Maximally Flexible Assignment of Orthogonal Variable Spreading Factor Codes for Multi-Rate Traffic

In universal terrestrial radio access (UTRA) systems, orthogonal variable spreading factor (OVSF) codes are used to support different transmission rates for different users. In this paper, we first define the flexibility index to measure the capability of an assignable code set in supporting multirate traffic classes. Based on this index, two single-code assignment schemes, nonrearrangeable and rearrangeable compact assignments, are proposed. Both schemes can offer maximal flexibility for the resulting code tree after each code assignment. We then present an analytical model and derive the call blocking probability, system throughput and fairness index. Analytical and simulation results show that the proposed schemes are efficient, stable and fair

A comparison of digital transmission techniques under multichannel conditions at 2.4 GHz in the ISM BAND

In order to meet the observation quality criteria of micro-UAVs, and particularly in the context of the « Trophée Micro-Drones », ISAE/SUPAERO is studying technical solutions to transmit a high data rate from a video payload onboard a micro-UAV. The laboratory has to consider the impact of multipath and shadowing effects on the emitted signal. Therefore fading resistant transmission techniques are considered. This techniques paper have to reveal an optimum trade-off between three parameters, namely: the characteristics of the video stream, the complexity of the modulation and coding scheme, and the efficiency of the transmission, in term of BER

Final report on the evaluation of RRM/CRRM algorithms

Deliverable public del projecte EVERESTThis deliverable provides a definition and a complete evaluation of the RRM/CRRM algorithms selected in D11 and D15, and evolved and refined on an iterative process. The evaluation will be carried out by means of simulations using the simulators provided at D07, and D14.Preprin

Improving 3G network throughput by new service and joint design.

Li Ning.Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.Includes bibliographical references (leaves 52-55).Abstracts in English and Chinese.Acknowledgments --- p.iiAbstract --- p.iii哲學碩士論文摘要 --- p.ivChapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Research Background --- p.2Chapter 1.2 --- Contributions of the Thesis --- p.5Chapter 1.3 --- Organization of the Thesis --- p.6Chapter Chapter 2 --- Properties of OVSF Codes --- p.7Chapter 2.1 --- Tree-Structured Generation of OVSF Codes --- p.7Chapter 2.2 --- OVSF Codes Assignment --- p.10Chapter Chapter 3 --- Support Delayable Traffic in Wireless Networks --- p.14Chapter 3.1 --- System Model --- p.15Chapter 3.2 --- Scheduling Algorithm with Burst Adaptation --- p.17Chapter 3.3 --- Performance Analysis --- p.22Chapter 3.4 --- Simulation Results --- p.24Chapter Chapter 4 --- Allocate OVSF Codes with Joint Design --- p.30Chapter 4.1 --- Combine Number of Active Users and Error-Control Coding Scheme --- p.31Chapter 4.1.1 --- System Model --- p.31Chapter 4.1.2 --- Scheduling Algorithm Description --- p.33Chapter 4.1.3 --- Simulation Results --- p.35Chapter 4.2 --- Combine Power Adaptation and Error-Control Coding Scheme --- p.39Chapter 4.2.1 --- System Model --- p.39Chapter 4.2.2 --- Scheduling Algorithm Description --- p.41Chapter 4.2.3 --- Simulation Results --- p.44Chapter Chapter 5 --- Conclusion --- p.50Bibliography --- p.5

Interference Suppression in WCDMA with Adaptive Thresholding based Decision Feedback Equaliser

WCDMA is considered as one of the 3G wireless standards by 3GPP. Capacity calculation shows that WCDMA systems have more capacity compared to any other multiple access technique such as time division multiple access (TDMA) or frequency division multiple access (FDMA). So it is widely used. Rake receivers are used for the detection of transmitted data in case of WCDMA communication systems due to its resistance to multipath fading. But rake receiver treat multiuser interference (MUI) as AWGN and have limitation in overcoming the effect of multiple access interference (MAI) when the SNR is high. A de-correlating matched filter has been used in this thesis, which eliminates and improves system performance. But the given receiver works well only in the noise free environment. A DFE, compared to linear equaliser, gives better performance at severe ISI condition. The only problem in this equalisation technique is to select the number of symbols that are to be fed back. This thesis gives an idea on multiple symbol selection, based on sparity where an adaptive thresholding algorithm is used that computes the number of symbols to feedback. Simulated results show a significant performance improvement for Regularised Rake receiver along with thresholding in terms of BER compared to a rake receiver, de-correlating rake receiver and regularised rake receiver. The performance of the receiver in different channels is also analysed

OFCDM systems over fading channels

Along with the fast growing demand of information exchange, telecommunication systems are required to provide fast and reliable service to high-data-rate applications such as video conference, real-time broadcasting, and on-line gaming. In downlink transmission, orthogonal frequency and code division multiplexing (OFCDM) has been an attractive technique for high-data-rate applications. With two-dimensional spreading, in both time domain and frequency domain, OFCDM achieves diversity gains in multiuser scenarios. Moreover, the adjustable spreading factors (SF) give OFCDM systems the flexibility in transmission rate and diversity gain. In this thesis, we focus on the downlink of OFCDM communication systems. The performance of OFCDM systems is investigated over Ricean fading channels with Rayleigh fading as special case. Code division multiple access (CDMA) technique is used to support multiuser communications, where users can transmit at the same time using the same frequency with the help of code sequences. We compare different combining methods that are employed to achieve diversity gain. Moreover, channel correlation is examined to see its effect on the system performance. We also propose to combine multiple-input and multiple-output (MIMO) techniques, specifically space-time block coding (STBC), with OFCDM systems. By adding spatial diversity, a MIMO system can provide more reliable transmission compared to a single-input and single-output (SISO) system. The space-time scheme used in our study is Alamouti scheme [1], which employs N = 2 and M antennas at the transmitter side and receiver side respectively. In the thesis, we explain the system structure, transmission and detection methods, and system performance of such MIMO-OFCDM systems. In our study, the expressions of system bit error rate (BER) are considered under the condition that no multi-code interference (MCI) is present. The accuracy of the BER expressions is verified when compared with the simulated ones for both SISO and MIMO-OFCDM systems with different combining methods. These comparisons are carried over different channels and with different system parameters to explore the benefits of OFCDM based systems. Both analytical and simulation results show the large diversity gains achieved when incorporating STBC with OFCDM

Bandwidth allocation for wireless multimedia systems.

Chen Chung-Shue.Thesis (M.Phil.)--Chinese University of Hong Kong, 2001.Includes bibliographical references (leaves 100-102).Abstracts in English and Chinese.Chapter 1. --- Introduction --- p.1Chapter 1.1 --- Evolution to 3G Mobile --- p.2Chapter 1.1.1 --- First Generation --- p.2Chapter 1.1.2 --- Second Generation --- p.3Chapter 1.1.3 --- Third Generation --- p.3Chapter 1.2 --- UTRA Framework --- p.5Chapter 1.2.1 --- FDD and TDD --- p.6Chapter 1.2.2 --- Channel Spreading --- p.6Chapter 1.2.3 --- OVSF Code Tree --- p.8Chapter 1.3 --- Cellular Concepts --- p.10Chapter 1.3.1 --- System Capacity --- p.10Chapter 1.3.2 --- Multiple Access --- p.11Chapter 1.3.3 --- Resource Management --- p.15Chapter 1.4 --- Organization of the Thesis --- p.16Chapter 2. --- Analysis on Multi-rate Operations --- p.18Chapter 2.1 --- Related Works in Multi-rate Operations --- p.18Chapter 2.1.1 --- Variable Spreading Factor --- p.19Chapter 2.1.2 --- Data Time-multiplexing --- p.20Chapter 2.1.3 --- Multi-carrier Transmission --- p.21Chapter 2.1.4 --- Hybrid TDMA/CDMA --- p.23Chapter 2.2 --- Problems in Multi-rate Operations --- p.24Chapter 2.2.1 --- Conventional CDMA --- p.24Chapter 2.2.2 --- Data Time-multiplexing --- p.25Chapter 2.2.3 --- MC-CDMA --- p.25Chapter 2.2.4 --- TD-CDMA --- p.27Chapter 2.3 --- Multi-user multi-rate Operations --- p.28Chapter 3. --- Bandwidth Allocation --- p.29Chapter 3.1 --- Most Regular Binary Sequence --- p.30Chapter 3.1.1 --- Properties of MRBS --- p.31Chapter 3.1.2 --- Construction of MRCS --- p.32Chapter 3.1.3 --- Zero-one Sequence under MRBS --- p.33Chapter 3.2 --- MRBS in TD-CDMA --- p.35Chapter 3.2.1 --- Time Slot Optimization --- p.36Chapter 3.2.2 --- Sequence Generator --- p.37Chapter 3.3 --- Most Regular Code Sequence --- p.38Chapter 3.3.1 --- Properties of MRCS --- p.38Chapter 3.2.2 --- Construction of MRCS --- p.41Chapter 3.3.3 --- Fraction-valued Sequence under MRCS --- p.42Chapter 3.3.4 --- LCC and UCC --- p.45Chapter 3.4 --- MRCS in WCDMA --- p.46Chapter 3.4.1 --- Spreading Factor Optimization --- p.46Chapter 3.4.2 --- Code Generator --- p.48Chapter 3.4.3 --- Uplink and Downlink --- p.50Chapter 4. --- Multi-access Control --- p.52Chapter 4.1 --- Conflict and Resolution --- p.53Chapter 4.1.1 --- Conflicts in MRBS and MRCS --- p.53Chapter 4.1.2 --- Resolution with Buffering --- p.55Chapter 4.2 --- MRBS Transmission Scheduling --- p.56Chapter 4.2.1 --- Slot Scheduling on MRBS --- p.56Chapter 4.2.2 --- Properties of Scheduling Algorithm --- p.59Chapter 4.2.3 --- Scheduled MRBS --- p.71Chapter 4.3 --- MRCS Transmission Scheduling --- p.73Chapter 4.3.1 --- Slot Scheduling on MRCS --- p.73Chapter 4.3.2 --- Properties of Scheduling Algorithm --- p.75Chapter 4.3.3 --- Scheduled MRBS --- p.76Chapter 4.4 --- Performance Evaluation --- p.78Chapter 4.4.1 --- Simulation on Algorithm --- p.78Chapter 4.4.2 --- Resource Utilization and Delay Bound --- p.79Chapter 4.4.3 --- Blocking Model and System Capacity --- p.80Chapter 4.4.4 --- Numerical Analysis --- p.86Chapter 5. --- Conclusions and Future works --- p.92Appendix A --- p.94Appendix B --- p.98Bibliography --- p.10

Wideband Channel Sounding Techniques for Dynamic Spectrum Access Networks

In recent years, cognitive radio has drawn extensive research attention due to its ability to improve the efficiency of spectrum usage by allowing dynamic spectrum resource sharing between primary and secondary users. The concept of cognitive radio was first presented by Joseph Mitola III and Gerald Q. Maguire, Jr., in which either network or wireless node itself changes particular transmission and reception parameters to execute its tasks efficiently without interfering with the primary users [1]. Such a transceiving mechanism and network environment is called the dynamic spectrum access (DSA) network. The Federal Communications Commission (FCC) allows any type of transmission in unlicensed bands at any time as long as their transmit power level obeys specific FCC regulations. Performing channel sounding as a secondary user in such an environment becomes a challenge due to the rapidly changing network environment and also the limited transmission power. Moreover, to obtain the long term behavior of the channel in the DSA network is impractical with conventional channel sounders due to frequent changes in frequency, transmission bandwidth, and power. Conventional channel sounding techniques need to be adapted accordingly to be operated in the DSA networks. In this dissertation, two novel channel sounding system frameworks are proposed. The Multicarrier Direct Sequence Swept Time-Delay Cross Correlation (MC-DS-STDCC) channel sounding technique is designed for the DSA networks aiming to perform channel sounding across a large bandwidth with minimal interference. It is based on the STDCC channel sounder and Multicarrier Direct Sequence Code Division Multiple Access (MC-DS-CDMA) technique. The STDCC technique, defined by Parsons [2], was first employed by Cox in the measurement of 910 MHz band [3{6]. The MC-DS-CDMA technique enables the channel sounder to be operated at different center frequencies with low transmit power. Hence, interference awareness and frequency agility are achieved. The OFDM-based channel sounder is an alternative to the MC-DS-STDCC technique. It utilizes user data as the sounding signal such that the interference is minimized during the course of transmission. Furthermore, the OFDM-based channel sounder requires lower sampling rate than the MC-DS-STDCC system since no spreading is necessary

Code-division multiplexing

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 395-404).(cont.) counterpart. Among intra-cell orthogonal schemes, we show that the most efficient broadcast signal is a linear superposition of many binary orthogonal waveforms. The information set is also binary. Each orthogonal waveform is generated by modulating a periodic stream of finite-length chip pulses with a receiver-specific signature code that is derived from a special class of binary antipodal, superimposed recursive orthogonal code sequences. With the imposition of practical pulse shapes for carrier modulation, we show that multi-carrier format using cosine functions has higher bandwidth efficiency than the single-carrier format, even in an ideal Gaussian channel model. Each pulse is shaped via a prototype baseband filter such that when the demodulated signal is detected through a baseband matched filter, the resulting output samples satisfy the Generalized Nyquist criterion. Specifically, we propose finite-length, time overlapping orthogonal pulse shapes that are g-Nyquist. They are derived from extended and modulated lapped transforms by proving the equivalence between Perfect Reconstruction and Generalized Nyquist criteria. Using binary data modulation format, we measure and analyze the accuracy of various Gaussian approximation methods for spread-spectrum modulated (SSM) signalling ...We study forward link performance of a multi-user cellular wireless network. In our proposed cellular broadcast model, the receiver population is partitioned into smaller mutually exclusive subsets called cells. In each cell an autonomous transmitter with average transmit power constraint communicates to all receivers in its cell by broadcasting. The broadcast signal is a multiplex of independent information from many remotely located sources. Each receiver extracts its desired information from the composite signal, which consists of a distorted version of the desired signal, interference from neighboring cells and additive white Gaussian noise. Waveform distortion is caused by time and frequency selective linear time-variant channel that exists between every transmitter-receiver pair. Under such system and design constraints, and a fixed bandwidth for the entire network, we show that the most efficient resource allocation policy for each transmitter based on information theoretic measures such as channel capacity, simultaneously achievable rate regions and sum-rate is superposition coding with successive interference cancellation. The optimal policy dominates over its sub-optimal alternatives at the boundaries of the capacity region. By taking into account practical constraints such as finite constellation sets, frequency translation via carrier modulation, pulse shaping and real-time signal processing and decoding of finite-length waveforms and fairness in rate distribution, we argue that sub-optimal orthogonal policies are preferred. For intra-cell multiplexing, all orthogonal schemes based on frequency, time and code division are equivalent. For inter-cell multiplexing, non-orthogonal code-division has a larger capacity than its orthogonalby Ceilidh Hoffmann.Ph.D