Abstract:
A radiotelephone comprises both a Mobile Station Modem, a Bluetooth radio frequency unit, an interface between them and other supporting hardware/software, allowing utilization by a subscriber to implement a truly Universal remote control device An embodiment of the present invention includes an interface for connecting a mobile station modem to a radio frequency unit equipped for transmitting and receiving a frequency hopped signal, a serial bus interface operably connected between the Mobile Station Modem and the Bluetooth radio frequency unit including a plurality of bi-directional serial data connections. The preferred embodiment further includes a bi-directional serial data connection for transmitting data for transmission connected between the Mobile Station Modem and the Bluetooth radio frequency unit and a synchronous detector and transmit enabling serial data connection for receiving an enabling indication valid data at said radio frequency unit from the Mobile Station Modem.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    I. Field of the Invention  
           [0002]    The present invention relates to digital wireless communication systems. More particularly, preferred embodiments of the invention are directed to a short range radio frequency transceiver unit and an interface with a peripheral modem thereto.  
           [0003]    II. Description of the Related Art  
           [0004]    In the field of wireless communications, moving data between long distances is fast becoming the norm. However, moving data the short distances within a building or room is still much more troublesome. The Bluetooth standard for radio connectivity addresses this problem. Bluetooth is a Radio Frequency (RF) technology based on the IEEE 802.11 standard for wireless LANs. Operating in the 2.45 GHz frequency band, the technology will connect devices within a range of up to 100 feet at speeds up to 2 Mbps.  
           [0005]    Bluetooth utilizes spread spectrum technology that hops signals from one frequency to another at set time intervals. This method allows for operation in electrically noisy environments while the frequency hopping combined with data encryption provides increased security. An additional feature includes an auto initiate feature. The auto initiate feature requires no user intervention by allowing devices to send and receive information without the user&#39;s permission or knowledge.  
           [0006]    Through the air connectivity between devices at short range is well known. Infrared links, like the type based on the popular IrDA standard, already allow users to transfer information between compatible devices simply by pointing and beaming. Wireless LANs have also been available for many years. Bluetooth will enable users to connect to a wide range of computing and telecommunications devices without the need to buy, carry, or connect cables. It delivers opportunities for rapid communications with access points, ad hoc connections, and in the future, cable replacement, and possibly for automatic, unconscious, connections between devices. Bluetooth&#39;s power-efficient radio technology can be used with: Phones and pagers; Modems; Local area network (LAN) access devices; Headsets; Notebook, desktop, and handheld computers.  
           [0007]    More background information may be found on the Bluetooth Special Interest Group (SIG) Internet Web page which may be found at http://www.bluetooth.com, the contents of which is hereby incorporated by reference as of the date of this filing.  
           [0008]    What is needed is a method and apparatus for efficiently interfacing a wireless modem to a Bluetooth radio frequency transceiver unit with a cost effective design and methodology. Additionally, what is needed is a Code Division Multiple Access (CDMA) wireless modem efficiently interfaced with a Bluetooth radio frequency transceiver unit to allow a wireless telephone to act as a universal interface to a wide variety of consumer electronics and other peripheral devices.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention is a novel and improved method and apparatus for connecting a wireless radiotelephone to a number of peripheral devices via the Bluetooth™ interface.  
           [0010]    The method and apparatus include an optimized interface between a Mobile Station Modem and a Bluetooth radio frequency unit. A radiotelephone comprises both a Mobile Station Modem, a Bluetooth radio frequency unit, an interface between them and other supporting hardware/software, allowing utilization by a subscriber to implement a truly Universal remote control device. An embodiment of the present invention includes an interface for connecting a mobile station modem to a radio frequency unit equipped for transmitting and receiving a frequency hopped signal, a serial bus interface operably connected between the Mobile Station Modem and the Bluetooth radio frequency unit including a plurality of bi-directional serial data connections. The preferred embodiment further includes a bi-directional serial data connection for transmitting data for transmission connected between the Mobile Station Modem and the Bluetooth radio frequency unit and a synchronous detector and transmit enabling serial data connection for receiving an enabling indication valid data at said radio frequency unit from the Mobile Station Modem. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 illustrates a modem/RFU system in which a preferred embodiment of the present invention resides and operates.  
         [0012]    [0012]FIG. 2 illustrates a Bluetooth Radio Frequency Unit and associated interface to a Mobile Station Modem.  
         [0013]    [0013]FIG. 3 illustrates a Mobile Station Modem and associated interface to a Bluetooth Radio Frequency Unit.  
         [0014]    [0014]FIG. 4 illustrates a timing diagram of a Serial Bus Interface between a Bluetooth Radio Frequency Unit and A Mobile Station Modem..  
         [0015]    [0015]FIG. 5 depicts in flowchart format a method of operation of an interface between a Bluetooth Radio Frequency Unit and A Mobile Station Modem. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    Referring to FIG. 1, System  100  includes a Mobile Station Modem (MSM)  300  coupled to a Bluetooth RF Unit (BT RFU)  200  through an interface  124 . System  100  is also connected to oscillator  112  which supplies a timing reference to both MSM  300  and BT RFU  200 . BT RFU  200  supplies a Bluetooth compatible signal to Power Amplifier  110 , which is then fed into Transmit/ Receive (T/R) switch  108  before passing through an RF filter  106  on the path  104  to an antenna  126 .  
         [0017]    Interface  124  includes multiple signal paths between MSM  300  and BT RFU  200 . Bi-directional Rx/Tx signal path  118  transfers data between the MSM  300  and BT RFU  200 . Sync-Det/Tx-En (Synchronization Detection/Transmit Enable) path  116  is a path for the Sync-Det/Tx-En signal to be transmitted from MSM  300  to BT RFU  200 . This signal indicates to the BT RFU  200  that data is being transmitted from MSM  300  to BT RFU  200  along data path  118 .  
         [0018]    Voltage reference V ref  is supplied to both MSM  300  and BT RFU  200  from V ref    102  along path V DD -MSM  114 . A clock reference signal is supplied from BT RFU  200  to MSM  300  on path CLK-Ref  122 .  
         [0019]    A Serial Bus Interface is supplied between BT RFU  200  and MSM  300  on bi-directional path SBI  120  and is asynchronous to the 12 MHz clock reference supplied on line Clk-Ref  122 . In a preferred embodiment, a 3-wire SBI  120  along with Sync-Det/Tx-En  116  comprise the main interface to control and program BT RFU  200  from MSM  300 .  
         [0020]    The SBI interface  120  operates at clock rates between 100 Khz and 5 MHz. The clocks transition only when the interface is active and in use. During initialization, MSM  300  configures BT RFU  200 .The BT RFU is identified by a specific address via the SBI  120 . The MSM  300  configures the TCXO frequency and other RFU specific functions.  
         [0021]    Functions of the SBI and Sync-Det/Tx-En control lines include programming the hop frequency, received Signal Strength Indicator (RSSI), BT RFU reset, PLL lock indication, Rx-Sel/Tx-Sel, Sync-Det signaling, Power On/Off etc. In a preferred embodiment, the SBI protocol is a subset of the standard general SBI interface used by QUALCOMM.  
         [0022]    The independence of the BT RFU allows for direct VCO modulation control and independent control of I/Q modulation.  
         [0023]    BT RFU performs the necessary tasks on the Rx path  118  to translate the BT RF signal from 2.4 GHz down to and including Rx path data slicing. MSM  300  performs the symbol recovery. The architecture is optimized to minimize MSM and BT RFU overhead.  
         [0024]    MSM  300  receives Rx oversampled data, allowing MSM  300  to perform symbol recovery practically independently of the BT RFU  200 . Likewise, BT RFU  200  performs data slicing practically independently of MSM  300 .  
         [0025]    The amount of real time feedback between MSM  300  and BT RFU  200  for optimal Rx path operation is a signal along Sync-det/Tx-enable path that tells the RFU when the MSM symbol recovery circuits have achieved synchronization with a BT packet.  
         [0026]    BT RFU  200  performs the necessary tasks on Tx path  118  to translate the raw baseband data., pre-BT Gaussian Frequency Shift Keyed (GFSK) modulation up to RF frequencies (2.4 GHz). Tx path data Gaussian filter, digital to analog converter (DAC) and other GFSK are located on the BT RFU  200  in a preferred embodiment. The architecture is optimized to insure minimized I/O, one data and one control pin/data path on Tx path  118  and practical independence from RF Phase Locked Loop (PLL).  
         [0027]    In the exemplary system of FIG. 2, BT RFU  200  is depicted in block diagram form. Interface  124  is connected to BT RFU  200 . V dd  Digital I/O  225  receives a reference input from V DD -MSM  114 . Low Noise Amplifier (LNA)  205  receives an input signal from antenna  126 , where it is downconverted to an appropriate frequency by mixer  210 . The downconverted signal is passed through IF filter  215  to a level detector  220  before it is sent to Data Slicer with Sync-Det Input  230 . Data Slicer with Sync-Det Input  230 , if enabled by the signal from Sync-Det/Tx-En line  116 , decimates the oversampled signal for passage to T/R Duplex block  235  where it is placed on Rx/Tx data line  118 . If transmission from the BT RFU is enabled, then data from Rx/Tx data line  118  is conveyed to Tx Gaussian Filter  240 , and converted to an analog signal in DAC  245 . The analog signal is then passed to Transmit Module (Tx Mod)  260  for upconversion using Phase Locked Loop (PLL)  255  and Voltage Controlled Oscillator (VCO)  250  before being passed on to driver amplifier  280  and then to antenna  126 .  
         [0028]    With respect to FIG. 3, MSM  300  is depicted in block diagram form. Interface  124  connects with MSM  300  in a similar fashion that just described with respect to FIG. 2. V dd  Digital I/O  305  receives a reference input from V DD  -MSM  114 . MSM core  320  formats data and control information intended for BT RFU  200  before transmitting data to Rx and Tx data module  315 . Appropriate symbols are transmitted to time tracking and symbol acquisition module to enable the Sync Detect/ Transmit Enable  
         [0029]    (Sync-Det/Tx-En) path  116 . Sync-Det/Tx-En path  116  is connected to and fed by time tracking and symbol acquisition module  310 . Tx Data whitening module  325  is also connected to Rx and Tx data module  315 , and in turn transmits/receives data to T/R Duplex block  330 . Transmit / control instructions are conveyed over SBI  120  via serial interface and control circuitry  335 . Clocks and timers module  340  is connected to clock reference signal path  122  and provides clocking to various components (connections not shown).  
         [0030]    Description by Example  
         [0031]    In an exemplary embodiment of the present invention, the interface may be implemented between an MSM device  300  and an RFU device  200  in a mobile phone (not shown) which can use the Bluetooth (BT) RF link  104  to communicate with an external device, such as a PC (not shown) for the purpose of synchronizing an address book. When the phone powers on, the MSM  300  and RFU  200  are reset and the BT interface and logic enters a sleep state. The phone software may also force a sleep state by issuing a Serial Bus Interface (SBI) write to the RFU RESET register and resetting the MSM logic. The phone user may request synchronization of the address book by pressing a key on the phone. The phone software detects this key press and establishes a BT RF link with the PC. The address book data is transferred over the RF link and then the link is disconnected. The procedure to establish the link requires many protocol steps but for the BT interface and logic the identical sequences to send and receive packets are repeated over and over. Each time the phone software receives a packet the following sequence is performed:  
         [0032]    The MSM  300  awakens the RFU  200  from the sleep state by an SBI write to the CONFIG register  272  within the serial interface and control circuitry  270 . The BT interface and logic will then be in an idle state.  
         [0033]    The MSM  300  begins the receive sequence with an SBI write to the RFU HOP register  274  to set the receive mode and frequency. This arms the RFU and puts the BT interface and logic in the ready state.  
         [0034]    The RFU timing will be set precisely by a strobe from the MSM to RFU on the Sync_Det/Tx_En  116  hardware signal which sets the BT interface and logic into the start state. In the start state the RFU initializes its logic, warms up the frequency synthesizers and begins sending a serial data stream to the MSM after 180 us.  
         [0035]    When the MSM detects a synchronization pattern for a data packet in the data stream it sets the Sync_Det/Tx_En  116  signal high to put the BT interface and logic into the go state.  
         [0036]    At the end of the receive data packet the Sync_Det/Tx_En  116  goes low and the BT interface and logic returns to the idle state.  
         [0037]    The transmit sequence is similar to the receive sequence except that the transmit mode is set in the HOP register. After the phone has used the receive and transmit sequences to send protocol messages and establish a link, the same receive and transmit sequences will be used to transfer the address book data. When the data transfer is complete the BT link will be shut down and the BT interface and logic returned to the sleep state.  
         [0038]    [0038]FIG. 4 is a timing diagram of the 3 wire Serial Bus Interface (SBI)  120 . As shown in a preferred embodiment. signal SBCK is rapidly oscillating clock signal, that when logically combined with signal SBST when held to a logical low enables the data transfer through data signal and line SBDT.  
         [0039]    The SBI write registers are reset to 0 and bidirectional pins are put into an input state by an BT RFU  200  detection of a power up reset condition or by a write to the SBI reset register. These resets put the BT RFU  200  in a low power mode with the SBI interface still operational. The state of the BT RFU write registers is maintained as long as power is supplied, regardless of the state of the clocks.  
         [0040]    The SBI write registers inside the BT RFU are as follows in Tables 1 and 2:  
                           TABLE 1                       REG_ADD   Bit#   Name   Description                   0x00   —   Reset   Write to address resets RFU.       0x01   6:0   Hop   Hop frequency for this slot. f=2400 MHz+Hop                   MHz       0x01   7   Rx_Sel/Tx_Sel   A write to the hop register will enable either the                   receive or transmit mode as selected by this bit.                   A 1 is to select Rx and a 0 selects Tx.                   The low to high (active) transition of the                   Sync_Det/Tx_En pin will start RFU timing for                   the selected mode.       0x02   0   Sleep/   0 sets the RFU immediately into sleep mode                   and inactive except for the SBI interface and                   Clk_Ref.                   1 takes the RFU out of sleep mode and allows                   other portions of RFU to be turned on with their                   specific signaling       0x02   1   CLK_On   1 turns on 12 MHz clock output. Set to 0 to                   turn off 12 MHz clock output and force                   Clk_Ref to 0.       0x02   3:2   PLL_Sel   Select the input clock frequency.                   00 = 19.2 MHz                   01 = 19.68 MHz                   10 = 19.8 Mhz                   11 = External 12 Mhz xtal       0x03   4:0   Pwr_Cntl   Output attenuation in 2 dB steps. 0x00 = 0 dB                   attenuation and 0x1F = 62 dB attenuation.                   Accuracy is ±2 dB.       0x04   7:0   assigned   TBD       0x05-0x3F   —   —   Reserved.       0x40-0x7F   —   —   Write registers available for device testing.                  
 
         [0041]    [0041]                           TABLE 2                       REG_ADD   Bit#   Name   Description                   0x80   —   —   Reserved.       0x81   3:0   ID   Device identification number.       0x81   7:4   ID   TBD. Manufacturer ID number.       0x82   6:0   RSSI   Receive Signal Strength Indicator. 0 to −127                   dBm. The value is latched at the second                   Sync_Det/Tx_En rising edge during a receive slot                   i.e. the end of the sync id sequence and shall have                   an accuracy of ±4 dB within the range −20 dBm to                   −80 dBm.       0x82   7   PLL_Lock   1 when PLL lock detected.       0x83-0xBF   —   —   Reserved.       0xC0-0xFF   —   —   Read registers available for device testing.                    
         [0042]    The SBI data transfer format is composed of 29 fixed bits as illustrated in FIG. 4 and as follows in Table 3:  
                       TABLE 3                       Bit   Name   Description                   1   Start   Always 1. Falling edge of SBCK only.       2-9   SLAVE_ADD   0x41 for the RFU.       10   CLK   Always 1.       11   R/W   MSBit of register address byte.               1 when Data is transferred from Slave to               Master.               0 when Data is transferred from Master to               Slave.       12-18   REG_ADD   7 LSBits of register address.       19   CLK   Always 1.       20-27   Data   8 bits of data. MSB at cycle 20.       28   CLK   Always 1.       29   Stop   Always 1. Rising edge of SBCK only.                  
 
         [0043]    [0043]           
         [0044]    The sequence of information shown adjacent to SBDT is device address, register address and then the data, with each field transmitted with the most significant bit first. Control data is transferred between MSM  300  and BT RFU  200  one byte at a time. Control bits become effective during the CLK cycle at bit  28 . When status data from the slave device (BT RFU) is being read, the data pin is driven by the BT RFU only during the 8 clock cycles of the Data field Bit  11  of Table 3 With respect to FIG. 5, the normal continuous operation of System  100  will be detailed beginning with START  505 . During normal operations, the following functions are performed over SBI  120 . The 12 MHz reference is turned on and sent to the MSM  300  core in step  510 . In step  520 , the Sync-Det/Tx-En path is utilized to begin Start Slot operation timing. In step  530  the Local oscillator (PLL) hop frequency is programmed by MSM  300  in BT RFU  200 . In step  540 , the optional step of performing a PLL lock indication read is undertaken. In step  550 , the next available time slot is designated as either a receive (Rx) or transmit (Tx) from the unit as a whole. The BT RFU is then reset in step  560 , while in step  570  the Receive Signal Strength Indicator (RSSI) is read. Finally, the transmit (Tx) power control is set for Power Amplifier (PA)  110  in step  580  before control passes to STOP  585 . Of course control returns to START and the process repeats indefinitely until some action or condition interrupts the process.  
         [0045]    The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. The various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.