The Effects of Adjacent Channel Rejection and Adjacent Channel
Interference on 802.11 WLAN Performance
2
SPLY005
The escalating deployment of wireless networking technology as well as other wireless
technologies in the same unlicensed spectrum is rapidly increasing the radio frequency (RF)
interference for Wi-Fi® (802.11) products, threatening the data throughput performance of
wireless local area networks (WLAN). At the same time, the market is demanding higher data
throughput rates for new WLAN applications like multimedia audio and video, streaming media,
voice over WLAN, and others that require quality of service (QoS) capabilities and low packet
error rates. As a consequence of an increasing amount of in-band and adjacent band
interference in the environment for WLAN equipment, the design of radios and digital filtering
has become critical. This white paper analyzes the sources of adjacent channel interference
(ACI) and the radio design practices that can improve a WLAN's adjacent channel rejection
(ACR) for better overall performance.
Overview
The problem of ACI and a need for improved RF receiver performance for Wi-Fi and WLAN
technology in both the 2.4 GHz and 5.x GHx unlicensed bands has come to the attention of
manufacturers, system designers, integrators and the Federal Communications Commission
(FCC). In fact, when the FCC released an additional 250 MHz of spectrum for 802.11 WLANs
starting at 5.4 GHz, it noted that regulatory changes soon may be needed in WLAN's crowded
band of the spectrum. The FCC may soon issue a "Notice of Inquiry" (NOI) that would gather
information on the possibility of establishing a governmental standard for radio receiver design
in this spectrum.
What's at Stake?
Future WLAN market growth could be adversely affected unless the interference problem is
addressed. Currently, the performance of a WLAN access point (AP) or client station can be
interfered with by other WLAN APs and stations in close proximity to it and other non-802.11
devices which operate in the same unlicensed band. The situation is similar to that which the
cellular telephone industry faced and solved with channel frequency reuse solutions. As the
802.11 market grows and the density of WLAN technology increases, the problem will be
exacerbated in applications such as the following:
• Corporate/enterprise deployments
• Dense commercial hot-spot deployments (strip malls, etc.)
• Residential apartment building deployments
• High density urban deployments
The performance of WLANs can be hampered by a number of sources of interference, including
the following non-802.11 equipment:
• Cordless phones (2.4 or 5.x GHz)
• Bluetooth™ personal area networking devices (2.4 GHz)
o Bluetooth wireless headphones are a special case
• Pulse radar (Using the 5.4 GHz band for pulse radar is under review in the U.S.)
• Microwave ovens (50 percent duty cycle creates pulse jamming in the 2.4 GHz band.)
• Low energy RF lighting sources (2.4 GHz)
评论0