Communication apparatus and communication system

There is disclosed a communication apparatus which wirelessly communicates information with a first other communication apparatus by a first communication method and using a second frequency band which is at least partially overlapping a first frequency band usable according to the first communication method. The communication apparatus includes a first communicator which implements the wireless information communication with the first other communication apparatus by the first communication method, and a requestor which requests the first other communication apparatus, where at least there is a possibility that a field strength of an external radio wave in the second frequency band is equal to or larger than a predetermined threshold, to increase the number of times the first other communication apparatus sends information when making the wireless information communication with the communication apparatus using the second frequency band, as compared to where there is not the possibility.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent Application No. 2007-46496, which was filed on Feb. 27, 2007, the disclosure of which is herein incorporated by reference in its entity.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a communication apparatus that makes a wireless communication by a communication method, and particularly to a communication apparatus that can maintain an excellent communication quality in a wireless communication even when the wireless communication is subjected to interference by an external radio wave.

2. Description of Related Art

There are known communication apparatuses capable of wirelessly communicating information or data by various methods that use respective frequency bands, which in some cases overlap with one another.

When such overlapping of the frequency bands used in the wireless communications made by the communication apparatuses occurs, the wireless communications interfere with one another, inviting an increase in a transfer error rate of each wireless communication. In particular, when the transfer error rate is thus increased in a communication made by a communication apparatus that wirelessly communicates audio data, such as digital cordless telephone and radio communication equipment, there arises a problem that the audio quality deteriorates.

To deal with the problem, JP-A-6-224837 (see paragraph [0012] of JP-A-6-224837) proposes a mobile wireless telephone system in which a transmitting unit sends same audio data repeatedly a plurality of times, and a receiving unit selects a non-erroneous one of a received plurality of pieces of the same audio data, and converts the selected piece of the audio data into an audio signal, which is outputted or played.

The mobile wireless telephone system can decrease the transfer error rate and accordingly maintain an excellent communication or audio quality. However, the receiving unit should repeatedly implement a same reception processing for all the pieces of the audio data, consuming a lot of electricity.

In view of this, JP-A-11-341534 (see paragraph [0019] of JP-A-11-341534) proposes a paging receiver that receives information in units of subframes and detects an error in received information subframe by subframe. When any error is not found or detected in a subframe, the subframe is received. The subframe reception of which is thus complete will not be received again. More specifically, when the “self-frame” is received by the paging receiver the next and following times, a processing of receiving the subframe is not implemented, thereby reducing the power consumption.

However, the paging receiver should implement a processing of detecting an error for every subframe, thereby making the processing in the paging receiver to receive information relatively complex as a whole.

SUMMARY OF THE INVENTION

This invention has been developed in view of the above-described situations, and it is an object of the invention, therefore, to provide a communication apparatus and a communication system which can decrease the transfer error rate with a simple processing while saving power.

To attain the above object, the invention provides a communication apparatus which wirelessly communicates information with a first other communication apparatus by a first communication method and using a second frequency band which is at least partially overlapping a first frequency band usable according to the first communication method. The communication apparatus includes (a) a first communicator which implements the wireless information communication with the first other communication apparatus by the first communication method, and (b) a requestor which requests the first other communication apparatus, where at least there is a possibility that a field strength of an external radio wave in the second frequency band is equal to or larger than a predetermined threshold, to increase the number of times the first other communication apparatus sends information when making the wireless information communication with the communication apparatus using the second frequency band, as compared to where there is not the possibility.

According to the communication apparatus, the first communicator wirelessly communicates with the first other communication apparatus, using the second frequency band, and by the first communication method according to which a first frequency band is used. At least a part of the second frequency band overlaps the first frequency band.

Where there is a possibility that the field strength of the external radio wave in the second frequency band is equal to or larger than the predetermined threshold, the requestor requests the first other communication apparatus to increase the number of times the first other communication apparatus sends the communication apparatus information through, or using, the second frequency band, as compared to where there is not such a possibility.

That is, when the field strength of the external radio wave in the second frequency band is equal to or larger than the threshold, there is a risk of increase in a transfer error rate of the wireless communication made between the first communicator and the first other communication apparatus through the second frequency band, due to interference by the external radio wave, which results in degradation in the communication quality.

According to the communication apparatus of the invention, however, when making a wireless communication with the first other communication apparatus using the second frequency band, the communication apparatus receives information from the first other communication apparatus repeatedly a number of times that is larger than that in the case where there is not the above-described possibility, as a result of the request made by the requester. Thus, even when situated in an environment where the communication quality might otherwise degrade due to the interference with the external radio wave, the communication apparatus can maintain an excellent communication quality.

On the other hand, where there is not the possibility that the field strength of the external radio wave is equal to or larger than the threshold, in other words, where there is not a possibility that the external radio wave interferes with the wireless communication made between the communication apparatus and the first other communication apparatus using the second frequency band, the number of times the first other communication apparatus sends information is made relatively small, thereby enabling to save power while maintaining an excellent communication quality.

According to a first preferable form of the communication apparatus, the requestor includes a field-strength measuring portion for measuring the field strength of the external radio wave in the second frequency band, and requests the first other communication apparatus, where the field strength measured by the field-strength measuring portion is equal to or larger than the predetermined threshold, to increase the number of times as compared to where the field strength measured is smaller than the predetermined threshold.

In the communication apparatus of the first preferable form, the request to increase the number of times is made on the basis of the measurement of the field strength of the external radio wave. Thus, without making complex the processing to receive the information, the excellent communication quality can be maintained while power is saved, with stability.

According to a second preferable form of the communication apparatus, the communication apparatus further includes a second communicator which wirelessly communicates information with a second other communication apparatus, which is different from the first other communication apparatus, by a second communication method according to which the second frequency band is usable, and the requestor requests the first other communication apparatus, while the second communicator is held in a state capable of making the wireless communication with the second other communication apparatus, to increase the number of times as compared to while the second communicator is not held in the state.

In the communication apparatus of the second preferable form, the first communicator makes a wireless communication with the first other communication apparatus by the first communication method according to which the first frequency band is usable, and the second communicator makes a wireless communication with the second other communication apparatus by the second communication method according to which the second frequency band is usable, with the second frequency band at least partially overlapping the first frequency band.

While the second communicator is held in the state capable of making the wireless communication, the communication apparatus determines that there is the possibility that the field strength of the external radio wave in the second frequency band is equal to or larger than the threshold, and thus the requestor requests the first other communication apparatus to increase the number of times the first other communication apparatus wirelessly sends information through or using the first frequency band as compared to while the second communicator is not held in the state capable of making the wireless communication. Thus, while the second communicator is held in the state capable of making the wireless communication, the first other communication apparatus sends information the increased number of times.

The second frequency band, through which the second communicator makes the wireless communication, at least partially overlaps the first frequency band through which the first communicator makes the wireless communication. Hence, while the second communicator is held in the state capable of making the wireless communication, the wireless communication made by the first communicator through or using the first frequency band might interfere with the wireless communication made by the second communicator through or using the second frequency band, which results in degradation in the communication quality of the wireless communication made by the first communicator.

According to the communication apparatus of the second preferable form, however, while the second communicator is in the state capable of making the wireless communication, the first other communication apparatus sends information the increased number of times in the wireless communication between the first communicator and the first other communication apparatus, as a result of the request made by the requester. Thus, even in an environment where the communication quality of the wireless communication made by the first communicator might otherwise degrade due to the interference with the wireless communication made by the second communicator, the excellent communication quality of the wireless communication made by the first communicator can be maintained.

On the other hand, while the second communicator is not held in the state capable of making the wireless communication, the number of times the first other communication apparatus sends information is not increased. That is, where there is not the possibility that the wireless communication made by the second communicator interfere with the wireless communication made by the first communicator, the number of times is not unnecessarily increased, thereby saving power.

The processing to maintain the excellent communication quality while saving power is implemented on the basis of whether the second communicator is held in the state capable of making the wireless communication or not. Hence, it is enabled to maintain the excellent communication quality while saving power, without making complex the processing to receive information.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, there will be described one presently preferred embodiment of the invention, by referring to the accompanying drawings.

Referring first toFIGS. 1 and 2, there will be described a MFP (Multi Function Peripheral)1including a communication apparatus according to one embodiment of the invention.FIG. 1is an external view of the MFP1.

The MFP1has various functions such as speech communication function, facsimile function, printer function, scanner function, and copy function. In this embodiment, the MFP1takes the form of a base unit of a digital cordless telephone system, and is used mainly for making a speech communication with a digital cordless handset31or a cordless unit (shown inFIG. 3) of the digital cordless telephone system and an external apparatus (not shown) connected with the digital cordless telephone system via a telephone line network100(shown inFIG. 3). The MFP1can also function as a communication apparatus capable of wireless data communication with an access point51(shown inFIG. 3) in compliance with a wireless LAN standard.

As shown inFIG. 1, the MFP1includes a main housing2and an upper housing3. The main housing2is box-shaped and open on the upper side. The upper housing3is attached to the main housing2at a lateral side (i.e., at the left-hand side as seen inFIG. 1) to be vertically movable with respect to the main housing2such that the upper housing3is turned around a pivot shaft portion (not shown) such as hinge or hinge portion. The main housing2and the upper housing3are formed of synthetic resin by injection molding.

At a front side of the upper housing3(i.e., the lower side as seen inFIG. 1), an operation panel30is disposed. The operation panel30includes a first manual operation portion15having numerical buttons, a communication start button, a function button, and others. A user manipulates the first manual operation portion15to turn on/off the MFP1, select a function to be implemented, and input various instructions.

The operation panel30further includes a first display portion16that may be a liquid crystal display (LCD). On the first display portion16are presented a menu, the operation status of the MFP1, and others, in response to a manipulation of the first manual operation portion15. That is, the user manipulates the first manual operation portion15to have information corresponding to the manipulation be presented on the first display portion16. Thus, the user can view various kinds of information such as the communication status between the MFP1and the access point51and that between the MFP1and the cordless handset31.

In the upper housing3, a scanner portion20is disposed on the rear side (i.e., on the upper side as seen inFIG. 1) of the operation panel30. The scanner portion20includes a document reading table201functioning as a FBS (Flatbed Scanner), and a document cover203having an ADF (Auto Document Feeder)202. The document cover203is attached to the document reading table201at the rear side of the MFP1by means of a hinge (not shown) such that the document cover203is movable or openable/closable relative to the document reading table201. Although not shown, a platen glass is disposed at an upper surface of the document reading table201, and an image reading unit is disposed inside the document reading table201.

On the other hand, in the main housing2is disposed a printer portion21, which is an image recording apparatus of inkjet type that records an image on a recording sheet by selectively ejecting ink droplets on the basis of image data read by the scanner portion20or inputted from an external device. It is noted, however, that the image recording apparatus or the printer portion may not be of inkjet type, but various other recording methods such as electrophotography or thermal transfer can be employed as a method of image recording.

At the front side of the MFP1or of the printer portion21, an opening5is formed. In the opening5is extractably inserted a sheet supply cassette211, on which a plurality of recording sheets are stacked. Over the sheet supply cassette211is disposed a sheet catch tray212onto which a recording sheet on which an image has been recorded is ejected.

Inside the main housing2and inside the printer portion21, a sheet feed path extends upward from a rear side of the sheet supply cassette211and then turns frontward in a U-like shape to be connected to the sheet catch tray212. In the printer portion2, a sheet supply unit and a printhead (neither shown) are also disposed. The sheet supply unit supplies or picks up the recording sheets one by one from the rear side of the sheet supply cassette211. The printhead is disposed in the sheet feed path and ejects ink droplets onto a surface of the recording sheet being fed along the sheet feed path to record an image.

On a left side wall2aof the main housing2, a base handset24(shown inFIG. 3) and a support portion (not shown) that supports the base handset24while the MFP1is in a standby mode are disposed, so as to enable a speech communication with the cordless handset31or with an external apparatus through the telephone line network100. Thus, the MFP1is constituted by a main body and the support portion

A wireless communication unit81is attached to a right rear end portion of the main housing2. The wireless communication unit81includes a casing82of synthetic resin, and accommodates a communication board (not shown) including a first digital-cordless-communication control portion26(shown inFIG. 3), detailed description of which will be provided later. In brief, the first digital-cordless-communication control portion26wirelessly connects the base handset24of the MFP1as the base unit the cordless handset31located at a position remote from the MFP1, and has a first cordless-phone antenna27protruding from the casing82to transmit and receive signals.

As described above, the MFP1has the base handset24attached to the MFP1as the base unit, and the wireless communication unit81that wirelessly connects the base handset24to the cordless handset31. Thus, the base handset24and the cordless handset31are selectively used as desired, and further a communication can be made between the base handset24and the cordless handset31.

The main housing2has four corners including a corner2A and a corner2B that are opposed to each other. A wireless communication unit board (or a wireless LAN board)60including a wireless LAN communication control portion18(shown inFIG. 3), and a main circuit board (not shown) for electrically controlling operations of devices included in the MFP1, are disposed inside the corner2A. The wireless communication unit81accommodating the communication board including the first digital-cordless-communication control portion26is attached to the corner2B.

According to the MFP1, the wireless LAN board60including the wireless LAN communication control portion18and the main circuit board (not shown) are disposed apart from the wireless communication unit81accommodating the communication board (not shown) including the first digital-cordless-communication control portion26, as described above. Thus, the wireless LAN board60including the wireless LAN communication control portion18, the communication board including the first digital-cordless-communication control portion26, and the main circuit board do not tend to suffer from noise.

FIG. 2is a front elevational view of the wireless LAN board60including the wireless LAN communication control portion18. As shown inFIG. 2, the wireless LAN board60is constructed such that a circuit module60bis mounted on a surface of a glass epoxy substrate60awith a connector60cdisposed at a portion of the circuit module60b. A harness60dfor wiring is detachably connected with the connector60c.

As shown inFIG. 2, a main antenna portion60eand a sub antenna portion60fare formed on the surface of the substrate60aand in the vicinity of the circuit module60b. The main antenna portion60eis disposed at a lateral side of the circuit module60b, and the sub antenna portion60fis disposed at an upper side of the circuit module60b. The main and sub antenna portions60eand60fcooperate to constitute a wireless LAN antenna19(shown inFIG. 3), by means of which the wireless LAN communication control portion18and the access point51are wirelessly connected to each other.

Main sources of noise are a power source board (not shown) and the communication board including the first digital-cordless-communication control portion26. The first cordless-phone antenna27(i.e., an antenna for the telephone system) is connected with the communication board including the first digital-cordless-communication control portion26. Since the first cordless-phone antenna27is adapted to communications using intense radio waves, the first cordless-phone antenna27can be a high noise source particularly.

Hence, if the communication board (not shown) including the first digital-cordless-communication control portion26is disposed at a position close to the wireless LAN board60that wirelessly sends and receives data, the wireless LAN communication control portion18might be subjected to noise and unable to operate normally.

According to the MFP1, however, the wireless LAN board60is disposed at the front left corner2A of the main housing2, and the communication board including the first digital-cordless-communication control portion26is disposed at the opposing corner, i.e., the rear right corner2B of the main housing2. Thus, inside a single housing, namely, the main housing2, of the MFP1, the wireless LAN board60is positionally separated as much as possible from the communication board including the first digital-cordless-communication control portion26, in order that an operation of the wireless LAN board60does not tend to be adversely affected by an operation of the communication board including the first digital-cordless-communication control portion26. This arrangement is employed as an effective countermeasure to noise. Thus, the wireless LAN board60can make a normal communication.

Referring next toFIG. 3, which is a block diagram illustrating an electrical structure of the MFP1and the cordless handset31. The cordless handset31is a communication apparatus according to an embodiment of the invention, similarly to the MFP1. Further, the MFP1and the cordless handset31cooperate to constitute a communication system according to an embodiment of the invention.

As shown inFIG. 3, the MFP1mainly includes a first CPU11, a first ROM12, a first RAM13, a first flash memory14, the first manual operation portion15, the first display portion16, a speaker portion17, the wireless LAN communication control portion18, the wireless LAN antenna19, the scanner portion20, the printer portion21, a modem22, a line control portion23, the base handset24, a timing circuit25, and the first digital-cordless-communication control portion26. These members11-26are connected with one another through a first bus line28.

The first CPU11is an arithmetic unit that controls the members connected with one another via the first bus line28, in accordance with fixed values and programs stored in the first ROM12, the first RAM13, and the first flash memory14, or in accordance with various kinds of signals communicated through the wireless IAN communication control portion18, the line control portion23, and the first digital-cordless-communication control portion26.

The first ROM12is a memory not rewritable and includes a first control program area12awhere various kinds of control programs executed in the MFP1are stored. The control programs stored in the first control program area12ainclude programs for implementing processings illustrated inFIGS. 5,6and8A described later.

The first RAM13is a rewritable memory for temporarily storing various kinds of data. The first RAM13has a number n of multi-reception flags13a1-13an, i.e., a first multi-reception flag13a1, a second multi-reception f lag13a2, and a nth multi-reception flag13an, and a number n of multi-transmission flags, i.e., a first multi-transmission flag13b1, a second multi-transmission flag13b2, . . . and a nth multi-transmission flag13bn.

The first to nth multi-reception flags13a1-13anare assigned to respective frequency channels that are used when the MFP1functions as a digital cordless telephone and makes a wireless communication with the cordless handset31by utilizing FHSS technology.

Each of the multi-reception flags13a1-13anindicates a number of times a data piece is transmitted from the cordless handset31to the MFP1through a corresponding one of the channels. In other words, the multi-reception flag13a1-13anindicates whether a number of times a data piece is to be received by the MFP1from the cordless handset31through a corresponding channel is set at one or two. The value of the multi-reception flag13a1-13anis “OFF” when the number of times a data piece is received from the cordless handset31is set at one, and the value of the multi-reception flag13a1-13anis “ON” when the number of times a data piece is received from the cordless handset31is set at two.

For instance, the value of the first multi-reception flag13a1being “ON” means that the number of times a data piece is received by the MFP1through one of the channels which is associated with the first multi-reception flag13a1is set at two, and the value of the second multi-reception flag13a2being “OFF” means that the number of times a data piece is received by the MFP1through another channel which is associated with the second multi-reception flag13a2is set at one.

The values of the multi-reception flags13a1-13anare initialized or set to “OFF” when the MFP1is turned on, and suitably set to one of “ON” and “OFF” depending on the level of a field strength of an external radio wave in a reception-number setting processing (shown inFIG. 5and described later) that is repeatedly executed at predetermined time intervals, e.g., 10 ms. A detailed description on the switching of the values of the multi-reception flags13a1-13anwill be provided later.

The first to nth multi-transmission flags13b-13bnare assigned to respective frequency channels that are used when the MFP1functions as the digital cordless telephone and makes a wireless communication with the cordless handset31by utilizing FHSS technology.

Each of the multi-transmission flags13b1-13bnindicates whether a number of times the MFP1transmits a data piece to the cordless handset31through a corresponding one of the channels is set at one or two. The value of the multi-transmission flag13b1-13bnis “OFF” when the number of times a data piece is transmitted to the cordless handset31is set at one, and the value of the multi-transmission flag13b1-13bnis “ON” when the number of times a data piece is transmitted to the cordless handset31is set at two.

For instance, the value of the first multi-transmission flag13b1being “ON” means that the number of times a data piece is transmitted to the cordless handset31through one of the channels which is associated with the first multi-transmission flag13b1is set at two, and the value of the second multi-reception flag13b2being “OFF” means that the number of times a data piece is transmitted to the cordless handset31through another channel which is associated with the second multi-transmission flag13b2is set at one.

The values of the multi-transmission flags13b1-13bnare initialized or set to “OFF” when the MFP1is turned on, and thereafter suitably set to one of “ON” and “OFF” depending on a request from the cordless handset31as another communication apparatus, in a transmission-number setting processing (illustrated inFIG. 6and described later) that is repeatedly executed at predetermined time intervals, e.g., 10 ms. A detailed description on the switching of the values of the multi-transmission flags13b1-13bnwill be provided later.

The first flash memory14is a rewritable non-volatile memory. Data stored in the first flash memory14is retained after the MFP1is turned off. The speaker portion17outputs various kinds of sounds depending on the situations to inform the user of the situations for instance, the various kinds of sounds include an operation sound outputted when the first manual operation portion15is manipulated, an alarm sound outputted when an error occurs, and a ring alert outputted when a call is incoming.

The scanner portion20operates to read an image on a document sheet set on the document reading table201. The first display portion16can present the image, and printable data of the image can be generated on the basis of which the printer portion21can record the image. The data of the image read by the scanner portion20is stored in a predetermined memory area in the first RAM13in a case where the MFP1is placed in one of a facsimile mode, a scanner mode, and a copy mode. The printer portion21operates to record an image on a recording sheet supplied from the sheet supply cassette211on the basis of an instruction from the first CPU11.

The modem22modulates data to be transmitted that is stored in the first RAM13, into an image signal transmittable to the telephone line network100, and sends the modulated data to the telephone line network100through the line control portion23. The modem22also receives an image signal inputted from the telephone line network100through the line control portion23, and demodulates the image signal into image data that can be presented on the first display portion16or recordable by the printer portion21. The line control portion23is connected with the telephone line network100, and operates to send a dial signal to the telephone line network100and respond to a ring signal from the telephone line network100.

The base handset24is used for making a speech communication with the cordless handset31or an external apparatus (not shown) connected with the MFP1via the telephone line network100. The base handset24has a microphone and a speaker (neither shown). The microphone converts a sound into an audio signal and outputs the audio signal to the circuit control portion23, and the speaker converts an audio signal inputted from the circuit control portion23into a sound and outputs the sound to the external space.

The base handset24is electrically connected to the line control portion23or the first digital-cordless-communication control portion26when the base handset24is pickup up or lifted off the support portion of the MFP1, that is, when an “off-hook” operation is made. When the base handset24is replaced onto the support portion of the MFP1, that is, when an “on-hook” operation is made, the base handset24is disconnected from the line control portion23or the digital cordless communication control portion26. The timing circuit25is a known circuit that has an internal clock representing the current time and calculates a time period by comparing a time at which a counting of time is commenced to the current time.

The first digital-cordless-communication control portion26constitutes a part of the communication board, and is connected with the first cordless-phone antenna27. When the base handset24and the first digital-cordless-communication control portion26are connected to each other as a result of an off-hook operation of the base handset24or for other reasons, the MFP1and the cordless handset31are wirelessly connected to each other.

In the present embodiment, the MFP1and the cordless handset31wirelessly communicates with each other by a FHSS method, according to which a plurality of channels having respective center frequencies and defined across a frequency band (2.4000-2.4835 GHz) are usable. The frequency band of 2.4000-2.4835 GHz is dedicated to digital cordless telephone system according to communications standards.

When an audio signal is sent from the base handset24to the digital cordless communication control portion26, the audio signal is converted into a digital signal for communication and outputted or sent to the cordless handset31. On the other hand, when a digital signal for communication is received from the cordless handset31, the digital signal is converted into an audio signal and outputted to the base handset24.

The first digital-cordless-communication control portion26includes a first received-field-strength measuring portion26a, which measures a field strength of an external radio wave received through the first cordless-phone antenna27. The first digital-cordless-communication control portion26further includes a first frequency-hopping control portion (not shown) including a hopping pattern table, a hopping counter, and a clock, for implementing a wireless communication with the cordless handset31by the FHSS method.

The wireless LAN communication control portion18constitutes a part of the wireless LAN board60, and is connected with the wireless LAN antenna19including the main antenna portion60eand the sub antenna portion60e. The wireless LAN communication control portion18is wirelessly connected with the access point51as a wireless LAN station thorough the wireless LAN antenna19. Thus, the MFP1can make a data communication with wireless LAN terminals61,62that are wirelessly connected with the access point51.

The wireless LAN communication control portion18is wirelessly connected with the access point51via the wireless LAN antenna19, and with a LAN200via the access point51. Thus, the MFP1can make a data communication with an external apparatus (not shown) connected to the LAN200.

The access point51is a wireless LAN device known as a communication device and wirelessly connected with a plurality of wireless LAN apparatuses such as the MFP1and the wireless LAN terminals61,62, so as to function as a relay device for connecting these wireless LAN apparatuses to the LAN200.

On the other hand, as shown inFIG. 3, the cordless handset31mainly includes a second CPU32, a second ROM33, a second RAM34, and a second flash memory35, a second manual operation portion36, a second display portion37, a transceiver circuit38, and a second digital-cordless-communication control portion39. These members32-39are connected with one another through a second bus line40.

The second CPU32is an arithmetic unit that controls the members connected with one another via the second bus line40, in accordance with fixed values and programs stored in the second ROM33, the second RAM34, and the second flash memory35, or in accordance with various kinds of signals communicated through the wireless LAN communication control portion39.

The second ROM33is a memory not rewritable and includes a second control program area33awhere various kinds of control programs executed in the cordless handset31are stored. The control programs stored in the second control program area33ainclude programs for implementing processings illustrated inFIGS. 6,7and8B and described later.

The second RAM34is a rewritable memory for temporarily storing various kinds of data. The second RAM34has a number n of multi-transmission flags34a1-34an, i.e., a first multi-reception flag34a1, a second multi-reception flag34a2, . . . and a nth multi-reception flag34an, and a number n of multi-transmission flags, i.e., a first multi-transmission flag34b1, a second multi-transmission flag34b2, . . . and a nth multi-transmission flag34bn.

The first to nth multi-reception flags34a1-34anare assigned to respective frequency channels that are used when the cordless handset31functions as a digital cordless telephone and makes a wireless communication with the MFP1by the FHSS method.

Each of the multi-reception flags34a1-34anindicates whether a number of times a data piece is transmitted from the MFP1to the cordless handset31through a corresponding one of the channels is set at one or two. The value of the multi-reception flag34a1-34anis “OFF” when the number of times a data piece is received from the MFP1is set at one, and the value of the34a1-34anflag is “ON” when the number of times a data piece is received from the MFP1is set at two.

For instance, the value of the first multi-reception flag34a1being “ON” means that the number of times a data piece is received by the cordless handset31through one of the channels which is associated with the first multi-reception flag34a1is set at two, and the value of the second multi-reception flag34a2being “OFF” means that the number of times a data piece is received by the cordless handset31through another channel which is associated with the second multi-reception flag34a2is set at one.

The values of the multi-reception flags34a1-34anare initialized or set to “OFF” when the cordless handset31is turned on, and thereafter suitably set to one of “ON” and “OFF” depending on a field strength of an external radio wave in a reception-number setting processing (illustrated inFIG. 7and described later) that is executed at constant intervals, e.g., 10 ms. A detailed description on the switching of the values of the multi-reception flags34a1-34anwill be provided later.

The first to nth multi-transmission flags34b1-34bnassigned to respective frequency channels that are used when the cordless handset31functions as the digital cordless telephone and makes a wireless communication with the MFP1by the FHSS method.

Each of the multi-transmission flags34b1-34bnindicates whether a number of times the cordless handset31transmits a data piece to the MFP1through a corresponding one of the channels is set at one or two. The value of the multi-transmission flag34b1-34bnis “OFF” when the number of times a data piece is transmitted to the MFP1is set at one, and the value of the multi-transmission flag34b1-34bnis “ON” when the number of times a data piece is transmitted to the MFP1is set at two.

For instance, the value of the first multi-transmission flag34b1being “ON” means that the number of times a data piece is transmitted to the MFP1through one of the channels which is associated with the first multi-transmission flag34b1is set at two, and the value of the second multi-reception flag34b2being “OFF” means that the number of times a data piece is transmitted to the MFP1through another channel which is associated with the second multi-transmission flag34b2is set at one.

The values of the multi-transmission flags34b1-34bnare initialized or set to “OFF” when the cordless handset31is turned on, and thereafter suitably set to one of “ON” and “OFF” depending on a request from the MFP1in a transmission-number setting processing (illustrated inFIG. 6and described later) that is executed at constant intervals, e.g., 10 ms. A detailed description on the switching of the values of the multi-transmission flags34b1-34bnwill be provided later.

The second flash memory35is a rewritable non-volatile memory. Data stored in the second flash memory35is retained after the cordless handset31is turned off. The second manual operation portion36is manipulated when the user inputs an instruction related to management of the cordless handset31, and when a speech communication is made between the cordless handset31and the MFP1or an external apparatus (not shown) connected to the cordless handset31via the MFP1and the telephone line network100. The second manual operation portion36has numerical buttons (or a numeric keypad), a communication start button, a function button, and others. The second display portion37operates, when a manipulation to manage the cordless handset31is made, and when a speech communication between the cordless handset31and the MFP1or an external apparatus (not shown) is made, to present a telephone number inputted through the second manipulation portion36, and various kinds of information during a speech communication for instance, the second display portion37is constituted by a display device such as LCD.

The transceiver circuit38is a device for enabling a speech communication with the MFP1or an external apparatus (not shown) connected to the cordless handset31via the telephone line network100. The transceiver circuit38is connected with a microphone and a speaker (neither shown). The microphone converts a sound into an audio signal and inputs the audio signal to the transceiver circuit38. The speaker converts the audio signal inputted from the transceiver circuit38into a sound and outputs the sound to the external space. The speaker also outputs various kinds of sounds depending on the situations to inform the user of the situations for instance, the various kinds of sounds include an operation sound outputted when the second manual operation portion36is manipulated, an alarm sound outputted when an error occurs, and a ring alert outputted when a call is incoming.

The transceiver circuit38is connected to the second digital-cordless-communication control portion39when the user manipulates the second manual operation portion36in order to start a speech communication. The transceiver circuit38is disconnected from the second digital-cordless-communication control portion39when the user manipulates the second manual operation portion36in order to terminate the speech communication.

With the second digital-cordless-communication control portion39, a second cordless-phone antenna47is connected. When the transceiver circuit38and the second digital-cordless-communication control portion39are connected to each other, by the manipulation of the second manual operation portion36to start a speech communication or in other ways, a wireless communication is established between the cordless handset31and the MFP1, by the FHSS method as described above.

When an audio signal is sent to the second digital-cordless-communication control portion39from the transceiver circuit38, the second digital-cordless-communication control portion39converts the audio signal into a digital signal for wireless communication, which is sent out or outputted to the MFP1. On the other hand, when a digital signal for wireless communication as sent from the MFP1is received by the second digital-cordless-communication control portion39, the second digital-cordless-communication control portion39converts the digital signal into an audio signal, which is outputted to the transceiver circuit38.

The second digital-cordless-communication control portion39includes a second received-field-strength measuring portion39a, which measures a field strength of an external radio wave received through the second cordless-phone antenna47. The second digital-cordless-communication control portion39further includes a second frequency-hopping control portion (not shown) including a hopping pattern table, a hopping counter, and a clock, for implementing a wireless communication with the MFP1by the FHSS method.

Referring now toFIG. 4, there will be described an interference by an external radio wave to the wireless communication (indicated by imaginary line C) between the MFP1and the cordless handset31, when the MFP1and the cordless handset31function as a base unit and a cordless unit of a digital cordless telephone system, respectively.

FIG. 4is a schematic view of a system including the MFP1and the cordless handset31functioning as a base unit and cordless handset of a digital cordless telephone system and making a wireless communication, and wireless LAN apparatuses X1, X2as sources of external radio waves affecting operations of the MFP1and the cordless handset31. The wireless LAN apparatuses X1, X2may be various apparatuses capable of communication using wireless LAN technology, such as access point and wireless LAN printer.

Generally, usable frequency bands are dedicated to respective communication methods or communication standards, and frequency channels are defined corresponding to respective center frequencies of the frequency bands.

For instance, a frequency band of 2.4000-2.4835 GHz is used by digital cordless telephone system, that is, used when a wireless communication is made between a base unit (corresponding to the MFP1in the present embodiment) and a cordless unit (corresponding to the cordless handset31) of a digital cordless telephone system, and between cordless handsets of a digital cordless telephone system. A frequency band of 2.4000-2.497 GHz is used when a wireless communication is made in compliance with wireless communication standards such as IEEE802.11b/g that is a wireless LAN standard allowing connection and communication between a terminal apparatus (corresponding to the MFP1in the present embodiment) and an access point (corresponding to the access point51and the wireless LAN apparatuses X1, X2in the present embodiment).

As described above, wireless communications can be made by various apparatuses through or using a same frequency band. Such wireless communications interfere with one another due to overlapping of the frequency bands used in the wireless communications, resulting in increase in a transfer error rate of each of the wireless communications, degrading the communication quality thereof.

For instance, as shown inFIG. 4, where a speech communication is made between the MFP1and the cordless handset31respectively functioning as a base unit and a cordless unit of a digital cordless telephone system, in the form of a wireless communication (indicated by imaginary line C) in compliance with the digital cordless telephone standard, when external wireless LAN apparatuses X1, X2respectively make wireless communications in compliance with a wireless LAN standard or standards, the frequency band used by the digital cordless telephone system and the frequency band(s) used by the wireless LAN communications overlap with each other, which might result in interference between the wireless communication mad through the digital cordless telephone system (i.e., the wireless communication between the MFP1and the cordless handset31), and the wireless LAN communications respectively made by the wireless LAN apparatuses X1, X2. When such interference occurs, the transfer error rates of the communications increase and the communication qualities thereof degrade, which causes degradation in the speech communication made through the digital cordless telephone system, for instance.

Referring toFIG. 4, from the standpoint of the MFP1and the cordless handset31, the wireless LAN apparatuses X1, X2are sources of external radio waves adversely affecting the communication between the MFP1and the cordless handset31. The level of the interference of each of the external radio waves with the communication between the MFP1and the cordless handset31depends on the level of the field strength of the external radio wave as received by the MFP1and the cordless handset31. That is, the level of the interference of the external radio wave with the wireless communication made through the digital cordless telephone system or between the MFP1and the cordless handset31increases with the level of the field strength of the external radio wave.

The level of the field strength of the external radio wave as received by the MFP1and the cordless handset31depends on factors including a positional relationship between the MFP1or the cordless handset31and the sources of the external radio waves (i.e., the wireless LAN apparatuses X1, X2). For instance, as shown inFIG. 4, an external radio wave W1emitted from the wireless LAN apparatus X1is received by the first cordless-phone antenna27of the MFP1that is away from the wireless LAN apparatus X1by a distance L1, and also received by the second cordless-phone antenna47of the cordless handset31that is away from the wireless LAN apparatus X1by a distance L2. Since the distance L1is smaller than the distance L2, the field strength of the external radio wave WI as detected at the MFP1takes a value larger than that as detected at the cordless handset31. Hence, the external radio wave W1affects the speech communication more seriously at the MFP1than at the cordless handset31.

In this case, depending on the level of the field strength of the external radio wave W1, there occurs a state where the quality of audio received by the cordless handset31(i.e., the communication quality or speech quality at the cordless handset31) does not degrade, but the quality of the audio received by the MFP1considerably degrades.

For instance, when the external radio wave W1is emitted from the wireless LAN apparatus X1through or using a frequency channel 1 ch for making a wireless LAN communication, there occurs a state where when a wireless communication is made between the cordless handset31and the MFP1through or using a frequency channel overlapping the frequency channel 1 ch, the quality of the audio received by the cordless handset31does not degrade, but the quality of the audio received by the MFP1considerably degrades.

The cordless handset31recognizes that the quality of the audio received by itself is not adversely affected by the external radio wave W1emitted through the channel 1 ch, but can not recognize that there is a possibility that the MFP1is adversely affected by the external radio wave W1. That is, the cordless handset31can not recognize that when the cordless handset31makes a wireless communication with the MFP1using a frequency channel overlapping the frequency channel 1 ch, the quality of audio received by the MFP1is considerably poor.

On the other hand, an external radio wave W2emitted from the wireless LAN apparatus X2is received by the first cordless-phone antenna27of the MFP1that is away from the wireless LAN apparatus X2by a distance L3, and also received by the second cordless-phone antenna47of the cordless handset31that is away from the wireless LAN apparatus X2by a distance L4. Since the distance L3is larger than the distance L4, the field strength of the external radio wave W2as detected at the cordless handset31takes a value larger than that as detected at the MFP1. Hence, the external radio wave W2affects the speech communication more seriously at the cordless handset31than at the MFP1.

In this case, depending on the level of the field strength of the external radio wave W2, there occurs a state where the quality of audio received by the MFP1does not degrade, but the quality of audio received by the cordless handset31considerably degrades.

For instance, when the external radio wave W2is emitted from the wireless LAN apparatus X2through or using a frequency channel11 ch for making a wireless LAN communication, there occurs a state where when a wireless communication is made between the FMP1and the cordless handset31by using a frequency channel overlapping the frequency channel 11 ch, the quality of the audio received by the MFP1does not degrade, but the quality of the audio received by the cordless handset31considerably degrades.

The MFP1recognizes that the quality of the audio received by itself is not adversely affected by the external radio wave W2emitted through the channel111 ch, but can not recognize that there is a possibility that the cordless handset31is adversely affected by the external radio wave W2. That is, the MFP1can not recognize that when the MFP1makes a wireless communication with the cordless handset31through or using a frequency channel overlapping the frequency channel 11 ch, the quality of the audio received by the cordless handset31is considerably poor.

In the present embodiment, the MFP1is capable of making a wireless communication by functioning as a base unit of a digital cordless telephone system, and of making a wireless communication through a wireless LAN. A radio wave emitted from the wireless LAN antenna19of the MFP1is received as an external radio wave W3having a relatively high field strength by the first cordless-phone antenna27of the MFP1. When the MFP1makes a wireless communication with the cordless handset31, this wireless communication is subjected to interference by the external radio wave W3, resulting in degradation in the quality of the audio received by the MFP1in the wireless speech communication with the cordless handset31.

Referring next toFIGS. 5-8, there will be described a way of inhibiting the degradation in the quality of the received audio or in the communication quality, in the wireless communication between the MFP1and the cordless handset31, even in the presence of an external radio wave, so as to maintain an excellent communication quality.

FIG. 5is a flowchart illustrating a reception-number setting processing executed by the first CPU11of the MFP1. The reception-number setting processing ofFIG. 5is initiated when the MFP1is turned on, and repeatedly executed while the MFP1is on. During the repeated execution of the reception-number setting processing, the frequency channel, which is used in a wireless communication made through the digital cordless telephone system and is to be observed, is switched from one to another at constant time intervals (e.g., 10 ms).

As shown inFIG. 5, the reception-number setting processing is initiated with step S51when the MFP1is turned on. In step S51, initial settings are made, that is, the value of the frequency channel to be observed is set at an initial value, which corresponds to one of a plurality of frequency channels to be used in the wireless communication, and the first to nth multi-reception flags13a1-13anare set to “OFF”. By making the initial settings in step S51, the number of times the MFP1receives audio data from the cordless handset31is set at an initial value, that is one.

After step S51, the processing flow goes to step S52in which it is determined whether a wireless LAN communication is being made by the MFP1, that is, whether the wireless LAN communication control portion18is operating or in a standby state. When it is determined that a wireless LAN communication is being made, an affirmative decision (YES) is made in step S52, and the processing flow goes to step S53to send a request for multi-slot transmission with respect to the currently observed channel, to the cordless handset31.

After step S53, the processing flow goes to step S54to set one of the first to nth multi-reception flags13a1-13anthat corresponds to the currently observed channel to “ON”, and then goes to step S55in which the channel to be observed is updated or switched to another or the next channel. Then, the processing flow returns to step S52.

On the other hand, when it is determined in step S52that a wireless LAN communication is not being made, a negative decision (NO) is made, and the processing flow goes to step S56in which it is determined whether a field strength of an external radio wave emitted through or using a channel overlapping the currently observed channel, which field strength is measured by the first received-field-strength measuring portion26a, is equal to or larger than a predetermined threshold (e.g., −70 dbm) or not.

When it is determined in step S56that the field strength of the external radio wave emitted through or using the channel overlapping the currently observed channel is equal to or larger than the predetermined threshold, an affirmative decision (YES) is made and the processing flow goes to steps S53-S55. After step S55in which the channel to be observed is updated or switched to another or the next channel, the processing flow returns to step S52.

On the other hand, when it is determined in step S56that the field strength of the external radio wave emitted through or using the frequency channel overlapping the currently observed channel is smaller than the predetermined threshold, a negative decision (NO) is made and the processing flow goes to step S57to send the cordless handset31a request for a single-slot transmission with respect to the currently observed channel.

After step S57, the processing flow goes to step S58in which one of the first to nth multi-reception flags13a1-13anthat corresponds to the currently observed channel is set to “OFF”, and then goes to step S55to update or switch the channel to be observed to another or the next channel. Then, the processing flow returns to step S52.

When the request for multi-slot transmission is sent in step S53to the cordless handset31with respect to the currently observed channel, the cordless handset31sets to two the number of times the cordless handset31is to send audio data to the MFP1through or using the currently observed channel in the wireless communication with the MFP1, as shown inFIG. 6.

When the request for single-slot transmission is sent in step S57to the cordless handset31with respect to the currently observed channel, the cordless handset31sets to one the number of times the cordless handset31sends audio data to the MFP1through or using the currently observed channel in the wireless communication with the MFP1, as shown inFIG. 6.

Thus, according to the reception-number setting processing executed in the MFP1, when there is detected an external radio wave, which uses one of the channels usable by the MFP1to wirelessly communicate with the cordless handset31, and which has a field strength equal to or larger than the predetermined threshold, it is assumed that there is a possibility that the external radio wave interferes with the wireless communication between the MFP1and the cordless handset31, and the MFP1requests the cordless handset31to send data a number of times larger than the initial value (i.e., once), that is, twice, when the channel used by the external radio wave is used for the wireless communication between the MFP1and the cordless handset31. As a result, when the MFP1receives audio data from the cordless handset31through or using the channel, the audio data is received twice, or two pieces of the same audio data are received. Hence, even in the presence of the external radio wave that might interfere with the wireless communication between the MFP1and the cordless handset31and degrade the communication quality thereof, the communication quality is actually inhibited from degrading but is maintained excellently.

On the other hand, when there is detected an external radio wave, which uses one of the channels usable by the MFP1to wirelessly communicate with the cordless handset31, and which has a field strength smaller than the predetermined threshold, it is assumed that the external radio wave does not interfere with the wireless communication between the MFP1and the cordless handset31, and the MFP1requests the cordless handset31to send data a number of times that corresponds to the initial value (i.e., once) when the channel used by the external radio wave is used for the wireless communication between the MFP1and the cordless handset31. As a result, when the MFP1receives audio data from the cordless handset31through or using the channel that is free from the risk of degradation in the communication quality, the audio data is received once. Hence, the number of times data is received is not unnecessarily increased but is minimized, thereby saving power.

In the reception-number setting processing executed in the MFP1, a series of steps S52-S58is reiterated in a very short cycle, e.g., of 10 ms. Hence, when a wireless LAN communication is being made, audio data is received from the cordless handset31twice through or using substantially all the channels. As described above, a radio wave emitted from the wireless LAN antenna19highly probably interferes with the wireless communication between the MFP1and the cordless handset31. Hence, while a wireless LAN communication is being made, audio data is received twice through all the channels so as to inhibit degradation in the communication quality of the communication between the MFP1and the cordless handset31and to excellently maintain the communication quality.

The change or setting in the number of times the MFP1receives audio data from the cordless handset31is made in the reception-number setting processing such that the MFP1itself detects in step S52or S56a channel using which the wireless communication with the cordless handset31might interfere with an external radio wave, and requests the cordless handset31to increase the number of times the cordless handset31sends the MFP1audio data on the basis of the result of the detection. Hence, when there is an external radio wave that interferes with the wireless communication between the MFP1and the cordless handset31, the audio quality of the communication made through the frequency channel used by the external radio wave can be excellently maintained with stability.

With regard to the channel the wireless communication between the MFP1and the cordless handset31made using which is found by the MFP1and in step S52or S53to be free from the risk of interference with the external radio wave, the MFP1requests the cordless handset31to set at the initial value the number of times the cordless handset31sends audio data to the MFP1through or using the channel. Hence, the communication quality is not sacrificed for power saving.

Thus, according to the reception-number setting processing shown inFIG. 5and executed in the MFP1, the communication quality is excellently maintained while power is saved, without implementing a complex processing such as one for determining whether an error is included in every subframe.

FIG. 6is a flowchart illustrating a transmission-number setting processing executed by the second CPU32in the cordless handset31. The transmission-number setting processing ofFIG. 6is initiated when the cordless handset31is turned on, and repeatedly executed while the cordless handset31is on. During the repeated execution of the transmission-number setting processing, the frequency channel, which is used in a wireless communication made through the digital cordless telephone system and is to be observed, is switched from one to another at constant time intervals (e.g., 10 ms).

As shown inFIG. 6, the transmission-number setting processing is initiated with step S61when the cordless handset31is turned on. In step S61, initial settings are made, that is, the value of the channel to be observed is set at an initial value, which corresponds to one of a plurality of frequency channels to be used in the wireless communication, and the first to nth multi-transmission flags13b1-13bnare set to “OFF”. By making the initial settings in step S61, the number of times the cordless handset31sends audio data to the MFP1is set at an initial value, that is one.

After step S61, the processing flow goes to step S62in which it is determined whether a request for multi-slot transmission is received from the MFP1. When it is determined that a request for multi-slot transmission is received therefrom, an affirmative decision (YES) is made in step S62, and the processing flow goes to step S63to set one of the first to nth multi-transmission flags34b1-34bnin the cordless handset31that corresponds to the currently observed channel to “ON”. The processing flow then goes to step S64to update or switch the channel to be observed to another or the next channel, and returns to step S61. As a result of the implementation of step S63, when the cordless handset31sends audio data to the MFP1through or using the channel in question, the audio data is sent twice.

On the other hand, when it is determined in step S62that a request for multi-slot transmission is not received from the MFP1, a negative decision (NO) is made and the processing flow goes to step S65in which it is determined whether a request for single-slot transmission is received from the MFP1.

When it is determined in step S65that a request for single-slot transmission is received from the FMP1, an affirmative decision (YES) is made and the processing flow goes to step S66in which one of the first to nth multi-transmission flags34b1-34bnin the cordless handset31that corresponds to the currently observed channel is set to “OFF”. Then, the processing flow goes to step S64to update or switch the channel to be observed to another or the next channel, and returns to step S61. As a result of the implementation of step S66, when the cordless handset31sends audio data to the MFP1through or using the channel in question, the audio data is sent once.

On the other hand, when it is determined in step S65that a request for single-slot transmission is not received from the FMP1, a negative decision (NO) is made and the processing flow goes to step S64to update or switch the channel to be observed to another or the next channel, and returns to step S61. That is, when the cordless handset31receives neither a request for multi-slot transmission nor a request for single-slot transmission from the MFP1, the channel to be observed is updated or switched to another or the next channel, without changing the value of one of the first to nth multi-transmission flags34b1-34bnin the cordless handset31that corresponds to the currently observed frequency channel.

According to the transmission-number setting processing executed in the cordless handset31, the number of times the cordless handset31sends audio data to the MFP1is changed or set according to a request from the MFP1that is one of a request for multi-slot transmission or a request for single-slot transmission.

As described above, when the MFP1determines in the reception-number setting processing illustrated inFIG. 5on the basis of the field strength of the external radio wave that the MFP1receives, that the wireless communication using a channel might interfere with the external radio wave, the MFP1sends a request for multi-slot transmission with respect to the channel. On the other hand, when the MFP1determines that the wireless communication using a channel is not subjected to interference by the external radio wave, the MFP1sends a request for single-slot transmission with respect to the channel.

Hence, the number of times the cordless handset31sends audio data to the MFP1is set in the transmission-number setting processing to a number appropriate for the environment in which the MFP1is situated, thereby enabling maintenance of an excellent communication quality as well as power saving.

FIG. 7is a flowchart illustrating a reception-number setting processing executed by the second CPU32in the cordless handset31. The reception-number setting processing ofFIG. 7is initiated when the cordless handset31is turned on, and repeatedly executed while the cordless handset31is on. During the repeated execution of the reception-number setting processing, the frequency channel, which is used in a wireless communication made through the digital cordless telephone system and is to be observed, is switched from one to another at constant time intervals (e.g., 10 ms).

As shown inFIG. 7, the reception-number setting processing is initiated with step S71when the cordless handset31is turned on. In step S71, initial settings are made, that is, the value of the channel to be observed is set at an initial value, which corresponds to one of a plurality of frequency channels to be used in the wireless communication, and the first to nth multi-reception flags34a1-34anare set to “OFF”. By making the initial settings in step S71, the number of times the MFP1sends audio data to the cordless handset31is set at an initial value, that is one.

After step S71, the processing flow goes to step S72in which it is determined whether a field strength of an external radio wave of a frequency channel overlapping the currently observed channel, which field strength is measured by the second received-field-strength measuring portion39a, is equal to or larger than a predetermined threshold (e.g., −70 dbm) or not.

When it is determined in step S72that the field strength of the external radio wave of the frequency channel overlapping the currently observed channel is equal to or larger than the predetermined threshold, an affirmative decision (YES) is made and the processing flow goes to step S73to send the MFP1a request for multi-slot transmission with respect to the currently observed channel.

After step S73, the processing flow goes to step S74to set to “ON” one of the first to nth multi-reception flags34a1-34anthat corresponds to the currently observed channel, and then to step S75to update or switch the channel to be observed to another or the next channel. Thereafter, the processing flow returns to step S72.

On the other hand, when it is determined in step S72that the field strength of the external radio wave of the frequency channel overlapping the currently observed channel is smaller than the predetermined threshold, a negative decision (NO) is made and the processing flow goes to step S76to send the MFP1a request for single-slot transmission with respect to the currently observed channel.

After step S76, the processing flow goes to step S77to set to “OFF” one of the first to nth multi-reception flags34a1-34anthat corresponds to the currently observed channel, and then goes to step S75to update or switch the channel to be observed to another or the next channel. The processing flow then returns to step S72.

When a request for multi-slot transmission is sent to the MFP1with respect to the currently observed channel in step S73, the MFP1sets to two the number of times the MFP1sends audio data to the cordless handset31when the MFP1makes a wireless communication with the cordless handset31through or using the channel in question, as shown inFIG. 6.

When a request for single-slot transmission is sent to the MFP1with respect to the currently observed channel in step S76, the MFP1sets to one the number of times the MFP1sends audio data to the cordless handset31when the MFP1makes a wireless communication with the cordless handset31through or using the channel in question, as shown inFIG. 6.

According to the reception-number setting processing executed in the cordless handset31, when there is detected an external radio wave, which is emitted through or using one of the channels that are used by the cordless handset31to wirelessly communicate with the MFP1, and which has a field strength equal to or larger than the predetermined threshold, it is assumed that there is a possibility that the external radio wave interferes with the wireless communication between the MFP1and the cordless handset31, and the cordless handset31requests the MFP1to send audio data a number of times larger than the initial value (i.e., once), that is, twice, when the wireless communication between the MFP1and the cordless handset31is made through the channel used by the external radio wave. As a result, when the cordless handset31receives audio data from the MFP1through the channel, the audio data is received twice, in other words, two pieces of same audio data is received. Hence, even in the presence of the external radio wave that might interfere with the wireless communication between the MFP1and the cordless handset31and degrade the communication quality of the wireless communication, the communication quality is inhibited from degrading but is excellently maintained.

On the other hand, when there is detected an external radio wave, which is emitted through or using one of the channels that are used by the cordless handset31to wirelessly communicate with the MFP1, and which has a field strength smaller than the predetermined threshold, it is assumed that the external radio wave does not interfere with the wireless communication between the MFP1and the cordless handset31, and the cordless handset31requests the MFP1to send audio data a number of times that corresponds to the initial value (i.e., once) when the wireless communication between the MFP1and the cordless handset31is made through the channel used by the external radio wave. As a result, when the cordless handset31receives audio data from the MFP1through the channel that is free from the risk of degradation in the communication quality of the audio data communication, the audio data is received once. Hence, the number of times data is received is not unnecessarily increased but is minimized, thereby saving power.

The change or setting of the number of times the cordless handset31receives audio data from the MFP1is made in the reception-number setting processing such that the cordless handset31itself detects in step S72a channel using which the wireless communication with the MFP1might interfere with an external radio wave, and requests the MFP1to increase the number of times the MFP1sends the cordless handset31audio data on the basis of the result of the detection. Hence, when there is an external radio wave that might interfere with the wireless communication between the MFP1and the cordless handset31, the communication quality of the wireless communication made through the channel used by the external radio wave can be excellently maintained with stability.

With regard to the channel the wireless communication between the MFP1and the cordless handset31made using which is found by the cordless handset31and in step S72to be free from the risk of interference with the external radio wave, the cordless handset31requests the MFP1to set at the initial value the number of times the MFP1sends audio data to the cordless handset31through or using the channel. Hence, the communication quality is not sacrificed for power saving.

Thus, according to the reception-number setting processing shown inFIG. 7and executed in the cordless handset31, the communication quality of the wireless communication between the MFP1and the cordless handset31is excellently maintained while power is saved, without implementing a complex processing such as one for determining whether an error is included in every subframe.

It is noted that when a request for multi- or single-slot transmission is sent from the cordless handset31to the MFP1in the reception-number setting processing shown inFIG. 7and executed in the cordless handset31, a processing in the MFP1to change or set the number of times the MFP1sends audio data to the cordless handset31is executed in response to the request, in the similar way as in the transmission-number setting processing shown inFIG. 6and executed in the cordless handset31.

More specifically, the transmission-number setting processing executed by the second CPU32in the cordless handset31is illustrated in the flowchart ofFIG. 6, and the above description on the transmission-number setting processing executed by the first CPU11in the MFP1applies to the transmission-number setting processing executed by the second CPU32in the cordless handset31, except the following modifications made: the term “cordless handset 31” is replaced by the term “MFP 1”, and vice versa, and the term “first to nth multi-transmission flags34b1-34bn” is replaced with “first to nth multi-transmission flags13b1-13bn”.

According to the transmission-number setting processing executed by the first CPU11of the MFP1, the number of times the MFP1sends audio data to the cordless handset31is changed or set in response to and in accordance with the request for multi- or single-slot transmission sent from the cordless handset31. Thus, the number of times the MFP1sends audio data to the cordless handset31is set in the transmission-number setting processing to a number appropriate for the environment in which the cordless handset31is situated, thereby enabling maintenance of an excellent communication quality as well as power saving.

FIGS. 8A and 8Bare flowcharts illustrating communication processings implemented in the MFP1and the cordless handset31, respectively, when a wireless communication is made between the MFP1and the cordless handset31by a FHSS method. These communication processings illustrated inFIGS. 8A and 8Bare executed in synchronization with each other.

The communication processing executed in the MFP1and illustrated inFIG. 8Ais mainly implemented by the first digital-cordless-communication control portion26, and is initiated when the cordless handset31sends the MFP1a request for initiation of a communication in response to a request for connection sent from the MFP1to the cordless handset31, or when the MFP1sends a request for initiation of a communication to the cordless handset31in response to a request for connection sent from the cordless handset31to the MFP1.

The request for connection is sent from the MFP1to the cordless handset31when a user at the MFP1makes the “off-hook” operation to place the MFP1in an “off-hook” state, and presses down the communication start button disposed in the manual operation portion15so as to initiate a speech communication with the cordless handset31. The request for initiation of a communication is sent from the cordless handset31to the MFP1, when a user at or holding the cordless handset31makes the “off-hook” operation to place the cordless handset31in an “off-hook” state, and presses the communication start button disposed in the manual operation portion36so as to initiate a speech communication with the MFP1. Similarly, the request for connection is sent from the cordless handset31to the MFP1when a user at or holding the cordless handset31makes the “off-hook” operation to place the cordless handset31in the “off-hook” state, and presses down the communication start button disposed in the manual operation portion36so as to initiate a speech communication with the MFP1. The request for initiation of a communication is sent from the MFP1to the cordless handset31, when a user at the MFP1makes the “off-hook” operation to place the MFP1in the “off-hook” state, and presses the communication start button disposed in the first manual operation portion15so as to initiate a speech communication with the cordless handset31.

The present communication processing in the MFP1begins with step S81, in which initial settings of a wireless communication by the FHSS method are made, and it is started to convert an analog audio signal inputted from the base handset24into digital audio data and sequentially record the digital audio data to a transmission buffer (not shown) in the first RAM13, and to sequentially record digital audio data received from the cordless handset31to a reception buffer (not shown) in the first RAM13.

In the following step S82, it is referred to whether the current value of the multi-transmission flag13b for the channel currently in question (i.e., one of the first to nth multi-transmission flags13b1-13bn) is “ON”. When the value of the multi-transmission flag13bis “ON”, an affirmative decision (YES) is made in step S82, and the processing flow goes to step S83to twice send audio data from the transmission buffer to the cordless handset31.

On the other hand, when it is determined in step S82that the value of the multi-transmission flag13breferred to is “OFF”, that is, when a negative decision (NO) is made in step S82, the processing flow goes to step S88to once send audio data from the transmission buffer to the cordless handset31.

After either of steps S83and S88, the processing flow goes to step S84in which it is referred to whether the current value of the multi-reception flag13afor the channel currently in question (i.e., one of the first to nth multi-reception flags13a1-3an) is “ON”. When the value of the multi-reception flag13ais “ON”, an affirmative decision (YES) is made in step S84, and the processing flow goes to step S85to twice receive the same audio data from the cordless handset31through the channel currently in question, record the two data pieces of the same audio data to the reception buffer, and select a non-erroneous one of the two data pieces, which selected one is converted into an analog audio signal which is outputted from the base handset24.

On the other hand, when the value of the multi-reception flag13ais “OFF”, a negative decision (NO) is made in step S84, and the processing flow goes to step S89to only once receive the audio data from the cordless handset31through the channel currently in question, store or record the audio data in the reception buffer, and convert the stored audio data into an analog audio signal which is outputted from the base handset24.

After either of steps S85and S89, the processing flow goes to step S86to determine whether the communication with the cordless handset31is terminated. When it is determined in step S86that the communication with the cordless handset31is not terminated yet, that is, when a negative decision (NO) is made, the processing flow goes to step S87in which the channel used for the communication is updated or changed to another channel, and then goes back to step S82. On the other hand, when it is determined in step S86that the communication with the cordless hand set31is terminated, that is, when an affirmative decision (YES) is made, the processing flow of this cycle is terminated and the MFP1is placed in a standby mode.

The communication processing at the cordless handset31shown inFIG. 8Bis implemented mainly by the second digital-cordless-communication control portion39. Similar to the above-described communication processing at the MFP1, this processing is activated when the cordless handset31sends a request for initiation of a communication to the MFP1in response to a request for connection received from the MFP1, or when the MFP1sends a request for initiation of a communication to the cordless handset31in response to a request for connection received from the cordless handset31.

The present communication processing in the cordless handset31begins with step S91, in which initial settings of a wireless communication by the FHSS method are made, and it is started to convert an analog audio signal inputted from the microphone connected with the transceiver circuit38into digital audio data and sequentially record the digital audio data in a transmission buffer (not shown) in the RAM34, and to sequentially record digital audio data received from the MFP1to a reception buffer (not shown) in the RAM34.

In the following step S92, it is referred to whether the current value of the multi-reception flag34a for the channel currently in question (i.e., one of the first to nth multi-reception flags34a1-34an) is “ON”. When the value of the multi-reception flag34ais “ON”, an affirmative decision (YES) is made in step S92, and the processing flow goes to step S93to twice receive same audio data, in other words, receive two pieces of same audio data, from the MFP1through the channel currently in question, record the two data pieces of the same audio data to the reception buffer, and select a non-erroneous one of the two data pieces, which selected one is converted into an analog audio signal which is outputted from the speaker connected with the transceiver circuit38.

On the other hand, when it is determined in step S92that the value of the multi-reception flag34areferred to is “OFF”, that is, when a negative decision (NO) is made in step S92, the processing flow goes to step S98to convert audio data sent from the MFP only once through the channel in question and stored in the reception buffer, into an analog audio signal which is outputted from the speaker connected with the transceiver circuit38.

After either of steps S93and S98, the processing flow goes to step S94in which it is referred to whether the current value of the multi-transmission flag34b for the channel currently in question (i.e., one of the first to nth multi-transmission flags34b1-34bn) is “ON”. When the value of the multi-transmission flag34bis “ON”, an affirmative decision (YES) is made, and the processing flow goes to step S95to twice send same audio data from the transmission buffer to the MFP1through the channel currently in question.

On the other hand, when the value of the multi-transmission flag34bis “OFF”, a negative decision (NO) is made in step S94, and the processing flow goes to step S99to only once send audio data from the transmission buffer to the MFP1through the channel in question.

After either of steps S95and S99, the processing flow goes to step S96to determine whether the communication with the MFP1is terminated. When it is determined in step S96that the communication with the MFP1is not terminated yet, that is, when a negative decision (NO) is made in step S96, the processing flow goes to step S97in which the channel used for the communication is updated or changed to another channel, and then goes back to step S92. On the other hand, when it is determined in step S96that the communication with the MFP1is terminated, that is, when an affirmative decision (YES) is made in step S96, the processing flow of this cycle is terminated and the cordless handset31is placed in a standby mode.

As described above, each of the values of the one of the first to nth multi-reception flags13a1-13anand the one of the first to nth multi-transmission flags13b1-13bnof the MFP1, and the one of the first to nth multi-reception flags34a1-34anand the one of the first to nth multi-transmission flags34b1-34bnof the cordless handset31, is appropriately set at one of “ON” and “OFF” depending on the environments in which the MFP1and the cordless handset31are respectively situated, before the channel corresponding the flags is used for the wireless speech communication. Hence, in the communication system according to the embodiment which includes the MFP1and the cordless handset31can maintain an excellent quality of the received audio as well as save power.

As described above, when the field strength of an external radio wave received by the MFP1or the cordless handset31as a communication apparatus is equal to or larger than the predetermined threshold, the MFP1or the cordless handset31determines that there is a possibility that the external radio wave interferes with the communication made by the MFP1or the cordless handset31and degrades the quality of the communication, and thus sends a request for multi-slot communication to the other of the cordless handset31and the MFP1as another communication apparatus so as to receive audio data a number of times that is larger than the initial value, which is twice in the present embodiment, when a channel that overlaps a frequency band or channel used by the external radio wave is used for the communication made by the MFP1or the cordless handset31. Thus, it is enabled to excellently maintain the quality of the audio wirelessly received in the speech communication made through or using the frequency band used by the external radio wave having the field strength equal to or larger than the threshold.

On the other hand, when the field strength of the received external radio wave is smaller than the threshold, the MFP1or the cordless handset31determines that there is not the possibility that the communication quality degrades due to interference with the external radio wave, and sends the other communication apparatus, i.e., the other of the MFP1and the cordless handset31, a request for single-slot transmission so as to receive audio data a number of times that corresponds to the initial value, which is once in this embodiment, when a channel that overlaps the frequency band used by the external radio wave is used for the communication with the other of the MFP1and the cordless handset31. In this case, where a request for multi-slot transmission, which requests to twice send audio data in this embodiment, is already sent, that is, where the number of times audio data is to be sent from the other of the MFP1and the cordless handset31is already set at two, the number of times audio data is to be sent from the other of the MFP1and the cordless handset31is restored from two to the initial value, i.e., one, in response to the request for single-slot transmission. Thus, the number of times audio data is to be received through a channel free from the risk of degradation in the communication quality due to interference by the external radio wave is not unnecessarily increased, thereby saving power.

In the MFP1, the first digital-cordless-communication control portion26implementing the wireless communication through the digital cordless telephone system, and the wireless LAN communication control portion18implementing the wireless communication through the wireless LAN (i.e., wireless LAN communication) which might interfere with the former communication made through the digital cordless telephone system, are both accommodated in a single housing, i.e., the main housing2. Hence, the MFP1sends the cordless handset31a request for multi-slot transmission with respect to all the channels in order that audio data is received a number of times larger than the initial value (that is twice in this embodiment) through each of the channels while the wireless communication through the wireless LAN is being made. Thus, even in the environment where the communication quality of the communication with the cordless handset31might degrade due to interference with the wireless LAN communication, an excellent quality of the audio communicated between the MFP1and the cordless handset31through the digital cordless telephone system is excellently maintained.

In particular, since the information communicated between the wireless communication between the MFP1and the cordless handset31is audio data communicated through a digital cordless telephone system, the embodiment can enjoy an effect that even in the presence of an external radio wave having a relatively high field strength, or even while the wireless LAN communication control portion18is making a wireless LAN communication, the quality of the received and played audio does not degrade but is maintained excellently.

Since the wireless communication between the MFP1and the cordless handset31is made by a FSHH method, the number of times audio data is to be sent from one of the MFP1and the cordless handset31to the other thereof is increased from the initial value with respect to only a part of the channels that might be subjected to interference with an external radio wave. With respect to the rest of the channels, that is, the channel or channels that is/are determined to not be subjected to interference by an external radio wave, the number of times audio data is to be sent from the other of the MFP1and the cordless handset31is set at the initial value, or is not unnecessarily increased but is minimized, thereby saving power. Thus, the embodiment enjoys an effect that in a wireless communication using the FHSS method that allows for high level of voice privacy, an excellent communication quality is maintained while saving power during the communication.

The reception-number setting processings executed in the MFP1and the cordless handset31and illustrated inFIGS. 5 and 7, respectively, and the transmission-number setting processings executed in the MFP1and the cordless handset31and described above with reference toFIG. 6, are implemented repeatedly and continuously while the MFP1and the cordless handset31are on. Hence, irrespective of whether the MFP1and the cordless handset31are communicating with each other or in a standby mode waiting for initiation of a speech communication, a recognition on the environments in which the MFP1and the cordless handset31are respectively situated in is kept refreshed. Thus, before a communication is made, the number of times the audio data is to be sent and received through each channel can be appropriately determined in accordance with the recognition, thereby enabling to maintain with stability an excellent communication quality.

Although there has been described one embodiment of the invention, it is to be understood that the invention is not limited to the details of the embodiment, but may be otherwise embodied with various modifications and improvements that may occur to those skilled in the art, without departing from the scope and spirit of the invention defined in the appended claims.

For instance, although the MFP1and the cordless handset31as a base unit and a cordless unit of a digital cordless telephone system have been described above as communication apparatuses wirelessly communicating audio data, the invention is also applicable to a radio apparatus such as transceiver.

In the above-described embodiment, the number of times to send and receive data, which is set at one of the initial value and a number larger than the initial value, is that of communication between a base unit (i.e., the MFP1) and a cordless handset (i.e., the cordless handset31) of a digital cordless telephone system for wirelessly communicating audio data. However, application of the invention is not limited thereto, but the invention is equally applicable to a communication apparatus for making a wireless communication by other communication methods such as wireless LAN communication.

In the above-described embodiment, the MFP1and the cordless handset31of a digital cordless telephone system wirelessly communicate with each other by a FHSS method. However, the invention is applicable to a case where the wireless communication between the MFP1and the cordless handset31is made such that the channel used in the communication is fixed to a single channel.

In the above-described embodiment the initial and increased values of the number of times data is sent and received are one and two, respectively. However, these numbers are given by way of example, and may be predetermined to any other numbers as long as the increased number is larger than the initial value.

Although in the above-described embodiment the access point51is employed as an apparatus making a wireless communication with the MFP1through a wireless LAN, other wireless LAN apparatuses, such as wireless LAN printer, may be employed in place of the access point51, as long as the wireless LAN apparatus can wirelessly communicate with the MFP through a wireless LAN.