One of two popular spread spectrum transmission technologies for wireless networking, the other being frequency hopping. Direct sequencing can be used for both wireless local area network (LAN) connections and as part of a cellular telephone technology.
Direct sequencing systems transmit data 1 bit at a time instead of packaging data into multibit packets, as in frequency hopping. Each bit of data is transmitted simultaneously over a range of frequencies in the 902 to 928–MHz frequency band. Spreading the data over multiple frequencies reduces signal loss due to noise and interference.
In direct sequencing, the transmitter feeds each bit of the data stream into a signal spreader that multiplies the input, creating a wideband signal. The wideband signal is then amplified and broadcast by using an antenna.
Graphic D-27. Direct sequencing.
Direct sequencing has a faster theoretical maximum data transmission rate than frequency hopping, but in practice the two methods provide similar throughput for wireless transmission of data because of protocol overhead in typical wireless communication systems.