1 Context
There are much more wireless phone subscribers than wired phone subscribers.
The are much more mobile-broadband-connected devices than fixed-broadband-connected devices.
We need to face two different challenges:
- wireless: communication over wireless link
- mobility: handling the mobile user who changes point of attachment to the network
2 Introduction
2.1 Elements of a wireless network
- Wireless Hosts
- laptop, smartphone, IoT
- these run applications
- these may be stationary (non-mobile) or mobile
- wireless does not always mean mobility! (a laptop that never leaves the office but is connected via wifi is wireless but not mobile)
- Base Station / Wifi Access Points
- these are typically connected to the wired network
- these are a relay: they are responsible for sending packets between the wired network and the wireless hosts in its “area”
- Wireless Link
- they are typically used to connect mobile users to the base stations
- multiple access protocol coordinate the link access
- various transmission rates, distances and frequency bands
2.2 Characteristics of different wireless links
Different wireless Links have different characteristics, link bandwidth and range:
- WiFi is the commercial name for the 802.11 technology
- Bluetooth is the commercial name for the 802.15.1 technology: short range, low energy, “high” (lol) bandwidth
- 802.15.4 is short range, low energy and low bandwidth
2.3 Classification of Wireless Networks
There are different classes of wireless networks:
- Infrastructured Mode:
- the base station connects mobiles into a wired network
- handoff: mobiles when moving change the base station providing connection into the wired network, the change is called handoff
- Ad hoc Mode:
- no base stations
- nodes can only transmit to other nodes within link coverage
- nodes organize themselves into a network and route among themselves
2.3.1 Wireless Network Taxonomy
| Single Hop | Multiple Hops | |
|---|---|---|
| Infrastructure-based | Host connects to base station which connects to the larger internet: WiFi, cellular networks | Host may have to relay through several wireless nodes to connect to the larger internet: |
| No base station, no connection to the larger internet: | No base station, no connection to larger internet. May have torelay each other a given wireless node: |