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Delay Compensation Arrangement for Processing Symbols Received by a CDMA Receiver Using a Generic Finger Approach

IP.com Disclosure Number: IPCOM000012291D
Published in the IP.com Journal: Volume 3 Issue 5 (2003-05-25)
Included in the Prior Art Database: 2003-May-25
Document File: 5 page(s) / 791K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

Radio propagation in mobile channels is characterised by multiple reflections. Obstacles resulting in a so-called multipath progagation cause these reflections. A CDMA (Code Division Multiple Access) receiver can separate multipath components and combine them coherently to obtain multipath diversity. In this approach the delay compensation buffer is arranged after the descrambling, despreading and integrate units (rake fingers). The organisation and hardware realisation of the delay compensation buffer is solved by this invention in such a manner that allows the delay compensation of the multipath components with their numerous spreading factor (SF) and code configurations in a generic finger environment. The invention is the transition from a rigid allocation scheme of rake fingers and a rigid storage scheme for received symbols to a solution, which is characterized by a flexible allocation of rake fingers and such an organisation of the delay compensation buffer, that allows to handle the numerous spreading factor and code configurations an even transitions of spreading factors in a flexible, programmable manner with low hardware effort.

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© SIEMENS AG 2003 file: 2003J05787.doc page: 1

Delay Compensation Arrangement for Processing Symbols Received by a CDMA Receiver Using a Generic Finger Approach

Idea: Kai Kasprick, DE-Munich; Dr. Markus Ali-Hackl, DE-Munich; Thomas Hindelang, DE-Munich

Radio propagation in mobile channels is characterised by multiple reflections. Obstacles resulting in a so-called multipath progagation cause these reflections. A CDMA (Code Division Multiple Access) receiver can separate multipath components and combine them coherently to obtain multipath diversity.

In this approach the delay compensation buffer is arranged after the descrambling, despreading and integrate units (rake fingers). The organisation and hardware realisation of the delay compensation buffer is solved by this invention in such a manner that allows the delay compensation of the multipath components with their numerous spreading factor (SF) and code configurations in a generic finger environment.

The invention is the transition from a rigid allocation scheme of rake fingers and a rigid storage scheme for received symbols to a solution, which is characterized by a flexible allocation of rake fingers and such an organisation of the delay compensation buffer, that allows to handle the numerous spreading factor and code configurations an even transitions of spreading factors in a flexible, programmable manner with low hardware effort.

Delay Compensation Buffer

The delay compensation buffer (DCB) is used to compensate the delay of the multipath components caused by multipath propagation. The DCB stores the delay components of the data channels. The DCB is realised as a linear addressable buffer (see figure 1). The DCB is logically split into delay sets (DS). The DS are used to store the related delay components of the received symbols. One deoeay set can store a fixed maximum number k of delay components of symbols, usually in the range k = 12..24. The number of base stations can be configured very flexible. Assuming a DS with k = 12, there could be a receiver configuration of 3 base stations with 6-3-3 paths or 6 base stations with a path configuration 4-2-2-2-1-1. The number of DS is related with the delay to be compensated. The DCB is realised as a circular buffer. It is filled from low to high addresses. If the current address exceeds the maximum buffer size, an address wrap is done.

According to 3GPP (Third Generation Partnership Project) TS 25.306 the UE (User Equipment) must be able to receive several DPCH (Dedicated Physical Channel) channels simultaneously. The DPCHs can differ in number and spreading factor. The DCB must be able to store all DPCHs and must handle transitions of SFs. By adjustment of the delay sets and delay set groups higher data rates and a larger number of simultaneous received codes can be handled.

Storage Scheme 1

High...