Abstract:
A wireless network terminal tunes to a high data rate (“HDR”) HDR carrier when in an idle state. The terminal periodically scans a 1×RTT carrier for pages, SMS and other information. Should the scan detect an incoming communication on the 1×RTT carrier, any existing HDR packet session is terminated so that the terminal may tune to the 1×RTT carrier to receive the incoming communication. If the coverage area does not support an HDR carrier, the terminal tunes to the 1×RTT carrier and periodically scans for an HDR carrier.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of priority to U.S. Provisional Application Ser. No. 60/187,547, filed Mar. 7, 2000. 

   FIELD OF THE INVENTION 
   The present invention relates to wireless communication systems. More particularly, the present invention pertains to methods and apparatus for dual mode operation in a wireless communication system. 
   BACKGROUND OF THE INVENTION 
   The third generation (or “3G”) of wireless communication services promises to bring unity to a fractured worldwide cellular market. 3G systems will permit seamless travel not presently available in the splintered U.S. mobile telephone service. In addition, 3G systems promise a wide array of high-speed broadband data transmission and processing, including video, on-board navigation, and Internet access. 
   One wireless standard designed to support  3 G services is cdma2000™, defined by the ITU in its IMT-2000 vision. Phase one of the cdma2000 standard effort, known as “1×RTT” (i.e., Radio Transmission Technology), has already been completed and published by the Telecommunications Industry Association (TIA). 1×RTT refers to cdma2000 implementation within existing spectrum allocations for cdmaOne—1.25 MHz carriers. The technical term is derived from N=1 (i.e., use of the same 1.25 MHz carrier as in cdmaOne) and the “1×” means one time 1.25 MHz. 1×RTT is backward compatible with cdmaONE networks, but offers twice the voice capacity, data rates of up to 144 kbps, and overall quality improvements. 
   Also employing a 1.25 MHz channel is the High Data Rate (HDR) technology. HDR is RF compatible with cdmaOne and 1×RTT systems and permits side-by-side deployment of transmitters and antennas in existing CDMA towers. Unlike 1×RTT, which is optimized for circuit switched services, HDR is spectrally optimized for best effort packet data transmission. HDR delivers very high-speed CDMA wireless Internet access at peak data rates greater than 1.8 Megabits per second. Notably, unlike 1×RTT, the control and data channel in an HDR carrier are time multiplexed. 
   Because of its high speed Internet access, it is preferable to conduct data communications over an HDR carrier, rather than on a 1×RTT carrier. Nevertheless, because HDR is packet based, it does not accommodate real time applications very well. Thus, a user of an HDR carrier who wishes to place a voice communication would need to use a carrier such as 1×RTT. U.S. patent application Ser. No. 09/474,056, filed Dec. 28, 1999, which is fully incorporated herein by reference, discloses a hybrid network supporting both 1×RTT and HDR carriers. The hybrid network coordinates communication over either the 1×RTT or the HDR carrier as circumstances dictate. Such a hybrid network, however, requires the changes necessary in 1×RTT and HDR protocol to support this coordination. 
   SUMMARY OF THE INVENTION 
   In accordance with a first aspect of the invention, methods and apparatus are provided for transferring communications at a terminal within an overlapping coverage area having an all-services carrier and a best-efforts carrier, wherein the all-services carrier supports real-time and non-real-time services and the best-efforts carrier supports only non-real-time services. In one embodiment, the all-services carrier is a 1×RTT carrier and the best-efforts carrier is an HDR carrier. (Note: There are always two carriers for both 1×RTT and HDR: one for the forward link and one for the reverse link. As used herein, “carrier” will collectively refer to both the forward and reverse link carriers.) 
   In a preferred embodiment, a terminal tunes to a HDR carrier when in an idle state. The terminal periodically scans a 1×RTT carrier for pages, SMS and other information such as information sent via wavelength communications. Should the scan detect an incoming communication on the 1×RTT carrier, any existing HDR packet data communication is terminated so that the terminal may tune to the 1×RTT carrier to receive the incoming communication. If the coverage area does not support an HDR carrier, the terminal tunes to the 1×RTT carrier and periodically scans for an HDR carrier. 
   In another preferred embodiment, a terminal is provided with a transceiver capable of being tuned to a HDR carrier or to a 1×RTT carrier, and a processor capable of tuning the transceiver based on the type of communication the terminal is engaged in. Thus, the processor tunes the transceiver to a HDR carrier for non-real-time packet data communications, and to a 1×RTT carrier for voice communications or packet data communications. 
   In accordance with another aspect of the invention, a wireless communications network includes an HDR carrier for non-real-time packet data communications, a 1×RTT carrier for 1×RTT communications or packet data communications, and a plurality of terminals. Each terminal is provided with a transceiver capable of being tuned to a HDR carrier or to a 1×RTT carrier, and a processor capable of tuning the transceiver based on the type of communication the terminal is engaged in, such as the terminal described above. 
   As will be apparent to those skilled in the art, other and further aspects and advantages of the present invention will appear hereinafter. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the present invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numerals refer to like components, and in which: 
       FIG. 1  is a block diagram of both a 1×RTT and an HDR network having an overlapping coverage area. 
       FIG. 2  is a communication flow diagram according to one embodiment of the invention. 
       FIG. 3  is a communication flow diagram according to one embodiment of the invention. 
       FIG. 4  is a communication flow diagram according to one embodiment of the invention. 
       FIG. 5  is a block diagram illustrating a terminal capable of dual mode operation in accordance with one embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  illustrates coverage area  100  supported by both a 1×RTT and an HDR network. Users at terminals such as a laptop computer  110  having a wireless transceiver or a handset  115  may communicate over either an HDR carrier  120  or a 1×RTT carrier  125  as long as the terminal is configured for dual mode operation. The 1×RTT carrier  125  carries 1×RTT communications, which may include voice, packet data, or other multi services such as Short Message Services (SMS) or broadcast information services. The HDR carrier  120  is a carrier used only for the transmission of non-real-time packet data. An HDR transmitter  130  under the control of an HDR base station controller  135  transmits the HDR carrier  120 . The HDR base station controller  135  couples to a packet data core network  155 . Packet data from the Internet  150  couples through the packet data core network  155  to the HDR base station controller and ultimately to the terminals  110  and  115 . 
   Voice communications are carried only by the 1×RTT carrier  125  transmitted by a 1×RTT transmitter  131  under the control of a 1×RTT base station controller  136 . A mobile switching center  140  connects a public switched telephone network (PSTN)  145  with the 1×RTT base station controller  136 . Packet data from the Internet  150  couples to the mobile switching center  140  through an ISP server  160 . Alternatively, packet data can be connected directly to BSC  136  through the packet data core  155 . 
   Unlike the hybrid network disclosed in the above-incorporated application Ser. No. 09/474,056, the 1×RTT and HDR carriers are separate and independent. Rather than having the network supply the coordination between these carriers, the present invention uses intelligence supplied by the terminals to control whether communications will be received on a given carrier. Thus, the present invention may be denoted a “terminal-centric” approach in contrast to the “network-centric” approach disclosed in application Ser. No. 09/474,056. 
   Towards this end, the present invention has two main embodiments: one in which packet data communications are not transferred between the HDR and 1×RTT carriers, and one in which packet data communications are transferred between the HDR and 1×RTT carriers using standard 1×RTT packet data hand-over procedures. It should be noted that acquiring a carrier signal usually encompasses the steps of tuning the terminal to the correct frequency, synchronizing the terminal timing to the correct network timing, and then registering with the network. This process is well known in the art, however, and the invention does not depend on any particular method of acquiring a carrier. Therefore, in the discussion below, the process of acquiring a carrier will simply be referred to as tuning the terminal to the carrier. The first embodiment will now be described further: 
   No Packet Data Hand-Over Embodiment 
   In this embodiment the terminal tunes to the HDR carrier as the default carrier if this carrier is available. A sample communication flow procedure is illustrated in  FIG. 2 . Here, the HDR carrier  120  is available so that the terminal “camps on” and monitors this channel. The user then initiates one or more non-real-time packet data communications over the HDR carrier  120  at step  200 . As demonstrated at steps  205  and  210 , the terminal may periodically place the HDR packet data communication on hold and tune to the 1×RTT carrier to look for incoming 1×RTT communications directed to the terminal over the 1×RTT carrier. At step  205 , because no voice communications were detected on the 1×RTT carrier, the terminal returns to the HDR carrier and resumes the non-real-time packet data communication. At step  210 , however, the terminal detects an incoming 1×RTT communication on the 1×RTT carrier. Thus, the terminal automatically discontinues the HDR packet data communication and establishes an active 1×RTT communication. Upon termination of the 1×RTT communication at step  215 , the terminal tunes to the HDR carrier to re-establish the HDR packet data communication. In an alternative embodiment, the terminal may query the user whether or not to accept the incoming 1×RTT communication at step  210 . In such a case, only an affirmative response by the user would lead to establishment of the active 1×RTT communication. Otherwise, the terminal would return to the HDR carrier and re-establish the HDR packet data communication. For example, where the incoming 1×RTT communication is a voice communication, the terminal tunes to the 1×RTT carrier and establishes a voice communication. Once the voice communication is terminated, the terminal tunes to the HDR carrier to re-establish any HDR packet data communications that the terminal was previously engaged in. 
   When a user of the terminal initiates a 1×RTT communication, such as a voice communication, the communication must be carried out over the 1×RTT carrier. This can be illustrated in  FIG. 2 . Therefore, if a non-real-time packet data communication is in progress over the HDR carrier (step  200 ) when the user initiates a voice communication, then the non-real-time packet data communication must be put on hold while the terminal is tuned to the 1×RTT carrier (step  210 ). The voice communication is then commenced on the 1×RTT carrier. Upon termination of the voice communication, the terminal is tuned to the HDR carrier and the non-real-time packet data communication is re-established (step  215 ). 
   Note that the above scenarios require the terminal to be in the footprint or coverage area of both an HDR and a 1×RTT transmitter.  FIG. 3  presents the communication flow scenario if an HDR carrier is unavailable. Because the default mode is to camp on the HDR carrier, the terminal will periodically scan for the availability of the HDR carrier at steps  220  and  230 . At step  220 , no HDR carrier is available so the terminal must re-tune to the 1×RTT carrier. However, at step  230 , the terminal, having moved into an area of HDR coverage, detects and tunes to the HDR carrier. Note that if a 1×RTT packet data communication had been established prior to step  230 , this 1×RTT packet data communication would have to be terminated before the terminal could camp on the HDR carrier. Subsequent to step  230 , the terminal could re-establish the packet data communication on the HDR carrier. 
   1×RTT Packet Data Hand-Over Embodiment 
   This embodiment differs from the previously-described embodiment by employing basic 1×RTT packet data hand-over procedures to maintain continuity of packet data communications between the HDR and 1×RTT carriers.  FIG. 4  shows the communication flow for a transition from HDR to the 1×RTT carrier. At step  250 , the terminal establishes an HDR packet data communication. At step  260 , the terminal tunes to the 1×RTT carrier to establish a 1×RTT communication. The impetus to tune to the 1×RTT carrier may have resulted from a periodic scan such as discussed with respect to  FIG. 2  or may have resulted from the user desiring to place a voice communication. Because the terminal is tuned to the 1×RTT carrier while an active HDR packet data communication is in progress, the terminal sends a hand-over request to the network prior to step  260 . As the terminal tunes to the 1×RTT network, a standard 1×RTT packet hand-over procedure is followed to transfer the packet data communication to the 1×RTT carrier. Thus, at step  270 , an active 1×RTT and an active data communication are present on the 1×RTT carrier. Upon termination of the 1×RTT communication at step  280 , the terminal again sends a 1×RTT hand-over request to the network with information about the target HDR base station controller. 
   Just as discussed with respect to  FIG. 3 , the terminal may be in an area not supporting an HDR carrier. The terminal would, while camping on the 1×RTT carrier, periodically scan for the presence of an HDR carrier. Upon detecting the HDR carrier, should the terminal have an active 1×RTT packet data communication in progress, it will send a 1×RTT hand-over request to the network as discussed with respect to  FIG. 4 . The request should contain information about the target base station controller. In addition, point-to-point protocol (PPP) state information will be transferred between the HDR and 1×RTT base station controllers. Upon acknowledgement from the network of the hand-over request, the terminal tunes to the HDR carrier and the packet data communication resumes as a non-real-time packet data communication. 
     FIG. 5  illustrates an example architecture for a terminal in accordance with one embodiment of the invention. Terminal  500  comprises an antenna  502  for receiving Radio Frequency (RF) carrier signals. For example, antenna  502  may receive 1×RTT carrier  125  signals and HDR carrier  120  signals. Antenna  502  is also configured to transmit RF signals that are encoded with data to be communicated to the network. Duplexer  504  is coupled to antenna  502  and switches the antenna between receive and transmit paths within terminal  500 . 
   The receive path comprises a Low Noise Amplifier (LNA)  506  that amplifies the received RF carrier signals to a suitable level for further processing. The amplified signal is then passed to a demodulation circuit  510 . In a typical receive path, demodulation circuit  510  will consist of two stages. In the first stage, an RF mixer  512  mixes the received RF signal down to an Intermediate Frequency (IF) signal by mixing the RF received signal with an RF Local Oscillator (RFLO)  522  signal. In the second stage, the IF signal is mixed with an IFLO  524  in order to step the IF signal down to a baseband signal. The baseband signal is then coupled to a processor  526  that decodes any data contained in the baseband signal. Generically, processor  526  is typically referred to as a baseband processor. 
   Conversely, in the transmit path, data to be communicated to the network is encoded onto a baseband signal by processor  526  and coupled to modulation circuit  520 . Modulation circuit  520  mixes the baseband signal up to an IF signal in mixer  518  by mixing the baseband signal with IFLO  524 . The IF signal is then mixed up to an RF signal in mixer  516  by mixing the IF signal with RFLO  522 . The RF signal is then amplified by a Power Amplifier (PA)  508  to ensure that the RF signal transmitted by antenna  502  is of sufficient power. 
   In the transmit path, RFLO  522  must be tuned to produce the correct RF carrier signal. For example, if terminal  500  is communicating non-real-time packet data, then RFLO  522  must be tuned to produce an RF signal with the appropriate HDR carrier frequency. If, on the other hand, terminal  500  is engaged in voice communication, then RFLO must be tuned to produce a RF signal with the appropriate 1×RTT carrier frequency. 
     FIG. 5  illustrates that in a typical embodiment, processor  526  controls the tuning of RFLO  522 . Processor  526  also tunes IFLO  524  if required; however, IFLO  524  may remain at the same frequency with only RFLO  522  being tuned. In fact, those skilled in the art will understand that some embodiments of terminal  500  may not include IFLO  524  or mixers  514  and  518 . In this case, RF mixer  512  converts the received RF carrier directly to baseband, and RF mixer  516  converts the baseband signal coupled from processor  526  directly to an RF signal. This type of architecture is termed direct conversion architecture. 
   Regardless of the specific architecture, the transmit and receive paths are typically included in one unit termed a transceiver. Therefore, in a typical embodiment, processor  526  is responsible for tuning the transceiver to the appropriate carrier in order to carry out the processes of  FIGS. 2 ,  3 , and  4 . 
   While the many aspects of the present invention are susceptible to various modifications and alternative forms, specific examples thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the invention is not to be limited to the particular forms or methods disclosed, but to the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the scope of the appended claims.