Abstract:
Methods and apparatus for exchanging information with a dormant target communication device provide for locating a dormant target communication device by a wireless infrastructure, forwarding information to the dormant target communication device by the wireless infrastructure, and allowing the dormant target communication device, upon receiving said information from the wireless structure, to start forwarding information to the wireless structure.

Description:
FIELD  
         [0001]    The present invention relates to exchanging information in wireless communications systems. More specifically, the present invention relates to methods and apparatus for exchanging air-interface information with a dormant target communication device in a wireless communication network.  
         BACKGROUND  
         [0002]    When the packet data service in a wireless communications system is active, resources in the infrastructure, e.g., base station transceiver subsystem (BTS), base station controller (BSC), packet control function (PCF), and the radio link are actively assigned to the participating communication devices. After a period of inactivity in a communication device, the corresponding traffic channel may transition to a dormant packet data session to conserve system capacity, reduce service cost, and save battery life. However, the act of transitioning the dormant packet data session back to an active packet data session is accompanied by a considerable delay in the system response.  
           [0003]    There is a need, therefore, for mechanisms to efficiently exchange information with a dormant communication device.  
         SUMMARY  
         [0004]    The disclosed embodiments provide novel and improved methods and apparatus for exchanging information with a dormant target communication device in a wireless communication network. In one aspect, a method for exchanging information with the dormant target communication device in a wireless communication system provides for locating a dormant target communication device by a wireless infrastructure, forwarding information to the dormant target communication device by the wireless infrastructure, and setting a timer upon its expiration the dormant target communication device may start forwarding information to the wireless infrastructure. In one aspect, the information is communicated as short data bursts.  
           [0005]    In one aspect, a method for exchanging information with a dormant target communication device in a wireless communication system provides for locating a dormant target communication device by a wireless infrastructure, forwarding information to the dormant target communication device by the wireless infrastructure, and forwarding a release order to the dormant target communication device, thereby allowing the dormant target communication device to start forwarding information to the wireless infrastructure.  
           [0006]    In one aspect, a method for exchanging information with a dormant target communication device in a wireless communication system provides for locating a dormant target communication device by a wireless infrastructure, forwarding information to the dormant target communication device by the wireless infrastructure, and allowing the dormant target communication device, upon receiving said information from the wireless structure, to start forwarding information to the wireless structure.  
           [0007]    In one aspect, an apparatus for exchanging information with a dormant target communication device in a wireless communication system includes a memory unit, a receiver, a transmitter, and a processor communicatively coupled with the memory unit, the receiver, and the transmitter. The processor is capable of carrying out the above-mentioned methods. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The features and advantages of the present invention will become more apparent from the detailed description of the embodiments set forth below:  
         [0009]    [0009]FIG. 1 illustrates a group communications system;  
         [0010]    [0010]FIG. 2 through FIG. 6 illustrate call flows for exchanging information with a dormant communication device; and  
         [0011]    [0011]FIG. 7 illustrates one embodiment for a communication device and a base station. 
     
    
     DETAILED DESCRIPTION  
       [0012]    Before several embodiments are explained in detail, it is to be understood that the scope of the invention should not be limited to the details of the construction and the arrangement of the components set forth in the following description or illustrated in the drawings. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.  
         [0013]    [0013]FIG. 1 illustrates a functional block diagram of a group communication system  100 , for implementing one embodiment. Group communication system  100  is also known as a push-to-talk (PTT) system, a net broadcast service (NBS), a dispatch system, or a point-to-multi-point communication system. In one embodiment, group communication system  100  includes a group call server  102 , which may be deployed in either a centralized deployment or a regionalized deployment.  
         [0014]    Group communication devices (CDs)  104  and  106 , which may be deployed such as cdma2000 handset, for example, may request packet data sessions using a data service option. Each CD may use the session to register its Internet Protocol (IP) address with the group call server to perform group call initiations. In one embodiment, group call server  102  is connected to the service provider&#39;s packet data service nodes (PDSNs) through service provider&#39;s network  116 . CDs  104  and  106 , upon requesting packet data sessions from the wireless infrastructure, may have IP connectivity to group call server  102  through the PDSNs  114 . Each PDSN may interface to a base station controller (BSC) through a packet control function (PCF)  108  and a network  112 . The PCF may be co-located with the BSC within a base station (BS)  110 .  
         [0015]    A packet data service node may fall in one of several states, e.g., active or connected state, dormant state, and null or inactive state. In the active or connected state, a active traffic channel exists between the participating CD and the BS or BSC, and either side may send data. In the dormant state, no active traffic channel exists between the participating CD and the BSC, but a point-to-point protocol (PPP) link is maintained between the participating CD and the PDSN. In the null or inactive state, there is no active traffic channel between the participating CD and the BSC, and no PPP link is maintained between the participating CD and the PDSN.  
         [0016]    After powering up, CDs  104  and  106  may request packet data sessions. As part of establishing a packet data session, each CD may be assigned an IP address. Each CD may perform a registration process to notify group call server  102  of the CD&#39;s IP address. Registration may be performed using an IP protocol, such as session initiation protocol (SIP) over user datagram protocol (UDP). The IP address of a CD may be used to contact the CD when the corresponding user is invited into a group call.  
         [0017]    Once a group call is established, CDs  104  and  106  and group call server  102  may exchange media and signaling messages. In one embodiment, media may be exchanged between the participating CDs and the group call server by using real-time protocol (RTP) over UDP. The signaling messages may also be exchanged by using a signaling protocol over UDP.  
         [0018]    Group communication system  100  performs several different functions in order to operate group call services. The functions that relate to the user side include user registration, group call initiation, group call termination, sending alerts to group participants, late join to a group call, talker arbitration, adding members to a group, removing members from a group, un-registering a member, and authentication. The functions that relate to system preparation and operation include administration and provisioning, scalability, and reliability.  
       PTT Latency  
       [0019]    In one embodiment, when the packet data service is active, resources in the infrastructure, e.g., base station transceiver subsystem (BTS), base station controller (BSC), packet control function (PCF), and the radio link are actively assigned to the participating CDs. In an IP-based dispatch service, while there is an active conversation going on between group members, the packet data connection for each participating CD remains active. However, after a period of inactivity, i.e., “hang time,” the traffic channels assigned to the participating CDs may be released and the participating CDs may transition to the dormant state.  
         [0020]    The transition to the dormant state conserves system capacity and reduces service cost and battery drain. When the packet data sessions are active, even if no data packets are being exchanged, radio frequency (RF) energy may still be transmitted by the participating CDs, albeit at a low level, to maintain synchronization and power control with the base station. These transmissions may cause a significant power drain on the participating CDs. In the dormant state, however, the participating CDs may not perform RF transmission. To conserve power and extend battery life, the hang time may be set to transition the participating CDs to dormant mode after extended periods of no data transmission.  
         [0021]    In the case of an active group call, while the packet data services for all participating CDs are active, new PTT requests have very low latency. However, if the participating CDs have previously transitioned to the dormant state, PTT latency may be much longer. During packet data dormancy state, information associated with the packet data session, which may include the CDs&#39; IP address, may be maintained. However, state information associated with layers below PPP, such as active traffic layers, may be released and/or de-allocated.  
         [0022]    In some infrastructures, to wake up dormant packet data sessions, the traffic channels must be reallocated, the resources must be reassigned, and the radio link protocol (RLP) layer must be reinitialized. The effect of this is that after a group has not talked for a while, when a group member presses the PTT button to request the floor, PTT latency for the first talk spurt is generally much longer than for subsequent talk spurts. While this is relatively infrequent, it may affect the utility of the group call service, and should be minimized.  
         [0023]    To reduce PTT latency, the group call signaling, such as the floor-control requests, floor-control announcements, and dormancy wakeup messages, may be transmitted on some available common channels. This eliminates waiting for dedicated traffic channels to be re-established. Common channels may be always available, regardless of the state of the participating CDs, and may not require being requested and reassigned each time a group member initiates a group call. Therefore, the group call signaling messages may be exchanged even when the participating CDs are dormant. In one embodiment dedicated traffic channels for the caller&#39;s CD and listeners&#39; CDs may be re-established in parallel.  
         [0024]    In one embodiment, a dormant caller&#39;s CD may send a floor-control request to the wireless infrastructure over some available reverse common channel, such as reverse access channel and reverse enhanced access channel. The caller&#39;s CD may also receive a response to the floor-control request on some available forward common channel, such as forward paging channel and forward common control channel. In one embodiment, dormant listener&#39; CDs may receive dormancy wakeup messages on some available forward common channel, such as forward paging channel and forward common control channel.  
       Short Data Burst Call-signaling Messages  
       [0025]    In one embodiment, a significant reduction in dormancy wakeup time may be achieved through the use of short data burst (SDB) messages, as provided in “TIA/EIA/IS-2000 Standards for cdma2000 Spread Spectrum Systems,” such as TIA/EIA/IS-707-A-2, “Data Service Option Standard for Spread Spectrum Systems, Addedum 2,” June 2000, and TIA/EIA/IS-2001-A, “Interoperability Specification (IOS) for cdma2000 Access Network Interfaces,” August 2001, hereinafter referred to as “the cdma2000 standard.” In one embodiment, SDB messages may be sent over a dedicated active channel, such as the forward fundamental channel (FCH) or forward dedicated common control channel (F-DCCH). SDB messages may also be sent over a common active channel, such as the reverse access channel (R-ACH), reverse enhanced access channel (R-EACH), forward common control channel (F-CCCH), or paging channel (PCH). SDB messages may be transported by radio burst protocol (RBP), which maps the messages onto an appropriate and available active layer channel. Because SDB messages may carry arbitrary IP traffic and may be sent over common active channels, SDB messages provide a mechanism to exchange group call signaling when participating CDs have no available dedicated traffic channel.  
       Mobile-Originated Call-signaling Messages  
       [0026]    In one embodiment, media-signaling messages may carry IP datagrams over the reverse link or mobile-originated link. A talker&#39;s CD may signal the group call server quickly whenever the talker requests the floor and a dedicated reverse traffic channel is not immediately available. Assuming the talker&#39;s CD has released all dedicated traffic channels, the talker&#39;s CD may immediately forward the floor control request over a reverse common channel of a wireless infrastructure, which may relay the request to the group call server. For example, either the reverse access channel or the reverse enhanced access channel may be used to send such messages when a dedicated reverse channel is not available. In one embodiment, the talker&#39;s CD may transmit a floor-control request to the group call server as SDB messages.  
       Network-Originated Call-signaling Messages  
       [0027]    In one embodiment, after receiving the floor-control request, the group call server may burst media-signaling messages to a group of dormant target CDs and trigger the dormant target CDs to re-establish their dedicated traffic channels. In one embodiment, the packet control function (PCF) receives a small amount of information, e.g., packet data, from the packet data serving node (PDSN), which may be destined for a dormant target CD. The PCF may determine to send the information to the base station controller (BSC) in a special form. In one embodiment, the special form includes short data burst (SDB) format, as specified in the TIA/EIA/IS-707-A-2, “Data Service Option Standard for Spread Spectrum Systems,” Addendum 2, dated June 2000 (IS-707-A-2). The TIA/EIA/IS-2001-A, “Interoperability Specification (IOS) for cdma2000 Access Network Interfaces,” dated August 2001 (IS-2001-A) standard defines several options for the BSC to deliver SDB messages to target CDs.  
         [0028]    According to the IS-2001-A standard, for example, when a small amount of data destined for a dormant target CD is received at the PCF, the PCF may choose to send the received data to the BSC in SDB format. If the BSC determines that short data bursts may be used to deliver the data to the dormant target CD, the BSC may send the data directly to the dormant target CD over a signaling channel. The BSC may also send the data to the MSC for delivery to the dormant target CD via an application data delivery service (ADDS) Page. The data may be delivered to the MSC using a BSC service request/response procedure. If the BSC is unsuccessful in delivering the SDB data to the dormant target CD on its own, the BSC may choose to send the data to the MSC for delivery to the dormant target CD via the ADDS Page procedure.  
         [0029]    [0029]FIG. 2 shows a call-flow procedure for exchanging information with a dormant target CD, according to one embodiment. The packet data session is in the dormant state with PPP connected. The PDSN sends packet data  202  to the BSC/PCF on the existing PPP connection associated with the dormant target CD. The BSC/PCF determines, in step  204 , whether the received packet data may be sent to the dormant target CD in short data bursts (SDB) form. In case the BSC/PCF determines that the received packet data may be sent to the dormant target CD in SDB form, BSC/PCF locates the dormant target CD. BSC/PCF locates the dormant target CD by sending a general page message  206  to the CD or using the location information already cached. The page message may be based on a service option (SO), such as “SO  33 .” After the BSC/PCF receives a page response  208 , and sends an acknowledge message (ACK order)  210  to the dormant target CD, the BSC/PCF sends the received packet data to the dormant target CD in SDB form  212 . The BSC/PCF indicates in message  212  to the dormant target CD whether the dormant target CD needs to send an Ack order upon receiving message  212 . If an Ack order is required, and an Ack order  214  is received from the dormant target CD, BSC/PCF may also send an Ack order  216 , acknowledging that BSC/PCF has received the Ack order  214  form the dormant target CD.  
         [0030]    In one embodiment, after Ack order  216  is sent to the dormant target CD, BCS/PCF sets a timer  218 , T 42  timer, upon its expiration the dormant target CD may transition from access state to idle state and start forwarding information in a SDB message  220  to the BSC/BCF. If mobile-initiated message  220  requires an Ack order, BSC/PCF sends Ack order  222  to the dormant target CD.  
         [0031]    [0031]FIG. 3 shows a call-flow procedure for exchanging information with a dormant target CD, according to one embodiment. The packet data session is in the dormant state with PPP connected. The PDSN sends packet data  302  to the BSC/PCF on the existing PPP connection associated with the dormant target CD. The BSC/PCF determines, in step  304 , whether the received packet data may be sent to the dormant target CD in short data bursts (SDB) form. In case the BSC/PCF determines that the received packet data may be sent to the dormant target CD in SDB form, BSC/PCF sends a general page message  306  to locate the dormant target CD. The page message may be based on a service option (SO), such as “SO  33 .” After the BSC/PCF receives a page response  308 , and sends an acknowledge message (ACK order)  310  to the dormant target CD, the BSC/PCF sends the received packet data to the dormant target CD in SDB form  312 . The BSC/PCF indicates in message  312  to the dormant target CD whether the dormant target CD needs to send an Ack order upon receiving message  312 . If an Ack order is required, and Ack order  314  is received from the dormant target CD, BSC/PCF may also send Ack order  316 , acknowledging that BSC/PCF has received Ack order  314  from the dormant target CD.  
         [0032]    In one embodiment, after Ack order  316  is communicated with the dormant target CD, BSC/PCF sends “release order”  318  to the dormant target CD to allow the CD to cancel its timer. Upon receiving release order  318 , the dormant target CD cancels the T 42   m  timer  320  and transitions from access state into idle state, which allows the dormant target CD to send a SDB message  322  to the BSC/BCF. The dormant target CD may transition from the system access state into the idle state after going through system determination sub-state. However, the dormant target CD may transition from the system access state into the idle state without going through the system determination sub-state, to reduce time delay. If the mobile-initiated SDB message  322  requires an Ack order message, BSC/PCF sends Ack order  324  to the dormant target CD.  
         [0033]    [0033]FIG. 4 shows a call-flow procedure for exchanging information with a dormant target CD, according to one embodiment. In this embodiment, the call flow procedure, illustrated by  402  through  422 , is similar to the call flow procedure described in FIG. 2, but the page message  406  is based on an unused service option (SO), other than “SO  33 ,” such as a proprietary SO, so that other BSC/PCF call processing that are designed based on “SO  33 ” need not be modified for SDB delivery.  
         [0034]    [0034]FIG. 5 shows a call-flow procedure for exchanging information with a dormant target CD, according to one embodiment. In this embodiment, the call flow procedure, illustrated by  502  through  524 , is similar to the call flow procedure described in FIG. 3, but page message  506  based on an unused service option (SO), other than “SO  33 ,” such as a proprietary SO, so that other BSC/PCF call processing that are designed based on “SO  33 ” need not be modified for SDB delivery.  
         [0035]    [0035]FIG. 6 shows a call-flow procedure for exchanging information with a dormant target CD, according to one embodiment. The packet data session is in the dormant state with PPP connected. The PDSN sends packet data  602  to the BSC/PCF on the existing PPP connection associated with the dormant target CD. The BSC/PCF determines whether the received packet data may be sent to the dormant target CD in short data bursts (SDB) form. In case the BSC/PCF determines that the received packet data may be sent to the dormant target CD in SDB form, BSC/PCF sends a general page message  606  to locate the dormant target CD. The page message may be based on a proprietary service option (SO), such as “SO 0×8026.” 
         [0036]    The BSC/PCF uses the proprietary SO to page the dormant target CD to indicate to the dormant target CD that there is a SDB message that needs to be delivered to the dormant target CD. Using the proprietary SO allows the dormant target CD to independently transition into idle state, without having the BSC/PCF to send a release order. The messages  606  through  616  are similar to those shown in FIG. 3, with all implementation variations. Upon receiving Ack order  616  at the dormant target CD, the dormant target CD cancels the T 42   m  timer  618  and transitions from access state into idle state, which allows the dormant target CD to send a SDB message  620  to the BSC/BCF. The dormant target CD may transition from the system access state into the idle state after going through system determination sub-state. However, the dormant target CD may transition from the system access state into the idle state without going through the system determination sub-state, to reduce time delay. If the mobile-initiated SDB message  620  requires an Ack order message, BSC/PCF sends Ack order  622  to the dormant target CD.  
         [0037]    [0037]FIG. 7 is a simplified block diagram of an embodiment of a BSC/PCF  704  and a communication device  706 , which are capable of implementing various disclosed embodiments. For a particular communication, voice, data, packet data, and/or alert messages may be exchanged between BSC/PCF  704  and communication device  706 , via an air interface  708 . Various types of messages may be transmitted, such as messages used to establish a communication session between the base station and the communication device, registration and paging messages, and messages used to control a data transmission (e.g., power control, data rate information, acknowledgment, and so on). Some of these message types are described in further detail below.  
         [0038]    For the reverse link, at communication device  706 , voice and/or packet data (e.g., from a data source  710 ) and messages (e.g., from a controller  730 ) are provided to a transmit (TX) data processor  712 , which formats and encodes the data and messages with one or more coding schemes to generate coded data. Each coding scheme may include any combination of cyclic redundancy check (CRC), convolutional, turbo, block, and other coding, or no coding at all. The voice, packet data, and messages may be coded using different schemes, and different types of messages may be coded differently.  
         [0039]    The coded data is then provided to a modulator (MOD)  714  and further processed (e.g., covered, spread with short PN sequences, and scrambled with a long PN sequence assigned to the user terminal). The modulated data is then provided to a transmitter unit (TMTR)  716  and conditioned (e.g., converted to one or more analog signals, amplified, filtered, and quadrature modulated) to generate a reverse link signal. The reverse link signal is routed through a duplexer (D)  718  and transmitted via an antenna  720  to BSC/PCF  704 .  
         [0040]    At BSC/PCF  704 , the reverse link signal is received by an antenna  750 , routed through a duplexer  752 , and provided to a receiver unit (RCVR)  754 . Alternatively, the antenna may be part of the wireless operator network, and the connection between the antenna and the BS/BSC may be routed through the Internet. BSC/PCF  704  may receive media information and alert messages from remote access device  706 . Receiver unit  754  conditions (e.g., filters, amplifies, down converts, and digitizes) the received signal and provides samples. A demodulator (DEMOD)  756  receives and processes (e.g., despreads, decovers, and pilot demodulates) the samples to provide recovered symbols. Demodulator  756  may implement a rake receiver that processes multiple instances of the received signal and generates combined symbols. A receive (RX) data processor  758  then decodes the symbols to recover the data and messages transmitted on the reverse link. The recovered voice/packet data is provided to a data sink  760  and the recovered messages may be provided to a controller  770 . Controller  770  may include instructions for receiving and sending information, receiving and sending Ack order messages, receiving and sending responses to Ack order messages, sending information, sending paging messages and receiving responses thereto, and interpreting and sending service option numbers. The processing by demodulator  756  and RX data processor  758  are complementary to that performed at remote access device  706 . Demodulator  756  and RX data processor  758  may further be operated to process multiple transmissions received via multiple channels, e.g., a reverse fundamental channel (R-FCH) and a reverse supplemental channel (R-SCH). Also, transmissions may be simultaneously from multiple mobile stations, each of which may be transmitting on a reverse fundamental channel, a reverse supplemental channel, or both.  
         [0041]    On the forward link, at BSC/PCF  704 , voice and/or packet data (e.g., from a data source  762 ) and messages (e.g., from controller  770 ) are processed (e.g., formatted and encoded) by a transmit (TX) data processor  764 , further processed (e.g., covered and spread) by a modulator (MOD)  766 , and conditioned (e.g., converted to analog signals, amplified, filtered, and quadrature modulated) by a transmitter unit (TMTR)  768  to generate a forward link signal. The forward link signal is routed through duplexer  752  and transmitted via antenna  750  to remote access device  706 . Forward link signals include paging signals.  
         [0042]    At communication device  706 , the forward link signal is received by antenna  720 , routed through duplexer  718 , and provided to a receiver unit  722 . Receiver unit  722  conditions (e.g., down converts, filters, amplifies, quadrature modulates, and digitizes) the received signal and provides samples. The samples are processed (e.g., despreaded, decovered, and pilot demodulated) by a demodulator  724  to provide symbols, and the symbols are further processed (e.g., decoded and checked) by a receive data processor  726  to recover the data and messages transmitted on the forward link. The recovered data is provided to a data sink  728 , and the recovered messages may be provided to controller  730 . Controller  730  may include instructions for receiving and sending information, receiving and sending Ack order messages, receiving and sending responses to Ack order messages, sending information, receiving paging messages and sending responses thereto, transitioning to and from idle state, and receiving and interpreting service option numbers. Therefore, the disclosed embodiments provide for a significant reduction in the exchanging information with target CDs that are dormant and have no active traffic channel.  
         [0043]    The disclosed methods and apparatuses provide for an efficient mechanism for exchanging information with dormant target CDs, using service option numbers that signify that information is being communicated in short data burst (SDB) form.  
         [0044]    Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and protocols. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.  
         [0045]    Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.  
         [0046]    The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but, in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.  
         [0047]    The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor, such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.  
         [0048]    The description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments, e.g., in an instant messaging service or any general wireless data communication applications, without departing from the spirit or scope of the invention. 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. The word “exemplary” is used exclusively herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.