Hello, everyone!
Today, I will continue on the topic of IEEE 802.11 standard for WLANs.
A second fundamental characteristic of the IEEE 802.11 standards is the adoption of a media access control (MAC) protocol called Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). The main reason is that IEEE 802.11-based systems are half duplex, i.e., a station cannot carrier-sense/receive while it is sending, and it is hence impossible to detect a collision as in the case of transmissions over twisted copper wires (e.g., using Ethernet).
A major advantage of the CSMA/CA method is that channel access procedures are simple and cheap to implement, as they do not impose stringent timing requirements on the radio interface. Furthermore, CSMA/CA protocols are scalable and they provide easy support for mobility and decentralised network architectures, from classical ad hoc
networks to emerging people-centric networks.
On the negative side, CSMA/CA protocols can only provide a best effort transmission service and major efforts have been dedicated to the design of mechanisms for supporting better QoS, such as in the IEEE 802.11e amendment.
The perceived shortcomings of the first WLAN products have driven the evolution of the IEEE 802.11 standards. In particular, throughput enhancements have been a key priority in the IEEE 802.11 technology development. The key enabler for high-throughput WLANs was the adoption of new physical-layer techniques. The first of these techniques was the orthogonal frequency-division multiplexing (OFDM), which allowed achieving maximum data rates up to 54 Mb/s.
However, it is only with the adoption of the IEEE 802.11n amendment in 2009 that the throughput performance of WLANs came close to that of a wired Ethernet network, as a result of the introduction of multiple-input multiple-output (MIMO) technologies. At the same time, new amendments to the original standard were proposed to foster a more diversified use of WLAN products in various application domains.
For instance, the IEEE 802.11p amendment was approved in 2010. This defines enhancements to the IEEE 802.11 standards to support vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication (together referred to as V2X) in the 5.9 GHz band, which is licensed for Intelligent Transportation Systems (ITS).
Following the same diversification strategy, the IEEE 802.11s amendment was approved in 2011; this described how wireless mesh networks should operate on top of the existing IEEE 802.11 MAC protocol. This includes the specification of new infrastructure-based elements needed for mesh networking and the routing protocol to establish mesh paths between these elements.
You're welcome to like and comment!
