Tree-structured generation of orthogonal spreading codes with different lengths for forward link of DS-CDMA mobile radio

Adachi, Fumiyuki; Sawahashi, Mamoru; Okawa, Koichi

doi:10.1049/el:19970022

Cited by 291 publications

(173 citation statements)

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“…In chip-interleaved DS-CDMA, the MUD problem is converted into a set of equivalent single-user equalization problems and single-user FDE can be used to provide good performance in a multiuser/multipath environment, provided that the propagation channel delays including transmit timings offsets of different users are within a guard interval (GI) [8]. Recently, we have introduced 2-dimensional (2D) spreading using orthogonal variable spreading factor (OVSF) codes [9] to the chip-interleaved DS-CDMA uplink transmission [10] to offer users flexible multirate/multi-connection services.…”

Section: Introductionmentioning

confidence: 99%

Joint Frequency-Domain Differential Detection and Equalization for 2-Dimensional Spread/Chip-Interleaved DS-CDMA Uplink Transmissions

Liu

Adachi

2006

IEEE Vehicular Technology Conference

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Abstract-The multiple-access interference (MAI) limits the performance of the DS-CDMA uplink transmission. 2 dimensional (2D) spread/chip-interleaved DS-CDMA is an MAI-free system, where single-user coherent frequencydomain equalization (FDE) can be used instead of complicated multiuser detection (MUD). However, coherent FDE needs channel estimation. Pilot-assisted channel estimation is not reliable in a fast fading environment. In this paper, we apply joint frequencydomain differential detection and equalization (FDDDE) that requires no channel estimation to 2D spread/chipinterleaved DS-CDMA in a multiuser/multipath environment. The filter coefficient used in FDDDE is updated by estimating the normalized Doppler frequency. Computer simulation results show that 2D spread/chipinterleaved DS-CDMA using FDDDE is robust against fast fading.

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Section: Introductionmentioning

confidence: 99%

Joint Frequency-Domain Differential Detection and Equalization for 2-Dimensional Spread/Chip-Interleaved DS-CDMA Uplink Transmissions

Liu

Adachi

2006

IEEE Vehicular Technology Conference

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“…The OVSF codes are normally represented as a code tree, namely an OVSF codetree, which is formally defined in [1,14]. The normal data rates of OVSF codes are always the square of the lowest-data-rate codes.…”

Section: Introductionmentioning

confidence: 99%

A Fast Code-Assignment Strategy for a WCDMA Rotated-OVSF Tree with Code-Locality Capability

2005

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Abstract. In this paper, a new channelization code tree structure, namely an ROVSF (rotated-orthogonal variable spreading factor) code tree, is defined and investigated. Most existing code assignment schemes are investigated on the OVSF (orthogonal variable spreading factor) code tree in WCDMA systems. The main work of this investigation is to exploit and justify the new properties of the ROVSF code tree. We show that the ROVSF code tree offers the same code capability to that of the conventional OVSF code tree, but our ROVSF code tree additionally has the code-locality capability. With the code-locality capability, a fast code-assignment strategy is developed on the ROVSF code tree. Compared to existing code assignment schemes on OVSF code trees, a fast code assignment scheme is developed with lower search costs and a low blocking rate, due to its code-locality capability. Finally, the simulation results illustrate that our proposed scheme on the ROVSF code tree actually has lower search costs and a better blocking rate.

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“…Another form of orthogonal variable rate codes is known as tree structure orthogonal codes, these codes were first proposed in [9]. The structure of these codes is illustrated in Figure 2, all codes are orthogonal so long as they are neither a mother code of a subsequent code or are within the same arm of the tree.…”

Section: Uplink Calibration Systemmentioning

confidence: 99%

Calibration architectures for use in UTRA adaptive antenna basestations

Morris

Simmonds²,

Beach³

Gateway to 21st Century Communications Village. VTC 1999-Fall. IEEE VTS 50th Vehicular Technology Conference (Cat. No.99CH36324

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The ACTS Smart Universal BEAMforining (SUNBEAM) The SUNBEAM ProjectThe SUNBEAM (Smart UNiversal BEAMforming) project has been set up under the EU ACTS research programme and builds on the success of the ACTS TSUNAMI I1 project [l]. The SUNBEAM project intends to develop innovative basestation array processing architectures, enabling technologies (antenna, digital signal processing, analogue R.F. etc) and algorithms for UMTS that are sufficiently flexible to support a range of different second and third generation air interface standards. Members of the consortium are also addressing the development and evaluation of spatial-temporal channel models.amplitude and phase weights applied to the transmitted signals.In the case of both SUNBEAM and TSUNAMI I1 this is implemented in digital baseband signal processing P I .The aim of an adaptive antenna basestation is to provide greater spectral efficiency in cellular networks [3]. These systems operate through adaptation of their radiation pattern in response to the environment in which they operate, allowing received and transmitted signals to be manipulated to provide optimal signal combination according to the requirements of the system. For example, adaptive antennas can be used effectively to determine; wanted signal bearing estimation (DOA [4]), interference suppression (SFIR [ 5 ] ) and, in the case of TDMA systems, the support of more than one user in a single channel (SDMA [6]). II Adaptive Antenna Array Operational RequirementsMost beamformer algorithms rely on the accuracy of the electrical paths to determine optimal signal combination or interference reduction, in particular when supporting full duplex transmission. As a result, a change in the characteristics of one signal path may drastically affect the operation of the system. Time variant distortions occur in the transceiver chain due to small environmental changes such as: temperature, electrical and mechanical variations and even changes in the channel centre frequency and channel gain. These distortions will effectively alter the transfer function of each adaptive antenna path. These errors in the individual paths can alter the position and depths of the nulls required for accurate steering of the adaptive antenna, which severely degrades the An adaptive antenna system operates by filtering within the spatial domain, through modification of the transmitted or received antenna array signals with respect to time, frequency and spatial response. This is accomplished by means of 0-7803-5435-4/99/$10.M) 0 1999 IEEE

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Tree-structured generation of orthogonal spreading codes with different lengths for forward link of DS-CDMA mobile radio

Cited by 291 publications

References 1 publication

Joint Frequency-Domain Differential Detection and Equalization for 2-Dimensional Spread/Chip-Interleaved DS-CDMA Uplink Transmissions

Joint Frequency-Domain Differential Detection and Equalization for 2-Dimensional Spread/Chip-Interleaved DS-CDMA Uplink Transmissions

A Fast Code-Assignment Strategy for a WCDMA Rotated-OVSF Tree with Code-Locality Capability

Calibration architectures for use in UTRA adaptive antenna basestations

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