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MEASURING THE PERFORMANCE OF A DIGITAL CHANNEL

IP.com Disclosure Number: IPCOM000007170D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2002-Mar-01
Document File: 6 page(s) / 214K

Publishing Venue

Motorola

Related People

Eliezer Fogel: AUTHOR [+2]

Abstract

The direct measurement of the BER is a proce- dure that involves a great amount of time and mate- rial. Thus, a parameter has been chosen which requires less hardware for its measurement and is strongly correlated to the BER. We call this param- eter the Scattering Measure. In the following, we describe the parameter and the simulation results that led us to claim its equivalence to the BER. Then, we give an outline for the implementation of the measurement and discuss its advantages over a direct measurement of the BER. The scattering measure is discussed within the context of the QUAD-16QAM modulation used in the MIRS project but is rele- vant to any digital communication signal.

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MO-LA Technical Developments Volume 22 June 1994

MEASURING THE PERFORMANCE OF A DIGITAL CHANNEL

by Eliezer Fogel and Jossy Sayir

  The direct measurement of the BER is a proce- dure that involves a great amount of time and mate- rial. Thus, a parameter has been chosen which requires less hardware for its measurement and is strongly correlated to the BER. We call this param- eter the Scattering Measure. In the following, we describe the parameter and the simulation results that led us to claim its equivalence to the BER. Then, we give an outline for the implementation of the measurement and discuss its advantages over a direct measurement of the BER. The scattering measure is discussed within the context of the QUAD-16QAM modulation used in the MIRS project but is rele- vant to any digital communication signal.

subchannel and according to the symbol that was sent, resulting in 4 times 16 clusters containing a cloud of received points each. Figure 1 illustrates a typical received constellation for one of the four subchannels. One can clearly distinguish the 16 clusters.

   Note: The knowledge of the sent symbol is actu- ally not needed. The Scattering Measure can be cal- culated using the received symbols post detection. Thus data synchronization of receiver with the trans- mitter is actually not needed (unlike the BER meas- urement case.)

  The parameter we compute is inspired by the scattering criteria as described in "Pattern Classifi- cation and Scene Analysis" (R. 0. Duda, P E. Hart, John Wiley & Sons Inc. 1973) paragraph 6.8.3. In words, we measure the average distance between the clouds with respect to the average thickness of the clouds in each cluster. This is computed as follows:

DESCRlPTlON OF THE SCATTERING MEASURE

  The parameter we measure is based on constel- lation statistics. We transmit a sequence of known symbols through a (noiseless) channel using QUAD- 16QAM modulation and perform statistical meas- urements on the received points. The received points in the constellation are classified according to the

mi = Mm vector for the ilh cluster

(Ki is the set of "i received points in the ith CIUSW~)

Total mean vexor

Si = x(x - mi)(x - mi)' Scatter mattix for the i'h cluster

where AT denotes A transposed.

s, = jJsi i=i

Within-cluster scatter matrix

S, = Tni (mi - m)(mi - m)r Between-cluster scztter matrix iii,

0 Motorola, inc. 1994

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0 M MO-LA

Technical Developments Volume 22 June 1994

  The within-cluster and the between-cluster scat- ter matrices are computed for each subchannel. Based on these matrices, there are several scalar measures that one could compute. We chose one that remains invariant under linear transformation. The reason for doing so is that we wish to perform our meas- urement before the interpolation algorithm in the receiver. The interpolation algorithm has been con- ceived to eliminate the effects of frequency-selective

fading. For an ideal no...