Parallel Soft Spherical Detection for Coded MIMO Systems

This Chapter briefly evaluates different multiple-input multiple-output (MIMO) detection techniques in the literature as the candidates for the next generation wireless systems. The authors evaluate the associated problems and solutions with these methods. The focus of the chapter is on two categories of MIMO decoding: i) hard detection and ii) soft detection. These techniques significantly increase the capacity of wireless communications systems. Theoretically, a-posteriori probability (APP) MIMO decoder with soft information can achieve the capacity of a MIMO system. A sub-optimum APP detector is proposed for iterative joint detection/decoding in a MIMO wireless communication system employing an outer code. The proposed detector searches inside a given sphere in a parallel manner to simultaneously find a list of m-best points based on an additive metric. The metric is formed by combining the channel output and the a-priori information. The parallel structure of the proposed method is suitable for hardware parallelization. The radius of the sphere and the value of m are selected according to the channel condition to reduce the complexity. Numerical results are provided showing a significant reduction in the average complexity (for a similar performance and peak complexity) as compared to the best earlier known method. This positions the proposed algorithm as a candidate for the next generation wireless systems. The proposed scheme is applied for the decoding of the rate 2, 4 × 2 MIMO code employed in the IEEE 802.16e standard.

Wireless Collaboration

To achieve performance gains in the wireless channel, spatial diversity is employed. These higher order transmit diversity gains generally require multiple transmit antennas at the source. This requirement is not always possible in real world applications, where practical concerns limit the number of antennas a wireless device can have. Recently, a new method to achieve transmit diversity has been proposed: collaborative communications. In this framework, a node in a wireless network can use the resources of other idle nodes and form what can be viewed as a virtual transmitting antenna array. This chapter presents an overview of the development of collaborative communications. Two-phase protocols that can achieve collaboration are presented. A discussion on the improvement of collaborative communications protocols is given. A broader perspective of collaborative communications is given by discussing ideas such as power allocation and multiple relays.

Capacity Estimation of OFDMA-Based Wireless Cellular Networks

The usage of wireless cellular network architecture increases the capacity of a wireless system, by combining cells into clusters in which channels are uniquely assigned per cell and reusing such clusters throughout the network. Unfortunately, a cellular network system may become interference limited regarding its capacity instead of noise/range limited due to intensive resources reuse like time, frequency and space. Using as input the physical layer parameters and deployment scenario, an analytical approach is proposed for capacity estimation of networks based on Orthogonal Frequency Division Multiple Access (OFDMA) technology whose subchannels are composed of distributed subcarriers. This innovative approach is based on a new analytical method for SINR calculation based on a proposed subcarrier collision probability model. The usage of such method is exemplified for a single-hop sectorized Mobile WiMAX cellular network and the results are validated against published works.

Configurable and Scalable Turbo Decoder for 4G Wireless Receivers

The increasing requirements of high data rates and quality of service (QoS) in fourth-generation (4G) wireless communication require the implementation of practical capacity approaching codes. In this chapter, the application of Turbo coding schemes that have recently been adopted in the IEEE 802.16e WiMax standard and 3GPP Long Term Evolution (LTE) standard are reviewed. In order to process several 4G wireless standards with a common hardware module, a reconfigurable and scalable Turbo decoder architecture is presented. A parallel Turbo decoding scheme with scalable parallelism tailored to the target throughput is applied to support high data rates in 4G applications. High-level decoding parallelism is achieved by employing contention-free interleavers. A multi-banked memory structure and routing network among memories and MAP decoders are designed to operate at full speed with parallel interleavers. A new on-line address generation technique is introduced to support multiple Turbo interleaving patterns, which avoids the interleaver address memory that is typically necessary in the traditional designs. Design trade-offs in terms of area and power efficiency are analyzed for different parallelism and clock frequency goals.

Aspects of OFDM-Based 3G LTE Terminal Implementation

3GPP standardized an evolved UTRAN (E-UTRAN) within the release 8 Long Term Evolution (LTE) project. Targets include higher spectral efficiency, lower latency, and higher peak data rate in comparison with previous 3GPP air interfaces. The E-UTRAN air interface is based on OFDMA and MIMO in downlink and on SCFDMA in uplink. Main challenges for a terminal implementation include an efficient realization of fast and precise synchronization, MIMO channel estimation and equalization, and a turbo decoder for data rates of up to 75 Mbps per spatial MIMO stream. In this study, the authors outline the current 3GPP LTE standard and highlight some implementation details of an LTE terminal. Efficient sample algorithms are presented for key components in the baseband signal processing including synchronization, cell search, channel estimation and equalization, and turbo channel decoder. Their performances, computational and memory requirements, and relevant implementation challenges are discussed.

Cross-Layer Joint Optimization of Multimedia Transmissions over IP Based Wireless Networks

The traditional approach consisting in separately optimizing each module of a transmission chain has shown limitations in the case of wireless communications where delay, power limitation and error-prone channels are experienced. This is why modern designers focus on a more integrated strategy to establish the heterogeneous 21st century networks, such as 3G (i.e. UMTS) system and its evolutions (i.e. Beyond 3G or 4G like LTE or future 5G systems). Indeed, it was shown in several studies that optimal allocation of user and system resources could be effectively achieved with the co-operative optimization of communication system components. In this chapter, an innovative Joint-Source Channel Coding and Decoding (JSCC/D) system is described and its performance over an IPv6-based Network infrastructure is assessed. A particular focus is put on the application controller, the key component to realize the adaptation strategies. Conclusions and considerations about the system implementation are also proposed, and the interest of a possible extension to a point-to-multipoint scenario is explained.

A New Approach to BSOFDM

This chapter discusses a new concept for Block Spread OFDM called Parallel Concatenated Spreading matrices OFDM (PCSM-OFDM) which was first presented in (Raad, I. and Huang, X. 2007). While BSOFDM improved the overall BER performance on OFDM in frequency selective channels, this new approach further improves the BER of BSOFDM by over 3dB gain. This uses coding gain to achieve this and is similar in concept to the well known error correction codes Turbo Codes. This is done by copying the data at the transmitter n times in parallel and multiplexing.

Survey of Cross-Layer Optimization Techniques for Wireless Networks

The explosive development of Internet and wireless communication has made personal communication more convenient. People can use a handy wireless device to transfer different kinds of data such as voice data, text data, and multimedia data. Multimedia streaming, video conferencing, and on-line interactive 3D games are expected to attract an increasing number of users in the future. The bandwidth requirement would be high and the heterogeneous terminals would generally provide limited resource, such as low processing power, low battery life and limited data rate capabilities. These applications would be the major challenge for wireless networks. Although the traditional layered protocol stacks have been used for many years, they are not suitable for the next generation wireless networks and the mobile systems. Due to the time varying transmission of the wireless channel and the dynamic resource requirements of different application, the traditional layered approach to the mobile multimedia communication is full of challenges to meet the user requirement on performance and efficiency. Cross-layer design is an interesting research topic that actively exploits the dependence between different protocol layers to obtain performance gains. The authors performed a survey and introduced the cross-layer design principles and issues for different research topics, including QoS, mobility, security, application, and the next generation wireless communication.

An End-to-End QoS Framework for Vehicular Mobile Networks

In recent years we have witnessed a great demand for high speed Internet access in vehicular environment, e.g., trains, buses and medical transport. This chapter introduces an integrated architecture for 4G vehicular mobile networks, which aims to guarantee high quality in provisioned triple-play traffic services (video, voice, and data) to road users. Within this architecture which is based on a cross layer design approach, our contributions can be described in three folds. Firstly, the authors introduce simple and efficient probing mechanisms which are integrated with network resource reservation policies for multihomed vehicular networks. Secondly, packet, flow and user splitting mechanisms have been integrated with end admission traffic control and scheduling mechanisms to guarantee even traffic load distribution among available air interfaces. Finally, the whole architecture has been evaluated under OMNeT++, where results illustrate the impact of network mobility on quality in provisioned services offered to a multihomed NEMO.