Patent Publication Number: US-8543174-B2

Title: Methods and apparatus for reducing power consumption for mobile devices using broadcast-to-unicast message conversion

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of and claims priority to U.S. non-provisional patent application having application Ser. No. 13/078,692 and filing date of 1 Apr. 2011, now U.S. Pat. No. 8,280,457, which is a continuation of and claims priority to U.S. non-provisional patent application having application Ser. No. 11/413,880 and filing date of 28 Apr. 2006, now U.S. Pat. No. 7,953,457, each application being hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Field of the Technology 
     The present application relates generally to mobile communication devices which communicate with wireless communication networks such as wireless local area networks (WLANs), and more particularly to configuring a mobile device to refrain from receiving and processing broadcast messages so that it may operate in a low power mode while configuring the network to convert broadcast messages needed by the mobile device into unicast messages for the mobile device. 
     2. Description of the Related Art 
     In wireless communication networks, such as wireless local area networks (WLANs) which operate in accordance with 802.11-based standards, broadcast messages of different types are sent to all mobile communication devices within a WLAN. Commonly, mobile communication devices will switch out of their low power mode to decode the broadcast messages and determine if they are of any interest to the device. Many of these mobile devices are battery-powered devices which need to efficiently utilize their batteries for extending operating time. 
     Broadcast messages transmitted from the WLAN may be one of several different message types, while the mobile communication device may accept broadcast messages of only some of the specific message types. Each time the mobile communication device switches out of low power mode to monitor an incoming message, it consumes an increased amount of battery power due to enabling additional receiver circuitry. This is wasteful when the broadcast messages are not of the type needed by the mobile communication device. 
     Accordingly, what are needed are methods and apparatus for the mobile communication device to switch out of low power mode only when the broadcast messages are needed for that mobile communication device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of present invention will now be described by way of example with reference to attached figures, wherein: 
         FIG. 1  is a block diagram which illustrates a communication system which includes one or more wireless communication networks (e.g. wireless local area networks (WLANs) and mobile terminals which operate in such networks; 
         FIG. 2  is a more detailed schematic diagram of a mobile terminal in the WLAN  FIG. 1 , namely, a mobile station of the preferred embodiment; 
         FIG. 3  is an illustration showing relevant layers of common standard protocols for messages used in the WLAN; 
         FIG. 4  is an illustration of frame formatting for messages in used in the WLAN; 
         FIG. 5  is a flowchart of one illustrative method for a mobile device to conserve power and receive broadcast messages as unicast messages from the network in a Broadcast-to-Unicast (BtU) message procedure; 
         FIG. 6  is a flowchart of a configuration technique for authentication and registration with a BtU server in the network by a mobile terminal; and 
         FIG. 7  is a flowchart of a BtU message procedure for the BtU server for sending broadcast information in unicast messages. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     According to the present application, a battery-powered mobile device in a WLAN is configured to normally refrain from receiving broadcast messages so that it may remain in a low power mode of operation. A network server is configured to convert broadcast messages into unicast messages for receipt by the mobile device, only if the message or protocol type of the broadcast message is one in which the mobile device needs to process. As the mobile device is still configured to receive unicast messages, it will receive and decode such unicast messages and process the broadcast information within them accordingly. Advantageously, battery power is conserved at the mobile device. 
       FIG. 1  is a block diagram which illustrates a communication system  100  which includes a public network  102  (e.g. the Internet) and a private network  104 . In the present embodiment, private network  104  is or includes a wireless local area network (WLAN). Terminals may connect to their associated networks through access points (APs)  106 ,  108 ,  122 ,  132 , and  142  as shown. Preferably, at least some of the APs are wireless APs of the WLAN and at least some of the terminals are mobile/wireless communication devices which interface and connect through these wireless APs; such terminals and APs operate in accordance with well-known IEEE 802.11 standards. The terminals shown in public network  102  include terminals  110  and  112  which interface with AP  106 , and terminals  114 ,  116 , and  118  which interface with AP  108 . The terminals shown in private network  104  include terminals  134 ,  136 ,  138  which interface with AP  132 , and terminals  144  and  146  which interface with AP  142 . Private network  104  is protected by a firewall  124  which may include a virtual private network (VPN) concentrator  126  for establishing and maintaining secure VPN connections far terminals outside of private network  104 . 
     Private network  104  which includes the WLAN provides various data and communication services to its terminals. For example, private network  104  may provide for voice telephony communication services for its terminals with use of Voice over IP (VoIP) communications. For these types of services, private network  104  may utilize servers such as a VoIP server or an e-mail server, as examples. Communication system  100  may also include at least one session server which is a session initiation protocol (SIP) server. In the present embodiment, communication system  100  has a session server  121  in public network  102  and a session server  130  in private network  104 . Note that some communication applications utilized by terminals, such VoIP applications, require the use of SIP. SIP is well documented in standard documents such as Request For Comments (RFC) 3261. 
     Private network  104  also has a broadcast-to-unicast (BtU) server  128  which assists in converting broadcast messages to unicast messages for mobile terminals according to the present application, which is described in more detail below in relation to  FIGS. 3-7 . BtU server  128  utilizes a BtU server database  150  which contains terminal or client information that is pertinent for converting and sending broadcast messages as unicast messages. BtU server  128  and database  150  are described in more detail below in relation to  FIGS. 6-7 . 
     Referring now to  FIG. 2 , electrical components of a typical mobile station (MS)  202  (one type of mobile terminal of  FIG. 1 ) which operates with wireless APs of communication system  100  of  FIG. 1  will be described. Mobile station  202  is preferably a two-way communication device having at least voice and advanced data communication capabilities, including the capability to communicate with other computer systems. Also preferably, mobile station  202  is a wireless communication device which operates in accordance with an IEEE 802.11 standards. Depending on the functionality provided by mobile station  202 , it may be referred to as a data messaging device, a two-way pager, a cellular telephone with data messaging capabilities, a wireless Internet appliance, or a data communication device (with or without telephony capabilities). 
     As shown in  FIG. 2 , mobile station  202  is adapted to wirelessly communicate with AP  190  which may be a wireless AP of the present application. For communication with AP  190 , mobile station  202  utilizes communication subsystem  211 . Depending on the type of device, mobile station  202  may also be adapted to wirelessly communicate with other systems such as cellular telecommunication systems. With such configuration, mobile station  202  may be referred to as a “dual mode” mobile station. Although mobile station  202  may have separate and independent subsystems for these purposes, at least some portions or components of these otherwise different subsystems may be shared where possible. 
     Communication subsystem  211  includes a receiver  212 , a transmitter  214 , and associated components, such as one or more (preferably embedded or internal) antenna elements  216  and  218 , local oscillators (LOs)  213 , and a processing module such as a baseband (BB) and media access control (MAC) processing module  220 . As will be apparent to those skilled in the field of communications, the particular design of communication subsystem  211  depends on the communication network in which mobile station  202  is intended to operate. In the present application, communication subsystem  211  (including its associated processor/processing components) are operative in accordance with IEEE 802.11 standards. 
     Mobile station  202  may send and receive communication signals through the network after required network procedures have been completed. Signals received by antenna  216  through the network are input to receiver  212 , which may perform such common receiver functions as signal amplification, frequency down conversion, filtering, channel selection, and like, and in example shown in  FIG. 2 , analog-to-digital (A/D) conversion. A/D conversion of a received signal allows more complex communication functions such as demodulation and decoding to be performed in BB/MAC processing module  220 . In a similar manner, signals to be transmitted are processed, including modulation and encoding, for example, by BB/MAC processing module  220 . These processed signals are input to transmitter  214  for digital-to-analog (D/A) conversion, frequency up conversion, filtering, amplification and transmission through the network via antenna  218 . BB/MAC processing module  220  not only processes communication signals, but may also provide for receiver and transmitter control. 
     Note that receiver  212  and transmitter  214  may share one or more antennas through an antenna switch (not shown in  FIG. 2 ), instead of having two separate dedicated antennas  216  and  218  as shown. 
     Since mobile station  202  is a portable battery-powered device, it also includes a battery interface  254  for receiving one or more rechargeable batteries  256 . Such a battery  256  provides electrical power to most if not all electrical circuitry in mobile station  202 , and battery interface  254  provides for a mechanical and electrical connection for it. Battery interface  254  is coupled to a regulator (not shown in  FIG. 2 ) that provides power V+ to all of the circuitry. 
     Mobile station  202  includes a microprocessor  238  (one type of processor or controller) that controls overall operation of mobile station  202 . This control includes the broadcast-to-unicast (Btu) techniques of the present application. Communication functions, including at least data and voice communications, are performed through communication subsystem  211 . Microprocessor  238  also interacts with additional device subsystems such as a display  222 , a flash memory  224 , a random access memory (RAM)  226 , auxiliary input/output (I/O) subsystems  228 , a serial port  230 , a keyboard  232 , a speaker  234 , a microphone  236 , a short-range communications subsystem  240 , and any other device subsystems generally designated at  242 . Some of the subsystems shown in  FIG. 2  perform communication-related functions, whereas other subsystems may provide “resident” or on-device functions. Notably, some subsystems, such as keyboard  232  and display  222 , for example, may be used for both communication-related functions, such as entering a text message for transmission over a communication network, and device-resident functions such as a calculator or task list. Operating system software used by microprocessor  238  is preferably stored in a persistent store such as flash memory  224 , which may alternatively be a read-only memory (ROM) or similar storage element (not shown). Those skilled in the art will appreciate that the operating system, specific device applications, or parts thereof, may be temporarily loaded into a volatile store such as RAM  220 . 
     Microprocessor  238 , in addition to its operating system functions, preferably enables execution of software applications on mobile station  202 . A predetermined set of applications that control basic device operations, including at least data and voice communication applications, will normally be installed on mobile station  202  during its manufacture. A preferred application that may be loaded onto mobile station  202  may be a personal information manager (PIM) application having the ability to organize and manage data items relating to user such as, but not limited to, e-mail, calendar events, voice mails, appointments, and task items. Naturally, one or more memory stores are available on mobile station and a removable memory module, such as a Subscriber Identity Module (SIM) (not shown), to facilitate storage of PIM data items and other information. 
     The PIM application preferably has the ability to send and receive data items via the wireless network. In a preferred embodiment, PIM data items are seamlessly integrated, synchronized, and updated via the wireless network, with the wireless device user&#39;s corresponding data items stored and/or associated with a host computer system thereby creating a mirrored host computer on mobile station  202  with respect to such items. This is especially advantageous where the host computer system is the wireless device user&#39;s office computer system. Additional applications may also be loaded onto mobile station  202  through network, an auxiliary I/O subsystem  228 , serial port  230 , short-range communications subsystem  240 , or any other suitable subsystem  242 , and installed by a user in RAM  226  or preferably a non-volatile store (not shown) for execution by microprocessor  238 . Such flexibility in application installation increases the functionality of mobile station  202  and may provide enhanced on-device functions, communication-related functions, or both. For example, secure communication applications may enable electronic commerce functions and other such financial transactions to be performed using mobile station  202 . 
     In a data communication mode, a received signal such as a text message, an e-mail message, or web page download will be processed by communication subsystem  211  and input to microprocessor  238 . Microprocessor  238  will preferably further process the signal for output to display  222  or alternatively to auxiliary I/O device  228 . A user of mobile station  202  may also compose data items, such as e-mail messages, for example, using keyboard  232  in conjunction with display  222  and possibly auxiliary I/O device  228 . Keyboard  232  is preferably a complete alphanumeric keyboard and/or telephone-type keypad. These composed items may be transmitted over a communication network through communication subsystem  211 . 
     For voice communications, the overall operation of mobile station  202  is substantially similar, except that the received signals would be output to speaker  234  and signals for transmission would be generated by microphone  236 . Alternative voice or audio I/O subsystems, such as a voice message recording subsystem, may also be implemented on mobile station  202 . Although voice or audio signal output is preferably accomplished primarily through speaker  234 , display  222  may also be used to provide an indication of the identity of a calling party, duration of a voice call, or other voice call related information, as some examples. 
     Serial port  230  in  FIG. 2  is normally implemented in a personal digital assistant (PDA)-type communication device for which synchronization with a user&#39;s desktop computer is a desirable, albeit optional, component. Serial port  230  enables a user to set preferences through an external device or software application and extends the capabilities of mobile station  202  by providing for information or software downloads to mobile station  202  other than through a wireless communication network. The alternate download path may, for example, be used to load an encryption key onto mobile station  202  through a direct and thus reliable and trusted connection to thereby provide secure device communication. Short-range communications subsystem  240  of  FIG. 2  is an additional optional component that provides for communication between mobile station  202  and different systems or devices, which need not necessarily be similar devices. For example, subsystem  240  may include an infrared device and associated circuits and components, or a Bluetooth™ communication module to provide for communication with similarly enabled systems and devices. Bluetooth™ is a registered trademark of Bluetooth SIG, Inc. 
     Although a specific mobile station  202  has just been described, any suitable mobile communication device or terminal may be part of the inventive methods and apparatus which will be described in fuller detail below. Note that many components of mobile station  202  shown and described may not be included (e.g. a full QWERTY keypad may be optional). 
     According to the present application, a mobile terminal (e.g. terminal  134  of  FIG. 1 ) is configured to normally refrain from receiving broadcast messages so that it may remain in a low power mode. A network server (e.g. BtU server  128  of  FIG. 1 ) is configured to convert certain broadcast messages into unicast messages for receipt by the mobile terminal only if the message or protocol type (e.g. sub network access protocol (SNAP) type) of the broadcast message is one which the mobile terminal is configured to process. Since it is coupled within the same network, the network server receives all of the same broadcast messages intended for receipt by mobile terminals. Broadcast messages have a destination MAC address of “FF:FF:FF:FF:FF:FF” and therefore are discernible by the network server and mobile terminals. As the mobile terminal is still configured to receive unicast messages, it will therefore receive and decode these special unicast messages and process the broadcast information within them accordingly. 
     In general, a mobile terminal needs to receive a broadcast message of a particular type only if it is programmed to process such message to achieve a particular application result (i.e. it has an application program for processing the broadcast message). Examples of different types of broadcast messages in this particular environment (e.g. environment using SNAP types) include Internet protocol (IP) types, address resolution protocol (ARP) types, extensible authentication protocol over LAN (EAPOL) types, Intel types, and network basic input/output system (NetBIOS) types (Microsoft), to name but a few. Such messages are communicated in layer two (i.e. the data link layer) or layer three (i.e. the network layer) associated with the open system interconnection (OSI) seven-layer model. 
     To help further illustrate such messaging,  FIG. 3  is an illustration showing pertinent layers  300  of common Institute of Electrical and Electronics Engineers (IEEE) communication standard protocols for the communication of messages. It will be apparent to those skilled in art that such protocols will be adapted to a particular network or networks in which mobile terminals are intended to operate. A transmission control function  302  shown in layer one (L1) is in the physical layer (PL) of the OSI model. A framing function  304  shown in layer two (L2) is in the data link (DL) layer. The IEEE 802.3 standard for Ethernet communication defines an additional data link layer protocol called Logical Link Control (LLC) protocol  308  which is in L2. The IEEE 802.11 standard for Ethernet uses the same LLC protocol  308  that was defined for IEEE 802.3 standard for Ethernet. The LLC protocol  308  operates on top of a media access control (MAC) protocol  306  defined in original Ethernet standard. When LLC protocol  308  is used, the MAC layer service data unit (SDU), also called the message payload data, further encapsulated, which adds two additional headers. 
       FIG. 4  is an illustration of a frame format structure  400  of an IEEE 802.3 physical channel. The IEEE 802.3 standard defines Ethernet protocol, which is also used to define 802.11 WLAN standards. Each block in frame format structure  400  represents a series of data bits that show a specific structure of an 802.3 communicated signal. Each series of data bits consumes a specified time during each transmission as defined in 802.3 standards documents. Therefore, the bit pattern blocks shown in each row of frame format structure  400  are time-dependent-place-holders containing data bits. A logical link control (LLC) protocol is based on high level data link control (HDLC) protocol and uses an extended 2-byte address. A first address byte indicates a destination service access point (DSAP) address  402  and a second address byte indicates a source service access point (SSAP) address  404 . The address bytes identify the network protocol entities which use link layer service. A control field is also provided which may support a number of HDLC modes, such as Type 1 (connection-less link protocol), Type 2 (connection-oriented protocol) and Type 3 (connection-less acknowledged protocol). 
     A sub network access protocol (SNAP) header  406  is used when the LLC protocol carries IP packets and contains information which would otherwise have been carried in the 2-byte MAC frame type field. Note that since the maximum size of an Ethernet frame is fixed, the maximum size of SDU is reduced to 1492 bytes (the maximum transmission unit (MTU) in IP) when LLC/SNAP encapsulation is used. The SNAP is a standard for the transmission of IP datagrams over IEEE 802 type networks. IP datagrams may be sent on IEEE 802 networks encapsulated within the LLC and SNAP data link layers (L2) and the physical network layers (L3). The SNAP is included in an extension of the LLC header and is used for encapsulating IP datagrams and ARP requests, and replies on IEEE 802 networks. The SNAP header follows the LLC header and contains an organization code indicating that the following 16 bits specify an EtherType code. The mapping of 32-bit Internet addresses to 16 or 48 bit IEEE 802 addresses is done using a dynamic discovery procedure of the ARP, IEEE 802 networks may have 16-bit or 48-bit physical addresses. The SNAP allows use of either size of address within a given IEEE 802 network. The SNAP header contains 40 bits of which 24 bits are an IEEE-assigned Organizationally Unique Identifier (OUI), and 16 bits are a Protocol Identifier (PID). The Internet Assigned Numbers Authority (IANA) OUI, 00-00-5E, may be used in SNAP headers with the appropriate PID to identify the protocols. 
     Mobile communication devices, such as mobile terminal  134  of  FIG. 1 , may be configured to process broadcast messages associated with a limited number of message or protocol types (e.g. different SNAP types). There are many different possible types of broadcast messages which are broadcasted in the network, and many different mobile terminals that will are configured to process any one or all of the several different message types. For example, a mobile terminal may be required to receive and process broadcast messages having SNAP types associated with ARP and IP, but not those broadcast messages associated with any other SNAP types such as NetBIOS and Intel. A mobile device configured to receive broadcast messages having SNAP types associated with NetBIOS, for example, may be viewed a nuisance to other mobile terminals in the network that have no need to process such messages. 
       FIG. 5  is a flowchart of one illustrative method for a mobile device to receive broadcast messages as unicast messages from a wireless communication network (e.g. an 802.11-based wireless local area network (WLAN)). The method of  FIG. 5  may be performed by the mobile device, and/or be embodied in a computer program product which includes a computer readable medium (e.g. memory) and computer instructions stored in the computer readable medium which are executable by one or more processors. The flowchart of  FIG. 5  will be discussed in combination with the components of the communication system of  FIG. 1 . With use of the method of  FIG. 5 , a mobile device will operate in a low power mode more often while not becoming active during every message broadcasted by the BtU server. 
     In  FIG. 5 , the wireless network broadcast-to-unicast (BtU) procedure is initiated when the mobile communication device or mobile terminal (e.g. terminal  134  of  FIG. 1 ) is located within a coverage area of an access point (e.g. AP  132  of  FIG. 1 ) of a communication network (e.g. private network  104  of  FIG. 1 ) having an 802.11-based WLAN. When the mobile terminal is operating, it searches for APs within its coverage range. Beginning at a start block  502  of  FIG. 5 , the mobile terminal will successfully access the WLAN through an AP (e.g. AP  132  of  FIG. 1 ) (step  504  of  FIG. 5 ). Once the mobile terminal has gained access to the WLAN, and assuming the mobile terminal is equipped with the proper programming needed to decode BtU messages, the mobile terminal will be authenticated by the BtU server (e.g. BtU server  128  of  FIG. 1 ) (step  505  of  FIG. 5 ). In general, authentication involves verifying that the mobile terminal is permitted to utilize the BtU service provided by the EAU server, to receive and decode BtU messages. Any one of several authentication techniques may be utilized in step  506 , such as password authentication. 
     If the mobile terminal is permitted to utilize the BtU server, where the authentication steps are executed correctly and successfully, the mobile terminal will then attempt to register with the BtU server (step  508  of  FIG. 5 ). Registration with the BtU server at least involves providing an indication or request to the BtU server to operate to receive and process BtU messages. Registration may also involve or require the mobile terminal to send its required message or protocol types for broadcast messages that it needs to process. Note that a BtU server database (e.g.  FIG. 1 ) is utilized for storing identifications of mobile terminals of the WLAN in association with their respective message or protocol types for broadcast messages that are required to be received and processed by them. Table 1, which will be described in detail later below, reveals an example database list associated with several mobile terminals (“clients”), where each mobile terminal is associated with one or more particular SNAP types. 
     If either authentication or registration with the BtU server fails, then the mobile terminal will operate in a conventional mode which does not involve the BtU server (step  510  of  FIG. 5 ). On the other hand, if the mobile terminal successfully authenticates and registers with the BtU server, the mobile terminal will begin operation in a programmed receiver mode that allows only unicast messages to be received. Here, the mobile terminal refrains from operating to receive and process standard broadcast messages and instead operates in a low power mode. Such receiver mode may be an endless loop operation, as shown in  FIG. 5 . Thus, the mobile terminal places its receiver in a low power mode of operation (step  512  of  FIG. 5 ). 
     In some applications, this type of low power mode is referred to as a receiver “sleep” mode. Low power mode is an operating condition where selected circuit blocks are disabled or powered down until needed as one method of conserving battery power of the mobile terminal. During low power mode, some circuit blocks will be active in order to detect radio signals and other signaling, if necessary. Although many mobile terminals utilize some type of low power mode for operation, mobile terminals of the present application extend their low power mode during those times that broadcast messages would otherwise be received and processed. 
     The receiver within the mobile terminal will remain in low power mode until a unicast message is detected on the receiving channel (step  514  of  FIG. 5 ). Once a unicast message is detected, the receiver within terminal will be powered on to identify if the unicast message is intended for the mobile terminal (step  516  of  FIG. 5 ). Identifying whether the message is intended for the mobile terminal involves attaching a MAC and IP address to each unicast message and configuring the mobile terminal to compare the MAC and IP address of the received message with its own MAC and IP address. The mobile terminal will accept the message if the addresses are a match, but otherwise reject the message when the addresses are not a match. If the unicast message is not intended for the mobile terminal, programming within memory or a microcontroller device within the mobile terminal will instruct the receiver within the mobile terminal to resume its low power mode at step  512 . If the unicast message is intended for the mobile terminal, and is successfully identified by the mobile terminal receiver and its associated circuitry and programming code, the mobile terminal will operate to receive and decode the unicast message (step  518  of  FIG. 5 ). 
     Once the unicast message has been received, the next step for the receiver operation is to determine if the unicast message is a broadcast-to-unicast (BtU) message or if it is simply a standard unicast message that is intended for the mobile terminal (step  520  of  FIG. 5 ). If the unicast message is a standard unicast message, the mobile terminal will process the message information in a conventional manner (step  522  of  FIG. 5 ). If the message is a BtU message, as may be indicated by the presence of a unique message format in the form of a header or some other indicator, then the mobile terminal proceeds to process the BtU message in steps  524 ,  526 , and  528 . 
     The mobile terminal decapsulates the unicast message to reveal the underlying broadcast payload information (step  524  of  FIG. 5 ), injects the broadcast payload information at the appropriate protocol layer (step  526  of  FIG. 5 ), and subsequently processes the broadcast information as if it were received as a broadcast message (step  528  of  FIG. 5 ). Regardless of whether or not the unicast message received is a BtU message or a conventional unicast message, after the message information is processed, the next step is to switch back to low power mode and wait for any other unicast message (step  512  of  FIG. 5 ). The flowchart in  FIG. 5  shows a continuous loop operation to repeat the steps in  FIG. 5 . Although it is not shown in this flowchart, the loop operation could be terminated by a manual switch or programming choice within the mobile device or by powering down all circuits within the mobile device. 
     Preferably, the mobile terminal makes specific use of a Delivery Traffic Information Map (DTIM) period defined in 802.11 networks for achieving low power operation throughout steps  512 ,  514 , and  516  of  FIG. 5 . The DTIM period specifies how often the mobile terminal will exit its sleep cycle to receive broadcast messages. Some conventional networks specify that the DTIM period should be configured to a very low value (e.g. 100 ms), which undesirably increases mobile terminal power consumption. In the present application, however, after successfully registering with the BtU server in step  508  of  FIG. 5 , the mobile terminal effectively sets the DTIM period to “infinity” and therefore does not wake up to receive any broadcast messages. Other settings may be possible to achieve low power consumption. 
       FIG. 6  is a flowchart for describing an illustrative configuration procedure for establishing the BtU service for a mobile terminal. This procedure occurs prior to operation described in relation to  FIGS. 5 and 7 . The method of  FIG. 6  may be performed by the BtU server of the WLAN, and/or be embodied in a computer program product which includes a computer readable medium (e.g. memory) and computer instructions stored in the storage medium which are executable by one or more processors. 
     Beginning at a start block  602  of  FIG. 6 , the mobile device gains access to the WLAN through an access point (AP) of the WLAN (step  604  of  FIG. 6 ). Association, authentication, and other related processes for establishing WLAN communications are well-documented procedures within 802.11 standards, and will be apparent to those skilled in art of WLAN techniques and practices. Upon gaining access to the WLAN, the mobile terminal is configured to identify a preference to operate in the low power mode using the BtU service and stores an address of the BtU server of the WLAN. At some point in time, the BtU server receives an authentication request from the mobile terminal to gain permission to use its BtU service (step  606  of  FIG. 6 ). If the mobile terminal provides the BtU server with the proper authentication information (e.g., appropriate password, key code, etc.), then the mobile terminal is positively authenticated by the BtU server so that it may utilize the BtU server (step  608  of  FIG. 6 ). 
     Next in  FIG. 6 , the BtU server receives a registration request from the authenticated mobile terminal in order to activate the BtU service (step  610  of  FIG. 6 ). Registration steps may include the action of the mobile terminal providing identification information that will be used by the BtU server to deliver BtU messages. Identification information may include the mobile terminal MAC address, IP address, the required message types (e.g., IP, ARP, EAPOL, etc.), as well as any other pertinent identifying information pertaining to the mobile terminal. If the registration request is received and accepted, then the mobile device is positively registered to receive BtU messages from the WLAN (step  612  of  FIG. 6 ). Upon approving authentication and registration to the requesting mobile terminal, the configuration procedure will conclude and normal WLAN operations will commence (step  614  of  FIG. 6 ). 
     Table 1 below is an example of information that may be stored by the BtU server in the BtU server database upon registration (e.g. in relation to step  612  of  FIG. 6 ). As mentioned above, each client name (column 1 of Table 1) and identification information of the mobile terminal (such as MAC address and/or IP address or other) is stored in association with each message or protocol type that is needed for the mobile terminal. This is done for each mobile terminal operating in the WLAN. Message types include ARP, IP, EAPOL, Intel, NetBIOS, to name but a few. Again, the example in Table 1 shows one possible way to store client information in a BtU server database. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Example of a BtU Server Client Database List. 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                 Message or 
                   
               
               
                 Client 
                   
                   
                 Protocol 
                 BtU 
               
               
                 # 
                 MAC Address 
                 IP Address 
                 Type 
                 Conversion? 
               
               
                   
               
               
                 A 
                 111222333001 
                 111.111.111.001 
                 ARP, IP, 
                 Yes 
               
               
                   
                   
                   
                 EAPOL 
               
               
                 B 
                 111222333005 
                 111.111.111.005 
                 NetBIOS 
                 No 
               
               
                 C 
                 111222333006 
                 111.111.111.006 
                 ARP, IP 
                 Yes 
               
               
                 D 
                 111222333010 
                 111.111.111.00A 
                 EAPOL 
                 Yes 
               
               
                 E 
                 111222333015 
                 111.111.111.00F 
                 ARP, IP 
                 Yes 
               
               
                 F 
                 111222333017 
                 111.111.111.011 
                 ARP, IP 
                 Yes 
               
               
                 G 
                 111222333024 
                 111.111.111.018 
                 NetBIOS 
                 No 
               
               
                 H 
                 111222333026 
                 111.111.111.01A 
                 Intel 
                 No 
               
               
                 I 
                 111222333032 
                 111.111.111.020 
                 ARP, IP, 
                 Yes 
               
               
                   
                   
                   
                 EAPOL 
               
               
                   
               
            
           
         
       
     
     The BtU server database may also include information about the registration status or availability of the mobile terminal (“BtU Conversion?”). In the example of Table 1, if a mobile terminal has registered with the BtU server, then it is configured to receive BtU messages and the database will contain a “Yes” entry in the “BtU conversion?” column. After the mobile terminal successfully registers with the BtU server, the mobile terminal will operate in the low power mode and refrain from receiving broadcast messages, and receive BtU messages and convert them accordingly. 
     As a further technique to save processing time and to avoid re-entering BtU server information each time a mobile terminal becomes active in the ULAN the BtU server database may retain the desired message or protocol types of the mobile terminal even after the mobile terminal has left the WLAN. When the mobile terminal leaves the WLAN, the BtU server will mark the registration status column with a “No” entry in the “BtU conversion” column and will refrain from converting broadcast messages to unicast messages for the mobile terminal during its unavailability. 
       FIG. 7  is a flowchart of one illustrative method for a wireless communication network (e.g. an 802.11-based wireless local area network (WLAN)) to send broadcast messages as unicast messages for a mobile device. The method of  FIG. 7  may be performed by the WLAN and/or BtU server of the WLAN, and/or be embodied in a computer program product which includes a computer readable medium (e.g. memory) and computer instructions stored in the storage medium which are executable by one or more processors. 
     Beginning at a start block  702  of  FIG. 7 , a BtU server of the WLAN monitors traffic for broadcast messages (step  704  of  FIG. 7 ). The broadcast messages may be received at the BtU server through a wired or wireless network connection. Broadcast messages have a destination MAC address of “FF:FF:FF:FF:FF:FF” and therefore are discernible by the BtU server and mobile terminals. Once a broadcast message is received (step  706  of  FIG. 7 ), the BtU server will identify the message or protocol type of the broadcast message (step  708  of  FIG. 7 ). Next, the BtU server queries its BtU server database to determine which registered clients need this type of broadcast message information (step  710  of  FIG. 7 ). A query to the BtU server database may be based on the identified message or protocol type of the current broadcast message, with a query response that returns one or more identifications of mobile terminals that are required to receive and process such broadcast information. 
     After identifying the message or protocol type of the broadcast message, and identifying which registered clients need such type of broadcast message, the BtU server will convert the broadcast message into a unicast message(s) directed to the identified mobile terminal(s) (step  712  of  FIG. 7 ). Conversion of broadcast messages into unicast message may be performed by removing the broadcast message payload and inserting it into a unicast message format, which is performed for each identified active client registered with the BtU server client database. Finally, the BtU server will send the broadcast message payload, encapsulated within a unicast message, to all active clients registered on the WLAN BtU server (step  714  of  FIG. 7 ). The flowchart in  FIG. 7  shows a continuous loop operation once the BtU message processing begins. Although it is not shown in this flowchart, the continuous loop operation could be terminated by a manual switch or a received message, or by powering down all circuits within the mobile device. 
     Thus, methods and apparatus for use in reducing power consumption in battery-powered mobile communication devices in wireless local area networks (WLANs) have been described. In one illustrative example, a mobile device in a WLAN is configured to normally refrain from receiving broadcast messages so that it may remain in a low power mode of operation. A network server is configured to convert broadcast messages into unicast messages for receipt by the mobile device only if the message or protocol type of the broadcast message is one in which the mobile device needs to process. As the mobile device is still configured to receive unicast messages, it will receive and decode such a unicast message and process the broadcast information within it accordingly. Advantageously, battery power is conserved at the mobile device. 
     The above-described embodiments of the present application are intended to be examples only. Those of skill in the art may effect alterations, modifications and variations to the particular embodiments without departing from the scope of the application. The invention described herein in the recited claims intends to cover and embrace all suitable changes in technology.