IEEE802.11 WLAN Standards Activity
Wireless LAN (WLAN) is a shared-medium communications network that broadcasts information over wireless links for all stations to receive. IEEE802.11 defines a family of WLAN standards that include original 802.11, 802.11a, 802.11b, 802.11e, 802.11g, 802.11h and 802.11i. In the original 802.11 standard published in 1997, the MAC (Medium access control) and PHY (Physical layer) definitions are described. The other 802.11 standards are either the enhancements to the original MAC for QoS (Quality of service) and security, or the extension to the original PHY for high-speed data transmission. Our activities in IEEE802.11 are focused on contributing to 802.11a and 802.11e, which are the supplement to PHY for high-speed transmission in 5 GHz, and enhancement of MAC for LAN applications with QoS, respectively.
Background & Objective: WLAN is widely considered to play a major role in wireless multimedia communications that require high-speed transmission with QoS. These technologies need to be standardized. 802.11a defines a high-speed PHY in 5 GHz based on OFDM (Orthogonal Frequency Division Multiplexing) to support up to 54 Mbps data transmission. 802.11e defines an enhancement of MAC to support LAN applications with QoS.
Technical Discussion: 802.11a uses OFDM technology for high data rate transmission. The main idea behind OFDM is to divide the high-speed data stream into several parallel streams of reduced data rate, and to transmit each of them on a separate subcarrier that are made orthogonal to each other. Therefore, spectral overlapping among subcarriers is allowed since the orthogonality will ensure that the receiver can separate the OFDM subcarriers, and a better spectral efficiency can be achieved. In 802.11e standard, a prioritized scheme is used to ensure that high priority users get more bandwidth allocation than low priority users. This is done by a so-called Hybrid Coordination Function (HCF) at MAC. The HCF uses an enhanced contention-based channel access method (EDCF), which operates at stations, concurrently with a polled channel access mechanism operated at AP (access point) to guarantee different data transmissions with required QoS.
Contacts:
Philip Orlik
Jinyun Zhang
Technology Areas:
Digital Communications
Networks
Modification Date: January 23, 2007
