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Reducing Packet Error Rates in OFDM for 802.11 WLAN

IP.com Disclosure Number: IPCOM000124290D
Publication Date: 2005-Apr-14
Document File: 2 page(s) / 17K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that reduces the packet error rate (PER) in OFDM by transmitting certain packets at a lower rate. Benefits include reduced PER without increasing the time packets are in the air.

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Reducing Packet Error Rates in OFDM for 802.11 WLAN

Disclosed is a method that reduces the packet error rate (PER) in OFDM by transmitting certain packets at a lower rate. Benefits include reduced PER without increasing the time packets are in the air.

Background

PER is the probability that a transmitted packet will not reach its intended receiver. In most cases, the lower the transmittal rate, the lower the PER. However, this may adversely affect the overall throughput, because the lower rate tends to occupy the air for a longer period. A rate-scaling algorithm is responsible for balancing the need for a faster throughput with the need to reduce the PER.

The OFDM transmission is comprised of symbols. The symbols are in the air the same amount of time, regardless of the transmission rate. However, the number of data bits in each symbol is defined by the rate. For example, with a rate of 54Mbps, each symbol contains 216 data bits, which is 27 bytes. Even if there is only one data byte to be transmitted, a whole symbol will be used to carry 26 unused data bytes.

General Description

In the disclosed method, the number of data bits per symbol is different for each rate. There are packet lengths that can be transmitted using several rates with the same number of symbols. When transmitting these packets, the PER is reduced but the airtime remains the same.

When a packet is transmitted, the disclosed method calculates the number of symbols needed in order to transmit the packet at...