propagation environment. .

When the GI length is fixed, in a propagation environment in which the block radius is small and there are many high buildings, since the probability of generating a large delayed wave is low, there is little possibility that the transmission capacity is deteriorated by inter-symbol interference. However, in OFDM communication, since the guard section is basically a large loss, in an environment where a large delay wave is not generated, if the guard section is extended more than necessary, the transmission capacity is lowered.

On the other hand, in an open area where the block radius is large and there are few buildings, and in a propagation environment where there are reflectors such as mountains, the probability of generating a high-power delayed wave is high. And the influence of the delayed wave causes interference between symbols, which causes a decrease in transmission capacity.

Furthermore, when it is assumed that the OFDM wireless communication system of most base stations and most mobile stations, the transmission capacity is further reduced.

In the above-described mobile communication, since the propagation environment changes constantly, various types of delayed waves are generated. Therefore, in the OFDM wireless communication in which the length of the guard section is fixed, the transmission capacity is lowered, and the communication system is inefficient.

Further, in the method of Patent Document 1, the downlink and the uplink are frequency-phase In the FDD (Frequency Division Duplex) mode, the shorter the communication frame length, the higher the transmission speed can be. However, it is a problem in the TDD (Time Division Duplex) method in which the downlink and the uplink are the same.

That is, if the mode is implemented in the TDD mode, the guard period required to switch between the downlink and the uplink will increase. The guard period is a section in which fixed time communication is not performed, and is lost from the viewpoint of the system. Therefore, if implemented in the TDD mode, on the other hand, the frame length can be shortened by shortening the guard period, which is accompanied by the loss caused by the increase of the guard period.

Because of the above problems, in the method disclosed in Patent Document 1, in the communication method using the TDD method, even if the guard zone can be reduced, the transfer speed cannot be improved.

An object of the present invention is to provide a radio base station apparatus, a communication terminal apparatus, a communication processing method, and a program for causing a computer to execute the communication processing method, which can suppress the influence of inter-symbol interference and increase the transmission capacity.

A radio base station apparatus according to an aspect of the present invention includes: a receiving unit that estimates delay spreads for a plurality of mobile stations one by one based on signals respectively received from a plurality of mobile stations; and a scheduling unit that transmits the delays according to delays estimated by the receiving unit Determining the length of the protection section one by one, and calculating the number of symbols of the data symbols that can be inserted into the frame, that is, the number of symbols, for the mobile station by the length of the determined protection section and the data symbol of the predetermined length; The segment adding unit adds a guard segment having a length determined by the scheduling unit corresponding to the mobile station to the front end of the data symbol destined for the mobile station, and generates a scheduling unit with the mobile station as a destination. Calculating the frame of the data symbol corresponding to the number of symbols of the mobile station; the scheduling unit determines the number of symbols when the mobile station calculates the number of symbols so that "the number of symbols" is "x" The total length of the guard zone and the data symbol becomes less than a predetermined length.

A communication terminal according to an aspect of the present invention includes: a receiving unit that estimates a delay spread according to a signal received from a wireless base station; and a scheduling unit that determines a length of the guard segment according to a delay spread estimated by the receiving unit, and Determining the length of the protection section and the data symbol of the predetermined length to calculate the number of data symbols that can be inserted into the frame, that is, the number of symbols; and the additional section of the protection section, the length determined by the scheduling section Protection The segment is attached to the front end of the data symbol of the destination of the wireless base station, and the frame of the data symbol including the number of symbols calculated by the scheduling unit is generated as the destination of the wireless base station; the scheduling unit, When the number of symbols is calculated, the number of symbols is determined such that "the number of symbols" × "the total length of the guard segment and the data symbol" becomes equal to or less than a predetermined length.

A communication processing method according to an aspect of the present invention includes the steps of: estimating delay spreads for a plurality of mobile stations one by one according to signals respectively received from a plurality of mobile stations; determining the length of the guard segments one by one for the mobile station according to the estimated delay spread And determining, by the data unit of the length of the protection section and the predetermined length, the number of data symbols that can be inserted into the frame by the mobile station, that is, the number of symbols; and the length determined corresponding to the mobile station The guard zone is attached to the front end of the data symbol destined for the mobile station, and the mobile station is destined to generate a frame containing the data symbols corresponding to the number of symbols of the mobile station; In the case of the symbol number, the number of symbols is determined such that "the number of symbols" × "the total length of the guard segment and the data symbol" becomes equal to or less than a predetermined length.

A program of the present invention is for causing a computer to perform a process of estimating delay spreads for a plurality of mobile stations one by one according to signals respectively received from a plurality of mobile stations; determining a guard zone for the mobile station one by one according to the estimated delay spread The length of the segment; the number of data symbols that can be inserted into the frame by the mobile station is calculated by the length of the guard segment determined by the determined length and the data symbol of the predetermined length; that is, the number of symbols is determined corresponding to the mobile station; a guard segment of length is attached to the front end of the data symbol destined for the mobile station, and a frame containing the data symbol corresponding to the number of symbols of the mobile station is generated for the mobile station; When the station calculates the number of symbols, the number of symbols is determined such that "the number of symbols" × "the total length of the guard segment and the data symbol" becomes equal to or less than a predetermined length.

(Best form of implementing the invention)

The configuration of the wireless device of the present embodiment will now be described. Hereinafter, a case where the wireless device of the present embodiment is a wireless base station will be described.

Fig. 3 is a block diagram showing a configuration example of the wireless device of the embodiment. The configuration shown in FIG. 3 is an example of the use of the IEEE 802.16e standard that is assumed to be used in mobile communication.

As shown in FIG. 3, the wireless device 10 includes a radio processing unit 108 that transmits and receives radio waves via the antenna 100, an OFDM reception unit 101, a scheduling unit 102, a control unit 103, a sequence parallel conversion unit 104, and a subcarrier modulation unit 105. An IFFT (Inverse Fast Fourier Transform) unit 106 and a guard segment adding unit 107.

The signals received from the respective mobile stations via the antenna 100 are sent to the OFDM reception unit 101. The OFDM receiving unit 101 is a circuit that removes the guard segment from the received signal and performs FFT of the received signal and demodulation of the subcarrier. Furthermore, the OFDM reception unit 101 has a circuit for estimating delay spread based on signals from the respective mobile stations.

The data signal demodulated by the OFDM reception unit 101 is sent to the network (not shown) side, and the delayed distribution information is sent to the scheduling unit 102.

The wireless device 10 is provided with a CPU (Central Processing Unit) (not shown) and a memory (not shown), and the scheduling unit 102 is virtually configured by the CPU executing the program. The scheduling unit 102 determines the length of the guard section per mobile station in the following manner from the delay spread of each mobile station. The scheduling unit 102 obtains the difference between the desired wave and the delayed wave from the preamble in the inserted frame. For example, a signal that expects a direct arrival of a wave system is also a signal reflected from a building wall or ground. The desired wave is the first signal received among these received signals. The difference in these waves is proportional to the delay spread. Further, the scheduling unit 102 calculates the length of the guard section in accordance with the difference. The scheduling portion 102 shortens the length of the guard section when the difference is small, and lengthens the length of the guard section when the difference is large. That is, the scheduler 102 calculates the length of the guard segment that is proportional to the delay spread. Furthermore, the scheduling unit 102 calculates the number of data symbols that can be loaded into the frame 1 from the obtained guard segment length and the data symbol length. Hereinafter, the number of data symbols inserted into the frame 1 is simply referred to as "symbol number".

The control unit 103 is a circuit that receives the information on the number of symbols from the scheduling unit 102, and controls the sequence parallel conversion unit 104 and the segment adding unit 107 in response to the schedule information including the information indicating the number of symbols of the frame. .

The sequence parallel conversion unit 104 is a circuit that converts data input from the network into parallel data into serial data. The subcarrier modulation unit 105 is connected to the subsequent stage of the sequence parallel conversion unit 104, and modulates the sequence data. The IFFT section 106 is a circuit that converts signals arranged on the frequency axis to the time axis.

The guard segment adding unit 107 is a circuit that adds a signal of the length of the guard segment determined by the scheduling unit 102 to the front end of the data symbol via the control unit 103. The frame containing the data symbols of the attached guard zone is transmitted from the antenna 100 via the wireless processing unit 108 connected to the subsequent section of the guard zone attaching section 107. Assign a frame to each mobile station and assign each frame to 1 user.

Next, the operation of the wireless device 10 shown in FIG. 3 will be described. Fig. 4 is a view showing an example of the case where the wireless device shown in Fig. 3 is used in an actual environment. The wireless device 10 shown in FIG. 3 is provided in the base station 301 shown in FIG.

A base station 301 is provided at the center of the service area 3 shown in FIG. The service area 3 corresponds to a range in which the base station 301 can perform wireless communication with the mobile station, that is, a communication circle. Further, as shown in FIG. 4, there are three mobile stations 302, 303, and 304 having different distances from the base station 301. Further, as shown in FIG. 4, the buildings 402, 403, and 404 are scattered. In the mobile communication, as shown in FIG. 4, a plurality of mobile stations 302, 303, and 304 communicate with one base station 301.

When signals are transmitted from the mobile stations 302, 303, and 304 to the base station 301, the delayed wave 32u of the mobile station 302 is generated due to the influence of the building 402, and the delayed wave 33u of the mobile station 303 is generated due to the influence of the building 403, and The delayed wave 34u of the mobile station 304 is generated by the influence of 404. The delayed wave 32u of the mobile station 302 arrives at the antenna 100 of the base station 301 at a time d1 later than the expected wave 32d. The delayed wave 33u of the mobile station 303 arrives at the antenna 100 of the base station 301 at a time d2 later than the expected wave 33d. The delayed wave 34u of the mobile station 304 arrives at the antenna 100 of the base station 301 at a time d3 later than the expected wave 34d.

Figure 5 is a diagram showing a frame of a pattern when a base station receives signals transmitted from respective mobile stations shown in Figure 4; The frame is used to indicate the respective delay amounts of the delayed waves 32u, 33u, 34u. From Fig. 5, it is known that the relationship d1 < d2 < d3. In addition, the subchannels used by each mobile station are fixed.

Fig. 6 is a flow chart showing the operational sequence of the wireless device of the embodiment.

In FIG. 3, the signals of the mobile stations received by the antenna 100 are demodulated by the OFDM reception unit 101 via the radio processing unit 108, and the delay spread is estimated (step S101). The demodulated signal is sent to the network side, and information on the reception status of each mobile station, such as the delay spread information of each mobile station and the reception characteristics of the subcarrier, is sent to the scheduling unit 102.

The scheduling unit 102 determines the length of each guard segment from the reception status of each mobile station in the following manner. In the present embodiment, the scheduling unit 102 calculates the guard segment length in response to the delay spread per mobile station in the following manner (step S102). The scheduling unit 102 shortens the length of the guard section for the mobile station with a small delay spread, and lengthens the length of the guard section for the mobile station with a large delay spread. The length of the guard section is proportional to the delay spread of the mobile station and should vary depending on the delay spread.

The method of determining the length of the guard section of the scheduling section 102 will be specifically described below with reference to FIG. The mobile station 302 shown in FIG. 5 shortens the guard section length when the delay time of the delay wave 32u with respect to the desired wave 32d is small, and as the mobile station 304, when the delay wave 34u is delayed relative to the desired wave 34d, When the time is large, the length of the protection section is extended.

Next, the scheduling unit 102 calculates the guard zone time in which the number of frames can be reduced from the determined length of the guard zone. Then, the scheduling unit 102 calculates the number of symbols that can be added to the 1-frame from the calculation result, and determines the number of symbols of the 1-frame weight. Further, the scheduling unit 102 sends the information of the determined guard segment length of the mobile station and the number of symbols of the frame amount to the control unit 103.

The sequence juxtaposition unit 104 converts the data sent from the network side into a parallel sequence, and sends the data to the subcarrier modulation unit 105 based on the schedule information from the control unit 103 containing the information of the 1-frame number of symbols. . Each subcarrier is modulated by the subcarrier modulation section 105, and the data on the frequency axis is converted into data on the time axis by the IFFT section 106. During the continuous communication of the mobile station, the mobile station monopolizes one subcarrier.

The guard zone adding unit 107 determines the length of the guard zone determined by the scheduler 102 in response to the mobile station, and the data symbol of the mobile station for the destination is in accordance with the notification by the control unit 103. An additional guard section is added (step S103). Second, defense The guard segment adding unit 107 transmits the frame including the data symbol corresponding to the number of symbols of the mobile station calculated by the scheduling unit 102 as an OFDM signal from the antenna 100 via the wireless processing unit 108.

Next, the frame of the communication processing method of the present embodiment is compared with the frame shown in FIG.

Fig. 7 is a view showing a frame of the communication processing method of the embodiment and a frame shown in Fig. 2; Fig. 7 is a diagram showing the frames of the mobile stations of the users 1 to 4 respectively.

As shown in FIG. 7, in the case where the GI length is fixed and the case of Patent Document 1, when the number of symbols of the frame of the user 1 to the user 4 is totaled, the total value of both is 16. On the other hand, in the present embodiment, when the number of symbols of the frame of the user 1 to the user 4 is totaled in the case of the same frame length as the above two examples, the value is 18.

In this embodiment, as shown in FIG. 7, the lengths of the protection sections of the user 2 and the user 4 are long, and the number of data symbols of each user is four, and the lengths of the protection sections of the user 1 and the user 3 are short, and the respective data symbols are The number of yuan is five. This is because the data symbols can be added to the frame in the signals of the user 1 and the user 3 in response to the shortened length of the guard segment. As can be seen from Fig. 7, in the present embodiment, the transfer capacity can be improved as compared with the case of the fixed GI long time and Patent Document 1.

Further, in the present embodiment, the communication processing method of the radio base station apparatus from the uplink to the downlink has been described. However, the communication processing method of the present embodiment can be performed not only on the base station side but also as a communication terminal of the mobile station. It is carried out from the downlink to the uplink communication. Fig. 8 is a block diagram showing a configuration example of the communication terminal device of the embodiment. The same components as those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted. The communication terminal device 300 shown in FIG. 8 includes an input unit 110 that inputs sound and an output unit 111 that outputs sound, in addition to the configuration of the wireless device 10 shown in FIG. At this time, the operation of each communication terminal device 300 and the wireless device 10 is performed in the same manner, and the length of the guard zone is determined in accordance with the delay spread of the signal received from the base station device, and detailed description thereof will be omitted.

In the present embodiment, the delay spread is calculated from the delayed waves generated by various propagation environments, and the guard segment is dynamically changed by the determination value. For mobile stations that exist in a propagation environment where delay spread is small, the length of the guard section is shortened. on the other hand, For mobile stations located in a propagation environment where the delay spread is large, the length of the guard section is extended. Further, when the length of the guard zone in the frame is finally shortened, the shortened amount of time is allocated to the additional amount of the data symbol. As a result, the transmission capacity of the entire communication system can be increased.

Further, since the difference between the desired wave and the delayed wave is different between each of the mobile stations and the mobile stations, the guard zone can be set for each mobile station. For the mobile station having the short difference, the length of the guard section is shortened, and the transmission capacity can be increased by allocating the shortened amount of time to the symbol data. On the other hand, for the mobile station having a large difference, the length of the guard section is lengthened, and the decrease in the transmission capacity caused by the inter-symbol interference can be suppressed.

Further, in the present embodiment, communication for assigning one frame to one user is performed. During the communication duration of a certain user, since the user monopolizes the subcarrier, there is no case where the subcarrier is shared by most users on the time axis.

Further, in the present embodiment, the scheduling unit 102 calculates the length of the guard section in proportion to the delay spread. Therefore, it is not necessary to prepare a pattern of the lengths of the plurality of guard sections in advance.

Further, in the present embodiment, since the length of the guard zone is determined by calculation every frame (short time of each millisecond level), communication processing can be performed more real-time.

Furthermore, since the guard section of the OFDM radio communication is set to be long in consideration of inter-symbol interference, when the GI length is fixed and compared with the case of the present embodiment, the present embodiment can transmit the entire communication system. Capacity increase.

In the present embodiment, the scheduling unit 102 is configured by the CPU executing a program. However, a dedicated circuit for operating the equivalent scheduling unit 102 may be provided in the wireless device.

Further, the present invention is not limited to the above embodiment. The present invention can also be applied to a wireless communication system having a guard section such as MC-CDMA (Multi-Carrier Code Division Multiple Access) communication.

As an example of the effect of the present invention, the influence of inter-symbol interference can be suppressed and the transmission capacity can be increased.

The present invention has been described above with reference to the embodiments, but the invention is not limited to the above embodiments. The configuration and details of the present invention can be variously changed within the scope of the present invention.

In addition, the present application claims priority based on the Japanese Patent Application No. 2009-085550 filed on March 31, 2009, and the entire disclosure thereof.

10‧‧‧Wireless devices

32d, 33d, 34d‧‧‧ expectation waves

32u, 33u, 34u‧‧‧ delay wave

100‧‧‧Antenna

101‧‧‧OFDM receiving department

102‧‧‧Relocation Department

103‧‧‧Control Department

104‧‧‧Sequence Parallel Conversion Department

105‧‧‧Subcarrier modulation

106‧‧‧IFFT Department

107‧‧‧protection section additional section

108‧‧‧Wireless Processing Department

110‧‧‧ Input Department

111‧‧‧Output Department

300‧‧‧Communication terminal

301‧‧‧Base station

302, 303, 304‧‧‧ mobile stations

402, 403, 404‧‧ ‧ construction

D1, d2, d3‧‧ ‧ time

S101~S103‧‧‧Steps

Figure 1 illustrates the guard section.

FIG. 2 is a communication processing method for comparing related technologies.

Fig. 3 is a block diagram showing a configuration example of the wireless device of the embodiment.

Fig. 4 is a view showing an example of the case where the wireless device shown in Fig. 3 is used in an actual environment.

Figure 5 is a diagram showing a frame of a pattern when a base station receives signals transmitted from respective mobile stations shown in Figure 4;

Fig. 6 is a flow chart showing the operational sequence of the wireless device of the embodiment.

Fig. 7 is a view showing a frame of the communication processing method of the embodiment and a frame shown in Fig. 2;

Fig. 8 is a block diagram showing a configuration example of the communication terminal device of the embodiment.

10. . . Wireless device

100. . . antenna

101. . . OFDM receiving unit

102. . . Scheduling department

103. . . Control department

104. . . Sequence side-by-side conversion

105. . . Subcarrier modulation unit

106. . . IFFT Department

107. . . Protection section add-on

108. . . Wireless processing unit

Claims (8)

A radio base station apparatus includes: a receiving unit that estimates delay spreads for each of the plurality of mobile stations one by one according to signals respectively received from the plurality of mobile stations; and the scheduling unit for the mobile stations according to the delay spread estimated by the receiving unit Determining the length of the protection section one by one, and calculating the number of the symbol elements of the insertable frame, that is, the number of symbols, for the mobile station by the length of the determined protection section and the data symbol of the predetermined length; a guard segment adding unit that attaches a guard segment corresponding to the length determined by the mobile station to the front end of the data symbol destined for the mobile station, and generates the mobile station as a destination a frame including a data symbol corresponding to the number of symbols of the mobile station calculated by the scheduling unit; and the scheduling unit determines the number of symbols when each mobile station calculates the number of symbols to cause " The symbol number x "the total length of the guard segment and the data symbol" becomes equal to or less than a predetermined length. The wireless base station apparatus of claim 1, wherein the scheduling section calculates a length of the guard section proportional to the magnitude of the delay spread. A communication terminal includes: a receiving unit that estimates a delay spread based on a signal received from a wireless base station; and a scheduling unit that determines a length of the guard segment based on the delay spread estimated by the receiving unit, and determines the protection The length of the segment and the data symbol of the predetermined length are used to calculate the number of the symbol elements that can be inserted into the frame, that is, the number of symbols; and the protection section additional portion, the protection zone of the length determined by the scheduling portion a segment is attached to a front end of the data symbol of the wireless base station, and a frame containing the data symbol of the symbol number calculated by the scheduling unit is generated by the wireless base station; the row When calculating the number of symbols, the program determines the number of symbols such that "the number of symbols" × "the total length of the guard segment and the data symbol" becomes equal to or less than a predetermined length. For example, the communication terminal of claim 3, wherein the scheduling unit The length of the guard segment proportional to the magnitude of the delay spread is calculated. A communication processing method comprising the steps of: estimating a delay spread for each of the plurality of mobile stations one by one according to signals respectively received from a plurality of mobile stations; determining a length of the guard section for the mobile station one by one according to the estimated delay spread; Determining the length of the guard segment and the data symbol of the predetermined length to calculate, for the mobile station, the number of the data symbols that can be inserted into the frame, that is, the number of symbols; and the length determined corresponding to the mobile station a guard segment is attached to the front end of the data symbol destined for the mobile station, and a frame containing the data symbol corresponding to the symbol number of the mobile station is generated with the mobile station as a destination; When the mobile station calculates the number of symbols, the number of symbols is determined such that "the number of symbols" × "the total length of the guard segment and the data symbol" becomes equal to or less than a predetermined length. The communication processing method of claim 5, wherein, when determining the length of the guard segment, calculating the length of the guard segment proportional to the magnitude of the delay spread. A program for causing a computer to perform a process of estimating a delay spread for each of the plurality of mobile stations one by one based on signals received from a plurality of mobile stations; determining a length of the guard section for the mobile station one by one according to the estimated delay spread Calculating the number of the data symbols that can be inserted into the frame by the mobile station by the length of the guard segment determined by the determined length and the data symbol of the predetermined length, that is, the number of symbols; the number corresponding to the mobile station a guard segment of length attached to the front end of the data symbol destined for the mobile station, and a frame containing the data symbol corresponding to the symbol number of the mobile station is generated with the mobile station as a destination; When each mobile station calculates the number of symbols, the number of symbols is determined such that "the number of symbols" × "the total length of the guard segment and the data symbol" becomes predetermined The length is below. The program of claim 7, wherein the length of the guard segment is calculated in proportion to the magnitude of the delay spread when determining the length of the guard segment.