Trading System in the Wireless Data Transmission Transparent

As a traffic management using advanced technology leader, Colorado Spring City traffic intersection controller in many MDS used spread spectrum radio.
I. System Overview
     MDS radio data transmission has been in the trading system has been widely used (lottery, ATM, point of sale credit card terminals, etc.). For example, in the lottery system, MDS wireless system can achieve multiple remote terminals (up to several thousand) with the main central processing user requests a wireless connection between devices. The communication is wireless data transmission through multiple delivery channels, without relying on the public telephone system or other wired communication medium. The advantages of wireless communication: practical, saving the user the line rental, and the network operator can directly control the entire system.

A typical transaction data transmission network configuration

MDS wireless data transmission system is simple. 5W installed in the center of a wireless master. Through an EIA-232 data interface cable to connect to the user's home computer. In order to achieve maximum reliability, to provide redundant wireless master (1 +1) function. When the primary module failure (which is unlikely), hot-swappable spare modules can be realized in order to maintain data communications. Central master station usually omnidirectional antenna to transmit and receive signals for all directions.
     Installed a small remote transmitter power of 5W radio stations, their data through an EIA-232 Interface cable to connect to the user terminal. General use of directional antennas in the remote, it can achieve maximum transmission distance and effective anti-interference and prevent interference to other users.
     Lottery terminal users to use wireless devices without the need for complex operations. They will be simple as long as the information input terminal, and data through a wireless link is sent and processed. Assuming send a message is acceptable, then the host computer through the wireless master to return a confirmation message, and lottery tickets printed by the user terminal. This completes the transaction.
     Data rate of any trading system is the main factor. For thousands of potential situations the terminal, the transaction will be any significant delay could soon lead to unacceptable congestion. A wireless system to provide very fast data rates to prevent the communication rate slowed. This data rate is calculated in milliseconds. (For a detailed analysis, see the following "wireless system performance").
     Compared with dial-up telephone, as opposed to the call waiting time, providing real-time wireless communication advantage. When sending data, radio terminals will be activated causing the information is immediately sent to the wireless master.

Second, the point - multipoint (P-MP) wireless system details
     A typical microwave data transmission system includes a wireless master (full dual hot backup) and remote radio stations, working in a 12.5 or 25KHZ bandwidth channel (half-way features). For a channel full-duplex master two different frequencies.
     Wireless master of all the cellular radio remote at the same time (all the remote is assigned the same frequency) a polling command. Radio Remote EIA-232 interfaces through a poll command will be transferred to the terminal. Information is specified in the polling address of the terminal through the EIA-232 interface to make a response, communication radio sending master. Features with full two-way wireless master station can accept from a remote radio station in response to a radio station at the same time send a polling command.
     The main station and the wireless remote sites can communicate directly, and for most asynchronous protocols, data transmission is transparent. Usually the lottery system, each master station configuration 20 and 50 remote sites, depending on system performance ﹑ radio channel and the terminal reliability of the density. In order to meet the scale of the system, can increase the master.
     NM-100 wireless master and NR-100 is usually applied to the remote site transaction data system. These wireless radio frequency range from 230 to 960MHZ. (Other frequency ranges can consult the manufacturer.) Data for these products through the channel speed can be achieved in 12.5KHZ 9600bps, or 25KHZ the channel to 19,200 bps.

Third, the wireless system performance
    The following content is based on the assumption of performance analysis:
    ● Point - Multi-point (P-MP) wireless communication systems will use the NM-100 wireless master and NR-100 remote master, they rate in 4800 or 9600bps (system traffic) run.
    ● No polling process lottery transactions is 2 bytes 2 bytes of output and input.
    ● polling process with the transaction output to 30 bytes and 60 bytes of input.
    ● largest wireless system can be wireless by the main station and 800 composed of 16,000 remote sites.
    ● AP-MP from one wireless cellular wireless master station and 10 km radius of 50 remote sites within the composition.
    ● in each wireless master and its corresponding remote site between the existence of a reliable wireless link.

Fourth, the application summary 1: No user transaction system polling:
To 9600bps data rate, wireless systems in about 18 milliseconds to send a 2 byte polling command and accept the 2-byte response.
Master data processing time = 6 ms = 2.2 ms to send
Remote processing time = 8 ms
Data reception = 2.2 ms
Total 18.4 ms
Application Summary 2: users trading system polling:
To 9600bps data rate, wireless systems in about 108 milliseconds to send a 30 byte polling command and response received 60 bytes.
Master processing time = 31.5 ms
Data sent = 8 ms
Remote processing time = 62.5 ms
Data reception = 6 ms
Total 108 ms
    Note: For a given system of processing time and response time, there is no accurate information and therefore can not list the exact polling time. However, the above overview of wireless communications equipment specified with MDS can be easily achieved every 3-5 seconds to respond to poll and get all the terminals.
The expansion of the frequency reuse radio channel capacity
     Full range of wireless antennas and use the master remote positioning of the antenna using traditional methods, the same radio channel on the distance between two wireless master station should be 150 km. This is based on the topology of the layout in the line of sight and maximum transmission distance in the case.
     In practice, trees, buildings and grounds will be reduced to the maximum distance to 100-120 km. By analyzing the signal strength, antenna size, location, location and topology layout will re-use the frequency range down to 60 or 70 kilometers. In the southern United States, a major power facilities designed 900MHZ system, making the frequency in some regions near to re-apply to 40-50 km. This is through the use of horizontal and vertical polarization antenna, antenna height restrictions in the whole cell in the guarantee and the same signal level can be achieved. In the particular case to determine the minimum distance requirements, MDS can provide further assistance.
The lottery system has been installed a partial list

GTECH project by the GTECH wireless systems installation and maintenance.