1: Main points of knowledge
Overview of wireless networks and mobile technologies, wireless links and network characteristics
Two: Overview
1: A wireless host, as in a wired network, a host is an end-system device that runs an application.
2: Wireless link, the host is connected to a base station or another wireless host through a wireless communication link.
3: The base station, which is responsible for sending and receiving data to and from the wireless host associated with it, the base station is usually responsible for coordinating the transmission of multiple wireless hosts associated with it. Cell towers in cellular networks and access points for 802.11 wireless LANs are examples of base stations
4: Network infrastructure, these components can be combined in many different ways to form different types of wireless networks. A wireless network is classified a according to two criteria: whether a packet in the wireless network spans one wireless hop or multiple wireless hops. b: Is there any infrastructure such as base stations in the network.
5: Single hop, based on infrastructure. These networks have base stations connected to larger wired networks such as the Internet. In addition, all communications between the base station and the wireless host go through one wireless hop. This is the type of 802.11 network you use in the classroom, coffee shop, or library, and the 3G cellular network we'll learn about.
6: Single hop, no infrastructure. In these networks, there are no base stations connected to the wireless network. However, as we shall see, one node in such a single-hop network can coordinate the transmissions of other nodes. Bluetooth networks and 802.11 networks with ad hoc mode are single-hop, infrastructure-less networks
7: Jump more. based on infrastructure. A base station appears to be wired to a larger network. However, certain wireless nodes may have to relay their communications over other wireless in order to communicate via the base station. Certain wireless sensor networks and so-called wireless mesh networks are of this type.
8: Multi-hop, no infrastructure. There are no base stations in these networks, and a node may have to relay messages between several other wireless nodes in order to reach its destination. Nodes may also be mobile, changing connection relationships among multiple nodes. A class of networks is called mobile ad hoc networks. If the mobile node is vehicular, the network is a vehicular ad hoc network. As you can imagine, developing a protocol for such a network is a challenge, the subject of a lot of ongoing research.
Three: Wireless link and network characteristics
1: Decreasing signal strength
2: Interference from other sources
3: Multipath propagation