Frequency Domain Hybrid-ARQ Chase Combining for Broadband MIMO CDMA Systems

In this paper, we consider high-speed wireless packet access using code division multiple access (CDMA) and multiple-input multiple-output (MIMO). Current wireless standards, such as high speed packet access (HSPA), have adopted multi-code transmission and hybrid-automatic repeat request (ARQ) as major technologies for delivering high data rates. The key technique in hybrid-ARQ, is that erroneous data packets are kept in the receiver to detect/decode retransmitted ones. This strategy is refereed to as packet combining. In CDMA MIMO-based wireless packet access, multi-code transmission suffers from severe performance degradation due to the loss of code orthogonality caused by both interchip interference (ICI) and co-antenna interference (CAI). This limitation results in large transmission delays when an ARQ mechanism is used in the link layer. In this paper, we investigate efficient minimum mean square error (MMSE) frequency domain equalization (FDE)-based iterative (turbo) packet combining for cyclic prefix (CP)-CDMA MIMO with Chase-type ARQ. We introduce two turbo packet combining schemes: i) In the first scheme, namely "chip-level turbo packet combining", MMSE FDE and packet combining are jointly performed at the chip-level. ii) In the second scheme, namely "symbol-level turbo packet combining", chip-level MMSE FDE and despreading are separately carried out for each transmission, then packet combining is performed at the level of the soft demapper. The computational complexity and memory requirements of both techniques are quite insensitive to the ARQ delay, i.e., maximum number of ARQ rounds. The throughput is evaluated for some representative antenna configurations and load factors to show the gains offered by the proposed techniques.Comment: Submitted to IEEE Transactions on Vehicular Technology (Apr 2009

Enhanced Wireless Access Technologies and Experiments for W-CDMA Communications

This article reviews enhanced wireless access technologies and experimental evaluations of the wideband DS-CDMA physical layer employing intercell asynchronous operation with a three-step fast cell search method, pilot symbol-assisted coherent links, signal-to-interference plus background noise power ratio-based fast transmit power control, site diversity (soft/softer handover), and transmit diversity in the forward link. The article also presents link-capacity-enhancing techniques such as using an interference canceller and adaptive antenna array diversity receiver/transmitter, and experimental results in a real multipath fading channel. The laboratory and field experiments exemplify superior techniques of the W-CDMA physical layer and the potential of the IC and AAAD transceiver to decrease the mobile transmit power in the reverse link and multipath interference from high-rate users with large transmit power in the forward link

Efficient Radio Resource Allocation Schemes and Code Optimizations for High Speed Downlink Packet Access Transmission

An important enhancement on the Wideband Code Division Multiple Access (WCDMA) air interface of the 3G mobile communications, High Speed Downlink Packet Access (HSDPA) standard has been launched to realize higher spectral utilization efficiency. It introduces the features of multicode CDMA transmission and Adaptive Modulation and Coding (AMC) technique, which makes radio resource allocation feasible and essential. This thesis studies channel-aware resource allocation schemes, coupled with fast power adjustment and spreading code optimization techniques, for the HSDPA standard operating over frequency selective channel. A two-group resource allocation scheme is developed in order to achieve a promising balance between performance enhancement and time efficiency. It only requires calculating two parameters to specify the allocations of discrete bit rates and transmitted symbol energies in all channels. The thesis develops the calculation methods of the two parameters for interference-free and interference-present channels, respectively. For the interference-present channels, the performance of two-group allocation can be further enhanced by applying a clustering-based channel removal scheme. In order to make the two-group approach more time-efficient, reduction in matrix inversions in optimum energy calculation is then discussed. When the Minimum Mean Square Error (MMSE) equalizer is applied, optimum energy allocation can be calculated by iterating a set of eigenvalues and eigenvectors. By using the MMSE Successive Interference Cancellation (SIC) receiver, the optimum energies are calculated recursively combined with an optimum channel ordering scheme for enhancement in both system performance and time efficiency. This thesis then studies the signature optimization methods with multipath channel and examines their system performances when combined with different resource allocation methods. Two multipath-aware signature optimization methods are developed by applying iterative optimization techniques, for the system using MMSE equalizer and MMSE precoder respectively. A PAM system using complex signature sequences is also examined for improving resource utilization efficiency, where two receiving schemes are proposed to fully take advantage of PAM features. In addition by applying a short chip sampling window, a Singular Value Decomposition (SVD) based interference-free signature design method is presented

Coded Parity Packet Transmission Method for Two Group Resource Allocation

Gap value control is investigated when the number of source and parity packets is adjusted in a concatenated coding scheme whilst keeping the overall coding rate fixed. Packet-based outer codes which are generated from bit-wise XOR combinations of the source packets are used to adjust the number of both source packets. Having the source packets, the number of parity packets, which are the bit-wise XOR combinations of the source packets can be adjusted such that the gap value, which measures the gap between the theoretical and the required signal-to-noise ratio (SNR), is controlled without changing the actual coding rate. Consequently, the required SNR reduces, yielding a lower required energy to realize the transmission data rate. Integrating this coding technique with a two-group resource allocation scheme renders efficient utilization of the total energy to further improve the data rates. With a relatively small-sized set of discrete data rates, the system throughput achieved by the proposed two-group loading scheme is observed to be approximately equal to that of the existing loading scheme, which is operated with a much larger set of discrete data rates. The gain obtained by the proposed scheme over the existing equal rate and equal energy loading scheme is approximately 5 dB. Furthermore, a successive interference cancellation scheme is also integrated with this coding technique, which can be used to decode and provide consecutive symbols for inter-symbol interference (ISI) and multiple access interference (MAI) mitigation. With this integrated scheme, the computational complexity is signi cantly reduced by eliminating matrix inversions. In the same manner, the proposed coding scheme is also incorporated into a novel fixed energy loading, which distributes packets over parallel channels, to control the gap value of the data rates although the SNR of each code channel varies from each other

Coded Parity Packet Transmission Method for Two Group Resource Allocation

Gap value control is investigated when the number of source and parity packets is adjusted in a concatenated coding scheme whilst keeping the overall coding rate fixed. Packet-based outer codes which are generated from bit-wise XOR combinations of the source packets are used to adjust the number of both source packets. Having the source packets, the number of parity packets, which are the bit-wise XOR combinations of the source packets can be adjusted such that the gap value, which measures the gap between the theoretical and the required signal-to-noise ratio (SNR), is controlled without changing the actual coding rate. Consequently, the required SNR reduces, yielding a lower required energy to realize the transmission data rate. Integrating this coding technique with a two-group resource allocation scheme renders efficient utilization of the total energy to further improve the data rates. With a relatively small-sized set of discrete data rates, the system throughput achieved by the proposed two-group loading scheme is observed to be approximately equal to that of the existing loading scheme, which is operated with a much larger set of discrete data rates. The gain obtained by the proposed scheme over the existing equal rate and equal energy loading scheme is approximately 5 dB. Furthermore, a successive interference cancellation scheme is also integrated with this coding technique, which can be used to decode and provide consecutive symbols for inter-symbol interference (ISI) and multiple access interference (MAI) mitigation. With this integrated scheme, the computational complexity is signi cantly reduced by eliminating matrix inversions. In the same manner, the proposed coding scheme is also incorporated into a novel fixed energy loading, which distributes packets over parallel channels, to control the gap value of the data rates although the SNR of each code channel varies from each other

IST-2000-30148 I-METRA: D3.1 Design, analysis and selection of suitable algorithms

This deliverable contains a description of the space-time coding algorithms to be simulated within the I-METRA project. Different families of algorithms have been selected and described in this document with the objective of evaluating their performance. One of the main objectives of the I-METRA project is to impact into the current standardisation efforts related to the introduction of Multiple Input Multiple Output (MIMO) configurations into the High Speed Downlink and Uplink Packet Access concepts of UMTS (HSDPA and HSUPA). This required a review of the current specifications for these systems and the analysis of the impact of the potential incorporation of the selected MIMO schemes.Preprin

The new enhancement of UMTS: HSDPA and HSUPA

During the last two decades, the world of the mobile communications grew a lot, as a consequence of the increasing necessity of people to communicate. Now, the mobile communications still need to improve for satisfies the user demands. The new enhancement of UMTS in concrete HSDPA and HSUPA is one of these improvements that the society needs. HSDPA and HSUPA which together are called HSPA, give to the users higher data rates in downlink and uplink. The higher data rates permit to the operators give more different types of services and at the same time with better quality. As a result, people can do several new applications with their mobile terminals like applications that before a computer and internet connection were required, now it is possible to do directly with the mobile terminal. This thesis consists in study these new technologies denominated HSDPA and HSUPA and thus know better the last tendencies in the mobile communications. Also it has a roughly idea about the future tendencies

Coding schemes for multicode CDMA systems.

Zhao Fei.Thesis (M.Phil.)--Chinese University of Hong Kong, 2003.Includes bibliographical references (leaves 87-89).Abstracts in English and Chinese.Chapter 1. --- Introduction --- p.1Chapter 1.1 --- Multirate Scheme --- p.2Chapter 1.1.1 --- VSF Scheme --- p.3Chapter 1.1.2 --- Multicode Scheme --- p.5Chapter 1.2 --- Multicode CDMA System --- p.7Chapter 1.2.1 --- System Model --- p.7Chapter 1.2.2 --- Envelope Variation of Multicode Signal --- p.9Chapter 1.2.3 --- Drawback of Multicode Scheme --- p.11Chapter 1.3 --- Organization of the Thesis --- p.13Chapter 2. --- Related Work on Minimization of PAP of Multicode CDMA --- p.15Chapter 2.1 --- Constant Amplitude Coding --- p.16Chapter 2.2 --- Multidimensional Multicode Scheme --- p.22Chapter 2.3 --- Precoding for Multicode Scheme --- p.25Chapter 2.4 --- Summary --- p.26Chapter 3. --- Multicode CDMA System with Constant Amplitude Transmission --- p.27Chapter 3.1 --- System Model --- p.28Chapter 3.2 --- Selection of Hadamard Code Sequences --- p.31Chapter 3.3 --- The Optimal Receiver for the Multicode System --- p.37Chapter 3.3.1 --- The Maximum-Likelihood Sequence Detector --- p.38Chapter 3.3.2 --- Maximum A Posteriori Probability Detector --- p.41Chapter 4. --- Multicode CDMA System Combined with Error-Correcting Codes --- p.45Chapter 4.1 --- Hamming Codes --- p.46Chapter 4.2 --- Gallager's Codes --- p.48Chapter 4.2.1 --- Encoding of Gallager's Codes --- p.48Chapter 4.2.2 --- Multicode Scheme combined with Gallager's Code --- p.52Chapter 4.2.3 --- Iterative Decoding of the Multicode Scheme --- p.55Chapter 4.3 --- Zigzag Codes --- p.59Chapter 4.4 --- Simulation Results and Discussion --- p.62Chapter 5. --- Multicode CDMA System with Bounded PAP Transmission --- p.68Chapter 5.1 --- Quantized Multicode Scheme --- p.69Chapter 5.1.1 --- System Model --- p.69Chapter 5.1.2 --- Interference of Code Channels --- p.71Chapter 5.2 --- Parallel Multicode Scheme --- p.74Chapter 5.2.1 --- System Model --- p.74Chapter 5.2.2 --- Selection of Hadamard Code Sequences --- p.75Chapter 6. --- Conclusions and Future Work --- p.82Chapter 6.1 --- Conclusions --- p.82Chapter 6.2 --- Future Work --- p.84Bibliography --- p.8