Zebra ML-1499-LAK1-01R Datasheet download pdf (Page 36)

AP-5131 Access Point Product Reference Guide

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to another. The bridge forwards packets addressed to unknown systems to the Default Interface

(Ethernet).

The AP-5131 internal stack interface handles all messages directed to the AP-5131. Each AP-5131

stores information on destinations and their interfaces to facilitate forwarding. When a user sends

an ARP (Address Resolution Protocol) request packet, the AP-5131 forwards it over all enabled

interfaces except over the interface the ARP request packet was received.

On receiving the ARP response packet, the AP-5131 database keeps a record of the destination

address along with the receiving interface. With this information, the AP-5131 forwards any directed

packet to the correct destination. Transmitted ARP request packets echo back to other MUs. The

AP-5131 removes from its database the destination or interface information that is not used for a

specified time. The AP refreshes its database when it transmits or receives data from these

destinations and interfaces.

1.2.4 Media Types

The AP-5131 radio interface conforms to IEEE 802.11a/b/g specifications. The interface operates at

a maximum 54Mbps (802.11a radio) using direct-sequence radio technology. The AP-5131 supports

multiple-cell operations with fast roaming between cells. Within a direct-sequence system, each cell

can operates independently. Adding cells to the network provides increased coverage area and total

system capacity.

The RS-232 serial port provides a Command Line Interface (CLI) connection. The serial link supports

a direct serial connection. The AP-5131 is a Data Terminal Equipment (DTE) device with male pin

connectors for the RS-232 port. Connecting the AP-5131 to a PC requires a null modem serial cable.

1.2.5 Direct-Sequence Spread Spectrum

Spread spectrum (broadband) uses a narrowband signal to spread the transmission over a segment

of the radio frequency band or spectrum. Direct-sequence is a spread spectrum technique where the

transmitted signal is spread over a particular frequency range. The Symbol AP-5131 uses Direct-

Sequence Spread Spectrum (DSSS) for radio communication.

Direct-sequence systems communicate by continuously transmitting a redundant pattern of bits

called a chipping sequence. Each bit of transmitted data is mapped into chips by the AP-5131 and

rearranged into a pseudorandom spreading code to form the chipping sequence. The chipping

sequence is combined with a transmitted data stream to produce the AP -5131’s output signal.

MUs receiving a direct-sequence transmission use the spreading code to map the chips within the

chipping sequence back into bits to recreate the original data transmitted by the AP-5131.

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Zebra ML-1499-LAK1-01R Datasheet Page 36