Design and implementation of an OFDMA-TDD physical layer for WiMAX applications

[Abstract]: This work describes the design, implementation, and performance evaluation of an orthogonal frequency division multiple access (OFDMA) time-division duplexing (TDD) physical layer (PHY) compliant with the worldwide interoperability for microwave access (WiMAX) standard using a costeffective software-defined radio (SDR) platform containing field programmable gate array (FPGA) and digital signal processor (DSP) modules. We show that the proposed SDR architecture is capable of supporting the wide variety of configuration options described in the WiMAX standard while fulfilling the stringent requirements of WiMAX OFDMA TDD PHYs. The architecture allows for the implementation of all TDD functionalities in the downlink and the uplink at both the base station and the mobile station. The proposed design is shown to efficiently use the available FPGA and DSP resources. We also carried out specific experiments that take into account the frame and the downlink map messages detection over ITU-R wireless channel models to illustrate the performance of the proposed design. Finally, we discuss the utilization of the proposed hardware architecture to implement the wirelessMAN-advanced air interface.This work has been partially supported by Indra Sistemas S.A., the Spanish Ministry of Defence with the technical direction of PEC/ITM under grant DN8644-COINCIDENTE, MINECO of Spain under grant TEC2010-19545-C04-01 and Xunta de Galicia, Spain, under grant 2012/287. The authors wish to thank J. M. Camas-Albar from Indra Sistemas S.A. for his help.Xunta de Galicia; 2012/28

Real-time validation of a SDR implementation of TDD WiMAX standard

[Abstract]: This paper focuses on the validation of an innovative software- defined radio architecture for a WiMAX system based on commercially available field-programmable gate array and digital signal processor modules. We provide a realtime implementation of a standard-compliant time-division duplex physical layer including a mobile and a base station as well as downlink and uplink communications, thus obtaining a full-featured physical layer. Additionally, a set of different configurations are supported as described in the standard and in the WiMAX Forum. The main contribution of the paper consists in a reproducible and repeatable validation of the implementation in representative scenarios. At the same time, a characterization of the performance exhibited by the system is provided based on bit error rate measurements carried out using a custom-made, real-time channel emulator.This work has been partially supported by Indra Sistemas S.A. and the Spanish Ministry of Defence with the technical direction of PEC/ITM under grant DN8644-COINCIDENTE. The authors wish to thank J. M. Camas- Albar from Indra Sistemas S.A. for his help. This work has been additionally funded by Xunta de Galicia, Ministerio de Ciencia e Innovación of Spain, and FEDER funds of the European Union under grants with numbers 10TIC003CT, 09TIC008105PR, TEC2010-19545- C04-01, and CSD2008-00010.Xunta de Galicia; 10TIC003CTXunta de Galicia; 09TIC008105P

Random Access in Uplink Massive MIMO Systems: How to exploit asynchronicity and excess antennas

Massive MIMO systems, where the base stations are equipped with hundreds of antennas, are an attractive way to handle the rapid growth of data traffic. As the number of users increases, the initial access and handover in contemporary networks will be flooded by user collisions. In this work, we propose a random access procedure that resolves collisions and also performs timing, channel, and power estimation by simply utilizing the large number of antennas envisioned in massive MIMO systems and the inherent timing misalignments of uplink signals during network access and handover. Numerical results are used to validate the performance of the proposed solution under different settings. It turns out that the proposed solution can detect all collisions with a probability higher than 90%, at the same time providing reliable timing and channel estimates. Moreover, numerical results demonstrate that it is robust to overloaded situations.Comment: submitted to IEEE Globecom 2016, Washington, DC US

A Real-Time Implementation of the Mobile WiMAX ARQ and Physical Layer

This version of the article has been accepted for publication, after peer review and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: https://doi.org/10.1007/s11265-014-0890-3.[Abstract] This paper presents an innovative software-defined radio architecture for the real-time implementation of WiMAX transceivers. The architecture consists of commercially available field-programmable gate array and digital signal processor modules. We show how the architecture can be used for the real-time implementation of a full-featured standard-compliant time-division duplex WiMAX physical layer together with the ARQ functionality of the MAC layer. Both the mobile and the base station contain a transmitter and a receiver to enable real-time concurrent downlink and uplink communications. The design supports the different configurations defined by the standard and the WiMAX Forum. This work also provides the verification and validation of the proposed real-time implementation based on repeatable and reproducible performance evaluation considering the reference scenarios defined by the WiMAX Forum, including both static and mobile scenarios. Typical figures of merit such as physical-layer bit and frame error rates and MAC-layer throughput are obtained with the help of a custom-made real-time channel emulator implementing the channel models defined by the WiMAX Forum.This work has been partially supported by Indra Sistemas S.A. and the Spanish Ministry of Defence with the technical direction of PEC/ITM under grant DN8644-COINCIDENTE. The authors wish to thank J. M. Camas-Albar from Indra Sistemas S.A. for his help. This work has been additionally funded by Xunta de Galicia, Ministerio de Ciencia e Innovacin of Spain, and FEDER funds of the European Union under grants with numbers 2012/287, TEC2010-19545-C04-01, and CSD2008-00010.Xunta de Galicia; 2012/28

Handover analysis over mobile WiMAX technology.

As new mobile devices and mobile applications continue to growth, so does the data traffic demand for broadband services access and the user needs toward mobility, thereby, wireless application became today the fastest solution and lowest cost implementation unlike traditional wired deployment such as optical fibers and digital lines. WiMAX technology satisfies this gap through its high network performance over the air interface and high data rates based on the IEEE 802.16-2004 standards, this original specification does not support mobility. Therefore, the IEEE introduces a new standard that enables mobility profiles under 802.16e-2005, from which three different types of handovers process are introduced as hard handover (HHO), macro diversity handover (MDHO) and fast base station switching (FBSS) handover. The objective of this master thesis is to analyze how the handover process affects network performance. The analysis propose three scenarios, built over OPNET simulator to measure the most critical wireless parameter and performance indicator such as throughput, handover success rate, packet drop, delay and network usage.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

WiMAX: Performance Analysis and Enhancement of Real-time Bandwidth Request

This paper carried out a study on the bandwidth request for real-time polling services. In our study, we discovered that although the base station granted the subscriber station an allocation to send the bandwidth request, the subscriber station may not be able to allocate the bandwidth request to the allocation. It is due to processing delay and multicast polling in the subscriber station, which results the bandwidth request being padded unintentionally. The loss of bandwidth requests will cause the degradation of the real-time polling service performance. Therefore, we propose a scheme to overcome this problem. The results of the experiment show that the proposed scheme improves the performance of real-time polling services

Multi-User Ranging Code Detection in OFDMA System Using MMLD Algorithm for Improving Detection Performance

Successive user detection algorithm is used to observe the multi user ranging signals and calculate there corresponding parameters. Using IEEE 802.16 specification in Orthogonal Frequency Division Multiple Access (OFDMA), initial ranging method designed an algorithm called Moment Maximum Likelihood Detection (MMLD) to detect the codes assigned and predicting offset timing. The objective function which is derived from the Expectation Maximization (EM) algorithm is used in the MMLD to cancel the channel estimation errors and Multiple Access Interference (MAI). To reduce the MAI over the iteration, the Maximum Likelihood Estimation (MLE) algorithm is designed in the MMLD. The experimental results indicate that the system is highly accurate

Improved random channel access for OFDMA wireless networks

In this paper we propose a new random channel access protocol to reduce the channel access delay in a multichannel orthogonal frequency division multiple access (OFDMA) wireless networks. In particular, we propose a two dimensional random walk through time and frequency domain slots simultaneously to reduce the random channel access delay for the IEEE 802.16e-2005 based WiMAX media access control (MAC) protocol. We prove through simulation that our proposed scheme improves upon the existing random channel access mechanism with truncated binary back-off, currently implemented in WiMAX. We demonstrated that with our proposed channel access mechanism, a mobile node with real time traffic requirements will have minimum service disruption due to the reduced delay in the initial ranging and the bandwidth request phase while changing rooms