Radio communication device, radio communication program, and radio communication method

Abstract

To provide a radio communication device in which a high-speed handover is easily executed.SOLUTION: The present invention provides a communication device that divides a communication period into a plurality of slots, and performs communication with a base station using a certain slot in the communication period as a slot for transmitting control information. The communication device includes: first means of searching for the base station which can communicate with an own device by receiving the control information from each base station; second means of performing evaluation by determining whether or not it is matched to a plurality of conditions in a slot unit transmitting the control information when an own connection destination is selected from each base station searched for, and performing evaluation for adding about the slot in the case where the slot with one interval in view of each slot under the evaluation is used as a slot for transmitting the control information; and third means of selecting the connection destination from the inner side of the base station using the slot with the highest evaluation as the slot for transmitting the control information.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wireless communication device, a wireless communication program, and a wireless communication method, and can be applied to a wireless communication device that performs wireless communication via a base station, for example. [Background technology]

[0002] Conventionally, in a wireless communication system, a wireless communication terminal generally selects the optimal base station from among multiple base stations by measuring the received electric field strength of control signals transmitted by the multiple base stations, listing each control signal in order of highest received electric field strength, and selecting the one with the highest received electric field strength (Patent Documents 1, 2, etc.).

[0003] FIG. 7 shows a sequence in which a PHS terminal makes a call via a PHS base station in a PHS (Personal Handy-phone System).

[0004] The PHS terminal waits for a PHS base station (hereafter referred to as "CS") that is receiving radio waves above a certain level (a state in which the terminal captures radio waves from the CS and waits for the next operation) (S1). When a call is received from the CS or a call is made by the PHS operator, the PHS terminal starts the operation of connecting to the CS.

[0005] First, the PHS terminal performs a CS search to list the surrounding CSs by reception field strength and select the CS to use (S2). The PHS terminal collects information transmitted from the selected CS (the CS with the strongest reception field strength) and judges whether it is a connectable CS or not (S3). If the PHS terminal judges it to be a connectable CS, it requests the CS to allocate a call channel (TCH) that can be used for communication (S4). When the PHS terminal receives allocation (designation) of a usable TCH from the CS, it performs processing to synchronize with the CS in order to use the TCH (synchronization burst & link establishment) (S5). The PHS terminal then performs processing to connect the call (S7 to S9) and communicates with the other party using the allocated TCH.

[0006] By the way, when a PHS terminal moves away from the CS that is currently being used for a call, the quality of the call deteriorates. In this case, the PHS terminal uses three slots other than the slot used for the call channel (TCH) to perform a search, and if it detects the control channel (CCH) of another CS, it connects to the detected CS while keeping the call. This allows the PHS terminal to achieve handover (high-speed handover) without interruption of voice.

[0007] For example, Fig. 8 shows an example in which a PHS terminal making a call through CS1 in slot 0 executes a high-speed handover due to movement. As shown in Fig. 8(B), the PHS terminal searches unused slots 1-3 and detects CS2 broadcasting a CCH in slot 1. As shown in Fig. 8(C), while keeping the call with CS1, the PHS terminal is assigned slot 2 by CS2 and executes TCH synchronization and connection processing. As shown in Fig. 8(D), when the PHS terminal transitions to a call in progress with CS2, it stops radio communication with CS1 and completes the high-speed handover.

[0008] There are two types of handovers in PHS: the fast handover mentioned above and the normal handover. In the normal handover, the call is stopped and connection processing is performed with the CS of the handover destination.

[0009] Although normal handovers have a long voice interruption time, they can be performed even in places with poor signal conditions. On the other hand, fast handovers, as mentioned above, perform connection processing with the destination CS without interrupting the call. Although fast handovers have almost no voice interruption time, they are premised on being performed in places with relatively good signal conditions.

[0010] In PHS, a fast handover is better than a normal handover in terms of voice disconnection time, so a normal handover is performed only when a fast handover is not possible. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2011-211254 A [Patent Document 2] JP 2000-101510 A Summary of the Invention [Problem to be solved by the invention]

[0012] However, since high-speed handover searches using unused slots that are not being used for a call while the call continues, there is a problem that if the slot being used for the call is the same as the slot broadcasting the CCH of the handover destination candidate (CS), the CS cannot be detected even if searched.

[0013] For example, in Fig. 9, CS2, which is a candidate for handover, broadcasts CCH in slot 0 (because the time axis overlaps with slot 0 during a call), so it is not searched and CS2 cannot be detected. In this case, the PHS terminal has no choice but to perform a normal handover, which involves a long voice interruption time.

[0014] Therefore, there is a demand for a wireless communication device, a wireless communication program, and a wireless communication method that can perform handover as quickly as possible and provide good speech quality without interruption of voice. [Means for solving the problem]

[0015] The first invention is a wireless communication device that performs wireless communication with a wireless base station that divides a unit communication period into a plurality of slots and uses a certain slot within the unit communication period as a control information slot for transmitting control information, the wireless communication device having: (1) a first wireless communication control means that searches for each of the wireless base stations that can communicate with the device by receiving the control information from the plurality of wireless base stations; (2) a second wireless communication control means that, when selecting a connection destination for itself from the searched wireless base stations, first evaluates a point-adding method based on whether or not a plurality of conditions are met for each slot for transmitting the control information, and, if there is a wireless base station that uses a slot one spaced from each slot being evaluated as a slot for transmitting the control information, evaluates the slot being evaluated by adding a point; and (3) a third wireless communication control means that selects a connection destination for itself from the wireless base station that uses the slot that is evaluated highest by the second wireless communication control means as a slot for transmitting the control information.

[0016] A second wireless communication program of the present invention is characterized in that it causes a computer mounted on a wireless communication device that divides a unit communication period into a plurality of slots and performs wireless communication with a wireless base station that uses a certain slot within the unit communication period as a control information slot for transmitting control information to function as: (1) a first wireless communication control means that searches for each of the plurality of wireless base stations with which the device can communicate by receiving the control information from the wireless base stations; (2) a second wireless communication control means that, when selecting a connection destination from among the searched wireless base stations, first evaluates a point-adding method based on whether or not a plurality of conditions are met for each slot for transmitting the control information, and, if there is a wireless base station that uses a slot one spaced from each slot being evaluated as a slot for transmitting the control information, evaluates the slot being evaluated by adding a point; and (3) a third wireless communication control means that selects a connection destination from among the wireless base stations that use the slot evaluated highest by the second wireless communication control means as a slot for transmitting the control information.

[0017] A third wireless communication method of the present invention is a wireless communication method used for a wireless communication device that performs wireless communication with a wireless base station that divides a unit communication period into a plurality of slots and uses a certain slot within the unit communication period as a control information slot for transmitting control information, the wireless communication device comprising a first wireless communication control means, a second wireless communication control means, and a third wireless communication control means, (1) the first wireless communication control means searches for each of the plurality of wireless base stations with which the device can communicate by receiving the control information from the plurality of wireless base stations, (2) the second wireless communication control means, when selecting its own connection destination from among the searched wireless base stations, first evaluates a point-adding method based on whether or not a plurality of conditions are met for each slot for transmitting the control information, and in that case, if there is a wireless base station that uses a slot one spaced from each slot being evaluated as a slot for transmitting the control information, evaluates the slot being evaluated to add points, and (3) the third wireless communication control means selects its own connection destination from among the wireless base stations that use the slot evaluated highest by the second wireless communication control means as a slot for transmitting the control information. Effect of the Invention

[0018] According to the present invention, it is possible to perform handover as quickly as possible, and improve the quality of speech without interrupting voice. [Brief description of the drawings]

[0019] [Figure 1] 1 is a block diagram showing a configuration of a PHS terminal according to an embodiment. [Diagram 2] 4 is a flowchart showing a characteristic operation (CS search process) of the PHS terminal according to the embodiment. [Diagram 3] FIG. 11 is an explanatory diagram illustrating an example of a candidate CS table according to the embodiment. [Figure 4] FIG. 11 is an explanatory diagram illustrating an example of a slot-by-slot candidate CS table according to the embodiment; [Diagram 5] FIG. 13 is an explanatory diagram illustrating an example of a selection condition weighting table according to the embodiment. [Figure 6] FIG. 11 is an explanatory diagram illustrating an example of a slot-by-slot weighting candidate CS table according to the embodiment; [Figure 7] FIG. 2 is a sequence diagram showing a process in which a PHS terminal makes a call through a PHS base station. [Figure 8] FIG. 1 is an explanatory diagram showing an example (successful example) of high-speed handover in PHS. [Figure 9] FIG. 1 is an explanatory diagram showing an example (failure example) of high-speed handover in PHS. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] (A) Main embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a wireless communication device, a wireless communication program, and a wireless communication method according to the present invention will be described in detail with reference to the drawings.

[0021] (A-1) Configuration of the embodiment FIG. 1 is a block diagram showing the configuration of a PHS terminal according to an embodiment.

[0022] 1, the PHS terminal 10 has a wireless communication unit 11, a communication control unit 12, an RSSI acquisition unit 13, an RSSI comparison unit 14, and a CS data storage unit 15. The PHS terminal 10 may be configured entirely in hardware (for example, using a dedicated semiconductor chip), or may be configured partially in software.

[0023] The wireless communication unit 11 captures incoming radio waves, converts the radio wave signal into an electric signal, and provides the received signal to the communication control unit 12, or converts a transmission signal from the communication control unit 12 into a radio wave signal and sends it out. The wireless communication unit 11 also has a function (wireless module chip) of measuring an RSSI value, and notifies the communication control unit 12 of the received electric field strength (RSSI value) when receiving radio waves from CS20 (CS20-1 to CS20-n). In this embodiment, it is assumed that the wireless communication method is the PHS method.

[0024] The communication control unit 12 controls the communication of the PHS system. The communication control unit 12 is characterized by the process when performing the above-mentioned CS search. That is, the communication control unit 12 first evaluates the searched connection candidate CS 20 on a slot-by-slot basis based on whether or not it matches a plurality of conditions (weighted evaluation), and then selects the CS 20 with the highest reception electric field strength as its own connection destination from among the CS 20 using the most highly evaluated slot as the transmission slot of the CCH.

[0025] In this embodiment, one of the conditions is that there is another CS 20 that is highly likely to be able to perform a high-speed handover in the subsequent handover.

[0026] As described above, CS preferentially designates the slot next to the slot broadcasting CCH as the traffic channel. For example, in the above-mentioned FIG. 8, C2 designates slot 2, which is the slot next to slot 1 used as CCH, as TCH. In fast handover, since the connection operation with the detected CS is performed while keeping the call, the CS using the same slot as TCH as CCH cannot be detected. For example, in the above-mentioned example of FIG. 9, slot 0, which is the same slot as TCH, is used as CCH, so unlike FIG. 8, CS2 cannot be detected.

[0027] Considering the above two properties, when selecting the first CS before handover, it is necessary to select a CS that increases the possibility of a later high-speed handover. And the condition that increases the possibility of a high-speed handover is that there is a CS broadcasting the CCH in a slot one slot away from the slot broadcasting the CCH.

[0028] For example, when the candidate CSs to which the CS20 is connected are in the candidate CS table T1 as shown in Fig. 3 described later, the CSs with the highest reception field strength were simply selected in the past. On the other hand, in this embodiment, when the communication control unit 12 detects a plurality of slots (CCH transmission slots) of the CS20 (0, 1, 3 in the example), the CS20s with a high possibility of high-speed handover being possible and spaced apart by one slot (1, 3 in the example) may be CSs to which high-speed handover can be performed later, so the communication control unit 12 selects an appropriate CS20 as the connection destination, taking this into consideration. Further details of the communication control unit 12 will be described in the section on operation.

[0029] The RSSI acquisition unit 13 acquires the reception electric field strength when the wireless communication unit 11 receives broadcast information (CCH) from each CS 20 via the communication control unit 12. The RSSI acquisition unit 13 also stores the acquired reception electric field strength in the CS data storage unit 15, acquires information on the CS 20 including the reception electric field strength from the CS data storage unit 15 in response to a request from the communication control unit 12, and provides the information to the communication control unit 12.

[0030] The RSSI comparator 14 compares the received electric field strength of each CS 20 of the connection candidates in accordance with the communication control unit 12 .

[0031] The CS data storage unit 15 stores information about the CSs 20 including the received electric field strength of each CS 20.

[0032] (A-2) Operation of the embodiment Next, the operation of the PHS terminal 10 according to the embodiment having the above-mentioned configuration will be described. Since the present embodiment is characterized by the CS search process shown in Fig. 7, the following description will focus on the CS search process.

[0033] FIG. 2 is a flowchart showing a characteristic operation (CS search process) of the PHS terminal according to the embodiment.

[0034] <s21> The communication control unit 12 uses the RSSI acquisition unit 13 to perform a surrounding base station RSSI acquisition process to acquire the reception electric field strength of the CS20 that can be received within a certain time (e.g., 300 ms) in order to detect the CS20 that exists around the PHS terminal 10. Here, this surrounding base station RSSI acquisition process is a process that is executed before a call (before a call channel is used), and acquires the reception electric field strength of the CS20 using the four downlink slots (slot 0, slot 1, slot 2, slot 3) shown in Fig. 8 (Fig. 9).

[0035] Fig. 3 is an explanatory diagram showing an example of a candidate CS table showing candidates for CS20 listed as connection destinations of a PHS terminal according to an embodiment. In Fig. 3, the candidate CS table T1 shows items of "CS ID" showing an ID for identifying each candidate CS20, "received electric field strength" showing the received electric field strength when a CCH is received from each CS20, and "CCH transmission slot" showing the slot in which each CS20 transmits a CCH. The specific configuration of the candidate CS table T1 is not limited, and other information (date and time, etc.) may be added, for example.

[0036] <s22> The communication control unit 12 acquires the candidate CS table T1 from the RSSI acquisition unit 13, and performs a sorting process for each CCH transmission slot, which sorts the candidate CS table T1 for each CCH slot.

[0037] Fig. 4 is an explanatory diagram showing an example of a slot-by-slot candidate CS table T2 obtained by sorting the candidate CS table T1 according to the embodiment. In Fig. 4, the slot-by-slot candidate CS table T2 has the above-mentioned items of "CCH transmission slot", "CS ID", and "received electric field strength". The slot-by-slot candidate CS table T2 is obtained by simply sorting the candidate CS table T1 by CCH transmission slot, so the contents of each record (data) are the same as those of the candidate CS table T1.

[0038] <s23> The communication control unit 12 performs weighting processing on the data for each slot in the slot candidate CS table T2.

[0039] 5 is an explanatory diagram showing an example of a selection condition weighting table T3 according to an embodiment. In FIG. 5, the selection condition weighting table T3 has items of "number" for identifying the record of each selection condition, "condition" indicating each condition to which weighting is applied, and "weighting" indicating the weighting value when each condition is applied.

[0040] The record numbered 1 indicates that a weight of +10 is assigned to CS20, which is a connection candidate, when the received electric field strength value (RSSI value) is equal to or greater than 50. Note that, although "50" is shown as the threshold value of the received electric field strength in FIG. 5, the threshold value is not particularly limited.

[0041] Also, record number 2 indicates that a weight of +2 is assigned according to the number of CS20 sorted for each slot. For example, if the number of candidate CS20s transmitting in CCH transmission slot 2 is 3, the weight is +6.

[0042] Moreover, record number 3 indicates that if there is a CS with a relationship of one slot between them, a weighting of +2 is assigned to each of the related slots.

[0043] 5 shows three conditions numbered 1 to 3, but the number of conditions is not particularly limited, and the weighting value of each condition is not particularly limited either.

[0044] The result of weighting the data for each slot in the slot-by-slot candidate CS table T2 using the selection condition weighting table T3 is the slot-by-slot weighted candidate CS table in FIG.

[0045] Fig. 6 is an explanatory diagram showing an example of a slot-by-slot weighting candidate CS table T4 according to the embodiment. In Fig. 6, the slot-by-slot weighting candidate CS table T4 has an item of "weighting" indicating a value (weighting value) weighted according to a condition for each CCH transmission slot, in addition to the above-mentioned "CCH transmission slot", "CS ID", and "received electric field strength".

[0046] For example, CCH transmission slot 0 has one CS20 (+2) with a received electric field strength of 50 or more (+10), so the "weighting" is +12.

[0047] In addition, CCH transmission slot 1 has a total of two CS20s (+4), including a CS20 (CS ID 4C557FB1454) with a received field strength of 50 or more (+10). In addition, there is also a CS20 (+2) in the slot (slot 3) one slot away from the slot in question (slot 1), so in total, the "weighting" of CCH transmission slot 1 is +16.

[0048] CCH transmission slot 3 has one CS20 (+2) with a received field strength of 50 or more (+10), and there is also a CS20 (+2) in the slot (slot 1) one slot away from that slot (slot 3), so in total, the "weighting" of CCH transmission slot 3 is +14.

[0049] <s24> The communication control unit 12 performs a maximum weighted slot selection process to select the slot with the largest weighted value in the weighting process of step S23 described above. In the example of Fig. 6, slot 1 with a weighted value of +16 is selected.

[0050] <s25> Next, the communication control unit 12 performs maximum RSSICS selection processing to select as the optimal CS the CS with the highest received electric field strength in the slot selected in step S24 above, using the RSSI comparison unit 14. In the example of Fig. 6, since the CS 20 with CS ID "4C557FB1454" has the highest electric field strength of "69" in CS 20 in CCH transmission slot 1, the CS 20 with CS ID "4C557FB1454" is selected as the CS 20 to connect to, and the CS search processing ends.

[0051] (A-3) Effects of the embodiment According to this embodiment, the following effects are obtained.

[0052] When the PHS terminal 10 selects CS20 as the connection destination for a call or the like, instead of selecting the CS20 with the strongest received electric field strength as in the past, the PHS terminal 10 selects CS20 taking into consideration the condition that "there is a CS with one slot spaced apart," which is easier to execute a high-speed handover.

[0053] Therefore, even if the connection with the existing CS 20 deteriorates due to the PHS terminal 10 moving, etc., and a handover is performed, the CS 20 is selected in advance considering the conditions that make it easier to perform a high-speed handover, so the possibility of performing a high-speed handover is improved. Therefore, the PHS terminal 10 can provide speech quality with almost no voice disconnection time. [Explanation of symbols]

[0054] 10...PHS terminal, 11...wireless communication unit, 12...communication control unit, 13...RSSI acquisition unit, 14...RSSI comparison unit, 15...CS data storage unit, T1...candidate CS table, T2...per-slot candidate CS table, T3...selection condition weighting table, T4...per-slot weighting candidate CS table.

Claims

1. A wireless communication device that performs wireless communication with a wireless base station that divides a unit communication period into a plurality of slots and uses a certain slot within the unit communication period as a slot for transmitting control information, a first wireless communication control means for receiving the control information from a plurality of the wireless base stations and searching for each of the wireless base stations capable of communicating with the wireless communication device; a second wireless communication control means for, when selecting a connection destination from among the searched wireless base stations, first evaluating a point-adding method based on whether or not a plurality of conditions are met for each slot for transmitting the control information, and, when there is a wireless base station that uses a slot that is spaced from each slot under evaluation as a slot for transmitting the control information, evaluating the slot under evaluation to add a point; a third wireless communication control means for selecting a connection destination from among the wireless base stations that use the slot that is most highly evaluated by the second wireless communication control means as a slot for transmitting the control information; A wireless communication device comprising:

2. 2. The wireless communication device according to claim 1, wherein said wireless base station and said wireless communication device communicate with each other by wireless radio waves of a PHS system.

3. A computer installed in a wireless communication device that performs wireless communication with a wireless base station that divides a unit communication period into a plurality of slots and uses a certain slot in the unit communication period as a slot for transmitting control information. a first wireless communication control means for receiving the control information from a plurality of the wireless base stations and searching for each of the wireless base stations capable of communicating with the wireless communication device; a second wireless communication control means for, when selecting a connection destination from among the searched wireless base stations, first evaluating a point-adding method based on whether or not a plurality of conditions are met for each slot for transmitting the control information, and, when there is a wireless base station that uses a slot that is spaced from each slot under evaluation as a slot for transmitting the control information, evaluating the slot under evaluation to add a point; a third wireless communication control means for selecting a connection destination from among the wireless base stations using the slot evaluated most highly by the second wireless communication control means as a slot for transmitting the control information; A wireless communication program characterized by causing the wireless communication program to function as described above.

4. A wireless communication method for a wireless communication device that performs wireless communication with a wireless base station, the method comprising: dividing a unit communication period into a plurality of slots; and using a certain slot in the unit communication period as a slot for transmitting control information, the method comprising: The wireless communication device includes a first wireless communication control means, a second wireless communication control means, and a third wireless communication control means, the first wireless communication control means receives the control information from a plurality of the wireless base stations to search for each of the wireless base stations capable of communicating with the wireless communication device; the second wireless communication control means, when selecting its own connection destination from among the searched wireless base stations, first evaluates a point-adding method based on whether or not a plurality of conditions are met for each slot for transmitting the control information, and in this case, when there is a wireless base station that uses a slot that is spaced one space from each slot under evaluation as a slot for transmitting the control information, performs an evaluation to add a point to the slot under evaluation; The third wireless communication control means selects a connection destination from among the wireless base stations that uses the slot that is most highly evaluated by the second wireless communication control means as a slot for transmitting the control information.

23. A wireless communication method comprising:

Images