Patent Publication Number: US-2015066710-A1

Title: Method and system for associating display modules with nodes

Description:
FIELD OF THE INVENTION 
     The present invention relates to a system for wirelessly distributing goods-related visual information to a plurality of electronic shelf labels (ESLs) and, in particular, to a system for distributing goods-related visual information to ESLs with improved wireless reliability. 
     BACKGROUND OF THE INVENTION 
     There have been a number of proposals in the prior art to automate the display of goods-related information in retail establishments, warehouses, supply chains, etc., by using electronic shelf labels (ESLs). To the extent that such systems replace printed tags that have been conventionally used by such establishments these systems are appealing in that they reduce or eliminate the need to reprint and manually replace the printed tags each time the goods-related information of an item is changed. This is beneficial in the sense that it reduces or eliminates the labor required to manually replace the printed tags and the difficulty in manually replacing a large number of printed tags at once. 
     Although automating the display of goods-related information through the use of wireless ESLs has solved many problems associated with printed tags, the implementation of these systems have brought about new problems for retail establishments. 
     Wireless ESLs in the prior art rely on infrared, acoustic, or radio-frequency wireless signals to receive information from one or more nodes to update one or more visual displays. The ESLs are pre-assigned to a particular node in a network by, for example, a store manager of the retail establishment. The assignment of the ESL to a particular node is typically based on criteria that are unrelated to signal quality and network traffic. An ESL assigned to a node in this way suffers from deficiencies such as, for example, the inability to dynamically reconfigure itself in situations where the wireless link between the ESL and the node is too weak. Because of this deficiency, there is a lag in receiving signals from the node, which consequently delays the updating of information displayed by the ESL. In extreme cases, deterioration of signal propagation might cause an ESL to become unreachable by the node to which it is assigned. This causes price-related discrepancies at check-out and retail establishments may potentially face great financial losses due to such discrepancies. Therefore, there exists a need to improve the reliability of wireless links between ESLs and nodes in the prior art. 
     SUMMARY OF THE INVENTION 
     Hereinafter, the term “display module” will be used, instead of the more colloquial term “electronic shelf label,” to reflect the fact that such a device might not be necessarily affixed to an edge of a shelf. 
     In many applications, electronic display modules might be affixed to or placed near a variety of objects, other than shelves, where a programmable display of information might be desired. Although the description of embodiments of the present invention will make reference to retail establishments, it will be clear to those skilled in the art, after reading this disclosure, how to make and use electronic display systems in accordance with the present invention for use in establishments other than retail establishments. For example, and without limitation, such systems might be used in warehouses to assist with inventory maintenance, or in other situations where display of information associated with goods or other items might be desired. 
     Electronic display systems in accordance with some embodiments of the present invention comprise a plurality of wireless nodes and a plurality of wireless display modules. These nodes are pre-programmed with a “white-list” that identifies one or more display modules that the nodes are to associate with. However, because the quality of the wireless link between a node and a display module may degrade over time, embodiments of the present invention provides a mechanism to dynamically and automatically update the “white-list” so as to associate the display module with a node that will provide a stronger and more reliable wireless link. The present invention and its advantages will be described in more detail below. 
     Some embodiments of the present invention comprise: receiving, by a display module, a first beacon on a first wireless channel, wherein the first beacon is autonomously and continually broadcasted by a first node in a network without receiving any beacon requests from the display module; receiving, by the display module, a second beacon on a second wireless channel, wherein the second beacon is autonomously and continually broadcasted by a second node in the network without receiving any beacon requests from the display module; and transmitting, by the display module, a first request for association, wherein the first request is transmitted to either the first node or the second node based on an ordering between a first signal strength of the first beacon and a second signal strength of the second beacon. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a schematic diagram of the salient components of a system in accordance with an illustrative embodiment of the present invention. 
         FIG. 2   a  through  FIG. 2   f  depicts a flowchart of the salient tasks associated with the operation of the illustrative embodiment of the present invention. 
         FIG. 3  depicts a flowchart of the salient tasks associated with the operation of task  202  and task  208  in accordance with the illustrative embodiment of the present invention. 
         FIG. 4  depicts a flowchart of the salient tasks associated with the operation of task  210 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts a schematic diagram of the salient components of system  100  in accordance with an illustrative embodiment of the present invention. System  100  comprises: server  102 ; database  104 ; nodes  112  and  120 ; wireless channels  132  and  134 ; and display module  130 . 
     Server  102  comprises memory  106 , processor  108 , and network interface  110 . Processor  108  can be a general or special purpose processor, while memory  106  can be random access memory (RAM), read-only memory (ROM), dynamic random-access memory (DRAM), or any combination thereof. 
     Memory  106  is configured to store one or more computer-readable instructions which, when executed by processor  108 , enable server  102  to transmit queries to and receive responses from database  104 . In accordance with the illustrative embodiment, the signaling between server  102  and database  104  pertain to, for example, and without limitation, goods-related information and data about the mapping of display modules to nodes. 
     Furthermore, executing the computer-readable instructions stored in memory  106  by processor  108  enables server  102  to communicate one or more commands to nodes  112  and  120 . In accordance with the illustrative embodiment, the commands instruct the nodes to, for example, and without limitation, associate with or disassociate from a particular node in the network. The tasks performed by server  102  will be discussed in more detail below, with respect to  FIG. 2   a  through  FIG. 2   f.    
     Although the illustrative embodiments comprises one server, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which system  100  comprises any number of servers (e.g., two servers, three servers, and so on). Further, each of these servers may comprise, for example, substantially the same or different hardware and software elements than server  102 . 
     Database  104  comprises hardware and software that enables it to store, for example, and without limitation, goods-related information and data about the mapping of display modules to nodes. The hardware and software of database  104  also enables it to receive queries from and transmit responses to server  102 . Although the illustrative embodiments comprises one database, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which system  100  comprises any number of databases (e.g., two databases, three databases, and so on). Further, each of these databases may comprise, for example, substantially the same or different hardware and software elements than database  104 . 
     Nodes  112  and  120  respectively comprise memories  114  and  122 , processors  116  and  124 , and network interfaces  118  and  126 . Each of the processors can be a general or special purpose processor, while each of the memories can be random access memory (RAM), read-only memory (ROM), dynamic random-access memory (DRAM), or any combination thereof. 
     The memories of nodes  112  and  120  are configured to store one or more computer-readable instructions which, when executed by their respective processors, enable them to carry-out the tasks of the illustrative embodiment, as well as alternative embodiments of the present invention. The tasks performed by nodes  112  and  120  will be described in more detail below, with reference to  FIG. 2   a  through  FIG. 2   f.    
     Network interfaces  118  and  126  comprise the necessary circuitry for enabling nodes  112  and  120  to transmit and receive signals to and from server  102 , either wirelessly or through a dedicated wireline connection. In accordance with the illustrative embodiment, network interfaces  118  and  126  also comprise a transmitter and a receiver for enabling nodes  112  and  120  to wirelessly transmit and receive signals to and from one or more display modules in the network. 
     Although the illustrative embodiments comprises two nodes, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which system  100  comprises any number of nodes (e.g., ten nodes, a hundred nodes, a thousand nodes, and so on). 
     Further, it will also be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which each node in the network comprises more or less the same hardware elements and computer-readable instructions as nodes  112  and  120  for carrying-out the tasks of  FIG. 2   a  through  FIG. 2   f.    
     Display module  130  comprise memory  132 , processor  134 , network interface  136 , and display  138 . Processor  134  can be a general or special purpose processor, while memory  132  can be random access memory (RAM), read-only memory (ROM), dynamic random-access memory (DRAM), or any combination thereof. 
     Memory  132  of display module  130  is configured to store one or more computer-readable instructions which, when executed by processor  134 , enables display module  130  to carry-out the tasks of the illustrative embodiment, as well as alternative embodiments of the present invention. The tasks performed by display module  130  will be described in more detail below, with reference to  FIG. 2   a  through  FIG. 2   f.    
     Network interface  136  of display module  130  comprises the necessary circuitry for enabling the display module to transmit and receive signals to and from nodes  112  and  120 . In accordance with the illustrative embodiment, network interface  136  comprises a transmitter and a receiver for enabling display module  130  to wirelessly transmit and receive signals to and from one or more nodes in the network. 
     Display  138  employed by module  130  can be, for example, and without limitation, a liquid-crystal display (LCD), a light-emitting diode (LED), a bistable cholesteric display (BCD), an electronic ink display, etc. However, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which display  138  can be any type or combination of displays. 
     Although the illustrative embodiments comprises one display module, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which system  100  comprises any number of display modules (e.g., ten display modules, a hundred display modules, a thousand display modules, and so on). 
     Further, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which each display module in the network comprises more or less the same hardware elements and computer-readable instructions as display module  130  for carrying-out the tasks of  FIG. 2   a  through  FIG. 2   f.    
       FIG. 2   a  depicts some of the salient tasks associated with the illustrative embodiment of the present invention. In accordance with the illustrative embodiment, the flowchart begins with display module  130  being powered-on or exiting a “sleep” mode. Once display module  130  enters an active state, the illustrative embodiment moves to task  202 . 
     At task  202 , display module  130  monitors each wireless channel in the network for beacons. The beacons are autonomously and continually broadcasted by nodes in the network on their respective wireless channels without receiving any beacon requests from display module  130 ; or any other display modules in system  100  for that matter. 
     As an example, node  112  (i.e., a “first” node) autonomously and continually broadcasts a beacon (i.e., a “first” beacon) onto wireless channel  132  (i.e., a “first” wireless channel) without receiving any beacon requests from display module  130 . Likewise, node  120  (i.e., a “second” node) autonomously and continually broadcasts a beacon (i.e., a “second” beacon) onto wireless channel  134  (i.e., a “second” wireless channel) without receiving any beacon requests from display module  130 . 
     Although the illustrative embodiment only depicts two wireless channels, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments in which system  100  comprises a number of wireless channels (e.g., three wireless channels, ten wireless channels, and so on) and a number of nodes that autonomously and continually broadcast beacons on their respective wireless channels. 
     In accordance with the illustrative embodiment, display module  130  may or may not receive any beacons while monitoring the wireless channels at task  202 . In situations where display module  130  receive a beacon while monitoring a particular wireless channel, display module  130  is configured to determine the signal strength of the received beacon. Once determined, display module  130  stores the signal strength of the received beacon in memory  132 , along with an identifier of the node that broadcasted the beacon. Task  202  will be described in more detail below, with reference to  FIG. 3 . 
     At task  204 , display module  130  determines if there are any signal strengths of beacons stored in memory  132  as a result of monitoring the wireless channels in the network. If display module  130  determines that there are no signal strengths of beacons stored in memory  132 , the illustrative embodiment moves to task  206 . On the other hand, if display module  130  determines that there are one or more signal strengths of beacons stored in memory  132 , the illustrative embodiment moves to task  208 . 
     At task  206 , display module  130  enters a sleep mode for a predefined time in response to determining that there are no signal strengths of beacons stored in memory  132 . The predefined time can be, for example, and without limitation, thirty-minutes, one-hour, five-hours, and so on. In accordance with the illustrative embodiment, display module  130  is pre-configured by a system administrator with the predefined time for entering and exiting sleep mode. Further, display module  130  in accordance with the illustrative embodiment is configured to automatically and dynamically update the predefined time for entering and exiting sleep mode based on certain characteristics of the network or changes that are made to system  100 . In any event, display module  130  will eventually exit sleep mode after a predefined time so as to repeat task  202  of monitoring each wireless channel in the network for beacons. 
     At task  208 , display module  130  sorts the signal strengths and identifiers stored in memory  132  in response to determining that there are indeed signal strengths of beacons stored in memory  132 . In accordance with the illustrative embodiment, memory  132  comprises the following signal strengths and identifiers after performing task  202 :
         a “first” signal strength of a beacon that is broadcasted by node  112  on wireless channel  132 , wherein the first signal strength is stored in memory  132  along with an identifier of node  112 ; and   a “second” signal strength of a beacon that is broadcasted by node  120  on wireless channel  134 , wherein the second signal strength is stored in memory  132  along with an identifier of node  120 . These signal strengths and identifiers stored in memory  132  are sorted by display module  130  in an order of decreasing signal strengths, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which the signal strengths and identifiers are sorted in any order.       

     For example, and without limitation, the identifier of node  112  would precede the identifier of node  120  in the sorted list if display module  130  determines that the first signal strength is stronger than the second signal strength. In this example, the first signal strength of the beacon broadcasted by node  112  would likewise precede the second signal strength of the beacon broadcasted by node  120  in the sorted list. 
     Although the example above describes memory  132  as storing only two signal strengths, it will be clear to those skilled in the art, after reading this disclosure, how to make and us alternative embodiments of the present invention in which memory  132  stores a number of signal strengths (e.g., five signal strengths, ten signal strengths, and so on) and a number of identifiers of nodes (e.g., five identifiers, ten identifiers, and so on) as a result of performing task  202 . 
     For the purpose of enabling the reader of this disclosure to more easily understand the present invention, the sorting performed by the illustrative embodiment causes the identifier of node  112  to precede the identifier of node  120  in the sorted list. Likewise, the sorting display module  130  causes the first signal strength to precede the second signal strength in the sorted list. Having sorted the identifiers and signal strengths in this way, display module  130  transmit a request for association to a node in the network based on an order of decreasing signal strength using the sorted list. 
     Since the first signal strength and the identifier of node  112  appear at the top of the sorted list, and because display module  130  is configured to transmit requests for association based on an order of decreasing signal strengths using the sorted list, display module  130  will initially transmit the request (i.e., a “first” request) to node  112  (i.e., a “first” node) via wireless channel  132  (i.e., a “first” wireless channel). 
     In addition to transmitting the request to node  112 , display module  130  also transmits its unique identifier to node  112  via wireless channel  132 . The unique identifier in accordance with the illustrative embodiment is the Media Access Control (MAC) address of display module  130 . However, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which other types of unique identifiers can be used, so long as the identifier can uniquely distinguish one display module from other display modules in the network. Task  208  will be described in more detail below, with reference to  FIG. 3 . 
     At task  210 , node  112  receives the request and the MAC address from display module  130  via wireless channel  132 . Once received, node  112  determines if the MAC address of display module  130  matches one of a plurality of identifiers in a predefined list (i.e., a “first” predefined list) stored in memory  114 . The predefined list is, for example, a “white-list” that comprises one or more identifiers of display modules in which node  112  is configured to associate with. Furthermore, the predefined list is assigned to node  112  by server  102 , wherein a copy of the predefined list is either stored in memory  106  of server  102  or database  104 . 
     Having described the illustrative embodiment of the present invention thus far, it should be noted at this point of the disclosure that two scenarios can occur after node  112  receives the request and the MAC address from display module  130 . 
     In the first scenario, node  112  transmits an affirmative response to display module  130  via wireless channel  132  if it determines that the MAC address matches one of the identifiers in the predefined list. This scenario corresponds to tasks  214 ,  216 ,  218 ,  220 , and  222  of  FIG. 2   b , which will be described in more detail below. 
     In the second scenario, node  112  ignores the request for association transmitted by display module  130  if it determines that the MAC address does not match one of the identifiers in the predefined list. This scenario corresponds to the tasks of  FIG. 2   c  through  FIG. 2   f , which will be described in more detail below. 
     First Scenario—Node Determines that there is a Match 
       FIG. 2   b . At task  212 , display module  130  monitors wireless channel  132  and determines whether an affirmative response (i.e., a “first” affirmative response) to the request has been received from node  112  within a predefined time (i.e., a “first” predefined time). 
     At task  214 , display module  130  receives the affirmative response from node  112  via wireless channel  132  within the predefined time as a result of the determination performed at task  210 —i.e., node  112  determines that the MAC address matches one of the identifiers in the predefined list. By receiving the affirmative response, this enables display module  130  to establish an association with node  112 . From this point on, display module  130  and node  112  will perform the necessary signaling to establish an association with each other and, thereafter, communicate via wireless channel  132 . 
     At task  216 , display module  130  monitors wireless channel  132  for one or more commands transmitted by node  112 . In accordance with the illustrative embodiment, the one or more commands can be, for example, and without limitation, commands to update goods-related visual information on display  138 , wherein the goods-related visual information can be the price, quantity, image, text, etc. of an item. In accordance with alternative embodiments, the commands are to update goods-related visual information on display  138  so as to reflect changes that might have occurred in database  104 . 
     At task  218 , display module  130  receives the one or more commands from node  112  via wireless channel  132 . 
     At task  220 , display module  130  updates the goods-related visual information on display  138  in response to receiving the one or more commands. That is, processor  134  of display module  130  executes the computer-readable instructions of the commands and updates the goods-related visual information on display  138 . 
     At task  222 , display module  130  either continues to wait for commands from node  112  or enters a “sleep” mode for a predefined time until repeating task  202 . 
     In general, the scenario described above may occur when a system administrator has correctly determined from the onset that the most reliable wireless link for display module  130  to receive commands is to associate it with node  112 . 
     Stated differently, the system administrator has correctly included the MAC address of display module  130  in the predefined list (which is assigned to node  112  by server  102 ) with the expectation that such pairing would result in the most reliable wireless link for display module  130  to receive commands. The system administrator&#39;s expectation might have been a result of intuitively determining that a more reliable wireless link can be achieved if the display module is paired with a node that is geographically located in the same department of a retail establishment. 
     In sum, the scenario described above pertains to the situation in which the predefined list of node  112  has been correctly configured by a system administrator to include the MAC address of display module  130 . 
     Second Scenario—Node Determines that there is No Match 
     In this scenario, the predefined list of node  120  is configured by a system administrator from the onset to include the MAC address of display module  130  (for the reasons discussed above). Since the pairing of display module  130  to node  120  is believed to produce the most reliable wireless link, the system administrator does not include the MAC address of display module  130  in the predefined list of node  112 . 
     However, because of various changes that might have occurred in system  100  or the network, the wireless link between node  120  and display module  130  has become unreliable. This second scenario provides a mechanism for re-associating display module  130  to node  112  to achieve a more reliable wireless link. 
       FIG. 2   c . At task  212 , display module  130  monitors wireless channel  132  and determines whether an affirmative response (i.e., a “first” affirmative response) to the request has been received from node  112  within a predefined time (i.e., a “first” predefined time). 
     At task  224 , display module  130  retrieves the sorted list of signal strengths from memory  132  in response to determining that it has not received the affirmative response from node  112  via wireless channel  132  within the predefined time. The reason why display module  130  did not receive the affirmative response is because node  112  ignored the request for association as a result of determining that the MAC address of display module  130  is not in the predefined list, per task  210  above. 
     Using the sorted list, display module  130  determines the next strongest signal strength (relative to the first signal strength) in the sorted list. According to the illustrative embodiment, the second signal strength (which corresponds to the beacon broadcasted by node  120 ) has the next strongest signal strength in the sorted list. As such, display module  130  transmits a request for association (i.e., a “second” request) along with its MAC address to node  120  (i.e., a “second” node) via wireless channel  134  (i.e., a “second” wireless channel). 
     At task  226 , node  120  receives the request and the MAC address from display module  130  via wireless channel  134 . Once received, node  120  determines if the MAC address of display module  130  matches one of a plurality of identifiers in a predefined list (i.e., a “second” predefined list) stored in memory  122 . The predefined list is, for example, a “white-list” that comprises one or more identifiers of display modules in which node  120  is configured to associate with. 
     At task  228 , display module  130  monitors wireless channel  134  and determines whether an affirmative response (i.e., a “second” affirmative response) to the request has been received from node  120  within a predefined time (i.e., a “second” predefined time). 
     If display module  130  determines that an affirmative response from node  120  has not been received within the predefined time, the illustrative embodiment repeats task  224 . In other words, display module repeats the step of iteratively transmitting requests for association to other nodes in the network in an order of decreasing signal strengths using the sorted list. When none of these nodes respond to the request with an affirmative response, then display module  130  enters a “sleep” mode for a predefined time before repeating task  202 . 
     On the other hand, if display module  130  determines that the affirmative response from node  120  has been received via wireless channel  134  within the predefined time, the illustrative embodiment moves to task  230 . In accordance with the illustrative embodiment, display module  130  receives the affirmative response from node  120  via wireless channel  134  within the predefined time. By receiving the affirmative response, this enables display module  130  to establish an association with node  120 . From this point on, display module  130  and node  120  will perform the necessary signaling to establish an association with each other and, thereafter, communicate via wireless channel  134 . 
     At task  230 , node  120  transmits a command to display module  130  via wireless channel  134 , wherein the command instructs display module  130  to upload the sorted list stored in memory  132  to node  120  via wireless channel  134 . 
     At task  232 , display module  130  transmits the sorted list to node  120  via wireless channel  134  after receiving the command. 
     At task  234 , node  120  receives the sorted list and determines if its identifier is at the top of the sorted list. If the identifier of node  120  is at the top of the sorted list, then the illustrative embodiment moves to task  236 , which will be described in more detail below, with reference to  FIG. 2   d . On the other hand, if the identifier of node  120  is not at the top of the sorted list, then the illustrative embodiment moves to task  244 , which will be described in more detail below, with reference to  FIG. 2   e.    
     Identifier of Node is Determined to be at the to of the Sorted List 
       FIG. 2   d . At task  234 , node  120  receives the sorted list and determines if its identifier is at the top of the sorted list. In this exemplary scenario, node  120  determines that its identifier is indeed at the top of the sorted list and, therefore, continues to associate with display module  130 . 
     At task  236 , display module  130  monitors wireless channel  134  for one or more commands transmitted by node  120 . In accordance with the illustrative embodiment, the one or more commands can be, for example, and without limitation, commands to update goods-related visual information on display  138 , wherein the goods-related visual information can be the price, quantity, image, text, etc. of an item. In accordance with alternative embodiments, the commands are to update the goods-related visual information on display  138  so as to reflect changes that might have occurred in database  104 . 
     At task  238 , display module  130  receives the one or more commands from node  120  via wireless channel  134 . 
     At task  240 , display module  130  updates the goods-related visual information on display  138  in response to receiving the one or more commands. That is, processor  134  of display module  130  executes the computer-readable instructions of the commands and updates the goods-related visual information on display  138 . 
     At task  242 , display module  130  either continues to wait for commands from node  120  or enters a “sleep” mode for a predefined time until repeating task  202 . 
     Identifier of Node is not at the to of the Sorted List 
       FIG. 2   e . At task  234 , node  120  receives the sorted list and determines if its identifier is at the top of the sorted list. In this exemplary scenario, node  120  determines that its identifier is not at the top of the sorted list. 
     At task  244 , node  120  transmits the sorted list to server  102  in response to determining that its identifier is not at the top of the sorted list. The MAC address of display module  130  is likewise transmitted from node  120  to server  102 . 
     At task  246 , server  102  processes the sorted list to determine why display module  130  did not initially associate with the node at the top of the list—namely, node  112  according to the illustrative embodiment. 
     The advantage of this determination is that the association between display module  130  and node  120  can be dynamically reconfigured such that display module  130  associates with node  112 . By dynamically reconfiguring system  100  in this way, it enables display module  130  to associate with a node in the network that would presumably provide a more reliable wireless link. Since the signal strength of the beacon broadcasted by node  112  is determined to be the strongest at task  208 , associating display module  130  with node  112  would be advantageous as a more reliable wireless link can be established for transmitting commands to, and receiving signals from, display module  130 . 
     In order for server  102  to determine why display module did not initially associate with node  112 , server  102  analyzes the service set identifier (SSID) of node  112  to see whether it belongs to the network of system  100 . If the SSID of node  112  does not belong to system  100 , then server  102  continues allowing display module  130  to associate with node  120 . This situation may occur, for example, when node  112  belongs to a network that is in a different building or retail establishment. 
     On the other hand, when server  102  determines that the SSID of node  112  belongs to system  100 , server  102  retrieves a copy of the predefined list assigned to node  112 . Since server  102  is the one that pre-configured each node in the network with a predefined list of display modules to associate with, server  102  can simply retrieve the predefined list from its own memory or from database  104 . 
     In any case, once server  102  retrieves the predefined list, it determines if the MAC address of display module  130  is in the predefined list assigned to node  112 . When server  102  determines that the MAC address of display module  130  is not in the predefined list, server  102  transmits a command to node  112  and another command to node  120 . 
     At task  248 , node  112  receives the command (i.e., a “first” command) from server  102 . Responsive to the command, node  112  includes the MAC address of display module  130  in its predefined list that is stored in memory  114 . 
     At task  250 , node  120  receives the other command (i.e., a “second” command) from server  102 . Responsive to the command, node  120  removes the MAC address of display module  130  from its predefined list that is stored in memory  122 . 
     At task  252 , node  120  disassociates from display module  130  as a result of removing the MAC address of display module  130  from its predefined list. 
     At task  254 , display module  130  retrieves the sorted list from its memory after disassociating from node  120  and thereafter transmits a request for association (i.e., a “third” request) based on an order of decreasing signal strengths using the sorted list. Since the signal strength and identifier of node  112  precedes the signal strength and identifier of node  120  in the sorted list as determined at task  208 , display module  130  transmits the request and its MAC address to node  112  via wireless channel  132 . 
     At task  256  of  FIG. 2   f , node  112  receives the request and the MAC address from display module  130  via wireless channel  132 . 
     At tasks  258  and  260 , node  112  determines if the MAC address of display module  130  matches one of a plurality of identifiers in the predefined list stored in memory  114 . 
     At task  262 , display module  112  ignores the request received from display module  130  if the MAC address of display module  130  does not match one of the plurality of identifiers in the predefined list stored in memory  114 . However, this would not be the case since, as described above, the predefined list stored in node  112  has be updated to include the MAC address of display module  130  at task  248 . 
     At task  264 , display module  112  transmits an affirmative response (i.e., a “third” affirmative response) to display module  130  via wireless channel  132  in response to determining that the MAC address of display module  130  does indeed match one of the plurality of identifiers in the predefined list stored in memory  114 . 
     At task  266 , display module  130  receives the affirmative response from node  112  via wireless channel  132  within the predefined time. By receiving the affirmative response, this enables display module  130  to establish an association with node  112 . From this point on, display module  130  and node  112  will perform the necessary signaling to establish an association with each other and, thereafter, communicate via wireless channel  132 . 
     Once the association has been established, display module  130  monitors wireless channel  132  for one or more commands transmitted by node  112 . In accordance with the illustrative embodiment, display module  130  receives one or more commands from node  112  via wireless channel  132  and updates the goods-related visual information on display  138 . The one or more commands can be, for example, and without limitation, commands to update one or more goods-related visual information on display  138  to reflect changes that might have occurred in database  104 . Further, the goods-related visual information can be, for example, and without limitation, the price, quantity, image, text, etc. of an item. After updating display  138 , display module either continues to wait for commands from node  112  or enters a “sleep” mode for a predefined time until repeating task  202   
       FIG. 3  depicts a flowchart of the salient tasks associated with the operation of task  202  and task  208  in accordance with the illustrative embodiment of the present invention. 
     At task  302 , display module  130  turns-on its receiver and tunes it to a particular wireless channel in the network, without ever turning-on its transmitter. More specifically, the transmitter of display module  130  remains in an off state from tasks  202 ,  204 , and  206 , up until task  208 . In accordance with the illustrative embodiment, display module  130  initially tunes its receiver to wireless channel  132  (i.e., a “first” wireless channel). 
     At task  304 , display module  130  monitors&#39; wireless channel  132  for beacons. As discussed at the beginning of this disclosure, the beacons are autonomously and continually broadcasted by node  112  (i.e., a “first” node) via wireless channel  132 . 
     At task  306 , display module  130  determines if it has received a beacon while monitoring wireless channel  132  within a predefined time. If display module  130  received a beacon (i.e., a “first” beacon) via wireless channel  132  within the predefined time, the illustrative embodiment moves to task  308 ; otherwise, the illustrative embodiment moves to task  310 . 
     At task  308 , display module  130  stores a signal strength (i.e., a “first” signal strength) and an identifier of node  112  (i.e., a “first” identifier”) in memory  132 . 
     At task  310 , display module  130  determines if it has monitored all the wireless channels in the network. If display module  130  did not monitor all the wireless channels in the network, the illustrative embodiment moves back to task  312 ; otherwise, the illustrative embodiment moves to task  204  of  FIG. 2   a.    
     At task  312 , display module re-tunes its receiver to another wireless channel in the network. In accordance with the illustrative embodiment, display module re-tunes its receiver to wireless channel  134  (i.e., a “second” wireless channel) and repeats tasks  304 ,  306 ,  308 ,  310 , and  312 . 
     For completeness, at task  304 , display module  130  monitors wireless channel  134  for beacons. As discussed at the beginning of this disclosure, the beacons are autonomously and continually broadcasted by node  120  (i.e., a “second” node) via wireless channel  134 . 
     At task  306 , display module  130  determines if it has received a beacon while monitoring wireless channel  134  within a predefined time. If display module  130  received a beacon (i.e., a “second” beacon) via wireless channel  134  within the predefined time, the illustrative embodiment moves to task  308 ; otherwise, the illustrative embodiment moves to task  310 . 
     At task  308 , display module  130  stores a signal strength (i.e., a “second” signal strength) and an identifier of node  120  (i.e., a “second” identifier”) in memory  132 . 
     At task  310 , display module  130  determines if it has monitored all the wireless channels in the network. If display module  130  did not monitor all the wireless channels in the network, the illustrative embodiment moves back to task  312 ; otherwise, the illustrative embodiment moves to task  204  of  FIG. 2   a.    
     It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which display module  130  will re-tune its receiver according to task  312  and repeat the tasks of  304 ,  306 ,  308 ,  310 , and  312  until all wireless channels in the network have been monitored. Once all of the wireless channels in the network have been monitored for beacons, the illustrative embodiment moves to task  204 . Depending on the outcome of the determination performed at task  204 , display module  130  will either perform the salient operations of task  206  or task  208 . 
     At task  314 , display module  130  sorts the signal strengths and identifiers stored in memory  132  in an order of decreasing signal strengths. In accordance with the illustrative embodiment, the first and second signal strengths are sorted by display module  130  such that the identifier of node  112  precedes the identifier of node  120  in the sorted list. 
     Since the first signal strength and the identifier of node  112  appear at the top of the sorted list, and because display module  130  is configured to transmit requests for association based on an order of decreasing signal strengths using the sorted list, display module  130  initially transmits a request for association (i.e., a “first” request) to node  112  via wireless channel  132 . Once the request has been transmitted, the illustrative embodiment moves to task  210  of  FIG. 2   a.    
       FIG. 4  depicts a flowchart of the salient tasks associated with the operation of task  210 . 
     At task  402 , node  112  receives the request and the MAC address from display module  130  via wireless channel  132 . 
     At tasks  404  and  406 , node  112  determines if the MAC address of display module  130  matches one of a plurality of identifiers in a predefined list (i.e., a “first” predefined list) stored in memory  114 . The predefined list is, for example, a “white-list” that comprises one or more identifiers of display modules in which node  112  is configured to associate with. 
     At task  408 , node  112  ignores the request for association from display module  130  if the determination reveals that the MAC address does not match one of the identifiers in the predefined list. 
     At task  410 , node  112  transmits an affirmative response (i.e., a “first” affirmative response) to display module  130  in response to determining that the MAC address matches one of the identifiers in the predefined list. Once the affirmative response has been transmitted, the illustrative embodiment moves to task  212  of  FIG. 2   a.    
     It is to be understood that the disclosure teaches just one example of the illustrative embodiment and that many variations of the invention can easily be devised by those skilled in the art after reading this disclosure and that the scope of the present invention is to be determined by the following claims.