Turbo interleaving apparatus and method

Abstract

A 2-dimensional interleaving method is disclosed. The method comprises dividing a frame of input information bits into a plurality of groups and sequentially storing the divided groups in a memory; permuting the information bits of the groups according to a given rule and shifting an information bit existing at the last position of the last group to a position preceding the last position; and selecting the groups according to a predetermined order, and selecting one of the information bits in the selected group.

Description

PRIORITY [0001]This application claims priority to an application entitled “Turbo Interleaving Apparatus and Method” filed in the Korean Industrial Property Office on May 19, 1999 and assigned Serial No. 99-18928 and an application filed in the Korean Industrial Property Office on May 21, 1999 and assigned Serial No. 99-18560, the contents of which are hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates generally to a turbo encoder used for radio communication systems (including satellite, ISDN, digital cellular, W-CDMA, and IMT-2000 systems), and in particular, to an internal interleaver of a turbo encoder.[0004]2. Description of the Related Art[0005]In general, an interleaver used for a turbo encoder randomizes an address of input information word and improves a distance property of a codeword. In particular, it has been decided that a turbo code will be used in a supplemental channel (or data transmission ...

AI Technical Summary

Benefits of technology

The present invention provides an interleaving device and method for analyzing properties of a turbo interleaver and a property of a critical information sequence pattern (CISP) to improve performance of the turbo interleaver. The method involves dividing a frame of input information bits into a plurality of groups and sequentially storing the divided groups in a memory, permuting the information bits of the groups according to a given rule and shifting an information bit existing at the last position of the last group to a position preceding the last position, and selecting the groups according to a predetermined order, and selecting one of the information bits in the selected group. This method improves the performance of the turbo interleaver and solves the problem of decreased free distance when an input information word has a Hamming weight 1 in a prime interleaver (PIL) that is the turbo interleaver specified in the UMTS specification.

Problems solved by technology

However, so far, such interleavers are mere algorithms designed to improve their performances in terms of scientific researches rather than implementation.

Therefore, when implementing an actual system, the hardware implementation complexity must be taken into consideration.

However, an increase in interleaver size causes a geometric increase in calculations.

Therefore, in general, it is not possible to implement the interleaver for the large frame size.

Although the above criteria are applicable to a general turbo interleaver, it is difficult to clearly analyze the properties when the interleaver increases in size.

In addition, another problem occurring when designing the turbo interleaver is that the minimum free distance of the turbo code varies according to the type of the input codeword.

However, in most cases, when the input information word has 2 information bits of ‘1’, the minimum free distance is formed and most error events occur in this condition.

However, most of these turbo interleavers have the problems of the CSIP with Hamming weight 1, and the details of implementing these turbo interleavers are still not defined.

However, this was not fully considered for the existing turbo interleavers.(3) The Prime interleaver (PIL) designated as the working assumption of the turbo code interleaver defined by the UMTS specification involves such problems, thus having degraded free distance performance.

Images