Method of optimizing electronic price label systems

A method of optimizing electronic price label (EPL) systems which employs a three-dimensional graph of retry levels in a transaction establishment. The method includes the steps of determining locations of EPLs within the transaction establishment, determining locations of transmit and receive antennas that are used by a computer to communicate with the EPLs, determining retry levels for the EPLs, mapping the retry levels to locations within the transaction establishment, producing a three-dimensional graph of the retry levels within the area of the transaction establishment, and determining, from the graph, subareas within the area having retry levels above a predetermined maximum retry level. Once the subareas having higher retry levels are determined, the locations of the transmit and receive antennas may be changed and/or interfering structures may be moved until the retry levels of the subareas are below the predetermined maximum retry level.

BACKGROUND OF THE INVENTION 
The present invention relates to electronic price label (EPL) systems used 
in transaction establishments, and more specifically to a method of 
optimizing electronic price label systems. 
EPL systems typically include a plurality of EPLs for each merchandise item 
in a store. EPLs typically display the price of corresponding merchandise 
items on store shelves and are typically attached to a rail along the 
leading edge of the shelves. A store may contain thousands of EPLs to 
display the prices of the merchandise items. The EPLs are coupled to a 
central server from where information about the EPLs is typically 
maintained in an EPL data file. Price information displayed by the EPLs is 
obtained from the PLU file. 
Installation of wireless EPLs requires proper placement of transmit and 
receive antennas to maximize the probability that an addressed EPL will 
receive a message from the server. Proper placement can result in a lower 
EPL system cost since fewer antennas are required consistent with the need 
to maximize price change speeds. 
Therefore, it would be desirable to provide a method of optimizing 
electronic price label systems. 
SUMMARY OF THE INVENTION 
In accordance with the teachings of the present invention, a method of 
optimizing electronic price label systems is provided. 
The method includes the steps of determining locations of EPLs with the 
transaction establishment, determining locations of transmit and receive 
antennas that are used by a computer to communicate with the EPLs, 
determining retry levels for the EPLs, mapping the retry levels to 
locations within the transaction establishment, producing a 
three-dimensional graph of the retry levels within the area of the 
transaction establishment, and determining, from the graph, subareas 
within the area having retry levels above a predetermined maximum retry 
level. Once the subareas having higher retry levels are determined, the 
locations of the transmit and receive antennas may be changed and/or 
interfering structures may be moved until the retry levels of the subareas 
are below the predetermined maximum retry level. 
It is accordingly an object of the present invention to provide a method of 
optimizing electronic price label systems. 
It is another object of the present invention to provide a method of 
optimizing electronic price label systems which can locate areas of poor 
reception within a transaction establishment. 
It is another object of the present invention to provide a method of 
optimizing electronic price label systems which can produce a three 
dimensional plot representing reception capability throughout a 
transaction establishment. 
It is another object of the present invention to provide a method of 
optimizing electronic price label systems which maximizes reception 
throughout a transaction establishment while minimizing the cost of an 
electronic price label system. 
It is another object of the present invention to provide a method of 
optimizing electronic price label systems which balances system cost 
against price change frequencies.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1, EPL system 10 includes computer 12, storage medium 
14, communication base stations (CBSs) 15a-d, electronic price labels 
(EPLs) 18a-d, display 22, and printer 23. 
Computer 12 executes EPL control software 20, EPL runtime analyzer 26, and 
EPL optimization software 32. EPL control software 20 records, schedules, 
and transmits all messages to EPLs 18a-d through CBSs 15a-d, and receives 
and analyzes status messages from EPLs 18a-d through CBSs 15a-d. Such 
messages include queries to individual EPLs requesting an acknowledgment 
signal from the individual EPLs. EPL control software 20 also maintains 
and uses EPL data file 28, which contains item information, identification 
information, item price verifier information, and status information for 
each of EPLs 18a-d. 
EPL control software 20 primarily includes data scheduler 34 and CBS 
manager 36. Data scheduler 34 schedules EPL price change messages to be 
sent to EPLs 18a-d through CBSs 15a-d. 
CBS manager 36 schedules the actual transmission of price change messages 
to EPLs 18a-d and the reception of status messages from EPLs 18a-d for 
predetermined time slots. In order to schedule transmissions and 
receptions, CBS manager 36 reads the status flag from EPL data file 28. 
Although, CBS manager 36 may also receive status information from an 
executing application. Status flags are organized in accordance with the 
information in Table I: 
TABLE I 
______________________________________ 
Status Flag Interpretation 
______________________________________ 
0 EPL is inactive. 
1 1 send, then 1 receive 
2 2 sends, then 2 receives 
4 4 sends, then 4 receives 
8 8 sends, then 8 receives 
16 16 sends, then 16 receives 
255 EPL faulty 
______________________________________ 
Thus, for example, a status flag of "4" tells CBS manager 36 to request all 
of CBSs 15a-d to transmit a price change to one of EPLs 18a-d in four 
different time frames. Each frame contains twelve time slots managed by 
CBS manager 36 and CBSs 15a-d. CBS manager 36 listens for a response from 
the one EPL in the four time frames. If the response comes into CBS 
manager 36 in any of the first, second, or third time frames, the 
remaining time frames are reported. CBS manager 36 writes the number of 
time frames required to receive a response from the one EPL in EPL log 
file 30. 
CBS manager 36 monitors signal strength and noise information during each 
response time frame. It records signal-to-noise (S/N) ratio information 
for each EPL in EPL log file 30 if the first attempt fails. 
CBS manager 36 also performs transmission retries if the first transmission 
attempt fails. CBS manager 36 temporarily promotes the EPL to a higher 
retry status and attempts to communicate with the EPL again. CBS manager 
36 logs a status message following the communication attempt. This status 
message includes the status (Good or Bad) and S/N ratios for further 
analysis at a later time by runtime analyzer 26. 
Runtime analyzer 26 reads the status flag and S/N data in EPL log file 30 
and makes determinations that may result in the status flag of a 
particular one of EPLs 18a-d being changed. Runtime analyzer 26 determines 
peak and average S/N ratios for each of EPLs 18a-d, and establishes S/N 
thresholds and ranges for each status flag. Runtime analyzer 26 reads log 
file 30 for the measured S/N ratio to determine whether it is too low, and 
if it is, changes the status flag. To do this, runtime analyzer 26 
compares the recorded S/N ratio with a predetermined S/N range associated 
with the recorded status flag. If the recorded ratio is not within the 
predetermined S/N range, runtime analyzer 26 determines the correct range 
and status flag and modifies EPL data file 28 accordingly. 
Runtime analyzer 26 is preferably run continuously to reset the system and 
re-initialize runtime analyzer 26, unless computer 12 is involved within 
processor-intensive tasks, such as batch processing. 
EPL optimization software 32 uses the message retry values for each EPL and 
location information stored within configuration file 27 to determine 
areas in the store that interfere with reception of messages by EPLs. EPL 
system configuration file 27 tells computer 12 how system 10 is 
configured, i.e., the addresses of EPL system components and there 
location within transaction establishment relative to other components 
within system 10, and the location of different types of goods in the 
system. EPL optimization software 32 reads retry level data from EPL data 
file 28 and creates EPL retry level data file 29 which EPL optimization 
software 32 can display or print on display 22 and printer 23. 
EPL optimization software 32 may be any data analysis program. The Excel 
spreadsheet program from Microsoft was used to generate the graphs in 
FIGS. 5 and 6. 
Storage medium 14 is preferably a fixed disk drive. Storage medium 14 
stores EPL system configuration file 27, EPL data file 28, EPL retry level 
data file 29, and EPL log file 30. 
CBSs 15a-d are connected together in series. Here, only four CBSs are 
shown. CBSs 15a-d each include one transmit antenna 37 and up to four 
receive antennas 38 for transmitting and receiving messages between CBSs 
15a-d and EPLs 18a-d. CBSs 15a-d each include CBS circuitry 39 which 
controls operation of each CBS. 
Turning now to FIG. 2, EPLs 18a-d each include battery 40, transmit and 
receive antenna 42, display 46, memory 47, and EPL circuitry 48. 
Battery 40 provides power to EPLs 18a-d. 
Transmit and receive antenna 42 receives price change and status messages 
from CBS 15a-d. 
Transmit and receive antenna 42 transmits responses to price change and 
status messages to CBS 15a-d. 
Display 46 displays price and possibly additional information. Display 46 
is preferably a liquid crystal display and includes glass 49. 
Memory 47 stores price verifier information. Preferably, the price verifier 
information is a checksum of the displayed price. 
EPL circuitry 48 controls the internal operation of EPLs 18a-d. 
Turning now to FIG. 3, a map of a transaction establishment illustrates the 
location of shelves 50 and EPLs 18a-d. 
The locations of EPLs 18a-5d are referenced to a two-dimensional coordinate 
system in which rows are identified by numerals and columns are identified 
by letters. 
In this example, receive antennas 38 are located at 3A, 7A, 3D, 7D, 3G, 7G, 
3H, 7H, 3J, 7J, 3K, 7K, 3M, and 7M. Transmit antennas 37 are located at 
5C, 5F, 5I, and 5L. 
Turning now to FIG. 4, the operation of EPL optimization software 32 is 
explained in more detail, beginning with START 60. 
In step 62, computer 12 reads the location information from configuration 
file 27. 
In step 64, computer 12 reads the retry level data from retry level data 
file 29. 
In step 66, computer 12 sorts the retry level data by location. 
In step 68, computer 12 computes a mean retry level for each location. 
Computer 12 may also compute a median retry level or some other type of 
simplified data measure. 
In step 70, computer 12 exports the mean retry levels to a graphing 
application, such as the Graph application from Microsoft that works 
within the Excel spreadsheet program. 
In step 72, computer 12 displays information in response to user queries. 
These queries may include requests for information, such as a request for 
the areas having mean retry levels above a predetermined retry level. 
EPL optimization software 32 displays the two-dimensional or 
three-dimensional plots of FIGS. 5 and 6. FIG. 5 is a plot of all of the 
average retry levels throughout the store. FIG. 6 is effectively a 
horizontal cross-section of FIG. 5 because it illustrates where a single 
predetermined retry level is found within the store. 
For this purpose, the data can be stored as a spreadsheet file, such as a 
Microsoft Excel spreadsheet file. The Microsoft Excel spreadsheet program 
may then be used to generate the two-dimensional or three-dimensional plot 
from the spreadsheet file. 
In step 74, computer 12 initiates printing of the mean retry level graphs 
of FIGS. 5 and 6 and/or graphs of user-requested information. 
A user can examine areas having high retry levels from and make adjustments 
in the location of the CBS transmit antennas 37 and CBS receive antennas 
38. Adjustments may include adding additional CBSs to cover high retry 
level areas and removing or relocating interfering structures. New retry 
levels may be calculated and plotted to determine whether the adjustments 
resulted in lower retry levels in the affected areas. The process 
continues iteratively until all areas of the store have retry levels below 
a predetermined maximum retry level. 
In step 76, the method ends. 
Although the present invention has been described with particular reference 
to certain preferred embodiments thereof, variations and modifications of 
the present invention can be effected within the spirit and scope of the 
following claims.