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Reduced Complexity Channel Tracking Algorithm for UMTS-FDD Mobile Phones

IP.com Disclosure Number: IPCOM000019759D
Original Publication Date: 2003-Oct-25
Included in the Prior Art Database: 2003-Oct-25
Document File: 2 page(s) / 118K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

The performance of a digital mobile receiver operating in frequency-selective propagation environments is significantly affected by the accuracy of the employed channel estimation. Without sufficient accuracy the receiver cannot equalize the transmission channel and is therefore not able to coherently demodulate the received symbols. Additionally, if the receiver is moving, the impulse response of the transmission channel is time-varying meaning that the channel taps are fading. In order to cope with the time-varying channel coefficients the receiver must be able to track them. Currently, channel estimation is based on the rake-receiver principle. This algorithm does not hold any tracking abilities. Only the number of estimates to be averaged can be adopted. Up to now the well known Kalman filter (KF) algorithm is employed for tracking the time-varying channel coefficients. But even though it results in superior performance it is computationally demanding. It is therefore desirable to use an algorithm of roughly the same performance but with much less complexity.

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© SIEMENS AG 2003 file: 2003J12320.doc page: 1

Reduced Complexity Channel Tracking Algorithm for UMTS-FDD Mobile Phones

Idea: Heino Gerlach, DE-Munich

The performance of a digital mobile receiver operating in frequency-selective propagation environments is significantly affected by the accuracy of the employed channel estimation. Without sufficient accuracy the receiver cannot equalize the transmission channel and is therefore not able to coherently demodulate the received symbols. Additionally, if the receiver is moving, the impulse response of the transmission channel is time-varying meaning that the channel taps are fading. In order to cope with the time-varying channel coefficients the receiver must be able to track them.

Currently, channel estimation is based on the rake-receiver principle. This algorithm does not hold any tracking abilities. Only the number of estimates to be averaged can be adopted. Up to now the well known Kalman filter (KF) algorithm is employed for tracking the time-varying channel coefficients. But even though it results in superior performance it is computationally demanding. It is therefore desirable to use an algorithm of roughly the same performance but with much less complexity.

It is hereby proposed to replace the KF algorithm by the following simple channel tracking algorithm, written compactly in matrix-vector notation as:

[g36] [g36] [g36]

1 1

kkkH( )

k k k

z[g97] [g97] [g45] [g45] [g61] [g43] [g215][g45] hh Γ c c h

with the diagonal weighting matrix of dimension (L,L) and

[g61]0 1 L-1

Γ

   1 diag{ , ,..., } ( )

[g98] [g98] [g98]

[g115] [g115] [g115]

[g43]u n c

,

where diag {} denotes a matrix with the elements in brackets on the main diagonal, and the row vector with L samples of the CPICH (Common Pilot Channel):

[g61]1 1

c ,

and the column vector with estimates of the L independent channel coefficients

[g36] [g36] [g36] [g36]

0 1 1

  [ ( ), ( ),..., ( )]T k L

  [g61][g45]h khk h k h .

In these equati...