Which spread spectrum technology does the 802.11b standard define for operation?
A.
IR
B.
DSSS
C.
FHSS
D.
DSSS and FHSS
E.
IR. FHSS, and DSSS
Explanation:
This question is to examine the knowledge point about the wireless.
The differences of performance and capacity of the Wireless local area network mainly depends on the applied FHSS or DSSS, as well as the applied modulation type, to achieve. Up to now, if we compare the parameters of existing products in detail, we can see that the DSSS technology shows relative advantage in the applications which require optimum reliability, while FHSS technology plays relative advantage in the applications which require low cost. In the selection of wireless products, we have to pay attention which spread-spectrum technology, DSSS or FHSS, is chosen by manufacturers. We must prudence the market positioning of end view products because they can solve the transmission capability and characteristic of the wireless LAN, including anti-interference ability, usable distance range, bandwidth size, and the data transfer size. Generally, DSSS uses the full bandwidth to transmit data to quicken its transmission speed, which means a greater potential to higher transmission frequency in the future. DSSS technology is applicable to a fixed environment, or to applications which have higher quality requirement, therefore, mostly applications, such as wireless plant, wireless hospital, network community, branch school networking, are applied to DSSS wireless technology products.FHSS is mostly used in fast-moving endpoint, for example, mobile phone applies FHSS technology in wireless transmission technology part. Due to the small FHSS transmission range, though under the same transmission environment, the required technology devices of FHSS is more than those of DSSS and the price of FHSS will probably be higher as a whole. As to the current business requirement, high-speed mobile endpoint applications are relatively less, while mostly pay attention to the transmission rate, as well as the stability of transmission. Therefore, the DSSS technology will be the mainstream of the future development of wireless networking products.
why???