How wireless local area networks (WLANs) are different
Wireless station (STA)
In the design of wired LANs it is implicitly assumed that an address is equivalent to a physical location.
LAN中一个物理地址认为对应一个实际的地址.
The STA is an addressable destination, but not (in general) a fixed location.
WiFi网络中的地址并不是固定的地址.
For example, a single addressable unit might simultaneously be a portable STA, a quality-of-service (QoS) STA, a dependent STA, and a hidden STA.
Media impact on design and performance
Use a medium that has neither absolute nor readily observable boundaries outside of which STAs with PHY transceivers are known to be unable to receive network frames.
物理介质没有边界,STA无法确定是否能接收到网络报文.
Are unprotected from other signals that are sharing the medium.
物理介质和其他设备信号共享(蓝牙, 微波炉?)
Communicate over a medium significantly less reliable than wired PHYs.
传输可靠性比LAN差
Have dynamic topologies
网络拓扑结构动态变化.
Lack full connectivity, and therefore the assumption normally made that every STA can hear every other STA is invalid (i.e., STAs might be “hidden” from each other)
缺乏全连接信息, 无法假定一个STA可以接收到另一个STA的信号
Have time-varying and asymmetric propagation properties.
传输介质状态随时变化,传播不对称性.
Might experience interference from logically disjoint IEEE 802.11 networks operating in overlapping areas.
The impact of handling mobile STAs
Mobile STAs typically are battery powered. Hence power management is an important consideration.
需考虑省电相关机制.
Interaction with other IEEE 802/non-IEEE-802
LLC : IEEE-802.3, RSN : IEEE-802.1X, WME : QoS, AKM?