Changes between Version 4 and Version 5 of 802.11/wlan_exp/app_notes/tutorial_hop_mac
- Timestamp:
- Jul 30, 2015, 4:16:38 PM (9 years ago)
Legend:
- Unmodified
- Added
- Removed
- Modified
-
802.11/wlan_exp/app_notes/tutorial_hop_mac
v4 v5 7 7 In many communication systems, it is advantageous to "hop" between many different frequencies. These systems, which fall under a broad class of techniques called [https://en.wikipedia.org/wiki/Spread_spectrum spread spectrum], can provide robustness against interference and jamming. 8 8 9 In this tutorial, we will modify the Mango 802.11 Reference Design to enable frequency hopping and we will use the [wiki:802.11/wlan_exp WLAN Experiments Framework] to evaluate the changes. Specifically, we will implement the frequency hopping behavior in two different ways . First, we will use [wiki:./slow_hopping Slow Hopping Approach] that remains interoperable with standard Wi-Fi clients. This design uses existing 802.11 management frame parameters to instruct client stations to hop to a new center frequency. However, these management frame parameters were never intended for fast frequency hopping; they were intended for an AP to shift its network to a different frequency over long time scales (e.g., after the detection of a radar system when using [https://en.wikipedia.org/wiki/IEEE_802.11h-2003 Dynamic Frequency Selection]).9 In this tutorial, we will modify the Mango 802.11 Reference Design to enable frequency hopping and we will use the [wiki:802.11/wlan_exp WLAN Experiments Framework] to evaluate the changes. Specifically, we will implement the frequency hopping behavior in two different ways: 10 10 11 We can improve the frequency hopping rate significantly by breaking compatibility and interoperability with Wi-Fi devices. In the [wiki:./fast_hopping Fast Hopping Approach], we will employ an 'a priori' known frequency hopping schedule at each WARP v3 node in the network rather than explicitly communicate the intention to hop in a management frame. The key challenge here is ensuring that each device remains synchronized despite sharing no absolute time reference. 11 1. First, we will use [wiki:./slow_hopping Slow Hopping Approach] that remains interoperable with standard Wi-Fi clients. This design uses existing 802.11 management frame parameters to instruct client stations to hop to a new center frequency. However, these management frame parameters were never intended for fast frequency hopping; they were intended for an AP to shift its network to a different frequency over long time scales (e.g., after the detection of a radar system when using [https://en.wikipedia.org/wiki/IEEE_802.11h-2003 Dynamic Frequency Selection]). 12 13 2. Alternatively, we can improve the frequency hopping rate significantly by breaking compatibility and interoperability with Wi-Fi devices. In the [wiki:./fast_hopping Fast Hopping Approach], we will employ an 'a priori' known frequency hopping schedule at each WARP v3 node in the network rather than explicitly communicate the intention to hop in a management frame. The key challenge here is ensuring that each device remains synchronized despite sharing no absolute time reference.