ALOHA With Collision Resolution(ALOHA-CR): Theory and Software Defined Radio Implementation

A cross-layer scheme, namely ALOHA With Collision Resolution (ALOHA-CR), is proposed for high throughput wireless communications in a cellular scenario. Transmissions occur in a time-slotted ALOHA-type fashion but with an important difference: simultaneous transmissions of two users can be successful. If more than two users transmit in the same slot the collision cannot be resolved and retransmission is required. If only one user transmits, the transmitted packet is recovered with some probability, depending on the state of the channel. If two users transmit the collision is resolved and the packets are recovered by first over-sampling the collision signal and then exploiting independent information about the two users that is contained in the signal polyphase components. The ALOHA-CR throughput is derived under the infinite backlog assumption and also under the assumption of finite backlog. The contention probability is determined under these two assumptions in order to maximize the network throughput and maintain stability. Queuing delay analysis for network users is also conducted. The performance of ALOHA-CR is demonstrated on the Wireless Open Access Research Platform (WARP) test-bed containing five software defined radio nodes. Analysis and test-bed results indicate that ALOHA-CR leads to significant increase in throughput and reduction of service delays

WARP, a UnifiedWireless Network Testbed for Education and Research

In this paper, we introduce the Wireless Open-Access Research Platform (WARP) developed at CMC lab, Rice University. WARP provides a scalable and configurable platform mainly designed to prototype wireless communication algorithms for educational and research oriented applications. Its programmability and flexibility makes it easy to implement various physical and network layer protocols and standards. Moreover, the online open-access WARP repository is used to document and share different wireless architectures and cross-layer designs developed at educational and research centers. This repository is a fast and easy solution for students and researchers with a wide range of backgrounds in hardware implementation and algorithm development to collaborate and initiate multi-disciplinary system designs.Nokia CorporationXilinx Inc.National Science Foundatio

An FPGA implementation of OFDM transceiver for LTE applications

The paper presents a real-time transceiver using an Orthogonal Frequency-Division Multiplexing (OFDM) signaling scheme. The transceiver is implemented on a Field- Programmable Gate Array (FPGA) through Xilinx System Generator for DSP and includes all the blocks needed for the transmission path of OFDM. The transmitter frame can be reconfigured for different pilot and data schemes. In the receiver, time-domain synchronization is achieved thr ough a joint maximum likelihood (ML) symbol arrival-time and carrier frequency offset (CFO) estimator through the redundant information contained in the cyclic prefix (CP). A least-squares channel estimation retrieves the channel state information and a simple zero-forcing scheme has been implemented for channel equalization. Results show that a rough implementation of the signal path can be impleme nted by using only Xilinx System Generator for DSP

Implementation of a High Throughput Soft MIMO Detector on GPU

Multiple-input multiple-output (MIMO) significantly increases the throughput of a communication system by employing multiple antennas at the transmitter and the receiver. To extract maximum performance from a MIMO system, a computationally intensive search based detector is needed. To meet the challenge of MIMO detection, typical suboptimal MIMO detectors are ASIC or FPGA designs. We aim to show that a MIMO detector on Graphic processor unit (GPU), a low-cost parallel programmable co-processor, can achieve high throughput and can serve as an alternative to ASIC/FPGA designs. However, careful architecture aware software design is needed to leverage the performance offered by GPU. We propose a novel soft MIMO detection algorithm, multi-pass trellis traversal (MTT), and show that we can achieve ASIC/FPGA-like performance and handle different configurations in software on GPU. The proposed design can be used to accelerate wireless physical layer simulations and to offload MIMO detection processing in wireless testbed platforms.NokiaNokia Siemens Networks (NSN)Texas InstrumentsXilinxNational Science Foundatio

Building Programmable Wireless Networks: An Architectural Survey

In recent times, there have been a lot of efforts for improving the ossified Internet architecture in a bid to sustain unstinted growth and innovation. A major reason for the perceived architectural ossification is the lack of ability to program the network as a system. This situation has resulted partly from historical decisions in the original Internet design which emphasized decentralized network operations through co-located data and control planes on each network device. The situation for wireless networks is no different resulting in a lot of complexity and a plethora of largely incompatible wireless technologies. The emergence of "programmable wireless networks", that allow greater flexibility, ease of management and configurability, is a step in the right direction to overcome the aforementioned shortcomings of the wireless networks. In this paper, we provide a broad overview of the architectures proposed in literature for building programmable wireless networks focusing primarily on three popular techniques, i.e., software defined networks, cognitive radio networks, and virtualized networks. This survey is a self-contained tutorial on these techniques and its applications. We also discuss the opportunities and challenges in building next-generation programmable wireless networks and identify open research issues and future research directions.Comment: 19 page

Implementations of Multi-Antenna Systems in a USRP Based SDR using Simulink

Software Radio systems are one of the most versatile and cost effective systems for pro- totyping communications techniques in use today. Through the use of minimal hardware, typically only an RF front end, an SDR allows for as much of the signal processing as possible to be done via software. The benefits of utilizing software for signal processing in place of hardware are numerous. In some cases, like this work, parameters of operation may need to be dynamic or the objective of the work is academic research of new techniques. In some cases like these, swapping out costly signal processing hardware for signal processing software makes more sense. Additionally, the use of multi-antenna systems is becoming more and more common. In mid-2011, Mathworks released support for standard SISO (single input, single output) communications with the NI USRP (National Instruments Universal Software Radio Peripheral) but has yet to release support for any SIMO, MISO, or MIMO applications. In this work, we produce a testbed for proof of SIMO concepts and performance improvements in MATLAB and Simulink along with outlining preliminary work in implementing the MISO method of Alamouti STBC. The processes used to implement the discussed techniques will be outlined and discussed including results from testing with the USRPs in Simulink