U.S. patent application number 11/483885 was filed with the patent office on 2006-11-09 for apparatus and method for removing signal interference in a local radio communication device mounted in a mobile terminal.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Kyong-Joon Chun, Jung-Chul Huh, Joung-Kyou Park.
Application Number | 20060252373 11/483885 |
Document ID | / |
Family ID | 19709354 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060252373 |
Kind Code |
A1 |
Huh; Jung-Chul ; et
al. |
November 9, 2006 |
Apparatus and method for removing signal interference in a local
radio communication device mounted in a mobile terminal
Abstract
Disclosed is a method for removing signal interference in a
local radio communication device mounted in a mobile terminal. The
method comprises receiving information on a channel in use from the
mobile terminal in session; determining based on the received
channel information whether a harmonic component of a channel
frequency used by the mobile terminal belongs to a frequency band
used by the local radio communication device; and assigning a
channel in a frequency band with none of the harmonic component
among the frequency band used by the local radio communication
device as a channel of the local radio communication device, when
the harmonic component of the channel frequency used by the mobile
terminal belongs to the frequency band used by the local radio
communication device.
Inventors: |
Huh; Jung-Chul; (Seoul,
KR) ; Chun; Kyong-Joon; (Seoul, KR) ; Park;
Joung-Kyou; (Seoul, KR) |
Correspondence
Address: |
DILWORTH & BARRESE, LLP
333 EARLE OVINGTON BLVD.
UNIONDALE
NY
11553
US
|
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon-si
KR
|
Family ID: |
19709354 |
Appl. No.: |
11/483885 |
Filed: |
July 10, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10144176 |
May 13, 2002 |
|
|
|
11483885 |
Jul 10, 2006 |
|
|
|
Current U.S.
Class: |
455/41.2 ;
375/E1.036; 455/63.1 |
Current CPC
Class: |
H04W 84/18 20130101;
H04B 1/715 20130101; H04B 2001/7152 20130101; H04B 2001/7154
20130101 |
Class at
Publication: |
455/041.2 ;
455/063.1 |
International
Class: |
H04B 7/00 20060101
H04B007/00; H04B 1/00 20060101 H04B001/00; H04B 15/00 20060101
H04B015/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 11, 2001 |
KR |
P2001-25789 |
Claims
1. An apparatus for removing signal interference in a Bluetooth
radio device mounted in a mobile terminal, comprising: a duplexer
connected to an antenna of the mobile terminal; a power amplifier
in a transmitter of the mobile terminal; and a filter interposed
between the duplexer and the power amplifier, for reducing a third
harmonic component of mobile terminal's transmission frequency,
which causes signal interference during communication between
Bluetooth radio devices.
2. The apparatus as claimed in claim 1, wherein the filter
comprises a low-pass filter for passing a frequency lower than the
third harmonic band of the mobile terminal's transmission
frequency, which causes signal interference during the Bluetooth
communication.
3. The apparatus as claimed in claim 1, wherein the filter
comprises a band rejection filter for reducing the third harmonic
component of the mobile terminal's transmission frequency, which
causes signal interference during the Bluetooth communication.
4. An apparatus for removing signal interference in a Bluetooth
radio device mounted in a mobile terminal, comprising: an antenna;
and a duplexer connected to the antenna, for separating a
transmission signal from a reception signal, the duplexer having an
attenuation characteristic of reducing a third harmonic component
of a mobile terminal's transmission frequency, which causes signal
interference during Bluetooth communication.
Description
PRIORITY
[0001] This application is a divisional of application Ser. No.
10/144,176 filed in the United States Patent and Trademark Office
on May 13, 2002, and claims priority to an application entitled
"Apparatus and Method for Removing Signal Interference in a Local
Radio Communication Device Mounted in a Mobile Terminal" filed in
the Korean Industrial Property Office on May 11, 2001 and assigned
Ser. No. 2001-25789, the contents of which are hereby incorporated
by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to a radio
communication system, and in particular, to an apparatus and method
for removing signal interference in a Bluetooth radio device
mounted in a mobile terminal.
[0004] 2. Description of the Related Art
[0005] Recently, the radio communication and computer industries
have become aware that it is possible to realize a radio device and
a radio link at a low cost. Such radio device and radio link enable
communication between small, portable communication devices, making
it possible to remove complicated connection cables between the
communication devices. To this end, active research has been
carried out. For example, the so-called "Bluetooth" standard has
been defined by Ericsson Co., Sweden. The Bluetooth aims to provide
mobility to small, short-range radio communication devices, and
utility services to business users. The Bluetooth has defined an
optimum technical characteristic for the portable computer and
communication devices. In particular, the Bluetooth has been
designed to provide low-cost, high-efficiency, high-capacity voice
and data networking. In a local (or short-range) radio
communication system supporting the Bluetooth standard, voice and
data can be exchanged in real time between communication devices
such as a mobile phone, a notebook computer and a desktop computer,
located within a short distance of less than 10 m, through a radio
link. The Bluetooth local radio communication system includes a
master for transmitting voice/data, and a plurality of slaves for
receiving voice/data. The master can be replaced by one of the
slaves, and vice versa. That is, the master and the slaves are
changeable according to the subject (device) that transmits the
voice/data. The radio link defined by the Bluetooth can guarantee
information security and prevent interference between information.
In addition, the Bluetooth radio device can be manufactured in the
form of a microchip, so that it can be easily mounted in the
communication devices. Further, the Bluetooth radio device is
designed to operate in the (2.4 GHz) band, a worldwide compatible
frequency band. The Bluetooth standard specifies two power levels:
a low power level for indoor operation and a high power level for
inhouse operation. (In-house is defined as a range corresponding to
local distance capable of receiving a service. In general, it means
a range capable of being serviced within a house or a building of
the company. Additionally, indoor indicates a shorter range than
that of the in-house, for example, within a room.) The Bluetooth
technology supports both point-to-point connection and
point-to-multipoint connection. In the case of the
point-to-multipoint connection, each master can communicate with a
maximum of 7 slaves.
[0006] The Bluetooth radio communication system uses an ISM
(Industrial, Scientific, Medical) band of 2.4 to 2.4835 GHz, which
can be used without government licensing. Since the ISM band used
by the Bluetooth radio communication system is open to the public,
the Bluetooth radio communication system should be able to tolerate
various unpredictable interferences in the ISM band. In order to
resolve the interference problem, the Bluetooth radio communication
system adopts a frequency hopping spectrum spreading technique. The
Bluetooth radio communication system separately supports a 79
hopping technique and a 23 hopping technique, considering a
difference in available frequencies of the respective nations. The
79 hopping technique is adopted by certain nations including the
United States and South Korea, while the 23 hopping technique is
adopted by other nations such as Spain.
[0007] FIGS. 1A to 1C illustrate a Bluetooth standard frequency
band and its RF channels. Referring to FIG. 1A, the Bluetooth
standard frequency band ranges from 2.4 to 2.4835 GHz, and 79 1
MHz-bandwidth channels are allocated in the operating frequency
range of 2.4015 to 2.4805 GHz. As a result, each of the 79 channels
has a center frequency of f=(2402+k)MHz, where k=0, . . . , 78.
Specifically, FIG. 1A illustrates a frequency band of the 79
hopping technique and its RF channels.
[0008] FIGS. 1B and 1C illustrate frequency bands of the 23 hopping
technique and their RF channels. Specifically, FIG. 1B illustrates
a frequency band of the 23 hopping technique adopted by France and
its RF channels, wherein 23 1 MHz-bandwidth channels are allocated
in an operating frequency range of 2.4535 to 2.4765 GHz. As a
result, each of the 23 channels has a center frequency of
f=(2454+k)MHz, where k=0, . . ., 22. Further, FIG. 1C illustrates a
frequency band of the 23 hopping technique adopted by Spain and its
RF channels, wherein 23 1 MHz-bandwidth channels are allocated in
an operating frequency range of 2.4485 to 2.4715 GHz. As a result,
each of the 23 channels has a center frequency of f=(2449+k)MHz,
where k=0,. . . , 22.
[0009] Meanwhile, in a CDMA (Code Division Multiple Access) mobile
terminal mounted with a Bluetooth radio device, a part of a third
harmonic component of the CDMA transmission frequency belongs to
(or overlaps with) the Bluetooth standard frequency band, thus
causing interference during the Bluetooth communication. The CDMA
transmission frequency provides 20 FAs (Frequency assignments) with
a channel gap of 1.23 MHz, and third harmonic components of FA=1
and FA=2 frequencies among the 20 FA frequencies belong to the
Bluetooth standard frequency band. The FA=1 transmission frequency
is 824.640 MHz and the FA=2 transmission frequency is 825.870 MHz.
Therefore, as shown in FIG. 2, the third harmonic of the FA=1
transmission frequency is 2473.92 MHz, and the third harmonic of
the FA=2 transmission frequency is 2477.61 MHz.
[0010] Therefore, the third harmonic of the FA=1 CDMA transmission
frequency interferes with a hopping frequency of 2473, 2474 or 2475
MHz (channel center frequency) of the Bluetooth radio device, while
the third harmonic of the FA=2 CDMA transmission frequency
interferes with a hopping frequency of 2477 and 2478 MHz of the
Bluetooth radio device.
SUMMARY OF THE INVENTION
[0011] It is, therefore, an object of the present invention to
provide an apparatus and method for removing signal interference
during Bluetooth communication in a Bluetooth radio device mounted
in a mobile terminal.
[0012] It is another object of the present invention to provide a
method for removing signal interference in a Bluetooth radio device
mounted in a CDMA mobile terminal.
[0013] To achieve the above and other objects, there is provided a
method for removing signal interference in a local radio
communication device mounted in a mobile terminal. The method
comprises receiving information on a channel in use from the mobile
terminal in session; determining based on the received channel
information whether a harmonic component of a channel frequency
used by the mobile terminal belongs to a frequency band used by the
local radio communication device; and assigning a channel in a
frequency band with none of the harmonic component among the
frequency band used by the local radio communication device as a
channel of the local radio communication device, when the harmonic
component of the channel frequency used by the mobile terminal
belongs to the frequency band used by the local radio communication
device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The above and other objects, features and advantages of the
present invention will become more apparent from the following
detailed description when taken in conjunction with the
accompanying drawings in which:
[0015] FIGS. 1A to 1C illustrate a Bluetooth standard frequency
band and its RF channels;
[0016] FIG. 2 illustrates that a third harmonic component of a CDMA
transmission frequency partially belongs to a Bluetooth standard
frequency band;
[0017] FIG. 3 illustrates a structure of a mobile terminal mounted
with a Bluetooth radio device according to an embodiment of the
present invention;
[0018] FIG. 4 illustrates a procedure for generating a hopping
frequency in a 79 hopping mode by the Bluetooth radio device in
order to remove signal interference occurring during Bluetooth
communication according to an embodiment of the present
invention;
[0019] FIG. 5 illustrates a procedure for generating a hopping
frequency in a 23 hopping mode by the Bluetooth radio device in
order to remove signal interference occurring during Bluetooth
communication according to an embodiment of the present
invention;
[0020] FIG. 6 illustrates a state transition diagram for explaining
a procedure for exchanging information between the Bluetooth radio
device and the mobile terminal according to an embodiment of the
present invention;
[0021] FIG. 7 illustrates a state transition diagram for explaining
a process in which a mobile terminal informs a base station of
installation of the Bluetooth radio device, and then is assigned a
transmission channel from the base station;
[0022] FIG. 8 illustrates a protocol for message exchange between
the Bluetooth radio device mounted in the mobile terminal and the
Bluetooth radio device mounted in another device according to an
embodiment of the present invention; and
[0023] FIGS. 9A and 9B illustrate a structure of a mobile terminal
transmitter including a filter arranged in a preceding stage of an
antenna in order to remove the third harmonic component of the
mobile terminal's transmission frequency, which causes signal
interference during the Bluetooth communication.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] A preferred embodiment of the present invention will be
described herein below with reference to the accompanying drawings.
In the following description, well-known functions or constructions
are not described in detail since they would obscure the invention
in unnecessary detail.
[0025] Although the invention will be described with reference to a
case where a third harmonic component of a part of the CDMA
transmission frequency band overlaps with a frequency for the
Bluetooth radio communication, causing signal interference, it will
be understood by those skilled in the art that the invention can
also be applied to a case where a third harmonic component of a
transmission frequency band for other communication systems other
than the CDMA system overlaps with the frequency for the Bluetooth
radio communication, causing the signal interference.
[0026] When the third harmonic component of a part of the CDMA
transmission frequency band overlaps with a frequency for the
Bluetooth radio communication, signal interference occurs. Thus,
the present invention provides three different methods in order to
remove the signal interference.
[0027] (1) First Method
[0028] A Bluetooth radio device receives transmission channel
information of a CDMA mobile terminal, and determines whether
hopping must be performed at a hopping frequency which overlaps
with a third harmonic component of the CDMA transmission channel.
If so, the Bluetooth radio device shifts to a hopping frequency
adjacent to the overlapped hopping frequency, and performs the
hopping at the shifted hopping frequency.
[0029] (2) Second Method
[0030] The CDMA mobile terminal mounted with the Bluetooth radio
device informs a base station of installation of the Bluetooth
radio device, so that the base station can assigns channels,
excluding FA=1 and FA=2 frequencies which affect the Bluetooth
channels. When it is inevitable to assign the FA=1 and FA=2
frequencies, the CDMA mobile terminal assigns the FA=1 and FA=2
frequencies as late as possible. This method will be described with
reference to FIG. 7.
[0031] (3) Third Method
[0032] The CDMA mobile terminal reduces a magnitude of the third
harmonic component of the CDMA transmission frequency by adding a
low-pass filter or a band rejection filter in front of a stage for
radiating the transmission frequency through an antenna. This
method will be described with reference to FIGS. 9A and 9B.
[0033] FIG. 3 illustrates a structure of a mobile terminal mounted
or interfacing with a Bluetooth radio device according to an
embodiment of the present invention. In FIG. 3, reference numeral
210 represents a Bluetooth radio device and reference numeral 220
represents a mobile terminal.
[0034] Referring to FIG. 3, the Bluetooth radio device 210 includes
an RF (Radio Frequency) transmitter 211, an RF receiver 212, a
baseband processor 213, a controller 214, and an antenna ANT2. The
baseband processor 213 and the controller 214 in the Bluetooth
radio device 210 are connected to a terminal controller 221 in the
mobile terminal 220 by a host control interface (HCI), and exchange
HCI packets including a control command and user data with the
mobile terminal 220. The RS232C, USB (Universal Serial Bus), UART
(Universal Asynchronous Receiver/Transmitter) and standard PC
(Personal Computer) interfaces are generally used for the HCI. The
HCI packet is divided into command, event and data packets. The RF
transmitter 211 modulates a transmission data packet provided from
the baseband processor 213 into an RF signal and amplifies the RF
signal before transmission. The RF receiver 212 receives an RF
signal, and amplifies the RF signal while suppressing a noise
component in the received RF signal. Further, the RF receiver
down-converts the amplified RF signal to a baseband signal, and
provides the baseband signal to the baseband processor 213. During
transmission, the baseband processor 213 adds an access code and a
header to an HCI data packet provided from the terminal controller
221 in the mobile terminal 220, converts the HCI data packet to a
transmission data packet, and wirelessly transmits the transmission
data packet through the RF transmitter 211. During reception, the
baseband processor 213 converts a data packet received from the RF
receiver 212 to an HCI packet and provides the HCI packet to the
terminal controller 221. The controller 214 controls the Bluetooth
radio device 210 based on a command packet provided from the
terminal controller 221, and provides information output from the
baseband processor 213 to the mobile terminal 221 as an HCI
packet.
[0035] The mobile terminal 220 includes the terminal controller
221, a memory 222, a key input device 223, a display 224, a BBA
(Base Band Analog part) 225, an RF transmitter 226, an RF receiver
227, a duplexer 228, and an antenna ANT1. The terminal controller
221 controls the overall operation of the mobile terminal 220. The
memory 222 is comprised of a ROM (Read Only Memory) for storing
control data and a control program, an EEPROM (Electrically
Erasable and Programmable ROM), a non-volatile memory (NVM), for
storing telephone numbers and associated names, and a RAM (Random
Access Memory) for temporarily storing data generated during
execution of the control program. The key input device 223, having
a key matrix structure, includes keys for Internet search and data
communication and provides the terminal controller 221 with a key
input signal according to a key input by the user. The display 224
displays a state related to the data/voice communication and an
operating state of the mobile terminal 220, under the control of
the controller 221. For reception, the BBA 225 down-converts an IF
(Intermediate Frequency) signal to an analog baseband signal, and
converts the analog baseband signal to digital data. For
transmission, the BBA 225 converts digital data to an analog
baseband signal and up-converts the analog baseband signal to an IF
signal. The RF transmitter 226 and the RF receiver 227,
constituting an RF transceiver, are arranged between the BBA 225
and the duplexer 228. The duplexer 228 provides an RF signal
received through the antenna ANTI to the RF receiver 227, and
transmits a modulated RF signal output from the RF transmitter 226
through the antenna ANT1.
[0036] If the third harmonic component of a part of the CDMA
transmission frequency band overlaps with a frequency for the
Bluetooth radio communication, signal interference occurs during
the Bluetooth communication. The first method for eliminating the
signal interference according to the present invention will be
described with reference to FIGS. 4, 5, 6, and 8.
[0037] (1) First Method
[0038] A Bluetooth radio device receives transmission channel
information of a CDMA mobile terminal, and determines whether
hopping must be performed at a hopping frequency which overlaps
with a third harmonic component of the CDMA transmission channel.
If so, the Bluetooth radio device shifts to a hopping frequency
adjacent to the overlapped hopping frequency, and performs the
hopping at the shifted hopping frequency. This method will be
described with reference to FIGS. 4 to 6 and 8.
[0039] FIG. 4 illustrates a procedure for generating a hopping
frequency in a 79 hopping mode by the Bluetooth radio device 210 in
order to remove signal interference occurring during Bluetooth
communication according to an embodiment of the present invention.
FIG. 5 illustrates a procedure for generating a hopping frequency
in a 23 hopping mode by the Bluetooth radio device 210 in order to
remove signal interference occurring during Bluetooth communication
according to an embodiment of the present invention.
[0040] In order to hop at an interference-free frequency during
Bluetooth communication, the Bluetooth radio device 210 must
acquire channel information of the transmission frequency of the
mobile terminal 220 mounted with the Bluetooth radio device 210.
Therefore, the Bluetooth radio device 210 receives information on
the transmission channel of the mobile terminal 220. To this end,
the terminal controller 221 of the mobile terminal 220 exchanges
information with the controller 214 in the Bluetooth radio device
210 through HCI (Host Controller Interface; see Bluetooth
Specification Version 1.0A, p.516). The HCI includes UART and
USB.
[0041] FIG. 6 illustrates a state transition diagram for explaining
a procedure for exchanging information between the Bluetooth radio
device 210 and the mobile terminal 220 through the HCI according to
an embodiment of the present invention. Referring to FIG. 6, the
mobile terminal 220 determines a system type of the terminal upon
power-up. In the embodiment of the present invention, the mobile
terminal 220 provides system type information indicating its system
type to the Bluetooth radio device 210 through the HCI. The reason
for transmitting the system type information is because it is not
necessary to consider a GSM (Group Special Mobile, or Global System
for Mobile telecommunications) terminal, since it does not affect
the Bluetooth communication. Meanwhile, since an AMPS (Advanced
Mobile Phone Service) system also uses nearly the same frequency as
the CDMA system, the mobile terminal 220 is able to provide the
Bluetooth radio device 210 with the system type information through
the HCI. However, since the AMPS system is not used as widely as
the CDMA system and the GSM system, the AMPS system will not be
considered in the embodiment of the present invention, for
simplicity.
[0042] The controller 214 in the Bluetooth radio device 210
receives the system type information provided from the mobile
terminal 220 through the HCI in its initialization state after
power-up. The Bluetooth radio device 210 recognizes the system
type, i.e., whether the mobile terminal 220 is a CDMA terminal or
GSM terminal, based on the system type information. Thereafter, the
Bluetooth radio device 210 may perform connection and
disconnection.
[0043] After determining the system type, the mobile terminal 220
may transition to a pilot channel acquisition state, a synchronous
channel acquisition state, an idle state, a system access state, a
traffic channel state and a call release state, as further
illustrated in FIG. 6. In the embodiment of the present invention,
the mobile terminal 220 transmits its transmission channel
information to the Bluetooth radio device 210 through the HCI
during a call, i.e., in the traffic channel state. The Bluetooth
radio device 210 receives the transmission channel information of
the mobile terminal 220 from the mobile terminal 220 in session
through the HCI in step 400 of FIG. 4 and step 500 of FIG. 5. Upon
receiving the transmission channel information of the mobile
terminal 220 in session, the Bluetooth radio device 210 generates a
new hopping frequency by performing step 402 of FIG. 4 or 502 of
FIG. 5 according to the hopping mode.
[0044] With continued reference to the 79 hopping mode of FIG. 4,
after receipt of the transmission channel information of the mobile
terminal 220, the Bluetooth radio device 210 determines in step 402
whether the FA of the CDMA transmission channel of the mobile
terminal 220 in session is FA=1. If FA=1, the Bluetooth radio
device 210 hop-shifts the hopping frequency of 2473, 2474 or 2475
MHz to another hopping frequency by performing steps 404 and 406.
In the embodiment of the present invention, the Bluetooth radio
device 210 hop-shifts to a hopping frequency of 2472 MHz. If
FA.noteq.1 in step 402, the Bluetooth radio device 210 determines
in step 408 whether FA=2. If FA=2, the Bluetooth radio device 210
hop-shifts the hopping frequency of 2477 or 2478 MHz to another
hopping frequency by performing steps 410 and 412. In the
embodiment of the present invention, the Bluetooth radio device 210
hop-shifts to a hopping frequency of 2479 MHz. The hopping
frequencies, as well known in the art, are created by a selection
box of the controller 214 by receiving UAP/LAP (Upper Address
Part/Lower Address Part) of a BD (Bluetooth Device) address and a
master clock.
[0045] With reference to the 23 hopping mode of FIG. 5, after
receipt of the transmission channel information of the mobile
terminal 220, the Bluetooth radio device 210 determines in step 502
of FIG. 5 whether FA of the CDMA transmission channel of the mobile
terminal 220 in session is FA=1. If FA=1, the Bluetooth radio
device 210 hop-shifts the hopping frequency of 2743, 2744 or 2745
MHz to another frequency by performing steps 504 and 506. In the
embodiment of the present invention, the Bluetooth radio device 210
hop-shifts to a hopping frequency of 2472 MHz.
[0046] When the Bluetooth radio device 210 mounted in the mobile
terminal 220 hops at an interference-free frequency during
Bluetooth communication as stated above, the Bluetooth radio device
210 informs other Bluetooth radio devices of the hop-shifting.
[0047] FIG. 8 illustrates a protocol for message exchange between
the Bluetooth radio device 210 mounted in the mobile terminal 220
and the Bluetooth radio device mounted in another device according
to an embodiment of the present invention. For example, the
"another device" includes a personal computer (PC), a notebook PC,
a printer and home appliances, including another mobile terminal
mounted with the Bluetooth radio device.
[0048] A message exchange operation between two Bluetooth radio
devices will be described herein below by way of example. Upon
receiving an Inquiry Request message by a registration request of a
Bluetooth radio device mounted in another device, the Bluetooth
radio device 210 mounted in the mobile terminal 220 continuously
transmits an Inquiry Indication message to the Bluetooth radio
device mounted in another device. The Bluetooth radio device
mounted in another device acquires Bluetooth device address BD_ADDR
of the Bluetooth radio device 210, and then performs hopping by
acquiring hopping frequency information using the information. As
described above, the Bluetooth radio device 210 mounted in the
mobile terminal 220 performs new hopping (or hop-shifting) in order
to avoid signal interference during Bluetooth communication, caused
by the third harmonic component of the CDMA transmission channel,
and provides the new hopping information to the Bluetooth radio
device mounted in the other device in the Inquiry Indication
process. Then, the hopping between the Bluetooth radio device 210
in the mobile terminal 220 and the Bluetooth radio device in
another device is performed avoiding signal interference due to the
third harmonic component of the CDMA transmission channel
frequency.
[0049] The procedure performed in the processes #4 to #7 of FIG. 8
is a general procedure performed between the Bluetooth radio
devices to recognize nearby Bluetooth devices. In this procedure,
the Bluetooth radio device mounted in another device transmits a
Read_Remote_Name_Request message to the Bluetooth radio device 210
mounted in the mobile terminal 220. Upon receiving the
Read_Remote_Name_Request message, the Bluetooth radio device 210
transmits a Read_Remote_Name_Confirm message to the Bluetooth radio
device mounted in another device. As a result, the Bluetooth radio
device mounted in another device acquires a Remote Name of the
Bluetooth radio device 210 mounted in the mobile terminal 220. In
general, the Bluetooth radio devices have their own unique BD
addresses, but cannot recognize the type of the other device, so
that the user gives a unique Remote Name to each Bluetooth radio
device. For example, when an IP (Internet Protocol) address in a
computer network corresponds to the BD address BD_ADDR, a computer
name corresponds to the Remote Name. By acquiring the Remote Name,
the Bluetooth radio device recognizes a list of Telephony Gates
found in the vicinity of the Bluetooth radio device. Thereafter,
the two Bluetooth radio devices are subject to pairing by
exchanging a Paring Request message and a Pairing Confirm
message.
[0050] In FIG. 2, "X" represents the channels interfering with the
hopping frequency. Therefore, the Bluetooth radio device 210
performs Bluetooth communication using the hopping frequency
channels excluding the interference channels.
[0051] (2) Second Method
[0052] The CDMA mobile terminal mounted with the Bluetooth radio
device informs a base station of installation of the Bluetooth
radio device, so that the base station can assign channels,
excluding FA=1 and FA=2 frequencies which principally affect the
Bluetooth channels. In this case the Bluetooth radio device has no
interference from the third harmonic component of the CDMA
transmission channel. Thus there is no need for rejecting the
interference. However if the base station inevitably must assign
the FA=1 and FA=2 frequencies to the CDMA mobile terminal, the CDMA
mobile terminal is then able to transmit using the FA=1 or FA=2
frequencies. In this case the Bluetooth radio device takes into
account interference of the third harmonic component of the CDMA
transmission channel by applying a hopping method, such as in the
above first method or the below third method. Thus there is need to
reject the interference. That is, the second method aims to use
frequencies other than the hopping frequencies existing in a
position where the third harmonic component of a part of the CDMA
transmission frequency band overlaps with the frequency for the
Bluetooth communication. For example, the Bluetooth radio
communication system supporting the 79 hopping technique uses a 71
hopping technique excluding a frequency band of from 2473 to 2480
MHz including 2473, 2474, 2475, 2477 and 2478 MHz, which are
affected by signal interference. Further, the Bluetooth radio
communication system supporting the 23 hopping technique uses a 19
hopping technique excluding a frequency band of from 2473 to 2476
MHz, since the frequencies of 2473, 2474 and 2475 MHz are affected
the signal interference.
[0053] FIG. 7 illustrates a state transition diagram for explaining
a process in which a CDMA mobile terminal 220 informs a base
station 700 of installation of the Bluetooth radio device, and then
is assigned a transmission channel (excluding FA=1 and FA=2
frequencies) from the base station 700. The second method will be
described with reference to FIG. 7.
[0054] In FIG. 7, the right-hand side procedure is performed by the
mobile terminal 220, while the left-hand side procedure is
performed by the base station 700. After power-up, the mobile
terminal 220 informs the base station 700 of installation of the
Bluetooth radio device in an initialization state. The base station
700 then assigns a channel to the mobile terminal 220 excluding the
FA=1 and FA=2 frequencies which may interfere with the Bluetooth
radio device. After the initialization state, the mobile terminal
220 may transition to an idle state, a system access state and a
traffic channel state. In the traffic channel state, the mobile
terminal 220 communicates with the other party's mobile subscriber
through the channel (excluding the FA=1 and FA=2 frequencies)
assigned by the base station 700.
[0055] (3) Third Method
[0056] The CDMA mobile terminal reduces a magnitude of the third
harmonic component of the CDMA transmission frequency by adding a
low-pass filter or a band rejection filter in front of a stage for
radiating the transmission frequency through an antenna. FIGS. 9A
and 9B illustrate a structure of a mobile terminal transmitter
including a filter arranged in a preceding stage of an antenna in
order to remove the third harmonic component of the mobile
terminal's transmission frequency, which causes signal interference
during the Bluetooth communication. Referring to FIG. 9A, a
low-pass filter 900 for removing the third harmonic component of
the FA=1 and FA=2 transmission frequencies of the CDMA mobile
terminal is interposed between a power amplifier (PA) 902 and a
duplexer 228 in the transmitter of the CDMA mobile terminal. The
low-pass filter 900 passes frequencies lower than the third
harmonic component frequency of the FA=1 and FA=2 frequencies,
which causes the signal interference during the Bluetooth
communication. Referring to FIG. 9B, a band rejection filter 910
for rejecting the third harmonic component of the FA=1 and FA=2
transmission frequencies of the CDMA mobile terminal, which causes
signal interference during the Bluetooth communication, is
interposed between the power amplifier (PA) 902 and the duplexer
228 in the transmitter of the CDMA mobile terminal. By providing
the low-pass filter 900 or the band rejection filter 910, the third
harmonic component of the FA=1 and FA=2 transmission frequencies of
the mobile terminal is rejected, thus removing the signal
interference during the Bluetooth communication.
[0057] As an alternative method, a duplexer having a good
attenuation characteristic for power of the third harmonic
component of the FA=1 and FA=2 transmission frequencies for the
CDMA mobile terminal is used as the duplexer for splitting the
transmission signals from the reception signals. That is, the
duplexer 228 connected to the antenna ANT1 is designed to have an
attenuation characteristic capable of removing the third harmonic
component of the transmission frequency for the mobile terminal,
which causes signal interference during the Bluetooth
communication. The attenuation characteristic of the duplexer
according to an embodiment of the present invention will be
described in detail herein below. Commonly, maximum transmission
power of the CDMA power amplifier 902 is about 28 dBm, and power of
the third harmonic component of the transmission frequency from the
CDMA power amplifier 902 is 30 dBc in the worst case and normally
35 to 40 dBc. Therefore, in the worst case, the power of the third
harmonic component becomes -2 dBm (=28 dBm-30 dBc). Thereafter, the
duplexer 228 attenuates transmission power of the third harmonic
component by about 5 to 10 dBm. As a result, the transmission power
of the third harmonic component of about -7 to -12 dBm (=-2 dBm-(5
to 10 dBm) is transmitted through the antenna ANT1, thus causing an
influence on the Bluetooth communication. However, according the
Bluetooth radio specifications, power of a reference input signal
should be about -70 dBm, and when a signal is larger than the
reference input signal by 10 dBm (i.e., -60 dBm), performance for
co-channel interference is required within 1 dB. As a result, the
third harmonic component permits only a signal of less than -71
dBm. Therefore, in the embodiment of the present invention, the
duplexer attenuates the third harmonic component by at least 70
dBm. It is difficult to design a duplexer capable of attenuating
the third harmonic component by more than 70 dBm. However, it is
preferable that the duplexer is designed to reduce the third
harmonic component as much as possible without affecting an in-band
signal in order to remove interference due to the third harmonic
component of the transmission frequency. By doing so, it is
possible to remove an influence of third harmonic component of the
FA=1 and FA=2 transmission frequencies for the CDMA mobile
terminal, even without using the low-pass filter 900 or the band
rejection filter 910.
[0058] As described above, the present invention can perform the
Bluetooth communication between Bluetooth radio devices without
signal interference, even when the third harmonic component of a
part of the CDMA transmission frequency overlaps with a frequency
for the Bluetooth communication.
[0059] While the invention has been shown and described with
reference to a certain preferred embodiment thereof, it will be
understood by those skilled in the art that various changes in form
and details may be made therein without departing from the spirit
and scope of the invention as defined by the appended claims. For
example, the next generation Bluetooth communication system will
raise its operating frequency range in order to increase a data
rate. If the 5 GHz-ISM band (5.725 to 5.825 GHz) is used as the
operating frequency band for the Bluetooth communication, the
operation frequency band of about 5.725 to 5.825 GHz may partially
overlap with a third harmonic component band (5760 to 5940 MHz) of
a transmission frequency band (1920 to 1980 MHz) of the third
generation mobile communication system. Therefore, the third
generation mobile communication system may also interfere with the
Bluetooth communication of 5 GHz-ISM band due to the third harmonic
component of its transmission frequency band. In such a case, the
present invention can be applied.
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