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This article analyzes security vulnerabilities in bandwidth allocation and request mechanisms that are specified in the IEEE 802.16 Standard, and introduces a bandwidth request adversary model called UL-BRA based on these vulnerabilities. The goal of UL-BRA is to abuse the bandwidth request/grant operation of a WiMAX network, resulting in a significant decrease of the overall uplink transmission performance of the network. To overcome the challenge caused by the vulnerabilities of the standard, we propose a security patch incorporating a real-time anomaly detection and restoration (RADR) mechanism, which combines an MCDR scheme with an ATD scheme in order to eliminate the impacts of UL-BRA in real-time. We verify the effectiveness of RADR under UL-BRA threats via simulations, and demonstrate the effectiveness of the proposed patch in mitigating the threats of UL-BRA. [ABSTRACT FROM PUBLISHER]

In IEEE 802.16 specifications, a CRC field can be attached in the rear of a WiMAX MPDU. Thus, each intermediate node (relay node or base station) in an 802.16-based multihop network can perform error detection on a received WiMAX MPDU. On the sender, the ARQ mechanism will be enabled to retransmit the MPDU if a transmission error occurs and an ACK message cannot be received. However, the ARQ mechanism is unsuitable for real-time traffic due to the delay consideration and the CRC field becomes an option to reduce the overhead of a WiMAX MPDU. Once the CRC field is removed from a WiMAX MPDU, the error occurrence cannot be detected by the intermediate nodes in time, and the erroneous data is still forwarded in the network but discarded by the destination. The resources of nodes in a network are wasted. Hence, the error detection mechanism should be retained for real-time traffic, but the overhead of CRC should be reduced. In this paper, we study an efficient discrete-error-checking scheme (DECS) to reduce the CRC overhead for real-time traffic. The DECS only needs several CRC checking bits, which are attached behind some WiMAX MPDUs. The DECS can efficiently provide the error detection for the intermediate nodes to discard these erroneous and useless data early. Thus, the utilization of node resources and wireless bandwidth can be improved significantly. [ABSTRACT FROM AUTHOR]

WiMAX network services cannot generally be provided for special purpose devices such as credit card systems and surveillance systems since they are designed to operate only with WCM which should be installed on personal computer/smart card (PC/SC) with Windows platform. In this paper, we propose a design and implementation technique called tiny- WiMAX Connection Manager (t- WCM) for non-PC/SC WCM to provide WiMAX services to special purpose devices. The t- WCM is composed mainly of three units; WiMAX module Control Unit (WCU), Data Surveillance Unit (DSU), and External device Program Unit (EPU). It also has TCP/IP protocol stack and RTOS kernel, and performs data transmission between external end user `s device and remote server system over WiMAX networks. For the performance evaluation of the proposed t- WCM, we have implemented the t- WCM and tested it under a commercial mobile WiMAX network environment. From the experimental results, the t- WCM is verified to show almost equal stability and delay performances with the legacy WCM and xDSL, and especially better than 1xEV-DO. As a result, it has a strong possibility to apply the t- WCM to many types of special purpose embedded systems, and consequently to provide various WiMAX network services to them. [ABSTRACT FROM AUTHOR]

To support fast and efficient handovers in mobile WIMAX, we propose Fast Intra-Network and Cross-layer Handover (FINCH) for intradomain (intra-CSN) mobility management. FINCH is a complementary protocol to Mobile IP (MIP), which deals with interdomain (inter-CSN) mobility management in mobile WiMAX. FINCH can reduce not only the handover latency but also the end-to- end latency for MIP. Paging extension for FINCH is also proposed to enhance the energy efficiency. The proposed FINCH is especially suitable for real-time services in frequent handover environment, which is important for future mobile WiMAX networks. In addition, FINCH is a generic protocol for other IEEE 802-series standards. This is especially beneficial for the integration of heterogeneous networks, for instance, the integration of WiMAX and WiFi networks. Both mathematical analysis and simulation are developed to analyze and compare the performance of FINCH with other protocols. The results show that FINCH can support fast and efficient link layer and intradomain handovers. The numerical results can also be used to select proper network configurations. [ABSTRACT FROM AUTHOR]

The IEEE 802.16e World Interoperability for Microwave Access (WiMax) system plays an important role in the future wireless metropolilan area network (WMAN). Orthogonal frequency division multiple access (OFDMA), adopted in the IEEE 802.16e WiMax system, has many advantages in the physical layer and also poses many challenges for radio resource allocation. One of interesting radio resource allocation issue in the OFDMA system is to partition the overall radio resource (bandwidth and time duration) into two portions: one for random access and the other for connection-oriented access. In the IEEE 802.16e WiMax system, a truncated binary back-off algorithm is adopted to resolve the contention in random access, while the time-division OFDMA is used for the connection-oriented access. The main contribution of this paper is to design an analytical approach to determine the optimal amount of reserved radio resource in both time and frequency domains for random access, with the objective of maximizing the overall efficiency of radio resource while satisfying the delay requirements for supporting real-time services. Furthermore, an analytical model for calculating the access latency and the efficiency of the reserved radio resources is developed. [ABSTRACT FROM AUTHOR]

The IEEE 802.16 standard for wireless metropolitan area networks (WMANs) is defined to meet the need for wide-range broadband wireless access at low cost. The objective of this paper is to study how to exploit spectral reuse in re- source allocation in an IEEE 802.16 mesh network, which includes routing tree construction (RTC), bandwidth allocation, time-slot assignment, and bandwidth guarantee of real-time flows. The proposed spectral reuse framework covers bandwidth allocation at the application layer, RTC and resource sharing at the medium access control (MAC) layer, and channel reuse at the physical layer. To the best of our knowledge, this is the first paper that formally quantifies spectral reuse in IEEE 802.16 mesh networks and exploits spectral efficiency under an integrated framework. Simulation results show that the proposed schemes significantly improve the throughput of IEEE 802.16 mesh networks. [ABSTRACT FROM AUTHOR]

With the rapid evolution of wireless standards and increasing demand for multi-standard products, the need for flexible RF and baseband solutions is growing. Flexibility is required to be able to adapt to unstable standards and requirements without costly hardware re-spins, and also to enable hardware reuse between products and between multiple wireless standards in the same device, ultimately saving both development cost and silicon area. In this paper a fully programmable baseband processor suitable for standards such as DVB-T/H and mobile WiMAX is presented. The processor is based on the SIMT architecture which utilizes a unique type of vector instructions to provide processing parallelism while minimizing the control complexity of the processor. The architecture has been demonstrated in a prototype chip which was proven in a complete DVB-T/H system demonstrator. The chip occupies 11 mm2 in a 0.12 μm CMOS process. It includes 1.5 Mbit of single port SRAM and 200 k logic gates. The measured power consumption for the highest DVB-T/H data rate (31.67 MBit/s) is 70 mW at 70 MHz. This outperforms both area and power figures of previously presented non-programmable DVB-T/H solutions. [ABSTRACT FROM AUTHOR]

This paper describes a dual signal path (MIMO) low power, high performance direct conversion WiBro/WiMAX 802.16e radio transceiver optimized for mobile applications and for coexistence with co-located Cellular and WLAN/Bluetooth systems. The direct-conversion transceiver is designed to be very flexible in respect of biasing and programmability, both to allow power consumption to be traded adaptively versus performance, and flexibility for any changes in the new transmission standard. Signal loopback and transmit power detection techniques are used in conjunction with the baseband modem processor to calibrate transmitter LO leakage and the transceiver and receiver IQ imbalances. The receiver achieves a noise figure (NF) of less than 2.5 dB over an operational frequency range of 2.3-2.7 GHz, and the gain is tunable from 0 dB to 97 dB in 1 dB steps. The maximum linear transmit power is 2.5 dBm and the transmit gain can be digitally controlled over a 75 dB range. The transceiver is fabricated in a 0.25 µm SiGe BiCMOS process and consumes 65/103 mA from a 2.8 V supply in OFDMA Rx/Tx modes, respectively. [ABSTRACT FROM AUTHOR]

In this paper a novel technique for reducing the peak to average power ratio (PAPR) in OFDM systems by using the combination of the dummy sequence insertion (DSI) and partial transmit sequence (PTS) is proposed. In DSI increasing the number of dummy sequence decrease the transmission efficiency (TE) and in PTS the complexity increases when the number of subblock increases. Unlike the conventional PTS which needs several inverse fast fourier transform (IFFT) operations, the proposed DSI-PTS technique requires half IFFT operations only, while the PAPR performance is even better. So, it can remarkably reduce the computational complexity. Simulation results are examined with IEEE 802.16-2004 standard. By applying the DSI-PTS method about 0.5 dB reduction in PAPR at complementary cumulative distribution function (CCDF) of 0.01% is achieved compared to the conventional PTS while the complexity is reduced1. [ABSTRACT FROM AUTHOR]