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Spur mitigation techniques

Inactive Publication Date: 2005-03-17
ATHEROS COMM INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Benefits of technology

In accordance with the present invention, various techniques can be used to mitigate the effects of spurs on a received signal. In general, these techniques work by either

Problems solved by technology

Thus, if a spur coincides with or otherwise affects a sub-channel, then th

Method used

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DETAILED DESCRIPTION OF THE DRAWINGS

Spurs can cause receiver performance degradation in various ways. For example, spurs can corrupt information in the received signal used for data decoding, signal detection, timing, and frequency offset. Multiple techniques, described below, can be used to mitigate the effects of spurs. These techniques can ignore and / or cancel the spurs.

Pilot Mask

One known pilot-tracking algorithm is discussed in U.S. patent application Ser. No. 10 / 263,415, entitled “Decision Feedback Channel Estimation and Pilot Tracking For OFDM Systems”, filed on Oct. 1, 2002, and incorporated by reference herein. In one embodiment, this pilot-tracking algorithm can use the four pilots on the pilot sub-channels as well as information from certain data sub-channels to compute frequency offset. For example, the 48 data sub-channels could be partitioned into 4 groups, wherein each group includes 12 sub-channels. The receiver could then select the sub-channel in each group h...

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Abstract

Spurs cause significant problems with signal detecting, amplifier gain adjustment, and signal decoding. Various techniques can be used to mitigate the effects of spurs on a received signal. Generally, these techniques work by either canceling or ignoring the spurs. For example, a pilot mask can be used to ignore pilot information in one or more sub-channels. A Viterbi mask can determine the weighting given to bits in a sub-channel based on spur and data rate information. Channel interpolation can compute a pseudo channel estimate for a sub-channel known to have a spur location can be computed by interpolating the channel estimates of adjacent good sub-channels. Filtering of the received signal using a low-pass filter, a growing box filter, or a low-pass filter with self-correlation can be used to cancel a spur.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wireless local area networks (WLANs) and in particular to various techniques that ignore or cancel spurs, thereby improving receiver performance. 2. Discussion of the Related Art Wireless local area networks (WLANs) are becoming increasingly popular as communication networks. The IEEE 802.11 standards provide guidelines for the operation of devices operating in WLANs. To address multipath and other conditions, a wireless system can employ various techniques. One such technique is Orthogonal Frequency Division Multiplexing (OFDM). In an OFDM system, a signal can be split into multiple narrowband channels (called sub-channels) at different frequencies. For example, current 802.11a and 802.11g OFDM systems include 52 sub-channels. Thus, a transmitted signal could be represented by X−26. . . x−1. . . x26, wherein both negative and positive side frequencies are included. In this configuration, eac...

Claims

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Application Information

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IPC IPC(8): H04L27/26
CPCH04L1/0045H04L27/2647H04L25/0232
Inventor CHOI, WON-JOONGILBERT, JEFFREY M.WANG, YI-HSIUZHANG, XIAORU
Owner ATHEROS COMM INC
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