Browse Prior Art Database

CHANNEL BER AND SIGNAL QUALITY ESTIMATION FOR TRELLIS CODED MODULATION

IP.com Disclosure Number: IPCOM000007572D
Original Publication Date: 1995-Nov-01
Included in the Prior Art Database: 2002-Apr-08
Document File: 2 page(s) / 107K

Publishing Venue

Motorola

Related People

Troy Beukema: AUTHOR

Abstract

To estimate the integrity of a digital communi- cations channel, it is often desired to compute some type of error metric at the receiver. Two typical error metrics are channel BER (hard decision errors in the channel) and signal quality (variance of soil deci- sion errors). Further, it is desired to accurately esti- mate these metrics in the absence of a prior knowl- edge of the transmitted data. This invention describes method/apparatus to 1) estimate channel BER, 2) compute near exact channel BER, and 3) accurately estimate channel signal quality on a digital commu- nications channel using trellis coded modulation (TCM). TCM is used in both voice and data in the MIRS system, hence, this invention is applicable to estimate channel BER/SQE for MIRS data, voice, and control channels.

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M-ROLA Technical Developments

CHANNEL BER AND SIGNAL QUALITY ESTIMATION FOR TRELLIS CODED MODULATlOrj

by Troy Beukema

ABSTRACT

  To estimate the integrity of a digital communi- cations channel, it is often desired to compute some type of error metric at the receiver. Two typical error metrics are channel BER (hard decision errors in the channel) and signal quality (variance of soil deci- sion errors). Further, it is desired to accurately esti- mate these metrics in the absence of a prior knowl- edge of the transmitted data. This invention describes method/apparatus to 1) estimate channel BER, 2) compute near exact channel BER, and 3) accurately estimate channel signal quality on a digital commu- nications channel using trellis coded modulation (TCM). TCM is used in both voice and data in the MIRS system, hence, this invention is applicable to estimate channel BER/SQE for MIRS data, voice, and control channels.

DESCRIPTION

  This invention takes advantage of the error correcting capability of TCM codes to produce a high quality estimate of the transmitted data at the receiver. The output of the TCM decoder is then re-encoded at the receiver. The process of re-encoding the data produces a sequence of symbols at the receiver which represent an improved estimate of the actual transmitted channel symbols. The data bits which represent the re-encoded data allow for- mation of the channel BER metric. The vector dif- ference between the re-encoded symbols and the actual received symbols allow formation of a signal quality metric. If a CRC on the transmitted data is used, the receiver can form near exact channel BER estimates, since it knows that the re-encoded sym- bols are correct. A block diagram of the algorithm

is shown in Figure 1. The estimated channel BER generated by the algorithm is refered to as Hypo- thetical Error Rate Output (HERO), the CRC quali- lied channel BER is referred to as Near Exact Error Rate Output (NEERO), and the channel signal qual- ity output is referred to as Improved Signal Quality E...