JP2008211657A - Radio communication method and radio communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication system and a communication method which improves probability that location registration and handover of a terminal are performed even under radio wave environment with significant interference wave. <P>SOLUTION: The radio communication method of an FDMA/TDMA system uses a TDMA system for dividing one frame of predetermined time into time slots comprised of: a plurality of downlink slots as communication from a base station to a plurality of terminals; and a plurality of uplink slots as communication from the plurality of terminals to the base station in combination, together with an FDMA system or an OFDMA system for dividing a frequency band into a plurality of communication channels. One channel of the frequency band is considered as a notification channel for transmitting notification information including base station information from the base station to the terminals and furthermore, communication is performed by including the notification information in a guard interval provided between the downlink slot and the uplink slot of each of the plurality of communication channels. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an OFDMA or FDMA / TDMA wireless communication method and wireless communication system.

  In an FDMA / TDMA wireless communication system, as a channel configuration of a wireless part between a base station and a terminal, generally, a broadcast information channel that broadcasts information from the base station to a terminal in its own cell in one direction; The communication channel is used for transmission / reception of user data.

  In such a wireless communication system, a specific channel is secured as a broadcast information channel from among a plurality of frequency channels possessed by each base station, and broadcasts such as base station information to a terminal newly connected to a predetermined base station. I use it.

  Each terminal newly starting connection to a predetermined base station by hand-over or power-on etc. first receives base station information from the broadcast information channel, then moves to the communication channel and starts its own communication Was.

  For example, in Patent Document 1, a time slot in which an initial supplemental channel is transmitted is determined based on a random number obtained by receiving a frequency channel including a channel group for control information communication and having an initial supplemental channel ICH. A communication method is disclosed.

Further, in Patent Document 2, communication is performed by sharing a plurality of narrowband channels between a parent device and a plurality of child devices, and the parent device circulates a plurality of channels used for communication set in advance. A communication method for receiving a signal transmitted from a machine and avoiding a channel having a bad line state is disclosed.
JP-A-11-98571 JP 2004-147124 A

  However, when an interference wave is generated in an information broadcast channel for FDMA / TDMA wireless communication in an area where the radio wave environment is poor, the base station receives a new terminal from the new terminal even if there is no interference wave in the communication channel. The communication cannot be accommodated. Therefore, in a radio wave environment where interference waves are significant, there arises a problem that location registration and handover of the terminal cannot be performed.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems, and to provide a wireless communication system and a communication method that improve the possibility of terminal location registration and handover even in a radio wave environment where interference waves are significant. It is.

In order to solve the above-described problem, a wireless communication method according to the present invention includes a plurality of downlink slots for communication from a base station to a terminal and a plurality of uplinks for communication from the terminal to the base station for one frame of a predetermined time. An FDMA / TDMA wireless communication method using a TDMA system that divides a frequency slot into link slots and an FDMA system or an OFDMA system that divides a frequency band into a plurality of communication channels. One channel is a broadcast channel for transmitting broadcast information including base station information from the base station to the terminal, and is further provided between each of the downlink slot and the uplink slot of the plurality of communication channels. Communication is performed by including the broadcast information in the guard interval.
According to the above configuration, since one channel in the frequency band is a broadcast channel, and broadcast information is also included in each guard interval of a plurality of communication channels, the broadcast information is a frequency band of the broadcast channel. Since it can be obtained from other sources, the terminal can obtain broadcast information including base station information and the like even in a radio wave environment where there are many interference waves in which a specific channel (frequency band) is disturbed by interference waves. The possibility increases, and the possibility of terminal location registration and handover can be improved.

Further, the terminal acquires the broadcast information from the broadcast channel, and when the signal quality level of the broadcast channel becomes a level less than a predetermined threshold, the terminal selects one of the plurality of communication channels. And receiving broadcast information from the guard interval of the communication channel.
As a result, even when the broadcast channel is blocked by interference waves and the signal quality level is deteriorated and cannot be received, if there is a communication channel that is not blocked by interference waves among the plurality of communication channels, this communication By extracting the broadcast information included in the guard interval of the channel, the terminal can obtain base station information and the like, so that the possibility of terminal location registration and handover can be improved.
Further, the base station divides the broadcast information and divides it into a plurality of frames for transmission.
Thereby, even when the broadcast information does not fit within the guard interval in one frame, the base station can transmit all the broadcast information.
Further, the base station transmits the divided broadcast information including information indicating an order for recombining the broadcast information.
Thus, the terminal that has received the divided notification information can easily re-synthesize the notification information.
In addition, while the terminal is receiving the notification information from the guard interval of the communication channel, if the signal quality level of the communication channel becomes a level below a predetermined threshold, other communication channels are received, The broadcast information is continuously received from the guard interval.
As a result, even when an interference wave suddenly occurs during reception of broadcast information and the signal quality level deteriorates and cannot be received, there is a communication channel that is not disturbed by the generated interference wave. The broadcast information can be continuously received by extracting the broadcast information included in the guard interval of the communication channel.

In addition, a wireless communication system according to the present invention performs communication between a base station and a plurality of terminals, and transmits one frame for a predetermined time to a plurality of downlink slots for communication from the base station to the plurality of terminals. An FDMA / FDMA / OFDMA scheme that divides a frequency band into a plurality of communication channels and a TDMA scheme that divides a plurality of uplink slots into time slots that are communications from the plurality of terminals to the base station. A wireless communication system employing a TDMA scheme, wherein the base station uses one channel of the frequency band as a broadcast channel, transmits broadcast information including base station information to a terminal, and the base station , Provided between the downlink slot and the uplink slot of each of the plurality of communication channels To over de interval, and transmits the moistened with broadcast information to the terminal.
According to the above configuration, since one channel in the frequency band is a broadcast channel, and broadcast information is also included in each guard interval of a plurality of communication channels, the broadcast information is a frequency band of the broadcast channel. Since it can be obtained from other sources, the terminal can obtain broadcast information including base station information and the like even in a radio wave environment where there are many interference waves in which a specific channel (frequency band) is disturbed by interference waves. It is possible to construct a wireless communication system that increases the possibility and can improve the possibility of terminal location registration and handover.

Further, the terminal acquires the broadcast information from the broadcast channel, and receives a communication channel from the plurality of communication channels when a signal quality level for the broadcast channel is a level lower than a predetermined threshold. The broadcast information is acquired from the guard interval of the communication channel.
As a result, even when the broadcast channel is blocked by interference waves and the signal quality level is deteriorated and cannot be received, if there is a communication channel that is not blocked by interference waves among the plurality of communication channels, this communication By extracting the broadcast information included in the guard interval of the channel, the terminal can obtain base station information and the like, so that the possibility of terminal location registration and handover can be improved.
Further, the base station divides the broadcast information and divides it into a plurality of frames for transmission.
Thereby, even when the broadcast information does not fit within the guard interval in one frame, the base station can transmit all the broadcast information.
Further, the base station includes information indicating an order for recombining the divided broadcast information, and transmits the information to the terminal.
Thus, the terminal that has received the divided notification information can easily re-synthesize the notification information.
In addition, while the terminal is receiving the notification information from the guard interval of the communication channel, if the signal quality level of the communication channel becomes a level below a predetermined threshold, other communication channels are received, The broadcast information is continuously received from the guard interval.
As a result, even when an interference wave suddenly occurs during reception of broadcast information and the signal quality level deteriorates and cannot be received, there is a communication channel that is not disturbed by the generated interference wave. The broadcast information can be continuously received by extracting the broadcast information included in the guard interval of the communication channel.

  The present invention can provide a wireless communication system and a communication method that improve the possibility of terminal location registration and handover even in a radio wave environment where interference waves are significant.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a wireless communication system according to the present invention will be described in detail with reference to the drawings.
The radio communication system according to the present embodiment is a radio communication system suitable for a wide-area radio communication system, and the configuration of the communication method is based on a TDMA system that divides one frame of a predetermined time into a plurality of time slots. This is a FDMA / TDMA wireless communication system that uses an FDMA scheme or an OFDMA scheme that divides a given frequency band into a plurality of communication channels.

  FIG. 1 is a schematic diagram of notification of base station information to a newly connected terminal in the wireless communication system according to the present embodiment, and FIG. 2 is a diagram for explaining a frame configuration in the FDMA / TDMA wireless communication system. FIG.

  FIG. 1 shows transmission / reception frames from the base station CS to the terminals TS1 to TS3 in the FDMA / TDMA wireless communication system. The terminals TS1 and TS2 are currently communicating with the base station CS, and transmission and reception data are transmitted in the hatched time slots in the transmission / reception frame. On the other hand, when the terminal TS3 newly connected to the base station CS cannot receive the original broadcast channel due to the interference wave, the terminal TS3 receives broadcast information included in the guard interval GI and obtains broadcast information such as base station information.

  FIG. 2 shows a frame configuration in an FDMA / TDMA wireless communication system. A plurality of (eight) frequency bands divided by FDMA are used as communication channels, respectively. One band is used as a broadcast channel, and broadcast information such as base station information is transmitted to the terminal in this broadcast channel. The Further, the same information as the broadcast channel broadcast information is transmitted in the guard interval GI. When the broadcast information corresponding to one broadcast channel does not fit in one interval GI, the broadcast information is divided and transmitted in a plurality of guard intervals GI.

  FIG. 3 shows an example of a frame configuration in which broadcast information is inserted into the guard time GI. Before the broadcast information is inserted, as shown in FIG. 3A, the downlink (communication from the base station to the terminal) slot Down includes an information symbol in which the up-ramp RU, the synchronization signal SS, and information are mounted. It consists of a down ramp RD and a guard time GT in the slot. A guard interval GI exists between the downlink slot Down and the uplink (communication from the terminal to the base station) slot Up.

  Then, as shown in FIG. 3B, after the broadcast information is inserted, the broadcast information synchronization signal IS is transmitted to the portion where the downlink ramp RD of the downlink slot Down and the guard time GT in the slot exist. Inserted into the portion where the guard interval GI exists, the divided notification information DI is inserted, and then the down ramp RD is inserted. That is, only the last downlink slot Down (out of the three downlink slots Down) delays the down-ramp to transmit the synchronization signal and broadcast information (divided broadcast information). Note that the synchronization signal IS for broadcast information also includes an order bit used for recombining the divided broadcast information DI (for example, the order of 256 slots can be expressed by an 8-bit order bit).

As an example of an FDMA / TDMA wireless communication system, for example, 1 frame is 5 ms, downlink slot Down is 1090 μs, upstream ramp RU is 10 μs, synchronization signal SS is 32 μs, downstream ramp RD is 10 μs, and guard time GT is 14 μs. In the system, the information symbol of the downlink slot Down is 1056 μs.
When the broadcast information included in the information symbol of the downlink slot Down is divided and inserted into the guard interval GI between the downlink slot Down and the uplink slot Up, 24 μs is required as the synchronization signal IS for the broadcast information Therefore, the divided notification information DI is 75 μs.

  The broadcast information is the amount of information within the information symbol of the downlink slot Down, and when this broadcast information is inserted into the guard interval GI, the broadcast information DI divided only needs to be 1056/75 = 14.08 at the maximum. Therefore, broadcast information can be transmitted if there are at most 15 frames.

  Therefore, the broadcast information can be transmitted if the time of 15 × 5 ms = 75 ms. At this level, there is no problem with connection to a new base station due to handover or power-on.

Next, an example of a control flow in the radio communication system according to the present embodiment will be described. FIG. 4 is a flowchart showing an example of a control flow in the radio communication system according to the present embodiment.
Here, the signal quality level is defined as follows.
A signal quality level is high when the RSSI value is high and the error rate is low.
Even if the RSSI is low, if the RSSI is stable and the error rate is extremely low, the signal quality level is high.
-Even if RSSI is high, if the error rate is high, the signal quality level is low.

  As shown in FIG. 4, when the terminal is turned on or the signal quality level of the base station radio wave during communication falls below a predetermined threshold (step S1), it is transmitted from the base stations around the terminal. It is determined whether or not the broadcast channel to be received can receive a predetermined threshold at the above signal quality level (step S2).

  If the broadcast channel is receivable at a signal quality level equal to or higher than a predetermined threshold (step S2: Yes), the terminal is determined to be able to communicate, or the handover is determined to be successful, and the terminal Based on the base station information obtained from the broadcast information included in the broadcast channel, communication is started by connecting to a new base station (step S5).

  On the other hand, if the broadcast channel is not receivable at a signal quality level equal to or higher than a predetermined threshold due to interference caused by an interference wave (step S2: No), for example, as shown in FIG. It is determined whether or not there is a receivable communication channel among the communication channels in the frequency band (step S3). If all communication channels in the system frequency band cannot be received (step S3: No), the terminal determines that communication is impossible. Alternatively, it is determined that the handover has failed, and the communication is disconnected (step S6).

  On the other hand, when there is a communication channel that can receive a predetermined threshold at a signal quality level above (step S3: Yes), broadcast information included in the guard interval of the receivable communication channel is received and (handover is performed). The terminal starts communication by connecting to a new base station based on the base station information obtained from the broadcast information (step S4).

  In addition, while the terminal receives the broadcast information from the guard interval of the communication channel, the signal quality level of the communication channel is less than a predetermined threshold due to sudden interference caused by interference waves. In such a case, another communication channel that is not disturbed by the generated interference wave may be received, and reception of broadcast information may be continued from the guard interval of that communication channel.

It is a schematic diagram of the alerting | reporting of the base station information to the newly connected terminal in the radio | wireless communications system of embodiment which concerns on this invention. It is explanatory drawing explaining the frame structure in the radio | wireless communications system of the FDMA / TDMA system of embodiment which concerns on this invention. FIG. 3 is an explanatory diagram showing an example in which broadcast information is inserted into a guard time GI in the frame configuration of FIG. 2. It is a flowchart which shows an example of the control flow in the radio | wireless communications system which concerns on this Embodiment.

Explanation of symbols

CS Base Station DI Divided Broadcast Information Down Downlink Slot GI Guard Interval GT Guard Time IS Sync Signal for Broadcast Information RD Down Ramp RU Up Ramp SS Sync Signal TS1-TS3 Terminal Up Uplink Slot

Claims (10)

TDMA that divides one frame of a predetermined time into a plurality of downlink slots that are communications from a base station to a plurality of terminals and a time slot that consists of a plurality of uplink slots that are communications from the plurality of terminals to the base station An FDMA / TDMA wireless communication method using a FDMA method or an OFDMA method for dividing a frequency band into a plurality of communication channels,
One channel in the frequency band is a broadcast channel for transmitting broadcast information including base station information from the base station to the terminal,
The wireless communication method further includes performing communication by including the broadcast information in a guard interval provided between the downlink slot and the uplink slot of each of the plurality of communication channels. The terminal acquires the broadcast information from the broadcast channel,
When the signal quality level of the broadcast channel becomes a level lower than a predetermined threshold, receiving one communication channel of the plurality of communication channels and obtaining broadcast information from a guard interval of the communication channel. The wireless communication method according to claim 1, wherein:   The radio communication method according to claim 1 or 2, wherein the base station divides the broadcast information and performs transmission in a plurality of frames.   The wireless communication method according to claim 3, wherein the base station transmits information including an order for recombining the divided broadcast information.   While the terminal receives broadcast information from the guard interval of the communication channel, when the signal quality level of the communication channel becomes a level lower than a predetermined threshold, the other channel is received and the guard is received. 5. The wireless communication method according to claim 2, wherein reception of broadcast information is continued from an interval. Communicating between a base station and a plurality of terminals, and communicating one frame for a predetermined time from the base station to the plurality of terminals and a plurality of downlink slots and communication from the plurality of terminals to the base station A wireless communication system that employs an FDMA / TDMA system that combines an FDMA system or an OFDMA system that divides a frequency band into a plurality of communication channels in addition to a TDMA system that divides the time slot into a plurality of uplink slots. ,
The base station uses one channel of the frequency band as a broadcast channel, transmits broadcast information including base station information to the terminal,
Furthermore, the base station includes the broadcast information included in the guard interval provided between the downlink slot and the uplink slot of each of the plurality of communication channels, and transmits the information to the terminal. Wireless communication system. The terminal acquires the broadcast information from the broadcast channel,
When the signal quality level for the broadcast channel is a level less than a predetermined threshold, one communication channel of the plurality of communication channels is received, and broadcast information is acquired from a guard interval of the communication channel. The wireless communication system according to claim 6.   The radio communication system according to claim 6 or 7, wherein the base station divides the broadcast information and performs transmission in a plurality of frames.   The radio communication system according to claim 8, wherein the base station includes information indicating an order for recombining the divided broadcast information and transmits the information to a terminal.   While the terminal receives broadcast information from the guard interval of the communication channel, when the signal quality level of the communication channel becomes a level lower than a predetermined threshold, the other channel is received and the guard is received. The radio communication system according to any one of claims 7 to 9, wherein reception of broadcast information is continued from an interval.

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