Abstract:
A method and subscriber unit used for communicating in voiced communications are disclosed. The method for use in a subscriber unit may include receiving, from a cellular base station, a first signal at a first data rate and a first modulation scheme, transmitting a second signal, to the cellular base station, indicative of a subscriber station capability to receive a third signal at a second date rate and a second modulation type, and receiving, from the cellular base station, based on the transmitted second signal, a third signal at the second data rate and second modulation type.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 12/946,258, filed Nov. 15, 2010, which is a continuation of U.S. patent application Ser. No. 10/852,024, filed May 24, 2004, now U.S. Pat. No. 7,835,308, issued Nov. 16, 2010, which is a continuation of U.S. patent application Ser. No. 10/086,664, filed Feb. 28, 2002, now U.S. Pat. No. 6,741,609, issued May 25, 2004, which is a continuation of application Ser. No. 09/354,042, filed Jul. 15, 1999, now U.S. Pat. No. 6,608,825, issued Aug. 19, 2003, which is a continuation of application Ser. No. 08/671,067, filed Jun. 27, 1996, now U.S. Pat. No. 5,953,346, issued Sep. 14, 1999, which are incorporated by reference as if fully set forth. 
     
    
     FIELD OF INVENTION 
       [0002]    This invention generally relates to wireless communication systems. More particularly, the invention relates to a wireless digital CDMA communication system that selectively adjusts the data transmission rate depending upon the bandwidth required by the communication without the loss of data during the transmission rate adjustment. 
       BACKGROUND 
       [0003]    The telecommunications industry has recently experienced strong growth in the use of wireless technology including cellular, satellite and microwave communications. As the popularity and use of wireless communication systems has increased, the finite bandwidth allocated to each type of wireless communication has become increasingly valuable. Since it is unlikely that additional bandwidth to support user growth will be allocated for existing applications, many of the recent advances in telecommunication hardware and software have been directed toward increasing the transmission rate of data while utilizing the same or a decreased bandwidth. 
         [0004]    One of the problems associated with wireless communication of data is that many different types of communicating nodes are currently in use including computers, facsimile machines, automatic calling and answering equipment and other types of data networks. These nodes may be able to communicate at a plurality of different data rates and must be properly synchronized to avoid losing data during the establishment or maintenance of a communication. 
         [0005]    The establishment and synchronization of communications is currently performed using a variety of different techniques. For example, the system disclosed in U.S. Pat. No. 4,384,307 (Kuzmik et al.) includes a communication adapter for interfacing a transceiver to a communication line. The system requires bit level manipulation of data to properly synchronize two communicating nodes. Reformatting of data using this technique is computationally expensive and prone to errors. 
         [0006]    Another type of system is disclosed in U.S. Pat. No. 4,583,124 (Tsuji et al.) which permits two nodes to quickly establish synchronization at a desired communication speed by storing information concerning each communicating node in memory. However, requiring an originating node to store information about each receiving node is impractical given today&#39;s communication environment. 
         [0007]    Accordingly, there is a need for a simple and effective technique for switching the data transmission rate of a communication network to the required rate while preserving the integrity of the data transmitted between two communicating nodes. 
       SUMMARY 
       [0008]    The present invention is a CDMA communication system which prevents the transmission of data between communicating nodes until the data communication rate required by the communicating nodes has been completely established throughout the system. The system selectively suppresses the confirmation tone that a receiving node sends to an originating node. Accordingly, the transmission of voice, facsimile or modem data is prevented until the communication path has been established at the desired communication rate. This permits the system to reliably transport encoded data at a plurality of data rates across a telecommunication system which may lack precise synchronization. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic overview of a code division multiple access communication system in accordance with the present invention; 
           [0010]      FIG. 2  is a block diagram of the communication system of  FIG. 1  connected to originating and terminating nodes; 
           [0011]      FIG. 3  is a flow diagram of the establishment of a communication channel between originating and terminating nodes in accordance with the prior art; 
           [0012]      FIG. 4  is a flow diagram of the establishment of a communication channel between originating and terminating nodes in accordance with the present invention; and 
           [0013]      FIG. 5  is a block diagram of a base station in accordance with the teachings of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0014]    The preferred embodiment will be described with reference to the drawing figures where identical numerals represent similar elements throughout. A communication network  10  embodying the present invention is shown in  FIG. 1 . The communication network  10  generally comprises one or more base stations  14 , each of which is in wireless communication with a plurality of subscriber units  16 , which may be fixed or mobile. Each subscriber unit  16  communicates with either the closest base station  14  or the base station  14  which provides the strongest communication signal. The base stations  14  also communicate with a base station controller  20  which coordinates communications among the base stations  14 . The communication network  10  may also be connected to a public switched telephone network (PSTN)  22 , wherein the base station controller  20  also coordinates communications between the base stations  14  and the PSTN  22 . Preferably, each base station  14  communicates with the base station controller  20  over a wireless link. Although the link between the base stations  14  and the base station controller  20  is shown as a wireless link, it should be apparent to those skilled in the art that a land line between the base stations  14  and the base station controller  20  may be provided. This is particularly applicable when a base station  14  is in close proximity to the base station controller  20 . 
         [0015]    The base station controller  20  performs several functions. Primarily, the base station controller  20  provides all of the overhead, administrative and maintenance (OA&amp;M) signaling associated with establishing and maintaining all of wireless communications between the subscriber units  16 , the base stations  14 , and the base station controller  20 . The base station controller  20  also provides an interface between the wireless communication system  10  and the PSTN  22 . This interface includes multiplexing and demultiplexing of a plurality of communication signals that enter and leave the system  10  via the base station controller  20 . Although the wireless communication system  10  is shown employing antennas to transmit RF signals, one skilled in the art will recognize that communications may be accomplished by microwave satellite uplinks. 
         [0016]    Referring to  FIG. 2 , the communication system  10  is generally connected to originating nodes  40  and terminating nodes  44 . In order to conserve as much bandwidth as possible, the communication system  10  selectively allots the bandwidth required for supporting the data transmission rate required by the originating and terminating nodes  40 ,  44 . In this manner, the system  10  ensures that the bandwidth is utilized efficiently. Voiced communications may be effectively transmitted across a 32 Kb/s adaptive pulse code modulation (ADPCM) channel. However, a high speed fax or data modem signal requires at least a 64 Kb/s pulse code modulation (PCM) signal to reliably transmit the communication. Many other types of modulation techniques and data transmission rates may also be utilized by originating and terminating nodes  40 ,  44 . The system  10  must be able to effectively allocate bandwidth and dynamically switch between these data communication rates and modulation schemes on demand. 
         [0017]    The communication system  10  provides a communication link between the originating and terminating nodes  40 ,  44 . The originating and terminating nodes  40 ,  44  may comprise computers, facsimile machines, automatic calling and answering equipment, data networks or any combination of this equipment. For robust communication of data it is imperative to ensure that the communication system  10  switches to the data transmission rate required by the communicating nodes  40 ,  44  prior to the transmission of any data. 
         [0018]    Referring to  FIG. 3 , the typical procedure for establishing communications between originating nodes  40  and terminating nodes  44  is shown. The originating node  40  periodically transmits a calling tone (step  100 ) which indicates that a data communication, (not a voice communication), is to be transmitted. The calling tone which is sent from the originating node  40  to the terminating node  44  is detected by the terminating node  44  (step  102 ) which initiates several actions. First, the terminating node  44  prepares to send a data communication (step  104 ). Next, the terminating node  44  transmits an answering tone (step  106 ) to the originating node  40  to confirm that the terminating node  44  has received the calling tone. Upon receipt of the answering tone (step  108 ), the originating node  40  begins the transmission of data (step  110 ), which is received by the terminating node  44  (step  112 ). With the communication link established at the data transmission rate, the originating and terminating  40 ,  44  nodes transmit and receive data until termination of the communication. 
         [0019]    One problem with this process is that the transmission rate of the communication system  10  is transparent to both the originating and terminating nodes  40 ,  44 . Modification of the transmission rate from a low rate (that supports voice communication) to a high rate (that supports encoded data communication) ensures that data will be reliably and quickly transmitted over a communication channel. However, the new transmission rate must be completely established throughout the communication system  10  to prevent false interpretation of tones transmitted by the originating node  40 . The originating node  40  may begin transmission of data at a high rate before the system  10  has fully switched from  32  Kb/s ADPCM to 64 Kb/s PCM resulting in loss of data. 
         [0020]    In order to obviate tone misinterpretation and to prevent the resulting erroneous operation of the originating or terminating nodes  40 ,  44 , the present invention blocks the transmission of the confirming tone to the originating node  40  until the new data transmission rate has been completely established throughout the communication system  10 . This prevents the reception of the answering tone at the originating node  40  and ensures the reliable transportation of encoded data at a higher rate across a communication system  10  which lacks the precise synchronization which would otherwise be required. 
         [0021]    The operation of the system  10  of the present invention will be explained with reference to  FIG. 4 . The communication system  10  facilitates communications between an originating node  40  and a terminating node  44 . As shown, the actions of the originating node  40  (steps  202 ,  212  and  214 ) and the actions of the terminating node  44  (steps  206 ,  207 ,  208  and  218 ) are the same as in  FIG. 3 . The operation of the communication system  10  is transparent to both the originating node  40  and the terminating node  44 . 
         [0022]    In operation, the originating node  40  periodically transmits a calling tone (step  202 ) which indicates a data communication. The communication system  10  performs several actions in response to receipt of the calling tone (step  204 ). First, the calling tone is received at 32 Kb/s ADPCM which is the standard communication setting for voice communications. The system  10  detects the calling tone and initiates a switch to 64 Kb/s PCM in order to handle the high-speed data transmission. This switch must be implemented by the base station  14 , the subscriber unit  16  and the base station controller  20 . Although the system  10  immediately begins the switching over to the new data transmission rate, the process takes approximately 1500 msec to implement. Accordingly, the system  10  transmits the calling tone to the terminating node  44  at 32 Kb/s ADPCM. 
         [0023]    The terminating node  44  detects the calling tone (step  206 ) and prepares to send a data communication (step  207 ). The terminating node  44  subsequently transmits the answering tone (step  208 ) which, when received by the originating node, will cause the originating node  40  to begin transmission of data. 
         [0024]    The communication system  10  receives the answering tone from the terminating node  44 . However, the system  10  does not forward the answering tone to the originating node  40  until the switch to 64 Kb/s PCM has been established throughout the system  10 . After the system  10  has confirmed that the switch to 64 Kb/s PCM has been achieved, it permits the answering tone to pass through to the originating node  40 , which receives the tone (step  212 ). In response to the answering tone, the originating node  40  begins transmission of data (step  214 ). The system  10  receives the data and begins transmission of data at the new data transmission rate ( 64  Kb/s PCM) (step  216 ) to the terminating node  44  which receives the data (step  218 ). Since the communication channel has been established, the originating and terminating nodes  40 ,  44  continue to communicate over the system  10  in this manner (steps  214 ,  216  and  218 ) until the communication is terminated. 
         [0025]    Referring to  FIG. 5 , a more detailed block diagram of the base station controller  20  is shown. The base station controller  20  controls at least a portion of the communication link between two communicating nodes  40 ,  44 . This link comprises the transmission path  300  from a first communicating node to the base station controller  20 , the transmission path  302  within the base station controller  20 , and the transmission path  304  from the base station controller  20  to the second communicating node. The transmission paths  300 ,  304  to and from the base station controller  20  may include a plurality of base stations  14  and subscriber units  16  which are controlled by the base station controller  20 . 
         [0026]    It should be appreciated by those of skill in the art that the establishment of a communication channel between communicating nodes  40 ,  44  is a complex procedure involving a plurality of tasks performed by the base station  14 , the subscriber unit  16  and the base station controller  20 . A detailed description of the entire procedure is outside the scope of the present invention. Accordingly, only those portions of the procedure for establishment of a communication channel relevant to the present invention will be described hereinafter. 
         [0027]    The communications between an originating node  40  and a terminating node  44  are transmitted over a virtual channel as is well known by those of skill in the art. Since the entire spectrum is used by the CDMA communication system  10 , communications from the originating node  40  to the terminating node  44  are transmitted over the same frequency band as communications from the terminating node  44  to the originating node  40 . After the virtual channel has been established, the originating and terminating nodes  40 ,  44  may freely communicate. 
         [0028]    The base station controller  20  includes a calling tone detector  310 , a microprocessor  312  and an answering tone blocker  314 . The calling tone detector  310  monitors the communication channel which has been established in order to detect the calling tone. When a calling tone is transmitted from an originating node  40 , the calling tone detector  310  detects the calling tone, which causes the base station controller  20  to initiate the switch to a higher data transmission rate. The microprocessor  312  subsequently informs any other base stations  14  or subscriber units  16  through which the communication is to be routed (hereinafter called communicating equipment) to initiate the switch to the higher data transmission rate. 
         [0029]    The microprocessor  312  activates the answering tone blocker  314  which will prevent the answering tone from being transmitted through the system  10 . Each piece of communicating equipment  14 ,  16 ,  20  transmits an acknowledgment to the microprocessor  312  of the base station controller  20  when the higher data transmission rate has been achieved. The microprocessor  312  subsequently deactivates the answering tone blocker  314  which permits the answering tone to be forwarded to the originating node  40 . The communicating nodes  40 ,  44  commence data transmission over the communication system  10  at the higher data transmission rate. 
         [0030]    Although the invention has been described in part by making detailed reference to the preferred embodiment, such detail is intended to be instructive rather than restrictive. For example, the functions performed by the base station controller  20  shown in  FIG. 5  may, in an alternative embodiment, be performed by a base station  14  coupled with either the originating or terminating nodes  40 . The functions of a base station  14  may also be combined with the base station controller  20 , to form a master base station. Additionally, different data rates and modulation schemes may be employed. It will be appreciated by those skilled in the art that many variations may be made in the structure and mode of operation without departing from the spirit and scope of the invention as disclosed in the teachings herein. 
         [0031]    Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone (without the other features and elements of the preferred embodiments) or in various combinations with or without other features and elements of the present invention. 
         [0032]    Hereafter, a wireless transmit/receive unit (WTRU) includes but is not limited to a user equipment, mobile station, fixed or mobile subscriber unit, pager, or any other type of device capable of operating in a wireless environment. When referred to hereafter, a base station includes but is not limited to a Node-B, site controller, access point or any other type of interfacing device in a wireless environment.